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Sample records for cathode catalyst layer

  1. Highly Durable Direct Methanol Fuel Cell with Double-Layered Catalyst Cathode

    Directory of Open Access Journals (Sweden)

    Jing Liu

    2015-01-01

    Full Text Available Polymer electrolyte membrane (PEM is one of the key components in direct methanol fuel cells. However, the PEM usually gets attacked by reactive oxygen species during the operation period, resulting in the loss of membrane integrity and formation of defects. Herein, a double-layered catalyst cathode electrode consisting of Pt/CeO2-C as inner catalyst and Pt/C as outer catalyst is fabricated to extend the lifetime and minimize the performance loss of DMFC. Although the maximum power density of membrane electrode assembly (MEA with catalyst cathode is slightly lower than that of the traditional one, its durability is significantly improved. No obvious degradation is evident in the MEA with double-layered catalyst cathode within durability testing. These results indicated that Pt/CeO2-C as inner cathode catalyst layer greatly improved the stability of MEA. The significant reason for the improved stability of MEA is the ability of CeO2 to act as free-radical scavengers.

  2. Inhibition of microbial growth on air cathodes of single chamber microbial fuel cells by incorporating enrofloxacin into the catalyst layer.

    Science.gov (United States)

    Liu, Weifeng; Cheng, Shaoan; Sun, Dan; Huang, Haobin; Chen, Jie; Cen, Kefa

    2015-10-15

    The inevitable growth of aerobic bacteria on the surface of air cathodes is an important factor reducing the performance stability of air cathode single-chamber membrane-free microbial fuel cells (MFCs). Thus searching for effective methods to inhibit the cathodic microbial growth is critical for the practical application of MFCs. In this study, enrofloxacin (ENR), a broad spectrum fluoroquinolone antibiotic, was incorporated into the catalyst layer of activated carbon air cathodes (ACACs) to inhibit the cathodic microbial growth. The biomass content on ACACs was substantially reduced by 60.2% with ENR treatment after 91 days of MFCs operation. As a result of the inhibited microbial growth, the oxygen reduction catalytic performance of the ENR treated ACACs was much stable compared to the fast performance decline of the untreated control. Consequently, a quite stable electricity production was obtained for the MFCs with the ENR treated ACACs, in contrast with a 22.5% decrease in maximum power density of the MFCs with the untreated cathode. ENR treatment of ACACs showed minimal effects on the anode performance. These results indicate that incorporating antibiotics into ACACs should be a simple and effective strategy to inhibit the microbial growth and improve the long-term stability of the performance of air cathode and the electricity production of MFCs.

  3. Pore network model of the cathode catalyst layer of proton exchange membrane fuel cells: Analysis of water management and electrical performance

    OpenAIRE

    El Hannach, Mohamed; Prat, Marc; Pauchet, Joël

    2012-01-01

    International audience; A pore network modeling approach is developed to study multiphase transport phenomena inside a porous structure representative of the Cathode Catalyst Layer (CCL) of Proton Exchange Membrane Fuel Cell. A full coupling between two-phase transport, charge transport and heat transport is considered. The liquid water evaporation is also taken into account. The current density profile and the liquid water distribution and production are investigated to understand the liquid...

  4. Methanol-Tolerant Cathode Catalyst Composite For Direct Methanol Fuel Cells

    Science.gov (United States)

    Zhu, Yimin; Zelenay, Piotr

    2006-03-21

    A direct methanol fuel cell (DMFC) having a methanol fuel supply, oxidant supply, and its membrane electrode assembly (MEA) formed of an anode electrode and a cathode electrode with a membrane therebetween, a methanol oxidation catalyst adjacent the anode electrode and the membrane, an oxidant reduction catalyst adjacent the cathode electrode and the membrane, comprises an oxidant reduction catalyst layer of a platinum-chromium alloy so that oxidation at the cathode of methanol that crosses from the anode through the membrane to the cathode is reduced with a concomitant increase of net electrical potential at the cathode electrode.

  5. Catalysts, Protection Layers, and Semiconductors

    DEFF Research Database (Denmark)

    Chorkendorff, Ib

    2015-01-01

    Hydrogen is the simplest solar fuel to produce and in this presentation we shall give a short overview of the pros and cons of various tandem devices [1]. The large band gap semiconductor needs to be in front, but apart from that we can chose to have either the anode in front or back using either...... acid or alkaline conditions. Since most relevant semiconductors are very prone to corrosion the advantage of using buried junctions and using protection layers offering shall be discussed [2-4]. Next we shall discuss the availability of various catalysts for being coupled to these protections layers...... and how their stability may be evaluated [5, 6]. Examples of half-cell reaction using protection layers for both cathode and anode will be discussed though some of recent examples under both alkaline and acidic conditions. Si is a very good low band gap semiconductor and by using TiO2 as a protection...

  6. Highly Durable Supportless Pt Hollow Spheres Designed for Enhanced Oxygen Transport in Cathode Catalyst Layers of Proton Exchange Membrane Fuel Cells.

    Science.gov (United States)

    Dogan, Didem C; Cho, Seonghun; Hwang, Sun-Mi; Kim, Young-Min; Guim, Hwanuk; Yang, Tae-Hyun; Park, Seok-Hee; Park, Gu-Gon; Yim, Sung-Dae

    2016-10-10

    Supportless Pt catalysts have several advantages over conventional carbon-supported Pt catalysts in that they are not susceptible to carbon corrosion. However, the need for high Pt loadings in membrane electrode assemblies (MEAs) to achieve state-of-the-art fuel cell performance has limited their application in proton exchange membrane fuel cells. Herein, we report a new approach to the design of a supportless Pt catalyst in terms of catalyst layer architecture, which is crucial for fuel cell performance as it affects water management and oxygen transport in the catalyst layers. Large Pt hollow spheres (PtHSs) 100 nm in size were designed and prepared using a carbon template method. Despite their large size, the unique structure of the PtHSs, which are composed of a thin-layered shell of Pt nanoparticles (ca. 7 nm thick), exhibited a high surface area comparable to that of commercial Pt black (PtB). The PtHS structure also exhibited twice the durability of PtB after 2000 potential cycles (0-1.3 V, 50 mV/s). A MEA fabricated with PtHSs showed significant improvement in fuel cell performance compared to PtB-based MEAs at high current densities (>800 mA/cm(2)). This was mainly due to the 2.7 times lower mass transport resistance in the PtHS-based catalyst layers compared to that in PtB, owing to the formation of macropores between the PtHSs and high porosity (90%) in the PtHS catalyst layers. The present study demonstrates a successful example of catalyst design in terms of catalyst layer architecture, which may be applied to a real fuel cell system.

  7. Highly active carbon supported Pd cathode catalysts for direct formic acid fuel cells

    Science.gov (United States)

    Mikolajczuk-Zychora, A.; Borodzinski, A.; Kedzierzawski, P.; Mierzwa, B.; Mazurkiewicz-Pawlicka, M.; Stobinski, L.; Ciecierska, E.; Zimoch, A.; Opałło, M.

    2016-12-01

    One of the drawbacks of low-temperature fuel cells is high price of platinum-based catalysts used for the electroreduction of oxygen at the cathode of the fuel cell. The aim of this work is to develop the palladium catalyst that will replace commonly used platinum cathode catalysts. A series of palladium catalysts for oxygen reduction reaction (ORR) were prepared and tested on the cathode of Direct Formic Acid Fuel Cell (DFAFC). Palladium nanoparticles were deposited on the carbon black (Vulcan) and on multiwall carbon nanotubes (MWCNTs) surface by reduction of palladium(II) acetate dissolved in ethanol. Hydrazine was used as a reducing agent. The effect of functionalization of the carbon supports on the catalysts physicochemical properties and the ORR catalytic activity on the cathode of DFAFC was studied. The supports were functionalized by treatment in nitric acid for 4 h at 80 °C. The structure of the prepared catalysts has been characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscope (TEM) and cyclic voltammetry (CV). Hydrophilicity of the catalytic layers was determined by measuring contact angles of water droplets. The performance of the prepared catalysts has been compared with that of the commercial 20 wt.% Pt/C (Premetek) catalyst. The maximum power density obtained for the best palladium catalyst, deposited on the surface of functionalized carbon black, is the same as that for the commercial Pt/C (Premetek). Palladium is cheaper than platinum, therefore the developed cathode catalyst is promising for future applications.

  8. Oxygen-reducing catalyst layer

    Energy Technology Data Exchange (ETDEWEB)

    O' Brien, Dennis P. (Maplewood, MN); Schmoeckel, Alison K. (Stillwater, MN); Vernstrom, George D. (Cottage Grove, MN); Atanasoski, Radoslav (Edina, MN); Wood, Thomas E. (Stillwater, MN); Yang, Ruizhi (Halifax, CA); Easton, E. Bradley (Halifax, CA); Dahn, Jeffrey R. (Hubley, CA); O' Neill, David G. (Lake Elmo, MN)

    2011-03-22

    An oxygen-reducing catalyst layer, and a method of making the oxygen-reducing catalyst layer, where the oxygen-reducing catalyst layer includes a catalytic material film disposed on a substrate with the use of physical vapor deposition and thermal treatment. The catalytic material film includes a transition metal that is substantially free of platinum. At least one of the physical vapor deposition and the thermal treatment is performed in a processing environment comprising a nitrogen-containing gas.

  9. Novel anti-flooding poly(dimethylsiloxane) (PDMS) catalyst binder for microbial fuel cell cathodes

    KAUST Repository

    Zhang, Fang

    2012-11-01

    Poly(dimethylsiloxane) (PDMS) was investigated as an alternative to Nafion as an air cathode catalyst binder in microbial fuel cells (MFCs). Cathodes were constructed around either stainless steel (SS) mesh or copper mesh using PDMS as both catalyst binder and diffusion layer, and compared to cathodes of the same structure having a Nafion binder. With PDMS binder, copper mesh cathodes produced a maximum power of 1710 ± 1 mW m -2, while SS mesh had a slightly lower power of 1680 ± 12 mW m -2, with both values comparable to those obtained with Nafion binder. Cathodes with PDMS binder had stable power production of 1510 ± 22 mW m -2 (copper) and 1480 ± 56 mW m -2 (SS) over 15 days at cycle 15, compared to a 40% decrease in power with the Nafion binder. Cathodes with the PDMS binder had lower total cathode impedance than those with Nafion. This is due to a large decrease in diffusion resistance, because hydrophobic PDMS effectively prevented catalyst sites from filling up with water, improving oxygen mass transfer. The cost of PDMS is only 0.23% of that of Nafion. These results showed that PDMS is a very effective and low-cost alternative to Nafion binder that will be useful for large scale construction of these cathodes for MFC applications. © 2012 Elsevier B.V.

  10. Cathodic catalysts in bioelectrochemical systems for energy recovery from wastewater.

    Science.gov (United States)

    Liu, Xian-Wei; Li, Wen-Wei; Yu, Han-Qing

    2014-11-21

    Bioelectrochemical systems (BESs), in which microorganisms are utilized as a self-regenerable catalyst at the anode of an electrochemical cell to directly extract electrical energy from organic matter, have been widely recognized as a promising technology for energy-efficient wastewater treatment or even for net energy generation. However, currently BES performance is constrained by poor cathode reaction kinetics. Thus, there is a strong impetus to improve the cathodic catalysis performance through proper selection and design of catalysts. This review introduces the fundamentals and current development status of various cathodic catalysts (including electrocatalysts, photoelectrocatalysts and bioelectrocatalysts) in BES, identifies their limitations and influential factors, compares their catalytic performances in terms of catalytic efficiency, stability, selectivity, etc., and discusses the possible optimization strategies and future research directions. Special focus is given on the analysis of how the catalytic performance of different catalysts can be improved by fine tuning their physicochemical or physiological properties.

  11. Enhanced stability of multilayer graphene-supported catalysts for polymer electrolyte membrane fuel cell cathodes

    Science.gov (United States)

    Marinkas, A.; Hempelmann, R.; Heinzel, A.; Peinecke, V.; Radev, I.; Natter, H.

    2015-11-01

    One of the biggest challenges in the field of polymer electrolyte membrane fuel cells (PEMFC) is to enhance the lifetime and the long-term stability of PEMFC electrodes, especially of cathodes, furthermore, to reduce their platinum loading, which could lead to a cost reduction for efficient PEMFCs. These demands could be achieved with a new catalyst support architecture consisting of a composite of carbon structures with significant different morphologies. A highly porous cathode catalyst support layer is prepared by addition of various carbon types (carbon black particles, multi-walled carbon nanotubes (MWCNT)) to multilayer graphene (MLG). The reported optimized cathodes shows extremely high durability and similar performance to commercial standard cathodes but with 89% lower Pt loading. The accelerated aging protocol (AAP) on the membrane electrode assemblies (MEA) shows that the presence of MLG increases drastically the durability and the Pt-extended electrochemical surface area (ECSA). In fact, after the AAP slightly enhanced performance can be observed for the MLG-containing cathodes instead of a performance loss, which is typical for the commercial carbon-based cathodes. Furthermore, the presence of MLG drastically decreases the ECSA loss rate. The MLG-containing cathodes show up to 6.8 times higher mass-normalized Pt-extended ECSA compared to the commercial standard systems.

  12. Impact of liquid water on oxygen reaction in cathode catalyst layer of proton exchange membrane fuel cell: A simple and physically sound model

    Science.gov (United States)

    Zhang, Xiaoxian; Gao, Yuan

    2016-06-01

    When cells work at high current density, liquid water accumulates in their catalyst layer (CL) and the gaseous oxygen could dissolve into the water and the ionomer film simultaneously; their associated dissolved concentrations in equilibrium with the gaseous oxygen are also different. Based on a CL acquired using tomography, we present new methods in this paper to derive agglomerate models for partly saturated CL by viewing the movement and reaction of the dissolved oxygen in the two liquids (water and ionomer) and the agglomerate as two independent random processes. Oxygen dissolved in the water moves differently from oxygen dissolved in the ionomer, and to make the analysis tractable, we use an average distribution function to describe the average movement of all dissolved oxygen. A formula is proposed to describe this average distribution function, which, in combination with the exponential distribution assumed in the literature for oxygen reaction, leads to a simple yet physically sound agglomerate model. The model has three parameters which can be directly calculated from CL structure rather than by calibration. We explain how to calculate these parameters under different water contents for a given CL structure, and analyse the impact of liquid water on cell performance.

  13. Neutral hydrophilic cathode catalyst binders for microbial fuel cells

    KAUST Repository

    Saito, Tomonori

    2011-01-01

    Improving oxygen reduction in microbial fuel cell (MFC) cathodes requires a better understanding of the effects of the catalyst binder chemistry and properties on performance. A series of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) polymers with systematically varying hydrophilicity were designed to determine the effect of the hydrophilic character of the binder on cathode performance. Increasing the hydrophilicity of the PS-b-PEO binders enhanced the electrochemical response of the cathode and MFC power density by ∼15%, compared to the hydrophobic PS-OH binder. Increased cathode performance was likely a result of greater water uptake by the hydrophilic binder, which would increase the accessible surface area for oxygen reduction. Based on these results and due to the high cost of PS-b-PEO, the performance of an inexpensive hydrophilic neutral polymer, poly(bisphenol A-co-epichlorohydrin) (BAEH), was examined in MFCs and compared to a hydrophilic sulfonated binder (Nafion). MFCs with BAEH-based cathodes with two different Pt loadings initially (after 2 cycles) had lower MFC performance (1360 and 630 mW m-2 for 0.5 and 0.05 mg Pt cm-2) than Nafion cathodes (1980 and 1080 mW m -2 for 0.5 and 0.05 mg Pt cm-2). However, after long-term operation (22 cycles, 40 days), power production of each cell was similar (∼1200 and 700-800 mW m-2 for 0.5 and 0.05 mg Pt cm-2) likely due to cathode biofouling that could not be completely reversed through physical cleaning. While binder chemistry could improve initial electrochemical cathode performance, binder materials had less impact on overall long-term MFC performance. This observation suggests that long-term operation of MFCs will require better methods to avoid cathode biofouling. © 2011 The Royal Society of Chemistry.

  14. Diffusion layer characteristics for increasing the performance of activated carbon air cathodes in microbial fuel cells

    KAUST Repository

    Zhang, Xiaoyuan

    2016-01-01

    The characteristics of several different types of diffusion layers were systematically examined to improve the performance of activated carbon air cathodes used in microbial fuel cells (MFCs). A diffusion layer of carbon black and polytetrafluoroethylene (CB + PTFE) that was pressed onto a stainless steel mesh current collector achieved the highest cathode performance. This cathode also had a high oxygen mass transfer coefficient and high water pressure tolerance (>2 m), and it had the highest current densities in abiotic chronoamperometry tests compared to cathodes with other diffusion layers. In MFC tests, this cathode also produced maximum power densities (1610 ± 90 mW m−2) that were greater than those of cathodes with other diffusion layers, by 19% compared to Gore-Tex (1350 ± 20 mW m−2), 22% for a cloth wipe with PDMS (1320 ± 70 mW m−2), 45% with plain PTFE (1110 ± 20 mW m−2), and 19% higher than those of cathodes made with a Pt catalyst and a PTFE diffusion layer (1350 ± 50 mW m−2). The highly porous diffusion layer structure of the CB + PTFE had a relatively high oxygen mass transfer coefficient (1.07 × 10−3 cm s−1) which enhanced oxygen transport to the catalyst. The addition of CB enhanced cathode performance by increasing the conductivity of the diffusion layer. Oxygen mass transfer coefficient, water pressure tolerance, and the addition of conductive particles were therefore critical features for achieving higher performance AC air cathodes.

  15. Excimer emission from cathode boundary layer discharges

    Science.gov (United States)

    Moselhy, Mohamed; Schoenbach, Karl H.

    2004-02-01

    The excimer emission from direct current glow discharges between a planar cathode and a ring-shaped anode of 0.75 and 1.5 mm diameter, respectively, separated by a gap of 250 μm, was studied in xenon and argon in a pressure range from 75 to 760 Torr. The thickness of the "cathode boundary layer" plasma, in the 100 μm range, and a discharge sustaining voltage of approximately 200 V, indicates that the discharge is restricted to the cathode fall and the negative glow. The radiant excimer emittance at 172 nm increases with pressure and reaches a value of 4 W/cm2 for atmospheric pressure operation in xenon. The maximum internal efficiency, however, decreases with pressure having highest values of 5% for 75 Torr operation. When the discharge current is reduced below a critical value, the discharge in xenon changes from an abnormal glow into a mode showing self-organization of the plasma. Also, the excimer spectrum changes from one with about equal contributions from the first and second continuum to one that is dominated by the second continuum emission. The xenon excimer emission intensity peaks at this discharge mode transition. In the case of argon, self-organization of the plasma was not seen, but the emission of the excimer radiation (128 nm) again shows a maximum at the transition from abnormal to normal glow. As was observed with xenon, the radiant emittance of argon increases with pressure, and the efficiency decreases. The maximum radiant emittance is 1.6 W/cm2 for argon at 600 Torr. The maximum internal efficiency is 2.5% at 200 Torr. The positive slope of the current-voltage characteristics at maximum excimer emission in both cases indicates the possibility of generating intense, large area, flat excimer lamps.

  16. Power generation using carbon mesh cathodes with different diffusion layers in microbial fuel cells

    KAUST Repository

    Luo, Yong

    2011-11-01

    An inexpensive carbon material, carbon mesh, was examined to replace the more expensive carbon cloth usually used to make cathodes in air-cathode microbial fuel cells (MFCs). Three different diffusion layers were tested using carbon mesh: poly(dimethylsiloxane) (PDMS), polytetrafluoroethylene (PTFE), and Goretex cloth. Carbon mesh with a mixture of PDMS and carbon black as a diffusion layer produced a maximum power density of 1355 ± 62 mW m -2 (normalized to the projected cathode area), which was similar to that obtained with a carbon cloth cathode (1390 ± 72 mW m-2). Carbon mesh with a PTFE diffusion layer produced only a slightly lower (6.6%) maximum power density (1303 ± 48 mW m-2). The Coulombic efficiencies were a function of current density, with the highest value for the carbon mesh and PDMS (79%) larger than that for carbon cloth (63%). The cost of the carbon mesh cathode with PDMS/Carbon or PTFE (excluding catalyst and binder costs) is only 2.5% of the cost of the carbon cloth cathode. These results show that low cost carbon materials such as carbon mesh can be used as the cathode in an MFC without reducing the performance compared to more expensive carbon cloth. © 2011 Elsevier B.V.

  17. Cathodic electrocatalyst layer for electrochemical generation of hydrogen peroxide

    Science.gov (United States)

    Rhodes, Christopher P. (Inventor); Tennakoon, Charles L. K. (Inventor); Singh, Waheguru Pal (Inventor); Anderson, Kelvin C. (Inventor)

    2011-01-01

    A cathodic gas diffusion electrode for the electrochemical production of aqueous hydrogen peroxide solutions. The cathodic gas diffusion electrode comprises an electrically conductive gas diffusion substrate and a cathodic electrocatalyst layer supported on the gas diffusion substrate. A novel cathodic electrocatalyst layer comprises a cathodic electrocatalyst, a substantially water-insoluble quaternary ammonium compound, a fluorocarbon polymer hydrophobic agent and binder, and a perfluoronated sulphonic acid polymer. An electrochemical cell using the novel cathodic electrocatalyst layer has been shown to produce an aqueous solution having between 8 and 14 weight percent hydrogen peroxide. Furthermore, such electrochemical cells have shown stable production of hydrogen peroxide solutions over 1000 hours of operation including numerous system shutdowns.

  18. Polymer coatings as separator layers for microbial fuel cell cathodes

    KAUST Repository

    Watson, Valerie J.

    2011-03-01

    Membrane separators reduce oxygen flux from the cathode into the anolyte in microbial fuel cells (MFCs), but water accumulation and pH gradients between the separator and cathode reduces performance. Air cathodes were spray-coated (water-facing side) with anion exchange, cation exchange, and neutral polymer coatings of different thicknesses to incorporate the separator into the cathode. The anion exchange polymer coating resulted in greater power density (1167 ± 135 mW m-2) than a cation exchange coating (439 ± 2 mW m-2). This power output was similar to that produced by a Nafion-coated cathode (1114 ± 174 mW m-2), and slightly lower than the uncoated cathode (1384 ± 82 mW m-2). Thicker coatings reduced oxygen diffusion into the electrolyte and increased coulombic efficiency (CE = 56-64%) relative to an uncoated cathode (29 ± 8%), but decreased power production (255-574 mW m-2). Electrochemical characterization of the cathodes ex situ to the MFC showed that the cathodes with the lowest charge transfer resistance and the highest oxygen reduction activity produced the most power in MFC tests. The results on hydrophilic cathode separator layers revealed a trade off between power and CE. Cathodes coated with a thin coating of anion exchange polymer show promise for controlling oxygen transfer while minimally affecting power production. © 2010 Elsevier B.V. All rights reserved.

  19. Catalyst morphology matters for lithium-oxygen battery cathodes

    Science.gov (United States)

    Oakes, Landon; Muralidharan, Nitin; Cohn, Adam P.; Pint, Cary L.

    2016-12-01

    The effectiveness of using catalyst nanoparticles to reduce the overpotential and energy efficiency of lithium-oxygen (or lithium-air) batteries (LOBs) is usually attributed to the inherent catalytic properties of individual nanoparticles. Here, we demonstrate that the morphology of the catalyst layer is equally important in maintaining integrity of the catalyst coating during product formation in LOBs. We demonstrate this by comparing the performance of smooth, conformal coated Mn2O3 catalyst nanoparticles prepared by electric field-assisted deposition, and more irregular coatings using conventional film assembly techniques both on three-dimensional mesh substrates. Smooth coatings lead to an improved overpotential of 50 mV during oxygen reduction and 130 mV during oxygen evolution in addition to a nearly 2X improvement in durability compared to the more irregular films. In situ electrochemical impedance spectroscopy combined with imaging studies elucidates a mechanism of morphology-directed deactivation of catalyst layers during charging and discharging that must be overcome at practical electrode scales to achieve cell-level performance targets in LOBs.

  20. Microbial Fuel Cell Cathodes With Poly(dimethylsiloxane) Diffusion Layers Constructed around Stainless Steel Mesh Current Collectors

    KAUST Repository

    Zhang, Fang

    2010-02-15

    A new and simplified approach for making cathodes for microbial fuel cells (MFCs) was developed by using metal meshcurrent collectorsandinexpensive polymer/carbon diffusion layers (DLs). Rather than adding a current collector to a cathode material such as carbon cloth, we constructed the cathode around the metal mesh itself, thereby avoiding the need for the carbon cloth or other supporting material. A base layer of poly(dimethylsiloxane) (PDMS) and carbon black was applied to the air-side of a stainless steel mesh, and Pt on carbon black with Nafion binder was applied to the solutionside as catalyst for oxygen reduction. The PDMS prevented water leakage and functioned as a DL by limiting oxygen transfer through the cathode and improving coulombic efficiency. PDMS is hydrophobic, stable, and less expensive than other DL materials, such as PTFE, that are commonly applied to air cathodes. Multiple PDMS/carbon layers were applied in order to optimize the performance of the cathode. Two PDMS/ carbon layers achieved the highest maximum power density of 1610 ± 56 mW/m 2 (normalized to cathode projected surface area; 47.0 ± 1.6 W/m3 based on liquid volume). This power output was comparable to the best result of 1635 ± 62 mW/m2 obtained using carbon cloth with three PDMS/carbon layers and a Pt catalyst. The coulombic efficiency of the mesh cathodes reached more than 80%, and was much higher than the maximum of 57% obtained with carbon cloth. These findings demonstrate that cathodes can be constructed around metal mesh materials such as stainless steel, and that an inexpensive coating of PDMS can prevent water leakage and lead to improved coulombic efficiencies. © 2010 American Chemical Society.

  1. Cathodes for lithium-air battery cells with acid electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Yangchuan; Huang, Kan; Li, Yunfeng

    2016-07-19

    In various embodiments, the present disclosure provides a layered metal-air cathode for a metal-air battery. Generally, the layered metal-air cathode comprises an active catalyst layer, a transition layer bonded to the active catalyst layer, and a backing layer bonded to the transition layer such that the transition layer is disposed between the active catalyst layer and the backing layer.

  2. Cold cathodes based on carbonic nanostructured layered structures

    Directory of Open Access Journals (Sweden)

    Belyanin A. F.

    2013-06-01

    Full Text Available The paper describes formation conditions for and the structure of diamond-like materials films used in the manufacture of layered cold cathodes of emission electronics devices. The authors study the structure and field emission properties of layered structures with polycluster diamond and diamond-like carbon films (DCF formed by various methods. It has been found that the best emission properties are characteristic of DCFs obtained by cathode sputtering. Emission from the surface of such films occurs on the boundaries of the globules.

  3. Impact of salinity on cathode catalyst performance in microbial fuel cells (MFCs)

    KAUST Repository

    Wang, Xi

    2011-10-01

    Several alternative cathode catalysts have been proposed for microbial fuel cells (MFCs), but effects of salinity (sodium chloride) on catalyst performance, separate from those of conductivity on internal resistance, have not been previously examined. Three different types of cathode materials were tested here with increasingly saline solutions using single-chamber, air-cathode MFCs. The best MFC performance was obtained using a Co catalyst (cobalt tetramethoxyphenyl porphyrin; CoTMPP), with power increasing by 24 ± 1% to 1062 ± 9 mW/m2 (normalized to the projected cathode surface area) when 250 mM NaCl (final conductivity of 31.3 mS/cm) was added (initial conductivity of 7.5 mS/cm). This power density was 25 ± 1% higher than that achieved with Pt on carbon cloth, and 27 ± 1% more than that produced using an activated carbon/nickel mesh (AC) cathode in the highest salinity solution. Linear sweep voltammetry (LSV) was used to separate changes in performance due to solution conductivity from those produced by reductions in ohmic resistance with the higher conductivity solutions. The potential of the cathode with CoTMPP increased by 17-20 mV in LSVs when the NaCl addition was increased from 0 to 250 mM independent of solution conductivity changes. Increases in current were observed with salinity increases in LSVs for AC, but not for Pt cathodes. Cathodes with CoTMPP had increased catalytic activity at higher salt concentrations in cyclic voltammograms compared to Pt and AC. These results suggest that special consideration should be given to the type of catalyst used with more saline wastewaters. While Pt oxygen reduction activity is reduced, CoTMPP cathode performance will be improved at higher salt concentrations expected for wastewaters containing seawater. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

  4. Electrodeposited ultrafine TaOx/CB catalysts for PEFC cathode application: Their oxygen reduction reaction kinetics

    KAUST Repository

    Seo, Jeongsuk

    2014-12-01

    Ultrafine TaOx nanoparticles were electrodeposited on carbon black (CB) powder in a nonaqueous Ta complex solution at room temperature, and the resultant TaOx/CB catalysts were assessed as oxygen reduction reaction (ORR) electrocatalysts for polymer electrolyte fuel cell (PEFC) cathodes. The Ta electrodeposition process was scaled up using a newly designed working electrode containing a CB dense layer, without introducing any binder such as the ionomer Nafion in the electrode for electrodeposition. The electrodeposited TaOx/CB powders were removed from the deposition electrode and subsequent H2 treatment at varying temperatures between 523 and 1073 K was attempted to increase the ORR performance. The TaOx/CB samples were characterized by SEM, STEM, XPS, and EELS measurements. XPS and EELS results indicated the reduced nature of the Ta species caused by the high-temperature treatment in H2, while STEM images clearly revealed that the TaOx particles aggregated as the treatment temperature increased. When the TaOx/CB catalyst, which was treated at 873 K for 2 h, was deposited on a glassy carbon substrate with Nafion ionomer, it resulted in the highest activity among the samples investigated, giving an onset potential of 0.95 VRHE at -2 μA cm-2 in a 0.1 M H2SO4 solution. Moreover, the long-term stability test with 10,000 cycles of the voltammetry only led to a 6% loss in the ORR currents, demonstrating the high stability of the TaOx/CB catalysts. Kinetic analysis by R(R)DE indicated that the four-electron transfer pathway in the ORR process was dominant for this TaOx/CB catalyst, and Tafel plots showed a slope corresponding to a one-electron reaction for the rate-determining step.

  5. Modelling cathode spots in glow discharges in the cathode boundary layer geometry

    CERN Document Server

    Almeida, P G C; Bieniek, M S

    2015-01-01

    Self-organized patterns of cathode spots in glow discharges are computed in the cathode boundary layer geometry, which is the one employed in most of the experiments reported in the literature. The model comprises conservation and transport equations of electrons and a single ion species, written in the drift-diffusion and local-field approximations, and Poisson's equation. Multiple solutions existing for the same value of the discharge current and describing modes with different configurations of cathode spots are computed by means of a stationary solver. The computed solutions are compared to their counterparts for plane-parallel electrodes, and experiments. All of the computed spot patterns have been observed in the experiment.

  6. Evaluation of low-cost cathode catalysts for high yield biohydrogen production in microbial electrolysis cell.

    Science.gov (United States)

    Wang, L; Chen, Y; Ye, Y; Lu, B; Zhu, S; Shen, S

    2011-01-01

    As an ideal fuel due to the advantages of no pollution, high combustion heat and abundant sources, hydrogen gas can be produced from organic matter through the electrohydrogenesis process in microbial electrolysis cells. But in many MECs, platinum is often used as catalyst, which limits the practical applications of MECs. To reduce the cost of the MECs, Ni-based alloy cathodes were developed by electrodepositing. In this paper hydrogen production using Ni-W-P cathode was studied for the first time in a single-chamber membrane-free MEC. At an applied voltage of 0.9 V, MECs with Ni-W-P cathodes obtained a hydrogen production rate of 1.09 m3/m3/day with an cathodic hydrogen recovery of 74%, a Coulombic efficiency of 56% and an electrical energy efficiency relative to electrical input of 139%, which was the best result of reports in this study. The Ni-W-P cathode demonstrated a better electrocatalytic activity than the Ni-Ce-P cathode and achieved a comparable performance to the Pt cathode in terms of hydrogen production rate, Coulombic efficiency, cathodic hydrogen recovery and electrical energy efficiency at 0.9 V.

  7. Highly durable and active non-precious air cathode catalyst for zinc air battery

    Science.gov (United States)

    Chen, Zhu; Choi, Ja-Yeon; Wang, Haijiang; Li, Hui; Chen, Zhongwei

    The electrochemical stability of non-precious FeCo-EDA and commercial Pt/C cathode catalysts for zinc air battery have been compared using accelerated degradation test (ADT) in alkaline condition. Outstanding oxygen reduction reaction (ORR) stability of the FeCo-EDA catalyst was observed compared with the commercial Pt/C catalyst. The FeCo-EDA catalyst retained 80% of the initial mass activity for ORR whereas the commercial Pt/C catalyst retained only 32% of the initial mass activity after ADT. Additionally, the FeCo-EDA catalyst exhibited a nearly three times higher mass activity compared to that of the commercial Pt/C catalyst after ADT. Furthermore, single cell test of the FeCo-EDA and Pt/C catalysts was performed where both catalysts exhibited pseudolinear behaviour in the 12-500 mA cm -2 range. In addition, 67% higher peak power density was observed from the FeCo-EDA catalyst compared with commercial Pt/C. Based on the half cell and single cell tests the non-precious FeCo-EDA catalyst is a very promising ORR electrocatalyst for zinc air battery.

  8. Hydrogen production with nickel powder cathode catalysts in microbial electrolysis cells

    KAUST Repository

    Selembo, Priscilla A.

    2010-01-01

    Although platinum is commonly used as catalyst on the cathode in microbial electrolysis cells (MEC), non-precious metal alternatives are needed to reduce costs. Cathodes were constructed using a nickel powder (0.5-1 μm) and their performance was compared to conventional electrodes containing Pt (0.002 μm) in MECs and electrochemical tests. The MEC performance in terms of coulombic efficiency, cathodic, hydrogen and energy recoveries were similar using Ni or Pt cathodes, although the maximum hydrogen production rate (Q) was slightly lower for Ni (Q = 1.2-1.3 m3 H2/m3/d; 0.6 V applied) than Pt (1.6 m3 H2/m3/d). Nickel dissolution was minimized by replacing medium in the reactor under anoxic conditions. The stability of the Ni particles was confirmed by examining the cathodes after 12 MEC cycles using scanning electron microscopy and linear sweep voltammetry. Analysis of the anodic communities in these reactors revealed dominant populations of Geobacter sulfurreduces and Pelobacter propionicus. These results demonstrate that nickel powder can be used as a viable alternative to Pt in MECs, allowing large scale production of cathodes with similar performance to systems that use precious metal catalysts. © 2009 Professor T. Nejat Veziroglu.

  9. Manganese dioxide as a new cathode catalyst in microbial fuel cells

    Science.gov (United States)

    Li, Xiang; Hu, Boxun; Suib, Steven; Lei, Yu; Li, Baikun

    This study focused on manganese oxides with a cryptomelane-type octahedral molecular sieve (OMS-2) structure to replace platinum as a cathode catalyst in microbial fuel cells (MFCs). Undoped (ud-OSM-2) and three catalysts doped with cobalt (Co-OMS-2), copper (Cu-OMS-2), and cerium (Ce-OMS-2) to enhance their catalytic performances were investigated. The novel OMS-2 cathodes were examined in granular activated carbon MFC (GACMFC) with sodium acetate as the anode reagent and oxygen in air as the cathode reagent. The results showed that after 400 h of operation, the Co-OMS-2 and Cu-OMS-2 exhibited good catalytic performance in an oxygen reduction reaction (ORR). The voltage of the Co-OMS-2 GACMFC was 217 mV, and the power density was 180 mW m -2. The voltage of the Cu-OMS-2 GACMFC was 214 mV and the power density was 165 mW m -2. The internal resistance (R in) of the OMS-2 GACMFCs (18 ± 1 Ω) was similar to that of the platinum GACMFCs (17 Ω). Furthermore, the degradation rates of organic substrates in the OMS-2 GACMFCs were twice those in the platinum GACMFCs, which enhance their wastewater treatment efficiencies. This study indicated that using OMS-2 manganese oxides to replace platinum as a cathodic catalyst enhances power generation, increases contaminant removal, and substantially reduces the cost of MFCs.

  10. Monte Carlo simulation of the PEMFC catalyst layer

    Institute of Scientific and Technical Information of China (English)

    WANG Hongxing; CAO Pengzhen; WANG Yuxin

    2007-01-01

    The performance of the polymer electrolyte membrane fuel cell (PEMFC) is greatly controlled by the structure of the catalyst layer.Low catalyst utilization is still a significant obstacle to the commercialization of the PEMFC.In order to get a fundamental understanding of the electrode structure and to find the limiting factor in the low catalyst utilization,it is necessary to develop the mechanical model on the effect of catalyst layer structure on the catalyst utilization and the performance of the PEMFC.In this work,the structure of the catalyst layer is studied based on the lattice model with the Monte Carlo simulation.The model can predict the effects of some catalyst layer components,such as Pt/C catalyst,electrolyte and gas pores,on the utilization of the catalyst and the cell performance.The simulation result shows that the aggregation of conduction grains can greatly affect the degree of catalyst utilization.The better the dispersion of the conduction grains,the larger the total effective area of the catalyst is.To achieve higher utilization,catalyst layer components must be distributed by means of engineered design,which can prevent aggregation.

  11. Carbon supported ruthenium chalcogenide as cathode catalyst in a microfluidic formic acid fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Gago, A.S.; Alonso-Vante, N. [Laboratory of Electrocatalysis, UMR-CNRS 6503, Universite de Poitiers, 40 Avenue du Recteur Pineau, F-86022 Potiers Cedex (France); Morales-Acosta, D.; Arriaga, L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S.C. Parque Tecnologico Queretaro Sanfandila, P.O. Box 064, Pedro Escobedo, 76703, Queretaro (Mexico)

    2011-02-01

    This work reports the electrochemical measurements of 20 wt.% Ru{sub x}Se{sub y}/C for oxygen reduction reaction (ORR) in presence of different concentration of HCOOH and its use as cathode catalyst in a microfluidic formic acid fuel cell ({mu}FAFC). The results were compared to those obtained with commercial Pt/C. Half-cell electrochemical measurements showed that the chalcogenide catalyst has a high tolerance and selectivity towards ORR in electrolytes containing up to 0.1 M HCOOH. The depolarization effect was higher on Pt/C than on Ru{sub x}Se{sub y}/C by a factor of ca. 23. Both catalysts were evaluated as cathode of a {mu}FAFC operating with different concentrations of HCOOH. When 0.5 M HCOOH was used, maximum current densities of 11.44 mA cm{sup -2} and 4.44 mA cm{sup -2} were obtained when the cathode was Ru{sub x}Se{sub y}/C and Pt/C, respectively. At 0.5 M HCOOH, the peak power density of the {mu}FAFC was similar for both catalysts, ca. 1.9 mW cm{sup -2}. At 5 M HCOOH the power density of the {mu}FAFC using Ru{sub x}Se{sub y}, was 9.3 times higher than the obtained with Pt/C. (author)

  12. Poly(vinylidene fluoride-co-hexafluoropropylene) phase inversion coating as a diffusion layer to enhance the cathode performance in microbial fuel cells

    Science.gov (United States)

    Yang, Wulin; Zhang, Fang; He, Weihua; Liu, Jia; Hickner, Michael A.; Logan, Bruce E.

    2014-12-01

    A low cost poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) phase inversion coating was developed as a cathode diffusion layer to enhance the performance of microbial fuel cells (MFCs). A maximum power density of 1430 ± 90 mW m-2 was achieved at a PVDF-HFP loading of 4.4 mg cm-2 (4:1 polymer:carbon black), with activated carbon as the oxygen reduction cathode catalyst. This power density was 31% higher than that obtained with a more conventional platinum (Pt) catalyst on carbon cloth (Pt/C) cathode with a poly(tetrafluoroethylene) (PTFE) diffusion layer (1090 ± 30 mW m-2). The improved performance was due in part to a larger oxygen mass transfer coefficient of 3 × 10-3 cm s-1 for the PVDF-HFP coated cathode, compared to 1.7 × 10-3 cm s-1 for the carbon cloth/PTFE-based cathode. The diffusion layer was resistant to electrolyte leakage up to water column heights of 41 ± 0.5 cm (4.4 mg cm-2 loading of 4:1 polymer:carbon black) to 70 ± 5 cm (8.8 mg cm-2 loading of 4:1 polymer:carbon black). This new type of PVDF-HFP/carbon black diffusion layer could reduce the cost of manufacturing cathodes for MFCs.

  13. Poly(vinylidene fluoride-co-hexafluoropropylene) phase inversion coating as a diffusion layer to enhance the cathode performance in microbial fuel cells

    KAUST Repository

    Yang, Wulin

    2014-12-01

    A low cost poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) phase inversion coating was developed as a cathode diffusion layer to enhance the performance of microbial fuel cells (MFCs). A maximum power density of 1430 ± 90 mW m-2 was achieved at a PVDF-HFP loading of 4.4 mg cm-2 (4:1 polymer:carbon black), with activated carbon as the oxygen reduction cathode catalyst. This power density was 31% higher than that obtained with a more conventional platinum (Pt) catalyst on carbon cloth (Pt/C) cathode with a poly(tetrafluoroethylene) (PTFE) diffusion layer (1090 ± 30 mW m-2). The improved performance was due in part to a larger oxygen mass transfer coefficient of 3 × 10-3 cm s-1 for the PVDF-HFP coated cathode, compared to 1.7 × 10-3 cm s -1 for the carbon cloth/PTFE-based cathode. The diffusion layer was resistant to electrolyte leakage up to water column heights of 41 ± 0.5 cm (4.4 mg cm-2 loading of 4:1 polymer:carbon black) to 70 ± 5 cm (8.8 mg cm-2 loading of 4:1 polymer:carbon black). This new type of PVDF-HFP/carbon black diffusion layer could reduce the cost of manufacturing cathodes for MFCs. © 2014 Elsevier B.V. All rights reserved.

  14. Modeling Low-Platinum-Loading Effects in Fuel-Cell Catalyst Layers

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Wonseok; Weber, Adam Z.

    2011-01-20

    The cathode catalyst layer within a proton-exchange-membrane fuel cell is the most complex and critical, yet least understood, layer within the cell. The exact method and equations for modeling this layer are still being revised and will be discussed in this paper, including a 0.8 reaction order, existence of Pt oxides, possible non-isopotential agglomerates, and the impact of a film resistance towards oxygen transport. While the former assumptions are relatively straightforward to understand and implement, the latter film resistance is shown to be critically important in explaining increased mass-transport limitations with low Pt-loading catalyst layers. Model results demonstrate agreement with experimental data that the increased oxygen flux and/or diffusion pathway through the film can substantially decrease performance. Also, some scale-up concepts from the agglomerate scale to the more macroscopic porous-electrode scale are discussed and the resulting optimization scenarios investigated.

  15. Performance and microbial ecology of air-cathode microbial fuel cells with layered electrode assemblies.

    Science.gov (United States)

    Butler, Caitlyn S; Nerenberg, Robert

    2010-05-01

    Microbial fuel cells (MFCs) can be built with layered electrode assemblies, where the anode, proton exchange membrane (PEM), and cathode are pressed into a single unit. We studied the performance and microbial community structure of MFCs with layered assemblies, addressing the effect of materials and oxygen crossover on the community structure. Four MFCs with layered assemblies were constructed using Nafion or Ultrex PEMs and a plain carbon cloth electrode or a cathode with an oxygen-resistant polytetrafluoroethylene diffusion layer. The MFC with Nafion PEM and cathode diffusion layer achieved the highest power density, 381 mW/m(2) (20 W/m(3)). The rates of oxygen diffusion from cathode to anode were three times higher in the MFCs with plain cathodes compared to those with diffusion-layer cathodes. Microsensor studies revealed little accumulation of oxygen within the anode cloth. However, the abundance of bacteria known to use oxygen as an electron acceptor, but not known to have exoelectrogenic activity, was greater in MFCs with plain cathodes. The MFCs with diffusion-layer cathodes had high abundance of exoelectrogenic bacteria within the genus Geobacter. This work suggests that cathode materials can significantly influence oxygen crossover and the relative abundance of exoelectrogenic bacteria on the anode, while PEM materials have little influence on anode community structure. Our results show that oxygen crossover can significantly decrease the performance of air-cathode MFCs with layered assemblies, and therefore limiting crossover may be of particular importance for these types of MFCs.

  16. Load cycle durability of a graphitized carbon black-supported platinum catalyst in polymer electrolyte fuel cell cathodes

    Science.gov (United States)

    Takei, Chikara; Kakinuma, Katsuyoshi; Kawashima, Kazuhito; Tashiro, Keisuke; Watanabe, Masahiro; Uchida, Makoto

    2016-08-01

    We focus on Pt degradation occurring during fuel cell vehicle (FCV) combined drive cycles involving load and open circuit voltage (OCV) just after startup and during idling. Load cycle durability is evaluated as a function of OCV/load holding time, load rate and relative humidity (RH) with a graphitized carbon black-supported platinum catalyst (Pt/GCB) in the cathode. The degradation of Pt/GCB is suppressed for shorter OCV holding times, lower load rates and lower RH. Scanning ion microscopy (SIM) images of membrane cross-sections indicate that the amount of Pt deposited in the membrane decreases during drive cycles involving load with short OCV holding times. Investigations of the Pt distribution in the cathode catalyst layer (CL) by using scanning TEM-EDX show that the dissolution of Pt is suppressed on the membrane side in the CL. The Pt dissolution is accelerated by the high Pt oxidation due to the long OCV holding time. A load cycle with both long OCV holding time and low load inhibits the Pt2+ migration into the membrane but accelerates the Pt particle growth due to electrochemical Ostwald ripening; meanwhile, a load cycle with long OCV holding time at lower RH prevents both the Pt dissolution and particle growth.

  17. Mesoporous nitrogen-rich carbon materials as cathode catalysts in microbial fuel cells

    KAUST Repository

    Ahn, Yongtae

    2014-12-01

    The high cost of the catalyst material used for the oxygen reduction reaction in microbial fuel cell (MFC) cathodes is one of the factors limiting practical applications of this technology. Mesoporous nitrogen-rich carbon (MNC), prepared at different temperatures, was examined as an oxygen reduction catalyst, and compared in performance to Pt in MFCs and electrochemical cells. MNC calcined at 800 °C produced a maximum power density of 979 ± 131 mW m-2 in MFCs, which was 37% higher than that produced using MNC calined at 600 °C (715 ± 152 mW m-2), and only 14% lower than that obtained with Pt (1143 ± 54 mW m-2). The extent of COD removal and coulombic efficiencies were the same for all cathode materials. These results show that MNC could be used as an alternative to Pt in MFCs. © 2014 Elsevier B.V. All rights reserved.

  18. Nonactivated and Activated Biochar Derived from Bananas as Alternative Cathode Catalyst in Microbial Fuel Cells

    Directory of Open Access Journals (Sweden)

    Haoran Yuan

    2014-01-01

    Full Text Available Nonactivated and activated biochars have been successfully prepared by bananas at different thermotreatment temperatures. The activated biochar generated at 900°C (Biochar-act900 exhibited improved oxygen reduction reaction (ORR and oxygen evolution reaction (OER performances in alkaline media, in terms of the onset potential and generated current density. Rotating disk electron result shows that the average of 2.65 electrons per oxygen molecule was transferred during ORR of Biochar-act900. The highest power density of 528.2 mW/m2 and the maximum stable voltage of 0.47 V were obtained by employing Biochar-act900 as cathode catalyst, which is comparable to the Pt/C cathode. Owning to these advantages, it is expected that the banana-derived biochar cathode can find application in microbial fuel cell systems.

  19. Nonactivated and activated biochar derived from bananas as alternative cathode catalyst in microbial fuel cells.

    Science.gov (United States)

    Yuan, Haoran; Deng, Lifang; Qi, Yujie; Kobayashi, Noriyuki; Tang, Jiahuan

    2014-01-01

    Nonactivated and activated biochars have been successfully prepared by bananas at different thermotreatment temperatures. The activated biochar generated at 900°C (Biochar-act900) exhibited improved oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performances in alkaline media, in terms of the onset potential and generated current density. Rotating disk electron result shows that the average of 2.65 electrons per oxygen molecule was transferred during ORR of Biochar-act900. The highest power density of 528.2 mW/m(2) and the maximum stable voltage of 0.47 V were obtained by employing Biochar-act900 as cathode catalyst, which is comparable to the Pt/C cathode. Owning to these advantages, it is expected that the banana-derived biochar cathode can find application in microbial fuel cell systems.

  20. Anode- electrolyte- cathode sets of unitary SOFC with electro-catalysts deposited on previously sintered porous support

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, L.F.V.; Souza, F.M.B.; Fiuza, R.P.; Alencar, M.G.F.; Silva, M.A.; Boaventura, J.S. [Chemistry Inst., Salvador (Brazil). Dept. of Physical Chemistry

    2009-07-01

    The solid oxide fuel cell (SOFC) can be used in a broad range of applications. YSZ (yttria stabilized zirconia) and GDC (gadolinia doped ceria) are components of the anode/electrolyte set and LSM (manganite of strontium and lanthanum) ink are components of the cathode. In this study, different combinations of sodium bicarbonate, graphite and citric acid were used to form the electrocatalyst on nickel and iron. After sintering, the set was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and surface area by BET. The pellets had good porosity and the anode-cathode-electrolyte interfaces had good inter-layer adherence. The catalyst was evenly dispersed on the support. The final porous structure did not have any surface area loss compared to the original powder. The mixed agents were found to be good pore formatting agents, with characteristics that were favourable for achieving good sets of anode-cathode-electrolytes. The final structure had good pore distribution and formation. The anode had good surface area and good tack from the interface anode/electrolyte.

  1. Iron-based cathode catalyst with enhanced power density in polymer electrolyte membrane fuel cells.

    Science.gov (United States)

    Proietti, Eric; Jaouen, Frédéric; Lefèvre, Michel; Larouche, Nicholas; Tian, Juan; Herranz, Juan; Dodelet, Jean-Pol

    2011-08-02

    H(2)-air polymer-electrolyte-membrane fuel cells are electrochemical power generators with potential vehicle propulsion applications. To help reduce their cost and encourage widespread use, research has focused on replacing the expensive Pt-based electrocatalysts in polymer-electrolyte-membrane fuel cells with a lower-cost alternative. Fe-based cathode catalysts are promising contenders, but their power density has been low compared with Pt-based cathodes, largely due to poor mass-transport properties. Here we report an iron-acetate/phenanthroline/zeolitic-imidazolate-framework-derived electrocatalyst with increased volumetric activity and enhanced mass-transport properties. The zeolitic-imidazolate-framework serves as a microporous host for phenanthroline and ferrous acetate to form a catalyst precursor that is subsequently heat treated. A cathode made with the best electrocatalyst from this work, tested in H(2)-O(2,) has a power density of 0.75 W cm(-2) at 0.6 V, a meaningful voltage for polymer-electrolyte-membrane fuel cells operation, comparable with that of a commercial Pt-based cathode tested under identical conditions.

  2. Cathode catalysts for primary phosphoric acid fuel cells

    Science.gov (United States)

    1981-01-01

    Alkylation or carbon Vulcan XC-72, the support carbon, was shown to provide the most stable bond type for linking cobalt dehydrodibenzo tetraazannulene (CoTAA) to the surface of the carbon; this result is based on data obtained by cyclic voltammetry, pulse voltammetry and by release of 14C from bonded CoTAA. Half-cell tests at 100 C in 85% phosphoric acid showed that CoTAA bonded to the surface of carbon (Vulcan XC-72) via an alkylation procedure is a more active catalyst than is platinum based on a factor of two improvement in Tafel slope; dimeric CoTAA had catalytic activity equal to platinum. Half-cell tests also showed that bonded CoTAA catalysts do not suffer a loss in potential when air is used as a fuel rather than oxygen. Commercially available polytetrafluroethylene (PTFE) was shown to be unstable in the fuel cell environment with degradation occurring in 2000 hours or less. The PTFE was stressed at 200 C in concentrated phosphoric acid as well as electrochemically stressed in 150 C concentrated phosphoric acid; the surface chemistry of PTFE was observed to change significantly. Radiolabeled PTFE was prepared and used to verify that such chemical changes also occur in the primary fuel cell environment.

  3. Improvement of low-humidity performance of PEMFC by addition of hydrophilic SiO 2 particles to catalyst layer

    Science.gov (United States)

    Jung, Un Ho; Park, Ki Tae; Park, Eun Hee; Kim, Sung Hyun

    Hydrophilic SiO 2 particles are added to the catalyst layer of a fuel cell membrane-electrode assembly (MEA) to improve wettability and performance at low-humidity conditions. The SiO 2 added MEAs are prepared by spraying technique and the contact angle is measured by the sessile drop method. The effects of SiO 2 additions of 0, 20, 40 and 60 wt.% (based on Pt/C) are investigated for various relative humidity levels in the anode and the cathode. The increased wettability of the cathode catalyst layer exerts an adverse effect on cell performance by causing flooding; this result demonstrates the hydrophilicity of SiO 2. With 40 wt.% addition of SiO 2 to the anode catalyst layer, the current density at 0.6 V and 0% relative humidity of the anode is 93% of that at 100% relative humidity. By comparison, the performance of a cell using a MEA with no added SiO 2 is only 85% of that at 0% relative humidity. A MEA with SiO 2 addition in the anode gives a higher performance at 60% relative humidity of the cathode than one with an undoped MEA. Increased wettability of the anode catalyst layer caused by SiO 2 addition renders it easy to absorb water from back diffusion.

  4. Methodology for the design of accelerated stress tests for non-precious metal catalysts in fuel cell cathodes

    Science.gov (United States)

    Sharabi, Ronit; Wijsboom, Yair Haim; Borchtchoukova, Nino; Finkelshtain, Gennadi; Elbaz, Lior

    2016-12-01

    In this work we propose systematic methods for testing non-precious group metal catalysts and support degradation alkaline fuel cell cathodes. In this case study, we used a cathode composed of a pyrolyzed non-precious metal catalyst (NPMC) on activated carbon. The vulnerabilities of the cathode components were studied in order to develop the methodology and design an accelerated stress test (AST) for NPMC-based cathode in alkaline environment. Cyclic voltammetry (CV), chronoamperometry (CA) and impedance spectroscopy (EIS) were used to characterize the electrochemical behavior of the cathode and to follow the changes that occur as a result of exposing the cathodes to extreme operating conditions. Rotating ring disk electrode (RRDE) was used to study the cathodes kinetics; Raman spectroscopy and X-ray fluorescence (XRF) were used to study the structural changes in the electrode surface as well as depletion of the catalysts' active sites from the electrode. The changes in the composition of the electrode and catalyst were detected using X-ray diffraction (XRD). For the first time, we show that NPMC degrade rapidly at low operating potentials whereas the support degrades at high operating potentials and developed a tailor-made AST to take these into account.

  5. Membrane fuel cell cathode catalysts based on titanium oxide supported platinum nanoparticles.

    Science.gov (United States)

    Gebauer, Christian; Jusys, Zenonas; Wassner, Maximilian; Hüsing, Nicola; Behm, R Jürgen

    2014-07-21

    The potential of platinum catalysts supported on pure, nitrogen-, or carbon-doped titania for application in the oxygen reduction reaction (ORR), as a cathode catalyst in polymer electrolyte membrane fuel cells, is investigated. The oxide supports are synthesized by using a sol-gel route. Modification with nitrogen and carbon doping is achieved by thermal decomposition of urea and the structure-directing agent P123. Platinum nanoparticles are prepared by reduction of a Pt(IV) salt in ethylene glycol and subsequently immobilized on different support materials. Structural and electronic properties of the support materials and the resulting catalysts are characterized by various methods, including X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. These results and electrochemical characterization of the support materials and platinum nanoparticle catalysts indicate distinct support effects in the catalysts. The electrocatalytic performance of these catalysts in the ORR, as determined in rotating ring disc electrode measurements, is promising. Also here, distinct support effects can be identified. Correlations with the structural/electronic and the electrochemical properties are discussed, as well as the role of metal-support interactions.

  6. High catalytic activity and pollutants resistivity using Fe-AAPyr cathode catalyst for microbial fuel cell application

    OpenAIRE

    Carlo Santoro; Alexey Serov; Claudia W. Narvaez Villarrubia; Sarah Stariha; Sofia Babanova; Kateryna Artyushkova; Schuler, Andrew J.; Plamen Atanassov

    2015-01-01

    For the first time, a new generation of innovative non-platinum group metal catalysts based on iron and aminoantipyrine as precursor (Fe-AAPyr) has been utilized in a membraneless single-chamber microbial fuel cell (SCMFC) running on wastewater. Fe-AAPyr was used as an oxygen reduction catalyst in a passive gas-diffusion cathode and implemented in SCMFC design. This catalyst demonstrated better performance than platinum (Pt) during screening in “clean” conditions (PBS), and no degradation in ...

  7. Hydrothermal synthesis of nanostructured manganese oxide as cathodic catalyst in a microbial fuel cell fed with leachate.

    Science.gov (United States)

    Haoran, Yuan; Lifang, Deng; Tao, Lu; Yong, Chen

    2014-01-01

    Much effort has been devoted to the synthesis of novel nanostructured MnO2 materials because of their unique properties and potential applications as cathode catalyst in Microbial fuel cell. Hybrid MnO2 nanostructures were fabricated by a simple hydrothermal method in this study. Their crystal structures, morphology, and electrochemical characters were carried out by FESEM, N2-adsorption-desorption, and CV, indicating that the hydrothermally synthesized MnO2 (HSM) was structured by nanorods of high aspect ratio and multivalve nanoflowers and more positive than the naturally synthesized MnO2 (NSM), accompanied by a noticeable increase in oxygen reduction peak current. When the HSM was employed as the cathode catalyst in air-cathode MFC which fed with leachate, a maximum power density of 119.07 mW/m(2) was delivered, 64.68% higher than that with the NSM as cathode catalyst. Furthermore, the HSM via a 4-e pathway, but the NSM via a 2-e pathway in alkaline solution, and as 4-e pathway is a more efficient oxygen reduction reaction, the HSM was more positive than NSM. Our study provides useful information on facile preparation of cost-effective cathodic catalyst in air-cathode MFC for wastewater treatment.

  8. Hydrothermal Synthesis of Nanostructured Manganese Oxide as Cathodic Catalyst in a Microbial Fuel Cell Fed with Leachate

    Directory of Open Access Journals (Sweden)

    Yuan Haoran

    2014-01-01

    Full Text Available Much effort has been devoted to the synthesis of novel nanostructured MnO2 materials because of their unique properties and potential applications as cathode catalyst in Microbial fuel cell. Hybrid MnO2 nanostructures were fabricated by a simple hydrothermal method in this study. Their crystal structures, morphology, and electrochemical characters were carried out by FESEM, N2-adsorption-desorption, and CV, indicating that the hydrothermally synthesized MnO2 (HSM was structured by nanorods of high aspect ratio and multivalve nanoflowers and more positive than the naturally synthesized MnO2 (NSM, accompanied by a noticeable increase in oxygen reduction peak current. When the HSM was employed as the cathode catalyst in air-cathode MFC which fed with leachate, a maximum power density of 119.07 mW/m2 was delivered, 64.68% higher than that with the NSM as cathode catalyst. Furthermore, the HSM via a 4-e pathway, but the NSM via a 2-e pathway in alkaline solution, and as 4-e pathway is a more efficient oxygen reduction reaction, the HSM was more positive than NSM. Our study provides useful information on facile preparation of cost-effective cathodic catalyst in air-cathode MFC for wastewater treatment.

  9. Optimization of Layered Cathode Materials for Lithium-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Christian Julien

    2016-07-01

    Full Text Available This review presents a survey of the literature on recent progress in lithium-ion batteries, with the active sub-micron-sized particles of the positive electrode chosen in the family of lamellar compounds LiMO2, where M stands for a mixture of Ni, Mn, Co elements, and in the family of yLi2MnO3•(1 − yLiNi½Mn½O2 layered-layered integrated materials. The structural, physical, and chemical properties of these cathode elements are reported and discussed as a function of all the synthesis parameters, which include the choice of the precursors and of the chelating agent, and as a function of the relative concentrations of the M cations and composition y. Their electrochemical properties are also reported and discussed to determine the optimum compositions in order to obtain the best electrochemical performance while maintaining the structural integrity of the electrode lattice during cycling.

  10. Development of Ultra-Low Platinum Alloy Cathode Catalysts for PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Popov, Branko N. [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemical Engineering; Weidner, John [Univ. of South Carolina, Columbia, SC (United States)

    2016-01-07

    The goal of this project is to synthesize a low cost PEM fuel cell cathode catalyst and support with optimized average mass activity, stability of mass activity, initial high current density performance under H2/air (power density), and catalyst and support stability able to meet 2017 DOE targets for electrocatalysts for transportation applications. Pt*/ACCS-2 catalyst was synthesized according to a novel methodology developed at USC through: (i) surface modification, (ii) metal catalyzed pyrolysis and (iii) chemical leaching to remove excess meal used to dope the support. Pt* stands for suppressed platinum catalyst synthesized with Co doped platinum. The procedure results in increasing carbon graphitization, inclusion of cobalt in the bulk and formation of non-metallic active sites on the carbon surface. Catalytic activity of the support shows an onset potential of 0.86 V for the oxygen reduction reaction (ORR) with well-defined kinetic and mass transfer regions and 2.5% H2O2 production. Pt*/ACCS-2 catalyst durability under 0.6-1.0 V potential cycling and support stability under 1.0-1.5 V potential cycling was evaluated. The results indicated excellent catalyst and support performance under simulated start-up/shut down operating conditions (1.0 – 1.5 V, 5000 cycles) which satisfy DOE 2017 catalyst and support durability and activity. The 30% Pt*/ACCS-2 catalyst showed high initial mass activity of 0.34 A/mgPGM at 0.9 ViR-free and loss of mass activity of 45% after 30,000 cycles (0.6-1.0 V). The catalyst performance under H2-air fuel cell operating conditions showed only 24 mV (iR-free) loss at 0.8 A/cm2 with an ECSA loss of 42% after 30,000 cycles (0.6-1.0 V). The support stability under 1.0-1.5 V potential cycling showed mass activity loss of 50% and potential loss of 8 mV (iR-free) at 1.5 A/cm2. The ECSA loss was 22% after 5,000 cycles. Furthermore, the Pt*/ACCS-2 catalyst showed an

  11. Manganese Detection with a Metal Catalyst Free Carbon Nanotube Electrode: Anodic versus Cathodic Stripping Voltammetry.

    Science.gov (United States)

    Yue, Wei; Bange, Adam; Riehl, Bill L; Riehl, Bonnie D; Johnson, Jay M; Papautsky, Ian; Heineman, William R

    2012-10-01

    Anodic stripping voltammetry (ASV) and cathodic stripping voltammetry (CSV) were used to determine Mn concentration using metal catalyst free carbon nanotube (MCFCNT) electrodes and square wave stripping voltammetry (SWSV). The MCFCNTs are synthesized using a Carbo Thermal Carbide Conversion method which results in a material that does not contain residual transition metals. Detection limits of 120 nM and 93 nM were achieved for ASV and CSV, respectively, with a deposition time of 60 s. CSV was found to be better than ASV in Mn detection in many aspects, such as limit of detection and sensitivity. The CSV method was used in pond water matrix addition measurements.

  12. Manganese Detection with a Metal Catalyst Free Carbon Nanotube Electrode: Anodic versus Cathodic Stripping Voltammetry

    Science.gov (United States)

    Yue, Wei; Bange, Adam; Riehl, Bill L.; Riehl, Bonnie D.; Johnson, Jay M.; Papautsky, Ian; Heineman, William R.

    2013-01-01

    Anodic stripping voltammetry (ASV) and cathodic stripping voltammetry (CSV) were used to determine Mn concentration using metal catalyst free carbon nanotube (MCFCNT) electrodes and square wave stripping voltammetry (SWSV). The MCFCNTs are synthesized using a Carbo Thermal Carbide Conversion method which results in a material that does not contain residual transition metals. Detection limits of 120 nM and 93 nM were achieved for ASV and CSV, respectively, with a deposition time of 60 s. CSV was found to be better than ASV in Mn detection in many aspects, such as limit of detection and sensitivity. The CSV method was used in pond water matrix addition measurements. PMID:24235806

  13. Final Report - Advanced Cathode Catalysts and Supports for PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Debe, Mark

    2012-09-28

    The principal objectives of the program were development of a durable, low cost, high performance cathode electrode (catalyst and support), that is fully integrated into a fuel cell membrane electrode assembly with gas diffusion media, fabricated by high volume capable processes, and is able to meet or exceed the 2015 DOE targets. Work completed in this contract was an extension of the developments under three preceding cooperative agreements/grants Nos. DE-FC-02-97EE50473, DE-FC-99EE50582 and DE-FC36- 02AL67621 which investigated catalyzed membrane electrode assemblies for PEM fuel cells based on a fundamentally new, nanostructured thin film catalyst and support system, and demonstrated the feasibility for high volume manufacturability.

  14. Immobilization of a Metal-Nitrogen-Carbon Catalyst on Activated Carbon with Enhanced Cathode Performance in Microbial Fuel Cells.

    Science.gov (United States)

    Yang, Wulin; Logan, Bruce E

    2016-08-23

    Applications of microbial fuel cells (MFCs) are limited in part by low power densities mainly due to cathode performance. Successful immobilization of an Fe-N-C co-catalyst on activated carbon (Fe-N-C/AC) improved the oxygen reduction reaction to nearly a four-electron transfer, compared to a twoelectron transfer achieved using AC. With acetate as the fuel, the maximum power density was 4.7±0.2 W m(-2) , which is higher than any previous report for an air-cathode MFC. With domestic wastewater as a fuel, MFCs with the Fe-N-C/AC cathode produced up to 0.8±0.03 W m(-2) , which was twice that obtained with a Pt-catalyzed cathode. The use of this Fe-N-C/AC catalyst can therefore substantially increase power production, and enable broader applications of MFCs for renewable electricity generation using waste materials.

  15. IMPROVEMENT OF THE PERFORMANCE OF THE DISPENSER CATHODE WITH Re AS A MIDDLE LAYER

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A new type of dispenser cathode with dual-layer (Os-W/Re) is developed. The cathode coated with Os-W/Re shows better emission performance than the cathode coated with Os-W alloy. X-ray Photoelectron Spectroscopy (XPS) spectra demonstrate that ternary alloy coating (Os-W-Re) formed on the surface of the cathode with dual-layer (Os-W/Re) after full activation is the major reason why it has better emission than the cathode with Os-W alloy. The surface of each variety of the cathode is characterized with Scanning Electron Microscope (SEM) before and after activation: the emitting surface of the cathode with Os-W alloy after ageing appeared non-adherence (flaking) in localized areas, which is one of the reasons for non-uniform emission.However, the surface of the cathode with dual-layer (Os-W/Re) does not present film peeling under the same conditions. Thus it ensures better emission uniformity and functional reliability for the dispenser cathode.

  16. Application of graphene-based nanomaterials as novel cathode catalysts for improving power generation in single chamber microbial fuel cells

    Science.gov (United States)

    Valipour, Alireza; Ayyaru, Sivasankaran; Ahn, Youngho

    2016-09-01

    The low catalytic activity, limited resources, complexity and costs, and non-environmentally friendly nature are key factors limiting the application of non-precious metals and their composites at the cathode in microbial fuel cells (MFCs). This study evaluated the feasibility of graphene-based nanomaterials (RGOHI-AcOH vs. RGO/Ni nanoparticle composite) as novel cathode catalysts in single chamber air-cathode MFCs. A series of MFCs with different catalyst loadings were produced. The electrochemical behavior of the MFCs were evaluated by cyclic voltammetry (CV) and impedance spectroscopy (EIS). As a result, the MFCs with the RGOHI-AcOH cathodes showed greater maximum power densities (>37%) than those with the RGO/Ni nanoparticle cathodes. In the MFCs, the highest maximum power density of 1683 ± 23 mW/m2 (CE = 72 ± 3%), which covers 77% of that estimated for Pt/C (2201 ± 45 mW/m2, CE = 81 ± 4%), was obtained from the double loading RGOHI-AcOH cathodes. Among the MFCs with the RGO/Ni nanoparticle composite cathodes, those loaded with a double catalyst (1015 ± 28 mW/m2, CE = 70 ± 2%) showed better power performance than the others. Both CV and EIS showed good agreement with the MFC results. This study suggests that the RGOHI-AcOH cathode, particularly with a double catalyst loading, is promising for sustainable low-cost green materials, stable power generation and the long-term operation of MFCs.

  17. Use of Pyrolyzed Iron Ethylenediaminetetraacetic Acid Modified Activated Carbon as Air–Cathode Catalyst in Microbial Fuel Cells

    KAUST Repository

    Xia, Xue

    2013-08-28

    Activated carbon (AC) is a cost-effective catalyst for the oxygen reduction reaction (ORR) in air-cathode microbial fuel cells (MFCs). To enhance the catalytic activity of AC cathodes, AC powders were pyrolyzed with iron ethylenediaminetetraacetic acid (FeEDTA) at a weight ratio of FeEDTA:AC = 0.2:1. MFCs with FeEDTA modified AC cathodes and a stainless steel mesh current collector produced a maximum power density of 1580 ± 80 mW/m2, which was 10% higher than that of plain AC cathodes (1440 ± 60 mW/m 2) and comparable to Pt cathodes (1550 ± 10 mW/m2). Further increases in the ratio of FeEDTA:AC resulted in a decrease in performance. The durability of AC-based cathodes was much better than Pt-catalyzed cathodes. After 4.5 months of operation, the maximum power density of Pt cathode MFCs was 50% lower than MFCs with the AC cathodes. Pyridinic nitrogen, quaternary nitrogen and iron species likely contributed to the increased activity of FeEDTA modified AC. These results show that pyrolyzing AC with FeEDTA is a cost-effective and durable way to increase the catalytic activity of AC. © 2013 American Chemical Society.

  18. Core-shell Au-Pd nanoparticles as cathode catalysts for microbial fuel cell applications

    Science.gov (United States)

    Yang, Gaixiu; Chen, Dong; Lv, Pengmei; Kong, Xiaoying; Sun, Yongming; Wang, Zhongming; Yuan, Zhenhong; Liu, Hui; Yang, Jun

    2016-01-01

    Bimetallic nanoparticles with core-shell structures usually display enhanced catalytic properties due to the lattice strain created between the core and shell regions. In this study, we demonstrate the application of bimetallic Au-Pd nanoparticles with an Au core and a thin Pd shell as cathode catalysts in microbial fuel cells, which represent a promising technology for wastewater treatment, while directly generating electrical energy. In specific, in comparison with the hollow structured Pt nanoparticles, a benchmark for the electrocatalysis, the bimetallic core-shell Au-Pd nanoparticles are found to have superior activity and stability for oxygen reduction reaction in a neutral condition due to the strong electronic interaction and lattice strain effect between the Au core and the Pd shell domains. The maximum power density generated in a membraneless single-chamber microbial fuel cell running on wastewater with core-shell Au-Pd as cathode catalysts is ca. 16.0 W m−3 and remains stable over 150 days, clearly illustrating the potential of core-shell nanostructures in the applications of microbial fuel cells. PMID:27734945

  19. Core-shell Au-Pd nanoparticles as cathode catalysts for microbial fuel cell applications

    Science.gov (United States)

    Yang, Gaixiu; Chen, Dong; Lv, Pengmei; Kong, Xiaoying; Sun, Yongming; Wang, Zhongming; Yuan, Zhenhong; Liu, Hui; Yang, Jun

    2016-10-01

    Bimetallic nanoparticles with core-shell structures usually display enhanced catalytic properties due to the lattice strain created between the core and shell regions. In this study, we demonstrate the application of bimetallic Au-Pd nanoparticles with an Au core and a thin Pd shell as cathode catalysts in microbial fuel cells, which represent a promising technology for wastewater treatment, while directly generating electrical energy. In specific, in comparison with the hollow structured Pt nanoparticles, a benchmark for the electrocatalysis, the bimetallic core-shell Au-Pd nanoparticles are found to have superior activity and stability for oxygen reduction reaction in a neutral condition due to the strong electronic interaction and lattice strain effect between the Au core and the Pd shell domains. The maximum power density generated in a membraneless single-chamber microbial fuel cell running on wastewater with core-shell Au-Pd as cathode catalysts is ca. 16.0 W m‑3 and remains stable over 150 days, clearly illustrating the potential of core-shell nanostructures in the applications of microbial fuel cells.

  20. Innovative gas diffusion layers and their water removal characteristics in PEM fuel cell cathode

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Kui; Zhou, Biao [Department of Mechanical, Automotive and Materials Engineering, University of Windsor, Ont. (Canada)

    2007-06-20

    Liquid water transport is one of the key challenges regarding the water management in a proton exchange membrane (PEM) fuel cell. Conventional gas diffusion layers (GDLs) do not allow a well-organized liquid water flow from catalyst layer to gas flow channels. In this paper, three innovative GDLs with different micro-flow channels were proposed to solve liquid water flooding problems that conventional GDLs have. This paper also presents numerical investigations of air-water flow across the proposed innovative GDLs together with a serpentine gas flow channel on PEM fuel cell cathode by use of a commercial computational fluid dynamics (CFD) software package FLUENT. The results showed that different designs of GDLs will affect the liquid water flow patterns significantly, thus influencing the performance of PEM fuel cells. The detailed flow patterns of liquid water were shown. Several gas flow problems for the proposed different kinds of innovative GDLs were observed, and some useful suggestions were given through investigating the flow patterns inside the proposed GDLs. (author)

  1. Investigation of Corrosion and Cathodic Protection in Reinforced Concrete. II: Properties of Steel Surface Layers

    NARCIS (Netherlands)

    Koleva, D.A.; De Wit, J.H.W.; Van Breugel, K.; Lodhi, Z.F.; Ye, G.

    2007-01-01

    The present study explores the formation of corrosion products on the steel surface (using as-received low carbon construction steel) in reinforced concrete in conditions of corrosion and subsequent transformation of these layers in conditions of cathodic protection (CP).

  2. Manufacturing of Electrolyte and Cathode Layers SOFC Using Atmospheric Spraying Method and Its Characterization

    Directory of Open Access Journals (Sweden)

    S. Sulistyo

    2012-12-01

    Full Text Available The use of Solid Oxide Fuel Cell (SOFC has created various interest in many parties, due to its capability to convert gases into electricity. The main requirement of SOFC cell components is to be produced as thin as possible to minimize the losses of electrical resistance, as well as able to support internal and external loads. This paper discusses the procedure of making a thin electrolyte layer, as well as a porous thin layer cathode using atmospheric spraying technique. The procedure of spraying was in room temperature with the process of sintering at temperature of 13500 C held for 3 hours. The SOFC characterization of electrolyte and cathode microstructure was determined by using the SEM, FESEM, XRD and impedance spectroscopy, to measure the impedance of SOFC cells. The results show that the thickness of thin layer electrolyte and porous cathode obtained of about 20 µm and 4 µm, respectively. Also the SOFC cell impedance was measured of 2.3726 x 106 Ω at room temperature. The finding also demonstrated that although the materials (anode, cathode and electrolyte possess different coefficient thermal expansion, there was no evidence of flaking layers which seen the materials remain intact. Thus, the atmospheric spraying method can offer an alternative method to manufacturing of SOFC thin layer electrolyte and cathode. [Key words: SOFC; spraying method; electrolyte; cathode

  3. Application of multiple graphene layers as catalyst support material in fuel cells

    OpenAIRE

    Saner, Burcu; YÜRÜM, YUDA; Yurum, Yuda

    2010-01-01

    The fuel cell electrode layer is a significant part of a fuel cell. The electrode layer is composed of the catalyst and porous electrode or gas diffusion layer. Catalyst has critical importance due to the influence on the cost and durability of fuel cells. The production of novel catalyst support materials could open up new ways in order to ensure the catalytic activity by lowering the amount of catalyst loaded [1]. At this point, utilization of multiple graphene layers as catalyst support...

  4. Air-cathode preparation with activated carbon as catalyst, PTFE as binder and nickel foam as current collector for microbial fuel cells.

    Science.gov (United States)

    Cheng, Shaoan; Wu, Jiancheng

    2013-08-01

    A cathode is a critical factor that limits the practical application of microbial fuel cells (MFCs) in terms of cost and power generation. To develop a cost-effective cathode, we investigate a cathode preparation technique using nickel foam as a current collector, activated carbon as a catalyst and PTFE as a binder. The effects of the type and loading of conductive carbon, the type and loading of activated carbon, and PTFE loading on cathode performance are systematically studied by linear sweep voltammetry (LSV). The nickel foam cathode MFC produces a power density of 1190±50 mW m(-2), comparable with 1320 mW m(-2) from a typical carbon cloth Pt cathode MFC. However, the cost of a nickel foam activated carbon cathode is 1/30 of that of carbon cloth Pt cathode. The results indicate that a nickel foam cathode could be used in scaling up the MFC system.

  5. Metal-air batteries: from oxygen reduction electrochemistry to cathode catalysts.

    Science.gov (United States)

    Cheng, Fangyi; Chen, Jun

    2012-03-21

    Because of the remarkably high theoretical energy output, metal-air batteries represent one class of promising power sources for applications in next-generation electronics, electrified transportation and energy storage of smart grids. The most prominent feature of a metal-air battery is the combination of a metal anode with high energy density and an air electrode with open structure to draw cathode active materials (i.e., oxygen) from air. In this critical review, we present the fundamentals and recent advances related to the fields of metal-air batteries, with a focus on the electrochemistry and materials chemistry of air electrodes. The battery electrochemistry and catalytic mechanism of oxygen reduction reactions are discussed on the basis of aqueous and organic electrolytes. Four groups of extensively studied catalysts for the cathode oxygen reduction/evolution are selectively surveyed from materials chemistry to electrode properties and battery application: Pt and Pt-based alloys (e.g., PtAu nanoparticles), carbonaceous materials (e.g., graphene nanosheets), transition-metal oxides (e.g., Mn-based spinels and perovskites), and inorganic-organic composites (e.g., metal macrocycle derivatives). The design and optimization of air-electrode structure are also outlined. Furthermore, remarks on the challenges and perspectives of research directions are proposed for further development of metal-air batteries (219 references).

  6. Study of an unitised bidirectional vanadium/air redox flow battery comprising a two-layered cathode

    Science.gov (United States)

    grosse Austing, Jan; Nunes Kirchner, Carolina; Hammer, Eva-Maria; Komsiyska, Lidiya; Wittstock, Gunther

    2015-01-01

    The performance of a unitised bidirectional vanadium/air redox flow battery (VARFB) is described. It contains a two-layered cathode consisting of a gas diffusion electrode (GDE) with Pt/C catalyst for discharging and of an IrO2 modified graphite felt for charging. A simple routine is shown for the modification of a graphite felt with IrO2. A maximum energy efficiency of 41.7% at a current density of 20 mA cm-2 as well as an average discharge power density of 34.6 mW cm-2 at 40 mA cm-2 were obtained for VARFB operation at room temperature with the novel cathode setup. A dynamic hydrogen electrode was used to monitor half cell potentials during operation allowing to quantify the contribution of the cathode to the overall performance of the VARFB. Four consecutive cycles revealed that crossover of vanadium ions took place and irreversible degradation processes within the reaction unit lead to a performance decrease.

  7. Highly stable precious metal-free cathode catalyst for fuel cell application

    Science.gov (United States)

    Serov, Alexey; Workman, Michael J.; Artyushkova, Kateryna; Atanassov, Plamen; McCool, Geoffrey; McKinney, Sam; Romero, Henry; Halevi, Barr; Stephenson, Thomas

    2016-09-01

    A platinum group metal-free (PGM-free) oxygen reduction reaction (ORR) catalyst engineered for stability has been synthesized using the sacrificial support method (SSM). This catalyst was comprehensively characterized by physiochemical analyses and tested for performance and durability in fuel cell membrane electrode assemblies (MEAs). This catalyst, belonging to the family of Fe-N-C materials, is easily scalable and can be manufactured in batches up to 200 g. The fuel cell durability tests were performed in a single cell configuration at realistic operating conditions of 0.65 V, 1.25 atmgauge air, and 90% RH for 100 h. In-depth characterization of surface chemistry and morphology of the catalyst layer before and after durability tests were performed. The failure modes of the PGM-free electrodes were derived from structure-to-property correlations. It is suggested that under constant voltage operation, the performance loss results from degradation of the electrode pore structure, while under carbon corrosion accelerated test protocols the failure mode is catalyst corrosion.

  8. Continuous flow membrane-less air cathode microbial fuel cell with spunbonded olefin diffusion layer.

    Science.gov (United States)

    Tugtas, Adile Evren; Cavdar, Pelin; Calli, Baris

    2011-11-01

    The power production performance of a membrane-less air-cathode microbial fuel cell was evaluated for 53 days. Anode and cathode electrodes and the micro-fiber cloth separator were configured by sandwiching the separator between two electrodes. In addition, the air-facing side of the cathode was covered with a spunbonded olefin sheet instead of polytetrafluoroethylene (PTFE) coating to control oxygen diffusion and water loss. The configuration resulted in a low resistance of about 4Ω and a maximum power density of 750 mW/m2. However, as a result of a gradual decrease in the cathode potential, maximum power density decreased to 280 mW/m2. The declining power output was attributed to loss of platinum catalyst (8.26%) and biomass growth (38.44%) on the cathode. Coulombic efficiencies over 55% and no water leakage showed that the spunbonded olefin sheet covering the air-facing side of the cathode can be a cost-effective alternative to PTFE coating.

  9. Silver-Copper Nanoalloy Catalyst Layer for Bifunctional Air Electrodes in Alkaline Media.

    Science.gov (United States)

    Wu, Xiaoqiang; Chen, Fuyi; Jin, Yachao; Zhang, Nan; Johnston, Roy L

    2015-08-19

    A carbon-free and binder-free catalyst layer composed of a Ag-Cu nanoalloy on Ni foam was used as the air cathode in a zinc-air battery for the first time. The Ag-Cu catalyst was prepared using pulsed laser deposition. The structures of the catalysts were found to consist of crystalline Ag-Cu nanoalloy particles with an average size of 2.58 nm embedded in amorphous Cu films. As observed in the X-ray photoelectron spectra, the Ag 3d core levels shifted to higher binding energies, whereas the Cu 2p core levels shifted to lower binding energies, indicating alloying of the silver and copper. Rotating disk electrode measurements indicated that the oxygen reduction reaction (ORR) proceeded through a four-electron pathway on the Ag50Cu50 and Ag90Cu10 nanoalloy catalysts in alkaline solution. Moreover, the catalytic activity of Ag50Cu50 in the ORR is more efficient than that of Ag90Cu10. By performing charge and discharge cycling measurements, the Ag50Cu50 catalyst layer was confirmed to have a maximum power density of approximately 86.3 mW cm(-2) and an acceptable cell voltage at 0.863 V for current densities up to 100 mA cm(-2) in primary zinc-air batteries. In addition, a round-trip efficiency of approximately 50% at a current density of 20 mA cm(-2) was also obtained in the test.

  10. Carbon corrosion of proton exchange membrane fuel cell catalyst layers studied by scanning transmission X-ray microscopy

    Science.gov (United States)

    Hitchcock, Adam P.; Berejnov, Viatcheslav; Lee, Vincent; West, Marcia; Colbow, Vesna; Dutta, Monica; Wessel, Silvia

    2014-11-01

    Scanning Transmission X-ray Microscopy (STXM) at the C 1s, F 1s and S 2p edges has been used to investigate degradation of proton exchange membrane fuel cell (PEM-FC) membrane electrode assemblies (MEA) subjected to accelerated testing protocols. Quantitative chemical maps of the catalyst, carbon support and ionomer in the cathode layer are reported for beginning-of-test (BOT), and end-of-test (EOT) samples for two types of carbon support, low surface area carbon (LSAC) and medium surface area carbon (MSAC), that were exposed to accelerated stress testing with upper potentials (UPL) of 1.0, 1.2, and 1.3 V. The results are compared in order to characterize catalyst layer degradation in terms of the amounts and spatial distributions of these species. Pt agglomeration, Pt migration and corrosion of the carbon support are all visualized, and contribute to differing degrees in these samples. It is found that there is formation of a distinct Pt-in-membrane (PTIM) band for all EOT samples. The cathode thickness shrinks due to loss of the carbon support for all MSAC samples that were exposed to the different upper potentials, but only for the most aggressive testing protocol for the LSAC support. The amount of ionomer per unit volume significantly increases indicating it is being concentrated in the cathode as the carbon corrosion takes place. S 2p spectra and mapping of the cathode catalyst layer indicates there are still sulfonate groups present, even in the most damaged material.

  11. Protected Sulfur Cathode with Mixed Conductive Coating Layer for Lithium Sulfur Battery

    Science.gov (United States)

    Jin, Jun; Wen, Zhaoyin; Wang, Qingsong; Gu, Sui; Huang, Xiao; Chen, Chunhua

    2016-10-01

    A mixed conductive coating layer composed of lithium ion conductive ceramic powder, carbon and binder was introduced on the surface of a sulfur electrode. This coating layer is designed to suppress the migration of lithium polysulfides from the sulfur electrode, and improve the cycling capacity of a lithium sulfur battery. The protected sulfur cathode with a mixed conductive coating layer delivered an initial specific capacity of 1236 mAh g-1 at 0.5C and maintained a capacity of 842 mAh g-1 after 100 cycles. In particular, a soft package battery with protected cathode exhibits improved cycling capacity and excellent rate performance.

  12. Carbon Supported Ag Nanoparticles as High Performance Cathode Catalyst for Anion Exchange Membrane Fuel Cell

    Directory of Open Access Journals (Sweden)

    Le eXin

    2013-09-01

    Full Text Available A solution phase-based nanocapsule method was successfully developed to synthesize non-precious metal catalyst - carbon supported Ag nanoparticles (Ag/C. XRD patterns and TEM image show Ag nanoparticles with a small average size (5.4 nm and narrow size distribution (2-9 nm are uniformly dispersed on the carbon black Vulcan XC-72 support. The intrinsic activity and pathway of oxygen reduction reaction (ORR on the Ag/C and commercial Pt/C were investigated using rotating ring disc electrode (RRDE tests at room temperature. The results confirmed that the 4-electron pathway of ORR proceeds on small Ag nanoparticles, and showed comparable ORR activities on the self-prepared Ag/C and a commercial Pt/C. A single H2-O2 anion exchange membrane fuel cell with the Ag/C cathode catalyst exhibited an open circuit potential of 0.98 V and a peak power density of 190 mW/cm2 at 80 oC.

  13. Electrocatalytic Activity and Stability of M-Fe Catalysts Synthesized by Polymer Complex Method for PEFC Cathode

    KAUST Repository

    Ou, Yiwei

    2011-11-01

    The polymerized complex (PC) method was used to synthesize highly dispersed iron-based catalysts for the oxygen reduction reaction (ORR). The catalysts were prepared with an addition of 1,10-phenanthroline (Phen) and transition metals (M), such as Ta, Ti, and W, in an attempt to enhance the ORR activity and durability of the catalysts. The composition and properties of the catalysts were characterized by thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalyst components, after extensive dissolution in a strong acid solution, were characterized by inductively coupled plasma mass spectroscopy and ultraviolet-visible spectroscopy. It was found that the Ti-Fe catalyst showed improved ORR performance, and the Ta-Fe catalyst showed enhanced stability towards ORR in acidic solution. The catalytic activity and stability for ORR was observed by adding Ti or Ta into the catalyst formulation, suggesting that the interaction between added hetero-ions (Ti and Ta) and ionic Fe active sites was beneficial for the ORR. A single-cell test with the synthesized catalyst in the cathode initially generated a high power density, but the low stability remains an issue to be solved.

  14. Reconstruction of microstructure in catalyst layer of PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Rong, F.; Huang, C.; Liu, Z.S.; Song, D.T.; Wang, Q.P. [National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation

    2007-07-01

    Different microstructures of catalyst layer (CL) have been experimentally studied to improve the performance of the proton membrane exchange (PEM) fuel cell. These experiments have revealed the microstructure in catalyst layers can be considered as one kind of random media and its changes will have significant influence on the performance of PEM fuel cell. This paper presented the results of a study that applied the filtering method and stochastic optimization to reconstruct the microstructure based on the statistical information of catalyst layers. The filtering method changes the Gauss distributed signals to three-phase microstructure reconstruction while the stochastic optimization method, refines the microstructure reconstruction to fit the statistical features of experimental images. Based on the physical properties as well as the mass ratio, the statistical feature extraction based on image process of catalyst layer and the reconstruction procedure was proposed. The paper discussed evaluation of phase statistical information, initial reconstruction based on filtering method, stochastic optimization for reconstruction, as well as a summary of the study. It was concluded that the results of the filtering method as the initial pattern of stochastic optimization could make the error (between the final result and the experimental target) less than that of the random initial value and saved the computational time simultaneously. 13 refs., 6 figs.

  15. Uncovering the role of cathode buffer layer in organic solar cells

    Science.gov (United States)

    Qi, Boyuan; Zhang, Zhi-Guo; Wang, Jizheng

    2015-01-01

    Organic solar cells (OSCs) as the third generation photovoltaic devices have drawn intense research, for their ability to be easily deposited by low-cost solution coating technologies. However the cathode in conventional OSCs, Ca, can be only deposited by thermal evaporation and is highly unstable in ambient. Therefore various solution processible cathode buffer layers (CBLs) are synthesized as substitute of Ca and show excellent effect in optimizing performance of OSCs. Yet, there is still no universal consensus on the mechanism that how CBL works, which is evidently a critical scientific issue that should be addressed. In this article detailed studies are targeted on the interfacial physics at the interface between active layer and cathode (with and without treatment of a polar CBL) by using ultraviolet photoelectron spectroscopy, capacitance-voltage measurement, and impedance spectroscopy. The experimental data demonstrate that CBL mainly takes effect in three ways: suppressing surface states at the surface of active layer, protecting the active layer from being damaged by thermally evaporated cathode, and changing the energy level alignment by forming dipole moments with active layer and/or cathode. Our findings here provide a comprehensive picture of interfacial physics in devices with and without CBL.

  16. Application of nitrogen-doped carbon powders as low-cost and durable cathodic catalyst to air-cathode microbial fuel cells.

    Science.gov (United States)

    Shi, Xinxin; Feng, Yujie; Wang, Xin; Lee, He; Liu, Jia; Qu, Youpeng; He, Weihua; Kumar, S M Senthil; Ren, Nanqi

    2012-03-01

    Given few in-depth studies available on the application of nitrogen-doped carbon powders (NDCP) to air-cathode microbial fuel cells (ACMFCs), a low-cost and durable catalyst of NDCP was prepared and used as cathodic catalyst of ACMFCs. Compared to the untreated carbon powders, the N-doped treatment significantly increased the maximum power density (MPD) of ACMFC. A two-step pretreatment of heat treatment and hydrochloric acid immersion can further obviously increase the MPD. With a reasonably large loading of catalyst, the MPD of NDCP based ACMFC was comparable to that of carbon-supported platinum (Pt/C) based ACMFC, while the cost was dramatically reduced. The pretreatment increased the key nitrogen functional groups, pyridinic-like and pyrrolic-like nitrogen. A third new key nitrogen functional group, nitrogen oxide, was discovered and the mechanism of its contribution was explained. Compared to the inherent deterioration problem of Pt/C, NDCP exhibited high stability and was superior for long-term operation of ACMFCs.

  17. Investigation of Cathode Catalysts for Intermediate-temperature H2S-Air Fuel Cells%中温H2S-空气燃料电池阴极催化剂的研究

    Institute of Scientific and Technical Information of China (English)

    钟理; 罗京莉; K.Chuang

    2007-01-01

    Cathode catalysts comprising composite NiO, NiO-Pt, or LiNiO2 have been developed for electrochemical oxidation of hydrogen sulfide in intermediate-temperature solid oxide fuel cells (ITSOFCs).All catalysts exhibited good electrical conductivity and catalytic activity at operating temperature.Composite NiO catalysts were found to be more active and have lower over potential and higher current density than pure Pt although the electrical conductivity of NiO itself is lower than that of Pt.This problem has been overcome by either admixing as high as 10% (by mass) Ag powder into NiO cathode layer or using composite NiO catalysts such as NiO-Pt and LiNiO2 catalysts.Composite catalysts like NiO with Ag, electrolyte and starch admixed, NiO-Pt, which was prepared from a mixture of NiO and Pt powders, by admixing electrolyte and starch, and LiNiO2, which is derived from the reaction of LiOH-H2O and NiO with electrolyte and starch admixed have been shown to be feasible and effective in an intermediate-temperature H2S-air fuel cell.A fuel cell using Li2SO4-based proton-conducting membrane as electrolyte, metal sulfides as anode catalysts, and composite NiO as cathode catalysts produced a maximum current density about 300mA·cm-2 and maximum power density over 80mW·cm-2 at 680℃ .

  18. Synthesis and application of polypyrrole/carrageenan nano-bio composite as a cathode catalyst in microbial fuel cells.

    Science.gov (United States)

    Esmaeili, Chakavak; Ghasemi, Mostafa; Heng, Lee Yook; Hassan, Sedky H A; Abdi, Mahnaz M; Daud, Wan Ramli Wan; Ilbeygi, Hamid; Ismail, Ahmad Fauzi

    2014-12-19

    A novel nano-bio composite polypyrrole (PPy)/kappa-carrageenan(KC) was fabricated and characterized for application as a cathode catalyst in a microbial fuel cell (MFC). High resolution SEM and TEM verified the bud-like shape and uniform distribution of the PPy in the KC matrix. X-ray diffraction (XRD) has approved the amorphous structure of the PPy/KC as well. The PPy/KC nano-bio composites were then studied as an electrode material, due to their oxygen reduction reaction (ORR) ability as the cathode catalyst in the MFC and the results were compared with platinum (Pt) as the most common cathode catalyst. The produced power density of the PPy/KC was 72.1 mW/m(2) while it was 46.8 mW/m(2) and 28.8 mW/m(2) for KC and PPy individually. The efficiency of the PPy/KC electrode system is slightly lower than a Pt electrode (79.9 mW/m(2)) but due to the high cost of Pt electrodes, the PPy/KC electrode system has potential to be an alternative electrode system for MFCs.

  19. Application of Co-naphthalocyanine (CoNPc) as alternative cathode catalyst and support structure for microbial fuel cells.

    Science.gov (United States)

    Kim, Jung Rae; Kim, Jy-Yeon; Han, Sang-Beom; Park, Kyung-Won; Saratale, G D; Oh, Sang-Eun

    2011-01-01

    Co-naphthalocyanine (CoNPc) was prepared by heat treatment for cathode catalysts to be used in microbial fuel cells (MFCs). Four different catalysts (Carbon black, NPc/C, CoNPc/C, Pt/C) were compared and characterized using XPS, EDAX and TEM. The electrochemical characteristics of oxygen reduction reaction (ORR) were compared by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The Co-macrocyclic complex improves the catalyst dispersion and oxygen reduction reaction of CoNPc/C. The maximum power of CoNPc/C was 64.7 mW/m(2) at 0.25 mA as compared with 81.3 mW/m(2) of Pt/C, 29.7 mW/m(2) of NPc/C and 9.3 mW/m(2) of carbon black when the cathodes were implemented in H-type MFCs. The steady state cell, cathode and anode potential of MFC with using CoNPc/C were comparable to those of Pt/C.

  20. PGM-free Fe-N-C catalysts for oxygen reduction reaction: Catalyst layer design

    Science.gov (United States)

    Stariha, Sarah; Artyushkova, Kateryna; Workman, Michael J.; Serov, Alexey; Mckinney, Sam; Halevi, Barr; Atanassov, Plamen

    2016-09-01

    This work studies the morphology of platinum group metal-free (PGM-free) iron-nitrogen-carbon (Fe-N-C) catalyst layers for the oxygen reduction reaction (ORR) and compares catalytic performance via polarization curves. Three different nitrogen-rich organic precursors are used to prepare the catalysts. Using scanning electron microscopy (SEM) and focused ion beam (FIB) tomography, the porosity, Euler number (pore connectivity), overall roughness, solid phase size and pore size are calculated for catalyst surfaces and volumes. Catalytic activity is determined using membrane electrode assembly (MEA) testing. It is found that the dominant factor in MEA performance is transport limitations. Through the 2D and 3D metrics it is concluded that pore connectivity has the biggest effect on transport performance.

  1. Mechanical behaviour of PEM fuel cell catalyst layers during regular cell operation

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2010-11-01

    Full Text Available Damage mechanisms in a proton exchange membrane fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling, and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the mechanical behaviour of the catalyst layers during regular cell operation, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operating conditions and in real cell geometry (three-dimensional. In this work, full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to investigate the behaviour of the cathode and anode catalyst layers during the cell operation. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model. In addition, the temperature and humidity dependent material properties are utilize in the simulation for the membrane. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and deformation that have limited experimental data.

  2. [Performance of microbial fuel cells with Fe/C catalyst carbon felt air-cathode for treating landfill leachate].

    Science.gov (United States)

    Tang, Yu-Lan; Peng, Man; Yu, Yan; He, Ya-Ting; Fu, Jin-Xiang; Zhao, Yu-Hua

    2012-06-01

    Ferric nitrate/activated carbon powder catalyst was obtained through impregnation and Fe/C catalyst was adsorbed on carbon felt as air cathode electrodes. Effects of activated carbon powder dosage and ferric nitrate concentration on electricity generation of MFC with landfill leachate as fuel were measured. Performances of cathodes obtained at different ferric nitrate concentrations were evaluated by cyclic voltammetry tests. The results showed that with the increase of activated carbon powder dosage or the iron nitrate concentration, MFC produce electrical properties showed a decreasing trend after the first rise. When the activated carbon powder dosage was 1 g and the iron nitrate concentration was 0.25 mol x L(-1), it was proved to be an optimum cell performance for 4199.8 mW x m(-3) output power and 465 omega apparent resistance. Under the optimal ratio rang between ferric nitrate and activated carbon powder, MFC apparent resistance decreased and the power density increased respectively with the increase of catalyst total dosage. The best produce electrical properties of MFC with Fe/C catalyst for 0.25 mol x L(-1) iron nitrate and 1 g activated carbon powder dosage was observed by cyclic voltammetry tests. The output power of MFC and the removal quantity increased with the concentration of inlet and the maximum values were respectively 5478.92 mW x m(-3) and 1505.2 mg x L(-1). the maximum removal rates of COD achieved at 89.1%.

  3. Formation of Ti-N graded bioceramic layer by DC hollow-cathode plasma nitriding

    Institute of Scientific and Technical Information of China (English)

    ZHENG Chuan-lin

    2004-01-01

    Ti-N graded ceramic layer was formed on titanium by using DC hollow-cathode plasma nitriding technique. The structure of Ti-N layer was analyzed using X-ray diffractometry(XRD) with Cu Kα radiation, and the microhardness( HV0.1) was measured from the surface to inner along the cross section of Ti-N layer. The results indicate that the Ti-N graded layer is composed of ε-Ti2 N, δ-TiN and α-Ti(N) phases. Mechanism discussion shows that hollow-cathode discharge can intensify gas ionization, increase current density and enhance the nitriding potential, which directly increases the thickness of the diffusion coatings compared with traditional nitriding methods.

  4. Cathode-Electrolyte Interfaces with CGO Barrier Layers in SOFC

    DEFF Research Database (Denmark)

    Knibbe, Ruth; Hjelm, Johan; Menon, Mohan

    2010-01-01

    Electron microscopy characterization across the cathode–electrolyte interface of two different types of intermediate temperature solid oxide fuel cells (IT-SOFC) is performed to understand the origin of the cell performance disparity. One IT-SOFC cell had a sprayed-cosintered Ce0.90Gd0.01O1.95 (CGO......10) barrier layer, the other had a barrier layer deposited by pulsed laser deposition (PLD) CGO10. Scanning electron microscopy, transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD) investigations conclude that the major source of the cell performance difference...... is attributed to CGO–YSZ interdiffusion in the sprayed-cosintered barrier layer. From TEM and EBSD work, a dense CGO10 PLD layer is found to be deposited epitaxially on the 8YSZ electrolyte substrate—permitting a small amount of SrZrO3 formation and minimizing CGO–YSZ interdiffusion....

  5. Nitrogen-doped graphene/CoNi alloy encased within bamboo-like carbon nanotube hybrids as cathode catalysts in microbial fuel cells

    Science.gov (United States)

    Hou, Yang; Yuan, Heyang; Wen, Zhenhai; Cui, Shumao; Guo, Xiaoru; He, Zhen; Chen, Junhong

    2016-03-01

    Cost-effective catalysts are of key importance to the successful deployment of microbial fuel cells (MFCs) for electricity generation from organic wastes. Herein, a novel catalyst prepared by one-step synthesis strategy is reported. The catalyst features N-doped bamboo-like carbon nanotube (BCNT) in which CoNi-alloy is encapsulated at the end and/or the middle section of the tube with many graphene layers inside inner cavities of BCNT (N-G@CoNi/BCNT). The prepared N-G@CoNi/BCNT exhibits a high oxygen reduction reaction (ORR) activity with an early onset potential of 0.06 V vs. Ag/AgCl and a comparable exchange current density to that of commercial Pt/C. The excellent catalytic activity is further evidenced by a high electron transfer number of 3.63. When being applied in MFCs, the N-G@CoNi/BCNT yields an average current density of 6.7 A m-2, slightly lower than that of Pt/C but with a less mass transfer potential loss. The cost of the N-G@CoNi/BCNT for constructing a 1-m2 cathode electrode is 200 times lower than that of Pt/C. With such a competitive price and excellent electrocatalytic-activity resulting from its unique morphology, CoNi-alloy/nitrogen dopants, considerable specific surface area, and carbon-coated alloy/graphene hybridization, the present catalyst is a promising candidate for ORR catalysts in MFCs for energy recovery from wastes.

  6. The function of microporous layers and the interaction between the anode and cathode in DMFCs

    DEFF Research Database (Denmark)

    Zhang, H. F.; Wang, SY; Pei, PC

    2008-01-01

    A combined effect of microporous layers (MPLs) on direct methanol fuel cells (DMFCs) is investigated. From the distribution of the outstanding carbon loading combinations of the cathode MPL and anode MPL as well as the evolutions of polarization curves, a combined effect in which the contributions...... of the two MPLs interdepend is observed. A further discussion indicates that either MPL in DMFCs is of double roles: a side role of obstructing mass transfers and a main role of adjusting an interaction between the anode and cathode. It is inferred that it is the combination of the two roles that produces...

  7. Modeling hydrodynamic flows in plasma fluxes when depositing metal layer on the surface of catalyst converters

    Science.gov (United States)

    Chinakhov, D. A.; Sarychev, V. D.; Granovsky, A. Yu; Solodsky, S. A.; Nevsky, S. A.; Konovalov, S. V.

    2017-01-01

    Air pollution with harmful substances resulting from combustion of liquid hydrocarbons and emitted into atmosphere became one of the global environmental problems in the late 20th century. The systems of neutralization capable to reduce toxicity of exhaust gases several times are very important for making environmentally safer combustion products discharged into the atmosphere. As revealed in the literature review, one of the most promising purification procedures is neutralization of burnt gases by catalyst converter systems. The principal working element in the converter is a catalytic layer of metals deposited on ceramics, with thickness 20-60 micron and a well-developed micro-relief. The paper presents a thoroughly substantiated new procedure of deposing a nano-scale surface layer of metal-catalyst particles, furthering the utilization of catalysts on a new level. The paper provides description of mathematical models and computational researches into plasma fluxes under high-frequency impulse input delivered to electrode material, explorations of developing Kelvin-Helmholtz, Marangoni and magnetic hydrodynamic instabilities on the surface of liquid electrode metal droplet in the nano-scale range of wavelengths to obtain a flow of nano-meter particles of cathode material. The authors have outlined a physical and mathematical model of magnetic and hydrodynamic instability for the case of melt flowing on the boundary with the molten metal with the purpose to predict the interphase shape and mutual effect of formed plasma jet and liquid metal droplet on the electrode in the nano-scale range of wavelengths at high-frequency impact on the boundary “electrode-liquid layer”.

  8. Catalyst layers for PEMFC manufactured by flexography printing process: performances and structure

    Energy Technology Data Exchange (ETDEWEB)

    Bois, C.; Blayo, A.; Chaussy, D. [Laboratory of Pulp and Paper Science and Graphic Arts (LGP2) (UMR 5518 CNRS-CTP-INPG), Grenoble Institute of Technology (INP Grenoble - PAGORA), St Martin d' Heres (France); Vincent, R.; Mercier, A.G.; Nayoze, C. [Commissariat a l' Energie Atomique et aux Energies Alternatives (CEA)/DRT/LITEN, Laboratoire des Composants Piles a Combustible, Electrolyse et Modelisation (LCPEM), Grenoble (France)

    2012-04-15

    This article focuses on the potential of a classic printing process, flexography, for manufacturing proton exchange membrane fuel cells (PEMFCs). Gas diffusion electrodes (GDEs) are produced by deposition of a water-based catalyst ink on a gas diffusion layer (GDL). The affinity between the ink and the GDL is quantified. Thus, the strong hydrophobic character of the GDL and the poor printability of the ink are demonstrated. However, the permeability of the GDL allows developing a multilayer protocol. The deposition by superimposition of ink layers allows control of the platinum amount and to obtain catalyst layers with a similar density of platinum nanoparticles to coated samples. At similar platinum loading, flexography and coating made catalyst layers offer similar performances, which confirm the relevance of flexography in catalyst layer manufacturing. Structural characterization shows that manufacturing protocol and process has an influence on catalyst layer microstructure. However, catalyst layer cracking and aggregation are increased with the catalyst layer thickness, diminishing the charge and gas diffusion into the catalyst layer resulting in performance degradation. Consequently, a catalyst layer with 0.46 mgPt cm{sup -2} reaches similar performances to catalyst layers with 1.77 and 2.01 times less platinum loading. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Potential of porous Co3O4 nanorods as cathode catalyst for oxygen reduction reaction in microbial fuel cells.

    Science.gov (United States)

    Kumar, Ravinder; Singh, Lakhveer; Zularisam, A W; Hai, Faisal I

    2016-11-01

    This study aims to investigate the potential of porous Co3O4 nanorods as the cathode catalyst for oxygen reduction reaction (ORR) in aqueous air cathode microbial fuel cells (MFCs). The porous Co3O4 nanorods were synthesized by a facile and cost-effective hydrothermal method. Three different concentrations (0.5mg/cm(2), 1mg/cm(2), and 2mg/cm(2)) of Co3O4 nanorods coated on graphite electrodes were used to test its performance in MFCs. The results showed that the addition of porous Co3O4 nanorods enhanced the electrocatalytic activity and ORR kinetics significantly and the overall resistance of the system was greatly reduced. Moreover, the MFC with a higher concentration of the catalyst achieved a maximum power density of 503±16mW/m(2), which was approximately five times higher than the bare graphite electrode. The improved catalytic activity of the cathodes could be due to the porous properties of Co3O4 nanorods that provided the higher number of active sites for oxygen.

  10. Atomic Layer Deposited Catalysts for Fuel Cell Applications

    DEFF Research Database (Denmark)

    Johansson, Anne-Charlotte Elisabeth Birgitta

    layer deposition (ALD), on the other hand, is a highly suitable and still relatively unexplored approach for the synthesis of noble metal catalysts. It is a vapor phase growth method, primarily used to deposit thin lms. ALD is based on self-limiting chemical reactions of alternately injected precursors...... for the realization of such tiny devices. It is a mature technology, suitable for mass production, where versatile structuring is available at the micro and nano regime. Carbon black supported catalysts synthesized by wet chemistry methods are not readily applicable for standard microfabrication techniques. Atomic...... on the sample surface. Its unique growth characteristic enables conformal and uniform lms of controlled thickness and composition. In certain conditions ALD commences by island growth, resulting in discrete nanoparticle formation, which is generally preferred for catalytic applications. Pt-Ru is the best...

  11. Function mechanism of carbide layer on surface of La2O3-Mo cathode

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The ion implanting method has been taken for implanting lanthanum ions into the surface layer of molybdenum wires in order to study the function of carbide layer on the surface of La2O3-Mo cathode in the emission. The function mechanism has been discussed by using XPS and AES methods. The results show that the carbide layer mainly acts as a reduction reagent to produce metallic lanthanum. Moreover, it can store the activator substance and carry them to the surface. Based on the research results, the carbonization technique has been changed. By applying the new technique, the lifetime of the La2O3-Mo cathode has been improved from 14  h to more than 1  000  h—the minimum lifetime for practical uses.

  12. Dynamics of cathode spots in low-pressure arc plasma removing oxide layer on steel surfaces

    Science.gov (United States)

    Tang, Z. L.; Yang, K.; Liu, H. X.; Zhang, Y. C.; Li, H.; Zhu, X. D.

    2016-03-01

    The dynamics of cathode spots has been investigated in low-pressure arc plasma for removing oxide layer on low carbon steel surfaces. The motion of cathode spots was observed with a high speed camera, and the arc voltage was analyzed by fast Fourier transform. The spots move on clean steel surface as a random walk, and the low-frequency components dominated the voltage waveform. However, the spots on steel surfaces with oxide layer tend to burn on the rim of the eroded area formed in the previous arcing, and the low-frequency components decrease correspondingly. The "color" of the colored random noise for arc voltage varies from the approximate brown noise for clean steel surface to pink noise for thick oxide layer, where the edge effect of boundary is considered to play a significant role.

  13. High catalytic activity and pollutants resistivity using Fe-AAPyr cathode catalyst for microbial fuel cell application.

    Science.gov (United States)

    Santoro, Carlo; Serov, Alexey; Narvaez Villarrubia, Claudia W; Stariha, Sarah; Babanova, Sofia; Artyushkova, Kateryna; Schuler, Andrew J; Atanassov, Plamen

    2015-11-13

    For the first time, a new generation of innovative non-platinum group metal catalysts based on iron and aminoantipyrine as precursor (Fe-AAPyr) has been utilized in a membraneless single-chamber microbial fuel cell (SCMFC) running on wastewater. Fe-AAPyr was used as an oxygen reduction catalyst in a passive gas-diffusion cathode and implemented in SCMFC design. This catalyst demonstrated better performance than platinum (Pt) during screening in "clean" conditions (PBS), and no degradation in performance during the operation in wastewater. The maximum power density generated by the SCMFC with Fe-AAPyr was 167 ± 6 μW cm(-2) and remained stable over 16 days, while SCMFC with Pt decreased to 113 ± 4 μW cm(-2) by day 13, achieving similar values of an activated carbon based cathode. The presence of S(2-) and showed insignificant decrease of ORR activity for the Fe-AAPyr. The reported results clearly demonstrate that Fe-AAPyr can be utilized in MFCs under the harsh conditions of wastewater.

  14. Advanced cathode materials for polymer electrolyte fuel cells based on pt/ metal oxides: from model electrodes to catalyst systems.

    Science.gov (United States)

    Fabbri, Emiliana; Pătru, Alexandra; Rabis, Annett; Kötz, Rüdiger; Schmidt, Thomas J

    2014-01-01

    The development of stable catalyst systems for application at the cathode side of polymer electrolyte fuel cells (PEFCs) requires the substitution of the state-of-the-art carbon supports with materials showing high corrosion resistance in a strongly oxidizing environment. Metal oxides in their highest oxidation state can represent viable support materials for the next generation PEFC cathodes. In the present work a multilevel approach has been adopted to investigate the kinetics and the activity of Pt nanoparticles supported on SnO2-based metal oxides. Particularly, model electrodes made of SnO2 thin films supporting Pt nanoparticles, and porous catalyst systems made of Pt nanoparticles supported on Sb-doped SnO2 high surface area powders have been investigated. The present results indicate that SnO2-based supports do not modify the oxygen reduction reaction mechanism on the Pt nanoparticle surface, but rather lead to catalysts with enhanced specific activity compared to Pt/carbon systems. Different reasons for the enhancement in the specific activity are considered and discussed.

  15. Nanoscale Surface Modification of Lithium-Rich Layered-Oxide Composite Cathodes for Suppressing Voltage Fade.

    Science.gov (United States)

    Zheng, Fenghua; Yang, Chenghao; Xiong, Xunhui; Xiong, Jiawen; Hu, Renzong; Chen, Yu; Liu, Meilin

    2015-10-26

    Lithium-rich layered oxides are promising cathode materials for lithium-ion batteries and exhibit a high reversible capacity exceeding 250 mAh g(-1) . However, voltage fade is the major problem that needs to be overcome before they can find practical applications. Here, Li1.2 Mn0.54 Ni0.13 Co0.13 O2 (LLMO) oxides are subjected to nanoscale LiFePO4 (LFP) surface modification. The resulting materials combine the advantages of both bulk doping and surface coating as the LLMO crystal structure is stabilized through cationic doping, and the LLMO cathode materials are protected from corrosion induced by organic electrolytes. An LLMO cathode modified with 5 wt % LFP (LLMO-LFP5) demonstrated suppressed voltage fade and a discharge capacity of 282.8 mAh g(-1) at 0.1 C with a capacity retention of 98.1 % after 120 cycles. Moreover, the nanoscale LFP layers incorporated into the LLMO surfaces can effectively maintain the lithium-ion and charge transport channels, and the LLMO-LFP5 cathode demonstrated an excellent rate capacity.

  16. Suppressing Manganese Dissolution from Lithium Manganese Oxide Spinel Cathodes with Single-Layer Graphene

    Energy Technology Data Exchange (ETDEWEB)

    Jaber-Ansari, Laila; Puntambekar, Kanan P.; Kim, Soo; Aykol, Muratahan; Luo, Langli; Wu, Jinsong; Myers, Benjamin D.; Iddir, Hakim; Russell, John T.; Saldana, Spencer J.; Kumar, Rajan; Thackeray, Michael M.; Curtiss, Larry A.; Dravid, Vinayak P.; Wolverton, Christopher M.; Hersam, Mark C.

    2015-06-24

    Spinel-structured LiMn 2 O 4 (LMO) is a desirable cathode material for Li-ion batteries due to its low cost, abundance, and high power capability. However, LMO suffers from limited cycle life that is triggered by manganese dissolution into the electrolyte during electrochemical cycling. Here, it is shown that single-layer graphene coatings suppress manganese dissolution, thus enhancing the performance and lifetime of LMO cathodes. Relative to lithium cells with uncoated LMO cathodes, cells with graphene-coated LMO cathodes provide improved capacity retention with enhanced cycling stability. X-ray photoelectron spectroscopy reveals that graphene coatings inhibit manganese depletion from the LMO surface. Additionally, transmission electron microscopy demonstrates that a stable solid electrolyte interphase is formed on graphene, which screens the LMO from direct contact with the electrolyte. Density functional theory calculations provide two mechanisms for the role of graphene in the suppression of manganese dissolution. First, common defects in single-layer graphene are found to allow the transport of lithium while concurrently acting as barriers for manganese diffusion. Second, graphene can chemically interact with Mn 3+ at the LMO electrode surface, promoting an oxidation state change to Mn 4+ , which suppresses dissolution.

  17. High-Capacity Layered-Spinel Cathodes for Li-Ion Batteries.

    Science.gov (United States)

    Nayak, Prasant Kumar; Levi, Elena; Grinblat, Judith; Levi, Mikhael; Markovsky, Boris; Munichandraiah, N; Sun, Yang Kook; Aurbach, Doron

    2016-09-08

    Li and Mn-rich layered oxides with the general structure x Li2 MnO3 ⋅(1-x) LiMO2 (M=Ni, Mn, Co) are promising cathode materials for Li-ion batteries because of their high specific capacity, which may be greater than 250 mA h g(-1) . However, these materials suffer from high first-cycle irreversible capacity, gradual capacity fading, limited rate capability and discharge voltage decay upon cycling, which prevent their commercialization. The decrease in average discharge voltage is a major issue, which is ascribed to a structural layered-to-spinel transformation upon cycling of these oxide cathodes in wide potential ranges with an upper limit higher than 4.5 V and a lower limit below 3 V versus Li. By using four elements systems (Li, Mn, Ni, O) with appropriate stoichiometry, it is possible to prepare high capacity composite cathode materials that contain LiMn1.5 Ni0.5 O4 and Lix Mny Niz O2 components. The Li and Mn-rich layered-spinel cathode materials studied herein exhibit a high specific capacity (≥200 mA h g(-1) ) with good capacity retention upon cycling in a wide potential domain (2.4-4.9 V). The effect of constituent phases on their electrochemical performance, such as specific capacity, cycling stability, average discharge voltage, and rate capability, are explored here. This family of materials can provide high specific capacity, high rate capability, and promising cycle life. Using Co-free cathode materials is also an obvious advantage of these systems.

  18. Importance of OH(-) transport from cathodes in microbial fuel cells.

    Science.gov (United States)

    Popat, Sudeep C; Ki, Dongwon; Rittmann, Bruce E; Torres, César I

    2012-06-01

    Cathodic limitation in microbial fuel cells (MFCs) is considered an important hurdle towards practical application as a bioenergy technology. The oxygen reduction reaction (ORR) needs to occur in MFCs under significantly different conditions compared to chemical fuel cells, including a neutral pH. The common reason cited for cathodic limitation is the difficulty in providing protons to the catalyst sites. Here, we show that it is not the availability of protons, but the transport of OH(-) from the catalyst layer to the bulk liquid that largely governs cathodic potential losses. OH(-) is a product of an ORR mechanism that has not been considered dominant before. The accumulation of OH(-) at the catalyst sites results in an increase in the local cathode pH, resulting in Nernstian concentration losses. For Pt-based gas-diffusion cathodes, using polarization curves developed in unbuffered and buffered solutions, we quantified this loss to be >0.3 V at a current density of 10 Am(-2) . We show that this loss can be partially overcome by replacing the Nafion binder used in the cathode catalyst layer with an anion-conducting binder and by providing additional buffer to the cathode catalyst directly in the form of CO(2) , which results in enhanced OH(-) transport. Our results provide a comprehensive analysis of cathodic limitations in MFCs and should allow researchers to develop and select materials for the construction of MFC cathodes and identify operational conditions that will help minimize Nernstian concentration losses due to pH gradients.

  19. Suppression of Cross Contamination in Multi-Layer Thin Film Prepared by Using Rotating Hexagonal Sputtering Cathode.

    Science.gov (United States)

    Park, Se Yeon; Choi, Bum Ho; Lee, Jong Ho

    2015-01-01

    In this study, single- and multi-layered thin films were prepared on a glass substrate using a newly developed rotating hexagonal sputtering cathode in a single chamber. The rotatinghexagonal sputtering cathode can install up to six different sputtering targets or six single targets in a cathode. Using the rotating hexagonal cathode, we prepared a single-layered AZO film and a multi-layer film to evaluate the performance of hexagonal gun. Cross-contamination, which is often observed in multi-layer thin film preparation, was suppressed to nearly zero by controlling process parameters and revising hardware. Energy-saving effects of five-layered glass were also verified by measuring the temperature.

  20. Aqueous Solution Processed Photoconductive Cathode Interlayer for High Performance Polymer Solar Cells with Thick Interlayer and Thick Active Layer.

    Science.gov (United States)

    Nian, Li; Chen, Zhenhui; Herbst, Stefanie; Li, Qingyuan; Yu, Chengzhuo; Jiang, Xiaofang; Dong, Huanli; Li, Fenghong; Liu, Linlin; Würthner, Frank; Chen, Junwu; Xie, Zengqi; Ma, Yuguang

    2016-09-01

    An aqueous-solution-processed photoconductive cathode interlayer is developed, in which the photoinduced charge transfer brings multiple advantages such as increased conductivity and electron mobility, as well as reduced work function. Average power conversion efficiency over 10% is achieved even when the thickness of the cathode interlayer and active layer is up to 100 and 300 nm, respectively.

  1. Layered cathode materials for lithium ion rechargeable batteries

    Science.gov (United States)

    Kang, Sun-Ho; Amine, Khalil

    2007-04-17

    A number of materials with the composition Li.sub.1+xNi.sub..alpha.Mn.sub..beta.Co.sub..gamma.M'.sub..delta.O.sub.2-- zF.sub.z (M'=Mg,Zn,Al,Ga,B,Zr,Ti) for use with rechargeable batteries, wherein x is between about 0 and 0.3, .alpha. is between about 0.2 and 0.6, .beta. is between about 0.2 and 0.6, .gamma. is between about 0 and 0.3, .delta. is between about 0 and 0.15, and z is between about 0 and 0.2. Adding the above metal and fluorine dopants affects capacity, impedance, and stability of the layered oxide structure during electrochemical cycling.

  2. Characterization of pore network structure in catalyst layers of polymer electrolyte fuel cells

    OpenAIRE

    El Hannach, Mohamed; Soboleva, Tatyana; Malek, Kourosh; Franco, Alejandro A.; Prat, Marc; Pauchet, Joël; Holdcroft, Steven

    2014-01-01

    International audience; We model and validate the effect of ionomer content and Pt nanoparticles on nanoporous structure of catalyst layers in polymer electrolyte fuel cells. By employing Pore network modeling technique and analytical solutions, we analyze and reproduce experimental N2-adsorption isotherms of carbon, Pt/ carbon and catalyst layers with various ionomer contents. The porous catalyst layer structures comprise of Ketjen Black carbon, Pt and Nafion ionomer. The experimental pore s...

  3. Bifunctional Ag/Fe/N/C Catalysts for Enhancing Oxygen Reduction via Cathodic Biofilm Inhibition in Microbial Fuel Cells.

    Science.gov (United States)

    Dai, Ying; Chan, Yingzi; Jiang, Baojiang; Wang, Lei; Zou, Jinlong; Pan, Kai; Fu, Honggang

    2016-03-23

    Limitation of the oxygen reduction reaction (ORR) in single-chamber microbial fuel cells (SC-MFCs) is considered an important hurdle in achieving their practical application. The cathodic catalysts faced with a liquid phase are easily primed with the electrolyte, which provides more surface area for bacterial overgrowth, resulting in the difficulty in transporting protons to active sites. Ag/Fe/N/C composites prepared from Ag and Fe-chelated melamine are used as antibacterial ORR catalysts for SC-MFCs. The structure-activity correlations for Ag/Fe/N/C are investigated by tuning the carbonization temperature (600-900 °C) to clarify how the active-constituents of Ag/Fe and N-species influence the antibacterial and ORR activities. A maximum power density of 1791 mW m(-2) is obtained by Ag/Fe/N/C (630 °C), which is far higher than that of Pt/C (1192 mW m(-2)), only having a decline of 16.14% after 90 days of running. The Fe-bonded N and the cooperation of pyridinic N and pyrrolic N in Ag/Fe/N/C contribute equally to the highly catalytic activity toward ORR. The ·OH or O2(-) species originating from the catalysis of O2 can suppress the biofilm growth on Ag/Fe/N/C cathodes. The synergistic effects between the Ag/Fe heterojunction and N-species substantially contribute to the high power output and Coulombic efficiency of Ag/Fe/N/C catalysts. These new antibacterial ORR catalysts show promise for application in MFCs.

  4. Li-rich layer-structured cathode materials for high energy Li-ion batteries

    Science.gov (United States)

    Li, Liu; Lee, Kim Seng; Lu, Li

    2014-08-01

    Li-rich layer-structured xLi2MnO3 ṡ (1 - x)LiMO2 (M = Mn, Ni, Co, etc.) materials have attracted much attention due to their extraordinarily high reversible capacity as the cathode material in Li-ion batteries. To better understand the nature of this type of materials, this paper reviews history of development of the Li-rich cathode materials, and provides in-depth study on complicated crystal structures and reaction mechanisms during electrochemical charge/discharge cycling. Despite the fabulous capability at low rate, several drawbacks still gap this type of high-capacity cathode materials from practical applications, for instance the large irreversible capacity loss at first cycle, poor rate capability, severe voltage decay and capacity fade during electrochemical charge/discharge cycling. This review will also address mechanisms for these inferior properties and propose various possible solutions to solve above issues for future utilization of these cathode materials in commercial Li-ion batteries.

  5. An Integrated, Layered-Spinel Composite Cathode for Energy Storage Applications

    Science.gov (United States)

    Hagh, Nader; Skandan, Ganesh

    2012-01-01

    At low operating temperatures, commercially available electrode materials for lithium-ion batteries do not fully meet the energy and power requirements for NASA fs exploration activities. The composite cathode under development is projected to provide the required energy and power densities at low temperatures and its usage will considerably reduce the overall volume and weight of the battery pack. The newly developed composite electrode material can provide superior electrochemical performance relative to a commercially available lithium cobalt system. One advantage of using a composite cathode is its higher energy density, which can lead to smaller and lighter battery packs. In the current program, different series of layered-spinel composite materials with at least two different systems in an integrated structure were synthesized, and the volumetric and gravimetric energy densities were evaluated. In an integrated network of a composite electrode, the effect of the combined structures is to enhance the capacity and power capabilities of the material to levels greater than what is possible in current state-of-the-art cathode systems. The main objective of the current program is to implement a novel cathode material that meets NASA fs low temperature energy density requirements. An important feature of the composite cathode is that it has at least two components (e.g., layered and spinel) that are structurally integrated. The layered material by itself is electrochemically inactive; however, upon structural integration with a spinel material, the layered material can be electrochemically activated, thereby delivering a large amount of energy with stable cycling. A key aspect of the innovation has been the development of a scalable process to produce submicronand micron-scale particles of these composite materials. An additional advantage of using such a composite electrode material is its low irreversible loss (.5%), which is primarily due to the unique activation

  6. Modeling the cathode in a proton exchange membrane fuel cell using density functional theory How the carbon support can affect durability and activity of a platinum catalyst

    Science.gov (United States)

    Groves, Michael Nelson

    The current global energy and environmental challenges need to be addressed by developing a new portfolio of clean power producing devices. The proton exchange membrane fuel cell has the potential to be included and can fit into a variety of niches ranging from portable electronics to stationary residential applications. One of the many barriers to commercial viability is the cost of the cathode layer which requires too much platinum metal to achieve a comparable power output as well as would need to be replaced more frequently when compared to conventional sources for most applications. Using density functional theory, an ab initio modeling technique, these durability and activity issues are examined for platinum catalysts on graphene and carbon nanotube supports. The carbon supports were also doped by replacing individual carbon atoms with other second row elements (beryllium, boron, nitrogen, and oxygen) and the effect on the platinum-surface interaction along with the interaction between the platinum and the oxygen reduction reaction intermediates are discussed. Keywords: proton exchange membrane fuel cell, density functional theory, platinum catalyst, oxygen reduction reaction, doped carbon surfaces

  7. Transport parameters of thin, supported cathode layers in solid oxide fuel cells (SOFCs); Transportparameter duenner, getraegerter Kathodenschichten der oxidkeramischen Brennstoffzelle

    Energy Technology Data Exchange (ETDEWEB)

    Wedershoven, Christian

    2010-12-22

    The aim of this work was to determine the transport properties of thin cathode layers, which are part of the composite layer of a fabricated anode-supported solid oxide fuel cell (SOFC). The transport properties of the anode and cathode have a significant influence on the electrochemical performance of a fuel cell stack and therefore represent an important parameter when designing fuel cell stacks. In order to determine the transport parameters of the cathode layers in a fabricated SOFC, it is necessary to permeate the thin cathode layer deposited on the gas-tight electrolyte with a defined gas transport. These thin cathode layers cannot be fabricated as mechanically stable single layers and cannot therefore be investigated in the diffusion and permeation experiments usually used to determine transport parameters. The setup of these experiments - particularly the sample holder - was therefore altered in this work. The result of this altered setup was a three-dimensional flow configuration. Compared to the conventional setup, it was no longer possible to describe the gas transport in the experiments with an analytical one-dimensional solution. A numerical solution process had to be used to evaluate the measurements. The new setup permitted a sufficiently symmetrical gas distribution and thus allowed the description of the transport to be reduced to a two-dimensional description, which significantly reduced the computational effort required to evaluate the measurements. For pressure-induced transport, a parametrized coherent expression of transport could be derived. This expression is equivalent to the analytical description of the transport in conventional measurement setups, with the exception of parameters that describe the geometry of the gas diffusion. In this case, a numerical process is not necessary for the evaluation. Using the transport parameters of mechanically stable anode substrates, which can be measured both in the old and the new setups, the old and

  8. Long-term performance of activated carbon air cathodes with different diffusion layer porosities in microbial fuel cells

    KAUST Repository

    Zhang, Fang

    2011-08-01

    Activated carbon (AC) air-cathodes are inexpensive and useful alternatives to Pt-catalyzed electrodes in microbial fuel cells (MFCs), but information is needed on their long-term stability for oxygen reduction. AC cathodes were constructed with diffusion layers (DLs) with two different porosities (30% and 70%) to evaluate the effects of increased oxygen transfer on power. The 70% DL cathode initially produced a maximum power density of 1214±123mW/m 2 (cathode projected surface area; 35±4W/m 3 based on liquid volume), but it decreased by 40% after 1 year to 734±18mW/m 2. The 30% DL cathode initially produced less power than the 70% DL cathode, but it only decreased by 22% after 1 year (from 1014±2mW/m 2 to 789±68mW/m 2). Electrochemical tests were used to examine the reasons for the degraded performance. Diffusion resistance in the cathode was found to be the primary component of the internal resistance, and it increased over time. Replacing the cathode after 1 year completely restored the original power densities. These results suggest that the degradation in cathode performance was due to clogging of the AC micropores. These findings show that AC is a cost-effective material for oxygen reduction that can still produce ~750mW/m 2 after 1 year. © 2011 Elsevier B.V.

  9. Highly-dispersed Ta-oxide catalysts prepared by electrodeposition in a non-aqueous plating bath for polymer electrolyte fuel cell cathodes

    KAUST Repository

    Seo, Jeongsuk

    2012-01-01

    The Ta-oxide cathode catalysts were prepared by electrodeposition in a non-aqueous solution. These catalysts showed excellent catalytic activity and have an onset potential of 0.92 V RHE for the oxygen reduction reaction (ORR). The highly-dispersed Ta species at the nanometer scale on the carbon black was an important contributor to the high activity. © 2012 The Royal Society of Chemistry.

  10. Nickel oxide and carbon nanotube composite (NiO/CNT) as a novel cathode non-precious metal catalyst in microbial fuel cells.

    Science.gov (United States)

    Huang, Jianjian; Zhu, Nengwu; Yang, Tingting; Zhang, Taiping; Wu, Pingxiao; Dang, Zhi

    2015-10-15

    Comparing with the precious metal catalysts, non-precious metal catalysts were preferred to use in microbial fuel cells (MFCs) due to the low cost and high oxygen reduction reaction (ORR) efficiency. In this study, the transmission electron microscope and X-ray diffraction as well as Raman investigation revealed that the prepared nanoscale NiO was attached on the surface of CNT. Cyclic voltammogram and rotating ring-disk electrode tests showed that the NiO/CNT composite catalyst had an apparent oxygen reduction peak and 3.5 electron transfer pathway was acquired under oxygen atmosphere. The catalyst performance was highly dependent on the percentage of NiO in the CNT nanocomposites. When 77% NiO/CNT nano-sized composite was applied as cathode catalyst in membrane free single-chamber air cathode MFC, a maximum power density of 670 mW/m(2) and 0.772 V of OCV was obtained. Moreover, the MFC with pure NiO (control) could not achieve more than 0.1 V. All findings suggested that NiO/CNT could be a potential cathode catalyst for ORR in MFCs.

  11. Development of high-performance cathode catalyst of polypyrrole modified carbon supported CoOOH for direct borohydride fuel cell

    Science.gov (United States)

    He, Yan; Zhu, Cai; Chen, Kaijian; Wang, Juan; Qin, Haiying; Liu, Jiabin; Yan, Shuai; Yang, Ke; Li, Aiguo

    2017-01-01

    Polypyrrole modified carbon supported CoOOH electrocatalyst (CoOOH-PPy-C) is prepared by impregnation-chemical method, and the catalytic properties for the oxygen reduction reaction (ORR) in alkaline media are investigated. The X-ray diffraction and transmission electron microscopy results confirm the presence of the expected CoOOH. The electrochemical tests show that the CoOOH-PPy-C catalyst exhibits good electrocatalytic activity towards ORR. The direct borohydride fuel cell using CoOOH-PPy-C as the cathode catalyst demonstrates a good stability performance. There is only 4% decrease of the cell voltage after 80-h operation. The ORR occurs an average 4-electron transfer pathway on the CoOOH-PPy-C catalyst. The good catalytic activity towards ORR benefits from the Cosbnd N bond, which is identified by X-ray photoelectron spectroscopy test. X-ray absorption fine structure experiments further show that two nearest O atoms are substituted by two N atoms bonding to Co ion at a distance of 1.64 Å. The CoOOH-PPy-C exhibits better electrochemical properties than the Co(OH)2 counterpart even though the valence state of Co ion is +3 in CoOOH-PPy-C. Those results indicate that the bonding of Co ion with N atoms should be a key issue regardless the valence of Co ion.

  12. EFFECT OF PRETREATMENT ON PT-CO/C CATHODE CATALYSTS FOR THE OXYGEN-REDUCTION REACTION

    Energy Technology Data Exchange (ETDEWEB)

    Fox, E.; Colon-Mercado, H.

    2010-01-19

    Carbon supported Pt and Pt-Co electrocatalysts for the oxygen reduction reaction in low temperature fuel cells were prepared by the reduction of the metal salts with sodium borohydride and sodium formate. The effect of surface treatment with nitric acid on the carbon surface and Co on the surface of carbon prior to the deposition of Pt was studied. The catalysts where Pt was deposited on treated carbon the ORR reaction preceded more through the two electron pathway and favored peroxide production, while the fresh carbon catalysts proceeded more through the four electron pathway to complete the oxygen reduction reaction. NaCOOH reduced Pt/C catalysts showed higher activity that NaBH{sub 4} reduced Pt/C catalysts. It was determined that the Co addition has a higher impact on catalyst activity and active surface area when used with NaBH{sub 4} as reducing agent as compared to NaCOOH.

  13. PRELIMINARY IN-SITU X-RAY ABSORPTION FINE STRUCTURE EXAMINATION OF PT/C AND PTCO/C CATHODE CATALYSTS IN AN OPERATIONAL POLYMER ELECTROLYTE FUEL CELL

    Energy Technology Data Exchange (ETDEWEB)

    Phelan, B.T.; Myers, D.J.; Smith, M.C.

    2009-01-01

    State-of-the-art polymer electrolyte fuel cells require a conditioning period to reach optimized cell performance. There is insuffi cient understanding about the behavior of catalysts during this period, especially with regard to the changing environment of the cathode electrocatalyst, which is typically Pt nanoparticles supported on high surface area Vulcan XC-72 carbon (Pt/C). The purpose of this research was to record preliminary observations of the changing environment during the conditioning phase using X-Ray Absorption Fine Structure (XAFS) spectroscopy. XAFS was recorded for a Pt/C cathode at the Pt L3-edge and a PtCo/C cathode at both the Pt L3-edge and Co K-edge. Using precision machined graphite cell-blocks, both transmission and fl uorescence data were recorded at Sector 12-BM-B of Argonne National Laboratory’s Advanced Photon Source. The fl uorescence and transmission edge steps allow for a working description of the changing electrocatalyst environment, especially water concentration, at the anode and cathode as functions of operating parameters. These features are discussed in the context of how future analysis may correlate with potential, current and changing apparent thickness of the membrane electrode assembly through loss of catalyst materials (anode, cathode, carbon support). Such direct knowledge of the effect of the conditioning protocol on the electrocatalyst may lead to better catalyst design. In turn, this may lead to minimizing, or even eliminating, the conditioning period.

  14. Hollow Spheres of Iron Carbide Nanoparticles Encased in Graphitic Layers as Oxygen Reduction Catalysts

    DEFF Research Database (Denmark)

    Hu, Yang; Jensen, Jens Oluf; Zhang, Wei

    2014-01-01

    Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low‐temperature fuel cells. A novel type of catalysts prepared by high‐pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting...... of uniform iron carbide (Fe3C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR......). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide‐based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts....

  15. Regenerable Cu-intercalated MnO2 layered cathode for highly cyclable energy dense batteries

    Science.gov (United States)

    Yadav, Gautam G.; Gallaway, Joshua W.; Turney, Damon E.; Nyce, Michael; Huang, Jinchao; Wei, Xia; Banerjee, Sanjoy

    2017-03-01

    Manganese dioxide cathodes are inexpensive and have high theoretical capacity (based on two electrons) of 617 mAh g-1, making them attractive for low-cost, energy-dense batteries. They are used in non-rechargeable batteries with anodes like zinc. Only ~10% of the theoretical capacity is currently accessible in rechargeable alkaline systems. Attempts to access the full capacity using additives have been unsuccessful. We report a class of Bi-birnessite (a layered manganese oxide polymorph mixed with bismuth oxide (Bi2O3)) cathodes intercalated with Cu2+ that deliver near-full two-electron capacity reversibly for >6,000 cycles. The key to rechargeability lies in exploiting the redox potentials of Cu to reversibly intercalate into the Bi-birnessite-layered structure during its dissolution and precipitation process for stabilizing and enhancing its charge transfer characteristics. This process holds promise for other applications like catalysis and intercalation of metal ions into layered structures. A large prismatic rechargeable Zn-birnessite cell delivering ~140 Wh l-1 is shown.

  16. Solution-processed cathode interfacial layer materials for high-efficiency polymer solar cells

    Directory of Open Access Journals (Sweden)

    Biao Xiao

    2015-09-01

    Full Text Available Polymer solar cells (PSCs are a new type of renewable energy source currently being extensively investigated due to perceived advantages; such as being lightweight, low-cost and because of the unlimited materials resource. The power conversion efficiency of state-of-the-art PSCs has increased dramatically in the past few years, obtained mainly through the development of new electron donor polymers, acceptors, and novel device structures through the use of various electrode interfacial materials. In this short review, recent progress in solution-processed cathode interfacial layers that could significantly improve device performances is summarized and highlighted.

  17. Copper nitride nanocubes: size-controlled synthesis and application as cathode catalyst in alkaline fuel cells.

    Science.gov (United States)

    Wu, Haibin; Chen, Wei

    2011-10-05

    Copper nitride nanocubes are synthesized in a facile one-phase process. The crystal size could be tuned easily by using different primary amines as capping agents. Such Pt-free nanocrystals exhibit electrocatalytic activity toward oxygen reduction and appear to be promising cathodic electrocatalysts in alkaline fuel cells.

  18. Hollow Spheres of Iron Carbide Nanoparticles Encased in Graphitic Layers as Oxygen Reduction Catalysts

    DEFF Research Database (Denmark)

    Hu, Yang; Jensen, Jens Oluf; Zhang, Wei;

    2014-01-01

    of uniform iron carbide (Fe3C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR......). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide‐based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts....

  19. Electrochemical impedance study and performance of PdNi nanoparticles as cathode catalyst in a polymer electrolyte membrane fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Ramos-Sanchez, G.; Santana-Salinas, A.; Vazquez-Huerta, G.; Solorza-Feria, O. [Inst. Politenico Nacional, Centro de Investigacion y de Estudios Avanzados, Mexico City (Mexico). Dept. de Quimica

    2010-07-15

    Polymer electrolyte membrane fuel cells (PEMFC) convert the energy stored in hydrogen and oxygen molecules directly into electricity. However, technical and economic challenges must be overcome to address cost, performance and stability issues associated with membrane electrode assemblies (MEA). The oxygen reduction reaction (ORR) which takes place in the cathode is the limiting reaction due to the slow kinetics of ORR on metals, including platinum (Pt). For that reason, much research has gone into finding catalyst materials with a similar or greater performance than Pt. Bimetallic palladium (Pd) based catalysts have been considered as alternative materials for ORR. In this study, a carbon-dispersed bimetallic PdNi was prepared by borohydride reduction using PdCl{sub 2} and NiCl{sub 2} as precursors in a tetrahydrofuran (THF) solution. The PdNi loading and weight percentage were optimized using the Simplex method. The MEA performance was evaluated at optimum conditions using the PdNi electrocatalyst as the cathode and a Pt-Etek carbon cloth as the anode. The maximum power density of 122 mW per cm{sup 2} was reached with 45 percent of PdNi wt percent at 30 psi and 80 degrees C. The catalytic activity and the mechanism of the ORR on PdNi, in 0.5M H{sub 2}SO{sub 4} was investigated using electrochemical impedance spectroscopy. The Tafel slope and the charge transfer coefficient were obtained from the impedance spectra at optimum condition of PdNi loading and PdNi wt percent. 24 refs., 2 tabs., 5 figs.

  20. New insights into non-precious metal catalyst layer designs for proton exchange membrane fuel cells: Improving performance and stability

    Science.gov (United States)

    Banham, Dustin; Kishimoto, Takeaki; Sato, Tetsutaro; Kobayashi, Yoshikazu; Narizuka, Kumi; Ozaki, Jun-ichi; Zhou, Yingjie; Marquez, Emil; Bai, Kyoung; Ye, Siyu

    2017-03-01

    The activity of non-precious metal catalysts (NPMCs) has now reached a stage at which they can be considered as possible alternatives to Pt for some proton exchange membrane fuel cell (PEMFC) applications. However, despite significant efforts over the past 50 years on catalyst development, only limited studies have been performed on NPMC-based cathode catalyst layer (CCL) designs. In this work, an extensive ionomer study is performed to investigate the impact of ionomer equivalent weight on performance, which has uncovered two crucial findings. Firstly, it is demonstrated that beyond a critical CCL conductance, no further improvement in performance is observed. The procedure used to determine this critical conductance can be used by other researchers in this field to aid in their design of high performing NPMC-based CCLs. Secondly, it is shown that the stability of NPMC-based CCLs can be improved through the use of low equivalent weight ionomers. This represents a completely unexplored pathway for further stability improvements, and also provides new insights into the possible degradation mechanisms occurring in NPMC-based CCLs. These findings have broad implications on all future NPMC-based CCL designs.

  1. Performance of a Double Catalyst Fuel Cell Cathode with a Tubular Oxygen Breathing and Preliminary Reduction Zone

    Institute of Scientific and Technical Information of China (English)

    Lu(i)s A. Waack BAMBACE; Miriam NISHIMORI; Fernando M. RAMOS; Demétrio BASTOS -NETTO

    2005-01-01

    @@ This paper discusses a mathematical model for a liquid phase reacting flow occurring at the cathode of a patent pending novel fuel cell geometry, where a non homogeneous catalysis carried by gold and Prussian Blue, with the first reducing air O2 and the second the resulting H2O2. The breathing zone is porous walls microtubes, with three different types of pores in its walls. Inside the microtubes there is water solution of sulfuric acid. The microtubes possess an external layer of extremely porous polymer hydrophobic agent. A Prussian Blue thin porous layer is over the selective membrane. Appropriate porous and tubular connecting elements close the fluid loop. The asymmetry induces proper current and electric potential profiles, which leads to a mainly electrocapillary electrokinetic flow, which enhances the oxygen transport and assures the H2O2 flow to its reduction layer.

  2. A multi-layered Fe2O3/graphene composite with mesopores as a catalyst for rechargeable aprotic lithium-oxygen batteries

    Science.gov (United States)

    Feng, Ningning; Mu, Xiaowei; Zheng, Mingbo; Wang, Chaoqiang; Lin, Zixia; Zhang, Xueping; Shi, Yi; He, Ping; Zhou, Haoshen

    2016-09-01

    Aprotic Li-O2 batteries have attracted a huge amount of interest in the past decade owing to their extremely high energy density. However, identifying a desirable cathodic catalyst for this promising battery system is one of the biggest challenges at present. In this work, a multi-layered Fe2O3/graphene nanosheets (Fe2O3/GNS) composite with sandwich structure was synthesized using an easy thermal casting method, and served as a cathodic catalyst for aprotic Li-O2 batteries. The aprotic Li-O2 cell with the Fe2O3/GNS catalyst demonstrated a better reversibility, lower overpotential for oxygen evolution, and a higher Coulombic efficiency (close to 100%) than those of pure GNS. An excellent rate performance and good cycle stability were also confirmed. The results, characterized by ex and in situ methods, revealed that the dominant discharge product Li2O2 was decomposed below 4.35 V. This superior electrochemical performance is mainly attributed to the unique sandwich structure of the Fe2O3/GNS catalyst with mesopores, which can provide substantially more catalytic sites and prevent direct contact between carbon and Li2O2.

  3. N-doped graphitic layer encased cobalt nanoparticles as efficient oxygen reduction catalysts in alkaline media

    Science.gov (United States)

    Han, Ce; Bo, Xiangjie; Zhang, Yufan; Li, Mian; Nsabimana, Anaclet; Guo, Liping

    2015-03-01

    Nitrogen doped graphitic layer encased cobalt (N-C@Co) nanoparticles, as novel non-precious-metal catalysts for the oxygen reduction reaction (ORR), were fabricated by a facile method using cyanamide and cobalt nitrate as precursors. The N-C@Co catalysts exhibited comparable catalytic performance, better stability and improved methanol tolerance towards the ORR than those of the commercial Pt/C catalyst.Nitrogen doped graphitic layer encased cobalt (N-C@Co) nanoparticles, as novel non-precious-metal catalysts for the oxygen reduction reaction (ORR), were fabricated by a facile method using cyanamide and cobalt nitrate as precursors. The N-C@Co catalysts exhibited comparable catalytic performance, better stability and improved methanol tolerance towards the ORR than those of the commercial Pt/C catalyst. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07571d

  4. A solar-powered microbial electrolysis cell with a platinum catalyst-free cathode to produce hydrogen.

    Science.gov (United States)

    Chae, Kyu-Jung; Choi, Mi-Jin; Kim, Kyoung-Yeol; Ajayi, Folusho F; Chang, In-Seop; Kim, In S

    2009-12-15

    This paper reports successful hydrogen evolution using a dye-sensitized solar cell (DSSC)-powered microbial electrolysis cell (MEC) without a Pt catalyst on the cathode, indicating a solution for the inherent drawbacks of conventional MECs, such as the need for an external bias and catalyst. DSSCs fabricated by assembling a ruthenium dye-loaded TiO(2) film and platinized FTO glass with an I(-)/I(3)(-) redox couple were demonstrated as an alternative bias (V(oc) = 0.65 V). Pt-loaded (0.3 mg Pt/cm(2)) electrodes with a Pt/C nanopowder showed relatively faster hydrogen production than the Pt-free electrodes, particularly at lower voltages. However, once the applied photovoltage exceeded a certain level (0.7 V), platinum did not have any additional effect on hydrogen evolution in the solar-powered MECs: hydrogen conversion efficiency was almost comparable for either the plain (71.3-77.0%) or Pt-loaded carbon felt (79.3-82.0%) at >0.7 V. In particular, the carbon nanopowder-coated electrode without Pt showed significantly enhanced performance compared to the plain electrode, which indicates efficient electrohydrogenesis, even without Pt by enhancing the surface area. As the applied photovoltage was increased, anodic methanogenesis decreased gradually, resulting in increasing hydrogen yield.

  5. Fundamental degradation mechanisms of layered oxide Li-ion battery cathode materials: Methodology, insights and novel approaches

    Energy Technology Data Exchange (ETDEWEB)

    Hausbrand, R., E-mail: hausbrand@surface.tu-darmstadt.de; Cherkashinin, G.; Ehrenberg, H.; Gröting, M.; Albe, K.; Hess, C.; Jaegermann, W.

    2015-02-15

    Graphical abstract: - Highlights: • Description of recent in operando and in situ analysis methodology. • Surface science approach using photoemission for analysis of cathode surfaces and interfaces. • Ageing and fatigue of layered oxide Li-ion battery cathode materials from the atomistic point of view. • Defect formation and electronic structure evolution as causes for cathode degradation. • Significance of interfacial energy alignment and contact potential for side reactions. - Abstract: This overview addresses the atomistic aspects of degradation of layered LiMO{sub 2} (M = Ni, Co, Mn) oxide Li-ion battery cathode materials, aiming to shed light on the fundamental degradation mechanisms especially inside active cathode materials and at their interfaces. It includes recent results obtained by novel in situ/in operando diffraction methods, modelling, and quasi in situ surface science analysis. Degradation of the active cathode material occurs upon overcharge, resulting from a positive potential shift of the anode. Oxygen loss and eventual phase transformation resulting in dead regions are ascribed to changes in electronic structure and defect formation. The anode potential shift results from loss of free lithium due to side reactions occurring at electrode/electrolyte interfaces. Such side reactions are caused by electron transfer, and depend on the electron energy level alignment at the interface. Side reactions at electrode/electrolyte interfaces and capacity fade may be overcome by the use of suitable solid-state electrolytes and Li-containing anodes.

  6. Simulation of the atomic and ionic densities in the ionization layer of a plasma arc with a binary cathode

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, D; Marin, J A Sillero; Munoz-Serrano, E; Casado, E, E-mail: f92orhed@uco.e [Departamento de Fisica, Universidad de Cordoba, 14071 Cordoba (Spain)

    2009-04-21

    A physical model was developed to study the behaviour of the cathode material evaporated from a thoriated tungsten cathode of an atmospheric-pressure argon plasma arc. The densities of tungsten and thorium atoms and ions in the ionization layer were obtained, and the influence of the different physical processes on the evaporated cathode material was established. It was found that almost all of the neutral atoms evaporated from the cathode are ionized near the beginning of the ionization layer, i.e. near the boundary between the sheath and the ionization layer. Thorium ions are concentrated in a 4 {mu}m region near the beginning of this layer, while tungsten ions are found in a region of 9 {mu}m. The contribution of the electric force to the velocity of ions is the dominant contribution only near the beginning of the ionization layer. At a distance from the interface between the sheath and the ionization layer greater than 3.8 {mu}m in the case of thorium ions, and greater than 5 {mu}m in the case of tungsten ions, the contributions of the density gradient forces and the frictional forces are more important than the electric force contribution.

  7. Intercalation of Mg-ions in layered V2O5 cathode materials for rechargeable Mg-ion batteries

    DEFF Research Database (Denmark)

    Sørensen, Daniel Risskov; Johannesen, Pætur; Christensen, Christian Kolle;

    The development of functioning rechargeable Mg-ion batteries is still in its early stage, and a coarse screening of suitable cathode materials is still on-going. Within the intercalation-type cathodes, layered crystalline materials are of high interest as they are known to perform well in Li......-ion intercalation batteries and are also increasingly being explored for Na-ion batteries. Here, we present an investigation of the layered material orthorhombic V2O5, which is a classical candidate for an ion-intercalation material having a high theoretical capacity1. We present discharge-curves for the insertion...

  8. MnCo2O4 nanowires anchored on reduced graphene oxide sheets as effective bifunctional catalysts for Li-O2 battery cathodes.

    Science.gov (United States)

    Kim, Jong Guk; Kim, Youngmin; Noh, Yuseong; Kim, Won Bae

    2015-05-22

    A hybrid composite system of MnCo2 O4 nanowires (MCO NWs) anchored on reduced graphene oxide (RGO) nanosheets was prepared as the bifunctional catalyst of a Li-O2 battery cathode. The catalysts can be obtained from the hybridization of one-dimensional MCO NWs and two-dimensional RGO nanosheets. As O2 -cathode catalysts for Li-O2 cells, the MCO@RGO composites showed a high initial discharge capacity (ca. 11092.1 mAh gcarbon (-1) ) with a high rate performance. The Li-O2 cells could run for more than 35 cycles with high reversibility under a limited specific capacity of 1000 mAh gcarbon (-1) with a low potential polarization of 1.36 V, as compared with those of pure Ketjenblack and MCO NWs. The high cycling stability, low potential polarization, and rate capability suggest that the MCO@RGO composites prepared here are promising catalyst candidates for highly reversible Li-O2 battery cathodes.

  9. Final Report: Cathode Catalysis in Hydrogen/Oxygen Fuel Cells: New Catalysts, Mechanism, and Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Gewirth, Andrew A. [Univ. of Illinois, Urbana, IL (United States). Dept. of Chemistry; Kenis, Paul J. [Univ. of Illinois, Urbana, IL (United States). Dept. of Chemical and Biomolecular Engineering; Nuzzo, Ralph G. [Univ. of Illinois, Urbana, IL (United States). Dept. of Chemistry; Rauchfuss, Thomas B. [Univ. of Illinois, Urbana, IL (United States). Dept. of Chemistry

    2016-01-18

    In this research, we prosecuted a comprehensive plan of research directed at developing new catalysts and new understandings relevant to the operation of low temperature hydrogen-oxygen fuel cells. The focal point of this work was one centered on the Oxygen Reduction Reaction (ORR), the electrochemical process that most fundamentally limits the technological utility of these environmentally benign energy conversion devices. Over the period of grant support, we developed new ORR catalysts, based on Cu dimers and multimers. In this area, we developed substantial new insight into design rules required to establish better ORR materials, inspired by the three-Cu active site in laccase which has the highest ORR onset potential of any material known. We also developed new methods of characterization for the ORR on conventional (metal-based) catalysts. Finally, we developed a new platform to study the rate of proton transfer relevant to proton coupled electron transfer (PCET) reactions, of which the ORR is an exemplar. Other aspects of work involved theory and prototype catalyst testing.

  10. Development of carbon free diffusion layer for activated carbon air cathode of microbial fuel cells.

    Science.gov (United States)

    Yang, Wulin; Kim, Kyoung-Yeol; Logan, Bruce E

    2015-12-01

    The fabrication of activated carbon air cathodes for larger-scale microbial fuel cells requires a diffusion layer (DL) that is highly resistant to water leakage, oxygen permeable, and made using inexpensive materials. A hydrophobic polyvinylidene fluoride (PVDF) membrane synthesized using a simple phase inversion process was examined as a low cost ($0.9/m(2)), carbon-free DL that prevented water leakage at high pressure heads compared to a polytetrafluoroethylene/carbon black DL ($11/m(2)). The power density produced with a PVDF (20%, w/v) DL membrane of 1400±7mW/m(2) was similar to that obtained using a wipe DL [cloth coated with poly(dimethylsiloxane)]. Water head tolerance reached 1.9m (∼19kPa) with no mesh supporter, and 2.1m (∼21kPa, maximum testing pressure) with a mesh supporter, compared to 0.2±0.05m for the wipe DL. The elimination of carbon black from the DL greatly simplified the fabrication procedure and further reduced overall cathode costs.

  11. A Comparison of Fick and Maxwell-Stefan Diffusion Formulations in PEMFC Cathode Gas Diffusion Layers

    CERN Document Server

    Lindstrom, Michael

    2013-01-01

    This paper explores the mathematical formulations of Fick and Maxwell-Stefan diffusion in the context of polymer electrolyte membrane fuel cell cathode gas diffusion layers. Formulations of diffusion combined with mass-averaged Darcy flow are considered for three component gases. Fick formulations can be considered as approximations of Maxwell-Stefan in a certain sense. For this application, the formulations can be compared computationally in a simple, one dimensional setting. We observe that the predictions of the formulations are very similar, despite their seemingly different structure. Analytic insight is given to the result. In addition, it is seen that for both formulations, diffusion laws are small perturbations from bulk flow. The work is also intended as a reference to multi-component gas diffusion formulations in the fuel cell setting.

  12. Vapor phase hydrogenation of furfural over nickel mixed metal oxide catalysts derived from layered double hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Sulmonetti, Taylor P.; Pang, Simon H.; Claure, Micaela Taborga; Lee, Sungsik; Cullen, David A.; Agrawal, Pradeep K.; Jones, Christopher W.

    2016-05-01

    The hydrogenation of furfural is investigated over various reduced nickel mixed metal oxides derived from layered double hydroxides (LDHs) containing Ni-Mg-Al and Ni-Co-Al. Upon reduction, relatively large Ni(0) domains develop in the Ni-Mg-Al catalysts, whereas in the Ni-Co-Al catalysts smaller metal particles of Ni(0) and Co(0), potentially as alloys, are formed, as evidenced by XAS, XPS, STEM and EELS. All the reduced Ni catalysts display similar selectivities towards major hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol), though the side products varied with the catalyst composition. The 1.1Ni-0.8Co-Al catalyst showed the greatest activity per titrated site when compared to the other catalysts, with promising activity compared to related catalysts in the literature. The use of base metal catalysts for hydrogenation of furanic compounds may be a promising alternative to the well-studied precious metal catalysts for making biomass-derived chemicals if catalyst selectivity can be improved in future work by alloying or tuning metal-oxide support interactions.

  13. Surface reconstruction and chemical evolution of stoichiometric layered cathode materials for lithium-ion batteries.

    Science.gov (United States)

    Lin, Feng; Markus, Isaac M; Nordlund, Dennis; Weng, Tsu-Chien; Asta, Mark D; Xin, Huolin L; Doeff, Marca M

    2014-03-27

    The present study sheds light on the long-standing challenges associated with high-voltage operation of LiNi(x)Mn(x)Co(1-2x)O2 cathode materials for lithium-ion batteries. Using correlated ensemble-averaged high-throughput X-ray absorption spectroscopy and spatially resolved electron microscopy and spectroscopy, here we report structural reconstruction (formation of a surface reduced layer, to transition) and chemical evolution (formation of a surface reaction layer) at the surface of LiNi(x)Mn(x)Co(1-2x)O2 particles. These are primarily responsible for the prevailing capacity fading and impedance buildup under high-voltage cycling conditions, as well as the first-cycle coulombic inefficiency. It was found that the surface reconstruction exhibits a strong anisotropic characteristic, which predominantly occurs along lithium diffusion channels. Furthermore, the surface reaction layer is composed of lithium fluoride embedded in a complex organic matrix. This work sets a refined example for the study of surface reconstruction and chemical evolution in battery materials using combined diagnostic tools at complementary length scales.

  14. Sulfur-infiltrated graphene-based layered porous carbon cathodes for high-performance lithium-sulfur batteries.

    Science.gov (United States)

    Yang, Xi; Zhang, Long; Zhang, Fan; Huang, Yi; Chen, Yongsheng

    2014-05-27

    Because of advantages such as excellent electronic conductivity, high theoretical specific surface area, and good mechanical flexibility, graphene is receiving increasing attention as an additive to improve the conductivity of sulfur cathodes in lithium-sulfur (Li-S) batteries. However, graphene is not an effective substrate material to confine the polysulfides in cathodes and stable the cycling. Here, we designed and synthesized a graphene-based layered porous carbon material for the impregnation of sulfur as cathode for Li-S battery. In this composite, a thin layer of porous carbon uniformly covers both surfaces of the graphene and sulfur is highly dispersed in its pores. The high specific surface area and pore volume of the porous carbon layers not only can achieve a high sulfur loading in highly dispersed amorphous state, but also can act as polysulfide reservoirs to alleviate the shuttle effect. When used as the cathode material in Li-S batteries, with the help of the thin porous carbon layers, the as-prepared materials demonstrate a better electrochemical performance and cycle stability compared with those of graphene/sulfur composites.

  15. Conductive polymer layers to limit transfer of fuel reactants to catalysts of fuel cells to reduce reactant crossover

    Energy Technology Data Exchange (ETDEWEB)

    Stanis, Ronald J.; Lambert, Timothy N.

    2016-12-06

    An apparatus of an aspect includes a fuel cell catalyst layer. The fuel cell catalyst layer is operable to catalyze a reaction involving a fuel reactant. A fuel cell gas diffusion layer is coupled with the fuel cell catalyst layer. The fuel cell gas diffusion layer includes a porous electrically conductive material. The porous electrically conductive material is operable to allow the fuel reactant to transfer through the fuel cell gas diffusion layer to reach the fuel cell catalyst layer. The porous electrically conductive material is also operable to conduct electrons associated with the reaction through the fuel cell gas diffusion layer. An electrically conductive polymer material is coupled with the fuel cell gas diffusion layer. The electrically conductive polymer material is operable to limit transfer of the fuel reactant to the fuel cell catalyst layer.

  16. Effect of catalyst distribution in the active layers of proton exchange membrane fuel cells; Effet de la distribution du catalyseur dans les couches actives de piles a combustible de type PEMFC

    Energy Technology Data Exchange (ETDEWEB)

    Bultel, Y.; Durand, R.; Ozil, P. [Ecole Nationale Superieure d' Electrochimie et d' Electrometallurgie, Lab. d' Electrochimie et de Physico-chimie des Materiaux et des Interfaces, UMR 5631, 38 - Grenoble (France); Antoine, O. [Geneva Univ., Dept. de Chimie Minerale, Analytique et Appliquee, Sciences 2 (Switzerland)

    2000-07-01

    The aim of this work is to study the influence of the distribution of the platinum catalyst in the active layers on the performances of proton exchange membrane fuel cells (PEMFC) electrodes. In the one hand, the results predicted by the classical models and those in which the active layers is modified have been compared; these results have allowed to demonstrate theoretically the effect of the discrete distribution of the platinum catalyst in the form of nano-particles. On the other hand, the influence of a distribution gradient of the platinum catalyst for porous and non-porous active layers of PEMFC cathode has been experimentally demonstrated and predicted by numerical simulations. (O.M.)

  17. Effective proton conductivity of catalyst layers in proton exchange membrane fuel cells%质子交换膜燃料电池催化层的有效质子电导率

    Institute of Scientific and Technical Information of China (English)

    杜春雨; 史鹏飞; 程新群; 尹鸽平

    2005-01-01

    A numerical model was presented to predict the specific proton conductivity of the catalyst layer in Proton Exchange Membrane Fuel Cells (PEMFC). This model was derived from the random packed spheres with simple cubic, body-centered cubic and face-centered cubic structures. The effects of sphe reradius rs, bulk proton conductivity kb, contact parameter γ and contact angle a on proton transfer within a homogeneous agglomerate sphere consisting of carbon-supported catalyst and electrolyte were analyzed. A correlation equation of specific proton conductivity was obtained by data fitting. The real effective proton conductivity in the catalyst layer was measured by addition to a standard Membrane Electrolyte Assembly of an inactive composite layer in the electrolyte path between the anode and cathode. The model was validated by good agreement between calculations and measured data.

  18. Heat transfer effects on the methanol-steam reforming with partially filled catalyst layers

    Energy Technology Data Exchange (ETDEWEB)

    Chein, Rei-Yu.; Chen, Li-Chang [Department of Mechanical Engineering, National Chung-Hsing University, Taichung City, Taiwan 402 (China); Chen, Yen-Cho [Department of Energy and Resources, National United University, Miaoli City, Taiwan 360 (China); Chung, J.N. [Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611-6300 (United States)

    2009-07-15

    The heat transfer effects on a methanol-steam reforming (MSR) process are numerically investigated using a circular reformer with a partially (referred to as the wall-coated reformer) or entirely filled catalyst layer (referred to as the packed-bed reformer). The catalyst layer is formed by packing CuO/ZnO/Al{sub 2}O{sub 3} catalyst particles with a certain porosity and permeability. The fluid flow characteristics are strongly affected by the catalyst-layer thickness. As a consequence, the heat and mass transfer also depend on the catalyst-layer thickness. Under heat supplied by wall heat flux conditions, it is found that higher reforming temperature can be obtained for the wall-coated reformer compared with the packed-bed reformer. This results in the wall-coated reformer having a better methanol conversion efficiency compared with the packed-bed reformer. Based on our study, the minimum heat transfer coefficient, maximum methanol conversion and maximum carbon monoxide production are obtained when the catalyst-layer thickness is 90% of the reformer radius. (author)

  19. Bimetallic Nickel/Ruthenium Catalysts Synthesized by Atomic Layer Deposition for Low-Temperature Direct Methanol Solid Oxide Fuel Cells.

    Science.gov (United States)

    Jeong, Heonjae; Kim, Jun Woo; Park, Joonsuk; An, Jihwan; Lee, Tonghun; Prinz, Fritz B; Shim, Joon Hyung

    2016-11-09

    Nickel and ruthenium bimetallic catalysts were heterogeneously synthesized via atomic layer deposition (ALD) for use as the anode of direct methanol solid oxide fuel cells (DMSOFCs) operating in a low-temperature range. The presence of highly dispersed ALD Ru islands over a porous Ni mesh was confirmed, and the Ni/ALD Ru anode microstructure was observed. Fuel cell tests were conducted using Ni-only and Ni/ALD Ru anodes with approximately 350 μm thick gadolinium-doped ceria electrolytes and platinum cathodes. The performance of fuel cells was assessed using pure methanol at operating temperatures of 300-400 °C. Micromorphological changes of the anode after cell operation were investigated, and the content of adsorbed carbon on the anode side of the operated samples was measured. The difference in the maximum power density between samples utilizing Ni/ALD Ru and Pt/ALD Ru, the latter being the best catalyst for direct methanol fuel cells, was observed to be less than 7% at 300 °C and 30% at 350 °C. The improved electrochemical activity of the Ni/ALD Ru anode compared to that of the Ni-only anode, along with the reduction of the number of catalytically active sites due to agglomeration of Ni and carbon formation on the Ni surface as compared to Pt, explains this decent performance.

  20. Determination of optimal parameters for dual-layer cathode of polymer electrolyte fuel cell using computational intelligence-aided design.

    Science.gov (United States)

    Chen, Yi; Huang, Weina; Peng, Bei

    2014-01-01

    Because of the demands for sustainable and renewable energy, fuel cells have become increasingly popular, particularly the polymer electrolyte fuel cell (PEFC). Among the various components, the cathode plays a key role in the operation of a PEFC. In this study, a quantitative dual-layer cathode model was proposed for determining the optimal parameters that minimize the over-potential difference η and improve the efficiency using a newly developed bat swarm algorithm with a variable population embedded in the computational intelligence-aided design. The simulation results were in agreement with previously reported results, suggesting that the proposed technique has potential applications for automating and optimizing the design of PEFCs.

  1. Catalysts for ultrahigh current density oxygen cathodes for space fuel cell applications

    Science.gov (United States)

    Tryk, Donald A.; Yeager, E.

    1992-01-01

    The objective was to identify promising electrocatalyst/support systems for oxygen cathodes capable of operating at ultrahigh current densities in alkaline fuel cells. Such cells will require operation at relatively high temperatures and O2 pressures. A number of materials were prepared, including Pb-Ru and Pb-Ir pyrochlores, RuO2 and Pt-doped RuO2, lithiated NiO and La-Ni perovskites. Several of these materials were prepared using techniques that had not been previously used to prepare them. Particularly interesting was the use of the alkaline solution technique to prepare Pt-doped and Pb-Ru pyrochlores in high area form. Also interesting was the use of the fusion (melt) method for preparing the Pb-Ru pyrochlore. Several of the materials were also deposited with platinum. Well-crystallized Pb2Ru2O(7-y) was used to fabricate very high performance O2 cathodes with good stability in room temperature KOH. This material was also found to be stable over a useful potential range at approx. 140 C in concentrated KOH. For some of the samples, fabrication of the gas-fed electrodes could not be fully optimized during this project period. Future work may be directed at this problem. Pyrochlores that were not well-crystallized were found to be unstable in alkaline solution. Very good O2 reduction performance and stability were observed with Pb2RuO(7-y) in a carbon-based gas-fed electrode with an anion-conducting membrane placed on the electrolyte side of the electrode. The performance came within a factor of about two of that observed without carbon. High area platinum and gold supported on several conductive metal oxide supports were examined. Only small improvements in O2 reduction performance at room temperature were observed for Pb2Ru2O(7-y) as a support because of the high intrinsic activity of the pyrochlore. In contrast, a large improvement was observed for Li-doped NiO as a support for Pt. Very poor performance was observed for Au deposited on Li-NiO at approx. 150 C

  2. Controlled assembly of layer-by-layer stacking continuous graphene oxide films and their application for actively modulated field electron emission cathodes

    Science.gov (United States)

    Huang, Yuan; She, Juncong; Yang, Wenjie; Deng, Shaozhi; Xu, Ningsheng

    2014-03-01

    A featured ``vapor transportation'' assembly technique was developed to attain layer-by-layer stacking continuous graphene oxide (GO) films on both flat and concavo-concave surfaces. Few-layer (layer number MOSFET). The field emission current of the GO cathode can be precisely controlled by the MOSFET gate voltage (VGS). A current modulation range from 1 × 10-10 A to 6.9 × 10-6 A (4 orders of magnitude) was achieved by tuning the VGS from 0.812 V to 1.728 V. Due to the self-acting positive feedback of the MOSFET, the emission current fluctuation was dramatically reduced from 57.4% (non-control) to 3.4% (controlled). Furthermore, the integrated GO cathode was employed for a lab-prototype display pixel application demonstrating the active modulation of the phosphor luminance, i.e. from 0.01 cd m-2 to 34.18 cd m-2.

  3. Ni And Co Segregations On Selective Surface Facets And Rational Design Of Layered Lithium Transition-metal Oxide Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei; Zheng, Jianming; Zheng, Jiaxin; Wang, Zhiguo; Teng, Gaofeng; Kuppan, Saravanan; Xiao, Jie; Chen, Guoying; Pan, Feng; Zhang, Jiguang; Wang, Chong M.

    2016-05-05

    The chemical processes occurring on the surface of cathode materials during battery cycling play a crucial role in determining battery’s performance. However, our understanding on such surface chemistry is far from clear due to the complexity of redox chemistry during battery charge/discharge. In this work, through intensive aberration corrected STEM investigation on eight layered oxide cathode materials, we report two important findings on the pristine oxides. First, Ni and Co show strong plane selectivity when building up their respective surface segregation layers (SSL). Specifically, Ni-SSL is exclusively developed on (200)m facet in Li-Mn-rich oxides (monoclinic C2/m symmetry) and (012)h facet in Mn-Ni equally rich oxides (hexagonal R-3m symmetry), while Co-SSL has a strong preference to (20-2)m plane with minimal Co-SSL also developed on some other planes in LMR cathodes. Structurally, Ni-SSLs tend to form spinel-like lattice while Co-SSLs are in a rock-salt-like structure. Secondly, by increasing Ni concentration in these layered oxides, Ni and Co SSLs can be suppressed and even eliminated. Our findings indicate that Ni and Co SSLs are tunable through controlling particle morphology and oxide composition, which opens up a new way for future rational design and synthesis of cathode materials.

  4. Passivation Layer and Cathodic Redox Reactions in Sodium-Ion Batteries Probed by HAXPES.

    Science.gov (United States)

    Doubaji, Siham; Philippe, Bertrand; Saadoune, Ismael; Gorgoi, Mihaela; Gustafsson, Torbjorn; Solhy, Abderrahim; Valvo, Mario; Rensmo, Håkan; Edström, Kristina

    2016-01-08

    The cathode material P2-Nax Co2/3 Mn2/9 Ni1/9 O2, which could be used in Na-ion batteries, was investigated through synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). Nondestructive analysis was made through the electrode/electrolyte interface of the first electrochemical cycle to ensure access to information not only on the active material, but also on the passivation layer formed at the electrode surface and referred to as the solid permeable interface (SPI). This investigation clearly shows the role of the SPI and the complexity of the redox reactions. Cobalt, nickel, and manganese are all electrochemically active upon cycling between 4.5 and 2.0 V; all are in the 4+ state at the end of charging. Reduction to Co(3+), Ni(3+), and Mn(3+) occurs upon discharging and, at low potential, there is partial reversible reduction to Co(2+) and Ni(2+). A thin layer of Na2 CO3 and NaF covers the pristine electrode and reversible dissolution/reformation of these compounds is observed during the first cycle. The salt degradation products in the SPI show a dependence on potential. Phosphates mainly form at the end of the charging cycle (4.5 V), whereas fluorophosphates are produced at the end of discharging (2.0 V).

  5. Alkaline earth layered benzoates as reusable heterogeneous catalysts for the methyl esterification of benzoic acid

    Directory of Open Access Journals (Sweden)

    Swamy Arêa Maruyama

    2012-01-01

    Full Text Available This paper describes the synthesis and characterization of layered barium, calcium and strontium benzoates and evaluates the potential of these materials as catalysts in the synthesis of methyl benzoate. The methyl esterification of benzoic acid was investigated, where the effects of temperature, alcohol:acid molar ratio and amount of catalyst were evaluated. Ester conversions of 65 to 70% were achieved for all the catalysts under the best reaction conditions. The possibility of recycling these metallic benzoates was also demonstrated, evidenced by unaltered catalytic activity for three consecutive reaction cycles.

  6. Oxygen cathode based on a layer-by-layer self-assembled laccase and osmium redox mediator

    Energy Technology Data Exchange (ETDEWEB)

    Szamocki, R.; Flexer, V. [INQUIMAE-DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina); Levin, L.; Forchiasin, F. [Micologia Experimental, Departamento de Biodiversidad y Biologia Experimental. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina); Calvo, E.J. [INQUIMAE-DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina)], E-mail: calvo@qi.fcen.uba.ar

    2009-02-28

    Trametes trogii laccase has been studied as biocatalyst for the oxygen electro-reduction in three different systems: (i) soluble laccase was studied in solution; (ii) an enzyme monolayer was tethered to a gold surface by dithiobis N-succinimidyl propionate (DTSP), with a soluble osmium pyridine-bipyridine redox mediator in both cases. The third case (iii) consisted in the sequential immobilization of laccase and the osmium complex derivatized poly(allylamine) self-assembled layer-by-layer (LbL) on mercaptopropane sulfonate modified gold to produce an all integrated and wired enzymatic oxygen cathode. The polycation was the same osmium complex covalently bound to poly-(ally-lamine) backbone (PAH-Os), the polyanion was the enzyme adsorbed from a solution of a suitable pH so that the protein carries a net negative charge. The adsorption of laccase was studied by monitoring the mass uptake with a quartz crystal microbalance and the oxygen reduction electrocatalysis was studied by linear scan voltammetry. While for the three cases, oxygen electrocatalysis mediated by the osmium complex was observed, for tethered laccase direct electron transfer in the absence of redox mediator was also apparent but no electrocatalysis for the oxygen reduction was recorded in the absence of mediator in solution. For the fully integrated LbL self-assembled laccase and redox mediator (case iii) a catalytic reduction of oxygen could be recorded at different oxygen partial pressures and different electrolyte pH. The tolerance of the reaction to methanol and chloride was also investigated.

  7. Enhanced Oxygen and Hydroxide Transport in a Cathode Interface by Efficient Antibacterial Property of a Silver Nanoparticle-Modified, Activated Carbon Cathode in Microbial Fuel Cells.

    Science.gov (United States)

    Li, Da; Qu, Youpeng; Liu, Jia; Liu, Guohong; Zhang, Jie; Feng, Yujie

    2016-08-17

    A biofilm growing on an air cathode is responsible for the decreased performance of microbial fuel cells (MFCs). For the undesired biofilm to be minimized, silver nanoparticles were synthesized on activated carbon as the cathodic catalyst (Ag/AC) in MFCs. Ag/AC enhanced maximum power density by 14.6% compared to that of a bare activated carbon cathode (AC) due to the additional silver catalysis. After operating MFCs over five months, protein content on the Ag/AC cathode was only 38.3% of that on the AC cathode, which resulted in a higher oxygen concentration diffusing through the Ag/AC cathode. In addition, a lower pH increment (0.2 units) was obtained near the Ag/AC catalyst surface after biofouling compared to 0.8 units of the AC cathode, indicating that less biofilm on the Ag/AC cathode had a minor resistance on hydroxide transported from the catalyst layer interfaces to the bulk solution. Therefore, less decrements of the Ag/AC activity and MFC performance were obtained. This result indicated that accelerated transport of oxygen and hydroxide, benefitting from the antibacterial property of the cathode, could efficiently maintain higher cathode stability during long-term operation.

  8. Layered SiC Sheets: A Potential Catalyst for Oxygen Reduction Reaction

    Science.gov (United States)

    Zhang, P.; Xiao, B. B.; Hou, X. L.; Zhu, Y. F.; Jiang, Q.

    2014-01-01

    The large-scale practical application of fuel cells cannot come true if the high-priced Pt-based electrocatalysts for oxygen reduction reaction (ORR) cannot be replaced by other efficient, low-cost, and stable electrodes. Here, based on density functional theory (DFT), we exploited the potentials of layered SiC sheets as a novel catalyst for ORR. From our DFT results, it can be predicted that layered SiC sheets exhibit excellent ORR catalytic activity without CO poisoning, while the CO poisoning is the major drawback in conventional Pt-based catalysts. Furthermore, the layered SiC sheets in alkaline media has better catalytic activity than Pt(111) surface and have potential as a metal-free catalyst for ORR in fuel cells.

  9. Layered SiC sheets: a potential catalyst for oxygen reduction reaction.

    Science.gov (United States)

    Zhang, P; Xiao, B B; Hou, X L; Zhu, Y F; Jiang, Q

    2014-01-22

    The large-scale practical application of fuel cells cannot come true if the high-priced Pt-based electrocatalysts for oxygen reduction reaction (ORR) cannot be replaced by other efficient, low-cost, and stable electrodes. Here, based on density functional theory (DFT), we exploited the potentials of layered SiC sheets as a novel catalyst for ORR. From our DFT results, it can be predicted that layered SiC sheets exhibit excellent ORR catalytic activity without CO poisoning, while the CO poisoning is the major drawback in conventional Pt-based catalysts. Furthermore, the layered SiC sheets in alkaline media has better catalytic activity than Pt(111) surface and have potential as a metal-free catalyst for ORR in fuel cells.

  10. Inverted Organic Solar Cells with Improved Performance using Varied Cathode Buffer Layers

    Institute of Scientific and Technical Information of China (English)

    Zhi-qiang Guan; Jun-sheng Yu; Yue Zang; Xing-xin Zeng

    2012-01-01

    Organic solar cells with inverted planar heterojunction structure based on subphthalocyanine and C60 were fabricated using several kinds of materials as cathode buffer layer (CBL),including tris-8-hydroxy-quinolinato aluminum (Alq3),bathophenanthroline (Bphen),bathocuproine,2,3,8,9,14,15-hexakis-dodecyl-sulfanyl-5,6,11,12,17,18-hexaazatrinaphthylene (HATNA),and an inorganic compound of Cs2CO3.The influence of the lowest unoccupied molecular orbital level and the electron mobility of organic CBL on the solar cells performance was compared.The results showed that Alq3,Bphen,and HATNA could significantly improve the device performance.The highest efficiency was obtained from device with annealed HATNA as CBL and increased for more than 7 times compared with device without CBL.Furthermore,the simulation results with space charge-limited current theory indicated that the Schottky barrier at the organic/electrode interface in inverted OSC structure was reduced for 27% by inserting HATNA CBL.

  11. Electrochemical Effects of Atomic Layer Deposition on Cathode Materials for Lithium Batteries

    Science.gov (United States)

    Scott, Isaac David

    One of the greatest challenges of modern society is to stabilize a consistent energy supply that will meet our growing energy demand while decreasing the use of fossil fuels and the harmful green house gases which they produce. Developing reliable and safe solutions has driven research into exploring alternative energy sources for transportation including fuel cells, hydrogen storage, and lithium-ion batteries (LIBs). For the foreseeable future, though, rechargeable batteries appear to be the most practically viable power source. To deploy LIBs in next-generation vehicles, it is essential to develop electrodes with durability, high energy density, and high power. Unfortunately, the power capability of LIBs is generally hindered by Li+-ion diffusion in micrometer-sized materials and the formation of an insulating solid electrolyte interface (SEI) layer on the surface of the active material. In addition, degradation of the battery material due to chemical and electrochemical reactions with the electrolyte lead to both capacity fade and safety concerns both at room and higher temperatures. The current study focuses on mitigating these issues for high voltage cathode materials by both using nanoscale particles to improve Li+-ion diffusion and using ultrathin nanoscale coatings to protect the battery materials from undesirable side reactions. The electrode material is coated with Al2O3 using atomic layer deposition (ALD), which is a method to grow conformal thin films with atomic thickness (angstrom level control) using sequential, self-limiting surface reactions. First, nano-LiCoO 2 is employed to demonstrate the effectiveness of ALD coatings and demonstrates a profound increase in rate performance (>250% improvement) over generally employed micrometer-sized particles. Second, the cathode materials LiNi 0.8Co0.15Al0.05O2, LiNi0.33Mn 0.33Co0.33O2, LiMn2O4, and LiNi0.5Mn1.5O4 were used to demonstrate the benefits ALD coatings have on thermal runaway. The results show a

  12. Study on the reversible capacity loss of layered oxide cathode during low-temperature operation

    Science.gov (United States)

    Li, Yiyang; Qian, Kun; He, Yan-Bing; Kaneti, Yusuf Valentino; Liu, Dongqing; Luo, Dan; Li, Hai; Li, Baohua; Kang, Feiyu

    2017-02-01

    In this study, commercial Li(Ni1/3Co1/3Mn1/3)O2/graphite (NCM/C) lithium-ion batteries were cycled at -10 °C under different current rates ranging from 0.2 C to 1C. Electrochemical measurements and post-mortem analysis were performed to identify the root causes of the degradation in the electrochemical performance of the cells. The results reveal that apart from the increase of lithium plating on the anode, there is a considerable and abnormal capacity loss on the NCM cathode with the increase in current rate. The different degradation mechanisms including the loss of lithium inventory (LLI) and the specific capacity loss of NCM material (LAM) during cycling at -10 °C were analyzed quantitatively. It is shown that the evolution trend of LLI with the increase in current rate (8.6%, 35.0%, 55.8% for 0.2 C, 0.5 C and 1 C respectively) corresponds closely to that of the capacity loss of the full-cells (8.6%, 45.5%, 63.6% for 0.2 C, 0.5 C and 1 C, respectively), which is different to the trend of LAM (7.2%, 8.8%, 22.3% for 0.2 C, 0.5 C and 1 C, respectively). Further analysis by XRD and HR-TEM clearly indicates that the crystallinity of the hexagonal layered structure of NCM was greatly impaired after low-temperature cycling at -10 °C, and spinel phase can be observed among the layered structure.

  13. Optimization of fuel cell membrane electrode assemblies for transition metal ion-chelating ordered mesoporous carbon cathode catalysts

    Directory of Open Access Journals (Sweden)

    Johanna K. Dombrovskis

    2014-12-01

    Full Text Available Transition metal ion-chelating ordered mesoporous carbon (TM-OMC materials were recently shown to be efficient polymer electrolyte membrane fuel cell (PEMFC catalysts. The structure and properties of these catalysts are largely different from conventional catalyst materials, thus rendering membrane electrode assembly (MEA preparation parameters developed for conventional catalysts not useful for applications of TM-OMC catalysts. This necessitates development of a methodology to incorporate TM-OMC catalysts in the MEA. Here, an efficient method for MEA preparation using TM-OMC catalyst materials for PEMFC is developed including effects of catalyst/ionomer loading and catalyst/ionomer-mixing and application procedures. An optimized protocol for MEA preparation using TM-OMC catalysts is described.

  14. Optimization of fuel cell membrane electrode assemblies for transition metal ion-chelating ordered mesoporous carbon cathode catalysts

    OpenAIRE

    Johanna K. Dombrovskis; Cathrin Prestel; Anders E. C. Palmqvist

    2014-01-01

    Transition metal ion-chelating ordered mesoporous carbon (TM-OMC) materials were recently shown to be efficient polymer electrolyte membrane fuel cell (PEMFC) catalysts. The structure and properties of these catalysts are largely different from conventional catalyst materials, thus rendering membrane electrode assembly (MEA) preparation parameters developed for conventional catalysts not useful for applications of TM-OMC catalysts. This necessitates development of a methodology to incorporate...

  15. Nitrogen-Doped Carbon Nanoparticle-Carbon Nanofiber Composite as an Efficient Metal-Free Cathode Catalyst for Oxygen Reduction Reaction.

    Science.gov (United States)

    Panomsuwan, Gasidit; Saito, Nagahiro; Ishizaki, Takahiro

    2016-03-23

    Metal-free nitrogen-doped carbon materials are currently considered at the forefront of potential alternative cathode catalysts for the oxygen reduction reaction (ORR) in fuel cell technology. Despite numerous efforts in this area over the past decade, rational design and development of a new catalyst system based on nitrogen-doped carbon materials via an innovative approach still present intriguing challenges in ORR catalysis research. Herein, a new kind of nitrogen-doped carbon nanoparticle-carbon nanofiber (NCNP-CNF) composite with highly efficient and stable ORR catalytic activity has been developed via a new approach assisted by a solution plasma process. The integration of NCNPs and CNFs by the solution plasma process can lead to a unique morphological feature and modify physicochemical properties. The NCNP-CNF composite exhibits a significantly enhanced ORR activity through a dominant four-electron pathway in an alkaline solution. The enhancement in ORR activity of NCNP-CNF composite can be attributed to the synergistic effects of good electron transport from highly graphitized CNFs as well as abundance of exposed catalytic sites and meso/macroporosity from NCNPs. More importantly, NCNP-CNF composite reveals excellent long-term durability and high tolerance to methanol crossover compared with those of a commercial 20 wt % supported on Vulcan XC-72. We expect that NCNP-CNF composite prepared by this synthetic approach can be a promising metal-free cathode catalyst candidate for ORR in fuel cells and metal-air batteries.

  16. Nanoporous silver cathode surface treated by atomic layer deposition of CeO(x) for low-temperature solid oxide fuel cells.

    Science.gov (United States)

    Neoh, Ke Chean; Han, Gwon Deok; Kim, Manjin; Kim, Jun Woo; Choi, Hyung Jong; Park, Suk Won; Shim, Joon Hyung

    2016-05-06

    We evaluated the performance of solid oxide fuel cells (SOFCs) with a 50 nm thin silver (Ag) cathode surface treated with cerium oxide (CeO(x)) by atomic layer deposition (ALD). The performances of bare and ALD-treated Ag cathodes were evaluated on gadolinia-doped ceria (GDC) electrolyte supporting cells with a platinum (Pt) anode over 300 °C-450 °C. Our work confirms that ALD CeO(x) treatment enhances cathodic performance and thermal stability of the Ag cathode. The performance difference between cells using a Ag cathode optimally treated with an ALD CeO(x) surface and a reference Pt cathode is about 50% at 450 °C in terms of fuel cell power output in our experiment. The bare Ag cathode completely agglomerated into islands during fuel cell operation at 450 °C, while the ALD CeO(x) treatment effectively protects the porosity of the cathode. We also discuss the long-term stability of ALD CeO(x)-treated Ag cathodes related to the microstructure of the layers.

  17. Biofouling inhibition and enhancing performance of microbial fuel cell using silver nano-particles as fungicide and cathode catalyst.

    Science.gov (United States)

    Noori, Md T; Jain, Sumat C; Ghangrekar, M M; Mukherjee, C K

    2016-11-01

    Morphological analysis of biofouling developed on cathode surface in an air-cathode microbial fuel cell (MFC) was performed. For sustaining power production and enhancing Coulombic efficiency (CE) of MFC, studies were conducted to inhibit cathode biofouling using different loadings of silver nanoparticles (Ag-NPs) with 5% and 10% Ag in carbon black powder. In MFC without using Ag-NPs in cathode (MFC-C), cathode biofouling increased the charge transfer resistance (Rct) from 1710Ω.cm(2) to 2409Ω.cm(2), and reduced CE by 32%; whereas in MFC with 10% Ag in cathode Rct increased by only 5%. Power density of 7.9±0.5W/m(3) in MFC using 5% Ag and 9.8±0.3W/m(3) in MFC using 10% Ag in cathode was 4.6 and 5.7-folds higher than MFC-C. These results suggest that the Ag-NPs effectively inhibit the fungal biofouling on cathode surface of MFCs and enhanced the power recovery and CE by improving cathode kinetics.

  18. Suppressing the chromium disproportionation reaction in O3-type layered cathode materials for high capacity sodium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Ming-Hui; Wang, Yong; Shadike, Zulipiya; Yue, Ji-Li; Hu, Enyuan; Bak, Seong-Min; Zhou, Yong-Ning; Yang, Xiao-Qing; Fu, Zheng-Wen

    2017-01-01

    Chromium-based layered cathode materials suffer from the irreversible disproportionation reaction of Cr4+ to Cr3+ and Cr6+, which hinders the reversible multi-electron redox of Cr ions in layered cathodes, and limits their capacity and reversibility. To address this problem, a novel O3-type layer-structured transition metal oxide of NaCr1/3Fe1/3Mn1/3O2 (NCFM) was designed and studied as a cathode material. A high reversible capacity of 186 mA h g-1 was achieved at a current rate of 0.05C in a voltage range of 1.5 to 4.2 V. X-ray diffraction revealed an O3 → (O3 + P3) → (P3 + O3'') → O3'' phase-transition pathway for NCFM during charge. X-ray absorption, X-ray photoelectron and electron energy-loss spectroscopy measurements revealed the electronic structure changes of NCFM during Na+ deintercalation/intercalation processes. It is confirmed that the disproportionation reaction of Cr4+ to Cr3+ and Cr6+ can be effectively suppressed by Fe3+ and Mn4+ substitution. These results demonstrated that the reversible multi-electron oxidation/reduction of Cr ions can be achieved in NCFM during charge and discharge accompanied by CrO6 octahedral distortion and recovery.

  19. Imidazole-Functionalized Fullerene as a Vertically Phase-Separated Cathode Interfacial Layer of Inverted Ternary Polymer Solar Cells.

    Science.gov (United States)

    Li, Dan; Liu, Qing; Zhen, Jieming; Fang, Zhimin; Chen, Xiang; Yang, Shangfeng

    2017-01-25

    By using a facile one-pot nucleophilic addition reaction, we synthesized a novel imidazole (IMZ)-functionalized fullerene (C60-IMZ), and applied it as a third component of inverted ternary polymer solar cells (PSCs), leading to dramatic efficiency enhancement. According to FT-IR, XPS spectroscopic characterizations, and elemental analysis, the chemical structure of C60-IMZ was determined with the average IMZ addition number estimated to be six. The lowest unoccupied molecular orbital (LUMO) level of C60-IMZ measured by cyclic voltammetry was -3.63 eV, which is up-shifted relative to that of 6,6-phenyl C61-butyric acid methyl ester (PC61BM). Upon doping C60-IMZ as a third component into an active layer blend of poly(3-hexylthiophene) (P3HT) and PC61BM, the power conversion efficiency (PCE) of the inverted ternary PSCs was 3.4% under the optimized doping ratio of 10 wt %, dramatically higher than that of the control device ITO/P3HT:PC61BM/MoO3/Ag based on the binary P3HT:PC61BM blend (1.3%). The incorporation of C60-IMZ results in enhancement of the absorption of P3HT:PC61BM blend film, increase of the electron mobility of the device, and rougher film surface of the P3HT:PC61BM active layer beneficial for interfacial contact with the Ag anode. Furthermore, C60-IMZ doped in P3HT:PC61BM blend may migrate to the surface of ITO cathode via vertical phase separation as revealed by XPS depth analysis, consequently forming a cathode interfacial layer (CIL), which can lower the work function (WF) of ITO cathode. Thus, the interfacial contact between the active layer and ITO cathode is improved, facilitating electron transport from the active layer to ITO cathode. The effectiveness of C60-IMZ as a vertically phase-separated CIL on efficiency enhancement of inverted ternary PSCs is further verified by doping it into another active layer system comprised of a low-bandgap conjugated polymer, poly(thieno[3,4-b]-thiophene/benzodithiophene) (PTB7), blended with [6,6]-phenyl C71

  20. Optimization of the Energy Level Alignment between the Photoactive Layer and the Cathode Contact Utilizing Solution-Processed Hafnium Acetylacetonate as Buffer Layer for Efficient Polymer Solar Cells.

    Science.gov (United States)

    Yu, Lu; Li, Qiuxiang; Shi, Zhenzhen; Liu, Hao; Wang, Yaping; Wang, Fuzhi; Zhang, Bing; Dai, Songyuan; Lin, Jun; Tan, Zhan'ao

    2016-01-13

    The insertion of an appropriate interfacial buffer layer between the photoactive layer and the contact electrodes makes a great impact on the performance of polymer solar cells (PSCs). Ideal interfacial buffer layers could minimize the interfacial traps and the interfacial barriers caused by the incompatibility between the photoactive layer and the electrodes. In this work, we utilized solution-processed hafnium(IV) acetylacetonate (Hf(acac)4) as an effective cathode buffer layer (CBL) in PSCs to optimize the energy level alignment between the photoactive layer and the cathode contact, with the short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) all simultaneously improved with Hf(acac)4 CBL, leading to enhanced power conversion efficiencies (PCEs). Ultraviolet photoemission spectroscopy (UPS) and scanning Kelvin probe microscopy (SKPM) were performed to confirm that the interfacial dipoles were formed with the same orientation direction as the built-in potential between the photoactive layer and Hf(acac)4 CBL, benefiting the exciton separation and electron transport/extraction. In addition, the optical characteristics and surface morphology of the Hf(acac)4 CBL were also investigated.

  1. Solid Catalyst with Ionic Liquid Layer (SCILL). A concept to improve the selectivity of selective hydrogenations

    Energy Technology Data Exchange (ETDEWEB)

    Jess, A.; Korth, W. [Bayreuth Univ. (Germany). Chair of Chemical Engineering

    2011-07-01

    Catalytic hydrogenations are important for refinery processes, petrochemical applications as well as for numerous processes of the fine chemicals industry. In some cases, hydrogenations consist of a sequence of consecutive reactions, and the desired product is the intermediate. An important goal is then a high yield and selectivity to the intermediate, if possible at a high conversion degree. The selectivity to an intermediate primarily depends on the chemical nature of the catalyst, but may also be influenced by diffusion processes. Ionic liquids (ILs) are low melting salts (< 100 C) and represent a promising solvent class. This paper focuses on the concept of a Solid Catalyst with Ionic Liquid Layer (SCILL), where the solid catalyst is coated with a thin IL layer to improve the selectivity. (orig.)

  2. Optical characteristics of silicon nanowires grown from tin catalyst layers on silicon coated glass

    KAUST Repository

    Ball, Jeremy

    2012-08-20

    The optical characteristics of silicon nanowires grown on Si layers on glass have been modeled using the FDTD (Finite Difference Time Domain) technique and compared with experimental results. The wires were grown by the VLS (vapour-liquid-solid) method using Sn catalyst layers and exhibit a conical shape. The resulting measured and modeled absorption, reflectance and transmittance spectra have been investigated as a function of the thickness of the underlying Si layer and the initial catalyst layer, the latter having a strong influence on wire density. High levels of absorption (>90% in the visible wavelength range) and good agreement between the modeling and experiment have been observed when the nanowires have a relatively high density of ∼4 wires/μ m2. The experimental and modeled results diverge for samples with a lower density of wire growth. The results are discussed along with some implications for solar cell fabrication. © 2012 Optical Society of America.

  3. Catalyst-Free Bottom-Up Synthesis of Few-Layer Hexagonal Boron Nitride Nanosheets

    Directory of Open Access Journals (Sweden)

    Shena M. Stanley

    2015-01-01

    Full Text Available A novel catalyst-free methodology has been developed to prepare few-layer hexagonal boron nitride nanosheets using a bottom-up process. Scanning electron microscopy and transmission electron microscopy (both high and low resolution exhibit evidence of less than ten layers of nanosheets with uniform dimension. X-ray diffraction pattern and other additional characterization techniques prove crystallinity and purity of the product.

  4. Atomic to Nanoscale Investigation of Functionalities of an Al2O3 Coating Layer on a Cathode for Enhanced Battery Performance

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei; Zheng, Jianming; Zhang, Xiaofeng; Xu, Rui; Amine, Khalil; Xiao, J; Zhang, Ji-Guang; Wang, Chong-Min

    2016-02-09

    Surface coating has been identified as an effective approach for enhancing the capacity retention of layered structure cathode. However, the underlying operating mechanism of such a thin coating layer, in terms of surface chemical functionality and capacity retention, remains unclear. In this work, we use aberration-corrected scanning transmission electron microscopy and high-efficiency spectroscopy to probe the delicate functioning mechanism of an Al2O3 coating layer on a Li1.2Ni0.2Mn0.6O2 cathode. We discovered that in terms of surface chemical function, the Al2O3 coating suppresses the side reaction between the cathode and the electrolyte during battery cycling. At the same time, the Al2O3 coating layer also eliminates the chemical reduction of Mn from the cathode particle surface, therefore preventing the dissolution of the reduced Mn into the electrolyte. In terms of structural stability, we found that the Al2O3 coating layer can mitigate the layer to spinel phase transformation, which otherwise will be initiated from the particle surface and propagate toward the interior of the particle with the progression of battery cycling. The atomic to nanoscale effects of the coating layer observed here provide insight into the optimized design of a coating layer on a cathode to enhance the battery properties.

  5. A novel nano-sulfur/polypyrrole/graphene nanocomposite cathode with a dual-layered structure for lithium rechargeable batteries

    Science.gov (United States)

    Zhang, Yongguang; Zhao, Yan; Konarov, Aishuak; Gosselink, Denise; Soboleski, Hayden Greentree; Chen, P.

    2013-11-01

    A method for synthesizing nano-sulfur/polypyrrole/graphene nanosheet (nano-S/PPy/GNS) ternary composite with a dual-layered structure is described. By taking advantage of both capillary force driven self-assembly of polypyrrole on graphene nanosheets and adhesion ability of polypyrrole to sulfur, we develop a stable and ordered nano-S/PPy/GNS composite cathode for lithium/sulfur (Li/S) batteries. The high dispersion of nanoscopic sulfur on the surface of PPy/GNS composite and good electrical conductivity of GNS seems to benefit the sulfur utilization and the reactivity of the composite. Furthermore, PPy plays an important role in retarding diffusion of polysulfides out of the electrode. The resulting nano-S/PPy/GNS composite cathode delivers a high initial capacity of 1415.7 mAh g-1, remaining a reversible capacity of 641.5 mAh g-1 after 40 cycles at 0.1 C rate.

  6. Easy-to-operate and low-temperature synthesis of gram-scale nitrogen-doped graphene and its application as cathode catalyst in microbial fuel cells.

    Science.gov (United States)

    Feng, Leiyu; Chen, Yinguang; Chen, Lang

    2011-12-27

    Nitrogen-doped graphene (NG), with unique electronic properties, is showing great promise for a wide range of practical applications. However, the reported approaches for NG synthesis are usually complex, require high temperatures, produce lower atomic ratios of nitrogen to carbon (N/C), and do not deliver products in a reasonably large quantity. Here we report an easy-to-operate and low-temperature method to synthesize NG in gram-scale quantities with a denotation process. High-resolution transmission electron microscopy, Raman spectroscopy, and X-ray diffraction characterization suggested that the synthesized NG films were uniformly multilayered and had a high crystalline quality. In the graphene sheets the existence of nitrogen substitution with an atomic ratio of N/C 12.5%, which was greater than those reported in the literature, was confirmed by X-ray photoelectron spectroscopic analysis. In the neutral phosphate buffer solution, the synthesized NG was demonstrated to act as a metal-free electrode with excellent electrocatalytic activity and long-term operation stability for oxygen reduction via a combination of two-electron and four-electron pathways. When the NG was applied as the cathode catalyst of microbial fuel cells (MFCs), the obtained maximum power density was comparable to that of conventional platinum catalyst. More importantly, MFCs with NG produced power more stably and less expensively than those with Pt catalyst, indicating that the synthesized NG might be used as a good alternative to Pt catalyst in MFCs with a long run.

  7. Layered metal laurates as active catalysts in the methyl/ethyl esterification reactions of lauric acid

    Energy Technology Data Exchange (ETDEWEB)

    Lisboa, Fabio da Silva; Cordeiro, Claudiney S.; Wypych, Fernando, E-mail: wypych@ufpr.br [Centro de Pesquisas em Quimica Aplicada (CEPESQ), Departamento de Quimica, Universidade Federal do Parana, Curitiba, PR (Brazil); Gardolinski, Jose Eduardo F. da Costa [Laboratorio de Analise de Minerais e Rochas (LAMIR), Departamento de Geologia, Universidade Federal do Parana, Curitiba, PR (Brazil)

    2012-07-01

    In this work we report the synthesis, characterization and investigation of the catalytic activity of layered copper(II), manganese(II), lanthanum(III) and nickel(II) laurates in the methyl and ethyl esterification reactions of lauric acid. In the methyl esterification, conversions between 80 and 90% were observed for all catalysts, while for the ethyl esterification only manganese laurate showed reasonable catalytic activity, with conversions close to 75%. Reuse of copper and lanthanum laurates in three cycles of reaction was also investigated and both catalysts preserved the structure and retained catalytic activity close to that observed for the first reaction cycle. (author)

  8. Nano-nitride cathode catalysts of Ti, Ta, and Nb for polymer electrolyte fuel cells: Temperature-programmed desorption investigation of molecularly adsorbed oxygen at low temperature

    KAUST Repository

    Ohnishi, Ryohji

    2013-01-10

    TiN, NbN, TaN, and Ta3N5 nanoparticles synthesized using mesoporous graphitic (mpg)-C3N4 templates were investigated for the oxygen reduction reaction (ORR) as cathode catalysts for polymer electrolyte fuel cells. The temperature-programmed desorption (TPD) of molecularly adsorbed O2 at 120-170 K from these nanoparticles was examined, and the resulting amount and temperature of desorption were key factors determining the ORR activity. The size-dependent TiN nanoparticles (5-8 and 100 nm) were then examined. With decreasing particle size, the density of molecularly adsorbed O2 per unit of surface area increased, indicating that a decrease in particle size increases the number of active sites. It is hard to determine the electrochemical active surface area for nonmetal electrocatalysts (such as oxides or nitrides), because of the absence of proton adsorption/desorption peaks in the voltammograms. In this study, O2-TPD for molecularly adsorbed O2 at low temperature demonstrated that the amount and strength of adsorbed O2 were key factors determining the ORR activity. The properties of molecularly adsorbed O2 on cathode catalysts are discussed against the ORR activity. © 2012 American Chemical Society.

  9. Co3O4 nanoparticle-modified MnO2 nanotube bifunctional oxygen cathode catalysts for rechargeable zinc-air batteries

    Science.gov (United States)

    Du, Guojun; Liu, Xiaogang; Zong, Yun; Hor, T. S. Andy; Yu, Aishui; Liu, Zhaolin

    2013-05-01

    We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone.We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone. Electronic supplementary information (ESI) available: Zinc-air cell device, XPS survey scan and power density of the cell. See DOI: 10.1039/c3nr00300k

  10. Effects of cathode electrolyte interfacial (CEI) layer on long term cycling of all-solid-state thin-film batteries

    Science.gov (United States)

    Wang, Ziying; Lee, Jungwoo Z.; Xin, Huolin L.; Han, Lili; Grillon, Nathanael; Guy-Bouyssou, Delphine; Bouyssou, Emilien; Proust, Marina; Meng, Ying Shirley

    2016-08-01

    All-solid-state lithium-ion batteries have the potential to not only push the current limits of energy density by utilizing Li metal, but also improve safety by avoiding flammable organic electrolyte. However, understanding the role of solid electrolyte - electrode interfaces will be critical to improve performance. In this study, we conducted long term cycling on commercially available lithium cobalt oxide (LCO)/lithium phosphorus oxynitride (LiPON)/lithium (Li) cells at elevated temperature to investigate the interfacial phenomena that lead to capacity decay. STEM-EELS analysis of samples revealed a previously unreported disordered layer between the LCO cathode and LiPON electrolyte. This electrochemically inactive layer grew in thickness leading to loss of capacity and increase of interfacial resistance when cycled at 80 °C. The stabilization of this layer through interfacial engineering is crucial to improve the long term performance of thin-film batteries especially under thermal stress.

  11. A catalyst layer optimisation approach using electrochemical impedance spectroscopy for PEM fuel cells operated with pyrolysed transition metal-N-C catalysts

    Science.gov (United States)

    Malko, Daniel; Lopes, Thiago; Ticianelli, Edson A.; Kucernak, Anthony

    2016-08-01

    The effect of the ionomer to carbon (I/C) ratio on the performance of single cell polymer electrolyte fuel cells is investigated for three different types of non-precious metal cathodic catalysts. Polarisation curves as well as impedance spectra are recorded at different potentials in the presence of argon or oxygen at the cathode and hydrogen at the anode. It is found that a optimised ionomer content is a key factor for improving the performance of the catalyst. Non-optimal ionomer loading can be assessed by two different factors from the impedance spectra. Hence this observation could be used as a diagnostic element to determine the ideal ionomer content and distribution in newly developed catalyst-electrodes. An electrode morphology based on the presence of inhomogeneous resistance distribution within the porous structure is suggested to explain the observed phenomena. The back-pressure and relative humidity effect on this feature is also investigated and supports the above hypothesis. We give a simple flowchart to aid optimisation of electrodes with the minimum number of trials.

  12. A Spinel-integrated P2-type Layered Composite: High-rate Cathode for Sodium-ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jianming; Yan, Pengfei; Kan, Wang Hay; Wang, Chong M.; Manthiram, Arumugam

    2016-01-14

    Sodium-ion batteries (SIB) are being intensively investigated, owing to the natural abundance and low cost of Na resources. However, the SIBs still suffer from poor rate capability due to the large ionic radius of Na+ ion and the significant kinetic barrier to Na+-ion transport. Here, we present an Fd-3m spinel-integrated P2-type layered composite (P2 + Fd-3m) material as a high-rate cathode for SIBs. The P2 + Fd-3m composite material Na0.50Ni1/6Co1/6Mn2/3O2 shows significantly enhanced discharge capacity, energy density, and rate capability as compared to the pure P2-type counterpart. The composite delivers a high capacity of 85 mA h g-1 when discharging at a very high current density of 1500 mA g-1 (10C rate) between 2.0 and 4.5 V, validating it as a promising cathode candidate for high-power SIBs. The superior performance is ascribed to the improved kinetics in the presence of the integrated-spinel phase, which facilitates fast electron transport to coordinate with the timely Na+-ion insertion/extraction. The findings of this work also shed light on the importance of developing lattice doping, surface coating, and electrolyte additives to further improve the structural and interfacial stability of P2-type cathode materials and fully realize their practical applications in sodium-ion batteries.

  13. Growth of transition metals on cerium tungstate model catalyst layers

    Science.gov (United States)

    Skála, T.; Tsud, N.; Stetsovych, V.; Mysliveček, J.; Matolín, V.

    2016-10-01

    Two model catalytic metal/oxide systems were investigated by photoelectron spectroscopy and scanning tunneling microscopy. The mixed-oxide support was a cerium tungstate epitaxial thin layer grown in situ on the W(1 1 0) single crystal. Active particles consisted of palladium and platinum 3D islands deposited on the tungstate surface at 300 K. Both metals were found to interact weakly with the oxide support and the original chemical state of both support and metals was mostly preserved. Electronic and morphological changes are discussed during the metal growth and after post-annealing at temperatures up to 700 K. Partial transition-metal coalescence and self-cleaning from the CO and carbon impurities were observed.

  14. Atomic layer deposition overcoating: tuning catalyst selectivity for biomass conversion.

    Science.gov (United States)

    Zhang, Hongbo; Gu, Xiang-Kui; Canlas, Christian; Kropf, A Jeremy; Aich, Payoli; Greeley, Jeffrey P; Elam, Jeffrey W; Meyers, Randall J; Dumesic, James A; Stair, Peter C; Marshall, Christopher L

    2014-11-01

    The terraces, edges, and facets of nanoparticles are all active sites for heterogeneous catalysis. These different active sites may cause the formation of various products during the catalytic reaction. Here we report that the step sites of Pd nanoparticles (NPs) can be covered precisely by the atomic layer deposition (ALD) method, whereas the terrace sites remain as active component for the hydrogenation of furfural. Increasing the thickness of the ALD-generated overcoats restricts the adsorption of furfural onto the step sites of Pd NPs and increases the selectivity to furan. Furan selectivities and furfural conversions are linearly correlated for samples with or without an overcoating, though the slopes differ. The ALD technique can tune the selectivity of furfural hydrogenation over Pd NPs and has improved our understanding of the reaction mechanism. The above conclusions are further supported by density functional theory (DFT) calculations.

  15. Atomic-Resolution Visualization of Distinctive Chemical Mixing Behavior of Ni, Co and Mn with Li in Layered Lithium Transition-Metal Oxide Cathode Materials

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zheng, Jianming [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lv, Dongping [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wei, Yi [Peking Univ., Beijing (China); Zheng, Jiaxin [Peking Univ., Beijing (China); Wang, Zhiguo [Univ. of Electronic Science and Technology of China, Chengdu (China); Kuppan, Saravanan [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Yu, Jianguo [Idaho National Lab. (INL), Idaho Falls, ID (United States); Luo, Langli [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Edwards, Danny J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Olszta, Matthew J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Amine, Khalil [Argonne National Lab. (ANL), Argonne, IL (United States); Liu, Jun [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Xiao, Jie [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Pan, Feng [Peking Univ., Beijing (China); Chen, Guoying [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Zhang, Jiguang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wang, Chong M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-07-06

    Capacity and voltage fading of layer structured cathode based on lithium transition metal oxide is closely related to the lattice position and migration behavior of the transition metal ions. However, it is scarcely clear about the behavior of each of these transition metal ions. We report direct atomic resolution visualization of interatomic layer mixing of transition metal (Ni, Co, Mn) and lithium ions in layer structured oxide cathodes for lithium ion batteries. Using chemical imaging with aberration corrected scanning transmission electron microscope (STEM) and DFT calculations, we discovered that in the layered cathodes, Mn and Co tend to reside almost exclusively at the lattice site of transition metal (TM) layer in the structure or little interlayer mixing with Li. In contrast, Ni shows high degree of interlayer mixing with Li. The fraction of Ni ions reside in the Li layer followed a near linear dependence on total Ni concentration before reaching saturation. The observed distinctively different behavior of Ni with respect to Co and Mn provides new insights on both capacity and voltage fade in this class of cathode materials based on lithium and TM oxides, therefore providing scientific basis for selective tailoring of oxide cathode materials for enhanced performance.

  16. Physically adsorbed fullerene layer on positively charged sites on zinc oxide cathode affords efficiency enhancement in inverted polymer solar cell.

    Science.gov (United States)

    Cheng, Yu-Shan; Liao, Sih-Hao; Li, Yi-Lun; Chen, Show-An

    2013-07-24

    We present a novel idea for overcoming the drawback of poor contact between the ZnO cathode and active layer interface in an inverted polymer solar cell (i-PSC), simply by incorporating an electron-acceptor self-assembled monolayer (SAM)--tetrafluoroterephthalic acid (TFTPA)--on the ZnO cathode surface to create an electron-poor surface of TFTPA on ZnO. The TFTPA molecules on ZnO are anchored on the ZnO surface by reacting its carboxyl groups with hydroxyl groups on the ZnO surface, such that the tetrafluoroterephthalate moieties lay on the surface with plane-on electron-poor benzene rings acting as positive charge centers. Upon coating a layer of fullerenes on top of it, the fullerene molecules can be physically adsorbed by Coulombic interaction and facilitate a promoted electron collection from the bulk. The active layer is composed of the mid bandgap polymer poly(3-hexylthiophene) (P3HT) or low bandgap polymer, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl

  17. Multi-Directional Growth of Aligned Carbon Nanotubes Over Catalyst Film Prepared by Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Zhou Kai

    2010-01-01

    Full Text Available Abstract The structure of vertically aligned carbon nanotubes (CNTs severely depends on the properties of pre-prepared catalyst films. Aiming for the preparation of precisely controlled catalyst film, atomic layer deposition (ALD was employed to deposit uniform Fe2O3 film for the growth of CNT arrays on planar substrate surfaces as well as the curved ones. Iron acetylacetonate and ozone were introduced into the reactor alternately as precursors to realize the formation of catalyst films. By varying the deposition cycles, uniform and smooth Fe2O3 catalyst films with different thicknesses were obtained on Si/SiO2 substrate, which supported the growth of highly oriented few-walled CNT arrays. Utilizing the advantage of ALD process in coating non-planar surfaces, uniform catalyst films can also be successfully deposited onto quartz fibers. Aligned few-walled CNTs can be grafted on the quartz fibers, and they self-organized into a leaf-shaped structure due to the curved surface morphology. The growth of aligned CNTs on non-planar surfaces holds promise in constructing hierarchical CNT architectures in future.

  18. Layered transition metal carboxylates: efficient reusable heterogeneous catalyst for epoxidation of olefins.

    Science.gov (United States)

    Sen, Rupam; Bhunia, Susmita; Mal, Dasarath; Koner, Subratanath; Miyashita, Yoshitaro; Okamoto, Ken-Ichi

    2009-12-01

    Layered metal carboxylates [M(malonato)(H(2)O)(2)](n) (M = Ni(II) and Mn(II)) that have a claylike structure have been synthesized hydrothermally and characterized. The interlayer separation in these layered carboxylates is comparable to that of the intercalation distance of the naturally occurring clay materials or layered double hydroxides (LDHs). In this study, we have demonstrated that, instead of intercalating the metal complex into layers of the clay or LDH, layered transition metal carboxylates, [M(malonato)(H(2)O)(2)](n), as such can be used as a recyclable heterogeneous catalyst in olefin epoxidation reaction. Metal carboxylates [M(malonato)(H(2)O)(2)](n) exhibit excellent catalytic performance in olefin epoxidation reaction.

  19. Electrocatalysis for dioxygen reduction by a μ-oxo decavanadium complex in alkaline medium and its application to a cathode catalyst in air batteries

    Science.gov (United States)

    Dewi, Eniya Listiani; Oyaizu, Kenichi; Nishide, Hiroyuki; Tsuchida, Eishun

    The redox behavior of a decavanadium complex [(VO) 10(μ 2-O) 9(μ 3-O) 3(C 5H 7O 2) 6] ( 1) was studied using cyclic voltammetry under acidic and basic conditions. The reduction potential of V(V) was found at less positive potentials for higher pH electrolyte solutions. The oxygen reduction at complex 1 immobilized on a modified electrode was examined using cyclic voltammetry and rotating ring-disk electrode techniques in the 1 M KOH solutions. On the basis of measurements using a rotating disk electrode (RDE), the complex 1 was found to be highly active for the direct four-electron reduction of dioxygen at -0.2 V versus saturated calomel electrode (SCE). The complex 1 as a reduction catalyst of O 2 with a high selectivity was demonstrated using rotating ring-disk voltammograms in alkaline solutions. The application of complex 1 as an oxygen reduction catalyst at the cathode of zinc-air cell was also examined. The zinc-air cell with the modified electrode showed a stable discharge potential at approximately 1 V with discharge capacity of 80 mAh g -1 which was about five times larger than that obtained with the commonly used manganese dioxide catalyst.

  20. Improvement of Energy Capacity with Vitamin C Treated Dual-Layered Graphene-Sulfur Cathodes in Lithium-Sulfur Batteries.

    Science.gov (United States)

    Kim, Jin Won; Ocon, Joey D; Kim, Ho-Sung; Lee, Jaeyoung

    2015-09-07

    A graphene-based cathode design for lithium-sulfur batteries (LSB) that shows excellent electrochemical performance is proposed. The dual-layered cathode is composed of a sulfur active layer and a polysulfide absorption layer, and both layers are based on vitamin C treated graphene oxide at various degrees of reduction. By controlling the degree of reduction of graphene, the dual-layered cathode can increase sulfur utilization dramatically owing to the uniform formation of nanosized sulfur particles, the chemical bonding of dissolved polysulfides on the oxygen-rich sulfur active layer, and the physisorption of free polysulfides on the absorption layer. This approach enables a LSB with a high specific capacity of over 600 mAh gsulfur (-1) after 100 cycles even under a high current rate of 1C (1675 mA gsulfur (-1) ). An intriguing aspect of our work is the synthesis of a high-performance dual-layered cathode by a green chemistry method, which could be a promising approach to LSBs with high energy and power densities.

  1. Efficiency enhancement of polymer solar cells by applying poly(vinylpyrrolidone) as a cathode buffer layer via spin coating or self-assembly.

    Science.gov (United States)

    Wang, Haitao; Zhang, Wenfeng; Xu, Chenhui; Bi, Xianghong; Chen, Boxue; Yang, Shangfeng

    2013-01-01

    A non-conjugated polymer poly(vinylpyrrolidone) (PVP) was applied as a new cathode buffer layer in P3HT:PCBM bulk heterojunction polymer solar cells (BHJ-PSCs), by means of either spin coating or self-assembly, resulting in significant efficiency enhancement. For the case of incorporation of PVP by spin coating, power conversion efficiency (PCE) of the ITO/PEDOT:PSS/P3HT:PCBM/PVP/Al BHJ-PSC device (3.90%) is enhanced by 29% under the optimum PVP spin-coating speed of 3000 rpm, which leads to the optimum thickness of PVP layer of ~3 nm. Such an efficiency enhancement is found to be primarily due to the increase of the short-circuit current (J(sc)) (31% enhancement), suggesting that the charge collection increases upon the incorporation of a PVP cathode buffer layer, which originates from the conjunct effects of the formation of a dipole layer between P3HT:PCBM active layer and Al electrodes, the chemical reactions of PVP molecules with Al atoms, and the increase of the roughness of the top Al film. Incorporation of PVP layer by doping PVP directly into the P3HT:PCBM active layer leads to an enhancement of PCE by 13% under the optimum PVP doping ratio of 3%, and this is interpreted by the migration of PVP molecules to the surface of the active layer via self-assembly, resulting in the formation of the PVP cathode buffer layer. While the formation of the PVP cathode buffer layer is fulfilled by both fabrication methods (spin coating and self-assembly), the dependence of the enhancement of the device performance on the thickness of the PVP cathode buffer layer formed by self-assembly or spin coating is different, because of the different aggregation microstructures of the PVP interlayer.

  2. Improving performance and lifetime of small-molecule organic photovoltaic devices by using bathocuproine-fullerene cathodic layer.

    Science.gov (United States)

    Liu, Shun-Wei; Lee, Chih-Chien; Su, Wei-Cheng; Yuan, Chih-Hsien; Shu, Yi-Sheng; Chang, Wen-Chang; Guo, Jhih-Yan; Chiu, Chien-Feng; Li, Ya-Ze; Su, Tsung-Hao; Chen, Kuan-Ting; Chang, Po-Chien; Yeh, Tzu-Hung; Liu, Yu-Hsuan

    2015-05-06

    In this study, we compared the use of neat bathocuproine (BCP) and BCP:C60 mixed buffer layers in chloroboron subphthalocyanine (SubPc)/C60 bilayer organic photovoltaic (OPV) devices and analyzed their influence on device performance. Replacing the conventional BCP with BCP:C60 enabled manipulating the optical field distribution for optimizing the optical properties of the devices. Estimation of the interfacial barrier indicated that the insertion of the BCP:C60 between the C60 and electrode can effectively reduce the barrier for electrons and enhance electron collection at the electrode. Temperature-dependent measurements of the OPV devices performed to calculate the barrier height at the SubPc/C60 interface suggested that band bending was larger when the BCP:C60 buffer layer was used, reflecting increased exciton dissociation efficiency. In addition, the device lifetime was considerably improved when the BCP:C60 buffer layer was used. The device performance was stabilized after the photodegradation of the active layers, thereby increasing the device lifetime compared with the use of the neat BCP buffer layer. Atomic force microscopy images showed that the neat BCP was easily crystallized and could degrade the cathodic interface, whereas the blend of C60 and BCP suppressed the crystallization of BCP. Therefore, the optimal buffer layer improved both the device performance and the device lifetime.

  3. Effect of the semi-conductive properties of the passive layer on the current provided by stainless steel microbial cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Pons, Liz; Delia, Marie-Line; Basseguy, Regine [Laboratoire de Genie Chimique, CNRS - Universite de Toulouse, 4 allee Emile Monso BP 84234, 31030 Toulouse (France); Bergel, Alain, E-mail: alain.bergel@ensiacet.f [Laboratoire de Genie Chimique, CNRS - Universite de Toulouse, 4 allee Emile Monso BP 84234, 31030 Toulouse (France)

    2011-02-15

    Geobacter sulfurreducens biofilms were formed under constant polarisation at -0.6 V vs. Ag/AgCl on stainless steel cathodes to catalyse the reduction of fumarate. The time-evolution of the current strongly depended on the quality of the inoculum. Inoculating with young cells significantly shortened the initial lag-phase and using the same inoculum improved the reproducibility of the current-time curves. The whole set of experiments showed that 254SMO stainless steel provided higher current densities (on average 14.1 A/m{sup 2}) than biofilms formed on 316L stainless steel (on average 4.5 A/m{sup 2}). Biofilm coverage assessed by epifluorescent microscopy showed that coverage ratios were generally higher for 316L than for 254SMO. It must be concluded that 254SMO is more efficient in transferring electrons to bacterial cells than 316L. Mott-Schottky diagrams recorded on both materials under conditions of electrolysis in the absence of microorganisms showed that the surface oxide layers had similar n-type semi-conductive behaviour for potential values higher than the flat band potential. In contrast, 316L exhibited slight p-type behaviour at potential lower than the flat band potential, while 254SMO did not. The higher electrochemical performances of biocathodes formed on 254SMO are explained by semi-conductive properties of its passive layer, which prevented the p-type behaviour occurring in cathodic electrolysis conditions.

  4. Layered double hydroxide catalyst for the conversion of crude vegetable oils to a sustainable biofuel

    Science.gov (United States)

    Mollaeian, Keyvan

    Over the last two decades, the U.S. has developed the production of biodiesel, a mixture of fatty acid methyl esters, using chiefly vegetable oils as feedstocks. However, there is much concern about the availability of high-quality vegetable oils for longterm biodiesel production. Problems have also risen due to the production of glycerol, an unwanted byproduct, as well as the need for process wash water. Therefore, this study was initiated to produce not only fatty acid methyl esters (FAMEs) but also fatty acid glycerol carbonates (FAGCs) by replacing methanol with dimethyl carbonate (DMC). The process would have no unnecessary byproducts and would be a simplified process compared to traditional biodiesel. In addition, this altering of the methylating agent could convert triglycerides, free fatty acids, and phospholipids to a sustainable biofuel. In this project, Mg-Al Layered Double Hydroxide (LDH) was optimized by calcination in different temperature varied from 250°C to 450°C. The gallery between layers was increased by intercalating sodium dodecylsulfate (SDS). During catalyst preparation, the pH was controlled ~10. In our experiment, triazabicyclodecene (TBD) was attached with trimethoxysilane (3GPS) as a coupling agent, and N-cetyl-N,N,N-trimethylammonium bromide (CTAB) was added to remove SDS from the catalyst. The catalyst was characterized by XRD, FTIR, and Raman spectroscopy. The effect of the heterogeneous catalyst on the conversion of canola oil, corn oil, and free fatty acids was investigated. To analyze the conversion of lipid oils to biofuel an in situ Raman spectroscopic method was developed. Catalyst synthesis methods and a proposed mechanism for converting triglycerides and free fatty acids to biofuel will be presented.

  5. Understanding the effect of an in situ generated and integrated spinel phase on a layered Li-rich cathode material using a non-stoichiometric strategy.

    Science.gov (United States)

    Zhang, Jicheng; Gao, Rui; Sun, Limei; Li, Zhengyao; Zhang, Heng; Hu, Zhongbo; Liu, Xiangfeng

    2016-09-14

    Recently, spinel-layered integrated Li-rich cathode materials have attracted great interest due to the large enhancement of their electrochemical performances. However, the modification mechanism and the effect of the integrated spinel phase on Li-rich layered cathode materials are still not very clear. Herein, we have successfully synthesized the spinel-layered integrated Li-rich cathode material using a facile non-stoichiometric strategy (NS-LNCMO). The rate capability (84 mA h g(-1)vs. 28 mA h g(-1), 10 C), cycling stability (92.4% vs. 80.5%, 0.2 C), low temperature electrochemical capability (96.5 mA h g(-1)vs. 59 mA h g(-1), -20 °C), initial coulomb efficiency (92% vs. 79%) and voltage fading (2.77 V vs. 3.02 V, 200 cycles@1 C) of spinel-layered integrated Li-rich cathode materials have been significantly improved compared with a pure Li-rich phase cathode. Some new insights into the effect of the integrated spinel phase on a layered Li-rich cathode have been proposed through a comparison of the structure evolution of the integrated and Li-rich only materials before and after cycling. The Li-ion diffusion coefficient of NS-LNCMO has been enlarged by about 3 times and almost does not change even after 100 cycles indicating an enhanced structure stability. The integration of the spinel phase not only enhances the structure stability of the layered Li-rich phase during charging-discharging but also expands the interslab spacing of the Li-ion diffusion layer, and elongates TM-O covalent bond lengths, which lowers the activation barrier of Li(+)-transportation, and alleviates the structure strain during the cycling procedure.

  6. Hydrocarbon oxidation over catalysts prepared by the molecular layer deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Koltsov, S.I.; Smirnov, V.M.; Postnov, V.N.; Postnova, A.M.; Aleskovskii, V.B.

    1980-01-01

    By depositing consecutive uniform monolayers of phosphorus pentoxide and vanadium pentoxide on a large-surface-area (240 sq m/g) silica gel, active and selective catalysts for hydrocarbon oxidation were obtained. Thus, in piperylene oxidation by air at 330/sup 0/-430/sup 0/C and 2000-18,000/hr space velocity, a productive capacity of 220 g/l./hr with 41 mole % each maleic anhydride yield and selectivity was achieved over a SiO/sub 2/-P/sub 2/O/sub 5//P/sub 2/O/sub 5//V/sub 2/O/sub 5/ catalyst (120 sq cm/g surface area), compared with 80 g/l./hr for a P/sub 2/O/sub 5/-V/sub 2/O/sub 5/ catalyst prepared by impregnation. In benzene oxidation, maleic anhydride yields of 52 and 60% and selectivities of 63 and 79% were achieved over SiO/sub 2/-P/sub 2/O/sub 5//V/sub 2/O/sub 5/ and SiO/sub 2/-P/sub 2/O/sub 5//P/sub 2/O/sub 5//P/sub 2/O/sub 5//V/sub 2/O/sub 5/ catalysts, respectively, compared with a 6% yield and very low selectivity over the impregnated P/sub 2/O/sub 5/-V/sub 2/O/sub 5/ catalyst. The molecular-layer catalysts retained their total activity for 100 hr on stream and permitted to reduce the oxidation temperature by 50/sup 0/-70/sup 0/C.

  7. In situ grown carbon nanotubes on carbon paper as integrated gas diffusion and catalyst layer for proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Tang Zhe [Department of Materials Science and Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 117574 (Singapore); Poh, Chee Kok; Tian Zhiqun; Lin Jianyi [Institute of Chemical and Engineering Sciences, 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore); Ng, How Y. [Division of Environmental Science and Engineering, 9 Engineering Drive 2, Singapore 117576 (Singapore); Chua, Daniel H.C., E-mail: msechcd@nus.edu.s [Department of Materials Science and Engineering, National University of Singapore, 7 Engineering Drive 1, Singapore 117574 (Singapore)

    2011-04-15

    In situ grown carbon nanotubes (CNTs) on carbon paper as an integrated gas diffusion layer (GDL) and catalyst layer (CL) were developed for proton exchange membrane fuel cell (PEMFC) applications. The effect of their structure and morphology on cell performance was investigated under real PEMFC conditions. The in situ grown CNT layers on carbon paper showed a tunable structure under different growth processes. Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) demonstrated that the CNT layers are able to provide extremely high surface area and porosity to serve as both the GDL and the CL simultaneously. This in situ grown CNT support layer can provide enhanced Pt utilization compared with the carbon black and free-standing CNT support layers. An optimum maximum power density of 670 mW cm{sup -2} was obtained from the CNT layer grown under 20 cm{sup 3} min{sup -1} C{sub 2}H{sub 4} flow with 0.04 mg cm{sup -2} Pt sputter-deposited at the cathode. Furthermore, electrochemical impedance spectroscopy (EIS) results confirmed that the in situ grown CNT layer can provide both enhanced charge transfer and mass transport properties for the Pt/CNT-based electrode as an integrated GDL and CL, in comparison with previously reported Pt/CNT-based electrodes with a VXC72R-based GDL and a Pt/CNT-based CL. Therefore, this in situ grown CNT layer shows a great potential for the improvement of electrode structure and configuration for PEMFC applications.

  8. Sm1.5Sr0.5MO4 (M=Ni,Co,Fe) Cathode Catalysts for Ammonia Synthesis at Atmospheric Pressure and Low Temperature

    Institute of Scientific and Technical Information of China (English)

    XU,Gaochao; LIU,Ruiquan

    2009-01-01

    Sm1.5Sr0.5MO4 (M=Ni,Co,Fe) (SSM) catalysts were prepared by a sol-gel method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).Ammonia was synthesized from wet hydrogen and dry nitrogen at atmospheric pressure and low temperature (25-100 ℃) with applied voltage,using SSM as a cathode,Ni-Ce0.5Sm0.2O2-δ(Ni-SDC) as an anode,and silver-platinum film as a current collector,Nation proton exchange membrane as a proton permeating membrane.Several important factors on ammonia synthesis were investigated and the optimal synthetic temperature was found,at which the highest rate of evolution of ammonia was up to 1.05×10-8 mol·cm- 2·S-1.

  9. Self-Supporting Metal-Organic Layers as Single-Site Solid Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Lingyun; Lin, Zekai; Peng, Fei; Wang, Weiwei; Huang, Ruiyun; Wang, Cheng; Yan, Jiawei; Liang, Jie; Zhang, Zhiming; Zhang, Teng; Long, Lasheng; Sun, Junliang; Lin, Wenbin (StockholmU); (UC); (Xiamen)

    2016-03-08

    Metal–organic layers (MOLs) represent an emerging class of tunable and functionalizable two-dimensional materials. In this work, the scalable solvothermal synthesis of self-supporting MOLs composed of [Hf6O4(OH)4(HCO2)6] secondary building units (SBUs) and benzene-1,3,5-tribenzoate (BTB) bridging ligands is reported. The MOL structures were directly imaged by TEM and AFM, and doped with 4'-(4-benzoate)-(2,2',2''-terpyridine)-5,5''-dicarboxylate (TPY) before being coordinated with iron centers to afford highly active and reusable single-site solid catalysts for the hydrosilylation of terminal olefins. MOL-based heterogeneous catalysts are free from the diffusional constraints placed on all known porous solid catalysts, including metal–organic frameworks. This work uncovers an entirely new strategy for designing single-site solid catalysts and opens the door to a new class of two-dimensional coordination materials with molecular functionalities.

  10. Atomic layer deposited cobalt oxide: An efficient catalyst for NaBH{sub 4} hydrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Nandi, Dip K.; Manna, Joydev; Dhara, Arpan; Sharma, Pratibha; Sarkar, Shaibal K., E-mail: shaibal.sarkar@iitb.ac.in [Department of Energy Science and Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India)

    2016-01-15

    Thin films of cobalt oxide are deposited by atomic layer deposition using dicobalt octacarbonyl [Co{sub 2}(CO){sub 8}] and ozone (O{sub 3}) at 50 °C on microscope glass substrates and polished Si(111) wafers. Self-saturated growth mechanism is verified by x-ray reflectivity measurements. As-deposited films consist of both the crystalline phases; CoO and Co{sub 3}O{sub 4} that gets converted to pure cubic-Co{sub 3}O{sub 4} phase upon annealing at 500 °C under ambient condition. Elemental composition and uniformity of the films is examined by x-ray photoelectron spectroscopy and secondary ion-mass spectroscopy. Both as-deposited and the annealed films have been successfully tested as a catalyst for hydrogen evolution from sodium borohydride hydrolysis. The activation energy of the hydrolysis reaction in the presence of the as-grown catalyst is found to be ca. 38 kJ mol{sup −1}. Further implementation of multiwalled carbon nanotube, as a scaffold layer, improves the hydrogen generation rate by providing higher surface area of the deposited catalyst.

  11. Novel growth method of carbon nanotubes using catalyst-support layer developed by alumina grit blasting.

    Science.gov (United States)

    Watanabe, Hiromichi; Ishii, Juntaro; Ota, Keishin

    2016-08-19

    We propose an efficient method of growing carbon nanotube (CNT) arrays on a variety of metals, alloys, and carbon materials using chemical vapor deposition (CVD) assisted by a simple surface treatment of the materials. The main feature of this method is the application of grit blasting with fine alumina particles to the development of a catalyst-support layer required for the growth of CNTs on various conductive materials, including ultra-hard metals such as tungsten. Auger electron spectroscopy shows that grit blasting can form a non-continuous layer where alumina nanoparticles are embedded as residues in the blasting media left on the treated surfaces. This work reveals that such a non-continuous alumina layer can behave as the catalyst-support layer, which is generally prepared by sputter or a vacuum evaporation coating process that considerably restricts the practical applications of CNTs. We have attempted to grow CNTs on grit-blasted substrates of eighteen conventionally used conductive materials using CVD together with a floating iron catalyst. The proposed method was successful in growing multi-walled CNT arrays on the grit-blasted surfaces of all the examined materials, demonstrating its versatility. Furthermore, we found that the group IV metal oxide films thermally grown on the as-received substrates can support the catalytic activity of iron nanoparticles in the CVD process just as well as the alumina film developed by grit blasting. Spectral emissivity of the CNT arrays in the visible and infrared wavelength ranges has been determined to assess the applicability of the CNT arrays as a black coating media.

  12. Novel growth method of carbon nanotubes using catalyst-support layer developed by alumina grit blasting

    Science.gov (United States)

    Watanabe, Hiromichi; Ishii, Juntaro; Ota, Keishin

    2016-08-01

    We propose an efficient method of growing carbon nanotube (CNT) arrays on a variety of metals, alloys, and carbon materials using chemical vapor deposition (CVD) assisted by a simple surface treatment of the materials. The main feature of this method is the application of grit blasting with fine alumina particles to the development of a catalyst-support layer required for the growth of CNTs on various conductive materials, including ultra-hard metals such as tungsten. Auger electron spectroscopy shows that grit blasting can form a non-continuous layer where alumina nanoparticles are embedded as residues in the blasting media left on the treated surfaces. This work reveals that such a non-continuous alumina layer can behave as the catalyst-support layer, which is generally prepared by sputter or a vacuum evaporation coating process that considerably restricts the practical applications of CNTs. We have attempted to grow CNTs on grit-blasted substrates of eighteen conventionally used conductive materials using CVD together with a floating iron catalyst. The proposed method was successful in growing multi-walled CNT arrays on the grit-blasted surfaces of all the examined materials, demonstrating its versatility. Furthermore, we found that the group IV metal oxide films thermally grown on the as-received substrates can support the catalytic activity of iron nanoparticles in the CVD process just as well as the alumina film developed by grit blasting. Spectral emissivity of the CNT arrays in the visible and infrared wavelength ranges has been determined to assess the applicability of the CNT arrays as a black coating media.

  13. Investigating the performance of catalyst layer micro-structures with different platinum loadings

    Energy Technology Data Exchange (ETDEWEB)

    Khakaz-Baboli, Moben; Harvey, David; Pharoah, Jon

    2012-07-01

    In this study a four-phase micro-structure of a PEFC catalyst layer was reconstructed by randomly placing overlapping spheres for each solid catalyst phase. The micro-structure was mirrored to make a micro-structure. A body-fit computational mesh was produced for the reconstructed micro-structure in OpenFOAM. Associated conservation equations were solved within all the phases with electrochemical reaction as the boundary condition at the interface between ionomer and platinum phases. The study is focused on the platinum loading of CL. The polarization curves of the micro-structure performance have been compared for different platinum loadings. This paper gives increased insight into the relatively greater losses at decreased platinum loadings.

  14. Study of pyrolyzed hemin/C as non-platinum cathodic catalyst for direct methanol fuel cells

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Biological reduction of O2 to H2O justifies a serious look at heme as a potential O2 reduction reaction(ORR) catalyst for low temperature fuel cells.In this study,a novel non-platinum electrocatalyst for ORR was prepared through hemin,which is hydrochloride of heme,supported on Black Pearls 2000 carbon black(Hm-BP) pyrolyzed at 700-900℃ in Ar atmosphere.The physical and electrocatalytic properties of as-prepared catalysts were characterized by TGA,XRD,XPS,TEM,rotating disk electrode(RDE) and rotating ring disk electrode(RRDE).It has found that the catalyst treated at 750℃(Hm-BP-750) exhibits the best property among the Hm-BP catalysts prepared.The onset potential of ORR on the Hm-BP-750 at 30℃ was measured ca.0.90 V(vs.RHE) in 0.1 M H2SO4,and mass current density was reached 15.3 mA mg-1 at 0.75 V.It has revealed that O2 could be reduced directly to water in a 4e process between 0.9 and 0.83V,and the yield of H2O2 was 0-18% in the potential range of 0.83-0.63 V.This methanol-tolerant catalyst also presents excellent stability in medium-term test of direct methanol fuel cell at 80℃.

  15. Ca/Alq3 hybrid cathode buffer layer for the optimization of organic solar cells based on a planar heterojunction

    Science.gov (United States)

    El Jouad, Z.; Barkat, L.; Stephant, N.; Cattin, L.; Hamzaoui, N.; Khelil, A.; Ghamnia, M.; Addou, M.; Morsli, M.; Béchu, S.; Cabanetos, C.; Richard-Plouet, M.; Blanchard, P.; Bernède, J. C.

    2016-11-01

    Use of efficient anode cathode buffer layer (CBL) is crucial to improve the efficiency of organic photovoltaic cells. Here we show that using a double CBL, Ca/Alq3, allows improving significantly cell performances. The insertion of Ca layer facilitates electron harvesting and blocks hole collection, leading to improved charge selectivity and reduced leakage current, whereas Alq3 blocks excitons. After optimisation of this Ca/Alq3 CBL using CuPc as electron donor, it is shown that it is also efficient when SubPc is substituted to CuPc in the cells. In that case we show that the morphology of the SubPc layer, and therefore the efficiency of the cells, strongly depends on the deposition rate of the SubPc film. It is necessary to deposit slowly (0.02 nm/s) the SubPc films because at higher deposition rate (0.06 nm/s) the films are porous, which induces leakage currents and deterioration of the cell performances. The SubPc layers whose formations are kinetically driven at low deposition rates are more uniform, whereas those deposited faster exhibit high densities of pinholes.

  16. High-Performanced Cathode with a Two-Layered R-P Structure for Intermediate Temperature Solid Oxide Fuel Cells.

    Science.gov (United States)

    Huan, Daoming; Wang, Zhiquan; Wang, Zhenbin; Peng, Ranran; Xia, Changrong; Lu, Yalin

    2016-02-01

    Driven by the mounting concerns on global warming and energy crisis, intermediate temperature solid-oxide fuel cells (IT-SOFCs) have attracted special attention for their high fuel efficiency, low toxic gas emission, and great fuel flexibility. A key obstacle to the practical operation of IT-SOFCs is their sluggish oxygen reduction reaction (ORR) kinetics. In this work, we applied a new two-layered Ruddlesden-Popper (R-P) oxide, Sr3Fe2O7-δ (SFO), as the material for oxygen ion conducting IT-SOFCs. Density functional theory calculation suggested that SFO has extremely low oxygen ion formation energy and considerable energy barrier for O(2-) diffusion. Unfortunately, the stable SrO surface of SFO was demonstrated to be inert to O2 adsorption and dissociation reaction, and thus restricts its catalytic activity toward ORR. Based on this observation, Co partially substituted SFO (SFCO) was then synthesized and applied to improve its surface vacancy concentration to accelerate the oxygen adsorptive reduction reaction rate. Electrochemical performance results suggested that the cell using the SFCO single phase cathode has a peak power density of 685 mW cm(-2) at 650 °C, about 15% higher than those when using LSCF cathode. Operating at 200 mA cm(-2), the new cell using SFCO is quite stable within the 100-h' test.

  17. Measurement of a new parameter representing the gas transport properties of the catalyst layers of polymer electrolyte fuel cells.

    Science.gov (United States)

    Iden, Hiroshi; Ohma, Atsushi; Tokunaga, Tomomi; Yokoyama, Kouji; Shinohara, Kazuhiko

    2016-05-14

    The optimization of the catalyst layers is necessary for obtaining a better fuel cell performance and reducing fuel cell cost. Although the ionomer coverage of the Pt catalyst is said to be a key parameter in this regard, the proportion of Pt either directly or indirectly covered by the ionomer is thought to be an important parameter with regard to gas transport (indirectly covered Pt: its gas transport paths are completely blocked by the ionomer even if it does not directly cover Pt). In this study, a new technique has been developed for evaluating the proportion of Pt covered indirectly or directly by the ionomer, which is defined as the "capped proportion", based on the carbon monoxide (CO) adsorption properties at different temperatures. The validity of the method was thoroughly examined by identifying the CO adsorption properties of the components of the catalyst layers. The capped proportion and oxygen transport resistance in the catalyst layers showed a good correlation, indicating that the capped proportion is a dominant factor of oxygen transport resistance. This technique thus enables the evaluation of the dominant factor of the gas transport properties of the catalyst layers. The method has another significant advantage in that it does not require a membrane electrode assembly, let alone electrochemical measurement, which should be helpful for catalyst layer optimization.

  18. Metal-free selenium doped carbon nanotube/graphene networks as a synergistically improved cathode catalyst for oxygen reduction reaction

    Science.gov (United States)

    Jin, Zhiping; Nie, Huagui; Yang, Zhi; Zhang, Jing; Liu, Zheng; Xu, Xiangju; Huang, Shaoming

    2012-09-01

    The ongoing search for new non-precious-metal catalysts (NPMCs) with excellent electrocatalytic performance to replace Pt-based catalysts has been viewed as an important strategy to promote the development of fuel cells. Recent studies have proven that carbon materials doped with atoms which have a relatively small atomic size (e.g. N, B, P or S), have also shown pronounced catalytic activity. Herein, we demonstrate the successful fabrication of CNT/graphene doped with Se atoms, which has a relatively large atomic size, by a simple, economical, and scalable approach. The electrocatalytic performance of the resulting Se-doped CNT-graphene catalyst exhibits excellent catalytic activity, long-term stability, and a high methanol tolerance compared to commercial Pt/C catalysts. Our results confirmed that combining CNTs with graphene is an effective strategy to synergistically improve ORR activity. More importantly, it is also suggested that the development of graphite materials doped with Se or other heteroatoms of large size will open up a new route to obtain ideal NPMCs with realistic value for fuel cell applications.The ongoing search for new non-precious-metal catalysts (NPMCs) with excellent electrocatalytic performance to replace Pt-based catalysts has been viewed as an important strategy to promote the development of fuel cells. Recent studies have proven that carbon materials doped with atoms which have a relatively small atomic size (e.g. N, B, P or S), have also shown pronounced catalytic activity. Herein, we demonstrate the successful fabrication of CNT/graphene doped with Se atoms, which has a relatively large atomic size, by a simple, economical, and scalable approach. The electrocatalytic performance of the resulting Se-doped CNT-graphene catalyst exhibits excellent catalytic activity, long-term stability, and a high methanol tolerance compared to commercial Pt/C catalysts. Our results confirmed that combining CNTs with graphene is an effective strategy to

  19. Understanding Voltage Decay in Lithium-Rich Manganese-Based Layered Cathode Materials by Limiting Cutoff Voltage.

    Science.gov (United States)

    Yang, Jingsong; Xiao, Lifen; He, Wei; Fan, Jiangwei; Chen, Zhongxue; Ai, Xinping; Yang, Hanxi; Cao, Yuliang

    2016-07-27

    The effect of the cutoff voltages on the working voltage decay and cyclability of the lithium-rich manganese-based layered cathode (LRMO) was investigated by electrochemical measurements, electrochemical impedance spectroscopy, ex situ X-ray diffraction, transmission electron microscopy, and energy dispersive spectroscopy line scan technologies. It was found that both lower (2.0 V) and upper (4.8 V) cutoff voltages cause severe voltage decay with cycling due to formation of the spinel phase and migration of the transition metals inside the particles. Appropriate cutoff voltage between 2.8 and 4.4 V can effectively inhibit structural variation as the electrode demonstrates 92% capacity retention and indiscernible working voltage decay over 430 cycles. The results also show that phase transformation not only on high charge voltage but also on low discharge voltage should be addressed to obtain highly stable LRMO materials.

  20. Multi-variable mathematical models for the air-cathode microbial fuel cell system

    Science.gov (United States)

    Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

    2016-05-01

    This research adopted the version control system into the model construction for the single chamber air-cathode microbial fuel cell (MFC) system, to understand the interrelation of biological, chemical, and electrochemical reactions. The anodic steady state model was used to consider the chemical species diffusion and electric migration influence to the MFC performance. In the cathodic steady state model, the mass transport and reactions in a multi-layer, abiotic cathode and multi-bacteria cathode biofilm were simulated. Transport of hydroxide was assumed for cathodic pH change. This assumption is an alternative to the typical notion of proton consumption during oxygen reduction to explain elevated cathode pH. The cathodic steady state model provided the power density and polarization curve performance results that can be compared to an experimental MFC system. Another aspect considered was the relative contributions of platinum catalyst and microbes on the cathode to the oxygen reduction reaction (ORR). Simulation results showed that the biocatalyst in a cathode that includes a Pt/C catalyst likely plays a minor role in ORR, contributing up to 8% of the total power calculated by the models.

  1. Enhanced catalytic activity and inhibited biofouling of cathode in microbial fuel cells through controlling hydrophilic property

    Science.gov (United States)

    Li, Da; Liu, Jia; Wang, Haiman; Qu, Youpeng; Zhang, Jie; Feng, Yujie

    2016-11-01

    The hydrophilicity of activated carbon cathode directly determines the distribution of three-phase interfaces where oxygen reduction occurs. In this study, activated carbon cathodes are fabricated by using hydrophobic polytetrafluoroethylene (PTFE) and amphiphilic LA132 at various weight ratio to investigate the effect of hydrophilic property on cathode performance. Contact angle tests confirm the positive impact of LA132 content on hydrophilicity. Cathode with 67 wt% LA132 content shows the highest electrochemical activity as exchange current density increases by 71% and charge transfer resistance declines by 44.6% compared to that of PTFE cathode, probably due to the extended reaction interfaces by optimal hydrophilicity of cathode so that oxygen reduction is facilitated. As a result, the highest power density of 1171 ± 71 mW m-2 is obtained which is 14% higher than PTFE cathode. In addition to the hydrophilicity, this cathode had more negative charged surface of catalyst layer, therefore the protein content of cathodic biofilm decreased by 47.5%, indicating the effective bacterial inhibition when 67 wt% LA132 is used. This study shows that the catalytic activity of cathode is improved by controlling proper hydrophilicity of cathode, and that biofilm can be reduced by increasing hydrophilicity and lowering the surface potential.

  2. Surface and bulk modified high capacity layered oxide cathodes with low irreversible capacity loss

    Science.gov (United States)

    Manthiram, Arumugam (Inventor); Wu, Yan (Inventor)

    2010-01-01

    The present invention includes compositions, surface and bulk modifications, and methods of making of (1-x)Li[Li.sub.1/3Mn.sub.2/3]O.sub.2.xLi[Mn.sub.0.5-yNi.sub.0.5-yCo.sub.2- y]O.sub.2 cathode materials having an O3 crystal structure with a x value between 0 and 1 and y value between 0 and 0.5, reducing the irreversible capacity loss in the first cycle by surface modification with oxides and bulk modification with cationic and anionic substitutions, and increasing the reversible capacity to close to the theoretical value of insertion/extraction of one lithium per transition metal ion (250-300 mAh/g).

  3. Catalytic characterization of bi-functional catalysts derived from Pd–Mg–Al layered double hydroxides

    Indian Academy of Sciences (India)

    N N Das; S C Srivastava

    2002-08-01

    Hydrotalcite like precursors containing PdII–MgII–AlIII with varying molar ratios, (Pd + Mg)/Al ≈ 3 and Mg/Pd ≈ 750 to 35, were prepared by coprecipitation of metal nitrates at constant pH. Characterization of samples as synthesized and their calcined products by elemental analyses, powder XRD, TG–DTA, FT–IR spectroscopy, TPR and N2 physisorption indicated a well crystalline hydrotalcite like structure with incorporation of Pd2+ in the brucite layers. Thermal decomposition of hydrotalcite precursors at intermediate temperatures led to amorphous mixed oxides, Pd/MgAl(O), which on reduction yielded bi-functional catalyst, Pd°/MgAl(O). The resultant catalysts with acid, base and hydrogenating sites, were highly active and selective for one-step synthesis of methyl isobutyl ketone (MIBK) from acetone and hydrogen. The results showed an optimal balance between acid-base and metallic sites were required to increase the selectivity of MIBK and stability of the catalysts.

  4. Composition and Morphology of Product Layers in the Steel/Cement Paste Interface in Conditions of Corrosion and Cathodic Protection in Reinforced Concrete

    NARCIS (Netherlands)

    Koleva, D.A.; Van Breugel, K.; De Wit, J.H.W.; Fraaij, A.L.A.; Boshkov, N.

    2007-01-01

    The present study explores the formation of corrosion products on the steel surface in reinforced concrete in conditions of corrosion and subsequent transformation of these layers in conditions of cathodic protection (CP). Of particular interest was to investigate if the introduced pulse CP (as cost

  5. Fundamental Investigations and Rational Design of Durable High-Performance SOFC Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yu [Georgia Inst. of Technology, Atlanta, GA (United States); Ding, Dong [Georgia Inst. of Technology, Atlanta, GA (United States); Wei, Tao [Georgia Inst. of Technology, Atlanta, GA (United States); Liu, Meilin [Georgia Inst. of Technology, Atlanta, GA (United States)

    2016-03-31

    The main objective of this project is to unravel the degradation mechanism of LSCF cathodes under realistic operating conditions with different types of contaminants, aiming towards the rational design of cathodes with high-performance and enhanced durability by combining a porous backbone (such as LSCF) with a thin catalyst coating. The mechanistic understanding will help us to optimize the composition and morphology of the catalyst layer and microstructure of the LSCF backbone for better performance and durability. More specifically, the technical objectives include: (1) to unravel the degradation mechanism of LSCF cathodes under realistic operating conditions with different types of contaminants using in situ and ex situ measurements performed on specially-designed cathodes; (2) to examine the microstructural and compositional evolution of LSCF cathodes as well as the cathode/electrolyte interfaces under realistic operating conditions; (3) to correlate the fuel cell performance instability and degradation with the microstructural and morphological evolution and surface chemistry change of the cathode under realistic operating conditions; (4) to explore new catalyst materials and electrode structures to enhance the stability of the LSCF cathode under realistic operating conditions; and (5) to validate the long term stability of the modified LSCF cathode in commercially available cells under realistic operating conditions. We have systematically evaluated LSCF cathodes in symmetrical cells and anode supported cells under realistic conditions with different types of contaminants such as humidity, CO2, and Cr. Electrochemical models for the design of test cells and understanding of mechanisms have been developed for the exploration of fundamental properties of electrode materials. It is demonstrated that the activity and stability of LSCF cathodes can be degraded by the introduction of contaminants. The microstructural and compositional evolution of LSCF

  6. A Transient Model for Fuel Cell Cathode-Water Propagation Behavior inside a Cathode after a Step Potential

    Directory of Open Access Journals (Sweden)

    Der-Sheng Chan

    2010-04-01

    Full Text Available Most of the voltage losses of proton exchange membrane fuel cells (PEMFC are due to the sluggish kinetics of oxygen reduction on the cathode and the low oxygen diffusion rate inside the flooded cathode. To simulate the transient flooding in the cathode of a PEMFC, a transient model was developed. This model includes the material conservation of oxygen, vapor, water inside the gas diffusion layer (GDL and micro-porous layer (MPL, and the electrode kinetics in the cathode catalyst layer (CL. The variation of hydrophobicity of each layer generated a wicking effect that moves water from one layer to the other. Since the GDL, MPL, and CL are made of composite materials with different hydrophilic and hydrophobic properties, a linear function of saturation was used to calculate the wetting contact angle of these composite materials. The balance among capillary force, gas/liquid pressure, and velocity of water in each layer was considered. Therefore, the dynamic behavior of PEMFC, with saturation transportation taken into account, was obtained in this study. A step change of the cell voltage was used to illustrate the transient phenomena of output current, water movement, and diffusion of oxygen and water vapor across the entire cathode.

  7. Power generation by packed-bed air-cathode microbial fuel cells

    KAUST Repository

    Zhang, Xiaoyuan

    2013-08-01

    Catalysts and catalyst binders are significant portions of the cost of microbial fuel cell (MFC) cathodes. Many materials have been tested as aqueous cathodes, but air-cathodes are needed to avoid energy demands for water aeration. Packed-bed air-cathodes were constructed without expensive binders or diffusion layers using four inexpensive carbon-based materials. Cathodes made from activated carbon produced the largest maximum power density of 676±93mW/m2, followed by semi-coke (376±47mW/m2), graphite (122±14mW/m2) and carbon felt (60±43mW/m2). Increasing the mass of activated carbon and semi-coke from 5 to ≥15g significantly reduced power generation because of a reduction in oxygen transfer due to a thicker water layer in the cathode (~3 or ~6cm). These results indicate that a thin packed layer of activated carbon or semi-coke can be used to make inexpensive air-cathodes for MFCs. © 2013 Elsevier Ltd.

  8. A facile cathode design combining Ni-rich layered oxides with Li-rich layered oxides for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Song, Bohang; Li, Wangda; Yan, Pengfei; Oh, Seung-Min; Wang, Chong-Min; Manthiram, Arumugam

    2016-09-01

    A facile synthesis method was developed to prepare xLi2MnO3·(1-x)LiNi0.7Co0.15Mn0.15O2 (x = 0, 0.03, 0.07, 0.10, 0.20, and 0.30 as molar ratio) cathode materials, combining the advantages of high specific capacity from Ni-rich layered phase and surface chemical stability from Li-rich layered phase. X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM) and electrochemical charge/discharge performance confirm the formation of a Li-rich layered phase with C2/m symmetry. Most importantly, high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) reveals a spatial relationship that Li-rich nano-domain islands are integrated into a conventional Ni-rich layered matrix (R$\\bar{3}$m). This is the first time that Li-rich phase has been directly observed inside a particle at the nano-scale, when the overall composition of layered compounds (Li1+δNixMnyM1-x-y-δO2, M refers to transition metal elements) is Ni-rich (x > 0.5) rather than Mn-rich (y > 0.5). Remarkably, xLi2MnO3·(1-x)LiNi0.7Co0.15Mn0.15O2 cathode with optimized x value shows superior electrochemical performance at C/3, i.e., 170 mA h g-1 with 90.3 % of capacity retention after 400 cycles at 25 °C and 164 mA h g-1 with 81.3 % capacity retention after 200 cycles at 55 °C.

  9. Graphene layer encapsulated metal nanoparticles as a new type of non-precious metal catalysts for oxygen reduction

    DEFF Research Database (Denmark)

    Hu, Yang; Zhong, Lijie; Jensen, Jens Oluf

    2016-01-01

    Cheap and efficient non-precious metal catalysts for oxygen reduction have been a focus of research in the field of low-temperature fuel cells. This review is devoted to a brief summary of the recent work on a new type of catalysts, i.e., the graphene layer encapsulated metal nanoparticles....... The discussion is focused on the synthesis, structure, mechanism, performance, and further research....

  10. Intragranular Cracking as a Critical Barrier For High-voltage Usage of Layer-structured Cathode for Lithium-ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei; Zheng, Jianming; Gu, Meng; Xiao, Jie; Zhang, Jiguang; Wang, Chongmin

    2017-01-16

    LiNi1/3Mn1/3Co1/3O2 (NMC333) layered cathode is often fabricated as secondary particles of consisting of densely packed primary particles, which offers advantage of high energy density and alleviation of cathode side reactions/corrosions, but introduces other drawbacks, such as intergranular cracking. Here, we report unexpected observations on the nucleation and growth of intragranular cracks in the commercial NMC333 layered cathode by using advanced S/TEM. We found that the formation of the intragranular cracks is directly associated with high voltage cycling, which is an electrochemically driven and diffusion controlled process. The intragranular cracks were noticed to be characteristically initiated from grain interior, a consequence of dislocation based crack incubation mechanism. This observation is in sharp contrast with the general theoretical models, predicting the initiation of intragranular cracks from grain boundaries or particle surface. Our study indicates that maintain a structural stability is the key step toward high voltage operation of layered cathode materials.

  11. Evaluation of a cathode gas channel with a water absorption layer/waste channel in a PEFC by using visualization technique

    Energy Technology Data Exchange (ETDEWEB)

    Sugiura, Kimihiko; Nakata, Motoki; Yodo, Tadakatsu; Nishiguchi, Yusuke; Yamauchi, Makoto [Osaka Prefectural College of Technology, 26-12 Saiwai, Neyagawa, Osaka 572-8572 (Japan); Itoh, Yasuhiko [SANYO Electric Co., Ltd., 1-1-1 Sakata, Oizumi-machi, Ora-gun, Gunma 370-0596 (Japan)

    2005-08-18

    The polymer electrolyte fuel cell (PEFC) cathode is a performance-limiting component due to the slower oxygen reduction kinetics and mass transport limitations imposed by water generated in an electrochemical reaction. This water assists the performance of the PEFC by preventing drying of the polymer electrolyte. Conversely, the water hinders the transport of the reactant species by blocking the pores in the gas diffusion layer. Moreover, the effective electrode area is decreased, causing the cathode channel to become clogged with supersaturated water from the gas diffusion layer. This problem is overcome by separating the gas channel and the waste channel, and installing a water absorption layer (WAL). The new 'WAL type' gas channel has an installed WAL in which the designed waste channel is compared with the gas flow characteristics of a conventional cathode gas channel by using the visualization technique. Gas flowing into the WAL type separator is barely blocked before the WAL absorbs water condensed in the cathode gas channel. Therefore, the WAL type separator effectively improves the PEFC performance. (author)

  12. Interface control of atomic layer deposited oxide coatings by filtered cathodic arc deposited sublayers for improved corrosion protection

    Energy Technology Data Exchange (ETDEWEB)

    Härkönen, Emma, E-mail: emma.harkonen@helsinki.fi [Laboratory of Inorganic Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki (Finland); Tervakangas, Sanna; Kolehmainen, Jukka [DIARC-Technology Inc., Espoo (Finland); Díaz, Belén; Światowska, Jolanta; Maurice, Vincent; Seyeux, Antoine; Marcus, Philippe [Laboratoire de Physico-Chimie des Surfaces, CNRS (UMR 7075) – Chimie ParisTech (ENSCP), F-75005 Paris (France); Fenker, Martin [FEM Research Institute, Precious Metals and Metals Chemistry, D-73525 Schwäbisch Gmünd (Germany); Tóth, Lajos; Radnóczi, György [Research Centre for Natural Sciences HAS, (MTA TKK), Budapest (Hungary); Ritala, Mikko [Laboratory of Inorganic Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki (Finland)

    2014-10-15

    Sublayers grown with filtered cathodic arc deposition (FCAD) were added under atomic layer deposited (ALD) oxide coatings for interface control and improved corrosion protection of low alloy steel. The FCAD sublayer was either Ta:O or Cr:O–Ta:O nanolaminate, and the ALD layer was Al{sub 2}O{sub 3}–Ta{sub 2}O{sub 5} nanolaminate, Al{sub x}Ta{sub y}O{sub z} mixture or graded mixture. The total thicknesses of the FCAD/ALD duplex coatings were between 65 and 120 nm. Thorough analysis of the coatings was conducted to gain insight into the influence of the FCAD sublayer on the overall coating performance. Similar characteristics as with single FCAD and ALD coatings on steel were found in the morphology and composition of the duplex coatings. However, the FCAD process allowed better control of the interface with the steel by reducing the native oxide and preventing its regrowth during the initial stages of the ALD process. Residual hydrocarbon impurities were buried in the interface between the FCAD layer and steel. This enabled growth of ALD layers with improved electrochemical sealing properties, inhibiting the development of localized corrosion by pitting during immersion in acidic NaCl and enhancing durability in neutral salt spray testing. - Highlights: • Corrosion protection properties of ALD coatings were improved by FCAD sublayers. • The FCAD sublayer enabled control of the coating-substrate interface. • The duplex coatings offered improved sealing properties and durability in NSS. • The protective properties were maintained during immersion in a corrosive solution. • The improvements were due to a more ideal ALD growth on the homogeneous FCAD oxide.

  13. Influence of Ni Catalyst Layer and TiN Diffusion Barrier on Carbon Nanotube Growth Rate

    Directory of Open Access Journals (Sweden)

    Mérel Philippe

    2010-01-01

    Full Text Available Abstract Dense, vertically aligned multiwall carbon nanotubes were synthesized on TiN electrode layers for infrared sensing applications. Microwave plasma-enhanced chemical vapor deposition and Ni catalyst were used for the nanotubes synthesis. The resultant nanotubes were characterized by SEM, AFM, and TEM. Since the length of the nanotubes influences sensor characteristics, we study in details the effects of changing Ni and TiN thickness on the physical properties of the nanotubes. In this paper, we report the observation of a threshold Ni thickness of about 4 nm, when the average CNT growth rate switches from an increasing to a decreasing function of increasing Ni thickness, for a process temperature of 700°C. This behavior is likely related to a transition in the growth mode from a predominantly “base growth” to that of a “tip growth.” For Ni layer greater than 9 nm the growth rate, as well as the CNT diameter, variations become insignificant. We have also observed that a TiN barrier layer appears to favor the growth of thinner CNTs compared to a SiO2 layer.

  14. Elucidating the degradation mechanism of the cathode catalyst of PEFCs by a combination of electrochemical methods and X-ray fluorescence spectroscopy.

    Science.gov (United States)

    Monzó, J; van der Vliet, D F; Yanson, A; Rodriguez, P

    2016-08-10

    In this study, we report a methodology which enables the determination of the degradation mechanisms responsible for catalyst deterioration under different accelerated stress protocols (ASPs) by combining measurements of the electrochemical surface area (ECSA) and Pt content (by X-ray fluorescence). The validation of this method was assessed on high surface area unsupported Pt nanoparticles (Pt-NPs), Pt nanoparticles supported on TaC (Pt/TaC) and Pt nanoparticles supported on Vulcan carbon (Pt/Vulcan). In the load cycle protocol, the degradation of Pt-NPs and Pt/Vulcan follows associative processes (e.g. agglomeration) in the first 2000 cycles, however, in successive cycles the degradation goes through dissociative processes such as Pt dissolution, as is evident from a similar decay of ECSA and Pt content. In contrast, the degradation mechanism for Pt nanoparticles dispersed on TaC occurs continuously through the dissociative processes (e.g. Pt dissolution or particle detachment), with similar decay rates of both Pt content and ECSA. In the start-up/shut-down protocol, high surface area Pt-NPs follow associative processes (e.g. Ostwald ripening) in the first 4000 cycles, after which the degradation continues through dissociative processes. On the other hand, dissociative mechanisms always govern the degradation of Pt/TaC under start-up/shut-down protocol conditions. Finally, we report that Pt nanoparticles supported on TaC exhibit the highest catalytic activity and long term durability of the three nanoparticle systems tested. This makes Pt/TaC a potentially valuable catalyst system for application in polymer electrolyte fuel cell cathodes.

  15. The Effect of a CGO Barrier Layer on the Performance of LSM/YSZ SOFC Cathodes

    DEFF Research Database (Denmark)

    Kammer Hansen, Kent; Menon, Mohan; Knudsen, Jesper

    2010-01-01

    by spin coating. Electrochemical impedance spectroscopy (EIS) was used to evaluate the performance of the LSM/YSZ composite electrodes. It was shown that the CGO barrier layer affects both the performance of the LSM/YSZ composite electrodes and the series resistance of the cells. This indicates...

  16. A stable lithium-rich surface structure for lithium-rich layered cathode materials

    Science.gov (United States)

    Kim, Sangryun; Cho, Woosuk; Zhang, Xiaobin; Oshima, Yoshifumi; Choi, Jang Wook

    2016-11-01

    Lithium ion batteries are encountering ever-growing demand for further increases in energy density. Li-rich layered oxides are considered a feasible solution to meet this demand because their specific capacities often surpass 200 mAh g-1 due to the additional lithium occupation in the transition metal layers. However, this lithium arrangement, in turn, triggers cation mixing with the transition metals, causing phase transitions during cycling and loss of reversible capacity. Here we report a Li-rich layered surface bearing a consistent framework with the host, in which nickel is regularly arranged between the transition metal layers. This surface structure mitigates unwanted phase transitions, improving the cycling stability. This surface modification enables a reversible capacity of 218.3 mAh g-1 at 1C (250 mA g-1) with improved cycle retention (94.1% after 100 cycles). The present surface design can be applied to various battery electrodes that suffer from structural degradations propagating from the surface.

  17. Nb-doped TiO2 cathode catalysts for oxygen reduction reaction of polymer electrolyte fuel cells

    KAUST Repository

    Arashi, Takuya

    2014-09-01

    Nb-doped TiO2 particles were studied as electrocatalysts for the oxygen reduction reaction (ORR) under acidic conditions. The Nb-doped TiN nanoparticles were first synthesized by meso-porous C3N4 and then fully oxidized to Nb-doped TiO2 by immersing in 0.1 M H 2SO4 at 353 K for 24 h. Although the ORR activity of the as-obtained sample was low, a H2 treatment at relatively high temperature (1173 K) dramatically improved the ORR performance. An onset potential as high as 0.82 VRHE was measured. No degradation of the catalysts was observed during the oxidation-reduction cycles under the ORR condition for over 127 h. H2 treatment at temperatures above 1173 K caused the formation of a Ti4O7 phase, resulting in a decrease in ORR current. Elemental analysis indicated that the Nb-doped TiO 2 contained 25 wt% residual carbon. Calcination in air at 673 or 973 K eliminated the residual carbon in the catalyst, which was accompanied by a dramatic decrease in ORR activity. This post-calcination process may reduce the conductivity of the sample by filling the oxygen vacancies, and the carbon residue in the particle aggregates may enhance the electrocatalytic activity for ORR. The feasibility of using conductive oxide materials as electrocatalysts is discussed. © 2013 Elsevier B.V.

  18. A novel (ex situ) method to quantify oxygen diffusion coefficient of polymer fuel cells backing and catalyst layers

    Science.gov (United States)

    Baricci, Andrea; Casalegno, Andrea

    2016-09-01

    Limiting current density of oxygen reduction reaction in polymer electrolyte fuel cells is determined by several mass transport resistances that lower the concentration of oxygen on the catalyst active site. Among them, diffusion across porous media plays a significant role. Despite the extensive experimental activity documented in PEMFC literature, only few efforts have been dedicated to the measurement of the effective transport properties in porous layers. In the present work, a methodology for ex situ measurement of the effective diffusion coefficient and Knudsen radius of porous layers for polymer electrolyte fuel cells (gas diffusion layer, micro porous layer and catalyst layer) is described and applied to high temperature polymer fuel cells State of Art materials. Regression of the measured quantities by means of a quasi 2D physical model is performed to quantify the Knudsen effect, which is reported to account, respectively, for 30% and 50% of the mass transport resistance in micro porous layer and catalyst layer. On the other side, the model reveals that pressure gradient consequent to permeation in porous layers of high temperature polymer fuel cells has a negligible effect on oxygen concentration in relevant operating conditions.

  19. Surface science investigations of SEI layer in Li-ion battery cathodes. Oxidation states and surface reactions

    Energy Technology Data Exchange (ETDEWEB)

    Cherkashinin, G.; Ensling, D.; Schmid, S.; Bhuvaneswari, S.; Song, J.; Jacke, S.; Jaegermann, W. [Technische Univ. Darmstadt (Germany). Fachbereich Materialwissenschaft; Nikolowski, K.; Ehrenberg, H. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. for Complex Materials

    2010-07-01

    Surface electronic properties of the promising Li-ion cathode materials such as LiMo{sub 2} (Ni, Co, Mn) and LiFePO{sub 4} as well as evolution of electrolyte-cathode interfaces formed after contact to the electrolyte, due to electrochemical charging and after cycling were systematically studied using conventional electronic spectroscopy methods (XPS, UPS) and synchrotron photoelectron spectroscopy (SXPS, XAS). To study fundamental surface properties of the oxides we investigated both thin film cathodes in-situ, where the surfaces are not contaminated by impurities, and synthesized powder cathodes used in industry. (orig.)

  20. Advance of air cathode catalysts for zinc-air batteries%锌空电池空气电极催化剂的研究进展

    Institute of Scientific and Technical Information of China (English)

    李山梅; 刘丹宪

    2011-01-01

    论述了目前碱性锌空气电池空气电极用催化剂的种类组成,结构特征,制备方法以及催化剂特点,分析了各种催化剂的优劣和目前存在的问题.对于一次电池空气电极而言,锰氧化物系列催化剂性能较佳,而钙钛矿系列催化剂更适用于二次空气电极.载体的选择和物质的导电性也关系到空气电极整体的阻抗的大小,也是影响空气电极性能的重要因素.%The species composition, structural characteristics, synthesis method, and catalytic property of air cathodes for alkali zinc-air batteries were reviewed in this paper. The advantages and disadvantages and the problem of catalysts was analyzed. For the primary battery, the catalytic property of manganite oxides performed best, while perovskite-type oxides were even more suitable for secondary battery air electrodes. However, due to the resistance reduction, carrier selection and conductivity of materials played an important role in its electrode performance too.

  1. Intragranular cracking as a critical barrier for high-voltage usage of layer-structured cathode for lithium-ion batteries

    Science.gov (United States)

    Yan, Pengfei; Zheng, Jianming; Gu, Meng; Xiao, Jie; Zhang, Ji-Guang; Wang, Chong-Min

    2017-01-01

    LiNi1/3Mn1/3Co1/3O2-layered cathode is often fabricated in the form of secondary particles, consisting of densely packed primary particles. This offers advantages for high energy density and alleviation of cathode side reactions/corrosions, but introduces drawbacks such as intergranular cracking. Here, we report unexpected observations on the nucleation and growth of intragranular cracks in a commercial LiNi1/3Mn1/3Co1/3O2 cathode by using advanced scanning transmission electron microscopy. We find the formation of the intragranular cracks is directly associated with high-voltage cycling, an electrochemically driven and diffusion-controlled process. The intragranular cracks are noticed to be characteristically initiated from the grain interior, a consequence of a dislocation-based crack incubation mechanism. This observation is in sharp contrast with general theoretical models, predicting the initiation of intragranular cracks from grain boundaries or particle surfaces. Our study emphasizes that maintaining structural stability is the key step towards high-voltage operation of layered-cathode materials.

  2. Hydrothermal synthesis of highly crystalline RuS{sub 2} nanoparticles as cathodic catalysts in the methanol fuel cell and hydrochloric acid electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yanjuan [Key Laboratory of Marine Chemistry Theory and Technology, Minisry of Education Ocean University of China, Qingdao, 266100 (China); College of Material Science and Engineering, Key Laboratory of Automobile Materials of Ministry of Education, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Li, Nan, E-mail: lin@jlu.edu.cn [College of Material Science and Engineering, Key Laboratory of Automobile Materials of Ministry of Education, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Yanagisawa, Kazumichi [Research Laboratory of Hydrothermal Chemistry, Kochi University, Kochi 780-8520 (Japan); Li, Xiaotian [College of Material Science and Engineering, Key Laboratory of Automobile Materials of Ministry of Education, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Yan, Xiao [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China)

    2015-05-15

    Highlights: • Highly crystalline RuS{sub 2} nanoparticles have been first synthesized by a “one-step” hydrothermal method. • The product presents a pure cubic phase of stoichiometric ratio RuS{sub 2} with average particle size of 14.8 nm. • RuS{sub 2} nanoparticles were used as cathodic catalysts in methanol fuel cell and hydrochloric acid electrolysis. • The catalyst outperforms commercial Pt/C in methanol tolerance and stability towards Cl{sup −}. - Abstract: Highly crystalline ruthenium sulfide (RuS{sub 2}) nanoparticles have been first synthesized by a “one-step” hydrothermal method at 400 °C, using ruthenium chloride and thiourea as reactants. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy/energy disperse spectroscopy (SEM/EDS), thermo gravimetric-differential thermal analyze (TG-DTA), transmission electron microscopy equipped with selected area electron diffraction (TEM/SAED). Fourier transform infrared spectra (IR), and X-ray photoelectron spectroscopy (XPS). XRD result illustrates that the highly crystalline product presents a pure cubic phase of stoichiometric ratio RuS{sub 2} and the average particle size is 14.8 nm. SEM and TEM images display the products have irregular shape of 6–25 nm. XPS analyst indicates that the sulfur exists in the form of S{sub 2}{sup 2−}. Cyclic voltammetry (CV), rotating disk electrode (RDE), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) measurements are conducted to evaluate the electrocatalytic activity and stability of the highly crystalline RuS{sub 2} nanoparticles in oxygen reduction reaction (ORR) for methanol fuel cell and hydrochloric acid electrolysis. The results illustrate that RuS{sub 2} is active towards oxygen reduction reaction. Although the activity of RuS{sub 2} is lower than that of Pt/C, the RuS{sub 2} catalyst outperforms commercial Pt/C in methanol tolerance and stability towards Cl{sup −}.

  3. An extended stochastic reconstruction method for catalyst layers in proton exchange membrane fuel cells

    Science.gov (United States)

    Kang, Jinfen; Moriyama, Koji; Kim, Seung Hyun

    2016-09-01

    This paper presents an extended, stochastic reconstruction method for catalyst layers (CLs) of Proton Exchange Membrane Fuel Cells (PEMFCs). The focus is placed on the reconstruction of customized, low platinum (Pt) loading CLs where the microstructure of CLs can substantially influence the performance. The sphere-based simulated annealing (SSA) method is extended to generate the CL microstructures with specified and controllable structural properties for agglomerates, ionomer, and Pt catalysts. In the present method, the agglomerate structures are controlled by employing a trial two-point correlation function used in the simulated annealing process. An off-set method is proposed to generate more realistic ionomer structures. The variations of ionomer structures at different humidity conditions are considered to mimic the swelling effects. A method to control Pt loading, distribution, and utilization is presented. The extension of the method to consider heterogeneity in structural properties, which can be found in manufactured CL samples, is presented. Various reconstructed CLs are generated to demonstrate the capability of the proposed method. Proton transport properties of the reconstructed CLs are calculated and validated with experimental data.

  4. Catalyst synthesis and evaluation using an integrated atomic layer deposition synthesis–catalysis testing tool

    Energy Technology Data Exchange (ETDEWEB)

    Camacho-Bunquin, Jeffrey; Shou, Heng; Marshall, Christopher L. [Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Aich, Payoli [Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States); Beaulieu, David R.; Klotzsch, Helmut; Bachman, Stephen [Arradiance Inc., Sudbury, Massachusetts 01776 (United States); Hock, Adam [Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Stair, Peter [Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Department of Chemistry, Northwestern University, Evanston, Illinois 60208 (United States)

    2015-08-15

    An integrated atomic layer deposition synthesis-catalysis (I-ALD-CAT) tool was developed. It combines an ALD manifold in-line with a plug-flow reactor system for the synthesis of supported catalytic materials by ALD and immediate evaluation of catalyst reactivity using gas-phase probe reactions. The I-ALD-CAT delivery system consists of 12 different metal ALD precursor channels, 4 oxidizing or reducing agents, and 4 catalytic reaction feeds to either of the two plug-flow reactors. The system can employ reactor pressures and temperatures in the range of 10{sup −3} to 1 bar and 300–1000 K, respectively. The instrument is also equipped with a gas chromatograph and a mass spectrometer unit for the detection and quantification of volatile species from ALD and catalytic reactions. In this report, we demonstrate the use of the I-ALD-CAT tool for the synthesis of platinum active sites and Al{sub 2}O{sub 3} overcoats, and evaluation of catalyst propylene hydrogenation activity.

  5. Identifying active functionalities on few-layered graphene catalysts for oxidative dehydrogenation of isobutane.

    Science.gov (United States)

    Dathar, Gopi Krishna Phani; Tsai, Yu-Tung; Gierszal, Kamil; Xu, Ye; Liang, Chengdu; Rondinone, Adam J; Overbury, Steven H; Schwartz, Viviane

    2014-02-01

    The general consensus in the studies of nanostructured carbon catalysts for oxidative dehydrogenation (ODH) of alkanes to olefins is that the oxygen functionalities generated during synthesis and reaction are responsible for the catalytic activity of these nanostructured carbons. Identification of the highly active oxygen functionalities would enable engineering of nanocarbons for ODH of alkanes. Few-layered graphenes were used as model catalysts in experiments to synthesize reduced graphene oxide samples with varying oxygen concentrations, to characterize oxygen functionalities, and to measure the activation energies for ODH of isobutane. Periodic density functional theory calculations were performed on graphene nanoribbon models with a variety of oxygen functionalities at the edges to calculate their thermal stability and to model reaction mechanisms for ODH of isobutane. Comparing measured and calculated thermal stability and activation energies leads to the conclusion that dicarbonyls at the zigzag edges and quinones at armchair edges are appropriately balanced for high activity, relative to other model functionalities considered herein. In the ODH of isobutane, both dehydrogenation and regeneration of catalytic sites are relevant at the dicarbonyls, whereas regeneration is facile compared with dehydrogenation at quinones. The catalytic mechanism involves weakly adsorbed isobutane reducing functional oxygen and leaving as isobutene, and O2 in the feed, weakly adsorbed on the hydrogenated functionality, reacting with that hydrogen and regenerating the catalytic sites.

  6. Pore-Network Modeling of Water and Vapor Transport in the Micro Porous Layer and Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell

    NARCIS (Netherlands)

    Qin, C.; Hassanizadeh, S.M.; van Oosterhout, L.M.

    2016-01-01

    In the cathode side of a polymer electrolyte fuel cell (PEFC), a micro porous layer (MPL) added between the catalyst layer (CL) and the gas diffusion layer (GDL) plays an important role in water management. In this work, by using both quasi-static and dynamic pore-network models, water and vapor tra

  7. Synthesis of Nitrogen-Doped Carbon Nanocoils with Adjustable Morphology using Ni–Fe Layered Double Hydroxides as Catalyst Precursors

    Directory of Open Access Journals (Sweden)

    Tomohiro Iwasaki

    2015-01-01

    Full Text Available Nitrogen-doped carbon nanocoils (CNCs with adjusted morphologies were synthesized in a one-step catalytic chemical vapour deposition (CVD process using acetoni‐ trile as the carbon and nitrogen source. The nickel iron oxide/nickel oxide nanocomposites, which were derived from nickel–iron layered double hydroxide (LDH precur‐ sors, were employed as catalysts for the synthesis of CNCs. In this method, precursor-to-catalyst transformation, catalyst activation, formation of CNCs, and nitrogen doping were all performed in situ in a single process. The morphology (coil diameter, coil pitch, and fibre diameter and nitrogen content of the synthesized CNCs was indi‐ vidually adjusted by modulation of the catalyst composi‐ tion and CVD reaction temperature, respectively. The adjustable ranges of the coil diameter, coil pitch, fibre diameter, and nitrogen content were confirmed to be approximately 500±100 nm, 600±100 nm, 100±20 nm, and 1.1±0.3 atom%, respectively.

  8. Ag/C nanoparticles as an cathode catalyst for a zinc-air battery with a flowing alkaline electrolyte

    Science.gov (United States)

    Han, Jia-Jun; Li, Ning; Zhang, Tian-Yun

    The cyclic voltammetry indicated that the oxygen reduction reaction (ORR) proceeded by the four-electron pathway mechanism on larger Ag particles (174 nm), and that the ORR proceeded by the four-electron pathway and the two-electron pathway mechanisms on finer Ag particles (4.1 nm), simultaneously. The kinetics towards ORR was measured at a rotating disk electrode (RDE) with Ag/C electrode. The number of exchanged electrons for the ORR was found to be close to four on larger Ag particles (174 nm) and close to three on finer Ag particles (4.1 nm). The zinc-air battery with Ag/C catalysts (25.9 nm) was fabricated and examined.

  9. Investigation of the electrospun carbon web as the catalyst layer for vanadium redox flow battery

    Science.gov (United States)

    Wei, Guanjie; Fan, Xinzhuang; Liu, Jianguo; Yan, Chuanwei

    2014-12-01

    Polyacrylonitrile (PAN) carbon nonwoven web consisting of 100-200 nm ultrafine fibers has been developed by electrospinning and subsequent carbonization process at 1000 °C for different times. The surface morphology, composition, structure, and electrical conductivity of the electrospun carbon webs (ECWs) as well as their electrochemical properties toward vanadium redox couples have been characterized. With the increasing of carbonization time, the electrochemical reversibility of the vanadium redox couples on the ECW is enhanced greatly. As the carbonization time increases up to 120 min, the hydrogen evolution is facilitated while the reversibility is promoted a little bit further. The excellent performance of ECW may be attributed to the conversion of fibers carbon structure and improvement of electrical conductivity. Due to the good electrochemical activity and freestanding 3-dimensional structure, the ECW carbonized for 90 min is used as catalyst layer in vanadium redox flow battery (VRFB) and enhances the cell performance.

  10. Reduced graphene oxide with ultrahigh conductivity as carbon coating layer for high performance sulfur@reduced graphene oxide cathode

    Science.gov (United States)

    Zhao, Hongbin; Peng, Zhenhuan; Wang, Wenjun; Chen, Xikun; Fang, Jianhui; Xu, Jiaqiang

    2014-01-01

    We developed hydrogen iodide (HI) reduction of rGO and surfactant-assisted chemical reaction- deposition method to form hybrid material of sulfur (S) encapsulated in reduced graphene oxide (rGO) sheets for rechargeable lithium batteries. The surfactant-assisted chemical reaction-deposition method strategy provides intimate contact between the S and graphene oxide. Chemical reduced rGO with high conductivity as carbon coating layer prevented the dissolution of polysulfide ions and improved the electron transfer. This novel core-shell structured S@rGO composites with high S content showed high reversible capacity, good discharge capacity retention and enhanced rate capability used as cathodes in rechargeable Li/S cells. We demonstrated here that an electrode prepared from a S@rGO with up to 85 wt% S maintains a stable discharge capacity of about 980 mAh g-1 at 0.05 C and 570 mAh g-1 at 1C after 200 cycles charge/discharge. These results emphasize the importance of rGO with high electrical conductivity after HI-reduced rGO homogeneously coating on the surface of S, therefore, effectively alleviating the shuttle phenomenon of polysulfides in organic electrolyte. Our surfactant-assisted chemical reaction-HI reduction approach should offer a new technique for the design and synthesis of battery electrodes based on highly conducting carbon materials.

  11. Theory, Investigation and Stability of Cathode Electrocatalytic Activity

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Dong; Liu, Mingfei; Lai, Samson; Blinn, Kevin; Liu, Meilin

    2012-09-30

    The main objective of this project is to systematically characterize the surface composition, morphology, and electro-catalytic properties of catalysts coated on LSCF, aiming to establish the scientific basis for rational design of high-performance cathodes by combining a porous backbone (such as LSCF) with a thin catalyst coating. The understanding gained will help us to optimize the composition and morphology of the catalyst layer and microstructure of the LSCF backbone for better performance. More specifically, the technical objectives include: (1) to characterize the surface composition, morphology, and electro-catalytic properties of catalysts coated on LSCF; (2) to characterize the microscopic details and stability of the LSCF-catalyst (e.g., LSM) interfaces; (3) to establish the scientific basis for rational design of high-performance cathodes by combining a porous backbone (such as LSCF) with a thin catalyst coating; and (4) to demonstrate that the performance and stability of porous LSCF cathodes can be enhanced by the application of a thin-film coating of LSM through a solution infiltration process in small homemade button cells and in commercially available cells of larger dimension. We have successfully developed dense, conformal LSM films with desired structure, composition, morphology, and thickness on the LSCF surfaces by two different infiltration processes: a non-aqueous and a water-based sol-gel process. It is demonstrated that the activity and stability of LSCF cathodes can be improved by the introduction of a thin-film LSM coating through an infiltration process. Surface and interface of the LSM-coated LSCF cathode were systematically characterized using advanced microscopy and spectroscopy techniques. TEM observation suggests that a layer of La and Sr oxide was formed on LSCF surfaces after annealing. With LSM infiltration, in contrast, we no longer observe such La/Sr oxide layer on the LSM-coated LSCF samples after annealing under similar

  12. A Chemical-Adsorption Strategy to Enhance the Reaction Kinetics of Lithium-Rich Layered Cathodes via Double-Shell Surface Modification.

    Science.gov (United States)

    Guo, Lichao; Li, Jiajun; Cao, Tingting; Wang, Huayu; Zhao, Naiqin; He, Fang; Shi, Chunsheng; He, Chunnian; Liu, Enzuo

    2016-09-21

    Sluggish surface reaction kinetics hinders the power density of Li-ion battery. Thus, various surface modification techniques have been applied to enhance the electronic/ionic transfer kinetics. However, it is challenging to obtain a continuous and uniform surface modification layer on the prime particles with structure integration at the interface. Instead of classic physical-adsorption/deposition techniques, we propose a novel chemical-adsorption strategy to synthesize double-shell modified lithium-rich layered cathodes with enhanced mass transfer kinetics. On the basis of experimental measurement and first-principles calculation, MoO2S2 ions are proved to joint the layered phase via chemical bonding. Specifically, the Mo-O or Mo-S bonds can flexibly rotate to bond with the cations in the layered phase, leading to the good compatibility between the thiomolybdate adsorption layer and layered cathode. Followed by annealing treatment, the lithium-excess-spinel inner shell forms under the thiomolybdate adsorption layer and functions as favorable pathways for lithium and electron. Meanwhile, the nanothick MoO3-x(SO4)x outer shell protects the transition metal from dissolution and restrains electrolyte decomposition. The double-shell modified sample delivers an enhanced discharge capacity almost twice as much as that of the unmodified one at 1 A g(-1) after 100 cycles, demonstrating the superiority of the surface modification based on chemical adsorption.

  13. A high performance layered transition metal oxide cathode material obtained by simultaneous aluminum and iron cationic substitution

    Science.gov (United States)

    El Mofid, Wassima; Ivanov, Svetlozar; Konkin, Alexander; Bund, Andreas

    2014-12-01

    The method of self-combustion synthesis was applied to prepare double Al- and Fe-substituted LiNi0.6Mn0.2Co0.15Al0.025Fe0.025O2 (NMCAF) and non-substituted LiNi0.6Mn0.2Co0.2O2 (NMC-3:1:1) cathode materials for lithium ion batteries. The novel NMCAF structure obtained by simultaneous cationic substitution showed an improved capacity and high stability during electrochemical cycling. X-ray diffraction patterns proved that both materials have a layered α-NaFeO2 type structure with a good hexagonal ordering. It was found that NMCAF has increased a and c lattice parameters due to a structural expansion caused by Al and Fe ion substitution. Rietveld refinement analysis revealed a significant decrease of the cationic mixing after the metal substitution, suggesting a structural stabilization. Electron paramagnetic resonance (EPR) spectroscopy showed that Al and Fe substitution markedly influenced the EPR spectrum of NMC-(3:1:1). The EPR spectral lines of both materials are attributed to Mn4+ and Ni2+ present in the structure. The change in the Ni2+ line after the metal substitution suggests a redistribution of the Ni ions in the structure, which can be related to the diminished cation mixing in the NMCAF. The improved electrochemical behavior of NMCAF is closely connected to the stabilization of the layered structure and the reduction of the cation mixing after metal substitution.

  14. Mesoporous CuCo2O4 nanoparticles as an efficient cathode catalyst for Li-O2 batteries

    Science.gov (United States)

    Wang, Peng-Xiang; Shao, Lin; Zhang, Nai-Qing; Sun, Ke-Ning

    2016-09-01

    Extremely high energy density and environment friendly reaction make Li-O2 batteries a promising energy storage system. In order to improve the energy efficiency and cycle life of Li-O2 battery, spinel mesoporous CuCo2O4 was successfully synthesized by a facile hydrothermal method and investigated in Li-O2 batteries. The electrochemical measurements show that mesoporous CuCo2O4 possess higher oxygen reduction and oxygen evolution activity than bulk CuCo2O4 both in alkaline and non-aqueous solution. Owing to the inherent catalytic activity, high conductivity and facile mass transfer of mesoporous CuCo2O4, Li-O2 battery shows enhanced electrochemical performances, including much lower charge overpotential and a high capacity up to 5288 mAh g-1. When restricting the discharge capacity at 500 mAh g-1, it could operate over 80 cycles and exhibit superior cycle stability. These results indicate that mesoporous CuCo2O4 nanoparticles are appropriate bifunctional catalysts for Li-O2 batteries.

  15. A sodium layered manganese oxides as 3V cathode materials for secondary lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Bach, S.; Pereira-Ramos, J.P. [Laboratoire d' Electrochimie, Catalyse et Synthese Organique, CNRS, UMR 7582, 2, rue Henri-Dunant, 94320 Thiais (France); Willmann, P. [CNES, 18, Avenue Edouard Belin, 31401-Toulouse, Cedex 9 (France)

    2006-10-25

    The synthesis of a new anhydrous sodium manganese oxide {alpha}-Na{sub 0.66}MnO{sub 2.13} obtained via a sol-gel process in organic medium is reported. The partial and limited removal of sodium ions from the layered host lattice (hexagonal symmetry; a=2.84A, c=11.09A) allows to get a high and stable specific capacity of 180mAhg{sup -1} at C/20 in the cycling limits 4.3/2V with a mean working voltage of 3V without the emergence of a spinel phase. By introducing acetylene black in solution during the sol-gel reaction, a composite material containing 8wt.% AB has been obtained. The rate capability is shown to be significantly improved leading to an increase of the available specific capacity with for instance 200 and 90mAhg{sup -1} at C/20 and C rate. This effect is ascribed to a better electronic contact between particles and/or the modification of the oxide surface which makes the intercalation process more homogeneous and more efficient. (author)

  16. A sodium layered manganese oxides as 3 V cathode materials for secondary lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Bach, S. [Laboratoire d' Electrochimie, Catalyse et Synthese Organique, CNRS, UMR 7582, 2, rue Henri-Dunant, 94320 Thiais (France)]. E-mail: bach@glvt-cnrs.fr; Pereira-Ramos, J.P. [Laboratoire d' Electrochimie, Catalyse et Synthese Organique, CNRS, UMR 7582, 2, rue Henri-Dunant, 94320 Thiais (France); CNES, 18, Avenue Edouard Belin, 31401-Toulouse, Cedex 9 (France); Willmann, P. [CNES, 18, Avenue Edouard Belin, 31401-Toulouse, Cedex 9 (France)

    2006-10-25

    The synthesis of a new anhydrous sodium manganese oxide {alpha}-Na{sub 0.66}MnO{sub 2.13} obtained via a sol-gel process in organic medium is reported. The partial and limited removal of sodium ions from the layered host lattice (hexagonal symmetry; a = 2.84 A, c = 11.09 A) allows to get a high and stable specific capacity of 180 mAh g{sup -1} at C/20 in the cycling limits 4.3/2 V with a mean working voltage of 3 V without the emergence of a spinel phase. By introducing acetylene black in solution during the sol-gel reaction, a composite material containing 8 wt.% AB has been obtained. The rate capability is shown to be significantly improved leading to an increase of the available specific capacity with for instance 200 and 90 mAh g{sup -1} at C/20 and C rate. This effect is ascribed to a better electronic contact between particles and/or the modification of the oxide surface which makes the intercalation process more homogeneous and more efficient.

  17. Progress of non-precious metal oxide cathode catalysts microbial fuel cells%微生物燃料电池非贵金属氧化物阴极催化剂研究进展

    Institute of Scientific and Technical Information of China (English)

    邓丽芳; 袁浩然; 陈勇

    2012-01-01

    Microbial fue1 cell(MFC) is a device directly converting chemical energy in the organic matter into electricity with the microbial catalysts,which has been paid much attention because of its advantages of abundant resource,mild reaction condition and high theoretical efficiency.In order to clarify the research direction and development trend of non-precious metal oxide cathode catalysts,the research progress of two main non-precious metal oxide cathode catalysts(manganese dioxide and titanium dioxide) of MFC are summarized.The possible catalytic reaction mechanisms are analyzed also.Then,the application prospects of non-precious metal oxide cathode catalysts about MFC are discussed: 1) Cathode material modification,including replacement of metal oxides,doping,and morphological features change,etc.2) Cathode materials morphology modification: by hydrothermal synthesis,liquid phase deposition,sol gel method,etc.%微生物燃料电池(Microbial Fuel Cell,MFC)是一种利用微生物将底物中的化学能直接转化为电能的理想产电装置,具有产电与废弃物处置双重功效.为探究非贵金属氧化物作为微生物燃料电池阴极催化剂可能的研究方向和发展趋势,主要总结了近几年来两种主要非贵金属氧化物(二氧化锰、二氧化钛)作为微生物燃料电池阴极催化剂的最新研究进展,并分析了其可能的催化反应机制.随后,对其发展方向提出了自己的见解:1)阴极材料改性:包括金属氧化物替换、掺杂、形貌特征改变等;2)阴极材料结构形貌改性:水热合成、液相沉积、溶胶凝胶等方法.

  18. Novel bifunctional double-layer catalysts for application in microreactors for direct DME synthesis

    OpenAIRE

    Lee, Seungcheol

    2016-01-01

    This thesis describes experimental research toward the selective and efficient DME production from syngas in microstructured reactors using bifunctional catalysts. Two catalysts, Cu/ZnO/Al2O3 and ZSM-5, catalyze syngas conversion to methanol and methanol conversion to DME, respectively. The catalysts were prepared and successfully introduced in microchannel reactor for direct DME synthesis.

  19. Nanoscale study of reactive transport in catalyst layer of proton exchange membrane fuel cells with precious and non-precious catalysts using lattice Boltzmann method

    CERN Document Server

    Chen, Li; Kang, Qinjun; Holby, Edward F; Tao, Wen-Quan

    2014-01-01

    High-resolution porous structures of catalyst layer (CL) with multicomponent in proton exchange membrane fuel cells are reconstructed using a reconstruction method called quartet structure generation set. Characterization analyses of nanoscale structures are implemented including pore size distribution, specific area and phase connectivity. Pore-scale simulation methods based on the lattice Boltzmann method are developed and used to predict the macroscopic transport properties including effective diffusivity and proton conductivity. Nonuniform distributions of ionomer in CL generates more tortuous pathway for reactant transport and greatly reduces the effective diffusivity. Tortuosity of CL is much higher than conventional Bruggeman equation adopted. Knudsen diffusion plays a significant role in oxygen diffusion and significantly reduces the effective diffusivity. Reactive transport inside the CL is also investigated. Although the reactive surface area of non-precious metal catalyst (NPMC) CL is much higher t...

  20. On the actual cathode mixed potential in direct methanol fuel cells

    Science.gov (United States)

    Zago, M.; Bisello, A.; Baricci, A.; Rabissi, C.; Brightman, E.; Hinds, G.; Casalegno, A.

    2016-09-01

    Methanol crossover is one of the most critical issues hindering commercialization of direct methanol fuel cells since it leads to waste of fuel and significantly affects cathode potential, forming a so-called mixed potential. Unfortunately, due to the sluggish anode kinetics, it is not possible to obtain a reliable estimation of cathode potential by simply measuring the cell voltage. In this work we address this limitation, quantifying the mixed potential by means of innovative open circuit voltage (OCV) tests with a methanol-hydrogen mixture fed to the anode. Over a wide range of operating conditions, the resulting cathode overpotential is between 250 and 430 mV and is strongly influenced by methanol crossover. We show using combined experimental and modelling analysis of cathode impedance that the methanol oxidation at the cathode mainly follows an electrochemical pathway. Finally, reference electrode measurements at both cathode inlet and outlet provide a local measurement of cathode potential, confirming the reliability of the innovative OCV tests and permitting the evaluation of cathode potential up to typical operating current. At 0.25 A cm-2 the operating cathode potential is around 0.85 V and the Ohmic drop through the catalyst layer is almost 50 mV, which is comparable to that in the membrane.

  1. 锂离子电池层状正极材料的研究进展%Research Process on Layer Cathode Material for Li-ion Batteries

    Institute of Scientific and Technical Information of China (English)

    杨世霞

    2012-01-01

    The paper mainly introduced the research process on layer cathode materials- LiCoO2, LiNiO2, Li MnO2 at present. The advantages and disadvantages of the three layer cathode materials were displayed, and also ways of the modification of LiCoO2 and LiNiO2: doping and coating. The structure and the properties of the layer cathode materials are prompted severely through modification which pointed out a way for the more widely apply of Li-ion batteries. What was more, I showed a prospect of apply of the cathode materials on Li-ion batteries.%文絮主要综述当前锂离子电池层状正极材料-LiCoO2、LiNiO2、LiMnO2的研究进展。阐述了三种层状盐结构正极材料的优缺点,对LiCoO2和LiNiO2正极材料的改性方法:掺杂和包覆处理。通过改性,层状正极材料豹结构和性能均有较大改善,为锂离子电池更为广泛的工业应用指明道路。对锂离子电池正极材料未来的应用前景做了一些展槊。

  2. A Search for the Optimum Lithium Rich Layered Metal Oxide Cathode Material for Li-Ion Batteries

    Science.gov (United States)

    Ates, Mehmet Nurullah; Mukerjee, Sanjeev; Abraham, K. M.

    2015-01-01

    We report the results of a comprehensive study of the relationship between electrochemical performance in Li cells and chemical composition of a series of Li rich layered metal oxides of the general formula xLi2MnO3 · (1-x)LiMn0.33Ni0.33Co0.33O2 in which x = 0,1, 0.2, 0,3, 0.5 or 0.7, synthesized using the same method. In order to identify the cathode material having the optimum Li cell performance we first varied the ratio between Li2MnO3 and LiMO2 segments of the composite oxides while maintaining the same metal ratio residing within their LiMO2 portions. The materials with the overall composition 0.5Li2MnO3 · 0.5LiMO2 containing 0.5 mole of Li2MnO3 per mole of the composite metal oxide were found to be the optimum in terms of electrochemical performance. The electrochemical properties of these materials were further tuned by changing the relative amounts of Mn, Ni and Co in the LiMO2 segment to produce xLi2MnO3 · (1-x)LiMn0.50Ni0.35Co0.15O2 with enhanced capacities and rate capabilities. The rate capability of the lithium rich compound in which x = 0.3 was further increased by preparing electrodes with about 2 weight-percent multiwall carbon nanotube in the electrode. Lithium cells prepared with such electrodes were cycled at the 4C rate with little fade in capacity for over one hundred cycles. PMID:26478598

  3. Atomic layer deposition-Sequential self-limiting surface reactions for advanced catalyst "bottom-up" synthesis

    Science.gov (United States)

    Lu, Junling; Elam, Jeffrey W.; Stair, Peter C.

    2016-06-01

    Catalyst synthesis with precise control over the structure of catalytic active sites at the atomic level is of essential importance for the scientific understanding of reaction mechanisms and for rational design of advanced catalysts with high performance. Such precise control is achievable using atomic layer deposition (ALD). ALD is similar to chemical vapor deposition (CVD), except that the deposition is split into a sequence of two self-limiting surface reactions between gaseous precursor molecules and a substrate. The unique self-limiting feature of ALD allows conformal deposition of catalytic materials on a high surface area catalyst support at the atomic level. The deposited catalytic materials can be precisely constructed on the support by varying the number and type of ALD cycles. As an alternative to the wet-chemistry based conventional methods, ALD provides a cycle-by-cycle "bottom-up" approach for nanostructuring supported catalysts with near atomic precision. In this review, we summarize recent attempts to synthesize supported catalysts with ALD. Nucleation and growth of metals by ALD on oxides and carbon materials for precise synthesis of supported monometallic catalyst are reviewed. The capability of achieving precise control over the particle size of monometallic nanoparticles by ALD is emphasized. The resulting metal catalysts with high dispersions and uniformity often show comparable or remarkably higher activity than those prepared by conventional methods. For supported bimetallic catalyst synthesis, we summarize the strategies for controlling the deposition of the secondary metal selectively on the primary metal nanoparticle but not on the support to exclude monometallic formation. As a review of the surface chemistry and growth behavior of metal ALD on metal surfaces, we demonstrate the ways to precisely tune size, composition and structure of bimetallic metal nanoparticles. The cycle-by-cycle "bottom up" construction of bimetallic (or multiple

  4. Development and evaluation of carbon and binder loading in low-cost activated carbon cathodes for air-cathode microbial fuel cells

    KAUST Repository

    Wei, Bin

    2012-01-01

    Activated carbon (AC) air cathodes were constructed using variable amounts of carbon (43-171 mg cm-2) and an inexpensive binder (10 wt% polytetrafluoroethylene, PTFE), and with or without a porous cloth wipe-based diffusion layer (DL) that was sealed with PDMS. The cathodes with the highest AC loading of 171 mg cm-2, and no diffusion layer, produced 1255 ± 75 mW m-2 and did not appreciably vary in performance after 1.5 months of operation. Slightly higher power densities were initially obtained using 100 mg cm-2 of AC (1310 ± 70 mW m-2) and a PDMS/wipe diffusion layer, although the performance of this cathode decreased to 1050 ± 70 mW m-2 after 1.5 months, and 1010 ± 190 mW m-2 after 5 months. AC loadings of 43 mg cm-2 and 100 mg cm-2 did not appreciably affect performance (with diffusion layers). MFCs with the Pt catalyst and Nafion binder initially produced 1295 ± 13 mW m-2, but the performance decreased to 930 ± 50 mW m -2 after 1.5 months, and then to 890 ± 20 mW m-2 after 5 months. Cathode performance was optimized for all cathodes by using the least amount of PTFE binder (10%, in tests using up to 40%). These results provide a method to construct cathodes for MFCs that use only inexpensive AC and a PTFE, while producing power densities similar to those of Pt/C cathodes. The methods used here to make these cathodes will enable further tests on carbon materials in order to optimize and extend the lifetime of AC cathodes in MFCs. © 2012 The Royal Society of Chemistry.

  5. Unexpected high power performance of atomic layer deposition coated Li[Ni1/3Mn1/3Co1/3]O2 cathodes

    Science.gov (United States)

    Kim, Ji Woo; Travis, Jonathan J.; Hu, Enyuan; Nam, Kyung-Wan; Kim, Seul Cham; Kang, Chan Soon; Woo, Jae-Ha; Yang, Xiao-Qing; George, Steven M.; Oh, Kyu Hwan; Cho, Sung-Jin; Lee, Se-Hee

    2014-05-01

    Electric-powered transportation requires an efficient, low-cost, and safe energy storage system with high energy density and power capability. Despite its high specific capacity, the current commercially available cathode material for today's state-of-art Li-ion batteries, lithium nickel-manganese-cobalt oxide Li[Ni1/3 Mn1/3Co1/3]O2 (NMC), suffers from poor cycle life for high temperature operation and marginal rate capability resulting from irreversible degradation of the cathode material upon cycling. Using an atomic-scale surface engineering, the performance of Li[Ni1/3Mn1/3Co1/3]O2 in terms of rate capability and high temperature cycle-life is significantly improved. The Al2O3 coating deposited by atomic layer deposition (ALD) dramatically reduces the degradation in cell conductivity and reaction kinetics. This durable ultra-thin Al2O3-ALD coating layer also improves stability for the NMC at an elevated temperature (55 °C). The experimental results suggest that a highly durable and safe cathode material enabled by atomic-scale surface modification could meet the demanding performance and safety requirements of next-generation electric vehicles.

  6. Catalytic Combustion of Low Concentration Methane over Catalysts Prepared from Co/Mg-Mn Layered Double Hydroxides

    Directory of Open Access Journals (Sweden)

    Hongfeng Liu

    2014-01-01

    Full Text Available A series of Co/Mg-Mn mixed oxides were synthesized through thermal decomposition of layered double hydroxides (LDHs precursors. The resulted catalysts were then subjected for catalytic combustion of methane. Experimental results revealed that the Co4.5Mg1.5Mn2LDO catalyst possessed the best performance with the T90=485°C. After being analyzed via XRD, BET-BJH, SEM, H2-TPR, and XPS techniques, it was observed that the addition of cobalt had significantly improved the redox ability of the catalysts whilst certain amount of magnesium was essential to guarantee the catalytic activity. The presence of Mg was helpful to enhance the oxygen mobility and, meanwhile, improved the dispersion of Co and Mn oxides, preventing the surface area loss after calcination.

  7. Seed layer stimulated growth of crystalline high Al containing (Al,Cr){sub 2}O{sub 3} coatings deposited by cathodic arc evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Pohler, M., E-mail: markus.pohler@stud.unileoben.ac.at [Christian Doppler Laboratory for Advanced Hard Coatings at the Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Franz-Josef-Straße 18, A-8700 Leoben (Austria); Franz, R. [Christian Doppler Laboratory for Advanced Hard Coatings at the Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Franz-Josef-Straße 18, A-8700 Leoben (Austria); Ramm, J. [OC Oerlikon Balzers AG, Iramali 18, 9469 Balzers (Liechtenstein); Polcik, P. [PLANSEE Composite Materials GmbH, Siebenbürgerstraße 23, 86983 Lechbruck am See (Germany); Mitterer, C. [Christian Doppler Laboratory for Advanced Hard Coatings at the Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Franz-Josef-Straße 18, A-8700 Leoben (Austria)

    2014-01-01

    Single layer and dual layer (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} coatings were synthesised by cathodic arc evaporation with different Al contents to study their growth characteristics. It was demonstrated that variations in the Al content, the energy of incident particles and the coating thickness control the crystallinity and the coating texture. Analysis by X-ray diffraction revealed a distinct (110) out of plane orientation after transition from a fine grained nucleation zone to a columnar growth mode. Furthermore, the impact of (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} seed layers with x = 0.25 and 0.5 on the growth of (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} top layers with x = 0.7 and 0.85 was evaluated in detail. According to X-ray diffraction and transmission electron microscopy, the development of the corundum-type crystal structure of the top layer was promoted by local epitaxy if the low Al containing seed layer exhibited a pronounced columnar structure. In this way, crystalline corundum-type coatings with an Al content up to x = 0.85 were obtained. - Highlights: • Industrial scale cathodic arc deposition of corundum type (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} coatings • Discussion of the growth characteristics for different Al/Cr ratios • Characterisation of growth regimes in dual layer coatings • Template stimulated growth of crystalline corundum-type (Al{sub 0.85}Cr{sub 0.15}){sub 2}O{sub 3} coatings • Influence of bias voltage and seed layer thickness on the template effect.

  8. CO-induced inversion of the layer sequence of a model CoCu catalyst

    Science.gov (United States)

    Collinge, Greg; Xiang, Yizhi; Barbosa, Roland; McEwen, Jean-Sabin; Kruse, Norbert

    2016-06-01

    Experimental X-ray photoelectron spectroscopy (XPS) and theoretical density functional theory (DFT) calculations reveal the electronic and structural properties of CoCu catalysts before and after CO adsorption. DFT calculations show that, prior to CO adsorption, CoCu has a high tendency to self-assemble into a Co@Cu core-shell structure, which is in accordance with previous atom probe tomography (APT) results for CoCu-based systems and the known mutually low miscibility of Co and Cu. We demonstrate that Co and Cu are electronically immiscible using a density of states (DOS) analysis wherein neither metal's electronic structure is greatly perturbed by the other in "mixed" CoCu. However, CO adsorption on Co is in fact weakened in CoCu compared to CO adsorption on pure Co despite being electronically unchanged in the alloy. Differential charge density analysis suggests that this is likely due to a lower electron density made available to Co by Cu. CO adsorption at coverages up to 1.00 ML are then investigated on a Cu/Co(0001) model slab to demonstrate CO-induced segregation effects in CoCu. Accordingly, a large driving force for a Co surface enrichment is found. At high coverages, CO can completely invert the layer sequence of Co and Cu. This result is echoed by XPS evidence, which shows that the surface Co/Cu ratio of CoCu is much larger in the presence of CO than in H2.

  9. Tris(2,2,2-trifluoroethyl) phosphite as an electrolyte additive for high-voltage lithium-ion batteries using lithium-rich layered oxide cathode

    Science.gov (United States)

    Pires, Julie; Castets, Aurore; Timperman, Laure; Santos-Peña, Jesùs; Dumont, Erwan; Levasseur, Stéphane; Tessier, Cécile; Dedryvère, Rémi; Anouti, Mérièm

    2015-11-01

    In this paper, we report positive effect of Tris(2,2,2-trifluoroethyl) phosphite (TTFP) as additive during initial activation and cycling of Li-rich-NMC xLi2MnO3-(1 - x)LiMO2 (x >> 1; M = Ni, Co, Mn) cathode in EC/DMC + 1 M LiPF6 electrolyte. Firstly conductivity and viscosity of electrolyte with x wt.% TTFP; 0 wt.% NMC full cell is maintained after 50 cycles at C rate. Finally, XPS analysis of Li-rich -NMC electrodes show presence of TTFP on the surface during cycling and confirm the presence of Mn3+ at the end of discharge. The convergence of all characterizations indicates that TTFP should act as a catalyst to several surface reactions which are beneficial to long cycling cell performances.

  10. Diagnosing, Optimizing and Designing Ni & Mn based Layered Oxides as Cathode Materials for Next Generation Li-ion Batteries and Na-ion Batteries

    Science.gov (United States)

    Liu, Haodong

    The progressive advancements in communication and transportation has changed human daily life to a great extent. While important advancements in battery technology has come since its first demonstration, the high energy demands needed to electrify the automotive industry have not yet been met with the current technology. One considerable bottleneck is the cathode energy density, the Li-rich layered oxide compounds xLi2MnO3.(1-x)LiMO 2 (M= Ni, Mn, Co) (0.5= Co) (0.5=discharge capacities greater than 280 mAh g-1 (almost twice the practical capacity of LiCoO 2). In this work, neutron diffraction under operando battery cycling is developed to study the lithium and oxygen dynamics of Li-rich compounds that exhibits oxygen activation at high voltage. The measured lattice parameter changes and oxygen position show movement of oxygen and lattice contractions during the high voltage plateau until the end of charge. Lithium migration kinetics for the Li-rich material is observed under operando conditions for the first time to reveal the rate of lithium extraction from the lithium layer and transition metal layer are related to the different charge and discharge characteristics. In the second part, a combination of multi-modality surface sensitive tools was applied in an attempt to obtain a complete picture to understand the role of NH4F and Al2O3 surface co-modification on Li-rich. The enhanced discharge capacity of the modified material can be primary assigned to three aspects: decreased irreversible oxygen loss, the activation of cathode material was facilitated with pre-activated Mn3+ on the surface, and stabilization of the Ni redox pair. These insights will provide guidance for the surface modification in high voltage cathode battery materials of the future. In the last part, the idea of Li-rich has transferred to the Na-ion battery cathode. A new O3 - Na0.78Li0.18Ni0.25Mn 0.583Ow is prepared as the cathode material for Na-ion batteries, delivering exceptionally high

  11. Electrocatalytic activity of atomic layer deposited Pt–Ru catalysts onto N-doped carbon nanotubes

    DEFF Research Database (Denmark)

    Johansson, Anne-Charlotte Elisabeth Birgitta; Larsen, Jackie Vincent; Verheijen, Marcel A.

    2014-01-01

    (ethylcyclopentadienyl)ruthenium (Ru(EtCp)2), respectively. O2 was used as the reactant in both processes. The composition of the catalysts was easily tuned by varying the Pt-to-Ru ALD cycle ratio. The catalysts were tested toward the CO oxidation and methanol oxidation reaction (MOR) in a three-electrode electrochemical set...

  12. Effect of ethylene glycol bis (propionitrile) ether (EGBE) on the performance and interfacial chemistry of lithium-rich layered oxide cathode

    Science.gov (United States)

    Hong, Pengbo; Xu, Mengqing; Zheng, Xiongwen; Zhu, Yunmin; Liao, Youhao; Xing, Lidan; Huang, Qiming; Wan, Huaping; Yang, Yongjun; Li, Weishan

    2016-10-01

    Ethylene glycol bis (propionitrile) ether (EGBE) is used as an electrolyte additive to improve the cycling stability and rate capability of Li/Li1.2Mn0.54Ni0.13Co0.13O2 cells at high operating voltage (4.8 V). After 150 cycles, cells with 1.0 wt% of EGBE containing electrolyte have remarkable cycling performance, 89.0% capacity retention; while the cells with baseline electrolyte only remain 67.4% capacity retention. Linear sweep voltammetry (LSV) and computation results demonstrate that EGBE preferably oxidizes on the cathode surface compared to the LiPF6/carbonate electrolyte. In order to further understand the effects of EGBE on Li1.2Mn0.54Ni0.13Co0.13O2 cathode upon cycling at high voltage, electrochemical behaviors and ex-situ surface analysis of Li1.2Mn0.54Ni0.13Co0.13O2 are investigated via electrochemical impedance spectroscopy (EIS), scanning electron spectroscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and inductive coupled plasma spectroscopy (ICP-MS). The improved cycling performance can be attributed to more stable and robust surface layer yield via incorporation of EGBE, which mitigates the oxidation of electrolyte on the cathode electrode, and also inhibits the dissolution of bulk transition metal ions as well upon cycling at high voltage.

  13. Binder free three-dimensional sulphur/few-layer graphene foam cathode with enhanced high-rate capability for rechargeable lithium sulphur batteries

    Science.gov (United States)

    Xi, Kai; Kidambi, Piran R.; Chen, Renjie; Gao, Chenlong; Peng, Xiaoyu; Ducati, Caterina; Hofmann, Stephan; Kumar, R. Vasant

    2014-05-01

    A novel ultra-lightweight three-dimensional (3-D) cathode system for lithium sulphur (Li-S) batteries has been synthesised by loading sulphur on to an interconnected 3-D network of few-layered graphene (FLG) via a sulphur solution infiltration method. A free-standing FLG monolithic network foam was formed as a negative of a Ni metallic foam template by CVD followed by etching away of Ni. The FLG foam offers excellent electrical conductivity, an appropriate hierarchical pore structure for containing the electro-active sulphur and facilitates rapid electron/ion transport. This cathode system does not require any additional binding agents, conductive additives or a separate metallic current collector thus decreasing the weight of the cathode by typically ~20-30 wt%. A Li-S battery with the sulphur-FLG foam cathode shows good electrochemical stability and high rate discharge capacity retention for up to 400 discharge/charge cycles at a high current density of 3200 mA g-1. Even after 400 cycles the capacity decay is only ~0.064% per cycle relative to the early (e.g. the 5th cycle) discharge capacity, while yielding an average columbic efficiency of ~96.2%. Our results indicate the potential suitability of graphene foam for efficient, ultra-light and high-performance batteries.A novel ultra-lightweight three-dimensional (3-D) cathode system for lithium sulphur (Li-S) batteries has been synthesised by loading sulphur on to an interconnected 3-D network of few-layered graphene (FLG) via a sulphur solution infiltration method. A free-standing FLG monolithic network foam was formed as a negative of a Ni metallic foam template by CVD followed by etching away of Ni. The FLG foam offers excellent electrical conductivity, an appropriate hierarchical pore structure for containing the electro-active sulphur and facilitates rapid electron/ion transport. This cathode system does not require any additional binding agents, conductive additives or a separate metallic current collector

  14. High performance planar p-i-n perovskite solar cells with crown-ether functionalized fullerene and LiF as double cathode buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaodong; Zhou, Yi, E-mail: yizhou@suda.edu.cn, E-mail: songbo@suda.edu.cn, E-mail: liyf@iccas.ac.cn; Song, Bo, E-mail: yizhou@suda.edu.cn, E-mail: songbo@suda.edu.cn, E-mail: liyf@iccas.ac.cn [Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu 215123 (China); Lei, Ming [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Li, Yongfang, E-mail: yizhou@suda.edu.cn, E-mail: songbo@suda.edu.cn, E-mail: liyf@iccas.ac.cn [Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu 215123 (China); Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2015-08-10

    Double cathode buffer layers (CBLs) composed of fullerene derivative functionalized with a crown-ether end group in its side chain (denoted as PCBC) and a LiF layer were introduced between the PCBM acceptor layer and the top cathode in planar p-i-n perovskite solar cells (pero-SCs) based on CH{sub 3}NH{sub 3}PbI{sub 3−X}Cl{sub X}. The devices with the PCBC/LiF double CBLs showed significant improvements in power conversion efficiency (PCE) and long-term stability when compared to the device with LiF single CBL. Through optimizing the spin-coating speed of PCBC, a maximum PCE of 15.53% has been achieved, which is approximately 15% higher than that of the device with single LiF CBL. The remarkable improvement in PCE can be attributed to the formation of a better ohmic contact in the CBL between PCBC and LiF/Al electrode arising from the dipole moment of PCBC, leading to the enhanced fill factor and short-circuit current density (J{sub sc}). Besides the PCE, the long-term stability of the devices with PCBC interlayer is also superior to that of the device with LiF single CBL, which is due to the more effective protection for the perovskite/PCBM interface.

  15. Single-Step Fabrication Using a Phase Inversion Method of Poly(vinylidene fluoride) (PVDF) Activated Carbon Air Cathodes for Microbial Fuel Cells

    KAUST Repository

    Yang, Wulin

    2014-10-14

    Air cathodes used in microbial fuel cells (MFCs) need to have high catalytic activity for oxygen reduction, but they must also be easy to manufacture, inexpensive, and watertight. A simple one-step, phase inversion process was used here to construct an inexpensive MFC cathode using a poly(vinylidene fluoride) (PVDF) binder and an activated carbon catalyst. The phase inversion process enabled cathode preparation at room temperatures, without the need for additional heat treatment, and it produced for the first time a cathode that did not require a separate diffusion layer to prevent water leakage. MFCs using this new type of cathode produced a maximum power density of 1470 ± 50 mW m–2 with acetate as a substrate, and 230 ± 10 mW m–2 with domestic wastewater. These power densities were similar to those obtained using cathodes made using more expensive materials or more complex procedures, such as cathodes with a polytetrafluoroethylene (PTFE) binder and a poly(dimethylsiloxane) (PDMS) diffusion layer, or a Pt catalyst. Even though the PVDF cathodes did not have a diffusion layer, they withstood up to 1.22 ± 0.04 m of water head (∼12 kPa) without leakage, compared to 0.18 ± 0.02 m for cathodes made using PTFE binder and PDMS diffusion layer. The cost of PVDF and activated carbon ($3 m–2) was less than that of the stainless steel mesh current collector ($12 m–2). PVDF-based AC cathodes therefore are inexpensive, have excellent performance in terms of power and water leakage, and they can be easily manufactured using a single phase inversion process at room temperature.

  16. Gradient Mn-La-Pt Catalysts with Three-layered Structure for Li-O2 battery.

    Science.gov (United States)

    Cai, Kedi; Yang, Rui; Lang, Xiaoshi; Zhang, Qingguo; Wang, Zhenhua; He, Tieshi

    2016-10-12

    Gradient Mn-La-Pt catalysts with three-layered structure of manganese dioxide (MnO2), lanthanum oxide (La2O3), and Platinum (Pt) for Li-O2 battery are prepared in this study. The mass ratio of the catalysts is respectively 5:2:3, 4:2:4, and 3:2:5 (MnO2: La2O3: Pt) which is start from the side of the electrolyte. The relationship between morphology structure and electrochemical performance of gradient catalyst is investigated by energy dispersive spectrometry and constant current charge/discharge test. The Li-O2 battery based on gradient Mn-La-Pt catalysts shows high discharge specific capacity (2707 mAh g(-1)), specific energy density (8400 Wh kg(-1)) and long cycle life (56 cycles). The improvement of the Li-O2 battery discharge capacity is attributed to the gradient distribution of MnO2 and Pt and the involvement of La2O3 that can improve the energy density of the battery. More important, this work will also provide new ideas and methods for the research of other metal-air battery.

  17. A comparative parametric study of a catalytic plate methane reformer coated with segmented and continuous layers of combustion catalyst for hydrogen production

    Science.gov (United States)

    Mundhwa, Mayur; Parmar, Rajesh D.; Thurgood, Christopher P.

    2017-03-01

    A parametric comparison study is carried out between segmented and conventional continuous layer configurations of the coated combustion-catalyst to investigate their influence on the performance of methane steam reforming (MSR) for hydrogen production in a catalytic plate reactor (CPR). MSR is simulated on one side of a thin plate over a continuous layer of nickel-alumina catalyst by implementing an experimentally validated surface microkinetic model. Required thermal energy for the MSR reaction is supplied by simulating catalytic methane combustion (CMC) on the opposite side of the plate over segmented and continuous layer of a platinum-alumina catalyst by implementing power law rate model. The simulation results of both coating configurations of the combustion-catalyst are compared using the following parameters: (1) co-flow and counter-flow modes between CMC and MSR, (2) gas hourly space velocity and (3) reforming-catalyst thickness. The study explains why CPR designed with the segmented combustion-catalyst and co-flow mode shows superior performance not only in terms of high hydrogen production but also in terms of minimizing the maximum reactor plate temperature and thermal hot-spots. The study shows that the segmented coating requires 7% to 8% less combustion-side feed flow and 70% less combustion-catalyst to produce the required flow of hydrogen (29.80 mol/h) on the reforming-side to feed a 1 kW fuel-cell compared to the conventional continuous coating of the combustion-catalyst.

  18. Application of a Coated Film Catalyst Layer Model to a High Temperature Polymer Electrolyte Membrane Fuel Cell with Low Catalyst Loading Produced by Reactive Spray Deposition Technology

    Directory of Open Access Journals (Sweden)

    Timothy D. Myles

    2015-10-01

    Full Text Available In this study, a semi-empirical model is presented that correlates to previously obtained experimental overpotential data for a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC. The goal is to reinforce the understanding of the performance of the cell from a modeling perspective. The HT-PEMFC membrane electrode assemblies (MEAs were constructed utilizing an 85 wt. % phosphoric acid doped Advent TPS® membranes for the electrolyte and gas diffusion electrodes (GDEs manufactured by Reactive Spray Deposition Technology (RSDT. MEAs with varying ratios of PTFE binder to carbon support material (I/C ratio were manufactured and their performance at various operating temperatures was recorded. The semi-empirical model derivation was based on the coated film catalyst layer approach and was calibrated to the experimental data by a least squares method. The behavior of important physical parameters as a function of I/C ratio and operating temperature were explored.

  19. Metal-mediated Layer-by-layer Films of Multi-metalloporphyrin Arrays:a Novel Switchable Catalyst System

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    1 Results Metalloporphyrins as one kind of effective catalysts have received considerable attention in the past two decades,because of their selective oxidation of hydrocarbons and other organic compound under mild conditions.Great efforts have been made to oxidize or epoxidize the hydrocarbons and cycloparaffin with the oxidants such as PhIO,H2O2 catalyzed by the metalloporphyrins.However,the metalloporphyrins are normally dissolved in the reaction solution or immobilized on silica or other porous supp...

  20. Layer-structured LiNi0.8Co0.2O2: A new triple (H+/O2-/e-) conducting cathode for low temperature proton conducting solid oxide fuel cells

    Science.gov (United States)

    Fan, Liangdong; Su, Pei-Chen

    2016-02-01

    Solid oxide fuel cells with proton conducting electrolytes (H-SOFCs) show great potential for more efficient energy conversion over their oxygen ionic conducting counterparts at temperatures below 650 °C, providing a comparably high performance cathode material can be available. A brief review of current development of cathode materials shows that materials with triple (oxygen ionic, protonic, and electronic) conducting properties are most promising for H-SOFCs. In this work, a triple-conducting LiNi0.8Co0.2O2 (LNCO) with layered structure, allowing simultaneous conduction of intrinsic oxygen ion and electron as well as the extrinsic proton, is proposed as a cathode material for H-SOFC. The electrochemical impedance spectroscopy analysis of LNCO shows the good oxygen reduction reaction (ORR) activity with a considerably low activation energy of 0.88 eV, and an evident water uptake capability those facilitate the cathode reaction process. Fuel cells using LNCO cathode on a BaZr0.1Ce0.7Y0.2O3 proton-conducting electrolyte render a peak power density of 410 mW cm-2 at 650 °C under H2/air condition, which is higher than most of the typical cathode materials reported with similar cell configurations. This work also demonstrated a new series of simple and low cost cathode materials simultaneously possessing interesting triple-conduction and good ORR activities for low temperature H-SOFCs.

  1. Understanding the interfacial phenomena of a 4.7 V and 55 °C Li-ion battery with Li-rich layered oxide cathode and grap2hite anode and its correlation to high-energy cycling performance

    Science.gov (United States)

    Pham, Hieu Quang; Hwang, Eui-Hyung; Kwon, Young-Gil; Song, Seung-Wan

    2016-08-01

    Research progress of high-energy performance and interfacial phenomena of Li1.13Mn0.463Ni0.203Co0.203O2 cathode and graphite anode in a 55 °C full-cell under an aggressive charge cut-off voltage to 4.7 V (4.75 V vs. Li/Li+) is reported. Although anodic instability of conventional electrolyte is the critical issue on high-voltage and high-temperature cell operation, interfacial phenomena and the solution to performance improvement have not been reported. Surface spectroscopic evidence revealed that structural degradation of both cathode and anode materials, instability of surface film at cathode, and metal-dissolution from cathode and -deposition at anode, and a rise of interfacial resistance with high-voltage cycling in 55 °C conventional electrolyte are resolved by the formation of a stable surface film with organic/inorganic mixtures at cathode and solid electrolyte interphase (SEI) at anode using blended additives of fluorinated linear carbonate and vinylene carbonate. As a result, significantly improved cycling stability of 77% capacity retention delivering 227-174 mAhg-1 after 50 cycles is obtained, corresponding to 819-609 Wh per kg of cathode active material. Interfacial stabilization approach would pave the way of controlling the performance and safety, and widening the practical application of Li-rich layered oxide cathode materials and high-voltage electrolyte materials in various high-energy density Li-ion batteries.

  2. Alloy catalyst material

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a novel alloy catalyst material for use in the synthesis of hydrogen peroxide from oxygen and hydrogen, or from oxygen and water. The present invention also relates to a cathode and an electrochemical cell comprising the novel catalyst material, and the process use...

  3. Design of Efficient Catalysts with Double Transition Metal Atoms on C2N Layer.

    Science.gov (United States)

    Li, Xiyu; Zhong, Wenhui; Cui, Peng; Li, Jun; Jiang, Jun

    2016-05-05

    Heterogeneous catalysis often involves molecular adsorptions to charged catalyst site and reactions triggered by catalyst charges. Here we use first-principles simulations to design oxygen reduction reaction (ORR) catalyst based on double transition metal (TM) atoms stably supported by 2D crystal C2N. It not only holds characters of low cost and high durability but also effectively accumulates surface polarization charges on TMs and later deliveries to adsorbed O2 molecule. The Co-Co, Ni-Ni, and Cu-Cu catalysts exhibit high adsorption energies and extremely low dissociation barriers for O2, as compared with their single-atom counterparts. Co-Co on C2N presents less than half the value of the reaction barrier of bulk Pt catalysts in the ORR rate-determining steps. These catalytic improvements are well explained by the dependences of charge polarization on various systems, which opens up a new strategy for optimizing TM catalytic performance with the least metal atoms on porous low-dimensional materials.

  4. Effect of the compactness of the lithium chloride layer formed on the carbon cathode on the electrochemical reduction of SOCl{sub 2} electrolyte in Li-SOCl{sub 2} batteries

    Energy Technology Data Exchange (ETDEWEB)

    Seung-Bok Lee; Su-Il Pyun [Korea Advanced Institute of Science and Technology, Taejon (Korea). Dept. of Materials Science and Engineering; Eung-Jo Lee [Hana Tek Co Ltd., Kyounggi (Korea). R and D Center

    2001-07-01

    Effect of the compactness of the lithium chloride layer formed on the carbon cathode on the electrochemical reduction of SOCl{sub 2} electrolyte in Li-SOCl{sub 2} primary battery was investigated using ac-impedance spectroscopy and potentiostatic current transient technique. From the facts that the straight lines of the Nyquist plots of the ac-impedance spectra and the peak-like runs of the plot of It{sup 1/2} versus log t were observed from the pure carbon cathode, it was suggested that the porous layer of lithium chloride deposited on the pure carbon cathode was relatively compact enough to strongly impede the diffusion of SOCl{sub 2} through it, and hence the rate-controlling step for overall SOCl{sub 2} reduction is changed from the 'interfacial reaction between the pure carbon cathode and electrolyte' to the 'diffusion of SOCl{sub 2} through the porous lithium chloride layer'. On the other hand, any of the straight lines of the Nyquist plots of the ac-impedance spectra and of the peak-like courses of the plot of It{sup 1/2} versus log t can not be found in the Co-phthalocyanine (Pc)-incorporated carbon cathode. Thus, it was concluded that the porous layer of lithium chloride formed on the Co-Pc-incorporated carbon cathode was relatively porous enough to considerably facilitate the diffusion of SOCl{sub 2} through it, and hence the overall reduction rate of SOCl{sub 2} is governed by the 'interfacial reaction between the Co-Pc-incorporated carbon cathode and electrolyte' throughout the whole discharge of the Li-SOCl{sub 2} batteries. (author)

  5. Improving Morphological Quality and Uniformity of Hydrothermally Grown ZnO Nanowires by Surface Activation of Catalyst Layer

    Science.gov (United States)

    Murillo, Gonzalo; Lozano, Helena; Cases-Utrera, Joana; Lee, Minbaek; Esteve, Jaume

    2017-01-01

    This paper presents a study about the dependence of the hydrothermal growth of ZnO nanowires (NWs) with the passivation level of the active surface of the Au catalyst layer. The hydrothermal method has many potential applications because of its low processing temperature, feasibility, and low cost. However, when a gold thin film is utilized as the seed material, the grown NWs often lack morphological homogeneity; their distribution is not uniform and the reproducibility of the growth is low. We hypothesize that the state or condition of the active surface of the Au catalyst layer has a critical effect on the uniformity of the NWs. Inspired by traditional electrochemistry experiments, in which Au electrodes are typically activated before the measurements, we demonstrate that such activation is a simple way to effectively assist and enhance NW growth. In addition, several cleaning processes are examined to find one that yields NWs with optimal quality, density, and vertical alignment. We find cyclic voltammetry measurements to be a reliable indicator of the seed-layer quality for subsequent NW growth. Therefore, we propose the use of this technique as a standard procedure prior to the hydrothermal synthesis of ZnO NWs to control the growth reproducibility and to allow high-yield wafer-level processing.

  6. Co3O4-Pt/graphene as air cathode catalyst for lithium-air battery%四氧化三钴-铂/石墨烯锂空气电池阴极材料

    Institute of Scientific and Technical Information of China (English)

    顾大明; 杨丹丹; 李加展; 王余; 于晨涛

    2015-01-01

    It is reported that the preparation of Co3 O4-Pt/graphene hybrid and its use as air cathode catalyst for enhanced specific capacity in Lithium-air battery. Co3O4-Pt/graphene was synthesized by a two-step method. More specifically, Pt/graphene was prepared by microwave-assisted polyol process, and then it was mixed with Co3 O4 uniformly to get highly efficient Co3O4-Pt/graphene as air-cathode catalyst. Micromorphology, composition and compositional dispersion of the obtained hybrid catalyst were then characterized by X-ray diffraction ( XRD ) , scanning electron microscopy ( SEM ) , X-ray energy dispersive spectroscopy ( XEDS ) , transmission electron microscopy (TEM),Raman Spectroscopy(Ram). Co3O4-Pt/graphene air cathode catalyst was assembled with metal lithium anode, LiPF6/EC-DMC-EMC electrolyte, and PP/PE/PP to construct a lithium-air battery. The constant current charge-discharge tests of the lithium-air battery exhibit enhanced specific capacity: the discharge specific capacity reaches up to 8 000 mAh/g and the voltage is above 2. 6 V, which is superior to alternative cathode catalysts. The enhanced performance of lithium-air battery is attributed to the joint effect of preparation process, composition, and compositional dispersion.%为提高锂空气电池的比容量,采用微波辅助乙二醇还原法将H2 PtCl6 ·6H2 O及氧化石墨还原为Pt/石墨烯,再将其与Co3 O4混合均匀,得到高效Co3 O4-Pt/石墨烯锂空气电池复合阴极材料,作为对比,同时制备了Co3 O4-石墨、Co3 O4-石墨烯等阴极材料,用其与金属锂阳极、LiPF6/EC-DMC-EMC电解液、PP/PE/PP隔膜组装锂空气电池.用X射线衍射( XRD)、扫描电子显微镜( SEM)、透射电子显微镜( TEM)、X射线能量散射能谱( XEDS)、拉曼光谱( Ram)等方法对材料的微观形貌、组成及各组分在材料中的分散程度进行了表征,对电池进行恒流充放电测试,结果显示,Co3 O4-Pt/石墨烯阴极材料的比容量可超过8 000 m

  7. The platinum catalyst layer in polymer-electrolyte fuel cells[Dissertation 17127]; Die Platinkatalysatorschicht in Polymerelektrolyt-Brennstoffzellen. Beitraege zum Verstaendnis und zur Optimierung

    Energy Technology Data Exchange (ETDEWEB)

    Reiner, A.

    2007-07-01

    This illustrated, comprehensive dissertation by Dr. Andreas Reiner presents an in-depth analysis of polymer electrolyte fuel cells (PEFC) and in particular, their platinum catalyst layer. First of all, the thermodynamics and kinetics involved are reviewed, along with components, their efficiencies and the catalyst layer. The methods used, including scanning electron microscope, x-ray and Rutherford spectroscopy are discussed. The structure and composition of co-sputtered catalyst layers and their production are described. Electro-chemical activation and the electro-chemical properties of the layers are discussed. The second part of the dissertation deals with the principle of hydrogen under-potential deposition. This method provides information about the electrochemically active platinum surface fraction. The results of investigations made are presented and discussed.

  8. PEM fuel cell cathode carbon corrosion due to the formation of air/fuel boundary at the anode

    Science.gov (United States)

    Tang, Hao; Qi, Zhigang; Ramani, Manikandan; Elter, John F.

    The impacts of unprotected start up and shut down on fuel cell performance degradation was investigated using both single cell and dual cell configurations. It was found that the air/fuel boundary developed at the anode side after a fuel cell shut down or during its restart caused extremely quick degradation of the cathode. The thickness, the electrochemical active surface area, and the performance of the cathode catalyst layer were significantly reduced. By using a dual cell configuration, cathode potential as high as two times of open circuit voltage was measured, and the corrosion current flowing externally between the two cells was detected and quantified. Carbon catalyst-support corrosion/oxidation at such a high potential was largely responsible for the accelerated fuel cell performance degradation.

  9. Crystalline TiO2: A Generic and Effective Electron-Conducting Protection Layer for Photoanodes and -cathodes

    DEFF Research Database (Denmark)

    Mei, Bastian Timo; Pedersen, Thomas; Malacrida, Paolo;

    2015-01-01

    Stabilizing efficient photoabsorbers for solar water splitting has recently shown significant progress with the development of various protection layers. Suitable protection layers for tandem devices should be conductive, transparent, and stable in strongly acidic or alkaline solutions. This paper...

  10. Hairy foam : thin layers of carbon nanofibers as catalyst support for liquid phase reactions

    NARCIS (Netherlands)

    Chinthaginjala, Jitendra Kumar

    2010-01-01

    Catalytic multiphase reactors are at the heart of many chemical industries. They allow efficient contact between gas and/or liquid reactant phases with solid catalysts increasing reaction rates. In practice, the higher reaction rates can be taken advantage of only under the condition that the transf

  11. Cobalt based layered perovskites as cathode material for intermediate temperature Solid Oxide Fuel Cells: A brief review

    Science.gov (United States)

    Pelosato, Renato; Cordaro, Giulio; Stucchi, Davide; Cristiani, Cinzia; Dotelli, Giovanni

    2015-12-01

    Nowadays, the cathode is the most studied component in Intermediate Temperature-Solid Oxide Fuel Cells (IT-SOFCs). Decreasing SOFCs operating temperature implies slow oxygen reduction kinetics and large polarization losses. Double perovskites with general formula REBaCo2O5+δ are promising mixed ionic-electronic conductors, offering a remarkable enhancement of the oxygen diffusivity and surface exchange respect to disordered perovskites. In this review, more than 250 compositions investigated in the literature were analyzed. The evaluation was performed in terms of electrical conductivity, Area Specific Resistance (ASR), chemical compatibility with electrolytes and Thermal Expansion Coefficient (TEC). The most promising materials have been identified as those bearing the mid-sized rare earths (Pr, Nd, Sm, Gd). Doping strategies have been analyzed: Sr doping on A site promotes higher electrical conductivity, but worsen ASR and TECs; B-site doping (Fe, Ni, Mn) helps lowering TECs, but is detrimental for the electrochemical properties. A promising boost of the electrochemical activity is obtained by simply introducing a slight Ba under-stoichiometry. Still, the high sensitivity of the electrochemical properties against slight changes in the stoichiometry hamper a conclusive comparison of all the investigated compounds. Opportunities for an improvement of double perovskite cathodes performance is tentatively foreseen in combining together the diverse effective doping strategies.

  12. Cathodic arcs

    OpenAIRE

    Anders, Andre

    2003-01-01

    Cathodic arc plasma deposition has become the technology of choice for hard, wear and corrosion resistant coatings for a variety of applications. The history, basic physics of cathodic arc operation, the infamous macroparticle problem and common filter solutions, and emerging high-tech applications are briefly reviewed. Cathodic arc plasmas stand out due to their high degree of ionization, with important consequences for film nucleation, growth, and efficient utilization of substrate bia...

  13. Mg-Cu-Al layered double hydroxides based catalysts for the reduction of nitrates in aqueous solutions

    Directory of Open Access Journals (Sweden)

    Vulić Tatjana J.

    2010-01-01

    Full Text Available The secondary waste and bacterial contamination in physico-chemical and biological separation processes used today for nitrate removal from ground water make novel catalytic technologies that convert nitrates to unharmful gaseous nitrogen, very attractive for scientific research. The Mg-Cu-Al layered double hydroxide (LDH based catalysts with different Mg/Al ratio were investigated in water denitrification reaction in the presence of hydrogen and with solely copper as an active phase. Since LDHs have ion exchange properties and their derived mixed oxides possess memory effect (restoration of layered structure after thermal decomposition, their adsorption capacity for nitrates was also measured in the same model system. All studied samples showed nitrate removal from 23% to 62% following the decrease in Al content, as well as the substantial adsorption capacity ranging from 18% to 38%. These results underlie the necessity to take into account the effects of the adsorption in all future investigations.

  14. Preparation of Pt nanowires as cathode catalyst for PEMFC and its application in stack%PEMFC用Pt纳米线阴极催化剂的制备及在电堆中的应用

    Institute of Scientific and Technical Information of China (English)

    常丰瑞; 黄俭标; 马建新; 杨代军; 李冰; 严泽宇; 顾荣鑫

    2014-01-01

    Carbon supported platinum nanowires (Pt NWs/C), acting as cathode catalyst for proton exchange membrane fuel cell (PEMFC), were synthesized by reducing H2PtCl6 with HCOOH at room temperature without assistance of template. The catalyst microstructure and morphology were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The Pt NWs/C had an average cross-sectional diameter of (4.0±0.2) nm and a length of 15-25 nm. Good electrocatalytic performance and oxygen reduction reaction (ORR) of the as-prepared catalyst was characterized by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). Two membrane electrode assemblies (MEAs) were fabricated, with Pt NWs/C and Pt/C as cathode catalyst respectively, and tested for comparison. The maximum power densities of Pt NWs/C and Pt/C, respectively were 705.6 mW·cm-2 and 674.4 mW·cm-2. Afterwards, an 18-cell stack with Pt NWs/C as cathode catalyst and a 20-cell stack with Pt/C as cathode catalyst were built for testing. Maximum power densities were 409.2 mW·cm-2 and 702.7 mW·cm-2, and coefficients of variation (Cv) of individual cell were 16.1% and 4.36% at the maximum power density, respectively. Data analysis indicated that Pt NWs/C for the cathode in a MEA exhibited good catalytic activity at a scale-up level, however, as compared with the commercial Pt/C catalyst, CV performance and uniformity should be improved. This work not only sheds light on the scale-up possibility of Pt NWs/C catalyst, but also provides a possibility for further durability test before its application in a fuel cell vehicle.%采用无模板法制备了用于质子交换膜燃料电池(PEMFC)的碳载铂纳米线(Pt NWs/C)阴极催化剂,使用透射电镜(TEM)和X射线衍射图谱技术(XRD)对催化剂的微观结构和形貌进行了表征。研究结果表明,制备的铂催化剂具有纳米线的结构,平均截面直径为(4.0±0.2)nm,线长为15~25 nm。利用循环伏

  15. Efficient degradation of dye pollutants using dioxygen mediated by iron(Ⅱ) 2,2'-bipyridine loaded layered clay catalyst under visible irradiation

    Institute of Scientific and Technical Information of China (English)

    CHENG Mingming; SUN Zhenying; MA Wanhong; CHEN Chuncheng; ZHAO Jincai; WANG Zhengping

    2006-01-01

    The organic-inorganic layered solid catalyst Fe(bpy)32+-laponite was able to photodegrade Rhodamine B (RhB) by activation of dioxygen under visible irradiation (λ>420 nm), while the homogeneous aqueous solution Fe(bpy)32+ showed no photoactivity. The catalyst could be repeatedly used and retained its reactivity. The hybrid catalyst could be separated from the suspension by centrifugation or sedimentation. The TOC removal yield of RhB was measured. Reactive oxygen species (ROS) formed during degradation was detected by EPR. A possible mechanism was proposed on the basis of the experimental results.

  16. Enhancing the cyclability of Li-O2 batteries using PdM alloy nanoparticles anchored on nitrogen-doped reduced graphene as the cathode catalyst

    Science.gov (United States)

    Leng, Limin; Li, Jing; Zeng, Xiaoyuan; Song, Huiyu; Shu, Ting; Wang, Haishui; Liao, Shijun

    2017-01-01

    An efficient ORR/OER catalyst was developed by anchoring highly dispersed bimetallic PdM (M = Fe, Co, Ni) alloy nanoparticles on nitrogen-doped reduced graphene oxide (N-rGO). This new type of catalyst exhibited excellent ORR/OER activity, and the addition of transition metals also significantly improved catalytic stability, with the catalyst containing Fe (PdFe/N-rGO) exhibiting the best stability. A battery using this PdFe/N-rGO catalyst was capable of long-term stable cycling for 400 cycles (2000 h) with a limited capacity of 1000 mAh g-1 at 400 mA g-1, which was much longer than a battery with Pd/N-rGO as the catalyst (only 80 cycles, 400 h). We attribute the high performance of these catalysts to the high surface area of N-rGO, the anchoring of highly dispersed Pd alloy nanoparticles, and the prevention of Pd alloy nanoparticle aggregation and dissolution by the presence of the transition metals.

  17. Substrate temperature influence on the properties of GaN thin films grown by hollow-cathode plasma-assisted atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Alevli, Mustafa, E-mail: mustafaalevli@marmara.edu.tr; Gungor, Neşe [Department of Physics, Faculty of Arts and Sciences, Marmara University, Goztepe, 34722 Istanbul (Turkey); Haider, Ali; Kizir, Seda; Leghari, Shahid A.; Biyikli, Necmi, E-mail: biyikli@unam.bilkent.edu.tr [Institute of Materials Science and Nanotechnology, Bilkent University, Bilkent, 06800 Ankara, Turkey and National Nanotechnology Research Center (UNAM), Bilkent University, Bilkent, 06800 Ankara (Turkey)

    2016-01-15

    Gallium nitride films were grown by hollow cathode plasma-assisted atomic layer deposition using triethylgallium and N{sub 2}/H{sub 2} plasma. An optimized recipe for GaN film was developed, and the effect of substrate temperature was studied in both self-limiting growth window and thermal decomposition-limited growth region. With increased substrate temperature, film crystallinity improved, and the optical band edge decreased from 3.60 to 3.52 eV. The refractive index and reflectivity in Reststrahlen band increased with the substrate temperature. Compressive strain is observed for both samples, and the surface roughness is observed to increase with the substrate temperature. Despite these temperature dependent material properties, the chemical composition, E{sub 1}(TO), phonon position, and crystalline phases present in the GaN film were relatively independent from growth temperature.

  18. High surface area graphite as alternative support for proton exchange membrane fuel cell catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira-Aparicio, P.; Folgado, M.A. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Avda. Complutense 22, E-28040 Madrid (Spain); Daza, L. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Avda. Complutense 22, E-28040 Madrid (Spain); Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie, 2 Campus de Cantoblanco, E-28049 Madrid (Spain)

    2009-07-01

    The suitability of a high surface area graphite (HSAG) as proton exchange membrane fuel cell (PEMFC) catalyst support has been evaluated and compared with that of the most popular carbon black: the Vulcan XC72. It has been observed that Pt is arranged on the graphite surface resulting in different structures which depend on the catalysts synthesis conditions. The influence that the metal particle size and the metal-support interaction exert on the catalysts degradation rate is analyzed. Temperature programmed oxidation (TPO) under oxygen containing streams has been shown to be a useful method to assess the resistance of PEMFC catalysts to carbon corrosion. The synthesized Pt/HSAG catalysts have been evaluated in single cell tests in the cathode catalytic layer. The obtained results show that HSAG can be a promising alternative to the traditionally used Vulcan XC72 carbon black when suitable catalysts synthesis conditions are used. (author)

  19. The effect of inhomogeneous compression on water transport in the cathode of a PEM fuel cell

    DEFF Research Database (Denmark)

    Olesen, Anders Christian; Berning, Torsten; Kær, Søren Knudsen

    2011-01-01

    A three-dimensional, multi-component, two-fluid model developed in the commercial CFD package CFX 13 (ANSYS inc.), is used to investigate the effect of porous media compression on transport phenomenon of a PEM Fuel cell (PEMFC). The PEMFC model only consist of the cathode channel, gas diffusion...... layer, micro-porous layer and catalyst layer, excluding the membrane and anode. In the porous media liquid water transport is described by the capillary pressure gradient, momentum loss via the Darcy-Forchheimer equation and mass transfer between phases by a non-equilibrium phase change model...

  20. Titanium oxide:fullerene composite films as electron collector layer in organic solar cells and the use of an easy-deposition cathode

    Science.gov (United States)

    Pérez-Gutiérrez, Enrique; Maldonado, José-Luis; Nolasco, Jairo; Ramos-Ortíz, Gabriel; Rodríguez, Mario; Torre, Ulises Mendoza-De la; Meneses-Nava, Marco-Antonio; Barbosa-García, Oracio; García-Ortega, Héctor; Farfán, Norberto; Granados, Giovana; Santillan, Rosa; Juaristi, Eusebio

    2014-06-01

    Here is reported the use of a titanium oxide:fullerene (TiOx:PC71BM) composite film as electron collector layer in organic photovoltaic devices (OPV cells). OPV cells were fabricated under the bulk heterojunction architecture: the active layer was a blend of either the photoconductor polymer MEH-PPV or P3HT with the fullerene derivative PC71BM. As cathode the eutectic alloy of Bi, In and Sn, known as Field’s metal, was used. The melting point of this alloy is above 62 °C, which makes it suitable for a vacuum-free deposition process and easy and fast device test. Cell fabrication and testing were carried out at normal room conditions. For OPV cells based on MEH-PPV, the composite thin electron collector layer improved the power conversion efficiency (η) from 1.12% to 2.07%, thus the η increase was about 85%. Meanwhile, for devices based on P3HT the use of the composite film improved the photocurrent in almost 1 mA/cm2 and the efficiency slightly increase from 2.48% to 2.68%.

  1. Improvement in the Lifetime of Planar Organic Photovoltaic Cells through the Introduction of MoO3 into Their Cathode Buffer Layers

    Directory of Open Access Journals (Sweden)

    Linda Cattin

    2014-03-01

    Full Text Available Recently, MoO3, which is typically used as an anode buffer layer in organic photovoltaic cells (OPVCs, has also been used as a cathode buffer layer (CBL. Here, we check its efficiency as a CBL using a planar heterojunction based on the CuPc/C60 couple. The CBL is a bi-layer tris-(8-hydroxyquinoline aluminum (Alq3/MoO3. We show that the OPVC with MoO3 in its CBL almost immediately exhibits lower efficiency than those using Alq3 alone. Nevertheless, the OPVCs increase their efficiency during the first five to six days of air exposure. We explain this evolution of the efficiency of the OPVCs over time through the variation in the MoO3 work function due to air contamination. By comparison to a classical OPVC using a CBL containing only Alq3, if it is found that the initial efficiency of the latter is higher, this result is no longer the same after one week of exposure to ambient air. Indeed, this result is due to the fact that the lifetime of the cells is significantly increased by the presence of MoO3 in the CBL.

  2. Modification of Ni-Rich FCG NMC and NCA Cathodes by Atomic Layer Deposition: Preventing Surface Phase Transitions for High-Voltage Lithium-Ion Batteries.

    Science.gov (United States)

    Mohanty, Debasish; Dahlberg, Kevin; King, David M; David, Lamuel A; Sefat, Athena S; Wood, David L; Daniel, Claus; Dhar, Subhash; Mahajan, Vishal; Lee, Myongjai; Albano, Fabio

    2016-05-26

    The energy density of current lithium-ion batteries (LIBs) based on layered LiMO2 cathodes (M = Ni, Mn, Co: NMC; M = Ni, Co, Al: NCA) needs to be improved significantly in order to compete with internal combustion engines and allow for widespread implementation of electric vehicles (EVs). In this report, we show that atomic layer deposition (ALD) of titania (TiO2) and alumina (Al2O3) on Ni-rich FCG NMC and NCA active material particles could substantially improve LIB performance and allow for increased upper cutoff voltage (UCV) during charging, which delivers significantly increased specific energy utilization. Our results show that Al2O3 coating improved the NMC cycling performance by 40% and the NCA cycling performance by 34% at 1 C/-1 C with respectively 4.35 V and 4.4 V UCV in 2 Ah pouch cells. High resolution TEM/SAED structural characterization revealed that Al2O3 coatings prevented surface-initiated layered-to-spinel phase transitions in coated materials which were prevalent in uncoated materials. EIS confirmed that Al2O3-coated materials had significantly lower increase in the charge transfer component of impedance during cycling. The ability to mitigate degradation mechanisms for Ni-rich NMC and NCA illustrated in this report provides insight into a method to enable the performance of high-voltage LIBs.

  3. Modification of Ni-Rich FCG NMC and NCA Cathodes by Atomic Layer Deposition: Preventing Surface Phase Transitions for High-Voltage Lithium-Ion Batteries

    Science.gov (United States)

    Mohanty, Debasish; Dahlberg, Kevin; King, David M.; David, Lamuel A.; Sefat, Athena S.; Wood, David L.; Daniel, Claus; Dhar, Subhash; Mahajan, Vishal; Lee, Myongjai; Albano, Fabio

    2016-05-01

    The energy density of current lithium-ion batteries (LIBs) based on layered LiMO2 cathodes (M = Ni, Mn, Co: NMC; M = Ni, Co, Al: NCA) needs to be improved significantly in order to compete with internal combustion engines and allow for widespread implementation of electric vehicles (EVs). In this report, we show that atomic layer deposition (ALD) of titania (TiO2) and alumina (Al2O3) on Ni-rich FCG NMC and NCA active material particles could substantially improve LIB performance and allow for increased upper cutoff voltage (UCV) during charging, which delivers significantly increased specific energy utilization. Our results show that Al2O3 coating improved the NMC cycling performance by 40% and the NCA cycling performance by 34% at 1 C/-1 C with respectively 4.35 V and 4.4 V UCV in 2 Ah pouch cells. High resolution TEM/SAED structural characterization revealed that Al2O3 coatings prevented surface-initiated layered-to-spinel phase transitions in coated materials which were prevalent in uncoated materials. EIS confirmed that Al2O3-coated materials had significantly lower increase in the charge transfer component of impedance during cycling. The ability to mitigate degradation mechanisms for Ni-rich NMC and NCA illustrated in this report provides insight into a method to enable the performance of high-voltage LIBs.

  4. Novel low-cost Fenton-like layered Fe-titanate catalyst: preparation, characterization and application for degradation of organic colorants.

    Science.gov (United States)

    Chen, Yongzhou; Li, Nian; Zhang, Ye; Zhang, Lide

    2014-05-15

    Novel low-cost layered Fe-titanate catalyst for photo-Fenton degradation of organic contaminants was successfully developed by ion exchange of Fe(3+) with Na(+) layered nano Na-titanates which was prepared by alkali hydrothermal method. The as prepared materials were characterized by powder X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectrometer (EDX). The catalytic activity of the Fe-titanate catalyst was evaluated by the decolorization of three different dyes (rhodamine 6G (R6G), methyl blue (MB), and methyl orange (MO)) under UV irradiation at room temperature. Effect of several important factors such as Fe loading in the catalyst, initial solution pH, catalyst dosage, H2O2 amount, and reaction time was systematically studied. It was found that the decolorization was very efficient for all three dyes. The efficiency reached 98% for R6G, 98.5% for MB, and 97% for MO, respectively, under optimal conditions. The oxidation process was quick, and only 15 min is needed for all three dyes. Moreover, the Fe-titanate catalyst could be used in a wider and near neutral pH range compared with classic Fenton systems which need to be operated at around pH 3.0. Kinetic analysis results showed that the oxidation kinetics was accurately represented by pseudo-first-order model. More importantly, the catalyst was very stable and could be reused for at least four cycles when operated under near neutral pH. The Fe leaching from the catalyst measured was almost negligible, which not only demonstrated the stability of the catalyst, but also avoided the formation of secondary Fe pollution. Therefore, the reported Fe-titanates are promising nanomaterials which can be used as Fenton like catalyst for the degradation of organic contaminant in wastewater.

  5. Numerical analysis on effect of diffusion layer characteristics on water flooding in PEMFC cathode%PEMFC阴极扩散层结构特性对水淹影响的数值分析

    Institute of Scientific and Technical Information of China (English)

    李英; 周勤文; 周晓慧

    2013-01-01

    GDL (gas diffusion layer) is one of the critical components of a fuel cell and its basic functions are to provide channels for diffusion of gas from fluid to catalyst layer and for drain of liquid water from catalyst layer to fluid. In order to meet service conditions, the understanding for structure-performance of GDL is very essential, such as key parameters structure, porosity, hydrophobicity, hydrophilicity, gas permeability, transport properties, water management and their roles. A mathematics model of ID and two-phase was built for GDL in cathode of proton exchange membrane fuel cell (PEMFC). A direct numerical procedure was applied for combined equations of the model and Leverett's and Fick's laws to analyze the profiles of liquid water saturation and oxygen concentration across the gas diffusion layer. The effect of GDL characteristics, such as porosity, thickness, contact angle and absolute permeability was discussed. The results show that its hydrophobicity is helpful for removal of liquid water. The effect of contact tangle on liquid water saturation and oxygen mass transfer becomes less and GDL porosity and thickness has little effect on liquid water saturation at the hydrophobic condition, but porosity and thickness of GDL play an important role in oxygen transfer. For practical use, both GDL porosity and thickness increase, there is no significant difference for limiting current density. Tafel slope and limiting current density predicted by the model agree well with the experimental observation from literatures.%建立质子交换膜燃料电池一维两相传递模型,通过达西定律和菲克定律的联立求解得到扩散层中的液体饱和度和氧气浓度分布.考察扩散层特性参数孔隙率、厚度、接触角、渗透率对阴极水淹的影响,结果表明扩散层表面憎水将有助于液态水移出,但当达到憎水条件后,增大接触角对液态水传输和氧气传质的影响逐渐变小.憎水条件下孔隙率和

  6. Catalytic synthesis of nitrogen-doped multi-walled carbon nanotubes using layered double hydroxides as catalyst precursors

    Indian Academy of Sciences (India)

    Yong Cao; Yun Zhao; Qingxia Li; Qingze Jiao

    2009-03-01

    The nitrogen (N)-doped carbon (CN) nanotubes were synthesized by pyrolysis of ethylenediamine with Ni1.07Mg1.01AlO3.58, Ni1.99Mg0.29AlO3.78, and Ni2.31Mg0.08AlO3.89 mixed oxides as catalysts at 650°C. Those mixed oxides were obtained by calcination of corresponding layered double hydroxide precursors (LDHs). Structure and composition of LDHs and mixed oxides were characterized by X-ray diffraction (XRD) and Inductively coupled plasma spectrum. X-ray photoelectron spectroscopy and transmission electron microscope were used to characterize the N content, proportion of pyridine-like N structure and morphology of CN nanotubes. The results showed that the tubes grown with Ni2.31Mg0.08AlO3.89 as catalysts had more obvious bamboo-like structure, larger diameter than those grown with Ni1.07Mg1.01AlO3.58 and Ni1.99Mg0.29AlO3.78. The N content and proportion of graphitic-like N structures increased with the content of Ni2+ increasing in LDH precursors. The morphology, N content and pyridine-like N structures for CN nanotubes can be controlled to a certain extent by varying the content of Ni2+ in LDH precursors.

  7. Carbon nanotube growth on nanozirconia under strong cathodic polarization in steam and carbon dioxide

    DEFF Research Database (Denmark)

    Tao, Youkun; Ebbesen, Sune Dalgaard; Zhang, Wei

    2014-01-01

    large cathodic polarizations specifically at the first 1 to 2 μm Ni-YSZ active cathode layer next to the YSZ electrolyte. High resolution transmission electron microscopy (HRTEM) shows that the CNTs are multi-walled with diameters of approximately 20 nm and the catalyst particles have diameters...... in the range of 5 to 25 nm. The results of HRTEM and energy dispersive X-ray spectroscopy (EDS) analysis confirm that the catalyst particles attached to the CNT are cubic zirconia. Most of the zirconia particles are located at one end of the CNTs, but particles embedded in the walls or inside the CNTs are also......}}{{\\cdot \\cdot \\hfill \\atop {\\rm {\\rm o}}\\hfill}}}} $=Oxygen vacancy, ${{{\\rm {\\rm O}}{{{\\rm {\\rm x}}\\hfill \\atop {\\rm {\\rm o}}\\hfill}}}}$=occupied site of oxygen in zirconia. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim....

  8. Direct fabrication of metal-free hollow graphene balls with a self-supporting structure as efficient cathode catalysts of fuel cell

    Science.gov (United States)

    Lu, Yanqi; Liu, Mingda; Nie, Huagui; Gu, Cancan; Liu, Ming; Yang, Zhi; Yang, Keqin; Chen, Xi'an; Huang, Shaoming

    2016-06-01

    Despite the good progress in developing carbon catalysts for oxygen reduction reaction (ORR), the current metal-free carbon catalysts are still far from satisfactory for large-scale applications of fuel cell. Developing hollow graphene balls with a self-supporting structure is considered to be an ideal method to inhibit graphene stacking and improve their catalytic performance. Herein, we fabricated metal-free hollow graphene balls with a self-supporting structure, through using a new strategy that involves direct metal-free catalytic growth from assembly of SiO2 spheres. To our knowledge, although much researches involving the synthesis of graphene balls have been reported, investigations into the direct metal-free catalytic growth of hollow graphene balls are rare. Furthermore, the electrocatalytic performance shows that the resulting hollow graphene balls have significantly high catalytic activity. More importantly, such catalysts also possess much improved stability and better methanol tolerance in alkaline media during the ORR compared with commercial Pt/C catalysts. The outstanding performances coupled with an easy and inexpensive preparing method indicated the great potential of the hollow graphene balls with a self-supporting structure in large-scale applications of fuel cell.

  9. Selective-area catalyst-free MBE growth of GaN nanowires using a patterned oxide layer.

    Science.gov (United States)

    Schumann, T; Gotschke, T; Limbach, F; Stoica, T; Calarco, R

    2011-03-04

    GaN nanowires (NWs) were grown selectively in holes of a patterned silicon oxide mask, by rf-plasma-assisted molecular beam epitaxy (PAMBE), without any metal catalyst. The oxide was deposited on a thin AlN buffer layer previously grown on a Si(111) substrate. Regular arrays of holes in the oxide layer were obtained using standard e-beam lithography. The selectivity of growth has been studied varying the substrate temperature, gallium beam equivalent pressure and patterning layout. Adjusting the growth parameters, GaN NWs can be selectively grown in the holes of the patterned oxide with complete suppression of the parasitic growth in between the holes. The occupation probability of a hole with a single or multiple NWs depends strongly on its diameter. The selectively grown GaN NWs have one common crystallographic orientation with respect to the Si(111) substrate via the AlN buffer layer, as proven by x-ray diffraction (XRD) measurements. Based on the experimental data, we present a schematic model of the GaN NW formation in which a GaN pedestal is initially grown in the hole.

  10. Interfacial chemical reaction and multiple gap state formation on three layer cathode in organic light-emitting diode: Ca/BaF2/Alq3

    Science.gov (United States)

    Kim, Tae Gun; Lee, Hyunbok; Yi, Yeonjin; Lee, Seung Mi; Kim, Jeong Won

    2015-07-01

    A three layer cathode is a promising stack structure for long lifetime and high efficiency in organic light-emitting diodes. The interfacial chemical reactions and their effects on electronic structures for alkaline-earth metal (Ca, Ba)/Alq3 [tris(8-hydroxyquinolinato)aluminum] and Ca/BaF2/Alq3 are investigated using in-situ X-ray and ultraviolet photoelectron spectroscopy, as well as molecular model calculation. The BaF2 interlayer initially prevents direct contact between Alq3 and the reactive Ca metal, but it is dissociated into Ba and CaF2 by the addition of Ca. As the Ca thickness increases, the Ca penetrates the interlayer to directly participate in the reaction with the underlying Alq3. This series of chemical reactions takes place irrespective of the BaF2 buffer layer thickness as long as the Ca overlayer thickness is sufficient. The interface reaction between the alkaline-earth metal and Alq3 generates two energetically separated gap states in a sequential manner. This phenomenon is explained by step-by-step charge transfer from the alkaline-earth metal to the lowest unoccupied molecular orbital states of Alq3, forming new occupied states below the Fermi level.

  11. Interfacial chemical reaction and multiple gap state formation on three layer cathode in organic light-emitting diode: Ca/BaF{sub 2}/Alq{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Gun; Kim, Jeong Won, E-mail: jeongwonk@kriss.re.kr [Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Daejeon 305-340 (Korea, Republic of); Korea University of Science and Technology (UST), 206 Gajeong-ro, Daejeon 305-350 (Korea, Republic of); Lee, Hyunbok [Department of Physics, Kangwon National University, 1 Gangwondaehak-gil, Chuncheon-si, Gangwon-do 200-701 (Korea, Republic of); Yi, Yeonjin [Institute of Physics and Applied Physics, Yonsei University, 50 Yonsei-ro, Seodaemoon-Gu, Seoul 120-749 (Korea, Republic of); Lee, Seung Mi [Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Daejeon 305-340 (Korea, Republic of)

    2015-07-14

    A three layer cathode is a promising stack structure for long lifetime and high efficiency in organic light-emitting diodes. The interfacial chemical reactions and their effects on electronic structures for alkaline-earth metal (Ca, Ba)/Alq{sub 3} [tris(8-hydroxyquinolinato)aluminum] and Ca/BaF{sub 2}/Alq{sub 3} are investigated using in-situ X-ray and ultraviolet photoelectron spectroscopy, as well as molecular model calculation. The BaF{sub 2} interlayer initially prevents direct contact between Alq{sub 3} and the reactive Ca metal, but it is dissociated into Ba and CaF{sub 2} by the addition of Ca. As the Ca thickness increases, the Ca penetrates the interlayer to directly participate in the reaction with the underlying Alq{sub 3}. This series of chemical reactions takes place irrespective of the BaF{sub 2} buffer layer thickness as long as the Ca overlayer thickness is sufficient. The interface reaction between the alkaline-earth metal and Alq{sub 3} generates two energetically separated gap states in a sequential manner. This phenomenon is explained by step-by-step charge transfer from the alkaline-earth metal to the lowest unoccupied molecular orbital states of Alq{sub 3}, forming new occupied states below the Fermi level.

  12. α,α'-Diarylacenaphtho[1,2-c]phosphole P-oxides: divergent synthesis and application to cathode buffer layers in organic photovoltaics.

    Science.gov (United States)

    Matano, Yoshihiro; Saito, Arihiro; Suzuki, Yuto; Miyajima, Tooru; Akiyama, Seiji; Otsubo, Saika; Nakamoto, Emi; Aramaki, Shinji; Imahori, Hiroshi

    2012-10-01

    A divergent method for the synthesis of α,α'-diarylacenaphtho[1,2-c]phosphole P-oxides has been established; α,α'-dibromoacenaphtho[c]phosphole P-oxide, which was prepared through a Ti(II)-mediated cyclization of 1,8-bis(trimethylsilylethynyl)naphthalene, underwent a Stille coupling with three different kinds of aryltributylstannanes to afford the α,α'-diarylacenaphtho[c]phosphole P-oxides in moderate to good yields. X-ray crystallographic analyses and UV/Vis absorption/fluorescence measurements have revealed that the degree of π-conjugation, the packing motif, the electron-accepting ability, and the thermal stability of the acenaphtho[c]phosphole π-systems are finely tunable with the α-aryl substituents. All the P=O and P=S derivatives exhibited high stability in their electrochemically reduced state. To use this class of arene-fused phosphole π-systems as n-type semiconducting materials, we evaluated device performances of the bulk heterojunction organic photovoltaics (OPV) that consist of poly(3-hexylthiophene), an indene-C(70) bisadduct, and a cathode buffer layer. The insertion of the diarylacenaphtho[c]phosphole P-oxides as the buffer layer was found to improve the power conversion efficiency of the polymer-based OPV devices.

  13. Low-Temperature Solution-Processed SnO2 Nanoparticles as a Cathode Buffer Layer for Inverted Organic Solar Cells.

    Science.gov (United States)

    Tran, Van-Huong; Ambade, Rohan B; Ambade, Swapnil B; Lee, Soo-Hyoung; Lee, In-Hwan

    2017-01-18

    SnO2 recently has attracted particular attention as a powerful buffer layer for organic optoelectronic devices due to its outstanding properties such as high electron mobility, suitable band alignment, and high optical transparency. Here, we report on facile low-temperature solution-processed SnO2 nanoparticles (NPs) in applications for a cathode buffer layer (CBL) of inverted organic solar cells (iOSCs). The conduction band energy of SnO2 NPs estimated by ultraviolet photoelectron spectroscopy was 4.01 eV, a salient feature that is necessary for an appropriate CBL. Using SnO2 NPs as CBL derived from a 0.1 M precursor concentration, P3HT:PC60BM-based iOSCs showed the best power conversion efficiency (PCE) of 2.9%. The iOSC devices using SnO2 NPs as CBL revealed excellent long-term device stabilities, and the PCE was retained at ∼95% of its initial value after 10 weeks in ambient air. These solution-processed SnO2 NPs are considered to be suitable for the low-cost, high throughput roll-to-roll process on a flexible substrate for optoelectronic devices.

  14. Electrical conduction and dielectric relaxation properties of AlN thin films grown by hollow-cathode plasma-assisted atomic layer deposition

    Science.gov (United States)

    Altuntas, Halit; Bayrak, Turkan; Kizir, Seda; Haider, Ali; Biyikli, Necmi

    2016-07-01

    In this study, aluminum nitride (AlN) thin films were deposited at 200 °C, on p-type silicon substrates utilizing a capacitively coupled hollow-cathode plasma source integrated atomic layer deposition (ALD) reactor. The structural properties of AlN were characterized by grazing incidence x-ray diffraction, by which we confirmed the hexagonal wurtzite single-phase crystalline structure. The films exhibited an optical band edge around ˜5.7 eV. The refractive index and extinction coefficient of the AlN films were measured via a spectroscopic ellipsometer. In addition, to investigate the electrical conduction mechanisms and dielectric properties, Al/AlN/p-Si metal-insulator-semiconductor capacitor structures were fabricated, and current density-voltage and frequency dependent (7 kHz-5 MHz) dielectric constant measurements (within the strong accumulation region) were performed. A peak of dielectric loss was observed at a frequency of 3 MHz and the Cole-Davidson empirical formula was used to determine the relaxation time. It was concluded that the native point defects such as nitrogen vacancies and DX centers formed with the involvement of Si atoms into the AlN layers might have influenced the electrical conduction and dielectric relaxation properties of the plasma-assisted ALD grown AlN films.

  15. Mesh optimization for microbial fuel cell cathodes constructed around stainless steel mesh current collectors

    KAUST Repository

    Zhang, Fang

    2011-02-01

    Mesh current collectors made of stainless steel (SS) can be integrated into microbial fuel cell (MFC) cathodes constructed of a reactive carbon black and Pt catalyst mixture and a poly(dimethylsiloxane) (PDMS) diffusion layer. It is shown here that the mesh properties of these cathodes can significantly affect performance. Cathodes made from the coarsest mesh (30-mesh) achieved the highest maximum power of 1616 ± 25 mW m-2 (normalized to cathode projected surface area; 47.1 ± 0.7 W m-3 based on liquid volume), while the finest mesh (120-mesh) had the lowest power density (599 ± 57 mW m-2). Electrochemical impedance spectroscopy showed that charge transfer and diffusion resistances decreased with increasing mesh opening size. In MFC tests, the cathode performance was primarily limited by reaction kinetics, and not mass transfer. Oxygen permeability increased with mesh opening size, accounting for the decreased diffusion resistance. At higher current densities, diffusion became a limiting factor, especially for fine mesh with low oxygen transfer coefficients. These results demonstrate the critical nature of the mesh size used for constructing MFC cathodes. © 2010 Elsevier B.V. All rights reserved.

  16. A comparative study of Pt/C cathodes in Sn 0.9In 0.1P 2O 7 and H 3PO 4 ionomers for high-temperature proton exchange membrane fuel cells

    Science.gov (United States)

    Jin, Y. C.; Okada, M.; Hibino, T.

    New Pt/C cathodes with many reaction sites for the oxygen reduction reaction as well as high tolerance to Pt corrosion have been designed for high-temperature proton exchange membrane fuel cells (PEMFCs), wherein a composite mixture of Sn 0.9In 0.1P 2O 7 (SIPO) and sulfonated polystyrene-b-poly(ethylene/butylene)-b-polystyrene (sSEBS) functioned as an ionomer. The microstructure of the Pt-SIPO-sSEBS/C cathode was characterized by homogeneous distribution of the ionomer over the catalyst layer and close contact between the ionomer and the Pt/C powder. As a result, the activation and concentration overpotentials of the Pt-SIPO-sSEBS/C cathode between 100 and 200 °C were lower than those of an H 3PO 4-impregnated Pt/C cathode, which suggests that the present ionomer can avoid poisoning of Pt by phosphate anions and the limitation of gas diffusion through the catalyst layer. Moreover, agglomeration of Pt in the Pt-SIPO-sSEBS/C cathode was not observed during a durability test at 150 °C for 6 days, although it was significant in the Pt-H 3PO 4/C cathode. Therefore, it is concluded that the Pt-SIPO-sSEBS/C electrode is a very promising cathode candidate for high-temperature PEMFCs.

  17. Cathodic arcs

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre

    2003-10-29

    Cathodic arc plasma deposition has become the technology of choice for hard, wear and corrosion resistant coatings for a variety of applications. The history, basic physics of cathodic arc operation, the infamous macroparticle problem and common filter solutions, and emerging high-tech applications are briefly reviewed. Cathodic arc plasmas standout due to their high degree of ionization, with important consequences for film nucleation, growth, and efficient utilization of substrate bias. Industrial processes often use cathodic arc plasma in reactive mode. In contrast, the science of arcs has focused on the case of vacuum arcs. Future research directions include closing the knowledge gap for reactive mode, large area coating, linear sources and filters, metal plasma immersion process, with application in high-tech and biomedical fields.

  18. Bifunctional quaternary ammonium compounds to inhibit biofilm growth and enhance performance for activated carbon air-cathode in microbial fuel cells

    Science.gov (United States)

    Li, Nan; Liu, Yinan; An, Jingkun; Feng, Cuijuan; Wang, Xin

    2014-12-01

    The slow diffusion of hydroxyl out of the catalyst layer as well as the biofouling on the surface of cathode are two problems affecting power for membrane-less air-cathode microbial fuel cells (MFCs). In order to solve both of them simultaneously, here we simply modify activated carbon air-cathode using a bifunctional quaternary ammonium compound (QAC) by forced evaporation. The maximum power density reaches 1041 ± 12 mW m-2 in an unbuffered medium (0.5 g L-1 NaCl), which is 17% higher than the control, probably due to the accelerated anion transport in the catalyst layer. After 2 months, the protein content reduced by a factor of 26 and the power density increases by 33%, indicating that the QAC modification can effectively inhibit the growth of cathodic biofilm and improve the stability of performance. The addition of NaOH and QAC epoxy have a negative effect on power production due to the clogging of pores in catalyst layer.

  19. 层状钴基正极材料的改性研究%Modification of layered Co-based cathode material

    Institute of Scientific and Technical Information of China (English)

    杨占旭; 乔庆东; 任铁强; 李琪

    2012-01-01

    Layered LiCoO2 has been the dominant cathode material for commercial Li-ion batteries because of its ease of production, good rate capability and stable discharge voltage platform. However, layered LiCoO2 shows poor overcharge tolerance and thermal stability, which restrict its commercialization. In this article, the progress in ion substitution and surface treatment of layered LiCoO2 to improve the structural and thermal stability at home and abroad has been described in detail. The mechanism has been discussed as well.%层状LiCoO2是目前商品化的主要正极材料,具有易于制备、较好的倍率性能以及放电电压平稳等优点,但其抗过充电性能和热稳定性差限制了其应用.详细阐述了国内外关于层状LiCoO2正极材料的改性研究进展,包括体相掺杂和表面包覆改性两种方法提高材料的抗过充电性能和热稳定性,并对体相掺杂和表面包覆层状LiCoO2正极材料电化学性能提高的机理进行了讨论.

  20. A novel Pt/Cr/Ru/C cathode catalyst for direct methanol fuel cells (DMFC) with simultaneous methanol tolerance and oxygen promotion

    Energy Technology Data Exchange (ETDEWEB)

    Perez, G.; Zinola, C.F. [Laboratorio de Electroquimica Fundamental, Facultad de Ciencias, Universidad de la Republica, Igua 4225, C.P. 11400, Montevideo (Uruguay); Pastor, E. [Departamento de Quimica Fisica, Facultad de Quimica, Universidad de La Laguna, Astrofisico F. Sanchez s/n, 38071 La Laguna, Tenerife (Spain)

    2009-12-15

    New carbon supported electrocatalysts Pt/Cr/Ru with distinct compositions and preparation methods were studied with the help of different electrochemical and spectroscopic techniques. The purposes of obtaining these catalysts lie on their possibilities towards methanol/oxygen fuel cells. In this sense, the oxygen reduction reaction and methanol oxidation reaction were analyzed using stationary and fluid dynamic methodologies. Pt{sub 7.8}/Ru{sub 1.3}/Cr{sub 0.5} and Pt{sub 8.0}/Ru{sub 2.0}/Cr{sub 0.1} were the most interesting prepared substrates, on which the first one shows the best catalytic properties towards methanol oxidation and the second the finest performance towards oxygen reduction reaction. Reaction orders with respect to oxygen for the oxygen reduction reaction were obtained being equal to 1/2 at potentials lower than 0.80 V for both catalysts. Polarization curves run for this reaction depicted two Tafel slopes, i.e. 0.09 V dec{sup -1} above 0.8 V and 0.20 V dec{sup -1} below 0.8 V for both catalysts. An analysis of the most likely mechanism for the oxygen reduction was proposed on the base of those reaction orders and Tafel slopes. (author)

  1. Transport phenomena within the porous cathode for a proton exchange membrane fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Juanfang; Oshima, Nobuyuki; Kurihara, Eru; Saha, Litan Kumar [Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 (Japan)

    2010-10-01

    A two-phase, one-dimensional steady model is developed to analyze the coupled phenomena of cathode flooding and mass-transport limiting for the porous cathode electrode of a proton exchange membrane fuel cell. In the model, the catalyst layer is treated not as an interface between the membrane and gas diffusion layer, but as a separate computational domain with finite thickness and pseudo-homogenous structure. Furthermore, the liquid water transport across the porous electrode is driven by the capillary force based on Darcy's law. And the gas transport is driven by the concentration gradient based on Fick's law. Additionally, through Tafel kinetics, the transport processes of gas and liquid water are coupled. From the numerical results, it is found that although the catalyst layer is thin, it is very crucial to better understand and more correctly predict the concurrent phenomena inside the electrode, particularly, the flooding phenomena. More importantly, the saturation jump at the interface of the gas diffusion layer and catalyst layers is captured, when the continuity of the capillary pressure is imposed on the interface. Elsewise, the results show further that the flooding phenomenon in the CL is much more serious than that in the GDL, which has a significant influence on the mass transport of the reactants. Moreover, the saturation level inside the cathode is determined, to a great extent, by the surface overpotential, the absolute permeability of the porous electrode, and the boundary value of saturation at the gas diffusion layer-gas channel interface. In order to prevent effectively flooding, it should remove firstly the liquid water accumulating inside the CL and keep the boundary value of liquid saturation as low as possible. (author)

  2. An ethylene glycol intercalated monometallic layered double hydroxide based on iron as an efficient bifunctional catalyst.

    Science.gov (United States)

    Nagarajan, Rajamani; Gupta, Pankaj; Singh, Poonam; Chakraborty, Pinki

    2016-11-01

    Given the fact that the literature describing the intercalation of organic molecules in monometallic LDH systems is scarce, the present investigation is aimed at the generation of ethylene glycol intercalated Fe(II)-Fe(III) LDH with the objective of enhancing the surface area for further catalytic applications of industrially important and environmentally harmful organics. The solvothermal reaction of FeCl3 with urea in an ethylene glycol medium yielded a brown colored powder which was characterized employing a wide range of analytical techniques including high resolution powder X-ray diffraction (PXRD), scanning electron microscopy, thermal analysis, X-ray photo electron spectroscopy (XPS), elemental (C, H, N and S) analysis, UV-visible, photoluminescence spectroscopy measurements, BET surface area and pore-size analysis. The observed reflections in the PXRD pattern were indexed in a rhombohedral symmetry with a = 3.175 and c = 31.9 Å. Combining the results from the Fe 2p core level analysis and anion contents from elemental and thermogravimetric analysis, a formula of Fe(2+)1.06 Fe(3+)0.94 (O2C2H4) (OH)4 was deduced for the sample. The intercalation of EG in the interlayer was confirmed from FTIR and Raman spectroscopy measurements. The d-d transitions of the Fe(3+)-ion and the charge transfer transition of the Fe(ii)-Fe(iii) lattice were evident in the UV-visible spectrum. Blue indigoid emission bands arising from the transitions present in the Fe(3+)-ion were noticed in the photoluminescence spectrum. The measured BET surface area and pore diameter of the sample were 144 m(2) g(-1) and 12.5 nm, respectively. Almost instant decolourisation of the Xylenol Orange (XO) dye occurred in the presence of H2O2 and the LDH sample as catalyst. Similar observations were encountered for Methyl Orange (MO) and Methylene Blue (MB) dyes. All these reactions followed pseudo first-order kinetics. The industrially important reductive conversion of nitro aromatics was catalyzed

  3. Suppressing capacity fading and voltage decay of Li-rich layered cathode material by a surface nano-protective layer of CoF2 for lithium-ion batteries

    Science.gov (United States)

    Chong, Shaokun; Chen, Yuanzhen; Yan, Wuwei; Guo, Shengwu; Tan, Qiang; Wu, Yifang; Jiang, Tao; Liu, Yongning

    2016-11-01

    Li-rich layered oxides have been regarded as valuable cathode materials for high energy density lithium-ion batteries. However, high initial irreversible capacity, bad rate capability, as well as serious capacity fading and voltage decay hinder their commercial application. In this paper, a nano CoF2 protective layer is coated on the surface of Li1.2Ni0.2Mn0.6O2 via a facial wet chemistry method. A high initial discharge capacity of 264.4 mAh g-1 is obtained for 0.5% CoF2-coated sample and 259.1 mAh g-1 for 1% CoF2-coated sample owing to the suppression of irreversible release of O2 and the contribution of electrochemical conversion of CoF2/LiF. Furthermore, 1% CoF2-coated sample exhibits the excellent rate capability of 167.5 mAh g-1 at 5 C rate, the superior cycling stability with the capacity retention of 241.0 mAh g-1 and the ameliorative voltage drop of 0.312 V at 0.1C after 100 cycles. The enhanced rate performance as well as stability of capacity and voltage can be attributed to the nano coatings which inhibit the electrolyte-electrode side reaction, enhance the electrochemical kinetics and mitigate structure transition from layered to spinel phase.

  4. Nanoporous BiVO4 photoanodes with dual-layer oxygen evolution catalysts for solar water splitting.

    Science.gov (United States)

    Kim, Tae Woo; Choi, Kyoung-Shin

    2014-02-28

    Bismuth vanadate (BiVO4) has a band structure that is well-suited for potential use as a photoanode in solar water splitting, but it suffers from poor electron-hole separation. Here, we demonstrate that a nanoporous morphology (specific surface area of 31.8 square meters per gram) effectively suppresses bulk carrier recombination without additional doping, manifesting an electron-hole separation yield of 0.90 at 1.23 volts (V) versus the reversible hydrogen electrode (RHE). We enhanced the propensity for surface-reaching holes to instigate water-splitting chemistry by serially applying two different oxygen evolution catalyst (OEC) layers, FeOOH and NiOOH, which reduces interface recombination at the BiVO4/OEC junction while creating a more favorable Helmholtz layer potential drop at the OEC/electrolyte junction. The resulting BiVO4/FeOOH/NiOOH photoanode achieves a photocurrent density of 2.73 milliamps per square centimenter at a potential as low as 0.6 V versus RHE.

  5. The features of CNT growth on catalyst-content amorphous alloy layer by CVD-method

    Science.gov (United States)

    Dubkov, S.; Bulyarskii, S.; Pavlov, A.; Trifonov, A.; Kitsyuk, E.; Mierczynski, P.; Maniecki, T.; Ciesielski, R.; Gavrilov, S.; Gromov, D.

    2016-12-01

    This work is devoted to the CVD-synthesis of arrays of carbon nanotubes (CNTs) on Co-Zr-N-(O), Ni-Nb-N-(O), Co- Ta-N-(O) catalytic alloy films from gas mixture of C2H2+NH3+Ar at a substrate temperature of about 550°C.Heating of the amorphous alloy causes its crystallization and squeezing of the catalytic metal onto the surface. As a result, small catalyst particles are formed on the surface. The CNT growth takes place after wards on these particles. It should be noted that the growth of CNT arrays on these alloys is insensitive to the thickness of alloy film, which makes this approach technically attractive. In particular, the possibility of local CNT growth at the ends of the Co-Ta-N-(O) film and three-level CNT growth at the end of more complex structure SiO2/Ni-Nb-N-O/SiO2/Ni-Nb-N-O/SiO2/Ni-Nb-N-O/SiO2 is demonstrated.

  6. Layered double hydroxide-based nanomaterials as highly efficient catalysts and adsorbents.

    Science.gov (United States)

    Li, Changming; Wei, Min; Evans, David G; Duan, Xue

    2014-11-01

    Layered double hydroxides (LDHs) are a class of anion clays consisting of brucite-like host layers and interlayer anions, which have attracted increasing interest in the fields of catalysis/adsorption. By virtue of the versatility in composition, morphology, and architecture of LDH materials, as well as their unique structural properties (intercalation, topological transformation, and self-assembly with other functional materials), LDHs display great potential in the design and fabrication of nanomaterials applied in photocatalysis, heterogeneous catalysis, and adsorption/separation processes. Taking advantage of the structural merits and various control synthesis strategies of LDHs, the active center structure (e.g., crystal facets, defects, geometric and electronic states, etc.) and macro-nano morphology can be facilely manipulated for specific catalytic/adsorbent processes with largely enhanced performances. In this review, the latest advancements in the design and preparation of LDH-based functional nanomaterials for sustainable development in catalysis and adsorption are summarized.

  7. Electrochemical Kinetics and Performance of Layered Composite Cathode Material Li[Li0.2Ni0.2Mn0.6]O2

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jianming; Shi, Wei; Gu, Meng; Xiao, Jie; Zuo, Pengjian; Wang, Chong M.; Zhang, Jiguang

    2013-10-10

    Lithium-rich, manganese-rich (LMR) layered composite cathode material Li[Li0.2Ni0.2Mn0.6]O2 has been successfully prepared by a co-precipitation method and its structure is confirmed by XRD characterization. The material delivers a high discharge capacity of 281 mAh g-1, when charged and discharged at a low current density of 10 mA g-1. However, significant increase of cell polarization and decrease of discharge capacity are observed at voltages below 3.5 V with increasing current densities. Galvanostatic intermittent titration technique (GITT) analysis demonstrates that lithium ion intercalation/de-intercalation reactions in this material are kinetically controlled by Li2MnO3 and its activated MnO2 component. The relationship between the electrochemical kinetics and rate performance as well as cycling stability has been systematically investigated. High discharge capacity of 149 mAh g-1 can be achieved at 10 C charge rate and C/10 discharge rate. The result demonstrates that the Li2MnO3 based material could withstand high charge rate (except initial activation process), which is very promising for practical applications. A lower discharge current density is preferred to overcome the kinetic barrier of lithium ion intercalation into MnO2 component, in order to achieve higher discharge capacity even at high charge rates.

  8. In situ characterization of charge rate dependent stress and structure changes in V2O5 cathode prepared by atomic layer deposition

    Science.gov (United States)

    Jung, Hyun; Gerasopoulos, Konstantinos; Talin, A. Alec; Ghodssi, Reza

    2017-02-01

    The insertion/extraction of lithium into/from various host materials is the basic process by which lithium-ion batteries reversible store charge. This process is generally accompanied by strain in the host material, inducing stress which can lead to capacity loss. Therefore, understanding of both the structural changes and the associated stress - investigated almost exclusively separate to date - is a critical factor for developing high-performance batteries. Here, we report an in situ method, which utilizes Raman spectroscopy in parallel with optical interferometry to study effects of varying charging rates (C-rates) on the structure and stress in a V2O5 thin film cathode. Abrupt stress changes at specific crystal phase transitions in the Lisbnd Vsbnd O system are observed and the magnitude of the stress changes with the amount of lithium inserted into the electrode are correlated. A linear increase in the stress as a function of x in LixV2O5 is observed, indicating that C-rate does not directly contribute to larger intercalation stress. However, a more rapid increase in disorder within the LixV2O5 layers is correlated with higher C-rate. Ultimately, these experiments demonstrate how the simultaneous stress/Raman in situ approach can be utilized as a characterization platform for investigating various critical factors affecting lithium-ion battery performance.

  9. Layered Lithium-Rich Oxide Nanoparticles Doped with Spinel Phase: Acidic Sucrose-Assistant Synthesis and Excellent Performance as Cathode of Lithium Ion Battery.

    Science.gov (United States)

    Chen, Min; Chen, Dongrui; Liao, Youhao; Zhong, Xiaoxin; Li, Weishan; Zhang, Yuegang

    2016-02-01

    Nanolayered lithium-rich oxide doped with spinel phase is synthesized by acidic sucrose-assistant sol-gel combustion and evaluated as the cathode of a high-energy-density lithium ion battery. Physical characterizations indicate that the as-synthesized oxide (LR-SN) is composed of uniform and separated nanoparticles of about 200 nm, which are doped with about 7% spinel phase, compared to the large aggregated ones of the product (LR) synthesized under the same condition but without any assistance. Charge/discharge demonstrates that LR-SN exhibits excellent rate capability and cyclic stability: delivering an average discharge capacity of 246 mAh g(-1) at 0.2 C (1C = 250 mA g(-1)) and earning a capacity retention of 92% after 100 cycles at 4 C in the lithium anode-based half cell, compared to the 227 mA g(-1) and the 63% of LR, respectively. Even in the graphite anode-based full cell, LR-SN still delivers a capacity of as high as 253 mAh g(-1) at 0.1 C, corresponding to a specific energy density of 801 Wh kg(-1), which are the best among those that have been reported in the literature. The separated nanoparticles of the LR-SN provide large sites for charge transfer, while the spinel phase doped in the nanoparticles facilitates lithium ion diffusion and maintains the stability of the layered structure during cycling.

  10. Layered-MnO₂ Nanosheet Grown on Nitrogen-Doped Graphene Template as a Composite Cathode for Flexible Solid-State Asymmetric Supercapacitor.

    Science.gov (United States)

    Liu, Yongchuan; Miao, Xiaofei; Fang, Jianhui; Zhang, Xiangxin; Chen, Sujing; Li, Wei; Feng, Wendou; Chen, Yuanqiang; Wang, Wei; Zhang, Yining

    2016-03-02

    Flexible solid-state supercapacitors provide a promising energy-storage alternative for the rapidly growing flexible and wearable electronic industry. Further improving device energy density and developing a cheap flexible current collector are two major challenges in pushing the technology forward. In this work, we synthesize a nitrogen-doped graphene/MnO2 nanosheet (NGMn) composite by a simple hydrothermal method. Nitrogen-doped graphene acts as a template to induce the growth of layered δ-MnO2 and improves the electronic conductivity of the composite. The NGMn composite exhibits a large specific capacitance of about 305 F g(-1) at a scan rate of 5 mV s(-1). We also create a cheap and highly conductive flexible current collector using Scotch tape. Flexible solid-state asymmetric supercapacitors are fabricated with NGMn cathode, activated carbon anode, and PVA-LiCl gel electrolyte. The device can achieve a high operation voltage of 1.8 V and exhibits a maximum energy density of 3.5 mWh cm(-3) at a power density of 0.019 W cm(-3). Moreover, it retains >90% of its initial capacitance after 1500 cycles. Because of its flexibility, high energy density, and good cycle life, NGMn-based flexible solid state asymmetric supercapacitors have great potential for application in next-generation portable and wearable electronics.

  11. Surface-modified concentration-gradient Ni-rich layered oxide cathodes for high-energy lithium-ion batteries

    Science.gov (United States)

    Liao, Jin-Yun; Manthiram, Arumugam

    2015-05-01

    Concentration-gradient layered Li[Ni0.8Co0.2]0.7[Ni0.2Mn0.8]0.3O2 oxide with Ni-rich in the core and Mn-rich in the surface region has been synthesized through a condition-controlled tank reactor reaction. While the Ni-rich core facilitates high capacity, the Mn-rich surface enables good cyclability and thermal stability. The concentration-gradient sample exhibits a higher capacity of 204 mA h g-1 at C/5 rate with superior cyclability and thermal stability compared to the constant-concentration LiNi0.62Co0.14Mn0.24O2 sample, which has the same net Ni, Co, and Mn contents as those present in the concentration-gradient sample. The concentration-gradient sample was also coated with a thin layer of Al2O3 on the surface to stabilize the electrode/electrolyte interface and thereby further improve the electrochemical performance. Both the structural (gradient structure) and surface (Al2O3 coating) modifications help suppress side reactions between electrode and electrolyte and reduce the decline in voltage during cycling. The Al2O3-coated concentration-gradient sample exhibits improved long-term cyclability, rate capability, and thermal stability compared to the pristine uncoated sample.

  12. Platinium Nanoparticles Deposited on Oxygen-Containing Functional Groups at Carbon Vulcane XC-72 as a Cathode Catalyst for Direct Methanol Fuel Cell

    Institute of Scientific and Technical Information of China (English)

    Sajjad; Sadaghat; Sharehjini; Ahmad; Nozad; Golikand; Mohammad; Yari

    2007-01-01

    1 Results Surface oxidized carbon vulcane XC-72 as catalyst support, prepared by chemically anchoring Pt onto the surface modified carbon vulcane XC-72. The nanoparticles of Pt are synthesized by reduction of H2PtCl6 with sodium borohydride in a 5.5 buffer solution of sodium citrate, the complexation of citrate with metal ions is beneficial to the formation of nanoparticles. For comparison, an electrode is prepared by E-Tek Pt/C 20 Wt% with a typical Pt loading of 50 μg·cm-2, that shows higher specifi...

  13. Transesterification of edible, non-edible and used cooking oils for biodiesel production using calcined layered double hydroxides as reusable base catalysts.

    Science.gov (United States)

    Sankaranarayanan, Sivashunmugam; Antonyraj, Churchil A; Kannan, S

    2012-04-01

    Fatty acid methyl esters (FAME) were produced from edible, non-edible and used cooking oils with different fatty acid contents by transesterification with methanol using calcined layered double hydroxides (LDHs) as solid base catalysts. Among the catalysts, calcined CaAl2-LDH (hydrocalumite) showed the highest activity with >90% yield of FAME using low methanol:oil molar ratio (catalyzed process for production of biodiesel in high yields from a wide variety of triglyceride oils including used oils is possible using optimized conditions.

  14. The Effect of Inhomogeneous Compression on Water Transport in the Cathode of a Proton Exchange Membrane Fuel Cell

    DEFF Research Database (Denmark)

    Olesen, Anders Christian; Berning, Torsten; Kær, Søren Knudsen

    2012-01-01

    A three-dimensional, multicomponent, two-fluid model developed in the commercial CFD package CFX 13 (ANSYS Inc.) is used to investigate the effect of porous media compression on water transport in a proton exchange membrane fuel cell (PEMFC). The PEMFC model only consist of the cathode channel, gas...... diffusion layer, microporous layer, and catalyst layer, excluding the membrane and anode. In the porous media liquid water transport is described by the capillary pressure gradient, momentum loss via the Darcy-Forchheimer equation, and mass transfer between phases by a nonequilibrium phase change model...

  15. Modular Polyoxometalate-Layered Double Hydroxide Composites as Efficient Oxidative Catalysts.

    Science.gov (United States)

    Chen, Yang; Yao, Zhixiao; Miras, Haralampos N; Song, Yu-Fei

    2015-07-20

    The exploitation of intercalation techniques in the field of two-dimensional layered materials offers unique opportunities for controlling chemical reactions in confined spaces and developing nanocomposites with desired functionality. In this study, the exploitation of the novel and facile "one-pot" anion-exchange method for the functionalization of layered double hydroxides (LDHs) is demonstrated. As a proof-of-concept, we demonstrate the intercalation of a series of polyoxometalate (POM) clusters, Na3[PW12O40]⋅15 H2O (Na3PW12), K6[P2W18O62]⋅14 H2O (K6P2W18), and Na9LaW10O36⋅32 H2O (Na9LaW10) into tris(hydroxymethyl)aminomethane (Tris)-modified layered double hydroxides (LDHs) under ambient conditions without the necessity of degassing CO2. Investigation of the resultant intercalated materials of Tris-LDHs-PW12 (1), Tris-LDH-P2W18 (2), and Tris-LDH-LaW10 (3) for the degradation of methylene blue (MB), rhodamine B (RB) and crystal violet (CV) has been carried out, where Tris-LDH-PW12 reveals the best performance in the presence of H2O2. Additionally, degradation of a mixture of RB, MB and CV by Tris-LDH-PW12 follows the order of CV>MB>RB, which is directly related to the designed accessible area of the interlayer space. Also, the composite can be readily recycled and reused at least ten cycles without measurable decrease of activity.

  16. A study of thermally activated Mg–Fe layered double hydroxides as potential environmental catalysts

    Directory of Open Access Journals (Sweden)

    MILICA S. HADNAĐEV-KOSTIĆ

    2010-09-01

    Full Text Available Layered double hydroxides (LDHs and mixed oxides derived after thermal decomposition of LDHs with different Mg–Fe contents were investigated. These materials were chosen because of the possibility to tailor their various properties, such as ion-exchange capability, redox and acid–base and surface area. Layered double hydroxides, [Mg1-xFex(OH2](CO3x/2×mH2O (where x presents the content of trivalent ions, x = M(III/(M(II + M(III were synthesized using the low supersaturation precipitation method. The influence of different Mg/Fe ratios on the structure and surface properties of the LDH and derived mixed oxides was investigated in correlation to their catalytic properties in the chosen test reaction (Fischer–Tropsch synthesis. It was determined that the presence of active sites in the mixed oxides is influenced by the structural properties of the initial LDH and by the presence of additional Fe phases. Furthermore, a synthesis outside the optimal range for the synthesis of single phase LDHs leads to the formation of metastable, multiphase systems with specific characteristics and active sites.

  17. Recent Advances in Solid Catalysts Obtained by Metalloporphyrins Immobilization on Layered Anionic Exchangers: A Short Review and Some New Catalytic Results

    Directory of Open Access Journals (Sweden)

    Shirley Nakagaki

    2016-02-01

    Full Text Available Layered materials are a very interesting class of compounds obtained by stacking of two-dimensional layers along the basal axis. A remarkable property of these materials is their capacity to interact with a variety of chemical species, irrespective of their charge (neutral, cationic or anionic. These species can be grafted onto the surface of the layered materials or intercalated between the layers, to expand or contract the interlayer distance. Metalloporphyrins, which are typically soluble oxidation catalysts, are examples of molecules that can interact with layered materials. This work presents a short review of the studies involving metalloporphyrin immobilization on two different anionic exchangers, Layered Double Hydroxides (LDHs and Layered Hydroxide Salts (LHSs, published over the past year. After immobilization of anionic porphyrins, the resulting solids behave as reusable catalysts for heterogeneous oxidation processes. Although a large number of publications involving metalloporphyrin immobilization on LDHs exist, only a few papers have dealt with LHSs as supports, so metalloporphyrins immobilized on LHSs represent a new and promising research field. This work also describes new results on an anionic manganese porphyrin (MnP immobilized on Mg/Al-LDH solids with different nominal Mg/Al molar ratios (2:1, 3:1 and 4:1 and intercalated with different anions (CO32− or NO3−. The influence of the support composition on the MnP immobilization rates and the catalytic performance of the resulting solid in cyclooctene oxidation reactions will be reported.

  18. Method of fabricating electrode catalyst layers with directionally oriented carbon support for proton exchange membrane fuel cell

    Science.gov (United States)

    Liu, Di-Jia [Naperville, IL; Yang, Junbing [Bolingbrook, IL

    2012-03-20

    A membrane electrode assembly (MEA) of the invention comprises an anode and a cathode and a proton conductive membrane therebetween, the anode and the cathode each comprising a patterned sheet of longitudinally aligned transition metal-containing carbon nanotubes, wherein the carbon nanotubes are in contact with and are aligned generally perpendicular to the membrane, wherein a catalytically active transition metal is incorporated throughout the nanotubes.

  19. Atomic layer deposition of NiS and its application as cathode material in dye sensitized solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Mahuli, Neha [Center for Research in Nanotechnology and Sciences, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Sarkar, Shaibal K., E-mail: shaibal.sarkar@iitb.ac.in [Department of Energy Science and Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India)

    2016-01-15

    Nickel sulfide (NiS) is grown by atomic layer deposition (ALD) using sequential exposures of bis(2,2,6,6-tetramethylheptane-3,5-dionate)nickel(II) [Ni(thd){sub 2}] and hydrogen sulfide (H{sub 2}S) at 175 °C. Complementary combinations of in situ and ex situ characterization techniques are used to understand the deposition chemistry and the nature of film growth. The saturated growth rate of ca. 0.21 Å per ALD cycle is obtained, which is constant within the ALD temperature window (175–250 °C). As deposited films on glass substrates are found polycrystalline without any preferred orientation. Electrical transport measurement reveals degenerative/semimetallic characteristics with a carrier concentration of ca. 9 × 10{sup 22} cm{sup −3} at room temperature. The ALD grown NiS thin film demonstrates high catalytic activity for the reduction of I{sup −}/I{sub 3}{sup −} electrolyte that opens its usage as cost-effective counter electrode in dye sensitized solar cells, replacing Pt.

  20. Molybdenum Disulfide as a Protection Layer and Catalyst for Gallium Indium Phosphide Solar Water Splitting Photocathodes.

    Science.gov (United States)

    Britto, Reuben J; Benck, Jesse D; Young, James L; Hahn, Christopher; Deutsch, Todd G; Jaramillo, Thomas F

    2016-06-02

    Gallium indium phosphide (GaInP2) is a semiconductor with promising optical and electronic properties for solar water splitting, but its surface stability is problematic as it undergoes significant chemical and electrochemical corrosion in aqueous electrolytes. Molybdenum disulfide (MoS2) nanomaterials are promising to both protect GaInP2 and to improve catalysis because MoS2 is resistant to corrosion and also possesses high activity for the hydrogen evolution reaction (HER). In this work, we demonstrate that GaInP2 photocathodes coated with thin MoS2 surface protecting layers exhibit excellent activity and stability for solar hydrogen production, with no loss in performance (photocurrent onset potential, fill factor, and light-limited current density) after 60 h of operation. This represents a 500-fold increase in stability compared to bare p-GaInP2 samples tested in identical conditions.

  1. Molybdenum Disulfide as a Protection Layer and Catalyst for Gallium Indium Phosphide Solar Water Splitting Photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Britto, Reuben J.; Benck, Jesse D.; Young, James L.; Hahn, Christopher; Deutsch, Todd G.; Jaramillo, Thomas F.

    2016-06-02

    Gallium indium phosphide (GaInP2) is a semiconductor with promising optical and electronic properties for solar water splitting, but its surface stability is problematic as it undergoes significant chemical and electrochemical corrosion in aqueous electrolytes. Molybdenum disulfide (MoS2) nanomaterials are promising to both protect GaInP2 and to improve catalysis since MoS2 is resistant to corrosion and also possesses high activity for the hydrogen evolution reaction (HER). In this work, we demonstrate that GaInP2 photocathodes coated with thin MoS2 surface protecting layers exhibit excellent activity and stability for solar hydrogen production, with no loss in performance (photocurrent onset potential, fill factor, and light limited current density) after 60 hours of operation. This represents a five-hundred fold increase in stability compared to bare p-GaInP2 samples tested in identical conditions.

  2. Performance equations for cathodes in polymer electrolyte fuel cells with non-uniform water flooding in gas diffusers

    Science.gov (United States)

    Hsuen, Hsiao-Kuo

    The performance equations for cathodes of polymer electrolyte fuel cells (PEFCs) that describe the dependence of cathode potential on current density are developed. Formulation of the performance equations starts from the reduction of a one-dimensional model that considers, in detail, the potential losses pertinent to the limitations of electron conduction, oxygen diffusion, proton migration, and the oxygen reduction reaction. In particular, non-uniform accumulation of liquid water in the gas diffuser, which partially blocks the gas channels and imposes a greater resistance for oxygen transport, is taken into account. Reduction of the one-dimensional model is implemented by approximating the oxygen concentration profile in the catalyst layer with a parabolic polynomial or a piecewise parabolic one determined by the occurrence of oxygen depletion. The final forms of the equations are obtained by applying the method of weighted residuals over the catalyst layer. The weighting function is selected in such a way that the weighted residuals can be analytically integrated. Potential losses caused by the various limiting processes can be quantitatively estimated by the performance equations. Thus, they provide a convenient diagnostic tool for the cathode performance. Computational results reveal that the performance equations agree well with the original one-dimensional model over an extensive range of parameter values. This indicates that the present performance equations can be used as a substitute for the one-dimensional model to provide quantitatively correct predictions for the cathode performance of PEFCs.

  3. Atomic Layer Deposition of Pt Nanoparticles within the Cages of MIL-101: A Mild and Recyclable Hydrogenation Catalyst

    Directory of Open Access Journals (Sweden)

    Karen Leus

    2016-03-01

    Full Text Available We present the in situ synthesis of Pt nanoparticles within MIL-101-Cr (MIL = Materials Institute Lavoisier by means of atomic layer deposition (ALD. The obtained Pt@MIL-101 materials were characterized by means of N2 adsorption and X-ray powder diffraction (XRPD measurements, showing that the structure of the metal organic framework was well preserved during the ALD deposition. X-ray fluorescence (XRF and transmission electron microscopy (TEM analysis confirmed the deposition of highly dispersed Pt nanoparticles with sizes determined by the MIL-101-Cr pore sizes and with an increased Pt loading for an increasing number of ALD cycles. The Pt@MIL-101 material was examined as catalyst in the hydrogenation of different linear and cyclic olefins at room temperature, showing full conversion for each substrate. Moreover, even under solvent free conditions, full conversion of the substrate was observed. A high concentration test has been performed showing that the Pt@MIL-101 is stable for a long reaction time without loss of activity, crystallinity and with very low Pt leaching.

  4. Stochastic reconstruction and a scaling method to determine effective transport coefficients of a proton exchange membrane fuel cell catalyst layer

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, R. [Centro de Investigacion en Energia, UNAM, Privada Xochicalco S/N, 62580 Temixco (Mexico); Andaverde, J. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, UAEM, Av. Universidad 1001, Col. Chamilpa, 62210 Cuernavaca (Mexico); Escobar, B. [Instituto Tecnologico de Cancun, Av. Kabah 3, 77515 Cancun (Mexico); Cano, U. [Instituto de Investigaciones Electricas, Av. Reforma 113, col. Palmira, 62490 Cuernavaca (Mexico)

    2011-02-01

    This work uses a method for the stochastic reconstruction of catalyst layers (CLs) proposing a scaling method to determine effective transport properties in proton exchange membrane fuel cell (PEMFC). The algorithm that generates the numerical grid makes use of available information before and after manufacturing the CL. The structures so generated are characterized statistically by two-point correlation functions and by the resultant pore size distribution. As an example of this method, the continuity equation for charge transport is solved directly on the three-dimensional grid of finite control volumes (FCVs), to determine effective electrical and proton conductivities of different structures. The stochastic reconstruction and the electrical and proton conductivity of a 45 {mu}m side size cubic sample of a CL, represented by more than 3.3 x 10{sup 12} FVCs were realized in a much shorter time compared with non-scaling methods. Variables studied in an example of CL structure were: (i) volume fraction of dispersed electrolyte, (ii) total CL porosity and (iii) pore size distribution. Results for the conduction efficiency for this example are also presented. (author)

  5. 3D-nanoarchitectured Pd/Ni catalysts prepared by atomic layer deposition for the electrooxidation of formic acid

    Directory of Open Access Journals (Sweden)

    Loïc Assaud

    2014-02-01

    Full Text Available Three-dimensionally (3D nanoarchitectured palladium/nickel (Pd/Ni catalysts, which were prepared by atomic layer deposition (ALD on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an acidic medium (0.5 M H2SO4. Both deposition processes, Ni and Pd, with various mass content ratios have been continuously monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orientation along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activities are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the cluster size effect, electronic interactions between Pd and Ni, or diffusion effects.

  6. 3D-nanoarchitectured Pd/Ni catalysts prepared by atomic layer deposition for the electrooxidation of formic acid.

    Science.gov (United States)

    Assaud, Loïc; Monyoncho, Evans; Pitzschel, Kristina; Allagui, Anis; Petit, Matthieu; Hanbücken, Margrit; Baranova, Elena A; Santinacci, Lionel

    2014-01-01

    Three-dimensionally (3D) nanoarchitectured palladium/nickel (Pd/Ni) catalysts, which were prepared by atomic layer deposition (ALD) on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an acidic medium (0.5 M H2SO4). Both deposition processes, Ni and Pd, with various mass content ratios have been continuously monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orientation along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activities are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the cluster size effect, electronic interactions between Pd and Ni, or diffusion effects.

  7. Re-examination of the Pt Particle Size Effect on the Oxygen Reduction Reaction for Ultrathin Uniform Pt/C Catalyst Layers without Influence from Nafion

    Energy Technology Data Exchange (ETDEWEB)

    Shinozaki, Kazuma; Morimoto, Yu; Pivovar, Bryan S.; Kocha, Shyam S.

    2016-09-01

    The platinum 'particle size effect' on the oxygen reduction reaction (ORR) has been re-evaluated using commercial Pt/C catalysts (2-10 nm Pt particle) and polycrystalline Pt (poly-Pt) in 0.1 M HClO4 with a rotating disk electrode method. Nafion-free catalyst layers were employed to obtain specific activities (SA) that were not perturbed (suppressed) by sulfonate anion adsorption/blocking. By using ultrathin uniform catalyst layers, O2 diffusion limitation was minimized as confirmed from the high SAs of our supported catalysts that were comparable to unsupported sputtered Pt having controlled sizes. The specific activity (SA) steeply increased for the particle sizes in the range -2-10 nm (0.8-1.8 mA/cm2Pt at 0.9 V vs. RHE) and plateaued over -10 nm to 2.7 mA/cm2Pt for bulk poly-Pt. On the basis of the activity trend for the range of particle sizes studied, it appears that the effect of carbon support on activity is negligible. The experimental results and the concomitant profile of SA vs. particle size was found to be in an agreement to a truncated octahedral particle model that assumes active terrace sites.

  8. Graphene growth at the interface between Ni catalyst layer and SiO2/Si substrate.

    Science.gov (United States)

    Lee, Jeong-Hoon; Song, Kwan-Woo; Park, Min-Ho; Kim, Hyung-Kyu; Yang, Cheol-Woong

    2011-07-01

    Graphene was synthesized deliberately at the interface between Ni film and SiO2/Si substrate as well as on top surface of Ni film using chemical vapor deposition (CVD) which is suitable for large-scale and low-cost synthesis of graphene. The carbon atom injected at the top surface of Ni film can penetrate and reach to the Ni/SiO2 interface for the formation of graphene. Once we have the graphene in between Ni film and SiO2/Si substrate, the substrate spontaneously provides insulating SiO2 layer and we may easily get graphene/SiO2/Si structure simply by discarding Ni film. This growth of graphene at the interface can exclude graphene transfer step for electronic application. Raman spectroscopy and optical microscopy show that graphene was successfully synthesized at the back of Ni film and the coverage of graphene varies with temperature and time of synthesis. The coverage of graphene at the interface depends on the amount of carbon atoms diffused into the back of Ni film.

  9. Comparison of trimethylgallium and triethylgallium as “Ga” source materials for the growth of ultrathin GaN films on Si (100) substrates via hollow-cathode plasma-assisted atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Alevli, Mustafa, E-mail: mustafaalevli@marmara.edu.tr [Department of Physics, Marmara University, Göztepe Kadıköy, 34722 İstanbul (Turkey); Haider, Ali; Kizir, Seda; Leghari, Shahid A.; Biyikli, Necmi, E-mail: biyikli@unam.bilkent.edu.tr [Institute of Materials Science and Nanotechnology, Bilkent University, Bilkent, 06800 Ankara, Turkey and National Nanotechnology Research Center (UNAM), Bilkent University, Bilkent, 06800 Ankara (Turkey)

    2016-01-15

    GaN films grown by hollow cathode plasma-assisted atomic layer deposition using trimethylgallium (TMG) and triethylgallium (TEG) as gallium precursors are compared. Optimized and saturated TMG/TEG pulse widths were used in order to study the effect of group-III precursors. The films were characterized by grazing incidence x-ray diffraction, atomic force microscopy, x-ray photoelectron spectroscopy, and spectroscopic ellipsometry. Refractive index follows the same trend of crystalline quality, mean grain, and crystallite sizes. GaN layers grown using TMG precursor exhibited improved structural and optical properties when compared to GaN films grown with TEG precursor.

  10. Applying Infrared Thermography as a Quality-Control Tool for the Rapid Detection of Proton-Electrolyte-Membrane-Fuel-Cell Catalyst-Layer-Thickness Variations

    Energy Technology Data Exchange (ETDEWEB)

    Aieta, N. V.; Das, P. K.; Perdue, A.; Bender, G.; Herring, A. M.; Weber, A. Z.; Ulsh, M. J.

    2012-08-01

    As fuel cells become more prominent, new manufacturing and production methods are needed to enable increased volumes with high quality. One necessary component of this industrial growth will be the accurate measurement of the variability of a wide range of material properties during the manufacturing process. In this study, a method to detect defects in fuel cell catalyst layers is investigated through experiment and mathematical simulation. The method uses infrared thermography and direct-current electronic-excitation methods to detect variations in platinum-containing catalyst-layer thickness with high spatial and temporal resolution. Data analysis, operating-condition impacts, and detection limits are explored, showing the measurement of defects on the millimeter length scale. Overall, the experimental and modeling results demonstrate great potential of this technique as a nondestructive method to measure defects that is amenable to use on roll-to-roll manufacturing lines.

  11. Full cell simulation and the evaluation of the buffer system on air-cathode microbial fuel cell

    Science.gov (United States)

    Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

    2017-04-01

    This paper presents a computational model of a single chamber, air-cathode MFC. The model considers losses due to mass transport, as well as biological and electrochemical reactions, in both the anode and cathode half-cells. Computational fluid dynamics and Monod-Nernst analysis are incorporated into the reactions for the anode biofilm and cathode Pt catalyst and biofilm. The integrated model provides a macro-perspective of the interrelation between the anode and cathode during power production, while incorporating microscale contributions of mass transport within the anode and cathode layers. Model considerations include the effects of pH (H+/OH- transport) and electric field-driven migration on concentration overpotential, effects of various buffers and various amounts of buffer on the pH in the whole reactor, and overall impacts on the power output of the MFC. The simulation results fit the experimental polarization and power density curves well. Further, this model provides insight regarding mass transport at varying current density regimes and quantitative delineation of overpotentials at the anode and cathode. Overall, this comprehensive simulation is designed to accurately predict MFC performance based on fundamental fluid and kinetic relations and guide optimization of the MFC system.

  12. Efficient small molecular organic light emitting diode with graphene cathode covered by a Sm layer with nano-hollows and n-doped by Bphen:Cs2CO3 in the hollows.

    Science.gov (United States)

    Yao, Li; Li, Lei; Qin, Laixiang; Ma, Yaoguang; Wang, Wei; Meng, Hu; Jin, Weifeng; Wang, Yilun; Xu, Wanjin; Ran, Guangzhao; You, Liping; Qin, Guogang

    2017-03-10

    Graphene is a favorable candidate for electrodes of organic light emitting diodes (OLEDs). Graphene has quite a high work function of ∼4.5 eV, and has been extensively studied when used as anodes of OLEDs. In order to use graphene as a cathode, the electron injection barrier between the graphene cathode and the electron transport layer has to be low enough. Using 4,7-diphenyl-1,10-phenanthroline (Bphen):Cs2CO3 to n-dope graphene is a very good method, but the electron injection barrier between the n-doped graphene and Bphen:Cs2CO3 is still too high to be ∼1.0 eV. In this work, in order to further reduce the electron injection barrier, a novel method is suggested. On the graphene cathode, a Sm layer with a lot of nano-hollows, and subsequently a layer of Bphen:Cs2CO3, are deposited. The Bphen:Cs2CO3 can n-dope graphene in the nano-hollows, and the Fermi level of the graphene rises. The nano Sm layer is very easily oxidized. Oxygen adsorbed on the surface of graphene may react with Sm to form an O(-)-Sm(+) dipole layer. On the areas of the Sm oxide dipole layer without nano-hollows, the electron injection barrier can be further lowered by the dipole layer. Electrons tend to mainly inject through the lower electron barrier where the dipole layer exists. Based on this idea, an effective inverted small molecular OLED with the structure of graphene/1 nm Sm layer with a lot of nano-hollows/Bphen:Cs2CO3/Alq3:C545T/NPB/MoO3/Al is presented. The maximum current efficiency and maximum power efficiency of the OLED with a 1 nm Sm layer are about two and three times of those of the reference OLED without any Sm layer, respectively.

  13. Efficient small molecular organic light emitting diode with graphene cathode covered by a Sm layer with nano-hollows and n-doped by Bphen:Cs2CO3 in the hollows

    Science.gov (United States)

    Yao, Li; Li, Lei; Qin, Laixiang; Ma, Yaoguang; Wang, Wei; Meng, Hu; Jin, Weifeng; Wang, Yilun; Xu, Wanjin; Ran, Guangzhao; You, Liping; Qin, Guogang

    2017-03-01

    Graphene is a favorable candidate for electrodes of organic light emitting diodes (OLEDs). Graphene has quite a high work function of ∼4.5 eV, and has been extensively studied when used as anodes of OLEDs. In order to use graphene as a cathode, the electron injection barrier between the graphene cathode and the electron transport layer has to be low enough. Using 4,7-diphenyl-1,10-phenanthroline (Bphen):Cs2CO3 to n-dope graphene is a very good method, but the electron injection barrier between the n-doped graphene and Bphen:Cs2CO3 is still too high to be ∼1.0 eV. In this work, in order to further reduce the electron injection barrier, a novel method is suggested. On the graphene cathode, a Sm layer with a lot of nano-hollows, and subsequently a layer of Bphen:Cs2CO3, are deposited. The Bphen:Cs2CO3 can n-dope graphene in the nano-hollows, and the Fermi level of the graphene rises. The nano Sm layer is very easily oxidized. Oxygen adsorbed on the surface of graphene may react with Sm to form an O‑–Sm+ dipole layer. On the areas of the Sm oxide dipole layer without nano-hollows, the electron injection barrier can be further lowered by the dipole layer. Electrons tend to mainly inject through the lower electron barrier where the dipole layer exists. Based on this idea, an effective inverted small molecular OLED with the structure of graphene/1 nm Sm layer with a lot of nano-hollows/Bphen:Cs2CO3/Alq3:C545T/NPB/MoO3/Al is presented. The maximum current efficiency and maximum power efficiency of the OLED with a 1 nm Sm layer are about two and three times of those of the reference OLED without any Sm layer, respectively.

  14. Structural integrity--Searching the key factor to suppress the voltage fade of Li-rich layered cathode materials through 3D X-ray imaging and spectroscopy techniques

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yahong; Hu, Enyuan; Yang, Feifei; Corbett, Jeff; Sun, Zhihong; Lyu, Yingchun; Yu, Xiqian; Liu, Yijin; Yang, Xiao-Qing; Li, Hong (BNL); (SLAC); (UCSF); (Donghua); (Chinese Aca. Sci.)

    2016-10-24

    Li-rich layered materials are important cathode compounds used in commercial lithium ion batteries, which, however, suffers from some drawbacks including the so-called voltage fade upon electrochemical cycling. Here, our study employs novel transmission X-ray microscopy to investigate the electrochemical reaction induced morphological and chemical changes in the Li-rich Li2Ru0.5Mn0.5O3 cathode particles at the meso to nano scale. We performed combined X-ray spectroscopy, diffraction and microscopy experiments to systematically study this cathode material's evolution upon cycling as well as to establish a comprehensive understanding of the structural origin of capacity fade through 2D and 3D fine length scale morphology and heterogeneity change of this material. This work suggests that atomic manipulation (e.g. doping, substitution etc.) or nano engineering (e.g. nano-sizing, heterogeneous structure) are important strategies to mitigate the internal strain and defects induced by extensive lithium insertion/extraction. It also shows that maintaining the structural integrity is the key in designing and synthesizing lithium-rich layered materials with better cycle stability.

  15. Alleviating Surface Degradation of Nickel-Rich Layered Oxide Cathode Material by Encapsulating with Nanoscale Li-Ions/Electrons Superionic Conductors Hybrid Membrane for Advanced Li-Ion Batteries.

    Science.gov (United States)

    Li, Lingjun; Xu, Ming; Yao, Qi; Chen, Zhaoyong; Song, Liubin; Zhang, Zhian; Gao, Chunhui; Wang, Peng; Yu, Ziyang; Lai, Yanqing

    2016-11-16

    Nickel-rich layered oxide cathode materials for advanced lithium-ion batteries have received much attention recently because of their high specific capacities and significant reduction of cost. However, these cathodes are facing a fundamental challenge of loss in performance as a result of surface lithium residue, side reactions with the electrolyte and structure rearrangement upon long-term cycling. Herein, by capturing the lithium residue on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM) cathode material as Li source, we propose a hybrid coating strategy incorporating lithium ions conductor LixAlO2 with superconductor LixTi2O4 to overcome those obstinate issues. By taking full advantage of this unique hybrid nanomembrane coating architecture, both the lithium ion diffusion ability and electronic conductivity of LiNi0.8Co0.1Mn0.1O2 cathode material are improved, resulting in remarkably enhanced electrochemical performances during high voltage operation, including good cycle performance, high reversible capacity, and excellent rate capability. A high initial discharge capacity of 227 mAh g(-1) at 4.4 V cutoff voltage with Coulombic efficiency of 87.3%, and reversible capacity of 200 mAh g(-1) with 98% capacity retention after 100 cycles at a current density of 0.5 C can be attained. The improved electrochemical performance can be attributed to the synergetic contribution from the removal of lithium residues and the unique hybrid nanomembrane coating architecture. Most importantly, this surface modification technique could save some cost, simplify the technical procedure, and show great potential to optimize battery performance, apply in a large scale and extend to all nickel-rich cathode material.

  16. Corrosion Resistance Behavior of Single-Layer Cathodic Arc PVD Nitride-Base Coatings in 1M HCl and 3.5 pct NaCl Solutions

    Science.gov (United States)

    Adesina, Akeem Yusuf; Gasem, Zuhair M.; Madhan Kumar, Arumugam

    2017-01-01

    The electrochemical behavior of single-layer TiN, CrN, CrAlN, and TiAlN coatings on 304 stainless steel substrate, deposited using state-of-the-art and industrial size cathodic arc PVD machine, were evaluated in 1M HCl and 3.5 pct NaCl solutions. The corrosion behavior of the blank and coated substrates was analyzed by electrochemical impedance spectroscopy (EIS), linear polarization resistance, and potentiodynamic polarization. Bond-coat layers of pure-Ti, pure-Cr, alloyed-CrAl, and alloyed-TiAl for TiN, CrN, CrAlN, and TiAlN coatings were, respectively, first deposited for improved coating adhesion before the actual coating. The average coating thickness was about 1.80 µm. Results showed that the corrosion potentials (E corr) of the coated substrates were shifted to more noble values which indicated improvement of the coated substrate resistance to corrosion susceptibility. The corrosion current densities were lower for all coated substrates as compared to the blank substrate. Similarly, EIS parameters showed that these coatings possessed improved resistance to defects and pores in similar solution compared to the same nitride coatings developed by magnetron sputtering. The charge transfer resistance (R ct) can be ranked in the following order: TiAlN > CrN > TiN > CrAlN in both media except in NaCl solution where R ct of TiN is lowest. While the pore resistance (R po) followed the order: CrAlN > CrN > TiAlN > TiN in HCl solution and TiAlN > CrN > CrAlN > TiN in NaCl solution. It is found that TiAlN coating has the highest protective efficiencies of 79 and 99 pct in 1M HCl and 3.5 pct NaCl, respectively. SEM analysis of the corroded substrates in both media was also presented.

  17. Corrosion Resistance Behavior of Single-Layer Cathodic Arc PVD Nitride-Base Coatings in 1M HCl and 3.5 pct NaCl Solutions

    Science.gov (United States)

    Adesina, Akeem Yusuf; Gasem, Zuhair M.; Madhan Kumar, Arumugam

    2017-04-01

    The electrochemical behavior of single-layer TiN, CrN, CrAlN, and TiAlN coatings on 304 stainless steel substrate, deposited using state-of-the-art and industrial size cathodic arc PVD machine, were evaluated in 1M HCl and 3.5 pct NaCl solutions. The corrosion behavior of the blank and coated substrates was analyzed by electrochemical impedance spectroscopy (EIS), linear polarization resistance, and potentiodynamic polarization. Bond-coat layers of pure-Ti, pure-Cr, alloyed-CrAl, and alloyed-TiAl for TiN, CrN, CrAlN, and TiAlN coatings were, respectively, first deposited for improved coating adhesion before the actual coating. The average coating thickness was about 1.80 µm. Results showed that the corrosion potentials ( E corr) of the coated substrates were shifted to more noble values which indicated improvement of the coated substrate resistance to corrosion susceptibility. The corrosion current densities were lower for all coated substrates as compared to the blank substrate. Similarly, EIS parameters showed that these coatings possessed improved resistance to defects and pores in similar solution compared to the same nitride coatings developed by magnetron sputtering. The charge transfer resistance ( R ct) can be ranked in the following order: TiAlN > CrN > TiN > CrAlN in both media except in NaCl solution where R ct of TiN is lowest. While the pore resistance ( R po) followed the order: CrAlN > CrN > TiAlN > TiN in HCl solution and TiAlN > CrN > CrAlN > TiN in NaCl solution. It is found that TiAlN coating has the highest protective efficiencies of 79 and 99 pct in 1M HCl and 3.5 pct NaCl, respectively. SEM analysis of the corroded substrates in both media was also presented.

  18. Influence of the cathode architecture in the frequency response of self-breathing proton exchange membrane fuel cells

    Science.gov (United States)

    Ferreira-Aparicio, P.; Chaparro, A. M.

    2014-12-01

    Self-breathing proton exchange membrane fuel cells are apparently simple devices, but efficient water management is critical for their performance. The cathode configuration should guarantee balanced rates between O2 accessibility from the circumventing air and H2O removal, and a good electric contact between catalyst layers and current collectors at the same time. By applying progressive modifications to the initial concept of a conventional PEMFC, the effect of the cathode architecture on cell performance has been analyzed. Frequency response analyses of the cell during steady-state potentiostatic stepping have yielded relevant information regarding limitations originated by the cathode impedance under high current load conditions. The primitive cell design has been optimized for self-breathing operation by means of this diagnostic tool. The thickness of the perforated plate in the cathode has been found to be one of the main factors contributing to limit oxygen accessibility when a high current load is demanded. Adequate cathode architecture is critical for reducing mass transport limitations in the catalytic layer and enhancing performance under self-breathing conditions.

  19. The Science and Engineering of Durable Ultralow PGM Catalysts- 2012 DOE-EERE-FCT annual progress report

    Energy Technology Data Exchange (ETDEWEB)

    Garzon, Fernando H. [Los Alamos National Laboratory

    2012-07-16

    Minimizing the quantity of Pt group metals used in polymer membrane fuel cells (PEMFCs) is one of the remaining grand challenges for fuel cell commercialization. Tremendous progress has been achieved over the last two decades in decreasing the Pt loading required for efficient fuel cell performance. Unfortunately, the fluctuations in the price of Pt represent a substantial barrier to the economics of widespread fuel cell use. Durability and impurity tolerance are also challenges that are tightly coupled to fuel cell Pt electrode loading. Traditional approaches to decreasing the amount of Pt required for good performance include: (1) Increasing mass activity by decreasing Pt particle size by supporting on carbon; (2) Alloy formulation Pt-Co, Pt-Cr alloys to improve mass activity; (3) Increasing Pt utilization by optimization of electronic and ionic contact of the Pt particles; (4) Improving conductivity of the electronic and ionic conducting constituents of the membrane electrode assembly; and (5) Improving reactant to and product mass transport away from the electroactive sites. Recent novel approaches include the nanoengineering of core shell catalysts and Pt particles of unusual geometries such as nanowires/whiskers. The success of the aforementioned approaches has been great; however further advances using such approaches have been hampered by a lack of underlining scientific understanding of the catalyst activity, particle growth mechanisms, and optimization strategies for designing composite electrodes The objectives of this report are: (1) Development of durable, high mass activity Platinum Group Metal (PGM) cathode catalysts-enabling lower cost fuel cells; (2) Elucidation of the fundamental relationships between PGM catalyst shape, particle size and activity to help design better catalysts; (3) Optimization of the cathode electrode layer to maximize the performance of PGM catalysts-improving fuel cell performance and lowering cost; (4) Understanding the

  20. Synthesis and electrochemical characterization of palladium-based cathode catalysts, resistant to the presence of methanol; Sintesis y caracterizacion electroquimica de catalizadores catodicos base paladio, resistentes a la presencia de metanol

    Energy Technology Data Exchange (ETDEWEB)

    Salvador, Jose J. [Centro de Investigacion y de Estudios Avanzados del IPN, Mexico D.F. (Mexico)] e-mail: jsalvador@cinvestav.mx; Collins, Virginia H. [Centro de Investigacion en Materiales Avanzados, Chihuahua, Chihuahua (Mexico); Solorza Feria, Omar [Centro de Investigacion y de Estudios Avanzados del IPN, Mexico D.F. (Mexico)

    2009-09-15

    This work presents the synthesis and characterization of palladium-based electrocatalysts (PdSn and PdPtSn) prepared with the salt-reduction method for oxygen reduction reaction (ORR). The compounds obtained are characterized by sweep electron microscopy, electron transmission microscopy and x-ray diffraction of powder. The electrocatalysts obtained had particle sizes less than 10 nm. The evaluation of the catalytic activity of the catalysts was performed using cyclic voltametry and rotating disc electrode. These experiments were conducted in an H{sub 2}SO{sub 4} 0.5 M solution with different methanol concentrations. The presence of methanol improved the catalytic activity of PdSn, but did not show any effect on the PdPtSn alloy. The performance of the DMFC mono cell using PdPtSn as a cathode showed a potential of 10 mW cm{sup -2} at 50 degrees Celsius. [Spanish] En este trabajo se presenta la sintesis y caracterizacion de electrocatalizadores de base Paladio (PdSn y PdPtSn) preparados mediante el metodo de reduccion de sales, para la reaccion de reduccion de oxigeno (RRO). Los compuestos obtenidos se caracterizaron por microscopia electronica de barrido, microscopia electronica de transmision y difraccion de rayos X de polvos. Los electrocatalizadores obtenidos presentaron un tamano de particula menores a 10 nm. La evaluacion de la actividad catalitica de los catalizadores se llevo a cabo mediante voltametria Ciclica y electrodo de disco rotatorio, estos experimentos fueron realizados en una solucion de H{sub 2}SO{sub 4} 0.5 M con diferentes concentraciones de metanol. La presencia de metanol mejoro la actividad catalitica de PdSn, pero no mostro ningun efecto sobre la aleacion PdPtSn. El desempeno de la monocelda de DMFC usando como catodo PdPtSn, mostro una potencia de 10 mW cm{sup -2} a 50 grados centigrados.

  1. Selective hydrogenation of 1,3-butadiene from crude C{sub 4} cracker stream with a solid catalyst with ionic liquid layer (SCILL). DSC and solubility study

    Energy Technology Data Exchange (ETDEWEB)

    Mangartz, T.; Korth, W.; Kern, C.; Jess, A. [Bayreuth Univ. (Germany). Dept. of Chemical Engineering

    2013-11-01

    In petroleum as well as in fine chemical industry, selective catalytic hydrogenation is an important reaction. The selective hydrogenation of 1,3-butadiene (BD) to butene (trans-,1- and cis-butene) from the crude C4 steam cracker fraction represents one example, but under today's technical conditions undesired butane forms inevitably in relevant amounts. To increase the butene yield, the concept of Solid Catalyst with Ionic Liquid Layer (SCILL) was employed. The SCILL catalyst, in contrast to the uncoated catalyst, yielded a remarkably high selectivity to butenes (S{sub butenes} > 99 %) even at high residence times or at high hydrogen partial pressure. Nearly no butane (S{sub butane} {approx} 0 %) was analytically detected. We expected that due to different solubility, the poorer soluble compounds discharged from the ionic liquid and, thus, caused the shift in selectivity to a great extent. Temperature dependent solubility measurements in the used ionic liquid ([DMIM][DMP]) revealed that the order of increasing solubility is 1,3-butadiene > butenes > butane which matches the assumption. However, since differences in solubility cannot explain this SCILL effect satisfyingly, ionic liquids are expected to affect the surface of the catalyst (side-specific ligand-type effect). Investigations using spectroscopic methods (e.g. FTIR) confirmed this suggestion. (orig.)

  2. Control of thickness and chemical properties of atomic layer deposition overcoats for stabilizing Cu/γ-Al2 O3 catalysts.

    Science.gov (United States)

    O'Neill, Brandon J; Sener, Canan; Jackson, David H K; Kuech, Thomas F; Dumesic, James A

    2014-12-01

    Whereas sintering and leaching of copper nanoparticles during liquid-phase catalytic processing can be prevented by using atomic layer deposition (ALD) to overcoat the nanoparticles with AlOx , this acidic overcoat leads to reversible deactivation of the catalyst by resinification and blocking of the pores within the overcoat during hydrogenation of furfural. We demonstrate that decreasing the overcoat thickness from 45 to 5 ALD cycles is an effective method to increase the rate per gram of catalyst and to decrease the rate of deactivation for catalysts pretreated at 673 K, and a fully regenerable copper catalyst can be produced with only five ALD cycles of AlOx . Moreover, although an overcoat of MgOx does not lead to stabilization of copper nanoparticles against sintering and leaching during liquid-phase hydrogenation reactions, the AlOx overcoat can be chemically modified to decrease acidity and deactivation through the addition of MgOx , while maintaining stability of the copper nanoparticles.

  3. Optical properties of lamps with cold emission cathode

    Science.gov (United States)

    Kalenik, Jerzy; Czerwosz, ElŻbieta; Biernacki, Krzysztof; Rymarczyk, Joanna; Stepińska, Izabela

    2016-12-01

    A luminescent lamp was constructed and tested. Phosphor excited by electrons is the source of light. The source of electrons is field emission cathode. The cathode is covered with nickel-carbon layer containing carbon nanotubes that enhance electron emission from the cathode. Results of luminance measurements are presented. Luminance is high enough for lighting application.

  4. High performance, high durability non-precious metal fuel cell catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Thomas E.; Atanasoski, Radoslav; Schmoeckel, Alison K.

    2016-03-15

    This invention relates to non-precious metal fuel cell cathode catalysts, fuel cells that contain these catalysts, and methods of making the same. The fuel cell cathode catalysts are highly nitrogenated carbon materials that can contain a transition metal. The highly nitrogenated carbon materials can be supported on a nanoparticle substrate.

  5. Lipon coatings for high voltage and high temperature Li-ion battery cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Dudney, Nancy J.; Liang, Chengdu; Nanda, Jagjit; Veith, Gabriel M.; Kim, Yoongu; Martha, Surendra Kumar

    2017-02-14

    A lithium ion battery includes an anode and a cathode. The cathode includes a lithium, manganese, nickel, and oxygen containing compound. An electrolyte is disposed between the anode and the cathode. A protective layer is deposited between the cathode and the electrolyte. The protective layer includes pure lithium phosphorus oxynitride and variations that include metal dopants such as Fe, Ti, Ni, V, Cr, Cu, and Co. A method for making a cathode and a method for operating a battery are also disclosed.

  6. Highly Dispersed Alloy Catalyst for Durability

    Energy Technology Data Exchange (ETDEWEB)

    Murthi, Vivek S.; Izzo, Elise; Bi, Wu; Guerrero, Sandra; Protsailo, Lesia

    2013-01-08

    Achieving DOE's stated 5000-hr durability goal for light-duty vehicles by 2015 will require MEAs with characteristics that are beyond the current state of the art. Significant effort was placed on developing advanced durable cathode catalysts to arrive at the best possible electrode for high performance and durability, as well as developing manufacturing processes that yield significant cost benefit. Accordingly, the overall goal of this project was to develop and construct advanced MEAs that will improve performance and durability while reducing the cost of PEMFC stacks. The project, led by UTC Power, focused on developing new catalysts/supports and integrating them with existing materials (membranes and gas diffusion layers (GDLs)) using state-of-the-art fabrication methods capable of meeting the durability requirements essential for automotive applications. Specifically, the project work aimed to lower platinum group metals (PGM) loading while increasing performance and durability. Appropriate catalysts and MEA configuration were down-selected that protects the membrane, and the layers were tailored to optimize the movements of reactants and product water through the cell to maximize performance while maintaining durability.

  7. Stabilizing interface layer of LiNi0.5Co0.2Mn0.3O2 cathode materials under high voltage using p-toluenesulfonyl isocyanate as film forming additive

    Science.gov (United States)

    Dong, Peng; Wang, Ding; Yao, Yao; Li, Xue; Zhang, Yingjie; Ru, Juanjian; Ren, Ting

    2017-03-01

    p-Toluenesulfonyl isocyanate (PTSI) is introduced as electrolyte additive in a bid to enhance the electrochemical performances of LiNi0.5Co0.2Mn0.3O2 cathode materials under high voltage. A less resistive and stable film on the cathode surface derived from PTSI oxidation which taken place prior to the carbonate solvents is formed. As a result, the discharge capacity retention of Li/LiNi0.5Co0.2Mn0.3O2 cell is elevated from 71.4% to 86.2% after 100 cycles at room temperature, and from 32.3% to 54.5% after 100 cycles at 55 °C. In addition, the Li/LiNi0.5Co0.2Mn0.3O2 half cell with PTSI exhibits superior rate capability compared to that in baseline electrolyte. The improved performance is not only ascribed to the thin protective layer originated from PTSI decomposition which prevent the successive breakdown of the electrolyte on cathode surface, but it is also attributed to the sbnd Sdbnd O group in PTSI serves as the weak base site to restrain the reactivity of PF5, resulting in the suppression of LiF formation and HF generation.

  8. Development of advanced catalytic layer based on vertically aligned conductive polymer arrays for thin-film fuel cell electrodes

    Science.gov (United States)

    Jiang, Shangfeng; Yi, Baolian; Cao, Longsheng; Song, Wei; Zhao, Qing; Yu, Hongmei; Shao, Zhigang

    2016-10-01

    The degradation of carbon supports significantly influences the performance of proton exchange membrane fuel cells (PEMFCs), particularly in the cathode, which must be overcome for the wide application of fuel cells. In this study, advanced catalytic layer with electronic conductive polymer-polypyrrole (PPy) nanowire as ordered catalyst supports for PEMFCs is prepared. A platinum-palladium (PtPd) catalyst thin layer with whiskerette shapes forms along the long axis of the PPy nanowires. The resulting arrays are hot-pressed on both sides of a Nafion® membrane to construct a membrane electrode assembly (without additional ionomer). The ordered thin catalyst layer (approximately 1.1 μm) is applied in a single cell as the anode and the cathode without additional Nafion® ionomer. The single cell yields a maximum performance of 762.1 mW cm-2 with a low Pt loading (0.241 mg Pt cm-2, anode + cathode). The advanced catalyst layer indicates better mass transfer in high current density than that of commercial Pt/C-based electrode. The mass activity is 1.08-fold greater than that of DOE 2017 target. Thus, the as-prepared electrodes have the potential for application in fuel cells.

  9. Influence of lithium content on high rate cycleability of layered Li 1+ xNi 0.30Co 0.30Mn 0.40O 2 cathodes for high power lithium-ion batteries

    Science.gov (United States)

    Santhanam, R.; Jones, Philip; Sumana, Adusumilli; Rambabu, B.

    Layered Li 1+ xNi 0.30Co 0.30Mn 0.40O 2 (x = 0, 0.05, 0.10, 0.15) materials have been synthesized using citric acid assisted sol-gel method. The materials with excess lithium showed distinct differences in the structure and the charge and discharge characteristics. The rate capability tests were performed and compared on Li 1+ xNi 0.30Co 0.30Mn 0.40O 2 (x = 0, 0.05, 0.10, 0.15) cathode materials. Among these materials, Li 1.10Ni 0.30Co 0.30Mn 0.40O 2 cathode demonstrated higher discharge capacity than that of the other cathodes. Upon extended cycling at 1C and 8C, Li 1.10Ni 0.30Co 0.30Mn 0.40O 2 showed better capacity retention when compared to other materials with different lithium content. Li 1.10Ni 0.30Co 0.30Mn 0.40O 2 exhibited 93 and 90% capacity retention where as Li 1.05Ni 0.30Co 0.30Mn 0.40O 2, Li 1.15Ni 0.30Co 0.30Mn 0.40O 2, and Li 1.00Ni 0.30Co 0.30Mn 0.40O 2 exhibited only 84, 71, and 63% (at 1C), and 79, 66 and 40% (at 10C) capacity retention, respectively, after 40 cycles. The enhanced high rate cycleability of Li 1.10Ni 0.30Co 0.30Mn 0.40O 2 cathode is attributed to the improved structural stability due to the formation of appropriate amount of Li 2MnO 3-like domains in the transition metal layer and decreased Li/Ni disorder (i.e., Ni content in the Li layer).

  10. Butanol Dehydration over V2O5-TiO2/MCM-41 Catalysts Prepared via Liquid Phase Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Jong-Ki Jeon

    2013-04-01

    Full Text Available MCM-41 was used as a support and, by using atomic layer deposition (ALD in the liquid phase, a catalyst was prepared by consecutively loading titanium oxide and vanadium oxide to the support. This research analyzes the effect of the loading amount of vanadium oxide on the acidic characteristics and catalytic performance in the dehydration of butanol. The physical and chemical characteristics of the TiO2-V2O5/MCM-41 catalysts were analyzed using XRF, BET, NH3-TPD, XRD, Py-IR, and XPS. The dehydration reaction of butanol was performed in a fixed bed reactor. For the samples with vanadium oxide loaded to TiO2/MCM-41 sample using the liquid phase ALD method, it was possible to increase the loading amount until the amount of vanadium oxide reached 12.1 wt %. It was confirmed that the structural properties of the mesoporous silica were retained well after titanium oxide and vanadium loading. The NH3-TPD and Py-IR results indicated that weak acid sites were produced over the TiO2/MCM-41 samples, which is attributed to the generation of Lewis acid sites. The highest activity of the V2O5(12.1-TiO2/MCM-41 catalyst in 2-butanol dehydration is ascribed to it having the highest number of Lewis acid sites, as well as the highest vanadium dispersion.

  11. Efficient indium-tin-oxide free inverted organic solar cells based on aluminum-doped zinc oxide cathode and low-temperature aqueous solution processed zinc oxide electron extraction layer

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Dazheng; Zhang, Chunfu, E-mail: cfzhang@xidian.edu.cn; Wang, Zhizhe; Zhang, Jincheng; Tang, Shi; Wei, Wei; Sun, Li; Hao, Yue, E-mail: yhao@xidian.edu.cn [State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, School of Microelectronics, Xidian University, No. 2 South Taibai Road, Xi' an 710071 (China)

    2014-06-16

    Indium-tin-oxide (ITO) free inverted organic solar cells (IOSCs) based on aluminum-doped zinc oxide (AZO) cathode, low-temperature aqueous solution processed zinc oxide (ZnO) electron extraction layer, and poly(3-hexylthiophene-2, 5-diyl):[6, 6]-phenyl C{sub 61} butyric acid methyl ester blend were realized in this work. The resulted IOSC with ZnO annealed at 150 °C shows the superior power conversion efficiency (PCE) of 3.01%, if decreasing the ZnO annealing temperature to 100 °C, the obtained IOSC also shows a PCE of 2.76%, and no light soaking issue is observed. It is found that this ZnO film not only acts as an effective buffer layer but also slightly improves the optical transmittance of AZO substrates. Further, despite the relatively inferior air-stability, these un-encapsulated AZO/ZnO IOSCs show comparable PCEs to the referenced ITO/ZnO IOSCs, which demonstrates that the AZO cathode is a potential alternative to ITO in IOSCs. Meanwhile, this simple ZnO process is compatible with large area deposition and plastic substrates, and is promising to be widely used in IOSCs and other relative fields.

  12. Performance of a solid oxide fuel cell with cathode containing a functional layer of LSM/YSZ film; Desempenho de uma celula a combustivel de oxido solido com catodo contendo uma camada funcional de filme LSM/YSZ

    Energy Technology Data Exchange (ETDEWEB)

    Pires, Filipe Oliveira; Domingues, Rosana Z.; Brant, Marcia C.; Silva, Charles L.; Matencio, Tulio [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Quimica]. E-mail: filipequiufmg@ufmg.br

    2008-07-01

    Performance of a SOFC may be evaluated by using the AC-Impedance and measuring power (P V x I). The objective of this study was to compare the performance of a fuel cell with LSM as a cathode and another one containing an additional functional composite film LSM/YSZ between the LSM and YSZ. Also it was studied variation in second cell resistance and power according to the temperature, hydrogen flux and operation time. For both cells platinum was used as anode. At 800 deg C was observed, in open current circuit, when the composite layer was introduced a decrease in resistance and high power. These results show an improvement of SOFC cathode performance with the introduction of composite LSM/YSZ layer. The maximum performance of the cell was achieved with 100 mL/min hydrogen flow at 800 deg C. The experiments also showed a performance improvement at 850 deg C. The cell behavior was stable during 318 hours of test. (author)

  13. Optical characteristics of nanocrystalline Al{sub x}Ga{sub 1−x}N thin films deposited by hollow cathode plasma-assisted atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Goldenberg, Eda, E-mail: goldenberg@unam.bilkent.edu.tr [UNAM – National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Ozgit-Akgun, Cagla; Biyikli, Necmi [Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey); Kemal Okyay, Ali [Department of Electrical and Electronics Engineering, Bilkent University, Ankara 06800 (Turkey)

    2014-05-15

    Gallium nitride (GaN), aluminum nitride (AlN), and Al{sub x}Ga{sub 1−x}N films have been deposited by hollow cathode plasma-assisted atomic layer deposition at 200 °C on c-plane sapphire and Si substrates. The dependence of film structure, absorption edge, and refractive index on postdeposition annealing were examined by x-ray diffraction, spectrophotometry, and spectroscopic ellipsometry measurements, respectively. Well-adhered, uniform, and polycrystalline wurtzite (hexagonal) GaN, AlN, and Al{sub x}Ga{sub 1−x}N films were prepared at low deposition temperature. As revealed by the x-ray diffraction analyses, crystallite sizes of the films were between 11.7 and 25.2 nm. The crystallite size of as-deposited GaN film increased from 11.7 to 12.1 and 14.4 nm when the annealing duration increased from 30 min to 2 h (800 °C). For all films, the average optical transmission was ∼85% in the visible (VIS) and near infrared spectrum. The refractive indices of AlN and Al{sub x}Ga{sub 1−x}N were lower compared to GaN thin films. The refractive index of as-deposited films decreased from 2.33 to 2.02 (λ = 550 nm) with the increased Al content x (0 ≤ x ≤ 1), while the extinction coefficients (k) were approximately zero in the VIS spectrum (>400 nm). Postdeposition annealing at 900 °C for 2 h considerably lowered the refractive index value of GaN films (2.33–1.92), indicating a significant phase change. The optical bandgap of as-deposited GaN film was found to be 3.95 eV, and it decreased to 3.90 eV for films annealed at 800 °C for 30 min and 2 h. On the other hand, this value increased to 4.1 eV for GaN films annealed at 900 °C for 2 h. This might be caused by Ga{sub 2}O{sub 3} formation and following phase change. The optical bandgap value of as-deposited Al{sub x}Ga{sub 1−x}N films decreased from 5.75 to 5.25 eV when the x values decreased from 1 to 0.68. Furthermore, postdeposition annealing did not

  14. Preparation of manganese oxide immobilized on SBA-15 by atomic layer deposition as an efficient and reusable catalyst for selective oxidation of benzyl alcohol in the liquid phase

    Energy Technology Data Exchange (ETDEWEB)

    Mahdavi, Vahid, E-mail: v-mahdavi@araku.ac.ir; Mardani, Mahdieh

    2015-04-01

    Manganese oxide supported on mesoporous silica SBA-15 catalyst (Mn-SBA-15) was tested with Mn contents in the range of 0.8–23 wt%. Samples were prepared by the controlled grafting process of atomic layer deposition (ALD). Other sample was prepared for comparisons by the wet impregnation method. These samples were characterized by the techniques of ICP, XRD, SEM, Raman, FT-IR spectroscopy, diffuse reflectance UV–Vis, TGA-DSC, and N{sub 2} absorption–desorption surface area measurement. Results indicated that anchored manganese oxide particles have been successfully synthesized over the surface of SBA-15. These samples contained Red-Ox ion pairs of Mn{sup 2+} and Mn{sup 3+} highly dispersed on the mesoporous silica surface. The impregnated sample exhibited lower surface area and contained Red-Ox ion pairs of Mn{sup 3+} and Mn{sup 4+} more aggregated particles on the SBA-15 surface. Results determined Mn-SBA-15 as an efficient and selective catalyst for oxidation of benzyl alcohol with tert-butylhydroperoxide in liquid phase. In accordance with expectations, there was a negligible amount of leaching of immobilized manganese oxide from the support during the reaction, because of strong surface interaction between manganese oxide and hydroxyls groups. The influences of reaction temperature, reaction time, solvent, TBHP/benzyl alcohol molar ratio, amount of catalyst and reusability were investigated. Under optimized conditions (0.2 g catalyst, TBHP/benzyl alcohol molar ratio 1, solvent acetonitrile; T = 90 °C; reaction time 8 h), results achieved 70% conversion of benzyl alcohol and 100% selectivity to benzaldehyde. - Highlights: • Manganese oxide immobilized on SBA-15 were prepared by atomic layer deposition (ALD). • Oxidation of benzyl alcohol to benzaldehyde over this catalyst were investigated. • Effects of loading of manganese oxide, T, oxidant/alcohol ratio were investigated. • The leaching of manganese oxide from support during the reaction was

  15. Ca3Co4O9+δ, a growing potential SOFC cathode material: impact of the layer composition and thickness on the electrochemical properties

    NARCIS (Netherlands)

    Rolle, A.; Abbas, H.A.A.; Huo, D.; Capoen, E.; Mentré, O.; Vannier, R.N.; Daviero-Minaud, S.; Boukamp, B.A.

    2016-01-01

    The thermoelectric material Ca3Co4O9 + δ (CCO), with an electronic conductivity of σe = 240 S·cm− 1 at 650 °C and a good chemical and mechanical compatibility with the standard Ce0.9Gd0.1O1.95 electrolyte (CGO, TEC: 9–10 · 10− 6 K− 1), was recently identified as a potential cathode material for soli

  16. Preparation, structure study and electrochemistry of layered H2V3O8 materials: High capacity lithium-ion battery cathode

    Science.gov (United States)

    Sarkar, Sudeep; Bhowmik, Arghya; Pan, Jaysree; Bharadwaj, Mridula Dixit; Mitra, Sagar

    2016-10-01

    The present study explores H2V3O8 as high capacity cathode material for lithium-ion batteries (LIB's). Despite having high discharge capacity, H2V3O8 material suffers from poor electrochemical stability for prolonged cycle life. Ultra-long H2V3O8 nanobelts with ordered crystallographic patterns are synthesized via a hydrothermal process to mitigate this problem. The growth of the crystal is facile along [001] direction, and the most common surface is (001) as suggested by Wulff construction study. Electrochemical performance of H2V3O8 cathode is tested against Li/Li+ at various current rates. At 50 mA g-1current rate, it delivers a discharge capacity of 308 mAh g-1, whereas, at 3000 mA g-1, an initial discharge capacity of 144 mAh g-1 is observed and stabilized at 100 mAh g-1 till 500 cycles. Further, the density functional theory (DFT) based simulations study of both the pristine and lithiated phase of H2V3O8 cathode materials is undertaken. DFT study reveals the presence of hydrogen as hydroxyl unit in the framework of the host. In correlation, the magnetic property of vanadium atoms is examined in detail with through partial density of states (PDOS) calculation during three stage lithiation processes and evaluating various potential steps involved in lithium insertion.

  17. Investigation on the origin of diffusion impedance in the porous cathode of a proton exchange membrane fuel cell (PEMFC) via electrochemical impedance spectroscopy (EIS)

    Energy Technology Data Exchange (ETDEWEB)

    Mainka, J.; Maranzana, G.; Dillet, J.; Didierjean, S.; Lottin, O. [Nancy Univ., Centre national de la recherche scientifique, Vandoeuvre les Nancy (France). Laboratoire d' Energetique et de Mecanique Theorique et Appliquee

    2009-07-01

    This study provided a preliminary examination of the impact of gas flow rate on the impedance characteristics of a proton exchange membrane fuel cell (PEMFC). The mass transport phenomena within the porous cathode of PEMFCs can be analyzed through electrochemical impedance spectroscopy (EIS). The geometrical description of the electrodes chosen to complete the EIS interpretations is a form of the agglomerate model, where the agglomerates are a mixture of carbon powder and catalyst particles, whereas the electrolyte is assumed to cover only the pore surfaces. Therefore, the reactants access the active catalyst sites by passing successively through the gas diffusion layer (GDL), the pores of the electrode, and finally through a thin electrolyte layer. The fuel cell equivalent electrical circuit is based on a Butler-Volmer formalism that takes into consideration oxygen diffusion in the pores of the GDL and/or the active layer through a Warburg element. The results reveal that in the cathode, the mass transfer limiting layer is most likely the active layer, provided liquid water is present within the pores. Under normal operating conditions, the mass transport resistance of the gas diffusion layer is negligible, as is the fine electrolyte layer coating the agglomerate.

  18. Open-source FCPEM-Performance & Durability Model Consideration of Membrane Properties on Cathode Degradation

    Energy Technology Data Exchange (ETDEWEB)

    Knights, Shanna [Ballard Fuel Cell Systems, Bend, OR (United States); Harvey, David [Ballard Fuel Cell Systems, Bend, OR (United States)

    2017-01-20

    The durability of PEM fuel cells is a primary requirement for large scale commercialization of these power systems in transportation and stationary market applications which target operational lifetimes of 5,000 hours and 60,000 hours by 2020, respectively. Key degradation modes contributing to fuel cell lifetime limitations have been largely associated with the platinum-based cathode catalyst layer. Furthermore, as fuel cells are driven to low cost materials and lower catalyst loadings in order to meet the cost targets for commercialization, the catalyst durability has become even more important. While over the past few years significant progress has been made in identifying the underlying causes of fuel cell degradation and key parameters that greatly influence the degradation rates, many gaps with respect to knowledge of the driving mechanisms still exist; in particular, the acceleration of the mechanisms due to different membrane compositions remains an area not well understood. The focus of this project extension was to enhance the predictive capability of the PEM Fuel Cell Performance & Durability Model called FC-APOLLO (Application Package for Open-source Long Life Operation) by including interaction effects of membrane transport properties such as water transport, changes in proton conductivity, and overall water uptake/adsorption and the state of the catalyst layer local conditions to further understand the driving forces for platinum dissolution.

  19. Plasma versus thermal annealing for the Au-catalyst growth of ZnO nanocones and nanowires on Al-doped ZnO buffer layers

    Science.gov (United States)

    Güell, Frank; Martínez-Alanis, Paulina R.; Roso, Sergio; Salas-Pérez, Carlos I.; García-Sánchez, Mario F.; Santana, Guillermo; Marel Monroy, B.

    2016-06-01

    We successfully synthesized ZnO nanocones and nanowires over polycrystalline Al-doped ZnO (AZO) buffer layers on fused silica substrates by a vapor-transport process using Au-catalyst thin films. Different Au film thicknesses were thermal or plasma annealed in order to analyze their influence on the ZnO nanostructure growth morphology. Striking differences have been observed. Thermal annealing generates a distribution of Au nanoclusters and plasma annealing induces a fragmentation of the Au thin films. While ZnO nanowires are found in the thermal-annealed samples, ZnO nanocones and nanowires have been obtained on the plasma-annealed samples. Enhancement of the preferred c-axis (0001) growth orientation was demonstrated by x-ray diffraction when the ZnO nanocones and nanowires have been grown over the AZO buffer layer. The transmittance spectra of the ZnO nanocones and nanowires show a gradual increase from 375 to 900 nm, and photoluminescence characterization pointed out high concentration of defects leading to observation of a broad emission band in the visible range from 420 to 800 nm. The maximum emission intensity peak position of the broad visible band is related to the thickness of the Au-catalyst for the thermal-annealed samples and to the plasma power for the plasma-annealed samples. Finally, we proposed a model for the plasma versus thermal annealing of the Au-catalyst for the growth of the ZnO nanocones and nanowires. These results are promising for renewable energy applications, in particular for its potential application in solar cells.

  20. Selective oxidation catalysts obtained by immobilization of iron(III) porphyrins on thiosalicylic acid-modified Mg-Al layered double hydroxides.

    Science.gov (United States)

    de Freitas Castro, Kelly Aparecida Dias; Wypych, Fernando; Antonangelo, Ariana; Mantovani, Karen Mary; Bail, Alesandro; Ucoski, Geani Maria; Ciuffi, Kátia Jorge; Cintra, Thais Elita; Nakagaki, Shirley

    2016-09-15

    Nitrate-intercalated Mg-Al layered double hydroxides (LDHs) were synthesized and exfoliated in formamide. Reaction of the single layer suspension with thiosalicylic acid under different conditions afforded two types of solids: LDHA1, in which the outer surface was modified with the anion thiosalicylate, and LDHA2, which contained the anion thiosalicylate intercalated between the LDH layers. LDHA1 and LDHA2 were used as supports to immobilize neutral (FeP1 and FeP2) and anionic (FeP3) iron(III) porphyrins. For comparison purposes, the iron(III) porphyrins (FePs) were also immobilized on LDH intercalated with nitrate anions obtained by the co-precipitation method. Chemical modification of LDH facilitated immobilization of the FePs through interaction of the functionalizing groups in LDH with the peripheral substituents on the porphyrin ring. The resulting FePx-LDHAy solids were characterized by X-ray diffraction (powder) and UV-Vis and EPR spectroscopies and were investigated as catalysts in the oxidation of cyclooctene and cyclohexane. The immobilized neutral FePs and their homogeneous counterparts gave similar product yields in the oxidation of cyclooctene, suggesting that immobilization of the FePs on the thiosalicylate-modified LDHs only supported the catalyst species without interfering in the catalytic outcome. On the other hand, in the oxidation of cyclohexane, the thiosalicylate anions on the outer surface of LDHA1 or intercalated between the LDHA2 layers influenced the catalytic activity of FePx-LDHAy, leading to different efficiency and selectivity results. FeP1-LDHA2 performed the best (29.6% alcohol yield) due to changes in the polarity of the surface of the support and the presence of FeP1. Interestingly, FeP1 also performed better in solution as compared to the other FePs. Finally, it was possible to recycle FeP1-LDHA2 at least three times.

  1. Performance enhancement of air-breathing proton exchange membrane fuel cell through utilization of an effective self-humidifying platinum-carbon catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Poh, Chee Kok; Lin, Jianyi [Institute of Chemical Engineering and Sciences, 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore); Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Tian, Zhiqun; Lim, San Hua [Institute of Chemical Engineering and Sciences, 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore); Bussayajarn, Narissara [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore); Tang, Zhe; Chua, Daniel [Department of Materials Science and Engineering, National University of Singapore, Singapore (Singapore); Su, Fabing [State Key Laboratory of Multi-phase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Feng, Yuan Ping [Department of Physics, National University of Singapore, Singapore 117542 (Singapore)

    2010-12-15

    One issue with air-breathing proton exchange membrane fuel cells (AB-PEMFCs) is that the reactants are not externally humidified, and thus the membrane or the catalyst layers might dry out due to electro-osmotic drag, diffusion and evaporation at the opening cathode. This results in a drop in internal ionic conductivity and thus in cell performance. Here, the preparation and characterization of self-humidifying carbon-supported Pt catalyst using citric acid modified carbon black (CA-CB) as the catalyst support are reported. Pt/CA-CB is highly hydrophilic due to the functional groups attached on the carbon support, which endows the ability to retain water in the membrane electrolyte assembly (MEA) and thereby help to improve the performance of AB-PEMFCs. A maximum power density of 204 mW cm{sup -2} can be achieved in an air-breathing PEMFC stack using Pt/CA-CB, a thick polymer membrane (NRE212) and a circular opening cathode. A 23.4% enhancement in the output power density is obtained by using Pt/CA-CB in place of a commercial catalyst when oblique slit cathodes are employed. This self-humidifying catalyst is particularly suitable for portable PEMFC applications. (author)

  2. Erosion behaviour of composite Al-Cr cathodes in cathodic arc plasmas in inert and reactive atmospheres

    CERN Document Server

    Franz, Robert; Hawranek, Gerhard; Polcik, Peter

    2015-01-01

    Al$_{x}$Cr$_{1-x}$ composite cathodes with Al contents of x = 0.75, 0.5 and 0.25 were exposed to cathodic arc plasmas in Ar, N$_2$ and O$_2$ atmospheres and their erosion behaviour was studied. Cross-sectional analysis of the elemental distribution of the near-surface zone in the cathodes by scanning electron microscopy revealed the formation of a modified layer for all cathodes and atmospheres. Due to intermixing of Al and Cr in the heat-affected zone, intermetallic Al-Cr phases formed as evidenced by X-ray diffraction analysis. Cathode poisoning effects in the reactive N$_2$ and O$_2$ atmospheres were non-uniform as a result of the applied magnetic field configuration. With the exception of oxide islands on Al-rich cathodes, reactive layers were absent in the circular erosion zone, while nitrides and oxides formed in the less eroded centre region of the cathodes.

  3. High Performance Cathodes for Li-Air Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Yangchuan

    2013-08-22

    The overall objective of this project was to develop and fabricate a multifunctional cathode with high activities in acidic electrolytes for the oxygen reduction and evolution reactions for Li-air batteries. It should enable the development of Li-air batteries that operate on hybrid electrolytes, with acidic catholytes in particular. The use of hybrid electrolytes eliminates the problems of lithium reaction with water and of lithium oxide deposition in the cathode with sole organic electrolytes. The use of acid electrolytes can eliminate carbonate formation inside the cathode, making air breathing Li-air batteries viable. The tasks of the project were focused on developing hierarchical cathode structures and bifunctional catalysts. Development and testing of a prototype hybrid Li-air battery were also conducted. We succeeded in developing a hierarchical cathode structure and an effective bifunctional catalyst. We accomplished integrating the cathode with existing anode technologies and made a pouch prototype Li-air battery using sulfuric acid as catholyte. The battery cathodes contain a nanoscale multilayer structure made with carbon nanotubes and nanofibers. The structure was demonstrated to improve battery performance substantially. The bifunctional catalyst developed contains a conductive oxide support with ultra-low loading of platinum and iridium oxides. The work performed in this project has been documented in seven peer reviewed journal publications, five conference presentations, and filing of two U.S. patents. Technical details have been documented in the quarterly reports to DOE during the course of the project.

  4. High-performance hydrogen fuel cell using nitrate reduction reaction on a non-precious catalyst.

    Science.gov (United States)

    Han, Sang-Beom; Song, You-Jung; Lee, Young-Woo; Ko, A-Ra; Oh, Jae-Kyung; Park, Kyung-Won

    2011-03-28

    The H(2)-NO(3)(-) electrochemical cell using nitrate reduction on a non-precious cathode catalyst shows much improved efficiency despite ∼75% reduction of Pt metal loading as compared to typical PEMFCs using typical ORR on precious catalysts.

  5. Prevention of the water flooding by micronizing the pore structure of gas diffusion layer for polymer electrolyte fuel cell

    Science.gov (United States)

    Hiramitsu, Yusuke; Sato, Hitoshi; Hori, Michio

    In polymer electrolyte fuel cells, high humidity must be established to maintain high proton conductivity in the polymer electrolyte. However, the water that is produced electrochemically at the cathode catalyst layer can condense in the cell and cause an obstruction to the diffusion of reaction gas in the gas diffusion layer and the gas channel. This leads to a sudden decrease of the cell voltage. To combat this, strict water management techniques are required, which usually focus on the gas diffusion layer. In this study, the use of specially treated carbon paper as a flood-proof gas diffusion layer under extremely high humidity conditions was investigated experimentally. The results indicated that flooding originates at the interface between the gas diffusion layer and the catalyst layer, and that such flooding could be eliminated by control of the pore size in the gas diffusion layer at this interface.

  6. Layered P2-Na2/3Co1/2Ti1/2O2 as a high-performance cathode material for sodium-ion batteries

    Science.gov (United States)

    Sabi, Noha; Doubaji, Siham; Hashimoto, Kazuki; Komaba, Shinichi; Amine, Khalil; Solhy, Abderrahim; Manoun, Bouchaib; Bilal, Essaid; Saadoune, Ismael

    2017-02-01

    Layered oxides are regarded as promising cathode materials for sodium-ion batteries. We present Na2/3Co1/2Ti1/2O2 as a potential new cathode material for sodium-ion batteries. The crystal features and morphology of the pristine powder were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The cathode material is evaluated in galvanostatic charge-discharge and galvanostatic intermittent titration tests, as well as ex-situ X-ray diffraction analysis. Synthesized by a high-temperature solid state reaction, Na2/3Co1/2Ti1/2O2 crystallizes in P2-type structure with P63/mmc space group. The material presents reversible electrochemical behavior and delivers a specific discharge capacity of 100 mAh g-1 when tested in Na half cells between 2.0 and 4.2 V (vs. Na+/Na), with capacity retention of 98% after 50 cycles. Furthermore, the electrochemical cycling of this titanium-containing material evidenced a reduction of the potential jumps recorded in the NaxCoO2 parent phase, revealing a positive impact of Ti substitution for Co. The ex-situ XRD measurements confirmed the reversibility and stability of the material. No structural changes were observed in the XRD patterns, and the P2-type structure was stable during the charge/discharge process between 2.0 and 4.2 V vs. Na+/Na. These outcomes will contribute to the progress of developing low cost electrode materials for sodium-ion batteries.

  7. Catalyst containing oxygen transport membrane

    Science.gov (United States)

    Christie, Gervase Maxwell; Wilson, Jamie Robyn; van Hassel, Bart Antonie

    2012-12-04

    A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a high average pore diameter and the intermediate porous layer has a lower permeability and lower pore diameter than the porous support layer. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

  8. Electrochemical Impedance Studies of SOFC Cathodes

    DEFF Research Database (Denmark)

    Hjelm, Johan; Søgaard, Martin; Wandel, Marie

    2007-01-01

    impedance of the cathode at intermediate operating temperatures. The perovskite is of the La-Sr-Co-Fe type. The EIS response of symmetrical cells with a thick (similar to 200 mu m) gadolinia doped ceria electrolyte was compared with the impedance contribution of the cathode of a full anode supported cell....... The full cells had a Ni-YSZ anode and anode support, a thin YSZ electrolyte, and a CGO barrier layer. The symmetric and full cell cathode responses were compared at open-circuit voltage. Humidified hydrogen was used as the fuel in the full cell measurements. Differential analysis of the impedance data...

  9. Influence of Ti(4+) on the electrochemical performance of Li-rich layered oxides - high power and long cycle life of Li2Ru1-xTixO3 cathodes.

    Science.gov (United States)

    Kalathil, Abdul Kareem; Arunkumar, Paulraj; Kim, Da Hye; Lee, Jong-Won; Im, Won Bin

    2015-04-01

    Li-rich layered oxides are the most attractive cathodes for lithium-ion batteries due to their high capacity (>250 mAh g(-1)). However, their application in electric vehicles is hampered by low power density and poor cycle life. To address these, layered Li2Ru0.75Ti0.25O3 (LRTO) was synthesized and the influence of electroinactive Ti(4+) on the electrochemical performance of Li2RuO3 was investigated. LRTO exhibited a reversible capacity of 240 mAh g(-1) under 14.3 mA g(-1) with 0.11 mol of Li loss after 100 cycles compared to 0.22 mol of Li for Li2Ru0.75Sn0.25O3. More Li(+) can be extracted from LRTO (0.96 mol of Li) even after 250 cycles at 143 mA g(-1) than Li2RuO3 (0.79 mol of Li). High reversible Li extraction and long cycle life were attributed to structural stability of the LiM2 layer in the presence of Ti(4+), facilitating the lithium diffusion kinetics. The versatility of the Li2MO3 structure may initiate exploration of Ti-based Li-rich layered oxides for vehicular applications.

  10. Layered perovskite oxide Y0.8Ca0.2BaCoFeO5+δas a novel cathode material for intermediate-temperature solid oxide fuel cells

    Institute of Scientific and Technical Information of China (English)

    余良浩; 陈永红; 顾庆文; 田冬; 卢肖永; 孟广耀; 林彬

    2015-01-01

    A layered perovskite oxide Y0.8Ca0.2BaCoFeO5+δ(YCBCF) was synthesized as a novel cathode material for intermedi-ate-temperature solid oxide fuel cells (IT-SOFCs) by citric acid-nitrates self-propagating combustion method. The phase and micro-structure of YCBCF were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The aver-age thermal expansion coefficient (TEC) of YCBCF was 14.6×10–6 K–1, which was close to other materials of SOFC at the range of RT–1000 ºC. An open-circuit potential of 0.75 V and a maximum output power density of 426 mW/cm2 were obtained at 650 ºC in a Sm0.2Ce0.8O1.9 (SDC)-based anode-supported SOFC by using humidified (~3%H2O) hydrogen as fuel and static air as oxidant. The results indicated that the YCBCF was a promising cathode candidate for IT-SOFCs.

  11. Room temperature large-scale synthesis of layered frameworks as low-cost 4 V cathode materials for lithium ion batteries

    Science.gov (United States)

    Hameed, A. Shahul; Reddy, M. V.; Nagarathinam, M.; Runčevski, Tomče; Dinnebier, Robert E.; Adams, Stefan; Chowdari, B. V. R.; Vittal, Jagadese J.

    2015-11-01

    Li-ion batteries (LIBs) are considered as the best available technology to push forward the production of eco-friendly electric vehicles (EVs) and for the efficient utilization of renewable energy sources. Transformation from conventional vehicles to EVs are hindered by the high upfront price of the EVs and are mainly due to the high cost of LIBs. Hence, cost reduction of LIBs is one of the major strategies to bring forth the EVs to compete in the market with their gasoline counterparts. In our attempt to produce cheaper high-performance cathode materials for LIBs, an rGO/MOPOF (reduced graphene oxide/Metal-Organic Phosphate Open Framework) nanocomposite with ~4 V of operation has been developed by a cost effective room temperature synthesis that eliminates any expensive post-synthetic treatments at high temperature under Ar/Ar-H2. Firstly, an hydrated nanocomposite, rGO/K2[(VO)2(HPO4)2(C2O4)]·4.5H2O has been prepared by simple magnetic stirring at room temperature which releases water to form the anhydrous cathode material while drying at 90 °C during routine electrode fabrication procedure. The pristine MOPOF material undergoes highly reversible lithium storage, however with capacity fading. Enhanced lithium cycling has been witnessed with rGO/MOPOF nanocomposite which exhibits minimal capacity fading thanks to increased electronic conductivity and enhanced Li diffusivity.

  12. Room temperature large-scale synthesis of layered frameworks as low-cost 4 V cathode materials for lithium ion batteries.

    Science.gov (United States)

    Hameed, A Shahul; Reddy, M V; Nagarathinam, M; Runčevski, Tomče; Dinnebier, Robert E; Adams, Stefan; Chowdari, B V R; Vittal, Jagadese J

    2015-11-23

    Li-ion batteries (LIBs) are considered as the best available technology to push forward the production of eco-friendly electric vehicles (EVs) and for the efficient utilization of renewable energy sources. Transformation from conventional vehicles to EVs are hindered by the high upfront price of the EVs and are mainly due to the high cost of LIBs. Hence, cost reduction of LIBs is one of the major strategies to bring forth the EVs to compete in the market with their gasoline counterparts. In our attempt to produce cheaper high-performance cathode materials for LIBs, an rGO/MOPOF (reduced graphene oxide/Metal-Organic Phosphate Open Framework) nanocomposite with ~4 V of operation has been developed by a cost effective room temperature synthesis that eliminates any expensive post-synthetic treatments at high temperature under Ar/Ar-H2. Firstly, an hydrated nanocomposite, rGO/K2[(VO)2(HPO4)2(C2O4)]·4.5H2O has been prepared by simple magnetic stirring at room temperature which releases water to form the anhydrous cathode material while drying at 90 °C during routine electrode fabrication procedure. The pristine MOPOF material undergoes highly reversible lithium storage, however with capacity fading. Enhanced lithium cycling has been witnessed with rGO/MOPOF nanocomposite which exhibits minimal capacity fading thanks to increased electronic conductivity and enhanced Li diffusivity.

  13. Room temperature large-scale synthesis of layered frameworks as low-cost 4 V cathode materials for lithium ion batteries

    Science.gov (United States)

    Hameed, A. Shahul; Reddy, M. V.; Nagarathinam, M.; Runčevski, Tomče; Dinnebier, Robert E; Adams, Stefan; Chowdari, B. V. R.; Vittal, Jagadese J.

    2015-01-01

    Li-ion batteries (LIBs) are considered as the best available technology to push forward the production of eco-friendly electric vehicles (EVs) and for the efficient utilization of renewable energy sources. Transformation from conventional vehicles to EVs are hindered by the high upfront price of the EVs and are mainly due to the high cost of LIBs. Hence, cost reduction of LIBs is one of the major strategies to bring forth the EVs to compete in the market with their gasoline counterparts. In our attempt to produce cheaper high-performance cathode materials for LIBs, an rGO/MOPOF (reduced graphene oxide/Metal-Organic Phosphate Open Framework) nanocomposite with ~4 V of operation has been developed by a cost effective room temperature synthesis that eliminates any expensive post-synthetic treatments at high temperature under Ar/Ar-H2. Firstly, an hydrated nanocomposite, rGO/K2[(VO)2(HPO4)2(C2O4)]·4.5H2O has been prepared by simple magnetic stirring at room temperature which releases water to form the anhydrous cathode material while drying at 90 °C during routine electrode fabrication procedure. The pristine MOPOF material undergoes highly reversible lithium storage, however with capacity fading. Enhanced lithium cycling has been witnessed with rGO/MOPOF nanocomposite which exhibits minimal capacity fading thanks to increased electronic conductivity and enhanced Li diffusivity. PMID:26593096

  14. Air humidity and water pressure effects on the performance of air-cathode microbial fuel cell cathodes

    KAUST Repository

    Ahn, Yongtae

    2014-02-01

    To better understand how air cathode performance is affected by air humidification, microbial fuel cells were operated under different humidity conditions or water pressure conditions. Maximum power density decreased from 1130 ± 30 mW m-2 with dry air to 980 ± 80 mW m -2 with water-saturated air. When the cathode was exposed to higher water pressures by placing the cathode in a horizontal position, with the cathode oriented so it was on the reactor bottom, power was reduced for both with dry (1030 ± 130 mW m-2) and water-saturated (390 ± 190 mW m-2) air. Decreased performance was partly due to water flooding of the catalyst, which would hinder oxygen diffusion to the catalyst. However, drying used cathodes did not improve performance in electrochemical tests. Soaking the cathode in a weak acid solution, but not deionized water, mostly restored performance (960 ± 60 mW m-2), suggesting that there was salt precipitation in the cathode that was enhanced by higher relative humidity or water pressure. These results showed that cathode performance could be adversely affected by both flooding and the subsequent salt precipitation, and therefore control of air humidity and water pressure may need to be considered for long-term MFC operation. © 2013 Elsevier B.V. All rights reserved.

  15. Air humidity and water pressure effects on the performance of air-cathode microbial fuel cell cathodes

    Science.gov (United States)

    Ahn, Yongtae; Zhang, Fang; Logan, Bruce E.

    2014-02-01

    To better understand how air cathode performance is affected by air humidification, microbial fuel cells were operated under different humidity conditions or water pressure conditions. Maximum power density decreased from 1130 ± 30 mW m-2 with dry air to 980 ± 80 mW m-2 with water-saturated air. When the cathode was exposed to higher water pressures by placing the cathode in a horizontal position, with the cathode oriented so it was on the reactor bottom, power was reduced for both with dry (1030 ± 130 mW m-2) and water-saturated (390 ± 190 mW m-2) air. Decreased performance was partly due to water flooding of the catalyst, which would hinder oxygen diffusion to the catalyst. However, drying used cathodes did not improve performance in electrochemical tests. Soaking the cathode in a weak acid solution, but not deionized water, mostly restored performance (960 ± 60 mW m-2), suggesting that there was salt precipitation in the cathode that was enhanced by higher relative humidity or water pressure. These results showed that cathode performance could be adversely affected by both flooding and the subsequent salt precipitation, and therefore control of air humidity and water pressure may need to be considered for long-term MFC operation.

  16. Catalyst containing oxygen transport membrane

    Energy Technology Data Exchange (ETDEWEB)

    Lane, Jonathan A.; Wilson, Jamie R.; Christie, Gervase Maxwell; Petigny, Nathalie; Sarantopoulos, Christos

    2017-02-07

    A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a microstructure exhibiting substantially uniform pore size distribution as a result of using PMMA pore forming materials or a bi-modal particle size distribution of the porous support layer materials. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

  17. SSZ-52, a zeolite with an 18-layer aluminosilicate framework structure related to that of the DeNOx catalyst Cu-SSZ-13.

    Science.gov (United States)

    Xie, Dan; McCusker, Lynne B; Baerlocher, Christian; Zones, Stacey I; Wan, Wei; Zou, Xiaodong

    2013-07-17

    A new zeolite (SSZ-52, |(C14H28N)6Na6(H2O)18|[Al12Si96O216]), related to the DeNOx catalyst Cu-SSZ-13 (CHA framework type), has been synthesized using an unusual polycyclic quaternary ammonium cation as the structure-directing agent. By combining X-ray powder diffraction (XPD), high-resolution transmission electron microscopy (HRTEM) and molecular modeling techniques, its porous aluminosilicate framework structure (R3m, a = 13.6373(1) Å, c = 44.7311(4) Å), which can be viewed as an 18-layer stacking sequence of hexagonally arranged (Si,Al)6O6 rings (6-rings), has been elucidated. The structure has a three-dimensional 8-ring channel system and is a member of the ABC-6 family of zeolites (those that can be described in terms of 6-ring stacking sequences) like SSZ-13, but it has cavities that are twice as large. The code SFW has been assigned to this new framework type. The large cavities contain pairs of the bulky organic cations. HRTEM and XPD simulations show that stacking faults do occur, but only at the 5-10% level. SSZ-52 has considerable potential as a catalyst in the areas of gas conversion and sequestration.

  18. CO₂ electroreduction at bare and Cu-decorated Pd pseudomorphic layers: catalyst tuning by controlled and indirect supporting onto Au(111).

    Science.gov (United States)

    Januszewska, Aneta; Jurczakowski, Rafal; Kulesza, Pawel J

    2014-12-02

    We report here the results of electrochemical studies on CO2 electroreduction at multilayered catalyst composed of the monatomic layer of copper covering palladium overlayers (0.8-10 monolayers) deposited on the well-defined Au(111) surface. These multilayered systems were obtained by successive underpotential deposition steps: Pd on Au(111) as well as Cu on Pd/Au(111). Low index orientation of Au substrate was chosen to compare Pd overlayers with bulk Pd(111), which is known to reduce CO2 to CO adsorbates in acidic solutions. The process of CO2 electroreduction was studied by using classical transient electrochemical methods. Catalytic activity of bare Pd layers was investigated in acidic and neutral solutions. In the latter case, much higher activity of Pd overlayers was observed. The results showed that the palladium layer thickness significantly changed the catalytic activities of both bare Pd overlayers and the one Cu monolayer covered electrodes toward CO2 electroreduction. Results show that catalytic activity can be finely tuned by using the multilayered near-surface-alloy approach.

  19. Synthesis of Ni/Mg/Al Layered Double Hydroxides and Their Use as Catalyst Precursors in the Preparation of Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yun; JIAO Qing-ze; LIANG Ji; LI Chun-hua

    2005-01-01

    Ni/Mg/Al layered double hydroxides(LDHs) with different n(Ni):n(Mg):n(Al) ratio values were prepared via a coprecipitation reaction. Then Ni/Mg/Al mixed oxides were obtained by calcination of these LDHs precursors. Carbon nanotubes were produced in the catalytic decomposition of propane over the Ni/Mg/Al mixed oxide catalysts. The quality of as-made nanotubes was investigated by SEM and TEM. The nanotubes were multiwall with a high length-diameter ratio and appeared to be flexible. The catalytic activities of these mixed oxides increased with increasing the Ni content. The Ni/Mg/Al mixed oxide with the highest Ni content [n(Ni)/n(Mg)/n(Al)=1/1/1] showed the highest activity and the carbon nanotubes grown on its surface had the best quality.

  20. Power generation using an activated carbon and metal mesh cathode in a microbial fuel cell

    KAUST Repository

    Zhang, Fang

    2009-11-01

    An inexpensive activated carbon (AC) air cathode was developed as an alternative to a platinum-catalyzed electrode for oxygen reduction in a microbial fuel cell (MFC). AC was cold-pressed with a polytetrafluoroethylene (PTFE) binder to form the cathode around a Ni mesh current collector. This cathode construction avoided the need for carbon cloth or a metal catalyst, and produced a cathode with high activity for oxygen reduction at typical MFC current densities. Tests with the AC cathode produced a maximum power density of 1220 mW/m2 (normalized to cathode projected surface area; 36 W/m3 based on liquid volume) compared to 1060 mW/m2 obtained by Pt catalyzed carbon cloth cathode. The Coulombic efficiency ranged from 15% to 55%. These findings show that AC is a cost-effective material for achieving useful rates of oxygen reduction in air cathode MFCs. © 2009 Elsevier B.V. All rights reserved.

  1. Oxidation catalyst

    Science.gov (United States)

    Ceyer, Sylvia T.; Lahr, David L.

    2010-11-09

    The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

  2. Methanol-Tolerant Platinum-Palladium Catalyst Supported on Nitrogen-Doped Carbon Nanofiber for High Concentration Direct Methanol Fuel Cells

    Directory of Open Access Journals (Sweden)

    Jiyoung Kim

    2016-08-01

    Full Text Available Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC. The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR activities and the electrochemical double layer compared with common carbon black (CB. To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF–supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected.

  3. LOW TEMPERATURE CATHODE SUPPORTED ELECTROLYTES

    Energy Technology Data Exchange (ETDEWEB)

    Harlan U. Anderson; Fatih Dogan; Vladimir Petrovsky

    2002-03-31

    This project has three main goals: Thin Films Studies, Preparation of Graded Porous Substrates and Basic Electrical Characterization and testing of Planar Single Cells. This period has continued to address the problem of making dense 1/2 to 5 {micro}m thick dense layers on porous substrates (the cathode LSM). Our current status is that we are making structures of 2-5 cm{sup 2} in area, which consist of either dense YSZ or CGO infiltrated into a 2-5 {micro}m thick 50% porous layer made of either nanoncrystalline CGO or YSZ powder. This composite structure coats a macroporous cathode or anode; which serves as the structural element of the bi-layer structure. These structures are being tested as SOFC elements. A number of structures have been evaluated both as symmetrical and as button cell configuration. Results of this testing indicates that the cathodes contribute the most to cell losses for temperatures below 750 C. In this investigation different cathode materials were studied using impedance spectroscopy of symmetric cells and IV characteristics of anode supported fuel cells. Cathode materials studied included La{sub 0.8}Sr{sub 0.2}Co{sub 0.2}Fe{sub 0.8}O{sub 3} (LSCF), La{sub 0.7}Sr{sub 0.2}MnO{sub 3} (LSM), Pr{sub 0.8}Sr{sub 0.2}Fe{sub 0.8}O{sub 3} (PSCF), Sm{sub 0.8}Sr{sub 0.2}Co{sub 0.2}Fe{sub 0.8}O{sub 3} (SSCF), and Yb{sub .8}Sr{sub 0.2}Co{sub 0.2}Fe{sub 0.8}O{sub 3} (SSCF). A new technique for filtering the Fourier transform of impedance data was used to increase the sensitivity of impedance analysis. By creating a filter specifically for impedance spectroscopy the resolution was increased. The filter was tailored to look for specific circuit elements like R//C, Warburg, or constant phase elements. As many as four peaks can be resolved using the filtering technique on symmetric cells. It may be possible to relate the different peaks to material parameters, like the oxygen exchange coefficient. The cathode grouped in order from lowest to highest ASR is

  4. 微生物燃料电池MnO2/S-AC泡沫镍空气阴极的制备及其性能%Preparation and properties of nickel foam air cathode with MnO2/S-AC catalyst for microbial fuel cells

    Institute of Scientific and Technical Information of China (English)

    杨斯琦; 刘中良; 侯俊先; 周宇

    2015-01-01

    The kinetics of oxygen reduction of cathode catalyst is a critical factor that limits the performance of microbial fuel cells (MFCs). The composite catalyst of three composite proportion(1:3, 1:1 and 3:1), which were prepared by reacting KMnO4 with supercapacitor activated carbon (S-AC),were tested as air-cathode catalyst of microbial fuel cells (MFCs) for oxygen reduction. X-ray diffraction (XRD) was used to characterize the catalysts, energy dispersive X-Ray Spectroscopy to estimate the quality of MnO2, scanning electron microscopy (SEM) to observe the surface morphology, and BET method to examine surface area and pore distribution characteristics, to analyze the factors affecting the performance of the composite catalyst. With increasing of composite proportion, the MnO2 sheets gathered into nano-particles (300—500 nm) on the surface of S-AC. At the same time, there is the decrease of the internal and external surface area MnO2/S-AC. Nickel foam air-cathode was made with different catalysts, and tested in air-cathode MFCs to study the effect on MFC performance by linear sweep voltammetry (LSV), polarization curves and power density curve. When the feeding ratio of KMnO4: S-AC is 1:3,the maximum power density was 321.2 mW·m?2, which was increased by about 20% over the S-AC loading MFC. However, when the feeding ratio was increased to 1:1 and 3:1, the maximum power density decreased to 240.9 and 160.3 mW·m?2. MnO2/S-AC composite catalyst within a certain ratio range could effectively improve the performance of air-cathode and MFC, which helps to the expansion application of air-cathode MFC.%利用超级电容器活性炭(S-AC)直接还原KMnO4制备出复合比例分别为1:3、1:1和3:1的MnO2/S-AC复合催化剂,进而负载于泡沫镍上制得MnO2/S-AC泡沫镍空气阴极.通过X射线衍射(XRD)、扫描电镜(SEM)、能量散射X 射线谱(EDX)和比表面积(BET)及孔分布测试对所制复合催化剂表征可知,随复合比例

  5. One-pot Low-temperature Synthesis of Nitrogen-doped Graphene and It Application as Cathode Catalyst in Microbial Fuel Cells for Electricity Generation%氮掺杂石墨烯的一步法低温合成及用作微生物燃料电池阴极催化剂的产电特性

    Institute of Scientific and Technical Information of China (English)

    付融冰; 杨兰琴; 冯雷雨; 郭伟

    2014-01-01

    利用爆炸法低温合成了氮掺杂石墨烯(NG),并通过高分辨透射电子显微镜、 X射线光电子能谱仪、Raman光谱仪以及X射线衍射仪对其进行了表征.电化学性能检测结果表明,所合成的NG在中性磷酸盐电解液中具有优异的氧还原催化活性,完全能够与贵重金属铂催化剂( Pt/C)相媲美,氧还原催化稳定性甚至优于Pt/C.当NG用作微生物燃料电池( MFCs)的阴极氧还原催化剂时,在外阻为1000赘情况下, MFCs的最大功率密度为1345 mW/m2,产电稳定性优于以Pt/C为阴极催化剂的MFCs,可以成为Pt催化剂的理想替代品.%Nitrogen-doped graphene ( NG ) was synthesized by denotation process at low temperature, and characterized by high-resolution transmission electron microscopy( HRTEM) , X-ray photoelectron spectrometry ( XPS) , Raman spectrometry and X-ray diffraction( XRD) . Electrochemical examinations demonstrated that in the neutral phosphate electrolyte the synthesized NG had an excellent electrocatalytic activity for oxygen reduc-tion reaction( ORR) , comparable to that of platinum catalyst( Pt/C) , and its electrocatalytic stability was even better than Pt/C. When NG was used as cathode catalyst in single-chamber microbial fuel cells( MFCs) , the maximal power density at external resistance of 1000 was 1345 mW/m2 , and the stability of power genera-tion in MFCs even outperformed that with Pt/C as cathode catalyst, indicating that NG might be a perfect al-ternative to Pt catalyst in MFCs.

  6. Deactivation and poisoning of fuel cell catalysts

    Science.gov (United States)

    Ross, P. N., Jr.

    1985-06-01

    The deactivation and poisoning phenomena reviewed are: the poisoning of anode (fuel electrode) catalyst by carbon monoxide and hydrogen sulfide; the deactivation of the cathode (air electrode) catalyst by sintering; and the deactivation of the cathode by corrosion of the support. The anode catalyst is Pt supported on a conductive, high area carbon black, usually at a loading of 10 w/o. This catalyst is tolerant to some level of carbon monoxide or hydrogen sulfide or both in combination, the level depending on temperature and pressure. Much less is known about hydrogen sulfide poisoning. Typical tolerance levels are 2% CO, and 10 ppM H2S. The cathode catalyst is typically Pt supported on a raphitic carbon black, usually a furnace black heat-treated to 2700 C. The Pt loading is typically 10 w/o, and the dispersion (or percent exposed) as-prepared is typically 30%. The loss of dispersion in use depends on the operational parameters, most especially the cathode potential history, i.e., higher potentials cause more rapid decrease in dispersion. The mechanism of loss of dispersion is not well known. The graphitic carbon support corrodes at a finite rate that is also potential dependent. Support corrosion causes thickening of the electrolyte film between the gas pores and the catalyst particles, which in turn causes increased diffusional resistance and performance loss.

  7. Composition and growth behavior of the surface and electrolyte decomposition layer of/on a commercial lithium ion battery LixNi1/3Mn1/3Co1/3O2 cathode determined by sputter depth profile X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Niehoff, Philip; Winter, Martin

    2013-12-23

    A detailed X-ray photoelectron spectroscopy (XPS) study of the surface and electrolyte decomposition layer of a LixNi1/3Mn1/3Co1/3O2 (NMC) cathode from commercial NMC/graphite cells by intense sputter depth profiling (SDP) using a polyatomic ion gun is provided. Cathodes of a cell after electrochemical formation and a cell at a state of initial capacity (SOIC) of 80%, which was reached after 2500 full cycles at 30 °C, are investigated.

  8. Carbon-Based Air-Breathing Cathodes for Microbial Fuel Cells

    Directory of Open Access Journals (Sweden)

    Irene Merino-Jimenez

    2016-08-01

    Full Text Available A comparison between different carbon-based gas-diffusion air-breathing cathodes for microbial fuel cells (MFCs is presented in this work. A micro-porous layer (MPL based on carbon black (CB and an activated carbon (AC layer were used as catalysts and applied on different supporting materials, including carbon cloth (CC, carbon felt (CF, and stainless steel (SS forming cathode electrodes for MFCs treating urine. Rotating ring disk electrode (RRDE analyses were done on CB and AC to: (i understand the kinetics of the carbonaceous catalysts; (ii evaluate the hydrogen peroxide production; and (iii estimate the electron transfer. CB and AC were then used to fabricate electrodes. Half-cell electrochemical analysis, as well as MFCs continuous power performance, have been monitored. Generally, the current generated was higher from the MFCs with AC electrodes compared to the MPL electrodes, showing an increase between 34% and 61% in power with the AC layer comparing to the MPL. When the MPL was used, the supporting material showed a slight effect in the power performance, being that the CF is more powerful than the CC and the SS. These differences also agree with the electrochemical analysis performed. However, the different supporting materials showed a bigger effect in the power density when the AC layer was used, being the SS the most efficient, with a power generation of 65.6 mW·m−2, followed by the CC (54 mW·m−2 and the CF (44 mW·m−2.

  9. Synthesis and characterization of layered Li(Ni1/3Mn1/3Co1/3)O2 cathode materials by spray-drying method

    Institute of Scientific and Technical Information of China (English)

    LIU Zhi-min; HU Guo-rong; PENG Zhong-dong; DENG Xin-rong; LIU Ye-xiang

    2007-01-01

    Spherical Li(Ni1/3Mn1/3Co1/3)O2 was prepared via the homogenous precursors produced by solution spray-drying method. The precursors were sintered at different temperatures between 600 and 1 000 ℃ for 10 h. The impacts of different sintering temperatures on the structure and electrochemical performances of Li(Ni1/3Mn1/3Co1/3)O2 were compared by means of X-ray diffractometry(XRD), scanning electron microscopy(SEM), and charge/discharge test as cathode materials for lithium ion batteries. The experimental results show that the spherical morphology of the spray-dried powers maintains during the subsequent heat treatment and the specific capacity increases with rising sintering temperature. When the sintering temperature rises up to 900 ℃, Li(Ni1/3Mn1/3Co1/3)O2 attains a reversible capacity of 153 mA·h/g between 3.00 and 4.35 V at 0.2C rate with excellent cyclability.

  10. Designing nanobowl arrays of mesoporous TiO₂ as an alternative electron transporting layer for carbon cathode-based perovskite solar cells.

    Science.gov (United States)

    Zheng, Xiaoli; Wei, Zhanhua; Chen, Haining; Zhang, Qianpeng; He, Hexiang; Xiao, Shuang; Fan, Zhiyong; Wong, Kam Sing; Yang, Shihe

    2016-03-28

    In this work, we have designed a mesoporous TiO2 nanobowl (NB) array with pore size, bowl size and film thickness being easily controllable by the sol-gel process and the polystyrene (PS) template diameter. Based on the TiO2 NB array, we fabricated carbon cathode based perovskite solar cells (C-PSCs) to investigate the impact of TiO2 NB nanostructures on the performance of the as-obtained C-PSCs devices. As expected, the TiO2 NB based devices show a higher power conversion efficiency (PCE) than that of the planar counterpart, mainly due to the enhanced light absorption arising from the NB-assisted light management, the improved pore-filling of high quality perovskite crystals and the increased interface contact for rapid electron extraction and fast charge transport. Leveraging these advantages of the novel TiO2 NB film, the 220 nm-PS templated TiO2 NB based devices performed the best on both light absorption capability and charge extraction, and achieved a PCE up to 12.02% with good stability, which is 37% higher than that of the planar counterpart. These results point to a viable and convenient route toward the fabrication of TiO2 ETL nanostructures for high performance PSCs.

  11. Fuel cell development for transportation: Catalyst development

    Energy Technology Data Exchange (ETDEWEB)

    Doddapaneni, N. [Sandia National Lab., Albuquerque, NM (United States)

    1996-04-01

    Fuel cells are being considered as alternate power sources for transportation and stationary applications. With proton exchange membrane (PEM) fuel cells the fuel crossover to cathodes causes severe thermal management and cell voltage drop due to oxidation of fuel at the platinized cathodes. The main goal of this project was to design, synthesize, and evaluate stable and inexpensive transition metal macrocyclic catalysts for the reduction of oxygen and be electrochemically inert towards anode fuels such as hydrogen and methanol.

  12. Direct charge carrier injection into Ga2O3 thin films using an In2O3 cathode buffer layer: their optical, electrical and surface state properties

    Science.gov (United States)

    Cui, W.; Zhao, X. L.; An, Y. H.; Guo, D. Y.; Qing, X. Y.; Wu, Z. P.; Li, P. G.; Li, L. H.; Cui, C.; Tang, W. H.

    2017-04-01

    Conductive Ga2O3 thin films with an In2O3 buffer layer have been prepared on c-plane sapphire substrates using a laser molecular beam epitaxy technique. The effects of the In2O3 buffer layer on the structure and optical, electrical and surface state properties of the Ga2O3 films have been studied. The change in conductivity of the thin films is attributed to different thicknesses of the In2O3 buffer layer, which determine the concentration of charge carriers injected into the upper Ga2O3 layer from the interface of the bilayer thin films. In addition, the increase in flat band voltage shift and capacitance values as the In2O3 buffer layer thickens are attributed to the increase in surface state density, which also contributes to the rapid shrinkage of the optical band gap of the Ga2O3. With transparency to visible light, high n-type conduction and the ability to tune the optical band gap and surface state density, we propose that Ga2O3/In2O3 bilayer thin film is an ideal n-type semiconductor for fabrication of transparent power devices, solar cell electrodes and gas sensors.

  13. Development of cathode material for lithium-ion batteries

    Directory of Open Access Journals (Sweden)

    Rustam Mukhtaruly Turganaly

    2014-08-01

    Full Text Available The electrochemical characteristics of the cathode material coated with carbon layer has been developed. Various carbon coating methods. There  has been carried out a comparative electrochemical analysis of the coated and uncoated with carbon cathode material. 

  14. DOE Award No. DE-FC36-03GO13108 NOVEL NON-PRECIOUS METAL CATALYSTS FOR PEMFC: CATALYST SELECTION THROUGH MOLECULAR MODELING AND DURABILITY STUDIES Final Report (September 2003 – October 2008)

    Energy Technology Data Exchange (ETDEWEB)

    Branko N. Popov

    2009-02-20

    catalytic activity and selectivity for ORR as the Pt catalyst. A theoretical analysis is made of the four-electron reduction reaction of oxygen to water over the mixed anion and cation (202) surface of pentlandite structure Co9Se8, one of several selenide phases. Reversible potentials for forming adsorbed reaction intermediates in acid are predicted using adsorption energies calculated with the Vienna ab initio simulation program (VASP) and the known bulk solution values together in a linear Gibbs energy relationship. The effect of hydrophobic and structural properties of a single/dual-layer cathode gas diffusion layer on mass transport in PEM fuel cells was studied using an analytical expression. The simulations indicated that liquid water transport at the cathode is controlled by the fraction of hydrophilic surface and the average pore diameter in the cathode gas diffusion layer. The optimized hydrophobicity and pore geometry in a dual-layer cathode GDL leads to an effective water management, and enhances the oxygen diffusion kinetics.

  15. DOE Award No. DE-FC36-03GO13108 NOVEL NON-PRECIOUS METAL CATALYSTS FOR PEMFC: CATALYST SELECTION THROUGH MOLECULAR MODELING AND DURABILITY STUDIES Final Report (September 2003 – October 2008)

    Energy Technology Data Exchange (ETDEWEB)

    Branko N. Popov

    2009-03-03

    catalytic activity and selectivity for ORR as the Pt catalyst. A theoretical analysis is made of the four-electron reduction reaction of oxygen to water over the mixed anion and cation (202) surface of pentlandite structure Co9Se8, one of several selenide phases. Reversible potentials for forming adsorbed reaction intermediates in acid are predicted using adsorption energies calculated with the Vienna ab initio simulation program (VASP) and the known bulk solution values together in a linear Gibbs energy relationship. The effect of hydrophobic and structural properties of a single/dual-layer cathode gas diffusion layer on mass transport in PEM fuel cells was studied using an analytical expression. The simulations indicated that liquid water transport at the cathode is controlled by the fraction of hydrophilic surface and the average pore diameter in the cathode gas diffusion layer. The optimized hydrophobicity and pore geometry in a dual-layer cathode GDL leads to an effective water management, and enhances the oxygen diffusion kinetics.

  16. Influence of Drying Temperature on the Structural, Optical, and Electrical Properties of Layer-by-Layer ZnO Nanoparticles Seeded Catalyst

    Directory of Open Access Journals (Sweden)

    S. S. Shariffudin

    2012-01-01

    Full Text Available Layer-by-layer zinc oxide (ZnO nanoparticles have been prepared using sol-gel spin coating technique. The films were dried at different temperature from 100°C to 300°C to study its effect to the surface morphology, optical and electrical properties of the films. Film dried at 200°C shows the highest (0 0 2 peak of X-ray diffraction pattern which is due to complete decomposition of zinc acetate and complete vaporization of the stabilizer and solvent. It was found that the grain size increased with the increased of drying temperature from 100 to 200°C, but for films dried at above 200°C, the grain size decreased. Photoluminescence measurements show a sharp ultraviolet emission centred at 380 nm and a very low intensity visible emission. Blue visible emission was detected for sample dried at temperature below 200°C, while for films dried above 250°C, the visible emission is red shifted. The films were transparent in the visible range from 400 to 800 nm with average transmittance of above 85%. Linear I-V characteristics were shown confirming the ohmic behaviour of the gold contacts to the films. A minimum resistivity was given by 5.08 Ω · cm for the film dried at 300°C.

  17. Catalyst and electrode research for phosphoric acid fuel cells

    Science.gov (United States)

    Antoine, A. C.; King, R. B.

    1987-01-01

    An account is given of the development status of phosphoric acid fuel cells' high performance catalyst and electrode materials. Binary alloys have been identified which outperform the baseline platinum catalyst; it has also become apparent that pressurized operation is required to reach the desired efficiencies, calling in turn for the use of graphitized carbon blacks in the role of catalyst supports. Efforts to improve cell performance and reduce catalyst costs have led to the investigation of a class of organometallic cathode catalysts represented by the tetraazaannulenes, and a mixed catalyst which is a mixture of carbons catalyzed with an organometallic and a noble metal.

  18. Planar-Focusing Cathodes

    CERN Document Server

    Lewellen, J W

    2005-01-01

    Conventional pi-mode rf photoinjectors typically use magnetic solenoids for emittance compensation. This provides independent focusing strength, but can complicate rf power feed placement, introduce asymmetries (due to coil crossovers), and greatly increase the cost of the photoinjector. Cathode-region focusing can also provide for a form of emittance compensation. Typically this method strongly couples focusing strength to the field gradient on the cathode, however, and also requires altering the longitudinal position of the cathode to change the focusing. We propose a new method for achieving cathode-region variable-strength focusing for emittance compensation. The new method reduces the coupling to the gradient on the cathode, and does not require a change in the longitudinal position of the cathode. Expected performance for an S-band system is similar to conventional solenoid-based designs. This paper presents the results of rf cavity and beam dynamics simulations of the new design.

  19. Cathode encapsulation of OLEDs by atomic layer deposited Al2O3 films and Al2O3/a-SiNx:H stacks

    NARCIS (Netherlands)

    Keuning, W.; Van de Weijer, P.; Lifka, H.; Kessels, W.M.M.; Creatore, M.

    2011-01-01

    Al2O3 thin films synthesized by plasma-enhanced atomic layer deposition(ALD) at room temperature (25 ºC) have been tested as water vapor per-meation barriers for OLED devices. Silicon nitride films (a-SiNx:H)deposited by plasma-enhanced chemical vapor deposition (PE-CVD) servedas reference and were

  20. CeO2 nanocubes-graphene oxide as durable and highly active catalyst support for proton exchange membrane fuel cell.

    Science.gov (United States)

    Lei, M; Wang, Z B; Li, J S; Tang, H L; Liu, W J; Wang, Y G

    2014-12-10

    Rapid degradation of cell performance still remains a significant challenge for proton exchange membrane fuel cell (PEMFC). In this work, we develop novel CeO2 nanocubes-graphene oxide nanocomposites as durable and highly active catalyst support for proton exchange membrane fuel cell. We show that the use of CeO2 as the radical scavenger in the catalysts remarkably improves the durability of the catalyst. The catalytic activity retention of Pt-graphene oxide-8 wt.% CeO2 nanocomposites reaches as high as 69% after 5000 CV-cycles at a high voltage range of 0.8-1.23 V, in contrast to 19% for that of the Pt-graphene oxide composites. The excellent durability of the Pt-CeO2 nanocubes-graphene oxide catalyst is attributed to the free radical scavenging activity of CeO2, which significantly slows down the chemical degradation of Nafion binder in catalytic layers, and then alleviates the decay of Pt catalysts, resulting in the excellent cycle life of Pt-CeO2-graphene oxide nanocomposite catalysts. Additionally, the performance of single cell assembled with Nafion 211 membrane and Pt-CeO2-graphene oxide catalysts with different CeO2 contents in the cathode as well as the Pt-C catalysts in the anode are also recorded and discussed in this study.

  1. Microscopic Investigations into the Effect of Surface Treatment of Cathode and Electron Transport Layer on the Performance of Inverted Organic Solar Cells.

    Science.gov (United States)

    Gupta, Shailendra Kumar; Jindal, Rajeev; Garg, Ashish

    2015-08-05

    Surface treatments of various layers in organic solar cells play a vital role in determining device characteristics. In this manuscript, we report on the influence of surface treatment of indium tin oxide (ITO) electrode and electron transport layer (ETL), ZnO, on the photovoltaic performance of inverted organic solar cells (IOSC) and their correlation with the surface chemistry and surface potential as studied using X-ray photoelectron spectroscopy (XPS) and Kelvin probe force microscopy (KPFM), using the device structure glass/ITO/ZnO/P3HT: PCBM/MoO3/(Au or Ag) (P3HT, poly(3-hexylthiophene-2,5-diyl), and PCBM, phenyl-C61-butyric acid methyl ester). Our results show that although ozonization of ITO leads to an improvement in the device power conversion efficiency, the ozonization of a subsequent ZnO layer results in a decreased performance mainly because of a decrease in the fill factor (FF). However, subsequent methanol (CH3OH) treatment of ZnO layer on an ozonized ITO electrode shows substantial improvement with device efficiencies exceeding ∼4% along with superior reproducibility of the devices. Furthermore, a detailed analysis of the surface wettability, chemistry, and surface potential using contact angle measurements, XPS, and KPFM attribute the improvements to the elimination of surface defects and the changes in the surface potential. Finally, impedance analysis suggests that methanol treatment of the ZnO layers leads to the development of a favorable nanophase structure with higher conductivity, which is otherwise indiscernible using microscopic methods.

  2. Cathodic Protection Model Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Performs Navy design and engineering of ship and submarine impressed current cathodic protection (ICCP) systems for underwater hull corrosion control and...

  3. Effect of cathode gas humidification on performance and durability of Solid Oxide Fuel Cells

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Hagen, Anke; Liu, Yi-Lin

    2010-01-01

    The effect of cathode inlet gas humidification was studied on single anode supported Solid Oxide Fuel Cells (SOFC's). The studied cells were Risø 2 G and 2.5 G. The former consists of a LSM:YSZ composite cathode, while the latter consists of a LSCF:CGO composite cathode on a CGO protection layer...

  4. Highly stable Na2/3 (Mn0.54 Ni0.13 Co0.13 )O2 cathode modified by atomic layer deposition for sodium-ion batteries.

    Science.gov (United States)

    Kaliyappan, Karthikeyan; Liu, Jian; Lushington, Andrew; Li, Ruying; Sun, Xueliang

    2015-08-10

    For the first time, atomic layer deposition (ALD) of Al2 O3 was adopted to enhance the cyclic stability of layered P2-type Na2/3 (Mn0.54 Ni0.13 Co0.13 )O2 (MNC) cathodes for use in sodium-ion batteries (SIBs). Discharge capacities of approximately 120, 123, 113, and 105 mA h g(-1) were obtained for the pristine electrode and electrodes coated with 2, 5, and 10 ALD cycles, respectively. All electrodes were cycled at the 1C discharge current rate for voltages between 2 and 4.5 V in 1 M NaClO4 electrolyte. Among the electrodes tested, the Al2 O3 coating from 2 ALD cycles (MNC-2) exhibited the best electrochemical stability and rate capability, whereas the electrode coated by 10 ALD cycles (MNC-10) displayed the highest columbic efficiency (CE), which exceeded 97 % after 100 cycles. The enhanced electrochemical stability observed for ALD-coated electrodes could be a result of the protection effects and high band-gap energy (Eg =9.00 eV) of the Al2 O3 coating layer. Additionally, the metal-oxide coating provides structural stability against mechanical stresses occurring during the cycling process. The capacity, cyclic stability, and rate performance achieved for the MNC electrode coated with 2 ALD cycles of Al2 O3 reveal the best results for SIBs. This study provides a promising route toward increasing the stability and CE of electrode materials for SIB application.

  5. Photocatalytic hydrogen production on SOLECTRO {sup registered} titanium dioxide layers. Development and characterization of an efficient catalyst; Photokatalytische Wasserstoffgewinnung an SOLECTRO {sup registered} -Titandioxidschichten. Entwicklung und Charakterisierung eines geeigneten Katalysators

    Energy Technology Data Exchange (ETDEWEB)

    Saborowski, Sarah

    2010-03-03

    A catalyst for photocatalytic hydrogen production from methanol and water was developed on the basis of SOLECTRO {sup registered} titanium dioxide layers. A test facility was constructed in which several modified catalysts could be tested for this reaction. Detailed characterization of the electronic and optical characteristics of these catalysts made it possible to gain deeper insight into the processes involved in the reaction. (orig.) [German] Auf Basis der SOLECTRO {sup registered} -TiO{sub 2} -Schichten wurde ein Katalysator fuer die photokatalytische Wasserstoffdarstellung aus Methanol und Wasser entwickelt. Der Aufbau einer geeigneten Versuchsanlage ermoeglichte es, verschieden modifizierte Katalysatoren fuer diese Reaktion zu testen. Durch die ausfuehrliche Charakterisierung insbesondere der elektronischen und optischen Eigenschaften dieser Katalysatoren konnten vertiefende Erkenntnisse zu den waehrend der Reaktion ablaufenden Prozessen gewonnen werden. (orig.)

  6. Gold Nanoparticles Supported on a Layered Double Hydroxide as Efficient Catalysts for the One-Pot Synthesis of Flavones.

    Science.gov (United States)

    Yatabe, Takafumi; Jin, Xiongjie; Yamaguchi, Kazuya; Mizuno, Noritaka

    2015-11-02

    Flavones are a class of natural products with diverse biological activities and have frequently been synthesized by step-by-step procedures using stoichiometric amounts of reagents. Herein, a catalytic one-pot procedure for the synthesis of flavone and its derivatives is developed. In the presence of gold nanoparticles supported on a Mg-Al layered double hydroxide (Au/LDH), various kinds of flavones can be synthesized starting from 2'-hydroxyacetophenones and benzaldehydes (or benzyl alcohols). The present one-pot procedure consists of a sequence of several reactions, and Au/LDH can catalyze all these different types of reactions. The catalysis is shown to be truly heterogeneous, and Au/LDH can be readily recovered and reused.

  7. Effect of cathode model on arc attachment for short high-intensity arc on a refractory cathode

    Science.gov (United States)

    Javidi Shirvan, Alireza; Choquet, Isabelle; Nilsson, Håkan

    2016-12-01

    Various models coupling the refractory cathode, the cathode sheath and the arc at atmospheric pressure exist. They assume a homogeneous cathode with a uniform physical state, and differ by the cathode layer and the plasma arc model. However even the most advanced of these models still fail in predicting the extent of the arc attachment when applied to short high-intensity arcs such as gas tungsten arcs. Cathodes operating in these conditions present a non-uniform physical state. A model taking into account the first level of this non-homogeneity is proposed based on physical criteria. Calculations are done for 5 mm argon arcs with a thoriated tungsten cathode. The results obtained show that radiative heating and cooling of the cathode surface are of the same order. They also show that cathode inhomogeneity has a significant effect on the arc attachment, the arc temperature and pressure. When changing the arc current (100 A, 200 A) the proposed model allows predicting trends observed experimentally that cannot be captured by the homogeneous cathode model unless restricting a priori the size of the arc attachment. The cathode physics is thus an important element to include to obtain a comprehensive and predictive arc model.

  8. Cationic fluorinated polymer binders for microbial fuel cell cathodes

    KAUST Repository

    Chen, Guang

    2012-01-01

    Fluorinated quaternary ammonium-containing polymers were used as catalyst binders in microbial fuel cell (MFC) cathodes. The performance of the cathodes was examined and compared to NAFION ® and other sulfonated aromatic cathode catalyst binders using linear sweep voltammetry (LSV), impedance spectroscopy, and performance tests in single chamber air-cathode MFCs. The cathodes with quaternary ammonium functionalized fluorinated poly(arylene ether) (Q-FPAE) binders showed similar current density and charge transfer resistance (R ct) to cathodes with NAFION ® binders. Cathodes containing either of these fluorinated binders exhibited better electrochemical responses than cathodes with sulfonated or quaternary ammonium-functionalized RADEL ® poly(sulfone) (S-Radel or Q-Radel) binders. After 19 cycles (19 d), the power densities of all the MFCs declined compared to the initial cycles due to biofouling at the cathode. MFC cathodes with fluorinated polymer binders (1445 mW m -2, Q-FPAE-1.4-H; 1397 mW m -2, Q-FPAE-1.4-Cl; 1277 mW m -2, NAFION ®; and 1256 mW m -2, Q-FPAE-1.0-Cl) had better performance than those with non-fluorinated polymer binders (880 mW m -2, S-Radel; 670 mW m -2, Q-Radel). There was a 15% increase in the power density using the Q-FPAE binder with a 40% higher ion exchange capacity (Q-FPAE-1.4-H compared to Q-FPAE-1.0-Cl) after 19 cycles of operation, but there was no effect on the power production due to counter ions in the binder (Cl -vs. HCO 3 -). The highest-performance cathodes (NAFION ® and Q-FPAE binders) had the lowest charge transfer resistances (R ct) in fresh and in fouled cathodes despite the presence of thick biofilms on the surface of the electrodes. These results show that fluorinated binders may decrease the penetration of the biofilm and associated biopolymers into the cathode structure, which helps to combat MFC performance loss over time. © 2012 The Royal Society of Chemistry.

  9. Graphene-oxide-supported CuAl and CoAl layered double hydroxides as enhanced catalysts for carbon-carbon coupling via Ullmann reaction

    Science.gov (United States)

    Ahmed, Nesreen S.; Menzel, Robert; Wang, Yifan; Garcia-Gallastegui, Ainara; Bawaked, Salem M.; Obaid, Abdullah Y.; Basahel, Sulaiman N.; Mokhtar, Mohamed

    2017-02-01

    Two efficient catalyst based on CuAl and CoAl layered double hydroxides (LDHs) supported on graphene oxide (GO) for the carbon-carbon coupling (Classic Ullmann Homocoupling Reaction) are reported. The pure and hybrid materials were synthesised by direct precipitation of the LDH nanoparticles onto GO, followed by a chemical, structural and physical characterisation by electron microscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), surface area measurements and X-ray photoelectron spectroscopy (XPS). The GO-supported and unsupported CuAl-LDH and CoAl-LDH hybrids were tested over the Classic Ullman Homocoupling Reaction of iodobenzene. In the current study CuAl- and CoAl-LDHs have shown excellent yields (91% and 98%, respectively) at very short reaction times (25 min). GO provides a light-weight, charge complementary and two-dimensional material that interacts effectively with the 2D LDHs, in turn enhancing the stability of LDH. After 5 re-use cycles, the catalytic activity of the LDH/GO hybrid is up to 2 times higher than for the unsupported LDH.

  10. Preservation of Fe complexes into layered double hydroxides improves the efficiency and the chemical stability of Fe complexes used as heterogeneous photo-Fenton catalysts

    Science.gov (United States)

    Huang, Zhujian; Wu, Pingxiao; Gong, Beini; Lu, Yonghong; Zhu, Nengwu; Hu, Zhixian

    2013-12-01

    Fe complexes ([Fe(Ox)3]3- and [Fe(Cit)2]3-) have been heterogenized through preservation into MgAl-layered double hydroxides (LDHs). The SEM images and N2 adsorption-desorption isotherm showed that the obtained products were mesoporous materials and the specific surface area of LDHs/Fe-complex composites were obviously greater than pristine LDHs, which is beneficial for the adsorption of organic pollutants. Measurement of adsorptive and heterogeneous photo-Fenton degradation of methylene blue (MB) suggested that the LDHs/Fe-complex composites had an excellent adsorption capacity at different pHs and the adsorption isotherm modeled well with the Langmuir equation. The enhancement of adsorption capacity may be attributed to the external hydroxyl groups of LDHs. MB was enriched on the surface of LDHs/Fe-complex composites, which favors MB degradation in situ. The obtained composites displayed an high photocatalytic activity in a pH range from 4.0 to 6.0 with dissolved Fe cation at a low concentration. Therefore, Fe complexes intercalated into LDHs can be an effective heterogeneous Fenton catalyst for oxidation of organic pollutants in a relatively wide pH range.

  11. Stepwise mechanism and H2O-assisted hydrolysis in atomic layer deposition of SiO2 without a catalyst.

    Science.gov (United States)

    Fang, Guo-Yong; Xu, Li-Na; Wang, Lai-Guo; Cao, Yan-Qiang; Wu, Di; Li, Ai-Dong

    2015-01-01

    Atomic layer deposition (ALD) is a powerful deposition technique for constructing uniform, conformal, and ultrathin films in microelectronics, photovoltaics, catalysis, energy storage, and conversion. The possible pathways for silicon dioxide (SiO2) ALD using silicon tetrachloride (SiCl4) and water (H2O) without a catalyst have been investigated by means of density functional theory calculations. The results show that the SiCl4 half-reaction is a rate-determining step of SiO2 ALD. It may proceed through a stepwise pathway, first forming a Si-O bond and then breaking Si-Cl/O-H bonds and forming a H-Cl bond. The H2O half-reaction may undergo hydrolysis and condensation processes, which are similar to conventional SiO2 chemical vapor deposition (CVD). In the H2O half-reaction, there are massive H2O molecules adsorbed on the surface, which can result in H2O-assisted hydrolysis of the Cl-terminated surface and accelerate the H2O half-reaction. These findings may be used to improve methods for the preparation of SiO2 ALD and H2O-based ALD of other oxides, such as Al2O3, TiO2, ZrO2, and HfO2.

  12. Stannum doping of layered LiNi 3/8Co 2/8Mn 3/8O 2 cathode materials with high rate capability for Li-ion batteries

    Science.gov (United States)

    Li, Jiangang; He, Xiangming; Zhao, Rusong; Wan, Chunrong; Jiang, Changyin; Xia, Dingguo; Zhang, Shichao

    Sn doped lithium nickel cobalt manganese composite oxide of LiNi 3/8Co 2/8Mn 3/8- xSn xO 2 (0 ≤ x ≤ 0.10) was synthesized by stannum substitute of manganese to enhance its rate capability at first time. Its structure and electrochemical properties were characterized by X-ray diffraction (XRD), SEM, cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) and charge/discharge tests. LiNi 3/8Co 2/8Mn 3/8- xSn xO 2 had stable layered structure with α-NaFeO 2 type as x up to 0.05, meanwhile, its chemical diffusion coefficient D Li of Li-ion was enhanced by almost one order of magnitude, leading to notable improvement of the rate capability of LiNi 3/8Co 2/8Mn 3/8O 2. The compound of x = 0.10 showed the best rate capability among Sn doped samples, but its discharge capacity reduced markedly due to secondary phase Li 2SnO 3 and increase of cation-disorder. The compound with x = 0.05 showed high rate capability with initial discharge capacity in excess of 156 mAh g -1. It is a promising alternative cathode material for EV application of Li-ion batteries.

  13. Effect of cooling method on the electrochemical performance of layered-spinel composite cathode Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3}

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yunjian [School of Material Science and Technology, Jiangsu University, Zhenjiang 212013 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Wang, Qiliang; Gao, Yanyong [School of Material Science and Technology, Jiangsu University, Zhenjiang 212013 (China); Pan, Jun [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Su, Mingru, E-mail: lyjian122331@163.com [School of Material Science and Technology, Jiangsu University, Zhenjiang 212013 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Hai, Bin; Zhu, Guangyan; Liu, Sanbing [Chery Science Research Institute, Chery Automobile Co., Ltd, Wuhu 241006 (China)

    2015-10-15

    Layered-spinel composite cathode material Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3} has been synthesized and cooled by different methods (naturally cooled within the furnace and cooled in liquid nitrogen). The effect of cooling methods on physical and electrochemical properties are discussed using the characterizations of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), charge/discharge, cyclic and rate tests. The layered-spinel composite structure has been detected in Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3} electrodes from the XRD patterns and TEM images. XPS results show that the content of Mn{sup 3+} in the Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3} cooled in liquid nitrogen is more than that of Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3} cooled with furnace. The electrochemical performance results show that the Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3} cooled in liquid nitrogen has higher initial discharge capacity, coulomb efficiency, better cyclic and rate performance compared with Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3} cooled with furnace. EIS results show that the charge transfer resistance (R{sub ct}) of Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3} cooled in liquid nitrogen is lower than that of Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3} cooled with furnace. The improved cyclic and rate performances of Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3} cooled in liquid nitrogen cathode are attributed to the lower R{sub ct} and more content of Mn{sup 3+}. - Graphical abstract: Layered-spinel composite cathode material Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.3} have been synthesized and cooled by different methods (naturally cooled within the furnace (‘a’) and cooled in liquid nitrogen (‘b’)). Compared with cooled with furnace (‘a’), the Li{sub 1.1}Ni{sub 0.25}Mn{sub 0.75}O{sub 2

  14. Electro-catalysts for hydrogen production from ethanol for use in SOFC anodes

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Marcos Aurelio da; Paz Fiuza, Raigenis da; Guedes, Bruna C.; Pontes, Luiz A.; Boaventura, Jaime Soares [UFBA, Salvador, Bahia (Brazil). Energy and Materials Science Group

    2010-07-01

    Nickel and cobalt catalysts, supported on YSZ, were prepared by wet impregnation, with and without citric acid; the metal load was 10 and 35% by weight. The catalyst composition was studied by XRF, XPS and SEM-EDS. At low metal concentration, the results of these techniques presented comparables figures; at high concentration, SEM-EDS suggested a non-uniform distribution. The analysis showed that the solids were mixed oxides and formed an alloy after reduction. The surface passivation was possible under controlled conditions. The catalytic test with the steam reforming of ethanol indicated that the metal load had almost no effect on the catalytic activity, but decreased its selectivity. Afterwards, a unitary SOFC was prepared with deposition of the cathode layer. AFM and EIS were used for the characterization of SOFC components. They showed that the electro-catalyst surface was almost all covered with the metal phase, including the large pore walls of the anode. The YSZ phase dominates the material conductance of the complete SOFC assembly (anode/electrolyte/cathode). The unitary SOFC was tested with hydrogen, gaseous ethanol or natural gas; the SOFC operating with ethanol and hydrogen fuel presented virtually no over-potential. (orig.)

  15. Synthesis and characterization of multi-layer core-shell structural LiFeBO3/C as a novel Li-battery cathode material

    Science.gov (United States)

    Zhang, Bao; Ming, Lei; Zheng, Jun-chao; Zhang, Jia-feng; Shen, Chao; Han, Ya-dong; Wang, Jian-long; Qin, Shan-e.

    2014-09-01

    A multi-layer core-shell structural LiFeBO3/C has been successfully synthesized via spray-drying and carbothermal method using LiBO2·8H2O, Fe(NO3)3·9H2O, and citric acid as starting materials. The Rietveld refinement results indicate the sample consists of two phases: LiFeBO3 [94(6)% w/w], and LiFeO2 [6(4)% w/w]. SEM images show that the LiFeBO3 powders consist of rough similar-spherical particles with a size distribution ranging from 1 μm to 5 μm. TEM results present that the LiFeBO3 spherical particles are well coated by nano-carbon webs and form a multi-layer core-shell structure. The amount of carbon was determined to be 6.50% by C/S analysis. The prepared LiFeBO3-LiFeO2/C presents an initial discharge capacity of 196.5 mAh g-1 at the current density of 10 mA g-1 between 1.5 and 4.5 V, and it can deliver a discharge capacity of 136.1 mAh g-1 after 30 cycles, presents excellent electrochemical properties, indicating the surface sensitivity in the air was restrained.

  16. Interaction between Nafion ionomer and noble metal catalyst for PEMFCs

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma

    The implement of polymer impregnation in electrode structure (catalyst layer) decreasing the noble metal catalyst loading by a factor of ten , , is one of the essential mile stones in the evolution of Proton Exchange Membrane Fuel Cells’ development among the application of catalyst support...... and electrode deposition etc. In fuel cell reactions, both electrons and protons are involved. Impregnation of Nafion ionomer in catalyst layer effectively increases the proton-electron contact, enlarge the reaction zone, extend the reaction from the surface to the entire electrode. Therefore, the entire...... catalyst layer conducts both electrons and protons so that catalyst utilization in the layer is improved dramatically. The catalyst layer will in turn generate and sustain a higher current density. One of the generally adapted methods to impregnate Nafion into the catalyst layer is to mix the catalysts...

  17. The double sheath on cathodes of discharges burning in cathode vapour

    Energy Technology Data Exchange (ETDEWEB)

    Benilov, M S; Benilova, L G [Departamento de Fisica, Universidade da Madeira, Largo do MunicIpio, 9000 Funchal (Portugal)

    2010-09-01

    The model of a collisionless near-cathode space-charge sheath with ionization of atoms emitted by the cathode surface is considered. Numerical calculations showed that the mathematical problem is solvable and its solution is unique. In the framework of this model, the sheath represents a double layer with a potential maximum, with the ions which are produced before the maximum returning to the cathode surface and those produced after the maximum escaping into the plasma. Numerical results are given in a form to be readily applicable in analysis of discharges burning in cathode vapour, such as vacuum arcs. In particular, the results indicate that the ion backflow coefficient in such discharges exceeds 0.5, in agreement with values extracted from the experiment.

  18. Efficient plasma-enhanced method for layered LiNi1/3Co1/3Mn1/3O2 cathodes with sulfur atom-scale modification for superior-performance Li-ion batteries.

    Science.gov (United States)

    Jiang, Qianqian; Chen, Ning; Liu, Dongdong; Wang, Shuangyin; Zhang, Han

    2016-06-01

    In order to improve the electrochemical performance of LiNi1/3Co1/3Mn1/3O2 as a lithium insertion positive electrode material, atom-scale modification was realized to obtain the layered oxysulfide LiNi1/3Co1/3Mn1/3O2-xSx using a novel plasma-enhanced doping strategy. The structure and electrochemical performance of LiNi1/3Co1/3Mn1/3O2-xSx are investigated systematically, which confirms that the S doping can make the structure stable and benefit the electrochemical performance. The phys-chemical characterizations indicate that oxygen atoms in the initial LiNi1/3Co1/3Mn1/3O2 have been partially replaced by S atoms. It should be pointed out that the atom-scale modification does not significantly alter the intrinsic structure of the cathode. Compared to the pristine material, the LiNi1/3Co1/3Mn1/3O2-xSx shows a superior performance with a higher capacity (200.4 mA h g(-1)) and a significantly improved cycling stability (maintaining 94.46% of its initial discharge capacity after 100 cycles). Moreover, it has an excellent rate performance especially at elevated performance, which is probably due to the faster Li(+) transportation after S doping into the layered structure. All the results show that the atom-scale modification with sulfur atoms on LiNi1/3Co1/3Mn1/3O2, which significantly improved the electrochemical performance, offers a novel anionic doping strategy to realize the atom-scale modification of electrode materials to improve their electrochemical performance.

  19. Intrinsic Origins of Crack Generation in Ni-rich LiNi0.8Co0.1Mn0.1O2 Layered Oxide Cathode Material

    Science.gov (United States)

    Lim, Jin-Myoung; Hwang, Taesoon; Kim, Duho; Park, Min-Sik; Cho, Kyeongjae; Cho, Maenghyo

    2017-01-01

    Ni-rich LiNi0.8Co0.1Mn0.1O2 layered oxide cathodes have been highlighted for large-scale energy applications due to their high energy density. Although its specific capacity is enhanced at higher voltages as Ni ratio increases, its structural degradation due to phase transformations and lattice distortions during cycling becomes severe. For these reasons, we focused on the origins of crack generation from phase transformations and structural distortions in Ni-rich LiNi0.8Co0.1Mn0.1O2 using multiscale approaches, from first-principles to meso-scale phase-field model. Atomic-scale structure analysis demonstrated that opposite changes in the lattice parameters are observed until the inverse Li content x = 0.75 then, structure collapses due to complete extraction of Li from between transition metal layers. Combined-phase investigations represent the highest phase barrier and steepest chemical potential after x = 0.75, leading to phase transformations to highly Li-deficient phases with an inactive character. Abrupt phase transformations with heterogeneous structural collapse after x = 0.81 (~220 mAh g‑1) were identified in the nanodomain. Further, meso-scale strain distributions show around 5% of anisotropic contraction with lower critical energy release rates, which cause not only micro-crack generations of secondary particles on the interfaces between the contracted primary particles, but also mechanical instability of primary particles from heterogeneous strain changes.

  20. Cathode materials: A personal perspective

    Energy Technology Data Exchange (ETDEWEB)

    Goodenough, John B. [Texas Materials Institute, University of Texas at Austin, ETC 9.102, 1 University Station, Austin, TX 78712-1063 (United States)

    2007-12-06

    A thermodynamically stable rechargeable battery has a voltage limited by the window of the electrolyte. An aqueous electrolyte has a window of 1.2 eV, which prevents achieving the high energy density desired for many applications. A non-aqueous electrolyte with a window of 5 eV requires Li{sup +} rather than H{sup +} as the working ion. Early experiments with Li{sub x}TiS{sub 2} cathodes showed competitive capacity and rate capability, but problems with a lithium anode made the voltage of a safe cell based on a sulfide cathode too low to be competitive with a nickel/metal-hydride battery. Transition-metal oxides can give voltages of 4.5 V versus Li{sup +}/Li{sup 0}. However, the challenge with oxides has been to obtain a competitive capacity and rate capability while retaining a high voltage with low-cost, environmentally friendly cathode materials. Comparisons will be made between layered Li{sub 1-x}MO{sub 2}, spinels Li{sub 1-x}[M{sub 2}]O{sub 4}, and olivines Li{sub 1-x}MPO{sub 4} having 0 < x < 1. Although higher capacities can be obtained with layered Li{sub 1-x}MO{sub 2} compounds, which have enabled the wireless revolution, their metastability makes them unlikely to be used in power applications. The spinel and olivine framework structures have been shown to be capable of charge/discharge rates of over 10C with a suitable temperature range for plug-in hybrid vehicles. (author)

  1. High efficiency solution processed fluorescent yellow organic light-emitting diode through fluorinated alcohol treatment at the emissive layer/cathode interface

    Science.gov (United States)

    Ng, Calvin Yi Bin; Yeoh, Keat Hoe; Whitcher, Thomas J.; Azrina Talik, Noor; Woon, Kai Lin; Saisopa, Thanit; Nakajima, Hideki; Supruangnet, Ratchadaporn; Songsiriritthigul, Prayoon

    2014-01-01

    We compare solvent treatments using fluorinated alcohol (2,2,3,3,4,4,5,5-octafluoro- 1-pentanol) and ethanol in improving the efficiency of a polymer organic light-emitting diode (OLED) by spin coating the solvent on top of the emissive layer. The presence of fluorinated alcohol is confirmed using x-ray photoelectron spectroscopy. The electron current is found to be significantly enhanced following solvent treatment while the hole current remains the same. The solvent treatment by fluorinated alcohol on top of a ‘super-yellow’ poly-(p-phenylenevinylene) (SY-PPV) based OLED results in efficiency as high as 19.2 lm W-1 (20.9 cd A-1) at a brightness of 1000 cd m-2. The improvement of device efficiency through the use of fluorinated alcohol treatment can be attributed to its large dipole, which lowers the electron injection barrier. This work also suggests that fluorinated alcohol might be a better trap passivator for electrons than ethanol.

  2. Effect of nickel and iron on structural and electrochemical properties of O3 type layer cathode materials for sodium-ion batteries

    Science.gov (United States)

    Hwang, Jang-Yeon; Myung, Seung-Taek; Aurbach, Doron; Sun, Yang-Kook

    2016-08-01

    We investigate that the effect of Ni and Fe contents on structural and electrochemical properties of O3-type layered Na[Ni0.75-xFexMn0.25]O2 (x = 0.4, 0.45, 0.5, and 0.55) in which Mn is fixed at 25%. As increasing the Ni contents, the capacities are gradually higher while the capacity retention and thermal properties are inferior. When Fe contents are increased, by contrast, the electrode exhibits stable capacity retention and satisfactory thermal stability although the resulting capacity slightly decreases. Structural investigation of post cycled electrodes indicate that lattice variation is greatly suppressed from x = 0.5 in Na[Ni0.75-xFexMn0.25]O2. This indicates that an appropriate amount of Fe into the Na[Ni0.75-xFexMn0.25]O2 stabilizes the crystal structure and this leads to the good cycling performances. Also, the better structural stability obtained by Fe addition is responsible for the less heat generation at elevated temperature for the desodiated Na1-δ[Ni0.75-xFexMn0.25]O2 (x = 0.4, 0.45, 0.5, and 0.55) caused by less evaporation of oxygen from the crystal structure.

  3. A three-dimensional pore-scale model of the cathode electrode in polymer-electrolyte membrane fuel cell by lattice Boltzmann method

    Science.gov (United States)

    Molaeimanesh, G. R.; Akbari, M. H.

    2014-07-01

    High power density, low operation temperature, high efficiency and low emissions have granted proton exchange membrane (PEM) fuel cells the most promising future among all types of fuel cells. The porous electrodes of PEM fuel cells have a complicated, non-homogeneous, anisotropic microstructure. Therefore, pore-scale modeling techniques such as lattice Boltzmann method, which can capture non-homogeneous and anisotropic microstructures, have recently gained a great attention. In the present study, a three-dimensional lattice Boltzmann model of a PEM fuel cell cathode electrode is proposed in which electrochemical reaction on the catalyst layer and microstructure of GDL are taken into account. The model enables us to simulate single-phase, multi-species reactive flow in a heterogeneous, anisotropic gas diffusion layer through an active approach. To show the capability of the proposed model, reactive flow in three reconstructed GDLs with different anisotropic characteristics is simulated to investigate the effects of GDL microstructure on species and current density distributions. The results demonstrate that when carbon fibers are more likely oriented normal to the catalyst layer, species density distribution is thicker and more disturbed. Current density also experiences a larger variation on the catalyst layer in such a case.

  4. Poly(vinyl alcohol) separators improve the coulombic efficiency of activated carbon cathodes in microbial fuel cells

    KAUST Repository

    Chen, Guang

    2013-09-01

    High-performance microbial fuel cell (MFC) air cathodes were constructed using a combination of inexpensive materials for the oxygen reduction cathode catalyst and the electrode separator. A poly(vinyl alcohol) (PVA)-based electrode separator enabled high coulombic efficiencies (CEs) in MFCs with activated carbon (AC) cathodes without significantly decreasing power output. MFCs with AC cathodes and PVA separators had CEs (43%-89%) about twice those of AC cathodes lacking a separator (17%-55%) or cathodes made with platinum supported on carbon catalyst (Pt/C) and carbon cloth (CE of 20%-50%). Similar maximum power densities were observed for AC-cathode MFCs with (840 ± 42 mW/m2) or without (860 ± 10 mW/m2) the PVA separator after 18 cycles (36 days). Compared to MFCs with Pt-based cathodes, the cost of the AC-based cathodes with PVA separators was substantially reduced. These results demonstrated that AC-based cathodes with PVA separators are an inexpensive alternative to expensive Pt-based cathodes for construction of larger-scale MFC reactors. © 2013 Elsevier B.V. All rights reserved.

  5. Cu2O Photocathode for Low Bias Photoelectrochemical Water Splitting Enabled by NiFe-Layered Double Hydroxide Co-Catalyst

    Science.gov (United States)

    Qi, Huan; Wolfe, Jonathan; Fichou, Denis; Chen, Zhong

    2016-08-01

    Layered double hydroxides (LDHs) are bimetallic hydroxides that currently attract considerable attention as co-catalysts in photoelectrochemical (PEC) systems in view of water splitting under solar light. A wide spectrum of LDHs can be easily prepared on demand by tuning their chemical composition and structural morphology. We describe here the electrochemical growth of NiFe-LDH overlayers on Cu2O electrodes and study their PEC behavior. By using the modified Cu2O/NiFe-LDH electrodes we observe a remarkable seven-fold increase of the photocurrent intensity under an applied voltage as low as -0.2 V vs Ag/AgCl. The origin of such a pronounced effect is the improved electron transfer towards the electrolyte brought by the NiFe-LDH overlayer due to an appropriate energy level alignment. Long-term photostability tests reveal that Cu2O/NiFe-LDH photocathodes show no photocurrent loss after 40 hours of operation under light at -0.2 V vs Ag/AgCl low bias condition. These improved performances make Cu2O/NiFe-LDH a suitable photocathode material for low voltage H2 production. Indeed, after 8 hours of H2 production under -0.2 V vs Ag/AgCl the PEC cell delivers a 78% faradaic efficiency. This unprecedented use of Cu2O/NiFe-LDH as an efficient photocathode opens new perspectives in view of low biasd or self-biased PEC water splitting under sunlight illumination.

  6. SOFC LSM:YSZ cathode degradation induced by moisture: An impedance spectroscopy study

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Mogensen, Mogens Bjerg

    2011-01-01

    The cause of the degradation effect of moisture during operation of LSM cathode based SOFCs has been investigated by means of a detailed impedance characterization on LSM:YSZ composite cathode based SOFCs. Further the role of YSZ as cathode composite material was studied by measurements on SOFCs...... with a LSM:CGO composite cathode on a CGO interdiffusion barrier layer. It was found that both types of cathodes showed similar electrochemical characteristics towards the presence of moisture during operation. Upon addition and removal of moisture in the fed air the impedance study showed a change...... in the high frequency cathode arc, which is associated with the charge transport/transfer at the LSM/YSZ interface. On prolonged operation with the presence of moisture an ongoing increase in the high frequency cathode arc resulted in a permanent loss of cathode/electrolyte contact and thus increase...

  7. Nanostructured sulfur cathodes

    KAUST Repository

    Yang, Yuan

    2013-01-01

    Rechargeable Li/S batteries have attracted significant attention lately due to their high specific energy and low cost. They are promising candidates for applications, including portable electronics, electric vehicles and grid-level energy storage. However, poor cycle life and low power capability are major technical obstacles. Various nanostructured sulfur cathodes have been developed to address these issues, as they provide greater resistance to pulverization, faster reaction kinetics and better trapping of soluble polysulfides. In this review, recent developments on nanostructured sulfur cathodes and mechanisms behind their operation are presented and discussed. Moreover, progress on novel characterization of sulfur cathodes is also summarized, as it has deepened the understanding of sulfur cathodes and will guide further rational design of sulfur electrodes. © 2013 The Royal Society of Chemistry.

  8. Cathodic hydrodimerization of nitroolefins

    OpenAIRE

    Michael Weßling; Hans J. Schäfer

    2015-01-01

    Nitroalkenes are easily accessible in high variety by condensation of aldehydes with aliphatic nitroalkanes. They belong to the group of activated alkenes that can be hydrodimerized by cathodic reduction. There are many olefins with different electron withdrawing groups used for cathodic hydrodimerization, but not much is known about the behaviour of the nitro group. Synthetic applications of this group could profit from the easy access to nitroolefins in large variety, the C–C bond formation...

  9. The influence of cathode material on electrochemical degradation of trichloroethylene in aqueous solution.

    Science.gov (United States)

    Rajic, Ljiljana; Fallahpour, Noushin; Podlaha, Elizabeth; Alshawabkeh, Akram

    2016-03-01

    In this study, different cathode materials were evaluated for electrochemical degradation of aqueous phase trichloroethylene (TCE). A cathode followed by an anode electrode sequence was used to support reduction of TCE at the cathode via hydrodechlorination (HDC). The performance of iron (Fe), copper (Cu), nickel (Ni), aluminum (Al) and carbon (C) foam cathodes was evaluated. We tested commercially available foam materials, which provide large electrode surface area and important properties for field application of the technology. Ni foam cathode produced the highest TCE removal (68.4%) due to its high electrocatalytic activity for hydrogen generation and promotion of HDC. Different performances of the cathode materials originate from differences in the bond strength between atomic hydrogen and the material. With a higher electrocatalytic activity than Ni, Pd catalyst (used as cathode coating) increased TCE removal from 43.5% to 99.8% for Fe, from 56.2% to 79.6% for Cu, from 68.4% to 78.4% for Ni, from 42.0% to 63.6% for Al and from 64.9% to 86.2% for C cathode. The performance of the palladized Fe foam cathode was tested for degradation of TCE in the presence of nitrates, as another commonly found groundwater species. TCE removal decreased from 99% to 41.2% in presence of 100 mg L(-1) of nitrates due to the competition with TCE for HDC at the cathode. The results indicate that the cathode material affects TCE removal rate while the Pd catalyst significantly enhances cathode activity to degrade TCE via HDC.

  10. Tandem cathode for proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Siahrostami, Samira; Björketun, Mårten E.; Strasser, Peter

    2013-01-01

    The efficiency of proton exchange membrane fuel cells is limited mainly by the oxygen reduction reaction at the cathode. The large cathodic overpotential is caused by correlations between binding energies of reaction intermediates in the reduction of oxygen to water. This work introduces a novel...... reaction intermediate each, and they occur on different catalyst surfaces. As a result they can be optimized independently and the fundamental problem associated with the four-electron catalysis is avoided. A combination of density functional theory calculations and published experimental data is used...

  11. Organic photovoltaic solar cells with cathode modified by ZnO.

    Science.gov (United States)

    Kim, Hyeong Pil; Yusoff, Abd Rashid Bin Mohd; Jang, Jin

    2013-07-01

    Solution processed cathode organic photovoltaic cells (OPVs) utilizing thin layer of ZnO with 27% increase in power conversion efficiency (PCE) to control devices have been demonstrated. Devices without the presence of ZnO layer have much lower PCE than the ones with ZnO layer. Cathode modification layer can be used to reduce photogenerated excitions and finally improve the performance of the OPVs. The successful demonstrations of OPVs with an introduction of ZnO cathode layer give promise of further device progresses.

  12. Cathode materials review

    Energy Technology Data Exchange (ETDEWEB)

    Daniel, Claus, E-mail: danielc@ornl.gov; Mohanty, Debasish, E-mail: danielc@ornl.gov; Li, Jianlin, E-mail: danielc@ornl.gov; Wood, David L., E-mail: danielc@ornl.gov [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS6472 Oak Ridge, TN 37831-6472 (United States)

    2014-06-16

    The electrochemical potential of cathode materials defines the positive side of the terminal voltage of a battery. Traditionally, cathode materials are the energy-limiting or voltage-limiting electrode. One of the first electrochemical batteries, the voltaic pile invented by Alessandro Volta in 1800 (Phil. Trans. Roy. Soc. 90, 403-431) had a copper-zinc galvanic element with a terminal voltage of 0.76 V. Since then, the research community has increased capacity and voltage for primary (nonrechargeable) batteries and round-trip efficiency for secondary (rechargeable) batteries. Successful secondary batteries have been the lead-acid with a lead oxide cathode and a terminal voltage of 2.1 V and later the NiCd with a nickel(III) oxide-hydroxide cathode and a 1.2 V terminal voltage. The relatively low voltage of those aqueous systems and the low round-trip efficiency due to activation energies in the conversion reactions limited their use. In 1976, Wittingham (J. Electrochem. Soc., 123, 315) and Besenhard (J. Power Sources 1(3), 267) finally enabled highly reversible redox reactions by intercalation of lithium ions instead of by chemical conversion. In 1980, Goodenough and Mizushima (Mater. Res. Bull. 15, 783-789) demonstrated a high-energy and high-power LiCoO{sub 2} cathode, allowing for an increase of terminal voltage far beyond 3 V. Over the past four decades, the international research community has further developed cathode materials of many varieties. Current state-of-the-art cathodes demonstrate voltages beyond any known electrolyte stability window, bringing electrolyte research once again to the forefront of battery research.

  13. Cathode materials review

    Science.gov (United States)

    Daniel, Claus; Mohanty, Debasish; Li, Jianlin; Wood, David L.

    2014-06-01

    The electrochemical potential of cathode materials defines the positive side of the terminal voltage of a battery. Traditionally, cathode materials are the energy-limiting or voltage-limiting electrode. One of the first electrochemical batteries, the voltaic pile invented by Alessandro Volta in 1800 (Phil. Trans. Roy. Soc. 90, 403-431) had a copper-zinc galvanic element with a terminal voltage of 0.76 V. Since then, the research community has increased capacity and voltage for primary (nonrechargeable) batteries and round-trip efficiency for secondary (rechargeable) batteries. Successful secondary batteries have been the lead-acid with a lead oxide cathode and a terminal voltage of 2.1 V and later the NiCd with a nickel(III) oxide-hydroxide cathode and a 1.2 V terminal voltage. The relatively low voltage of those aqueous systems and the low round-trip efficiency due to activation energies in the conversion reactions limited their use. In 1976, Wittingham (J. Electrochem. Soc., 123, 315) and Besenhard (J. Power Sources 1(3), 267) finally enabled highly reversible redox reactions by intercalation of lithium ions instead of by chemical conversion. In 1980, Goodenough and Mizushima (Mater. Res. Bull. 15, 783-789) demonstrated a high-energy and high-power LiCoO2 cathode, allowing for an increase of terminal voltage far beyond 3 V. Over the past four decades, the international research community has further developed cathode materials of many varieties. Current state-of-the-art cathodes demonstrate voltages beyond any known electrolyte stability window, bringing electrolyte research once again to the forefront of battery research.

  14. Cr(VI) reduction at rutile-catalyzed cathode in microbial fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yan; Lu, Anhuai; Ding, Hongrui; Yan, Yunhua; Wang, Changqiu; Zen, Cuiping; Wang, Xin [The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871 (China); Jin, Song [MWH Americas, 3665 JFK Parkway, Suite 206, Fort Collins, CO 80525 (United States); Department of Civil and Architectural Engineering, University of Wyoming, Laramie, WY 82071 (United States)

    2009-07-15

    Cathodic reduction of hexavalent chromium (Cr(VI)) and simultaneous power generation were successfully achieved in a microbial fuel cell (MFC) containing a novel rutile-coated cathode. The selected rutile was previously characterized to be sensitive to visible light and capable of both non-photo- and photocatalysis. In the MFCs containing rutile-coated cathode, Cr(VI) was rapidly reduced in the cathode chamber in presence and absence of light irradiation; and the rate of Cr(VI) reduction under light irradiation was substantially higher than that in the dark. Under light irradiation, 97% of Cr(VI) (initial concentration 26 mg/L) was reduced within 26 h, which was 1.6 x faster than that in the dark controls in which only background non-photocatalysis occurred. The maximal potential generated under light irradiation was 0.80 vs. 0.55 V in the dark controls. These results indicate that photocatalysis at the rutile-coated cathode in the MFCs might have lowered the cathodic overpotential, and enhanced electron transfer from the cathode to Cr(VI) for its reduction. In addition, photoexcited electrons generated during the cathode photocatalysis might also have contributed to the higher Cr(VI) reduction rates when under light irradiation. This work assessed natural rutile as a novel cathodic catalyst for MFCs in power generation; particularly it extended the practical merits of conventional MFCs to cathodic reduction of environmental contaminants such as Cr(VI). (author)

  15. Homogeneous catalysts

    CERN Document Server

    Chadwick, John C; Freixa, Zoraida; van Leeuwen, Piet W N M

    2011-01-01

    This first book to illuminate this important aspect of chemical synthesis improves the lifetime of catalysts, thus reducing material and saving energy, costs and waste.The international panel of expert authors describes the studies that have been conducted concerning the way homogeneous catalysts decompose, and the differences between homogeneous and heterogeneous catalysts. The result is a ready reference for organic, catalytic, polymer and complex chemists, as well as those working in industry and with/on organometallics.

  16. Erosion behavior of composite Al-Cr cathodes in cathodic arc plasmas in inert and reactive atmospheres

    Energy Technology Data Exchange (ETDEWEB)

    Franz, Robert, E-mail: robert.franz@unileoben.ac.at; Mendez Martin, Francisca; Hawranek, Gerhard [Montanuniversität Leoben, Franz-Josef-Strasse 18, 8700 Leoben (Austria); Polcik, Peter [Plansee Composite Materials GmbH, Siebenbürgerstrasse 23, 86983 Lechbruck am See (Germany)

    2016-03-15

    Al{sub x}Cr{sub 1−x} composite cathodes with Al contents of x = 0.75, 0.5, and 0.25 were exposed to cathodic arc plasmas in Ar, N{sub 2}, and O{sub 2} atmospheres and their erosion behavior was studied. Cross-sectional analysis of the elemental distribution of the near-surface zone in the cathodes by scanning electron microscopy revealed the formation of a modified layer for all cathodes and atmospheres. Due to intermixing of Al and Cr in the heat-affected zone, intermetallic Al-Cr phases formed as evidenced by x-ray diffraction analysis. Cathode poisoning effects in the reactive N{sub 2} and O{sub 2} atmospheres were nonuniform as a result of the applied magnetic field configuration. With the exception of oxide islands on Al-rich cathodes, reactive layers were absent in the circular erosion zone, while nitrides and oxides formed in the less eroded center region of the cathodes.

  17. Filtered cathodic arc source

    Science.gov (United States)

    Falabella, Steven; Sanders, David M.

    1994-01-01

    A continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45.degree. to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles.

  18. Cathodic Cage Plasma Nitriding: An Innovative Technique

    OpenAIRE

    Sousa,R.R.M.; de Araújo, F. O.; J. A. P. da Costa; Brandim,A.S.; R. A. de Brito; C. Alves

    2012-01-01

    Cylindrical samples of AISI 1020, AISI 316, and AISI 420 steels, with different heights, were simultaneously treated by a new technique of ionic nitriding, entitled cathodic cage plasma nitriding (CCPN), in order to evaluate the efficiency of this technique to produce nitrided layers with better properties compared with those obtained using conventional ionic nitriding technique. This method is able to eliminate the edge effect in the samples, promoting a better uniformity of temperature, and...

  19. Cathode Strip Chambers (CSC) Sag Measurements and Predictions

    CERN Document Server

    Kriesel, K; Loveless, D

    1997-01-01

    We describe the measurements of sag on P1A 2 layer prototype Cathode Strip Chamber and compare the results with calculated values. Using this information we predict the sag of P1 6-layer chamber with the present design for the aluminium frame, and compare this value to measured sag.

  20. Highly Efficient Micro Cathode Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek Company, Inc. proposes to develop a micro thermionic cathode that requires extremely low power and provides long lifetime. The basis for the cathode is a...

  1. Advanced Cathode Electrolyzer (ACE) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed innovation is a static, cathode-fed, 2000 psi, balanced-pressure Advanced Cathode Electrolyzer (ACE) based on PEM electrolysis technology. It...

  2. Organometallic catalysts for primary phosphoric acid fuel cells

    Science.gov (United States)

    Walsh, Fraser

    1987-01-01

    A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 hr. in full cell at 160 to 200 C in phosphoric acid H3PO4, and was shown to provide stable performance. The mixed catalyst contains an organometallic to catalyze electroreduction of oxygen to hydrogen peroxide and a metal to catalyze further electroreduction of the hydrogen peroxide to water. Cathodes containing an exemplar mixed catalyst (e.g., Co bisphenyl TAA/Mn) operate at approximately 650 mV vs DHE in 160 C, 85% H3PO4 with oxygen as reactant. In developing this mixed catalyst, a broad spectrum of TAAs were prepared, tested in half-cell and in a rotating ring-disk electrode system. TAAs found to facilitate the production of hydrogen peroxide in electroreduction were shown to be preferred TAAs for use in the mixed catalyst. Manganese (Mn) was identified as a preferred metal because it is capable of catalyzing hydrogen peroxide electroreduction, is lower in cost and is of less strategic importance than platinum, the cathode catalyst normally used in the fuel cell.

  3. Miniaturized cathodic arc plasma source

    Science.gov (United States)

    Anders, Andre; MacGill, Robert A.

    2003-04-15

    A cathodic arc plasma source has an anode formed of a plurality of spaced baffles which extend beyond the active cathode surface of the cathode. With the open baffle structure of the anode, most macroparticles pass through the gaps between the baffles and reflect off the baffles out of the plasma stream that enters a filter. Thus the anode not only has an electrical function but serves as a prefilter. The cathode has a small diameter, e.g. a rod of about 1/4 inch (6.25 mm) diameter. Thus the plasma source output is well localized, even with cathode spot movement which is limited in area, so that it effectively couples into a miniaturized filter. With a small area cathode, the material eroded from the cathode needs to be replaced to maintain plasma production. Therefore, the source includes a cathode advancement or feed mechanism coupled to cathode rod. The cathode also requires a cooling mechanism. The movable cathode rod is housed in a cooled metal shield or tube which serves as both a current conductor, thus reducing ohmic heat produced in the cathode, and as the heat sink for heat generated at or near the cathode. Cooling of the cathode housing tube is done by contact with coolant at a place remote from the active cathode surface. The source is operated in pulsed mode at relatively high currents, about 1 kA. The high arc current can also be used to operate the magnetic filter. A cathodic arc plasma deposition system using this source can be used for the deposition of ultrathin amorphous hard carbon (a-C) films for the magnetic storage industry.

  4. Cathode material for lithium batteries

    Science.gov (United States)

    Park, Sang-Ho; Amine, Khalil

    2013-07-23

    A method of manufacture an article of a cathode (positive electrode) material for lithium batteries. The cathode material is a lithium molybdenum composite transition metal oxide material and is prepared by mixing in a solid state an intermediate molybdenum composite transition metal oxide and a lithium source. The mixture is thermally treated to obtain the lithium molybdenum composite transition metal oxide cathode material.

  5. Research of Air Cathodes for Aluminum Air Batteries

    Science.gov (United States)

    2006-05-31

    Catalysts used in the existing cathodes include: platinum, silver, manganese and cobalt . Ruthenium is known for its catalytic ability and has received much...manganese, silver, cobalt , platinum, and ruthenium. The carbons used were Black Pearls 2000, proprietary carbons, Vulcan XC-72R, and Vapor Grown...discharge, the dissolved aluminate ion produced in this reaction precipitates out as crystalline hydrargillite (aluminum hydroxide): In addition to

  6. Atomic Layer Deposition of Al2O3-Ga2O3 Alloy Coatings for Li[Ni0.5Mn0.3Co0.2]O2 Cathode to Improve Rate Performance in Li-Ion Battery.

    Science.gov (United States)

    Laskar, Masihhur R; Jackson, David H K; Guan, Yingxin; Xu, Shenzhen; Fang, Shuyu; Dreibelbis, Mark; Mahanthappa, Mahesh K; Morgan, Dane; Hamers, Robert J; Kuech, Thomas F

    2016-04-27

    Metal oxide coatings can improve the electrochemical stability of cathodes and hence, their cycle-life in rechargeable batteries. However, such coatings often impose an additional electrical and ionic transport resistance to cathode surfaces leading to poor charge-discharge capacity at high C-rates. Here, a mixed oxide (Al2O3)1-x(Ga2O3)x alloy coating, prepared via atomic layer deposition (ALD), on Li[Ni0.5Mn0.3Co0.2]O2 (NMC) cathodes is developed that has increased electron conductivity and demonstrated an improved rate performance in comparison to uncoated NMC. A "co-pulsing" ALD technique was used which allows intimate and controlled ternary mixing of deposited film to obtain nanometer-thick mixed oxide coatings. Co-pulsing allows for independent control over film composition and thickness in contrast to separate sequential pulsing of the metal sources. (Al2O3)1-x(Ga2O3)x alloy coatings were demonstrated to improve the cycle life of the battery. Cycle tests show that increasing Al-content in alloy coatings increases capacity retention; whereas a mixture of compositions near (Al2O3)0.5(Ga2O3)0.5 was found to produce the optimal rate performance.

  7. Power generation using an activated carbon fiber felt cathode in an upflow microbial fuel cell

    KAUST Repository

    Deng, Qian

    2010-02-01

    An activated carbon fiber felt (ACFF) cathode lacking metal catalysts is used in an upflow microbial fuel cell (UMFC). The maximum power density with the ACFF cathode is 315 mW m-2, compared to lower values with cathodes made of plain carbon paper (67 mW m-2), carbon felt (77 mW m-2), or platinum-coated carbon paper (124 mW m-2, 0.2 mg-Pt cm-2). The addition of platinum to the ACFF cathode (0.2 mg-Pt cm-2) increases the maximum power density to 391 mW m-2. Power production is further increased to 784 mW m-2 by increasing the cathode surface area and shaping it into a tubular form. With ACFF cutting into granules, the maximum power is 481 mW m-2 (0.5 cm granules), and 667 mW m-2 (1.0 cm granules). These results show that ACFF cathodes lacking metal catalysts can be used to substantially increase power production in UMFC compared to traditional materials lacking a precious metal catalyst. © 2009 Elsevier B.V.

  8. Smart cathodic protection systems

    NARCIS (Netherlands)

    Polder, R.B.; Leggedoor, J.; Schuten, G.; Sajna, S.; Kranjc, A.

    2010-01-01

    Cathodic protection delivers corrosion protection in concrete structures exposed to aggressive environments, e.g. in de-icing salt and marine climates. Working lives of a large number of CP systems are at least more than 13 years and probably more than 25 years, provided a minimum level of maintenan

  9. SOFC Cathode Mechanisms

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Zachau-Christiansen, Birgit; Bay, Lasse

    1996-01-01

    The transient response of SOFC oxygen cathodes shows a characteristic inductive hysteresis and correspondingly the impedance diagram combines one or two capacitive arcs with a low frequency inductive arc. These features are discussed on the basis of a three step reaction sequence taken from...

  10. High redox and performance stability of layered SmBa(0.5)Sr(0.5)Co(1.5)Cu(0.5)O(5+δ) perovskite cathodes for intermediate-temperature solid oxide fuel cells.

    Science.gov (United States)

    Jun, Areum; Shin, Jeeyoung; Kim, Guntae

    2013-12-07

    Cobalt-containing cathodes often encounter problems such as high thermal expansion coefficients (TEC) and poor stability, making them unsuitable for practical use as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). This study focuses on the effects of Cu doping in the Co site of SmBa0.5Sr0.5Co2O5+δ in terms of structural characteristics, electrical properties, electrochemical performance, redox properties, and performance stability as an IT-SOFC cathode material. The TEC value of a SmBa0.5Sr0.5Co1.5Cu0.5O5+δ (SBSCCu50) sample is 12.8 × 10(-6) K(-1), which is lower than that (13.7 × 10(-6) K(-1)) of a SmBa0.5Sr0.5Co2O5+δ (SBSCO) sample at 700 °C. SBSCCu50 showed higher redox stability at lower p(O2) and a more stable cell power output while retaining desirable electrochemical performance, as compared with SBSCO. SBSCCu50 displayed reduced TEC values and enhanced redox and performance stability, as well as satisfactory electrical properties and electrochemical performance under typical fuel cell operating conditions. The results indicate that SBSCCu50 is a promising material as a cathode for IT-SOFCs.

  11. Cathodic Aromatic C,C Cross-Coupling Reaction via Single Electron Transfer Pathway.

    Science.gov (United States)

    Qu, Yang; Tateno, Hiroyuki; Matsumura, Yoshimasa; Kashiwagi, Tsuneo; Atobe, Mahito

    2017-03-07

    We have successfully developed a novel cathodic cross-coupling reaction of aryl halides with arenes. Utilization of the cathodic single electron transfer (SET) mechanism for activation of aryl halides enables the cross-coupling reaction to proceed without the need for any transition metal catalysts or single electron donors in a mild condition. The SET from a cathode to an aryl halide initiates a radical chain by giving an anion radical of the aryl halide. The following propagation cycle also consists entirely of anion radical intermediates.

  12. Cathodic Aromatic C,C Cross-Coupling Reaction via Single Electron Transfer Pathway

    Directory of Open Access Journals (Sweden)

    Yang Qu

    2017-03-01

    Full Text Available We have successfully developed a novel cathodic cross-coupling reaction of aryl halides with arenes. Utilization of the cathodic single electron transfer (SET mechanism for activation of aryl halides enables the cross-coupling reaction to proceed without the need for any transition metal catalysts or single electron donors in a mild condition. The SET from a cathode to an aryl halide initiates a radical chain by giving an anion radical of the aryl halide. The following propagation cycle also consists entirely of anion radical intermediates.

  13. Modification of porosity in the catalyst layer of membrane electrode assemblies using pore-forming agents; Modificacion de la porosidad en la capa catalitica de ensambles membrana-electrodo empleando agentes formadores de poros

    Energy Technology Data Exchange (ETDEWEB)

    Flores Hernandez, J. Roberto [Instituto de Investigaciones Electricas Cuernavaca, Morelos (Mexico)] e-mail: jrflores@iie.org.mx; Reyes, Brenda [UNAM. Facultad de Quimica, Mexico D.F. (Mexico); Barbosa P., Romeli [Centro de Investigacion en Energia, UNAM, Temixco, Morelos (Mexico); Cano Castillo, Ulises; Albarran, Lorena [Instituto de Investigaciones Electricas Cuernavaca, Morelos (Mexico)

    2009-09-15

    Membrane electrode assemblies (MEA) are the most important part of PEM fuel cells since their interface results in the electrochemical reactions that make the generation of electricity possible. The MEA is composed of a proton exchange membrane, both sides of which are impregnated with a catalyst layer, normally of carbon-supported platinum. Depending on the technique used for its fabrication (atomization, serigraphy, brush methods, chemical reduction, etc.), the properties of the MEA can be different in terms of porosity, distribution of the catalyst, thickness and structure of the catalyst layer, and the quality of the union between the catalyst layer and the membrane, etc. Currently, the porosity of the electrodes is generated by isopropanol evaporation (solvent used in the dye) during the fabrication process conducted in the Instituto de Investigaciones Electricas (IIE). This document presents the results obtained from adding a porous agent to the catalytic dye base composition used in the fabrication of MEA at the IIE. [Spanish] Los Ensambles Membrana-Electrodo (MEA's) son la parte mas importante en las celdas de combustibles tipo PEM, ya que en su interfaz se llevan a cabo las reacciones electroquimicas que hacen posible la generacion de electricidad. El MEA esta compuesto de una membrana de intercambio protonico a la cual se le impregna en ambos lados una capa catalitica normalmente de platino soportado en carbon. Dependiendo de la tecnica empleada en su fabricacion (atomizado, serigrafia, brocha, reduccion quimica, etc.), las propiedades del MEA pueden ser diferentes en cuanto a porosidad, distribucion del catalizador, grosor y estructura de la capa catalitica, asi como la calidad de la union entre la capa catalizadora y la membrana, etc. Actualmente, la porosidad de los electrodos es generada por la evaporacion del isopropanol (solvente utilizado en la tinta) durante el proceso de fabricacion que se realiza en el Instituto de Investigaciones

  14. Plasma characterization on carbon fiber cathode by spectroscopic diagnostics

    Institute of Scientific and Technical Information of China (English)

    Liu Lie; Li Li-Min; Xu Qi-Fu; Chang Lei; Wen Jian-Chun

    2009-01-01

    This paper mainly investigates plasma characterization on carbon fiber cathodes with and without cesium iodide (CsI) coating powered by a~300 ns,~200 kV accelerating pulse. It was found that the CsI layers can not only improve the diode voltage,but also maintain a stable perveance.This indicates a slowly changed diode gap or a low cathode plasma expansion velocity.By spectroscopic diagnostics,in the vicinity of the cathode surface the average plasma density and temperature were found to be~3×1014 cm-3 and~5 eV,respectively,for an electron current density of~40 A/cm2.Furthermore,there exists a multicomponent plasma expansion toward the anode.The plasma expansion velocity,corresponding to the carbon and hydrogen ions,is estimated to be~1.5 cm/μs.Most notably,Cs spectroscopic line was obtained only at the distance ≤0.5 mm from the cathode surface.Carbon and hydrogen ions are obtained up to the distance of 2.5 mm from the cathode surface.Cs ions almost remain at the vicinity of the cathode surface.These results show that the addition of Cal enables a slow cathode plasma expansion toward the anode,providing a positive prospect for developing long-pulse electron beam sources.

  15. Au/Si载体负载单层Pt催化剂的制备及其电催化性能的研究%Preparation of Mono-layer Pt Catalyst Supported on Au/Si and Its Electrochemical Properties

    Institute of Scientific and Technical Information of China (English)

    佟浩; 张艳玲; 朱佳佳; 张校刚; 何卫; 杨苏东; 何建平

    2012-01-01

    By using underpotential deposition method,the mono-layer of Pt was prepared on the Au/Si supports fabricated by electroless deposition of Au on Si.The morphology and electrochemical properties of Pt/Au/Si catalyst was characterized by TEM and CV methods.The results show that the mass activity of mono-layer Pt supported on Au/Si is 8 times higher than that of commercial E-TEK(Pt/C) catalyst.Compared with the other multi-layer of Pt,the utilization ratio of mono-layer of Pt is the highest,leading to the higher electro-catalytic properties toward methanol and CO oxidation.%以Si纳米粉为载体,通过化学镀的方法在其表面部分沉积纳米Au颗粒后,再通过欠电位的方法在Au颗粒表面沉积了单层及亚单层的Pt.通过透射电子显微镜(TEM),循环伏安(CV)等方法对所制备的Pt/Au/Si催化剂进行了形貌及电化学性能的表征.结果表明,该单层Pt覆盖的Au/Si催化剂对于甲醇的质量电催化活性是商业E-TEK(Pt/C)的8倍,相比于不同层数的Pt,单层覆盖时Pt的利用率最高,该单层Pt负载Au/Si催化剂对于抑制CO的中毒的性能也比商业E-TEK(Pt/C)有明显的提高.

  16. High surface area stainless steel brushes as cathodes in microbial electrolysis cells.

    Science.gov (United States)

    Call, Douglas F; Merrill, Matthew D; Logan, Bruce E

    2009-03-15

    Microbial electrolysis cells (MECs) are an efficient technology for generating hydrogen gas from organic matter, but alternatives to precious metals are needed for cathode catalysts. We show here that high surface area stainless steel brush cathodes produce hydrogen at rates and efficiencies similar to those achieved with platinum-catalyzed carbon cloth cathodes in single-chamber MECs. Using a stainless steel brush cathode with a specific surface area of 810 m2/m3, hydrogen was produced at a rate of 1.7 +/- 0.1 m3-H2/m3-d (current density of 188 +/- 10 A/m3) at an applied voltage of 0.6 V. The energy efficiency relative to the electrical energy input was 221 +/- 8%, and the overall energy efficiency was 78 +/- 5% based on both electrical energy and substrate utilization. These values compare well to previous results obtained using platinum on flat carbon cathodes in a similar system. Reducing the cathode surface area by 75% decreased performance from 91 +/- 3 A/m3 to 78 +/- 4 A/m3. A brush cathode with graphite instead of stainless steel and a specific surface area of 4600 m2/m3 generated substantially less current (1.7 +/- 0.0 A/m3), and a flat stainless steel cathode (25 m2/m3) produced 64 +/- 1 A/m3, demonstrating that both the stainless steel and the large surface area contributed to high current densities. Linear sweep voltammetry showed that the stainless steel brush cathodes both reduced the overpotential needed for hydrogen evolution and exhibited a decrease in overpotential over time as a result of activation. These results demonstrate for the first time that hydrogen production can be achieved at rates comparable to those with precious metal catalysts in MECs without the need for expensive cathodes.

  17. Joule heat generation in thermionic cathodes of high-pressure arc discharges

    Energy Technology Data Exchange (ETDEWEB)

    Benilov, M. S.; Cunha, M. D. [Departamento de Fisica, CCCEE, Universidade da Madeira, Largo do Municipio, 9000 Funchal (Portugal)

    2013-02-14

    The nonlinear surface heating model of plasma-cathode interaction in high-pressure arcs is extended to take into account the Joule effect inside the cathode body. Calculation results are given for different modes of current transfer to tungsten cathodes of different configurations in argon plasmas of atmospheric or higher pressures. Special attention is paid to analysis of energy balances of the cathode and the near-cathode plasma layer. In all the cases, the variation of potential inside the cathode is much smaller than the near-cathode voltage drop. However, this variation can be comparable to the volt equivalent of the energy flux from the plasma to the cathode and then the Joule effect is essential. Such is the case of the diffuse and mixed modes on rod cathodes at high currents, where the Joule heating causes a dramatic change of thermal and electrical regimes of the cathode. The Joule heating has virtually no effect over characteristics of spots on rod and infinite planar cathodes.

  18. A cobalt polypyrrole composite catalyzed cathode for the direct borohydride fuel cell

    Science.gov (United States)

    Qin, H. Y.; Liu, Z. X.; Yin, W. X.; Zhu, J. K.; Li, Z. P.

    A cobalt polypyrrole carbon (Co-PPY-C) composite has been attempted for use as a cathode catalyst in a direct borohydride fuel cell (DBFC). A Co-PPY-C composite has been fabricated in laboratory and characterized by the field emission scanning electron microscopy, transmission electron microscopy, as well as X-ray photoemission spectroscopy. Fabricated Co-PPY-C catalyst demonstrates good short-term durability and activity which are comparable to those obtained from the Pt/C catalyst. A maximum power density of 65 mW cm -2 has been achieved at ambient conditions. This research concludes that metallo-organic coordination compounds would be potential candidates for use as cathode catalysts in the DBFC.

  19. Thermal and electrical influences from bulk plasma in cathode heating modeling

    Science.gov (United States)

    Chen, Tang; Wang, Cheng; Zhang, Xiao-Ning; Zhang, Hao; Xia, Wei-Dong

    2017-02-01

    In this paper, a numerical calculation is performed for the purpose of estimating the thermal and electrical influences from bulk plasma in cathode heating modeling, in other words researching the necessity of a coupling bulk plasma in near-cathode layer modeling. The proposed model applied in the present work is an improved one from previous work. In this model, the near-cathode region is divided into two parts: the sheath and the ionization layer. The Schottky effect at the cathode surface is considered based on the analytic solution of a 1D sheath model. It is noted that the arc column is calculated simultaneously in the near-cathode region and the cathode bulk. An application is presented for an atmospheric free burning argon arc with arc currents of 50 A-600 A. The modeling results show three interesting points: (1) at the cathode surface, energy transport due to heat conduction of heavy particles and electrons is comparable to total heating flux, no matter whether the arc discharge is performed in a high (400 A) or low current (50 A) situation; (2) the electrical influence from bulk plasma on the cathode heating modeling becomes obvious in a high current situation (>400 A) for the spot mode; (3) the near-cathode layer voltage drop ({{U}\\text{tot}} ) is larger in the diffuse mode than in the spot mode for the same current, which is just the opposite to that for decoupled modeling.

  20. Photoconductive Cathode Interlayer for Highly Efficient Inverted Polymer Solar Cells.

    Science.gov (United States)

    Nian, Li; Zhang, Wenqiang; Zhu, Na; Liu, Linlin; Xie, Zengqi; Wu, Hongbin; Würthner, Frank; Ma, Yuguang

    2015-06-10

    A highly photoconductive cathode interlayer was achieved by doping a 1 wt % light absorber, such as perylene bisimide, into a ZnO thin film, which absorbs a very small amount of light but shows highly increased conductivity of 4.50 × 10(-3) S/m under sunlight. Photovoltaic devices based on this kind of photoactive cathode interlayer exhibit significantly improved device performance, which is rather insensitive to the thickness of the cathode interlayer over a broad range. Moreover, a power conversion efficiency as high as 10.5% was obtained by incorporation of our photoconductive cathode interlayer with the PTB7-Th:PC71BM active layer, which is one of the best results for single-junction polymer solar cells.

  1. Verification of high efficient broad beam cold cathode ion source

    Science.gov (United States)

    Abdel Reheem, A. M.; Ahmed, M. M.; Abdelhamid, M. M.; Ashour, A. H.

    2016-08-01

    An improved form of cold cathode ion source has been designed and constructed. It consists of stainless steel hollow cylinder anode and stainless steel cathode disc, which are separated by a Teflon flange. The electrical discharge and output characteristics have been measured at different pressures using argon, nitrogen, and oxygen gases. The ion exit aperture shape and optimum distance between ion collector plate and cathode disc are studied. The stable discharge current and maximum output ion beam current have been obtained using grid exit aperture. It was found that the optimum distance between ion collector plate and ion exit aperture is equal to 6.25 cm. The cold cathode ion source is used to deposit aluminum coating layer on AZ31 magnesium alloy using argon ion beam current which equals 600 μA. Scanning electron microscope and X-ray diffraction techniques used for characterizing samples before and after aluminum deposition.

  2. Dynamic Aspects of Solid Solution Cathodes for Electrochemical Power Sources

    DEFF Research Database (Denmark)

    Atlung, Sven; West, Keld; Jacobsen, Torben

    1979-01-01

    , in particularfor vehicle propulsion, and electrochemical and constructional factors. It isargued that the energy obtainable at a given load is limited by saturation ofthe surface layers of cathode particles with cations, and that the time beforesaturation occurs is determined by diffusion of cations and electrons...... into thehost lattice. Expressions are developed for plane, cylindrical, and sphericalparticles, giving the relation between battery load and the amount of cathodematerial utilized before saturation. The particle shape and a single parameterQ is used to describe cathode performance. Q is the ratio between...... dischargetime at 100% utilization of the cathode at the given load, and the timeconstant for diffusion through the cathode particles. This description is extendedto cover short peak loads characteristic of vehicle propulsion. On thebasis of estimated parameters for the Li/TiS2 couple with LiClO4-propylene...

  3. Abrasive-assisted Nickel Electroforming Process with Moving Cathode

    Science.gov (United States)

    REN, Jianhua; ZHU, Zengwei; XIA, Chunqiu; QU, Ningsong; ZHU, Di

    2017-03-01

    In traditional electroforming process for revolving parts with complex profiles, the drawbacks on surface of deposits, such as pinholes and nodules, will lead to varying physical and mechanical properties on different parts of electroformed components. To solve the problem, compositely moving cathode is employed in abrasive-assisted electroforming of revolving parts with complicated profiles. The cathode translates and rotates simultaneously to achieve uniform friction effect on deposits without drawbacks. The influences of current density and translation speed on the microstructure and properties of the electroformed nickel layers are investigated. It is found that abrasive-assisted electroforming with compound cathode motion can effectively remove the pinholes and nodules, positively affect the crystal nucleation, and refine the grains of layer. The increase of current density will lead to coarse microstructure and lower micro hardness, from 325 HV down to 189 HV. While, faster translational linear speed produces better surface quality and higher micro hardness, from 236 HV up to 283 HV. The weld-ability of the electroformed layers are also studied through the metallurgical analysis of welded joints between nickel layer and 304 stainless steel. The electrodeposited nickel layer shows fine performance in welding. The novel compound motion of cathode promotes the mechanical properties and refines the microstructure of deposited layer.

  4. Development of membrane electrode assemblies for solid polymer fuel cells with higher performance, lower cost and carbon monoxide tolerance: improved cathode structures

    Energy Technology Data Exchange (ETDEWEB)

    Ralph, T.; Collis, N.; Edwards, N.

    1997-09-01

    Pre-commercial prototype solid polymer fuel cell (SPFC) modules and systems are presently available for sale. The widespread use of the technology has been limited, however, principally because of the high capital cost and insufficient power density. The UK Department of Trade and Industry`s Advanced Fuel Cells R and D Strategy has identified that the SPFC could, after appropriate development, be suitable for small scale combined heat and power and transportation applications in the UK. Key technology developments required to meet the cost and performance targets include increasing the power density of the membrane electrode assembly (MEA), reducing the platinum loading of the electrode materials and identifying anode catalysts with increased tolerance to reformate operation. The objectives of this project were to establish a SPFC single cell test facility at Johnson Matthey Technology Centre (JMTC) and evaluate the performance of a multicomponent cathode structure developed in a previous DTI supported project. The cathode combined two components in a multicomponent layer. This comprised an `ionomer` component consisting of a platinum catalyst which had been pre-impregnated with soluble polymer electrolyte, to enhance the platinum utilisation. This component was intimately mixed with a `gas transport` component, composed of a carbon/PTFE mixture, to provide gas transport channels. A Nafion surface coating to link together isolated pockets of `ionomer` component in the electrode depth completed the fabrication. (Author)

  5. Catalyst mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Masel, Richard I.; Rosen, Brian A.

    2017-02-14

    Catalysts that include at least one catalytically active element and one helper catalyst can be used to increase the rate or lower the overpotential of chemical reactions. The helper catalyst can simultaneously act as a director molecule, suppressing undesired reactions and thus increasing selectivity toward the desired reaction. These catalysts can be useful for a variety of chemical reactions including, in particular, the electrochemical conversion of CO.sub.2 or formic acid. The catalysts can also suppress H.sub.2 evolution, permitting electrochemical cell operation at potentials below RHE. Chemical processes and devices using the catalysts are also disclosed, including processes to produce CO, OH.sup.-, HCO.sup.-, H.sub.2CO, (HCO.sub.2).sup.-, H.sub.2CO.sub.2, CH.sub.3OH, CH.sub.4, C.sub.2H.sub.4, CH.sub.3CH.sub.2OH, CH.sub.3COO.sup.-, CH.sub.3COOH, C.sub.2H.sub.6, O.sub.2, H.sub.2, (COOH).sub.2, or (COO.sup.-).sub.2, and a specific device, namely, a CO.sub.2 sensor.

  6. Photo-oxidation catalysts

    Science.gov (United States)

    Pitts, J. Roland; Liu, Ping; Smith, R. Davis

    2009-07-14

    Photo-oxidation catalysts and methods for cleaning a metal-based catalyst are disclosed. An exemplary catalyst system implementing a photo-oxidation catalyst may comprise a metal-based catalyst, and a photo-oxidation catalyst for cleaning the metal-based catalyst in the presence of light. The exposure to light enables the photo-oxidation catalyst to substantially oxidize absorbed contaminants and reduce accumulation of the contaminants on the metal-based catalyst. Applications are also disclosed.

  7. Synthesis and Electrochemical Evaluation of Carbon Supported Pt-Co Bimetallic Catalysts Prepared by Electroless Deposition and Modified Charge Enhanced Dry Impregnation

    OpenAIRE

    John Meynard M. Tengco; Bahareh Alsadat Tavakoli Mehrabadi; Yunya Zhang; Akkarat Wongkaew; John R. Regalbuto; Weidner, John W.; John R. Monnier

    2016-01-01

    Carbon-supported bimetallic Pt-Co cathode catalysts have been previously identified as higher activity alternatives to conventional Pt/C catalysts for fuel cells. In this work, a series of Pt-Co/C catalysts were synthesized using electroless deposition (ED) of Pt on a Co/C catalyst prepared by modified charge enhanced dry impregnation. X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) characterization of the base catalyst showed highly dispersed particles. A basic E...

  8. The design of cathode for organic photovoltaic devices

    Science.gov (United States)

    Song, De; Shi, Feng; Xia, Xuan; Li, Ye; Duanmu, Qingduo

    2016-11-01

    We have discussed the effect of the residual gas in the Al metal cathode deposition process and consequently influence the performance of organic photovoltaic devices (such as organic photoelectron detector or solar cell). We believe that the origin of degradation in Jsc and FF from the Al cathode device should be the formation of AlOx in the C60-Al interface, which contaminate the interface and plays a role like an energy barrier that block the charge collect process. To solve this problem the Ag and Alq3 layer had been inserted before the Al. Owing to the advantageous of Alq3 and Ag layer, the device which Al cathode prepared at a lower vacuum condition exhibits a comparable performance to that device which Al cathode deposited in regular situation. As an additional benefit, since the introducing of Alq3/Ag layer in the VOPc/C60 organic photovoltaic device performs a better near-infrared response, this phenomenon has been confirmed by means of both simulation and experimental data. So the design of our new cathode structure provides a degree of freedom to modulate the light absorption for organic photovoltaic devices in short-wave and long-wave.

  9. Surface Carbonization of Mo-La2O3 Cathode

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The carbonized structures of Mo-La2O3 cathode specimens have been investigated by means of FE SEM and XRD, respectively. The substructure of carbonized layer in the Mo-La2O3 cathode has been found for the first time. The results showed that the carbonized layer with uniform Mo2C was helpful to emission,while the demixing carbonized layer with a compact MoC outside layer was harmful to emission. The uniform Mo2C layer consists of coarse particles with lots of grain boundary crevices as well as holes arranging perpendic ular to the wire axle and up to surface, which was beneficial to the migration of activated rare-earth in activa tion and operating.

  10. Performance of metal alloys as hydrogen evolution reaction catalysts in a microbial electrolysis cell

    NARCIS (Netherlands)

    Jeremiasse, A.W.; Bergsma, J.; Kleijn, J.M.; Saakes, M.; Buisman, C.J.N.; Cohen Stuart, M.A.; Hamelers, H.V.M.

    2011-01-01

    H2 can be produced from organic matter with a microbial electrolysis cell (MEC). To decrease the energy input and increase the H2 production rate of an MEC, a catalyst is used at the cathode. Platinum is an effective catalyst, but its high costs stimulate searching for alternatives, such as non-nobl

  11. Modeling of PEM fuel cell Pt/C catalyst degradation

    Science.gov (United States)

    Bi, Wu; Fuller, Thomas F.

    Pt/C catalyst degradation remains as one of the primary limitations for practical applications of proton exchange membrane (PEM) fuel cells. Pt catalyst degradation mechanisms with the typically observed Pt nanoparticle growth behaviors have not been completely understood and predicted. In this work, a physics-based Pt/C catalyst degradation model is proposed with a simplified bi-modal particle size distribution. The following catalyst degradation processes were considered: (1) dissolution of Pt and subsequent electrochemical deposition on Pt nanoparticles in cathode; (2) diffusion of Pt ions in the membrane electrode assembly (MEA); and (3) Pt ion chemical reduction in membrane by hydrogen permeating through the membrane from the negative electrode. Catalyst coarsening with Pt nanoparticle growth was clearly demonstrated by Pt mass exchange between small and large particles through Pt dissolution and Pt ion deposition. However, the model is not adequate to predict well the catalyst degradation rates including Pt nanoparticle growth, catalyst surface area loss and cathode Pt mass loss. Additional catalyst degradation processes such as new Pt cluster formation on carbon support and neighboring Pt clusters coarsening was proposed for further simulative investigation.

  12. Cumulative effect of transition metals on nitrogen and fluorine co-doped graphite nanofibers: an efficient and highly durable non-precious metal catalyst for the oxygen reduction reaction.

    Science.gov (United States)

    Peera, S Gouse; Arunchander, A; Sahu, A K

    2016-08-14

    Nitrogen and fluorine co-doped graphite nanofibers (N/F-GNF) and their cumulative effect with Fe and Co have been developed as an alternative non-precious metal catalyst for efficient oxygen reduction reaction (ORR) in acidic media. The synergistic effect between the doped hetero atoms and the co-ordinated Fe and Co towards ORR activity and durability of the catalyst is deeply investigated. A high ORR onset potential comparable with commercial Pt/C catalyst is observed with the Fe-Co/NF-GNF catalyst, which indicates that this catalyst is a potential alternative to Pt/C. A fivefold increase in mass activity is achieved by the Fe-Co/NF-GNF catalyst compared to the simple N/F-GNF catalyst, which endorses the significant role of transition metal atoms in enhancing ORR activity. The advanced Fe-Co/NF-GNF catalyst also exhibits complete tolerance to CH3OH and CO. The Fe-Co/NF-GNF catalyst also exhibits excellent durability towards the ORR with only a 10 mV negative shift in its half wave potential after a 10 000 repeated potential cycling test, whereas in the case of a commercial Pt/C catalyst there was an ∼110 mV negative shift under similar environmental conditions. More stringent corrosive test cycles were also performed by maintaining the cell as high as 1.4 V with a later decrease to 0.6 V vs. RHE for 300 cycles, which showed the excellent durability of the Fe-Co/NF-GNF catalyst in comparison with the Pt/C catalyst. XPS analysis of the Fe-Co/NF-GNF catalyst presents the ORR active chemical states of N (pyridinic-N and graphitic-N) and F (semi-ionic-F) and the co-ordinated sites of Fe and Co species with the dopants. The excellent performance and durability of the Fe-Co/NF-GNF catalyst is due to the synergistic effect between the hetero atoms dopants (N and F) and strong co-ordinating bonds of M-N-C, which protect the graphene layers around the metallic species and greatly mitigates the leaching of Co and Fe during the long term cycling test. The high activity

  13. Highly dispersed metal catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Xin; West, William L.; Rhodes, William D.

    2016-11-08

    A supported catalyst having an atomic level single atom structure is provided such that substantially all the catalyst is available for catalytic function. A process of forming a single atom catalyst unto a porous catalyst support is also provided.

  14. Exfoliation and reassembly of cobalt oxide nanosheets into a reversible lithium-ion battery cathode.

    Science.gov (United States)

    Compton, Owen C; Abouimrane, Ali; An, Zhi; Palmeri, Marc J; Brinson, L Catherine; Amine, Khalil; Nguyen, SonBinh T

    2012-04-10

    An exfoliation-reassembly-activation (ERA) approach to lithium-ion battery cathode fabrication is introduced, demonstrating that inactive HCoO(2) powder can be converted into a reversible Li(1-x) H(x) CoO(2) thin-film cathode. This strategy circumvents the inherent difficulties often associated with the powder processing of the layered solids typically employed as cathode materials. The delamination of HCoO(2) via a combination of chemical and mechanical exfoliation generates a highly processable aqueous dispersion of [CoO(2) ](-) nanosheets that is critical to the ERA approach. Following vacuum-assisted self-assembly to yield a thin-film cathode and ion exchange to activate this material, the generated cathodes exhibit excellent cyclability and discharge capacities approaching that of low-temperature-prepared LiCoO(2) (~83 mAh g(-1) ), with this good electrochemical performance attributable to the high degree of order in the reassembled cathode.

  15. Suitable alkaline for graphene peeling grown on metallic catalysts using chemical vapor deposition

    Science.gov (United States)

    Karamat, S.; Sonuşen, S.; Çelik, Ü.; Uysallı, Y.; Oral, A.

    2016-04-01

    In chemical vapor deposition, the higher growth temperature roughens the surface of the metal catalyst and a delicate method is necessary for the transfer of graphene from metal catalyst to the desired substrates. In this work, we grow graphene on Pt and Cu foil via ambient pressure chemical vapor deposition (AP-CVD) method and further alkaline water electrolysis was used to peel off graphene from the metallic catalyst. We used different electrolytes i.e., sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH) and barium hydroxide Ba(OH)2 for electrolysis, hydrogen bubbles evolved at the Pt cathode (graphene/Pt/PMMA stack) and as a result graphene layer peeled off from the substrate without damage. The peeling time for KOH and LiOH was ∼6 min and for NaOH and Ba(OH)2 it was ∼15 min. KOH and LiOH peeled off graphene very efficiently as compared to NaOH and Ba(OH)2 from the Pt electrode. In case of copper, the peeling time is ∼3-5 min. Different characterizations like optical microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy were done to analyze the as grown and transferred graphene samples.

  16. Iron-rich nanoparticle encapsulated, nitrogen doped porous carbon materials as efficient cathode electrocatalyst for microbial fuel cells

    Science.gov (United States)

    Lu, Guolong; Zhu, Youlong; Lu, Lu; Xu, Kongliang; Wang, Heming; Jin, Yinghua; Jason Ren, Zhiyong; Liu, Zhenning; Zhang, Wei

    2016-05-01

    Developing efficient, readily available, and sustainable electrocatalysts for oxygen reduction reaction (ORR) in neutral medium is of great importance to practical applications of microbial fuel cells (MFCs). Herein, a porous nitrogen-doped carbon material with encapsulated Fe-based nanoparticles (Fe-Nx/C) has been developed and utilized as an efficient ORR catalyst in MFCs. The material was obtained through pyrolysis of a highly porous organic polymer containing iron(II) porphyrins. The characterizations of morphology, crystalline structure and elemental composition reveal that Fe-Nx/C consists of well-dispersed Fe-based nanoparticles coated by N-doped graphitic carbon layer. ORR catalytic performance of Fe-Nx/C has been evaluated through cyclic voltammetry and rotating ring-disk electrode measurements, and its application as a cathode electrocatalyst in an air-cathode single-chamber MFC has been investigated. Fe-Nx/C exhibits comparable or better performance in MFCs than 20% Pt/C, displaying higher cell voltage (601 mV vs. 591 mV), maximum power density (1227 mW m-2 vs. 1031 mW m-2) and Coulombic efficiency (50% vs. 31%). These findings indicate that Fe-Nx/C is more tolerant and durable than Pt/C in a system with bacteria metabolism and thus holds great potential for practical MFC applications.

  17. Development of low emissivity layer systems for large area glass coating. Subproject: up-scaling of the processes to the large area cathode and development of applicable test procedures. Final report; Entwicklung von Waermedaemmungs-Schichtsystemen fuer die grossflaechige Glasbeschichtung. Teilprojekt: Skalierung der Prozesse auf die Grosskathode und Entwicklung anwendungsnaher Testverfahren. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Nahr, J.; Dietrich, A.; Hong Dietrich Xian

    1998-12-31

    Within the project work was done in the area of development of coatings, the up-scaling of processes, the development of test procedures and the area of process optimization/process monitoring. The test procedure for coated isolating glazings produced important results to the long-term stability of different types of low-e coatings. The new development layer systems on the base of double-silver have very good optical and heat-conserving properties. The TwinMag-cathode developed by Leybold was successfully scaled-up to the large area cathode and integrated into the production process of a coater for architectural glazings. A tool for the puls-sputtering of silver was successfully tested at a large area cathode. Negativ effects to the properties of the coating were not found. A program for automatical and continuous aquisition of process- and product data was developed with the aim of total quality control. (orig.) [Deutsch] Im Rahmen des Verbundprojektes wurden Arbeiten zur Schichtentwicklung, zur Hochskalierung verschiedener Prozesse, zur Entwicklung von Testverfahren und zur Prozessoptimierung/Prozessueberwachung durchgefuehrt. Das Labortestverfahren fuer beschichtete Isolierglaeser hat wichtige Erkenntnisse zur Langzeitstabilitaet verschiedener Low-E-Schichten gebracht. Die beiden neuentwickelten Schichtsysteme auf Doppelsilberbasis weisen sehr gute optische und waermetechnische Eigenschaften auf. Das vom Projektpartner Leybold entwickelte Konzept der TwinMag-Kathode gepaart mit der Mittelfrequenztechnik wurde erfolgreich auf einer Grosskathode fuer eine Architekturglasbeschichtungsanlage hochskaliert und in den Produktionsprozess integriert. Ein Geraet zum Pulssputtern von Silber erwies in Tests an der Grosskathode seine Funktionstuechtigkeit. Negative Auswirkungen auf die Schichteigenschaften konnten nicht gefunden werden. Ein Programm zur automatischen und kontinuierlichen Erfassung der Prozess- und Produktdaten wurde entwickelt mit dem Ziel einer umfassenden

  18. Fuel cell cathode air filters: Methodologies for design and optimization

    Science.gov (United States)

    Kennedy, Daniel M.; Cahela, Donald R.; Zhu, Wenhua H.; Westrom, Kenneth C.; Nelms, R. Mark; Tatarchuk, Bruce J.

    Proton exchange membrane (PEM) fuel cells experience performance degradation, such as reduction in efficiency and life, as a result of poisoning of platinum catalysts by airborne contaminants. Research on these contaminant effects suggests that the best possible solution to allowing fuel cells to operate in contaminated environments is by filtration of the harmful contaminants from the cathode air. A cathode air filter design methodology was created that connects properties of cathode air stream, filter design options, and filter footprint, to a set of adsorptive filter parameters that must be optimized to efficiently operate the fuel cell. Filter optimization requires a study of the trade off between two causal factors of power loss: first, a reduction in power production due to poisoning of the platinum catalyst by chemical contaminants and second, an increase in power requirements to operate the air compressor with a larger pressure drop from additional contaminant filtration. The design methodology was successfully applied to a 1.2 kW fuel cell using a programmable algorithm and predictions were made about the relationships between inlet concentration, breakthrough time, filter design, pressure drop, and compressor power requirements.

  19. Enhanced microbial electrosynthesis with three-dimensional graphene functionalized cathodes fabricated via solvothermal synthesis

    DEFF Research Database (Denmark)

    Aryal, Nabin; Halder, Arnab; Tremblay, Pier-Luc

    2016-01-01

    The biological reduction of CO2 into multicarbon chemicals can be driven by electrons derived from the cathode of a bioelectrochemical reactor via microbial electrosynthesis (MES). To increase MES productivity, conditions for optimal electron transfer between the cathode and the microbial catalyst...... must be implemented. Here, we report the development of a 3D-graphene functionalized carbon felt composite cathode enabling faster electron transfer to the microbial catalyst Sporomusa ovata in a MES reactor. Modification with 3D-graphene network increased the electrosynthesis rate of acetate from CO2...... by 6.8 fold. It also significantly improved biofilm density and current consumption. A 2-fold increase in specific surface area of the 3D-graphene/carbon felt composite cathode explained in part the formation of more substantial biofilms compared to untreated control. Furthermore, in cyclic voltammetry...

  20. Anode Simulation and Cathode Design for Electrolytic Dressing of Diamond Profile Wheel

    Institute of Scientific and Technical Information of China (English)

    ZOU Feng; YU Aibing; TAN Yefa

    2005-01-01

    The design methods of anode and cathode are proposed for precision profile grinding. Based on the electrolytic machining theory, electrolytic equilibrium condition and Faraday′s law of electrolysis are applied to establishing the mathematical model of profile diamond dressing process-es. A finite element method (FEM) program is developed to solve the inverse boundary problem of Laplace′s equation. Desired anode contour or cathode shape is determined by computing the distribution of electric potential layer by layer. Electrolytic machining experiment is carried out to verify the simulated anode shape. The research result shows that shape deviation between designed cathode and profile wheel increases with the value of angle between feed rate and the normal to anode surface. The shape of simulated anode is consistent with the contour of metal-bonded diamond profile wheel for a given cathode. Based on the anode contour, cathode shape can also be designed accurately.

  1. Fullerene derivative-doped zinc oxide nanofilm as the cathode of inverted polymer solar cells with low-bandgap polymer (PTB7-Th) for high performance.

    Science.gov (United States)

    Liao, Sih-Hao; Jhuo, Hong-Jyun; Cheng, Yu-Shan; Chen, Show-An

    2013-09-14

    Modification of a ZnO cathode by doping it with a hydroxyl-containing derivative - giving a ZnO-C60 cathode - provides a fullerene-derivative-rich surface and enhanced electron conduction. Inverted polymer solar cells with the ZnO-C60 cathode display markedly improved power conversion efficiency compared to those with a pristine ZnO cathode, especially when the active layer includes the low-bandgap polymer PTB7-Th.

  2. High-performance lanthanum-ferrite-based cathode for SOFC

    DEFF Research Database (Denmark)

    Wang, W.G.; Mogensen, Mogens Bjerg

    2005-01-01

    (La0.6Sr0.4)(1-x)Co0.2Fe0.8O3/Ce0.9Gd0.1O3 (LSCF/CGO) composite cathodes were investigated for SOFC application at intermediate temperature, i.e., 500-700 degreesC. The LSCF/CGO cathodes have been studied on three types of tape-casted electrolyte substrates including CGO electrolyte, Yttrium......C were obtained using LSCF/CGO cathode on CGO electrolyte. On the YSZ electrolyte with thin layer CGO coating, R-p of 0.6 Omega cm(2) at 600 degreesC and 0.12 Omega cm(2) at 700 degreesC were obtained. On the YSZ electrolyte directly, R-p of 1.0 Omega cm(2) at 600 degreesC and 0.13 Omega cm(2) at 700...... degreesC were achieved. These results are roughly six times better than our typical LSM cathodes. Slightly higher R-s was observed in the samples with LSCF/CGO cathode on the YSZ electrolyte with CGO coating due to extra contribution from the thin CGO layer and the CGO/YSZ interface. For the samples...

  3. Heterogeneous Catalysts

    NARCIS (Netherlands)

    Dakka, J.; Sheldon, R.A.; Sanderson, W.A.

    1997-01-01

    Abstract of GB 2309655 (A) Heterogeneous catalysts comprising one or more metal compounds selected from the group consisting of tin, molybdenum, tungsten, zirconium and selenium compounds deposited on the surface of a silicalite are provided. Preferably Sn(IV) and/or Mo(VI) are employed. The cat

  4. Cathodic hydrodimerization of nitroolefins

    Directory of Open Access Journals (Sweden)

    Michael Weßling

    2015-07-01

    Full Text Available Nitroalkenes are easily accessible in high variety by condensation of aldehydes with aliphatic nitroalkanes. They belong to the group of activated alkenes that can be hydrodimerized by cathodic reduction. There are many olefins with different electron withdrawing groups used for cathodic hydrodimerization, but not much is known about the behaviour of the nitro group. Synthetic applications of this group could profit from the easy access to nitroolefins in large variety, the C–C bond formation with the introduction of two nitro groups in a 1,4-distance and the conversions of the nitro group by reduction to oximes and amines, the conversion into aldehydes and ketones via the Nef reaction and base catalyzed condensations at the acidic CH bond. Eight 1-aryl-2-nitro-1-propenes have been electrolyzed in an undivided electrolysis cell to afford 2,5-dinitro-3,4-diaryl hexanes in high yield. The 4-methoxy-, 4-trifluoromethyl-, 2-chloro- and 2,6-difluorophenyl group and furthermore the 2-furyl and 2-pyrrolyl group have been applied. The reaction is chemoselective as only the double bond but not the nitro group undergoes reaction, is regioselective as a ß,ß-coupling with regard to the nitro group and forms preferentially two out of six possible diastereomers as major products.

  5. Cathodic hydrodimerization of nitroolefins.

    Science.gov (United States)

    Weßling, Michael; Schäfer, Hans J

    2015-01-01

    Nitroalkenes are easily accessible in high variety by condensation of aldehydes with aliphatic nitroalkanes. They belong to the group of activated alkenes that can be hydrodimerized by cathodic reduction. There are many olefins with different electron withdrawing groups used for cathodic hydrodimerization, but not much is known about the behaviour of the nitro group. Synthetic applications of this group could profit from the easy access to nitroolefins in large variety, the C-C bond formation with the introduction of two nitro groups in a 1,4-distance and the conversions of the nitro group by reduction to oximes and amines, the conversion into aldehydes and ketones via the Nef reaction and base catalyzed condensations at the acidic CH bond. Eight 1-aryl-2-nitro-1-propenes have been electrolyzed in an undivided electrolysis cell to afford 2,5-dinitro-3,4-diaryl hexanes in high yield. The 4-methoxy-, 4-trifluoromethyl-, 2-chloro- and 2,6-difluorophenyl group and furthermore the 2-furyl and 2-pyrrolyl group have been applied. The reaction is chemoselective as only the double bond but not the nitro group undergoes reaction, is regioselective as a ß,ß-coupling with regard to the nitro group and forms preferentially two out of six possible diastereomers as major products.

  6. Methods for batch fabrication of cold cathode vacuum switch tubes

    Energy Technology Data Exchange (ETDEWEB)

    Walker, Charles A. (Albuquerque, NM); Trowbridge, Frank R. (Albuquerque, NM)

    2011-05-10

    Methods are disclosed for batch fabrication of vacuum switch tubes that reduce manufacturing costs and improve tube to tube uniformity. The disclosed methods comprise creating a stacked assembly of layers containing a plurality of adjacently spaced switch tube sub-assemblies aligned and registered through common layers. The layers include trigger electrode layer, cathode layer including a metallic support/contact with graphite cathode inserts, trigger probe sub-assembly layer, ceramic (e.g. tube body) insulator layer, and metallic anode sub-assembly layer. Braze alloy layers are incorporated into the stacked assembly of layers, and can include active metal braze alloys or direct braze alloys, to eliminate costs associated with traditional metallization of the ceramic insulator layers. The entire stacked assembly is then heated to braze/join/bond the stack-up into a cohesive body, after which individual switch tubes are singulated by methods such as sawing. The inventive methods provide for simultaneously fabricating a plurality of devices as opposed to traditional methods that rely on skilled craftsman to essentially hand build individual devices.

  7. Fabrication and performance of La0.8Sr0.2MnO3/YSZ graded composite cathodes for SOFC

    Institute of Scientific and Technical Information of China (English)

    SUN Kening; PIAO Jinhua; ZHANG Naiqing; CHEN Xinbing; XU Shen; ZHOU Derui

    2008-01-01

    The performance of multi-layer (1-x)La0.8Sr0.2MnO3/xYSZ graded composite cathodes was studied as electrode materials for intermediate solid oxide fuel cells (SOFC). The thermal expansion coefficient, electrical conductivity, and electrochemical performance of multi-layer composite cathodes were investigated. The thermal expansion coefficient and electrical conductivity decreased with the increase in YSZ content. The (1-x)La0.8Sr0.2MnO3/xYSZ composite cathode greatly increased the length of the active triple phase boundary line (TPBL) among electrode, electrolyte, and gas phase, leading to a decrease in polarization resistance and an increase in polarization current density. The polarization current density of the triple-layer graded composite cathode (0.77 A/cm2) was the highest and that of the monolayer cathode (0.13 A/cm2) was the lowest. The polarization resistance (Rp) of the triple-layer graded composite cathode was only 0.182Ω·cm2 and that of the monolayer composite cathode was 0.323Ω·cm2. The power density of the triple-layer graded composite cathode was the highest and that of the monolayer composite cathode was the lowest. The triple-layer graded composite cathode had superior performance.

  8. The conditions for electrodeposition of insoluble hydroxides at a cathode surface

    DEFF Research Database (Denmark)

    Hansen, P.Gregers

    1959-01-01

    The pH values obtained in the vicinity of a cathode surface where hydrogen evolution takes place are discussed using the concept of a diffusion layer. It is shown that a given current density I determines a hydrogen ion concentration Cmax in the solution, above which no hydroxide deposition...... at the cathode can be expected to take place. The shape of the pH distribution makes it possible to define a hydroxyl ion layer, the thickness of which approaches zero as the hydrogen ion concentration approaches Cmax. It is found that relatively high pH values (11–13) are easily obtained at a cathode surface...

  9. Advanced catalyst supports for PEM fuel cell cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Du, Lei; Shao, Yuyan; Sun, Junming; Yin, Geping; Liu, Jun; Wang, Yong

    2016-11-01

    Electrocatalyst support materials are key components for polymer exchange membrane (PEM) fuel cells, which play a critical role in determining electrocatalyst durability and activity, mass transfer and water management. The commonly-used supports, e.g. porous carbon black, cannot meet all the requirements under the harsh operation condition of PEM fuel cells. Great efforts have been made in the last few years in developing alternative support materials. In this paper, we selectively review recent progress on three types of important support materials: carbon, non-carbon and hybrid carbon-oxides nanocomposites. A perspective on future R&D of electrocatalyst support materials is also provided.

  10. High Performance and Durable Low PGM Cathode Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Liu, Jun [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shao, Yuyan [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cheng, Yingwen [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Borup, Rodney L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Rockward, Tommy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Brosha, Eric Lanich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-08-17

    There is a strong need to decrease the amount of Pt electrocatalyst used in fuel cells and increase its durability for transportation application. Conventional strategies include Pt nanocrystals and Pt alloy with well-controlled structures, durable carbon support, non-carbon support, etc. We have developed the so-called “metal-metal oxide-carbon” triple junction concept to stabilize Pt and protect carbon from corrosion. It also improved the activity of Pt. The good performance was not achieved in fuel cell test mainly because of the transport issue due to the use of 2D graphene. In this project, our main goal is to demonstrate the concept in fuel cell device test using 3D porous graphene as support so that the transport issue could be addressed.

  11. QE data for Pb/Nb deposited photo cathode samples

    CERN Document Server

    Sekutowicz, J

    2010-01-01

    This report outlines progress in the development of photo-cathodes for a hybrid lead/niobium (Pb/Nb) superconducting SRF electron injector. We have coated eight Nb samples with lead to study and determine deposition conditions leading to high quality emitting area. The results show that the oxide layer significantly influences the quantum efficiency (QE) of all measured cathodes. In addition, we learned that although the laser cleaning enhanced the QE substantially, the film morphology was strongly modified. That observation convinced us to make the coatings thicker and therefore more robust.

  12. Electrochemical surface characterization and O2 reduction kinetics of Se surface-modified ru nanoparticle-based RuSe(y)/C catalysts.

    Science.gov (United States)

    Colmenares, L; Jusys, Z; Behm, R J

    2006-12-05

    The electrochemical properties of Se surface-modified Ru/C catalysts (RuSey/C with y = 0 to 1) and their O2 reduction characteristics were determined in model studies under well-defined mass transport conditions, combining quantitative differential electrochemical mass spectrometry and double-disk electrode thin-layer flow-cell measurements. Surface characterization of the catalysts including the quantitative evaluation of the active surface area was performed by electrochemical/mass spectrometric (combined H-upd adsorption, preadsorbed CO monolayer oxidation, Cu-upd adsorption/stripping, and RuOx formation) methods. The suitability of these methods for the determination of the active surface area in the high and low Se coverage regime are discussed, and COad stripping is found to be the most relevant method for the present catalysts. The kinetic parameters for the ORR (activity and selectivity) under quasi-steady-state conditions and their variation with Se modification were evaluated in potentiostatic flow-cell measurements. Modification of Ru/C catalyst by Se improves the O2 reduction activity and reduces the tendency for H2O2 formation in the technically relevant potential region of 0.6-0.8 VRHE, but even for the best catalyst compositions a significant ( approximately 0.2 VRHE) overpotential for O2 reduction on the RuSey/C catalysts remains compared to that for the Pt/C catalyst, and we find H2O2 yields of at least 1% at typical cathode operation potentials. Consequences of the relatively high H2O2 yields for membrane/electrode stability in practical applications are discussed.

  13. Growth of single and bilayer graphene by filtered cathodic vacuum arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Kesarwani, A. K.; Panwar, O. S., E-mail: ospanwar@mail.nplindia.ernet.in; Bisht, Atul [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India and Academy of Scientific and Innovative Research (AcSIR), CSIR Campus, New Delhi 110012 (India); Dhakate, S. R. [Physics and Engineering of Carbon Materials, Division of Materials Physics and Engineering, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India and Academy of Scientific and Innovative Research (AcSIR), CSIR Campus, New Delhi 110012 (India); Rakshit, R. K. [Quantum Phenomena and Applications Group, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India and Academy of Scientific and Innovative Research (AcSIR), CSIR Campus, New Delhi 110012 (India); Singh, V. N. [Electron and Ion Microscopy, Sophisticated and Analytical Instruments, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India and Academy of Scientific and Innovative Research (AcSIR), CSIR Campus, New Delhi 110012 (India); Kumar, Ashish [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India)

    2016-03-15

    The authors present a viable process to grow the high quality graphene films with control over number of layers by the filtered cathodic vacuum arc (FCVA) technique. In the FCVA process, the different carbon concentrations can be controlled by precisely tuning the arc time (1–4 s). The arc generated carbon was deposited on the nickel catalyst at 800 °C, annealed for 10 min, and cooled down to room temperature in the presence of hydrogen gas, resulting in the graphene films with control over number of layers. Prior to arcing, hydrogen etching of nickel was carried out to clean the surface of the substrate. A growth model to prepare the high quality graphene has also been proposed. The as-grown graphene films were transferred to different substrates and are characterized by Raman spectroscopy, optical microscopy, high resolution transmission electron microscopy, and atomic force microscopy to determine the number of layers present in these films. Raman spectra of the prepared graphene films exhibit change in the G peak position from 1582.4 to 1578.1 cm{sup −1}, two-dimensional (2D) peak shifts from 2688.5 to 2703.8 cm{sup −1}, the value of I{sub 2D}/I{sub G} increased from 0.38 to 3.82, and the full width at half maxima of 2D peak changed from 41 to 70 cm{sup −1}, for different layers of graphene films. The high resolution transmission electron microscopy image revealed that the graphene films prepared for 1 and 2 s arc times have single and bi- or trilayered structures, respectively.

  14. Electronic modification of Pt via Ti and Se as tolerant cathodes in air-breathing methanol microfluidic fuel cells.