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Sample records for based electrocatalysts prepared

  1. Electrocatalysts using porous polymers and method of preparation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Di-Jia; Yuan, Shengwen; Goenaga, Gabriel A.

    2016-08-02

    A method of producing an electrocatalyst article using porous polymers. The method creates a porous polymer designed to receive transition metal groups disposed at ligation sites and activating the transition metals to form an electrocatalyst which can be used in a fuel cell. Electrocatalysts prepared by this method are also provided. A fuel cell which includes the electrocatalyst is also provided.

  2. Preparation and characterization of electrocatalysts based on palladium for electro-oxidation of alcohols in alkaline medium

    International Nuclear Information System (INIS)

    In this study Pd/C, Au/C, PdAu/C, PdAuPt/C, PdAuBi/C and PdAuIr/C electrocatalysts were prepared by the sodium borohydride reduction method for the electrochemical oxidation of methanol, ethanol and ethylene glycol. This methodology consists in mix an alkaline solution of sodium borohydride to a mixture containing water/isopropyl alcohol, metallic precursors and the Vulcan XC 72 carbon support. The electrocatalysts were characterized by energy dispersive X-ray (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry. The electrochemical oxidation of the alcohols was studied by chronoamperometry using a thin porous coating technique. The mechanism of ethanol electro-oxidation was studied by Fourier Transformed Infrared (FTIR) in situ. The most effective electrocatalysts were tested in alkaline single cells directly fed with methanol, ethanol or ethylene glycol. Preliminary studies showed that the most suitable atomic composition for preparing the ternary catalysts is 50:45:05. Electrochemical data in alkaline medium show that the electrocatalysts PdAuPt/C (50:45:05) showed the better activity for methanol electro oxidation, while PdAuIr/C was the most active for ethanol oxidation and PdAuBi/C (50:45:05) was the most effective for ethylene glycol oxidation in alkaline medium. These results show that the addition of gold in the composition of electrocatalysts increases their catalytic activities. The spectroelectrochemical FTIR in situ data permitted to conclude that C-C bond is not broken and the acetate is formed. (author)

  3. PtRu/C electrocatalysts prepared using electron beam irradiation

    OpenAIRE

    Dionísio Furtunato da Silva; Almir Oliveira Neto; Eddy Segura Pino; Michele Brandalise; Marcelo Linardi; Estevam Vitorio Spinacé

    2007-01-01

    PtRu/C electrocatalysts (carbon-supported PtRu nanoparticles) were prepared submitting water/ethylene glycol mixtures containing Pt(IV) and Ru(III) ions and the carbon support to electron beam irradiation. The electrocatalysts were characterized by energy dispersive X ray analysis (EDX), X ray diffraction (XRD) and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts showed superior performance for methanol electro-oxi...

  4. PtRu/C electrocatalysts prepared using electron beam irradiation

    Directory of Open Access Journals (Sweden)

    Dionísio Furtunato da Silva

    2007-12-01

    Full Text Available PtRu/C electrocatalysts (carbon-supported PtRu nanoparticles were prepared submitting water/ethylene glycol mixtures containing Pt(IV and Ru(III ions and the carbon support to electron beam irradiation. The electrocatalysts were characterized by energy dispersive X ray analysis (EDX, X ray diffraction (XRD and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts showed superior performance for methanol electro-oxidation at room temperature compared to commercial PtRu/C electrocatalyst.

  5. Preparation and electrocatalytic properties of tungsten carbide electrocatalysts

    Institute of Scientific and Technical Information of China (English)

    马淳安; 张文魁; 成旦红; 周邦新

    2002-01-01

    The tungsten carbide(WC) electrocatalysts with definite phase components and high specific surface area were prepared by gas-solid reduction method. The crystal structure, phase components and electrochemical properties of the as-prepared materials were characterized by XRD, BET(Brunauer Emmett and Teller Procedure) and electrochemical test techniques. It is shown that the tungsten carbide catalysts with definite phase components can be obtained by controlling the carburizing conditions including temperature, gas flowing rate and duration time. The electrocatalysts with the major phase of W2C show higher electrocatalytic activity for the hydrogen evolution reaction. The electrocatalysts with the major phase of WC are suitable to be used as the anodic electrocatalyst for hydrogen anodic oxidation, which exhibit higher hydrogen anodic oxidation electrocatalytic properties in HCl solutions.

  6. Palladium-based electrocatalysts and fuel cells employing such electrocatalysts

    Science.gov (United States)

    Masel; Richard I. , Zhu; Yimin , Larsen; Robert T.

    2010-08-31

    A direct organic fuel cell includes a fluid fuel comprising formic acid, an anode having an electrocatalyst comprising palladium nanoparticles, a fluid oxidant, a cathode electrically connected to the anode, and an electrolyte interposed between the anode and the cathode.

  7. Preparation of supported electrocatalyst comprising multiwalled carbon nanotubes

    Science.gov (United States)

    Wu, Gang; Zelenay, Piotr

    2013-08-27

    A process for preparing a durable non-precious metal oxygen reduction electrocatalyst involves heat treatment of a ball-milled mixture of polyaniline and multiwalled carbon nanotubes in the presence of a Fe species. The catalyst is more durable than catalysts that use carbon black supports. Performance degradation was minimal or absent after 500 hours of operation at constant cell voltage of 0.40 V.

  8. Facile electrospinning preparation of phosphorus and nitrogen dual-doped cobalt-based carbon nanofibers as bifunctional electrocatalyst

    Science.gov (United States)

    Wang, Zhuang; Zuo, Pengjian; Fan, Liquan; Han, Jianan; Xiong, Yueping; Yin, Geping

    2016-04-01

    A novel electrochemical catalyst of phosphorus and nitrogen dual-doped cobalt-based carbon nanofibers (Cosbnd Nsbnd P-CNFs) is prepared by a facile and cost-effective electrospinning technique. Excellent features of the porous carbon nanofibers with large amounts of Co atoms, N/P-doping effect, abundant pyridinic-N and Cosbnd Nx clusters as catalytic active sites, and the advantages of the structure and composition result in a high catalytic efficiency. In alkaline or acidic media, Cosbnd Nsbnd P-CNFs exhibits remarkable electrocatalytic activities and kinetics for oxygen reduction reaction (ORR), superior methanol tolerance and stability, and a similar four-electron pathway. In addition, Cosbnd Nsbnd P-CNFs also shows excellent performance for hydrogen evolution reaction (HER), offering a low onset potential of -0.216 V and a stable current density of 10 mA cm-2 at potential of -0.248 V. The mechanism of ORR and HER catalytic active site arises from the doping of N/P atoms in the Co-based CNFs, which is responsible for the excellent electrocatalytic performance. Due to the excellent catalytic efficiencies, Cosbnd Nsbnd P-CNFs act as a promising catalyst material for fuel cells and water splitting technologies.

  9. Platinum-based oxygen reduction electrocatalysts.

    Science.gov (United States)

    Wu, Jianbo; Yang, Hong

    2013-08-20

    An efficient oxygen reduction reaction (ORR) offers the potential for clean energy generation in low-temperature, proton-exchange membrane fuel cells running on hydrogen fuel and air. In the past several years, researchers have developed high-performance electrocatalysts for the ORR to address the obstacles of high cost of the Pt catalyst per kilowatt of output power and of declining catalyst activity over time. Current efforts are focused on new catalyst structures that add a secondary metal to change the d-band center and the surface atomic arrangement of the catalyst, altering the chemisorption of those oxygencontaining species that have the largest impact on the ORR kinetics and improving the catalyst activity and cost effectiveness. This Account reviews recent progress in the design of Pt-based ORR electrocatalysts, including improved understanding of the reaction mechanisms and the development of synthetic methods for producing catalysts with high activity and stability. Researchers have made several types of highly active catalysts, including an extended single crystal surface of Pt and its alloy, bimetallic nanoparticles, and self-supported, low-dimensional nanostructures. We focus on the design and synthetic strategies for ORR catalysts including controlling the shape (or facet) and size of Pt and its bimetallic alloys, and controlling the surface composition and structure of core-shell, monolayer, and hollow porous structures. The strong dependence of ORR performance on facet and size suggests that synthesizing nanocrystals with large, highly reactive {111} facets could be as important, if not more important, to increasing their activity as simply making smaller nanoparticles. A newly developed carbon-monoxide (CO)-assisted reduction method produces Pt bimetallic nanoparticles with controlled facets. This CO-based approach works well to control shapes because of the selective CO binding on different, low-indexed metal surfaces. Post-treatment under

  10. Electrocatalysts with platinum, cobalt and nickel preparations by mechanical alloyed and CVD for the reaction of oxygen reduction; Electrocatalizadores a base de platino, cobalto y niquel preparados por aleado mecanico y CVD para la reaccion de reduccion de oxigeno

    Energy Technology Data Exchange (ETDEWEB)

    Garcia C, M. A. [ININ, 52750 La Marquesa, Estado de Mexico (Mexico)

    2008-07-01

    In this research, the molecular oxygen reduction reaction (ORR) was investigated on electrocatalysts of Co, Ni, Pt and their alloys CoNi, PtCo, PtNi and PtCoNi by using H{sub 2}SO{sub 4} 0.5 and KOH 0.5 M solutions as electrolytes. The electrocatalysts were synthesized by Mechanical Alloying (MA) and Chemical Vapor Deposition (CVD) processes. For MA, metallic powders were processed during 20 h of milling in a high energy SPEX 8000 mill. For CVD, a hot-wall reactor was utilized and Co, Ni and Pt acetilactetonates were used as precursors. Films were deposited at a total pressure of 1 torr and temperatures of 400-450 C. Electrocatalysts were characterized by X-Ray Diffraction (XRD). Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Electrocatalysts prepared by mechanical alloying showed a homogeneously dispersed agglomeration of particles with nano metric size. Electrocatalysts obtained by CVD showed, in some cases, non uniform films, with particles of nano metric size, as well. The electrocatalytic performance was evaluated by using the Rotating Disk Electrode technique (RDE). Electrocatalysts prepared by MA showed higher activity than those obtained by CVD. All electrocatalysts were evaluated in alkaline media. Only electrocatalysts containing Pt were evaluated in acid media, because those materials with Co, Ni and their alloys showed instability in acidic media. Most electrocatalysts followed a mechanism for the ORR producing a certain proportion of H{sub 2}O{sub 2}. All electrocatalysts, exhibited a fair or good electrocatalytic activity in comparison with other similar reported materials. It was found that MA and CVD are appropriate processes to prepare electrocatalysts for the ORR with particles of nano metric size and performing with an acceptable catalytic activity. PtCoNi 70-23-7% by MA and PtCoNi-CVD electrocatalysts showed the highest activity in alkaline media, while in acidic

  11. Preparation and characterization of electrocatalysts based on palladium for electro-oxidation of alcohols in alkaline medium; Preparacao e caracterizacao de eletrocatalisadores a base de paladio para oxidacao eletroquimica de alcoois em meio alcalino

    Energy Technology Data Exchange (ETDEWEB)

    Brandalise, Michele

    2012-07-01

    In this study Pd/C, Au/C, PdAu/C, PdAuPt/C, PdAuBi/C and PdAuIr/C electrocatalysts were prepared by the sodium borohydride reduction method for the electrochemical oxidation of methanol, ethanol and ethylene glycol. This methodology consists in mix an alkaline solution of sodium borohydride to a mixture containing water/isopropyl alcohol, metallic precursors and the Vulcan XC 72 carbon support. The electrocatalysts were characterized by energy dispersive X-ray (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry. The electrochemical oxidation of the alcohols was studied by chronoamperometry using a thin porous coating technique. The mechanism of ethanol electro-oxidation was studied by Fourier Transformed Infrared (FTIR) in situ. The most effective electrocatalysts were tested in alkaline single cells directly fed with methanol, ethanol or ethylene glycol. Preliminary studies showed that the most suitable atomic composition for preparing the ternary catalysts is 50:45:05. Electrochemical data in alkaline medium show that the electrocatalysts PdAuPt/C (50:45:05) showed the better activity for methanol electro oxidation, while PdAuIr/C was the most active for ethanol oxidation and PdAuBi/C (50:45:05) was the most effective for ethylene glycol oxidation in alkaline medium. These results show that the addition of gold in the composition of electrocatalysts increases their catalytic activities. The spectroelectrochemical FTIR in situ data permitted to conclude that C-C bond is not broken and the acetate is formed. (author)

  12. Synthesis and characterization of nanostructured palladium-based alloy electrocatalysts

    Science.gov (United States)

    Sarkar, Arindam

    Low temperature fuel cells like proton exchange membrane fuel cells (PEMFC) are expected to play a crucial role in the future hydrogen economy, especially for transportation applications. These electrochemical devices offer significantly higher efficiency compared to conventional heat engines. However, use of exotic and expensive platinum as the electrocatalyst poses serious problems for commercial viability. In this regard, there is an urgent need to develop low-platinum or non-platinum electrocatalysts with electrocatalytic activity for the oxygen reduction reaction (ORR) superior or comparable to that of platinum. This dissertation first investigates non-platinum, palladium-based alloy electrocatalysts for ORR. Particularly, Pd-M (M = Mo and W) alloys are synthesized by a novel thermal decomposition of organo-metallic precursors. The carbon-supported Pd-M (M = Mo, W) electrocatalyts are then heat treated up to 900°C in H2 atmosphere and investigated for their phase behavior. Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements reveal that the alloying of Pd with Mo or W significantly enhances the catalytic activity for ORR as well as the stability (durability) of the electrocatalysts. Additionally, both the alloy systems exhibit high tolerance to methanol, which is particularly advantageous for direct methanol fuel cells (DMFC). The dissertation then focuses on one-pot synthesis of carbon-supported multi-metallic Pt-Pd-Co nanoalloys by a rapid microwave-assisted solvothermal (MW-ST) method. The multi-metallic alloy compositions synthesized by the MW-ST method show much higher catalytic activity for ORR compared to their counterparts synthesized by the conventional borohydride reduction method. Additionally, a series of Pt encapsulated Pd-Co nanoparticle electrocatalysts are synthesized by the MW-ST method and characterized to understand their phase behavior, surface composition, and electrocatalytic activity for ORR. Finally, the dissertation

  13. Selenide-Based Electrocatalysts and Scaffolds for Water Oxidation Applications

    KAUST Repository

    Xia, Chuan

    2015-11-05

    Selenide-based electrocatalysts and scaffolds on carbon cloth are successfully fabricated and demonstrated for enhanced water oxidation applications. A max­imum current density of 97.5 mA cm−2 at an overpotential of a mere 300 mV and a small Tafel slope of 77 mV dec−1 are achieved, suggesting the potential of these materials to serve as advanced oxygen evolution reaction catalysts.

  14. Métodos de preparação de nanopartículas metálicas suportadas em carbono de alta área superficial, como eletrocatalisadores em células a combustível com membrana trocadora de prótons Methods of preparation of metal nanoparticles supported on high surface area carbon as electrocatalysts in proton exchange membrane fuel cells

    Directory of Open Access Journals (Sweden)

    Estevam V. Spinacé

    2004-08-01

    Full Text Available Fuel cells are attracting much interest as efficient and clean energy conversion devices. The main components of low temperature fuel cells are the electrocatalysts used to promote the anodic and cathodic reactions, which are based on platinum and platinum alloys. These electrocatalysts are normally prepared in the form of metal nanoparticles supported on a conductive material, usually high surface area carbon, to improve catalyst utilization and reduce cost. This work presents and comments some methods used presently to produce these electrocatalysts. The performances of the produced electrocatalysts are compared to that of state-of-the-art commercial E-TEK electrocatalysts.

  15. Electrocatalysts with platinum, cobalt and nickel preparations by mechanical alloyed and CVD for the reaction of oxygen reduction

    International Nuclear Information System (INIS)

    In this research, the molecular oxygen reduction reaction (ORR) was investigated on electrocatalysts of Co, Ni, Pt and their alloys CoNi, PtCo, PtNi and PtCoNi by using H2SO4 0.5 and KOH 0.5 M solutions as electrolytes. The electrocatalysts were synthesized by Mechanical Alloying (MA) and Chemical Vapor Deposition (CVD) processes. For MA, metallic powders were processed during 20 h of milling in a high energy SPEX 8000 mill. For CVD, a hot-wall reactor was utilized and Co, Ni and Pt acetilactetonates were used as precursors. Films were deposited at a total pressure of 1 torr and temperatures of 400-450 C. Electrocatalysts were characterized by X-Ray Diffraction (XRD). Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Electrocatalysts prepared by mechanical alloying showed a homogeneously dispersed agglomeration of particles with nano metric size. Electrocatalysts obtained by CVD showed, in some cases, non uniform films, with particles of nano metric size, as well. The electrocatalytic performance was evaluated by using the Rotating Disk Electrode technique (RDE). Electrocatalysts prepared by MA showed higher activity than those obtained by CVD. All electrocatalysts were evaluated in alkaline media. Only electrocatalysts containing Pt were evaluated in acid media, because those materials with Co, Ni and their alloys showed instability in acidic media. Most electrocatalysts followed a mechanism for the ORR producing a certain proportion of H2O2. All electrocatalysts, exhibited a fair or good electrocatalytic activity in comparison with other similar reported materials. It was found that MA and CVD are appropriate processes to prepare electrocatalysts for the ORR with particles of nano metric size and performing with an acceptable catalytic activity. PtCoNi 70-23-7% by MA and PtCoNi-CVD electrocatalysts showed the highest activity in alkaline media, while in acidic electrolyte PtCoNi 70-8-22% by

  16. CuZn Alloy- Based Electrocatalyst for CO2 Reduction

    KAUST Repository

    Alazmi, Amira

    2014-06-01

    ABSTRACT CuZn Alloy- Based Electrocatalyst for CO2 Reduction Amira Alazmi Carbon dioxide (CO2) is one of the major greenhouse gases and its emission is a significant threat to global economy and sustainability. Efficient CO2 conversion leads to utilization of CO2 as a carbon feedstock, but activating the most stable carbon-based molecule, CO2, is a challenging task. Electrochemical conversion of CO2 is considered to be the beneficial approach to generate carbon-containing fuels directly from CO2, especially when the electronic energy is derived from renewable energies, such as solar, wind, geo-thermal and tidal. To achieve this goal, the development of an efficient electrocatalyst for CO2 reduction is essential. In this thesis, studies on CuZn alloys with heat treatments at different temperatures have been evaluated as electrocatalysts for CO2 reduction. It was found that the catalytic activity of these electrodes was strongly dependent on the thermal oxidation temperature before their use for electrochemical measurements. The polycrystalline CuZn electrode without thermal treatment shows the Faradaic efficiency for CO formation of only 30% at applied potential ~−1.0 V vs. RHE with current density of ~−2.55 mA cm−2. In contrast, the reduction of oxide-based CuZn alloy electrode exhibits 65% Faradaic efficiency for CO at lower applied potential about −1.0 V vs. RHE with current density of −2.55 mA cm−2. Furthermore, stable activity was achieved over several hours of the reduction reaction at the modified electrodes. Based on electrokinetic studies, this improvement could be attributed to further stabilization of the CO2•− on the oxide-based Cu-Zn alloy surface.

  17. A new attitude to environment: Preparation of an efficient electrocatalyst for methanol oxidation based on Ni-doped P zeolite nanoparticles synthesized from stem sweep ash

    International Nuclear Information System (INIS)

    Graphical abstract: - Abstract: Amorphous silica powder was extracted from stem sweep (SS) which grows in the southern parts of the Caspian Sea (Mazandran province, Iran) and used in the preparation of P zeolite nanoparticles. X-ray diffraction, scanning electronic microscopy, transmission electron microscopy and FT-IR techniques were used to characterize P zeolite nanoparticles. SEM and TEM showed the presence of nearly spherical nanoparticles with sizes in the nanometer range. Ni2+ ions could introduced into the pores of P zeolite nanoparticles through exchange with Na+ ions to modify zeolite and improve their electrochemical properties. To surmount the overvoltage of methanol oxidation on carbon paste electrode (CPE), Ni (II)-doped P zeolite (Ni/P) mixed with CPE was used as modified electrode (Ni/P-CPE). Electrochemical techniques such as cyclic voltammetry and chronoamperometry were applied to modified electrode in order to investigate the role of zeolite in electrocatalytic process of methanol oxidation. The current intensity of methanol oxidation increases impressively on Ni/P-CPE in the presence of methanol and in comparison with CPE that means the catalyst can reduce the overvoltage of methanol oxidation. Ni/P nanoparticles provide the active sites on modified electrode to catalyze the oxidation of methanol in alkaline solution. Some parameters such as potential scan rates and methanol concentration investigated to describe the mechanism of catalysis of methanol oxidation on Ni/P. In contrast to some expensive materials such as noble metals, Ni-doped P zeolite play effective role in reduction of methanol oxidation overvoltage by some valuable advantage such as inexpensive and environmentally friend nature and simplicity of preparation

  18. Tungsten based electrocatalyst for fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Christian, Joel B. [OSRAM SYLVANIA Inc., Global Tungsten and Powders R and D, Hawes Street, Towanda, PA 18848 (United States); Materials Science and Engineering, SUNY Binghamton, Binghamton, NY 13902 (United States); Smith, Sean P.E. [OSRAM SYLVANIA Inc., Global Tungsten and Powders R and D, Hawes Street, Towanda, PA 18848 (United States); Whittingham, M. Stanley [Materials Science and Engineering, SUNY Binghamton, Binghamton, NY 13902 (United States); Abruna, Hector D. [Cornell University, Department of Chemistry and Chemical Biology, Ithaca, NY 14653 (United States)

    2007-08-15

    A barrier to the widespread use of fuel cells is their reliance on expensive and scarce platinum and other precious metal catalysts. We present a catalyst for hydrogen oxidation, prepared electrochemically from high-purity aqueous tungstate salt precursors. The 24-electron reduction of ammonium metatungstate ((NH{sub 4}){sub 6}[H{sub 2}W{sub 12}O{sub 40}]) yields a material with electrocatalytic activity towards the oxidation of hydrogen in acid electrolyte which approaches 25% that of platinum. Moreover, the tungstate catalyst is unusually tolerant to CO and H{sub 2}S contaminants in the fuel stream. (author)

  19. Effect of Pt:Sn atomic ratio on the preparation of PtSn/C electrocatalysts using electron beam irradiation

    International Nuclear Information System (INIS)

    PtSn/C electrocatalysts were prepared with Pt:Sn atomic ratios of 3:1, 1:1 and 1:3 in water/2-propanol using electron beam irradiation. The obtained materials were characterized by EDX, XRD and cyclic voltammetry. The ethanol electro-oxidation was studied by chronoamperometry. The XRD diffractograms of the PtSn/C electrocatalysts showed typical face-centered cubic (fcc) structure of platinum and the presence of a SnO2 phase (cassiterite). The mean crystallite sizes of Pt fcc phase was in the range of 3.0-3.5 nm. The PtSn/C electrocatalysts were active for ethanol electro-oxidation at room temperature and the material prepared with Pt:Sn atomic ratio of 1:1 showed the best activity. (author)

  20. Preparation and evaluation of advanced electrocatalysts for phosphoric acid fuel cells

    Science.gov (United States)

    Stonehart, P.; Baris, J.; Hochmuth, J.; Pagliaro, P.

    1981-01-01

    Two cooperative phenomena are required the development of highly efficient porous electrocatalysts: (1) is an increase in the electrocatalytic activity of the catalyst particle; and (2) is the availability of that electrocatalyst particle for the electromechanical reaction. The two processes interact with each other so that improvements in the electrochemical activity must be coupled with improvements in the availability of the electrocatalyst for reaction. Cost effective and highly reactive electrocatalysts were developed. The utilization of the electrocatalyst particles in the porous electrode structures was analyzed. It is shown that a large percentage of the electrocatalyst in anode structures is not utilized. This low utilization translates directly into a noble metal cost penalty for the fuel cell.

  1. Structure-activity relationship in high-performance iron-based electrocatalysts for oxygen reduction reaction

    Science.gov (United States)

    Song, Ping; Wang, Ying; Pan, Jing; Xu, Weilin; Zhuang, Lin

    2015-12-01

    A sustainable Iron (Fe), Nitrogen (N) co-doped high performance Fe-Nx/C electrocatalyst for oxygen reduction reaction (ORR) is synthesized simply based on nitric acid oxidation of cheap carbon black. The obtained optimal nonprecious metal electrocatalyst shows high ORR performance in both alkaline and acidic conditions and possesses appreciable performance/price ratio due to its low cost. Furthermore, the structure-activity relationship of different active sites on Fe-Nx/C is revealed systematically: Fe-N4/2-C > Fe4-N-C > N-C >> Fe4-C ≥ C, from both experimental and theoretical points of view.

  2. Carbon-based electrocatalysts for advanced energy conversion and storage

    OpenAIRE

    Zhang, Jintao; Xia, Zhenhai; Dai, Liming

    2015-01-01

    Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play curial roles in electrochemical energy conversion and storage, including fuel cells and metal-air batteries. Having rich multidimensional nanoarchitectures [for example, zero-dimensional (0D) fullerenes, 1D carbon nanotubes, 2D graphene, and 3D graphite] with tunable electronic and surface characteristics, various carbon nanomaterials have been demonstrated to act as efficient metal-free electrocatalysts for ORR and OER ...

  3. A novel electroless method to prepare a platinum electrocatalyst on diamond for fuel cell applications

    Science.gov (United States)

    Lyu, Xiao; Hu, Jingping; Foord, John S.; Wang, Qiang

    2013-11-01

    A novel electroless deposition method was demonstrated to prepare a platinum electrocatalyst on boron doped diamond (BDD) substrates without the need for pre-activation. This green method addresses the uniformity and particle size issues associated with electrodeposition and circumvents the pre-activation procedure which is necessary for conventional electroless deposition. The inert BDD substrate formed a galvanic couple with an iron wire, to overcome the activation barrier associated with conventional electroless deposition on diamond, leading to the formation of Pt nanoparticles on the electrode surface in a galvanic process coupled to a chemical process. When sodium hypophosphite was employed as the reducing agent to drive the electroless reaction Pt deposits which were contaminated with iron and phosphorus resulted. In contrast, the reducing agent ascorbic acid gave rise to high purity Pt nanoparticles. Optimal deposition conditions with respect to bath temperature, pH value and stabilizing additives are identified. Using this approach, high purity and uniformly distributed platinum nanoparticles are obtained on the diamond electrode surface, which demonstrate a high electrochemical activity towards methanol oxidation.

  4. Highly dispersed TaOx nanoparticles prepared by electrodeposition as oxygen reduction electrocatalysts for polymer electrolyte fuel cells

    KAUST Repository

    Seo, Jeongsuk

    2013-06-06

    Based on the chemical stability of group IV and V elements in acidic solutions, TaOx nanoparticles prepared by electrodeposition in an ethanol-based Ta plating bath at room temperature were investigated as novel nonplatinum electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs). Electrodeposition conditions of Ta complexes and subsequent various heat treatments for the deposited TaOx were examined for the best performance of the ORR. TaOx particles on carbon black (CB), electrodeposited at a constant potential of -0.5 V Ag/AgCl for 10 s and then heat-treated by pure H2 flow at 523 K for 1 h, showed excellent catalytic activity with an onset potential of 0.93 VRHE (for 2 μA cm-2) for the ORR. Surface characterizations of the catalysts were performed by scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The loading amounts of the electrodeposited material on the CB were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). All the physical results suggested that high dispersion of TaOx particles on the CB surface with 2-3 nm size was critical and key for high activity. The chemical identity and modified surface structure for the deposited TaOx catalysts before and after H 2 heat treatment were analyzed by X-ray photoelectron spectroscopy (XPS). The formation of more exposed active sites on the electrode surface and enhanced electroconductivity of the tantalum oxide promoted from the H 2 treatment greatly improved the ORR performance of the electrodeposited TaOx nanoparticles on CB. Finally, the highly retained ORR activity after an accelerated durability test in an acidic solution confirmed and proved the chemical stability of the oxide nanoparticles. The high utilization of the electrodeposited TaOx nanoparticles uniformly dispersed on CB for the ORR was comparable to that of commercial Pt/CB catalysts

  5. Preparation of highly active and stable polyaniline-cobalt-carbon nanotube electrocatalyst for oxygen reduction reaction in polymer electrolyte membrane fuel cell

    International Nuclear Information System (INIS)

    This paper established an in-situ synthesis strategy that the mixing solution of aniline, CNTs and CoCl2 was directly reduced to prepare polyaniline-cobalt-carbon nanotube (PANI-Co-CNT) electrocatalyst. Furthermore, this strategy was effectively modified by pretreating CoCl2 precursor with citric acid (CA), forming 2-4 nm cobalt nanoparticles uniformly distributed on PANI-CNT support with porous structure. The control experiments revealed various PANI states in the growth stage, further proposing the self-assembly mechanisms in these two routes with and without CA pretreatment. These two PANI-Co-CNT electrocatalysts were also checked by oxygen reduction reaction (ORR) in acid environment, to corroborate their basically 4-electron processes. Inspiringly, the large activity and stability for the pretreated route could be comparable with those of the advanced electrocatalysts. All these progresses lay a bottom-up approach for future electrocatalysts

  6. Glycerol electro-oxidation in alkaline medium using Pd/C and PdSn/C electrocatalysts prepared by electron beam irradiation

    International Nuclear Information System (INIS)

    Carbon-supported metal nanoparticles were prepared for fuel cell applications by radiation-induced reduction of metal ions precursors. Pd/C and PdSn/C electrocatalysts (Pd:Sn atomic ratio 90:10), prepared by using electron beam irradiation, were tested for glycerol electro-oxidation in single alkaline direct glycerol fuel cell (ADGFC). EDX analysis showed that the Pd:Sn atomic ratio is very similar to the nominal one. X-ray diffractograms of PdSn/C electrocatalyst showed the presence of Pd (fcc) phase. Cyclic voltammetry (CV) indicated that Pd/C and PdSn/C electrocatalysts have good activity for glycerol electro-oxidation, at room temperature. Experiments with single ADGFC were carried out from 60 to 90 deg C, using Pd/C and PdSn/C electrocatalysts and glycerol 2.0 mol.L-1, as fuel. The best performance was obtained at 85 deg C, for both electrocatalysts. The Pd/C and PdSn/C electrocatalysts showed similar performance (34 mW cm-2), at 85 deg C. (author)

  7. Glycerol electro-oxidation in alkaline medium using Pd/C and PdSn/C electrocatalysts prepared by electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Geraldes, Adriana Napoleao; Silva, Dionisio Fortunato da; Pino, Eddy Segura; Spinace, Estevan Vitorio; Oliveira Neto, Almir; Linardi, Marcelo, E-mail: drinager@ig.com.br, E-mail: dfsilva@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Santos, Mauro Coelhos dos [Universidade Federal do ABC (LEMN/UFABC), Santo Andre, SP (Brazil)

    2013-07-01

    Carbon-supported metal nanoparticles were prepared for fuel cell applications by radiation-induced reduction of metal ions precursors. Pd/C and PdSn/C electrocatalysts (Pd:Sn atomic ratio 90:10), prepared by using electron beam irradiation, were tested for glycerol electro-oxidation in single alkaline direct glycerol fuel cell (ADGFC). EDX analysis showed that the Pd:Sn atomic ratio is very similar to the nominal one. X-ray diffractograms of PdSn/C electrocatalyst showed the presence of Pd (fcc) phase. Cyclic voltammetry (CV) indicated that Pd/C and PdSn/C electrocatalysts have good activity for glycerol electro-oxidation, at room temperature. Experiments with single ADGFC were carried out from 60 to 90 deg C, using Pd/C and PdSn/C electrocatalysts and glycerol 2.0 mol.L{sup -1}, as fuel. The best performance was obtained at 85 deg C, for both electrocatalysts. The Pd/C and PdSn/C electrocatalysts showed similar performance (34 mW cm{sup -2}), at 85 deg C. (author)

  8. Ethanol electro-oxidation in alkaline medium using Pd/MWCNT and PdAuSn/MWCNT electrocatalysts prepared by electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Geraldes, Adriana Napoleao; Silva, Dionisio Furtunato da; Andrade e Silva, Leonardo Gondin de; Spinace, Estevam Vitorio; Oliveira Neto, Almir, E-mail: drinager@ig.com.br, E-mail: dfsilva@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Santos, Mauro Coelho dos [Universidade Federal do ABC (LEMN/CCNH/UFABC), Santo Andre, SP (Brazil)

    2015-07-01

    Environmental problems and the world growing demand for energy has mobilized the scientific community in finding of clean and renewable energy sources. In this context, fuel cells appear as appropriate technology for generating electricity through alcohols electro-oxidation. Multi Wall Carbon Nanotubes (MWCNT)-supported Pd and trimetallic PdAuSn (Pd:Au:Sn 50:10:40 atomic ratio) electrocatalysts were prepared using electron beam irradiation. The obtained materials were characterized by VC, Chronoamperometry, EDX, TEM and XRD. The catalytic activities of electrocatalysts toward ethanol electro-oxidation were evaluated in alkaline medium in a single alkaline direct ethanol fuel cell (ADEFC) in a range temperature 60 to 90 deg C. The best performances were obtained at 85 deg C: 33 mW.cm{sup -2} and 31 mW.cm{sup -2} for Pd/ MWCNT and PdAuSn/MWCNT electrocatalysts, respectively. X-ray diffractograms of electrocatalysts showed the presence of Pd-rich (fcc) and Au-rich (fcc) phases. Cyclic voltammetry and chronoamperometry experiments showed that PdAuSn/MWCNT electrocatalyst demonstrated similar activity toward ethanol electro-oxidation at room temperature, compared to electrocatalyst Pd/MWCNT. (author)

  9. Ethanol electro-oxidation in alkaline medium using Pd/c and PdRh/C electrocatalysts prepared by electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio Furtunato da; Geraldes, Adriana Napoleao; Pino, Eddy Segura; Spinace, Estevam Vitorio; Oliveira Neto, Almir; Linardi, Marcelo, E-mail: dfsilva@ipen.br, E-mail: drinager@ig.com.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    In this study, carbon-supported Pd (Pd/C) and bimetallic PdRh (Pd:Rh 90:10 atomic ratio) (PdRh/C) electrocatalysts were prepared using electron beam irradiation. The morphology and composition of the obtained materials were characterized by Cyclic voltammetry (VC), Chronoamperometry (CA), Energy dispersive X-ray (EDX), X-ray Diffraction (XRD) and Thermo-gravimetric analysis (TGA). The catalytic activities of the electrocatalysts toward the ethanol electro-oxidation were evaluated in alkaline medium in a single alkaline direct ethanol fuel cell (ADEFC), in a range temperature of 50 to 85 deg C. The best performances were obtained at 85 deg C (25 mW.cm{sup -2}) and 75 deg C (38 mW.cm{sup -2}) for Pd/C and PdRh/C electrocatalysts, respectively. The XRD of the PdRh/C electrocatalyst showed the presence of Pd-rich (fcc) phase. CV and CA experiments showed that PdRh/C electrocatalyst demonstrated superior activity toward ethanol electro-oxidation at room temperature, compared to Pd/C electrocatalyst. (author)

  10. Binary and ternary palladium based electrocatalysts for alkaline direct glycerol fuel cell

    Science.gov (United States)

    Geraldes, Adriana Napoleão; da Silva, Dionisio Furtunato; e Silva, Leonardo Gondim de Andrade; Spinacé, Estevam Vitório; Neto, Almir Oliveira; dos Santos, Mauro Coelho

    2015-10-01

    Pd/C, PdAu/C 50:50, PdSn/C 50:50, PdAuSn/C 50:40:10 and PdAuSn/C 50:10:40 electrocatalysts are prepared using an electron beam irradiation reduction method and tested for glycerol electro-oxidation in alkaline medium. X-Ray diffraction (XRD), Energy dispersive X-ray analysis (EDX), Transmission electron Microscopy (TEM) and Cyclic Voltammetry (CV) are used to characterize the resulting materials. The activity for glycerol electro-oxidation is tested in alkaline medium at room temperature using Cyclic Voltammetry and Chronoamperometry (CA) and in a single alkaline direct glycerol fuel cell (ADGFC) at temperature range of 60-90 °C. EDX analysis demonstrate that Pd:Au:Sn atomic ratios are very similar to the nominal ones. X-ray diffractograms of PdAuSn/C electrocatalysts evidence the presence of Pd (fcc), Au (fcc) and SnO2 phases. TEM analysis demonstrates a good dispersion of the nanoparticles on the carbon support with some agglomerates. Cyclic Voltammetry experiments suggest that PdAuSn/C electrocatalysts demonstrate better results. In single fuel cell tests, at 85 °C, using 2.0 mol L-1 glycerol in 2.0 mol L-1 KOH solutions, the electrocatalyst PdAuSn/C 50:40:10 demonstrate highest power density (51 mW cm-2) and the 120 h durability tests demonstrate a 210 μV h-1 degradation rate.

  11. Carbon supported nanoparticles Pt Ru (Pt Ru/C electrocatalysts) prepared using electron beam irradiation; Preparacao de nanoparticulas de PtRu suportadas em carbono (eletrocatalisadores PtRu/C) utilizando feixe de eletrons

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio F. da; Oliveira Neto, Almir; Pino, Eddy S.; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Programa de Celulas a Combustivel], e-mail: espinace@ipen.br, e-mail: dfsilva@ipen.br

    2006-07-01

    Carbon-supported Pt Ru (electrocatalysts PtRu/C nanoparticles) were prepared submitting a water/ethylene glycol mixture containing Pt(IV) and Ru(III) ions and the carbon support to electron beam irradiation. The PtRu/C electrocatalysts were characterized by EDX, XRD and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts were more active for methanol electro-oxidation than the commercial PtRu/C ETEK electrocatalyst at ambient temperature. (author)

  12. Synthesis and characterization of nanostructured electrocatalysts based on nickel and tin for hydrogen peroxide electrogeneration

    International Nuclear Information System (INIS)

    Highlights: • 9% SnNi/C 6:1 was the best choice for H2O2 electrogeneration among all materials. • 9% SnNi/C 6:1 transferred 2.2 electrons and had a H2O2 percentage efficiency of 88%. • X-ray diffraction analysis identified a phase for 9% SnNi/C 6:1 (Ni3Sn4). • Ni3Sn4 is a structure tolerant of defects that can increase oxygen diffusion. -- Abstract: This work describes both the preparation and the characterization of nanostructured materials based on tin and nickel. Composite materials of SnNi/C were prepared by the polymeric precursor method and were supported on Vulcan XC-72R, which is a high surface area carbon, for a comparative study. Three proportions on carbon were evaluated: 6%, 9% and 13%. Binary materials were prepared varying the atomic ratios of Sn and Ni at 6:1, 3:1, 1:1, 1:3 and 1:6 for each percentage composition tested. The materials were characterized by X-ray diffraction to determine the mean crystallites sizes of the important phases for the catalytic process, such as Ni3Sn, Ni3Sn2 and Ni3Sn4, and by energy dispersive spectroscopy (EDS) measurements to determine the percentage composition of the material with highest catalytic activity. The results showed that the binary material prepared with 9% metal load at a ratio of 6:1 Sn:Ni was the best material for H2O2 electrogeneration. This material showed the highest ring current, which was a consequence of the highest amount of H2O2 production having a ring current higher than that obtained for the ORR for Vulcan carbon. The best electrocatalyst transferred 2.2 electrons in the ORR with an 88% yield of H2O2, while the Vulcan carbon, which is the reference material for the 2-electron transfer reaction, produced just a 63% yield of H2O2. Thus, based on these results, 9% Sn:Ni (6:1) is a promising material to be used in H2O2 electrogeneration and in AOPs. This result is likely due to the presence of acid oxygen-containing species on carbon and to the large defect concentration in Ni3Sn4 lattice

  13. Optical measurements of platinum based electrocatalysts for the electrooxidation of methanol

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, K. [Institute for Analytical and Chemical Technologies, Department of Electrochemistry, Vienna University of Technology, A-1060 Vienna (Austria); Kronberger, H.; Fafilek, G. [ECHEM Centre of Competence in Applied Electrochemistry, Wiener Neustadt (Austria); Institute for Analytical and Chemical Technologies, Department of Electrochemistry, Vienna University of Technology, A-1060 Vienna (Austria); Nauer, G. [ECHEM Centre of Competence in Applied Electrochemistry, Wiener Neustadt (Austria); Institute of Physical Chemistry, University of Vienna, Vienna (Austria); Besenhard, J.O. [ECHEM Centre of Competence in Applied Electrochemistry, Wiener Neustadt (Austria); Institute of Chemical Technology of Inorganic Materials, Graz University of Technology, Graz (Austria)

    2003-08-01

    In a combinatorial electrochemistry experiment quinine was used as a pH sensitive fluorescing indicator to detect the catalytic activity of methanol oxidation catalysts. During electrochemical experiments the surface of the electrode array was monitored with a CCD camera. The dependence of the intensity of the fluorescence on the applied potential was used as an analytical tool; to investigate the electrochemical performance of Pt based electrocatalysts, for the electrooxidation of methanol, in both short and long term tests. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  14. A DFT-based genetic algorithm search for AuCu nanoalloy electrocatalysts for CO2 reduction

    DEFF Research Database (Denmark)

    Lysgaard, Steen; Mýrdal, Jón Steinar Garðarsson; Hansen, Heine Anton;

    2015-01-01

    Using a DFT-based genetic algorithm (GA) approach, we have determined the most stable structure and stoichiometry of a 309-atom icosahedral AuCu nanoalloy, for potential use as an electrocatalyst for CO2 reduction. The identified core–shell nano-particle consists of a copper core interspersed...

  15. Metallated porphyrin based porous organic polymers as efficient electrocatalysts

    Science.gov (United States)

    Lu, Guolong; Zhu, Youlong; Xu, Kongliang; Jin, Yinghua; Ren, Zhiyong Jason; Liu, Zhenning; Zhang, Wei

    2015-10-01

    Developing efficient, stable and low-cost catalysts for Oxygen Reduction Reaction (ORR) is of great significance to many emerging technologies including fuel cells and metal-air batteries. Herein, we report the development of a cobalt(ii) porphyrin based porous organic polymer (CoPOP) and its pyrolyzed derivatives as highly active ORR catalysts. The as-synthesized CoPOP exhibits high porosity and excellent catalytic performance stability, retaining ~100% constant ORR current over 50 000 s in both alkaline and acidic media. Pyrolysis of CoPOP at various temperatures (600 °C, 800 °C, and 1000 °C) yields the materials consisting of graphitic carbon layers and cobalt nanoparticles, which show greatly enhanced catalytic activity compared to the as-synthesized CoPOP. Among them, CoPOP-800/C pyrolyzed at 800 °C shows the highest specific surface area and ORR activity, displaying the most positive half-wave potential (0.825 V vs. RHE) and the largest limited diffusion current density (5.35 mA cm-2) in an alkaline medium, which are comparable to those of commercial Pt/C (20 wt%) (half-wave potential 0.829 V vs. RHE, limited diffusion current density 5.10 mA cm-2). RDE and RRDE experiments indicate that CoPOP-800/C directly reduces molecular oxygen to water through a 4-e- pathway in both alkaline and acidic media. More importantly, CoPOP-800/C exhibits excellent durability and methanol-tolerance under acidic and alkaline conditions, which surpass the Pt/C (20 wt%) system.Developing efficient, stable and low-cost catalysts for Oxygen Reduction Reaction (ORR) is of great significance to many emerging technologies including fuel cells and metal-air batteries. Herein, we report the development of a cobalt(ii) porphyrin based porous organic polymer (CoPOP) and its pyrolyzed derivatives as highly active ORR catalysts. The as-synthesized CoPOP exhibits high porosity and excellent catalytic performance stability, retaining ~100% constant ORR current over 50 000 s in both

  16. Preparation of PtSnCu/C and PtSn/C electrocatalysts and activation by dealloying processes for ethanol electrooxidation

    International Nuclear Information System (INIS)

    PtSnCu/C (with different Pt:Sn:Cu atomic ratios) and PtSn/C (50:50) electrocatalysts were prepared by borohydride (BR) and alcohol-reduction (AR) processes using H2PtCl6.6H2O, SnCl2.2H2O and CuCl2.2H2O as metal sources, NaBH4 and ethylene glycol as reducing agents, 2-propanol and ethylene glycol/water as solvents and carbon black as support. In a further step, these electrocatalysts were activated by chemical (CD) and electrochemical (ED) dealloying processes through acid treatment and thin porous coating technique, respectively. These materials were characterized by energy dispersive X-ray, Xray diffraction, transmission electron microscopy, line scan energy dispersive Xray and cyclic voltammetry. Electrochemical studies for ethanol electro-oxidation were performed by cyclic voltammetry, chronoamperometry and in single Direct Ethanol Fuel Cell using Membrane Electrode Assembly (MEA). The anodic effluents were analysed by gas chromatography. The X-ray diffractograms of the as-synthesized electrocatalysts showed the typical face-centered cubic structure (FCC) of platinum and its alloys. After dealloying, the X-ray diffractograms showed that the Pt FCC structure was preserved. The crystallite sizes of the assynthesized electrocatalysts were in the range of PtSnCu/C (50:40:10) AR/ED > PtSnCu/C (50:10:40) BR/CD. PtSn/C (50:50) BR/CD, PtSnCu/C (50:10:40) BR/CD, PtSnCu/C (50:40:10) AR/CD electrocatalysts and Pt/C BASF, PtSn/C (75:25) BASF commercial electrocatalysts were tested in single Direct Ethanol Fuel Cell. The results showed the following performance for ethanol electro-oxidation: PtSn/C (50:50) BR/CD > PtSnCu/C (50:40:10) AR/CD > PtSnCu/C > PtSn/C (75:25) BASF > PtSnCu/C (50:10:40) BR/CD > Pt/C BASF. (author)

  17. Oxygen Reduction Electrocatalysts Based on Coupled Iron Nitride Nanoparticles with Nitrogen-Doped Carbon

    Directory of Open Access Journals (Sweden)

    Min Jung Park

    2016-06-01

    Full Text Available Aimed at developing a highly active and stable non-precious metal electrocatalyst for oxygen reduction reaction (ORR, a novel FexNy/NC nanocomposite—that is composed of highly dispersed iron nitride nanoparticles supported on nitrogen-doped carbon (NC—was prepared by pyrolyzing carbon black with an iron-containing precursor in an NH3 atmosphere. The influence of the various synthetic parameters such as the Fe precursor, Fe content, pyrolysis temperature and pyrolysis time on ORR performance of the prepared iron nitride nanoparticles was investigated. The formed phases were determined by experimental and simulated X-ray diffraction (XRD of numerous iron nitride species. We found that Fe3N phase creates superactive non-metallic catalytic sites for ORR that are more active than those of the constituents. The optimized Fe3N/NC nanocomposite exhibited excellent ORR activity and a direct four-electron pathway in alkaline solution. Furthermore, the hybrid material showed outstanding catalytic durability in alkaline electrolyte, even after 4,000 potential cycles.

  18. One-step preparation of optically transparent Ni-Fe oxide film electrocatalyst for oxygen evolution reaction

    International Nuclear Information System (INIS)

    Graphical abstract: The optically transparent Ni-Fe oxide films are deposited on FTO substrates by one-step reactive magnetron co-sputtering. The optimal electrocatalytic activity for oxygen evolution reaction is achieved at an atomic ratio of Fe/Ni = 3:7, which is a very promising cocatalyst for photoelectrochemical water splitting owing to its optical transparency and high electrochemical activity. Display Omitted -- Abstract: Optically transparent cocatalyst film materials is very desirable for improved photoelectrochemical (PEC) oxygen evolution reaction (OER) over light harvesting photoelectrodes which require the exciting light to irradiate through the cocatalyst side, i.e., front-side illumination. In view of the reaction overpotential at electrode/electrolyte interface, the OER electrocatalysts have been extensively used as cocatalysts for PEC water oxidation on photoanode. In this work, the feasibility of a one-step fabrication of the transparent thin film catalyst for efficient electrochemical OER is investigated. The Ni-Fe bimetal oxide films, ∼ 200 nm in thickness, are used for study. Using a reactive magnetron co-sputtering technique, transparent (> 50% in wavelength range 500-2000 nm) Ni-Fe oxide films with high electrocatalytic activities were successfully prepared at room temperature. Upon optimization, the as-prepared bimetal oxide film with atomic ratio of Fe/Ni = 3:7 demonstrates the lowest overpotential for the OER in aqueous KOH solution, as low as 329 mV at current density of 2 mA cm−2, which is 135 and 108 mV lower than that of as-sputtered FeOx and NiOx thin films, respectively. It appears that this fabrication strategy is very promising to deposit optically transparent cocatalyst films on photoabsorbers for efficient PEC water splitting

  19. Preparation and physical/electrochemical characterization of Pt/poly(vinylferrocenium) electrocatalyst for methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Celebi, Mutlu Soenmez; Pekmez, Kadir; Oezyoeruek, Haluk; Yildiz, Attila [Hacettepe University, Faculty of Science, Department of Chemistry, 06532 Ankara (Turkey)

    2008-08-15

    Preparation and characterization of a platinum (Pt)-based catalyst using a redox polymer, poly(vinylferrocenium) (PVF{sup +}), as the support material was described. Pt was obtained from aqueous solution of K{sub 2}PtCl{sub 4} in the complex form. Pt particles were reduced by chemical and electrochemical means. Chemical reduction was performed using aqueous hydrazine solution and electrochemical reduction was carried out in H{sub 2}SO{sub 4} solution. The Pt/PVF{sup +} catalyst system showed catalytic activity towards methanol oxidation. Cyclic voltammetry was used for the electrochemical characterization of the catalyst system. Scanning electron microscopy (SEM) images and energy dispersive X-ray spectrum (EDS) of the catalyst system were also recorded. The system was tested in a single fuel cell configuration at ambient temperature and atmospheric pressure. The open circuit voltage (OCV) was 680 mV for the system and the maximum power density was 0.31 mW cm{sup -2} at a current density of 0.63 mA cm{sup -2}. Catalytic activity of Pt/PVF{sup +} system towards methanol oxidation was comparable with the related catalysts in the literature. (author)

  20. Investigation of nano Pt and Pt-based alloys electrocatalysts for direct methanol fuel cells and their properties

    Directory of Open Access Journals (Sweden)

    Chunguang Suo

    2014-03-01

    Full Text Available The electrocatalysts used in micro direct methanol fuel cell (μDMFC, such as Pt/C and Pt alloy/C, prepared by liquid-phase NaBH4 reduction method have been investigated. XC-72 (Cobalt corp. Company, U.S.A is chosen as the activated carrier for the electrocatalysts to keep the catalysts powder in the range of several nanometers. The XRD, SEM, EDX analyses indicated that the catalysts had small particle size in several nanometers, in excellent dispersed phase and the molar ratio of the precious metals was found to be optimal. The performances of the DMFCs using cathodic catalyst with Pt percentage of 30wt% and different anodic catalysts (Pt-Ru, Pt-Ru-Mo were tested. The polarization curves and power density curves of the cells were measured to determine the optimal alloy composition and condition for the electrocatalysts. The results showed that the micro direct methanol fuel cell with 30wt% Pt/C as the cathodic catalyst and n(Pt:n(Ru:n(Mo = 3:2:2 PtRuMo/C as the anodic catalyst at room temperature using 2.0mol/L methanol solution has the best performances.

  1. Novel osmium-based electrocatalysts for oxygen reduction and hydrogen oxidation in acid conditions

    Energy Technology Data Exchange (ETDEWEB)

    Uribe-Godinez, J.; Borja-Arco, E.; Altamirano-Gutierrez, A.; Jimenez-Sandoval, O. [Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional (Cinvestav), Unidad Queretaro, Apartado Postal 1-798, Queretaro, Qro. 76001 (Mexico); Castellanos, R.H. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada-Queretaro, Av. Cerro Blanco No. 141, Col. Colinas del Cimatario, Queretaro, Qro. 76090 (Mexico)

    2008-03-01

    In this work, novel osmium electrocatalysts for oxygen reduction and hydrogen oxidation in 0.5 M H{sub 2}SO{sub 4}, have been developed. The syntheses were performed by thermolysis of Os{sub 3}(CO){sub 12} and Os{sub 3}(CO){sub 12}/Vulcan {sup registered}, in two reaction media, N{sub 2} (in the absence of solvents) and n-octane, in order to evaluate the effect of these parameters on the electrocatalytic activity of the new materials. In the solvent-free pathway, different reaction temperatures (in the 120-320 C range) and times (5, 7 and 10 h) were explored; the syntheses in n-octane were done at reflux temperature, for 30 and 72 h. The products were characterized structurally by FT-IR spectroscopy, X-ray diffraction and scanning electron microscopy, and electrochemically by room temperature rotating disk electrode measurements, using cyclic and linear sweep voltammetry. Some materials prepared in both reaction media can efficiently perform the hydrogen oxidation and/or oxygen reduction reaction, i.e. those prepared by pyrolysis of Os{sub 3}(CO){sub 12}/Vulcan {sup registered} in N{sub 2}, at 180 C/7 h, 320 C/5 h, 320 C/7 h and 320 C/10 h, as well as the materials synthesized in n-octane (from both Os precursors); the latter, in addition, have the important property of being tolerant to carbon monoxide to some extent, in contrast to platinum, which is easily deactivated even by traces of CO. (author)

  2. Preparation of PtRu/C anode electrocatalysts using gamma radiation for methanol electro-oxidation; Preparacao de eletrocatalisadores PtRu/C utilizando radiacao gama para aplicacao como anodo na oxidacao direta de metanol

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio Fortunato da

    2006-07-01

    Pt Ru/C (carbon-supported Pt Ru nanoparticles) anode electrocatalysts were prepared using radiolytic process (gamma radiation) and tested for methanol electro-oxidation. In this process, water/2-propanol and water/ethylene glycol solutions containing the metallic ions and the carbon support were submitted to gamma radiation under stirring. The water/alcohol ratio (v/v) and the total dose (kGy) were studied. A nominal Pt Ru atomic ratio of 50:50 were used in all experiments. The electrocatalysts were characterized by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry (CV). The electro-oxidation of methanol was studied by cyclic voltammetry using the thin porous coating technique. The electrocatalysts prepared in water/2-propanol showed crystallite size in the range of 3-5 nm and Pt Ru atomic ratio of 50:50. The electrocatalysts prepared in water/ethylene glycol showed crystallite size (2-3 nm) smaller than the ones obtained in water/2-propanol, however, the Pt Ru atomic ratios obtained were approximately 80:20, showing that only part of ruthenium ions were reduced. For methanol oxidation the electrocatalytic activity depends on the water/2-propanol and water/ethylene glycol ratio used in the reaction medium. The electrocatalysts prepared in water/2-propanol showed inferior performance to the ones prepared in water/ethylene glycol, which showed similar or superior performances (amperes per gram of platinum) to the commercial electrocatalyst from E-TEK. (author)

  3. Fundamental study of nanostructured electro-catalysts with reduced noble metal content for PEM based water electrolysis

    Science.gov (United States)

    Kadakia, Sandeep Karan

    Identification and development of non-noble metal based electro-catalysts or electro-catalysts with significant reduction of expensive noble metal contents (E.g. IrO2, Pt) with comparable electrochemical performance as the standard noble metal/metal oxide for proton exchange membrane (PEM) based water electrolysis would constitute a major breakthrough in the generation of hydrogen by water electrolysis. Accomplishing such a system would not only result reduction of the overall capital costs of PEM based water electrolyzers, but also help attain the targeted hydrogen production cost [oxygen evolution reaction (OER) in PEM based water electrolysis. Furthermore, corrosion resistant SnO2 and NbO 2 support has been doped with F and coupled with IrO2 or RuO2 for use as an OER electro-catalyst. A solid solution of SnO 2:F or NbO2:F with only 20 - 30 mol.% IrO2 or RuO2 yielding a rutile structure in the form of thin films and bulk nanoparticles displays similar electrochemical activity and stability as pure IrO2/RuO2. This would lead to more than 70 mol.% reduction in the noble metal oxide content. Novel nanostructured ternary (Ir,Sn,Nb)O 2 thin films of different compositions have also been studied. It has been shown that (Ir0.40Sn0.30Nb 0.30)O2 shows similar electrochemical activity and enhanced chemical robustness as compared to pure IrO2. F doping of the ternary (Ir,Sn,Nb)O2 catalyst helps in further decreasing the noble metal oxide content of the catalyst. As a result, these reduced noble metal oxide catalyst systems would potentially be preferred as OER electro-catalysts for PEM electrolysis. The excellent performance of the catalysts coupled with its robustness would make them great candidates for contributing to significant reduction in the overall capital costs of PEM based water electrolyzers. This thesis provides a detailed fundamental study of the synthesis, materials, characterization, theoretical studies and detailed electrochemical response and potential

  4. Preparation of supported PtRu/C electrocatalyst for direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Luhua [Direct Alcohol Fuel Cell Laboratory, Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, CAS (China); Sun Gongquan [Direct Alcohol Fuel Cell Laboratory, Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, CAS (China); Zhao Xinsheng [Direct Alcohol Fuel Cell Laboratory, Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, CAS (China); Zhou Zhenhua [Headwater NanoKinetix Inc. (United States); Yan Shiyou [Direct Alcohol Fuel Cell Laboratory, Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, CAS (China); Tang Shuihua [Direct Alcohol Fuel Cell Laboratory, Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, CAS (China); Wang Guoxiong [Direct Alcohol Fuel Cell Laboratory, Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, CAS (China); Zhou Bing [Headwater NanoKinetix Inc. (United States); Xin Qin [Direct Alcohol Fuel Cell Laboratory, Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, CAS (China) and State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, CAS (China)]. E-mail: xinqin@dicp.ac.cn

    2005-04-15

    In this work, high-surface supported PtRu/C were prepared with Ru(NO)(NO{sub 3}){sub 3} and [Pt(H{sub 2}NCH{sub 2}CH{sub 2}NH{sub 2}){sub 2}]Cl{sub 2} as the precursors and hydrogen as a reducing agent. XRD and TEM analyses showed that the PtRu/C catalysts with different loadings possessed small and homogeneous metal particles. Even at high metal loading (40 wt.% Pt, 20 wt.% Ru) the mean metal particle size is less than 4 nm. Meanwhile, the calculated Pt crystalline lattice parameter and Pt (2 2 0) peak position indicated that the geometric structure of Pt was modified by Ru atoms. Among the prepared catalysts, the lattice parameter of 40-20 wt.% PtRu/C contract most. Cyclic voltammetry (CV), chronoamperometry (CA), CO stripping and single direct methanol fuel cell tests jointly suggested that the 40-20 wt.% PtRu/C catalyst has the highest electrochemical activity for methanol oxidation00.

  5. Application of green chemistry techniques to prepare electrocatalysts for direct methanol fuel cells.

    Science.gov (United States)

    Shimizu, Kenichi; Wang, Joanna S; Wai, Chien M

    2010-03-25

    A series of green techniques for synthesizing carbon nanotube-supported platinum nanoparticles and their high electrocatalytic activity toward methanol fuel cell applications are reported. The techniques utilize either the supercritical fluid carbon dioxide or water as a medium for depositing platinum nanoparticles on surfaces of multiwalled or single-walled carbon nanotubes. The catalytic properties of the carbon nanotubes-supported Pt nanoparticle catalysts prepared by four different techniques are compared for anodic oxidation of methanol and cathodic reduction of oxygen using cyclic voltammetry. One technique using galvanic exchange of Pt(2+) in water with zerovalent iron present on the surfaces of as-grown single-walled carbon nanotubes produces a Pt catalyst that shows an unusually high catalytic activity for reduction of oxygen but a negligible activity for oxidation of methanol. This fuel-selective catalyst may have a unique application as a cathode catalyst in methanol fuel cells to alleviate the problems caused by crossover of methanol through the polymer electrolyte membrane. PMID:19827801

  6. Application of green chemistry techniques to prepare electrocatalysts for direct methanol fuel cells.

    Science.gov (United States)

    Shimizu, Kenichi; Wang, Joanna S; Wai, Chien M

    2010-03-25

    A series of green techniques for synthesizing carbon nanotube-supported platinum nanoparticles and their high electrocatalytic activity toward methanol fuel cell applications are reported. The techniques utilize either the supercritical fluid carbon dioxide or water as a medium for depositing platinum nanoparticles on surfaces of multiwalled or single-walled carbon nanotubes. The catalytic properties of the carbon nanotubes-supported Pt nanoparticle catalysts prepared by four different techniques are compared for anodic oxidation of methanol and cathodic reduction of oxygen using cyclic voltammetry. One technique using galvanic exchange of Pt(2+) in water with zerovalent iron present on the surfaces of as-grown single-walled carbon nanotubes produces a Pt catalyst that shows an unusually high catalytic activity for reduction of oxygen but a negligible activity for oxidation of methanol. This fuel-selective catalyst may have a unique application as a cathode catalyst in methanol fuel cells to alleviate the problems caused by crossover of methanol through the polymer electrolyte membrane.

  7. An efficient bifunctional electrocatalyst for water splitting based on cobalt phosphide

    Science.gov (United States)

    Yang, Libin; Qi, Honglan; Zhang, Chengxiao; Sun, Xuping

    2016-06-01

    The development of highly efficient electrocatalysts for water splitting is critical for various renewable-energy technologies. In this letter, we demonstrate a cobalt phosphide nanowire array grown on a Ti mesh (CoP/TM) behaving as a bifunctional electrocatalyst for water splitting. The CoP/TM electrode delivers 10 mA cm-2 at an overpotential of 72 mV for the hydrogen evolution reaction (HER) and 310 mV for the oxygen evolution reaction (OER) in 1.0 M KOH. Furthermore, its corresponding two-electrode alkaline electrolyzer displays 10 mA cm-2 at 1.64 V.

  8. Lead-ruthenium pyrochlores as oxygen electrocatalysts

    Science.gov (United States)

    Anderson, E. B.; Taylor, E. J.; Moniz, G. A.

    1990-01-01

    An investigation of lead-ruthenium pyrochlores of the structure Pb2(Ru/2-x/Pb/x/) O7-y for use as oxygen electrocatalysts in alkaline media is discussed. Lead-ruthenium pyrochlore mixed metal oxides were prepared and characterized by X-ray diffraction, BET surface area, dry powder conductivity, and chemical stability. Gas diffusion electrodes were developed specifically for the lead-ruthenium pyrochlore materials. Also investigated were the effects of varying electrode fabrication parameters on the oxygen reduction performance of the lead-ruthenium pyrochlore electrocatalyst. Long-term stability performance was also evaluated. The oxygen reduction performance of the pyrochlore electrocatalyst is considerably higher than that of the state-of-the-art gold-platinum alloy electrocatalyst currently used by NASA. Furthermore, the pyrochlore electrocatalysts are attractive candidates for high-performance pressurized alkaline fuel cells.

  9. One-step preparation of optically transparent Ni-Fe oxide film electrocatalyst for oxygen evolution reaction

    OpenAIRE

    Doudou Zhang; Lijian Meng; Jingying Shi; Nan Wang; Shengzhong (Frank) Liu; Can Li

    2015-01-01

    Optically transparent cocatalyst film materials is very desirable for improved photoelectrochemical (PEC) oxygen evolution reaction (OER) over light harvesting photoelectrodes which require the exciting light to irradiate through the cocatalyst side, i.e., front-side illumination. In view of the reaction overpotential at electrode/electrolyte interface, the OER electrocatalysts have been extensively used as cocatalysts for PEC water oxidation on photoanode. In this work, the feasi...

  10. Preparation of cobalt silicide on graphene as Pt electrocatalyst supports for highly efficient and stable methanol oxidation in acidic media

    International Nuclear Information System (INIS)

    Nanostructured CoSi with the diameter of 1-3 nm on graphene have been successfully synthesized by metal organic chemical vapor deposition (MOCVD) of Co(SiCl3)(CO)4 as a precursor supported on graphene. Pt electrocatalysts are then loaded on the CoSi/graphene composites (Pt/CoSi-graphene) using an intermittent microwave heating method. The above materials are characterized by XRD, Raman, TEM, EDS and cyclic voltammograms measurements. The results show that Pt/CoSi-graphene gives 3.2 times higher peak current density than that of commercial Pt/C(TKK) electrocatalyst at the same Pt loadings. In addition, Pt/CoSi-graphene shows superior activity and stability to commercial Pt/graphene for methanol oxidationin in acidic media. The improved catalytic activity and stability is due to the synergistic effect (electron-donating) of CoSi to Pt. Since Pt/CoSi-graphene carries higher catalytic activity and stability comparing with Pt/graphene, less Pt will be required for the same performance and it will in turn reduce the cost of fuel cell electrocatalyst

  11. Facile preparation of Ag-Cu bifunctional electrocatalysts for zinc-air batteries

    International Nuclear Information System (INIS)

    Highlights: • Ag-Cu dendrites are observed for the first time to exhibit high catalytic activity for oxygen reduction reaction. • Ag-Cu dendrites are directly synthesized through galvanic displacement on the current collector layer made of Ni foams. • A bifunctional air cathode is fabricated using Ag-Cu dendrites as a carbon-free, binder-free catalyst layer. • Both the primary and rechargeable zinc–air batteries fabricated by Ag-Cu catalysts exhibit excellent performance. - ABSTRACT: An inexpensive, facile galvanic displacement reaction for the direct growth of silver–copper (Ag-Cu) catalysts on nickel foams is developed for the first time. The resulting Ag-Cu catalysts exhibit dendritic morphologies. Ag and Cu atoms are in their metallic state while the presence of CuO and Cu2O are limited on the surface of catalyst. The catalysts demonstrate high catalytic activity for oxygen reduction reaction (ORR) in alkaline solution, as evaluated by both linear scanning voltammetry and rotating disk electrode polarization measurements. The ORR catalysed by Ag-Cu catalyst in alkaline solution proceeds through a four-electron pathway. An air cathode is fabricated using Ag-Cu catalyst as a carbon-free, binder-free catalyst layer. Using this Ag-Cu catalyst based air cathode, both the primary and rechargeable zinc-air batteries show excellent battery performance. The specific capacity of the primary zinc-air battery is 572 mAh g−1. Especially, the rechargeable zinc-air battery shows high round-trip efficiency, appealing stability at a long charge-discharge cycle period

  12. Benchmarking Pt-based electrocatalysts for low temperature fuel cell reactions with the rotating disk electrode

    DEFF Research Database (Denmark)

    Pedersen, Christoffer Mølleskov; Escribano, Maria Escudero; Velazquez-Palenzuela, Amado Andres;

    2015-01-01

    We present up-to-date benchmarking methods for testing electrocatalysts for polymer exchange membrane fuel cells (PEMFC), using the rotating disk electrode (RDE) method. We focus on the oxygen reduction reaction (ORR) and the hydrogen oxidation reaction (HOR) in the presence of CO. We have chosen...

  13. A novel electrocatalyst for oxygen evolution reaction based on rational anchoring of cobalt carbonate hydroxide hydrate on multiwall carbon nanotubes

    Science.gov (United States)

    Zhang, Yuxia; Xiao, Qingqing; Guo, Xin; Zhang, Xiaoxue; Xue, Yifei; Jing, Lin; Zhai, Xue; Yan, Yi-Ming; Sun, Kening

    2015-03-01

    Cobalt carbonate hydroxide hydrate (CCHH) nanosheets have been densely and strongly anchored onto mildly oxidized multiwalled carbon nanotubes with the assistance of diethylenetriamine (DETA). The resulted hybrid (CCHH/MWCNT) is used as high efficient electrocatalyst for water oxidation with an extremely low onset potential of ∼1.47 V vs. RHE and an overpotential of 285 mV to achieve a current density of 10 mA cm-2 in 1.0 mol L-1 KOH. The CCHH/MWCNT electrode affords a Tafel slope of 51 mV/decade and an exchange current density of 2.5 × 10-7 A cm-2. Moreover, the CCHH/MWCNT catalyst delivers a high faradic efficiency of 95% and possesses remarkable stability for long-term electrolysis of water. By contrast, neither MWCNT nor CCHH exhibits apparent catalytical activity towards water oxidation. Importantly, we demonstrate that DETA plays crucial role in determining the morphology, structure of the CCHH/MWCNT, therefore resulting in an enhanced performance for water oxidation. This work not only provides a novel cobalt-based electrocatalyst for oxygen evolution, but also offers a useful and viable approach to deliberately synthesize functional nanocomposites for applications in energy conversion and storage.

  14. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction.

    Science.gov (United States)

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E; Lowe, Michael A; Lin, Feng; Nordlund, Dennis; Liu, Hongfang; Muller, David A; Xin, Huolin L; Abruña, Héctor D

    2016-01-01

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd-Co-Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications. PMID:27336795

  15. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction

    Science.gov (United States)

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E.; Lowe, Michael A.; Lin, Feng; Nordlund, Dennis; Liu, Hongfang; Muller, David A.; Xin, Huolin L.; Abruña, Héctor D.

    2016-06-01

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd-Co-Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications.

  16. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction

    Science.gov (United States)

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E.; Lowe, Michael A.; Lin, Feng; Nordlund, Dennis; Liu, Hongfang; Muller, David A.; Xin, Huolin L.; Abruña, Héctor D.

    2016-01-01

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd–Co–Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications. PMID:27336795

  17. Preparation and characterization of PtRu/C, PtBi/C, PtRuBi/C electrocatalysts for direct electro-oxidation of ethanol in PEM fuels cells using the method of reduction by sodium borohydride

    International Nuclear Information System (INIS)

    Pt/C, PtBi/C, PtRu/C and PtRuBi/C electrocatalysts were prepared by a borohydride reduction methodology and tested for ethanol oxidation. This methodology consists in mix a solution with sodium hydroxide and sodium borohydride to a mixture containing water/isopropyl alcohol, metallic precursors and the Vulcan XC 72 carbon support. It was studied the addition method of borohydride (drop by drop addition or rapid addition). The obtained electrocatalysts were characterized by energy dispersive X ray spectroscopy (EDX), thermogravimetric analysis (TGA), X ray diffraction (XRD), transmission electron microscope (TEM) and cyclic voltammetry. The ethanol electro-oxidation was studied by cyclic voltammetry and chronoamperometry using the thin porous coating technique. The electrocatalysts were tested in real conditions of operation by unit cell tests. The stability of PtRuBi/C electrocatalysts was evaluated by cyclic voltammetry, chronoamperometry using the ultra-thin porous coating technique and ring-disk electrode. The PtRuBi/C electro catalyst apparently presented a good performance for ethanol electro-oxidation but experimental evidences showed accentuated bismuth dissolution. (author)

  18. Preparation and characterizations of platinum electrocatalysts supported on thermally treated CeO2–C composite support for polymer electrolyte membrane fuel cells

    International Nuclear Information System (INIS)

    Highlights: • CeO2–C composite support was prepared by a sol-gel approach with an average particle size of 2.5 nm. • The crystallinity of ceria was tuned by thermal treatment from 400 °C to 600 °C. • Well correlated Pt–ceria interaction was found for the Pt electrocatalysts in PEMFCs. - Abstract: A sol–gel approach was used to synthesize highly dispersed carbon-supported ceria composite support (CeO2–C) having an average particle size of 2.5 nm with sodium citrate as a ligand. The CeO2–C composite was then heated in N2 atmosphere at different temperatures to induce crystallinity variation. Pt electrocatalysts were prepared by the conventional ethylene glycol method using the thermally treated composite support (CeO2–C-T) and then characterized by X-ray diffraction and transmission electron microscopy. Electrochemical evaluations of Pt/CeO2–C-T catalytic activity were performed for methanol oxidation and oxygen reduction reactions. An optimized heating temperature was found at 550 °C for CeO2–C, and Pt/CeO2–C-550 demonstrated the highest mass activity of 0.71 A mg−1 for methanol oxidation (∼100% that of Pt/C-JM from Johnson Matthey) and 17 mV more positive shift of the half-wave potential for oxygen reduction relative to that of Pt/C–JM. The maximum power density of the membrane electrode assembly (MEA) with Pt/CeO2–C-550 cathode catalyst in a H2/air polymer electrolyte membrane fuel cell was 678 mW cm−2, which was 7% higher than that of MEA prepared with Pt/C–JM under identical operating conditions. Heating CeO2–C at 550 °C induced increased crystallinity without sacrificing particle agglomeration, which was beneficial for Pt dispersion (reduced particle size). Meanwhile catalytic activity was further enhanced because of Pt–metal oxide interactions and the known oxygen buffer capability of CeO2

  19. Platinum Nanoparticles Supported on Nitrobenzene-Functionalized Multiwalled Carbon Nanotube as Efficient Electrocatalysts for Methanol Oxidation Reaction

    International Nuclear Information System (INIS)

    Graphical abstract: Multiwalled carbon nanotube was functionalized with nitrobenzene as a promising support material for Pt-based electrocatalysts (Pt-NB-MWCNT) for methanol oxidation. The as-prepared catalysts have higher electrocatalytic activity in terms of both mass and specific activities, and improved durability for methanol oxidation reaction than as compared to the undoped materials. - Highlights: • Multiwalled carbon nanotube was functionalized with nitrobenzene as a support material for Pt-based electrocatalysts for methanol oxidation. • The electronic properties of carbon nanotubes were modified by the nitrobenzene functionalization. • Nitrobenzene-functionalized electrocatalysts revealing the improved electrocatalytic performance of Pt-NB-MWCNT catalyst for the methanol oxidation reaction. - Abstract: A novel method of molecular covalently functionalized multiwalled carbon nanotube using nitrobenzene group is prepared and used as a promising support material of Pt-based electrocatalysts (denoted as Pt-NB-MWCNT) for methanol oxidation reaction. The physical and chemical characteristics are performed by X-ray powder diffraction, transmission electron microscopy, Raman spectroscopy, thermogravimetric and X-ray photoelectron spectroscopy. The electrocatalytic are evaluated by cyclic voltammetry and chronoamperometry techniques. Compared with the un-functionalized Pt-MWCNT catalyst, Pt-NB-MWCNTs show more uniform particle dispersion, smaller particle size, improved activity and durability for methanol oxidation reaction. The nitrobenzene group is demonstrated to promote the electrocatalytic activity of Pt-MWCNT for methanol oxidation significantly. The results represent a novel approach to functionalize MWCNT in a simple and economic way to prepare efficient electrocatalysts for methanol oxidation

  20. Bimetallic electrocatalysts on titanium dioxide-based supports for methanol oxidation and oxygen evolution

    Science.gov (United States)

    Fuentes, Roderick Eliel

    Electrocatalysts are essential for the development of active and durable fuel cells and hydrogen production technologies. Generally, electrochemical processes of energy conversion and hydrogen generation in a Proton Exchange Membrane (PEM) utilize precious metals, such as platinum, iridium and ruthenium, as electrocatalysts. For the methanol oxidation and oxygen evolution reaction, a bimetallic structure can be used to enhance kinetics and increase stability. It is desired to support electrocatalysts to disperse nanoparticles on the surface and promote better catalyst utilization. Traditionally, carbon has been used as an electrochemical support because it has a high surface area and high electrical conductivity. The problem with carbon is that it is not a very stable material and can corrode at voltages more than 0.9 V, affecting performance of the electrochemical reaction. Therefore, it would be useful to support electrocatalysts in a stable material with suitable conductivity. Using titanium dioxide as a support can be advantageous due to its corrosion-resistant capability. TiO2 exhibit different crystalline structures, such as anatase and rutile, which can have an effect on catalytic activity. Unfortunately, it is not conductive; hence, it is not used in electrochemical applications. However, it can be doped with niobium to increase electronic conductivity; but, it usually come at the expense of surface area. In this work, TiO 2 and Nb-TiO2 were studied as platinum/ruthenium and iridium/ruthenium nanoparticles supports for the electrochemical oxidation of methanol and oxygen evolution, respectively. Even though the conductivity of our supports was very low, adding a considerable loading of nanoparticles increased conductivity of the composite material (support + catalyst) to acceptable levels. Using cyclic voltammetry (CV) and direct methanol fuel cell tests creating a membrane electrode assembly (MEA), Pt-Ru supported on Nb-TiO2 and TiO 2 showed superior

  1. Development of plurimetallic electrocatalysts prepared by decomposition of polymeric precursors for EtOH/O{sub 2} fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Palma, Livia M.; Almeida, Thiago S.; Andrade, Adalgisa R. de, E-mail: ardandra@ffclrp.usp.br [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto, SP (Brazil)

    2012-03-15

    This work aimed to develop plurimetallic electrocatalysts composed of Pt, Ru, Ni, and Sn supported on C by decomposition of polymeric precursors (DPP), at a constant metal:carbon ratio of 40:60 wt.%, for application in direct ethanol fuel cell (DEFC). The obtained nanoparticles were physico-chemically characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). XRD results revealed a face-centered cubic crystalline Pt with evidence that Ni, Ru, and Sn atoms were incorporated into the Pt structure. Electrochemical characterization of the nanoparticles was accomplished by cyclic voltammetry (CV) and chronoamperometry (CA) in slightly acidic medium (0.05 mol L{sup -1}H{sub 2}SO{sub 4}), in the absence and presence of ethanol. Addition of Sn to PtRuNi/C catalysts significantly shifted the ethanol and CO onset potentials toward lower values, thus increasing the catalytic activity, especially for the quaternary composition Pt{sub 64}Sn{sub 15}Ru{sub 13}Ni{sub 8}/C. Electrolysis of ethanol solutions at 0.4 V vs. RHE allowed determination of acetaldehyde and acetic acid as the main reaction products. The presence of Ru in alloys promoted formation of acetic acid as the main product of ethanol oxidation. The Pt{sub 64}Sn{sub 15}Ru{sub 13}Ni{sub 8}/C catalyst displayed the best performance for DEFC. (author)

  2. Highly active and stable hydrogen evolution electrocatalysts based on molybdenum compounds on carbon nanotube-graphene hybrid support.

    Science.gov (United States)

    Youn, Duck Hyun; Han, Suenghoon; Kim, Jae Young; Kim, Jae Yul; Park, Hunmin; Choi, Sun Hee; Lee, Jae Sung

    2014-05-27

    Highly active and stable electrocatalysts for hydrogen evolution have been developed on the basis of molybdenum compounds (Mo2C, Mo2N, and MoS2) on carbon nanotube (CNT)-graphene hybrid support via a modified urea-glass route. By a simple modification of synthetic variables, the final phases are easily controlled from carbide, nitride to sulfide with homogeneous dispersion of nanocrystals on the CNT-graphene support. Among the prepared catalysts, Mo2C/CNT-graphene shows the highest activity for hydrogen evolution reaction with a small onset overpotential of 62 mV and Tafel slope of 58 mV/dec as well as an excellent stability in acid media. Such enhanced catalytic activity may originate from its low hydrogen binding energy and high conductivity. Moreover, the CNT-graphene hybrid support plays crucial roles to enhance the activity of molybdenum compounds by alleviating aggregation of the nanocrystals, providing a large area to contact with electrolyte, and facilitating the electron transfer.

  3. Enhanced Methanol Tolerance of Highly Pd rich Pd-Pt Cathode Electrocatalysts in Direct Methanol Fuel Cells

    International Nuclear Information System (INIS)

    Methanol crossover critically restricts the practical application of direct methanol fuel cells (DMFCs). To resolve this crucial difficulty from the standpoint of electrocatalysis, an electrode material having high activity for the oxygen reduction reaction and low activity for the methanol oxidation reaction compared to widely used Pt-based electrodes is needed for DMFC cathodes. In this research carbon-supported Pd-rich Pd–Pt bimetallic nanoparticle electrocatalysts with 60 wt.% metal content were prepared for this purpose by sodium borohydride reduction of metal chlorides. The physical features of the prepared nanoparticles were investigated by transmission electron microscopy, energy dispersive X-ray spectroscopy, atomic absorption spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption near edge spectroscopy. Methanol tolerance was tested by means of rotating disk electrode (RDE) voltammetry using oxygen-saturated methanol-containing electrolyte solutions as the anode fuel for DMFC unit cell performance tests. In the RDE measurements, Pd-rich electrocatalysts (carbon-supported Pd19Pt1 nanoparticles) showed excellent methanol tolerance compared with Pd-free Pt electrocatalyst. When Pd19Pt1 nanoparticles were used as a DMFC cathode catalyst, unit cell performance tests showed that the i-V curves of the Pd19Pt1 electrocatalyst decreased slightly with increasing methanol concentration, while that of the Pt electrocatalyst decreased rapidly. The results in a liquid-feed DMFC unit cell test were in good agreement with the methanol tolerant characteristics identified in the RDE measurements

  4. Electrocatalyst compositions

    Science.gov (United States)

    Mallouk, Thomas E.; Chan, Benny C.; Reddington, Erik; Sapienza, Anthony; Chen, Guoying; Smotkin, Eugene; Gurau, Bogdan; Viswanathan, Rameshkrishnan; Liu, Renxuan

    2001-09-04

    Compositions for use as catalysts in electrochemical reactions are described. The compositions are alloys prepared from two or more elemental metals selected from platinum, molybdenum, osmium, ruthenium, rhodium, and iridium. Also described are electrode compositions including such alloys and electrochemical reaction devices including such catalysts.

  5. Highly active and durable methanol oxidation electrocatalyst based on the synergy of platinum–nickel hydroxide–graphene

    Science.gov (United States)

    Huang, Wenjing; Wang, Hongtao; Zhou, Jigang; Wang, Jian; Duchesne, Paul N.; Muir, David; Zhang, Peng; Han, Na; Zhao, Feipeng; Zeng, Min; Zhong, Jun; Jin, Chuanhong; Li, Yanguang; Lee, Shuit-Tong; Dai, Hongjie

    2015-01-01

    Active and durable electrocatalysts for methanol oxidation reaction are of critical importance to the commercial viability of direct methanol fuel cell technology. Unfortunately, current methanol oxidation electrocatalysts fall far short of expectations and suffer from rapid activity degradation. Here we report platinum–nickel hydroxide–graphene ternary hybrids as a possible solution to this long-standing issue. The incorporation of highly defective nickel hydroxide nanostructures is believed to play the decisive role in promoting the dissociative adsorption of water molecules and subsequent oxidative removal of carbonaceous poison on neighbouring platinum sites. As a result, the ternary hybrids exhibit exceptional activity and durability towards efficient methanol oxidation reaction. Under periodic reactivations, the hybrids can endure at least 500,000 s with negligible activity loss, which is, to the best of our knowledge, two to three orders of magnitude longer than all available electrocatalysts. PMID:26602295

  6. Highly active and durable methanol oxidation electrocatalyst based on the synergy of platinum-nickel hydroxide-graphene.

    Science.gov (United States)

    Huang, Wenjing; Wang, Hongtao; Zhou, Jigang; Wang, Jian; Duchesne, Paul N; Muir, David; Zhang, Peng; Han, Na; Zhao, Feipeng; Zeng, Min; Zhong, Jun; Jin, Chuanhong; Li, Yanguang; Lee, Shuit-Tong; Dai, Hongjie

    2015-01-01

    Active and durable electrocatalysts for methanol oxidation reaction are of critical importance to the commercial viability of direct methanol fuel cell technology. Unfortunately, current methanol oxidation electrocatalysts fall far short of expectations and suffer from rapid activity degradation. Here we report platinum-nickel hydroxide-graphene ternary hybrids as a possible solution to this long-standing issue. The incorporation of highly defective nickel hydroxide nanostructures is believed to play the decisive role in promoting the dissociative adsorption of water molecules and subsequent oxidative removal of carbonaceous poison on neighbouring platinum sites. As a result, the ternary hybrids exhibit exceptional activity and durability towards efficient methanol oxidation reaction. Under periodic reactivations, the hybrids can endure at least 500,000 s with negligible activity loss, which is, to the best of our knowledge, two to three orders of magnitude longer than all available electrocatalysts. PMID:26602295

  7. Nanofibrous electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Di Jia; Shui, Jianglan; Chen, Chen

    2016-05-24

    A nanofibrous catalyst and method of manufacture. A precursor solution of a transition metal based material is formed into a plurality of interconnected nanofibers by electro-spinning the precursor solution with the nanofibers converted to a catalytically active material by a heat treatment. Selected subsequent treatments can enhance catalytic activity.

  8. NiO/SiC nanocomposite prepared by atomic layer deposition used as a novel electrocatalyst for nonenzymatic glucose sensing.

    Science.gov (United States)

    Yang, Peng; Tong, Xili; Wang, Guizhen; Gao, Zhe; Guo, Xiangyun; Qin, Yong

    2015-03-01

    NiO nanoparticles are deposited onto SiC particles by atomic layer deposition (ALD). The structure of the NiO/SiC hybrid material is investigated by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The size of the NiO nanoparticles is flexible and can be adjusted by altering the cycle number of the NiO ALD. Electrochemical measurements illustrate that NiO/SiC prepared with 600 cycles for NiO ALD exhibits the highest glucose sensing ability in alkaline electrolytes with a low detection limit of 0.32 μM (S/N = 3), high sensitivity of 2.037 mA mM(-1) cm(-2), a linear detection range from approximately 4 μM to 7.5 mM, and good stability. Its sensitivity is about 6 times of that for commercial NiO nanoparticles and NiO/SiC nanocomposites prepared by a traditional incipient wetness impregnation method. It is revealed that the superior electrochemical ability of ALD NiO/SiC is ascribed to the strong interaction between NiO and the SiC substrate and the high dispersity of NiO nanoparticles on the SiC surface. These results suggest that ALD is an effective way to deposit NiO on SiC for nonenzymatic glucose sensing.

  9. A Modular, Energy-Based Approach to the Development of Nickel Containing Molecular Electrocatalysts for Hydrogen Production and Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, Wendy J.; Helm, Monte L.; DuBois, Daniel L.

    2013-08-01

    This review discusses the development of molecular electrocatalysts for H2 production and oxidation based on nickel. A modular approach is used in which the structure of the catalyst is divided into first second and outer coordination spheres. The first coordination sphere consists of the ligands bound directly to the metal center, and this coordination sphere can be used to control such factors as the presence or absence of vacant coordination sites, redox potentials, hydride acceptor abilities and other important thermodynamic parameters. The second coordination sphere is defined as functional groups such as pendant acids or bases that can interact with bound substrates such as H2 molecules and hydride ligands, but that do not form strong bonds with the metal center. These functional groups can play diverse roles such as assisting the heterolytic cleavage of H2, controlling intra- and intermolecular proton transfer reactions, and provide a physical pathway for coupling proton and electron transfer reactions. By controlling both the hydride donor/acceptor ability of the catalysts using the first coordination sphere and the proton acceptor/donor abilities of the functional groups in the second coordination sphere, catalysts can be designed that are biased toward H2 production, H2 oxidation, or that are bidirectional (catalyzing both H2 oxidation and production). The outer coordination sphere is defined as that portion of the catalytic system that are not in the first and second coordination spheres. This coordination sphere can assist in the delivery of protons and electrons to and from the catalytically active site, thereby adding another important avenue for controlling catalytic activity. Many features of these simple catalytic systems are good models for enzymes and they provide the opportunity to probe certain aspects of catalysis that may be difficult in enzymes themselves, but that can provide insights into enzyme function and reactivity.

  10. A rational approach to the optimization of efficient electrocatalysts for the next generation Fuel Cells

    OpenAIRE

    Favaro, Marco

    2014-01-01

    The PhD project has been performed in the Surfaces and Catalysts group active in the Department of Chemical Sciences, within the frame of the grant “A rational approach to the optimization of efficient electrocatalysts for the next generation Fuel Cells”, funded by CARIPARO foundation. The project has been focused on the preparation and characterization of new carbon-based materials for applications in Polymer Electrolyte Membrane Fuel Cells (PEMFCs), also known as oxygen-hydrogen FCs. The pr...

  11. Preparation of Bimetallic Pd-Co Nanoparticles on Graphene Support for Use as Methanol Tolerant Oxygen Reduction Electrocatalysts

    Directory of Open Access Journals (Sweden)

    R. N. Singh

    2012-12-01

    Full Text Available Graphene-supported (40-x wt% Pd x wt% Co (0≤x≤13.33 alloys/composites have been prepared by a microwave-assisted polyol reduction method and been investigated for their structural and electrocatalytic properties for the oxygen reduction reaction (ORR in 0.5 M H2SO4 at 298 K. The study demonstrated that the bimetallic Pd-Co composite nanoparticles are, in fact, alloy nanoparticles with fcc crystalline structure. Partial substitution of Pd by Co (from 3.64 to 13.33 wt% in 40 wt% Pd/graphene decreases the lattice parameter as well as the crystallite size and increases the apparent catalytic activity, the latter, however, being the greatest with 8 wt% Co. The ORR activity of the active 32 wt% Pd 8wt% Co is found to be considerably low when it was deposited on the support multiwall carbon nanotubes under similar conditions. The rotating disk electrode study indicated that the ORR on 32 wt% Pd 8 wt% Co/GNS in 0.5 M H2SO4 follows approximately the four-electron pathway.

  12. A water soluble electro-catalyst for generating hydrogen based on a cobalt(III) complex supported by 1,10-phenanthroline

    Science.gov (United States)

    Peng, Qiu-Xia; Tang, Ling-Zhi; Ren, Shi-Tao; Ye, Li-Ping; Deng, Yuan-Fu; Zhan, Shu-Zhong

    2016-10-01

    As we know, coordinatively unsaturated complexes can catalyze hydrogen generation via an unstable hydride intermediate. In this paper, we report an electrocatalyst based on a water soluble coordinatively saturated complex, [(phen)2Co(CN)2]·NO31 that is formed by the reaction of 1,10-phenanthroline (phen), Co(NO3)2·6H2O and tetracyanoethylene (TCNE). Its structure has been characterized by physics-chemical and spectroscopic methods. Complex 1 can electrocatalyze hydrogen evolution both from acetic acid and aqueous buffer.

  13. Influence of method of preparation of Pt Ru/C electrocatalysts on the catalytic activity for the ethanol oxidation reaction in acidic medium; Influencia do metodo de preparacao de eletrocatalisadores PtRu/C sobre a atividade catalitica frente a reacao de oxidacao de etanol em meio acido

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Walber dos Santos; Silva, Uriel Lean Valente; Souza, Jose Pio Iudice de, E-mail: jpio@ufpa.br [Universidade Federal do Para, (UFPA), Belem, PA (Brazil). Instituto de Ciencias Exatas e Naturais. Faculdade de Quimica

    2013-09-01

    In this work the influence of variations in the borohydrate reduction method on the properties of Pt Ru/C electrocatalysts was investigated. The electrocatalysts were prepared using 1:1 ; 2:1; 5:1; 50:1 and 250:1 molar ratios of NaBH{sub 4} to metals. The reduction was also performed by dripping or by fast addition of the solution. The results showed that Pt Ru nanoparticles obtained by fast addition had the smallest crystallite sizes. It was also noted that the catalytic activity increased as the borohydrate:metal molar ratio increased. The Pt Ru/C electrocatalysts (50:1) obtained by fast addition presented the best catalytic activity for ethanol electro-oxidation. (author)

  14. Fe local structure in Pt-free nitrogen-modified carbon based electrocatalysts: XAFS study

    Science.gov (United States)

    Witkowska, Agnieszka; Giuli, Gabriele; Renzi, Marco; Marzorati, Stefania; Yiming, Wubulikasimu; Nobili, Francesco; Longhi, Mariangela

    2016-05-01

    The paper presents a new results on the bonding environment (coordination number and geometry) and on oxidation states of Fe in nitrogen-modified Fe/C composites used as Pt-free catalysts for oxygen reduction in Direct Hydrogen Fuel Cells. Starting from glucose or fructose, two catalysts displaying different electrochemical performance were prepared and studied in the form of pristine powder and thin catalytic layer of electrode by Fe K-edge XAFS spectroscopy. The results show how the Fe local structure varies as a function of different synthesis conditions and how changes in the structural properties of the catalysts are related to fuel cell electrochemical performance increase during a cell activation period.

  15. A mini review on NiFe-based materials as highly active oxygen evolution reaction electrocatalysts

    OpenAIRE

    Gong, Ming; Dai, Hongjie

    2014-01-01

    Oxygen evolution reaction (OER) electrolysis, as an important reaction involved in water splitting and rechargeable metal-air battery, has attracted increasing attention for clean energy generation and efficient energy storage. Nickel/iron (NiFe)-based compounds have been known as active OER catalysts since the last century, and renewed interest has been witnessed in recent years on developing advanced NiFe-based materials for better activity and stability. In this review, we present the earl...

  16. Preparation of onion-like Pt-terminated Pt-Cu bimetallic nano-sized electrocatalysts for oxygen reduction reaction in fuel cells

    Science.gov (United States)

    Lim, Taeho; Kim, Ok-Hee; Sung, Yung-Eun; Kim, Hyun-Jong; Lee, Ho-Nyun; Cho, Yong-Hun; Kwon, Oh Joong

    2016-06-01

    Onion-like Pt-terminated Pt-Cu bimetallic nano-sized electrocatalysts (Pt/Cu/Pt/C) were synthesized by using an electroless deposition method. The synthesized Pt/Cu/Pt/C consisted of a Pt-enriched shell, a sandwiched Pt-Cu alloy layer, and a Pt core. The Pt/Cu/Pt/C showed higher electrocatalytic activity toward oxygen reduction reaction in half-cell test than that of commercial Pt/C due to an electronic structure change in the Pt-enriched shell, resulting from the sandwiched Pt-Cu alloy layer underneath. The stability of the Pt/Cu/Pt/C was examined by using both half-cell and single-cell degradation tests. In both tests, the Pt/Cu/Pt/C exhibited stronger resistance to catalyst degradation than that of the commercial Pt/C. It is notable that cell performance with the Pt/Cu/Pt/C was fully recovered by N2 purging after single-cell degradation testing, indicating there was no permanent damage to the electrocatalyst during the test. It is suggested that thermodynamically-stable structure of the Pt/Cu/Pt/C contributed to the improved stability.

  17. Activity and Stability of RuOx Based Electrocatalysts for the Oxygen Evolution Reaction

    DEFF Research Database (Denmark)

    Paoli, Elisa Antares

    delocalized hydrogen refueling stations. The sluggish kinetics of OER and the high costs of the materials represent some of the biggest technological challenges for PEM electrolysers. The current technology relies on Pt group based materials and in particular ruthenium and iridium are the most active...... and stable OER catalysts. To contain costs and precious metals supply, the mass activity should be maximized. However, in order to define the properties of a catalyst, knowing the distinction between geometric and electronic effects is fundamental. It is not trivial to determine the intrinsic catalytic...... activity on oxides and studies on well-defined surfaces are required. Notably, industrial applications demand maximized surface-to-bulk ratio, hence fabrication of catalysts in nanoparticulate form. In this perspective, this project aimed at investigating well-defined mass-selected ruthenium and ruthenium...

  18. A metal-organic framework-derived bifunctional oxygen electrocatalyst

    Science.gov (United States)

    Xia, Bao Yu; Yan, Ya; Li, Nan; Wu, Hao Bin; Lou, Xiong Wen (David); Wang, Xin

    2016-01-01

    Oxygen electrocatalysis is of great importance for many energy storage and conversion technologies, including fuel cells, metal-air batteries and water electrolysis. Replacing noble metal-based electrocatalysts with highly efficient and inexpensive non-noble metal-based oxygen electrocatalysts is critical for the practical applications of these technologies. Here we report a general approach for the synthesis of hollow frameworks of nitrogen-doped carbon nanotubes derived from metal-organic frameworks, which exhibit higher electrocatalytic activity and stability for oxygen reduction and evolution than commercial Pt/C electrocatalysts. The remarkable electrochemical properties are mainly attributed to the synergistic effect from chemical compositions and the robust hollow structure composed of interconnected crystalline nitrogen-doped carbon nanotubes. The presented strategy for controlled design and synthesis of metal-organic framework-derived functional nanomaterials offers prospects in developing highly active electrocatalysts in electrochemical energy devices.

  19. Platinum-carbon black-titanium dioxide nanocomposite electrocatalysts for fuel cell applications

    Indian Academy of Sciences (India)

    Satheesh Sambandam; Vinodh Valluri; Wilaiwan Chanmanee; Norma R De Tacconi; Wesley A Wampler; Wen-Yuan Lin; Thomas F Carlson; Vijay Ramani; Krishnan Rajeshwar

    2009-09-01

    New-generation Pt/C-TiO2 nanocomposite electrocatalysts for fuel cells, prepared by a heterogeneous photocatalytic method, have been characterized using techniques such as cyclic voltammetry, rotating disk electrode (RDE) voltammetry, and electrochemical impedance spectroscopy (EIS). Importantly, galvanostatic data confirm the superior stability of these materials against corrosion under anodic polarization conditions relative to commercial benchmark fuel cell electrocatalysts. EIS spectra from ETEK 5, SIDCAT 405 and SIDCAT 410 membrane electrode assemblies (MEAs) were fit to a Randles equivalent circuit with a Warburg element to show the presence of O2 transport limitation arising from the use of thicker electrodes (lower Pt loading on carbon). The use of a constant phase element (CPE) instead of pure capacitor was justified from the fit procedure as CPE represents the porous electrode system more precisely with its distributive elements. EIS spectra from Tanaka, SIDCAT 451 and SIDCAT 452 MEAs (thinner electrodes) were fit to a Randles circuit with a pure capacitor and no Warburg element. The use of a transmission line model for fitting these data independently provided information about the catalyst layer resistance while all other parameters matched well with that of the Randles circuit. The effective proton transport in cathodes was quantified using polarization data for both classes of MEAs. Trends in the previously reported performance of MEAs prepared using these electrocatalysts were justified based on the relative contributions of kinetic, Ohmic and mass transfer losses to the overall overpotential, which in turn were estimated from impedance and polarization data analyses.

  20. Improved Durability of Electrocatalyst Based on Coating of Carbon Black with Polybenzimidazole and their Application in Polymer Electrolyte Fuel Cells.

    Science.gov (United States)

    Fujigaya, Tsuyohiko; Hirata, Shinsuke; Berber, Mohamed R; Nakashima, Naotoshi

    2016-06-15

    Improvement of durability of the electrocatalyst has been the key issue to be solved for the practical application of polymer electrolyte membrane fuel cells. One of the promising strategies to improve the durability is to enhance the oxidation stability of the carbon-supporting materials. In this report, we describe in detail the mechanism of the stability improvement of carbon blacks (CBs; Vulcan and Ketjen) by coating with polybenzimidazole (PBI). Nitrogen adsorption experiments reveal that the PBI coating of CBs results in the capping of the gates of the CB-micropores by the PBI. Since the surface of the micropores inside the CBs are inherently highly oxidized, the capping of such pores effectively prevents the penetration of the electrolyte into the pore and works to avoid the further oxidation of interior of the micropore, which is proved by cyclic voltammogram measurements. Above mechanism agrees very well with the dramatic enhancement of the durability of the membrane electrode assembly fabricated using Pt on the PBI-coated CBs as an electrocatalyst compared to the conventional Pt/CB (PBI-non coated) catalyst.

  1. Metal-Carbon Hybrid Electrocatalysts Derived from Ion-Exchange Resin Containing Heavy Metals for Efficient Hydrogen Evolution Reaction.

    Science.gov (United States)

    Zhou, Yucheng; Zhou, Weijia; Hou, Dongman; Li, Guoqiang; Wan, Jinquan; Feng, Chunhua; Tang, Zhenghua; Chen, Shaowei

    2016-05-01

    Transition metal-carbon hybrids have been proposed as efficient electrocatalysts for hydrogen evolution reaction (HER) in acidic media. Herein, effective HER electrocatalysts based on metal-carbon composites are prepared by controlled pyrolysis of resin containing a variety of heavy metals. For the first time, Cr2 O3 nanoparticles of 3-6 nm in diameter homogeneously dispersed in the resulting porous carbon framework (Cr-C hybrid) is synthesized as efficient HER electrocatalyst. Electrochemical measurements show that Cr-C hybrids display a high HER activity with an onset potential of -49 mV (vs reversible hydrogen electrode), a Tafel slope of 90 mV dec(-1) , a large catalytic current density of 10 mA cm(-2) at -123 mV, and the prominent electrochemical durability. X-ray photoelectron spectroscopic measurements confirm that electron transfer occurs from Cr2 O3 into carbon, which is consistent with the reported metal@carbon systems. The obtained correlation between metals and HER activities may be exploited as a rational guideline in the design and engineering of HER electrocatalysts. PMID:27061759

  2. Synthesis of Pt and Pt-Fe nanoparticles supported on MWCNTs used as electrocatalysts in the methanol oxidation reaction

    Institute of Scientific and Technical Information of China (English)

    J.R.Rodriguez; R.M.F´elix; E.A.Reynoso; Y.Gochi-Ponce; Y.Verde Gómez; S.Fuentes Moyado; G.Alonso-N ´uñez

    2014-01-01

    This work reports a feasible synthesis of highly-dispersed Pt and Pt-Fe nanoparticles supported on multiwall carbon nanotubes (MWCNTs) without Fe and multiwall carbon nanotubes with iron (MWCNTs-Fe) which applied as electrocatalysts for methanol electrooxidation. A Pt coordination complex salt was synthesized in an aqueous solution and it was used as precursor to prepare Pt/MWCNTs, Pt/MWCNTs-Fe, and Pt-Fe/MWCNTs using FeCl2·4H2O as iron source which were named S1, S2 and S3, respectively. The coordination complex of platinum (TOA)2PtCl6 was obtained by the chemical reaction between (NH4)2PtCl6 with tetraoctylammonium bromide (TOAB) and it was characterized by FT-IR and TGA. The materials were characterized by Raman spectroscopy, SEM, EDS, XRD, TEM and TGA. The electrocatalytic activity of Pt-based supported on MWCNTs in the methanol oxidation was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). Pt-Fe/MWCNTs electrocatalysts showed the highest electrocatalytic activity and stability among the tested electrocatalysts due to that the addition of”Fe”promotes the OH species adsorption on the electrocatalyst surface at low potentials, thus, enhancing the activity toward the methanol oxidation reaction (MOR).

  3. Electrocatalysts of platinum, cobalt and nickel prepared by mechanical alloying for the oxygen reduction reaction in H2SO4 0.5M

    International Nuclear Information System (INIS)

    Metallic powders of Pt, Co and Nickel were processed by mechanical alloyed and electrocatalysts were synthesized for the oxygen reduction reaction, applicable in fuel cells. The structural and morphological characterization was carried out using X-ray Diffraction, scanning electron microscopy and transmission electron microscopy. It was found that the alloyed powders formed agglomerates that consist of crystalline particles of nano metric size. Its were obtained polarization curves by the Electrode of Rotational Disk technique in a solution of H2SO4 0.5 M, used as electrolyte, to evaluate the electrocatalytic activity of mechanically alloyed powders. Tafel graphics were built to determine the kinetic parameters of each electro catalyst. The PtCoNi alloy exhibited the biggest electrocatalytic activity, with the smallest over potential for the oxygen reduction reaction. (Author)

  4. Preparation, characterization and evaluation of electrocatalysts supported on functionalized carbon black for polymer exchange membrane fuel cell applications; Preparacao, caracterizacao e avaliacao de eletrocatalisadores suportados em carbono funcionalizado para aplicacao em celulas a combustivel tipo PEM

    Energy Technology Data Exchange (ETDEWEB)

    Carmo, Marcelo do

    2008-12-18

    The fuel cell technology associated with the growing exigency of low environmental impact energy became prosperous in the world energy scenery. The fuel cell is basically a device that converts directly the chemical energy of a fuel into electrical and thermal energy with a continuous operation by the constant feed of a fuel. Especially, the carbon black Vulcan XC72 is usually employed as an electro catalyst support, and some factors as an accessible and high surface area in order to get maximum particles dispersion, pore size, adequate pore distribution and the presence of functional groups in the carbon black surface are considered fundamental characteristics for an innovative materials development. However, the Vulcan XC72 still reveals insufficient conditions for these purposes. This study consists in the preparation and in the physical chemical characterization of functionalized carbon black by hydrogen peroxide and by polymeric chains with proton conduction properties, and its posterior utilization as electro catalyst support for PEMFC and DMFC application. After the carbon functionalization, an improvement in the carbon black dispersion in water media was observed, a beneficial effect for electro catalyst preparation. It was also observed, that the functional groups and the polymeric chains worked as stabilizers in the particle growing, producing much more homogeneous electrocatalysts, exhibiting smaller average particle size. Especially, in the case of polymeric chains functionalization, a decrease in the ohmic drop was observed for this system, attributed to an improvement in the proton transference. (author)

  5. Preparation of PtSnCu/C and PtSn/C electrocatalysts and activation by dealloying processes for ethanol electrooxidation; Preparacao de eletrocatalisadores PtSnCu/C e PtSn/C e ativacao por processos de dealloying para aplicacao na oxidacao eletroquuimica do etanol

    Energy Technology Data Exchange (ETDEWEB)

    Crisafulli, Rudy

    2013-06-01

    PtSnCu/C (with different Pt:Sn:Cu atomic ratios) and PtSn/C (50:50) electrocatalysts were prepared by borohydride (BR) and alcohol-reduction (AR) processes using H{sub 2}PtCl{sub 6}.6H{sub 2}O, SnCl{sub 2}.2H{sub 2}O and CuCl{sub 2}.2H{sub 2}O as metal sources, NaBH{sub 4} and ethylene glycol as reducing agents, 2-propanol and ethylene glycol/water as solvents and carbon black as support. In a further step, these electrocatalysts were activated by chemical (CD) and electrochemical (ED) dealloying processes through acid treatment and thin porous coating technique, respectively. These materials were characterized by energy dispersive X-ray, Xray diffraction, transmission electron microscopy, line scan energy dispersive Xray and cyclic voltammetry. Electrochemical studies for ethanol electro-oxidation were performed by cyclic voltammetry, chronoamperometry and in single Direct Ethanol Fuel Cell using Membrane Electrode Assembly (MEA). The anodic effluents were analysed by gas chromatography. The X-ray diffractograms of the as-synthesized electrocatalysts showed the typical face-centered cubic structure (FCC) of platinum and its alloys. After dealloying, the X-ray diffractograms showed that the Pt FCC structure was preserved. The crystallite sizes of the assynthesized electrocatalysts were in the range of <=2 nm to 3 nm and after dealloying there were no significant variations in sizes. The energy dispersive Xray analysis of the as-synthesized electrocatalysts showed a Pt:Sn and Pt:Sn:Cu atomic ratios similar to the nominal values. After chemical and electrochemical dealloying of the electrocatalysts the ranged Pt:Sn and Pt:Sn:Cu atomic ratios showed that Cu and Sn atoms were removed. However, chemical dealloying process proved to be more efficient for removing Cu and electrochemical dealloying for removing Sn. The line scan energy dispersive X-ray analysis showed that acid and electrochemical treatments were efficient to dealloying Cu and/or Sn superficial atoms of

  6. Electrocatalysts for medium temperature PEM water electrolysis

    OpenAIRE

    Zlotorowicz, Agnieszka

    2013-01-01

    The main subject of this PhD thesis is the fabrication and investigation the electrochemical behavior of anode catalysts appropriate for medium- temperature proton exchange membrane (PEM) water electrolysis (WE) operating in the range 100 oC through 200 oC. These catalysts were based on metal oxides, primarily IrO2 and its mixtures with some other oxides, and investigated as oxygen evolution electrocatalysts. A central research challenge in this project has been to understand the interaction ...

  7. Electrocatalysts for hydrogen energy

    CERN Document Server

    Losiewicz, Bozena

    2015-01-01

    This special topic volume deals with the development of novel solid state electrocatalysts of a high performance to enhance the rates of the hydrogen or oxygen evolution. It contains a description of various types of metals, alloys and composites which have been obtained using electrodeposition in aqueous solutions that has been identified to be a technologically feasible and economically superior technique for the production of the porous electrodes. The goal was to produce papers that would be useful to both the novice and the expert in hydrogen technologies. This volume is intended to be us

  8. Influência do método de preparação de eletrocatalisadores PtRu/C sobre a atividade catalítica frente à reação de oxidação de etanol em meio ácido Influence of method of preparation of PtRu/C electrocatalysts on the catalytic activity for the ethanol oxidation reaction in acidic medium

    Directory of Open Access Journals (Sweden)

    Walber dos Santos Gomes

    2013-01-01

    Full Text Available In this work the influence of variations in the borohydrate reduction method on the properties of PtRu/C electrocatalysts was investigated. The electrocatalysts were prepared using 1:1 ; 2:1; 5:1; 50:1 and 250:1 molar ratios of NaBH4 to metals. The reduction was also performed by dripping or by fast addition of the solution. The results showed that PtRu nanoparticles obtained by fast addition had the smallest crystallite sizes. It was also noted that the catalytic activity increased as the borohydrate:metal molar ratio increased. The PtRu/C electrocatalyst (50:1 obtained by fast addition presented the best catalytic activity for ethanol electro-oxidation.

  9. A highly selective copper-indium bimetallic electrocatalyst for the electrochemical reduction of aqueous CO2to CO

    KAUST Repository

    Rasul, Shahid

    2014-12-23

    The challenge in the electrochemical reduction of aqueous carbon dioxide is in designing a highly selective, energy-efficient, and non-precious-metal electrocatalyst that minimizes the competitive reduction of proton to form hydrogen during aqueous CO2 conversion. A non-noble metal electrocatalyst based on a copper-indium (Cu-In) alloy that selectively converts CO2 to CO with a low overpotential is reported. The electrochemical deposition of In on rough Cu surfaces led to Cu-In alloy surfaces. DFT calculations showed that the In preferentially located on the edge sites rather than on the corner or flat sites and that the d-electron nature of Cu remained almost intact, but adsorption properties of neighboring Cu was perturbed by the presence of In. This preparation of non-noble metal alloy electrodes for the reduction of CO2 provides guidelines for further improving electrocatalysis.

  10. Electrocatalyst materials for fuel cells based on the polyoxometalates [PMo(12-n)VnO40](3+n)- (n = 0-3)

    International Nuclear Information System (INIS)

    We report on the use of the polyoxometalate acids of the series [PMo(12-n)VnO40](3+n)- (n = 0-3) as electrocatalysts in both the anode and the cathode of polymer-electrolyte membrane (PEM) fuel cells. The heteropolyacids were incorporated as catalysts in a commercial gas diffusion electrode based on Vulcan XC-72 carbon which strongly adsorbed a low loading of the catalyst, ca. 0.1 mg/cm2. The moderate activity observed was independent of the number of vanadium atoms in the polyoxometalate. In the anode the electrochemistry is dominated by the V3+/4+ couple. With a platinum reference wire in contact with the anode, polarization curves are obtained withVOC of 650 mV and current densities of 10 mA cm-2 at 100 mV at 80 deg. C. These catalysts showed an order of magnitude more activity on the cathode after moderate heat treatment than on the anode,VOC = 750 mV, current densities of 140 mA cm-2 at 100 mV. The temperature dependence of the catalysts was also investigated and showed increasing current densities could be achieved on the anode up to 139 deg. C and the cathode to 100 deg. C showing the potential for these materials to work at elevated temperatures

  11. Bifunctional electrocatalyst for oxygen/air electrodes

    International Nuclear Information System (INIS)

    Highlights: • Nano-Silver powder was prepared by chemical method. • Ag catalyst was characterized by SEM and XRD studies. • Ag was investigated as bi-functional electrocatalyst for oxygen/air electrodes. • Ag shows good electrochemical activity towards OER and ORR reactions. - Abstract: Nano-Silver powder has been studied as bi-functional electrocatalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline medium. Ag nano-powder has been prepared by a simple wet chemical method with Silver nitrate as precursor and Glucose as reducing agent. X-ray Diffraction and Scanning Electron Microscopy studies were carried out to characterize the Silver catalyst. Electrochemical oxygen evolution characterization shows anodic peak typically at the range between 0.350 and 0.514 V Vs Hg/HgO corresponding to Silver oxidation followed by the onset of oxygen evolution at 0.706 V. Oxygen reduction reaction studies carried out using Rotating Disc Electrode (RDE) confirm the four electron reaction mechanism. Ag catalyst shows promising characteristics for oxygen evolution and oxygen reduction

  12. Pt, PtCo and PtNi electrocatalysts prepared with mechanical alloying for oxygen reduction reaction in alkaline medium; Electrocatalizadores de Pt, PtCo y PtNi preparados por aleado mecanico para la reaccion de reduccion de oxigeno en medio alcalino

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Contreras, M.A.; Fernandez-Valverde, S.M. [Instituto Nacional de Investigaciones Nucleares, Ocoyoacac, Estado de Mexico (Mexico)]. E-mail: miguel.garcia@inin.gob.mx; Vargas-Garcia, J.R. [ESIQIE-IPN, Mexico D.F. (Mexico

    2009-09-15

    Pt, PtCo and PtNi electrocatalysts were prepared using mechanical alloying and their electrocatalytic activity was investigated for oxygen reduction reaction (ORR) in KOH 0.5 M using cyclic voltametry and rotary disc electrode (RDE) techniques. The electrocatalysts were characterized using x-ray diffraction, sweep electron microscopy, dispersive x-ray transmission and chemical analysis. The physical characterization indicated that all the electrocatalysts are alloys formed by agglomerated particles composed of nanocrystals. The chemical analysis showed the presence of iron in the alloys. For the electrocatalytic evaluation, polarization curves and Koutecky-Levich and Tafel graphs were obtained to determine the kinetic parameters of the electrocatalysts in the study. With the same experimental conditions, the PtCo presented better electrocatalytic performance with a higher exchange current density. [Spanish] Se prepararon electrocatalizadores de Pt, PtCo y PtNi por aleado mecanico y se investigo su actividad electrocatalitica para la reaccion de reduccion de oxigeno (RRO) en KOH 0.5 M utilizando las tecnicas de Voltametria ciclica y Electrodo de Disco Rotatorio. Los electrocatalizadores se caracterizaron por difraccion de rayos X, Microscopia electronica de Barrido, de Transmision y analisis quimico por dispersion de rayos X. La caracterizacion fisica indico que todos los electrocatalizadores son aleaciones formadas de particulas aglomeradas, compuestas de nanocristales. El analisis quimico mostro la presencia de hierro en las aleaciones. Para la evaluacion electrocatalitica se obtuvieron curvas de polarizacion, graficas de Koutecky-Levich y de Tafel para determinar los parametros cineticos de los electrocatalizadores en estudio. En las mismas condiciones experimentales, el PtCo presento el mejor desempeno electrocatalitico con la densidad de corriente de intercambio mas alta.

  13. Applicability of analytical protocols for the characterisation of carbon-supported platinum group metal fuel cell electrocatalysts

    Directory of Open Access Journals (Sweden)

    V. Linkov

    2010-01-01

    Full Text Available The nanoparticulate size of fuel cell electrocatalysts raises significant challenges in the analytical techniques used in their structural and electrochemical characterisation. For this reason, the applicability of analytical protocols in the qualitative and quantitative characterisation of nanophase fuel cell electrocatalysts was investigated. A set of structural and chemical properties influencing the performance of the electrocatalysts was identified. A large range of analytical tools was employed in characterising the electrocatalysts of interest. High accuracy and precision in the quantitative and qualitative structural and electrochemical characterisation of Pt/C and Pt-Ru/C nanophase electrocatalysts was demonstrated. Certain techniques were deemed to be highly applicable in discriminating between high- and low-performance electrocatalysts based on their structural and electrochemical properties. The goal of this effort is to contribute to the development of South Africa’s capabilities in the emerging hydrogen economy.

  14. WC as a non-platinum hydrogen evolution electrocatalyst for high temperature PEM water electrolysers

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Petrushina, Irina; Christensen, Erik;

    2012-01-01

    Tungsten carbide (WC) nanopowder was tested as a non-platinum cathode electrocatalyst for polymer electrolyte membrane (PEM) water electrolysers, operating at elevated temperatures. It was prepared in thermal plasma reactor with confined plasma jet from WO3 precursor in combination with CH4...... carburizing agent. The results of the investigation showed that the activity of tungsten carbide as cathode electrocatalyst increases significantly with temperature and this effect is more pronounced than for platinum, especially, at 150 °C....

  15. Performance PtSnRh electrocatalysts supported on carbon-Sb{sub 2}O{sub 5}.SbO{sub 2} for the electro-oxidation of ethanol, prepared by an alcohol-reduction process; Desempenho de eletrocatalisadores PtSnRh suportados em carbono-Sb{sub 2}O{sub 5}.SnO{sub 2} para a oxidacao eletroquimica do etanol, preparados pelo metodo de reducao por alcool

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Jose Carlos

    2013-07-01

    PtSnRh electrocatalysts supported on carbon-Sb{sub 2}O{sub 5}.SnO{sub 2}, with metal loading of 20 wt%, were prepared by an alcohol-reduction process, using H{sub 2}PtCl{sub 6}.6H{sub 2}O (Aldrich), RhCl{sub 3}.xH{sub 2}O (Aldrich) and SnCl{sub 2}.2H{sub 2}O (Aldrich), as source of metals; Sb{sub 2}O{sub 5}.SnO{sub 2} (ATO) and carbon Vulcan XC72, as support; and ethylene glycol as reducing agent. The electrocatalysts obtained were characterized physically by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diffractograms showed which PtSnRh/C-ATO electrocatalysts had FCC structure of Pt and Pt alloys, besides several peaks associated with SnO{sub 2} and ATO. The average sizes of crystallites were between 2 and 4 nm. TEM micrographs showed a good distribution of the nanoparticles on the support. The average sizes of particles were between 2 and 3 nm, with good agreement for the average size of the crystallites. The performances of the electrocatalysts were analyzed by electrochemical techniques and in real conditions of operation using single direct ethanol fuel cell. In the chronoamperometry at 50 deg C, the electrocatalysts with carbon (85 wt%) and ATO (15 wt%) support, showed the best activity, and the atomic proportions which achieved the best results were PtSnRh(70:25:05) e (90:05:05). PtSnRh(70:25:05)/85C+15ATO electrocatalysts showed the best performance in a direct ethanol fuel cell. (author)

  16. Investigation of Supported Pd-Based Electrocatalysts for the Oxygen Reduction Reaction: Performance, Durability and Methanol Tolerance

    Directory of Open Access Journals (Sweden)

    Carmelo Lo Vecchio

    2015-11-01

    Full Text Available Next generation cathode catalysts for direct methanol fuel cells (DMFCs must have high catalytic activity for the oxygen reduction reaction (ORR, a lower cost than benchmark Pt catalysts, and high stability and high tolerance to permeated methanol. In this study, palladium catalysts supported on titanium suboxides (Pd/TinO2n–1 were prepared by the sulphite complex route. The aim was to improve methanol tolerance and lower the cost associated with the noble metal while enhancing the stability through the use of titanium-based support; 30% Pd/Ketjenblack (Pd/KB and 30% Pd/Vulcan (Pd/Vul were also synthesized for comparison, using the same methodology. The catalysts were ex-situ characterized by physico-chemical analysis and investigated for the ORR to evaluate their activity, stability, and methanol tolerance properties. The Pd/KB catalyst showed the highest activity towards the ORR in perchloric acid solution. All Pd-based catalysts showed suitable tolerance to methanol poisoning, leading to higher ORR activity than a benchmark Pt/C catalyst in the presence of low methanol concentration. Among them, the Pd/TinO2n–1 catalyst showed a very promising stability compared to carbon-supported Pd samples in an accelerated degradation test of 1000 potential cycles. These results indicate good perspectives for the application of Pd/TinO2n–1 catalysts in DMFC cathodes.

  17. Rational Design of Competitive Electrocatalysts for Hydrogen Fuel Cells.

    Science.gov (United States)

    Stolbov, Sergey; Alcántara Ortigoza, Marisol

    2012-02-16

    The large-scale application of one of the most promising clean and renewable sources of energy, hydrogen fuel cells, still awaits efficient and cost-effective electrocatalysts for the oxygen reduction reaction (ORR) occurring on the cathode. We demonstrate that truly rational design renders electrocatalysts possessing both qualities. By unifying the knowledge on surface morphology, composition, electronic structure, and reactivity, we solve that trimetallic sandwich-like structures are an excellent choice for optimization. Their constituting species are expected to couple synergistically yielding reaction-environment stability, cost-effectiveness, and tunable reactivity. This cooperative-action concept enabled us to predict two advantageous ORR electrocatalysts: Pd/Fe/W(110) and Au/Ru/W(110). Density functional theory calculations of the reaction free-energy diagrams suggest that these materials are more active toward ORR than the so-far best Pt-based catalysts. Our designing concept advances also a general approach for engineering advanced materials. PMID:26286047

  18. Hierarchically porous carbons with optimized nitrogen doping as highly active electrocatalysts for oxygen reduction

    Science.gov (United States)

    Liang, Hai-Wei; Zhuang, Xiaodong; Brüller, Sebastian; Feng, Xinliang; Müllen, Klaus

    2014-09-01

    Development of efficient, low-cost and stable electrocatalysts as the alternative to platinum for the oxygen reduction reaction is of significance for many important electrochemical devices, such as fuel cells, metal-air batteries and chlor-alkali electrolysers. Here we report a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation. Our protocol allows for the simultaneous optimization of both porous structures and surface functionalities of nitrogen-doped carbons. Accordingly, the prepared catalysts show the highest oxygen reduction reaction activity (half-wave potential of 0.85 V versus reversible hydrogen electrode with a low loading of 0.1 mg cm-2) in alkaline media among all reported metal-free catalysts. Significantly, when used for constructing the air electrode of zinc-air battery, our metal-free catalyst outperforms the state-of the-art platinum-based catalyst.

  19. Coelectrodeposition of Ternary Mn-Oxide/Polypyrrole Composites for ORR Electrocatalysts: A Study Based on Micro-X-ray Absorption Spectroscopy and X-ray Fluorescence Mapping

    Directory of Open Access Journals (Sweden)

    Benedetto Bozzini

    2015-08-01

    Full Text Available Low energy X-ray fluorescence (XRF and soft X-ray absorption (XAS microspectroscopies at high space-resolution are employed for the investigation of the coelectrodeposition of composites consisting of a polypyrrole(PPy-matrix and Mn-based ternary dispersoids, that have been proposed as promising electrocatalysts for oxygen-reduction electrodes. Specifically, we studied Mn–Co–Cu/PP, Mn–Co–Mg/PPy and Mn–Ni–Mg/PPy co-electrodeposits. The Mn–Co–Cu system features the best ORR electrocatalytic activity in terms of electron transfer number, onset potential, half-wave potential and current density. XRF maps and micro-XAS spectra yield compositional and chemical state distributions, contributing unique molecular-level information on the pulse-plating processes. Mn, Ni, Co and Mg exhibit a bimodal distribution consisting of mesoscopic aggregates of micrometric globuli, separated by polymer-rich ridges. Within this common qualitative scenario, the individual systems exhibit quantitatively different chemical distribution patterns, resulting from specific electrokinetic and electrosorption properties of the single components. The electrodeposits consist of Mn3+,4+-oxide particles, accompanied by combinations of Co0/Co2+, Ni0/Ni2+ and Cu0,+/Cu2+ resulting from the alternance of cathodic and anodic pulses. The formation of highly electroactive Mn3+,4+ in the as-fabricated material is a specific feature of the ternary systems, deriving from synergistic stabilisation brought about by two types of bivalent dopants as well as by galvanic contact to elemental metal; this result represents a considerable improvement in material quality with respect to previously studied Mn/PPy and Mn-based/PPy binaries.

  20. Influence of carbon nanofiber properties as electrocatalyst support on the electrochemical performance for PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Sebastian, D.; Suelves, I.; Moliner, R.; Lazaro, M.J. [Instituto de Carboquimica (CSIC), Energy and Environment, C/Miguel Luesma Castan 4, 50018 Zaragoza (Spain); Calderon, J.C.; Gonzalez-Exposito, J.A.; Pastor, E. [Universidad de La Laguna, Dpto de Quimica-Fisica, Avda. Astrofisico Francisco Sanchez s/n, 38071 La Laguna, Tenerife (Spain); Martinez-Huerta, M.V. [Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, 28049 Madrid (Spain)

    2010-09-15

    Novel carbonaceous supports for electrocatalysts are being investigated to improve the performance of polymer electrolyte fuel cells. Within several supports, carbon nanofibers blend two properties that rarely coexist in a material: a high mesoporosity and a high electrical conductivity, due to their particular structure. Carbon nanofibers have been obtained by catalytic decomposition of methane, optimizing growth conditions to obtain carbon supports with different properties. Subsequently, the surface chemistry has been modified by an oxidation treatment, in order to create oxygen surface groups of different nature that have been observed to be necessary to obtain a higher performance of the electrocatalyst. Platinum has then been supported on the as-prepared carbon nanofibers by different deposition methods and the obtained catalysts have been studied by different electrochemical techniques. The influence of carbon nanofibers properties and functionalization on the electrochemical behavior of the electrocatalysts has been studied and discussed, obtaining higher performances than commercial electrocatalysts with the highest electrical conductive carbon nanofibers as support. (author)

  1. Preparation and characterization of PtRu/C, PtBi/C, PtRuBi/C electrocatalysts for direct electro-oxidation of ethanol in PEM fuels cells using the method of reduction by sodium borohydride; Preparacao e caracterizacao de eletrocatalisadores PtRu/C, PtBi/C, PtRuBi/C para eletro-oxidacao direta de etanol em celulas a combustivel tipo PEM utilizando a metodologia da reducao via borohidreto de sodio

    Energy Technology Data Exchange (ETDEWEB)

    Brandalise, Michele

    2010-07-01

    Pt/C, PtBi/C, PtRu/C and PtRuBi/C electrocatalysts were prepared by a borohydride reduction methodology and tested for ethanol oxidation. This methodology consists in mix a solution with sodium hydroxide and sodium borohydride to a mixture containing water/isopropyl alcohol, metallic precursors and the Vulcan XC 72 carbon support. It was studied the addition method of borohydride (drop by drop addition or rapid addition). The obtained electrocatalysts were characterized by energy dispersive X ray spectroscopy (EDX), thermogravimetric analysis (TGA), X ray diffraction (XRD), transmission electron microscope (TEM) and cyclic voltammetry. The ethanol electro-oxidation was studied by cyclic voltammetry and chronoamperometry using the thin porous coating technique. The electrocatalysts were tested in real conditions of operation by unit cell tests. The stability of PtRuBi/C electrocatalysts was evaluated by cyclic voltammetry, chronoamperometry using the ultra-thin porous coating technique and ring-disk electrode. The PtRuBi/C electro catalyst apparently presented a good performance for ethanol electro-oxidation but experimental evidences showed accentuated bismuth dissolution. (author)

  2. Study of the oxygen reduction reaction using Pt-Rare earths (La, Ce, Er) electrocatalysts for application of PEM fuel cells; Estudo da reacao de reducao do oxigenio utilizando eletrocatalisadores a base de Pt-terras raras (La, Ce, Er) para aplicacao em celulas a combustivel tipo PEM

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Thiago Bueno

    2013-07-01

    The complexity of the oxygen reduction reaction (ORR) and its potential losses make it responsible for the most part of efficiency losses at the Fuel Cells. For this reaction the electrocatalyst witch is most appropriated and shows better performance is platinum, a noble metal that elevates the cost, raising barriers for Fuel Cells technology to enter the market. First this work focuses on reducing the amount of platinum used in the cathode, by being replaced by rare earths. The most common methods of synthesis involves a large amount of steps and this work proposed to prepare the electrocatalyst through a simpler way that would not take so many steps and time to be done. Using an ultrasound mixer the electrocatalyst was prepared mixing platinum supported on carbon black and the rare earths lanthanum, cerium and erbium oxides to be applied in a half-cell study of the ORR. The Koutecky-Levich plots shows that among the electrocatalysts prepared the Pt80Ce20/C had the catalytic activity close to the commercial BASF platinum on carbon black, suggesting that the reaction was taken by the 4-electron path. As found in some works in literature, among the rare earth used to study the ORR, cerium is the one witch shows the better performance because it is able to store and provide oxygen. This feature is of great interest for the ORR because this reaction is first order to the oxygen concentration. Results show that is possible to reduce the amount of platinum maintaining the same electrocatalyst activity. (author)

  3. Atomically monodisperse nickel nanoclusters as highly active electrocatalysts for water oxidation

    Science.gov (United States)

    Joya, Khurram S.; Sinatra, Lutfan; Abdulhalim, Lina G.; Joshi, Chakra P.; Hedhili, M. N.; Bakr, Osman M.; Hussain, Irshad

    2016-05-01

    Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these Ni NCs are found to be Ni4(PET)8 and Ni6(PET)12 and are highly active electrocatalysts for oxygen evolution without any pre-conditioning. Ni4(PET)8 are slightly better catalysts than Ni6(PET)12 which initiate oxygen evolution at an amazingly low overpotential of ~1.51 V (vs. RHE; η ~ 280 mV). The peak oxygen evolution current density (J) of ~150 mA cm-2 at 2.0 V (vs. RHE) with a Tafel slope of 38 mV dec-1 is observed using Ni4(PET)8. These results are comparable to the state-of-the-art RuO2 electrocatalyst, which is highly expensive and rare compared to Ni-based materials. Sustained oxygen generation for several hours with an applied current density of 20 mA cm-2 demonstrates the long-term stability and activity of these Ni NCs towards electrocatalytic water oxidation. This unique approach provides a facile method to prepare cost-effective, nanoscale and highly efficient electrocatalysts for water oxidation.Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these

  4. Progress on Electrocatalysts of Hydrogen Evolution Reaction Based on Carbon Fiber Materials%基于碳纤维材料基底的电解水制氢催化剂的研究进展

    Institute of Scientific and Technical Information of China (English)

    佟珊珊; 王雪靖; 李庆川; 韩晓军

    2016-01-01

    Hydrogen evolution from water electrolysis is one of the effective ways to obtain clean hydrogen energy in the future. Pt-based materials are the efficient catalysts in hydrogen evolution reaction, but it is expensive, difficult to recycle, which impedes its application in the development of hydrogen energy and economy. Therefore, it is the key trend to develop efficient non-noble metal electrocatalysts with the aim of providing cost-competitive hydrogen energy. In this review, we highlighted the recent research efforts toward the synthesis of noble metal-free electrocatalysts for the hydrogen evolution reaction ( HER) , mainly focusing on nanomaterial catalysts supported on carbon fiber materials. We reviewed several important kinds of heterogeneous non-noble metal electrocatalysts, including sulfides, selenides, carbides, phosphides, and oxides. In the discussion, emphasis was given to the synthetic methods of these HER electrocatalysts, and the strategies for performance improvement. In addition, this paper also briefly summarized the application of carbon fiber material as substrate in the field of electroanalytical chemistry.%电解水制氢技术是未来获得清洁氢能源的有效途径之一。铂作为高效的电解水制氢催化剂,由于其价格昂贵,难以回收,不利于氢能源与氢经济的发展,因此发展高效的非贵金属电催化剂,使电解水制氢过程更加高效、经济化是十分关键的科学问题。本文综述了近年来电解水制氢催化剂的研究进展,重点集中在以碳纤维材料为基底的非贵金属催化剂领域。总结了几类重要的多相异质非贵金属催化剂,包括磷化物、硫化物、硒化物、碳化物、氧化物催化剂等,重点探讨了各种析氢催化剂的合成方法和性能提高策略。同时,本文也简要概述了碳纤维基底材料在电分析化学检测方面的应用研究。

  5. Synthesis and characterization of catalysts and electrocatalysts using combinatorial methods

    Science.gov (United States)

    Ramanathan, Ramnarayanan

    This thesis documents attempts at solving three problems. Bead-based parallel synthetic and screening methods based on matrix algorithms were developed. The method was applied to search for new heterogeneous catalysts for dehydrogenation of methylcyclohexane. The most powerful use of the method to date was to optimize metal adsorption and evaluate catalysts as a function of incident energy, likely to be important in the future, should availability of energy be an optimization parameter. This work also highlighted the importance of order of addition of metal salts on catalytic activity and a portion of this work resulted in a patent with UOP LLC, Desplaines, Illinois. Combinatorial methods were also investigated as a tool to search for carbon-monoxide tolerant anode electrocatalysts and methanol tolerant cathode electrocatalysts, resulting in discovery of no new electrocatalysts. A physically intuitive scaling criterion was developed to analyze all experiments on electrocatalysts, providing insight for future experiments. We attempted to solve the CO poisoning problem in polymer electrolyte fuel cells using carbon molecular sieves as a separator. This approach was unsuccessful in solving the CO poisoning problem, possibly due to the tendency of the carbon molecular sieves to concentrate CO and CO 2 in pore walls.

  6. Biomimetic Synthesis of Noble Metal Nanoparticles and Their Applications as Electro-catalysts in Fuel Cells

    OpenAIRE

    Li, Yujing

    2012-01-01

    Today, proton electrolyte membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) are attractive power conversion devices that generate fairly low or even no pollution, and considered to be potential to replace conventional fossil fuel based power sources on automobiles. The operation and performance of PEMFC and DMFC depend largely on electro-catalysts positioned between the electrode and the membranes. The most commonly used electro-catalysts for PEMFC and DMFC are Pt-based noble me...

  7. Atomically Monodisperse Nickel Nanoclusters as Highly Active Electrocatalysts for Water Oxidation

    KAUST Repository

    Joya, Khurram

    2016-04-08

    Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these Ni NCs are found to be Ni4(PET)8 and Ni6(PET)12 and are highly active electrocatalysts for oxygen evolution without any pre-conditioning. Ni4(PET)8 are slightly better catalysts than Ni6(PET)12 and initiate the oxygen evolution at an amazingly low overpotential of ~1.51 V (vs RHE; η ≈ 280 mV). The peak oxygen evolution current density (J) of ~150 mA cm–2 at 2.0 V (vs. RHE) with a Tafel slope of 38 mV dec–1 is observed using Ni4(PET)8. These results are comparable to the state-of-the art RuO2 electrocatalyst, which is highly expensive and rare compared to Ni-based materials. Sustained oxygen generation for several hours with an applied current density of 20 mA cm–2 demonstrates the long-term stability and activity of these Ni NCs towards electrocatalytic water oxidation. This unique approach provides a facile method to prepare cost-effective, nanoscale and highly efficient electrocatalysts for water oxidation.

  8. Metal molybdate nanorods as non-precious electrocatalysts for the oxygen reduction

    Science.gov (United States)

    Wu, Tian; Zhang, Lieyu

    2015-12-01

    Development of non-precious electrocatalysts with applicable electrocatalytic activity towards the oxygen reduction reaction (ORR) is important to fulfill broad-based and large-scale applications of metal/air batteries and fuel cells. Herein, nickel and cobalt molybdates with uniform nanorod morphology are synthesized using a facile one-pot hydrothermal method. The ORR activity of the prepared metal molybdate nanorods in alkaline media are investigated by using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperomety in rotating disk electrode (RDE) techniques. The present study suggests that the prepared metal molybdate nanorods exhibit applicable electrocatalytic activities towards the ORR in alkaline media, promising the applications as non-precious cathode in fuel cells and metal-air batteries.

  9. Development of Refractory Ceramics for The Oxygen Evolution Reaction (OER) Electrocatalyst Support for Water Electrolysis at elevated temperatures

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Prag, Carsten Brorson; Polonsky, J.;

    2012-01-01

    Commercial TaC and Si3N4 powders were tested as possible electrocatalyst support materials for the Oxygen Evolution Reaction (OER) for PEM water electrolysers, operating at elevated temperatures. TaC and Si3N4 were characterised by thermogravimmetric and differential thermal analysis for their......-film method was used for electrochemical analysis of the prepared electrocatalysts. SEMEDX, BET and powder conductivity measurements were used as complementary techniques to complete characterisation of the electrocatalysts. Additionally, they were compared in their properties with previously reported data...

  10. Microporous La0.8Sr0.2MnO3 perovskite nanorods as efficient electrocatalysts for lithium-air battery

    Science.gov (United States)

    Lu, Fanliang; Wang, Yarong; Jin, Chao; Li, Fan; Yang, Ruizhi; Chen, Fanglin

    2015-10-01

    Efficient electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the most critical factor to influence the performance of lithium-air batteries. We present La0.8Sr0.2MnO3 (LSM) perovskite nanorods as high active electrocatalyst fabricated via a soft template method for lithium-air batteries. The as-prepared LSM nanorods are microporous with numerous defects and large surface area (20.6 m2 g-1), beneficial to the ORR and OER in the discharge and charge processes, respectively. Lithium-air batteries based on the microporous LSM nanorods electrocatalysts show enhanced electrochemical performances, including high first discharge specific capacity (6890 mAh g-1(electrode) at 200 mA g-1), low overpotential, good rate capability (up to 400 mA g-1), and cycle stability (only 1.1% voltage loss after 30 circles of specific capacity limit of 1000 mAh g-1 tested at 200 mA g-1). The improved performance might be due to the synergistic effect of the unique microporous and one-dimensional structure and numerous defects of the prepared LSM catalyst.

  11. Electrocatalysts for carbon dioxide conversion

    Energy Technology Data Exchange (ETDEWEB)

    Masel, Richard I; Salehi-Khojin, Amin

    2015-04-21

    Electrocatalysts for carbon dioxide conversion include at least one catalytically active element with a particle size above 0.6 nm. The electrocatalysts can also include a Helper Catalyst. The catalysts can be used to increase the rate, modify the selectivity or lower the overpotential of electrochemical conversion of CO.sub.2. Chemical processes and devices using the catalysts also include processes to produce CO, 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, (COOH).sub.2, or (COO.sup.-).sub.2, and a specific device, namely, a CO.sub.2 sensor.

  12. Oxygen reduction using platinum electrocatalysts prepared by liquid phase photo-deposition; Reduccion de oxigeno mediante electrocatalizadores de platino preparados por foto-deposicion en fase liquida

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Camacho, B.; Perez-Galindo, J. A.; Valenzuela, M. A.; Gonzalez-Huerta, R. G. [Instituto Politecnico Nacional, ESIQIE, Mexico D.F. (Mexico)]. E-mail: rosgonzalez_h@yahoo.com.mx

    2009-09-15

    This work presents the synthesis and characterization of nanometric-sized Pt/C electrochemical catalysts using impregnation and liquid phase photo-deposition methods. Two platinum precursors were used, C{sub 10}H{sub 14}O{sub 4}Pt (Pt acetylacetonate, Pt(acac){sub 2}) and H{sub 2}PtCl{sub 6} (hexachloroplatinic acid) to study the effect on the particle size and the electrocatalytic behavior in the oxygen reduction reaction. The characterization of the catalysts was done using x-ray diffraction, hydrogen chemisorption and transmission electron microscopy. The electrochemical study was conducted with cyclic voltamperometry and rotary disc electrode (RDE) techniques. Pt (E-tek) was used as a reference catalyst. The peaks of the platinum were identified based on the x-ray diffraction results, and correspond to crystalline phases (111) and (200), whose intensity was greater when using H{sub 2}PtCl{sub 6} versus Pt(acac){sub 2}. The hydrogen chemisorption and transmission electron microscopy tests found that the larger-sized particle (1-5 nm) and greater metallic dispersion was obtained using Pt(acac){sub 2} as a platinum precursor and liquid phase photo-deposition. It was also found that this material presented the best electrochemical response, showing a open-circuit potential of 0.96 V and over-potential of 0.05 V with respect to H{sub 2}PtCl{sub 6} and of 0.22 V with respect to the catalyst obtained using impregnation. [Spanish] En este trabajo se presenta la sintesis y caracterizacion electroquimica de catalizadores de tamano nanometrico de Pt/C empleando los metodos de impregnacion y foto-deposicion en fase liquida. Se utilizaron dos precursores del platino C{sub 10}H{sub 14}O{sub 4}Pt (acetil-acetonato de Pt, Pt(acac){sub 2}) y H2PtCl6 (acido hexacloroplatinico), para estudiar el efecto que tienen sobre el tamano de particula y el comportamiento electrocatalitico en la reaccion de reduccion de oxigeno. La caracterizacion de los catalizadores se realizo mediante

  13. Ni-based electrocatalyst for water oxidation developed In-situ in a HCO3 -/CO2 system at near-neutral pH

    KAUST Repository

    Joya, Khurram Saleem

    2014-03-10

    Electrochemically generated NiOx nanoworms from a neutral bicarbonate system split water into dioxygen and protons with tremendous efficiency and stability. The NiOx electrocatalyst follows a pH-potential dependence, revealing a PCET (proton coupled electron transfer) mechanism of one electron and one proton oxidation. It does not require proton abstracting phosphate or borate buffers for electrogeneration and catalysis, and shows promising activity for anodic oxidation of water in phosphate, borate, and carbonate buffers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. An Efficient Bi-functional Electrocatalyst Based on Strongly Coupled CoFe2O4/Carbon Nanotubes Hybrid for Oxygen Reduction and Oxygen Evolution

    International Nuclear Information System (INIS)

    Cobalt ferrite (CoFe2O4) spinel oxide is a promising electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, the catalytic activity of CoFe2O4 is limited by its poor electronic conductivity. In this study, CoFe2O4 strongly coupled with carbon nanotubes (CoFe2O4/CNTs) hybrid has been fabricated to address this issue. The as-synthesized CoFe2O4/CNTs hybrid exhibits excellent electrocatalytic activities for both the ORR and OER in alkaline solution. The onset potential of CoFe2O4/CNTs for ORR is −0.124 V (vs. Ag/AgCl), which is much higher than that of the CoFe2O4 + CNTs mixture (−0.259 V). Meanwhile, the CoFe2O4/CNTs hybrid shows much higher activity for OER as compared to the CoFe2O4 + CNT mixture. The onset potential of the former is 54 mV higher than that of the latter. The CoFe2O4/CNTs also holds high stability for both the ORR and OER, outperforming the CoFe2O4 + CNTs mixture. The excellent electrocatalytic activity and stability of the CoFe2O4/CNTs hybrid for both the ORR and OER make it a potential bi-functional electrocatalysts for metal-air batteries

  15. Co@Co3 O4 @PPD Core@bishell Nanoparticle-Based Composite as an Efficient Electrocatalyst for Oxygen Reduction Reaction.

    Science.gov (United States)

    Wang, Zhijuan; Li, Bing; Ge, Xiaoming; Goh, F W Thomas; Zhang, Xiao; Du, Guojun; Wuu, Delvin; Liu, Zhaolin; Andy Hor, T S; Zhang, Hua; Zong, Yun

    2016-05-01

    Durable electrocatalysts with high catalytic activity toward oxygen reduction reaction (ORR) are crucial to high-performance primary zinc-air batteries (ZnABs) and direct methanol fuel cells (DMFCs). An efficient composite electrocatalyst, Co@Co3 O4 core@shell nanoparticles (NPs) embedded in pyrolyzed polydopamine (PPD) is reported, i.e., in Co@Co3 O4 @PPD core@bishell structure, obtained via a three-step sequential process involving hydrothermal synthesis, high temperature calcination under nitrogen atmosphere, and gentle heating in air. With Co@Co3 O4 NPs encapsulated by ultrathin highly graphitized N-doped carbon, the catalyst exhibits excellent stability in aqueous alkaline solution over extended period and good tolerance to methanol crossover effect. The integration of N-doped graphitic carbon outer shell and ultrathin nanocrystalline Co3 O4 inner shell enable high ORR activity of the core@bishell NPs, as evidenced by ZnABs using catalyst of Co@Co3 O4 @PPD in air-cathode which delivers a stable voltage profile over 40 h at a discharge current density of as high as 20 mA cm(-2) . PMID:27031907

  16. Facile one-pot synthesis of CoS2-MoS2/CNTs as efficient electrocatalyst for hydrogen evolution reaction

    Science.gov (United States)

    Liu, Yan-Ru; Hu, Wen-Hui; Li, Xiao; Dong, Bin; Shang, Xiao; Han, Guan-Qun; Chai, Yong-Ming; Liu, Yun-Qi; Liu, Chen-Guang

    2016-10-01

    Ternary hybrid cobalt disulfide-molybdenum disulfides supported on carbon nanotubes (CoS2-MoS2/CNTs) electrocatalysts have been prepared via a simple hydrothermal method. CNTs as support may provide good conductivity and low the agglomeration of layered MoS2 structure. CoS2 with intrinsic metallic conductivity may enhance the activity of the ternary hybrid electrocatalysts for hydrogen evolution reaction (HER). X-ray diffraction (XRD) data confirm the formation of ternary hybrid nanocomposites composed of CNTs, CoS2 and amorphous MoS2. Scanning electron microscopy (SEM) images show that strong combination between MoS2, CNTs and regular orthohexagonal CoS2 has been obtained. The dispersion of each component is good and no obvious agglomeration can be observed. It is found that compared with CoS2/CNTs and MoS2/CNTs, the ternary CoS2-MoS2/CNTs have the better activity for HER with a low onset potential of 70 mV (vs. RHE) and a small Talel slope of 67 mV dec-1, and are extremely stable after 1000 cycles. In addition, the optimal doping ratio of Co to Mo is 2:1, which have better HER activity. It is proved that the introduction of carbon materials and Co atoms could improve the performances of MoS2-based electrocatalysts for HER.

  17. Nanostructured electrocatalysts with tunable activity and selectivity

    Science.gov (United States)

    Mistry, Hemma; Varela, Ana Sofia; Kühl, Stefanie; Strasser, Peter; Cuenya, Beatriz Roldan

    2016-04-01

    The field of electrocatalysis has undergone tremendous advancement in the past few decades, in part owing to improvements in catalyst design at the nanoscale. These developments have been crucial for the realization of and improvement in alternative energy technologies based on electrochemical reactions such as fuel cells. Through the development of novel synthesis methods, characterization techniques and theoretical methods, rationally designed nanoscale electrocatalysts with tunable activity and selectivity have been achieved. This Review explores how nanostructures can be used to control electrochemical reactivity, focusing on three model reactions: O2 electroreduction, CO2 electroreduction and ethanol electrooxidation. The mechanisms behind nanoscale control of reactivity are discussed, such as the presence of low-coordinated sites or facets, strain, ligand effects and bifunctional effects in multimetallic materials. In particular, studies of how particle size, shape and composition in nanostructures can be used to tune reactivity are highlighted.

  18. Synthesis methods of low-Pt-loading electrocatalysts for proton exchange membrane fuel cell systems

    Energy Technology Data Exchange (ETDEWEB)

    Esmaeilifar, A.; Ghazanfari, E. [Fuel Cell Laboratory, Green Research Center, Iran University of Science and Technology, Tehran (Iran); Rowshanzamir, S. [Fuel Cell Laboratory, Green Research Center, Iran University of Science and Technology, Tehran (Iran); School of Chemical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114 (Iran); Eikani, M.H. [Department of Chemical Industries, Iranian Research Organization for Science and Technology (IROST), Tehran (Iran)

    2010-09-15

    While the use of a high level of platinum (Pt) loading in proton exchange membrane fuel cells (PEMFCs) can amplify the trade off towards higher performance and longer lifespan for these PEMFCs, the development of PEMFC electrocatalysts with low-Pt-loadings and high-Pt-utilization is critical and the limited supply and high cost of the Pt used in PEMFC electrocatalysts necessitate a reduction in the Pt level. In order to make such electrocatalysts commercially feasible, cost-effective and innovative, catalyst synthesis methods are needed for Pt loading reduction and performance optimization. Since a Pt-deposited carbon nanotube (CNT) shows higher performance than a commercial Pt-deposited carbon black (CB) with reducing 60% Pt load per electrode area in PEMFCs, use of CNTs in preparing electrocatalysts becomes considerable. This paper reviews the literature on the synthesis methods of carbon-supported Pt electrocatalysts for PEMFC catalyst loading reduction through the improvement of catalyst utilization and activity. The features of electroless deposition (ED) method, deposition on sonochemically treated CNTs, polyol process, electrodeposition method, sputter-deposition technique, {gamma}-irradiation method, microemulsion method, aerosol assisted deposition (AAD) method, Pechini method, supercritical deposition technique, hydrothermal method and colloid method are discussed and characteristics of each one are considered. (author)

  19. Platinum monolayer electrocatalysts for oxygen reduction: effect of substrates, and long-term stability

    Directory of Open Access Journals (Sweden)

    J. ZHANG

    2005-03-01

    Full Text Available We describe a novel concept for a Ptmonolayer electrocatalyst and present the results of our electrochemical, X-ray absorption spectroscopy, and scanning tunneling microscopy studies. The electrocatalysts were prepared by a new method for depositing Pt monolayers involving the galvanic displacement by Pt of an underpotentially deposited Cu monolayer on substrates of Au (111, Ir(111, Pd(111, Rh(111 and Ru(0001 single crylstals, and Pd nanoparticles. The kinetics of O2 reduction showed significant enhancement with Pt monolayers on Pd(111 and Pd nanoparticle surfaces in comparisonwith the reaction on Pt(111 and Pt nanoparticles, respectively. This increase in catalytic activity is attributed partly to the decreased formation of PtOH, as shown by in situ X-ray absorption spectroscopy. The results illustrate that placing a Pt monolayer on a suitable substrate of metal nanoparticles is an attractive way of designing better O2 reduction electrocatalysts with very low Pt contents.

  20. Kocite /sup R/ materials for electrocatalysts novel approach to carbonaceous supports

    International Nuclear Information System (INIS)

    Kocite materials are composite structures of a thin film semiconducting pyropolymer chemically bonded to the surface of a high-surface-area alumina support. For use in H3PO4 fuel cells, the alumina substrate is leached from the composite structure leaving a high-surface-area carbonaceous support, which is then impregnated with catalytically active materials. With process modification, alterations of the pore structure or pyropolymer structure of these supports can be achieved, producing different types of Kocite electrocatalysts. In this paper, the preparation, characterization and testing of such Kocite electrocatalysts will be reviewed, including results on support corrosion, catalytic metal agglomeration during electrocatalyst aging and the performance in model H3PO4 fuel cells

  1. Nanoparticle Superlattices as Efficient Bifunctional Electrocatalysts for Water Splitting.

    Science.gov (United States)

    Li, Jun; Wang, Yongcheng; Zhou, Tong; Zhang, Hui; Sun, Xuhui; Tang, Jing; Zhang, Lijuan; Al-Enizi, Abdullah M; Yang, Zhongqin; Zheng, Gengfeng

    2015-11-18

    The solar-driven water splitting process is highly attractive for alternative energy utilization, while developing efficient, earth-abundant, bifunctional catalysts for both oxygen evolution reaction and hydrogen evolution reaction has remained as a major challenge. Herein, we develop an ordered CoMnO@CN superlattice structure as an efficient bifunctional water-splitting electrocatalyst, in which uniform Co-Mn oxide (CoMnO) nanoparticles are coated with a thin, continuous nitrogen-doped carbon (CN) framework. The CoMnO nanoparticles enable optimized OER activity with effective electronic structure configuration, and the CN framework serves as an excellent HER catalyst. Importantly, the ordered superlattice structure is beneficial for enhanced reactive sites, efficient charge transfer, and structural stability. This bifunctional superlattice catalyst manifests optimized current densities and electrochemical stability in overall water splitting, outperforming most of the previously reported single- or bifunctional electrocatalysts. Combining with a silicon photovoltaic cell, this CoMnO@CN superlattice bifunctional catalyst enables unassisted solar water splitting continuously for ∼5 days with a solar-to-hydrogen conversion efficiency of ∼8.0%. Our discovery suggests that these transition metal oxide-based superlattices may serve as a unique structure modality for efficient bifunctional water splitting electrocatalysts with scale-up potentials. PMID:26496655

  2. Nanoparticle Superlattices as Efficient Bifunctional Electrocatalysts for Water Splitting.

    Science.gov (United States)

    Li, Jun; Wang, Yongcheng; Zhou, Tong; Zhang, Hui; Sun, Xuhui; Tang, Jing; Zhang, Lijuan; Al-Enizi, Abdullah M; Yang, Zhongqin; Zheng, Gengfeng

    2015-11-18

    The solar-driven water splitting process is highly attractive for alternative energy utilization, while developing efficient, earth-abundant, bifunctional catalysts for both oxygen evolution reaction and hydrogen evolution reaction has remained as a major challenge. Herein, we develop an ordered CoMnO@CN superlattice structure as an efficient bifunctional water-splitting electrocatalyst, in which uniform Co-Mn oxide (CoMnO) nanoparticles are coated with a thin, continuous nitrogen-doped carbon (CN) framework. The CoMnO nanoparticles enable optimized OER activity with effective electronic structure configuration, and the CN framework serves as an excellent HER catalyst. Importantly, the ordered superlattice structure is beneficial for enhanced reactive sites, efficient charge transfer, and structural stability. This bifunctional superlattice catalyst manifests optimized current densities and electrochemical stability in overall water splitting, outperforming most of the previously reported single- or bifunctional electrocatalysts. Combining with a silicon photovoltaic cell, this CoMnO@CN superlattice bifunctional catalyst enables unassisted solar water splitting continuously for ∼5 days with a solar-to-hydrogen conversion efficiency of ∼8.0%. Our discovery suggests that these transition metal oxide-based superlattices may serve as a unique structure modality for efficient bifunctional water splitting electrocatalysts with scale-up potentials.

  3. Preparation of PtSn/C, PtRu/C, PtRh/C, PtRuRh/C and PtSnRh/C electrocatalysts using an alcohol-reduction process for methanol and ethanol oxidation; Preparacao e caracterizacao de eletrocatalisadores PtRu, PtSn, PtRh, PtRuRh e PtSnRh para oxidacao direta de alcoois em celulas a combustivel tipo PEM utilizando a metodologia da reducao por alcool

    Energy Technology Data Exchange (ETDEWEB)

    Dias, Ricardo Rodrigues

    2009-07-01

    In this work, Pt/C, PtRh (90:10), PtRh/C (50:50), PtSn/C (50:50), PtRu (50:50)/C, PtRuRh/C (50:40:10) and PtSnRh/C (50:40:10) were prepared by an alcohol-reduction process with metal loading of 20 wt.% using H{sub 2}PtCl{sub 6}.6H{sub 2}O (Aldrich), SnCl{sub 2}.2H{sub 2}O (Aldrich),and RhCl{sub 2}.XH{sub 2}O (Aldrich) as metals sources and Vulcan XC72 as support. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry (CV). The electro-oxidation of ethanol was studied by CV, chronoamperomety at room temperature in acid medium and tests at 100 deg C on a single cell of a direct methanol or ethanol fuel cell. The EDX analysis showed that the metal atomic ratios of the obtained electrocatalysts were similar to the nominal atomic ratios used in the preparation. The diffractograms of electrocatalysts prepared showed four peaks at approximately 2{theta} =40 deg, 47 deg, 67 deg and 82 deg, which are associated with the (111), (200), (220) and (311) planes, respectively, of a face cubic-centered (fcc) structure characteristic of platinum and platinum alloys. The average crystallite sizes using the Scherrer equation and the calculated values were in the range of 2-3 nm. For Pt Sn/C and PtSnRh/C two additional peaks were observed at 2 = 34 deg and 52 deg that were identified as a SnO{sub 2} phase. Pt Sn/C (50:50) and PtSnRh/C (50:40:10) electro catalyst showed the best performance for ethanol oxidation at room temperature. For methanol oxidation at room temperature Pt Ru/C, Pt Sn/C and PtRuRh/C electrocatalysts showed the best performance. Tests at 100 deg C on a single cell of a direct ethanol fuel cell PtSnRh/C showed the best performance, for methanol oxidation PtRuRh/C showed the best performance. (author)

  4. Highly stable PtRuTiO{sub x}/C anode electrocatalyst for direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Juan; Jiang, Luhua; Yan, Shiyou; Mao, Qing [Direct Alcohol Fuel Cell Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Graduate School of the Chinese Academy of Science, Beijing 100039 (China); Sun, Gongquan [Direct Alcohol Fuel Cell Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Xin, Qin [Direct Alcohol Fuel Cell Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China)

    2007-04-15

    In the present investigation, PtRuTiO{sub x}/C electrocatalyst was prepared by a modified polyol synthesis method and the as-prepared electrocatalyst was treated under the reductive atmosphere (30 vol% H{sub 2} in Ar) at 500 C for 2 h (denoted as PtRuTiO{sub x}/C-500) to enhance the interaction between the metal particles and the support. For comparison, the commercial PtRu/C electrocatalyst was also treated by the same procedure as PtRuTiO{sub x}/C (denoted as PtRu/C-500). Transmission electron microscopy results indicated that PtRuTiO{sub x}/C electrocatalyst exhibited not only a uniform dispersion and narrow size distribution with a smaller particle size, but also excellent stability during the thermal treatment. In contrast, the commercial PtRu/C electrocatalyst is not stable during the thermal treatment and the metal particles greatly agglomerated. The results of CO-stripping voltammetry, single direct methanol fuel cell tests and life-time test jointly showed that PtRuTiO{sub x}/C-500 had better durability than commercial PtRu/C while keeping a desirable activity toward methanol electro-oxidation, which may be attributed to the addition of titanium oxide that improved the interaction between noble metal particles and the support. (author)

  5. Highly Porous Carbon Derived from MOF-5 as a Support of ORR Electrocatalysts for Fuel Cells.

    Science.gov (United States)

    Khan, Inayat Ali; Qian, Yuhong; Badshah, Amin; Nadeem, Muhammad Arif; Zhao, Dan

    2016-07-13

    The development of highly competent electrocatalysts for the sluggish oxygen reduction reaction (ORR) at cathodes of proton-exchange membrane fuel cells (PEMFCs) is extremely important for their long-term operation and wide applications. Herein, we present highly efficient ORR electrocatalysts based on Pt/Ni bimetallic nanoparticles dispersed on highly porous carbon obtained via pyrolysis of a metal-organic framework MOF-5. In comparison to the commercial Pt/C (20%), the electrocatalyst Pt-Ni/PC 950 (15:15%) in this study exhibits a pronounced positive shift of 90 mV in Eonset. In addition, it also demonstrates excellent long-term stability and durability during the 500-cycle continue-oxygen-supply (COS) accelerating durability tests (ADTs). The significantly improved activity and stability of Pt-Ni/PC 950 (15:15%) can be attributed to the Pt electron interaction with Ni and carbon support as has been proved in X-ray and microscopic analysis.

  6. Rational design of competitive electrocatalysts for the oxygen reduction reaction in hydrogen fuel cells

    Science.gov (United States)

    Stolbov, Sergey; Alcántara Ortigoza, Marisol

    2012-02-01

    The large-scale application of one of the most promising clean and renewable sources of energy, hydrogen fuel cells, still awaits efficient and cost-effective electrocatalysts for the oxygen reduction reaction (ORR) occurring on the cathode. We demonstrate that truly rational design renders electrocatalysts possessing both qualities. By unifying the knowledge on surface morphology, composition, electronic structure and reactivity, we solve that sandwich-like structures are an excellent choice for optimization. Their constituting species couple synergistically yielding reaction-environment stability, cost-effectiveness and tunable reactivity. This cooperative-action concept enabled us to predict two advantageous ORR electrocatalysts. Density functional theory calculations of the reaction free-energy diagrams confirm that these materials are more active toward ORR than the so far best Pt-based catalysts. Our designing concept advances also a general approach for engineering materials in heterogeneous catalysis.

  7. New electrocatalyst support for high temperature PEM fuel cells (HT-PEMFC)

    Energy Technology Data Exchange (ETDEWEB)

    Boaventura, M.; Brandao, L.; Mendes, A. [Porto Univ. (PT). Lab. de Engenharia de Processos, Ambiente e Energia (LEPAE)

    2010-07-01

    This work compares the performance of electrocatalysts based on platinum supported in single-wall carbon nanohorns (Pt-SWNH) and supported in carbon black (Pt-carbon black) during high temperature PEM fuel operation. MEAs made of phosphoric acid doped polybenzimidazole (PBI/H{sub 3}PO{sub 4}) were characterized by polarization curves, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), at 160 C. The Pt-SWNH electrocatalyst presented a higher electrochemical surface area (ESA) when compared to Pt-carbon black. However, electrochemical experiments showed a higher ohmic resistance of the Pt-SWNH electrode related to a higher hydrophobic character of the SWNH carbon. (orig.)

  8. Electrocatalysts for the oxygen evolution electrode in water electrolysers using proton exchange membranes : synthesis and characterisation

    OpenAIRE

    Marshall, Aaron

    2005-01-01

    Electrocatalysts based on IrO2 have been synthesised and characterised using a wide range of techniques. These oxide materials were primarily developed as oxygen evolution electrocatalysts for proton exchange membrane (PEM) water electrolysis. This development has enabled high performances to be achieved in a PEM water electrolysis cell. Overall the best result was obtained with an Ir0.6Ru0.4O2 anode and 20 wt% Pt/C cathode, with a cell voltage of 1.567 V at 1 A cm−2 and 80 °C when using Nafi...

  9. A hydrogen-evolving Ni(P2N2)2 electrocatalyst covalently attached to a glassy carbon electrode: preparation, characterization, and catalysis. comparisons with the homogeneous analogue.

    Science.gov (United States)

    Das, Atanu K; Engelhard, Mark H; Bullock, R Morris; Roberts, John A S

    2014-07-01

    A hydrogen-evolving homogeneous Ni(P2N2)2 electrocatalyst with peripheral ester groups has been covalently attached to a 1,2,3-triazolyllithium-terminated planar glassy carbon electrode surface. Coupling proceeds with both the Ni(0) and the Ni(II) complexes. X-ray photoemission spectra show excellent agreement between the Ni(0) coupling product and its parent complex, and voltammetry of the surface-confined system shows that a single species predominates with a surface density of 1.3 × 10(-10) mol cm(-2), approaching the value estimated for a densely packed monolayer. With the Ni(II) system, both photoemission and voltammetric data show speciation to unidentified products on coupling, and the surface density is 6.7 × 10(-11) mol cm(-2). The surface-confined Ni(0) complex is an electroctalyst for hydrogen evolution, showing the onset of catalytic current at the same potential as the soluble parent complex. Decomposition of the surface-confined species is observed in acidic acetonitrile. This is interpreted to reflect the lability of the Ni(II)-phosphine interaction and the basicity of the free phosphine and bears on concurrent efforts to implement surface-confined Ni(P2N2)2 complexes in electrochemical or photoelectrochemical devices.

  10. Oxygen reduction on carbon supported Pt-W electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Meza, D.; Morales, U.; Salgado, L. [Departamento de Quimica, Area de Electroquimica, Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco 186, Col. Vicentina, 09340 Distrito Federal (Mexico); Roquero, P. [Unidad de Investigacion en Catalisis, Facultad de Quimica, UNAM, Ciudad Universitaria, 04510 Distrito Federal (Mexico)

    2010-11-15

    The catalytic activity of Pt-W electrocatalysts towards oxygen reduction reaction (ORR) was studied. Pt-W/C materials were prepared by thermolysis of tungsten and platinum carbonyl complexes in 1-2 dichloro-benzene during 48 h. The precursors were mixed to obtain relations of Pt:W: 50:50 and 80:20%w, respectively. The Pt carbonyl complex was previously synthesized by bubbling CO in a chloroplatinic acid solution. The synthesized materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV) and a rotating disk electrode (RDE). The results show that both materials (Pt{sub 50}W{sub 50}/C and Pt{sub 80}W{sub 20}/C) have a crystalline phase associated with metallic platinum and an amorphous phase related with tungsten and carbon. The particle size of the electrocatalysts depends on the relationship between platinum and tungsten. Finally, both materials exhibit catalytic activity for oxygen reduction. (author)

  11. Performance of Nafion-TiO{sub 2} hybrid membranes and PtSn/C electrocatalysts in PEM type fuel cells fed with ethanol and H{sub 2}/CO at high temperature; Desempenho de membranas hibridas Nafion-TiO{sub 2} e eletrocatisadores de PtSn/C em celulas a combustivel do tipo PEM alimentadas com etanol e com H{sub 2}/CO em alta temperatura

    Energy Technology Data Exchange (ETDEWEB)

    Isidoro, Roberta Alvarenga

    2010-07-01

    In this work, Nafion-TiO{sub 2} hybrid electrolytes and PtSn/C electrocatalysts were synthesized for the application in direct ethanol fuel cell operating at high temperature (130 degree C). For this purpose, TiO{sub 2} particles were incorporated in commercial Nafion membranes by an 'in situ' sol gel route. The resulting materials were characterized by gravimetric analysis, water uptake, DSC, XRD and EDX. Electrocatalysts based on carbon dispersed platinum-tin (PtSn/C), with different composition, were produced by alcohol-reduction method and were employed as anodic electrode. The electrocatalysts were characterized by XRD, EDX, XPS and transmission electronic spectroscopy. The electrochemical characterization was conducted by cyclic voltametry, carbon monoxide linear anodic voltammetry (CO stripping), and chronoamperometry. Membrane-electrodes assembly (MEAs) were formed with PtSn/C anodes, Pt/C cathodes and Nafion-TiO{sub 2} hybrids. The performance of these MEA was evaluated in single-cell fed with H2/CO mixture or ethanol solution at the anode and oxygen at the cathode in the temperature range of 80-130 degree C. The analysis showed that the hybrid membranes improved the DEFC performance due to crossover suppression and that PtSn/C 70:30 electrocatalysts, prepared by an alcohol reduction process, showed better performance in ethanol oxidation. (author)

  12. Development of Refractory Ceramics for The Oxygen Evolution Reaction (OER) Electrocatalyst Support for Water Electrolysis at elevated temperatures

    OpenAIRE

    Nikiforov, Aleksey; Prag, Carsten Brorson; Polonsky, J; Petrushina, Irina; Christensen, Erik; Bjerrum, Niels

    2012-01-01

    Commercial TaC and Si3N4 powders were tested as possible electrocatalyst support materials for the Oxygen Evolution Reaction (OER) for PEM water electrolysers, operating at elevated temperatures. TaC and Si3N4 were characterised by thermogravimmetric and differential thermal analysis for their thermal stability. The Adams fusion method was implemented to deposit IrO2 on the support surfaces. A series of electrocatalysts was prepared with a composition of (IrO2)x(TaC/ Si3N4)1-x,where x represe...

  13. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    Science.gov (United States)

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-07-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.

  14. Performance of a PEM water electrolyser using a TaC-supported iridium oxide electrocatalyst

    DEFF Research Database (Denmark)

    Polonský, J.; Mazúr, P.; Paidar, M.;

    2014-01-01

    Polymer electrolyte membrane (PEM) water electrolysis is an attractive way of producing carbon-free hydrogen. One of the drawbacks of this method is the need for precious metal-based electrocatalysts. This calls for a highly efficient utilization of the precious metal, which can be obtained by di...

  15. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts.

    Science.gov (United States)

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S; Kumta, Prashant N

    2016-01-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations. PMID:27380719

  16. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    Science.gov (United States)

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-01-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations. PMID:27380719

  17. Photochemically modified ATO NPs as conductive support of Pt electrocatalysts for proton exchange membrane fuel cells

    International Nuclear Information System (INIS)

    Antimony-doped tin oxide (ATO) nanoparticles (NPs) were covalently modified with a benzophenone-silicate photoreactive organic molecule to enable the UV-mediated photoreduction of Pt(IV) on the surface of the ATO NPs to give Pt(0) NPs. The successfully synthesized Pt/ATO nanocomposites (NCs) that were based on these novel hybrid photoreactive ATO NPs showed a much better Pt dispersion than Pt/ATO NCs prepared by traditional methods. The size of the Pt NPs was below 2.8 nm for all the NCs. The prepared NCs were studied with respect to their properties as durable and active electrocatalysts for proton exchange membrane fuel cells. They were subjected to fuel-cell-relevant electrochemical characterization by rotating disc electrode cyclic voltammetry. The electrochemically active surface area was found to be significantly lower for the novel NCs than for the standard Pt/C catalyst, while on the other hand, their specific electrocatalytic activity towards the oxygen reduction reaction (ORR) was found to exceed that of the reference Pt/C by several times. The ORR activity in terms of the mass of Pt was comparable to, or greater than, that of the Pt/C. The stability towards electrochemical ageing was greatly improved for Pt/ATO NCs relative to Pt/C

  18. Photochemically modified ATO NPs as conductive support of Pt electrocatalysts for proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Ostrovsky, Stella [Bar-Ilan University, Department of Chemistry, Nanomaterials Research Center, Institute of Nanotechnology and Advanced Materials (Israel); Larsen, Mikkel Juul, E-mail: mjl@ird.dk [IRD Fuel Cells A/S (Denmark); Peled, Anna; Lellouche, Jean-Paul, E-mail: lellouj@mail.biu.ac.il [Bar-Ilan University, Department of Chemistry, Nanomaterials Research Center, Institute of Nanotechnology and Advanced Materials (Israel)

    2015-06-15

    Antimony-doped tin oxide (ATO) nanoparticles (NPs) were covalently modified with a benzophenone-silicate photoreactive organic molecule to enable the UV-mediated photoreduction of Pt(IV) on the surface of the ATO NPs to give Pt(0) NPs. The successfully synthesized Pt/ATO nanocomposites (NCs) that were based on these novel hybrid photoreactive ATO NPs showed a much better Pt dispersion than Pt/ATO NCs prepared by traditional methods. The size of the Pt NPs was below 2.8 nm for all the NCs. The prepared NCs were studied with respect to their properties as durable and active electrocatalysts for proton exchange membrane fuel cells. They were subjected to fuel-cell-relevant electrochemical characterization by rotating disc electrode cyclic voltammetry. The electrochemically active surface area was found to be significantly lower for the novel NCs than for the standard Pt/C catalyst, while on the other hand, their specific electrocatalytic activity towards the oxygen reduction reaction (ORR) was found to exceed that of the reference Pt/C by several times. The ORR activity in terms of the mass of Pt was comparable to, or greater than, that of the Pt/C. The stability towards electrochemical ageing was greatly improved for Pt/ATO NCs relative to Pt/C.

  19. Copper-modified covalent triazine frameworks as non-noble-metal electrocatalysts for oxygen reduction.

    Science.gov (United States)

    Iwase, Kazuyuki; Yoshioka, Tatsuro; Nakanishi, Shuji; Hashimoto, Kazuhito; Kamiya, Kazuhide

    2015-09-14

    The electrochemical oxygen reduction reaction (ORR) is an important cathode reaction of various types of fuel cells. The development of electrocatalysts composed only of abundant elements is a key goal because currently only platinum is a suitable catalyst for ORR. Herein, we synthesized copper-modified covalent triazine frameworks (CTF) hybridized with carbon nanoparticles (Cu-CTF/CPs) as efficient electrocatalysts for the ORR in neutral solutions. The ORR onset potential of the synthesized Cu-CTF/CP was 810 mV versus the reversible hydrogen electrode (RHE; pH 7), the highest reported value at neutral pH for synthetic Cu-based electrocatalysts. Cu-CTF/CP also displayed higher stability than a Cu-based molecular complex at neutral pH during the ORR, a property that was likely as a result of the covalently cross-linked structure of CTF. This work may provide a new platform for the synthesis of durable non-noble-metal electrocatalysts for various target reactions. PMID:26227987

  20. Significant Enhancement of Water Splitting Activity of N-Carbon Electrocatalyst by Trace Level Co Doping.

    Science.gov (United States)

    Bayatsarmadi, Bita; Zheng, Yao; Tang, Youhong; Jaroniec, Mietek; Qiao, Shi-Zhang

    2016-07-01

    Replacement of precious metal electrocatalysts with highly active and cost efficient alternatives for complete water splitting at low voltage has attracted a growing attention in recent years. Here, this study reports a carbon-based composite co-doped with nitrogen and trace amount of metallic cobalt (1 at%) as a bifunctional electrocatalyst for water splitting at low overpotential and high current density. An excellent electrochemical activity of the newly developed electrocatalyst originates from its graphitic nanostructure and highly active Co-Nx sites. In the case of carefully optimized sample of this electrocatalyst, 10 mA cm(-2) current density can be achieved for two half reactions in alkaline solutions-hydrogen evolution reaction and oxygen evolution reaction-at low overpotentials of 220 and 350 mV, respectively, which are smaller than those previously reported for nonprecious metal and metal-free counterparts. Based on the spectroscopic and electrochemical investigations, the newly identified Co-Nx sites in the carbon framework are responsible for high electrocatalytic activity of the Co,N-doped carbon. This study indicates that a trace level of the introduced Co into N-doped carbon can significantly enhance its electrocatalytic activity toward water splitting. PMID:27246288

  1. Targeted design of α-MnO2 based catalysts for oxygen reduction

    DEFF Research Database (Denmark)

    Lehtimaeki, Matti; Hoffmannova, Hana; Boytsova, Olga;

    2016-01-01

    The paper focuses on theoretical and experimental aspects of an oxide surface optimization for oxygen reduction reaction (ORR). Various doped α-MnO2 based electrocatalysts were prepared by microwave-assisted hydrothermal synthesis and electrochemically characterized to validate density functional...

  2. Synthesis and characterization of NiFe2O4 electrocatalyst for the hydrogen evolution reaction in alkaline water electrolysis using different polymer binders

    Science.gov (United States)

    Chanda, Debabrata; Hnát, Jaromír; Paidar, Martin; Schauer, Jan; Bouzek, Karel

    2015-07-01

    NiFe2O4 electrocatalyst for the hydrogen evolution reaction (HER) has been synthesized using the co-precipitation method of the respective metal ions from water solution. After calcination of the precipitate, the resulting electrocatalyst was characterized by a broad range of techniques to obtain information on its crystallographic structure, specific surface area, morphology and chemical composition. The electrocatalytic activity towards HER in alkaline water electrolysis was investigated by means of linear sweep voltammetry. The catalyst showed promising electrocatalytic properties. Subsequently three types of binders were used to prepare a cathode catalytic layer based on a catalyst synthesized on top of a nickel foam support, namely an anion-selective quaternized poly(phenylene oxide) (qPPO) ionomer, an electroneutral polymer polytetrafluoroethylene and cation-selective Nafion®. The resulting membrane-electrode assemblies (MEAs), based on an anion-selective membrane, were tested in an alkaline water electrolyzer. In a single-cell test the MEA with a qPPO ionomer exhibited higher HER activity compared to the remaining binders tested. The current density obtained using a MEA containing qPPO binder attained a value of 125 mA cm-2 at a cell voltage of 1.85 V. The stability of the MEA containing qPPO binder was examined by continuous operation for 143 h, followed by 55 h intermittent electrolysis.

  3. Metal oxide electrocatalysts for alternative energy technologies

    Science.gov (United States)

    Pacquette, Adele Lawren

    This dissertation focuses on the development of metal oxide electrocatalysts with varying applications for alternative energy technologies. Interest in utilizing clean, renewable and sustainable sources of energy for powering the planet in the future has received much attention. This will address the growing concern of the need to reduce our dependence on fossil fuels. The facile synthesis of metal oxides from earth abundant metals was explored in this work. The electrocatalysts can be incorporated into photoelectrochemical devices, fuel cells, and other energy storage devices. The first section addresses the utilization of semiconductors that can harness solar energy for water splitting to generate hydrogen. An oxysulfide was studied in order to combine the advantageous properties of the stability of metal oxides and the visible light absorbance of metal chalcogenides. Bi 2O2S was synthesized under facile hydrothermal conditions. The band gap of Bi2O2S was smaller than that of its oxide counterpart, Bi2O3. Light absorption by Bi 2O2S was extended to the visible region (>600 nm) in comparison to Bi2O3. The formation of a composite with In 2O3 was formed in order to create a UV irradiation protective coating of the Bi2O2S. The Bi2O2S/In 2O3 composite coupled with a dye CrTPP(Cl) and cocatalysts Pt and Co3O4 was utilized for water splitting under light irradiation to generate hydrogen and oxygen. The second section focuses on improving the stability and light absorption of semiconductors by changing the shapes and morphologies. One of the limitations of semiconductor materials is that recombination of electron-hole pairs occur within the bulk of the materials instead of migration to the surface. Three-dimensional shapes, such as nanorods, can prevent this recombination in comparison to spherical particles. Hierarchical structures, such as dendrites, cubes, and multipods, were synthesized under hydrothermal conditions, in order to reduce recombination and improve

  4. Characterization of composite materials of electroconductive polymer and cobalt as electrocatalysts for the oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Martinez Millan, W.; Toledano Thompson, T.; Smit, Mascha A. [Centro de Investigacion Cientifica de Yucatan (CICY), Unidad de Materiales, Calle 43 No. 130, Col. Chuburna de Hidalgo, 97200 Merida, Yucatan (Mexico); Arriaga, L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica S.C. (CIDETEQ), Parque Tecnologico Queretaro, 76700 Queretaro Sanfandila, Queretaro (Mexico)

    2009-01-15

    Platinum-free electrocatalysts based on electroconductive polymer, modified with cobalt, were prepared and characterized for the oxygen reduction reaction (ORR). The carbon-supported materials were: carbon/polyaniline/cobalt, carbon/polypyrrole/cobalt and carbon/poly(3-methylthiophene)/cobalt. Also the corresponding cobalt-free precursors were studied. EDAX studies show that in cobalt-modified catalysts, significant percentages of cobalt, between 5 and 7% in weight, are present. FTIR, TGA, and EDAX studies confirmed that the addition of cobalt modifies the chemical structure of C-Pani, C-Ppy, and C-P3MT materials. Cyclic voltammetry shows reduction peaks corresponding to the ORR for all materials and kinetic parameters were calculated based on lineal voltammetry using RDE at different rotating speeds. It was found that C-P3MT-Co has highest exchange current densities, followed by C-Ppy and C-Ppy-Co. All samples have Tafel slopes between -110 and -120 V/dec, indicating that the first electron transfer is the decisive step in the global ORR. Potentiostatic tests showed an adequate stability of cobalt-modified samples in acid medium at ORR potentials. Based on the potential range at which ORR occurs, the exchange current density and stability tests, it is concluded that the best material for potential application as fuel cell cathode catalyst is C-Ppy-Co. (author)

  5. Metal-free carbonaceous electrocatalysts and photocatalysts for water splitting.

    Science.gov (United States)

    Xu, You; Kraft, Markus; Xu, Rong

    2016-05-31

    Water splitting driven by sunlight or renewable resource-derived electricity has attracted great attention for sustainable production of hydrogen from water. Current research interest in this field is focused on the development of earth-abundant photo- or electrocatalytic materials with high activity and long-term stability for hydrogen and/or oxygen evolution reactions. Due to their unique properties and characteristics, carbon and related carbon-based materials show great potential to replace some of the existing precious metal catalysts in water splitting technology. This tutorial review summarizes the recent significant progress in the fabrication and application of metal-free carbonaceous materials as photo- or electrocatalysts for water splitting. Synthetic strategies and applications of various carbonaceous materials, including graphitic carbon nitride (g-C3N4), graphene, carbon nanotubes (CNTs) as well as other forms of carbon-containing materials, for electrochemical or photochemical water splitting are presented, accompanied by a discussion of the key scientific issues and prospects for the future development of metal-free photo- and electrocatalysts. PMID:27094875

  6. Highly Efficient Electrocatalysts for Oxygen Reduction Reaction Based on 1D Ternary Doped Porous Carbons Derived from Carbon Nanotube Directed Conjugated Microporous Polymers

    KAUST Repository

    He, Yafei

    2016-10-11

    © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.One-dimensional (1D) porous materials have shown great potential for gas storage and separation, sensing, energy storage, and conversion. However, the controlled approach for preparation of 1D porous materials, especially porous organic materials, still remains a great challenge due to the poor dispersibility and solution processability of the porous materials. Here, carbon nanotube (CNT) templated 1D conjugated microporous polymers (CMPs) are prepared using a layer-by-layer method. As-prepared CMPs possess high specific surface areas of up to 623 m2 g-1 and exhibit strong electronic interactions between p-type CMPs and n-type CNTs. The CMPs are used as precursors to produce heteroatom-doped 1D porous carbons through direct pyrolysis. As-produced ternary heteroatom-doped (B/N/S) 1D porous carbons possess high specific surface areas of up to 750 m2 g-1, hierarchical porous structures, and excellent electrochemical-catalytic performance for oxygen reduction reaction. Both of the diffusion-limited current density (4.4 mA cm-2) and electron transfer number (n = 3.8) for three-layered 1D porous carbons are superior to those for random 1D porous carbon. These results demonstrate that layered and core-shell type 1D CMPs and related heteroatom-doped 1D porous carbons can be rationally designed and controlled prepared for high performance energy-related applications.

  7. Pomegranate-Inspired Design of Highly Active and Durable Bifunctional Electrocatalysts for Rechargeable Metal-Air Batteries.

    Science.gov (United States)

    Li, Ge; Wang, Xiaolei; Fu, Jing; Li, Jingde; Park, Moon Gyu; Zhang, Yining; Lui, Gregory; Chen, Zhongwei

    2016-04-11

    Rational design of highly active and durable electrocatalysts for oxygen reactions is critical for rechargeable metal-air batteries. Herein, we report the design and development of composite electrocatalysts based on transition metal oxide nanocrystals embedded in a nitrogen-doped, partially graphitized carbon framework. Benefiting from the unique pomegranate-like architecture, the composite catalysts possess abundant active sites, strong synergetic coupling, enhanced electron transfer, and high efficiencies in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The Co3 O4 -based composite electrocatalyst exhibited a high half-wave potential of 0.842 V for ORR, and a low overpotential of only 450 mV at the current density of 10 mA cm(-2) for OER. A single-cell zinc-air battery was also fabricated with superior durability, holding great promise in the practical implementation of rechargeable metal-air batteries. PMID:26970076

  8. Preparations, characterizations and applications of chitosan-based nanoparticles

    Science.gov (United States)

    Liu, Chenguang; Tan, Yulong; Liu, Chengsheng; Chen, Xiguang; Yu, Lejun

    2007-07-01

    Chitosan is a natural polysaccharide prepared by the N-deacetylation of chitin. In this paper we have reviewed the methods of preparation of chitosan-based nanoparticles and their pharmaceutical applications. There are five methods of their preparations: emulsion cross-linking, emulsion-droplet coalescence, ionic gelation, reverse micellar method and chemically modified chitosan method. Chitosan nanoparticles are used as carriers for low molecular weight drug, vaccines and DNA. Releasing characteristics, biodistribution and applications are also summarized.

  9. Preparations, Characterizations and Applications of Chitosan-based Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Chitosan is a natural polysaccharide prepared by the N-deacetylation of chitin. In this paper we have reviewed the methods of preparation of chitosan-based nanoparticles and their pharmaceutical applications. There are five methods of their preparations: emulsion cross-linking, emulsion-droplet coalescence, ionic gelation, reverse micellar method and chemically modified chitosan method. Chitosan nanoparticles are used as carriers for low molecular weight drug, vaccines and DNA. Releasing characteristics, biodistribution and applications are also summarized.

  10. Multiphase Nanostructure of a Quinary Metal Oxide Electrocatalyst Reveals a New Direction for OER Electrocatalyst Design

    OpenAIRE

    Haber, Joel A.; Anzenburg, Eitan; Yano, Junko; Kisielowski, Christian; Gregoire, John M.

    2015-01-01

    Ce-rich mixed metal oxides comprise a recently discovered class of -electrocatalysts for the oxygen evolution reaction (OER). In particular, at current densities below 10 mA cm^(−2), Ni_(0.3)Fe_(0.07)Co_(0.2)Ce_(0.43)O_x exhibits ¬superior activity compared to the corresponding transition metal oxides, despite the relative inactivity of ceria. To elucidate the enhanced activity and underlying catalytic mechanism, detailed structural characterization of this quinary oxide electrocatalyst is re...

  11. Promotional effect of upper Ru oxides as methanol tolerant electrocatalyst for the oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Montiel, M.; Hernandez-Fernandez, P.; Ocon, P. [Departamento de Quimica-Fisica Aplicada C-II, Campus UAM, 28049 Madrid (Spain); Fierro, J.L.G.; Rojas, S. [Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, 28049 Madrid (Spain)

    2009-06-15

    The role of Ru on the oxygen reduction reaction in the presence of methanol has been investigated. To this end a series of carbon supported Pt based electrocatalysts containing Ru and Co have been prepared and thoroughly characterized. The catalytic performance on the oxygen reduction reaction (ORR) both in the presence and in the absence of methanol by linear sweep voltammetry on rotating disk electrode has been studied. In spite of its documented ability towards methanol and CO oxidation, when Ru-containing catalysts are subjected to excursions to potentials more positive than 0.8 V vs. NHE they develop a certain tolerance to the presence of methanol. This feature is attributed to the formation of upper oxide Ru species that impede the methanol oxidation reaction to occur under the typical reaction conditions of the oxygen reduction process, i.e. potentials more positive than 0.7 V vs. NHE and oxygen saturated atmospheres. The evolution of Ru species with the applied potential has been investigated by XPS, identifying the presence of upper oxidized Ru phases. (author)

  12. Fabrication of electrocatalyst based on nitrogen doped graphene as highly efficient and durable support for using in polymer electrolyte fuel cell

    Science.gov (United States)

    Heydari, Ahmad; Gharibi, Hussein

    2016-09-01

    In this work, we have used an efficient approach to prepare nitrogen-doped graphene supported Pt nanoparticles (Pt/N-rGO). The nitrogen-doped graphene nanocomposites (N-rGO) were derived from pyrolysis of graphene oxide/polyaniline composites in nitrogen atmosphere. X-ray powder diffraction, FTIR spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and Transmission and Scanning electron microscopy (TEM&SEM) were used to characterize the morphology and microstructure of the prepared catalysts. The TEM and elemental mapping images indicate that metal nanoparticles are more uniformly dispersed on the surface of N-doped graphene than other supports, and Pt nanoparticles dispersed without any aggregation. The catalytic activity and durability of the catalysts was evaluated by various electrochemical techniques. Compared to undoped Pt/rGO and commercial Pt/C catalysts, an enhanced electrocatalytic activity was obtained in the case of the Pt/N-rGO with optimized composition and nanostructure. The maximum power density of MEA for Pt/N-rGO was 1.4 times more than that of MEA fabricated by commercial Pt/C 20%.

  13. Self-supported electrocatalysts for advanced energy conversion processes

    Directory of Open Access Journals (Sweden)

    Tian Yi Ma

    2016-06-01

    Full Text Available The biggest challenge in developing new energy conversion technologies such as rechargeable metal-air batteries, regenerated fuel cells and water splitting devices is to find suitable catalysts that can efficiently and stably catalyze the key electrochemical processes involved. This paper reviews the new development of self-supported electrocatalysts in three categories: electrocatalysts growing on rigid substrates, electrocatalysts growing on soft substrates, and free-standing catalyst films. They are distinct and superior to the conventional powdery electrocatalysts, showing advantages in controllable nanostructure and chemical component, flexible electrode configuration, and outstanding catalytic performance. The self-supported electrocatalysts with various architectures like nanowire/plate/pillar arrays and porous films, composed of metals, metal oxides/selenides/phosphides, organic polymers, carbons and their corresponding hybrids, are presented and discussed. These catalysts exhibit high activity, durability and selectivity toward oxygen reduction, oxygen evolution, and/or hydrogen evolution reactions. The perspectives on the relevant areas are also proposed.

  14. Synergistic catalyst-support interactions in a graphene-Mn3O4 electrocatalyst for vanadium redox flow batteries

    OpenAIRE

    Ejigu, Andinet; Edwards, Matthew; Walsh, Darren A

    2015-01-01

    The development of vanadium redox flow batteries (VRFBs) is partly limited by the sluggishness of the electrochemical reactions at conventional carbon-based electrodes. The VO2+/VO2+ redox reaction is particularly sluggish and improvements in battery performance require the development of new electrocatalysts for this reaction. In this study, synergistic catalyst-support interactions in a nitrogen-doped, reduced-graphene oxide/Mn3O4 (N-rGO- Mn3O4) composite electrocatalyst for VO2+/VO2+ elect...

  15. Nanostructured Electrocatalysts for All-Vanadium Redox Flow Batteries.

    Science.gov (United States)

    Park, Minjoon; Ryu, Jaechan; Cho, Jaephil

    2015-10-01

    Vanadium redox reactions have been considered as a key factor affecting the energy efficiency of the all-vanadium redox flow batteries (VRFBs). This redox reaction determines the reaction kinetics of whole cells. However, poor kinetic reversibility and catalytic activity towards the V(2+)/V(3+) and VO(2+)/VO2(+) redox couples on the commonly used carbon substrate limit broader applications of VRFBs. Consequently, modified carbon substrates have been extensively investigated to improve vanadium redox reactions. In this Focus Review, recent progress on metal- and carbon-based nanomaterials as an electrocatalyst for VRFBs is discussed in detail, without the intention to provide a comprehensive review on the whole components of the system. Instead, the focus is mainly placed on the redox chemistry of vanadium ions at a surface of various metals, different dimensional carbons, nitrogen-doped carbon nanostructures, and metal-carbon composites. PMID:25899910

  16. Nanostructured Electrocatalysts for All-Vanadium Redox Flow Batteries.

    Science.gov (United States)

    Park, Minjoon; Ryu, Jaechan; Cho, Jaephil

    2015-10-01

    Vanadium redox reactions have been considered as a key factor affecting the energy efficiency of the all-vanadium redox flow batteries (VRFBs). This redox reaction determines the reaction kinetics of whole cells. However, poor kinetic reversibility and catalytic activity towards the V(2+)/V(3+) and VO(2+)/VO2(+) redox couples on the commonly used carbon substrate limit broader applications of VRFBs. Consequently, modified carbon substrates have been extensively investigated to improve vanadium redox reactions. In this Focus Review, recent progress on metal- and carbon-based nanomaterials as an electrocatalyst for VRFBs is discussed in detail, without the intention to provide a comprehensive review on the whole components of the system. Instead, the focus is mainly placed on the redox chemistry of vanadium ions at a surface of various metals, different dimensional carbons, nitrogen-doped carbon nanostructures, and metal-carbon composites.

  17. A cobalt-nitrogen complex on N-doped three-dimensional graphene framework as a highly efficient electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Jiang, Yuanyuan; Lu, Yizhong; Wang, Xiaodan; Bao, Yu; Chen, Wei; Niu, Li

    2014-11-01

    The high cost and limited natural abundance of platinum hinder its widespread applications as the oxygen reduction reaction (ORR) electrocatalyst for fuel cells. Carbon-supported materials containing metals such as Fe or Co as well as nitrogen have been proposed to reduce the cost without obvious lowering the performance compared to Pt-based electrocatalysts. In this work, based on the pyrolyzed corrin structure of vitamin B12 on the simultaneously reduced graphene support (g-VB12), we construct an efficient oxygen reduction electrocatalyst with very positive half-wave potential (only ~30 mV deviation from Pt/C), high selectivity (electron transfer number close to 4) and excellent durability (only 11 mV shift of the half-wave potential after 10 000 potential cycles). The admirable performance of this electrocatalyst can be attributed to the homogeneous distribution of abundant Co-Nx active sites, and a well-defined three-dimensional mesoporous structure of the N-doped graphene support. The high activity and long-term stability of the low cost g-VB12 make it a promising ORR electrocatalyst in alkaline fuel cells.The high cost and limited natural abundance of platinum hinder its widespread applications as the oxygen reduction reaction (ORR) electrocatalyst for fuel cells. Carbon-supported materials containing metals such as Fe or Co as well as nitrogen have been proposed to reduce the cost without obvious lowering the performance compared to Pt-based electrocatalysts. In this work, based on the pyrolyzed corrin structure of vitamin B12 on the simultaneously reduced graphene support (g-VB12), we construct an efficient oxygen reduction electrocatalyst with very positive half-wave potential (only ~30 mV deviation from Pt/C), high selectivity (electron transfer number close to 4) and excellent durability (only 11 mV shift of the half-wave potential after 10 000 potential cycles). The admirable performance of this electrocatalyst can be attributed to the homogeneous

  18. Nanoporous molybdenum carbide wires as an active electrocatalyst towards the oxygen reduction reaction.

    Science.gov (United States)

    Liao, Lei; Bian, Xiaojun; Xiao, Jingjing; Liu, Baohong; Scanlon, Micheál D; Girault, Hubert H

    2014-06-01

    A non-precious metal electrocatalyst has been developed for the oxygen reduction reaction based on nanoporous molybdenum carbide (nano-Mo2C) wires through a facile calcination of sub-nanometer periodic organic-inorganic hybrid nanowires. The highly dispersed Mo2C wires were composed of 10-15 nm nanocrystals with a mesopore size of 3.3 nm. The properties of nano-Mo2C wires were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and N2 adsorption/desorption porosimetry. The highly active surface area and enriched nanoporosity for nano-Mo2C wires are unique features that make them a high-performance electrocatalyst for oxygen reduction in an alkaline medium. The electrocatalysis and reaction kinetics results show that nano-Mo2C-based materials can be developed as new catalysts with high activity at low cost for electrochemical energy conversion applications.

  19. Preparation and Properties of Tung Oil-Based Polyurethane

    Institute of Scientific and Technical Information of China (English)

    袁才登; 赵晓明; 邵丽英; 唐克华

    2014-01-01

    Tung oil-based polyols were synthesized by the esterification and transesterification between Tung oil-based anhydride and butanediol. The hydroxyl values of the polyols prepared were tested and discussed. Polyurethane was prepared by using Tung oil-based polyols and/or poly(propylene glycol) as polyols and by using isophorone diisocyanate as isocyanate. The effect of the ratio of Tung oil-based polyols to poly(propylene glycol) on the proper-ties of polyurethane prepared was investigated by the water resistance, alcohol resistance and hardness tests. The re-sults show that Tung oil-based polyols are effective to improve the hardness, water resistance and alcohol resistance of polyurethane.

  20. A facile and general strategy for the synthesis of porous flowerlike Pt-based nanocrystals as effective electrocatalysts for alcohol oxidation

    Science.gov (United States)

    Huang, Da-Bing; Yuan, Qiang; He, Pei-Lei; Wang, Kai; Wang, Xun

    2016-08-01

    In this paper, porous flowerlike Pt-based (Pt, PdPt, RhPt and RhPdPt) nanocrystals were successfully achieved by a simple, economic, environmentally friendly route under the same synthetic conditions at 85 °C. The electrocatalytic properties of these flowerlike Pt-based nanocrystals toward alcohols (glycol, glycerol, methanol and ethanol) oxidation were investigated and they displayed enhanced catalytic performance compared with commercial Pt black. Among them, porous Pd45.5Pt54.5 nanoflowers showed the best catalytic performance with significant mass activity and long-term stability. More importantly, the current synthesis strategy can be easily amplified to gram-scale production.In this paper, porous flowerlike Pt-based (Pt, PdPt, RhPt and RhPdPt) nanocrystals were successfully achieved by a simple, economic, environmentally friendly route under the same synthetic conditions at 85 °C. The electrocatalytic properties of these flowerlike Pt-based nanocrystals toward alcohols (glycol, glycerol, methanol and ethanol) oxidation were investigated and they displayed enhanced catalytic performance compared with commercial Pt black. Among them, porous Pd45.5Pt54.5 nanoflowers showed the best catalytic performance with significant mass activity and long-term stability. More importantly, the current synthesis strategy can be easily amplified to gram-scale production. Electronic supplementary information (ESI) available: Experimental details, digital photos, TEM, XRD, CVs, EDX and tables. See DOI: 10.1039/c6nr04927c

  1. A facile and general strategy for the synthesis of porous flowerlike Pt-based nanocrystals as effective electrocatalysts for alcohol oxidation.

    Science.gov (United States)

    Huang, Da-Bing; Yuan, Qiang; He, Pei-Lei; Wang, Kai; Wang, Xun

    2016-08-21

    In this paper, porous flowerlike Pt-based (Pt, PdPt, RhPt and RhPdPt) nanocrystals were successfully achieved by a simple, economic, environmentally friendly route under the same synthetic conditions at 85 °C. The electrocatalytic properties of these flowerlike Pt-based nanocrystals toward alcohols (glycol, glycerol, methanol and ethanol) oxidation were investigated and they displayed enhanced catalytic performance compared with commercial Pt black. Among them, porous Pd45.5Pt54.5 nanoflowers showed the best catalytic performance with significant mass activity and long-term stability. More importantly, the current synthesis strategy can be easily amplified to gram-scale production. PMID:27443246

  2. SEM method for direct visual tracking of nanoscale morphological changes of platinum based electrocatalysts on fixed locations upon electrochemical or thermal treatments.

    Science.gov (United States)

    Zorko, Milena; Jozinović, Barbara; Bele, Marjan; Hodnik, Nejc; Gaberšček, Miran

    2014-05-01

    A general method for tracking morphological surface changes on a nanometer scale with scanning electron microscopy (SEM) is introduced. We exemplify the usefulness of the method by showing consecutive SEM images of an identical location before and after the electrochemical and thermal treatments of platinum-based nanoparticles deposited on a high surface area carbon. Observations reveal an insight into platinum based catalyst degradation occurring during potential cycling treatment. The presence of chloride clearly increases the rate of degradation. At these conditions the dominant degradation mechanism seems to be the platinum dissolution with some subsequent redeposition on the top of the catalyst film. By contrast, at the temperature of 60°C, under potentiostatic conditions some carbon corrosion and particle aggregation was observed. Temperature treatment simulating the annealing step of the synthesis reveals sintering of small platinum based composite aggregates into uniform spherical particles. The method provides a direct proof of induced surface phenomena occurring on a chosen location without the usual statistical uncertainty in usual, random SEM observations across relatively large surface areas.

  3. Operando Analysis of NiFe and Fe Oxyhydroxide Electrocatalysts for Water Oxidation: Detection of Fe⁴⁺ by Mössbauer Spectroscopy.

    Science.gov (United States)

    Chen, Jamie Y C; Dang, Lianna; Liang, Hanfeng; Bi, Wenli; Gerken, James B; Jin, Song; Alp, E Ercan; Stahl, Shannon S

    2015-12-01

    Nickel-iron oxides/hydroxides are among the most active electrocatalysts for the oxygen evolution reaction. In an effort to gain insight into the role of Fe in these catalysts, we have performed operando Mössbauer spectroscopic studies of a 3:1 Ni:Fe layered hydroxide and a hydrous Fe oxide electrocatalyst. The catalysts were prepared by a hydrothermal precipitation method that enabled catalyst growth directly on carbon paper electrodes. Fe(4+) species were detected in the NiFe hydroxide catalyst during steady-state water oxidation, accounting for up to 21% of the total Fe. In contrast, no Fe(4+) was detected in the Fe oxide catalyst. The observed Fe(4+) species are not kinetically competent to serve as the active site in water oxidation; however, their presence has important implications for the role of Fe in NiFe oxide electrocatalysts. PMID:26601790

  4. Alloys of platinum and early transition metals as oxygen reduction electrocatalysts.

    Science.gov (United States)

    Greeley, J; Stephens, I E L; Bondarenko, A S; Johansson, T P; Hansen, H A; Jaramillo, T F; Rossmeisl, J; Chorkendorff, I; Nørskov, J K

    2009-10-01

    The widespread use of low-temperature polymer electrolyte membrane fuel cells for mobile applications will require significant reductions in the amount of expensive Pt contained within their cathodes, which drive the oxygen reduction reaction (ORR). Although progress has been made in this respect, further reductions through the development of more active and stable electrocatalysts are still necessary. Here we describe a new set of ORR electrocatalysts consisting of Pd or Pt alloyed with early transition metals such as Sc or Y. They were identified using density functional theory calculations as being the most stable Pt- and Pd-based binary alloys with ORR activity likely to be better than Pt. Electrochemical measurements show that the activity of polycrystalline Pt(3)Sc and Pt(3)Y electrodes is enhanced relative to pure Pt by a factor of 1.5-1.8 and 6-10, respectively, in the range 0.9-0.87 V. PMID:21378936

  5. Ni/Pd-Decorated Carbon NFs as an Efficient Electrocatalyst for Methanol Oxidation in Alkaline Medium

    Science.gov (United States)

    Mohamed, Ibrahim M. A.; Khalil, Khalil Abdelrazek; Mousa, Hamouda M.; Barakat, Nasser A. M.

    2016-09-01

    In this study, Ni/Pd-decorated carbon nanofibers (NFs) were fabricated as an electrocatalyst for methanol oxidation. These NFs were synthesized based on carbonization of poly(vinyl alcohol), which has high carbon content compared to many polymers used to prepare carbon NFs. Typically, calcination of an electrospun mat composed of nickel acetate, palladium acetate, and poly(vinyl alcohol) can produce Ni/Pd-doped carbon NFs. The introduced NFs were characterized by scanning electron microscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy, line TEM energy dispersive x-ray spectrometry, field emission scanning electron microscopy, and x-ray powder diffraction. These physicochemical characterizations are acceptable tools to investigate the crystallinity and chemistry of the fabricated Ni/Pd-carbon NFs. Accordingly, the prepared NFs were tested to enhance the economic and catalytic behavior of methanol electrooxidation. Experimentally, the obtained onset potential was small compared to many reported materials; 0.32 V (versus Ag/AgCl as a reference electrode). At the same time, the current density changed from 5.08 mA/cm2 in free methanol at 0.6 V to 12.68 mA/cm2 in 0.1 mol/L methanol, which can be attributed to the MeOH oxidation. Compared to nanoparticles, the NFs have a distinct effect on the electrocatalytic performance of material due to the effect of the one-dimensional structure, which facilitates the electron transfer. Overall, the presented work opens a new way for non-precious one-dimensional nanostructured catalysts for direct methanol fuel cell technology.

  6. Tantalum carbide as a novel support material for anode electrocatalysts in polymer electrolyte membrane water electrolysers

    DEFF Research Database (Denmark)

    Polonský, Jakub; Petrushina, Irina; Christensen, Erik;

    2012-01-01

    in a mixture of trifluoromethanesulfonic acid (TFMSA) and hydrogen peroxide at 130 °C. The liquid phase was subsequently analysed using ICP-MS with respect to the occurrence of ions potentially originating from the support material tested. The TaC support selected was additionally characterised...... and was equal to 0.1, 0.3, 0.5, 0.7, 0.9 and 1. The thin-film method was used for electrochemical characterisation of the electrocatalysts prepared. SEM–EDX analysis, X-ray diffraction, N2 adsorption (BET) and powder conductivity measurements were used as complementary techniques to complete characterisation...

  7. An ex-situ and in-situ evaluation of carbides as potential electrocatalysts

    Science.gov (United States)

    Weigert, Erich

    previously shown hydrogen electrooxidation activity, but demonstrated a nearly identical stability range to MoC in an identical electrolyte. Within these stable ranges of operation, neither surface demonstrated activity towards methanol electrooxidation. These surfaces are also found to undergo rapid decomposition at higher operating potentials, which could be disadvantageous for use in DMFC's. Despite these findings for molybdenum carbides, in-situ CV studies reveal that tungsten monocarbides (WC) show significant activity towards methanol oxidation in acidic solution and a larger range of stability. Steady-state Chronoamperometry (CA) measurements show an enhanced performance for methanol electrooxidation on WC and sub-monolayer Pt-modified WC surfaces by comparison with Pt surfaces. Surface science studies demonstrate that the WC and Pt-modified WC surfaces remained stable during the CA measurements. To further bridge the materials and pressure gaps mentioned earlier, polycrystalline thin films of WC were synthesized on various carbon substrates commonly used in fuel cell applications. The activity of WC and Pt-modified WC PVD films surfaces towards methanol and adsorbed CO species in ex-situ CV experiments enabled a discussion of the advantages and limitations of the WC electrocatalyst when produced using larger scale synthesis methods. To further aid this investigation, WC nanomaterials with and without Pt-modification were integrated as the anode electrocatalyst in DMFC devices. These fuel cells were used in a preliminary study to identify the most basic performance characteristics of the anode. Additionally, these findings motivate a discussion of the relative ease with which WC-based electrocatalysts may be integrated into fuel cells using proven fabrication techniques.

  8. Electrocatalysts for fuel cells; Electrocatalizadores para celdas de combustible

    Energy Technology Data Exchange (ETDEWEB)

    Garcia C, M. A.; Fernandez V, S. M. [ININ, Depto. de Quimica, Apdo. Postal 18-1027, Col. Escandon, Mexico 11801, D. F. (Mexico); Vargas G, J. R. [IPN, Depto. de Ingenieria Metalurgica, Mexico 07300, D. F. (Mexico)

    2008-07-01

    It was investigated the oxygen reduction reaction (fundamental reaction in fuel cells) on electrocatalysts of Pt, Co, Ni and their alloys CoNi, PtCo, PtNi, PtCoNi in H{sub 2}SO{sub 4} 0.5 M and KOH 0.5 M as electrolyte. The electrocatalysts were synthesized using mechanical alloying processes and chemical vapor deposition. The electrocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray spectroscopy. The evaluation was performed using electrocatalytic technique of rotating disk electrode and kinetic parameters were determined for each electro catalyst. We report the performance of all synthesized electrocatalysts in acid and alkaline means. (Author)

  9. MoS2/Nitrogen-doped graphene as efficient electrocatalyst for oxygen reduction reaction

    International Nuclear Information System (INIS)

    Graphical abstract: A simple yet effective method was developed for generating an electrocatalyst for oxygen reduction reaction by deposited MoS2 sheets on nitrogen-doped graphene (NG). Due to the synergistic effect of MoS2 and NG, enhancement of electrocatalytic oxygen-reduction was realized. Display Omitted -- Highlights: • MoS2/Nitrogen-doped graphene (NG) composites were obtained by physically mixing method. • MoS2 sheets deposited NG could be used as effective electrocatalyst for ORR. • Enhanced electrocatalytic activity is due to the synergistic effect of MoS2 and NG. • The ORR is a four-electron process based on Koutecky-Levich equation. -- Abstract: A simple yet effective strategy was developed to generate a non-precious oxygen electrode electrocatalyst of MoS2/nitrogen-doped graphene (NG) by physical mixing MoS2 sheets with NG. The micrometer-sized MoS2 sheets were obtained through ultrasonication exfoliation of the bulk MoS2, only showing little oxygen reduction reaction (ORR) activity. MoS2/NG hybrid was obtained by loading MoS2 sheets onto NG through ultrasonication, and the resulting nanocomposites exhibited improved electrocatalytic activity for ORR with dominant 4 electron pathway in alkaline solutions. The exposed active edges as well as the synergistic effect and reduced resistance connection jointly make the MoS2/NG composite a highly competitive ORR catalyst

  10. Control of the composition of Pt-Ni electrocatalysts in surfactant-free synthesis using neat N-formylpiperidine

    Science.gov (United States)

    Zhang, Na; Tsao, Kai-Chieh; Pan, Yung-Tin; Yang, Hong

    2016-01-01

    This paper describes the facile and surfactant-free synthesis of faceted Pt-Ni alloy nanoparticle electrocatalysts using neat N-formylpiperidine as a new type of solvent. Unlike the widely-used colloidal synthesis based on long-carbon chain surfactants, nanoparticles made in neat N-formylpiperidine possess a directly accessible surface for electrocatalytic reactions, making it a very attractive alternative solvent. The area-specific oxygen reduction reaction (ORR) activity is much higher than the commercial Pt/C catalyst reference and reaches a maximum of 1.12 mA cm-2 for the Pt-Ni alloy nanoparticles. We observed that the freshly formed Pt-Ni alloy could have controllable bulk and near surface compositions under the same initial reaction conditions and precursor ratio. The change in the composition could be attributed to the effect of CO on the formation of uniform nuclei at the initial stage, and a different deposition rate between Pt and Ni metals during the growth. The well-defined Pt-Ni nanoparticle catalysts show strong composition-dependent catalytic behavior in ORR, highlighting the important role of controlling the growth kinetics in the preparation of active Pt-Ni ORR catalysts.This paper describes the facile and surfactant-free synthesis of faceted Pt-Ni alloy nanoparticle electrocatalysts using neat N-formylpiperidine as a new type of solvent. Unlike the widely-used colloidal synthesis based on long-carbon chain surfactants, nanoparticles made in neat N-formylpiperidine possess a directly accessible surface for electrocatalytic reactions, making it a very attractive alternative solvent. The area-specific oxygen reduction reaction (ORR) activity is much higher than the commercial Pt/C catalyst reference and reaches a maximum of 1.12 mA cm-2 for the Pt-Ni alloy nanoparticles. We observed that the freshly formed Pt-Ni alloy could have controllable bulk and near surface compositions under the same initial reaction conditions and precursor ratio. The change

  11. Preparation of Pt Ru/C + rare earths by the method of reduction by alcohol for the electro-oxidation of ethanol; Preparacao de eletrocatalisadores PtRu/C + terras raras pelo metodo da reducao por alcool para a eletro-oxidacao do etanol

    Energy Technology Data Exchange (ETDEWEB)

    Tusi, M.M.; Rodrigues, R.M.S.; Spinace, E.V.; Oliveira Neto, A., E-mail: aolivei@ipen.b, E-mail: espinace@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2010-07-01

    PtRu/C electrocatalyst was prepared in a single step, while that PtRu/85%C-15%Ce, PtRu/85%C-15%La, PtRu/85%C-15%Nd and PtRu/85%C-15%Er electrocatalyst were prepared in a two step. In the first step a Carbon Vulcan XC72 + rare earth supports were prepared. In the second step PtRu electrocatalyst were prepared by an alcohol-reduction process using ethylene glycol as solvent and reducing agent and supported on Vulcan XC72 + earth rare. The obtained electrocatalysts were characterized by EDAX, XRD and chronoamperometry. The electro-oxidation of ethanol was studied by chronoamperometry at room temperature. PtRu/85%C- 15%Ce electrocatalyst showed a significant increase of performance for ethanol oxidation compared to PtRu/C electrocatalyst. (author)

  12. Metallic Co4N Porous Nanowire Arrays Activated by Surface Oxidation as Electrocatalysts for the Oxygen Evolution Reaction.

    Science.gov (United States)

    Chen, Pengzuo; Xu, Kun; Fang, Zhiwei; Tong, Yun; Wu, Junchi; Lu, Xiuli; Peng, Xu; Ding, Hui; Wu, Changzheng; Xie, Yi

    2015-12-01

    Designing highly efficient electrocatalysts for oxygen evolution reaction (OER) plays a key role in the development of various renewable energy storage and conversion devices. In this work, we developed metallic Co4N porous nanowire arrays directly grown on flexible substrates as highly active OER electrocatalysts for the first time. Benefiting from the collaborative advantages of metallic character, 1D porous nanowire arrays, and unique 3D electrode configuration, surface oxidation activated Co4N porous nanowire arrays/carbon cloth achieved an extremely small overpotential of 257 mV at a current density of 10 mA cm(-2), and a low Tafel slope of 44 mV dec(-1) in an alkaline medium, which is the best OER performance among reported Co-based electrocatalysts to date. Moreover, in-depth mechanistic investigations demonstrate the active phases are the metallic Co4N core inside with a thin cobalt oxides/hydroxides shell during the OER process. Our finding introduces a new concept to explore the design of high-efficiency OER electrocatalysts. PMID:26437900

  13. New methods for preparing mercury-based ferrofluids

    DEFF Research Database (Denmark)

    Linderoth, Søren; Rasmussen, L.H.; Mørup, Steen

    1991-01-01

    Metallic ferrofluids based on magnetic particles in mercury have been produced by two new methods. Alloy particles of Fe-B, Fe-Co-B, Fe-Ni-B, and Co-B were prepared by reduction of the transition metal ions in aqueous solutions by NaBH4 and subsequently suspended in mercury. In one preparation......, the metallic mercury was added to the solution with precipitates and in another method produced simultaneously with the precipitates by reduction of mercury ions to metallic mercury. The samples were characterized by magnetization and Mössbauer spectroscopy measurements. Journal of Applied Physics...

  14. Fuel cell membrane preparation: effects of base polymer

    Energy Technology Data Exchange (ETDEWEB)

    Brack, H.P.; Scherer, G.G. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    Radiation grafted films and membranes prepared from the partially fluorinated base copolymer poly(ethylene-alt-tetrafluoroethylene) or ETFE have better mechanical properties than those prepared from poly(tetrafluoroethylene-co-hexafluoropropylene) or FEP. The influence of the base copolymer film type on the grafting rate and yields is reported in the present investigation. An understanding of the effects of these parameters is important so that the grafting process can be carried out reproducibly in as short a time as possible. The grafting rate and yield as a function of the irradiation dose has been found to be much higher for the partially fluorinated base copolymer ETFE. (author) 2 figs., 1 tab., 5 refs.

  15. Perovskites As Electrocatalysts for Alkaline Water Electrolysis

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey Valerievich; De La Osa Puebla, Ana Raquel; Jensen, Jens Oluf;

    2014-01-01

    Water electrolysis is a promising technology for the production of hydrogen as a sustainable energy storage source, combined with solar or wind power. In this work various electrocatalysts for the Oxygen Evolution Reaction (OER) electrode were synthesized and characterized by several techniques...... such as X-ray diffraction, electrical conductivity, scanning electron microscopy (SEM), energy dispersive microscopy (EDX) and rotating disk electrode. The perovskites tested in this work were both produced by a ball-milling technique and by an auto-combustion synthesis, which appeared to be a fast...... powder electric conductivity which varied by several orders of magnitude, as shown on Figure 3. 1 H. Nijjar, J. Lamonier, O. Mentr'e, J. Giraudon, H. Batis, Appl. Catal. B, 106, 149–159, 2011 2 J.O’M. Bockris and T. Otagawa J. Phys. Chem. 87:2960-2971, 1983. [Formula]...

  16. Comparative assessment of synthetic strategies toward active platinum-rhodium-tin electrocatalysts for efficient ethanol electro-oxidation

    Science.gov (United States)

    Erini, Nina; Krause, Paul; Gliech, Manuel; Yang, Ruizhi; Huang, Yunhui; Strasser, Peter

    2015-10-01

    The present work explores the effect of autoclave-based autogenous-pressure vs. ambient pressure conditions on the synthesis and properties of carbon-supported Pt-Rh-Sn nanoparticle electrocatalysts. The Pt-Rh-Sn nanoparticles were characterized by X-ray spectroscopy, electron microscopy and mass spectroscopy and deployed as catalysts for the electrocatalytic ethanol oxidation reaction. Pt-Rh-Sn catalysts precipitated with carbon already present showed narrow particle size distribution around 7 nm, while catalysts supported on carbon after particle formation showed broader size distribution ranging from 8 to 16 nm, similar metal loadings between 40 and 48 wt.% and similar atomic ratios of Pt:Rh:Sn of 30:10:60. The highest ethanol oxidation activity at low overpotentials associated with exceptionally early ethanol oxidation onset potential was observed for ambient-pressure catalysts with the active ternary alloy phase formed in presence of the carbon supports. In contrast, catalysts prepared under ambient pressure in a two-step approach, involving alloy particle formation followed by particle separation and subsequent deposition on the carbon support, yielded the highest overall mass activities. Based on the observed synthesis-activity correlations, a comparative assessment is provided of the synthetic techniques at high vs. low pressures, and in presence and absence of carbon support. Plausible hypotheses in terms of particle dispersion and interparticle distance accounting for these observed differences are discussed.

  17. Preparation and characterization of new polyesters derived from schiff bases

    International Nuclear Information System (INIS)

    Summary: Three polyesters have been prepared by the reaction of terephthaloyl chloride on Schiff bases derived from 4- hydroxybenzyldehyde and meso- stilbenediamine, ethylenediamine or 4-nitrophenylenediamine.The polymers were obtained in good yield (85% theoritical) and were characterized by C,H,N elemental analyses, FT-IR, UV and visible spectroscopy and thermal analyses (TGA ,DTA). The results obtained were compared with that of Schiff base monomers .The viscosities measurements of the polyesters and their Schiff base monomers supported the polymers formation. (author)

  18. Preparation and characterization of crosslinked chitosan-based nanofibers

    Institute of Scientific and Technical Information of China (English)

    Ying Shan Zhou; Dong Zhi Yang; Jun Nie

    2007-01-01

    Crosslinked chitosan-based nanofibers were successfully prepared via electrospinning technique with heat mediated chemical crosslinking followed. The structure, morphology and mechanical property of nanofibers were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), Instron machine, respectively. The results showed that, nanofibers exhibited a smooth surface and regular morphology, and tensile strength of nanofibers improved with increasing of triethylene glycol dimethacrylate (TEGDMA) content.

  19. Triblock polymer mediated synthesis of Ir-Sn oxide electrocatalysts for oxygen evolution reaction

    Science.gov (United States)

    Li, Guangfu; Yu, Hongmei; Wang, Xunying; Yang, Donglei; Li, Yongkun; Shao, Zhigang; Yi, Baolian

    2014-03-01

    Over the past several decades, tremendous effort has been put into developing cost-effective, highly active and durable electrocatalysts for oxygen evolution reaction (OER) in the proton exchange membrane water electrolyzer. This report explores an advanced and effective "soft" material-assistant method to fabricate Ir0.6Sn0.4O2 electrocatalysts with a 0.6/0.4 ratio of Ir/Sn in precursors. Adopting a series of characterization methods, the collective results suggest that the surfactant-material F127 content, as an important factor, can efficiently control the formation of Ir-Sn oxides with varying surface properties and morphologies, such as the grainy and rod-shaped structures. Associating with the half-cell and single electrolyzer, it is affirmed that the optimal ratio of (Ir + Sn)/F127 is 100 for the preparation of S100-Ir0.6Sn0.4O2 with obviously enhanced activity and sufficient durability under the electrolysis circumstances. The lowest cell voltages obtained at 80 °C are 1.631 V at 1000 mA cm-2, and 1.820 V at 2000 mA cm-2, when applying S100-Ir0.6Sn0.4O2 OER catalyst and Ti-material diffusion layer on the anode side and Nafion® 115 membrane. Furthermore, the noble-metal Ir loading in the same cell decreases to 0.77 mg cm-2. These results highlight that Ir-Sn oxide synthesized by the soft-material method is a promising OER electrocatalyst.

  20. Identification of catalytic sites for oxygen reduction and oxygen evolution in N-doped graphene materials: Development of highly efficient metal-free bifunctional electrocatalyst.

    Science.gov (United States)

    Yang, Hong Bin; Miao, Jianwei; Hung, Sung-Fu; Chen, Jiazang; Tao, Hua Bing; Wang, Xizu; Zhang, Liping; Chen, Rong; Gao, Jiajian; Chen, Hao Ming; Dai, Liming; Liu, Bin

    2016-04-01

    Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical to renewable energy conversion and storage technologies. Heteroatom-doped carbon nanomaterials have been reported to be efficient metal-free electrocatalysts for ORR in fuel cells for energy conversion, as well as ORR and OER in metal-air batteries for energy storage. We reported that metal-free three-dimensional (3D) graphene nanoribbon networks (N-GRW) doped with nitrogen exhibited superb bifunctional electrocatalytic activities for both ORR and OER, with an excellent stability in alkaline electrolytes (for example, KOH). For the first time, it was experimentally demonstrated that the electron-donating quaternary N sites were responsible for ORR, whereas the electron-withdrawing pyridinic N moieties in N-GRW served as active sites for OER. The unique 3D nanoarchitecture provided a high density of the ORR and OER active sites and facilitated the electrolyte and electron transports. As a result, the as-prepared N-GRW holds great potential as a low-cost, highly efficient air cathode in rechargeable metal-air batteries. Rechargeable zinc-air batteries with the N-GRW air electrode in a two-electrode configuration exhibited an open-circuit voltage of 1.46 V, a specific capacity of 873 mAh g(-1), and a peak power density of 65 mW cm(-2), which could be continuously charged and discharged with an excellent cycling stability. Our work should open up new avenues for the development of various carbon-based metal-free bifunctional electrocatalysts of practical significance. PMID:27152333

  1. Preparation and Properties of Alkali Activated Metakaolin-Based Geopolymer

    Directory of Open Access Journals (Sweden)

    Liang Chen

    2016-09-01

    Full Text Available The effective activation and utilization of metakaolin as an alkali activated geopolymer precursor and its use in concrete surface protection is of great interest. In this paper, the formula of alkali activated metakaolin-based geopolymers was studied using an orthogonal experimental design. It was found that the optimal geopolymer was prepared with metakaolin, sodium hydroxide, sodium silicate and water, with the molar ratio of SiO2:Al2O3:Na2O:NaOH:H2O being 3.4:1.1:0.5:1.0:11.8. X-ray diffraction (XRD and Fourier transform infrared spectroscopy (FT-IR were adopted to investigate the influence of curing conditions on the mechanical properties and microstructures of the geopolymers. The best curing condition was 60 °C for 168 h, and this alkali activated metakaolin-based geopolymer showed the highest compression strength at 52.26 MPa. In addition, hollow micro-sphere glass beads were mixed with metakaolin particles to improve the thermal insulation properties of the alkali activated metakaolin-based geopolymer. These results suggest that a suitable volume ratio of metakaolin to hollow micro-sphere glass beads in alkali activated metakaolin-based geopolymers was 6:1, which achieved a thermal conductivity of 0.37 W/mK and compressive strength of 50 MPa. By adjusting to a milder curing condition, as-prepared alkali activated metakaolin-based geopolymers could find widespread applications in concrete thermal protection.

  2. Polymer-based tubular microbots: role of composition and preparation

    Science.gov (United States)

    Gao, Wei; Sattayasamitsathit, Sirilak; Uygun, Aysegul; Pei, Allen; Ponedal, Adam; Wang, Joseph

    2012-03-01

    The influence of the composition and electropolymerization conditions upon the propulsion of new template-prepared polymer-based bilayer microtubular microbots is described. The effects of different electropolymerized outer layers, including polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI), and of various inner catalytic metal surfaces (Ag, Pt, Au, Ni-Pt alloy), upon the movement of such bilayer microtubes are evaluated and compared. Electropolymerization conditions, such as the monomer concentration and medium (e.g. surfactant, electrolyte), have a profound effect upon the morphology and locomotion of the resulting microtubes. The most efficient propulsion is observed using PEDOT/Pt microbots that offer a record-breaking speed of over 1400 body lengths s-1 at physiological temperature, which is the fastest relative speed reported to date for all artificial micro/nanomotors. An inner Pt-Ni alloy surface is shown useful for combining magnetic control and catalytic fuel decomposition within one layer, thus greatly simplifying the preparation of magnetically-guided microbots. Polymer-based microbots with an inner gold layer offer efficient biocatalytic propulsion in low peroxide level in connection to an immobilized catalase enzyme. Metallic Au/Pt bilayer microbots can also be prepared electrochemically to offer high speed propulsion towards potential biomedical applications through functionalization of the outer gold surface. Such rational template preparation and systematic optimization of highly efficient microbots hold considerable promise for diverse practical applications.The influence of the composition and electropolymerization conditions upon the propulsion of new template-prepared polymer-based bilayer microtubular microbots is described. The effects of different electropolymerized outer layers, including polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI), and of various inner catalytic metal

  3. Preparation and properties of copper-oil-based nanofluids

    Directory of Open Access Journals (Sweden)

    Xie Wenjie

    2011-01-01

    Full Text Available Abstract In this study, the lipophilic Cu nanoparticles were synthesized by surface modification method to improve their dispersion stability in hydrophobic organic media. The oil-based nanofluids were prepared with the lipophilic Cu nanoparticles. The transport properties, viscosity, and thermal conductivity of the nanofluids have been measured. The viscosities and thermal conductivities of the nanofluids with the surface-modified nanoparticles have higher values than the base fluids do. The composition has more significant effects on the thermal conductivity than on the viscosity. It is valuable to prepare an appropriate oil-based nanofluid for enhancing the heat-transfer capacity of a hydrophobic system. The effects of adding Cu nanoparticles on the thermal oxidation stability of the fluids were investigated by measuring the hydroperoxide concentration in the Cu/kerosene nanofluids. The hydroperoxide concentrations are observed to be clearly lower in the Cu nanofluids than in their base fluids. Appropriate amounts of metal nanoparticles added in a hydrocarbon fuel can enhance the thermal oxidation stability.

  4. Industrial Preparation of Bauxite-based Mullite Raw Material

    Institute of Scientific and Technical Information of China (English)

    YANG Zhongzheng; DING Baohua

    2008-01-01

    Bauxite-based mullite grogs were prepared with grade II bauxite(≤3mm)and coal gangue(≤3mm)as starting materials with formula of w(Al2O3)=68%~72%.Mill the mixture to particle size≤0.044mm by wet milling to homogenize chemical composition. After shaping by wet extrusion and drying, the materials were fired at 1550℃, 1600℃ and 1700℃ for 6 hours respectively. After cooling apparent porosity and bulk density of fired materials were tested. The results show as follows: the appropriate sintering temperature for bauxite-based mullite with homogeneous and consistent composition and microstructure and properties is 1600℃,at which the mullite has apparent porosity≤1.5%,bulk density≥2.81g·cm-3and refractoriness under load is 1610-1650℃.Compared with the laboratory results, the sintering temperature is lowered about 100℃,bulk density increased 0.06g?cm-3.The industrial feasibility of preparing bauxite-based mullite grogs with the processing is confirmed.

  5. Preparation of perlite-based carbon dioxide absorbent.

    Science.gov (United States)

    He, H; Wu, L; Zhu, J; Yu, B

    1994-02-01

    A new highly efficient carbon dioxide absorbent consisting of sodium hydroxide, expanded perlite and acid-base indicator was prepared. The absorption efficiency, absorption capacity, flow resistance and color indication for the absorbent were tested and compared with some commercial products. The absorbent can reduce the carbon dioxide content in gases to 3.3 ppb (v/v) and absorbs not less than 35% of its weight of carbon dioxide. Besides its large capacity and sharp color indication, the absorbent has an outstanding advantage of small flow resistance in comparison with other commercial carbon dioxide absorbents. Applications in gas analysis and purification were also investigated.

  6. Cobalt Phosphide Hollow Polyhedron as Efficient Bifunctional Electrocatalysts for the Evolution Reaction of Hydrogen and Oxygen.

    Science.gov (United States)

    Liu, Mengjia; Li, Jinghong

    2016-01-27

    The development of efficient and low-cost hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts for renewable-energy conversion techniques is highly desired. A kind of hollow polyhedral cobalt phosphide (CoP hollow polyhedron) is developed as efficient bifunctional electrocatalysts for HER and OER templated by Co-centered metal-organic frameworks. The as-prepared CoP hollow polyhedron, which have large specific surface area and high porosity providing rich catalytic active sites, show excellent electrocatalytic performances for both HER and OER in acidic and alkaline media, respectively, with onset overpotentials of 35 and 300 mV, Tafel slopes of 59 and 57 mV dec(-1), and a current density of 10 mA cm(-2) at overpotentials of 159 and 400 mV for HER and OER, respectively, which are remarkably superior to those of particulate CoP (CoP particles) and comparable to those of commercial noble-metal catalysts. In addition, the CoP hollow polyhedron also show good durability after long-term operations. PMID:26711014

  7. Efficient Photoelectrochemical Water Oxidation by Metal-Doped Bismuth Vanadate Photoanode with Iron Oxyhydroxide Electrocatalyst

    Directory of Open Access Journals (Sweden)

    Eun Jin Joo

    2016-01-01

    Full Text Available Intensive attention has been currently focused on the discovery of semiconductor and proficient cocatalysts for eventual applications to the photoelectrochemical water splitting system. A W-Mo-doped BiVO4 semiconductor was prepared by the surfactant-assisted thermal decomposition method on a fluorine-doped tin oxide conductive film. The W-Mo-doped BiVO4 films showed a porous morphology with the grain sizes of about 270 nm. Because the hole diffusion length of BiVO4 is about 100 nm, the W-Mo-doped BiVO4 film in this study is an ideal candidate for the photoelectrochemical water oxidation. Iron oxyhydroxide (FeOOH electrocatalyst was chemically deposited on the W-Mo-doped BiVO4 to investigate the effect of the electrocatalyst on the semiconductor. The W-Mo-doped BiVO4/FeOOH composite electrode showed enhanced activity compared to the pristine W-Mo-doped BiVO4 electrode for water oxidation reaction. The chemical deposition is a promising method for the deposition of FeOOH on semiconductor.

  8. A new electrocatalyst and its application method for vanadium redox flow battery

    Science.gov (United States)

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

    2015-08-01

    The edge plane in carbon structure has good electrocatalytic activity toward vanadium redox reaction. To apply it in vanadium redox flow battery (VRFB) practically, the graphite nanopowders (GNPs) containing amounts of edge planes are used as electrocatalyst and embedded in the electrospun carbon nanofibers (ECNFs) by different mass ratios to make composite electrodes. The morphology and electrochemical activity of the GNPs and the composite electrodes containing them are characterized. Compared with the pristine ECNFs, the composite electrodes show much higher electrochemical activity. With the increase of GNPs content in composite electrodes, the electrochemical reversibility of the vanadium redox couples also increases. It proves the addition of GNPs can surely improve the electrochemical activity of ECNFs. Among the composite electrodes, the ECNFs containing 30 nm GNP by mass ratio of 1:50 show the best electrochemical activity, largest active surface area and excellent stability. Due to the high performance of GNP/ECNFs composite electrode and its relatively low cost preparation process, the GNPs are expected to be used as electrocatalyst in VRFB on a large scale to improve the cell performance.

  9. Nanostructured electrocatalyst for fuel cells : silica templated synthesis of Pt/C composites.

    Energy Technology Data Exchange (ETDEWEB)

    Stechel, Ellen Beth; Switzer, Elise E.; Fujimoto, Cy H.; Atanassov, Plamen Borissov; Cornelius, Christopher James; Hibbs, Michael R.

    2007-09-01

    Platinum-based electrocatalysts are currently required for state-of-the-art fuel cells and represent a significant portion of the overall fuel cell cost. If fuel cell technology is to become competitive with other energy conversion technologies, improve the utilization of precious metal catalysts is essential. A primary focus of this work is on creating enhanced nanostructured materials which improve precious-metal utilization. The goal is to engineer superior electrocatalytic materials through the synthesis, development and investigation of novel templated open frame structures synthesized in an aerosol-based approach. Bulk templating methods for both Pt/C and Pt-Ru composites are evaluated in this study and are found to be limited due to the fact that the nanostructure is not maintained throughout the entire sample. Therefore, an accurate examination of structural effects was previously impossible. An aerosol-based templating method of synthesizing nanostructured Pt-Ru electrocatalysts has been developed wherein the effects of structure can be related to electrocatalytic performance. The aerosol-based templating method developed in this work is extremely versatile as it can be conveniently modified to synthesize alternative materials for other systems. The synthesis method was able to be extended to nanostructured Pt-Sn for ethanol oxidation in alkaline media. Nanostructured Pt-Sn electrocatalysts were evaluated in a unique approach tailored to electrocatalytic studies in alkaline media. At low temperatures, nanostructured Pt-Sn electrocatalysts were found to have significantly higher ethanol oxidation activity than a comparable nanostructured Pt catalyst. At higher temperatures, the oxygen-containing species contribution likely provided by Sn is insignificant due to a more oxidized Pt surface. The importance of the surface coverage of oxygen-containing species in the reaction mechanism is established in these studies. The investigations in this work present

  10. Preparation and Evaluation of Inhalable Itraconazole Chitosan Based Polymeric Micelles

    Directory of Open Access Journals (Sweden)

    Esmaeil Moazeni

    2012-12-01

    Full Text Available Background: This study evaluated the potential of chitosan based polymeric micelles as a nanocarrier system for pulmonary delivery of itraconazole (ITRA.Methods: Hydrophobically modified chitosan were synthesized by conjugation of stearic acid to the hydrophilic depolymerized chitosan. FTIR and 1HNMR were used to prove the chemical structure and physical properties of the depolymerized and the stearic acid grafted chitosan. ITRA was entrapped into the micelles and physicochemical properties of the micelles were investigated. Fluorescence spectroscopy, dynamic laser light scattering andtransmission electron microscopy were used to characterize the physicochemical properties of the prepared micelles. The in vitro pulmonary profile of polymeric micelles was studied by an air-jet nebulizer connected to a twin stage impinger.Results: The polymeric micelles prepared in this study could entrap up to 43.2±2.27 μg of ITRA per milliliter. All micelles showed mean diameter between 120–200 nm. The critical micelle concentration of the stearic acid grafted chitosan was found to be 1.58×10-2 mg/ml. The nebulization efficiency was up to 89% and the fine particle fraction (FPF varied from 38% to 47%. The micelles had enough stability to remain encapsulation of the drug during nebulization process.Conclusions: In vitro data showed that stearic acid grafted chitosan based polymeric micelles has a potential to be used as nanocarriers for delivery of itraconazole through inhalation.

  11. Preparation of salt-based colloid palladium of high concentration

    Institute of Scientific and Technical Information of China (English)

    ZHENG Ya-jie; XIAO Fa-xin; YI Dan-qing; GONG Zhu-qing; LI Xin-hai

    2005-01-01

    A kind of salt-based colloid palladium of high concentration was prepared,with concentration up to 3.6g/L on amount of PdCl2.The optimal preparation conditions of the salt-based colloid palladium were that the PdCl2and NaGl concentrations were respectively 3.6g/L and 175g/L,mole ratio of Sn to Pd was 50:1,reaction temperature was 20-35 ℃,with urea,ascorbic acid and vanillin added in a proper amount.The test results of optimal condition show that the time of starting hydrogen-deposition is 9 s,the time of completely coating copper on a test substrate is 2 min,the stability time of colloid palladium is 98 h after it is diluted into 0.1g/L(on amount of PdCl2)when the solution temperature is 20 ℃,the backlight lever of electroless copper plating layer is 10th grade of 10-grade system,the adhesion force of the copper layer is up to GB5270-85 of China,and the average particle size of the colloid palladium is 81 nm measured by Master Sizer.

  12. Novel hydrogel-based preparation-free EEG electrode.

    Science.gov (United States)

    Alba, Nicolas Alexander; Sclabassi, Robert J; Sun, Mingui; Cui, Xinyan Tracy

    2010-08-01

    The largest obstacles to signal transduction for electroencephalography (EEG) recording are the hair and the epidermal stratum corneum of the skin. In typical clinical situations, hair is parted or removed, and the stratum corneum is either abraded or punctured using invasive penetration devices. These steps increase preparation time, discomfort, and the risk of infection. Cross-linked sodium polyacrylate gel swelled with electrolyte was explored as a possible skin contact element for a prototype preparation-free EEG electrode. As a superabsorbent hydrogel, polyacrylate can swell with electrolyte solution to a degree far beyond typical contemporary electrode materials, delivering a strong hydrating effect to the skin surface. This hydrating power allows the material to increase the effective skin contact surface area through wetting, and noninvasively decrease or bypass the highly resistive barrier of the stratum corneum, allowing for reduced impedance and improved electrode performance. For the purposes of the tests performed in this study, the polyacrylate was prepared both as a solid elastic gel and as a flowable paste designed to penetrate dense scalp hair. The gel can hold 99.2% DI water or 91% electrolyte solution, and the water content remains high after 29 h of air exposure. The electrical impedance of the gel electrode on unprepared human forearm is significantly lower than a number of commercial ECG and EEG electrodes. This low impedance was maintained for at least 8 h (the longest time period measured). When a paste form of the electrode was applied directly onto scalp hair, the impedance was found to be lower than that measured with commercially available EEG paste applied in the same manner. Time-frequency transformation analysis of frontal lobe EEG recordings indicated comparable frequency response between the polyacrylate-based electrode on unprepared skin and the commercial EEG electrode on abraded skin. Evoked potential recordings demonstrated

  13. Novel cobalt quantum dot/graphene nanocomposites as highly efficient electrocatalysts for water splitting

    Science.gov (United States)

    Govindhan, Maduraiveeran; Mao, Brennan; Chen, Aicheng

    2016-01-01

    A cost-effective, non-noble metal based high-performance electrocatalyst for the oxygen evolution reaction (OER) is critical to energy conversion and storage processes. Here, we report on a facile and effective in situ strategy for the synthesis of an advanced nanocomposite material that is comprised of cobalt quantum dots (Co QDs, ~3.2 nm), uniformly dispersed on reduced graphene oxide (rGO) as a highly efficient OER electrocatalyst platform. This nanocomposite electrocatalyst afforded a mass activity of 1250 A g-1 at a low overpotential (η) of 0.37 V, a small Tafel slope of ~37 mV dec-1 and a turnover frequency (TOF) of 0.188 s-1 in 0.1 M KOH, comparing favorably with state-of-the-art RuO2, IrO2 and Pt/C catalysts. The synergy between abundant catalytically active sites through the fine dispersion of Co QDs, and enhanced electron transfer generated from the graphene resulted in first-rate electrocatalytic properties toward the OER. These merits coupled with the higher stability of the nanocomposite hold great promise for triggering breakthroughs in electrocatalysis for water splitting.A cost-effective, non-noble metal based high-performance electrocatalyst for the oxygen evolution reaction (OER) is critical to energy conversion and storage processes. Here, we report on a facile and effective in situ strategy for the synthesis of an advanced nanocomposite material that is comprised of cobalt quantum dots (Co QDs, ~3.2 nm), uniformly dispersed on reduced graphene oxide (rGO) as a highly efficient OER electrocatalyst platform. This nanocomposite electrocatalyst afforded a mass activity of 1250 A g-1 at a low overpotential (η) of 0.37 V, a small Tafel slope of ~37 mV dec-1 and a turnover frequency (TOF) of 0.188 s-1 in 0.1 M KOH, comparing favorably with state-of-the-art RuO2, IrO2 and Pt/C catalysts. The synergy between abundant catalytically active sites through the fine dispersion of Co QDs, and enhanced electron transfer generated from the graphene resulted in

  14. A rhodium/silicon co-electrocatalyst design concept to surpass platinum hydrogen evolution activity at high overpotentials.

    Science.gov (United States)

    Zhu, Lili; Lin, Haiping; Li, Youyong; Liao, Fan; Lifshitz, Yeshayahu; Sheng, Minqi; Lee, Shuit-Tong; Shao, Mingwang

    2016-01-01

    Currently, platinum-based electrocatalysts show the best performance for hydrogen evolution. All hydrogen evolution reaction catalysts should however obey Sabatier's principle, that is, the adsorption energy of hydrogen to the catalyst surface should be neither too high nor too low to balance between hydrogen adsorption and desorption. To overcome the limitation of this principle, here we choose a composite (rhodium/silicon nanowire) catalyst, in which hydrogen adsorption occurs on rhodium with a large adsorption energy while hydrogen evolution occurs on silicon with a small adsorption energy. We show that the composite is stable with better hydrogen evolution activity than rhodium nanoparticles and even exceeding those of commercial platinum/carbon at high overpotentials. The results reveal that silicon plays a key role in the electrocatalysis. This work may thus open the door for the design and fabrication of electrocatalysts for high-efficiency electric energy to hydrogen energy conversion. PMID:27447292

  15. Palladium-cobalt particles as oxygen-reduction electrocatalysts

    Science.gov (United States)

    Adzic, Radoslav; Huang, Tao

    2009-12-15

    The present invention relates to palladium-cobalt particles useful as oxygen-reducing electrocatalysts. The invention also relates to oxygen-reducing cathodes and fuel cells containing these palladium-cobalt particles. The invention additionally relates to methods for the production of electrical energy by using the palladium-cobalt particles of the invention.

  16. Strong-Coupled Cobalt Borate Nanosheets/Graphene Hybrid as Electrocatalyst for Water Oxidation Under Both Alkaline and Neutral Conditions.

    Science.gov (United States)

    Chen, Pengzuo; Xu, Kun; Zhou, Tianpei; Tong, Yun; Wu, Junchi; Cheng, Han; Lu, Xiuli; Ding, Hui; Wu, Changzheng; Xie, Yi

    2016-02-12

    Developing highly active catalysts for the oxygen evolution reaction (OER) is of paramount importance for designing various renewable energy storage and conversion devices. Herein, we report the synthesis of a category of Co-Pi analogue, namely cobalt-based borate (Co-Bi ) ultrathin nanosheets/graphene hybrid by a room-temperature synthesis approach. Benefiting from the high surface active sites exposure yield, enhanced electron transfer capacity, and strong synergetic coupled effect, this Co-Bi NS/G hybrid shows high catalytic activity with current density of 10 mA cm(-2) at overpotential of 290 mV and Tafel slope of 53 mV dec(-1) in alkaline medium. Moreover, Co-Bi NS/G electrocatalysts also exhibit promising performance under neutral conditions, with a low onset potential of 235 mV and high current density of 14.4 mA cm(-2) at 1.8 V, which is the best OER performance among well-developed Co-based OER electrocatalysts to date. Our finding paves a way to develop highly active OER electrocatalysts. PMID:26757358

  17. Highly efficient and durable TiN nanofiber electrocatalyst supports

    Science.gov (United States)

    Kim, Hyun; Cho, Min Kyung; Kwon, Jeong An; Jeong, Yeon Hun; Lee, Kyung Jin; Kim, Na Young; Kim, Min Jung; Yoo, Sung Jong; Jang, Jong Hyun; Kim, Hyoung-Juhn; Nam, Suk Woo; Lim, Dong-Hee; Cho, Eunae; Lee, Kwan-Young; Kim, Jin Young

    2015-11-01

    To date, carbon-based materials including various carbon nanostructured materials have been extensively used as an electrocatalyst support for proton exchange membrane fuel cell (PEMFC) applications due to their practical nature. However, carbon dissolution or corrosion caused by high electrode potential in the presence of O2 and/or water has been identified as one of the main failure modes for the device operation. Here, we report the first TiN nanofiber (TNF)-based nonwoven structured materials to be constructed via electrospinning and subsequent two-step thermal treatment processes as a support for the PEMFC catalyst. Pt catalyst nanoparticles (NPs) deposited on the TNFs (Pt/TNFs) were electrochemically characterized with respect to oxygen reduction reaction (ORR) activity and durability in an acidic medium. From the electrochemical tests, the TNF-supported Pt catalyst was better and more stable in terms of its catalytic performance compared to a commercially available carbon-supported Pt catalyst. For example, the initial oxygen reduction performance was comparable for both cases, while the Pt/TNF showed much higher durability from an accelerated degradation test (ADT) configuration. It is understood that the improved catalytic roles of TNFs on the supported Pt NPs for ORR are due to the high electrical conductivity arising from the extended connectivity, high inertness to the electrochemical environment and strong catalyst-support interactions.To date, carbon-based materials including various carbon nanostructured materials have been extensively used as an electrocatalyst support for proton exchange membrane fuel cell (PEMFC) applications due to their practical nature. However, carbon dissolution or corrosion caused by high electrode potential in the presence of O2 and/or water has been identified as one of the main failure modes for the device operation. Here, we report the first TiN nanofiber (TNF)-based nonwoven structured materials to be constructed via

  18. [Peculicidal activity of plant essential oils and their based preparations].

    Science.gov (United States)

    Lopatina, Iu V; Eremina, O Iu

    2014-01-01

    The peculicidal activity of eight plant essential oils in 75% isopropyl alcohol was in vitro investigated. Of them, the substances that were most active against lice were tea tree (Melaleuca), eucalyptus, neem, citronella (Cymbopogon nardus), and clove (Syzygium aromaticum) oils; KT50 was not more than 3 minutes on average; KT95 was 4 minutes. After evaporating the solvent, only five (tea tree, cassia, clove, anise (Anisum vulgare), and Japanese star anise (Illicium anisatum) oils) of the eight test botanical substances were active against lice. At the same time, KT50 and KT95 showed 1.5-5-fold increases. Citronella and anise oils had incomplete ovicidal activity. Since the lice were permethrin-resistant, the efficacy of preparations based on essential oils was much higher than permethrin. PMID:25296426

  19. Highly Selective and Stable Reduction of CO2 to CO by a Graphitic Carbon Nitride/Carbon Nanotube Composite Electrocatalyst.

    Science.gov (United States)

    Lu, Xunyu; Tan, Tze Hao; Ng, Yun Hau; Amal, Rose

    2016-08-16

    A stable and selective electrocatalyst for CO2 reduction was fabricated by covalently attaching graphitic carbon nitride onto multiwall carbon nanotubes (g-C3 N4 /MWCNTs). The as-prepared composite is able to reduce CO2 exclusively to CO with a maximum Faraday efficiency of 60 %, and no decay in the catalytic activity was observed even after 50 h of reaction. The enhanced catalytic activity towards CO2 reduction is attributed to the formation of active carbon-nitrogen bonds, high specific surface area, and improved material conductivity of the g-C3 N4 /MWCNT composite.

  20. Microwave Assisted Synthesis of Osmium Electrocatalysts for the Oxygen Reduction Reaction in the Absence and Presence of Aqueous Methanol

    Directory of Open Access Journals (Sweden)

    Edgar Borja-Arco

    2011-01-01

    Full Text Available Osmium electrocatalysts for the oxygen reduction reaction (ORR were prepared by microwave irradiation of Os3(CO12 at different experimental conditions. The materials obtained were structurally characterized by FT-IR, micro-Raman spectroscopy and X-ray diffraction. Their chemical compositions were obtained by EDS. The electrocatalytic properties for the oxygen reduction reaction were evaluated by rotating disk electrode measurements in 0.5 mol L-1 H2SO4, in the absence and presence of aqueous methanol. The kinetic parameters, such as Tafel slope, exchange current density, and charge transfer coefficient are reported.

  1. Electrodeposition of nickel-phosphorus nanoparticles film as a Janus electrocatalyst for electro-splitting of water

    Science.gov (United States)

    Liu, Qian; Gu, Shuang; Li, Chang Ming

    2015-12-01

    Nickel-phosphorus nanoparticles film on copper foam (Ni-P/CF) was prepared by electrodeposition. This electrocatalyst shows high catalytic activity and durability toward both hydrogen and oxygen evolution reactions in basic electrolytes. The results show that Ni-P/CF can deliver a current density of 10 mA cm-2 at an overpotential of 98 mV for hydrogen production and 325 mV for oxygen generating. A two-electrode water electrolyzer using Ni-P/CF as cathode and anode produces 10 mA cm-2 at a cell voltage of 1.68 V with high stability.

  2. Electrocatalysts of platinum, cobalt and nickel prepared by mechanical alloying for the oxygen reduction reaction in H{sub 2}SO{sub 4} 0.5M; Electrocatalizadores de Platino, Cobalto y Niquel preparados por Aleado Mecanico para la reaccion de reduccion de oxigeno en H{sub 2}SO{sub 4} 0.5M

    Energy Technology Data Exchange (ETDEWEB)

    Garcia C, M.A.; Fernandez V, S.M.; Vargas G, J.R. [lNIN, Depto. de Quimica, 52750 La Marquesa, Estado de Mexico (Mexico)

    2007-07-01

    Metallic powders of Pt, Co and Nickel were processed by mechanical alloyed and electrocatalysts were synthesized for the oxygen reduction reaction, applicable in fuel cells. The structural and morphological characterization was carried out using X-ray Diffraction, scanning electron microscopy and transmission electron microscopy. It was found that the alloyed powders formed agglomerates that consist of crystalline particles of nano metric size. Its were obtained polarization curves by the Electrode of Rotational Disk technique in a solution of H{sub 2}SO{sub 4} 0.5 M, used as electrolyte, to evaluate the electrocatalytic activity of mechanically alloyed powders. Tafel graphics were built to determine the kinetic parameters of each electro catalyst. The PtCoNi alloy exhibited the biggest electrocatalytic activity, with the smallest over potential for the oxygen reduction reaction. (Author)

  3. Preparation of bacterial cellulose based hydrogels and their viscoelastic behavior

    Science.gov (United States)

    Shah, Rushita; Vyroubal, Radek; Fei, Haojei; Saha, Nabanita; Kitano, Takeshi; Saha, Petr

    2015-04-01

    Bacterial cellulose (BC) based hydrogels have been prepared in blended with carboxymethylcellulose and polyvinyl pyrrolidone by using heat treatment. The properties of BC-CMC and BC-PVP hydrogels were compared with pure BC, CMC and PVP hydrogels. These hydrogels were investigated by measuring their structural, morphological and viscoelastic properties. Through the morphological images, alignment of the porous flake like structures could be seen clearly within the inter-polymeric network of the hydrogels. Also, the detail structure analysis of the polymers blended during the hydrogel formation confirms their interactions with each other were studied. Further, the viscoelastic behavior of all the hydrogels in terms of elastic and viscous property was studied. It is observed that at 1% strain, including CMC and PVP hydrogels, all the BC based hydrogels exhibited the linear trend throughout. Also the elastic nature of the material remains high compared to viscous nature. Moreover, the changes could be noticed in case of blended polymer based hydrogels. The values of complex viscosity (η*) decreases with increase in angular frequency within the range of ω = 0.1-100 rad.s-1.

  4. Recent Advances in Inorganic Heterogeneous Electrocatalysts for Reduction of Carbon Dioxide.

    Science.gov (United States)

    Zhu, Dong Dong; Liu, Jin Long; Qiao, Shi Zhang

    2016-05-01

    In view of the climate changes caused by the continuously rising levels of atmospheric CO2 , advanced technologies associated with CO2 conversion are highly desirable. In recent decades, electrochemical reduction of CO2 has been extensively studied since it can reduce CO2 to value-added chemicals and fuels. Considering the sluggish reaction kinetics of the CO2 molecule, efficient and robust electrocatalysts are required to promote this conversion reaction. Here, recent progress and opportunities in inorganic heterogeneous electrocatalysts for CO2 reduction are discussed, from the viewpoint of both experimental and computational aspects. Based on elemental composition, the inorganic catalysts presented here are classified into four groups: metals, transition-metal oxides, transition-metal chalcogenides, and carbon-based materials. However, despite encouraging accomplishments made in this area, substantial advances in CO2 electrolysis are still needed to meet the criteria for practical applications. Therefore, in the last part, several promising strategies, including surface engineering, chemical modification, nanostructured catalysts, and composite materials, are proposed to facilitate the future development of CO2 electroreduction. PMID:26996295

  5. Studies on State and Structure of Noble Metals in Electrocatalyst Made by Coprecipitation Method

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The electrocatalysts of Pt/C, PtRu/C and Ru/C were prepared by the impregnation method. The facet characterization, the dispersion and the particle size for the catalysts were determined by means of X-ray diffraction and transmission electron microscopy. X-ray photoelectron spectroscopy was also used to analyze the state and the valency of the noble metals. The results show that the particle size was in nanometer range and the binary metals have come into being an alloy. The platinum in the catalysts existed in zero valency. The valency of the ruthenium on the surface is different from that in the body, while the ruthenium on the surface existed in oxide-form. PtRu/C and Pt/C are of good activity to the electrooxidation of hydrogen except Ru/C. PtRu/C is more tolerant of CO than Pt/C, and CO is only adsorbed on Pt.

  6. Electrocatalysts and their Supporting Materials for Proton Exchange Membrane Fuel Cells: Activity and Durability Studies

    DEFF Research Database (Denmark)

    Permyakova, Anastasia Aleksandrovna

    This thesis describes investigations conducted exploring the activity, stability and durability of supported nano-particulate, bulk and thin film electrocatalysts used in proton exchange membrane fuel cells (PEMFCs). The effects of different factors and conditions on the reactions involved...... instruments: TEM (FEI Tecnai T20 G2), EDS, AFM, XRD (PANalytical Multipurpose Diffractometer) and FTIR-IR. Chapter 3 describes the results of synthesis and testing of the Pt nanoparticulate catalyst supported by PBI wrapped Graphene for oxygen reduction reaction in PEMFCs. The physiochemical material’s...... presented. Electrochemical characterisation showed a gradual improvement of activity for carbon monoxide and methanol electro-oxidation when higher Si contents were employed in the Pt-Si alloy. Chapter 5 describes the preparation, material characterisation and initial electrochemical measurements...

  7. Nitrogen-doped Graphene-Supported Transition-metals Carbide Electrocatalysts for Oxygen Reduction Reaction

    Science.gov (United States)

    Chen, Minghua; Liu, Jilei; Zhou, Weijiang; Lin, Jianyi; Shen, Zexiang

    2015-05-01

    A novel and facile two-step strategy has been designed to prepare high performance bi-transition-metals (Fe- and Mo-) carbide supported on nitrogen-doped graphene (FeMo-NG) as electrocatalysts for oxygen reduction reactions (ORR). The as-synthesized FeMo carbide -NG catalysts exhibit excellent electrocatalytic activities for ORR in alkaline solution, with high onset potential (-0.09 V vs. saturated KCl Ag/AgCl), nearly four electron transfer number (nearly 4) and high kinetic-limiting current density (up to 3.5 mA cm-2 at -0.8 V vs. Ag/AgCl). Furthermore, FeMo carbide -NG composites show good cycle stability and much better toxicity tolerance durability than the commercial Pt/C catalyst, paving their application in high-performance fuel cell and lithium-air batteries.

  8. Graphene Paper Doped with Chemically Compatible Prussian Blue Nanoparticles as Nanohybrid Electrocatalyst

    DEFF Research Database (Denmark)

    Zhu, Nan; Han, Shuang; Gan, Shiyu;

    2013-01-01

    Along with reduced graphene oxide (RGO), water soluble Prussian blue nanoparticles (PBNPs, around 6 nm) are synthesized and broadly characterized. These two types of highly stable, low‐cost and chemically compatible nanomaterials are exploited as building ingredients to prepare electrically...... oxidation and detection of glucose. The present work demonstrates a facile and highly reproducible way to construct free‐standing and flexible graphene paper doped with electroactive catalyst. Thanks to high stability, low‐cost and efficient electrocatalytic characteristics, this kind of nanohybrid material...... enhanced and functionally endorsed nanohybrid electrocatalysts, which are further transformed into free‐standing graphene papers. PBNPs doped graphene papers show highly efficient electrocatalysis towards reduction of hydrogen peroxide and can be used alone as flexible chemical sensors for potential...

  9. Properties of Ferrofluids Prepared with an Isoparaffin Base.

    Science.gov (United States)

    Kim, Jong-Hee; Park, Keun-Bae

    2016-06-01

    Magnetite nanoparticles were synthesized by adding ammonium hydroxide to an iron chloride solution. An unsaturated oleate surfactant was adsorbed on the magnetic particles, and a nonionic Span 20 surfactant was applied onto the oleate-adsorbed particles to form a bilayer structure. The bilayer nanoparticles formed stable dispersions with isoparaffin as the liquid base. The experimental parameters were determined at each concentration to prepare isoparaffin-based ferrofluids with concentrations of 200, 300, 400 and 500 mg/mL; these were characterized by density, dispersion, magnetization and viscosity. The density of the fluids increased in proportion to the concentration from 0.93 g/mL to 1.22 g/mL, whereas the dispersion stability decreased from 97% to 69% with increasing ferrofluid concentration. The saturation magnetization of the ferrofluids depended upon the content of particles in the fluid, with values of 17.8 to 42.2 mT at the concentrations of 200 to 500 mg/mL, respectively. The fluid viscosity increased exponentially with the concentration increase in the same range, from 5.1 cP to 53.7 cP at 20 degrees C and from 3.2 cP to 25.6 cP at 40 degrees C. PMID:27427732

  10. PREPARATION AND CHARACTERIZATION OF AMIDATED PECTIN BASED POLYMER ELECTROLYTE MEMBRANES

    Institute of Scientific and Technical Information of China (English)

    R.K.Mishra; A.Anis; S.Mondal; M.Dutt; A.K.Banthia

    2009-01-01

    The work presents the synthesis and characterization of ami dated pectin(AP)based polymer electrolyte membranes(PEM)crosslinked with glutaraldehyde(GA).The prepared membranes are characterized by Fourier transform infrared spectroscopy(FTIR),organic elemental analysis,X-ray diffraction studies(XRD),thermogravimetric analysis (TGA)and impedance spectroscopy.Mechanical properties of the membranes are evaluated by tensile tests.The degree of amidation(DA),molar and mass reaction yields(YM and YN)are calculated based on the results of organic elemental analysis.FTIR spectroscopy indicated the presence of primary and secondary amide absorption bands.XRD pattern of membranes clearly indicates that there is a considerable increase in crystallinity as compared to parent pectin.TGA studies indicate that AP is less thermally stable than reference pectin.A maximum room temperature conductivity of 1.098×10-3 Scm-1 is obtained in the membrane,which is designated as AP-3.These properties make them good candidates for low cost biopolymer electrolyte membranes for fuel cell applications.

  11. The influence of copper in dealloyed binary platinum–copper electrocatalysts on methanol electroxidation catalytic activities

    International Nuclear Information System (INIS)

    In this study, we prepared and characterized carbon paper-supported dealloyed binary Pt–Cu core–shell electrocatalysts (denoted as PtxCu(100−x)/CP) by cyclic co-electrodeposition and selective copper dealloying in an acidic medium, and we investigated the effect of the copper content in the samples on the catalytic activities toward methanol electroxidation reaction (MOR). X-ray photo-emission spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) indicated that the structure of dealloyed binary Pt–Cu catalysts possessed a Pt-rich shell and a Cu rich core. X-ray absorption near edge spectroscopy (XANES) displayed that the oxidation states of Pt and Cu were zero and one, respectively, implying the formation of metallic Pt and Cu2O, respectively. X-ray diffraction spectroscopy (XRD) confirmed that Cu was inserted into a face-centered cubic Pt structure forming Pt–Cu alloys. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) displayed a cubic shape of Pt/CP and a spherical shape of PtxCu(100−x)/CP with several hundred nanometer sizes of agglomeration that depended on the Cu content. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were performed to confirm that the sample of Pt70Cu30/CP exhibited the best catalytic activities in terms of the specific current, current density, catalytic poisoning tolerance, and stability. - Graphical abstract: Display Omitted - Highlights: • Binary electrocatalysts of PtxCu(100−x)/CP were prepared by cyclic co-electrodeposition and selective copper dealloying. • The structures of PtxCu(100−x)/CP were a Pt rich shell and a Cu rich core. • The Pt70Cu30/CP was the excellent catalytic activity towards methanol electrooxidation and COads tolerance

  12. High-surface-area, dual-function oxygen electrocatalysts for space power applications

    Science.gov (United States)

    Ham, David O.; Moniz, Gary; Taylor, E. Jennings

    1987-01-01

    The processes of hydration/dehydration and carbonation/decarbonation are investigated as an approach to provide higher surface area mixed metal oxides that are more active electrochemically. These materials are candidates for use as electrocatalysts and electrocatalyst supports for alkaline electrolyzers and fuel cells. For the case of the perovskite, LaCoO3 , higher surface areas were achieved with no change in structure and a more active oxygen electrocatalyst.

  13. Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices

    OpenAIRE

    McCrory, Charles C. L.; Jung, Suho; Ferrer, Ivonne M.; Chatman, Shawn M.; Peters, Jonas C.; Jaramillo, Thomas F.

    2015-01-01

    Objective comparisons of electrocatalyst activity and stability using standard methods under identical conditions are necessary to evaluate the viability of existing electrocatalysts for integration into solar-fuel devices as well as to help inform the development of new catalytic systems. Herein, we use a standard protocol as a primary screen for evaluating the activity, short-term (2 h) stability, and electrochemically active surface area (ECSA) of 18 electrocatalysts for the hydrogen evolu...

  14. Pd-Au Electrocatalysts for Hydrogen Evolution Reaction at Neutral pH

    OpenAIRE

    Elitsa Chorbadzhiyska; Mario Mitov; Georgi Hristov; Nina Dimcheva; Lori Nalbandian; Antigoni Evdou; Yolina Hubenova

    2014-01-01

    Pd-Au codeposits with different ratio of both metals were electrodeposited on carbon felt, characterized by scanning electron microscopy, and investigated as electrocatalysts towards hydrogen evolution reaction in neutral phosphate buffer solution. The quantities of the produced hydrogen gas with different electrocatalysts, estimated from data obtained by chronoamperometry, were confirmed by mass spectrometry analysis. The highest hydrogen evolution rate was achieved with the electrocatalysts...

  15. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting.

    Science.gov (United States)

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng-Chang; Wang, Di-Yan; Yang, Jiang; Hwang, Bing-Joe; Dai, Hongjie

    2015-10-01

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2 O3 -blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2 O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2 O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20 mA cm(-2) at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. The non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells. PMID:26307213

  16. Electrochemical activation of nanostructured carbon-supported PtRuMo electrocatalyst for methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Huerta, M.V., E-mail: mmartinez@icp.csic.e [Instituto de Catalisis y Petroleoquimica, CSIC, Marie Curie 2, 28049 Madrid (Spain); Tsiouvaras, N.; Pena, M.A.; Fierro, J.L.G. [Instituto de Catalisis y Petroleoquimica, CSIC, Marie Curie 2, 28049 Madrid (Spain); Rodriguez, J.L.; Pastor, E. [Departamento de Quimica Fisica, Universidad de La Laguna, Astrofisico Francisco Sanchez s/n, 38071 Tenerife (Spain)

    2010-11-01

    The factors controlling the behavior and the stability of electrocatalysts based on Pt, Ru and Mo nanoparticles during exhaustive electrochemical treatment are examined. Along this treatment, it has been observed that in the case of ternary catalysts there are pronounced changes in the structure of their surface resulting in electrode activation for methanol and CO electrooxidation, whereas the activity of binary PtRu/C and PtMo/C catalysts decreases. Therefore, the role of both Ru and Mo is crucial for the electrochemical activation of the catalyst, though metal losses do occur during electrochemical process. For the first time a detailed study of this phenomenon is presented, including characterization by HRTEM, TXRF, XRD, electrochemical measurements and in situ Fourier transform infrared spectroscopy (FTIR). In order to get a deeper insight into the surface structure, chemical state, and stability of the electrocatalyst under reaction conditions, a combination of cyclic voltammetry, chronoamperometry and X-ray photoelectron spectroscopy (XPS) has been used. By comparing bulk and surface composition, our results point out to the key role of the geometric effect enhanced by previous reduction of the nanoparticles. At the end of the electrochemical treatment, Mo-PtRu/C catalysts surface was restructured with substantial enrichment in Pt and a less pronounced Mo surface enrichment, while Ru is incorporated into the Pt-Mo overlayer. These results underline the possibility of further optimization of the surface structure and composition producing PtRuMo nanoparticles with high methanol and CO oxidation activity.

  17. Preparation of polyol esters based on vegetable and animal fats.

    Science.gov (United States)

    Gryglewicz, S; Piechocki, W; Gryglewicz, G

    2003-03-01

    The possibility of using some natural fats: rapeseed oil, olive oil and lard, as starting material for the preparation of neopentyl glycol (NPG) and trimethylol propane (TMP) esters is reported. The syntheses of final products were performed by alcoholysis of fatty acid methyl esters, obtained from natural fats studied, with the appropriate polyhydric alcohol using calcium methoxide as a catalyst. The basic physicochemical properties of the NPG and TMP esters synthesized were the following: viscosity at 40 degrees C in the range of 13.5-37.6 cSt, pour point between -10.5 and -17.5 degrees C and very high viscosity indices, higher than 200. Generally, the esters of neopentyl alcohols were characterized by higher stability in thermo-oxidative conditions in comparison to native triglycerides. Due to the low content of polyunsaturated acids, the olive oil based esters showed the highest thermo-oxidative resistance. Also, methyl esters of fatty acids of lard would constitute a good raw material for the synthesis of lubricating oils, provided that their saturated acids content was lowered. This permits synthesis of NPG and TMP esters with a lower pour point (below -10 degrees C) than natural lard (+33 degrees C). PMID:12733572

  18. Preparation of polyol esters based on vegetable and animal fats.

    Science.gov (United States)

    Gryglewicz, S; Piechocki, W; Gryglewicz, G

    2003-03-01

    The possibility of using some natural fats: rapeseed oil, olive oil and lard, as starting material for the preparation of neopentyl glycol (NPG) and trimethylol propane (TMP) esters is reported. The syntheses of final products were performed by alcoholysis of fatty acid methyl esters, obtained from natural fats studied, with the appropriate polyhydric alcohol using calcium methoxide as a catalyst. The basic physicochemical properties of the NPG and TMP esters synthesized were the following: viscosity at 40 degrees C in the range of 13.5-37.6 cSt, pour point between -10.5 and -17.5 degrees C and very high viscosity indices, higher than 200. Generally, the esters of neopentyl alcohols were characterized by higher stability in thermo-oxidative conditions in comparison to native triglycerides. Due to the low content of polyunsaturated acids, the olive oil based esters showed the highest thermo-oxidative resistance. Also, methyl esters of fatty acids of lard would constitute a good raw material for the synthesis of lubricating oils, provided that their saturated acids content was lowered. This permits synthesis of NPG and TMP esters with a lower pour point (below -10 degrees C) than natural lard (+33 degrees C).

  19. Preparation of collagen-based materials for wound dressing

    Institute of Scientific and Technical Information of China (English)

    吴志谷; 盛志勇; 孙同柱; 耿淼; 黎君友; 姚咏明; 黄祖琇

    2003-01-01

    Objective To describe the methods which were used to develop collagen-based materials for wound dressing.Methods Fresh frozen bovine tendon was treated with 0.05 mol/L acetic acid at pH 3.2 for 48-72 hours, homogenized, filtered, mixed with 8% chondroitin sulphate, for creating a deaerated 1.5%-2.5% collagen solution. The solution was lyophilized in either a pre-frozen or non-pre-frozen mould. The collagen sponge was then cross-linked with 0.25% glutaraldehyde for 24 hours. Three other types of wound dressings were developed using a similar method: collagen membrane with a polyurethane membrane onlay, polyurethane-coated collagen membrane and collagen membrane on gauze.Results It was demonstrated that the use of frozen bovine tendon was stable, and that the prepared collagen sponge contained pores of 50-400 μm in diameter. Conclusions Collagen could be used as wound dressing.

  20. Atomic states and properties of Ru-electrocatalyst

    Institute of Scientific and Technical Information of China (English)

    PENG Hong-jian; XIE You-qing; WEI De-liang

    2006-01-01

    Using the one-atom theory(OA), the atomic states of Ru-electrocatalyst with hcp structure was determined as [Kr](4dn)3.78(4dc)2.22(5sc)1.77(5sf)0.23. The potential curve, elasticity and the temperature dependence of linear thermal expansion coefficient and bulk modulus of hcp-Ru were calculated quantitatively. The atomic states of this metal with fcc and bcc structure and liquid state were also studied. According to its atomic states, the relationship between the atomic states and catalytic performance was explained qualitatively and these supplied Ru-metal and electrocatalyst with complete data for optimum designation in accordance with metal material systematic sicence.

  1. Correcting for Electrocatalyst Desorption and Inactivation in Chronoamperometry Experiments

    OpenAIRE

    Fourmond, Vincent; Lautier, Thomas; Baffert, Carole; Leroux, Fanny; Liebgott, Pierre Pol; Dementin, Sébastien; Rousset, Marc; Arnoux, Pascal; Pignol, David; Meynial Salles, Isabelle; Soucaille, Philippe; Bertrand, Patrick; Léger, Christophe

    2009-01-01

    Chronoamperometric experiments with adsorbed electrocatalysts are commonly performed either for analytical purposes or for studying the catalytic mechanism of a redox enzyme. In the context of amperometric sensors, the current may be recorded as a function of time while the analyte concentration is being increased to determine a linearity range. In mechanistic studies of redox enzymes, chronoamperometry proved powerful for untangling the effects of electrode potential and time, which are conv...

  2. Benchmarking Heterogeneous Electrocatalysts for the Oxygen Evolution Reaction

    OpenAIRE

    McCrory, Charles C. L.; Jung, Suho; Peters, Jonas C.; Jaramillo, Thomas F.

    2013-01-01

    Objective evaluation of the activity of electrocatalysts for water oxidation is of fundamental importance for the development of promising energy conversion technologies including integrated solar water-splitting devices, water electrolyzers, and Li-air batteries. However, current methods employed to evaluate oxygen-evolving catalysts are not standardized, making it difficult to compare the activity and stability of these materials. We report a protocol for evaluating the activity, stability,...

  3. Preparation of Metallic and Polymer Nanoparticles, Responsive Nanogels and Nanofibers by Radiation Initiated Reactions

    International Nuclear Information System (INIS)

    Synthesis of nanomaterials have become the focus of intensive research due to their numerous applications in diverse fields such as electronics, optics, ceramics, metallurgy, pulp and paper, environmental, pharmaceutics, biotechnology and biomedical fields. Due to expanding demand for the nanomaterials with defined properties, extensive research activities have been focused on the synthesis and characterization of “functional nanomaterials”. Our research group launched into research activities on the preparation of varieties of functional materials using radiation as the source for inducing functionalities ino these new nanomaterials. Importantly, we kept final goals for specific applications. Thus, we have prepared few interesting functional nanomaterials such as metal nanoparticles decorated multi wall carbon nanotubes, pore filled functional electrospun nanofibers and nanocables based on conducting polymer and carbon nanotubes and demonstrated their applications toward electrocatalysts, polymer electrolyte in energy devices and biosensors. In the forthcoming sections, a brief outline on the use of radiation for the preparation of those functional nanomaterials are presented. (author)

  4. Carbon nanotubes/heteroatom-doped carbon core-sheath nanostructures as highly active, metal-free oxygen reduction electrocatalysts for alkaline fuel cells.

    Science.gov (United States)

    Sa, Young Jin; Park, Chiyoung; Jeong, Hu Young; Park, Seok-Hee; Lee, Zonghoon; Kim, Kyoung Taek; Park, Gu-Gon; Joo, Sang Hoon

    2014-04-14

    A facile, scalable route to new nanocomposites that are based on carbon nanotubes/heteroatom-doped carbon (CNT/HDC) core-sheath nanostructures is reported. These nanostructures were prepared by the adsorption of heteroatom-containing ionic liquids on the walls of CNTs, followed by carbonization. The design of the CNT/HDC composite allows for combining the electrical conductivity of the CNTs with the catalytic activity of the heteroatom-containing HDC sheath layers. The CNT/HDC nanostructures are highly active electrocatalysts for the oxygen reduction reaction and displayed one of the best performances among heteroatom-doped nanocarbon catalysts in terms of half-wave potential and kinetic current density. The four-electron selectivity and the exchange current density of the CNT/HDC nanostructures are comparable with those of a Pt/C catalyst, and the CNT/HDC composites were superior to Pt/C in terms of long-term durability and poison tolerance. Furthermore, an alkaline fuel cell that employs a CNT/HDC nanostructure as the cathode catalyst shows very high current and power densities, which sheds light on the practical applicability of these new nanocomposites. PMID:24554521

  5. Electrodeposited ultrafine NbOx, ZrOx, and TaO x nanoparticles on carbon black supports for oxygen reduction electrocatalysts in acidic media

    KAUST Repository

    Seo, Jeongsuk

    2013-09-06

    A remarkable electrocatalytic activity was obtained for the oxygen reduction reaction (ORR) in acidic solutions on ultrafine nano-oxide catalysts based on group IV or V elements. By potentiostatic electrodepostion in nonaqueous solutions at 298 K followed by heat treatment in H2 gas, highly dispersed fine nanoparticles of NbOx, ZrOx, and TaOx with sizes of less than 5 nm were prepared and deposited on carbon black (CB) loaded electrodes. These oxide nanoparticles showed high catalytic activities with high onset potentials of 0.96 VRHE (NbOx), 1.02 VRHE (ZrOx), and 0.93 V RHE (TaOx) for the ORR. Owing to the high chemical stability of group IV and V oxides, the catalysts were very stable during the ORR in acidic solutions. Surface characterization and chemical identification were performed using scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). All results clearly indicate the formation of nano-oxide electrocatalysts that show an outstanding ORR performance, whereas the bulk oxides are not active because of the absence of electronic conductivity. The present work demonstrates potential candidates for highly stable, non-noble-metal cathode catalysts for polymer electrolyte fuel cells (PEFCs), where the catalysts are exposed to highly acidic and oxidizing conditions. © 2013 American Chemical Society.

  6. In situ growth of NixSy controlled by surface treatment of nickel foam as efficient electrocatalyst for oxygen evolution reaction

    Science.gov (United States)

    Shang, Xiao; Li, Xiao; Hu, Wen-Hui; Dong, Bin; Liu, Yan-Ru; Han, Guan-Qun; Chai, Yong-Ming; Liu, Yun-Qi; Liu, Chen-Guang

    2016-08-01

    In situ growth of NixSy with different crystal phases supported on different surface-treated (acidification or oxidation) nickel foam (NF) has been successfully achieved by a facile solvothermal process. XRD and SEM results show that crystal phase and morphology of NixSy have been greatly affected by the surface treatment of NF. XRD results show that the mixture crystal phases of NixSy have been obtained on both acid-treated NF (NF(a)) and oxidant treated NF (NF(o)). NixSy/NF(a) contains Ni3S2 and NiS, whereas NixSy/NF(o) has Ni3S2 and NiS2, implying different crystal phases derived from different surface treatment of NF. SEM images also reveal the different morphology of two samples based on pre-treatment support. NixSy/NF(a) displays unique conical agglomeration surrounded by porous structure. NixSy/NF(o) has the disorder stacking structure of nanosheets. Electrochemical measurements for oxygen evolution reaction (OER) show the enhanced performances of NixSy/NF(a) than NixSy/NF(o) and pure Ni3S2/NF as contrast samples, implying that NiS outperforms other types of NixSy. The mechanisms of sulfurization path of different surface-treated NF have been discussed. The facile surface treatment of NF may provide a new strategy to prepare excellent electrocatalysts for OER.

  7. A novel sputtered Pd mesh architecture as an advanced electrocatalyst for highly efficient hydrogen production

    Science.gov (United States)

    de Lucas-Consuegra, Antonio; de la Osa, Ana R.; Calcerrada, Ana B.; Linares, José J.; Horwat, David

    2016-07-01

    This study reports the preparation, characterization and testing of a sputtered Pd mesh-like anode as an advanced electrocatalyst for H2 production from alkaline ethanol solutions in an Alkaline Membrane Electrolyzer (AEM). Pd anodic catalyst is prepared by magnetron sputtering technique onto a microfiber carbon paper support. Scanning Electron Microscopy images reveal that the used preparation technique enables to cover the surface of the carbon microfibers exposed to the Pd target, leading to a continuous network that also maintains part of the original carbon paper macroporosity. Such novel anodic architecture (organic binder free) presents an excellent electro-chemical performance, with a maximum current density of 700 mA cm-2 at 1.3 V, and, concomitantly, a large H2 production rate with low energy requirement compared to water electrolysis. Potassium hydroxide emerges as the best electrolyte, whereas temperature exerts the expected promotional effect up to 90 °C. On the other hand, a 1 mol L-1 ethanol solution is enough to guarantee an efficient fuel supply without any mass transfer limitation. The proposed system also demonstrates to remain stable over 150 h of operation along five consecutives cycles, producing highly pure H2 (99.999%) at the cathode and potassium acetate as the main anodic product.

  8. Considering the Future of University-Based Teacher Preparation

    Science.gov (United States)

    Fraser, James W.

    2014-01-01

    In this commentary, James W. Fraser, a noted historian of education, cites examples from several teacher education programs at more than 30 universities partnering with the Woodrow Wilson Teaching Fellowships in various ways. Additionally, Fraser reviews decades of challenges to traditional teacher preparation, looks at some current reforms, and…

  9. Preparation and properties of starch-based colloidal microgels

    NARCIS (Netherlands)

    Dziechciarek, Y.; Soest, van J.J.G.; Philipse, A.P.

    2002-01-01

    Novel starch microgels were prepared by emulsion cross-linking and characterized with respect to shape, volume, and mass density. Starch microgels appear to be negatively charged (similar to-50 mV), with a particle size varying as a function of the type of cross-linker (ca. 0.25-10 mum). Environment

  10. Rare earth metal oxides as BH4-tolerance cathode electrocatalysts for direct borohydride fuel cells

    Institute of Scientific and Technical Information of China (English)

    NI Xuemin; WANG Yadong; GUO Feng; YAO Pei; PAN Mu

    2012-01-01

    Rare earth metal oxides (REMO) as cathode electrocatalysts in direct borohydride fuel cell (DBFC) were investigated.The REMO electrocatalysts tested showed favorable activity to the oxygen electro-reduction reaction and strong tolerance to the attack of BH4- in alkaline electrolytes.The simple membraneless DBFCs using REMO as cathode electrocatalyst and using hydrogen storage alloy as anodic electrocatalyst exhibited an open circuit of about 1 V and peak power of above 60 mW/cm2.The DBFC using Sm2O3 as cathode electrocatalyst showed a relatively better performance.The maximal power density of 76.2 mW/cm2 was obtained at the cell voltage of 0.52 V.

  11. Cotton Wool Derived Carbon Fiber Aerogel Supported Few-Layered MoSe2 Nanosheets As Efficient Electrocatalysts for Hydrogen Evolution.

    Science.gov (United States)

    Zhang, Youfang; Zuo, Lizeng; Zhang, Longsheng; Huang, Yunpeng; Lu, Hengyi; Fan, Wei; Liu, Tianxi

    2016-03-23

    Recent studies have proven that newly emerging two-dimensional molybdenum diselenide (MoSe2) is a promising noble-metal-free electrocatalyst for hydrogen evolution reaction (HER). Increasing the exposures of the active edges of MoSe2 nanostructures is a key issue to fully realize the excellent electrochemical properties of MoSe2. In this work, a few-layered MoSe2/carbon fiber aerogel (CFA) hybrids have been facilely obtained through the combination of high-temperature carbonization and one-pot solvothermal reaction. CFA derived from cotton wool is used as a three-dimensional conductive network for construction of hierarchical MoSe2/CFA hybrids, where few-layered MoSe2 nanosheets are uniformly and perpendicularly decorated on the surfaces of CFA. In the designed and prepared hybrids, CFA effectively increases the exposures of the active edges of MoSe2 nanosheets as well as provides reduced lengths for both electron transportation and ion diffusion. Therefore, the obtained optimal MoSe2/CFA hybrid exhibits excellent electrochemical activity as HER electrocatalyst with a small onset potential of -0.104 V vs reversible hydrogen electrode and a small Tafel slope of 62 mV per decade, showing its great potential as a next-generation Pt-free electrocatalyst for HER.

  12. Cotton Wool Derived Carbon Fiber Aerogel Supported Few-Layered MoSe2 Nanosheets As Efficient Electrocatalysts for Hydrogen Evolution.

    Science.gov (United States)

    Zhang, Youfang; Zuo, Lizeng; Zhang, Longsheng; Huang, Yunpeng; Lu, Hengyi; Fan, Wei; Liu, Tianxi

    2016-03-23

    Recent studies have proven that newly emerging two-dimensional molybdenum diselenide (MoSe2) is a promising noble-metal-free electrocatalyst for hydrogen evolution reaction (HER). Increasing the exposures of the active edges of MoSe2 nanostructures is a key issue to fully realize the excellent electrochemical properties of MoSe2. In this work, a few-layered MoSe2/carbon fiber aerogel (CFA) hybrids have been facilely obtained through the combination of high-temperature carbonization and one-pot solvothermal reaction. CFA derived from cotton wool is used as a three-dimensional conductive network for construction of hierarchical MoSe2/CFA hybrids, where few-layered MoSe2 nanosheets are uniformly and perpendicularly decorated on the surfaces of CFA. In the designed and prepared hybrids, CFA effectively increases the exposures of the active edges of MoSe2 nanosheets as well as provides reduced lengths for both electron transportation and ion diffusion. Therefore, the obtained optimal MoSe2/CFA hybrid exhibits excellent electrochemical activity as HER electrocatalyst with a small onset potential of -0.104 V vs reversible hydrogen electrode and a small Tafel slope of 62 mV per decade, showing its great potential as a next-generation Pt-free electrocatalyst for HER. PMID:26927526

  13. A CoFe2O4/graphene nanohybrid as an efficient bi-functional electrocatalyst for oxygen reduction and oxygen evolution

    Science.gov (United States)

    Bian, Weiyong; Yang, Zhenrong; Strasser, Peter; Yang, Ruizhi

    2014-03-01

    Development of efficient electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) remain key issues for the commercialization of fuel cells and metal-air batteries. In this study, A CoFe2O4/graphene nanohybrid is facilely synthesized via a two-step process and applied as an electrocatalyst for the ORR and the OER. The as-prepared CoFe2O4/graphene nanohybrid demonstrates excellent catalytic activity for the ORR. At the same mass loading, the Tafel slope of CoFe2O4/graphene electrocatalyst for the ORR is comparable to that of the commercial Pt/C (20 wt% Pt on Vulcan XC-72, Johnson Matthey). The ORR on CoFe2O4/graphene mainly favours a direct 4e- reaction pathway. The CoFe2O4/graphene nanohybrid also affords high catalytic activity for the OER. The chronoamperometric tests show that CoFe2O4/graphene catalyst exhibits excellent stability for both the ORR and the OER, outperforming the commercial Pt/C. The high electrocatalytic activity and durability of CoFe2O4/graphene nanohybrid are attributed to the strong coupling between CoFe2O4 nanoparticles and graphene.

  14. Self-assembled platinum nanoparticles on sulfonic acid-grafted graphene as effective electrocatalysts for methanol oxidation in direct methanol fuel cells

    Science.gov (United States)

    Lu, Jinlin; Li, Yanhong; Li, Shengli; Jiang, San Ping

    2016-02-01

    In this article, sulfonic acid-grafted reduced graphene oxide (S-rGO) were synthesized using a one-pot method under mild conditions, and used as Pt catalyst supports to prepare Pt/S-rGO electrocatalysts through a self-assembly route. The structure, morphologies and physicochemical properties of S-rGO were examined in detail by techniques such as atomic force microscope (AFM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The S-rGO nanosheets show excellent solubility and stability in water and the average particle size of Pt nanoparticles supported on S-rGO is ~3.8 nm with symmetrical and uniform distribution. The electrocatalytic properties of Pt/S-rGO were investigated for methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs). In comparison to Pt supported on high surface area Vulcan XC-72 carbon (Pt/VC) and Pt/rGO, the Pt/S-rGO electrocatalyst exhibits a much higher electrocatalytic activity, faster reaction kinetics and a better stability. The results indicate that Pt/S-rGO is a promising and effective electrocatalyst for MOR of DMFCs.

  15. PREPARATION AND CHARACTERIZATION OF POLYMER-BASED SPHERICAL ACTIVATED CARBONS

    Institute of Scientific and Technical Information of China (English)

    Zhao-lian Zhu; Ai-min Li; Ming-fang Xia; Jin-nan Wan; Quan-xing Zhang

    2008-01-01

    A series of spherical activated carbons(SACs)with different pore structures were prepared from chloromethylated polydivinylbenzene by ZnCl2 activation.The effects of activation temperature and retention time on the yield and textural properties of the resulting SACs were studied.All the SACs are generated with high yield of above 65% and exhibit relatively high mesopore fraction(me%) of 35.7%-43.6% compared with conventional activated carbons.The sample zlc28 prepared at 800℃ for 2 h has the largest BET surface area of 891m2g-1 and pore volume of 0.489 cm3g-1,SEM and XRD analyses of zlc28 verify the presence of developed porous structure composed of disordered micrographite stacking with large amounts of interspaces in the order of nanometers.

  16. Preparation of Zirconia Based Packing Material and Its Evaluation

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new reversed-phase packing (C18-PBD-ZrO2) was prepared by depositing and cross-linking 1-octadecene (ODE or C18) and polybutadiene (PBD) onto the surface of porous zirconia microspheres (5~10 mm in diameter) which were synthesized by a sol-gel process. These novel column packings possess high mechanical and chemical stability,wider usable pH range and can be used to separate basic compounds with no observable peak tailing.

  17. Preparation of a New Polyoxometalate-based Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    Xiao Hong WANG; Feng LI; Jing Fu LIU; M. T. POPE

    2004-01-01

    Polyoxometalates (POMs) (-K8 H6 [Si2W18Ti6O77] (Si2W18Ti6) loaded starch nanop-articles have been prepared and structurally characterized by elemental analyses, IR spectra and 29Si spectroscopy. The particle size of Si2W18Ti6 /starch was estimated by a Transmission electron microscope (TEM) and a 1000HSA MALVIRN Zetasizer instrument. The result shows that the polyoxometalate retained the parent structure after encapsulated by starch microspheres.

  18. Preparation and Characterization of Amino Acids-Based Trimethoprim Salts

    Directory of Open Access Journals (Sweden)

    Afzal R. Mohammed

    2012-02-01

    Full Text Available Trimethoprim (TMP is a dihydrofolate reductase (DHFR inhibitor which prevents the conversion of dihydrofolic acid into tetrahydrofolic acid, resulting in the depletion of the latter and leading to bacterial death. Oral bioavailability of TMP is hindered by both its low solubility and low permeability. This study aims to prepare novel salts of TMP using anionic amino acids; aspartic and glutamic acid as counter ions in order to improve solubility and dissolution. TMP salts were prepared by lyophilisation and characterized using FT-IR spectroscopy, proton nuclear magnetic resonance (1HNMR, Differential Scanning Calorimetry (DSC and Thermogravimetric analysis (TGA. Both the amino acids formed salts with TMP in a 1:1 molar ratio and showed a 280 fold improvement in solubility. Investigation of the microbiological activity of the prepared salts against TMP sensitive Escherichia coli showed that the new salts not only retained antibacterial activity but also exhibited higher zone of inhibition which was attributed to improved physicochemical characters such as higher solubility and dissolution. The results are an important finding that could potentially impact on faster onset of antibacterial activity and reduced therapeutic dose when administered to patients. Studies are underway investigating the effect of ion-pairing TMP with amino acids on the permeability profile of the drug.

  19. Cobalt diselenide nanoparticles embedded within porous carbon polyhedra as advanced electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Wu, Renbing; Xue, Yanhong; Liu, Bo; Zhou, Kun; Wei, Jun; Chan, Siew Hwa

    2016-10-01

    Highly efficient and cost-effective electrocatalyst for the oxygen reduction reaction (ORR) is crucial for a variety of renewable energy applications. Herein, strongly coupled hybrid composites composed of cobalt diselenide (CoSe2) nanoparticles embedded within graphitic carbon polyhedra (GCP) as high-performance ORR catalyst have been rationally designed and synthesized. The catalyst is fabricated by a convenient method, which involves the simultaneous pyrolysis and selenization of preformed Co-based zeolitic imidazolate framework (ZIF-67). Benefiting from the unique structural features, the resulting CoSe2/GCP hybrid catalyst shows high stability and excellent electrocatalytic activity towards ORR (the onset and half-wave potentials are 0.935 and 0.806 V vs. RHE, respectively), which is superior to the state-of-the-art commercial Pt/C catalyst (0.912 and 0.781 V vs. RHE, respectively).

  20. Iron Carbide Nanoparticles Encapsulated in Mesoporous Fe-N-Doped Graphene-Like Carbon Hybrids as Efficient Bifunctional Oxygen Electrocatalysts.

    Science.gov (United States)

    Jiang, Hongliang; Yao, Yifan; Zhu, Yihua; Liu, Yanyan; Su, Yunhe; Yang, Xiaoling; Li, Chunzhong

    2015-09-30

    It is highly crucial and challenging to develop bifunctional oxygen electrocatalysts for oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) in rechargeable metal-air batteries and unitized regenerative fuel cells (URFCs). Herein, a facile and cost-effective strategy is developed to prepare mesoporous Fe-N-doped graphene-like carbon architectures with uniform Fe3C nanoparticles encapsulated in graphitic layers (Fe3C@NG) via a one-step solid-state thermal reaction. The optimized Fe3C@NG800-0.2 catalyst shows comparable ORR activity with the state-of-the-art Pt/C catalyst and OER activity with the benchmarking RuO2 catalyst. The oxygen electrode activity parameter ΔE (the criteria for judging the overall catalytic activity of bifunctional electrocatalysts) value for Fe3C@NG800-0.2 is 0.780 V, which surpasses those of Pt/C and RuO2 catalysts as well as those of most nonprecious metal catalysts. Significantly, excellent long-term catalytic durability holds great promise in fields of rechargeable metal-air batteries and URFCs. PMID:26371772

  1. N-doped graphene coupled with Co nanoparticles as an efficient electrocatalyst for oxygen reduction in alkaline media

    Science.gov (United States)

    Zhang, Geng; Lu, Wangting; Cao, Feifei; Xiao, Zhidong; Zheng, Xinsheng

    2016-01-01

    Development of low-cost and highly efficient electrocatalysts for oxygen reduction reaction (ORR) is still a great challenge for the large-scale application of fuel cells and metal-air batteries. Herein, a noble metal-free ORR electrocatalyst in the form of N-doped graphene coupled with part of Co nanoparticles encased in N-doped graphitic shells (named as SUCo-0.03-800) is prepared by facile one-step pyrolysis of the mixture of sucrose, urea and cobalt nitrate. The novel structure is confirmed by High Resolution-TEM, XRD, XPS and Raman spectroscopy. SUCo-0.03-800 presents comparable ORR catalytic activity to commercial Pt/C catalyst with a dominating four-electron pathway under alkaline conditions, and both of its mass activity and volume activity also outperform Co-free N-doped graphene and other Co/N-C hybrids with higher Co content, which may probably be ascribed to the high specific surface area, novel structure and synergistic effect between encased Co nanoparticles and N-doped graphitic shell. Additionally, SUCo-0.03-800 also shows outstanding stability and improved selectivity towards ORR, making it a promising alternative to Pt with potential application in fuel cells and metal-air batteries.

  2. Electro-catalytic activity of Ni–Co-based catalysts for oxygen evolution reaction

    Energy Technology Data Exchange (ETDEWEB)

    Ju, Hua [School of Urban Rail Transportation, Soochow University, Suzhou 215006 (China); Li, Zhihu [College of Physics, Optoelectronics and Energy, Soochow University, Moye Rd. 688, Suzhou 215006 (China); Xu, Yanhui, E-mail: xuyanhui@suda.edu.cn [College of Physics, Optoelectronics and Energy, Soochow University, Moye Rd. 688, Suzhou 215006 (China)

    2015-04-15

    Graphical abstract: The electro-catalytic activity of different electro-catalysts with a porous electrode structure was compared considering the real electrode area that was evaluated by cyclic measurement. - Highlights: • Ni–Co-based electro-catalysts for OER have been studied and compared. • The real electrode area is calculated and used for assessing the electro-catalysts. • Exchange current and reaction rate constant are estimated. • Ni is more useful for OER reaction than Co. - Abstract: In the present work, Ni–Co-based electrocatalysts (Ni/Co = 0:6, 1:5, 2:4, 3:3, 4:2, 5:1 and 6:0) have been studied for oxygen evolution reaction. The phase structure has been analyzed by X-ray diffraction technique. Based on the XRD and SEM results, it is believed that the synthesized products are poorly crystallized. To exclude the disturbance of electrode preparation technology on the evaluation of electro-catalytic activity, the real electrode surface area is calculated based on the cyclic voltammetry data, assumed that the specific surface capacitance is 60 μF cm{sup −2} for metal oxide electrode. The real electrode area data are used to calculate the current density. The reaction rate constant of OER at different electrodes is also estimated based on basic reaction kinetic equations. It is found that the exchange current is 0.05–0.47 mA cm{sup −2} (the real surface area), and the reaction rate constant has an order of magnitude of 10{sup −7}–10{sup −6} cm s{sup −1}. The influence of the electrode potential on OER rate has been also studied by electrochemical impedance spectroscopy (EIS) technique. Our investigation has shown that the nickel element has more contribution than the cobalt; the nickel oxide has the best electro-catalytic activity toward OER.

  3. Electro-catalytic activity of Ni–Co-based catalysts for oxygen evolution reaction

    International Nuclear Information System (INIS)

    Graphical abstract: The electro-catalytic activity of different electro-catalysts with a porous electrode structure was compared considering the real electrode area that was evaluated by cyclic measurement. - Highlights: • Ni–Co-based electro-catalysts for OER have been studied and compared. • The real electrode area is calculated and used for assessing the electro-catalysts. • Exchange current and reaction rate constant are estimated. • Ni is more useful for OER reaction than Co. - Abstract: In the present work, Ni–Co-based electrocatalysts (Ni/Co = 0:6, 1:5, 2:4, 3:3, 4:2, 5:1 and 6:0) have been studied for oxygen evolution reaction. The phase structure has been analyzed by X-ray diffraction technique. Based on the XRD and SEM results, it is believed that the synthesized products are poorly crystallized. To exclude the disturbance of electrode preparation technology on the evaluation of electro-catalytic activity, the real electrode surface area is calculated based on the cyclic voltammetry data, assumed that the specific surface capacitance is 60 μF cm−2 for metal oxide electrode. The real electrode area data are used to calculate the current density. The reaction rate constant of OER at different electrodes is also estimated based on basic reaction kinetic equations. It is found that the exchange current is 0.05–0.47 mA cm−2 (the real surface area), and the reaction rate constant has an order of magnitude of 10−7–10−6 cm s−1. The influence of the electrode potential on OER rate has been also studied by electrochemical impedance spectroscopy (EIS) technique. Our investigation has shown that the nickel element has more contribution than the cobalt; the nickel oxide has the best electro-catalytic activity toward OER

  4. Tungsten disulphide nanorattle: A new type of high performance electrocatalyst for hydrogen evolution reaction

    Science.gov (United States)

    Wen, Yan; Xia, Yongde; Zhang, Shaowei

    2016-03-01

    A new form of nanorattle, WS2@WS2 nanorattle, is prepared for the first time by direct sulphidation of pre-synthesised W@WS2 nanorattle template at 350 °C. Its microstructural and crystalline structures are characterized, and its electrocatalytic activity and stability in the hydrogen evolution reaction examined. WS2 nanoflakes are formed in-situ from sulphidation of the original W cores, and remain in the final WS2@WS2 nanorattles. They are well dispersed, exposing effectively their edges (catalytically active sites) to the reacting species. Consequently, the as-prepared WS2@WS2 nanorattles exhibit excellent electrocatalytic activity and stability. This finding, along with the novel synthesis technique developed, makes WS2@WS2 nanorattle a very promising electrocatalyst for future hydrogen generation. Furthermore, the synthesis strategy used in this work can be readily extended/modified to fabricate other important types of transitional metal nanorattles (e.g., MoS2@MoS2 MoSe2@MoS2 and WC@WS2), potentially benefiting more application areas.

  5. Atomic states and properties of Pt-electrocatalyst

    Institute of Scientific and Technical Information of China (English)

    PENG Hongjian; XIE Youqing

    2006-01-01

    Using the one-atom theory (OA), the atomic state of Pt-electrocatalyst with fcc structure was determined as follows: [Xe] (5dn)6.48 (5dc)2.02 (6Sc)1.48(6sf)0.02. The atomic states of this metal with hcp and bcc structures of primary characteristic crystals and liquid state was also studied. According to its atomic states, the relationship between the atomic states and crystalline structure, catalytic performance and conductivity was explained qualitatively. The potential curve, the temperature dependence of bulk modulus and linear thermal expansion coefficient of fcc-Pt were calculated quantitatively.

  6. ETEM Studies of Electrodes and Electro-catalysts

    DEFF Research Database (Denmark)

    Jooss, Christian; Mildner, Stephanie; Beleggia, Marco;

    2016-01-01

    Environmental TEM is an excellent tool for gaining insight into the atomic and electronic structure of electro-catalysts under operating conditions. Several electrochemical reactions such as oxidation/reduction processes of electrodes, heterogeneous gas phase catalysis of water splitting...... sample holders. To illustrate how this can be achieved, we present the results of a bias-controlled electro-corrosion experiment. We will discuss some of the main experimental and theoretical challenges for the development of controlled electrochemistry studies in transmission electron microscopes....

  7. Enhanced methanol electro-oxidation reaction on Pt-CoOx/MWCNTs hybrid electro-catalyst

    Science.gov (United States)

    Nouralishahi, Amideddin; Rashidi, Ali Morad; Mortazavi, Yadollah; Khodadadi, Abbas Ali; Choolaei, Mohammadmehdi

    2015-04-01

    The electro-catalytic behavior of Pt-CoOx/MWCNTs in methanol electro-oxidation reaction (MOR) is investigated and compared to that of Pt/MWCNTs. The electro-catalysts were synthesized by an impregnation method using NaBH4 as the reducing agent. The morphological and physical characteristics of samples are examined by XRD, TEM, ICP and EDS techniques. In the presence of CoOx, Pt nanoparticles were highly distributed on the support with an average particle size of 2 nm, an obvious decrease from 5.1 nm for Pt/MWCNTs. Cyclic voltammetry, CO-stripping, Chronoamperometry, and electrochemical impedance spectroscopy (EIS) measurements are used to study the electrochemical behavior of the electro-catalysts. The results revealed a considerable enhancement in the oxidation kinetics of COads on Pt active sites by the participation of CoOx. Compared to Pt/MWCNTs, Pt-CoOx/MWCNTs sample has a larger electrochemical active surface area (ECSA) and higher electro-catalytic activity and stability toward methanol electro-oxidation. According to the results of cyclic voltammetry, the forward anodic peak current density enhances more than 89% at the optimum atomic ratio of Pt:Co = 2:1. Furthermore, inclusion of cobalt oxide species causes the onset potential of methanol electro-oxidation reaction to shift 84 mV to negative values compared to that on Pt/MWCNTs. Based on EIS data, dehydrogenation of methanol is the rate-determining step of MOR on both Pt/MWCNTs and Pt-CoOx/MWCNTs, at small overpotentials. However, at higher overpotentials, the oxidation of adsorbed oxygen-containing groups controls the total rate of MOR process.

  8. Preparation of Amperometric Glucose Biosensor Based on 4-Mercaptobenzoic Acid

    Science.gov (United States)

    Wang, Huihui; Ohnuki, Hitoshi; Endo, Hideaki; Izumi, Mitsuru

    A novel glucose biosensor was fabricated by a combination of a self-assembled monolayer (SAM) of 4-mercaptobenzoic acid and the Langmuir-Blodgett (LB) technique. Because of the catalysis of Prussian Blue contained in the LB film layers, the prepared amperometric biosensor worked at a very low potential range around 0.0 V vs. Ag/AgCl. The optimum operating conditions for glucose biosensor were investigated by varying the glucose oxidase immobilization time, the applied potential and the pH of buffer solution. The steady-state current responses of the glucose biosensor showed a good linear relationship to glucose concentrations from 0.1 mM to 154 mM.

  9. Agricultural Residues Based Composites 1. Preparation of Fibrous Agricultural Residues

    International Nuclear Information System (INIS)

    The aim of this study is to use agricultural residues as bagasse, cotton stalks, rice straw, linen and linen fibers, which are produced in Egypt in huge amounts annually to produce composites with cement or gypsum. Also the effect of physical and chemical treatments of the fibers and the addition of some additives to the composites was studied. The mechanical properties of the produced composites also the effect of its firing at temperatures up to 800 degree C was tested after dipping in water for different time intervals (1-90 days). In this paper we considered only the preparation of different types of fibers, its grinding and separation to different fiber lengths (ca. 0.4 to 1.5 mm). The percent of each fiber length and its chemical and physical analysis is found

  10. MoO2-CoO coupled with a macroporous carbon hybrid electrocatalyst for highly efficient oxygen evolution

    Science.gov (United States)

    Li, B. B.; Liang, Y. Q.; Yang, X. J.; Cui, Z. D.; Qiao, S. Z.; Zhu, S. L.; Li, Z. Y.; Yin, K.

    2015-10-01

    Cost-effective electrocatalysts for oxygen evolution reactions are attractive for energy conversion and storage processes. A high-performance oxygen evolution reaction (OER) electrocatalyst composed of 3D ordered microporous carbon and a MoO2 skeleton modified by cobalt oxide nanoparticles (MoO2-CoO-Carbon) is produced through a template method. This unique 3DOM structure finely combines the larger surface area of the 3D carbon skeleton and MoO2 as well as stablizes anchoring sites for CoO nanocrystals on the skeleton. The synergistic effect between the catalytic activity between MoO2 and CoO as well as the enhanced electron transport arising from the carbon skeleton contributed to superior electrocatalytic OER properties of MoO2-CoO-Carbon. The M200-C-Carbon hybrid with an overpotential as low as 0.24 V is among the best reported Mo-based OER catalysts. Moreover, the turnover frequency at an overpotential of 0.35 V is 6 times as high as that of commercial RuO2.Cost-effective electrocatalysts for oxygen evolution reactions are attractive for energy conversion and storage processes. A high-performance oxygen evolution reaction (OER) electrocatalyst composed of 3D ordered microporous carbon and a MoO2 skeleton modified by cobalt oxide nanoparticles (MoO2-CoO-Carbon) is produced through a template method. This unique 3DOM structure finely combines the larger surface area of the 3D carbon skeleton and MoO2 as well as stablizes anchoring sites for CoO nanocrystals on the skeleton. The synergistic effect between the catalytic activity between MoO2 and CoO as well as the enhanced electron transport arising from the carbon skeleton contributed to superior electrocatalytic OER properties of MoO2-CoO-Carbon. The M200-C-Carbon hybrid with an overpotential as low as 0.24 V is among the best reported Mo-based OER catalysts. Moreover, the turnover frequency at an overpotential of 0.35 V is 6 times as high as that of commercial RuO2. Electronic supplementary information (ESI

  11. Cobalt nanoparticles embedded in N-doped carbon as an efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions

    Science.gov (United States)

    Su, Yunhe; Zhu, Yihua; Jiang, Hongliang; Shen, Jianhua; Yang, Xiaoling; Zou, Wenjian; Chen, Jianding; Li, Chunzhong

    2014-11-01

    Cobalt based catalysts are promising bifunctional electrocatalysts for both oxygen reduction and oxygen evolution reactions (ORR and OER) in unitized regenerative fuel cells (URFCs) operating with alkaline electrolytes. Here we report a hybrid composite of cobalt nanoparticles embedded in nitrogen-doped carbon (Co/N-C) via a solvothermal carbonization strategy. With the synergistic effect arising from the N-doped carbon and cobalt nanoparticles in the composite, the Co/N-C hybrid catalyst exhibits highly efficient bifunctional catalytic activity and excellent stability toward both ORR and OER. The ΔE (oxygen electrode activity parameter for judging the overall electrocatalytic activity of a bifunctional electrocatalyst) value for Co/N-C is 0.859 V, which is smaller than those of Pt/C and most of the non-precious metal catalysts in previous studies. Furthermore, the Co/N-C composite also shows better bifunctional catalytic activity than its oxidative counterparts, which could be attributed to the high specific surface area and the efficient charge transfer ability of the composite, as well as the good synergistic effect between N-doped carbon and the Co nanoparticles in the Co/N-C composite.Cobalt based catalysts are promising bifunctional electrocatalysts for both oxygen reduction and oxygen evolution reactions (ORR and OER) in unitized regenerative fuel cells (URFCs) operating with alkaline electrolytes. Here we report a hybrid composite of cobalt nanoparticles embedded in nitrogen-doped carbon (Co/N-C) via a solvothermal carbonization strategy. With the synergistic effect arising from the N-doped carbon and cobalt nanoparticles in the composite, the Co/N-C hybrid catalyst exhibits highly efficient bifunctional catalytic activity and excellent stability toward both ORR and OER. The ΔE (oxygen electrode activity parameter for judging the overall electrocatalytic activity of a bifunctional electrocatalyst) value for Co/N-C is 0.859 V, which is smaller than those

  12. The influence of copper in dealloyed binary platinum–copper electrocatalysts on methanol electroxidation catalytic activities

    Energy Technology Data Exchange (ETDEWEB)

    Poochai, Chatwarin [Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Veerasai, Waret, E-mail: waret.vee@mahidol.ac.th [Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Somsook, Ekasith [Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Dangtip, Somsak [Department of Physics, and NANOTEC COE at Mahidol University, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand)

    2015-08-01

    In this study, we prepared and characterized carbon paper-supported dealloyed binary Pt–Cu core–shell electrocatalysts (denoted as Pt{sub x}Cu{sub (100−x)/}CP) by cyclic co-electrodeposition and selective copper dealloying in an acidic medium, and we investigated the effect of the copper content in the samples on the catalytic activities toward methanol electroxidation reaction (MOR). X-ray photo-emission spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) indicated that the structure of dealloyed binary Pt–Cu catalysts possessed a Pt-rich shell and a Cu rich core. X-ray absorption near edge spectroscopy (XANES) displayed that the oxidation states of Pt and Cu were zero and one, respectively, implying the formation of metallic Pt and Cu{sub 2}O, respectively. X-ray diffraction spectroscopy (XRD) confirmed that Cu was inserted into a face-centered cubic Pt structure forming Pt–Cu alloys. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) displayed a cubic shape of Pt/CP and a spherical shape of Pt{sub x}Cu{sub (100−x)/}CP with several hundred nanometer sizes of agglomeration that depended on the Cu content. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were performed to confirm that the sample of Pt{sub 70}Cu{sub 30}/CP exhibited the best catalytic activities in terms of the specific current, current density, catalytic poisoning tolerance, and stability. - Graphical abstract: Display Omitted - Highlights: • Binary electrocatalysts of Pt{sub x}Cu{sub (100−x)}/CP were prepared by cyclic co-electrodeposition and selective copper dealloying. • The structures of Pt{sub x}Cu{sub (100−x)}/CP were a Pt rich shell and a Cu rich core. • The Pt{sub 70}Cu{sub 30}/CP was the excellent catalytic activity towards methanol electrooxidation and CO{sub ads} tolerance.

  13. Electrocatalysts for Nonaqueous Lithium–Air Batteries: Status, Challenges, and Perspective

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Yuyan; Park, Seh Kyu; Xiao, Jie; Zhang, Jiguang; Wang, Yong; Liu, Jun

    2012-05-04

    Li-air battery has recently emerged as a potentially transformational energy storage technology for both transportation and stationary energy storage applications due to its very high specific energy. However, its practical application is currently limited by the poor power capability, poor cyclability and low energy efficiency, all of which are largely determined by interfacial reactions on oxygen electrocatalysts in air electrode. In this article, we review the fundamental understanding of oxygen electrocatalysis in nonaqueous electrolytes, the status and challenges of oxygen electrocatalysts, and provide a perspective on new electrocatalysts design and development.

  14. Pomegranate-like N,P-Doped Mo2C@C Nanospheres as Highly Active Electrocatalysts for Alkaline Hydrogen Evolution.

    Science.gov (United States)

    Chen, Yu-Yun; Zhang, Yun; Jiang, Wen-Jie; Zhang, Xing; Dai, Zhihui; Wan, Li-Jun; Hu, Jin-Song

    2016-09-27

    Well-defined pomegranate-like N,P-doped Mo2C@C nanospheres were prepared by simply using phosphomolybdic acid (PMo12) to initiate the polymerization of polypyrrole (PPy) and as a single source for Mo and P to produce N,P-doped Mo2C nanocrystals. The existence of PMo12 at the molecular scale in the polymer network allows the formation of pomegranate-like Mo2C@C nanospheres with a porous carbon shell as peel and Mo2C nanocrystals well-dispersed in the N-doped carbon matrix as seeds. This nanostructure provides several favorable features for hydrogen evolution application: (1) the conductive carbon shell and matrix effectively prevent the aggregation of Mo2C nanocrystals and facilitate electron transportation; (2) the uniform N,P-doping in the carbon shell/matrix and plenty of Mo2C nanocrystals provide abundant catalytically highly active sites; and (3) nanoporous structure allows the effective exposure of active sites and mass transfer. Moreover, the uniform distribution of P and Mo from the single source of PMo12 and N from PPy in the polymeric PPy-PMo12 precursor guarantees the uniform N- and P-co-doping in both the graphitic carbon matrix and Mo2C nanocrystals, which contributes to the enhancement of electrocatalytic performance. As a result, the pomegranate-like Mo2C@C nanospheres exhibit extraordinary electrocatalytic activity for the hydrogen evolution reaction (HER) in terms of an extremely low overpotential of 47 mV at 10 mA cm(-2) in 1 M KOH, which is one of the best Mo-based HER catalysts. The strategy for preparing such nanostructures may open up opportunities for exploring low-cost high-performance electrocatalysts for various applications.

  15. Robotic, MEMS-based Multi Utility Sample Preparation Instrument for ISS Biological Workstation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This project will develop a multi-functional, automated sample preparation instrument for biological wet-lab workstations on the ISS. The instrument is based on a...

  16. Preparation of poly(epsilon-caprolactone)-based tissue engineering scaffolds by stereolithography

    NARCIS (Netherlands)

    Elomaa, Laura; Teixeira, Sandra; Hakala, Risto; Korhonen, Harri; Grijpma, Dirk W.; Seppala, Jukka V.

    2011-01-01

    A photocrosslinkable poly(epsilon-caprolactone) (PCL)-based resin was developed and applied using stereolithography. No additional solvents were required during the structure preparation process. Three-armed PCL oligomers of varying molecular weights were synthesized, functionalized with methacrylic

  17. Facile preparation of superhydrophobic surfaces based on metal oxide nanoparticles

    Science.gov (United States)

    Bao, Xue-Mei; Cui, Jin-Feng; Sun, Han-Xue; Liang, Wei-Dong; Zhu, Zhao-Qi; An, Jin; Yang, Bao-Ping; La, Pei-Qing; Li, An

    2014-06-01

    A novel method for fabrication of superhydrophobic surfaces was developed by facile coating various metal oxide nanoparticles, including ZnO, Al2O3 and Fe3O4, on various substrates followed by treatment with polydimethylsiloxane (PDMS) via chemical vapor deposition (CVD) method. Using ZnO nanoparticles as a model, the changes in the surface chemical composition and crystalline structures of the metal oxide nanoparticles by PDMS treatment were investigated by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The results show that the combination of the improved surface roughness generated from of the nanoparticles aggregation with the low surface-energy of silicon-coating originated from the thermal pyrolysis of PDMS would be responsible for the surface superhydrophobicity. By a simple dip-coating method, we show that the metal oxide nanoparticles can be easily coated onto the surfaces of various textural and dimensional substrates, including glass slide, paper, fabric or sponge, for preparation of superhydrophobic surfaces for different purpose. The present strategy may provide an inexpensive and new route to surperhydrophobic surfaces, which would be of technological significance for various practical applications especially for separation of oils or organic contaminates from water.

  18. A novel clay-based catalytic material: Preparation and properties

    Energy Technology Data Exchange (ETDEWEB)

    Lussier, R.J. (W.R. Grace Co.-Conn., Baltimore, Md. (USA))

    1991-05-01

    A novel acid-leached calcined laolin has been prepared by careful control of the calcination and acid leach conditions. A narrow calcination window gives an extremely acid-reactive calcined kaolin, which develops high surface areas at a rate much faster than that of samples calcined outside this range. This more acid active calcined kaolin also allows the use of extremely low levels of acid, which results in most of the alumina being in the solid phase during the entire leach step. Al{sup 27} NMR results indicate that most acid-reactive calcined clay has the lowest level of octahedral and the highest level of five-coordinate Al. Acids containing anions that do not complex with aluminum such as hydrochloric, nitric, or aluminum chloride work in this process, while acids containg anions that complex with aluminum such a sulfuric or phosphoric do not lead to the same high surface area, catalytically active products. Properly calcined and leached materials show a broad distribution of pores centered at about 40 (angstrom).

  19. Preparation of microporous activated carbons based on carbonized apricot shells

    OpenAIRE

    Vladimir Pavlenko; Sergey Anurov; Zulkhair Mansurov; Bijsenbaev Makhmut; Tatyana Konkova; Seithan Azat; Sandugash Tanirbergenova; Nurzhamal Zhylybaeva

    2014-01-01

    Results of applying the method of thermo-oxidative modification of fiber, based on the shell of apricot along with producing on its base microporous activated carbons that have high specific surface area and a significant amount of micropores were presented. The paper contains analysis and interpretation data of changes in the structure and composition of samples, which occurring as a result of thermal degradation of lignocellulosic materials. Morphological features of the surface of produced...

  20. Pyrolysis of Animal Bones with Vitamin B12: A Facile Route to Efficient Transition Metal-Nitrogen-Carbon (TM-N-C) Electrocatalysts for Oxygen Reduction.

    Science.gov (United States)

    Dou, Meiling; He, Duanpeng; Shao, Wenhao; Liu, Haijing; Wang, Feng; Dai, Liming

    2016-02-24

    By pyrolyzing cattle bones, hierarchical porous carbon (HPC) networks with a high surface area (2520 m(2)  g(-1) ) and connected pores were prepared at a low cost and large scale. Subsequent co-pyrolysis of HPC with vitamin B12 resulted in the formation of three-dimensional (3D) hierarchically structured porous cobalt-nitrogen-carbon (Co-N-HPC) electrocatalysts with a surface area as high as 859 m(2)  g(-1) as well as a higher oxygen reduction reaction (ORR) electrocatalytic activity, better operation stability, and higher tolerance to methanol than the commercial Pt/C catalyst in alkaline electrolyte.

  1. Engineering the Activity and Stability of Pt-Alloy Cathode Fuel-Cell Electrocatalysts by Tuning the Pt-Pt Distance

    DEFF Research Database (Denmark)

    Escribano, Maria Escudero; Malacrida, Paolo; Vej-Hansen, Ulrik Grønbjerg;

    2014-01-01

    One of the main obstacles to the commercialisation of low-temperature fuel cells is the slow kinetics of the oxygen reduction reaction (ORR). In order to decrease the ORR overpotential and reduce the Pt loading we need to develop more active and stable electrocatalysts. A fruitful strategy......-Escribano, et al., in preparation, 2014. [6] P. Strasser, et al. Nature Chem., 2010, 2, 454. Fig. (A) ORR kinetic current density at 0.9 V vs. RHE as a function of the lattice parameter and the Pt-Pt distance for Pt5Ln and Pt. (B) Kinetic current density of Pt5Ln and Pt before and after a stability test...

  2. Co3O4 NPs Embedded in N-doped Carbon Fibers as a Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions

    Science.gov (United States)

    Guo, Yao-Fang; Liu, Ting; Sun, Ke-Ning

    2016-05-01

    Oxygen reduction and evolution reactions are important and major challenges to Li-air batteries. In this report, a three-dimensional (3D) bifunctional electrocatalyst was prepared by embedding Co3O4 nanoparticles into nitrogen-doped carbon nanofibers (denoted as Co3O4-NCNF) by a facile method. The Co3O4-NCNF possesses a high specific surface area(403.5 m2/g) and porous structure. The Co3O4-NCNF exhibits an excellent catalytic activity and long-time durability for both oxygen reduction and evolution reactions in alkaline solutions.

  3. Evaluation of preparation methods for MS-based analysis of intestinal epithelial cell proteomes

    DEFF Research Database (Denmark)

    Hesselager, Marianne Overgaard; Codrea, Marius Cosmin; Bendixen, Emøke

    2015-01-01

    are low in abundance, and large amounts of sample is needed for their preparation and for undertaking MS-based analysis. The aim of this study was to evaluate three different methods for isolation and preparation of pig intestinal epithelial cells for MS-based analysis of the proteome. Samples were...... analyzed by LC and electrospray QTOF-MS. The methods were evaluated according to efficiency, purity, transmembrane protein recovery, as well as for suitability to large-scale preparations. Our data clearly demonstrate that mucosal shaving is by far the best-suited method for in-depth MS analysis in terms...

  4. Methods for preparing colloidal nanocrystal-based thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kagan, Cherie R.; Fafarman, Aaron T.; Choi, Ji-Hyuk; Koh, Weon-kyu; Kim, David K.; Oh, Soong Ju; Lai, Yuming; Hong, Sung-Hoon; Saudari, Sangameshwar Rao; Murray, Christopher B.

    2016-05-10

    Methods of exchanging ligands to form colloidal nanocrystals (NCs) with chalcogenocyanate (xCN)-based ligands and apparatuses using the same are disclosed. The ligands may be exchanged by assembling NCs into a thin film and immersing the thin film in a solution containing xCN-based ligands. The ligands may also be exchanged by mixing a xCN-based solution with a dispersion of NCs, flocculating the mixture, centrifuging the mixture, discarding the supernatant, adding a solvent to the pellet, and dispersing the solvent and pellet to form dispersed NCs with exchanged xCN-ligands. The NCs with xCN-based ligands may be used to form thin film devices and/or other electronic, optoelectronic, and photonic devices. Devices comprising nanocrystal-based thin films and methods for forming such devices are also disclosed. These devices may be constructed by depositing NCs on to a substrate to form an NC thin film and then doping the thin film by evaporation and thermal diffusion.

  5. ABSORBENT MATERIALS BASED ON KRAFT PULP: PREPARATION AND MATERIAL CHARACTERIZATION

    Directory of Open Access Journals (Sweden)

    Fredrik Wernersson Brodin,

    2012-02-01

    Full Text Available Today, petroleum-based superabsorbents are widely used, but interest in renewable alternatives is on the rise. This study presents two wood-based absorbent materials suitable for various absorption applications as an alternative to petroleum-based products. Never-dried bleached kraft pulp was treated with TEMPO-oxidation, and new carboxylate and aldehyde groups were introduced. It was found that the aldehyde groups contributed to the wet integrity of the absorbent materials, possibly by the formation of hemiacetal bonds. After oxidation, the pulp fibers were gradually disintegrated, and size analysis showed that the disintegration rate was enhanced by an increase in the charge of the oxidant. Freeze drying produced a porous foam with a large surface area that enabled a rapid absorption rate as well as a reasonably high absorption capacity even for absorption under load. Air drying formed a compact film with a slow absorption rate but with a high final capacity for absorption.

  6. Preparation of stable ultrahydrophobic and superoleophobic silica-based coating.

    Science.gov (United States)

    Nimittrakoolchai, On-Uma; Supothina, Sitthisuntorn

    2012-06-01

    Silica-Based coatings having excellent water- and oil-repellent properties and good weathering stability have been deposited onto glass surface by a simple one-step dip coating technique. To achieve ultra water repellency and super oil repellency, the chemical composition of SiO2 nanoparticle employed as surface roughness enhancer and trichloro(1H,1H,2H,2H-perfluorooctyl)silane employed as surface-energy reducing substance was varied. At the optimum synthesis condition, the coating exhibited very high contact angles of 173.2, 146.7 and 147.6 degrees for water, ethylene glycol and seed oil, respectively. The achievement of excellent water- and oil-repellency is also described based on the presence of air trapped in micropore of the coating in addition to its high surface roughness and low surface free energy. The coatings have good weathering stability based on natural and accelerated weathering tests indicating feasibility for practical use.

  7. PREPARATION AND CHARACTERISTICS OF A PAPER-BASED ULTRAFILTRATION MEMBRANE

    Directory of Open Access Journals (Sweden)

    Jian Wang,

    2011-11-01

    Full Text Available A novel process involving a paper-based ultrafiltration (UF membrane was developed via paper coating technology. The membrane employed a paper sheet as support layer and a coated thin film layer of adhesive. The proper selection of paper sheet support layer was crucial to the performance of the ultrafiltration membrane. A paper sheet with beating degree of 85oSR and basis weight of 50g/m2 was chosen as the support. PVA was chosen as the adhesive. The paper-based ultrafiltration membrane achieved high retention performance while using a simple production process and keeping the production cost low. Disadvantages of the membrane included low porosity and low pure water flux. So further investigation is still needed to produce a fully satisfactory paper-based ultrafiltration membrane.

  8. Preparation of microporous activated carbons based on carbonized apricot shells

    Directory of Open Access Journals (Sweden)

    Vladimir Pavlenko

    2014-10-01

    Full Text Available Results of applying the method of thermo-oxidative modification of fiber, based on the shell of apricot along with producing on its base microporous activated carbons that have high specific surface area and a significant amount of micropores were presented. The paper contains analysis and interpretation data of changes in the structure and composition of samples, which occurring as a result of thermal degradation of lignocellulosic materials. Morphological features of the surface of produced activated carbons were studied by using SEM microscopy; the pore structure and specific surface area were investigated using the method of low-temperature nitrogen adsorption.

  9. Preparation of microemulsions with soybean oil-based surfactants

    Science.gov (United States)

    Emulsions are widely applied in food, cosmeceutical and medicinal formulations. Smaller and highly stable droplets of emulsions are important for their application. This research reports that by using soybean oil-based surfactants, the higher stabilized oil-in-water emulsions were obtained via an ul...

  10. Competency-Based Behavioral Interviewing: How To Prepare and Win!

    Science.gov (United States)

    Beasley, Steven E.; Washington, Tom

    Competencies derived from experience; skills; knowledge; values; or other distinguishing qualities and motivations can contribute to a person's job performance. Counselors can use competency-based behavioral interviewing to allow a candidate to demonstrate certain skills they have used in the workplace. By using such past experiences, an employer…

  11. Preparing Instructional Designers for Game-Based Learning: Part 1

    Science.gov (United States)

    Hirumi, Atsusi; Appelman, Bob; Rieber, Lloyd; Van Eck, Richard

    2010-01-01

    Like many rapidly growing industries, advances in video game technology are far outpacing research on its design and effectiveness. Relatively little is understood about how to apply what we know about teaching and learning to optimize game-based learning. For the most part, instructional designers know little about game development and video game…

  12. Facile Synthesis of Nitrogen and Sulfur Dual-doped Hierarchical Micro/mesoporous Carbon Foams as Efficient Metal-free Electrocatalysts for Oxygen Reduction Reaction

    International Nuclear Information System (INIS)

    It’s almost hardly to realize the large-scale practical application of fuel cells if the costly noble metal-based electrocatalysts for oxygen reduction reaction (ORR) cannot be replaced by other efficient, stable, and low-cost non-precious metal or even metal-free ORR electrocatalysts. Herein, we report the novel design and synthesis of N and S dual-doped hierarchical micro/mesoporous carbon (NS-MC) foams via high temperature treatment of polyaniline coated sulfur sphere composite without any side products. The highlight of our method lies in its environmental concept of green synthesis and simplicity for no use of toxic gas (NH3 or H2S) or templates (SiO2 or MgO). The main focus of this research is to develop a high-performance metal-free ORR electrocatalyst as well as to gain insight into the synergistic effects originating from multiple-element doping on ORR performance. It is found that much graphitic-N and thiophene-S binding configurations formed for NS-MC foams at 1000 °C, which shows excellent electrocatalytic activity (high onset potential (0.051 V vs. Ag/AgCl (sat.KCl)), large diffusion-limiting current density (5.61 mA cm−2 at 1600 rpm) and kinetic current density (22.22 mA cm−2 at −0.25 V)), high selectivity towards methanol and long durability compared to commercial Pt/C with a nearly four-electron transfer passway when they are employed as metal-free catalyst for ORR. Besides, the desired NS-MC1000 shows a strong amperometric response towards ethanol indicating its potential application as an anode metal-free electrocatalyst in the alkaline direct ethanol fuel cell

  13. Synthesis of Hollow Platinum-Palladium Nanospheres with a Dendritic Shell as Efficient Electrocatalysts for Methanol Oxidation.

    Science.gov (United States)

    Lu, Qingqing; Wang, Hongjing; Eid, Kamel; Alothman, Zeid Abdullah; Malgras, Victor; Yamauchi, Yusuke; Wang, Liang

    2016-07-01

    Engineering the size, composition, and morphology of platinum-based nanomaterials can provide a great opportunity to improve the utilization efficiency of electrocatalysts and reinforce their electrochemical performances. Herein, three-dimensional platinum-palladium hollow nanospheres with a dendritic shell (PtPd-HNSs) are successfully fabricated through a facile and economic route, during which SiO2 microspheres act as the hard template for the globular cavity, whereas the triblock copolymer F127 contributes to the formation of the dendritic shell. In contrast with platinum hollow nanospheres (Pt-HNSs) and commercial platinum on carbon (Pt/C) catalyst, the novel architecture shows a remarkable activity and durability toward the methanol oxidation reaction (MOR) owing to the coupled merits of bimetallic nanodendrites and a hollow interior. As a proof of concept, this strategy is also extended to trimetallic gold-palladium-platinum hollow nanospheres (AuPdPt-HNSs), which paves the way towards the controlled synthesis of other bi- or multimetallic platinum-based hollow electrocatalysts. PMID:27283867

  14. 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.

  15. Pulse electrodeposited nickel-indium tin oxide nanocomposite as an electrocatalyst for non-enzymatic glucose sensing.

    Science.gov (United States)

    Sivasakthi, P; Ramesh Bapu, G N K; Chandrasekaran, Maruthai

    2016-01-01

    Nickel and nickel-ITO nanocomposite on mild steel substrate were prepared by pulse electrodeposition method from nickel sulphamate electrolyte and were examined as electrocatalysts for non-enzymatic glucose sensing. The surface morphology, chemical composition, preferred orientation and oxidation states of the nickel metal ion in the deposits were characterized by SEM, EDAX, XRD and XPS. Electrochemical sensing of glucose was studied by cyclic voltammetry and amperometry. The modified Ni-ITO nanocomposite electrode showed higher electrocatalytic activity for the oxidation of glucose in alkaline medium and exhibited a linear range from 0.02 to 3.00 mM with a limit of detection 3.74 μM at a signal-to-noise ratio of 3. The higher selectivity, longer stability and better reproducibility of this electrode compared to nickel in the sensing of glucose are pointers for exploitation in practical clinical applications.

  16. Stability and spinodal decomposition of the solid-solution phase in the ruthenium-cerium-oxide electro-catalyst.

    Science.gov (United States)

    Li, Yanmei; Wang, Xin; Shao, Yanqun; Tang, Dian; Wu, Bo; Tang, Zhongzhi; Lin, Wei

    2015-01-14

    The phase diagram of Ru-Ce-O was calculated by a combination of ab initio density functional theory and thermodynamic calculations. The phase diagram indicates that the solubility between ruthenium oxide and cerium oxide is very low at temperatures below 1100 K. Solid solution phases, if existing under normal experimental conditions, are metastable and subject to a quasi-spinodal decomposition to form a mixture of a Ru-rich rutile oxide phase and a Ce-rich fluorite oxide phase. To study the spinodal decomposition of Ru-Ce-O, Ru0.6Ce0.4O2 samples were prepared at 280 °C and 450 °C. XRD and in situ TEM characterization provide proof of the quasi-spinodal decomposition of Ru0.6Ce0.4O2. The present study provides a fundamental reference for the phase design of the Ru-Ce-O electro-catalyst. PMID:25418197

  17. Mask process matching using a model based data preparation solution

    Science.gov (United States)

    Dillon, Brian; Saib, Mohamed; Figueiro, Thiago; Petroni, Paolo; Progler, Chris; Schiavone, Patrick

    2015-10-01

    Process matching is the ability to precisely reproduce the signature of a given fabrication process while using a different one. A process signature is typically described as systematic CD variation driven by feature geometry as a function of feature size, local density or distance to neighboring structures. The interest of performing process matching is usually to address differences in the mask fabrication process without altering the signature of the mask, which is already validated by OPC models and already used in production. The need for such process matching typically arises from the expansion of the production capacity within the same or different mask fabrication facilities, from the introduction of new, perhaps more advanced, equipment to deliver same process of record masks and/or from the re-alignment of processes which have altered over time. For state-of-the-art logic and memory mask processes, such matching requirements can be well below 2nm and are expected to reduce below 1nm in near future. In this paper, a data preparation solution for process matching is presented and discussed. Instead of adapting the physical process itself, a calibrated model is used to modify the data to be exposed by the source process in order to induce the results to match the one obtained while running the target process. This strategy consists in using the differences among measurements from the source and target processes, in the calibration of a single differential model. In this approach, no information other than the metrology results is required from either process. Experimental results were obtained by matching two different processes at Photronics. The standard deviation between both processes was of 2.4nm. After applying the process matching technique, the average absolute difference between the processes was reduced to 1.0nm with a standard deviation of 1.3nm. The methods used to achieve the result will be described along with implementation considerations, to

  18. Cu-doped carbon nitride: Bio-inspired synthesis of H2-evolving electrocatalysts using graphitic carbon nitride (g-C3N4) as a host material

    Science.gov (United States)

    Zou, Xiaoxin; Silva, Rafael; Goswami, Anandarup; Asefa, Tewodros

    2015-12-01

    Splitting water effectively to produce hydrogen (H2) requires the development of non-noble-metal electrocatalysts that are able to make this reaction feasible and energy efficient. Herein, we present a novel "structure upgrading" synthetic approach for the design and synthesis of bio-inspired hydrogen-evolving electrocatalysts based on earth-abundant elements. Using g-C3N4 - an inexpensive inorganic polymer material - as a host material for copper ions, novel Cu-doped g-C3N4 materials with supramolecular structure, efficient electrocatalytic activity and modest overpotentials for hydrogen evolution reaction (HER) are synthesized. Compared with most single-molecule analogs of hydrogenases that work only in organic media, the supramolecular Cu-doped g-C3N4 materials can serve as heterogeneous electrocatalysts with greater stability and good catalytic activity for HER in aqueous media. The materials afford a current density as high as 10 mA cm-2 at an overpotential as low as 390 mV, and work well in acidic media for, at least, 43 h.

  19. The preparation of aramid fibres in silicone based composite materials

    OpenAIRE

    L.A. Dobrzański; A. J. Nowak; A. Pusz; M. Górniak

    2011-01-01

    Purpose: The evaluation of modified aramid fibres – Kevlar – as reinforcement in silicon materials used in medicine.Design/methodology/approach: Samples of laminated material based on modified aramid fibres and medical silicone were made by a method of manual formation of laminates that is impregnation of reinforcement with matrix to hardening silicone process using hardening methods connected with heat. Created material was observed on Scanning Electron Microscopy manufactured by Zeiss.Findi...

  20. Preparation of stable ultrahydrophobic and superoleophobic silica-based coating.

    Science.gov (United States)

    Nimittrakoolchai, On-Uma; Supothina, Sitthisuntorn

    2012-06-01

    Silica-Based coatings having excellent water- and oil-repellent properties and good weathering stability have been deposited onto glass surface by a simple one-step dip coating technique. To achieve ultra water repellency and super oil repellency, the chemical composition of SiO2 nanoparticle employed as surface roughness enhancer and trichloro(1H,1H,2H,2H-perfluorooctyl)silane employed as surface-energy reducing substance was varied. At the optimum synthesis condition, the coating exhibited very high contact angles of 173.2, 146.7 and 147.6 degrees for water, ethylene glycol and seed oil, respectively. The achievement of excellent water- and oil-repellency is also described based on the presence of air trapped in micropore of the coating in addition to its high surface roughness and low surface free energy. The coatings have good weathering stability based on natural and accelerated weathering tests indicating feasibility for practical use. PMID:22905559

  1. Novel Epoxy Resin/SiO2 Nanocomposites Preparation Method Based on Diminutive Bubbles Explosion

    Institute of Scientific and Technical Information of China (English)

    NIE Peng; ZHAO Xue-zeng; CHEN Fang; WANG Wei-jie; BAI Yong-ping

    2006-01-01

    To obtain suspended dispersion of nano-particles in liquid without any dispersant, a novel epoxy resin/SiO2 nanocomposites preparation method based on diminutive bubbles explosion is presented. And, corresponding nanocomposites preparation system was designed. The preparation system applies compressed gas as transmission medium to carry nanomaterials into epoxy resin solution. The compressed gas with nanomaterials turns into diminutive bubbles distributing in epoxy resin/SiO2. The great pressure difference between inner and outer-bubbles led to bubbles inflation and explosion. During the bubble inflation, bubble oscillation may generate. The stretching rate may reach 106 s-1, which favors more homogeneous dispersion of nanoparticles. During the bubbles explosion the released energy and the explosion shock waves disperse the nanoparticles into epoxy resin solution. By using the preparation system, epoxy resin/SiO2 nanocomposites were prepared. The SiO2 dispersed into epoxy as the configuration of 15 nm - 30 nm particles.

  2. Electrocatalyst for oxygen reduction with reduced platinum oxidation and dissolution rates

    Science.gov (United States)

    Adzic, Radoslav; Zhang, Junliang; Vukmirovic, Miomir

    2012-11-13

    The invention relates to platinum-metal oxide composite particles and their use as electrocatalysts in oxygen-reducing cathodes and fuel cells. The invention particularly relates to methods for preventing the oxidation of the platinum electrocatalyst in the cathodes of fuel cells by use of these platinum-metal oxide composite particles. The invention additionally relates to methods for producing electrical energy by supplying such a fuel cell with an oxidant, such as oxygen, and a fuel source, such as hydrogen.

  3. Highly acid-durable carbon coated Co3O4 nanoarrays as efficient oxygen evolution electrocatalysts

    KAUST Repository

    Yang, Xiulin

    2016-04-21

    Most oxygen evolution reaction (OER) electrocatalysts are not stable in corrosive acids. Even the expensive RuO2 or IrO2, the most acid-resistant oxides, can be dissolved at an oxidative potential. Herein, we realize that the failures of OER catalysts are mostly caused by the weak interface between catalysts and the substrates. Hence, the study of the interface structure between catalysts and substrates is critical. In this work, we observe that the cheap OER catalysts Co3O4 can be more durable than the state-of-the-art RuO2 if the interface quality is good enough. The Co3O4 nanosheets deposited on carbon paper (Co3O4/CP) is prepared by electroplating of Co-species and followed by a two-step calcination process. The 1st step occurs in vacuum in order to maintain the surface integrity of the carbon paper and converts Co-species to Co(II)O. The 2nd step is a calcination in ambient conditions which enables the complete transformation of Co(II)O to Co3O4 without degrading the mechanical strength of the Co3O4-CP interface. Equally important, an in situ formation of a layer of amorphous carbon on top of Co3O4 further enhances the OER catalyst stability. Therefore, these key advances make the Co3O4 catalyst highly active toward the OER in 0.5 M H2SO4 with a small overpotential (370 mV), to reach 10 mA/cm2. The observed long lifetime for 86.8 h at a constant current density of 100 mA/cm2, is among the best of the reported in literature so far, even longer than the state-of-art RuO2 on CP. Overall, our study provides a new insight and methodology for the construction of a high-performance and high stability OER electrocatalysts in corrosive acidic environments.

  4. Ethanol Oxidation Reaction Using PtSn/C+Ce/C Electrocatalysts: Aspects of Ceria Contribution

    International Nuclear Information System (INIS)

    The ethanol oxidation reaction (EOR) was investigated using PtSn/C + Ce/C electrocatalysts in different mass ratios (58:42, 53:47, and 42:58) prepared using the polymeric precursor method. Transmission electron microscopy (TEM) experiments showed particles sizes in the range of 3 to 7 nm. Changes in the net parameters observed for Pt suggest the incorporation of Sn into the Pt crystalline network with the formation of an alloy mixture with the SnO2 phase. Among the PtSn/C + Ce/C catalysts investigated, the 53:47 composition showed the highest activity towards the EOR. In this case, the j versus t curves obtained in the presence of ethanol in acidic media exhibited a current density 90% higher than that observed with the commercial PtSn/C (ETEK). Correspondingly, during the experiments performed on single direct ethanol fuel cells, the maximum power density obtained using PtSn/C + Ce/C (53:47) as the anode was approximately 60% higher than that obtained using the commercial catalyst. FTIR data showed that the observed behavior for ethanol oxidation may be explained in terms of a synergic effect of bifunctional mechanism with electronic effects, in addition to a chemical effect of ceria that provides oxygen-containing species to oxidize acetaldehyde to acetic acid

  5. Amorphous nickel/cobalt tungsten sulfide electrocatalysts for high-efficiency hydrogen evolution reaction

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Amorphous nickel/cobalt tungsten sulfides were synthesized by a thermolytic process. • Amorphous NiWS and CoWS could realize hydrogen evolution efficiently. • Ni/Co promotion and annealing alter the porous structure and chemical bonding states. • Active sites on the surface of amorphous WSx are increased with Ni or Co doping. • Amorphous NiWS and CoWS have immense potentials in water splitting devices. - Abstract: The hydrogen evolution reaction (HER), an appealing solution for future energy supply, requires efficient and inexpensive electrocatalysts with abundant active surface sites. Although crystalline MoS2 and WS2 are promising candidates, their activity is dominated by edge sites. Amorphous tungsten sulfide prepared so far lacks the required active sites and its application has thus been hampered. In this work, nickel and cobalt incorporated amorphous tungsten sulfide synthesized by a thermolytic process is demonstrated to enhance the HER efficiency dramatically. The amorphous nickel tungsten sulfide (amorphous NiWS) annealed at 210 °C delivers the best HER performance in this system boasting a Tafel slope of 55 mV per decade and current density of 8.6 mA cm−2 at 250 mV overpotential in a sustained test for 24 h. The introduction of Ni or Co into the catalyst and subsequent thermal treatment alters the porous structure and chemical bonding states thereby increasing the density of active sites on the surface

  6. PREPARATION OF A LIGNIN-BASED COMPOSITE AND ITS PROPERTIES

    OpenAIRE

    Jian Li; Shujun Li; Haigang Wang; Yang Yang; Guowan Guo

    2011-01-01

    Enzymatic hydrolysis (EH) lignin was modified with formaldehyde. TG-DSC and PY-GC-MS analysis methods were adopted to characterize the differences between EH lignin and the modified lignin. The modified lignin was then mixed with wood sawdust and made into a lignin-based composite under the following conditions: pressure of 2 to 5 MPa, temperature of 175 to 190 oC, and the modified lignin dosage of 20% to 70%. The effects of pressure, temperature, and the modified lignin dosage on the propert...

  7. One-pot synthesis of hierarchical Ni2P/MoS2 hybrid electrocatalysts with enhanced activity for hydrogen evolution reaction

    Science.gov (United States)

    Liu, Yan-Ru; Hu, Wen-Hui; Li, Xiao; Dong, Bin; Shang, Xiao; Han, Guan-Qun; Chai, Yong-Ming; Liu, Yun-Qi; Liu, Chen-Guang

    2016-10-01

    A simple one-pot synthesis method has been used to fabricate novel Ni2P/MoS2 hybrid electrocatalysts for hydrogen evolution reaction (HER). Owing to the weak conductivity and layered structure of MoS2, Ni2P nanoparticles with excellent conductivity and activity have been doped into MoS2 for improving the electrocatalytic performances for HER. The structure and morphology of the as-prepared Ni2P/MoS2 hybrid nanostructures are characterized. XRD and XPS show the elemental composition and valence of Ni2P/MoS2. SEM and TEM confirm that the close interaction of the hybrid materials and good dispersion of Ni2P nanoparticles. The as-synthesized Ni2P/MoS2 hybrid electrocatalysts exhibit excellent activity with onset overpotential of 75 mV and Tafle slope of 76 mV dec-1, which are much better than that of pure MoS2. The enhanced stability of the as-prepared Ni2P/MoS2 for HER has also been observed. The improved performances for HER may be ascribed to the better conductivity and dispersion of MoS2 nanosheets in Ni2P/MoS2 hybrid electrocatalysts. The small size and good dispersion of Ni2P nanoparticles also contributed to the enhancement of HER activity. Compared with mechanically mixed MoS2 and Ni2P (Ni2P-MoS2), Ni2P/MoS2 hybrid materials demonstrate better electrochemical performances for HER, implying the existence of synergistic effect between Ni2P and MoS2 on HER activity.

  8. A facile route to prepare cellulose-based films.

    Science.gov (United States)

    Xu, Qin; Chen, Chen; Rosswurm, Katelyn; Yao, Tianming; Janaswamy, Srinivas

    2016-09-20

    Cellulose is the most abundant renewable and biodegradable material available in nature. Its insoluble character in water as well as common organic and inorganic liquids, however, curtails the wholesome utility. The continuous rise for biodegradable products based on cellulose coupled with its intrinsic ability to form a viable substitute for the petroleum-based materials necessitates the critical need for solubilizing the cellulose. Herein, we demonstrate the feasibility of ZnCl2 solutions, especially the 64-72% concentrations, to dissolve cellulose. FTIR results suggest that Zn(2+) ions promote Zn⋯O3H interactions, which in-turn weaken the intrinsic O3H⋯O5 hydrogen bonds that are responsible for strengthening the cellulose chains. Interestingly, Ca(2+) ions promote interactions among the Zn-cellulose chains leading to the formation of nano fibrils and yield gelling solutions. The tensile strength of the Ca(2+) added Zn-cellulose films increases by around 250% compared to the Zn-cellulose films. Overall, utilization of inorganic salt solutions to solubilize and crosslink cellulose is cost-effective, recyclable and certainly stands out tall among the other available systems. More importantly, the proposed protocol is simple and is a "green" process, and thus its large-scale adaptability is quite feasible. We strongly believe that the outcome opens up a new window of opportunities for cellulose in the biomedical, pharmaceutical, food and non-food applications. PMID:27261751

  9. Electrocatalysts for direct alcohol fuel cells

    OpenAIRE

    Celorrio, V.

    2013-01-01

    The properties of CNC as well as their surface chemistry can be tuned by an adequate choice of synthesis conditions, favouring the formation of surface oxygen groups. Platinum-based catalysts have been supported on CNCs through different synthesis methods and their catalytic activity has been proven. These results prove that CNCs are promising candidates as alternative to replace Vulcan in order to improve the performance of the direct alcohol fuel cells. In addition, it can be affirmed that ...

  10. Bio-inspired routes for synthesizing efficient nanoscale platinum electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Jennifer N. [Univ. of California, San Diego, CA (United States); Wang, Joseph [Univ. of California, San Diego, CA (United States)

    2014-08-31

    The overall objective of the proposed research is to use fundamental advances in bionanotechnology to design powerful platinum nanocrystal electrocatalysts for fuel cell applications. The new economically-viable, environmentally-friendly, bottom-up biochemical synthetic strategy will produce platinum nanocrystals with tailored size, shape and crystal orientation, hence leading to a maximum electrochemical reactivity. There are five specific aims to the proposed bio-inspired strategy for synthesizing efficient electrocatalytic platinum nanocrystals: (1) isolate peptides that both selectively bind particular crystal faces of platinum and promote the nucleation and growth of particular nanocrystal morphologies, (2) pattern nanoscale 2-dimensional arrays of platinum nucleating peptides from DNA scaffolds, (3) investigate the combined use of substrate patterned peptides and soluble peptides on nanocrystal morphology and growth (4) synthesize platinum crystals on planar and large-area carbon electrode supports, and (5) perform detailed characterization of the electrocatalytic behavior as a function of catalyst size, shape and morphology. Project Description and Impact: This bio-inspired collaborative research effort will address key challenges in designing powerful electrocatalysts for fuel cell applications by employing nucleic acid scaffolds in combination with peptides to perform specific, environmentally-friendly, simultaneous bottom-up biochemical synthesis and patterned assembly of highly uniform and efficient platinum nanocrystal catalysts. Bulk synthesis of nanoparticles usually produces a range of sizes, accessible catalytic sites, crystal morphologies, and orientations, all of which lead to inconsistent catalytic activities. In contrast, biological systems routinely demonstrate exquisite control over inorganic syntheses at neutral pH and ambient temperature and pressures. Because the orientation and arrangement of the templating biomolecules can be precisely

  11. Copper base materials prepared by gel-casting process

    Institute of Scientific and Technical Information of China (English)

    LIU Weihua; JIA Chengchang; SHI Yantao; HAN Yuepeng

    2008-01-01

    Gel-casting process was developed as a new molding process in the field of copper base powder metallurgy to manufacture metal parts with excellent performance and complex shapes.Through changing the parameters of gel-casting process,such as dispersant and solid loading,the corresponding effects on the rheology of Cu slurries,molding and sintering behaviors were studied.The results show that the viscosity of Cu slurries was significantly reduced with an increase in dispersant.The most appropriate solid loading was found to be 61% and the sintering temperature was 910℃ in these experiments.After the optimization of parameters of gel-casting process,copper composite parts with relatively high density and better properties were obtained.

  12. Facilities for preparing actinide or fission product-based targets

    CERN Document Server

    Sors, M

    1999-01-01

    Research and development work is currently in progress in France on the feasibility of transmutation of very long-lived radionuclides such as americium, blended with an inert medium such as magnesium oxide and pelletized for irradiation in a fast neutron reactor. The process is primarily designed to produce ceramics for nuclear reactors, but could also be used to produce targets for accelerators. The Actinide Development Laboratory is part of the ATALANTE complex at Marcoule, where the CEA investigates reprocessing, liquid and solid waste treatment and vitrification processes. The laboratory produces radioactive sources; after use, their constituents are recycled, notably through R and D programs requiring such materials. Recovered americium is purified, characterized and transformed for an experiment known as ECRIX, designed to demonstrate the feasibility of fabricating americium-based ceramics and to determine the reactor transmutation coefficients.

  13. CO responses of sensors based on cerium oxide thick films prepared from clustered spherical nanoparticles.

    Science.gov (United States)

    Izu, Noriya; Matsubara, Ichiro; Itoh, Toshio; Akamatsu, Takafumi; Shin, Woosuck

    2013-03-08

    Various types of CO sensors based on cerium oxide (ceria) have been reported recently. It has also been reported that the response speed of CO sensors fabricated from porous ceria thick films comprising nanoparticles is extremely high. However, the response value of such sensors is not suitably high. In this study, we investigated methods of improving the response values of CO sensors based on ceria and prepared gas sensors from core-shell ceria polymer hybrid nanoparticles. These hybrid nanoparticles have been reported to have a unique structure: The core consists of a cluster of ceria crystallites several nanometers in size. We compared the characteristics of the sensors based on thick films prepared from core-shell nanoparticles with those of sensors based on thick films prepared from conventionally used precipitated nanoparticles. The sensors prepared from the core-shell nanoparticles exhibited a resistance that was ten times greater than that of the sensors prepared from the precipitated nanoparticles. The response values of the gas sensors based on the core-shell nanoparticles also was higher than that of the sensors based on the precipitated nanoparticles. Finally, improvements in sensor response were also noticed after the addition of Au nanoparticles to the thick films used to fabricate the two types of sensors.

  14. Preparation and Characterization of a Polymer-Based "Molecular Accordion".

    Science.gov (United States)

    Karoyo, Abdalla H; Wilson, Lee D

    2016-03-29

    A urethane-based polymer material, denoted HDI-1, was obtained from the addition reaction of β-cyclodextrin (β-CD) with 1,6-hexamethylene diisocyanate (HDI) at the 1:1 mole ratio. In aqueous solution and ambient temperature conditions, HDI-1 adopts a compact (coiled) morphology where the cross-linker units become coiled and are partially self-included in the annular hydroxyl (interstitial) region of β-CD. As the temperature is raised or as p-nitrophenol (PNP) was included within the β-CD cavity and the noninclusion sites of the polymer, an extended (uncoiled) morphology was adopted. The equilibrium distribution between the extended and the compact forms of HDI-1 is thermally and chemically switchable, in accordance with the hydration properties and host-guest chemistry of this responsive polymer system. The molecular structure of this water-soluble urethane polymer and its host-guest complexes with PNP were investigated using spectroscopic (Raman, (1)H NMR, induced circular dichroism), dynamic light scattering (DLS), and calorimetric (DSC) methods in aqueous solution at ambient pH, and compared with native β-CD. This study reports on the unique supramolecular properties of a polymer that resembles a thermally and chemically responsive "molecular accordion". PMID:26931298

  15. Preparation and characterization of a novel ionizing electromagnetic radiation shielding material: Hematite filled polyester based composites

    Science.gov (United States)

    Eren Belgin, E.; Aycik, G. A.; Kalemtas, A.; Pelit, A.; Dilek, D. A.; Kavak, M. T.

    2015-10-01

    Isophthalic polyester (PES) based and natural mineral (hematite) filled composites were prepared and characterized for ionizing electromagnetic radiation shielding applications. Density evaluation and microscopic studies of the composites were carried out. Shielding performances of the composites were investigated for three different IEMR energy regions as low, intermediate and high. The mass attenuation coefficient of the prepared composites reached 98% of the elemental lead. In addition, the studied composites were superior to lead by virtue of their non-toxic nature.

  16. Electrocatalysts for direct alcohol fuel cells

    Directory of Open Access Journals (Sweden)

    V. Celorrio

    2013-01-01

    Full Text Available The properties of CNC as well as their surface chemistry can be tuned by an adequate choice of synthesis conditions, favouring the formation of surface oxygen groups. Platinum-based catalysts have been supported on CNCs through different synthesis methods and their catalytic activity has been proven. These results prove that CNCs are promising candidates as alternative to replace Vulcan in order to improve the performance of the direct alcohol fuel cells. In addition, it can be affirmed that the reactivity of Au-Pd core-shell nanostructures toward CO and HCOOH electro-oxidation is not only determined by the composition and structure of Pd overlayer but also by interaction with the support.

  17. Atomic-level Electron Microscopy of Metal and Alloy Electrocatalysts

    DEFF Research Database (Denmark)

    Deiana, Davide

    This thesis presents the application of transmission electron microscopy techniques towards the characterisation of novel metal nanoparticle catalysts. Two main subjects have been covered: first, the sintering-resistance behaviour of monomodal mass-selected Pt cluster catalysts have been studied...... by means of ex situ Scanning Transmission Electron Microscopy (STEM) in combination with in situ indirect nanoplasmonic sensing. Secondly, electron microscopy imaging and spectroscopy have been used for the characterisation of novel metal alloy nanoparticle electrocatalysts for the Oxygen Reduction...... and its dissolution into the electrolyte. The formed Pt-rich shell prevents further dissolution of the rare earth metal protecting the alloyed core. Pt−Hg and Pd−Hg have been identified by Density Functional Theory (DFT) calculations as promising candidates for the electrochemical production of hydrogen...

  18. PREPARATION AND THE CULTURE OF LO2 CELLS ON PVA-BASED MICROCARRIERS

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong; YU Yaoting; PAN Jilun; WANG lianyong

    2001-01-01

    Using polyvinyl alcohol (PVA) as raw material and vacuum pump oil as oil phase medium,PVA-based microcarriers were prepared by suspension method The diameters of the beads were 100-180 μ m. LO2 cells were cultured on PVA-based microcarriers and cytodexⅢ microcarriers.Morphology, attachment and growth rate of LO2 cells were studied.

  19. PREPARATION AND THE CULTURE OF LO2 CELLS ON PVA—BASED MICROCARRIERS

    Institute of Scientific and Technical Information of China (English)

    ZHANGHong; YUYaoting; 等

    2001-01-01

    Using polyvinyl alcohol(PVA) as raw material and vacuum pump oil as oil phase medium,PVA-based microcarriers were prepared by suspension method,The diameters of the beads were 100-180um,LO2 cells were cultured on PVA-based microcarriers and cytodexⅢ microcarriers.Morphology,attachment and growth rate of LO2 cells were studied.

  20. Structural Characterization of Bimetallic Nanocrystal Electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Cullen, David A [ORNL

    2016-01-01

    catalytic activity. A volcano relationship was observed for the core-shell nanoicosahedra having different Pd-shell thicknesses as Pd content is increased (Figure 2g). Durability tests are ongoing for the AuPd system; however, promising ORR materials and morphologies have also been synthesized for a more cost-effective Cu-based system of Cu-CuM (M = Pd, Rh, Pt) core-alloy-shell nanocrystals. The synthesis, characterization, and catalytic behavior of different high-index faceted morphologies of Cu-based materials towards ORR and methanol oxidation catalysis will be discussed, where we show how they exceed the performance of commercial Pd- and Pt- based catalysts. The development of new materials and their characterization is critical to understanding the effects of structure and composition on catalysis. Future efforts are directed at resolving these structures and more industrially relevant fuel cell catalysts in 3D through electron tomography.[4] References: [1] X. Huang, et al., Science 348 (2015) p. 1230. [2] P. Strasser, et al., Nat. Chem. 2 (2010) p. 454. [3] C. Chen, et al., Science 343 (2014) p. 1339. [4] Microscopy performed as part of a user project through ORNL s Center for Nanophase Materials Sciences, which is a U.S. DOE Office of Science User Facility, and instrumentation provided by the U.S. DOE Office of Nuclear Energy, Fuel Cycle R&D Program, and the Nuclear Science User Facilities.

  1. Platinum Dendritic-Flowers Prepared by Tellurium Nanowires Exhibit High Electrocatalytic Activity for Glycerol Oxidation.

    Science.gov (United States)

    Zuo, Yunpeng; Wu, Long; Cai, Kai; Li, Tingting; Yin, Wenmin; Li, Dian; Li, Na; Liu, Jiawei; Han, Heyou

    2015-08-19

    Dentritic Pt-based nanomaterials with enriched edge and corner atoms have recently attracted considerable attention as electrocatalysts. Meanwhile, Pt(111) facets are generally considered more active for the glycerol oxidation reaction (GOR). Thus, it is significant to construct the rational design and synthesis of dentritic Pt whose surface is mostly enclosed by {111} facets. Reported herein is a unique Pt-branched structure enriched by a large amount of valency unsaturated atoms prepared by the aggravation of the galvanic replacement strategy. The synthesis is developed to generate highly crystallized Pt nanoflowers using Te nanowires as a template. Furthermore, the electrochemical results show that Pt nanoflower is an excellent catalyst with higher mass activity and better structure stability than commercial Pt/C (20% Pt) for glycerol electro-oxidation. Besides, the template-broken approach could provide a novel potential way to synthesize Pt-based or other noble metals/alloys for their advanced functional applications. PMID:26226502

  2. Correcting for electrocatalyst desorption and inactivation in chronoamperometry experiments.

    Science.gov (United States)

    Fourmond, Vincent; Lautier, Thomas; Baffert, Carole; Leroux, Fanny; Liebgott, Pierre-Pol; Dementin, Sébastien; Rousset, Marc; Arnoux, Pascal; Pignol, David; Meynial-Salles, Isabelle; Soucaille, Phillippe; Bertrand, Patrick; Léger, Christophe

    2009-04-15

    Chronoamperometric experiments with adsorbed electrocatalysts are commonly performed either for analytical purposes or for studying the catalytic mechanism of a redox enzyme. In the context of amperometric sensors, the current may be recorded as a function of time while the analyte concentration is being increased to determine a linearity range. In mechanistic studies of redox enzymes, chronoamperometry proved powerful for untangling the effects of electrode potential and time, which are convoluted in cyclic voltammetric measurements, and for studying the energetics and kinetics of inhibition. In all such experiments, the fact that the catalyst's coverage and/or activity decreases over time distorts the data. This may hide meaningful features, introduce systematic errors, and limit the accuracy of the measurements. We propose a general and surprisingly simple method for correcting for electrocatalyst desorption and inactivation, which greatly increases the precision of chronoamperometric experiments. Rather than subtracting a baseline, this consists in dividing the current, either by a synthetic signal that is proportional to the instant electroactive coverage or by the signal recorded in a control experiment. In the latter, the change in current may result from film loss only or from film loss plus catalyst inactivation. We describe the different strategies for obtaining the control signal by analyzing various data recorded with adsorbed redox enzymes: nitrate reductase, NiFe hydrogenase, and FeFe hydrogenase. In each case we discuss the trustfulness and the benefit of the correction. This method also applies to experiments where electron transfer is mediated, rather than direct, providing the current is proportional to the time-dependent concentration of catalyst. PMID:19298055

  3. Degradation of Bimetallic Model Electrocatalysts ___ an in situ XAS Study

    Energy Technology Data Exchange (ETDEWEB)

    Friebel, Daniel

    2011-06-22

    One of the major challenges in the development of clean energy fuel cells is the performance degradation of the electrocatalyst, which, apart from poisoning effects, can suffer from corrosion due to its exposure to a harsh environment under high potentials. In this communication, we demonstrate how interactions of Pt with a transition metal support affect not only, as commonly intended, the catalytic activity, but also the reactivity of Pt towards oxide formation or dissolution. We use two well-defined single-crystal model systems, Pt/Rh(111) and Pt/Au(111) and a unique x-ray spectroscopy technique with enhanced energy resolution to monitor the potential-dependent oxidation state of Pt, and find two markedly different oxidation mechanisms on the two different substrates. This information can be of great significance for future design of more active and more stable catalysts. We have studied the potential-induced degradation of Pt monolayer model electrocatalysts on Rh(111) and Au(111) single-crystal substrates. The anodic formation of Pt oxides was monitored using in situ high energy resolution fluorescence detection x-ray absorption spectroscopy (HERFD XAS). Although Pt was deposited on both substrates in a three-dimensional island growth mode, we observed remarkable differences during oxide formation that can only be understood in terms of strong Pt-substrate interactions throughout the Pt islands. Anodic polarization of Pt/Rh(111) up to +1.6 V vs. RHE (reversible hydrogen electrode) leads to formation an incompletely oxidized passive layer, whereas formation of PtO2 and partial Pt dissolution is observed for Pt/Au(111).

  4. Methanol resistant ruthenium electrocatalysts for oxygen reduction synthesized by pyrolysis of Ru{sub 3}(CO){sub 12} in different atmospheres

    Energy Technology Data Exchange (ETDEWEB)

    Altamirano-Gutierrez, A.; Jimenez-Sandoval, O.; Uribe-Godinez, J.; Borja-Arco, E. [Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional (Cinvestav), Unidad Queretaro, Apartado Postal 1-798, Queretaro, Qro. 76001 (Mexico); Castellanos, R.H. [Universidad del Papaloapan, Campus Tuxtepec, Circuito Central No. 200, Col. Parque Industrial, Tuxtepec, Oax. 68301 (Mexico); Olivares-Ramirez, J.M. [Universidad Tecnologica de San Juan del Rio, Av. La Palma No. 125, Col. Vista Hermosa, San Juan del Rio, Qro. 76800 (Mexico)

    2009-10-15

    Novel ruthenium electrocatalysts for the oxygen reduction reaction (ORR) were prepared by pyrolysis of Ru{sub 3}(CO){sub 12} in three atmospheres: neutral (N{sub 2}), partially oxidative (air) and partially reductive (70:30 N{sub 2}/H{sub 2}), at temperatures in the 80-700 C range. The materials were characterized by FT-IR spectroscopy, X-ray diffraction and scanning electron microscopy. A thermogravimetric analysis of the Ru{sub 3}(CO){sub 12} precursor in the three atmospheres was also performed. The electrocatalytic properties of the materials were evaluated by rotating disk electrode measurements in 0.5 mol L{sup -1} H{sub 2}SO{sub 4}. The kinetic parameters, such as the Tafel slope, exchange current density and charge transfer coefficient, are reported. The catalysts prepared in N{sub 2} and N{sub 2}/H{sub 2}, in general, show a higher performance than those synthesized in air. In the two nitrogen containing atmospheres, a pyrolysis temperature of 360 C seems to lead to better electrocatalytic properties for the ORR. The new electrocatalysts are also tolerant to methanol concentrations as high as 2.0 mol L{sup -1}. (author)

  5. Platinum-monolayer Electrocatalysts: Palladium Interlayer on IrCo Alloy Core Improves Activity in Oxygen-reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Gong, K.; Chen, W.-F.; Sasaki, K.; Su, D.; Vukmirovic, M.B.; Zhou, W.; Izzo, E.L.; Perez-Acosta, C.; Hirunsit, P.; Balbuena, P.B.; Adzic, R.R.

    2010-11-15

    We describe the synthesis and electrocatalytic properties of a new low-Pt electrocatalyst consisting of an IrCo core, a Pd interlayer, and a surface Pt monolayer, emphasizing the interlayer's role in improving electrocatalytic activity for the oxygen-reduction reaction on Pt in HClO{sub 4} solution. We prepared the IrCo alloys by decomposing, at 800 C, hexacyanometalate, KCoIr(CN){sub 6}, adsorbed on the carbon surfaces. The synthesis of Ir{sub 3}Co/C involved heating a mix of metal salts and carbon in hydrogen at 500 C. Thereafter, we placed a palladium and/or platinum monolayer on them via the galvanic displacement of an underpotentially deposited copper monolayer. The electrocatalysts were characterized using structural- and electrochemical-techniques. For PtML/PdML/IrCo/C, we observed a Pt mass activity of 1.18 A/mg{sub (Pt)} and the platinum-group-metals mass of 0.16 A/mg{sub (Pt, Pd, Ir)}. In comparison, without a Pd interlayer, i.e., Pt{sub ML}/IrCo/C, the activities of 0.15 A/mg{sub (Pt)} and 0.036 A/mg{sub (Pt, Pd, Ir)} were considerably lower. We consider that the palladium interlayer plays an essential role in achieving high catalytic activity by adjusting the electronic interaction of the platinum monolayer with the IrCo core, so that it accelerates the kinetics of adsorption and desorption of the intermediates of oxygen reduction. A similar trend was observed for Pt{sub ML}/Pd{sub ML} and Pt{sub ML} deposited on Ir{sub 3}Co/C alloy core. We used density functional theory to interpret the observed phenomena.

  6. Preparation and testing of plant seed meal-based wood adhesives.

    Science.gov (United States)

    He, Zhongqi; Chapital, Dorselyn C

    2015-01-01

    Recently, the interest in plant seed meal-based products as wood adhesives has steadily increased, as these plant raw materials are considered renewable and environment-friendly. These natural products may serve as alternatives to petroleum-based adhesives to ease environmental and sustainability concerns. This work demonstrates the preparation and testing of the plant seed-based wood adhesives using cottonseed and soy meal as raw materials. In addition to untreated meals, water washed meals and protein isolates are prepared and tested. Adhesive slurries are prepared by mixing a freeze-dried meal product with deionized water (3:25 w/w) for 2 hr. Each adhesive preparation is applied to one end of 2 wood veneer strips using a brush. The tacky adhesive coated areas of the wood veneer strips are lapped and glued by hot-pressing. Adhesive strength is reported as the shear strength of the bonded wood specimen at break. Water resistance of the adhesives is measured by the change in shear strength of the bonded wood specimens at break after water soaking. This protocol allows one to assess plant seed-based agricultural products as suitable candidates for substitution of synthetic-based wood adhesives. Adjustments to the adhesive formulation with or without additives and bonding conditions could optimize their adhesive properties for various practical applications.

  7. Carbon-based composite electrocatalysts for low temperature fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Popov, Branko N. (Columbia, SC); Lee, Jog-Won (Columbia, SC); Subramanian, Nalini P. (Kennesaw, GA); Kumaraguru, Swaminatha P. (Honeoye Falls, NY); Colon-Mercado, Hector R. (Columbia, SC); Nallathambi, Vijayadurga (T-Nagar, IN); Li, Xuguang (Columbia, SC); Wu, Gang (West Columbia, SC)

    2009-12-08

    A process for synthesis of a catalyst is provided. The process includes providing a carbon precursor material, oxidizing the carbon precursor material whereby an oxygen functional group is introduced into the carbon precursor material, and adding a nitrogen functional group into the oxidized carbon precursor material.

  8. Iridium-based Electrocatalysts for the Oxygen Evolution Reaction

    OpenAIRE

    Reksten, Anita

    2016-01-01

    English version: This thesis covers several topics related to the anodic catalyst for the oxygen evolution reaction (OER) in polymer electrolyte membrane (PEM) water electrolysis. Water electrolysis is considered one of the viable options for large-scale hydrogen production and is relevant as a storage medium for renewable energy sources. The OER is a significant contributor to loss in PEM electrolyzers, and currently expensive and rare noble metal oxides such as iridium and ruthenium...

  9. Enhanced methanol electro-oxidation reaction on Pt-CoOx/MWCNTs hybrid electro-catalyst

    International Nuclear Information System (INIS)

    Highlights: • Promoting effects of Cobalt oxide on methanol electro-oxidation over Pt/MWCNTs are investigated. • Higher activity, about 2.9 times, and enhanced stability are observed on Pt-CoOx/MWCNTs. • Electrochemical active surface area of Pt nanoparticles is significantly improved upon CoOx addition. • Bi-functional mechanism is facilitated in presence of CoOx. - Abstract: The electro-catalytic behavior of Pt-CoOx/MWCNTs in methanol electro-oxidation reaction (MOR) is investigated and compared to that of Pt/MWCNTs. The electro-catalysts were synthesized by an impregnation method using NaBH4 as the reducing agent. The morphological and physical characteristics of samples are examined by XRD, TEM, ICP and EDS techniques. In the presence of CoOx, Pt nanoparticles were highly distributed on the support with an average particle size of 2 nm, an obvious decrease from 5.1 nm for Pt/MWCNTs. Cyclic voltammetry, CO-stripping, Chronoamperometry, and electrochemical impedance spectroscopy (EIS) measurements are used to study the electrochemical behavior of the electro-catalysts. The results revealed a considerable enhancement in the oxidation kinetics of COads on Pt active sites by the participation of CoOx. Compared to Pt/MWCNTs, Pt-CoOx/MWCNTs sample has a larger electrochemical active surface area (ECSA) and higher electro-catalytic activity and stability toward methanol electro-oxidation. According to the results of cyclic voltammetry, the forward anodic peak current density enhances more than 89% at the optimum atomic ratio of Pt:Co = 2:1. Furthermore, inclusion of cobalt oxide species causes the onset potential of methanol electro-oxidation reaction to shift 84 mV to negative values compared to that on Pt/MWCNTs. Based on EIS data, dehydrogenation of methanol is the rate-determining step of MOR on both Pt/MWCNTs and Pt-CoOx/MWCNTs, at small overpotentials. However, at higher overpotentials, the oxidation of adsorbed oxygen-containing groups controls the

  10. Fast and efficient molecular electrocatalysts for H2 production: Using hydrogenase enzymes as guides

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jenny Y.; Bullock, R. Morris; Rakowski DuBois, Mary; DuBois, Daniel L.

    2011-01-15

    Hydrogen generation using solar energy will require the development of efficient electrocatalysts for proton reduction. This article discusses the important role that proton movement plays in hydrogenase enzymes and potentials devices for solar generation. Studies of hydrogenase enzymes provide many import design principles for the development of simpler molecular catalysts. These principles are illustrated with examples from the literature and from the authors’ laboratories. In particular, pendant bases incorporated in the second coordination sphere of catalytic molecules play a number of important roles that are crucial to efficient catalysis. These include acting as relays to move protons between the metal center and solution, promoting intra- and inter-molecular proton transfer reactions, coupling proton and electron transfer reactions, assisting heterolytic cleavage of hydrogen, and stabilizing critical reaction intermediates. The importance of controlling proton movement on the molecular scale underscores the importance of a similar degree of control in devices designed for the solar production of hydrogen or any fuel generation process involving multiple electrons and protons. This material is based upon work supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

  11. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal-nitrogen coordination

    Science.gov (United States)

    Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev

    2015-06-01

    Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon-nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation.

  12. Electrospun carbon nanofibers/electrocatalyst hybrids as asymmetric electrodes for vanadium redox flow battery

    Science.gov (United States)

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

    2015-05-01

    To improve the electrochemical activity of polyacrylonitrile (PAN)-based electrospun carbon nanofibers (ECNFs) toward vanadium redox couples, the multi-wall carbon nanotubes (CNTs) and Bi-based compound as electrocatalyst have been embedded in the ECNFs to make composite electrode, respectively. The morphology and electrochemical properties of pristine ECNFs, CNTs/ECNFs and Bi/ECNFs have been characterized. Among the three kinds of electrodes, the CNTs/ECNFs show best electrochemical activity toward VO2+/VO2+ redox couple, while the Bi/ECNFs present the best electrochemical activity toward V2+/V3+ redox couple. Furthermore, the high overpotential of hydrogen evolution on Bi/ECNFs makes the side-reaction suppressed. Because of the large property difference between the two composite electrodes, the CNTs/ECNFs and Bi/ECNFs are designed to act as positive and negative electrode for vanadium redox flow battery (VRFB), respectively. It not only does improve the kinetics of two electrode reactions at the same time, but also reduce the kinetics difference between them. Due to the application of asymmetric electrodes, performance of the cell is improved greatly.

  13. Flexible Pedagogies: Employer Engagement and Work-Based Learning. Flexible Pedagogies: Preparing for the Future Series

    Science.gov (United States)

    Kettle, Jane

    2013-01-01

    This publication focuses on national and international policy initiatives to develop a better understanding of work-based learners and the types of flexibility that may well enhance their study especially pedagogically. As part of our five-strand research project "Flexible Pedagogies: preparing for the future" it: (1) highlights the…

  14. Diversity Preparedness: A Reflection on Pre-Service Teacher Preparation in Private, Faith-Based Colleges

    Science.gov (United States)

    Maclin, ShaRhonda A.

    2012-01-01

    The purpose of this exploratory, quantitative study is to evaluate the diversity preparedness of teacher education graduates from private, faith-based colleges. More specifically, the study identifies how teacher education graduates perceive their preparation to work with diversity issues in the classroom. Participants shared their perceptions of…

  15. Preparing Instructional Designers for Game-Based Learning: Part III. Game Design as a Collaborative Process

    Science.gov (United States)

    Hirumi, Atsusi; Appelman, Bob; Rieber, Lloyd; Van Eck, Richard

    2010-01-01

    In this three part series, four professors who teach graduate level courses on the design of instructional video games discuss their perspectives on preparing instructional designers to optimize game-based learning. Part I set the context for the series and one of four panelists discussed what he believes instructional designers should know about…

  16. Unfolding Case-Based Practicum Curriculum Infusing Crisis, Trauma, and Disaster Preparation

    Science.gov (United States)

    Greene, Catie A.; Williams, Amy E.; Harris, Pamela N.; Travis, Sterling P.; Kim, Sharon Y.

    2016-01-01

    The authors evaluated an unfolding case-based approach to a practicum in counseling course infusing crisis, trauma, and disaster preparation for changes in students' crisis self-efficacy across a semester. The course, informed by constructivist-developmental pedagogy and centered on the unfolding case, resulted in significant increases in…

  17. A Competency-Based Approach to the Master's Degree Preparation of Higher Education Professionals

    Science.gov (United States)

    Ott, Molly; Baca, Evelyn; Cisneros, Jesus; Bates, Evan

    2015-01-01

    The purpose of this manuscript is to describe a competency-based approach to designing and assessing master's level professional preparation programs in the field of higher education administration. Given the absence of a universal set of competencies defined for HEA master's degree programs, the authors draw from the CAHEP (2010) and Wright…

  18. Embedding Evidence-Based Practice in Pre-Service Teacher Preparation

    Science.gov (United States)

    Bain, Alan; Lancaster, Julie; Zundans, Lucie; Parkes, Robert John

    2009-01-01

    In this study, the authors sought to establish the differential effects on achievement of embedding evidence-based practice in the design of an inclusive education teacher preparation course. Embedded design involves creating self-repeating patterns in the instructional design of a course by expressing essential design features at multiple levels…

  19. Carbon-based Composite Electrodes: Preparation, Characterization and Application in Electroanalysis

    NARCIS (Netherlands)

    Corb, I.; Manea, F.; Radovan, C.; Pop, A.; Burtica, G.; Malchev, P.G.; Picken, S.J.; Schoonman, J.

    2007-01-01

    Electrodes based on carbon, i.e., expanded graphite (20%, wt.)-epoxy composite (20EG-Epoxy) and expanded graphite (20%, wt.)-polystyrene composite (20EG-PS) have been prepared, characterized using scanning electron microscopy (SEM) and cyclic voltammetry (CV), and tested as anodic sensors. The elect

  20. Characterization of Network Structure of Polyacrylamide Based Hydrogels Prepared By Radiation Induced Polymerization

    International Nuclear Information System (INIS)

    In this study network structure of polyacrylamide based hydrogels prepared by radiation induced polymerization has been investigated. Polyacrylamide based hydrogels in the rod form were prepared by copolymerization of acrylamide(AAm) with hydroxyl ethyl methacrylate(HEMA) and methyl acrylamide(MAAm) in the presence of cross-linking agent and water by gamma rays at ambient temperature. Molecular weight between cross-links and effective cross-link density of hydrogels were calculated from swelling as well as shear modulus data obtained from compression tests. The results have shown that simple compression analyses can be used for the determination of effective cross-link density of hydrogels without any need to some polymer-solvent based parameters as in the case of swelling based determinations. Diffusion of water into hydrogels was examined by analyzing water absorption kinetics and the effect of network, structure on the diffusion type and coefficient was discussed

  1. Preparation and Adsorption Properties of PAM Based Adsorbents for Plasma Lipoproteins

    Institute of Scientific and Technical Information of China (English)

    Hai Tao LI; Zhi YUAN; Xin Fu CHEN; Bin LIU; Bin SHEN; Bing Lin HE

    2004-01-01

    Crosslinked macroporous polyacrylamide(PAM)was prepared with inverse phase suspension polymerization technique.After treatment with hydrazine,the polymer was functionalized with chloroacetic acid,trifluoroacetic acid diethylenetriaminepentaacetic acid (DEPAA), and maleic acid, respectively,and PAM based adsorbents bearing carboxyl functional groups for low density lipoprotein(LDL)apheresis use were obtained.The blood compatibility and the adsorption properties for plasma lipoproteins of PAM based adsorbents were investigated.

  2. A Paradigm Shift to Outcomes-Based Higher Education: Policies, Principles and Preparations

    OpenAIRE

    Romer C. Castillo

    2014-01-01

    This article presents the policies regarding Outcomes-Based Education (OBE) System of the Commission on Higher Education and explores some of the principles of OBE that abound the literature. It is intended to help Batangas State University, particularly the College of Accountancy, Business, Economics and International Hospitality Management, prepare for a paradigm shift to an outcomes-based higher education. It does not claim nor attempt to be a comprehensive review or treatise on OBE. Rat...

  3. SAS 9 Study Guide Preparing for the Base Programming Certification Exam for SAS 9

    CERN Document Server

    Hezaveh, Ali

    2011-01-01

    A thorough and self-contained treatment for SAS® users preparing for the Base Programming Certification Exam for SAS® 9-complete with explanations, tips, and practice exam questions SAS® 9 Study Guide is designed to help users of SAS® 9 become familiar with the fine points of the software as well as develop solid study strategies that will shorten preparation time and ensure successful exam results. The following five study topics are addressed with a focused chapter devoted to each: accessing data; creating data structures; managing data; generating reports; and handling errors. SAS® 9 Study

  4. Preparation and characterization of amidated pectin based hydrogels for drug delivery system.

    Science.gov (United States)

    Mishra, R K; Datt, M; Pal, K; Banthia, A K

    2008-06-01

    In the current studies attempts were made to prepare hydrogels by chemical modification of pectin with ethanolamine (EA) in different proportions. Chemically modified pectin products were crosslinked with glutaraldehyde reagent for preparing hydrogels. The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), organic elemental analysis, X-ray diffraction studies (XRD), swelling studies, biocompatibility and hemocompatibility studies. Mechanical properties of the prepared hydrogels were evaluated by tensile test. The hydrogels were loaded with salicylic acid (used as a model drug) and drug release studies were done in a modified Franz's diffusion cell. FTIR spectroscopy indicated the presence of primary and secondary amide absorption bands. XRD studies indicated increase in crystallinity in the hydrogels as compared to unmodified pectin. The degree of amidation (DA) and molar and mass reaction yields (YM and YN) was calculated based on the results of organic elemental analysis. The hydrogels showed good water holding properties and were found to be compatible with B-16 melanoma cells & human blood.

  5. A sol-gel based surface treatment for preparation of water repellent antistatic textiles

    Science.gov (United States)

    Textor, Torsten; Mahltig, Boris

    2010-01-01

    In this paper a surface treatment is described for preparation of hydrophobic sol-gel coatings that simultaneously offer antistatic properties for an appropriate finishing of textiles and refinement of polymer foils. Sol-gel based formulations are modified with both hydrophilic and hydrophobic components simultaneously. Hydrophobic components are, e.g., alkoxysilanes modified with alkyl chains while the hydrophilic ones are amino-functionalized alkoxysilanes. The basic idea is that due to an enrichment of hydrophobic groups at the solid/air interface the surface of the as prepared coatings will be hydrophobic while the deeper region will be more hydrophilic. Textiles finished with these coatings exhibit sufficient water repellence and simultaneously absorb sufficient amounts of humidity in the deeper areas of the coating guaranteeing antistatic properties. This concept offers interesting approaches for the preparation of multifunctional surface coatings not only focussing on combining water repellence with antistatic properties for textile materials.

  6. Preparation and characterization of a novel ionizing electromagnetic radiation shielding material: Hematite filled polyester based composites

    International Nuclear Information System (INIS)

    Isophthalic polyester (PES) based and natural mineral (hematite) filled composites were prepared and characterized for ionizing electromagnetic radiation shielding applications. Density evaluation and microscopic studies of the composites were carried out. Shielding performances of the composites were investigated for three different IEMR energy regions as low, intermediate and high. The mass attenuation coefficient of the prepared composites reached 98% of the elemental lead. In addition, the studied composites were superior to lead by virtue of their non-toxic nature. - Highlights: • Isophytalitic polyester-natural mineral (hematite) filled composites were prepared. • Ionizing electromagnetic radiation shielding performances were investigated. • Density evaluation and microscopic studies were carried out. • Attenuation coefficients were determined for different energies. • The mass attenuation coefficients reached 98% of the elemental lead

  7. Fast and efficient molecular electrocatalysts for H{sub 2} production: Using hydrogenase enzymes as guides

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jenny Y.; Bullock, R. Morris; DuBois, M. Rakowski; DuBois, Daniel L.

    2011-01-01

    Hydrogen generation using solar energy will require the development of efficient electrocatalysts for proton reduction. This article discusses the important role that proton movement plays in hydrogenase enzymes and potential devices for solar generation. Studies of hydrogenase enzymes provide many important design principles for the development of simpler molecular catalysts. These principles are illustrated with examples from the literature and from the authors’ laboratories. In particular, pendant bases incorporated in the second coordination sphere of catalytic molecules play a number of important roles that are crucial to efficient catalysis. These roles include acting as relays to move protons between the metal center and solution, promoting intra- and intermolecular proton transfer reactions, coupling proton and electron transfer reactions, assisting heterolytic cleavage of hydrogen, and stabilizing critical reaction intermediates. The importance of controlling proton movement on the molecular scale underscores the importance of a similar degree of control in devices designed for the solar production of hydrogen or any fuel generation process involving multiple electrons and protons.

  8. Pentlandite rocks as sustainable and stable efficient electrocatalysts for hydrogen generation

    Science.gov (United States)

    Konkena, Bharathi; junge Puring, Kai; Sinev, Ilya; Piontek, Stefan; Khavryuchenko, Oleksiy; Dürholt, Johannes P.; Schmid, Rochus; Tüysüz, Harun; Muhler, Martin; Schuhmann, Wolfgang; Apfel, Ulf-Peter

    2016-01-01

    The need for sustainable catalysts for an efficient hydrogen evolution reaction is of significant interest for modern society. Inspired by comparable structural properties of [FeNi]-hydrogenase, here we present the natural ore pentlandite (Fe4.5Ni4.5S8) as a direct ‘rock' electrode material for hydrogen evolution under acidic conditions with an overpotential of 280 mV at 10 mA cm−2. Furthermore, it reaches a value as low as 190 mV after 96 h of electrolysis due to surface sulfur depletion, which may change the electronic structure of the catalytically active nickel–iron centres. The ‘rock' material shows an unexpected catalytic activity with comparable overpotential and Tafel slope to some well-developed metallic or nanostructured catalysts. Notably, the ‘rock' material offers high current densities (≤650 mA cm−2) without any loss in activity for approximately 170 h. The superior hydrogen evolution performance of pentlandites as ‘rock' electrode labels this ore as a promising electrocatalyst for future hydrogen-based economy. PMID:27461840

  9. 3D arrays of molybdenum sulphide nanosheets on Mo meshes: Efficient electrocatalysts for hydrogen evolution reaction

    International Nuclear Information System (INIS)

    3D arrays of molybdenum sulphide nanosheets on Mo mesh exhibited enhanced electro-catalytic activity for hydrogen evolution reaction. - Highlights: • 3D arrays of molybdenum sulphide nanosheets were obtained by a facile hydrothermal method. • The mesh structure could be beneficial to promote the electrolyte diffusion onto the electrode surface and thus promote the electron transfer. • 3D arrays of molybdenum sulphide nanosheets demonstrate an enhanced HER activity with a low onset overpotential of 120 mV and a Tafel slope of 46 mV/dec. - Abstract: Molybdenum sulphide has emerged as a promising electrocatalyst for hydrogen evolution reaction (HER). Toward further improving its activity, tremendous efforts have been made to preferentially expose active edge sites of molybdenum sulphide-based catalysts by engineering their surface structure. In this work, 3D arrays of molybdenum sulphide nanosheets were synthesized by hydrothermal treatment of Mo mesh in aqueous thiourea solution. Their compositional, morphological and structural properties as well as electrocatalytic activities were investigated in details. The results reveal that 3D arrays of molybdenum sulphide nanosheets demonstrate an enhanced HER activity with a low onset overpotential of 120 mV and a Tafel slope of 46 mV/dec, which is superior to that of 2D arrays molybdenum sulphide nanosheets grown on Mo foil. The high activity for HER can be ascribed to the superstructure of the catalysts with a large fraction of edge sites and a high surface area

  10. Pentlandite rocks as sustainable and stable efficient electrocatalysts for hydrogen generation

    Science.gov (United States)

    Konkena, Bharathi; Junge Puring, Kai; Sinev, Ilya; Piontek, Stefan; Khavryuchenko, Oleksiy; Dürholt, Johannes P.; Schmid, Rochus; Tüysüz, Harun; Muhler, Martin; Schuhmann, Wolfgang; Apfel, Ulf-Peter

    2016-07-01

    The need for sustainable catalysts for an efficient hydrogen evolution reaction is of significant interest for modern society. Inspired by comparable structural properties of [FeNi]-hydrogenase, here we present the natural ore pentlandite (Fe4.5Ni4.5S8) as a direct `rock' electrode material for hydrogen evolution under acidic conditions with an overpotential of 280 mV at 10 mA cm-2. Furthermore, it reaches a value as low as 190 mV after 96 h of electrolysis due to surface sulfur depletion, which may change the electronic structure of the catalytically active nickel-iron centres. The `rock' material shows an unexpected catalytic activity with comparable overpotential and Tafel slope to some well-developed metallic or nanostructured catalysts. Notably, the `rock' material offers high current densities (<=650 mA cm-2) without any loss in activity for approximately 170 h. The superior hydrogen evolution performance of pentlandites as `rock' electrode labels this ore as a promising electrocatalyst for future hydrogen-based economy.

  11. Highly Efficient and Robust Nickel Phosphides as Bifunctional Electrocatalysts for Overall Water-Splitting.

    Science.gov (United States)

    Li, Jiayuan; Li, Jing; Zhou, Xuemei; Xia, Zhaoming; Gao, Wei; Ma, Yuanyuan; Qu, Yongquan

    2016-05-01

    To search for the efficient non-noble metal based and/or earth-abundant electrocatalysts for overall water-splitting is critical to promote the clean-energy technologies for hydrogen economy. Herein, we report nickel phosphide (NixPy) catalysts with the controllable phases as the efficient bifunctional catalysts for water electrolysis. The phases of NixPy were determined by the temperatures of the solid-phase reaction between the ultrathin Ni(OH)2 plates and NaH2PO2·H2O. The NixPy with the richest Ni5P4 phase synthesized at 325 °C (NixPy-325) delivered efficient and robust catalytic performance for hydrogen evolution reaction (HER) in the electrolytes with a wide pH range. The NixPy-325 catalysts also exhibited a remarkable performance for oxygen evolution reaction (OER) in a strong alkaline electrolyte (1.0 M KOH) due to the formation of surface NiOOH species. Furthermore, the bifunctional NixPy-325 catalysts enabled a highly performed overall water-splitting with ∼100% Faradaic efficiency in 1.0 M KOH electrolyte, in which a low applied external potential of 1.57 V led to a stabilized catalytic current density of 10 mA/cm(2) over 60 h. PMID:27064172

  12. Pentlandite rocks as sustainable and stable efficient electrocatalysts for hydrogen generation.

    Science.gov (United States)

    Konkena, Bharathi; Junge Puring, Kai; Sinev, Ilya; Piontek, Stefan; Khavryuchenko, Oleksiy; Dürholt, Johannes P; Schmid, Rochus; Tüysüz, Harun; Muhler, Martin; Schuhmann, Wolfgang; Apfel, Ulf-Peter

    2016-01-01

    The need for sustainable catalysts for an efficient hydrogen evolution reaction is of significant interest for modern society. Inspired by comparable structural properties of [FeNi]-hydrogenase, here we present the natural ore pentlandite (Fe4.5Ni4.5S8) as a direct 'rock' electrode material for hydrogen evolution under acidic conditions with an overpotential of 280 mV at 10 mA cm(-2). Furthermore, it reaches a value as low as 190 mV after 96 h of electrolysis due to surface sulfur depletion, which may change the electronic structure of the catalytically active nickel-iron centres. The 'rock' material shows an unexpected catalytic activity with comparable overpotential and Tafel slope to some well-developed metallic or nanostructured catalysts. Notably, the 'rock' material offers high current densities (≤650 mA cm(-2)) without any loss in activity for approximately 170 h. The superior hydrogen evolution performance of pentlandites as 'rock' electrode labels this ore as a promising electrocatalyst for future hydrogen-based economy. PMID:27461840

  13. Preparation of New Type Ni-P Micro/Nano Metal Material Based on Bacteria Shape

    Institute of Scientific and Technical Information of China (English)

    Xin Liang; Jianhua Liu; Songmei Li

    2009-01-01

    A new type of Ni-P alloy with rod-shape was prepared by electroless deposition method based on the shape of Nocadia, a kind of bacteria. The material was characterized by microbiological method, scanning elec-tron microscope, energy dispersion spectroscopy, transmission electron microscopy, fourier transform infrared spectroscopy, X-ray diffraction and vibrant sample magnetometer. It was found that Ni-P alloy deposited on Nocadia surface was amorphous when pH=8.0. The amount of Ni crystalline increased with pH of plating solution. Ni-P nano-particles deposited on active locations on the surface at the initial stage, and then ho-mogeneous Ni-P film formed with time. Nocadia remained their original rod shape after Ni-P nano-particles deposition. The new type metal material formed of Ni-P alloy with nano-particles was prepared. The mag-netization of the material prepared at pH=9.7 is greater than that prepared at pH=8.0. The magnetic loss of the material prepared at pH=9.7 is less than 0.1. The dielectric loss exceeds 0.3 when frequency is higher than 14 GHz, which is 1.5 at 18 GHz. The new type Ni-P metal material with Nocadia shape has dielectric loss property.

  14. Preparation of six quinazoline schiff bases and their inhibitory effect on HHCC and Bcap-37 cells

    Institute of Scientific and Technical Information of China (English)

    陈惠; 孙晓莉; 刘志红; 张生勇; 药立波

    2003-01-01

    Objective: To prepare six quinazoline schiff bases by six steps of chemistry organic synthesis and test their inhibitory effect on hepatomacellular carcinoma cells HHCC and mammary cancer cell Bcap-37, furthmore,to compare their antitumor activities on these two kinds of cells. Methods: 2-Amino-5-nitro-benzylcarbonitrile was the initial material, and it was under the reaction of hydrolysis, ring-closing, halogenation, addition, reduction and substitution in turn to get the six quinazoline schiff bases, MTT method was adopted to compare their anticancer activities against the two cancer cells. Result and Conclusion: Six 6-imine-4-halo substituted anilinoquinozolines were prepared. The anticancer activities against both HHCC and Bcap-37were found, furthermore, they have more potency that on HHCC than on Bcap-37. In the six compounds, the schiff base Ⅵ is the most potent compound.

  15. Cobalt oxide and nitride particles supported on mesoporous carbons as composite electrocatalysts for dye-sensitized solar cells

    Science.gov (United States)

    Chen, Ming; Shao, Leng-Leng; Gao, Ze-Min; Ren, Tie-Zhen; Yuan, Zhong-Yong

    2015-07-01

    The composite electrocatalysts of cobalt oxide/mesoporous carbon and cobalt nitride/mesoporous carbon are synthesized via a convenient oxidation and subsequent ammonia nitridation of cobalt particles-incorporated mesoporous carbon, respectively. The cobalt oxide and nitride particles are uniformly imbedded in mesoporous carbon matrix, forming the unique composites with high surface area and mesopore architecture, and the resultant composites are evaluated as counter electrode materials, exhibiting good catalytic activity for the reduction of triiodide. The composites of cobalt nitride and mesoporous carbon are superior to the counterparts of cobalt oxide and mesoporous carbon in catalyzing the triiodide reduction, and the dye-sensitized solar cell with the composites achieves an optimum power conversion efficiency of 5.26%, which is comparable to the one based on the conventional Pt counter electrode (4.88%).

  16. Pt/Pd electrocatalyst electrons for fuel cells

    Science.gov (United States)

    Stonehart, P.

    1981-11-03

    This invention relates to improved electrochemical cells and to novel electrodes for use therein. In particular, the present invention comprises a fuel cell used primarily for the consumption of impure hydrogen fuels containing carbon monoxide or carbonaceous fuels where the electrode in contact with the fuel is not substantially poisoned by carbon monoxide. The anode of the fuel cell comprises a Pd/Pt alloy supported on a graphitized or partially graphitized carbon material. Fuel cells which comprise as essential elements a fuel electrode, an oxidizing electrode, and an electrolyte between said electrodes are devices for the direct production of electricity through the electrochemical combustion of a fuel and oxidant. These devices are recognized for their high efficiency as energy conversion units, since unlike conventional combustion engines, they are not subject to the limitations of the Carnot heat cycle. It is the primary object of the present invention to provide an electrode having high electrochemical activity for an electrochemical cell. It is another object of the present invention to provide an electrode having an electro-catalyst which is highly resistant to the corrosive environment of an electrochemical cell.

  17. Palladium modified gold nanoparticles as electrocatalysts for ethanol electrooxidation

    Science.gov (United States)

    Chen, Huimei; Xing, Zelong; Zhu, Shangqiang; Zhang, Lulu; Chang, Qiaowan; Huang, Jiale; Cai, Wen-Bin; Kang, Ning; Zhong, Chuan-Jian; Shao, Minhua

    2016-07-01

    Resemblin, g core-shell electrocatalysts consisting of a Au core and Pd shell (Au@Pd) are synthesized via a Cu underpotential deposition (UPD)-Pd-displacement method. The Pd shell is non-uniform consisting of tiny Pd clusters with a coverage of 0.5-0.6. The ethanol oxidation reaction (EOR) activity of this kind of structure is much higher than Pd/C in an alkaline solution. The forward peak current density of Au@Pd is 5.4 times higher than that of Pd/C. Furthermore, the onset potential for EOR of the former is ∼100 mV more negative. An interesting particle size dependent EOR activity is also observed. With increasing the Au particle size (2.9, 5.8 and 6.5 nm), the EOR activity increases. The strain and ligand effects from the Au core, together with the bifunctional reaction mechanism in the Au-Pd system may be reasons for the enhanced activity in Au@Pd catalysts.

  18. A facile method to prepare a high performance solid-state flexible paper-based supercapacitor

    Energy Technology Data Exchange (ETDEWEB)

    Shieh, Jen-Yu; Zhang, Sheng-Hui; Wu, Cheng-Hung [Institute of Electro-Optical and Materials Science, National Formosa University, 64 Wenhua Road, Huwei, Yunlin 63208, Taiwan (China); Yu, Hsin Her, E-mail: hhyu@nfu.edu.tw [Department of Biotechnology, National Formosa University, 64 Wenhua Road, Huwei, Yunlin 63208, Taiwan (China)

    2014-09-15

    Graphical abstract: A flexible paper-based supercapacitor was assembled into a sandwich structure, which exhibits well-retained triangular-shaped curves. The cycle life stability of this device still retains about 96% of the initial capacitance after 2000 cycles at a scan rate of 400 mV/s. An as-fabricated paper-based supercapacitor could light a red LED well after charging at constant potential of 3 V. - Highlights: • A facile approach is proposed to fabricate paper-based supercapacitors. • Apple pectin is an excellent dispersant for MWCNTs. • Paper provides a strong binding and flexible characteristic for electrode. • A paper-based supercapacitor could light a red LED after charging. • This device shows excellent electrochemical performance and cycling stability. - Abstract: We propose a low cost and simple method to prepare a paper-based supercapacitor in this study. Multi-walled carbon nanotubes (MWCNTs) were dispersed with a pectin solution under an ultrasonic homogenizer. Carbon nanotube suspension was prepared using a centrifuge to eliminate impurities. The dispersed MWCNTs suspension was dropped and dried onto the shallow surface of commercial copy paper. A paper-based conductive paper was formed as the electrodes. The electrical conductivity and dispersed morphology of the paper-based conductive paper were examined by four probes, atomic force microscope (AFM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The solid-state electrolyte was prepared by casting a solution of phosphoric acid and polyvinyl alcohol onto a glass plate. The paper-based supercapacitor was constructed with one solid-state electrolyte inserted between two electrodes, which were assembled into a sandwich structure by hot press. The specific capacitance and cycle-life stability of the paper-based supercapacitor was investigated by cyclic voltammetry analysis.

  19. Core-Shell Co/CoO Integrated on 3D Nitrogen Doped Reduced Graphene Oxide Aerogel as an Enhanced Electrocatalyst for the Oxygen Reduction Reaction.

    Science.gov (United States)

    Wang, Meng; Hou, Yuyang; Slade, Robert C T; Wang, Jiazhao; Shi, Dongqi; Wexler, David; Liu, Huakun; Chen, Jun

    2016-01-01

    Here, we demonstrate that Cobalt/cobalt oxide core-shell nanoparticles integrated on nitrogen-doped (N-doped) three-dimensional reduced graphene oxide aerogel-based architecture (Co/CoO-NGA) were synthesized through a facile hydrothermal method followed by annealing treatment. The unique endurable porous structure could provide sufficient mass transfer channels and ample active sites on Co/CoO-NGA to facilitate the catalytic reaction. The synthesized Co/CoO-NGA was explored as an electrocatalyst for the oxygen reduction reaction, showing comparable oxygen reduction performance with excellent methanol resistance and better durability compared with Pt/C.

  20. Core-Shell Co/CoO Integrated on 3D Nitrogen Doped Reduced Graphene Oxide Aerogel as an Enhanced Electrocatalyst for the Oxygen Reduction Reaction.

    Science.gov (United States)

    Wang, Meng; Hou, Yuyang; Slade, Robert C T; Wang, Jiazhao; Shi, Dongqi; Wexler, David; Liu, Huakun; Chen, Jun

    2016-01-01

    Here, we demonstrate that Cobalt/cobalt oxide core-shell nanoparticles integrated on nitrogen-doped (N-doped) three-dimensional reduced graphene oxide aerogel-based architecture (Co/CoO-NGA) were synthesized through a facile hydrothermal method followed by annealing treatment. The unique endurable porous structure could provide sufficient mass transfer channels and ample active sites on Co/CoO-NGA to facilitate the catalytic reaction. The synthesized Co/CoO-NGA was explored as an electrocatalyst for the oxygen reduction reaction, showing comparable oxygen reduction performance with excellent methanol resistance and better durability compared with Pt/C. PMID:27597939

  1. Recent Progress in Cobalt-Based Heterogeneous Catalysts for Electrochemical Water Splitting.

    Science.gov (United States)

    Wang, Jiahai; Cui, Wei; Liu, Qian; Xing, Zhicai; Asiri, Abdullah M; Sun, Xuping

    2016-01-13

    Water electrolysis is considered as the most promising technology for hydrogen production. Much research has been devoted to developing efficient electrocatalysts for hydrogen production via the hydrogen evolution reaction (HER) and oxygen production via the oxygen evolution reaction (OER). The optimum electrocatalysts can drive down the energy costs needed for water splitting via lowering the overpotential. A number of cobalt (Co)-based materials have been developed over past years as non-noble-metal heterogeneous electrocatalysts for HER and OER. Recent progress in this field is summarized here, especially highlighting several important bifunctional catalysts. Various approaches to improve or optimize the electrocatalysts are introduced. Finally, the current existing challenges and the future working directions for enhancing the performance of Co-implicated electrocatalysts are proposed. PMID:26551487

  2. Tantalum carbide as a novel support material for anode electrocatalysts in polymer electrolyte membrane water electrolysers

    OpenAIRE

    Polonský, Jakub; Petrushina, Irina; Christensen, Erik; Bouzek, K.; Prag, Carsten Brorson; Andersen, Jens Enevold Thaulov; Bjerrum, Niels

    2012-01-01

    Iridium oxide (IrO2) currently represents a state of the art electrocatalyst for anodic oxygen evolution. Since iridium is both expensive and scarce, the future practical application of this process makes it essential to reduce IrO2 loading on the anodes of PEM water electrolysers. In the present study an approach to utilising a suitable electrocatalyst support was followed. Of the materials selected from a literature review, TaC has proved to be stable under the conditions of the accelerated...

  3. Preparation and research on poisoning resistant Zr-Co based hydrogen storage alloys

    Institute of Scientific and Technical Information of China (English)

    LI Hualing; WANG Shumao; JIANG Lijun; ZHANG Lidong; LIU Xiaopeng; LI Zhinian

    2008-01-01

    At present,all hydrogen storage alloys are poisoned by hydrogen mixed with CO,CO2,etc,which decreases the hydrogen storage property sharply.Zr-Co based hydrogen storage alloys with good poisoning resistance were prepared by alloying,fluorinating,and electroless plating.The experiment results show that the poisoning resistance of the Zr-Co based alloy was improved remarkably after the treatments.The poisoning resistance mechanism of the Zr-Co based hydrogen storage alloys was analyzed.

  4. Structuralization of Ca(2+)-Based Metal-Organic Frameworks Prepared via Coordination Replication of Calcium Carbonate.

    Science.gov (United States)

    Sumida, Kenji; Hu, Ming; Furukawa, Shuhei; Kitagawa, Susumu

    2016-04-01

    The emergence of metal-organic frameworks (MOFs) as potential candidates to supplant existing adsorbent types in real-world applications has led to an explosive growth in the number of compounds available to researchers, as well as in the diversity of the metal salts and organic linkers from which they are derived. In this context, the use of carbonate-based precursors as metal sources is of interest due to their abundance in mineral deposits and their reaction chemistry with acids, resulting in just water and carbon dioxide as side products. Here, we have explored the use of calcium carbonate as a metal source and demonstrate its versatility as a precursor to several known frameworks, as well as a new flexible compound based on the 2,5-dihydroxybenzoquinone (H2dhbq) linker, Ca(dhbq)(H2O)2. Furthermore, inspired by the ubiquity and unique structures of biomineralized forms of calcium carbonate, we also present examples of the preparation of superstructures of Ca-based MOFs via the coordination replication technique. In all, the results confirm the suitability of carbonate-based metal sources for the preparation of MOFs and further expand upon the growing scope of coordination replication as a convenient strategy for the preparation of structuralized materials. PMID:27002690

  5. Comparison of Preparation Methods of Copper Based PGMFree Diesel-Soot Oxidation Catalysts

    Directory of Open Access Journals (Sweden)

    R. Prasad

    2011-05-01

    Full Text Available CuO-CeO2 systems have been proposed as a promising catalyst for low temperature diesel-soot oxidation. CuO-CeO2 catalysts prepared by various methods were examined for air oxidation of the soot in a semi batch tubular flow reactor. The air oxidation of soot was carried out under tight contact with soot/catalyst ratio of 1/10. Air flow rate was 150 ml/min, soot-catalyst mixture was 110 mg, heating rate was 5 0C/min. Prepared catalysts were calcined at 500 0C and their stability was examined by further heating to 800 0C for 4 hours. It was found that the selectivity of all the catalysts was nearly 100% to CO2 production. It was observed that the activity and stability of the catalysts greatly influenced by the preparation methods. The strong interaction between CuO and CeO2 is closely related to the preparation route that plays a crucial role in the soot oxidation over the CuO-CeO2 catalysts. The ranking order of the preparation methods of the catalysts in the soot oxidation performance is as follows: sol-gel > urea nitrate combustion > Urea gelation method > thermal decomposition > co-precipitation. Copyright © 2011 BCREC UNDIP. All rights reserved.(Received: 27th June 2010, Revised: 7th August 2010; Accepted: 13rd October 2010[How to Cite: R. Prasad, V.R. Bella. (2011. Comparison of Preparation Methods of Copper Based PGMFree Diesel-Soot Oxidation Catalysts. Bulletin of Chemical Reaction Engineering and Catalysis, 6(1: 15-21. doi:10.9767/bcrec.6.1.822.15-21][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.822.15-21 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/822 | View in 

  6. Preparation and Characterization of Azadirachtin Alginate-Biosorbent Based Formulations: Water Release Kinetics and Photodegradation Study.

    Science.gov (United States)

    Flores-Céspedes, Francisco; Martínez-Domínguez, Gerardo P; Villafranca-Sánchez, Matilde; Fernández-Pérez, Manuel

    2015-09-30

    The botanical insecticide azadirachtin was incorporated in alginate-based granules to obtain controlled release formulations (CRFs). The basic formulation [sodium alginate (1.47%) - azadirachtin (0.28%) - water] was modified by the addition of biosorbents, obtaining homogeneous hybrid hydrogels with high azadirachtin entrapment efficiency. The effect on azadirachtin release rate caused by the incorporation of biosorbents such as lignin, humic acid, and olive pomace in alginate formulation was studied by immersion of the granules in water under static conditions. The addition of the biosorbents to the basic alginate formulation reduces the rate of release because the lignin-based formulation produces a slower release. Photodegradation experiments showed the potential of the prepared formulations in protecting azadirachtin against simulated sunlight, thus improving its stability. The results showed that formulation prepared with lignin provided extended protection. Therefore, this study provides a new procedure to encapsulate the botanical insecticide azadirachtin, improving its delivery and photostability. PMID:26345112

  7. 78 FR 29120 - Notice of Intent To Prepare an Environmental Impact Statement for the Main Operating Base 2 (MOB...

    Science.gov (United States)

    2013-05-17

    ... of Intent To Prepare an Environmental Impact Statement for the Main Operating Base 2 (MOB-2) for the... prepare an Environmental Impact Statement (EIS) for the Main Operating Base 2 (MOB-2) for the beddown of... the MOB-2 at existing Air National Guard (ANG) installations within the continental United States....

  8. PREPARATION AND CHARACTERIZATION OF ACETIC ACID LIGNIN-BASED EPOXY BLENDS

    OpenAIRE

    Fangeng Chen,; Pan Feng

    2012-01-01

    Lignin-based epoxy resin (LER) was prepared from phenolated lignin (PL) and epichlorohydrin (ECH) in the presence of sodium hydroxide. The eucalyptus acetic acid lignin (AAL) was first reacted with phenol in the presence of sulfuric acid to obtain PL. Then, PL was reacted with ECH in aqueous sodium hydroxide to obtain LER. LER was mixed with diglycidyl ether of bisphenol A (E-44) and then cured with triethylenetetramine (TETA). The initial thermal degradation temperature (Td) of the cured epo...

  9. Technology of prognostication of sporting achievements of badminton players on the stage of preliminary base preparation.

    Directory of Open Access Journals (Sweden)

    Shyyan V.N.

    2011-08-01

    Full Text Available In the article the technology of evaluation of potential capabilities of badminton players is displayed 12-14 years. The functional, pedagogical and psychophysiological criteria which became a component parts of the developed analytical models of sportsmen-badminton players are explored. The criterion for the quantitative estimation of perspective is offered, which allows on the 9-ti point scale to estimate perspective of badminton players on the stage of preliminary base preparation.

  10. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation

    OpenAIRE

    Helms, Eric R; Aragon, Alan A.; Fitschen, Peter J

    2014-01-01

    The popularity of natural bodybuilding is increasing; however, evidence-based recommendations for it are lacking. This paper reviewed the scientific literature relevant to competition preparation on nutrition and supplementation, resulting in the following recommendations. Caloric intake should be set at a level that results in bodyweight losses of approximately 0.5 to 1%/wk to maximize muscle retention. Within this caloric intake, most but not all bodybuilders will respond best to consuming ...

  11. Influence of electrode preparation on the electrochemical behaviour of carbon-based supercapacitors

    OpenAIRE

    Ruiz Ruiz, Vanesa; Blanco Rodríguez, Clara; Granda Ferreira, Marcos; Menéndez López, Rosa María; Santamaría Ramírez, Ricardo

    2007-01-01

    [EN] This work investigates the influence of electrode preparation on the electrochemical behaviour of carbon-based supercapacitors. Studies were performed using the same activated carbon and polymer polyvynilidene fluoride (PVDF) in the same proportions (10 wt.% PVDF). Only the way in which these components were mixed was modified. The procedure for mixing the activated carbon and the polymer has a significant influence on the electrochemical behaviour of the electrode used in a supercapacit...

  12. Comparison of Diagnostic Cytomorphology of Atypical Squamous Cells in Liquid-Based Preparations and Conventional Smears

    OpenAIRE

    Lee, Jung Dal; Oh, Young-Ha; Lee, Seong Ok; Kim, Jong Yull

    2012-01-01

    Background The aims of this study were to compare the cytomorphologic features diagnostic of atypical squamous cells (ASC) in liquid-based preparations (LBPs) and conventional Pap (CP) smears and to cytomorphologically assess the performance of the Cell Scan 1500™ in cervical cytology practice. Methods Cervicovaginal smears were obtained from 938 women. Two smears were obtained simultaneously from each individual, one for an LBP and the other for a CP smear; the smears were independently exam...

  13. Preparation and Properties of Biocomposite Based on Natural Rubber and Bagasse Nanocellulose

    OpenAIRE

    Jarnthong Methakarn; Wang Fei; Wei Xiao Yi; Wang Rui; Li Ji Hua

    2015-01-01

    Biocomposite based on natural rubber (NR) and bagasse nanocellulose (BNC) was prepared in latex state. The mechanical, morphological and thermal properties of NR/BNC biocomposite were investigated. It was found that the addition of 3 wt% of BNC in NR film caused significant increase in modulus at 100% and 300% elongations and improved thermal stability of NR/BNC biocomposite. However, the strength at break and elongation at break of the biocomposite were not enhanced correlating to the morpho...

  14. The PZC-based Tc-99m generator preparation and its performance test

    International Nuclear Information System (INIS)

    This paper described the preparation of Tc-99m generator prepared with Japan distributing Mo adsorbent PZC and irradiated nature MoO3 and its performance test. Four Tc-99m generators were prepared with different batches of PZC and reactor irradiated nature MoO3. The adsorption capacity of PZC to Mo is approximately 200mgMo/gPZC. The adsorption efficiency of three batches PZC is good (>90%) and that of one batch of PZC is not good enough (∼83%). The loss of fine powder (The PZC is fragile) is quite different with the different preparation process of PZC. The elution efficiency is 80-90% and has the up trend with the elution date. The Mo breakthrough can be controlled to acceptable level by connecting HZO safe column containing 1.0g HZO. All the specifications of eluted from PZC-based Tc-99m generator can meet the requirements under Sodium Pertechnetate injection in China Pharmacopoeia. (author)

  15. Nanosized IrxRu1-xO2 electrocatalysts for oxygen evolution reaction in proton exchange membrane water electrolyzer

    Science.gov (United States)

    Hanh Pham, Hong; Nguyen, Ngoc Phong; Linh Do, Chi; Thang Le, Ba

    2015-01-01

    Normally in proton exchange membrane water electrolysis (PEMWE), the anode has the largest overpotential at typical operating current densities. By development of the electrocatalytic material used for the oxygen evolving electrode, great improvements in efficiency can be performed. In electrochemistry, rare metallic oxides RuO2 and IrO2 exhibit the best catalytic properties for the oxygen evolution reaction (OER) in acid electrolytes compared to other noble metals. RuO2 is the most active catalyst and IrO2 is the most stable catalyst. An oxide containing both elements is therefore expected to be a good catalyst for the OER. In this study IrxRu1-xO2 nanosized powder electrocatalysts for oxygen evolution reaction is synthesized by hydrolysis method. Cyclic voltammetry, anodic polarization and galvanostatic measurements were conducted in solution of 0.5 M H2SO4 to investigate electrocatalytic behavior and stability of the electrocatalyst. The mechanisms of the thermal decomposition process of RuCl3.nH2O and IrCl3.mH2O precursors to form oxide powders were studied by means of thermal gravity analysis (TGA). X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used analysis for determination of the crystallographic structure, morphology and catalysts particle size. Based on the given results, the IrxRu1-xO2 (x = 0.5 0.7) compounds were found to be more active than pure IrO2 and more stable than pure RuO2.

  16. Semimetallic MoP2: an active and stable hydrogen evolution electrocatalyst over the whole pH range

    Science.gov (United States)

    Pu, Zonghua; Saana Amiinu, Ibrahim; Wang, Min; Yang, Yushi; Mu, Shichun

    2016-04-01

    Developing efficient non-precious metal hydrogen evolution reaction (HER) electrocatalysts is a great challenge for sustainable hydrogen production from water. In this communication, for the first time, semimetallic MoP2 nanoparticle films on a metal Mo plate (MoP2 NPs/Mo) are fabricated through a facile two-step strategy. When used as a binder-free hydrogen evolution cathode, the as-prepared MoP2 NPs/Mo electrode exhibits superior HER catalytic activity at all pH values. At a current density of 10 mA cm-2, the catalyst displays overpotentials of 143, 211 and 194 mV in 0.5 M H2SO4, 1.0 M phosphate buffer solution and 1.0 M KOH, respectively. Furthermore, it exhibits excellent stability over a wide pH range. Thus, this in situ route opens up a new avenue for the fabrication of highly efficient, cost-effective and binder-free non-precious catalysts for water splitting and other electrochemical devices.Developing efficient non-precious metal hydrogen evolution reaction (HER) electrocatalysts is a great challenge for sustainable hydrogen production from water. In this communication, for the first time, semimetallic MoP2 nanoparticle films on a metal Mo plate (MoP2 NPs/Mo) are fabricated through a facile two-step strategy. When used as a binder-free hydrogen evolution cathode, the as-prepared MoP2 NPs/Mo electrode exhibits superior HER catalytic activity at all pH values. At a current density of 10 mA cm-2, the catalyst displays overpotentials of 143, 211 and 194 mV in 0.5 M H2SO4, 1.0 M phosphate buffer solution and 1.0 M KOH, respectively. Furthermore, it exhibits excellent stability over a wide pH range. Thus, this in situ route opens up a new avenue for the fabrication of highly efficient, cost-effective and binder-free non-precious catalysts for water splitting and other electrochemical devices. Electronic supplementary information (ESI) available: Experimental section and figures. See DOI: 10.1039/c6nr00820h

  17. A corrosion resistant cerium oxide based coating on aluminum alloy 2024 prepared by brush plating

    Energy Technology Data Exchange (ETDEWEB)

    Tang Junlei; Han Zhongzhi [School of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Zuo Yu, E-mail: zuoy@mail.buct.edu.cn [School of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Tang Yuming [School of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)

    2011-01-15

    Cerium oxide based coatings were prepared on AA2024 Al alloy by brush plating. The characteristic of this technology is that hydrogen peroxide, which usually causes the plating solution to be unstable, is not necessary in the plating electrolyte. The coating showed laminated structures and good adhesive strength with the substrate. X-ray diffraction and X-ray photoelectron spectroscopy analysis showed that the coatings were composed of Ce(III) and Ce(IV) oxides. The brush plated coatings on Al alloys improved corrosion resistance. The influence of plating parameters on structure and corrosion resistance of the cerium oxide based coating was studied.

  18. Correlating microstructure and activity for polysulfide reduction and oxidation at WS2 electrocatalysts

    DEFF Research Database (Denmark)

    Stephens, Ifan E.L.; Ducati, Caterina; Fray, Derek J.

    2013-01-01

    The polysulfide reduction and oxidation activity of WS2 electrocatalysts was studied. This was undertaken with a specific view to improve the efficiency of the polysulfide-bromine redox flow battery, for large scale energy storage. Using data from the literature, it is estimated that the catalyst...

  19. Efficient ceramic anodes infiltrated with binary and ternary electrocatalysts for SOFCs operating at low temperatures

    DEFF Research Database (Denmark)

    Abdul Jabbar, Mohammed Hussain; Høgh, Jens Valdemar Thorvald; Zhang, Wei;

    2012-01-01

    the binary Pd–CGO and Pt–CGO due to the particle coarsening of Ni nanoparticles. High resolution transmission electron microscopic analysis on the best performing Ni–Pt–CGO electrocatalyst infiltrated anode reveals the formation of Ni–Pt nanocrystalline alloy and a homogenous distribution of nanoparticles...

  20. High-Throughput Bubble Screening Method for Combinatorial Discovery of Electrocatalysts for Water Splitting

    OpenAIRE

    Xiang, Chengxiang; Suram, Santosh K.; Haber, Joel A.; Guevarra, Dan W.; Soedarmadji, Ed; Jin, Jian; Gregoire, John M.

    2014-01-01

    Combinatorial synthesis and screening for discovery of electrocatalysts has received increasing attention, particularly for energy-related technologies. High-throughput discovery strategies typically employ a fast, reliable initial screening technique that is able to identify active catalyst composition regions. Traditional electrochemical characterization via current–voltage measurements is inherently throughput-limited, as such measurements are most readily performed by serial screening. Pa...

  1. Immobilization of molecular cobalt electrocatalyst by hydrophobic interaction with hematite photoanode for highly stable oxygen evolution

    KAUST Repository

    Joya, Khurram

    2015-07-15

    A unique modification of a hematite photoanode with perfluorinated Co-phthalocyanine (CoFPc) by strong binding associated with hydrophobic interaction is demonstrated. The resultant molecular electrocatalyst – hematite photoanode hybrid material showed significant onset shift and high stability for photoelectrochemical oxidation evolution reaction (OER).

  2. MethylC-seq library preparation for base-resolution whole-genome bisulfite sequencing.

    Science.gov (United States)

    Urich, Mark A; Nery, Joseph R; Lister, Ryan; Schmitz, Robert J; Ecker, Joseph R

    2015-03-01

    Current high-throughput DNA sequencing technologies enable acquisition of billions of data points through which myriad biological processes can be interrogated, including genetic variation, chromatin structure, gene expression patterns, small RNAs and protein-DNA interactions. Here we describe the MethylC-sequencing (MethylC-seq) library preparation method, a 2-d protocol that enables the genome-wide identification of cytosine DNA methylation states at single-base resolution. The technique involves fragmentation of genomic DNA followed by adapter ligation, bisulfite conversion and limited amplification using adapter-specific PCR primers in preparation for sequencing. To date, this protocol has been successfully applied to genomic DNA isolated from primary cell culture, sorted cells and fresh tissue from over a thousand plant and animal samples.

  3. Preparations, properties and applications of chitosan based nanofibers fabricated by electrospinning

    Directory of Open Access Journals (Sweden)

    2011-04-01

    Full Text Available Chitosan is soluble in most acids. The protonation of the amino groups on the chitosan backbone inhibits the electrospinnability of pure chitosan. Recently, electrospinning of nanofibers based on chitosan has been widely researched and numerous nanofibers containing chitosan have been prepared by decreasing the number of the free amino groups of chitosan as the nanofibiers have enormous possibilities for better utilization in various areas. This article reviews the preparations and properties of the nanofibers which were electrospun from pure chitosan, blends of chitosan and synthetic polymers, blends of chitosan and protein, chitosan derivatives, as well as blends of chitosan and inorganic nanoparticles, respectively. The applications of the nanofibers containing chitosan such as enzyme immobilization, filtration, wound dressing, tissue engineering, drug delivery and catalysis are also summarized in detail.

  4. Polylactide-based microspheres prepared using solid-state copolymerized chitosan and d,l-lactide.

    Science.gov (United States)

    Demina, T S; Akopova, T A; Vladimirov, L V; Zelenetskii, A N; Markvicheva, E A; Grandfils, Ch

    2016-02-01

    Amphiphilic chitosan-g-poly(d,l-lactide) copolymers have been manufactured via solid-state mechanochemical copolymerization and tailored to design polyester-based microspheres for tissue engineering. A single-step solid-state reactive blending (SSRB) using low-temperature co-extrusion has been used to prepare these copolymers. These materials have been valorized to stabilize microspheres processed by an oil/water emulsion evaporation technique. Introduction of the copolymers either in water or in the oil phase of the emulsion allowed to replace a non-degradable emulsifier typically used for microparticle preparation. To enhance cell adhesion, these copolymers were also tailored to bring amino-saccharide positively charged segments to the microbead surface. Size distribution, surface morphology, and total microparticle yield have been studied and optimized as a function of the copolymer composition. PMID:26652381

  5. Preparation of ferric-activated sludge-based adsorbent from biological sludge for tetracycline removal.

    Science.gov (United States)

    Yang, Xin; Xu, Guoren; Yu, Huarong; Zhang, Zhao

    2016-07-01

    Ferric activation was novelly used to produce sludge-based adsorbent (SBA) from biological sludge through pyrolysis, and the adsorbents were applied to remove tetracycline from aqueous solution. The pyrolysis temperature and mass ratio (activator/dried sludge) greatly influenced the surface area and pore characteristics of SBA. Ferric activation could promote the porous structure development of adsorbents, and the optimum preparation conditions were pyrolysis temperature 750°C and mass ratio (activator/dried sludge) 0.5. In batch experiments, ferric-activated SBA showed a higher adsorption capacity for tetracycline than non-activated SBA, because the enhanced mesoporous structure favored the diffusion of tetracycline into the pores, the iron oxides and oxygen-containing functional groups in the adsorbents captured tetracycline by surface complexation. The results indicate that ferric activation is an effective approach for preparing adsorbents from biological sludge to remove tetracycline, providing a potential option for waste resource recovery. PMID:27038265

  6. Preparation of Graphene Oxide-Based Hydrogels as Efficient Dye Adsorbents for Wastewater Treatment

    Science.gov (United States)

    Guo, Haiying; Jiao, Tifeng; Zhang, Qingrui; Guo, Wenfeng; Peng, Qiuming; Yan, Xuehai

    2015-06-01

    Graphene oxide (GO) sheets exhibit superior adsorption capacity for removing organic dye pollutants from an aqueous environment. In this paper, the facile preparation of GO/polyethylenimine (PEI) hydrogels as efficient dye adsorbents has been reported. The GO/PEI hydrogels were achieved through both hydrogen bonding and electrostatic interactions between amine-rich PEI and GO sheets. For both methylene blue (MB) and rhodamine B (RhB), the as-prepared hydrogels exhibit removal rates within about 4 h in accordance with the pseudo-second-order model. The dye adsorption capacity of the hydrogel is mainly attributed to the GO sheets, whereas the PEI was incorporated to facilitate the gelation process of GO sheets. More importantly, the dye-adsorbed hydrogels can be conveniently separated from an aqueous environment, suggesting potential large-scale applications of the GO-based hydrogels for organic dye removal and wastewater treatment.

  7. Preparation and characterization of plasticized high molecular weight PVC-based polymer electrolytes

    Indian Academy of Sciences (India)

    S Ramesh; Geok Bee Teh; Rong-Fuh Louh; Yong Kong Hou; Pung Yen Sin; Lim Jing Yi

    2010-02-01

    Poly(vinyl chloride) (PVC)-based polymer electrolytes films consisting of lithium trifluromethanesulfonate (LiCF3SO3)-ethylene carbonate (EC) were prepared by the solution-casting method. Ionic conductivities of the electrolytes have been determined by an impedance studies in the temperature range of 298–373 K. Complexation of the prepared electrolytes is studied by X-ray diffraction (XRD) analysis. Thermogravimetric analysis (TGA) was used to confirm the thermal stability of the polymer electrolytes. The conductivity–temperature plots were found to follow an Arrhenius nature. All these films are found to be thermally stable until 132–167°C.

  8. Zinc-oxide-based sorbents and processes for preparing and using same

    Science.gov (United States)

    Gangwal, Santosh Kumar; Turk, Brian Scott; Gupta, Raghubir Prasael

    2010-03-23

    Zinc oxide-based sorbents, and processes for preparing and using them are provided. The sorbents are preferably used to remove one or more reduced sulfur species from gas streams. The sorbents comprise an active zinc component, optionally in combination with one or more promoter components and/or one or more substantially inert components. The active zinc component is a two phase material, consisting essentially of a zinc oxide (ZnO) phase and a zinc aluminate (ZnAl.sub.2O.sub.4) phase. Each of the two phases is characterized by a relatively small crystallite size of typically less than about 500 Angstroms. Preferably the sorbents are prepared by converting a precursor mixture, comprising a precipitated zinc oxide precursor and a precipitated aluminum oxide precursor, to the two-phase, active zinc oxide containing component.

  9. Improved characterization of EV preparations based on protein to lipid ratio and lipid properties.

    Directory of Open Access Journals (Sweden)

    Xabier Osteikoetxea

    Full Text Available In recent years the study of extracellular vesicles has gathered much scientific and clinical interest. As the field is expanding, it is becoming clear that better methods for characterization and quantification of extracellular vesicles as well as better standards to compare studies are warranted. The goal of the present work was to find improved parameters to characterize extracellular vesicle preparations. Here we introduce a simple 96 well plate-based total lipid assay for determination of lipid content and protein to lipid ratios of extracellular vesicle preparations from various myeloid and lymphoid cell lines as well as blood plasma. These preparations included apoptotic bodies, microvesicles/microparticles, and exosomes isolated by size-based fractionation. We also investigated lipid bilayer order of extracellular vesicle subpopulations using Di-4-ANEPPDHQ lipid probe, and lipid composition using affinity reagents to clustered cholesterol (monoclonal anti-cholesterol antibody and ganglioside GM1 (cholera toxin subunit B. We have consistently found different protein to lipid ratios characteristic for the investigated extracellular vesicle subpopulations which were substantially altered in the case of vesicular damage or protein contamination. Spectral ratiometric imaging and flow cytometric analysis also revealed marked differences between the various vesicle populations in their lipid order and their clustered membrane cholesterol and GM1 content. Our study introduces for the first time a simple and readily available lipid assay to complement the widely used protein assays in order to better characterize extracellular vesicle preparations. Besides differentiating extracellular vesicle subpopulations, the novel parameters introduced in this work (protein to lipid ratio, lipid bilayer order, and lipid composition, may prove useful for quality control of extracellular vesicle related basic and clinical studies.

  10. Education of the impellent-plastic expressiveness at a stage of specialized base preparation in art gymnastics.

    Directory of Open Access Journals (Sweden)

    Kravchuk T.N.

    2010-12-01

    Full Text Available In the given article is proved and opened the technique of education of the impellent-plastic expressiveness at a stage of specialized base preparation in art gymnastics. Criteria and modern requirements to the impellent-plastic expressiveness of gymnasts are analyzed. Its basic components are defined: musical-rhythmic preparation; mastering by skills of expressive movement; choreographic preparation; studying of elements of national and ball dances.

  11. Semiconductor-Electrocatalyst Interfaces: Theory, Experiment, and Applications in Photoelectrochemical Water Splitting.

    Science.gov (United States)

    Nellist, Michael R; Laskowski, Forrest A L; Lin, Fuding; Mills, Thomas J; Boettcher, Shannon W

    2016-04-19

    Light-absorbing semiconductor electrodes coated with electrocatalysts are key components of photoelectrochemical energy conversion and storage systems. Efforts to optimize these systems have been slowed by an inadequate understanding of the semiconductor-electrocatalyst (sem|cat) interface. The sem|cat interface is important because it separates and collects photoexcited charge carriers from the semiconductor. The photovoltage generated by the interface drives "uphill" photochemical reactions, such as water splitting to form hydrogen fuel. Here we describe efforts to understand the microscopic processes and materials parameters governing interfacial electron transfer between light-absorbing semiconductors, electrocatalysts, and solution. We highlight the properties of transition-metal oxyhydroxide electrocatalysts, such as Ni(Fe)OOH, because they are the fastest oxygen-evolution catalysts known in alkaline media and are (typically) permeable to electrolyte. We describe the physics that govern the charge-transfer kinetics for different interface types, and show how numerical simulations can explain the response of composite systems. Emphasis is placed on "limiting" behavior. Electrocatalysts that are permeable to electrolyte form "adaptive" junctions where the interface energetics change during operation as charge accumulates in the catalyst, but is screened locally by electrolyte ions. Electrocatalysts that are dense, and thus impermeable to electrolyte, form buried junctions where the interface physics are unchanged during operation. Experiments to directly measure the interface behavior and test the theory/simulations are challenging because conventional photoelectrochemical techniques do not measure the electrocatalyst potential during operation. We developed dual-working-electrode (DWE) photoelectrochemistry to address this limitation. A second electrode is attached to the catalyst layer to sense or control current/voltage independent from that of the

  12. Semiconductor-Electrocatalyst Interfaces: Theory, Experiment, and Applications in Photoelectrochemical Water Splitting.

    Science.gov (United States)

    Nellist, Michael R; Laskowski, Forrest A L; Lin, Fuding; Mills, Thomas J; Boettcher, Shannon W

    2016-04-19

    Light-absorbing semiconductor electrodes coated with electrocatalysts are key components of photoelectrochemical energy conversion and storage systems. Efforts to optimize these systems have been slowed by an inadequate understanding of the semiconductor-electrocatalyst (sem|cat) interface. The sem|cat interface is important because it separates and collects photoexcited charge carriers from the semiconductor. The photovoltage generated by the interface drives "uphill" photochemical reactions, such as water splitting to form hydrogen fuel. Here we describe efforts to understand the microscopic processes and materials parameters governing interfacial electron transfer between light-absorbing semiconductors, electrocatalysts, and solution. We highlight the properties of transition-metal oxyhydroxide electrocatalysts, such as Ni(Fe)OOH, because they are the fastest oxygen-evolution catalysts known in alkaline media and are (typically) permeable to electrolyte. We describe the physics that govern the charge-transfer kinetics for different interface types, and show how numerical simulations can explain the response of composite systems. Emphasis is placed on "limiting" behavior. Electrocatalysts that are permeable to electrolyte form "adaptive" junctions where the interface energetics change during operation as charge accumulates in the catalyst, but is screened locally by electrolyte ions. Electrocatalysts that are dense, and thus impermeable to electrolyte, form buried junctions where the interface physics are unchanged during operation. Experiments to directly measure the interface behavior and test the theory/simulations are challenging because conventional photoelectrochemical techniques do not measure the electrocatalyst potential during operation. We developed dual-working-electrode (DWE) photoelectrochemistry to address this limitation. A second electrode is attached to the catalyst layer to sense or control current/voltage independent from that of the

  13. Evidence-based public health education as preparation for medical school.

    Science.gov (United States)

    Riegelman, Richard K; Garr, David R

    2008-04-01

    The Institute of Medicine has recommended that all undergraduates have access to public health education. An evidence-based public health framework including curricula such as "Public Health 101" and "Epidemiology 101" was recommended for all colleges and universities by arts and sciences, public health, and clinical health professions educators as part of the Consensus Conference on Undergraduate Public Health Education. These courses should foster critical thinking whereby students learn to broadly frame options, critically analyze data, and understand the uncertainties that remain. College-level competencies or learning outcomes in research literature reading, determinants of health, basic understanding of health care systems, and the synergies between health care and public health can provide preparation for medical education. Formally tested competencies could substitute for a growing list of prerequisite courses. Grounded in principles similar to those of evidence-based medicine, evidence-based public health includes problem description, causation, evidence-based recommendations for intervention, and implementation considering key issues of when, who, and how to intervene. Curriculum frameworks for structuring "Public Health 101" and "Epidemiology 101" are provided by the Consensus Conference that lay the foundation for teaching evidence-based public health as well as evidence-based medicine. Medical school preparation based on this foundation should enable the Clinical Prevention and Population Health Curriculum Framework, including the evidence base for practice and health systems and health policy, to be fully integrated into the four years of medical school. A faculty development program, curriculum guide, interest group, and clear student interest are facilitating rapid acceptance of the need for these curricula.

  14. Process to prepare stable trifluorostyrene containing compounds grafted to base polymers using a solvent/water mixture

    Science.gov (United States)

    Roelofs, Mark Gerrit; Yang, Zhen-Yu; Han, Amy Qi

    2010-06-15

    A fluorinated ion exchange polymer is prepared by grafting at least one grafting monomer derived from trifluorostyrene on to at least one base polymer in a organic solvent/water mixture. These ion exchange polymers are useful in preparing catalyst coated membranes and membrane electrode assemblies used in fuel cells.

  15. The University of Nebraska at Omaha/Westside Community Schools Competency Based, Field Oriented Teacher Preparation Program.

    Science.gov (United States)

    Bunsen, Dale M.

    Developmental activities and experiences of the University of Nebraska at Omaha/Omaha Westside Community Schools' five-year teacher preparation program are described. The program is designed to prepare classroom educators in a field-oriented, competency-based program involving a fifth year, partially-paid, pre-teaching experience. Program…

  16. Characterization of AZO and Ag based films prepared by RF magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Dagang [Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong (China); Jiang, Shouxiang, E-mail: kinor.j@polyu.edu.hk [Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong (China); Zhao, Hongmei [Department of Prosthodontics, The Affiliated Hospital of Qingdao University, Qingdao (China); Shang, Songmin; Chen, Zhuoming [Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong (China)

    2014-12-15

    Highlights: • Highly infrared reflective AZO and Ag based films were prepared. • Ag showed better crystallization on AZO film than on glass substrate. • Infrared reflection rate was inversely proportional to the film sheet resistance. • Film with infrared reflection of 97% in FIR region was acquired. - Abstract: Ag, AZO/Ag, Ag/AZO and AZO/Ag/AZO films were prepared on glass substrates by radio frequency (RF) magnetron sputtering technology. The prepared films were systematically investigated by X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), UV–visible spectrophotometer, a four-point probe system and Fourier Transform Infrared Spectroscopy. The results indicated that Ag inner layer starts forming a continuous film at the thickness of 10 nm and Ag layer presents superior crystallization on AZO substrate than that on glass substrate. The continuous Ag inner layer film provided the highest average visible transmittance of 85.4% (AZO/Ag/AZO). The lowest sheet resistance of 3.21 Ω/sq and the highest infrared reflection rate of 97% in FIR region can be obtained on AZO/Ag (15 nm)/AZO film. The high infrared reflection property of the AZO/Ag/AZO coating makes it a promising candidate for solar control films.

  17. Preparation and characterization of novel antibacterial castor oil-based polyurethane membranes for wound dressing application.

    Science.gov (United States)

    Yari, Abbas; Yeganeh, Hamid; Bakhshi, Hadi; Gharibi, Reza

    2014-01-01

    Preparation of novel antibacterial and cytocompatible polyurethane membranes as occlusive dressing, which can provide moist and sterile environment over mild exudative wounds is considered in this work. In this regard, an epoxy-terminated polyurethane (EPU) prepolymer based on castor oil and glycidyltriethylammonium chloride (GTEAC) as a reactive bactericidal agent were synthesized. Polyurethane membranes were prepared through cocuring of EPU and different content of GTEAC with 1,4-butane diamine. The physical and mechanical properties, as well as cytocompatibility and antibacterial performance of prepared membranes were studied. Depending on their chemical formulations, the equilibrium water absorption and water vapor transmission rate values of the membranes were in ranges of 3-85% and 53-154g m(-2) day(-1), respectively. Therefore, these transparent membranes can maintain for a long period the moist environment over the wounds with low exudates. Detailed cytotoxicity analysis of samples against mouse L929 fibroblast and MCA-3D keratinocyte cells showed good level of cytocompatibility of membranes after purification via extraction of residual unreacted GTEAC moieties. The antibacterial activity of the membranes against Escherichia coli and Staphylococcus aureus bacteria was also studied. The membrane containing 50% GTEAC exhibited an effective antibacterial activity, while showed acceptable cytocompatibility and therefore, can be applied as an antibacterial occlusive wound dressing.

  18. Preparation, Properties, and Self-Assembly Behavior of PTFE-Based Core-Shell Nanospheres

    Directory of Open Access Journals (Sweden)

    Katia Sparnacci

    2012-01-01

    Full Text Available Nanosized PTFE-based core-shell particles can be prepared by emulsifier-free seed emulsion polymerization technique starting from spherical or rod-like PTFE seeds of different size. The shell can be constituted by the relatively high Tg polystyrene and polymethylmethacrylate as well as by low Tg polyacrylic copolymers. Peculiar thermal behavior of the PTFE component is observed due to the high degree of PTFE compartmentalization. A very precise control over the particle size can be exerted by properly adjusting the ratio between the monomers and the PTFE seed. In addition, the particle size distribution self-sharpens as the ratio monomer/PTFE increases. Samples with uniformity ratios suited to build 2D and 3D colloidal crystals are easily prepared. In particular, 2D colloidal crystal of spheres leads to very small 2D nanostructuration, useful for the preparation of masks with a combination of nanosphere lithography and reactive ion etching. 3D colloidal crystals were also obtained featuring excellent opal quality, which is a direct consequence of the monodispersity of colloids used for their growth.

  19. Building Energy Storage Panel Based on Paraffin/Expanded Perlite: Preparation and Thermal Performance Study

    Directory of Open Access Journals (Sweden)

    Xiangfei Kong

    2016-01-01

    Full Text Available This study is focused on the preparation and performance of a building energy storage panel (BESP. The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP, which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM was incorporated into expanded perlite (EP through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC, scanning electron microscope (SEM, best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1 the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2 the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3 in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency.

  20. Highly Stretchable and Sensitive Strain Sensor Based on Facilely Prepared Three-Dimensional Graphene Foam Composite.

    Science.gov (United States)

    Li, Jinhui; Zhao, Songfang; Zeng, Xiaoliang; Huang, Wangping; Gong, Zhengyu; Zhang, Guoping; Sun, Rong; Wong, Ching-Ping

    2016-07-27

    Wearable strain sensors with excellent stretchability and sensitivity have emerged as a very promising field which could be used for human motion detection and biomechanical systems, etc. Three-dimensional (3D) graphene foam (GF) has been reported before for high-performance strain sensors, however, some problems such as high cost preparation, low sensitivity, and stretchability still remain. In this paper, we report a highly stretchable and sensitive strain sensor based on 3D GF and polydimethylsiloxane (PDMS) composite. The GF is prepared by assembly process from graphene oxide via a facile and scalable method and possesses excellent mechanical property which facilitates the infiltration of PDMS prepolymer into the graphene framework. The as-prepared strain sensor can be stretched as high as 30% of its original length and the gauge factor of this sensor is as high as 98.66 under 5% of applied strain. Moreover, the strain sensor shows long-term stability in 200 cycles of stretching-relaxing. Implementation of the device for monitoring the bending of elbow and finger results in reproducibility and various responses in the form of resistance change. Thus, the developed strain sensors exhibit great application potential in fields of biomechanical systems and human-interactive applications. PMID:27384320

  1. General Self-Assembly Route toward Sparsely Studded Noble-Metal Nanocrystals inside Graphene Hollow Sphere Network for Ultrastable Electrocatalyst Utilization.

    Science.gov (United States)

    Lou, Xinyuan; Wu, Ping; Zhang, Anping; Zhang, Ruoqing; Tang, Yawen

    2015-09-16

    Herein, we rationally design and construct a novel type of sparsely studded noble-metal nanocrystals inside graphene hollow sphere network (abbreviated as noble-metal@G HSN) through an electrostatic-attraction-directed self-assembly approach. The formation of Pt@G and Pd@G hollow sphere networks have been illustrated as examples using SiO2 spheres as templates. Moreover, the electrocatalytic performance of the Pt@G HSN for methanol oxidation reaction has been examined as a proof-of-concept demonstration of the compositional and structural superiorities of noble-metal@G HSN toward electrocatalyst utilization. The as-prepared Pt@G HSN manifests higher catalytic activity and markedly enhanced long-term durability in comparison with commercial Pt/C catalyst. PMID:26305582

  2. Preparation of liquefied wood-based resins and their application in molding material

    Institute of Scientific and Technical Information of China (English)

    Zhang Qiu-hui; Zhao Guang-jie; Yu Li-li; Jie Shu-jun

    2007-01-01

    To investigate value in use of liquefied wood-based resin applications in molding material, Chinese fir (Cunninghamia lanceolata) and poplar (Populus tomentosa) wood meal were liquefied in phenol. The reactant was co-condensed with formaldehyde to obtain liquefied wood-based resin. For this paper, we investigated the characterization of the resin and its application in molding material. The result shows that the basic properties of liquefied wood-based resin were satisfactory; the bonding strength of plywood prepared with liquefied Chinese fir and liquefied poplar resin can reach 1.54 and 1.00 MPa, respectively. The compression strengths of the molding material prepared with two kinds of liquefied wood resin were 73.01 and 73.58 MPa, almost the same as that of PF resin molding material. The limiting volume swelling of molding material made with liquefied Chinese resin and liquefied poplar resin were 8.5% and 8.3%, thickness swelling rates of water absorption were 3.3% and 4.2%, and the maximum weight ratios of water absorption were 25.9% and 26.2%, respectively. The soil burial test result shows that the weight loss rate of the molding materials made with liquefied Chinese resin and liquefied poplar resin were 8.3% and 9.1% and that of the PF resin molding material was 7.9%. After the soil internment test, the reduction ratio of compression strength of the two kinds of molding material achieved 16.9%and 17.7%, while that of the PF resin molding material was 15.4%. The test results of wood fungi inoculation on the three surfaces of the molding material indicate the breeding rate of molding material prepared with liquefied Chinese resin and liquefied poplar resin were at level 4 and that of PF resin molding material was at level 1 of the ISO standard.

  3. Photoelectrocatalytic hydrogen production using nanoparticulate titania and a novel Pt/carbon electrocatalyst: The concept of the "Photoelectrocatalytic Leaf"

    Science.gov (United States)

    Pop, Lucian-Cristian; Dracopoulos, Vassilios; Lianos, Panagiotis

    2015-04-01

    Photoelectrocatalytic hydrogen production was realized my means of a double electrode carrying photocatalyst and electrocatalyst, deposited side by side on an FTO electrode, acting as a "Photoelectrocatalytic Leaf". As photocatalyst we used plain commercial nanoparticulate titania and as electrocatalyst a conductive carbon film made by a commercial carbon paste enriched with a small quantity of Pt nanoparticles (0.0134 mg/cm2). This quantity of Pt is much smaller than used in other applications and it may be further optimized. Hydrogen was produced in an alkaline environment in the presence of ethanol acting as sacrificial agent. A few variants of electrode geometry were studied in order to set the basic terms for efficient hydrogen production. It was found that optimal electrode geometry necessitates a much larger area for photocatalyst coverage than electrocatalyst and that it is preferable to divide photocatalyst and electrocatalyst areas in alternating zones.

  4. Pt monolayer shell on hollow Pd core electrocatalysts: Scale up synthesis, structure, and activity for the oxygen reduction reaction

    Directory of Open Access Journals (Sweden)

    Vukmirovic Miomir B.

    2013-01-01

    Full Text Available We report on synthesis, characterization and the oxygen reduction reaction (ORR kinetics of Pt monolayer shell on Pd(hollow, or Pd-Au(hollow core electrocatalysts. Comparison between the ORR catalytic activity of the electrocatalysts with hollow cores and those of Pt solid and Pt hollow nanoparticles has been obtained using the rotating disk electrode technique. Hollow nanoparticles were made using Ni or Cu nanoparticles as sacrificial templates. The Pt ORR specific and mass activities of the electrocatalysts with hollow cores were found considerably higher than those of the electrocatalysts with the solid cores. We attribute this enhanced Pt activity to the smooth surface morphology and hollow-induced lattice contraction, in addition to the mass-saving geometry of hollow particles.

  5. Preparation and Properties of ε-Fe3N-Based Magnetic Fluid

    Directory of Open Access Journals (Sweden)

    Huang Wei

    2008-01-01

    Full Text Available AbstractIn this work, ε-Fe3N nanoparticles and ε-Fe3N-based magnetic fluid were synthesized by chemical reaction of iron carbonyl and ammonia gas. The size of ε-Fe3N nanoparticles was tested by TEM and XRD. Stable ε-Fe3N-based magnetic fluid was prepared by controlling the proper ratio of carrier liquid and surfactant. The saturation magnetization of stable ε-Fe3N-based magnetic fluid was calculated according to the volume fraction of the particles in the fluid. The result shows that both the calculated and measured magnetizations increase by increasing the particle concentration. With the increasing concentration of the ε-Fe3N particles, the measured value of the magnetic fluid magnetization gradually departs from the calculated magnetization, which was caused by agglomeration affects due to large volume fraction and large particle size.

  6. Preparation and Characterization of Er2O3 Nanocrystals by Schiff Base Salt Combustion Method

    Institute of Scientific and Technical Information of China (English)

    刘建华; 孙杰; 李松梅

    2003-01-01

    The nanocrystals Er2O3 were prepared by using a combustion method with Schiff base as a chelating agent. The Er(Ⅲ) coordanation compound of Schiff base, obtained from erbium nitrate and retinal Schiff base, underwent a combustion process and voluminous ashes formed when calcimining the complex in air. Pure cubic Er2O3 nanocrystals with a diameter of 13 nm were produced. The nanocrystals were homogeneous and rigid coacervation was not observed. The photoluminescence emission spectrum of the erbium(Ⅲ) oxide nanocrystals shows that it has a characteristic peak at 1.54 μm, and some other shoulder peaks appear on both sides of the main peak.

  7. Preparation and characterization of bio-based hybrid film containing chitosan and silver nanowires.

    Science.gov (United States)

    Shahzadi, Kiran; Wu, Lin; Ge, Xuesong; Zhao, Fuhua; Li, Hui; Pang, Shuping; Jiang, Yijun; Guan, Jing; Mu, Xindong

    2016-02-10

    A bio-based hybrid film containing chitosan (CS) and silver nanowires (AgNWs) has been prepared by a simple casting technique. X-ray diffraction (XRD), Fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and UV-visible spectroscopy were employed to characterize the structure of bio-based film. The bio-based hybrid film showed unique performance compared with bare chitosan film. The incorporated nano-silver could improve the strength properly. The results revealed that AgNWs in CS film, improved its tensile strength more than 62% and Young modulus 55% compared with pure chitosan film. On the other hand tensile strength was increased 36.7% with AgNPs. Importantly, the film also exhibited conductivity and antibacterial properties, which may expand its future application.

  8. Metal Complexes of Macrocyclic Schiff-Base Ligand: Preparation, Characterisation, and Biological Activity

    Science.gov (United States)

    Ahmed, Riyadh M.; Yousif, Enaam I.; Hasan, Hasan A.; Al-Jeboori, Mohamad J.

    2013-01-01

    A new macrocyclic multidentate Schiff-base ligand Na4L consisting of two submacrocyclic units (10,21-bis-iminomethyl-3,6,14,17-tricyclo[17.3.1.18,12]tetracosa-1(23),2,6,8,10,12(24),13,17,19,21,-decaene-23,24-disodium) and its tetranuclear metal complexes with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) are reported. Na4L was prepared via a template approach, which is based on the condensation reaction of sodium 2,4,6-triformyl phenolate with ethylenediamine in mole ratios of 2 : 3. The tetranuclear macrocyclic-based complexes were prepared from the reaction of the corresponding metal chloride with the ligand. The mode of bonding and overall geometry of the compounds were determined through physicochemical and spectroscopic methods. These studies revealed tetrahedral geometries about Mn, Co, and Zn atoms. However, square planar geometries have been suggested for NiII and CuII complexes. Biological activity of the ligand and its metal complexes against Gram positive bacterial strain Staphylococcus aureus and Gram negative bacteria Escherichia coli revealed that the metal complexes become more potentially resistive to the microbial activities as compared to the free ligand. However, these metal complexes do not exhibit any effects on the activity of Pseudomonas aeruginosa bacteria. There is therefore no inhibition zone. PMID:23935414

  9. Preparation of Polyacrylate-based Conductive Coatings and Its PTC Effect

    Institute of Scientific and Technical Information of China (English)

    XIONG Chuan-xi; HU Hui-rong; ZHOU Zhi-yong; ZHANG Yi; DONG Li-jie

    2004-01-01

    Polyacrylate- based conductive coatings were prepared from polyacrylate emulsion as matrix andcarbon black (CB) whose surface was treated with titanate coupling agent as conducting particles. One kind oforganic crystal was added to study its effects on the electrical conductivity and PTC ( positive temperature coeffi-cient ) effect of the conductive coatings. Experimental results show that the coatings containing only polyacrylateemulsion and CB exhibit an excellent electrical conductivity but bad PTC effect, and when organic crystal is added,PTC effect is characterized and can increase by 2 orders of magtitude. The critical transformation temperature ofpolyacrylate emulsion/CB PTC composites is decided by melting point of organic crystals.

  10. PREPARATION AND CHARACTERIZATION OF MODIFIED STARCH-BASED BIODEGRADABLE MATERIALS EINFORCED WITH PULP FIBER

    Institute of Scientific and Technical Information of China (English)

    Lingfang Ji; Shucai Li

    2004-01-01

    Native com starch and hydroxypropyl starch (HPS)based plastic films were prepared using the short pulp fiber as reinforcement and the glycerol as the plasticizer. The results of tensile test showed that the tensile strength and the elongation at break increased with the pulp contents. With the glycerol contents,the elongation at break increased considerably, but the tensile strength decreased. The water uptake of the films decreased with the pulp contents and hydroxypropylation, but increased with the glycerol contents. So it is concluded that the films was reinforced by pulp fiber and hydroxypropylation.

  11. PREPARATION AND CHARACTERIZATION OF MODIFIED STARCH-BASED BIODEGRADABLE MATERIALS REINFORCED WITH PULP FIBER

    Institute of Scientific and Technical Information of China (English)

    LingfangJi; ShucaiLi

    2004-01-01

    Native corn starch and hydroxypropyl starch (HPS) based plastic films were prepared using the short pulp fiber as reinforcement and the glycerol as the plasticizer. The results of tensile test showed that the tensile strength and the elongation at break increased with the pulp contents. With the glycerol contents, the elongation at break increased considerably, but the tensile strength decreased. The water uptake of the films decreased with the pulp contents and hydroxypropylation, but increased with the glycerol contents. So it is concluded that the films was reinforced by pulp fiber and hydroxypropylation.

  12. Preparation of GaN-on-Si based thin-film flip-chip LEDs

    Institute of Scientific and Technical Information of China (English)

    Zhang Shaohua; Feng Bo; Sun Qian; Zhao Hanmin

    2013-01-01

    GaN based MQW epitaxial layers were grown on Si (111) substrate by MOCVD using A1N as the buffer layer.High light extraction LEDs were prepared by substrate transferring technology in combination with thin-film and flip-chip design.The blue and white 1.1 × 1.1 mm2 LED lamps are measured.The optical powers and external quantum efficiency for silicone encapsulated blue lamp are 546 mW,and 50.3% at forward current of 350 mA,while the photometric light output for a white lamp packaged with standard YAG phosphor is 120.1 lm.

  13. Preparation and application of highly porous aerogel-based bioactive materials in dentistry

    Science.gov (United States)

    Kuttor, Andrea; Szalóki, Melinda; Rente, Tünde; Kerényi, Farkas; Bakó, József; Fábián, István; Lázár, István; Jenei, Attila; Hegedüs, Csaba

    2014-03-01

    In this study, the possibility of preparation and application of highly porous silica aerogel-based bioactive materials are presented. The aerogel was combined with hydroxyapatite and β-tricalcium phosphate as bioactive and osteoinductive agents. The porosity of aerogels was in the mesoporous region with a maximum pore diameter of 7.4 and 12.7 nm for the composite materials. The newly developed bioactive materials were characterized by scanning electron microscopy. The in vitro biological effect of these modified surfaces was also tested on SAOS-2 osteogenic sarcoma cells by confocal laser scanning microscopy.

  14. Cavity-based single atom preparation and high-fidelity hyperfine state readout

    OpenAIRE

    Gehr R.; Volz J.; Dubois G.; Steinmetz T.; Colombe Y.; Lev B.L.; Long R.; Esteve J.; Reichel J.

    2010-01-01

    We prepare and detect the hyperfine state of a single 87Rb atom coupled to a fiber-based high finesse cavity on an atom chip. The atom is extracted from a Bose-Einstein condensate and trapped at the maximum of the cavity field, resulting in a reproducibly strong atom-cavity coupling. We use the cavity reflection and transmission signal to infer the atomic hyperfine state with a fidelity exceeding 99.92% in a read-out time of 100 microseconds. The atom is still trapped after detection.

  15. Preparation and Properties of Biocomposite Based on Natural Rubber and Bagasse Nanocellulose

    Directory of Open Access Journals (Sweden)

    Jarnthong Methakarn

    2015-01-01

    Full Text Available Biocomposite based on natural rubber (NR and bagasse nanocellulose (BNC was prepared in latex state. The mechanical, morphological and thermal properties of NR/BNC biocomposite were investigated. It was found that the addition of 3 wt% of BNC in NR film caused significant increase in modulus at 100% and 300% elongations and improved thermal stability of NR/BNC biocomposite. However, the strength at break and elongation at break of the biocomposite were not enhanced correlating to the morphological result obtained from scanning electron microscope (SEM.

  16. Thermo-optically driven adaptive mirror based on thermal expansion: preparation and resolution

    Science.gov (United States)

    Reinert, Felix; Lüthy, W.

    2005-12-01

    A thermo-optically driven adaptive mirror is presented. It is based on the thermal expansion of a thin film heated with a light pattern. We describe a procedure for the preparation of a silicon elastomer with a high-quality optical surface. This material, Sylgard 184, has a high linear thermal expansion coefficient of 3.1μ10-4 K-1. Surface modulations are recorded in an interferometer. Modulations of 350 nm result at an intensity of 370 mW/cm2. The resolution is measured with a line pattern. The contrast drops to 30 % at 1.6 line pairs per millimeter (lp/mm).

  17. Simple Method for the Preparation of Composites Based on PA6 and Partially Exfoliated Graphite

    Directory of Open Access Journals (Sweden)

    Orietta Monticelli

    2012-01-01

    Full Text Available In the present work, the preparation of composite systems based on polyamide 6 (PA6 and exfoliated graphite was attempted by applying a simple procedure, which consists of a preliminary dispersion/exfoliation of graphite in the monomer, namely, ɛ-caprolactam (CL, and a subsequent polymerization of the above system. Atomic force microscopy (AFM demonstrated specific interactions between CL and graphite surface. The dispersion of graphite in the monomer and polymer was assessed by scanning (SEM and transmission (TEM electron microscopy, while mechanical tests allowed to evaluate the influence of graphite on the polymer properties.

  18. Fast preparation and thermal transport property of TiCoSb-based half-Heusler compounds

    Institute of Scientific and Technical Information of China (English)

    Xie Wen-Jie; Tang Xin-Feng; Zhang Qing-Jie

    2007-01-01

    TiCoSb-based half-Heusler compounds with the substitution of Zr for Ti have been prepared quickly by combining high-energy ball milling method with spark plasma sintering technique, and their thermal transport properties have been investigated. With the increase of the concentration of Zr, the thermal conductivity of Ti1-xZrxCoSb compounds decreases significantly. Compared with the thermal conductivity of TiCoSb compound, that of Ti0.5Zr0.5CoSb decreases by 200% at 1000 K.

  19. Heating Treated Carbon Nanotubes As Highly Active Electrocatalysts for Oxygen Reduction Reaction

    International Nuclear Information System (INIS)

    Graphical abstract: Heating treatment for multi-walled carbon nanotubes in the air introduces abundant structure defects which improve catalytic performances for oxygen reduction reaction (ORR). There is a positive correlation between the defect levels and ORR activities. The product shows better methanol tolerance and long-term durability than commercial Pt/C which makes it applicable in fuel cells. - Abstract: Carbon nanotubes (CNTs) have been widely developed for electrochemical energy conversion and storage devices for replacement of high-cost Pt-based catalysts. In this paper, a simple and convenient method is developed for improving the catalytic activity of CNTs in a controlled way. By simple heating treatment in the air, the multi-walled carbon nanotubes (MWCNTs) change with special morphologies, compositions and abundant defects (denoted as h-CNT). Those defects significantly improve the electrocatalytic performances for oxygen reduction reaction (ORR) which proceeds in a nearly four-electron pathway. The heating conditions have important effects on the structures and defect properties of h-CNTs which show a positive correlation between the defect levels and ORR performances. The small amounts of iron residues originated from nanotube growth and nitrogen doping during heating treatment also contribute to some catalytic activity. The inner walls of h-CNT remain intact during heating treatment and provide sufficient conductivity which facilitates charge transport during ORR. The h-CNT electrocatalyst shows better methanol tolerance and long-term durability than commercial Pt/C in alkaline media which makes it an alternative cathode catalyst in fuel cells

  20. Kinetic Analysis of Competitive Electrocatalytic Pathways: New Insights into Hydrogen Production with Nickel Electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Wiedner, Eric S.; Brown, Houston J.; Helm, Monte L.

    2016-01-20

    The hydrogen production electrocatalyst Ni(PPh2NPh2)22+ (1) is capable of traversing multiple electrocatalytic pathways. When using dimethylformamidium, DMF(H)+, the mechanism of formation of H2 catalyzed by 1 changes from an ECEC to an EECC mechanism as the potential approaches the Ni(I/0) couple. Two recent electrochemical methods, current-potential analysis and foot-of-the-wave analysis (FOWA), were performed on 1 to measure the detailed chemical kinetics of the competing ECEC and EECC pathways. A sensitivity analysis was performed on the electrochemical methods using digital simulations to gain a better understanding of their strengths and limitations. Notably, chemical rate constants were significantly underestimated when not accounting for electron transfer kinetics, even when electron transfer was fast enough to afford a reversible non-catalytic wave. The EECC pathway of 1 was found to be faster than the ECEC pathway under all conditions studied. Using buffered DMF: DMF(H)+ mixtures led to an increase in the catalytic rate constant (kobs) of the EECC pathway, but kobs for the ECEC pathway did not change when using buffered acid. Further kinetic analysis of the ECEC path revealed that added base increases the rate of isomerization of the exo-protonated Ni(0) isomers to the catalytically active endo-isomers, but decreases the net rate of protonation of Ni(I). FOWA on 1 did not provide accurate rate constants due to incomplete reduction of the exo-protonated Ni(I) intermediate at the foot of the wave, but FOWA could be used to estimate the reduction potential of this previously undetected intermediate. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  1. Electrocatalysts having platium monolayers on palladium, palladium alloy, and gold alloy core-shell nanoparticles, and uses thereof

    Science.gov (United States)

    Adzic, Radoslav; Mo, Yibo; Vukmirovic, Miomir; Zhang, Junliang

    2010-12-21

    The invention relates to platinum-coated particles useful as fuel cell electrocatalysts. The particles are composed of a noble metal or metal alloy core at least partially encapsulated by an atomically thin surface layer of platinum atoms. The invention particularly relates to such particles having a palladium, palladium alloy, gold alloy, or rhenium alloy core encapsulated by an atomic monolayer of platinum. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

  2. Synthesis of platinum nanoparticle electrocatalysts by atomic layer deposition

    Science.gov (United States)

    Lubers, Alia Marie

    successful hydrogen pumping catalysts, comparable to a commercial Pt/C catalyst. Synthesized Pt/C materials were also used as PEMFC catalysts. We found the ALD catalysts with lower platinum loading to be competitive with a commercial fuel cell catalyst, especially when exhibiting similar platinum particle characteristics. The functionalized carbon helped produce smaller and more dispersed platinum particles; however, it encouraged carbon corrosion within an electrode, severing electrical connections and lowering energy production. The most suitable chemistry for competitive Pt/C catalysts was produced by platinum ALD on unmodified carbon using hydrogen as a reactant. ALD is a promising method for fabricating electrocatalysts, which could help fuel cells become an economically viable alternative to fossil fuels.

  3. Easy synthesis approach of Pt-nanoparticles on polyaniline surface: an efficient electro-catalyst for methanol oxidation reaction

    Science.gov (United States)

    Mondal, Sanjoy; Malik, Sudip

    2016-10-01

    A facile room temperature and surfactant free synthesis of platinum nanoparticles (Pt-NPs) on benzene tetra-carboxylic acid doped polyaniline (BDP) tube has been successfully demonstrated by solution dipping method. Preparation of Pt-NPs has been done through a red-ox reaction between BDP tubes and Pt-salt, as BDP itself acts as nontoxic reducing agent as well as template cum stabilizer for Pt-NPs. In BDP@Pt composites, ∼2.5 ± 0.5 nm spherical shaped Pt-NPs as observed from TEM studies are nicely decorated on the surface of BDP. The population or the loading density of Pt-NPs on BDP tube is greatly controlled by changing the w/w ratio of BDP to H2PtCl6. Synthesized BDP@Pt composites are subsequently employed as an efficient electro-catalyst for methanol oxidation reaction (MOR) in acidic medium. Furthermore, the observed catalytic activity is consequently ∼12 times higher than that of commercially available Pt/C catalyst. Depending on the loading density of Pt-NPs on BDP tubes, the efficiency and carbon monoxide (CO) tolerance ability of composites have been explored.

  4. Magnesiothermic synthesis of sulfur-doped graphene as an efficient metal-free electrocatalyst for oxygen reduction

    Science.gov (United States)

    Wang, Jiacheng; Ma, Ruguang; Zhou, Zhenzhen; Liu, Guanghui; Liu, Qian

    2015-01-01

    Efficient metal-free electrocatalysts for oxygen reduction reaction (ORR) are highly expected in future low-cost energy systems. We have successfully prepared crumpled, sheet-like, sulfur-doped graphene by magnesiothermic reduction of easily available, low-cost, nontoxic CO2 (in the form of Na2CO3) and Na2SO4 as the carbon and sulfur sources, respectively. At high temperature, Mg can reduce not only carbon in the oxidation state of +4 in CO32− to form graphene, but also sulfur in SO42− from its highest (+6) to lowest valence which was hybridized into the carbon sp2 framework. Various characterization results show that sulfur-doped graphene with only few layers has an appropriate sulfur content, hierarchically robust porous structure, large surface area/pore volume, and highly graphitized textures. The S-doped graphene samples exhibit not only a high activity for ORR with a four-electron pathway, but also superior durability and tolerance to MeOH crossover to 40% Pt/C. This is mainly ascribed to the combination of sulfur-related active sites and hierarchical porous textures, facilitating fast diffusion of oxygen molecules and electrolyte to catalytic sites and release of products from the sites. PMID:25790856

  5. LANDSAT Digital Data Base Preparation for the Pennsylvania Defoliation Application Pilot Test

    Science.gov (United States)

    Mcleod, R. G.; Zobrist, A. L.

    1982-01-01

    A LANDSAT digital mosaic data base for the State of Pennsylvania was prepared for use in the development of an automated system to annually estimate the extent and severity of Gypsy Moth defoliation of hardward forests. The techniques for detecting the defoliation and development of a geographic information system (GIS) to assess damage is being developed jointly by NASA/Goddard Space Flight Center and Pennsylvania State University using the JPL prepared mosaic base. The JPL processing involved the use of ground control points from the Master Data Processor for planimetric control, resampling of the LANDSAT data to 57 x 57 meter pixels, realignment to north, and reprojection to the Universal Transverse Mercator (UTM) projection in UTM zones 17 and 18. The completed mosaic for each UTM zone was subdivided into 1 degree of latitude by 2 degrees of longitude quadrangles for easy data handling. Consideration is given to the issues of mapping standards, sensor and spacecraft platform characteristics, and their implication to geographic information systems operation. Methods for obtaining measures of accuracy for LANDSAT mosaics are reviewed.

  6. Direct investigation of (sub-) surface preparation artifacts in GaAs based materials by FIB sectioning.

    Science.gov (United States)

    Belz, Jürgen; Beyer, Andreas; Torunski, Torsten; Stolz, Wolfgang; Volz, Kerstin

    2016-04-01

    The introduction of preparation artifacts is almost inevitable when producing samples for (scanning) transmission electron microscopy ((S)TEM). These artifacts can be divided in extrinsic artifacts like damage processes and intrinsic artifacts caused by the deviations from the volume strain state in thin elastically strained material systems. The reduction and estimation of those effects is of great importance for the quantitative analysis of (S)TEM images. Thus, optimized ion beam preparation conditions are investigated for high quality samples. Therefore, the surface topology is investigated directly with atomic force microscopy (AFM) on the actual TEM samples. Additionally, the sectioning of those samples by a focused ion beam (FIB) is used to investigate the damage depth profile directly in the TEM. The AFM measurements show good quantitative agreement of sample height modulation due to strain relaxation to finite elements simulations. Strong indications of (sub-) surface damage by ion beams are observed. Their influence on high angle annular dark field (HAADF) imaging is estimated with focus on thickness determination by absolute intensity methods. Data consolidation of AFM and TEM measurements reveals a 3.5nm surface amorphization, negligible surface roughness on the scale of angstroms and a sub-surface damage profile in the range of up to 8.0nm in crystalline gallium arsenide (GaAs) and GaAs-based ternary alloys. A correction scheme for thickness evaluation of absolute HAADF intensities is proposed and applied for GaAs based materials. PMID:26855206

  7. The Use of an Edible Mushroom-Derived Renewable Carbon Material as a Highly Stable Electrocatalyst towards Four-Electron Oxygen Reduction

    Directory of Open Access Journals (Sweden)

    Chaozhong Guo

    2015-12-01

    Full Text Available The development of highly stable and efficient electrocatalysts for sluggish oxygen reduction reaction (ORR is exceedingly significant for the commercialization of fuel cells but remains a challenge. We here synthesize a new nitrogen-doped biocarbon composite material (N-BC@CNP-900 as a nitrogen-containing carbon-based electrocatalyst for the ORR via facile all-solid-state multi-step pyrolysis of bioprotein-enriched enoki mushroom as a starting material, and inexpensive carbon nanoparticles as the inserting matrix and conducting agent at controlled temperatures. Results show that the N-BC@CNP-900 catalyst exhibits the best ORR electrocatalytic activity with an onset potential of 0.94 V (versus reversible hydrogen electrode, RHE and high stability. Meanwhile, this catalyst significantly exhibits good selectivity of the four-electron reaction pathway in an alkaline electrolyte. It is notable that pyridinic- and graphtic-nitrogen groups that play a key role in the enhancement of the ORR activity may be the catalytically active structures for the ORR. We further propose that the pyridinic-nitrogen species can mainly stabilize the ORR activity and the graphitic-nitrogen species can largely enhance the ORR activity. Besides, the addition of carbon support also plays an important role in the pyrolysis process, promoting the ORR electrocatalytic activity.

  8. Palladium Nanoparticles Supported on Nitrogen and Sulfur Dual-Doped Graphene as Highly Active Electrocatalysts for Formic Acid and Methanol Oxidation.

    Science.gov (United States)

    Zhang, Xin; Zhu, Jixin; Tiwary, Chandra Sekhar; Ma, Zhongyuan; Huang, Huajie; Zhang, Jianfeng; Lu, Zhiyong; Huang, Wei; Wu, Yuping

    2016-05-01

    Optimized designing of highly active electrocatalysts has been regarded as a critical point to the development of portable fuel cell systems with high power density. Here we report a facile and cost-effective strategy to synthesis of ultrafine Pd nanoparticles (NPs) supported on N and S dual-doped graphene (NS-G) nanosheets as multifunctional electrocatalysts for both direct formic acid fuel cell and direct methanol fuel cell. The incorporation of N and S atoms into graphene frameworks is achieved by a thermal treatment process, followed by the controlled growth of Pd NPs via a solvothermal approach. Owning to the unique structural features as well as the strong synergistic effects, the resulting Pd/NS-G hybrid exhibits outstanding electrocatalytic performance toward both formic acid and methanol electro-oxidation, such as higher anodic peak current densities and more exceptional catalytic stability than those of Pd/Vulcan XC-72R and Pd/undoped graphene catalysts. These findings open up new possibility in the construction of advanced Pd-based catalysts, which is conducive to solving the current bottlenecks of fuel cell technologies. PMID:27082661

  9. Preparation and evaluation of a novel therapeutic dairy-based drink for phenylketonuria

    Directory of Open Access Journals (Sweden)

    Ahmed M. Abdel-Salam

    2010-02-01

    Full Text Available Background: People with phenylketonuria need to eat a special diet which contains a low level of phenylalanine. Most of these special diets have high protein levels which contain phenylalanine. Control of phenylalanine levels in the early years of life is crucial and remains important throughout childhood, especially for cognitive function and behavior. Aims: The current study evaluated the biological and sensory properties of a novel dairy-based drink for patients with phenylketonuria (PKU. Methods and Materials: The novel dairy-based drink was prepared by emulsifying corn germ oil with casein glycomacropeptide (GMP solution in milk permeates. The chemical composition and sensory properties of the dairy-based drink were determined. In addition, the dairy-based drink was nutritionally evaluated using patient volunteers. These patients followed a strict diet limiting phenylalanine in their food. Phenylalanine levels were measured before and after three days of consuming the dairy-based drink. Results: The results of the sensory evaluation showed that the product was ranked that there were decreases in “good” and was acceptable by all test panels and volunteers. Serum phenylalanine levels in all volunteers decreased between 30% - 80%. Conclusions: The data obtained from the sensory evaluation and the decreases in serum phenylalanine levels encourage us to utilize this formulated dairy-based drink for therapeutic feeding of PKU patients.

  10. Preparation and evaluation of a novel therapeutic dairy-based drink for phenylketonuria

    Directory of Open Access Journals (Sweden)

    Ahmed M Abdel-Salam

    2010-01-01

    Full Text Available Background: People with phenylketonuria need to eat a special diet which contains a low level of phenylalanine. Most of these special diets have high protein levels which contain phenylalanine. Control of phenylalanine levels in the early years of life is crucial and remains important throughout childhood, especially for cognitive function and behavior. Aims: The current study evaluated the biological and sensory properties of a novel dairy-based drink for patients with phenylketonuria (PKU. Methods and Materials: The novel dairy-based drink was prepared by emulsifying corn germ oil with casein glycomacropeptide (GMP solution in milk permeates. The chemical composition and sensory properties of the dairy-based drink were determined. In addition, the dairy-based drink was nutritionally evaluated using patient volunteers. These patients followed a strict diet limiting phenylalanine in their food. Phenylalanine levels were measured before and after three days of consuming the dairy-based drink. Results: The results of the sensory evaluation showed that the product was ranked that there were decreases in "good" and was acceptable by all test panels and volunteers. Serum phenylalanine levels in all volunteers decreased between 30% - 80%. Conclusions : The data obtained from the sensory evaluation and the decreases in serum phenylalanine levels encourage us to utilize this formulated dairy-based drink for therapeutic feeding of PKU patients.

  11. Preparation and tunneling characteristics of MOS structures for Si-based IR light emitters

    Energy Technology Data Exchange (ETDEWEB)

    Suckow, Stephan [IHP/BTU Joint Lab., Cottbus (Germany); Kittler, Martin; Seifert, Winfried; Arguirov, Tzanimir [IHP/BTU Joint Lab., Cottbus (Germany); IHP, Frankfurt (Oder) (Germany); Schmidt, Manfred; Stegemann, Bert; Angermann, Heike [Hahn-Meitner-Institut Berlin (Germany)

    2008-07-01

    Si based light emitters, such as MOS structures based on dislocation networks, are attractive candidates for the generation of electroluminescence in the IR spectral range to be applied e.g. in optical on-chip interconnects. In the present work the preparation of an appropriate MOS structure that facilitates efficient charge carrier injection is explored and its charge carrier tunneling and recombination characteristics are analyzed. In this respect MOS structures with ultra-thin tunnel oxides fabricated by wet-chemical oxidation of Si wafers and thermally deposited Ti contacts turned out to produce the most efficient and reliable results. Moreover, electroluminescence measurements revealed an anomalous temperature behavior of band-to-band recombination with enhanced intensity at higher temperature (300 K). As photoluminescence intensity inversely increases with decreasing temperature, this effect is clearly correlated to efficient minority charge carrier injection via the MOS contact and points towards an application as room temperature IR light emitter.

  12. Preparation and characterization of manganese ferrite-based magnetic liposomes for hyperthermia treatment of cancer

    Science.gov (United States)

    Pradhan, Pallab; Giri, Jyotsnendu; Banerjee, Rinti; Bellare, Jayesh; Bahadur, Dhirendra

    2007-04-01

    Comparative evaluation of two different methods of magnetic liposomes preparation, namely thin film hydration (TFH) and double emulsion (DE) with different molar ratios of egg-phosphatidyl choline (egg-PC) and cholesterol using lauric acid coated manganese ferrite-based aqueous magnetic fluid, is reported. TFH was found to be a better method of encapsulation and TFH 2:1 (egg-PC: cholesterol) magnetic liposomes showed the highest encapsulation efficiency and comparable heating ability to that of magnetic fluids. Stealth TFH 2:1 magnetic liposomes containing DSPE-PEG 2000 were three-fold more cytocompatible as compared to the magnetic fluid. Stealth TFH 2:1 manganese ferrite-based magnetic liposomes might be useful for hyperthermia treatment of cancer.

  13. Preparation and characterization of manganese ferrite-based magnetic liposomes for hyperthermia treatment of cancer

    Energy Technology Data Exchange (ETDEWEB)

    Pradhan, Pallab [School of Biosciences and Bioengineering, Mumbai (India); Giri, Jyotsnendu [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Mumbai 400076 (India); Banerjee, Rinti [School of Biosciences and Bioengineering, Mumbai (India); Bellare, Jayesh [School of Biosciences and Bioengineering, Mumbai (India); Bahadur, Dhirendra [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Mumbai 400076 (India)]. E-mail: dhirenb@iitb.ac.in

    2007-04-15

    Comparative evaluation of two different methods of magnetic liposomes preparation, namely thin film hydration (TFH) and double emulsion (DE) with different molar ratios of egg-phosphatidyl choline (egg-PC) and cholesterol using lauric acid coated manganese ferrite-based aqueous magnetic fluid, is reported. TFH was found to be a better method of encapsulation and TFH 2:1 (egg-PC: cholesterol) magnetic liposomes showed the highest encapsulation efficiency and comparable heating ability to that of magnetic fluids. Stealth TFH 2:1 magnetic liposomes containing DSPE-PEG{sub 2000} were three-fold more cytocompatible as compared to the magnetic fluid. Stealth TFH 2:1 manganese ferrite-based magnetic liposomes might be useful for hyperthermia treatment of cancer.

  14. Design and preparation of Zn-based materials possessing both high damping and good mechanical properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new idea of design and manufacture of metal-based materials possessing both high damping and good mechanical properties was proposed. The key of the idea is the combination of fining restriction-damping structures, using all mechanisms and taking advantages of different materials. Based upon this idea a foam ZA27 was prepared by the technology of prefabricated salt-mass centrifugal seeping foundry, its tensile strength and compressive strength are 83~119 MPa and 100~189 MPa, respectively. The damping properties of the foam ZA27 increase remarkably after the carpenter pastern or rosin (the damping-increased materials) was immerged into it, which approaches to the level of viscous-elastic polymer materials (Q-1≥20×10-3).

  15. Rapid preparation and characterization of methacrylate-based monoliths for chromatographic and electrophoretic separation.

    Science.gov (United States)

    Fan, Li-Qun; Zhang, Yu-Ping; Gong, Wen-Jun; Qu, Ling-Bo; Lee, Kwang-Pill

    2010-01-01

    Butyl-methacrylate-based porous monoliths were rapidly prepared in the fused-silica capillary with a 10-cm stripe of polyimide removed from its exterior. The photopolymerization could be carried out in 150 s using ethylene glycol dimethacrylate as a cross-linking agent; 1-propanol, 1,4-butanediol, and water as tri-porogenic solvents; and Irgacure 1800 as a photo-initiator. The effect of different morphologies on the efficiency and retention properties was investigated using pressure-assisted CEC (p-CEC), CEC, and low pressure-assisted liquid chromatography modes (LPLC). Baseline separation of the model analytes was respectively achieved including thiourea, toluene, naphthalene, and biphenyl with the lowest theoretical height up to 8.0 microm for thiourea in the mode of p-CEC. Furthermore, the influence of the tri-porogenic solvents on the morphology of methacrylate-based monoliths was systematically studied with mercury intrusion porosimetry and scanning electron microscopy. PMID:20515536

  16. Preparation, Characterization, and Analytical Application of Ramipril Membrane-Based Ion-Selective Electrode

    Directory of Open Access Journals (Sweden)

    Hassan Arida

    2009-01-01

    Full Text Available The fabrication and electrochemical evaluation of two PVC membrane-based Ion-Selective electrodes responsive for ramipril drug have been proposed. The sensitive membranes were prepared using ramipril-phosphomolibdate and ramipril-tetraphenylborate ion-pair complexes as electroactive sensing materials in plasticized PVC support. The electrodes based on these materials provide near-Nernestian response (sensitivity of 53±0.5–54±0.5 mV/concentration decade covering the concentration range of 1.0×10-2–1.0×10-5 mol L−1 with a detection limit of 3.0×10-6–4.0×10-6 mol L−1. The suggested electrodes have been successfully used in the determination of ramipril drug in some pharmaceutical formulations using direct potentiometry with average recovery of >96% and mean standard deviation of <3% (n=5.

  17. Preparation and Photocatalytic Property of TiO2/Diatomite-Based Porous Ceramics Composite Materials

    Directory of Open Access Journals (Sweden)

    Shuilin Zheng

    2012-01-01

    Full Text Available The diatomite-based porous ceramics was made by low-temperature sintering. Then the nano-TiO2/diatomite-based porous ceramics composite materials were prepared by hydrolysis deposition method with titanium tetrachloride as the precursor of TiO2 and diatomite-based porous as the supporting body of the nano-TiO2. The structure and microscopic appearance of nano-TiO2/diatomite-based porous ceramics composite materials was characterized by XRD and SEM. The photocatalytic property of the composite was investigated by the degradation of malachite green. Results showed that, after calcination at 550°C, TiO2 thin film loaded on the diatomite-based porous ceramics is anatase TiO2 and average grain size of TiO2 is about 10 nm. The degradation ratio of the composite for 5 mg/L malachite green solution reached 86.2% after irradiation for 6 h under ultraviolet.

  18. Preparation and characterization of Fe-based bulk metallic glasses in plate form

    Energy Technology Data Exchange (ETDEWEB)

    Lavorato, G.C. [INTECIN (FIUBA-CONICET), Paseo Colon 850, Capital Federal (Argentina); Dipartimento di Chimica IFM and NIS, Universita di Torino, Torino (Italy); Fiore, G.; Castellero, A.; Baricco, M. [Dipartimento di Chimica IFM and NIS, Universita di Torino, Torino (Italy); Moya, J.A., E-mail: jmoya.fi.uba@gmail.com [IESIING, Facultad de Ingenieria e Informatica, UCASAL, Salta (Argentina); CONICET (Argentina)

    2012-08-15

    Amorphous alloys with composition (at%) Fe{sub 48}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Gd{sub 2} (alloy A) and Fe{sub 48}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Y{sub 2} (alloy B) were prepared either using pure elements (A and B1) and a commercial AISI430 steel as a base material (B2). When prepared from pure elements both alloys (A and B1) could be cast in plate form with a fixed thickness of 2 mm and variable lengths between 10 and 20 mm by means of copper-mold injection in air atmosphere. In the case of alloy B2, prepared using commercial grade raw materials, rods of 2 mm diameter were obtained. X-ray diffraction and scanning electron microscopy observations confirmed that an amorphous structure was obtained in all the as-cast samples. A minor fraction of crystalline phases (oxides and carbides) was detected on the as-cast surface. Differential scanning calorimetry measurements showed a glass transition temperature at 856 K for alloy A and 841 K for alloy B1, and an onset crystallization temperature of 887 K for alloy A and 885 K for alloy B1. In the case of alloy B2 a slightly different crystallization sequence was observed. Values of hardness ({approx}13 GPa) and the Young modulus ({approx}180 GPa) were measured by nanoindentation for both the alloys. The effects of adverse casting conditions (such as air atmosphere, non-conventional injection copper mold casting and partial replacement of pure elements with commercial grade raw materials) on the glass formation and properties of the alloy are discussed.

  19. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation.

    Science.gov (United States)

    Helms, Eric R; Aragon, Alan A; Fitschen, Peter J

    2014-01-01

    The popularity of natural bodybuilding is increasing; however, evidence-based recommendations for it are lacking. This paper reviewed the scientific literature relevant to competition preparation on nutrition and supplementation, resulting in the following recommendations. Caloric intake should be set at a level that results in bodyweight losses of approximately 0.5 to 1%/wk to maximize muscle retention. Within this caloric intake, most but not all bodybuilders will respond best to consuming 2.3-3.1 g/kg of lean body mass per day of protein, 15-30% of calories from fat, and the reminder of calories from carbohydrate. Eating three to six meals per day with a meal containing 0.4-0.5 g/kg bodyweight of protein prior and subsequent to resistance training likely maximizes any theoretical benefits of nutrient timing and frequency. However, alterations in nutrient timing and frequency appear to have little effect on fat loss or lean mass retention. Among popular supplements, creatine monohydrate, caffeine and beta-alanine appear to have beneficial effects relevant to contest preparation, however others do not or warrant further study. The practice of dehydration and electrolyte manipulation in the final days and hours prior to competition can be dangerous, and may not improve appearance. Increasing carbohydrate intake at the end of preparation has a theoretical rationale to improve appearance, however it is understudied. Thus, if carbohydrate loading is pursued it should be practiced prior to competition and its benefit assessed individually. Finally, competitors should be aware of the increased risk of developing eating and body image disorders in aesthetic sport and therefore should have access to the appropriate mental health professionals.

  20. Synthesis and Study of Guest-Rebinding of MIP Based on MAA Prepared using Theophylline Template

    Science.gov (United States)

    Nurhayati, T.; Yanti; Royani, I.; Widayani; Khairurrijal

    2016-08-01

    A molecularly imprinted polymer (MIP) based on methacrylic acid (MAA) monomer and theophylline template has been synthesized using a modified bulk polymerization method. Theophylline was employed as a template and it formed a complex with MAA through hydrogen bonding. Self-assembly of template-monomer was followed by cross-linking process using ethylene glycol dimethacrylate (EGDMA) cross-linker. The polymerization process was initiated by thermal decomposition of benzoyl peroxide (BPO) as the initiator at 60oC after cooling treatment at -5oC. After 7 hours, a rigid polymer was obtained and followed by grinding the polymer and removing the template. As a reference, a nonimprinted polymer (NIP) has also been synthesized using similar procedure by excluding the template. FTIR study was carried out to investigate the presence of theophylline in the as- prepared polymer, MIP, and NIP. The spectra indicated that theophylline was successfully incorporated in the as-prepared polymer. This result was also confirmed by EDS analysis showing that N atoms of the as-prepared polymer were derived from amino group of theophylline. Furthermore, the polymer particles of MIP were irregular in shape and size as shown by its SEM image. The capability of guest-rebinding of the MIP was analyzed through Batchwise guest-binding experiment. The results showed that for initial concentration of theophylline in methanol/chloroform (1/1, v/v) of 0.333 mM, the binding capacity of the MIP was 23.22 /mol/g. Compared to the MIP, the adsorption capacity of the NIP was only 3.73 /mol/g. This result shows that MIP has higher affinity than NIP.

  1. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation.

    Science.gov (United States)

    Helms, Eric R; Aragon, Alan A; Fitschen, Peter J

    2014-01-01

    The popularity of natural bodybuilding is increasing; however, evidence-based recommendations for it are lacking. This paper reviewed the scientific literature relevant to competition preparation on nutrition and supplementation, resulting in the following recommendations. Caloric intake should be set at a level that results in bodyweight losses of approximately 0.5 to 1%/wk to maximize muscle retention. Within this caloric intake, most but not all bodybuilders will respond best to consuming 2.3-3.1 g/kg of lean body mass per day of protein, 15-30% of calories from fat, and the reminder of calories from carbohydrate. Eating three to six meals per day with a meal containing 0.4-0.5 g/kg bodyweight of protein prior and subsequent to resistance training likely maximizes any theoretical benefits of nutrient timing and frequency. However, alterations in nutrient timing and frequency appear to have little effect on fat loss or lean mass retention. Among popular supplements, creatine monohydrate, caffeine and beta-alanine appear to have beneficial effects relevant to contest preparation, however others do not or warrant further study. The practice of dehydration and electrolyte manipulation in the final days and hours prior to competition can be dangerous, and may not improve appearance. Increasing carbohydrate intake at the end of preparation has a theoretical rationale to improve appearance, however it is understudied. Thus, if carbohydrate loading is pursued it should be practiced prior to competition and its benefit assessed individually. Finally, competitors should be aware of the increased risk of developing eating and body image disorders in aesthetic sport and therefore should have access to the appropriate mental health professionals. PMID:24864135

  2. Preparation of low-platinum-content platinum-nickel, platinum-cobalt binary alloy and platinum-nickel-cobalt ternary alloy catalysts for oxygen reduction reaction in polymer electrolyte fuel cells

    Science.gov (United States)

    Li, Mu; Lei, Yanhua; Sheng, Nan; Ohtsuka, Toshiaki

    2015-10-01

    A series of low-platinum-content platinum-nickel (Pt-Ni), platinum-cobalt (Pt-Co) binary alloys and platinum-nickel-cobalt (Pt-Ni-Co) ternary alloys electrocatalysts were successfully prepared by a three-step process based on electrodeposition technique and studied as electrocatalysts for oxygen reduction reaction (ORR) in polymer-electrolyte fuel cells. Kinetics of ORR was studied in 0.5 M H2SO4 solution on the Pt-Ni, Pt-Co and Pt-Ni-Co alloys catalysts using rotating disk electrode technique. Both the series of Pt-Ni, Pt-Co binary alloys and the Pt-Ni-Co ternary alloys catalysts exhibited an obvious enhancement of ORR activity in comparison with pure Pt. The significant promotion of ORR activities of Pt-Ni and Pt-Co binary alloys was attributed to the enhancement of the first electron-transfer step, whereas, Pt-Ni-Co ternary alloys presented a more complicated mechanism during the electrocatalysis process but a much more efficient ORR activities than the binary alloys.

  3. Influence of surface preparation on fracture load of resin composite-based repairs

    Science.gov (United States)

    Mateos-Palacios, Rocío; Román-Rodríguez, Juan-Luis; Solá-Ruíz, María-Fernanda; Fons-Font, Antonio

    2015-01-01

    The purpose of the present study is to evaluate the fracture load of composite-based repairs to fractured zirconium oxide (Z) crowns and to ceramic-fused-to-metal (CM) crowns, comparing different mechanical surface preparation methods. A total of 75 crowns were repaired; samples then underwent dynamic loading and thermocycling. Final fracture load values for failure of the repaired crowns were measured and the type of fracture registered. Group I: CM: Surface preparation with a diamond bur + 9.5% Hydrofluoric Acid (HF) etching; Group II): CM: air-particle (Al2O3) + 9.5% HF; Group III: CM: Silica coating (SiO2); Group IV): Z: air-particle (Al2O3) + HF 9.5%; Group V) Z: Silica coating (SiO2). Of the three CM groups, Group I (CM-diamond bur) showed the highest mean failure value, with significant difference in comparison with Group III (CM-silica coating). For the zirconia groups, the highest value was obtained by Group V (silica coating). Key words:Crown, ceramic-fused-to-metal, zirconia, resin-composite, ceramic covering. PMID:25810848

  4. Preparation and chromatographic performance of polymer-based anion exchangers for ion chromatography: A review.

    Science.gov (United States)

    Zatirakha, A V; Smolenkov, A D; Shpigun, O A

    2016-01-21

    In the last decade the developments in the field of ion chromatography (IC) were aimed at increasing the efficiency, sensitivity and rapidity of analysis, as well as on improving separation selectivity. Since selectivity and efficiency to the large extent depend on the surface chemistry of the stationary phase, the development of novel anion exchangers remains one of the priority tasks in modern IC. The exact chemistry of commercially available resins is not known and not many literature data devoted to the procedures of preparing anion exchangers for IC have become available in the last 10-15 years. However, the knowledge about the surface chemistry of anion exchangers can provide understanding of the trends in selectivity and efficiency changes, as well as help with the choice of the stationary phase type suitable for solving a particular analytical task. The current review is devoted to the methods of preparing anion exchangers based on polystyrene-divinylbenzene (PS-DVB) and ethylvinylbenzene-divinylbenzene (EVB-DVB) for IC of inorganic and small organic anions and is aimed at demonstrating the improvement of their performance over the years, which was brought by the development of the new types of stationary phase architecture.

  5. Bio-based polyurethane prepared from Kraft lignin and modified castor oil

    Directory of Open Access Journals (Sweden)

    L. B. Tavares

    2016-11-01

    Full Text Available Current challenges highlight the need for polymer research using renewable natural sources as a substitute for petroleum-based polymers. The use of polyols obtained from renewable sources combined with the reuse of industrial residues such as lignin is an important agent in this process. Different compositions of polyurethane-type materials were prepared by combining technical Kraft lignin (TKL with castor oil (CO or modified castor oil (MCO1 and MCO2 to increase their reactivity towards diphenylmethane diisocyanate (MDI. The results indicate that lignin increases the glass transition temperature, the crosslinking density and improves the ultimate stress especially for those prepared from MCO2 and 30% lignin content from 8.2 MPa (lignin free to 23.5 MPa. Scanning electron microscopy (SEM micrographs of rupture surface after uniaxial tensile tests show ductile-to-brittle transition. The results show the possibility to develop polyurethane-type materials, varying technical grade Kraft lignin content, which cover a wide range of mechanical properties (from large elastic/low Young modulus to brittle/high Young modulus polyurethanes.

  6. Modification of inkjet printer for polymer sensitive layer preparation on silicon-based gas sensors

    Science.gov (United States)

    Li, Tianjian; Dong, Ying; Yuan, Dengpeng; Liu, Yujin

    2015-04-01

    Inkjet printing is a versatile, low cost deposition technology with the capabilities for the localized deposition of high precision, patterned deposition in a programmable way, and the parallel deposition of a variety of materials. This paper demonstrates a new method of modifying the consumer inkjet printer to prepare polymer-sensitive layers on silicon wafer for gas sensor applications. A special printing tray for the modified inkjet printer to support a 4-inch silicon wafer is designed. The positioning accuracy of the deposition system is tested, based on the newly modified printer. The experimental data show that the positioning errors in the horizontal direction are negligibly small, while the positioning errors in the vertical direction rise with the increase of the printing distance of the wafer. The method for making suitable ink to be deposited to form the polymer-sensitive layer is also discussed. In the testing, a solution of 0.1 wt% polyvinyl alcohol (PVA) was used as ink to prepare a sensitive layer with certain dimensions at a specific location on the surface of the silicon wafer, and the results prove the feasibility of the methods presented in this article.

  7. Modification of inkjet printer for polymer sensitive layer preparation on silicon-based gas sensors

    Directory of Open Access Journals (Sweden)

    Tianjian Li

    2015-04-01

    Full Text Available Inkjet printing is a versatile, low cost deposition technology with the capabilities for the localized deposition of high precision, patterned deposition in a programmable way, and the parallel deposition of a variety of materials. This paper demonstrates a new method of modifying the consumer inkjet printer to prepare polymer-sensitive layers on silicon wafer for gas sensor applications. A special printing tray for the modified inkjet printer to support a 4-inch silicon wafer is designed. The positioning accuracy of the deposition system is tested, based on the newly modified printer. The experimental data show that the positioning errors in the horizontal direction are negligibly small, while the positioning errors in the vertical direction rise with the increase of the printing distance of the wafer. The method for making suitable ink to be deposited to form the polymer-sensitive layer is also discussed. In the testing, a solution of 0.1 wt% polyvinyl alcohol (PVA was used as ink to prepare a sensitive layer with certain dimensions at a specific location on the surface of the silicon wafer, and the results prove the feasibility of the methods presented in this article.

  8. Characterization of activated carbon prepared from chlorella-based algal residue.

    Science.gov (United States)

    Chang, Yuan-Ming; Tsai, Wen-Tien; Li, Ming-Hsuan

    2015-05-01

    The chlorella-based microalgal residue (AR) was tested as a novel precursor for preparing activated carbons. A combined carbonization-activation process with flowing N2 and CO2 gases was used to prepare the carbon materials at the activation temperatures of 800-1000 °C and the residence times of 0-30 min in this work. The elemental contents, pore properties and scanning electron microscopy (SEM) observations of the resulting activated carbons have been performed. The results showed that activation temperature may be the most important parameter for determining their pore properties. The maximal Brunauer-Emmett-Teller (BET) surface area and total pore volume of the resulting activated carbon, which was produced at the activation temperature of 950 °C with the residence time of 30 min, were 840 m(2)/g and 0.46 cm(3)/g, respectively. More interestingly, the resulting activated carbons have significant nitrogen contents of 3.6-9.6 wt%, which make them lower carbon contents (i.e., 54.6-68.4 wt%) than those of commercial activated carbons.

  9. Influence of surface preparation on fracture load of resin composite-based repairs.

    Science.gov (United States)

    Agustín-Panadero, Rubén; Mateos-Palacios, Rocío; Román-Rodríguez, Juan-Luis; Solá-Ruíz, María-Fernanda; Fons-Font, Antonio

    2015-02-01

    The purpose of the present study is to evaluate the fracture load of composite-based repairs to fractured zirconium oxide (Z) crowns and to ceramic-fused-to-metal (CM) crowns, comparing different mechanical surface preparation methods. A total of 75 crowns were repaired; samples then underwent dynamic loading and thermocycling. Final fracture load values for failure of the repaired crowns were measured and the type of fracture registered. Group I: CM: Surface preparation with a diamond bur + 9.5% Hydrofluoric Acid (HF) etching; Group II): CM: air-particle (Al2O3) + 9.5% HF; Group III: CM: Silica coating (SiO2); Group IV): Z: air-particle (Al2O3) + HF 9.5%; Group V) Z: Silica coating (SiO2). Of the three CM groups, Group I (CM-diamond bur) showed the highest mean failure value, with significant difference in comparison with Group III (CM-silica coating). For the zirconia groups, the highest value was obtained by Group V (silica coating). Key words:Crown, ceramic-fused-to-metal, zirconia, resin-composite, ceramic covering.

  10. Preparation and Recipe Optimization of Water-based Architectural Heat Insulation Coatings

    Institute of Scientific and Technical Information of China (English)

    CHEN Lijun; SHI Hongxin; XIANG Juping; WU Hongke

    2008-01-01

    Water-based architectural heat insulation coatings were studied to overcome the drawbacks of conventional inorganic silicate heat insulation coatings.The heat insulation coatings were prepared with the method of mechanical agitation when the mixed organic polymer emulsions were used as binder of the coatings and the mixed heat insulating aggregates were applied as powder,and some assistants were also added.Water temperature difference in the plastic container,which was coated with heat insulation coatings,represented the heat-insulating property of the coatings.The influences of components of mixed polymer emulsion,mass ratio of polymer emulsion to powder,particle size of heat insulating aggregates,added amount of air entraining admixture and the match of thickeners on the properties of the coatings were studied.The experimental results show that the heat insulation coatings with good finishing,heat-insulation property and artificial weathering can be prepared when the binder is composed of 66.92% styrene-acrylic emulsion,16.59% elastic emulsion and 16.49% silicone-acrylic emulsion,the mass ratio of polymer emulsion to powder is 0.45,the particle size of heat insulating aggregates is in the rang of 200 and 250 mesh size,the added amount of sericite is 15%,and the added amount of air entraining admixture is in the range of 1.0% and 1.5% and the thickeners are the mixtures of ASE-60 and RM-5000.

  11. Redistribution of mineral elements in wheat grain when applying the complex enzyme preparations based on phytase

    Directory of Open Access Journals (Sweden)

    Elena Kuznetsova

    2016-01-01

    Full Text Available Biogenic minerals play an important role in the whole human nutrition, but they are included in the grain of the phytates that reduces their bioavailability. Whole wheat bread is generally considered a healthy food, but the presence of mineral elements in it is insignificant, because of weak phytate degradation. From all sources of exogenous phytase the most productive are microscopic fungi. To accelerate the process of transition hard mineral elements are mobilized to implement integrated cellulolytic enzyme preparation based on the actions of phytase (producer is Penicillium canescens. Phytase activity was assessed indirectly by the rate of release of phosphate from the substrate. It has been established that the release rate of the phosphoric acid substrate is dependent on the composition of the drug and the enzyme complex is determined by the presence of xylanase. The presented experimental data shows that a cellulase treatment of the grain in conjunction with the β-glucanase or xylanase leading to an increase in phytase activity could be 1.4 - 2.3 times as compared with the individual enzymes. As a result of concerted action of enzymes complex preparation varies topography grain, increase the pore sizes in seed and fruit shells that facilitate the penetration of the enzyme phytase in the aleurone layer to the site of phytin hydrolysis and leads to an increase in phytase activity. In terms of rational parameters of enzymatic hydrolysis, the distribution of mineral elements in the anatomical parts of the grain after processing complex enzyme preparation with the help of X-ray detector EMF miniCup system in a scanning electron microscope JEOL JSM 6390 were investigated. When processing enzyme preparation wheat trend in the distribution of mineral elements, characteristic of grain - the proportion of these elements in the aleurone layer decreases, and in the endosperm increases. Because dietary fiber and phytate found together in the

  12. Chitosan-based hydrogel for dye removal from aqueous solutions: Optimization of the preparation procedure

    Science.gov (United States)

    Gioiella, Lucia; Altobelli, Rosaria; de Luna, Martina Salzano; Filippone, Giovanni

    2016-05-01

    The efficacy of chitosan-based hydrogels in the removal of dyes from aqueous solutions has been investigated as a function of different parameters. Hydrogels were obtained by gelation of chitosan with a non-toxic gelling agent based on an aqueous basic solution. The preparation procedure has been optimized in terms of chitosan concentration in the starting solution, gelling agent concentration and chitosan-to-gelling agent ratio. The goal is to properly select the material- and process-related parameters in order to optimize the performances of the chitosan-based dye adsorbent. First, the influence of such factors on the gelling process has been studied from a kinetic point of view. Then, the effects on the adsorption capacity and kinetics of the chitosan hydrogels obtained in different conditions have been investigated. A common food dye (Indigo Carmine) has been used for this purpose. Noticeably, although the disk-shaped hydrogels are in the bulk form, their adsorption capacity is comparable to that reported in the literature for films and beads. In addition, the bulk samples can be easily separated from the liquid phase after the adsorption process, which is highly attractive from a practical point of view. Compression tests reveal that the samples do not breakup even after relatively large compressive strains. The obtained results suggest that the fine tuning of the process parameters allows the production of mechanical resistant and highly adsorbing chitosan-based hydrogels.

  13. [Acute pancreatitis. Evidence-based practice guidelines, prepared by the Hungarian Pancreatic Study Group].

    Science.gov (United States)

    Hritz, István; Czakó, László; Dubravcsik, Zsolt; Farkas, Gyula; Kelemen, Dezső; Lásztity, Natália; Morvay, Zita; Oláh, Attila; Pap, Ákos; Párniczky, Andrea; Sahin-Tóth, Miklós; Szentkereszti, Zsolt; Szmola, Richárd; Szücs, Ákos; Takács, Tamás; Tiszlavicz, László; Hegyi, Péter

    2015-02-15

    Acute pancreatitis is one of the most common diseases of the gastrointestinal tract associated with significant morbidity and mortality that requires up-to-date and evidence based treatment guidelines. The Hungarian Pancreatic Study Group proposed to prepare evidence based guideline for the medical and surgical management of acute pancreatitis based on the available international guidelines and evidence. The preparatory and consultation task force appointed by the Hungarian Pancreatic Study Group translated and, if it was necessary, complemented and/or modified the international guidelines. All together 42 relevant clinical questions were defined in 11 topics (Diagnosis and etiology, Prognosis, Imaging, Fluid therapy, Intensive care management, Prevention of infectious complications, Nutrition, Biliary interventions, Post-endoscopic retrograde cholangio-pancreatography pancreatitis, Indication, timing and strategy for intervention in necrotizing pancreatitis, Timing of cholecystectomy [or endoscopic sphincterotomy]). Evidence was classified according to the UpToDate® grading system. The draft of the guideline was presented and discussed at the consensus meeting on September 12, 2014. 25 clinical questions with almost total (more than 95%) and 17 clinical questions with strong (more than 70%) agreement were accepted. The present guideline is the first evidence based acute pancreatitis guideline in Hungary. The guideline may provide important help for tuition, everyday practice and for establishment of proper finance of acute pancreatitis. Therefore, the authors believe that these guidelines will widely become as basic reference in Hungary.

  14. Investigation of methanol oxidation on a highly active and stable Pt–Sn electrocatalyst supported on carbon–polyaniline composite for application in a passive direct methanol fuel cell

    International Nuclear Information System (INIS)

    Highlights: • PtSn/C-PANI performed superior in the MOR compared with a commercial PtRu/C. • Catalytic activity of PtRu/C was highly reduced during the accelerated durability test. • Anode of the PtSn/C-PANI in a passive DMFC lowered methanol crossover by 30%. - Abstract: Polyaniline fiber (PANI) was synthesized and utilized to fabricate a vulcan–polyaniline (C-PANI) composite. Pt/C-PANI and PtSn/C-PANI electro-catalysts with different Pt:Sn atomic ratios were prepared by the impregnation method. These electro-catalysts, along with commercial PtRu/C (Electrochem), were characterized with respect to their structural and electrochemical properties in methanol oxidation reaction (MOR). PtSn(70:30)/C-PANI showed excellent performance in MOR, the obtained maximum current density being about 40% and 50% higher than that for PtRu/C and Pt/C-PANI, respectively. It was also found that the CO tolerance and stability of PtSn(70:30)/C-PANI was considerably higher than that of PtRu/C. Finally, the performance of these two materials was compared in a passive direct methanol fuel cell (DMFC). The DMFC test results demonstrated that the membrane electrode assembly (MEA) prepared using PtSn(70:30)/C-PANI anode catalyst performed more satisfactorily in terms of maximum power density and lower methanol crossover

  15. Nickel sulfide microsphere film on Ni foam as an efficient bifunctional electrocatalyst for overall water splitting.

    Science.gov (United States)

    Zhu, Wenxin; Yue, Xiaoyue; Zhang, Wentao; Yu, Shaoxuan; Zhang, Yuhuan; Wang, Jing; Wang, Jianlong

    2016-01-25

    Developing low-cost, efficient, and bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an appealing yet challenging task. Herein, for the first time, a NiS microsphere film was grown in situ on Ni foam (NiS/Ni foam) via a sulfurization reaction as an efficient bifunctional electrocatalyst for overall water splitting with superior activity and good durability. This NiS/Ni foam electrode delivers 20 mA cm(-2) at an overpotential of 158 mV for the HER and 50 mA cm(-2) at an overpotential of 335 mV for the OER in 1.0 M KOH. This bifunctional electrode also enables a high-efficiency alkaline water electrolyzer with 10 mA cm(-2) at a cell voltage of only 1.64 V, which could be promising in water splitting devices for large-scale hydrogen production. PMID:26661579

  16. Selecting Sample Preparation Workflows for Mass Spectrometry-Based Proteomic and Phosphoproteomic Analysis of Patient Samples with Acute Myeloid Leukemia

    Directory of Open Access Journals (Sweden)

    Maria Hernandez-Valladares

    2016-08-01

    Full Text Available Global mass spectrometry (MS-based proteomic and phosphoproteomic studies of acute myeloid leukemia (AML biomarkers represent a powerful strategy to identify and confirm proteins and their phosphorylated modifications that could be applied in diagnosis and prognosis, as a support for individual treatment regimens and selection of patients for bone marrow transplant. MS-based studies require optimal and reproducible workflows that allow a satisfactory coverage of the proteome and its modifications. Preparation of samples for global MS analysis is a crucial step and it usually requires method testing, tuning and optimization. Different proteomic workflows that have been used to prepare AML patient samples for global MS analysis usually include a standard protein in-solution digestion procedure with a urea-based lysis buffer. The enrichment of phosphopeptides from AML patient samples has previously been carried out either with immobilized metal affinity chromatography (IMAC or metal oxide affinity chromatography (MOAC. We have recently tested several methods of sample preparation for MS analysis of the AML proteome and phosphoproteome and introduced filter-aided sample preparation (FASP as a superior methodology for the sensitive and reproducible generation of peptides from patient samples. FASP-prepared peptides can be further fractionated or IMAC-enriched for proteome or phosphoproteome analyses. Herein, we will review both in-solution and FASP-based sample preparation workflows and encourage the use of the latter for the highest protein and phosphorylation coverage and reproducibility.

  17. PREPARATION AND CHARACTERIZATION OF ION EXCHANGE MEMBRANES BASED ON POLYVINYLIDENE FLUORIDE

    Institute of Scientific and Technical Information of China (English)

    Bo Tian; Chuan-wei Yan; Fu-hui Wang

    2004-01-01

    A new ion exchange membrane based on polyvinylidene fluoride (PVDF) and sulfonated poly(styrenedivinylbenzene) was prepared by in-situ polymerization. The incorporation of sulfonic groups into the polyvinylidene fluoride composite membrane was confirmed by infrared spectroscopy (IR), ion exchange capacity (IEC) and energy dispersive X-ray analysis (EDAX). Area resistance, IEC and water uptake of the treated membrane were evaluated. When area resistance in NaCl aqueous solution at 25℃, IEC is as high as 2.43 millimoles per gram of the wet membrane. The hydrophilicity of PVDF membrane is also significantly improved after treatment. When 60% of crosslinked membrane was sulfonated at 80℃ for 6 h, water uptake of the treated membrane can attain 64.7%.

  18. Ubbelohde viscometer measurement of water-based Fe3O4 magnetic fluid prepared by coprecipitation

    Science.gov (United States)

    Gu, H.; Tang, X.; Hong, R. Y.; Feng, W. G.; Xie, H. D.; Chen, D. X.; Badami, D.

    2013-12-01

    Fe3O4 nanoparticles were prepared by co-precipitation and coated by sodium dodecyl benzene sulfonate (SDBS) to obtain water-based magnetic fluid. The viscosity of the magnetic fluid was measured using an Ubbelohde viscometer. The effects of magnetic particles volume fraction, surfactant mass fraction and temperature on the viscosity were studied. Experimental results showed that the magnetic fluid with low magnetic particle volume fraction behaved as a Newtonian fluid and the viscosity of the magnetic fluid increased with an increase of the suspended magnetic particles volume fraction. The experimental data was compared with the results of a theoretically derived equation. The viscosity of the magnetic fluid also increased with an increase in surfactant mass portion, while it decreased with increasing temperature. Moreover, the viscosity increased with increasing the magnetic field intensity. Increasing the temperature and the surfactant mass fraction weakened the influence of the magnetic field on the viscosity of the magnetic fluid.

  19. A new method to prepare water based Fe3O4 ferrofluid with high stabilization

    Science.gov (United States)

    Guo, Tongxiao; Bian, Xiufang; Yang, Chuncheng

    2015-11-01

    A new method to prepare water based Fe3O4 ferrofluid with high stabilization has been reported in this paper. Oleic acid/ polyethylene glycol 4000 (PEG 4000)/agar/oleic acid have been used as surfactants and added to the fluid one after another. X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS) method, Fourier transform infrared (FT-IR) spectra and thermogravimetric analysis (TGA) have been used to characterize the structure, component and morphology of magnetic nanoparticles, respectively. We have observed the microstructure of chain-like (or stick-like) structure under applied magnetic field, which composes of several nanoparticles in the width direction and hundreds of nanoparticles in the length direction. Vibrating sample magnetometer (VSM) and Gouy magnetic balance (GMB) have been used to measure the magnetic properties and stability of the ferrofluid. The result shows that the magnetic nanoparticles have high saturation magnetization and the ferrofluid has high stability under magnetic and gravitational field.

  20. FragIt: A Tool to Prepare Input Files for Fragment Based Quantum Chemical Calculations

    CERN Document Server

    Steinmann, Casper; Hansen, Anne S; Jensen, Jan H

    2012-01-01

    Near linear scaling fragment based quantum chemical calculations are becoming increasingly popular for treating large systems with high accuracy and is an active field of research. However, it remains difficult to set up these calculations without expert knowledge. To facilitate the use of such methods, software tools need to be available for support, setup and lower the barrier of entry for usage by non-experts. We present a fragmentation methodology and accompanying tools called FragIt to help setup these calculations. It uses the SMARTS language to find chemically appropriate substructures in structures and is used to prepare input files for the fragment molecular orbital method in the GAMESS program package. We present patterns of fragmentation for proteins and polysaccharides, specifically D-galactopyranose for use in cyclodextrins.

  1. Agarose- and alginate-based biopolymers for sample preparation: Excellent green extraction tools for this century.

    Science.gov (United States)

    Sanagi, Mohd Marsin; Loh, Saw Hong; Wan Ibrahim, Wan Nazihah; Pourmand, Neda; Salisu, Ahmed; Wan Ibrahim, Wan Aini; Ali, Imran

    2016-03-01

    Recently, there has been considerable interest in the use of miniaturized sample preparation techniques before the chromatographic monitoring of the analytes in unknown complex compositions. The use of biopolymer-based sorbents in solid-phase microextraction techniques has achieved a good reputation. A great variety of polysaccharides can be extracted from marine plants or microorganisms. Seaweeds are the major sources of polysaccharides such as alginate, agar, agarose, as well as carrageenans. Agarose and alginate (green biopolymers) have been manipulated for different microextraction approaches. The present review is focused on the classification of biopolymer and their applications in multidisciplinary research. Besides, efforts have been made to discuss the state-of-the-art of the new microextraction techniques that utilize commercial biopolymer interfaces such as agarose in liquid-phase microextraction and solid-phase microextraction.

  2. PREPARATION AND CHARACTERIZATION OF ACETIC ACID LIGNIN-BASED EPOXY BLENDS

    Directory of Open Access Journals (Sweden)

    Fangeng Chen

    2012-05-01

    Full Text Available Lignin-based epoxy resin (LER was prepared from phenolated lignin (PL and epichlorohydrin (ECH in the presence of sodium hydroxide. The eucalyptus acetic acid lignin (AAL was first reacted with phenol in the presence of sulfuric acid to obtain PL. Then, PL was reacted with ECH in aqueous sodium hydroxide to obtain LER. LER was mixed with diglycidyl ether of bisphenol A (E-44 and then cured with triethylenetetramine (TETA. The initial thermal degradation temperature (Td of the cured epoxy blends decreased with the increase in LER content. The residue ratio at 500 °C of the cured epoxy blends (R500, however, increased with the LER content. The maximum adhesive shear strength of the cured epoxy blends was obtained at 20 wt% of LER. The water absorption of epoxy blends increased with increasing the content of LER. SEM photos showed that increasing the content of LER increased inhomogeneity and porosity of epoxy blends.

  3. Ground-based activities in preparation of SELENE ISS experiment on self-rewetting fluids

    Science.gov (United States)

    Savino, R.; Abe, Y.; Castagnolo, D.; Celata, G. P.; Kabov, O.; Kawaji, M.; Sato, M.; Tanaka, K.; Thome, J. R.; Van Vaerenbergh, S.

    2011-12-01

    SELENE (SELf rewetting fluids for thermal ENErgy management) is a microgravity experiment proposed to the European Space Agency (ESA) in response to the Announcement of Opportunities for Physical Sciences. Main objectives of the microgravity research onboard ISS include the quantitative investigation of heat transfer performances of "self-rewetting fluids" and "nano self-rewetting fluids" in model heat pipes and validation of adequate theoretical and numerical modelling able to predict their behaviour in microgravity conditions. This article summarizes the results of ground-based research activities in preparation of the microgravity experiments. They include: 1) thermophysical properties measurements; 2) study of thermo-soluto-capillary effects in micro-channels; 3) numerical modelling; 4) thermal and concentration distribution measurements with optical (e.g. interferometric) and intrusive techniques; 5) surface tension-driven effects and thermal performances test on different capillary structures and heat pipes; 6) breadboards development and support to definition of scientific requirements.

  4. Preparation of Expanded Graphite-based Composites 0by One Step Impregnation

    Institute of Scientific and Technical Information of China (English)

    LIU Chengbao; CHEN Zhigang; CHEN Hong; MIAO Zhi; FU Meng

    2011-01-01

    A new method for preparing expanded graphite-based composites (EGCs) was developed. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM) and nitrogen adsorption. The experimental results indicated that the EGCs was not simply mechanical mixture of EG and activated carbon, instead the activated carbon was coated on the surface of interior and external pores of the EG in the form of thin carbon layer. The thickness of the activated carbon layer was nearly one hundred nanometers by calculation. It was shown that the higher the impregnation ratio and the activation temperature were, the easier the porosity development would be. And the BET surface area and the total pore volume were as high as 1978 m2/g and 0.9917 cm3/g respectively at 350 C with an impregnation ratio of 0.9.

  5. Efficacy of multimedia learning modules as preparation for lecture-based tutorials in electromagnetism

    CERN Document Server

    Moore, J Christopher

    2014-01-01

    We have investigated the efficacy of online, multimedia learning modules (MLMs) as preparation for in-class, lecture-based tutorials in electromagnetism in a physics course for natural science majors (biology and marine science). Specifically, we report the results of a multiple-group pre/post-test research design comparing two groups receiving different treatments with respect to activities preceding participation in Tutorials in Introductory Physics. The different pre-tutorial activities where as follows: (1) students were assigned reading from a traditional textbook, followed by a traditional lecture; and (2) students completed online multimedia learning modules developed by the Physics Education Research Group at the University of Illinois at Urbana Champaign (UIUC), and commercially known as smartPhysics. The MLM treatment group earned significantly higher mid-term examination scores and larger gains in content knowledge as measured by the Conceptual Survey of Electricity and Magnetism (CSEM). Student at...

  6. Preparation and fluorescent properties of a complex probe based on inorganic QDs and organic dye

    International Nuclear Information System (INIS)

    A novel complex fluorescent probe based on quantum dots and organic dye (QDs-TO) was designed and prepared by incorporating a benzothiazole derivative into QDs-1-(3-amidepropyl)-4-methylquinoline. The complex probe was characterized by FT-IR and TG/DTA. The emission wavelength of QDs-1-(3-amidepropyl)-4-methylquinoline was found at 475 nm and a new peak corresponding to QDs-TO appeared at 550 nm, indicating that benzothiazole derivative can react with QDs-1-(3-amidepropyl)-4-methylquinoline to afford QDs-TO. Furthermore, the emission wavelength of QDs shifted blue while the characteristic peak of TO shifted red during the reaction. This suggests that the probe may be useful for biological labeling in offering an efficient method to study the interrelation between quantum dots and organic dyes.

  7. Effect of an alcohol-based caries detector on the surface tension of sodium hypochlorite preparations.

    Science.gov (United States)

    Rossi-Fedele, Giampiero; Guastalli, Andrea R

    2015-01-01

    The purpose of this study was to evaluate the effect of an alcohol-based caries detector (Kurakay) on the surface tension of a conventional sodium hypochlorite (NaOCl) preparation, and a product containing a surface-active agent (Chlor-XTRA). The surface tensions of the following solutions were tested: NaOCl, a mixture of NaOCl and Kurakay 9:1 w/w, Chlor-XTRA, a mixture of Chlor-XTRA and Kurakay 9:1 w/w. Ten measurements per test solution were made at 20°C, using an optical method called the "Pendant drop method", with a commercially available apparatus. The addition of Kurakay reduced the surface tension for NaOCl (p0.05). Statistically significant differences between the NaOCl and Chlor-XTRA groups were found (proot canal irrigants in vitro, the related changes in surface tension are a possible source of bias. PMID:25672387

  8. Carbon-based Composite Electrodes: Preparation, Characterization and Application in Electroanalysis

    Directory of Open Access Journals (Sweden)

    Joop Schoonman

    2007-11-01

    Full Text Available Electrodes based on carbon, i.e., expanded graphite (20%, wt.-epoxy composite(20EG-Epoxy and expanded graphite (20%, wt.-polystyrene composite (20EG-PS havebeen prepared, characterized using scanning electron microscopy (SEM and cyclicvoltammetry (CV, and tested as anodic sensors. The electrodes exhibited good mechanicalresistance and low electrical resistances. Scan rate dependent cyclic voltammetry responsesat 20EG-Epoxy and 20EG-PS composite electrodes, which were exemplified for thiourea(TU, a toxic sulphur organic compound selected as testing target analyte in 0.1 M Na2SO4 supporting electrolyte, were investigated. The obtained voltammetric data were inaccordance with those for a random array of microelectrodes. The voltammetric andchronoamperometric detection results of TU in tap water samples, without a supplementaryaddition of supporting electrolyte, at 20EG-Epoxy electrode proved its use for directanalysis of environmental samples.

  9. Sorbents based on crown ethers: preparation and application for the sorption of strontium

    Science.gov (United States)

    Bezhin, N. A.; Dovhyi, I. I.

    2015-12-01

    The key approaches to the synthesis of crown ether-based sorbents, including immobilization both with and without covalent bonding, are reviewed. Examples of sorbent preparation using anodic oxidation, chemical modification of polymers, polycondensation reactions, chemical modification of inorganic supports and radiochemical synthesis for covalent bonding of crown ether moieties are considered. Immobilization methods without covalent bonding including support synthesis in the presence of crown ethers, impregnation of supports with a crown ether solution and the use of powdered crown ether as a sorbent are presented. The applications of sorbents for selective removal of strontium from solutions of radioactive waste and spent nuclear fuel, for radiochemical analysis (determination of strontium in water, soil and biological materials) and for separation of strontium and yttrium isotopes are discussed. The bibliography includes 114 references.

  10. Laser-based surface preparation of composite laminates leads to improved electrodes for electrical measurements

    KAUST Repository

    Almuhammadi, Khaled

    2015-10-19

    Electrical impedance tomography (EIT) is a low-cost, fast and effective structural health monitoring technique that can be used on carbon fiber reinforced polymers (CFRP). Electrodes are a key component of any EIT system and as such they should feature low resistivity as well as high robustness and reproducibility. Surface preparation is required prior to bonding of electrodes. Currently this task is mostly carried out by traditional sanding. However this is a time consuming procedure which can also induce damage to surface fibers and lead to spurious electrode properties. Here we propose an alternative processing technique based on the use of pulsed laser irradiation. The processing parameters that result in selective removal of the electrically insulating resin with minimum surface fiber damage are identified. A quantitative analysis of the electrical contact resistance is presented and the results are compared with those obtained using sanding.

  11. A novel colloid probe preparation method based on chemical etching technique

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Several fundamental problems in hydrophobic force measurements using atomic force microscope (AFM) are discussed in this paper. A novel method for colloid probe preparation based on chemical etching technology is proposed, which is specially fit for the unique demands of hydrophobic force measurements by AFM. The features of three different approaches for determining spring constants of rectangular cantilevers, including geometric dimension, Cleveland and Sader methods are compared. The influences of the sizes of the colloids on the measurements of the hydrophobic force curves are investigated. Our experimental results showed that by selecting colloid probe with proper spring constant and tip size, the hydrophobic force and the complete hydrophobic interaction force curve can be measured by using AFM.

  12. Influence of a psyllium-based fibre preparation on faecal and serum parameters.

    Science.gov (United States)

    Burton, R; Manninen, V

    1982-01-01

    A fibre made of psyllium husk was given to 12 elderly patients for 4 months in order to investigate their faecal output and selected serum parameters. The fibre significantly improved bowel function and faecal output confirming its value as a non-irritant, harmless bulk-forming laxative. Serum cholesterol was decreased by 20% while triglycerides remained unchanged. There was a significant reduction in serum calcium after withdrawal of the fibre supplement. There were no significant changes in serum iron, total iron binding capacity, fibrinogen, or in the haematological parameters (ESR, haemoglobin, leucocyte count) attributable to the fibre. The high phytate content of the fibre does not appear to have any clinically significant effect on mineral absorption. It is suggested that dietary fibre (at least psyllium-based fibre preparations) may have significant cholesterol lowering capacity due to the binding of bile-acids in the intestine. PMID:6963098

  13. Preparation of poly(ε-caprolactone)-based tissue engineering scaffolds by stereolithography.

    Science.gov (United States)

    Elomaa, Laura; Teixeira, Sandra; Hakala, Risto; Korhonen, Harri; Grijpma, Dirk W; Seppälä, Jukka V

    2011-11-01

    A photocrosslinkable poly(ε-caprolactone) (PCL)-based resin was developed and applied using stereolithography. No additional solvents were required during the structure preparation process. Three-armed PCL oligomers of varying molecular weights were synthesized, functionalized with methacrylic anhydride, and photocrosslinked, resulting in high gel content networks. Stereolithography was used to build designed porous scaffolds using the resin containing PCL macromer, Irgacure 369 photoinitiator, inhibitor and dye. A suitable resin viscosity was obtained by heating the resin during the curing process. The scaffolds precisely matched the computer-aided designs, with no observable material shrinkage. The average porosity was 70.5 ± 0.8%, and the average pore size was 465 μm. The pore network was highly interconnected. The photocrosslinkable, biodegradable PCL resin is well suited for the solvent-free fabrication of tissue engineering scaffolds by stereolithography.

  14. Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

    KAUST Repository

    Song, HyonMin

    2012-09-27

    Hybrid alloys among gold, palladium and platinum become a new category of catalysts primarily due to their enhanced catalytic effects. Enhancement means not only their effectiveness, but also their uniqueness as catalysts for the reactions that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core-shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au compared to Ag, Pd, and Pt helps to produce hollow Au cores first, followed by Pd or Pt shell growth. Continuous and highly crystalline shell growth was observed in Au@Pd core-shell NPs, but the sporadic and porous-like structure was observed in Au@Pt core-shell NPs. Along with hollow core-shell NPs, hollow porous Pt and hollow Au NPs are also prepared from Ag seed NPs. Twin boundaries which are typically observed in large size (>20 nm) Au NPs were not observed in hollow Au NPs. This absence is believed to be due to the role of the hollows, which significantly reduce the strain energy of edges where the two lattice planes meet. In ethanol oxidation reactions in alkaline medium, hollow Au@Pd core-shell NPs show highest current density in forward scan. Hollow Au@Pt core-shell NPs maintain better catalytic activities than metallic Pt, which is thought to be due to the better crystallinity of Pt shells as well as the alloy effect of Au cores. © 2012 The Royal Society of Chemistry.

  15. Preparation of Chitosan-Based Hemostatic Sponges by Supercritical Fluid Technology

    Directory of Open Access Journals (Sweden)

    Hu-Fan Song

    2014-03-01

    Full Text Available Using ammonium bicarbonate (AB particles as a porogen, chitosan (CS-based hemostatic porous sponges were prepared in supercritical carbon dioxide due to its low viscosity, small surface tension, and good compatibility with organic solvent. Fourier transform infrared spectroscopy (FTIR spectra demonstrated that the chemical compositions of CS and poly-(methyl vinyl ether-co-maleic anhydride (PVM/MA were not altered during the phase inversion process. The morphology and structure of the sponge after the supercritical fluid (SCF process were observed by scanning electron microscopy (SEM. The resulting hemostatic sponges showed a relatively high porosity (about 80% with a controllable pore size ranging from 0.1 to 200 µm. The concentration of PVM/MA had no significant influence on the porosity of the sponges. Comparative experiments on biological assessment and hemostatic effect between the resulting sponges and Avitene® were also carried out. With the incorporation of PVM/MA into the CS-based sponges, the water absorption rate of the sponges increased significantly, and the CS-PVM/MA sponges showed a similar water absorption rate (about 90% to that of Avitene®. The results of the whole blood clotting experiment and animal experiment also demonstrated that the clotting ability of the CS-PVM/MA sponges was similar to that of Avitene®. All these results elementarily verified that the sponges prepared in this study were suitable for hemostasis and demonstrated the feasibility of using SCF-assisted phase inversion technology to produce hemostatic porous sponges.

  16. Preparation and Characterization of Chitosan-Based Core-Shell Microcapsules Containing Clove Oil.

    Science.gov (United States)

    Jiang, Ping; Li, Duxin; Xiao, Ya; Yang, Xingxing; Liu, Yuejun

    2015-01-01

    The biodegradable microcapsules based on chitosan for a controlled delivery of clove oil were prepared by the single coagulation process. The effect of chitosan concentration, core to shell ratio, types of emulsifier, flocculating agent and hardening agent on the microcapsule diameter and the particle size distribution of microcapsule were investigated. The optimized conditions for the preparation of microcapsules with well-defined structure and narrow dispersibility were under that (1) the concentration of chitosan was 1.0 wt%, (2) clove oil to chitosan ratio was 75:25, (3) OP-10 and 10 wt% sodium sulfate were used as emulsifier and flocculating agent respectively, and (4) the concentration hardening agent glyoxal was 1 wt% based on the weight of chitosan. The uniform spherical structures with smooth surfaces with a particle size distribution of 1-15 μm were evidenced by SEM images of microcapsules. Core-shell, hetero-structures were confirmed by optical micrograph. The chemical component of the microcapsules was determined by FTIR. Thermal analysis showed the microcapsules were thermally stable below 150 degrees C. It was found that the pH value and temperature play important roles on the release rate of clove oil from the microcapsules. The release volume of clove oil from microcapsules at pH = 7, and pH = 10 were smaller than that at pH = 2. And the release volume of Clove oil from microcapsules at 60 degrees C was smaller than that at 20 degrees C and 40 degrees C, which showed a sustained and prolonged release. PMID:26328411

  17. Multivariate analysis for the optimization of polysaccharide-based nanoparticles prepared by self-assembly.

    Science.gov (United States)

    Pistone, Sara; Qoragllu, Dafina; Smistad, Gro; Hiorth, Marianne

    2016-10-01

    Polysaccharide-based nanoparticles are promising carriers for drug delivery applications. The particle size influences the biodistribution of the nanoparticles; hence size distributions and polydispersity index (PDI) are critical characteristics. However, the preparation of stable particles with a low PDI is a challenging task and is usually based on empirical trials. In this study, we report the use of multivariate evaluation to optimize the formulation factors for the preparation of alginate-zinc nanoparticles by ionotropic gelation. The PDI was selected as the response variable. Particle size, size distributions, zeta potential and pH of the samples were also recorded. Two full factorial (mixed-level) designs were analyzed by partial least squares regression (PLS). In the first design, the influence of the polysaccharide and the crosslinker concentrations were studied. The results revealed that size distributions with a low PDI were obtained by using a low polysaccharide concentrations (0.03-0.05%) and a zinc concentration of 0.03% (w/w). However, a high polysaccharide concentration can be advantageous for drug delivery systems. Therefore, in the second design, a high alginate concentration was used (0.09%) and a reduction in the PDI was obtained by simultaneously increasing the ionic strength of the solvent and the zinc concentration. The multivariate analysis also revealed the interaction between the factors in terms of their effects on the PDI; hence, compared to traditional univariate analyses, the multivariate analysis allowed us to obtain a more complete understanding of the effects of the factors scrutinized. In addition, the results are considered useful in order to avoid extensive empirical tests for future formulation studies. PMID:27288663

  18. Preparation, structure and properties of Fe-based bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2010-06-01

    Full Text Available Purpose: The work presents preparation methods, structure characterization and chosen properties analysis of Fe-based bulk metallic glasses in as-cast state.Design/methodology/approach: The studies were performed on Fe43Co14Ni14B20Si5Nb4 metallic glass in form of rings, plates and rods. The amorphous structure of tested samples was examined by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM methods. The thermal properties of the glassy samples was measured using differential scanning calorimetry (DSC. The soft magnetic properties examination of tested material contained coercive force, initial magnetic permeability and magnetic permeability relaxation measurements. Findings: The XRD and TEM investigations revealed that the studied as-cast samples were amorphous. Broad diffraction halo is typical for metallic amorphous structures that have a large degree of short-range order. The characteristics of the fractured surfaces showed different zones, which might correspond with different amorphous structures of studied materials. The temperature interval of the supercooled liquid region (ΔTx defined by the difference between Tg and Tx, is as large as 56 K for the rod with diameter of 3 mm. Differences in coercivity and magnetic permeability between samples with different thickness might be resulted by some difference of amorphous structure.Practical implications: The centrifugal casting method and the pressure die casting method are useful to produce bulk amorphous materials in form of rings, plats and rods.Originality/value: The preparation of studied Fe-based bulk metallic glass in form of rings, plates and rods is important for the future progress in research and practical application of that glassy materials.

  19. Highly Active Non-PGM Catalysts Prepared from Metal Organic Frameworks

    Directory of Open Access Journals (Sweden)

    Heather M. Barkholtz

    2015-06-01

    Full Text Available Finding inexpensive alternatives to platinum group metals (PGMs is essential for reducing the cost of proton exchange membrane fuel cells (PEMFCs. Numerous materials have been investigated as potential replacements of Pt, of which the transition metal and nitrogen-doped carbon composites (TM/Nx/C prepared from iron doped zeolitic imidazolate frameworks (ZIFs are among the most active ones in catalyzing the oxygen reduction reaction based on recent studies. In this report, we demonstrate that the catalytic activity of ZIF-based TM/Nx/C composites can be substantially improved through optimization of synthesis and post-treatment processing conditions. Ultimately, oxygen reduction reaction (ORR electrocatalytic activity must be demonstrated in membrane-electrode assemblies (MEAs of fuel cells. The process of preparing MEAs using ZIF-based non-PGM electrocatalysts involves many additional factors which may influence the overall catalytic activity at the fuel cell level. Evaluation of parameters such as catalyst loading and perfluorosulfonic acid ionomer to catalyst ratio were optimized. Our overall efforts to optimize both the catalyst and MEA construction process have yielded impressive ORR activity when tested in a fuel cell system.

  20. SCIENTIFIC BASIS FOR THE PREPARATION AND CHARACTERIZATION OF IRON BASED TRADITIONAL DRUG ANNABHEDI SINDOORAM: A MATERIALISTIC APPROACH

    Directory of Open Access Journals (Sweden)

    Keerthy Unni

    2013-04-01

    Full Text Available Iron based traditional Ayurvedic drug Annabhedi Sindooram is used therapeutically for the treatment of diseases like Anaemia, Leucoderma, Prolapse of rectum and uterus, Spleenic disorders. The preparation method of iron based Indian traditional drug Annabhedi Sindooram involves conversion of a pure metal into its mixed oxide by drying and incineration. Commercially available ferrous sulphate is used as the source of iron for the preparation of Annabhedi. The structural and textural properties of the starting materials and the prepared drug were characterized systematically by different characterization techniques like PXRD, Zeta Potential Analysis, particle analysis, FTIR, ICP –AES, SEM and BET surface area analysis. The results obtained by characterization of the samples clearly explain the formation of Fe2O3, reduction in particle size, modification of surface energy and formation of metal complex with organic moieties. The strict post and pre preparation conditions followed play an important role in the morphology and medicinal activity of the drug Annabhedi Sindooram.

  1. Preparation of Weak Cation Exchange Packings Based on Monodisperse Poly (chloromethylstyrene-co-divinylbenzene) Particles and Its Chromatographic Properties

    Institute of Scientific and Technical Information of China (English)

    卫引茂; 陈强; 耿信笃

    2001-01-01

    Monodisperse poly ( chloromethylstyrene-co-divinylbenzene )particles were firstly prepared by a two-step swelling method.Based on this media, one kind of weak cation ion exchange packings was prepared. It was demonstrated that the prepared packings have comparative advantages for biopolymer separation with high column efficiency, low interstitial volume and low column backpressure, and have good resolution to proteins. The effects of salt concentration and pH of mobile phase on protein retentions were investigated. The properties of the weak cation ion exchange packings were evaluated by the unified retention model for mixed-mode interaction mechanison in ion exchange and hydrophobic interaction chromatography.

  2. Physics or Mathematics Preparation - which is the better predictor of performance in a first, calculus-based college physics course?

    Science.gov (United States)

    Chase, Norma

    2011-11-01

    Data spanning fifteen semesters and including more than 1200 students showed far less than the anticipated difference in performance between students with quite diverse levels of physics preparation. Students ranged from those with no prior physics course work to those with two or more years of HS physics and prior courses in college physics. Less prior physics training frequently coincided with better performance in the first calculus-based course. Preparation in mathematics, on the other hand, appeared critically important; students at the extremes of the math preparation spectrum were concentrated at the corresponding extremes of the physics grade distribution.

  3. Study on Carbon Nanotubes Prepared from Catalytic Decomposition of CH4 over Lanthanum Containing Ni-Base Catalysts

    Institute of Scientific and Technical Information of China (English)

    Wang Minwei; Li Fengyi

    2004-01-01

    A series of lanthanum containing Ni-base catalysts were prepared by citric acid complex method.Carbon nanotubes (CNT) were synthesized bY catalytic decomposing CH4 over these catalysts and characterized by XRD, TEM and TGA.It is found that the addition of lanthanum can not increase the yield of carbon nanotube, but can make the diameter of carbon nanotube thinner and even.The more the lanthanum addsr, the thinner the diameter of CNTs becomes.With the CNTs prepared on Ni-Mg catalyst, the CNTs prepared on Ni-La-Mg catalyst has better crystallinity and thermal stability.

  4. Synthesis and electrochemical characterization of highly tolerant Pd electrocatalysts as cathodes in direct ethylene glycol fuel cells (DEGFC)

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Varela, F.J.; Fraire Luna, S. [Cinvestav, Unidad Saltillo, Ramos Arizpe, Coahuila (Mexico)] e-mail: javier.varela@cinvestav.edu.mx; Savadogo, O. [Laboratoire d' Electrochimie et de Materiaux Energetiques, Ecole Polytechnique de Montreal, Montreal, QC (Canada)

    2009-09-15

    Highly selective Pd electrocatalysts were synthesized by the formic acid method and evaluated as cathodes for DEGFC applications. In rotating disc measurements in acid medium, the Pd/C cathode showed important catalytic activity for the Oxygen Reduction Reaction (ORR). In the presence of ethylene glycol (EG, C{sub 2}H{sub 6}O{sub 2}), Pd/C exhibited an excellent electrochemical behavior and full tolerance to the organic molecule. No current density peaks associated to the EG oxidation reaction emerged and the shift in onset potential for the ORR (Eonset) toward more negative potentials was negligible on this cathode. Moreover, the evaluation of Pd/C in a DEGFC operating at 80 degrees Celsius demonstrated its high performance as cathode. As a comparison, commercial Pt/C was tested under the same conditions showing a limited selectivity for the ORR. The detrimental effect of EG on the Pt electrocatalysts resulted in high intensity current density peaks due to the oxidation of EG and a significant shift in Eonset. Given these results, it is expected that highly efficient Pd-based cathodes can find application in DEGFCs. [Spanish] Se sintetizaron electrocatalizadores altamente selectivos mediante el metodo de acido formico y se evaluaron como catodos en aplicaciones de CCGED. En mediciones de disco rotatorio en medio acido, el catodo Pd/C mostro importante actividad catalitica en la reaccion de reduccion de oxigeno (RRO). En la presencia de glicol de etileno (GE, C{sub 2}H{sub 6}O{sub 2}), Pd/C exhibio un excelente comportamiento electromecanico y tolerancia total a la molecula organica. No surgieron picos de densidad de corriente asociados con la reaccion de oxidacion de GE y el corrimiento en el potencial de inicio para la RRO (Einicio) hacia potenciales mas negativos fue despreciable en este catodo. Como comparacion, se probo un Pt/C bajo las mismas condiciones y se observo una selectividad limitada para el RRO. El efecto perjudicial de GE en el electrocatalizador

  5. Preparing a 21st century workforce: is it time to consider clinically based, competency-based training of health practitioners?

    Science.gov (United States)

    Nancarrow, Susan A; Moran, Anna M; Graham, Iain

    2014-02-01

    Health workforce training in the 21st century is still based largely on 20th century healthcare paradigms that emphasise professionalisation at the expense of patient-focussed care. This is illustrated by the paradox of increased training times for health workers that have corresponded with workforce shortages, the limited career options and pathways for paraprofessional workers, and inefficient clinical training models that detract from, rather than add to, service capacity. We propose instead that a 21st century health workforce training model should be: situated in the clinical setting and supported by outsourced university training (not the other way around); based on the achievement of specific milestones rather than being time-defined; and incorporate para-professional career pathways that allow trainees to 'step-off' with a useable qualification following the achievement of specific competencies. Such a model could be facilitated by existing technology and clinical training infrastructure, with enormous potential for economies of scale in the provision of formal training. The benefits of a clinically based, competency-based model include an increase in clinical service capacity, and clinical training resources become a resource for the delivery of healthcare, not just education. Existing training models are unsustainable, and are not preparing a workforce with the flexibility the 21st century demands.

  6. Cu,N-codoped Hierarchical Porous Carbons as Electrocatalysts for Oxygen Reduction Reaction.

    Science.gov (United States)

    Yu, Haiyan; Fisher, Adrian; Cheng, Daojian; Cao, Dapeng

    2016-08-24

    It remains a huge challenge to develop nonprecious electrocatalysts with high activity to substitute commercial Pt catalysts for oxygen reduction reactions (ORR). Here, the Cu,N-codoped hierarchical porous carbon (Cu-N-C) with a high content of pyridinic N was synthesized by carbonizing Cu-containing ZIF-8. Results indicate that Cu-N-C shows excellent ORR electrocatalyst properties. First of all, it nearly follows the four-electron route, and its electron transfer number reaches 3.92 at -0.4 V. Second, both the onset potential and limited current density of Cu-N-C are almost equal to those of a commercial Pt/C catalyst. Third, it exhibits a better half-wave potential (∼16 mV) than a commercial Pt/C catalyst. More importantly, the Cu-N-C displays better stability and methanol tolerance than the Pt/C catalyst. All of these good properties are attributed to hierarchical structure, high pyridinic N content, and the synergism of Cu and N dopants. The metal-N codoping strategy can significantly enhance the activity of electrocatalysts, and it will provide reference for the design of novel N-doped porous carbon ORR catalysts. PMID:27490846

  7. Cu,N-codoped Hierarchical Porous Carbons as Electrocatalysts for Oxygen Reduction Reaction.

    Science.gov (United States)

    Yu, Haiyan; Fisher, Adrian; Cheng, Daojian; Cao, Dapeng

    2016-08-24

    It remains a huge challenge to develop nonprecious electrocatalysts with high activity to substitute commercial Pt catalysts for oxygen reduction reactions (ORR). Here, the Cu,N-codoped hierarchical porous carbon (Cu-N-C) with a high content of pyridinic N was synthesized by carbonizing Cu-containing ZIF-8. Results indicate that Cu-N-C shows excellent ORR electrocatalyst properties. First of all, it nearly follows the four-electron route, and its electron transfer number reaches 3.92 at -0.4 V. Second, both the onset potential and limited current density of Cu-N-C are almost equal to those of a commercial Pt/C catalyst. Third, it exhibits a better half-wave potential (∼16 mV) than a commercial Pt/C catalyst. More importantly, the Cu-N-C displays better stability and methanol tolerance than the Pt/C catalyst. All of these good properties are attributed to hierarchical structure, high pyridinic N content, and the synergism of Cu and N dopants. The metal-N codoping strategy can significantly enhance the activity of electrocatalysts, and it will provide reference for the design of novel N-doped porous carbon ORR catalysts.

  8. Preparation and characterization of polymer composites based on charge-transfer complex of phenothiazine–iodine in polystyrene

    Indian Academy of Sciences (India)

    R A Singh; R K Gupta; S K Singh

    2005-08-01

    Polymer composites based on charge-transfer complex of phenothiazine and iodine with polystyrene have been prepared in different weight ratios and characterized by FTIR, XRD, mechanical, microstructure and electrical properties (d.c. as well as a.c.). These composites show semiconducting behaviour as the conductivity increases with increasing temperature. Low percolation threshold (10% wt CTC) has been found indicating that processable conducting polymers with improved mechanical properties can be prepared by this method.

  9. Preparation of water-soluble nanographite and its application in water-based cutting fluid

    Science.gov (United States)

    Chen, Qiang; Wang, Xue; Wang, Zongting; Liu, Yu; You, Tingzheng

    2013-01-01

    Water-soluble nanographite was prepared by in situ emulsion polymerization using methacrylate as polymeric monomer. The dispersion stability and dispersion state of graphite particles were evaluated by UV-visible spectrophotometry and scanning electron microscopy, respectively. The water-soluble nanographite was then added into the water-based cutting fluid as lubricant additive. The lubrication performance of water-based cutting fluid with the nanographite additive was studied on four-ball friction tester and surface tensiometer. Results indicate that the modification method of in situ emulsion polymerization realizes the uniform and stabilized dispersion of nanographite in aqueous environment. The optimal polymerization condition is 70°C (polymerization temperature) and 5 h (polymerization time). The addition of nanographite decreases the friction coefficient and wear scar diameter by 44% and 49%. Meanwhile, the maximum non-seizure load ( P B ) increases from 784 to 883 N, and the value of surface tension (32.76 × 10-3 N/m) is at low level. Nanographite additive improves apparently the lubrication performance of water-based cutting fluid.

  10. Before Student Teaching: How Undergraduate Students in Early Childhood Teacher Preparation Programs Describe Their Early Classroom-Based Experience

    Science.gov (United States)

    Maynard, Christine; La Paro, Karen M.; Johnson, Amy V.

    2014-01-01

    Classroom-based experiences, alternatively known as practica, are an integral component of undergraduate teacher preparation programs, which provide students essential opportunities to apply knowledge in practice. Though much is known about student teaching, much less is known about students' earlier classroom-based experiences. This…

  11. Enhanced methanol electro-oxidation reaction on Pt-CoO{sub x}/MWCNTs hybrid electro-catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Nouralishahi, Amideddin, E-mail: Nouralishahi@ut.ac.ir [Catalysis and Nanostructured Materials Research Laboratory, School of Chemical Engineering, University of Tehran, P.O. Box 11155/4563, Tehran (Iran, Islamic Republic of); Caspian Faculty of Engineering, University of Tehran, P.O. Box 43841-119, Rezvanshahr (Iran, Islamic Republic of); Catalysis and Nanotechnology Research Division, Research Institute of Petroleum Industry (RIPI), P.O. Box 14665-1998, Tehran (Iran, Islamic Republic of); Rashidi, Ali Morad, E-mail: Rashidiam@ripi.ir [Catalysis and Nanotechnology Research Division, Research Institute of Petroleum Industry (RIPI), P.O. Box 14665-1998, Tehran (Iran, Islamic Republic of); Mortazavi, Yadollah, E-mail: Mortazav@ut.ac.ir [Catalysis and Nanostructured Materials Research Laboratory, School of Chemical Engineering, University of Tehran, P.O. Box 11155/4563, Tehran (Iran, Islamic Republic of); Khodadadi, Abbas Ali, E-mail: Khodadad@ut.ac.ir [Catalysis and Nanostructured Materials Research Laboratory, School of Chemical Engineering, University of Tehran, P.O. Box 11155/4563, Tehran (Iran, Islamic Republic of); Choolaei, Mohammadmehdi, E-mail: Choolaeimm@ripi.ir [Catalysis and Nanotechnology Research Division, Research Institute of Petroleum Industry (RIPI), P.O. Box 14665-1998, Tehran (Iran, Islamic Republic of)

    2015-04-30

    Highlights: • Promoting effects of Cobalt oxide on methanol electro-oxidation over Pt/MWCNTs are investigated. • Higher activity, about 2.9 times, and enhanced stability are observed on Pt-CoO{sub x}/MWCNTs. • Electrochemical active surface area of Pt nanoparticles is significantly improved upon CoO{sub x} addition. • Bi-functional mechanism is facilitated in presence of CoO{sub x}. - Abstract: The electro-catalytic behavior of Pt-CoO{sub x}/MWCNTs in methanol electro-oxidation reaction (MOR) is investigated and compared to that of Pt/MWCNTs. The electro-catalysts were synthesized by an impregnation method using NaBH{sub 4} as the reducing agent. The morphological and physical characteristics of samples are examined by XRD, TEM, ICP and EDS techniques. In the presence of CoO{sub x}, Pt nanoparticles were highly distributed on the support with an average particle size of 2 nm, an obvious decrease from 5.1 nm for Pt/MWCNTs. Cyclic voltammetry, CO-stripping, Chronoamperometry, and electrochemical impedance spectroscopy (EIS) measurements are used to study the electrochemical behavior of the electro-catalysts. The results revealed a considerable enhancement in the oxidation kinetics of CO{sub ads} on Pt active sites by the participation of CoO{sub x}. Compared to Pt/MWCNTs, Pt-CoO{sub x}/MWCNTs sample has a larger electrochemical active surface area (ECSA) and higher electro-catalytic activity and stability toward methanol electro-oxidation. According to the results of cyclic voltammetry, the forward anodic peak current density enhances more than 89% at the optimum atomic ratio of Pt:Co = 2:1. Furthermore, inclusion of cobalt oxide species causes the onset potential of methanol electro-oxidation reaction to shift 84 mV to negative values compared to that on Pt/MWCNTs. Based on EIS data, dehydrogenation of methanol is the rate-determining step of MOR on both Pt/MWCNTs and Pt-CoO{sub x}/MWCNTs, at small overpotentials. However, at higher overpotentials, the

  12. [Design and Preparation of Plant Bionic Materials Based on Optical and Infrared Features Simulation].

    Science.gov (United States)

    Jiang, Xiao-jun; Lu, Xu-liang; Pan, Jia-liang; Zhang, Shuan-qin

    2015-07-01

    Due to the life characteristics such as physiological structure and transpiration, plants have unique optical and infrared features. In the optical band, because of the common effects of chlorophyll and water, plant leafs show spectral reflectance characteristics change in 550, 680, 1400 and 1900 nm significantly. In the infrared wave band, driven by transpiration, plants could regulate temperature on their own initiative, which make the infrared characteristics of plants different from artificial materials. So palnt bionic materials were proposed to simulate optical and infrared characteristics of plants. By analyzing formation mechanism of optical and infrared features about green plants, the component design and heat-transfer process of plants bionic materials were studied, above these the heat-transfer control formulation was established. Based on water adsorption/release compound, optical pigments and other man-made materials, plant bionic materials preparation methods were designed which could simulate the optical and infrared features of green plants. By chemical casting methods plant bionic material films were prepared, which use polyvinyl alcohol as film forming and water adsorption/release compound, and use optical pigments like chrome green and macromolecule yellow as colouring materials. The research conclusions achieved by testings figured out: water adsorption/release testing showed that the plant bionic materials with a certain thickness could absorb 1.3 kg water per square meter, which could satisfy the water usage of transpiration simulation one day; the optical and infrared simulated effect tests indicated that the plant bionic materials could preferably simulate the spectral reflective performance of green plants in optical wave band (380-2500 nm, expecially in 1400 and 1900 nm which were water absorption wave band of plants), and also it had similar daily infrared radiation variations with green plants, daily average radiation temperature

  13. The Intersection of Inquiry-Based Science and Language: Preparing Teachers for ELL Classrooms

    Science.gov (United States)

    Weinburgh, Molly; Silva, Cecilia; Smith, Kathy Horak; Groulx, Judy; Nettles, Jenesta

    2014-08-01

    As teacher educators, we are tasked with preparing prospective teachers to enter a field that has undergone significant changes in student population and policy since we were K-12 teachers. With the emphasis placed on connections, mathematics integration, and communication by the New Generation Science Standards (NGSS) (Achieve in Next generation science standards, 2012), more research is needed on how teachers can accomplish this integration (Bunch in Rev Res Educ 37:298-341, 2013; Lee et al. in Educ Res 42(4):223-233, 2013). Science teacher educators, in response to the NGSS, recognize that it is necessary for pre-service and in-service teachers to know more about how instructional strategies in language and science can complement one another. Our purpose in this study was to explore a model of integration that can be used in classrooms. To do this, we examined the change in science content knowledge and academic vocabulary for English language learners (ELLs) as they engaged in inquiry-based science experience utilizing the 5R Instructional Model. Two units, erosion and wind turbines, were developed using the 5R Instructional Model and taught during two different years in a summer school program for ELLs. We analyzed data from interviews to assess change in conceptual understanding and science academic vocabulary over the 60 h of instruction. The statistics show a clear trend of growth supporting our claim that ELLs did construct more sophisticated understanding of the topics and use more language to communicate their knowledge. As science teacher educators seek ways to prepare elementary teachers to help preK-12 students to learn science and develop the language of science, the 5R Instructional Model is one pathway.

  14. Review of sample preparation strategies for MS-based metabolomic studies in industrial biotechnology.

    Science.gov (United States)

    Causon, Tim J; Hann, Stephan

    2016-09-28

    Fermentation and cell culture biotechnology in the form of so-called "cell factories" now play an increasingly significant role in production of both large (e.g. proteins, biopharmaceuticals) and small organic molecules for a wide variety of applications. However, associated metabolic engineering optimisation processes relying on genetic modification of organisms used in cell factories, or alteration of production conditions remain a challenging undertaking for improving the final yield and quality of cell factory products. In addition to genomic, transcriptomic and proteomic workflows, analytical metabolomics continues to play a critical role in studying detailed aspects of critical pathways (e.g. via targeted quantification of metabolites), identification of biosynthetic intermediates, and also for phenotype differentiation and the elucidation of previously unknown pathways (e.g. via non-targeted strategies). However, the diversity of primary and secondary metabolites and the broad concentration ranges encompassed during typical biotechnological processes means that simultaneous extraction and robust analytical determination of all parts of interest of the metabolome is effectively impossible. As the integration of metabolome data with transcriptome and proteome data is an essential goal of both targeted and non-targeted methods addressing production optimisation goals, additional sample preparation steps beyond necessary sampling, quenching and extraction protocols including clean-up, analyte enrichment, and derivatisation are important considerations for some classes of metabolites, especially those present in low concentrations or exhibiting poor stability. This contribution critically assesses the potential of current sample preparation strategies applied in metabolomic studies of industrially-relevant cell factory organisms using mass spectrometry-based platforms primarily coupled to liquid-phase sample introduction (i.e. flow injection, liquid

  15. [Design and Preparation of Plant Bionic Materials Based on Optical and Infrared Features Simulation].

    Science.gov (United States)

    Jiang, Xiao-jun; Lu, Xu-liang; Pan, Jia-liang; Zhang, Shuan-qin

    2015-07-01

    Due to the life characteristics such as physiological structure and transpiration, plants have unique optical and infrared features. In the optical band, because of the common effects of chlorophyll and water, plant leafs show spectral reflectance characteristics change in 550, 680, 1400 and 1900 nm significantly. In the infrared wave band, driven by transpiration, plants could regulate temperature on their own initiative, which make the infrared characteristics of plants different from artificial materials. So palnt bionic materials were proposed to simulate optical and infrared characteristics of plants. By analyzing formation mechanism of optical and infrared features about green plants, the component design and heat-transfer process of plants bionic materials were studied, above these the heat-transfer control formulation was established. Based on water adsorption/release compound, optical pigments and other man-made materials, plant bionic materials preparation methods were designed which could simulate the optical and infrared features of green plants. By chemical casting methods plant bionic material films were prepared, which use polyvinyl alcohol as film forming and water adsorption/release compound, and use optical pigments like chrome green and macromolecule yellow as colouring materials. The research conclusions achieved by testings figured out: water adsorption/release testing showed that the plant bionic materials with a certain thickness could absorb 1.3 kg water per square meter, which could satisfy the water usage of transpiration simulation one day; the optical and infrared simulated effect tests indicated that the plant bionic materials could preferably simulate the spectral reflective performance of green plants in optical wave band (380-2500 nm, expecially in 1400 and 1900 nm which were water absorption wave band of plants), and also it had similar daily infrared radiation variations with green plants, daily average radiation temperature

  16. Development and Study of Tantalum and Niobium Carbides as Electrocatalyst Supports for the Oxygen Electrode for PEM Water Electrolysis at Elevated Temperatures

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Petrushina, Irina; Prag, Carsten Brorson;

    2013-01-01

    Polymer electrolyte membrane (PEM) water electrolysis is a prospective method of producing hydrogen. We focused on one of its issues – the lack of a suitable support material for the anode electrocatalyst. TaC and NbC were studied as possible electrocatalyst supports for the PEM water electrolysi...

  17. [Discussion on research and development of new traditional Chinese medicine preparation process based on idea of QbD].

    Science.gov (United States)

    Feng, Yi; Hong, Yan-Long; Xian, Jie-Chen; Du, Ruo-Fei; Zhao, Li-Jie; Shen, Lan

    2014-09-01

    Traditional processes are mostly adopted in traditional Chinese medicine (TCM) preparation production and the quality of products is mostly controlled by terminal. Potential problems of the production in the process are unpredictable and is relied on experience in most cases. Therefore, it is hard to find the key points affecting the preparation process and quality control. A pattern of research and development of traditional Chinese medicine preparation process based on the idea of Quality by Design (QbD) was proposed after introducing the latest research achievement. Basic theories of micromeritics and rheology were used to characterize the physical property of TCM raw material. TCM preparation process was designed in a more scientific and rational way by studying the correlation among enhancing physical property of raw material, preparation process and product quality of preparation. So factors affecting the quality of TCM production would be found out and problems that might occur in the pilot process could be predicted. It would be a foundation for the R&D and production of TCM preparation as well as support for the "process control" of TCMIs gradually realized in the future.

  18. Preparation and characterization of novel bionanocomposite based on soluble soybean polysaccharide and halloysite nanoclay.

    Science.gov (United States)

    Alipoormazandarani, Niloofar; Ghazihoseini, Seyedehzahra; Mohammadi Nafchi, Abdorreza

    2015-12-10

    In this research, casting method was used to prepare novel polysaccharide-based bio-nanocomposite films with halloysite nanoclay (HNC). HNC was incorporated into soluble soybean polysaccharide (SSPS) at different concentrations (e.g., 1, 3, and 5%, w/w). Functional properties of SSPS films were evaluated following by ASTM standards. Incorporating HNC to SSPS matrix decreased water vapor permeability from 7.41 × 10(-11) to 3.27 × 10(-11) (gm(-1) s(-1) Pa(-1)) and oxygen permeability from 202 to 84 cm(3)(μm m(-2) day(-1) atm(-1)). By addition of HNC to SSPS films, glass transition temperature, tensile strength, and heat seal strength was increased and elongation at break was decreased. Uniform and smooth surface morphology revealed by scanning electron microscopy and shows no sign of phase separation among the film constitutes. In summary, HNC has the potential to be a filler in SSPS-based films for use in food and non-food packaging industries. PMID:26428181

  19. Preparation and properties of environmental-friendly coatings based on carboxymethyl cellulose nitrate ester & modified alkyd.

    Science.gov (United States)

    Duan, Hongtao; Shao, Ziqiang; Zhao, Ming; Zhou, Zhenwen

    2016-02-10

    Amphipathic coating basic film-forming material carboxymethyl cellulose nitrate ester (CMCN) was synthesized and characterizations of CMCN with different ratio of functional groups were studied. Ratios of functional groups on each repeating units of CMCN have great importance in the decision of CMCN properties using as an amphipathic coating basic film-forming material and ratios of functional groups were the most concerned of the study. Ratios of functional groups on each repeating units of CMCN were measured by elemental analyzer and calculated. Series of experiments were conducted using different ratios of functional groups of CMCN. Thermal properties of CMCN were measured by FT-IR and TG. Densities of CMCN powders were measured. Aqueous coatings based on CMCN/alkyd (after chemical modified by coconut oil) were prepared and morphology & rheology of CMCN hydrophilic dispersions were measured using an Anton-Paar-Strasse 20A-8054 Graz analyzer. Contact angles between films based on CMCN and deionized water were recorded. Other properties of films were measured. CMCN with the etherification of carboxymethyl groups at 0.35-0.40, nitrate ester groups at 1.96-2.19 and hydroxyl groups at 0.46-0.64 per d-glucose was considered as the best film forming material.

  20. Preparation and characterization of plasticized palm-based polyurethane solid polymer electrolyte

    International Nuclear Information System (INIS)

    Palm-based polyurethane solid polymer electrolyte was prepared via prepolymerization method between palm kernel oil based polyols (PKO-p) and 2,4’-diphenylmethane diisocyanate (2,4’-MDI) in acetone at room temperature with the vary amount of lithium trifuoromethanesulfonate (LiCF3SO3) salt and polyethylene glycol (PEG). The film was analyzed using attenuated total reflection infrared (ATR-IR) spectroscopy, electrochemical impedance spectroscopy (EIS) and X-ray diffractometry (XRD). EIS result indicated ionic conductivity obtained with 30 wt% LiCF3SO3 increased to 6.55 × 10−6 S cm−1 when 10 wt.% of plasticizer was added into the system. FTIR analysis showed the interaction between lithium ions and amine (-N-H) at 3600–3100 cm−1, carbonyl (-C=O) at 1750–1650 cm−1 and ether (-C-O-C-) at 1150–1000 cm−1 of the polyurethane forming polymer-salt complexes. The XRD result confirmed that LiCF3SO3 salt completely dissociated within the polyurethane film with the absence of crystalline peaks of LiCF3SO3

  1. Electroplated Fe-Co-Ni films prepared from deep-eutectic-solvent-based plating baths

    Science.gov (United States)

    Yanai, Takeshi; Shiraishi, Kotaro; Akiyoshi, Toshiki; Azuma, Keita; Watanabe, Yoshimasa; Ohgai, Takeshi; Morimura, Takao; Nakano, Masaki; Fukunaga, Hirotoshi

    2016-05-01

    We fabricated soft magnetic films from DES-based plating baths, and investigated magnetic properties of the plated films. The plating baths were obtained by stirring the mixture of choline chloride, ethylene glycol, FeCl2 ṡ 4H2O, NiCl2 ṡ 6H2O and CoCl2 ṡ 6H2O. The composition of the electroplated film depended on the amount of the reagent in the plating bath, and we consequently obtained the films with various composition. The current efficiency of the plating process shows high values (> 88 %) in the wide composition range. The soft magnetic films with low coercivity were obtained at the Fe compositions of ≈ 30 at.% and > 80 at.%, and we found that low coercivity could be realized by the control of the film composition. We also found that the Fe-rich films prepared from DES-based plating bath have some advantages as a soft magnetic phase for a nanocomposite magnet due to their high saturation magnetization and very fine crystal structure.

  2. Preparation and characterization of plasticized palm-based polyurethane solid polymer electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Daud, Farah Nadia; Ahmad, Azizan; Badri, Khairiah Haji [School of Chemical Science and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan (Malaysia)

    2013-11-27

    Palm-based polyurethane solid polymer electrolyte was prepared via prepolymerization method between palm kernel oil based polyols (PKO-p) and 2,4’-diphenylmethane diisocyanate (2,4’-MDI) in acetone at room temperature with the vary amount of lithium trifuoromethanesulfonate (LiCF{sub 3}SO{sub 3}) salt and polyethylene glycol (PEG). The film was analyzed using attenuated total reflection infrared (ATR-IR) spectroscopy, electrochemical impedance spectroscopy (EIS) and X-ray diffractometry (XRD). EIS result indicated ionic conductivity obtained with 30 wt% LiCF3SO3 increased to 6.55 × 10{sup −6} S cm{sup −1} when 10 wt.% of plasticizer was added into the system. FTIR analysis showed the interaction between lithium ions and amine (-N-H) at 3600–3100 cm{sup −1}, carbonyl (-C=O) at 1750–1650 cm{sup −1} and ether (-C-O-C-) at 1150–1000 cm{sup −1} of the polyurethane forming polymer-salt complexes. The XRD result confirmed that LiCF{sub 3}SO{sub 3} salt completely dissociated within the polyurethane film with the absence of crystalline peaks of LiCF{sub 3}SO{sub 3}.

  3. Preparation and characterization of Co/PAN-based carbon fibrous composites

    Science.gov (United States)

    Zhixin, J.; Yongyi, Y.; Gang, J.

    2011-07-01

    The cobalt/polyacrylonitrile (Co/PAN)-based carbon fibrous composites were prepared. The PAN incorporated with cobalt ions was in situ polymerized by initiating the complex solution of acrylonitrile (AN)/cobalt (II) chloride (CoCl2) in which the contents of cobalt ions were 0 wt.%, 0.29 wt.%, 0.56 wt.% and 1.14 wt.%, respectively. The ultrathin blue fibers were formed from the cobalt/PAN composites by the electrospinning method. The electrospun cobalt-incorporated PAN fibers were successfully stabilized in air and subsequently carbonized to form the carbon fibrous composites in a nitrogen (N2) atmosphere. Based on the scanning electron microscopy (SEM), we noticed that beads and beaded fibers were produced during the electrospinning process. When the content of cobalt ions in the complex solution was as high as 1.14 wt.%, there were many honeycomb-like structures and nanopores formed in both stabilized and carbonized fibers. The X-ray photoelectron spectra (XPS) were used to characterize the structure of the composite fibers.

  4. Electroplated Fe-Co-Ni films prepared from deep-eutectic-solvent-based plating baths

    Directory of Open Access Journals (Sweden)

    Takeshi Yanai

    2016-05-01

    Full Text Available We fabricated soft magnetic films from DES-based plating baths, and investigated magnetic properties of the plated films. The plating baths were obtained by stirring the mixture of choline chloride, ethylene glycol, FeCl2 ⋅ 4H2O, NiCl2 ⋅ 6H2O and CoCl2 ⋅ 6H2O. The composition of the electroplated film depended on the amount of the reagent in the plating bath, and we consequently obtained the films with various composition. The current efficiency of the plating process shows high values (> 88 % in the wide composition range. The soft magnetic films with low coercivity were obtained at the Fe compositions of ≈ 30 at.% and > 80 at.%, and we found that low coercivity could be realized by the control of the film composition. We also found that the Fe-rich films prepared from DES-based plating bath have some advantages as a soft magnetic phase for a nanocomposite magnet due to their high saturation magnetization and very fine crystal structure.

  5. Preparation, characterization, and in vitro antimicrobial assessment of nanocarrier based formulation of nadifloxacin for acne treatment.

    Science.gov (United States)

    Kumar, A; Agarwal, S P; Ahuja, A; Ali, J; Choudhry, R; Baboota, S

    2011-02-01

    The objective of the present study was to develop a nanocarrier based formulation of nadifloxacin and to investigate its in vitro antimicrobial effect against Propionibacterium acnes. Nanocarrier based microemulsion formulations were prepared by aqueous titration method, using oleic acid as oil phase, Tween-80 as surfactant and ethanol as co-surfactant in different ratios. This procedure yielded monodisperse microemulsions exhibiting a mean droplet size in the range of 95-560 nm. This range of particle size is good to treat follicle related disorders like acne vulgaris because the size of follicles is in the range of 50-100 microm. Furthermore the optimized formulations were characterized for surface morphology by transmission electron microscopy and refractive index. The permeation studies were carried out using rat skin mounted in Franz diffusion cells. Flux of the optimised formulation was 2.24 times that of control. The diameter of inhibition zone of the microemulsion was found good but smaller than that of a clindamycin disc because of the higher therapeutic efficacy of clindamycin against P. acnes. The results indicated that the developed microemulsion shows promising results against P. acnes bacteria and may be a good approach for acne treatment. PMID:21434572

  6. Screening of electrocatalysts for direct ammonia fuel cell: Ammonia oxidation on PtMe (Me: Ir, Rh, Pd, Ru) and preferentially oriented Pt(1 0 0) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Vidal-Iglesias, F.J.; Solla-Gullon, J.; Montiel, V.; Feliu, J.M.; Aldaz, A. [Instituto de Electroquimica, Universidad de Alicante, Apartado 99, 03080 Alicante (Spain)

    2007-09-27

    Ammonia has attracted attention as a possible fuel for direct fuel cells since it is easy to handle and to transport as liquid or as concentrated aqueous solution. However, on noble metal electrodes ammonia oxidation is a sluggish reaction and the electrocatalyst needs to be improved for developing efficient ammonia fuel cells. In this work, ammonia electrooxidation reaction on 3-4-nm bimetallic PtMe (Ir, Rh, Pd, Ru) and on preferentially oriented Pt(1 0 0) nanoparticles is reported. PtMe nanoparticles have been prepared by using water-in-oil microemulsions to obtain a narrow size distribution whereas preferentially oriented Pt nanoparticles have been prepared through colloidal routes. Among all the bimetallic samples tested, only Pt{sub 75}Ir{sub 25} and Pt{sub 75}Rh{sub 25} nanoparticles show, at the low potential range, an enhancement of the oxidation density current with respect to the behaviour found for pure platinum nanoparticles prepared by the same method. In addition, two Pt(1 0 0) preferentially oriented nanoparticles of different particle size (4 and 9 nm) have been also studied. These oriented nanoparticles show higher current densities than polycrystalline Pt nanoparticles due to the sensitivity of ammonia oxidation toward the presence of surface sites with square symmetry. The reactivity of the different 4-nm nanoparticles parallels well with that expected from bulk PtMe alloys and Pt single crystal electrodes. (author)

  7. Screening of electrocatalysts for direct ammonia fuel cell: Ammonia oxidation on PtMe (Me: Ir, Rh, Pd, Ru) and preferentially oriented Pt(1 0 0) nanoparticles

    Science.gov (United States)

    Vidal-Iglesias, F. J.; Solla-Gullón, J.; Montiel, V.; Feliu, J. M.; Aldaz, A.

    Ammonia has attracted attention as a possible fuel for direct fuel cells since it is easy to handle and to transport as liquid or as concentrated aqueous solution. However, on noble metal electrodes ammonia oxidation is a sluggish reaction and the electrocatalyst needs to be improved for developing efficient ammonia fuel cells. In this work, ammonia electrooxidation reaction on 3-4-nm bimetallic PtMe (Ir, Rh, Pd, Ru) and on preferentially oriented Pt(1 0 0) nanoparticles is reported. PtMe nanoparticles have been prepared by using water-in-oil microemulsions to obtain a narrow size distribution whereas preferentially oriented Pt nanoparticles have been prepared through colloidal routes. Among all the bimetallic samples tested, only Pt 75Ir 25 and Pt 75Rh 25 nanoparticles show, at the low potential range, an enhancement of the oxidation density current with respect to the behaviour found for pure platinum nanoparticles prepared by the same method. In addition, two Pt(1 0 0) preferentially oriented nanoparticles of different particle size (4 and 9 nm) have been also studied. These oriented nanoparticles show higher current densities than polycrystalline Pt nanoparticles due to the sensitivity of ammonia oxidation toward the presence of surface sites with square symmetry. The reactivity of the different 4-nm nanoparticles parallels well with that expected from bulk PtMe alloys and Pt single crystal electrodes.

  8. Free MoS2 Nanoflowers Grown on Graphene by Microwave-Assisted Synthesis as Highly Efficient Non-Noble-Metal Electrocatalysts for the Hydrogen Evolution Reaction

    Science.gov (United States)

    Cao, Jiamu; Zhang, Xuelin; Zhang, Yufeng; Zhou, Jing; Chen, Yinuo; Liu, Xiaowei

    2016-01-01

    Advanced approaches to preparing non-noble-metal electrocatalysts for the hydrogen evolution reaction (HER) are considered to be a significant breakthrough in promoting the exploration of renewable resources. In this work, a hybrid material of MoS2 nanoflowers (NFs) on reduced graphene oxide (rGO) was synthesized as a HER catalyst via an environmentally friendly, efficient approach that is also suitable for mass production. Small-sized MoS2 NFs with a diameter of ca. 190 nm and an abundance of exposed edges were prepared by a hydrothermal method and were subsequently supported on rGO by microwave-assisted synthesis. The results show that MoS2 NFs were distributed uniformly on the remarkably reduced GO and preserved the outstanding original structural features perfectly. Electrochemical tests show that the as-prepared hybrid material exhibited excellent HER activity, with a small Tafel slope of 80 mV/decade and a low overpotential of 170 mV. PMID:27556402

  9. Survival rates of porcelain laminate restoration based on different incisal preparation designs: An analysis

    Directory of Open Access Journals (Sweden)

    Ashish Shetty

    2011-01-01

    Conclusions : The study found that the window preparation was of the most conservative type. Incisal coverage was better than no incisal coverage and, in incisal coverage, two predictable designs - incisal overlap and butt were reported. In butt preparation, no long-term follow-up studies have been performed as yet. In general, incisal overlap was preferred for healthy normal tooth with sufficient thickness and incisal butt preparation was preferred for worn tooth and fractured teeth.

  10. Preparation and characterization of high performance Schiff-base liquid crystal diepoxide polymer

    International Nuclear Information System (INIS)

    Graphical abstract: The specific effects of highly conjugated Schiff-base moiety on thermal properties of the Schiff-base epoxy polymer were proposed first by us. From the point of view of structure-properties relationship, it can be considered that owing to the presence of the Schiff-base group, the high performance liquid crystal diepoxide polymer displayed improved thermal stability. Highlights: ► In this work, we first proposed that specific effects of highly conjugated Schiff-base moiety on thermal properties of the Schiff-base epoxy polymer. ► As one aim of this study, the thermal and thermal-oxidative stabilities of the thermosets were studied by TGA under nitrogen and under air. ► The second aim of this study was to further understand the thermal degradation mechanism. ► For thermal degradation mechanism of this polymer under nitrogen, TG-IR was used to investigate volatile components, and SEM/EDS was used to explore morphologies and chemical components of the residual char. ► From the point of view of structure-properties relationship, it can be considered that owing to the presence of the Schiff-base group, the high performance liquid crystal diepoxide polymer displayed the improved thermal stability. - Abstract: A novel Schiff-base liquid crystal diepoxide polymer was prepared via a thermal copolymerization of a Schiff-base epoxy monomer (PBMBA) with a diamine co-monomer (MDA). We first proposed that specific effects of highly conjugated Schiff-base moiety on thermal properties of the Schiff-base epoxy polymer (PBMBA/MDA). Thermal degradation behavior of the polymer was characterized using thermogravimetric analysis (TGA) under nitrogen and under air, respectively. Thermogravimetric data obtained from TGA under nitrogen and under air reveal that PBMBA/MDA exhibits higher thermal stability compared with bisphenol-A type epoxy polymer (DGEBA/MDA) and other mesogene-containing epoxy polymer. It is worth pointing out that the outstanding residual

  11. Preparation, electrochemical characterization and antibacterial study of polystyrene-based magnesium–strontium phosphate composite membrane

    International Nuclear Information System (INIS)

    The electrochemical characterizations of polystyrene-based magnesium–strontium phosphate (MSP) composite membrane have been worked on, as a function of membrane thickness, porosity and moisture content etc. Polystyrene-based magnesium–strontium phosphate composite membrane was characterized by XRD, FTIR, SEM, and antibacterial studies. The membrane was found to be crystalline in nature with uniform arrangement of particles, no sign of visible cracks and shows excellent inhibitory results against Escherichia coli and Pseudomonas aeruginosa bacteria. The membrane potentials of inorganic membrane were measured with uni-univalent electrolytes solution using saturated calomel electrodes and followed the order LiCl > NaCl > KCl, thus, the membrane was found to be cation selective. Membrane potential data have been used to calculate transport number, mobility ratio, distribution coefficient, charge effectiveness, and also to derive the fixed-charge density which is a central parameter governing the membrane phenomena by utilizing the Teorell, Meyer, and Sievers method. The order of surface charge density for uni-univalent electrolytes solution was found to be LiCl 2 (mol/l) at different concentrations of KCl electrolyte solution for polystyrene-based MSP composite membranes prepared at different pressures of 100–160 MPa. Highlights: ► The membrane was found to be crystalline in nature. ► Membrane potential of electrolytes followed the order LiCl > NaCl > KCl. ► The order of surface charge density was found to be LiCl < NaCl < KCl. ► The membrane show excellent results against E. coli and P. aeruginosa bacteria.

  12. Fabrication and characterization of Fe-based amorphous coatings prepared by high-velocity arc spraying

    International Nuclear Information System (INIS)

    Highlights: • Fe-based cored wires were designed to achieve high glass forming ability. • Novel highly amorphous coatings were fabricated by arc spray technology. • The as-obtained amorphous coating possessed high thermal stability up to 873 K. • The as-obtained amorphous coating exhibited a high bonding strength over 44 MPa. - Abstract: Fe-based coatings with a high amorphous content were firstly developed by the traditional twin wires arc spray technology. In consideration of empirical rules, including the multi-component system, an optimal concentration of small atoms, negative heat of mixing and an appropriate atom size mismatch among the main components, the cored wires were designed to contain eight elements, which have an optimized atomic volume strain criterion λn, in range of 0.14–0.21, to render the coatings a high glass forming ability. Then the coatings were prepared using the above-designed cored wires through a rapid arc spray melting and solidification process. Crystalline phases could not be identified from the XRD patterns within the XRD resolution limits, suggesting that the as-sprayed coatings were approximately comprised of fully amorphous phases. With a dense structure and a low porosity of only 2%, the amorphous Fe-based coatings exhibited an attractive combination of high hardness (900–1100 HV0.3) and superior bonding strength (44.9–54.8 MPa). The coating at λn = 0.21 had the lowest Gibbs free energy difference ΔG, exhibited the largest super-cooled liquid region ΔTx, Lu’s criterion factor γ value and the heat of crystallization (ΔH) values, which indicating the highest GFA

  13. Fe-based bulk metallic glasses prepared by centrifugal casting method

    Directory of Open Access Journals (Sweden)

    R. Babilas

    2011-10-01

    Full Text Available Purpose: The work presents a casting method, structure characterization and analysis of chosen properties of Fe-based bulk metallic glasses in as-cast state.Design/methodology/approach: The studies were performed on Fe72B20Si4Nb4, Fe36Co36B19Si5Nb4, Fe43Co14Ni14B20Si5Nb4 metallic glasses in form of rings. The amorphous structure of tested samples was examined by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM methods. The crystallization behaviour of the studied alloys was examined by differential thermal analysis (DTA. The soft magnetic property examinations of tested materials contained initial magnetic permeability and measurements of magnetic permeability relaxation.Findings: The XRD and TEM investigations revealed that the studied as-cast bulk glassy samples in forms of ring were amorphous for all tested alloys. The SEM images showed that fractures of studied rings indicated two structurally different zones, which contained “river” patterns and “smooth” areas. The samples of studied alloys presented two stage crystallization process, which was observed for all tested rings with different thickness. The changes of crystallization temperatures versus the thickness of the glassy samples were stated. The magnetic permeability relaxation, which is directly proportional to the microvoids concentration in amorphous structure decreased with increase of sample thickness. These results could be assumed as the change of amorphous structure in function of thickness.Practical implications: The centrifugal casting method is very simple, useful and effective method to produce bulk amorphous materials in the form of rings or tubes.Originality/value: The preparation of bulk metallic glasses in the form of rings for three different Fe-based alloy systems is very important for the future progress in research and practical applications of iron-based bulk amorphous materials.

  14. Bimetallic alloy electrocatalysts with multilayered platinum-skin surfaces

    Science.gov (United States)

    Stamenkovic, Vojislav R.; Wang, Chao; Markovic, Nenad M.

    2016-01-26

    Compositions and methods of preparing a bimetallic alloy having enhanced electrocatalytic properties are provided. The composition comprises a PtNi substrate having a surface layer, a near-surface layer, and an inner layer, where the surface layer comprises a nickel-depleted composition, such that the surface layer comprises a platinum skin having at least one atomic layer of platinum.

  15. Subnanometer Molybdenum Sulfide on Carbon Nanotubes as a Highly Active and Stable Electrocatalyst for Hydrogen Evolution Reaction.

    Science.gov (United States)

    Li, Ping; Yang, Zhi; Shen, Juanxia; Nie, Huagui; Cai, Qiran; Li, Luhua; Ge, Mengzhan; Gu, Cancan; Chen, Xi'an; Yang, Keqin; Zhang, Lijie; Chen, Ying; Huang, Shaoming

    2016-02-10

    Electrochemically splitting water for hydrogen evolution reaction (HER) has been viewed as a promising approach to produce renewable and clean hydrogen energy. However, searching for cheap and efficient HER electrocatalysts to replace the currently used Pt-based catalysts remains an urgent task. Herein, we develop a one-step carbon nanotube (CNT) assisted synthesis strategy with CNTs' strong adsorbability to mediate the growth of subnanometer-sized MoS(x) on CNTs. The subnanometer MoS(x)-CNT hybrids achieve a low overpotential of 106 mV at 10 mA cm(-2), a small Tafel slope of 37 mV per decade, and an unprecedentedly high turnover frequency value of 18.84 s(-1) at η = 200 mV among all reported non-Pt catalysts in acidic conditions. The superior performance of the hybrid catalysts benefits from the presence of a higher number of active sites and the abundant exposure of unsaturated S atoms rooted in the subnanometer structure, demonstrating a new class of subnanometer-scale catalysts. PMID:26765150

  16. Bifunctional non-noble metal oxide nanoparticle electrocatalysts through lithium-induced conversion for overall water splitting

    Science.gov (United States)

    Wang, Haotian; Lee, Hyun-Wook; Deng, Yong; Lu, Zhiyi; Hsu, Po-Chun; Liu, Yayuan; Lin, Dingchang; Cui, Yi

    2015-06-01

    Developing earth-abundant, active and stable electrocatalysts which operate in the same electrolyte for water splitting, including oxygen evolution reaction and hydrogen evolution reaction, is important for many renewable energy conversion processes. Here we demonstrate the improvement of catalytic activity when transition metal oxide (iron, cobalt, nickel oxides and their mixed oxides) nanoparticles (~20 nm) are electrochemically transformed into ultra-small diameter (2-5 nm) nanoparticles through lithium-induced conversion reactions. Different from most traditional chemical syntheses, this method maintains excellent electrical interconnection among nanoparticles and results in large surface areas and many catalytically active sites. We demonstrate that lithium-induced ultra-small NiFeOx nanoparticles are active bifunctional catalysts exhibiting high activity and stability for overall water splitting in base. We achieve 10 mA cm-2 water-splitting current at only 1.51 V for over 200 h without degradation in a two-electrode configuration and 1 M KOH, better than the combination of iridium and platinum as benchmark catalysts.

  17. Controlled synthesis of Pt/CS/PW{sub 12}-GNs composite as an anodic electrocatalyst for direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhongshui; Lei, Fengling; Ye, Lingting; Zhang, Xiaofeng; Lin, Shen, E-mail: shenlin@fjnu.edu.cn [Fujian Normal University, College of Chemistry & Chemical Engineering (China)

    2015-04-15

    Controlled assembly in aqueous solution was used to synthesize the well-organized Pt/CS/PW{sub 12}-GNs composite. By the aid of linear cationic polysaccharide chitosan, 2-D distribution worm-like Pt nanoparticles with their length and width of 15–20 and 3–4 nm, respectively, were formed on the surface of CS/PW{sub 12}-GNs using HCOOH as a reducing agent at room temperature. The introduction of CS leads to well dispersion of worm-like Pt nanoparticles, the electroactivity of H{sub 3}PW{sub 12}O{sub 40} (PW{sub 12}) alleviates CO poisoning toward Pt particles, and graphene nanosheets (GNs) ensure excellent electrical conductivity of the composites. The combined action among different components results in significantly enhanced catalytic activity of Pt/CS/PW{sub 12}-GNs toward methanol oxidation and better tolerance of CO. The as-synthesized Pt/CS/PW{sub 12}-GNs exhibit the forward peak current density of 445 mA mg{sup −1}, which is much higher than that (220 mA mg{sup −1}) for Pt/C-JM (the commercially available Johnson Matthey Hispec4000 catalyst, simplified as Pt/C-JM) and some recently reported Pt/graphene-based nanomaterials. The construction of 2-D distribution worm-like Pt nanoparticles and facile wet chemical synthesis strategy provide a promising way to develop superior performance electrocatalysts for direct methanol fuel cells applications.

  18. Effects of Instructional Preparation Strategies on Problem Solving in a Web-Based Learning Environment

    Science.gov (United States)

    Lee, Young-Jin

    2010-01-01

    This study reports the effects of different types of instructional preparation strategies on the problem solving performance of college students taking an introductory physics class. Students were divided into four equally skilled groups and solved the same physics problems after receiving different instructional preparations (engaging in…

  19. Bio-based barium alginate film: Preparation, flame retardancy and thermal degradation behavior.

    Science.gov (United States)

    Liu, Yun; Zhang, Chuan-Jie; Zhao, Jin-Chao; Guo, Yi; Zhu, Ping; Wang, De-Yi

    2016-03-30

    A bio-based barium alginate film was prepared via a facile ionic exchange and casting approach. Its flammability, thermal degradation and pyrolysis behaviors, thermal degradation mechanism were studied systemically by limiting oxygen index (LOI), vertical burning (UL-94), microscale combustion calorimetry (MCC), thermogravimetric analysis (TGA) coupled with Fourier transform infrared analysis (FTIR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). It showed that barium alginate film had much higher LOI value (52.0%) than that of sodium alginate film (24.5%). Moreover, barium alginate film passed the UL-94 V-0 rating, while the sodium alginate film showed no classification. Importantly, peak of heat release rate (PHRR) of barium alginate film in MCC test was much lower than that of sodium alginate film, suggested that introduction of barium ion into alginate film significantly decreased release of combustible gases. TG-FTIR and Py-GC-MS results indicated that barium alginate produced much less flammable products than that of sodium alginate in whole thermal degradation procedure. Finally, a possible degradation mechanism of barium alginate had been proposed. PMID:26794953

  20. Preparation of Metakaolin Based Geopolymer and Its Three- dimensional Pore Structural Characterization

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yunsheng; ZHANG Wenhua; SUN Wei; LI Zongjin; LIU Zhiyong

    2015-01-01

    Three types of pure geopolymer pastes (poly-sialate PS, poly- sialate-siloxo PSS, and poly-sialate-siloxo PSDS) werefi rst prepared by alkali (NaOH and KOH) activated metakaolin. Then a void space network was employed to simulate the 3-D pore-throat distribution across the unit cell of the various hardened geopolymer pastes with reference to their experimental mercury intrusion curves. Based on the simulated 3-D pore-throat structure models, a wide range of pore-level properties such as porosity, connectivity, permeability and tortuosity of various geopolymer pastes were calculated. The 3-D structural model and calculated parameters showed that most of the pores in Na-PS geopolymer paste was very small size pores ranging from 0 to 100 nm. A few very large pores were spread amongst the small pores, resulting in a very high penetration pressure, permeability resistance. Unlike Na-PS geopolymer paste, pore size with medium size of Na-PSS, K-PS and K-PSS geopolymer pastes distributed uniformly across the unit cell, and the size changes of adjacent pores in the 3 geopolymer pastes were little, producing higher penetration pressure, lower permeability, smaller connectivity and larger tortuosity. In contrast, pores in Na-PSDS and K-PSDS geopolymer pastes were relatively large and distributed concentratively, which caused samples to be easily penetrated by mercury, methane and nitrogenetc under relatively low pressures.