Effects of p-substituents on electrochemical CO oxidation by Rh porphyrin-based catalysts.

Science.gov (United States)

Yamazaki, Shin-ichi; Yamada, Yusuke; Takeda, Sahori; Goto, Midori; Ioroi, Tsutomu; Siroma, Zyun; Yasuda, Kazuaki

2010-08-21

Electrochemical CO oxidation by several carbon-supported rhodium tetraphenylporphyrins with systematically varied meso-substituents was investigated. A quantitative analysis revealed that the p-substituents on the meso-phenyl groups significantly affected CO oxidation activity. The electrocatalytic reaction was characterized in detail based on the spectroscopic and X-ray structural results as well as electrochemical analyses. The difference in the activity among Rh porphyrins is discussed in terms of the properties of p-substituents along with a proposed reaction mechanism. Rhodium tetrakis(4-carboxyphenyl)porphyrin (Rh(TCPP)), which exhibited the highest activity among the porphyrins tested, oxidized CO at a high rate at much lower potentials (means that CO is electrochemically oxidized by this catalyst when a slight overpotential is applied during the operation of a proton exchange membrane fuel cell. This catalyst exhibited little H(2) oxidation activity, in contrast to Pt-based catalysts.

Effect of Amine Adlayer on Electrochemical Uric Acid Sensor Conducted on Electrochemically Reduced Graphene Oxide

Energy Technology Data Exchange (ETDEWEB)

Park, Sumi; Kim, Kyuwon [Incheon National University, Incheon (Korea, Republic of)

2016-03-15

The electrochemical biosensing efficiency of uric acid (UA) detection on an electrochemically reduced graphene oxide (ERGO)-decorated electrode surface was studied by using various amine linkers used to immobilize ERGO. The amine linkers aminoethylphenyldiazonium , 2,2'-(ethylenedioxy)bis(ethylamine), 3-aminopro-pyltriethoxysilane, and polyethyleneimine were coated on indium-tin-oxide electrode surfaces through chemical or electrochemical deposition methods. ERGO-decorated surfaces were prepared by the electrochemical reduction of graphene oxide (GO), which was immobilized on the amine-coated electrode surfaces through the electrostatic interaction between GO and the ammonium ion of the linker on the surface. We monitored the sensing results of electrochemical UA detection with differential pulse voltammetry. The ERGO-modified surface presented electrocatalytic oxidation of UA and ascorbic acid. Among the different amines tested, 3-aminopropyltriethoxysilane provided the best biosensing performance in terms of sensitivity and reproducibility.

Effect of Amine Adlayer on Electrochemical Uric Acid Sensor Conducted on Electrochemically Reduced Graphene Oxide

International Nuclear Information System (INIS)

Park, Sumi; Kim, Kyuwon

2016-01-01

The electrochemical biosensing efficiency of uric acid (UA) detection on an electrochemically reduced graphene oxide (ERGO)-decorated electrode surface was studied by using various amine linkers used to immobilize ERGO. The amine linkers aminoethylphenyldiazonium , 2,2'-(ethylenedioxy)bis(ethylamine), 3-aminopro-pyltriethoxysilane, and polyethyleneimine were coated on indium-tin-oxide electrode surfaces through chemical or electrochemical deposition methods. ERGO-decorated surfaces were prepared by the electrochemical reduction of graphene oxide (GO), which was immobilized on the amine-coated electrode surfaces through the electrostatic interaction between GO and the ammonium ion of the linker on the surface. We monitored the sensing results of electrochemical UA detection with differential pulse voltammetry. The ERGO-modified surface presented electrocatalytic oxidation of UA and ascorbic acid. Among the different amines tested, 3-aminopropyltriethoxysilane provided the best biosensing performance in terms of sensitivity and reproducibility.

Pyro-Electrochemical Reduction of a Mixture of Rare Earth Oxides and NiO in LiCl molten Salt

Energy Technology Data Exchange (ETDEWEB)

Lee, Min Woo; Jeong, Sang Mun [Department of Chemical Engineering, Chungbuk National University, Cheongju (Korea, Republic of)

2017-06-15

An electrochemical reduction of a mixture of NiO and rare earth oxides has been conducted to increase the reduction degree of rare earth oxides. Cyclic voltammetry (CV) measurement was carried out to determine the electrochemical reduction behavior of the mixed oxide in molten LiCl medium. Constant voltage electrolysis was performed with various supplied charges to understand the mechanism of electrochemical reduction of the mixed oxide as a working electrode. After completion of the electrochemical reduction, crystal structure of the reaction intermediates was characterized by using an X-ray diffraction method. The results clearly demonstrate that the rare earth oxide was converted to RE-Ni intermetallics via co-reduction with NiO.

CEC mechanism in electrochemical oxidation of nitrocatechol-boric acid complexes

International Nuclear Information System (INIS)

Rafiee, Mohammad; Nematollahi, Davood; Salehzadeh, Hamid

2011-01-01

Graphical abstract: Display Omitted Highlights: → Nitrochetechol and its anionic form undergo complex reaction with boric acid. → The electron transfer of complex is coupled with both proceeding and following chemical reactions. → Electrochemical behavior of complex is resolved by diagnostic criteria and digital simulation. - Abstract: The electrochemical behavior of nitrocatechols-boric acid complexes in aqueous solution has been studied using cyclic voltammetry. The results indicate that nitrocatechol-boric acid complex derivatives are involved in the CEC mechanism. In this work, the impact of empirical parameters on the shape of the voltammograms is examined based on a CEC mechanism. In addition, homogeneous rate constants of both the preceding and the following reactions were estimated by comparing the experimental cyclic voltammograms with the digitally simulated results. The calculated dissociation constants for the complexes (K d ) and for ring cleavage of nitroquinone (k f2 ) were found to vary in the following order: 4-nitrocatechol > 3-methylnitrocatechol > 3-metoxynitrocatechol.

Study for electrochemical behavior of uranium oxide in a molten LiCl-Li2O system

International Nuclear Information System (INIS)

Park, Sung Bin; Park, Byung Heung; Seo, Chung Seok; Jung, Ki Jung; Park, Seong Won

2005-01-01

Interest in the electrolytic reduction of uranium oxide is increasing in the treatment of spent fuel oxides. With complicated and expensive procedures many reactive metals can be prepared in a pure metal form, the electrochemical reduction of a metal oxide has been recently proposed in metallurgy. The electrochemical reduction process is simple and rapid when compared to the conventional processes. The process can reduce the production costs and be applicable to a wide range of metal oxides. Chen et al. proposed the direct electrochemical reduction of titanium dioxide to titanium in a molten calcium chloride. Argonne National Laboratory (ANL) has reported the experimental results of an electrochemical reduction of the uranium oxide fuel in a bench-scale apparatus with a cyclic voltammetry, and has designed high-capacity reduction (HCR) cells and conducted three kg-scale UO 2 reduction runs. Gourishankar et al. classified the mechanisms of the electrolytic reduction of the metal oxides in a LiCl-Li 2 O molten salt system into two types; the simultaneous reduction and the direct electrochemical reduction. The uranium oxide in LiCl-Li 2 O molten salt was converted to uranium metal according to two mechanisms. Korea Atomic Energy Research Institute (KAERI) has developed the Advanced Spent Fuel Conditioning Process (ACP) to be an innovative technology in handling the PWR spent fuel. As part of ACP, the electrolytic reduction process (ER process) is the electrochemical reduction process of uranium oxide to uranium metal in molten salt. The ER process has advantages in a technical stability, an economic potential and a good proliferation resistance. KAERI has reported on the good experimental results of an electrochemical reduction of the uranium oxide in a 20 kg HM/batch lab-scale. In this work, cyclic voltammograms for a LiCl-3 wt% Li 2 O system and an U 3 O 8 -LiCl-3 wt% Li 2 O system with the integrated cathode assembly have been obtained. From the cyclic

Oxidation mechanism of flavanone taxifolin. Electrochemical and spectroelectrochemical investigation

International Nuclear Information System (INIS)

Kocábová, Jana; Fiedler, Jan; Degano, Ilaria; Sokolová, Romana

2016-01-01

Highlights: • The oxidation mechanism of flavanone taxifolin was proposed. • The oxidation is specific and differs from oxidation of flavonol quercetin. • A benzofuranon common for quercetin is NOT the taxifolin oxidation product. • The absence of C2–C3 double bond is crucial in taxifolin oxidation. - Abstract: The oxidation of taxifolin on glassy carbon electrode in acetonitrile was studied by cyclic voltammetry, UV–vis and IR spectroelectrochemistry. The oxidation products were identified using HPLC-ESI-MS/MS. The two-electron oxidation mechanism differs from that of flavonols (e.g. quercetin) due to the absence of the double bond between atoms C-2 and C-3. As confirmed by IR spectroelectrochemistry, quinone at ring B is formed as low stable intermediate. The oxidation pathway leads to the formation of hydroxylated derivative of taxifolin 2′,3,3′,4′,5,7-hexahydroxyflavone accompanied by the 2,3-desaturation.

Solar-mediated thermo-electrochemical oxidation of sodium dodecyl benzene sulfonate by modulating the effective oxidation potential and pathway for green remediation of wastewater

Science.gov (United States)

Gu, Di; Gao, Simeng; Jiang, TingTing; Wang, Baohui

2017-01-01

To match the relentless pursuit of three research hot points - efficient solar utilization, green and sustainable remediation of wastewater and advanced oxidation processes, solar-mediated thermo-electrochemical oxidation of surfactant was proposed and developed for green remediation of surfactant wastewater. The solar thermal electrochemical process (STEP), fully driven with solar energy to electric energy and heat and without an input of other energy, sustainably serves as efficient thermo-electrochemical oxidation of surfactant, exemplified by SDBS, in wastewater with the synergistic production of hydrogen. The electrooxidation-resistant surfactant is thermo-electrochemically oxidized to CO2 while hydrogen gas is generated by lowing effective oxidation potential and suppressing the oxidation activation energy originated from the combination of thermochemical and electrochemical effect. A clear conclusion on the mechanism of SDBS degradation can be proposed and discussed based on the theoretical analysis of electrochemical potential by quantum chemical method and experimental analysis of the CV, TG, GC, FT-IR, UV-vis, Fluorescence spectra and TOC. The degradation data provide a pilot for the treatment of SDBS wastewater that appears to occur via desulfonation followed by aromatic-ring opening. The solar thermal utilization that can initiate the desulfonation and activation of SDBS becomes one key step in the degradation process. PMID:28294180

Electrochemical oxidation and detection of sodium urate in alkaline ...

African Journals Online (AJOL)

Electrochemical behaviour of copper oxides electrode in the presence of sodium urate was investigated. The correlation between the anodic oxidation and the amperometric detection of sodium urate in the alkaline medium on copper oxides electrode was analysed by cyclic voltammetry (CV) and electrochemical ...

Electrochemical Oxidation of Glycerol Using Gold Electrode

International Nuclear Information System (INIS)

Mohamed Rozali Othman; Amirah Ahmad

2015-01-01

Cyclic voltammetry, potential linear V and chronocuolometry methods were carried out to gain electrochemical behavior of glycerol at a gold electrode. Potassium hydroxide and sulfuric acid were chosen to be the electrolyte for the electro-oxidation of this organic compound. Besides gold plate electrode, gold composite electrode (Au-PVC) was also used as the working electrode. The Au-PVC composite electrode was characterized by Scanning Electron Microscopy (SEM) to determine its morphological aspects before and after used in electrochemical oxidation of glycerol. In alkaline solution, the adsorption of hydroxide species onto the surface of both gold plate and composite Au-PVC electrodes occurs at potential around 500 mV vs SCE. However, at gold plate electrode, there was a small, broad peak before the drastic escalation of current densities which indicates the charge transfer of the chemisorbed OH - anion. In acidic media, the gold oxide was formed after potential 1.0 V. From the cyclic voltammogram glycerol undergo oxidation twice in potassium hydroxide at gold plate and Au-PVC composite electrodes, while in sulfuric acid, oxidation reaction happened once for glycerol on the gold plate electrode. Overall, electrochemical oxidation of glycerol was more effective in alkaline media. Tafel graph which plotted from potential linear V method shows that Au-PVC composite electrode is better than gold plate electrode for the electro-oxidation of glycerol in alkaline solution. Electrochemical oxidation of glycerol products as analyzed by Gas Chromatography-Mass Spectrometry (GC-MS) produced several carboxylic acids and phenolic compounds. (author)

Effect of oxide ion concentration on the electrochemical oxidation of carbon in molten LiCl

International Nuclear Information System (INIS)

Yun, J. W.; Choi, I. K.; Park, Y. S.; Kim, W. H.

2001-01-01

The continuous measurement of lithium oxide concentration was required in DOR (Direct Oxide Reduction) process, which converts spent nuclear fuel to metal form, for the reactivity monitor and effective control of the process. The concentration of lithium oxide was measured by the electrochemical method, which was based on the phenomenon that carbon atoms of glassy carbon electrode electrochemically react with oxygen ions of lithium oxide in molten LiCl medium. From the results of electrode polarization experiments, the trend of oxidation rate of carbon atoms was classified into two different regions, which were proportional and non-proportional ones, dependent on the amount of lithium oxide. Below about 2.5 wt % Li 2 O, as the carbon atom ionization rate was fast enough for reacting with diffusing lithium oxide to the surface of carbon electrode. In this concentration range, the oxidation rate of carbon atoms was controlled by the diffusion of lithium oxide, and the concentration of lithium oxide could be measured by electrochemical method. But, above 2.5 wt % Li 2 O, the oxidation rate of carbon atoms was controlled by the applied electrochemical potential, because the carbon atom ionization rate was suppressed by the huge amounts of diffusing Li 2 O. Above this concentration, the electrochemical method was not applicable to determine the concentration of lithium oxide

Mechanism of the electrochemical hydrogen reaction on smooth tungsten carbide and tungsten electrodes

International Nuclear Information System (INIS)

Wiesener, K.; Winkler, E.; Schneider, W.

1985-01-01

The course of the electrochemical hydrogen reaction on smooth tungsten-carbide electrodes in hydrogen saturated 2.25 M H 2 SO 4 follows a electrochemical sorption-desorption mechanism in the potential range of -0.4 to +0.1 V. At potentials greater than +0.1 V the hydrogen oxidation is controlled by a preliminary chemical sorption step. Concluding from the similar behaviour of tungsten-carbide and tungsten electrodes after cathodic pretreatment, different tungsten oxides should be involved in the course of the hydrogen reaction on tungsten carbide electrodes. (author)

Innovative oxide materials for electrochemical energy conversion and oxygen separation

Science.gov (United States)

Belousov, V. V.

2017-10-01

Ion-conducting solid metal oxides are widely used in high-temperature electrochemical devices for energy conversion and oxygen separation. However, liquid metal oxides possessing unique electrochemical properties still remain of limited use. The review demonstrates the potential for practical applications of molten oxides. The transport properties of molten oxide materials are discussed. The emphasis is placed on the chemical diffusion of oxygen in the molten oxide membrane materials for electrochemical energy conversion and oxygen separation. The thermodynamics of these materials is considered. The dynamic polymer chain model developed to describe the oxygen ion transport in molten oxides is discussed. Prospects for further research into molten oxide materials are outlined. The bibliography includes 145 references.

Solid oxide electrochemical reactor science.

Energy Technology Data Exchange (ETDEWEB)

Sullivan, Neal P. (Colorado School of Mines, Golden, CO); Stechel, Ellen Beth; Moyer, Connor J. (Colorado School of Mines, Golden, CO); Ambrosini, Andrea; Key, Robert J. (Colorado School of Mines, Golden, CO)

2010-09-01

Solid-oxide electrochemical cells are an exciting new technology. Development of solid-oxide cells (SOCs) has advanced considerable in recent years and continues to progress rapidly. This thesis studies several aspects of SOCs and contributes useful information to their continued development. This LDRD involved a collaboration between Sandia and the Colorado School of Mines (CSM) ins solid-oxide electrochemical reactors targeted at solid oxide electrolyzer cells (SOEC), which are the reverse of solid-oxide fuel cells (SOFC). SOECs complement Sandia's efforts in thermochemical production of alternative fuels. An SOEC technology would co-electrolyze carbon dioxide (CO{sub 2}) with steam at temperatures around 800 C to form synthesis gas (H{sub 2} and CO), which forms the building blocks for a petrochemical substitutes that can be used to power vehicles or in distributed energy platforms. The effort described here concentrates on research concerning catalytic chemistry, charge-transfer chemistry, and optimal cell-architecture. technical scope included computational modeling, materials development, and experimental evaluation. The project engaged the Colorado Fuel Cell Center at CSM through the support of a graduate student (Connor Moyer) at CSM and his advisors (Profs. Robert Kee and Neal Sullivan) in collaboration with Sandia.

Chitosan/graphene oxide nanocomposite films with enhanced interfacial interaction and their electrochemical applications

International Nuclear Information System (INIS)

He, Linghao; Wang, Hongfang; Xia, Guangmei; Sun, Jing; Song, Rui

2014-01-01

Graphical abstract: Nanocomposites by introducing graphene oxide (GO) into chitosan (CS) matrix were prepared and the effect of GO on the crystallization, thermal stability and mechanical properties of the films were investigated. In addition, the electrochemical behavior of the CS/GO modified electrode was comparatively studied with that of the neat CS-modified electrode. - Highlights: • Graphene oxide (GO) with well dispersion in the biopolymer chitosan (CS) matrix. • Detectable interactions do exist between the GO nanosheets and CS segments. • The addition of minor GO can improve the electrochemical activity of the neat CS. - Abstract: A series of chitosan (CS) nanocomposites incorporated with graphene oxide (GO) nanosheets were facilely prepared by sonochemical method. Characterized by scanning electron microscopy, the obtained nanocomposites showed fine dispersion of GO in the CS matrix. Meanwhile, a marked interfacial interaction was also revealed as the values of glass transition temperature, the decomposition temperature and the storage modulus were significantly increased with the addition of GO. Furthermore, the well dispersed GO nanosheets could significantly improve the electrochemical activity of the CS as demonstrated by the electrochemical behaviors of pure CS and the GO/CS composite electrodes. Hence, the GO/CS nanocomposites film could be a promising candidate in the fabrication of electrochemical biosensors

Manganese oxide-based materials as electrochemical supercapacitor electrodes.

Science.gov (United States)

Wei, Weifeng; Cui, Xinwei; Chen, Weixing; Ivey, Douglas G

2011-03-01

Electrochemical supercapacitors (ECs), characteristic of high power and reasonably high energy densities, have become a versatile solution to various emerging energy applications. This critical review describes some materials science aspects on manganese oxide-based materials for these applications, primarily including the strategic design and fabrication of these electrode materials. Nanostructurization, chemical modification and incorporation with high surface area, conductive nanoarchitectures are the three major strategies in the development of high-performance manganese oxide-based electrodes for EC applications. Numerous works reviewed herein have shown enhanced electrochemical performance in the manganese oxide-based electrode materials. However, many fundamental questions remain unanswered, particularly with respect to characterization and understanding of electron transfer and atomic transport of the electrochemical interface processes within the manganese oxide-based electrodes. In order to fully exploit the potential of manganese oxide-based electrode materials, an unambiguous appreciation of these basic questions and optimization of synthesis parameters and material properties are critical for the further development of EC devices (233 references).

Integrating electrochemical oxidation into forward osmosis process for removal of trace antibiotics in wastewater.

Science.gov (United States)

Liu, Pengxiao; Zhang, Hanmin; Feng, Yujie; Shen, Chao; Yang, Fenglin

2015-10-15

During the rejection of trace pharmaceutical contaminants from wastewater by forward osmosis (FO), disposal of the FO concentrate was still an unsolved issue. In this study, by integrating the advantages of forward osmosis and electrochemical oxidation, a forward osmosis process with the function of electrochemical oxidation (FOwEO) was established for the first time to achieve the aim of rejection of trace antibiotics from wastewater and treatment of the concentrate at the same time. Results demonstrated that FOwEO (current density J=1 mA cm(-2)) exhibited excellent rejections of antibiotics (>98%) regardless of different operation conditions, and above all, antibiotics in the concentrate were well degraded (>99%) at the end of experiment (after 3h). A synergetic effect between forward osmosis and electrochemical oxidation was observed in FOwEO, which lies in that antibiotic rejections by FO were enhanced due to the degradation of antibiotics in the concentrate, while the electrochemical oxidation capacity was improved in the FOwEO channel, of which good mass transfer and the assist of indirect oxidation owing to the reverse NaCl from draw solution were supposed to be the mechanism. This study demonstrated that the FOwEO has the capability to thoroughly remove trace antibiotics from wastewater. Copyright © 2015 Elsevier B.V. All rights reserved.

A high-performance flexible fibre-shaped electrochemical capacitor based on electrochemically reduced graphene oxide.

Science.gov (United States)

Li, Yingru; Sheng, Kaixuan; Yuan, Wenjing; Shi, Gaoquan

2013-01-11

A fibre-shaped solid electrochemical capacitor based on electrochemically reduced graphene oxide has been fabricated, exhibiting high specific capacitance and rate capability, long cycling life and attractive flexibility.

Nanomaterials-based electrochemical sensors for nitric oxide

International Nuclear Information System (INIS)

Dang, Xueping; Hu, Hui; Wang, Shengfu; Hu, Shengshui

2015-01-01

Electrochemical sensing has been demonstrated to represent an efficient way to quantify nitric oxide (NO) in challenging physiological environments. A sensing interface based on nanomaterials opens up new opportunities and broader prospects for electrochemical NO sensors. This review (with 141 refs.) gives a general view of recent advances in the development of electrochemical sensors based on nanomaterials. It is subdivided into sections on (i) carbon derived nanomaterials (such as carbon nanotubes, graphenes, fullerenes), (ii) metal nanoparticles (including gold, platinum and other metallic nanoparticles); (iii) semiconductor metal oxide nanomaterials (including the oxides of titanium, aluminum, iron, and ruthenium); and finally (iv) nanocomposites (such as those formed from carbon nanomaterials with nanoparticles of gold, platinum, NiO or TiO 2 ). The various strategies are discussed, and the advances of using nanomaterials and the trends in NO sensor technology are outlooked in the final section. (author)

Electrochemical oxidation of cholesterol in acetonitrile leads to the formation of cholesta-4,6-dien-3-one

International Nuclear Information System (INIS)

Hosokawa, Yu-Ya; Hakamata, Hideki; Murakami, Tomonori; Aoyagi, Sakae; Kuroda, Minpei; Mimaki, Yoshihiro; Ito, Ayumi; Morosawa, Sayaka; Kusu, Fumiyo

2009-01-01

Cholesterol was shown to be oxidized at the glassy carbon electrode in an acetonitrile-2-propanol mixture and this oxidation reaction was applied to the determination of serum total cholesterol by high-performance liquid chromatography with electrochemical detection (K. Hojo, H. Hakamata, A. Ito, A. Kotani, C. Furukawa, Y.Y. Hosokawa, F. Kusu, J. Chromatogr. A 1166 (2007) 135-141). To gain insight into the detection mechanisms of cholesterol, an electrolytic product of cholesterol was collected and characterized by infrared spectroscopy, one- and two-dimensional nuclear magnetic resonance, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The three techniques, together with comparisons of literature spectral data, confirmed the formation of cholesta-4,6-dien-3-one. The conversion of cholesterol to cholesta-4,6-dien-3-one, a four-electron, four-proton electrochemical process, has been proposed as an electrochemical oxidation mechanism of cholesterol in acetonitrile.

Electrochemical advanced oxidation processes: today and tomorrow. A review.

Science.gov (United States)

Sirés, Ignasi; Brillas, Enric; Oturan, Mehmet A; Rodrigo, Manuel A; Panizza, Marco

2014-01-01

In recent years, new advanced oxidation processes based on the electrochemical technology, the so-called electrochemical advanced oxidation processes (EAOPs), have been developed for the prevention and remediation of environmental pollution, especially focusing on water streams. These methods are based on the electrochemical generation of a very powerful oxidizing agent, such as the hydroxyl radical ((•)OH) in solution, which is then able to destroy organics up to their mineralization. EAOPs include heterogeneous processes like anodic oxidation and photoelectrocatalysis methods, in which (•)OH are generated at the anode surface either electrochemically or photochemically, and homogeneous processes like electro-Fenton, photoelectro-Fenton, and sonoelectrolysis, in which (•)OH are produced in the bulk solution. This paper presents a general overview of the application of EAOPs on the removal of aqueous organic pollutants, first reviewing the most recent works and then looking to the future. A global perspective on the fundamentals and experimental setups is offered, and laboratory-scale and pilot-scale experiments are examined and discussed.

Preparation and electrochemical characterization of MnOOH nanowire-graphene oxide

International Nuclear Information System (INIS)

Wang Lin; Wang Dianlong

2011-01-01

Highlights: → MnOOH nanowire-graphene oxide composites are prepared by hydrothermal reaction in distilled water or 5% ammonia aqueous solution at 130 deg. C, with MnO 2 -graphene oxide composites which are synthesized by a redox reaction between KMnO 4 and graphene oxide. → MnO 2 is deoxidized to MnOOH on graphene oxide through hydrothermal reaction without any extra reductants. → It is found that the electrochemical resistance of MnOOH nanowire-graphene oxide composites decreases and the capacitance increases to 76 F g -1 when hydrothermal reaction is conducted in ammonia aqueous solution. → MnOOH nanowire-graphene oxide composites prepared by hydrothermal reaction in 5% ammonia aqueous solution have excellent capacitance retention ratio at scan rate from 5 mV s -1 to 40 mV s -1 . - Abstract: MnOOH nanowire-graphene oxide composites are prepared by hydrothermal reaction in distilled water or 5% ammonia aqueous solution at 130 deg. C with MnO 2 -graphene oxide composites which are synthesized by a redox reaction between KMnO 4 and graphene oxide. Powder X-ray diffraction (XRD) analyses and energy dispersive X-ray analyses (EDAX) show MnO 2 is deoxidized to MnOOH on graphene oxide through hydrothermal reaction without any extra reductants. The electrochemical capacitance of MnOOH nanowire-graphene oxide composites prepared in 5% ammonia aqueous solution is 76 F g -1 at current density of 0.1 A g -1 . Moreover, electrochemical impedance spectroscopy (EIS) suggests the electrochemical resistance of MnOOH nanowire-graphene oxide composites is reduced when hydrothermal reaction is conducted in ammonia aqueous solution. The relationship between the electrochemical capacitance and the structure of MnOOH nanowire-graphene oxide composites is characterized by cyclic voltammetry (CV) and field emission scanning electron microscopy (FESEM). The results indicate the electrochemical performance of MnOOH nanowire-graphene oxide composites strongly depends on their

Synthesis and electrochemical behavior of nanostructured cauliflower-shape Co-Ni/Co-Ni oxides composites

International Nuclear Information System (INIS)

Gupta, Vinay; Kawaguchi, Toshikazu; Miura, Norio

2009-01-01

Nanostructured Co-Ni/Co-Ni oxides were electrochemically deposited onto stainless steel electrode by electrochemical method and characterized for their structural and supercapacitive properties. The SEM images indicated that the obtained Co-Ni/Co-Ni oxides had cauliflower-type nanostructure. The X-ray diffraction pattern showed the formation of Co 3 O 4 , NiO, Co and Ni. The EDX elemental mapping images indicated that Ni, Co and O are distributed uniformly. The deposited Co-Ni/Co-Ni oxides showed good supercapacitive characteristics with a specific capacitance of 331 F/g at 1 mA/cm 2 current density in 1 M KOH electrolyte. A mechanism of the formation of cauliflower-shape Co-Ni/Co-Ni oxides was proposed. A variety of promising applications in the fields such as energy storage devices and sensors can be envisioned from Co-Ni/Co-Ni oxides

Electrochemical, Chemical and Enzymatic Oxidations of Phenothiazines

NARCIS (Netherlands)

Blankert, B.; Hayen, H.; van Leeuwen, S.M.; Karst, U.; Bodoki, E.; Lotrean, S.; Sandulescu, R.; Mora Diaz, N.; Dominguez, O.; Arcos, J.; Kauffmann, J.-M.

2005-01-01

The oxidation of several phenothiazine drugs (phenothiazine, promethazine hydrochloride, promazine hydrochloride, trimeprazine hydrochloride and ethopropazine hydrochloride) has been carried out in aqueous acidic media by electrochemical, chemical and enzymatic methods. The chemical oxidation was

Electrochemical Multi-Coloration of Molybdenum Oxide Bronzes

International Nuclear Information System (INIS)

Lee, Sangmin; Saji, Viswanathan S.; Lee, Chiwoo

2013-01-01

We report a simple electrochemical approach in fabricating multiple colored molybdenum (Mo) oxide bronzes on the surface of a Mo-quartz electrode. A three step electrochemical batch process consisting of linear sweep voltammetry and anodic oxidation followed by cathodic reduction in neutral K 2 SO 4 electrolyte at different end potentials, viz. -0.62, -0.80 and -1.60 V (vs. Hg/HgSO 4 ) yielded red, blue and yellow colored bronzes. The samples produced were analyzed by XRD, EDS, and SIMS. The color variation was suggested to be associated with the cations intercalation into the oxide formed and the simultaneous structural changes that occurred during the cathodic reduction in neutral aqueous medium

Electrochemical Multi-Coloration of Molybdenum Oxide Bronzes

Energy Technology Data Exchange (ETDEWEB)

Lee, Sangmin; Saji, Viswanathan S.; Lee, Chiwoo [Korea Univ., Seoul (Korea, Republic of)

2013-08-15

We report a simple electrochemical approach in fabricating multiple colored molybdenum (Mo) oxide bronzes on the surface of a Mo-quartz electrode. A three step electrochemical batch process consisting of linear sweep voltammetry and anodic oxidation followed by cathodic reduction in neutral K{sub 2}SO{sub 4} electrolyte at different end potentials, viz. -0.62, -0.80 and -1.60 V (vs. Hg/HgSO{sub 4}) yielded red, blue and yellow colored bronzes. The samples produced were analyzed by XRD, EDS, and SIMS. The color variation was suggested to be associated with the cations intercalation into the oxide formed and the simultaneous structural changes that occurred during the cathodic reduction in neutral aqueous medium.

Peptide methionine sulfoxide reductase A (MsrA): direct electrochemical oxidation on carbon electrodes.

Science.gov (United States)

Enache, T A; Oliveira-Brett, A M

2013-02-01

The direct electrochemical behaviour of peptide methionine sulfoxide reductase A (MsrA) adsorbed on glassy carbon and boron doped diamond electrodes surface, was studied over a wide pH range by cyclic and differential pulse voltammetry. MsrA oxidation mechanism occurs in three consecutive, pH dependent steps, corresponding to the oxidation of tyrosine, tryptophan and histidine amino acid residues. At the glassy carbon electrode, the first step corresponds to the oxidation of tyrosine and tryptophan residues and occurs for the same potential. The advantage of boron doped diamond electrode was to enable the separation of tyrosine and tryptophan oxidation peaks. On the second step occurs the histidine oxidation, and on the third, at higher potentials, the second tryptophan oxidation. MsrA adsorbs on the hydrophobic carbon electrode surface preferentially through the three hydrophobic domains, C1, C2 and C3, which contain the tyrosine, tryptophan and histidine residues, and tryptophan exists only in these regions, and undergo electrochemical oxidation. Copyright © 2012 Elsevier B.V. All rights reserved.

Nitrogen-doped reduced graphene oxide electrodes for electrochemical supercapacitors.

Science.gov (United States)

Nolan, Hugo; Mendoza-Sanchez, Beatriz; Ashok Kumar, Nanjundan; McEvoy, Niall; O'Brien, Sean; Nicolosi, Valeria; Duesberg, Georg S

2014-02-14

Herein we use Nitrogen-doped reduced Graphene Oxide (N-rGO) as the active material in supercapacitor electrodes. Building on a previous work detailing the synthesis of this material, electrodes were fabricated via spray-deposition of aqueous dispersions and the electrochemical charge storage mechanism was investigated. Results indicate that the functionalised graphene displays improved performance compared to non-functionalised graphene. The simplicity of fabrication suggests ease of up-scaling of such electrodes for commercial applications.

Electrochemical investigations of ion-implanted oxide films

International Nuclear Information System (INIS)

Schultze, J.W.; Danzfuss, B.; Meyer, O.; Stimming, U.

1985-01-01

Oxide films (passive films) of 40-50 nm thickness were prepared by anodic polarization of hafnium and titanium electrodes up to 20 V. Multiple-energy ion implantation of palladium, iron and xenon was used in order to obtain modified films with constant concentration profiles of the implanted ions. Rutherford backscattering, X-ray photoelectron spectroscopy measurements and electrochemical charging curves prove the presence of implanted ions, but electrochemical and photoelectrochemical measurements indicate that the dominating effect of ion implantation is the disordering of the oxide film. The capacity of hafnium electrodes increases as a result of an increase in the dielectric constant D. For titanium the Schottky-Mott analysis shows that ion implantation causes an increase in D and the donor concentration N. Additional electronic states in the band gap which are created by the implantation improve the conductivity of the semiconducting or insulating films. This is seen in the enhancement of electron transfer reactions and its disappearance during repassivation and annealing. Energy changes in the band gap are derived from photoelectrochemical measurements; the absorption edge of hafnium oxide films decreases by approximately 2 eV because of ion implantation, but it stays almost constant for titanium oxide films. All changes in electrochemical behavior caused by ion implantation show little variation with the nature of the implanted ion. Hence the dominating effect seems to be a disordering of the oxide. (Auth.)

Electrochemical degradation of Novacron Yellow C-RG using boron-doped diamond and platinum anodes: Direct and Indirect oxidation

International Nuclear Information System (INIS)

Rocha, J.H. Bezerra; Gomes, M.M. Soares; Santos, E. Vieira dos; Moura, E.C. Martins de; Silva, D. Ribeiro da; Quiroz, M.A.; Martínez-Huitle, C.A.

2014-01-01

Graphical abstract: - Highlights: • Nature of electrode material decides the electrocatalytic mechanism followed. • Electrogenerated strong oxidants on BDD surface improve the color and organic load removal. • Chlorine active species act in solution cage oxidizing organic matter. - Abstract: The present study discusses the electrochemical degradation process of a textile dye, Novacron Yellow C-RG (NY), dissolved in synthetic wastewaters, via direct and indirect oxidation. Experiments were conducted using boron-doped diamond (BDD) and platinum supported on Ti (Pt/Ti) electrodes in the absence and presence of NaCl in the solution. The direct process for removing color is relatively similar for both anodes, while the electrochemical degradation is significantly accelerated by the presence of halogen salt in the solution. Interestingly, it does not depend on applied current density, but rather on NaCl concentration. Therefore, the electrochemical processes (direct/indirect) favor specific oxidation pathways depending on electrocatalytic material. Whereas, the Pt/Ti anode favors preferentially color removal by direct and indirect oxidation (100% of color removal) due to the fragmentation of the azo dye group; BDD electrode favors color and organic load removals in both processes (95% and up to 87%, respectively), due to the rupture of dye in different parts of its chemical structure. Parameters of removal efficiency and energy consumption for the electrochemical process were estimated. Finally, an explanation has been attempted for the role of halide, in relation with the oxygen evolution reaction, concomitant with the electrochemical incineration as well as electrocatalytic mechanisms, for each one of the electrodes used

Treatment of Radioactive Organic Wastes by an Electrochemical Oxidation

International Nuclear Information System (INIS)

Kim, K.H.; Ryue, Y.G.; Kwak, K.K.; Hong, K.P.; Kim, D.H.

2007-01-01

A waste treatment system by using an electrochemical oxidation (MEO, Mediated Electrochemical Oxidation) was installed at KAERI (Korea Atomic Energy Research Institute) for the treatment of radioactive organic wastes, especially EDTA (Ethylene Diamine Tetraacetic Acid) generated during the decontamination activity of nuclear installations. A cerium and silver mediated electrochemical oxidation technique method has been developed as an alternative for an incineration process. An experiment to evaluate the applicability of the above two processes and to establish the conditions to operate the pilot-scale system has been carried out by changing the concentration of the catalyst and EDTA, the operational current density, the operating temperature, and the electrolyte concentration. As for the results, silver mediated oxidation was more effective in destructing the EDTA wastes than the cerium mediated oxidation process. For a constant volume of the EDTA wastes, the treatment time for the cerium-mediated oxidation was 9 hours and its conversion ratio of EDTA to water and CO 2 was 90.2 % at 80 deg. C, 10 A, but the treatment time for the silver-mediated oxidation was 3 hours and its conversion ratio was 89.2 % at 30 deg. C, 10 A. (authors)

Elucidation of the electrochromic mechanism of nanostructured iron oxides films

Energy Technology Data Exchange (ETDEWEB)

Garcia-Lobato, M.A.; Martinez, Arturo I.; Castro-Roman, M. [Center for Research and Advanced Studies of the National Polytechnic Institute, Cinvestav Campus Saltillo, Carr. Saltillo-Monterrey Km. 13, Ramos Arizpe, Coah. 25900 (Mexico); Perry, Dale L. [Mail Stop 70A1150, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); Zarate, R.A. [Departamento de Fisica, Facultad de Ciencias, Universidad Catolica del Norte, Casilla 1280, Antofagasta (Chile); Escobar-Alarcon, L. (Departamento de Fisica, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico)

2011-02-15

Nanostructured hematite thin films were electrochemically cycled in an aqueous solution of LiOH. Through optical, structural, morphological, and magnetic measurements, the coloration mechanism of electrochromic iron oxide thin films was elucidated. The conditions for double or single electrochromic behavior are given in this work. During the electrochemical cycling, it was found that topotactic transformations of hexagonal crystal structures are favored; i.e. {alpha}-Fe{sub 2}O{sub 3} to Fe(OH){sub 2} and subsequently to {delta}-FeOOH. These topotactic redox reactions are responsible for color changes of iron oxide films. (author)

Surface Properties of PAN-based Carbon Fibers Modified by Electrochemical Oxidization in Organic Electrolyte Systems

Directory of Open Access Journals (Sweden)

WU Bo

2016-09-01

Full Text Available PAN-based carbon fibers were modified by electrochemical oxidization using fatty alcohol polyoxyethylene ether phosphate (O3P, triethanolamine (TEOA and fatty alcohol polyoxyethylene ether ammonium phosphate (O3PNH4 as organic electrolyte respectively. Titration analysis, single fiber fracture strength measurement and field emission scanning electron microscopy (FE-SEM were used to evaluate the content of acidic functional group on the surface, mechanical properties and surface morphology of carbon fiber. The optimum process of electrochemical treatment obtained is at 50℃ for 2min and O3PNH4 (5%, mass fraction as the electrolyte with current density of 2A/g. In addition, the surface properties of modified carbon fibers were characterized by X-ray photoelectron spectroscopy (XPS and single fiber contact angle test. The results show that the hydrophilic acidic functional groups on the surface of carbon fiber which can enhance the surface energy are increased by the electrochemical oxidation using O3PNH4 as electrolyte, almost without any weakening to the mechanical properties of carbon fiber.

Physical, mechanical and electrochemical characterization of all-perovskite intermediate temperature solid oxide fuel cells

Science.gov (United States)

Mohammadi, Alidad

Strontium- and magnesium-doped lanthanum gallate (LSGM) has been considered as a promising electrolyte for solid oxide fuel cell (SOFC) systems in recent years due to its high ionic conductivity and chemical stability over a wide range of oxygen partial pressures and temperatures. This research describes synthesis, physical and mechanical behavior, electrochemical properties, phase evolution, and microstructure of components of an all-perovskite anode-supported intermediate temperature solid oxide fuel cell (ITSOFC), based on porous La 0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) anode, La0.8Sr0.2Ga0.8Mg0.2O 2.8 (LSGM) electrolyte, and porous La0.6Sr0.4Fe 0.8Co0.2O3 (LSCF) cathode. The phase evolution of synthesized LSGM and LSCM powders has been investigated, and it has been confirmed that there is no reaction between LSGM and LSCM at sintering temperature. Using different amounts of poreformers and binders as well as controlling firing temperature, porosity of the anode was optimized while still retaining good mechanical integrity. The effect of cell operation conditions under dry hydrogen fuel on the SOFC open circuit voltage (OCV) and cell performance were also investigated. Characterization study of the synthesized LSGM indicates that sintering at 1500°C obtains higher electrical conductivity compared to the currently published results, while conductivity of pellets sintered at 1400°C and 1450°C would be slightly lower. The effect of sintering temperature on bulk and grain boundary resistivities was also discussed. The mechanical properties, such as hardness, Young's modulus, fracture toughness and modulus of rupture of the electrolyte were determined and correlated with scanning electron microscopy (SEM) morphological characterization. Linear thermal expansion and thermal expansion coefficient of LSGM were also measured.

MECHANISTIC STUDY OF COLCHICINE’s ELECTROCHEMICAL OXIDATION

International Nuclear Information System (INIS)

Bodoki, Ede; Chira, Ruxandra; Zaharia, Valentin; Săndulescu, Robert

2015-01-01

Colchicine, as one of the most ancient drugs of human kind, is still in the focal point of the current research due to its multimodal mechanism of action. The elucidation of colchicine’s still unknown redox properties may play an important role in deciphering its beneficial and harmful implications over the human body. Therefore, a systematic mechanistic study of colchicine’s oxidation has been undertaken by electrochemistry coupled to mass spectrometry using two different types of electrolytic cells, in order to clarify the existing inconsistencies with respect to this topic. At around 1 V vs. Pd/H 2 , initiated by a one-electron transfer, the oxidation of colchicine sets off leading to a cation radical, whose further oxidation may evolve on several different pathways. The main product of the anodic electrochemical reaction, regardless of the carrier solution’s pH is represented by a 7-hydroxy derivative of colchicine. At more anodic potentials (above 1.4 V vs. Pd/H 2 ) compounds arising from epoxidation and/or multiple hydroxylation occur. No di- or tridemethylated quinone structures, as previously suggested in the literature for the electrolytic oxidation of colchicine, has been detected in the mass spectra.

Aluminum Oxide Formation On Fecral Catalyst Support By Electro-Chemical Coating

Directory of Open Access Journals (Sweden)

Yang H.S.

2015-06-01

Full Text Available FeCrAl is comprised essentially of Fe, Cr, Al and generally considered as metallic substrates for catalyst support because of its advantage in the high-temperature corrosion resistance, high mechanical strength, and ductility. Oxidation film and its adhesion on FeCrAl surface with aluminum are important for catalyst life. Therefore various appropriate surface treatments such as thermal oxidation, Sol, PVD, CVD has studied. In this research, PEO (plasma electrolytic oxidation process was applied to form the aluminum oxide on FeCrAl surface, and the formed oxide particle according to process conditions such as electric energy and oxidation time were investigated. Microstructure and aluminum oxide particle on FeCrAl surface after PEO process was observed by FE-SEM and EDS with element mapping analysis. The study presents possibility of aluminum oxide formation by electro-chemical coating process without any pretreatment of FeCrAl.

Microfluidic electrochemical sensor for on-line monitoring of aerosol oxidative activity.

Science.gov (United States)

Sameenoi, Yupaporn; Koehler, Kirsten; Shapiro, Jeff; Boonsong, Kanokporn; Sun, Yele; Collett, Jeffrey; Volckens, John; Henry, Charles S

2012-06-27

Particulate matter (PM) air pollution has a significant impact on human morbidity and mortality; however, the mechanisms of PM-induced toxicity are poorly defined. A leading hypothesis states that airborne PM induces harm by generating reactive oxygen species in and around human tissues, leading to oxidative stress. We report here a system employing a microfluidic electrochemical sensor coupled directly to a particle-into-liquid sampler (PILS) system to measure aerosol oxidative activity in an on-line format. The oxidative activity measurement is based on the dithiothreitol (DTT) assay, where, after being oxidized by PM, the remaining reduced DTT is analyzed by the microfluidic sensor. The sensor consists of an array of working, reference, and auxiliary electrodes fabricated in a poly(dimethylsiloxane)-based microfluidic device. Cobalt(II) phthalocyanine-modified carbon paste was used as the working electrode material, allowing selective detection of reduced DTT. The electrochemical sensor was validated off-line against the traditional DTT assay using filter samples taken from urban environments and biomass burning events. After off-line characterization, the sensor was coupled to a PILS to enable on-line sampling/analysis of aerosol oxidative activity. Urban dust and industrial incinerator ash samples were aerosolized in an aerosol chamber and analyzed for their oxidative activity. The on-line sensor reported DTT consumption rates (oxidative activity) in good correlation with aerosol concentration (R(2) from 0.86 to 0.97) with a time resolution of approximately 3 min.

Fabrication of Electrochemically Reduced Graphene Oxide Modified Gas Diffusion Electrode for In-situ Electrochemical Advanced Oxidation Process under Mild Conditions

International Nuclear Information System (INIS)

Dong, Heng; Su, Huimin; Chen, Ze; Yu, Han; Yu, Hongbing

2016-01-01

With aim to develop an efficient heterogeneous metal-free cathodic electrochemical advance oxidation process (CEAOP) for persistent organic pollutants (POPs) removal from wastewater under mild conditions, electrochemically reduced graphene oxide (ERGO)-modified gas diffusion electrode (GDE) was prepared for oxygen-containing radicals production via electrochemical oxygen reduction reaction (ORR). A detailed physical characterization was carried out by SEM, Raman spectroscopy, XRD and XPS. The electrocatalytic behavior for ORR was investigated by electrochemical measurements and electrolysis experiments under constant current density. Bisphenol A (BPA) of 20 mg L −1 was used as a model of POPs to evaluate the performance of the CEAOP with ERGO-modified GDE. The results showed that the defects concentration and electrochemical active sites of the ERGO was increased as the reduction time (30 min, 60 min and 120 min), leading to different catalysis on ORR. ·O 2 generation via one-electron ORR was found under the electrocatalysis of ERGO (60 min and 120 min), contributing to a complete degradation of BPA within 20 min and a mineralization current efficiency (MCE) of 74.60%. An alternative metal-free CEAOP independent of Fenton reaction was established based on ERGO-modified GDE for POPs removal from wastewater under mild conditions.

Electrochemical properties and electrocatalytic activity of conducting polymer/copper nanoparticles supported on reduced graphene oxide composite

Science.gov (United States)

Ehsani, Ali; Jaleh, Babak; Nasrollahzadeh, Mahmoud

2014-07-01

Reduced graphene oxide (rGO) was used to support Cu nanoparticles. As electro-active electrodes for supercapacitors composites of reduced graphene oxide/Cu nanoparticles (rGO/CuNPs) and polytyramine (PT) with good uniformity are prepared by electropolymerization. Composite of rGO/CuNPs-PT was synthesized by cyclic voltammetry (CV) methods and electrochemical properties of film were investigated by using electrochemical techniques. The results show that, the rGO/CuNPs-PT/G has better capacitance performance. This is mainly because of the really large surface area and the better electronic and ionic conductivity of rGO/CuNPs-PT/G, which lead to greater double-layer capacitance and faradic pseudo capacitance. Modified graphite electrodes (rGO/CuNPs-PT/G) were examined for their redox process and electrocatalytic activities towards the oxidation of methanol in alkaline solutions. The methods of cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) were employed. In comparison with a Cu-PT/G (Graphite), rGO/CuNPs-PT/G modified electrode shows a significantly higher response for methanol oxidation. A mechanism based on the electro-chemical generation of Cu(III) active sites and their subsequent consumptions by methanol have been discussed.

Electrochemical characterization of oxide film formed at high temperature on Alloy 690

Energy Technology Data Exchange (ETDEWEB)

Abraham, Geogy J., E-mail: gja@barc.gov.in [Materials Science Division, BARC, Mumbai 400 085 (India); Bhambroo, Rajan [Deptt. of Metallurgical Engg. and Mat. Sci., IIT Bombay, Mumbai 400 076 (India); Kain, V. [Materials Science Division, BARC, Mumbai 400 085 (India); Shekhar, R. [CCCM, BARC, Hyderabad 500 062 (India); Dey, G.K. [Materials Science Division, BARC, Mumbai 400 085 (India); Raja, V.S. [Deptt. of Metallurgical Engg. and Mat. Sci., IIT Bombay, Mumbai 400 076 (India)

2012-02-15

Highlights: Black-Right-Pointing-Pointer GD-QMS studies of high temperature oxide film formed on Alloy 690. Black-Right-Pointing-Pointer Defect density reduced with increase in temperature. Black-Right-Pointing-Pointer Electrochemical behaviour of oxide film correlated to the Cr-content in oxide. - Abstract: High temperature passivation studies on Alloy 690 were carried out in lithiated water at 250 Degree-Sign C, 275 Degree-Sign C and 300 Degree-Sign C for 72 h. The passive films were characterized by glow discharge-quadrupole mass spectroscopy (GD-QMS) for compositional variation across the depth and micro laser Raman spectroscopy for oxide composition on the surface. The defect density in the oxide films was established from the Mott-Schottky analysis using electrochemical impedance spectroscopy. Electrochemical experiments at room temperature in chloride medium revealed best passivity behaviour by the oxide film formed at 300 Degree-Sign C for 72 h. The electrochemical studies were correlated to the chromium (and oxygen) content of the oxide films. Autoclaving at 300 Degree-Sign C resulted in the best passive film formation on Alloy 690 in lithiated water.

Kinetic mechanism for modeling of electrochemical reactions.

Science.gov (United States)

Cervenka, Petr; Hrdlička, Jiří; Přibyl, Michal; Snita, Dalimil

2012-04-01

We propose a kinetic mechanism of electrochemical interactions. We assume fast formation and recombination of electron donors D- and acceptors A+ on electrode surfaces. These mediators are continuously formed in the electrode matter by thermal fluctuations. The mediators D- and A+, chemically equivalent to the electrode metal, enter electrochemical interactions on the electrode surfaces. Electrochemical dynamics and current-voltage characteristics of a selected electrochemical system are studied. Our results are in good qualitative agreement with those given by the classical Butler-Volmer kinetics. The proposed model can be used to study fast electrochemical processes in microsystems and nanosystems that are often out of the thermal equilibrium. Moreover, the kinetic mechanism operates only with the surface concentrations of chemical reactants and local electric potentials, which facilitates the study of electrochemical systems with indefinable bulk.

Electrochemical Oxidation of PAHs in Water from Harbor Sediment Purification

DEFF Research Database (Denmark)

Muff, Jens; Søgaard, Erik Gydesen

2010-01-01

generated oxidant solution with a free chlorine concentration of 2 gL-1. Both strategies resulted in a successful degradation of 5 PAHs to fulfil the discharge limit on 0.010 µgL-1. The intermixing-with-oxidant approach can also be applied as a method to address the actual sediment matrix....... of the discharge water addressing primarily polycyclic aromatic hydrocarbons (PAHs). PAHs are by-products of incomplete combustion of organic materials with recalcitrant and strong mutagenic/carcinogenic properties, due to their benzene analogue structures. PAHs are hydrophobic compounds and their persistence...... evidence for the importance of the indirect oxidation mechanism in the degradation of the PAHs. The proof-of-concept study was conducted both by a direct treatment approach and an intermixing-with-oxidant approach, where the contaminated water was intermixed in different ratios with an electrochemically...

Destructive electronics from electrochemical-mechanically triggered chemical dissolution

International Nuclear Information System (INIS)

Sim, Kyoseung; Wang, Xu; Yu, Cunjiang; Li, Yuhang; Linghu, Changhong; Song, Jizhou; Gao, Yang

2017-01-01

The considerable need to enhance data and hardware security suggest one possible future for electronics where it is possible to destroy them and even make them disappear physically. This paper reports a type of destructive electronics which features fast transience from chemical dissolution on-demand triggered in an electrochemical-mechanical manner. The detailed materials, mechanics, and device construction of the destructive electronics are presented. Experiment and analysis of the triggered releasing and transience study of electronic materials, resistors and metal-oxide-semiconductor field effect transistors illustrate the key aspects of the destructive electronics. The reported destructive electronics is useful in a wide range of areas from security and defense, to medical applications (paper)

Electrochemical impedance spectroscopy investigation on indium tin oxide films under cathodic polarization in NaOH solution

International Nuclear Information System (INIS)

Gao, Wenjiao; Cao, Si; Yang, Yanze; Wang, Hao; Li, Jin; Jiang, Yiming

2012-01-01

The electrochemical corrosion behaviors of indium tin oxide (ITO) films under the cathodic polarization in 0.1 M NaOH solution were investigated by electrochemical impedance spectroscopy. The as-received and the cathodically polarized ITO films were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction for morphological, compositional and structural studies. The results showed that ITO films underwent a corrosion process during the cathodic polarization and the main component of the corrosion products was body-centered cubic indium. The electrochemical impedance parameters were related to the effect of the cathodic polarization on the ITO specimens. The capacitance of ITO specimens increased, while the charge transfer resistance and the inductance decreased with the increase of the polarization time. The proposed mechanism indicated that the corrosion products (metallic indium) were firstly formed during the cathodic polarization and then absorbed on the surface of the ITO film. As the surface was gradually covered by indium particles, the corrosion process was suppressed. - Highlights: ► Cathodic polarization of indium tin oxide (ITO) in 0.1 M NaOH. ► Cathodic polarization studied with electrochemical impedance spectroscopy. ► ITO underwent a corrosion attack during cathodic polarization, indium was observed. ► Electrochemical parameters of ITO were obtained using equivalent electrical circuit. ► A corrosion mechanism is proposed.

High-performance symmetric electrochemical capacitor based on graphene foam and nanostructured manganese oxide

Directory of Open Access Journals (Sweden)

Abdulhakeem Bello

2013-08-01

Full Text Available We have fabricated a symmetric electrochemical capacitor with high energy and power densities based on a composite of graphene foam (GF with ∼80 wt% of manganese oxide (MnO2 deposited by hydrothermal synthesis. Raman spectroscopy and X-ray diffraction measurements showed the presence of nanocrystalline MnO2 on the GF, while scanning and transmission electron microscopies showed needle-like manganese oxide coated and anchored onto the surface of graphene. Electrochemical measurements of the composite electrode gave a specific capacitance of 240 Fg−1 at a current density of 0.1 Ag−1 for symmetric supercapacitors using a two-electrode configuration. A maximum energy density of 8.3 Whkg−1 was obtained, with power density of 20 kWkg−1 and no capacitance loss after 1000 cycles. GF is an excellent support for pseudo-capacitive oxide materials such as MnO2, and the composite electrode provided a high energy density due to a combination of double-layer and redox capacitance mechanisms.

Electrochemical oxidation of 4-morpholinoaniline in aqueous solutions: Synthesis of a new trimer of 4-morpholinoaniline

International Nuclear Information System (INIS)

Esmaili, Roya; Nematollahi, Davood

2011-01-01

Research highlights: → Electrochemical study of 4-morpholinoaniline in various pHs. → Electrochemical trimerization of 4-morpholinoaniline in aqueous solution. → Green method for the synthesis of '4-morpholinoaniline-trimer'. → Potential-pH diagram for 4-morpholinoaniline. - Abstract: Electrochemical oxidation of 4-morpholinoaniline has been studied in various pHs using cyclic voltammetry and controlled-potential coulometry. The electrochemical trimerization of 4-morpholinoaniline is described and its mechanism has been studied in aqueous solution. This method provides a green, reagent-less, and environmentally friendly procedure with high atom economy, for the synthesis of '4-morpholinoaniline-trimer' using a carbon electrode in an undivided cell in good yield and purity.

Electrochemical performance of 3D porous Ni-Co oxide with electrochemically exfoliated graphene for asymmetric supercapacitor applications

International Nuclear Information System (INIS)

Kim, Dae Kyom; Hwang, Minsik; Ko, Dongjin; Kang, Jeongmin; Seong, Kwang-dong; Piao, Yuanzhe

2017-01-01

Graphical abstract: The paper reported the Ni-Co oxide/electrochemically exfoliated graphene nanocomposites with 3D porous nano-architectures (NC-EEG) using a simple low temperature solution method combined with a thermal annealing treatment. 3D porous architectures provide large surface areas and shorten electron diffusion pathways for high performance asymmetric supercapacitors. Display Omitted -- Highlights: •A simple low temperature solution method was used for preparing NC-EEG. •Graphene sheets were obtained by electrochemically exfoliation process. •A high capacity of NC-EEG in a three-electrode system, as high as 649 C g −1 , was recorded. •Asymmetric supercapacitor based on NC-EEG exhibited excellent energy density and power density. -- Abstract: Ni-Co oxide, one of the binary metal oxides, has many advantages for use in high-performance supercapacitor electrode materials due to its relatively high electronic conductivity and improved electrochemical performance. In this work, Ni-Co oxide/electrochemically exfoliated graphene nanocomposites (NC-EEG) are successfully synthesized using a simple low temperature solution method combined with a thermal annealing treatment. Graphene sheets are directly obtained by an electrochemical exfoliation process with graphite foil, which is very simple, environmentally friendly, and has a relatively short reaction time. This electrochemically exfoliated graphene (EEG) can improve the electrical conductivity of the Ni-Co oxide nanostructures. The as-prepared NC-EEG nanocomposites have 3D porous architectures that can provide large surface areas and shorten electron diffusion pathways. Electrochemical properties were performed by cyclic voltammetry and galvanostatic charge/discharge in a 6 M KOH electrolyte. The NC-EEG nanocomposites exhibited a high capacity value of 649 C g −1 at a current density of 1.0 A g −1 . The asymmetric supercapacitors, manufactured on the basis of NC-EEG nanocomposites as a positive

Facile synthesis of cuprous oxide nanowires decorated graphene oxide nanosheets nanocomposites and its application in label-free electrochemical immunosensor.

Science.gov (United States)

Wang, Huan; Zhang, Yong; Wang, Yulan; Ma, Hongmin; Du, Bin; Wei, Qin

2017-01-15

In this work, the assembly between one-dimensional (1D) nanomaterials and two-dimensional (2D) nanomaterials was achieved by a simple method. Cuprous oxide nanowires decorated graphene oxide nanosheets (Cu 2 O@GO) nanocomposites were synthesized for the first time by a simple electrostatic self-assembly process. The nanostructure was well confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM) images. Taking advantages of good electrocatalytic activity and high specific surface area of Cu 2 O@GO nanocomposites, a label-free electrochemical immunosensor was developed by employing Cu 2 O@GO as signal amplification platform for the quantitative detection of alpha fetoprotein (AFP). In addition, toluidine blue (TB) was used as the electron transfer mediator to provide the electrochemical signal, which was adsorbed on graphene oxide nanosheets (GO NSs) by electrostatic attraction. The detection mechanism was based on the monitoring of the electrochemical current response change of TB by the square wave voltammetry (SWV) when immunoreaction occurred on the surface of electrode. Under optimal conditions, the proposed immunosensor displayed a high sensitivity and a low detection limit. This designed method may provide an effective method in the clinical diagnosis of AFP and other tumor markers. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrochemical oxidation of drug residues in water by the example of tetracycline, gentamicin and Aspirin {sup trademark}

Energy Technology Data Exchange (ETDEWEB)

Weichgrebe, D.; Danilova, E.; Rosenwinkel, K.H. [Inst. of Water Quality and Waste Management, Univ. of Hannover, Hannover (Germany); Vedenjapin, A.; Baturova, M. [Inst. of Organic Chemistry, Russian Academy of Science, Moscow (Russian Federation)

2003-07-01

The electrochemical oxidation as a method to destroy drug residues like Aspirin {sup trademark}, tetracycline or gentamicin in water was investigated with C-Anode (modified by manganese oxides) and Pt Anode. The mechanism of Aspirin {sup trademark} and tetracycline oxidation and the influence of the biocide effect was observed using GC-MS and three different microbiological tests. In general the biological availability increases with progressive oxidation of the antibiotics. (orig.)

Operating mechanisms of electrolytes in magnesium ion batteries: chemical equilibrium, magnesium deposition, and electrolyte oxidation.

Science.gov (United States)

Kim, Dong Young; Lim, Younhee; Roy, Basab; Ryu, Young-Gyoon; Lee, Seok-Soo

2014-12-21

Since the early nineties there have been a number of reports on the experimental development of Mg electrolytes based on organo/amide-magnesium chlorides and their transmetalations. However, there are no theoretical papers describing the underlying operating mechanisms of Mg electrolytes, and there is no clear understanding of these mechanisms. We have therefore attempted to clarify the operating mechanisms of Mg electrolytes by studying the characteristics of Mg complexes, solvation, chemical equilibrium, Mg-deposition processes, electrolyte-oxidation processes, and oxidative degradation mechanism of RMgCl-based electrolytes, using ab initio calculations. The formation and solvation energies of Mg complexes highly depend on the characteristics of R groups. Thus, changes in R groups of RMgCl lead to changes in the equilibrium position and the electrochemical reduction and oxidation pathways and energies. We first provide a methodological scheme for calculating Mg reduction potential values in non-aqueous electrolytes and electrochemical windows. We also describe a strategy for designing Mg electrolytes to maximize the electrochemical windows and oxidative stabilities. These results will be useful not only for designing improved Mg electrolytes, but also for developing new electrolytes in the future.

Electrochemical non-enzymatic glucose sensors

International Nuclear Information System (INIS)

Park, Sejin; Boo, Hankil; Chung, Taek Dong

2006-01-01

The electrochemical determination of glucose concentration without using enzyme is one of the dreams that many researchers have been trying to make come true. As new materials have been reported and more knowledge on detailed mechanism of glucose oxidation has been unveiled, the non-enzymatic glucose sensor keeps coming closer to practical applications. Recent reports strongly imply that this progress will be accelerated in 'nanoera'. This article reviews the history of unraveling the mechanism of direct electrochemical oxidation of glucose and making attempts to develop successful electrochemical glucose sensors. The electrochemical oxidation of glucose molecules involves complex processes of adsorption, electron transfer, and subsequent chemical rearrangement, which are combined with the surface reactions on the metal surfaces. The information about the direct oxidation of glucose on solid-state surfaces as well as new electrode materials will lead us to possible breakthroughs in designing the enzymeless glucose sensing devices that realize innovative and powerful detection. An example of those is to introduce nanoporous platinum as an electrode, on which glucose is oxidized electrochemically with remarkable sensitivity and selectivity. Better model of such glucose sensors is sought by summarizing and revisiting the previous reports on the electrochemistry of glucose itself and new electrode materials

pH-sensor properties of electrochemically grown iridium oxide

NARCIS (Netherlands)

Olthuis, Wouter; Robben, M.A.M.; Bergveld, Piet; Bos, M.; van der Linden, W.E.

1990-01-01

The open-circuit potential of an electrochemically grown iridium oxide film is measured and shows a pH sensitivity between −60 and −80 mV/pH. This sensitivity is found to depend on the state of oxidation of the iridium oxide film; for a higher state of oxidation (or more of the oxide in the high

Mechanism of potentiostatic deposition of MnO2 and electrochemical characteristics of the deposit in relation to carbohydrate oxidation

International Nuclear Information System (INIS)

Das, Debasmita; Sen, Pratik Kumar; Das, Kaushik

2008-01-01

Cyclic voltammetric (CV) and chronoamperometric (CA) studies on potentiostatic deposition of MnO 2 on Pt from Mn(II) solution in very weakly alkaline media show the process to be controlled by a one-electron transfer step, which means that the deposition proceeds through the generation of Mn(III). The electrocatalytic activity of the deposited electrode towards carbohydrate oxidation is found to be maximum at an optimum amount of deposition. Chronopotentiometric (CP) and CV measurements show that the oxidation of carbohydrates on the deposited electrodes follows a catalytic EC (electrochemical-chemical) mechanism via electrolytic formation of Mn(V) and its subsequent consumption either by disproportionation or by chemical reaction in the presence of carbohydrates. The rate constants of the reaction of Mn(V) with dextrose and fructose have been obtained from CA results. The relative order of the oxidation currents for dextrose and fructose as well as their dependence on carbohydrate concentration has been discussed. Replacement of Pt by carbon as the electrode support material does not affect the electrocatalytic activity of the MnO 2 deposit. The observed linear variation of the steady state oxidation currents with carbohydrate concentration can be exploited for analytical application

Two-Step Electrochemical Intercalation and Oxidation of Graphite for the Mass Production of Graphene Oxide.

Science.gov (United States)

Cao, Jianyun; He, Pei; Mohammed, Mahdi A; Zhao, Xin; Young, Robert J; Derby, Brian; Kinloch, Ian A; Dryfe, Robert A W

2017-12-06

Conventional chemical oxidation routes for the production of graphene oxide (GO), such as the Hummers' method, suffer from environmental and safety issues due to their use of hazardous and explosive chemicals. These issues are addressed by electrochemical oxidation methods, but such approaches typically have a low yield due to inhomogeneous oxidation. Herein we report a two-step electrochemical intercalation and oxidation approach to produce GO on the large laboratory scale (tens of grams) comprising (1) forming a stage 1 graphite intercalation compound (GIC) in concentrated sulfuric acid and (2) oxidizing and exfoliating the stage 1 GIC in an aqueous solution of 0.1 M ammonium sulfate. This two-step approach leads to GO with a high yield (>70 wt %), good quality (>90%, monolayer), and reasonable oxygen content (17.7 at. %). Moreover, the as-produced GO can be subsequently deeply reduced (3.2 at. % oxygen; C/O ratio 30.2) to yield highly conductive (54 600 S m -1 ) reduced GO. Electrochemical capacitors based on the reduced GO showed an ultrahigh rate capability of up to 10 V s -1 due to this high conductivity.

Electrochemical and Electron Paramagnetic Resonance Study of the Mechanism of Oxidation of Phenazine-di-N-oxide in the Presence of Isopropyl alcohol at Glassy Carbon and Single-Walled Carbon Nanotube Electrodes

International Nuclear Information System (INIS)

Kulakovskaya, S.I.; Kulikov, A.V.; Sviridova, L.N.; Stenina, E.V.

2014-01-01

Graphical abstract: - Highlights: • The mechanism of oxidation of phenazine-di-N-oxide in the presence of isopropyl alcohol was studied. • The results are explained in terms of the E 1 C 1 E 2 C 2 mechanism of the two-stage electrode process. • The total two-electron catalytic oxidation of i-PrOH in the complex with the phenazine-di-N-oxide radical cation was assumed to occur. - Abstract: The mechanism of oxidation of phenazine-di-N-oxide in the presence of isopropyl alcohol was studied by cyclic voltammetry at glassy carbon (GC) and single-walled carbon nanotubes (SWCNT) electrodes in 0.1 M LiClO 4 solutions in acetonitrile. The adsorption of phenazine-di-N-oxide at SWCNT electrode in 0.1 M LiClO 4 solution in acetonitrile was investigated by measurement of the dependence of the differential double layer capacitance of the electrode C on potential E. The effect of isopropyl alcohol on the shape of cyclic voltammograms (CVs) of phenazine-di-N-oxide and the intensity of Electron Paramagnetic Resonance (EPR) signal of its radical cation was investigated. The catalytic currents were recorded at the oxidation of phenazine-di-N-oxide at SWCNT and GC electrodes in the presence of isopropyl alcohol. The results were explained in terms of the E 1 C 1 E 2 C 2 mechanism of two-stage electrode process characterized by catalytic current recorded at the second electrode stage. The overall two-electron catalytic oxidation of isopropyl alcohol in complex with the phenazine-di-N-oxide radical cation was assumed to occur. It was shown that SWCNT electrodes can be used in the electrocatalytic oxidation of organic compounds in the presence of electrochemically generated phenazine-di-N-oxide radical cation

Progress in electrochemical synthesis of magnetic iron oxide nanoparticles

International Nuclear Information System (INIS)

Ramimoghadam, Donya; Bagheri, Samira; Hamid, Sharifah Bee Abd

2014-01-01

Recently, magnetic iron oxide particles have been emerged as significant nanomaterials due to its extensive range of application in various fields. In this regard, synthesis of iron oxide nanoparticles with desirable properties and high potential applications are greatly demanded. Therefore, investigation on different iron oxide phases and their magnetic properties along with various commonly used synthetic techniques are remarked and thoroughly described in this review. Electrochemical synthesis as a newfound method with unique advantages is elaborated, followed by design approaches and key parameters to control the properties of the iron oxide nanoparticles. Additionally, since the dispersion of iron oxide nanoparticles is as important as its preparation, surface modification issue has been a serious challenge which is comprehensively discussed using different surfactants. Despite the advantages of the electrochemical synthesis method, this technique has been poorly studied and requires deep investigations on effectual parameters such as current density, pH, electrolyte concentration etc. - Highlights: • IONPs are applied in chemical industries, medicine, magnetic storage etc. • Electrochemical synthesis (EC) is convenient, eco-friendly, selective and low-cost. • EC key factors are current density, pH, electrolyte concentration, electrode type. • Organic, inorganic and biological materials can be used to modify IONPs’ surface. • The physicochemical properties of IONPs can be controlled by adding surfactants

Effect of graphene oxide nanoplatelets on electrochemical properties of steel substrate in saline media

International Nuclear Information System (INIS)

Chaudhry, A.U.; Mittal, Vikas; Mishra, Brajendra

2015-01-01

There has been increased interest in using graphene oxide (GO) in various industrial applications such as working fluids, lubricants, oil and gas fields, heavy metal removal from water, anticorrosion paints and coatings etc. We studied electrochemical properties of steel in the presence of suspended GO in saline media. GO suspension has been characterized using Transmission electron microscopy (TEM) and X-ray diffractometer (XRD). We measured the effect of the GO concentration (0–15 ppm) on electrochemical properties of steel using different techniques: open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and potentiodynamic (PD) methods. Results indicate that the suppression of corrosion is directly proportional to increasing GO concentrations in saline environments. Surface morphology of corroded samples was examined using Scanning Electron Microscopy (SEM). Identification of the elements at accumulated layer was estimated from peaks of energy dispersive x-ray spectroscopy (EDX) and XRD. Increased protection abilities with increasing GO concentration have been attributed to the domination of salt layer presence at the surface of steel which occurs via precipitation of sodium chloride. Surface analysis confirm that there is no direct effect of GO on the protection behavior of steel. The presence of GO in the solution can enhance the precipitation of NaCl due to the decreased solubility NaCl which further slows down the corrosion. The pourbaix diagram shows that GO forms an anionic compound with sodium which may enhance the precipitation at working electrode. - Graphical abstract: Display Omitted - Highlights: • Electrochemical properties of steel in saline media containing nano graphene oxide. • Effect of concentration of graphene oxide on electrochemical properties. • Mechanism of corrosion reduction due to the presence of graphene oxide

Electrochemical oxidation of phenol in a parallel plate reactor using ruthenium mixed metal oxide electrode

Energy Technology Data Exchange (ETDEWEB)

Yavuz, Yusuf [Anadolu Universitesi, Cevre Sor. Uyg. ve Aras. Merkezi, Eskisehir (Turkey); Koparal, A. Savas [Anadolu Universitesi, Cevre Sor. Uyg. ve Aras. Merkezi, Eskisehir (Turkey)]. E-mail: askopara@anadolu.edu.tr

2006-08-21

In this study, electrochemical oxidation of phenol was carried out in a parallel plate reactor using ruthenium mixed metal oxide electrode. The effects of initial pH, temperature, supporting electrolyte concentration, current density, flow rate and initial phenol concentration on the removal efficiency were investigated. Model wastewater prepared with distilled water and phenol, was recirculated to the electrochemical reactor by a peristaltic pump. Sodium sulfate was used as supporting electrolyte. The Microtox'' (registered) bioassay was also used to measure the toxicity of the model wastewater during the study. As a result of the study, removal efficiency of 99.7% and 88.9% were achieved for the initial phenol concentration of 200 mg/L and chemical oxygen demand (COD) of 480 mg/L, respectively. In the same study, specific energy consumption of 1.88 kWh/g phenol removed and, mass transfer coefficient of 8.62 x 10{sup -6} m/s were reached at the current density of 15 mA/cm{sup 2}. Electrochemical oxygen demand (EOD), which can be defined as the amount of electrochemically formed oxygen used for the oxidation of organic pollutants, was 2.13 g O{sub 2}/g phenol. Electrochemical oxidation of petroleum refinery wastewater was also studied at the optimum experimental conditions obtained. Phenol removal of 94.5% and COD removal of 70.1% were reached at the current density of 20 mA/cm{sup 2} for the petroleum refinery wastewater.

Treatment of aqueous wastes contaminated with Congo Red dye by electrochemical oxidation and ozonation processes

International Nuclear Information System (INIS)

Faouzi Elahmadi, Mohammed; Bensalah, Nasr; Gadri, Abdellatif

2009-01-01

Synthetic aqueous wastes polluted with Congo Red (CR) have been treated by two advanced oxidation processes: electrochemical oxidation on boron doped diamond anodes (BDD-EO) and ozonation under alkaline conditions. For same concentrations, galvanostatic electrolyses have led to total COD and TOC removals but ozonation process can reach only 85% and 81% of COD and TOC removals, respectively. UV-vis qualitative analyses have shown different behaviors of CR molecules towards ozonation and electrochemical oxidation. Rapid discoloration has been observed during ozonation, whereas color persistence till the end of galvanostatic electrolyses has been seen during BDD-EO process. It seems that the oxidation mechanisms involved in the two processes are different: simultaneous destruction of azoic groups is suggested during ozonation process but consecutive destruction of these groups is proposed during BDD-EO. However, energetic study has evidenced that BDD-EO appears more efficient and more economic than ozonation in terms of TOC removals. These results have been explained by the fact that during BDD-EO, other strong oxidants electrogenerated from the electrolyte oxidation such as persulfates and direct-oxidation of CR and its byproducts on BDD anodes complement the hydroxyl radicals mediated oxidation to accomplish the total mineralization of organics.

Cuprous oxide thin films grown by hydrothermal electrochemical deposition technique

International Nuclear Information System (INIS)

Majumder, M.; Biswas, I.; Pujaru, S.; Chakraborty, A.K.

2015-01-01

Semiconducting cuprous oxide films were grown by a hydrothermal electro-deposition technique on metal (Cu) and glass (ITO) substrates between 60 °C and 100 °C. X-ray diffraction studies reveal the formation of cubic cuprous oxide films in different preferred orientations depending upon the deposition technique used. Film growth, uniformity, grain size, optical band gap and photoelectrochemical response were found to improve in the hydrothermal electrochemical deposition technique. - Highlights: • Cu 2 O thin films were grown on Cu and glass substrates. • Conventional and hydrothermal electrochemical deposition techniques were used. • Hydrothermal electrochemical growth showed improved morphology, thickness and optical band gap

Synthesis and Microstructural Characterization of Manganese Oxide Electrodes for Application as Electrochemical Supercapacitors

Science.gov (United States)

Babakhani, Banafsheh

nucleation and growth mechanisms of Mn oxide electrodes, the effects of supersaturation ratio on the morphology and crystal structure of electrodeposited Mn oxide were studied. By changing deposition parameters, including deposition current density, electrolyte composition, pH and temperature, a series of nanocrystalline Mn oxide electrodes with various morphologies (continuous coatings, rod-like structures, aggregated rods and thin sheets) and an antifluorite-type crystal structure was obtained. Mn oxide thin sheets showed instantaneous nucleation and single crystalline growth; rods had a mix of instantaneous/progressive nucleation and polycrystalline growth and continuous coatings formed by progressive nucleation and polycrystalline growth. Electrochemical analysis revealed the best capacitance behaviour obtained for Mn oxide thin sheets followed by Mn oxide rods, with dimensions on the microscale, and then continuous coatings. The highest specific capacitance (˜230 Fg-1) and capacitance retention rates (˜88%) were obtained for Mn oxide thin sheets after 250 cycles in 0.5 M Na2 SO4 at 20 mVs-1.

Synthesis and electrochemical properties of tin oxide-based composite by rheological technique

International Nuclear Information System (INIS)

He Zeqiang; Li Xinhai; Xiong Lizhi; Wu Xianming; Xiao Zhuobing; Ma Mingyou

2005-01-01

Novel rheological technique was developed to synthesize tin oxide-based composites. The microstructure, morphology, and electrochemical performance of the materials were investigated by X-ray diffraction, scanning electron microscopy and electrochemical methods. The particles of tin oxide-based materials form an inactive matrix. The average size of the particles is about 150 nm. The material delivers a charge capacity of more than 570 mAh g -1 . The capacity loss per cycle is about 0.15% after being cycled 30 times. The good electrochemical performance indicates that this kind of tin oxide-based material is promising anode for lithium-ion battery

Solid-phase electrochemical reduction of graphene oxide films in alkaline solution

Science.gov (United States)

Basirun, Wan J.; Sookhakian, Mehran; Baradaran, Saeid; Mahmoudian, Mohammad R.; Ebadi, Mehdi

2013-09-01

Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO.

Electrochemical Oxidation by Square-Wave Potential Pulses in the Imitation of Oxidative Drug Metabolism

NARCIS (Netherlands)

Nouri-Nigjeh, Eslam; Permentier, Hjalmar P.; Bischoff, Rainer; Bruins, Andries P.

2011-01-01

Electrochemistry combined with mass spectrometry (EC-MS) is an emerging analytical technique in the imitation of oxidative drug metabolism at the early stages of new drug development. Here, we present the benefits of electrochemical oxidation by square-wave potential pulses for the oxidation of

Methanol oxidation reaction on core-shell structured Ruthenium-Palladium nanoparticles: Relationship between structure and electrochemical behavior

Science.gov (United States)

Kübler, Markus; Jurzinsky, Tilman; Ziegenbalg, Dirk; Cremers, Carsten

2018-01-01

In this work the relationship between structural composition and electrochemical characteristics of Palladium(Pd)-Ruthenium(Ru) nanoparticles during alkaline methanol oxidation reaction is investigated. The comparative study of a standard alloyed and a precisely Ru-core-Pd-shell structured catalyst allows for a distinct investigation of the electronic effect and the bifunctional mechanism. Core-shell catalysts benefit from a strong electronic effect and an efficient Pd utilization. It is found that core-shell nanoparticles are highly active towards methanol oxidation reaction for potentials ≥0.6 V, whereas alloyed catalysts show higher current outputs in the lower potential range. However, differential electrochemical mass spectrometry (DEMS) experiments reveal that the methanol oxidation reaction on core-shell structured catalysts proceeds via the incomplete oxidation pathway yielding formaldehyde, formic acid or methyl formate. Contrary, the alloyed catalyst benefits from the Ru atoms at its surface. Those are found to be responsible for high methanol oxidation activity at lower potentials as well as for complete oxidation of CH3OH to CO2 via the bifunctional mechanism. Based on these findings a new Ru-core-Pd-shell-Ru-terrace catalyst was synthesized, which combines the advantages of the core-shell structure and the alloy. This novel catalyst shows high methanol electrooxidation activity as well as excellent selectivity for the complete oxidation pathway.

Oxidative electrochemical aryl C-C coupling of spiropyrans

NARCIS (Netherlands)

Ivashenko, Oleksii; van Herpt, Jochem T.; Rudolf, Petra; Feringa, Ben L.; Browne, Wesley R.

2013-01-01

The isolation and definitive assignment of the species formed upon electrochemical oxidation of nitro-spiropyran (SP) is reported. The oxidative aryl C-C coupling at the indoline moiety of the SP radical cation to form covalent dimers of the ring-closed SP form is demonstrated. The coupling is

Influencing Mechanism of Electrochemical Treatment on Preparation of CNTs-grafted on Carbon Fibers

Directory of Open Access Journals (Sweden)

SONG Lei

2017-11-01

Full Text Available Based on electrochemical anodic oxidation, an innovative technique was developed to efficiently obtain the uniform catalyst coating on continuous carbon fibers. Through systematic investigation on the effect of electrochemical modified strength on the physical and chemical characteristics of carbon fiber surface, catalyst particles and the morphology of CNTs-grafted carbon fibers, tensile strength of multi-scale reinforcement and the interlaminar shear strength of its reinforced composites, the electrochemical modification process on carbon fibre surface was optimized. The results show that the morphology and distribution of catalyst particles not only affect the morphology of CNTs deposited on the surface of carbon fibres,but also affect the mechanical properties of multi-scale reinforcement and its reinforced composites of CNTs-grafted carbon fibers.

Electrochemical reduction of cerium oxide into metal

Energy Technology Data Exchange (ETDEWEB)

Claux, Benoit [CEA, Valduc, F-21120 Is-sur-Tille (France); Universite de Grenoble, LEPMI-ENSEEG, 1130 rue de la Piscine, BP75, F-38402 St Martin d' Heres Cedex (France); Serp, Jerome, E-mail: jerome.serp@cea.f [CEA, Valduc, F-21120 Is-sur-Tille (France); Fouletier, Jacques [Universite de Grenoble, LEPMI-ENSEEG, 1130 rue de la Piscine, BP75, F-38402 St Martin d' Heres Cedex (France)

2011-02-28

The Fray Farthing and Chen (FFC) and Ono and Suzuki (OS) processes were developed for the reduction of titanium oxide to titanium metal by electrolysis in high temperature molten alkali chloride salts. The possible transposition to CeO{sub 2} reduction is considered in this study. Present work clarifies, by electro-analytical techniques, the reduction pathway leading to the metal. The reduction of CeO{sub 2} into metal was feasible via an indirect mechanism. Electrolyses on 10 g of CeO{sub 2} were carried out to evaluate the electrochemical process efficiency. Ca metal is electrodeposited at the cathode from CaCl{sub 2}-KCl solvent and reacts chemically with ceria to form not only metallic cerium, but also cerium oxychloride.

Electrochemical/chemical oxidation of bisphenol A in a four-electron/two-proton process in aprotic organic solvents

International Nuclear Information System (INIS)

Chan, Ya Yun; Yue, Yanni; Li, Yongxin; Webster, Richard D.

2013-01-01

Graphical abstract: - Highlights: • Bisphenol A undergoes a chemically irreversible voltammetric oxidation process. • Chemical oxidation was performed to overcome adsorption effects that cause electrode fouling. • A new product was isolated from chemical oxidation with 4 mol equiv. of the one-electron oxidant, NO + . • The oxidative mechanism was proposed to be a four-electron/two-proton process. - Abstract: The electrochemical behavior of bisphenol A (BPA) was examined using cyclic voltammetry, bulk electrolysis and chemical oxidation in aprotic organic solvents. It was found that BPA undergoes a chemically irreversible voltammetric oxidation process to form compounds that cannot be electrochemically converted back to the starting materials on the voltammetric timescale. To overcome the effects of electrode fouling during controlled potential electrolysis experiments, NO + was used as a one-electron chemical oxidant. A new product, hydroxylated bisdienone was isolated from the chemical oxidation of BPA with 4 mol equiv of NO + SbF 6 − in low water content CH 3 CN. The structure of the cation intermediate species was deduced and it was proposed that BPA is oxidized in a four-electron/two-proton process to form a relatively unstable dication which reacts quickly in the presence of water in acetonitrile (in a mechanism that is similar to phenols in general). However, as the water content of the solvent increased it was found that the chemical oxidation mechanism produced a nitration product in high yield. The findings from this study provide useful insights into the reactions that can occur during oxidative metabolism of BPA and highlight the possibility of the role of a bisdienone cation as a reactive metabolite in biological systems

Electrochemical reduction of nitrous oxide on La1-xSrxFeO3 perovskites

DEFF Research Database (Denmark)

Kammer Hansen, Kent

2010-01-01

The electrochemical reduction of nitrous oxide and oxygen has been studied on cone-shaped electrodes of La1-xSrxFeO3-delta perovskites in an all solid state cell, using cyclic voltammetry. It was shown that the activity of the La1-xSrxFeO3-delta perovskites for the electrochemical reduction...... of nitrous oxide mainly depends on the amount of Fe(III) and oxide ion vacancies. The activity of the La1-xSrxFeO3-delta perovskites towards the electrochemical reduction of nitrous oxide is much lower than the activity of the La1-xSrxFeO3-delta perovskites towards the electrochemical reduction of oxygen...

From Two-Phase to Three-Phase: The New Electrochemical Interface by Oxide Electrocatalysts

Science.gov (United States)

Xu, Zhichuan J.

2018-03-01

Electrochemical reactions typically occur at the interface between a solid electrode and a liquid electrolyte. The charge exchange behaviour between these two phases determines the kinetics of electrochemical reactions. In the past few years, significant advances have been made in the development of metal oxide electrocatalysts for fuel cell and electrolyser reactions. However, considerable gaps remain in the fundamental understanding of the charge transfer pathways and the interaction between the metal oxides and the conducting substrate on which they are located. In particular, the electrochemical interfaces of metal oxides are significantly different from the traditional (metal) ones, where only a conductive solid electrode and a liquid electrolyte are considered. Oxides are insulating and have to be combined with carbon as a conductive mediator. This electrode configuration results in a three-phase electrochemical interface, consisting of the insulating oxide, the conductive carbon, and the liquid electrolyte. To date, the mechanistic insights into this kind of non-traditional electrochemical interface remain unclear. Consequently conventional electrochemistry concepts, established on classical electrode materials and their two-phase interfaces, are facing challenges when employed for explaining these new electrode materials. [Figure not available: see fulltext.

Obtention of superconductivity by room temperature electrochemical oxidation of La2CuO4

International Nuclear Information System (INIS)

Casan-Pastor, N.; Fuertes, A.; Gomez-Romero, P.

1993-01-01

The undoped oxide La2CuO4 has required traditionally synthesis under high pressure of oxygen (and high temperatures) to incorporate excess oxygen into its structure and become a superconductor. The electrochemical oxidation of this same oxide at room temperature and pressure constitutes a striking example of the use of an alternative driving force for the oxidation of oxides to become superconductors. Electrochemical treatment of oxides has been frequently applied to their reduction with cationic intercalation. Oxidations of these solid with the concomitant intercalation of anions into their lattice shows also great promises. The paper reports recent results in the electrochemical oxidation of La2CuO4 and other cuprates, showing also the important role of post-oxidation thermal treatments on the properties of the resulting solids

Electrochemical Thinning for Anodic Aluminum Oxide and Anodic Titanium Oxide

Energy Technology Data Exchange (ETDEWEB)

Lee, In Hae; Jo, Yun Kyoung; Kim, Yong Tae; Tak, Yong Sug; Choi, Jin Sub [Inha University, Incheon (Korea, Republic of)

2012-05-15

For given electrolytes, different behaviors of anodic aluminum oxide (AAO) and anodic titanium oxide (ATO) during electrochemical thinning are explained by ionic and electronic current modes. Branched structures are unavoidably created in AAO since the switch of ionic to electronic current is slow, whereas the barrier oxide in ATO is thinned without formation of the branched structures. In addition, pore opening can be possible in ATO if chemical etching is performed after the thinning process. The thinning was optimized for complete pore opening in ATO and potential-current behavior is interpreted in terms of ionic current-electronic current switching.

Electrochemical treatment of wastewater: A case study of reduction of DNT and oxidation of chlorinated phenols

Energy Technology Data Exchange (ETDEWEB)

Rodgers, J.D.; Bunce, N.J.; Jedral, W.

1999-07-01

Electrochemical treatment is under consideration as a treatment option for several recalcitrant compounds. In this work the authors investigate the oxidation of chlorophenols and the reduction of nitroaromatics. In the case of chlorinated phenols, they explore the problem of anode fouling which has hampered electrolytic treatment of phenolic compounds by examining phenols differing in the extent of chlorination, according to the mechanism of oxidation at different electrode types. Linear sweep voltammograms at a Pt anode were interpreted in terms of deposition of oligomers on the anode surface. Passivation increased in parallel with the uncompensated resistance of the solution and occurred only at potentials at which water is oxidized, suggesting that the formation of the oligomer film involves attack of hydroxyl radicals on electrochemically oxidized substrate. Relative reactivities of congeners were anode-dependent, due to different mechanisms of oxidation: direct electron transfer oxidation at PbO{sub 2} and hydroxyl radical attack at SnO{sub 2} and IrO{sub 2}. Voltammetry of 2,6-dinitrotoluene (DNT) was consistent with literature values. DNT was reduced at several cathodes with the most promising result at Ni-plated Ni wire. At current densities {lt} 0.1 mA cm{sup {minus}2}, current efficiencies {gt} 50% could be achieved with 4-chlorophenol at all three anodes and for 2,6-DNT at Ni-plated Ni wire.

Electrochemical treatment of an oxide material, application to superconductors, and obtained superconductors

International Nuclear Information System (INIS)

Grenier, J.C.; Pouchard, M.; Wattiaux, A.

1991-01-01

The present invention describes the electrochemical treatment of a superconductor oxide so as to modify its stoichiometry. These materials comprise in their anionic lattice oxygenated and hydrogenated species. These treated materials are prepared by an electrochemical process in which the oxide is an electrode in a liquid electrolysis. 3 refs., 3 figs

Manganese oxide/graphene oxide composites for high-energyaqueous asymmetric electrochemical capacitors

CSIR Research Space (South Africa)

Jafta, CJ

2013-11-01

Full Text Available A high-energy aqueous asymmetric electrochemical capacitor was developed using manganese diox-ide ( -MnO2)/graphene oxide (GO) nanocomposites. The nanostructured -MnO2was prepared frommicron-sized commercial electrolytic manganese dioxide (EMD) via...

Study of Electrochemical Oxidation and Quantification of the Pesticide Pirimicarb Using a Boron-Doped Diamond Electrode

International Nuclear Information System (INIS)

Selva, Thiago Matheus Guimarães; De Araujo, William Reis; Bacil, Raphael Prata; Paixão, Thiago Regis Longo Cesar

2017-01-01

Highlights: •A complete electro-oxidation mechanism of the pesticide Pirimicarb was proposed. •The electrochemical mechanism was supported by voltammetry techniques and mass spectrometry data. •An electroanalytical method using boron-doped diamond electrode was proposed to quantify Pirimicarb in natural waters. •The proposed analytical method is simple, low-cost, accurate and portable. -- Abstract: An electrochemical study of the carbamate pesticide pirimicarb (PMC), which acts on the central nervous system, was performed using a boron-doped diamond working electrode. Cyclic, differential pulse, and square-wave voltammetry experiments across a wide pH range (2.0 to 8.0) showed three irreversible oxidation processes in the voltammetric behavior of PMC. The two first processes were pH-dependent, while the third was not. The three oxidation process were independent of each other, and each involved the transfer of one electron. A reaction proposal for the electrochemical oxidation of PMC is shown, and it is supported by mass spectrometry experiments. After this, an analytical method for PMC quantification in water samples by differential pulse (DP) voltammetry is proposed. The optimal DP voltammetric parameters (step potential, amplitude potential, and scan rate) were optimized using experimental design, and an analytical curve was obtained from 2.0 to 219 μmol L −1 with an estimated detection limit of 1.24 μmol L −1 . The accuracy of the proposed method was evaluated by the addition and recovery method, with recoveries ranging from 88.6 to 96.3%. Some highlights of the proposed analytical method are its simplicity, reliability, and portability.

Implementation of advanced electrochemical oxidation for radiochemical concentrate treatment

International Nuclear Information System (INIS)

Velin, Anna; Bengtsson, Bernt; Lundblad, Magnus

2012-09-01

Water treatments in Nuclear Power Plants include ion exchange, evaporation and mechanical filtration techniques. These technologies are used to control the chemical release and to treat coolant in light water reactor types from chemicals and most importantly, from radioactive nuclides. Most of the conventional methods are efficient, but at the same time producing aqueous concentrates with high organic load. Before final storage, the level of organic content of those concentrates must be reduced. Advanced electrochemical oxidation with Boron Doped Diamond (BDD) electrodes are being investigated in laboratory- and pilot scale for treatment of dilute and concentrated aqueous waste streams at Vattenfall-Ringhals NPP. BDD anodes and cathodes are having high over potential against water electrolysis, and therefore well suitable for oxidation of organics. Dilute wastewater, such as laundry water, which has an initial COD level of around 500 mg/l, was reduced to a level of < 20 mg/l in the laboratory. Evaporator concentrates, with a TS content of 3% and pH of 7-8, were treated in pilot scale of 800 liters, working in batch operation mode, at temperatures between 25-50 deg. C. Initial COD levels between 2500 and 8000 mg/l in concentrate was reduced to < 100 mg/l at the first tests and later to < 300 mg/l. The advanced electrochemical oxidation is proven to be a promising technique for radioactive concentrate treatment. Long-term operation is still ongoing to evaluate the performance of the electrodes, cell components and overall process efficiency. (authors)

Electrochemical mechanism of uranium mononitride dissolution in aqueous solutions of nitric acid

Energy Technology Data Exchange (ETDEWEB)

Ershov, Boris G. [Russian Academy of Sciences, Moscow (Russian Federation). Frumkin Inst. of Physical Chemistry and Electrochemistry

2017-09-01

It was shown that the dissolution of UN with metallic conduction follows an electrochemical mechanism when it proceeds in contact with an electrically conductive medium (HNO{sub 3} solution). According to this mechanism, the oxidation of UN (at the anode) passes an electron into the UN matrix, which is a conductor, and can then reduce nitric acid in a parallel reaction a short distance away at another exposed surface of the UN (at the cathode). As a result, the reduction of HNO{sub 3} affords NO and NO{sub 2}, while oxidation of uranium mononitride affords NH{sub 3}, N{sub 2}, and N{sub 2}O. The occurrence of these two separate processes accounts for the composition and yields of the products formed from UN and HNO{sub 3} as well as for the nitrogen isotope distribution between them when UN and HNO{sub 3} were labeled with {sup 14} N or {sup 15}N. A mathematical equation describing the dependence of N{sub 2} and N{sub 2}O yields on HNO{sub 3} concentration was derived. It was also shown that the calculated value of standard electromotive force of the galvanic pair formed on the UN surface during its dissolution in HNO{sub 3} is high enough to initiate and support the electrochemical mechanism of its dissolution in nitric acid.

Electrochemical mechanism of eugenol at a Cu doped gold nanoparticles modified glassy carbon electrode and its analytical application in food samples

International Nuclear Information System (INIS)

Lin, Xiaoyun; Ni, Yongnian; Kokot, Serge

2014-01-01

Graphical abstract: A simple one-step electrodeposition method was used to fabricate a Cu doped gold nanoparticles modified glassy carbon electrode. An electrochemical reaction mechanism for o-methoxy phenols was suggested. In addition, the above Cu@AuNPs/GCE was successfully employed for the analysis of eugenol in food samples. - Highlights: • One-step construction of the Cu@AuNPs/GCE electrode. • The modified electrode showed high sensitivity for the analysis of eugenol. • Electrochemical mechanism of eugenol by use of Cu@AuNPs/GCE was inferred. • The novel method was successfully employed for analysis of eugenol in food samples. - Abstract: A simple one-step electrodeposition method was used to construct a glassy carbon electrode (GCE), which has been modified with Cu doped gold nanoparticles (GNPs), i.e. a Cu@AuNPs/GCE. This electrode was characterized with the use of scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The eugenol was electrocatalytically oxidized at the Cu@AuNPs/GCE. At this electrode, in comparison with the behavior at the GCE alone, the corresponding oxidation peak current was enhanced and the shift of the oxidation potentials to lower values was observed. Electrochemical behavior of eugenol at the Cu@AuNPs/GCE was investigated with the use of the cyclic voltammetry (CV) technique, and additionally, in order to confirm the electrochemical reaction mechanism for o-methoxy phenols, CVs for catechol, guaiacol and vanillin were investigated consecutively. Based on this work, an electrochemical reaction mechanism for o-methoxy phenols was suggested, and in addition, the above Cu@AuNPs/GCE was successfully employed for the analysis of eugenol in food samples

Electrochemical synthesis and characterization of copper (I oxide

Directory of Open Access Journals (Sweden)

Bugarinović Sanja J.

2009-01-01

Full Text Available The quest and need for clean and economical energy sources have increased interest in the development of thin film cells technologies. Electrochemical deposition is an attractive method for synthesis of thin films. It offers the advantages of low synthesis temperature, low cost and high purity. Copper (I oxide or cuprous oxide is an oxide semiconductor which is used as the anodic material in the form of thin film in lithium batteries and solar cells. The cathodic process of synthesis of cuprous oxide thin film is carried out in a potentiostatic mode from the organic electrolyte. The process parameters are chosen in that way to accomplish maximum difference between the potentials at which Cu2O and CuO are obtained. The electrochemical characterization was carried out by cyclic voltammetry. The electrodeposition techniques are particularly well suited for the deposition of single elements but it is also possible to carry out simultaneous depositions of several elements and syntheses of well-defined alternating layers of metals and oxides with thicknesses down to a few nm. Nanomaterials exhibit novel physical properties and play an important role in fundamental research. In addition, cuprous oxide is commonly used as a pigment, a fungicide, and an antifouling agent for marine paints. It is insoluble in water and organic solvents. This work presents the examinations of the influence of bath, temperature, pH and current density on the characteristics of electrochemically synthesized cuprous oxide. In the 'classic' process of synthesis, which is carried out under galvanostatic conditions on the anode, the grain size of the powder decreases with the increase in current density while the grain colour becomes lighter. The best commercial quality of the Cu2O (grain size, colour, content of choride was obtained at the temperature of 80°C, concentration of NaCl of 3 mol/dm3 and current density of 400 A/m2.

3,5-Diamino-1,2,4-triazole@electrochemically reduced graphene oxide film modified electrode for the electrochemical determination of 4-nitrophenol

International Nuclear Information System (INIS)

Kumar, Deivasigamani Ranjith; Kesavan, Srinivasan; Baynosa, Marjorie Lara; Shim, Jae-Jin

2017-01-01

Highlights: •Triazole film was formed on electrochemically reduced graphene oxide. •pDAT@ERGO/GC was utilized for the electrochemical determination of 4-nitrophenol. •pDAT@ERGO/GC electrode offered wide concentration and nanomolar detection limit. •The fabricated electrode was employed in water sample analyses. -- Abstract: In this study, an eco-friendly benign method for the modification of electrochemically reduced graphene oxide (ERGO) on glassy carbon (GC) surface and electrochemical polymerized 3,5-diamino-1,2,4-triazole (DAT) film composite (pDAT@ERGO/GC) electrode was developed. The surface morphologies of the pDAT@ERGO/GC modified electrode were analyzed by field emission scanning electron microscopy (FESEM). FESEM images indicated that the ERGO supported pDAT has an almost homogeneous morphology structure with a size of 70 to 80 nm. It is due to the water oxidation reaction occurred while pDAT@ERGO/GC fabrication peak at +1.4 V leads to O 2 evolution and oxygen functional group functionalization on ERGO, which confirmed by X-ray photoelectron spectroscopy (XPS). In contrast, the bare GC modified with pDAT showed randomly arranged irregular bulky morphology structure compared to those of pDAT@ERGO/GC. Electrochemical reduction of graphene oxide was confirmed by Raman spectroscopy, XPS, and electrochemical impedance spectroscopy (EIS). The pDAT@ERGO/GC modified electrode was used for the electrochemical determination of 4-nitrophenol (4-NP). The 4-NP oxidation peak was observed at +0.25 V, and the differential pulse voltammetry demonstrated wide concentration range (5–1500 μM), high sensitivity (0.7113 μA μM −1 ), and low limit of detection (37 nM). Moreover, the pDAT@ERGO/GC electrode was applied to real water sample analysis by standard addition method, where in good recoveries (97.8% to 102.4%) were obtained.

Improved Electrochemical Detection of Zinc Ions Using Electrode Modified with Electrochemically Reduced Graphene Oxide

Czech Academy of Sciences Publication Activity Database

Kudr, J.; Richtera, L.; Nejdl, L.; Xhaxhiu, K.; Vítek, Petr; Rutkay-Nedecky, B.; Hynek, D.; Kopel, P.; Adam, V.; Kižek, R.

2016-01-01

Roč. 9, č. 1 (2016), UNSP 31 ISSN 1996-1944 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : carbon * cyclic voltammetry * electrochemical impedance spectroscopy * electrochemistry * graphene oxide * heavy metal detection * reduced graphene oxide Subject RIV: CG - Electrochemistry OBOR OECD: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals , electrolysis) Impact factor: 2.654, year: 2016

Electrochemical and Spectroscopic Study of Mononuclear Ruthenium Water Oxidation Catalysts: A Combined Experimental and Theoretical Investigation

KAUST Repository

de Ruiter, J. M.

2016-09-20

One of the key challenges in designing light-driven artificial photosynthesis devices is the optimization of the catalytic water oxidation process. For this optimization it is crucial to establish the catalytic mechanism and the intermediates of the catalytic cycle, yet a full description is often difficult to obtain using only experimental data. Here we consider a series of mononuclear ruthenium water oxidation catalysts of the form [Ru(cy)(L)(H2O)](2+) (cy = p-cymene, L = 2,2\\'-bipyridine and its derivatives). The proposed catalytic cycle and intermediates are examined using density functional theory (DFT), radiation chemistry, spectroscopic techniques, and electrochemistry to establish the water oxidation mechanism. The stability of the catalyst is investigated using online electrochemical mass spectrometry (OLEMS). The comparison between the calculated absorption spectra of the proposed intermediates with experimental spectra, as well as free energy calculations with electrochemical data, provides strong evidence for the proposed pathway: a water oxidation catalytic cycle involving four proton-coupled electron transfer (PCET) steps. The thermodynamic bottleneck is identified as the third PCET step, which involves O-O bond formation. The good agreement between the optical and thermodynamic data and DFT predictions further confirms the general applicability of this methodology as a powerful tool in the characterization of water oxidation catalysts and for the interpretation of experimental observables.

Electrochemical studies on nanometal oxide-activated carbon composite electrodes for aqueous supercapacitors

Science.gov (United States)

Ho, Mui Yen; Khiew, Poi Sim; Isa, Dino; Chiu, Wee Siong

2014-11-01

In present study, the electrochemical performance of eco-friendly and cost-effective titanium oxide (TiO2)-based and zinc oxide-based nanocomposite electrodes were studied in neutral aqueous Na2SO3 electrolyte, respectively. The electrochemical properties of these composite electrodes were studied using cyclic voltammetry (CV), galvanostatic charge-discharge (CD) and electrochemical impedance spectroscopy (EIS). The experimental results reveal that these two nanocomposite electrodes achieve the highest specific capacitance at fairly low oxide loading onto activated carbon (AC) electrodes, respectively. Considerable enhancement of the electrochemical properties of TiO2/AC and ZnO/AC nanocomposite electrodes is achieved via synergistic effects contributed from the nanostructured metal oxides and the high surface area mesoporous AC. Cations and anions from metal oxides and aqueous electrolyte such as Ti4+, Zn2+, Na+ and SO32- can occupy some pores within the high-surface-area AC electrodes, forming the electric double layer at the electrode-electrolyte interface. Additionally, both TiO2 and ZnO nanoparticles can provide favourable surface adsorption sites for SO32- anions which subsequently facilitate the faradaic processes for pseudocapacitive effect. These two systems provide the low cost material electrodes and the low environmental impact electrolyte which offer the increased charge storage without compromising charge storage kinetics.

Electrochemical processing of spent nuclear fuels: An overview of oxide reduction in pyroprocessing technology

Directory of Open Access Journals (Sweden)

Eun-Young Choi

2015-12-01

Full Text Available The electrochemical reduction process has been used to reduce spent oxide fuel to a metallic form using pyroprocessing technology for a closed fuel cycle in combination with a metal-fuel fast reactor. In the electrochemical reduction process, oxides fuels are loaded at the cathode basket in molten Li2O–LiCl salt and electrochemically reduced to the metal form. Various approaches based on thermodynamic calculations and experimental studies have been used to understand the electrode reaction and efficiently treat spent fuels. The factors that affect the speed of the electrochemical reduction have been determined to optimize the process and scale-up the electrolysis cell. In addition, demonstrations of the integrated series of processes (electrorefining and salt distillation with the electrochemical reduction have been conducted to realize the oxide fuel cycle. This overview provides insight into the current status of and issues related to the electrochemical processing of spent nuclear fuels.

Electrochemical characterization of anode passivation mechanisms in copper electrorefining

Science.gov (United States)

Moats, Michael Scott

Anode passivation can decrease productivity and quality while increasing costs in modern copper electrorefineries. This investigation utilized electrochemical techniques to characterize the passivation behavior of anode samples from ten different operating companies. It is believed that this collection of anodes is the most diverse set ever to be assembled to study the effect of anode composition on passivation. Chronopotentiometry was the main electrochemical technique, employing a current density of 3820 A m-2. From statistical analysis of the passivation characteristics, increasing selenium, tellurium, silver, lead and nickel were shown to accelerate passivation. Arsenic was the only anode impurity that inhibited passivation. Oxygen was shown to accelerate passivation when increased from 500 to 1500 ppm, but further increases did not adversely affect passivation. Nine electrolyte variables were also examined. Increasing the copper, sulfuric acid or sulfate concentration of the electrolyte accelerated passivation. Arsenic in the electrolyte had no effect on passivation. Chloride and optimal concentrations of thiourea and glue delayed passivation. Linear sweep voltammetry, cyclic voltammetry, and impedance spectroscopy provided complementary information. Analysis of the electrochemical results led to the development of a unified passivation mechanism. Anode passivation results from the formation of inhibiting films. Careful examination of the potential details, especially those found in the oscillations just prior to passivation, demonstrated the importance of slimes, copper sulfate and copper oxide. Slimes confine dissolution to their pores and inhibit diffusion. This can lead to copper sulfate precipitation, which blocks more of the surface area. Copper oxide forms because of the resulting increase in potential at the interface between the copper sulfate and anode. Ultimate passivation occurs when the anode potential is high enough to stabilize the oxide film in

Chemically grown, porous, nickel oxide thin-film for electrochemical supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Inamdar, A.I.; Kim, YoungSam; Im, Hyunsik [Department of Semiconductor Science, Dongguk University, Seoul 100-715 (Korea, Republic of); Pawar, S.M.; Kim, J.H. [Department of Materials Science and Engineering, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Kim, Hyungsang [Department of Physics, Dongguk University, Seoul 100-715 (Korea, Republic of)

2011-02-15

A porous nickel oxide film is successfully synthesized by means of a chemical bath deposition technique from an aqueous nickel nitrate solution. The formation of a rock salt NiO structure is confirmed with XRD measurements. The electrochemical supercapacitor properties of the nickel oxide film are examined using cyclic voltammetery (CV), galvanostatic and impedance measurements in two different electrolytes, namely, NaOH and KOH. A specific capacitance of {proportional_to}129.5 F g{sup -1} in the NaOH electrolyte and {proportional_to}69.8 F g{sup -1} in the KOH electrolyte is obtained from a cyclic voltammetery study. The electrochemical stability of the NiO electrode is observed for 1500 charge-discharge cycles. The capacitative behaviour of the NiO electrode is confirmed from electrochemical impedance measurements. (author)

Electrochemical catalytic activities of nanoporous palladium rods for methanol electro-oxidation

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiaoguang; Wang, Weimin; Qi, Zhen; Zhao, Changchun; Ji, Hong; Zhang, Zhonghua [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (MOE), School of Materials Science and Engineering, Shandong University, Jingshi Road 73, Jinan 250061 (China)

2010-10-01

A novel electrocatalyst, nanoporous palladium (npPd) rods can be facilely fabricated by dealloying a binary Al{sub 80}Pd{sub 20} alloy in a 5 wt.% HCl aqueous solution under free corrosion conditions. The microstructure of these nanoporous palladium rods has been characterized using scanning electron microscopy and transmission electron microscopy. The results show that each Pd rod is several microns in length and several hundred nanometers in diameter. Moreover, all the rods exhibit a typical three-dimensional bicontinuous interpenetrating ligament-channel structure with length scale of 15-20 nm. The electrochemical experiments demonstrate that these peculiar nanoporous palladium rods (mixed with Vulcan XC-72 carbon powders to form a npPd/C catalyst) reveal a superior electrocatalytic performance toward methanol oxidation in the alkaline media. In addition, the electrocatalytic activity obviously depends on the metal loading on the electrode and will reach to the highest level (223.52 mA mg{sup -1}) when applying 0.4 mg cm{sup -2} metal loading on the electrode. Moreover, a competing adsorption mechanism should exist when performing methanol oxidation on the surface of npPd rods, and the electro-oxidation reaction is a diffusion-controlled electrochemical process. Due to the advantages of simplicity and high efficiency in the mass production, the npPd rods can act as a promising candidate for the anode catalyst for direct methanol fuel cells (DMFCs). (author)

Electrochemical Oxidation of Phenol using a Flow-through Micro ...

African Journals Online (AJOL)

The electrochemical oxidation of phenol to benzoquinone followed by the reduction to hydroquinone and catechol was demonstrated by constructing a three-dimensional porous micro-flow cell from lead dioxideand lead. The electrodes were made by using the principles of curing and formation of lead oxide material that ...

Review of Fabrication Methods, Physical Properties, and Applications of Nanostructured Copper Oxides Formed via Electrochemical Oxidation

Directory of Open Access Journals (Sweden)

Wojciech J. Stepniowski

2018-05-01

Full Text Available Typically, anodic oxidation of metals results in the formation of hexagonally arranged nanoporous or nanotubular oxide, with a specific oxidation state of the transition metal. Recently, the majority of transition metals have been anodized; however, the formation of copper oxides by electrochemical oxidation is yet unexplored and offers numerous, unique properties and applications. Nanowires formed by copper electrochemical oxidation are crystalline and composed of cuprous (CuO or cupric oxide (Cu2O, bringing varied physical and chemical properties to the nanostructured morphology and different band gaps: 1.44 and 2.22 eV, respectively. According to its Pourbaix (potential-pH diagram, the passivity of copper occurs at ambient and alkaline pH. In order to grow oxide nanostructures on copper, alkaline electrolytes like NaOH and KOH are used. To date, no systemic study has yet been reported on the influence of the operating conditions, such as the type of electrolyte, its temperature, and applied potential, on the morphology of the grown nanostructures. However, the numerous reports gathered in this paper will provide a certain view on the matter. After passivation, the formed nanostructures can be also post-treated. Post-treatments employ calcinations or chemical reactions, including the chemical reduction of the grown oxides. Nanostructures made of CuO or Cu2O have a broad range of potential applications. On one hand, with the use of surface morphology, the wetting contact angle is tuned. On the other hand, the chemical composition (pure Cu2O and high surface area make such materials attractive for renewable energy harvesting, including water splitting. While compared to other fabrication techniques, self-organized anodization is a facile, easy to scale-up, time-efficient approach, providing high-aspect ratio one-dimensional (1D nanostructures. Despite these advantages, there are still numerous challenges that have to be faced, including the

Chitosan-iron oxide nanocomposite based electrochemical aptasensor for determination of malathion

Energy Technology Data Exchange (ETDEWEB)

Prabhakar, Nirmal, E-mail: nirmalprabhakar@gmail.com; Thakur, Himkusha; Bharti, Anu; Kaur, Navpreet

2016-10-05

An electrochemical aptasensor based on chitosan-iron oxide nanocomposite (CHIT-IO) film deposited on fluorine tin Oxide (FTO) was developed for the detection of malathion. Iron oxide nanoparticles were prepared by co-precipitation method and characterized by Transmission electron microscopy and UV–Visible spectroscopy. The biotinylated DNA aptamer sequence specific to the malathion was immobilized onto the iron oxide doped-chitosan/FTO electrode by using streptavidin as linking molecule. Various characterization studies like Field Emission-Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Electrochemical studies were performed to attest the successful fabrication of bioelectrodes. Experimental parameters like aptamer concentration, response time, stability of electrode and reusability studies were optimized. Aptamer immobilized chitosan-iron oxide nanocomposite (APT/SA/CHIT-IO/FTO) bioelectrodes exhibited LOD of about 0.001 ng/mL within 15 min and spike-in studies revealed about 80–92% recovery of malathion from the lettuce leaves and soil sample. - Highlights: • An electrochemical aptasensor for the detection of Malathion has been developed. • Chitosan-iron oxide NP deposited FTO sheets provides platform for aptamer immobilization. • Aptasensor has efficiency to detect malathion upto 0.001 ng/mL within 15 min.

Macro-mechanics controls quantum mechanics: mechanically controllable quantum conductance switching of an electrochemically fabricated atomic-scale point contact.

Science.gov (United States)

Staiger, Torben; Wertz, Florian; Xie, Fangqing; Heinze, Marcel; Schmieder, Philipp; Lutzweiler, Christian; Schimmel, Thomas

2018-01-12

Here, we present a silver atomic-scale device fabricated and operated by a combined technique of electrochemical control (EC) and mechanically controllable break junction (MCBJ). With this EC-MCBJ technique, we can perform mechanically controllable bistable quantum conductance switching of a silver quantum point contact (QPC) in an electrochemical environment at room temperature. Furthermore, the silver QPC of the device can be controlled both mechanically and electrochemically, and the operating mode can be changed from 'electrochemical' to 'mechanical', which expands the operating mode for controlling QPCs. These experimental results offer the perspective that a silver QPC may be used as a contact for a nanoelectromechanical relay.

Application of oxide fine-mesh electrodes composed of Sb-SnO2 for the electrochemical oxidation of Cibacron Marine FG using an SPE filter-press reactor

International Nuclear Information System (INIS)

Da Silva, Leonardo M.; Gonçalves, Ismael C.; Teles, José J.S.; Franco, Débora V.

2014-01-01

Highlights: • Oxide fine-mesh electrodes composed of Sb-SnO 2 (OFM-Sb-SnO 2 ) were fabricated and applied to the decolourisation and mineralisation of dye solutions using an SPE filter-press reactor. • An electrode mechanism was proposed for the irreversible parallel reactions comprising the oxygen evolution reaction (OER) and the electrochemical advanced oxidation process (EAOP) during the electrolysis of electrolyte-free dye solutions. • The reduction in current efficiency for the OER during the oxidation of Cibacron Marine FG (CMFG) increased the electrode stability. - Abstract: Oxide fine-mesh electrodes composed of tin dioxide doped with antimony (OFM-Sb-SnO 2 ), which had different percentages of Sb, were prepared using the thermal decomposition method on a stainless steel fine-mesh support for application in a solid polymer electrolyte (SPE) filter-press reactor. The electrochemical oxidation of Cibacron ® Marine FG (CMFG) was carried out during recirculation through a plug-flow reactor, using electrolyte-free dye solutions. An influence of the Sb content on the electrochemical oxidation of CMFG was verified. The highest combustion rate of CMFG was obtained using an electrode containing 6.57 mol% Sb. Studies were carried out as a function of the initial dye concentration (IDC) and the applied current density (j) for this particular electrode composition. It was verified that the decolourisation and mineralisation reactions were affected considerably by IDC and j. In trying to interpret the experimental findings, an electrode mechanism was proposed for the irreversible parallel reactions comprising the oxygen evolution reaction (OER) and the advanced oxidation process (EAOP). The instantaneous current efficiency (ICE) for the mineralisation reaction was calculated for the different cases using the average mass-transport coefficient () and the initial limiting current (j L 0 ) values. The energy consumption (EC) was also calculated for the

Simultaneously Coupled Mechanical-Electrochemical-Thermal Simulation of Lithium-Ion Cells: Preprint

Energy Technology Data Exchange (ETDEWEB)

Zhang, Chao; Santhanagopalan, Shriram; Sprague, Michael A.; Pesaran, Ahmad A.

2016-08-01

Understanding the combined electrochemical-thermal and mechanical response of a system has a variety of applications, for example, structural failure from electrochemical fatigue and the potential induced changes of material properties. For lithium-ion batteries, there is an added concern over the safety of the system in the event of mechanical failure of the cell components. In this work, we present a generic multi-scale simultaneously coupled mechanical-electrochemical-thermal model to examine the interaction between mechanical failure and electrochemical-thermal responses. We treat the battery cell as a homogeneous material while locally we explicitly solve for the mechanical response of individual components using a homogenization model and the electrochemical-thermal responses using an electrochemical model for the battery. A benchmark problem is established to demonstrate the proposed modeling framework. The model shows the capability to capture the gradual evolution of cell electrochemical-thermal responses, and predicts the variation of those responses under different short-circuit conditions.

Electrochemical and theoretical characterization of the electro-oxidation of dimethoxycurcumin

Science.gov (United States)

Arrue, Lily; Barra, Tomas; Camarada, María Belén; Zarate, Ximena; Schott, Eduardo

2017-06-01

Dimethoxycurcumin (DMC) ((1E,6E)-1-(3,4-dimethoxycyclohexyl)-7-(3,4-dimethoxyphenyl) hepta-1,6- diene-3,5-dione) is a natural polyphenolic compound that appears together with curcumin in turmeric. Both molecules have wide range biological activities as antioxidant, anti-inflammatory and anti-carcinogenic agent. To evaluate the oxidation process and kinetics for DMC, the rate constant, electron transfer and diffusion coefficients for the electrochemical oxidation were determined. Therefore, its electrochemical behavior over a platinum electrode in anhydrous media was investigated. Furthermore, DFT calculations were performed to give a rational explanation to the obtained results. All the results support the fact that the central sbnd CH2sbnd group is the most reactive against an oxidation process.

Boron-doped diamond electrodes for the electrochemical oxidation and cleavage of peptides.

Science.gov (United States)

Roeser, Julien; Alting, Niels F A; Permentier, Hjalmar P; Bruins, Andries P; Bischoff, Rainer

2013-07-16

Electrochemical oxidation of peptides and proteins is traditionally performed on carbon-based electrodes. Adsorption caused by the affinity of hydrophobic and aromatic amino acids toward these surfaces leads to electrode fouling. We compared the performance of boron-doped diamond (BDD) and glassy carbon (GC) electrodes for the electrochemical oxidation and cleavage of peptides. An optimal working potential of 2000 mV was chosen to ensure oxidation of peptides on BDD by electron transfer processes only. Oxidation by electrogenerated OH radicals took place above 2500 mV on BDD, which is undesirable if cleavage of a peptide is to be achieved. BDD showed improved cleavage yield and reduced adsorption for a set of small peptides, some of which had been previously shown to undergo electrochemical cleavage C-terminal to tyrosine (Tyr) and tryptophan (Trp) on porous carbon electrodes. Repeated oxidation with BDD electrodes resulted in progressively lower conversion yields due to a change in surface termination. Cathodic pretreatment of BDD at a negative potential in an acidic environment successfully regenerated the electrode surface and allowed for repeatable reactions over extended periods of time. BDD electrodes are a promising alternative to GC electrodes in terms of reduced adsorption and fouling and the possibility to regenerate them for consistent high-yield electrochemical cleavage of peptides. The fact that OH-radicals can be produced by anodic oxidation of water at elevated positive potentials is an additional advantage as they allow another set of oxidative reactions in analogy to the Fenton reaction, thus widening the scope of electrochemistry in protein and peptide chemistry and analytics.

Electrochemical Dissolution of Iridium and Iridium Oxide Particles in Acidic Media: Transmission Electron Microscopy, Electrochemical Flow Cell Coupled to Inductively Coupled Plasma Mass Spectrometry, and X-ray Absorption Spectroscopy Study.

Science.gov (United States)

Jovanovič, Primož; Hodnik, Nejc; Ruiz-Zepeda, Francisco; Arčon, Iztok; Jozinović, Barbara; Zorko, Milena; Bele, Marjan; Šala, Martin; Šelih, Vid Simon; Hočevar, Samo; Gaberšček, Miran

2017-09-13

Iridium-based particles, regarded as the most promising proton exchange membrane electrolyzer electrocatalysts, were investigated by transmission electron microscopy and by coupling of an electrochemical flow cell (EFC) with online inductively coupled plasma mass spectrometry. Additionally, studies using a thin-film rotating disc electrode, identical location transmission and scanning electron microscopy, as well as X-ray absorption spectroscopy have been performed. Extremely sensitive online time-and potential-resolved electrochemical dissolution profiles revealed that Ir particles dissolve well below oxygen evolution reaction (OER) potentials, presumably induced by Ir surface oxidation and reduction processes, also referred to as transient dissolution. Overall, thermally prepared rutile-type IrO 2 particles are substantially more stable and less active in comparison to as-prepared metallic and electrochemically pretreated (E-Ir) analogues. Interestingly, under OER-relevant conditions, E-Ir particles exhibit superior stability and activity owing to the altered corrosion mechanism, where the formation of unstable Ir(>IV) species is hindered. Due to the enhanced and lasting OER performance, electrochemically pre-oxidized E-Ir particles may be considered as the electrocatalyst of choice for an improved low-temperature electrochemical hydrogen production device, namely a proton exchange membrane electrolyzer.

Synthesis of magnetite nanoparticles using electrochemical oxidation

Directory of Open Access Journals (Sweden)

Ye. Ya. Levitin

2014-08-01

Full Text Available The monodisperse magnetite nanoparticles are promising for use in the biomedical industry for targeted drug delivery, cell separation and biochemical products, Magnetic Resonance Imaging, immunological studies, etc. Classic method for the synthesis of magnetite is the chemical condensation Elmore’s, it is simple and cheap, but it is complicated by the formation of side compounds which impair the magnetic properties of the final product. Biological and medical purposes require high purity magnetite nanoparticles. Electrochemical methods of producing nanoparticles of magnetite acquire significant spread. The kinetics of electrochemical processes are a function of a larger number of parameters than the kinetics of conventional chemical reaction, thus electrochemical reactions can be thinner and more completely adjusted to give a predetermined size nanoparticles. In the kinetics of the electrochemical oxidation and reduction the important role is played by the nature of the electrode. In many industrial processes, it is advisable to use lead dioxide anodes with titanium current lead. Purpose of the work To determine the optimum conditions of electrochemical oxidation of Fe2+ Fe3+to produce magnetite with high purity and improved magnetic characteristics. Materials and methods Electrochemical studies were carried out in a glass cell ЯСЭ-2 using a potentiostat ПИ-50-1.1 and a recording device ПДА1. Reference electrode - silver chloride ЭВЛ1М 3.1, potentials listed on the hydrogen scale. The test solution contained 80 g/ l FeSO4×7H2O and H2SO4(to pH 1. The pH of the solution was measured with a pH–meter « рН–150». Concentration ratio of Fe3+/Fe2+in the solution was measured by permanganometric method. Magnetite particle sizes were measured by an electron microscope computer ЭВМ-100Л, an increasing is 2×105. Saturation magnetization was evaluated by the magnetization curve, for the measured sample in the field with strength

Indirect Electrochemical Oxidation with Multi Carbon Electrodes for Restaurant Wastewater Treatment

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I Dewa Ketut Sastrawidana

2018-01-01

Full Text Available The removal of organic matter from the restaurant wastewater was investigated using the electrochemical oxida-tion method with multi carbon electrodes in a parallel construction. The degradation process was monitored by the measurement of COD concentration as a function of electrolysis time. The effectof operating parameter conditions on COD removal were investigated including initial pH, distance between electrodes, and the applied voltage difference.The results showed that the treatment of restaurant wastewater containing 2 g/L chloride ion using the electrochemical oxidation technique at the operation conditions characterized by: pH 5, distance between electrode of 10 cm and applied voltage of 12 V, enabled to obtained COD removal of 92.84% within 90 min electrolysis time. It is can be concluded that the indirect electrochemical oxidation method with multi carbon electrodes can be used effectivelyas an alternative technology for reducing COD and may be potentially applied for removal organic pollutants from wastewater at the industrial scale.

ELECTROCHEMICAL DETERMINATION OF ETHANOL, 2- PROPANOL AND 1-BUTANOL ON GLASSY CARBON ELECTRODE MODIFIED WITH NICKEL OXIDE FILM

Directory of Open Access Journals (Sweden)

A. Benchettara

2014-12-01

Full Text Available In this work, we present the modification of a glassy carbon electrode with nickel oxide film which is performed in two successive steps. In the first one, the electrochemical deposition of metallic nickel on the glassy carbon electrode (GCE is achieved in 0.1M boric acid; in the second step, the metallic deposit is anodically oxidized in 0.1M NaOH. These two operations were carried out in a three electrode cell with a filiform platinum auxiliary electrode, a SCE as potential reference and a working microelectrode of modified glassy carbon with nickel oxides. This electrode is characterized by several electrochemical techniques and is used for the catalytic determination of ethanol, 2-propanol and 1-butanol in 0.1 M NaOH. The proposed chemical mechanism shows that NiO2 acts as a mediator.

ELECTROCHEMICAL DETERMINATION OF ETHANOL, 2- PROPANOL AND 1-BUTANOL ON GLASSY CARBON ELECTRODE MODIFIED WITH NICKEL OXIDE FILM

Directory of Open Access Journals (Sweden)

A. Benchettara

2015-07-01

Full Text Available In this work, we present the modification of a glassy carbon electrode with nickel oxide film which is performed in two successive steps. In the first one, the electrochemical deposition of metallic nickel on the glassy carbon electrode (GCE is achieved in 0.1M boric acid; in the second step, the metallic deposit is anodically oxidized in 0.1M NaOH. These two operations were carried out in a three electrode cell with a filiform platinum auxiliary electrode, a SCE as potential reference and a working microelectrode of modified glassy carbon with nickel oxides. This electrode is characterized by several electrochemical techniques and is used for the catalytic determination of ethanol, 2-propanol and 1-butanol in 0.1 M NaOH. The proposed chemical mechanism shows that NiO2 acts as a mediator.

Morphological reason for enhancement of electrochemical double layer capacitances of various acetylene blacks by electrochemical polarization

International Nuclear Information System (INIS)

Kim, Taegon; Ham, Chulho; Rhee, Choong Kyun; Yoon, Seong-Ho; Tsuji, Masaharu; Mochida, Isao

2008-01-01

Enhancement of electrochemical capacitance and morphological variations of various acetylene blacks caused by electrochemical polarization are presented. Acetylene blacks of different mean particle diameters were modified by air-oxidation and heat treatment to diversify the morphologies of the acetylene blacks before electrochemical polarization. The various acetylene blacks were electrochemically oxidized at 1.6 V (vs. Ag/AgCl) for 10 s and the polarization step was repeated until the capacitance values did not change any longer. These polarization steps enhanced the capacitances of the acetylene blacks and the specific enhancement factors range from 2 to 5.5. Such an enhancement is strongly related to morphological modification as revealed by transmission electron microscopic observations. The electrochemical polarization resulted in formation of tiny graphene sheets on the wide graphitic carbon surfaces, which were most responsible for the observed capacitive enhancement. Although the pseudo-capacitance increased after polarization by forming oxygenated species on the surfaces, its contribution to the total capacitance was less than 10%. The mechanism of the formation of the tiny graphene sheets during the electrochemical oxidation is described schematically

Electrochemical study of stress corrosion cracking of copper alloys

International Nuclear Information System (INIS)

Malki, Brahim

1999-01-01

This work deals with the electrochemical study of stress corrosion of copper alloys in aqueous environment. Selective dissolution and electrochemical oxidation are two key-points of the stress corrosion of these alloys. The first part of this thesis treats of these aspects applied to Cu-Au alloys. Measurements have been performed using classical electrochemical techniques (in potentio-dynamic, potentio-static and galvano-static modes). The conditions of occurrence of an electrochemical noise is analysed using signal processing techniques. The impact on the behavior of Cu 3 Au are discussed. In the second part, the stress corrosion problem is addressed in the case of surface oxide film formation, in particular for Cu-Zn alloys. We have found useful to extend this study to mechanical stress oxidation mechanisms in the presence of an oscillating potential electrochemical system. The aim is to examine the influence of these new electrochemical conditions (galvano-static mode) on the behavior of stressed brass. Finally, the potential distribution at crack tip is calculated in order to compare the different observations [fr

Waste treatment in NUCEF facility with silver mediated electrochemical oxidation technique

International Nuclear Information System (INIS)

Umeda, M.; Sugikawa, S.

2000-01-01

Silver mediated electrochemical oxidation technique has been considered one of promising candidates for alpha-bearing waste treatment. Destruction tests of organic compounds, such as insoluble tannin, TBP and dodecane, were carried out by this technique and the experimental data such as destruction rates, current efficiencies and intermediates were obtained. These compounds could be completely mineralized without the formation of reactive organic nitrate associated to safety hazards. On the basis of these results, the applicability of silver mediated electrochemical oxidation technique to waste treatment in NUCEF was evaluated. (authors)

Electrochemically Formed Ultrafine Metal Oxide Nanocatalysts for High-Performance Lithium–Oxygen Batteries

Energy Technology Data Exchange (ETDEWEB)

Liu, Bin; Yan, Pengfei; Xu, Wu; Zheng, Jianming; He, Yang; Luo, Langli; Bowden, Mark E.; Wang, Chong-Min; Zhang, Ji-Guang

2016-08-10

Lithium-oxygen (Li-O2) battery has an extremely high theoretical specific energy density as compared with conventional energy storage systems. However, practical application of Li-O2 battery system still faces significant challenges, especially its poor cyclability. In this work, we report a new approach to synthesis ultrafine metal oxide nanocatalysts through an electrochemical pre-lithiation process. This process reduces the size of NiCo2O4 (NCO) particles from 20~30 nm to a uniformly distributed domain of ~ 2 nm and largely improved their catalytic activity. Structurally, the pre-lithiated NCO NWs are featured by ultrafine NiO/CoO nanoparticles, which show high stability during prolonged cycles in terms of morphology and the particle size, therefore maintaining an excellent catalytic effect to oxygen reduction and evolution reactions. Li-O2 battery using this catalyst has demonstrated an initial capacity of 29,280 mAh g-1 and has retained a stable capacity of over 1,000 mAh g-1 after 100 cycles based on the weight of NCO active material. Direct in-situ TEM observation conclusively reveals the lithiation/delithiation process of as-prepared NCO NWs, clarifying the NCO/Li electrochemical reaction mechanism that can be extended to other transition-metal oxides and providing the in depth understandings on the catalysts and battery chemistries of other ternary transition-metal oxides.

Status of test results of electrochemical organic oxidation of a tank 241-SY-101 simulated waste

International Nuclear Information System (INIS)

Colby, S.A.

1994-06-01

This report presents scoping test results of an electrochemical waste pretreatment process to oxidize organic compounds contained in the Hanford Site's radioactive waste storage tanks. Electrochemical oxidation was tested on laboratory scale to destroy organics that are thought to pose safety concerns, using a nonradioactive, simulated tank waste. Minimal development work has been applied to alkaline electrochemical organic destruction. Most electrochemical work has been directed towards acidic electrolysis, as in the metal purification industry, and silver catalyzed oxidation. Alkaline electrochemistry has traditionally been associated with the following: (1) inefficient power use, (2) electrode fouling, and (3) solids handling problems. Tests using a laboratory scale electrochemical cell oxidized surrogate organics by applying a DC electrical current to the simulated tank waste via anode and cathode electrodes. The analytical data suggest that alkaline electrolysis oxidizes the organics into inorganic carbonate and smaller carbon chain refractory organics. Electrolysis treats the waste without adding chemical reagents and at ambient conditions of temperature and pressure. Cell performance was not affected by varying operating conditions and supplemental electrolyte additions

Multilayered films of cobalt oxyhydroxide nanowires/manganese oxide nanosheets for electrochemical capacitor

Energy Technology Data Exchange (ETDEWEB)

Zheng, Huajun [State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, Zhejiang University of Technology, Hangzhou 310014 (China); ARC Centre of Excellence for Functional Nanomaterials, School of Chemical Engineering and AIBN, The University of Queensland, St Lucia, Brisbane, QLD 4072 (Australia); Tang, Fengqiu; Mukherji, Aniruddh; Yan, Xiaoxia; Wang, Lianzhou (Max) Lu, Gao Qing [ARC Centre of Excellence for Functional Nanomaterials, School of Chemical Engineering and AIBN, The University of Queensland, St Lucia, Brisbane, QLD 4072 (Australia); Lim, Melvin [Division of Environmental and Water Resources Engineering, School of Civil and Environmental Engineering, Nanyang Technological University, 639798 (Singapore)

2010-01-15

Multilayered films of cobalt oxyhydroxide nanowires (CoOOHNW) and exfoliated manganese oxide nanosheet (MONS) are fabricated by potentiostatic deposition and electrostatic self-assembly on indium-tin oxide coated glass substrates. The morphology and chemical composition of these films are characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectra (XPS) and the potential application as electrochemical supercapacitors are investigated using cyclic voltammetry and charge-discharge measurements. These ITO/CoOOHNW/MONS multilayered film electrodes exhibit excellent electrochemical capacitance properties, including high specific capacitance (507 F g{sup -1}) and long cycling durability (less 2% capacity loss after 5000 charge/discharge cycles). These characteristics indicate that these newly developed films may find important application for electrochemical capacitors. (author)

Electrochemical oxidation of niclosamide at a glassy carbon ...

African Journals Online (AJOL)

Cyclic voltammetry, square-wave voltammetry and controlled potential electrolysis have been used to study the electrochemical oxidation behaviour of niclosamide at a glassy carbon electrode. The number of electrons transferred, the wave characteristics, the diffusion coefficient and reversibility of the reactions have been ...

Classifying the mechanisms of electrochemical shock in ion-intercalation materials

OpenAIRE

Woodford, William; Carter, W. Craig; Chiang, Yet-Ming

2014-01-01

“Electrochemical shock” – the electrochemical cycling-induced fracture of materials – contributes to impedance growth and performance degradation in ion-intercalation batteries, such as lithium-ion. Using a combination of micromechanical models and acoustic emission experiments, the mechanisms of electrochemical shock are identified, classified, and modeled in targeted model systems with different composition and microstructure. A particular emphasis is placed on mechanical degradation occurr...

Kinetic study on electrochemical oxidation of catechols in the ...

Indian Academy of Sciences (India)

glassy carbon electrode in different experimental conditions. The electrogenerated ... cancer activities.5 Catechols can be easily oxidized electrochemically to ... from unity and approaches to zero in basic solution. This behavior is related to the ...

effect of electrochemical oxidation of a viscose rayon based ...

African Journals Online (AJOL)

DJFLEX

KEYWORDS: Viscose rayon based activated carbon cloth; Sorption isotherms; Electrochemical oxidation; Arsenic .... (AAS ) in acetylene-air flame emission mode. 2.9. Quality ..... of the EO ACC thereby restricting the number of binding sites for ...

Porous Ni-Co-Mn oxides prisms for high performance electrochemical energy storage

Science.gov (United States)

Zhao, Jianbo; Li, Man; Li, Junru; Wei, Chengzhen; He, Yuyue; Huang, Yixuan; Li, Qiaoling

2017-12-01

Porous Ni-Co-Mn oxides prisms have been successfully synthesized via a facile route. The process involves the preparation of nickel-cobalt-manganese acetate hydroxide by a simple co-precipitation method and subsequently the thermal treatment. The as-synthesized Ni-Co-Mn oxides prisms had a large surface area (96.53 m2 g-1) and porous structure. As electrode materials for supercapacitors, porous Ni-Co-Mn oxides prisms showed a high specific capacitance of 1623.5 F g-1 at 1.0 A g-1. Moreover, the porous Ni-Co-Mn oxides prisms were also employed as positive electrode materials to assemble flexible solid-state asymmetric supercapacitors. The resulting flexible device had a maximum volumetric energy density (0.885 mW h cm-3) and power density (48.9 mW cm-3). Encouragingly, the flexible device exhibited good cycling stability with only about 2.2% loss after 5000 charge-discharge cycles and excellent mechanical stability. These results indicate that porous Ni-Co-Mn oxides prisms have the promising application in high performance electrochemical energy storage.

Electrochemical Oxidation of Cyanide Using Platinized Ti Electrodes

Directory of Open Access Journals (Sweden)

Aušra VALIŪNIENĖ

2013-12-01

Full Text Available The cyanide-containing effluents are dangerous ecological hazards and must be treated before discharging into the environment. Anodic oxidation is one of the best ways to degrade cyanides. Pt anodes as the most efficient material for the cyanide electrochemical degradation are widely used. However, these electrodes are too expensive for industrial purposes. In this work Ti electrodes covered with nano-sized Pt particle layer were prepared and used for the anodic oxidation of cyanide ions. Surface images of Ti electrodes and Ti electrodes covered with different thickness layer of Pt were compared and characterized by the atomic force microscopy (AFM. The products formed in the solution during the CN- ions electrooxidation were examined by the Raman spectroscopy. An electrochemical Fast Fourier transformation (FFT impedance spectroscopy was used to estimate the parameters that reflect real surface roughness of Pt-modified Ti electrodes.DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2514

Mechanisms of electrochemical reduction and oxidation of nitric oxide

NARCIS (Netherlands)

Vooys, de A.C.A.; Beltramo, G.L.; Riet, van B.; Veen, van J.A.R.; Koper, M.T.M.

2004-01-01

A summary is given of recent work on the reactivity of nitric oxide on various metal electrodes. The significant differences between the reactivity of adsorbed NO and NO in solution are pointed out, both for the reduction and the oxidation reaction(s). Whereas adsorbed NO can be reduced only to

The oxidation mechanism of the antioxidant quercetin in nonaqueous media

Energy Technology Data Exchange (ETDEWEB)

Sokolova, Romana, E-mail: romana.sokolova@jh-inst.cas.cz [J. Heyrovsky Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejskova 3, 18223 Prague (Czech Republic); Degano, Ilaria [Department of Chemistry and Industrial Chemistry, University of Pisa, Via Risorgimento 35, 56100 Pisa (Italy); Ramesova, Sarka; Bulickova, Jana; Hromadova, Magdalena; Gal, Miroslav; Fiedler, Jan [J. Heyrovsky Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejskova 3, 18223 Prague (Czech Republic); Valasek, Michal [Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nam. 2, 16610 Prague 6 (Czech Republic)

2011-08-30

The knowledge of the degradation pathways of natural dyes used in medieval textiles is necessary for the restoration of their original color. Quercetin, one of such colorants, reportedly yields the wide spectrum of oxidation products in different types of media. This study deals with electrochemical oxidation mechanism of quercetin in nonaqueous solution, which has not been yet attempted. The final oxidation product at the first oxidation wave was identified by HPLC-DAD and GC-MS techniques as 2-(3',4'-dihydroxybenzoyl)-2,4,6-trihydroxybenzofuran-3(2H)-one. The apparent two-electron process at the potential of the first oxidation wave yields current-voltage shapes with one-electron characteristics. The in situ spectroelectrochemistry measurements proved the oxidation mechanism leading through a short-lived anion radical. Two possibilities of the oxidation mechanism are discussed: two one-electron transfers, which do not have identical but similar redox potentials, or the presence of a disproportionation chemical reaction following the first one electron transfer. The quinone formed in either case is stable only on the time scale of a fast spectroelectrochemistry and undergoes fast hydroxylation reaction, where 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxybenzofuran-3-one is formed. This compound is oxidized at the potential of the second oxidation wave of quercetin.

The oxidation mechanism of the antioxidant quercetin in nonaqueous media

International Nuclear Information System (INIS)

Sokolova, Romana; Degano, Ilaria; Ramesova, Sarka; Bulickova, Jana; Hromadova, Magdalena; Gal, Miroslav; Fiedler, Jan; Valasek, Michal

2011-01-01

The knowledge of the degradation pathways of natural dyes used in medieval textiles is necessary for the restoration of their original color. Quercetin, one of such colorants, reportedly yields the wide spectrum of oxidation products in different types of media. This study deals with electrochemical oxidation mechanism of quercetin in nonaqueous solution, which has not been yet attempted. The final oxidation product at the first oxidation wave was identified by HPLC-DAD and GC-MS techniques as 2-(3',4'-dihydroxybenzoyl)-2,4,6-trihydroxybenzofuran-3(2H)-one. The apparent two-electron process at the potential of the first oxidation wave yields current-voltage shapes with one-electron characteristics. The in situ spectroelectrochemistry measurements proved the oxidation mechanism leading through a short-lived anion radical. Two possibilities of the oxidation mechanism are discussed: two one-electron transfers, which do not have identical but similar redox potentials, or the presence of a disproportionation chemical reaction following the first one electron transfer. The quinone formed in either case is stable only on the time scale of a fast spectroelectrochemistry and undergoes fast hydroxylation reaction, where 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxybenzofuran-3-one is formed. This compound is oxidized at the potential of the second oxidation wave of quercetin.

Studies on room temperature electrochemical oxidation and its effect on the transport properties of TBCCO films

International Nuclear Information System (INIS)

Shirage, P M; Shivagan, D D; Pawar, S H

2004-01-01

A novel room temperature electrochemical process for the synthesis of single-phase Tl 2 Ba 2 Ca 2 Cu 3 O 10 (TBCCO/Tl-2223) superconducting films has been developed. Electrochemical parameters were optimized by studying linear sweep voltammetry (LSV), cyclic voltammetry (CV) and chronoamperometry (CA) for the deposition of Tl-Ba-Ca-Cu alloy at room temperature. The superconducting films of the TBCCO were obtained by two oxidation techniques. In the first technique, the electrodeposited Tl-Ba-Ca-Cu alloyed films were oxidized at various temperatures in flowing oxygen atmosphere. In the second technique, stoichiometric electrocrystallization to get Tl 2 Ba 2 Ca 2 Cu 3 O 10 (Tl-2223) was completed by electrochemically intercalating oxygen species into Tl-Ba-Ca-Cu alloy at room temperature for various lengths of time. The oxygen content in the samples was varied by varying the electrochemical oxidation period, and the changes in the crystal structure, superconducting transition temperature (T c ) and critical current density (J c ) were recorded. The high temperature furnace oxidation technique was replaced by the room temperature electrochemical oxidation technique. The dependence of superconducting parameters on oxygen content is correlated with structure-property relations

Nitrogen-doped graphene: effect of graphite oxide precursors and nitrogen content on the electrochemical sensing properties.

Science.gov (United States)

Megawati, Monica; Chua, Chun Kiang; Sofer, Zdenek; Klímová, Kateřina; Pumera, Martin

2017-06-21

Graphene, produced via chemical methods, has been widely applied for electrochemical sensing due to its structural and electrochemical properties as well as its ease of production in large quantity. While nitrogen-doped graphenes are widely studied materials, the literature showing an effect of graphene oxide preparation methods on nitrogen quantity and chemical states as well as on defects and, in turn, on electrochemical sensing is non-existent. In this study, the properties of nitrogen-doped graphene materials, prepared via hydrothermal synthesis using graphite oxide produced by various classical methods using permanganate or chlorate oxidants Staudenmaier, Hummers, Hofmann and Brodie oxidation methods, were studied; the resulting nitrogen-doped graphene oxides were labeled as ST-GO, HU-GO, HO-GO and BR-GO, respectively. The electrochemical oxidation of biomolecules, such as ascorbic acid, uric acid, dopamine, nicotinamide adenine nucleotide and DNA free bases, was carried out using cyclic voltammetry and differential pulse voltammetry techniques. The nitrogen content in doped graphene oxides increased in the order ST-GO graphene followed this trend, as shown in the cyclic voltammograms. This is a very important finding that provides insight into the electrocatalytic effect of N-doped graphene. The nitrogen-doped graphene materials exhibited improved sensitivity over bare glassy carbon for ascorbic acid, uric acid and dopamine detection. These studies will enhance our understanding of the effects of graphite oxide precursors on the electrochemical sensing properties of nitrogen-doped graphene materials.

Electrochemical behavior of uranium oxide in a LiCl-Li2O molten salt with the integrated cathode assembly

International Nuclear Information System (INIS)

Park, Sung Bin; Park, Byung Heung; Kang, Dae Seoung; Kwon, Seon Gil; Seo, Chung Seok; Park, Seong Won

2005-01-01

Electrochemical reduction of uranium oxide to uranium metal was studied in a LiCl-Li 2 O molten salt system. By means of a cyclic voltammetry and a chronopotentiometry, the electrolytic reduction of uranium oxide has been studied to establish the reduction mechanisms and the effects of the thickness of the uranium oxide on the overpotential of the cathode and anode were investigated. From the voltamograms, the reduction potentials of the uranium oxide and Li 2 O were obtained and the two mechanisms of the electrolytic reduction were considered with regards to the applied cathode potential. In the chronopotentiograms, the exchange current, the transfer coefficient and the maximum allowable current based on the Tafel behavior were obtained according to the thickness of the uranium oxide which is loaded into the porous MgO membrane. (author)

Tuning inner-layer oxygen functional groups of reduced graphene oxide by potentiostatic oxidation for high performance electrochemical energy storage devices

International Nuclear Information System (INIS)

Wang, Huixin; Feng, Bingmei; Ye, Yifan; Guo, Jinghua; Fang, Hai-Tao

2017-01-01

Graphical abstract: Tuning inner-layer oxygen functional groups of reduced graphene oxide by potentiostatic oxidation in carbonate-based electrolyte improves the electrochemical performance. - Abstract: The electrochemical lithiation/delithiation of oxygen-containing functional groups (OCFGs) of nanocarbon materials, particularly graphene, have attracted intensive interest in recent years. Here, we propose a controllable potentiostatic oxidation approach to tune the OCFGs of as-prepared reduced graphene oxide (rGO) in a carbonate-based electrolyte to improve the specific capacity and rate capability. By X-Ray absorption spectroscopy in total fluorescence yield mode and X-Ray diffraction, we confirm that potentiostatic oxidations generate new OCFGs in the inner-layer of rGO. The content of OCFGs increases as oxidation potential being elevated. Such increasing of OCFGs in quantity significantly enhances the capacity. For instance, the specific capacity of 170.4 mAh g −1 for pristine rGO electrode is increased to 290.5 mAh g −1 after the oxidation at 5.0 V. We demonstrate that oxidations at moderate potentials can reduce the electrochemical and ohmic polarizations of rGO electrodes without deteriorating diffusion dynamic, thereby improving rate capability. After the optimal oxidation at 4.7 V, rGO electrode exhibits an excellent rate capability, delivering 58.4 mAh g −1 at 20 A g −1 .

Selective Electrochemical Generation of Hydrogen Peroxide from Water Oxidation

DEFF Research Database (Denmark)

Viswanathan, Venkatasubramanian; Hansen, Heine Anton; Nørskov, Jens K.

2015-01-01

evolution and form hydrogen peroxide. Using density functional theory calculations, we show that the free energy of adsorbed OH* can be used to determine selectivity trends between the 2e(-) water oxidation to H2O2 and the 4e(-) oxidation to O2. We show that materials which bind oxygen intermediates...... sufficiently weakly, such as SnO2, can activate hydrogen peroxide evolution. We present a rational design principle for the selectivity in electrochemical water oxidation and identify new material candidates that could perform H2O2 evolution selectively....

Kinetic studies of electrochemical generation of Ag(II) ion and catalytic oxidation of selected organics

International Nuclear Information System (INIS)

Zawodzinski, C.; Smith, W.H.; Martinez, K.R.

1993-01-01

The goal of this research is to develop a method to treat mixed hazardous wastes containing selected organic compounds and heavy metals, including actinide elements. One approach is to destroy the organic via electrochemical oxidation to carbon dioxide, then recover the metal contaminants through normally accepted procedures such as ion exchange, precipitation, etc. The authors have chosen to study the electrochemical oxidation of a simple alcohol, iso-propanol. Much of the recent work reported involved the use of an electron transfer mediator, usually the silver(I)/(II) redox couple. This involved direct electrochemical generation of the mediator at the anode of a divided cell followed by homogeneous reaction of the mediator with the organic compound. In this study the authors have sought to compare the mediated reaction with direct electrochemical oxidation of the organic. In addition to silver(I)/(II) they also looked at the cobalt(II)/(III) redox coupled. In the higher oxidation state both of these metal ions readily hydrolyze in aqueous solution to ultimately form insoluble oxide. The study concluded that in a 6M nitric acid solution at room temperature iso-propanol can be oxidized to carbon dioxide and acetic acid. Acetic acid is a stable intermediate and resists further oxidation. The presence of Co(III) enhances the rate or efficiency of the reaction

Coupling ultraviolet light and ultrasound irradiation with Conductive-Diamond Electrochemical Oxidation for the removal of progesterone

International Nuclear Information System (INIS)

Vidales, María J. Martín de; Barba, Silvia; Sáez, Cristina; Cañizares, Pablo; Rodrigo, Manuel A.

2014-01-01

Highlights: • Single sonolysis and photolysis technologies entail a slight progesterone removal and nil mineralization. • Synergistic effects of irradiating UV light and US are clearly observed in the oxidation rate. • The energy required by CDSEO and CDSPEO prevents against their application. • CDSEO mainly favors the mass transfer of organics to the conductive-diamond surface. • CDPEO promotes the formation of radicals in the bulk solution. - Abstract: This work focusses on the improvement of the efficiency of Conductive Diamond Electrochemical Oxidation (CDEO) by coupling US and UV irradiation in the degradation of progesterone from wastewater. Results show that CDEO is a promising technology for the degradation of progesterone, just the opposite of that observed for single sonolysis and photolysis technologies, which only entail a slight removal of progesterone and nil mineralization. Coupling UV light and US irradiations with CDEO seems to have a very positive effect, improving results obtained by single CDEO very significantly. Conductive Diamond Sono Electrochemical Oxidation (CDSEO) mainly seems to improve the transfer of pollutants to the conductive-diamond surface, while Conductive Diamond Photo Electrochemical Oxidation (CDPEO) seems to promote the formation of radicals from oxidants produced electrochemically. Soft oxidation conditions are obtained with the single application of both irradiation technologies, whereas an efficient mineralization is attained with CDEO, CDSEO, CDPEO and Conductive Diamond Sono-Photo Electrochemical Oxidation (CDSPEO). However, the high energy demands of US irradiation technologies advices against the use of CDSEO and CDSPEO

Nickel oxide/hydroxide nanoplatelets synthesized by chemical precipitation for electrochemical capacitors

International Nuclear Information System (INIS)

Wu, M.-S.; Hsieh, H.-H.

2008-01-01

Nickel hydroxide powder prepared by directly chemical precipitation method at room temperature has a nanoplatelet-like morphology and could be converted into nickel oxide at annealing temperature higher than 300 deg. C, confirmed by the thermal gravimetric analysis and X-ray diffraction. Annealing temperature influences significantly both the electrical conductivity and the specific surface area of nickel oxide/hydroxide powder, and consequently determines the capacitor behavior. Electrochemical capacitive behavior of the synthesized nickel hydroxide/oxide film is investigated by cyclic voltammetry and electrochemical impedance spectroscope methods. After 300 deg. C annealing, the highest specific capacitance of 108 F g -1 is obtained at scan rate of 10 mV s -1 . When annealing temperature is lower than 300 deg. C, the electrical conductivity of nickel hydroxide dominates primarily the capacitive behavior. When annealing temperature is higher than 300 deg. C, both electrical conductivity and specific surface area of the nickel oxide dominate the capacitive behavior

Macro-mechanics controls quantum mechanics: mechanically controllable quantum conductance switching of an electrochemically fabricated atomic-scale point contact

Science.gov (United States)

Staiger, Torben; Wertz, Florian; Xie, Fangqing; Heinze, Marcel; Schmieder, Philipp; Lutzweiler, Christian; Schimmel, Thomas

2018-01-01

Here, we present a silver atomic-scale device fabricated and operated by a combined technique of electrochemical control (EC) and mechanically controllable break junction (MCBJ). With this EC-MCBJ technique, we can perform mechanically controllable bistable quantum conductance switching of a silver quantum point contact (QPC) in an electrochemical environment at room temperature. Furthermore, the silver QPC of the device can be controlled both mechanically and electrochemically, and the operating mode can be changed from ‘electrochemical’ to ‘mechanical’, which expands the operating mode for controlling QPCs. These experimental results offer the perspective that a silver QPC may be used as a contact for a nanoelectromechanical relay.

Characterization of electro-oxidation catalysts using scanning electrochemical and mass spectral methods

Science.gov (United States)

Jambunathan, Krishnakumar

Low temperature fuel cells have many potential benefits, including high efficiency, high energy density and environmental friendliness. However, logistically appealing fuels for this system, such as reformed hydrocarbons or alcohols, exhibit poor performance because of catalyst poisoning that occurs during oxidation at the anode. This research focuses on the analysis of several model fuels and catalyst materials to understand the impact of catalyst poisoning on reactivity. Two novel experimental tools were developed based upon the local measurement of catalyst performance using scanning, reactivity mapping probes. The Scanning Electrochemical Microscope (SECM) was used to directly measure the rate constant for hydrogen oxidation in the presence and absence of dissolved CO. The Scanning Differential Electrochemical Mass Spectrometer (SDEMS) was exploited to measure the partial and complete oxidation products of methanol and ethanol oxidation. The reactivity of Pt and Pt/Ru catalysts towards the hydrogen oxidation reaction in the absence and presence of adsorbed CO was elucidated using the SECM. Steady state rate constant measurements in the absence of CO showed that the rate of hydrogen oxidation reaction exceeded 1 cms-1 . Steady state rate constant measurements in the presence of CO indicated that the platinum surface is completely inactive due to adsorbed CO. Addition of as little as 6% Ru to the Pt electrode was found to significantly improve the activity of the electrode towards CO removal. SDEMS was used to study the electro-oxidation of methanol on Pt xRuy electrodes at different electrode potentials and temperatures. Screening measurements performed with the SDEMS showed that PtxRu y electrodes containing 6--40% Ru had the highest activity for methanol oxidation. Current efficiencies for CO2 were also calculated under different conditions. SDEMS was also used to study the electro-oxidation of ethanol on Pt xRuy electrodes. The reaction was found to occur

Structural, electrical, and electrochemical characterization of Ni--Pr oxide thick films

Energy Technology Data Exchange (ETDEWEB)

Mari, C; Scolari, V; Fiori, G; Pizzini, S

1977-03-01

Oxides with metallic conductivity could and have been used instead of noble metals as insert electrodes in aqueous solutions as well as electrodes for high temperature fuel cells and electrolyzers and as catalysts for the conversion of exhaust gases from internal combustion engines. The aim of this paper is to report the results of a physico-chemical characterization (structure, morphology, electrochemical behavior) of Ni--Pr oxides which have been proposed as electrode materials for high temperature fuel cells. The electrochemical characterization was carried out in aqueous solutions at room temperature and with solid electrolytes at high temperature. Evidence has been found in the former case for an oxide electrode type of behavior. In the high temperature case, very low overvoltage values have been observed during cathodic oxygen reduction, while the electrode undergoes a reaction with oxygen during anodic oxygen evolution.

Nanostructured core-shell electrode materials for electrochemical capacitors

Science.gov (United States)

Jiang, Long-bo; Yuan, Xing-zhong; Liang, Jie; Zhang, Jin; Wang, Hou; Zeng, Guang-ming

2016-11-01

Core-shell nanostructure represents a unique system for applications in electrochemical energy storage devices. Owing to the unique characteristics featuring high power delivery and long-term cycling stability, electrochemical capacitors (ECs) have emerged as one of the most attractive electrochemical storage systems since they can complement or even replace batteries in the energy storage field, especially when high power delivery or uptake is needed. This review aims to summarize recent progress on core-shell nanostructures for advanced supercapacitor applications in view of their hierarchical architecture which not only create the desired hierarchical porous channels, but also possess higher electrical conductivity and better structural mechanical stability. The core-shell nanostructures include carbon/carbon, carbon/metal oxide, carbon/conducting polymer, metal oxide/metal oxide, metal oxide/conducting polymer, conducting polymer/conducting polymer, and even more complex ternary core-shell nanoparticles. The preparation strategies, electrochemical performances, and structural stabilities of core-shell materials for ECs are summarized. The relationship between core-shell nanostructure and electrochemical performance is discussed in detail. In addition, the challenges and new trends in core-shell nanomaterials development have also been proposed.

A Critical Review of Spinel Structured Iron Cobalt Oxides Based Materials for Electrochemical Energy Storage and Conversion

Directory of Open Access Journals (Sweden)

Hongyan Gao

2017-11-01

Full Text Available Iron cobalt oxides, such as typical FeCo2O4 and CoFe2O4, are two spinel structured transitional metal oxide materials with excellent electrochemical performance. As the electrodes, they have been widely applied in the current energy storage and conversion processes such as supercapacitors, Lithium-ion batteries and fuel cells. Based on synthesis approaches and controlled conditions, these two materials exhibited broad morphologies and nanostructures and thus distinct electrochemical performance. Some of them have shown promising applications as electrodes in energy storage and conversion. The incorporation with other materials to form composites further improved their performance. This review briefly summarized the recent applications of FeCo2O4 and CoFe2O4 in energy storage and conversion, current understandings on mechanisms and especially the relevance of morphologies and structures and composites to electrochemical performance. Some recommendations were finally put forward addressing current issues and future prospects on electrodes of FeCo2O4 and CoFe2O4 based materials in energy storage and conversion, implying there was still space to further optimize their performance.

Zn2+-Doped Polyaniline/Graphene Oxide as Electrode Material for Electrochemical Supercapacitors

Science.gov (United States)

Xu, Hui; Tang, Jing; Chen, Yong; Liu, Jian; Pu, Jinjuan; Li, Qi

2017-10-01

Electrodes based on Zn2+-doped polyaniline/graphene oxide (Zn2+/PANI/GO) were synthesized on stainless steel mesh substrates in H2SO4 solution via electrochemical codeposition. Different concentrations of graphene oxide (GO) were incorporated into the films to improve the electrochemical performance of the electrodes. Electrochemical properties of the films were tested by cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy, in a three-electrode system. The maximum specific capacitance of the Zn2+/PANI/GO film with a GO concentration of 15 mg L-1 was found to be 1266 F g-1 at a scan rate of 3 mV s-1. This value was higher than that of a Zn2+ doped polyaniline (Zn2+/PANI) film (814 F g-1). The Zn2+/PANI/GO film also showed good cycling stability, retaining over 86% of its initial capacitance after 1000 cycles. These results indicate that the Zn2+/PANI/GO composites can be applied as high performance supercapacitor electrodes.

Fractional surface termination of diamond by electrochemical oxidation.

Science.gov (United States)

Hoffmann, René; Obloh, Harald; Tokuda, Norio; Yang, Nianjun; Nebel, Christoph E

2012-01-10

The crystalline form of sp(3)-hybridized carbon, diamond, offers various electrolyte-stable surface terminations. The H-termination-selective attachment of nitrophenyl diazonium, imaged by AFM, shows that electrochemical oxidation can control the fractional hydrogen/oxygen surface termination of diamond on the nanometer scale. This is of particular interest for all applications relying on interfacial electrochemistry, especially for biointerfaces.

Electrochemical activity of heavy metal oxides in the process of ...

Indian Academy of Sciences (India)

Unknown

2002-02-02

Feb 2, 2002 ... Electrochemical activity of heavy metal oxides in the process of chloride induced .... represents the protective barrier moderating the chloride attack which ... inhibitors and their influence on the physical properties of. Portland ...

Alkaline electrochemical advanced oxidation process for chromium oxidation at graphitized multi-walled carbon nanotubes.

Science.gov (United States)

Xue, Yudong; Zheng, Shili; Sun, Zhi; Zhang, Yi; Jin, Wei

2017-09-01

Alkaline electrochemical advanced oxidation processes for chromium oxidation and Cr-contaminated waste disposal were reported in this study. The highly graphitized multi-walled carbon nanotubes g-MWCNTs modified electrode was prepared for the in-situ electrochemical generation of HO 2 - . RRDE test results illustrated that g-MWCNTs exhibited much higher two-electron oxygen reduction activity than other nanocarbon materials with peak current density of 1.24 mA cm -2 , %HO 2 - of 77.0% and onset potential of -0.15 V (vs. Hg/HgO). It was originated from the highly graphitized structure and good electrical conductivity as illustrated from the Raman, XRD and EIS characterizations, respectively. Large amount of reactive oxygen species (HO 2 - and ·OH) were in-situ electro-generated from the two-electron oxygen reduction and chromium-induced alkaline electro-Fenton-like reaction. The oxidation of Cr(III) was efficiently achieved within 90 min and the conversion ratio maintained more than 95% of the original value after stability test, offering an efficient and green approach for the utilization of Cr-containing wastes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of Salts and Metal Oxides on Electrochemical and Optical Properties of Streptococcus mutans

Science.gov (United States)

Kawai, Tsuyoshi; Nagame, Seigo; Kambara, Masaki; Yoshino, Katsumi

1994-10-01

The effects of calcium salts and metal oxide powders on electrochemical, optical and biological properties of Streptococcus mutans have been studied as a novel method to determine the strain. Electrochemical signals of Streptococcus mutans show remarkable decrease in the presence of saturated calcium salts such as CaHPO4, Ca3(PO4)2, and Ca5(PO4)3OH depending on the strains of Streptococcus mutans: Ingbritt, NCTC-10449, or GS-5. The number of viable cells also decreases upon addition of these powders. The effects of metal oxides such as ZnO and BaTiO3 on the electrochemical characteristics and photoluminescence of Streptococcus mutans have also been studied.

Destination of organic pollutants during electrochemical oxidation of biologically-pretreated dye wastewater using boron-doped diamond anode

Energy Technology Data Exchange (ETDEWEB)

Zhu, Xiuping [Department of Environmental Engineering, Peking University, the Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing100871 (China); Ni, Jinren, E-mail: nijinren@iee.pku.edu.cn [Department of Environmental Engineering, Peking University, the Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing100871 (China); Wei, Junjun; Xing, Xuan; Li, Hongna [Department of Environmental Engineering, Peking University, the Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing100871 (China)

2011-05-15

Electrochemical oxidation of biologically-pretreated dye wastewater was performed in a boron-doped diamond (BDD) anode system. After electrolysis of 12 h, the COD was decreased from 532 to 99 mg L{sup -1} (<100 mg L{sup -1}, the National Discharge Standard of China). More importantly, the destination of organic pollutants during electrochemical oxidation process was carefully investigated by molecular weight distribution measurement, resin fractionation, ultraviolet-visible spectroscopy, HPLC and GC-MS analysis, and toxicity test. As results, most organic pollutants were completely removed by electrochemical oxidation and the rest was primarily degraded to simpler compounds (e.g., carboxylic acids and short-chain alkanes) with less toxicity, which demonstrated that electrochemical oxidation of biologically-pretreated dye wastewater with BDD anode was very effective and safe. Especially, the performance of BDD anode system in degradation of large molecular organics such as humic substances makes it very promising in practical applications as an advanced treatment of biologically-pretreated wastewaters.

Destination of organic pollutants during electrochemical oxidation of biologically-pretreated dye wastewater using boron-doped diamond anode.

Science.gov (United States)

Zhu, Xiuping; Ni, Jinren; Wei, Junjun; Xing, Xuan; Li, Hongna

2011-05-15

Electrochemical oxidation of biologically-pretreated dye wastewater was performed in a boron-doped diamond (BDD) anode system. After electrolysis of 12h, the COD was decreased from 532 to 99 mg L(-1) (destination of organic pollutants during electrochemical oxidation process was carefully investigated by molecular weight distribution measurement, resin fractionation, ultraviolet-visible spectroscopy, HPLC and GC-MS analysis, and toxicity test. As results, most organic pollutants were completely removed by electrochemical oxidation and the rest was primarily degraded to simpler compounds (e.g., carboxylic acids and short-chain alkanes) with less toxicity, which demonstrated that electrochemical oxidation of biologically-pretreated dye wastewater with BDD anode was very effective and safe. Especially, the performance of BDD anode system in degradation of large molecular organics such as humic substances makes it very promising in practical applications as an advanced treatment of biologically-pretreated wastewaters. Copyright © 2011 Elsevier B.V. All rights reserved.

Destination of organic pollutants during electrochemical oxidation of biologically-pretreated dye wastewater using boron-doped diamond anode

International Nuclear Information System (INIS)

Zhu, Xiuping; Ni, Jinren; Wei, Junjun; Xing, Xuan; Li, Hongna

2011-01-01

Electrochemical oxidation of biologically-pretreated dye wastewater was performed in a boron-doped diamond (BDD) anode system. After electrolysis of 12 h, the COD was decreased from 532 to 99 mg L -1 ( -1 , the National Discharge Standard of China). More importantly, the destination of organic pollutants during electrochemical oxidation process was carefully investigated by molecular weight distribution measurement, resin fractionation, ultraviolet-visible spectroscopy, HPLC and GC-MS analysis, and toxicity test. As results, most organic pollutants were completely removed by electrochemical oxidation and the rest was primarily degraded to simpler compounds (e.g., carboxylic acids and short-chain alkanes) with less toxicity, which demonstrated that electrochemical oxidation of biologically-pretreated dye wastewater with BDD anode was very effective and safe. Especially, the performance of BDD anode system in degradation of large molecular organics such as humic substances makes it very promising in practical applications as an advanced treatment of biologically-pretreated wastewaters.

Electrochemical Water Oxidation by a Catalyst-Modified Metal-Organic Framework Thin Film

Energy Technology Data Exchange (ETDEWEB)

Lin, Shaoyang; Pineda-Galvan, Yuliana; Maza, William A.; Epley, Charity C.; Zhu, Jie; Kessinger, Matthew C.; Pushkar, Yulia; Morris, Amanda J. (VP); (Purdue)

2016-12-15

Water oxidation, a key component in artificial photosynthesis, requires high overpotentials and exhibits slow reaction kinetics that necessitates the use of stable and efficient heterogeneous water-oxidation catalysts (WOCs). Here, we report the synthesis of UiO-67 metal–organic framework (MOF) thin films doped with [Ru(tpy)(dcbpy)OH2]2+ (tpy=2,2':6',2''-terpyridine, dcbpy=5,5'-dicarboxy-2,2'-bipyridine) on conducting surfaces and their propensity for electrochemical water oxidation. The electrocatalyst oxidized water with a turnover frequency (TOF) of (0.2±0.1) s-1 at 1.71 V versus the normal hydrogen electrode (NHE) in buffered solution (pH~7) and exhibited structural and electrochemical stability. The electroactive sites were distributed throughout the MOF thin film on the basis of scan-ratedependent voltammetry studies. This work demonstrates a promising way to immobilize large concentrations of electroactive WOCs into a highly robust MOF scaffold and paves the way for future photoelectrochemical water-splitting systems.

Electrochemical activity of heavy metal oxides in the process of ...

Indian Academy of Sciences (India)

Unknown

2002-02-02

Feb 2, 2002 ... Electrochemical activity of heavy metal oxides in the process of chloride induced .... decrease of pH value by MeOx, a synergism of acidic and chloride ... inhibitors and their influence on the physical properties of. Portland ...

In-situ electrochemical impedance spectroscopy measurements of zirconium alloy oxide conductivity: Relationship to hydrogen pickup

International Nuclear Information System (INIS)

Couet, Adrien; Motta, Arthur T.; Ambard, Antoine; Livigni, Didier

2017-01-01

Highlights: • In-situ electrochemistry on zirconium alloys in 360 °C pure water show oxide layer resistivity changes during corrosion. • A linear relationship is observed between oxide resistivity and instantaneous hydrogen pickup fraction. • The resistivity of the oxide layer formed on Zircaloy-4 (and thus its hydrogen pickup fraction) is higher than on Zr-2.5Nb. - Abstract: Hydrogen pickup during nuclear fuel cladding corrosion is a critical life-limiting degradation mechanism for nuclear fuel. Following a program dedicated to zirconium alloys, corrosion, it has been hypothesized that oxide electronic resistivity determines hydrogen pickup. In-situ electrochemical impedance spectroscopy experiments were performed on Zircaloy-4 and Zr-2.5Nb alloys in 360 °C water. The oxide resistivity was measured as function of time. The results show that as the oxide resistivity increases so does the hydrogen pickup fraction. The resistivity of the oxide layer formed on Zircaloy-4 is higher than on Zr-2.5Nb, resulting in a higher hydrogen pickup fraction of Zircaloy-4, compared to Zr-2.5Nb.

Exploring the kinetic and thermodynamic aspects of four-electron electrochemical reactions: electrocatalysis of oxygen evolution by metal oxides and biological systems.

Science.gov (United States)

Wang, Vincent C-C

2016-08-10

Finding fundamental and general mechanisms for electrochemical reactions, such as the oxygen evolution reaction (OER) from water and reduction of CO2, plays vital roles in developing the desired electrocatalysts for facilitating solar fuel production. Recently, density functional theory (DFT) calculations have shown that there is a universal scaling relation of adsorption energy between key intermediate species, HO(ad) and HOO(ad), on the surface of metal oxides as OER electrocatalysts. In this paper, a kinetic and thermodynamic model for the four-electron electrochemical reaction based on previous OER mechanisms proposed by DFT calculations is developed to further investigate the electrocatalytic properties over a wide range of metal oxides and photosystem II. The OER activity of metal oxides (i.e. electrocatalytic current) calculated from the DFT-calculated equilibrium potentials with kinetic properties, such as the rate constants for interfacial electron transfer and catalytic turnover, can lead to a volcano-shaped trend that agrees with the results observed in experiments. In addition, the kinetic aspects of the impact on the electrocatalysts are evaluated. Finally, comparing the results of metal oxides and photosystem II, and fitting experimental voltammograms give further insights into kinetic and thermodynamic roles. Here, the general guidelines for designing OER electrocatalysts with unified kinetic and thermodynamic properties are presented.

Surface Characterization and Electrochemical Oxidation of Metal Doped Uranium Dioxide

Energy Technology Data Exchange (ETDEWEB)

Lee, Jeongmook; Kim, Jandee; Youn, Young-Sang; Kim, Jong-Goo; Ha, Yeong-Keong; Kim, Jong-Yun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

Trivalent element in UO{sub 2} matrix makes the oxygen vacancy from loss of oxygen for charge compensation. Tetravalent element alters lattice parameter of UO{sub 2} due to diameter difference between the tetravalent element and replaced U. These structural changes have significant effect on not only relevant fuel performance but also the kinetics of fuel oxidation. Park and Olander explained the stabilization of Ln (III)-doped UO{sub 2} against oxidation based on oxygen potential calculations. In this work, we have been investigated the effect of Gd{sup 3+} and Th{sup 4+} doping on the UO{sub 2} structure with Raman spectroscopy and X-ray diffraction to characterize the surface structure of nuclear fuel material. For Gd doped UO{sub 2}, its electrochemical oxidation behaviors are also investigated. The Gd and Th doped uranium dioxide solid solution pellets with various doping level were investigated by XRD, Raman spectroscopy, SEM, electrochemical experiments to investigate surface structure and electro chemical oxidation behaviors. The lattice parameter evaluated from XRD spectra indicated the formation of solid solutions. Raman spectra showed the existence of the oxygen vacancy. SEM images showed the grain structure on the surface of Gd doped uranium dioxide depending on doping level and oxygen-to-metal ratio.

Electrochemical label-free and sensitive nanobiosensing of DNA hybridization by graphene oxide modified pencil graphite electrode.

Science.gov (United States)

Ahour, F; Shamsi, A

2017-09-01

Based on the strong interaction between single-stranded DNA (ss-DNA) and graphene material, we have constructed a novel label-free electrochemical biosensor for rapid and facile detection of short sequences ss-DNA molecules related to hepatitis C virus 1a using graphene oxide modified pencil graphite electrode. The sensing mechanism is based on the superior adsorption of single-stranded DNA to GO over double stranded DNA (ds-DNA). The intrinsic guanine oxidation signal measured by differential pulse voltammetry (DPV) has been used for duplex DNA formation detection. The probe ss-DNA adsorbs onto the surface of GO via the π- π* stacking interactions leading to a strong background guanine oxidation signal. In the presence of complementary target, formation of helix which has weak binding ability to GO induced ds-DNA to release from the electrode surface and significant variation in differential pulse voltammetric response of guanine bases. The results indicated that the oxidation peak current was proportional to the concentration of complementary strand in the range of 0.1 nM-0.5 μM with a detection limit of 4.3 × 10 -11  M. The simple fabricated electrochemical biosensor has high sensitivity, good selectivity, and could be applied as a new platform for a range of target molecules in future. Copyright © 2017 Elsevier Inc. All rights reserved.

Electrochemical oxidation of loop diuretic furosemide in aqueous acid medium and its analytical application

Directory of Open Access Journals (Sweden)

Shikandar D. Bukkitgar

2016-12-01

Full Text Available An investigation of oxidative–reductive mechanisms of pharmaceutically important molecules gives us information about the metabolic fact of targeted drug. As compared to recent ongoing, time-consuming and costly techniques, there is an urgent needing for development of a sensitive technique, which can help easy understanding of these pathways. Therefore, in the present work, an effective, low-cost and time-saving technique to investigate the reaction mechanism of furosemide in aqueous acid medium is attempted. Furosemide undergoes two-proton and two-electron transfer reaction. The product obtained was analysed by UV spectra. It was found that the chemical oxidation and electrochemical oxidation of furosemide follows two different pathways. In addition, an effective technique has been developed to determine furosemide in its trace level. Good recoveries and low detection limit accomplished the magnitude of the proposed method. The proposed method was adopted for furosemide determination in human urine and pharmaceutical samples.

Synthesis of binary bismuth-cadmium oxide nanorods with sensitive electrochemical sensing performance

International Nuclear Information System (INIS)

Wen, Yong; Pei, Lizhai; Wei, Tian

2017-01-01

Binary bismuth-cadmium oxide nanorods have been synthesized by a simple hydrothermal process without templates and additives. X-ray diffraction and high-resolution transmission electron microscopy reveal that the nanorods possess single crystalline tetragonal Bi 2 CdO 4 phase. Scanning electron microscopy and transmission electron microscopy images show that the length and diameter of the nanorods are 20-300 nm and 5-10 μm, respectively. The formation of the binary bismuth-cadmium oxide nanorods is closely related to the hydrothermal parameters. The electrochemical sensing performance of the binary bismuth-cadmium oxide nanorods has been investigated using the nanorods as glassy carbon electrode modifiers. The detection limit is 0.19 μM with a linear range of 0.0005-2 mM. The nanorod-modified glassy carbon electrode exhibits good electrocatalytic activity toward L-cysteine and great application potential for electrochemical sensors.

Surface properties of nanostructured NiO undergoing electrochemical oxidation in 3-methoxy-propionitrile

International Nuclear Information System (INIS)

Bonomo, Matteo; Marrani, Andrea Giacomo; Novelli, Vittoria; Awais, Muhammad; Dowling, Denis P.; Vos, Johannes G.; Dini, Danilo

2017-01-01

Highlights: • NiO porous thin films were prepared via RDS technique. • NiO electrodes were characterized in a nitrile based electrochemical cell. • NiO electrodes were studied by means of XPS. • The XP spectra excluded the formation of phases other than NiO. • The presence of ClO 4 − as charge balancing species was evidenced. - Abstract: Nanostructured nickel oxide (NiO) was deposited in the configuration of thin film (thickness, l = 2–6 μm) onto fluorine-doped tin oxide (FTO) substrates via plasma-assisted rapid discharge sintering (RDS). Electrochemical cycling of RDS NiO in 3-methoxy-propionitrile (3-MPN) revealed two characteristic peaks of NiO oxidation which were associated to the surface-confined redox processes Ni(II) → Ni(III) and Ni(III) → Ni(IV). Grazing angle X-ray photoelectron spectroscopy (XPS) was conducted ex-situ on NiO electrodes in both pristine and oxidized states. Oxidized NiO samples for XPS experiments were obtained in the potentiostatic mode through the polarization of NiO at its two characteristic potentials of oxidation. The XPS analysis allowed to ascertain the electronic structure of the nanoporous NiO framework, and verify the adsorption of perchlorate and chloride anions onto NiO surface due to the compensation of the charge stored in oxidized NiO. XPS also revealed that the spectrum within the region characteristic of Ni 2p ionization does not vary considerably with the state of charge of the nickel centres. This finding is in evident contrast to what has been observed for the same system when it undergoes electrochemical oxidation in aqueous electrolyte.

Surface properties of nanostructured NiO undergoing electrochemical oxidation in 3-methoxy-propionitrile

Energy Technology Data Exchange (ETDEWEB)

Bonomo, Matteo [Department of Chemistry, University of Rome “La Sapienza”, Piazzale Aldo Moro 5, 00185 Rome (Italy); Marrani, Andrea Giacomo, E-mail: andrea.marrani@uniroma1.it [Department of Chemistry, University of Rome “La Sapienza”, Piazzale Aldo Moro 5, 00185 Rome (Italy); Novelli, Vittoria [Department of Chemistry, University of Rome “La Sapienza”, Piazzale Aldo Moro 5, 00185 Rome (Italy); Awais, Muhammad [Department of Industrial Engineering, “King Abdulaziz” University, Rabigh (Saudi Arabia); Solar Energy Conversion Strategic Research Cluster, University College Dublin (UCD), Belfield, Dublin 4 (Ireland); Dowling, Denis P. [Solar Energy Conversion Strategic Research Cluster, University College Dublin (UCD), Belfield, Dublin 4 (Ireland); School of Mechanical and Materials Engineering, University College Dublin (UCD), Belfield, Dublin 4 (Ireland); Vos, Johannes G. [School of Chemical Sciences, Dublin City University (DCU), Glasnevin, Dublin 9 (Ireland); Dini, Danilo [Department of Chemistry, University of Rome “La Sapienza”, Piazzale Aldo Moro 5, 00185 Rome (Italy); Solar Energy Conversion Strategic Research Cluster, University College Dublin (UCD), Belfield, Dublin 4 (Ireland)

2017-05-01

Highlights: • NiO porous thin films were prepared via RDS technique. • NiO electrodes were characterized in a nitrile based electrochemical cell. • NiO electrodes were studied by means of XPS. • The XP spectra excluded the formation of phases other than NiO. • The presence of ClO{sub 4}{sup −} as charge balancing species was evidenced. - Abstract: Nanostructured nickel oxide (NiO) was deposited in the configuration of thin film (thickness, l = 2–6 μm) onto fluorine-doped tin oxide (FTO) substrates via plasma-assisted rapid discharge sintering (RDS). Electrochemical cycling of RDS NiO in 3-methoxy-propionitrile (3-MPN) revealed two characteristic peaks of NiO oxidation which were associated to the surface-confined redox processes Ni(II) → Ni(III) and Ni(III) → Ni(IV). Grazing angle X-ray photoelectron spectroscopy (XPS) was conducted ex-situ on NiO electrodes in both pristine and oxidized states. Oxidized NiO samples for XPS experiments were obtained in the potentiostatic mode through the polarization of NiO at its two characteristic potentials of oxidation. The XPS analysis allowed to ascertain the electronic structure of the nanoporous NiO framework, and verify the adsorption of perchlorate and chloride anions onto NiO surface due to the compensation of the charge stored in oxidized NiO. XPS also revealed that the spectrum within the region characteristic of Ni 2p ionization does not vary considerably with the state of charge of the nickel centres. This finding is in evident contrast to what has been observed for the same system when it undergoes electrochemical oxidation in aqueous electrolyte.

Electrochemical oxidation of methanol and formic acid in fuel cell processes

Energy Technology Data Exchange (ETDEWEB)

Seland, Frode

2005-07-01

The main objectives of the thesis work were: (1), to study the oxidation of methanol and formic acid on platinum electrodes by employing conventional and advanced electrochemical methods, and (2), to develop membrane electrode assemblies based on polybenzimidazole membranes that can be used in fuel cells up to 200 C. D.c. voltammetry and a.c. voltammetry studies of methanol and formic acid on polycrystalline platinum in sulphuric acid electrolyte were performed to determine the mechanism and kinetics of the oxidation reactions. A combined potential step and fast cyclic voltammetry experiment was employed to investigate the time dependence primarily of methanol oxidation on platinum. Charge measurements clearly demonstrated the existence of a parallel path at low potentials and short times without formation of adsorbed CO. Furthermore, experimental results showed that only the serial path, via adsorbed CO, exists during continuous cycling, with the first step being diffusion controlled dissociative adsorption of methanol directly from the bulk electrolyte. The saturation charge of adsorbed CO derived from methanol was found to be significantly lower than CO derived from formic acid or dissolved CO. This was attributed to the site requirements of the dehydrogenation steps, and possibly different compositions of linear, bridged or multiply bonded CO. The coverage of adsorbed CO from formic acid decreased significantly at potentials just outside of the hydrogen region (0.35 V vs. RHE), while it did not start to decrease significantly until about 0.6 V vs. RHE for methanol. Adsorbed CO from dissolved CO rapidly oxidized at potentials above about 0.75 V due to formation of platinum oxide. Data from a.c. voltammograms from 0.5 Hz up to 30 kHz were assembled into electrochemical impedance spectra (EIS) and analyzed using equivalent circuits. The main advantages of collecting EIS spectra from a.c. voltammetry experiments are the ability to directly correlate the impedance

Synthesis and characterization of a nanocomposite of goethite nanorods and reduced graphene oxide for electrochemical capacitors

International Nuclear Information System (INIS)

Shou Qingliang; Cheng Jipeng; Zhang Li; Nelson, Bradley J.; Zhang Xiaobin

2012-01-01

We report a one-step synthesis of a nanocomposite of goethite (α-FeOOH) nanorods and reduced graphene oxide (RGO) using a solution method in which ferrous cations serve as a reducing agent of graphite oxide (GO) to graphene and a precursor to grow goethite nanorods. As-prepared goethite nanorods have an average length of 200 nm and a diameter of 30 nm and are densely attached on both sides of the RGO sheets. The electrochemical properties of the nanocomposite were characterized by cyclic voltammetry (CV) and chronopotentiometry (CP) charge–discharge tests. The results showed that goethite/RGO composites have a high electrochemical capacitance of 165.5 F g −1 with an excellent recycling capability making the material promising for electrochemical capacitors. - Graphical abstract: The reduced graphene oxide sheets are decorated with goethite nanorods. The as-prepared composite exhibits a high electrochemical capacitance with good recycling capability, which is promising for supercapacitor applications. Higlights: ► Ferrous ions act as reductant of graphite oxide and precursor of goethite nanorods. ► Goethite nanorods are attached on both sides of the reduced graphene oxide sheets. ► Composite exhibits a high specific capacitance and a good recycling capability. ► Composite is promising for supercapacitor applications.

Advantages of electrodes with dendrimer-protected platinum nanoparticles and carbon nanotubes for electrochemical methanol oxidation.

Science.gov (United States)

Siriviriyanun, Ampornphan; Imae, Toyoko

2013-04-14

Electrochemical sensors consisting of electrodes loaded with carbon nanotubes and Pt nanoparticles (PtNPs) protected by dendrimers have been developed using a facile method to fabricate them on two types of disposable electrochemical printed chips with a screen-printed circular gold or a screen-printed circular glassy carbon working electrode. The electrochemical performance of these sensors in the oxidation of methanol was investigated by cyclic voltammetry. It was revealed that such sensors possess stable durability and high electrocatalytic activity: the potential and the current density of an anodic peak in the oxidation of methanol increased with increasing content of PtNPs on the electrodes, indicating the promotion of electrocatalytic activity in relation to the amount of catalyst. The low anodic potential suggests the easy electrochemical reaction, and the high catalyst tolerance supports the almost complete oxidation of methanol to carbon dioxide. The significant performance of these sensors in the detection of methanol oxidation comes from the high electrocatalytic ability of PtNPs, excellent energy transfer of carbon nanotubes and the remarkable ability of dendrimers to act as binders. Thus these systems are effective for a wide range of applications as chemical, biomedical, energy and environmental sensors and as units of direct methanol fuel cells.

Direct electrochemical reduction of solid uranium oxide in molten fluoride salts

Science.gov (United States)

Gibilaro, Mathieu; Cassayre, Laurent; Lemoine, Olivier; Massot, Laurent; Dugne, Olivier; Malmbeck, Rikard; Chamelot, Pierre

2011-07-01

The direct electrochemical reduction of UO 2 solid pellets was carried out in LiF-CaF 2 (+2 mass.% Li 2O) at 850 °C. An inert gold anode was used instead of the usual reactive sacrificial carbon anode. In this case, oxidation of oxide ions present in the melt yields O 2 gas evolution on the anode. Electrochemical characterisations of UO 2 pellets were performed by linear sweep voltammetry at 10 mV/s and reduction waves associated to oxide direct reduction were observed at a potential 150 mV more positive in comparison to the solvent reduction. Subsequent, galvanostatic electrolyses runs were carried out and products were characterised by SEM-EDX, EPMA/WDS, XRD and microhardness measurements. In one of the runs, uranium oxide was partially reduced and three phases were observed: nonreduced UO 2 in the centre, pure metallic uranium on the external layer and an intermediate phase representing the initial stage of reduction taking place at the grain boundaries. In another run, the UO 2 sample was fully reduced. Due to oxygen removal, the U matrix had a typical coral-like structure which is characteristic of the pattern observed after the electroreduction of solid oxides.

Amplified electrochemical determination of maltol in food based on graphene oxide-wrapped tin oxide@carbon nanospheres.

Science.gov (United States)

Gan, Tian; Sun, Junyong; Yu, Miaomiao; Wang, Kaili; Lv, Zhen; Liu, Yanming

2017-01-01

The study presents a new approach for rapid and ultrasensitive detection of maltol using a glassy carbon electrode (GCE) modified with graphene oxide-wrapped tin oxide@carbon nanospheres (SnO2@C@GO). The morphological and components properties of SnO2@C@GO nanocomposites were investigated by means of X-ray diffraction spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, and electrochemical impedance spectroscopy. SnO2@C@GO nanocomposite on a GCE had a synergetic effect on the electrochemical oxidation of maltol by means of square wave voltammetry. Under the optimum conditions, anodic peak current response of maltol was linear with its concentration in the range of 80nM-10μM, and a detection limit of 12nM was achieved for maltol. The experiment results presented that the method showed good selectivity, sensitivity, reproducibility, and long-term stability, as well as excellent potential for use as an ideal inexpensive voltammetric method applicable for complex food matrices. Copyright © 2016 Elsevier Ltd. All rights reserved.

Synthesis of binary bismuth-cadmium oxide nanorods with sensitive electrochemical sensing performance

Energy Technology Data Exchange (ETDEWEB)

Wen, Yong [Xinjiang Univ., Xinjiang (China). School of Civil Engineering and Architecture; Pei, Lizhai; Wei, Tian [Anhui Univ. of Technology, Anhui (China). School of Materials Science and Engineering

2017-07-15

Binary bismuth-cadmium oxide nanorods have been synthesized by a simple hydrothermal process without templates and additives. X-ray diffraction and high-resolution transmission electron microscopy reveal that the nanorods possess single crystalline tetragonal Bi{sub 2}CdO{sub 4} phase. Scanning electron microscopy and transmission electron microscopy images show that the length and diameter of the nanorods are 20-300 nm and 5-10 μm, respectively. The formation of the binary bismuth-cadmium oxide nanorods is closely related to the hydrothermal parameters. The electrochemical sensing performance of the binary bismuth-cadmium oxide nanorods has been investigated using the nanorods as glassy carbon electrode modifiers. The detection limit is 0.19 μM with a linear range of 0.0005-2 mM. The nanorod-modified glassy carbon electrode exhibits good electrocatalytic activity toward L-cysteine and great application potential for electrochemical sensors.

Cycle aging studies of lithium nickel manganese cobalt oxide-based batteries using electrochemical impedance spectroscopy

NARCIS (Netherlands)

Maheshwari, Arpit; Heck, Michael; Santarelli, Massimo

2018-01-01

The cycle aging of a commercial 18650 lithium-ion battery with graphite anode and lithium nickel manganese cobalt (NMC) oxide-based cathode at defined operating conditions is studied by regular electrochemical characterization, electrochemical impedance spectroscopy (EIS) and post-mortem analysis.

Electrochemical behavior and voltammetric determination of acetaminophen based on glassy carbon electrodes modified with poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite films

International Nuclear Information System (INIS)

Zhu, Wencai; Huang, Hui; Gao, Xiaochun; Ma, Houyi

2014-01-01

Poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite film modified glassy carbon electrodes (4-ABA/ERGO/GCEs) were fabricated by a two-step electrochemical method. The electrochemical behavior of acetaminophen at the modified electrode was investigated by means of cyclic voltammetry. The results indicated that 4-ABA/ERGO composite films possessed excellent electrocatalytic activity towards the oxidation of acetaminophen. The electrochemical reaction of acetaminophen at 4-ABA/ERGO/GCE is proved to be a surface-controlled process involving the same number of protons and electrons. The voltammetric determination of acetaminophen performed with the 4-ABA/ERGO modified electrode presents a good linearity in the range of 0.1–65 μM with a low detection limit of 0.01 μM (S/N = 3). In the case of using the 4-ABA/ERGO/GCE, acetaminophen and dopamine can be simultaneously determined without mutual interference. Furthermore, the 4-ABA/ERGO/GCE has good reproducibility and stability, and can be used to determine acetaminophen in tablets. - Highlights: • The 4-ABA/ERGO/GCE was fabricated by a two-step electrochemical method. • Electrochemical behavior of acetaminophen at the 4-ABA/ERGO/GCE was investigated. • The electrochemical sensor exhibited a low detection limit and good selectivity. • This sensor was applied to the detection of acetaminophen in commercial tablets

Electrochemical behavior and voltammetric determination of acetaminophen based on glassy carbon electrodes modified with poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite films

Energy Technology Data Exchange (ETDEWEB)

Zhu, Wencai [Key Laboratory for Colloid and Interface Chemistry of State Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); School of Chemistry and Chemical Engineering, Qilu Normal University, Jinan 250013 (China); Huang, Hui; Gao, Xiaochun [Key Laboratory for Colloid and Interface Chemistry of State Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Ma, Houyi, E-mail: hyma@sdu.edu.cn [Key Laboratory for Colloid and Interface Chemistry of State Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)

2014-12-01

Poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite film modified glassy carbon electrodes (4-ABA/ERGO/GCEs) were fabricated by a two-step electrochemical method. The electrochemical behavior of acetaminophen at the modified electrode was investigated by means of cyclic voltammetry. The results indicated that 4-ABA/ERGO composite films possessed excellent electrocatalytic activity towards the oxidation of acetaminophen. The electrochemical reaction of acetaminophen at 4-ABA/ERGO/GCE is proved to be a surface-controlled process involving the same number of protons and electrons. The voltammetric determination of acetaminophen performed with the 4-ABA/ERGO modified electrode presents a good linearity in the range of 0.1–65 μM with a low detection limit of 0.01 μM (S/N = 3). In the case of using the 4-ABA/ERGO/GCE, acetaminophen and dopamine can be simultaneously determined without mutual interference. Furthermore, the 4-ABA/ERGO/GCE has good reproducibility and stability, and can be used to determine acetaminophen in tablets. - Highlights: • The 4-ABA/ERGO/GCE was fabricated by a two-step electrochemical method. • Electrochemical behavior of acetaminophen at the 4-ABA/ERGO/GCE was investigated. • The electrochemical sensor exhibited a low detection limit and good selectivity. • This sensor was applied to the detection of acetaminophen in commercial tablets.

Structure, temperature and frequency dependent electrical conductivity of oxidized and reduced electrochemically exfoliated graphite

Science.gov (United States)

Radoń, Adrian; Włodarczyk, Patryk; Łukowiec, Dariusz

2018-05-01

The article presents the influence of reduction by hydrogen in statu nascendi and modification by hydrogen peroxide on the structure and electrical conductivity of electrochemically exfoliated graphite. It was confirmed that the electrochemical exfoliation can be used to produce oxidized nanographite with an average number of 25 graphene layers. The modified electrochemical exfoliated graphite and reduced electrochemical exfoliated graphite were characterized by high thermal stability, what was associated with removing of labile oxygen-containing groups. The presence of oxygen-containing groups was confirmed using Fourier-transform infrared spectroscopy. Influence of chemical modification by hydrogen and hydrogen peroxide on the electrical conductivity was determined in wide frequency (0.1 Hz-10 kHz) and temperature range (-50 °C-100 °C). Material modified by hydrogen peroxide (0.29 mS/cm at 0 °C) had the lowest electrical conductivity. This can be associated with oxidation of unstable functional groups and was also confirmed by analysis of Raman spectra. The removal of oxygen-containing functional groups by hydrogen in statu nascendi resulted in a 1000-fold increase in the electrical conductivity compared to the electrochemical exfoliated graphite.

An electrochemical study of the flow rate effect on the oxide film of SA106 Gr.C piping

International Nuclear Information System (INIS)

Hong, S. M.; Kim, J. H.; Kim, I. S.

2002-01-01

Effect of water flow rate on the oxide film of SA106 Gr.C piping was evaluated quantitatively through electrochemical method. It was carried out with weight change experiments, polarization tests, and EIS tests with rig that simulates water flow. Without water flow, the oxide film is so stable that it effectively blocks current exchange. With water flow, the oxide film was damaged and electrochemical current density and oxide film properties, C dl and R p were significantly changed

On the Theory of Oxidation-Reduction Reactions Involving Electron Transfer. V. Comparison and Properties of Electrochemical and Chemical Rate Constants

Science.gov (United States)

Marcus, R. A.

1962-01-01

Using a theory of electron transfers which takes cognizance of reorganization of the medium outside the inner coordination shell and of changes of bond lengths inside it, relations between electrochemical and related chemical rate constants are deduced and compared with the experimental data. A correlation is found, without the use of arbitrary parameters. Effects of weak complexes with added electrolytes are included under specified conditions. The deductions offer a way of coordinating a variety of data in the two fields, internally as well as with each those in another. For example, the rate of oxidation or reduction of a series of related reactants by one reagent is correlated with that of another and with that of the corresponding electrochemical oxidation-reduction reaction, under certain specified conditions. These correlations may also provide a test for distinguishing an electron from an atom transfer mechanism. (auth)

A Study on Electrochemical Reduction of Rare Earth Oxides in Molten LiCl-Li2O Salt

International Nuclear Information System (INIS)

Lee, Min Woo; Jeong, Sang Mun; Lee, See Hoon; Sohn, Jung Min

2016-01-01

In this study, the electrochemical reduction of RE 2 O 3 (RE = Nd or Ce) has been conducted via co-reduction NiO to increase the reduction degree of the rare earth oxides in molten molten LiCl containing 1wt% Li 2 O. The electrochemical reduction behavior of the mixed RE 2 O 3 -NiO oxide has been investigated and the reduction path of RE 2 O 3 has been proposed. An electorchemical spent fuel processing technology, pyroprocessing, has been developed for recycling of spent fuel to be applied to a sodium-cooled fast reactor. The spent fuel is reduced in the oxide reduction process. It is well known that the rare earth oxides are hardly reduced due to their electrochemical and thermodynamic stability. The rare earth oxides unreduced in the reduction process can cause problems via reaction with UCl 3 in the electrorefiner. To tackle those problems, the electrochemical reduction of rare earth oxide has been conducted via co-reduction of NiO in LiCl molten salt containing 1 wt% Li 2 O. The reduction of the oxide mixture starts from the reduction of NiO to Ni, followed by that of RE 2 O 3 on the produced Ni to form intermetallic RENi 5 . The mixed oxide pellets were successfully reduced to the RENi5 alloy by constant electrolysis at 3.0 V at 650 .deg. C. The crucial aspect to these results is that the thermodynamically stable rare-earth oxide, Nd 2 O 3 was successfully converted to the metal in the presence of NiO.

Preparation of the electrochemically formed spinel-lithium manganese oxides

Energy Technology Data Exchange (ETDEWEB)

Katakura, Katsumi; Wada, Kohei; Kajiki, Yoshiyuki; Yamamoto, Akiko [Department of Chemical Engineering, Nara National College of Technology, 22 Yata-cho Yamotokoriyama, Nara 639-1080 (Japan); Ogumi, Zempachi [Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)

2009-04-01

Electrochemically formed spinel-lithium manganese oxides were synthesized from manganese hydroxides prepared by a cathodic electrochemical precipitation from various concentrations of manganese nitrate solutions. Two types of manganese hydroxides were formed from diluted and concentrated Mn(NO{sub 3}){sub 2} aqueous solutions. Uniform and equi-sized disk shaped Mn(OH){sub 2} crystals of 0.2-5 {mu}m in diameter were obtained on a Pt substrate after the electrochemical precipitation from lower concentration of ranging from 2 mmol dm{sup -3} to 2 mol dm{sup -3} Mn(NO{sub 3}){sub 2} aq., while the grass blade-like precipitate which is ascribed to manganese hydroxide with 20-80 {mu}m long and 1-5 {mu}m wide were formed from concentrated Mn(NO{sub 3}){sub 2} aq. Both manganese hydroxides gave the electrochemically formed spinel-LiMn{sub 2}O{sub 4} onto a Pt sheet, which is ready for electrochemical measurement, after calcination of the Li incorporated precipitate at 750 C without any additives. While the shape and size of the secondary particle frameworks (aggregates) of the electrochemically formed spinel-LiMn{sub 2}O{sub 4} can be controlled by the electrolysis conditions, the nanostructured primary crystals of 200 nm in diameter were obtained in all cases except that the fiber-like nanostructured spinel-LiMn{sub 2}O{sub 4} crystals with 200 nm in diameter were obtained from concentrated Mn(NO{sub 3}){sub 2} aq. Though these two types of electrochemically formed spinel-LiMn{sub 2}O{sub 4} showed well-shaped CVs even in higher scan rates, it would be suitable for high power density battery applications. These behaviors are assumed to be ascribed to the crystal size and shape of the processed spinel-LiMn{sub 2}O{sub 4}. (author)

Electrochemical sensing of glucose by reduced graphene oxide-zinc ferrospinels

Energy Technology Data Exchange (ETDEWEB)

Shahnavaz, Zohreh, E-mail: zohreh.shahnavaz@siswa.um.edu.my [Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Woi, Pei Meng, E-mail: pmwoi@um.edu.my [Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Center of Ionic Liquids, University of Malaya, 50603 Kuala Lumpur (Malaysia); Alias, Yatimah, E-mail: yatimah70@um.edu.my [Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Center of Ionic Liquids, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2016-08-30

Highlights: • A facile in situ hydrothermal method for ZnFe{sub 2}O{sub 4} nanoparticles incorporation into graphene oxide sheets. • Excellent selectivity, reproducibility and stability properties compared to others Zn-based glucose sensor. • Amount of reduced graphene oxide directly affected the electro-catalytic activity of ZnFe{sub 2}O{sub 4}/rGO nanocomposite towards glucose detection. - Abstract: We have developed ZnFe{sub 2}O{sub 4} magnetic nanoparticles/reduced graphene oxide nanosheets modified glassy carbon (ZnFe{sub 2}O{sub 4}/rGO/GCE) electrode as a novel system for the electrochemical glucose sensing. Via a facile in situ hydrothermal route, the reduction of GO and the formation of ZnFe{sub 2}O{sub 4} nanoparticles occurred simultaneously. This enables the ZnFe{sub 2}O{sub 4} nanoparticles dispersed on the reduced graphene sheet. Characterization of nanocomposite by X-ray diffraction (XRD) and transmission electron microscopy (TEM) clearly demonstrate the successful attachment of ZnFe{sub 2}O{sub 4} nanoparticles to graphene sheets. Electrochemical studies revealed that the ZnFe{sub 2}O{sub 4}/rGO/GCE possess excellent electrocatalytic activities toward the oxidation of glucose and the performance of sensor is enhanced by integration of graphene nanosheets with ZnFe{sub 2}O{sub 4} nanoparticles.

V2O5 xerogel-poly(ethylene oxide) hybrid material: Synthesis, characterization, and electrochemical properties

International Nuclear Information System (INIS)

Guerra, Elidia M.; Ciuffi, Katia J.; Oliveira, Herenilton P.

2006-01-01

In this work, we report the synthesis, characterization, and electrochemical properties of vanadium pentoxide xerogel-poly(ethylene oxide) (PEO) hybrid materials obtained by varying the average molecular weight of the organic component as well as the components' ratios. The materials were characterized by X-ray diffraction, ultraviolet/visible and infrared spectroscopies, thermogravimetric analysis, scanning electron microscopy, electron paramagnetic resonance, and cyclic voltammetry. Despite the presence of broad and low intensity peaks, the X-ray diffractograms indicate that the lamellar structure of the vanadium pentoxide xerogel is preserved, with increase in the interplanar spacing, giving evidence of a low-crystalline structure. We found that the electrochemical behaviour of the hybrid materials is quite similar to that found for the V 2 O 5 xerogel alone, and we verified that PEO leads to stabilization and reproducibility of the Li + electrochemical insertion/de-insertion into the V 2 O 5 xerogel structure, which makes these materials potential components of lithium ion batteries. - Graphical abstract: The synthesis, structural and electrochemical properties of vanadium pentoxide xerogel-poly(ethylene oxide) hybrid materials have been described. Despite the presence of broad and low intensity peaks, the X-ray diffractograms indicate that the lamellar structure of the vanadium pentoxide xerogel is preserved. The cyclic voltammetry technique demonstrated that PEO intercalation provides an improvement in the electrochemical properties, mainly with respect to the lithium electroinsertion process into the oxide matrix

Aqueous electrochemical mechanisms in actinide residue processing. 1998 annual progress report

International Nuclear Information System (INIS)

Blanchard, D.L. Jr.; Burns, C.J.; Morris, D.E.; Smith, W.H.

1998-01-01

'New and/or improved solutions to the stabilization and volume reduction of nuclear materials processing residues are urgently needed. Mediated electrochemical oxidation/reduction (MEO/R) processes are one such approach for incinerator ash, combustibles, and other solid residues. However, questions remain concerning the mechanisms of these processes, and how they might be optimized. In addition, further research is merited to extend their range of applicability. Recent advances in the study of heterogeneous electron transfer in solid substrates have opened the door for the re-examination of electron transfer processes associated with redox mediated actinide dissolution. The authors develop a deeper understanding of the thermodynamic and mechanistic aspects of heterogeneous electron transfer that lie at the heart of these MEO/R processes. They will also develop and test new approaches based on the results of these fundamental studies using actual residue materials. Key aspects of this proposal include: (1) determination of the potential windows for oxidation/reduction of colloidal actinide oxides and actinide-bearing oxide and organic substrates and the e transfer kinetic parameters that govern the current--overpotential characteristics; (2) development of adaptations of mediation schemes and application of co-mediation reagents for oxidative and reductive dissolution based on complexation of the surface-bound or solid-phase actinides and/or the dissolved redox mediator;and (3) execution of bench-scale tests of new MEO/R schemes on actual residue materials.'

Study and optimisation of manganese oxide-based electrodes for electrochemical supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Staiti, P.; Lufrano, F. [CNR-ITAE, Istituto di Tecnologie Avanzate per l' Energia ' ' Nicola Giordano' ' , Via Salita S. Lucia n. 5, 98126 S. Lucia, Messina (Italy)

2009-02-01

A manganese oxide material was synthesised by an easy precipitation method based on reduction of potassium permanganate(VII) with a manganese(II) salt. The material was treated at different temperatures to study the effect of thermal treatment on capacitive property. The best capacitive performance was obtained with the material treated at 200 C. This material was used to prepare electrodes with different amounts of polymer binder, carbon black and graphite fibres to individuate the optimal composition that gave the best electrochemical performances. It was found that graphite fibres improve the electrochemical performance of electrodes. The highest specific capacitance (267 F g{sup -1} MnO{sub x}) was obtained with an electrode containing 70% of MnO{sub x}, 15% of carbon black, 10% of graphite fibres and 5% of PVDF. This electrode, with CB/GF ratio of 1.5, showed a higher utilization of manganese oxide. The results reported in the present paper further confirmed that manganese oxide is a very interesting material for supercapacitor application. (author)

Mediated electrochemical oxidation of mixed wastes

International Nuclear Information System (INIS)

Chiba, Z.

1993-04-01

The Mediated Electrochemical Oxidation (MEO) process was studied for destroying low-level combustible mixed wastes at Rocky Flats Plant. Tests were performed with non-radioactive surrogate materials: Trimsol for contaminated cutting oils, and reagent-grade cellulose for contaminated cellulosic wastes. Extensive testing was carried out on Trimsol in both small laboratory-scale apparatus and on a large-scale system incorporating an industrial-size electrochemical cell. Preliminary tests were also carried out in the small-scale system with cellulose. Operating and system parameters that were studied were: use of a silver-nitric acid versus a cobalt-sulfuric acid system, effect of electrolyte temperature, effect of acid concentration, and effect of current density. Destruction and coulombic efficiencies were calculated using data obtained from continuous carbon dioxide monitors and total organic carbon (TOC) analysis of electrolyte samples. For Trimsol, the best performance was achieved with the silver-nitrate system at high acid concentrations, temperatures, and current densities. Destruction efficiencies of 99% or greater, and coulombic efficiencies up to 70% were obtained. For the cellulose, high destruction efficiencies and reasonable coulombic efficiencies were obtained for both silver-nitrate and cobalt-sulfate systems

Electrochemical heterogeneity and chemical stability of anodic oxide films of barrier type on certain valve metals and alloys

International Nuclear Information System (INIS)

Isaev, N.I.; Yakovlev, V.B.

1986-01-01

Direct current and alternating current electrochemical methods are used to study kinetic regularities and mechanism of titanium films dissolution in NaOH and H 2 SO 4 concentrated solutions. Piece-line dependence of oxidized electrode specific reverse capacitance on the time of C c -1 =α i -β i τ type is stated. Effective activation energy and dissolution reaction apparent order are determined by agressive ions. For amorphous alloys films interrelation of structure heterogeneity, film composition and resistance to pitting corrosion is shown. Decrease of oxide protecting properties is due to crystallization of originally amorphous films

One step paired electrochemical synthesis of iron and iron oxide nanoparticles

Directory of Open Access Journals (Sweden)

Ordoukhanian Juliet

2016-09-01

Full Text Available In this study, a new one step paired electrochemical method is developed for simultaneous synthesis of iron and iron oxide nanoparticles. iron and iron oxide are prepared as cathodic and anodic products from iron (ii sulfate aqueous solution in a membrane divided electrolytic cell by the pulsed current electrosynthesis. Because of organic solvent-free and electrochemical nature of the synthesis, the process could be considered as green and environmentally friendly. The reduction of energy consumption and low cost are the other significant advantages of this new method that would have a great application potential in the chemical industry. The nanostructure of prepared samples was characterized by Fourier transform infrared spectroscopy (FT-IR, X-ray diffraction (XRD, scanning electron microscopy (SEM and transmission electron microscopy (TEM. The magnetic properties were studied by vibrating sample magnetometer (VsM.

LABORATORY EVALUATION OF A MICROFLUIDIC ELECTROCHEMICAL SENSOR FOR AEROSOL OXIDATIVE LOAD.

Science.gov (United States)

Koehler, Kirsten; Shapiro, Jeffrey; Sameenoi, Yupaporn; Henry, Charles; Volckens, John

2014-05-01

Human exposure to particulate matter (PM) air pollution is associated with human morbidity and mortality. The mechanisms by which PM impacts human health are unresolved, but evidence suggests that PM intake leads to cellular oxidative stress through the generation of reactive oxygen species (ROS). Therefore, reliable tools are needed for estimating the oxidant generating capacity, or oxidative load, of PM at high temporal resolution (minutes to hours). One of the most widely reported methods for assessing PM oxidative load is the dithiothreitol (DTT) assay. The traditional DTT assay utilizes filter-based PM collection in conjunction with chemical analysis to determine the oxidation rate of reduced DTT in solution with PM. However, the traditional DTT assay suffers from poor time resolution, loss of reactive species during sampling, and high limit of detection. Recently, a new DTT assay was developed that couples a Particle-Into-Liquid-Sampler with microfluidic-electrochemical detection. This 'on-line' system allows high temporal resolution monitoring of PM reactivity with improved detection limits. This study reports on a laboratory comparison of the traditional and on-line DTT approaches. An urban dust sample was aerosolized in a laboratory test chamber at three atmospherically-relevant concentrations. The on-line system gave a stronger correlation between DTT consumption rate and PM mass (R 2 = 0.69) than the traditional method (R 2 = 0.40) and increased precision at high temporal resolution, compared to the traditional method.

Surface properties of nanostructured NiO undergoing electrochemical oxidation in 3-methoxy-propionitrile

Science.gov (United States)

Bonomo, Matteo; Marrani, Andrea Giacomo; Novelli, Vittoria; Awais, Muhammad; Dowling, Denis P.; Vos, Johannes G.; Dini, Danilo

2017-05-01

Nanostructured nickel oxide (NiO) was deposited in the configuration of thin film (thickness, l = 2-6 μm) onto fluorine-doped tin oxide (FTO) substrates via plasma-assisted rapid discharge sintering (RDS). Electrochemical cycling of RDS NiO in 3-methoxy-propionitrile (3-MPN) revealed two characteristic peaks of NiO oxidation which were associated to the surface-confined redox processes Ni(II) → Ni(III) and Ni(III) → Ni(IV). Grazing angle X-ray photoelectron spectroscopy (XPS) was conducted ex-situ on NiO electrodes in both pristine and oxidized states. Oxidized NiO samples for XPS experiments were obtained in the potentiostatic mode through the polarization of NiO at its two characteristic potentials of oxidation. The XPS analysis allowed to ascertain the electronic structure of the nanoporous NiO framework, and verify the adsorption of perchlorate and chloride anions onto NiO surface due to the compensation of the charge stored in oxidized NiO. XPS also revealed that the spectrum within the region characteristic of Ni 2p ionization does not vary considerably with the state of charge of the nickel centres. This finding is in evident contrast to what has been observed for the same system when it undergoes electrochemical oxidation in aqueous electrolyte.

Cross-flow electrochemical reactor cells, cross-flow reactors, and use of cross-flow reactors for oxidation reactions

Science.gov (United States)

Balachandran, Uthamalingam; Poeppel, Roger B.; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Udovich, Carl A.

1994-01-01

This invention discloses cross-flow electrochemical reactor cells containing oxygen permeable materials which have both electron conductivity and oxygen ion conductivity, cross-flow reactors, and electrochemical processes using cross-flow reactor cells having oxygen permeable monolithic cores to control and facilitate transport of oxygen from an oxygen-containing gas stream to oxidation reactions of organic compounds in another gas stream. These cross-flow electrochemical reactors comprise a hollow ceramic blade positioned across a gas stream flow or a stack of crossed hollow ceramic blades containing a channel or channels for flow of gas streams. Each channel has at least one channel wall disposed between a channel and a portion of an outer surface of the ceramic blade, or a common wall with adjacent blades in a stack comprising a gas-impervious mixed metal oxide material of a perovskite structure having electron conductivity and oxygen ion conductivity. The invention includes reactors comprising first and second zones seprated by gas-impervious mixed metal oxide material material having electron conductivity and oxygen ion conductivity. Prefered gas-impervious materials comprise at least one mixed metal oxide having a perovskite structure or perovskite-like structure. The invention includes, also, oxidation processes controlled by using these electrochemical reactors, and these reactions do not require an external source of electrical potential or any external electric circuit for oxidation to proceed.

Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

Science.gov (United States)

Alver, Ü.; Tanrıverdi, A.

2016-08-01

In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

Performance of a Steel/Oxide Composite Waste Form for Combined Waste Steams from Advanced Electrochemical Processes

International Nuclear Information System (INIS)

Indacochea, J. E.; Gattu, V. K.; Chen, X.; Rahman, T.

2017-01-01

The results of electrochemical corrosion tests and modeling activities performed collaboratively by researchers at the University of Illinois at Chicago and Argonne National Laboratory as part of workpackage NU-13-IL-UIC-0203-02 are summarized herein. The overall objective of the project was to develop and demonstrate testing and modeling approaches that could be used to evaluate the use of composite alloy/ceramic materials as high-level durable waste forms. Several prototypical composite waste form materials were made from stainless steels representing fuel cladding, reagent metals representing metallic fuel waste streams, and reagent oxides representing oxide fuel waste streams to study the microstructures and corrosion behaviors of the oxide and alloy phases. Microelectrodes fabricated from small specimens of the composite materials were used in a series of electrochemical tests to assess the corrosion behaviors of the constituent phases and phase boundaries in an aggressive acid brine solution at various imposed surface potentials. The microstructures were characterized in detail before and after the electrochemical tests to relate the electrochemical responses to changes in both the electrode surface and the solution composition. The results of microscopic, electrochemical, and solution analyses were used to develop equivalent circuit and physical models representing the measured corrosion behaviors of the different materials pertinent to long-term corrosion behavior. This report provides details regarding (1) the production of the composite materials, (2) the protocol for the electrochemical measurements and interpretations of the responses of multi-phase alloy and oxide composites, (3) relating corrosion behaviors to microstructures of multi-phase alloys based on 316L stainless steel and HT9 (410 stainless steel was used as a substitute) with added Mo, Ni, and/or Mn, and (4) modeling the corrosion behaviors and rates of several alloy/oxide composite

Performance of a Steel/Oxide Composite Waste Form for Combined Waste Steams from Advanced Electrochemical Processes

Energy Technology Data Exchange (ETDEWEB)

Indacochea, J. E. [Univ. of Illinois, Chicago, IL (United States); Gattu, V. K. [Univ. of Illinois, Chicago, IL (United States); Chen, X. [Univ. of Illinois, Chicago, IL (United States); Rahman, T. [Univ. of Illinois, Chicago, IL (United States)

2017-06-15

The results of electrochemical corrosion tests and modeling activities performed collaboratively by researchers at the University of Illinois at Chicago and Argonne National Laboratory as part of workpackage NU-13-IL-UIC-0203-02 are summarized herein. The overall objective of the project was to develop and demonstrate testing and modeling approaches that could be used to evaluate the use of composite alloy/ceramic materials as high-level durable waste forms. Several prototypical composite waste form materials were made from stainless steels representing fuel cladding, reagent metals representing metallic fuel waste streams, and reagent oxides representing oxide fuel waste streams to study the microstructures and corrosion behaviors of the oxide and alloy phases. Microelectrodes fabricated from small specimens of the composite materials were used in a series of electrochemical tests to assess the corrosion behaviors of the constituent phases and phase boundaries in an aggressive acid brine solution at various imposed surface potentials. The microstructures were characterized in detail before and after the electrochemical tests to relate the electrochemical responses to changes in both the electrode surface and the solution composition. The results of microscopic, electrochemical, and solution analyses were used to develop equivalent circuit and physical models representing the measured corrosion behaviors of the different materials pertinent to long-term corrosion behavior. This report provides details regarding (1) the production of the composite materials, (2) the protocol for the electrochemical measurements and interpretations of the responses of multi-phase alloy and oxide composites, (3) relating corrosion behaviors to microstructures of multi-phase alloys based on 316L stainless steel and HT9 (410 stainless steel was used as a substitute) with added Mo, Ni, and/or Mn, and (4) modeling the corrosion behaviors and rates of several alloy/oxide composite

Electro-oxidation of the dye azure B: kinetics, mechanism, and by-products.

Science.gov (United States)

Olvera-Vargas, Hugo; Oturan, Nihal; Aravindakumar, C T; Paul, M M Sunil; Sharma, Virender K; Oturan, Mehmet A

2014-01-01

In this work, the electrochemical degradation of the dye azure B in aqueous solutions was studied by electrochemical advanced oxidation processes (EAOPs), electro-Fenton, and anodic oxidation processes, using Pt/carbon-felt and boron-doped diamond (BDD)/carbon-felt cells with H₂O₂ electrogeneration. The higher oxidation power of the electro-Fenton (EF) process using BDD anode was demonstrated. The oxidative degradation of azure B by the electrochemically generated hydroxyl radicals ((•)OH) follows a pseudo-first-order kinetics. The apparent rate constants of the oxidation of azure B by (•)OH were measured according to pseudo-first-order kinetic model. The absolute rate constant of azure B hydroxylation reaction was determined by competition kinetics method and found to be 1.19 × 10(9) M(-1) s(-1). It was found that the electrochemical degradation of the dye leads to the formation of aromatic by-products which are then oxidized to aliphatic carboxylic acids before their almost mineralization to CO₂ and inorganic ions (sulfate, nitrate, and ammonium). The evolution of the TOC removal and time course of short-chain carboxylic acids during treatment were also investigated.

Optical and structural properties of porous zinc oxide fabricated via electrochemical etching method

International Nuclear Information System (INIS)

Ching, C.G.; Lee, S.C.; Ooi, P.K.; Ng, S.S.; Hassan, Z.; Hassan, H. Abu; Abdullah, M.J.

2013-01-01

Highlights: • Hillock like porous structure zinc oxide was obtained via electrochemical etching. • Anisotropic dominance etching process by KOH etchant. • Reststrahlen features are sensitive to multilayer porous structure. • Determination of porosity from IR reflectance spectrum. -- Abstract: We investigated the optical and structural properties of porous zinc oxide (ZnO) thin film fabricated by ultraviolet light-assisted electrochemical etching. This fabrication process used 10 wt% potassium hydroxide solution as an electrolyte. Hillock-like porous ZnO films were successfully fabricated according to the field emission scanning electron microscopy results. The cross-sectional study of the sample indicated that anisotropic-dominated etching process occurred. However, the atomic force microscopic results showed an increase in surface roughness of the sample after electrochemical etching. A resonance hump induced by the porous structure was observed in the infrared reflectance spectrum. Using theoretical modeling technique, ZnO porosification was verified, and the porosity of the sample was determined

Real-time investigation of antibiotics-induced oxidative stress and superoxide release in bacteria using an electrochemical biosensor.

Science.gov (United States)

Liu, Xiaobo; Marrakchi, Mouna; Jahne, Michael; Rogers, Shane; Andreescu, Silvana

2016-02-01

The involvement of oxidative stress in the mechanism of antibiotics-meditated cell death is unclear and subject to debate. The kinetic profile and a quantitative relationship between the release of reactive oxygen species (ROS), bacteria and antibiotic type remain elusive. Here we report direct measurements and analytical quantification of the release of superoxide radicals (O2(·-)), a major contributor to ROS, in antibiotics-treated bacterial cultures using a cytochrome c electrochemical biosensor. The specificity of electrochemical measurements was established by the addition of superoxide dismutase (SOD) which decreased the O2(·-) signal. Measurements using a general ROS-specific fluorescence dye and colony forming units (CFU) assays were performed side-by-side to determine the total ROS and establish the relationship between ROS and the degree of lethality. Exposure of Escherichia coli and Listeria monocytogenes cultures to antibiotics increased the release of O2(·-) radicals in a dose-dependent manner, suggesting that the transmembrane generation of ROS may occur as part of the antibiotic action. The study provides a quantitative methodology and fundamental knowledge to further explore the role of oxidative stress in antibiotics-meditated bacterial death and to assess physiological changes associated with the complex metabolic events related to oxidative stress and bacterial resistance. Copyright © 2015 Elsevier Inc. All rights reserved.

Sulfur tolerant composite cermet electrodes for solid oxide electrochemical cells

Science.gov (United States)

Isenberg, Arnold O.

1987-01-01

An electrochemical apparatus is made containing an exterior electrode bonded to the exterior of a tubular, solid, oxygen ion conducting electrolyte where the electrolyte is also in contact with an interior electrode, said exterior electrode comprising particles of an electronic conductor contacting the electrolyte, where a ceramic metal oxide coating partially surrounds the particles and is bonded to the electrolyte, and where a coating of an ionic-electronic conductive material is attached to the ceramic metal oxide coating and to the exposed portions of the particles.

Electrochemically oxidized electronic and ionic conducting nanostructured block copolymers for lithium battery electrodes.

Science.gov (United States)

Patel, Shrayesh N; Javier, Anna E; Balsara, Nitash P

2013-07-23

Block copolymers that can simultaneously conduct electronic and ionic charges on the nanometer length scale can serve as innovative conductive binder material for solid-state battery electrodes. The purpose of this work is to study the electronic charge transport of poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-PEO) copolymers electrochemically oxidized with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt in the context of a lithium battery charge/discharge cycle. We use a solid-state three-terminal electrochemical cell that enables simultaneous conductivity measurements and control over electrochemical doping of P3HT. At low oxidation levels (ratio of moles of electrons removed to moles of 3-hexylthiophene moieties in the electrode), the electronic conductivity (σe,ox) increases from 10(-7) S/cm to 10(-4) S/cm. At high oxidation levels, σe,ox approaches 10(-2) S/cm. When P3HT-PEO is used as a conductive binder in a positive electrode with LiFePO4 active material, P3HT is electrochemically active within the voltage window of a charge/discharge cycle. The electronic conductivity of the P3HT-PEO binder is in the 10(-4) to 10(-2) S/cm range over most of the potential window of the charge/discharge cycle. This allows for efficient electronic conduction, and observed charge/discharge capacities approach the theoretical limit of LiFePO4. However, at the end of the discharge cycle, the electronic conductivity decreases sharply to 10(-7) S/cm, which means the "conductive" binder is now electronically insulating. The ability of our conductive binder to switch between electronically conducting and insulating states in the positive electrode provides an unprecedented route for automatic overdischarge protection in rechargeable batteries.

The electrochemical oxidation of organic waste and activated graphite by Ag2+ in nitric acid: a literature study

International Nuclear Information System (INIS)

Van Alsenoy, V.; Rahier, A.

1996-08-01

Organic wastes and activated moderator graphite can be processed by means of combustion, but the incineration of organic waste poses emission problems. The Belgian Nuclear Research Centre SCK-CEN has experience with the treatment of organic wastes. Moreover, the treatment of radioactive graphite will be required since the BR-1 reactor is moderated with 492 tons of graphite. The strong oxidising properties of Ag 2+ are already used in the chemical and nuclear industry to destroy organic waste. We aim to apply the process on radioactive graphite, organic resins and effluents. The reaction mechanisms will be studied, taking into account the thermodynamic and kinetic properties of the different reactions involved. As a first step, this document gives a literature study of the electrochemical oxidation using Ag 2+ . This document presents a thorough literature study, and shows that the oxidative properties of the Ag 2+ ion, which can easily be formed in nitric acid by means of electrolysis, make it an ideal candidate to oxidize organic molecules into carbon dioxide and water on a perfectly well controlled manner. The process has already been used to destroy explosives and toxic organic waste in the nuclear and chemical industry. Chemical, thermodynamic and kinetic aspects of some of the reactions involved are already known and described, other reaction mechanisms are still unknown. On the basis of the information collected so far, the Research and Development group of the Radioactive Waste and Cleanup unit has proposed to start a research programme to define, test, demonstrate and finally apply a safe process for the treatment of radioactive organic material and graphite by electrochemical oxidation using Ag 2+ . Available data confirm that the oxidation of organic material can be carried out safely, leading to the formation of water and carbon dioxide

Hydroxyapatite/gelatin functionalized graphene oxide composite coatings deposited on TiO2 nanotube by electrochemical deposition for biomedical applications

International Nuclear Information System (INIS)

Yan, Yajing; Zhang, Xuejiao; Mao, Huanhuan; Huang, Yong; Ding, Qiongqiong; Pang, Xiaofeng

2015-01-01

Highlights: • Graphene oxide cross-linked gelatin was firstly employed as reinforcement fillers in hydroxyapatite coatings by electrochemical deposition process on TiO 2 nanotube arrays. • Gelatin functionalized graphene oxide induced the formation of hydroxyapatite coatings. • The success of gelatin and graphene oxide incorporation was evidenced with FTIR and XPS. • The synthesized composite coatings showed good biocompatibility and no adverse effect in cell culture tests. - Abstract: Graphene oxide cross-linked gelatin was employed as reinforcement fillers in hydroxyapatite coatings by electrochemical deposition process on TiO 2 nanotube arrays (TNs). The TNs were grown on titanium by electrochemical anodization in hydrofluoric electrolyte using constant voltage. Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Field emission scanning electron microscopy equipped with energy dispersive X-ray analysis and biological studies were used to characterize the coatings. The corrosion resistance of the coatings was also investigated by electrochemical method in simulated body fluid solution

In vitro degradation and electrochemical corrosion evaluations of microarc oxidized pure Mg, Mg-Ca and Mg-Ca-Zn alloys for biomedical applications.

Science.gov (United States)

Pan, Yaokun; He, Siyu; Wang, Diangang; Huang, Danlan; Zheng, Tingting; Wang, Siqi; Dong, Pan; Chen, Chuanzhong

2015-02-01

Calcium phosphate (CaP) ceramic coatings were fabricated on pure magnesium (Mg) and self-designed Mg-0.6Ca, Mg-0.55Ca-1.74Zn alloys by microarc oxidation (MAO). The coating formation, growth and biomineralization mechanisms were discussed. The coating degradability and bioactivity were evaluated by immersion tests in trishydroxymethyl-aminomethane hydrochloric acid (Tris-HCl) buffer and simulated body fluid (SBF) solutions, respectively. The coatings and corrosion products were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) and fourier transform infrared spectrometer (FT-IR). The electrochemical workstation was used to investigate the electrochemical corrosion behaviors of substrates and coatings. Results showed that Mg-0.55Ca-1.74Zn alloy exhibits the highest mechanical strength and electrochemical corrosion resistance among the three alloys. The MAO-coated Mg-0.55Ca-1.74Zn alloy has the potential to be served as a biodegradable implant. Copyright © 2014 Elsevier B.V. All rights reserved.

Electrochemical oxidation of biological pretreated and membrane separated landfill leachate concentrates on boron doped diamond anode

Energy Technology Data Exchange (ETDEWEB)

Zhou, Bo, E-mail: 357436235@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Yu, Zhiming, E-mail: zhiming@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Wei, Qiuping, E-mail: qiupwei@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Long, HangYu, E-mail: 55686385@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Xie, Youneng, E-mail: 1187272844@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Wang, Yijia, E-mail: 503630433@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)

2016-07-30

Highlights: • High quality boron-doped diamond film electrodes were synthesized on Nb substrates. • Electrochemical oxidation on boron-doped diamond anode is an effective method for treating landfill leachate concentrates. • Optimal operating conditions for electrochemical oxidation of landfill leachate concentrates is determined. • 87.5% COD removal and 74.06% NH{sub 3}−N removal were achieved after 6 h treatment. - Abstract: In the present study, the high quality boron-doped diamond (BDD) electrodes with excellent electrochemical properties were deposited on niobium (Nb) substrates by hot filament chemical vapor deposition (HFCVD) method. The electrochemical oxidation of landfill leachate concentrates from disc tube reverse osmosis (DTRO) process over a BDD anode was investigated. The effects of varying operating parameters, such as current density, initial pH, flow velocity and cathode material on degradation efficiency were also evaluated following changes in chemical oxygen demand (COD) and ammonium nitrogen (NH{sub 3}−N). The instantaneous current efficiency (ICE) was used to appraise different operating conditions. As a result, the best conditions obtained were as follows, current density 50 mA cm{sup −2}, pH 5.16, flow velocity 6 L h{sup −1}. Under these conditions, 87.5% COD and 74.06% NH{sub 3}−N removal were achieved after 6 h treatment, with specific energy consumption of 223.2 kWh m{sup −3}. In short, these results indicated that the electrochemical oxidation with BDD/Nb anode is an effective method for the treatment of landfill leachate concentrates.

The cooperative electrochemical oxidation of chlorophenols in anode-cathode compartments

International Nuclear Information System (INIS)

Wang Hui; Wang Jianlong

2008-01-01

By using a self-made carbon/polytetrafluoroethylene (C/PTFE) O 2 -fed as the cathode and Ti/IrO 2 /RuO 2 as the anode, the degradation of three organic compounds (phenol, 4-chlorophenol, and 2,4-dichlorophenol) was investigated in the diaphragm (with terylene as diaphragm material) electrolysis device by electrochemical oxidation process. The result indicated that the concentration of hydrogen peroxide (H 2 O 2 ) was 8.3 mg/L, and hydroxyl radical (HO·) was determined in the cathodic compartment by electron spin resonance spectrum (ESR). The removal efficiency for organic compounds reached about 90% after 120 min, conforming to the sequence of phenol, 4-chlorophenol, and 2,4-dichlorophenol. And the dechlorination degree of 4-chlorophenol exceeded 90% after 80 min. For H 2 O 2 , HO· existed in the catholyte and reduction dechlorination at the cathode, the mineralization of organics in the cathodic compartment was better than that in the anodic compartment. The degradation of organics was supposed to be cooperative oxidation by direct or indirect electrochemical oxidation at the anode and H 2 O 2 , HO· produced by oxygen reduction at the cathode. High-performance liquid chromatography (HPLC) allowed identifying phenol as the dechlorination product of 4-chlorophenol in the cathodic compartment, and hydroquinone, 4-chlorocatechol, benzoquinone, maleic, fumaric, oxalic, and formic acids as the main oxidation intermediates in the cathodic and anodic compartments. A reaction scheme involving all these intermediates was proposed

Electrochemical behavior and voltammetric determination of acetaminophen based on glassy carbon electrodes modified with poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite films.

Science.gov (United States)

Zhu, Wencai; Huang, Hui; Gao, Xiaochun; Ma, Houyi

2014-12-01

Poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite film modified glassy carbon electrodes (4-ABA/ERGO/GCEs) were fabricated by a two-step electrochemical method. The electrochemical behavior of acetaminophen at the modified electrode was investigated by means of cyclic voltammetry. The results indicated that 4-ABA/ERGO composite films possessed excellent electrocatalytic activity towards the oxidation of acetaminophen. The electrochemical reaction of acetaminophen at 4-ABA/ERGO/GCE is proved to be a surface-controlled process involving the same number of protons and electrons. The voltammetric determination of acetaminophen performed with the 4-ABA/ERGO modified electrode presents a good linearity in the range of 0.1-65 μM with a low detection limit of 0.01 μM (S/N=3). In the case of using the 4-ABA/ERGO/GCE, acetaminophen and dopamine can be simultaneously determined without mutual interference. Furthermore, the 4-ABA/ERGO/GCE has good reproducibility and stability, and can be used to determine acetaminophen in tablets. Copyright © 2014 Elsevier B.V. All rights reserved.

Copper-substituted perovskite compositions for solid oxide fuel cell cathodes and oxygen reduction electrodes in other electrochemical devices

Science.gov (United States)

Rieke, Peter C [Pasco, WA; Coffey, Gregory W [Richland, WA; Pederson, Larry R [Kennewick, WA; Marina, Olga A [Richland, WA; Hardy, John S [Richland, WA; Singh, Prabhaker [Richland, WA; Thomsen, Edwin C [Richland, WA

2010-07-20

The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells. Also provided are electrochemical devices that include active oxygen reduction electrodes, such as solid oxide fuel cells, sensors, pumps and the like. The compositions comprises a copper-substituted ferrite perovskite material. The invention also provides novel methods for making and using the electrode compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having cathodes comprising the compositions.

Small-angle neutron scattering and cyclic voltammetry study on electrochemically oxidized and reduced pyrolytic carbon

International Nuclear Information System (INIS)

Braun, A.; Kohlbrecher, J.; Baertsch, M.; Schnyder, B.; Koetz, R.; Haas, O.; Wokaun, A.

2004-01-01

The electrochemical double layer capacitance and internal surface area of a pyrolytic carbon material after electrochemical oxidation and subsequent reduction was studied with cyclic voltammetry and small-angle neutron scattering. Oxidation yields an enhanced internal surface area (activation), and subsequent reduction causes a decrease of this internal surface area. The change of the Porod constant, as obtained from small-angle neutron scattering, reveals that the decrease in internal surface area is not caused merely by a closing or narrowing of the pores, but by a partial collapse of the pore network

Electrochemical advanced oxidation processes as decentralized water treatment technologies to remediate domestic washing machine effluents.

Science.gov (United States)

Dos Santos, Alexsandro Jhones; Costa, Emily Cintia Tossi de Araújo; da Silva, Djalma Ribeiro; Garcia-Segura, Sergi; Martínez-Huitle, Carlos Alberto

2018-03-01

Water scarcity is one of the major concerns worldwide. In order to secure this appreciated natural resource, management and development of water treatment technologies are mandatory. One feasible alternative is the consideration of water recycling/reuse at the household scale. Here, the treatment of actual washing machine effluent by electrochemical advanced oxidation processes was considered. Electrochemical oxidation and electro-Fenton technologies can be applied as decentralized small-scale water treatment devices. Therefore, efficient decolorization and total organic abatement have been followed. The results demonstrate the promising performance of solar photoelectro-Fenton process, where complete color and organic removal was attained after 240 min of treatment under optimum conditions by applying a current density of 66.6 mA cm -2 . Thus, electrochemical technologies emerge as promising water-sustainable approaches.

Electrochemical conversion of solid Nb{sub 2}O{sub 5} to Nb in sodium chloride melt as proof of oxygen ionisation mechanism of electrodeoxidation

Energy Technology Data Exchange (ETDEWEB)

Sri Maha Vishnu, D., E-mail: smvd2@cam.ac.uk [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 (India); Presently with Materials Chemistry Group, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS (United Kingdom); Sanil, N.; Mohandas, K.S. [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 (India)

2016-08-25

The direct electrochemical reduction of a solid metal oxide (MO{sub x}) to metal (M) in calcium chloride melt (FFC Cambridge process) has been proposed to take place via. oxygen ionisation mechanism, MO{sub x} + 2xe{sup −} → M + xO{sup 2−}. However, generation of calcium metal and reduction of the oxide with it too becomes possible under the applied potential condition (3.1 V) of an FFC cell. The unique chemistry of calcium chloride melt, upon cathodic polarisation, makes it difficult to distinguish between the reduction by electrons and calcium metal. Hence in order to confirm the oxygen ionisation theory of electro-deoxidation, electrochemical deoxidation experiments were carried out with sintered Nb{sub 2}O{sub 5} pellet electrodes in molten sodium chloride at 1173 K. The pellets were found reduced to Nb metal. Sodiothermic reduction of Nb{sub 2}O{sub 5} is thermodynamically not feasible (Nb{sub 2}O{sub 5} + 10Na → 5Na{sub 2}O + 2Nb, ΔG°{sub 1173K} = 102.1 kJ) and hence the observed reduction of the oxide is attributed to electrons. This study, for the first time, gives reliable experimental evidence to the oxygen ionisation mechanism of electro-reduction of solid oxides in the FFC process. The experimental results also prove that the electro-reduction of oxides can occur in melts, which otherwise were considered unsuitable from thermodynamic considerations. - Highlights: • In NaCl melt: Negligible O{sup 2−} ion solubility & Na reduction of Nb{sub 2}O{sub 5} to Nb – absent. • Nb{sub 2}O{sub 5} could be electrochemically reduced to spongy Nb in NaCl melt at 1173 K. • Mechanism: Nb{sub 2}O{sub 5} → Na−Nb−O compounds + suboxides of Nb → Na{sub x}NbO{sub y} → Nb. • Metallothermic reduction of oxide in melt - not mandatory for electrodeoxidation. • In FFC Cambridge process: Metallothermic reduction is not essential but desirable.

Hydrothermal-reduction synthesis of manganese oxide nanomaterials for electrochemical supercapacitors.

Science.gov (United States)

Zhang, Xiong; Chen, Yao; Yu, Peng; Ma, Yanwei

2010-11-01

In the present work, amorphous manganese oxide nanomaterials have been synthesized by a common hydrothermal method based on the redox reaction between MnO4(-) and Fe(2+) under an acidic condition. The synthesized MnO2 samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and electrochemical studies. XRD results showed that amorphous manganese oxide phase was obtained. XPS quantitative analysis revealed that the atomic ratio of Mn to Fe was 3.5 in the MnO2 samples. TEM images showed the porous structure of the samples. Electrochemical properties of the MnO2 electrodes were studied using cyclic voltammetry and galvanostatic charge-discharge cycling in 1 M Na2SO4 aqueous electrolyte, which showed excellent pseudocapacitance properties. A specific capacitance of 192 Fg(-1) at a current density of 0.5 Ag(-1) was obtained at the potential window from -0.1 to 0.9 V (vs. SCE).

Electrochemical Oxidation of Sulfamethazine on Multi-Walled Nanotube Film Coated Glassy Carbon Electrode

Directory of Open Access Journals (Sweden)

L. Fotouhi

2014-04-01

Full Text Available The electrochemical oxidation of sulfamethazine (SMZ has been studied at a multi-walled carbon nanotubes modified glassy carbon electrode (MWCNT-GCE by cyclic voltammetry. This modified electrode (MWCNT-GCE exhibited excellent electrocatalytic behavior toward the oxidation of SMZ as evidenced by the enhancement of the oxidation peak current and the shift in the anodic potential to less positive values (170 mV in comparison with the bare GCE. The formal potential, E0', of SMZ is pH dependent with a slope of 54 mV per unit of pH, close to the anticipated Nerstian value of 59 mV for a 2-electron and 2-proton oxidation process. A detailed analysis of cyclic voltammograms gave fundamental electrochemical parameters including the electroactive surface coverage (Г, the transfer coefficient (a, the heterogeneous rate constant (ks. Under the selected conditions, the peak current shows two dynamic linear ranges of 10-200 mM and 300-3000 mM with the detection limit of 6.1 mM. The method was successfully applied to analyze SMZ in serum sample

In situ chemical synthesis of ruthenium oxide/reduced graphene oxide nanocomposites for electrochemical capacitor applications.

Science.gov (United States)

Kim, Ji-Young; Kim, Kwang-Heon; Yoon, Seung-Beom; Kim, Hyun-Kyung; Park, Sang-Hoon; Kim, Kwang-Bum

2013-08-07

An in situ chemical synthesis approach has been developed to prepare ruthenium oxide/reduced graphene oxide (RGO) nanocomposites. It is found that as the C/O ratio increases, the number density of RuO2 nanoparticles decreases, because the chemical interaction between the Ru ions and the oxygen-containing functional groups provides anchoring sites where the nucleation of particles takes place. For electrochemical capacitor applications, the microwave-hydrothermal process was carried out to improve the conductivity of RGO in RuO2/RGO nanocomposites. The significant improvement in capacitance and high rate capability might result from the RuO2 nanoparticles used as spacers that make the interior layers of the reduced graphene oxide electrode available for electrolyte access.

Electrochemical study on the cationic promotion of the catalytic SO2 oxidation in pyrosulfate melts

DEFF Research Database (Denmark)

Petrushina, Irina; Bjerrum, Niels; Cappeln, Frederik Vilhelm

1998-01-01

The electrochemical behavior of the molten V2O5-M2S2O7 (M = K, Cs, or Na) system was studied using a gold working electrode at 440 degrees C in argon and air atmosphere. The aim of the present investigation was to find a possible correlation between the promoting effect of Cs+ and Na+ ions...... on the catalytic oxidation of SO2 in the V2O5-M2S2O7 system and the effect of these alkali cations on the electrochemical behavior of V2O5 in the alkali pyrosulfate melts It has been shown that Na+ ions had a promoting effect on the V(V) reversible arrow V(IV) electrochemical reaction. Sodium ions accelerate both...... in the catalytic SO, oxidation most likely is the oxidation of V(IV) to V(V) and the Na+ and Cs+ promoting effect is based on the acceleration of this stage. It has also been proposed that voltammetric measurements can be used for fast optimization of the composition of the vanadium catalyst (which...

Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

International Nuclear Information System (INIS)

Alver, Ü.; Tanrıverdi, A.

2016-01-01

Highlights: • Boron doped ZnO particles are fabricated and embedded into reduced graphene oxide (RGO) by hydrothermal method. • RGO/ZnO:B composites are used as electrodes for supercapacitors. • Presence of boron in RGO/ZnO composites caused increasing the stability and specific capacitance of electrodes. - Abstract: In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Alver, Ü., E-mail: ualver@ktu.edu.tr [Karadeniz Technical University, Dept. of Metallurgical and Materials Engineering, 61080 Trabzon (Turkey); Tanrıverdi, A. [Kahramanmaras Sutcu Imam University, Department of Physics, 46100 Kahramanmaraş (Turkey)

2016-08-15

Highlights: • Boron doped ZnO particles are fabricated and embedded into reduced graphene oxide (RGO) by hydrothermal method. • RGO/ZnO:B composites are used as electrodes for supercapacitors. • Presence of boron in RGO/ZnO composites caused increasing the stability and specific capacitance of electrodes. - Abstract: In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

Effect of Different Binders on the Electrochemical Performance of Metal Oxide Anode for Lithium-Ion Batteries

Science.gov (United States)

Wang, Rui; Feng, Lili; Yang, Wenrong; Zhang, Yinyin; Zhang, Yanli; Bai, Wei; Liu, Bo; Zhang, Wei; Chuan, Yongming; Zheng, Ziguang; Guan, Hongjin

2017-10-01

When testing the electrochemical performance of metal oxide anode for lithium-ion batteries (LIBs), binder played important role on the electrochemical performance. Which binder was more suitable for preparing transition metal oxides anodes of LIBs has not been systematically researched. Herein, five different binders such as polyvinylidene fluoride (PVDF) HSV900, PVDF 301F, PVDF Solvay5130, the mixture of styrene butadiene rubber and sodium carboxymethyl cellulose (SBR+CMC), and polyacrylonitrile (LA133) were studied to make anode electrodes (compared to the full battery). The electrochemical tests show that using SBR+CMC and LA133 binder which use water as solution were significantly better than PVDF. The SBR+CMC binder remarkably improve the bonding capacity, cycle stability, and rate performance of battery anode, and the capacity retention was about 87% after 50th cycle relative to the second cycle. SBR+CMC binder was more suitable for making transition metal oxides anodes of LIBs.

Graphene electrode modified with electrochemically reduced graphene oxide for label-free DNA detection.

Science.gov (United States)

Li, Bing; Pan, Genhua; Avent, Neil D; Lowry, Roy B; Madgett, Tracey E; Waines, Paul L

2015-10-15

A novel printed graphene electrode modified with electrochemically reduced graphene oxide was developed for the detection of a specific oligonucleotide sequence. The graphene oxide was immobilized onto the surface of a graphene electrode via π-π bonds and electrochemical reduction of graphene oxide was achieved by cyclic voltammetry. A much higher redox current was observed from the reduced graphene oxide-graphene double-layer electrode, a 42% and 36.7% increase, respectively, in comparison with that of a bare printed graphene or reduced graphene oxide electrode. The good electron transfer activity is attributed to a combination of the large number of electroactive sites in reduced graphene oxide and the high conductivity nature of graphene. The probe ssDNA was further immobilized onto the surface of the reduced graphene oxide-graphene double-layer electrode via π-π bonds and then hybridized with its target cDNA. The change of peak current due to the hybridized dsDNA could be used for quantitative sensing of DNA concentration. It has been demonstrated that a linear range from 10(-7)M to 10(-12)M is achievable for the detection of human immunodeficiency virus 1 gene with a detection limit of 1.58 × 10(-13)M as determined by three times standard deviation of zero DNA concentration. Copyright © 2015 Elsevier B.V. All rights reserved.

A Study on Electrochemical Reduction of Rare Earth Oxides in Molten LiCl-Li{sub 2}O Salt

Energy Technology Data Exchange (ETDEWEB)

Lee, Min Woo; Jeong, Sang Mun; Lee, See Hoon [Chungbook National University, Chungju (Korea, Republic of); Sohn, Jung Min [Chonbuk National University, Jeonju (Korea, Republic of)

2016-05-15

In this study, the electrochemical reduction of RE{sub 2}O{sub 3} (RE = Nd or Ce) has been conducted via co-reduction NiO to increase the reduction degree of the rare earth oxides in molten molten LiCl containing 1wt% Li{sub 2}O. The electrochemical reduction behavior of the mixed RE{sub 2}O{sub 3}-NiO oxide has been investigated and the reduction path of RE{sub 2}O{sub 3} has been proposed. An electorchemical spent fuel processing technology, pyroprocessing, has been developed for recycling of spent fuel to be applied to a sodium-cooled fast reactor. The spent fuel is reduced in the oxide reduction process. It is well known that the rare earth oxides are hardly reduced due to their electrochemical and thermodynamic stability. The rare earth oxides unreduced in the reduction process can cause problems via reaction with UCl{sub 3} in the electrorefiner. To tackle those problems, the electrochemical reduction of rare earth oxide has been conducted via co-reduction of NiO in LiCl molten salt containing 1 wt% Li{sub 2}O. The reduction of the oxide mixture starts from the reduction of NiO to Ni, followed by that of RE{sub 2}O{sub 3} on the produced Ni to form intermetallic RENi{sub 5}. The mixed oxide pellets were successfully reduced to the RENi5 alloy by constant electrolysis at 3.0 V at 650 .deg. C. The crucial aspect to these results is that the thermodynamically stable rare-earth oxide, Nd{sub 2}O{sub 3} was successfully converted to the metal in the presence of NiO.

Electrochemical studies on vanadium oxides, 9

International Nuclear Information System (INIS)

Miura, Takashi; Yamamoto, Masahiro; Takahashi, Hirobumi; Kishi, Tomiya; Nagai, Takashi

1979-01-01

The mechanism of the anodic oxidation of various organic compounds-including methanol, formaldehyde, formic acid, ethanol, acetaldehyde and acetic acid-at illuminated vanadium pentoxide (V 2 O 5 ) single crystal electrodes were investigated in aqueous solutions of an H 2 SO 4 -K 2 SO 4 system of about pH 2, in which oxygen evolution from water molecules had previously been confirmed to occur with a current efficiency of about 100%. It was shown that all the organics were oxidized by the so called hole-current doubling mechanism, and that the oxygen evolution reaction, which competed with the above oxidation reaction at the hole-capturing step from the valence band of the electrode, proceeded by the simple hole-capturing mechanism, not followed by an electron injection step into the conduction band. Furthermore, it is considered that chloride ions added to the electrolytes tended to hinder hole-current doubling oxidation owing to their reactivity with the holes at the illuminated V 2 O 5 electrodes. (author)

Characterization of Schottky barrier diodes fabricated from electrochemical oxidation of {alpha} phase brass

Energy Technology Data Exchange (ETDEWEB)

Bond, John W., E-mail: jwb13@le.ac.u [Forensic Research Centre, University of Leicester, Leicester LE1 7 EA (United Kingdom)

2011-04-01

By careful selection of chloride ion concentration in aqueous sodium chloride, electrochemical oxidation of {alpha} phase brass is shown to permit fabrication of either p-type copper (I) oxide/metal or n-type zinc oxide/metal Schottky barrier diodes. X-ray photoelectron and Auger electron spectroscopies provide evidence that barrier formation and rectifying qualities depend on the relative surface abundance of copper (I) oxide and zinc oxide. X-ray diffraction of the resulting diodes shows polycrystalline oxides embedded in amorphous oxidation products that have a lower relative abundance than the diode forming oxide. Conventional I/V characteristics of these diodes show good rectifying qualities. When neither of the oxides dominate, the semiconductor/metal junction displays an absence of rectification.

Electrochemical supramolecular recognition of hemin-carbon composites

Science.gov (United States)

Le, Hien Thi Ngoc; Jeong, Hae Kyung

2018-04-01

Hemin-graphite oxide-carbon nanotube (hemin-GO-CNT) and hemin-thermally reduced graphite oxide-carbon nanotube (hemin-TRGO-CNT) composites are synthesized and investigated for the electrochemical supramolecular recognition by electron transfer between biomolecules (dopamine and hydrogen peroxide) and the composite electrodes. Redox reaction mechanisms of two composites with dopamine and hydrogen peroxide are explained in detail by using cyclic voltammetry and differential pulse voltammetry. Hemin-TRGO-CNT displays higher electrochemical detection for dopamine and hydrogen peroxide than that of hemin-GO-CNT, exhibiting enhancement of the electron transfer due to the effective immobilization of redox couple of hemin (Fe2+/Fe3+) on the TRGO-CNT surface.

Corrosion-electrochemical and mechanical properties of aluminium-berylium alloys alloyed by rare-earth metals

International Nuclear Information System (INIS)

Safarov, A.M.; Odinaev, Kh.E.; Shukroev, M.Sh.; Saidov, R.Kh.

1997-01-01

In order to study influence of rare earth metals on corrosion-electrochemical and mechanical properties of aluminium-berylium alloys the alloys contain 1 mass % beryllium and different amount of rare earth metals were obtained.-electrochemical and mechanical properties of aluminium-berylium alloys. The electrochemical characteristics of obtained alloys, including stationary potential, potentials of passivation beginning and full passivation, potentials of pitting formation and re passivation were defined.

Feasibility of electrochemical oxidation process for treatment of saline wastewater

Directory of Open Access Journals (Sweden)

Kavoos Dindarloo

2015-09-01

Full Text Available Background: High concentration of salt makes biological treatment impossible due to bacterial plasmolysis. The present research studies the process of electrochemical oxidation efficiency and optimal levels as important factors affecting pH, salt concentration, reaction time and applied voltage. Methods: The sample included graphite electrodes with specifications of 2.5 cm diameter and 15 cm height using a reactor with an optimum capacity of 1 L. Sixty samples were obtained with the aid of the experiments carried out in triplicates for each factor at 5 different levels. The entire experiments were performed based on standard methods for water and waste water treatments. Results: Analysis of variance carried out on effect of pH, salt concentration, reaction time and flow intensity in elimination of chemical oxygen demand (COD showed that they are significant factors affecting this process and reduce COD with a coefficient interval of 95% and test power of 80%. Scheffe test showed that at optimal level, a reaction time of 1 hour, 10 g/L concentration, pH = 9 and 15 V electrical potential difference were obtained. Conclusion: Waste waters containing salt may contribute to the electro-oxidation process due to its cations and anions. Therefore, the process of electrochemical oxidation with graphite electrodes could be a proper strategy for the treatment of saline wastewater where biological treatment is not possible.

The electrochemical oxidation of organic waste and activated graphite by Ag{sup 2+} in nitric acid: a literature study

Energy Technology Data Exchange (ETDEWEB)

Van Alsenoy, V.; Rahier, A.

1996-08-01

Organic wastes and activated moderator graphite can be processed by means of combustion, but the incineration of organic waste poses emission problems. The Belgian Nuclear Research Centre SCK-CEN has experience with the treatment of organic wastes. Moreover, the treatment of radioactive graphite will be required since the BR-1 reactor is moderated with 492 tons of graphite. The strong oxidising properties of Ag{sup 2+} are already used in the chemical and nuclear industry to destroy organic waste. We aim to apply the process on radioactive graphite, organic resins and effluents. The reaction mechanisms will be studied, taking into account the thermodynamic and kinetic properties of the different reactions involved. As a first step, this document gives a literature study of the electrochemical oxidation using Ag{sup 2+}. This document presents a thorough literature study, and shows that the oxidative properties of the Ag{sup 2+} ion, which can easily be formed in nitric acid by means of electrolysis, make it an ideal candidate to oxidize organic molecules into carbon dioxide and water on a perfectly well controlled manner. The process has already been used to destroy explosives and toxic organic waste in the nuclear and chemical industry. Chemical, thermodynamic and kinetic aspects of some of the reactions involved are already known and described, other reaction mechanisms are still unknown. On the basis of the information collected so far, the Research and Development group of the Radioactive Waste and Cleanup unit has proposed to start a research programme to define, test, demonstrate and finally apply a safe process for the treatment of radioactive organic material and graphite by electrochemical oxidation using Ag{sup 2+}. Available data confirm that the oxidation of organic material can be carried out safely, leading to the formation of water and carbon dioxide.

Enhanced catalytic and dopamine sensing properties of electrochemically reduced conducting polymer nanocomposite doped with pure graphene oxide.

Science.gov (United States)

Wang, Wenting; Xu, Guiyun; Cui, Xinyan Tracy; Sheng, Ge; Luo, Xiliang

2014-08-15

Significantly enhanced catalytic activity of a nanocomposite composed of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) doped with graphene oxide (GO) was achieved through a simple electrochemical reduction process. The nanocomposite (PEDOT/GO) was electrodeposited on an electrode and followed by electrochemical reduction, and the obtained reduced nanocomposite (PEDOT/RGO) modified electrode exhibited lowered electrochemical impedance and excellent electrocatalytic activity towards the oxidation of dopamine. Based on the excellent catalytic property of PEDOT/RGO, an electrochemical sensor capable of sensitive and selective detection of DA was developed. The fabricated sensor can detect DA in a wide linear range from 0.1 to 175μM, with a detection limit of 39nM, and it is free from common interferences such as uric acid and ascorbic acid. Copyright © 2014 Elsevier B.V. All rights reserved.

Electrochemical investigation of thermically treated graphene oxides as electrode materials for vanadium redox flow battery

International Nuclear Information System (INIS)

Di Blasi, O.; Briguglio, N.; Busacca, C.; Ferraro, M.; Antonucci, V.; Di Blasi, A.

2015-01-01

Highlights: • Graphene oxide is synthesized at high temperatures in a reducing environment. • Treated graphene oxide-based electrodes are prepared by the wet impregnation method. • Electrochemical performance is evaluated as a function of the physico-chemical properties. - Abstract: Thermically treated graphene oxides (TT-GOs) are synthesized at different temperatures, 100 °C, 150 °C, 200 °C and 300 °C in a reducing environment (20% H 2 /He) and investigated as electrode materials for vanadium redox flow battery (VRFB) applications. The treated graphene oxide-based electrodes are prepared by the wet impregnation method using carbon felt (CF) as support. The main aim is to achieve a suitable distribution of the dispersed graphene oxides on the CF surface in order to investigate the electrocatalytic activity for the VO 2+ /VO 2 + and V 2+ /V 3+ redox reactions in the perspective of a feasible large area electrodes scale-up for battery configuration of practical interest. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are carried out in a three electrode half-cell to characterize the electrochemical properties of the TT-GO-based electrodes. Physico-chemical characterizations are carried out to corroborate the electrochemical results. The TT-GO sample treated at 100 °C (TT-GO-100) shows the highest electrocatalytic activity in terms of peak to peak separation (ΔE = 0.03 V) and current density intensity (∼0.24 A cm −2 at 30 mV/s) both toward the VO 2+ /VO 2 + and V 2+ /V 3+ redox reactions. This result is correlated to the presence of hydroxyl (−OH) and carboxyl (−COOH) species that act as active sites. A valid candidate is individuated as effective anode and cathode electrode in the perspective of electrodes scale-up for battery configuration of practical interest

Behaviour of zirconium oxidation and is oxide films in alkali halide solutions as studied by electrochemical techniques

International Nuclear Information System (INIS)

Saleh, H.E.M.

1996-01-01

Study of the properties of Zr electrode and the oxide films that cover the metal surface is of extreme importance due to their wide applications in chemical and nuclear industry. In this thesis the electrochemical behaviour of Zr electrode in alkali halide solutions and with various surface conditions was studied, Also the galvanostatic oxidation of the metal in addition to the open circuit and impedance measurements were employed. Chapter I is a literature survey of the electrochemistry of Zr metal with particular emphasis on the stability and growth process of Zr in different media. Chapter II contains the experimental part, including details of the electrochemical techniques used in the measurements. The electrode impedance was always balanced as a series capacitance Cs and resistance Rs.Chapter III includes the experimental results and discussion. It is divide into sections, A and B. Section A includes the results of some experimental parameters which affect the reactivity of the oxide growth process on the zirconium surface, such as surface pre - treatment, electrolyte composition, the effect of different alkali halide anions, as well as the triiodide ion. 9 tabs.,26 figs.,67 refs

Electrochemical characteristics of flexible micro supercapacitors with reduced graphene oxide-carbon nanotubes composite electrodes

Science.gov (United States)

Yang, Kyungwhan; Cho, Kyoungah; Kim, Sangsig

2018-06-01

In this study, we fabricate solid-state flexible micro-supercapacitors (MSCs) with reduced graphene oxide-carbon nanotube (rGO-CNT) composite electrodes and investigate the electrochemical characteristics by comparing with those of an MSC with rGO electrodes. Regarding the resistance-capacitance time constant and IR drop, the addition of CNTs into the rGO electrodes shows a significant effect owing to both the decrease in the resistance and the increase in the permeability of the electrolytes. Compared to the rGO MSCs, the rGO-CNT MSCs show an excellent areal capacitance of 2.6 mF/cm2, a smaller IR drop of 11 mV, a lower RC time constant of 6 ms, and faster charging/discharging rates with a high scan rate ability up to 100 V/s. The mechanical stability of the flexible rGO-CNT MSCs is verified by 1000 bending cycles. In addition, the electrochemical characteristics of the flexible rGO-CNT MSCs are maintained regardless of the MSC array type.

Electrochemically reduced graphene oxide-based electrochemical sensor for the sensitive determination of ferulic acid in A. sinensis and biological samples

Energy Technology Data Exchange (ETDEWEB)

Liu, Linjie [School of Pharmacy, Lanzhou University, Lanzhou 730000 (China); Gou, Yuqiang [Lanzhou Military Command Center for Disease Prevention and Control, Lanzhou 730000 (China); Gao, Xia; Zhang, Pei; Chen, Wenxia; Feng, Shilan [School of Pharmacy, Lanzhou University, Lanzhou 730000 (China); Hu, Fangdi, E-mail: hufd@lzu.edu.cn [School of Pharmacy, Lanzhou University, Lanzhou 730000 (China); Li, Yingdong, E-mail: lydj412@163.com [Gansu College of Tradition Chinese Medicine, Lanzhou 730000 (China)

2014-09-01

An electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE) was used as a new voltammetric sensor for the determination of ferulic acid (FA). The morphology and microstructure of the modified electrodes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy analysis, and the electrochemical effective surface areas of the modified electrodes were also calculated by chronocoulometry method. Sensing properties of the electrochemical sensor were investigated by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that ERGO was electrodeposited on the surface of GCE by using potentiostatic method. The proposed electrode exhibited electrocatalytic activity to the redox of FA because of excellent electrochemical properties of ERGO. The transfer electron number (n), electrode reaction rate constant (k{sub s}) and electron-transfer coefficient (α) were calculated as 1.12, 1.24 s{sup −1}, and 0.40, respectively. Under the optimized conditions, the oxidation peak current was proportional to FA concentration at 8.49 × 10{sup −8} mol L{sup −1} to 3.89 × 10{sup −5} mol L{sup −1} with detection limit of 2.06 × 10{sup −8} mol L{sup −1}. This fabricated sensor also displayed acceptable reproducibility, long-term stability, and high selectivity with negligible interferences from common interfering species. The voltammetric sensor was successfully applied to detect FA in A. sinensis and biological samples with recovery values in the range of 99.91%-101.91%. - Highlights: • A novel ERGO–based electrochemical sensor of FA was successfully fabricated by using one-step electrodeposition method. • The electrode reaction was an adsorption–diffusion mixed controlled process. • The low detection limit with good selectivity and sensitivity were obtained. • This method was applied for the determination of FA in A. sinensis and biological samples.

Controlled synthesis and electrochemical properties of vanadium oxides with different nanostructures

International Nuclear Information System (INIS)

Zhang, Yifu; Zhou, Min; Huang, Chi; Chen, Chongxue; Cao, Yuliang; Fan, Meijuan; Li, Houbin; Liu, Xinghai; Xie, Guangyong

2012-01-01

Vanadium oxides (V 3 O 7 .H 2 O and VO 2 ) with different morphologies have been selectively synthesized by a facile hydrothermal approach using glucose as the reducing and structure-directing reagent. The as-obtained V 3 O 7 .H 2 O nanobelts have a length up to several tens of micrometers, width of about 60-150 nm and thickness of about 5-10 nm, while the as-prepared VO 2 (B) nanobelts have a length of about 1.0- 7 μm, width, 80-140 nm and thickness, 2-8 nm. It was found that the quantity of glucose, the reaction temperature and the reaction time had significant influence on the compositions and morphologies of final products. Vanadium oxides with different morphologies were easily synthesized by controlling the concentration of glucose. The formation mechanism was also briefly discussed, indicating that glucose played different roles in synthesizing various vanadium oxides. The phase transition from VO 2 (B) to VO 2 (M) were investigated and the phase transition temperature of the VO 2 (M) appeared at around 68 deg C. Furthermore, the electrochemical properties of V 3 O 7 .H 2 O nanobelts, VO 2 (B) nanobelts and VO 2 (B) nanosheets were investigated and they exhibited a high initial discharge capacity of 296, 247 and 227 mAh/g, respectively. (author)

Square-wave stripping voltammetric determination of caffeic acid on electrochemically reduced graphene oxide-Nafion composite film.

Science.gov (United States)

Filik, Hayati; Çetintaş, Gamze; Avan, Asiye Aslıhan; Aydar, Sevda; Koç, Serkan Naci; Boz, İsmail

2013-11-15

An electrochemical sensor composed of Nafion-graphene nanocomposite film for the voltammetric determination of caffeic acid (CA) was studied. A Nafion graphene oxide-modified glassy carbon electrode was fabricated by a simple drop-casting method and then graphene oxide was electrochemically reduced over the glassy carbon electrode. The electrochemical analysis method was based on the adsorption of caffeic acid on Nafion/ER-GO/GCE and then the oxidation of CA during the stripping step. The resulting electrode showed an excellent electrocatalytical response to the oxidation of caffeic acid (CA). The electrochemistry of caffeic acid on Nafion/ER-GO modified glassy carbon electrodes (GCEs) were studied by cyclic voltammetry and square-wave adsorption stripping voltammetry (SW-AdSV). At optimized test conditions, the calibration curve for CA showed two linear segments: the first linear segment increased from 0.1 to 1.5 and second linear segment increased up to 10 µM. The detection limit was determined as 9.1×10(-8) mol L(-1) using SW-AdSV. Finally, the proposed method was successfully used to determine CA in white wine samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Revisiting the electrochemical oxidation of ammonia on carbon-supported metal nanoparticle catalysts

International Nuclear Information System (INIS)

Li, Zhe-Fei; Wang, Yuxuan; Botte, Gerardine G.

2017-01-01

Highlights: • A procedure to pretreat electrocatalysts to study the ammonia oxidation is provided. • N ads and O/OH ads were identified as the major deactivation species that prevent ammonia oxidatoin. • The electrocatalytic activity, thermodynamics, and possible deactivation mechanisms for ammonia oxidation were elucidated. • The onset potential for ammonia oxidation is related to the hydrogen binding energy of the catalyst. • Ammonia electro-oxidation involves a complex decoupled electron and proton transfer process. - Abstract: The ammonia electro-oxidation reaction (AOR) has been studied due to its promising applications in ammonia electrolysis, wastewater remediation, direct ammonia fuel cells, and sensors. However, it is difficult to compare and analyze the reported electrocatalytic activity of AOR reliably, likely due to the variation in catalyst synthesis, electrode composition, electrode morphology, and testing protocol. In this paper, the electro-oxidation of ammonia on different carbon-supported precious metal nanoparticle catalysts was revisited. The effect of experimental conditions, electrochemical test parameters, electrocatalytic activity, thermodynamics, and possible deactivation mechanism of the catalysts were investigated. Pt/C catalyst possesses the highest electrocatalytic activity, while Ir/C and Rh/C show lower overpotential. The onset potential of the AOR is related to the hydrogen binding energy of the catalyst. N ads is one major cause of deactivation accompanied with the formation of surface O/OH ads at high potentials. The coulombic efficiency of N ads formation on Pt is about 1% initially and gradually decreases with reaction time. Increase in ammonia concentration leads to increase in current density, while increase in hydroxyl ions concentration can enhance the current density and reduce the overpotential simultaneously. The slopes of AOR onset potential and hydrogen adsorption/desorption potential of Pt/C as a function of p

Direct electrochemistry and electrocatalysis of lobetyolin via magnetic functionalized reduced graphene oxide film fabricated electrochemical sensor

International Nuclear Information System (INIS)

Sun, Bolu; Gou, Xiaodan; Bai, Ruibin; Abdelmoaty, Ahmed Attia Ahmed; Ma, Yuling; Zheng, Xiaoping; Hu, Fangdi

2017-01-01

A novel lobetyolin electrochemical sensor based on a magnetic functionalized reduced graphene oxide/Nafion nanohybrid film has been introduced in this work. The magnetic functionalized reduced graphene oxide was characterized by fourier transform infrared spectroscopy, atomic force microscope, X-ray diffraction, transmission electron microscopy and thermogravimetric analysis. The scanning electron microscopy characterized the morphology and microstructure of the prepared sensors, and the electrochemical effective surface areas of the prepared sensors were also calculated by chronocoulometry method. The electrochemical behavior of lobetyolin on the magnetic functionalized reduced graphene oxide/Nafion nanohybrid modified glassy carbon electrode was investigated by cyclic voltammetry and differential pulse voltammetry in a phosphate buffer solution of pH 6.0. The electron-transfer coefficient (α), electron transfer number (n), and electrode reaction rate constant (Κs) were calculated as 0.78, 0.73, and 4.63 s −1 , respectively. Under the optimized conditions, the sensor based on magnetic functionalized reduced graphene oxide/Nafion showed a linear voltammetric response to the lobetyolin concentration at 1.0 × 10 −7 to 1.0 × 10 −4 mol/L with detection limit (S/N = 3)of 4.3 × 10 −8 mol/L. The proposed sensor also displayed acceptable reproducibility, long-term stability, and high selectivity, and performs well for analysis of lobetyolin in real samples. The voltammetric sensor was successfully applied to detect lobetyolin in Codonopsis pilosula with recovery values in the range of 96.12% –102.66%. - Graphical abstract: Schematic diagram of the synthesis of MrGO hybrid and the fabrication process of the MrGO/Nafion/GCE for determination of lobetyolin. Display Omitted - Highlights: • The MrGO/Nafion@GCE electrochemical sensor was successfully fabricated. • The prepared MrGO was characterized by AFM, XRD, FTIR, VSM, TEM and SEM. • The proposed

Direct electrochemistry and electrocatalysis of lobetyolin via magnetic functionalized reduced graphene oxide film fabricated electrochemical sensor

Energy Technology Data Exchange (ETDEWEB)

Sun, Bolu [School of Pharmacy, Lanzhou University, Lanzhou 730000 (China); Gou, Xiaodan [School of Chemistry and Chemical Engineering, Nanjing University, 210046 (China); Bai, Ruibin; Abdelmoaty, Ahmed Attia Ahmed; Ma, Yuling; Zheng, Xiaoping [School of Pharmacy, Lanzhou University, Lanzhou 730000 (China); Hu, Fangdi, E-mail: hufd@lzu.edu.cn [School of Pharmacy, Lanzhou University, Lanzhou 730000 (China)

2017-05-01

A novel lobetyolin electrochemical sensor based on a magnetic functionalized reduced graphene oxide/Nafion nanohybrid film has been introduced in this work. The magnetic functionalized reduced graphene oxide was characterized by fourier transform infrared spectroscopy, atomic force microscope, X-ray diffraction, transmission electron microscopy and thermogravimetric analysis. The scanning electron microscopy characterized the morphology and microstructure of the prepared sensors, and the electrochemical effective surface areas of the prepared sensors were also calculated by chronocoulometry method. The electrochemical behavior of lobetyolin on the magnetic functionalized reduced graphene oxide/Nafion nanohybrid modified glassy carbon electrode was investigated by cyclic voltammetry and differential pulse voltammetry in a phosphate buffer solution of pH 6.0. The electron-transfer coefficient (α), electron transfer number (n), and electrode reaction rate constant (Κs) were calculated as 0.78, 0.73, and 4.63 s{sup −1}, respectively. Under the optimized conditions, the sensor based on magnetic functionalized reduced graphene oxide/Nafion showed a linear voltammetric response to the lobetyolin concentration at 1.0 × 10{sup −7} to 1.0 × 10{sup −4} mol/L with detection limit (S/N = 3)of 4.3 × 10{sup −8} mol/L. The proposed sensor also displayed acceptable reproducibility, long-term stability, and high selectivity, and performs well for analysis of lobetyolin in real samples. The voltammetric sensor was successfully applied to detect lobetyolin in Codonopsis pilosula with recovery values in the range of 96.12% –102.66%. - Graphical abstract: Schematic diagram of the synthesis of MrGO hybrid and the fabrication process of the MrGO/Nafion/GCE for determination of lobetyolin. Display Omitted - Highlights: • The MrGO/Nafion@GCE electrochemical sensor was successfully fabricated. • The prepared MrGO was characterized by AFM, XRD, FTIR, VSM, TEM and SEM. �

Materials for electrochemical capacitors

Science.gov (United States)

Simon, Patrice; Gogotsi, Yury

2008-11-01

Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

Microwave synthesis of metal nanocatalysts for the electrochemical oxidation of small biomolecules

DEFF Research Database (Denmark)

Jensen, Kathrine Schiørring Steen; Sun, Hongyu; Werchmeister, Rebecka Maria Larsen

2017-01-01

Electrochemical oxidation of small biomolecules provides an approach to generate clean energy from a sustainable resource. It serves as a principle for anode reactions in fuel cells to convert energy stored in chemical bonds into electrical power. Efficient and robust nanocatalysts are essential ...

Boron-Doped Diamond Electrodes for the Electrochemical Oxidation and Cleavage of Peptides

NARCIS (Netherlands)

Roeser, Julien; Alting, Niels F. A.; Permentier, Hjalmar P.; Bruins, Andries P.; Bischoff, Rainer

2013-01-01

Electrochemical oxidation of peptides and proteins is traditionally performed on carbon-based electrodes. Adsorption caused by the affinity of hydrophobic and aromatic amino acids toward these surfaces leads to electrode fouling. We compared the performance of boron-doped diamond (BDD) and glassy

Effects of electrochemical-deposition method and microstructure on the capacitive characteristics of nano-sized manganese oxide

International Nuclear Information System (INIS)

Shinomiya, Takuya; Gupta, Vinay; Miura, Norio

2006-01-01

The amorphous nano-structured manganese oxide was electrochemically deposited onto a stainless-steel electrode. The structure and surface morphology of the obtained manganese oxide were studied by means of X-ray diffraction analysis and scanning electron microscopy. The capacitive characteristics of the manganese oxide electrodes were investigated by means of cyclic voltammetry and constant current charge-discharge cycling. The morphological and capacitive characteristics of the hydrous manganese oxide was found to be strongly influenced by the electrochemical deposition conditions. The highest specific capacitance value of ca. 410 F g -1 and the specific power of ca. 54 kW kg -1 were obtained at 400 mV s -1 sweep rate of potentiodynamic deposition condition. The cyclic-life data showed that the specific capacitance was highly stable up to 10,000 cycles examined. This suggests the excellent cyclic stability of the obtained amorphous hydrous manganese oxide for supercapacitor application

Effects of electrochemical-deposition method and microstructure on the capacitive characteristics of nano-sized manganese oxide

Energy Technology Data Exchange (ETDEWEB)

Shinomiya, Takuya; Gupta, Vinay; Miura, Norio [Art, Science and Technology Center for Cooperative Research, Kyushu University, Kasuga-shi, Fukuoka 816-8580 (Japan)

2006-06-01

The amorphous nano-structured manganese oxide was electrochemically deposited onto a stainless-steel electrode. The structure and surface morphology of the obtained manganese oxide were studied by means of X-ray diffraction analysis and scanning electron microscopy. The capacitive characteristics of the manganese oxide electrodes were investigated by means of cyclic voltammetry and constant current charge-discharge cycling. The morphological and capacitive characteristics of the hydrous manganese oxide was found to be strongly influenced by the electrochemical deposition conditions. The highest specific capacitance value of ca. 410Fg{sup -1} and the specific power of ca. 54kWkg{sup -1} were obtained at 400mVs{sup -1} sweep rate of potentiodynamic deposition condition. The cyclic-life data showed that the specific capacitance was highly stable up to 10,000 cycles examined. This suggests the excellent cyclic stability of the obtained amorphous hydrous manganese oxide for supercapacitor application. (author)

Research progress in the electrochemical synthesis of ferrate(VI)

International Nuclear Information System (INIS)

Macova, Zuzana; Bouzek, Karel; Hives, Jan; Sharma, Virender K.; Terryn, Raymond J.; Baum, J. Clayton

2009-01-01

There is renewed interest in the +6 oxidation state of iron, ferrate (VI) (Fe VI O 4 2- ), because of its potential as a benign oxidant for organic synthesis, as a chemical in developing cleaner ('greener') technology for remediation processes, and as an alternative for environment-friendly battery cathodes. This interest has led many researchers to focus their attention on the synthesis of ferrate(VI). Of the three synthesis methods, electrochemical, wet chemical and thermal, electrochemical synthesis has received the most attention due to its ease and the high purity of the product. Moreover, electrochemical processes use an electron as a so-called clean chemical, thus avoiding the use of any harmful chemicals to oxidize iron to the +6 oxidation state. This paper reviews the development of electrochemical methods to synthesize ferrate(VI). The approaches chosen by different laboratories to overcome some of the difficulties associated with the electrochemical synthesis of ferrate(VI) are summarized. Special attention is paid to parameters such as temperature, anolyte, and anode material composition. Spectroscopic work to understand the mechanism of ferrate(VI) synthesis is included. Recent advances in two new approaches, the use of an inert electrode and molten hydroxide salts, in the synthesis of ferrate(VI) are also reviewed. Progress made in the commercialization of ferrate(VI) continuous production is briefly discussed as well

Influence of oxidation level on capacitance of electrochemical capacitors fabricated with carbon nanotube/carbon paper composites

International Nuclear Information System (INIS)

Hsieh, C.-T.; Chen, W.-Y.; Cheng, Y.-S.

2010-01-01

Gaseous oxidation of carbon papers (CPs) decorated with carbon nanotubes (CNTs) with varying degrees of oxidation was conducted to investigate the influence of surface oxides on the performance of electrochemical capacitors fabricated with oxidized CNT/CP composites. The oxidation period was found to significantly enhance the O/C atomic ratio on the composites, and the increase in oxygen content upon oxidation is mainly contributed by the formation of C=O and C-O groups. The electrochemical behavior of the capacitors was tested in 1 M H 2 SO 4 within a potential of 0 and 1 V vs. Ag/AgCl. Both superhydrophilicity and specific capacitance of the oxidized CNT/CP composites were found to increase upon oxidation treatment. A linearity increase of capacitance with O/C ratio can be attributed to the increase of the population of surface oxides on CNTs, which imparts excess sites for redox reaction (pseudocapacitance) and for the formation of double-layer (double-layer capacitance). The technique of ac impedance combined with equivalent circuit clearly showed that oxidized CNT/CP capacitor imparts not only enhanced capacitance but also a low equivalent series resistance.

Activated carbon electrodes: electrochemical oxidation coupled with desalination for wastewater treatment.

Science.gov (United States)

Duan, Feng; Li, Yuping; Cao, Hongbin; Wang, Yi; Crittenden, John C; Zhang, Yi

2015-04-01

The wastewater usually contains low-concentration organic pollutants and some inorganic salts after biological treatment. In the present work, the possibility of simultaneous removal of them by combining electrochemical oxidation and electrosorption was investigated. Phenol and sodium chloride were chosen as representative of organic pollutants and inorganic salts and a pair of activated carbon plate electrodes were used as anode and cathode. Some important working conditions such as oxygen concentration, applied potential and temperature were evaluated to reach both efficient phenol removal and desalination. Under optimized 2.0 V of applied potential, 38°C of temperature, and 500 mL min(-1) of oxygen flow, over 90% of phenol, 60% of TOC and 20% of salinity were removed during 300 min of electrolysis time. Phenol was removed by both adsorption and electrochemical oxidation, which may proceed directly or indirectly by chlorine and hypochlorite oxidation. Chlorophenols were detected as degradation intermediates, but they were finally transformed to carboxylic acids. Desalination was possibly attributed to electrosorption of ions in the pores of activated carbon electrodes. The charging/regeneration cycling experiment showed good stability of the electrodes. This provides a new strategy for wastewater treatment and recycling. Copyright © 2014 Elsevier Ltd. All rights reserved.

Post-treatment of reclaimed waste water based on an electrochemical advanced oxidation process

Science.gov (United States)

Verostko, Charles E.; Murphy, Oliver J.; Hitchens, G. D.; Salinas, Carlos E.; Rogers, Tom D.

1992-01-01

The purification of reclaimed water is essential to water reclamation technology life-support systems in lunar/Mars habitats. An electrochemical UV reactor is being developed which generates oxidants, operates at low temperatures, and requires no chemical expendables. The reactor is the basis for an advanced oxidation process in which electrochemically generated ozone and hydrogen peroxide are used in combination with ultraviolet light irradiation to produce hydroxyl radicals. Results from this process are presented which demonstrate concept feasibility for removal of organic impurities and disinfection of water for potable and hygiene reuse. Power, size requirements, Faradaic efficiency, and process reaction kinetics are discussed. At the completion of this development effort the reactor system will be installed in JSC's regenerative water recovery test facility for evaluation to compare this technique with other candidate processes.

High temperature oxidation and electrochemical investigations on nickel-base alloys

International Nuclear Information System (INIS)

Obigodi-Ndjeng, Georgia

2011-01-01

This study examined high-temperature oxidation behavior of different Ni-base alloys. In addition, electrochemical characterization of the alloy's corrosion behavior was carried out, including comparison of the properties of native passive films grown at room temperature and high temperature oxide scales. PWA 1483 (single-crystalline Ni-base superalloy) and model alloys Ni-Cr-X (where X is either Co or Al) were oxidized at 800 and 900 C in air for different time periods. The superalloy showed the best oxidation behavior at both temperatures, which might be due to the fact that the oxidation growth function is subparabolic for the model alloys and parabolic for the superalloy at 800 C. At higher temperatures, changes in the kinetics are induced, as the oxides grow faster, thus only PWA 1483 growth follows the parabolic law. Different scales in a typical sandwich form were detected, with the inner layer comprised of mostly Cr 2 O 3 , the middle layer was mixture of different oxides and spinels, depending on the alloying elements, and the oxide at the interface oxygen/oxide was found to be NiO. The influence of sample preparation could also be shown, as rougher surfaces change the oxidation kinetics from parabolic and subparabolic for polished samples to linear. The influence of moisture on the oxidation behavior of the 2 nd generation single crystal Ni-base superalloys (PWA 1484, PWA 1487, CMSX 4, Rene N5 and Rene N5+) was studied at 1000 C after 100 h oxidation period. It was found that the moisture increased the oxidation rate and mostly the transient oxides growth rate. The water vapor content in air also influenced the behavior of these alloys, as they showed a higher mass gain in air + 30% water vapor than in air + 10% water vapor. The alloys PWA 1484 and CMSX 4 showed respectively the worst and best behavior in all the studied atmospheres. The addition of reactive elements, such as Yttrium, Hafnium and Lanthanum is likely to enhance the oxidation behavior of PWA

Electrochemical oxidation of propene by use of LSM₁₅/CGO₁₀ electrochemical reactor

DEFF Research Database (Denmark)

Ippolito, Davide; Andersen, Kjeld Bøhm; Kammer Hansen, Kent

2012-01-01

The propene catalytic oxidation was studied over an 11-layers porous electrochemical reactor made by La0.85Sr0.15MnO3 and Ce0.9Gd0.1O1.95 with the objective to simulate the abatement of exhaust gases emitted from Diesel engines. This work shows the possibility to enhance the catalytic activity th...... of catalysis (EPOC) was found at low temperature....

Electrochemical behaviour of iron and AISI 304 stainless steel in simulated acid rain solution

Energy Technology Data Exchange (ETDEWEB)

Pilic, Zora; Martinovic, Ivana [Mostar Univ. (Bosnia and Herzegovina). Dept. of Chemistry

2016-10-15

The growth mechanism and properties of the oxide films on iron and AISI 304 stainless steel were studied in simulated acid rain (pH 4.5) by means of electrochemical techniques and atomic absorption spectrometry. The layer-pore resistance model was applied to explain a potentiodynamic formation of surface oxides. It was found that the growth of the oxide film on iron takes place by the low-field migration mechanism, while that on the stainless steel takes place by the high-field mechanism. Kinetic parameters were determined. Impedance measurements revealed that Fe surface film has no protective properties at the open circuit potential, while the resistance of stainless steel oxide film is very high. The concentration of the metallic ions released into solution and measured by atomic absorption spectroscopy was in accordance with the results obtained from the electrochemical techniques.

The impact of electrochemical reduction potentials on the electrocatalytic activity of graphene oxide toward the oxygen reduction reaction in an alkaline medium

International Nuclear Information System (INIS)

Toh, Shaw Yong; Loh, Kee Shyuan; Kamarudin, Siti Kartom; Daud, Wan Ramli Wan

2016-01-01

We report the synthesis of graphene via the electrochemical reduction of graphene oxide (GO). In this study, GO nanosheets from aqueous dispersion were pre-assembled on a glassy carbon (GC) electrode and then electrochemically reduced in 1 M KOH under various constant reduction potentials in the range of −0.6 V to −1.5 V (vs. Ag/AgCl). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses revealed that the graphitic structure was substantially restored in the resulting electrochemically reduced graphene oxide (ERGO). The ERGO electrodes exhibited significantly enhanced catalytic activity toward the oxygen reduction reaction (ORR) in an alkaline medium compared with the initial GO electrode. Of the ERGO electrodes produced at various cathodic potentials, the ERGO-1.2 V electrode, which was produced at a reduction potential of −1.2 V, demonstrated the best catalytic activity toward the ORR in an alkaline medium. The ORR on GO and ERGO electrodes was shown to proceed via a two-electron mechanism at low overpotentials. The agreement between the spectroscopy results and electrochemical measurements provide strong evidence that the enhanced ORR catalytic activity is mainly attributed to the restoration of GO’s graphitic structure. Furthermore, the ERGO-1.2 V electrode showed excellent tolerance to the methanol poisoning effect compared with a Pt/C catalyst electrode.

Detailed dynamic solid oxide fuel cell modeling for electrochemical impedance spectra simulation

Energy Technology Data Exchange (ETDEWEB)

Hofmann, Ph. [Laboratory of Steam Boilers and Thermal Plants, School of Mechanical Engineering, Thermal Engineering Section, National Technical University of Athens, Heroon Polytechniou 9, 15780 Athens (Greece); Panopoulos, K.D. [Institute for Solid Fuels Technology and Applications, Centre for Research and Technology Hellas, 4th km. Ptolemais-Mpodosakeio Hospital, Region of Kouri, P.O. Box 95, GR 502, 50200 Ptolemais (Greece)

2010-08-15

This paper presents a detailed flexible mathematical model for planar solid oxide fuel cells (SOFCs), which allows the simulation of steady-state performance characteristics, i.e. voltage-current density (V-j) curves, and dynamic operation behavior, with a special capability of simulating electrochemical impedance spectroscopy (EIS). The model is based on physico-chemical governing equations coupled with a detailed multi-component gas diffusion mechanism (Dusty-Gas Model (DGM)) and a multi-step heterogeneous reaction mechanism implicitly accounting for the water-gas-shift (WGS), methane reforming and Boudouard reactions. Spatial discretization can be applied for 1D (button-cell approximation) up to quasi-3D (full size anode supported cell in cross-flow configuration) geometries and is resolved with the finite difference method (FDM). The model is built and implemented on the commercially available modeling and simulations platform gPROMS trademark. Different fuels based on hydrogen, methane and syngas with inert diluents are run. The model is applied to demonstrate a detailed analysis of the SOFC inherent losses and their attribution to the EIS. This is achieved by means of a step-by-step analysis of the involved transient processes such as gas conversion in the main gas chambers/channels, gas diffusion through the porous electrodes together with the heterogeneous reactions on the nickel catalyst, and the double-layer current within the electrochemical reaction zone. The model is an important tool for analyzing SOFC performance fundamentals as well as for design and optimization of materials' and operational parameters. (author)

Synthesis of multilayered structure of nano-dimensional silica glass/reduced graphene oxide for advanced electrochemical applications.

Science.gov (United States)

Ghosh, Arnab; Miah, Milon; Majumder, Chinmoy; Bag, Shekhar; Chakravorty, Dipankar; Saha, Shyamal Kumar

2018-03-28

During the past few years, intensive research has been carried out to design new functional materials for superior electrochemical applications. Due to low storage capacity and low charge transport, silica based glasses have not yet been investigated for their supercapacitive behavior. Therefore, in the present study, a multilayered structure of silica-based nanoglass and reduced graphene oxide has been designed to remarkably enhance the specific capacitance by exploiting the porosity, large surface area, sufficient dangling bonds in the nanoglass and high electrical conductivity of rGO. The charge transport in the composite structure is also investigated to understand the electrochemical properties. It is found that Simmons tunneling or direct tunneling is the dominant mechanism of charge conduction between the graphene layers via the potential barrier of silica nanoglass phase. We believe that this study will open up a new area in the design of glass-based two-dimensional nanocomposites for superior supercapacitor applications.

The influence of TiO2 and aeration on the kinetics of electrochemical oxidation of phenol in packed bed reactor

International Nuclear Information System (INIS)

Wang Lizhang; Zhao Yuemin; Fu Jianfeng

2008-01-01

The electrochemical oxidation of phenolic wastewater in a lab-scale reactor, packed into granular activated carbon (GAC) with Ti/SnO 2 anodes and stainless steel cathodes, was interpreted in this study. GAC saturated rapidly if it was only used as sorbent, but application of suitable electric energy for the system simultaneously could recover the adsorption ability of GAC and maintain the continuous running effectively. The titanium dioxide (TiO 2 ) as catalyst and airflow were also applied to the electrochemical reactor to examine the enhancement for phenol oxidation process. Results revealed that the electrochemical degradation of phenol could be reasonably described by first-order kinetics. In addition, it was illustrated that acid region, increased voltage, more dosage of TiO 2 and higher aeration intensity were all beneficial parameters for phenol oxidation rates. By inspecting the relationship between the rate constants (k) and influencing factors, respectively, an overall kinetic model for phenol oxidation was proposed. The kinetics obtained from the experiments under corresponding electrochemical conditions could provide an accurate estimation of phenol concentration effluent and better design of the packed bed reactor

Facile solvothermal synthesis of a graphene nanosheet-bismuth oxide composite and its electrochemical characteristics

International Nuclear Information System (INIS)

Wang Huanwen; Hu Zhongai; Chang Yanqin; Chen Yanli; Lei Ziqiang; Zhang Ziyu; Yang Yuying

2010-01-01

This work demonstrates a novel and facile route for preparing graphene-based composites comprising of metal oxide nanoparticles and graphene. A graphene nanosheet-bismuth oxide composite as electrode materials of supercapacitors was firstly synthesized by thermally treating the graphene-bismuth composite, which was obtained through simultaneous solvothermal reduction of the colloidal dispersions of negatively charged graphene oxide sheets in N,N-dimethyl formamide (DMF) solution of bismuth cations at 180 o C. The morphology, composition, and microstructure of the composites together with pure graphite oxide, and graphene were characterized using powder X-ray diffraction (XRD), FT-IR, field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetry and differential thermogravimetry (TG-DTG). The electrochemical behaviors were measured by cyclic voltammogram (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). The specific capacitance of 255 F g -1 (based on composite) is obtained at a specific current of 1 A g -1 as compared with 71 F g -1 for pure graphene. The loaded-bismuth oxide achieves a specific capacitance as high as 757 F g -1 even at 10 A g -1 . In addition, the graphene nanosheet-bismuth oxide composite electrode exhibits the excellent rate capability and well reversibility.

Facile solvothermal synthesis of a graphene nanosheet-bismuth oxide composite and its electrochemical characteristics

Energy Technology Data Exchange (ETDEWEB)

Wang Huanwen [Key Laboratory of Eco-Environment-Related Polymer Materials of Ministry of Education, Key Laboratory of Polymer Materials of Gansu Province, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Hu Zhongai, E-mail: zhongai@nwnu.edu.c [Key Laboratory of Eco-Environment-Related Polymer Materials of Ministry of Education, Key Laboratory of Polymer Materials of Gansu Province, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Chang Yanqin; Chen Yanli; Lei Ziqiang; Zhang Ziyu; Yang Yuying [Key Laboratory of Eco-Environment-Related Polymer Materials of Ministry of Education, Key Laboratory of Polymer Materials of Gansu Province, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China)

2010-12-01

This work demonstrates a novel and facile route for preparing graphene-based composites comprising of metal oxide nanoparticles and graphene. A graphene nanosheet-bismuth oxide composite as electrode materials of supercapacitors was firstly synthesized by thermally treating the graphene-bismuth composite, which was obtained through simultaneous solvothermal reduction of the colloidal dispersions of negatively charged graphene oxide sheets in N,N-dimethyl formamide (DMF) solution of bismuth cations at 180 {sup o}C. The morphology, composition, and microstructure of the composites together with pure graphite oxide, and graphene were characterized using powder X-ray diffraction (XRD), FT-IR, field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetry and differential thermogravimetry (TG-DTG). The electrochemical behaviors were measured by cyclic voltammogram (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). The specific capacitance of 255 F g{sup -1} (based on composite) is obtained at a specific current of 1 A g{sup -1} as compared with 71 F g{sup -1} for pure graphene. The loaded-bismuth oxide achieves a specific capacitance as high as 757 F g{sup -1} even at 10 A g{sup -1}. In addition, the graphene nanosheet-bismuth oxide composite electrode exhibits the excellent rate capability and well reversibility.

Treatment of winery wastewater by electrochemical methods and advanced oxidation processes.

Science.gov (United States)

Orescanin, Visnja; Kollar, Robert; Nad, Karlo; Mikelic, Ivanka Lovrencic; Gustek, Stefica Findri

2013-01-01

The aim of this research was development of new system for the treatment of highly polluted wastewater (COD = 10240 mg/L; SS = 2860 mg/L) originating from vine-making industry. The system consisted of the main treatment that included electrochemical methods (electro oxidation, electrocoagulation using stainless steel, iron and aluminum electrode sets) with simultaneous sonication and recirculation in strong electromagnetic field. Ozonation combined with UV irradiation in the presence of added hydrogen peroxide was applied for the post-treatment of the effluent. Following the combined treatment, the final removal efficiencies of the parameters color, turbidity, suspended solids and phosphates were over 99%, Fe, Cu and ammonia approximately 98%, while the removal of COD and sulfates was 77% and 62%, respectively. A new approach combining electrochemical methods with ultrasound in the strong electromagnetic field resulted in significantly better removal efficiencies for majority of the measured parameters compared to the biological methods, advanced oxidation processes or electrocoagulation. Reduction of the treatment time represents another advantage of this new approach.

Electrochemically Scavenging the Silica Impurities at the Ni-YSZ Triple Phase Boundary of Solid Oxide Cells

DEFF Research Database (Denmark)

Tao, Youkun; Shao, Jing; Cheng, Shiyang

2016-01-01

Silica impurity originated from the sealing or raw materials of the solid oxide cells (SOCs) accumulating at the. Ni-YSZ triple phase boundaries (TPBs) is known as one major reason for electrode passivation. Here we report nanosilica precipitates inside Ni grains instead of blocking the TPBs when...... operating the SOCs at vertical bar i vertical bar >= 1.5 A cm-2 for electrolysis of H2O/CO2. An electrochemical scavenging mechanism was proposed to explain this unique behavior: the removal of silica proceeded through the reduction of the silica to Si under strong cathodic polarization, followed by bulk...

Lithium alloys and metal oxides as high-capacity anode materials for lithium-ion batteries

International Nuclear Information System (INIS)

Liang, Chu; Gao, Mingxia; Pan, Hongge; Liu, Yongfeng; Yan, Mi

2013-01-01

Highlights: •Progress in lithium alloys and metal oxides as anode materials for lithium-ion batteries is reviewed. •Electrochemical characteristics and lithium storage mechanisms of lithium alloys and metal oxides are summarized. •Strategies for improving electrochemical lithium storage properties of lithium alloys and metal oxides are discussed. •Challenges in developing lithium alloys and metal oxides as commercial anodes for lithium-ion batteries are pointed out. -- Abstract: Lithium alloys and metal oxides have been widely recognized as the next-generation anode materials for lithium-ion batteries with high energy density and high power density. A variety of lithium alloys and metal oxides have been explored as alternatives to the commercial carbonaceous anodes. The electrochemical characteristics of silicon, tin, tin oxide, iron oxides, cobalt oxides, copper oxides, and so on are systematically summarized. In this review, it is not the scope to retrace the overall studies, but rather to highlight the electrochemical performances, the lithium storage mechanism and the strategies in improving the electrochemical properties of lithium alloys and metal oxides. The challenges and new directions in developing lithium alloys and metal oxides as commercial anodes for the next-generation lithium-ion batteries are also discussed

Electrochemical oxidation of methanol on Pt3Co bulk alloy

Directory of Open Access Journals (Sweden)

S. LJ. GOJKOVIC

2003-11-01

Full Text Available The electrochemical oxidation of methanol was investigated on a Pt3Co bulk alloy in acid solutions. Kinetic parameters such as transfer coefficient, reaction orders with respect to methanol and H+ ions and energy of activation were determined. It was found that the rate of methanol oxidation is significantly diminished by rotation of the electrode. This effect was attributed to the diffusion of formaldehyde and formic acid from the electrode surface. Stirring of the electrolyte also influenced the kinetic parameters of the reaction. It was speculated that the predominant reaction pathway and rate determining step are different in the quiescent and in the stirred electrolyte. Cobalt did not show a promoting effect on the rate of methanol oxidation on the Pt3Co bulk alloy with respect to a pure Pt surface.

Preparation of AAO-CeO2 nanotubes and their application in electrochemical oxidation desulfurization of diesel

Science.gov (United States)

Du, Xiaoqing; Yang, Yumeng; Yi, Chenxi; Chen, Yu; Cai, Chao; Zhang, Zhao

2017-02-01

The coaxial arrays of AAO-CeO2 NTs have been successfully galvanostatically deposited on an anode, characterized and adopted as a catalyst for removing organic sulfurs from diesel. The influence of the main electrochemical oxidation factors on the efficiency of desulfurization have also been investigated. The results show that the fabrication process of AAO-CeO2 NTs is accompanied by the formation of a new phase, namely Al3Ce, and the main oxidation products of the diesel are soluble inorganic sulphides, especially Ce2(SO4)3. When compared with dibenzothiophene and 4, 6-dimethyldibenzothiophene, benzothiophene is much more easily removed, with a removal efficiency that reaches 87.2%. Finally, a possible electrochemical oxidation desulfurization pathway for diesel is proposed.

Synthesis, characterisation and electrochemical evaluation of reduced graphene oxide modified antimony nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Silwana, Bongiwe; Horst, Charlton van der [Natural Resources and the Environment (NRE), Council for Scientific and Industrial Research (CSIR), Stellenbosch 7600 (South Africa); SensorLab, Department of Chemistry, University of the Western Cape, Bellville 7535 (South Africa); Iwuoha, Emmanuel [SensorLab, Department of Chemistry, University of the Western Cape, Bellville 7535 (South Africa); Somerset, Vernon, E-mail: vsomerset@csir.co.za [Natural Resources and the Environment (NRE), Council for Scientific and Industrial Research (CSIR), Stellenbosch 7600 (South Africa)

2015-10-01

This paper demonstrates some aspects on the synthesis and characterisation of nanoparticles of metallic alloys using polyvinyl alcohol as a stabiliser, which combines high surface area and superior hybrid properties. The present experimental design was to synthesise a nanocomposite of reduced graphene oxide and antimony nanoparticles to be used as thin films for macro- and micro-carbon electrodes for enhancing sensing of different toxic metal pollutants in the environment. The synthetic process of reduced graphene oxide was done using the modified Hummers method while antimony pentachloride was reduced with sodium borohydride into nanoparticles of antimony using polyvinyl-alcohol as a stabiliser. The systematic investigation of morphology was done by scanning electron microscopy and high resolution-transmission electron microscope, which revealed the synthesis of a product, consists of reduced graphene oxide antimony nanoparticles. The electrochemical behaviour of the reduced graphene oxide antimony nanoparticles coated on a glassy carbon electrode was performed using voltammetric and impedance techniques. Electrochemical impedance measurements showed that the overall resistance, including the charge–transfer resistance, was smaller with reduced graphene oxide antimony nanoparticles than reduced graphene oxide and antimony nanoparticles, on their own. Evaluation of the reduced graphene oxide antimony nanoparticle sensor in the stripping voltammetry has shown a linear working range for concentration of platinum (II) between 6.0 × 10{sup −6}–5.4 × 10{sup −5} μg L{sup −1} with limit of detection of 6 × 10{sup −6} μg L{sup −1} (signal-to-noise ratio = 3), which is below the World Health Organisation guidelines for freshwater. - Highlights: • Reduced graphene oxide modified antimony nanoparticles were chemically synthesised. • TEM results show rGO-Sb nanoparticles with a diameter range of between 2 and 20 nm. • Impedance results confirm

Destruction of commercial pesticides by cerium redox couple mediated electrochemical oxidation process in continuous feed mode

International Nuclear Information System (INIS)

Balaji, Subramanian; Chung, Sang Joon; Ryu, Jae-Yong; Moon, Il Shik

2009-01-01

Mediated electrochemical oxidation was carried out for the destruction of commercial pesticide formulations using cerium(IV) in nitric acid as the mediator electrolyte solution in a bench scale set up. The mediator oxidant was regenerated in situ using an electrochemical cell. The real application of this sustainable process for toxic organic pollutant destruction lies in its ability for long term continuous operation with continuous organic feeding and oxidant regeneration with feed water removal. In this report we present the results of fully integrated MEO system. The task of operating the continuous feed MEO system for a long time was made possible by continuously removing the feed water using an evaporator set up. The rate of Ce(IV) regeneration in the electrochemical cell and the consumption for the pesticide destruction was matched based on carbon content of the pesticides. It was found that under the optimized experimental conditions for Ce(III) oxidation, organic addition and water removal destruction efficiency of ca. 99% was obtained for all pesticides studied. It was observed that the Ce(IV) concentration was maintained nearly the same throughout the experiment. The stable operation for 6 h proved that the process can be used for real applications and for possible scale up for the destruction of larger volumes of toxic organic wastes.

Probing Structural Changes in Poly(3-hexylthiophene) (P3HT) During Electrochemical Oxidation with In Situ X-ray Scattering

Science.gov (United States)

Thelen, Jacob L.; Patel, Shrayesh N.; Javier, Anna E.; Balsara, Nitash P.

2014-03-01

Mixtures of poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-b-PEO) block copolymer and lithium bis(trifluromethanesulfonyl) imide (LiTFSI) salt can microphase separate into electron (P3HT) and ion (PEO/LiTFSI) conducting domains. P3HT is a semicrystalline polymer with intrinsically semiconducting electronic properties. Electrochemical oxidation (doping) of the P3HT block provides the P3HT-b-PEO/LiTFSI mixtures with electronic conductivity suitable for lithium battery operation. Due to the presence of the solid-state electrolyte (PEO/LiTFSI) in intimate contact with the microphase separated P3HT domains, electrochemical oxidation of P3HT can be performed entirely in the solid state; therefore, P3HT-b-PEO/LiTFSI provides a unique opportunity to study the structural changes in P3HT induced by oxidation. We use in situ x-ray scattering techniques to probe structural changes in P3HT during electrochemical oxidation and correlate these changes with previously observed enhancements in electron mobility. Supported by the Joint Center for Energy Storage Research (JCESR).

Fracture of crystalline silicon nanopillars during electrochemical lithium insertion

KAUST Repository

Lee, S. W.; McDowell, M. T.; Berla, L. A.; Nix, W. D.; Cui, Y.

2012-01-01

in a solid can result in dramatic structural transformations and associated changes in mechanical behavior: This is particularly evident during electrochemical cycling of novel battery electrodes, such as alloying anodes, conversion oxides, and sulfur

Electrochemical fabrication of CdS/Co nanowire arrays in porous aluminum oxide templates

CERN Document Server

Yoon, C H

2002-01-01

A procedure for preparing semiconductor/metal nanowire arrays is described, based on a template method which entails electrochemical deposition into nanometer-wide parallel pores of anodic aluminum oxide films on aluminum. Aligned CdS/Co heterostructured nanowires have been prepared by ac electrodeposition in the anodic aluminum oxide templates. By varying the preparation conditions, a variety of CdS/Co nanowire arrays were fabricated, whose dimensional properties could be adjusted.

The study of redox mechanism of dobutamine at different pH media by electrochemical and in situ spectroelectrochemical methods

International Nuclear Information System (INIS)

Yang Gongjun; Xu Jingjuan; Chen Hongyuan

2004-01-01

Based on the comprehensive analyses of the experimental results of the electrochemical methods, in situ UV-Vis absorption spectra, in situ electron spin resonance (ESR), and attenuated total-internal reflection (ATR) as well as the calculation of UV-Vis absorption data by PM3 Semi-Empirical method, a reaction mechanism for the redox processes of dobutamine was presented. When the anodic sweep is carried out, dobutamine firstly undergoes a free radical reaction with one-electron and one-proton to form semi-quinone free radicals, which will continuously convert to its corresponding quinone form by further electrochemical oxidation reaction. The formed quinone cannot only undergo a cyclization process by chemical reaction to produce a new compound, which can be reduced at more negative potential, but also be reduced to form dobutamine again when subsequent cathodic sweep is followed. The cyclization rate is depended upon pH values, and it increases with the increase of pH. In neutral medium, the corresponding oxidation form of the cyclization reaction product is easy to convert to melanin

Electrochemical oxidation of COD from real textile wastewaters: Kinetic study and energy consumption.

Science.gov (United States)

Zou, Jiaxiu; Peng, Xiaolan; Li, Miao; Xiong, Ying; Wang, Bing; Dong, Faqin; Wang, Bin

2017-03-01

In the present study, the electrochemical oxidation of real wastewaters discharged by textile industry was carried out using a boron-doped diamond (BDD) anode. The effect of operational variables, such as applied current density (20-100 mA·cm -2 ), NaCl concentration added to the real wastewaters (0-3 g·L -1 ), and pH value (2.0-10.0), on the kinetics of COD oxidation and on the energy consumption was carefully investigated. The obtained experimental results could be well matched with a proposed kinetic model, in which the indirect oxidation mediated by electrogenerated strong oxidants would be described through a pseudo-first-order kinetic constant k. Values of k exhibited a linear increase with increasing applied current density and decreasing pH value, and an exponential increase with NaCl concentration. Furthermore, high oxidation kinetics resulted in low specific energy consumption, but this conclusion was not suitable to the results obtained under different applied current density. Under the optimum operational conditions, it only took 3 h to complete remove the COD in the real textile wastewaters and the specific energy consumption could be as low as 11.12 kWh·kg -1  COD. The obtained results, low energy consumption and short electrolysis time, allowed to conclude that the electrochemical oxidation based on BDD anodes would have practical industrial application for the treatment of real textile wastewater. Copyright © 2016 Elsevier Ltd. All rights reserved.

Optimization of reaction parameters for the electrochemical oxidation of lidocaine with a Design of Experiments approach

NARCIS (Netherlands)

Gul, Turan; Bischoff, Rainer; Permentier, Hjalmar

2015-01-01

Identification of potentially toxic oxidative drug metabolites is a crucial step in the development of new drugs. Electrochemical methods are useful to study oxidative drug metabolism, but are not widely used to synthesize metabolites for follow-up studies. Careful optimization of reaction

Electrochemical oxidation of recalcitrant organic compounds in biologically treated municipal solid waste leachate in a flow reactor.

Science.gov (United States)

Quan, Xuejun; Cheng, Zhiliang; Chen, Bo; Zhu, Xincai

2013-10-01

Biologically-treated municipal solid waste (MSW) leachate still contains many kinds of bio-recalcitrant organic matter. A new plate and frame electrochemical reactor was designed to treat these materials under flow conditions. In the electrochemical oxidation process, NH3 and color could be easily removed by means of electro-generated chlorine/hypochlorite within 20 min. The effects of major process parameters on the removal of organic pollutants were investigated systematically. Under experimental conditions, the optimum operation parameters were current density of 65 mA/cm2, flow velocity of 2.6 cm/sec in electrode gap, and initial chloride ion concentration of 5000 mg/L. The COD in the leachate could be reduced below 100 mg/L after 1 hr of treatment. The kinetics and mechanism of COD removal were investigated by simultaneously monitoring the COD change and chlorine/hypochlorite production. The kinetics of COD removal exhibited a two-stage kinetic model, and the decrease of electro-generated chlorine/hypochlorite production was the major mechanism for the slowing down of the COD removal rate in the second stage. The narrowing of the electrode gap is beneficial for COD removal and energy consumption.

Effect of ammonium-salt solutions on the surface properties of carbon fibers in electrochemical anodic oxidation

Energy Technology Data Exchange (ETDEWEB)

Qian Xin, E-mail: qx3023@nimte.ac.cn [National Engineering Laboratory of Carbon Fiber Preparation Technology, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Wang Xuefei; Ouyang Qin; Chen Yousi; Yan Qing [National Engineering Laboratory of Carbon Fiber Preparation Technology, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

2012-10-15

Highlights: Black-Right-Pointing-Pointer Longitudinal grooves on the fiber surface became more well-defined and much deeper after surface treatment. Black-Right-Pointing-Pointer The concentration of oxygen and nitrogen on the fiber surface increased after surface treatment. Black-Right-Pointing-Pointer The intensity of oxidative reaction varied with the change of ammonium-salt solutions. Black-Right-Pointing-Pointer The higher the concentration of OH{sup -} ions in the electrolytes, the violent the oxidative reaction happened. - Abstract: The surfaces of polyacrylonitrile-based carbon fibers were treated by an electrochemical anodic method. Three different kinds of ammonium-salt solutions namely NH{sub 4}HCO{sub 3}, (NH{sub 4}){sub 2}CO{sub 3} and (NH{sub 4}){sub 3}PO{sub 4} were respectively chosen as the electrolytes. The effect of these electrolytes on the surface structure was studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed that longitudinal grooves on the fiber surface became more well-defined and much deeper after surface treatment, and the root mean square roughness (RMS) of carbon fiber surface increased from 4.6 nm for untreated fibers to 13.5 nm for treated fibers in (NH{sub 4}){sub 3}PO{sub 4} electrolytes. The concentration of oxygen and nitrogen atomic on the fiber surface increased after surface treatment. The tensile strength of oxidized fibers had an obvious decrease, whereas the interlaminar shear strength (ILSS) value of corresponding carbon fiber reinforced polymers (CFRPs) increased in a large extent. The intensity of oxidative reaction varied with the change of ammonium-salt solutions and electrochemical oxidation in (NH{sub 4}){sub 3}PO{sub 4} electrolyte was of the most violence. The corresponding mechanism was also discussed and the result showed that the higher the concentration of OH{sup -} ions in the electrolytes, the violent the oxidative

Electrochemical and surface analytical investigation of the effects of Zn concentrations on characteristics of oxide films on 304 stainless steel in borated and lithiated high temperature water

International Nuclear Information System (INIS)

Liu, Xiahe; Wu, Xinqiang; Han, En-Hou

2013-01-01

Highlights: • Zn injection changed composition and structure of oxide films on 304 SS. • A few ppb Zn altered electrochemical behaviour, more Zn injection had little effect. • ≤50 ppb Zn injection could significantly affect formation of Zn-bearing oxides. • A modified PDM is proposed to explain inhibition mechanism of Zn injection. -- Abstract: The characteristics of oxide films formed on 304 stainless steel (SS) in borated and lithiated high temperature water with Zn injection of 0 ppb to100 ppb were investigated using in-situ potentiodynamic polarization curves, electrochemical impedance spectra at 573.15 K and ex-situ X-ray photoelectron spectroscopy (XPS). There was a high inhibition effect of Zn injection on the growth of oxide films in the testing solution. The lowest growth rate was corresponding to the highest Zn-injected level. The ≤50 ppb Zn injection based on plant experience could significantly affect the formation of Zn-bearing oxides on the surfaces, while >50 ppb Zn injection showed no obvious influence on the oxide films. A modified point defect model was proposed to discuss the effects of injected Zn concentrations on the oxide films on 304 SS in high temperature water

Degradation of Acetaminophen and Its Transformation Products in Aqueous Solutions by Using an Electrochemical Oxidation Cell with Stainless Steel Electrodes

Directory of Open Access Journals (Sweden)

Miguel Ángel López Zavala

2016-09-01

Full Text Available In this study, a novel electrochemical oxidation cell using stainless steel electrodes was found to be effective in oxidizing acetaminophen and its transformation products in short reaction times. Aqueous solutions of 10 mg/L-acetaminophen were prepared at pH 3, 5, 7, and 9. These solutions were electrochemically treated at direct current (DC densities of 5.7 mA/cm2, 7.6 mA/cm2, and 9.5 mA/cm2. The pharmaceutical and its intermediates/oxidation products were determined by using high pressure liquid chromatography (HPLC. The results showed that electrochemical oxidation processes occurred in the cell. Acetaminophen degradation rate constants increased proportionally with the increase of current intensity. High current densities accelerated the degradation of acetaminophen; however, this effect diminished remarkably at pH values greater than 5. At pH 3 and 9.5 mA/cm2, the fastest degradation of acetaminophen and its intermediates/oxidation products was achieved. To minimize the wear down of the electrodes, a current density ramp is recommended, first applying 9.5 mA/cm2 during 2.5 min or 7.6 mA/cm2 during 7.5 min and then continuing the electrochemical oxidation process at 5.7 mA/cm2. This strategy will hasten the acetaminophen oxidation, extend the electrode’s life, and shorten the reaction time needed to degrade the pharmaceutical and its intermediates/oxidation products. DC densities up to 9.5 mA/cm2 can be supplied by photovoltaic cells.

The mechanism of mediated oxidation of carboxylates with ferrocene as redox catalyst in absence of grafting effects. An experimental and theoretical approach

International Nuclear Information System (INIS)

Hernández-Muñoz, Lindsay S.; Galano, Annia; Astudillo-Sánchez, Pablo D.; Abu-Omar, Mahdi M.; González, Felipe J.

2014-01-01

Graphical abstract: - Highlights: • The mechanism of mediated oxidation of carboxylates. • Thermodynamics of the mediated Kolbe and Non-Kolbe mechanisms. • The oxidation of acetate and diphenylacetate ions by using ferrocene as redox catalyst. • Simulation and DFT calculations of the mediated oxidation of carboxylates. • Radical and carbocationic pathways in the carboxylate oxidation in acetonitrile. - Abstract: The oxidation of tetrabutylammonium carboxylates by using ferrocene derivatives as redox mediators has been recently used to perform the covalent grafting of carbon surfaces with organic and organometallic groups. Due to the intervention of this surface process, a partial description of the reaction mechanism has only been stated. Therefore, this article concerns about two features of the oxidation of carboxylates mediated by ferrocene. In the first part, it is discussed that in the oxidation of acetate ions by using ferrocene as redox catalyst, the gap between both oxidation potentials is very high, which means that the homogeneous electron transfer between the acetate ion and the electrochemically generated ferrocenium ion is energetically unfavorable. However, by using density functional theory calculations, it has been shown that the whole set of coupled chemical reactions involved either in a Kolbe or Non-Kolbe pathway drive the overall mechanisms towards a thermodynamically favorable situation. In order to avoid the strong covalent grafting process that occurs during the mediated oxidation of acetate ions, the second part of this work deals with the oxidation of tetrabutylammonium diphenylacetate by using ferrocene as a redox mediator in acetonitrile on glassy carbon electrodes. With this carboxylate, no electrode inhibition process occurs and, therefore cyclic voltammetry simulation was done to propose the electrochemical and chemical steps that are present when a carboxylate oxidation is performed in the presence of ferrocene derivatives

Electrochemical Study of Bromide in the Presence of 1,3-Indandione. Application to the Electrochemical Synthesis of Bromo Derivatives of 1,3-Indandione

OpenAIRE

Nematollahi, D.; Akaberi, N.

2001-01-01

The electrochemical oxidation of bromide in the presence of 1,3-indandione (1) in water/acetic acid and methanol/acetic acid mixtures has been studied by cyclic voltammetry and controlled-potential coulometry. The results indicate the participation of 1,3-indandione in the bromination reaction. On the basis of the electroanalytical and preparative results a reaction mechanism including electron transfer, chemical reaction and regeneration of bromide was discussed. The electrochemical synthesi...

Electrochemical Reduction of Oxygen and Nitric Oxide at Low Temperature on La1−xSrxFeO3−δ Cathodes

DEFF Research Database (Denmark)

Kammer Hansen, Kent

2014-01-01

A series of six strontium-substituted lanthanum ferrites (La1-xSrxFeO3-delta, x = 0.00, 0.05, 0.15, 0.25, 0.35, and 0.50) were synthesized using the glycine-nitrate process and evaluated as cathodes for the electrochemical reduction of oxygen and nitric oxide in the temperature range 200 to 400...... degrees C, using cone-shaped electrodes and cyclic voltammetry. It was shown that the ferrites had a higher activity towards the electrochemical reduction of nitric oxide than towards the electrochemical reduction of oxygen, in the investigated temperature range. The highest activity towards...... the electrochemical reduction of nitric oxide was found for La0.95Sr0.05FeO3-delta at 400 degrees C. This compound also showed the highest activity towards the electrochemical reduction of oxygen at 400 degrees C. The highest apparent selectivity was found for the compound LaFeO3 at 200 degrees C. The materials...

Highly efficient and energy-saving sectional treatment of landfill leachate with a synergistic system of biochemical treatment and electrochemical oxidation on a boron-doped diamond electrode

International Nuclear Information System (INIS)

Zhao Guohua; Pang Yaning; Liu Lei; Gao Junxia; Lv Baoying

2010-01-01

In this paper, a synergistic combination of the biochemical treatment and electrochemical oxidation (SBEO) of landfill leachate with sectional treatment on a boron-doped diamond (BDD) electrode is proposed. The first stage involves the synergistic system of biochemical treatment and electrochemical oxidation. Then, the second stage is followed by individual biochemical treatment. Comparisons among the SBEO, electrochemical oxidation, biochemical treatment and biochemical treatment with the pretreatment of electrochemical oxidation are made systematically, which show that this method is both highly efficient and energy-saving. The higher TOC removal and low energy cost on the BDD electrode can be explained by the conversion of the bio-refractory pollutants to biodegradable organics in the electrochemical oxidation process, improving the current efficiency and reducing the energy cost. The treated wastewater is degraded only with biochemical treatment in the second stage, which further improves efficiency and reduced the energy cost.

Electrochemical Energy Storage Applications of CVD Grown Niobium Oxide Thin Films.

Science.gov (United States)

Fiz, Raquel; Appel, Linus; Gutiérrez-Pardo, Antonio; Ramírez-Rico, Joaquín; Mathur, Sanjay

2016-08-24

We report here on the controlled synthesis, characterization, and electrochemical properties of different polymorphs of niobium pentoxide grown by CVD of new single-source precursors. Nb2O5 films deposited at different temperatures showed systematic phase evolution from low-temperature tetragonal (TT-Nb2O5, T-Nb2O5) to high temperature monoclinic modifications (H-Nb2O5). Optimization of the precursor flux and substrate temperature enabled phase-selective growth of Nb2O5 nanorods and films on conductive mesoporous biomorphic carbon matrices (BioC). Nb2O5 thin films deposited on monolithic BioC scaffolds produced composite materials integrating the high surface area and conductivity of the carbonaceous matrix with the intrinsically high capacitance of nanostructured niobium oxide. Heterojunctions in Nb2O5/BioC composites were found to be beneficial in electrochemical capacitance. Electrochemical characterization of Nb2O5/BioC composites showed that small amounts of Nb2O5 (as low as 5%) in conjunction with BioCarbon resulted in a 7-fold increase in the electrode capacitance, from 15 to 104 F g(-1), while imparting good cycling stability, making these materials ideally suited for electrochemical energy storage applications.

Polymer-directed synthesis of metal oxide-containing nanomaterials for electrochemical energy storage

Science.gov (United States)

Mai, Yiyong; Zhang, Fan; Feng, Xinliang

2013-12-01

Metal oxide-containing nanomaterials (MOCNMs) of controllable structures at the nano-scale have attracted considerable interest because of their great potential applications in electrochemical energy storage devices, such as lithium-ion batteries (LIBs) and supercapacitors. Among many structure-directing agents, polymers and macromolecules, including block copolymers (BCPs) and graphene, exhibit distinct advantages in the template-assisted synthesis of MOCNMs. In this feature article, we introduce the controlled preparation of MOCNMs employing BCPs and graphene as structure-directing agents. Typical synthetic strategies are presented for the control of structures and sizes as well as the improvement of physical properties and electrochemical performance of MOCNMs in LIBs and supercapacitors.

Comparative DEMS study on the electrochemical oxidation of carbon blacks

DEFF Research Database (Denmark)

Ashton, Sean James; Arenz, Matthias

2012-01-01

Publication year: 2012 Source:Journal of Power Sources, Volume 217 Sean J. Ashton, Matthias Arenz The intention of the study presented here is to compare the electrochemical oxidation tendencies of a pristine Ketjen Black EC300 high surface area (HSA) carbon black, and four graphitised counterparts...... heat-treated between 2100 and 3200 °C, such as those typically used as corrosion resistant carbon (CRC) supports for polymer electrolyte membrane fuel cell (PEMFC) catalysts. A methodology combining cyclic voltammetry (CV) and differential electrochemical mass spectrometry (DEMS) is used, which allows......; however, CRC samples graphitised =2800 °C did not exhibit this same behaviour. Highlights ¿ We quantitatively determine electrooxidation of carbon support materials. ¿ We can distinguish between the total and partial electrooxidation. ¿ Non or mildly heat treated carbon forms passivating layer. ¿ Heat...

High-performance symmetric electrochemical capacitor based on graphene foam and nanostructured manganese oxide

CSIR Research Space (South Africa)

Bello, A

2013-01-01

Full Text Available We have fabricated a symmetric electrochemical capacitor with high energy and power densities based on a composite of graphene foam (GF) with 80 wt% of manganese oxide (MnO(sub2)) deposited by hydrothermal synthesis. Raman spectroscopy and X...

Tailoring the Electrochemical and Mechanical Properties of PEDOT:PSS Films for Bioelectronics

KAUST Repository

Elmahmoudy, Mohammed

2017-02-21

The effect of 3-glycidoxypropyltrimethoxysilane (GOPS) content in poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) dispersions on the properties of films spun cast from these formulations is investigated. It has been found out that the concentration of GOPS has a tremendous, yet gradual impact on the electrical, electrochemical, and mechanical properties of the PEDOT:PSS/GOPS films and that there is an optimum concentration which maximizes a particular feature of the film such as its water uptake or elasticity. The benefits of aqueous stability and mechanical strength with GOPS are to be compensated by an increase in the electrochemical impedance. GOPS aids obtaining excellent mechanical integrity in aqueous media with still highly conducting properties. Moreover, active devices like organic electrochemical transistors that contain 1 wt% GOPS, which is a concentration that leads to film with high electrical conductivity with sufficient mechanical stability and softness, exhibit steady performance over three weeks. These results suggest that variations in the concentration of such an additive like GOPS can enable a facile co-optimization of electrical and mechanical properties of a conducting polymer film for in vivo bioelectronics application.

Electrochemical energy storage devices using electrodes incorporating carbon nanocoils and metal oxides nanoparticles

KAUST Repository

Baby, Rakhi Raghavan

2011-07-28

Carbon nanocoil (CNC) based electrodes are shown to be promising candidates for electrochemical energy storage applications, provided the CNCs are properly functionalized. In the present study, nanocrystalline metal oxide (RuO 2, MnO2, and SnO2) dispersed CNCs were investigated as electrodes for supercapacitor applications using different electrochemical methods. In the two electrode configuration, the samples exhibited high specific capacitance with values reaching up to 311, 212, and 134 F/g for RuO2/CNCs, MnO2/CNCs, and SnO2/CNCs, respectively. The values obtained for specific capacitance and maximum storage energy per unit mass of the composites were found to be superior to those reported for metal oxide dispersed multiwalled carbon nanotubes in two electrode configuration. In addition, the fabricated supercapacitors retained excellent cycle life with ∼88% of the initial specific capacitance retained after 2000 cycles. © 2011 American Chemical Society.

A Molecularly Imprinted Polymer with Incorporated Graphene Oxide for Electrochemical Determination of Quercetin

Directory of Open Access Journals (Sweden)

Xiwen He

2013-04-01

Full Text Available The molecularly imprinted polymer based on polypyrrole film with incorporated graphene oxide was fabricated and used for electrochemical determination of quercetin. The electrochemical behavior of quercetin on the modified electrode was studied in detail using differential pulse voltammetry. The oxidation peak current of quercetin in B-R buffer solution (pH = 3.5 at the modified electrode was regressed with the concentration in the range from 6.0 × 10−7 to 1.5 × 10−5 mol/L (r2 = 0.997 with a detection limit of 4.8 × 10−8 mol/L (S/N = 3. This electrode showed good stability and reproducibility. In the above mentioned range, rutin or morin which has similar structures and at the same concentration as quercetin did not interfere with the determination of quercetin. The applicability of the method for complex matrix analysis was also evaluated.

Simultaneous Electrochemical Detection of Dopamine and Ascorbic Acid Using an Iron Oxide/Reduced Graphene Oxide Modified Glassy Carbon Electrode

Directory of Open Access Journals (Sweden)

Teo Peik-See

2014-08-01

Full Text Available The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe3O4/rGO/GCE and its simultaneous detection of dopamine (DA and ascorbic acid (AA is described here. The Fe3O4/rGO nanocomposite was synthesized via a simple, one step in-situ wet chemical method and characterized by different techniques. The presence of Fe3O4 nanoparticles on the surface of rGO sheets was confirmed by FESEM and TEM images. The electrochemical behavior of Fe3O4/rGO/GCE towards electrocatalytic oxidation of DA was investigated by cyclic voltammetry (CV and differential pulse voltammetry (DPV analysis. The electrochemical studies revealed that the Fe3O4/rGO/GCE dramatically increased the current response against the DA, due to the synergistic effect emerged between Fe3O4 and rGO. This implies that Fe3O4/rGO/GCE could exhibit excellent electrocatalytic activity and remarkable electron transfer kinetics towards the oxidation of DA. Moreover, the modified sensor electrode portrayed sensitivity and selectivity for simultaneous determination of AA and DA. The observed DPVs response linearly depends on AA and DA concentration in the range of 1–9 mM and 0.5–100 µM, with correlation coefficients of 0.995 and 0.996, respectively. The detection limit of (S/N = 3 was found to be 0.42 and 0.12 µM for AA and DA, respectively.

The electrochemical transfer reactions and the structure of the iron|oxide layer|electrolyte interface

International Nuclear Information System (INIS)

Petrović, Željka; Metikoš-Huković, Mirjana; Babić, Ranko

2012-01-01

The thickness, barrier (protecting) and semiconducting properties of the potentiostatically formed oxide films on the pure iron electrode in an aqueous borate buffer solution were investigated by electrochemical quartz crystal nanobalance (EQCN), electrochemical impedance spectroscopy (EIS), and Mott–Schottky (MS) analysis. The thicknesses of the prepassive Fe(II)hydroxide layer (up to monolayer) nucleated on the bare iron surface and the passive Fe(II)/Fe(III) layer (up to 2 nm), deposited on the top of the first one, were determined using in situ gravimetry. Electronic properties of iron prepassive and passive films as well as ionic and electronic transfer reactions at the film|solution interface were discussed on the basis of a band structure model of the surface oxide film and the potential distribution at the interface. The anodic oxide film formation and cathodic decomposition are coupled processes and their reversible inter-conversion is mediated by the availability of free charge carriers on the electrode|solution interface. The structure of the reversible double layer at the iron oxide|solution interface was discussed based on the concept of the specific adsorption of the imidazolium cation on the negatively charged electrode surface at pH > pH pzc .

Enhancing the water oxidation activity of Ni2P nanocatalysts by iron-doping and electrochemical activation

International Nuclear Information System (INIS)

Liu, Guang; He, Dongying; Yao, Rui; Zhao, Yong; Li, Jinping

2017-01-01

Highlights: •A sol-gel method for synthesis of Fe-doping Ni 2 P nanocatalysts was present. •Fe-doping Ni 2 P sample exhibited high OER activity after electrochemical activation. •In situ formed Fe-NiOOH layer on activated Fe-Ni 2 P provided more active OER sites. -- Abstract: In this work, we reported a facile and safe route for synthesis of Ni 2 P nanocatalysts by sol-gel method and demonstrated that the oxygen evolution reaction (OER) activity of Ni 2 P nanocatalysts can be dramatically enhanced by iron-doping and electrochemical activation. Compared with the fresh Fe-doped Ni 2 P nanocatalysts, a stable Fe-NiOOH layer was formed on the surface of Fe-doped Ni 2 P nanoparticles by electrochemical activation, thus promoting the charge transfer ability and surface electrochemically active sites generation for the electrochemical activated Fe-doped Ni 2 P nanocatalysts, ultimately accounting for the improvement of water oxidation activity, which was evidenced by cyclic voltammograms (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectra (XPS) as well as high-resolution transmission electron microscopy (HR-TEM) measurements. For water oxidation reaction in 1 M KOH solution, the electrochemical activated Fe-doped Ni 2 P nanocatalysts can attain 10 mA/cm 2 at an overpotential of 292 mV with Tafel slope of 50 mV/dec, which was also much better than that of individual Ni 2 P, Fe 2 P nanocatalysts as well as commercial RuO 2 electrocatalyst. Moreover, long-term stability performance by chronoamperometric and chronopotentiometric tests for the activated Fe-doped Ni 2 P nanocatalysts exhibited no obvious decline within 56 h. It was demonstrated that modulating the OER catalytic activity for metal phosphide by iron-doping and electrochemical activation may provide new opportunities and avenues to engineer high performance electrocatalysts for water splitting.

Force-dominated non-equilibrium oxidation kinetics of tantalum

International Nuclear Information System (INIS)

Kar, Prasenjit; Wang, Ke; Liang, Hong

2008-01-01

Using a combined electrochemical and mechanical manipulation technique, we compared the equilibrium and non-equilibrium oxidation processes and states of tantalum. Experimentally, a setup was developed with an electrochemical system attached to a sliding mechanical configuration capable of friction force measurement. The surface chemistry of a sliding surface, i.e., tantalum, was modified through the electrolyte. The mechanically applied force was fixed and the dynamics of the surface was monitored in situ through a force sensor. The formation of non-equilibrium oxidation states of tantalum was found in oxidation limiting environment of acetic acid. An oxidative environment of deionized water saturated with KCl was used as comparison. We proposed a modified Arrhenius-Eyring equation in which the mechanical factor was considered. We found that the mechanical energy induced the non-stable-state reactions leading to metastable oxidation states of tantalum. This equation can be used to predict mechanochemical reactions that are important in many industrial applications

Novel Insights into the Electrochemical Detection of Nitric Oxide in Biological Systems

Czech Academy of Sciences Publication Activity Database

Pekarová, Michaela; Lojek, Antonín; Hrbáč, J.; Kuchta, R.; Kadlec, J.; Kubala, Lukáš

2014-01-01

Roč. 60, č. 1 (2014), s. 8-12 ISSN 0015-5500 R&D Projects: GA MŠk(CZ) EE2.3.30.0030; GA ČR(CZ) GP13-40882P Institutional support: RVO:68081707 Keywords : nitric oxide * electrochemical detector * biological systems Subject RIV: BO - Biophysics Impact factor: 1.000, year: 2014

Solid oxide fuel cells fueled with reducible oxides

Science.gov (United States)

Chuang, Steven S.; Fan, Liang Shih

2018-01-09

A direct-electrochemical-oxidation fuel cell for generating electrical energy includes a cathode provided with an electrochemical-reduction catalyst that promotes formation of oxygen ions from an oxygen-containing source at the cathode, a solid-state reduced metal, a solid-state anode provided with an electrochemical-oxidation catalyst that promotes direct electrochemical oxidation of the solid-state reduced metal in the presence of the oxygen ions to produce electrical energy, and an electrolyte disposed to transmit the oxygen ions from the cathode to the solid-state anode. A method of operating a solid oxide fuel cell includes providing a direct-electrochemical-oxidation fuel cell comprising a solid-state reduced metal, oxidizing the solid-state reduced metal in the presence of oxygen ions through direct-electrochemical-oxidation to obtain a solid-state reducible metal oxide, and reducing the solid-state reducible metal oxide to obtain the solid-state reduced metal.

Electrochemical Glucose Oxidation Using Glassy Carbon Electrodes Modified with Au-Ag Nanoparticles: Influence of Ag Content

Directory of Open Access Journals (Sweden)

Nancy Gabriela García-Morales

2015-01-01

Full Text Available This paper describes the application of glassy carbon modified electrodes bearing Aux-Agy nanoparticles to catalyze the electrochemical oxidation of glucose. In particular, the paper shows the influence of the Ag content on this oxidation process. A simple method was applied to prepare the nanoparticles, which were characterized by transmission electron microscopy, Ultraviolet-Visible spectroscopy, X-ray diffraction spectroscopy, and cyclic voltammetry. These nanoparticles were used to modify glassy carbon electrodes. The effectiveness of these electrodes for electrochemical glucose oxidation was evaluated. The modified glassy carbon electrodes are highly sensitive to glucose oxidation in alkaline media, which could be attributed to the presence of Aux-Agy nanoparticles on the electrode surface. The voltammetric results suggest that the glucose oxidation speed is controlled by the glucose diffusion to the electrode surface. These results also show that the catalytic activity of the electrodes depends on the Ag content of the nanoparticles. Best results were obtained for the Au80-Ag20 nanoparticles modified electrode. This electrode could be used for Gluconic acid (GA production.

Electrochemical promotion of oxidative coupling of methane on platinum/polybenzimidazole catalyst

DEFF Research Database (Denmark)

Petrushina, Irina; Bandur, Viktor; Bjerrum, Niels

2002-01-01

The electrochemical promotion of catalytic methane oxidation was studied using a (CH4,O-2,Ar), Pt\\polybenzimidazole (PBI)-H3PO4\\Pt,(H-2,Ar) fuel cell at 135degreesC. It has been found that C2H2, CO2, and water are the main oxidation products. Without polarization the yield of C2H2 was 0......, meaning that there was a maximum promotion effect at a polarization of -0.15 V, or 0.45 V catalyst potential vs. a hydrogen electrode (3.8% C2H2 yield). The catalytic rate enhancement ratio, r(C-2)/r(o)(C-2), at this maximum was 4.2. There was no C2H2 production at polarization greater than or equal to0.......9% and the yield of CO2 was 7.3%. This means that C-2 open-circuit selectivity was approximately 11%. Open-circuit voltage was around 0.6 V. It has been shown that the CH4 --> C2H2 catalytic reaction can be electrochemically promoted at negative polarization and exhibits a clear "volcano-type'' promotion behavior...

Thermally Reduced Graphene Oxide Electrochemically Activated by Bis-Spiro Quaternary Alkyl Ammonium for Capacitors.

Science.gov (United States)

He, Tieshi; Meng, Xiangling; Nie, Junping; Tong, Yujin; Cai, Kedi

2016-06-08

Thermally reduced graphene oxide (RGO) electrochemically activated by a quaternary alkyl ammonium-based organic electrolytes/activated carbon (AC) electrode asymmetric capacitor is proposed. The electrochemical activation process includes adsorption of anions into the pores of AC in the positive electrode and the interlayer intercalation of cations into RGO in the negative electrode under high potential (4.0 V). The EA process of RGO by quaternary alkyl ammonium was investigated by X-ray diffraction and electrochemical measurements, and the effects of cation size and structure were extensively evaluated. Intercalation by quaternary alkyl ammonium demonstrates a small degree of expansion of the whole crystal lattice (d002) and a large degree of expansion of the partial crystal lattice (d002) of RGO. RGO electrochemically activated by bis-spiro quaternary alkyl ammonium in propylene carbonate/AC asymmetric capacitor exhibits good activated efficiency, high specific capacity, and stable cyclability.

In vitro degradation and electrochemical corrosion evaluations of microarc oxidized pure Mg, Mg–Ca and Mg–Ca–Zn alloys for biomedical applications

International Nuclear Information System (INIS)

Pan, Yaokun; He, Siyu; Wang, Diangang; Huang, Danlan; Zheng, Tingting; Wang, Siqi; Dong, Pan; Chen, Chuanzhong

2015-01-01

Calcium phosphate (CaP) ceramic coatings were fabricated on pure magnesium (Mg) and self-designed Mg–0.6Ca, Mg–0.55Ca–1.74Zn alloys by microarc oxidation (MAO). The coating formation, growth and biomineralization mechanisms were discussed. The coating degradability and bioactivity were evaluated by immersion tests in trishydroxymethyl–aminomethane hydrochloric acid (Tris–HCl) buffer and simulated body fluid (SBF) solutions, respectively. The coatings and corrosion products were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) and fourier transform infrared spectrometer (FT-IR). The electrochemical workstation was used to investigate the electrochemical corrosion behaviors of substrates and coatings. Results showed that Mg–0.55Ca–1.74Zn alloy exhibits the highest mechanical strength and electrochemical corrosion resistance among the three alloys. The MAO-coated Mg–0.55Ca–1.74Zn alloy has the potential to be served as a biodegradable implant. - Highlights: • Ca and Zn are suitable alloying elements in the development of novel Mg implants. • Micropore and crack are two factors affecting the MAO coating corrosion behavior. • Dissolution and precipitation of apatites on MAO coating are reversible reactions

In vitro degradation and electrochemical corrosion evaluations of microarc oxidized pure Mg, Mg–Ca and Mg–Ca–Zn alloys for biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Pan, Yaokun; He, Siyu; Wang, Diangang, E-mail: wangdg@sdu.edu.cn; Huang, Danlan; Zheng, Tingting; Wang, Siqi; Dong, Pan; Chen, Chuanzhong, E-mail: czchen@sdu.edu.cn

2015-02-01

Calcium phosphate (CaP) ceramic coatings were fabricated on pure magnesium (Mg) and self-designed Mg–0.6Ca, Mg–0.55Ca–1.74Zn alloys by microarc oxidation (MAO). The coating formation, growth and biomineralization mechanisms were discussed. The coating degradability and bioactivity were evaluated by immersion tests in trishydroxymethyl–aminomethane hydrochloric acid (Tris–HCl) buffer and simulated body fluid (SBF) solutions, respectively. The coatings and corrosion products were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) and fourier transform infrared spectrometer (FT-IR). The electrochemical workstation was used to investigate the electrochemical corrosion behaviors of substrates and coatings. Results showed that Mg–0.55Ca–1.74Zn alloy exhibits the highest mechanical strength and electrochemical corrosion resistance among the three alloys. The MAO-coated Mg–0.55Ca–1.74Zn alloy has the potential to be served as a biodegradable implant. - Highlights: • Ca and Zn are suitable alloying elements in the development of novel Mg implants. • Micropore and crack are two factors affecting the MAO coating corrosion behavior. • Dissolution and precipitation of apatites on MAO coating are reversible reactions.

Influence of oxalic acid on the dissolution kinetics of manganese oxide

Science.gov (United States)

Godunov, E. B.; Artamonova, I. V.; Gorichev, I. G.; Lainer, Yu. A.

2012-11-01

The kinetics and electrochemical processes of the dissolution of manganese oxides with various oxidation states in sulfuric acid solutions containing oxalate ion additives is studied under variable conditions (concentration, pH, temperature). The parameters favoring a higher degree of the dissolution of manganese oxides in acidic media are determined. The optimal conditions are found for the dissolution of manganese oxides in acidic media in the presence of oxalate ions. The mechanism proposed for the dissolution of manganese oxides in sulfuric acid solutions containing oxalic acid is based on the results of kinetic and electrochemical studies. The steps of the dissolution mechanism are discussed.

Electrochemical oxidation of 3,5-di-tert-butylcatechol: Synthesis and characterization of the formed ortho-benzoquinhydrone derivative

International Nuclear Information System (INIS)

Nematollahi, D.; Shayani-Jam, H.

2006-01-01

Electrochemical oxidation of 3,5-di-tert-butylcatechol (1) has been studied in ethanol/water mixtures by means of cyclic voltammetry and controlled-potential coulometry. The results revealed that 3,5-di-tert-butyl-1,2-benenzoquinone (2) derived from oxidation of 3,5-di-tert-butylcatechol participate in noncovalently linked interactions with 1 converted to an ortho-benzoquinhydrone (3). The structure of 3 was characterized by MS, IR, 1 H NMR and 13 C NMR. The 1 H NMR studies reveal that the benzoquinhydrone complex 3 is stabilized by one H-bonding interaction. In this work we derived a novel ortho-bezoquinhydrone type complex (3) based on electrochemical oxidation of 3,5-di-tert-butylcatechol at carbon electrode in an undivided cell

Electrochemical oxidation of ethanol using PtRh/C electrocatalysts in alkaline medium and synthesized by sodium borohydride and alcohol reduction

International Nuclear Information System (INIS)

Fontes, Eric Hossein

2017-01-01

PtRh/C were prepared by the following atomic proportions: (100,0), (0,100), (90,10), (70,30) and (50,50). The methods employed in the synthesis of these materials were reduction by sodium borohydride and reduction by alcohol. The metal salts used were H 2 PtCl 6 3•6H 2 0 and (RhNO 3 ) 3 , the support used was Carbon black XC72 and the bulk metal composition was 20% and 80% of support. The electrocatalysts were characterized by Energy Dispersive X-ray spectroscopy, X-ray diffraction and Transmission electron microscopy. The ethanol electrochemical oxidation mechanism was investigated by in situ Fourier Transform Infrared Spectroscopy couple to an Attenuated Total Reflection technique. The electrocatalytic activity were evaluated by Cyclic Voltammetry, Linear Sweep Voltammetry and Chronoamperometry techniques. The Fuel Cells tests were made in a single direct alcohol fuel cell with alkaline membrane. The working electrodes were prepared by a thin porous coating technique. X-ray diffraction allowed to verify metallic alloys, segregate phases and to calculate the percentage of metallic alloys. It was else possible to identify crystallographic phases. Infrared Spectroscopy allowed to verify that the electrochemical oxidation of ethanol was carried out by an incomplete mechanism. PtRh(70:30)/C prepared by sodium borohydride produced large amounts of carbon dioxide and acetaldehyde. Rh/C showed electrocatalytic activity when compared with other materials studied.

Metallic oxide reduction in molten chlorides: electrochemical solvent regeneration

International Nuclear Information System (INIS)

Martin, A.

2005-11-01

We consider the reaction MeO 2 + 2 Ca → Me + 2 CaO in CaCl 2 at 850 C. We want to re-use the molten media, which is a CaO-CaCl 2 melt at the end of the reaction. For that we want to de-oxidize it. When we electrolyse CaO we obtain Ca and O 2 ; it presents three difficult points that we want to solve: (1) it is difficult to oxidize O 2 - without oxidizing Cl - because their oxidation potential are very closed, (2) the chemical or electrochemical anodic corrosion, (3) the anodically produced gas dissolution in the mell One way of avoiding chlorine gas evolution is to prevent chloride ions from reaching the anode, for example using a selective membrane. Furthermore, the best prevention of the anodically produced gas dissolution in the melt can be done with a compartment, physically separating the anode from the rest of the reactional media. Thus in this work we have used an yttria stabilized zirconia membrane as a selective membrane for the deoxidation of a CaO-CaCl 2 melt at 850 C. (author)

Remediation of a winery wastewater combining aerobic biological oxidation and electrochemical advanced oxidation processes.

Science.gov (United States)

Moreira, Francisca C; Boaventura, Rui A R; Brillas, Enric; Vilar, Vítor J P

2015-05-15

Apart from a high biodegradable fraction consisting of organic acids, sugars and alcohols, winery wastewaters exhibit a recalcitrant fraction containing high-molecular-weight compounds as polyphenols, tannins and lignins. In this context, a winery wastewater was firstly subjected to a biological oxidation to mineralize the biodegradable fraction and afterwards an electrochemical advanced oxidation process (EAOP) was applied in order to mineralize the refractory molecules or transform them into simpler ones that can be further biodegraded. The biological oxidation led to above 97% removals of dissolved organic carbon (DOC), chemical oxygen demand (COD) and 5-day biochemical oxygen demand (BOD5), but was inefficient on the degradation of a bioresistant fraction corresponding to 130 mg L(-1) of DOC, 380 mg O2 L(-1) of COD and 8.2 mg caffeic acid equivalent L(-1) of total dissolved polyphenols. Various EAOPs such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), UVA photoelectro-Fenton (PEF) and solar PEF (SPEF) were then applied to the recalcitrant effluent fraction using a 2.2 L lab-scale flow plant containing an electrochemical cell equipped with a boron-doped diamond (BDD) anode and a carbon-PTFE air-diffusion cathode and coupled to a photoreactor with compound parabolic collectors (CPCs). The influence of initial Fe(2+) concentration and current density on the PEF process was evaluated. The relative oxidative ability of EAOPs increased in the order AO-H2O2 < EF < PEF ≤ SPEF. The SPEF process using an initial Fe(2+) concentration of 35 mg L(-1), current density of 25 mA cm(-2), pH of 2.8 and 25 °C reached removals of 86% on DOC and 68% on COD after 240 min, regarding the biologically treated effluent, along with energy consumptions of 45 kWh (kg DOC)(-1) and 5.1 kWh m(-3). After this coupled treatment, color, odor, COD, BOD5, NH4(+), NO3(-) and SO4(2-) parameters complied with the legislation targets and, in addition, a total

Kinetic investigation of vanadium (V)/(IV) redox couple on electrochemically oxidized graphite electrodes

International Nuclear Information System (INIS)

Wang, Wenjun; Wei, Zengfu; Su, Wei; Fan, Xinzhuang; Liu, Jianguo; Yan, Chuanwei; Zeng, Chaoliu

2016-01-01

Highlights: • The VO_2"+/VO"2"+ redox reaction of the electrode could be facilitated to some extent with the increasing anodic corrosion. • A real reaction kinetic equation for the oxidation of VO"2"+ on the electrochemically oxidized electrode has been firstly obtained. • The establishment of the kinetic equation is conducive to predict polarization behaviors of the electrodes in engineering application. - Abstract: The morphology, surface composition, wettability and the kinetic parameters of the electrochemically oxidized graphite electrodes obtained under different anodic polarization conditions have been examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle measurements, steady-state polarization and cyclic voltammetry (CV) tests, with an attempt to investigate the inherent correlation between the physicochemical properties and the kinetic characteristics for carbon electrodes used in an all-vanadium redox flow battery (VRFB). When the anodic polarization potential raises up to 1.8 V vs. SCE, the anodic corrosion of the graphite might happen and a large number of oxygen-containing functional groups generate. The VO_2"+/VO"2"+ redox reaction can be facilitated and the reaction reversibility tends to become better with the increasing anodic potential, possibly owing to the increased surface oxides and the resulting improved wettability of the electrode. Based on this, a real reaction kinetic equation for the oxidation of VO"2"+ has been obtained on the electrode polarized at 1.8 V vs. SCE and it can be also well used to predict the polarization behavior of the oxidized electrode in vanadium (IV) acidic solutions.

Enhanced photocatalytic performance of ZnO nanostructures by electrochemical hybridization with graphene oxide

Science.gov (United States)

Pruna, A.; Wu, Z.; Zapien, J. A.; Li, Y. Y.; Ruotolo, A.

2018-05-01

Synthesis of zinc oxide (ZnO) nanostructures is reported by electrochemical deposition from an aqueous electrolyte in presence of graphene oxide (GO) with varying oxidation degree. The properties of hybrids were investigated by scanning electron microscopy, X-ray diffraction, Raman, Fourier-Transform Infrared and X-ray photoelectron spectroscopy techniques and photocatalytic measurements. The results indicated the electrodeposition of ZnO in presence of GO with increased oxygen content led to marked differences in the morphology while Raman measurements indicated an increased defect level both in the ZnO and the electrochemically reduced GO (ErGO) within the hybrids. The decrease in C/O atomic ratio of GO (from 0.79 to 0.71) employed for the electrodeposition of ZnO resulted in an increase in photocatalytic efficiency for methylene blue degradation under UV irradiation from 4-folds to 10-folds with respect to non-hybridized ZnO. The observed synergetic effect of cathodic deposition potential and oxygen content in GO towards improving the photocatalytic activity of immobilized ZnO is expected to contribute to further development of more effective deposition approaches for the preparation of high performance hybrid nanostructures.

Photo-assisted electrochemical oxidation of the urea onto TiO2-nanotubes modified by hematite

Directory of Open Access Journals (Sweden)

Waleed M. Omymen

2017-12-01

Full Text Available The electrochemical oxidation of the urea in near neutral pH is investigated on platinum electrode. It is shown that oxidation reaction is practically inhibited up to the potentials of ∼0.9 V. The same reaction is investigated onto electrochemically obtained titanium dioxide nanotubes modified by hematite using facile, low-cost successive ion layer adsorption and reaction (SILAR method. It is shown that such system possesses electrocatalytic activity at very low potentials, and activity can be further improved by the illumination of the electrode in the photo-assisted reaction. The possible application of the photoactive anode is considered in the application of urea based water electrolysis and urea based fuel cell. Keywords: Photoelectrochemical cell, Water electrolysis, Fuel cell, SILAR

Preparing cuprous oxide nanomaterials by electrochemical method for non-enzymatic glucose biosensor

Science.gov (United States)

Nguyen, Thu-Thuy; Huy, Bui The; Hwang, Seo-Young; Vuong, Nguyen Minh; Pham, Quoc-Thai; Nghia, Nguyen Ngoc; Kirtland, Aaron; Lee, Yong-Ill

2018-05-01

Cuprous oxide (Cu2O) nanostructure has been synthesized using an electrochemical method with a two-electrode system. Cu foils were used as electrodes and NH2(OH) was utilized as the reducing agent. The effects of pH and applied voltages on the morphology of the product were investigated. The morphology and optical properties of Cu2O particles were characterized using scanning electron microscopy, x-ray diffraction, and diffuse reflectance spectra. The synthesized Cu2O nanostructures that formed in the vicinity of the anode at 2 V and pH = 11 showed high uniform distribution, small size, and good electrochemical sensing. These Cu2O nanoparticles were coated on an Indium tin oxide substrate and applied to detect non-enzyme glucose as excellent biosensors. The non-enzyme glucose biosensors exhibited good performance with high response, good selectivity, wide linear detection range, and a low detection limit at 0.4 μM. Synthesized Cu2O nanostructures are potential materials for a non-enzyme glucose biosensor.

Coupled Mechanical-Electrochemical-Thermal Analysis of Failure Propagation in Lithium-ion Batteries

Energy Technology Data Exchange (ETDEWEB)

Zhang, Chao; Santhanagopalan, Shriram; Pesaran, Ahmad

2016-07-28

This is a presentation given at the 12th World Congress for Computational Mechanics on coupled mechanical-electrochemical-thermal analysis of failure propagation in lithium-ion batteries for electric vehicles.

Direct electrochemical imidation of aliphatic amines via anodic oxidation.

Science.gov (United States)

Zhang, Li; Su, Ji-Hu; Wang, Sujing; Wan, Changfeng; Zha, Zhenggen; Du, Jiangfeng; Wang, Zhiyong

2011-05-21

Direct electrochemical synthesis of sulfonyl amidines from aliphatic amines and sulfonyl azides was realized with good to excellent yields. Traditional tertiary amine substrates were broadened to secondary and primary amines. The reaction intermediates were observed and a reaction mechanism was proposed and discussed. © The Royal Society of Chemistry 2011

An overview on the removal of synthetic dyes from water by electrochemical advanced oxidation processes.

Science.gov (United States)

Nidheesh, P V; Zhou, Minghua; Oturan, Mehmet A

2018-04-01

Wastewater containing dyes are one of the major threats to our environment. Conventional methods are insufficient for the removal of these persistent organic pollutants. Recently much attention has been received for the oxidative removal of various organic pollutants by electrochemically generated hydroxyl radical. This review article aims to provide the recent trends in the field of various Electrochemical Advanced Oxidation Processes (EAOPs) used for removing dyes from water medium. The characteristics, fundamentals and recent advances in each processes namely anodic oxidation, electro-Fenton, peroxicoagulation, fered Fenton, anodic Fenton, photoelectro-Fenton, sonoelectro-Fenton, bioelectro-Fenton etc. have been examined in detail. These processes have great potential to destroy persistent organic pollutants in aqueous medium and most of the studies reported complete removal of dyes from water. The great capacity of these processes indicates that EAOPs constitute a promising technology for the treatment of the dye contaminated effluents. Copyright © 2018 Elsevier Ltd. All rights reserved.

Electrochemical Oxidation of Cysteine at a Film Gold Modified Carbon Fiber Microelectrode Its Application in a Flow—Through Voltammetric Sensor

Science.gov (United States)

Wang, Lai-Hao; Huang, Wen-Shiuan

2012-01-01

A flow-electrolytical cell containing a strand of micro Au modified carbon fiber electrodes (CFE) has been designedand characterized for use in a voltammatric detector for detecting cysteine using high-performance liquid chromatography. Cysteine is more efficiently electrochemical oxidized on a Au /CFE than a bare gold and carbon fiber electrode. The possible reaction mechanism of the oxidation process is described from the relations to scan rate, peak potentials and currents. For the pulse mode, and measurements with suitable experimental parameters, a linear concentration from 0.5 to 5.0 mg·L−1 was found. The limit of quantification for cysteine was below 60 ng·mL−1. PMID:22737024

Enriching distinctive microbial communities from marine sediments via an electrochemical-sulfide-oxidizing process on carbon electrodes

Directory of Open Access Journals (Sweden)

Shiue-Lin eLi

2015-02-01

Full Text Available Sulfide is a common product of marine anaerobic respiration, and a potent reactant biologically and geochemically. Here we demonstrate the impact on microbial communities with the removal of sulfide via electrochemical methods. The use of differential pulse voltammetry revealed that the oxidation of soluble sulfide was seen at + mV (vs. SHE at all pH ranges tested (from pH = 4 to 8, while non-ionized sulfide, which dominated at pH = 4 was poorly oxidized via this process. Two mixed cultures (CAT and LA were enriched from two different marine sediments (from Catalina Island, CAT; from the Port of Los Angeles, LA in serum bottles using a seawater medium supplemented with lactate, sulfate, and yeast extract, to obtain abundant biomass. Both CAT and LA cultures were inoculated in electrochemical cells (using yeast-extract-free seawater medium as an electrolyte equipped with carbon-felt electrodes. In both cases, when potentials of +630 or 130 mV (vs. SHE were applied, currents were consistently higher at +630 then at 0 mV, indicating more sulfide being oxidized at the higher potential. In addition, higher organic-acid and sulfate conversion rates were found at +630 mV with CAT, while no significant differences were found with LA at different potentials. The results of microbial-community analyses revealed a decrease in diversity for both CAT and LA after electrochemical incubation. In addition, some bacteria (e.g., Clostridium and Arcobacter not well known to be capable of extracellular electron transfer, were found to be dominant in the electrochemical cells. Thus, even though the different mixed cultures have different tolerances for sulfide, electrochemical-sulfide removal can lead to major population changes.

Novel quasi-symmetric solid oxide fuel cells with enhanced electrochemical performance

KAUST Repository

Chen, Yonghong

2016-02-16

Symmetrical solid oxide fuel cell (SSOFC) using same materials as both anode and cathode simultaneously has gained extensively attentions, which can simplify fabrication process, minimize inter-diffusion between components, enhance sulfur and coking tolerance by operating the anode as the cathode in turn. With keeping the SSOFC\\'s advantages, a novel quasi-symmetrical solid oxide fuel cell (Q-SSOFC) is proposed to further improve the performance, which optimally combines two different SSOFC electrode materials as both anode and cathode simultaneously. PrBaFe2O5+δ (PBFO) and PrBaFe1.6Ni0.4O5+δ (PBFNO, Fe is partially substituted by Ni.) are prepared and applied as both cathode and anode for SSOFC, which exhibit desirable chemical and thermal compatibility with Sm0.8Ce0.2O1.9 (SDC) electrolyte. PBFO cathode exhibits higher oxygen reduction reaction (ORR) activity than PBFNO cathode in air, whereas PBFNO anode exhibits higher hydrogen oxidation reaction (HOR) activity than PBFO anode in H2. The as-designed Q-SSOFC of PBFNO/SDC/PBFO exhibits higher electrochemical performance than the conventional SSOFCs of both PBFO/SDC/PBFO and PBFNO/SDC/PBFNO. The superior performance of Q-SSOFC is attributed to the lowest polarization resistance (Rp). The newly developed Q-SSOFCs open doors for further improvement of electrochemical performance in SSOFC, which hold more promise for various potential applications. © 2016 Elsevier B.V. All rights reserved.

Electrodeposited nickel oxide and graphene modified carbon ionic liquid electrode for electrochemical myglobin biosensor

International Nuclear Information System (INIS)

Sun, Wei; Gong, Shixing; Deng, Ying; Li, Tongtong; Cheng, Yong; Wang, Wencheng; Wang, Lei

2014-01-01

By using ionic liquid 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) as the substrate electrode, graphene (GR) and nickel oxide (NiO) were in situ electrodeposited step by step to get a NiO/GR nanocomposite modified CILE. Myoglobin (Mb) was further immobilized on the surface of NiO/GR/CILE with a Nafion film to get the electrochemical sensor denoted as Nafion/Mb/NiO/GR/CILE. Cyclic voltammetric experiments indicated that a pair of well-defined quasi-reversible redox peaks appeared in pH 3.0 phosphate buffer solution with the formal peak potential (E 0′ ) located at − 0.188 V (vs. SCE), which was the typical characteristics of Mb Fe(III)/Fe(II) redox couples. So the direct electron transfer of Mb was realized and promoted due to the presence of the NiO/GR nanocomposite on the electrode. Based on the cyclic voltammetric data, the electrochemical parameters of Mb on the modified electrode were calculated. The Mb modified electrode showed an excellent electrocatalytic activity towards the reduction of different substrates including trichloroacetic acid and H 2 O 2 . Therefore a third-generation electrochemical Mb biosensor based on NiO/GR/CILE was constructed with good stability and reproducibility. - Highlights: • Graphene and nickel oxide nanocomposites were prepared by electrodeposition. • Electrochemical myoglobin sensor was prepared on a nanocomposite modified electrode. • Direct electrochemistry and electrocatalysis of myglobin were realized

Electrochemical oxidation of 2,4,5-trichlorophenoxyacetic acid by metal-oxide-coated Ti electrodes.

Science.gov (United States)

Maharana, Dusmant; Xu, Zesheng; Niu, Junfeng; Rao, Neti Nageswara

2015-10-01

Electrochemical oxidation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) over metal-oxide-coated Ti anodes, i.e., Ti/SnO2-Sb/Ce-PbO2, Ti/SnO2-Sb and Ti/RuO2, was examined. The degradation efficiency of over 90% was attained at 20 min at different initial concentrations (0.5-20 mg L(-1)) and initial pH values (3.1-11.2). The degradation efficiencies of 2,4,5-T on Ti/SnO2-Sb/Ce-PbO2, Ti/SnO2-Sb and Ti/RuO2 anodes were higher than 99.9%, 97.2% and 91.5% at 30 min, respectively, and the respective total organic carbon removal ratios were 65.7%, 54.6% and 37.2%. The electrochemical degradation of 2,4,5-T in aqueous solution followed pseudo-first-order kinetics. The compounds, i.e., 2,5-dichlorohydroquinone and 2,5-dihydroxy-p-benzoquinone, have been identified as the main aromatic intermediates by liquid chromatography-mass spectrometry. The results showed that the energy efficiencies of 2,4,5-T (20 mg L(-1)) degradation with Ti/SnO2-Sb/Ce-PbO2 anode at the optimal current densities from 2 to 16 mA cm(-2) ranged from 8.21 to 18.73 kWh m(-3). Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of the electrochemical passivation on the corrosion behaviour of austenitic stainless steel

International Nuclear Information System (INIS)

Barbucci, A.; Delucchi, M.; Panizza, M.; Farne, G.; Cerisola, G.

2004-01-01

Cold rolled SS is also fruitfully used in deep drawing however the presence of scales or oxides on the surface reduces the life of the tools and emphasises creep phenomena of the material. Then a cleaning of the SS surface from these impurities is necessary. Oxides can be formed during the hot rolling preceding the cold one, or during the annealing performed between the several steps of thickness reduction. The annealing helps to decrease the work hardening occurring during the process. Normally this heat treatment is performed in reducing atmosphere of pure hydrogen (bright annealing), but even in this conditions oxides are formed on the SS surface. To avoid this uncontrolled oxide growth one method recently applied is an electrochemical cleaning performed in an electrolytic solution containing chrome, generally called electrochemical passivation. The electrochemical passivation allows the dissolution of the contaminating hard particles on the strips. Few scientific contributions are available in literature, which explain in detail the process mechanism. The aim of this work is to investigate if the electrochemical passivated surface acts in a different way with regard to corrosion phenomena with respect to conventional SS. Electrochemical measurements like polarisation, chrono-amperometries and surface analysis were used to investigate the corrosion behaviour of electrochemically passivated AISI 304L and AISI 305. The effect of some process parameters were considered, too. (authors)

Effect of the electrochemical passivation on the corrosion behaviour of austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Barbucci, A.; Delucchi, M.; Panizza, M.; Farne, G.; Cerisola, G. [DICheP, University of Genova, P.le Kennedy 1, 16129 Genova (Italy)

2004-07-01

Cold rolled SS is also fruitfully used in deep drawing however the presence of scales or oxides on the surface reduces the life of the tools and emphasises creep phenomena of the material. Then a cleaning of the SS surface from these impurities is necessary. Oxides can be formed during the hot rolling preceding the cold one, or during the annealing performed between the several steps of thickness reduction. The annealing helps to decrease the work hardening occurring during the process. Normally this heat treatment is performed in reducing atmosphere of pure hydrogen (bright annealing), but even in this conditions oxides are formed on the SS surface. To avoid this uncontrolled oxide growth one method recently applied is an electrochemical cleaning performed in an electrolytic solution containing chrome, generally called electrochemical passivation. The electrochemical passivation allows the dissolution of the contaminating hard particles on the strips. Few scientific contributions are available in literature, which explain in detail the process mechanism. The aim of this work is to investigate if the electrochemical passivated surface acts in a different way with regard to corrosion phenomena with respect to conventional SS. Electrochemical measurements like polarisation, chrono-amperometries and surface analysis were used to investigate the corrosion behaviour of electrochemically passivated AISI 304L and AISI 305. The effect of some process parameters were considered, too. (authors)

The influence of TiO{sub 2} and aeration on the kinetics of electrochemical oxidation of phenol in packed bed reactor

Energy Technology Data Exchange (ETDEWEB)

Wang Lizhang [College of Environment and Spatial Informatics, China University of Mining and Technology, South Jiefang Road, Quanshan District, Xuzhou City, Jiangsu 221008 (China)], E-mail: wlzh0731@126.com; Zhao Yuemin [School of Chemical Engineering and Technology, China University of Mining and Technology, South Jiefang Road, Quanshan District, Xuzhou City, Jiangsu 221008 (China)], E-mail: ymzhao@cumt.edu.cn; Fu Jianfeng [Department of Environmental Engineering, Southeast University, Nanjing City, Jiangsu 210096 (China)

2008-12-30

The electrochemical oxidation of phenolic wastewater in a lab-scale reactor, packed into granular activated carbon (GAC) with Ti/SnO{sub 2} anodes and stainless steel cathodes, was interpreted in this study. GAC saturated rapidly if it was only used as sorbent, but application of suitable electric energy for the system simultaneously could recover the adsorption ability of GAC and maintain the continuous running effectively. The titanium dioxide (TiO{sub 2}) as catalyst and airflow were also applied to the electrochemical reactor to examine the enhancement for phenol oxidation process. Results revealed that the electrochemical degradation of phenol could be reasonably described by first-order kinetics. In addition, it was illustrated that acid region, increased voltage, more dosage of TiO{sub 2} and higher aeration intensity were all beneficial parameters for phenol oxidation rates. By inspecting the relationship between the rate constants (k) and influencing factors, respectively, an overall kinetic model for phenol oxidation was proposed. The kinetics obtained from the experiments under corresponding electrochemical conditions could provide an accurate estimation of phenol concentration effluent and better design of the packed bed reactor.

Increased electrochemical properties of ruthenium oxide and graphene/ruthenium oxide hybrid dispersed by polyvinylpyrrolidone

International Nuclear Information System (INIS)

Chen, Yao; Zhang, Xiong; Zhang, Dacheng; Ma, Yanwei

2012-01-01

Highlights: ► A good dispersion of RuO 2 and graphene/RuO 2 is obtained by polyvinylpyrrolidone. ► PVP as a dispersant also can prevent the formation of metal Ru in graphene/RuO 2 . ► The max capacitances of the hybrid and RuO 2 reach 435 and 597 F g −1 at 0.2 A g −1 . ► The hybrid shows the best rate capability of 39% at 50 A g −1 . - Abstract: Ruthenium oxide has been prepared by a sol–gel method. Polyvinylpyrrolidone (PVP) as an excellent polymeric dispersant is adopted to prevent aggregation of ruthenium oxide. In order to enhance the rate capability of ruthenium oxide, graphene with residual oxygen functional groups as a 2D support has been merged into ruthenium oxide. These oxygen functional groups not only favor to form stable few layers of graphene colloids, but also offer the sites to anchor ruthenium oxide nanoparticles. X-ray diffraction infers that PVP can also hinder the partial formation of Ru by blocking the direct contact between the Ru 3+ and the graphene in the sol–gel synthesis of the hybrids. The ruthenium oxide and the graphene/ruthenium oxide hybrids dispersed by PVP have superior electrochemical properties due to good dispersing and protecting ability of PVP. Especially, the hybrids using PVP exhibit the best rate capability, indicating that the composites possess an advanced structure of combining sheets and particles in nano-scale.

Evaluation of mechanically treated cerium (IV) oxides as corrosion inhibitors for galvanized steel

Energy Technology Data Exchange (ETDEWEB)

Deflorian, F., E-mail: flavio.deflorian@ing.unitn.it [Department of Materials Engineering and Industrial Technology, University of Trento, Via Mesiano 77, 38123 Trento (Italy); Fedel, M.; Rossi, S. [Department of Materials Engineering and Industrial Technology, University of Trento, Via Mesiano 77, 38123 Trento (Italy); Kamarchik, P. [PPG Industries, Coatings Innovation Center, 4325 Rosanna Drive, Allison Park, PA 15101 (United States)

2011-09-30

The use of cerium salts as corrosion inhibitors for hot dip galvanized steel has been object of a numerous studies in the last few years. The role of cerium ions as corrosion inhibitors was proved: cerium is able to block the cathodic sites of the metal, forming insoluble hydroxides and oxides on the zinc surface. This fact leads to a dramatic decrease of the cathodic current densities and, therefore, to a reduction the overall corrosion processes. On the other hand, the potential of cerium oxides as corrosion inhibitors was also proposed. However, the real effectiveness of this kind of anticorrosive pigments has not been clarified yet. In this work cerium (IV) oxides are considered as corrosion inhibitors for galvanized steel. The corrosion inhibition mechanism of mechanically treated (milled) CeO{sub 2} alone and in combination with milled SiO{sub 2} nanoparticles was investigated. For this purpose milled CeO{sub 2}, CeO{sub 2} and SiO{sub 2} milled together and milled SiO{sub 2} particles were studied as corrosion inhibitors in water solution. Therefore, the different mechanically treated particles were dispersed in 0.1 M NaCl solution to test their effectiveness as corrosion inhibitors for galvanized steel. The galvanized steel was immersed in the different solutions and the corrosion inhibition efficiency of the different particles was measured by means of electrochemical techniques. For this purpose, electrochemical impedance spectroscopy (EIS) measurements were carried out, monitoring the evolution of the corrosion processes occurring at the metal surface with the immersion time in the solution. The effect of the different pigments was also investigated by carrying out anodic and cathodic polarization measurements. The polarization curves were acquired under conditions of varied pH. The experimental measurements suggest that the mechanical treatment performed on the SiO{sub 2} and CeO{sub 2} particles promote the formation of an effective corrosion pigment

Inverse spinel transition metal oxides for lithium-ion storage with different discharge/charge conversion mechanisms

International Nuclear Information System (INIS)

Wang, Jiawei; Ren, Yurong; Huang, Xiaobing; Ding, Jianning

2016-01-01

Highlights: • Inverse spinel structure relieves the irreversible phase transition of electrodes. • Anodes with the same structure show different discharge/charge conversion mechanisms. • High reversible capacity confirms the potential feasibility of composites. - Abstract: Inverse spinel transition metal oxides (Fe 3 O 4 , MnFe 2 O 4 , Fe 3 O 4 /reduced graphene oxide and MnFe 2 O 4 /reduced graphene oxide) are prepared by a facile ethylene-glycol-assisted hydrothermal method. The stability of inverse spinel structure and the high specific surface area of nanoscale provide transition metal oxides with high specific capacity. And the surface modification with reduced graphene oxide improves the poor conductivity of pristine transition metal oxides. Pristine Fe 3 O 4 and MnFe 2 O 4 deliver the high initial discharge capacity of 1137.1 and 1088.9 mAh g −1 , respectively. Fe 3 O 4 /reduced graphene oxide and MnFe 2 O 4 /reduced graphene oxide get the reversible capacity of 645.8 and 720 mAh g −1 , respectively, even after 55 cycles. The different discharge/charge conversion mechanisms make them different capacity stability. The great electrochemical performances of composites offer electrodes with suitable characteristics for high-performance energy storage application.

Electrochemical deposition of gold-platinum alloy nanoparticles on an indium tin oxide electrode and their electrocatalytic applications

Energy Technology Data Exchange (ETDEWEB)

Song Yan; Ma Yuting; Wang Yuan [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China); Di Junwei, E-mail: djw@suda.edu.c [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China); Tu Yifeng [Department of Chemistry, Soochow University, Suzhou, Jiangsu 215123 (China)

2010-07-01

Gold-platinum (Au-Pt) hybrid nanoparticles (Au-PtNPs) were successfully deposited on an indium tin oxide (ITO) surface using a direct electrochemical method. The resulting nanoparticles were characterized by scanning electron microscopy (SEM), UV-vis spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and electrochemical methods. It was found that the size of the Au-PtNPs depends on the number of electrodeposition cycles. Au-PtNPs obtained by 20 electrodeposition cycles had a cauliflower-shaped structure with an average diameter of about 60 nm. These Au-PtNPs exhibited alloy properties. Electrochemical measurements showed that the charge transfer resistivity was significantly decreased for the Au-PtNPs/ITO electrode. Additionally, the Au-PtNPs displayed an electrocatalytic activity for nitrite oxidation and oxygen reduction. The Au-PtNPs/ITO electrodes reported herein could possibly be used as electrocatalysts and sensors.

Crystal size effect on the electrochemical oxidation of formate on carbon-supported palladium nanoparticles

International Nuclear Information System (INIS)

Santos, Rayana Marcela Izidoro da Silva; Nakazato, Roberto Zenhei; Ciapina, Eduardo Goncalves

2016-01-01

Full text: The electrochemical oxidation of formate in alkaline electrolytes has emerged an a promising anodic reaction in the Direct Formate Fuel Cells[1]. Although palladium is considered to be one of the best electro catalyst for the oxidation of formate, important structure-activity relationships are still not understood. In the present work, we investigated the effect of the size of the palladium crystals in the electrochemical oxidation of formate in 0.1 mol L -1 KOH. Carbon-supported palladium nanoparticles (Pd/C) were prepared by chemical reduction of palladium (II) chloride in aqueous media by sodium borohydride in the presence of varying quantities of sodium citrate in the reaction media to obtain metallic crystals with distinct sizes. Analysis of the X-ray diffraction profile revealed the presence of palladium crystals in the range of 6 to 19 nm. Potentiostatic oxidation of formate on the distinct Pd/C samples revealed a volcano-like dependence of the specific activity with the size of the palladium crystals, presenting the highest activity for crystals around 7.5 nm. Reference: [1] A.M. Bartrom, J.L. Haan, The direct formate fuel cell with an alkaline anion exchange membrane, J. Power Sources. 214 (2012) 68-74. (author)

Progress in the electrochemical modification of graphene-based materials and their applications

International Nuclear Information System (INIS)

Chakrabarti, M.H.; Low, C.T.J.; Brandon, N.P.; Yufit, V.; Hashim, M.A.; Irfan, M.F.; Akhtar, J.; Ruiz-Trejo, E.; Hussain, M.A.

2013-01-01

Highlights: • Six means of functionalizing graphene electrochemically is reviewed. • Electrochemical functionalization is relatively new to other standard methods. • The technique is expected to improve graphene's application range considerably. -- Abstract: Graphene is a 2D allotrope of carbon with exciting properties such as extremely high electronic conductivity and superior mechanical strength. It has considerable potential for applications in fields such as bio-sensors, electrochemical energy storage and electronics. In most cases, graphene has been functionalized and modified with other materials to prepare composites. This work reviews the electrochemical modification of graphene. Commencing with a brief history, a summary of several different means of modifying graphene to effect diverse applications is provided. This is followed by a discussion on different composite materials that have been prepared with reduced graphene oxide prior to moving onto a detailed consideration of six different methods of electrochemically modifying graphene to prepare composite materials. These methods involve cathodic reduction of graphene oxide, electrophoretic deposition, electro-deposition techniques, electrospinning, electrochemical doping and electrochemical polymerization. Finally a consideration on the applications of electrochemically modified graphene composite materials in various fields is presented prior to discussing some prospects in enhancing the electrochemical process to realize excellent and economic composite materials in bulk

Electrochemical oxidation of pulp and paper making wastewater assisted by transition metal modified kaolin

International Nuclear Information System (INIS)

Wang Bo; Gu Lin; Ma Hongzhu

2007-01-01

The electrochemical oxidation of pulp and paper making wastewater assisted by transition metal (Co, Cu) modified kaolin in a 200 ml electrolytic batch reactor with graphite plate as electrodes was investigated. H 2 O 2 , which produced on the surface of porous graphite cathode, would react with the catalysts to form strong oxidant (hydroxyl radicals) that can in turn destruct the pollutants adsorbed on the surface of kaolin. The transition metal (Co, Cu) modified kaolin was also characterized by XRD and SEM before and after the modification and the results showed that the transition metals were completely supported on kaolin and formed a porous structure with big BET surface. The mechanism was proposed on the basis of XPS analysis of the catalyst after the degradation process. Series of experiments were also done to prove the synergetic effect of the combined oxidation system and to find out the optimal operating parameters such as initial pH, current density and amount of catalyst. From the results it can be founded that when the initial pH was at 3, current density was 30 mA cm -2 ; catalyst dose was 30 g dm -3 , COD (chemical oxygen demand) removal could reach up to 96.8% in 73 min

Electrodeposition of Manganese-Nickel Oxide Films on a Graphite Sheet for Electrochemical Capacitor Applications

Directory of Open Access Journals (Sweden)

Hae-Min Lee

2014-01-01

Full Text Available Manganese-nickel (Mn-Ni oxide films were electrodeposited on a graphite sheet in a bath consisting of manganese acetate and nickel chloride, and the structural, morphological, and electrochemical properties of these films were investigated. The electrodeposited Mn-Ni oxide films had porous structures covered with nanofibers. The X-ray diffractometer pattern revealed the presence of separate manganese oxide (g-MnO2 and nickel oxide (NiO in the films. The electrodeposited Mn-Ni oxide electrode exhibited a specific capacitance of 424 F/g in Na2SO4 electrolyte. This electrode maintained 86% of its initial specific capacitance over 2000 cycles of the charge-discharge operation, showing good cycling stability.

Characterization of a stirred tank electrochemical cell for water disinfection processes

International Nuclear Information System (INIS)

Polcaro, A.M.; Vacca, A.; Mascia, M.; Palmas, S.; Pompei, R.; Laconi, S.

2007-01-01

Laboratory experiments were performed to characterize the behaviour of an electrochemical cell equipped with boron-doped diamond anodes and to verify its effectiveness in water disinfection. The hydrodynamic regime was determined when the cell worked either in batch or in continuous mode. Galvanostatic electrolyses of aqueous 1 mM Na 2 SO 4 solutions were performed to investigate on the oxidant production in different experimental conditions. The same solutions contaminated by E. coli, enterococci and coliforms were used as test media to verify the effectiveness of the system in the disinfection process. Experimental results indicated that the major inactivation mechanism of bacteria in the electrochemical cell is a disinfection by electrochemically generated oxidants, however a cooperative effect of superficial reaction has to be taken into account. The great capability of BDD anode to produce reactive oxygen species (ROS) and other oxidizing species during the electrolysis allows to establish a chlorine-free disinfection process

Electrochemical Water Oxidation and Stereoselective Oxygen Atom Transfer Mediated by a Copper Complex.

Science.gov (United States)

Kafentzi, Maria-Chrysanthi; Papadakis, Raffaello; Gennarini, Federica; Kochem, Amélie; Iranzo, Olga; Le Mest, Yves; Le Poul, Nicolas; Tron, Thierry; Faure, Bruno; Simaan, A Jalila; Réglier, Marius

2018-04-06

Water oxidation by copper-based complexes to form dioxygen has attracted attention in recent years, with the aim of developing efficient and cheap catalysts for chemical energy storage. In addition, high-valent metal-oxo species produced by the oxidation of metal complexes in the presence of water can be used to achieve substrate oxygenation with the use of H 2 O as an oxygen source. To date, this strategy has not been reported for copper complexes. Herein, a copper(II) complex, [(RPY2)Cu(OTf) 2 ] (RPY2=N-substituted bis[2-pyridyl(ethylamine)] ligands; R=indane; OTf=triflate), is used. This complex, which contains an oxidizable substrate moiety (indane), is used as a tool to monitor an intramolecular oxygen atom transfer reaction. Electrochemical properties were investigated and, upon electrolysis at 1.30 V versus a normal hydrogen electrode (NHE), both dioxygen production and oxygenation of the indane moiety were observed. The ligand was oxidized in a highly diastereoselective manner, which indicated that the observed reactivity was mediated by metal-centered reactive species. The pH dependence of the reactivity was monitored and correlated with speciation deduced from different techniques, ranging from potentiometric titrations to spectroscopic studies and DFT calculations. Water oxidation for dioxygen production occurs at neutral pH and is probably mediated by the oxidation of a mononuclear copper(II) precursor. It is achieved with a rather low overpotential (280 mV at pH 7), although with limited efficiency. On the other hand, oxygenation is maximum at pH 8-8.5 and is probably mediated by the electrochemical oxidation of an antiferromagnetically coupled dinuclear bis(μ-hydroxo) copper(II) precursor. This constitutes the first example of copper-centered oxidative water activation for a selective oxygenation reaction. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Continuous electrochemical oxidation of biomass derived 5-(hydroxymethyl)furfural into 2,5-furandicarboxylic acid

NARCIS (Netherlands)

Latsuzbaia, R.; Bisselink, R.; Anastasopol, A.; Meer, van der H.; Heck, van R.; Yagüe, M.S.; Zijlstra, M.; Roelands, M.; Crockatt, M.; Goetheer, E.; Giling, E.

2018-01-01

Abstract: A continuous electrochemical process with integrated product separation has been developed for production of 2,5-furandicarboxylic acid (FDCA) by oxidation of 5-(hydroxymethyl)furfural (HMF) in aqueous alkaline media on non-noble Ni/NiOOH foam electrodes at ambient conditions. Initially,

A new way for preparing superconducting materials: the electrochemical oxidation of La2CuO4

International Nuclear Information System (INIS)

Wattiaux, A.; Park, J.C.; Grenier, J.C.; Pouchard, M.

1990-01-01

The electrochemical oxidation in alkaline medium is described as a new way for preparing superconducting oxides at room temperature. The application of this method to La 2 CuO 4 gave rise to a metallic material with a superconducting behaviour below 39 K and whose physical and chemical features appear as quite promising [fr

Electrochemically reduced graphene oxide-modified screen-printed carbon electrodes for a simple and highly sensitive electrochemical detection of synthetic colorants in beverages.

Science.gov (United States)

Jampasa, Sakda; Siangproh, Weena; Duangmal, Kiattisak; Chailapakul, Orawon

2016-11-01

A simple and highly sensitive electrochemical sensor based on an electrochemically reduced graphene oxide-modified screen-printed carbon electrode (ERGO-SPCE) for the simultaneous determination of sunset yellow (SY) and tartrazine (TZ) was proposed. An ERGO film was coated onto the electrode surface using a cyclic voltammetric method and then characterized by scanning electron microscopy (SEM). In 0.1M phosphate buffer at a pH of 6, the two oxidation peaks of SY and TZ appeared separately at 0.41 and 0.70V, respectively. Surprisingly, the electrochemical response remarkably increased approximately 90- and 20-fold for SY and TZ, respectively, using the modified electrode in comparison to the unmodified electrode. The calibration curves exhibited linear ranges from 0.01 to 20.0µM for SY and from 0.02 to 20.0µM for TZ. The limits of detection were found to be 0.50 and 4.50nM (at S/N=3) for SY and TZ, respectively. Furthermore, this detection platform provided very high selectivity for the measurement of both colorants. This electrochemical sensor was successfully applied to determine the amount of SY and TZ in commercial beverages. Comparison of the results obtained from this proposed method to those obtained by an in-house standard technique proved that this developed method has good agreement in terms of accuracy for practical applications. This sensor offers an inexpensive, rapid and sensitive determination. The proposed system is therefore suitable for routine analysis and should be an alternative method for the analysis of food colorants. Copyright © 2016 Elsevier B.V. All rights reserved.

A study of the dissolution mechanism by chemical and electrochemical oxidation-reduction of actinide dioxides (UO2, NpO2, PuO2, and AmO2) in an acid aqueous medium

International Nuclear Information System (INIS)

Berger, P.

1991-01-01

The plan followed to describe our study will be as follows: In a first part, we will review the general properties of MO 2 oxides (M = U, Np, Pu, and Am), as well as the dissolution methods known so far. We will emphasize, in particular, the great similarities in their structures, properties, and methods of dissolution, which justifies a parallel study of these oxides using an electrochemical method. The second part will concern the experimental study of the dissolution under electrolysis. We will, first of all, investigate its thermodynamic aspect, with the calculation of the free enthalpies of dissolution; and we will next show the phenomena of oxidizing dissolution and reducing dissolution using carbon paste electrodes. In a third part, we will present the test results on oxidizing dissolution in solutions that are highly enriched with oxygen-18. The isotopic analysis of the oxygen in the actinyl ions formed, deduced from the Raman spectra of the solutions, will make it possible to demonstrate the existence of a first oxidation step involving the participation of the solid. In the fourth part, we will summarize the experimental observations that might contribute to a better understanding of the mechanisms of oxidizing dissolution. A fifth and last part will be devoted to the presentation of a simple model of the dissolution of oxides in a carbon paste electrode under a constant current

Electrochemical oxidation of organic carbonate based electrolyte solutions at lithium metal oxide electrodes

Energy Technology Data Exchange (ETDEWEB)

Imhof, R; Novak, P [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1999-08-01

The oxidative decomposition of carbonate based electrolyte solutions at practical lithium metal oxide composite electrodes was studied by differential electrochemical mass spectrometry. For propylene carbonate (PC), CO{sub 2} evolution was detected at LiNiO{sub 2}, LiCoO{sub 2}, and LiMn{sub 2}O{sub 4} composite electrodes. The starting point of gas evolution was 4.2 V vs. Li/Li{sup +} at LiNiO{sub 2}, whereas at LiCoO{sub 2} and LiMn{sub 2}O{sub 4}, CO{sub 2} evolution was only observed above 4.8 V vs. Li/Li{sup +}. In addition, various other volatile electrolyte decomposition products of PC were detected when using LiCoO{sub 2}, LiMn{sub 2}O4, and carbon black electrodes. In ethylene carbonate / dimethyl carbonate, CO{sub 2} evolution was only detected at LiNiO{sub 2} electrodes, again starting at about 4.2 V vs. Li/Li{sup +}. (author) 3 figs., 2 refs.

Method of making sulfur tolerant composite cermet electrodes for solid oxide electrochemical cells

Science.gov (United States)

Isenberg, Arnold O.

1989-01-01

An electrochemical apparatus is made containing an exterior electorde bonded to the exterior of a tubular, solid, oxygen ion conducting electrolyte where the electrolyte is also in contact with an interior electrode, said exterior electrode comprising particles of an electronic conductor contacting the electrolyte, where a ceramic metal oxide coating partially surrounds the particles and is bonded to the electrolyte, and where a coating of an ionic-electronic conductive material is attached to the ceramic metal oxide coating and to the exposed portions of the particles.

Enhanced electrochemical oxidation of synthetic dyeing wastewater using SnO2-Sb-doped TiO2-coated granular activated carbon electrodes with high hydroxyl radical yields

International Nuclear Information System (INIS)

Li, Xinyang; Wu, Yue; Zhu, Wei; Xue, Fangqing; Qian, Yi; Wang, Chengwen

2016-01-01

Highlights: • We study granular activated carbon (GAC) electrodes coated with catalysts. • GAC coated with ATOT demonstrates an impressive ·OH yield. • This electrode can be used in continuous-flow three-dimensional electrode reactors. • We use Rhodamine B as a model organic compound for removal. • The GAC/ATOT performs better than all other electrodes examined. - Abstract: In this study, granular activated carbon (GAC) coated with SnO 2 -Sb doped TiO 2 (GAC/ATOT) with a high hydroxyl radical (·OH) yield is prepared via the sol-gel method. This material is utilized as a granular electrode in a continuous-flow three-dimensional electrode reactor (CTDER) for the enhanced treatment of synthetic dyeing wastewater containing Rhodamine B (RhB). We then characterize the physical properties, electrochemical properties, and electrochemical oxidation performance of the granular electrode. The results show that using the GAC/ATOT electrode in a CTDER significantly enhances the chemical oxygen demand (COD) removal, decreases the energy consumption, and improves the current efficiency of the wastewater. This is primarily attributed to the higher catalytic activity of GAC/ATOT for ·OH production compared to that of other candidates, such as TiO 2 coated GAC (GAC/T), Sb doped SnO 2 coated GAC (GAC/ATO), and pure GAC. The mechanism of the enhanced electrochemical oxidation afforded by using GAC/ATOT indicates that the high ·OH yield in the reactor packed with GAC/ATOT electrodes contributes to the enhanced electrochemical oxidation performance with respect to organic compounds.

Performance of electrochemical oxidation and photocatalysis in terms of kinetics and energy consumption. New insights into the p-cresol degradation.

Science.gov (United States)

Escudero, Carlos J; Iglesias, Olalla; Dominguez, Sara; Rivero, Maria J; Ortiz, Inmaculada

2017-06-15

This work reports the comparative performance of two Advanced Oxidation Processes (AOPs), electrochemical oxidation and photocatalysis, as individual technological alternatives for the treatment of effluents containing p-cresol. First, the influence of operating parameters in the oxidation and mineralization yield was carried out together with kinetic analysis. Boron Doped Diamond (BDD), RuO 2 and Pt as anodic materials, Na 2 SO 4 and NaCl as supporting electrolytes and different current densities were evaluated in electrochemical oxidation whereas the effect of TiO 2 concentration and radiation was studied in the photocatalytic degradation. Then, the parameter Electrical Energy per Order (E EO ) was calculated to compare the energy consumption in both AOPs, concluding that under the studied conditions the electrochemical treatment with BDD, Na 2 SO 4 and 125 A m -2 showed the best energy efficiency, with an E EO of 5.83 kW h m -3 order -1 for p-cresol and 58.05 kW h m -3 order -1 for DOC removal, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

Highly sensitive electrochemical detection of methyl salicylate using electroactive gold nanoparticles.

Science.gov (United States)

Umasankar, Yogeswaran; Ramasamy, Ramaraja P

2013-11-07

Electrochemical sensing of methyl salicylate, a key plant volatile has been achieved using a gold nanoparticle (AuNP) modified screen printed carbon electrode (SPCE). The electrochemical response of planar gold electrodes, SPCE and AuNP-SPCE in alkaline electrolyte in the presence and absence of methyl salicylate were studied to understand the amperometric response of various electrochemical reactions. The reaction mechanism includes hydrolysis of methyl salicylate and the oxidation of negative species. The electrochemical responses were recorded using cyclic voltammetry and differential pulse voltammetry techniques, where the results showed characteristic signals for methyl salicylate oxidation. Among the examined electrodes, AuNP-SPCE possessed three fold better sensitivity than planar gold and 35 times better sensitivity than SPCE (at 0.5 V). The methyl salicylate sensing by AuNP-SPCE possessed 95% of its methyl salicylate response. The electroanalytical results of soybean extract showed that AuNP-SPCE can be employed for the determination of methyl salicylate in real samples.

Evaluation of the aniline chemical oxidation process using multiple simultaneous electrochemical responses

International Nuclear Information System (INIS)

Cristovan, Fernando H.; Lemos, Sherlan G.; Santos, Janaina S.; Trivinho-Strixino, Francisco; Pereira, Ernesto C.; Mattoso, Luiz H.C.; Kulkarni, Rashmi; Manohar, Sanjeev K.

2010-01-01

In this paper we show the simultaneous evaluation of the electrochemical impedance, the open circuit potential and the mass variation of the polyaniline deposited on a metal substrate during chemical oxidation of aniline. We detected that the final properties of the polymer could be practically defined after the inflection point of the potential profile. Considering a series connection of R and C, impedance Z was decomposed into the resistive and capacitive components. The resistivity and permittivity show a slight change after the inflection point in the potential profile. Impedance data and mass changes during synthesis also contributed to a better definition of the induction period. We described the system as whole, which relates to an electronic transport and to an electronic charge storage process. Although very simple, this model helps us to interpret and correlate different techniques to explain the results. In addition, we demonstrated that the in situ evaluation of the parameters described above offers new insights on the chemical synthesis mechanism of polyaniline.

Electrochemical catalytic treatment of phenol wastewater

International Nuclear Information System (INIS)

Ma Hongzhu; Zhang Xinhai; Ma Qingliang; Wang Bo

2009-01-01

The slurry bed catalytic treatment of contaminated water appears to be a promising alternative for the oxidation of aqueous organic pollutants. In this paper, the electrochemical oxidation of phenol in synthetic wastewater catalyzed by ferric sulfate and potassium permanganate adsorbed onto active bentonite in slurry bed electrolytic reactor with graphite electrode has been investigated. In order to determine the optimum operating condition, the orthogonal experiments were devised and the results revealed that the system of ferric sulfate, potassium permanganate and active bentonite showed a high catalytic efficiency on the process of electrochemical oxidation phenol in initial pH 5. When the initial concentration of phenol was 0.52 g/L (the initial COD 1214 mg/L), up to 99% chemical oxygen demand (COD) removal was obtained in 40 min. According to the experimental results, a possible mechanism of catalytic degradation of phenol was proposed. Environmental estimation was also done and the results showed that the treated wastewater have little impact on plant growth and could totally be applied to irrigation.

Electrochemical catalytic treatment of phenol wastewater

Energy Technology Data Exchange (ETDEWEB)

Ma Hongzhu, E-mail: hzmachem@snnu.edu.cn [Institute of Energy Chemistry, School of Chemistry and Materials Science, Shaanxi Normal University, Xi' an 710062 (China); Zhang Xinhai [Institute of Energy Chemistry, School of Chemistry and Materials Science, Shaanxi Normal University, Xi' an 710062 (China); Ma Qingliang [Department of Applied Physics, College of Sciences, Taiyuan University of Technology, 030024 Taiyuan (China); Wang Bo [Institute of Energy Chemistry, School of Chemistry and Materials Science, Shaanxi Normal University, Xi' an 710062 (China)

2009-06-15

The slurry bed catalytic treatment of contaminated water appears to be a promising alternative for the oxidation of aqueous organic pollutants. In this paper, the electrochemical oxidation of phenol in synthetic wastewater catalyzed by ferric sulfate and potassium permanganate adsorbed onto active bentonite in slurry bed electrolytic reactor with graphite electrode has been investigated. In order to determine the optimum operating condition, the orthogonal experiments were devised and the results revealed that the system of ferric sulfate, potassium permanganate and active bentonite showed a high catalytic efficiency on the process of electrochemical oxidation phenol in initial pH 5. When the initial concentration of phenol was 0.52 g/L (the initial COD 1214 mg/L), up to 99% chemical oxygen demand (COD) removal was obtained in 40 min. According to the experimental results, a possible mechanism of catalytic degradation of phenol was proposed. Environmental estimation was also done and the results showed that the treated wastewater have little impact on plant growth and could totally be applied to irrigation.

Electrochemical oxidation of tetracycline antibiotics using a Ti/IrO2 anode for wastewater treatment of animal husbandry.

Science.gov (United States)

Miyata, M; Ihara, I; Yoshid, G; Toyod, K; Umetsu, K

2011-01-01

In animal husbandry, antibiotics are widely used to treat and prevent diseases or to promote growth. The use of antibiotics for domestic animals enables to promote safety of livestock products and enhance productivity. Tetracycline antibiotics (TCs) are one of the primarily used groups of antibiotics for cattle and swine. However, the unintentional spreading of antibiotics from animal waste to the environment may leave out drug residues, promoting resistant strains of bacteria, and will adversely affect the ecosystem and human health. To prevent the spread of veterinary antibiotics in the environment, it is required to treat residual antibiotics in livestock wastewater. In this study, we investigated the electrochemical oxidation of TCs to treat livestock wastewater. The concentrations of TCs in aqueous solutions were reduced from 100 mg/L to less than 0.6 mg/L by 6 h of electrochemical treatment using a Ti/IrO2 anode with Na2SO4 electrolyte. The concentration of oxytetracycline (OTC) in livestock wastewater was also reduced from 100 mg/L to less than 0.7 mg/L by the same treatment. Thus, the electrochemical oxidation using a Ti/IrO2 anode with Na2SO4 electrolyte was found to be effective for degradation of TCs. The results suggest that the electrochemical oxidation method is a promising treatment for TCs in livestock wastewater.

Electrochemical Synthesis of Polypyrrole, Reduced Graphene Oxide, and Gold Nanoparticles Composite and Its Application to Hydrogen Peroxide Biosensor

Directory of Open Access Journals (Sweden)

Baoyan Wu

2016-11-01

Full Text Available Here we report a facile eco-friendly one-step electrochemical approach for the fabrication of a polypyrrole (PPy, reduced graphene oxide (RGO, and gold nanoparticles (nanoAu biocomposite on a glassy carbon electrode (GCE. The electrochemical behaviors of PPy–RGO–nanoAu and its application to electrochemical detection of hydrogen peroxide were investigated by cyclic voltammetry. Graphene oxide and pyrrole monomer were first mixed and casted on the surface of a cleaned GCE. After an electrochemical processing consisting of the electrooxidation of pyrrole monomer and simultaneous electroreduction of graphene oxide and auric ions (Au3+ in aqueous solution, a PPy–RGO–nanoAu biocomposite was synthesized on GCE. Each component of PPy–RGO–nanoAu is electroactive without non-electroactive substance. The obtained PPy–RGO–nanoAu/GCE exhibited high electrocatalytic activity toward hydrogen peroxide, which allows the detection of hydrogen peroxide at a negative potential of about −0.62 V vs. SCE. The amperometric responses of the biosensor displayed a sensitivity of 40 µA/mM, a linear range of 32 µM–2 mM, and a detection limit of 2.7 µM (signal-to-noise ratio = 3 with good stability and acceptable reproducibility and selectivity. The results clearly demonstrate the potential of the as-prepared PPy–RGO–nanoAu biocomposite for use as a highly electroactive matrix for an amperometric biosensor.

Catalytic and electrochemical behaviour of solid oxide fuel cell operated with simulated-biogas mixtures

Science.gov (United States)

Dang-Long, T.; Quang-Tuyen, T.; Shiratori, Y.

2016-06-01

Being produced from organic matters of wastes (bio-wastes) through a fermentation process, biogas mainly composed of CH4 and CO2 and can be considered as a secondary energy carrier derived from solar energy. To generate electricity from biogas through the electrochemical process in fuel cells is a state-of-the-art technology possessing higher energy conversion efficiency without harmful emissions compared to combustion process in heat engines. Getting benefits from high operating temperature such as direct internal reforming ability and activation of electrochemical reactions to increase overall system efficiency, solid oxide fuel cell (SOFC) system operated with biogas becomes a promising candidate for distributed power generator for rural applications leading to reductions of environmental issues caused by greenhouse effects and bio-wastes. CO2 reforming of CH4 and electrochemical oxidation of the produced syngas (H2-CO mixture) are two main reaction processes within porous anode material of SOFC. Here catalytic and electrochemical behavior of Ni-ScSZ (scandia stabilized-zirconia) anode in the feed of CH4-CO2 mixtures as simulated-biogas at 800 °C were evaluated. The results showed that CO2 had strong influences on both reaction processes. The increase in CO2 partial pressure resulted in the decrease in anode overvoltage, although open-circuit voltage was dropped. Besides that, the simulation result based on a power-law model for equimolar CH4-CO2 mixture revealed that coking hazard could be suppressed along the fuel flow channel in both open-circuit and closed-circuit conditions.

Holey two-dimensional transition metal oxide nanosheets for efficient energy storage

Science.gov (United States)

Peng, Lele; Xiong, Pan; Ma, Lu; Yuan, Yifei; Zhu, Yue; Chen, Dahong; Luo, Xiangyi; Lu, Jun; Amine, Khalil; Yu, Guihua

2017-04-01

Transition metal oxide nanomaterials are promising electrodes for alkali-ion batteries owing to their distinct reaction mechanism, abundant active sites and shortened ion diffusion distance. However, detailed conversion reaction processes in terms of the oxidation state evolution and chemical/mechanical stability of the electrodes are still poorly understood. Herein we explore a general synthetic strategy for versatile synthesis of various holey transition metal oxide nanosheets with adjustable hole sizes that enable greatly enhanced alkali-ion storage properties. We employ in-situ transmission electron microscopy and operando X-ray absorption structures to study the mechanical properties, morphology evolution and oxidation state changes during electrochemical processes. We find that these holey oxide nanosheets exhibit strong mechanical stability inherited from graphene oxide, displaying minimal structural changes during lithiation/delithiation processes. These holey oxide nanosheets represent a promising material platform for in-situ probing the electrochemical processes, and could open up opportunities in many energy storage and conversion systems.

Preliminary Electrochemical Characterization of Anode Supported Solid Oxide Cell (AS-SOC) Produced in the Institute of Power Engineering Operated in Electrolysis Mode (SOEC)

Science.gov (United States)

Kupecki, Jakub; Motyliński, Konrad; Skrzypkiewicz, Marek; Wierzbicki, Michał; Naumovich, Yevgeniy

2017-12-01

The article discusses the operation of solid oxide electrochemical cells (SOC) developed in the Institute of Power Engineering as prospective key components of power-to-gas systems. The fundamentals of the solid oxide cells operated as fuel cells (SOFC - solid oxide fuel cells) and electrolysers (SOEC - solid oxide fuel cells) are given. The experimental technique used for electrochemical characterization of cells is presented. The results obtained for planar cell with anodic support are given and discussed. Based on the results, the applicability of the cells in power-to-gas systems (P2G) is evaluated.

Structural, optical and electrochemical properties of F-doped vanadium oxide transparent semiconducting thin films

Energy Technology Data Exchange (ETDEWEB)

Mousavi, M.; Khorrami, G.H. [University of Bojnord, Department of Physics, Faculty of Basic Science, Bojnord (Iran, Islamic Republic of); Kompany, A. [Ferdowsi University of Mashhad, Department of Physics, Mashhad (Iran, Islamic Republic of); Yazdi, S.T. [Payame Noor University (PNU), Department of Physics, Tehran (Iran, Islamic Republic of)

2017-12-15

In this study, F-doped vanadium oxide thin films with doping levels up to 60 at % were prepared by spray pyrolysis method on glass substrates. To measure the electrochemical properties, some films were deposited on fluorine-tin oxide coated glass substrates. The effect of F-doping on the structural, electrical, optical and electrochemical properties of vanadium oxide samples was investigated. The X-ray diffractographs analysis has shown that all the samples grow in tetragonal β-V{sub 2}O{sub 5} phase structure with the preferred orientation of [200]. The intensity of (200) peak belonging to β-V{sub 2}O{sub 5} phase was strongest in the undoped vanadium oxide film. The scanning electron microscopy images show that the samples have nanorod- and nanobelt-shaped structure. The size of the nanobelts in the F-doped vanadium oxide films is smaller than that in the pure sample and the width of the nanobelts increases from 30 to 70 nm with F concentration. With increasing F-doping level from 10 to 60 at %, the resistivity, the transparency and the optical band gap decrease from 111 to 20 Ω cm, 70 to 50% and 2.4 to 2.36 eV, respectively. The cyclic voltammogram (CV) results show that the undoped sample has the most extensive CV and by increasing F-doping level from 20 to 60 at %, the area of the CV is expanded. The anodic and cathodic peaks in F-doped samples are stronger. (orig.)

Electrocatalytic oxidative determination of reserpine at electrochemically functionalized single walled carbon nanotube with polyaniline

International Nuclear Information System (INIS)

Dar, Riyaz Ahmad; Naikoo, Gowhar Ahmad; Pitre, Krishna Sadashive

2013-01-01

Graphical abstract: Electrode oxidation mechanism of reserpine at PANI modified-SWCNT/CPE. -- Highlights: • Electropolymerization of polyaniline at SWCNT/CPE. • CV, EIS, CC SEM techniques were used for characterization of electrode. • Electrode showed electrocatalytic activity towards anodic oxidation of reserpine. • Oxidation process as irreversible and adsorption-controlled. • Reserpine in bark of Rauwolfia serpentina and in its pharmaceutical formulations. -- Abstract: In the present work a polyaniline film was successfully deposited by electropolymerization on single walled carbon nanotube paste electrode. The electrode was characterized using cyclic voltammetry, electrochemical impedance spectroscopy, chronocoulometry and scanning electron microscopy. The modified electrode showed electrocatalytic behaviour towards the anodic oxidation of reserpine. The adsorptive stripping voltammetric behaviour of reserpine at polyaniline film modified single walled carbon nanotube paste electrode (modified-SWCNTPE) was investigated and validated in pharmaceuticals and biological fluids by cyclic voltammetry (CV) and adsorptive stripping differential pulse voltammetry (AdSDPV) in 0.02 M phosphate buffer in the pH range of 2.5–8.5. Cyclic voltammetry has shown that the oxidation process is irreversible over the pH range studied and exhibited an adsorption-controlled behaviour. Further, the overall electrode process is mainly diffusion controlled with adsorption effects. The proposed more sensitive AdSDPV method allow quantitation over the range 0.085 μg mL −1 to 0.87 μg mL −1 with the detection limit of 0.407 ng mL −1 and has been successfully used to determine reserpine in bark of Rauwolfia serpentina and in its pharmaceutical formulations

Effect of calcination temperature on microstructure and electrochemical performance of lithium-rich layered oxide cathode materials

International Nuclear Information System (INIS)

Ma, Quanxin; Peng, Fangwei; Li, Ruhong; Yin, Shibo; Dai, Changsong

2016-01-01

Highlights: • A series of Li-rich layered oxide cathode materials (Li_1_._2Mn_0_._5_6Ni_0_._1_6Co_0_._0_8O_2) were successfully synthesized via a two-step synthesis method. • The effects of calcination temperature on the cathode materials were researched in detail. • A well-crystallized layered structure was obtained as the calcination temperature increased. • The samples calcined in a range of 850–900 °C exhibited excellent electrochemical performance. - Abstract: Lithium-rich layered oxide cathode materials (Li_1_._2Mn_0_._5_6Ni_0_._1_6Co_0_._0_8O_2 (LLMO)) were synthesized via a two-step synthesis method involving co-precipitation and high-temperature calcination. The effects of calcination temperature on the cathode materials were studied in detail. Structural and morphological characterizations revealed that a well-crystallized layered structure was obtained at a higher calcination temperature. Electrochemical performance evaluation revealed that a cathode material obtained at a calcination temperature of 850 °C delivered a high initial discharge capacity of 266.8 mAh g"−"1 at a 0.1 C rate and a capacity retention rate of 95.8% after 100 cycles as well as excellent rate capability. Another sample calcinated at 900 °C exhibited good cycling stability. It is concluded that the structural stability and electrochemical performance of Li-rich layered oxide cathode materials were strongly dependent on calcination temperatures. The results suggest that a calcination temperature in a range of 850–900 °C could promote electrochemical performance of this type of cathode materials.

Effect of calcination temperature on microstructure and electrochemical performance of lithium-rich layered oxide cathode materials

Energy Technology Data Exchange (ETDEWEB)

Ma, Quanxin; Peng, Fangwei; Li, Ruhong; Yin, Shibo; Dai, Changsong, E-mail: changsd@hit.edu.cn

2016-11-15

Highlights: • A series of Li-rich layered oxide cathode materials (Li{sub 1.2}Mn{sub 0.56}Ni{sub 0.16}Co{sub 0.08}O{sub 2}) were successfully synthesized via a two-step synthesis method. • The effects of calcination temperature on the cathode materials were researched in detail. • A well-crystallized layered structure was obtained as the calcination temperature increased. • The samples calcined in a range of 850–900 °C exhibited excellent electrochemical performance. - Abstract: Lithium-rich layered oxide cathode materials (Li{sub 1.2}Mn{sub 0.56}Ni{sub 0.16}Co{sub 0.08}O{sub 2} (LLMO)) were synthesized via a two-step synthesis method involving co-precipitation and high-temperature calcination. The effects of calcination temperature on the cathode materials were studied in detail. Structural and morphological characterizations revealed that a well-crystallized layered structure was obtained at a higher calcination temperature. Electrochemical performance evaluation revealed that a cathode material obtained at a calcination temperature of 850 °C delivered a high initial discharge capacity of 266.8 mAh g{sup −1} at a 0.1 C rate and a capacity retention rate of 95.8% after 100 cycles as well as excellent rate capability. Another sample calcinated at 900 °C exhibited good cycling stability. It is concluded that the structural stability and electrochemical performance of Li-rich layered oxide cathode materials were strongly dependent on calcination temperatures. The results suggest that a calcination temperature in a range of 850–900 °C could promote electrochemical performance of this type of cathode materials.

Structure dependent electrochemical performance of Li-rich layered oxides in lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Fu, Fang; Yao, Yuze; Wang, Haiyan; Xu, Gui-Liang; Amine, Khalil; Sun, Shi-Gang; Shao, Minhua

2017-04-08

Rational and precise control of the structure and dimension of electrode materials is an efficient way to improve their electrochemical performance. In this work, solvothermal or co-precipitation method is used to synthesize lithium-rich layered oxide materials of Li1.2Mn0.56Co0.12Ni0.12O2 (LLO) with various morphologies and structures, including microspheres, microrods, nanoplates, and irregular nanoparticles. These materials exhibit strong structure- dependent electrochemical properties. The porous hierarchical structured LLO microrods exhibit the best performance, delivering a discharge capacity of 264.6 mAh g(-1) at 0.5 C with over 91% retention after 100 cycles. At a high rate of 5 C, a high discharge capacity of 173.6 mAh g(-1) can be achieved. This work reveals the relationship between the morphologies and electrochemical properties of LLO cathode materials, and provides a feasible approach to fabricating robust and high-performance electrode materials for lithium-ion batteries.

Kinetics and mechanism of the deep electrochemical oxidation of sodium diclofenac on a boron-doped diamond electrode

Science.gov (United States)

Vedenyapina, M. D.; Borisova, D. A.; Rosenwinkel, K.-H.; Weichgrebe, D.; Stopp, P.; Vedenyapin, A. A.

2013-08-01

The kinetics and mechanism of the deep oxidation of sodium diclofenac on a boron-doped diamond electrode are studied to develop a technique for purifying wastewater from pharmaceutical products. The products of sodium diclofenac electrolysis are analyzed using cyclic voltammetry and nuclear magnetic resonance techniques. It is shown that the toxicity of the drug and products of its electrolysis decreases upon its deep oxidation.

Understanding of carbon-based supercapacitors ageing mechanisms by electrochemical and analytical methods

Science.gov (United States)

Liu, Yinghui; Soucaze-Guillous, Benoît; Taberna, Pierre-Louis; Simon, Patrice

2017-10-01

In order to shed light on ageing mechanisms of Electrochemical Double Layer Capacitor (EDLC), two kinds of activated carbons are studied in tetraethyl ammonium tetrafluoroborate (Et4NBF4) in acetonitrile. In floating mode, it turns out that two different ageing mechanisms are observed, depending on the activated carbon electrode materials used. On one hand, carbon A exhibits a continuous capacitance and series resistance fall-off; on the other hand, for carbon B, only the series resistance degrades after ageing while the capacitance keeps unchanged. Additional electrochemical characterizations (Electrochemical Impedance Spectroscopy - EIS - and diffusion coefficient calculations) were carried out showing that carbon A's ageing behavior is suspected to be primarily related to the carbon degradation while for carbon B a passivation occurs leading to the formation of a Solid Electrolyte Interphase-Like (SEI-L) film. These hypotheses are supported by TG-IR and Raman spectroscopy analysis. The outcome forms the latter is an increase of carbon defects on carbon A on positive electrode.

Coating of tips for electrochemical scanning tunneling microscopy by means of silicon, magnesium, and tungsten oxides

Science.gov (United States)

Salerno, Marco

2010-09-01

Different combinations of metal tips and oxide coatings have been tested for possible operation in electrochemical scanning tunneling microscopy. Silicon and magnesium oxides have been thermally evaporated onto gold and platinum-iridium tips, respectively. Two different thickness values have been explored for both materials, namely, 40 and 120 nm for silicon oxide and 20 and 60 nm for magnesium oxide. Alternatively, tungsten oxide has been grown on tungsten tips via electrochemical anodization. In the latter case, to seek optimal results we have varied the pH of the anodizing electrolyte between one and four. The oxide coated tips have been first inspected by means of scanning electron microscopy equipped with microanalysis to determine the morphological results of the coating. Second, the coated tips have been electrically characterized ex situ for stability in time by means of cyclic voltammetry in 1 M aqueous KCl supporting electrolyte, both bare and supplemented with K3[Fe(CN)6] complex at 10 mM concentration in milliQ water as an analyte. Only the tungsten oxide coated tungsten tips have shown stable electrical behavior in the electrolyte. For these tips, the uncoated metal area has been estimated from the electrical current levels, and they have been successfully tested by imaging a gold grating in situ, which provided stable results for several hours. The successful tungsten oxide coating obtained at pH=4 has been assigned to the WO3 form.

Removal of colour and COD from wastewater containing acid blue 22 by electrochemical oxidation

Energy Technology Data Exchange (ETDEWEB)

Panizza, Marco [Dipartimento di Ingegneria Chimica e di Processo ' G.B. Bonino' , Universita degli Studi di Genova, p.le J.F. Kennedy 1, 16129 Genova (Italy)], E-mail: marco.panizza@unige.it; Cerisola, Giacomo [Dipartimento di Ingegneria Chimica e di Processo ' G.B. Bonino' , Universita degli Studi di Genova, p.le J.F. Kennedy 1, 16129 Genova (Italy)

2008-05-01

Electrochemical oxidation of synthetic wastewater containing acid blue 22 on a boron-doped diamond electrode (BDD) was studied, using cyclic voltammetry and bulk electrolysis. The influence of current density, dye concentration, flow rate, and temperature was investigated, in order to find the best conditions for COD and colour removal. It was found that, during oxidation, a polymeric film, causing BDD deactivation, was formed in the potential region of water stability, and that it was removed by anodic polarisation at high potentials in the region of O{sub 2} evolution. Bulk electrolysis results showed that the electrochemical process was suitable for completely removing COD and effectively decolourising wastewaters, due to the production of hydroxyl radicals on the diamond surface. In particular, under optimal experimental conditions of flow rates (i.e. 300 dm{sup 3} h{sup -1}) and current density (i.e. 20 mA cm{sup -2}), 97% of COD was removed in 12 h electrolysis, with 70 kWh m{sup -3}energy consumption.

Removal of colour and COD from wastewater containing acid blue 22 by electrochemical oxidation

International Nuclear Information System (INIS)

Panizza, Marco; Cerisola, Giacomo

2008-01-01

Electrochemical oxidation of synthetic wastewater containing acid blue 22 on a boron-doped diamond electrode (BDD) was studied, using cyclic voltammetry and bulk electrolysis. The influence of current density, dye concentration, flow rate, and temperature was investigated, in order to find the best conditions for COD and colour removal. It was found that, during oxidation, a polymeric film, causing BDD deactivation, was formed in the potential region of water stability, and that it was removed by anodic polarisation at high potentials in the region of O 2 evolution. Bulk electrolysis results showed that the electrochemical process was suitable for completely removing COD and effectively decolourising wastewaters, due to the production of hydroxyl radicals on the diamond surface. In particular, under optimal experimental conditions of flow rates (i.e. 300 dm 3 h -1 ) and current density (i.e. 20 mA cm -2 ), 97% of COD was removed in 12 h electrolysis, with 70 kWh m -3 energy consumption

Treatment of a Textile Effluent by Electrochemical Oxidation and Coupled System Electooxidation–Salix babylonica

Directory of Open Access Journals (Sweden)

Alejandra Sánchez-Sánchez

2018-01-01

Full Text Available The removal of pollutants from textile wastewater via electrochemical oxidation and a coupled system electrooxidation—Salix babylonica, using boron-doped diamond electrodes was evaluated. Under optimal conditions of pH 5.23 and 3.5 mA·cm−2 of current density, the electrochemical method yields an effective reduction of chemical oxygen demand by 41.95%, biochemical oxygen demand by 83.33%, color by 60.83%, and turbidity by 26.53% at 300 minutes of treatment. The raw and treated wastewater was characterized by infrared spectroscopy to confirm the degradation of pollutants. The wastewater was oxidized at 15-minute intervals for one hour and was placed in contact with willow plants for 15 days. The coupled system yielded a reduction of the chemical oxygen demand by 14%, color by 85%, and turbidity by 93%. The best efficiency for the coupled system was achieved at 60 minutes, at which time the plants achieved more biomass and photosynthetic pigments.

Electrochemical hydrogen property improved in nano-structured perovskite oxide LaFeO3 for Ni/MH battery

Science.gov (United States)

Wang, Qiang; Deng, Gang; Chen, Zhiqian; Chen, Yungui; Cheng, Nanpu

2013-02-01

Perovskite oxide LaFeO3, as a novel candidate for the electrode of Ni/MH battery, holds high specific capacity and good cyclical durability at elevated temperatures. However, the poor electrochemical kinetics is a bottleneck for the application of this type of material. By use of nano-structured materials, there are greatly enhanced values of exchange current density I0 and hydrogen diffusion coefficient D, which resulted in an improvement of electrochemical kinetics, a much higher specific capacity and excellent stability during cycling for nano-structured LaFeO3. In theory, there is a significant possibility of further advancing the hydrogen reaction kinetics of perovskite type oxides for Ni/MH battery.

Fabrication of a novel PbO2 electrode with a graphene nanosheet interlayer for electrochemical oxidation of 2-chlorophenol

International Nuclear Information System (INIS)

Duan, Xiaoyue; Zhao, Cuimei; Liu, Wei; Zhao, Xuesong; Chang, Limin

2017-01-01

Highlights: • A novel PbO 2 electrode with a GNS interlayer (GSN-PbO 2 ) was prepared. • The GNS interlayer reduced grain size of β-PbO 2 crystals. • The GNS interlayer enhanced electrochemical activity of PbO 2 electrode. • The lifetime of GSN-PbO 2 electrode was 1.93 times that of PbO 2 electrode. • An electrochemical mineralization mechanism of 2-chlorophenol was proposed. - Abstract: A novel PbO 2 electrode with a graphene nanosheet interlayer (marked as GNS-PbO 2 ) was prepared combining electrophoretic deposition and electro-deposition technologies. The micro morphology, crystal structure and surface chemical states of GNS-PbO 2 electrodes were characterized using scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Their electrochemical properties and stability were determined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ·OH radicals test and accelerated life test, and compared with traditional PbO 2 electrodes. Besides, their potential application in the electrochemical degradation of 2-chlorophenol (2-CP) was investigated. The GNS-PbO 2 electrode possessed perfect octahedral β-PbO 2 microcrystals, and its grain size was much smaller than that of traditional PbO 2 electrode. It exhibited higher electrochemical activity than traditional PbO 2 electrode due to its larger electrochemical active surface area and stronger ·OH radicals generation ability. The service lifetime of GNS-PbO 2 electrode (107.9 h) was 1.93 times longer than that of traditional PbO 2 electrode (55.9 h). The electrochemical degradation rate constant of 2-CP on GNS-PbO 2 electrode (k app = 2.75 × 10 −2 min −1 ) is much higher than for PbO 2 electrode (k app = 1.76 × 10 −2 min −1 ). 2-CP oxidation yielded intermediates including aromatic compounds (catechol, phenol and ortho-benzoquinone) and organic acids (oxalic acid, maleic acid and

Tribological performance of titanium samples oxidized by fs-laser radiation, thermal heating, or electrochemical anodization

Science.gov (United States)

Kirner, S. V.; Slachciak, N.; Elert, A. M.; Griepentrog, M.; Fischer, D.; Hertwig, A.; Sahre, M.; Dörfel, I.; Sturm, H.; Pentzien, S.; Koter, R.; Spaltmann, D.; Krüger, J.; Bonse, J.

2018-04-01

Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms.

Study of the electrochemical oxidation of Am with lacunary heteropolyanions and silver nitrate

International Nuclear Information System (INIS)

Chartier, D.

1999-01-01

Electrochemical oxidation of Am(III) with certain lacunary heteropolyanions (LHPA α 2 -P 2 W 17 O 61 10- or αSiW 11 O 39 8- ) and silver nitrate is an efficient way to prepare Am(VI). This document presents bibliographic data and an experimental study of the process. Thus, it has been established that Am(IV) is an intermediate species in the reaction and occurs in 1:1 (Amt IV LHPA) or 1:2 (Am IV (LHAP) 2 ) complexes with the relevant LHPA. These 1:1 complexes of Am(IV) have been identified and isolated in this work whereas 1:2 complexes were known from previous studies. The reactivity of these complexes in oxidation shows that 1:1 complexes of Am(IV) are oxidised much more quickly than 1:2 complexes. Apparent stability constants of Am(III) and Am(IV) complexes with the relevant LHPA have been measured for a 1 M nitric acid medium. Thermodynamic data of the reaction are then assessed: redox potentials of Am pairs are computed for a 1 M nitric acid medium containing various amount of LHPA ligands. Those results show that the role of LHPA is to stabilize the intermediate species Am(IV) by lowering the Am(IV)/Am(III) pair potential of about 1 Volt. Nevertheless, if this stabilisation is too strong (i.e. of tungsto-silicate), the oxidation of Am(IV) requires high anodic potential (more than 2 V/ENH). Then, the faradic yield of the oxidation of americium is poor because of water oxidation. This study has also shown that the main role of silver is to catalyze the electrochemical oxidation of Am IV (LHPA) X complexes. Indeed, these oxidations without silver are extremely slow. An oxygen tracer experiment has been performed during the oxidation of Am(III) in Am(VI). It has been shown that the oxygen atoms of Am(VI) (AMO 2 2+ ) come from water molecules of the solvent and not from the complexing oxygen atoms of the ligands. (author)

Electrochemical oxidation of 243Am(III) in nitric acid by a terpyridyl-derivatized electrode

Energy Technology Data Exchange (ETDEWEB)

Dares, C. J.; Lapides, A. M.; Mincher, B. J.; Meyer, T. J.

2015-11-05

A high surface area, tin-doped indium oxide electrode surface-derivatized with a terpyridine ligand has been applied to the oxidation of trivalent americium to Am(V) and Am(VI) in nitric acid. Potentials as low as 1.8 V vs. the saturated calomel electrode are used, 0.7 V lower than the 2.6 V potential for one-electron oxidation of Am(III) to Am(IV) in 1 M acid. This simple electrochemical procedure provides, for the first time, a method for accessing the higher oxidation states of Am in non-complexing media for developing the coordination chemistries of Am(V) and Am(VI) and, more importantly, for separation of americium from nuclear waste streams.

Simulating Linear Sweep Voltammetry from First-Principles: Application to Electrochemical Oxidation of Water on Pt(111) and Pt₃Ni(111)

DEFF Research Database (Denmark)

Viswanathan, Venkatasubramanian; Hansen, Heine Anton; Rossmeisl, Jan

2012-01-01

Cyclic voltammetry is a fundamental experimental method for characterizing adsorbates on electrochemical surfaces. We present a model for the electrochemical solid–liquid interface, and we simulate the linear sweep voltammogram of the electrochemical oxidation of H2O on Pt(111) and Pt3Ni(111...

The strategies of DNA immobilization and hybridization detection mechanism in the construction of electrochemical DNA sensor: A review

Directory of Open Access Journals (Sweden)

Jahwarhar Izuan Abdul Rashid

2017-11-01

Full Text Available In recent years, electrochemical deoxyribonucleic acid (DNA sensor has recently emerged as promising alternative clinical diagnostic devices especially for infectious disease by exploiting DNA recognition events and converting them into an electrochemical signal. This is because the existing DNA diagnostic method possesses certain drawbacks such as time-consuming, expensive, laborious, low selectivity and sensitivity. DNA immobilization strategies and mechanism of electrochemical detection are two the most important aspects that should be considered before developing highly selective and sensitive electrochemical DNA sensor. Here, we focus on some recent strategies for DNA probes immobilization on the surface of electrochemical transducer such as adsorption, covalent bonding and Avidin/Streptavidin-Biotin interaction on the electrode surface for specific interaction with its complementary DNA target. A numerous approach for DNA hybridization detection based electrochemical technique that frequently used including direct DNA electrochemical detection and label based electrochemical (redox-active indicator, enzyme label and nanoparticles were also discussed in aiming to provide general guide for the design of electrochemical DNA sensor. We also discussed the challenges and suggestions to improve the application of electrochemical DNA sensor at point-care setting. Keywords: Electrochemical DNA sensor, DNA immobilization, DNA hybridization, Electrochemical mechanism

Carboxyl functionalized carbon fibers with preserved tensile strength and electrochemical performance used as anodes of structural lithium-ion batteries

International Nuclear Information System (INIS)

Feng, Mengjie; Wang, Shubin; Yu, Yalin; Feng, Qihang; Yang, Jiping; Zhang, Boming

2017-01-01

Highlights: • Carboxyl functionalized CF is acquired by simple chemical oxidation method. • These CF have preserved the tensile strength, better electrochemical properties. • The presence of H_3PO_4 prevented the turbostratic carbon from over-oxidization. • There CF can be used as anodes of multifunctional structural battery. • The preservation and improvement is result from the hindered over-oxidization. - Abstract: Carboxyl functionalized carbon fibers with preserved tensile strength and electrochemical properties were acquired through a simple chemical oxidation method, and the proposed underlying mechanism was verified. The surface of carboxyl functionalizing carbon fibers is necessary in acquiring functional groups on the surface of carbon fibers to further improve the thermal, electrical or mechanical properties of the fibers. Functionalization should preserve the tensile strength and electrochemical properties of carbon fibers, because the anodes of structural batteries need to have high strength and electrochemical properties. Functionalized with mixed H_2SO_4/HNO_3 considerably reduced the tensile strength of carbon fibers. By contrast, the appearance of H_3PO_4 preserved the tensile strength of functionalized carbon fibers, reduced the dispersion level of tensile strength values, and effectively increased the concentration of functional acid groups on the surface of carbon fibers. The presence of phosphoric acid hindered the over-oxidation of turbostratic carbon, and consequently preserved the tensile strength of carbon fibers. The increased proportion of turbostratic carbon on the surface of carbon fibers concurrently enhanced the electrochemical properties of carbon fibers.

An electrochemical analysis of AZ91 Mg alloy processed by plasma electrolytic oxidation followed by static annealing

Energy Technology Data Exchange (ETDEWEB)

Ko, Y.G. [School of Materials Science and Engineering, Yeungnam University, 214-1 Dae-Dong, Gyeongsan 712-749, Gyeongbuk (Korea, Republic of); Lee, K.M.; Lee, B.U. [Department of Metallurgy and Materials Engineering, Hanyang University, Ansan 425-791 (Korea, Republic of); Shin, D.H., E-mail: dhshin@hanyang.ac.kr [Department of Metallurgy and Materials Engineering, Hanyang University, Ansan 425-791 (Korea, Republic of)

2011-06-15

Research highlights: > The amount of MgO in the oxide film increased with increasing annealing temperature. > The dehydration reaction resulted in the formation of micro-cracks in the oxide film. > Electrochemical response of the PEO-treated sample annealed at 150 deg. C was improved. - Abstract: In this study, the effect of subsequent annealing on the electrochemical response of AZ91 Mg alloy coated via plasma electrolytic oxidation (PEO) was investigated. PEO coating was carried out on the Mg alloy under AC condition in an alkaline silicate electrolyte, and the PEO-coated samples underwent several subsequent annealing treatments at three different temperatures of 100, 150, and 200 deg. C. The surface morphologies of the coating layers were observed via a scanning electron microscope (SEM) and their constituent compounds were characterized by qualitative observation based on X-ray photoelectron spectroscopy (XPS). In addition, the corrosion protection properties of the PEO-coated sample were examined by electrochemical impedance spectroscopy (EIS) in a 3.5 wt% NaCl solution with a focus on exploring the effect of subsequent annealing on the electrochemical response in a quantitative manner. SEM and XPS observations evidenced that the subsequent annealing at temperatures higher than 150 deg. C resulted in significant morphological changes due to the dehydration reaction of Mg(OH){sub 2} to form MgO. Thus, it was found that the sample annealed at 150 deg. C exhibited a better corrosion resistance than the other samples, which were analyzed by taking an equivalent circuit model into account.

Low temperature oxidation of hydrocarbons using an electrochemical reactor

DEFF Research Database (Denmark)

Ippolito, Davide

conversion was a complex function of multiple variables: the microstructure of the backbone, the polarization resistance of the electrodes, both at OCV and under polarization, the electrical and morphological properties of the infiltrated material and the specific reaction conditions like the propene......This study investigated the use of a ceramic porous electrochemical reactor for the deep oxidation of propene. Two electrode composites, La0.85Sr0.15MnO3±d/Ce0.9Gd0.1O1.95 (LSM/CGO) and La0.85Sr0.15FeMnO3/Ce0.9Gd0.1O1.95 (LSF/CGO), were produced in a 5 single cells stacked configuration and used...... prolonged polarization was able to partially counteract the instability of the infiltrated Ce0.9Gd0.1O1.95. This project demonstrated the possibility to enhance the oxidation of propene by polarization in a porous ceramic reactor. The infiltration of different active materials helped to increase...

Oxidation of organics in water in microfluidic electrochemical reactors: Theoretical model and experiments

International Nuclear Information System (INIS)

Scialdone, Onofrio; Guarisco, Chiara; Galia, Alessandro

2011-01-01

The electrochemical oxidation of organics in water performed in micro reactors on boron doped diamond (BDD) anode was investigated both theoretically and experimentally in order to find the influence of various operative parameters on the conversion and the current efficiency CE of the process. The electrochemical oxidation of formic acid (FA) was selected as a model case. High conversions for a single passage of the electrolytic solution inside the cell were obtained by operating with proper residence times and low distances between cathode and anode. The effect of initial concentration, flow rate and current density was investigated in detail. Theoretical predictions were in very good agreement with experimental results for both mass transfer control, oxidation reaction control and mixed kinetic regimes in spite of the fact that no adjustable parameters was used. Mass transfer process was successfully modelled by considering for simplicity a constant Sh number (e.g., a constant mass transfer coefficient k m ) for a process performed with no high values of the current intensity to minimize the effect of the gas bubbling on the flowdynamic pattern. For mixed kinetic regimes, two different modelling approaches were used. In the first one, the oxidation of organics at BDD was assumed to be mass transfer controlled and to occur with an intrinsic 100% CE when applied current density is higher than the limiting current density. In the second case, the CE of the process was modelled assuming that the competition between organic and water oxidation depends only on the electrodic material and on the nature and the concentration of the organic. In the latter case a better agreement between experimental data and theoretical predictions was observed.

Electrochemical Modeling and Performance of a Lithium- and Manganese-Rich Layered Transition-Metal Oxide Positive Electrode

Energy Technology Data Exchange (ETDEWEB)

Dees, Dennis W.; Abraham, Daniel P; Lu, Wenquan; Gallagher, Kevin G.; Bettge, Martin; Jansen, Andrew N

2015-01-21

The impedance of a lithium- and manganese-rich layered transition-metal oxide (MR-NMC) positive electrode, specifically Li_1.2Ni_0.15Mn_0.55Co_0.1O₂, is compared to two other transition-metal layered oxide materials, specifically LiNi_0.8Co_0.15Al_0.05O₂ (NCA) and Li_1.05(Ni_1/3Co_1/3Mn_1/3)_0.95O₂ (NMC). A more detailed electrochemical impedance spectroscopy (EIS) study is conducted on the LMR-NMC electrode, which includes a range of states-of-charge (SOCs) for both current directions (i.e. charge and discharge) and two relaxation times (i.e. hours and one hundred hours) before the EIS sweep. The LMR-NMC electrode EIS studies are supported by half-cell constant current and galvanostatic intermittent titration technique (GITT) studies. Two types of electrochemical models are utilized to examine the results. The first type is a lithium ion cell electrochemical model for intercalation active material electrodes that includes a complex active material/electrolyte interfacial structure. In conclusion, the other is a lithium ion half-cell electrochemical model that focuses on the unique composite structure of the bulk LMR-NMC materials.

Electrochemical stability and transformations of fluorinated poly(2,6-dimethyl-1,4-phenylene oxide)

NARCIS (Netherlands)

Pud, A.A.; Rogalsky, S.P.; Ghapoval, G.S.; Kharitonov, A.P.; Kemperman, Antonius J.B.

2000-01-01

Fluorination of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) leads to narrowing of its window of electrochemical stability in a cathodic range of potentials. It is found this is connected with appearance of both perfluorinated and incompletely fluorinated units in the polymer. The former units are

Preparation of silver nanoparticles/graphene nanosheets as a catalyst for electrochemical oxidation of methanol

Energy Technology Data Exchange (ETDEWEB)

Han, Kun; Miao, Peng; Tang, Yuguo, E-mail: tangyg@sibet.ac.cn [Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Tong, Hui; Zhu, Xiaoli [Laboratory of Biosensing Technology, School of Life Sciences, Shanghai University, Shanghai 200444 (China); Liu, Tao; Cheng, Wenbo [Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163 (China)

2014-02-03

In this report, silver nanoparticles (AgNPs) decorated graphene nanosheets have been prepared based on the reduction of Ag ions by hydroquinone, and their catalytic performance towards the electrochemical oxidation of methanol is investigated. The synthesis of the nano-composite is confirmed by transmission electron microscope measurements and UV-vis absorption spectra. Excellent electrocatalytic performance of the material is demonstrated by cyclic voltammograms. This material also contributes to the low peak potential of methanol oxidation compared with most of the other materials.

Optimization of the nitrous vapors experimental conditions production by nitric acid electrochemical reduction

International Nuclear Information System (INIS)

Lemaire, M.

1996-01-01

Gaseous nitrogen oxides (NO and NO 2 ) involved as oxidizing agents in nuclear fuel reprocessing can be produced by electrochemical reduction of nitric acid. This is an interesting alternative to the existing process because no wastes are generated. voltammetric studies on a platinum electrode show that two reduction potential regions are observed in concentrated nitric acid solutions, between 0,05 V SHE and between 0,5 V SHE and 1 V SHE . The highest potential region reduction mechanism was studied by: classical micro-electrolysis methods, macro-electrolysis methods, infrared spectroscopy coupled to electrochemistry. It was determined that the origin of nitric acid reduction is the electrochemical reduction of nitrous acid in nitric oxide which chemically reduces nitric acid. This reaction produces nitrous acid back which indicate an auto-catalytic behaviour of nitric acid reduction mechanism. Nitrogen dioxide evolution during nitric reduction can also explained by an other chemical reaction. If the potential value of platinum electrode is above 0,8 V SHE , products of the indirect nitric acid reduction are nitrous acid, nitrogen oxide and nitrogen dioxide. Below this value nitric oxide can be reduced in nitrous oxide. Thus the potential value is the most important parameter for the nitrogen oxides production selectivity. However, owing to the auto-catalytic character of the reduction mechanism, potential value can be controlled during intentiostatic industrial electrolysis. (author)

Design and Electrochemical Study of Platinum-Based Nanomaterials for Sensitive Detection of Nitric Oxide in Biomedical Applications

Directory of Open Access Journals (Sweden)

Maduraiveeran Govindhan

2016-11-01

Full Text Available The extensive physiological and regulatory roles of nitric oxide (NO have spurred the development of NO sensors, which are of critical importance in neuroscience and various medical applications. The development of electrochemical NO sensors is of significant importance, and has garnered a tremendous amount of attention due to their high sensitivity and selectivity, rapid response, low cost, miniaturization, and the possibility of real-time monitoring. Nanostructured platinum (Pt-based materials have attracted considerable interest regarding their use in the design of electrochemical sensors for the detection of NO, due to their unique properties and the potential for new and innovative applications. This review focuses primarily on advances and insights into the utilization of nanostructured Pt-based electrode materials, such as nanoporous Pt, Pt and PtAu nanoparticles, PtAu nanoparticle/reduced graphene oxide (rGO, and PtW nanoparticle/rGO-ionic liquid (IL nanocomposites, for the detection of NO. The design, fabrication, characterization, and integration of electrochemical NO sensing performance, selectivity, and durability are addressed. The attractive electrochemical properties of Pt-based nanomaterials have great potential for increasing the competitiveness of these new sensors and open up new opportunities in the creation of novel NO-sensing technologies for biological and medical applications.

The mechanisms of pyrite oxidation and leaching: A fundamental perspective

Science.gov (United States)

Chandra, A. P.; Gerson, A. R.

2010-09-01

Pyrite is the earth's most abundant sulfide mineral. Its frequent undesirable association with minerals of economic value such as sphalerite, chalcopyrite and galena, and precious metals such as gold necessitates costly separation processes such as leaching and flotation. Additionally pyrite oxidation is a major contributor to the environmental problem of acid rock drainage. The surface oxidation reactions of pyrite are therefore important both economically and environmentally. Significant variations in electrical properties resulting from lattice substitution of minor and trace elements into the lattice structure exist between pyrite from different geographical locations. Furthermore the presence of low coordination surface sites as a result of conchoidal fracture causes a reduction in the band gap at the surface compared to the bulk thus adding further electrochemical variability. Given the now general acceptance after decades of research that electrochemistry dominates the oxidation process, the geographical location, elemental composition and semi-conductor type (n or p) of pyrite are important considerations. Aqueous pyrite oxidation results in the production of sulfate and ferrous iron. However other products such as elemental sulfur, polysulfides, hydrogen sulfide, ferric hydroxide, iron oxide and iron(III) oxyhydroxide may also form. Intermediate species such as thiosulfate, sulfite and polythionates are also proposed to occur. Oxidation and leach rates are generally influenced by solution Eh, pH, oxidant type and concentration, hydrodynamics, grain size and surface area in relation to solution volume, temperature and pressure. Of these, solution Eh is most critical as expected for an electrochemically controlled process, and directly correlates with surface area normalised rates. Studies using mixed mineral systems further indicate the importance of electrochemical processes during the oxidation process. Spatially resolved surface characterisation of fresh

Mediated electrochemical oxidation treatment for Rocky Flats combustible low-level mixed waste. Final report, FY 1993 and 1994

International Nuclear Information System (INIS)

Chiba, Z.; Lewis, P.R.; Murguia, L.C.

1994-09-01

Mediated Electrochemical Oxidation (MEO) is an aqueous process which destroys hazardous organics by oxidizing a mediator at the anode of an electrochemical cell; the mediator in turn oxidizes the organics within the bulk of the electrolyte. With this process organics can be nearly completely destroyed, that is, the carbon and hydrogen present in the hydrocarbon are almost entirely mineralized to carbon dioxide and water. The MEO process is also capable of dissolving radioactive materials, including difficult-to-dissolve compounds such as plutonium oxide. Hence, this process can treat mixed wastes, by destroying the hazardous organic components of the waste, and dissolving the radioactive components. The radioactive material can be recovered if desired, or disposed of as non-mixed radioactive waste. The process is inherently safe, since the hazardous and radioactive materials are completely contained in the aqueous phase, and the system operates at low temperatures (below 80 degree C) and at ambient pressures

Electrochemical properties of copper-based compounds with polyanion frameworks

Energy Technology Data Exchange (ETDEWEB)

Mizuno, Yoshifumi; Hata, Shoma; Suzuki, Kota; Hirayama, Masaaki; Kanno, Ryoji, E-mail: kanno@echem.titech.ac.jp

2016-03-15

The copper-based polyanion compounds Li{sub 6}CuB{sub 4}O{sub 10} and Li{sub 2}CuP{sub 2}O{sub 7} were synthesized using a conventional solid-state reaction, and their electrochemical properties were determined. Li{sub 6}CuB{sub 4}O{sub 10} showed reversible capacity of 340 mA g{sup −1} at the first discharge–charge process, while Li{sub 2}CuP{sub 2}O{sub 7} showed large irreversible capacity and thus low charge capacity. Ex situ X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) measurements revealed that the electrochemical Li{sup +} intercalation/deintercalation reaction in Li{sub 6}CuB{sub 4}O{sub 10} occurred via reversible Cu{sup 2+}/Cu{sup +} reduction/oxidation reaction. These differences in their discharge/charge mechanisms are discussed based on the strength of the Cu–O covalency via their inductive effects. - Graphical abstract: Electrochemical properties for Cu-based polyanion compounds were investigated. The electrochemical reaction mechanisms are strongly affected by their Cu–O covalentcy. - Highlights: • Electrochemical properties of Cu-based polyanion compounds were investigated. • The Li{sup +} intercalation/deintercalation reaction progressed in Li{sub 6}CuB{sub 4}O{sub 10}. • The electrochemical displacement reaction progressed in Li{sub 2}CuP{sub 2}O{sub 7}. • The strength of Cu–O covalency affects the reaction mechanism.

Morphology, structural and optical properties of iron oxide thin film photoanodes in photoelectrochemical cell: Effect of electrochemical oxidation

Science.gov (United States)

Maabong, Kelebogile; Machatine, Augusto G.; Hu, Yelin; Braun, Artur; Nambala, Fred J.; Diale, Mmantsae

2016-01-01

Hematite (α-Fe2O3) is a promising semiconductor as photoanode in solar hydrogen production from photoelectrolysis of water due to its appropriate band gap, low cost and high electrochemical stability in aqueous caustic electrolytes. Operation of such photoanode in a biased photoelectrochemical cell constitutes an anodization with consequent redox reactions at the electrode surface. α-Fe2O3 thin film photoanodes were prepared by simple and inexpensive dip coating method on fluorine doped tin oxide (FTO) glass substrate, annealed in air at 500 °C for 2 h, then electrochemically oxidized (anodized) in 1 M KOH at 500 mV for 1 min in dark and light conditions. Changes in structural properties and morphology of α-Fe2O3 nanoparticles films were investigated by XRD, Raman spectroscopy and a high resolution FE-SEM. The average grain size was observed to increase from 57 nm for pristine samples to 73 and 77 nm for anodized samples in dark and light respectively. Broadening and red shift in Raman spectra in anodized samples may be attributed to lattice expansion upon oxidation. The UV-visible measurements revealed enhanced absorption in the photoanodes after the treatment. The findings suggest that the anodization of the photoelectrode in a biased cell causes not only changes of the molecular structure at the surface, but also changes in the crystallographic structure which can be detected with x-ray diffractometry.

Morphology, structural and optical properties of iron oxide thin film photoanodes in photoelectrochemical cell: Effect of electrochemical oxidation

International Nuclear Information System (INIS)

Maabong, Kelebogile; Machatine, Augusto G.; Hu, Yelin; Braun, Artur; Nambala, Fred J.; Diale, Mmantsae

2016-01-01

Hematite (α-Fe_2O_3) is a promising semiconductor as photoanode in solar hydrogen production from photoelectrolysis of water due to its appropriate band gap, low cost and high electrochemical stability in aqueous caustic electrolytes. Operation of such photoanode in a biased photoelectrochemical cell constitutes an anodization with consequent redox reactions at the electrode surface. α-Fe_2O_3 thin film photoanodes were prepared by simple and inexpensive dip coating method on fluorine doped tin oxide (FTO) glass substrate, annealed in air at 500 °C for 2 h, then electrochemically oxidized (anodized) in 1 M KOH at 500 mV for 1 min in dark and light conditions. Changes in structural properties and morphology of α-Fe_2O_3 nanoparticles films were investigated by XRD, Raman spectroscopy and a high resolution FE-SEM. The average grain size was observed to increase from ~57 nm for pristine samples to 73 and 77 nm for anodized samples in dark and light respectively. Broadening and red shift in Raman spectra in anodized samples may be attributed to lattice expansion upon oxidation. The UV–visible measurements revealed enhanced absorption in the photoanodes after the treatment. The findings suggest that the anodization of the photoelectrode in a biased cell causes not only changes of the molecular structure at the surface, but also changes in the crystallographic structure which can be detected with x-ray diffractometry.

Morphology, structural and optical properties of iron oxide thin film photoanodes in photoelectrochemical cell: Effect of electrochemical oxidation

Energy Technology Data Exchange (ETDEWEB)

Maabong, Kelebogile [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Laboratory of High Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland); Department of Physics, University of Botswana, Private Bag 002, Gaborone (Botswana); Machatine, Augusto G. [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Hu, Yelin [Laboratory of High Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland); Laboratory for Photonics and Interfaces, EPFL, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Braun, Artur [Laboratory of High Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland); Nambala, Fred J. [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); University of Zambia, Box 32379, Great East Road Campus, Lusaka (Zambia); Diale, Mmantsae, E-mail: mmantsae.diale@up.ac.za [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Laboratory of High Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland)

2016-01-01

Hematite (α-Fe{sub 2}O{sub 3}) is a promising semiconductor as photoanode in solar hydrogen production from photoelectrolysis of water due to its appropriate band gap, low cost and high electrochemical stability in aqueous caustic electrolytes. Operation of such photoanode in a biased photoelectrochemical cell constitutes an anodization with consequent redox reactions at the electrode surface. α-Fe{sub 2}O{sub 3} thin film photoanodes were prepared by simple and inexpensive dip coating method on fluorine doped tin oxide (FTO) glass substrate, annealed in air at 500 °C for 2 h, then electrochemically oxidized (anodized) in 1 M KOH at 500 mV for 1 min in dark and light conditions. Changes in structural properties and morphology of α-Fe{sub 2}O{sub 3} nanoparticles films were investigated by XRD, Raman spectroscopy and a high resolution FE-SEM. The average grain size was observed to increase from ~57 nm for pristine samples to 73 and 77 nm for anodized samples in dark and light respectively. Broadening and red shift in Raman spectra in anodized samples may be attributed to lattice expansion upon oxidation. The UV–visible measurements revealed enhanced absorption in the photoanodes after the treatment. The findings suggest that the anodization of the photoelectrode in a biased cell causes not only changes of the molecular structure at the surface, but also changes in the crystallographic structure which can be detected with x-ray diffractometry.

A mechanical actuator driven electrochemically by artificial molecular muscles.

Science.gov (United States)

Juluri, Bala Krishna; Kumar, Ajeet S; Liu, Yi; Ye, Tao; Yang, Ying-Wei; Flood, Amar H; Fang, Lei; Stoddart, J Fraser; Weiss, Paul S; Huang, Tony Jun

2009-02-24

A microcantilever, coated with a monolayer of redox-controllable, bistable [3]rotaxane molecules (artificial molecular muscles), undergoes reversible deflections when subjected to alternating oxidizing and reducing electrochemical potentials. The microcantilever devices were prepared by precoating one surface with a gold film and allowing the palindromic [3]rotaxane molecules to adsorb selectively onto one side of the microcantilevers, utilizing thiol-gold chemistry. An electrochemical cell was employed in the experiments, and deflections were monitored both as a function of (i) the scan rate (+0.4 V) and reducing (artificial molecular muscles, were compared with (i) data from nominally bare microcantilevers precoated with gold and (ii) those coated with two types of control compounds, namely, dumbbell molecules to simulate the redox activity of the palindromic bistable [3]rotaxane molecules and inactive 1-dodecanethiol molecules. The comparisons demonstrate that the artificial molecular muscles are responsible for the deflections, which can be repeated over many cycles. The microcantilevers deflect in one direction following oxidation and in the opposite direction upon reduction. The approximately 550 nm deflections were calculated to be commensurate with forces per molecule of approximately 650 pN. The thermal relaxation that characterizes the device's deflection is consistent with the double bistability associated with the palindromic [3]rotaxane and reflects a metastable contracted state. The use of the cooperative forces generated by these self-assembled, nanometer-scale artificial molecular muscles that are electrically wired to an external power supply constitutes a seminal step toward molecular-machine-based nanoelectromechanical systems (NEMS).

Catalytic and electrochemical behaviour of solid oxide fuel cell operated with simulated-biogas mixtures

Energy Technology Data Exchange (ETDEWEB)

Dang-Long, T., E-mail: 3TE14098G@kyushu-u.ac.jp [Department of Hydrogen Energy Systems, Faculty of Engineering, Kyushu University Motooka 744, Nishiku, Fukuoka, 810-0395 (Japan); Quang-Tuyen, T., E-mail: tran.tuyen.quang.314@m.kyushu-u.ac.jp [International Research Center for Hydrogen Energy, Kyushu University Motooka 744, Nishiku, Fukuoka, 810-0395 (Japan); Shiratori, Y., E-mail: shiratori.yusuke.500@m.kyushu-u.ac.jp [Department of Hydrogen Energy Systems, Faculty of Engineering, Kyushu University Motooka 744, Nishiku, Fukuoka, 810-0395 (Japan); International Research Center for Hydrogen Energy, Kyushu University Motooka 744, Nishiku, Fukuoka, 810-0395 (Japan)

2016-06-03

Being produced from organic matters of wastes (bio-wastes) through a fermentation process, biogas mainly composed of CH{sub 4} and CO{sub 2} and can be considered as a secondary energy carrier derived from solar energy. To generate electricity from biogas through the electrochemical process in fuel cells is a state-of-the-art technology possessing higher energy conversion efficiency without harmful emissions compared to combustion process in heat engines. Getting benefits from high operating temperature such as direct internal reforming ability and activation of electrochemical reactions to increase overall system efficiency, solid oxide fuel cell (SOFC) system operated with biogas becomes a promising candidate for distributed power generator for rural applications leading to reductions of environmental issues caused by greenhouse effects and bio-wastes. CO{sub 2} reforming of CH{sub 4} and electrochemical oxidation of the produced syngas (H{sub 2}–CO mixture) are two main reaction processes within porous anode material of SOFC. Here catalytic and electrochemical behavior of Ni-ScSZ (scandia stabilized-zirconia) anode in the feed of CH{sub 4}–CO{sub 2} mixtures as simulated-biogas at 800 °C were evaluated. The results showed that CO{sub 2} had strong influences on both reaction processes. The increase in CO{sub 2} partial pressure resulted in the decrease in anode overvoltage, although open-circuit voltage was dropped. Besides that, the simulation result based on a power-law model for equimolar CH{sub 4}−CO{sub 2} mixture revealed that coking hazard could be suppressed along the fuel flow channel in both open-circuit and closed-circuit conditions.

Electrochemical oxidation and electroanalytical determination of xylitol at a boron-doped diamond electrode.

Science.gov (United States)

Lourenço, Anabel S; Sanches, Fátima A C; Magalhães, Renata R; Costa, Daniel J E; Ribeiro, Williame F; Bichinho, Kátia M; Salazar-Banda, Giancarlo R; Araújo, Mário C U

2014-02-01

Xylitol is a reduced sugar with anticariogenic properties used by insulin-dependent diabetics, and which has attracted great attention of the pharmaceutical, cosmetics, food and dental industries. The detection of xylitol in different matrices is generally based on separation techniques. Alternatively, in this paper, the application of a boron-doped diamond (BDD) electrode allied to differing voltammetric techniques is presented to study the electrochemical behavior of xylitol, and to develop an analytical methodology for its determination in mouthwash. Xylitol undergoes two oxidation steps in an irreversible diffusion-controlled process (D=5.05 × 10(-5)cm(2)s(-1)). Differential pulse voltammetry studies revealed that the oxidation mechanism for peaks P1 (3.4 ≤ pH ≤ 8.0), and P2 (6.0 ≤ pH ≤ 9.0) involves transfer of 1H(+)/1e(-), and 1e(-) alone, respectively. The oxidation process P1 is mediated by the (•)OH generated at the BDD hydrogen-terminated surface. The maximum peak current was obtained at a pH of 7.0, and the electroanalytical method developed, (employing square wave voltammetry) yielded low detection (1.3 × 10(-6) mol L(-1)), and quantification (4.5 × 10(-6) mol L(-1)) limits, associated with good levels of repeatability (4.7%), and reproducibility (5.3%); thus demonstrating the viability of the methodology for detection of xylitol in biological samples containing low concentrations. © 2013 Elsevier B.V. All rights reserved.

Investigation of the direct and indirect electrochemical oxidation of hydrazine in nitric acid medium on platinum

International Nuclear Information System (INIS)

Cames, B.

1997-01-01

In nuclear fuel processing by the PUREX process, the purification of plutonium in nitric acid medium requires the oxidation of Pu(III) to Pu(IV), and of hydrazinium nitrate to nitrogen. The study helped to characterize the electrochemical behavior of the oxidation of hydrazinium nitrate and the reduction of nitric acid to nitrous acid, a compound which can chemically oxidize hydrazinium nitrate and Pu(III). Electro-analytical studies on polycrystalline platinum showed that hydrazine is oxidized in two potential zones, which depend on the surface texture of the platinum anode. Electrolysis in separate compartments, carried out in medium-acid media (2 and 4 mo/l) in the potential zone where these processes take place, showed that, at 0.9 V/ECS, the hydrazine oxidation reactions involved are: a four-electron process (75 %) with nitrogen formation and a one-electron process (25 %) with formation of nitrogen and ammonium ion. By contrast, electrolysis carried out at 0.65 V/ECS (with reactivation of the electrode at - 0.2 V/ECS to remove the poison from the platinum) allowed the selective oxidation of hydrazine to nitrogen by the four-electron reaction. Nitric acid can only be reduced to nitrous acid in the absence of hydrazine. For medium-acid media (≤ 6 mol/l), this reaction takes place at potentials below - 0.2 V/ECS. However, the production rate of nitrous acid (partial order 0 with respect to nitric acid) is very low compared with the values obtained for strongly-acid media (6 to 10 mol/l) at the potential of - 0.1 V/ECS. Note that, in concentrated nitric medium, the selectivity of the reduction reaction is 47 to 85 % for nitrous acid, depending on the nitric acid concentration (6 to 10 mol/l) and the potential imposed (- 0.1 ≤ E ≤ 0.6 V/ECS). A kinetic study helped to determine the hydrazine oxidation rates as a function of the operating conditions. In all cases, the reaction rate is of partial order 0 with respect to hydrazine. These studies accordingly

Electrochemical Corrosion Behavior of Oxidation Layer on Fe30Mn5Al Alloy

Directory of Open Access Journals (Sweden)

ZHU Xue-mei

2017-08-01

Full Text Available The Fe30Mn5Al alloy was oxidized at 800℃ in air for 160h, the oxidation-induced layer about 15μm thick near the scale-metal interface was induced to transform to ferrite and become enriched in Fe and depletion in Mn. The effect of the oxidation-induced Mn depletion layer on the electrochemical corrosion behavior of Fe30Mn5Al alloy was evaluated. The results show that in 1mol·L-1 Na2SO4 solution, the anodic polarization curve of the Mn depletion layer exhibits self-passivation, compared with Fe30Mn5Al austenitic alloy, and the corrosion potential Evs SCE is increased to -130mV from -750mV and the passive current density ip is decreased to 29μA/cm2 from 310μA/cm2. The electrochemical impedance spectroscopy(EIS of the Mn depletion layer has the larger diameter of capacitive arc, the higher impedance modulus|Z|, and the wider phase degree range, and the fitted polarization resistant Rt is increased to 9.9kΩ·cm2 from 2.7kΩ·cm2 by using an equivalent electric circuit of Rs-(Rt//CPE. The high insulation of the Mn depletion layer leads to an improved corrosion resistance of Fe30Mn5Al austenitic alloy.

The nanostructure of microbially-reduced graphene oxide fosters thick and highly-performing electrochemically-active biofilms

Science.gov (United States)

Virdis, Bernardino; Dennis, Paul G.

2017-07-01

Biofilms of electrochemically-active organisms are used in microbial electrochemical technologies (METs) to catalyze bioreactions otherwise not possible at bare electrodes. At present, however, achievable current outputs are still below levels considered sufficient for economic viability of large-scale METs implementations. Here, we report three-dimensional, self-aggregating biofilm composites comprising of microbial cells embedded with microbially-reduced graphene oxide (rGO) nanoparticles to form a thick macro-porous network with superior electrochemical properties. In the presence of metabolic substrate, these hybrid biofilms are capable of producing up to five times more catalytic current than the control biofilms. Cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy, show that in spite of the increased thickness, the biofilms amended with GO display lower polarization/charge transfer resistance compared to the controls, which we ascribe to the incorporation of rGO into the biofilms, which (1) promotes fast electron transfer, yet conserving a macroporous structure that allows free diffusion of reactants and products, and (2) enhances the interfacial dynamics by allowing a higher load of microbial cells per electrode surface area. These results suggest an easy-to-apply and cost-effective method to produce high-performing electrochemically-active biofilms in situ.

Written-in conductive patterns on robust graphene oxide biopaper by electrochemical microstamping.

Science.gov (United States)

Hu, Kesong; Tolentino, Lorenzo S; Kulkarni, Dhaval D; Ye, Chunhong; Kumar, Satish; Tsukruk, Vladimir V

2013-12-16

The silk road: By employing silk fibroin as a binder between graphene oxide films and aluminum foil for a facile, highly localized reduction process, conductive paper is reinvented. The flexible, robust biographene papers have high toughness and electrical conductivity. This electrochemical written-in approach is readily applicable for the fabrication of conductive patterned papers with complex circuitries. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electropolishing of AISI-304 stainless steel using an oxidizing solution originally used for electrochemical coloration

International Nuclear Information System (INIS)

Andrade, Leonardo S.; Xavier, Sandro C.; Rocha-Filho, Romeu C.; Bocchi, Nerilso; Biaggio, Sonia R.

2005-01-01

Chemical polishing or electropolishing, instead of mechanical polishing, are recommended for the attainment of metallic surface polishes without the introduction of contaminants or tensions in the surface layers of the metal. The fundamental difference between the chemical and electrochemical polishing processes is that in the latter anodic currents/potentials are used to help in the dissolution and passivation of the metal. In this paper, the use of an oxidizing electrolytic solution (2.5 mol L -1 CrO 3 + 5.0 mol L -1 H 2 SO 4 ) originally employed in electrochemical coloration processes is reported for the electropolishing of AISI-314 stainless steel. Parameters involved in this electropolishing process, such as temperature, current density and time, were optimized so as to attain the best possible results evaluated by the obtained surface brightness measured by reflectance spectra. Surface analyses by scanning electron microscopy allowed a clear correlation between obtained brightness and surface smoothing. The best conditions obtained for the electropolishing process are: temperature of 45 deg. C, electrolysis time of 10 min and current density of around 25 A dm -2 . It should be pointed out that an electropolishing process signature (periodic oscillations of the cell potential) was established; this may be an important tool for optimizing and monitoring electropolishing processes

Structural and Electrochemical Properties of Lithium Nickel Oxide Thin Films

Directory of Open Access Journals (Sweden)

Gyu-bong Cho

2014-01-01

Full Text Available LiNiO2 thin films were fabricated by RF magnetron sputtering. The microstructure of the films was determined by X-ray diffraction and field-emission scanning electron microscopy. The electrochemical properties were investigated with a battery cycler using coin-type half-cells. The LiNiO2 thin films annealed below 500°C had the surface carbonate. The results suggest that surface carbonate interrupted the Li intercalation and deintercalation during charge/discharge. Although the annealing process enhanced the crystallization of LiNiO2, the capacity did not increase. When the annealing temperature was increased to 600°C, the FeCrNiO4 oxide phase was generated and the discharge capacity decreased due to an oxygen deficiency in the LiNiO2 thin film. The ZrO2-coated LiNiO2 thin film provided an improved discharge capacity compared to bare LiNiO2 thin film suggesting that the improved electrochemical characteristic may be attributed to the inhibition of surface carbonate by ZrO2 coating layer.

Electrochemical capacitor

Science.gov (United States)

Anderson, Marc A.; Liu, Kuo -Chuan; Mohr, Charles M.

1999-10-05

An inexpensive porous metal oxide material having high surface area, good conductivity and high specific capacitance is advantageously used in an electrochemical capacitor. The materials are formed in a sol-gel process which affords control over the properties of the resultant metal oxide materials.

Physical and electrochemical study of cobalt oxide nano- and microparticles

Energy Technology Data Exchange (ETDEWEB)

Alburquenque, D. [Dpto. de Química de los Materiales, USACh, Av. L.B.O.‘Higgins 3363, 9170022 Santiago (Chile); Dpto. de Metalurgia, USACh, Av. Ecuador 3469, 9170124, Santiago (Chile); Vargas, E. [Dpto. de Física, USACh and CEDENNA, Av. Ecuador 3493, 9170124 Santiago (Chile); Dpto. de Metalurgia, USACh, Av. Ecuador 3469, 9170124, Santiago (Chile); Denardin, J.C.; Escrig, J. [Dpto. de Física, USACh and CEDENNA, Av. Ecuador 3493, 9170124 Santiago (Chile); Marco, J.F. [Instituto de Química Física “Rocasolano”, CSIC, c/Serrano 119, 28006 Madrid (Spain); Ortiz, J. [Dpto. de Química de los Materiales, USACh, Av. L.B.O.‘Higgins 3363, 9170022 Santiago (Chile); Gautier, J.L., E-mail: juan.gautier@usach.cl [Dpto. de Química de los Materiales, USACh, Av. L.B.O.‘Higgins 3363, 9170022 Santiago (Chile)

2014-07-01

Cobalt oxide nanocrystals of size 17–21 nm were synthesized by a simple reaction between cobalt acetate (II) and dodecylamine. On the other hand, micrometric Co{sub 3}O{sub 4} was prepared using the ceramic method. The structural examination of these materials was performed using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM and HRTEM). XRD studies showed that the oxides were pure, well-crystallized, spinel cubic phases with a-cell parameter of 0.8049 nm and 0.8069 nm for the nano and micro-oxide, respectively. The average particle size was 19 nm (nano-oxide) and 1250 μm (micro-oxide). Morphological studies carried out by SEM and TEM analyses have shown the presence of octahedral particles in both cases. Bulk and surface properties investigated by X-ray photoelectron spectroscopy (XPS), point zero charge (pzc), FTIR and cyclic voltammetry indicated that there were no significant differences in the composition on both materials. The magnetic behavior of the samples was determined using a vibrating sample magnetometer. The compounds showed paramagnetic character and no coercivity and remanence in all cases. Galvanostatic measurements of electrodes formed with nanocrystals showed better performance than those built with micrometric particles. - Highlights: • Spinel Co{sub 3}O{sub 4} nanoparticles and microparticles with same structure but with different cell parameters, particle size and surface area were synthesized. • Oxide nanoparticles showed better electrochemical behavior than micrometric ones due to area effect.

Electrochemical Determination of Baicalin in Traditional Chinese Medicine Based on the Enhancement Effect of MoO3-Reduced Graphene Oxide Nanocomposite

Science.gov (United States)

Hu, Weibing; Zhang, Wen; Wang, Meng; Feng, Fu

2018-02-01

The nanocomposites of MoO3-reduced graphene oxide (MoO3-RGO) were synthesized by hydrothermal reduction using MoCl5 and graphene oxide as precursors. The resulting composites were characterized with scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and Raman spectra, and were further used to modify the glassy carbon electrode (GCE). After optimizing the parameters, the electrochemical behavior of baicalin on different types of electrodes was investigated. The MoO3-RGO composite-modified GCE exhibited remarkably enhanced electrochemical signals of baicalin. After 90 s, under open circuit potential, oxidation and reduction peaks appeared at 0.207 V and 0.103 V, respectively. A sensitive and simple electrochemical method was proposed for the determination of baicalin in which the calibration curve ranges from 1.0 × 10-9 M to 4.3 × 10-5 M, and the detection limit is 3.81 × 10-10 M.

MnO2-Graphene Oxide-PEDOT:PSS Nanocomposite for an Electrochemical Supercapacitor

Science.gov (United States)

Patil, Dipali S.; Pawar, Sachin A.; Shin, Jae Cheol; Kim, Hyo Jin

2018-04-01

A ternary nanocomposite with poly (3,4 ethylene dioxythiophene:poly(styrene sulfonate) (PEDOT:PSS)-MnO2 nanowires-graphene oxide (PMn-GO) was synthesized by using simple chemical route. The formation of the nanocomposite was analyzed by using X-ray diffraction and X-ray photoelectron spectroscopy. Field-emission scanning microscopy (FESEM) revealed the formation of MnO2 nanowires and graphene oxide nanosheets. The highest specific capacitance (areal capacitance) of 841 Fg -1 (177 mFcm -2) at 10 mVs -1 and energy density of 0.593 kWhkg -1 at 0.5 mA were observed for PMn-GO, indicating a constructive synergistic effect of PEDOT:PSS, MnO2 nanowires and graphene oxide. The achieved promising electrochemical characteristics showed that this ternary nanocomposite is a good alternative as an electrode material for supercapacitor.

Boron-doped cadmium oxide composite structures and their electrochemical measurements

Energy Technology Data Exchange (ETDEWEB)

Lokhande, B.J., E-mail: bjlokhande@yahoo.com [Lab of Smart Mtrls Supercapacitive and Energy Studies, School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra (India); Ambare, R.C. [Lab of Smart Mtrls Supercapacitive and Energy Studies, School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra (India); Mane, R.S. [School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606 (India); Bharadwaj, S.R. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2013-08-01

Graphical abstract: Conducting nano-fibrous 3% boron doped cadmium oxide thin films were prepared by SILAR and its super capacitive properties were studied. - Highlights: • Samples are of nanofibrous nature. • All samples shows pseudocapacitive behavior. • 3% B doped CdO shows good specific capacitance. • 3% B doped CdO shows maximum 74.93% efficiency at 14 mA/cm{sup 2}. • 3% B doped CdO shows 0.8 Ω internal resistance. - Abstract: Boron-doped and undoped cadmium oxide composite nanostructures in thin film form were prepared onto stainless steel substrates by a successive ionic layer adsorption and reaction method using aqueous solutions of cadmium nitrate, boric acid and 1% H{sub 2}O{sub 2}. As-deposited films were annealed at 623 K for 1 h. The X-ray diffraction study shows crystalline behavior for both doped and undoped films with a porous topography and nano-wires type architecture, as observed in SEM image. Wettability test confirms the hydrophilic surface with 58° contact angle value. Estimated band gap energy is around 1.9 eV. Electrochemical behavior of the deposited films is attempted in 1 M KOH electrolyte using cyclic voltammetry (CV), electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Maximum values of the specific capacitance, specific energy and specific power obtained for 3% B doped CdO film at 2 mV/s scan rate are 20.05 F/g, 1.22 Wh/kg and 3.25 kW/kg, respectively.

Status of the DOE battery and electrochemical technology program. III

International Nuclear Information System (INIS)

Roberts, R.

1982-02-01

This report reviews the status of the Department of Energy Subelement on Electrochemical Storage Systems. It emphasizes material presented at the Fourth US Department of Energy Battery and Electrochemical Contractors' Conference, held June 2-4, 1981. The conference stressed secondary batteries, however, the aluminum/air mechanically rechargeable battery and selected topics on industrial electrochemical processes were included. The potential contributions of the battery and electrochemical technology efforts to supported technologies: electric vehicles, solar electric systems, and energy conservation in industrial electrochemical processes, are reviewed. The analyses of the potential impact of these systems on energy technologies as the basis for selecting specific battery systems for investigation are noted. The battery systems in the research, development, and demonstration phase discussed include: aqueous mobile batteries (near term) - lead-acid, iron/nickel-oxide, zinc/nickel-oxide; advanced batteries - aluminum/air, iron/air, zinc/bromine, zinc/ferricyanide, chromous/ferric, lithium/metal sulfide, sodium/sulfur; and exploratory batteries - lithium organic electrolyte, lithium/polymer electrolyte, sodium/sulfur (IV) chloroaluminate, calcium/iron disulfide, lithium/solid electrolyte. Supporting research on electrode reactions, cell performance modeling, new battery materials, ionic conducting solid electrolytes, and electrocatalysis is reviewed. Potential energy saving processes for the electrowinning of aluminum and zinc, and for the electrosynthesis of inorganic and organic compounds are included

Contribution to the identification of the processes kinetically limiting of the zirconium alloys oxidation; characterization of the oxide films formed at high temperature by solids electrochemistry

International Nuclear Information System (INIS)

Vermoyal, J.J.

2000-06-01

The corrosion behavior of zirconium alloys used for cladding tubes has been extensively studied under several oxidation conditions (temperature, steam, dry air, oxygen...) in order to clarify the mechanism(s) of oxide growth and breakdown. Oxidation rate is generally assumed to be controlled by oxygen diffusion inwards the oxide layer. Nevertheless, several experimental facts, such as acceleration or inhibition of corrosion rate in coupling conditions, suggest that electrochemical processes are involved as a rate determining step. This work is an attempt to shed light about the rate-limiting-mechanism of two zirconium alloys oxidation: Zircaloy-4 (Zy-4) and Zr-Nb(1%)O(0,13%). Impedance spectroscopy characterizations of oxide films formed in high temperature water and studied in gaseous atmosphere clearly show the difference of electrical properties between the two alloys. The in situ electrochemical and thermogravimetric investigations in gaseous medium, and the polarization effects on oxidation and hydridation of Zr alloys in PWRs conditions indicate that oxygen diffusion can be considered as the limiting kinetic step for Zy-4 oxidation. On the contrary, the acceleration of oxide growth on Zr-Nb(1%)O(0,13%) under anodic polarization in PWRs conditions (360 deg C) suggests that either the electronic conductivity in the oxide or an interfacial process at least partially control the oxidation rate. Catalytic effects observed in gaseous medium when noble metals increase the oxygen reduction rate would tend to corroborate the oxidation control of this alloy by an interfacial mechanism. An electrochemical description and a heterogeneous kinetics approach based on a diffusion-interfacial process as rate determining step are then proposed. (author)

Origin of the different behavior of some platinum decorated nanocarbons towards the electrochemical oxidation of hydrogen peroxide

International Nuclear Information System (INIS)

Malara, A.; Leonardi, S.G.; Bonavita, A.; Fazio, E.; Stelitano, S.; Neri, G.; Neri, F.; Santangelo, S.

2016-01-01

The electrochemical behavior of different platinum-decorated nanocarbons (Pt@C) towards the oxidation of hydrogen peroxide (H_2O_2) was investigated. Three different types of nanocarbons were considered: i) carbon black, ii) dahlia-like carbon nanohorns and iii) carbon nanotubes, which included both commercial (single-wall and multi-wall) and laboratory prepared (multi-wall) samples. Shape and size distribution of the platinum nanoparticles and morphology of the nanocarbons were analyzed by transmission electron microscopy. Their nanostructure was investigated by micro-Raman spectroscopy, while elemental composition of the samples and chemical bonding states were studied by X-ray photoelectron spectroscopy. Electrochemical behavior towards H_2O_2 oxidation was evaluated by means of cyclic voltammetry modifying the working screen-printed carbon electrode surface with the prepared Pt@C nanocomposites. Data obtained suggest that the size and dispersion of the Pt nanoparticles play a key role in increasing the sensitivity towards H_2O_2 detection. Thanks to the presence of smaller and more dispersed platinum particles and of a greater amount of platinum hydroxide, acting as intermediary in the H_2O_2 oxidation process, Pt@dahlia-like carbon nanohorns result to be the most promising platform for the development of H_2O_2 electrochemical sensors. - Highlights: • Different nanocarbons are decorated with Pt nanoparticles by wet impregnation method. • Pt@C-based hybrids are tested as active materials for sensing of hydrogen peroxide. • Sensor based on Pt@dahlia-like carbon nanohorns is the most performing device. • The origin of the different electrochemical behaviour is investigated. • Pt@C sensing performances are correlated with their structural and surface properties.

Structures and electrochemical performances of pyrolized carbons from graphite oxides for electric double-layer capacitor

Science.gov (United States)

Kim, Ick-Jun; Yang, Sunhye; Jeon, Min-Je; Moon, Seong-In; Kim, Hyun-Soo; Lee, Yoon-Pyo; An, Kye-Hyeok; Lee, Young-Hee

The structural features and the electrochemical performances of pyrolized needle cokes from oxidized cokes are examined and compared with those of KOH-activated needle coke. The structure of needle coke is changed to a single phase of graphite oxide after oxidation treatment with an acidic solution having an NaClO 3/needle coke composition ratio of above 7.5, and the inter-layer distance of the oxidized needle coke is expanded to 6.9 Å with increasing oxygen content. After heating at 200 °C, the oxidized needle coke is reduced to a graphite structure with an inter-layer distance of 3.6 Å. By contrast, a change in the inter-layer distance in KOH-activated needle coke is not observed. An intercalation of pyrolized needle coke, observed on first charge, occurs at 1.0 V. This value is lower than that of KOH-activation needle coke. A capacitor using pyrolized needle coke exhibits a lower internal resistance of 0.57 Ω in 1 kHz, and a larger capacitance per weight and volume of 30.3 F g -1 and 26.9 F ml -1, in the two-electrode system over the potential range 0-2.5 V compared with those of a capacitor using KOH-activation of needle coke. This better electrochemical performance is attributed to a distorted graphene layer structure derived from the process of the inter-layer expansion and shrinkage.

Effect of Aging on the Electrochemical Performance of LSM-YSZ Cathodes

DEFF Research Database (Denmark)

Baqué, L. C.; Jørgensen, Peter Stanley; Zhang, Wei

2015-01-01

resistance shows no clear tendency with aging time, while the ionic conductivity decreases up to ∼79%. Accordingly, the electrochemically active thickness contracts from 60–135 μm to 45–60 μm. The changes observed in the cathode transport and electrochemical properties are mostly explained by the evolution......Investigations of degradation mechanisms of solid oxide fuel cells are crucial for achieving a widespread commercialization of the technology. In this work, electrochemical impedance spectroscopy (EIS) was applied for studying the aging effect on LSM-YSZ cathodes exposed to humidified air at 900°C...... for up to 3000 h. EIS spectra were fitted by a transmission line model for estimating relevant parameters associated with the LSM/YSZ charge transfer reaction and the oxide ion conduction through the YSZ network. For the reference non-aged sample, the ionic conductivity values are the expected ones...

Pseudocapacitive Oxides and Sulfides for High-Performance Electrochemical Energy Storage

KAUST Repository

Xia, Chuan

2018-03-22

The intermittent nature of several sustainable energy sources such as solar and wind energy has ignited the demand of electrochemical energy storage devices in the form of batteries and electrochemical capacitors. The future generation of electrochemical capacitors will in large part depend on the use of pseudocapacitive materials in one or both electrodes. Developing pseudocapacitors to have both high energy and power density is crucial for future energy storage systems. This dissertation evaluates two different material systems to achieve high energy density pseudocapacitive energy storage. This research presents the successful preparation and application of ternary NiCo2S4, which is based on the surface redox mechanism, in the area of pseudocapacitive energy storage. Attention has been paid to understanding its basic physical properties which can impact its electrochemical behavior. Well-defined single- and double-shell NiCo2S4 hollow spheres were fabricated for pseudocapacitor applications, showing much improved electrochemical storage performance with good energy and power densities, as well as excellent cycling stability. To overcome the complexity of the preparation methods of NiCo2S4 nanostructures, a one-step approach was developed for the first time. Asymmetric pseudocapacitors using NiCo2S4 as cathode and graphene as anode were also fabricated to extend the operation voltage in aqueous electrolyte, and thus enhance the overall capacity of the cells. Furthermore, high-performance on-chip pseudocapacitive energy storage was demonstrated using NiCo2S4 as electrochemically active materials. This dissertation also involves another material system, intercalation pseudocapacitive VO2 (B), that displays a different charge storage mechanism from NiCo2S4. By constructing high-quality, atomically-thin two-dimensional (2D) VO2 (B) sheets using a general monomer-assisted approach, we demonstrate that a rational design of atomically thin, 2D nanostructures of

Carboxyl functionalized carbon fibers with preserved tensile strength and electrochemical performance used as anodes of structural lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Feng, Mengjie [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Wang, Shubin, E-mail: shubinwang@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Yu, Yalin; Feng, Qihang; Yang, Jiping; Zhang, Boming [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

2017-01-15

Highlights: • Carboxyl functionalized CF is acquired by simple chemical oxidation method. • These CF have preserved the tensile strength, better electrochemical properties. • The presence of H{sub 3}PO{sub 4} prevented the turbostratic carbon from over-oxidization. • There CF can be used as anodes of multifunctional structural battery. • The preservation and improvement is result from the hindered over-oxidization. - Abstract: Carboxyl functionalized carbon fibers with preserved tensile strength and electrochemical properties were acquired through a simple chemical oxidation method, and the proposed underlying mechanism was verified. The surface of carboxyl functionalizing carbon fibers is necessary in acquiring functional groups on the surface of carbon fibers to further improve the thermal, electrical or mechanical properties of the fibers. Functionalization should preserve the tensile strength and electrochemical properties of carbon fibers, because the anodes of structural batteries need to have high strength and electrochemical properties. Functionalized with mixed H{sub 2}SO{sub 4}/HNO{sub 3} considerably reduced the tensile strength of carbon fibers. By contrast, the appearance of H{sub 3}PO{sub 4} preserved the tensile strength of functionalized carbon fibers, reduced the dispersion level of tensile strength values, and effectively increased the concentration of functional acid groups on the surface of carbon fibers. The presence of phosphoric acid hindered the over-oxidation of turbostratic carbon, and consequently preserved the tensile strength of carbon fibers. The increased proportion of turbostratic carbon on the surface of carbon fibers concurrently enhanced the electrochemical properties of carbon fibers.

Preparation and electrochemical performances of nanoporous/cracked cobalt oxide layer for supercapacitors

Science.gov (United States)

Gobal, Fereydoon; Faraji, Masoud

2014-12-01

Nanoporous/cracked structures of cobalt oxide (Co3O4) electrodes were successfully fabricated by electroplating of zinc-cobalt onto previously formed TiO2 nanotubes by anodizing of titanium, leaching of zinc in a concentrated alkaline solution and followed by drying and annealing at 400 °C. The structure and morphology of the obtained Co3O4 electrodes were characterized by X-ray diffraction, EDX analysis and scanning electron microscopy. The results showed that the obtained Co3O4 electrodes were composed of the nanoporous/cracked structures with an average pore size of about 100 nm. The electrochemical capacitive behaviors of the nanoporous Co3O4 electrodes were investigated by cyclic voltammetry, galvanostatic charge-discharge studies and electrochemical impedance spectroscopy in 1 M NaOH solution. The electrochemical data demonstrated that the electrodes display good capacitive behavior with a specific capacitance of 430 F g-1 at a current density of 1.0 A g-1 and specific capacitance retention of ca. 80 % after 10 days of being used in electrochemical experiments, indicating to be promising electroactive materials for supercapacitors. Furthermore, in comparison with electrodes prepared by simple cathodic deposition of cobalt onto TiO2 nanotubes(without dealloying procedure), the impedance studies showed improved performances likely due to nanoporous/cracked structures of electrodes fabricated by dealloying of zinc, which provide fast ion and electron transfer routes and large reaction surface area with the ensued fast reaction kinetics.

Electrochemical Oxidation of EDTA in Nuclear Wastewater Using Platinum Supported on Activated Carbon Fibers