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Sample records for electrochemically prepared oxidation

  1. Preparation, characterization, and electrochemical application of mesoporous copper oxide

    SciTech Connect

    Cheng, Liang; Shao, Mingwang; Chen, Dayan; Zhang, Yuzhong

    2010-02-15

    Mesoporous CuO was successfully synthesized via thermal decomposition of CuC{sub 2}O{sub 4} precursors. These products had ring-like morphology, which was made up of nanoparticles with the average diameter of 40 nm. The electrochemical experiments showed that the mesoporous CuO decreased the overvoltage of the electrode and increased electron transference in the measurement of dopamine.

  2. Preparation of silver nanoparticles/graphene nanosheets as a catalyst for electrochemical oxidation of methanol

    SciTech Connect

    Han, Kun; Miao, Peng; Tang, Yuguo; Tong, Hui; Zhu, Xiaoli; Liu, Tao; Cheng, Wenbo

    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.

  3. Preparation and electrochemical performances of nanoporous/cracked cobalt oxide layer for supercapacitors

    NASA Astrophysics Data System (ADS)

    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.

  4. Electrochemical oxidation of cholesterol

    PubMed Central

    2015-01-01

    Summary Indirect cholesterol electrochemical oxidation in the presence of various mediators leads to electrophilic addition to the double bond, oxidation at the allylic position, oxidation of the hydroxy group, or functionalization of the side chain. Recent studies have proven that direct electrochemical oxidation of cholesterol is also possible and affords different products depending on the reaction conditions. PMID:25977713

  5. Facile and novel electrochemical preparation of a graphene-transition metal oxide nanocomposite for ultrasensitive electrochemical sensing of acetaminophen and phenacetin

    NASA Astrophysics Data System (ADS)

    Jiang, Lin; Gu, Shuqing; Ding, Yaping; Jiang, Feng; Zhang, Zhen

    2013-12-01

    A facile and novel preparation strategy based on electrochemical techniques for the fabrication of electrodeposited graphene (EGR) and zinc oxide (ZnO) nanocomposite was developed. The morphology and structure of the EGR-based nanocomposite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (XPS) and Raman spectroscopy. Meanwhile, the electrochemical performance of the nanocomposite was demonstrated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect of EGR and ZnO nanoparticles, an ultrasensitive electrochemical sensor for acetaminophen (AC) and phenacetin (PCT) was successfully fabricated. The linearity ranged from 0.02 to 10 μM for AC and 0.06 to 10 μM for PCT with high sensitivities of 54 295.82 μA mM-1 cm2 for AC and 21 344.66 μA mM-1 cm2 for PCT, respectively. Moreover, the practical applicability was validated to be reliable and desirable in pharmaceutical detections. The excellent results showed the promise of the proposed preparation strategy of EGR-transition metal oxide nanocomposite in the field of electroanalytical chemistry.A facile and novel preparation strategy based on electrochemical techniques for the fabrication of electrodeposited graphene (EGR) and zinc oxide (ZnO) nanocomposite was developed. The morphology and structure of the EGR-based nanocomposite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (XPS) and Raman spectroscopy. Meanwhile, the electrochemical performance of the nanocomposite was demonstrated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect of EGR and ZnO nanoparticles, an ultrasensitive electrochemical sensor for acetaminophen (AC) and phenacetin (PCT) was successfully fabricated. The linearity ranged from 0.02 to 10 μM for AC and 0.06 to 10

  6. Optical, electrochemical and structural properties of long-term cycled tungsten oxide films prepared by sol gel

    NASA Astrophysics Data System (ADS)

    Huang, Kai; Jia, Jianfeng; Pan, Qingtao; Yang, Feng; He, Deyan

    2007-06-01

    A peroxopolytungstic acid sol has been employed for preparing tungsten oxide (WO 3) films by sol-gel dip-coating technique. Three-electrode cells with 0.5 mol/L H 2SO 4 electrolyte were fabricated using the prepared WO 3 films as active working electrode. Optical, electrochemical and structural properties of the films as a function of coloration-bleaching cycle were characterized by ultraviolet-visible spectrophotometer, cyclic voltammetry (CV), X-ray diffraction (XRD), scanning electron microscopy (SEM). The films showed a stable behavior of reversible and reproducible electrochemical switching up to 1000 coloration-bleaching cycles. XRD peaks were found for the films being cycled more than 2000, and the irregular cracks, uniform nano-particles and novel nano-blades were observed on the long-term cycled film surface by SEM. The degradation of the electrochromic behavior is due to the film change to loose and crystallization after the long-term cycling.

  7. Facile preparation and electrochemical characterization of cobalt oxide/multi-walled carbon nanotube composites for supercapacitors

    NASA Astrophysics Data System (ADS)

    Lang, Junwei; Yan, Xingbin; Xue, Qunji

    A series of cobalt oxide/multi-walled carbon nanotube (Co 3O 4/MWCNT) composites are successfully synthesized by a facile chemical co-precipitation method followed by a simple thermal treatment process. The morphology and structure of as-obtained composites are characterized by X-ray diffraction, scanning electron microscopy, and N 2-adsorption/desorption measurements, and the electrochemical properties are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). For all Co 3O 4/MWCNT composites, MWCNTs are well dispersed in the loosely packed Co 3O 4 nanoparticles. Among them, the Co 3O 4-5%MWCNT composite exhibits the highest specific surface area of 137 m 2 g -1 and a mesoporous structure with a narrow distribution of pore size from 2 to 10 nm. Because of the synergistic effects coming from Co 3O 4 nanoparticles and MWCNTs, the electrochemical performances of pure Co 3O 4 material are significantly improved after adding MWCNTs. The Co 3O 4-5%MWCNT composite shows the largest specific capacitance of 418 F g -1 at a current density of 0.625 A g -1 in 2 M KOH electrolyte. Furthermore, this composite exhibits good cycling stability and lifetime. Therefore, based on the above investigation, such Co 3O 4/MWCNT composite could be a potential candidate for supercapacitors.

  8. Preparation and electrochemical characterization of lithium cobalt oxide nanoparticles by modified sol-gel method

    SciTech Connect

    Khomane, Ramdas B.; Agrawal, Amit C.; Kulkarni, B.D. Gopukumar, S. Sivashanmugam, A.

    2008-08-04

    Uniformly distributed nanoparticles of LiCoO{sub 2} have been synthesized through the simple sol-gel method in presence of neutral surfactant (Tween-80). The powders were characterized by X-ray diffractometry, transmission electron microscopy and electrochemical method including charge-discharge cycling performance. The powder calcined at a temperature of 900 deg. C for 5 h shows pure phase layered LiCoO{sub 2}. The results show that the particle size is reduced in presence of surfactant as compared to normal sol-gel method. Also, the sample prepared in presence of surfactant and calcined at 900 deg. C for 5 h shows the highest initial discharge capacity (106 mAh g{sup -1}) with good cycling stability as compared to the sample prepared without surfactant which shows the specific discharge capacity of 50 mAh g{sup -1}.

  9. Fabrication of Fe2O3 nanoflakes-based electrochemical solar cells prepared by facile thermal oxidation

    NASA Astrophysics Data System (ADS)

    Rashid, Norhana Mohamed; Kishi, Naoki; Soga, Tetsuo

    2016-06-01

    A Fe2O3 nanoflakes-based solar cell was successfully prepared by thermal oxidation of iron film on FTO glass. The short circuit current density (Jsc) of the cell increased with annealing time while the open circuit voltage was saturated after 1 h. This enhancement was caused by the increased surface area of the nanoflakes and improved electron transfer through the (110) crystal plane in the Fe2O3-based electrochemical solar cell. The overall photovoltaic performance significantly increased with ruthenium dye, which likely suppressed carrier recombination on the Fe2O3 surface.

  10. Effect of S-doping on structural, optical and electrochemical properties of vanadium oxide thin films prepared by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Mousavi, M.; Kompany, A.; Shahtahmasebi, N.; Bagheri-Mohagheghi, M.-M.

    2013-12-01

    In this research, S-doped vanadium oxide thin films, with doping levels from 0 to 40 at.%, are prepared by spray pyrolysis technique on glass substrates. For electrochemical measurements, the films were deposited on florin-tin oxide coated glass substrates. The effect of S-doping on structural, electrical, optical and electrochemical properties of vanadium oxide thin films was studied. The x-ray diffractometer analysis indicated that most of the samples have cubic β-V2O5 phase structure with preferred orientation along [200]. With increase in the doping levels, the structure of the samples tends to be amorphous. The scanning electron microscopy images show that the structure of the samples is nanobelt-shaped and the width of the nanobelts decreases from nearly 100 to 40 nm with increase in the S concentration. With increase in the S-doping level, the sheet resistance and the optical band gap increase from 940 to 4015 kΩ/square and 2.41 to 2.7 eV, respectively. The cyclic voltammogram results obtained for different samples show that the undoped sample is expanded and the sample prepared at 20 at.% S-doping level has sharper anodic and cathodic peaks.

  11. Preparation and electrochemical properties of multiwalled carbon nanotubes-nickel oxide porous composite for supercapacitors

    SciTech Connect

    Zheng Yanzhen; Zhang Milin . E-mail: dhyzyz@yahoo.com.cn; Gao Peng

    2007-09-04

    Porous nickel oxide/multiwalled carbon nanotubes (NiO/MWNTs) composite material was synthesized using sodium dodecyl phenyl sulfate as a soft template and urea as hydrolysis-controlling agent. Scanning electron microscopy (SEM) results show that the as-prepared nickel oxide nanoflakes aggregate to form a submicron ball shape with a porous structure, and the MWNTs with entangled and cross-linked morphology are well dispersed in the porous nickel oxide. The composite shows an excellent cycle performance at a high current of 2 A g{sup -1} and keeps a capacitance retention of about 89% over 200 charge/discharge cycles. A specific capacitance approximate to 206 F g{sup -1} has been achieved with NiO/MWNTs (10 wt.%) in 2 M KOH electrolyte. The electrical conductivity and the active sites for redox reaction of nickel oxide are significantly improved due to the connection of nickel nanoflakes by the long entangled MWNTs.

  12. Electrochemical preparation of nickel and copper oxides-decorated graphene composite for simultaneous determination of dopamine, acetaminophen and tryptophan.

    PubMed

    Liu, Bingdi; Ouyang, Xiaoqian; Ding, Yaping; Luo, Liqing; Xu, Duo; Ning, Yanqun

    2016-01-01

    In the present work, transition metal oxides decorated graphene (GR) have been fabricated for simultaneous determination of dopamine (DA), acetaminophen (AC) and tryptophan (Trp) using square wave voltammetry. Electro-deposition is a facile preparation strategy for the synthesis of nickel oxide (NiO) and copper oxide (CuO) nanoparticles. GR can be modified by using citric acid to produce more functional groups, which is conducive to the deposition of dispersed metal particles. The morphologies and interface properties of the obtained NiO-CuO/GR nanocomposite were examined by scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. Moreover, the electrochemical performances of the composite film were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode exhibited that the linear response ranges for detecting DA, AC and Trp were 0.5-20 μM, 4-400 μM and 0.3-40 μM, respectively, and the detection limits were 0.17 μM, 1.33 μM and 0.1 μM (S/N=3). Under optimal conditions, the sensor displayed high sensitivity, excellent stability and satisfactory results in real samples analysis. PMID:26695242

  13. Assessment of Electrodes Prepared from Wafers of Boron-doped Diamond for the Electrochemical Oxidation of Waste Lubricants

    SciTech Connect

    Taylor, G.T.; Sullivan, I.A.; Newey, A.W.E.

    2006-07-01

    Electrochemical oxidation using boron-doped diamond electrodes is being investigated as a treatment process for radioactively contaminated oily wastes. Previously, it was shown that electrodes coated with a thin film of diamond were able to oxidise a cutting oil but not a mineral oil. These tests were inconclusive, because the electrodes lost their diamond coating during operation. Accordingly, an electrode prepared from a 'solid' wafer of boron-doped diamond is being investigated to determine whether it will oxidise mineral oils. The electrode has been tested with sucrose, a cutting oil and an emulsified mineral oil. Before and after each test, the state of the electrode was assessed by cyclic voltammetry with the ferro/ferricyanide redox couple. Analysis of the cyclic voltammogram suggested that material accumulated on the surface of the electrode during the tests. The magnitude of the effect was in the order: - emulsified mineral oil > cutting oil > sucrose. Despite this, the results indicated that the electrode was capable of oxidising the emulsified mineral oil. Confirmatory tests were undertaken in the presence of alkali to trap the carbon dioxide, but they had to be abandoned when the adhesive holding the diamond in the electrode was attacked by the alkali. Etching of the diamond wafer was also observed at the end of the tests. Surface corrosion is now regarded as an intrinsic part of the electrochemical oxidation on diamond, and it is expected that the rate of attack will determine the service life of the electrodes. (authors)

  14. Facile preparation of polypyrrole/graphene oxide nanocomposites with large areal capacitance using electrochemical codeposition for supercapacitors

    NASA Astrophysics Data System (ADS)

    Zhou, Haihan; Han, Gaoyi; Xiao, Yaoming; Chang, Yunzhen; Zhai, Hua-Jin

    2014-10-01

    A simple and low-cost electrochemical codeposition method has been introduced to fabricate polypyrrole/graphene oxide (PPy/GO) nanocomposites and the areal capacitance of conducting polymer/GO composites is reported for the first time. Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) are implemented to determine the PPy/GO nanocomposites are successfully prepared and the interaction between PPy and GO. The as-prepared PPy/GO nanocomposites show the curly sheet-like morphology, superior capacitive behaviors and cyclic stability. Furthermore, the varying deposition time is implemented to investigate the impact of the loading amount on electrochemical behavior of the composites, and a high areal capacitance of 152 mF cm-2 is achieved at 10 mV s-1 CV scan. However, the thicker films caused by the long deposition time would result in larger diffusion resistance of electrolyte ions, consequently exhibit the relatively lower capacitance value at the high current density. The GCD tests indicate moderate deposition time is more suitable for the fast charge/discharge. Considering the very simple and effective synthetic process, the PPy/GO nanocomposites with relatively high areal capacitance are competitive candidate for supercapacitor application, and its capacitive performances can be easily tuned by varying the deposition time.

  15. Preparation of graphene/vanadium oxide nanocomposite monolith and its electrochemical performance

    SciTech Connect

    Deng, Lingjuan; Ma, Zhanying; Li, Xiaobo; Fan, Guang

    2015-10-15

    Graphical Abstract: Graphene/V{sub 2}O{sub 5}(G/V{sub 2}O{sub 5}) nanocomposite monolith is prepared in a mixture of ammonium vanadate, acetic acid and graphite oxide by one-step hydrothermal technology. Owing to the novel structure of ultralong V{sub 2}O{sub 5} nanobelts interpenetrated between the G nanosheets, the G/V{sub 2}O{sub 5} nanocomposite electrode shows higher specific capacitances and better cycle stability than those of G and V{sub 2}O{sub 5} electrodes for supercapaciors and lithium ion battaries. - Highlights: • G/V{sub 2}O{sub 5} nanocomposite monolith is prepared by one-step hydrothermal technology. • G/V{sub 2}O{sub 5} nanocomposite electrode shows much excellent capacitive property. • G/V{sub 2}O{sub 5} nanocomposite exhibits more stable cycle performance. - Abstract: Graphene/vanadium oxide nanocomposite (G/V{sub 2}O{sub 5}) monolith is prepared via a simple hydrothermal process. Owing to the intimate contact between the V{sub 2}O{sub 5} nanobelts and graphene nanosheets in the monolith, the nanocomposite shows excellent electric conductivity, and therefore makes the electrode–electrolyte contact better and Li{sup +} diffusion faster. A high specific capacitance of 163 F g{sup −1} has been achieved for G/V{sub 2}O{sub 5} electrode in 0.5 mol L{sup −1} K{sub 2}SO{sub 4} solution. The G/V{sub 2}O{sub 5} nanocomposite exhibits excellent cyclic performance with nearly 80% capacity retention at a current density of 5 A g{sup −1} in a testing range of 1000 cycles. Moreover, G/V{sub 2}O{sub 5} nanocomposite exhibits excellent discharge properties and cycle stability as an anode material for lithium ion batteries. The initial capacity is 1100 mAh g{sup −1} and the reversible capacity of 530 mAh g{sup −1} is maintained after 100 cycles at a current density of 50 mA g{sup −1}.

  16. Influence of concentration and volume of precursor on the electrochemical properties of vanadium oxide thin films prepared by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Ingole, R. S.; Fugare, B. Y.; Lokhande, B. J.

    2016-04-01

    Vanadium oxide (V2O5) thin films have been prepared by spray pyrolysis using different concentrations and volumes of precursor solution via aqueous route at 673K deposition temperature. The influences of concentration and volume on the structural, morphological and electrochemical properties of the deposited samples are studied well. X - ray diffraction study shows orthorhombic crystal structure with V2O5 phase, confirmed by FTIR spectroscopy. Scanning electron microscopy shows granular, homogeneous and dense surface morphology. Cyclic voltammetery of all samples carried at all scan rates. Samples prepared using 0.05M, 40 ml of precursor solution shows highest specific capacitance 428.25 F/gm at 5 mV/s, Charge discharge behavior exhibits specific energy 18.73 Wh/kg, specific power 36.00 kW/kg, columbic efficiency 87.50 %. Impedance spectroscopy study was carried in the frequency range 1mHz - 1MHz, reveals pseudocapacitive behavior of the electrode exhibiting internal resistance 1.34 ohm.

  17. Structural Characterization of Electrochemically Oxidized La 2CuO 4+ δParticles Prepared by a Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Mahía, José; Martínez-Lorenzo, José Luis; Blanco, M. Carmen; López-Quintela, M. Arturo

    1997-07-01

    The structure of powder samples of electrochemically oxidized La2CuO4+δwas studied using X-ray powder diffraction. The base La2CuO4material was prepared by a sol-gel method that allowed control of the mean particle size by calcining at different temperatures. The results show that the structure of the electrochemically oxidized samples is very sensitive to the synthesis method, particularly the calcination temperature,Tcal. The refined lattice parametersbandc, the unit cell volumeV, and the orthorhombicity of the oxidized samples are found to increase considerably whenTcaldecreases. These variations indicate an increase in the quantity of interstitial oxygen in the samples calcined at lower temperatures with respect to the interstitial oxygen presents in ceramic samples. Particle size distributions were determined by transmission electron microscopy. A decrease in the mean particle size whenTcaldecreases was observed.

  18. Preparation of cribriform sheet-like carbon-coated zinc oxide with improved electrochemical performance

    NASA Astrophysics Data System (ADS)

    Huang, Jianhang; Yang, Zhanhong; Xie, Xiaoe; Feng, Zhaobin; Zhang, Zheng

    2015-09-01

    Cribriform sheet-like carbon-coated ZnO are prepared using pyrrole as the carbon source. It is found that a sheet-like precursor will form when polymerizing pyrrole in the presence of ZnO particles. After the carbonization of precursor, cribriform sheet-like carbon-coated ZnO can be obtained. Morphology and structure analysis of as-prepared carbon-coated ZnO is conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The carbon overlayer not only present a barrier layer on the surface of the ZnO particles, which keeps relative high discharge capacity by inhibiting the active materials in electrode from dissolving into electrolyte, but also modify the surface status of ZnO particles so as to obtain more uniform current distribution and improved conductivity. As a result, when evaluated as an anode material for Zn/Ni cell, carbon-coated ZnO exhibit a more stable cycle performance than bare ZnO electrode.

  19. A green method to prepare Pd-Ag nanoparticles supported on reduced graphene oxide and their electrochemical catalysis of methanol and ethanol oxidation

    NASA Astrophysics Data System (ADS)

    Li, Lingzhi; Chen, Mingxi; Huang, Guanbo; Yang, Nian; Zhang, Li; Wang, Huan; Liu, Yu; Wang, Wei; Gao, Jianping

    2014-10-01

    Bimetallic palladium-silver nanoparticles (NPs) supported on reduced oxide graphene (RGO) with different Pd/Ag ratios (Pd-Ag/RGO) were prepared by an easy green method which did not use any additional reducing agents or a dispersing agent. During the process, simultaneous redox reactions between AgNO3, K2PdCl4 and graphene oxide (GO) led to bimetallic Pd-Ag NPs. The morphology and composition of the Pd-Ag/RGO were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and Raman spectroscopy. Cyclic voltammetry and chronoamperometry were used to investigate the electrochemical activities and stabilities of these Pd-Ag/RGO catalysts for the electro-oxidation of methanol and ethanol in alkaline media. Among the different Pd/Ag ratios, the Pd-Ag (1:1)/RGO had the best catalytic activities and stability. So it is a promising catalyst for direct alcohol fuel cell applications.

  20. Direct electrochemical oxidation of polyacrylates.

    PubMed

    Bellagamba, Riccardo; Comninellis, Christos; Vatistas, Nicolaos

    2002-10-01

    A promising elimination treatment of non-biodegradable organic pollutants is the direct electro-oxidation. In this work has been proposed the electrochemical elimination of polyacrylates by using boron-doped diamond (BDD) as anodic material. The complete elimination of organic contaminants has been obtained and this is the first case of successful electrochemical treatment of polymeric and bio-refractory species. The tests of the electrochemical oxidation have been conducted at constant current conditions and a complete elimination of organic species has been reached. The decrease of the COD value with time follows the behaviour of an ideal anode as in the case of low molecular organic compounds. PMID:12489259

  1. Structural characterization of electrochemically oxidized La{sub 2}CuO{sub 4+{delta}} particles prepared by a sol-gel method

    SciTech Connect

    Mahia, J.; Martinez-Lorenzo, J.L.; Blanco, M.C.; Lopez-Quintela, M.A.

    1997-07-01

    The structure of powder samples of electrochemically oxidized La{sub 2}CuO{sub 4+{delta}} was studied using X-ray powder diffraction. The base La{sub 2}CuO{sub 4} material was prepared by a sol-gel method that allowed control of the mean particle size by calcining at different temperatures. The results show that the structure of the electrochemically oxidized samples is very sensitive to the synthesis method, particularly the calcination temperature, T{sub cal}. The refined lattice parameters b and c, the unit cell volume V, and the orthorhombicity of the oxidized samples are found to increase considerably when T{sub cal} decreases. These variations indicate an increase in the quantity of interstitial oxygen in the samples calcined at lower temperatures with respect to the interstitial oxygen presents in ceramic samples. Particle size distributions were determined by transmission electron microscopy. A decrease in the mean particle size when T{sub cal} decreases was observed.

  2. Electrochemical oxidation of chemical weapons

    SciTech Connect

    Surma, J.E.

    1994-05-01

    Catalyzed electrochemical oxidation (CEO), a low-temperature electrochemical oxidation technique, is being examined for its potential use in destroying chemical warfare agents. The CEO process oxidizes organic compounds to form carbon dioxide and water. A bench-scale CEO system was used in three separate tests sponsored by the US Department of Energy`s (DOE) Office of Intelligence and National Security through the Advanced Concepts Program. The tests examined the effectiveness of CEO in destroying sarin (GB), a chemical nerve agent. The tests used 0.5 mL, 0.95 mL, and 1.0 mL of GB, corresponding to 544 mg, 816 mg, and 1,090 mg, respectively, of GB. Analysis of the off gas showed that, under continuous processing of the GB agent, destruction efficiencies of better than six 9s (99.9999% destroyed) could be achieved.

  3. Solid oxide electrochemical reactor science.

    SciTech Connect

    Sullivan, Neal P.; Stechel, Ellen Beth; Moyer, Connor J.; Ambrosini, Andrea; Key, Robert J.

    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.

  4. Electrochemical oxidation for landfill leachate treatment

    SciTech Connect

    Deng, Yang Englehardt, James D.

    2007-07-01

    This paper aims at providing an overview of electrochemical oxidation processes used for treatment of landfill leachate. The typical characteristics of landfill leachate are briefly reviewed, and the reactor designs used for electro-oxidation of leachate are summarized. Electrochemical oxidation can significantly reduce concentrations of organic contaminants, ammonia, and color in leachate. Pretreatment methods, anode materials, pH, current density, chloride concentration, and other additional electrolytes can considerably influence performance. Although high energy consumption and potential chlorinated organics formation may limit its application, electrochemical oxidation is a promising and powerful technology for treatment of landfill leachate.

  5. Oxidative electrochemical switching of photochromic diarylethene compounds

    NASA Astrophysics Data System (ADS)

    Fan, Congbin; Pu, Shouzhi; Liu, Weijun; Yang, Tianshe; Liu, Gang

    2008-12-01

    A series of photochromic diarylethenes compounds were synthesized and the electrochemistry and electrochemistry reaction mechanism properties were investigated. The cyclic voltammetry tests demonstrated that the colorless open-ring isomers were assigned to the unique oxidation process, but the color closed-ring isomers of these compounds were assigned to two oxidation processes. In addition, the electrochromism of diarylethene compound is observed in solution: The closed-ring reaction can be triggered by electrochemical oxidation, while the open-ring reaction must be photochemically driven. These oxidation processes properties can be useful as the oxidation processes electrochemical switching and the oxidation electrochemical switching properties of these different diarylethene isomers can be potential for electrochemistry data storages.

  6. Surface Morphology of Si(111) during Electrochemical Oxidation

    NASA Astrophysics Data System (ADS)

    Ando, A.; Miki, K.; Sakamoto, K.; Matsumoto, K.; Morita, Y.; Tokumoto, H.

    1997-03-01

    Topographical changes of hydrogen terminated Si(111) during electrochemical oxidation in a 0.2 M H_2SO4 aqueous solution have been investigated using atomic force microscopy (AFM). The hydrogen terminated surface with atomically flat terraces was prepared by dipping into a NH_4F aqueous solution. Electrochemical oxidation has been performed by a potentiostatic (constant potential) or a galvanostatic (constant current) method. AFM images show that the oxidation occured on the terraces and proceeded homogeneously. The surface became rough as the oxidation proceeded. However, step edges were still observed even after the charge of 50 mC/cm^2 was applied. Quantitative analysis of a relation between the charge and surface morphology will be discussed. the address below:

  7. Electrochemical preparation of poly(methylene blue)/graphene nanocomposite thin films

    SciTech Connect

    Erçarıkcı, Elif; Dağcı, Kader; Topçu, Ezgi; Alanyalıoğlu, Murat

    2014-07-01

    Highlights: • Poly(MB)/graphene thin films are prepared by a simple electrochemical approach. • Graphene layers in the film show a broad band in visible region of absorbance spectra. • Morphology of composite films indicates both disordered and ordered regions. • XRD reveals that nanocomposite films include rGO layers after electropolymerization process. • Chemically prepared graphene is better than electrochemically prepared graphene for electrooxidation of nitrite. - Abstract: Poly(methylene blue)/graphene nanocomposite thin films were prepared by electropolymerization of methylene blue in the presence of graphene which have been synthesized by two different methods of a chemical oxidation process and an electrochemical approach. Synthesized nanocomposite thin films were characterized by using cyclic voltammetry, UV–vis. absorption spectroscopy, powder X-ray diffraction, and scanning tunneling microscopy techniques. Electrocatalytical properties of prepared poly(methylene blue)/graphene nanocomposite films were compared toward electrochemical oxidation of nitrite. Under optimized conditions, electrocatalytical effect of nanocomposite films of chemically prepared graphene through electrochemical oxidation of nitrite was better than that of electrochemically prepared graphene.

  8. Surface photovoltage studies of Si nanocrystallites prepared by electrochemical etching

    NASA Astrophysics Data System (ADS)

    Patel, B. K.; Rath, S.; Sahu, S. N.

    2006-06-01

    Nanocrystalline Si has been prepared by anodic etching of Si in an electrolyte consisting of ethanol and HF. The structure and surface morphology have been studied using transmission electron microscopy which reveal the cubic structure and porous morphology of Si nanocrystals (NCs). Electrochemical etching has resulted in surface oxidation of Si NCs as confirmed from X-ray photoelectron spectroscopic measurements. The average size of the Si NCs has been estimated from the line broadening analysis of the Raman scattering. Unique optical transitions associated with porous Si/SiO2 quantum well (QW) like structure has been investigated by surface photovoltage (SPV) measurements.

  9. Preparation and electrochemical properties of polyaniline nanofibers using ultrasonication

    SciTech Connect

    Manuel, James; Kim, Miso; Fapyane, Deby; Chang, In Seop; Ahn, Hyo-Jun; Ahn, Jou-Hyeon

    2014-10-15

    Highlights: • Nanofibrous structured polyaniline (PANI) was prepared by simple ultrasonication. • PANI nanofibers prepared at 5 °C are uniform with an average diameter of 50 nm. • The conductivity is increased by 2 × 10{sup 8} times after doping with LiClO{sub 4}. • The cell with PANI-LiClO{sub 4} shows good cycle performance at high current densities. - Abstract: Polyaniline nanofibers have been successfully prepared by applying ultrasonic irradiation during oxidative polymerization of aniline in dilute hydrochloric acid and evaluated for suitability in lithium cells after doping with lithium perchlorate salt. Polyaniline nanofibers are confirmed by Fourier transform infrared spectroscopy, Fourier transform Raman spectroscopy, and transmission electron microscopy, and the efficiency of doping is confirmed by DC conductivity measurements at different temperatures. Electrochemical properties of nanofibers are evaluated, of which a remarkable increase in cycle stability is achieved when compared to polyaniline prepared by simple oxidative polymerization of aniline. The cell with nanofibrous polyaniline doped with LiClO{sub 4} delivers an initial discharge capacity value of 86 mA h g{sup −1} at 1 C-rate which is about 60% of theoretical capacity, and the capacity is slightly lowered during cycle and reaches 50% of theoretical capacity after 40 cycles. The cell delivers a stable and higher discharge capacity even at 2 C-rate compared to that of the cell prepared with bulk polyaniline doped with LiClO{sub 4}.

  10. Ductile mode electrochemical oxidation assisted micromachining for glassy carbon

    NASA Astrophysics Data System (ADS)

    Nam, Eunseok; Lee, Chan-Young; Jun, Martin B. G.; Min, Byung-Kwon

    2015-04-01

    Recently, a new mechanical machining process using electrochemical oxidation was reported. Electrochemical oxidation assisted micromachining was applied to the machining of glassy carbon. The material removal process of the electrochemical oxidation assisted micromachining consists of repeated cycles of oxidation followed by removal of the oxide layer. In this paper, we experimentally investigate and compare the critical chip thickness for ductile mode cutting in mechanical machining and electrochemical oxidation assisted micromachining of glassy carbon. The theoretical critical chip thickness is calculated for mechanical machining of glassy carbon and experimentally verified. The effect of electrochemical oxidation on the critical chip thickness for ductile mode micromachining is also studied for glassy carbon. It is found that the critical chip thickness is increased for the electrochemical oxidation assisted micromachining.

  11. Exfoliated graphite-ruthenium oxide composite electrodes for electrochemical supercapacitors

    NASA Astrophysics Data System (ADS)

    Mitra, Sagar; Lokesh, K. S.; Sampath, S.

    The performance of exfoliated graphite (EG)-ruthenium oxide (RuO x) composites as binderless electrodes is evaluated for electrochemical capacitors (ECs). A composite of EG-RuO x is prepared by a modified sol-gel process. The material is characterized using X-ray diffraction and microscopy. Electrochemical capacitors with the composite electrodes in the presence of aqueous sulfuric acid (H 2SO 4) electrolyte are evaluated using voltammetry, impedance and charge-discharge studies. Cyclic voltammetry reveals very stable current-voltage behaviour up to several thousands of cycles, as well as high specific capacitances, e.g., a few hundreds of farads per gram for the composite that contains 16.5 wt.% RuO x.

  12. ZIRCONIUM OXIDE NANOSTRUCTURES PREPARED BY ANODIC OXIDATION

    SciTech Connect

    Dang, Y. Y.; Bhuiyan, M.S.; Paranthaman, M. P.

    2008-01-01

    Zirconium oxide is an advanced ceramic material highly useful for structural and electrical applications because of its high strength, fracture toughness, chemical and thermal stability, and biocompatibility. If highly-ordered porous zirconium oxide membranes can be successfully formed, this will expand its real-world applications, such as further enhancing solid-oxide fuel cell technology. Recent studies have achieved various morphologies of porous zirconium oxide via anodization, but they have yet to create a porous layer where nanoholes are formed in a highly ordered array. In this study, electrochemical methods were used for zirconium oxide synthesis due to its advantages over other coating techniques, and because the thickness and morphology of the ceramic fi lms can be easily tuned by the electrochemical parameters, such as electrolyte solutions and processing conditions, such as pH, voltage, and duration. The effects of additional steps such as pre-annealing and post-annealing were also examined. Results demonstrate the formation of anodic porous zirconium oxide with diverse morphologies, such as sponge-like layers, porous arrays with nanoholes ranging from 40 to 75 nm, and nanotube layers. X-ray powder diffraction analysis indicates a cubic crystallographic structure in the zirconium oxide. It was noted that increased voltage improved the ability of the membrane to stay adhered to the zirconium substrate, whereas lower voltages caused a propensity for the oxide fi lm to fl ake off. Further studies are needed to defi ne the parameters windows that create these morphologies and to investigate other important characteristics such as ionic conductivity.

  13. Zirconium Oxide Nanostructures Prepared by Anodic Oxidation

    SciTech Connect

    Dang, Ying Yi; Bhuiyan, Md S; Paranthaman, Mariappan Parans

    2008-01-01

    Zirconium oxide is an advanced ceramic material highly useful for structural and electrical applications because of its high strength, fracture toughness, chemical and thermal stability, and biocompatibility. If highly-ordered porous zirconium oxide membranes can be successfully formed, this will expand its real-world applications, such as further enhancing solid-oxide fuel cell technology. Recent studies have achieved various morphologies of porous zirconium oxide via anodization, but they have yet to create a porous layer where nanoholes are formed in a highly ordered array. In this study, electrochemical methods were used for zirconium oxide synthesis due to its advantages over other coating techniques, and because the thickness and morphology of the ceramic films can be easily tuned by the electrochemical parameters, such as electrolyte solutions and processing conditions, such as pH, voltage, and duration. The effects of additional steps such as pre-annealing and post-annealing were also examined. Results demonstrate the formation of anodic porous zirconium oxide with diverse morphologies, such as sponge-like layers, porous arrays with nanoholes ranging from 40 to 75 nm, and nanotube layers. X-ray powder diffraction analysis indicates a cubic crystallographic structure in the zirconium oxide. It was noted that increased voltage improved the ability of the membrane to stay adhered to the zirconium substrate, whereas lower voltages caused a propensity for the oxide film to flake off. Further studies are needed to define the parameters windows that create these morphologies and to investigate other important characteristics such as ionic conductivity.

  14. Solid oxide electrochemical cell fabrication process

    DOEpatents

    Dollard, Walter J.; Folser, George R.; Pal, Uday B.; Singhal, Subhash C.

    1992-01-01

    A method to form an electrochemical cell (12) is characterized by the steps of thermal spraying stabilized zirconia over a doped lanthanum manganite air electrode tube (14) to provide an electrolyte layer (15), coating conductive particles over the electrolyte, pressurizing the outside of the electrolyte layer, feeding halide vapors of yttrium and zirconium to the outside of the electrolyte layer and feeding a source of oxygen to the inside of the electrolyte layer, heating to cause oxygen reaction with the halide vapors to close electrolyte pores if there are any and to form a metal oxide coating on and between the particles and provide a fuel electrode (16).

  15. Electrochemical preparation of sodium dodecylsulfate doped over-oxidized polypyrrole/multi-walled carbon nanotube composite on glassy carbon electrode and its application on sensitive and selective determination of anticancer drug: pemetrexed.

    PubMed

    Karadas, Nurgul; Ozkan, Sibel A

    2014-02-01

    Electrochemical oxidation of pemetrexed (PMX) was studied on bare, carboxylic acid functionalized multi-walled carbon nanotubes and over-oxidized polypyrrole modified (oo-PPy/MWCNTs-COOH/GCE) glassy carbon electrodes by cyclic and adsorptive stripping differential pulse voltammetric techniques. The oo-PPy/MWCNTs-COOH/GCE is very sensitive to the oxidation of PMX. The results proved that the over-oxidation of the PPy film gave a negative charge density on porous layer that improved the adsorption for PMX. The effects of pH, concentrations of MWCNTs and monomer, the number of cycles for the electropolymerization and the scan rate for sensor preparation were optimized. The MWCNTs-COOH and oo-PPy based sensor showed an excellent recognition capacity toward PMX. The linear responses have been obtained in the range from 8.00 × 10(-7)M to 1.00 × 10(-4)M with 2.04 × 10(-7)M detection limit for the bare GCE and from 1.00 × 10(-8)M to 1.00 × 10(-7)M with 3.28 × 10(-9)M detection limit for the modified GCE. The oxidation of PMX was controlled by the adsorption process on both types of electrode surfaces. The proposed methods were compared with the literature on UV spectrophotometric assay, which was carried out at an absorption maximum of 225 nm. The proposed method and the designed sensors have been successfully applied for the determination of PMX in pharmaceuticals. PMID:24401411

  16. Preparation of yolk-shell structured copper oxide@silica oxide spheres and their application in high performance electrochemical sensing of Formoterol fumarate residues in swine feed and tissues.

    PubMed

    Gan, Tian; Shi, Zhaoxia; Hu, Danyang; Lv, Zhen; Sun, Junyong; Liu, Yanming

    2016-01-01

    In this paper, we report a facile route to synthesize yolk-shell structured copper oxide@silica oxide (CuO@SiO2) spheres and their application to construct an electrochemical Formoterol fumarate (FF) sensor. The CuO@SiO2 was characterized by means of Fourier transform infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Further, FF was electrocatalytically oxidized at the CuO@SiO2 film modified glassy carbon electrode (GCE), which led to a sensitive determination of FF. The oxidation current of FF was linear with concentration in the range of 0.030-10 μM and the detection limit was found to be 5.0 nM (S/N = 3). The observed analytical parameters such as wide linear range, low detection limit and short response time were superior to previously reported FF sensors. Finally, it was demonstrated that the proposed sensor could be used for the selective determination of FF present in swine feed and tissues. PMID:26213008

  17. Morphological effects on the electrochemical performance of lithium-rich layered oxide cathodes, prepared by electrospinning technique, for lithium-ion battery applications

    SciTech Connect

    Min, Ji Won; Kalathil, Abdul Kareem; Yim, Chul Jin; Im, Won Bin

    2014-06-01

    Li-rich Li{sub 1.2}Ni{sub 0.17}Co{sub 0.17}Mn{sub 0.5}O{sub 2} cathode materials were synthesized by electrospinning technique with different polymers, and their structural, morphological, and electrochemical performances were investigated. It was found that the electrospinning process leads to the formation of a fiber and flower-like morphology, by using different polymers and heat treatment conditions. The nanostructured morphology provided these materials with high initial discharge capacity. The cycling stability was improved with agglomerated nano-particles, as compared with porous materials. - Highlights: • Fiber and flower-like Li-rich cathode was synthesized by simple electrospinning. • Polymer dependent morphology and electrochemical performance was investigated. • Well-organized porous structure facilitates the diffusion of lithium ions. • Technique could be applicable to other cathode materials as well.

  18. Electrochemical oxidation of phenol using graphite anodes

    SciTech Connect

    Awad, Y.M.; Abuzaid, N.S.

    1999-02-01

    The effects of current and pH on the electrochemical oxidation of phenol on graphite electrodes is investigated in this study. There was no sign of deterioration of the graphite bed after 5 months of operation. Phenol removal efficiency was a function of the current applied and was around 70% at a current of 2.2 A. The increase of phenol removal efficiency with current is attributed to the increase of ionic transport which increases the rate of electrode reactions responsible for the removal process. The percentage of complete oxidation of phenol increases with current, with a maximum value of about 50%. However, at pH 0.2 it is slightly higher than that at pH 0.5 at all currents. The phenol removal rate increases with increases of current and pH. While the current (CO{sub 2}) efficiency reaches a maximum value in the current range of 1.0--1.2 A, it increases with an increase of acid concentration. The findings of this study have important implications: while anodic oxidation of phenol on graphite can achieve acceptable removal of phenol, the extent of oxidation should not be overlooked.

  19. Direct electrochemical reduction of graphene oxide on ionic liquid doped screen-printed electrode and its electrochemical biosensing application.

    PubMed

    Ping, Jianfeng; Wang, Yixian; Fan, Kai; Wu, Jian; Ying, Yibin

    2011-10-15

    A novel electrochemical biosensing platform using electrochemically reduced graphene oxide (ER-GNO) modified electrode was proposed. This modified electrode was prepared by one-step electrodeposition of the exfoliated GNO sheets onto the ionic liquid doped screen-printed electrode (IL-SPE). The resulting ER-GNO/IL-SPE brought new capabilities for electrochemical devices by combining the advantages of ER-GNO and disposable electrode. Two important biomolecules, nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H(2)O(2)), were employed to study the electrochemical performance of the ER-GNO/IL-SPE, which exhibited more favorable electron transfer kinetics than the bare IL-SPE. On the basis of the greatly enhanced electrochemical reactivity of H(2)O(2) at the developed electrode, ER-GNO and glucose oxidase constructed disposable biosensor showed better analytical performance for the glucose detection compared with the IL-SPE based biosensor. The linear range for the detection of glucose was from 5.0 μM to 12.0 mM with a detection limit of 1.0 μM. This work provides a useful avenue for implementing ER-GNO as a new generation of electrochemical transducer in disposable electrode, which could expand the scope of graphene constructed electrochemical biosensing devices and hold great promise for routine sensing applications. PMID:21807494

  20. Removal of estrogens by electrochemical oxidation process.

    PubMed

    Cong, Vo Huu; Iwaya, Sota; Sakakibara, Yutaka

    2014-06-01

    Treatments of estrogens such as Estrone (E1), Estradiol (E2) and Ethinylestradiol (EE2) were conducted using an electrolytic reactor equipped with multi-packed granular glassy carbon electrodes. Experimental results showed that E1, E2 and EE2 were oxidized in the range of 0.45-0.85 V and were removed through electro-polymerization. Observed data from continuous experiments were in good agreement with calculated results by a mathematical model constructed based on mass transfer limitation. In continuous treatment of trace estrogens (1 μg/L), 98% of E1, E2 and EE2 were stably removed. At high loading rate (100 μg/L), removal efficiency of E1 was kept around 74%-88% for 21 days, but removal efficiency reduced due to passivation of electrodes. However, removal efficiency was recovered after electrochemical regeneration of electrodes in presence of ozone. Electric energy consumption was observed in the range of 1-2 Wh/m(3). From these results, we concluded that the present electrochemical process would be an alternative removal of estrogens. PMID:25079848

  1. Selective Electrochemical versus Chemical Oxidation of Bulky Phenol.

    PubMed

    Zabik, Nicole L; Virca, Carolyn N; McCormick, Theresa M; Martic-Milne, Sanela

    2016-09-01

    The electrochemical oxidation of selected tert-butylated phenols 2,6-di-tert-butyl-4-methylphenol (1), 2,6-di-tert-butylphenol (2), 2,4,6-tri-tert-butylphenol (3), 2-tert-butylphenol (4), and 4-tert-butylphenol (5) was studied in an aprotic environment using cyclic voltammetry, square-wave voltammetry, and UV-vis spectroscopy. All compounds exhibited irreversible oxidation of the corresponding phenol or phenolate ion. Compound 2 was selectively electrochemically oxidized, while other phenol analogues underwent mostly chemical oxidation. The electrochemical oxidation of 2 produced a highly absorbing product, 3,5,3',5'-tetra-tert-butyl-4,4'-diphenoquinone, which was characterized by X-ray crystal diffraction. The electrochemical oxidation was monitored as a function of electrochemical parameters and concentration. Experimental and theoretical data indicated that the steric hindrance, phenoxyl radical stability, and hydrogen bonding influenced the outcome of the electrochemical oxidation. The absence of the substituent at the para position and the presence of the bulky substituents at ortho positions were structural and electrostatic requirements for the selective electrochemical oxidation. PMID:27454828

  2. Preparation of tungsten oxide

    SciTech Connect

    Bulian, Christopher J.; Dye, Robert C.; Son, Steven F.; Jorgensen, Betty S.; Perry, W. Lee

    2009-09-22

    Tungsten trioxide hydrate (WO.sub.3.H.sub.2O) was prepared from a precursor solution of ammonium paratungstate in concentrated aqueous hydrochloric acid. The precursor solution was rapidly added to water, resulting in the crash precipitation of a yellow white powder identified as WO.sub.3.H.sub.2O nanosized platelets by x-ray diffraction and scanning electron microscopy. Annealing of the powder at 200.degree. C. provided cubic phase WO.sub.3 nanopowder, and at 400.degree. C. provided WO.sub.3 nanopowder as a mixture of monoclinic and orthorhombic phases.

  3. PREPARATION OF REFRACTORY OXIDE MICROSPHERE

    DOEpatents

    Haws, C.C. Jr.

    1963-09-24

    A method is described of preparing thorium oxide in the form of fused spherical particles about 1 to 2 microns in diameter. A combustible organic solution of thorium nitrate containing additive metal values is dispersed into a reflected, oxygen-fed flame at a temperature above the melting point of the resulting oxide. The metal additive is aluminum at a proportion such as to provide 1 to 10 weight per cent aluminum oxide in the product, silicon at the same proportion, or beryllium at a proportion of 12 to 25 weight per cent beryllium oxide in the product. A minor proportion of uranium values may also be provided in the solution. The metal additive lowers the oxide melting point and allows fusion and sphere formation in conventional equipment. The product particles are suitable for use in thorium oxide slurries for nuclear reactors. (AEC)

  4. Preparation of PZT Thin Films on Stainless Steel Using Electrochemical Reduction

    NASA Astrophysics Data System (ADS)

    Koinuma, Michio; Ohmura, Hideki; Fujioka, Yoshiro; Matsumoto, Yasumichi; Yamada, Satoshi

    1998-03-01

    PZT perovskite films which were strongly adhered to stainless steel were prepared by electrochemical reduction in solutions containing TiO 2+, ZrO 2+, and Pb 2+ions. The composition of the PZT films was easily controlled by the composition in the solution and the applied cathodic potential during the electrolysis. Heat treatment at 600°C was necessary for crystallization, because the as-deposited oxide films were amorphous. Pb was deposited as a metal, while Zr and Ti were deposited as oxides and/or hydroxides during the electrolysis. The average of the dielectric constants of the PZT films prepared by the present method was more than 500.

  5. Electrochemical oxidation of perfluorinated compounds in water.

    PubMed

    Niu, Junfeng; Li, Yang; Shang, Enxiang; Xu, Zesheng; Liu, Jinzi

    2016-03-01

    Perfluorinated compounds (PFCs) are persistent and refractory organic pollutants that have been detected in various environmental matrices and municipal wastewater. Electrochemical oxidation (EO) is a promising remediation technique for wastewater contaminated with PFCs. A number of recent studies have demonstrated that the "non-active" anodes, including boron-doped diamond, tin oxide, and lead dioxide, are effective in PFCs elimination in wastewater due to their high oxygen evolution potential. Many researchers have conducted experiments to investigate the optimal conditions (i.e., potential, current density, pH value, plate distance, initial PFCs concentration, electrolyte, and other factors) for PFCs elimination to obtain the maximal elimination efficiency and current efficiency. The EO mechanism and pathways of PFCs have been clearly elucidated, which undergo electron transfer, Kolbe decarboxylation or desulfonation, hydrolysis, and radical reaction. In addition, the safety evaluation and energy consumption evaluation of the EO technology have also been summarized to decrease toxic ion release from electrode and reduce the cost of this technique. Although the ultrasonication and hydrothermal techniques combined with the EO process can improve the removal efficiency and current efficiency significantly, these coupled techniques have not been commercialized and applied in industrial wastewater treatment. Finally, key challenges facing EO technology are listed and the directions for further research are pointed out (such as combination with other techniques, treatment for natural waters contaminated by low levels of PFCs, and reactor design). PMID:26745381

  6. Tutorial Review: Electrochemical Nitric Oxide Sensors for Physiological Measurements

    PubMed Central

    Privett, Benjamin J.; Shin, Jae Ho; Schoenfisch, Mark H.

    2013-01-01

    Summary The important biological roles of nitric oxide (NO) have prompted the development of analytical techniques capable of sensitive and selective detection of NO. Electrochemical sensing, more than any other NO-detection method, embodies the parameters necessary for quantifying NO in challenging physiological environments such as blood and the brain. Herein, we provide a broad overview of the field of electrochemical NO sensors, including design, fabrication, and analytical performance characteristics. Both electrochemical sensors and biological applications are detailed. PMID:20502795

  7. A hydrophobic three-dimensionally networked boron-doped diamond electrode towards electrochemical oxidation.

    PubMed

    He, Yapeng; Lin, Haibo; Wang, Xue; Huang, Weimin; Chen, Rongling; Li, Hongdong

    2016-06-28

    A boron-doped diamond electrode with a three-dimensional network was fabricated on a mesh titanium substrate. Properties such as higher surface area, enhanced mass transfer and a hydrophobic surface endowed the prepared electrode with excellent electrochemical oxidation ability towards contaminants. PMID:27264247

  8. Electrode electrolyte interlayers containing cerium oxide for electrochemical fuel cells

    DOEpatents

    Borglum, Brian P.; Bessette, Norman F.

    2000-01-01

    An electrochemical cell is made having a porous fuel electrode (16) and a porous air electrode (13), with solid oxide electrolyte (15) therebetween, where the air electrode surface opposing the electrolyte has a separate, attached, dense, continuous layer (14) of a material containing cerium oxide, and where electrolyte (16) contacts the continuous oxide layer (14), without contacting the air electrode (13).

  9. Oxide modified air electrode surface for high temperature electrochemical cells

    DOEpatents

    Singh, Prabhakar; Ruka, Roswell J.

    1992-01-01

    An electrochemical cell is made having a porous cermet electrode (16) and a porous lanthanum manganite electrode (14), with solid oxide electrolyte (15) between them, where the lanthanum manganite surface next to the electrolyte contains a thin discontinuous layer of high surface area cerium oxide and/or praseodymium oxide, preferably as discrete particles (30) in contact with the air electrode and electrolyte.

  10. PREPARATION OF REFRACTORY OXIDE CRYSTALS

    DOEpatents

    Grimes, W.R.; Shaffer, J.H.; Watson, G.M.

    1962-11-13

    A method is given for preparing uranium dioxide, thorium oxide, and beryllium oxide in the form of enlarged individual crystals. The surface of a fused alkali metal halide melt containing dissolved uranium, thorium, or beryllium values is contacted with a water-vapor-bearing inert gas stream at a rate of 5 to 10 cubic centimeters per minute per square centimeter of melt surface area. Growth of individual crystals is obtained by prolonged contact. Beryllium oxide-coated uranium dioxide crystals are prepared by disposing uranium dioxide crystals 5 to 20 microns in diameter in a beryllium-containing melt and contacting the melt with a water-vapor-bearing inert gas stream in the same manner. (AEC)

  11. Preparation and electrochemical performance of Pr2Ni0.6Cu0.4O4 cathode materials for intermediate-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Yifang; Cheng, Jigui; Jiang, Qiumei; Yang, Junfang; Gao, Jianfeng

    2011-03-01

    Cathode material Pr2Ni0.6Cu0.4O4 (PNCO) for intermediate-temperature solid oxide fuel cells (IT-SOFCs) is synthesized by a glycine-nitrate process using Pr6O11, NiO, and CuO powders as raw materials. X-ray diffraction analysis reveals that nanosized Pr2Ni0.6Cu0.4O4 powders with K2NiF4-type structure can be obtained from calcining the precursors at 1000 °C for 3 h. Scanning electron microscopy shows that the sintered PNCO samples have porous microstructure with a porosity of more than 30% and grain size smaller than 2 μm. A maximum conductivity of 130 S cm-1 is obtained from the PNCO samples sintered at 1050 °C. A single fuel cell based on the PNCO cathode with 30 μm Sm0.2Ce0.8O1.9 (SCO) electrolyte film and a 1 mm NiO-SCO anode support is constructed. The ohmic resistance of the single Ni-SCO/SCO/PNCO cell is 0.08 Ω cm2 and the area specific resistance (ASR) value is 0.19 Ω cm2 at 800 °C. Cell performance was also tested using humidified hydrogen (3% H2O) as fuel and air as oxidant. The single cell shows an open circuit voltage of 0.82 V and 0.75 V at 700 °C and 800 °C, respectively. Maximum power density is 238 mW cm-2 and 308 mW cm-2 at 700 °C and 800 °C, respectively. The preliminary tests have shown that Pr2Ni1-xCuxO4materials can be a good candidate for cathode materials of IT-SOFCs.

  12. Innovative oxide materials for electrochemical energy conversion

    NASA Astrophysics Data System (ADS)

    Wachsman, Eric D.

    2012-02-01

    Research in functional materials has progressed from those materials exhibiting structural to electronic functionality. The study of ion conducting ceramics ushers in a new era of ``chemically functional materials.'' This chemical functionality arises out of the defect equilibria of these materials, and results in the ability to transport chemical species and actively participate in chemical reactions at their surface. Moreover, this chemical functionality provides a promise for the future whereby the harnessing of our natural hydrocarbon energy resources can shift from inefficient and polluting combustion - mechanical methods to direct electrochemical conversion. The unique properties of these materials and their applications will be described. The focus will be on the application of ion conducting ceramics to energy conversion and storage, chemical sensors, chemical separation and conversion, and life support systems. Results presented will include development of record high power density (3 kW/kg) solid oxide fuel cells, NOx/CO species selective solid-state sensors, high yield membrane reactors, and regenerative life support systems that reduce CO2 to O2 and solid C.

  13. Physical and electrochemical study of cobalt oxide nano- and microparticles

    SciTech Connect

    Alburquenque, D.; Vargas, E.; Denardin, J.C.; Escrig, J.; Marco, J.F.; Gautier, J.L.

    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.

  14. Electrochemical preparation of carbon chains and nanoparticles

    NASA Astrophysics Data System (ADS)

    Kavan, Ladislav

    1999-09-01

    The composite of carbon with alkali metal fluoride, C-MF(M=Li, Na) was prepared by cathodic defluorination of perfluorinated hydrocarbons at room temperature. Raman spectra of C-MF from PTFE indicate carbon chains (oligoynes, 1974-2024 cm-1) in addition to graphite-like carbon (1300-1500 cm-1). The oligoyne-containing carbon is partly selforganized by cross linking towards graphene. Highly-organized carbons were prepared from friction-deposited PTFE films. AFM confirms perfect ordering of the precursor molecules (up to atomic resolution), but the corresponding carbonization product is rapidly reconstructed upon contact to air. Raman spectra of oriented carbons display high conjugation lengths (up to 18 sp-bonded carbon atoms). Cyclic perfluorinated precursors are also smoothly defluorinated to elemental carbon. TEM indicates that these carbons contain about 1% of carbonaceous nanoparticles, i.e. nanotubes and onions. Also small quantity of fullerene C60(≈0.01%) was detected in the toluene extract.

  15. Electrochemical and partial oxidation of methane

    NASA Astrophysics Data System (ADS)

    Singh, Rahul

    2008-10-01

    Hydrogen has been the most common fuel used for the fuel cell research but there remains challenging technological hurdles and storage issues with hydrogen fuel. The direct electrochemical oxidation of CH4 (a major component of natural gas) in a solid oxide fuel cell (SOFC) to generate electricity has a potential of commercialization in the area of auxiliary and portable power units and battery chargers. They offer significant advantages over an external reformer based SOFC, namely, (i) simplicity in the overall system architecture and balance of plant, (ii) more efficient and (iii) availability of constant concentration of fuel in the anode compartment of SOFC providing stability factor. The extreme operational temperature of a SOFC at 700-1000°C provides a thermodynamically favorable pathway to deposit carbon on the most commonly used Ni anode from CH4 according to the following reaction (CH4 = C + 2H2), thus deteriorating the cell performance, stability and durability. The coking problem on the anode has been a serious and challenging issue faced by the catalyst research community worldwide. This dissertation presents (i) a novel fabricated bi-metallic Cu-Ni anode by electroless plating of Cu on Ni anode demonstrating significantly reduced or negligible coke deposition on the anode for CH4 and natural gas fuel after long term exposure, (ii) a thorough microstructural examination of Ni and Cu-Ni anode exposed to H2, CH4 and natural gas after long term exposure at 750°C by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction and (iii) in situ electrochemical analysis of Ni and Cu-Ni for H2, CH4 and natural gas during long term exposure at 750°C by impedance spectroscopy. A careful investigation of variation in the microstructure and performance characteristics (voltage-current curve and impedance) of Ni and Cu-Ni anode before and after a long term exposure of CH4 and natural gas would allow us to test the validation of a

  16. Sensitive electrochemical detection of nitric oxide based on AuPt and reduced graphene oxide nanocomposites.

    PubMed

    Liu, Zhonggang; Forsyth, Heidi; Khaper, Neelam; Chen, Aicheng

    2016-06-20

    Since nitric oxide (NO) plays a critical role in many biological processes, its precise detection is essential toward an understanding of its specific functions. Here we report on a facile and environmentally compatible strategy for the construction of an electrochemical sensor based on reduced graphene oxide (rGO) and AuPt bimetallic nanoparticles. The prepared nanocomposites were further employed for the electroanalysis of NO using differential pulse voltammetry (DPV) and amperometric methods. The dependence of AuPt molar ratios on the electrochemical performance was investigated. Through the combination of the advantages of the high conductivity from rGO and highly electrocatalytic activity from AuPt bimetallic nanoparticles, the AuPt-rGO based NO sensor exhibited a high sensitivity of 7.35 μA μM(-1) and a low detection limit of 2.88 nM. Additionally, negligible interference from common ions or organic molecules was observed, and the AuPt-rGO modified electrode demonstrated excellent stability. Moreover, this optimized electrochemical sensor was practicable for efficiently monitoring the NO released from rat cardiac cells, which were stimulated by l-arginine (l-arg), showing that stressed cells generated over 10 times more NO than normal cells. The novel sensor developed in this study may have significant medical diagnostic applications for the prevention and monitoring of disease. PMID:27143513

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

    SciTech Connect

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

    2012-01-15

    We report a one-step synthesis of a nanocomposite of goethite ({alpha}-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{sup -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: Black-Right-Pointing-Pointer Ferrous ions act as reductant of graphite oxide and precursor of goethite nanorods. Black-Right-Pointing-Pointer Goethite nanorods are attached on both sides of the reduced graphene oxide sheets. Black-Right-Pointing-Pointer Composite exhibits a high specific capacitance and a good recycling capability. Black-Right-Pointing-Pointer Composite is promising for supercapacitor applications.

  18. Electrochemical glucose oxidation on dendritic cuprous oxide film fabricated by PSS-assisted electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Yang, Ming; Jin, Xiaoqi; Huang, Qiao

    2011-02-01

    Cuprous oxides (Cu 2O) with different morphologies were deposited on F-doped tin oxide (FTO) covered glass substrates by potentiostatic deposition. The as-deposited samples were characterized by XRD, BET surface area and SEM. The effects of Poly(styrene sulfonic acid) sodium salt (PSS) on the crystal morphologies of Cu 2O were studied. Different crystal morphologies of Cu 2O can be obtained by varying the concentrations of PSS in the electrolytes. The formation of dendritic microstructure in Cu 2O film depends on the concentration of PSS in the electrolyte. Dendritic Cu 2O crystals formed gradually with the increase of the concentration of PSS in the electrolyte from 0 to 4 g L -1. More symmetrical Cu 2O crystals appear when the concentration of PSS is changed from 4 to 8 g L -1. However, the Cu 2O nanoparticles formed instead of dendritic Cu 2O crystals if the concentration of PSS reaches to 12 g L -1, which is due to the slower diffusion rate of reactive species in high concentration of PSS. The as-deposited Cu 2O thin films with different morphologies all exhibit the electrochemical glucose oxidation properties. The improved performance of glucose oxidation is achieved on the dendritic Cu 2O film electrode. The result indicates that the dendritic microstructure is beneficial for decreasing the resistance and improving transportation and diffusion of reactants and products.

  19. In Situ Electrochemical Oxidation Tuning of Transition Metal Disulfides to Oxides for Enhanced Water Oxidation

    PubMed Central

    2015-01-01

    The development of catalysts with earth-abundant elements for efficient oxygen evolution reactions is of paramount significance for clean and sustainable energy storage and conversion devices. Our group demonstrated recently that the electrochemical tuning of catalysts via lithium insertion and extraction has emerged as a powerful approach to improve catalytic activity. Here we report a novel in situ electrochemical oxidation tuning approach to develop a series of binary, ternary, and quaternary transition metal (e.g., Co, Ni, Fe) oxides from their corresponding sulfides as highly active catalysts for much enhanced water oxidation. The electrochemically tuned cobalt–nickel–iron oxides grown directly on the three-dimensional carbon fiber electrodes exhibit a low overpotential of 232 mV at current density of 10 mA cm–2, small Tafel slope of 37.6 mV dec–1, and exceptional long-term stability of electrolysis for over 100 h in 1 M KOH alkaline medium, superior to most non-noble oxygen evolution catalysts reported so far. The materials evolution associated with the electrochemical oxidation tuning is systematically investigated by various characterizations, manifesting that the improved activities are attributed to the significant grain size reduction and increase of surface area and electroactive sites. This work provides a promising strategy to develop electrocatalysts for large-scale water-splitting systems and many other applications. PMID:27162978

  20. In Situ Electrochemical Oxidation Tuning of Transition Metal Disulfides to Oxides for Enhanced Water Oxidation.

    PubMed

    Chen, Wei; Wang, Haotian; Li, Yuzhang; Liu, Yayuan; Sun, Jie; Lee, Sanghan; Lee, Jang-Soo; Cui, Yi

    2015-08-26

    The development of catalysts with earth-abundant elements for efficient oxygen evolution reactions is of paramount significance for clean and sustainable energy storage and conversion devices. Our group demonstrated recently that the electrochemical tuning of catalysts via lithium insertion and extraction has emerged as a powerful approach to improve catalytic activity. Here we report a novel in situ electrochemical oxidation tuning approach to develop a series of binary, ternary, and quaternary transition metal (e.g., Co, Ni, Fe) oxides from their corresponding sulfides as highly active catalysts for much enhanced water oxidation. The electrochemically tuned cobalt-nickel-iron oxides grown directly on the three-dimensional carbon fiber electrodes exhibit a low overpotential of 232 mV at current density of 10 mA cm(-2), small Tafel slope of 37.6 mV dec(-1), and exceptional long-term stability of electrolysis for over 100 h in 1 M KOH alkaline medium, superior to most non-noble oxygen evolution catalysts reported so far. The materials evolution associated with the electrochemical oxidation tuning is systematically investigated by various characterizations, manifesting that the improved activities are attributed to the significant grain size reduction and increase of surface area and electroactive sites. This work provides a promising strategy to develop electrocatalysts for large-scale water-splitting systems and many other applications. PMID:27162978

  1. Porous structured vanadium oxide electrode material for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Reddy, Ravinder N.; Reddy, Ramana G.

    A nano porous vanadium oxide (V 2O 5) was prepared by sol-gel method. The preparation involved elutriation of aqueous sodium meta vanadate over a cation exchange resin. The product was characterized using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, surface area analysis and thermogravimetric analysis. Electrochemical characterization was done using cyclic voltammetry in a three electrode system consisting of a saturated calomel electrode as reference electrode, platinum mesh as a counter electrode, and V 2O 5 mounted on Ti mesh as the working electrode. Two molars of aqueous KCl, NaCl and LiCl were used as electrolytes. A maximum capacitance of 214 F g -1 was obtained at a scan rate of 5 mV s -1 in 2 M KCl. The effect of different electrolytes and the effect of concentration of KCl on the specific capacitance of V 2O 5 were studied. Specific capacitance faded rapidly over 100 cycles in 2 M KCl at a 5 mV s -1 scan rate.

  2. DEVELOPMENT OF ELECTROCHEMICAL REDUCTION TECHNOLOGY FOR SPENT OXIDE FUELS

    SciTech Connect

    Hur, Jin-Mok; Seo, Chung-Seok; Kim, Ik-Soo; Hong, Sun-Seok; Kang, Dae-Seung; Park, Seong-Won

    2003-02-27

    The Advanced Spent Fuel Conditioning Process (ACP) has been under development at Korea Atomic Energy Research Institute (KAERI) since 1997. The concept is to convert spent oxide fuel into metallic form and to remove high heat-load fission products such as Cs and Sr from the spent fuel. The heat power, volume, and radioactivity of spent fuel can decrease by a factor of a quarter via this process. For the realization of ACP, a concept of electrochemical reduction of spent oxide fuel in Li2O-LiCl molten salt was proposed and several cold tests using fresh uranium oxides have been carried out. In this new electrochemical reduction process, electrolysis of Li2O and reduction of uranium oxide are taking place simultaneously at the cathode part of electrolysis cell. The conversion of uranium oxide to uranium metal can reach more than 99% ensuring the feasibility of this process.

  3. Towards electrochemical purification of chemically reduced graphene oxide from redox accessible impurities.

    PubMed

    Tan, Shu Min; Ambrosi, Adriano; Khezri, Bahareh; Webster, Richard D; Pumera, Martin

    2014-04-21

    The electrochemical properties of graphene are highly sensitive to residual metallic impurities that persist despite various purification efforts. To accurately evaluate the electrochemical performance of graphene, highly purified materials free of metallic impurities are required. In this study, the partial purification of chemically reduced graphene oxides prepared via Hummers (CRGO-HU) and Staudenmaier (CRGO-ST) oxidation methods was performed through cyclic voltammetric (CV) scans executed in nitric acid, followed by CV measurements of cumene hydroperoxide (CHP). The purification of graphene was monitored by the changes in the peak current and potential of CHP which is sensitive to iron impurities. The CRGOs were characterised by inductively coupled plasma-mass spectrometry (ICP-MS), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and CV. The micrographs revealed CRGOs of similar morphologies, but with greater defects in CRGO-HU. The dependencies of CHP peak current and peak potential on the number of purification cycles exhibit greater efficiency of removing iron impurities from CRGO-HU than CRGO-ST. This can be attributed to the oxidative method that is used in CRGO-HU production, which exposes more defect sites for iron impurities to reside in. This facile electrochemical purification of graphenes can be utilised as a routine preparation and cleaning method of graphene before electrochemical measurements for analytes that show exceptional sensitivity towards electrocatalytic metallic impurities in sp(2) nanocarbon materials. PMID:24615543

  4. Preparation and electrochemical properties of urchin-like La0.8Sr0.2MnO3 perovskite oxide as a bifunctional catalyst for oxygen reduction and oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Jin, Chao; Cao, Xuecheng; Zhang, Liya; Zhang, Cong; Yang, Ruizhi

    2013-11-01

    An urchin-like La0.8Sr0.2MnO3 (LSM) perovskite oxide has been synthesized through a co-precipitation method with urea as a precipitator, and characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET analysis. SEM results show that a micro/nanocomposite with an urchin-like morphology has been obtained. The as-synthesized LSM perovskite oxide has a high specific surface area of 48 m2 g-1. The catalytic activity of the oxide for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in 0.1 M KOH solution has been studied by using a rotating-ring-disk electrode (RRDE). In the ORR test, a maximum cathodic current density of 5.2 mA cm-2 at -1.0 V (vs. Ag/AgCl) with 2500 rpm was obtained, and the ORR mainly favors a direct four-electron pathway. The results of anodic linear scanning voltammograms indicate that the urchin-like LSM perovskite oxide exhibits an encouraging catalytic activity for the OER. All electrochemical measurements suggest that the urchin-like LSM perovskite oxide could be used as a bifunctional catalyst for the ORR and the OER.

  5. One step hydrothermal synthesis of a carbon nanotube/cerium oxide nanocomposite and its electrochemical properties

    NASA Astrophysics Data System (ADS)

    Kalubarme, Ramchandra S.; Kim, Yong-Han; Park, Chan-Jin

    2013-09-01

    A carbon nanotube (CNT)/cerium oxide composite was prepared by a one-pot hydrothermal reaction in the presence of KOH and capping agent polyvinylpyrrolidone. The nanocomposite displayed pronounced capacitive behaviour with very small diffusion resistance. The electrochemical performance of the composite electrode in a symmetric supercapacitor displayed a high energy density of 35.9 Wh kg-1 corresponding to a specific capacitance of 289 F g-1. These composite electrodes also demonstrated a long cycle life with better capacity retention.

  6. Corrosion and Electrochemical Oxidation of a Pyrite by Thiobacillus ferrooxidans

    PubMed Central

    Mustin, C.; Berthelin, J.; Marion, P.; de Donato, P.

    1992-01-01

    The oxidation of a pure pyrite by Thiobacillus ferrooxidans is not really a constant phenomenon; it must be considered to be more like a succession of different steps which need characterization. Electrochemical studies using a combination of a platinum electrode and a specific pyrite electrode (packed-ground-pyrite electrode) revealed four steps in the bioleaching process. Each step can be identified by the electrochemical behavior (redox potentials) of pyrite, which in turn can be related to chemical (leachate content), bacterial (growth), and physical (corrosion patterns) parameters of the leaching process. A comparison of the oxidation rates of iron and sulfur indicated the nonstoichiometric bacterial oxidation of a pure pyrite in which superficial phenomena, aqueous oxidation, and deep crystal dissolution are successively involved. Images PMID:16348688

  7. Corrosion and electrochemical oxidation of a pyrite by Thiobacillus ferrooxidans

    SciTech Connect

    Mustin, C.; Berthelin, J. ); Marion, P.; Donato, P. de )

    1992-04-01

    The oxidation of a pure pyrite by Thiobacillus Ferrooxidans is not really a constant phenomenon; it must be considered to be more like a succession of different steps which need characterization. Electrochemical studies using a combination of a platinum electrode and a specific pyrite electrode (packed-ground-pyrite electrode) revealed four steps in the bioleaching process. Each step can be identified by the electrochemical behavior (redox potentials) of pyrite, which in turn can be related to chemical (leachate content), bacterial (growth), and physical (corrosion patterns) parameters of the leaching process. A comparison of the oxidation rates of iron and sulfur indicated the nonstoichiometric bacterial oxidation of a pure pyrite in which superficial phenomena, aqueous oxidation, and deep crystal dissolution are successively involved.

  8. Development of graphene-nanometre-sized cerium oxide-incorporated aluminium and its electrochemical evaluation

    NASA Astrophysics Data System (ADS)

    Ashraf, P. Muhamed; Thomas, Saly N.; Edwin, Leela

    2016-02-01

    Graphene-nanometre-sized cerium oxide-incorporated aluminium was prepared and its electrochemical and surface morphological characteristics were studied. The atomic force micrographs and scanning electron micrographs evaluation highlighted that the graphene and nanometre-sized cerium oxide in aluminium had decreased the surface roughness and improved the surface morphological characteristics. The graphene: nanometre-sized cerium oxide (ratios 1:2 or 2:1) with lesser amounts of particle in the matrix showed excellent corrosion resistance in the marine environment as evidenced by linear polarization, electrochemical impedance and weight loss studies. Introduction of graphene in the aluminium matrix showed a barrier separation between the outermost layer and inner layer, increased roughness and increased corrosion. The material is found to be a potential candidate for use in marine environment.

  9. Method of preparing porous, rigid ceramic separators for an electrochemical cell

    DOEpatents

    Bandyopadhyay, Gautam; Dusek, Joseph T.

    1981-01-01

    Porous, rigid separators for electrochemical cells are prepared by first calcining particles of ceramic material at temperatures above about 1200.degree. C. for a sufficient period of time to reduce the sinterability of the particles. A ceramic powder that has not been calcined is blended with the original powder to control the porosity of the completed separator. The ceramic blend is then pressed into a sheet of the desired shape and sintered at a temperature somewhat lower than the calcination temperature. Separator sheets of about 1 to 2.5 mm thickness and 30 to 70% porosity can be prepared by this technique. Ceramics such as yttria, magnesium oxide and magnesium-aluminum oxide have advantageously been used to form separators by this method.

  10. Method of preparing porous, rigid ceramic separators for an electrochemical cell. [Patent application

    DOEpatents

    Bandyopadhyay, G.; Dusek, J.T.

    Porous, rigid separators for electrochemical cells are prepared by first calcining particles of ceramic material at temperatures above about 1200/sup 0/C for a sufficient period of time to reduce the sinterability of the particles. A ceramic powder that has not been calcined is blended with the original powder to control the porosity of the completed separator. The ceramic blend is then pressed into a sheet of the desired shape and sintered at a temperature somewhat lower than the calcination temperature. Separator sheets of about 1 to 2.5 mm thickness and 30 to 70% porosity can be prepared by this technique. Ceramics such as yttria, magnesium oxide, and magnesium-aluminium oxide have advantageously been used to form separators by this method.

  11. Graphene oxide nanocapsules within silanized hydrogels suitable for electrochemical pseudocapacitors.

    PubMed

    Kataky, R; Hadden, J H L; Coleman, K S; Ntola, C N M; Chowdhury, M; Duckworth, A R; Dobson, B P; Campos, R; Pyner, S; Shenton, F

    2015-06-28

    Soft biocompatible gels comprised of rolled up graphene oxide nanocapsules within the pores of silanized hydrogels may be used as electrochemical pseudocapacitors with physiological glucose or KOH as a reducing agent, affording a material suitable for devices requiring pulses with characteristic time less than a second. PMID:25977943

  12. Alternating voltage induced electrochemical synthesis of three-dimensionalization copper oxide for lithium-ion battery application

    NASA Astrophysics Data System (ADS)

    Jing, Mingjun; Ding, Zhiying; Hou, Hongshuai; Zhang, Yan; Zou, Guoqiang; Li, Simin; Ji, Xiaobo

    2016-06-01

    Three-dimensional copper oxide structures composed of single crystal nanosheets have been successfully prepared by a green electrochemical alternating voltage approach. This special structure of copper oxide grown along the [0 1 0] direction can be effective to accommodate the volume expansion during charge-discharge cycles. The obtained product as anode materials in lithium-ion batteries displays outstanding electrochemical performances with a high reversible capacity of 635.2 mA h g-1 after 50 cycles at 100 mA g-1 close to the theoretical capacity of copper oxide (674 mA h g-1).

  13. Electrochemical oxidation of imazapyr with BDD electrode in titanium substrate.

    PubMed

    Souza, F L; Teodoro, T Q; Vasconcelos, V M; Migliorini, F L; Lima Gomes, P C F; Ferreira, N G; Baldan, M R; Haiduke, R L A; Lanza, M R V

    2014-12-01

    In this work we have studied the treatment of imazapyr by electrochemical oxidation with boron-doped diamond anode. Electrochemical degradation experiments were performed in a one-compartment cell containing 0.45 L of commercial formulations of herbicide in the pH range 3.0-10.0 by applying a density current between 10 and 150 mA cm(-2) and in the temperature range 25-45 °C. The maximum current efficiencies were obtained at lower current densities since the electrochemical system is under mass transfer control. The mineralization rate increased in acid medium and at higher temperatures. The treatment was able to completely degrade imazapyr in the range 4.6-100.0 mg L(-1), although the current charge required rises along with the increasing initial concentration of the herbicide. Toxicity analysis with the bioluminescent bacterium Vibrio fischeri showed that at higher pollutant concentrations the toxicity was reduced after the electrochemical treatment. To clarify the reaction pathway for imazapyr mineralization by OH radicals, LC-MS/MS analyses we performed together with a theoretical study. Ions analysis showed the formation of high levels of ammonium in the cathode. The main final products of the electrochemical oxidation of imazapyr with diamond thin film electrodes are formic, acetic and butyric acids. PMID:25461923

  14. Method of electrode fabrication for solid oxide electrochemical cells

    DOEpatents

    Jensen, Russell R.

    1990-01-01

    A process for fabricating cermet electrodes for solid oxide electrochemical cells by sintering is disclosed. First, a porous metal electrode is fabricated on a solid oxide cell, such as a fuel cell by, for example, sintering, and is then infiltrated with a high volume fraction stabilized zirconia suspension. A second sintering step is used to sinter the infiltrated zirconia to a high density in order to more securely attach the electrode to the solid oxide electrolyte of the cell. High performance fuel electrodes can be obtained with this process. Further electrode performance enhancement may be achieved if stabilized zirconia doped with cerium oxide, chromium oxide, titanium oxide, and/or praseodymium oxide for electronic conduction is used.

  15. Method of electrode fabrication for solid oxide electrochemical cells

    DOEpatents

    Jensen, R.R.

    1990-11-20

    A process for fabricating cermet electrodes for solid oxide electrochemical cells by sintering is disclosed. First, a porous metal electrode is fabricated on a solid oxide cell, such as a fuel cell by, for example, sintering, and is then infiltrated with a high volume fraction stabilized zirconia suspension. A second sintering step is used to sinter the infiltrated zirconia to a high density in order to more securely attach the electrode to the solid oxide electrolyte of the cell. High performance fuel electrodes can be obtained with this process. Further electrode performance enhancement may be achieved if stabilized zirconia doped with cerium oxide, chromium oxide, titanium oxide, and/or praseodymium oxide for electronic conduction is used. 5 figs.

  16. Decolorization of landfill leachate using electrochemical oxidation technique

    NASA Astrophysics Data System (ADS)

    Jumaah, Majd Ahmed; Othman, Mohamed Rozali

    2015-09-01

    The study was carried out to investigate the electrochemical oxidation of landfill leachate from the Jeram sanitary landfill leachate using charcoal base metallic composite electrodes. The control parameters used were applied voltage, Cl- concentration (as supporting electrolyte) and pH of the solution. The optimum conditions obtained were NaCl concentration of 1.5 % (w/v), applied voltage of 10 V, operating time 180 min and C60CG Co10PVC15 electrode as an anode.15 Electrochemical treatment using charcoal base metallic composite electrode was able to remove color up to 79%.

  17. Preparation and electrochemical characterization of polyaniline/activated carbon composites as an electrode material for supercapacitors.

    PubMed

    Oh, Misoon; Kim, Seok

    2012-01-01

    Polyaniline (PANI)/activated carbon (AC) composites were prepared by a chemical oxidation polymerization. To find an optimum ratio between PANI and AC which shows superior electrochemical properties, the preparation was carried out in changing the amount of added aniline monomers. The morphology of prepared composites was investigated by scanning electron microscopy (SEM) and transmission electron microscope (TEM). The structural and thermal properties were investigated by Fourier transform infrared spectra (FT-IR) and thermal gravimetric analysis (TGA), respectively. The electrochemical properties were characterized by cyclic voltammetry (CV). Composites showed a summation of capacitances that consisted of two origins. One is double-layer capacitance by ACs and the other is faradic capacitance by redox reaction of PANI. Fiber-like PANIs are coated on the surface of ACs and they contribute to the large surface for redox reaction. The vacancy among fibers provided the better diffusion and accessibility of ion. High capacitances of composites were originated from the network structure having vacancy made by PANI fibers. It was found that the composite prepared with 5 ml of aniline monomer and 0.25 g of AC showed the highest capacitance. Capacitance of 771 F/g was obtained at a scan rate of 5 mV/s. PMID:22524013

  18. Solid oxide materials research accelerated electrochemical testing

    SciTech Connect

    Windisch, C.; Arey, B.

    1995-08-01

    The objectives of this work were to develop methods for accelerated testing of cathode materials for solid oxide fuel cells under selected operating conditions. The methods would be used to evaluate the performance of LSM cathode material.

  19. Graphene Oxide Modified TiO2 Micro Whiskers and Their Photo Electrochemical Performance.

    PubMed

    Rambabu, Y; Jaiswal, Manu; Roy, Somnath C

    2016-05-01

    Harnessing the solar energy and producing clean fuel hydrogen through efficient photo-electrochemical water splitting has remained one of the most challenging endeavors in materials science. The core problem is to develop a suitable photo-catalyst material that absorbs a significant part of the solar spectrum and produces electron-hole pairs that can be easily separated without recombination. In the recent times, the composite of Titanium dioxide with graphene have been investigated to explore the advantages of both class of materials. Here we report on the photo-electrochemical properties of reduced graphene oxide functionalised TiO2 whiskers. The TiO2 whiskers are obtained from potassium titanium oxide (KTi8O16) synthesized through hydrothermal technique followed by ion exchange method and heat treatment. Graphene oxide was deposited on the as prepared TiO2 whiskers using hydrothermal method. As formed samples were characterized by Raman spectroscopy to confirm the presence of reduced graphene oxide (RGO) attached to TiO2 whiskers. Comparative photo electrochemical studies were carried out for TiO2 and reduced graphene oxide modified TiO2 whiskers. Among these, RGO modified TiO2 whiskers show significantly higher photo current density possibly due to enhancement in charge separation ability and longer electron life times. PMID:27483830

  20. Preparation of colloidal graphene in quantity by electrochemical exfoliation.

    PubMed

    Chen, Kunfeng; Xue, Dongfeng

    2014-12-15

    We reported the preparation of colloidal graphene in quantity via the anodic exfoliation of graphite in (NH4)2SO4 aqueous solution. In the currently designed electrochemical exfoliation route, mass high-quality graphene was produced within short reaction time, around 1h. The proposed electrochemical exfoliation mechanism showed that SO4(2-) and H2O can be intercalated into those graphite sheets, monolayer and few-layer graphene were obtained by the formation of gaseous SO2 and O2 within graphite sheets. Stability evaluation showed that our exfoliated colloidal graphene can be perfectly stabilized in DMF solvent more than 1 week. The colloidal graphene can be used to construct various simple and complex patterns by writing it on A4 paper, which can be applied to flexible printed electronic devices. Furthermore, colloidal graphene can show promising applications in the fabrication of binder- and additive-free electrodes for supercapacitors and lithium-ion batteries. Our present method shows huge potential for industrial-scale synthesis of high-quality graphene and further commercialization of graphene colloid for numerous advanced applications in flexible printed electronics and energy storage devices. PMID:25265584

  1. The electrochemical oxidation of methanol on a Pt/TNTs/Ti electrode enhanced by illumination

    NASA Astrophysics Data System (ADS)

    Wang, Y. Q.; Wei, Z. D.; Gao, B.; Qi, X. Q.; Li, L.; Zhang, Q.; Xia, M. R.

    A Pt/TNTs/Ti electrode is prepared by electrochemically depositing Pt using the modulated pulse current method onto high density, well ordered and uniformly distributed TiO 2 nanotubes (TNTs) on a Ti substrate. The results show that the performance and anti-poison ability of the Pt/TNTs/Ti electrode for methanol electro-oxidation under illumination is remarkably enhanced and is even better than the best bi-metallic Pt-Ru catalysts. CO poisoning is no longer a problem during methanol electro-oxidation with the Pt/TNTs/Ti electrode under illumination.

  2. Electrochemical phase diagrams for Ti oxides from density functional calculations

    NASA Astrophysics Data System (ADS)

    Huang, Liang-Feng; Rondinelli, James M.

    2015-12-01

    Developing an accurate simulation method for the electrochemical stability of solids, as well as understanding the physics related with its accuracy, is critically important for improving the performance of compounds and predicting the stability of new materials in aqueous environments. Herein we propose a workflow for the accurate calculation of first-principles electrochemical phase (Pourbaix) diagrams. With this scheme, we study the electrochemical stabilities of Ti and Ti oxides using density-functional theory. First, we find the accuracy of an exchange-correlation functional in predicting formation energies and electrochemical stabilities is closely related with the electronic exchange interaction therein. Second, the metaGGA and hybrid functionals with a more precise description of the electronic exchange interaction lead to a systematic improvement in the accuracy of the Pourbaix diagrams. Furthermore, we show that accurate Ti Pourbaix diagrams also require that thermal effects are included through vibrational contributions to the free energy. We then use these diagrams to explain various experimental electrochemical phenomena for the Ti-O system, and show that if experimental formation energies for Ti oxides, which contain contributions from defects owing to their generation at high (combustion) temperatures, are directly used to predict room temperature Pourbaix diagrams then significant inaccuracies result. In contrast, the formation energies from accurate first-principles calculations, e.g., using metaGGA and hybrid functionals, are found to be more reliable. Finally, to facilitate the future application of our accurate electrochemical phase equilibria diagrams, the variation of the Ti Pourbaix diagrams with aqueous ion concentration is also provided.

  3. Electrochemical deposition of conducting ruthenium oxide films from solution

    SciTech Connect

    Anderson, D.P.; Warren, L.F.

    1984-02-01

    In the last decade, ruthenium oxide, RuO /sub x/ (x less than or equal to 2), has been used extensively as the active anode electrocatalyst constituent for Cl/sub 2/ and O/sub 2/ evolution reactions, in chlorate production, and in metal electrowinning from mixed chloride-sulfate solutions. More recently, this material has been incorporated in several light-induced water electrolysis schemes and apparently possesses the ability to inhibit CdS photocorrosion by acting as a hole scavenger. The numerous applications for this catalyst material certainly warrant further studies of its electrochemical properties on a variety of substrates, e.g., semiconductors. The lack of a simple technique for controlled deposition of ruthenium oxide onto conducting substrates prompted us to investigate an electrochemical approach to this problem. We describe here a new way to electrochemically deposit conducting films of hydrated ruthenium oxide from an aqueous solution of the benzeneruthenium (II)aqua complex. The films slowly dissolve in aqueous electrolytes upon potential cycling, yet appear to be catalytic with regards to water oxidation.

  4. Direct electrochemical reduction of metal-oxides

    DOEpatents

    Redey, Laszlo I.; Gourishankar, Karthick

    2003-01-01

    A method of controlling the direct electrolytic reduction of a metal oxide or mixtures of metal oxides to the corresponding metal or metals. A non-consumable anode and a cathode and a salt electrolyte with a first reference electrode near the non-consumable anode and a second reference electrode near the cathode are used. Oxygen gas is produced and removed from the cell. The anode potential is compared to the first reference electrode to prevent anode dissolution and gas evolution other than oxygen, and the cathode potential is compared to the second reference electrode to prevent production of reductant metal from ions in the electrolyte.

  5. An Electrochemical Glucose Sensor Based on Zinc Oxide Nanorods.

    PubMed

    Marie, Mohammed; Mandal, Sanghamitra; Manasreh, Omar

    2015-01-01

    A glucose electrochemical sensor based on zinc oxide (ZnO) nanorods was investigated. The hydrothermal sol-gel growth method was utilized to grow ZnO nanorods on indium tin oxide-coated glass substrates. The total active area of the working electrode was 0.3 × 0.3 cm2 where titanium metal was deposited to enhance the contact. Well aligned hexagonal structured ZnO nanorods with a diameter from 68 to 116 nm were obtained. The excitonic peak obtained from the absorbance spectroscopy was observed at ~370 nm. The dominant peak of Raman spectroscopy measurement was at 440 cm(-1), matching with the lattice vibration of ZnO. The uniform distribution of the GOx and Nafion membrane that has been done using spin coating technique at 4000 rotations per minute helps in enhancing the ion exchange and increasing the sensitivity of the fabricated electrochemical sensor. The amperometric response of the fabricated electrochemical sensor was 3 s. The obtained sensitivity of the fabricated ZnO electrochemical sensor was 10.911 mA/mM·cm2 and the lower limit of detection was 0.22 µM. PMID:26263988

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

    NASA Astrophysics Data System (ADS)

    Babakhani, Banafsheh

    The aim of this thesis work was to synthesize Mn-based oxide electrodes with high surface area structures by anodic electrodeposition for application as electrochemical capacitors. Rod-like structures provide large surface areas leading to high specific capacitances. Since templated electrosynthesis of rods is not easy to use in practical applications, it is more desirable to form rod-like structures without using any templates. In this work, Mn oxide electrodes with rod-like structures (˜1.5 µm in diameter) were synthesized from a solution of 0.01 M Mn acetate under galvanostatic control without any templates, on Au coated Si substrates. The electrochemical properties of the synthesized nanocrystalline electrodes were investigated to determine the effect of morphology, chemistry and crystal structure on the corresponding electrochemical behavior of Mn oxide electrodes. Mn oxides prepared at different current densities showed a defective antifluoritetype crystal structure. The rod-like Mn oxide electrodes synthesized at low current densities (5 mAcm.2) exhibited a high specific capacitance due to their large surface areas. Also, specific capacity retention after 250 cycles in an aqueous solution of 0.5 M Na2SO4 at 100 mVs -1 was about 78% of the initial capacity (203 Fg-1 ). To improve the electrochemical capacitive behavior of Mn oxide electrodes, a sequential approach and a one-step method were adopted to synthesize Mn oxide/PEDOT electrodes through anodic deposition on Au coated Si substrates from aqueous solutions. In the former case, free standing Mn oxide rods (about 10 µm long and less than 1.5 µm in diameter) were first synthesized, then coated by electro-polymerization of a conducting polymer (PEDOT) giving coaxial rods. The one-step, co-electrodeposition method produced agglomerated Mn oxide/PEDOT particles. The electrochemical behavior of the deposits depended on the morphology and crystal structure of the fabricated electrodes, which were affected

  7. Method for preparing hollow metal oxide microsphere

    DOEpatents

    Schmitt, C.R.

    1974-02-12

    Hollow refractory metal oxide microspheres are prepared by impregnating resinous microspheres with a metallic compound, drying the impregnated microspheres, heating the microspheres slowly to carbonize the resin, and igniting the microspheres to remove the carbon and to produce the metal oxide. Zirconium oxide is given as an example. (Official Gazette)

  8. Nitrogen-doped reduced graphene oxide electrodes for electrochemical supercapacitors.

    PubMed

    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. PMID:24418938

  9. Playing peekaboo with graphene oxide: a scanning electrochemical microscopy investigation.

    PubMed

    Rapino, Stefania; Treossi, Emanuele; Palermo, Vincenzo; Marcaccio, Massimo; Paolucci, Francesco; Zerbetto, Francesco

    2014-11-01

    Scanning electrochemical microscopy (SECM) can image graphene oxide (GO) flakes on insulating and conducting substrates. The contrast between GO and the substrate is controlled by the electrostatic interactions that are established between the charges of the molecular redox mediator and the charges present in the sheet/substrate. SECM also allows quantitative measurement - at the nano/microscale - of the charge transfer kinetics between single monolayer sheets and agent molecules. PMID:25224581

  10. Electrochemical detection of nitric oxide production in perfused pig coronary artery: comparison of the performances of two electrochemical sensors.

    PubMed

    Villeneuve, N; Bedioui, F; Voituriez, K; Avaro, S; Vilaine, J P

    1998-08-01

    In situ direct measurement of nitric oxide (NO) in biological media is now possible by means of electrochemical detection. In the literature, there are principally two amperometric approaches based on the direct oxidation of NO either on a sensor made from platinum/ iridium (Pt/Ir) alloy coated with a three-layered membrane or on a nickel porphyrin and Nafion-coated carbon fiber electrode. Nonetheless, the exact nature of the experimental amperometric signal obtained with the Pt/Ir system was never authenticated as being related to NO. This study compared responses of two sensors to the inhibition effect of Nomega-nitro-L-arginine (L-NA) as the amperometric signals produced by 5-hydroxytryptamine (5-HT) on isolated pig coronary preparations. These amperometric signals could be attributed to NO only for the nickel porphyrin and Nafion-coated carbon fiber electrode. Indeed, voltammetric characterization of the electrochemical response demonstrated only variations of the baseline current upon additions of either SNAP or NO on the Pt/Ir electrode instead of anodic peak current displayed at 0.63-0.75 V for the other system. Nitrites induced baseline current variations with the Pt/Ir electrode, similar to those obtained with S-nitroso-N-acetyl-dl-penicillamine (SNAP) or NO. This study highlights the potential hazards and pitfalls that may be associated with the use of a Pt/Ir sensor calibrated with SNAP solutions for the detection of NO production in various biological systems. PMID:10100498

  11. Electrochemical process for the preparation of nitrogen fertilizers

    SciTech Connect

    Jiang, Junhua; Aulich, Ted R; Ignatchenko, Alexey V

    2015-04-14

    Methods and apparatus for the preparation of nitrogen fertilizers including ammonium nitrate, urea, urea-ammonium nitrate, and/or ammonia are disclosed. Embodiments include (1) ammonium nitrate produced via the reduction of a nitrogen source at the cathode and the oxidation of a nitrogen source at the anode; (2) urea or its isomers produced via the simultaneous cathodic reduction of a carbon source and a nitrogen source: (3) ammonia produced via the reduction of nitrogen source at the cathode and the oxidation of a hydrogen source or a hydrogen equivalent such as carbon monoxide or a mixture of carbon monoxide and hydrogen at the anode; and (4) urea-ammonium nitrate produced via the simultaneous cathodic reduction of a carbon source and a nitrogen source, and anodic oxidation of a nitrogen source.

  12. Electrochemical process for the preparation of nitrogen fertilizers

    DOEpatents

    Aulich, Ted R.; Olson, Edwin S.; Jiang, Junhua

    2013-03-19

    The present invention provides methods and apparatus for the preparation of nitrogen fertilizers including ammonium nitrate, urea, urea-ammonium nitrate, and/or ammonia utilizing a source of carbon, a source of nitrogen, and/or a source of hydrogen. Implementing an electrolyte serving as ionic charge carrier, (1) ammonium nitrate is produced via the reduction of a nitrogen source at the cathode and the oxidation of a nitrogen source at the anode; (2) urea or its isomers are produced via the simultaneous cathodic reduction of a carbon source and a nitrogen source; (3) ammonia is produced via the reduction of nitrogen source at the cathode and the oxidation of a hydrogen source at the anode; and (4) urea-ammonium nitrate is produced via the simultaneous cathodic reduction of a carbon source and a nitrogen source, and anodic oxidation of a nitrogen source. The electrolyte can be solid.

  13. Sulfur tolerant composite cermet electrodes for solid oxide electrochemical cells

    DOEpatents

    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.

  14. Ultrasonically enhanced electrochemical oxidation of ibuprofen.

    PubMed

    Thokchom, Binota; Kim, Kyungho; Park, Jeonghyuk; Khim, Jeehyeong

    2015-01-01

    A hybrid advanced oxidation process combining sonochemistry (US) and electrochemistry (EC) for the batch scale degradation of ibuprofen was developed. The performance of this hybrid reactor system was evaluated by quantifying on the degradation of ibuprofen under the variation in electrolytes, frequency, applied voltage, ultrasonic power density and temperature in aqueous solutions with a platinum electrode. Among the methods examined (US, EC and US/EC), the hybrid method US/EC resulted 89.32%, 81.85% and 88.7% degradations while using NaOH, H2SO4 and deionized water (DI), respectively, with a constant electrical voltages of 30V, an ultrasound frequency of 1000kHz, and a power density of 100WL(-1) at 298K in 1h. The degradation was established to follow pseudo first order kinetics. In addition, energy consumption and energy efficiencies were also calculated. The probable mechanism for the anodic oxidation of ibuprofen at a platinum electrode was also postulated. PMID:24844440

  15. Observable Electrochemical Oxidation of Carbon Promoted by Platinum Nanoparticles.

    PubMed

    Kou, Zongkui; Cheng, Kun; Wu, Hui; Sun, Ronghui; Guo, Beibei; Mu, Shichun

    2016-02-17

    The radical degradation of Pt-based catalysts toward oxygen reduction reaction (ORR), predominantly caused by the oxidation of carbon supports, heavily blocks the commercialization of polymer electrolyte membrane fuel cells (PEMFCs). As reported, the electrochemical oxidation of carbon could be accelerated by Pt catalysts; however, hitherto no direct evidence is present for the promotion of Pt catalysts. Herein, a unique ultrathin carbon layer (approximately 2.9 nm in thickness) covered Pt catalyst (Pt/C-GC) is designed and synthesized by a chemical vapor deposition (CVD) method. This magnifies the catalysis effect of Pt to carbon oxidation due to the greatly increased contact sites between the metal-support, making it easy to investigate the carbon oxidation process by observing the thinning of the carbon layer on Pt nanoparticles from TEM observations. Undoubtedly, this finding can better guide the structural design of the durable metal catalysts for PEMFCs and other applications. PMID:26788962

  16. Solar-powered electrochemical oxidation of organic compounds coupled with the cathodic production of molecular hydrogen.

    PubMed

    Park, Hyunwoong; Vecitis, Chad D; Hoffmann, Michael R

    2008-08-21

    A Bi-doped TiO2 anode, which is prepared from a mixed metal oxide coating deposited on Ti metal, is shown to be efficient for conventional water splitting. In this hybrid photovoltaic-electrochemical system, a photovoltaic (PV) cell is used to convert solar light to electricity, which is then used to oxidize a series of phenolic compounds at the semiconductor anode to carbon dioxide with the simultaneous production of molecular hydrogen from water/proton reduction at the stainless steel cathode. Degradation of phenol in the presence of a background NaCl electrolyte produces chlorinated phenols as reaction intermediates, which are subsequently oxidized completely to carbon dioxide and low-molecular weight carboxylic acids. The anodic current efficiency for the complete oxidation of phenolic compounds ranges from 3% to 17%, while the cathodic current efficiency and the energy efficiency for hydrogen gas generation range from 68% to 95% and 30% to 70%, respectively. PMID:18656909

  17. ELECTROCHEMICAL ADVANCED OXIDATION PROCESS UTILIZING NB-DOPED TIO2 ELECTRODES

    EPA Science Inventory

    An electrochemical advanced oxidation process has been developed utilizing electrodes which generate hydroxyl free radical (HO) by oxidizing water. All substrates tested are oxidized, mostly with reaction rates proportional to the corresponding rate constants for reaction with hy...

  18. ELECTROCHEMICAL ADVANCED OXIDATION PROCESS UTILIZING NB-DOPED TIO2 ELECTRODES

    EPA Science Inventory

    An electrochemical advanced oxidation process has been developed, utilizing electrodes which generate hydroxyl free radical (HO) by oxidizing water. All substrates tested are oxidized, mostly with reaction rates proportional to the corresponding rate constants for reaction with h...

  19. Electrochemical oxidation as a final treatment of synthetic tannery wastewater.

    PubMed

    Panizza, Marco; Cerisola, Giacomo

    2004-10-15

    Vegetable tannery wastewaters contain high concentrations of organics and other chemicals that inhibit the activity of microorganisms during biological oxidations, so biorefractory organics that are not removed by biological treatment must be eliminated by a tertiary or advanced wastewater treatment. In this paper, the applicability of electrochemical oxidation as a tertiary treatment of a vegetable tannery wastewater was investigated by performing galvanostatic electrolysis using lead dioxide (Ti/PbO2) and mixed titanium and ruthenium oxide (Ti/TiRuO2) as anodes under different experimental conditions. The experimental results showed that both the electrodes performed complete mineralization of the wastewater. In particular, the oxidation took place on the PbO2 anode by direct electron transfer and indirect oxidation mediated by active chlorine, while it occurred on the Ti/TiRuO2 anode only by indirect oxidation. Furthermore, the Ti/PbO2 gave a somewhat higher oxidation rate than that observed for the Ti/TiRuO2 anode. Although the Ti/TiRuO2 required almost the same energy consumption for complete COD removal, it was more stable and did not release toxic ions, so it was the best candidate for industrial applications. With the Ti/TiRuO2 anode, the rate of tannery wastewater oxidation increased with the current density, pH, and temperature of the solution. These results strongly indicate that electrochemical methods can be applied effectively as a final treatment of vegetable tannery wastewater allowing the complete removal of COD, tannin, and ammonium and decolorization. PMID:15543753

  20. Simultaneous Electrochemical Reduction and Delamination of Graphene Oxide Films.

    PubMed

    Wang, Xiaohan; Kholmanov, Iskandar; Chou, Harry; Ruoff, Rodney S

    2015-09-22

    Here we report an electrochemical method to simultaneously reduce and delaminate graphene oxide (G-O) thin films deposited on metal (Al and Au) substrates. During the electrochemical reaction, interface charge transfer between the G-O thin film and the electrode surface was found to be important in eliminating oxygen-containing groups, yielding highly reduced graphene oxide (rG-O). In the meantime, hydrogen bubbles were electrochemically generated at the rG-O film/electrode interface, propagating the film delamination. Unlike other metal-based G-O reduction methods, the metal used here was either not etched at all (for Au) or etched a small amount (for Al), thus making it possible to reuse the substrate and lower production costs. The delaminated rG-O film exhibits a thickness-dependent degree of reduction: greater reduction is achieved in thinner films. The thin rG-O films having an optical transmittance of 90% (λ = 550 nm) had a sheet resistance of 6390 ± 447 Ω/□ (ohms per square). rG-O-based stretchable transparent conducting films were also demonstrated. PMID:26257072

  1. Electrochemical & Thermochemical Behavior of Cerium(IV) Oxide delta

    NASA Astrophysics Data System (ADS)

    Chueh, William C.

    The mixed-valent nature of nonstoichiometric ceria (CeO2-delta ) gives rise to a wide range of intriguing properties, such as mixed ionic and electronic conduction and oxygen storage. Surface and transport behavior in rare-earth (samaria) doped and undoped ceria were investigated, with particular emphasis on applications in electrochemical and thermochemical energy conversion processes such as fuel cells and solar fuel production. The electrochemical responses of bulk-processed ceria with porous Pt and Au electrodes were analyzed using 1-D and 2-D transport models to decouple surface reactions, near-surface transport and bulk transport. Combined experimental and numerical results indicate that hydrogen electro-oxidation and hydrolysis near open-circuit conditions occur preferentially over the ceria | gas interface rather than over the ceria | gas | metal interface, with the rate-limiting step likely to be either surface reaction or transport through the surface oxygen vacancy depletion layer. In addition, epitaxial thin films of ceria were grown on zirconia substrates using pulsed-laser deposition to examine electrocatalysis over well-defined microstructures. Physical models were derived to analyze the electrochemical impedance response. By varying the film thickness, interfacial and chemical capacitance were decoupled, with the latter shown to be proportional to the small polaron densities. The geometry of microfabricated metal current collectors (metal = Pt, Ni) was also systematically varied to investigate the relative activity of the ceria | gas and the ceria | metal | gas interfaces. The data suggests that the electrochemical activity of the metal-ceria composite is only weakly dependent on the metal due to the relatively high activity of the ceria | gas interface. In addition to electrochemical experiments, thermochemical reduction-oxidation studies were performed on ceria. It was shown that thermally-reduced ceria, upon exposure to H 2O and/or CO2, can be

  2. FTIR spectra and normal-mode analysis of a tetranuclear Manganese adamantane-like complex in two electrochemically prepared oxidation states: Relevance to the oxygen-evolving complex of Photosystem II

    SciTech Connect

    Visser, Hendrik; Dube, Christopher E.; Armstrong, William H.; Sauer, Kenneth; Yachandra, Vittal K.

    2002-03-19

    The IR spectra and normal-mode analysis of the adamantane-like compound [Mn4O6(bpea)4]n+ in two oxidation states, MnIV4 and MnIIIMnIV3, that are relevant to the oxygen-evolving complex of photosystem II are presented. Mn-O vibrational modes are identified with isotopic exchange, 16O->18O, of the mono-(mu)-oxo bridging atoms in the complex. IR spectra of the MnIIIMnIV3 species are obtained by electrochemical reduction of the MnIV4 species using a spectroelectrochemical cell, based on attenuated total reflection [Visser et al. Anal Chem 2001, 73, 4374-4378]. A novel method of subtraction is used to reduce background contributions from solvent and ligand modes, and the difference and double-difference spectra are used in identifying Mn-O bridging modes that are sensitive to oxidation state change. Two strong IR bands are observed for the MnIV4 species at 745 and 707 cm-1 and a weaker band at 510 cm-1. Upon reduction, the MnIIIMnIV3 species exhibits two strong IR bands at 745 and 680 cm-1, and several weaker bands are observed in the 510 - 425 cm-1 range. A normal mode analysis is performed to assign all the relevant bridging modes in the oxidized MnIV4 and reduced MnIIIMnIV3 species. The calculated force constants for the MnIV4 species are = 3.15 mdynAngstrom, = 0.55 mdyn/Angstrom, and = 0.20 mdyn/Angstrom. The force constants for the MnIIIMnIV3 species are = 3.10 mdyn/Angstrom, = 2.45 mdyn/Angstrom, = 0.40, and = 0.15 mdyn/Angstrom. This study provides insights for the identification of Mn-O modes in the IR spectra of the photosynthetic oxygen-evolving complex during its catalytic cycle.

  3. METHOD FOR PREPARATION OF SINTERABLE BERYLLIUM OXIDE

    DOEpatents

    Sturm, B.J.

    1963-08-13

    High-purity beryllium oxide for nuclear reactor applications can be prepared by precipitation of beryllium oxalate monohydrate from aqueous solution at a temperature above 50 deg C and subsequent calcination of the precipitate. Improved purification with respect to metallic impurities is obtained, and the product beryllium oxide sinters reproducibly to a high density. (AEC)

  4. Fabrication of solid oxide fuel cell by electrochemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Riley, Brian; Szreders, Bernard E.

    1988-04-01

    In a high temperature solid oxide fuel cell (SOFC), the deposition of an impervious high density thin layer of electrically conductive interconnector material, such as magnesium doped lanthanum chromite, and of an electrolyte material, such as yttria stabilized zirconia, onto a porous support/air electrode substrate surface is carried out at high temperatures (approx. 1100 to 1300 C) by a process of electrochemical vapor deposition. In this process, the mixed chlorides of the specific metals involved react in the gaseous state with water vapor resulting in the deposit of an impervious thin oxide layer on the support tube/air electrode substrate of between 20 and 50 microns in thickness. An internal heater, such as a heat pipe, is placed within the support tube/air electrode substrate and induces a uniform temperature profile therein so as to afford precise and uniform oxide deposition kinetics in an arrangement which is particularly adapted for large scale, commercial fabrication of SOFCs.

  5. Fabrication of solid oxide fuel cell by electrochemical vapor deposition

    DOEpatents

    Riley, B.; Szreders, B.E.

    1988-04-26

    In a high temperature solid oxide fuel cell (SOFC), the deposition of an impervious high density thin layer of electrically conductive interconnector material, such as magnesium doped lanthanum chromite, and of an electrolyte material, such as yttria stabilized zirconia, onto a porous support/air electrode substrate surface is carried out at high temperatures (/approximately/1100/degree/ /minus/ 1300/degree/C) by a process of electrochemical vapor deposition. In this process, the mixed chlorides of the specific metals involved react in the gaseous state with water vapor resulting in the deposit of an impervious thin oxide layer on the support tube/air electrode substrate of between 20--50 microns in thickness. An internal heater, such as a heat pipe, is placed within the support tube/air electrode substrate and induces a uniform temperature profile therein so as to afford precise and uniform oxide deposition kinetics in an arrangement which is particularly adapted for large scale, commercial fabrication of SOFCs.

  6. Fabrication of solid oxide fuel cell by electrochemical vapor deposition

    DOEpatents

    Brian, Riley; Szreders, Bernard E.

    1989-01-01

    In a high temperature solid oxide fuel cell (SOFC), the deposition of an impervious high density thin layer of electrically conductive interconnector material, such as magnesium doped lanthanum chromite, and of an electrolyte material, such as yttria stabilized zirconia, onto a porous support/air electrode substrate surface is carried out at high temperatures (approximately 1100.degree.-1300.degree. C.) by a process of electrochemical vapor deposition. In this process, the mixed chlorides of the specific metals involved react in the gaseous state with water vapor resulting in the deposit of an impervious thin oxide layer on the support tube/air electrode substrate of between 20-50 microns in thickness. An internal heater, such as a heat pipe, is placed within the support tube/air electrode substrate and induces a uniform temperature profile therein so as to afford precise and uniform oxide deposition kinetics in an arrangement which is particularly adapted for large scale, commercial fabrication of SOFCs.

  7. Scalable and sustainable electrochemical allylic C-H oxidation.

    PubMed

    Horn, Evan J; Rosen, Brandon R; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D; Baran, Phil S

    2016-05-01

    New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as "classics". Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact. PMID:27096371

  8. Scalable and sustainable electrochemical allylic C–H oxidation

    NASA Astrophysics Data System (ADS)

    Horn, Evan J.; Rosen, Brandon R.; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D.; Baran, Phil S.

    2016-05-01

    New methods and strategies for the direct functionalization of C–H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C–H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as “classics”. Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C–H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C–H oxidation (demonstrated on 100 grams), enabling the adoption of this C–H oxidation strategy in large-scale industrial settings without substantial environmental impact.

  9. Electrochemically reduced graphene oxide on silicon nanowire arrays for enhanced photoelectrochemical hydrogen evolution.

    PubMed

    Meng, Huan; Fan, Ke; Low, Jingxiang; Yu, Jiaguo

    2016-09-21

    Photoelectrochemical (PEC) water splitting into hydrogen and oxygen by sunlight is a promising approach to solve energy and environmental problems. In this work, silicon nanowire arrays (SiNWs) photocathodes decorated with reduced graphene oxide (rGO) for PEC water splitting were successfully prepared by a flexible and scalable electrochemical reduction method. The SiNWs photocathode with the optimized rGO decoration (SiNWs/rGO20) shows an enhanced activity with a much higher photocurrent density and significantly positive shift of onset potential compared to the bare SiNWs arrays for the hydrogen evolution reaction (HER). The enhanced PEC activity is ascribed to the high electrical conductivity of rGO and improved separation of the photogenerated charge carriers. This work not only demonstrates a facile, rapid and tunable electrochemical reduction method to produce rGO, but also exhibits an efficient protocol to enhance the PEC water splitting of silicon-based materials. PMID:27461187

  10. A Straightforward Electrochemical Approach to Imine‐ and Amine‐bisphenolate Metal Complexes with Facile Control Over Metal Oxidation State

    PubMed Central

    Chapman, Michael R.; Henkelis, Susan E.; Kapur, Nikil

    2016-01-01

    Abstract Synthetic methods to prepare organometallic and coordination compounds such as Schiff‐base complexes are diverse, with the route chosen being dependent upon many factors such as metal–ligand combination and metal oxidation state. In this work we have shown that electrochemical methodology can be employed to synthesize a variety of metal–salen/salan complexes which comprise diverse metal–ligand combinations and oxidation states. Broad application has been demonstrated through the preparation of 34 complexes under mild and ambient conditions. Unprecedented control over metal oxidation state (MII/III/IV where M=Fe, Mn) is presented by simple modification of reaction conditions. Along this route, a general protocol‐switch is described which allows access to analytically pure FeII/III–salen complexes. Tuning electrochemical potential, selective metalation of a Mn/Ni alloy is also presented which exclusively delivers MnII/IV–salen complexes in high yield. PMID:27547645

  11. A Straightforward Electrochemical Approach to Imine- and Amine-bisphenolate Metal Complexes with Facile Control Over Metal Oxidation State.

    PubMed

    Chapman, Michael R; Henkelis, Susan E; Kapur, Nikil; Nguyen, Bao N; Willans, Charlotte E

    2016-08-01

    Synthetic methods to prepare organometallic and coordination compounds such as Schiff-base complexes are diverse, with the route chosen being dependent upon many factors such as metal-ligand combination and metal oxidation state. In this work we have shown that electrochemical methodology can be employed to synthesize a variety of metal-salen/salan complexes which comprise diverse metal-ligand combinations and oxidation states. Broad application has been demonstrated through the preparation of 34 complexes under mild and ambient conditions. Unprecedented control over metal oxidation state (M(II/III/IV) where M=Fe, Mn) is presented by simple modification of reaction conditions. Along this route, a general protocol-switch is described which allows access to analytically pure Fe(II/III)-salen complexes. Tuning electrochemical potential, selective metalation of a Mn/Ni alloy is also presented which exclusively delivers Mn(II/IV)-salen complexes in high yield. PMID:27547645

  12. Preparation of Conducting Polymers by Electrochemical Methods and Demonstration of a Polymer Battery

    ERIC Educational Resources Information Center

    Goto, Hiromasa; Yoneyama, Hiroyuki; Togashi, Fumihiro; Ohta, Reina; Tsujimoto, Akitsu; Kita, Eiji; Ohshima, Ken-ichi

    2008-01-01

    The electrochemical polymerization of aniline and pyrrole, and demonstrations of electrochromism and the polymer battery effect, are presented as demonstrations suitable for high school and introductory chemistry at the university level. These demonstrations promote student interest in the electrochemical preparation of conducting polymers, where…

  13. Microwave synthesis and electrochemical characterization of Mn/Ni mixed oxide for supercapacitor application

    SciTech Connect

    Prasankumar, T.; Jose, Sujin P.; Ilangovan, R.; Venkatesh, K. S.

    2015-06-24

    Nanostructured Mn/Ni mixed metal oxide was synthesized at ambient temperature by facile microwave irradiation technique. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. X-ray diffraction analysis confirmed the formation of Mn/Ni mixed oxide in rhombohedral phase and the grain size calculated was found to be 87 nm. The irregular spherical morphology of the prepared sample was exhibited by the SEM images. The characteristic peaks of FTIR at about 630 cm{sup −1} and 749 cm{sup −1} were attributed to the Mn-O and Ni-O stretching vibrations respectively. The presence of both Mn and Ni in the prepared sample was validated by the EDS spectra which in turn confirmed the formation of mixed oxide. Cyclic voltammetry and galvanostatic chargedischarge measurements were employed to investigate the electrochemical performance of the mixed oxide. The cyclic voltammetry curves demonstrated good capacitive performance of the sample in the potential window −0.2V to 0.9V. The charge discharge study revealed the suitability of the prepared mixed oxide for the fabrication of supercapacitor electrode.

  14. Corner heating in rectangular solid oxide electrochemical cell generators

    DOEpatents

    Reichner, Philip

    1989-01-01

    Disclosed is an improvement in a solid oxide electrochemical cell generator 1 having a rectangular design with four sides that meet at corners, and containing multiplicity of electrically connected fuel cells 11, where a fuel gas is passed over one side of said cells and an oxygen containing gas is passed into said cells, and said fuel is burned to form heat, electricity, and an exhaust gas. The improvement comprises passing the exhaust gases over the multiplicity of cells 11 in such a way that more of the heat in said exhaust gases flows at the corners of the generator, such as through channels 19.

  15. Synthesis and electrochemical performance of hierarchical nano-vanadium oxide.

    PubMed

    Mjejri, I; Sediri, F

    2016-10-15

    Hierarchically structured nano-vanadium oxides with different morphologies have been synthesized via a template-free hydrothermal route by adjusting the organic precursor quantities. The effects of molar ratio on structure, morphology and crystallite sized were investigated. The possible growth mechanism is also proposed. When evaluated as a cathode material for lithium-ion batteries, the vanadium oxyhydroxide H2V3O8 samples deliver very high charging capacity, good reversibility and a better cycling stability. The excellent electrochemical performance is attributed to multiple advantageous structural features. PMID:27442146

  16. Electrochemical process for the preparation of nitrogen fertilizers

    DOEpatents

    Aulich, Ted R.; Olson, Edwin S.; Jiang, Junhua

    2012-04-10

    The present invention provides methods and apparatus for the preparation of nitrogen fertilizers including ammonium nitrate, urea, urea-ammonium nitrate, and/or ammonia, at low temperature and pressure, preferably at ambient temperature and pressure, utilizing a source of carbon, a source of nitrogen, and/or a source of hydrogen or hydrogen equivalent. Implementing an electrolyte serving as ionic charge carrier, (1) ammonium nitrate is produced via the reduction of a nitrogen source at the cathode and the oxidation of a nitrogen source at the anode; (2) urea or its isomers are produced via the simultaneous cathodic reduction of a carbon source and a nitrogen source; (3) ammonia is produced via the reduction of nitrogen source at the cathode and the oxidation of a hydrogen source or a hydrogen equivalent such as carbon monoxide or a mixture of carbon monoxide and hydrogen at the anode; and (4) urea-ammonium nitrate is produced via the simultaneous cathodic reduction of a carbon source and a nitrogen source, and anodic oxidation of a nitrogen source. The electrolyte can be aqueous, non-aqueous, or solid.

  17. Graphenes prepared by Staudenmaier, Hofmann and Hummers methods with consequent thermal exfoliation exhibit very different electrochemical properties

    NASA Astrophysics Data System (ADS)

    Poh, Hwee Ling; Šaněk, Filip; Ambrosi, Adriano; Zhao, Guanjia; Sofer, Zdeněk; Pumera, Martin

    2012-05-01

    Large-scale fabrication of graphene is highly important for industrial and academic applications of this material. The most common large-scale preparation method is the oxidation of graphite to graphite oxide using concentrated acids in the presence of strong oxidants and consequent thermal exfoliation and reduction by thermal shock to produce reduced graphene. These oxidation methods typically use concentrated sulfuric acid (a) in combination with fuming nitric acid and KClO3 (Staudenmaier method), (b) in combination with concentrated nitric acid and KClO3 (Hofmann method) or (c) in the absence of nitric acid but in the presence of NaNO3 and KMnO4 (Hummers method). The evaluation of quality and applicability of the graphenes produced by these various methods is of high importance and is attempted side-by-side for the first time in this paper. Full-scale characterization of thermally reduced graphenes prepared by these standard methods was performed with techniques such as transmission and scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Their applicability for electrochemical devices was further evaluated by means of cyclic voltammetry techniques. We showed that while Staudenmaier and Hofmann methods (methods that do not use potassium permanganate as oxidant) generated thermally reduced graphenes with comparable electrochemical properties, the graphene prepared by the Hummers method which uses permanganate as oxidant showed higher heterogeneous electron transfer rates and lower overpotentials as compared to graphenes prepared by the Staudenmaier or Hofmann methods. This clearly shows that the methods of preparations have dramatic influences on the materials properties and, thus, such findings are of eminent importance for practical applications as well as for academic research.

  18. Functionalizing Aluminum Oxide by Ag Dendrite Deposition at the Anode during Simultaneous Electrochemical Oxidation of Al.

    PubMed

    Rafailović, Lidija D; Gammer, Christoph; Rentenberger, Christian; Trišović, Tomislav; Kleber, Christoph; Karnthaler, Hans Peter

    2015-11-01

    A novel synthesis strategy is presented for depositing metallic Ag at the anode during simultaneous electrochemical oxidation of Al. This unexpected result is achieved based on galvanic coupling. Metallic dendritic nanostructures well-anchored in a high surface area supporting matrix are envisioned to open up a new avenue of applications. PMID:26398487

  19. Electrochemically tunable thermal conductivity of lithium cobalt oxide

    NASA Astrophysics Data System (ADS)

    Cho, Jiung; Losego, Mark D.; Zhang, Hui Gang; Kim, Honggyu; Zuo, Jianmin; Petrov, Ivan; Cahill, David G.; Braun, Paul V.

    2014-06-01

    Using time-domain thermoreflectance, the thermal conductivity and elastic properties of a sputter deposited LiCoO2 film, a common lithium-ion cathode material, are measured as a function of the degree of lithiation. Here we report that via in situ measurements during cycling, the thermal conductivity of a LiCoO2 cathode reversibly decreases from ~5.4 to 3.7 W m-1 K-1, and its elastic modulus decreases from 325 to 225 GPa, as it is delithiated from Li1.0CoO2 to Li0.6CoO2. The dependence of the thermal conductivity on lithiation appears correlated with the lithiation-dependent phase behaviour. The oxidation-state-dependent thermal conductivity of electrolytically active transition metal oxides provides opportunities for dynamic control of thermal conductivity and is important to understand for thermal management in electrochemical energy storage devices.

  20. Electrochemically tunable thermal conductivity of lithium cobalt oxide.

    PubMed

    Cho, Jiung; Losego, Mark D; Zhang, Hui Gang; Kim, Honggyu; Zuo, Jianmin; Petrov, Ivan; Cahill, David G; Braun, Paul V

    2014-01-01

    Using time-domain thermoreflectance, the thermal conductivity and elastic properties of a sputter deposited LiCoO2 film, a common lithium-ion cathode material, are measured as a function of the degree of lithiation. Here we report that via in situ measurements during cycling, the thermal conductivity of a LiCoO2 cathode reversibly decreases from ~5.4 to 3.7 W m(-1) K(-1), and its elastic modulus decreases from 325 to 225 GPa, as it is delithiated from Li1.0CoO2 to Li0.6CoO2. The dependence of the thermal conductivity on lithiation appears correlated with the lithiation-dependent phase behaviour. The oxidation-state-dependent thermal conductivity of electrolytically active transition metal oxides provides opportunities for dynamic control of thermal conductivity and is important to understand for thermal management in electrochemical energy storage devices. PMID:24892640

  1. Polyaniline-grafted reduced graphene oxide for efficient electrochemical supercapacitors.

    PubMed

    Kumar, Nanjundan Ashok; Choi, Hyun-Jung; Shin, Yeon Ran; Chang, Dong Wook; Dai, Liming; Baek, Jong-Beom

    2012-02-28

    An alternative and effective route to prepare conducting polyaniline-grafted reduced graphene oxide (PANi-g-rGO) composite with highly enhanced properties is reported. In order to prepare PANi-g-rGO, amine-protected 4-aminophenol was initially grafted to graphite oxide (GO) via acyl chemistry where a concomitant partial reduction of GO occurred due to the refluxing and exposure of GO to thionyl chloride vapors and heating. Following the deprotection of amine groups, an in situ chemical oxidative grafting of aniline in the presence of an oxidizing agent was carried out to yield highly conducting PANi-g-rGO. Electron microscopic studies demonstrated that the resultant composite has fibrillar morphology with a room-temperature electrical conductivity as high as 8.66 S/cm and capacitance of 250 F/g with good cycling stability. PMID:22276770

  2. Selective electrochemical generation of hydrogen peroxide from water oxidation

    DOE PAGESBeta

    Viswanathan, Venkatasubramanian; Hansen, Heine A.; Norskov, Jens K.

    2015-10-08

    Water is a life-giving source, fundamental to human existence, yet over a billion people lack access to clean drinking water. The present techniques for water treatment such as piped, treated water rely on time and resource intensive centralized solutions. In this work, we propose a decentralized device concept that can utilize sunlight to split water into hydrogen and hydrogen peroxide. The hydrogen peroxide can oxidize organics while the hydrogen bubbles out. In enabling this device, we require an electrocatalyst that can oxidize water while suppressing the thermodynamically favored oxygen evolution and form hydrogen peroxide. Using density functional theory calculations, wemore » 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. Furthermore, we present a rational design principle for the selectivity in electrochemical water oxidation and identify new material candidates that could perform H2O2 evolution selectively.« less

  3. Selective electrochemical generation of hydrogen peroxide from water oxidation

    SciTech Connect

    Viswanathan, Venkatasubramanian; Hansen, Heine A.; Norskov, Jens K.

    2015-10-08

    Water is a life-giving source, fundamental to human existence, yet over a billion people lack access to clean drinking water. The present techniques for water treatment such as piped, treated water rely on time and resource intensive centralized solutions. In this work, we propose a decentralized device concept that can utilize sunlight to split water into hydrogen and hydrogen peroxide. The hydrogen peroxide can oxidize organics while the hydrogen bubbles out. In enabling this device, we require an electrocatalyst that can oxidize water while suppressing the thermodynamically favored oxygen 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. Furthermore, we present a rational design principle for the selectivity in electrochemical water oxidation and identify new material candidates that could perform H2O2 evolution selectively.

  4. Electrochemical formation of a composite polymer-aluminum oxide film

    NASA Astrophysics Data System (ADS)

    Runge-Marchese, Jude Mary

    1997-10-01

    The formation of polymer films through electrochemical techniques utilizing electrolytes which include conductive polymer is of great interest to the coatings and electronics industries as a means for creating electrically conductive and corrosion resistant finishes. One of these polymers, polyamino-benzene (polyaniline), has been studied for this purpose for over ten years. This material undergoes an insulator-to-metal transition upon doping with protonic acids in an acid/base type reaction. Review of prior studies dealing with polyaniline and working knowledge of aluminum anodization has led to the development of a unique process whereby composite polymer-aluminum oxide films are formed. The basis for the process is a modification of the anodizing electrolyte which results in the codeposition of polyaniline during aluminum anodization. A second process, which incorporates electrochemical sealing of the anodic layer with polyaniline was also developed. The formation of these composite films is documented through experimental processing, and characterized by way of scientific analysis and engineering tests. Analysis results revealed the formation of unique dual phase anodic films with fine microstructures which exhibited full intrusion of the columnar aluminum oxide structure with polyaniline, indicating the polymer was deposited as the metal oxidation proceeded. An aromatic amine derivative of polyaniline with aluminum sulfate was determined to be the reaction product within the aluminum oxide phase of the codeposited films. Scientific characterization determined the codeposition process yields completely chemically and metallurgically bound composite films. Engineering studies determined the films, obtained through a single step, exhibited superior wear and corrosion resistance to conventionally anodized and sealed films processed through two steps, demonstrating the increased manufacturing process efficiency that can be realized with the modification of the

  5. Morphology, structural and optical properties of iron oxide thin film photoanodes in photoelectrochemical cell: Effect of electrochemical oxidation

    NASA Astrophysics Data System (ADS)

    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.

  6. Preparation of polyphenols by oxidation of hydroxybenzaldehydes

    SciTech Connect

    Formanek, K.; Michelet, D.; Petre, D.

    1984-03-06

    Optionally aldehyde substituted polyphenols are prepared by oxidizing, with hydrogen peroxide, a hydroxybenzaldehyde bearing at least one aldehyde substituent ortho- and/or para- to the nuclear hydroxyl group, in an aqueous reaction medium and in the presence of an alkali or alkaline earth metal base, the process being characterized in that the pH of the reaction medium is continuously maintained at a value no greater than 7 throughout the course of the oxidation reaction. The subject process is well suited for the preparation of, e.g., hydroxy-p-vanillin from guaiacol, and the novel compound 2,4,6-triformylphenol.

  7. Process for preparing active oxide powders

    DOEpatents

    Berard, Michael F.; Hunter, Jr., Orville; Shiers, Loren E.; Dole, Stephen L.; Scheidecker, Ralph W.

    1979-02-20

    An improved process for preparing active oxide powders in which cation hydroxide gels, prepared in the conventional manner are chemically dried by alternately washing the gels with a liquid organic compound having polar characteristics and a liquid organic compound having nonpolar characteristics until the mechanical water is removed from the gel. The water-free cation hydroxide is then contacted with a final liquid organic wash to remove the previous organic wash and speed drying. The dried hydroxide treated in the conventional manner will form a highly sinterable active oxide powder.

  8. SERS speciation of the electrochemical oxidation-reduction of riboflavin.

    PubMed

    Bailey, Matthew R; Schultz, Zachary D

    2016-08-15

    The reduction and oxidation of the flavin system is an important electron transfer reaction in biological systems. Several reaction pathways exist to connect oxidized to fully reduced riboflavin, each with unique intermediates including a semi-quinone radical. By performing surface-enhanced Raman scattering (SERS) with simultaneous electrochemical detection of riboflavin at different pH values, we are able to correlate reversible changes in spectral features to the current changes observed in the cyclic voltammetry. Multivariate curve resolution analysis of the SERS spectra indicates that three distinct components were present at the SERS electrode at each pH during the potential sweep. To verify and better understand the variations in Raman bands across the voltammogram, density functional theory (DFT) calculations were performed to model the effect of pH and oxidation state on the riboflavin Raman spectrum. The calculated spectra show qualitative agreement with the species identified in the chemometric analysis. This combination of results indicates the presence of the oxidized, semi-quinone, and reduced forms of riboflavin and provides insight into the mechanism of the flavin redox system. PMID:27297697

  9. Electrochemical production of hydrogen coupled with the oxidation of arsenite.

    PubMed

    Kim, Jungwon; Kwon, Daejung; Kim, Kitae; Hoffmann, Michael R

    2014-01-01

    The production of hydrogen accompanied by the simultaneous oxidation of arsenite (As(III)) was achieved using an electrochemical system that employed a BiOx-TiO2 semiconductor anode and a stainless steel (SS) cathode in the presence of sodium chloride (NaCl) electrolyte. The production of H2 was enhanced by the addition of As(III) during the course of water electrolysis. The synergistic effect of As(III) on H2 production can be explained in terms of (1) the scavenging of reactive chlorine species (RCS), which inhibit the production of H2 by competing with water molecules (or protons) for the electrons on the cathode, by As(III) and (2) the generation of protons, which are more favorably reduced on the cathode than water molecules, through the oxidation of As(III). The addition of 1.0 mM As(III) to the electrolyte at a constant cell voltage (E cell) of 3.0 V enhanced the production of H2 by 12% even though the cell current (I cell) was reduced by 5%. The net effect results in an increase in the energy efficiency (EE) for H2 production (ΔEE) by 17.5%. Furthermore, the value ΔEE, which depended on As(III) concentration, also depended on the applied E cell. For example, the ΔEE increased with increasing As(III) concentration in the micromolar range but decreased as a function of E cell. This is attributed to the fact that the reactions between RCS and As(III) are influenced by both RCS concentration depending on E cell and As(III) concentration in the solution. On the other hand, the ΔEE decreased with increasing As(III) concentration in the millimolar range due to the adsorption of As(V) generated from the oxidation of As(III) on the semiconductor anode. In comparison to the electrochemical oxidation of certain organic compounds (e.g., phenol, 4-chlorophenol, 2-chlorophenol, salicylic acid, catechol, maleic acid, oxalate, and urea), the ΔEE obtained during As(III) oxidation (17.5%) was higher than that observed during the oxidation of the above organic compounds

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

    NASA Astrophysics Data System (ADS)

    Staiti, P.; Lufrano, F.

    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 -1 MnO x) was obtained with an electrode containing 70% of MnO 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.

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

    NASA Astrophysics Data System (ADS)

    Chen, Yonghong; Cheng, Zhuanxia; Yang, Yang; Gu, Qingwen; Tian, Dong; Lu, Xiaoyong; Yu, Weili; Lin, Bin

    2016-04-01

    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.

  12. Synthesis of Electrochemically Reduced Graphene Oxide Bonded to Thiodiazole-Pd and Applications to Biosensor.

    PubMed

    You, Jung-Min; Han, Hyoung Soon; Jeon, Seungwon

    2015-08-01

    A novel biosensor for the determination of hydrogen peroxide and glucose was developed based on EGN-TDZ-Pd, as an electrocatalyst. The preparation of graphene oxide (GO) nanosheets was functionalized by combining it with 5-amino-1,3,4-thiadiazole-2-thiol (TDZ) and by covalently bonding it to palladium (Pd) nanoparticles (GO-TDZ-Pd). In the electrochemical investigation, EGN-TDZ-Pd was characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry (CV) and chronoamperometry (CA) were used to characterize the performance of EGN-TDZ-Pd. The proposed H2O2 biosensor exhibited a wide linear range from 10 µM to 6.5 mM. Also, a glucose biosensor was prepared using glucose oxidase and EGN-TDZ-Pd placed onto a glassy carbon electrode (GCE). The GOx/EGN-TDZ-Pd/GCE was easily prepared using a rapid and simple procedure, and it was utilized for highly sensitive glucose determination. PMID:26369140

  13. Cuprous Sulfide/Reduced Graphene Oxide Hybrid Nanomaterials: Solvothermal Synthesis and Enhanced Electrochemical Performance

    NASA Astrophysics Data System (ADS)

    He, Zhanjun; Zhu, Yabo; Xing, Zheng; Wang, Zhengyuan

    2016-01-01

    The cuprous sulfide nanoparticles (CuS NPs)-decorated reduced graphene oxide (rGO) nanocomposites have been successfully prepared via a facile and efficient solvothermal synthesis method. Scanning electron microscopy and transmission electron microscopy images demonstrated that CuS micronspheres composed of nanosheets and distributed on the rGO layer in well-monodispersed form. Fourier-transform infrared spectroscopy analyses and x-ray photoelectron spectroscopy showed that graphene oxide (GO) had been reduced to rGO. The electrochemical performances of CuS/rGO nanocomposites were investigated by cyclic voltammetry and charge/discharge techniques, which showed that the specific capacitance of CuS/rGO nanocomposites was enhanced because of the introduction of rGO.

  14. Hydrothermal synthesis of layered sodium manganese oxide nanowires and their electrochemical performance.

    PubMed

    Liu, Xian-Ming; Huang, Zhen-Dong; Oh, Sei-Woon; Ma, Peng-Cheng; Ma, Jun; Li, Bao-Hua; Kim, Jang-Kyo

    2010-11-01

    A new method for preparing black birnessite nanowires is introduced. Layer-structured manganese oxide nanowires were synthesized by a facile hydrothermal method, and using both NaMnO4 and CH3CH2OH as the precursors in a concentrated NaOH solution. The structure, composition, appearance and electrochemical performance of the product were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), energy diffraction (ED), high-resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA) and constant current charge/discharge. The XRD patterns showed a single phase corresponding to a crystalline birnessite-based manganese oxide. TEM studies suggested their wire-like structures. The TGA measurement demonstrated that they possessed an excellent thermal stability up to 400 degrees C. In the potential window of 2.0-4.3 V, the product exhibited excellent cyclic stability and rapid charge-discharge performance. PMID:21137939

  15. Electrochemical oxidation and reuse of tannery saline wastewater.

    PubMed

    Sundarapandiyan, S; Chandrasekar, R; Ramanaiah, B; Krishnan, S; Saravanan, P

    2010-08-15

    In this present work, electrochemical treatment of saline wastewater with organic (protein) load was studied. The influence of the critical parameters of electro-oxidation such as pH, period, salt concentration and current density on the reduction of organic load was studied using graphite electrodes. It was found that current density of 0.024 A/cm(2) for a period of 2 h at pH 9.0 rendered best results in terms of reduction in COD and TKN. The energy requirement for the reduction of 1 kg of TKN and 1 kg of COD are 22.45 kWh and 0.80 kWh respectively at pH 9 and 0.024 A/cm(2). Reuse experiments were conducted at commercial scale. One of the saline waste streams in leather manufacturing process, pickling was treated and reused continuously thrice. The characteristics of the waste stream and the quality of the leathers indicate that the reuse of saline streams with intermittent electrochemical treatment is feasible. PMID:20435417

  16. Preparation of activated carbon from wet sludge by electrochemical-NaClO activation.

    PubMed

    Miao, Chen; Ye, Caihong; Zhu, Tianxing; Lou, Ziyang; Yuan, Haiping; Zhu, Nanwen

    2014-01-01

    Activated carbon (AC) from sludge is one potential solution for sewage sludge disposal, while the drying sludge is cost and time consuming for preparation. AC preparation from the wet sludge with electrochemical-NaClO activation was studied in this work. Three pretreatment processes, i.e. chemical activation, electrolysis and electrochemical-reagent reaction, were introduced to improve the sludge-derived AC properties, and the optimum dosage of reagent was tested from the 0.1:1 to 1:1 (mass rate, reagent:dried sludge). It was shown that the electrochemical-NaClO preparation is the best method under the test conditions, in which AC has the maximum Brunauer, Emmett and Teller area of 436 m²/g at a mass ratio of 0.7. Extracellular polymeric substances in sludge can be disintegrated by electrochemical-NaClO pretreatment, with a disintegration degree of more than 45%. The percentage of carbon decreased from 34.16 to 8.81 after treated by electrochemical-NaClO activation. Fourier transform infrared spectra showed that a strong C-Cl stretching was formed in electrochemical-NaClO prepared AC. The maximum adsorption capacity of AC reaches 109 mg/g on MB adsorption experiment at pH 10 and can be repeated for three times with high removal efficiency after regeneration. PMID:25176302

  17. Electrochemical characterization of transition metal oxide aerogels for secondary lithium batteries

    NASA Astrophysics Data System (ADS)

    Dong, Winny

    The ability of transition metals to exist in multiple valence states, along with the fact that many transition metal oxides have a layered structure, has made transition metal oxides prime candidates as electrodes for the emerging technology of secondary lithium batteries. Traditionally, the electrochemical behavior of these materials is considered to be intrinsic to the material. In order to obtain different electrochemical performance needs, different materials need to be selected. The principal objective of this dissertation is to correlate electrochemical behavior with the microstructure of a material, allowing a material to meet different application requirements through the control of its microstructure. In this research, three different studies are used to explore the interrelationship between microstructure and electrochemical behavior. Sol-gel chemistry is used exclusively to prepare the electrochemically active materials as this process enables one to control the resulting microstructure and morphology. The first study looks at the influence of the degree of crystallinity in MoO3 aerogels on lithium capacity. The degree of crystallinity is controlled through heat treatment and observed to affect the lithium capacity. The nanocrystalline MoO3 aerogel exhibited higher lithium capacity (1.5 Li/Mo) compared to both the amorphous (1.1 Li/Mo) and crystalline (1.1 Li/Mo) samples. The second study involves the synthesis of organic/inorganic hybrids, achieved by simultaneously polymerizing the polypyrrole network within the Mo-O-Mo network. The addition of the conducting polymer phase increases both the electrical conductivity (4 x 10-3 S/cm) and the lithium capacity (1.7 Li/Mo) compared to that of MoO3 aerogels. The third study emphasizes the use of the "sticky carbon" electrode to study the effects of high surface area and pore size on the lithium intercalation properties of V2O5 aerogels. A series of V2O 5 aerogels with varying surface areas (10 to 280 m2/g) is

  18. Flexible conducting polymer/reduced graphene oxide films: synthesis, characterization, and electrochemical performance

    NASA Astrophysics Data System (ADS)

    Yang, Wenyao; Zhao, Yuetao; He, Xin; Chen, Yan; Xu, Jianhua; Li, Shibin; Yang, Yajie; Jiang, Yadong

    2015-05-01

    In this paper, we demonstrate the preparation of a flexible poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonate)/reduced graphene oxide (PEDOT-PSS/RGO) film with a layered structure via a simple vacuum filtered method as a high performance electrochemical electrode. The PEDOT-PSS/RGO films are characterized by scanning electron microscopy (SEM), X-ray diffraction, Raman spectroscopy, and Fourier transform infrared (FT-IR) spectrometry. The results indicate that a layer-ordered structure is constructed in this nanocomposite during the vacuum filtering process. The electrochemical performances of the flexible films are characterized by electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge. The results reveal that a 193.7 F/g highly specific capacitance of nanocomposite film is achieved at a current density of 500 mA/g. This flexible and self-supporting nanocomposite film exhibits excellent cycling stability, and the capacity retention is 90.6 % after 1000 cycles, which shows promising application as high-performance electrode materials for flexible energy-storage devices.

  19. Decolourisation of simulated reactive dyebath effluents by electrochemical oxidation assisted by UV light.

    PubMed

    López-Grimau, V; Gutiérrez, M C

    2006-01-01

    This study is focused on the optimisation of the electrochemical decolourisation of textile effluents containing reactive dyes with the aim of making feasible-technically and economically-this method at industrial scale. Coloured waters were treated in continuous at low current density, to reduce the electrical consumption. Ti/PtO(x) electrodes were used to oxidize simulated dyebaths prepared with an azo/dichlorotriazine reactive dye (C.I. Reactive Orange 4). The decolourisation yield was dependent on the dyeing electrolyte (NaCl or Na(2)SO(4)). Dyeing effluents which contained from 0.5 to 20 gl(-1) of NaCl reached a high decolourisation yield, depending on the current density, immediately after the electrochemical process. These results were improved when the effluents were stored for several hours under solar light. After the electrochemical treatment the effluents were stored in a tank and exposed under different lighting conditions: UV light, solar light and darkness. The evolution of the decolourisation versus the time of storage was reported and kinetic constants were calculated. The time of storage was significantly reduced by the application of UV light. A dye mineralization study was also carried out on a concentrated dyebath. A TOC removal of 81% was obtained when high current density was applied for a prolonged treatment with recirculation. This treatment required a high electrical consumption. PMID:15893798

  20. Enhanced photocatalytic activity of electrochemically synthesized aluminum oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Pathania, Deepak; Katwal, Rishu; Kaur, Harpreet

    2016-03-01

    In this study, aluminum oxide (Al2O3) nanoparticles (NPs) were synthesized via an electrochemical method. The effects of reaction parameters such as supporting electrolytes, solvent, current and electrolysis time on the shape and size of the resulting NPs were investigated. The Al2O3 NPs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, thermogravimetric analysis/differential thermal analysis, energy-dispersive X-ray analysis, and ultraviolet-visible spectroscopy. Moreover, the Al2O3 NPs were explored for photocatalytic degradation of malachite green (MG) dye under sunlight irradiation via two processes: adsorption followed by photocatalysis; coupled adsorption and photocatalysis. The coupled process exhibited a higher photodegradation efficiency (45%) compared to adsorption followed by photocatalysis (32%). The obtained kinetic data was well fitted using a pseudo-first-order model for MG degradation.

  1. Vanadium oxides nanostructures: Hydrothermal synthesis and electrochemical properties

    SciTech Connect

    Mjejri, I.; Etteyeb, N.; Sediri, F.

    2014-12-15

    Highlights: • Vanadium oxides nanostructures were synthesized hydrothermally. • Reversible redox behavior with doping/dedoping process. • Doping/dedoping is easier for Li{sup +} to Na{sup +}. • Energy-related applications such as cathodes in lithium batteries. - Abstract: A facile and template-free one-pot strategy is applied to synthesize nanostructured vanadium oxide particles via a hydrothermal methodology. X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) have been used to characterize the structure and morphology of the samples. The products are gradually changed from sheet-shaped VO{sub 2}(B) to rod-like V{sub 3}O{sub 7}·H{sub 2}O with decreasing cyclohexanediol as both protective and reducing agent. The specific surface area of the VO{sub 2}(B) nanosheets and V{sub 3}O{sub 7}·H{sub 2}O nanorods was found to be 22 and 16 m{sup 2} g{sup −1}, respectively. Thin films of VO{sub 2}(B) and V{sub 3}O{sub 7}·H{sub 2}O deposited on ITO substrates were electrochemically characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The voltammograms show reversible redox behavior with doping/dedoping process corresponding to reversible cation intercalation/de-intercalation into the crystal lattice of the nanorods/nanosheets. This process is easier for the small Li{sup +} cation than larger ones Na{sup +}.

  2. Morphological and electrochemical properties of crystalline praseodymium oxide nanorods.

    PubMed

    Shamshi Hassan, M; Shaheer Akhtar, M; Shim, Kyung-Bo; Yang, O-Bong

    2010-01-01

    Highly crystalline Pr6O11 nanorods were prepared by a simple precipitation method of triethylamine complex at 500°C. Synthesized Pr6O11 nanorods were uniformly grown with the diameter of 12-15 nm and the length of 100-150 nm without any impurities of unstable PrO2 phase. The Pr6O11 nanorod electrodes attained a high electrical conductivity of 0.954 Scm-1 with low activation energy of 0.594 eV at 850°C. The electrochemical impedance study showed that the resistance of electrode was significantly decreased at high temperature, which resulted from its high conductivity and low activation energy. The reduced impedance and high electrical conductivity of Pr6O11 nanorod electrodes are attributed to the reduction of grain boundaries and high space charge width. PMID:20672103

  3. Electrochemical performance of a solid oxide fuel cell with an anode based on Cu-Ni/CeO2 for methane direct oxidation

    NASA Astrophysics Data System (ADS)

    Hornés, Aitor; Escudero, María J.; Daza, Loreto; Martínez-Arias, Arturo

    2014-03-01

    A CuNi-CeO2/YSZ/LSF solid oxide fuel cell has been fabricated and tested with respect to its electrochemical activity for direct oxidation of dry methane. The electrodes have been prepared by impregnation of corresponding porous YSZ layers, using reverse microemulsions as impregnating medium for the anode (constituted by Cu-Ni at 1:1 atomic ratio in combination with CeO2). On the basis of I-V electrochemical testing complemented by impedance spectroscopy (IS) measurements it is shown the ability of the SOFC for direct oxidation of methane in a rather stable way. Differences in the behavior as a function of operating temperature (1023-1073 K) are also revealed and examined on the basis of analysis of IS spectra.

  4. Electrochemical oxidation of butein at glassy carbon electrodes.

    PubMed

    Tesio, Alvaro Yamil; Robledo, Sebastián Noel; Fernández, Héctor; Zon, María Alicia

    2013-06-01

    The electrochemical oxidation of flavonoid butein is studied at glassy carbon electrodes in phosphate and citrate buffer solutions of different pH values, and 1M perchloric acid aqueous solutions by cyclic and square wave voltammetries. The oxidation peak corresponds to the 2e(-), 2H(+) oxidation of the 3,4-dihydroxy group in B ring of butein, given the corresponding quinone species. The overall electrode process shows a quasi-reversible behavior and an adsorption/diffusion mixed control at high butein bulk concentrations. At low butein concentrations, the electrode process shows mainly an adsorption control. Butein surface concentration values were obtained from the charge associated with the adsorbed butein oxidation peaks, which are in agreement with those values expected for the formation of a monolayer of adsorbate in the concentration range from 1 to 5μM. Square wave voltammetry was used to perform a full thermodynamic and kinetics characterization of the butein surface redox couple. Therefore, from the combination of the "quasi-reversible maximum" and the "splitting of the net square wave voltammetric peak" methods, values of (0.386±0.003) V, (0.46±0.04), and 2.7×10(2)s(-1) were calculated for the formal potential, the anodic transfer coefficient, and the formal rate constant, respectively, of the butein overall surface redox process in pH4.00 citrate buffer solutions. These results will be then used to study the interaction of butein, and other flavonoids with the deoxyribonucleic acid, in order to better understand the potential therapeutic applications of these compounds. PMID:23434740

  5. Decolorization of C. I. Reactive Orange 4 and Textile Effluents by Electrochemical Oxidation Technique using Silver-Carbon Composite Electrode.

    PubMed

    Nordin, Norazzizi; Fathrita Mohd Amir, Siti; Rahimi Yusop, Muhammad; Rozali Othman, Mohamed

    2015-01-01

    In this study, the electrochemical oxidation of C. I. Reactive Orange 4 (RO4) on a silver-carbon composite (AgC-PVC) electrode was studied using the cyclic voltammetry, potential liner V, and electrolysis methods. The AgC-PVC electrode was used as the working electrode in the electrochemical measurement of RO4 in the presence of NaCl as a supporting electrolyte. The UV-Vis spectra of RO4 after the electrochemical oxidation showed the complete decolorization of the solution. The electrolysis products were characterized using FTIR and GC-MS. The results showed that in the presence of OCl- as an active oxidant, RO4 molecules are broken down into several lower-molecular-weight molecules by the electrochemical technique. The electrode used was also able to reduce the COD, BOD(5) and surfactant contents in the textile effluents using a pilot scale reactor. This proved that the prepared AgC-PVC electrode was beneficial for removing both the color and other pollutants from textile effluents. PMID:26454599

  6. Effect of hydrothermal reaction time and alkaline conditions on the electrochemical properties of reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Vermisoglou, E. C.; Giannakopoulou, T.; Romanos, G.; Giannouri, M.; Boukos, N.; Lei, C.; Lekakou, C.; Trapalis, C.

    2015-12-01

    Reduced graphene oxide sheets (rGO) were prepared by hydrothermal treatment of aqueous dispersions of graphite oxide (GtO) applied for short (4 h) and prolonged reaction times (19-24 h). The effect of process duration as well as the alkaline conditions (pH ∼10) by addition of K2CO3 on the quality characteristics of the produced rGO materials was investigated. Both reduction and exfoliation occurred during this process as it was evidenced by FTIR and XRD data. SEM, TEM and HRTEM microscopy displayed highly exfoliated rGO materials. XPS verified that the re-establishment of the conjugated graphene network is more extensive for prolonged times of hydrothermal processing in accordance to Raman spectroscopy measurements. The sample produced under alkaline conditions bore fewer defects and almost 5 times higher BET surface area (∼181 m2/g) than the sample with no pH adjustment (∼34 m2/g) for the same hydrothermal reaction time (19 h), attributed to the developed microporosity. The specific capacitance of this material estimated by electrochemical impedance using three-electrode cell and KCl aqueous solution as an electrolyte was ∼400-500 F/g. When EDLC capacitors were fabricated from rGO materials the electrochemical testing in organic electrolyte i.e. TEABF4 in PC, revealed that the shortest hydrothermal reaction time (4 h) was more efficient resulting in capacitance around 60 F/g.

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

    PubMed

    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) batteries have an extremely high theoretical specific energy density when compared with conventional energy-storage systems. However, practical application of the Li-O2 battery system still faces significant challenges. In this work, we report a new approach for synthesis of ultrafine metal oxide nanocatalysts through an electrochemical prelithiation process. This process reduces the size of NiCo2O4 (NCO) particles from 20-30 nm to a uniformly distributed domain of ∼2 nm and significantly improves their catalytic activity. Structurally, the prelithiated NCO nanowires feature ultrafine NiO/CoO nanoparticles that are highly stable during prolonged cycles in terms of morphology and particle size, thus maintaining an excellent catalytic effect to oxygen reduction and evolution reactions. A Li-O2 battery using this catalyst demonstrated an initial capacity of 29 280 mAh g(-1) and retained a capacity of >1000 mAh g(-1) after 100 cycles based on the weight of the NCO active material. Direct in situ transmission electron microscopy observations conclusively revealed the lithiation/delithiation process of as-prepared NCO nanowires and provided in-depth understanding for both catalyst and battery chemistries of transition-metal oxides. This unique electrochemical approach could also be used to form ultrafine nanoparticles of a broad range of materials for catalyst and other applications. PMID:27380300

  8. Electrochemical Studies of Ceramic Carbon Electrodes Prepared with Sulfonated Organosilane Precursors

    NASA Astrophysics Data System (ADS)

    Eastcott, Jennie

    State-of-the-art electrodes for proton exchange membrane fuel cells (PEMFCs) contain platinum catalyst and a Nafion proton-conducting binder. Optimal conditions for Nafion functionality are at 80°C and 100% relative humidity (RH). Ceramic carbon electrodes (CCEs), consisting of carbon particles supported by ceramic binder network, may be an alternative electrode structure which replaces Nafion with organosilane materials. CCEs are also attractive for their high surface area and durable nature. CCEs have been fabricated via an in-situ sol-gel polymerization process. Development of a novel electrode fabrication procedure included direct spray-deposition of CCEs onto a microporous/gas diffusion layer to facilitate adhesion and facile electrode preparation. CCEs were composed of commercial carbon-supported platinum catalyst and 3-trihydroxysilyl-1-propanesulfonic acid (TPS) or TPS and tetraethylorthosilicate (TEOS) to vary the level of sulfonation. CCEs were initially tested electrochemically in a half-cell set-up to evaluate electrode functionality. An optimal loading of 42-48 wt% silane was determined for CCEs with only TPS to provide the highest electrochemically active surface area (ECSA) of platinum and proton conductivity. BET surface areas were low due to restriction of pore sizes by the sulfonated side chain. Composite CCEs of TPS/TEOS had enhanced electrochemical performance and high BET surface areas (>400 m 2 g-1), indicating high porosity. Excellent electrochemical results were obtained for the CCE with a TPS:TEOS ratio of 4:96 (40 wt% total silane). The sulfonated TPS/TEOS CCE (SS-CCE) was further evaluated in a fuel cell. Electrochemical studies showcased higher accessibility of catalyst sites and good proton conductivity compared to Nafion-containing cathodes. At 80°C and 100% relative humidity (RH), CCEs performed similarly to Nafion electrodes at low current density but suffered from mass transport limitations due to flooding at high current density

  9. Electrochemical, H2O2-Boosted Catalytic Oxidation System

    NASA Technical Reports Server (NTRS)

    Akse, James R.; Thompson, John O.; Schussel, Leonard J.

    2004-01-01

    An improved water-sterilizing aqueous-phase catalytic oxidation system (APCOS) is based partly on the electrochemical generation of hydrogen peroxide (H2O2). This H2O2-boosted system offers significant improvements over prior dissolved-oxygen water-sterilizing systems in the way in which it increases oxidation capabilities, supplies H2O2 when needed, reduces the total organic carbon (TOC) content of treated water to a low level, consumes less energy than prior systems do, reduces the risk of contamination, and costs less to operate. This system was developed as a variant of part of an improved waste-management subsystem of the life-support system of a spacecraft. Going beyond its original intended purpose, it offers the advantage of being able to produce H2O2 on demand for surface sterilization and/or decontamination: this is a major advantage inasmuch as the benign byproducts of this H2O2 system, unlike those of systems that utilize other chemical sterilants, place no additional burden of containment control on other spacecraft air- or water-reclamation systems.

  10. Electrochemically Reduced Water Protects Neural Cells from Oxidative Damage

    PubMed Central

    Hamasaki, Takeki; Kinjo, Tomoya; Nakamichi, Noboru; Teruya, Kiichiro; Kabayama, Shigeru

    2014-01-01

    Aging-related neurodegenerative disorders are closely associated with mitochondrial dysfunction and oxidative stresses and their incidence tends to increase with aging. Brain is the most vulnerable to reactive species generated by a higher rate of oxygen consumption and glucose utilization compared to other organs. Electrochemically reduced water (ERW) was demonstrated to scavenge reactive oxygen species (ROS) in several cell types. In the present study, the protective effect of ERW against hydrogen peroxide (H2O2) and nitric oxide (NO) was investigated in several rodent neuronal cell lines and primary cells. ERW was found to significantly suppress H2O2 (50–200 μM) induced PC12 and SFME cell deaths. ERW scavenged intracellular ROS and exhibited a protective effect against neuronal network damage caused by 200 μM H2O2 in N1E-115 cells. ERW significantly suppressed NO-induced cytotoxicity in PC12 cells despite the fact that it did not have the ability to scavenge intracellular NO. ERW significantly suppressed both glutamate induced Ca2+ influx and the resulting cytotoxicity in primary cells. These results collectively demonstrated for the first time that ERW protects several types of neuronal cells by scavenging ROS because of the presence of hydrogen and platinum nanoparticles dissolved in ERW. PMID:25383141

  11. Electrochemically reduced water protects neural cells from oxidative damage.

    PubMed

    Kashiwagi, Taichi; Yan, Hanxu; Hamasaki, Takeki; Kinjo, Tomoya; Nakamichi, Noboru; Teruya, Kiichiro; Kabayama, Shigeru; Shirahata, Sanetaka

    2014-01-01

    Aging-related neurodegenerative disorders are closely associated with mitochondrial dysfunction and oxidative stresses and their incidence tends to increase with aging. Brain is the most vulnerable to reactive species generated by a higher rate of oxygen consumption and glucose utilization compared to other organs. Electrochemically reduced water (ERW) was demonstrated to scavenge reactive oxygen species (ROS) in several cell types. In the present study, the protective effect of ERW against hydrogen peroxide (H2O2) and nitric oxide (NO) was investigated in several rodent neuronal cell lines and primary cells. ERW was found to significantly suppress H2O2 (50-200 μM) induced PC12 and SFME cell deaths. ERW scavenged intracellular ROS and exhibited a protective effect against neuronal network damage caused by 200 μM H2O2 in N1E-115 cells. ERW significantly suppressed NO-induced cytotoxicity in PC12 cells despite the fact that it did not have the ability to scavenge intracellular NO. ERW significantly suppressed both glutamate induced Ca(2+) influx and the resulting cytotoxicity in primary cells. These results collectively demonstrated for the first time that ERW protects several types of neuronal cells by scavenging ROS because of the presence of hydrogen and platinum nanoparticles dissolved in ERW. PMID:25383141

  12. Electrochemically Deposited Ceria Structures for Advanced Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Brown, Evan C.

    As the pursuit towards emissions reduction intensifies with growing interest and nascent technologies, solid oxide fuel cells (SOFCs) remain an illustrious candidate for achieving our goals. Despite myriad advantages, SOFCs are still too costly for widespread deployment, even as unprecedented materials developments have recently emerged. This suggests that, in addition to informed materials selection, the necessary power output--and, thereby, cost-savings--gains must come from the fuel cell architecture. The work presented in this manuscript primarily investigates cathodic electrochemical deposition (CELD) as a scalable micro-/nanoscale fabrication tool for engineering ceria-based components in a SOFC assembly. Also, polymer sphere lithography was utilized to deposit fully connected, yet fully porous anti-dot metal films on yttira-stabilized zirconia (YSZ) with specific and knowable geometries, useful for mechanistic studies. Particular attention was given to anode structures, for which anti-dot metal films on YSZ served as composite substrates for subsequent CELD of doped ceria. By tuning the applied potential, a wide range of microstructures from high surface area coatings to planar, thin films was possible. In addition, definitive deposition was shown to occur on the electronically insulating YSZ surfaces, producing quality YSZ|ceria interfaces. These CELD ceria deposits exhibited promising electrochemical activity, as probed by A.C. Impedance Spectroscopy. In an effort to extend its usefulness as a SOFC fabrication tool, the CELD of ceria directly onto common SOFC cathode materials without a metallic phase was developed, as well as templated deposition schemes producing ceria nanowires and inverse opals.

  13. Electrochemical and microstructural study of oxide films formed electrochemically at microcrystalline Al-Fe-V-Si alloys.

    PubMed

    Thomas, S C; Birss, V I; Steele, D; Tessier, D

    1995-07-01

    A recent advance in metallurgical technology has been the application of rapid solidification techniques to Al alloy production. FVS0812 is the designation given to a microcrystalline Al-based alloy consisting of 8 wt% Fe, 1 wt% V and 2 wt% Si. It is a two-phase alloy, consisting of ca. 27 vol percent of approximately spherical Fe-V-Si-rich dispersoids in an essentially pure Al matrix. The high strength, low density properties of this advanced material, and other related alloys, have not yet been realized, however, due, in part, to the inability of the alloy to form a thick, adherent, abrasion-resistant outer surface oxide film, a feature readily achieved at conventional Al alloys by normal anodizing methods. The present research has involved an electro-chemical study of oxide film growth at the 812 alloy, with the specific goals being to seek an understanding of the origin of the oxide film growth problem and ultimately to propose alternative approaches to the formation of a thick, stable oxide film at this material. The techniques used in this research have included electrochemical methodologies such as cyclic voltammetry and electrochemical impedance spectroscopy. Crucial information has been obtained through transmission electron microscopy (TEM) of ultramicrotomed specimens. Experiments were carried out initially in neutral borate solutions to characterize the compact barrier oxide film formed in this environment and expected to be present beneath the porous oxide film formed in the normal sulfuric acid anodizing medium.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7549001

  14. Costs of the electrochemical oxidation of wastewaters: a comparison with ozonation and Fenton oxidation processes.

    PubMed

    Cañizares, Pablo; Paz, Rubén; Sáez, Cristina; Rodrigo, Manuel A

    2009-01-01

    In the work described here the technical and economic feasibilities of three Advanced Oxidation Processes (AOPs) have been studied: Conductive-Diamond Electrochemical Oxidation (CDEO), Ozonation and Fenton oxidation. The comparison was made by assessing the three technologies with synthetic wastewaters polluted with different types of organic compounds and also with actual wastes (from olive oil mills and from a fine-chemical manufacturing plant). All three technologies were able to treat the wastes, but very different results were obtained in terms of efficiency and mineralization. Only CDEO could achieve complete mineralization of the pollutants for all the wastes. However, the efficiencies were found to depend on the concentration of pollutant (mass transfer control of the oxidation rate). Results obtained in the oxidation with ozone (at pH 12) or by Fenton's reagent were found to depend on the nature of the pollutants, and significant concentrations of oxidation-refractory compounds were usually accumulated during the treatment. Within the discharge limits that all of the technologies can reach, the economic analysis shows that the operating cost of Fenton oxidation is lower than either CDEO or ozonation, although CD\\EO can compete satisfactorily with the Fenton process in the treatment of several kinds of wastes. Likewise, the investment cost for the ozonation process seems to be higher than either CDEO or Fenton oxidation, regardless of the pollutant treated. PMID:18082930

  15. Enhanced electrochemical supercapacitance of binder-free nanoporous ternary metal oxides/metal electrode.

    PubMed

    Gao, J J; Qiu, H-J; Wen, Y R; Chiang, F-K; Wang, Y

    2016-07-15

    Free-standing nanoporous Ni-Cu-Mn mixed metal oxides on metal with a high surface area was fabricated by chemically dealloying a Ni8Cu12Mn80 single-phase precursor, followed by electrochemical oxidation in an alkaline solution. Electrochemical analysis shows that first Cu and Mn-based metal oxides formed by the electrochemical oxidation. Ni-based oxides grow later with the increase of electrochemical CV cycles and mix with the Cu/Mn oxides, forming a relatively stable mixed metal oxides thin film on metal ligament network. Due to the different electrochemical properties of each metal and the synergetic effect between them, the mixed ternary metal oxides formed on metal nano-ligament can operate stably between a wide potential window (1.5V) in 1.0M KOH aqueous solution when tested as a free-standing supercapacitor electrode. Due to the high volumetric surface area, wide operating potential window and excellent conductivity, the nanoporous metal oxides@metal composite exhibits a high volumetric capacitance (∼500Fcm(-3)), high energy density (∼38mWhcm(-3)) and good cycling stability. PMID:27089016

  16. Electrochemically Reduced Graphene Oxide Multilayer Films as Efficient Counter Electrode for Dye-Sensitized Solar Cells

    PubMed Central

    Xu, Xiaobao; Huang, Dekang; Cao, Kun; Wang, Mingkui; Zakeeruddin, Shaik M.; Grätzel, Michael

    2013-01-01

    We report on a new counter electrode for dye-sensitized solar cells (DSCs), which is prepared using layer-by-layer assembly of negatively charged graphene oxide and positively charged poly (diallyldimethylammonium chloride) followed by an electrochemical reduction procedure. The DSC devises using the heteroleptic Ru complex C106TBA as sensitizer and this new counter electrode reach power conversion efficiencies of 9.5% and 7.6% in conjunction with low volatility and solvent free ionic liquid electrolytes, respectively. The new counter electrode exhibits good durability (60°C for 1000 h in a solar simulator, 100 mW cm−2) during the accelerated tests when used in combination with an ionic liquid electrolyte. This work identifies a new class of electro-catalysts with potential for low cost photovoltaic devices. PMID:23508212

  17. Scalable Preparation of Ternary Hierarchical Silicon Oxide-Nickel-Graphite Composites for Lithium-Ion Batteries.

    PubMed

    Wang, Jing; Bao, Wurigumula; Ma, Lu; Tan, Guoqiang; Su, Yuefeng; Chen, Shi; Wu, Feng; Lu, Jun; Amine, Khalil

    2015-12-01

    Silicon monoxide is a promising anode candidate because of its high theoretical capacity and good cycle performance. To solve the problems associated with this material, including large volume changes during charge-discharge processes, we report a ternary hierarchical silicon oxide-nickel-graphite composite prepared by a facile two-step ball-milling method. The composite consists of nano-Si dispersed silicon oxides embedded in nano-Ni/graphite matrices (Si@SiOx /Ni/graphite). In the composite, crystalline nano-Si particles are generated by the mechanochemical reduction of SiO by ball milling with Ni. These nano-Si dispersed oxides have abundant electrochemical activity and can provide high Li-ion storage capacity. Furthermore, the milled nano-Ni/graphite matrices stick well to active materials and interconnect to form a crosslinked framework, which functions as an electrical highway and a mechanical backbone so that all silicon oxide particles become electrochemically active. Owing to these advanced structural and electrochemical characteristics, the composite enhances the utilization efficiency of SiO, accommodates its large volume expansion upon cycling, and has good ionic and electronic conductivity. The composite electrodes thus exhibit substantial improvements in electrochemical performance. This ternary hierarchical Si@SiOx /Ni/graphite composite is a promising candidate anode material for high-energy lithium-ion batteries. Additionally, the mechanochemical ball-milling method is low cost and easy to reproduce, indicating potential for the commercial production of the composite materials. PMID:26548901

  18. Boron-doped cadmium oxide composite structures and their electrochemical measurements

    SciTech Connect

    Lokhande, B.J.; Ambare, R.C.; Mane, R.S.; Bharadwaj, S.R.

    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.

  19. Chiral conducting surfaces via electrochemical oxidation of L-leucine-oligothiophenes.

    PubMed

    McTiernan, Christopher D; Omri, Karim; Chahma, M'hamed

    2010-09-17

    Polythiophenes bearing a specific chiral center such as L-leucine have been prepared via the electrochemical oxidation of a series of L-leucine functionalized oligothiophenes (monothiophenes and terthiophenes). These oligothiophenes have been prepared through the condensation of L-leucine methyl ester and the corresponding thiophene monomers in the presence of hydroxybenzotriazole (HOBt) and N,N'-dicyclohexylcarbodiimide (DCC) followed by hydrolysis of the esters. The electroactive polymers are electrochemically stable and exhibit excellent adhesive properties on electrode surfaces (platinum, gold, and glassy carbon) as well as interesting optical properties in both doped and undoped states. Hydrogen bonds between a free amino acid (L-leucine, D-leucine, L-alanine, D-alanine, and D/L-alanine) and the L-leucine based polythiophenes (chiral conducting surface) were probed using cyclic voltammetry. Preliminary results show that the capacitive current of a modified L-leucine-polythiophene electrode decreases as a result of the formation of a hydrogen bond barrier on the surface of the chiral conducting surface accompanied with a shift of the oxidation potential. Cyclic voltammetry responses resulting from the interaction of the chiral conducting surface with L and Dfree amino acid isomers are similar. The formation of hydrogen bonds between the chiral conducting surfaces and the free amino acids was characterized by (1)H NMR. A chemical shift was observed for the N-H group in monomer 6 as a result of the hydrogen bond formation between the L-leucine methyl ester (D-leucine methyl ester, D/L-leucine methyl ester) and monomer 6. PMID:20718451

  20. Nanoporous metal/oxide hybrid electrodes for electrochemical supercapacitors.

    PubMed

    Lang, Xingyou; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

    2011-04-01

    Electrochemical supercapacitors can deliver high levels of electrical power and offer long operating lifetimes, but their energy storage density is too low for many important applications. Pseudocapacitive transition-metal oxides such as MnO(2) could be used to make electrodes in such supercapacitors, because they are predicted to have a high capacitance for storing electrical charge while also being inexpensive and not harmful to the environment. However, the poor conductivity of MnO(2) (10(-5)-10(-6) S cm(-1)) limits the charge/discharge rate for high-power applications. Here, we show that hybrid structures made of nanoporous gold and nanocrystalline MnO(2) have enhanced conductivity, resulting in a specific capacitance of the constituent MnO(2) (~1,145 F g(-1)) that is close to the theoretical value. The nanoporous gold allows electron transport through the MnO(2), and facilitates fast ion diffusion between the MnO(2) and the electrolytes while also acting as a double-layer capacitor. The high specific capacitances and charge/discharge rates offered by such hybrid structures make them promising candidates as electrodes in supercapacitors, combining high-energy storage densities with high levels of power delivery. PMID:21336267

  1. Nanoporous metal/oxide hybrid electrodes for electrochemical supercapacitors

    NASA Astrophysics Data System (ADS)

    Lang, Xingyou; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

    2011-04-01

    Electrochemical supercapacitors can deliver high levels of electrical power and offer long operating lifetimes, but their energy storage density is too low for many important applications. Pseudocapacitive transition-metal oxides such as MnO2 could be used to make electrodes in such supercapacitors, because they are predicted to have a high capacitance for storing electrical charge while also being inexpensive and not harmful to the environment. However, the poor conductivity of MnO2 (10-5-10-6 S cm-1) limits the charge/discharge rate for high-power applications. Here, we show that hybrid structures made of nanoporous gold and nanocrystalline MnO2 have enhanced conductivity, resulting in a specific capacitance of the constituent MnO2 (~1,145 F g-1) that is close to the theoretical value. The nanoporous gold allows electron transport through the MnO2, and facilitates fast ion diffusion between the MnO2 and the electrolytes while also acting as a double-layer capacitor. The high specific capacitances and charge/discharge rates offered by such hybrid structures make them promising candidates as electrodes in supercapacitors, combining high-energy storage densities with high levels of power delivery.

  2. Electrochemical reduction of CO 2 in solid oxide electrolysis cells

    NASA Astrophysics Data System (ADS)

    Zhan, Zhongliang; Zhao, Lin

    This paper describes results on the electrochemical reduction of carbon dioxide using the same device as the typical planar nickel-YSZ cermet electrode supported solid oxide fuel cells (H 2-CO 2, Ni-YSZ|YSZ|LSCF-GDC, LSCF, air). Operation in both the fuel cell and the electrolysis mode indicates that the electrodes could work reversibly for the charge transfer processes. An electrolysis current density of ≈1 A cm -2 is observed at 800 °C and 1.3 V for an inlet mixtures of 25% H 2-75% CO 2. Mass spectra measurement suggests that the nickel-YSZ cermet electrode is highly effective for reduction of CO 2 to CO. Analysis of the gas transport in the porous electrode and the adsorption/desorption process over the nickel surface indicates that the cathodic reactions are probably dominated by the reduction of steam to hydrogen, whereas carbon monoxide is mainly produced via the reverse water gas shift reaction.

  3. Electrochemical and electrochromic behavior of reactively sputtered nickel oxide

    SciTech Connect

    Miller, E.L.; Rocheleau, R.E.

    1997-06-01

    Nickel oxide thin films were deposited by reactive sputtering in a 20% oxygen/argon atmosphere for use as oxygen evolution catalysts in the photoelectrochemical production of hydrogen. The optical properties of the films were also characterized to evaluate their application as window layers. The polycrystalline films deposited at residual gas pressures of 6 or 10 mTorr exhibited moderate activity for oxygen evolution in 1 N KOH and pronounced coloration and bleaching during alternating anodic/cathodic bias. Properties of these films were not sensitive to growth rate over the range studied, 0.5 to 4 {angstrom}/s. In contrast, films deposited at 2 mTorr exhibited poor activity for oxygen evolution and severely limited electrochromic behavior which the authors attribute to marked changes in the morphology and crystallinity in the low-pressure films. The films grown at 6 mTorr and higher tended to be more oriented, to have a higher degree of crystallinity, and higher oxygen content. Strong linkages between the electrochemical and optical behaviors observed in this work provide new insights into the processes involved in oxygen evolution reaction catalysis and electrochromism in reactively sputtered NiO{sub x} films. The results presented indicate that reactive sites located on or near grain boundaries are responsible for both behaviors.

  4. Electrochemical chlorine evolution at rutile oxide (110) surfaces.

    PubMed

    Hansen, Heine A; Man, Isabela C; Studt, Felix; Abild-Pedersen, Frank; Bligaard, Thomas; Rossmeisl, Jan

    2010-01-01

    Based on density functional theory (DFT) calculations we study the electrochemical chlorine evolution reaction on rutile (110) oxide surfaces. First we construct the Pourbaix surface diagram for IrO(2) and RuO(2), and from this we find the chlorine evolution reaction intermediates and identify the lowest overpotential at which all elementary reaction steps in the chlorine evolution reaction are downhill in free energy. This condition is then used as a measure for catalytic activity. Linear scaling relations between the binding energies of the intermediates and the oxygen binding energies at cus-sites are established for MO(2) (M being Ir, Ru, Pt, Ti). The linear relations form the basis for constructing a generalized surface phase diagram where two parameters, the potential and the binding energy of oxygen, are needed to determine the surface composition. We calculate the catalytic activity as function of the oxygen binding energy, giving rise to a Sabatier volcano. By combining the surface phase diagram and the volcano describing the catalytic activity, we find that the reaction mechanism differs depending on catalyst material. The flexibility in reaction path means that the chlorine evolution activity is high for a wide range of oxygen binding energies. We find that the required overpotential for chlorine evolution is lower than the overpotential necessary for oxygen evolution. PMID:20024470

  5. Eliminating degradation in solid oxide electrochemical cells by reversible operation

    NASA Astrophysics Data System (ADS)

    Graves, Christopher; Ebbesen, Sune Dalgaard; Jensen, Søren Højgaard; Simonsen, Søren Bredmose; Mogensen, Mogens Bjerg

    2015-02-01

    One promising energy storage technology is the solid oxide electrochemical cell (SOC), which can both store electricity as chemical fuels (electrolysis mode) and convert fuels to electricity (fuel-cell mode). The widespread use of SOCs has been hindered by insufficient long-term stability, in particular at high current densities. Here we demonstrate that severe electrolysis-induced degradation, which was previously believed to be irreversible, can be completely eliminated by reversibly cycling between electrolysis and fuel-cell modes, similar to a rechargeable battery. Performing steam electrolysis continuously at high current density (1 A cm-2), initially at 1.33 V (97% energy efficiency), led to severe microstructure deterioration near the oxygen-electrode/electrolyte interface and a corresponding large increase in ohmic resistance. After 4,000 h of reversible cycling, however, no microstructural damage was observed and the ohmic resistance even slightly improved. The results demonstrate the viability of applying SOCs for renewable electricity storage at previously unattainable reaction rates, and have implications for our fundamental understanding of degradation mechanisms that are usually assumed to be irreversible.

  6. Electrochemical Evaluation of Pyrite Films Prepared by Plasma Spraying

    SciTech Connect

    Guidotti, R.A.; Reinhardt, F.W.

    1998-10-30

    Thermally activated batteries use electrodes that are typically fabricated by cold pressing of powder. In the LiSi/FeS2 system, natural (mineral) pyrite is used for the cathode. In an effort to increase the energy density and specific energy of these batteries, flame and plasma spraying to form thin films of pyrite cathodes were evaluated. The films were deposited on a 304 stainless steel substrate (current collector) and were characterized by scanning electron microscopy and x-ray dlfllaction. The films were electrochemically tested in single cells at 5000C and the petiormance compared to that of standard cells made with cold-pressed powders. The best results were obtained with material deposited by de-arc plasma spraying with a proprietq additive to suppress thermal decomposion of the pyrite.

  7. Preparation of Polypyrrole-Protein Composite Films and the Electrochemically Controlled Release of Proteins.

    PubMed

    Jin, Juan; Huang, Zhongbing; Yin, Guangfu; Lin, Jiangli; Li, Qiuping; Han, Donghui

    2016-03-01

    It is fabricated that an electrically controlled release system based on the (poly-L-lactic acid)-mixed polypyrrole (PLLA-PPy) films through casting film of PPy and PLLA mixed solution on the glass plate, in which polyglutamic acid (PGlu)-doped PPy nanoparticles (NPs) with -50 nm diameter are synthesized via chemical oxidation. Surface conductivity of the composite film is (3.33 ± 2.01) x 10(-3) S/cm. Bovine serum albumin (BSA), as a model protein drug, is chemically linked onto the composite film via carbodiimide chemistry due to the good surface nano-structure of PLLA-PPy film. The releases of BSA from PLLA-PPy film under constant current and constant voltage can be achieved using the two-electrode electrochemical system. 6 h accumulative releases of BSA are 276 μg/cm2 and 176 μg/cm2 under 3 mA and 1 V electrical stimulation, respectively, accompanied with de-doping of PGlu and separation of a part of PPy NPs from the composite film. The results of cell experiment indicate that PGlu-doped PPy NPs in the prepared composite film have good cyto-compatibility. These results suggest that PPy-PLLA composite film would be able to be applied in the construction of degradable protein-drug-loaded scaffold for nerve tissue repair. PMID:27455630

  8. Preparation of urchinlike NiO nanostructures and their electrochemical capacitive behaviors

    SciTech Connect

    Liu Xianming; Zhang Xiaogang; Fu Shaoyun . E-mail: syfu@cl.cryo.ac.cn

    2006-03-09

    Urchinlike NiO nanostructures were prepared by thermal decomposition of the precursor obtained via a hydrothermal process using urea as a hydrolysis-controlling agent and polyethylene glycol (PEG) as a surfactant. The structure and morphology of the samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared absorption spectra (IR). Structure characterizations indicated urchinlike nanostructures for the nickel oxide samples with high purity. Electrochemical properties of urchinlike NiO were examined by cyclic voltammetry and galvanostatic charge-discharge measurements. The results showed that NiO calcined at 300 deg. C had a higher specific capacitance and better capacitive behavior than NiO calcined at 500 deg. C. The specific capacitance of about 290 and 170 F g{sup -1}, respectively, could be achieved with NiO calcined at 300 and 500 deg. C in the voltage range of 0.0-0.5 V. The calculated capacitances decreased with the increase of cycle number of the NiO sample. The specific capacitance of NiO calcined at 300 deg. C decreased to 217 F g{sup -1} after 500 cycles. It revealed that the NiO materials exhibited good cycling performance. NiO calcined at 300 deg. C possessed the high capacitance because it had the high surface redox reactivity due to its special nanostructures.

  9. Composite PEOn:NaTFSI polymer electrolyte: Preparation, thermal and electrochemical characterization

    NASA Astrophysics Data System (ADS)

    Serra Moreno, J.; Armand, M.; Berman, M. B.; Greenbaum, S. G.; Scrosati, B.; Panero, S.

    2014-02-01

    Membranes of sodium bis(trifluoromethanesulfonate) imide (NaTFSI) complexed with poly(ethylene oxide) (PEO) salt have been prepared by a solvent-free hot-pressing technique with different EO:Na molar ratio. All membranes show good ionic conductivities in the range of 10-3 S cm-1 above 70 °C. However, the more NaTFSI-concentrated samples are sticky gums due to the plasticizing nature of the anion. The PEO20:NaTFSI sample exhibits the compromise of conductivity, thermal and mechanical properties. The addition of nanometric SiO2 to the PEO20:NaTFSI membranes further enhances their mechanical properties. Moreover, the PEO20:NaTFSI + 5 wt.% SiO2 membranes show similar ionic conductivity and similar anodic electrochemical stability in comparison to the ceramic free PEO20:NaTFSI sample. In a Na(s)/polymer electrolyte/Na(s) symmetrical cell followed up to 30 days, the presence of the ceramic filler slightly increased the interface resistance in comparison to the ceramic-free membrane. Nuclear magnetic resonance determinations of anion diffusion coefficients and Na+ mobility suggest that presence of filler may have a positive affect on the cation transference number that is in accordance with the tNa+ transference number measurement.

  10. Nickel nanoparticles with hcp structure: Preparation, deposition as thin films and application as electrochemical sensor.

    PubMed

    Neiva, Eduardo G C; Oliveira, Marcela M; Marcolino, Luiz H; Zarbin, Aldo J G

    2016-04-15

    Hexagonal close packed (hcp) nickel nanoparticles stabilized by polyvinylpyrrolidone (PVP) were synthesized through the thermal treatment of face centered cubic (fcc) nickel nanoparticles. Controlling both the temperature of the heat treatment and the amount of PVP was possible the control of the hcp/fcc rate in the samples, where the higher Ni/PVP ratio produces only the hcp-nickel phase (average size of 8.9 nm) highly stable in air. The crystalline structure, the presence of PVP, the size of the nanoparticles and the stability of the hcp-nickel were confirmed using X-ray diffractometry, Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy, scanning electron microscopy and thermogravimetric analysis. Thin films of hcp and fcc nickel nanoparticles were prepared through a biphasic system and deposited over indium-doped tin oxide (ITO) substrates, which were electrochemically characterized and applied as glycerol amperometric sensors in NaOH medium. Parameters as the number of cycles applied and the scan rate were evaluated and indicate that hcp nickel nanoparticles are more reactive to form Ni(OH)2 and lead to more electroactive Ni(OH)2 structure. The hcp nickel nanoparticles-modified electrode showed the best sensitivity (0.258 μA L μmol(-1)) and detection limit (2.4 μmol L(-1)) toward glycerol. PMID:26821149

  11. Facile and controllable electrochemical reduction of graphene oxide and its applications

    SciTech Connect

    Shao, Yuyan; Wang, Jun; Engelhard, Mark H.; Wang, Chong M.; Lin, Yuehe

    2010-01-01

    Graphene oxide is electrochemically reduced which is called electrochemically reduced graphene oxide (ER-G). ER-G is characterized with scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The oxygen content is significantly decreased and the sp 2 carbon is restored after electrochemical reduction. ER-G exhibits much higher electrochemical capacitance and cycling durability than carbon nanotubes (CNTs) and chemically reduced graphene; the specific capacitance measured with cyclic voltammetry (20 mV/s) is ~165 F/g, ~86 F/g, and ~100 F/g for ER-G, CNTs, and chemically reduced graphene,1 respectively. The electrochemical reduction of oxygen and hydrogen peroxide was greatly enhanced on ER-G electrodes as compared with CNTs. ER-G has shown a good potential for applications in energy storage, biosensors, and electrocatalysis.

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

    PubMed Central

    2013-01-01

    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. PMID:24059434

  13. Direct and environmentally benign synthesis of manganese oxide/graphene composites from graphite for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Lee, Hae-Min; Jeong, Gyoung Hwa; Kang, Doo Won; Kim, Sang-Wook; Kim, Chang-Koo

    2015-05-01

    We develop a direct and environmentally benign method to prepare manganese oxide (Mn3O4)/graphene composites via one-step hydrothermal synthesis from graphite without using strong acids and toxic reducing agents. Structural and morphological analyses reveals that the irregularly shaped Mn3O4 nanoparticles are well-dispersed on the graphene flakes. Cyclic voltammetry and galvanostatic charge-discharge tests indicate that the charge-storing mechanism of the Mn3O4/graphene composites is pseudocapacitive. The Mn3O4/graphene composite exhibits a specific capacitance of 367 F/g at a current density of 5 A/g. After 3000 charge-discharge cycles, the Mn3O4/graphene electrode retains 91.8% of its initial specific capacitance. From electrochemical impedance spectra, it is evident that the changes in both the equivalent series resistance and charge-transfer resistance of the Mn3O4/graphene electrode before and after 3000 charge-discharge cycles are small, indicating good cycling and electrochemical stability of the Mn3O4/graphene electrode.

  14. Electrochemical deposition of silver on manganese dioxide coated reduced graphene oxide for enhanced oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Lee, Kyungmi; Ahmed, Mohammad Shamsuddin; Jeon, Seungwon

    2015-08-01

    We have prepared a reduced graphene oxide (rGO)-supported silver (Ag) and manganese dioxide (MnO2) deposited porous-like catalyst (denoted as rGO/MnO2/Ag) through a facile electrochemical deposition route and have been used as a cathode catalyst for oxygen reduction reaction (ORR) in alkaline fuel cells. The physical properties of rGO/MnO2/Ag have been investigated via several instrumental methods. This material exhibits a polycrystalline structure characterized by Ag/MnO2 microsphere formation as a result of Ostwald ripening. The X-ray diffraction and X-ray photoelectron spectroscopy data reveal that the MnO2 and Ag have been slightly alloyed and Mn presents with the dioxide form on rGO. The electrochemical properties of the electrocatalyst have been studied via several voltammetric methods. The results demonstrated that the rGO/MnO2/Ag has an excellent catalytic activity for ORR in alkaline media compared to the other tested electrodes. Particularly, it shows 1.2 times higher current density and better electron transfer rate at 0.3 V per O2 than that of 20 wt% Pt/C. The other kinetic analysis reveals that the O2 has reduced directly to H2O through a nearly four-electron pathway with better anodic fuel tolerance and duration performance than that of 20% Pt/C.

  15. Nanoporous zeolite and solid-state electrochemical devices for nitrogen-oxide sensing

    NASA Astrophysics Data System (ADS)

    Yang, Jiun-Chan

    Solid-state electrochemical gas sensing devices composed of stabilized-zirconia electrolyte have used extensively in the automobile and chemical industry. Two types of electrochemical devices, potentiometric and amperometric, were developed in this thesis for total NOx (NO + NO2) detection in harsh environments. In potentiometric devices, Pt covered with Pt containing zeolite Y (PtY) and WO3 were examined as the two electrode materials. Significant reactivity differences toward NOx between PtY and WO 3 led to the difference in non-electrochemical reactions and resulted in a electrode potential. With gases passing through a PtY filter, it was possible to remove interferences from 2000 ppm CO, 800 ppm propane, 10 ppm NH3, as well as to minimize effects of 1˜13% O2, CO2, and H2O. Total NOx concentration was measured by maintaining a temperature difference between the filter and the sensor. The sensitivity was significantly improved by connecting sensors in series. Amperometic devices were also developed to detect NOx passing through the PtY filter. By applying a low anodic potential of 80 mV, NO in the NOx equilibrated mixture can be oxidized at a Pt working electrode on the YSZ electrolyte at 500°C. The PtY can be held separate from the YSZ or coated onto the YSZ as a film. This design was demonstrated to exhibit total-NOx detection capability, a low NOx detection limit (< 1 ppm), high NOx selectivity relative to CO and oxygen, and linear dependence on NOx concentration. The non-electrochemical reactions around the triple-phase boundary were studied to understand the origin of the superior performance of WO3 on potentiometric NOx sensing. From TPD, DRIFTS, XRD, Raman, and catalytic activity measurements, the interfacial reactions between WO 3 and YSZ were found to dramatically reduce the NOx catalytic activity of YSZ. WO3 reacted with surface Y2O3 on YSZ and formed less catalytically active yttrium tungsten oxides and monoclinic ZrO2, which suppressed the non-electrochemical

  16. Ultrafast electrochemical preparation of graphene/CoS nanosheet counter electrodes for efficient dye-sensitized solar cells

    DOE PAGESBeta

    Zhu, Chongyang; Zhu, Yimei; Min, Huihua; Xu, Feng; Chen, Jing; Dong, Hui; Tong, Ling; Sun, Litao

    2015-10-05

    Utilizing inexpensive, high-efficiency counter electrodes (CEs) to replace the traditional platinum counterparts in dye-sensitized solar cells (DSSCs) is worthwhile. In this paper, we detail how we synchronously prepared composite CEs of CoS nanosheet arrays and reduced graphene oxide (rGO) layers for the first time via a low temperature, ultrafast one-step electrochemical strategy. With this approach, the whole fabrication process of the composite CEs was only a small percentage of the average time (~15 hours) using other methods. The DSSC assembled with the rGO–CoS composite CE achieved an enhanced power conversion efficiency (PCE) of 8.34%, which is dramatically higher than 6.27%more » of pure CoS CE-based DSSC and even exceeds 7.50% of Pt CE-based DSSC. The outstanding PCE breakthrough is undoubtedly attributed to the enhancement in electrocatalytic ability of the rGO–CoS composite CE due to the incorporation of highly conducting rGO layers and the GO layers-induced growth of CoS nanosheet arrays with higher density and larger surface area. Therefore, lower charge-transfer resistance and higher exchange current density can be achieved as corroborated by the electrochemical impedance spectra (EIS) and Tafel polarization curves (TPCs). As a result, further experiments also proved that the electrochemical strategy exhibited its universality of fabricating other graphene-enhanced chalcogenide functional composite films.« less

  17. Ultrafast electrochemical preparation of graphene/CoS nanosheet counter electrodes for efficient dye-sensitized solar cells

    SciTech Connect

    Zhu, Chongyang; Zhu, Yimei; Min, Huihua; Xu, Feng; Chen, Jing; Dong, Hui; Tong, Ling; Sun, Litao

    2015-10-05

    Utilizing inexpensive, high-efficiency counter electrodes (CEs) to replace the traditional platinum counterparts in dye-sensitized solar cells (DSSCs) is worthwhile. In this paper, we detail how we synchronously prepared composite CEs of CoS nanosheet arrays and reduced graphene oxide (rGO) layers for the first time via a low temperature, ultrafast one-step electrochemical strategy. With this approach, the whole fabrication process of the composite CEs was only a small percentage of the average time (~15 hours) using other methods. The DSSC assembled with the rGO–CoS composite CE achieved an enhanced power conversion efficiency (PCE) of 8.34%, which is dramatically higher than 6.27% of pure CoS CE-based DSSC and even exceeds 7.50% of Pt CE-based DSSC. The outstanding PCE breakthrough is undoubtedly attributed to the enhancement in electrocatalytic ability of the rGO–CoS composite CE due to the incorporation of highly conducting rGO layers and the GO layers-induced growth of CoS nanosheet arrays with higher density and larger surface area. Therefore, lower charge-transfer resistance and higher exchange current density can be achieved as corroborated by the electrochemical impedance spectra (EIS) and Tafel polarization curves (TPCs). As a result, further experiments also proved that the electrochemical strategy exhibited its universality of fabricating other graphene-enhanced chalcogenide functional composite films.

  18. Effect of electrochemical redox reaction on biochemical ammonium oxidation and chemical nitrite oxidation.

    PubMed

    Jeon, Bo Young; Seo, Ha Na; Kang, Seung Won; Park, Doo Hyun

    2010-03-01

    A modified graphite felt electrode with neutral red (NRelectrode) was shown to catalyze the chemical oxidation of nitrite to nitrate under aerobic conditions. The electrochemically oxidized NR-electrode (EO-NR-electrode) and reduced NR-electrode (ER-NR-electrode) catalyzed the oxidation of 1,094+/-39 mg/l and 382+/-45 mg/l of nitrite, respectively, for 24 h. The electrically uncharged NRelectrode (EU-NR-electrode) catalyzed the oxidation of 345+/-47 mg/l of nitrite for 24 h. The aerobic bacterial community immobilized in the EO-NR-electrode did not oxidize ammonium to nitrite; however, the aerobic bacterial community immobilized in the ER-NR-electrode bioelectrochemically oxidized 1,412+/-39 mg/l of ammonium for 48 h. Meanwhile, the aerobic bacterial community immobilized on the EU-NR-electrode biochemically oxidized 449+/-22 mg/l of ammonium for 48 h. In the continuous culture system, the aerobic bacterial community immobilized on the ER-NR-electrode bioelectrochemically oxidized a minimal 1,337+/-38 mg/l to a maximal 1,480+/-38 mg/l of ammonium to nitrate, and the community immobilized on the EU-NR-electrode biochemically oxidized a minimal 327+/-23 mg/l to a maximal 412+/-26 mg/l of ammonium to nitrate every two days. The bacterial communities cultivated in the ER-NR-electrode and EU-NR-electrode in the continuous culture system were analyzed by TGGE on the 20th and 50th days of incubation. Some ammoniumoxidizing bacteria were enriched on the ER-NR-electrode, but not on the EU-NR-electrode. PMID:20372016

  19. Preparation of a manganese titanate nanosensor: Application in electrochemical studies of captopril in the presence of para-aminobenzoic acid.

    PubMed

    Ghoreishi, Sayed Mehdi; Karamali, Elham; Khoobi, Asma; Enhessari, Morteza

    2015-10-15

    This study reports the synthesis and characterization of a novel nanostructure-based electrode for electrochemical studies and determination of captopril (CP). At first manganese titanate nanoceramics were synthesized by the sol-gel method. The structural evaluations of the pure nanopowders were investigated by different techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Then it was used to prepare a new nanostructured manganese titanate carbon paste electrode (MnTiO3/CPE). The characterization of the modified sensor was carried out by comprehensive techniques such as electrochemical impedance spectroscopy (EIS), SEM, and voltammetry. Subsequently, the modified electrode was used for CP catalytic oxidation in the presence of para-aminobenzoic acid (PABA) as a mediator. The results showed that PABA has high catalytic activity for CP oxidation. The electrochemical behavior of CP was studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CHA), and differential pulse voltammetry (DPV) techniques. Under the optimized conditions, the catalytic oxidation peak current of CP showed two linear dynamic concentration ranges of 1.0 × 10(-8) to 1.0 × 10(-7) and 1.0 × 10(-7) to 1.0 × 10(-6), with a detection limit of 1.6 nM (signal/noise = 3), using the DPV technique. Finally, the proposed method was successfully applied for determination of CP in pharmaceutical and biological samples. PMID:26226644

  20. Facile hydrothermal preparation of niobium pentaoxide decorated reduced graphene oxide nanocomposites for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Murugan, M.; Kumar, R. Mohan; Alsalme, Ali; Alghamdi, Abdulaziz; Jayavel, R.

    2016-04-01

    Facile synthesis of graphene-Nb2O5 composite has been reported. Graphene oxide was prepared by the modified Hummer's method. The metal oxide (Nb2O5) was introduced to the graphene to form the composite by the hydrothermal method. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared (FTIR) and thermo gravimetric analysis (TGA). SEM and TEM results revealed that the metal oxide particles are uniformly dispersed on the surface of thin sheets of well-defined multilayered graphene structure. Thermal stability of the graphene metal oxide nanocomposites was also investigated. The CV measurements reveal a significant enhancement in the specific capacitance reaching 321 Fg-1 at a scan rate of 10 mV s-1. With promising electrochemical characteristics, Nb2O5 decorated graphene nanocomposite are explored as potential electrode material for supercapacitor applications.

  1. Preparation and characterization of titanium dioxide nanotube array supported hydrated ruthenium oxide catalysts

    NASA Astrophysics Data System (ADS)

    Giang, Thi Phuong Ly; Tran, Thi Nhu Mai; Le, Xuan Tuan

    2012-03-01

    This work aimed at preparing and characterizing TiO2 nanotube supported hydrated ruthenium oxide catalysts. First of all, we succeeded in preparing TiO2 nanotube arrays by electrochemical anodization of titanium metal at 20 V for 8 h in a 1M H3PO4+0.5 wt% HF solution as evidenced from scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) results. The hydrated ruthenium oxide was then deposited onto TiO2 nanotubes by consecutive exchange of protons by Ru3+ ions, followed by formation of hydrated oxide during the alkali treatment. Further XPS measurements showed that the modified samples contain not only hydrated ruthenium oxide but also hydrated ruthenium species Ru(III)-OH.

  2. Preparation of Electrochemical Biosensor for Detection of Organophosphorus Pesticides

    PubMed Central

    Gothwal, Ashish; Beniwal, Puneet; Dhull, Vikas

    2014-01-01

    Polyvinyl chloride (PVC) can be used to develop reaction beaker which acts as electrochemical cell for the measurement of OP pesticides. Being chemically inert, corrosion resistant, and easy in molding to various shapes and size, PVC can be used for the immobilization of enzyme. Organophosphorus hydrolase was immobilized covalently onto the chemically activated inner surface of PVC beaker by using glutaraldehyde as a coupling agent. The carbon nanotubes paste working electrode was constructed for amperometric measurement at a potential of +0.8 V. The biosensor showed optimum response at pH 8.0 with incubation temperature of 40°C. Km and Imax for substrate (methyl parathion) were 322.58 µM and 1.1 µA, respectively. Evaluation study showed a correlation of 0.985, which was in agreement with the standard method. The OPH biosensor lost 50% of its initial activity after its regular use for 25 times over a period of 50 days when stored in 0.1 M sodium phosphate buffer, pH 8.0 at 4°C. No interference was observed by interfering species. PMID:25667593

  3. Preparation and electrochemical performance of ultra-short carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Xiao X.; Wang, Jian N.; Su, Lian F.

    Current carbon nanotubes (CNTs) are typically synthesized with micrometer lengths, low dispersion and low purity and thus oppose their applications in many fields. In this study, we make the first report on using a Fe compound (FeS) as a catalyst for controlling the length of CNTs to be less than 300 nm. This is achieved by dissolution of a proper proportion of ferrocene and thiophene in alcohol and pyrolysis of this solution at high temperature. Sulfur, resulting from the decomposition of thiophene, is shown to play key roles in promoting the growth of CNTs and limiting their length. The reason is suggested to be that FeS retards the dissociation of carbon source and diffusion of carbon in it as compared with pure Fe. Short CNTs from the present direct synthesis and from our previous solid-state cutting are used as an electrode material in Li-ion batteries and catalyst supports in fuel cells. Compared with conventional long CNTs, short CNTs show much better electrochemical performance. Due to the simplicity of the present synthetic technique, it may be used for mass production of short CNTs. Furthermore, the application of such a new material may be investigated in wide areas such as information technology, biomedicine, environmental and energy industries.

  4. Electrochemical gas-electricity cogeneration through direct carbon solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Xie, Yongmin; Cai, Weizi; Xiao, Jie; Tang, Yubao; Liu, Jiang; Liu, Meilin

    2015-03-01

    Solid oxide fuel cells (SOFCs), with yttrium stabilized zirconia (YSZ) as electrolyte, composite of strontium-doped lanthanum manganate (LSM) and YSZ as cathode, and cermet of silver and gadolinium-doped ceria (GDC) as anode, are prepared and tested with 5wt% Fe-loaded activated carbon as fuel and ambient air as oxidant. It is found that electricity and CO gas can be cogenerated in the direct carbon SOFCs through the electrochemical oxidation of CO and the Boudouard reaction. The gas-electricity cogeneration performances are investigated by taking the operating time of the DC-SOFCs as a measure of rate decrease of the Boudouard reaction. Three single cells and a two-cell-stack are tested and characterized in terms of electrical power output, CO production rate, electrical conversion efficiency, and overall conversion efficiency. It turns out that a rapid rate of the Boudouard reaction is necessary for getting high electrical power and CO production. Taking the emitted CO as part of the power output, an overall efficiency of 76.5% for the single cell, and of 72.5% for the stack, is obtained.

  5. Synthesis and Electrochemical Analyses of Manganese Oxides for Super-Capacitors.

    PubMed

    Kim, Taewoo; Hwang, Hyein; Jang, Jaeyong; Park, Inyeong; Shim, Sang Eun; Baeck, Sung-Hyeon

    2015-11-01

    δ-Phase and α-phase manganese oxides were prepared using a hydrothermal method and their electrochemical properties were characterized. The influence of calcination temperature on the properties of manganese oxides was studied. Crystallinities were studied by X-ray diffraction, and scanning and transmission electron microscopy were utilized to examine morphologies. Average pore sizes and specific surface areas of samples were analyzed using the Barret-Joyner-Halenda and Brunauer-Emmett-Teller methods, respectively. After calcination in the range 300 degrees C to 600 degrees C, changes in morphology and crystallinity were observed. The flower-like shape of as synthesized samples became nanorod-like and the δ-phase changed to the α-phase. These changes may have been due to the removal of water during calcination. Furthermore, a transition stage in which the two phases coexisted was observed. Synthesized manganese oxides were mixed with carbon by sonification, to increase electric conductivity and to induce a synergistic effect between pseudo-capacitor and electric double layer capacitor (EDLC). Specific capacitances and rate durability of each composite were investigated by cyclic voltammetry in 1 M Na2SO4 electrolyte at different scan rates. MnO2 calcined at 400 degrees C exhibited the highest capacitance, probably due to its high surface area and more porous structure. PMID:26726613

  6. Electrochemical synthesis of new magnetic mixed oxides of Sr and Fe: Composition, magnetic properties, and microstructure

    SciTech Connect

    Amigo, R.; Asenjo, J.; Krotenko, E.; Torres, F.; Tejada, J.; Brillas, E.

    2000-02-01

    An electrochemical method for the preparation of magnetic nanoparticles of new Sr-Fe oxides is presented in this work. It consists of the electrolysis of nitrate or chloride solutions with Sr{sup 2+} and Fe{sup 3+} salts using commercial Fe electrodes. Magnetic materials are collected as precipitates from nitrate media in the pH range 1-3 and from chloride media within the pH range 1--12. The presence of 100--300 ppm aniline in acidic nitrate media yields a decrease in energy cost and particle size. Inductively coupled plasma analysis of materials and energy-dispersive X-ray spectrometry of single particles confirm that they are composed of mixed oxides of Sr and Fe. All synthesized materials crystallize as inverse cubic spinels, usually with intermediate structures between magnetite and maghemite. They are formed by nanoparticles with average sizes from 2 nm to {approximately} 50 nm, as observed by scanning electron microscopy. The electrogenerated mixed oxides have higher saturation magnetization, but lower remanent magnetization and coercive field, than commercial strontium hexaferrite with micrometric particle size.

  7. An electrochemical dopamine aptasensor incorporating silver nanoparticle, functionalized carbon nanotubes and graphene oxide for signal amplification.

    PubMed

    Bahrami, Shokoh; Abbasi, Amir Reza; Roushani, Mahmoud; Derikvand, Zohreh; Azadbakht, Azadeh

    2016-10-01

    In this work, immobilization of a dopamine (DA) aptamer was performed at the surface of an amino functionalized silver nanoparticle-carbon nanotube graphene oxide (AgNPs/CNTs/GO) nanocomposite. A 58-mer DA-aptamer was immobilized through the formation of phosphoramidate bonds between the amino group of chitosan and the phosphate group of the aptamer at the 5' end. An AgNPs/CNTs/GO nanocomposite was employed as a highly catalytic label for electrochemical detection of DA based on electrocatalytic activity of the nanocomposite toward hydrogen peroxide (H2O2). Interaction of DA with the aptamer caused conformational changes of the aptamer which, in turn, decreased H2O2 oxidation and reduction peak currents. On the other hand, the presumed folding of the DA-aptamer complexes on the sensing interface inhibited the electrocatalytic activity of AgNPs/CNTs/GO toward H2O2. Sensitive quantitative detection of DA was carried out by monitoring the decrease of differential pulse voltammetric (DPV) responses of AgNPs/CNTs/GO nanocomposite toward H2O2 oxidation. The DPV signal linearly decreased with increased concentration of DA from 3 to 110nmolL(-1) with a detection limit of 700±19.23pmolL(-1). Simple preparation, low operation cost, speed and validity are the decisive factors of this method motivating its application to biosensing investigation. PMID:27474313

  8. Porous MnO2 prepared by sol-gel method for electrochemical supercapacitor

    NASA Astrophysics Data System (ADS)

    Bazzi, K.; Kumar, A.; Jayakumar, O. D.; Nazri, G. A.; Naik, V. M.; Naik, R.

    2015-03-01

    MnO2 has attracted great attention as material for electrochemical pseudocapacitor due to its high theoretical specific faradic capacitance (~ 1370 F .g-1) , environmental friendliness and wide potential window in both aqueous and nonaqueous electrolytes. However, the MnO2 has a low surface area which depresses its electrochemical performance. The amorphous α-MnO2 composite was synthesized by sol gel method in the presence of the tri-block copolymer P123. Our aim is to investigate the role of P123 on the electrochemical performance of MnO2. The samples with and without P123 were prepared and characterized by x-ray diffraction (XRD), SEM, TEM and Brunauer-Emmett-Teller (BET) method. The electrochemical performances of the amorphous MnO2 composites as the electrode materials for supercapacitors were evaluated by cyclic voltammetry and AC impedance measurements in a 1M Na2SO4 solution. The results show that the sample prepared without P123 exhibited a relatively low specific capacitance of 28F .g-1, whereas the porous MnO2 prepared with P123 exhibited 117 F .g-1at 5 mV/s. The results of crystalline MnO2 composites will also be presented. The authors acknowledge the support from the Richard J. Barber Foundation for Interdisciplinary Research.

  9. Electrochemical oxidation of drug residues in water by the example of tetracycline, gentamicine and aspirin.

    PubMed

    Weichgrebe, D; Danilova, E; Rosenwinkel, K H; Vedenjapin, A A; Baturova, M

    2004-01-01

    Electro-chemical oxidation as a method to destroy drug residues like aspirin, tetracycline or gentamicine in water was investigated with C-anodes (modified by manganese oxides) and Pt anodes. The mechanism of aspirin 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. PMID:15077972

  10. Preparation of Ferrotitanium Alloy from Ilmenite by Electrochemical Reduction in Chloride Molten Salts

    NASA Astrophysics Data System (ADS)

    Qi, Can-can; Hua, Yi-xin; Chen, Kong-hao; Jie, Ya-fei; Zhou, Zhong-ren; Ru, Juan-jian; Xiong, Li; Gong, Kai

    2016-02-01

    Ferrotitanium alloy is prepared by electrochemical reduction from ilmenite in LiCl-KCl and LiCl-KCl-CaCl2 molten salts, respectively. The products prepared are observed by x-ray diffraction (XRD). It is shown that Fe2Ti can be prepared from ilmenite in LiCl-KCl molten salt at 1073 K with a cell voltage of 3.2 V. Ilmenite can be electrochemically reduced to FeTi in LiCl-KCl-CaCl2 molten salt under the same condition. It is indicated that CaCl2 can promote the reaction and is favors the deoxidization of the FeTiO3.

  11. Preparation and Characterization of Graphene Oxide Paper

    SciTech Connect

    Dikin,D.; Stankovich, S.; Zimney, E.; Piner, R.; Dommett, G.; Evmenenko, G.; Nguyen, S.; Ruoff, R.

    2007-01-01

    Free-standing paper-like or foil-like materials are an integral part of our technological society. Their uses include protective layers, chemical filters, components of electrical batteries or supercapacitors, adhesive layers, electronic or optoelectronic components, and molecular storage. Inorganic 'paper-like' materials based on nanoscale components such as exfoliated vermiculite or mica platelets have been intensively studied and commercialized as protective coatings, high-temperature binders, dielectric barriers and gas-impermeable membranes. Carbon-based flexible graphite foils composed of stacked platelets of expanded graphite have long been used in packing and gasketing applications because of their chemical resistivity against most media, superior sealability over a wide temperature range, and impermeability to fluids. The discovery of carbon nanotubes brought about bucky paper, which displays excellent mechanical and electrical properties that make it potentially suitable for fuel cell and structural composite applications. Here we report the preparation and characterization of graphene oxide paper, a free-standing carbon-based membrane material made by flow-directed assembly of individual graphene oxide sheets. This new material outperforms many other paper-like materials in stiffness and strength. Its combination of macroscopic flexibility and stiffness is a result of a unique interlocking-tile arrangement of the nanoscale graphene oxide sheets.

  12. STEP wastewater treatment: a solar thermal electrochemical process for pollutant oxidation.

    PubMed

    Wang, Baohui; Wu, Hongjun; Zhang, Guoxue; Licht, Stuart

    2012-10-01

    A solar thermal electrochemical production (STEP) pathway was established to utilize solar energy to drive useful chemical processes. In this paper, we use experimental chemistry for efficient STEP wastewater treatment, and suggest a theory based on the decreasing stability of organic pollutants (hydrocarbon oxidation potentials) with increasing temperature. Exemplified by the solar thermal electrochemical oxidation of phenol, the fundamental model and experimental system components of this process outline a general method for the oxidation of environmentally stable organic pollutants into carbon dioxide, which is easily removed. Using thermodynamic calculations we show a sharply decreasing phenol oxidation potential with increasing temperature. The experimental results demonstrate that this increased temperature can be supplied by solar thermal heating. In combination this drives electrochemical phenol removal with enhanced oxidation efficiency through (i) a thermodynamically driven decrease in the energy needed to fuel the process and (ii) improved kinetics to sustain high rates of phenol oxidation at low electrochemical overpotential. The STEP wastewater treatment process is synergistic in that it is performed with higher efficiency than either electrochemical or photovoltaic conversion process acting alone. STEP is a green, efficient, safe, and sustainable process for organic wastewater treatment driven solely by solar energy. PMID:22965739

  13. Silver vanadium phosphorous oxide, Ag 2VO 2PO 4: Chimie douce preparation and resulting lithium cell electrochemistry

    NASA Astrophysics Data System (ADS)

    Kim, Young Jin; Marschilok, Amy C.; Takeuchi, Kenneth J.; Takeuchi, Esther S.

    Recently, we have shown silver vanadium phosphorous oxide (Ag 2VO 2PO 4, SVPO) to be a promising cathode material for lithium based batteries. Whereas the first reported preparation of SVPO employed an elevated pressure, hydrothermal approach, we report herein a novel ambient pressure synthesis method to prepare SVPO, where our chimie douce preparation is readily scalable and provides material with a smaller, more consistent particle size and higher surface area relative to SVPO prepared via the hydrothermal method. Lithium electrochemical cells utilizing SVPO cathodes made by our new process show improved power capability under constant current and pulse conditions over cells containing cathode from SVPO prepared via the hydrothermal method.

  14. Nanocrystals of Uranium Oxide: Controlled Synthesis and Enhanced Electrochemical Performance of Hydrogen Evolution by Ce Doping.

    PubMed

    Hu, Shi; Li, Haoyi; Liu, Huiling; He, Peilei; Wang, Xun

    2015-06-10

    A preliminary study of the growth of 0D, 1D, and 2D nanostructures of uranium oxides with feature sizes from several nanometers down to 1 nm are presented. Cerium is successfully doped into these oxides and its influence on the growth dynamics and electrochemical performance investigated. PMID:25627103

  15. Rapid and simple preparation of a reagentless glucose electrochemical biosensor.

    PubMed

    Zheng, Dan; Vashist, Sandeep Kumar; Al-Rubeaan, Khalid; Luong, John H T; Sheu, Fwu-Shan

    2012-08-21

    A rapid and simple procedure was developed for the preparation of a highly stable and leach-proof glucose oxidase (GOx)-bound glassy carbon electrode (GCE). Crosslinked GOx via glutaraldehyde was drop-cast on a KOH-pretreated GCE followed by drop-casting of 3-aminopropyltriethoxysilane (APTES) to form a stable bioactive layer. At -0.45 V, the biosensor exhibited a wide dynamic detection range of 0.5-48 mM for commercial glucose and 1.3-28.2 mM for Sugar-Chex blood glucose linearity standards. Several endogenous electroactive substances and drug metabolites commonly found in blood were tested and provoked no signal response. To our knowledge, the developed procedure is the most rapid method for preparing a glucose biosensor. The biosensor suffered no biofouling after 7 days of immersion in Sugar-Chex blood glucose. With excellent production reproducibility, GOx-bound electrodes stored dry at room temperature retained their initial activity after several weeks. PMID:22763782

  16. Electrochemical oxidation of fluoroquinolone antibiotics: Mechanism, residual antibacterial activity and toxicity change.

    PubMed

    Zhu, Linyan; Santiago-Schübel, Beatrix; Xiao, Hongxia; Hollert, Henner; Kueppers, Stephan

    2016-10-01

    In this paper, we studied the electrochemical oxidation mechanisms of three typical fluoroquinolone antibiotics (FQs), and investigated residual antibacterial activity and toxicity changes after oxidation processes. Electrochemistry coupled to mass spectrometry (EC-MS) was used to study the oxidation processes of ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL). Eight oxidation products for each parent compound were identified and their chemical structures were elucidated. The transformation trend of each product, with the continuous increase of voltage from 0 to 3000 mV, was recorded by online EC-MS. The oxidation pathways were proposed based on the structural information and transformation trends of oxidation products. We found the oxidation mechanisms of FQs consisted of the hydroxylation and cleavage of piperazinyl ring via reactions with hydroxyl radicals, while the fluoroquinolone core remained intact. The antibacterial activity of the parent compounds and their oxidation mixtures was estimated using zone inhibition tests for gram-negative bacteria Salmonella typhimurium. It was found that the oxidation mixtures of CIP and NOR retained the antibacterial properties with lower activity compared to their parent compounds, while the antibacterial activity of OFL was almost eliminated after oxidation. Furthermore, the toxicity of the three FQs and their oxidation mixtures were evaluated using algal growth inhibition test (Desmodesmus subspicatus). The median effective concentration (EC50) values for the algal inhibition tests were calculated for the end point of growth rate. The toxicity of CIP and NOR to green algae after electrochemical oxidation, remained unchanged, while that of OFL significantly increased. The results presented in this paper contribute to an understanding of the electrochemical oxidation mechanisms of FQs, and highlight the potential environmental risks of FQs after electrochemical oxidation processes. PMID:27318447

  17. Hydrothermal preparation and electrochemical properties of Gd 3+ and Bi 3+, Sm 3+, La 3+, and Nd 3+ codoped ceria-based electrolytes for intermediate temperature-solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Dikmen, Sibel; Aslanbay, Hasan; Dikmen, Erdal; Şahin, Osman

    The structure, the thermal expansion coefficient, electrical conductivities of Ce 0.8Gd 0.2- xM xO 2- δ (for M: Bi, x = 0-0.1, and for M: Sm, La, and Nd, x = 0.02) solid solutions, prepared for the first time hydrothermally, are investigated. The uniformly small particle size (28-59 nm) of the materials allows sintering of the samples into highly dense ceramic pellets at 1300-1400 °C. The maximum conductivity, σ 700 °C around 4.46 × 10 -2 S cm -1 with E a = 0.52 eV, is found at x = 0.1 for Bi-co-doping. Among various metal-co-dopings, for x = 0.02, the maximum conductivity, σ 700 °C around 2.88 × 10 -2 S cm -1 with E a = 0.67 eV, is found for Sm-co-doping. The electrolytic domain boundary (EDB) of Ce 0.8Gd 0.1Bi 0.1O 2- δ is found to be 1.2 × 10 -19 atm, which is relatively lower than that of the singly doped samples. The thermal expansion coefficients, determined from high-temperature X-ray data are 11.6 × 10 -6 K -1 for the CeO 2, 12.1 × 10 -6 K -1 for Ce 0.8Gd 0.2O 2- δ, and increase with co-doping to 14.2 × 10 -6 K -1 for Ce 0.8Gd 0.18Bi 0.02O 2- δ. The maximum power densities for the single cell based on the codoped samples are higher than that of the singly doped sample. These results suggest that co-doping can further improve the electrical performance of ceria-based electrolytes.

  18. A novel system combining biocatalytic dephosphorylation of L-ascorbic acid 2-phosphate and electrochemical oxidation of resulting ascorbic acid.

    PubMed

    Kuwahara, Takashi; Homma, Toshimasa; Kondo, Mizuki; Shimomura, Masato

    2011-03-15

    An enzyme electrode was prepared with acid phosphatase (ACP) for development of a new electric power generation system using ascorbic acid 2-phosphate (AA2P) as a fuel. The properties of the electrode were investigated with respect to biocatalytic dephosphorylation of AA2P and electrochemical oxidation of resulting ascorbic acid (AA). The enzyme electrode was fabricated by immobilization of ACP through amide linkage onto a self-assembled monolayer of 3-mercaptopropionic acid on a gold electrode. AA2P was not oxidized on a bare gold electrode in the potential sweep range from -0.1 to +0.5 V vs. Ag/AgCl. However, the enzyme electrode gave an oxidation current in citric buffer solution of pH 5 containing 10 mM of AA2P. The oxidation current began to increase at +0.2V, and reached to 5.0 μA cm(-2) at +0.5 V. The potential +0.2 V corresponded to the onset of oxidation of ascorbic acid (AA). These results suggest that the oxidation current observed with the enzyme electrode is due to AA resulting from dephosphorylation of AA2P. The oxidation current increased with increasing concentration of AA2P and almost leveled off at around the concentration of 5mM. Thus the enzyme electrode brought about biocatalytic conversion of AA2P to AA, followed by electrochemical oxidation of the AA. The oxidation current is likely to be controlled by the biocatalytic reaction. PMID:21247749

  19. Writing nanopatterns with electrochemical oxidation on redox responsive organometallic multilayers by AFM

    NASA Astrophysics Data System (ADS)

    Song, Jing; Hempenius, Mark A.; Jing Chung, Hong; Julius Vancso, G.

    2015-05-01

    Nanoelectrochemical patterning of redox responsive organometallic poly(ferrocenylsilane) (PFS) multilayers is demonstrated by electrochemical dip pen lithography (EDPN). Local electrochemical oxidation and Joule heating of PFS multilayers from the tip are considered as relevant mechanisms related to structure generation. The influence of applied bias potential, tip velocity, and multilayer thickness on the pattern height and width were investigated.Nanoelectrochemical patterning of redox responsive organometallic poly(ferrocenylsilane) (PFS) multilayers is demonstrated by electrochemical dip pen lithography (EDPN). Local electrochemical oxidation and Joule heating of PFS multilayers from the tip are considered as relevant mechanisms related to structure generation. The influence of applied bias potential, tip velocity, and multilayer thickness on the pattern height and width were investigated. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01206f

  20. Highly sensitive electrochemical determination of Sunset Yellow based on the ultrafine Au-Pd and reduced graphene oxide nanocomposites.

    PubMed

    Wang, Jin; Yang, Beibei; Zhang, Ke; Bin, Duan; Shiraishi, Yukihide; Yang, Ping; Du, Yukou

    2016-11-01

    A sensitive and novel electrochemical sensor with Au-Pd and reduced graphene oxide (RGO) nanocomposites modified glassy carbon electrode (Au-Pd-RGO/GCE) was successfully fabricated by one-step synthesis method for the detection of Sunset Yellow. The as-prepared composites were uniformly dispersed on the surface of electrode with an average diameter of approximately 3.44nm, and the ultrafine nanoparticles effectively enhanced the electrochemical active surface area of GCE. The modified electrode had been characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and electrochemical tests. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results showed high stability and outstanding electrocatalytic activity of Au-Pd-RGO/GCE for the detection of SY with low detection limits (1.5 nM, S/N=3) and wide concentration ranges (0.686-331.686μM). The Au-Pd-RGO/GCE was further applied to detect SY in real samples with good recovery. Herein, the fabricated Au-Pd-RGO/GCE showed excellent sensitivity, stability and repeatability for the detection of SY and will be a promising application in electrochemical sensor. PMID:27475710

  1. Route of electrochemical oxidation of the antibiotic sulfamethoxazole on a mixed oxide anode.

    PubMed

    Hussain, Sajjad; Gul, Saima; Steter, Juliana R; Miwa, Douglas W; Motheo, Artur J

    2015-10-01

    The appearance of pharmaceutical compounds and their bioactive transformation products in aquatic environments is becoming an issue of increasing concern. In this study, the electrochemical oxidation of the widely used antibiotic sulfamethoxazole (SMX) was investigated using a commercial mixed oxide anode (Ti/Ru0.3Ti0.7O2) and a single compartment filter press-type flow reactor. The kinetics of SMX degradation was determined as a function of electrolyte composition, applied current density, and initial pH. Almost complete (98 %) degradation of SMX could be achieved within 30 min of electrolysis in 0.1 mol L(-1) NaCl solution at pH 3 with applied current densities ≥20 mA cm(-2). Nine major intermediates of the reaction were identified by LC-ESI-Q-TOF-MS (e.g., C6H9NO2S (m/z = 179), C6H4NOCl (m/z = 141), and C6H6O2 (m/z = 110)). The degradation followed various routes involving cleavage of the oxazole and benzene rings by hydroxyl and/or chlorine radicals, processes that could occur before or after rupture of the N-S bond, followed by oxidation of the remaining moieties. Analysis of the total organic carbon content revealed that the antibiotic was partially mineralized under the conditions employed and some inorganic ions, including NO3 (-) and SO4 (2-), could be identified. The results presented herein demonstrate the efficacy of the electrochemical process using a Ti/Ru0.3Ti0.7O2 anode for the remediation of wastewater containing the antibiotic SMX. PMID:26002364

  2. Kinetics of the electrochemical oxidation of 1,1-bis-hydroperoxy-4-methylcyclohexane on platinum

    NASA Astrophysics Data System (ADS)

    Vedenyapina, M. D.; Simakova, A. P.; Platonov, M. M.; Terent'ev, A. O.; Skundin, A. M.; Vedenyapin, A. A.

    2013-03-01

    The electrochemical synthesis of 3,12-dimethyl-7,8,15,16-tetraoxadispiro[5.2.5.2]hexadecane (1,2,4,5-tetraoxane) from 1,1-bis-hydroperoxy-4-methylcyclohexane on platinum electrode in a cell with separated and unseparated cathode and anode space in an aprotic solvent is conducted. The kinetics of electrochemical oxidation of 1,1-bis(hydroperoxy)-4-methylcyclohexane is studied. The current yield of the reaction is determined.

  3. Electrochemical preparation of MnO2 nanobelts through pulse base-electrogeneration and evaluation of their electrochemical performance

    NASA Astrophysics Data System (ADS)

    Aghazadeh, Mustafa; Maragheh, Mohammad Ghannadi; Ganjali, Mohammad Reza; Norouzi, Parviz; Faridbod, Farnoush

    2016-02-01

    Cathodic electrodeposition of MnO2 from a nitrate solution, via pulsed base (OH-) electrogeneration was performed for the first time. The deposition experiments were performed in a pulse current mode in typical on-times and off-times (i.e. ton = 1 s and toff = 1 s) with a peak current density of 2 mA cm-2 (Ia = 2 mA cm-2). The structural characterizations conducted by XRD and FTIR techniques revealed that the prepared MnO2 is composed of both α and γ phases. Morphological observation by SEM and TEM showed that the prepared MnO2 is made up of nanobelts with uniform shapes (an average diameter and length of 50 nm and 1 μm, respectively). Further electrochemical measurements by cyclic voltammetry and charge-discharge techniques revealed that the prepared MnO2 nanostructures have excellent capacitive behaviors, like a specific capacitance of 235.5 F g-1 and capacity retention of 91.3% after 1000 cycling at the scan rate of 25 mV s-1.

  4. Method of preparing a powdered, electrically insulative separator for use in an electrochemical cell

    DOEpatents

    Cooper, Tom O.; Miller, William E.

    1978-01-01

    A secondary electrochemical cell includes electrodes separated by a layer of electrically insulative powder. The powder includes refractory materials selected from the oxides and nitrides of metals and metaloids. The powdered refractory material, blended with electrolyte particles, is compacted as layers onto an electrode to form an integral electrode structure and assembled into the cell. The assembled cell is heated to its operating temperature leaving porous layers of electrically insulative, refractory particles, containing molten electrolyte between the electrodes.

  5. Combining electrochemical sensors with miniaturized sample preparation for rapid detection in clinical samples.

    PubMed

    Bunyakul, Natinan; Baeumner, Antje J

    2015-01-01

    Clinical analyses benefit world-wide from rapid and reliable diagnostics tests. New tests are sought with greatest demand not only for new analytes, but also to reduce costs, complexity and lengthy analysis times of current techniques. Among the myriad of possibilities available today to develop new test systems, amperometric biosensors are prominent players-best represented by the ubiquitous amperometric-based glucose sensors. Electrochemical approaches in general require little and often enough only simple hardware components, are rugged and yet provide low limits of detection. They thus offer many of the desirable attributes for point-of-care/point-of-need tests. This review focuses on investigating the important integration of sample preparation with (primarily electrochemical) biosensors. Sample clean up requirements, miniaturized sample preparation strategies, and their potential integration with sensors will be discussed, focusing on clinical sample analyses. PMID:25558994

  6. Combining Electrochemical Sensors with Miniaturized Sample Preparation for Rapid Detection in Clinical Samples

    PubMed Central

    Bunyakul, Natinan; Baeumner, Antje J.

    2015-01-01

    Clinical analyses benefit world-wide from rapid and reliable diagnostics tests. New tests are sought with greatest demand not only for new analytes, but also to reduce costs, complexity and lengthy analysis times of current techniques. Among the myriad of possibilities available today to develop new test systems, amperometric biosensors are prominent players—best represented by the ubiquitous amperometric-based glucose sensors. Electrochemical approaches in general require little and often enough only simple hardware components, are rugged and yet provide low limits of detection. They thus offer many of the desirable attributes for point-of-care/point-of-need tests. This review focuses on investigating the important integration of sample preparation with (primarily electrochemical) biosensors. Sample clean up requirements, miniaturized sample preparation strategies, and their potential integration with sensors will be discussed, focusing on clinical sample analyses. PMID:25558994

  7. Preparation and Characterization of Nanostructured Manganese Oxide for Supercapacitors.

    PubMed

    Jang, Jaeyong; Kim, Taewoo; Choi, Young Il; Park, Inyeong; Lim, Dongwook; Shim, Sang Eun; Baeck, Sung-Hyeon

    2016-05-01

    Nanostructured manganese oxides were synthesized by a sol-gel method using manganese acetate (MnAc2) and citric acid (C6H8O7,) as precursors, and characterized by Brunauer-Emmett-Teller (BET) analysis, Barrett-Joyner-Halenda (BJH), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The nano-rod structure of MnO2 developed gradually when the calcination temperature varied from 380 to 580 degrees C. As the pH increased, the pore size increased, while the specific surface area decreased. The effects of the pH and calcination temperature on the electrochemical properties of the nano-MnO2 electrode, including the supercapacitive behavior, were investigated by cyclic voltammetry (CV) tests. The tests were performed between 0 and 0.8 V versus Ag/AgCl in 1 M Na2SO4 electrolyte at various scan rates (10-200 mVs(-1)). The specific capacitance of the SP-380 sample, prepared at pH 6, was equal to 269.3 Fg(-1). After 300 cycles, approximately a 3.4% increase of the specific capacitance was measured, confirming the excellent cyclability. PMID:27483899

  8. Highly dispersible and stable copper terephthalate metal-organic framework-graphene oxide nanocomposite for an electrochemical sensing application.

    PubMed

    Wang, Xia; Wang, Qingxiang; Wang, Qinghua; Gao, Feng; Gao, Fei; Yang, Yizhen; Guo, Hongxu

    2014-07-23

    A highly dispersible and stable nanocomposite of Cu(tpa)-GO (Cu(tpa) = copper terephthalate metal-organic framework, GO = graphene oxide) was prepared through a simple ultrasonication method. The morphology and structure of the obtained composite were characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis, Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). On the basis of the characterization results, the binding mechanism of the Cu(tpa) and GO was speculated to be the cooperative interaction of π-π stacking, hydrogen bonding, and Cu-O coordination. The electrochemical sensing property of Cu(tpa)-GO composite was investigated through casting the composite on a glassy carbon electrode (GCE), followed by an electro-reduction treatment to transfer the GO in the composite to the highly conductive reduced form (electrochemically reduced graphene, EGR). The results demonstrated that the electrochemical signals and peak profiles of the two drugs of acetaminophen (ACOP) and dopamine (DA) were significantly improved by the modified material, owing to the synergistic effect from high conductivity of EGR and unique electron mediating action of Cu(tpa). Under the optimum conditions, the oxidation peak currents of ACOP and DA were linearly correlated to their concentrations in the ranges of 1-100 and 1-50 μM, respectively. The detection limits for ACOP and DA were estimated to be as low as 0.36 and 0.21 μM, respectively. PMID:25000168

  9. PREPARATION OF HIGH-DENSITY, COMPACTIBLE THORIUM OXIDE PARTICLES

    DOEpatents

    McCorkle, K.H.; Kleinsteuber, A.T.; Schilling, C.E.; Dean, O.C.

    1962-05-22

    A method is given for preparing millimeter-size, highdensity thorium oxide particles suitable for fabrication into nuclear reactor feel elements by means of vibratory compaction. A thorium oxide gel containing 3.7 to 7 weight per cent residual volatile nitrate and water is prepared by drying a thorium oxide sol. The gel is then slowly heated to a temperature of about 450DEC, and the resulting gel fragments are calcined. The starting sol is prepared by repeated dispersion of oxalate-source thorium oxide in a nitrate system or by dispersion of steam-denitrated thorium oxide in water. (AEC)

  10. Amplified inhibition of the electrochemical signal of ferrocene by enzyme-functionalized graphene oxide nanoprobe for ultrasensitive immunoassay.

    PubMed

    Lai, Guosong; Cheng, Hui; Xin, Dinghong; Zhang, Haili; Yu, Aimin

    2016-01-01

    A nanoprobe-induced signal inhibition mechanism was designed for ultrasensitive electrochemical immunoassay at a chitosan-ferrocene (CS-Fc) based immunosensor. The nanoprobe was prepared by covalently loading signal antibody and high-content horseradish peroxidase (HRP) on the graphene oxide (GO) nanocarrier. The immunosensor was prepared through the stepwise assembly of gold nanoparticles (Au NPs) and capture antibody at a CS-Fc modified electrode. After sandwich immunoreaction, the GO-HRP nanoprobes were quantitatively captured onto the immunosensor surface and thus induced the production of a layer of insoluble film through the enzymatically catalytic reaction of the HRP labels. Both the dielectric immunocomplex formed on the immunosensor surface and the enzymatic precipitate with low electroconductivity led to the electrochemical signal decease of the Fc indicator, which was greatly amplified by the multi-enzyme signal amplification of the nanoprobe. Based on this amplified signal inhibition mechanism, a new ultrasensitive electrochemical immunoassay method was developed. Using carcinoembryonic antigen as a model analyte, this method showed a wide linear range over 5 orders of magnitude with a detection limit down to 0.54 pg/mL. Besides, the immunosensor showed good specificity, acceptable reproducibility and stability as well as satisfactory reliability for the serum sample analysis. PMID:26703270

  11. Electrochemical Synthesis of Binary and Ternary Niobium-Containing Oxide Electrodes Using the p-Benzoquinone/Hydroquinone Redox Couple.

    PubMed

    Papa, Christopher M; Cesnik, Anthony J; Evans, Taylor C; Choi, Kyoung-Shin

    2015-09-01

    New electrochemical synthesis methods have been developed to obtain layered potassium niobates, KNb3O8 and K4Nb6O17, and perovskite-type KNbO3 as film-type electrodes. The electrodes were synthesized from aqueous solutions using the redox chemistry of p-benzoquinone and hydroquinone to change the local pH at the working electrode to trigger deposition of desired phases. In particular, the utilization of electrochemically generated acid via the oxidation of hydroquinone for inorganic film deposition was first demonstrated in this study. The layered potassium niobates could be converted to (H3O)Nb3O8 and (H3O)4Nb6O17 by cationic exchange, which, in turn, could be converted to Nb2O5 by heat treatment. The versatility of the new deposition method was further demonstrated for the formation of CuNb2O6 and AgNbO3, which were prepared by the deposition of KNb3O8 and transition metal oxides, followed by thermal and chemical treatments. Considering the lack of solution-based synthesis methods for Nb-based oxide films, the methods reported in this study will contribute greatly to studies involving the synthesis and applications of Nb-based oxide electrodes. PMID:26293515

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

    PubMed

    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

  13. Mapping Electrochemical Heterogeneity at Iron Oxide Surfaces: A Local Electrochemical Impedance Study.

    PubMed

    Lucas, Marie; Boily, Jean-François

    2015-12-22

    Alternating current scanning electrochemical microscopy (AC-SECM) was used for the first time to map key electrochemical attributes of oriented hematite (α-Fe2O3) single crystal surfaces at the micron-scale. Localized electrochemical impedance spectra (LEIS) of the (001) and (012) faces provided insight into the spatial variations of local double layer capacitance (C(dl)) and charge transfer resistance (R(ad)). These parameters were extracted by LEIS measurements in the 0.4-8000 Hz range to probe the impedance response generated by the redistribution of water molecules and charge carriers (ions) under an applied AC. These were attributed to local variations in the local conductivity of the sample surfaces. Comparison with global EIS measurements on the same samples uncovered highly comparable frequency-resolved processes, that were broken down into contributions from the bulk hematite, the interface as well as the microelectrode/tip assembly. This work paves the way for new studies aimed at mapping electrochemical processes at the mesoscale on this environmentally and technologically important material. PMID:26625255

  14. Electrochemical stability and restructuring and its impact on the electro-oxidation of CO: Pt modified Ru(0001) electrodes

    NASA Astrophysics Data System (ADS)

    Engstfeld, A. K.; Klein, J.; Brimaud, S.; Behm, R. J.

    2015-01-01

    Structural modifications during electrochemical measurements on well defined Pt modified Ru(0001) electrode surfaces, which were prepared and characterized under ultrahigh vacuum (UHV) conditions, and the influence of the restructuring on the CO oxidation reaction have been investigated in a set-up combining surface preparation and scanning tunneling microscopy characterization under UHV conditions (UHV-STM) and electrochemical flow cell measurements. Bare Ru(0001) and Pt monolayer island modified Ru(0001) electrodes with different Pt coverages were investigated, together with a Pt0.3Ru0.7/Ru(0001) monolayer surface alloy for comparison. Comparing bulk CO oxidation measurements performed upon cycling in base electrolyte (0.5 M H2SO4) to 0.90 VRHE with similar measurements performed after potential cycling to 1.05 VRHE, we find pronounced differences in the current-voltage characteristics, with a distinct new peak at low potentials in the positive-going scan in the latter case, which is centered at 0.67 VRHE. STM imaging performed before and after the electrocatalytic measurements revealed a distinct restructuring of the Pt monolayer island modified Ru(0001) surfaces upon potential cycling to 1.05 VRHE, while cycling to 0.90 VRHE maintains the original structure and morphology of the bimetallic surface. In contrast, for the bare Ru(0001) electrode, restructuring of steps is observed already upon potential cycling to 0.9 VRHE. Implications of these findings on the electrochemical stability of the electrodes as well as on the mechanistic understanding of the CO oxidation reaction on bimetallic PtRu electrode surfaces and on the activity of different mono- and bimetallic nanostructures are discussed.

  15. Note: Buoyant-force assisted liquid membrane electrochemical etching for nano-tip preparation.

    PubMed

    Zeng, Yongbin; Wang, Yufeng; Wu, Xiujuan; Xu, Kun; Qu, Ningsong

    2014-12-01

    A liquid membrane electrochemical etching process for preparing nano-tips is proposed by the introduction of buoyant force to the lower tip, in which the lower portion of the anodic wire is immersed into a floating layer. A mathematical model of this method is derived. Both calculation and experimental results demonstrate that the introduction of buoyant force can significantly decrease the tip radius. The lubricating oil and deionized water floating layers were tested for the processing of nano-tips. Further, high-aspect-ratio nano-electrodes were prepared by applying a relative vertical movement to the anodic wire. PMID:25554341

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

    PubMed

    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). PMID:25981800

  17. Great-enhanced performance of Pt nanoparticles by the unique carbon quantum dot/reduced graphene oxide hybrid supports towards methanol electrochemical oxidation

    NASA Astrophysics Data System (ADS)

    Hong, Tian-Zeng; Xue, Qiong; Yang, Zhi-Yong; Dong, Ya-Ping

    2016-01-01

    The Pt-carbon quantum dot (CQD)/reduced graphene oxide (RGO) catalysts are prepared by one pot reduction method and demonstrate ultraefficient performance towards methanol oxidation reaction (MOR). In the high content CQD products, Pt nanoparticles around 2-3 nm are dispersed uniformly on supporting materials. And the X-ray photoelectron spectroscopy analysis indicates that in the high content CQD products a large part of surface oxygen groups is contributed by CQD. The electrochemical tests reveal that the catalyst with the saturated CQD exhibits best performance in MOR: the mass and specific activity at forward peak position, the potential close to fuel cell operation and 3600 s of chronoamperometric curve are roughly 2-3 folds of the commercial Pt/C. Furthermore, the electrochemical data on the series of catalysts with different quantity of CQD disclose the improving tendency of MOR performance with the increasing content of CQD evidently. Overview the electrochemical and characterization results, we suggest CQD play multiple roles in the enhancement of Pt performance: present abundant nucleating and anchoring points to facilitate the formation of small size and uniform distributed Pt particles; act as spacer to alleviate restacking of RGO sheets; and provide fruitful surface oxygen groups to improve the antipoisonous ability of Pt.

  18. Influence of substrate preparation on the shaping of the topography of the surface of nanoceramic oxide layers

    NASA Astrophysics Data System (ADS)

    Bara, Marek; Kubica, Marek

    2014-02-01

    The paper discusses the shaping mechanism and changes occurring in the structure and topography of the surface of nanoceramic oxide layers during their formation. The paper presents the influence of substrate preparation on the surface topography of oxide layers. The layers were produced via hard anodizing on the EN AW-5251 aluminum alloy. The layers obtained were subjected to microscope examinations, image and chemical composition analyses, and stereometric examinations. Heredity of substrate properties in the topography of the surface of nanoceramic oxide layers formed as a result of electrochemical oxidation has been shown.

  19. Mediated electrochemical oxidation of organic wastes without electrode separators

    DOEpatents

    Farmer, Joseph C.; Wang, Francis T.; Hickman, Robert G.; Lewis, Patricia R.

    1996-01-01

    An electrochemical cell/electrolyte/mediator combination for the efficient destruction of organic contaminants using metal salt mediators in a sulfuric acid electrolyte, wherein the electrodes and mediator are chosen such that hydrogen gas is produced at the cathode and no cell membrane is required.

  20. Mediated electrochemical oxidation of organic wastes without electrode separators

    DOEpatents

    Farmer, J.C.; Wang, F.T.; Hickman, R.G.; Lewis, P.R.

    1996-05-14

    An electrochemical cell/electrolyte/mediator combination is described for the efficient destruction of organic contaminants using metal salt mediators in a sulfuric acid electrolyte, wherein the electrodes and mediator are chosen such that hydrogen gas is produced at the cathode and no cell membrane is required. 3 figs.

  1. Preparation and electrochemical properties of Co-Si 3N 4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Yao, S. M.; Xi, K.; Li, G. R.; Gao, X. P.

    Cobalt nanoparticles on an amorphous Si 3N 4 matrix were synthesized by direct ball-milling of Co and Si 3N 4 powders for an improvement of their electrochemical performance. The microstructure, morphology and chemical state of the ball-milled Co-Si 3N 4 composites are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of Co-Si 3N 4 composites was investigated by galvanostatic charge-discharge process and cyclic voltammetry (CV) technique. It is found that metallic Co nanoparticles of 10-20 nm in size are highly dispersed on the amorphous inactive Si 3N 4 matrix after the ball-milling. The composite with a Co/Si molar ratio of 2/1 shows the optimized electrochemical performance, including discharge capacity and cycle stability. The formation of Co nanoparticles with a good reaction activity is responsible for the discharge capacity of the composites. The reversible faradic reaction between Co and β-Co(OH) 2 is dominant for ball-milled Co-Si 3N 4 composite. The surface modification of the hydrogen storage PrMg 12-Ni composites using Co-Si 3N 4 composites can enhance the initial discharge capacity based on the hydrogen electrochemical oxidation and Co redox reaction.

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

    SciTech Connect

    Gupta, Vinay Kawaguchi, Toshikazu; Miura, Norio

    2009-01-08

    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{sub 3}O{sub 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{sup 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.

  3. Preparation and characterization of nano-structured lead oxide from spent lead acid battery paste.

    PubMed

    Li, Lei; Zhu, Xinfeng; Yang, Danni; Gao, Linxia; Liu, Jianwen; Kumar, R Vasant; Yang, Jiakuan

    2012-02-15

    As part of contribution for developing a green recycling process of spent lead acid battery, a nanostructural lead oxide was prepared under the present investigation in low temperature calcination of lead citrate powder. The lead citrate, the precursor for preparation of this lead oxide, was synthesized through leaching of spent lead acid battery paste in citric acid solution. Both lead citrate and oxide products were characterized by means of thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The results showed that the lead citrate was sheet-shape crystal of Pb(C(6)H(6)O(7)) · H(2)O. When the citrate was calcined in N(2) gas, β-PbO in the orthorhombic phase was the main product containing small amount of Pb and C and it formed as spherical particles of 50-60 nm in diameter. On combusting the citrate in air at 370°C (for 20 min), a mixture of orthorhombic β-PbO, tetragonal α-PbO and Pb with the particle size of 100-200 nm was obtained, with β-PbO as the major product. The property of the nanostructural lead oxide was investigated by electrochemical technique, such as cyclic voltammetry (CV). The CV measurements presented the electrochemical redox potentials, with reversibility and cycle stability over 15 cycles. PMID:22209588

  4. Ascorbic Acid Assisted Synthesis of Cobalt Oxide Nanostructures, Their Electrochemical Sensing Application for the Sensitive Determination of Hydrazine

    NASA Astrophysics Data System (ADS)

    Tahira, Aneela; Nafady, Ayman; Baloach, Quarratulain; Sirajuddin; Sherazi, Syed Tufail Hussain; Shaikh, Tayyaba; Arain, Munazza; Willander, Magnus; Ibupoto, Zafar Hussain

    2016-07-01

    This study describes, the synthesis of cobalt oxide nanostructures using ascorbic acid as a growth directing agent by the hydrothermal method. Ascorbic acid is used for the first time for the synthesis of cobalt oxide nanostructures and a unique morphology is prepared in the present study. The cobalt oxide nanostructures were characterized by scanning electron microcopy, x-ray diffraction, and x-ray photoelectron spectroscopy techniques. These analytical techniques demonstrated well defined morphology, good crystalline quality, and high purity of as prepared cobalt oxide nanostructures. The glassy carbon electrode was modified with cobalt oxide nanostructures for the development of a sensitive and selective electrochemical hydrazine sensor. The developed hydrazine sensor exhibits a linear range of 2-24 μM. The sensitivity and limit of detection of presented hydrazine sensors are 12,734 μA/mM/cm2 and 0.1 μM respectively. The developed hydrazine sensor is highly selective, stable, and reproducible. The proposed sensor is successfully applied for the detection of hydrazine from different water samples. The present study provides the development of an alternative tool for the reliable monitoring of hydrazine from environmental and biological samples.

  5. Ascorbic Acid Assisted Synthesis of Cobalt Oxide Nanostructures, Their Electrochemical Sensing Application for the Sensitive Determination of Hydrazine

    NASA Astrophysics Data System (ADS)

    Tahira, Aneela; Nafady, Ayman; Baloach, Quarratulain; Sirajuddin; Sherazi, Syed Tufail Hussain; Shaikh, Tayyaba; Arain, Munazza; Willander, Magnus; Ibupoto, Zafar Hussain

    2016-04-01

    This study describes, the synthesis of cobalt oxide nanostructures using ascorbic acid as a growth directing agent by the hydrothermal method. Ascorbic acid is used for the first time for the synthesis of cobalt oxide nanostructures and a unique morphology is prepared in the present study. The cobalt oxide nanostructures were characterized by scanning electron microcopy, x-ray diffraction, and x-ray photoelectron spectroscopy techniques. These analytical techniques demonstrated well defined morphology, good crystalline quality, and high purity of as prepared cobalt oxide nanostructures. The glassy carbon electrode was modified with cobalt oxide nanostructures for the development of a sensitive and selective electrochemical hydrazine sensor. The developed hydrazine sensor exhibits a linear range of 2-24 μM. The sensitivity and limit of detection of presented hydrazine sensors are 12,734 μA/mM/cm2 and 0.1 μM respectively. The developed hydrazine sensor is highly selective, stable, and reproducible. The proposed sensor is successfully applied for the detection of hydrazine from different water samples. The present study provides the development of an alternative tool for the reliable monitoring of hydrazine from environmental and biological samples.

  6. Formulation and method for preparing gels comprising hydrous aluminum oxide

    SciTech Connect

    Collins, Jack L.

    2014-06-17

    Formulations useful for preparing hydrous aluminum oxide gels contain a metal salt including aluminum, an organic base, and a complexing agent. Methods for preparing gels containing hydrous aluminum oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including aluminum, an organic base, and a complexing agent.

  7. Formulation and method for preparing gels comprising hydrous cerium oxide

    DOEpatents

    Collins, Jack L; Chi, Anthony

    2013-05-07

    Formulations useful for preparing hydrous cerium oxide gels contain a metal salt including cerium, an organic base, and a complexing agent. Methods for preparing gels containing hydrous cerium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including cerium, an organic base, and a complexing agent.

  8. Formulation and method for preparing gels comprising hydrous hafnium oxide

    DOEpatents

    Collins, Jack L; Hunt, Rodney D; Montgomery, Frederick C

    2013-08-06

    Formulations useful for preparing hydrous hafnium oxide gels contain a metal salt including hafnium, an acid, an organic base, and a complexing agent. Methods for preparing gels containing hydrous hafnium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including hafnium, an acid, an organic base, and a complexing agent.

  9. A comparison between conductive-diamond electrochemical oxidation and other advanced oxidation processes for the treatment of synthetic melanoidins.

    PubMed

    Cañizares, P; Hernández-Ortega, M; Rodrigo, M A; Barrera-Díaz, C E; Roa-Morales, G; Sáez, C

    2009-05-15

    In this study, three technologies classified as Advanced Oxidation Processes (Conductive-Diamond Electrochemical Oxidation (CDEO), ozonation and Fenton oxidation) have been compared to treat wastes produced in fermentation processes, and characterized by a significant color and a high organic load. Results of CDEO seem to strongly depend on the addition of an electrolyte salt, not only to decrease the energy cost but also to improve efficiency. The addition of sodium chloride as supporting electrolyte improves the removal percentages of organic load, indicating the important role of mediated oxidation processes carried out by the electrogenerated oxidants (hypochlorite). Fenton oxidation and ozonation seem to be less efficient, and mainly Fenton oxidation favors the accumulation of refractory compounds. The differences observed can be explained in terms of the contribution of hydroxyl radicals and other specific oxidation mechanisms involved in each technology. PMID:18789836

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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. PMID:25966924

  12. Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems.

    PubMed

    Park, Min-Sik; Kim, Jeonghun; Kim, Ki Jae; Lee, Jong-Won; Kim, Jung Ho; Yamauchi, Yusuke

    2015-12-14

    Transition metal oxides possessing two kinds of metals (denoted as AxB3-xO4, which is generally defined as a spinel structure; A, B = Co, Ni, Zn, Mn, Fe, etc.), with stoichiometric or even non-stoichiometric compositions, have recently attracted great interest in electrochemical energy storage systems (ESSs). The spinel-type transition metal oxides exhibit outstanding electrochemical activity and stability, and thus, they can play a key role in realising cost-effective and environmentally friendly ESSs. Moreover, porous nanoarchitectures can offer a large number of electrochemically active sites and, at the same time, facilitate transport of charge carriers (electrons and ions) during energy storage reactions. In the design of spinel-type transition metal oxides for energy storage applications, therefore, nanostructural engineering is one of the most essential approaches to achieving high electrochemical performance in ESSs. In this perspective, we introduce spinel-type transition metal oxides with various transition metals and present recent research advances in material design of spinel-type transition metal oxides with tunable architectures (shape, porosity, and size) and compositions on the micro- and nano-scale. Furthermore, their technological applications as electrode materials for next-generation ESSs, including metal-air batteries, lithium-ion batteries, and supercapacitors, are discussed. PMID:26549729

  13. Ultra-thin films on transparent conductor oxides for the development of spectro-electrochemical transducers

    NASA Astrophysics Data System (ADS)

    Grigore, E.; Delacôte, C.; Thobie-Gautier, C.; Boujtita, M.; Tessier, P. Y.

    2013-07-01

    Transparent C, Au and Pt films with thickness in the 5-10 nm range have been deposited by a DC magnetron sputtering system on commercial ITO (indium tin oxide) coated glass substrate for evaluation as electrode of spectro-electrochemical transducer. The transmission, over the investigated spectral range, is superior to 55% with the best transmission values obtained for C films (higher than 80%). The deposited films have been characterized by AFM, XPS and electrochemical methods. Results showed a low roughness, improved in comparison with uncoated electrodes. Electrochemical properties of the Au and Pt films evidenced a metallic behavior, which allowed qualifying them as conductive optically transparent electrodes for spectro-electrochemical devices.

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

    PubMed

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

    2016-06-01

    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. PMID:27180820

  15. Preparation and characterization of nanostructured NiO/MnO{sub 2} composite electrode for electrochemical supercapacitors

    SciTech Connect

    Liu Enhui Li Wen; Li Jian; Meng Xiangyun; Ding Rui; Tan Songting

    2009-05-06

    Nanostructured nickel-manganese oxides composite was prepared by the sol-gel and the chemistry deposition combination new route. The surface morphology and structure of the composite were characterized by scanning electron microscope and X-ray diffraction. The as-synthesized NiO/MnO{sub 2} samples exhibit higher surface area of 130-190 m{sup 2} g{sup -1}. Cyclic voltammetry and galvanostatic charge/discharge measurements were applied to investigate the electrochemical performance of the composite electrodes with different ratios of NiO/MnO{sub 2}. When the mass ratio of MnO{sub 2} and NiO in composite material is 80:20, the specific capacitance value of NiO/MnO{sub 2} calculated from the cyclic voltammetry curves is 453 F g{sup -1}, for pure NiO and MnO{sub 2} are 209, 330 F g{sup -1} in 6 mol L{sup -1} KOH electrolyte and at scan rate of 10 mV s{sup -1}, respectively. The specific capacitance of NiO/MnO{sub 2} electrode is much larger than that of each pristine component. Moreover, the composite electrodes showed high power density and stable electrochemical properties.

  16. Simple room-temperature preparation of high-yield large-area graphene oxide.

    PubMed

    Huang, N M; Lim, H N; Chia, C H; Yarmo, M A; Muhamad, M R

    2011-01-01

    Graphene has attracted much attention from researchers due to its interesting mechanical, electrochemical, and electronic properties. It has many potential applications such as polymer filler, sensor, energy conversion, and energy storage devices. Graphene-based nanocomposites are under an intense spotlight amongst researchers. A large amount of graphene is required for preparation of such samples. Lately, graphene-based materials have been the target for fundamental life science investigations. Despite graphene being a much sought-after raw material, the drawbacks in the preparation of graphene are that it is a challenge amongst researchers to produce this material in a scalable quantity and that there is a concern about its safety. Thus, a simple and efficient method for the preparation of graphene oxide (GO) is greatly desired to address these problems. In this work, one-pot chemical oxidation of graphite was carried out at room temperature for the preparation of large-area GO with ~100% conversion. This high-conversion preparation of large-area GO was achieved using a simplified Hummer's method from large graphite flakes (an average flake size of 500 μm). It was found that a high degree of oxidation of graphite could be realized by stirring graphite in a mixture of acids and potassium permanganate, resulting in GO with large lateral dimension and area, which could reach up to 120 μm and ~8000 μm(2), respectively. The simplified Hummer's method provides a facile approach for the preparation of large-area GO. PMID:22267928

  17. Electrochemical functionalization of polypyrrole through amine oxidation of poly(amidoamine) dendrimers: Application to DNA biosensor.

    PubMed

    Miodek, Anna; Mejri-Omrani, Nawel; Khoder, Rabih; Korri-Youssoufi, Hafsa

    2016-07-01

    Electrochemical patterning method has been developed to fabricate composite based on polypyrrole (PPy) film and poly(amidoamine) dendrimers of fourth generation (PAMAM G4). PPy layer was generated using electrochemical polymerization of pyrrole on a gold electrode. PPy film was then modified with PAMAM G4 using amines electro-oxidation method. Covalent bonding of PAMAM G4 and the formation of PPy-PAMAM composite was characterized using Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). Ferrocenyl groups were then attached to such surface as a redox marker. Electrochemical properties of the modified nanomaterial (PPy-PAMAM-Fc) were studied using both amperometric and impedimetric methods to demonstrate the efficiency of electron transfer through the modified PPy layer. The obtained electrical and electrochemical properties were compared to a composite where PPy bearing carboxylic acid functions was chemically modified with PAMAM G4 by covalent attachment through formation of amid bond (PPy-CONH-PAMAM). The above mentioned studies showed that electrochemical patterning does not disturb the electronic properties of PPy. The effect of the number of functional groups introduced by the electrochemical patterning was demonstrated through the association of various compounds (ethylenediamine, PAMAM G2 and PAMAM G6). We demonstrated that such compounds could be applied in the biosensors technology. The modified PPy-PAMAM-Fc was evaluated as a platform for DNA sensing. High performance in the DNA detection by variation of the electrochemical signal of ferrocene was obtained with detection limit of 0.4 fM. Furthermore, such approach of electrochemical patterning by oxidation of amines could be applied for chemical modification of PPy and open a new way in various biosensing application involving functionalized PPy. PMID:27154698

  18. Method for preparing hydrous zirconium oxide gels and spherules

    DOEpatents

    Collins, Jack L.

    2003-08-05

    Methods for preparing hydrous zirconium oxide spherules, hydrous zirconium oxide gels such as gel slabs, films, capillary and electrophoresis gels, zirconium monohydrogen phosphate spherules, hydrous zirconium oxide spherules having suspendable particles homogeneously embedded within to form a composite sorbent, zirconium monohydrogen phosphate spherules having suspendable particles of at least one different sorbent homogeneously embedded within to form a composite sorbent having a desired crystallinity, zirconium oxide spherules having suspendable particles homogeneously embedded within to form a composite, hydrous zirconium oxide fiber materials, zirconium oxide fiber materials, hydrous zirconium oxide fiber materials having suspendable particles homogeneously embedded within to form a composite, zirconium oxide fiber materials having suspendable particles homogeneously embedded within to form a composite and spherules of barium zirconate. The hydrous zirconium oxide spherules and gel forms prepared by the gel-sphere, internal gelation process are useful as inorganic ion exchangers, catalysts, getters and ceramics.

  19. Preparation and electrochemical property of Fe3O4/MWCNT nanocomposite

    NASA Astrophysics Data System (ADS)

    Zhao, Tingkai; Ji, Xianglin; Guo, Xinai; Jin, Wenbo; Dang, Alei; Li, Hao; Li, Tiehu

    2016-06-01

    Ferroferric oxide (Fe3O4)/functionalized multi-walled carbon nanotube (f-MWCNT) nanomaterials were synthesized by chemical deposition & hydrothermal method. Fe3O4/f-MWCNT composites possess the same ferrimagnetism as pure Fe3O4, and the composites will present certain orientation in magnetism. The saturation magnetization (Ms) is about 48.84 emu g-1 and the coercivity (Hc) is 19.19 Oe. The electrochemical analysis displays that the glassy carbon electrode coated with Fe3O4/f-MWCNT composite has a favorable promotion for the electrochemical response of H2O2. This process not only widely improved the redox current of H2O2, but also reduced the overpotential of redox process.

  20. Preparation and properties of a compound containing nickel in highest oxidation states

    SciTech Connect

    Nikol'skii, V.A.; Bekreneva, L.A.; Garmash, L.A.; Makashev, Yu.A.; Mikhailova, K.A.; Raikhel'son, L.B.; Shchelkunova, L.I.

    1986-04-10

    The purpose of this paper is to obtain nickel hydroxide oxide of the optimal composition both by chemical and by electrochemical oxidation for use as the cathode material in alkaline batteries. The authors selected the oxidation conditions (oxidant, component ratio) for production of gamma-NiOOH; hydrogen peroxide, potassium permanganate, and potassium persulfate were used as oxidants. Gamma-NiOOH was also obtained by electrochemical oxidation of nickel (II) oxide hydrate in alkaline solutions. In samples obtained by electrochemical oxidation virtually 100% of the nickel is in the highly oxidized state. It is shown that gamma-NiOOH obtained by both chemical and electrochemical oxidation is a complex individual compound containing nickel and in the highest oxidation states, Ni/sup 3 +/ and Ni/sup 4 +/, together with salt-forming potassium ions and water molecules. The gamma-NiOOH obtained may be used with success in galvanic cells.

  1. Electrochemical protection of zirconium in oxidizing hydrochloric acid solutions

    SciTech Connect

    Yuu, T-L.; Maguire, M.

    1984-06-01

    An electrochemical protection technique using cathodic polarization to maintain zirconium below its critical repassivation potential was used to avoid pitting and stress corrosion cracking (SCC) in hydrochloric acid (HCI) containing ferric ions (Fe/sup +3/). Corrosion and pit penetration rates are reported for pickled, abraded, and as-received surface conditions in 10, 20, and 37% HCI containing 50, 100, or 500 ppm Fe/sup +3/ at temperatures to boiling. The pickled surface was the least susceptible to pitting in the 64 day tests. Electrochemical protection is then evaluated for total immersion, partial immersion, U-bend, and constant strain rate tensile tests. Protection is effective in eliminating pitting and SCC in 10 and 20% HCI containing Fe/sup +3/.

  2. Electrochemical protection of Zr against SCC by oxidizing HCl solutions

    SciTech Connect

    Yaiu, T.; Maguire, M.

    1985-07-01

    Results are reported for electrochemical protection of zirconium in HCl containing 500 ppm ferric ions. Corrosion rate and pit propagation rate data as a function of acid concentration (10 to 37%) and temperature (25 to 107 C) are presented first as a basis for observations of SCC and/or intergranular attack associated with weld metals. U-bend, C-ring, sustained load tensile, and slow strain-rate tests were used and compared to define conditions where SCC occurs. Along with electrochemical protection, heat treatment and reducing the ferric ion concentration are presented as ways to alleviate local attack. Metallography was used both to define the mode of attack and to show the benefits of protection techniques.

  3. A new method for manufacturing graphene and electrochemical characteristic of graphene-supported Pt nanoparticles in methanol oxidation

    NASA Astrophysics Data System (ADS)

    Kakaei, Karim; Zhiani, Mohammad

    2013-03-01

    We report a Pt/graphene catalyst for the methanol oxidation. Graphene is synthesized from graphite electrodes using ionic liquid-assisted electrochemical exfoliation. Graphene-supported Pt electrocatalyst is then reduced by sodium borohydride with ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) as a stabilizing agent to prepare highly dispersed Pt nanoparticles on carbon graphene to use as methanol oxidation in direct methanol fuel cell (DMFC) catalysts. X-ray diffractometer and scanning electron microscopy technique are used to investigate the crystallite size and the surface morphologies respectively. The electrochemical characteristics of the Pt/graphene and commercial Pt/C catalysts are investigated by cyclic voltammetry (CV) in nitrogen saturated sulfuric acid aqueous solutions and in mixed sulfuric acid and methanol aqueous solutions. The catalytic activities of the Pt/graphene and Pt/C electrodes for methanol oxidation is 1315 A g-1 Pt and 725 A g-1 Pt, which can be revealed the particular properties of the exfoliated graphene supports. Furthermore, Pt/graphene exhibited a better sensitivity, signal-to-noise ratio, and stability than commercial Pt/C.

  4. Electrochemical Preparation of Al-Li-Er-Tm Alloys by Co-reduction

    NASA Astrophysics Data System (ADS)

    Sun, Yi; Zhang, Milin; Han, Wei; Li, Mei; Ye, Ke; Yang, Yusheng; Yan, Yongde; Zhang, Meng

    2013-12-01

    The electrochemical behavior of Al, Li, Er, and Tm was investigated on tungsten electrodes in LiCl-KCl-AlF3-ErCl3-TmCl3 melts. The results indicated that the co-reduction of Al, Li, Er, and Tm occurs at current densities more negative than -0.469 A cm-2 or applied potentials more negative than -2.31 V. The strengthen phases of Al3Er and Al3Tm were prepared by galvanostatic electrolysis and characterized by X-ray diffraction and scanning electron microscopy. ICP-AES analyses showed that the content of lithium, erbium, and thulium in Al-Li-Er-Tm alloys could be controlled by adjusting AlF3 concentration and electrochemical parameters.

  5. Graphene as a signal amplifier for preparation of ultrasensitive electrochemical biosensors

    PubMed Central

    Filip, Jaroslav; Kasák, Peter; Tkac, Jan

    2016-01-01

    Early diagnostics of diseases performed with minimal money and time consumption has become achievable due to recent advances in development of biosensors. These devices use biorecognition elements for selective interaction with an analyte and signal readout is obtained via different types of transducers. Operational characteristics of biosensors have been reported to improve substantially, when a diverse range of nanomaterials was employed. This review presents construction of electrochemical biosensors based on graphene, atomically thin 2D carbon crystals, which is currently intensively studied nanomaterial. The most attractive directions of graphene applications in biosensor preparation are discussed here including novel detection and amplification schemes exploiting graphene’s unique electrochemical, physical and chemical properties. The future of graphene-based biosensors is most likely bright, but there is still a lot of work to do to fulfill high expectations. PMID:27242391

  6. Electrochemical and structural properties of radio frequency sputtered cobalt oxide electrodes for thin-film supercapacitors

    NASA Astrophysics Data System (ADS)

    Kim, Han-Ki; Seong, Tae-Yeon; Lim, Jae-Hong; Cho, Won, Ii; Soo Yoon, Young

    The electrochemical and structural properties of cobalt oxide films which are deposited at different sputtering gas-ratios of O 2/(Ar+O 2) are investigated. In order to examine the electrochemical properties of the as-deposited films, all solid-state thin-film supercapacitors (TFSCs) are fabricated. There consist of Co 3O 4 electrodes and an amorphous LiPON thin-film electrolyte. It is shown that the capacitance behaviour of the Co 3O 4/LiPON/Co 3O 4 TFSCs is similar to bulk-type supercapacitor behaviour. It is further shown that the electrochemical behaviour of the TFSCs is dependent on the sputtering gas-ratios. The gas-ratio dependence of the capacitance of the oxide electrode films is discussed based on X-ray diffraction (XRD) and electrical results for the Co 3O 4 films.

  7. Photo-electrochemical Oxidation of Organic C1 Molecules over WO3 Films in Aqueous Electrolyte: Competition Between Water Oxidation and C1 Oxidation.

    PubMed

    Reichert, Robert; Zambrzycki, Christian; Jusys, Zenonas; Behm, R Jürgen

    2015-11-01

    To better understand organic-molecule-assisted photo-electrochemical water splitting, photo-electrochemistry and on-line mass spectrometry measurements are used to investigate the photo-electrochemical oxidation of the C1 molecules methanol, formaldehyde, and formic acid over WO3 film anodes in aqueous solution and its competition with O2 evolution from water oxidation O2 (+) and CO2 (+) ion currents show that water oxidation is strongly suppressed by the organic species. Photo-electro-oxidation of formic acid is dominated by formation of CO2 , whereas incomplete oxidation of formaldehyde and methanol prevails, with the selectivity for CO2 formation increasing with increasing potential and light intensity. The mechanistic implications for the photo-electro-oxidation of the organic molecules and its competition with water oxidation, which could be derived from this novel approach, are discussed. PMID:26382643

  8. Phenolic compounds as enhancers in enzymatic and electrochemical oxidation of veratryl alcohol and lignins.

    PubMed

    Díaz-González, María; Vidal, Teresa; Tzanov, Tzanko

    2011-03-01

    Sixteen phenolic compounds, 14 of which naturally occurring, were compared to the synthetic 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and violuric acid (VA) in terms of their ability to act as mediators/enhancers in: (1) laccase oxidation of veratryl alcohol as a lignin model compound, and (2) electrochemical oxidation of kraft and flax lignins. HPLC analysis revealed that the syringyl-type phenols methyl syringate and acetosyringone were the most efficient natural enhancers in the laccase oxidation of veratryl alcohol. Both compounds, though far from the performance of ABTS were able to generate veratraldehyde in amount similar to that obtained with VA. By contrast, the best performing phenolic enhancers for the electrochemical oxidation of lignins were sinapinaldehyde, vanillin, acetovanillone, and syringic acid. Catalytic efficiencies close to those achieved with ABTS and VA were calculated for these phenolic compounds. PMID:21110019

  9. Electrochemical oxidation stability of anions for modern battery electrolytes: a CBS and DFT study.

    PubMed

    Jónsson, Erlendur; Johansson, Patrik

    2015-02-01

    The electrochemical stability vs. oxidation is a crucial property of anions in order to be suitable as components in lithium-ion batteries. Here the applicability of a number of computational approaches and methods to assess this property, employing a wide selection of DFT functionals, has been studied using the CCSD(T)/CBS method as the reference. In all, the vertical anion oxidation potential, ΔEv, is a fair way to calculate the stability vs. oxidation, however, a functional of at least hybrid quality is recommended. In addition, the chemical hardness, η, is identified as a novel approach to calculate the stability vs. oxidation. PMID:25557392

  10. Synthesis, optical and electrochemical properties of ZnO nanowires/graphene oxide heterostructures

    NASA Astrophysics Data System (ADS)

    Zeng, Huidan; Cao, Ying; Xie, Shufan; Yang, Junhe; Tang, Zhihong; Wang, Xianying; Sun, Luyi

    2013-03-01

    Large-scale vertically aligned ZnO nanowires with high crystal qualities were fabricated on thin graphene oxide films via a low temperature hydrothermal method. Room temperature photoluminescence results show that the ultraviolet emission of nanowires grown on graphene oxide films was greatly enhanced and the defect-related visible emission was suppressed, which can be attributed to the improved crystal quality and possible electron transfer between ZnO and graphene oxide. Electrochemical property measurement results demonstrated that the ZnO nanowires/graphene oxide have large integral area of cyclic voltammetry loop, indicating that such heterostructure is promising for application in supercapacitors.