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1

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...

2

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...

3

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

4

Electrochemical advanced oxidation for cold incineration of the pharmaceutical ranitidine: mineralization pathway and toxicity evolution.  

PubMed

Ranitidine (RNTD) is a widely prescribed histamine H2-receptor antagonist whose unambiguous presence in water sources appointed it as an emerging pollutant. Here, the degradation of 0.1 mM of this drug in aqueous medium was studied by electrochemical advanced oxidation processes (EAOPs) like anodic oxidation with electrogenerated H2O2 and electro-Fenton using Pt/carbon-felt, BDD/carbon-felt and DSA-Ti/RuO2–IrO2/carbon-felt cells. The higher oxidation power of the electro-Fenton process using a BDD anode was demonstrated. The oxidative degradation of RNTD by the electrochemically generated OH radicals obeyed a pseudo-first order kinetics. The absolute rate constant for its hydroxylation reaction was 3.39 × 109 M?1 s?1 as determined by the competition kinetics method. Almost complete mineralization of the RNTN solution was reached by using a BDD anode in both anodic oxidation with electrogenerated H2O2 and electro-Fenton processes. Up to 11 cyclic intermediates with furan moiety were detected from the degradation of RNTD, which were afterwards oxidized to short-chain carboxylic acids before their mineralization to CO2 and inorganic ions such as NH4+, NO3? and SO42?. Based on identified products, a plausible reaction pathway was proposed for RNTD mineralization. Toxicity assessment by the Microtox® method revealed that some cyclic intermediates are more toxic than the parent molecule. Toxicity was quickly removed following the almost total mineralization of the treated solution. Overall results confirm the effectiveness of EAOPs for the efficient removal of RNTD and its oxidation by-products from water. PMID:25461930

Olvera-Vargas, Hugo; Oturan, Nihal; Brillas, Enric; Buisson, Didier; Esposito, Giovanni; Oturan, Mehmet A

2014-12-01

5

Efficient removal of insecticide "imidacloprid" from water by electrochemical advanced oxidation processes.  

PubMed

The oxidative degradation of imidacloprid (ICP) has been carried out by electrochemical advanced oxidation processes (EAOPs), anodic oxidation, and electro-Fenton, in which hydroxyl radicals are generated electrocatalytically. Carbon-felt cathode and platinum or boron-doped diamond (BDD) anodes were used in electrolysis cell. To determine optimum operating conditions, the effects of applied current and catalyst concentration were investigated. The decay of ICP during the oxidative degradation was well fitted to pseudo-first-order reaction kinetics and absolute rate constant of the oxidation of ICP by hydroxyl radicals was found to be k abs(ICP)?=?1.23?×?10(9) L mol(-1) s(-1). The results showed that both anodic oxidation and electro-Fenton process with BDD anode exhibited high mineralization efficiency reaching 91 and 94% total organic carbon (TOC) removal at 2 h, respectively. For Pt-EF process, mineralization efficiency was also obtained as 71%. The degradation products of ICP were identified and a plausible general oxidation mechanism was proposed. Some of the main reaction intermediates such as 6-chloronicotinic acid, 6-chloronicotinaldehyde, and 6-hydroxynicotinic acid were determined by GC-MS analysis. Before complete mineralization, formic, acetic, oxalic, and glyoxylic acids were identified as end-products. The initial chlorine and organic nitrogen present in ICP were found to be converted to inorganic anions Cl(-), NO?(-), and NH?(+). PMID:24671401

Turabik, Meral; Oturan, Nihal; Gözmen, Belgin; Oturan, Mehmet A

2014-07-01

6

Electrochemical advanced oxidation and biological processes for wastewater treatment: a review of the combined approaches.  

PubMed

As pollution becomes one of the biggest environmental challenges of the twenty-first century, pollution of water threatens the very existence of humanity, making immediate action a priority. The most persistent and hazardous pollutants come from industrial and agricultural activities; therefore, effective treatment of this wastewater prior to discharge into the natural environment is the solution. Advanced oxidation processes (AOPs) have caused increased interest due to their ability to degrade hazardous substances in contrast to other methods, which mainly only transfer pollution from wastewater to sludge, a membrane filter, or an adsorbent. Among a great variety of different AOPs, a group of electrochemical advanced oxidation processes (EAOPs), including electro-Fenton, is emerging as an environmental-friendly and effective treatment process for the destruction of persistent hazardous contaminants. The only concern that slows down a large-scale implementation is energy consumption and related investment and operational costs. A combination of EAOPs with biological treatment is an interesting solution. In such a synergetic way, removal efficiency is maximized, while minimizing operational costs. The goal of this review is to present cutting-edge research for treatment of three common and problematic pollutants and effluents: dyes and textile wastewater, olive processing wastewater, and pharmaceuticals and hospital wastewater. Each of these types is regarded in terms of recent scientific research on individual electrochemical, individual biological and a combined synergetic treatment. PMID:24965093

Ganzenko, Oleksandra; Huguenot, David; van Hullebusch, Eric D; Esposito, Giovanni; Oturan, Mehmet A

2014-07-01

7

Application of electrochemical advanced oxidation processes to the mineralization of the herbicide diuron.  

PubMed

Here, solutions with 0.185mM of the herbicide diuron of pH 3.0 have been treated by electrochemical advanced oxidation processes (EAOPs) like electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF) or solar PEF (SPEF). Trials were performed in stirred tank reactors of 100mL and in a recirculation flow plant of 2.5L using a filter-press reactor with a Pt or boron-doped diamond (BDD) anode and an air-diffusion cathode for H2O2 electrogeneration. Oxidant hydroxyl radicals were formed from water oxidation at the anode and/or in the bulk from Fenton's reaction between added Fe(2+) and generated H2O2. In both systems, the relative oxidation ability of the EAOPs increased in the sequence EO-H2O2

Pipi, Angelo R F; Sirés, Ignasi; De Andrade, Adalgisa R; Brillas, Enric

2014-08-01

8

Mineralization of the recalcitrant oxalic and oxamic acids by electrochemical advanced oxidation processes using a boron-doped diamond anode.  

PubMed

Oxalic and oxamic acids are the ultimate and more persistent by-products of the degradation of N-aromatics by electrochemical advanced oxidation processes (EAOPs). In this paper, the kinetics and oxidative paths of these acids have been studied for several EAOPs using a boron-doped diamond (BDD) anode and a stainless steel or an air-diffusion cathode. Anodic oxidation (AO-BDD) in the presence of Fe(2+) (AO-BDD-Fe(2+)) and under UVA irradiation (AO-BDD-Fe(2+)-UVA), along with electro-Fenton (EF-BDD), was tested. The oxidation of both acids and their iron complexes on BDD was clarified by cyclic voltammetry. AO-BDD allowed the overall mineralization of oxalic acid, but oxamic acid was removed much more slowly. Each acid underwent a similar decay in AO-BDD-Fe(2+) and EF-BDD, as expected if its iron complexes were not attacked by hydroxyl radicals in the bulk. The faster and total mineralization of both acids was achieved in AO-BDD-Fe(2+)-UVA due to the high photoactivity of their Fe(III) complexes that were continuously regenerated by oxidation of their Fe(II) complexes. Oxamic acid always released a larger proportion of NH(4)(+) than NO(3)(-) ion, as well as volatile NO(x) species. Both acids were independently oxidized at the anode in AO-BDD, but in AO-BDD-Fe(2+)-UVA oxamic acid was more slowly degraded as its content decreased, without significant effect on oxalic acid decay. The increase in current density enhanced the oxidation power of the latter method, with loss of efficiency. High Fe(2+) contents inhibited the oxidation of Fe(II) complexes by the competitive oxidation of Fe(2+) to Fe(3+). Low current densities and Fe(2+) contents are preferable to remove more efficiently these acids by the most potent AO-BDD-Fe(2+)-UVA method. PMID:21477836

Garcia-Segura, Sergi; Brillas, Enric

2011-04-01

9

Electrochemical oxidation of wastewater - opportunities and drawbacks.  

PubMed

Electrochemical oxidation by means of boron-doped diamond (BDD) anodes generates a very efficient oxidizing environment by forming hydroxyl radicals, providing effective water purification for elimination of persistent pollutants. In this project the degradation rates of organic and inorganic substances are investigated. Experiments were performed in laboratory and pilot scale with synthetic and industrial wastewaters. Performance parameters were evaluated in terms of total organic carbon/chemical oxygen demand (COD) removal, specific energy consumption and current efficiency. The integration of this advanced oxidation technology combined with conventional technology was then applied in a wastewater treatment concept of landfill leachate. The raw leachate with a low biochemical oxygen demand/COD ratio was electrochemically oxidized to prepare the purified leachate for discharge into a sewage system or a receiving water body. The cost estimation regarding operation and capital costs addresses the economics for the treatment of heavily polluted effluents. PMID:24037171

Woisetschläger, D; Humpl, B; Koncar, M; Siebenhofer, M

2013-01-01

10

Electrochemical oxidation of chlorinated phenols  

SciTech Connect

Electrochemical oxidation has been proposed as a remediation method for chlorinated phenols but is hampered by anode fouling. In this work the authors explore the mechanism of anode fouling by chlorinated phenols, compare structure vs reactivity for phenols differing in the extent of chlorination, and relate the efficiency of oxidation to the mechanism of oxidation at different electrode types. Linear sweep voltammograms at a Pt anode at several concentrations, sweep rates, and pH were interpreted in terms of deposition of oligomers on the anode surface. Chronopotentiometry at Pt showed that the oxidation potentials of the chlorinated phenol congeners ranged from +0.6 to +1.3 V vs SHE in the pH range 2--12; four electrons are transferred for mono- and trichlorophenols and two for pentachlorophenol. Passivation increased in parallel with the uncompensated resistance of the solution and occurred only at potentials at which water is oxidized, suggesting that the formation of the oligomer film involves attack of hydroxyl radicals on electrochemically oxidized substrate. Seven chlorinated phenols were electrolyzed at PbO{sub 2}, SnO{sub 2}, and IrO{sub 2} anodes. Relative reactivities of congeners were anode-dependent, due to different mechanisms of oxidation: direct electron-transfer oxidation at PbO{sub 2} and hydroxyl radical attack at SnO{sub 2} and IrO{sub 2} At current densities <0.1 mA cm{sup {minus}2}, current efficiencies >50% could be achieved with 4-chlorophenol at all three anodes.

Rodgers, J.D.; Jedral, W.; Bunce, N.J. [Univ. of Guelph, Ontario (Canada). Dept. of Chemistry and Biochemistry] [Univ. of Guelph, Ontario (Canada). Dept. of Chemistry and Biochemistry

1999-05-01

11

Surface characterization of electrochemically oxidized carbon fibers  

Microsoft Academic Search

High strength PAN-based carbon fibers were continuously electrochemically oxidized by applying current to the fibers serving as an anode in 1% wt aqueous KNO3. Progressive fiber weight loss occurred with increasing extents of electrochemical oxidation. XPS studies (C 1s and O 1s) indicated that the oxygen\\/carbon atomic ratio rose rapidly to 0.24 as the extent of electrochemical oxidation was increased

Z. R. Yue; W. Jiang; L. Wang; S. D. Gardner; C PITTMANJR

1999-01-01

12

Dechlorination by combined electrochemical reduction and oxidation.  

PubMed

Chlorophenols are typical priority pollutants listed by USEPA (U.S. Environmental Protection Agency). The removal of chlorophenol could be carried out by a combination of electrochemical reduction and oxidation method. Results showed that it was feasible to degrade contaminants containing chlorine atoms by electrochemical reduction to form phenol, which was further degraded on the anode by electrochemical oxidation. Chlorophenol removal rate was more than 90% by the combined electrochemical reduction and oxidation at current of 6 mA and pH 6. The hydrogen atom is a powerful reducing agent that reductively dechlorinates chlorophenols. The instantaneous current efficiency was calculated and the results indicated that cathodic reduction was the main contributor to the degradation of chlorophenol. PMID:15909345

Cong, Yan-qing; Wu, Zu-cheng; Tan, Tian-en

2005-06-01

13

Toxicity assessment of the water used for human consumption from the Cameron/Tuba City abandoned uranium mining area prior/after the combined electrochemical treatment/advanced oxidation.  

PubMed

The purpose of this work was detailed physicochemical, radiological, and toxicological characterization of the composite sample of water intended for human consumption in the Cameron/Tuba City abandoned uranium mining area before and after a combined electrochemical/advanced oxidation treatment. Toxicological characterization was conducted on human lymphocytes using a battery of bioassays. On the bases of the tested parameters, it could be concluded that water used for drinking from the tested water sources must be strictly forbidden for human and/or animal consumption since it is extremely cytogenotoxic, with high oxidative stress potential. A combined electrochemical treatment and posttreatment with ozone and UV light decreased the level of all physicochemical and radiological parameters below the regulated values. Consequently, the purified sample was neither cytotoxic nor genotoxic, indicating that the presented method could be used for the improvement of water quality from the sites highly contaminated with the mixture of heavy metals and radionuclides. PMID:25087498

Gajski, Goran; Oreš?anin, Višnja; Geri?, Marko; Kollar, Robert; Lovren?i? Mikeli?, Ivanka; Garaj-Vrhovac, Vera

2015-01-01

14

Electrochemical Characterization of Vanadium Oxide Nanostructured Electrode  

E-print Network

Electrochemical Characterization of Vanadium Oxide Nanostructured Electrode Elsa A. Olivetti of a vanadium pentoxide i.e., V2O5 phase formed within a rubbery block copolymer were developed carbon:vanadium oxide ratio demonstrated higher rate capability for the nanocomposite sample when paired

Sadoway, Donald Robert

15

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

PubMed

A fibre-shaped solid electrochemical capacitor based on electrochemically reduced graphene oxide has been fabricated, exhibiting high specific capacitance and rate capability, long cycling life and attractive flexibility. PMID:23183591

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

2013-01-11

16

Fabrication of advanced electrochemical energy materials using sol-gel processing techniques  

NASA Technical Reports Server (NTRS)

Advanced materials play an important role in electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. They are being used as both electrodes and electrolytes. Sol-gel processing is a versatile solution technique used in fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. The application of sol-gel processing in the fabrication of advanced electrochemical energy materials will be presented. The potentials of sol-gel derived materials for electrochemical energy applications will be discussed along with some examples of successful applications. Sol-gel derived metal oxide electrode materials such as V2O5 cathodes have been demonstrated in solid-slate thin film batteries; solid electrolytes materials such as beta-alumina for advanced secondary batteries had been prepared by the sol-gel technique long time ago; and high surface area transition metal compounds for capacitive energy storage applications can also be synthesized with this method.

Chu, C. T.; Chu, Jay; Zheng, Haixing

1995-01-01

17

Capacitance studies of cobalt oxide films formed via electrochemical precipitation  

E-print Network

Capacitance studies of cobalt oxide films formed via electrochemical precipitation Venkat prepared by electrochemically precipitating the hydroxide and heating it in air to form Co3O4, it is desirable to study the generality of the electrochemical precipitation technique as a means of fab- ricating

Weidner, John W.

18

Solid oxide electrochemical cell fabrication process  

DOEpatents

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).

Dollard, Walter J. (Churchill Borough, PA); Folser, George R. (Lower Burrell, PA); Pal, Uday B. (Cambridge, MA); Singhal, Subhash C. (Murrysville, PA)

1992-01-01

19

Degradation of pharmaceutical beta-blockers by electrochemical advanced oxidation processes using a flow plant with a solar compound parabolic collector.  

PubMed

The degradation of the beta-blockers atenolol, metoprolol tartrate and propranolol hydrochloride was studied by electro-Fenton (EF) and solar photoelectro-Fenton (SPEF). Solutions of 10 L of 100 mg L?¹ of total organic carbon of each drug in 0.1 M Na?SO? with 0.5 mM Fe²? of pH 3.0 were treated in a recirculation flow plant with an electrochemical reactor coupled with a solar compound parabolic collector. Single Pt/carbon felt (CF) and boron-doped diamond (BDD)/air-diffusion electrode (ADE) cells and combined Pt/ADE-Pt/CF and BDD/ADE-Pt/CF cells were used. SPEF treatments were more potent with the latter cell, yielding 95-97% mineralization with 100% of maximum current efficiency and energy consumptions of about 0.250 kWh g TOC?¹. However, the Pt/ADE-Pt/CF cell gave much lower energy consumptions of about 0.080 kWh g TOC?¹ with slightly lower mineralization of 88-93%, then being more useful for its possible application at industrial level. The EF method led to a poorer mineralization and was more potent using the combined cells by the additional production of hydroxyl radicals (•OH) from Fenton's reaction from the fast Fe²? regeneration at the CF cathode. Organics were also more rapidly destroyed at BDD than at Pt anode. The decay kinetics of beta-blockers always followed a pseudo first-order reaction, although in SPEF, it was accelerated by the additional production of •OH from the action of UV light of solar irradiation. Aromatic intermediates were also destroyed by hydroxyl radicals. Ultimate carboxylic acids like oxalic and oxamic remained in the treated solutions by EF, but their Fe(III) complexes were photolyzed by solar irradiation in SPEF, thus explaining its higher oxidation power. NO?? was the predominant inorganic ion lost in EF, whereas the SPEF process favored the production of NH?? ion and volatile N-derivatives. PMID:21693380

Isarain-Chávez, Eloy; Rodríguez, Rosa María; Cabot, Pere Lluís; Centellas, Francesc; Arias, Conchita; Garrido, José Antonio; Brillas, Enric

2011-08-01

20

Oxidation of artificial sweetener sucralose by advanced oxidation processes: a review.  

PubMed

Sucralose, a chlorinated carbohydrate, has shown its increased use as an artificial sweetener and persistently exists in wastewater treatment plant effluents and aquatic environment. This paper aims to review possible degradation of sucralose and related carbohydrates by biological, electrochemical, chemical, and advanced oxidation processes. Biodegradation of sucralose in waterworks did not occur significantly. Electrochemical oxidation of carbohydrates may be applied to seek degradation of sucralose. The kinetics of the oxidation of sucralose and the related carbohydrates by different oxidative species is compared. Free chlorine, ozone, and ferrate did not show any potential to degrade sucralose in water. Advanced oxidation processes, generating highly strong oxidizing agent hydroxyl radicals ((•)OH), have demonstrated effectiveness in transforming sucralose in water. The mechanism of oxidation of sucralose by (•)OH is briefly discussed. PMID:24687789

Sharma, Virender K; Oturan, Mehmet; Kim, Hyunook

2014-07-01

21

Tutorial Review: Electrochemical Nitric Oxide Sensors for Physiological Measurements  

PubMed Central

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

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

2013-01-01

22

Technology advancement of the electrochemical CO2 concentrating process  

NASA Technical Reports Server (NTRS)

Two multicell, liquid-cooled, advanced electrochemical depolarized carbon dioxide concentrator modules were fabricated. The cells utilized advanced, lightweight, plated anode current collectors, internal liquid cooling and lightweight cell frames. Both were designed to meet the carbon dioxide removal requirements of one-person, i.e., 1.0 kg/d (2.2 lb/d).

Schubert, F. H.; Heppner, D. B.; Hallick, T. M.; Woods, R. R.

1979-01-01

23

Advanced materials and electrochemical processes in high-temperature solid electrolytes  

SciTech Connect

Fuel cells for the direct conversion of fossil fuels to electric energy necessitates the use of high-temperature solid electrodes. This study has included: (1) determination of electrical transport, thermal and electrical properties to illucidate the effects of microstructure, phase equilibria, oxygen partial pressure, additives, synthesis and fabrication on these properties; (2) investigation of synthesis and fabrication of advanced oxide materials, such as La{sub 0.9}Sn{sub 0.1}MnO{sub 3}; and (3) application of new analytical techniques using complex impedance coupled with conventional electrochemical methods to study the electrochemical processes and behavior of materials for solid oxide fuel cells and other high-temperature electrolyte electrochemical process. 15 refs., 10 figs., 2 tabs. (BM)

Bates, J.L.; Chick, L.A.; Youngblood, G.E.; Weber, W.J.

1990-10-01

24

Oxide modified air electrode surface for high temperature electrochemical cells  

DOEpatents

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.

Singh, Prabhakar (Export, PA); Ruka, Roswell J. (Churchill Boro, Allegheny County, PA)

1992-01-01

25

pH sensor properties of electrochemically grown iridium oxide  

Microsoft Academic Search

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

W. Olthuis; M. A. M. Robben; P. Bergveld; M. Bos; Linden van der W. E

1990-01-01

26

Plasmonic imaging of electrochemical oxidation of single nanoparticles.  

PubMed

Measuring electrochemical activities of nanomaterials is critical for creating novel catalysts, for developing ultrasensitive sensors, and for understanding fundamental nanoelectrochemistry. However, traditional electrochemical methods measure a large number of nanoparticles, which wash out the properties of individual nanoparticles. We report here a study of transient electrochemical oxidation of single Ag nanoparticles during collision with an electrode and voltammetry of single nanoparticles immobilized on the electrode using a plasmonic-based electrochemical current microscopy. This technique images both electrochemical reaction and size of the same individual nanoparticle, enabling quantitative examination of size-dependent electrochemical activities at single nanoparticle level. The imaging capability further allows detection of the reaction kinetics of each individual nanoparticle and analysis of the average behaviors of multiple nanoparticles. The average kinetics and size dependence can be accurately described by the Tafel equation, but there is a large variability between different nanoparticles, which underscores the importance of single nanoparticle analysis. PMID:25140732

Fang, Yimin; Wang, Wei; Wo, Xiang; Luo, Yashuang; Yin, Shaowei; Wang, Yixian; Shan, Xiaonan; Tao, Nongjian

2014-09-10

27

Innovative oxide materials for electrochemical energy conversion  

NASA Astrophysics Data System (ADS)

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.

Wachsman, Eric D.

2012-02-01

28

Technology advancement of the electrochemical CO2 concentrating process  

NASA Technical Reports Server (NTRS)

The overall objectives of the present program are to: (1) improve the performance of the electrochemical CO2 removal technique by increasing CO2 removal efficiencies at pCO2 levels below 400 Pa, increasing cell power output and broadening the tolerance of electrochemical cells for operation over wide ranges of cabin relative humidity; (2) design, fabricate, and assemble development hardware to continue the evolution of the electrochemical concentrating technique from the existing level to an advanced level able to efficiently meet the CO2 removal needs of a spacecraft air revitalization system (ARS); (3) develop and incorporate into the EDC the components and concepts that allow for the efficient integration of the electrochemical technique with other subsystems to form a spacecraft ARS; (4) combine ARS functions to enable the elimination of subsystem components and interfaces; and (5) demonstrate the integration concepts through actual operation of a functionally integrated ARS.

Schubert, F. H.; Woods, R. R.; Hallick, T. M.; Heppner, D. B.

1978-01-01

29

ADVANCED OXIDATION PROCESS  

SciTech Connect

The removal of recalcitrant sulfur species, dibenzothiophene and its derivatives, from automotive fuels is an integral component in the development of cleaner burning and more efficient automobile engines. Oxidative desulfurization (ODS) wherein the dibenzothiophene derivative is converted to its corresponding sulfoxide and sulfone is an attractive approach to sulfur removal because the oxidized species are easily extracted or precipitated and filtered from the hydrocarbon phase. Fe-TAML{reg_sign} activators of hydrogen peroxide (TAML is Tetra-Amido-Macrocyclic-Ligand) catalytically convert dibenzothiophene and its derivatives rapidly and effectively at moderate temperatures (50-60 C) and ambient pressure to the corresponding sulfoxides and sulfones. The oxidation process can be performed in both aqueous systems containing alcohols such as methanol, ethanol, or t-butanol, and in a two-phase hydrocarbon/aqueous system containing tert-butanol or acetonitrile. In the biphasic system, essentially complete conversion of the DBT to its oxidized products can be achieved using slightly longer reaction times than in homogeneous solution. Among the key features of the technology are the mild reaction conditions, the very high selectivity where no over oxidation of the sulfur compounds occurs, the near stoichiometric use of hydrogen peroxide, the apparent lack of degradation of sensitive fuel components, and the ease of separation of oxidized products.

Dr. Colin P. Horwitz; Dr. Terrence J. Collins

2003-11-04

30

Electrochemical and partial oxidation of methane  

NASA Astrophysics Data System (ADS)

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 negligible coke formation on the novel fabricated anode by electroless plating process. Hydrogen is an environmentally cleaner source of energy. The recent increase in the demand of hydrogen as fuel for all types of fuel cells and petroleum refining process has boosted the need of production of hydrogen. Methane, a major component of natural gas is the major feedstock for production of hydrogen. The route of partial oxidation of methane to produce syngas (CO + H2) offers significant advantages over commercialized steam reforming process for higher efficiency and lower energy requirements. Partial oxidation of methane was studied by pulsing O2 into a CH4 flow over Rh/Al2O3 in a sequence of in situ infrared (IR) cell and fixed bed reactor at 773 K. The results obtained from the sequence of an IR cell followed by a fixed bed reactor show that (i) adsorbed CO produced possesses a long residence time, indicating that adsorbed oxygen leading to the formation of CO is significantly different from those leading to CO2 and (ii) CO2 is not an intermediate species for the formation of CO. In situ IR of pulse reaction coupled with alternating reactor sequence is an effective approach to study the primary and secondary reactions as well as the nature of their adsorbed species. As reported earlier, hydrogen remains to be the most effective fuel for fuel cells, the production of high purity hydrogen from naturally available resources such as coal, petroleum, and natural gas requires a number of energy-intensive steps, making fuel cell processes for stationary electric power generation prohibitively uneconomic. Direct use of coal or coal gas as the feed is a promising approach for low cost electricity generation. Coal gas solid oxide fuel cell was studied by pyrolyzing Ohio #5 coal to coal gas and transporting to a Cu anode solid oxide fuel cell to generate power. The study of coal-gas solid oxide fuel cell is divided into two sections, i.e., (i) understanding the composition of coal gas by in situ infrared spectroscopy combined with mass spectrometry and (ii) evaluating the perfo

Singh, Rahul

2008-10-01

31

Technology advancement of the electrochemical CO2 concentrating process  

NASA Technical Reports Server (NTRS)

A five-cell, liquid-cooled advanced electrochemical depolarized carbon dioxide concentrator module was fabricated. The cells utilized the advanced, lightweight, plated anode current collector concept and internal liquid-cooling. The five cell module was designed to meet the carbon dioxide removal requirements of one man and was assembled using plexiglass endplates. This one-man module was tested as part of an integrated oxygen generation and recovery subsystem.

Schubert, F. H.; Woods, R. R.; Hallick, T. M.; Heppner, D. B.

1977-01-01

32

Size dependent electrochemical properties of reduced graphite oxide  

NASA Astrophysics Data System (ADS)

Size dependent electrochemical properties of reduced graphite oxide are investigated. Two kinds, 5 and 149 ?m, of natural graphite as a precursor are used to synthesize graphite oxide and to reduce it by hydrazine. The precursor of smaller grain size provides efficient oxidation and reduction, resulting in improved electrochemical properties compared to the precursor of larger grain size for energy storage applications. Furthermore, the influence of hydrazine concentration on the reduction is investigated, finding that too much hydrazine causes side effects on the reduction.

Tran, Minh-Hai; Yang, Cheol-Soo; Yang, Sunhye; Kim, Ick-Jun; Jeong, Hae Kyung

2014-07-01

33

ADVANCED OXIDATION PROCESS  

SciTech Connect

The design of new, high efficiency and cleaner burning engines is strongly coupled with the removal of recalcitrant sulfur species, dibenzothiophene and its derivatives, from fuels. Oxidative desulfurization (ODS) wherein these dibenzothiophene derivatives are oxidized to their corresponding sulfoxides and sulfones is an approach that has gained significant attention. Fe-TAML{reg_sign} activators of hydrogen peroxide (TAML is Tetra-Amido-Macrocyclic-Ligand) convert in a catalytic process dibenzothiophene and its derivatives to the corresponding sulfoxides and sulfones rapidly at moderate temperatures (60 C) and ambient pressure. The reaction can be performed in both an aqueous system containing an alcohol (methanol, ethanol, or t-butanol) to solubilize the DBT and in a two-phase hydrocarbon/aqueous system where the alcohol is present in both phases and facilitates the oxidation. Under a consistent set of conditions using the FeBF{sub 2} TAML activator, the degree of conversion was found to be t-butanol > methanol > ethanol. In the cases of methanol and ethanol, both the sulfoxide and sulfone were observed while for t-butanol only the sulfone was detected. In the two-phase system, the alcohol may function as an inverse phase transfer agent. The oxidation was carried out using two different TAML activators. In homogeneous solution, approximately 90% oxidation of the DBT could be achieved using the prototype TAML activator, FeB*, by sonicating the solution at near room temperature. In bi-phasic systems conversions as high as 50% were achieved using the FeB* TAML activator and hydrogen peroxide at 100 C. The sonication method yielded only {approx}6% conversion but this may have been due to mixing.

Colin P. Horwitz; Terrence J. Collins

2003-10-22

34

MODERN WATER TREATMENT BY ELECTROCHEMICAL OXIDATION- A REVIEW  

E-print Network

Electrochemical oxidation (EO) as electrochemical method is unique by three aspects. The first is that is the most versatility process in water treatment area and covers: various industrial effluent treatment including, amongst others, distillery, agrochemical, pulp and paper, textile dyes, oilfield and metalplating wastes; hazardous effluent treatment including hospital wastes; removal of pathogens and persistent, pharmaceutical residues and biological from municipal wastewater treatment plant; removal of organic micro-pollutants such as pesticides and heavy metals such as arsenic and chromium from water. Another aspect is that EO is complementary with most other methods: chemical or electrochemical, and is often combined with one or more of them. And finally, this procedure is the most interdisciplinary of all. It includes: material science, (micro)biology, (electro)chemistry, environmental protection, water supply systems, etc. Key words: electrochemical oxidation, electrooxidation, wastewaters, synergistic methods, interdisciplinary approach, ecology.

Silvana B. Dimitrijevi?; Stevan P. Dimitrijevi?; Milovan D. Vukovi?

35

Ultrasonically enhanced electrochemical oxidation of ibuprofen.  

PubMed

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

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

2015-01-01

36

Electrochemical behavior of sintered oxide dispersion strengthened stainless steels  

Microsoft Academic Search

The electrochemical behavior of powder metallurgy (P\\/M) oxide dispersion strengthened stainless steels (SS) (316L and 434L) have been compared with standard 430 and 316 wrought samples in 0.05 mol\\/l sulfuric acid. The effects of sintering temperature and yttria addition on the electrochemical behavior have been studied. The behaviour of the dispersion strengthened SS was comparable to that of the straight

J Shankar; A Upadhyaya; R Balasubramaniam

2004-01-01

37

Cobalt vanadium oxide thin nanoplates: primary electrochemical capacitor application  

PubMed Central

Co3V2O8 thin nanoplates are firstly described as a kind of electrode material for supercapacitors. More importantly, from electrochemical measurements, the obtained Co3V2O8 nanoplate electrode shows a good specific capacitance (0.5?A g?1, 739?F g?1) and cycling stability (704?F g?1 retained after 2000 cycles). This study essentially offers a new kind of metal vanadium oxides as electrochemical active material for the development of supercapacitors. PMID:25023373

Zhang, Youjuan; Liu, Yuanying; Chen, Jing; Guo, Qifei; Wang, Ting; Pang, Huan

2014-01-01

38

Nanostructured Mn-based oxides for electrochemical energy storage and conversion.  

PubMed

Batteries and supercapacitors as electrochemical energy storage and conversion devices are continuously serving for human life. The electrochemical performance of batteries and supercapacitors depends in large part on the active materials in electrodes. As an important family, Mn-based oxides have shown versatile applications in primary batteries, secondary batteries, metal-air batteries, and pseudocapacitors due to their high activity, high abundance, low price, and environmental friendliness. In order to meet future market demand, it is essential and urgent to make further improvements in energy and power densities of Mn-based electrode materials with the consideration of multiple electron reaction and low molecular weight of the active materials. Meanwhile, nanomaterials are favourable to achieve high performance by means of shortening the ionic diffusion length and providing large surface areas for electrode reactions. This article reviews the recent efforts made to apply nanostructured Mn-based oxides for batteries and pseudocapacitors. The influence of structure, morphology, and composition on electrochemical performance has been systematically summarized. Compared to bulk materials and notable metal catalysts, nanostructured Mn-based oxides can promote the thermodynamics and kinetics of the electrochemical reactions occurring at the solid-liquid or the solid-liquid-gas interface. In particular, nanostructured Mn-based oxides such as one-dimensional MnO2 nanostructures, MnO2-conductive matrix nanocomposites, concentration-gradient structured layered Li-rich Mn-based oxides, porous LiNi0.5Mn1.5O4 nanorods, core-shell structured LiMnSiO4@C nanocomposites, spinel-type Co-Mn-O nanoparticles, and perovskite-type CaMnO3 with micro-nano structures all display superior electrochemical performance. This review should shed light on the sustainable development of advanced batteries and pseudocapacitors with nanostructured Mn-based oxides. PMID:25200459

Zhang, Kai; Han, Xiaopeng; Hu, Zhe; Zhang, Xiaolong; Tao, Zhanliang; Chen, Jun

2015-01-26

39

Electrochemical oxidation of californium in carbonae solutions  

Microsoft Academic Search

The electrolysis of trivalent californium, terbium and praseodimium in 2M K2CO3 solutions at pH 13.2 results in a partial oxidation of the trivalent ions to a higher oxidation state. Absorption spectra of Cf\\/III\\/ in 1M HCLO4 and in 2M K2O3 and that of oxidized californium in carbonate solution have been recorded. Incomplete oxidation is accounted to a reducing species generated

V. Ya. Frenkel; Yu. M. Kulyako; V. M. Chistyakov; I. A. Lebedev; B. F. Myasoedov; G. A. Timofeev; E. A. Erin

1986-01-01

40

Corrosion and Electrochemical Oxidation of a Pyrite by Thiobacillus ferrooxidans  

PubMed Central

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

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

1992-01-01

41

Hydrous ruthenium oxide as an electrode material for electrochemical capacitors  

Microsoft Academic Search

The hydrous ruthenium oxide has been formed by a sol-gel process. The precursor was obtained by mixing aqueous solutions of RuClâ·xHâO and alkalis. The hydrous ruthenium oxide powder was obtained by annealing the precursor at low temperatures. The crystalline structure and the electrochemical properties of the powder have been studied as a function of the annealing temperature. At lower annealing

J. P. Zheng; P. J. Cygan; T. R. Jow

1995-01-01

42

Electrochemical oxidation of imazapyr with BDD electrode in titanium substrate.  

PubMed

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

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

43

Method of electrode fabrication for solid oxide electrochemical cells  

DOEpatents

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.

Jensen, R.R.

1990-11-20

44

Method of electrode fabrication for solid oxide electrochemical cells  

DOEpatents

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.

Jensen, Russell R. (Murrysville, PA)

1990-01-01

45

Electrochemical Properties of Tungsten Oxide Nanowires Compared to Bulk Particles  

NASA Astrophysics Data System (ADS)

The electrochemical properties of oxygen-deficient tungsten oxide (W18O49) nanowires were investigated. The nanowires were prepared via a simple thermal evaporation method. The as-deposited nanowires were 60-90 nm in diameter and several micrometers long as measured by field-emission scanning electron microscopy. The crystal structure was indexed to the monoclinic W18O49 phase. The electrochemical properties of the nanowires and WO3 bulk particles were examined by cyclic voltammetry between 2 and 4 V vs Li/Li+. We found that the nanowires cycle better than the bulk particles.

Meda, Lamartine; Dangerfield, Aaron M.; Jones, Mila'na C.; White, Christian M.; Navulla, Anantharamulu

2012-11-01

46

Electrochemical patterning of tin oxide films  

Microsoft Academic Search

Interest in tin oxide films has grown recently because of their potential application for solar cell structures. The high conductivity of doped tin oxide, coupled with a high transmission coefficient to light from wavelengths in the violet into the infrared, makes it well suited for transparent conductive antireflection coatings and for forming heterojunctions with silicon or gallium arsenide. An additional

B. Jayant Baliga; S. K. Ghandhi

1977-01-01

47

Electrochemical and Structural Characterization of Nickel based Alloys Oxides  

NASA Astrophysics Data System (ADS)

The electrochemical and structural characterization of thermally grown oxides formed on nickel based alloys (type Inconel 600 and 690) at 350 °C and during different time was performed by impedance measurements and near field microscopy combining atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM). The impedance results allow discussing the influence of the oxidation time on the capacitance and the resistance of the oxide films. The results obtained by near field microscopy technique show that the film formed during low oxidation time has a small grain size and also a small surface roughness. The values of grain sizes determined in both cases along x- and y-axis are practically the same indicating a spherical shape of oxide grains and are slightly different between oxides formed on type inconel 600 and 690.

Hakiki, N. E.; Bubendorff, J. L.; Pirri, C.; Mechehoud, F.; Mehdaoui, A.; Belhadji, M.

48

Solid oxide materials research accelerated electrochemical testing  

SciTech Connect

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

Armstrong, T.R.; Windisch, C.; Arey, B.

1995-12-31

49

Preparation and electrochemical properties of Ce-Ru-SnO2 ternary oxide anode and electrochemical oxidation of nitrophenols.  

PubMed

A cerium doped ternary SnO(2) based oxides anode that is CeO(2)-RuO(2)-SnO(2) (Ce-Ru-SnO(2)) anode, was prepared by facile thermal decomposition technique. XRD was used to characterize the crystal structures of modified SnO(2) anodes. Electrochemical impedance spectroscopy (EIS) and accelerated life test were also utilized to study the electrochemical property of Ce-Ru-SnO(2) anode. The results indicated that Ce-Ru-SnO(2) anode possessed smaller charge transfer resistance and longer service life than other modified SnO(2) anodes. Oxidants, such as hydroxyl radicals, hydrogen peroxide and hypochlorite ions were determined. Electrochemical oxidation of nitrophenols (NPs) were conducted and compared with previous studies. The degradation of nitrophenols revealed two distinguishing laws for mononitrophenol and multinitrophenols. The Ce-Ru-SnO(2) anode is considered to be a promising material for the treatment of organic pollutants due to its high electrochemical activity and benign stability. PMID:22365388

Liu, Yuan; Liu, Huiling; Ma, Jun; Li, Junjing

2012-04-30

50

Sol-gel Technology and Advanced Electrochemical Energy Storage Materials  

NASA Technical Reports Server (NTRS)

Advanced materials play an important role in the development of electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. The sol-gel process is a versatile solution for use in the fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. This processing technique is particularly useful in producing porous materials with high surface area and low density, two of the most desirable characteristics for electrode materials. In addition,the porous surface of gels can be modified chemically to create tailored surface properties, and inorganic/organic micro-composites can be prepared for improved material performance device fabrication. Applications of several sol-gel derived electrode materials in different energy storage devices are illustrated in this paper. V2O5 gels are shown to be a promising cathode material for solid state lithium batteries. Carbon aerogels, amorphous RuO2 gels and sol-gel derived hafnium compounds have been studied as electrode materials for high energy density and high power density electrochemical capacitors.

Chu, Chung-tse; Zheng, Haixing

1996-01-01

51

Direct electrochemical reduction of metal-oxides  

DOEpatents

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.

Redey, Laszlo I. (Downers Grove, IL); Gourishankar, Karthick (Downers Grove, IL)

2003-01-01

52

Degradation of conazole fungicides in water by electrochemical oxidation.  

PubMed

The electrochemical oxidation (EO) treatment in water of three conazole fungicides, myclobutanil, triadimefon and propiconazole, has been carried out at constant current using a BDD/SS system. First, solutions of each fungicide were electrolyzed to assess the effect of the experimental parameters such as current, pH and fungicide concentration on the decay of each compound and total organic carbon abatement. Then a careful analysis of the degradation by-products was made by high performance liquid chromatography, ion chromatography and gas chromatography coupled with mass spectrometry in order to provide a detailed discussion on the original reaction pathways. Thus, during the degradation of conazole fungicides by the electrochemical oxidation process, aromatic intermediates, aliphatic carboxylic acids and Cl(-) were detected prior to their complete mineralization to CO2 while NO3(-) anions remained in the treated solution. This is an essential preliminary step towards the applicability of the EO processes for the treatment of wastewater containing conazole fungicides. PMID:24140400

Urzúa, J; González-Vargas, C; Sepúlveda, F; Ureta-Zañartu, M S; Salazar, R

2013-11-01

53

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

PubMed

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

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

2014-11-01

54

Facile and controllable electrochemical reduction of graphene oxide and its applications  

Microsoft Academic Search

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

Yuyan Shao; Jun Wang; Mark H. Engelhard; Chongmin Wang; Yuehe Lin

2010-01-01

55

Advances in solid oxide fuel cell technology  

Microsoft Academic Search

High temperature solid oxide fuel cells (SOFCs) offer a clean, pollution-free technology to electrochemically generate electricity at high efficiencies. These fuel cells provide many advantages over traditional energy conversion systems including high efficiency, reliability, modularity, fuel adaptability, and very low levels of NOx and SOx emissions. Furthermore, because of their high temperature of operation (?1000°C), natural gas fuel can be

S. C. Singhal

2000-01-01

56

Electrochemical oxidation of 5-hydroxytryptophol. I: Studies in acid solution.  

PubMed

The oxidation chemistry of the endogenous central nervous system indole 5-hydroxytryptophol (5-HTOL) has been studied at pH 2 using electrochemical methods. The first voltammetric oxidation peak (I) appears to involve an initial one-electron abstraction giving a transient radical cation that, in the rate-controlling step, deprotonates to give a neutral radical. A radical-substrate reaction then occurs to give a dimer radical which is further oxidized to yield three simple dimers (4,4'-,4,6'-, and 2,4'-linked). The neutral radical can be further oxidized (1e) to a quinone imine that, as a result of very fast follow-up chemistry and electrochemistry, yields tryptophol-4,5-dione (B) which has been isolated in pure form. Reactions between intermediate species also result in three dimers containing residues of 5-HTOL and B and an unusual oxygen-bridged trimer. PMID:2338638

Cheng, F C; Dryhurst, G

1990-03-01

57

Preparation and physicochemical and electrochemical characterization of exfoliated graphite oxide.  

PubMed

Exfoliated graphite oxide (EGO) is prepared by oxidizing exfoliated graphite (EG) using a mixture of KMnO(4)/H(2)SO(4). The physicochemical characterization of the EGO has been carried out using FT-Raman, FT-IR, XPS, NMR, and diffraction techniques. Colloidal form of EGO is subsequently prepared by ultrasonicating EGO in water. Thin films of EGO on a glassy carbon/gold surface are formed and the electrochemical and ion exchange properties have been studied using various redox systems such as K(4)[Fe(CN)(6)], ascorbic acid, and dopamine. The charge-based adsorption properties can be made use of, to either suppress or catalyze ascorbic acid oxidation. Adsorption and preconcentration of dopamine on the EGO film has been shown to electrocatalyze the oxidation of NADH. PMID:15120282

Ramesh, P; Bhagyalakshmi, S; Sampath, S

2004-06-01

58

ENCH 473 Electrochemical Energy Engineering ENCH 648K Advanced Batteries and Fuel Cells  

E-print Network

titration 4. Principle of battery 5. Li-ion batteries 6. Li-S and Li-air batteries 7. Flow batteries 8ENCH 473 Electrochemical Energy Engineering ENCH 648K Advanced Batteries and Fuel Cells Spring 2014 Syllabus Course: ENCH 473 Electrochemical Energy Engineering ENCH: 648K Advanced Batteries and Fuel Cells

Rubloff, Gary W.

59

Fabrication of solid oxide fuel cell by electrochemical vapor deposition  

DOEpatents

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.

Brian, Riley (Willimantic, CT); Szreders, Bernard E. (Oakdale, CT)

1989-01-01

60

Fabrication of solid oxide fuel cell by electrochemical vapor deposition  

DOEpatents

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.

Riley, B.; Szreders, B.E.

1988-04-26

61

The electrochemical oxidation of organic selenides and selenoxides  

SciTech Connect

The electrochemical oxidation of alkyl and aryl selenides was investigated in acetonitrile. The oxidation of diphenyl selenide and di(4-methylphenyl) selenide led primarily to the formation of their respective selenoxides, which were identified by exhaustive coulometric oxidation and {sup 1}H and {sup 13}C analysis of the products. The selenoxide itself was not observed in the cyclic voltammetry of the selenide for two reasons: first, the protonation of the selenoxide by the acid formed from the reaction of water with the cation radical and second, the formation of a selenoxide hydrate. The formation of the hydrate with diphenyl selenoxide was verified by isolation of the dimethoxy derivative. In addition to the selenoxide, selenonium compounds, formed by the coupling of the oxidized material, were also observed. The alkyl selenides were generally oxidized at a lower potential than the aryl selenides. This trend is different from the sulfur analogues, where the aryl sulfides are easier to oxidize than their alkyl counterparts. As a result, the difference in their redox potentials is relatively small. These differences may occur because the oxidation of aryl sulfides is more likely to take place on the aromatic ring, which leads to a greater yield of the coupled products (about 100%) when compared to the selenide analogue.

Ryan, M.D.; Yau, J.; Hack, M. [Marquette Univ., Milwaukee, WI (United States). Dept. of Chemistry

1997-06-01

62

Electrochemical oxidation of benzene on boron-doped diamond electrodes.  

PubMed

This work presents an electrochemical investigation of the benzene oxidation process in aqueous solution on boron-doped diamond (BDD) electrodes. Additionally, in order to determine the main products generated during the oxidation process, electrolysis and high performance liquid chromatography experiments were carried out. The complete degradation of this compound was performed aiming to a further application in waste water treatment. The cyclic voltammetry studies indicate that benzene is irreversibly oxidized in acid medium (H2SO4 0.5 M) on the BDD electrode surface at 2.0 V versus Ag/AgCl in a diffusion controlled process. During the cycling, other products are generated, and a pair of peaks was observed that can be associated with the oxi-reduction of anyone of the following species: hydroquinone, benzoquinone, resorcinol or catechol. The electrolysis experiments were carried out at 2.4 and 2.5 V on the BDD electrode surface in a solution containing 1x10(-2) M of benzene (below the saturation concentration in aqueous solution), for 3 and 5 h, respectively. The main products measured were: hydroquinone, resorcinol, p-benzoquinone, catechol and phenol. The complete electrochemical benzene degradation was performed in the electrolysis experiments using a rotating BDD disc electrode (2.5 V for 5 h) and the main products detected were all measured at concentrations lower than 10(-5) M in this condition. The boron-doped diamond electrode had proved to be a valuable tool for the electrochemical degradation of the benzene, a very stable chemical compound. PMID:17126378

Oliveira, Robson T S; Salazar-Banda, Giancarlo R; Santos, Mauro C; Calegaro, Marcelo L; Miwa, Douglas W; Machado, Sergio A S; Avaca, Luis A

2007-02-01

63

Platinum Electrodeposition at Unsupported Electrochemically Reduced Nanographene Oxide for Enhanced Ammonia Oxidation  

PubMed Central

The electrochemical reduction of highly oxidized unsupported graphene oxide nanosheets and its platinum electrodeposition was done by the rotating disk slurry electrode technique. Avoiding the use of a solid electrode, graphene oxide was electrochemically reduced in a slurry solution with a scalable process without the use of a reducing agent. Graphene oxide nanosheets were synthesized from carbon platelet nanofibers to obtain highly hydrophilic layers of less than 250 nm in width. The graphene oxide and electrochemically reduced graphene oxide/Pt (erGOx/Pt) hybrid materials were characterized through different spectroscopy and microscopy techniques. Pt nanoparticles with 100 facets, clusters, and atoms at erGOx were identified by high resolution transmission electron microscopy (HRTEM). Cyclic voltammetry was used to characterize the electrocatalytic activity of the highly dispersed erGOx/Pt hybrid material toward the oxidation of ammonia, which showed a 5-fold current density increase when compared with commercially available Vulcan/Pt 20%. This is in agreement with having Pt (100) facets present in the HRTEM images of the erGOx/Pt material. PMID:24417177

2015-01-01

64

Corner heating in rectangular solid oxide electrochemical cell generators  

DOEpatents

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.

Reichner, Philip (Plum Boro, PA)

1989-01-01

65

Kinetic model of the electrochemical oxidation of graphitic carbon in acidic environments.  

PubMed

The electrochemical oxidation of graphitic carbon results in the performance decay of electrochemical systems such as aqueous, acidic fuel cells, redox-flow batteries, and supercapacitors. An electrochemical mechanism and numerical model is proposed to explain long-standing questions. The model predicts carbon weight loss and surface oxide growth as a function of time, temperature, and potential. Experimentally observed phenomena are discussed and analyzed using the numerical model. Three mechanisms are concluded to contribute to the current decay commonly observed during electrochemical oxidation: mass loss, reversible passive oxide formation, and irreversible oxide formation. Although reversible passive oxide formation governs the current decay under potentiostatic oxidation, a reduction in the equilibrium catalytic oxide is the most significant decay mechanism under potential cycling. Finally, the model is used to determine the change in active site concentration resulting from high-temperature heat treatment of carbon black. PMID:20024428

Gallagher, Kevin G; Fuller, Thomas F

2009-12-28

66

Mediated Electrochemical Oxidation (MEO) based technology. Final report  

SciTech Connect

The goal of this CRADA was the continued research and development by LLNL, and the commercialization by EOSystems, Inc., of the waste treatment technology known as Mediated Electrochemical Oxidation. MEO is a non-thermal electrochemical technology developed in part at LLNL for the destruction of organic waste streams; this technology has wide applications in the government, manufacturing, biomedical and industrial sectors. The system uses an electrochemical cell to generate highly oxidizing {open_quote}mediators{close_quote} in an acidic aqueous solution, which subsequently react with organic waste and convert it to carbon dioxide and water. The broad research responsibilities of LLNL in this CRADA were the investigation of numerous cell electrode materials and materials of construction, the evaluation of the process chemistry, and the testing of a flow visualization cell and a functional prototype. Major deliverables included: a determination of suitable electrode materials, an investigation of the destruction efficiency for numerous organic substrates, the construction and testing of a flow visualization cell, and the testing of a functional prototype commercial cell. The responsibilities of EOSystems included the definition of the market and potential customers, the design and engineering of the flow visualization and prototype cells, and the commercialization of the MEO units. Deliverables included the selection of the process and ancillary systems, the design of a flow visualization cell, and the design and construction of a prototype cell. In general, most of the deliverables were met by both partners, although unexpected technical difficulties delayed some of the delivery dates and forced the adoption of a modified statement of work. However, the primary, original project goals were completed on-time and on-budget.

NONE

1996-07-18

67

Redox deposition of nanoscale metal oxides on carbon for next-generation electrochemical capacitors.  

PubMed

Transition metal oxides that mix electronic and ionic conductivity are essential active components of many electrochemical charge-storage devices, ranging from primary alkaline cells to more advanced rechargeable Li-ion batteries. In these devices, charge storage occurs via cation-insertion/deinsertion mechanisms in conjunction with the reduction/oxidation of metal sites in the oxide. Batteries that incorporate such metal oxides are typically designed for high specific energy, but not necessarily for high specific power. Electrochemical capacitors (ECs), which are typically composed of symmetric high-surface-area carbon electrodes that store charge via double-layer capacitance, deliver their energy in time scales of seconds, but at much lower specific energy than batteries. The fast, reversible faradaic reactions (typically described as "pseudocapacitance") of particular nanoscale metal oxides (e.g., ruthenium and manganese oxides) provide a strategy for bridging the power/energy performance gap between batteries and conventional ECs. These processes enhance charge-storage capacity to boost specific energy, while maintaining the few-second timescale of the charge-discharge response of carbon-based ECs. In this Account, we describe three examples of redox-based deposition of EC-relevant metal oxides (MnO2, FeOx, and RuO2) and discuss their potential deployment in next-generation ECs that use aqueous electrolytes. To extract the maximum pseudocapacitance functionality of metal oxides, one must carefully consider how they are synthesized and subsequently integrated into practical electrode structures. Expressing the metal oxide in a nanoscale form often enhances electrochemical utilization (maximizing specific capacitance) and facilitates high-rate operation for both charge and discharge. The "wiring" of the metal oxide, in terms of both electron and ion transport, when fabricated into a practical electrode architecture, is also a critical design parameter for achieving characteristic EC charge-discharge timescales. For example, conductive carbon must often be combined with the poorly conductive metal oxides to provide long-range electron pathways through the electrode. However, the ad hoc mixing of discrete carbon and oxide powders into composite electrodes may not support optimal utilization or rate performance. As an alternative, nanoscale metal oxides of interest for ECs can be synthesized directly on the surfaces of nanostructured carbons, with the carbon surface acting as a sacrificial reductant when exposed to a solution-phase, oxidizing precursor of the desired metal oxide (e.g., MnO4(-) for MnO2). These redox deposition methods can be applied to advanced carbon nanoarchitectures with well-designed pore structures. These architectures promote effective electrolyte infiltration and ion transport to the nanoscale metal oxide domains within the electrode architecture, which further enhances high-rate operation. PMID:22380783

Sassin, Megan B; Chervin, Christopher N; Rolison, Debra R; Long, Jeffrey W

2013-05-21

68

Oxidation of advanced steam turbine alloys  

SciTech Connect

Advanced or ultra supercritical (USC) steam power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections.

Holcomb, G.R.; Covino, B.S., Jr.; Bullard, S.J.; Ziomek-Moroz, M.

2006-03-01

69

Electrochemical oxidation of a textile dye wastewater using a Pt\\/Ti electrode  

Microsoft Academic Search

Textile dye wastewater (TDW) from a reactive azo dyeing process was treated by an electrochemical oxidation method using Ti\\/Pt as anode and stainless steel 304 as cathode. Due to the strong oxidizing potential of the chemicals produced (chlorine, oxygen, hydroxyl radicals and other oxidants) when the wastewater was passed through the electrolytic cell the organic pollutants were oxidized to carbon

A. G Vlyssides; M Loizidou; P. K Karlis; A. A Zorpas; D Papaioannou

1999-01-01

70

Surface reactivity of polypyrrole\\/iron-oxide nanoparticles: electrochemical and CS-AFM investigations  

Microsoft Academic Search

Composite materials based on iron-oxide nanoparticles (magnetite, hematite, and maghemite) and tetraoxalate-doped polypyrrole\\u000a (PPy) were electrochemically generated from aqueous solutions. Their composition was determined using electrochemical quartz\\u000a crystal microbalance experiments. The oxide percentage in mass was found to vary from 17 to 27% depending on the oxide identity.\\u000a They were all shown to be fascinating candidates as protective materials against

A. Pailleret; N. T. L. Hien; D. T. M. Thanh; C. Deslouis

2007-01-01

71

Mechanism of p-substituted phenol oxidation at a Ti4O7 reactive electrochemical membrane.  

PubMed

This research investigated the removal mechanisms of p-nitrophenol, p-methoxyphenol, and p-benzoquinone at a porous Ti4O7 reactive electrochemical membrane (REM) under anodic polarization. Cross-flow filtration experiments and density functional theory (DFT) calculations indicated that p-benzoquinone removal was primarily due to reaction with electrochemically formed OH(•), while the dominant removal mechanism of p-nitrophenol and p-methoxyphenol was a function of the anodic potential. At low anodic potentials (1.7-1.8 V/SHE), p-nitrophenol and p-methoxyphenol were removed primarily by an electrochemical adsorption/polymerization mechanism on the REM. Increasing anodic potentials (1.9-3.2 V/SHE) resulted in the electroassisted adsorption mechanism contributing far less to p-methoxyphenol removal compared to p-nitrophenol. DFT calculations indicated that an increase in anodic potential resulted in a shift in p-methoxyphenol removal from a 1e(-) direct electron transfer (DET) reaction that resulted in radical formation and significant adsorption/polymerization, to a 2e(-) DET reaction that formed nonadsorbing products (i.e., p-benzoquinone). However, the anodic potentials were too low for the 2e(-) DET reaction to be thermodynamically favorable for p-nitrophenol. The decreased COD adsorption for p-nitrophenol at higher anodic potentials was attributed to reaction of soluble/adsorbed organics with OH(•). These results provide the first mechanistic explanation for p-substituted phenolic compound removal during advanced electrochemical oxidation processes. PMID:24766505

Zaky, Amr M; Chaplin, Brian P

2014-05-20

72

Dynamic Complexity in the Electrochemical Oxidation of Thiourea Jiamin Feng, Qingyu Gao,, Xiaoli Lv, and Irving R. Epstein*,  

E-print Network

of such behavior in chemical or electrochemical systems has been reported. Initial studies of the electrochemicalDynamic Complexity in the Electrochemical Oxidation of Thiourea Jiamin Feng, Qingyu Gao,, Xiaoli LvVised Manuscript ReceiVed: April 16, 2008 We explored the temperature-dependent dynamics of the electrochemical

Epstein, Irving R.

73

A reduced graphene oxide based electrochemical biosensor for tyrosine detection  

NASA Astrophysics Data System (ADS)

In this paper, a ‘green’ and safe hydrothermal method has been used to reduce graphene oxide and produce hemin modified graphene nanosheet (HGN) based electrochemical biosensors for the determination of l-tyrosine levels. The as-fabricated HGN biosensors were characterized by UV-visible absorption spectra, fluorescence spectra, Fourier transform infrared spectroscopy (FTIR) spectra and thermogravimetric analysis (TGA). The experimental results indicated that hemin was successfully immobilized on the reduced graphene oxide nanosheet (rGO) through ?-? interaction. TEM images and EDX results further confirmed the attachment of hemin on the rGO nanosheet. Cyclic voltammetry tests were carried out for the bare glass carbon electrode (GCE), the rGO electrode (rGO/GCE), and the hemin-rGO electrode (HGN/GCE). The HGN/GCE based biosensor exhibits a tyrosine detection linear range from 5 × 10-7 M to 2 × 10-5 M with a detection limitation of 7.5 × 10-8 M at a signal-to-noise ratio of 3. The sensitivity of this biosensor is 133 times higher than that of the bare GCE. In comparison with other works, electroactive biosensors are easily fabricated, easily controlled and cost-effective. Moreover, the hemin-rGO based biosensors demonstrate higher stability, a broader detection linear range and better detection sensitivity. Study of the oxidation scheme reveals that the rGO enhances the electron transfer between the electrode and the hemin, and the existence of hemin groups effectively electrocatalyzes the oxidation of tyrosine. This study contributes to a widespread clinical application of nanomaterial based biosensor devices with a broader detection linear range, improved stability, enhanced sensitivity and reduced costs.

Wei, Junhua; Qiu, Jingjing; Li, Li; Ren, Liqiang; Zhang, Xianwen; Chaudhuri, Jharna; Wang, Shiren

2012-08-01

74

Electrochemically Reduced Water Protects Neural Cells from Oxidative Damage  

PubMed Central

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??M) induced PC12 and SFME cell deaths. ERW scavenged intracellular ROS and exhibited a protective effect against neuronal network damage caused by 200??M 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

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

2014-01-01

75

Electrochemically reduced water protects neural cells from oxidative damage.  

PubMed

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??M) induced PC12 and SFME cell deaths. ERW scavenged intracellular ROS and exhibited a protective effect against neuronal network damage caused by 200??M 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

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

2014-01-01

76

Oxidative and energetic efficiency of different electrochemical oxidation processes for chloroanilines abatement in aqueous medium.  

PubMed

The oxidative efficiency and energy consumption, in the degradation of chloroanilines by anodic oxidation, indirect oxidation with electrogenerated hydrogen peroxide and electro-Fenton have been compared, using a laboratory system driven by a LabVIEW virtual controller. Solutions were oxidized in an undivided cell, where H(2)O(2) was generated electrochemically by reduction of atmospheric oxygen bubbled at a carbon cloth cathode. The electro-Fenton process showed the best degradation power, in terms of efficiency of removal and energy consumption. This process was applied to the purification of a solution obtained by washing a polluted soil. Under laboratory conditions, electro-Fenton removed 75% COD of this wastewater with a specific energy consumption of 0.3kWh per gram of COD, corresponding to 41.8kWhm(-3). PMID:16466769

Meinero, Samuele; Zerbinati, Orfeo

2006-06-01

77

Improved electrochemical biosensor response via metal oxide pre-oxidation of chemical interferents  

NASA Astrophysics Data System (ADS)

Typical biological samples are inherently complicated. They may contain a myriad of compounds that are electroactive at the same potential as that used in many electrochemical biosensors. Therefore, a biosensor design feature must be included that either eliminates or blocks the interferents from generating false positive signals. The ability to use an insoluble compound, that of MnO II, in order to oxidize interferents such as ascorbic acid, acetaminophen and uric acid, was investigated in a prototype sensor system at a bias potential of 0.6 V versus Ag/AgCl. Unlike previous work with these materials, a difference between the ability for the metal oxide to oxidize the interferents was observed. Most effective was the capability of MnO II to oxidize uric acid. Alternatively, the MnO II had little effect on acetaminophen. The study is both introduced and results are discussed within the context of an implantable glucose sensor.

Houseknecht, Jamie G.; Tapsak, Mark A.

2007-09-01

78

Electrochemical treatment of mixed and hazardous wastes; Oxidation of ethylene glycol and benzene by silver (II)  

Microsoft Academic Search

This paper reports that, in the future, mediated electrochemical oxidation (MEO) may be used for the ambient temperature destruction of hazardous waste and for the conversion of mixed waste to low-level radioactive waste. The authors have studied the MEO of ethylene glycol and benzene, two model compounds, in an electrochemical reactor. The reactor had a rotating-cylinder anode that was operated

Joseph C. Farmer; F. T. Wang; R. A. Hawley-Fedder; P. R. Lewis; L. J. Summers; L. Foiles

1992-01-01

79

Oxidation of alloys for advanced steam turbines  

SciTech Connect

Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections.

Holcomb, Gordon R.; Covino, Bernard S., Jr.; Bullard, Sophie J.; Ziomek-Moroz, M.; Alman, David E.

2005-01-01

80

Production of Oxygen Gas and Liquid Metal by Electrochemical Decomposition of Molten Iron Oxide  

E-print Network

advocated molten oxide elec- trolysis (MOE) as a carbon-free alternative to existing metals extrac- tionProduction of Oxygen Gas and Liquid Metal by Electrochemical Decomposition of Molten Iron Oxide of Resource and Environmental Sciences, Wuhan University, China Molten oxide electrolysis (MOE

Sadoway, Donald Robert

81

Dependence of Electrochemical Properties of Vanadium Oxide Films on Their Nano-and Microstructures  

E-print Network

Dependence of Electrochemical Properties of Vanadium Oxide Films on Their Nano- and Microstructures Vanadium pentoxide (V2O5) has attracted a lot of attention as a Li intercalation host, due to its layered

Cao, Guozhong

82

HANDBOOK ON ADVANCED NONPHOTOCHEMICAL OXIDATION PROCESSES  

EPA Science Inventory

The purpose of this handbook is to summarize commercial-scale system performance and cost data for advanced nonphotochemical oxidation (ANPO) treatment of contaminated water, air, and soil. Similar information from pilot-and bench-scale evaluations of ANPO processes is also inclu...

83

HANDBOOK ON ADVANCED PHOTOCHEMICAL OXIDATION PROCESSES  

EPA Science Inventory

This handbook summarizes commercial-scale system performance and cost data for advanced photochemical oxidation (APO) treatment of contaminated water, air, and solids. Similar information from pilot- and bench-scale evaluations of APO processes is also included to supplement the...

84

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

PubMed

An in situ chemical synthesis approach has been developed to prepare ruthenium oxide/reduced graphene oxide (RGO) nanocomposites. It is found that as the C/O ratio increases, the number density of RuO2 nanoparticles decreases, because the chemical interaction between the Ru ions and the oxygen-containing functional groups provides anchoring sites where the nucleation of particles takes place. For electrochemical capacitor applications, the microwave-hydrothermal process was carried out to improve the conductivity of RGO in RuO2/RGO nanocomposites. The significant improvement in capacitance and high rate capability might result from the RuO2 nanoparticles used as spacers that make the interior layers of the reduced graphene oxide electrode available for electrolyte access. PMID:23765196

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

2013-08-01

85

Facile and controllable electrochemical reduction of graphene oxide and its applications  

SciTech Connect

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.

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

2010-01-01

86

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

PubMed

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

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

2013-01-01

87

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

PubMed Central

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

2013-01-01

88

Eliminating degradation in solid oxide electrochemical cells by reversible operation  

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

89

Eliminating degradation in solid oxide electrochemical cells by reversible operation.  

PubMed

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. PMID:25532070

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

2015-02-01

90

Electrochemical oxidation of textile industry wastewater by graphite electrodes.  

PubMed

In the present article, studies have been performed on the electrochemical (EC) oxidation of actual textile industry wastewater by graphite electrodes. Multi-response optimization of four independent parameters namely initial pH (pHo): 4-10, current density (j): 27.78-138.89 A/m(2), NaCl concentration (w): 0-2 g/L and electrolysis time (t): 10-130 min have been performed using Box-Behnken (BB) experimental design. It was aimed to simultaneously maximize the chemical oxygen demand (COD) and color removal efficiencies and minimize specific energy consumption using desirability function approach. Pareto analysis of variance (ANOVA) showed a high coefficient of determination value for COD (R(2) = 0.8418), color (R(2) = 0.7010) and specific energy (R(2) = 0.9125) between the experimental values and the predicted values by a second-order regression model. Maximum COD and color removal and minimum specific energy consumed was 90.78%, 96.27% and 23.58 kWh/kg COD removed, respectively, were observed at optimum conditions. The wastewater, sludge and scum obtained after treatment at optimum condition have been characterized by various techniques. UV-visible study showed that all azo bonds of the dyes present in the wastewater were totally broken and most of the aromatic rings were mineralized during EC oxidation with graphite electrode. Carbon balance showed that out of the total carbon eroded from the graphite electrodes, 27-29.2% goes to the scum, 71.1-73.3% goes into the sludge and rest goes to the treated wastewater. Thermogravimetric analysis showed that the generated sludge and scum can be dried and used as a fuel in the boilers/incinerators. PMID:24766597

Bhatnagar, Rajendra; Joshi, Himanshu; Mall, Indra D; Srivastava, Vimal C

2014-01-01

91

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

PubMed

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

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

2010-03-01

92

Advanced oxidation protein products as a novel marker of oxidative stress in uremia  

Microsoft Academic Search

Advanced oxidation protein products as a novel marker of oxidative stress in uremia. Evidence suggests an imbalance between antioxidant and oxidant-generating systems resulting in oxidative stress in uremic patients. As plasma proteins are critical targets for oxidants, we developed a novel spectrophotometric assay which allows to detect advanced oxidation protein products (AOPP) in uremic plasma. By size-exclusion chromatography AOPP are

Véronique Witko-Sarsat; Miriam Friedlander; Chantal Capeillère-Blandin; Thao Nguyen-Khoa; Anh Thu Nguyen; Johanna Zingraff; Paul Jungers; Béatrice Descamps-Latscha

1996-01-01

93

Advanced Oxidation Technology for Pulp Mill Effluent  

E-print Network

than 50% for a high grade chemical pulp. The difference (l-yield) is the water soluble extractives found in the process wash waters. These wash water streams are further processed to recover the wood extractives and process chemicals when...ADVANCED OXIDATION TECHNOLOGY FOR PULP MILL EFFLUENT J. ROBERT HART, MANAGER, EPRI PULP & PAPER OFFICE, ATLANTA, GA ABSTRACT The composition of effluent from various pulping processes can exhibit a wide range of physical and chemical...

Hart, J. R.

94

Evaluation of a postcolumn electrochemical reactor for oxidation of paralytic shellfish poison toxins.  

PubMed

A liquid chromatographic method using a postcolumn electrochemical reactor that oxidizes paralytic shellfish poison toxins to fluorescent derivatives has been developed. Several experimental parameters, including pH and oxidation potential, were investigated. For nonhydroxylated toxins, the sensitivity improved with increasing pH and voltage. At optimum operating conditions, the sensitivity for saxitoxin and gonyautoxins 2 and 3 was an order of magnitude greater than that for neosaxitoxin and B1 and 2 orders of magnitude greater than that for B2. The limit of detection for saxitoxin was 0.10 ng (signal-to-noise ratio, 3:1). Electrochemical oxidation products were similar to those formed in the prechromatographic periodate oxidation method. Shellfish and plankton extracts were analyzed with the electrochemical system, and results agreed well with those obtained with established methods. Shellfish samples contaminated at the regulatory limit of 0.8 microgram/g were readily analyzed by the method. PMID:7756884

Lawrence, J F; Wong, B

1995-01-01

95

Novel imazethapyr detoxification applying advanced oxidation processes.  

PubMed

Different degradation methods have been applied to assess the suitability of advanced oxidation process (AOPs) to promote mineralization of imazethapyr [(RS)-5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid], a widely used imidazolinone class herbicide, the persistence of which has been demonstrated in surface and ground waters destined to human uses. Independent of the oxidation process assessed, the decomposition of imazethapyr always followed a pseudo-first order kinetic. The direct UV-irradiation (UV) of the herbicide as well as its oxidation with ozone (O?), and hydrogen peroxide tied to UV-irradiation (H?O?/UV) were sufficiently slow to permit the identification of intermediate products, the formation pathway of which has been proposed. Ozonation joined to UV-irradiation (O?/UV), ozonation joined to titanium dioxide photo-catalysis (TiO?/UV+O?), sole photo-catalysis (TiO?/UV), and photo-catalysis reinforced with hydrogen peroxide-oxidation (TiO?/UV+H?O?) were characterized by a faster degradation and rapid formation of a lot of small molecules, which were quickly degraded to complete mineralization. The most effective oxidation methods were those using titanium dioxide photo-catalysis enhanced either by ozonation or hydrogen peroxide. Most of all, these last processes were useful to avoid the development of dangerous by-products. PMID:21726140

Stathis, Ioannis; Hela, Dimitra G; Scrano, Laura; Lelario, Filomena; Emanuele, Lucia; Bufo, Sabino A

2011-01-01

96

Capsid protein oxidation in feline calicivirus using an electrochemical inactivation treatment.  

PubMed

Pathogenic viral infections are an international public health concern, and viral disinfection has received increasing attention. Electrochemical treatment has been used for treatment of water contaminated by bacteria for several decades, and although in recent years several reports have investigated viral inactivation kinetics, the mode of action of viral inactivation by electrochemical treatment remains unclear. Here, we demonstrated the inactivation of feline calicivirus (FCV), a surrogate for human noroviruses, by electrochemical treatment in a developed flow-cell equipped with a screen-printed electrode. The viral infectivity titer was reduced by over 5 orders of magnitude after 15min of treatment at 0.9V vs. Ag/AgCl. Proteomic study of electrochemically inactivated virus revealed oxidation of peptides located in the viral particles; oxidation was not observed in the non-treated sample. Furthermore, transmission electron microscopy revealed that viral particles in the treated sample had irregular structures. These results suggest that electrochemical treatment inactivates FCV via oxidation of peptides in the structural region, causing structural deformation of virus particles. This first report of viral protein damage through electrochemical treatment will contribute to broadening the understanding of viral inactivation mechanisms. PMID:25310599

Shionoiri, Nozomi; Nogariya, Osamu; Tanaka, Masayoshi; Matsunaga, Tadashi; Tanaka, Tsuyoshi

2015-02-11

97

A Comparative study on oxidation of disperse dyes by electrochemical process, ozone, hypochlorite and fenton reagent  

Microsoft Academic Search

The results of an experimental study on the destruction of disperse dyes by chemical oxidation using ozone, hypochlorite and Fenton reagent (H2O2+Fe2+) are compared with the data obtained by electrochemical oxidation. While the results obtained during hypochlorite oxidation were not satisfactory (only 35% reduction of colour was achieved at a dose of 6gdm?3), ozonation enabled colour to be reduced by

Lidia Szpyrkowicz; Claudia Juzzolino; Santosh N Kaul

2001-01-01

98

Induced effects of advanced oxidation processes  

NASA Astrophysics Data System (ADS)

Hazardous organic wastes from industrial, military, and commercial activities represent one of the greatest challenges to human beings. Advanced oxidation processes (AOPs) are alternatives to the degradation of those organic wastes. However, the knowledge about the exact mechanisms of AOPs is still incomplete. Here we report a phenomenon in the AOPs: induced effects, which is a common property of combustion reaction. Through analysis EDTA oxidation processes by Fenton and UV-Fenton system, the results indicate that, just like combustion, AOPs are typical induction reactions. One most compelling example is that pre-feeding easily oxidizable organic matter can promote the oxidation of refractory organic compound when it was treated by AOPs. Connecting AOPs to combustion, it is possible to achieve some helpful enlightenment from combustion to analyze, predict and understand AOPs. In addition, we assume that maybe other oxidation reactions also have induced effects, such as corrosion, aging and passivation. Muchmore research is necessary to reveal the possibilities of induced effects in those fields.

Liu, Peng; Li, Chaolin; Zhao, Zhuanjun; Lu, Gang; Cui, Haibo; Zhang, Wenfang

2014-02-01

99

Induced effects of advanced oxidation processes.  

PubMed

Hazardous organic wastes from industrial, military, and commercial activities represent one of the greatest challenges to human beings. Advanced oxidation processes (AOPs) are alternatives to the degradation of those organic wastes. However, the knowledge about the exact mechanisms of AOPs is still incomplete. Here we report a phenomenon in the AOPs: induced effects, which is a common property of combustion reaction. Through analysis EDTA oxidation processes by Fenton and UV-Fenton system, the results indicate that, just like combustion, AOPs are typical induction reactions. One most compelling example is that pre-feeding easily oxidizable organic matter can promote the oxidation of refractory organic compound when it was treated by AOPs. Connecting AOPs to combustion, it is possible to achieve some helpful enlightenment from combustion to analyze, predict and understand AOPs. In addition, we assume that maybe other oxidation reactions also have induced effects, such as corrosion, aging and passivation. Muchmore research is necessary to reveal the possibilities of induced effects in those fields. PMID:24503715

Liu, Peng; Li, Chaolin; Zhao, Zhuanjun; Lu, Gang; Cui, Haibo; Zhang, Wenfang

2014-01-01

100

Induced effects of advanced oxidation processes  

PubMed Central

Hazardous organic wastes from industrial, military, and commercial activities represent one of the greatest challenges to human beings. Advanced oxidation processes (AOPs) are alternatives to the degradation of those organic wastes. However, the knowledge about the exact mechanisms of AOPs is still incomplete. Here we report a phenomenon in the AOPs: induced effects, which is a common property of combustion reaction. Through analysis EDTA oxidation processes by Fenton and UV-Fenton system, the results indicate that, just like combustion, AOPs are typical induction reactions. One most compelling example is that pre-feeding easily oxidizable organic matter can promote the oxidation of refractory organic compound when it was treated by AOPs. Connecting AOPs to combustion, it is possible to achieve some helpful enlightenment from combustion to analyze, predict and understand AOPs. In addition, we assume that maybe other oxidation reactions also have induced effects, such as corrosion, aging and passivation. Muchmore research is necessary to reveal the possibilities of induced effects in those fields. PMID:24503715

Liu, Peng; Li, Chaolin; Zhao, Zhuanjun; Lu, Gang; Cui, Haibo; Zhang, Wenfang

2014-01-01

101

Simultaneous electrochemical and 3D optical imaging of silver nanoparticle oxidation  

NASA Astrophysics Data System (ADS)

The oxidation of AgNPs at a thin-film gold electrode is simultaneously investigated via digital holography and electrochemistry. The use of holography allows, for the first time, the 3D visualization of the electrochemical interfacial region at a relatively high acquisition rate. It is demonstrated how the coupling of these two techniques provides complementary chemical information. The ensemble response of the oxidation of surface-adsorbed silver nanoparticles to AgCl is monitored electrochemically, whereas this process is difficult to observe optically. Conversely, the subsequent chemical dissolution of individual AgCl nanocrystals can be tracked optically due to the associated decrease in the scattered light intensity.

Batchelor-McAuley, Christopher; Martinez-Marrades, Ariadna; Tschulik, Kristina; Patel, Anisha N.; Combellas, Catherine; Kanoufi, Frédéric; Tessier, Gilles; Compton, Richard G.

2014-03-01

102

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

SciTech Connect

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.

Shou Qingliang [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Cheng Jipeng, E-mail: chengjp@zju.edu.cn [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Zhang Li, E-mail: lizhang@ethz.ch [Institute of Robotics and Intelligent Systems, ETH Zurich, CH-8092 Zurich (Switzerland); Nelson, Bradley J. [Institute of Robotics and Intelligent Systems, ETH Zurich, CH-8092 Zurich (Switzerland); Zhang Xiaobin [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

2012-01-15

103

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

104

Mediated electrochemical oxidation of organic wastes without electrode separators  

DOEpatents

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.

Farmer, Joseph C. (Newtown, PA); Wang, Francis T. (Danville, CA); Hickman, Robert G. (Livermore, CA); Lewis, Patricia R. (Livermore, CA)

1996-01-01

105

Mediated electrochemical oxidation of organic wastes without electrode separators  

DOEpatents

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.

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

1996-05-14

106

Design and Fabrication of Complementary Metal-Oxide-Semiconductor Sensor Chip for Electrochemical Measurement  

NASA Astrophysics Data System (ADS)

An electrochemical sensor has been developed on a single chip in which potentiostat and sensor electrodes are integrated. Sensor chips were fabricated using 5.0 ?m complementary metal-oxide-semiconductor (CMOS) technology. All processes including the CMOS process, postprocessing for fabricating sensor electrodes and passivation layers, and packaging were performed at Toyohashi University of Technology. The integration makes it possible to measure electrochemical signals without having to use a bulky external electrochemical system. The potential between the working electrode and the reference electrode was controlled using an on-chip potentiostat composed of CMOS transistors. The chip characteristics were verified by electrochemical measurement, namely, by cyclic voltammetry. Potassium ferricyanide solution was measured to obtain results that fit well to the theoretical formula. A clear proportional relationship between peak height and the concentration of the sample solution was obtained using the proposed sensor chip, and the dynamic range obtained was 0.10 to 8.0 mM.

Tomoyuki Yamazaki,; Takaaki Ikeda,; Yoshiko Kano,; Hidekuni Takao,; Makoto Ishida,; Kazuaki Sawada,

2010-04-01

107

Design and Fabrication of Complementary Metal-Oxide-Semiconductor Sensor Chip for Electrochemical Measurement  

NASA Astrophysics Data System (ADS)

An electrochemical sensor has been developed on a single chip in which potentiostat and sensor electrodes are integrated. Sensor chips were fabricated using 5.0 µm complementary metal-oxide-semiconductor (CMOS) technology. All processes including the CMOS process, postprocessing for fabricating sensor electrodes and passivation layers, and packaging were performed at Toyohashi University of Technology. The integration makes it possible to measure electrochemical signals without having to use a bulky external electrochemical system. The potential between the working electrode and the reference electrode was controlled using an on-chip potentiostat composed of CMOS transistors. The chip characteristics were verified by electrochemical measurement, namely, by cyclic voltammetry. Potassium ferricyanide solution was measured to obtain results that fit well to the theoretical formula. A clear proportional relationship between peak height and the concentration of the sample solution was obtained using the proposed sensor chip, and the dynamic range obtained was 0.10 to 8.0 mM.

Yamazaki, Tomoyuki; Ikeda, Takaaki; Kano, Yoshiko; Takao, Hidekuni; Ishida, Makoto; Sawada, Kazuaki

2010-04-01

108

Recent advances in the electrochemical construction of heterocycles  

PubMed Central

Summary Due to the fact that the major portion of pharmaceuticals and agrochemicals contains heterocyclic units and since the overall number of commercially used heterocyclic compounds is steadily growing, heterocyclic chemistry remains in the focus of the synthetic community. Enormous efforts have been made in the last decades in order to render the production of such compounds more selective and efficient. However, most of the conventional methods for the construction of heterocyclic cores still involve the use of strong acids or bases, the operation at elevated temperatures and/or the use of expensive catalysts and reagents. In this regard, electrosynthesis can provide a milder and more environmentally benign alternative. In fact, numerous examples for the electrochemical construction of heterocycles have been reported in recent years. These cases demonstrate that ring formation can be achieved efficiently under ambient conditions without the use of additional reagents. In order to account for the recent developments in this field, a selection of representative reactions is presented and discussed in this review. PMID:25550752

2014-01-01

109

Synthesis and electrochemical capacitance of long tungsten oxide nanorod arrays grown vertically on substrate  

SciTech Connect

Highlights: ? Growth of long amorphous tungsten oxide nanorods on a substrate. ? Formation of single-crystalline tungsten oxide nanorods by a heat-treatment. ? High electrochemical pseudocapacitance of 2.8 mF cm{sup ?2}. ? Excellent cyclability of psuedocapacitance up to 1000 cycles. -- Abstract: Long tungsten oxide nanorods are vertically grown on Al/W/Ti coated silicon substrates using a two-step anodization process. The first anodization of the Al film forms a mesh-like mask of anodic aluminum oxide, and the second anodization of the W film results in the formation of a buffer layer, a bottom nanorod, and a top nanorod of amorphous tungsten oxide. A pore-widening process prior to the second anodization leads to the enhancement of nanorod length above approximately 500 nm. After a heat-treatment, the tungsten oxide nanorods are crystallized to form a single crystalline structure while the buffer layer forms a polycrystalline structure. The crystalline tungsten oxide nanorods show a cyclic voltammogram retaining the quasi-rectangular shape of an electrochemically reversible faradaic redox reaction, i.e., a typical pseudocapacitive behavior. The maximum electrochemical capacitance per apparent surface area reaches approximately 2.8 mF cm{sup ?2} at the voltage scan rate of 20 mV s{sup ?1}, and the excellent cyclability of charge–discharge process is maintained up to 1000 cycles.

Park, Sun Hwa [Department of Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of)] [Department of Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of); Kim, Young Heon; Lee, Tae Geol; Shon, Hyun Kyong [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of)] [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Park, Hyun Min [Department of Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of) [Department of Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of); Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Song, Jae Yong, E-mail: jysong@kriss.re.kr [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Department of Nano Science, University of Science and Technology, Daejeon 305-350 (Korea, Republic of)

2012-11-15

110

ADVANCED OXIDATION TECHNOLOGIES FOR THE TREATMENT OF CONTAMINATED GROUNDWATER  

EPA Science Inventory

This paper presents information on two pilot-field applications of advanced oxidation technologies for contaminated groundwater with organics. he two UV/oxidation technologies were developed by Ultrox International of Santa Ana, California and Peroxidation Systems, Inc. of Tucson...

111

ADVANCED OXIDATION TECHNOLOGIES FOR THE TREATMENT OF CONTAMINATED GROUNDWATER  

EPA Science Inventory

This paper presents information on two pilot-field appliations of advanced oxidation technologies for contaminated groundwater with organis. The two UV/oxidation technologies were developed by Ultrox International of Santa Ana, California and Peroxidatrion Systems, Inc. of Tucso...

112

Advanced Electrochemical Technologies for Hydrogen Production by Alternative Thermochemical Cycles  

SciTech Connect

Hydrogen fuel is a potentially major solution to the problem of climate change, as well as addressing urban air pollution issues. But a key future challenge for hydrogen as a clean energy carrier is a sustainable, low-cost method of producing it in large capacities. Most of the world�s hydrogen is currently derived from fossil fuels through some type of reforming processes. Nuclear hydrogen production is an emerging and promising alternative to the reforming processes for carbon-free hydrogen production in the future. This report presents the main results of a research program carried out by a NERI Consortium, which consisted of Penn State University (PSU) (lead), University of South Carolina (USC), Tulane University (TU), and Argonne National Laboratory (ANL). Thermochemical water decomposition is an emerging technology for large-scale production of hydrogen. Typically using two or more intermediate compounds, a sequence of chemical and physical processes split water into hydrogen and oxygen, without releasing any pollutants externally to the atmosphere. These intermediate compounds are recycled internally within a closed loop. While previous studies have identified over 200 possible thermochemical cycles, only a few have progressed beyond theoretical calculations to working experimental demonstrations that establish scientific and practical feasibility of the thermochemical processes. The Cu-Cl cycle has a significant advantage over other cycles due to lower temperature requirements - around 530 oC and below. As a result, it can be eventually linked with the Generation IV thermal power stations. Advantages of the Cu-Cl cycle over others include lower operating temperatures, ability to utilize low-grade waste heat to improve energy efficiency, and potentially lower cost materials. Another significant advantage is a relatively low voltage required for the electrochemical step (thus low electricity input). Other advantages include common chemical agents and reactions going to completion without side reactions, and lower demands on materials of construction. Three university research groups from PSU, USC, and TU as well as a group from ANL have been collaborating on the development of enabling technologies for the Cu-Cl cycle, including experimental work on the Cu-Cl cycle reactions, modeling and simulation, and particularly electrochemical reaction for hydrogen production using a CuCl electrolyzer. The Consortium research was distributed over the participants and organized in the following tasks: (1) Development of CuCl electrolyzer (PSU), (2) Thermodynamic modeling of anolyte solution (PSU), (3) Proton conductive membranes for CuCl electrolysis (PSU), (4) Development of an analytical method for online analysis of copper compounds in highly concentrated aqueous solutions (USC), (5) Electrodialysis as a means for separation and purification of the streams exiting the electrolyzer in the Cu-Cl cycle (USC), (6) Development of nanostructured electrocatalysts for the Cu-Cl electrolysis (USC), (7) Cu-Cl electrolyzer modeling (USC), (8) Aspen Plus modeling of the Cu-Cl thermochemical cycle (TU), (9) International coordination of research on the development of the Cu-Cl thermochemical cycle (ANL). The results obtained in the project clearly demonstrate that the Cu-Cl alternative thermochemical cycle is a promising and viable technology to produce hydrogen efficiently.

The Pennsylvania State Univeristy: Serguei Lvov, Mike Chung, Mark Fedkin, Victor Balashov, Elena, Chalkova, Nikolay Akinfiev; University of South Carolina: Carol Stork, Thomas Davis, Francis Gadala-Maria, Thomas Stanford, John Weidner; Tulane University: Victor Law, John Prindle; ANL: Michele Lewis

2011-01-06

113

Electrochemical properties of metal-oxide-coated carbon electrodes prepared by atomic layer deposition.  

PubMed

Here we report on the electrochemical properties of carbon electrodes coated with thin layers of Al2O3 and SnO2. These oxide films were deposited using atomic layer deposition (ALD) and range in thickness from 1 to 6 nm. Electrochemical experiments show that the thinnest oxide layers contain defects that penetrate to the underlying carbon electrode. However, oxygenation of the carbon surface prior to ALD increases the surface concentration of nucleation sites for oxide growth and suppresses the defect density. Films of Al2O3 just ?3-4 nm in thickness are free of pinholes. Slightly thicker coatings of SnO2 are required for equivalent passivation. Both Al2O3 and SnO2 films are stable in both neutral and acidic electrolytes even after repeated voltammetric scanning. The results reported here open up the possibility of studying the effect of oxide supports on electrocatalytic reactions. PMID:25372303

Loussaert, James A; Fosdick, Stephen E; Crooks, Richard M

2014-11-18

114

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

PubMed

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, ?Ev, 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, ?, is identified as a novel approach to calculate the stability vs. oxidation. PMID:25557392

Jónsson, Erlendur; Johansson, Patrik

2015-02-01

115

Development of Advanced Electrochemical Sensors for DNA Detection at the Point of Care  

NASA Astrophysics Data System (ADS)

In the post-genomic era, ever-advancing capabilities in DNA detection and analysis have become vital to the detection of infectious diseases and the diagnosis of genetic abnormalities and inheritable diseases. The benefit of such capabilities, however, has yet to reach patients outside of centralized facilities. There thus exists an increasing need to decentralize DNA detection methods and to administer such diagnostics at the "point of care." Electrochemical-based DNA sensors present a compelling approach, but have yet to deliver satisfactory sensitivity, specificity, miniaturization, and real-time monitoring capability to meet the demand of point-of-care diagnostics. Motivated by their potential and their current limitations, in this dissertation, we present a series of strategies that we have undertaken in order to address the key shortcomings of electrochemical DNA sensors and advance them toward point-of-care applications. First, we report a single-step, single reagent, label-free, isothermal electrochemical DNA sensor based on the phenomenon of enzyme catalyzed target recycling amplification. Using this technique, we achieve improved detection limit in comparison to hybridization-based sensors without amplification. We also demonstrate greater than 16-fold amplification of signal at low target concentrations. Next, we present a novel electrochemical DNA sensor that detects single-nucleotide mismatched targets with unprecedented "polarity-switching" responses. This "bipolar" sensor employs a surface-bound and redox-modified (methylene blue) DNA probe architecture, and outputs a decreased Faradaic current when hybridized to a perfectly matched (PM) target, but conversely reports an increased Faradaic current when hybridized to a single-base mismatched (SM) target. Third, we describe the microfluidic electrochemical dynamic allele specific hybridization (microE-DASH) platform for versatile and rapid detection of single-nucleotide polymorphisms. Implementing electrochemical-based melting curve analysis within the microfluidic device, this platform directly detects PCR amplicon-like targets and distinguishes perfectly matched target from single-base mismatched target and heterozygote combination of both targets in 20 minutes. Finally, we present the microfluidic electrochemical quantitative loop-mediated isothermal amplification (MEQ-LAMP) platform for rapid, sensitive, and quantitative detection of pathogen genomic DNA at the point of care. DNA amplification is electrochemically monitored in real time within a monolithic microfluidic device, enabling the detection of as few as 16 copies of Salmonella genomic DNA via a single-step process in under an hour.

Hsieh, Kuangwen

116

Electrochemical synthesis of gold nanoparticles onto indium tin oxide glass and application in biosensors  

Microsoft Academic Search

A simple one-step method for the electrochemical deposition of gold nanoparticles (GNPs) onto bare indium tin oxide film coated glass substrate without any template or surfactant was investigated. The effect of electrolysis conditions such as potential range, temperature, concentration and deposition cycles were examined. The connectivity of GNPs was analyzed by UV–Vis absorption spectroscopy and scanning electron microscopy. The nanoparticles

Yanling Hu; Yan Song; Yuan Wang; Junwei di

2011-01-01

117

Solid State Ionics 109 (1998) 151157 The electrochemical stability of lithium-metal oxides against metal  

E-print Network

Solid State Ionics 109 (1998) 151­157 The electrochemical stability of lithium-metal oxides against of secondary lithium batteries with Li MO cathodes isx 2 investigated. Loss of active material due to metal preferably reduce before the lithium ion during charging. © 1998 Elsevier Science B.V. All rights reserved

Ceder, Gerbrand

118

Electrochemical impedance spectroscopy study of the passive oxide film on titanium for implant application  

Microsoft Academic Search

The surface oxide film on titanium and its long-term stability in biological environments play a decisive role for the biocompatibility of titanium implants. In this study, the passive oxide film formed on titanium and its natural growth in a phosphate buffered solution with and without an H2O2 addition have been investigated by electrochemical impedance spectroscopy (EIS) measurements over a period

J. Pan; D. Thierry; C. Leygraf

1996-01-01

119

Nanostructured metal oxide-based materials as advanced anodes for lithium-ion batteries.  

PubMed

The search for new electrode materials for lithium-ion batteries (LIBs) has been an important way to satisfy the ever-growing demands for better performance with higher energy/power densities, improved safety and longer cycle life. Nanostructured metal oxides exhibit good electrochemical properties, and they are regarded as promising anode materials for high-performance LIBs. In this feature article, we will focus on three different categories of metal oxides with distinct lithium storage mechanisms: tin dioxide (SnO(2)), which utilizes alloying/dealloying processes to reversibly store/release lithium ions during charge/discharge; titanium dioxide (TiO(2)), where lithium ions are inserted/deinserted into/out of the TiO(2) crystal framework; and transition metal oxides including iron oxide and cobalt oxide, which react with lithium ions via an unusual conversion reaction. For all three systems, we will emphasize that creating nanomaterials with unique structures could effectively improve the lithium storage properties of these metal oxides. We will also highlight that the lithium storage capability can be further enhanced through designing advanced nanocomposite materials containing metal oxides and other carbonaceous supports. By providing such a rather systematic survey, we aim to stress the importance of proper nanostructuring and advanced compositing that would result in improved physicochemical properties of metal oxides, thus making them promising negative electrodes for next-generation LIBs. PMID:22460594

Wu, Hao Bin; Chen, Jun Song; Hng, Huey Hoon; Lou, Xiong Wen David

2012-04-21

120

Nanostructured metal oxide-based materials as advanced anodes for lithium-ion batteries  

NASA Astrophysics Data System (ADS)

The search for new electrode materials for lithium-ion batteries (LIBs) has been an important way to satisfy the ever-growing demands for better performance with higher energy/power densities, improved safety and longer cycle life. Nanostructured metal oxides exhibit good electrochemical properties, and they are regarded as promising anode materials for high-performance LIBs. In this feature article, we will focus on three different categories of metal oxides with distinct lithium storage mechanisms: tin dioxide (SnO2), which utilizes alloying/dealloying processes to reversibly store/release lithium ions during charge/discharge; titanium dioxide (TiO2), where lithium ions are inserted/deinserted into/out of the TiO2 crystal framework; and transition metal oxides including iron oxide and cobalt oxide, which react with lithium ions via an unusual conversion reaction. For all three systems, we will emphasize that creating nanomaterials with unique structures could effectively improve the lithium storage properties of these metal oxides. We will also highlight that the lithium storage capability can be further enhanced through designing advanced nanocomposite materials containing metal oxides and other carbonaceous supports. By providing such a rather systematic survey, we aim to stress the importance of proper nanostructuring and advanced compositing that would result in improved physicochemical properties of metal oxides, thus making them promising negative electrodes for next-generation LIBs.

Wu, Hao Bin; Chen, Jun Song; Hng, Huey Hoon; Wen (David) Lou, Xiong

2012-03-01

121

Removal of the X-ray contrast media diatrizoate by electrochemical reduction and oxidation.  

PubMed

Due to their resistance to biological wastewater treatment, iodinated X-ray contrast media (ICM) have been detected in municipal wastewater effluents at relatively high concentrations (i.e., up to 100 ?g L(-1)), with hospitals serving as their main source. To provide a new approach for reducing the concentrations of ICMs in wastewater, electrochemical reduction at three-dimensional graphite felt and graphite felt doped with palladium nanoparticles was examined as a means for deiodination of the common ICM diatrizoate. The presence of palladium nanoparticles significantly enhanced the removal of diatrizoate and enabled its complete deiodination to 3,5-diacetamidobenzoic acid. When the system was employed in the treatment of hospital wastewater, diatrizoate was reduced, but the extent of electrochemical reduction decreased as a result of competing reactions with solutes in the matrix. Following electrochemical reduction of diatrizoate to 3,5-diacetamidobenzoic acid, electrochemical oxidation with boron-doped diamond (BDD) anodes was employed. 3,5-Diacetamidobenzoic acid disappeared from solution at a rate that was similar to that of diatrizoate, but it was more readily mineralized than the parent compound. When electrochemical reduction and oxidation were coupled in a three-compartment reactor operated in a continuous mode, complete deiodination of diatrizoate was achieved at an applied cathode potential of -1.7 V vs SHE, with the released iodide ions electrodialyzed in a central compartment with 80% efficiency. The resulting BDD anode potential (i.e., +3.4-3.5 V vs SHE) enabled efficient oxidation of the products of the reductive step. The presence of other anions (e.g., chloride) was likely responsible for a decrease in I(-) separation efficiency when hospital wastewater was treated. Reductive deiodination combined with oxidative degradation provides benefits over oxidative treatment methods because it does not produce stable iodinated intermediates. Nevertheless, the process must be further optimized for the conditions encountered in hospital wastewater to improve the separation efficiency of halide ions prior to the electrooxidation step. PMID:24261992

Radjenovic, Jelena; Flexer, Victoria; Donose, Bogdan C; Sedlak, David L; Keller, Jurg

2013-12-01

122

Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices  

DOEpatents

The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

2010-11-23

123

Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices  

DOEpatents

The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

2010-03-02

124

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

PubMed

Electrochemical oxidation of peptides and proteins is traditionally performed on carbon-based electrodes. Adsorption caused by the affinity of hydrophobic and aromatic amino acids toward these surfaces leads to electrode fouling. We compared the performance of boron-doped diamond (BDD) and glassy carbon (GC) electrodes for the electrochemical oxidation and cleavage of peptides. An optimal working potential of 2000 mV was chosen to ensure oxidation of peptides on BDD by electron transfer processes only. Oxidation by electrogenerated OH radicals took place above 2500 mV on BDD, which is undesirable if cleavage of a peptide is to be achieved. BDD showed improved cleavage yield and reduced adsorption for a set of small peptides, some of which had been previously shown to undergo electrochemical cleavage C-terminal to tyrosine (Tyr) and tryptophan (Trp) on porous carbon electrodes. Repeated oxidation with BDD electrodes resulted in progressively lower conversion yields due to a change in surface termination. Cathodic pretreatment of BDD at a negative potential in an acidic environment successfully regenerated the electrode surface and allowed for repeatable reactions over extended periods of time. BDD electrodes are a promising alternative to GC electrodes in terms of reduced adsorption and fouling and the possibility to regenerate them for consistent high-yield electrochemical cleavage of peptides. The fact that OH-radicals can be produced by anodic oxidation of water at elevated positive potentials is an additional advantage as they allow another set of oxidative reactions in analogy to the Fenton reaction, thus widening the scope of electrochemistry in protein and peptide chemistry and analytics. PMID:23763302

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

2013-07-16

125

Electrochemical stability of self-assembled alkylphosphate monolayers on conducting metal oxides.  

PubMed

Alkylphosphate self-assembled monolayers (SAMs) were prepared on Nb-doped SrTiO(3) (Nb-STO) conducting metal oxide substrates. Unlike thiols on gold, the alkylphosphate SAMs on Nb-STO exhibited an electrochemical stability over a wide voltage range from -2 to 2 V. Cyclic voltammetry showed that the SAM modification inhibited the electrochemical activity of the underlying conducting substrate with an efficiency dependent on the chain length. Impedance spectroscopy showed that SAM-modified Nb-STO substrates have a significantly higher resistance than bare substrates. PMID:21744865

Yildirim, Oktay; Yilmaz, M Deniz; Reinhoudt, David N; Blank, Dave H A; Rijnders, Guus; Huskens, Jurriaan

2011-08-16

126

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

Microsoft Academic Search

This invention discloses cross-flow electrochemical reactor cells containing oxygen permeable materials which have both electron conductivity and oxygen ion conductivity, cross-flow reactors, and electrochemical processes using cross-flow reactor cells having oxygen permeable monolithic cores to control and facilitate transport of oxygen from an oxygen-containing gas stream to oxidation reactions of organic compounds in another gas stream. These cross-flow electrochemical reactors

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

1994-01-01

127

Advanced fabrication process for combined atomic force-scanning electrochemical microscopy (AFM-SECM) probes.  

PubMed

An advanced software-controlled focused ion beam (FIB) patterning process for the fabrication of combined atomic force-scanning electrochemical microscopy (AFM-SECM) probes is reported. FIB milling is a standard process in scanning probe microscopy (SPM) for specialized SPM probe fabrication. For AFM-SECM, milling of bifunctional probes usually requires several milling steps. Milling such complex multi-layer/multi-material structures using a single milling routine leads to significantly reduced fabrication times and costs. Based on an advanced patterning routine, a semi-automated FIB milling routine for fabricating combined AFM-SECM probes with high reproducibility is presented with future potential for processing at a wafer level. The fabricated bifunctional probes were electrochemically characterized using cyclic voltammetry, and their performance for AFM-SECM imaging experiments was tested. Different insulation materials (Parylene-C and SixNy) have been evaluated with respect to facilitating the overall milling process, the influence on the electrochemical behavior and the long-term stability of the obtained probes. Furthermore, the influence of material composition and layer sequence to the overall shape and properties of the combined probes were evaluated. PMID:25259683

Eifert, Alexander; Mizaikoff, Boris; Kranz, Christine

2015-01-01

128

Oxidation of Carbon Supports at Fuel Cell Cathodes: Differential Electrochemical Mass Spectrometric Study  

NASA Astrophysics Data System (ADS)

The effects of O2 and the supported Pt nano-particles on the mechanisms and kinetics of the carbon support corrosion are investigated by monitoring the CO2 production using differential electrochemical mass spectrometry in a dual-thin layer flow cell. Carbon can be oxidized in different distinct potential regimes; O2 accelerates carbon oxidation, the rates of CO2 production from carbon oxidation in O2 saturated solution are two times of that in N2 saturated solution at the same potential; Pt can catalyze the carbon oxidation, with supported Pt nanoparticles, the overpotential for carbon oxidation is much smaller than that without loading in the carbon electrode. The mechanism for the enhanced carbon oxidation by Pt and O2 are discussed.

Li, Ming-fang; Tao, Qian; Liao, Ling-wen; Xu, Jie; Cai, Jun; Chen, Yan-xia

2010-08-01

129

Modified cermet fuel electrodes for solid oxide electrochemical cells  

DOEpatents

An exterior porous electrode (10), bonded to a solid oxygen ion conducting electrolyte (13) which is in contact with an interior electrode (14), contains coarse metal particles (12) of nickel and/or cobalt, having diameters from 3 micrometers to 35 micrometers, where the coarse particles are coated with a separate, porous, multiphase layer (17) containing fine metal particles of nickel and/or cobalt (18), having diameters from 0.05 micrometers to 1.75 micrometers and conductive oxide (19) selected from cerium oxide, doped cerium oxide, strontium titanate, doped strontium titanate and mixtures thereof.

Ruka, Roswell J. (Churchill Boro, PA); Spengler, Charles J. (Murrysville, PA)

1991-01-01

130

Enhancing electrochemical detection on graphene oxide-CNT nanostructured electrodes using magneto-nanobioprobes  

NASA Astrophysics Data System (ADS)

Graphene and related materials have come to the forefront of research in electrochemical sensors during recent years due to the promising properties of these nanomaterials. Further applications of these nanomaterials have been hampered by insufficient sensitivity offered by these nanohybrids for the type of molecules requiring lower detection ranges. Here, we report a signal amplification strategy based on magneto-electrochemical immunoassay which combines the advantages of carbon nanotube and reduced graphene oxide together with electrochemical bursting of magnetic nanoparticles into a large number of metal ions. Sensitive detection was achieved by precisely designing the nanohybrid and correlating the available metal ions with analyte concentration. We confirmed the ultrahigh sensitivity of this method for a new generation herbicide diuron and its analogues up to sub-picomolar concentration in standard water samples. The novel immune-detection platform showed the excellent potential applicability in rapid and sensitive screening of environmental pollutants or toxins in samples.

Sharma, Priyanka; Bhalla, Vijayender; Dravid, Vinayak; Shekhawat, Gajendera; Jinsong-Wu; Prasad, E. Senthil; Suri, C. Raman

2012-11-01

131

Enhancing electrochemical detection on graphene oxide-CNT nanostructured electrodes using magneto-nanobioprobes  

PubMed Central

Graphene and related materials have come to the forefront of research in electrochemical sensors during recent years due to the promising properties of these nanomaterials. Further applications of these nanomaterials have been hampered by insufficient sensitivity offered by these nanohybrids for the type of molecules requiring lower detection ranges. Here, we report a signal amplification strategy based on magneto-electrochemical immunoassay which combines the advantages of carbon nanotube and reduced graphene oxide together with electrochemical bursting of magnetic nanoparticles into a large number of metal ions. Sensitive detection was achieved by precisely designing the nanohybrid and correlating the available metal ions with analyte concentration. We confirmed the ultrahigh sensitivity of this method for a new generation herbicide diuron and its analogues up to sub-picomolar concentration in standard water samples. The novel immune-detection platform showed the excellent potential applicability in rapid and sensitive screening of environmental pollutants or toxins in samples. PMID:23166860

Sharma, Priyanka; Bhalla, Vijayender; Dravid, Vinayak; Shekhawat, Gajendera; Jinsong-Wu, J W; Prasad, E. Senthil; Suri, C. Raman

2012-01-01

132

Electrochemical behavior of reactively sputtered iron-doped nickel oxide  

Microsoft Academic Search

Iron-doped nickel oxide films were deposited by reactive sputtering from elemental and alloy targets in a 20% oxygen\\/argon atmosphere and were characterized for use as oxygen evolution catalysts. The incorporation of iron reduced the overpotential required for oxygen evolution by as much as 300 mV at a current density of 100 mA\\/cm² compared to undoped nickel oxide deposited under similar

Eric L. Miller; R. E. Rocheleau

1997-01-01

133

Tin Oxide Nanorod Array-Based Electrochemical Hydrogen Peroxide Biosensor  

NASA Astrophysics Data System (ADS)

SnO2 nanorod array grown directly on alloy substrate has been employed as the working electrode of H2O2 biosensor. Single-crystalline SnO2 nanorods provide not only low isoelectric point and enough void spaces for facile horseradish peroxidase (HRP) immobilization but also numerous conductive channels for electron transport to and from current collector; thus, leading to direct electrochemistry of HRP. The nanorod array-based biosensor demonstrates high H2O2 sensing performance in terms of excellent sensitivity (379 ?A mM-1 cm-2), low detection limit (0.2 ?M) and high selectivity with the apparent Michaelis-Menten constant estimated to be as small as 33.9 ?M. Our work further demonstrates the advantages of ordered array architecture in electrochemical device application and sheds light on the construction of other high-performance enzymatic biosensors.

Liu, Jinping; Li, Yuanyuan; Huang, Xintang; Zhu, Zhihong

2010-07-01

134

Electrochemical Deposition of Iron Nanoneedles on Titanium Oxide Nanotubes  

SciTech Connect

Iron as a catalyst has wide applications for hydrogen generation from ammonia, photodecomposition of organics, and carbon nanotube growth. Tuning the size and shape of iron is meaningful for improving the catalysis efficiency. It is the objective of this work to prepare nanostructured iron with high surface area via electrochemical deposition. Iron nanoneedles were successfully electrodeposited on Ti supported TiO2 nanotube arrays in a chlorine-based electrolyte containing 0.15 M FeCl2 {center_dot} 4H2O and 2.0 M HCl. Transmission electron microscopic analysis reveals that the average length of the nanoneedles is about 200 nm and the thickness is about 10 nm. It has been found that a high overpotential at the cathode made of Ti/TiO2 nanotube arrays is necessary for the formation of the nanoneedles. Cyclic voltammetry test indicates that the electrodeposition of iron nanoneedles is a concentration-limited process.

Gan Y. X.; Zhang L.; Gan B.J.

2011-10-01

135

Ruthenium Oxide Electrochemical Super Capacitor Optimization for Pulse Power Applications  

NASA Technical Reports Server (NTRS)

Electrical actuator systems are being pursued as alternatives to hydraulic systems to reduce maintenance time, weight and costs while increasing reliability. Additionally, safety and environmental hazards associated with the hydraulic fluids can be eliminated. For most actuation systems, the actuation process is typically pulsed with high peak power requirements but with relatively modest average power levels. The power-time requirements for electrical actuators are characteristic of pulsed power technologies where the source can be sized for the average power levels while providing the capability to achieve the peak requirements. Among the options for the power source are battery systems, capacitor systems or battery-capacitor hybrid systems. Battery technologies are energy dense but deficient in power density; capacitor technologies are power dense but limited by energy density. The battery-capacitor hybrid system uses the battery to supply the average power and the capacitor to meet the peak demands. It has been demonstrated in previous work that the hybrid electrical power source can potentially provide a weight savings of approximately 59% over a battery-only source. Electrochemical capacitors have many properties that make them well-suited for electrical actuator applications. They have the highest demonstrated energy density for capacitive storage (up to 100 J/g), have power densities much greater than most battery technologies (greater than 30kW/kg), are capable of greater than one million charge-discharge cycles, can be charged at extremely high rates, and have non-explosive failure modes. Thus, electrochemical capacitors exhibit a combination of desirable battery and capacitor characteristics.

Merryman, Stephen A.; Chen, Zheng

2000-01-01

136

Elementary reaction modeling of solid oxide electrolysis cells: Main zones for heterogeneous chemical/electrochemical reactions  

NASA Astrophysics Data System (ADS)

A theoretical model of solid oxide electrolysis cells considering the heterogeneous elementary reactions, electrochemical reactions and the transport process of mass and charge is applied to study the relative performance of H2O electrolysis, CO2 electrolysis and CO2/H2O co-electrolysis and the competitive behavior of heterogeneous chemical and electrochemical reactions. In cathode, heterogeneous chemical reactions exist near the outside surface and the electrochemical reactions occur near the electrolyte. According to the mathematical analysis, the mass transfer flux D ?c determines the main zone size of heterogeneous chemical reactions, while the charge transfer flux ? ?V determines the other one. When the zone size of heterogeneous chemistry is enlarged, more CO2 could react through heterogeneous chemical pathway, and polarization curves of CO2/H2O co-electrolysis could be prone to H2O electrolysis. Meanwhile, when the zone size of electrochemistry is enlarged, more CO2 could react through electrochemical pathway, and polarization curves of CO2/H2O co-electrolysis could be prone to CO2 electrolysis. The relative polarization curves, the ratio of CO2 participating in electrolysis and heterogeneous chemical reactions, the mass and charge transfer flux and heterogeneous chemical/electrochemical reaction main zones are simulated to study the effects of cathode material characteristics (porosity, particle diameter and ionic conductivity) and operating conditions (gas composition and temperature).

Li, Wenying; Shi, Yixiang; Luo, Yu; Cai, Ningsheng

2015-01-01

137

Electrochemical growth of vertically aligned ZnO nanorod arrays on oxidized bi-layer graphene electrode  

E-print Network

Electrochemical growth of vertically aligned ZnO nanorod arrays on oxidized bi-layer graphene arrays were directly grown on flexible and transparent oxidized bi-layer graphene electrodes by seedless-quality vertical ZnO NR arrays directly on oxidized bi-layer graphene electrodes from pure zinc nitrate aqueous

Hwang, Sung Woo

138

Photochemical, electrochemical, and photoelectrochemical water oxidation catalyzed by water-soluble mononuclear ruthenium complexes.  

PubMed

Two mononuclear ruthenium complexes [Ru(H2tcbp)(isoq)2] (1) and [Ru(H2tcbp)(pic)2] (2) (H4tcbp=4,4',6,6'-tetracarboxy-2,2'-bipyridine, isoq=isoquinoline, pic=4-picoline) are synthesized and fully characterized. Two spare carboxyl groups on the 4,4'-positions are introduced to enhance the solubility of 1 and 2 in water and to simultaneously allow them to tether to the electrode surface by an ester linkage. The photochemical, electrochemical, and photoelectrochemical water oxidation performance of 1 in neutral aqueous solution is investigated. Under electrochemical conditions, water oxidation is conducted on the deposited indium-tin-oxide anode, and a turnover number higher than 15,000 per water oxidation catalyst (WOC) 1 is obtained during 10?h of electrolysis under 1.42?V vs. NHE, corresponding to a turnover frequency of 0.41?s(-1). The low overpotential (0.17?V) of electrochemical water oxidation for 1 in the homogeneous solution enables water oxidation under visible light by using [Ru(bpy)3](2+) (P1) (bpy=2,2'-bipyridine) or [Ru(bpy)2(4,4'-(COOEt)2-bpy)](2+) (P2) as a photosensitizer. In a three-component system containing 1 or 2 as a light-driven WOC, P1 or P2 as a photosensitizer, and Na2S2O8 or [CoCl(NH3)5]Cl2 as a sacrificial electron acceptor, a high turnover frequency of 0.81?s(-1) and a turnover number of up to 600 for 1 under different catalytic conditions are achieved. In a photoelectrochemical system, the WOC 1 and photosensitizer are immobilized together on the photoanode. The electrons efficiently transfer from the WOC to the photogenerated oxidizing photosensitizer, and a high photocurrent density of 85??A?cm(-2) is obtained by applying 0.3?V bias vs. NHE. PMID:25205065

Li, Ting-Ting; Zhao, Wei-Liang; Chen, Yong; Li, Fu-Min; Wang, Chuan-Jun; Tian, Yong-Hua; Fu, Wen-Fu

2014-10-20

139

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

NASA Astrophysics Data System (ADS)

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 by the composition and pH of the electrolyte, temperature, current density and polymer deposition time. Mn oxide/PEDOT coaxial core/shell rods consisted of MnO2 with an antifluorite-type structure coated with amorphous PEDOT. The Mn oxide/PEDOT coaxial core/shell electrodes prepared by the sequential method showed significantly better specific capacity and redox performance properties relative to both uncoated Mn oxide rods and co- electrodeposited Mn oxide/PEDOT electrodes. The best specific capacitance for Mn oxide/PEDOT rods produced sequentially was ˜295 F g-1 with ˜92% retention after 250 cycles in 0.5 M Na2SO4 at 100 mV s-1. To further improve the electrochemical capacitive behavior of Mn oxide electrodes, Co-doped and Fe-doped Mn oxide electrodes with a rod-like morphology and antifluorite-type crystal structure were synthesized by anodic electrodeposition, on Au coated Si substrates, from dilute solutions of Mn acetate and Co sulphate and Mn acetate and Fe chloride. Also, Mn-Co oxide/PEDOT coaxial core/shell rods were synthesized by applying a shell of PEDOT on Mn-Co oxide electrodes. Mn-Co oxide/PEDOT electrodes consisted of MnO2, with partial Co 2+ and Co3+ ion substitution for Mn4+, and amorphous PEDOT. Mn-Fe oxide electrodes consisted of MnO2, with partial Fe2+ and Fe3+ ion substitution for Mn4+. Electrochemical analysis showed that the capacitance values for all deposits increased with increasing scan rate to 100 mVs -1, and then decreased after 100 mVs-1. The Mn-Co oxide/PEDOT electrodes showed improved specific capacity and electrochemical cyclability relative to uncoated Mn-Co oxides and Mn-Fe oxides. Mn-Co oxide/PEDOT electrodes with rod-like structures had high capacitances (up to 310 Fg -1) at a scan rate of 100 mVs-1 and maintained their capacitance after 500 cycles in 0.5 M Na2SO4 (91% retention). Capacitance reduction for the deposits was mainly due to the loss of Mn ions by dissolution in the electrolyte solution. To better understand the nucleation and growth mechanisms of Mn oxide electrodes, the effects of supersaturation ratio on the

Babakhani, Banafsheh

140

Advanced oxidation technologies for chemical demilitarization  

SciTech Connect

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory. The main project objective was to establish a technical basis for future program development in the area of chemical warfare agent destruction using a Los Alamos-developed advanced oxidation process: a two-stage device consisting of thermal packed-bed reactor (PBR) and a nonthermal plasma (NTP) reactor. Various compounds were evaluated as potential surrogates for chemical warfare (CW) agents. Representative effluent mass balances were projected for future comparisons with incinerators. The design and construction of lab-scale PBR/NTP reactors (consisting of a liquid injection and metering system, electric furnace, condensers, chemical traps, plasma reactors, power supplies, and chemical diagnostics) has been completed. This equipment, the experience gained from chemical-processing experiments, process modeling, and an initial demonstration of the feasibility of closed-loop operation, have provided a technical basis for further demonstrations and program development efforts.

Rosocha, L.A.; Korzekwa, R.A.; Monagle, M.; Coogan, J.J.; Tennant, R.A.; Brown, L.F.; Currier, R.P.

1996-12-31

141

An Investigation into the Effect of a Post-electroplating Electrochemical Oxidation Treatment on Tin Whisker Formation  

NASA Astrophysics Data System (ADS)

Since the `cracked oxide theory' was proposed by Tu in 1994,1 there has only been a limited number of studies that have sought to investigate the effect of the Sn oxide on whisker growth. The current study has used electrochemical oxidation to produce oxide films, which has enabled the effect of the surface oxide thickness on whisker growth to be established. The effect of oxide thickness on whisker growth has been investigated for tin electrodeposits on both Cu and brass substrates. The influence of applied oxidation potential on the thickness of the Sn oxide film has been investigated using x-ray photoelectron spectroscopy (XPS) for potassium bicarbonate-carbonate and borate buffer electrolyte solutions. Whisker growth from electrochemically oxidised Sn-Cu deposits on Cu and Sn deposits on brass has been investigated and compared with samples left to develop a native air-formed oxide. XPS studies show that the thickness of the electrochemically formed Sn oxide film is dependent on the applied oxidation potential and the total charge passed. Subsequent whisker growth studies demonstrate that electrochemically oxidised Sn-Cu deposits on Cu and Sn deposits on brass are significantly less susceptible to whisker growth than those having a native oxide film. For Sn deposits on brass, the electrochemically formed Sn oxide greatly reduces Zn oxide formation at the surface of the tin deposit, which results in whisker mitigation. For Sn-Cu deposits on Cu, the reduction in whisker growth must simply derive from the increased thickness of the Sn oxide, i.e. the Sn oxide film has an important role in stemming the development of whiskers.

Ashworth, M. A.; Haspel, D.; Wu, L.; Wilcox, G. D.; Mortimer, R. J.

2015-01-01

142

Degradation of the commercial surfactant nonylphenol ethoxylate by advanced oxidation processes.  

PubMed

Four different oxidation process, namely direct photolysis (DP) and three advanced oxidation processes (heterogeneous photocatalysis - HP, eletrochemical oxidation - EO and photo-assisted electrochemical oxidation - PEO) were applied in the treatment of wastewater containing nonylphenol ethoxylate (NPnEO). The objective of this work was to determine which treatment would be the best option in terms of degradation of NPnEO without the subsequent generation of toxic compounds. In order to investigate the degradation of the surfactant, the processes were compared in terms of UV/Vis spectrum, mineralization (total organic carbon), reaction kinetics, energy efficiency and phytotoxicity. A solution containing NPnEO was prepared as a surrogate of the degreasing wastewater, was used in the processes. The results showed that the photo-assisted processes degrade the surfactant, producing biodegradable intermediates in the reaction. On the other hand, the electrochemical process influences the mineralization of the surfactant. The process of PEO carried out with a 250W lamp and a current density of 10mA/cm(2) showed the best results in terms of degradation, mineralization, reaction kinetics and energy consumption, in addition to not presenting phytotoxicity. Based on this information, this process can be a viable alternative for treating wastewater containing NPnEO, avoiding the contamination of water resources. PMID:25262384

da Silva, Salatiel Wohlmuth; Klauck, Cláudia Regina; Siqueira, Marco Antônio; Bernardes, Andréa Moura

2015-01-23

143

Electrochemical impedance spectroscopy studies of lithium diffusion in doped manganese oxide  

SciTech Connect

Cathode performance is critical to lithium ion rechargeable battery performance; effects of doping lithium manganese oxide cathode materials on cathode performance are being investigated. In this paper, Li diffusion in Al-doped LiMn{sub 2}O{sub 4} was studied and found to be controlled by the quantity of Al dopant. Electrochemical cycling was conducted at 0.5mA/cm{sub 2}; electrochemical impedance spectra were taken at open circuit potential, with impedance being measured at 65 kHz-0.01 Hz. As the Al dopant level was increased, the Li diffusion rate decreased; this was attributed to the decreased lattice parameter of the doped oxide.

Johnson, B.J.; Doughty, D.H.; Voigt, J.A.; Boyle, T.J.

1996-06-01

144

A molecularly imprinted polymer with incorporated graphene oxide for electrochemical determination of quercetin.  

PubMed

The molecularly imprinted polymer based on polypyrrole film with incorporated graphene oxide was fabricated and used for electrochemical determination of quercetin. The electrochemical behavior of quercetin on the modified electrode was studied in detail using differential pulse voltammetry. The oxidation peak current of quercetin in B-R buffer solution (pH = 3.5) at the modified electrode was regressed with the concentration in the range from 6.0 × 10(-7) to 1.5 × 10(-5) mol/L (r2 = 0.997) with a detection limit of 4.8 × 10(-8) mol/L (S/N = 3). This electrode showed good stability and reproducibility. In the above mentioned range, rutin or morin which has similar structures and at the same concentration as quercetin did not interfere with the determination of quercetin. The applicability of the method for complex matrix analysis was also evaluated. PMID:23698263

Sun, Si; Zhang, Mengqi; Li, Yijun; He, Xiwen

2013-01-01

145

Nanospace interface for the electrochemical communication between redox-active biomolecules and metal oxide electrodes  

NASA Astrophysics Data System (ADS)

Oriented assembly and interfacial electron transfer of flavin coenzymes on titanium dioxide (TiO2) electrodes have been studied to develop the smart enzyme sensors or reactors. It was demonstrated that FMN and FAD were chemically adsorbed via phosphate moiety on TiO2 surface in weak acidic solutions to make monolayers. Quasi reversible slow electron transfer was observed on the FMN or FAD-adsorbed TiO2 electrodes. It was further demonstrated that the FMN-assembled TiO2 electrode electrochemically catalyzed the oxidation of NADH. The FMN-assembled TiO2 was then combined with some dehydrogenases and NADH to perform amperometric sensing for enzyme substrates. The results suggest that the assembled flavin coenzyme might be promising for a nanospace interface to achieve electrochemical communication between redox active biomolecules and the metal oxide electrodes.

Shinohara, Hiroaki

1996-02-01

146

Electrochemical investigations of advanced materials for microelectronic and energy storage devices  

NASA Astrophysics Data System (ADS)

A broad range of electrochemical techniques are employed in this work to study a selected set of advanced materials for applications in microelectronics and energy storage devices. The primary motivation of this study has been to explore the capabilities of certain modern electrochemical techniques in a number of emerging areas of material processing and characterization. The work includes both aqueous and non-aqueous systems, with applications in two rather general areas of technology, namely microelectronics and energy storage. The sub-systems selected for investigation are: (i) Electrochemical mechanical and chemical mechanical planarization (ECMP and CMP, respectively), (ii) Carbon nanotubes in combination with room temperature ionic liquids (ILs), and (iii) Cathode materials for high-performance Li ion batteries. The first group of systems represents an important building block in the fabrication of microelectronic devices. The second and third groups of systems are relevant for new energy storage technologies, and have generated immense interests in recent years. A common feature of these different systems is that they all are associated with complex surface reactions that dictate the performance of the devices based on them. Fundamental understanding of these reactions is crucial to further development and expansion of their associated technologies. It is the complex mechanistic details of these surface reactions that we address using a judicious combination of a number of state of the art electrochemical techniques. The main electrochemical techniques used in this work include: (i) Cyclic voltammetry (CV) and slow scan cyclic voltammetry (SSCV, a special case of CV); (ii) Galvanostatic (or current-controlled) measurements; (iii) Electrochemical impedance spectroscopy (EIS), based on two different methodologies, namely, Fourier transform EIS (FT-EIS, capable of studying fast reaction kinetics in a time-resolved mode), and EIS using frequency response analysis (employed to study slow reactions such as solid state diffusion of Li). The designs of both the experimental equipment and the control variables change for studying the different aqueous and non-aqueous systems. The protocols for data analysis also change depending on the systems. In addition, it often becomes necessary to combine different aspects of the different experimental methods to obtain the necessary information about the system(s) under study. The experimental strategies and the associated theoretical considerations for developing these strategies are discussed in appropriate contexts of this work. CNT electrodes in combination with IL electrolytes are potentially important for electrochemical super-capacitors. We have carried out electrochemical investigation of such a system involving a paper-electrode of multiwall CNT in the IL of 1-Ethyl-3-methyl imidazolium ethylsulfate (EMIM-EtSO4). Our study concentrated on the analytical aspects of cyclic voltammetry (CV) to probe the double layer capacitance of these relatively unconventional systems. (that involve rather large charge-discharge time constants). Both theoretical and experimental aspects of CV for such systems have been discussed, focusing in particular, on the effects of faradaic side-reactions, electrolyte resistance and voltage scan speeds. The results have been analyzed using an electrode equivalent circuit model, demonstrating a method to account for the typical artifacts expected in CV of CNT-IL interfaces. Chemical-mechanical planarization (CMP) of copper has now become an integral part of modern semiconductor fabrication technology. Recently, electrochemical-mechanical planarization (ECMP) has emerged as a possible extension of CMP, where through voltage-activated removal of Cu surface layers, one can substantially minimize the down-force necessary for mechanical polishing However, the detailed electrochemical factors that are central to designing efficient abrasive-free electrolytes for ECMP are not clearly understood at the present time. The present work has addressed this issue by

Goonetilleke, Pubudu Chaminda

147

Electrochemical and electrochromic behavior of reactively sputtered nickel oxide  

Microsoft Academic Search

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

Eric L. Miller; R. E. Rocheleau

1997-01-01

148

Advanced materials for solid oxide fuel cells  

SciTech Connect

Purpose of the research is to improve the properties of current state- of-the-art materials used for SOFCs. The project includes interconnect development, high-performance cathode, electrochemical testing, and accelerated testing. This document reports results of mechanical tests (bend strength, elastic modulus, fracture strength) of acceptor-substituted lanthanum chromite (interconnect material).

Armstrong, T.R.; Stevenson, J.; Paulik, S.

1996-12-31

149

Electrochemical oxidation behavior of nitrite on a chitosan-carboxylated multiwall carbon nanotube modified electrode  

Microsoft Academic Search

A novel chitosan-carboxylated multiwall carbon nanotube modified glassy carbon electrode (MC\\/GCE) was developed to investigate the oxidation behavior of nitrite using cyclic voltammetry and differential pulse voltammetry modes. The electrochemical mechanism of the MC\\/GCE towards nitrite was discussed. The MC\\/GCE exhibited fast response towards nitrite with a detection limit of 1×10?7moll?1 and a linear range of 5×10?7–1×10?4moll?1. The possible interference

Lingyan Jiang; Ruixia Wang; Xinming Li; Liping Jiang; Guanghan Lu

2005-01-01

150

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

151

Mediated electrochemical oxidation of organic wastes using a Co(III) mediator in a neutral electrolyte  

DOEpatents

An electrochemical cell with a Co(III) mediator and neutral pH anolyte provides efficient destruction of organic and mixed wastes. The organic waste is concentrated in the anolyte reservoir, where the cobalt mediator oxidizes the organics and insoluble radioactive species and is regenerated at the anode until all organics are converted to carbon dioxide and destroyed. The neutral electrolyte is non-corrosive, and thus extends the lifetime of the cell and its components.

Balazs, G. Bryan (Livermore, CA); Lewis, Patricia R. (Livermore, CA)

1999-01-01

152

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

PubMed

Block copolymers that can simultaneously conduct electronic and ionic charges on the nanometer length scale can serve as innovative conductive binder material for solid-state battery electrodes. The purpose of this work is to study the electronic charge transport of poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-PEO) copolymers electrochemically oxidized with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt in the context of a lithium battery charge/discharge cycle. We use a solid-state three-terminal electrochemical cell that enables simultaneous conductivity measurements and control over electrochemical doping of P3HT. At low oxidation levels (ratio of moles of electrons removed to moles of 3-hexylthiophene moieties in the electrode), the electronic conductivity (?e,ox) increases from 10(-7) S/cm to 10(-4) S/cm. At high oxidation levels, ?e,ox approaches 10(-2) S/cm. When P3HT-PEO is used as a conductive binder in a positive electrode with LiFePO4 active material, P3HT is electrochemically active within the voltage window of a charge/discharge cycle. The electronic conductivity of the P3HT-PEO binder is in the 10(-4) to 10(-2) S/cm range over most of the potential window of the charge/discharge cycle. This allows for efficient electronic conduction, and observed charge/discharge capacities approach the theoretical limit of LiFePO4. However, at the end of the discharge cycle, the electronic conductivity decreases sharply to 10(-7) S/cm, which means the "conductive" binder is now electronically insulating. The ability of our conductive binder to switch between electronically conducting and insulating states in the positive electrode provides an unprecedented route for automatic overdischarge protection in rechargeable batteries. PMID:23789816

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

2013-07-23

153

Characteristics of graphite felt electrode electrochemically oxidized for vanadium redox battery application  

Microsoft Academic Search

The graphite felt was oxidized at a positive electrode potential in sulfuric acid solution. The electrochemical performance of the treated graphite felt served as electrode for vanadium redox battery was investigated with FT-IR, SEM, XPS, BET, cyclic voltammetry and testing VRB system, respectively. The results show that the molar ratio of O to C increases from 0.085 to 0.15 due

Xiao-gang LI; Ke-long HUANG; Su-qin LIU; Ning TAN; Li-quan CHEN

2007-01-01

154

Breeding phenomenon of nickel in anode of solid oxide fuel cell via electrochemical reaction  

Microsoft Academic Search

The solid oxide fuel cell (SOFC) was constructed with NiO\\/YSZ (yttria stabilized zirconia) as anode supported substrate, with YSZ electrolyte, and La0.8Sr0.2MnO3 (LSM) cathode. Here, we show a novel phenomenon of that original Ni grains of micron-scale size in anode of SOFC can be segregated to form nano grains by electrochemical reaction at 800°C. This breeding function can enhance cell

Chun-Hsiu Wang; Maw-Chwain Lee; Ta-Jen Huang; Yang-Chuang Chang; Wei-Xin Kao; Tai-Nan Lin

2009-01-01

155

Electrochemical synthesis and sintering of nanocrystalline cerium(IV) oxide powders  

Microsoft Academic Search

Nanocrystalline CeOâ powders were prepared electrochemically by the cathodic electrogeneration of base, and their sintering behavior was investigated. X-ray diffraction and transmission electron microscopy revealed that the as-prepared powders were crystalline cerium(IV) oxide with the cubic fluorite structure. The lattice parameter of the electrogenerated material was 0.5419 nm. The powders consisted of nonaggregated, faceted particles. The average crystallite size was

Z. Zhou; Richard J. Phillips; Jay A. Switzer

1995-01-01

156

Electrodeposition and electrochemical reduction of epitaxial metal oxide thin films and superlattices  

NASA Astrophysics Data System (ADS)

The focus of this dissertation is the electrodeposition and electrochemical reduction of epitaxial metal oxide thin films and superlattices. The electrochemical reduction of metal oxides to metals has been studied for decades as an alternative to pyrometallurgical processes for the metallurgy industry. However, the previous work was conducted on bulk polycrystalline metal oxides. Paper I in this dissertation shows that epitaxial face-centered cubic magnetite (Fe3O4 ) thin films can be electrochemically reduced to epitaxial body-centered cubic iron (Fe) thin films in aqueous solution on single-crystalline Au substrates at room temperature. This technique opens new possibilities to produce special epitaxial metal/metal oxide heterojunctions and a wide range of epitaxial metallic alloy films from the corresponding mixed metal oxides. Electrodeposition, like biomineralization, is a soft solution processing method which can produce functional materials with special properties onto conducting or semiconducting solid surfaces. Paper II in this dissertation presents the electrodeposition of cobalt-substituted magnetite (CoxFe3-xO4, 0 of cobalt-substituted magnetite (CoxFe3-xO4, 0oxide (Co3O4) thin films on stainless steel and Au single-crystalline substrates. The crystalline Co3O4 thin films exhibit high catalytic activity towards the oxygen evolution reaction in an alkaline solution. A possible application of the electrodeposited Co 3O4 is the fabrication of highly active and low-cost photoanodes for photoelectrochemical water-splitting cells.

He, Zhen

157

Advanced EMU electrochemically regenerable CO2 and moisture absorber module breadboard  

NASA Technical Reports Server (NTRS)

The applicability of the Electrochemically Regenerable Carbon Dioxide and Moisture Absorption Technology to the advanced extravehicular mobility unit was demonstrated by designing, fabricating, and testing a breadboard Absorber Module and an Electrochemical Regenerator. Test results indicated that the absorber module meets or exceeds the carbon dioxide removal requirements specified for the design and can meet the moisture removal requirement when proper cooling is provided. CO2 concentration in the vent gas stream was reduced from 0.52 to 0.027 kPa (3.9 to 0.20 mm Hg) for the full five hour test period. Vent gas dew point was reduced from inlet values of 294 K (69 F) to 278 K (41 F) at the outlet. The regeneration of expended absorbent was achieved by the electrochemical method employed in the testing. An absorbent bed using microporous hydrophobic membrane sheets with circulating absorbent is shown to be the best approach to the design of an Absorber Module based on sizing and performance. Absorber Module safety design, comparison of various absorbents and their characteristics, moisture absorption and cooling study and subsystem design and operation time-lining study were also performed.

Lee, M. C.; Sudar, M.; Chang, B. J.

1988-01-01

158

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

SciTech Connect

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.

Han, Kun; Miao, Peng; Tang, Yuguo, E-mail: tangyg@sibet.ac.cn [Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Tong, Hui; Zhu, Xiaoli [Laboratory of Biosensing Technology, School of Life Sciences, Shanghai University, Shanghai 200444 (China); Liu, Tao; Cheng, Wenbo [Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163 (China)

2014-02-03

159

An Efficient CeO2 /CoSe2 Nanobelt Composite for Electrochemical Water Oxidation.  

PubMed

CeO2 /CoSe2 nanobelt composite for electrochemical water oxidation: A new CeO2 /CoSe2 nanobelt composite is developed as a highly effective water oxidation electrocatalyst by growing CeO2 nanoparticle CoSe2 nanobelts in situ via a simple polyol reduction route. The constructed hybrid catalyst shows extremely high oxgen evolution reaction (OER) activity, even beyond the state-of-the-art RuO2 catalyst in alkaline media. PMID:25115699

Zheng, Ya-Rong; Gao, Min-Rui; Gao, Qiang; Li, Hui-Hui; Xu, Jie; Wu, Zhen-Yu; Yu, Shu-Hong

2014-08-13

160

Formation and electrochemical characterization of anodic ZrO2-WO3 mixed oxide nanotubular arrays  

NASA Astrophysics Data System (ADS)

ZrO2-WO3 mixed oxide nanotubes were synthesized by a simple electrochemical anodization route. The oxide nanotubes contained a mixture of metastable hexagonal WO3 and monoclinic (and orthorhombic) ZrO2 phases, as well as a mixed-oxide ZrW2O8 phase that showed a metastable tetragonal symmetry. Evaluation of photo-activity of the materials showed generation of photo-potentials of -85 mV and -230 mV in the as-anodized and annealed conditions. Because of the mismatch in the band edge positions of the WO3 and ZrO2 phases and the resultant relaxation of photo-generated charge carriers, no significant photo-current density could be observed. The arrays of oxide nanotubes are considered for electrochemical capacitor application because of their morphology-assisted fast charge/discharge kinetics and large surface area. Presence of a large concentration of charge defects (on the order of 1021 cm-3) and the reported high proton conductivity of the ZrO2-WO3 mixed oxide rendered high capacitance, which decreased with an increase in the scan rate of cyclic voltammetry. The highest measured capacitance was 40.03 mF/cm2 at a scan rate of 10 mV/s and the lowest was 1.93 mF/cm2 at 1 V/s in 1 M sulfuric acid solution.

Whitman, Stuart R.; Raja, Krishnan S.

2014-06-01

161

Surface functionalization of fluorine-doped tin oxide samples through electrochemical grafting.  

PubMed

Transparent conductive oxides are emerging materials in several fields, such as photovoltaics, photoelectrochemistry, and optical biosensing. Their high chemical inertia, which ensured long-term stability on one side, makes challenging the surface modification of transparent conductive oxides; long-term robust modification, high yields, and selective surface modifications are essential prerequisite for any further developments. In this work, we aim at inducing chemical functionality on fluorine-doped tin oxide surfaces (one of the most inexpensive transparent conductive oxide) by means of electrochemical grafting of aryl diazonium cations. The grafted layers are fully characterized by photoemission spectroscopy, cyclic voltammetry, and atomic force microscopy showing linear correlation between surface coverage and degree of modification. The electrochemical barrier effect of modified surfaces was studied at different pH to characterize the chemical nature of the coating. We showed immuno recognition of biotin complex built onto grafted fluorine-doped tin oxides, which opens the perspective of integrating FTO samples with biological-based devices. PMID:24171474

Lamberti, F; Agnoli, S; Brigo, L; Granozzi, G; Giomo, M; Elvassore, N

2013-12-26

162

SULFATE RADICAL-BASED ADVANCED OXIDATION PROCESSES- ACS MEETING  

EPA Science Inventory

This paper will present an overview of sulfate radical-based advanced oxidation technologies for the destruction of environmentally toxic chemicals in wastewater, industrial water, groundwater and sources of water supply. The paper will include fundamental aspects of the generati...

163

Charge Transport Properties of P3HT-PEO block copolymers that are Electrochemically Oxidized in the Solid-State  

NASA Astrophysics Data System (ADS)

We report on the relationship between morphology and electronic/ionic charge transport of Poly(3-hexylthiophene)-b-Poly(ethylene oxide) (P3HT-b-PEO) and lithium bis-(trifluoromethanesulfonyl) imide (LiTFSI) mixtures. Using ac impedance spectroscopy, we show that P3HT-b-PEO/LiTFSI mixtures can conduct electronic and ionic charges simultaneously. The electronic resistance of P3HT-b-PEO can be controlled through the electrochemical oxidation of P3HT with LiTFSI. We designed an all solid-state electrochemical cell with three terminals to measure the electronic conductivity of P3HT-b-PEO under applied potentials. The addition of a third terminal within the P3HT-b-PEO layer allows for the in-situ measurement of the electronic conductivity as a function of the P3HT electrochemical oxidation level. Our experimental setup is unique in that electrochemical oxidation occurs in the presence of solid-polymer electrolyte. Previous studies on the electrochemical oxidation of polythiophenes have been done in the presence of a liquid electrolyte. The results of the in-situ electronic conductivity measurements as a function of electrochemical doping level and block copolymer composition will be presented.

Patel, Shrayesh; Javier, Anna; Balsara, Nitash

2013-03-01

164

Electrochemically-Controlled Compositional Oscillations of Oxide Surfaces  

SciTech Connect

Perovskite oxides can exhibit a wide range of interesting characteristics such as being catalytically active and electronically and/or ionically conducting, and thus they have been used in a number of solid-state devices such as solid oxide fuel cells and sensors. As the surface compositions of perovskites can greatly influence the catalytic properties, knowing and controlling their surface chemistries is crucial to enhance device performance. In this study, we demonstrate that the surface strontium (Sr) and cobalt (Co) concentrations of perovskite-based thin films can be controlled reversibly at elevated temperatures by applying small electrical potential biases. The surface chemistry changes of La0.8Sr0.2CoO3 (LSC113), LaSrCoO4 (LSC214), and LSC214-decorated LSC113 films (LSC113/214) were investigated in situ by utilizing synchrotron-based X-ray photoelectron spectroscopy (XPS), where the largest changes of surface Sr was found for the LSC113/214 surface. These findings offer the potential of reversibly controlling the surface functionality of perovskites.

Mutoro, Eva [Massachusetts Institute of Technology (MIT); Crumlin, Ethan [Massachusetts Institute of Technology (MIT); Pöpke, Hendrik [Institute of Physical Chemistry, Justus-Liebig-University Giessen; Luerssen, Bjoern [Institute of Physical Chemistry, Justus-Liebig-University Giessen; Amati, Matteo [Sincrotrone Trieste Elettra; Abyaneh, Majid [Sincrotrone Trieste, Basovizza, Italy; Biegalski, Michael D [ORNL; Christen, Hans M [ORNL; Gregoratti, Luca [Sincrotrone Trieste, Basovizza, Italy; Janek, Jürgen [Institute of Physical Chemistry, Justus-Liebig-University Giessen; Shao-Horn, Yang [Massachusetts Institute of Technology (MIT)

2012-01-01

165

Optimization and electrochemical characterization of RF-sputtered iridium oxide microelectrodes for electrical stimulation  

NASA Astrophysics Data System (ADS)

A reactively sputtered iridium oxide (IrOx) thin film has been developed as electrochemical modification material for microelectrodes to obtain high stability and charge storage capacity (CSC) in functional electrical stimulation. The effect of the oxygen flow and oxygen to argon ratio during sputtering process on the microstructure and electrochemical properties of the IrOx film is characterized. After optimization, the activated IrOx microelectrode shows the highest CSC of 36.15 mC cm-2 at oxygen flow of 25 sccm and oxygen to argon ratio of (2.5:1). Because the deposition process of the reactively sputtered iridium oxide is an exothermic reaction, it is difficult to form film patterning by the lift-off process. The lift-off process was focused on the partially carbonized photoresist (PR) and normal PR. The higher of the carbonization degree of PR reaches, the longer the immersion duration. However, the patterning process of the iridium oxide film becomes feasible when the sputtering pressure is increasing. The experimental results show that the iridium oxide films forms the pattern with the lowest duration of ultrasonic agitation when the deposition pressure is 4.2 Pa and pressure ratio between O2 and Ar pressure is 3:4.

Kang, Xiaoyang; Liu, Jingquan; Tian, Hongchang; Yang, Bin; NuLi, Yanna; Yang, Chunsheng

2014-02-01

166

A new electrochemical aptasensor based on electrocatalytic property of graphene toward ascorbic acid oxidation.  

PubMed

Based on the superior electrocatalytic property of graphene (GN) toward ascorbic acid (AA) oxidation, a new electrochemical aptasensor has been developed. Here, adenosine triphosphate (ATP) is used as the model to demonstrate the performance of the developed aptasensor. Briefly, GN is attached to the thiolated ATP binding aptamer (ABA) modified gold electrode through ?-? stacking interaction, resulting in a significant oxidation signal of AA. In the presence of ATP, the formation of ATP-ABA complex leads to the release of GN from sensing interface, resulting in a sharp decrease of the oxidation peak current of AA and an obviously positive shift of the related peak potential. Taking both the change values of the peak current and peak potential of AA oxidation as the response signals, ATP can be detected sensitively. This is the first time to demonstrate the application of GN as the nanocatalyst in an amplified aptasensor. It can be expected that GN, as nanocatalyst, should become the very promising amplifying-elements in DNA-based electrochemical biosensors. PMID:25618724

Wu, Liang; Xiong, Erhu; Yao, Yue; Zhang, Xia; Zhang, Xiaohua; Chen, Jinhua

2015-03-01

167

Tetradentate Schiff base ligands and their complexes: Synthesis, structural characterization, thermal, electrochemical and alkane oxidation  

NASA Astrophysics Data System (ADS)

Three Schiff base ligands (H2L1-H2L3) with N2O2 donor sites were synthesized by condensation of 1,5-diaminonapthalene with benzaldehyde derivatives. A series of Cu(II), Co(II), Ni(II), Mn(II) and Cr(III) complexes were prepared and characterized by spectroscopic and analytical methods. Thermal, electrochemical and alkane oxidation reactions of the ligands and their metal complexes were investigated. Extensive application of 1D (1H, 13C NMR) and 2D (COSY, HETCOR, HMBC and TOSCY) NMR techniques were used to characterize the structures of the ligands and establish the 1H and 13C resonance assignments of the three ligands. Ligands H2L1 and H2L3 were obtained as single crystals from THF solution and characterized by X-ray diffraction. Both molecules are centrosymmetric and asymmetric unit contains one half of the molecule. Catalytic alkane oxidation reactions with the transition metal complexes investigated using cyclohexane and cyclooctane as substrates. The Cu(II) and Cr(III) complexes showed good catalytic activity in the oxidation of cyclohexane and cyclooctane to desired oxidized products. Electrochemical and thermal properties of the compounds were also investigated.

Ceyhan, Gökhan; Köse, Muhammet; McKee, Vickie; Uru?, Serhan; Gölcü, Ay?egül; Tümer, Mehmet

168

Arsenic(III) detection using electrochemical-chemical-chemical redox cycling at bare indium-tin oxide electrodes.  

PubMed

Sensitive As(III) detection in ground water is of great importance for evaluating the quality of drinking water. We report a sensitive electrochemical method for As(III) detection based on electrochemical-chemical-chemical (ECC) redox cycling involving Ru(IV) [an oxidized species of Ru(III)(NH3)5NH2(2+)], As(III), and tris(3-carboxyethyl)phosphine (TCEP). Electrochemical oxidation of Ru(III)(NH3)5NH2(2+) formed from Ru(III)(NH3)6(3+) generates Ru(IV), which quickly oxidizes As(III). This electro-mediated oxidation of As(III) produces As(V), which is reduced back to As(III) by TCEP. Electrochemically generated Ru(IV) then reoxidizes As(III), allowing ECC redox cycling to occur at a high rate on bare indium-tin oxide (ITO) electrodes without modifying the surfaces with electrocatalytic materials. Because most interfering metal ions precipitate in a carbonate buffer, water samples are mixed with carbonate buffers prior to electrochemical measurements, rendering the effects of Cu(+), Cu(2+), Fe(2+), Fe(3+), and Pb(2+) insignificant. The detection limit calculated by ECC redox cycling using a chronocoulogram is 1.2 ?M, much lower than that obtained using only the electro-mediated oxidation of As(III) (90 ?M). PMID:25209319

Jeong, Jinkyo; Das, Jagotamoy; Choi, Moonjung; Jo, Jinkyung; Aziz, Md Abdul; Yang, Haesik

2014-11-21

169

Direct correlation of electrochemical behaviors with anti-thrombogenicity of semiconducting titanium oxide films.  

PubMed

Biomaterials-associated thrombosis is dependent critically upon electrochemical response of fibrinogen on material surface. The relationship between the response and anti-thrombogenicity of biomaterials is not well-established. Titanium oxide appears to have good anti-thrombogenicity and little is known about its underlying essential chemistry. We correlate their anti-thrombogenicity directly to electrochemical behaviors in fibrinogen containing buffer solution. High degree of inherent n-type doping was noted to contribute the impedance preventing charge transfer from fibrinogen into film (namely its activation) and consequently reduced degree of anti-thrombogenicity. The impedance was the result of high donor carrier density as well as negative flat band potential. PMID:23413233

Wan, Guojiang; Lv, Bo; Jin, Guoshou; Maitz, Manfred F; Zhou, Jianzhang; Huang, Nan

2014-01-01

170

Spinel lithium manganese oxide nanoparticles: unique molten salt synthesis strategy and excellent electrochemical performances.  

PubMed

As a promising candidate cathode material, spinel lithium manganese oxide nanoparticles were successfully synthesized through a novel molten salt synthesis route at relatively low temperature, using manganese dioxide nanowires as precursor. A variety of techniques were applied to characterize the spinel nanomaterial, including X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The average particle size of the resulting spinel nanoparticles was about 80 nm with narrow distribution. As cathode material for rechargeable lithium ion battery, the electrochemical properties were investigated. All the results show that the electrochemical performances of the homogeneous spinel nanoparticles were improved, which might be ascribed to large specific surface area, fairly narrow size distribution, and the unique synthesis strategy. PMID:19908558

Wang, Xiong; Zhu, Juanjuan; Liu, Yingjie

2009-11-01

171

Synthesis and optimizable electrochemical performance of reduced graphene oxide wrapped mesoporous TiO? microspheres.  

PubMed

A facile microwave solvothermal process is developed to prepare an anatase TiO2 anode material that maintains multiple properties including high surface area, high crystallinity, uniform mesoporous, perfect microspheres and uniform particle size. Using this fine anatase TiO? product, a TiO?/RGO (RGO: reduced graphene oxide) hybrid material is prepared under UV-light irradiation. Incorporation of RGO improves the electrochemical kinetics of the TiO? microspheres, which results in superior electrochemical performance in terms of specific capacity, rate capability and cycle stability. The material shows a discharge capacity of 155.8 mA h g(-1) at the 5 C rate. Even at the 60 C rate, a high discharge capacity of 83.6 mA h g(-1) is still obtained which is two times higher than that of pristine mesoporous TiO?. PMID:24604120

Yan, Xiao; Li, Yanjuan; Du, Fei; Zhu, Kai; Zhang, Yongquan; Su, Anyu; Chen, Gang; Wei, Yingjin

2014-04-21

172

Electroless Deposition of Conformed Nanoscale Iron Oxide on Carbon Nanoarchitectures for Electrochemical Charge Storage  

SciTech Connect

We describe a simple self-limiting electroless deposition process whereby conformal, nanoscale iron oxide (FeO{sub x}) coatings are generated at the interior and exterior surfaces of macroscopically thick ({approx}90 {micro}m) carbon nanofoam paper substrates via redox reaction with aqueous K{sub 2}FeO{sub 4}. The resulting FeO{sub x}-carbon nanofoams are characterized as device-ready electrode structures for aqueous electrochemical capacitors and they demonstrate a 3-to-7 fold increase in charge-storage capacity relative to the native carbon nanofoam when cycled in a mild aqueous electrolyte (2.5 M Li{sub 2}SO{sub 4}), yielding mass-, volume-, and footprint-normalized capacitances of 84 F g{sup -1}, 121 F cm{sup -3}, and 0.85 F cm{sup -2}, respectively, even at modest FeO{sub x} loadings (27 wt %). The additional charge-storage capacity arises from faradaic pseudocapacitance of the FeO{sub x} coating, delivering specific capacitance >300 F g{sup -1} normalized to the content of FeO{sub x} as FeOOH, as verified by electrochemical measurements and in situ X-ray absorption spectroscopy. The additional capacitance is electrochemically addressable within tens of seconds, a time scale of relevance for high-rate electrochemical charge storage. We also demonstrate that the addition of borate to buffer the Li{sub 2}SO{sub 4} electrolyte effectively suppresses the electrochemical dissolution of the FeO{sub x} coating, resulting in <20% capacitance fade over 1000 consecutive cycles.

Sassin, M.; Mansour, A; Pettigrew, K; Rolison, D; Long, J

2010-01-01

173

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

PubMed Central

The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe3O4/rGO/GCE) and its simultaneous detection of dopamine (DA) and ascorbic acid (AA) is described here. The Fe3O4/rGO nanocomposite was synthesized via a simple, one step in-situ wet chemical method and characterized by different techniques. The presence of Fe3O4 nanoparticles on the surface of rGO sheets was confirmed by FESEM and TEM images. The electrochemical behavior of Fe3O4/rGO/GCE towards electrocatalytic oxidation of DA was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The electrochemical studies revealed that the Fe3O4/rGO/GCE dramatically increased the current response against the DA, due to the synergistic effect emerged between Fe3O4 and rGO. This implies that Fe3O4/rGO/GCE could exhibit excellent electrocatalytic activity and remarkable electron transfer kinetics towards the oxidation of DA. Moreover, the modified sensor electrode portrayed sensitivity and selectivity for simultaneous determination of AA and DA. The observed DPVs response linearly depends on AA and DA concentration in the range of 1–9 mM and 0.5–100 ?M, with correlation coefficients of 0.995 and 0.996, respectively. The detection limit of (S/N = 3) was found to be 0.42 and 0.12 ?M for AA and DA, respectively. PMID:25195850

Peik-See, Teo; Pandikumar, Alagarsamy; Nay-Ming, Huang; Hong-Ngee, Lim; Sulaiman, Yusran

2014-01-01

174

ELECTROCHEMICAL REDUCTION PRIOR TO ELECTRO-FENTON OXIDATION OF AZO DYES. IMPACT OF THE PRE-TREATMENT ON  

E-print Network

1 ELECTROCHEMICAL REDUCTION PRIOR TO ELECTRO-FENTON OXIDATION OF AZO DYES. IMPACT OF THE PRE dyes, Orange II, Methyl red and Biebrich Scarlet by electro-Fenton and the effect : 10.1007/s11270-012-1385-0 #12;2 by the Fenton reaction led to the oxidation of by-products from

Paris-Sud XI, Université de

175

Polyoxometalate-reduced graphene oxide hybrid catalyst: synthesis, structure, and electrochemical properties.  

PubMed

The deposition of polyoxometalate (POM) on chemically reduced graphene oxide sheets was carried out through electron transfer interaction and electrostatic interaction between POM and graphene sheets to make a heterogeneous catalyst in aqueous media. Well dispersed individual phosphomolybdic acid (PMo) clusters were observed by electron microscopy and atomic force microscopy measurements. The interaction between polyoxometalate and the graphene sheet was confirmed by using various spectroscopic methods such as FT-IR, UV-vis, and Raman. The UV-visible, IR, and cyclic voltammetry results revealed alteration of the electronic structure of deposited PMo as a result of strong interaction with the graphene oxide surface. Electrochemical properties of the PMo-rGO catalyst were investigated in an aqueous acidic electrolyte. The hybrid catalyst showed enhanced electro-oxidation of nitrite compared with pure homogeneous PMo and rGO. PMID:24168268

Kim, Yong; Shanmugam, Sangaraju

2013-11-27

176

Steam Oxidation of Advanced Steam Turbine Alloys  

SciTech Connect

Power generation from coal using ultra supercritical steam results in improved fuel efficiency and decreased greenhouse gas emissions. Results of ongoing research into the oxidation of candidate nickel-base alloys for ultra supercritical steam turbines are presented. Exposure conditions range from moist air at atmospheric pressure (650°C to 800°C) to steam at 34.5 MPa (650°C to 760°C). Parabolic scale growth coupled with internal oxidation and reactive evaporation of chromia are the primary corrosion mechanisms.

Holcomb, Gordon R.

2008-01-01

177

Retarding of electrochemical oxidation of formate on the platinum anode by a coat of Nafion membrane  

NASA Astrophysics Data System (ADS)

It has been found that the faradaic efficiency is decreasing with the electrolysis time for electrochemical reduction of CO2 to formate on a Sn cathode with a Pt anode in an undivided electrolytic cell, because the oxidation of formed formate takes place on the Pt anode, which also limits seriously the highest concentration of formate in the system. Here, we report that a coat of Nafion membrane on the Pt anode can retard the oxidation of formate: even if the concentration of the formate in the electrolyte reaches to 0.12 mol L-1, the faradaic efficiency still maintains above 61.3%; in contrast, the oxidation reaction of the formate on the naked Pt electrode is very fast, when the concentration of the formate in the electrolyte reaches to 0.023 mol L-1, the faradaic efficiency decreases to 35.3%. This is very important because the separation of formic acid could not be economical when its concentration is not high enough, and it is also costly if the depleted solution allows too less of its concentration because the solution has to be reused in the electrochemical process.

Zhang, Rui; Lv, Weixin; Li, Guanghua; Mezaal, Mohammed Adnan; Li, Xiaojing; Lei, Lixu

2014-12-01

178

An electrochemical quartz crystal impedance study on cystine precipitation onto an Au electrode surface during cysteine oxidation in aqueous solution  

Microsoft Academic Search

Electrochemical quartz crystal impedance studies on l-cysteine oxidation in aqueous solutions were conducted. The precipitation of electrogenerated species on the Au electrode surface was found in acetic and phosphate buffers. Changes in the equivalent circuit parameters, resonant frequencies and half peak width of the conductance spectra (?fG1\\/2) obtained simultaneously during electrochemical experiments were discussed. Significant changes in the motional resistance

Qingji Xie; Youyu Zhang; Yu Yuan; Yanghui Guo; Xiangjun Wang; Shouzhuo Yao

2000-01-01

179

ADVANCED OXIDATION: OXALATE DECOMPOSITION TESTING WITH OZONE  

SciTech Connect

At the Savannah River Site (SRS), oxalic acid is currently considered the preferred agent for chemically cleaning the large underground Liquid Radioactive Waste Tanks. It is applied only in the final stages of emptying a tank when generally less than 5,000 kg of waste solids remain, and slurrying based removal methods are no-longer effective. The use of oxalic acid is preferred because of its combined dissolution and chelating properties, as well as the fact that corrosion to the carbon steel tank walls can be controlled. Although oxalic acid is the preferred agent, there are significant potential downstream impacts. Impacts include: (1) Degraded evaporator operation; (2) Resultant oxalate precipitates taking away critically needed operating volume; and (3) Eventual creation of significant volumes of additional feed to salt processing. As an alternative to dealing with the downstream impacts, oxalate decomposition using variations of ozone based Advanced Oxidation Process (AOP) were investigated. In general AOPs use ozone or peroxide and a catalyst to create hydroxyl radicals. Hydroxyl radicals have among the highest oxidation potentials, and are commonly used to decompose organics. Although oxalate is considered among the most difficult organic to decompose, the ability of hydroxyl radicals to decompose oxalate is considered to be well demonstrated. In addition, as AOPs are considered to be 'green' their use enables any net chemical additions to the waste to be minimized. In order to test the ability to decompose the oxalate and determine the decomposition rates, a test rig was designed, where 10 vol% ozone would be educted into a spent oxalic acid decomposition loop, with the loop maintained at 70 C and recirculated at 40L/min. Each of the spent oxalic acid streams would be created from three oxalic acid strikes of an F-area simulant (i.e., Purex = high Fe/Al concentration) and H-area simulant (i.e., H area modified Purex = high Al/Fe concentration) after nearing dissolution equilibrium, and then decomposed to {le} 100 Parts per Million (ppm) oxalate. Since AOP technology largely originated on using ultraviolet (UV) light as a primary catalyst, decomposition of the spent oxalic acid, well exposed to a medium pressure mercury vapor light was considered the benchmark. However, with multi-valent metals already contained in the feed, and maintenance of the UV light a concern; testing was conducted to evaluate the impact from removing the UV light. Using current AOP terminology, the test without the UV light would likely be considered an ozone based, dark, ferrioxalate type, decomposition process. Specifically, as part of the testing, the impacts from the following were investigated: (1) Importance of the UV light on the decomposition rates when decomposing 1 wt% spent oxalic acid; (2) Impact of increasing the oxalic acid strength from 1 to 2.5 wt% on the decomposition rates; and (3) For F-area testing, the advantage of increasing the spent oxalic acid flowrate from 40 L/min (liters/minute) to 50 L/min during decomposition of the 2.5 wt% spent oxalic acid. The results showed that removal of the UV light (from 1 wt% testing) slowed the decomposition rates in both the F & H testing. Specifically, for F-Area Strike 1, the time increased from about 6 hours to 8 hours. In H-Area, the impact was not as significant, with the time required for Strike 1 to be decomposed to less than 100 ppm increasing slightly, from 5.4 to 6.4 hours. For the spent 2.5 wt% oxalic acid decomposition tests (all) without the UV light, the F-area decompositions required approx. 10 to 13 hours, while the corresponding required H-Area decompositions times ranged from 10 to 21 hours. For the 2.5 wt% F-Area sludge, the increased availability of iron likely caused the increased decomposition rates compared to the 1 wt% oxalic acid based tests. In addition, for the F-testing, increasing the recirculation flow rates from 40 liter/minute to 50 liter/minute resulted in an increased decomposition rate, suggesting a better use of ozone.

Ketusky, E.; Subramanian, K.

2012-02-29

180

Advanced oxidation processes coupled with electrocoagulation for the exhaustive abatement of Cr-EDTA.  

PubMed

Using Cr-EDTA as a model system, a two-step method has been investigated for the abatement of persistent chromium complexes in water. The treatment consists of an oxidative decomposition of the organic ligands by means of ozonization or electrochemical oxidation at a boron doped diamond (BDD) electrode, followed by removal of the metal via electrochemical coagulation. In the designed synthetic waste, EDTA has been used both as a chelating agent and as a mimic of the organic content of a typical wastewater provided by a purification leather plant. A crucial point evaluated is the influence of the oxidative pretreatment on the chemical modification of the synthetic waste and hence on the electrocoagulation efficacy. Because of the great stability of Cr complexes, such as Cr-EDTA, the classical coagulation methods, based on ligand exchange between Cr(III) and Fe(II) or Fe(III), are ineffective toward Cr abatement in the presence of organic substances. On the contrary, when advanced oxidation processes (AOPs), such as ozonization or electrooxidation at a BDD anode are applied in series with electrocoagulation (EC), complete abatement of the recalcitrant Cr fraction can be achieved. ECs have been carried out by using Fe sacrificial anodes, with alternating polarization and complete Cr abatement (over 99%) has been obtained with modest charge consumption. It has been found that Cr(III) is first oxidized to Cr(VI) in the AOP preceding EC. Then, during EC, Cr(VI) is mainly reduced back to Cr(III) by electrogenerated Fe(II). Thus, Cr is mainly eliminated as Cr(III). However, a small fraction of Cr(VI) goes with the precipitate as confirmed by XPS analysis of the sludge. PMID:21255817

Durante, Christian; Cuscov, Marco; Isse, Abdirisak Ahmed; Sandonà, Giancarlo; Gennaro, Armando

2011-02-01

181

Applications of advanced electrochemical techniques in the study of microbial fuel cells and corrosion protection by polymer coatings  

Microsoft Academic Search

The results of a detailed evaluation of the properties of the anode and the cathode of a mediator-less microbial fuel cell (MFC) and the factors determining the power output of the MFC using different electrochemical techniques are presented in Chapter 1. In the MFC under investigation, the biocatalyst - Shewanella oneidensis MR-1 - oxidizes the fuel and transfers the electrons

Aswin Karthik Manohar

2010-01-01

182

Electrochemical oxidation of underivatized-nucleic acids at highly boron-doped diamond electrodes.  

PubMed

Boron-doped diamond (BDD) electrodes have been examined for the electrochemical oxidation of underivatized-nucleic acids in terms of single stranded and double stranded DNA. Cyclic voltammetry and square wave voltammetry have been used to study the oxidation reactions and to detect DNA without derivatization or hydrolysis steps. At the diamond electrode, at least two well-defined voltammetric peaks were observed for both single stranded and double stranded DNA. Diamond electrode is the first material to show a well-defined voltammetric peaks for adenine group oxidation directly in the helix structure of nucleic acid due to its wide potential window. For single stranded DNA, a third peak, related to the pyrimidine group oxidation was also observed. As-deposited diamond film with predominantly hydrogen-terminated surface exhibited superior performance over oxygen-terminated diamond in terms of sensitivity. However, by optimizing the ionic strength, sensitivity of O-terminated films could be improved. Linear calibration results have shown linearity of current with concentration in the range 0.1-8 microg mL(-1) for both guanine and adenine residues at as-deposited BDD. Detection limits (S/N = 3) of 3.7 and 10 ng mL(-1) for adenine and guanine residue in single stranded DNA, respectively, and 5.2 and 10 ng mL(-1) for adenine and guanine residue in double stranded DNA, respectively, were observed. This work shows the promising use of diamond as an electrochemical detector for direct detection of nucleic acids. The results also show the possibility of using the oxidation peak current of adenine group that is more sensitive for the direct detection of nucleicacids. PMID:12894832

Ivandini, T A; Sarada, B V; Rao, T N; Fujishima, A

2003-07-01

183

New advanced surface modification technique: titanium oxide ceramic surface implants: long-term clinical results  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to discuss the background to advanced surface modification technologies and to present a new technique, involving the formation of a titanium oxide ceramic coating, with relatively long-term results of its clinical utilization. Three general techniques are used to modify surfaces: the addition or removal of material and the change of material already present. Surface properties can also be changed without the addition or removal of material, through the laser or electron beam thermal treatment. The new technique outlined in this paper relates to the production of a corrosion-resistant 2000-2500 A thick, ceramic oxide layer with a coherent crystalline structure on the surface of titanium implants. The layer is grown electrochemically from the bulk of the metal and is modified by heat treatment. Such oxide ceramic-coated implants have a number of advantageous properties relative to implants covered with various other coatings: a higher external hardness, a greater force of adherence between the titanium and the oxide ceramic coating, a virtually perfect insulation between the organism and the metal (no possibility of metal allergy), etc. The coated implants were subjected to various physical, chemical, electronmicroscopic, etc. tests for a qualitative characterization. Finally, these implants (plates, screws for maxillofacial osteosynthesis and dental root implants) were applied in surgical practice for a period of 10 years. Tests and the experience acquired demonstrated the good properties of the titanium oxide ceramic-coated implants.

Szabo, Gyorgy; Kovacs, Lajos; Barabas, Jozsef; Nemeth, Zsolt; Maironna, Carlo

2001-11-01

184

Electrochemical tuning of layered lithium transition metal oxides for improvement of oxygen evolution reaction  

NASA Astrophysics Data System (ADS)

Searching for low-cost and efficient catalysts for the oxygen evolution reaction has been actively pursued owing to its importance in clean energy generation and storage. While developing new catalysts is important, tuning the electronic structure of existing catalysts over a wide electrochemical potential range can also offer a new direction. Here we demonstrate a method for electrochemical lithium tuning of catalytic materials in organic electrolyte for subsequent enhancement of the catalytic activity in aqueous solution. By continuously extracting lithium ions out of LiCoO2, a popular cathode material in lithium ion batteries, to Li0.5CoO2 in organic electrolyte, the catalytic activity is significantly improved. This enhancement is ascribed to the unique electronic structure after the delithiation process. The general efficacy of this methodology is demonstrated in several mixed metal oxides with similar improvements. The electrochemically delithiated LiCo0.33Ni0.33Fe0.33O2 exhibits a notable performance, better than the benchmark iridium/carbon catalyst.

Lu, Zhiyi; Wang, Haotian; Kong, Desheng; Yan, Kai; Hsu, Po-Chun; Zheng, Guangyuan; Yao, Hongbin; Liang, Zheng; Sun, Xiaoming; Cui, Yi

2014-07-01

185

Rapid Online Non-Enzymatic Protein Digestion Combining Microwave Heating Acid Hydrolysis and Electrochemical Oxidation  

PubMed Central

We report an online non-enzymatic method for site-specific digestion of proteins to yield peptides that are well suited for collision induced dissociation (CID) tandem mass spectrometry (MS/MS). The method combines online microwave heating acid hydrolysis at aspartic acid and online electrochemical oxidation at tryptophan and tyrosine. The combined microwave/electrochemical (microwave/echem) digestion is reproducible and produces peptides with an average sequence length of 10 amino acids. This peptide length is similar to the average peptide length of 9 amino acids obtained by digestion of proteins with the enzyme trypsin. As a result, the peptides produced by this novel non-enzymatic digestion method, when analyzed by ESI-MS, produce protonated molecules with mostly +1 and +2 charge states. The combination of these two non-enzymatic methods overcomes shortcomings with each individual method in that: i) peptides generated by the microwave-hydrolysis method have an average amino acid length of 16 amino acids, and ii) the inability of the electrochemical-cleavage method to reproducibly digest proteins with molecular masses above 4 kDa. Preliminary results are presented on the application and utility of this rapid online digestion (total of 6 min digestion time) on a series of standard peptides and proteins as well as an E. coli protein extract. PMID:21138252

Basile, Franco; Hauser, Nicolas

2010-01-01

186

Mineralization of citric acid wastewater by photo-electrochemical chlorine oxidation.  

PubMed

This work demonstrates a novel chloride photo-electrochemical method for mineralizing citric acid. The electrolytic reactor with a length of 12 cm, a width of 12 cm and a height of 30 cm held 2.5 L of solution, which was involved in the batch reaction. Both anode and cathode were made of titanium coated with RuO2/IrO2. The results revealed that the solution pH dominated the production of hypochlorous acid (HOCl) oxidant in the presence of NaCl as direct current electricity was used. The chloride electrochemical process at pH 5.5 removed 59% of total organic carbon (TOC) in 4 h (NaCl = 200 mM, current = 5 A). UV irradiation (254 nm) in the reactor induced the photo-electrochemical reaction, increasing the TOC removal from 59% to 99.4%. Finally, the reaction pathway for citric acid mineralization was discussed with reference to the detection of intermediates using a liquid chromatography-mass spectrometry (LC-MS). PMID:23500176

Chen, Kuan-Hsiang; Shih, Yu-Jen; Huang, Yao-Hui

2013-05-30

187

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

PubMed

Poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite film modified glassy carbon electrodes (4-ABA/ERGO/GCEs) were fabricated by a two-step electrochemical method. The electrochemical behavior of acetaminophen at the modified electrode was investigated by means of cyclic voltammetry. The results indicated that 4-ABA/ERGO composite films possessed excellent electrocatalytic activity towards the oxidation of acetaminophen. The electrochemical reaction of acetaminophen at 4-ABA/ERGO/GCE is proved to be a surface-controlled process involving the same number of protons and electrons. The voltammetric determination of acetaminophen performed with the 4-ABA/ERGO modified electrode presents a good linearity in the range of 0.1-65 ?M with a low detection limit of 0.01 ?M (S/N=3). In the case of using the 4-ABA/ERGO/GCE, acetaminophen and dopamine can be simultaneously determined without mutual interference. Furthermore, the 4-ABA/ERGO/GCE has good reproducibility and stability, and can be used to determine acetaminophen in tablets. PMID:25491797

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

2014-12-01

188

Effect of oxidation–reduction surface treatment on the electrochemical behavior of PAN-based carbon fibers  

Microsoft Academic Search

The relationship between surface functionality and electrochemical properties of polyacrylonitrile (PAN)-based carbon fibers (CFs) differentiated by the modification treatment was studied. Oxidative and non-oxidative treatments (i.e. oxidation with ammonium peroxydisulfate (1 M (NH4)2S2O8), and heating in hydrogen and argon atmosphere) were used for the modification. The chemical character of the CF surface was estimated by using the titration method and

Yu. V. Basova; H. Hatori; Y. Yamada; K. Miyashita

1999-01-01

189

Synthesis and optimizable electrochemical performance of reduced graphene oxide wrapped mesoporous TiO2 microspheres  

NASA Astrophysics Data System (ADS)

A facile microwave solvothermal process is developed to prepare an anatase TiO2 anode material that maintains multiple properties including high surface area, high crystallinity, uniform mesoporous, perfect microspheres and uniform particle size. Using this fine anatase TiO2 product, a TiO2/RGO (RGO: reduced graphene oxide) hybrid material is prepared under UV-light irradiation. Incorporation of RGO improves the electrochemical kinetics of the TiO2 microspheres, which results in superior electrochemical performance in terms of specific capacity, rate capability and cycle stability. The material shows a discharge capacity of 155.8 mA h g-1 at the 5 C rate. Even at the 60 C rate, a high discharge capacity of 83.6 mA h g-1 is still obtained which is two times higher than that of pristine mesoporous TiO2.A facile microwave solvothermal process is developed to prepare an anatase TiO2 anode material that maintains multiple properties including high surface area, high crystallinity, uniform mesoporous, perfect microspheres and uniform particle size. Using this fine anatase TiO2 product, a TiO2/RGO (RGO: reduced graphene oxide) hybrid material is prepared under UV-light irradiation. Incorporation of RGO improves the electrochemical kinetics of the TiO2 microspheres, which results in superior electrochemical performance in terms of specific capacity, rate capability and cycle stability. The material shows a discharge capacity of 155.8 mA h g-1 at the 5 C rate. Even at the 60 C rate, a high discharge capacity of 83.6 mA h g-1 is still obtained which is two times higher than that of pristine mesoporous TiO2. Electronic supplementary information (ESI) available: TGA of TiO2/RGO sample, XPS and AFM of the graphene oxide, SEM of TiO2 nanoparticles, SEM of the TiO2 and TiO2/RGO after cycles, rate performance of RGO, rate performance of TiO2/RGO with different contents of RGO. See DOI: 10.1039/c3nr06393c

Yan, Xiao; Li, Yanjuan; Du, Fei; Zhu, Kai; Zhang, Yongquan; Su, Anyu; Chen, Gang; Wei, Yingjin

2014-03-01

190

Advanced launch system. Advanced development oxidizer turbopump program  

NASA Technical Reports Server (NTRS)

On May 19, 1989, Pratt & Whitney was awarded contract NAS8-37595 by the National Aeronautics and Space Administration, Marshall Space Flight Center, Huntsville Alabama for an Advanced Development Program (ADP) to design, develop and demonstrate a highly reliable low cost, liquid oxygen turbopump for the Advanced Launch System (ALS). The ALS had an overall goal of reducing the cost of placing payloads in orbit by an order of magnitude. This goal would require a substantial reduction in life cycle costs, with emphasis on recurring costs, compared to current launch vehicles. Engine studies supporting these efforts were made for the Space Transportation Main Engine (STME). The emphasis on low cost required design simplification of components and subsystems such that the ground maintenance and test operations was minimized. The results of the Oxygen Turbopump ADP technology effort would provide data to be used in the STME. Initially the STME baseline was a gas generator cycle engine with a vacuum thrust level of 580,000 lbf. This was later increased to 650,000 lbf and the oxygen turbopump design approach was changed to reflect the new thrust level. It was intended that this ADP program be conducted in two phases. Phase 1, a basic phase, would encompass the preliminary design effort, and Phase II, an optional contract phase to cover design, fabrication and test evaluation of an oxygen turbopump at a component test facility at the NASA John C. Stennis Space Center in Mississippi. The basic phase included preliminary design and analysis, evaluation of low cost concepts, and evaluation of fabrication techniques. The option phase included design of the pump and support hardware, analysis of the final configuration to ensure design integrity, fabrication of hardware to demonstrate low cost, DVS Testing of hardware to verify the design, assembly of the turbopump and full scale turbopump testing. In December 1990, the intent of this ADP to support the design and development was changed. The design effort for the oxygen turbopump became part of the STME Phase B contract. The status of the pump design funded through this ADP was presented at the Preliminary Design Review (PDR) at the MSFC on October 24, 1990. Advancements in the design of the pump were subsequently continued under the Phase B Contract. The emphasis of this ADP became the demonstration of individual technologies that would have the greatest potential for reducing the recurring cost and increasing reliability. In October of 1992, overall program funding was reduced and work on this ADP was terminated.

1993-01-01

191

Electrochemical investigation of polyhalide ion oxidation-reduction on carbon nanotube electrodes for redox flow batteries  

SciTech Connect

Polyhalide ions (Br-/BrCl2-) are an important redox couple for redox flow batteries. The oxidation-reduction behavior of polyhalide ions on a carbon nanotube (CNT) electrode has been investigated with cyclic voltammetry and electrochemical impedance spectroscopy. The onset oxidation potential of Br-/BrCl2- is negatively shifted by >100 mV, and the redox current peaks are greatly enhanced on a CNT electrode compared with that on the most widely-used graphite electrode. The reaction resistance of the redox couple (Br-/BrCl2-) is decreased on a CNT electrode. The redox reversibility is increased on a CNT electrode even though it still needs further improvement. CNT is a promising electrode material for redox flow batteries.

Shao, Yuyan; Engelhard, Mark H.; Lin, Yuehe

2009-10-01

192

An electrochemical study of frustrated Lewis pairs: a metal-free route to hydrogen oxidation.  

PubMed

Frustrated Lewis pairs have found many applications in the heterolytic activation of H2 and subsequent hydrogenation of small molecules through delivery of the resulting proton and hydride equivalents. Herein, we describe how H2 can be preactivated using classical frustrated Lewis pair chemistry and combined with in situ nonaqueous electrochemical oxidation of the resulting borohydride. Our approach allows hydrogen to be cleanly converted into two protons and two electrons in situ, and reduces the potential (the required energetic driving force) for nonaqueous H2 oxidation by 610 mV (117.7 kJ mol(-1)). This significant energy reduction opens routes to the development of nonaqueous hydrogen energy technology. PMID:24720359

Lawrence, Elliot J; Oganesyan, Vasily S; Hughes, David L; Ashley, Andrew E; Wildgoose, Gregory G

2014-04-23

193

An Electrochemical Study of Frustrated Lewis Pairs: A Metal-Free Route to Hydrogen Oxidation  

PubMed Central

Frustrated Lewis pairs have found many applications in the heterolytic activation of H2 and subsequent hydrogenation of small molecules through delivery of the resulting proton and hydride equivalents. Herein, we describe how H2 can be preactivated using classical frustrated Lewis pair chemistry and combined with in situ nonaqueous electrochemical oxidation of the resulting borohydride. Our approach allows hydrogen to be cleanly converted into two protons and two electrons in situ, and reduces the potential (the required energetic driving force) for nonaqueous H2 oxidation by 610 mV (117.7 kJ mol–1). This significant energy reduction opens routes to the development of nonaqueous hydrogen energy technology. PMID:24720359

2014-01-01

194

Influence of hydrogen-oxidizing bacteria on the corrosion of low carbon steel: Local electrochemical investigations.  

PubMed

Low carbon steel has been considered a suitable material for component of the multi-barrier system employed on the geological disposal of high-level radioactive waste (HLW). A non negligible amount of dihydrogen (H2) is expected to be produced over the years within the geological repository due to the anoxic corrosion of metallic materials and also to the water radiolysis. The influence of the activity of hydrogen-oxidizing bacteria (HOB) and iron-reducing bacteria (IRB) on carbon steel corrosion is considered in this study because of the high availability of energetic nutriments (H2, iron oxides and hydroxides) produced in anoxic disposal conditions. Local electrochemical techniques were used for investigating the activity of IRB as a promoter of local corrosion in the presence of H2 as electron donor. A local consumption of H2 by the bacteria has been evidenced and impedance measurements indicate the formation of a thick layer of corrosion products. PMID:24177135

Moreira, Rebeca; Schütz, Marta K; Libert, Marie; Tribollet, Bernard; Vivier, Vincent

2014-06-01

195

Electrochemical and electrochromic properties of niobium oxide thin films fabricated by pulsed laser deposition  

SciTech Connect

Niobium oxide thin films have been successfully fabricated on the indium-tin oxide coated glasses by pulsed laser deposition in an O{sub 3}/O{sub 2} gas mixture. Films are characterized by X-ray diffraction and Raman spectrometry. Electrochemical and electrochromic properties of Nb{sub 2}O{sub 5} films are examined by cyclic voltammogram and potential step coupled with an in situ charge-coupled device spectrophotometer. The unique characteristics of absorption spectra of Nb{sub 2}O{sub 5} films are observed for the first time, and the optical absorption from the trapped electrons in the surface states plays an important role in the electrochromic phenomenon.

Fu, Z.W.; Kong, J.J.; Qin, Q.Z.

1999-10-01

196

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

PubMed

Human exposure to particulate matter (PM) air pollution is associated with human morbidity and mortality. The mechanisms by which PM impacts human health are unresolved, but evidence suggests that PM intake leads to cellular oxidative stress through the generation of reactive oxygen species (ROS). Therefore, reliable tools are needed for estimating the oxidant generating capacity, or oxidative load, of PM at high temporal resolution (minutes to hours). One of the most widely reported methods for assessing PM oxidative load is the dithiothreitol (DTT) assay. The traditional DTT assay utilizes filter-based PM collection in conjunction with chemical analysis to determine the oxidation rate of reduced DTT in solution with PM. However, the traditional DTT assay suffers from poor time resolution, loss of reactive species during sampling, and high limit of detection. Recently, a new DTT assay was developed that couples a Particle-Into-Liquid-Sampler with microfluidic-electrochemical detection. This 'on-line' system allows high temporal resolution monitoring of PM reactivity with improved detection limits. This study reports on a laboratory comparison of the traditional and on-line DTT approaches. An urban dust sample was aerosolized in a laboratory test chamber at three atmospherically-relevant concentrations. The on-line system gave a stronger correlation between DTT consumption rate and PM mass (R(2) = 0.69) than the traditional method (R(2) = 0.40) and increased precision at high temporal resolution, compared to the traditional method. PMID:24711675

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

2014-05-01

197

Removal of colour and COD from wastewater containing acid blue 22 by electrochemical oxidation.  

PubMed

Electrochemical oxidation of synthetic wastewater containing acid blue 22 on a boron-doped diamond electrode (BDD) was studied, using cyclic voltammetry and bulk electrolysis. The influence of current density, dye concentration, flow rate, and temperature was investigated, in order to find the best conditions for COD and colour removal. It was found that, during oxidation, a polymeric film, causing BDD deactivation, was formed in the potential region of water stability, and that it was removed by anodic polarisation at high potentials in the region of O(2) evolution. Bulk electrolysis results showed that the electrochemical process was suitable for completely removing COD and effectively decolourising wastewaters, due to the production of hydroxyl radicals on the diamond surface. In particular, under optimal experimental conditions of flow rates (i.e. 300 dm(3) h(-1)) and current density (i.e. 20 mA cm(-2)), 97% of COD was removed in 12h electrolysis, with 70 kWh m(-3) energy consumption. PMID:17869416

Panizza, Marco; Cerisola, Giacomo

2008-05-01

198

Processing, microstructural evolution and electrochemical performance relationships in solid oxide fuel cells  

NASA Astrophysics Data System (ADS)

The relationships between the processing parameters, microstructures and electrochemical performance of solid oxide fuel cell (SOFC) components were investigated. The operating regimes (i.e., reducing vs. oxidizing) as well as the elevated temperatures (e.g. 800°C) for their operation introduce several material challenges. Therefore, composite materials are employed to withstand operating conditions while providing sufficient electrochemical performance for fuel cell operation. Analyses on lanthanum-strontium manganite (LSM) - yttria stabilized zirconia (YSZ) compositions (45 vol%-55 vol%) by impedance spectroscopy demonstrated that two competing polarization mechanisms (i.e. charge-exchange and surface adsorption-diffusion of oxygen) limit performance. Optimization of microstructures resulted in total resistances as low as 0.040 Ohm cm2. Studies on Ag composites revealed that incorporation of up to 25 vol% oxide particles (LSM and YSZ) with sizes comparable to the Ag grains (~0.5 microm) can minimize the densification and coarsening of the Ag matrix. While the powder based oxide additions increased the stability limit of porous Ag composites from <550°C to 800°C, the use of nanostructured coatings increased the stability limit to 900°C for cathodes and current collectors. Investigations of Ni-YSZ anode microstructures demonstrated that uniform distribution of percolating isometric pores (>5 microm) allows forming desired continuous percolation of all phases (Ni, YSZ and pores) lowering activation polarization below 0.100 Ohm cm2 and maintaining significant electrical conductivity (>1000 S/cm). Identification of polarization mechanisms by deconvolution of impedance spectra and tailoring the corresponding microstructures was demonstrated as an effective method for optimization of SOFC components.

Sarikaya, Ayhan

199

Treatment of gasoline-contaminated waters by advanced oxidation processes  

Microsoft Academic Search

In this study, the efficiency of advanced oxidative processes (AOPs) was investigated toward the degradation of aqueous solutions containing benzene, toluene and xylenes (BTX) and gasoline-contaminated waters. The results indicated that BTX can be effectively oxidized by near UV-assisted photo-Fenton process. The treatment permits almost total degradation of BTX and removal of more than 80% of the phenolic intermediates at

Elaine Regina Lopes Tiburtius; Patricio Peralta-Zamora; Alexandre Emmel

2005-01-01

200

Direct electrochemical oxidation of S-captopril using gold electrodes modified with graphene-AuAg nanocomposites  

PubMed Central

In this paper, we present a novel approach for the electrochemical detection of S-captopril based on graphene AuAg nanostructures used to modify an Au electrode. Multi-layer graphene (Gr) sheets decorated with embedded bimetallic AuAg nanoparticles were successfully synthesized catalytically with methane as the carbon source. The two catalytic systems contained 1.0 wt% Ag and 1.0 wt% Au, while the second had a larger concentration of metals (1.5 wt% Ag and 1.5 wt% Au) and was used for the synthesis of the Gr-AuAg-1 and Gr-AuAg-1.5 multicomponent samples. High-resolution transmission electron microscopy analysis indicated the presence of graphene flakes that had regular shapes (square or rectangular) and dimensions in the tens to hundreds of nanometers. We found that the size of the embedded AuAg nanoparticles varied between 5 and 100 nm, with the majority being smaller than 20 nm. Advanced scanning transmission electron microscopy studies indicated a bimetallic characteristic of the metallic clusters. The resulting Gr-AuAg-1 and Gr-AuAg-1.5 samples were used to modify the surface of commonly used Au substrates and subsequently employed for the direct electrochemical oxidation of S-captopril. By comparing the differential pulse voltammograms recorded with the two modified electrodes at various concentrations of captopril, the peak current was determined to be well-defined, even at relatively low concentration (10?5 M), for the Au/Gr-AuAg-1.5 electrode. In contrast, the signals recorded with the Au/Gr-AuAg-1 electrode were poorly defined within a 5×10?6 to 5×10?3 M concentration range, and many of them overlapped with the background. Such composite materials could find significant applications in nanotechnology, sensing, or nanomedicine. PMID:24596464

Pogacean, Florina; Biris, Alexandru R; Coros, Maria; Lazar, Mihaela Diana; Watanabe, Fumiya; Kannarpady, Ganesh K; Al Said, Said A Farha; Biris, Alexandru S; Pruneanu, Stela

2014-01-01

201

Direct electrochemical oxidation of S-captopril using gold electrodes modified with graphene-AuAg nanocomposites.  

PubMed

In this paper, we present a novel approach for the electrochemical detection of S-captopril based on graphene AuAg nanostructures used to modify an Au electrode. Multi-layer graphene (Gr) sheets decorated with embedded bimetallic AuAg nanoparticles were successfully synthesized catalytically with methane as the carbon source. The two catalytic systems contained 1.0 wt% Ag and 1.0 wt% Au, while the second had a larger concentration of metals (1.5 wt% Ag and 1.5 wt% Au) and was used for the synthesis of the Gr-AuAg-1 and Gr-AuAg-1.5 multicomponent samples. High-resolution transmission electron microscopy analysis indicated the presence of graphene flakes that had regular shapes (square or rectangular) and dimensions in the tens to hundreds of nanometers. We found that the size of the embedded AuAg nanoparticles varied between 5 and 100 nm, with the majority being smaller than 20 nm. Advanced scanning transmission electron microscopy studies indicated a bimetallic characteristic of the metallic clusters. The resulting Gr-AuAg-1 and Gr-AuAg-1.5 samples were used to modify the surface of commonly used Au substrates and subsequently employed for the direct electrochemical oxidation of S-captopril. By comparing the differential pulse voltammograms recorded with the two modified electrodes at various concentrations of captopril, the peak current was determined to be well-defined, even at relatively low concentration (10(-5) M), for the Au/Gr-AuAg-1.5 electrode. In contrast, the signals recorded with the Au/Gr-AuAg-1 electrode were poorly defined within a 5×10(-6) to 5×10(-3) M concentration range, and many of them overlapped with the background. Such composite materials could find significant applications in nanotechnology, sensing, or nanomedicine. PMID:24596464

Pogacean, Florina; Biris, Alexandru R; Coros, Maria; Lazar, Mihaela Diana; Watanabe, Fumiya; Kannarpady, Ganesh K; Al Said, Said A Farha; Biris, Alexandru S; Pruneanu, Stela

2014-01-01

202

TREATMENT OF COMPLEX SYSTEMS ADVANCED OXIDATION PROCESSES  

Microsoft Academic Search

\\u000a Many water streams, both wastewater effluents and drinking8 water sources, contain pollutants that cannot be removed or destroyed\\u000a by conventional physical or biological treatment processes. In such cases it is necessary to seek alternatives. One approach\\u000a is to destroy the pollutant by application of a strong oxidizing agent. Chlorine is one candidate reagent, but it can produce\\u000a undesirable reaction products,

THOMAS W. CHAPMAN

203

Studies on electrochemical recovery of silver from simulated waste water from Ag(II)/Ag(I) based mediated electrochemical oxidation process.  

PubMed

In the Ag(II)/Ag(I) based mediated electrochemical oxidation (MEO) process, the spent waste from the electrochemical cell, which is integrated with the scrubber columns, contains high concentrations of precious silver as dissolved ions in both the anolyte and the catholyte. This work presents an electrochemical developmental study for the recovery of silver from simulated waste water from Ag(II)/Ag(I) based MEO process. Galvanostatic method of silver deposition on Ti cathode in an undivided cell was used, and the silver recovery rate kinetics of silver deposition was followed. Various experimental parameters, which have a direct bearing on the metal recovery efficiency, were optimized. These included studies with the nitric acid concentration (0.75-6M), the solution stirring rate (0-1400 rpm), the inter-electrode distance between the anode and the cathode (2-8 cm), the applied current density (29.4-88.2 mA cm(-2)), and the initial Ag(I) ion concentration (0.01-0.2M). The silver recovered by the present electrodeposition method was re-dissolved in 6M nitric acid and subjected to electrooxidation of Ag(I) to Ag(II) to ascertain its activity towards Ag(II) electrogeneration from Ag(I), which is a key factor for the efficient working of MEO process. Our studies showed that the silver metal recovered by the present electrochemical deposition method could be reused repeatedly for MEO process with no loss in its electrochemical activity. Some work on silver deposition from sulfuric acid solution of different concentrations was also done because of its promising features as the catholyte in the Ag(II) generating electrochemical cell used in MEO process, which include: (i) complete elimination of poisonous NO(x) gas liberation in the cathode compartment, (ii) reduced Ag(+) ion migration across Nafion membrane from anolyte to catholyte thereby diminished catholyte contamination, and (iii) lower cell voltage and hence lesser power consumption. PMID:18762320

Chandrasekara Pillai, K; Chung, Sang Joon; Moon, Il-Shik

2008-11-01

204

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

NASA Astrophysics Data System (ADS)

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 reactions around the triple-phase boundary. These two products also decreased the oxygen vacancy density around the triple-phase boundary, slowed down the electrochemical oxygen reduction reaction, and in turn increased the NOx signal. The surface nanostructure of electrodes was modified by wet chemical processes to change the non-electrochemical NOx reactions. A thin WO3 coating prepared from the peroxytungstate solution with well-defined triple-phase boundaries resulted in higher sensitivity and better response times than the electrode fabricated from commercial WO3 powders. The electrodeposited porous Pt layer greatly increased the surface area and led to a similar catalytic activity with PtY on NOx sensing. The modified electrodes demonstrated the importance of the surface nanostructure and interfacial species for potentiometric NOx sensing. The sensors composed of tungsten/H2O2 deposited sensing electrodes and more hydrothermal stable Pt-loaded siliceous zeolite Y (PtSY) reference electrodes have stable NO2 signal at 5-10% water in 600°C.

Yang, Jiun-Chan

205

High selectivity of benzene electrochemical oxidation to p-benzoquinone on modified PbO2 electrode  

NASA Astrophysics Data System (ADS)

In this paper, a modified Ti/SnO2-Sb2O3/PbO2 electrode was successfully synthesized. The interlayer SnO2-Sb2O3 was obtained through thermal decomposition and the surface layer by electrochemical deposition. The structures and morphology of the layers were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical property was carried out by cyclic voltammogrametry (CV) and the products obtained from electrochemical oxidation of benzene were investigated by gas chromatography and mass spectrometry (GC-MS). The results showed that the surface of the prepared electrode was mainly composed of tetragonal-shaped ?-PbO2 crystal with a pyramidal-angular structure. The oxidation potential of benzene was +1.8 V vs. Ag/AgCl. The electrochemical oxidation of benzene showed the high selectivity toward p-benzoquinone on the modified Ti/SnO2-Sb2O3/PbO2 electrode. And the optimal oxidation temperature for oxidation of benzene was 75 °C and the optimal temperature was 60 min.

Li, Xiaolin; Li, Xueming; Tang, Sui; Yang, Jianchun; Li, Wulin; Luo, Binbin; Yu, Yajiao; Li, Shanya

2014-08-01

206

?-Fe2O3 nanotubes-reduced graphene oxide composites as synergistic electrochemical capacitor materials  

NASA Astrophysics Data System (ADS)

We present a facile approach for the fabrication of a nanocomposite comprising ?-Fe2O3 nanotubes (NTs) anchored on reduced graphene oxide (rGO) for electrochemical capacitors (ECs). The hollow tubular structure of the ?-Fe2O3 NTs presents a high surface area for reaction, while the incorporation of rGO provides an efficient two-dimensional conductive pathway to allow fast, reversible redox reaction. As a result, the nanocomposite materials exhibit a specific capacitance which is remarkably higher (~7 times) than ?-Fe2O3 NTs alone. In addition, the nanocomposites show excellent cycling life and large negative potential window. These findings suggest that such nanocomposites are a promising candidate as negative electrodes in asymmetrical capacitors with neutral electrolytes.We present a facile approach for the fabrication of a nanocomposite comprising ?-Fe2O3 nanotubes (NTs) anchored on reduced graphene oxide (rGO) for electrochemical capacitors (ECs). The hollow tubular structure of the ?-Fe2O3 NTs presents a high surface area for reaction, while the incorporation of rGO provides an efficient two-dimensional conductive pathway to allow fast, reversible redox reaction. As a result, the nanocomposite materials exhibit a specific capacitance which is remarkably higher (~7 times) than ?-Fe2O3 NTs alone. In addition, the nanocomposites show excellent cycling life and large negative potential window. These findings suggest that such nanocomposites are a promising candidate as negative electrodes in asymmetrical capacitors with neutral electrolytes. Electronic supplementary information (ESI) available: Summary of electrochemical properties of various metal oxide-graphene materials composite electrodes (Table S1); experimental procedures, UV-Vis absorption spectra of GO and rGO (Fig. S1); X-ray photoemission spectra (XPS) of Fe2p (Fig. S2) and C1s (Fig. S3) core levels; percentage of various oxygenated functional groups from deconvolution of the C1s peak (Table S2); Ragone plot of ?-Fe2O3 NTs and ?-Fe2O3 NTs-rGO composites (Fig. S4); supplementary discussion on comparison of our prepared composite materials with various reported iron oxides-based materials (Table S3). See DOI: 10.1039/c2nr11902a

Lee, K. K.; Deng, S.; Fan, H. M.; Mhaisalkar, S.; Tan, H. R.; Tok, E. S.; Loh, K. P.; Chin, W. S.; Sow, C. H.

2012-04-01

207

Two-dimensional oxides: multifunctional materials for advanced technologies.  

PubMed

The last decade has seen spectacular progress in the design, preparation, and characterization down to the atomic scale of oxide ultrathin films of few nanometers thickness grown on a different material. This has paved the way towards several sophisticated applications in advanced technologies. By playing around with the low-dimensionality of the oxide layer, which sometimes leads to truly two-dimensional systems, one can exploit new properties and functionalities that are not present in the corresponding bulk materials or thick films. In this review we provide some clues about the most recent advances in the design of these systems based on modern electronic structure theory and on their preparation and characterization with specifically developed growth techniques and analytical methods. We show how two-dimensional oxides can be used in mature technologies by providing added value to existing materials, or in new technologies based on completely new paradigms. The fields in which two-dimensional oxides are used are classified based on the properties that are exploited, chemical or physical. With respect to chemical properties we discuss use of oxide ultrathin films in catalysis, solid oxide fuel cells, gas sensors, corrosion protection, and biocompatible materials; regarding the physical properties we discuss metal-oxide field effect transistors and memristors, spintronic devices, ferroelectrics and thermoelectrics, and solar energy materials. PMID:22847915

Pacchioni, Gianfranco

2012-08-13

208

Pretreatment of whole blood using hydrogen peroxide and UV irradiation. Design of the advanced oxidation process  

PubMed Central

A new process to pretreat blood samples has been developed. This process combines the Advanced Oxidation Process (AOP) treatment (using H2O2 and UV irradiation) with acid deactivation of the enzyme catalase in blood. A four-cell reactor has been designed and built in house. The effect of pH on the AOP process has been investigated. The kinetics of the pretreatment process shows that at high CH2O2,t = 0, the reaction is zeroth order with respect to CH2O2 and first order with respect to Cblood. The rate limiting process is photon flux from the UV lamp. Degradation of whole blood has been compared with that of pure hemoglobin samples. The AOP pretreatment of the blood samples has led to the subsequent determination of chromium and zinc concentrations in the samples using electrochemical methods. PMID:22841055

Bragg, Stefanie A.; Armstrong, Kristie C.; Xue, Zi-Ling

2013-01-01

209

Joining of Oxide Dispersion Strengthened Steels for Advanced Reactors  

NASA Astrophysics Data System (ADS)

The design, manufacture, and experimental analysis of structural materials capable of operation in the high temperatures, corrosive environments, and radiation damage spectra of future reactor designs remain one of the key pacing items for advanced reactor designs. The most promising candidate structural materials are vanadium-based refractory alloys, silicon carbide composites and oxide dispersion strengthened steels. Of these, oxide dispersion strengthened steels are a likely near-term candidate to meet required demands. This paper reviews different variants of oxide dispersion strengthened steels and discusses their capability with regard to high-temperature strength, corrosion resistance, and radiation damage resistance. Additionally, joining of oxide dispersion strengthened steels, which has been cited as a limiting factor preventing their use, is addressed and reviewed. Specifically, friction stir welding of these steels is reviewed as a promising joining method for oxide dispersion strengthened steels.

Baker, B. W.; Brewer, L. N.

2014-12-01

210

A comparative study on direct and indirect electrochemical oxidation of polyaromatic compounds.  

PubMed

This study has been performed to investigate the treatment of an industrial wastewater containing naphthalene- and anthraquinone-sulfonic acids, by direct and indirect electrolyses. The direct electrochemical oxidation has been carried out using boron-doped diamond and lead dioxide anodes, while the indirect electrolyses has been mediated by active chlorine electrogenerated on a platinum anode, or by hydrogen peroxide electrogenerated on a graphite felt cathode. For each type of electrolyses the effects of operating parameters, such as anode material, current density, chloride concentration, ferrous ions concentrations have been also investigated. Measurements of Chemical Oxygen Demand (COD) and colour fading have been used to compare the results of different electrolyses. Experimental data showed that the complete COD and colour removals have been obtained only by direct oxidation or by active chlorine mediated electrolyses. On the contrary using electrogenerated hydrogen peroxide the solution has been presented a residual COD and colour. In particular, it found that faster oxidation rate has been obtained by direct oxidation using a boron-doped diamond anodes at low current density. PMID:14756253

Panizza, Marco; Cerisola, Giacomo

2003-12-01

211

Surface Composition, Work Function, and Electrochemical Characteristics of Gallium-Doped Zinc Oxide  

SciTech Connect

Gallium-doped zinc oxide (GZO) possesses the electric conductivity, thermal stability, and earth abundance to be a promising transparent conductive oxide replacement for indium tin oxide electrodes in a number of molecular electronic devices, including organic solar cells and organic light emitting diodes. The surface chemistry of GZO is complex and dominated by the hydrolysis chemistry of ZnO, which influences the work function via charge transfer and band bending caused by adsorbates. A comprehensive characterization of the surface chemical composition and electrochemical properties of GZO electrodes is presented, using both solution and surface adsorbed redox probe molecules. The GZO surface is characterized using monochromatic X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy after the following pretreatments: (i) hydriodic acid etch, (ii) potassium hydroxide etch, (iii) RF oxygen plasma etching, and (iv) high-vacuum argon-ion sputtering. The O 1s spectra for the GZO electrodes have contributions from the stoichiometric oxide lattice, defects within the lattice, hydroxylated species, and carbonaceous impurities, with relative near-surface compositions varying with pretreatment. Solution etching procedures result in an increase of the work function and ionization potential of the GZO electrode, but yield different near surface Zn:Ga atomic ratios, which significantly influence charge transfer rates for a chemisorbed probe molecule. The near surface chemical composition is shown to be the dominant factor in controlling surface work function and significantly influences the rate of electron transfer to both solution and tethered probe molecules.

Ratcliff, E. L.; Sigdel, A. K.; Macech, M. R.; Nebesny, K.; Lee, P. A.; Ginley, D. S.; Armstrong, N. R.; Berry, J. J.

2012-06-30

212

Influences of graphene oxide support on the electrochemical performances of graphene oxide-MnO2 nanocomposites  

PubMed Central

MnO2 supported on graphene oxide (GO) made from different graphite materials has been synthesized and further investigated as electrode materials for supercapacitors. The structure and morphology of MnO2-GO nanocomposites are characterized by X-ray diffraction, X-ray photoemission spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and Nitrogen adsorption-desorption. As demonstrated, the GO fabricated from commercial expanded graphite (denoted as GO(1)) possesses more functional groups and larger interplane gap compared to the GO from commercial graphite powder (denoted as GO(2)). The surface area and functionalities of GO have significant effects on the morphology and electrochemical activity of MnO2, which lead to the fact that the loading amount of MnO2 on GO(1) is much higher than that on GO(2). Elemental analysis performed via inductively coupled plasma optical emission spectroscopy confirmed higher amounts of MnO2 loading on GO(1). As the electrode of supercapacitor, MnO2-GO(1) nanocomposites show larger capacitance (307.7 F g-1) and better electrochemical activity than MnO2-GO(2) possibly due to the high loading, good uniformity, and homogeneous distribution of MnO2 on GO(1) support. PMID:21951643

2011-01-01

213

Study and characterization of porous copper oxide produced by electrochemical anodization for radiometric heat absorber.  

PubMed

The aim of this work is to optimize the different parameters for realization of an absorbing cavity to measure the incident absolute laser energy. Electrochemical oxidation is the background process that allowed the copper blackening. A study of the blackened surface quality was undertaken using atomic force microscopy (AFM) analysis and ultraviolet-visible-infrared spectrophotometry using a Shimadzu spectrophotometer. A two-dimensional and three-dimensional visualization by AFM of the formed oxide coating showed that the copper surfaces became porous after electrochemical etching with different roughness. This aspect is becoming more and more important with decreasing current density anodization. In a 2 mol L(-1) of NaOH solution, at a temperature of 90°C, and using a 16 mA cm(2) constant density current, the copper oxide formed has a reflectivity of around 3% in the spectral range between 300 and 1,800 nm. Using the 'mirage effect' technique, the obtained Cu2O diffusivity and thermal conductivity are respectively equal to (11.5?±?0.5) 10 to 7 m(2) s(-1) and (370?±?20) Wm(-1) K(-1). This allows us to consider that our Cu2O coating is a good thermal conductor. The results of the optical and thermal studies dictate the choice of the cavity design. The absorbing cavity is a hollow cylinder machined to its base at an angle of 30°. If the included angle of the plane is 30° and the interior surface gives specular reflection, an incoming ray parallel to the axis will undergo five reflections before exit. So the absorption of the surface becomes closely near 0.999999. PMID:25349555

Ben Salem, Sonia; Achour, Zahra Ben; Thamri, Kamel; Touayar, Oualid

2014-01-01

214

Study and characterization of porous copper oxide produced by electrochemical anodization for radiometric heat absorber  

NASA Astrophysics Data System (ADS)

The aim of this work is to optimize the different parameters for realization of an absorbing cavity to measure the incident absolute laser energy. Electrochemical oxidation is the background process that allowed the copper blackening. A study of the blackened surface quality was undertaken using atomic force microscopy (AFM) analysis and ultraviolet-visible-infrared spectrophotometry using a Shimadzu spectrophotometer. A two-dimensional and three-dimensional visualization by AFM of the formed oxide coating showed that the copper surfaces became porous after electrochemical etching with different roughness. This aspect is becoming more and more important with decreasing current density anodization. In a 2 mol L -1 of NaOH solution, at a temperature of 90°C, and using a 16 mA cm2 constant density current, the copper oxide formed has a reflectivity of around 3% in the spectral range between 300 and 1,800 nm. Using the `mirage effect' technique, the obtained Cu2O diffusivity and thermal conductivity are respectively equal to (11.5 ± 0.5) 10 to 7 m2 s-1 and (370 ± 20) Wm-1 K-1. This allows us to consider that our Cu2O coating is a good thermal conductor. The results of the optical and thermal studies dictate the choice of the cavity design. The absorbing cavity is a hollow cylinder machined to its base at an angle of 30°. If the included angle of the plane is 30° and the interior surface gives specular reflection, an incoming ray parallel to the axis will undergo five reflections before exit. So the absorption of the surface becomes closely near 0.999999.

Ben Salem, Sonia; Achour, Zahra Ben; Thamri, Kamel; Touayar, Oualid

2014-10-01

215

Fabrication of cobalt porphyrin. Electrochemically reduced graphene oxide hybrid films for electrocatalytic hydrogen evolution in aqueous solution.  

PubMed

Here we report on an experimental study of an electrocatalyst for the hydrogen evolution reaction (HER) based on cobalt porphyrin and electrochemically reduced graphene oxide (ERGO) functional multilayer films, which are prepared by the alternating layer-by-layer (LBL) assembly of negatively charged graphene oxide (GO) and positively charged [tetrakis (N-methylpyridyl) porphyrinato] cobalt (CoTMPyP) in combination with an electrochemical reduction procedure. The resulting [ERGO@CoTMPyP]n multilayer films display relatively high electrocatalytic activity and superior stability toward HER in alkaline media. Electrochemical studies indicate that CoTMPyP in the multilayer films is the active catalyst for the reduction of protons to dihydrogen. PMID:24856539

Huang, Dekang; Lu, Jianfeng; Li, Shaohui; Luo, Yanping; Zhao, Chen; Hu, Bin; Wang, Mingkui; Shen, Yan

2014-06-17

216

Electrochemical reduction of porous 17 kg uranium oxide pellets by selection of an optimal cathode/anode surface area ratio  

NASA Astrophysics Data System (ADS)

This study examines how the cathode/anode surface area ratio affects the electrochemical reduction of uranium oxide in a molten Li 2O-LiCl electrolyte. A bench-scale test showed that a low cathode/anode surface area ratio is helpful for efficiently attaining a high current density and producing metallic uranium from uranium oxide in an Li 2O-LiCl electrolyte. A 17 kg uranium oxide electrolysis cell was set up with a cathode/anode surface area ratio of 2.6, and uranium oxide was successfully reduced to metallic uranium.

Choi, Eun-Young; Hur, Jin-Mok; Choi, In-Kyu; Kwon, Seon Gil; Kang, Dae-Seung; Hong, Sun Seok; Shin, Ho-Sup; Yoo, Min A.; Jeong, Sang Mun

2011-11-01

217

Preparation of Binary and Ternary Oxides by Molten Salt Method and its Electrochemical Properties  

NASA Astrophysics Data System (ADS)

We report simple binary oxides namely SnO2, TiO2, CuO, MnO2, Fe2O3, Co3O4 and ternary oxides like MnCo2O4 by molten salt method at a temperature range of 280°C to 950°C in air and discuss the effect of morphology, crystal structure and electrochemical properties of binary and ternary oxides. Materials were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area methods. XRD patterns showed all MSM prepared materials exhibited characteristic lattice parameter values. BET surface area varies depending on the nature of the material, molten salt and preparation temperature and the obtained values are in the range, 1 to 160 m2/g. Electrochemical properties were studied using cyclic voltammetry (CV) and electrochemical performance studies were carried in the voltage range, 0.005-1.0V for SnO2, 1.0-2.8V for TiO2 and Fe2O3, MCo2O4 (M = Co, Mn), MnO2 and CuO were cycled in the range, 0.005-3.0V. At a current rates of 30-100 mA/g and a scan rate of 0.058 mV/sec was used for galvanostatic cycling and cyclic voltammetry. SnO2 showed that an alloying-de-alloying reaction occurs at ˜0.2 and ˜0.5 V vs. Li. TiO2 main intercalation and de-interaction reactions at ˜1.7 and ˜1.8 V vs. Li. Co3O4, MnCo2O4, and MnO2 main discharge potentials at ˜1.2, 0.9V and 0.4V, resp. and charge potentials peak ˜2.0V and 1.5V vs. Li. CuO prepared at 750°C exhibited main anodic peak at ˜2.45V and cathodic peaks at ˜0.85V and ˜1.25V. We discussed the possible reaction mechanisms and Li-storage performance values in detail.

Reddy, M. V.; Theng, L. Pei; Soh, Hulbert; Beichen, Z.; Jiahuan, F.; Yu, C.; Ling, A. Yen; Andreea, L. Y.; Ng, C. H. Justin; Liang, T. J. L. Galen; Ian, M. F.; An, H. V. T.; Ramanathan, K.; Kevin, C. W. J.; Daryl, T. Y. W.; Hao, T. Yi; Loh, K. P.; Chowdari, B. V. R.

2013-07-01

218

The kinetics and electrochemical rate-determining step of aqueous pyrite oxidation  

NASA Astrophysics Data System (ADS)

Rate data available in the literature have been compiled for the reaction of pyrite with dissolved oxygen (DO) to produce a rate law that is applicable over four orders of magnitude in DO concentration over the pH range 2-10. The valid rate law is ? where r is the rate of pyrite destruction in units of mol m -2 s -1. A series of batch and mixed flow reactor experiments were performed to determine the effect of SO 42-, Cl -, ionic strength, and dissolved oxygen on the rate of reaction of pyrite with ferric iron. Of these, only dissolved oxygen was found to have any appreciable effect. Experimental results of the present study were combined with kinetic data reported in the literature to formulate rate laws that are applicable over a six order of magnitude range in Fe 3+ and Fe 2+ concentration for the pH range ~0.5-3.0. In N 2-purged solution, the rate law is ? and when dissolved oxygen is present, ? where r is the rate of pyrite destruction in mol m -2 s -1. Experiments were also performed in which a single pyrite sample was repeatedly reacted with ferric iron solutions of the same composition and identical surface area to mass of solution ratio ( A/ M). For each subsequent experiment, the rate of reaction slowed and the original behavior of the pyrite could not be reestablished by washing the pyrite with concentrated HNO 3 or EDTA. This behavior was interpreted as representative of a change in the electrochemical properties of the solid pyrite. Pretreating pyrite samples with aqueous solutions of ferrous iron and EDTA did not change the reaction rate with ferric iron; however, pretreatment with hydroxylamine hydrochloride lowered the rate significantly. The data presented are best modeled by a nonsite-specific Freundlich multilayer isotherm. Good correlation was found between Eh and rate for the aqueous oxidation of pyrite with DO and ferric iron. Because the fractional orders of reaction are difficult to explain with a purely molecular-based mechanism, a cathodic-anodic electrochemical mechanism is favored to explain the transfer of the electron from pyrite to the aqueous oxidant. Mechanistically, the results of this study suggest a nonsite specific interaction between dissolved oxidants and the pyrite surface. Rate correlates strongly with Eh ( Fe 3+/Fe 2+ ratio or DO concentration) and is consistent with an electrochemical mechanism where anodic and cathodic reactions occur at different places on the pyrite surface.

Williamson, Mark A.; Rimstidt, J. Donald

1994-12-01

219

Conductive indium-tin oxide nanowire and nanotube arrays made by electrochemically assisted deposition in template membranes: switching  

E-print Network

consisted of $25­50 nm in size crystalline grains with the cubic crystal structures of In(OH)3 and In2O3Conductive indium-tin oxide nanowire and nanotube arrays made by electrochemically assisted 22nd November 2010 DOI: 10.1039/c0nr00789g Tin-doped indium hydroxide (InSnOH) nanowires (NWs

220

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

NASA Astrophysics Data System (ADS)

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

Ehsani, Ali; Jaleh, Babak; Nasrollahzadeh, Mahmoud

2014-07-01

221

Involvement of nitric oxide in dopaminergic transmission in rat striatum: an in vivo electrochemical study.  

PubMed

In vivo electrochemical detection with a Nafion-coated carbon fiber working electrode, which provides information on the spatial and temporal dynamics of dopamine overflow, was used to investigate the involvement of nitric oxide (NO) in the dopaminergic transmission in the striatum of urethane-anesthetized Sprague-Dawley rats. A mixture of N-methyl-D-aspartate (NMDA) and nomifensine, a dopamine uptake blocker, was locally pressure-ejected to elicit a transient dopamine overflow from the dopamine-containing nerve terminals in the striatum. Local application of N omega-nitro-L-arginine methyl ester (L-NAME), which blocks endogenous NO formation, increased the magnitude of dopamine/release evoked by a subsequent NMDA and nomifensine application but resulted in no significant alteration in the time course. Furthermore, microejection of L-arginine, an NO precursor, or sodium nitroprusside (SNP), an NO generator, did not cause detectable changes in dopamine level in the striatal extracellular space. However, NMDA-induced dopamine release was profoundly inhibited with L-arginine or SNP pretreatment. In addition, NO affects dopamine uptake in rat striatum. Exogenous dopamine applied through a micropipette, reversibly and reproducibly, elicited an electrochemical signal. The time course of these signals was significantly prolonged by L-NAME treatment. These data suggest that NO is diversely involved in regulating dopaminergic transmission in rat striatum. PMID:7595488

Lin, A M; Kao, L S; Chai, C Y

1995-11-01

222

Multi-resistive Reduced Graphene Oxide Diode with Reversible Surface Electrochemical Reaction induced Carrier Control  

PubMed Central

The extended application of graphene-based electronic devices requires a bandgap opening in order to realize the targeted device functionality. Since the bandgap tuning of pristine graphene is limited to 360?meV, the chemical modification of graphene is considered essential to achieve a large bandgap opening at the expense of electrical properties degradation. Reduced graphene oxide (RGO) has attracted significant interest for fabricating graphene-based semiconductors since it has several advantages over other forms of chemically modified graphene; such as tunable bandgap opening, decent electrical properties, and easy synthesis. Because of the reduced bonding nature of RGO, the role of metastable oxygen in the RGO matrix is recently highlighted and it may offer emerging ionic devices. In this study, we show that multi-resistivity RGO/n-Si diodes can be obtained by controlling the RGO thickness at a nanometer scale. This is made possible by (1) a metastable lattice-oxygen drift within bulk RGO and (2) electrochemical ambient hydroxyl (OH) formation at the RGO surface. The effect demonstrated in a p-RGO/n-Si heterojunction diode is equivalent to electrochemically driven reversible electronic manipulation and therefore provides an important basis for the application of O bistability in RGO for chemical sensors and electrocatalysis. PMID:25007942

Seo, Hyungtak; Ahn, Seungbae; Kim, Jinseo; Lee, Young-Ahn; Chung, Koo-Hyun; Jeon, Ki-Joon

2014-01-01

223

Multi-resistive reduced graphene oxide diode with reversible surface electrochemical reaction induced carrier control.  

PubMed

The extended application of graphene-based electronic devices requires a bandgap opening in order to realize the targeted device functionality. Since the bandgap tuning of pristine graphene is limited to 360 meV, the chemical modification of graphene is considered essential to achieve a large bandgap opening at the expense of electrical properties degradation. Reduced graphene oxide (RGO) has attracted significant interest for fabricating graphene-based semiconductors since it has several advantages over other forms of chemically modified graphene; such as tunable bandgap opening, decent electrical properties, and easy synthesis. Because of the reduced bonding nature of RGO, the role of metastable oxygen in the RGO matrix is recently highlighted and it may offer emerging ionic devices. In this study, we show that multi-resistivity RGO/n-Si diodes can be obtained by controlling the RGO thickness at a nanometer scale. This is made possible by (1) a metastable lattice-oxygen drift within bulk RGO and (2) electrochemical ambient hydroxyl (OH) formation at the RGO surface. The effect demonstrated in a p-RGO/n-Si heterojunction diode is equivalent to electrochemically driven reversible electronic manipulation and therefore provides an important basis for the application of O bistability in RGO for chemical sensors and electrocatalysis. PMID:25007942

Seo, Hyungtak; Ahn, Seungbae; Kim, Jinseo; Lee, Young-Ahn; Chung, Koo-Hyun; Jeon, Ki-Joon

2014-01-01

224

Exhaled nitric oxide monitoring by quantum cascade laser: comparison with chemiluminescent and electrochemical sensors  

NASA Astrophysics Data System (ADS)

Fractional exhaled nitric oxide (FENO) is considered an indicator in the diagnostics and management of asthma. In this study we present a laser-based sensor for measuring FENO. It consists of a quantum cascade laser (QCL) combined with a multi-pass cell and wavelength modulation spectroscopy for the detection of NO at the sub-part-per-billion by volume (ppbv, 1?10-9) level. The characteristics and diagnostic performance of the sensor were assessed. A detection limit of 0.5 ppbv was demonstrated with a relatively simple design. The QCL-based sensor was compared with two market sensors, a chemiluminescent analyzer (NOA 280, Sievers) and a portable hand-held electrochemical analyzer (MINO®, Aerocrine AB, Sweden). FENO from 20 children diagnosed with asthma and treated with inhaled corticosteroids were measured. Data were found to be clinically acceptable within 1.1 ppbv between the QCL-based sensor and chemiluminescent sensor and within 1.7 ppbv when compared to the electrochemical sensor. The QCL-based sensor was tested on healthy subjects at various expiratory flow rates for both online and offline sampling procedures. The extended NO parameters, i.e. the alveolar region, airway wall, diffusing capacity, and flux were calculated and showed a good agreement with the previously reported values.

Mandon, Julien; Högman, Marieann; Merkus, Peter J. F. M.; van Amsterdam, Jan; Harren, Frans J. M.; Cristescu, Simona M.

2012-01-01

225

Electrochemical Encyclopedia  

NSDL National Science Digital Library

This site contains a compendium of 44 articles in electrochemistry. The articles cover a number of different topics including electrochemical capacitors, the electrochemistry of plant life, solid oxide fuel cells and electrolytic capacitors.

2011-06-09

226

Electrochemical oxide nanotube formation on the Ti-35Ta-xHf alloys for dental materials.  

PubMed

In this study, we investigated the electrochemical oxide nanotube formation on the Ti-35Ta-xHf alloys for dental materials. The Ti-35Ta-xHf alloys contained from 3 wt.% to 15 wt.% Hf were manufactured by arc melting furnace. The nanotube oxide layers were formed on Ti-35Ta-xHf alloy by anodic oxidation method in 1 M H3PO4 electrolytes containing 0.5 wt.% NaF and 0.8 wt.% NaF at room temperature. The surface characteristics of Ti-35Ta-xHf alloy and nanotube morphology were determined by FE-SEM, STEM, and XRD. The nano-porous surface of Ti-35Ta-xHf alloys showed in 0.5 wt% NaF solution and nanotubular surface showed in 0.8 wt% NaF solution, respectively. The highly ordered nanotube layer without regular knots was formed on the Ti-35Ta-15Hf alloy in the 0.5 wt% NaF solution compared to on Ti-35Ta-3Hf and Ti-35Ta-7Hf alloys in 0.8 wt% NaF solution. Also, the nanotube length of Ti-35Ta-xHf alloys increased as Hf content increased. PMID:22103212

Moon, Byung-Hak; Jeong, Yong-Hoon; Choe, Han-Cheol

2011-08-01

227

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

NASA Astrophysics Data System (ADS)

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.

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

2015-03-01

228

Detoxification of methyl-parathion pesticide in aqueous solutions by electrochemical oxidation.  

PubMed

Commercial methyl-parathion (MeP) was detoxified using an electrochemical method that employed a Ti/Pt anode and stainless steel 304 as cathode. Sodium chloride was added as electrolyte and the mixture was passed through an electrolytic cell for 2 h. Due to the strong oxidizing potential of the produced chemicals, the organic pollutants were wet oxidized to carbon dioxide and water. A number of experiments were run at laboratory scale. Reductions of COD and BOD(5) were both over 80% and the mean energy consumption was 18-8 kWh per kg(-1) COD reduced (COD(r)). The degradation of MeP was more effective when the pH of the brine solution was in the acid range than when it was in the alkaline range. From the results it can be concluded that electrolysis could be used as an oxidation pre-treatment stage for detoxification of toxic wastes with MeP. PMID:12628787

Arapoglou, D; Vlyssides, A; Israilides, C; Zorpas, A; Karlis, P

2003-03-17

229

Redox activity of surface oxygen anions in oxygen-deficient perovskite oxides during electrochemical reactions.  

PubMed

Surface redox-active centres in transition-metal oxides play a key role in determining the efficacy of electrocatalysts. The extreme sensitivity of surface redox states to temperatures, to gas pressures and to electrochemical reaction conditions renders them difficult to investigate by conventional surface-science techniques. Here we report the direct observation of surface redox processes by surface-sensitive, operando X-ray absorption spectroscopy using thin-film iron and cobalt perovskite oxides as model electrodes for elevated-temperature oxygen incorporation and evolution reactions. In contrast to the conventional view that the transition metal cations are the dominant redox-active centres, we find that the oxygen anions near the surface are a significant redox partner to molecular oxygen due to the strong hybridization between oxygen 2p and transition metal 3d electronic states. We propose that a narrow electronic state of significant oxygen 2p character near the Fermi level exchanges electrons with the oxygen adsorbates. This result highlights the importance of surface anion-redox chemistry in oxygen-deficient transition-metal oxides. PMID:25598003

Mueller, David N; Machala, Michael L; Bluhm, Hendrik; Chueh, William C

2015-01-01

230

Redox activity of surface oxygen anions in oxygen-deficient perovskite oxides during electrochemical reactions  

NASA Astrophysics Data System (ADS)

Surface redox-active centres in transition-metal oxides play a key role in determining the efficacy of electrocatalysts. The extreme sensitivity of surface redox states to temperatures, to gas pressures and to electrochemical reaction conditions renders them difficult to investigate by conventional surface-science techniques. Here we report the direct observation of surface redox processes by surface-sensitive, operando X-ray absorption spectroscopy using thin-film iron and cobalt perovskite oxides as model electrodes for elevated-temperature oxygen incorporation and evolution reactions. In contrast to the conventional view that the transition metal cations are the dominant redox-active centres, we find that the oxygen anions near the surface are a significant redox partner to molecular oxygen due to the strong hybridization between oxygen 2p and transition metal 3d electronic states. We propose that a narrow electronic state of significant oxygen 2p character near the Fermi level exchanges electrons with the oxygen adsorbates. This result highlights the importance of surface anion-redox chemistry in oxygen-deficient transition-metal oxides.

Mueller, David N.; Machala, Michael L.; Bluhm, Hendrik; Chueh, William C.

2015-01-01

231

Electrochemical oxidation and electroanalytical determination of xylitol at a boron-doped diamond electrode.  

PubMed

Xylitol is a reduced sugar with anticariogenic properties used by insulin-dependent diabetics, and which has attracted great attention of the pharmaceutical, cosmetics, food and dental industries. The detection of xylitol in different matrices is generally based on separation techniques. Alternatively, in this paper, the application of a boron-doped diamond (BDD) electrode allied to differing voltammetric techniques is presented to study the electrochemical behavior of xylitol, and to develop an analytical methodology for its determination in mouthwash. Xylitol undergoes two oxidation steps in an irreversible diffusion-controlled process (D=5.05 × 10(-5)cm(2)s(-1)). Differential pulse voltammetry studies revealed that the oxidation mechanism for peaks P1 (3.4 ? pH ? 8.0), and P2 (6.0 ? pH ? 9.0) involves transfer of 1H(+)/1e(-), and 1e(-) alone, respectively. The oxidation process P1 is mediated by the (•)OH generated at the BDD hydrogen-terminated surface. The maximum peak current was obtained at a pH of 7.0, and the electroanalytical method developed, (employing square wave voltammetry) yielded low detection (1.3 × 10(-6) mol L(-1)), and quantification (4.5 × 10(-6) mol L(-1)) limits, associated with good levels of repeatability (4.7%), and reproducibility (5.3%); thus demonstrating the viability of the methodology for detection of xylitol in biological samples containing low concentrations. PMID:24401449

Lourenço, Anabel S; Sanches, Fátima A C; Magalhães, Renata R; Costa, Daniel J E; Ribeiro, Williame F; Bichinho, Kátia M; Salazar-Banda, Giancarlo R; Araújo, Mário C U

2014-02-01

232

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

PubMed Central

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

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

2013-01-01

233

Graphene oxide as nanocarrier for sensitive electrochemical immunoassay of clenbuterol based on labeling amplification strategy.  

PubMed

A novel electrochemical immunosensor for sensitive detection of clenbuterol (CLB) is fabricated using glucose oxidase (GOD)-functionalized grahene oxide (GO) nanocomposites to label CLB. The immunosensor was constructed by layer-by-layer assembly colloidal prussian blue (PB), multiwalled carbon nanotubes (MWCNTs) and CLB antibodies (Abs) on a glassy carbon electrode (GCE). In this competitive immunoassay system, PB acts as the redox mediator to reduce H2O2 originated from the catalyst cycle of GOD. The high ratio of GOD to GO effectively amplified the signal for this competitive-type immunoassay. Under optimized conditions, the immunosensor shows a wide linear range from 0.5 to 1,000 ng/mL with a low detection limit of 0.25 ng/mL. The dual signal amplification of GOD-functionalized GO nanocomposites as a label is promising to be applied to design other sensitive immunosenseors. PMID:23598209

Lai, Yanjun; Bai, Jing; Shi, Xinhao; Zeng, Yanbo; Xian, Yuezhong; Hou, Jie; Jin, Litong

2013-03-30

234

Spinel manganese-nickel-cobalt ternary oxide nanowire array for high-performance electrochemical capacitor applications.  

PubMed

Aligned spinel Mn-Ni-Co ternary oxide (MNCO) nanowires are synthesized by a facile hydrothermal method. As an electrode of supercapacitors, the MNCO nanowire array on nickel foam shows an outstanding specific capacitance of 638 F g(-1) at 1 A g(-1) and excellent cycling stability. This exceptional performance benefits from its nanowire architecture, which can provide large reaction surface area, fast ion and electron transfer, and good structural stability. Furthermore, an asymmetric supercapacitor (ASC) with high energy density is assembled successfully by employing the MNCO nanowire array as positive electrode and carbon black as negative electrode. The excellent electrochemical performances indicate the promising potential application of the ASC device in the energy storage field. PMID:25247606

Li, Lu; Zhang, Yongqi; Shi, Fan; Zhang, Yijun; Zhang, Jiaheng; Gu, Changdong; Wang, Xiuli; Tu, Jiangping

2014-10-22

235

The electrochemical performance of thin-electrolyte solid oxide fuel cells  

SciTech Connect

Several benefits are realized by lowering the operating temperature of solid oxide fuel cells (SOFCs) from 1000C to temperatures in the 600 to 800C range. Among the advantages are decreased reaction between fuel cell components, shorter startup times, and the possibility of using metals in stack construction; however, the achievable power density in conventional SOFCs is too low. A strategy for overcoming this limitation is to decrease the thickness of this layer by approximately an order of magnitude. Thin (5 {mu}m) electrolyte SOFCs have recently been fabricated by Allied-Signal Aerospace Systems and Equipment Company (ASASE). The electrochemical performance of these cells has been studied and is discussed in this paper.

Zurawski, D.; Kueper, T.

1993-09-01

236

Solid oxide electrolysis cell analysis by means of electrochemical impedance spectroscopy: A review  

NASA Astrophysics Data System (ADS)

High temperature water electrolysis based on Solid Oxide Electrolysis Cell (SOEC) is a very promising solution to produce directly pure hydrogen. However, degradation issues occurring during operation still represent a scientific and technological barrier in view of its development at an industrial scale. Electrochemical Impedance Spectroscopy (EIS) is a powerful in-situ fundamental tool adapted to the study of SOEC systems. Hence, after a quick presentation of EIS principle and data analysis methods, this review demonstrates how EIS can be used: (i) to characterize the performance and mechanisms of SOEC electrodes; (ii) as a complementary tool to study SOEC degradation processes for different cell configurations, in addition to post-test tools such as scanning electron microscopy (SEM) or X-ray diffraction (XRD). The use of EIS to establish a systematic SOEC analysis is introduced as well.

Nechache, A.; Cassir, M.; Ringuedé, A.

2014-07-01

237

Solid flexible electrochemical supercapacitor using Tobacco mosaic virus nanostructures and ALD ruthenium oxide  

NASA Astrophysics Data System (ADS)

An all-solid electrochemical supercapacitor has been developed using a nanostructured nickel and titanium nitride template that is coated with ruthenium oxide by atomic layer deposition (ALD). The electrode morphology was based on a high surface area biotemplate of genetically modified Tobacco mosaic virus. The biotemplate automatically self-assembles at room temperature in aqueous solution. Nafion® perfluorosulfonate ionomer dispersion was cast on the electrodes and used as a solid proton-conducting electrolyte. A 5.8 F g-1 gravimetric capacity (578 µF cm-2 based on footprint) was achieved in Nafion electrolyte, and the device retained 80% of its capacity after 25?000 cycles. The technology presented here will enable thin, solid, flexible supercapacitors that are compatible with standard microfabrication techniques.

Gnerlich, M.; Pomerantseva, E.; Gregorczyk, K.; Ketchum, D.; Rubloff, G.; Ghodssi, R.

2013-11-01

238

?-Fe2O3 nanotubes-reduced graphene oxide composites as synergistic electrochemical capacitor materials.  

PubMed

We present a facile approach for the fabrication of a nanocomposite comprising ?-Fe(2)O(3) nanotubes (NTs) anchored on reduced graphene oxide (rGO) for electrochemical capacitors (ECs). The hollow tubular structure of the ?-Fe(2)O(3) NTs presents a high surface area for reaction, while the incorporation of rGO provides an efficient two-dimensional conductive pathway to allow fast, reversible redox reaction. As a result, the nanocomposite materials exhibit a specific capacitance which is remarkably higher (~7 times) than ?-Fe(2)O(3) NTs alone. In addition, the nanocomposites show excellent cycling life and large negative potential window. These findings suggest that such nanocomposites are a promising candidate as negative electrodes in asymmetrical capacitors with neutral electrolytes. PMID:22441701

Lee, K K; Deng, S; Fan, H M; Mhaisalkar, S; Tan, H R; Tok, E S; Loh, K P; Chin, W S; Sow, C H

2012-04-28

239

Electrochemical regeneration of sodium hypochlorite in the absorption-oxidation method of desorbing waste gases  

SciTech Connect

The electrochemical synthesis of sodium hypochlorite from a solution with a reduced concentration of sodium chloride is efficiently carried out with the use of ruthenium oxide-titanium anodes (ROTA). In this context they investigated the electrolysis of a solution of sodium chloride with concentrations equal to 20 and 50 kg/m/sup 3/ in a single cell flow-type electrolyzer with an ROTA and, for comparison, with a graphite anode under laboratory conditions. A flow-type electrolyzer was selected in view of the fact that it most closely satisfies the purposes of gas purification. The current efficiency with respect to sodium hypochlorite was almost two times higher, and the specific consumption of electrical energy was 1.6-1.8 times lower in the case of the ROTA than in the case of the graphite electrode. The yield of sodium chlorate remained on the same level in both cases.

Znamenskii, Yu.D.; Perchugov, G.Ya.

1988-07-10

240

Effluent characteristics of advanced treatment for biotreated coking wastewater by electrochemical technology using BDD anodes.  

PubMed

Effluent of biotreated coking wastewater comprises hundreds of organic and inorganic pollutants and has the characteristics of high toxicity and difficult biodegradation; thus, its chemical oxygen demand cannot meet drainage standards in China. A boron-doped diamond anode was selected for advanced treatment of biotreated coking wastewater, and considering the efficiency of the removal of total organic carbon and energy consumption, optimal conditions were obtained as current density of 75 mA cm(-2), electrolysis time of 1.5 h, and an electrode gap of 1.0 cm in an orthogonal test. Effluent characteristics were investigated at different electrolysis times. The ratio of the 5-day biochemical oxygen demand (BOD5) to the chemical oxygen demand increased from an initial value of 0.05 to 0.65 at 90 min. Fluorescence spectra were used to evaluate the evolution of refractory organics. Two fluorescence peaks for raw wastewater, corresponding to an aromatic protein-like substance II and humic acid-like substance, weakened at 30 and at 90 min, only the former was detected. The specific oxygen uptake rate was used to assess effluent toxicity, and an obvious inhibition effect was found at 15 min; then, it was significantly faded at 30 and 45 min. The BOD5/NO3 (-)-N ratio increased from an initial value of 0.48 to 1.25 at 45 min and then gradually dropped to 0.69 at 90 min. According to the above effluent characteristics, it is strongly suggested that electrochemical technology using boron-doped diamond anodes is combined with biological denitrification technology for the advanced treatment of biotreated coking wastewater. PMID:25432427

Wang, Chunrong; Zhang, Mengru; Liu, Wei; Ye, Min; Su, Fujin

2014-11-30

241

Electrochemical preparation of few layer-graphene nanosheets via reduction of oriented exfoliated graphene oxide thin films in acetamide–urea–ammonium nitrate melt under ambient conditions  

Microsoft Academic Search

Electrochemical reduction of exfoliated graphene oxide, prepared from pre-exfoliated graphite, in acetamide–urea–ammonium nitrate ternary eutectic melt results in few layer-graphene thin films. Negatively charged exfoliated graphene oxide is attached to positively charged cystamine monolyer self-assembled on a gold surface. Electrochemical reduction of the oriented graphene oxide film is carried out in a room temperature, ternary molten electrolyte. The reduced film

V. S. Dilimon; S. Sampath

2011-01-01

242

Graphene oxide functionalized with silver@silica-polyethylene glycol hybrid nanoparticles for direct electrochemical detection of quercetin.  

PubMed

A direct electrochemical detection of quercetin based on functionalized graphene oxide modified on gold-printed circuit board chip was demonstrated in this study. Functionalized graphene oxide materials are prepared by the covalent reaction of graphene oxide with silver@silica-polyethylene glycol nanoparticles (~12.35nm). Functionalized graphene oxide electrode shows a well-defined voltammetric response in phosphate buffered saline and catalyzes the oxidation of quercetin to quinone without the need of an enzyme. Significantly, the functionalized graphene oxide modified electrode exhibited a higher sensitivity than pristine gold-printed circuit board and graphene oxide electrodes, a wide concentration range of 7.5 to 1040nM and detection limit of 3.57nM. Developed biosensor platform is selective toward quercetin in the presence of an interferent molecule. PMID:24637169

Veerapandian, Murugan; Seo, Yeong-Tai; Yun, Kyusik; Lee, Min-Ho

2014-08-15

243

Electrochemical Modification of Indium Tin Oxide Using Di(4-nitrophenyl) Iodonium Tetrafluoroborate.  

PubMed

Optoelectronic applications often rely on indium tin oxide (ITO) as a transparent electrode material. Improvements in the performance of such devices as photovoltaics and light-emitting diodes often requires robust, controllable modification of the ITO surface to enhance interfacial charge transfer properties. In this work, modifier films were deposited onto ITO by the electrochemical reduction of di(4-nitrophenyl) iodonium tetrafluoroborate (DNP), allowing for control over surface functionalization. The surface coverage could be tuned from submonolayer to multilayer coverage by either varying the DNP concentration or the number of cyclic voltammetry (CV) grafting scans. Modification of ITO with 0.8 mM DNP resulted in near-monolayer surface coverage (4.95 × 10(14) molecules/cm(2)). X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of 4-nitrophenyl (NO2Ph) moieties on the ITO surface through the detection of a NO2 nitrogen signal at 405.6 eV after grafting. Further XPS evidence suggests that the NO2Ph radicals do not bond to the surface indium or tin sites, consistent with modification occurring either through bonding to surface hydroxyl groups or through strong physisorption on ITO. CV in the presence of an electroactive probe and electrochemical impedance spectroscopy (EIS) were used to investigate the electronic effects that modification via DNP has on ITO. Even at submonolayer coverage, the insulating organic films can reduce the current response to ferrocene oxidation and reduction by more than 25% and increase the charge transfer resistance by a factor of 10. PMID:25526354

Charlton, Matthew R; Suhr, Kristin J; Holliday, Bradley J; Stevenson, Keith J

2015-01-20

244

3D CFD ELECTROCHEMICAL AND HEAT TRANSFER MODEL OF AN INTERNALLY MANIFOLDED SOLID OXIDE ELECTROLYSIS CELL  

SciTech Connect

A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in an internally manifolded planar solid oxide electrolysis cell (SOEC) stack. This design is being evaluated at the Idaho National Laboratory for hydrogen production from nuclear power and process heat. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, operating potential, steam-electrode gas composition, oxygen-electrode gas composition, current density and hydrogen production over a range of stack operating conditions. Single-cell and five-cell results will be presented. Flow distribution through both models is discussed. Flow enters from the bottom, distributes through the inlet plenum, flows across the cells, gathers in the outlet plenum and flows downward making an upside-down ''U'' shaped flow pattern. Flow and concentration variations exist downstream of the inlet holes. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, oxygen-electrode and steam-electrode current density, and contact resistance from the base case are presented. Contour plots of local electrolyte temperature, current density, and Nernst potential indicate the effects of heat transfer, reaction cooling/heating, and change in local gas composition. Results are discussed for using this design in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production, cell thermal efficiency, cell electrical efficiency, and Gibbs free energy are discussed and reported herein.

Grant L. Hawkes; James E. O'Brien; Greg Tao

2011-11-01

245

Colour and organic removal of biologically treated coffee curing wastewater by electrochemical oxidation method.  

PubMed

The treatment of biologically treated wastewater of coffee-curing industry by the electrochemical oxidation using steel anode was investigated. Bench-scale experiments were conducted for activated sludge process on raw wastewater and the treated effluents were further treated by electrochemical oxidation method for its colour and organic content removal. The efficiency of the process was determined in terms of removal percentage of COD, BOD and colour during the course of reaction. Several operating parameters like time, pH and current density were examined to ascertain their effects on the treatment efficiency. Steel anode was found to be effective for the COD and colour removal with anode efficiency of 0.118 kgCOD x h(-1) x A(-1) x m(-2) and energy consumption 20.61 kWh x kg(-1) of COD at pH 9. The decrease in pH from 9 to 3 found to increase the anode efficiency from 0.118 kgCOD x h(-1) x A(-1) x m(-2) to 0.144 kWh x kg(-1) of COD while decrease the energy consumption from 20.61 kWh x kg(-1) of COD to 12.86 kWh x kg(-1) of COD. The pH of 5 was considered an ideal from the present treatment process as it avoids the addition of chemicals for neutralization of treated effluents and also economical with respect to energy consumption. An empirical relation developed for relationship between applied current density and COD removal efficiency showed strong predictive capability with coefficient of determination of 96.5%. PMID:12938980

Bejankiwar, Rajesh S; Lokesh, K S; Gowda, T P Halappa

2003-05-01

246

Aerosol synthesis and electrochemical analysis of niobium mixed-metal oxides for the ethanol oxidation reaction in acid and alkaline electrolyte  

NASA Astrophysics Data System (ADS)

Direct ethanol fuel cells are especially important among emerging electrochemical power systems with the potential to offset a great deal of the energy demand currently met through the use of fossil fuels. Ethanol can be refined from petroleum sources or attained from renewable biomass, and is more easily and safely stored and transported than hydrogen, methanol or gasoline. The full energy potential of ethanol in fuel cells can only be realized if the reaction follows a total oxidation pathway to produce CO2. This must be achieved by the development of advanced catalysts that are electrically conductive, stable in corrosive environments, contain a high surface area on which the reaction can occur, and exhibit a bi-functional effect for the ethanol oxidation reaction (EOR). The latter criterion is achievable in mixed-metal systems. Platinum is an effective metal for catalyzing surface reactions of many adsorbates and is usually implemented in the form of Pt nanoparticles supported on inexpensive carbon. This carbon is believed to be neutral in the catalysis of Pt. Instead, carbon can be replaced with carefully designed metals and metal oxides as co-catalysis or support structures that favorably alter the electronic structure of Pt slightly through a strong metal support interaction, while also acting as an oxygen source near adsorbates to facilitate the total oxidation pathway. Niobium mixed-metal-oxides were explored in this study as bi-functional catalyst supports to Pt nanoparticles. We developed a thermal aerosol synthesis process by which mesoporous powders of mixed-metal-oxides decorated with Pt nanoparticles could be obtained from liquid precursors within ˜5 seconds or less, followed by carefully refined chemical and thermal post-treatments. Exceptionally high surface areas of 170--180m2/g were achieved via a surfactant-templated 3D wormhole-type porosity, comparable on a per volume basis to commercial carbon blacks and high surface area silica supports. For the first time, in situ FTIR measurements in acid electrolyte showed that highly dispersed Pt nanoparticles (2--5nm) on NbRuyO z (at% 8Nb:1Ru) catalyze the formation of CO2 from ethanol in greater yield, and 0.35--0.4V lower, than Pt(111). Compared to conventional Pt/carbon, this indicates that, (1) Pt supported on NbRuyO z can be more effective at splitting the C---C bond in ethanol and, (2) the scission occurs at potentials more ideal for a higher efficiency fuel cell anode. Ex situ-microscopy revealed the polarization-induced two- and three-dimensional formation of Pt-NbOx interfacial adsorption sites responsible for the facilitation of the total oxidation pathway of ethanol. The results show that synthesis and post-treatment of niobia supports can bias the utility of Pt/niobia systems towards the ethanol oxidation reaction at the anode or the oxygen reduction reaction at the cathode. Experimental and computational-theoretical analyses indicate that the mechanism of interfacial site formation is dependent upon the local oxygen concentration, as well as the availability of multiple, energetically accessible oxidation states like those inherent to niobia. Future directions for the development of highly active, niobium-based materials tailored for efficient catalysis of the total oxidation pathway of ethanol are discussed.

Konopka, Daniel A.

247

Development of Advanced Electrochemical Emission Spectroscopy for Monitoring Corrosion in Simulated DOE Liquid Waste  

SciTech Connect

The different tasks that have been carried out under the current program are as follows: (1) Theoretical and experimental assessment of general corrosion of iron/steel in borate buffer solutions by using electrochemical impedance spectroscopy (EIS), ellipsometry and XPS techniques; (2) Development of a damage function analysis (DFA), which would help in predicting the accumulation of damage due to pitting corrosion in an environment prototypical of DOE liquid waste systems; (3) Experimental measurement of crack growth rate, acoustic emission signals, and coupling currents for fracture in carbon and low alloy steels as functions of mechanical (stress intensity), chemical (conductivity), electrochemical (corrosion potential, ECP), and microstructural (grain size, precipitate size, etc) variables in a systematic manner, with particular attention being focused on the structure of the noise in the current and its correlation with the acoustic emissions; (4) Development of fracture mechanisms for carbon and low alloy steels that are consistent with the crack growth rate, coupling current data and acoustic emissions; (5) Inserting advanced crack growth rate models for SCC into existing deterministic codes for predicting the evolution of corrosion damage in DOE liquid waste storage tanks; (6) Computer simulation of the anodic and cathodic activity on the surface of the steel samples in order to exactly predict the corrosion mechanisms; (7) Wavelet analysis of EC noise data from steel samples undergoing corrosion in an environment similar to that of the high level waste storage containers, to extract data pertaining to general, pitting and stress corrosion processes, from the overall data. The work has yielded a number of important findings, including an unequivocal demonstration of the role of chloride ion in passivity breakdown on nickel in terms of cation vacancy generation within the passive film, the first detection and characterization of individual micro fracture events in stress corrosion cracking, and the determination of kinetic parameters for the generation and annihilation of point defects in the passive film on iron. The existence of coupling between the internal crack environment and the external cathodic environment, as predicted by the coupled environment fracture model (CEFM), has also been indisputably established for the AISI 4340/NaOH system. It is evident from the studies that analysis of coupling current noise is a very sensitive tool for studying the crack tip processes in relation to the chemical, mechanical, electrochemical, and microstructural properties of the system. Experiments are currently being carried out to explore these crack tip processes by simultaneous measurement of the acoustic activity at the crack tip in an effort to validate the coupling current data. These latter data are now being used to deterministically predict the accumulation of general and localized corrosion damage on carbon in prototypical DOE liquid waste storage tanks. Computer simulation of the cathodic and anodic activity on the steel surfaces is also being carried out in an effort to simulate the actual corrosion process. Wavelet analysis of the coupling current data promises to be a useful tool to differentiate between the different corrosion mechanisms. Hence, wavelet analysis of the coupling current data from the DOE waste containers is also being carried out to extract data pertaining to general, pitting and stress corrosion processes, from the overall data which is bound to contain noise fluctuations due to any or all of the above mentioned processes.

Digby Macdonald; Brian Marx; Balaji Soundararajan; Morgan Smith

2005-07-28

248

The oriented growth of tungsten oxide in ordered mesoporous carbon and their electrochemical performance  

NASA Astrophysics Data System (ADS)

Electrocatalysts for hydrogen oxidation and methanol oxidation are the heart of the proton exchange membrane fuel cell. In spite of tremendous efforts, developing low-cost anodic electrocatalysts with high catalytic activity and corrosion resistance is still a great challenge. Here, we report a nanocomposite consisting of oriented WO3 nanorods grown in ordered mesoporous carbon as a high-performance functional catalyst carrier for proton exchange membrane fuel cells. As a result of the catalytic graphitization effect of tungsten compounds, the degree of graphitization and conductivity of mesoporous carbon film were improved even at a low temperature. Furthermore, compared with ordered mesoporous carbon, ordered mesoporous C-WO3 nanocomposites possess favorable hydrophilicity, excellent corrosion resistance and notable electrocatalytic activities. The unusual electrocatalytic activities arise from the ideal physical properties of the carrier and synergetic catalysis between Pt and WO3.Electrocatalysts for hydrogen oxidation and methanol oxidation are the heart of the proton exchange membrane fuel cell. In spite of tremendous efforts, developing low-cost anodic electrocatalysts with high catalytic activity and corrosion resistance is still a great challenge. Here, we report a nanocomposite consisting of oriented WO3 nanorods grown in ordered mesoporous carbon as a high-performance functional catalyst carrier for proton exchange membrane fuel cells. As a result of the catalytic graphitization effect of tungsten compounds, the degree of graphitization and conductivity of mesoporous carbon film were improved even at a low temperature. Furthermore, compared with ordered mesoporous carbon, ordered mesoporous C-WO3 nanocomposites possess favorable hydrophilicity, excellent corrosion resistance and notable electrocatalytic activities. The unusual electrocatalytic activities arise from the ideal physical properties of the carrier and synergetic catalysis between Pt and WO3. Electronic supplementary information (ESI) available: Additional structural characterizations and electrochemical measurements. See DOI: 10.1039/c4nr00396a

Wang, Tao; Tang, Jing; Fan, Xiaoli; Zhou, Jianhua; Xue, Hairong; Guo, Hu; He, Jianping

2014-04-01

249

Oxide Reduction in Advanced Metal Stacks for Microelectronic Applications Wentao Qin, Alex A. Volinsky1  

E-print Network

Oxide Reduction in Advanced Metal Stacks for Microelectronic Applications Wentao Qin, Alex A used for microelectronic interconnect applications. Interfacial oxides can cause device performance degradation and failure by significantly increasing electrical resistance. Interfacial oxide layers found

Volinsky, Alex A.

250

Advanced Oxidation Processes for Wastewater Treatment: State of the Art  

Microsoft Academic Search

The protection and conservation of natural resources is one of the main priorities of modern society. Water is perhaps our\\u000a most valuable resource, and thus should be recycled. Many of the current recycling techniques for polluted water only concentrate\\u000a the pollutant without degrading it or eliminating it. In this sense, advanced oxidation processes are possibly one of the\\u000a most effective

J. M. Poyatos; M. M. Muñio; M. C. Almecija; J. C. Torres; E. Hontoria; F. Osorio

2010-01-01

251

Evaluation of advanced oxidation process for the treatment of groundwater  

SciTech Connect

An advanced oxidation process utilizing ozone, ultraviolet radiation, and hydrogen peroxide was selected for the removal of chlorinated hydrocarbons, particularly trichlorethene and 1,2-dichlorethene, from groundwater underlying the US Department of Energy Kansas City Plant. Since the performance of this process for the removal of organics from groundwater is not well-documented, an evaluation was initiated to determine the performance of the treatment plant, document the operation and maintenance costs experience, and evaluate contaminant removal mechanisms. 11 refs., 3 figs.

Garland, S.B. II (Oak Ridge National Lab., TN (USA)); Peyton, G.R. (Illinois State Water Survey, Champaign, IL (USA)); Rice, L.E. (Allied-Signal Aerospace Co., Kansas City, MO (USA). Kansas City Div.)

1990-01-01

252

Electrochemical Urea Biosensor Based on Sol-gel Derived Nanostructured Cerium Oxide  

NASA Astrophysics Data System (ADS)

Urease (Urs) and glutamate dehydrogenase (GLDH) have been co-immobilized onto a nanostructured-cerium oxide (Nano-CeO2) film deposited onto a indium-tin-oxide (ITO) coated glass substrate by dip-coating via sol-gel process for urea detection. This nanostructured film has characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning electron microscope (SEM) and electrochemical techniques, respectively. The particle size of the Nano-CeO2 film has been found to be 23 nm. Electrochemcial response (CV) studies show that Ur-GLDH/Nano-CeO2/ITO bioelectrode is found to be sensitive in the 10-80 mg/dL urea concentration range and can detect urea concentration upto 0.1 mg/dL level. The value of Michaelis-Menten constant (Km) estimated using Lineweaver-Burke plot found as 6.09 mg/dL indicates enhancement in the affinity and/or activity of enzyme attached to their nanobiocomposite. This bioelectrode retained 95% of enzyme activity after 6 months at 4°C.

Ansari, Anees A.; Azahar, Md; Malhotra, B. D.

2012-04-01

253

Electrochemical Characteristics of Tin Oxide-Graphite as Anode Material for Lithium-ion Cells  

NASA Astrophysics Data System (ADS)

Tin oxide anode materials used in lithium-ion cells experience large volume changes during charging and discharging which cause substantial losses in capacity. In this work, the tin oxide-graphite composite is proposed as an alternative anode material to overcome this problem. The composite was synthesised from a solution of tin chloride dihydrate and graphite powders with citric acid as the chelating agent. In this sol-gel method, a solid phase is formed through a chemical reaction in a liquid phase at moderate temperature. The technique offers several advantages compared to the solid state synthesis technique such as the ability to maintain the homogeneous mixture of precursors during synthesis and to produce small particles. The electrochemical behaviour of the anode material was investigated by means of galvanostatic charge discharge technique. An initial reversible capacity of 748 mAh/g is obtained and nearly 600 mAh/g was retained upon the reaching the fifth cycle. This study shows that the presence of graphite is able to minimise the agglomeration of tin particles that causes large volume changes during cycling, thereby improving cyclability of the anode material.

Hasanaly, Siti Munirah

2010-03-01

254

THERMAL AND ELECTROCHEMICAL THREE DIMENSIONAL CFD MODEL OF A PLANAR SOLID OXIDE ELECTROLYSIS CELL  

SciTech Connect

A three-dimensional computational fluid dynamics (CFD) model has been created to model high-temperature steam electrolysis in a planar solid oxide electrolysis cell (SOEC). The model represents a single cell, as it would exist in an electrolysis stack. Details of the model geometry are specific to a stack that was fabricated by Ceramatec , Inc. and tested at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT2. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean model results are shown to compare favorably with experimental results obtained from an actual ten-cell stack tested at INL.

Grant Hawkes; Jim O'Brien; Carl Stoots; Steve Herring; Mehrdad Shahnam

2005-07-01

255

Vanadium Oxide Electrochemical Capacitors: An Investigation into Aqueous Capacitive Degradation, Alternate Electrolyte-Solvent Systems, Whole Cell Performance and Graphene Oxide Composite Electrodes  

NASA Astrophysics Data System (ADS)

Vanadium oxide has emerged as a potential electrochemical capacitor material due to its attractive pseudocapacitive performance; however, it is known to suffer from capacitive degradation upon sustained cycling. In this work, the electrochemical cycling behavior of anodically electrodeposited vanadium oxide films with various surface treatments in aqueous solutions is investigated at different pH. Quantitative compositional analysis and morphological studies provide additional insight into the mechanism responsible for capacitive degradation. Furthermore, the capacitance and impedance behavior of vanadium oxide electrochemical capacitor electrodes is compared for both aqueous and nonaqueous electrolyte-solvent systems. Alkali metal chloride and bromide electrolytes were studied in aqueous systems, and nonaqueous systems containing alkali metal bromides were studied in polar aprotic propylene carbonate (PC) or dimethyl sulfoxide (DMSO) solvents. The preferred aqueous and nonaqueous systems identified in the half-cell studies were utilized in symmetric vanadium oxide whole-cells. An aqueous system utilizing a 3.0 M NaCl electrolyte at pH 3.0 exhibited an excellent 96% capacitance retention over 3000 cycles at 10 mV s-1. An equivalent system tested at 500 mV s-1 displayed an increase in capacitance over the first several thousands of cycles, and eventually stabilized over 50,000 cycles. Electrodes cycled in nonaqueous 1.0 M LiBr in PC exhibited mostly non-capacitive charge-storage, and electrodes cycled in LiBr-DMSO exhibited a gradual capacitive decay over 10,000 cycles at 500 mV s-1. Morphological and compositional analyses, as well as electrochemical impedance modeling, provide additional insight into the cause of the cycing behavior. Lastly, reduced graphene oxide and vanadium oxide nanowire composites have been successfully synthesized using electrophoretic deposition for electrochemical capacitor electrodes. The composite material was found to perform with a higher capacitance than electrodes containing only vanadium oxide nanowires by a factor of 4.0 at 10 mV s-1 and 7.5 at 500 mV s-1. The thermally reduced composite material was examined in both symmetric and asymmetric whole cell electrochemical capacitor devices, and although the asymmetric cell achieved both higher energy and power density, the symmetric cell retained a higher capacitance over 50,000 cycles at 200 mV s-1.

Engstrom, Allison Michelle

256

A non-oxidative electrochemical approach to online measurements of dopamine release through laccase-catalyzed oxidation and intramolecular cyclization of dopamine.  

PubMed

A new electrochemical approach to selective online measurements of dopamine (DA) release in the cerebral microdialysate is demonstrated with a non-oxidative mechanism based on the distinct reaction properties of DA and the excellent biocatalytic activity of laccase. To make the successful transition of the distinct sequential reaction properties of DA from a conceptual determination protocol to a practical online analytical system, laccase enzyme is immobilized onto magnetite nanoparticles and the nanoparticles are confined into a fused-silica capillary through an external magnetic field to fabricate a magnetic microreactor. The microreactor is placed in the upstream of the thin-layer electrochemical flow cell to efficiently catalyze the oxidation of DA into its quinonoid form and thereby initialize the sequential reactions including deprotonation, intramolecular cyclization, disproportionation and/or oxidation to finally give 5,6-dihydroxyindoline quinone. The electrochemical reduction of the produced 5,6-dihydroxyindoline quinone at bare glassy carbon electrode is used as the readout for the DA measurement. The laccase-immobilized microreactor is also found to catalyze the oxidation of ascorbic acid (AA) and 3,4-dihydroxyphenylacetic acid (DOPAC) into electroinactive species and, as such, to eliminate the great interference from both species. Moreover, the successful transition of the mechanism for DA detection from the conventional oxidative electrochemical approach to the non-oxidative one substantially enables the measurements virtually interference-free from physiological levels of uric acid, 5-hydroxytryptamine, norepinephrine, and epinephrine. The current response is linear with DA concentration within a concentration range from 1 to 20 microM with a sensitivity of 3.97 nA/microM. The detection limit, based on a signal-to-noise ratio of 3, is calculated to be 0.3 microM. The high selectivity and the good linearity as well as the high stability of the online method make it very potential for continuous monitoring of cerebral DA release in physiological and pathological processes. PMID:19926273

Lin, Yuqing; Zhang, Zipin; Zhao, Lingzhi; Wang, Xiang; Yu, Ping; Su, Lei; Mao, Lanqun

2010-02-15

257

Electrochemical performance of nitrogen and oxygen radio-frequency plasma induced functional groups on tri-layered reduced graphene oxide  

NASA Astrophysics Data System (ADS)

Tri-layered reduced graphene oxide with better graphitization was synthesized and functioned using radio frequency N2 and O2 plasma. The layer numbers of reduced graphene oxide were determined by atomic force microscopy (AFM) and x-ray diffraction (XRD). The effect of plasma treatment on crystal structure, surface morphology and chemical composition were studied from XRD, transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), Fourier transforms infrared spectroscopy (FTIR) and Raman spectroscopy. The chemical species present in N2/O2 plasma during functionalization of tri-layered reduced graphene oxide was analyzed by optical emission spectroscopy. Tri-layered reduced graphene oxide and functioned tri-layered reduced graphene oxide exhibits higher electrochemical performance towards ferrocyanide redox reaction than glassy carbon and platinum electrode with much decrease in overpotential. This indicates that tri-layered reduced graphene oxide and N2/O2 functionalized tri-layered reduced graphene oxide are promising working electrodes in the application of electrochemical based biosensor.

Lavanya, J.; Gomathi, N.; Neogi, S.

2014-04-01

258

Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate  

PubMed Central

Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

2014-01-01

259

Comparative electrochemical analysis of crystalline and amorphous anodized iron oxide nanotube layers as negative electrode for LIB.  

PubMed

This work is a comparative study of the electrochemical performance of crystalline and amorphous anodic iron oxide nanotube layers. These nanotube layers were grown directly on top of an iron current collector with a vertical orientation via a simple one-step synthesis. The crystalline structures were obtained by heat treating the as-prepared (amorphous) iron oxide nanotube layers in ambient air environment. A detailed morphological and compositional characterization of the resultant materials was performed via transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Raman spectroscopy. The XRD patterns were further analyzed using Rietveld refinements to gain in-depth information on their quantitative phase and crystal structures after heat treatment. The results demonstrated that the crystalline iron oxide nanotube layers exhibit better electrochemical properties than the amorphous iron oxide nanotube layers when evaluated in terms of the areal capacity, rate capability, and cycling performance. Such an improved electrochemical response was attributed to the morphology and three-dimensional framework of the crystalline nanotube layers offering short, multidirectional transport lengths, which favor rapid Li(+) ions diffusivity and electron transport. PMID:24964233

Pervez, Syed Atif; Kim, Doohun; Farooq, Umer; Yaqub, Adnan; Choi, Jung-Hee; Lee, You-Jin; Doh, Chil-Hoon

2014-07-23

260

Virtual electrochemical nitric oxide analyzer using copper, zinc superoxide dismutase immobilized on carbon nanotubes in polypyrrole matrix.  

PubMed

In this work, we have designed and developed a novel and cost effective virtual electrochemical analyzer for the measurement of NO in exhaled breath and from hydrogen peroxide stimulated endothelial cells using home-made potentiostat. Here, data acquisition system (NI MyDAQ) was used to acquire the data from the electrochemical oxidation of NO mediated by copper, zinc superoxide dismutase (Cu,ZnSOD). The electrochemical control programs (graphical user-interface software) were developed using LabVIEW 10.0 to sweep the potential, acquire the current response and process the acquired current signal. The Cu,ZnSOD (SOD1) immobilized on the carbon nanotubes in polypyrrole modified platinum electrode was used as the NO biosensor. The electrochemical behavior of the SOD1 modified electrode exhibited the characteristic quasi-reversible redox peak at the potential, +0.06 V vs. Ag/AgCl. The biological interferences were eliminated by nafion coated SOD1 electrode and then NO was measured selectively. Further, this biosensor showed a wide linear range of response over the concentration of NO from 0.1 ?M to 1 mM with a detection limit of 0.1 ?M and high sensitivity of 1.1 ?A ?M(-1). The electroanalytical results obtained here using the developed virtual electrochemical instrument were also compared with the standard cyclic voltammetry instrument and found in agreement with each other. PMID:23141325

Madasamy, Thangamuthu; Pandiaraj, Manickam; Balamurugan, Murugesan; Karnewar, Santosh; Benjamin, Alby Robson; Venkatesh, Krishna Arun; Vairamani, Kanagavel; Kotamraju, Srigiridhar; Karunakaran, Chandran

2012-10-15

261

Bipolar plating of metal contacts onto oxide interconnection for solid oxide electrochemical cell  

DOEpatents

Disclosed is a method of forming an adherent metal deposit on a conducting layer of a tube sealed at one end. The tube is immersed with the sealed end down into an aqueous solution containing ions of the metal to be deposited. An ionically conducting aqueous fluid is placed inside the tube and a direct current is passed from a cathode inside the tube to an anode outside the tube. Also disclosed is a multi-layered solid oxide fuel cell tube which consists of an inner porous ceramic support tube, a porous air electrode covering the support tube, a non-porous electrolyte covering a portion of the air electrode, a non-porous conducting interconnection covering the remaining portion of the electrode, and a metal deposit on the interconnection.

Isenberg, Arnold O. (Forest Hills Boro, PA)

1987-01-01

262

Bipolar plating of metal contacts onto oxide interconnection for solid oxide electrochemical cell  

DOEpatents

Disclosed is a method of forming an adherent metal deposit on a conducting layer of a tube sealed at one end. The tube is immersed with the sealed end down into an aqueous solution containing ions of the metal to be deposited. An ionically conducting aqueous fluid is placed inside the tube and a direct current is passed from a cathode inside the tube to an anode outside the tube. Also disclosed is a multi-layered solid oxide fuel cell tube which consists of an inner porous ceramic support tube, a porous air electrode covering the support tube, a non-porous electrolyte covering a portion of the air electrode, a non-porous conducting interconnection covering the remaining portion of the electrode, and a metal deposit on the interconnection. 1 fig.

Isenberg, A.O.

1987-03-10

263

Detection of the short-lived cation radical intermediate in the electrochemical oxidation of n,n-dimethylaniline by scanning electrochemical microscopy.  

PubMed

The short-lived intermediate N,N-dimethylaniline (DMA) cation radical, DMA(•+), was detected during the oxidation of DMA in MeCN with 0.1 M tetra-n-butylammonium hexafluorophosphate. The detection was accomplished at steady state by scanning electrochemical microscopy (SECM) with ultramicroelectrodes using the tip generation/substrate collection mode. Cyclic voltammetry (CV) with a 2 mm Pt electrode indicates that DMA oxidation in acetonitrile is followed by a dimerization and two electrochemical reactions, which is consistent with previous results. The DMA(•+) intermediate is detected by SECM, where the DMA(•+) generated at the ca. 500 nm radius Pt tip is collected on a 5 ?m radius Pt substrate when the gap between the tip and the substrate is a few hundred nanometers. Almost all of the DMA(•+) is reduced at the substrate when the gap is 200 nm or less, yielding a dimerization rate constant of 2.5 × 10(8) M(-1)·s(-1) based on a simulation. This is roughly 3 orders of magnitude larger than the value estimated by fast-scan CV. We attribute this discrepancy to the effects of double-layer capacitance charging and adsorbed species in the high scan rate CV. PMID:25478724

Cao, Fahe; Kim, Jiyeon; Bard, Allen J

2014-12-31

264

Investigation of film formation properties during electrochemical oxidation of serotonin (5-HT) at polycrystalline boron doped diamond.  

PubMed

The change in surface morphology of oxygen-terminated polycrystalline boron doped diamond (pBDD) during electrochemical oxidation of the neurotransmitter serotonin (5-HT), resulting in a corresponding deterioration of the current signal, is investigated for the first time using both high resolution ex situ and in situ microscopy under a range of different electrochemical conditions. In situ electrochemical-atomic force microscopy (EC-AFM) reveals the formation of a granular film over the surface, which grows faster at higher-doped regions of the electrode surface and increases in thickness with repetitive potential cycles. The film properties were investigated using both cyclic voltammetry, with a range of redox species varying in charge, and conducting-AFM. These studies reveal the film to be positively charged and electrically insulating. The extent to which the film forms during 5-HT oxidation could be significantly minimised using different electrochemical procedures, as verified by voltammetry and in situ EC-AFM. Finally, even after extensive film formation, the original current signal could be recovered simply by leaving the electrode at open circuit potential for a short period of time, highlighting the suitability of BDD electrodes for neurotransmitter detection. PMID:24060971

Patel, Anisha N; Unwin, Patrick R; Macpherson, Julie V

2013-11-01

265

Synthesis, characterization, and electrochemical properties of ordered mesoporous carbons containing nickel oxide nanoparticles using sucrose and nickel acetate in a silica template  

NASA Astrophysics Data System (ADS)

New ordered mesoporous carbons containing nickel oxide nanoparticles have been successfully synthesized by carbonization of sucrose in the presence of nickel acetate inside SBA-15 mesoporous silica template. The obtained samples were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, and transmission electron microscopy (TEM). The NiO nanoparticles were embedded inside the mesoporous carbon framework due to the simultaneous pyrolysis of nickel acetate during carbonization. The electrochemical testing of the as-made nanocomposites showed a large specific capacitance of 230 F g -1 using 2 M KOH as the electrolyte at room temperature. This is attributed to the nanometer-sized NiO formed inside mesoporous carbons and the high surface area of the mesopores in which the NiO nanoparticles are formed. Furthermore, the synthetic process is proposed as a simple and general method for the preparation of new functionalized mesoporous carbon materials, for various applications in catalysis, sensor or advanced electrode material.

Cao, Yulin; Cao, Jieming; Zheng, Mingbo; Liu, Jinsong; Ji, Guangbin

2007-02-01

266

Electrochemical oxidation of reverse osmosis concentrate on boron-doped diamond anodes at circumneutral and acidic pH.  

PubMed

Electrochemical processes have been widely investigated for degrading organic contaminants present in wastewater. This study evaluated the performance of electrochemical oxidation using boron-doped diamond (BDD) electrodes by forming OH() for the treatment of reverse osmosis concentrate (ROC) from secondary-treated wastewater effluents. Since oxidation by OH() and active chlorine species (HClO/ClO(-)) is influenced by pH, the electrochemical oxidation of ROC was evaluated at controlled pH 6-7 and at pH 1-2 (no pH adjustment). A high concentration of chloride ions in the ROC enhanced the oxidation, and 7-11% of Coulombic efficiency for chemical oxygen demand (COD) removal was achieved with 5.2 Ah L(-1) of specific electrical charge. Complete COD removal was observed after 5.2 and 6.6 Ah L(-1), yet the corresponding dissolved organic carbon (DOC) removal was only 48% (at acidic pH) and 59% (at circumneutral pH). Although a higher operating pH seemed to enhance the participation of OH() in oxidation mechanisms, high concentrations of chloride resulted in the formation of significant concentrations of adsorbable organic chlorine (AOCl) after electrochemical oxidation at both pH. While adsorbable organic bromine (AOBr) was degraded at a higher applied electrical charge, a continuous increase in AOCl concentration (up to 0.88 mM) was observed until the end of the experiments (i.e. 10.9 Ah L(-1)). In addition, total trihalomethanes (tTHMs) and total haloacetic acids (tHAAs) were further degraded with an increase in electrical charge under both pH conditions, to final total concentrations of 1 and 4 ?M (tTHMs), and 12 and 22 ?M (tHAAs), at acidic and circumneutral pH, respectively. In particular, tHAAs were still an order of magnitude above their initial concentration in ROC after further electrooxidation. Where high chloride concentrations are present, it was found to be necessary to separate chloride from ROC prior to electrochemical oxidation in order to avoid the formation of chlorinated by-products. PMID:22995242

Bagastyo, Arseto Y; Batstone, Damien J; Kristiana, Ina; Gernjak, Wolfgang; Joll, Cynthia; Radjenovic, Jelena

2012-11-15

267

A reliable aerosol-spray-assisted approach to produce and optimize amorphous metal oxide catalysts for electrochemical water splitting.  

PubMed

An aerosol-spray-assisted approach (ASAA) is proposed and confirmed as a precisely controllable and continuous method to fabricate amorphous mixed metal oxides for electrochemical water splitting. The proportion of metal elements can be accurately controlled to within (5±5)?%. The products can be sustainably obtained, which is highly suitable for industrial applications. ASAA was used to show that Fe6Ni10O(x) is the best catalyst among the investigated Fe-Ni-O(x) series with an overpotential of as low as 0.286?V (10?mA?cm(-2)) and a Tafel slope of 48?mV/decade for the electrochemical oxygen evolution reaction. Therefore, this work contributes a versatile, continuous, and reliable way to produce and optimize amorphous metal oxide catalysts. PMID:24899118

Kuai, Long; Geng, Jing; Chen, Changyu; Kan, Erjie; Liu, Yadong; Wang, Qing; Geng, Baoyou

2014-07-14

268

Electrochemical investigation of atenolol oxidation and detection by using a multicomponent nanostructural assembly of amino acids and gold nanoparticles  

NASA Astrophysics Data System (ADS)

A novel nanostructured assembly based on poly(glutamic) acid/cysteine/gold nanoparticles was designed to modify the surface of a glassy carbon electrode (GCE) and used to study the atenolol oxidation. The GCE surface was initially covered by poly(glutamic) acid/cysteine layers followed by covalent attachment of citrate-capped 40 nm-AuNPs. The system excellent electrochemical performance was tested by Linear Sweep Voltammetry and Electrochemical Impedance Spectroscopy and allowed the detection of an atenolol oxidation peak (around +0.65 V/SCE) with a detection limit of 3.9 × 10-7 M. Such findings could be incorporated in highly sensitive detection technologies of various biological or chemical compounds and molecules.

Pruneanu, Stela; Pogacean, Florina; Grosan, Camelia; Pica, Elena Maria; Bolundut, Liviu Calin; Biris, Alexandru Sorin

2011-02-01

269

Development of Advanced Electrochemical Emission Spectroscopy for Monitoring Corrosion in Simulated DOE Liquid Waste  

SciTech Connect

Various forms of general and localized corrosion represent principal threats to the integrity of DOE liquid waste storage tanks. These tanks, which are of a single wall or double wall design, depending upon their age, are fabricated from welded carbon steel and contain a complex waste-form comprised of NaOH and NaNO{sub 3}, along with trace amounts of phosphate, sulfate, carbonate, and chloride. Because waste leakage can have a profound environmental impact, considerable interest exists in predicting the accumulation of corrosion damage, so as to more effectively schedule maintenance and repair. The different tasks that are being carried out under the current program are as follows: (1) Theoretical and experimental assessment of general corrosion of iron/steel in borate buffer solutions by using electrochemical impedance spectroscopy (EIS), ellipsometry and XPS techniques; (2) Development of a damage function analysis (DFA) which would help in predicting the accumulation of damage due to pitting corrosion in an environment prototypical of DOE liquid waste systems; (3) Experimental measurement of crack growth rate, acoustic emission signals and coupling currents for fracture in carbon and low alloy steels as functions of mechanical (stress intensity), chemical (conductivity), electrochemical (corrosion potential, ECP), and microstructural (grain size, precipitate size, etc) variables in a systematic manner, with particular attention being focused on the structure of the noise in the current and its correlation with the acoustic emissions; (4) Development of fracture mechanisms for carbon and low alloy steels that are consistent with the crack growth rate, coupling current data and acoustic emissions; (5) Inserting advanced crack growth rate models for SCC into existing deterministic codes for predicting the evolution of corrosion damage in DOE liquid waste storage tanks; (6) Computer simulation of the anodic and cathodic activity on the surface of the steel samples in order to exactly predict the corrosion mechanisms; (7) Wavelet analysis of EC noise data from steel samples undergoing corrosion in an environment similar to that of the high level waste storage containers, to extract data pertaining to general, pitting and stress corrosion processes, from the overall data. The Point Defect Model (PDM) is directly applied as the theoretical assessment method for describing the passive film formed on iron/steels. The PDM is used to describe general corrosion in the passive region of iron. In addition, previous work suggests that pit formation is due to the coalescence of cation vacancies at the metal/film interface which would make it possible to use the PDM parameters to predict the onset of pitting. This previous work suggests that once the critical vacancy density is reached, the film ruptures to form a pit. Based upon the kinetic parameters derived for the general corrosion case, two parameters relating to the cation vacancy formation and annihilation can be calculated. These two parameters can then be applied to predict the transition from general to pitting corrosion for iron/mild steels. If cation vacancy coalescence is shown to lead to pitting, it can have a profound effect on the direction of future studies involving the onset of pitting corrosion. The work has yielded a number of important findings, including an unequivocal demonstration of the role of chloride ion in passivity breakdown on nickel in terms of cation vacancy generation within the passive film, the first detection and characterization of individual micro fracture events in stress corrosion cracking, and the determination of kinetic parameters for the generation and annihilation of point defects in the passive film on iron. The existence of coupling between the internal crack environment and the external cathodic environment, as predicted by the coupled environment fracture model (CEFM), has also been indisputably established for the AISI 4340/NaOH system. It is evident from the studies that analysis of coupling current noise is a very sensitive tool f

Digby D. Macdonald; Brian M. Marx; Sejin Ahn; Julio de Ruiz; Balaji Soundararaja; Morgan Smith; and Wendy Coulson

2008-01-15

270

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

Microsoft Academic Search

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

Takashi Kuwahara; Toshimasa Homma; Mizuki Kondo; Masato Shimomura

2011-01-01

271

Electrochemical promotion of propane oxidation on Pt deposited on a dense ??-Al2O3 ceramic Ag+ conductor  

PubMed Central

A new kind of electrochemical catalyst based on a Pt porous catalyst film deposited on a ??-Al2O3 ceramic Ag+ conductor was developed and evaluated during propane oxidation. It was observed that, upon anodic polarization, the rate of propane combustion was significantly electropromoted up to 400%. Moreover, for the first time, exponential increase of the catalytic rate was evidenced during galvanostatic transient experiment in excellent agreement with EPOC equation. PMID:24790942

Tsampas, Mihalis N.; Kambolis, Anastasios; Obeid, Emil; Lizarraga, Leonardo; Sapountzi, Foteini M.; Vernoux, Philippe

2013-01-01

272

In-situ X-Ray Absorption Spectroscopy (XAS) Investigation of a Bifunctional Manganese Oxide Catalyst with High Activity for Electrochemical Water Oxidation and Oxygen Reduction  

PubMed Central

In-situ x-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in-situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs. RHE produces a disordered Mn3II,III,IIIO4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs. RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed MnIII,IV oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3II,III,IIIO4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the MnIII,IV oxide, rather than Mn3II,III,IIIO4, is the phase pertinent to the observed OER activity. PMID:23758050

Benck, Jesse D.; Gul, Sheraz; Webb, Samuel M.; Yachandra, Vittal K.; Yano, Junko; Jaramillo, Thomas F.

2013-01-01

273

In situ X-ray absorption spectroscopy investigation of a bifunctional manganese oxide catalyst with high activity for electrochemical water oxidation and oxygen reduction.  

PubMed

In situ X-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs RHE produces a disordered Mn3(II,III,III)O4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed Mn(III,IV) oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3(II,III,III)O4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the Mn(III,IV) oxide, rather than Mn3(II,III,III)O4, is the phase pertinent to the observed OER activity. PMID:23758050

Gorlin, Yelena; Lassalle-Kaiser, Benedikt; Benck, Jesse D; Gul, Sheraz; Webb, Samuel M; Yachandra, Vittal K; Yano, Junko; Jaramillo, Thomas F

2013-06-12

274

A novel approach for analyzing electrochemical properties of mixed conducting solid oxide fuel cell anode materials by impedance spectroscopy.  

PubMed

For application of acceptor-doped mixed conducting oxides as solid oxide fuel cell (SOFC) anodes, high electrochemical surface activity as well as acceptable electronic and ionic conductivity are crucial. In a reducing atmosphere, particularly the electronic conductivity of acceptor-doped oxides can become rather low and the resulting complex interplay of electrochemical reactions and charge transport processes makes a mechanistic interpretation of impedance measurements very complicated. In order to determine all relevant resistive and capacitive contributions of mixed conducting electrodes in a reducing atmosphere, a novel electrode design and impedance-based analysis technique is therefore introduced. Two interdigitating metallic current collectors are placed in a microelectrode, which allows in-plane measurements within the electrode as well as electrochemical measurements versus a counter electrode. Equivalent circuit models for quantifying the spectra of both measurement modes are developed and applied to simultaneously fit both spectra, using the same parameter set. In this manner, the electronic and ionic conductivity of the material as well as the area-specific resistance of the surface reaction and the chemical capacitance can be determined on a single microelectrode in a H2-H2O atmosphere. The applicability of this new tool was demonstrated in SrTi0.7Fe0.3O(3-?) (STFO) thin film microelectrodes, deposited on single-crystalline yttria-stabilized zirconia (YSZ) substrates. All materials parameters that contribute to the polarization resistance of STFO electrodes in a reducing atmosphere could thus be quantified. PMID:25219525

Nenning, A; Opitz, A K; Huber, T M; Fleig, J

2014-10-28

275

Mediated electrochemical oxidation of organic wastes using a Co (III) mediator in a nitric acid based system  

DOEpatents

An electrochemical cell with a Co(III) mediator and nitric acid electrolyte provides efficient destruction of organic and mixed wastes. The organic waste is concentrated in the anolyte reservoir, where the mediator oxidizes the organics and insoluble transuranic compounds and is regenerated at the anode until the organics are converted to CO.sub.2. The nitric acid is an excellent oxidant that facilitates the destruction of the organic components. The anode is not readily attacked by the nitric acid solution, thus the cell can be used for extended continual operation without electrode replacement.

Balazs, G. Bryan (Livermore, CA); Chiba, Zoher (Moraga, CA); Lewis, Patricia R. (Livermore, CA); Nelson, Norvell (Palo Alto, CA); Steward, G. Anthony (Los Altos Hills, CA)

1999-01-01

276

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

PubMed

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 ?A 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

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

2011-03-15

277

Seedless growth of zinc oxide flower-shaped structures on multilayer graphene by electrochemical deposition  

NASA Astrophysics Data System (ADS)

A seedless growth of zinc oxide (ZnO) structures on multilayer (ML) graphene by electrochemical deposition without any pre-deposited ZnO seed layer or metal catalyst was studied. A high density of a mixture of vertically aligned/non-aligned ZnO rods and flower-shaped structures was obtained. ML graphene seems to generate the formation of flower-shaped structures due to the stacking boundaries. The nucleation of ZnO seems to be promoted at the stacking edges of ML graphene with the increase of applied current density, resulting in the formation of flower-shaped structures. The diameters of the rods/flower-shaped structures also increase with the applied current density. ZnO rods/flower-shaped structures with high aspect ratio over 5.0 and good crystallinity were obtained at the applied current densities of -0.5 and -1.0 mA/cm2. The growth mechanism was proposed. The growth involves the formation of ZnO nucleation below 80°C and the enhancement of the growth of vertically non-aligned rods and flower-shaped structures at 80°C. Such ZnO/graphene hybrid structure provides several potential applications in sensing devices.

Aziz, Nur Suhaili Abd; Nishiyama, Tomoya; Rusli, Nurul Izni; Mahmood, Mohamad Rusop; Yasui, Kanji; Hashim, Abdul Manaf

2014-07-01

278

Electrochemical and biological characterization of coatings formed on Ti-15Mo alloy by plasma electrolytic oxidation.  

PubMed

?-Type titanium alloys are considered the future materials for bone implants. To improve the bioactivity of Ti-15Mo, the surface was modified using the plasma electrolytic oxidation (PEO) process. Tricalcium phosphate (TCP, Ca3PO4), wollastonite (CaSiO3) and silica (SiO2) were selected as additives in the anodizing bath to enhance the bioactivity of the coatings formed during the PEO process. Electrochemical analysis of the samples was performed in Ringer's solution at 37°C. The open-circuit potential (EOCP) as a function of time, corrosion potential (ECORR), corrosion current density (jCORR) and polarization resistance (Rp) of the samples were determined. Surface modification improved the corrosion resistance of Ti-15Mo in Ringer's solution. In vitro studies with MG-63 osteoblast-like cells were performed for 1, 3 and 7 days. After 24h, the cells were well adhered on the entire surfaces, and their number increased with increasing culture time. The coatings formed in basic solution with wollastonite exhibited better biological performance compared with the as-ground sample. PMID:25175202

Kazek-K?sik, Alicja; Krok-Borkowicz, Ma?gorzata; Pamu?a, El?bieta; Simka, Wojciech

2014-10-01

279

Electrochemical aptamer sensor for thrombin detection based on Au nanoneedle and enzymatic ascorbic acid oxidization.  

PubMed

In this article, we describe an aptamer-based sandwich-type electrochemical sensor for the detection of human alpha-thrombin. Au nanoneedles were synthesized in the hole of the naked polycarbonate (PC) template using electrodepositing strategy. The thiolated thrombin aptamer I was immobilized as the capture probe on the gold nanoneedles through Au-S bond. After the thrombin was captured, the biotinylated aptamer II, used as the detection probe, was bound to thrombin. Then, the streptavidin-conjugated alkaline phosphatase (SA-ALP) was linked to the biotinylated aptamer II and catalyze hydrolyzation reaction of ascorbic acid 2-phosphate to produce ascorbic acid. Differential pulse voltammetry was used to detect the oxidizing current of ascorbic acid, which is proportional to the concentration of thrombin bound on the electrode surface ranging from 0.24 nM to 150 nM with a detection limit of 0.1 nM at 3 sigma. This assay is rapid, simple, sensitive and highly specific. It could be applied to detect thrombin in complex real sample. PMID:23646773

Xu, Feng; Hua, Mei; Luo, Lei; Du, Huali; Yang, Yunhui

2013-01-01

280

Synthesis of Au/Graphene Oxide Composites for Selective and Sensitive Electrochemical Detection of Ascorbic Acid  

PubMed Central

In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15?V, a high sensitivity of 101.86??A mM?1 cm?2 to AA, a low detection limit of 100?nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application. PMID:25515430

Song, Jian; Xu, Lin; Xing, Ruiqing; Li, Qingling; Zhou, Chunyang; Liu, Dali; Song, Hongwei

2014-01-01

281

Application of electrochemically reduced graphene oxide on screen-printed ion-selective electrode.  

PubMed

In this study, a novel disposable all-solid-state ion-selective electrode using graphene as the ion-to-electron transducer was developed. The graphene film was prepared on screen-printed electrode directly from the graphene oxide dispersion by a one-step electrodeposition technique. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to demonstrate the large double layer capacitance and fast charge transfer of the graphene film modified electrode. On the basis of these excellent properties, an all-solid-state calcium ion-selective electrode as the model was constructed using the calcium ion-selective membrane and graphene film modified electrode. The mechanism about the graphene promoting the ion-to-electron transformation was investigated in detail. The disposable electrode exhibited a Nernstian slope (29.1 mV/decade), low detection limit (10(-5.8) M), and fast response time (less than 10 s). With the high hydrophobic character of graphene materials, no water film was formed between the ion-selective membrane and the underlying graphene layer. Further studies revealed that the developed electrode was insensitive to light, oxygen, and redox species. The use of the disposable electrode for real sample analysis obtained satisfactory results, which made it a promising alternative in routine sensing applications. PMID:22380625

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

2012-04-01

282

Electrochemical insertion of lithium, sodium, and magnesium in molybdenum(VI) oxide  

NASA Astrophysics Data System (ADS)

The electrochemical insertion of divalent magnesium cations into orthorhombic molybdenum(VI) oxide was studied with regard to their use as electroactive species in ion-transfer battery systems and compared to the insertion of Li + and Na +. Specific charges of up to 300 and 240 Ah kg -1 were obtained in organic, propylene carbonate-based electrolytes for the lithium and sodium insertion, respectively, in the first reduction half-cycle. Reversible Mg 2+ insertion could be demonstrated in a room temperature molten salt electrolyte consisting of 3 wt.% MgCl 2, 41 wt.% 1-ethyl-3-methylimidazolium chloride, and 56 wt.% AlCl 3. Specific charges of up to 160 Ah kg -1 were obtained with MoO 3 in the first reduction half-cycle. The Mg 2+ insertion process can be enhanced using an organic electrolyte with traces of H 2O. In 1 M Mg(ClO 4) 2/acetonitrile with 3 mol% of H 2O, specific charges of up to 210 Ah kg -1 were measured in the first reduction.

Spahr, M. E.; Novák, P.; Haas, O.; Nesper, R.

283

Synthesis of Au/Graphene Oxide Composites for Selective and Sensitive Electrochemical Detection of Ascorbic Acid  

NASA Astrophysics Data System (ADS)

In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15 V, a high sensitivity of 101.86 ?A mM-1 cm-2 to AA, a low detection limit of 100 nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application.

Song, Jian; Xu, Lin; Xing, Ruiqing; Li, Qingling; Zhou, Chunyang; Liu, Dali; Song, Hongwei

2014-12-01

284

Electrochemical oxidation of adenine using platinum electrodes modified with carbon nanotubes  

NASA Astrophysics Data System (ADS)

Single- (SWNTs), double- (DWNTs), and multi-walled (MWNTs) carbon nanotubes were synthesized by controlled Radio Frequency-catalytic Chemical Vapor Deposition (RF-cCVD). Their morphological and structural characteristics were identified using Transmission Electron Microscopy (TEM/HRTEM) and X-ray powder diffraction (XRD). Next, three platinum electrodes with identical amounts of each nanotube material (denoted Pt-SW, Pt-DW, and Pt-MW) were modified in order to test the electro-catalytic characteristics of the carbon nanotubes and further used for the electrochemical oxidation of adenine. The signal recorded with the Pt-SW electrode was very poor, due to the predominantly semiconducting properties of these nanotubes. In contrast, the signal recorded with Pt-DW or Pt-MW was well-defined, with the peak potentials at 1.07 and 1.01 V vs Ag/AgCl, respectively. In both cases, the detection limit (DL) for adenine was found to be 3×10-6 M.

Pogacean, Florina; Biris, Alexandru R.; Coros, Maria; Watanabe, Fumiya; Biris, Alexandru S.; Clichici, Simona; Filip, Adriana; Pruneanu, Stela

2014-05-01

285

Seedless growth of zinc oxide flower-shaped structures on multilayer graphene by electrochemical deposition  

PubMed Central

A seedless growth of zinc oxide (ZnO) structures on multilayer (ML) graphene by electrochemical deposition without any pre-deposited ZnO seed layer or metal catalyst was studied. A high density of a mixture of vertically aligned/non-aligned ZnO rods and flower-shaped structures was obtained. ML graphene seems to generate the formation of flower-shaped structures due to the stacking boundaries. The nucleation of ZnO seems to be promoted at the stacking edges of ML graphene with the increase of applied current density, resulting in the formation of flower-shaped structures. The diameters of the rods/flower-shaped structures also increase with the applied current density. ZnO rods/flower-shaped structures with high aspect ratio over 5.0 and good crystallinity were obtained at the applied current densities of ?0.5 and ?1.0 mA/cm2. The growth mechanism was proposed. The growth involves the formation of ZnO nucleation below 80°C and the enhancement of the growth of vertically non-aligned rods and flower-shaped structures at 80°C. Such ZnO/graphene hybrid structure provides several potential applications in sensing devices. PMID:25024694

2014-01-01

286

Synthesis of au/graphene oxide composites for selective and sensitive electrochemical detection of ascorbic Acid.  

PubMed

In this work, we present a novel ascorbic acid (AA) sensor applied to the detection of AA in human sera and pharmaceuticals. A series of Au nanoparticles (NPs) and graphene oxide sheets (Au NP/GO) composites were successfully synthesized by reduction of gold (III) using sodium citrate. Then the Au NP/GO composites were used to construct nonenzymatic electrodes in practical AA measurement. The electrode that has the best performance presents attractive analytical features, such as a low working potential of +0.15?V, a high sensitivity of 101.86??A mM(-1) cm(-2) to AA, a low detection limit of 100?nM, good reproducibility and excellent selectivity. And more,it was also employed to accurately and practically detect AA in human serum and clinical vitamin C tablet with the existence of some food additive. The enhanced AA electrochemical properties of the Au NP/GO modified electrode in our work can be attributed to the improvement of electroactive surface area of Au NPs and the synergistic effect from the combination of Au NPs and GO sheets. This work shows that the Au NP/GO/GCEs hold the prospect for sensitive and selective determination of AA in practical clinical application. PMID:25515430

Song, Jian; Xu, Lin; Xing, Ruiqing; Li, Qingling; Zhou, Chunyang; Liu, Dali; Song, Hongwei

2014-01-01

287

Electrochemical and spectral studies of the reactions of aquocobalamin with nitric oxide and nitrite ion.  

PubMed

Electrochemistry and Raman spectroscopy have shown that aquocob(III)alamin (Cbl(III)) can be reduced by nitric oxide (NO) to form Cbl(II) on an electrode surface. The Cbl(II) formed in this way can bind NO to form nitrosyl-cobalamin, Cbl(II)-NO, which is reduced to form Cbl(I) at about -1.0 V vs a KCl saturated Ag/AgCl reference electrode. In addition, nitrite was found to bind both Cbl(III) and Cbl(II) and a binding constant of 3.5 x 10(2) M(-1) was measured for (NO(2)-Cbl(II))(1-). UV-vis spectrophotometry and mass spectroscopy were used to show that Cbl(I) reduces NO to form Cbl(II)-NO and N(2)O and N(2), and this reaction is involved in the cyclic voltammetry of cobalamin in the presence of excess NO where a catalytic reduction of NO occurs involving the cycling of Cbl(II)-NO/Cbl(I). This redox couple is also involved in the electrochemical catalytic reduction of nitrite. These results can be used to explain a number of physiological effects involving NO interaction in biological systems with added cobalamin or with cobalamin in the methionine synthase enzyme. PMID:11978125

Zheng, Donghong; Yan, Lei; Birke, Ronald L

2002-05-01

288

Effect of annealing temperature on electrochemical luminescence properties of nanoporous fluorine-doped tin oxide films.  

PubMed

Nanoporous Fluorine-doped tin oxide (FTO) materials were synthesized by sol-gel combustion method for electrochemical luminescence (ECL) application. The influence of annealing temperature on the structures and morphology of the nanoporous FTO films was examined by X-ray diffraction (XRD), atomic force microscopy (AFM), optical transmittance and BET specific surface measurements. The naoporous FTO-based ECL cell is composed of FTO glass/nanoporous FTO/Ru(bpy)2+ electrolyte/FTO glass. The peak intensity of emitting light from the cell was obtained at the wavelength of about 615 nm, which corresponds to dark orange color. At 5 V bias, ECL efficiency of the cell using the 550 degrees C annealed FTO was about 975 cd/m2, which is much higher than those of other cells. The result shows that the nanoporous FTO layer was more effective for increasing ECL intensities. The sol-gel combustion method at annealing temperature of 550 degrees C could be employed to synthesize the nanoporous FTO materials with high porosity and ECL performance. PMID:23763189

Joo, Bong-Hyun; Yoon, Seog-Young; Sung, Youl-Moon

2013-04-01

289

Electrochemical synthesis and sintering of nanocrystalline cerium(IV) oxide powders  

SciTech Connect

Nanocrystalline CeO{sub 2} powders were prepared electrochemically by the cathodic electrogeneration of base, and their sintering behavior was investigated. X-ray diffraction and transmission electron microscopy revealed that the as-prepared powders were crystalline cerium(IV) oxide with the cubic fluorite structure. The lattice parameter of the electrogenerated material was 0.5419 nm. The powders consisted of nonaggregated, faceted particles. The average crystallite size was a function of the solution temperature. It increased from 10 nm at 29 C to 14 nm at 80 C. Consolidated powders were sintered in air at both a constant heating rate of 10 C/min and under isothermal conditions. The temperature at which sintering started (750 C) for nanocrystalline CeO{sub 2} powders was only about 100 C lower than that of coarser-grained powders (850 C). However, the sintering rate was enhanced. The temperature at which shrinkage stopped was 200--300 C lower with the nanoscale powder than with micrometer-sized powders. A sintered specimen with 99.8% of theoretical density and a grain size of about 350 nm was obtained by sintering at 1,300 C for 2 h.

Zhou, Z.; Phillips, R.J.; Switzer, J.A. [Univ. of Missouri, Rolla, MO (United States)

1995-04-01

290

Development of advanced mixed oxide fuels for plutonium management  

SciTech Connect

A number of advanced Mixed Oxide (MOX) fuel forms are currently being investigated at Los Alamos National Laboratory that have the potential to be effective plutonium management tools. Evolutionary Mixed Oxide (EMOX) fuel is a slight perturbation on standard MOX fuel, but achieves greater plutonium destruction rates by employing a fractional nonfertile component. A pure nonfertile fuel is also being studied. Initial calculations show that the fuel can be utilized in existing light water reactors and tailored to address different plutonium management goals (i.e., stabilization or reduction of plutonium inventories residing in spent nuclear fuel). In parallel, experiments are being performed to determine the feasibility of fabrication of such fuels. Initial EMOX pellets have successfully been fabricated using weapons-grade plutonium.

Eaton, S.; Beard, C.; Buksa, J.; Butt, D.; Chidester, K.; Havrilla, G.; Ramsey, K.

1997-06-01

291

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

NASA Astrophysics Data System (ADS)

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

Mohammadi, Alidad

292

Treatment of synthetic urine by electrochemical oxidation using conductive-diamond anodes.  

PubMed

In this work, the electrochemical oxidation of synthetic urine by anodic oxidation using boron-doped diamond as anode and stainless steel as cathode was investigated. Results show that complete depletion of chemical oxygen demand (COD) and total organic carbon (TOC) can be attained regardless of the current density applied in the range 20-100 mA cm(-2). Oxalic and oxamic acids, and, in lower concentrations, creatol and guanidine were identified as the main intermediates. Chloride ions play a very important role as mediators and contribute not only to obtain a high efficiency in the removal of the organics but also to obtain an efficient removal of nitrogen by the transformation of the various raw nitrogen species into gaseous nitrogen through chloramine formation. The main drawback of the technology is the formation of chlorates and perchlorates as final chlorine products. The increase of current density from 20 to 60 mA cm(-2) led to an increase in the rate of COD and TOC removals although the process becomes less efficient in terms of energy consumption (removals of COD and TOC after applying 18 Ah dm(-3) were 93.94 and 94.94 %, respectively, at 20 mA cm(-2) and 89.17 and 86.72 %, respectively, at 60 mA cm(-2)). The most efficient conditions are low current densities and high temperature reaching total mineralization at an applied charge as low as 20 kAh m(-3). This result confirmed that the electrolysis using diamond anodes is a very interesting technology for the treatment of urine. PMID:25399531

Dbira, Sondos; Bensalah, Nasr; Bedoui, Ahmed; Cañizares, Pablo; Rodrigo, Manuel A

2014-11-18

293

Electrochemical detection of catecholamine exocytosis using planar iridium oxide electrodes in nanoliter microfluidic cell culture volumes  

PubMed Central

Release of neurotransmitters and hormones by Ca2+ regulated exocytosis is a fundamental cellular/molecular process that is disrupted in a variety of psychiatric, neurological, and endocrine disorders. Therefore, this area represents a relevant target for drug and therapeutic development, efforts that will be aided by novel analytical tools and devices that provide mechanistically rich data with increased throughput. Toward this goal, we have electrochemically deposited iridium oxide (IrOx) films onto planar thin film platinum electrodes (20×300µm2) and utilized these for quantitative detection of catecholamine exocytosis from adrenal chromaffin cells trapped in a microfluidic network. The IrOx electrodes show a linear response to norepinephrine in the range of 0–400µM, with a sensitivity of 23.1±0.5mA/(M·mm2). The sensitivity of the IrOx electrodes does not change in the presence of ascorbic acid, a substance commonly found in biological samples. A replica molded polydimethylsiloxane (PDMS) microfluidic device with nanoliter sensing volumes was aligned and sealed to a glass substrate with the sensing electrodes. Small populations of chromaffin cells were trapped in the microfluidic sensing chamber and stimulated by rapid perfusion with high potassium (50mM) containing Tyrode’s solution at a flow rate of 1nL/s. Stimulation of the cells produced a rapid increase in current due to oxidation of the released catecholamines, with an estimated maximum concentration in the microfluidic device ~52µM. Thus, we demonstrate the utility of an integrated microfluidic network with IrOx electrodes for real-time quantitative detection of catecholamines released from small populations of cells. PMID:22398270

Ges, Igor A.; Currie, Kevin P.M.; Baudenbacher, Franz

2013-01-01

294

Recent advances in the use of ionic liquids for electrochemical sensing.  

PubMed

Ionic Liquids are salts that are liquid at (or just above) room temperature. They possess several advantageous properties (e.g. high intrinsic conductivity, wide electrochemical windows, low volatility, high thermal stability and good solvating ability), which make them ideal as non-volatile electrolytes in electrochemical sensors. This mini-review article describes the recent uses of ionic liquids in electrochemical sensing applications (covering the last 3 years) in the context of voltammetric sensing at solid/liquid, liquid/liquid interfaces and carbon paste electrodes, as well as their use in gas sensing, ion-selective electrodes, and for detecting biological molecules, explosives and chemical warfare agents. A comment on the future direction and challenges in this field is also presented. PMID:22013585

Silvester, Debbie S

2011-12-01

295

High-sensitivity paracetamol sensor based on Pd/graphene oxide nanocomposite as an enhanced electrochemical sensing platform.  

PubMed

Well-dispersed Pd nanoparticles were facilely anchored on graphene oxide (Pd/GO) via a one-pot chemical reduction of the Pd(2+) precursor without any surfactants and templates. The morphology and composition of the Pd/GO nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive analysis of X-ray (EDX). The stepwise fabrication process of the Pd/GO modified electrode and its electrochemical sensing performance towards paracetamol was evaluated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The experimental results indicate that the as-synthesized Pd nanoparticles are relatively uniform in size (5-10 nm) without large aggregation and uniformly distributed in the carbon matrix with the overall Pd content of 28.77 wt% in Pd/GO. Compared with the GO modified electrode, the Pd/GO modified electrode shows a better electrocatalytic activity to the oxidation of paracetamol with lower oxidation potential and larger peak current, so the Pd/GO nanocomposite can be used as an enhanced sensing platform for the electrochemical determination of paracetamol. The kinetic parameters of the paracetamol electro-oxidation at Pd/GO electrode were studied in detail, and the determination conditions were optimized. Under the optimal conditions, the oxidation peak current is linear to the paracetamol concentration in the ranges of 0.005-0.5 ?M and 0.5-80.0 ?M with a detection limit of 2.2 nM. Based on the high sensitivity and good selectivity of the Pd/GO modified electrode, the proposed method was successfully applied to the determination of paracetamol in commercial tablets and human urines, and the satisfactory results confirm the applicability of this sensor in practical analysis. PMID:24315879

Li, Junhua; Liu, Jinlong; Tan, Gongrong; Jiang, Jianbo; Peng, Sanjun; Deng, Miao; Qian, Dong; Feng, Yonglan; Liu, Youcai

2014-04-15

296

Nitrogen doped holey graphene as an efficient metal-free multifunctional electrochemical catalyst for hydrazine oxidation and oxygen reduction  

NASA Astrophysics Data System (ADS)

Electrocatalysts for anode or cathode reactions are at the heart of electrochemical energy conversion and storage devices. Molecular design of carbon based nanomaterials may create the next generation electrochemical catalysts for broad applications. Herein, we present the synthesis of a three-dimensional (3D) nanostructure with a large surface area (784 m2 g-1) composed of nitrogen doped (up to 8.6 at.%) holey graphene. The holey structure of graphene sheets (~25% of surface area is attributed to pores) engenders more exposed catalytic active edge sites. Nitrogen doping further improves catalytic activity, while the formation of the 3D porous nanostructure significantly reduces graphene nanosheet stacking and facilitates the diffusion of reactants/electrolytes. The three factors work together, leading to superb electrochemical catalytic activities for both hydrazine oxidation (its current generation ability is comparable to that of 10 wt% Pt-C catalyst) and oxygen reduction (its limiting current is comparable to that of 20 wt% Pt-C catalyst) with four-electron transfer processes and excellent durability.Electrocatalysts for anode or cathode reactions are at the heart of electrochemical energy conversion and storage devices. Molecular design of carbon based nanomaterials may create the next generation electrochemical catalysts for broad applications. Herein, we present the synthesis of a three-dimensional (3D) nanostructure with a large surface area (784 m2 g-1) composed of nitrogen doped (up to 8.6 at.%) holey graphene. The holey structure of graphene sheets (~25% of surface area is attributed to pores) engenders more exposed catalytic active edge sites. Nitrogen doping further improves catalytic activity, while the formation of the 3D porous nanostructure significantly reduces graphene nanosheet stacking and facilitates the diffusion of reactants/electrolytes. The three factors work together, leading to superb electrochemical catalytic activities for both hydrazine oxidation (its current generation ability is comparable to that of 10 wt% Pt-C catalyst) and oxygen reduction (its limiting current is comparable to that of 20 wt% Pt-C catalyst) with four-electron transfer processes and excellent durability. Electronic supplementary information (ESI) available: AFM images of GO sheets, nitrogen physisorption isotherms, XPS spectrum of RG, RDE curves of electrodes, CV curves of electrodes, and determination of the number of total electrons (n) involved in hydrazine oxidation. See DOI: 10.1039/c3nr34267k

Yu, Dingshan; Wei, Li; Jiang, Wenchao; Wang, Hong; Sun, Bo; Zhang, Qiang; Goh, Kunli; Si, Rongmei; Chen, Yuan

2013-03-01

297

Electropolymerized Polyaniline Stabilized Tungsten Oxide Nanocomposite Films: Electrochromic Behavior and Electrochemical  

E-print Network

Behavior and Electrochemical Energy Storage Huige Wei,, Xingru Yan,, Shijie Wu,§ Zhiping Luo, Suying Wei. The optical properties and electrochemical capacitive behaviors of the composite films for electrochromic (EC such as facile polymerization in aqueous media15-18 or nonaqueous media,19 versatile redox behavior, good

Guo, John Zhanhu

298

Screen-printed calcium-birnessite electrodes for water oxidation at neutral pH and an "electrochemical harriman series".  

PubMed

A mild screen-printing method was developed to coat conductive oxide surfaces (here: fluorine-doped tin oxide) with micrometer-thick layers of presynthesized calcium manganese oxide (Ca-birnessite) particles. After optimization steps concerning the printing process and layer thickness, electrodes were obtained that could be used as corrosion-stable water-oxidizing anodes at pH?7 to yield current densities of 1?mA?cm(-2) at an overpotential of less than 500?mV. Analyses of the electrode coatings of optimal thickness (?10??m) indicated that composition, oxide phase, and morphology of the synthetic Ca-birnessite particles were hardly affected by the screen-printing procedure. However, a more detailed analysis by X-ray absorption spectroscopy revealed small modifications of both the Mn redox state and the structure at the atomic level, which could affect functional properties such as proton conductivity. Furthermore, the versatile new screen-printing method was used for a comparative study of various transition-metal oxides concerning electrochemical water oxidation under "artificial leaf conditions" (neutral pH, fairly low overpotential and current density), for which a general activity ranking of RuO2 >Co3 O4 ?(Ca)MnOx ?NiO was observed. Within the group of screened manganese oxides, Ca-birnessite performed better than "Mn-only materials" such as Mn2 O3 and MnO2 . PMID:25346273

Lee, Seung Y; González-Flores, Diego; Ohms, Jonas; Trost, Tim; Dau, Holger; Zaharieva, Ivelina; Kurz, Philipp

2014-12-01

299

Electrochemical oxidation of ampicillin antibiotic at boron-doped diamond electrodes and process optimization using response surface methodology.  

PubMed

Electrochemical oxidation and process optimization of ampicillin antibiotic at boron-doped diamond electrodes (BDD) were investigated in a batch electrochemical reactor. The influence of operating parameters, such as ampicillin concentration, electrolyte concentration, current density, and reaction temperature, on ampicillin removal, COD removal, and energy consumption was analyzed in order to optimize the electrochemical oxidation process under specified cost-driven constraints using response surface methodology. Quadratic models for the responses satisfied the assumptions of the analysis of variance well according to normal probability, studentized residuals, and outlier t residual plots. Residual plots followed a normal distribution, and outlier t values indicated that the approximations of the fitted models to the quadratic response surfaces were very good. Optimum operating conditions were determined at 618 mg/L ampicillin concentration, 3.6 g/L electrolyte concentration, 13.4 mA/cm(2) current density, and 36 °C reaction temperature. Under response surface optimized conditions, ampicillin removal, COD removal, and energy consumption were obtained as 97.1 %, 92.5 %, and 71.7 kWh/kg CODr, respectively. PMID:24906830

Körbahti, Bahad?r K; Ta?yürek, Selin

2014-06-01

300

Electrochemical detection of Cu2+ through Ag nanoparticle assembly regulated by copper-catalyzed oxidation of cysteamine.  

PubMed

A highly sensitive and selective electrochemical sensor was developed for the detection of Cu(2+) by the assembly of Ag nanoparticles (AgNPs) at dithiobis[succinimidylpropionate] encapsulated Au nanoparticles (DSP-AuNPs), which was regulated by copper-catalyzed oxidation of cysteamine (Cys). The electrochemical sensor was constructed by layer-by-layer modification of glassy carbon electrode with carbon nanotubes, poly(amidoamine) dendrimers and DSP-AuNPs. In the absence of Cu(2+), Cys could bind to the surface of citrate-stabilized AgNPs via Ag-S bond, thus AgNPs could be assembled on the sensor surface through the reaction between DSP and Cys. In contrast, the copper-catalyzed oxidation of Cys by dissolved oxygen in the presence of Cu(2+) inhibited the Cys-induced aggregation of AgNPs, leading to the decrease of the electrochemical stripping signal of AgNPs. Under the optimized conditions, this method could detect Cu(2+) in the range of 1.0-1000 nM with a detection limit of 0.48 nM. The proposed Cu(2+) sensor showed good reproducibility, stability and selectivity. It has been satisfactorily applied to determine Cu(2+) in water samples. PMID:24389390

Cui, Lin; Wu, Jie; Li, Jie; Ge, Yanqiu; Ju, Huangxian

2014-05-15

301

Comparative studies on single-layer reduced graphene oxide films obtained by electrochemical reduction and hydrazine vapor reduction  

PubMed Central

The comparison between two kinds of single-layer reduced graphene oxide (rGO) sheets, obtained by reduction of graphene oxide (GO) with the electrochemical method and hydrazine vapor reduction, referred to as E-rGO and C-rGO, respectively, is systematically studied. Although there is no morphology difference between the E-rGO and C-rGO films adsorbed on solid substrates observed by AFM, the reduction process to obtain the E-rGO and C-rGO films is quite different. In the hydrazine vapor reduction, the nitrogen element is incorporated into the obtained C-rGO film, while no additional element is introduced to the E-rGO film during the electrochemical reduction. Moreover, Raman spectra show that the electrochemical method is more effective than the hydrazine vapor reduction method to reduce the GO films. In addition, E-rGO shows better electrocatalysis towards dopamine than does C-rGO. This study is helpful for researchers to understand these two different reduction methods and choose a suitable one to reduce GO based on their experimental requirements. PMID:22373422

2012-01-01

302

Metal-free dihydrogen oxidation by a borenium cation: a combined electrochemical/frustrated Lewis pair approach.  

PubMed

In order to use H2 as a clean source of electricity, prohibitively rare and expensive precious metal electrocatalysts, such as Pt, are often used to overcome the large oxidative voltage required to convert H2 into 2?H(+) and 2?e(-). Herein, we report a metal-free approach to catalyze the oxidation of H2 by combining the ability of frustrated Lewis pairs (FLPs) to heterolytically cleave H2 with the in?situ electrochemical oxidation of the resulting borohydride. The use of the NHC-stabilized borenium cation [(IiPr2)(BC8H14)](+) (IiPr2=C3H2(NiPr)2, NHC=N-heterocyclic carbene) as the Lewis acidic component of the FLP is shown to decrease the voltage required for H2 oxidation by 910?mV at inexpensive carbon electrodes, a significant energy saving equivalent to 175.6?kJ?mol(-1). The NHC-borenium Lewis acid also offers improved catalyst recyclability and chemical stability compared to B(C6F5)3, the paradigm Lewis acid originally used to pioneer our combined electrochemical/frustrated Lewis pair approach. PMID:25044562

Lawrence, Elliot J; Herrington, Thomas J; Ashley, Andrew E; Wildgoose, Gregory G

2014-09-01

303

Importance of glycolysis and oxidative phosphorylation in advanced melanoma  

PubMed Central

Serum lactate dehydrogenase (LDH) is a prognostic factor for patients with stage IV melanoma. To gain insights into the biology underlying this prognostic factor, we analyzed total serum LDH, serum LDH isoenzymes, and serum lactate in up to 49 patients with metastatic melanoma. Our data demonstrate that high serum LDH is associated with a significant increase in LDH isoenzymes 3 and 4, and a decrease in LDH isoenzymes 1 and 2. Since LDH isoenzymes play a role in both glycolysis and oxidative phosphorylation (OXPHOS), we subsequently determined using tissue microarray (TMA) analysis that the levels of proteins associated with mitochondrial function, lactate metabolism, and regulators of glycolysis were all elevated in advanced melanomas compared with nevic melanocytes. To investigate whether in advanced melanoma, the glycolysis and OXPHOS pathways might be linked, we determined expression of the monocarboxylate transporters (MCT) 1 and 4. Analysis of a nevus-to-melanoma progression TMA revealed that MCT4, and to a lesser extend MCT1, were elevated with progression to advanced melanoma. Further analysis of human melanoma specimens using the Seahorse XF24 extracellular flux analyzer indicated that metastatic melanoma tumors derived a large fraction of energy from OXPHOS. Taken together, these findings suggest that in stage IV melanomas with normal serum LDH, glycolysis and OXPHOS may provide metabolic symbiosis within the same tumor, whereas in stage IV melanomas with high serum LDH glycolysis is the principle source of energy. PMID:23043612

2012-01-01

304

Real-time electrochemical detection of extracellular nitric oxide in tobacco cells exposed to cryptogein, an elicitor of defence responses  

PubMed Central

It was previously reported that cryptogein, an elicitor of defence responses, induces an intracellular production of nitric oxide (NO) in tobacco. Here, the possibility was explored that cryptogein might also trigger an increase of NO extracellular content through two distinct approaches, an indirect method using the NO probe 4,5-diaminofluorescein (DAF-2) and an electrochemical method involving a chemically modified microelectrode probing free NO in biological media. While the chemical nature of DAF-2-reactive compound(s) is still uncertain, the electrochemical modified microelectrodes provide real-time evidence that cryptogein induces an increase of extracellular NO. Direct measurement of free extracellular NO might offer important new insights into its role in plants challenged by biotic stresses. PMID:18653691

Besson-Bard, Angélique; Griveau, Sophie; Bedioui, Fethi; Wendehenne, David

2008-01-01

305

Influence of albumin and inorganic ions on electrochemical corrosion behavior of plasma electrolytic oxidation coated magnesium for surgical implants  

NASA Astrophysics Data System (ADS)

Magnesium and its alloys are of great interest for biodegradable metallic devices. However, the degradation behavior and mechanisms of magnesium treated with coating in physiological environment in the presence of organic compound such as albumin have not been elucidated. In this study, the plasma electrolytic oxidation coated magnesium immersed in four different simulated body fluids: NaCl, PBS and with the addition of albumin to investigate the influence of protein and inorganic ions on degradation behavior by electrochemical methods. The results of electrochemical tests showed that aggressive corrosion took place in 0.9 wt.% NaCl solution; whereas albumin can act as an inhibitor, its adsorption impeded further dissolution of the coating. The mechanism was attributed to the synergistic effect of protein adsorption and precipitation of insoluble salts.

Wan, Peng; Lin, Xiao; Tan, LiLi; Li, Lugee; Li, WeiRong; Yang, Ke

2013-10-01

306

An electrochemical and computational study for discrimination of D- and L-cystine by reduced graphene oxide/?-cyclodextrin.  

PubMed

Here, we report a novel enantioselective electrochemical biosensor for the discrimination of cystine enantiomers (d- and l-cystine) using a chiral interface for the specific recognition of d- and l-cystine. The biosensor is based on reduced graphene oxide modified by ?-cyclodextrin (rGO/?-CD) at the GCE surface. During the preparation of rGO/?-CD/GCE, the modified electrode surfaces were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The electrochemical behaviours of the d- and l-cystine were investigated using the rGO/?-CD/GCE by CV and compared to bare GCE. A clear separation between the oxidation peak potentials of d- and l-cystine was observed at 1.32 and 1.42 V, respectively. The electrochemical discrimination performance of the fabricated chiral sensor was also examined by differential pulse voltammetry (DPV) in a mixed solution of d- and l-cystine. In addition, the DPV technique was used for the determination of d- and l-cystine at low concentration values in the range of 1.0-10.0 ?M. To investigate the amperometric response of rGO/?-CD/GCE towards d- and l-cystine, the chronoamperometry technique was used in the concentration range of 10.0-100.0 ?M. The interactions of the enantiomers with rGO/?-CD were modelled by molecular docking using AutoDock Vina, and the interaction energies were predicted to be -4.8 and -5.3 kcal mol(-1) for d- and l-cystine, respectively. The corresponding values of binding constants were calculated to be 3.32 × 10(3) and 7.71 × 10(3) M(-1), respectively. The experimental and molecular docking results indicate that the rGO/?-CD/GCE has a different affinity for each enantiomer. PMID:25382195

Zor, Erhan; Bingol, Haluk; Ramanaviciene, Almira; Ramanavicius, Arunas; Ersoz, Mustafa

2015-01-01

307

Electrochemically driven biocatalysis of the oxygenase domain of neuronal nitric oxide synthase in indium tin oxide nanoparticles/polyvinyl alcohol nanocomposite.  

PubMed

Nitric oxide synthase (NOS) plays a critical role in a number of key physiological and pathological processes. Investigation of electron-transfer reactions in NOS would contribute to a better understanding of the nitric oxide (NO) synthesis mechanism. Herein, we describe an electrochemically driven catalytic strategy, using a nanocomposite that consisted of the oxygenase domain of neuronal NOS (D290nNOSoxy), indium tin oxide (ITO) nanoparticles and polyvinyl alcohol (PVA). Fast direct electron transfer between electrodes and D290nNOSoxy was observed with the heterogeneous electron transfer rate constant (ket) of 154.8 ± 0.1s(-1) at the scan rate of 5 Vs(-1). Moreover, the substrate N(?)-hydroxy-L-arginine (NHA) was used to prove the concept of electrochemically driven biocatalysis of D290nNOSoxy. In the presence of the oxygen cosubstrate and tetrahydrobiopterin (BH4) cofactor, the addition of NHA caused the decreases of both oxidation current at +0.1 V and reduction current at potentials ranging from -0.149 V to -0.549 V vs Ag/AgCl. Thereafter, a series of control experiments such as in the absence of BH4 or D290nNOSoxy were performed. All the results demonstrated that D290nNOSoxy biocatalysis was successfully driven by electrodes in the presence of BH4 and oxygen. This novel bioelectronic system showed potential for further investigation of NOS and biosensor applications. PMID:23727770

Xu, Xuan; Wollenberger, Ulla; Qian, Jing; Lettau, Katrin; Jung, Christiane; Liu, Songqin

2013-12-01

308

Electrochemical oxidation of phenol at boron-doped diamond electrode. Application to electro-organic synthesis and wastewater treatment.  

PubMed

The electrochemical behaviour of a synthetic boron-doped diamond thin film electrode (BDD) has been studied in acid media containing phenol using cyclic voltammetry and bulk electrolysis. The results have shown that in the potential region of water stability direct electron transfers can occur on BDD surface resulting in electrode fouling due to the formation of a polymeric film on its surface. During electrolysis in the potential region of oxygen evolution, complex oxidation reactions can take place due to electrogenerated hydroxyl radicals. Electrode fouling is inhibited under these conditions. Depending on the experimental conditions, the electrogenerated hydroxyl radicals can lead to the combustion of phenol or to the selective oxidation of phenol to benzoquinone. The experimental results have also been compared to a theoretical model that permits the prediction of the evolution with time of phenol concentration, during its combustion, or during its selective oxidation to benzoquinone. PMID:12489265

Panizza, Marco; Michaud, Pierre-Alain; Iniesta, Jesus; Comninellis, Christos; Cerisola, Giacomo

2002-10-01

309

Degradation of 1-hydroxy-2,4-dinitrobenzene from aqueous solutions by electrochemical oxidation: role of anodic material.  

PubMed

Electrochemical oxidation (ECOx) of 1-hydroxy-2,4-dinitrobenzene (or 2,4-dinitrophenol: 2,4-DNP) in aqueous solutions by electrolysis under galvanostatic control was studied at Pb/PbO2, Ti/SnO2, Ti/IrxRuySnO2 and Si/BDD anodes as a function of current density applied. Oxidative degradation of 2,4-DNP has clearly shown that electrode material and the current density applied were important parameters to optimize the oxidation process. It was observed that 2,4-DNP was oxidized at few substrates to CO2 with different results, obtaining good removal efficiencies at Pb/PbO2, Ti/SnO2 and Si/BDD anodes. Trends in degradation way depend on the production of hydroxyl radicals (OH) on these anodic materials, as confirmed in this study. Furthermore, HPLC results suggested that two kinds of intermediates were generated, polyhydroxylated intermediates and carboxylic acids. The formation of these polyhydroxylated intermediates seems to be associated with the denitration step and substitution by OH radicals on aromatic rings, this being the first proposed step in the reaction mechanism. These compounds were successively oxidized, followed by the opening of aromatic rings and the formation of a series of carboxylic acids which were at the end oxidized into CO2 and H2O. On the basis of these information, a reaction scheme was proposed for each type of anode used for 2,4-D oxidation. PMID:24462986

Quiroz, Marco A; Sánchez-Salas, José L; Reyna, Silvia; Bandala, Erick R; Peralta-Hernández, Juan M; Martínez-Huitle, Carlos A

2014-03-15

310

UTILITY OF MECHANISTIC MODELS FOR DIRECTING ADVANCED SEPARATIONS RESEARCH & DEVELOPMENT ACTIVITIES: Electrochemically Modulated Separation Example  

SciTech Connect

The objective for this work was to demonstrate the utility of mechanistic computer models designed to simulate actinide behavior for use in efficiently and effectively directing advanced laboratory R&D activities associated with developing advanced separations methods.

Schwantes, Jon M.

2009-06-01

311

Allylic ionic liquid electrolyte-assisted electrochemical surface passivation of LiCoO2 for advanced, safe lithium-ion batteries.  

PubMed

Room-temperature ionic liquid (RTIL) electrolytes have attracted much attention for use in advanced, safe lithium-ion batteries (LIB) owing to their nonvolatility, high conductivity, and great thermal stability. However, LIBs containing RTIL-electrolytes exhibit poor cyclability because electrochemical side reactions cause problematic surface failures of the cathode. Here, we demonstrate that a thin, homogeneous surface film, which is electrochemically generated on LiCoO2 from an RTIL-electrolyte containing an unsaturated substituent on the cation (1-allyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, AMPip-TFSI), can avert undesired side reactions. The derived surface film comprised of a high amount of organic species from the RTIL cations homogenously covered LiCoO2 with a <25 nm layer and helped suppress unfavorable thermal reactions as well as electrochemical side reactions. The superior performance of the cell containing the AMPip-TFSI electrolyte was further elucidated by surface, electrochemical, and thermal analyses. PMID:25168309

Mun, Junyoung; Yim, Taeeun; Park, Jang Hoon; Ryu, Ji Heon; Lee, Sang Young; Kim, Young Gyu; Oh, Seung M

2014-01-01

312

Characterization of native and anodic oxide films formed on commercial pure titanium using electrochemical properties and morphology techniques  

NASA Astrophysics Data System (ADS)

Potentiostatically anodized oxide films on the surface of commercial pure titanium (cp-Ti) formed in sulfuric (0.5 M H 2SO 4) and in phosphoric (1.4 M H 3PO 4) acid solutions under variables anodizing voltages were investigated and compared with the native oxide film. Potentiodynamic polarization and electrochemical impedance spectroscopy, EIS, were used to predicate the different in corrosion behavior of the oxide film samples. Scanning electron microscope, SEM, and electron diffraction X-ray analysis, EDX, were used to investigate the difference in the morphology between different types of oxide films. The electrochemical characteristics were examined in phosphate saline buffer solution, PSB (pH 7.4) at 25 °C. Results have been shown that the nature of the native oxide film is thin and amorphous, while the process of anodization of Ti in both acid solutions plays an important role in changing the properties of passive oxide films. Significant increase in the corrosion resistance of the anodized surface film was recorded after 3 h of electrode immersion in PSB. On the other side, the coverage ( ?) of film formed on cp-Ti was differed by changing the anodized acid solution. Impedance results showed that both the native film and anodized film formed on cp-Ti consist of two layers. The resistance of the anodized film has reached to the highest value by anodization of cp-Ti in H 3PO 4 and the inner layer in the anodized film formed in both acid solutions is also porous.

Fadl-allah, Sahar A.; Mohsen, Q.

2010-08-01

313

Preparation of an electrochemically-formed spinel lithium manganese oxide and its charge-discharge behaviors  

NASA Astrophysics Data System (ADS)

Manganese hydroxides were prepared by a cathodic electrochemical precipitation from a manganese nitrate solution. The grass blade-like precipitate, which is ascribed to manganese hydroxide was 20-80 ?m long and 1-5 ?m wide and was spread out on a Pt substrate after the electrochemical precipitation. When the electrochemically precipitated manganese hydroxides were kept in an alkali metal hydroxide aqueous solution, such as NaOH, KOH and LiOH, the respective alkali metal ion was incorporated into the precipitate. Fiber-like nano-structured spinel-LiMn 2O 4 crystals 200 nm in diameter were obtained on a substrate by the calcination of the Li incorporated precipitate at 750 °C without any additives. The electrochemically-formed spinel-LiMn 2O 4 showed well-shaped CVs, even in higher scan rates. These behaviors are ascribed to the crystal size and shape of the processed spinel-LiMn 2O 4.

Katakura, Katsumi; Nishimura, Shin-ichi; Ogumi, Zempachi

314

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

NASA Astrophysics Data System (ADS)

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 ?-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 k?/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.

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

2013-12-01

315

Zeolite A functionalized with copper nanoparticles and graphene oxide for simultaneous electrochemical determination of dopamine and ascorbic acid.  

PubMed

A novel Cu-zeolite A/graphene modified glassy carbon electrode for the simultaneous electrochemical determination of dopamine (DA) and ascorbic acid (AA) has been described. The Cu-zeolite A/graphene composites were prepared using Cu(2+) functionalized zeolite A and graphene oxide as the precursor, and subsequently reduced by chemical agents. The composites were characterized by X-ray diffraction, Fourier transform infrared spectra and scanning electron microscopy. Based on the Cu-zeolite A/graphene-modified electrode, the potential difference between the oxidation peaks of DA and AA was over 200mV, which was adequate for the simultaneous electrochemical determination of DA and AA. Also the proposed Cu-zeolite/graphene-modified electrode showed higher electrocatalytic performance than zeolite/graphene electrode or graphene-modified electrode. The electrocatalytic oxidation currents of DA and AA were linearly related to the corresponding concentration in the range of 1.0×10(-7)-1.9×10(-5)M for DA and 2.0×10(-5)-2.0×10(-4)M for AA. Detection limits (S/N=3) were estimated to be 4.1×10(-8)M for DA and 1.1×10(-5)M for AA, respectively. PMID:22819046

He, Ping; Wang, Wei; Du, Licheng; Dong, Faqin; Deng, Yuequan; Zhang, Tinghong

2012-08-20

316

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

317

Oxidative Stress in Aging: Advances in Proteomic Approaches  

PubMed Central

Aging is a gradual, complex process in which cells, tissues, organs, and the whole organism itself deteriorate in a progressive and irreversible manner that, in the majority of cases, implies pathological conditions that affect the individual's Quality of Life (QOL). Although extensive research efforts in recent years have been made, the anticipation of aging and prophylactic or treatment strategies continue to experience major limitations. In this review, the focus is essentially on the compilation of the advances generated by cellular expression profile analysis through proteomics studies (two-dimensional [2D] electrophoresis and mass spectrometry [MS]), which are currently used as an integral approach to study the aging process. Additionally, the relevance of the oxidative stress factors is discussed. Emphasis is placed on postmitotic tissues, such as neuronal, muscular, and red blood cells, which appear to be those most frequently studied with respect to aging. Additionally, models for the study of aging are discussed in a number of organisms, such as Caenorhabditis elegans, senescence-accelerated probe-8 mice (SAMP8), naked mole-rat (Heterocephalus glaber), and the beagle canine. Proteomic studies in specific tissues and organisms have revealed the extensive involvement of reactive oxygen species (ROS) and oxidative stress in aging. PMID:24688629

Ortuño-Sahagún, Daniel; Pallàs, Mercè; Rojas-Mayorquín, Argelia E.

2014-01-01

318

The electrochemical oxidation of homocysteine at boron-doped diamond electrodes with application to HPLC amperometric detection.  

PubMed

The electrochemical oxidation of homocysteine was studied at as-deposited and anodized (oxidized) boron-doped diamond (BDD) thin film electrodes with cyclic voltammetry, flow injection analysis and high-pressure liquid chromatography with amperometric detection. At anodized boron-doped diamond electrodes, highly reproducible, well-defined cyclic voltammograms for homocysteine oxidation were obtained in acidic media, while as-deposited diamond did not provide a detectable signal. In alkaline media, however, the oxidation response was obtained both at as-deposited and anodized diamond electrodes. The potential sweep rate dependence of homocysteine oxidation (peak currents for 1 mM homocysteine linearly proportional to v(1/2), within the range of 0.01 to 0.3 V s(-1)) indicates that the oxidation involves a diffusing species, with negligible adsorption on the BDD surface at this concentration. In the flow system, BDD exhibited a highly reproducible amperometric response, with a peak variation less than 2%. An extremely low detection limit (1 nM) was obtained at 1.6 V vs. Ag/AgCl. In addition, the determination of homocysteine in a standard mixture with aminothiols and disulfide compounds by means of isocratic reverse-phase HPLC with amperometric detection at diamond electrodes has been investigated. The results showed excellent separation, with a detection limit of 1 pmol and a linear range of three orders of magnitude. PMID:12375837

Chailapakul, O; Siangproh, W; Sarada, B V; Terashima, C; Rao, Tata N; Tryk, D A; Fujishima, A

2002-09-01

319

Electrochemical modification of the passive oxide layer on a Ti film observed by in situ neutron reflectometry  

SciTech Connect

Anodization and the effect of subsequently applying cathodic potential to a thin-film Ti electrode in an aqueous NaCl solution have been studied with in situ neutron reflectometry. This new technique provides further insight into the processes underlying anodic oxide formation and hydrogen absorption under cathodic polarization. The results (Pilling-Bedworth ratio, anodization ratio, the onset of fluctuations in electrode current under cathodic potential, etc.) are generally in agreement with the literature, but this new technique provides further insight into the electrochemical processes. The anodized oxide is observed to be not porous, and has the density of the rutile structure for its entire thickness. However, it comprises two distinct regions: an inner region similar in thickness and composition to the original air-grown oxide, and an outer region containing a significant amount of hydrogen. The similarity of the inner region to the original oxide suggests that the underlying oxide growth mechanism for Ti is the point-defect model. Under applied cathodic potentials the overall oxide thickness remains constant, but the inner region is gradually converted to a material similar in hydrogen content to the outer region. The onset of massive hydrogen penetration seems to occur when the conversion is complete, or when the inner region has been reduced to only a few atomic layers.

Tun, Z. [National Research Council, Chalk River, Ontario (Canada). Chalk River Labs.] [National Research Council, Chalk River, Ontario (Canada). Chalk River Labs.; Noeel, J.J.; Shoesmith, D.W. [Atomic Energy of Canada Limited, Pinawa, Manitoba (Canada). Whiteshell Labs.] [Atomic Energy of Canada Limited, Pinawa, Manitoba (Canada). Whiteshell Labs.

1999-03-01

320

Graphene-Based Hybrids with Manganese Oxide Polymorphs as Tailored Interfaces for Electrochemical Energy Storage: Synthesis, Processing, and Properties  

NASA Astrophysics Data System (ADS)

Technological progress is determined to a greater extent by developments of novel materials or new combinations of known materials with different dimensionality and diverse functionality. In this work, we report on the synthesis and characterization of graphene-based hybrid nanomaterials coupled with transition-metal oxide polymorphs (nano/micro-manganese oxides, i.e., ?-MnO2 [Mn(IV)] and Mn3O4 [Mn(II, III)]). This lays the groundwork for high-performance electrochemical electrodes for alternative energy devices owing to their higher specific capacitance, wide operational potential window and stability through charge-discharge cycling, environmentally benignity, cost-effectiveness, easy processing, and reproducibility on a larger scale. To accomplish this, we strategically designed these hybrids by direct anchoring or physical adsorption of ?-MnO2 and Mn3O4 on variants of graphene, namely graphene oxide and its reduced form, via mixing dispersions of the constituents under mild ultrasonication and drop-casting, resulting in four different combinations. This facile approach affords strong chemical/physical attachment and is expected to result in coupling between the pseudocapacitive transition-metal oxides and supercapacitive nanocarbons showing enhanced activity/reactivity and reasonable areal density of tailored interfaces. We used a range of complementary analytical characterization tools to determine the structure and physical properties, such as scanning electron microscopy combined with energy-dispersive x-ray spectroscopy, atomic force microscopy, x-ray diffraction, resonance Raman spectroscopy combined with elemental Raman mapping, and transmission electron microscopy in conjunction with selected-area electron diffraction. All of these techniques reveal surface morphology, local (lattice dynamical) and average structure, and local charge transfer due to the physically (or chemically) adsorbed manganese oxide of synthesized hybrids that helps to establish microscopic structure-property-function correlations highlighting the surface structure and interfaces to further investigate their electrochemical supercapacitor properties.

Gupta, S.; van Meveren, M. M.; Jasinski, J.

2015-01-01

321

The electrochemical oxide growth behaviour on titanium in acid and alkaline electrolytes  

Microsoft Academic Search

Titanium implants have a thin oxide surface layer. The properties of this oxide layer may explain the good biocompatibility of titanium implants. Anodic oxidation results in a thickening of the oxide film, with possible improved biocompatability of anodized implants. The aim of the present study was twofold: (1) firstly, to characterize the growth behaviour of galvanostatically prepared anodic oxide films

Young-Taeg Sul; Carina B Johansson; Yongsoo Jeong; Tomas Albrektsson

2001-01-01

322

Electrochemical deposition of nanostructured manganese oxide on hierarchically porous graphene-carbon nanotube structure for ultrahigh-performance electrochemical capacitors  

NASA Astrophysics Data System (ADS)

A 3D graphene sheet-carbon nanotube (GS-CNT) structure with a good wetting property, high porosity, and large surface area is homogeneously deposited with active amorphous manganese oxide (a-MnOx) by potentiodynamic deposition. The flowery a-MnOx nanostructure with ultra-slender petals (ca. 5-8 nm) on the framework of hierarchically porous GS-CNT matrix not only enables nearly full utilization of a-MnOx but also retains sufficient conductivity and porosity for the high-rate charge-discharge application. The use of a-MnOx on the 3D GS-CNT material produces a specific capacitance of MnOx of 1200 F g-1 which is much-higher than that of a pure a-MnOx electrode (CS,Mn = 233 F g-1). The specific energy and specific power of a-MnOx/GS-CNT are respectively as high as 46.2 Wh kg-1 and 33.2 kW kg-1, revealing that our work conceptually provides a way to produce porous structures composed of graphene, carbon nanotubes, and various electroactive materials for high-performance energy storage devices.

Li, Shin-Ming; Wang, Yu-Sheng; Yang, Shin-Yi; Liu, Chia-Hong; Chang, Kuo-Hsin; Tien, Hsi-Wen; Wen, Niann-Tsyr; Ma, Chen-Chi M.; Hu, Chi-Chang

2013-03-01

323

Electrochemical preparation of N-doped cobalt oxide nanoparticles with high electrocatalytic activity for the oxygen-reduction reaction.  

PubMed

Nitrogen-doped CoO (N-CoO) nanoparticles with high electrocatalytic activity for the oxygen-reduction reaction (ORR) were fabricated by electrochemical reduction of CoCl2 in acetonitrile solution at cathodic potentials. The initially generated, highly reactive nitrogen-doped Co nanoparticles were readily oxidized to N-CoO nanoparticles in air. In contrast to their N-free counterparts (CoO or Co3 O4 ), N-CoO nanoparticles with a N content of about 4.6?% exhibit remarkable ORR electrocatalytic activity, stability, and immunity to methanol crossover in an alkaline medium. The Co?Nx active sites in the CoO nanoparticles are held responsible for the high ORR activity. This work opens a new path for the preparation of nitrogen-doped transition metal oxide nanomaterials, which are promising electrocatalysts for fuel cells. PMID:24616113

Yu, Hongtao; Li, Yunchao; Li, Xiaohong; Fan, Louzhen; Yang, Shihe

2014-03-17

324

Solid polymer electrolytes based on cross-linked polysiloxane- g-oligo(ethylene oxide): ionic conductivity and electrochemical properties  

NASA Astrophysics Data System (ADS)

Poly(siloxanes- g-oligo(ethylene oxide)) with acrylate groups at the terminal position were prepared and examined for the solid polymer electrolyte (SPE) by curing them. Poly(ethylene glycol) dimethyl ether (PEGDME) was added as a plasticizer. Conductivity of the resulting polymer electrolytes was greatly enhanced with increasing amounts of low molecular weight PEGDME. Maximum conductivity was found to be 8×10 -4 S/cm at 30 °C with an [EO]/[Li] ratio of about 8. These electrolytes showed oxidation stability up to 4.95 V against the lithium reference electrode. Reversible electrochemical plating/stripping of lithium was observed on the nickel electrode. The plating/stripping efficiency of lithium on nickel was measured to be about 53%.

Kang, Yongku; Lee, Wonsil; Hack Suh, Dong; Lee, Changjin

325

Electrochemical methane sensor  

DOEpatents

A method and instrument including an electrochemical cell for the detection and measurement of methane in a gas by the oxidation of methane electrochemically at a working electrode in a nonaqueous electrolyte at a voltage about 1.4 volts vs R.H.E. (the reversible hydrogen electrode potential in the same electrolyte), and the measurement of the electrical signal resulting from the electrochemical oxidation.

Zaromb, S.; Otagawa, T.; Stetter, J.R.

1984-08-27

326

Cross-link dimer formation of the acetaldehyde-derived cyclic 1,N(2)-Propano-2'-deoxyguanosine adduct using electrochemical oxidation.  

PubMed

The electrochemically oxidative lesion of the acetaldehyde-derived cyclic propano adduct 2 of 2'-deoxyguanosine 1 was identified as the cross-linked dimer 4 of adduct 2. Cross-link formation is explained by the nucleophilic preference of the exocyclic amino group in 2 to the carbocation 3 electrogenerated by 1-proton and 2-electron transfers. Dimer formation was also detected in duplex DNA during exposure to acetaldehyde followed by electrochemical oxidation. The dimer has been deduced to be an intrastrand cross-link generated specifically in the G-G sequence in duplex DNA, which is expected to contribute to acetaldehyde-mediated genotoxicity. PMID:19952460

Murakami, Hiroya; Esaka, Yukihiro; Uno, Bunji

2009-12-01

327

Simultaneous reduction of nitrate and oxidation of by-products using electrochemical method  

Microsoft Academic Search

Electrochemical denitrification was studied with an objective to enhance the selectivity of nitrate to nitrogen gas and to remove the by-products in an undivided electrochemical cell, in which Cu–Zn cathode and Ti\\/IrO2–Pt anode were assembled. In the presence of 0.50g\\/L NaCl as supporting electrolyte, the NO3?–N decreased from 100.0 to 9.7mg\\/L after 300min electrolysis; no ammonia and nitrite were detected

Miao Li; Chuanping Feng; Zhenya Zhang; Xiaohui Lei; Rongzhi Chen; Yinan Yang; Norio Sugiura

2009-01-01

328

Structural and electrochemical characterization of two proton conducting oxide thin films for a microfabricated solid oxide fuel cell  

E-print Network

The use of proton conducting oxide materials as an electrolyte offers the potential to reduce the operating temperature of a solid oxide fuel cell (SOFC), leading to improved thermal management and material compatibility. ...

Capozzoli, Peter M

2006-01-01

329

Effects of Tungsten Oxide Addition on the Electrochemical Performance of Nanoscale Tantalum Oxide-Based Electrocatalysts for Proton Exchange Membrane PEM Fuel Cells  

SciTech Connect

In the present study, the properties of a series of non-platinum based nanoscale tantalum oxide/tungsten oxide-carbon composite catalysts was investigated for potential use in catalyzing the oxygen reduction reaction (ORR) on the cathode side of a PEM fuel cell membrane electrode assembly. Electrochemical performance was measured using a half-cell test set up with a rotating disc electrode and compared with a commercial platinum-on-carbon (Pt/C) catalyst. Overall, all of the oxide-based composite catalysts exhibit high ORR on-set potentials, comparable to that of the baseline Pt/C catalyst. The addition of tungsten oxide as a dopant to tantalum oxide greatly improved mass specific current density. Maximum performance was achieved with a catalyst containing 32 mol% of tungsten oxide, which exhibited a mass specific current density ~8% that of the Pt/C catalyst at 0.6 V vs. the normal hydrogen electrode (NHE) and ~35% that of the Pt/C catalyst at 0.2 V vs. NHE. Results from X-ray photoelectron spectroscopy analysis indicated that the tungsten cations in the composite catalysts exist in the +6 oxidation state, while the tantalum displays an average valence of +5, suggesting that the addition of tungsten likely creates an oxygen excess in the tantalum oxide structure that influences its oxygen absorption kinetics. When the 32mol% tungsten doped catalyst loading on the working electrode was increased to five times that of the original loading (which was equivalent to that of the baseline Pt/C catalyst), the area specific current density improved four fold, achieving an area specific current density ~35% that of the Pt/C catalyst at 0.6 V vs. NHE.

Oh, Tak Keun; Kim, Jin Yong; Shin, Yongsoon; Engelhard, Mark H.; Weil, K. Scott

2011-08-01

330

Electrospun porous NiCo2O4 nanotubes as advanced electrodes for electrochemical capacitors.  

PubMed

Novel, porous NiCo2O4 nanotubes (NCO-NTs) are prepared by a single-spinneret electrospinning technique followed by calcination in air. The obtained NCO-NTs display a one-dimensional architecture with a porous structure and hollow interiors. The effect of precursor concentration on the morphologies of the products is investigated. Due to their unique structure, the prepared NCO-NT electrode exhibits a high specific capacitance (1647?F?g(-1) at 1?A?g(-1)), excellent rate capability (77.3?% capacity retention at 25?A?g(-1)), and outstanding cycling stability (6.4?% loss after 3000 cycles), which indicates it has great potential for high-performance electrochemical capacitors. The desirable enhanced capacitive performance of NCO-NTs can be attributed to the relatively large specific surface area of these porous and hollow one-dimensional nanostructures. PMID:23494864

Li, Linlin; Peng, Shengjie; Cheah, Yanling; Teh, Peifen; Wang, Jin; Wee, Grace; Ko, Yahwen; Wong, Chuiling; Srinivasan, Madhavi

2013-05-01

331

CEC mechanism in electrochemical oxidation of nitrocatechol–boric acid complexes  

Microsoft Academic Search

The electrochemical behavior of nitrocatechols–boric acid complexes in aqueous solution has been studied using cyclic voltammetry. The results indicate that nitrocatechol–boric acid complex derivatives are involved in the CEC mechanism. In this work, the impact of empirical parameters on the shape of the voltammograms is examined based on a CEC mechanism. In addition, homogeneous rate constants of both the preceding

Mohammad Rafiee; Davood Nematollahi; Hamid Salehzadeh

2011-01-01

332

Amperometric detection and electrochemical oxidation of aliphatic amines and ammonia on silver-lead oxide thin-film electrodes  

SciTech Connect

This thesis comprises three parts: Electrocatalysis of anodic oxygen-transfer reactions: aliphatic amines at mixed Ag-Pb oxide thin-film electrodes; oxidation of ammonia at anodized Ag-Pb eutectic alloy electrodes; and temperature effects on oxidation of ethylamine, alanine, and aquated ammonia.

Ge, Jisheng

1996-01-08

333

Industrial wastewater treatment by an advanced oxidation process.  

PubMed

The overall objective of this study was to evaluate an advanced oxidation process (AOP) used to treat oil and grease (O&G), total petroleum hydrocarbons (TPH), and chemical oxygen demand (COD) of industrial wastewaters generated during barge cleaning operations. This wastewater generally contains appreciable concentrations of O&G, TPH, COD, biochemical oxygen demand (BOD) and benzene, toluene, ethylbenzene and xylene (BTEX) compounds. A bench scale AOP test unit was designed and built for the treatment of the barge cleaning industrial wastewater. The AOP test unit was a 0.33 gpm mobile, modular unit consisting of two contact chambers, two counter current columns and two catalytic chambers. Six experiments were performed using the AOP unit to determine its effectiveness on the reduction of O&G, TPH, and COD. The wastewater was delivered to the AOP from a storage tank. The unit was run for a total of 120 minutes at various gas delivery rates of ozone for each treatment run. Influent and effluent samples were collected at 30 minutes intervals and analyzed for O&G, TPH, and COD. Significant reductions in O&G and TPH concentrations were observed. Oxygen alone indicated a 50% removal efficiency for O&G and TPH. The ozone treatment efficiency was 86% for O&G and TPH at a dosage rate of 12 SCFH and 82% for a dosage rate of 6 SCFH. PMID:11360442

Gunukula, R V; Tittlebaum, M E

2001-01-01

334

Separators for electrochemical cells  

SciTech Connect

Provided are separators for use in an electrochemical cell comprising (a) an inorganic oxide and (b) an organic polymer, wherein the inorganic oxide comprises organic substituents. Preferably, the inorganic oxide comprises an hydrated aluminum oxide of the formula Al.sub.2O.sub.3.xH.sub.2O, wherein x is less than 1.0, and wherein the hydrated aluminum oxide comprises organic substituents, preferably comprising a reaction product of a multifunctional monomer and/or organic carbonate with an aluminum oxide, such as pseudo-boehmite and an aluminum oxide. Also provided are electrochemical cells comprising such separators.

Carlson, Steven Allen; Anakor, Ifenna Kingsley

2014-11-11

335

Electrochemical synthesis based on the oxidation of 1-(4-(4-hydroxyphenyl)piperazin-1-yl)ethanone in the presence of nucleophiles.  

PubMed

Electrochemical syntheses of new arylthiobenzazoles were carried out by electrochemical oxidation of 1-(4-(4-hydroxyphenyl)piperazin-1-yl)ethanone in the presence of 2-mercaptobenzothiazole and 2-mercaptobenzoxazole. Our voltammetric data indicate that electrochemically generated p-quinone imine participates in a Michael addition reaction with 2-SH-benzazoles leading to the disubstituted 1-(4-(4-hydroxyphenyl)piperazin-1-yl)ethanone. Also, a plausible mechanism for the oxidation of 1-(4-(3,5-bis(benzo[d]thiazol-2-ylthio)-4-hydroxyphenyl) in the presence of p-toluenesulfinic acid is presented. 1-(4-(3,5-Bis(benzo[d]thiazol-2-ylthio)-4-hydroxyphenyl) was converted into 2-(benzo[d]thiazol-2-ylthio)-6-tosylcyclohexa-2,5-diene-1,4-dione through a Michael-type addition of p-toluenesulfinic acid to anodically generated p-quinone imine, replacing 2-mercaptobenzothiazole and followed by hydrolysis. PMID:23198901

Amani, Amene; Nematollahi, Davood

2012-12-21

336

Synthesis, characterization, and electrochemical properties of ordered mesoporous carbons containing nickel oxide nanoparticles using sucrose and nickel acetate in a silica template  

SciTech Connect

New ordered mesoporous carbons containing nickel oxide nanoparticles have been successfully synthesized by carbonization of sucrose in the presence of nickel acetate inside SBA-15 mesoporous silica template. The obtained samples were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, and transmission electron microscopy (TEM). The NiO nanoparticles were embedded inside the mesoporous carbon framework due to the simultaneous pyrolysis of nickel acetate during carbonization. The electrochemical testing of the as-made nanocomposites showed a large specific capacitance of 230 F g{sup -1} using 2 M KOH as the electrolyte at room temperature. This is attributed to the nanometer-sized NiO formed inside mesoporous carbons and the high surface area of the mesopores in which the NiO nanoparticles are formed. Furthermore, the synthetic process is proposed as a simple and general method for the preparation of new functionalized mesoporous carbon materials, for various applications in catalysis, sensor or advanced electrode material. - Graphical abstract: Schematic drawings of synthesis routes for the NiOCMK materials.

Cao Yulin [Nanomaterials Research Institute, College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Cao Jieming [Nanomaterials Research Institute, College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)], E-mail: jmcao@nuaa.edu.cn; Zheng Mingbo [Nanomaterials Research Institute, College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Liu Jinsong [Nanomaterials Research Institute, College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Ji Guangbin [Nanomaterials Research Institute, College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

2007-02-15

337

Au(III)-assisted core-shell iron oxide@poly(o-phenylenediamine) nanostructures for ultrasensitive electrochemical aptasensors based on DNase I-catalyzed target recycling.  

PubMed

A redox-active Au(III)-assisted core-shell iron oxide@poly(o-phenylenediamine) nanostructure was designed as a sensing platform for ultrasensitive electrochemical detection of small molecules (ATP, used as a model here) by coupling with DNase I-catalyzed target recycling. PMID:22286177

Liu, Bingqian; Cui, Yuling; Tang, Dianping; Yang, Huanghao; Chen, Guonan

2012-03-01

338

Corrosion electrochemical behavior of epoxy anticorrosive paints based on zinc molybdenum phosphate and zinc oxide  

Microsoft Academic Search

Electrochemical impedance spectroscopy (EIS) was applied as a principal tool to describe the efficiency of anticorrosive epoxy paints (primers) based on zinc molybdenum phosphate (ZMP) pigment. Steel-coated samples were exposed to a 0.5M NaCl solution. During the study the corrosion potential (Eoc) and Rp values also were monitored every 24h. It is discussed the incorporation of micronized ZnO (1?m) pigment

L. Veleva; J. Chin; B. del Amo

1999-01-01

339

Electrochemical properties of iron oxides/carbon nanotubes as anode material for lithium ion batteries  

NASA Astrophysics Data System (ADS)

A composited anode material with combined Fe3O4/FeO nanotube and carbon shell is synthesized by a facile hydrothermal method with subsequent CVD heat treatment. The as-prepared Fe3O4/FeO/C composite shows excellent cycle stability and rate capability as lithium ion battery anode. We study the effect of FeO on the electrochemical performances of the Fe3O4/FeO/C electrode. A capacity climbing phenomenon can be observed for the Fe3O4/FeO/C electrodes, which tends to be more evident with increasing FeO content. The 'extra capacity' is correlated with the reversible formation of polymeric gel-like film on the particle surface of active materials, which is electrochemical active towards Li ions. The FeO component presents a certain extent of catalytic role in assisting the formation of the gel-like film. Transmission electron microscope (TEM) and electrochemical impedance spectroscopy (EIS) analytical technique are combined to further confirm the reversible growth of the SEI gel-like film. High temperature promotes the formation of gel-like film, while the resistance from the film decreases remarkably with temperature due to the enhanced lithium ion conductivity. The film contributes little to the whole EIS resistance of Fe3O4/FeO nanotube/carbon electrode. Tentative explanations based on the current experiments and existing literature are made to explain such unusual finding.

Zeng, Zhipeng; Zhao, Hailei; Lv, Pengpeng; Zhang, Zijia; Wang, Jie; Xia, Qing

2015-01-01

340

Enhanced Yields of Iron-Oxidizing Bacteria by In Situ Electrochemical Reduction of Soluble Iron in the Growth Medium  

PubMed Central

An electrochemical apparatus for culturing chemolithotrophic bacteria that respire aerobically on ferrous ions is described. Enhanced yields of the bacteria were achieved by the in situ electrochemical reduction of soluble iron in the growth medium. When subjected to a direct current of 30 A for 60 days, a 45-liter culture of Thiobacillus ferrooxidans grew from 6 × 107 to 9.5 × 109 cells per ml. Growth of the bacterium within the electrolytic bioreactor was linear with time. A final cell density corresponding to 4.7 g of wet cell paste per liter was achieved, and a total of 320 g of wet cell paste was harvested from one culture. The apparatus was designed to deliver protons concomitantly with electrons; therefore, the pH of the culture remained stable at 1.6 ± 0.1 for the duration of growth. This laboratory-scale apparatus may be readily adapted to pilot or production scale. It is thus anticipated that abundant numbers of iron-oxidizing bacteria may be obtained for both fundamental and applied studies. PMID:16349344

Blake, Robert C.; Howard, Gary T.; McGinness, Stephen

1994-01-01

341

Facial-shape controlled precursors for lithium cobalt oxides and the electrochemical performances in lithium ion battery  

NASA Astrophysics Data System (ADS)

Two types of lithium cobalt oxides (LiCoO2) as cathode materials for lithium ion batteries are synthesized from two cobalt sources of different facial-shapes (octahedral and truncated-octahedral Co3O4) and Li2CO3 using solid state synthesis. From X-ray diffraction and scanning electron microscopy measurements, the reaction mechanism of the formation of LiCoO2 is investigated. It is revealed that LiCoO2 from octahedral Co3O4 with only {111} surfaces grows in one direction whereas the crystal orientation of LiCoO2 from truncated-octahedral Co3O4 with {111} and {100} surfaces is not unique and the spinel intermediates of LixCo2O4 are formed during synthesis. They show largely unequal rate and cycling performances for lithium ion battery, even though their outer appearances are nearly identical. Almost single-crystalline LiCoO2 from octahedral precursors shows much better electrochemical performances than LiCoO2 from truncated-octahedral precursors as a lithium ion battery cathode. By studying crystal orientation, it is shown that the poor electrochemical performances of LiCoO2 from truncated-octahedral Co3O4 are originated by crystal-mismatch between crystallites.

Shim, Jae-Hyun; Cho, Sang-Woo; Missiul, Aleksandr; Jung, Hyun-Ok; Lee, Sanghun

2015-01-01

342

Evaluation of the efficiency of monopolar and bipolar BDD electrodes for electrochemical oxidation of anthraquinone textile synthetic effluent for reuse.  

PubMed

The efficiency of the electrochemical degradation of synthetic wastewater containing an anthraquinone dye has been comparatively studied in two electrolytic cells with a synthetic boron-doped diamond (Si/BDD) as an anode. The first is an individual cell (Cell 1) with monopolar electrode BDD and the second (Cell 2) has two bipolar electrodes BDD self-polarized. The bulk electrolysis was performed at the same initial operating conditions in order to quantify the influence of the initial pH and current density on dye discoloration and global mineralization removal. The current efficiency and the consumption energy were also evaluated. When the same solutions have been comparatively treated with the two cells, a quite good mineralization is found in Cell 2. This result supposed more fraction of the applied current is used for the electrocombustion reaction on Cell 2 if compared to Cell 1 and small amount rest for the side reaction of oxygen evolution. The HPLC analyses confirmed this hypothesis and showed that the concentration trend of intermediates (sulfanilic acid, phthalate acid and salicylic acid) with electrolysis time was different on two cells. Phototoxicity tests show that the electrochemical oxidation with BDD electrodes could be useful as a pretreatment technique for reducing hazardous wastewater toxicity. PMID:23916748

Abdessamad, NourElHouda; Akrout, Hanene; Hamdaoui, Ghaith; Elghniji, Kais; Ksibi, Mohamed; Bousselmi, Latifa

2013-10-01

343

X-ray spectroscopy of electrochemically deposited iridium oxide films: detection of multiple sites through structural disorder.  

PubMed

We report the results of X-ray absorption spectroscopy studies on electrochemically deposited iridium oxide films. The emphasis of the study is the correlation of X-ray derived structural data with electrochemically controlled charge state. Data were acquired for films subject to redox cycling in neutral and alkaline aqueous media. In both cases, cyclic voltammetric responses show two redox couples, coulometrically of roughly equal magnitude. Assays of the iridium population (based on the iridium L(3) absorption edge amplitude) and the charge injected (based on integration of the voltammetric response) show that overall an average of ca. one electron per iridium atom is transferred. The absorption edge shifts indicate that the formal charge on the iridium changes, on average, from ca. 3.5+ to ca. 4.5+ across the entire process. EXAFS-derived changes in mean Ir-O distance and their mean square variation have been interpreted in terms of a two-site model, in which the two types of site have distinct redox potentials. Variations of local structure and disorder with potential are discussed and a generic model for structural disorder (parameterized via Debye-Waller factor) with diagnostic capability is developed. PMID:21173969

Hillman, A Robert; Skopek, Magdalena A; Gurman, Stephen J

2011-03-28

344

Lithium intercalation in sputter deposited antimony-doped tin oxide thin films: Evidence from electrochemical and optical measurements  

NASA Astrophysics Data System (ADS)

Transparent conducting oxides are used as transparent electrical contacts in a variety of applications, including in electrochromic smart windows. In the present work, we performed a study of transparent conducting antimony-doped tin oxide (ATO) thin films by chronopotentiometry in a Li+-containing electrolyte. The open circuit potential vs. Li was used to investigate ATO band lineups, such as those of the Fermi level and the ionization potential, as well as the dependence of these lineups on the preparation conditions for ATO. Evidence was found for Li+ intercalation when a current pulse was set in a way so as to drive ions from the electrolyte into the ATO lattice. Galvanostatic intermittent titration was then applied to determine the lithium diffusion coefficient within the ATO lattice. The electrochemical density of states of the conducting oxide was studied by means of the transient voltage recorded during the chronopotentiometry experiments. These measurements were possible because, as Li+ intercalation took place, charge compensating electrons filled the lowest part of the conduction band in ATO. Furthermore, the charge insertion modified the optical properties of ATO according to the Drude model.

Montero, J.; Guillén, C.; Granqvist, C. G.; Herrero, J.; Niklasson, G. A.

2014-04-01

345

Polypyrrole–titanium(IV) doped iron(III) oxide nanocomposites: Synthesis, characterization with tunable electrical and electrochemical properties  

SciTech Connect

Highlights: ? Synthesis and characterization of polymer nanocomposite based on titanium doped iron(III) oxide. ? Electrical conductivity increased 100 times in composite with respect to polymer. ? Electrochemical capacitance of polymer composites increased with nanooxide content. ? Thermal stability of the polymer enhanced with nano oxide content. -- Abstract: Titanium(IV)-doped synthetic nanostructured iron(III) oxide (NITO) and polypyrrole (PPy) nanocomposites was fabricated by in situ polymerization using FeCl{sub 3} as initiator. The polymer nanocomposites (PNCs) and pure NITO were characterized by X-ray diffraction, Föurier transform infrared spectroscopy, scanning electron microscopy, electron dispersive X-ray spectroscopy, transmission electron microscopy, etc. Thermo gravimetric and differential thermal analyses showed the enhancement of thermal stability of PNCs than the pure polymer. Electrical conductivity of the PNCs had increased significantly from 0.793 × 10{sup ?2} S/cm to 0.450 S/cm with respect to the PPy, and that had been explained by 3-dimensional variable range hopping (VRH) conduction mechanisms. In addition, the specific capacitance of PNCs had increased from 147 F/g to 176 F/g with increasing NITO content than that of pure NITO (26 F/g), presumably due to the growing of mesoporous structure with increasing NITO content in PNCs which reduced the charge transfer resistance significantly.

Nandi, Debabrata; Ghosh, Arup Kumar; Gupta, Kaushik [Department of Chemistry and Bio-Chemistry, Presidency University (Formerly Presidency College), Kolkata 700073 (India)] [Department of Chemistry and Bio-Chemistry, Presidency University (Formerly Presidency College), Kolkata 700073 (India); De, Amitabha [Chemical Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)] [Chemical Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Sen, Pintu [Variable Energy Cyclotrone Centre, 1/AF Bidhannagar, Kolkata 700064 (India)] [Variable Energy Cyclotrone Centre, 1/AF Bidhannagar, Kolkata 700064 (India); Duttachowdhury, Ankan [Chemical Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)] [Chemical Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Ghosh, Uday Chand, E-mail: ucghosh@yahoo.co.in [Department of Chemistry and Bio-Chemistry, Presidency University (Formerly Presidency College), Kolkata 700073 (India)

2012-08-15

346

Lithium intercalation in sputter deposited antimony-doped tin oxide thin films: Evidence from electrochemical and optical measurements  

SciTech Connect

Transparent conducting oxides are used as transparent electrical contacts in a variety of applications, including in electrochromic smart windows. In the present work, we performed a study of transparent conducting antimony-doped tin oxide (ATO) thin films by chronopotentiometry in a Li{sup +}-containing electrolyte. The open circuit potential vs. Li was used to investigate ATO band lineups, such as those of the Fermi level and the ionization potential, as well as the dependence of these lineups on the preparation conditions for ATO. Evidence was found for Li{sup +} intercalation when a current pulse was set in a way so as to drive ions from the electrolyte into the ATO lattice. Galvanostatic intermittent titration was then applied to determine the lithium diffusion coefficient within the ATO lattice. The electrochemical density of states of the conducting oxide was studied by means of the transient voltage recorded during the chronopotentiometry experiments. These measurements were possible because, as Li{sup +} intercalation took place, charge compensating electrons filled the lowest part of the conduction band in ATO. Furthermore, the charge insertion modified the optical properties of ATO according to the Drude model.

Montero, J., E-mail: jose.montero@angstrom.uu.se; Granqvist, C. G.; Niklasson, G. A. [Department of Engineering Sciences, The A°ngström Laboratory, Uppsala University, P.O. Box 534, SE-751 21 Uppsala (Sweden); Guillén, C.; Herrero, J. [Department of Energy, Ciemat, Avda. Complutense 40, Ed. 42, E-28040 Madrid (Spain)

2014-04-21

347

Comparative study on electrochemical 4-chlorophenol degradation in different diaphragm systems with combined reduction and oxidation properties.  

PubMed

Two diaphragm electrolysis systems, two-electrode (anode-cathode) and three-electrode (cathode-anode-cathode), were compared for the electrochemical degradation of 4-chlorophenol. The performance of these systems was improved by feeding with hydrogen gas and then with air, in aid of the combined processes of reduction and oxidation. The 4-chlorophenol degradation, dechlorination, and total organic carbon removal were monitored to characterize the difference between the two systems. The results indicated that the three-electrode system exhibited higher degradation percentages for 4-chlorophenol compared with that of the two-electrode system. The dechlorination property of the three-electrode system was stronger than that of the two-electrode system. In addition, the total organic carbon removal percentage of the anodic compartment in the three-electrode system was higher than that of the two-electrode system. The three-electrode system showed excellent treatment properties for 4-chlorophenol. PMID:25607679

Liu, S L; Wang, H; Bian, Z Y

2015-01-01

348

Achieving direct electrochemistry of glucose oxidase by one step electrochemical reduction of graphene oxide and its use in glucose sensing.  

PubMed

In this paper, the direct electrochemistry of glucose oxidase (GOD) was accomplished at a glassy carbon electrode modified with electrochemically reduced graphene oxide/sodium dodecyl sulfate (GCE/ERGO/SDS). A pair of reversible peaks is exhibited on GCE/ERGO/SDS/GOD by cyclic voltammetry. The peak-to-peak potential separation of immobilized GOD is 28mV in 0.1M phosphate buffer solution (pH7.0) with a scan rate of 50mV/s. The average surface coverage is 2.62×10(-10)molcm(-2). The resulting biosensor exhibited a good response to glucose with linear range from 1 to 8mM (R(2)=0.9878), good reproducibility and detection limit of 40.8?M. The results from the biosensor were similar (±5%) to those obtained from the clinical analyzer. PMID:25491807

Shamsipur, Mojtaba; Amouzadeh Tabrizi, Mahmoud

2014-12-01

349

Fabrication phosphomolybdic acid-reduced graphene oxide nanocomposite by UV photo-reduction and its electrochemical properties.  

PubMed

Phosphomolybdic acid-reduced graphene oxide (PMoA-rGO) nanocomposites are fabricated by a photochemical reduction method. They are characterized by ultraviolet-visible spectra, scanning electron microscope images, Fourier transform infrared spectroscopy, Raman spectra and X-ray photoelectron spectroscopy in order to confirm that oxygen-containing functional groups on GO are replaced by PMoA and that GO is reduced to rGO in the photo-reduction process. The electrochemical properties of PMoA-rGO are investigated by cyclic voltammetry, which shows that the PMoA-rGO modified glassy carbon electrode has high electrocatalytic activity in acid solution via a fast, surface-controlled electron transfer process. The results indicate that the use of rGO not only increases the electroactive surface area, but also facilitates electron transfer due to its high electric conductivity. PMID:23474670

Chen, Jie; Liu, Suling; Feng, Wei; Zhang, Guoquan; Yang, Fenglin

2013-04-21

350

Low-cost electrochemical treatment of indium tin oxide anodes for high-efficiency organic light-emitting diodes  

SciTech Connect

We demonstrate a simple low-cost approach as an alternative to conventional O{sub 2} plasma treatment to modify the surface of indium tin oxide (ITO) anodes for use in organic light-emitting diodes. ITO is functionalized with F{sup ?} ions by electrochemical treatment in dilute hydrofluoric acid. An electrode with a work function of 5.2?eV is achieved following fluorination. Using this electrode, a maximum external quantum efficiency of 26.0% (91?cd/A, 102?lm/W) is obtained, which is 12% higher than that of a device using the O{sub 2} plasma-treated ITO. Fluorination also increases the transparency in the near-infrared region.

Hui Cheng, Chuan, E-mail: chengchuanhui@dlut.edu.cn; Shan Liang, Ze; Gang Wang, Li; Dong Gao, Guo; Zhou, Ting; Ming Bian, Ji; Min Luo, Ying [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Tong Du, Guo, E-mail: dugt@dlut.edu.cn [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China)

2014-01-27

351

Antioxidant, electrochemical, thermal, antimicrobial and alkane oxidation properties of tridentate Schiff base ligands and their metal complexes  

NASA Astrophysics Data System (ADS)

In this study, two Schiff base ligands (HL 1 and HL 2) and their Cu(II), Co(II), Ni(II), Pd(II) and Ru(III) metal complexes were synthesized and characterized by the analytical and spectroscopic methods. Alkane oxidation activities of the metal complexes were studied on cyclohexane as substrate. The ligands and their metal complexes were evaluated for their antimicrobial activity against Corynebacterium xerosis, Bacillus brevis, Bacillus megaterium, Bacillus cereus, Mycobacterium smegmatis, Staphylococcus aureus, Micrococcus luteus and Enterococcus faecalis (as Gram-positive bacteria) and Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Yersinia enterocolitica, Klebsiella fragilis, Saccharomyces cerevisiae, and Candida albicans (as Gram-negative bacteria). The antioxidant properties of the Schiff base ligands were evaluated in a series of in vitro tests: 1,1-diphenyl-2-picrylhydrazyl (DPPH rad ) free radical scavenging and reducing power activity of superoxide anion radical generated non-enzymatic systems. Electrochemical and thermal properties of the compounds were investigated.

Ceyhan, Gökhan; Çelik, Cumali; Uru?, Serhan; Demirta?, ?brahim; Elmasta?, Mahfuz; Tümer, Mehmet

2011-10-01

352

3D CFD Electrochemical and Heat Transfer Model of an Integrated-Planar Solid Oxide Electrolysis Cells  

SciTech Connect

A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in a new novel integrated planar porous-tube supported solid oxide electrolysis cell (SOEC). The model is of several integrated planar cells attached to a ceramic support tube. This design is being evaluated with modeling at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, activation over-potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean per-cell area-specific-resistance (ASR) values decrease with increasing current density. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, cathode and anode exchange current density, and contact resistance from the base case are presented. Contour plots of local electrolyte temperature, current density, and Nernst potential indicated the effects of heat transfer, reaction cooling/heating, and change in local gas composition. Results are discussed for using this design in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production, cell thermal efficiency, cell electrical efficiency, and Gibbs free energy are discussed and reported herein.

Grant Hawkes; James E. O'Brien

2008-10-01

353

Self-organized high aspect ratio porous hafnium oxide prepared by electrochemical anodization  

Microsoft Academic Search

We report on the fabrication of self-organized porous hafnium oxide layers by anodization of hafnium in H 2SO 4 electrolytes containing NaF. The results show that porous hafnium oxide layers can be formed under a range of experimental conditions. A key factor affecting the morphology and the structure of porous oxide is the anodization potential. Using optimized anodization conditions, highly

Hiroaki Tsuchiya; Patrik Schmuki

2005-01-01

354

Graphene oxide nanoribbons (GNO), reduced graphene nanoribbons (GNR), and multi-layers of oxidized graphene functionalized with ionic liquids (GO-IL) for assembly of miniaturized electrochemical devices.  

PubMed

In this critical review, new nanomaterials based on graphene (GN) are described, especially those used for the assembly of miniaturized electrochemical transducers. In particular, the physicochemical properties and mechanical features of few layers of graphene (FLGs) are described, as is their use for assembly of chemically modified sensors, biosensors, and immunosensors. The FLGs described here were functionalized by chemical treatment in solution, resulting in oxidized and/or reduced surfaces, edges, and sides. The presence of oxygenated functionality strongly affects the electrocatalysis and the electron-transfer properties of several molecular targets, not only in the solid phase (e.g. in field-effect transistors, FETs) but also in liquid matrices (chemically modified electrodes and biosensors). In addition, "green chemistry" reagents, for example ionic liquids (ILs) can be used for exfoliation and intercalation of graphene planes, to obtain stable and homogeneous nanodispersions. The assembled sensors, biosensors, and immunosensors are extremely useful for electrochemical detection of several electro-active targets of importance in food analysis, environmental monitoring, and clinical diagnosis. A detailed description of each analytical application has been given in this critical review and brief remarks on the emerging disciplines of nanomedicine and nanofoods are also discussed. PMID:23274557

Valentini, F; Carbone, M; Palleschi, G

2013-04-01

355

Supporting electrodes for solid oxide fuel cells and other electrochemical devices  

DOEpatents

An electrode supported electrolyte membrane includes an electrode layer 630 facing an electrolyte layer 620. The opposing side of the electrode layer 630 includes a backing layer 640 of a material with a thermal expansion coefficient approximately equal to the thermal expansion coefficient of the electrolyte layer 620. The backing layer 640 is in a two dimensional pattern that covers only a portion of the electrolyte layer 630. An electrochemical cell such as a SOFC is formed by providing a cathode layer 610 on an opposing side of the electrolyte layer 620.

Sprenkle, Vincent L. (Richland, WA); Canfield, Nathan L. (Kennewick, WA); Meinhardt, Kerry (Kennewick, WA); Stevenson, Jeffry W. (Richland, WA)

2008-04-01

356

Advanced Oxidation Processes for Wastewater Treatment: Formation of Hydroxyl Radical and Application  

Microsoft Academic Search

Advanced oxidation processes (AOPs), defined as those technologies that utilize the hydroxyl radical (·OH) for oxidation, have received increasing attention in the research and development of wastewater treatment technologies in the last decades. These processes have been applied successfully for the removal or degradation of toxic pollutants or used as pretreatment to convert recalcitrant pollutants into biodegradable compounds that can

JIAN LONG WANG; LE JIN XU

2012-01-01

357

Advanced oxidation processes (AOPs) for wastewater treatment: Formation of hydroxyl radical (·OH) and application  

Microsoft Academic Search

Advanced oxidation processes (AOPs), defined as those technologies that utilize the hydroxyl radical (·OH) for oxidation, have received increasing attention in the research and development of wastewater treatment technologies in the last decades. These processes have been applied successfully for the removal or degradation of toxic pollutants, or used as pretreatment to convert recalcitrant pollutants into biodegradable compounds which can

JIANLONG WANG; LEJIN XU

2011-01-01

358

Evaluation of Resin Dissolution Using an Advanced Oxidation Process - 13241  

SciTech Connect

The ion-exchange resin is widely used in nuclear reactors, in cooling water purification and removing radioactive elements. Because of the long periods of time inside the reactor system, the resin becomes radioactive. When the useful life of them is over, its re-utilization becomes inappropriate, and for this reason, the resin is considered radioactive waste. The most common method of treatment is the immobilization of spent ion exchange resin in cement in order to form a solid monolithic matrix, which reduces the radionuclides release into the environment. However, the characteristic of contraction and expansion of the resin limits its incorporation in 10%, resulting in high cost in its direct immobilization. Therefore, it is recommended the utilization of a pre-treatment, capable of reducing the volume and degrading the resin, which would increase the load capacity in the immobilization. This work aims to develop a method of degradation of ion spent resins from the nuclear research reactor of Nuclear and Energy Research Institute (IPEN/CNEN-SP), Brazil, using the Advanced Oxidative Process (AOP) with Fenton's reagent (hydrogen peroxide and ferrous sulphate as catalyst). The resin evaluated was a mixture of cationic (IR 120P) and anionic (IRA 410) resins. The reactions were conducted by varying the concentration of the catalyst (25, 50, 100 e 150 mM) and the volume of the hydrogen peroxide, at three different temperatures, 50, 60 and 70 deg. C. The time of reaction was three hours. Total organic carbon content was determined periodically in order to evaluate the degradation as a function of time. The concentration of 50 mM of catalyst was the most effective in degrading approximately 99%, using up to 330 mL of hydrogen peroxide. The most effective temperature was about 60 deg. C, because of the decomposition of hydrogen peroxide in higher temperatures. TOC content was influenced by the concentration of the catalyst, interfering in the beginning of the degradation process. It was possible to correlate it with the final amount of non-degraded resins. These results show that these conditions were favorable to destroy the resins, indicating to be the AOP an effective technique to reduce the volume of the waste. (authors)

Goulart de Araujo, Leandro; Vicente de Padua Ferreira, Rafael; Takehiro Marumo, Julio [Nuclear and Energy Research Institute, Av. Lineu Prestes, 2242., Sao Paulo, SP. (Brazil)] [Nuclear and Energy Research Institute, Av. Lineu Prestes, 2242., Sao Paulo, SP. (Brazil); Passos Piveli, Roque; Campos, Fabio [The Polytechnic School of the University of Sao Paulo, Av. Prof. Almeida Prado, 83, trav.2. Sao Paulo, SP (Brazil)] [The Polytechnic School of the University of Sao Paulo, Av. Prof. Almeida Prado, 83, trav.2. Sao Paulo, SP (Brazil)

2013-07-01

359

Conversions of Mn oxides to nanolayered Mn oxide in electrochemical water oxidation at near neutral pH, all to a better catalyst: catalyst evolution.  

PubMed

Here, for the first time, it is reported that some Mn oxides after a few hours convert to a nanolayered Mn oxide when the compounds are used as water-oxidizing catalysts in a water electrolysis device at near neutral pH and in the presence of LiClO4. The new nanolayered Mn oxide is more active than other Mn oxides toward water oxidation. This result is very important for artificial photosynthetic systems that use Mn oxides as water-oxidizing catalysts. PMID:24149796

Najafpour, Mohammad Mahdi; Haghighi, Behzad; Sedigh, Davood Jafarian; Ghobadi, Mohadeseh Zarei

2013-12-28

360

Advanced chemical oxidation: Its present role and potential future in hazardous waste treatment  

Microsoft Academic Search

Chemical oxidation reactions involving hydroxyl radicals have been extremely effective in the destruction of organic pollutants. These advanced chemical oxidation processes (AOP) generally use a combination of oxidation agents (such as H[sub 2]O[sub 2] or O[sub 3]), irradiation (such as uv or ultrasound), and catalysts (such as metal ions or photocatalysts) as a means to generate hydroxyl radical. The hydroxyl

C. P. Huang; Chengdi Dong; Zhonghung Tang

1993-01-01

361

Zinc oxide inverse opal electrodes modified by glucose oxidase for electrochemical and photoelectrochemical biosensor.  

PubMed

The ZnO inverse opal photonic crystals (IOPCs) were synthesized by the sol-gel method using the polymethylmethacrylate (PMMA) as a template. For glucose detection, glucose oxidase (GOD) was further immobilized on the inwall and surface of the IOPCs. The biosensing properties toward glucose of the Nafion/GOD/ZnO IOPCs modified FTO electrodes were carefully studied and the results indicated that the sensitivity of ZnO IOPCs modified electrode was 18 times than reference electrode due to the large surface area and uniform porous structure of ZnO IOPCs. Moreover, photoelectrochemical detection for glucose using the electrode was realized and the sensitivity approached to 52.4 µA mM(-1) cm(-2), which was about four times to electrochemical detection (14.1 µA mM(-1) cm(-2)). It indicated that photoelectrochemical detection can highly improve the sensor performance than conventional electrochemical method. It also exhibited an excellent anti-interference property and a good stability at the same time. This work provides a promising approach for realizing excellent photoelectrochemical biosensor of similar semiconductor photoelectric material. PMID:24752145

Xia, Lei; Song, Jian; Xu, Ru; Liu, Dali; Dong, Biao; Xu, Lin; Song, Hongwei

2014-09-15

362

Effect of surface treatments on anodic oxide film growth and electrochemical properties of tantalum used for biomedical applications.  

PubMed

Self-expandable nitinol (nickel-titanium) alloys and 316L stainless steel are the most commonly used materials in the production of coronary stents. However, tantalum (Ta) has already been used to make stents for endovascular surgery and may constitute an alternative to other materials because of its better electrochemical performance, namely its higher corrosion resistance, as well as its radio-opacity. The characterization of wet polished, chemically polished, wet polished anodized, and chemically polished anodized Ta electrodes has been performed in a 0.15 M NaCl solution (simulated body fluid) using Ucorr = f(t) measurements, anodic polarizations, capacity measurements, anodic oxidations, and atomic force microscopy (AFM) imaging. Anodic polarization curves have shown that the abnormal current density peak with a maximum value around 1.65 V (critical applied potential, Uc) disappeared for the anodized electrodes indicating a probable relationship between the surface states and the film growth. These results are confirmed by capacity measurements. The behavior of wet polished and chemically polished electrodes during anodic oxidations seemingly indicated that for these particular treatments the film growth is different. The AFM images and roughness measurements have shown that chemical polishing produced smoother electrodes, a fact probably related to the differences in film growth. PMID:16443631

Silva, R A; Silva, I P; Rondot, B

2006-07-01

363

Synthesis, characterization and electrochemical studies of Ti-incorporated tungsten trioxides as platinum support for methanol oxidation  

NASA Astrophysics Data System (ADS)

Platinum supported on high surface area tungsten trioxide (WO 3) has received intensive attention in recent years, mainly because of its improved tolerance towards carbon monoxide (CO) poisoning during methanol oxidation and its enhanced electrocatalytic activity. However, the chemical instability of WO 3 in acid medium is a major issue that hinders its application in fuel cell electrodes. In the present work, the stability of WO 3 is shown to be improved by suitable Ti 4 substition in the WO 3 framework. However, the improvement in the stability of WO 3 in acid medium was found to be significant only at lower amounts of Ti 4 in the framework. On the other hand, the electrocatalytic activity of Pt loaded W 1- xTi xO 3/C ( x = 0.0, 0.05, 0.09 and 0.17) for methanol oxidation, evaluated by cyclic voltammetry, in acid medium follows the order: Pt-W 0.83Ti 017O 3/C > Pt-WO 3/C > Pt-W 0.91Ti 0.09O 3/C ˜ Pt-W 0.95Ti 0.05O 3/C. The trend in the activity observed correlates well with that of the increase in the ohmic resistance of the electrode determined by electrochemical impedance spectroscopy.

Raghuveer, V.; Viswanathan, B.

364

Destruction of EDTA using Ce(IV) mediated electrochemical oxidation: a simple modeling study and experimental verification.  

PubMed

Mediated electrochemical oxidation (MEO) is a recent development in the environmental research field for the complete destruction of organic pollutants. This study presents the destruction of EDTA by cerium(IV) MEO process in nitric acid medium. The destruction reaction was carried out in a continuous stirred tank reactor under various conditions. A simple kinetic model was developed to analyze and simulate the organic destruction in the MEO process. The model was based on the calculation of the total mass balance, the component mass balance, and the energy balance in the reactor and also in the heating jacket. The sensitivity to key operating conditions such as the initial EDTA concentration (50-200 mM), EDTA feeding time (30-180 min), reaction temperature (323-363 K), and the rate laws corresponding to zero-, first-, second-, and third-order reaction were analyzed. It was found that the model simulated agreed well with the experimental data for EDTA oxidation. The results obtained showed the suitability of the MEO process for the effective mineralization of high concentrations of EDTA. PMID:17363029

Lee, Jae-Wook; Chung, Sang-Joon; Balaji, Subramanian; Kokovkin, Vasily V; Moon, Il-Shik

2007-06-01

365

Oxidation of nitride films in aqueous solution: Correlation between surface analysis and electrochemical studies  

SciTech Connect

Ac impedance and dc polarization tests of 304 stainless steels coated by cathodic arc plasma deposition (CAPD) titanium nitride and zirconium nitride were conducted in aqueous chloride solution. Cyclic polarization data suggested passive films were formed over the nitride coatings which are most likely hydrated titanium oxide and zirconium oxides. ESCA analysis of fresh samples and samples exposed during impedance tests indicated a layer rich in oxygen over the ZrN coating after exposure but not over TiN coating. Chemical shifts in the Zr 3d{sub 5/2} core electrons indicate transformation from ZrN to its oxide; the shifts in Ti 2P{sub 3/2} did not support the change from TiN to its oxide. The influence of these shifts on corrosion protection is documented.

Brown, R.; Alias, M.N. [Univ. of Rhode Island, Kingston, RI (United States)

1994-12-31

366

Electrochemical lithiation and delithiation for control of magnetic properties of nanoscale transition metal oxides  

E-print Network

Transition metal oxides comprise a fascinating class of materials displaying a variety of magnetic and electronic properties, ranging from half-metallic ferromagnets like CrO2, ferrimagnetic semiconductors like Fey's, and ...

Sivakumar, Vikram

2008-01-01

367

Electrochemical monitoring of nitric oxide released by myenteric neurons of the guinea pig ileum  

PubMed Central

Nitric oxide (NO) released by myenteric neurons in isolated segments of guinea pig ileum was monitored in vitro using continuous amperometry. NO was detected as an oxidation current recorded with a boron-doped diamond microelectrode held at 1 V versus a Ag|AgCl reference electrode. This potential was sufficient to oxidise NO. Longitudinal muscle myenteric plexus (LMMP) and circular muscle strip preparations were used. In the LMMP preparation, NO release was evoked by superfusion of 1 ?M nicotine, which activates nicotinic acetylcholine receptors expressed by myenteric neurons and myenteric nerve endings. The oxidation current was ascribed to NO based on the following observations: (i) no response was detected at less positive potentials (0.75 V) at which only catecholamines and biogenic amines are oxidized, (ii) the current was abolished in the presence of the nitric oxide synthase antagonist, N-nitro-L-arginine (L-NNA) and (iii) oxidation currents were attenuated by addition of the NO scavenger, myoglobin, to the superfusing solution. In the LMMP preparation stimulated release produced a maximum current that corresponded nominally to 46 nM of NO. The oxidation currents decreased to 10 and 2 nM, respectively, when the tissue was perfused with tetrodotoxin and L-NNA. Oxidation currents recorded from circular muscle strips (stimulated using nicotine) were 3-fold larger than those recorded from the LMMP. This study shows that NO release can be detected from various in vitro preparations of the guinea pig ileum using real-time electroanalytical techniques. PMID:18694441

Patel, Bhavik Anil; Galligan, James J.; Swain, Greg M.; Bian, Xiaochun

2008-01-01

368

Electrochemical Reduction of CO2 to CH3OH at Copper Oxide Surfaces  

SciTech Connect

The direct reduction of CO{sub 2} to CH{sub 3}OH is known to occur at several types of electrocatalysts including oxidized Cu electrodes. In this work, we examine the yield behavior of an electrodeposited cuprous oxide thin film and explore relationships between surface chemistry and reaction behavior relative to air-oxidized and anodized Cu electrodes. CH{sub 3}OH yields (43 ?mol cm{sup ?2} h{sup ?1}) and Faradaic efficiencies (38%) observed at cuprous oxide electrodes were remarkably higher than air-oxidized or anodized Cu electrodes suggesting Cu(I) species may play a critical role in selectivity to CH{sub 3}OH. Experimental results also show CH{sub 3}OH yields are dynamic and the copper oxides are reduced to metallic Cu in a simultaneous process. Yield behavior is discussed in comparison with photoelectrochemical and hydrogenation reactions where the improved stability of Cu(I) species may allow continuous CH{sub 3}OH generation.

Le, Minh; Ren, Maoming; Zhang, Ziyu; Sprunger, Phillip T.; Kurtz, Richard L.; Flake, John C.

2011-01-01

369

Constraints on the oxidation state of the mantle: An electrochemical and sup 57 Fe Moessbauer study of mantle-derived ilmenites  

SciTech Connect

Ilmenite samples from four kimberlite localities were studied using electrochemical, Moessbauer spectroscopic, and microprobe analytical techniques in order to infer the oxidation state of their source regions in the mantle. The values of Fe{sup 3+}/{Sigma}Fe calculated from analyses, using three different electron microanalytical instruments assuming ilmenite stoichiometry, are consistently higher than those derived from the Moessbauer data, by as much as 100%. Furthermore, the range in Fe{sup 3+}/{Sigma}Fe calculated using the analyses from different instruments and/or different correction schemes is nearly as large. Thus Fe{sup 3+}/{Sigma}Fe calculated from microprobe analyses should be taken with caution, even if the precision appears high. {sup 57}Fe Moessbauer spectroscopy on the electrochemical experiment run products demonstrates that Fe{sup 3+}/{Sigma}Fe is significantly lower than it is for the natural C-bearing ilmenites. In contrast, the ilmenite that lacked C did not change Fe{sup 3+}/{Sigma}Fe during the electrochemical experiment. Examination of the reduced samples with SEM established that the natural, single-phase ilmenites exsolved during the electrochemical experiment to form ilmenite{sub ss} + spinel{sub ss}. The initial, reduced trends in the electrochemical experiments for the C-bearing ilmenites are attributed to disequilibrium interactions between the decomposing sample and the evolved gas in the electrochemical cell and do not represent the quenched mantle memory nor the intrinsic f{sub O{sub 2}} of the sample prior to reduction. Furthermore, the oxidized f{sub O{sub 2}} trend is interpreted, for the carbon-bearing samples, are representing the f{sub O{sub 2}} of the ilmenite{sub ss} + spinel{sub ss} assemblage and not the intrinsic f{sub o{sub 2}} of the mantle-derived ilemnite{sub ss}.

Virgo, D.; Luth, R.W. (Geophysical Laboratory, Washington, DC (USA)); Moats, M.A.; Ulmer, G.C. (Temple Univ., Philadelphia, PA (USA))

1988-07-01

370

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

SciTech Connect

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}.

Khomane, Ramdas B.; Agrawal, Amit C. [Chemical Engineering and Process Development Division, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008 (India); Kulkarni, B.D. [Chemical Engineering and Process Development Division, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008 (India)], E-mail: bd.kulkarni@ncl.res.in; Gopukumar, S. [Central Electrochemical Research Institute, Karaikudi 630006, Tamil Nadu (India)], E-mail: deepika_41@rediffmail.com; Sivashanmugam, A. [Central Electrochemical Research Institute, Karaikudi 630006, Tamil Nadu (India)

2008-08-04

371

Electrochemical deposition of iron sulfide thin films and heterojunction diodes with zinc oxide  

SciTech Connect

Iron sulfide thin films were fabricated by the electrochemical deposition method from an aqueous solution containing FeSO{sub 4} and Na{sub 2}S{sub 2}O{sub 3}. The composition ratio obtained was Fe:S:O = 36:56:8. In the photoelectrochemical measurement, a weak negative photo-current was observed for the iron sulfide films, which indicates that its conduction type is p-type. No peaks were observed in X-ray diffraction pattern, and thus the deposited films were considered to be amorphous. For a heterojunction with ZnO, rectification properties were confirmed in the current-voltage characteristics. Moreover, the current was clearly enhanced under AM1.5 illumination.

Kawai, Shoichi, E-mail: shoichi-kawai@denso.co.jp; Sobue, Susumu; Okuno, Eiichi [DENSO CORP. Research Laboratories, Komenoki, Nissin, Aichi 470-0111 (Japan); Yamazaki, Ryuta; Ichimura, Masaya [Department of Engineering Physics, Electronics and Mechanics, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

2014-03-01

372

Direct electrochemical synthesis of reduced graphene oxide (rGO)/copper composite films and their electrical/electroactive properties.  

PubMed

Electrical contact materials with excellent performances are crucial for the development and safe use of electrical contacts in different applications. In our work, reduced graphene oxide (rGO)/copper (Cu) composite films, as potential electrical contact materials, have been synthesized on copper foil with one-step electrochemical reduction deposition method. Cyclic voltammetry (CV) was used to define the deposition conditions, and confocal Raman microscopy (CRM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to characterize the chemical compositions, molecular and micro- and nano-structures of the composite films. Atomic force microscopy/scanning Kelvin probe force microscopy (AFM/SKPFM), conductive AFM (C-AFM) as well as impedance analysis were employed to evaluate the electroactive/electrical properties of the prepared composite films, respectively. The CRM and XPS results suggest that the rGO/Cu composite films can be synthesized through one-step electrochemical codeposition using suitable precursor solutions. Within a short deposition period, the growth of discrete nanograins in the composite film predominates, whereas pine-tree-leaf nanostructures are formed in the composite film when the deposition period is long, due to the chelating role of GO or rGO to regulate the growth rate of metallic copper nanograins. The electrical resistivity of the composite films is lower than the polished Cu foil and the electrodeposited Cu film, probably due to the higher conductivity (enhanced transfer of charge carriers) of the rGO incorporated in the composite films. The Volta potential variation in the rGO/Cu composite film is quite different from that in the electrodeposited Cu film. The electroactivity of the rGO/Cu composite films is higher than the electrodeposited Cu film, but lower than polished Cu foil, and the underlying mechanisms have been discussed. PMID:24787038

Xie, Guoxin; Forslund, Mattias; Pan, Jinshan

2014-05-28

373

Synthesis and characterization of reduced graphene oxide supported gold nanoparticles-poly(pyrrole-co-pyrrolepropylic acid) nanocomposite-based electrochemical biosensor.  

PubMed

A conducting poly(pyrrole-co-pyrrolepropylic acid) copolymer nanocomposite film (AuNP-PPy-PPa) incorporating gold nanoparticles (AuNP) was electrochemically grown using a single step procedure over electrochemically reduced graphene oxide (RGO) flakes deposited on a silane-modified indium-tin-oxide (ITO) glass plate. The RGO support base provided excellent mechanical and chemical stability to the polymer nanocomposite matrix. The porous nanostructure of AuNP-PPy-PPa/RGO provided a huge accessible area to disperse AuNP, and it avoided metallic agglomeration within the polymer matrix. The AuNP-PPy-PPa/RGO was characterized by high-resolution transmission electron microscopy (HRTEM), contact angle measurements, Fourier transform infrared spectroscopy (FTIR), and electrochemical techniques. The pendant carboxyl group of AuNP-PPy-PPa/RGO was covalently bonded with myoglobin protein antibody, Ab-Mb, for the construction of a bioelectrode. Electrochemical impedance spectroscopy technique was used for the characterization of the bioelectrode and as an impedimetric biosensor for the detection of human cardiac biomarker, Ag-cMb. The bioelectrode exhibited a linear impedimetric response to Ag-cMb in the range of 10 ng mL(-1) to 1 ?g mL(-1), in phosphate-buffered solution (PBS) (pH 7.4, 0.1 M KCl) with a sensitivity of 92.13 ? cm(2) per decade. PMID:24928550

Puri, Nidhi; Niazi, Asad; Srivastava, Avanish K; Rajesh

2014-10-01

374

Electrochemical fabrication and optical properties of porous tin oxide films with structural colors  

NASA Astrophysics Data System (ADS)

Photonic crystals with porous features not only provide the capability to control light but also enable structural colors that are environmentally sensitive. Here, we report a novel kind of tin oxide-based photonic crystal featuring periodically arranged air pores fabricated by the periodic anodization of tin foil. The existence of a photonic band gap in the fabricated structure is verified by its vivid color, and its reflective spectra which are responsive to environmental stimuli. Furthermore, the sample colors (i.e., the photonic band gap positions) can be easily adjusted by manipulating the anodization parameters. The theoretical modeling results of these tin oxide photonic crystals agree well with the reported experimental ones.

Cheng, Hua; Shu, Shiwei; Lu, Zhouguang; Lee, Chris; Zeng, Shanshan; Lu, Jian; Li, Yang Yang

2014-10-01

375

Effect of oxidant dosage on integrated electrochemical remediation of contaminant mixtures in soils.  

PubMed

Many sites are contaminated with contaminant mixtures, commonly heavy metals and polycyclic aromatic hydrocarbons (PAHs), which pose a great challenge for remediation. The objective of this research was to investigate coupled Fenton-like oxidation and electrokinetic remediation of low permeability soils contaminated with both heavy metals and PAHs. This remediation process aims at simultaneous oxidation of organic contaminants and removal of heavy metals. Fenton's reagent, consisting of hydrogen peroxide (H(2)O(2)) and native iron catalyst, is utilized for chemical oxidation. Laboratory batch and electrokinetic experiments were performed on kaolin (a low permeability soil) spiked with nickel and phenanthrene each at a concentration of 500 mg/kg of dry soil to represent typical heavy metal and PAH contaminants found at contaminated sites. Experiments were conducted using H(2)O(2) solution in 5%, 10%, 20% and 30% concentrations and also using deionized (DI) water as control. For electrokinetic experiments, a voltage gradient of 1 VDC/cm was applied and H(2)O(2) solution was introduced at the anode for a total duration of four weeks. Batch tests showed that phenanthrene oxidation increases from 76% to 87% when the H(2)O(2) concentration increases from 5% to 30%. The electrokinetic experiments showed substantial electroosmotic flow in all the tests. Approximately one pore volume of flow was generated in the DI baseline test and about 1.2-1.6 pore volumes were generated in case of H(2)O(2) tests. Phenanthrene was partially oxidized in the H(2)O(2) tests and its removal from the soil was insignificant. Oxidation of phenanthrene increased with increasing concentration of H(2)O(2); a maximum of 56% oxidation was observed with 30% H(2)O(2). Nickel migrated from anode to cathode. This migration was more pronounced in the H(2)O(2) tests as compared to the DI baseline test. Nickel precipitated in all the tests near the cathode due to high pH conditions. These results emphasize that the optimization of H(2)O(2)/catalyst concentration and voltage gradient as well as the control of soil pH are required to increase the removal of nickel and the oxidation of phenanthrene. PMID:18569299

Reddy, Krishna R; Karri, Madhusudhana R

2008-07-01

376

Electrochemical fabrication and optical properties of porous tin oxide films with structural colors  

SciTech Connect

Photonic crystals with porous features not only provide the capability to control light but also enable structural colors that are environmentally sensitive. Here, we report a novel kind of tin oxide-based photonic crystal featuring periodically arranged air pores fabricated by the periodic anodization of tin foil. The existence of a photonic band gap in the fabricated structure is verified by its vivid color, and its reflective spectra which are responsive to environmental stimuli. Furthermore, the sample colors (i.e., the photonic band gap positions) can be easily adjusted by manipulating the anodization parameters. The theoretical modeling results of these tin oxide photonic crystals agree well with the reported experimental ones.

Cheng, Hua; Shu, Shiwei; Lee, Chris; Zeng, Shanshan [Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, 83 Tat Chee Av. Hong Kong (Hong Kong); Centre for Functional Photonics, City University of Hong Kong, 83 Tat Chee Av. Hong Kong (Hong Kong); Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue (Hong Kong); Lu, Zhouguang [Department of Materials Science and Engineering, South University of Science and Technology of China, Shenzhen, Guangdong 518055 (China); Lu, Jian, E-mail: jianlu@cityu.edu.hk, E-mail: yangli@cityu.edu.hk [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon (Hong Kong); Centre for Advanced Structural Materials, City University of Hong Kong Shenzhen Research Institute, 8 Yuexing 1st Road, Shenzhen Hi-Tech Industrial Park, Nanshan District, Shenzhen (China); Li, Yang Yang, E-mail: jianlu@cityu.edu.hk, E-mail: yangli@cityu.edu.hk [Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, 83 Tat Chee Av. Hong Kong (Hong Kong); Centre for Functional Photonics, City University of Hong Kong, 83 Tat Chee Av. Hong Kong (Hong Kong); Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue (Hong Kong); City University of Hong Kong Shenzhen Research Institute, 8 Yuexing 1st Road, Shenzhen Hi-Tech Industrial Park, Nanshan District, Shenzhen (China)

2014-10-21

377

Ternary Self-Assembly of Ordered Metal Oxide-Graphene Nanocomposites for Electrochemical Energy Storage  

SciTech Connect

Surfactant or polymer directed self-assembly has been widely investigated to prepare nanostructured metal oxides, semiconductors and polymers, but this approach is mostly limited to two-phase materials, organic/inorganic hybrids, and nanoparticle or polymer-based nanocomposites. Self-assembled nanostructures from more complex, multiscale and multiphase building blocks have been explored with limited success. Here, we demonstrate a ternary self-assembly approach using graphene as fundamental building blocks to construct metal oxide-graphene nanocomposites. A new class of layered nanocomposites is formed containing stable, ordered alternating layers of nanocrystalline metal oxides with graphene/graphene stacks. Alternatively, the graphene material can be incorporated into liquid-crystal-templated nanoporous structures to form high surface area, conductive networks. The self-assembly method can be also used to fabricate free standing, flexible metal oxide-graphene nanocomposite films and electrodes. We investigate the Li-ion insertion properties of the self-assembled electrodes for energy storage and show that the SnO2-graphene nanocomposite films can achieve near theoretical specific energy density without a significant charge/discharge degradation.

Wang, Donghai; Kou, Rong; Choi, Daiwon; Yang, Zhenguo; Nie, Zimin; Li, Juan; Saraf, Laxmikant V.; Hu, Dehong; Zhang, Jiguang; Graff, Gordon L.; Liu, Jun; Pope, Michael A.; Aksay, Ilhan A.

2010-02-25

378

Covalent hybrid of spinel manganese-cobalt oxide and graphene as advanced oxygen reduction electrocatalysts.  

PubMed

Through direct nanoparticle nucleation and growth on nitrogen doped, reduced graphene oxide sheets and cation substitution of spinel Co(3)O(4) nanoparticles, a manganese-cobalt spinel MnCo(2)O(4)/graphene hybrid was developed as a highly efficient electrocatalyst for oxygen reduction reaction (ORR) in alkaline conditions. Electrochemical and X-ray near-edge structure (XANES) investigations revealed that the nucleation and growth method for forming inorganic-nanocarbon hybrids results in covalent coupling between spinel oxide nanoparticles and N-doped reduced graphene oxide (N-rmGO) sheets. Carbon K-edge and nitrogen K-edge XANES showed strongly perturbed C-O and C-N bonding in the N-rmGO sheet, suggesting the formation of C-O-metal and C-N-metal bonds between N-doped graphene oxide and spinel oxide nanoparticles. Co L-edge and Mn L-edge XANES suggested substitution of Co(3+) sites by Mn(3+), which increased the activity of the catalytic sites in the hybrid materials, further boosting the ORR activity compared with the pure cobalt oxide hybrid. The covalently bonded hybrid afforded much greater activity and durability than the physical mixture of nanoparticles and carbon materials including N-rmGO. At the same mass loading, the MnCo(2)O(4)/N-graphene hybrid can outperform Pt/C in ORR current density at medium overpotentials with stability superior to Pt/C in alkaline solutions. PMID:22280461

Liang, Yongye; Wang, Hailiang; Zhou, Jigang; Li, Yanguang; Wang, Jian; Regier, Tom; Dai, Hongjie

2012-02-22

379

Structural and electrochemical characterization and surface modification of layered solid solution oxide cathodes of lithium ion batteries  

NASA Astrophysics Data System (ADS)

Lithium ion batteries are widely used to power portable electronic devices such as cell phones and laptop computers due to their high energy density. However, the currently used layered LiCoO2 cathode could deliver only 50 % of its theoretical capacity in practical lithium ion cells (140 mAh/g) due to the chemical and structural instabilities at deep charge with (1-x) < 0.5 in Li1-xCoO2. Also, cobalt is relatively expensive and toxic. These difficulties have generated enormous interest in alternative cathode hosts. In this regard, solid solutions between layered Li[Li1/3Mn2/3]O2 (commonly designated as Li2MnO3) and LiMO2 (M = Mn, Ni, Co)) have become appealing as some of them exhibit much higher capacity (˜ 250 mAh/g on charging to 4.8 V) with lower cost and better safety compared to LiCoO 2. This dissertation investigates the (1-z) Li[Li1/3Mn 2/3]O2 - (z) Li[Mn0.5-yNi0.5-yCo 2y]O2 (y = 1/12, 1/6 and 1/3 and 0.25 = z = 0.75) layered oxide cathodes, which belong to a solid solution series between layered Li[Li 1/3Mn2/3]O2 and Li[Mn0.5-yNi0.5-y Co2y]O2, with an aim to develop a better understanding of the charge-discharge mechanisms and optimize the electrochemical performance of these materials. To accomplish this, the structural and electrochemical characterization of the (1- z) Li[Li1/3Mn2/3]O2 - (z) Li[Mn 0.5-yNi0.5-yCo2y]O2 cathodes is carried out. It is found that the amount of oxygen loss is related to the lithium content in the transition metal layer, and the Co and Mn4+ contents play a role in influencing the electrochemical behavior. In addition, the chemically delithiated samples are found to transform to O1 or P3 structure with a vanishing of the superlattice reflections arising from cationic ordering in the transition metal layer due to the incorporation of protons from the chemical delithiation medium, while the electrochemically charged samples retain the initial O3 structure. These layered solid solution oxides exhibit high irreversible capacity (IRC) loss (difference between first charge and discharge capacity) values (up to 100 mAh/g), which have been reduced significantly by modifying the cathode surface with other materials like Al2O3, AlPO 4, and F-. For example, compared to an IRC of 75 mAh/g and a first discharge capacity of 253 mAh/g for the pristine Li[Li0.2 Mn0.54Ni0.13Co0.13]O2 (y = 1/6 and z = 0.4), the 3 wt. % Al2O3 modified sample exhibits a lower IRC of 41 mAh/g and a higher first discharge capacity of 285 mAh/g, which is two times higher than that achieved with the LiCoO 2 cathode. A careful and systematic analysis of the experimentally observed capacity and IRC values suggest that part of the oxide ion vacancies created during first charge is retained in the layered lattice in contrast to the idealized model (elimination of all oxide ion vacancies) proposed in the literature. The surface modification helps to retain even more number of oxide ion vacancies in the lattice, which leads to a lower IRC and higher discharge capacity values. Additionally, bulk cationic and anionic substitutions of Al3+ and F- in Li[Li0.17Mn0.58Ni0.25 ]O2 (y = 0 and z = 0.5) are found to sensitively decrease the amount of oxygen loss from the lattice.

Wu, Yan

380

Influence of biologically relevant ligands on oxidation of reduced glucose oxidase by electrochemically generated [Ru III(bpy) 2XY] complexes  

Microsoft Academic Search

Complex formation between cis-[Ru(bpy)2(H2O)2]2+ (bpy=2,2?-bipyridyl) and some biologically relevant ligands (pyridines, imidazole, histidines) increases the rate constant for the oxidation of reduced glucose oxidase (generated in situ by d-glucose from the native enzyme) by the corresponding RuIII derivatives generated electrochemically. Almost a 20-fold rate acceleration is demonstrated by the cyclic voltammetry for histidine as ligand, the rate constant being ca.

Ekaterina S. Ryabova; Elisabeth Csöregi; Alexander D. Ryabov

2000-01-01

381

Electrochemical oxidation and nanomolar detection of acetaminophen at a carbon-ceramic electrode modified by carbon nanotubes: a comparison between multi walled and single walled carbon nanotubes  

Microsoft Academic Search

Carbon-ceramic electrodes (CCE) modified with carbon nanotubes were prepared, and the electrochemical behavior towards acetaminophen\\u000a (ACOP) was investigated using both a bare CCE and electrodes modified with either single walled carbon nanotubes (SWCNT) or\\u000a multi walled carbon nanotubes (MWCNT) in an effort to understand which of them is the better choice in terms of electrocatalyzing\\u000a the oxidation of ACOP, and

Biuck Habibi; Mojtaba Jahanbakhshi; Mohammad Hossein Pournaghiazar

2011-01-01

382

Cobalt oxide hollow microspheres with micro- and nano-scale composite structure: Fabrication and electrochemical performance  

SciTech Connect

Co{sub 3}O{sub 4} hollow microspheres with micro- and nano-scale composite structure self-assembled by nanosheets were successfully fabricated by the template-free wet-chemical approach. This method is simple, facile and effective. The Co{sub 3}O{sub 4} hollow microspheres with good purity and homogeneous size were well characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform IR (FTIR), thermogravimetric analysis (TGA) and inductively coupled plasma atomic emission spectrometer (ICP). The formation mechanism was deeply studied. The micro- and nano-scale composite structure constructed by the porous nanosheets promotes to improve the electrochemical properties of Co{sub 3}O{sub 4} hollow microspheres. The high discharge capacity of 1048 mAh g{sup -1} indicates it to be the potential application in electrode materials of Li-ion battery. - Graphical Abstract: Co{sub 3}O{sub 4} hollow microspheres self-assembled by nanosheets are successfully fabricated by a template-free wet-chemical approach. The hollow microspheres are in good morphology purity and homogeneous size. Co{sub 3}O{sub 4} hollow microspheres constructed by porous nanosheets show the high discharge capacity of 1048 mAh g{sup -1}, indicating it to be the potential electrode material of Li-ion battery.

Tao Feifei [State Key Laboratory of Coordination Chemistry, Laboratory of Solid State Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); School of Chemistry and Chemical Engineering, Shaoxing University, Shaoxing 312000 (China); Gao Cuiling [State Key Laboratory of Coordination Chemistry, Laboratory of Solid State Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Wen Zhenhai; Wang Qiang; Li Jinghong [Department of Chemistry, Qinghua University, Beijing 100084 (China); Xu Zheng, E-mail: zhengxu@netra.nju.edu.c [State Key Laboratory of Coordination Chemistry, Laboratory of Solid State Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)

2009-05-15

383

Surface Interrogation of CoPi Water Oxidation Catalyst by Scanning Electrochemical Microscopy.  

PubMed

Despite exhaustive spectroscopic investigations on the CoPi oxygen-evolving catalyst over the past several years, little is known about the surface cobalt sites and intermediates in direct contact with water that are responsible for the actual catalysis. Many studies thus far have been limited to ex situ characterizations or bulk film measurements, often in the absence of solvent. Here we describe an investigation of the CoPi catalyst by surface interrogation scanning electrochemical microscopy (SI-SECM). This method should allow us to selectively study surface atoms separately from the bulk in a solvent-filled environment. By SI-SECM, independent titrations of surface Co(III) and Co(IV) were performed, yielding a direct measurement of the surface active-site density of a CoPi electrode (11 Co/nm(2)). The pseudo-first-order reaction rate constants of Co(III) and Co(IV) with water were determined to be 0.19 and >2 s(-1), respectively, through time-dependent titration measurements. PMID:25562373

Ahn, Hyun S; Bard, Allen J

2015-01-21

384

Advanced Oxidation Technologies\\/Photocatalytic Treatment of Wastewater  

Microsoft Academic Search

7.1. Summary and conclusionsThe last two decennia have shown a growing interest in the photocatalytic treatment of wastewater, and more and more research has been carried out into the various aspects of photocatalysis, varying from highly fundamental aspects to practical application. However, despite all this research, there is still much to investigate. Suggested photocatalytic mechanisms, such as those for oxidation

J. Chen

1997-01-01

385

Advanced indium-tin oxide ceramics for sputtering targets  

Microsoft Academic Search

Indium-tin oxide (ITO) ceramic sputtering targets are widely used in formation of electrically conductive transparent thin films for electrodes in flat panel displays, solar cells, antistatic films and others, and which are commonly produced by a conventional dc magnetron sputtering process. The ceramic targets should be of high purity with a uniform microcrystalline structure and should possess high density and

E. Medvedovski; N. Alvarez; O. Yankov; M. K. Olsson

2008-01-01

386

Nitric oxide (NO): in vivo electrochemical monitoring in the dorsal horn of the spinal cord of the rat.  

PubMed

NO synthase (NOS) is largely distributed in the superficial and deep laminae of the dorsal horn as well as in dorsal root ganglion cells. It has been proposed that nitric oxide (NO) participates in the transmission of sustained, and possibly brief, nociceptive, inputs at the spinal level. The aim of this study was to check the ability of in vivo electrochemical monitoring of NO within the dorsal horn of the lumbar spinal cord (L3-L4 level) of chloral hydrate anesthetized or decerebrated spinalized rats. 30 microm diameter and 450 microm length treated carbon fiber electrodes coated with nickel(II) tetrakis (3-methoxy-4-hydroxy-phenyl) porphyrine and NafionR, and associated with differential normal pulse voltammetry, gave a peak of oxidation current around 650 mV (vs. Ag-AgCl) in vitro in NO solutions between 0.125 and 1.25 microM. In vivo, a 650 mV peak appeared which was stable (recording interval 2 min) for up to 3 h (+/-6%). Comparison between in vitro calibration and in vivo voltammograms gave an estimated in vivo extracellular concentration of 0.50 microM. In vivo, peaks decreased by 95% at 90 min and for up to 3 h after an i.p. injection of 100 mg/kg of the NOS inhibitor (NOSI) L-arginine-p-nitroanilide (L-ANA). At the same dose i.p., N(G)-nitro-L-arginine methyl ester (L-NAME) was almost ineffective after 90 min in animals paralyzed with pancuronium bromate or gallamine trethiodide. However, in non-curarized decerebrated spinalized animals, L-NAME depressed the voltammograms by 36% at 90 min. S-Ethylthiourea (80 mg/kg i.p.), also decreased the voltammograms by 45% at 140 min, and finally, 7-nitroindazole (7-NI, 90 mg/kg i.p), induced a important decrease of the 650 mV peak (23% of control) at 120 min. These results are in agreement with biochemical data showing the decrease of NOS activity within the lumbar spinal cord by L-NAME (45% of control at 90 min) and 7-NI (20% of control at 90 min). The NO donor hydroxylamine (30 mg/kg i.p.) significantly increased the peaks (140% at 90 min), and sodium nitroprusside (SNP, 20 mM) when directly superfused upon the spinal cord (200-300 microl min(-1)) induced a large increase in the peak (300% at 90 min). Moreover, SNP 60 min after L-ANA, or 90 min after L-NAME, rapidly restored the 650 mV peak up to control values. These results demonstrate the validity of electrochemical monitoring of NO within the dorsal horn of the spinal cord. The in vivo electrochemical detection of NO is in progress to study the implication of this messenger in the transmission of nociceptive messages at the spinal level. PMID:9409706

Rivot, J P; Barraud, J; Montécot, C; Jost, B; Besson, J M

1997-10-31

387

The oriented growth of tungsten oxide in ordered mesoporous carbon and their electrochemical performance.  

PubMed

Electrocatalysts for hydrogen oxidation and methanol oxidation are the heart of the proton exchange membrane fuel cell. In spite of tremendous efforts, developing low-cost anodic electrocatalysts with high catalytic activity and corrosion resistance is still a great challenge. Here, we report a nanocomposite consisting of oriented WO3 nanorods grown in ordered mesoporous carbon as a high-performance functional catalyst carrier for proton exchange membrane fuel cells. As a result of the catalytic graphitization effect of tungsten compounds, the degree of graphitization and conductivity of mesoporous carbon film were improved even at a low temperature. Furthermore, compared with ordered mesoporous carbon, ordered mesoporous C-WO3 nanocomposites possess favorable hydrophilicity, excellent corrosion resistance and notable electrocatalytic activities. The unusual electrocatalytic activities arise from the ideal physical properties of the carrier and synergetic catalysis between Pt and WO3. PMID:24733640

Wang, Tao; Tang, Jing; Fan, Xiaoli; Zhou, Jianhua; Xue, Hairong; Guo, Hu; He, Jianping

2014-05-21

388

Melting temperature of metal polycrystalline nanowires electrochemically deposited into the pores of anodic aluminum oxide.  

PubMed

The arrays of metallic nanowires are considered as promising precursors for 1D semiconductor nanostructures after appropriate treatment at temperatures close to the melting point. Therefore the melting behaviour of the metallic structures in oxide templates is a key parameter for the subsequent conversion process. The present paper focuses on understanding of the effect of mechanical stress generated during heating on the melting point of the metal nanowires deposited into the pores of anodic alumina. Extremely high local compressive stress appears due to the difference in the thermal coefficients of the oxide template and nanowires inside the pores. The effect of the composite structural parameter that may be related to the concentration of nanowires on the melting temperature has been investigated. A numerical model predicting the melting point has been developed for composites with indium, tin, and zinc nanowires. The simulation results obtained using the suggested model were compared with the experimental data. PMID:25101924

Shilyaeva, Yu I; Bardushkin, V V; Gavrilov, S A; Silibin, M V; Yakovlev, V B; Borgardt, N I; Volkov, R L; Smirnov, D I; Zheludkevich, M L

2014-09-28

389

Anion exchange membranes for electrochemical oxidation-reduction energy storage system  

NASA Technical Reports Server (NTRS)

Oxidation-reduction couples in concentrated solutions separated by appropriate ion selective membranes were considered as an attractive approach to bulk electrical energy storage. A key problem is the development of the membrane. Several promising types of anionic membranes are discussed which were developed and evaluated for redox energy storage systems. The copolymers of ethyleneglycoldimethacrylate with either 2-vinylpyridine or vinylbenzl chloride gave stable resistance values compared to the copolymer of vinylbenzlchloride and divinylbenzene which served as the baseline membrane. A polyvinylchloride film aminated with tetraethylenepentamine had a low resistance but a high ion transfer rate. A slurry coated vinylpyridine had the lowest ion transfer rate. All these membranes functioned well in laboratory cells at ambient temperatures with the acidic chloride oxidant/reductant system, Fe 3, Fe 2/Ti 3, Ti 4.

Odonnell, P. M.; Sheibley, D. W.; Gahn, R. F.

1977-01-01

390

Synthesis and H2 Gas Sensing Properties of Titanium Oxide Nanotube Arrays via Electrochemical Anodization  

NASA Astrophysics Data System (ADS)

Highly ordered titania nanotube (TNT) arrays were fabricated via anodization process in electrolytes containing HF and NH4F in ethylene glycol. Scanning electron microscopy images show the size and microstructure of arrays. Electrolyte and oxidation conditions optimized to get well-ordered TNTs. A hydrogen gas sensor based on TNT semiconductor was developed. The hydrogen sensor's results of arrays show high sensing amplitude which related to the anodizing conditions.

Alavi, Babak; Asl, Shahin Khameneh; Asl, Shahab Khameneh; Jale, Valiollah

2011-12-01

391

A model for the electrochemical reduction of metal oxides in molten salt electrolytes  

Microsoft Academic Search

The reduction of numerous metal oxides is being investigated by electro-deoxidation in molten salts due to the low-oxygen content advantage these processes offer. One of these processes is the Fray–Farthing–Chen (FFC) process that involves the direct reduction of titanium dioxide to titanium. A model for the multi-stage reduction of titanium dioxide to titanium is reported herein. The modeling approach adopted

Pritish Kar; James W. Evans

2008-01-01

392

Electrochemical oxidation of water on synthetic boron-doped diamond thin film anodes  

Microsoft Academic Search

Electrolysis in aqueous 1 M HClO4 and 1 M H2SO4 solutions has been carried out under galvanostatic conditions using boron-doped diamond electrodes (BDD). Analyses of the oxidation products have shown that in 1 M HClO4 the main reaction is oxygen evolution, while in H2SO4 the main reaction is the formation of H2S2O8. In both electrolytes small amounts of O3 and

P. A. Michaud; M. Panizza; L. Ouattara; T. Diaco; G. Foti; Ch. Comninellis

2003-01-01

393

Templating an N-heterocyclic carbene (NHC)-cyclometalated Cp*Ir(III)-based oxidation precatalyst on a pendant coordination platform: assessment of the oxidative behavior via electrochemical, spectroscopic and catalytic probes.  

PubMed

The coordination of metalloligands to derive modified properties of the metal functionality is one of the interesting strategies practiced in materials chemistry and catalysis. In this work, a pendant terpyridine ligand has been utilized for templating a Cp*Ir(III)(NHC)-based (NHC = N-heterocyclic carbene) oxidation precatalyst to assess its modified oxidative behavior via electrochemical, UV-vis spectroscopic, and catalytic probes. These studies suggested that the coordination-template enhances the electron-deficiency at the Ir(III) redox center and affects the nature of the oxidized high-valent Ir-oxo species during chemical oxidation. Moreover, both the premodified and postmodified Cp*Ir(III)(NHC)-based complexes were found to be equally efficient in catalytic sp(3) C-H oxidation reactions with NaIO4 as a mild sacrificial oxidant. PMID:25415183

Gupta, Suraj K; Choudhury, Joyanta

2015-01-21

394

Electrochemical and structural characterization of titanium-substituted manganese oxides based on Na0.44MnO2  

SciTech Connect

A series of titanium-substituted manganese oxides, Li{sub x}Ti{sub y}Mn{sub 1-y}O{sub 2} (y = 0.11, 0.22, 0.33, 0.44, and 0.55) with the Na{sub 0.44}MnO{sub 2} structure were prepared from Na{sub x}Ti{sub y}Mn{sub 1-y}O{sub 2} (x {approx} 0.44) precursors. The electrochemical characteristics of these compounds, which retain the unique double-tunnel structure during ion exchange, were examined in lithium/polymer electrolyte cells operating at 85 C. All of the substituted cathode materials intercalated lithium reversibly, with Li{sub x}Ti{sub 0.22}Mn{sub 0.78}O{sub 2} exhibiting the highest capacity in polymer cells, about 10-20% greater than that of unsubstituted Li{sub x}MnO{sub 2} made from Na{sub 0.44}MnO{sub 2}. In common with Li{sub x}MnO{sub 2}, the Ti-substituted materials exhibited good capacity retention over one hundred or more cycles, with some compositions exhibiting a fade rate of less than 0.03% per cycle.

Doeff, Marca M.; Richardson, Thomas J.; Hwang, Kwang-Taek

2004-03-01

395

In situ X-Ray Absorption Spectro-Electrochemical Study of Amorphous Tin-Based Composite Oxide Material  

SciTech Connect

We have measured the XAFS spectra of a sample of tin-based composite oxide (TCO) material with a nominal composition of Sn{sub 1.0}B{sub 0.56}P{sub 0.40}Al{sub 0.42}O{sub 3.47} during the discharge and charge cycles in an ''in situ'' configuration. Our results confirm the amorphous nature of TCO and show that Sn in TCO is coordinated with 3 oxygen atoms at a distance of 2.12 {angstrom}. Upon discharging, initially, Li interacts with the electrochemically active Sn-O center forming metallic Sn in the form of clusters containing just a few atoms. Upon further discharge, Li alloys with Sn forming initially highly dispersed forms of Li{sub 2}Sn{sub 5} and/or LiSn and then Li{sub 7}Sn{sub 3}, Li{sub 5}Sn{sub 2}, Li{sub 13}Sn{sub 5}, or Li{sub 7}Sn{sub 2}. The true nature of the formed alloys could be significantly different from that of the corresponding crystalline phases. Upon charging, metallic Sn is produced with a Sn-Sn distance intermediate to those of gray and white Sn.

Mansour, A. N.; Mukerjee, S.; Yang, X. Q.; McBreen, J.

1998-11-01

396

Enhanced electrochemical performance with surface coating by reactive magnetron sputtering on lithium-rich layered oxide electrodes.  

PubMed

Electrode films fabricated with lithium-rich layered 0.3Li2MnO3-0.7LiNi5/21Co5/21Mn11/21O2 cathode materials have been successfully modified with ZnO coatings via a reactive magnetron sputtering (RMS) process for the first time. The morphology and chemical composition of coating films on the electrodes have been in deep investigated by transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS) characterizations. The results clearly demonstrate that ZnO film coatings are ultrathin, dense, uniform, and fully covered on the electrodes. The RMS-2 min (deposition time) coated electrode exhibits much higher initial discharge capacity and coulombic efficiency with 316.0 mAh g(-1) and 89.1% than that of the pristine electrode with 283.4 mAh g(-1) and 81.7%. In addition, the discharge capacity also reaches 256.7 and 187.5 mAh g(-1) at 0.1 and 1.0 C-rate, as compared to that of 238.4 and 157.8 mAh g(-1) after 50 cycles. The improved electrochemical performances of RMS-coated electrodes are ascribed to the high-quality ZnO film coatings that reduce charge transfer resistance and effectively protect active material from electrolyte oxidation. PMID:24857766

Qiu, Bao; Wang, Jun; Xia, Yonggao; Wei, Zhen; Han, Shaojie; Liu, Zhaoping

2014-06-25

397

Role of electrolyte additives on in-vitro electrochemical behavior of micro arc oxidized titania films on Cp Ti  

NASA Astrophysics Data System (ADS)

The present work is aimed at studying the influence of electrolyte chemistry on the voltage-time (V-T) response characteristics, phase structure, surface morphology, film growth rate and corrosion properties of titania films fabricated by micro arc oxidation (MAO) on Cp Ti. The titania films were developed with a sodium phosphate based reference electrolyte comprising the additives such as sodium carbonate (Na2CO3), sodium nitrite (NaNO2) and urea (CO(NH2)2). The phase composition, surface morphology, elemental composition and thickness of the films were assessed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. The corrosion characteristics of the fabricated films were studied under Kokubo simulated body fluid (SBF) condition by potentiodynamic polarization, long term potential and linear polarization resistance (LPR) measurements and electrochemical impedance spectroscopy (EIS) methods. In addition, the corrosion characteristics of the grown films were analyzed by EIS curve fitting and equivalent circuit modeling. Salt spray test (SST) as per ASTM B 117 standard was also conducted to verify the corrosion resistance of the grown films. The XRD results showed that the titania films were composed of both anatase and rutile phases at different proportions. Besides, the films grown in carbonate and nitrite containing electrolyte systems showed an enhanced growth of their rutile phase in the [1 0 1] direction which could be attributed to the modifications introduced in the growth process by the abundant oxygen available during the process. The SEM-EDX and elemental mapping results showed that the respective electrolyte borne elements were incorporated and distributed uniformly in all the films. Among all the grown films under study, the film developed in carbonate containing electrolyte system exhibited considerably improved corrosion resistance due to suitable modifications in its structural and morphological characteristics. The rate of anatase to rutile phase transformation and the rutile growth direction were strongly influenced by the abundant oxidizing species available during the film growth process.

Venkateswarlu, K.; Rameshbabu, N.; Sreekanth, D.; Bose, A. C.; Muthupandi, V.; Babu, N. K.; Subramanian, S.

2012-07-01

398

Degradation of RDX by various advanced oxidation processes: I. Reaction rates  

Microsoft Academic Search

1, 3, 5-trinitrotriazacyclohexane (C3H6O6N6) or RDX is a heterocyclic nitramine compound that has been widely used as an explosive since the early 1900s. There is substantial interest in removing this compound from groundwater and other environmental media. Advanced oxidation processes (AOPs) are currently being tested as a treatment process for this compound. In this research five types of oxidation processes

Purnendu Bose; William H. Glaze; D. Scott Maddox

1998-01-01

399

DEGRADATION OF RDX BY VARIOUS ADVANCED OXIDATION PROCESSES: II. ORGANIC BY-PRODUCTS  

Microsoft Academic Search

This study resulted in the detection and identification of several organic by-products that were formed upon photolysis or oxidation of RDX by various advanced oxidation processes (AOPs). Photolysis of RDX by UV showed evidence of formation of two by-products, probably by the successive elimination of two equivalents of nitrous acid. These were tentatively identified as 1, 3-dinitro-1, 3, 5-triazacyclohex-5-ene and

Purnendu Bose; William H Glaze; D. Scott Maddox

1998-01-01

400

Treatment of statin compounds by advanced oxidation processes: Kinetic considerations and destruction mechanisms  

Microsoft Academic Search

This study examined the use of advanced oxidation\\/reduction processes (AO\\/RPs) for the destruction of cholesterol lowering statin pharmaceuticals. AO\\/RPs which utilize the oxidizing hydroxyl radical (OH) and reducing aqueous electron (e?aq), to degrade chemical contaminants are alternatives to traditional water treatment methods, and are alternatives as water reuse becomes more generally implemented. Four major statin pharmaceuticals, fluvastatin, lovastatin, pravastatin and

Behnaz Razavi; Weihua Song; Hanoz Santoke; William J. Cooper

2011-01-01

401

First-principles density functional theory study of cobalt (hydr)oxides and titanium dioxide for electrochemical oxygen evolution  

NASA Astrophysics Data System (ADS)

The spinel cobalt oxide Co3O4 is a magnetic semiconductor containing cobalt ions in Co2+ and Co3+ oxidation states. We have studied the electronic, magnetic and bonding properties of Co3O4 using density functional theory (DFT) at the Generalized Gradient Approximation (GGA), GGA+U, and PBE0 hybrid functional levels. (110) is a frequently exposed surface in Co3O4 nanomaterials. We employed DFT+U to study the atomic structures, energetics, magnetic and electronic properties of the two possible terminations, A and B, of this surface. These calculations predict A as the stable termination in a wide range of oxygen chemical potentials, consistent with recent experimental observations. The Co3+ ions do not have a magnetic moment in the bulk, but become magnetic at the surface, which leads to surface magnetic orderings different from the one in the bulk. Surface electronic states are present in the lower half of the bulk band gap and cause partial metallization of both surface terminations. These states are responsible for the charge compensation mechanism stabilizing both polar terminations. We also carried out DFT+U to study the interaction of water with the (110) surface of Co3O4, a widely used oxidation catalyst. Dissociative water adsorption is preferred from low coverage up to one monolayer on the A termination and up to one-half monolayer coverage on the B termination. On the latter, a mixed molecular and dissociated monolayer is more stable at full coverage. The computed structures are used to investigate the free energy changes during water oxidation on both surface terminations. Using first-principles density functional theory (DFT) calculations we determine the relative Gibbs free energies of CoO, Co(OH)2, Co 3O4, CoO(OH) and CoO2 in electrochemical environment. We find that CoO(OH) and CoO2 are the stable phases under oxidation conditions. These results, combined with surface structure studies of CoO(OH) (0001), show that a CoO2x-- (x=0~0.5) layer is present when the surface is exposed to solution under oxidation conditions. Study of the oxygen evolution reaction (OER) reveals however that natural surface of a CoO2x-- layer has a high overpotential, due to the difficulty of first deprotonation to form a surface OH species. Taken previous study of CoO(OH) (0112) surface into consideration, the OER reactivity of CoO(OH) could come from surface step-edge and defects. As a promising candidate electrode material for photoelectrochemical water splitting, TiO2 is perhaps the most studied oxide semiconductor in photocatalysis. Recent computational studies of the oxygen evolution reaction (OER) have shown that the first proton-coupled electron transfer is responsible for the high overpotential of the OER on TiO2 surfaces. Here, we report a study of the chemical dynamics of the first proton and electron transfers across the TiO2-water interface. Using a periodic model that includes an anatase slab and explicit water molecules, we sample the solvent configurations by ab-initio molecular dynamics and determine the energy profiles of the two electronic states involved in the electron transfer by the hybrid PBE0 functional. Our calculated energy profiles suggest that the first proton and electron transfers are sequential, with the electron transfer (ET) following the proton transfer (PT). The ET is facilitated by a shared-hole state, and there is no significant solvent reorganization barrier during the ET.

Chen, Jia

402

Advances in metal-induced oxidative stress and human disease.  

PubMed

Detailed studies in the past two decades have shown that redox active metals like iron (Fe), copper (Cu), chromium (Cr), cobalt (Co) and other metals undergo redox cycling reactions and possess the ability to produce reactive radicals such as superoxide anion radical and nitric oxide in biological systems. Disruption of metal ion homeostasis may lead to oxidative stress, a state where increased formation of reactive oxygen species (ROS) overwhelms body antioxidant protection and subsequently induces DNA damage, lipid peroxidation, protein modification and other effects, all symptomatic for numerous diseases, involving cancer, cardiovascular disease, diabetes, atherosclerosis, neurological disorders (Alzheimer's disease, Parkinson's disease), chronic inflammation and others. The underlying mechanism of action for all these metals involves formation of the superoxide radical, hydroxyl radical (mainly via Fenton reaction) and other ROS, finally producing mutagenic and carcinogenic malondialdehyde (MDA), 4-hydroxynonenal (HNE) and other exocyclic DNA adducts. On the other hand, the redox inactive metals, such as cadmium (Cd), arsenic (As) and lead (Pb) show their toxic effects via bonding to sulphydryl groups of proteins and depletion of glutathione. Interestingly, for arsenic an alternative mechanism of action based on the formation of hydrogen peroxide under physiological conditions has been proposed. A special position among metals is occupied by the redox inert metal zinc (Zn). Zn is an essential component of numerous proteins involved in the defense against oxidative stress. It has been shown, that depletion of Zn may enhance DNA damage via impairments of DNA repair mechanisms. In addition, Zn has an impact on the immune system and possesses neuroprotective properties. The mechanism of metal-induced formation of free radicals is tightly influenced by the action of cellular antioxidants. Many low-molecular weight antioxidants (ascorbic acid (vitamin C), alpha-tocopherol (vitamin E), glutathione (GSH), carotenoids, flavonoids, and other antioxidants) are capable of chelating metal ions reducing thus their catalytic activity to form ROS. A novel therapeutic approach to suppress oxidative stress is based on the development of dual function antioxidants comprising not only chelating, but also scavenging components. Parodoxically, two major antioxidant enzymes, superoxide dismutase (SOD) and catalase contain as an integral part of their active sites metal ions to battle against toxic effects of metal-induced free radicals. The aim of this review is to provide an overview of redox and non-redox metal-induced formation of free radicals and the role of oxidative stress in toxic action of metals. PMID:21414382

Jomova, Klaudia; Valko, Marian

2011-05-10

403

Low cost stable air electrode material for high temperature solid oxide electrolyte electrochemical cells  

DOEpatents

A low cost, lanthanide-substituted, dimensionally and thermally stable, gas permeable, electrically conductive, porous ceramic air electrode composition of lanthanide-substituted doped lanthanum manganite is provided which is used as the cathode in high temperature, solid oxide electrolyte fuel cells and generators. The air electrode composition of this invention has a much lower fabrication cost as a result of using a lower cost lanthanide mixture, either a natural mixture or an unfinished lanthanide concentrate obtained from a natural mixture subjected to incomplete purification, as the raw material in place of part or all of the higher cost individual lanthanum. The mixed lanthanide primarily contains a mixture of at least La, Ce, Pr, and Nd, or at least La, Ce, Pr, Nd and Sm in its lanthanide content, but can also include minor amounts of other lanthanides and trace impurities. The use of lanthanides in place of some or all of the lanthanum also increases the dimensional stability of the air electrode. This low cost air electrode can be fabricated as a cathode for use in high temperature, solid oxide fuel cells and generators. 4 figs.

Kuo, L.J.H.; Singh, P.; Ruka, R.J.; Vasilow, T.R.; Bratton, R.J.

1997-11-11

404

Protective effect of sulforaphane against oxidative stress: recent advances.  

PubMed

Sulforaphane [1-isothiocyanate-(4R)-(methylsulfinyl)butane] is a natural dietary isothiocyanate produced by the enzymatic action of the myrosinase on glucopharanin, a 4-methylsulfinylbutyl glucosinolate contained in cruciferous vegetables of the genus Brassica such as broccoli, brussel sprouts, and cabbage. Studies on this compound is increasing because its anticarcinogenic and cytoprotective properties in several in vivo experimental paradigms associated with oxidative stress such as focal cerebral ischemia, brain inflammation, intracerebral hemorrhage, ischemia and reperfusion induced acute renal failure, cisplatin induced-nephrotoxicity, streptozotocin-induced diabetes, carbon tetrachloride-induced hepatotoxicity and cardiac ischemia and reperfusion. This protective effect also has been observed in in vitro studies in different cell lines such as human neuroblastoma SH-SY5Y, renal epithelial proximal tubule LLC-PK1 cells and aortic smooth muscle A10 cells. Sulforaphane is considered an indirect antioxidant; this compound is able to induce many cytoprotective proteins, including antioxidant enzymes, through the Nrf2-antioxidant response element pathway. Heme oxygenase-1, NAD(P)H: quinone oxidoreductase, glutathione-S-transferase, gamma-glutamyl cysteine ligase, and glutathione reductase are among the cytoprotective proteins induced by sulforaphane. In conclusion, sulforaphane is a promising antioxidant agent that is effective to attenuate oxidative stress and tissue/cell damage in different in vivo and in vitro experimental paradigms. PMID:21129940

Guerrero-Beltrán, Carlos Enrique; Calderón-Oliver, Mariel; Pedraza-Chaverri, José; Chirino, Yolanda Irasema