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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

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

PubMed

Apart from a high biodegradable fraction consisting of organic acids, sugars and alcohols, winery wastewaters exhibit a recalcitrant fraction containing high-molecular-weight compounds as polyphenols, tannins and lignins. In this context, a winery wastewater was firstly subjected to a biological oxidation to mineralize the biodegradable fraction and afterwards an electrochemical advanced oxidation process (EAOP) was applied in order to mineralize the refractory molecules or transform them into simpler ones that can be further biodegraded. The biological oxidation led to above 97% removals of dissolved organic carbon (DOC), chemical oxygen demand (COD) and 5-day biochemical oxygen demand (BOD5), but was inefficient on the degradation of a bioresistant fraction corresponding to 130 mg L(-1) of DOC, 380 mg O2 L(-1) of COD and 8.2 mg caffeic acid equivalent L(-1) of total dissolved polyphenols. Various EAOPs such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), UVA photoelectro-Fenton (PEF) and solar PEF (SPEF) were then applied to the recalcitrant effluent fraction using a 2.2 L lab-scale flow plant containing an electrochemical cell equipped with a boron-doped diamond (BDD) anode and a carbon-PTFE air-diffusion cathode and coupled to a photoreactor with compound parabolic collectors (CPCs). The influence of initial Fe(2+) concentration and current density on the PEF process was evaluated. The relative oxidative ability of EAOPs increased in the order AO-H2O2 < EF < PEF ? SPEF. The SPEF process using an initial Fe(2+) concentration of 35 mg L(-1), current density of 25 mA cm(-2), pH of 2.8 and 25 °C reached removals of 86% on DOC and 68% on COD after 240 min, regarding the biologically treated effluent, along with energy consumptions of 45 kWh (kg DOC)(-1) and 5.1 kWh m(-3). After this coupled treatment, color, odor, COD, BOD5, NH4(+), NO3(-) and SO4(2-) parameters complied with the legislation targets and, in addition, a total dissolved polyphenols content of 0.35 mg caffeic acid equivalent L(-1) was found. Respirometry tests revealed low biodegradability enhancement along the SPEF process. PMID:25765168

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

2015-05-15

4

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

5

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

6

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

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

Decolorization and mineralization of Allura Red AC aqueous solutions by electrochemical advanced oxidation processes.  

PubMed

The decolorization and mineralization of solutions containing 230mgL(-1) of the food azo dye Allura Red AC at pH 3.0 have been studied upon treatment by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF). Experiments were performed with a stirred tank reactor containing a boron-doped diamond (BDD) or Pt anode and an air-diffusion cathode to generate H2O2. The main oxidants were hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between H2O2 and added Fe(2+). The oxidation ability increased in the sequence EO-H2O2oxidation of final oxalic and oxamic acids by BDD along with the photolysis of Fe(III)-oxalate species by UVA light accounted for the superiority of PEF with BDD. NH4(+), NO3(-) and SO4(2-) ions were released during the mineralization. PMID:25734532

Thiam, Abdoulaye; Sirés, Ignasi; Garrido, José A; Rodríguez, Rosa M; Brillas, Enric

2015-06-15

9

Solid oxide electrochemical reactor science.  

SciTech Connect

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

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

2010-09-01

10

Electrochemical Oxidation of 8-Oxoguanine  

Microsoft Academic Search

Abstract Electrochemical oxidation of DNA can occur at each of the four bases and guanine is the one that can suffer the easiest oxidative damage. The occurrence of the guanine oxidation product, 8-oxoguanine, as a consequence of DNA damage caused by DNA oxidation causes important mutagenic,lesions and hence it is very important to develop reliable methods,for its quantification. Electrochemical study

A. M. Oliveira Brett; J. A. P. Piedade; S. H. P. Serrano

2000-01-01

11

Removal of arsenic, phosphates and ammonia from well water using electrochemical/chemical methods and advanced oxidation: a pilot plant approach.  

PubMed

The purpose of this work was to develop a pilot plant purification system and apply it to groundwater used for human consumption, containing high concentrations of arsenic and increased levels of phosphates, ammonia, mercury and color. The groundwater used was obtained from the production well in the Vinkovci County (Eastern Croatia). Due to a complex composition of the treated water, the purification system involved a combined electrochemical treatment, using iron and aluminum electrode plates with simultaneous ozonation, followed by a post-treatment with UV, ozone and hydrogen peroxide. The removal of the contaminant with the waste sludge collected during the electrochemical treatment was also tested. The combined electrochemical and advanced oxidation treatment resulted in the complete removal of arsenic, phosphates, color, turbidity, suspended solids and ammonia, while the removal of other contaminants of interest was up to 96.7%. Comparable removal efficiencies were obtained by using waste sludge as a coagulant. PMID:24798899

Orescanin, Visnja; Kollar, Robert; Nad, Karlo; Halkijevic, Ivan; Kuspilic, Marin; Findri Gustek, Stefica

2014-01-01

12

Electrochemical oxidation of organic waste  

SciTech Connect

Both silver catalyzed and direct electrochemical oxidation of organic species are examined in analytical detail. This paper describes the mechanisms, reaction rates, products, intermediates, capabilities, limitations, and optimal reaction conditions of the electrochemical destruction of organic waste. A small bench-top electrocell being tested for the treatment of small quantities of laboratory waste is described. The 200-mL electrochemical cell used has a processing capacity of 50 mL per day, and can treat both radioactive and nonradioactive waste. In the silver catalyzed process, Ag(I) is electrochemically oxidized to Ag(II), which attacks organic species such as tributylphosphate (TBP), tetraphenylborate (TPB), and benzene. In direct electrochemical oxidation, the organic species are destroyed at the surface of the working electrode without the use of silver as an electron transfer agent. This paper focuses on the destruction of tributylphosphate (TBP), although several organic species have been destroyed using this process. The organic species are converted to carbon dioxide, water, and inorganic acids.

Almon, A.C.; Buchanan, B.R.

1990-01-01

13

Electrochemical oxidation of organic waste  

SciTech Connect

Both silver catalyzed and direct electrochemical oxidation of organic species are examined in analytical detail. This paper describes the mechanisms, reaction rates, products, intermediates, capabilities, limitations, and optimal reaction conditions of the electrochemical destruction of organic waste. A small bench-top electrocell being tested for the treatment of small quantities of laboratory waste is described. The 200-mL electrochemical cell used has a processing capacity of 50 mL per day, and can treat both radioactive and nonradioactive waste. In the silver catalyzed process, Ag(I) is electrochemically oxidized to Ag(II), which attacks organic species such as tributylphosphate (TBP), tetraphenylborate (TPB), and benzene. In direct electrochemical oxidation, the organic species are destroyed at the surface of the working electrode without the use of silver as an electron transfer agent. This paper focuses on the destruction of tributylphosphate (TBP), although several organic species have been destroyed using this process. The organic species are converted to carbon dioxide, water, and inorganic acids.

Almon, A.C.; Buchanan, B.R.

1990-12-31

14

Electrochemical carbon dioxide concentrator advanced technology tasks  

NASA Technical Reports Server (NTRS)

Technology advancement studies are reported on the basic electrochemical CO2 removal process to provide a basis for the design of the next generation cell, module and subsystem hardware. An Advanced Electrochemical Depolarized Concentrator Module (AEDCM) is developed that has the characteristics of low weight, low volume, high CO2, removal, good electrical performance and low process air pressure drop. Component weight and noise reduction for the hardware of a six man capacity CO2 collection subsystem was developed for the air revitalization group of the Space Station Prototype (SSP).

Schneider, J. J.; Schubert, F. H.; Hallick, T. M.; Woods, R. R.

1975-01-01

15

DEVELOPMENT OF ELECTROCHEMICAL REDUCTION TECHNOLOGY FOR SPENT OXIDE FUELS  

SciTech Connect

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

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

2003-02-27

16

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

17

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

18

Advanced oxygen sensor with oxide electrode materials  

Microsoft Academic Search

Calcium doped lanthanum and yttrium manganite electrode materials with oxygen deficiency and low polarization resistance (<30?cm2 at 600°C) were tested in new advanced electrochemical sensor for the oxygen measurements. Oxygen sensor with oxide electrodes was showing fast response (t95?5s at 600°C), good reproducibility (±0.04% O2) and long term stability at different oxygen concentration.

Pavel Shuk; Robert Jantz; Ulrich Guth

2011-01-01

19

Treatment of Radioactive Organic Wastes by an Electrochemical Oxidation  

Microsoft Academic Search

A waste treatment system by using an electrochemical oxidation (MEO, Mediated Electrochemical Oxidation) was installed at KAERI (Korea Atomic Energy Research Institute) for the treatment of radioactive organic wastes, especially EDTA (Ethylene Diamine Tetraacetic Acid) generated during the decontamination activity of nuclear installations. A cerium and silver mediated electrochemical oxidation technique method has been developed as an alternative for an

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

2007-01-01

20

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

21

Ductile mode electrochemical oxidation assisted micromachining for glassy carbon  

NASA Astrophysics Data System (ADS)

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

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

2015-04-01

22

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

23

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

PubMed

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

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

1995-07-01

24

Vanadium oxide electrode synthesized by electroless deposition for electrochemical capacitors  

NASA Astrophysics Data System (ADS)

A thin film vanadium oxide electrode was synthesized by a simple electroless deposition method. Surface and structural analyses revealed that the deposited oxide is a mixture of amorphous V2O5 and VO2. Electrochemical characterizations of the synthesized vanadium oxide showed capacitive behavior with good cycle life. The electroless deposition of vanadium oxide is inexpensive, easy to process, and environmentally benign, offering a promising route for electrode development for electrochemical capacitors.

Wu, Haoran; Lian, Keryn

2014-12-01

25

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

26

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

27

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

28

Oxalic acid mineralization by electrochemical oxidation processes.  

PubMed

In this study, two electrochemical oxidation processes were utilized to mineralize oxalic acid which was a major intermediate compound in the oxidation of phenols and other aromatic compounds. The anode rod and cathode net were made of a titanium coated with RuO(2)/IrO(2) (Ti-DSA) and stainless steel (S.S. net, SUS304), respectively. First, the Fered-Fenton process, which used H(2)O(2) and Fe(2+) as additive reagents, achieved 85% of TOC removal. It proceeded with ligand-to-metal charge-transfer (LMCT), which was evidenced by the accumulation of metallic foil on the selected cathode. However, in the absence of H(2)O(2)/Fe(2+), it showed a higher TOC removal efficiency while using Cl(-) only as an additive reagent due to the formation of hypochlorite on the anode. It was also found that the mineralization of oxalic acid by electrolysis generated hypochlorite better than the dosage of commercial hypochlorite without electricity. Also, pH value was a major factor that affected the mineralization efficiency of the oxalic acid due to the chlorine chemistry. 99% TOC removal could be obtained by Cl(-) electrolysis in an acidic environment. PMID:21320749

Huang, Yao-Hui; Shih, Yu-Jen; Liu, Cheng-Hong

2011-04-15

29

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

30

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

31

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

32

Recent advances in electrochemical impedance measurement  

Microsoft Academic Search

Summary form only given as follows: Accurate measurements of electrochemical impedance requires highly sophisticated instrumentation, especially in applications where small stimulating signals are employed. The combination of a frequency response analyser (FRA) and a potentiostat are the most widely utilised for these applications, but have limitations when measuring high impedances, or high frequency (>1 MHz). Some of these may be

N. J. Evans; B. Sayers

1994-01-01

33

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

34

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

35

Electrochemical oxidation of reverse osmosis concentrate on mixed metal oxide (MMO) titanium coated electrodes.  

PubMed

Reverse osmosis (RO) membranes have been successfully applied around the world for wastewater reuse applications. However, RO is a physical separation process, and besides the clean water stream (permeate) a reverse osmosis concentrate (ROC) is produced, usually representing 15-25% of the feed water flow and containing the organic and inorganic contaminants at higher concentrations. In this study, electrochemical oxidation was investigated for the treatment of ROC generated during the reclamation of municipal wastewater effluent. Using laboratory-scale two-compartment electrochemical systems, five electrode materials (i.e. titanium coated with IrO2-Ta2O5, RuO2-IrO2, Pt-IrO2, PbO2, and SnO2-Sb) were tested as anodes in batch mode experiments, using ROC from an advanced water treatment plant. The best oxidation performance was observed for Ti/Pt-IrO2 anodes, followed by the Ti/SnO2-Sb and Ti/PbO2 anodes. The effectiveness of the treatment appears to correlate with the formation of oxidants such as active chlorine (i.e. Cl2/HClO/ClO-). As a result, electro-generated chlorine led to the abundant formation of harmful by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs), particularly at Ti/SnO2-Sb and Ti/Pt-IrO2 anodes. The highest concentration of total HAAs (i.e. 2.7 mg L(-1)) was measured for the Ti/SnO2-Sb electrode, after 0.55 Ah L(-1) of supplied specific electrical charge. Irrespective of the used material, electrochemical oxidation of ROC needs to be complemented by a polishing treatment to alleviate the release of halogenated by-products. PMID:21802107

Bagastyo, Arseto Y; Radjenovic, Jelena; Mu, Yang; Rozendal, René A; Batstone, Damien J; Rabaey, Korneel

2011-10-15

36

Electrochemical behavior and determination of clozapine on a glassy carbon electrode modified by electrochemical oxidation.  

PubMed

The adsorptive and electrochemical behaviors of clozapine (CLZ) were investigated on a glassy carbon electrode that was electrochemically treated by anodic oxidation at +1.8 V, following potential cycling in the potential range from -0.8 to 1.0 V vs. Ag/AgCl reference electrode. Based on the obtained electrochemical results, an electrochemical-chemical (EC) mechanism was proposed to explain the electrochemical oxidation of CLZ. The resulting electrochemically pretreated glassy carbon electrode (EPGCE) showed good activity to improve the electrochemical response of the drug. CLZ was accumulated in a phosphate buffer (pH 6) at a certain time, and then determined by differential pulse voltammetry. The anodic and cathodic peak currents showed a linear function in the concentration ranges of 0.1 - 1, 1 - 10 and 10 - 100 microM with various accumulation times. The proposed method was successfully used for the determination of CLZ in pharmaceutical preparations. The preconcentration medium-exchange approach was utilized for the selective determination of the drug in spiked urine samples with satisfactory results. The recovery levels of the method reached 96% (RSD, 1.8%) and 90% (RSD, 2.8%) for urine and plasma samples, respectively. PMID:17420556

Farhadi, Khalil; Karimpour, Ahmad

2007-04-01

37

Electrochemical Assessment of Amperometric Oxidability Level in Water Pollution Monitoring  

Microsoft Academic Search

Three types of electrodes were obtained and characterized in order to use for detection of some electrochemical oxidable organics conventionally considered responsabile in COD parameter evaluation: electrodes based on undoped and Co-doped lead dioxide, electrodeposited from slight acidic solutions on stainless steel support; electrodes based on copper\\/copper oxides obtained in situ in alkaline medium by potential cycling between the selected

Florica Manea; Ciprian Radovan; Ilie Vlaicu

38

Recent advances in microdevices for electrochemical energy conversion and storage  

Microsoft Academic Search

SUMMARY The application of silicon microfabrication technologies to electrochemical devices allows reduction of overall device package to potentially increase volumetric power densities. This review first focuses on some exciting developments in microfuel cells, in particular, solid oxide fuel cells (SOFCs) and proton exchange membrane fuel cells (PEMFCs). The emphasis is given to innovative 2D processing methods, novel 2D architectures of

Gerardo Jose; Hyun Jin In; Ethan Crumlin; George Barbastathis; Yang Shao-Horn

2007-01-01

39

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

40

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

41

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

42

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

43

Progress in electrochemical synthesis of magnetic iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

Recently, magnetic iron oxide particles have been emerged as significant nanomaterials due to its extensive range of application in various fields. In this regard, synthesis of iron oxide nanoparticles with desirable properties and high potential applications are greatly demanded. Therefore, investigation on different iron oxide phases and their magnetic properties along with various commonly used synthetic techniques are remarked and thoroughly described in this review. Electrochemical synthesis as a newfound method with unique advantages is elaborated, followed by design approaches and key parameters to control the properties of the iron oxide nanoparticles. Additionally, since the dispersion of iron oxide nanoparticles is as important as its preparation, surface modification issue has been a serious challenge which is comprehensively discussed using different surfactants. Despite the advantages of the electrochemical synthesis method, this technique has been poorly studied and requires deep investigations on effectual parameters such as current density, pH, electrolyte concentration etc.

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

2014-11-01

44

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

2015-02-01

45

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

46

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

47

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

48

Zinc oxide nanostructures for electrochemical cortisol biosensing  

NASA Astrophysics Data System (ADS)

In this paper, we report on fabrication of a label free, highly sensitive and selective electrochemical cortisol immunosensors using one dimensional (1D) ZnO nanorods (ZnO-NRs) and two dimensional nanoflakes (ZnO-NFs) as immobilizing matrix. The synthesized ZnO nanostructures (NSs) were characterized using scanning electron microscopy (SEM), selective area diffraction (SAED) and photoluminescence spectra (PL) which showed that both ZnO-NRs and ZnO-NFs are single crystalline and oriented in [0001] direction. Anti-cortisol antibody (Anti-Cab) are used as primary capture antibodies to detect cortisol using electrochemical impedance spectroscopy (EIS). The charge transfer resistance increases linearly with increase in cortisol concentration and exhibits a sensitivity of 3.078 K?. M-1 for ZnO-NRs and 540 ?. M -1 for ZnO-NFs. The developed ZnO-NSs based immunosensor is capable of detecting cortisol at 1 pM. The observed sensing parameters are in physiological range. The developed sensors can be integrated with microfluidic system and miniaturized potentiostat to detect cortisol at point-of-care.

Vabbina, Phani Kiran; Kaushik, Ajeet; Tracy, Kathryn; Bhansali, Shekhar; Pala, Nezih

2014-05-01

49

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

50

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

51

Nanostructured transition metal oxides for aqueous hybrid electrochemical supercapacitors  

NASA Astrophysics Data System (ADS)

In this paper, we wish to present an overview of the research carried out in our laboratories with low-cost transition metal oxides (manganese dioxide, iron oxide and vanadium oxide) as active electrode materials for aqueous electrochemical supercapacitors. More specifically, the paper focuses on the approaches that have been used to increase the capacitance of the metal oxides and the cell voltage of the supercapacitor. It is shown that the cell voltage of an electrochemical supercapacitor can be increased significantly with the use of hybrid systems. The most relevant associations are Fe3O4 or activated carbon as the negative electrode and MnO2 as the positive. The cell voltage of the Fe3O4/MnO2 device is 1.8 V and this value was increased to 2.2 V by using activated carbon instead of Fe3O4. These two systems have shown superior behavior compared to a symmetric MnO2/MnO2 device which only works within a 1 V potential window in aqueous K2SO4. Furthermore, the activated carbon/MnO2 hybrid device exhibits a real power density of 605 W/kg (maximum power density =19.0 kW/kg) with an energy density of 17.3 Wh/kg. These values compete well with those of standard electrochemical double layer capacitors working in organic electrolytes.

Cottineau, T.; Toupin, M.; Delahaye, T.; Brousse, T.; Bélanger, D.

2006-03-01

52

Electrochemical properties of inorganic nanoporous oxide coated electrodes  

NASA Astrophysics Data System (ADS)

The ability to produce clean water and produce and store clean energy is essential to society. Hence, technologies that facilitate clean energy and clean water are of great importance. This study focused on utilizing nanoporous insulating oxide materials to alter the chemistry at the electrode/electrolyte interface to improve the performance of a number of clean energy and clean water technologies. Here we have shown that applying a thin-film of SiO2 nanoparticles to an electrochemical capacitor electrode can increase the energy storage capacity by up to 50% at high power ratings. We have developed a geometric model to describe the coating of the porous electrode to explain the increased performance at high power ratings. We have also shown that the coated electrochemical capacitor exhibits a higher capacitance when normalized to BET surface area, suggesting that the coated surface is behaving fundamentally differently than the uncoated surface. We attribute the increase in capacitance to the inherent surface potential of the oxide coating and have shown that if we alter the surface potential of the oxide, we can in turn alter the electrochemical capacitance. In addition, we have determined that when used in capacitive deionization systems, these coatings can increase ion removal and accelerate regeneration, allowing for higher efficiency and less waste water. We have demonstrated that a nanoporous oxide coating can increase the gas production rate and lower the overpotential of the hydrogen evolution reaction via water electrolysis on both stainless steel and carbon electrodes. In addition, this work presents data on utilizing nanoporous oxide coatings on Li-Ion battery cathodes to improve high temperature capacity fade. We also introduce a novel thin-film battery/electrochemical capacitor hybrid device, which can improve the performance of simple thin-film batteries.

Leonard, Kevin C.

53

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

54

Electrochemical oxidation of tantalum and titanium in nitrate melts  

SciTech Connect

The authors present the results of a study of the anode oxidation of tantalum and titanium in nitrate melts. The studies were conducted in NaNO/sub 3/-KNO/sub 3/ (50 mole %) at 515-660 K. They used various electrochemical methods: the volt-ampere curves with linear sweep of the potential and the chronopotentiometric and chronoamperometric dependences were recorded. Oxidation of the metals was realized under galvano- or potentiostatic conditions. X-ray diffraction studies of the oxides were made. The thickness of the oxide film was determined by gravimetric, volumetric, or spectrophotometric methods. In individual experiments the thickness of the oxide was estimated by means of electron microscopy.

Yurkinskii, V.P.; Firsova, E.G.; Makhalova, M.Yu.; Morachevskii, A.G.

1988-06-20

55

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

56

Electrochemical deposition of zinc oxide nanorods for hybrid solar cells  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) nanorod arrays for inorganic/organic hybrid solar cells were electrochemically deposited on indium tin oxide (ITO) substrates with a rotating disk electrode setup. The addition of a ZnO seed layer on the ITO prior to electrochemical deposition improved the morphology of the nanorods, resulting in nanorods with smaller and homogenous diameters as well as a higher degree of vertical orientation on to the substrate. The ZnO films deposited on the seeded ITO substrates had higher optical transmittance and lower concentration of defects. Chronoamperometric transient curves show that nucleation and coalescence occurred later for bare ITO substrates, indicating lower densities of initial nuclei, resulting in the growth of nanorods with larger diameters. The solar cell characteristics of the devices fabricated from the seeded ITO substrates were better. The seed layer also acts as a hole-blocking layer, preventing the direct contact between the hole-transporting polymer material and the ITO.

Torres Damasco Ty, Jennifer; Yanagi, Hisao

2015-04-01

57

Nitrogen-doped reduced graphene oxide electrodes for electrochemical supercapacitors.  

PubMed

Herein we use Nitrogen-doped reduced Graphene Oxide (N-rGO) as the active material in supercapacitor electrodes. Building on a previous work detailing the synthesis of this material, electrodes were fabricated via spray-deposition of aqueous dispersions and the electrochemical charge storage mechanism was investigated. Results indicate that the functionalised graphene displays improved performance compared to non-functionalised graphene. The simplicity of fabrication suggests ease of up-scaling of such electrodes for commercial applications. PMID:24418938

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

2014-02-14

58

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

59

Cobalt(III)-mediated oxidative destruction of phenol using divided electrochemical cell  

Microsoft Academic Search

Mediated electrochemical oxidation is one of the suitable processes for the destruction of hazardous organic compounds and\\u000a the dissolution of nuclear wastes at ambient temperature and pressure. The electrochemical oxidation of Co(II) was carried\\u000a out in an undivided and divided electrochemical cell. The formation of Co(III) was studied in an divided electrochemical cell\\u000a by varying conditions such as temperature and

Manickam Matheswaran; Sang Joon Chung; Il Shik Moon

2008-01-01

60

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

E-print Network

ENCH 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, with emphasis on the principle and performance of batteries, supercapacitors and fuel cells. The objective

Rubloff, Gary W.

61

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

62

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

63

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

64

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

65

Treatment of landfill leachate by electrochemical oxidation and anaerobic process.  

PubMed

The removal performance of typical refractory organic compounds in landfill leachate was investigated during the electrochemical (EC) oxidation and anaerobic process combined treatment system in this paper. The results indicated that the treatment of landfill leachate by the combined system was highly effective. The toxicity of leachate was notably decreased after the electrochemical oxidation process and the biodegradability was improved. The concentration of the organic acid with low molecular weight in the leachate increased from 28% to 90% based on the biodegradability assays after the EC oxidation process. The anaerobic digestion could further remove the residual organic compounds. At a hydraulic retention time (HRT) of 16 hours and an organic loading rate (OLR) of 8 kg COD/m3 d, the concentration of COD, SS, ALK, VA, N-TKN, N-NH4+ and P-PO4(3)- [corrected] in UASB effluent were 532, 12, 6744, 400, 540, 455 and 11.6 mg/L, respectively, with approximately 90% removal efficiency of COD. The organic compounds in the landfill leachate revealed different degradation characteristics in the combined system. p-chloroaniline, bisphenol A, 6-methyl-2-phenyl-quinoline, dimethylnaphthaline and N'-(2-methyl-4-chlorophenyl)-N-cyclohexyformamidine, classified into the first group in this paper, were completely removed by the EC oxidation and did not reappear in the effluent of the UASB reactor. Phenylacetic acid, 3-methyl-indole and N-cyclohexyl-acetamide, called the second group, were completely removed, but reappeared in the UASB reactor. 4-methyl-phenol, 3,4-dihydroisoquinoline, 2(3H)-benzothiazolone, exo-2-hydroxycineole and benzothiazole, the third group, were degraded little in the EC oxidation process, but extensively removed by the anaerobic process. Benzoic acid, benzenepropanoic acid and 2-cyano-3,5-dimethyl-1-hydroxypyrrole, the fourth group, concentration obviously increased in the EC process, but was completely removed in the UASB reactor. The content of volatile fatty acids (VFAs) markedly increased from 0.68% in the leachate to 16.18% in the effluent from the electrochemical oxidation process (EC(effl)). In addition, the degradation rate of organic compounds from the landfill leachate was different in the EC oxidation and anaerobic process. PMID:17571841

Li, Tinggang; Li, Xiufen; Chen, Jian; Zhang, Guoping; Wang, Hongchun

2007-05-01

66

Advanced materials for solid oxide fuel cells  

SciTech Connect

The purpose of this research is to improve the properties of the current state-of-the-art materials used for solid oxide fuel cells (SOFCs). The objectives are to: (1) develop materials based on modifications of the state-of-the-art materials; (2) minimize or eliminate stability problems in the cathode, anode, and interconnect; (3) Electrochemically evaluate (in reproducible and controlled laboratory tests) the current state-of-the-art air electrode materials and cathode/electrolyte interfacial properties; (4) Develop accelerated electrochemical test methods to evaluate the performance of SOFCs under controlled and reproducible conditions; and (5) Develop and test materials for use in low-temperature SOFCs.

Armstrong, T.; Stevenson, J.

1995-12-31

67

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

68

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

69

Electrochemical capacitance of nickel oxide nanotubes synthesized in anodic aluminum oxide templates  

Microsoft Academic Search

Nickel oxide (NiO) nanotubes for supercapacitors were synthesized by chemically depositing nickel hydroxide in anodic aluminum\\u000a oxide templates and thermally annealing at 360 °C. The synthesized nanotubes have been characterized by scanning electron\\u000a microscopy, transmission electron microscopy, and X-ray diffraction. The capacitive behavior of the NiO nanotubes was investigated\\u000a by cyclic voltammetry, galvanostatic charge–discharge experiment, and electrochemical impedance spectroscopy in 6 M

Juan Xu; Lan Gao; Jianyu Cao; Wenchang Wang; Zhidong Chen

70

Destruction of chlorinated organics by cobalt(III)-mediated electrochemical oxidation  

Microsoft Academic Search

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. In this paper, the authors study the Co(III) mediated electrochemical oxidation of ethylene glycol, 1,3-dichloro-2-propanol, 2-monochloro- 1-propanol, and isopropanol in sulfuric acid. The electrochemical reactor had a rotating cylinder anode that

Joseph C. Farmer; F. T. Wang; P. R. Lewis; L. J. Summers

1992-01-01

71

Electrochemically tunable thermal conductivity of lithium cobalt oxide  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

72

Electrochemically tunable thermal conductivity of lithium cobalt oxide.  

PubMed

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

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

2014-01-01

73

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

74

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

Microsoft Academic Search

Mediated electrochemical oxidation was carried out for the destruction of commercial pesticide formulations using cerium(IV) in nitric acid as the mediator electrolyte solution in a bench scale set up. The mediator oxidant was regenerated in situ using an electrochemical cell. The real application of this sustainable process for toxic organic pollutant destruction lies in its ability for long term continuous

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

2009-01-01

75

Cyclic voltammetric deposition of hydrous ruthenium oxide for electrochemical capacitors: effects of codepositing iridium oxide  

Microsoft Academic Search

The electrochemical and textural characteristics of various hydrous ruthenium–iridium oxides (denoted as (Ru+Ir)Ox·nH2O) grown by cyclic voltammetry (CV) were systematically studied for the application of electrochemical (EC) capacitors. The faradaic pseudocapacitance of (Ru+Ir)Ox·nH2O reached the maximum when the depositing solution contained 5 mM RuCl3·xH2O and 1 mM IrCl3·xH2O. The linear dependence of Ccp on Cq* measured respectively by chronopotentiometry (CP)

Chi-Chang Hu; Kwang-Huei Chang

2000-01-01

76

Size-dependent electrochemical oxidation of silver nanoparticles.  

PubMed

Here we quantify the electrochemical oxidation of Ag nanoparticles (NPs) as a function of size by electrostatically attaching Ag NPs synthesized by seed-mediated growth in the presence of citrate (diameter = 8 to 50 nm) to amine-functionalized indium-tin oxide coated glass electrodes (Glass/ITO), obtaining a linear sweep voltammogram from 0.1 V, where Ag(0) is stable, up to 1.0 V, and observing the peak potential (E(p)) for oxidation of Ag(0) to Ag(+). Electrostatic attachment to the organic linker presumably removes direct interactions between Ag and ITO and allows control over the total Ag coverage by altering the soaking time. This is important as both metal-electrode interactions and overall Ag coverage can affect E(p). E(p) shifts positive from an average of 275 to 382 mV as the Ag NP diameter increases for a constant Ag coverage and under conditions of planar diffusion, suggesting a shift in E(p) due to a thermodynamic shift in E(0) for the Ag/Ag(+) redox couple with size. The negative shift in E(p) with decreasing Ag NP radius follows the general trend predicted by theory and agrees with previous qualitative experimental observations. A better understanding of metal nanostructure oxidation is crucial considering their potential use in many different applications and the importance of metal corrosion processes at the nanoscale. PMID:20000318

Ivanova, Olga S; Zamborini, Francis P

2010-01-13

77

Mechanistic and kinetic study of ethylene glycol electrochemical oxidation  

SciTech Connect

The aqueous electrochemical oxidation of ethylene glycol to CO{sub 2} has potential significance in fuel cell technology. In our previous studies, a complex system of reaction pathways for ethylene glycol oxidation has been determined. In this study, cyclic voltammetry, chronoamperometry, and infrared spectroscopy are combined to measure the relative amounts of CO{sub 2} and adsorbed CO produced during the oxidation of ethylene glycol by a platinum electrode at 0.30 V/sce in 0.10 M perchloric acid solution. The results of these experiments are compared to similar results for glycol aldehyde, glyoxal, glycolic acid, glyoxilic acid and oxalic acid. A mathematical model based on these results is used to determine that 75% of the reacting ethylene glycol molecules are converted directly to CO{sub 2} by the scission of the carbon-carbon bond. The remaining reacting molecules are converted to glycol aldehyde and then oxidized to desorbed gylcolic acid and CO{sub 2} or adsorbed CO.

Wieland, B.; Lancaster, J.P.; Ye, X. [Eastern Michigan Univ., Ypsilanti, MI (United States)

1995-12-01

78

Current status of environmental, health, and safety issues of electrochemical capacitors for advanced vehicle applications  

SciTech Connect

Electrochemical capacitors are a candidate for traction power assists in hybrid electric vehicles (HEVs). Other advanced automotive applications, while not the primary focus of current development efforts, are also possible. These include load leveling high-energy batteries, power conditioning electronics, electrically hated catalysts, electric power steering, and engine starter power. Higher power and longer cycle life are expected for electrochemical capacitors than for batteries. Evaluation of environmental, health, and safety (EH and S) issues of electrochemical capacitors is an essential part of the development and commercialization of electrochemical capacitors for advanced vehicles. This report provides an initial EH and S assessment. This report presents electrochemical capacitor electrochemistry, materials selection, intrinsic material hazards, mitigation of those hazards, environmental requirements, pollution control options, and shipping requirements. Most of the information available for this assessment pertains to commercial devices intended for application outside the advanced vehicle market and to experiment or prototype devices. Electrochemical capacitors for power assists in HEVs are not produced commercially now. Therefore, materials for advanced vehicle electrochemical capacitors may change, and so would the corresponding EH and S issues. Although changes are possible, this report describes issues for likely electrochemical capacitor designs.

Vimmerstedt, L.J.; Hammel, C.J.

1997-04-01

79

Electrochemical investigations of advanced materials for microelectronic and energy storage devices  

Microsoft Academic Search

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

Pubudu Chaminda Goonetilleke

2008-01-01

80

Electrochemical test methods for advanced battery and semiconductor technology  

NASA Astrophysics Data System (ADS)

This dissertation consists of two studies. The first study was the evaluation of metallic materials for advanced lithium ion batteries and the second study was the determination of the dielectric constant k for the low-k materials. The advanced lithium ion battery is miniature for implantable medical devices and capable of being recharged from outside of the body using magnetic induction without physical connections. The stability of metallic materials employed in the lithium ion battery is one of the major safety concerns. Three types of materials---Pt-Ir alloy, Ti alloys, and stainless steels---were evaluated extensively in this study. The electrochemical characteristics of Pt-Ir alloy, Ti alloys, and stainless steels were evaluated in several types of battery electrolytes in order to determine the candidate materials for long-term use in lithium ion batteries. The dissolution behavior of these materials and the decomposition behavior of the battery electrolyte were investigated using the anodic potentiodynamic polarization (APP) technique. Lifetime prediction for metal dissolution was conducted using constant potential polarization (CPP) technique. The electrochemical impedance spectroscopy (EIS) technique was employed to investigate the metal dissolution behavior or the battery electrolyte decomposition at the open circuit potential (OCP). The scanning electron microscope (SEM) was used to observe the morphology changes after these tests. The effects of experimental factors on the corrosion behaviors of the metallic materials and stabilities of the battery electrolytes were also investigated using the 23 factorial design approach. Integration of materials having low dielectric constant k as interlayer dielectrics and/or low-resistivity conductors will partially solve the RC delay problem for the limiting performance of high-speed logic chips. The samples of JSR LKD 5109 material capped by several materials were evaluated by using EIS. The feasibility of using EIS to determine the dielectric constant k of the low-k materials was also evaluated in this study. The test results demonstrated that the EIS technique is a powerful method in the study of low-k materials.

Hsu, Chao-Hung

81

Removal of Chloride from Wastewater by Advanced Softening Process Using Electrochemically Generated Aluminum Hydroxide  

E-print Network

solubility. Chloride can be removed from water and wastewater by precipitation as calcium chloroaluminate using advanced softening process. This research was conducted to evaluate chloride removal using electrochemically generated aluminum hydroxide and lime...

Mustafa, Syed Faisal

2014-07-23

82

Electrochemical oxidation and reuse of tannery saline wastewater.  

PubMed

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

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

2010-08-15

83

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

84

Mechanistic studies of the electrochemical oxidation of Mn(II)  

SciTech Connect

The electrochemical oxidation of Mn(II) has been investigated using voltammetric and in-situ spectroelectrochemical techniques. Various experimental parameters were found to exert significant effects on the process and its products. The Mn(III) or MnO{sub 4}{sup {minus}} species is produced depending on the electrode potentials, concentrations of Mn(II), voltage scan rates, and initial potentials during potential scans. These effects are discussed in terms of the equilibrium reactions between Mn(III) and MnO{sub 2} films and relative stabilities of the products. The Mn(III) is shown to be produced from an early stage of the anodic potential scan and to undergo disproportionation-conproportionation reactions depending on the concentration of each species near the electrode surface.

Zhang, H.; Park, S.M. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemistry

1994-12-31

85

Microwave-electrochemical formation of colloidal zinc oxide at fluorine doped tin oxide electrodes  

Microsoft Academic Search

Colloidal ZnO is obtained during microwave-enhanced electrochemical deposition experiments from an aqueous solution containing 0 1 M Zn(NO(3))(2) and 0 02 M H(2)O(2) via repetitive negative going potential cycles from 03 to 0 8 V vs SCE The effects of temperature and temperature gradients on ZnO electro formation at fluorine doped tin oxide (FTO) electrodes are investigated with both a

Liza Rassaei; Robben Jaber; Stephen E. Flower; Karen J. Edler; Richard G. Compton; Tony D. James; Frank Marken

2010-01-01

86

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

87

Electrochemical, H2O2-Boosted Catalytic Oxidation System  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

88

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

89

Combination of Electrokinetic Separation and Electrochemical Oxidation for Acid Dye Removal from Soil  

Microsoft Academic Search

The remediation of kaolin soil contaminated with Acid Blue 25 was performed by a combination of electrokinetic separation and electrochemical degradation. The anionic dye was removed from the soil mainly by electroosmosis towards the cathode, with up to 89% removal being achieved at 30 mA for 7 days. The dye solution was completely mineralized in a separate electrochemical oxidation process using

You-Jin Lee; Hyoyeol Han; Seong-Hye Kim; Ji-Won Yang

2009-01-01

90

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

91

Electrochemical and In Situ Optical Studies of Supported Iridium Oxide Films in Aqueous Solutions  

E-print Network

Electrochemical and In Situ Optical Studies of Supported Iridium Oxide Films in Aqueous Solutions oxide IrOx films supported on Au microelec- trodes during charge and discharge have been investigated in its various states of oxidation were sought from in situ transmission measurements for IrOx films

Taylor, Philip L.

92

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

93

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

94

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

95

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

96

Iron Photolysis for Advanced Oxidation Processes  

E-print Network

of having harmful effects on the public if not properly eliminated. Advanced Oxidation Processes (AOPs Engineering Department, University of Arizona University of Arizona, Technology and Research Initiative Fund into effectively treating and recycling water to make use of what is accessible within such a low-water environment

Fay, Noah

97

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...

98

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...

99

Electrochemical instability of indium tin oxide (ITO) glass in acidic pH range during cathodic polarization  

Microsoft Academic Search

Indium tin oxide (ITO) glass substrates are widely used in electrochemical devices and as substrates for insitu spectro-electrochemical experiments owing to their interesting optical, electrical and electrochemical properties. In this work, we found ITO surfaces to undergo substantial changes in their properties on potentiodynamic stresses in the acidic pH range. The surface changes occurring during cathodic cycling of ITO were

M. Senthilkumar; J. Mathiyarasu; James Joseph; K. L. N. Phani; V. Yegnaraman

2008-01-01

100

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

Microsoft Academic Search

A novel room temperature electrochemical process for the synthesis of single-phase Tl2Ba2Ca2Cu3O10 (TBCCO\\/Tl-2223) superconducting films has been developed. Electrochemical parameters were optimized by studying linear sweep voltammetry (LSV), cyclic voltammetry (CV) and chronoamperometry (CA) for the deposition of Tl–Ba–Ca–Cu alloy at room temperature. The superconducting films of the TBCCO were obtained by two oxidation techniques. In the first technique, the

P M Shirage; D D Shivagan; S H Pawar

2004-01-01

101

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

Microsoft Academic Search

A novel room temperature electrochemical process for the synthesis of single-phase Tl2Ba2Ca2Cu3O10 (TBCCO\\/Tl-2223) superconducting films has been developed. Electrochemical parameters were optimized by studying linear sweep voltammetry (LSV), cyclic voltammetry (CV) and chronoamperometry (CA) for the deposition of Tl-Ba-Ca-Cu alloy at room temperature. The superconducting films of the TBCCO were obtained by two oxidation techniques. In the first technique, the

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

2004-01-01

102

Advanced Oxidation Technology for Pulp Mill Effluent  

E-print Network

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... parameters. The dissolved solids consist of the chemicals derived from the wood material plus the chemicals added to the specific pulping process. No one technology can adequately treat these effluent streams, rather a combination of treatment methods...

Hart, J. R.

103

Preparation and characterization of the electrodeposited NiCo oxide thin films for electrochemical capacitors  

Microsoft Academic Search

Nickel-cobalt (Ni-Co) oxide thin films were electrodeposited onto copper substrates in an electrolyte containing cobalt chloride\\u000a and nickel chloride, and the electrochemical capacitor behaviors of these films were investigated. The XRD pattern revealed\\u000a that the electrodeposited Ni-Co oxide thin film was comprised of NiCo2O4. In the SEM image, the electrodeposited Ni-Co oxide film was covered with hexagonal and cubical shaped

Sunil Ganpat Kandalkar; Hae-Min Lee; Seung Hye Seo; Kangtaek Lee; Chang-Koo Kim

2011-01-01

104

Characterization of advanced oxidation regenerated GACs  

SciTech Connect

Industrial and manufacturing processes that employ organic solvents, such as pharmaceutical production, spray booth coating applications, and petrochemical processing, constitute a major source of airborne volatile organic contaminants (VOCs) and hazardous air pollutants (HAPs). VOCs released into the atmosphere react with sunlight to create photochemical smog, oxidants and other pollutants, all of which are considered harmful to animal and plant life. There is thus a need for effective air pollution remediation technologies for such facilities. This paper explores the effects of regeneration by means of advanced oxidation involving UV and ozone, on several properties of granular activated carbons (GACs). The effects of reduction in surface areas and pore volumes, and surface oxidation due to this process of regeneration, on adsorption capacities of some model VOCs is investigated.

Singh, J. [Pennsylvania State Univ., Erie, PA (United States). Dept. of Civil and Environmental Engineering; Cannon, F.S. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Civil and Environmental Engineering

1995-11-01

105

Advances in electrochemical detection for study of neurodegenerative disorders.  

PubMed

Several severe neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and prion-associated transmissible spongiform encephalopathies, have been linked to dysregulation of specific proteins capable of self-assembly into deleterious fibrillar aggregates termed amyloids. A wide range of analytical techniques has been used to clarify the mechanisms of these protein-misfolding processes, in the hope of developing effective therapeutic treatment. Most of these studies have relied heavily on conventional methods of protein characterization, notably circular dichroism spectroscopy, thioflavin T fluorescence, transmission electron microscopy, and atomic force microscopy, which are particularly suitable for monitoring later-stage aggregate formation. Although electrochemical methods of protein detection have existed for some time, they have only recently gained prominence as a powerful tool for studying the early stages of protein aggregation during which the more toxic soluble amyloid species form. Electrochemical detection methods include direct detection of intrinsic redox-active amino acid residues, protein-catalyzed hydrogen evolution, use of extrinsic ?-sheet binding mediators, and impedance spectroscopy. In this review, we evaluate the use of electrochemistry for study of protein aggregation related to neurodegenerative disorders. PMID:23529415

Veloso, Anthony; Kerman, Kagan

2013-07-01

106

Destruction of aniline by mediated electrochemical oxidation with Ce(IV) and Co(III) as mediators  

Microsoft Academic Search

Mediated electrochemical oxidation has been employed to test the feasibility of treating soluble organic wastes. We report Ce(IV)- and Co(III)-mediated electrochemical oxidation of aniline at various electrodes in acidic media as an example of organic waste. Aniline was oxidized by an electrogenerated electron transfer mediator, Ce4+ or Co3+, in the anolyte and carbon dioxide was produced as a final oxidation

Y. H. Chung; S.-M. Park

2000-01-01

107

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

108

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

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

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

111

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

112

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

113

Iron Photolysis for Advanced Oxidation Processes  

E-print Network

.7 (H2SO4) 1mM H2O2 0.8mM H2O2 0.7mM H2O2 #12; Thanks to Water Sustainability Program and Saez research.05 mM FeII + 0.03 mM FeIII #12;Para-cresol degradation in photo- Fenton system 0 0.1 0.2 0.3 0.4 0.5 0 and ultraviolet light Advanced Oxidation #12;photo-Fenton system #12;Procedure 300 mL reactor, constantly stirred

Fay, Noah

114

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

115

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

116

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

117

Electrochemical Characteristics of AZ31 Magnesium Alloys with Microarc Oxidation Coating Alycia Berman1  

E-print Network

Electrochemical Characteristics of AZ31 Magnesium Alloys with Microarc Oxidation Coating Alycia arisen in recent years is the use of magnesium alloys due to their excellent mechanical properties. Magnesium alloys have many properties comparable to bone, including strength-to-weight ratio, density

Zhou, Yaoqi

118

Continuous treatment of textile wastewater by combined coagulation, electrochemical oxidation and activated sludge  

Microsoft Academic Search

Treatment of text wastewaters from a large dyeing and finishing mill by a continuous process of combined chemical coagulation, electrochemical oxidation and activated sludge treatment is investigated. The experimental results are assessed in terms of COD and color (turbidity) reductions to determine the overall treatment efficiency of the combined process. Operating variables, such as the wastewater flow rate, conductivity, pH,

Sheng H. Lin; Chi F. Peng

1996-01-01

119

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

Microsoft Academic Search

The goal of this research is to develop a method to treat mixed hazardous wastes containing selected organic compounds and heavy metals, including actinide elements. One approach is to destroy the organic via electrochemical oxidation to carbon dioxide, then recover the metal contaminants through normally accepted procedures such as ion exchange, precipitation, etc. The authors have chosen to study the

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

1993-01-01

120

Written-in conductive patterns on robust graphene oxide biopaper by electrochemical microstamping.  

PubMed

The silk road: By employing silk fibroin as a binder between graphene oxide films and aluminum foil for a facile, highly localized reduction process, conductive paper is reinvented. The flexible, robust biographene papers have high toughness and electrical conductivity. This electrochemical written-in approach is readily applicable for the fabrication of conductive patterned papers with complex circuitries. PMID:24214828

Hu, Kesong; Tolentino, Lorenzo S; Kulkarni, Dhaval D; Ye, Chunhong; Kumar, Satish; Tsukruk, Vladimir V

2013-12-16

121

Electrochemical protection of zirconium in oxidizing hydrochloric acid solutions  

SciTech Connect

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

Yuu, T-L.; Maguire, M.

1984-06-01

122

Manganese Oxide Film Electrodes Prepared by Electrostatic Spray Deposition for Electrochemical Capacitors  

Microsoft Academic Search

Porous manganese oxide thin film electrodes were prepared for use in electrochemical capacitors by electrostatic spray deposition. The as-prepared manganese oxide film showed ideal capacitive behavior after potential cycling within the range of 0.1 to 0.9 V vs saturated calomel electrode in a0 .1 MN a2SO4 electrolyte. Analysis of the X-ray diffraction, X-ray absorption spectroscopy, and Raman scattering data during

Kyung-Wan Nam; Kwang-Bum Kim

2006-01-01

123

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

Microsoft Academic Search

Polyhalide ions, Br?\\/BrCl2-(ClBr2-), are an important redox couple for redox flow batteries. The oxidation–reduction behavior of polyhalide ions on carbon nanotube (CNT) electrodes has been investigated with cyclic voltammetry and electrochemical impedance spectroscopy. The onset oxidation potential of Br?\\/BrCl2-(ClBr2-) is negatively shifted by>100mV, and the redox current peaks are greatly enhanced on the CNT electrode compared with that on the

Yuyan Shao; Mark H. Engelhard; Yuehe Lin

2009-01-01

124

Electrochemical oxidation of phenol for wastewater treatment using SnO 2 , anodes  

Microsoft Academic Search

The electrochemical oxidation of phenol for waste water treatment was studied on doped SnO2 anodes. Analysis of reaction intermediates and a carbon balance has shown that the main reaction is oxidation of phenol to CO2. This unexpected behaviour of the SnO2 anode is explained by a change of the chemical structure of the electrode surface during anodic polarization.

Ch. Comninellis; C. Pulgarin

1993-01-01

125

Preparation and electrochemical capacitance of cobalt oxide (Co 3O 4) nanotubes as supercapacitor material  

Microsoft Academic Search

Cobalt oxide (Co3O4) nanotubes have been successfully synthesized by chemically depositing cobalt hydroxide in anodic aluminum oxide (AAO) templates and thermally annealing at 500°C. The synthesized nanotubes have been characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The electrochemical capacitance behavior of the Co3O4 nanotubes electrode was investigated by cyclic voltammetry, galvanostatic charge–discharge studies

Juan Xu; Lan Gao; Jianyu Cao; Wenchang Wang; Zhidong Chen

2010-01-01

126

Indirect electrochemical oxidation of cyanide by hydrogen peroxide generated at a carbon cathode  

Microsoft Academic Search

The oxidation of cyanide was performed in aqueous sodium hydroxide solutions. Cyanide was oxidized over 90% to cyanate by hydrogen peroxide electrochemically generated at a 60ppi reticulated vitreous carbon electrode from oxygen reduction. Cyanide depletion was recorded as a function of time from the analysis of cyanide based on the titration procedure using silver nitrate with p-dimethylamino-benzal-rhodanine indicator. Cyanate was

Carlos Antonio Pineda Arellano; Susana Silva Martínez

2007-01-01

127

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; Lewis, ANL: Michele

2011-01-06

128

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

129

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

130

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

131

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...

132

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...

133

Electrochemical approaches for the fabrication and/or characterization of pure and hybrid templated mesoporous oxide thin films: a review.  

PubMed

Electrochemistry can be used for fabrication and characterization of mesoporous oxide films. First, this review provides insight into the methods used to prepare templated mesoporous thin films on an electrode surface, i.e., evaporation-induced self-assembly (EISA) and electrochemically assisted self-assembly (EASA). Electrochemical characterization of mass transport processes in pure and organically functionalized mesoporous oxide films is then discussed. The electrochemical response can be basically restricted by the electron/mass transfer reaction at the electrode-film interface and diffusion through mesopore channels. The contributions of cyclic voltammetry, hydrodynamic voltammetry, electrochemical impedance spectroscopy, and scanning electrochemical microscopy to the characterization of films with distinct mesostructures are finally described, with special emphasis on identification of conditions that can affect the electrochemical response recorded with such modified electrodes. PMID:22941177

Etienne, Mathieu; Guillemin, Yann; Grosso, David; Walcarius, Alain

2013-02-01

134

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

Microsoft Academic Search

The electrochemical and structural properties of cobalt oxide films which are deposited at different sputtering gas-ratios of O2\\/(Ar+O2) are investigated. In order to examine the electrochemical properties of the as-deposited films, all solid-state thin-film supercapacitors (TFSCs) are fabricated. There consist of Co3O4 electrodes and an amorphous LiPON thin-film electrolyte. It is shown that the capacitance behaviour of the Co3O4\\/LiPON\\/Co3O4 TFSCs

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

2001-01-01

135

Role of Nanostructure in Electrochemical Corrosion and High Temperature Oxidation: A Review  

NASA Astrophysics Data System (ADS)

The extremely fine grain size of nanocrystalline (nc) metallic alloys results in significantly different mechanical, electrochemical and oxidation properties as compared to the coarse-grained alloys of the same composition. Although the synthesis and attractive mechanical properties of nanocrystalline materials have been investigated and reviewed in great depth, the high temperature oxidation and electrochemical corrosion of these materials has received limited attention. The difference in the active dissolution and passivation behavior of nc alloys as compared to their microcrystalline counterparts varies for each alloy system. However, a unified theory explaining these phenomena still eludes us. In this context, this article reviews the progress in the electrochemical corrosion behavior of different nanocrystalline alloys, and hence, develops a better understanding of the effect of grain size, composition, interfacial phenomena and selective dissolution on corrosion of nanocrystalline alloys. This review also presents the role of nanometric grain size and the associated increase in grain boundary diffusion on the high temperature oxidation of nc alloys. The attractive possibility of enhanced oxidation resistance at lower alloying additions as compared to the coarse-grained alloys has been discussed. Although the primary focus of the article is on ferrous alloy systems, however, the lead studies on the role of ultrafine grain size in oxidation/corrosion behavior of other alloys systems have also been reviewed.

Mahesh, B. V.; Raman, R. K. Singh

2014-11-01

136

Linear Oligoarylamines: Electrochemical, EPR, and Computational Studies of Their Oxidative States.  

PubMed

A series of straight-chain oligoarylamines were synthesized and examined by electrochemical, spectroelectrochemical, electron paramagnetic resonance techniques, and density functional theory (DFT) calculation. Depending on their electrochemical characteristics, these oligoarylamines were classified into two groups: one containing an odd number and the other an even number of redox centers. In the systems with odd redox centers (N1, N3, and N5), each oxidation was associated with the loss of one electron. As for the systems with even redox centers (N2, N4, and N6), oxidation occurred by taking N2 as a unit. Absorption spectra of linear oligoarylamines at various oxidative states were obtained to investigate their charge transfer behaviors. Moreover, DFT-computed isotropic hyperfine coupling constants and spin density were in accordance with the EPR experiment, and gave a close examination of oligoarylamines at charged states. PMID:25664384

Cheng, Hsu-Chun; Chiu, Kuo Yuan; Lu, Shih Hua; Chen, Ching-Chin; Lee, Yen Wei; Yang, Te-Fang; Kuo, Ming Yu; Chen, Peter Ping-Yu; Su, Yuhlong Oliver

2015-03-12

137

Advanced ceramic materials and electrochemical processes at interfaces  

SciTech Connect

Significant progress has been made in controlling the sintering of complex chromites, used as electrical interconnects in solid oxide fuel cells. Small changes in stoichiometry of these ABO{sub 3}-type perovskites can be used to promote liquid-phase sintering and rapid densification. Sample compositions with a slight A-site enrichment were found to undergo two rapid densification steps, leading to a sintered material that was fully dense. Compositions with a slight A-site depletion underwent only the first rapid shrinkage event, and could not be sintered to full density. Temperatures required to sinter the lanthanum calcium chromites to full density have been lowered by several hundred degrees relative to that previously possible.

Chick, L.A.; Armstrong, T.R.; Bates, J.L.; Coffey, G.W.; Kingsley, J.J.; Maupin, G.D.; McCready, D.E.; Pederson, L.R. [Pacific Northwest Lab., Richland, WA (United States)

1993-07-01

138

Vanadium oxide nanodisks: Synthesis, characterization, and electrochemical properties  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Highly crystallined VO{sub 1.6}{center_dot}H{sub 2}O nanodisks have been synthesized by using a novel solid-solution-solid growth process. Black-Right-Pointing-Pointer The nanodisks are assembled from nanoparticles. Black-Right-Pointing-Pointer PEG-4000 plays an important role for the formation of the nanodisks. Black-Right-Pointing-Pointer The as-synthesized nanodisks exhibit good electrochemical behavior. -- Abstract: Highly crystallined VO{sub 1.6}{center_dot}H{sub 2}O nanodisks assembled from nanoparticles have been successfully fabricated under hydrothermal conditions by using bulk V{sub 2}O{sub 5} and Na{sub 2}S{sub 2}O{sub 3} as the starting materials in the presence of surfactant polyethylene glycol 4000 (PEG-4000). The nanodisks have a diameter of 200 nm and thickness of 40 nm. Hollow nanodisks are occasionally observed, which is similar to Chinese ancient copper coins. The formation of nanodisks can be ascribed to a novel solid-solution-solid growth mechanism. Compared with other methods, the solid state transformation method is simple and economic. In addition, the nanodisks exhibit good electrochemical behavior and promising to be used in lithium-ion battery.

Ren, Ling [Key Laboratory of Cluster Science, Ministry of Education of China, Department of Chemistry, Beijing Institute of Technology, Beijing 100081 (China)] [Key Laboratory of Cluster Science, Ministry of Education of China, Department of Chemistry, Beijing Institute of Technology, Beijing 100081 (China); Cao, Minhua, E-mail: caomh@bit.edu.cn [Key Laboratory of Cluster Science, Ministry of Education of China, Department of Chemistry, Beijing Institute of Technology, Beijing 100081 (China)] [Key Laboratory of Cluster Science, Ministry of Education of China, Department of Chemistry, Beijing Institute of Technology, Beijing 100081 (China); Shi, Shufeng [Department of Chemistry, Northeast Normal University, Changchun 13324 (China)] [Department of Chemistry, Northeast Normal University, Changchun 13324 (China); Hu, Changwen [Key Laboratory of Cluster Science, Ministry of Education of China, Department of Chemistry, Beijing Institute of Technology, Beijing 100081 (China)] [Key Laboratory of Cluster Science, Ministry of Education of China, Department of Chemistry, Beijing Institute of Technology, Beijing 100081 (China)

2012-01-15

139

Theoretical investigation of the activity of cobalt oxides for the electrochemical oxidation of water.  

PubMed

The presence of layered cobalt oxides has been identified experimentally in Co-based anodes under oxygen-evolving conditions. In this work, we report the results of theoretical investigations of the relative stability of layered and spinel bulk phases of Co oxides, as well as the stability of selected surfaces as a function of applied potential and pH. We then study the oxygen evolution reaction (OER) on these surfaces and obtain activity trends at experimentally relevant electro-chemical conditions. Our calculated volume Pourbaix diagram shows that ?-CoOOH is the active phase where the OER occurs in alkaline media. We calculate relative surface stabilities and adsorbate coverages of the most stable low-index surfaces of ?-CoOOH: (0001), (0112), and (1014). We find that at low applied potentials, the (1014) surface is the most stable, while the (0112) surface is the more stable at higher potentials. Next, we compare the theoretical overpotentials for all three surfaces and find that the (1014) surface is the most active one as characterized by an overpotential of ? = 0.48 V. The high activity of the (1014) surface can be attributed to the observation that the resting state of Co in the active site is Co(3+) during the OER, whereas Co is in the Co(4+) state in the less active surfaces. Lastly, we demonstrate that the overpotential of the (1014) surface can be lowered further by surface substitution of Co by Ni. This finding could explain the experimentally observed enhancement in the OER activity of Ni(y)Co(1-y)O(x) thin films with increasing Ni content. All energetics in this work were obtained from density functional theory using the Hubbard-U correction. PMID:23944254

Bajdich, Michal; García-Mota, Mónica; Vojvodic, Aleksandra; Nørskov, Jens K; Bell, Alexis T

2013-09-11

140

Performance Evaluation of SOFC System usingElectrochemical Direct Oxidation of Methane  

NASA Astrophysics Data System (ADS)

We evaluated the performance of systems composed of a solid oxide fuel cell (SOFC) using electrochemical direct oxidation of methane and a conventional steam-reforming-type SOFC (SRSOFC). Net thermal efficiency in an atmospheric partial-oxidation-type SOFC (POSOFC)-SRSOFC system was 8% higher than that in a simple SRSOFC system in the output range of more than 35 kW. The efficiency in a pressurized POSOFC-SRSOFC-gas-turbine (GT) system was slightly higher than that in a pressurized SRSOFC-GT system.

Yokoo, Masayuki; Take, Tetsuo; Ohtsu, Satoshi

141

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

142

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

NASA Astrophysics Data System (ADS)

A series of chitosan (CS) nanocomposites incorporated with graphene oxide (GO) nanosheets were facilely prepared by sonochemical method. Characterized by scanning electron microscopy, the obtained nanocomposites showed fine dispersion of GO in the CS matrix. Meanwhile, a marked interfacial interaction was also revealed as the values of glass transition temperature, the decomposition temperature and the storage modulus were significantly increased with the addition of GO. Furthermore, the well dispersed GO nanosheets could significantly improve the electrochemical activity of the CS as demonstrated by the electrochemical behaviors of pure CS and the GO/CS composite electrodes. Hence, the GO/CS nanocomposites film could be a promising candidate in the fabrication of electrochemical biosensors.

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

2014-09-01

143

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

144

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

145

Microfluidic Electrochemical Sensor for On-line Monitoring of Aerosol Oxidative Activity  

PubMed Central

Particulate matter (PM) air pollution has a significant impact on human morbidity and mortality; however, the mechanisms of PM-induced toxicity are poorly defined. A leading hypothesis states that airborne PM induces harm by generating reactive oxygen species (ROS) in and around human tissues, leading to oxidative stress. We report here, a system employing a microfluidic electrochemical sensor coupled directly to a Particle-into-Liquid-Sampler (PILS) system to measure aerosol oxidative activity in an on-line format. The oxidative activity measurement is based on the dithiothreitol assay (DTT assay) where after oxidized by PM, the remaining reduced DTT was analyzed by the microfluidic sensor. The sensor consists of an array of working, reference, and auxiliary electrodes fabricated in a poly(dimethylsiloxane) (PDMS)-based microfluidic device. Cobalt (II) phthalocyanine (CoPC)-modified carbon paste was used as the working electrode material allowing selective detection of reduced DTT. The electrochemical sensor was validated off-line against the traditional DTT assay using filter samples taken from urban environments and biomass burning events. After off-line characterization, the sensor was coupled to a PILS to enable on-line sampling/analysis of aerosol oxidative activity. Urban dust and industrial incinerator ash samples were aerosolized in an aerosol chamber and analyzed for their oxidative activity. The on-line sensor reported DTT consumption rates (oxidative activity) in good correlation with aerosol concentration (R2 from 0.86–.97) with a time-resolution of approximately 3 minutes. PMID:22651886

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

2012-01-01

146

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

PubMed

Particulate matter (PM) air pollution has a significant impact on human morbidity and mortality; however, the mechanisms of PM-induced toxicity are poorly defined. A leading hypothesis states that airborne PM induces harm by generating reactive oxygen species in and around human tissues, leading to oxidative stress. We report here a system employing a microfluidic electrochemical sensor coupled directly to a particle-into-liquid sampler (PILS) system to measure aerosol oxidative activity in an on-line format. The oxidative activity measurement is based on the dithiothreitol (DTT) assay, where, after being oxidized by PM, the remaining reduced DTT is analyzed by the microfluidic sensor. The sensor consists of an array of working, reference, and auxiliary electrodes fabricated in a poly(dimethylsiloxane)-based microfluidic device. Cobalt(II) phthalocyanine-modified carbon paste was used as the working electrode material, allowing selective detection of reduced DTT. The electrochemical sensor was validated off-line against the traditional DTT assay using filter samples taken from urban environments and biomass burning events. After off-line characterization, the sensor was coupled to a PILS to enable on-line sampling/analysis of aerosol oxidative activity. Urban dust and industrial incinerator ash samples were aerosolized in an aerosol chamber and analyzed for their oxidative activity. The on-line sensor reported DTT consumption rates (oxidative activity) in good correlation with aerosol concentration (R(2) from 0.86 to 0.97) with a time resolution of approximately 3 min. PMID:22651886

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

2012-06-27

147

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

148

Tin Oxide Nanorod Array-Based Electrochemical Hydrogen Peroxide Biosensor  

PubMed Central

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. PMID:20596358

2010-01-01

149

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

150

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

151

Mechanistic studies of water electrolysis and hydrogen electro-oxidation on high temperature ceria-based solid oxide electrochemical cells.  

PubMed

Through the use of ambient pressure X-ray photoelectron spectroscopy (APXPS) and a single-sided solid oxide electrochemical cell (SOC), we have studied the mechanism of electrocatalytic splitting of water (H2O + 2e(-) ? H2 + O(2-)) and electro-oxidation of hydrogen (H2 + O(2-) ? H2O + 2e(-)) at ?700 °C in 0.5 Torr of H2/H2O on ceria (CeO2-x) electrodes. The experiments reveal a transient build-up of surface intermediates (OH(-) and Ce(3+)) and show the separation of charge at the gas-solid interface exclusively in the electrochemically active region of the SOC. During water electrolysis on ceria, the increase in surface potentials of the adsorbed OH(-) and incorporated O(2-) differ by 0.25 eV in the active regions. For hydrogen electro-oxidation on ceria, the surface concentrations of OH(-) and O(2-) shift significantly from their equilibrium values. These data suggest that the same charge transfer step (H2O + Ce(3+) <-> Ce(4+) + OH(-) + H(•)) is rate limiting in both the forward (water electrolysis) and reverse (H2 electro-oxidation) reactions. This separation of potentials reflects an induced surface dipole layer on the ceria surface and represents the effective electrochemical double layer at a gas-solid interface. The in situ XPS data and DFT calculations show that the chemical origin of the OH(-)/O(2-) potential separation resides in the reduced polarization of the Ce-OH bond due to the increase of Ce(3+) on the electrode surface. These results provide a graphical illustration of the electrochemically driven surface charge transfer processes under relevant and nonultrahigh vacuum conditions. PMID:23822749

Zhang, Chunjuan; Yu, Yi; Grass, Michael E; Dejoie, Catherine; Ding, Wuchen; Gaskell, Karen; Jabeen, Naila; Hong, Young Pyo; Shavorskiy, Andrey; Bluhm, Hendrik; Li, Wei-Xue; Jackson, Gregory S; Hussain, Zahid; Liu, Zhi; Eichhorn, Bryan W

2013-08-01

152

Electrolytic destruction of spent tributylphosphate extractant using silver catalyzed electrochemical oxidation  

SciTech Connect

Silver catalyzed electrochemical oxidation of organic species is examined in analytical detail. This paper describes the mechanisms, reactions rates, products, intermediates, capabilities, limitations, and optimal reaction conditions of the electrochemical destruction of organic waste. A small bench-top electrocell being tested for the treatment of small quantity laboratory waste is described. The 200 mL electrochemical cell used has a processing capacity of 50 mL per day, and can treat both radioactive and non-radioactive waste. In the silver catalyzed process, Ag(I) is electrochemically oxidized to Ag(II) which attacks organic species such as tributylphosphate (TBP), tetraphenylborate (TPB), and benzene {sup 1,2}. This paper focuses on the destruction of tributylphosphate (TBP) although several organic species have been destroyed using this process. The organic species are converted to carbon dioxide, water, and inorganic acids. The process has the potential for RCRA (Resource Conservation and Recovery Act) waste treatment as well as disposal of large amounts of radioactive organic waste.

Almon, A.C.; Buchanan, B.R.

1990-01-01

153

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

154

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

155

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

156

Oxidative dissolution of chalcopyrite by Acidithiobacillus ferrooxidans analyzed by electrochemical impedance spectroscopy and atomic force microscopy.  

PubMed

The microbiological leaching of chalcopyrite (CuFeS(2)) is of great interest because of its potential application to many CuFeS(2)-rich ore materials. However, the efficiency of the microbiological process is very limited because this mineral is one of the most refractory to bacterial attack. Knowledge of bacterial role during chalcopyrite oxidation is very important in order to improve the efficiency of bioleaching operation. The oxidative dissolution of a massive chalcopyrite electrode by Acidithiobacillus ferrooxidans was evaluated by electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). A massive chalcopyrite electrode was utilized in a Tait-type electrochemical cell in acid medium for different immersion times in the presence or absence of bacterium. The differences observed in the impedance diagrams were correlated with the adhesion process of bacteria on the mineral surface. PMID:15219250

Bevilaqua, D; Diéz-Perez, I; Fugivara, C S; Sanz, F; Benedetti, A V; Garcia, O

2004-08-01

157

Electrochemical activation of Cp* iridium complexes for electrode-driven water-oxidation catalysis.  

PubMed

Organometallic iridium complexes bearing oxidatively stable chelate ligands are precursors for efficient homogeneous water-oxidation catalysts (WOCs), but their activity in oxygen evolution has so far been studied almost exclusively with sacrificial chemical oxidants. In this report, we study the electrochemical activation of Cp*Ir complexes and demonstrate true electrode-driven water oxidation catalyzed by a homogeneous iridium species in solution. Whereas the Cp* precursors exhibit no measurable O2-evolution activity, the molecular species formed after their oxidative activation are highly active homogeneous WOCs, capable of electrode-driven O2 evolution with high Faradaic efficiency. We have ruled out the formation of heterogeneous iridium oxides, either as colloids in solution or as deposits on the surface of the electrode, and found indication that the conversion of the precursor to the active molecular species occurs by a similar process whether carried out by chemical or electrochemical methods. This work makes these WOCs more practical for application in photoelectrochemical dyads for light-driven water splitting. PMID:25188635

Thomsen, Julianne M; Sheehan, Stafford W; Hashmi, Sara M; Campos, Jesús; Hintermair, Ulrich; Crabtree, Robert H; Brudvig, Gary W

2014-10-01

158

Characterization of high-temperature oxide films on stainless steels by electrochemical-impedance spectroscopy  

SciTech Connect

Oxide films formed on three stainless steels (UNS S30403; S44600; S30815) in air at 800 C were characterized by electrochemical-impedance spectroscopy (EIS). The film evolution vs. oxidation time was investigated from 1 to 1000 hr. A three-electrode electrochemical cell and 0.1 M Na{sub 2}SO{sub 4} solution were employed for EIS measurements. The spectra were interpreted in terms of a two-layer model of the films, where the capacitance and resistance obtained can be related to the thickness (or roughness) and defectiveness of the films. The results reveal that the oxide on S30403 grows and becomes defective, the oxide on S44600 thickens rapidly and retains its protective ability for a relatively long time, and the oxide on S30815 remains thin and resistive. The two-layer model is supported by surface characterization with SEM/EDS and in-depth profile of the oxide films obtained through glow discharge optical emission spectroscopy (GDOES).

Pan, J.; Leygraf, C. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Materials Science and Engineering] [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Materials Science and Engineering; Jargelius-Pettersson, R.F.A. [Swedish Inst. for Metals Research, Stockholm (Sweden)] [Swedish Inst. for Metals Research, Stockholm (Sweden); Linden, J. [SANDVIK Steel, Sandviken (Sweden). R and D Centre] [SANDVIK Steel, Sandviken (Sweden). R and D Centre

1998-12-01

159

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

160

Unexpected decomposition of the bis (trifluoromethylsulfonyl) amide anion during electrochemical copper oxidation in an ionic liquid  

Microsoft Academic Search

In this letter we report on the decomposition of the bis (trifluoromethylsulfonyl) amide (TFSA) anion under quite mild electrochemical conditions. The results show clearly that the TFSA anion can easily be decomposed during anodic oxidation of copper in the ionic liquid 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) amide [BMP] TFSA at 70°C leading to the formation of CuF2. At room temperature, however, no

A. S. Ismail; S. Zein El Abedin; O. Höfft; F. Endres

2010-01-01

161

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

162

Structural and electrochemical studies of Co oxide films formed by the sol-gel technique  

Microsoft Academic Search

Two different types of Co oxide films, each having a distinct electrochemical signature correlated with the film drying temperature, were formed using the sol-gel (SG) technique. Two different states of gelation of the film precursor were also explored. Cyclic voltammograms, collected in alkaline solutions for the low temperature films, displayed two pairs of peaks corresponding to the Co(II) to Co(III)

Anne C. Co; Jingbo Liu; Irina Serebrennikova; Cheryl M. Abel; Viola I. Birss

2005-01-01

163

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

Microsoft Academic Search

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,

G. Bryan Balazs; Patricia R. Lewis

1999-01-01

164

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

165

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

166

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. 2 figs.

Balazs, G.B.; Lewis, P.R.

1999-07-06

167

Electrochemical impedance spectroscopy investigation of spinel type cobalt oxide thin film electrodes in alkaline medium  

Microsoft Academic Search

Spinel type Co3O4 thin films, for the oxygen evolution reaction (OER) in 1 M KOH, have been prepared, on stainless steel supports, using the\\u000a thermal decomposition method at 400 °C. The electrochemical behaviour of the oxide film\\/1 M KOH interface was investigated\\u000a by cyclic voltammetry and impedance techniques. The impedance measurements were carried out at different positive potentials,\\u000a from the open circuit potential

E. Laouini; M. Hamdani; M. I. S. Pereira; J. Douch; M. H. Mendonça; Y. Berghoute; R. N. Singh

2008-01-01

168

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

169

Electrochemically deposited gallium oxide nanostructures on silicon substrates.  

PubMed

We report a synthesis of ?-Ga2O3 nanostructures on Si substrate by electrochemical deposition using a mixture of Ga2O3, HCl, NH4OH, and H2O. The presence of Ga3+ ions contributed to the deposition of Ga2O3 nanostructures on the Si surface with the assistance of applied potentials. The morphologies of the grown structures strongly depended on the molarity of Ga2O3 and pH level of electrolyte. ?-Ga2O3 nanodot-like structures were grown on Si substrate at a condition with low molarity of Ga2O3. However, Ga2O3 nanodot structures covered with nanorods on top of their surfaces were obtained at higher molarity, and the densities of nanorods seem to increase with the decrease of pH level. High concentration of Ga3+ and OH- ions may promote the reaction of each other to produce Ga2O3 nanorods in the electrolyte. Such similar nature of Ga2O3 nanorods was also obtained by using hydrothermal process. The grown structures seem to be interesting for application in electronic and optoelectronic devices as well as to be used as a seed structure for subsequent chemical synthesis of GaN by thermal transformation method. PMID:24629107

Ghazali, Norizzawati Mohd; Mahmood, Mohamad Rusop; Yasui, Kanji; Hashim, Abdul Manaf

2014-01-01

170

Electrochemically deposited gallium oxide nanostructures on silicon substrates  

PubMed Central

We report a synthesis of ?-Ga2O3 nanostructures on Si substrate by electrochemical deposition using a mixture of Ga2O3, HCl, NH4OH, and H2O. The presence of Ga3+ ions contributed to the deposition of Ga2O3 nanostructures on the Si surface with the assistance of applied potentials. The morphologies of the grown structures strongly depended on the molarity of Ga2O3 and pH level of electrolyte. ?-Ga2O3 nanodot-like structures were grown on Si substrate at a condition with low molarity of Ga2O3. However, Ga2O3 nanodot structures covered with nanorods on top of their surfaces were obtained at higher molarity, and the densities of nanorods seem to increase with the decrease of pH level. High concentration of Ga3+ and OH- ions may promote the reaction of each other to produce Ga2O3 nanorods in the electrolyte. Such similar nature of Ga2O3 nanorods was also obtained by using hydrothermal process. The grown structures seem to be interesting for application in electronic and optoelectronic devices as well as to be used as a seed structure for subsequent chemical synthesis of GaN by thermal transformation method. PMID:24629107

2014-01-01

171

Metallic nickel nitride nanosheets realizing enhanced electrochemical water oxidation.  

PubMed

Exploring efficient and inexpensive oxygen evolution reaction (OER) electrocatalysts is of great importance for various electrochemical energy storage and conversion technologies. Ni-based electrocatalysts have been actively pursued because of their promising activity and earth abundance. However, the OER efficiency for most of the developed Ni-based electrocatalysts has been intrinsically limited due to their low electrical conductivity and poor active site exposure yield. Herein, we report metallic Ni3N nanosheets as an efficient OER electrocatalyst for the first time. The first-principles calculations and electrical transport property measurements unravel that the Ni3N is intrinsically metallic, and the carrier concentration can be remarkably improved with dimensional confinement. The EXAFS spectra provide solid evidence that the Ni3N nanosheets have disordered structure resultant of dimensional reduction, which then could provide more active sites for OER. Benefiting from enhanced electrical conductivity with metallic behavior and atomically disordered structure, the Ni3N nanosheets realize intrinsically improved OER activity compared with bulk Ni3N and NiO nanosheets. Our finding suggests that metallic nitride nanosheets could serve as a new group of OER electrocatalysts with excellent property. PMID:25761452

Xu, Kun; Chen, Pengzuo; Li, Xiuling; Tong, Yun; Ding, Hui; Wu, Xiaojun; Chu, Wangsheng; Peng, Zhenmeng; Wu, Changzheng; Xie, Yi

2015-04-01

172

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

173

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

174

Electrochromic characterisation of electrochemically deposited nickel oxide films  

NASA Astrophysics Data System (ADS)

Electrochromic hydrated nickel oxide films have been cathodically deposited onto ITO-coated glass substrates from a solution of nickel sulphate and urea at room temperature. The in situ measurements of the response time during the colouring/bleaching process are reported. The dependence of the electrochromic properties on post-deposition heat treatment have been studied. A good optical modulation has been found for un-annealed samples, while samples annealed at higher temperatures showed smaller modulation. The extinction coefficient ( k) has been computed from spectrophotometrically measured transmittance and reflectance. The structural characteristics as well as the surface morphology of some nickel oxide samples were investigated using X-ray diffraction and SEM analysis.

Mahmoud, S. A.; Aly, S. A.; Abdel-Rahman, M.; Abdel-Hady, K.

2000-12-01

175

High-temperature "spectrochronopotentiometry": correlating electrochemical performance with in situ Raman spectroscopy in solid oxide fuel cells.  

PubMed

Carbon formation or "coking" on solid oxide fuel cell (SOFC) anodes adversely affects performance by blocking catalytic sites and reducing electrochemical activity. Quantifying these effects, however, often requires correlating changes in SOFC electrochemical efficiency measured during operation with results from ex situ measurements performed after the SOFC has been cooled and disassembled. Experiments presented in this work couple vibrational Raman spectroscopy with chronopotentiometry to observe directly the relationship between graphite deposited on nickel cermet anodes and the electrochemical performance of SOFCs operating at 725 °C. Raman spectra from Ni cermet anodes at open circuit voltage exposed to methane show a strong vibrational band at 1556 cm(-1) assigned to the "G" mode of highly ordered graphite. When polarized in the absence of a gas-phase fuel, these carbon-loaded anodes operate stably, oxidizing graphite to form CO and CO(2). Disappearance of graphite intensity measured in the Raman spectra is accompanied by a steep ?0.8 V rise in the cell potential needed to keep the SOFC operating under constant current conditions. Continued operation leads to spectroscopically observable Ni oxidation and another steep rise in cell potential. Time-dependent spectroscopic and electrochemical measurements pass through correlated equivalence points providing unequivocal, in situ evidence that identifies how SOFC performance depends on the chemical condition of its anode. Chronopotentiometric data are used to quantify the oxide flux necessary to eliminate the carbon initially present on the SOFC anode, and data show that the oxidation mechanisms responsible for graphite removal correlate directly with the electrochemical condition of the anode as evidenced by voltammetry and impedance measurements. Electrochemically oxidizing the Ni anode damages the SOFC significantly and irreversibly. Anodes that have been reconstituted following electrochemical oxidation of carbon and Ni show qualitatively different kinetics of carbon removal, and the electrochemical performance of these systems is characterized by low maximum currents and large polarization resistances. PMID:23046116

Kirtley, John D; Halat, David M; McIntyre, Melissa D; Eigenbrodt, Bryan C; Walker, Robert A

2012-11-20

176

P450-catalyzed vs. electrochemical oxidation of haloperidol studied by ultra-performance liquid chromatography/electrospray ionization mass spectrometry.  

PubMed

The metabolites formed via the major metabolic pathways of haloperidol in liver microsomes, N-dealkylation and ring oxidation to the pyridinium species, were produced by electrochemical oxidation and characterized by ultra-performance liquid chromatography/electrospray ionization mass spectrometry (UPLC/ESI-MS). Liver microsomal incubations and electrochemical oxidation in the presence of potassium cyanide (KCN) resulted in two diastereomeric cyano adducts, proposed to be generated from trapping of the endocyclic iminium species of haloperidol. Electrochemical oxidation of haloperidol in the presence of KCN gave a third isomeric cyano adduct, resulting from trapping of the exocyclic iminium species of haloperidol. In the electrochemical experiments, addition of KCN almost completely blocked the formation of the major oxidation products, namely the N-dealkylated products, the pyridinium species and a putative lactam. This major shift in product formation by electrochemical oxidation was not observed for the liver microsomal incubations where the N-dealkylation and the pyridinium species were the major metabolites also in the presence of KCN. The previously not observed dihydropyridinium species of haloperidol was detected in the samples, both from electrochemical oxidation and the liver microsomal incubations, in the presence of KCN. The presence of the dihydropyridinium species and the absence of the corresponding cyano adduct lead to the speculation that an unstable cyano adduct was formed, but that cyanide was eliminated to regenerate the stable conjugated system. The formation of the exocyclic cyano adduct in the electrochemical experiments but not in the liver microsomal incubations suggests that the exocyclic iminium intermediate, obligatory in the electrochemically mediated N-dealkylation, may not be formed in the P450-catalyzed reaction. PMID:20391593

Mali'n, Tove Johansson; Weidolf, Lars; Castagnoli, Neal; Jurva, Ulrik

2010-05-15

177

Characterization of transparent zinc oxide films prepared by electrochemical reaction  

Microsoft Academic Search

Transparent zinc oxide (ZnO) films have been grown by galvanostatic cathodic deposition onto conductive glasses from a simple aqueous zinc nitrate electrolyte maintained at 335 K. The as-deposited ZnO films were characterized with Fourier transform infrared absorption spectroscopy, x-ray diffraction, scanning electron microscopy, optical transmission and absorption studies, and measurement of sheet resistivity as a function of cathodic current density.

Masanobu Izaki; Takashi Omi

1997-01-01

178

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

179

Indirect Electrochemical Sensing of DNA Hybridization Based on the Catalytic Oxidation of Cobalt (II)  

PubMed Central

A new electrochemical approach for detecting target DNA is described. The scheme involves the catalytic oxidation of a cobalt bipyridine “reporter molecule” in solution. Probe/target DNA duplexes (ds-DNA), bound on an ITO electrode, selectively recruit redox catalyst molecules from solution. This surface-bound catalyst “turns on” the redox chemistry of the reporter molecule which is otherwise kinetically inert to oxidation on ITO. The mode of selective catalyst binding is intercalation between base pairs of ds-DNA. With this approach, we demonstrate detection of a 20-mer DNA target oligonucleotide at picomolar concentrations with outstanding signal-to-noise. PMID:17260990

Xue, Di; Elliott, C. Michael; Gong, Ping; Grainger, David W.; Bignozzi, Carlo A.; Caramori, Stefano

2008-01-01

180

Experimental study on electrochemical hydrogen pump of SrZrO{sub 3}-based oxide  

SciTech Connect

The electrochemical hydrogen pump properties of the SrZr{sub 0.8}In{sub 0.2}O{sub 3-{alpha}} proton conducting oxide were evaluated under various atmospheres, temperatures and the effect of oxygen gas in the cathode for the recovery of hydrogen isotopes. It was found that high temperature is not necessarily required and protonic conductivity of the proton conducting oxide rather than total conductivity should be observed to improve the performance of the hydrogen pump. Furthermore, the presence of oxygen in the cathode compartment plays an important role in the enhancement of the hydrogen pump performance. (authors)

Tanaka, M.; Asakura, Y.; Uda, T. [National Inst. for Fusion Science, Oroshi, Toki, Gifit, 509-5292 (Japan)

2008-07-15

181

Electrochemical performance evaluation of polyaniline\\/lithium manganese nickel oxide composites synthesized using surfactant agents  

Microsoft Academic Search

The effect of adding a non-ionic surfactant to disperse oxide particles on the electrochemical performance of PAni\\/LiMnNiO4 composites is evaluated by using cyclic voltammetry (CV), impedance measurements and constant-current charge\\/discharge cycling techniques. Three surfactants based on ethoxylated (EO) and propoxylated (PO) lauryl alcohols (3EO\\/6PO, L306; 4EO\\/5PO, L405; and 6EO\\/3PO, L603) were investigated. For comparative purposes, the oxide and polyaniline were

Silmara Neves; Sheila C. Canobre; Rafael S. Oliveira; Carla Polo Fonseca

2009-01-01

182

The electrochemical oxidation of chalcopyrite in ammoniacal solutions  

NASA Astrophysics Data System (ADS)

The anodic dissolution of chalcopyrite in ammoniacal solutions was investigated using electrochemical methods. At low overvoltages, the formation of a copper deficient sulfide layer, Cu1-xFeS2 through a charge transfer reaction is proposed based upon the dependence of the rest or open circuit potential on solution composition and the presence of a Tafel region of appropriate slope. In addition, a current peak that occurs at 10-4 A/cm2 is a function of the square root of the voltage scanning speed and is explained in terms of a charge transfer reaction. At larger overvoltages, constant potential experiments and mass balances performed at various anodic potentials indicate that the dissolution is consistent with the overall reaction, CuFeS2 + 4NH3 + 9OH- = Cu(NH3){4/+2} + Fe(OH)3 + S2O{3/=} + 3H2O + 9e -, although some copper may be released to solution in the cuprous state and some ferrous iron has been identified in the product film. Current vs time data taken during constant potential experiments were found to obey a linear rate relationship. This was interpreted in terms of the formation of a layer of constant thickness which is corroded at the outer interface at the same rate it is formed at the inner interface.. The model proposed is typical of the corrosion of some metals. An examination of the polarization curves shows the dissolution reaction to be first order with respect to [OH-]. The lack of dependence on [Cu2+] indicates that the catalytic effect of cupric ion during oxygen pressure leaching is related only to the cathodic reduction of O2 in agreement with the results of previous investigations.

Warren, G. W.; Wadsworth, M. E.

1984-06-01

183

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

184

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

PubMed

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

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

2008-08-21

185

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

186

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

NASA Astrophysics Data System (ADS)

Nanoporous/cracked structures of cobalt oxide (Co3O4) electrodes were successfully fabricated by electroplating of zinc-cobalt onto previously formed TiO2 nanotubes by anodizing of titanium, leaching of zinc in a concentrated alkaline solution and followed by drying and annealing at 400 °C. The structure and morphology of the obtained Co3O4 electrodes were characterized by X-ray diffraction, EDX analysis and scanning electron microscopy. The results showed that the obtained Co3O4 electrodes were composed of the nanoporous/cracked structures with an average pore size of about 100 nm. The electrochemical capacitive behaviors of the nanoporous Co3O4 electrodes were investigated by cyclic voltammetry, galvanostatic charge-discharge studies and electrochemical impedance spectroscopy in 1 M NaOH solution. The electrochemical data demonstrated that the electrodes display good capacitive behavior with a specific capacitance of 430 F g-1 at a current density of 1.0 A g-1 and specific capacitance retention of ca. 80 % after 10 days of being used in electrochemical experiments, indicating to be promising electroactive materials for supercapacitors. Furthermore, in comparison with electrodes prepared by simple cathodic deposition of cobalt onto TiO2 nanotubes(without dealloying procedure), the impedance studies showed improved performances likely due to nanoporous/cracked structures of electrodes fabricated by dealloying of zinc, which provide fast ion and electron transfer routes and large reaction surface area with the ensued fast reaction kinetics.

Gobal, Fereydoon; Faraji, Masoud

2014-12-01

187

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

188

Electrochemical carbon nanotube filter oxidative performance as a function of surface chemistry.  

PubMed

An electrochemical carbon nanotube filter has been reported to be effective for the removal and electrooxidation of aqueous chemicals and microorganisms. Here, we investigate how carbon nanotube (CNT) chemical surface treatments including calcination to remove amorphous carbon, acid treatment to remove internal residual metal oxide, formation of surficial oxy-functional groups, and addition of Sb-doped SnO(2) particles affect the electrooxidative filter performance. The various CNT samples are characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) and electrochemically evaluated by cyclic voltammetry, open circuit potential versus time analysis, and electrochemical impedance spectroscopy. Voltammetry results indicate that the near CNT surface pH is at least two units lower than the bulk pH. The electrooxidative performance of the various CNT samples is evaluated with 1 mM of methyl orange (MO) in 100 mM sodium sulfate at a flow rate of 1.5 mL min(-1). At both 2 and 3 V, the efficacy of electrochemical filtration is observed to be function of CNT surface chemistry. The samples with the greatest electrooxidation were the calcinated then HCl-treated CNTs, i.e., the CNTs with the most surficial sp(2)-bonded carbon, and the Sb-SnO(2)-coated CNTs, i.e., the CNTs with the most electrocatalytic surface area. At 3 V applied voltage, these CNT samples are able to oxidize 95% of the influent MO within the liquid residence time of <1.2 s. The broader applicability of electrochemical filtration is evaluated by challenging the C-CNT-HCl and C-CNT-HNO(3) networks with various organics including methylene blue, phenol, methanol, and formaldehyde. At 3 V applied voltage, both CNTs are able to degrade a fraction of all the organics with the extent organic degradation dependent on both CNT and organic properties. The C-CNT-HCl network generally had the better oxidative performance than the C-CNT-HNO(3) network with an exception being the positively charged methylene blue. The extent of MO degradation, steady-state current, anode potential, effluent pH, and back pressure are also measured as a function of applied voltage (1-3 V) and CNT surface chemistry. Mass spectrometry of electrochemical CNT filter effluent at 2 and 3 V is utilized to evaluate plausible electrooxidation products. Energy consumption as compared to state-of-the-art electrodes and strategies to tailor the CNT surface for a specific target molecule are discussed. PMID:21967752

Gao, Guandao; Vecitis, Chad D

2011-11-15

189

Electrochemical oxidation of phenolic wastes with boron-doped diamond anodes.  

PubMed

The electrochemical oxidation of several phenolic aqueous wastes has been studied using a bench-scale plant with a single-compartment electrochemical flow cell. Boron-doped diamond materials were used as the anode. Complete mineralization of the waste was obtained in the treatment of phenols not substituted with chlorine or nitrogen. Chlorinated phenolic compounds were transformed into carbon dioxide; volatile organochlorinated compounds and nitro-substituted phenols deal with the formation of polymeric materials. These polymeric materials behave as final products or treatment intermediates depending on the nature of the initial pollutant. The removal of nitro- or the chloro-group from the phenolic molecule seems to be one of the first stages in the treatment. Non-nitrogenated or chlorinated carboxylic acids have been found to be the main intermediates in the electrochemical oxidation of all the phenolic compounds tested. The efficiencies of the process depend strongly on the concentration of organic pollutants and on their nature, and not on the current density, at least in the operation range studied. PMID:15979123

Cañizares, P; Lobato, J; Paz, R; Rodrigo, M A; Sáez, C

2005-07-01

190

Recent advances in porous Pt-based nanostructures: synthesis and electrochemical applications.  

PubMed

Porous Pt-based nanostructured materials possess intriguing physical and chemical properties to generate promising potential for various important applications such as fuel cells, sensors, stimulation electrodes, mechanical actuators and catalysis. With the great advances in material science and nanotechnology, porous Pt-based nanomaterials with well-controlled composition, shape, and geometrical configuration have been rationally designed and fabricated. Importantly, their superior properties including unique pore structure, large specific surface area and excellent structural stability have fuelled up great interest to improve their current performance and to explore new applications. This tutorial review attempts to summarize the recent important progress towards the development of porous Pt-based nanostructured materials, with special emphasis on fabrication methods and advanced electrochemical applications, such as electrocatalysis and electrochemical sensors. The correlations between the composition and morphology of the catalysts and their catalytic properties are discussed based on some important and representative examples. Some key scientific issues and potential future directions of research in this field are also discussed. PMID:24458336

Xu, You; Zhang, Bin

2014-04-21

191

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

192

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

193

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

NASA Astrophysics Data System (ADS)

A facile and novel preparation strategy based on electrochemical techniques for the fabrication of electrodeposited graphene (EGR) and zinc oxide (ZnO) nanocomposite was developed. The morphology and structure of the EGR-based nanocomposite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (XPS) and Raman spectroscopy. Meanwhile, the electrochemical performance of the nanocomposite was demonstrated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect of EGR and ZnO nanoparticles, an ultrasensitive electrochemical sensor for acetaminophen (AC) and phenacetin (PCT) was successfully fabricated. The linearity ranged from 0.02 to 10 ?M for AC and 0.06 to 10 ?M for PCT with high sensitivities of 54 295.82 ?A mM-1 cm2 for AC and 21 344.66 ?A mM-1 cm2 for PCT, respectively. Moreover, the practical applicability was validated to be reliable and desirable in pharmaceutical detections. The excellent results showed the promise of the proposed preparation strategy of EGR-transition metal oxide nanocomposite in the field of electroanalytical chemistry.A facile and novel preparation strategy based on electrochemical techniques for the fabrication of electrodeposited graphene (EGR) and zinc oxide (ZnO) nanocomposite was developed. The morphology and structure of the EGR-based nanocomposite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (XPS) and Raman spectroscopy. Meanwhile, the electrochemical performance of the nanocomposite was demonstrated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect of EGR and ZnO nanoparticles, an ultrasensitive electrochemical sensor for acetaminophen (AC) and phenacetin (PCT) was successfully fabricated. The linearity ranged from 0.02 to 10 ?M for AC and 0.06 to 10 ?M for PCT with high sensitivities of 54 295.82 ?A mM-1 cm2 for AC and 21 344.66 ?A mM-1 cm2 for PCT, respectively. Moreover, the practical applicability was validated to be reliable and desirable in pharmaceutical detections. The excellent results showed the promise of the proposed preparation strategy of EGR-transition metal oxide nanocomposite in the field of electroanalytical chemistry. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03620k

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

2013-12-01

194

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

195

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

PubMed

Metal oxide-containing nanomaterials (MOCNMs) of controllable structures at the nano-scale have attracted considerable interest because of their great potential applications in electrochemical energy storage devices, such as lithium-ion batteries (LIBs) and supercapacitors. Among many structure-directing agents, polymers and macromolecules, including block copolymers (BCPs) and graphene, exhibit distinct advantages in the template-assisted synthesis of MOCNMs. In this feature article, we introduce the controlled preparation of MOCNMs employing BCPs and graphene as structure-directing agents. Typical synthetic strategies are presented for the control of structures and sizes as well as the improvement of physical properties and electrochemical performance of MOCNMs in LIBs and supercapacitors. PMID:24284837

Mai, Yiyong; Zhang, Fan; Feng, Xinliang

2014-01-01

196

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

197

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

198

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...

199

ADVANCED OXIDATION PROCESSES (AOP'S FOR THE TREATMENT OF CCL CHEMICALS  

EPA Science Inventory

Research on treatment of Contaminant Candidate List (CCL) chemicals is being conducted. Specific groups of contaminants on the CCL will be evaluated using numerous advanced oxidation processes (AOPs). Initially, these CCL contaminants will be evaluated in groups based on chemical...

200

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

201

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

Microsoft Academic Search

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

G. B. Balazs; Z. Chiba; P. R. Lewis; N. Nelson; G. A. Steward

1999-01-01

202

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

E-print Network

Conductive 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, it was possible to switch between NW and NT growth modes. InSnOH was converted into indium tin oxide (ITO

203

Alleviation of electrochemical oxidation for peptides and proteins in electrospray ionization: obtaining more accurate mass spectra with induced high voltage.  

PubMed

Accurate mass spectrometry (MS) signal for peptide/protein analysis, which could be affected by various MS conditions, plays an essential role in identification and quantification of biological samples. Herein, we tried to alleviate the possible interferences from electrochemical oxidations during electrospray ionization (ESI). Three most common electrochemical oxidation reactions in ESI include oxidation of analyte, solvent, and electrode. With introduction of induced electrospray ionization (IESI) (a variant form of ESI), these interferences were significantly alleviated for peptides/proteins. That effect was also tested with flow injection experiments with different solution flow rates, electrolyte concentrations and solvent compositions, which was to simulate various chromatography conditions in conventional liquid chromatography (LC) separations. For all chromatography conditions tested, electrochemical oxidation was significantly alleviated for the absence of physical contact between spray solution and electrode. PMID:25626082

Pei, Jiying; Zhou, Xuan; Wang, Xiaoqun; Huang, Guangming

2015-03-01

204

Cobalt (hydro)oxide electrodes under electrochemical conditions: a first principle study  

NASA Astrophysics Data System (ADS)

There is currently much interest in photoelectrochemical water splitting as a promising pathway towards sustainable energy production. A major issue of such photoelectrochemical devices is the limited efficiency of the anode, where the oxygen evolution reaction (OER) takes place. Cobalt (hydro)oxides, particularly Co3O4 and Co(OH)2, have emerged as promising candidates for use as OER anode materials. Interestingly, recent in-situ Raman spectroscopy studies have shown that Co3O4 electrodes undergo progressive oxidation and transform into oxyhydroxide, CoO(OH), under electrochemical working conditions. (Journal of the American Chemical Society 133, 5587 (2011))Using first principle electronic structure calculations, we provide insight into these findings by presenting results on the structural, thermodynamic, and electronic properties of cobalt oxide, hydroxide and oxydroxide CoO(OH), and on their relative stabilities when in contact with water under external voltage.

Chen, Jia; Selloni, Annabella

2013-03-01

205

Electrochemical behaviour of Teflon-bonded iron oxide electrodes in alkaline solutions  

NASA Astrophysics Data System (ADS)

The electrochemical behaviour af Teflon-bonded iron oxide electrodes in 5.35 M KOH +0.65 M LiOH solution that contains various additives (such as thiourea, ethylenediaminetetraacetic acid (EDTA), hexamine and sodium sulfide) is examined by cyclic voltammetry. chronopotentiometry, open-circuit potential (OCP) decay and charge/discharge studies. The incorporation of Na2S in the alkaline electrolyte improves the performance of iron oxide electrodes by increasing the value of the OCP and decreasing the transient time. Moreover, the addition of Na 2S gives maximum capacity for the iron oxide electrode and a value of zero for {dE }/{dt }. The addition of thiourea lowers the performance of pressed iron electrodes. Thus, the incorporation of Na 2S in the alkaline electrolyte is essential for improving the performance of these electrodes.

Periasamy, P.; Ramesh Babu, B.; Venkatakrishna Iyer, S.

206

Three-dimensional self-supported metal oxides for advanced energy storage.  

PubMed

The miniaturization of power sources aimed at integration into micro- and nano-electronic devices is a big challenge. To ensure the future development of fully autonomous on-board systems, electrodes based on self-supported 3D nanostructured metal oxides have become increasingly important, and their impact is particularly significant when considering the miniaturization of energy storage systems. This review describes recent advances in the development of self-supported 3D nanostructured metal oxides as electrodes for innovative power sources, particularly Li-ion batteries and electrochemical supercapacitors. Current strategies for the design and morphology control of self-supported electrodes fabricated using template, lithography, anodization and self-organized solution techniques are outlined along with different efforts to improve the storage capacity, rate capability, and cyclability. PMID:24700719

Ellis, Brian L; Knauth, Philippe; Djenizian, Thierry

2014-06-01

207

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

PubMed

Significantly enhanced catalytic activity of a nanocomposite composed of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) doped with graphene oxide (GO) was achieved through a simple electrochemical reduction process. The nanocomposite (PEDOT/GO) was electrodeposited on an electrode and followed by electrochemical reduction, and the obtained reduced nanocomposite (PEDOT/RGO) modified electrode exhibited lowered electrochemical impedance and excellent electrocatalytic activity towards the oxidation of dopamine. Based on the excellent catalytic property of PEDOT/RGO, an electrochemical sensor capable of sensitive and selective detection of DA was developed. The fabricated sensor can detect DA in a wide linear range from 0.1 to 175?M, with a detection limit of 39nM, and it is free from common interferences such as uric acid and ascorbic acid. PMID:24632460

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

2014-08-15

208

Oxidation-Reduction Resistance of Advanced Copper Alloys  

NASA Technical Reports Server (NTRS)

Resistance to oxidation and blanching is a key issue for advanced copper alloys under development for NASA's next generation of reusable launch vehicles. Candidate alloys, including dispersion-strengthened Cu-Cr-Nb, solution-strengthened Cu-Ag-Zr, and ODS Cu-Al2O3, are being evaluated for oxidation resistance by static TGA exposures in low-p(O2) and cyclic oxidation in air, and by cyclic oxidation-reduction exposures (using air for oxidation and CO/CO2 or H2/Ar for reduction) to simulate expected service environments. The test protocol and results are presented.

Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.; Humphrey, D. L.; Setlock, J. A.

2003-01-01

209

Thermomechanical and oxidation behaviour of high temperature advanced metallic alloys  

Microsoft Academic Search

The main focus of this paper is on materials for radiant burners application. Two advanced metallic alloys, a Ni and Fe-based alloy are studied and compared to a reference ferritic stainless steel. Oxidation kinetics of such alloys at different temperatures are reported. Oxide formation mechanisms are discussed. Furthermore, thermo-mechanical resistance and eventual strengthening mechanism in temperature are studied. Finally, technical

Ildiko Peter; Alessandro Zago; Marco Actis Grande; Daniele Ugues

2009-01-01

210

Advanced oxidation processes (AOP) for water purification and recovery  

Microsoft Academic Search

All advanced oxidation processes (AOP) are characterised by a common chemical feature: the capability of exploiting the high reactivity of HO radicals in driving oxidation processes which are suitable for achieving the complete abatement and through mineralization of even less reactive pollutants. The different AOP are considered and critically presented according to their specific features with reference, whenever possible, to

Roberto Andreozzi; Vincenzo Caprio; Amedeo Insola; Raffaele Marotta

1999-01-01

211

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

212

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

PubMed

The wastewater usually contains low-concentration organic pollutants and some inorganic salts after biological treatment. In the present work, the possibility of simultaneous removal of them by combining electrochemical oxidation and electrosorption was investigated. Phenol and sodium chloride were chosen as representative of organic pollutants and inorganic salts and a pair of activated carbon plate electrodes were used as anode and cathode. Some important working conditions such as oxygen concentration, applied potential and temperature were evaluated to reach both efficient phenol removal and desalination. Under optimized 2.0V of applied potential, 38°C of temperature, and 500mLmin(-1) of oxygen flow, over 90% of phenol, 60% of TOC and 20% of salinity were removed during 300min of electrolysis time. Phenol was removed by both adsorption and electrochemical oxidation, which may proceed directly or indirectly by chlorine and hypochlorite oxidation. Chlorophenols were detected as degradation intermediates, but they were finally transformed to carboxylic acids. Desalination was possibly attributed to electrosorption of ions in the pores of activated carbon electrodes. The charging/regeneration cycling experiment showed good stability of the electrodes. This provides a new strategy for wastewater treatment and recycling. PMID:25585871

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

2015-04-01

213

ZnO Nanorods Grown Electrochemically on Different Metal Oxide Underlays  

NASA Astrophysics Data System (ADS)

In this study we present results on electrochemically grown ZnO nanorods on different metal oxide underlays, such as ZnO seed layers with different morphologies, ZnS and TiO2 compact thin films produced by spray pyrolysis on transparent conductive oxide (TCO) substrates. Also in this work we present results on ZnO nanorods directly deposited on some chosen TCO substrates. The relationship between nanorod formation and substrate properties were studied. All ZnO nanorod layers were grown electrochemically using ZnCl2 aqueous solutions (c=0.2 mmol/L) at the bath temperature of 80 °C during one hour. The structural properties and morphology of metal oxide underlays and ZnO nanorods grown on them were studied by scanning electron microscopy (SEM), x-ray diffraction spectroscopy (XRD). Depending on the substrate morphology, ZnO rods with different dimension, orientation, shape and density were obtained. For instance, larger rods (d~200 nm, l~700 nm) were obtained on substrates, such as ITO/glass, FTO/glass and ZnO:In/ITO/glass. Smaller rods (d~60 nm, l~350 nm) were obtained on smooth, uniform and fine-grained underlays, such as ZnS and TiO2.

Gromyko, I.; Dedova, T.; Krunks, M.; Syritski, V.; Mere, A.; Mikli, V.; Unt, T.; Oja Acik, I.

2015-03-01

214

Activity analysis of mononuclear ruthenium ammine complex dispersed in a polymer membrane as an electrochemical water oxidation catalyst  

Microsoft Academic Search

The activity of an electrochemical water oxidation catalyst based on pentaamminechlororuthenium(III) ([Ru(NH3)5Cl]2+) complex incorporated in an electrode-coated Nafion membrane was investigated. The complex worked as an active electrochemical catalyst, and an optimum concentration for the turnover number (TN) of the catalyst in the O2 evolution was exhibited. The TN increased with the concentration at low concentrations, which was ascribed either

Kosato Kinoshita; Masayuki Yagi; Masao Kaneko

1999-01-01

215

Morphological, rheological and electrochemical studies ofpoly(ethylene oxide) electrolytes containing fumed silicananoparticles  

SciTech Connect

In this paper, the rheology and crystallization of composite Poly(Ethylene Oxide) (PEO) electrolytes were studied by dynamic mechanical analysis, DSC and polarized light microscopy. The effects of fumed silica nanoparticles on the conductivities of the polymer electrolytes at temperatures above and below their melting point were measured and related to their rheology and crystallization behavior, respectively. The electrolyte/electrode interfacial properties and cycling performances of the composite polymer electrolytes in Li/Li cells are also discussed. The measured electrochemical properties were found to depend heavily on the operational environments and sample processing history.

Xie, Jiangbing; Kerr, John B.; Duan, Robert G.; Han, Yongbong

2003-06-01

216

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

PubMed

An electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE) was used as a new voltammetric sensor for the determination of ferulic acid (FA). The morphology and microstructure of the modified electrodes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy analysis, and the electrochemical effective surface areas of the modified electrodes were also calculated by chronocoulometry method. Sensing properties of the electrochemical sensor were investigated by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that ERGO was electrodeposited on the surface of GCE by using potentiostatic method. The proposed electrode exhibited electrocatalytic activity to the redox of FA because of excellent electrochemical properties of ERGO. The transfer electron number (n), electrode reaction rate constant (ks) and electron-transfer coefficient (?) were calculated as 1.12, 1.24s(-1), and 0.40, respectively. Under the optimized conditions, the oxidation peak current was proportional to FA concentration at 8.49 × 10(-8)mol L(-1) to 3.89 × 10(-5)mol L(-1) with detection limit of 2.06 × 10(-8)mol L(-1). This fabricated sensor also displayed acceptable reproducibility, long-term stability, and high selectivity with negligible interferences from common interfering species. The voltammetric sensor was successfully applied to detect FA in A. sinensis and biological samples with recovery values in the range of 99.91%-101.91%. PMID:25063114

Liu, Linjie; Gou, Yuqiang; Gao, Xia; Zhang, Pei; Chen, Wenxia; Feng, Shilan; Hu, Fangdi; Li, Yingdong

2014-09-01

217

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

218

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

PubMed

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. PMID:24993836

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

2014-01-01

219

Simple and label-free electrochemical impedance Amelogenin gene hybridization biosensing based on reduced graphene oxide.  

PubMed

The increasing desire for sensitive, easy, low-cost, and label free methods for the detection of DNA sequences has become a vital matter in biomedical research. For the first time a novel label-free biosensor for sensitive detection of Amelogenin gene (AMEL) using reduced graphene oxide modified glassy carbon electrode (GCE/RGO) has been developed. In this work, detection of DNA hybridization of the target and probe DNA was investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The optimum conditions were found for the immobilization of probe on RGO surface and its hybridization with the target DNA. CV and EIS carried out in an aqueous solution containing [Fe(CN)6](3-/4-) redox pair have been used for the biosensor characterization. The biosensor has a wide linear range from 1.0×10(-20) to 1.0×10(-14)M with the lower detection limit of 3.2×10(-21)M. Moreover, the present electrochemical detection offers some unique advantages such as ultrahigh sensitivity, simplicity, and feasibility for apparatus miniaturization in analytical tests. The excellent performance of the biosensor is attributed to large surface-to-volume ratio and high conductivity of RGO, which enhances the probe absorption and promotes direct electron transfer between probe and the electrode surface. This electrochemical DNA sensor could be used for the detection of specific ssDNA sequence in real biological samples. PMID:24632459

Benvidi, Ali; Rajabzadeh, Nooshin; Mazloum-Ardakani, Mohammad; Heidari, Mohammad Mehdi; Mulchandani, Ashok

2014-08-15

220

Surface-modified reduced graphene oxide electrodes for capacitors by ionic liquids and their electrochemical properties  

NASA Astrophysics Data System (ADS)

In this work, reduced graphene oxide (rGO)/ionic liquids (IL) composites with different weight ratios of IL to rGO were synthesized by a simple method. In these composites, IL contributed to the exfoliation of rGO sheets and to the improvement of the electrochemical properties of the resulting composites by enhancing the ion diffusion and charge transport. The structure of the composites was examined by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The TEM images showed that IL was coated on the surface of rGO in a translucent manner. The electrochemical analysis of the prepared composites was carried out by performing cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS). Among the prepared composites, the one with a weight ratio of rGO to IL of 1:7 showed the highest specific capacitance of 147.5 F g-1 at a scan rate of 10 mV s-1. In addition, the rate capability and cycle performance of the composites were enhanced compared to pristine rGO. These enhanced properties make the composites suitable as electrode materials for the better performance supercapacitors.

Kim, Jieun; Kim, Seok

2014-03-01

221

Preliminary evaluation of hybrid electrochemical-thermochemical cycles for the production of hydrogen from water. [Lead oxide cycle  

Microsoft Academic Search

Water decomposition cycles, of the hybrid type, involving an electrochemical cell producing hydrogen, and an oxide, and a subsequent thermochemical process loop which liberates oxygen and regenerates the lower oxide (or metal), are evaluated. A prototype cycle based on the oxides of lead: HO + PbO H + PbO (electrolysis) PbO PbO + ¹\\/O (thermal decomposition) is presented. In principle,

Munger

1976-01-01

222

Electrochemical deposition of iridium (IV) oxide from alkaline solutions of iridium(III) oxide  

Microsoft Academic Search

Cyclic voltammetry is used to deposit films of hydrous iridium oxide onto glassy carbon electrodes from a basic solution of saturated iridium(III) oxide. An acidic solution of Ir(OH2)2Cl4? is first prepared from either IrCl63 or IrCl62?. When this solution is made basic, iridium (IV) oxide is deposited by oxygen generated from oxidation of hydroxide. A strongly adherent, bright blue deposit

John E. Baur; Thomas W. Spaine

1998-01-01

223

New innovative materials for advanced electrochemical applications in battery and fuel cell systems  

NASA Astrophysics Data System (ADS)

The advanced material POLYMET is an innovative high tech polymer with a three-dimensional polymeric structure metallized with an enclosing coating of different kinds of metals or alloys. The result is a range of tailor-made, microporous structures on a designable scale. By varying the metals and alloys, it is possible to draw upon extremely diverse areas of applications such as battery systems, fuel cells, filters or efficient catalysts as well as air regeneration systems, e.g. in aerospace. The three-dimensional structure of metallized high tech woven or non-woven materials or foams causes a lot of advantages such as high conductivity, high corrosion resistance, flexibility or mechanical strength. Therefore, POLYMET is suitable for, e.g. current collectors or gas diffusion layers in energy storage systems. They supply an economic and environmental alternative material to improve functional electrochemical systems.

Voß, S.; Kollmann, H.; Kollmann, W.

224

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

DOEpatents

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

Balachandran, Uthamalingam (Hinsdale, IL); Poeppel, Roger B. (Glen Ellyn, IL); Kleefisch, Mark S. (Naperville, IL); Kobylinski, Thaddeus P. (Lisle, IL); Udovich, Carl A. (Joliet, IL)

1994-01-01

225

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

226

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

227

A Non-Oxidative Approach towards Chemically and Electrochemically Functionalizing Si(111)  

PubMed Central

A general method for the non-oxidative functionalization of single-crystal silicon (111) surfaces is described. The silicon surface is fully acetylenylated using two-step chlorination/alkylation chemistry. A benzoquinone-masked primary amine is attached to this surface via Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (“click” chemistry). The benzoquinone is electrochemically reduced, resulting in quantitative cleavage of the molecule and exposing the amine terminus. Molecules presenting a carboxylic acid have been immobilized to the exposed amine sites. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and contact angle goniometry were utilized to characterize and quantitate each step in the functionalization process. This work represents a strategy for providing a general platform that can incorporate organic and biological molecules on Si(111) with minimal oxidation of the silicon surface. PMID:16848489

Rohde, Rosemary D.; Agnew, Heather D.; Yeo, Woon-Seok; Bailey, Ryan C.; Heath, James R.

2013-01-01

228

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

229

Electrochemical degradation of Nafion ionomer to functionalize carbon support for methanol electro-oxidation  

NASA Astrophysics Data System (ADS)

An effective electrochemical route to produce functional groups on carbon surface is demonstrated. Cyclic voltammetric (CV) sweeps are performed in 0.5 M H2SO4 electrolyte on electrodes containing carbon cloth, Vulcan XC72R, and Nafion ionomer. With supply of ambient oxygen, the generation of hydroxyl radicals from the oxygen reduction reaction during CV cycles initiates the decomposition of Nafion ionomer that leads to formation of oxygenated functional groups on the carbon surface. Ion chromatography confirms the dissolution of sulfate anions upon CV scans. Raman analysis suggests a minor alteration for the carbon structure. However, X-ray photoelectron spectroscopy indicates a significant increase of oxygenated functional groups in conjunction with notable reduction in the fluorine content. The amount of the oxygenated functional groups is determined by curve fitting of C 1s spectra with known constituents. These functional groups can also be found by immersing the as-prepared electrode in a solution containing concentrated residues from Nafion ionomer decomposition. The functionalized electrode allows a 170% increment of Pt ion adsorption as compared to the reference sample. After electrochemical reductions, the functionalized electrode reveals significant improvements in electrocatalytic abilities for methanol oxidation, which is attributed to the oxygenated functional groups that facilitates the oxidation of CO on Pt.

Hsieh, Yu-Chi; Chen, Jing-Yu; Wu, Pu-Wei

2011-10-01

230

Electrochemical oxidation of polyethylene glycol in electroplating solution using paraffin composite copper hexacyanoferrate modified (PCCHM) anode.  

PubMed

Electrochemical oxidation of polyethylene glycol (PEG) in an acidic (pH 0.18 to 0.42) and high ionic strength electroplating solution was investigated. The electroplating solution is a major source of wastewater in the printing wiring board industry. A paraffin composite copper hexacyanoferrate modified (PCCHM) electrode was used as the anode and a bare graphite electrode was used as the cathode. The changes in PEG and total organic carbon (TOC) concentrations during the course of the reaction were monitored. The efficiency of the PCCHM anode was compared with bare graphite anode and it was found that the former showed significant electrocatalytic property for PEG and TOC removal. Chlorides present in the solution were found to contribute significantly in the overall organic removal process. Short chain organic compounds like acetic acid, oxalic acid, formic acid and ethylene glycol formed during electrolysis were identified by HPLC method. Anode surface area and applied current density were found to influence the electro-oxidation process, in which the former was found to be dominating. Investigations of the kinetics for the present electrochemical reaction suggested that the two stage first-order kinetic model provides a much better representation of the overall mechanism of the process if compared to the generalized kinetic model. PMID:15559827

Bejankiwar, Rajesh S; Basu, Abir; Cementi, Max

2004-01-01

231

Electrochemical and microstructural characterization of the redox tolerance of solid oxide fuel cell anodes  

NASA Astrophysics Data System (ADS)

The most commonly used solid oxide fuel cell (SOFC) anode material is a two phase nickel and yttria stabilized zirconia (Ni/YSZ) cermet. During typical fuel cell operation, this material remains a cermet; however, the anode may reoxidize in a commercial SOFC system due to seal leakage, fuel supply interruption, or system shutdown. The cyclic reduction and oxidation (redox) of nickel will result in large bulk volume changes, which may have a significant effect on the integrity of interfaces within the fuel cell and thus may cause significant performance degradation. A baseline of the redox behaviour of an anode-supported SOFC was developed using electrochemical testing and electron microscopy. During redox tests, the cell's initial performance was characterized and then a small amount of air was blown over the anode in order to reoxidize the cell. The cell was then reduced and the electrochemical performance was remeasured in order to determine the amount of redox degradation. Cell performance decreased slightly after each redox cycle, especially for redox times greater than 1 hour. The microstructural changes that occurred after redox cycling were characterized using scanning and transmission electron microscopy (SEM and TEM). Redox cycling significantly changed the microstructure of the anode substrate in the cell.

Waldbillig, D.; Wood, A.; Ivey, D. G.

232

Amine functionalized graphene oxide/CNT nanocomposite for ultrasensitive electrochemical detection of trinitrotoluene.  

PubMed

Binding of electron-deficient trinitrotoluene (TNT) to the electron rich amine groups on a substrate form specific charge-transfer Jackson-Meisenheimer (JM) complex. In the present work, we report formation of specific JM complex on amine functionalized reduced graphene oxide/carbon nanotubes- (a-rGO/CNT) nanocomposite leading to sensitive detection of TNT. The CNT were dispersed using graphene oxide that provides excellent dispersion by attaching to CNT through its hydrophobic domains and solubilizes through the available OH and COOH groups on screen printed electrode (SPE). The GO was reduced electrochemically to form reduced graphene that remarkably increases electrochemical properties owing to the intercalation of high aspect CNT on graphene flakes as shown by TEM micrograph. The surface amine functionalization of dropcasted and rGO/CNT was carried out using a bi-functional cross linker ethylenediamine. The extent of amine functionalization on modified electrodes was confirmed using energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and confocal microscopy. The FTIR and Raman spectra further suggested the formation of JM complex between amine functionalized electrodes and TNT leading to a shift in peak intensity together with peak broadening. The a-rGO/CNT nanocomposite prepared electrode surface leads to ultra-trace detection of TNT upto 0.01 ppb with good reproducibility (n=3). The a-rGO/CNT sensing platform could be an alternate for sensitive detection of TNT explosive for various security and environmental applications. PMID:23416475

Sablok, Kavita; Bhalla, Vijayender; Sharma, Priyanka; Kaushal, Roohi; Chaudhary, Shilpa; Suri, C Raman

2013-03-15

233

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

234

Use of electrochemical oxidation and model peptides to study nucleophilic biological targets of reactive metabolites: the case of rimonabant.  

PubMed

Electrochemical oxidation of drug molecules is a useful tool to generate several different types of metabolites. In the present study we developed a model system involving electrochemical oxidation followed by characterization of the oxidation products and their propensity to modify peptides. The CB1 antagonist rimonabant was chosen as the model drug. Rimonabant has previously been shown to give high covalent binding to proteins in human liver microsomes and hepatocytes and the iminium ion and/or the corresponding aminoaldehyde formed via P450 mediated ?-carbon oxidation of rimonabant was proposed to be a likely contributor. This proposal was based on the observation that levels of covalent binding were significantly reduced when iminium species were trapped as cyanide adducts but also following addition of methoxylamine expected to trap aldehydes. Incubation of electrochemically oxidized rimonabant with peptides resulted in peptide adducts to the N-terminal amine with a mass increment of 64 Da. The adducts were shown to contain an addition of C5H4 originating from the aminopiperidine moiety of rimonabant. Formation of the peptide adducts required further oxidation of the iminium ion to short-lived intermediates, such as dihydropyridinium species. In addition, the metabolites and peptide adducts generated in human liver microsomes were compared with those generated by electrochemistry. Interestingly, the same peptide modification was found when rimonabant was coincubated with one of the model peptides in microsomes. This clearly indicated that reactive metabolite(s) of rimonabant identical to electrochemically generated species are also present in the microsomal incubations. In summary, electrochemical oxidation combined with peptide trapping of reactive metabolites identified a previously unobserved bioactivation pathway of rimonabant that was not captured by traditional trapping agents and that may contribute to the in vitro covalent binding. PMID:25210840

Thorsell, Annika; Isin, Emre M; Jurva, Ulrik

2014-10-20

235

V{sub 2}O{sub 5} xerogel-poly(ethylene oxide) hybrid material: Synthesis, characterization, and electrochemical properties  

SciTech Connect

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

Guerra, Elidia M. [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, 14040-901 Ribeirao Preto-SP (Brazil); Ciuffi, Katia J. [Universidade de Franca, Av. Dr. Armando Salles Oliveira 201, P.O. Box 82, 14404-600 Franca, SP (Brazil); Oliveira, Herenilton P. [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, 14040-901 Ribeirao Preto-SP (Brazil)]. E-mail: herepo@ffclrp.usp.br

2006-12-15

236

In situ XPS studies of perovskite oxide surfaces under electrochemical polarization.  

PubMed

An in situ XPS study of oxidation-reduction processes on three perovskite oxide electrode surfaces was carried out by incorporating the materials in an electrochemical cell mounted on a heated sample stage in an ultrahigh vacuum (UHV) chamber. Electrodes made of powdered LaCr(1-x)Ni(x)O(3-delta) (x = 0.4, 1) showed changes in the XPS features of all elements upon redox cycling between formal Ni3+ and Ni2+ oxidation stoichiometries, indicating the delocalized nature of the electronic states involved and strong mixing of O 2p to Ni 3d levels to form band states. The surface also showed changes in adsorption capacity for CO2 upon reduction as a result of increased nucleophilicity of surface oxygen. Another perovskite oxide, La(0.5)Sr(0.5)CoO(3-delta), laser deposited as highly oriented thin films on (100) oriented yttria-stabilized zirconia (YSZ), also showed evidence of both local and nonlocal effects in the XPS features upon redox cycling. In contrast to LaCr(1-x)Ni(x)O(3-delta), redox cycling mainly affected the XPS features of cobalt with little effect on oxygen. This signifies reduced participation of O 2p states in the conduction band of this material. Small changes in surface cation stoichiometry in this film were observed and attributed to mobility of the A-site Sr dopant under polarization. PMID:16851240

Vovk, Greg; Chen, Xiaohua; Mims, Charles A

2005-02-17

237

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

238

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

PubMed Central

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. PMID:25349555

2014-01-01

239

Destruction of estrogenic activity in water using UV advanced oxidation  

Microsoft Academic Search

The transformation of the steroidal Endocrine Disrupting Compounds (EDCs), 17-?-estradiol (E2) and 17-?-ethinyl estradiol (EE2) by direct UV photolysis and UV\\/H2O2 advanced oxidation was studied from the perspective of the removal of estrogenic activity associated with the compounds. First, experiments were performed to link the oxidation of E2 and EE2 with subsequent reduction in estrogenic activity. No statistically significant difference

Erik J. Rosenfeldt; Pei Jen Chen; Seth Kullman; Karl G. Linden

2007-01-01

240

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

241

Electrochemical oxidation of synthetic tannery wastewater in chloride-free aqueous media.  

PubMed

The electrochemical treatment of a synthetic tannery wastewater, prepared with several compounds used by finishing tanneries, was studied in chloride-free media. Boron-doped diamond (Si/BDD), antimony-doped tin dioxide (Ti/SnO(2)-Sb), and iridium-antimony-doped tin dioxide (Ti/SnO(2)-Sb-Ir) were evaluated as anode. The influence of pH and current density on the treatment was assessed by means of the parameters used to measure the level of organic contaminants in the wastewater; i.e., total phenols, chemical oxygen demand (COD), total organic carbon (TOC), and absorbance. Results showed that faster decrease in these parameters occurred when the Si/BDD anode was used. Good results were obtained with the Ti/SnO(2)-Sb anode, but its complete deactivation was reached after 4h of electrolysis at 25 mA cm(-2), indicating that the service life of this electrode is short. The Ti/SnO(2)-Sb-Ir anode is chemically and electrochemically more stable than the Ti/SnO(2)-Sb anode, but it is not suitable for the electrochemical treatment under the studied conditions. No significant changes were observed for electrolyses performed at different pH conditions with Si/BDD, and this electrode led to almost complete mineralization after 4h of electrolysis at 100 mA cm(-2). The increase in current density resulted in faster wastewater oxidation, with lower current efficiency and higher energy consumption. Si/BBD proved to be the best electrodic material for the direct electrooxidation of tannery wastewaters. PMID:20452722

Costa, Carla Regina; Montilla, Francisco; Morallón, Emilia; Olivi, Paulo

2010-08-15

242

New nanocrystalline manganese oxides as cathode materials for lithium batteries : electron microscopy, electrochemical and X-ray absorption studies  

E-print Network

1 New nanocrystalline manganese oxides as cathode materials for lithium batteries : electron.F. Abstract New nanostructured manganese oxi-iodides were prepared by redox reaction of sodium permanganate structure of these compounds, which contain octahedrally coordinated manganese atoms. The electrochemical

Paris-Sud XI, Université de

243

In vivo and In vitro Differences in the Charge-injection and Electrochemical Properties of Iridium Oxide Electrodes  

Microsoft Academic Search

The electrochemical response of activated iridium oxide (AIROF) electrodes implanted acutely in the subretinal space of the rabbit is compared with in vitro measurements in model electrolytes. Voltage transients during current pulsing, cyclic voltammetry, impedance spectroscopy and open-circuit potential measurements were compared. Subretinal charge injection by constant current pulsing required significantly greater driving voltages due to both higher access resistances

Stuart F. Cogan

2006-01-01

244

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

Microsoft Academic Search

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

G. Bryan Balazs; Zoher Chiba; Patricia R. Lewis; Norvell Nelson; G. Anthony Steward

1999-01-01

245

Electrochemical and structural characterizations of electrodeposited iridium oxide thin-film electrodes applied to neurostimulating electrical signal  

Microsoft Academic Search

Thin-film technology takes more and more importance in the development of biomedical devices dedicated to functional neurostimulation. Our research about the design of implantable neurostimulating electrode is oriented toward thin-film cuff electrodes based on PTFE substrate covered by a gold\\/iridium oxide film. A gold-sputtered film serves as adhesion layer and current collector whereas iridium oxide acts as an electrochemical actuator.

S. C Mailley; M Hyland; P Mailley; J. M McLaughlin; E. T McAdams

2002-01-01

246

Electrochemical and charge\\/discharge properties of the synthesized cobalt oxide as anode material in Li-ion batteries  

Microsoft Academic Search

The electrochemical and charge\\/discharge behaviors of cobalt oxide prepared by the calcination of cobalt hydroxide were studied by the cyclic voltammetry (CV) and galvanostatical charge\\/discharge methods. The cyclic voltammograms of cobalt oxide containing 20% carbon black were correlated well with the results in the charge\\/discharge behaviors of Li\\/CoO batteries. A cathodic peak with potential of 0.5V (versus Li\\/Li+) in the

Jing-Shan Do; Chien-Hsiang Weng

2006-01-01

247

An opto-electrochemical phosphate-ion sensor using a cobalt-oxide thin-film electrode  

Microsoft Academic Search

An opto-electrochemical phosphate-ion sensor was developed with a cobalt oxide thin-film electrode. The cobalt oxide (Co3O4) thin-film electrode showed a remarkable change of transmittance at 550–800 nm, under application of an anodic potential at 0.4 V vs. SCE, which was dependent on HPO42? concentration. The change of transmittance at 620 nm, the sensor signal, was almost linear to the logarithm

Youichi Shimizu; Yusuke Furuta

1998-01-01

248

Pretreatment of penicillin formulation effluent by advanced oxidation processes  

Microsoft Academic Search

A variety of advanced oxidation processes (AOPs; O3\\/OH?, H2O2\\/UV, Fe2+\\/H2O2, Fe3+\\/H2O2, Fe2+\\/H2O2\\/UV and Fe3+\\/H2O2\\/UV) have been applied for the oxidative pre-treatment of real penicillin formulation effluent (average COD0=1395mg\\/L; TOC0=920mg\\/L; BOD5,0?0mg\\/L). For the ozonation process the primary involvement of free radical species such as OH in the oxidative reaction could be demonstrated via inspection of ozone absorption rates. Alkaline ozonation and

Idil Arslan-Alaton; Serdar Dogruel

2004-01-01

249

Spontaneous electrochemical treatment for sulfur recovery by a sulfide oxidation/vanadium(V) reduction galvanic cell.  

PubMed

Sulfide is the product of the biological sulfate reduction process which gives toxicity and odor problems. Wastewaters or bioreactor effluents containing sulfide can cause severe environmental impacts. Electrochemical treatment can be an alternative approach for sulfide removal and sulfur recovery from such sulfide rich solutions. This study aims to develop a spontaneous electrochemical sulfide oxidation/vanadium(V) reduction cell with a graphite electrode system to recover sulfide as elemental sulfur. The effects of the internal and external resistance on the sulfide removal efficiency and electrical current produced were investigated at different pH. A high surface area of the graphite electrode is required in order to have as less internal resistance as possible. In this study, graphite powder was added (contact area >633 cm(2)) in order to reduce the internal resistance. A sulfide removal efficiency up to 91% and electrical charge of more than 400 C were achieved when using five graphite rods supplemented with graphite powder as the electrode at an external resistance of 30 ? and a sulfide concentration of 250 mg L(-1). PMID:25463589

Kijjanapanich, Pimluck; Kijjanapanich, Pairoje; Annachhatre, Ajit P; Esposito, Giovanni; Lens, Piet N L

2015-02-01

250

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

251

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

PubMed

Fractional exhaled nitric oxide (F(E)NO) is considered an indicator in the diagnostics and management of asthma. In this study we present a laser-based sensor for measuring F(E)NO. 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, 110(-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). F(E)NO 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. PMID:22352669

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

2012-01-01

252

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

253

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.

254

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

255

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

256

Mechanism for resistive switching in an oxide-based electrochemical metallization memory  

NASA Astrophysics Data System (ADS)

A comparison of the asymmetric OFF-state current-voltage characteristics between Cu/ZnO/Pt and Cu/ZnO/Al-doped ZnO (AZO) electrochemical metallization memory (ECM) cells demonstrates that the Cu filament rupture and rejuvenation occur at the ZnO/Pt (or AZO) interface, i.e., the cathodic interface. Therefore, the filament is most likely to have a conical shape, with wider and narrower diameters formed at the anodic and cathodic interfaces, respectively. It is inferred that the filament growth starts at the anode surface and stops at the cathode surface. Our results indicate that oxide-based ECM cells strongly differ from sulfide- and selenide-based ones in the resistive switching mechanism.

Peng, Shanshan; Zhuge, Fei; Chen, Xinxin; Zhu, Xiaojian; Hu, Benlin; Pan, Liang; Chen, Bin; Li, Run-Wei

2012-02-01

257

Impurities within carbon nanotubes govern the electrochemical oxidation of substituted hydrazines.  

PubMed

Electrochemistry and electrocatalysis on carbon nanomaterials is at the forefront of research. The presence of carbonaceous and metallic impurities within carbon nanotubes (CNTs) is a persistent problem. Here we show that the electrochemistry of the entire group of hydrazine compounds is governed by impurities within single-walled, double-walled and few-walled CNTs. The oxidation of organic substituted hydrazines at CNTs is driven by nanographitic impurities, in contrast to unsubstituted hydrazine, for which the electrochemistry is driven by metallic impurities within CNTs. This finding is unexpected, as one would assume that a whole group of compounds would be susceptible to "electrocatalysis" by only one type of impurity. This discovery should be taken into account when predicting the susceptibility of whole groups of compounds to electrocatalysis by metallic or nanographitic impurities. Our findings have strong implications on the electrochemical sensing of hydrazines and on the use of hydrazines as fuels for nanomotors. PMID:21556440

Stuart, Emma J E; Pumera, Martin

2011-06-14

258

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

259

In-situ quantification of solid oxide fuel cell electrode microstructure by electrochemical impedance spectroscopy  

NASA Astrophysics Data System (ADS)

Three-dimensional (3D) microstructure of solid oxide fuel cell electrodes plays critical roles in determining fuel cell performance. The state-of-the-art quantification technique such as X-ray computed tomography enables direct calculation of geometric factors by 3D microstructure reconstruction. Taking advantages of in-situ, fast-responding and low cost, electrochemical impedance spectroscopy represented by distribution of relaxation time (DRT) is a novel technique to estimate geometric properties of fuel cell electrodes. In this study, we employed the anode supported cells with the cell configuration of Ni-YSZ || YSZ || LSM-YSZ as an example and compared the tortuosity factor of pores of the anode substrate layer by X-ray computed tomography and DRT analysis. Good agreement was found, validating the feasibility of in-situ microstructural quantification by using the DRT technique.

Zhang, Yanxiang; Chen, Yu; Chen, Fanglin

2015-03-01

260

?-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

261

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

262

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

263

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

264

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

265

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

266

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

267

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

268

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

269

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

270

Electrochemical anodic oxidation of nitrogen doped carbon nanowall films: X-ray photoelectron and Micro-Raman spectroscopy study  

NASA Astrophysics Data System (ADS)

Unintentional nitrogen doped carbon nanowall (CNW) films were oxidized through anodic polarization in different applied potential windows, in a mild neutral K2SO4 electrolyte solution. Applied potentials in the range of [0-1], [0-1.5] and [0-2] V vs. SCE were explored. The films were characterized with X-ray photoelectron (XPS) and Micro-Raman spectroscopy, in order to investigate the surface chemistry and structural changes after treatment, respectively. The XPS analysis revealed that this electrochemical treatment leads to an increase of oxygen functional groups, and influences the nitrogen proportion and bonding configuration (such as pyridinic/pyridonic nitrogen) on the film surface at room temperature. In particular, an obvious enhancement of pyrrolic/pyridonic nitrogen doping of CNWs via electrochemical cycling in the range of [0-1.5] and [0-2] V vs. SCE was achieved. Such enhancement happened, because of the oxidation of nitrogen atoms in pyridine as a result of OH ions injection upon electrochemical cycling. Micro-Raman analysis indicates structural quality degradation with increasing the applied potential window. Moreover, the electrochemical capacitance of CNW films was increased after treatment in the range of [0-1] and [0-1.5] and decreased in the range of [0-2] V vs. SCE. The results show that harsh oxidation happened in the range [0-2] V.

Achour, A.; Vizireanu, S.; Dinescu, G.; Le Brizoual, L.; Djouadi, M.-A.; Boujtita, M.

2013-05-01

271

Advanced Launch System advanced development oxidizer turbopump program: Technical implementation plan  

NASA Technical Reports Server (NTRS)

The Advanced Launch Systems (ALS) Advanced Development Oxidizer Turbopump Program has designed, fabricated and demonstrated a low cost, highly reliable oxidizer turbopump for the Space Transportation Engine that minimizes the recurring cost for the ALS engines. Pratt and Whitney's (P and W's) plan for integrating the analyses, testing, fabrication, and other program efforts is addressed. This plan offers a comprehensive description of the total effort required to design, fabricate, and test the ALS oxidizer turbopump. The proposed ALS oxidizer turbopump reduces turbopump costs over current designs by taking advantage of design simplicity and state-of-the-art materials and producibility features without compromising system reliability. This is accomplished by selecting turbopump operating conditions that are within known successful operating regions and by using proven manufacturing techniques.

Ferlita, F.

1989-01-01

272

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

273

Electrochemical oxidation of landfill leachate in a flow reactor: optimization using response surface methodology.  

PubMed

Response surface methodology based on Box-Behnken (BBD) design was successfully applied to the optimization in the operating conditions of the electrochemical oxidation of sanitary landfill leachate aimed for making this method feasible for scale up. Landfill leachate was treated in continuous batch-recirculation system, where a dimensional stable anode (DSA(©)) coated with Ti/TiO2 and RuO2 film oxide were used. The effects of three variables, current density (milliampere per square centimeter), time of treatment (minutes), and supporting electrolyte dosage (moles per liter) upon the total organic carbon removal were evaluated. Optimized conditions were obtained for the highest desirability at 244.11 mA/cm(2), 41.78 min, and 0.07 mol/L of NaCl and 242.84 mA/cm(2), 37.07 min, and 0.07 mol/L of Na2SO4. Under the optimal conditions, 54.99 % of chemical oxygen demand (COD) and 71.07 ammonia nitrogen (NH3-N) removal was achieved with NaCl and 45.50 of COD and 62.13 NH3-N with Na2SO4. A new kinetic model predicted obtained from the relation between BBD and the kinetic model was suggested. PMID:25339535

Silveira, Jefferson E; Zazo, Juan A; Pliego, Gema; Bidóia, Edério D; Moraes, Peterson B

2015-04-01

274

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

275

Multivariate optimization for electrochemical oxidation of methyl orange: Pathway identification and toxicity analysis.  

PubMed

Electrochemical oxidation of methyl orange (Sodium 4-[(4-dimethylamino) phenyldiazenyl] benzenesulfonate) with lead dioxide coated on mild steel was modelled using response surface methodology (RSM) to analyze the influence of pH, NaCl dose and current on color and chemical oxygen demand (COD) removal. Higher current, acidic pH and 0.8-1.2 g L(-1) NaCl dose had an enhancing effect on the removal efficiencies. Interaction effect of the variables highlights the action of (•)OH and HOCl in the oxidation of methyl orange, where HOCl has effect at lower current range. More than 90% COD removal efficiency and ?100% color removal efficiency was obtained in 5 h at optimum conditions for an initial concentration of 50 mg L(-1). High performance liquid chromatography-mass spectroscopy (HPLC-MS) analysis carried out to identify degradation intermediates revealed the absence of chlorinated intermediates, which was further verified with Fourier transform infrared spectroscopy (FTIR) analysis. The postulated pathway of degradation indicated breakdown through dealkylation, deamination, desulfonation and cleavage of an azo bond and benzene ring. The degradation of methyl orange to smaller compounds was also confirmed by Ion Chromatography (IC). Cytotoxicity analysis on HaCaT cells revealed the intermediates to be more cytotoxic than the dye, possibly due to the aromatic amines and diazines formed during the degradation process. PMID:25594123

Pillai, Indu M Sasidharan; Gupta, Ashok K; Tiwari, Manoj K

2015-02-23

276

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

277

Influence of the reaction temperature on the electrochemical promoted catalytic behaviour of platinum impregnated catalysts for the reduction of nitrogen oxides under lean burn conditions  

Microsoft Academic Search

The aim of this work was to study the influence of the reaction temperature on the efficiency of the electrochemical promotion to improve the catalytic performance of a Pt impregnated catalyst for the reduction of nitrogen oxides under lean burn conditions. Open circuit catalytic and potential measurements were carried out in order to explain the potentiostatic behaviour of the electrochemical

Fernando Dorado; Antonio de Lucas-Consuegra; Carmen Jiménez; José Luis Valverde

2007-01-01

278

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

279

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. PMID:25593562

2014-01-01

280

Preparation and characterization of zinc oxide nanoparticles and their sensor applications for electrochemical monitoring of nucleic acid hybridization.  

PubMed

In this study, ZnO nanoparticles (ZNP) of approximately 30 nm in size were synthesized by the hydrothermal method and characterized by X-ray diffraction (XRD), Braun-Emmet-Teller (BET) N2 adsorption analysis and transmission electron microscopy (TEM). ZnO nanoparticles enriched with poly(vinylferrocenium) (PVF+) modified single-use graphite electrodes were then developed for the electrochemical monitoring of nucleic acid hybridization related to the Hepatitis B Virus (HBV). Firstly, the surfaces of polymer modified and polymer-ZnO nanoparticle modified single-use pencil graphite electrodes (PGEs) were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was also investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Subsequently, the polymer-ZnO nanoparticle modified PGEs were evaluated for the electrochemical detection of DNA based on the changes at the guanine oxidation signals. Various modifications in DNA oligonucleotides and probe concentrations were examined in order to optimize the electrochemical signals that were generated by means of nucleic acid hybridization. After the optimization studies, the sequence-selective DNA hybridization was investigated in the case of a complementary amino linked probe (target), or noncomplementary (NC) sequences, or target and mismatch (MM) mixture in the ratio of (1:1). PMID:21600741

Yumak, Tugrul; Kuralay, Filiz; Muti, Mihrican; Sinag, Ali; Erdem, Arzum; Abaci, Serdar

2011-09-01

281

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

282

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

PubMed Central

Sulfide is a common product of marine anaerobic respiration, and a potent reactant biologically and geochemically. Here we demonstrate the impact on microbial communities with the removal of sulfide via electrochemical methods. The use of differential pulse voltammetry revealed that the oxidation of soluble sulfide was seen at +30 mV (vs. SHE) at all pH ranges tested (from pH = 4 to 8), while non-ionized sulfide, which dominated at pH = 4 was poorly oxidized via this process. Two mixed cultures (CAT and LA) were enriched from two different marine sediments (from Catalina Island, CAT; from the Port of Los Angeles, LA) in serum bottles using a seawater medium supplemented with lactate, sulfate, and yeast extract, to obtain abundant biomass. Both CAT and LA cultures were inoculated in electrochemical cells (using yeast-extract-free seawater medium as an electrolyte) equipped with carbon-felt electrodes. In both cases, when potentials of +630 or +130 mV (vs. SHE) were applied, currents were consistently higher at +630 then at +130 mV, indicating more sulfide being oxidized at the higher potential. In addition, higher organic-acid and sulfate conversion rates were found at +630 mV with CAT, while no significant differences were found with LA at different potentials. The results of microbial-community analyses revealed a decrease in diversity for both CAT and LA after electrochemical incubation. In addition, some bacteria (e.g., Clostridium and Arcobacter) not well-known to be capable of extracellular electron transfer, were found to be dominant in the electrochemical cells. Thus, even though the different mixed cultures have different tolerances for sulfide, electrochemical-sulfide removal can lead to major population changes. PMID:25741331

Li, Shiue-Lin; Nealson, Kenneth H.

2015-01-01

283

Advanced oxidation of a pulp mill bleaching wastewater.  

PubMed

The degradation, by several advanced oxidation reactions, of a pulp mill ECF bleaching effluent, was studied. The initial biodegradability of the organic matter present in the effluent, estimated as the BOD5/COD, was low (0.3). When the effluent was submitted to ozonation and to five different advanced oxidation systems (O3/UV, O3/UV/ZnO, O3/UV/TiO2, O2/UV/ZnO, O2/UV/TiO2), the biodegradability increase significantly. After five minutes of reaction, the O3/UV system appears as the most efficient in to transform the organic matter to more biodegradable forms. A similar effect was observed when the effluent was submitted to an activated sludge treatment. The COD, TOC and toxicity reduction correlated well with the biodegradability enhancement after AOPs treatments. PMID:10520485

Yeber, M C; Rodríguez, J; Freer, J; Baeza, J; Durán, N; Mansilla, H D

1999-10-01

284

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

285

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

286

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

287

Effect of electrochemical oxidation of activated carbon fiber on competitive and noncompetitive sorption of trace toxic metal ions from aqueous solution  

Microsoft Academic Search

A viscose-rayon-based activated carbon cloth (ACC) was electrochemically oxidized to enhance its cation sorption capacity for comparison with as-received ACC. The ACCs were characterized by sodium capacity measurement, pH titration, zeta potential measurement, elemental analysis, Brunauer–Emmet–Teller surface area, and pore size distribution. Batch sorption experiments showed that electrochemically oxidized ACC (EO) is more effective for the removal of lead and

I. D. Harry; B. Saha; I. W. Cumming

2006-01-01

288

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

289

Electrochemical behaviour of stainless steels in media containing iron-oxidizing bacteria (IOB) by corrosion process modeling  

Microsoft Academic Search

Localized corrosion mechanism of stainless steel (SS) types UNS S30403 and UNS 31603 in the presence of iron-oxidizing bacteria Sphaerotilus spp. isolated from rust deposits was studied electrochemically. OCP transient, cyclic anodic and cathodic potentiodynamic polarization curves were measured on steel electrodes through their exposure to 3% NaCl solution supplemented with Sphaerotilus culture. The exposure period was composed of three

J. Starosvetsky; D. Starosvetsky; B. Pokroy; T. Hilel; R. Armon

2008-01-01

290

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

PubMed

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

291

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

NASA Astrophysics Data System (ADS)

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.

Tsampas, Michail; Kambolis, Anastasios; Obeid, Emil; Lizarraga, Leonardo; Sapountzi, Foteini; Vernoux, Philippe

2013-08-01

292

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

293

Electrochemical studies on selected oxides for intermediate temperature-solid oxide fuel cells  

NASA Astrophysics Data System (ADS)

Fuel cell technology holds the promise to change the way power is generated, transmitted, and utilized in our increasing demanding lifestyles. State of the art solid oxide fuel cells (SOFCs) utilize an all ceramic design and operate at 750--1000°C. Lower operating temperatures will significantly improve the economics of power generation using SOFCs. The aim of this dissertation was to evaluate and develop component materials for SOFCs, which could work efficiently at temperatures between 500--750°C. Erbia stabilized bismuth oxide (ESB) shows one of the highest oxygen ion conductivity among all solid electrolytes. However, due to positional and occupational ordering the conductivity decays below the transition temperature (˜600°C). The effect of direct current bias on the ordering phenomenon in ESB was studied using symmetrical cells with Ag-ESB electrodes. At 500°C, the endotherm, related to reverse transition, is enhanced by the applied bias at short time but with negligible change in conductivity decay. It is proposed that the conductivity decay with anneal time is related more to the positional ordering than occupational ordering. Ag-ESB electrodes showed good performance, though were unstable under high currents at 625°C due to Ag migration with oxygen flux. Novel bismuth ruthenate based cathodes were evaluated using impedance spectroscopy with symmetric cells on gadolinium doped ceria (GDC) electrolytes. Undoped bismuth ruthenate electrode showed area specific resistance (ASR) of 55.64 Ocm2 at 500°C and 1.45 Ocm 2 at 700°C in air. Doping with similar size Ca2+, Ag+, or Sr2+ on Bi3+ site did not improve the electrode performance significantly, while bismuth ruthenate-ESB composites showed 3--4 times lower electrode ASR. Bismuth ruthenate-ESB (62.5:37.5 wt%) composite showed the best performance of 18.4 Ocm 2 at 500°C and 0.32 Ocm2 at 700°C in air. Addition of the ESB phase is believed to reduce the rate limiting surface diffusion in oxygen reduction reaction. Anode supported thick film GDC electrolyte unit cells were developed for IT-SOFCs. A colloidal deposition technique was used to fabricate dense, thick GDC electrolyte films on porous Ni-GDC anode supports. Pre-sintering temperature of the anode and final sintering temperature of the anode/electrolyte bilayer were found to be the primary parameters determining the density of the film. The sintering temperature of LSCF-GDC (70:30 wt%) composite cathode was optimized to 1250--1350°C, which resulted in a maximum power density of 0.338 W/cm2 at 0.771 A/cm2, 700°C. Current interrupt showed that apart from the electrolyte layer, the ohmic polarization across the cell has significant contributions from the electrodes.

Jaiswal, Abhishek

294

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

295

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

296

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. 2 figs.

Balazs, G.B.; Chiba, Z.; Lewis, P.R.; Nelson, N.; Steward, G.A.

1999-06-15

297

Annealing effects on the physicochemical characteristics of hydrous ruthenium and ruthenium–iridium oxides for electrochemical supercapacitors  

Microsoft Academic Search

The electrochemical (EC) properties and stability of hydrous ruthenium oxide (denoted as RuOx·nH2O) and ruthenium–iridium oxide (denoted as (Ru+Ir)Oy·mH2O) were systematically investigated in 0.5M H2SO4 by cyclic voltammetry (CV) and chronopotentiometry (CP). The EC characteristics of RuOx·nH2O and (Ru+Ir)Oy·mH2O annealed at temperatures equal to\\/above 200°C were demonstrated to be more applicable for the EC supercapacitors. The crystalline information of these

Chi-Chang Hu; Yao-Huang Huang; Kwang-Huei Chang

2002-01-01

298

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

299

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

300

Voltage induced electrochemical reactions in the single lithium-rich layer-oxide nanoparticles.  

PubMed

As a crucial building block of the electrode in the lithium-ion battery (LIB), single nanoparticles that respond to an electric field have rarely been characterized experimentally. It is important to study the intrinsic properties of nanoparticles independently, excluding the effects from binders and additives. In this paper, isolated Li-rich layer-oxide (Li1.2Mn0.54Ni0.13Co0.13O2) nanoparticles are studied in comparison with individual Li2MnO3 and LiNi1/3Co1/3Mn1/3O2 nanoparticles. The bias triggered changes in morphology and material properties are characterized using dual-frequency scanning probe microscopy (SPM) techniques in ambient air, synthetic air, and an argon atmosphere. Inhomogeneous stiffness/composition is observed on single nanoparticles. The change in local Li(+)-ion concentration may contribute to the stiffness variation. Bias induced Li(+)-ion redistributions and electrochemical reactions are observed. Nanoparticles are fragmented at high voltage (>5 V) when an excessive amount of Li-ions are removed. This work further demonstrates the application of multi-frequency SPM techniques for the characterization of nanoparticles for energy storage applications. PMID:25798700

Li, Tao; Song, Bohang; Lu, Li; Zeng, Kaiyang

2015-04-01

301

Shape- and size-selective electrochemical synthesis of dispersed silver(I) oxide colloids.  

PubMed

Silver(I) oxide (Ag2O) micro- and nanoparticles were electrochemically synthesized by anodizing a sacrificial silver wire in a basic aqueous sulfate solution. Ag2O particles were released from the silver electrode surface during synthesis producing a visible sol "stream". The composition of these particles was established using selected area electron diffraction, X-ray diffraction, and X-ray photoelectron spectroscopy. The shape of Ag2O crystallites could be adjusted using the potential of the silver wire generator electrode. The generation of a dispersed Ag2O sol and the observed shape selectivity are both explained by a two-step mechanism involving the anodic dissolution of silver metal, Ag0 --> Ag+(aq) + 1e-, followed by the precipitation of Ag2O particles, 2Ag+ + 2OH- --> Ag2O(s) + H2O. Within 100 mV of the voltage threshold for particle growth, cubic particles with a depression in each face ("hopper crystals") were produced. The application of more positive voltages resulted in the generation of 8-fold symmetric "flower"-shaped particles formed as a consequence of fast growth in the <111> crystallographic direction. The diameter of flower particles was adjustable from 250 nm to 1.8 microm using the growth duration at constant potential. PMID:16277476

Murray, B J; Li, Q; Newberg, J T; Menke, E J; Hemminger, J C; Penner, R M

2005-11-01

302

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

303

Effect of electrochemical oxidation on biodegradability and toxicity of batik industry wastewater  

NASA Astrophysics Data System (ADS)

This study was conducted to investigate the increase in biodegradability and reduction in toxicity level in the batik wastewater treatment. Basically, the wastewater treatment from batik industry contained chemicals especially dyes which are not biodegradable and contains higher toxicity level because of the chemical compartment which comes out during the wastewater discharge and this could lead high risk in health wise to humans and all the aquatic living organisms. Thus, this research was carried to enhance the effectiveness of the electrochemical oxidation method by using the batik wastewater. Optimal parameters such as pH, time, distance between graphite electrodes and sodium chloride (NaCl) concentration as it activates as the electrolyte was done to obtain the removal of BOD, COD and color in the batik wastewater. The research study found that the removal of COD and color was high in the acidic conditions which are pH 5 with the removal of COD, 89.71% and color 93.89%. The ratio of BOD5/ COD successfully increased from 0.015 to 0.271 which mean it increase by 94.46% and the toxicity level using Toxtrax method (10017) also successfully reduced from 1.195% to 0.129% which means the samples which were slightly toxic were reduced to non-toxic level.

Subramaniam, Devagi; Halim, Azhar A.

2014-09-01

304

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

305

Magnetic behaviors of cerium oxide-based thin films deposited using electrochemical method  

NASA Astrophysics Data System (ADS)

Zn and Co multi-doped CeO2 thin films have been prepared using an anodic electrochemical method. The structures and magnetic behaviors are characterized by several techniques, in which the oxygen states in the lattice and the absorptive oxygen bonds at the surface are carefully examined. The absorptive oxygen bond is about 50% of the total oxygen bond by using a semi-quantitative method. The value of actual stoichiometry ?' is close to 2. The experimental results indicate that the thin films are of a cerium oxide-based solid solution with few oxygen vacancies in the lattice and many absorptive oxygen bonds at the surface. Week ferromagnetic behaviors were evidenced by observed M—H hysteresis loops at room temperature. Furthermore, an evidence of relative ferromagnetic contributions was revealed by the temperature dependence of magnetization. It is believed that the ferromagnetic contributions exhibited in the M—H loops originate from the absorptive oxygen on the surface rather than the oxygen vacancies in the lattice.

Peng, Ying-Zi; Li, Yuan; Bai, Ru; Huo, De-Xuan; Qian, Zheng-Hong

2014-09-01

306

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

307

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

2015-04-01

308

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

309

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

310

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

2015-03-01

311

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

312

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

313

Optical and electrochemical properties of ethynylaniline derivatives of phenothiazine, phenothiazine-5-oxide and phenothiazine-5,5-dioxide.  

PubMed

Three phenothiazine (PTZ) derivatives with varying degrees of sulfur oxidation states were synthesized as strong electron donors. The thioether, sulfoxide and sulfone PTZ-derivatives exhibited irreversible oxidation at 0.19 V, 0.29 V and 0.31 V versus ferrocene, respectively. Each PTZ derivative was emissive with lifetimes of 1.7 ns, 0.5 ns, and 0.5 ns and absolute quantum yields of 0.32, 0.23 and 0.23 for the thioether, sulfoxide and sulfone derivatives, respectively. Furthermore, these PTZ derivatives showed very large Stokes shifts ranging from 5600 cm(-1) to 2800 cm(-1). Calculations using DFT and TD-DFT methods resulted in an optimized ground state and the excited state geometries of the PTZ derivatives that compared favourably to experimental optical and electrochemical data. DFT calculations revealed that these butterfly shaped derivatives flatten upon excitation and this effect is greatest for the thioether PTZ derivative, resulting in the large Stokes shift. These potent electron donor systems also displayed electrochromic behaviour upon oxidation, which was attributed to a delocalized cation over the phenothiazine core and the appended ethynyl anilines. The electrochemically oxidized species had a wide absorption profile spanning from 300 nm to past 800 nm. PMID:24821592

Thériault, Kim D; Sutherland, Todd C

2014-06-28

314

Green synthesis of silver nanoparticles-graphene oxide nanocomposite and its application in electrochemical sensing of tryptophan.  

PubMed

A new kind of nanocomposite based on silver nanoparticles (AgNPs)/graphene oxide (GO) was conveniently achieved through a green and low-cost synthesis approach using glucose as a reducing and stabilizing agent, and the synthetic procedure can be easily used for the construction of a disposable electrochemical sensor on glassy carbon electrode (GCE). The nanocomposite was detailedly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). The experimental results demonstrated that the nanocomposite possessed the specific features of both silver nanoparticles and graphene, and the intrinsic high specific area and the fast electron transfer rate ascribed to the nanohybrid structure could improve its electrocatalytic performance greatly. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed to evaluate the electrochemical properties of AgNPs/GO/GCE towards tryptophan, and the AgNPs/GO film exhibited a distinctly higher activity for the electro-oxidation of tryptophan than GO film with tenfold enhancement of peak current. The oxidation mechanism and the kinetic parameters were investigated, and analysis operation conditions were optimized. Under the selected experimental conditions, the oxidation peak currents were proportional to tryptophan concentrations over the range of 0.01 ?M to 50.0 ?M and 50.0 ?M to 800.0 ?M, respectively. The detection limit was 2.0 nM (S/N=3). Moreover, the proposed method is free of interference from tyrosine and other coexisting species. The resulting sensor displays excellent repeatability and long-term stability; finally it was successfully applied to detect tryptophan in real samples with good recoveries, ranging from 99.0% to 103.0%. PMID:23202352

Li, Junhua; Kuang, Daizhi; Feng, Yonglan; Zhang, Fuxing; Xu, Zhifeng; Liu, Mengqin; Wang, Deping

2013-04-15

315

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

316

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

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

317

Vanadium oxide fluoride-graphite intercalation compounds: Structural characteristics and electrochemical insertion of lithium cations  

SciTech Connect

Graphite intercalation compounds of vanadium oxide fluoride, C{sub x}(VOF{sub 3})F, were synthesized in a fluorine atmosphere. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction measurements were used for their structural characterization. These experiments have suggested that cointercalation of fluorine and VOF{sub 3} in the carbon occurs involving local structural modifications and that excess oxygen was present in the graphite layers. The study of electrochemical insertion of lithium was carried out at 25 C in a LiClO{sub 4}-propylene carbonate electrolyte by chronopotentiometry and ac impedance measurements. The interfacial charge-transfer process, associated to the half-reaction occurring during the intercalation, was found to be independent of the intercalation ratio of lithium cations, y. The chemical diffusion coefficient, {tilde D}{sub Li}, and the conductivity, {sigma}{sub Li}, obtained were deduced from impedance data by considering the geometric surface area. Both are roughly constant for all the y-range: {tilde D}{sub Li} = 3.8 {times} 10{sup {minus}10} cm{sup 2}/s and {sigma}{sub Li} = 9.3 {times} 10{sup {minus}7} {Omega}{sup {minus}1} cm{sup {minus}1} for C{sub 17.7}(VOF{sub 3})F; {tilde D}{sub Li} = 4.5 {times} 10{sup {minus}10} cm{sup 2}/s and {sigma}{sub Li} = 2.7 {times} 10{sup {minus}7} {Omega}{sup {minus}1} cm{sup {minus}1} for C{sub 20.4}(VOF{sub 3})F.

Groult, H.; Devilliers, D. [Univ. Pierre et Marie Curie, Paris (France). Lab. d`Electrochimie; Kumagai, N. [Iwate Univ., Ueda, Morioka (Japan); Nakajima, T.; Matsuo, Y. [Kyoto Univ. (Japan)

1996-07-01

318

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

319

A new advanced surface modification technique--titanium oxide ceramic surface implants: the background and long-term results.  

PubMed

This paper discusses the background of advanced surface modification technologies and presents a new technique that forms a titanium oxide ceramic coating with relatively long-term clinical use. Three general techniques are used to modify surfaces: adding or removing material, or changing material already present. Surface properties can also be changed through laser or electron beam thermal treatment without adding or removing material. The new technique outlined in this paper describes producing a corrosion-resistant, 2000 A to 2500 A thick, coherent crystalline oxide ceramic layer on the surface of titanium implants. The layer is grown electrochemically from the bulk of the metal and modified by heat treatment. Compared with implants covered with other coatings, the improved properties of such oxide ceramic-coated implants include the advantages of higher external hardness and greater adherence between the titanium and the ceramic oxide coating. The virtually perfect insulation between the tissue and the metal prevents metal allergy. The coated implants were subjected to various physical and chemical tests and electron microscopy for a qualitative characterization. Finally, these implants (plates, screws for maxillofacial osteosynthesis, and dental root implants) were followed in surgical practice for 10 years. Tests demonstrated and the acquired experience confirmed the good properties of the titanium oxide ceramic-coated implants. PMID:10847966

Szabó, G; Kovács, L; Vargha, K; Barabás, J; Németh, Z

1999-01-01

320

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

321

Destruction of hazardous and mixed wastes using mediated electrochemical oxidation in a Ag(II)HNO3 bench scale system  

SciTech Connect

Mediated Electrochemical Oxidation (MEO) is a promising technology for the destruction of organic containing wastes and the remediation of mixed wastes containing transuranic components. The combination of a powerful oxidant and an acid solution allows the conversion of nearly all organics, whether present in hazardous or in mixed waste, to carbon dioxide. Insoluble transuranics are dissolved in this process and may be recovered by separation and precipitation. The oxidant, or mediator, is a multivalent transition metal ion which is cleanly recycled in a number of charge transfer steps in an electrochemical cell. The MEO technique offers several advantages which are inherent in the system. First, the oxidation/dissolution processes are accomplished at near ambient pressures and temperatures (30-70{degrees}C). Second, all waste stream components and oxidation products (with the exception of evolved gases) are contained in an aqueous environment. This electrolyte acts as an accumulator for inorganics which were present in the original waste stream, and the large volume of electrolyte provides a thermal buffer for the energy released during oxidation of the organics. Third, the generation of secondary waste is minimal, as the process needs no additional reagents. Finally, the entire process can be shut down by simply turning off the power, affording a level of control unavailable in some other techniques. Although the oxidation of organics and the dissolution of transuranics by higher valency metal ions has been known for some time, applying the MEO technology to waste treatment is a relatively recent development. Numerous groups, both in the United States and Europe, have made substantial progress in the last decade towards understanding the mechanistic pathways, kinetics, and engineering aspects of the process. At Lawrence Livermore National Laboratory, substantial contributions have been made to this knowledge base in these areas and others. Conceptual design and engineering development have been completed for a pilot plant-scale MEO system, and numerous data have been gathered on the efficacy of the process for a wide variety of anticipated waste components. This presentation will review the data collected at LLNL for a bench scale system based primarily on the use of a Ag(II) mediator in a nitric acid electrolyte; results from several other mediator/acid combinations will be included. Data obtained on the chemical, electrochemical, and engineering aspects will be presented. The topics of organics destruction, transuranic recovery, and some of the ancillary systems will be addressed, and areas requiring further study will be mentioned.

Balazs, B.; Chiba, Z.; Hsu, P.; Lewis, P.; Murguia, L.; Adamson, M.

1997-02-01

322

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

PubMed Central

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

323

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

324

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

NASA Astrophysics Data System (ADS)

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

Kakaei, Karim; Zhiani, Mohammad

2013-03-01

325

Design of a visible light driven photo-electrochemical/electro-Fenton coupling oxidation system for wastewater treatment.  

PubMed

In this study, we report on a photo-electrochemical/electro-Fenton oxidation (PEC/EF) system by coupling visible light driven photo-electrochemical oxidation (PEC) and electro-Fenton oxidation (EF) in an undivided cell. Bi2WO6 nanoplates deposited on FTO glass (Bi2WO6/FTO) and Fe@Fe2O3 core-shell nanowires supported on activated carbon fiber (Fe@Fe2O3/ACF) were used as the anode and the cathode in the PEC/EF system, respectively. This novel PEC/EF system showed much higher activity than the single PEC and EF systems on degradation of rhodamine B in aqueous solution at natural pH. Moreover, the degradation and the instantaneous current efficiencies of the PEC/EF system were increased by 154% and 26% in comparison with the sum of those of single PEC and EF systems, respectively. These significant enhancements could be attributed to the synergetic effect from better separation of photo-generated carriers in the photo-anode and the transfer of photo-electrons to the oxygen diffusion cathode to generate more electro-generated H2O2 and hydroxyl radicals on the Fenton cathode. The better separation of photo-generated carriers contribute more to the overall degradation enhancement than the photo-electrons generated H2O2 and the subsequent Fenton reaction on the cathode during the PEC/EF process. PMID:23017238

Ding, Xing; Ai, Zhihui; Zhang, Lizhi

2012-11-15

326

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

327

Graphene oxide nanoplatelets as excellent electrochemical active materials for VO 2+\\/ VO 2 + and V 2+\\/V 3+ redox couples for a vanadium redox flow battery  

Microsoft Academic Search

Graphene oxide nanoplatelets (GONPs) are presented as electrochemical active materials for VO2+\\/VO2+ and V2+\\/V3+ redox couples for a vanadium redox flow battery. The structures and electrochemical properties of GONPs treated at different temperatures were investigated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and cyclic voltammetry. The results indicate that GONPs treated at

Pengxian Han; Haibo Wang; Zhihong Liu; Xiao Chen; Wen Ma; Jianhua Yao; Yuwei Zhu; Guanglei Cui

328

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

329

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

330

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

SciTech Connect

In this work, the examination of electrochemical noise data comprised three main approaches: one, a computer simulation of the anodic and cathodic activity relating to corrosion on a metal surface; two, experimental modeling of the electrochemical environment inside nuclear waste storage containers and collection of EN generated; and three, Wavelet analysis of the EN data from the first two parts. The simulation of EN proved to be effective in replicating the EN data of both general and pitting corrosion. Using competition mechanisms for the anodic and cathodic sites on the surface, the long-term, low-frequency data generated by localized pitting corrosion was reproduced. Disabling one or more of the rules of the simulation eliminated the low-frequency character of the data, and eliminating all of the rules effectively reproduced general corrosion noise. The simulation accuracy benefited from comparison to experimental data, and conversely, it improved the EN analysis by providing theory for the underlying mechanisms. The experimental electrochemical cell modeled the important factors in nuclear waste storage containers for this EN study; mainly increased temperature and the concentrations of corrosion-inducing or inhibiting chemicals. It also provided a platform for studying how the EN was affected by the competing chemicals.

MacDonald, Digby D.

2005-06-01

331

Review: advances in electrochemical genosensors-based methods for monitoring blooms of toxic algae.  

PubMed

Harmful algal blooms (HABs), which have expanded worldwide in their occurrence and frequency, are a serious menace to aquatic ecosystems and humans. The development of rapid, accurate and cost-effective detection systems for toxic algal monitoring in aquatic environments is urgently required. Although many efforts have been devoted to develop reliable tools to monitor the entire spectrum of existing toxic algae, a portable semi-automated system that enables HAB monitoring at a low cost is still not available for general purchase. This work reviews the challenges and opportunities in translating the remarkable progress of electrochemical genosensors-based methods towards practical in situ HAB monitoring applications. It is specifically focused on reviewing the optimised methods for a detection system based on a sandwich hybridisation assay (SHA) performed over transducer platforms of different materials, geometries and dimensions and presenting the diverse advantages and disadvantages among them. Probe design and specificity and optimisation of the genosensor in terms of hybridisation conditions and electrochemical signal are discussed as well as their long-term stability and storage and semi-automation attempts. With continuous innovation and attention to key challenges, we expect semi-automatic devices containing DNA-based electrochemical biosensors to have an important impact upon monitoring of serious HAB events. PMID:23097073

Orozco, Jahir; Medlin, Linda K

2013-10-01

332

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

333

Enhancing electrochemical performance by control of transport properties in buffer layers - solid oxide fuel/electrolyser cells.  

PubMed

The current work demonstrates how tailoring the transport properties of thin ceria-based buffer layers in solid oxide fuel or electrolyser cells can provide the necessary phase stability against chemical interaction at the electrolyte/electrode interface, while also providing radical improvements in the electrochemical performance of the oxygen electrode. Half cells of Ce0.8R0.2O2-? + 2 mol% Co buffer layers (where R = Gd, Pr) with Nd2NiO4+? electrodes were fabricated by spin coating on dense YSZ electrolyte supports. Dramatic decreases in polarization resistance, Rp, of up to an order of magnitude, could be achieved in the order, Pr ? Gd < no buffer layer. The current article shows how this improvement can be related to increased levels of ambipolar conductivity in the mixed conducting buffer layer, which provides an additional parallel path for electrochemical reaction. This is an important breakthrough as it shows how electrode polarization resistance can be substantially improved, in otherwise identical electrochemical cells, solely by tailoring the transport properties of thin intermediate buffer layers. PMID:25857870

Ramasamy, Devaraj; Nasani, Narendar; Brandão, Ana D; Pérez Coll, Domingo; Fagg, Duncan P

2015-04-21

334

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

335

Pt-Fe catalyst nanoparticles supported on single-wall carbon nanotubes: Direct synthesis and electrochemical performance for methanol oxidation  

NASA Astrophysics Data System (ADS)

Single-wall carbon nanotubes (SWCNTs) supported Pt-Fe nanoparticles have been prepared by one-step hydrogen arc discharge evaporation of carbon electrode containing both Pt and Fe metal elements. The formation of SWCNTs and Pt-Fe nanoparticles occur simultaneously during the evaporation process. High-temperature hydrogen treatment and hydrochloric acid soaking have been carried out to purify and activate those materials in order to obtain a new type of Pt-Fe/SWCNTs catalyst for methanol oxidation. The Pt-Fe/SWCNTs catalyst performs much higher electrocatalytic activity for methanol oxidation, better stability and better durability than a commercial Pt/C catalyst according to the electrochemical measurements, indicating that it has a great potential for applications in direct methanol fuel cells.

Ma, Xiaohui; Luo, Liqiang; Zhu, Limei; Yu, Liming; Sheng, Leimei; An, Kang; Ando, Yoshinori; Zhao, Xinluo

2013-11-01

336

Reinforcement of a sugar-based bolaamphiphile/functionalized graphene oxide composite gel: rheological and electrochemical properties.  

PubMed

A sugar-based bolaamphiphile/graphene oxide composite hydrogel has been prepared using simple mixing. Unlike the corresponding sugar-based native gel, the composite gel exhibits a fibrillar structure with a 10-20 nm fiber diameter. The composite gel forms an interdigitated bilayer structure incorporating intermolecular hydrogen-bonding interactions. The composite gel formation did not change the beneficial electrical properties of graphene offering the potential for integration of this new material into electronic systems. Interestingly, the mechanical and electrochemical properties of the composite gel are both dramatically enhanced when compared to the native gel, thereby reflecting that the functionalized graphene oxide layers are efficiently intercalated within the composite gel structure. PMID:24093646

Lee, Ji Ha; Ahn, Junho; Masuda, Mitsutoshi; Jaworski, Justyn; Jung, Jong Hwa

2013-11-01

337

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

338

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

339

Oxidative stress in aging: advances in proteomic approaches.  

PubMed

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

340

Evaluation of an Oxide Layer on NI-CR-MO-W Alloy Using Electrochemical Impedance Spectroscopy and Surface Analysis  

SciTech Connect

High corrosion resistance under very aggressive conditions is a distinguishing property of Ni-Cr-Mo-W alloys. One such alloy, Alloy 22, is a candidate material for fabrication of the outer layer of high-level nuclear waste (HLNW) packages for the proposed HLNW repository at Yucca Mountain, Nevada, USA. We are using Electrochemical Impedance Spectroscopy (EIS), ex-situ X-Ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectroscopy (ToF SIMS) to characterize the electrochemical properties and composition of the protective oxide formed on Alloy 22 surfaces. These studies have been conducted at temperatures up to 90 C at potentials from -0.8 V to 0.8 V (vs. Ag/AgCl (sat'd KCl)) in deaerated 5 mol L{sup -1} NaCl solution. Using this combination of techniques, we can correlate the electrical (from EIS) and compositional properties (from XPS, ToF SIMS) of the oxide. At more negative potentials (-0.8 V to -0.4 V) the film exhibits a low charge transfer resistance and high capacitance, indicating the presence of a very defective film with a high concentration of electronic defects. The presence of additional elements in the equivalent circuit, corresponding to water reduction, supports this suggestion. At these potentials, surface analysis techniques show a thin oxide layer with a low concentration of Cr203. Increasing the potential (to between -0.2 and 0.2 V) leads to a major increase in overall interfacial resistance consistent with the formation of an oxide with a small concentration of electronic defects. At the same time, the surface analysis techniques show increases in the film thickness and the Cr{sub 2}O{sub 3} content. A further increase in potential to 0.8 V, in general, leads to a decrease in interfacial resistance throughout the film. When the Cr{sub 2}O{sub 3} barrier layer is degraded, then the higher oxidation states of Mo and W species (MO{sup VI}, W{sup VI}) increase in concentration and are stored in the outer part of the film (at temperatures up to 60 C). The storage of these high oxidation state ions generates a high interfacial capacitance. At high temperature (above 60 C), the XPS and EIS show that the high oxidation states of Mo and W are absent. We think this is because they dissolve from the oxide under those conditions.

D. Zagidulin; P. Jakupi; J.J. Noel; D.W. Shoesmith

2006-12-21

341

A new cleaning process combining non-ionic surfactant with diamond film electrochemical oxidation for polished silicon wafers  

NASA Astrophysics Data System (ADS)

This paper presents a new cleaning process for particle and organic contaminants on polished silicon wafer surfaces. It combines a non-ionic surfactant with boron-doped diamond (BDD) film anode electrochemical oxidation. The non-ionic surfactant is used to remove particles on the polished wafer's surface, because it can form a protective film on the surface, which makes particles easy to remove. The effects of particle removal comparative experiments were observed by metallographic microscopy, which showed that the 1% v/v non-ionic surfactant achieved the best result. However, the surfactant film itself belongs to organic contamination, and it eventually needs to be removed. BDD film anode electrochemical oxidation (BDD-EO) is used to remove organic contaminants, because it can efficiently degrade organic matter. Three organic contaminant removal comparative experiments were carried out: the first one used the non-ionic surfactant in the first step and then used BDD-EO, the second one used BDD-EO only, and the last one used RCA cleaning technique. The XPS measurement result shows that the wafer's surface cleaned by BDD-EO has much less organic residue than that cleaned by RCA cleaning technique, and the non-ionic surfactant can be efficiently removed by BDD-EO.

Baohong, Gao; Yadong, Zhu; Yuling, Liu; Shengli, Wang; Qiang, Zhou; Xiaoyan, Liu

2010-07-01

342

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

SciTech Connect

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

Taylor, G.T.; Sullivan, I.A.; Newey, A.W.E. [AWE, Aldermaston, Reading, RG7 4PR (United Kingdom)

2006-07-01

343

Electrochemical characteristics of the reduced graphene oxide/carbon nanotube/polypyrrole composites for aqueous asymmetric supercapacitors  

NASA Astrophysics Data System (ADS)

Polypyrrole (PPy) has been polymerized onto reduced graphene oxide/carbon nanotube (rGO/CNT) to form an rGO/CNT/PPy composite using the chemical oxidation method. The electrochemical characteristics of the above composite in various aqueous electrolytes are systematically compared for the asymmetric supercapacitor application. The electrochemical characteristics of rGO/CNT/PPy in the electrolytes containing K+ show improved reversibility and higher stability. Introducing XC-72 in preparing the electrode has been found to enhance the specific capacitance and the cycle stability of rGO/CNT/PPy. The charge storage stability of rGO/CNT/PPy + XC-72 in various potential windows has been evaluated through the potential bias stress test. An asymmetric supercapacitor (ASC) with a positive electrode of Mn3O4 and a negative electrode of rGO/CNT/PPy + XC-72 is successfully demonstrated, which shows specific energy and power of 14. Wh kg-1 and 6.62 kW kg-1 with a cell voltage of 1.6 V. This ASC with a cell voltage of 1.6 V shows excellent charge-discharge cycle stability and ideal capacitive behavior in NaNO3 even after the application of 3250 charge-discharge cycles.

Peng, Yu-Jung; Wu, Tzu-Ho; Hsu, Chun-Tsung; Li, Shin-Ming; Chen, Ming-Guan; Hu, Chi-Chang

2014-12-01

344

Oxidative Stress to the Cornea, Changes in Corneal Optical Properties, and Advances in Treatment of Corneal Oxidative Injuries  

PubMed Central

Oxidative stress is involved in many ocular diseases and injuries. The imbalance between oxidants and antioxidants in favour of oxidants (oxidative stress) leads to the damage and may be highly involved in ocular aging processes. The anterior eye segment and mainly the cornea are directly exposed to noxae of external environment, such as air pollution, radiation, cigarette smoke, vapors or gases from household cleaning products, chemical burns from splashes of industrial chemicals, and danger from potential oxidative damage evoked by them. Oxidative stress may initiate or develop ocular injury resulting in decreased visual acuity or even vision loss. The role of oxidative stress in the pathogenesis of ocular diseases with particular attention to oxidative stress in the cornea and changes in corneal optical properties are discussed. Advances in the treatment of corneal oxidative injuries or diseases are shown. PMID:25861412

Cejka, Cestmir; Cejkova, Jitka

2015-01-01

345

Mechanistic differences between electrochemical and gas-phase thermal oxidation of platinum-group transition metals as discerned by surface-enhanced Raman spectroscopy  

SciTech Connect

The oxidation of five Pt-group metals--platinum, palladium, iridium, rhodium, and ruthenium--is examined by means of surface-enhanced Raman spectroscopy (SERS) in aqueous electrochemical and gaseous dioxygen environments as a function of electrode potential and temperature, respectively, with the objective of intercomparing systematically the conditions required for surface oxide formation and discerning the reaction mechanisms involved. The SERS strategy, utilizing ultrathin Pt-group metal films electrodeposited on a gold substrate, enables monolayer-level metal oxide vibrational spectra to readily be obtained in both the electrochemical and gaseous environments. The SER spectra obtained during positive- and then negative-going potential excursions in aqueous 0.1 M HCLO{sub 4} display metal-oxygen vibrational bands signaling anodic oxide formation and subsequent removal at potentials consistent with corresponding voltammetric data. The nature of the amorphous oxides (or hydroxides) formed is deduced by comparison with bulk-phase metal oxide Raman spectra. The onset potentials for surface oxide formation are comparable to the thermodynamic potentials for the bulk-phase metal oxides. In contrast, the onset of surface oxidation even in ambient-pressure dioxygen uniformly requires elevated temperatures, {gt}200 C for each metal except for iridium, where oxide formation occurs at ca. 100 C. While spectral differences are evident, especially on palladium and ruthenium, the nature of the oxides formed in the electrochemical and gaseous systems is largely similar. The highly activated nature of the gaseous O{sub 2} oxidations is consistent with literature reports for Pt-group surfaces in ultrahigh vacuum as well as higher-pressure conditions. Likely reasons for the markedly more efficacious metal electrooxidations are discussed. Thermodynamic factors are not responsible, since the free-energy driving forces for the gaseous O{sub 2} oxidations are larger than for the electrochemical reactions at the applied potentials where surface oxidation for the latter processes proceeds at room temperature. The electrostatic driving forces for oxygen incorporation into the metal lattice (via high-field ion transport) are also typically more favorable for the gaseous systems, as evidenced by a comparison of the metal-solution and metal-gas surface potentials. The intrinsically more facile electrochemical processes thereby deduced are attributed to the occurrence of direct oxide production via a metal-oxygen place-exchange mechanism, expedited by interfacial solvation and therefore being energetically unfavorable in the anhydrous gas-phase environment. Other factors, such as the formation of precursor chemisorbed oxygen, are also considered.

Chan, H.Y.H.; Zou, S.; Weaver, M.J.

1999-12-16

346

A Kinetic Study of the Electrochemical Vapor Deposition of Solid Oxide Electrolyte Films on Porous Substrates  

Microsoft Academic Search

The electrochemical vapor deposition (EVD) method is a very promising technique for making gas-tight dense solid electrolyte films on porous substrates, In this paper, theoretical and experimental studies on the kinetics of the deposition of dense yttria-stabilized zirconia films on porous ceramic substrates by the EVD method are presented, The more system- atic theoretical analysis is based on a mode)

Y. S. Lin; L. G. J. de Haart; K. J. de Vries; A. J. Burggraaf

2009-01-01

347

Electrochemical impedance spectra of solid-oxide fuel cells and polymer membrane fuel cells  

Microsoft Academic Search

Electrochemical impedance spectroscopy (EIS) is a very useful method for the characterization of fuel cells. The anode and cathode transfer functions have been determined independently without a reference electrode using symmetric gas supply of hydrogen or oxygen on both electrodes of the fuel cell at open circuit potential (OCP). EIS are given for both polymer electrolyte fuel cells (PEFC) and

N. Wagner; W. Schnurnberger; B. Müller; M. Lang

1998-01-01

348

A comparative treatment of stabilized landfill leachate: Coagulation and activated carbon adsorption vs. electrochemical oxidation  

Microsoft Academic Search

This work investigated the treatment of a landfill leachate that had previously undergone biological treatment. Two treatment schemes were compared: the first one involved coagulation followed by activated carbon adsorption, whilst the second was electrochemical treatment. Coagulation with alum resulted in a 50% removal of chemical oxygen demand (COD). The optimum aluminium dose was 3 mM Al. Activated carbon adsorption

Chrystalla Papastavrou; Dionissios Mantzavinos; Evan Diamadopoulos

2009-01-01

349

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

350

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

351

Electrochemical response of ZrO 2-incorporated oxide layer on AZ91 Mg alloy processed by plasma electrolytic oxidation  

Microsoft Academic Search

ZrO2 nanoparticles well dispersed in an electrolyte were effectively incorporated in an oxidized surface passivation layer on AZ91 Mg alloy by a plasma electrolytic oxidation (PEO) process. The electrophoretic reaction and mechanical mixing in molten magnesium oxide were the main factors leading to incorporation of ZrO2 nanoparticles in the magnesium oxide layer. Incorporated ZrO2 nanoparticles were mainly located in pores

Kang Min Lee; Ki Ryong Shin; Seung Namgung; Bongyoung Yoo; Dong Hyuk Shin

2011-01-01

352

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

353

Experimental Approach to Controllably Vary Protein Oxidation While Minimizing Electrode Adsorption for Boron-Doped Diamond Electrochemical Surface Mapping Applications  

SciTech Connect

Oxidative protein surface mapping has become a powerful approach for measuring the solvent accessibility of folded protein structures. A variety of techniques exist for generating the key reagent hydroxyl radicals for these measurements; however, many of these approaches require use of radioactive sources or caustic oxidizing chemicals. The purpose of this research was to evaluate and optimize the use of boron-doped diamond (BDD) electrochemistry as a highly accessible tool for producing hydroxyl radicals as a means to induce a controllable level of oxidation on a range of intact proteins. These experiments utilize a relatively high flow rates to reduce protein residence time inside the electrochemical flow chamber, along with a unique cell activation approach to improve control over the intact protein oxidation yield. Studies were conducted to evaluate the level of protein adsorption onto the electrode surface. This report demonstrates a robust protocol for the use of BDD electrochemistry and high performance LC-MS/MS as a high-throughput experimental pipeline for probing higher order protein structure, and illustrates how it is complementary to predictive computational modeling efforts.

McClintock, Carlee [ORNL; Hettich, Robert {Bob} L [ORNL

2013-01-01

354

Separators for electrochemical cells  

DOEpatents

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

355

Advanced Surface Modification of Indium Tin Oxide for Improved Charge Injection in Organic Devices  

E-print Network

Advanced Surface Modification of Indium Tin Oxide for Improved Charge Injection in Organic Devices and involves sequential formation of a monolayer of a -conjugated organic semiconductor on the indium tin oxide, indium tin oxide, ITO) and cathode of organic light emitting diodes (OLEDs), or at electrodes in other

Schwartz, Jeffrey

356

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

357

Ethylene Oxidation over Platinum: In SituElectrochemically Controlled Promotion Using Na–??? Alumina and Studies with a Pt(111)\\/Na Model Catalyst  

Microsoft Academic Search

Electrochemically modified ethylene oxidation over a Pt film supported on the Na+ion conductor ??? alumina has been studied over a range of conditions encompassing both promotion and poisoning. The system exhibits reversible behavior, and the data are interpreted in terms of (i) Na-enhanced oxygen chemisorption and (ii) poisoning of the surface by accumulation of Na compounds. At low Na coverages

Ian R. Harkness; Christopher Hardacre; Richard M. Lambert; Ioannis V. Yentekakis; Constantinos G. Vayenas

1996-01-01

358

Spray absorption and electrochemical reduction of nitrogen oxides from flue gas.  

PubMed

This work developed an electrochemical reduction system which can effectively scrub NO× from flue gas by using aqueous solution of Fe(II)(EDTA) (ethylenediaminetetraacetate) as absorbent and electrolyte. This new system features (a) complete decomposition of NOX to harmless N2; and (b) fast regeneration of Fe(II)(EDTA) through electrochemical reaction. The Fe(II)(EDTA) solution was recycled and reused continuously during entire process, and no harmful waste was generated. The reaction mechanism was thoroughly investigated by using voltammetric, chromatographic and spectroscopic approaches. The operating conditions of the system were optimized based on NOX removal efficiency. Approximately 98% NO removal was obtained at the optimal condition. The interference of SO2 in flue gas and the system operating stability was also evaluated. PMID:23875953

Guo, Qingbin; Sun, Tonghua; Wang, Yalin; He, Yi; Jia, Jinping

2013-08-20

359

Mechanistic differences between electrochemical and gas-phase thermal oxidation of platinum-group transition metals as discerned by surface-enhanced Raman spectroscopy  

Microsoft Academic Search

The oxidation of five Pt-group metals--platinum, palladium, iridium, rhodium, and ruthenium--is examined by means of surface-enhanced Raman spectroscopy (SERS) in aqueous electrochemical and gaseous dioxygen environments as a function of electrode potential and temperature, respectively, with the objective of intercomparing systematically the conditions required for surface oxide formation and discerning the reaction mechanisms involved. The SERS strategy, utilizing ultrathin Pt-group

Ho Yeung H. Chan; Shouzhong Zou; Michael J. Weaver

1999-01-01

360

Electrochemical degradation of Nafion ionomer to functionalize carbon support for methanol electro-oxidation  

Microsoft Academic Search

An effective electrochemical route to produce functional groups on carbon surface is demonstrated. Cyclic voltammetric (CV) sweeps are performed in 0.5M H2SO4 electrolyte on electrodes containing carbon cloth, Vulcan XC72R, and Nafion ionomer. With supply of ambient oxygen, the generation of hydroxyl radicals from the oxygen reduction reaction during CV cycles initiates the decomposition of Nafion ionomer that leads to

Yu-Chi Hsieh; Jing-Yu Chen; Pu-Wei Wu

361

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

362

Applications of advanced oxidation processes: present and future.  

PubMed

The use of advanced oxidation processes (AOPs) to remove pollutants in various water treatment applications has been the subject of study for around 30 years. Most of the available processes (Fenton reagent, O3 under basic conditions, O3/H2O2, O3/UV, O3/solid catalyst, H2O2/M(n+), H2O2/UV, photo-assisted Fenton, H2O2/solid catalyst, H2O2/NaClO, TiO2/UV etc.) have been investigated in depth and a considerable body of knowledge has been built up about the reactivity of many pollutants. Various industrial applications have been developed, including ones for ground remediation (TCE, PCE), the removal of pesticides from drinking water, the removal of formaldehyde and phenol from industrial waste water and a reduction in COD from industrial waste water. The development of such AOP applications has been stimulated by increasingly stringent regulations, the pollution of water resources through agricultural and industrial activities and the requirement that industry meet effluent discharge standards. Nevertheless, it is difficult to obtain an accurate picture of the use of AOPs and its exact position in the range of water treatment processes has not been determined to date. The purpose of this overview is to discuss those processes and provide an indication of future trends. PMID:15077976

Suty, H; De Traversay, C; Cost, M

2004-01-01

363

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

364

The utilization of SiNWs/AuNPs-modified indium tin oxide (ITO) in fabrication of electrochemical DNA sensor.  

PubMed

This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using self-assembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0-178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4°C in silica gel. PMID:25491829

Rashid, Jahwarhar Izuan Abdul; Yusof, Nor Azah; Abdullah, Jaafar; Hashim, Uda; Hajian, Reza

2014-12-01

365

Graphene oxide nanoribbon-based sensors for the simultaneous bio-electrochemical enantiomeric resolution and analysis of amino acid biomarkers.  

PubMed

In this work, a straightforward in-situ measurement of l and d-amino acids (AAs) has been developed using disposable graphene oxide nanoribbon (GON) screen printed electrodes. For that, we took advantage of the electroactivity of certain clinically relevant AAs, such as tyrosine (Tyr) and methionine (Met), which are involved in important bacterial diseases (Bacillus subtilis and Vibrio cholera, respectively). The strategy is based on a dual electrochemical and enzymatic approach. The d-AA with the class enzyme d amino acid oxidase (DAAO) generates H2O2. This H2O2 is simultaneously detected with the l-AA, electroactive molecule by differential pulse voltammetry (DPV). These GON disposable platforms use just 50?L of sample and a total analysis time of 360s. Both l and d enantiomers calibration and quantitative analysis were explored and were simultaneously detected with accuracy and precision in urine samples. Any interference of uric acid and other electroactive AAs was noticed. This proposed electrochemical GON-based enantiomeric bio-sensor becomes a highly promising tool as future point of care for fast and reliable early diagnosis of diseases related to the presence of d-AAs. PMID:25562744

Martín, Aída; Batalla, Pilar; Hernández-Ferrer, Javier; Martínez, María Teresa; Escarpa, Alberto

2015-06-15

366

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

367

New innovative materials for advanced electrochemical applications in battery and fuel cell systems  

Microsoft Academic Search

The advanced material POLYMET is an innovative high tech polymer with a three-dimensional polymeric structure metallized with an enclosing coating of different kinds of metals or alloys. The result is a range of tailor-made, microporous structures on a designable scale. By varying the metals and alloys, it is possible to draw upon extremely diverse areas of applications such as battery

S Voß; H Kollmann; W Kollmann

2004-01-01

368

Hierarchically designed three-dimensional macro/mesoporous carbon frameworks for advanced electrochemical capacitance storage.  

PubMed

Mesoporous carbon (m-C) has potential applications as porous electrodes for electrochemical energy storage, but its applications have been severely limited by the inherent fragility and low electrical conductivity. A rational strategy is presented to construct m-C into hierarchical porous structures with high flexibility by using a carbon nanotube (CNT) sponge as a three-dimensional template, and grafting Pt nanoparticles at the m-C surface. This method involves several controllable steps including solution deposition of a mesoporous silica (m-SiO2 ) layer onto CNTs, chemical vapor deposition of acetylene, and etching of m-SiO2 , resulting in a CNT@m-C core-shell or a CNT@m-C@Pt core-shell hybrid structure after Pt adsorption. The underlying CNT network provides a robust yet flexible support and a high electrical conductivity, whereas the m-C provides large surface area, and the Pt nanoparticles improves interfacial electron and ion diffusion. Consequently, specific capacitances of 203 and 311?F?g(-1) have been achieved in these CNT@m-C and CNT@m-C@Pt sponges as supercapacitor electrodes, respectively, which can retain 96?% of original capacitance under large degree compression. PMID:25752493

Yang, Yanbing; Li, Peixu; Wu, Shiting; Li, Xinyang; Shi, Enzheng; Shen, Qicang; Wu, Dehai; Xu, Wenjing; Cao, Anyuan; Yuan, Quan

2015-04-13

369

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

370

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

371

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

372

Low-cost electrochemical treatment of indium tin oxide anodes for high-efficiency organic light-emitting diodes  

NASA Astrophysics Data System (ADS)

We demonstrate a simple low-cost approach as an alternative to conventional O2 plasma treatment to modify the surface of indium tin oxide (ITO) anodes for use in organic light-emitting diodes. ITO is functionalized with F- 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 O2 plasma-treated ITO. Fluorination also increases the transparency in the near-infrared region.

Hui Cheng, Chuan; Shan Liang, Ze; Tong Du, Guo; Gang Wang, Li; Dong Gao, Guo; Zhou, Ting; Ming Bian, Ji; Min Luo, Ying

2014-01-01

373

Degradation of cationic red X-GRL by electrochemical oxidation on modified PbO(2) electrode.  

PubMed

This work investigated the degradation of an azo dye, cationic red X-GRL, by electrochemical oxidation on a novel PbO(2) anode modified by fluorine resin. The influences of treatment time, electrolyte concentration, current density, temperature and initial dye concentration on the color and COD removal were critically examined. This process showed a high current efficiency and competitive energy consumption for effective treatment of dye wastewater containing a certain salt content. In the investigated electrolyte concentrations, high salt content exhibited insignificant promotion on the color and COD removal but favored the decrease of energy consumption. During treatment, the current efficiency decreased but the energy consumption increased with treatment time; thus, this method was more suitable for the pretreatment of high-concentrated azo dye wastewater. Based on the degradation intermediates identification, a simplified degradation pathway for cationic red X-GRL was proposed. PMID:17904735

Zhou, Minghua; He, Jianjian

2008-05-01

374

Development of a Silver-Copper Oxide Braze for Joining Metallic and Ceramic Components in Electrochemical Devices  

SciTech Connect

One of the challenges in manufacturing solid-state electrochemical devices, such as planar solid oxide fuel cells (pSOFC), is in joining the ceramic and metallic components such that the resulting joint is rugged and stable under continuous high temperature operation in an oxidizing atmosphere. A well proven method of joining dissimilar materials is by brazing. Unfortunately many of the commercially available ceramic-to-metal braze alloys exhibit oxidation behavior which is unacceptable for potential use in a pSOFC application. As a result, glass sealing is currently favored for stack assembly. However, the maximum operating temperature that a glass joint may be exposed to is limited by the softening point of the glass. In addition, high temperature glasses with appropriately matching coefficients of thermal expansion typically display signs of devitrification within the first few hours of exposure at operating temperature. As they crystallize, the carefully engineered expansion properties of these seal materials change significantly, ultimately limiting the number of thermal cycles and the rate of cycling at which the joints are capable of surviving. Recently, we have developed an alternative braze composition which designed specifically for use in air. The results of this study to date will be discussed.

Weil, K. Scott; Hardy, John S.; Kim, Jin Yong

2003-02-25

375

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

376

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

377

A bipolar electrochemical approach to constructive lithography: metal/monolayer patterns via consecutive site-defined oxidation and reduction.  

PubMed

Experimental evidence is presented, demonstrating the feasibility of a surface-patterning strategy that allows stepwise electrochemical generation and subsequent in situ metallization of patterns of carboxylic acid functions on the outer surfaces of highly ordered OTS monolayers assembled on silicon or on a flexible polymeric substrate. The patterning process can be implemented serially with scanning probes, which is shown to allow nanoscale patterning, or in a parallel stamping configuration here demonstrated on micrometric length scales with granular metal film stamps sandwiched between two monolayer-coated substrates. The metal film, consisting of silver deposited by evaporation through a patterned contact mask on the surface of one of the organic monolayers, functions as both a cathode in the printing of the monolayer patterns and an anodic source of metal in their subsequent metallization. An ultrathin water layer adsorbed on the metal grains by capillary condensation from a humid atmosphere plays the double role of electrolyte and a source of oxidizing species in the pattern printing process. It is shown that control over both the direction of pattern printing and metal transfer to one of the two monolayer surfaces can be accomplished by simple switching of the polarity of the applied voltage bias. Thus, the patterned metal film functions as a consumable "floating" stamp capable of two-way (forward-backward) electrochemical transfer of both information and matter between the contacting monolayer surfaces involved in the process. This rather unusual electrochemical behavior, resembling the electrochemical switching in nanoionic devices based on the transport of ions in solid ionic-electronic conductors, is derived from the nanoscale thickness of the water layer acting as an electrolyte and the bipolar (cathodic-anodic) nature of the water-coated metal grains in the metal film. The floating stamp concept introduced in this report paves the way to a series of unprecedented capabilities in surface patterning, which are particularly relevant to nanofabrication by chemical means and the engineering of a new class of molecular nanoionic systems. PMID:21661737

Zeira, Assaf; Berson, Jonathan; Feldman, Isai; Maoz, Rivka; Sagiv, Jacob

2011-07-01

378

Leaf-templated synthesis of 3D hierarchical porous cobalt oxide nanostructure as direct electrochemical biosensing interface with enhanced electrocatalysis.  

PubMed

A novel three-dimensional (3D) hierarchical porous cobalt oxide (Co3O4) architecture was first synthesized through a simple, cost-effective and environmentally friendly leaf-templated strategy. The Co3O4 nanoparticles (30-100 nm) with irregular shapes were interconnected with each other to form a 3D multilayer porous network structure, which provided high specific surface area and numerous electrocatalytic active sites. Subsequently, Co3O4 was successfully utilized as direct electrochemical sensing interface for non-enzymatic detection of H2O2 and glucose. By using chronoamperometry, the current response of the sensor at +0.31 V was linear with H2O2 concentration within 0.4-200 ?M with a low limit of detection (LOD) of 0.24 ?M (S/N=3) and a high sensitivity of 389.7 ?A mM(-1) cm(-2). Two linear ranges of 1-300 ?M (with LOD of 0.1 ?M and sensitivity of 471.5 ?A mM(-1) cm(-2)) and 4-12.5 mM were found at +0.59 V for glucose. In addition, the as-prepared sensor showed excellent stability and anti-interference performance for possible interferents such as ascorbic acid, uric acid, dopamine, acetaminophen and especially 0.15 M chloride ions. Similarly, other various metal oxide nanostructures may be also prepared using this similar strategy for possible applications in catalysis, electrochemical sensors, and fuel cells. PMID:25078713

Han, Lei; Yang, Da-Peng; Liu, Aihua

2015-01-15

379

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

380

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

381

Electroreduction-based electrochemical-enzymatic redox cycling for the detection of cancer antigen 15-3 using graphene oxide-modified indium-tin oxide electrodes.  

PubMed

We compare herein biosensing performance of two electroreduction-based electrochemical-enzymatic (EN) redox-cycling schemes [the redox cycling combined with simultaneous enzymatic amplification (one-enzyme scheme) and the redox cycling combined with preceding enzymatic amplification (two-enzyme scheme)]. To minimize unwanted side reactions in the two-enzyme scheme, ?-galactosidase (Gal) and tyrosinase (Tyr) are selected as an enzyme label and a redox enzyme, respectively, and Tyr is selected as a redox enzyme label in the one-enzyme scheme. The signal amplification in the one-enzyme scheme consists of (i) enzymatic oxidation of catechol into o-benzoquinone by Tyr and (ii) electroreduction-based EN redox cycling of o-benzoquinone. The signal amplification in the two-enzyme scheme consists of (i) enzymatic conversion of phenyl ?-d-galactopyranoside into phenol by Gal, (ii) enzymatic oxidation of phenol into catechol by Tyr, and (iii) electroreduction-based EN redox cycling of o-benzoquinone including further enzymatic oxidation of catechol to o-benzoquinone by Tyr. Graphene oxide-modified indium-tin oxide (GO/ITO) electrodes, simply prepared by immersing ITO electrodes in a GO-dispersed aqueous solution, are used to obtain better electrocatalytic activities toward o-benzoquinone reduction than bare ITO electrodes. The detection limits for mouse IgG, measured with GO/ITO electrodes, are lower than when measured with bare ITO electrodes. Importantly, the detection of mouse IgG using the two-enzyme scheme allows lower detection limits than that using the one-enzyme scheme, because the former gives higher signal levels at low target concentrations although the former gives lower signal levels at high concentrations. The detection limit for cancer antigen (CA) 15-3, a biomarker of breast cancer, measured using the two-enzyme scheme and GO/ITO electrodes is ca. 0.1 U/mL, indicating that the immunosensor is highly sensitive. PMID:24428396

Park, Seonhwa; Singh, Amardeep; Kim, Sinyoung; Yang, Haesik

2014-02-01

382

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

E-print Network

materials and demonstrate the utility of iridium in this application. An electrolysis cell fitted of Resource and Environmental Sciences, Wuhan University, China Molten oxide electrolysis (MOE and oxygen gas. Early efforts to produce metal by oxide electrolysis go back more than 100 years,4

Sadoway, Donald Robert

383

Advanced Cu chemical displacement technique for SiO2-based electrochemical metallization ReRAM application  

PubMed Central

This study investigates an advanced copper (Cu) chemical displacement technique (CDT) with varying the chemical displacement time for fabricating Cu/SiO2-stacked resistive random-access memory (ReRAM). Compared with other Cu deposition methods, this CDT easily controls the interface of the Cu-insulator, the switching layer thickness, and the immunity of the Cu etching process, assisting the 1-transistor-1-ReRAM (1T-1R) structure and system-on-chip integration. The modulated shape of the Cu-SiO2 interface and the thickness of the SiO2 layer obtained by CDT-based Cu deposition on SiO2 were confirmed by scanning electron microscopy and atomic force microscopy. The CDT-fabricated Cu/SiO2-stacked ReRAM exhibited lower operation voltages and more stable data retention characteristics than the control Cu/SiO2-stacked sample. As the Cu CDT processing time increased, the forming and set voltages of the CDT-fabricated Cu/SiO2-stacked ReRAM decreased. Conversely, decreasing the processing time reduced the on-state current and reset voltage while increasing the endurance switching cycle time. Therefore, the switching characteristics were easily modulated by Cu CDT, yielding a high performance electrochemical metallization (ECM)-type ReRAM. PMID:25364318

2014-01-01

384

Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine (WERF Report INFR6SG09)  

EPA Science Inventory

Carbamazepine is an anthropogenic pharmaceutical found in wastewater effluents that is quite resistant to removal by conventional wastewater treatment processes. Hydroxyl radical-based advanced oxidation processes can transform carbamazepine into degradation products but cannot m...

385

Copper recovery and gold enrichment from waste printed circuit boards by mediated electrochemical oxidation.  

PubMed

The present study aims to develop an eco-friendly chemical-electrochemical process for the simultaneous recovery of copper and separation of a gold rich residue from waste printed circuit boards (WPCBs). The process was carried out by employing two different types of reactors coupled in series: a leaching reactor with a perforated rotating drum, for the dissolution of base metals and a divided electrochemical reactor for the regeneration of the leaching solution with the parallel electrowinning of copper. The process performances were evaluated on the basis of the dissolution efficiency, current efficiency and specific energy consumptions. Finally a process scale up was realized taking into consideration the optimal values of the operating parameters. The laboratory scale leaching plant allowed the recovery of a high purity copper deposit (99.04wt.%) at a current efficiency of 63.84% and specific energy consumption of 1.75kWh/kg cooper. The gold concentration in the remained solid residue was 25 times higher than the gold concentration in the initial WPCB samples. PMID:24747374

Fogarasi, Szabolcs; Imre-Lucaci, Florica; Imre-Lucaci, Arpád; Ilea, Petru

2014-05-30

386

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

387

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

388

Review of iron-free Fenton-like systems for activating H2O2 in advanced oxidation processes.  

PubMed

Iron-catalyzed hydrogen peroxide decomposition for in situ generation of hydroxyl radicals (HO(•)) has been extensively developed as advanced oxidation processes (AOPs) for environmental applications. A variety of catalytic iron species constituting metal salts (in Fe(2+) or Fe(3+) form), metal oxides (e.g., Fe2O3, Fe3O4), and zero-valent metal (Fe(0)) have been exploited for chemical (classical Fenton), photochemical (photo-Fenton) and electrochemical (electro-Fenton) degradation pathways. However, the requirement of strict acidic conditions to prevent iron precipitation still remains the bottleneck for iron-based AOPs. In this article, we present a thorough review of alternative non-iron Fenton catalysts and their reactivity towards hydrogen peroxide activation. Elements with multiple redox states (like chromium, cerium, copper, cobalt, manganese and ruthenium) all directly decompose H2O2 into HO(•) through conventional Fenton-like pathways. The in situ formation of H2O2 and decomposition into HO(•) can be also achieved using electron transfer mechanism in zero-valent aluminum/O2 system. Although these Fenton systems (except aluminum) work efficiently even at neutral pH, the H2O2 activation mechanism is very specific to the nature of the catalyst and critically depends on its composition. This review describes in detail the complex mechanisms and emphasizes on practical limitations influencing their environmental applications. PMID:24857896

Bokare, Alok D; Choi, Wonyong

2014-06-30

389

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

390

Electrochemical oxidation of tramadol in low-salinity reverse osmosis concentrates using boron-doped diamond anodes.  

PubMed

The electrochemical treatment of low-salinity reverse osmosis (RO) concentrates was investigated using tramadol (100 ?M) as a model substance for persistent organic contaminants. Galvanostatic degradation experiments using boron-doped diamond electrodes at different applied currents were conducted in RO concentrates as well as in ultra-pure water containing either sodium chloride or sodium sulfate. Kinetic investigations revealed a significant influence of in-situ generated active chlorine besides direct anodic oxidation. Therefore, tramadol concentrations decreased more rapidly at elevated chloride content. Nevertheless, reduction of total organic carbon (TOC) was found to be comparatively low, demonstrating that transformation rather than mineralization was taking place. Early stage product formation could be attributed to both direct and indirect processes, including demethylation, hydroxylation, dehydration, oxidative aromatic ring cleavage and halogenation reactions. The latter led to various halogenated derivatives and resulted in AOX (adsorbable organic halogens) formation in the lower mg/L-range depending on the treatment conditions. Characterisation of transformation products (TPs) was achieved via MS(n) experiments and additional NMR measurements. Based on identification and quantification of the main TPs in different matrices and on additional potentiostatic electrolysis, a transformation pathway was proposed. PMID:25660808

Lütke Eversloh, Christian; Schulz, Manoj; Wagner, Manfred; Ternes, Thomas A

2015-04-01

391

Analysis for electrolytic oxidation and reduction of PbSO 4/Pb electrode by electrochemical QCM technique  

NASA Astrophysics Data System (ADS)

In situ observations of the mass change were carried out using the electrochemical quartz crystal microbalance (EQCM) technique for the active materials in a lead-acid battery during charge-discharge. Lead sulfate was formed on the surfaces of the pure Pb and Pb-Ca-Sn alloys immersed in 4.50 kmol m -3 H 2SO 4 solution at 298 K. The rates of PbSO 4 formation on the Pb-0.08 mass% Ca-Sn alloys, which are the choice materials for grids in the valve-regulated lead-acid battery (VRLA), were inhibited by the presence of Sn. This fact observed by the EQCM technique was in good agreement with the results determined by the prolonged corrosion test of 604.8 ks at 348 K. This state, in which the PbSO 4 exists in the surface and the underlying Pb is not thoroughly reacted, corresponds to the state of active materials after discharge. During electrolytic oxidation, i.e. the charging of the positive electrode, the reaction of PbSO 4?PbO 2 could take place to decrease the electrode mass when the current density exceeded a critical value. On the other hand, the reaction of PbSO 4?Pb could readily proceed at just one-fourth the current density of the electrolytic oxidation during the electrolytic reduction of the PbSO 4/Pb electrode, i.e. the charging of the negative electrode.

Taguchi, Masami; Sugita, Hiroshi

392

In vitro electrochemical investigations of advanced stainless steels for applications as orthopaedic implants  

Microsoft Academic Search

Potentiodynamic anodic polarization experiments on advanced stainless steels (SS), such as nitrogenbearing type 316L and 317L\\u000a SS, were carried out in Hank’s solution (8 g NaCl, 0.14 g CaCl2, 0.4 g KC1, 0.35 g NaHCO3, 1 g glucose, 0.1 g NaH2PO4, 0.1 g MgCl2, 0.06 g Na2HPO4 2H2O, 0.06 g MgSO4 7H2O\\/1000 mL) in order to assess the pitting and

M. Sivakumar; U. Kamachi Mudali; S. Rajeswari

1994-01-01

393

Microwave assisted synthesis of copper oxide and its application in electrochemical sensing  

NASA Astrophysics Data System (ADS)

Copper oxide nanopowders were prepared using copper acetate as the precursor and polyethylene glycol (PEG) as stabilizer in ethanol medium. The mixture containing copper acetate, sodium hydroxide and PEG was irradiated with microwave and nanometric copper oxide particles were formed within 8 min. The prepared nanoparticles were characterized using x-ray diffraction, UV-vis spectroscopy and scanning electron microscopy. The average particle size was found to be ~ 4 nm. This was used to modify glassy carbon electrode with PVDF & DMF as binder and used for sensing of carbohydrates (glucose and sucrose) and H2O2. The copper oxide nanoparticles showed excellent sensitivity in the range of 0.1 mM to 1 mM when choronoamperometry was carried out at 0.6 V Vs. Ag/AgCl. The observed sensitivity is much higher when compared with conventional micron sized copper oxide particles.

Felix, S.; Bala Praveen Chakkravarthy, R.; Nirmala Grace, A.

2015-02-01

394

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

395

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

396

Electrochemical oxidation of binary copper–nickel alloys in cryolite melts  

Microsoft Academic Search

Anodic oxidation of copper, nickel and two copper–nickel alloys was studied in cryolite melts at 1000°C. In an oxide-free melt, anodic dissolution of each material was observed, and the dissolution potential increases with the content of copper. SEM characterization of a Cu55–Ni45 alloy showed that nickel is selectively dissolved according to a de-alloying process. In an alumina-containing melt, a partial

L. Cassayre; P. Chamelot; L. Arurault; L. Massot; P. Palau; P. Taxil

2007-01-01

397

Critical factors in chemical characterization for the evaluation of decontamination in solids using advanced oxidation  

Microsoft Academic Search

Advanced oxidation technologies (AOT) have been applied to the treatment of numerous organic pollutants embedded in solid matrices (e.g., soil, sediments, sludge, etc.). Given potentially strong matrix-analyte interactions in solids, chemical characterization of both the target contaminants and their oxidation products is critical for the evaluation of any decontamination method. The success of AOT applications has been evaluated either directly

Alena Kubátová

2009-01-01

398

Optimizing the oxygen evolution reaction for electrochemical water oxidation by tuning solvent properties.  

PubMed

Electrochemical water-based energy cycles provide a most promising alternative to fossil-fuel sources of energy. However, current electrocatalysts are not adequate (high overpotential, lack of selectivity toward O2 production, catalyst degradation). We propose here mechanistic guidelines for experimental examination of modified catalysts based on the dependence of kinetic rates on the solvent dielectric constant. To illustrate the procedure we consider the fcc(111) platinum surface and show that the individual steps for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) change systematically with the polarizability of the medium. Thus changing this environmental variable can be used to tune the rate determining steps and the barriers, providing a means for screening and validating new systems to optimize the rate determining steps for the ORR and OER reaction pathways. PMID:25682836

Fortunelli, Alessandro; Goddard Iii, William A; Sementa, Luca; Barcaro, Giovanni

2015-02-26

399

Optimizing the oxygen evolution reaction for electrochemical water oxidation by tuning solvent properties  

NASA Astrophysics Data System (ADS)

Electrochemical water-based energy cycles provide a most promising alternative to fossil-fuel sources of energy. However, current electrocatalysts are not adequate (high overpotential, lack of selectivity toward O2 production, catalyst degradation). We propose here mechanistic guidelines for experimental examination of modified catalysts based on the dependence of kinetic rates on the solvent dielectric constant. To illustrate the procedure we consider the fcc(111) platinum surface and show that the individual steps for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) change systematically with the polarizability of the medium. Thus changing this environmental variable can be used to tune the rate determining steps and the barriers, providing a means for screening and validating new systems to optimize the rate determining steps for the ORR and OER reaction pathways.

Fortunelli, Alessandro; Goddard, William A., III; Sementa, Luca; Barcaro, Giovanni

2015-02-01

400

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

401

The ozonizer discharge as a gas-phase advanced oxidation process  

Microsoft Academic Search

In the past several years, there has been increased interest in gas-phase pollution control arising from a larger body of environmental regulations and a greater respect for the environment. One promising class of pollution-control technologies is that called advanced oxidation processes (AOPs). Ozonizers have been used for over a century in water treatment and for about two decades in advanced

Rosocha

1997-01-01

402

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

NASA Astrophysics Data System (ADS)

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 directly into the anode which consists of graphite felt. Oxygen is reduced at the cathode which consists of Pt-plated graphite felt. A proton exchange membrane separates the anode and the cathode compartments. The electrolyte was a PIPES buffer solution and lactate was used as the fuel. Separate tests were performed with the buffer solution containing lactate and with the buffer solution with lactate and MR-1 as anolytes. Electrochemical Impedance Spectroscopy (EIS) carried out at the open-circuit potential (OCP) has been used to determine the electrochemical properties of the anode and the cathode at different anolyte conditions. Cell voltage (V) -- current (I) curves were recorded using a potentiodynamic sweep between the open-circuit cell voltage and the short- circuit cell voltage. Power (P)-V curves were constructed from the recorded V-I data and the cell voltage, Vmax, at which the maximum power could be obtained, was determined. P- time (t) curves were obtained by applying Vmax or using a resistor between the anode and the cathode that would result in a similar cell voltage. Cyclic voltammograms (CV) were recorded for the anode for the different anolytes. Finally, anodic polarization curves were obtained for the anode with different anolytes and a cathodic polarization curve was recorded for the cathode. The internal resistance (Rint) of the MFC has been determined as a function of the cell voltage V using EIS for the MFC described above and a MFC in which stainless steel (SS) balls had been added to the anode compartment. The experimental values of Rint of the MFCs studied here are determined by the sum of the polarization resistance of the anode (Rap) and the cathode (Rcp), and therefore Rint depends on V. The ohmic contribution to the Rint was very small. It has been found that Rint decreased with decreasing cell voltage as the increasing current flow decreased R ap and Rcp. In the presence of MR-1, Rint was lower by a factor of about 100 than Rint of the MFC with buffer and lactate as anolyte. Additions of SS balls to the anode compartment produced a very large decrease of Rint. For the MFC containing SS balls in the anode compartment no significant further decrease of Rint could be observed when MR-1 was added to the anolyte. In Chapter 2, EIS has been used to determine the properties and stability of polymer coatings based on different chromate or chromate-free pretreatments and primers. Five sets of coated aluminum 2024 samples were exposed to 0.5N NaCl for a period of 31 days. Impedance spectra of the samples were measured during this period and the changes of the properties of the different coatings were studied as a function of time. From the analysis of the fit parameters of the impedance spectra, it was found that the corrosion protection of the coated samples depended on the type of primer used. The coating with the chromate based primer provided better corrosion protection than the coating with the chromate free primer. After 31 days of exposure, one sample from each set was scribed and exposed to 0.5N NaCl. The corrosion behavior of the scribed coatings was found to be dependent upon the type of pretreatment employed. The samples with the chromate conversion coating pretreatment showed better corrosion resistance in the scribed area than the samples that were treated by the trivalent chromium based method.

Manohar, Aswin Karthik

403

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

404

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

405

Petal-shaped poly(3,4-ethylenedioxythiophene)/sodium dodecyl sulfate-graphene oxide intercalation composites for high-performance electrochemical energy storage  

NASA Astrophysics Data System (ADS)

A facile and one-step electrochemical codeposition method is introduced for incorporating graphene oxide (GO) into poly(3,4-ethylenedioxythiophene) (PEDOT) films in the presence of sodium dodecyl sulfate (SDS). The as-prepared PEDOT/SDS-GO composites are characterized using scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The results show that PEDOT/SDS-GO composites possessing a unique petal-shaped morphology have been prepared successfully and exhibit an intercalated microstructure. With the purpose of electrochemical energy storage, the properties of electrochemical capacitance for composites have also been investigated with cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy tests. The electrochemical test results manifest the PEDOT/SDS-GO composites have superior capacitive behaviors and cyclic stability, and a high areal capacitance of 79.6 mF cm-2 is achieved at 10 mV s-1 cyclic voltammetry scan. Furthermore, the PEDOT/SDS-GO composites exhibit more superior capacitive performance than that of PEDOT/SDS, indicating the incorporation of GO into the composites effectively boosts the capacitive performance of PEDOT-based supercapacitor electrodes. We consider that this research further extends the application of GO and the composites prepared can be developed as the candidate for the fabrication of low-cost, high-performance supercapacitors for energy storage.

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

2014-12-01

406

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

407

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

408

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

409

An electrochemical ELISA-like immunosensor for miRNAs detection based on screen-printed gold electrodes modified with reduced graphene oxide and carbon nanotubes.  

PubMed

We design an electrochemical immunosensor for miRNA detection, based on screen-printed gold electrodes modified with reduced graphene oxide and carbon nanotubes. An original immunological approach is followed, using antibodies directed to DNA.RNA hybrids. An electrochemical ELISA-like amplification strategy was set up using a secondary antibody conjugated to horseradish peroxidase (HRP). Hydroquinone is oxidized into benzoquinone by the HRP/H2O2 catalytic system. In turn, benzoquinone is electroreduced into hydroquinone at the electrode. The catalytic reduction current is related to HRP amount immobilized on the surface, which itself is related to miRNA.DNA surface density on the electrode. This architecture, compared to classical optical detection, lowers the detection limit down to 10 fM. Two miRNAs were studied: miR-141 (a prostate biomarker) and miR-29b-1 (a lung cancer biomarker). PMID:24973539

Tran, H V; Piro, B; Reisberg, S; Huy Nguyen, L; Dung Nguyen, T; Duc, H T; Pham, M C

2014-12-15

410

Electrochemical water oxidation with cobalt-based electrocatalysts from pH 0-14: the thermodynamic basis for catalyst structure, stability, and activity.  

PubMed

Building upon recent study of cobalt-oxide electrocatalysts in fluoride-buffered electrolyte at pH 3.4, we have undertaken a mechanistic investigation of cobalt-catalyzed water oxidation in aqueous buffering electrolytes from pH 0-14. This work includes electrokinetic studies, cyclic voltammetric analysis, and electron paramagnetic resonance (EPR) spectroscopic studies. The results illuminate a set of interrelated mechanisms for electrochemical water oxidation in alkaline, neutral, and acidic media with electrodeposited Co-oxide catalyst films (CoO(x)(cf)s) as well as for a homogeneous Co-catalyzed electrochemical water oxidation reaction. Analysis of the pH dependence of quasi-reversible features in cyclic voltammograms of the CoO(x)(cf)s provides the basis for a Pourbaix diagram that closely resembles a Pourbaix diagram derived from thermodynamic free energies of formation for a family of Co-based layered materials. Below pH 3, a shift from heterogeneous catalysis producing O(2) to homogeneous catalysis yielding H(2)O(2) is observed. Collectively, the results reported here provide a foundation for understanding the structure, stability, and catalytic activity of aqueous cobalt electrocatalysts for water oxidation. PMID:21806043

Gerken, James B; McAlpin, J Gregory; Chen, Jamie Y C; Rigsby, Matthew L; Casey, William H; Britt, R David; Stahl, Shannon S

2011-09-14

411

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

412

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

413

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

414

Tailoring the structural and microstructural properties of nanosized tantalum oxide for high temperature electrochemical gas sensors.  

PubMed

Ta2O5 nanopowders to be used as sensing electrodes in high temperature electrochemical gas sensors for hydrocarbons detection were synthesized using a sol-gel method and their structural and microstructural properties were investigated. The as-synthesized powders were heated at different temperatures in the range 250-1000 degrees C and characterized by TG-DTA, XRD, SEM, TEM and FT-IR. This investigation allowed to identify the correct thermal treatments to achieve the microstructural, textural and functional stability of materials working at high temperature, preserving their nano-metric grain size. Planar sensors fabricated by using Ta2O5 powders treated at 750 degrees C showed promising results for the selective detection of propylene at high temperature (700 degrees C). The good stability of the sensing response after gas exposure at high temperature was correlated to the stable microstructure the electrodes. Thus, Ta2O5 powders seems good candidate as sensing electrode for sensors for automotive exhausts monitoring. PMID:19916469

Bonavita, Anna; Di Bartolomeo, Elisabetta; Chevallier, Laure; D'Ottavi, Cadia; Licoccia, Silvia; Traversa, Enrico

2009-07-01

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