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Showing papers on "Cyclic voltammetry published in 1999"


Journal ArticleDOI
TL;DR: Amorphous MnO2·nH2O in a mild 2 M KCl aqueous electrolyte proves to be an excellent electrode for a faradaic electrochemical capacitor cycled between −0.2 and +1.0 V versus SCE.

1,006 citations


Journal ArticleDOI
TL;DR: In this article, the electrochemical p-doping potentials of 10 soluble poly(1,4-phenylene vinylene) (PPV) derivatives and of the conjugated polymer blend in a light-emitting electrochemical cell (LEC) were measured by cyclic voltammetry.

801 citations


Journal ArticleDOI
TL;DR: In this paper, the electroanalytical behavior of thin electrodes is elucidated by the simultaneous application of three electro analytical techniques: slow scan-rate cyclic voltammetry (SSCV), potentiostatic intermittent titration technique, and electrochemical impedance spectroscopy.
Abstract: The electroanalytical behavior of thin electrodes is elucidated by the simultaneous application of three electroanalytical techniques: slow‐scan‐rate cyclic voltammetry (SSCV), potentiostatic intermittent titration technique, and electrochemical impedance spectroscopy. The data were treated within the framework of a simple model expressed by a Frumkin‐type sorption isotherm. The experimental SSCV curves were well described by an equation combining such an isotherm with the Butler‐Volmer equation for slow interfacial Li‐ion transfer. The apparent attraction constant was −4.2, which is characteristic of a quasi‐equilibrium, first‐order phase transition. Impedance spectra reflected a process with the following steps: ion migration in solution, ion migration through surface films, strongly potential‐dependent charge‐transfer resistance, solid‐state diffusion, and accumulation of the intercalants into the host materials. An excellent fit was found between these spectra and an equivalent circuit, including a Voigt‐type analog ( migration through multilayer surface films and charge transfer) in series with a finite‐length Warburg‐type element ( solid‐state diffusion), and a capacitor (Li accumulation). In this paper, we compare the solid‐state diffusion time constants and the differential intercalation capacities obtained by the three electroanalytical techniques. © 1999 The Electrochemical Society. All rights reserved.

594 citations


Journal Article
TL;DR: Anaerobically grown cells of an Fe(III)-reducing bacterium, Shewanella putrefaciens IR-1, were electrochemically active with an apparent reduction potential of about 0.15 V against a saturated calomel electrode in the cyclic voltammetry as mentioned in this paper.
Abstract: Anaerobically grown cells of an Fe(III)-reducing bacterium, Shewanella putrefaciens IR-1, were electrochemically active with an apparent reduction potential of about 0.15 V against a saturated calomel electrode in the cyclic voltammetry. The bacterium did not grow fermentatively on lactate, but grew in an anode compartment of a three-electrode electrochemical cell using lactate as an electron donor and the electrode as the electron acceptor. This property was shared by a large number of Fe(III)-reducing bacterial isolates. This is the first observation of a direct electrochemical reaction by an intact bacterial cell, which is believed to be possible due to the electron carrier(s) located at the cell surface involved in the reduction of the natural water insoluble electron acceptor, Fe(III).

479 citations


Journal ArticleDOI
TL;DR: In this article, the enzyme horseradish peroxidase (HRP) was used to polymerize aniline in the presence of a polyanionic template, sulfonated polystyrene.
Abstract: A novel strategy for the enzymatic synthesis of a water-soluble, conducting polyaniline (PANI)/sulfonated polystyrene (SPS) complex is presented. The enzyme horseradish peroxidase (HRP) is used to polymerize aniline in the presence of a polyanionic template, sulfonated polystyrene. The synthesis is simple, and the conditions are mild in that the polymerization may be carried out in a 4.3 pH buffered aqueous solution, with a stoichiometric amount of hydrogen peroxide and a catalytic amount of enzyme. UV−visible absorption, FTIR, GPC, elemental analysis, and conductivity measurements all confirm that the electroactive form of PANI, similar to that which is traditionally chemically synthesized, is formed and complexed to the SPS. The reversible redox activity of the polyaniline displays a unique hysteresis loop with pH change. Cyclic voltammetry studies show only one set of redox peaks over the potential range of −0.2 to 1.2V, which suggests that the PANI/SPS complex is oxidatively more stable. The conductiv...

469 citations


Journal ArticleDOI
TL;DR: In this paper, a general description of the electrochemical behavior of Mg electrodes in different types of polar aprotic systems was provided, including acetonitrile (AN), propylene carbonate (PC), and tetrahydrofuran (THF).

433 citations


Journal ArticleDOI
TL;DR: The effect of Nafion loading in the catalyst layer of cathodes for polymer electrolyte fuel cells (PEFCs) was investigated in this article, where an optimum loading was found to correspond to a minimum in the polarization resistance and in the oxygen reduction overpotential and a maximum in the electrochemical active area.

416 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of polymerization current density and monomer concentration on the formation of the film structure was studied with cyclic voltammetry, in situ UV-VIS-spectroelectrochemistry, electrochemical quartz crystal microbalance technique (EQCM), and in situ Fourier transform infrared (FTIR) spectroscopy using external and internal reflection techniques.

372 citations


Journal ArticleDOI
05 Mar 1999-Langmuir
TL;DR: In this article, a micellar aqueous solution containing sodium dodecyl sulfate (SDS) was used for the synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) films.
Abstract: Electrosynthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) films was performed in a micellar aqueous solution containing sodium dodecyl sulfate (SDS) by cyclic voltammetry, chronoamperometry, and chronopotentiometry on a platinum electrode. The electrocatalytic effect of SDS was characterized by a significant decrease of the EDOT oxidation potential (Ep) in the micellar medium relative to 0.1 M LiClO4 acetonitrile as well as aqueous solutions. Linear variation of Ep with SDS concentration indicated the formation of a pseudocomplex (Keq = 5.4 × 103 M-1). PEDOT films were characterized electrochemically and spectroscopically (UV−visible, X-ray photoelectron spectroscopy, IR, Raman spectra). Regular, well-ordered, and adherent films were obtained in SDS medium. The PEDOT film morphologies investigated by atomic force microscopy suggested the possible presence of columnar structures when the electrosynthesis is performed in the micellar medium.

330 citations


Journal ArticleDOI
TL;DR: In this paper, polythiophene (Pth) and polyparafluorophenylthiophen (PFPT) have been chemically synthesized for use as active materials in supercapacitor electrodes.

316 citations


Journal ArticleDOI
TL;DR: In this article, a formic acid decomposition reaction is examined as a probe of catalytic properties of polycrystalline platinum and palladized platinum electrodes, and it is shown that only a negligible amount of surface CO is formed.
Abstract: This is a comprehensive study in which a formic acid decomposition reaction is examined as a probe of catalytic properties of polycrystalline platinum and palladized platinum electrodes. The electrode potential varies in a broad range, and the reaction is carried out in perchloric acid and sulfuric acid solutions containing different concentrations of HCOOH. Analytical methods used to access the decomposition reaction are chronoamperometry and cyclic voltammetry. At very short times, we prove that only a negligible amount of surface CO is formed, and the CO unaffected decomposition reaction, leading to CO2 formation, can be interrogated. Surprisingly, the decomposition reaction displays Tafel behavior only in a very narrow potential range. This observation, made with both clean Pt and Pt/Pd electrodes, suggests that water−surface interactions, and/or (bi)sulfate−surface interactions, increase with increasing electrode potential and create a steric/electronic barrier for the decomposition of formic acid (a...

Journal ArticleDOI
TL;DR: A platinum electrode modified with electropolymerized films of 4-allyl-2-methoxyphenol (eugenol) by its oxidative polymerization from an alkaline solution by cyclic voltammetry was used to determine dopamine (DA) in an excess of ascorbic acid (AA) by differential pulsevoltammetry.
Abstract: A platinum electrode was modified with electropolymerized films of 4-allyl-2-methoxyphenol (eugenol) by its oxidative polymerization from an alkaline solution by cyclic voltammetry. The modified electrode was than used to determine dopamine (DA) in an excess of ascorbic acid (AA) by differential pulse voltammetry. The peak positions as well as relative sensitivity DA/AA were affected by the potential window applied for the polymerization. For polymerization between 0 and 2.2 V, the peak potentials recorded in a phosphate buffer solution (pH 7.4) were −61 and +152 mV vs Ag/AgCl for AA and DA, respectively. After a 5-min equilibration, relative sensitivity DA/AA was 164 and the current sensitivity for DA was 7.9 nA μM-1. The detection limit for S/N = 3 is 0.1 μM. The high selectivity and sensitivity for DA was found to be due to charge discrimination/analyte accumulation and an effect of catalytic mediation of redox sites. Chronocoulometric data reveal that DA is accumulated on the electrode as a monolayer....

Journal ArticleDOI
TL;DR: Amorphous a-V2O5·nH2O in mild KCl aqueous electrolyte proves to be an excellent electrode for a faradaic electrochemical capacitor as discussed by the authors.

Journal ArticleDOI
Abstract: Films of single-wall carbon nanotubes (SWCNTs) were cast from suspensions in several solvents on the surface of a Pt or Au electrode Cyclic voltammetry of the films in MeCN did not show well-resolved waves (as distinct from films of C_(60) prepared in a similar manner) However, the increase in the effective capacitance of the electrode with a SWCNT film at 05 V vs an AgQRE was 283 F/g, which is about twice that of carbon electrodes in nonaqueous solvents

Journal ArticleDOI
TL;DR: The present results indicate that diamond is a useful electrode material for the analytical detection of NADH, making it attractive for use in sensors based on enzyme-catalyzed reactions involving NADH as a cofactor.
Abstract: Conductive boron-doped chemical vapor-deposited diamond thin films, already known to have superior properties for general electroanalysis, including low background current and a wide potential window, are here shown to have additional advantages with respect to electrochemical oxidation of nicotinamide adenine dinucleotide (NADH), including high resistance to deactivation and insensitivity to dissolved oxygen. Cyclic voltammetry, amperometry, and the rotating disk electrode technique were used to study the reaction in neutral pH solution. Highly reproducible cyclic voltammograms for NADH oxidation were obtained at as-deposited diamond electrodes. The response was stable over several months of storage in ambient air, in contrast to glassy carbon electrodes, which deactivated within 1 h. The diamond electrode exhibited very high sensitivity for NADH, with an amperometric detection limit of 10 nM (S/N = 7). The response remained stable, even in the very low concentration range, for several months. In additio...

Journal ArticleDOI
TL;DR: In this paper, the electrochemical oxidation of dopamine, 4-methylcatechol, dihydroxyphenylacetic acid and hydroquinone was examined on several native and modified glassy carbon (GC) surfaces.
Abstract: The electrochemical oxidation of dopamine, 4-methylcatechol, dihydroxyphenylacetic acid, dihydroxyphenyl ethylene glycol, and hydroquinone was examined on several native and modified glassy carbon (GC) surfaces Treatment of polished GC with pyridine yielded small ΔEp values for cyclic voltammetry of all systems studied, implying fast electron-transfer kinetics Changes in surface oxide coverage had little effect on kinetics, nor did the charge of the catechol species or the solution pH Small ΔEp values correlated with catechol adsorption, and surface pretreatments that decreased adsorption also increased ΔEp Electron transfer from catechols was profoundly inhibited by a monolayer of nitrophenyl or (trifluoromethyl)phenyl (TFMP) groups on the GC surface, so that voltammetric waves were not observed The ΔEp increased monotonically with surface coverage of TFMP groups The results indicate that catechol adsorption to GC is required for fast electron transfer for the redox systems studied Unlike Ru(NH3)6

Journal ArticleDOI
12 Jun 1999-Langmuir
TL;DR: In this paper, the adsorption properties of a modified activated carbon with various oxygen-and/or nitrogen-containing surface groups toward copper ions were studied and the chemical properties of the modified carbon surface were estimated by standard neutralization titration with HCl, NaOH, and NaOC2H5.
Abstract: The adsorption properties of a modified activated carbon with various oxygen- and/or nitrogen-containing surface groups toward copper ions was studied. Previously de-ashed and chemically modified commercial activated carbon D-43/1 (Carbo-Tech, Essen, Germany) was used. The chemical properties of the modified carbon surface were estimated by standard neutralization titration with HCl, NaOH, and NaOC2H5. The adsorption of Cu2+ ions on three modified activated carbons from aqueous CuSO4 solution of various pH was measured. The carbon samples with adsorbed Cu2+ ions were analyzed by spectroscopic methods (X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy). In addition, an electrochemical measurement (cyclic voltammetry) was performed using powdered activated carbon electrodes.While the modification procedures employed alter the surface only slightly, they strongly influence the surface chemical structure. Basic groups are predominant in the heat-treated samples; acidic functional group...

Journal ArticleDOI
TL;DR: Oxygen-terminated diamond electrodes were prepared by exposing as-grown diamond thin films to oxygen plasma, and the apparent surface conductivity was not significantly changed after the oxygen plasma treatment as mentioned in this paper.

Journal ArticleDOI
TL;DR: Faradaic impedance spectroscopy and cyclic voltammetry are used to probe the electron-transfer resistance at the conductive support upon the accumulation of the insoluble product on the electrode surface, correlated with the amounts of H2O2 or glucose.
Abstract: Precipitation of an insoluble, insulating product on monolayer-functionalized electrodes enables the development of new electrochemical biosensors. Faradaic impedance spectroscopy and cyclic voltammetry are used to probe the electron-transfer resistance at the conductive support upon the accumulation of the insoluble product on the electrode surface. Similarly, microgravimetric quartz crystal microbalance, QCM, analyses were used to assay the formation of the precipitate on the electrode. A horseradish peroxidase, HRP, monolayer electrode is used to analyze H2O2 via the biocatalyzed oxidation of 4-chloro-1-naphthol (1) and the precipitation of the insoluble product (2). A bienzyme-layered electrode consisting of HRP and glucose oxidase, GOx, is used to sense glucose. Biocatalyzed oxidation of glucose by O2, in the presence of GOx, yields H2O2, and the generated hydrogen peroxide effects the formation of the insoluble product (2) in the presence of HRP. The insoluble product accumulated on the electrode, a...

Journal ArticleDOI
TL;DR: The electrochemical deposition of Ru on Pt(111) electrodes has been investigated by electron diffraction, Auger spectroscopy, and cyclic voltammetry in a closed UHV transfer system as mentioned in this paper.
Abstract: The electrochemical deposition of Ru on Pt(111) electrodes has been investigated by electron diffraction, Auger spectroscopy, and cyclic voltammetry in a closed UHV transfer system. At small coverages Ru formed a monatomic commensurate layer, at higher coverage mostly small islands with a bilayer height were detected. When the Pt was almost completely covered by Ru, three-dimensional clusters developed. The island structure of Ru changed upon electrooxidation of CO, reflecting an enhanced mobility of Ru. Adsorption and electrooxidation of CO have been studied on such Ru-modified Pt(111) electrodes using cyclic voltammetry and in situ FTIR spectroscopy. Compared to the pure metals, the Ru−CO bond is weakened, the Pt−CO bond strengthened on the modified electrodes. The catalytic activity of the Ru/Pt(111) electrode toward CO adlayer oxidation is higher than that of pure Ru and a PtRu alloy (50:50). It is concluded that the electrooxidation of CO takes place preferentially at the Ru islands, while CO adsorbe...

Journal ArticleDOI
TL;DR: In this paper, cyclic voltammetry was used to obtain the growth rate of RuO{sub x}{center_dot}nH{sub 2}O, represented by i{sub p} (peak current) of the cyclic voltage measurements, was constant up to cycle 120, but it decreased slightly between 120 and 240 cycles.
Abstract: Hydrous ruthenium oxide-coated titanium electrodes (RuO{sub x}{center_dot}nH{sub 2}O/Ti) with high pseudocapacitance were prepared by cyclic voltammetry from an aqueous chloride solution in the {minus}200 to 1000 mV range. The growth rate of RuO{sub x}{center_dot}nH{sub 2}O, represented by i{sub p} (peak current) of the cyclic voltammograms, was constant up to cycle 120, but it decreased slightly between 120 and 240 cycles. Voltammetric responses studied by cyclic voltammetry as well as the charging and discharging behavior examined by chronopotentiometry in 0.5 M H{sub 2}SO{sub 4} demonstrated the suitability of RuO{sub x}{center_dot}H{sub 2}O for use in electrochemical capacitors. X-ray diffraction spectra exhibited an amorphous structure of this hydrous oxide film. The oxide consisted of mixed oxyruthenium species with various oxidation states as demonstrated by X-ray photoelectron spectroscopy, and the RuO{sub x}{center_dot}nH{sub 2}O surface showed a porous morphology.

Journal ArticleDOI
TL;DR: In this paper, the electrochemical deposition of palladium onto Au(111) from chloride-containing solutions was investigated by in-situ STM and cyclic voltammetry.

Journal ArticleDOI
TL;DR: In this paper, two types of Li x Mn 2 O 4 electrodes comprised of active mass synthesized in two different ways were investigated in a standard solution (ethylene carbonate-dimethyl carbonate 1:3/LiAsF 6 1 M) using X-ray diffraction technique (XRD).

Journal ArticleDOI
TL;DR: In this paper, a spontaneous charge transfer reaction is observed prior to the application of an electrochemical driving force, in sharp contrast to previous observations in the graphite−H2SO4 system.
Abstract: Electrochemical doping of bisulfate ions into single wall carbon nanotube (SWNT) bundles has been studied using coulometry, cyclic voltammetry, mass-uptake measurements, and Raman scattering experiments. A spontaneous charge-transfer reaction is observed prior to the application of an electrochemical driving force, in sharp contrast to previous observations in the graphite−H2SO4 system. A mass increase of the SWNT sample and a concomitant upshift of the Raman-active tangential mode frequency indicate oxidation (i.e., removal of electrons) of the SWNT bundles. In fact, using Raman scattering, we were able to separate the spontaneous and electrochemical contributions to the overall charge transfer, resulting in the value of an upshift of 320 cm-1 per hole, per C-atom introduced into the carbon π-band by the bisulfate (HSO4-) dopant. This value may prove to be a universal measure of charge transfer in acceptor-type SWNT compounds. At a critical electrochemical doping, the SWNT bundles are driven into an “ove...

Journal ArticleDOI
TL;DR: In this paper, the electrocatalytic oxidation of hydrazine has been studied on a glassy carbon electrode modified by electrodeposition of chlorogenic acid (CGA), using cyclic voltammetry, chronoamperometry and rotating disk voltameters as diagnostic techniques.

Journal ArticleDOI
TL;DR: In this article, the performance of a mediator-less microbial fuel cell using electrochemically active bacteria in the presence of nitrate was evaluated using cyclic voltammetry and an applied potential at +200 mV against an Ag/AgCl reference electrode restored the electrochemical activity.
Abstract: Cyclic voltammetry demonstrated that cells of Shewanella putrefaciens grown under anaerobic conditions without nitrate were electrochemically active The electrochemical activity was inactivated reversibly by exposure to air, but not by nitrate Lactate and an applied potential at +200 mV against an Ag/AgCl reference electrode restored the electrochemical activity These findings can be used to improve the performance of a mediator-less microbial fuel cell using electrochemically active bacteria in the presence of nitrate

Journal ArticleDOI
TL;DR: In this article, a two to threefold enhancement of CO tolerance in a proton exchange membrane (PEM) fuel cell, exhibited by carbonsupported nanocrystalline PtMo/C as compared to the current state of the art PtRu/C electrocatalysts, was reported.
Abstract: E-TEK, Incorporated, Natick, Massachusetts 01760, USAWe report a two- to threefold enhancement of CO tolerance in a proton exchange membrane (PEM) fuel cell, exhibited by carbonsupported nanocrystalline PtMo/C as compared to the current state of the art PtRu/C electrocatalysts. The bulk of these nanocrys-tals were comprised of Pt alloyed with Mo in the ratio 8.7:1.3 as shown by both X-ray diffraction and in situ extended X-ray ab sorp-tion fine structure measurements. Rotating disk electrode measurements and cyclic voltammetry in a PEM fuel cell indicate theonset of CO oxidation at potentials as low as 0.1 V. Further, the oxidation of CO exhibits two distinct peaks, indicating redox b ehav-ior involving oxyhydroxides of Mo. This is supported by in situ X-ray absorption near edge structure measurements at the Mo Kedge.© 1999 The Electrochemical Society. S1099-0062(98)08-029-8. All rights reserved.Manuscript submitted August 10, 1998; revised manuscript received September 28, 1998. Available electronically October 30, 1998.

Journal ArticleDOI
TL;DR: In this article, a polymer (TPD-PPV) incorporating both efficient light-emitting and hole transporting moieties has been synthesized, which possesses excellent film-forming property, good thermal stability, and high electrochemical reversibility and stability.
Abstract: A polymer (TPD-PPV), incorporating both efficient light-emitting and hole transporting moieties has been synthesized. This polymer also possesses excellent film-forming property, good thermal stability, and high electrochemical reversibility and stability. The HOMO-LUMO energy levels were determined by cyclic voltammetry and UV-Vis measurement. The diode with the structure of ITO/CuPc/TPD-PPV/Al showed high rectification ratio (10 8 ) and low turn-on voltage (4.2 V). A bright green-yellow light-emission was observed in day-light under forward bias.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed an optimized tunneling microscope optimized for potentiodynamic imaging, i.e., the sample potential can be varied in a wide range during the scan of an image.
Abstract: One of the main topics in electrochemistry is the investigation of the potential controlled solid/liquid interface. As a local probe technique electrochemical scanning tunneling microscopy becomes more and more important for the analysis of atomic structures and local structuring effects. The described microscope is optimized for potentiodynamic imaging, i.e., the sample potential can be varied in a wide range during the scan of an image. In combination with cyclic voltammetry potential induced phase transitions on the surface can be imaged and directly correlated to distinctive profiles in the simultaneously recorded voltammogram. The new design grew out of the parallel development of the tunneling unit and the electrochemical periphery. This guarantees the best adaptation of tunneling microscopy to electrochemistry and vice versa. Low drift, high resolution, flexibility, reliability, and ease of handling are the characteristics of the new instrument.

Journal ArticleDOI
TL;DR: In this article, cyclic voltammetry was applied for the first studies to detect 2,4,6-trinitrotoluene (TNT) electrochemically in the gaseous phase.