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Showing papers on "Cyclic voltammetry published in 2002"


Journal ArticleDOI
TL;DR: In this paper, direct electron transfer from different Shewanella putrefaciens strains to an electrode was examined using cyclic voltammetry and a fuel cell type electrochemical cell.

944 citations


Journal ArticleDOI
TL;DR: In this article, Li(Ni 1/3 Co 1/1/3 Mn 1 /3 )O 2 was prepared by mixed hydroxide method and characterised by means of X-ray diffraction, Xray photoelectron spectroscopy (XPS), cyclic voltammetry and charge-discharge cycling.

904 citations


Journal ArticleDOI
Alfonso Pozio1, M. De Francesco1, Alessia Cemmi1, F. Cardellini1, Luca Giorgi1 
TL;DR: In this article, a detailed procedure for comparing high surface Pt/C catalysts was pointed out, and the real platinum metal surface area was evaluated by cyclic voltammetry on a thin porous coated disk electrode.

863 citations


Journal ArticleDOI
TL;DR: In this article, the authors used a 1:1 mixture of ethylene and dimethyl carbonates (EC-DMC) for Li-ion batteries and found that VC is a reactive additive that reacts on both the anode and the cathode surfaces.

766 citations


Journal ArticleDOI
Jianxiu Wang1, Meixian Li1, Zujin Shi1, Nanqiang Li1, Zhennan Gu1 
TL;DR: The electrochemistry of horse heart cytochrome c was studied by cyclic voltammetry at a glassy carbon electrode modified with single-wall carbon nanotubes (SWNTs) to determine the optimal conditions for activating the SWNT film-modified electrode.
Abstract: The electrochemistry of horse heart cytochrome c was studied by cyclic voltammetry at a glassy carbon electrode modified with single-wall carbon nanotubes (SWNTs). A pair of well-defined redox waves was obtained in cytochrome c aqueous solution at an activated SWNT film-modified electrode. The optimal conditions for activating the SWNT film-modified electrode has been determined. The electrode reaction of cytochrome c is a diffusion-controlled process. The peak current increases linearly with the concentration of cytochrome c in the range from 3.0 × 10-5−7.0 × 10-4 M. The detection limit is 1.0 × 10-5 M. The activated SWNT film was characterized by scanning electron microscopy. Furthermore, interaction of cytochrome c with adenine was characterized by electrochemical and spectral methods.

741 citations


Journal ArticleDOI
01 Apr 2002-Carbon
TL;DR: In this article, the influence of carbon-oxygen complexes on the performance of polyacrylonitrile-based activated carbon fabric capacitors was explored, and it was found that most of the oxygen functional groups created from the oxygen treatment were the carbonyl or quinone type.

570 citations


Journal ArticleDOI
TL;DR: In this paper, the supercapacitive properties of electrochemically grown composite films of multiwalled carbon nanotubes (MWNT) and polypyrrole (PPy), a conducting polymer, were reported.
Abstract: This work reports the supercapacitive properties of electrochemically grown composite films of multiwalled carbon nanotubes (MWNT) and polypyrrole (PPy), a conducting polymer. Scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy revealed that the nanoporous three-dimensional arrangement of PPy-coated MWNTs in these films facilitated improved electron and ion transfer relative to pure PPy films. The low-frequency capacitance was measured for films of varying thickness, revealing specific capacitances per mass (Cmass) and geometric area (Carea) as high as 192 F g-1 and 1.0 F cm-2, respectively. Rates of charge and discharge about an order of magnitude faster than similarly prepared pure PPy films were also observed.

558 citations


Journal ArticleDOI
TL;DR: Amorphous hydrous manganese oxide (a-MnO2·nH2O) was anodically deposited onto a graphite substrate from a MnSO4·5H 2O solution with pH of 6.4.

550 citations


Journal ArticleDOI
TL;DR: In this paper, a metal film over nanosphere (MFON) electrode was developed and characterized to solve the problem of the stability and reproducibility of most SERS-active electrode surfaces.
Abstract: The stability and reproducibility of most SERS-active electrode surfaces are far from ideal. We have focused on this problem by developing and characterizing a metal film over nanosphere (MFON) electrode which solves these shortcomings. Atomic force microscopy (AFM), cyclic voltammetry, and surface-enhanced Raman spectroscopy (SERS) of representative molecules were used to characterize and evaluate the electrochemical and SERS performance of MFON electrodes. Tremendous stability to extremely negative potential excursions is observed for MFON electrodes as compared to standard metal oxidation reduction cycle (MORC) roughened electrodes. Consequently, irreversible loss of SERS intensity at negative potentials is not observed on these MFON electrodes. We conclude that MFON electrodes present a significant advantage over MORC electrodes because SERS enhancement is not lost upon excursion to extremely negative potentials. This work demonstrates that the MFON substrate, while easily prepared and temporally stable, offers unprecedented stability and reproducibility for electrochemical SERS experiments. Furthermore, one can conclude that irreversible loss is not a distinguishing characteristic of electrochemical SERS and consequently cannot be used as evidence to support the chemical enhancement mechanism.

545 citations


Journal ArticleDOI
TL;DR: In this article, the nucleation mechanisms of copper during electrodeposition of thin films from sulfate solutions were studied by utilizing the electrochemical techniques (cyclic voltammetry and chronoamperometry) and atomic force microscopy (AFM).

537 citations


Journal ArticleDOI
17 Apr 2002-Langmuir
TL;DR: In this paper, a higher yield of functionalized carbon nanotubes (CNTs) was obtained by treatment of CNTs in HNO3 or H2SO4−K2Cr2O7.
Abstract: A higher yield of functionalized carbon nanotubes (CNTs) was obtained by treatment of CNTs in HNO3 or H2SO4−K2Cr2O7. The deposition of platinum nanoparticles and nanoclusters on these functionalized multiwalled carbon nanotubes by electroless plating was facilitated by a two-step sensitization-activation pretreatment. The deposition was sensitive to the aging time of the sensitizing solution and the pH of the plating solution. The resulting electrocatalysts were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry. XPS analysis showed that the Pt/CNT electrocatalysts contained 67.3% of Pt(0) and 32.7% of Pt(IV). Test runs on a single stack polymer electrolyte membrane fuel cell showed that these electrocatalysts are very promising for fuel cell applications.

Journal ArticleDOI
TL;DR: In this article, the performance and electrochemical characteristics of the sulfur electrode in the lithium/sulfur rechargeable cell were investigated using galvanostatic cycling and cyclic voltammetry.
Abstract: The cycling behavior and electrochemical characteristics of the sulfur electrode in the lithium/sulfur rechargeable cell were investigated using galvanostatic cycling and cyclic voltammetry. The cycling performance of the sulfur electrode was characterized in different solvents (triglyme, PEGDME 250 and 500). The variations of capacity and capacity fade rate were also measured as a function of the content of sulfur, carbon and binder. The capacity fade rate of the sulfur electrode was lower with a higher molecular weight solvent such as PEGDME 250 or 500. The content of carbon in the sulfur electrode plays an important role in capacity improvement. The best cell cycled for 600 deep cycles above 100 mAh/g of electrode, and 400 cycles above 160 mAh/g of electrode (80% of original capacity) at room temperature. © 2002 The Electrochemical Society. All rights reserved.

Journal ArticleDOI
TL;DR: In this article, a nanocomposite electrode of single-walled carbon nanotube (SWNT) and polypyrrole (Ppy) is fabricated to improve the specific capacitance of the supercapacitor.
Abstract: A nanocomposite electrode of single-walled carbon nanotube (SWNT) and polypyrrole (Ppy) is fabricated to improve the specific capacitance of the supercapacitor. The individual nanotubes and nanoparticles are uniformly coated with Ppy by in situ chemical polymerization of pyrrole. To characterize the SWNT-Ppy nanocomposite electrodes, a charge-discharge cycling test for measuring specific capacitance, cyclic voltammetry, and an ac impedance test are executed. The SWNT-Ppy nanocomposite electrode shows much higher specific capacitance than pure Ppy and as-grown SWNT electrodes, due to the uniformly coated Ppy on the SWNTs. The effects of the conducting agent added in the nanocomposite electrodes on specific capacitance and internal resistance of supercapacitors are also investigated. © 2002 The Electrochemical Society. All rights reserved.

Journal ArticleDOI
TL;DR: In this paper, the effect of cell temperature on the electrochemical reaction behavior of LiFePO4 was investigated by using cyclic voltammetry and electrochemical impedance spectroscopy (EIS).

Journal ArticleDOI
02 May 2002-Analyst
TL;DR: The voltammetric separation of dopamine and ascorbic acid was studied with cyclic voltammetry and indicated that the resolution of DA and AA was mainly attributable to the stereo porous interfacial layer formed from aggregated pores and inner cavities of the carbon nanotubes.
Abstract: The voltammetric separation of dopamine and ascorbic acid was studied with cyclic voltammetry at two kinds of carbon nanotube-modified electrodes (coated and intercalated) The anodic peak difference reached 270 mV under the present conditions The separation mechanism and effect factors were carefully studied Using various types of surfactants as coating dispersants of carbon nanotubes, it was demonstrated that the charge nature of the surfactants had a strong effect on the electrochemical behavior of dopamine and ascorbic acid When the oxidation solution of carbon nanotubes was changed from the most commonly used mixed concentrated nitric acid and sulfuric acid (1 + 3 v/v) to dilute nitric acid and to hydrochloric acid, the anodic peak separation value of dopamine and ascorbic acid increased significantly, and it was shown that carboxylic acid groups attached to the carbon nanotubes were an adverse factor for the discrimination of DA from AA These results indicated that the resolution of DA and AA was mainly attributable to the stereo porous interfacial layer formed from aggregated pores and inner cavities of the carbon nanotubes The modified electrodes exhibited an attractive ability to measure DA and AA simultaneously and showed good stability and reproducibility

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

Journal ArticleDOI
TL;DR: In this paper, a novel class of electrochemical supercapacitor electrode material has been electrochemically synthesized from a manganese halide complex in water-containing acetonitrile electrolyte at room temperature.

Journal ArticleDOI
Jun Chen1, Wei Li1, D.Z. Wang1, S.X Yang1, Jianguo Wen1, Z.F. Ren1 
01 Jul 2002-Carbon
TL;DR: In this paper, carbon nanotubes uniformly 50 nm in diameter were grown on graphite foil, and cyclic voltammetry (CV) showed that the carbon-graphite foil electrode has a high specific capacitance (115.7 F/g at a scan rate of 100 mV/s) and exhibits typical double-layer behavior.

Journal ArticleDOI
TL;DR: A glassy carbon electrode was modified with electropolymerized films of isonicotinic acid in pH 5.6 phosphate buffer solution (PBS) by cyclic voltammetry (CV) as mentioned in this paper.

Journal ArticleDOI
TL;DR: In this article, a solution of monodisperse nanocrystals with an absorption maximum at 537 nm was synthesized at 330 °C using TOPO (trioctylphosphineoxide) and TOP (tioctyl phosphine) as capping agents and Cd-acetate and Se powder as precursors.
Abstract: Electrogenerated chemiluminescence (ECL) was observed from TOPO-capped CdSe nanocrystals dissolved in CH2Cl2 containing 0.1 M TBAP. The solution of monodisperse nanocrystals with an absorption maximum at 537 nm was synthesized at 330 °C using TOPO (trioctylphosphineoxide) and TOP (trioctylphosphine) as capping agents and Cd-acetate and Se powder as precursors. The photoluminescence (PL) spectrum showed an emission maximum at 545 nm. Cyclic voltammetry and differential pulse voltammetry of this solution displayed no distinctive features, but light emission was observed through the annihilation of oxidized and reduced forms electrogenerated during cyclic potential scans or steps. The oxidized species was somewhat more stable than the reduced form. The ECL spectrum was substantially red shifted by ∼200 nm from the PL spectrum, suggesting that surface states play an important role in the emission process.

Journal ArticleDOI
TL;DR: Results represent a substantial revision of the derived and widely cited values of +0.39 V and −0.35 V for the NO/3NO− and NO/1NO− couples, respectively, and provide support for previous measurements obtained by electrochemical and photoelectrochemical means.
Abstract: A potential of about −0.8 (±0.2) V (at 1 M versus normal hydrogen electrode) for the reduction of nitric oxide (NO) to its one-electron reduced species, nitroxyl anion (3NO−) has been determined by a combination of quantum mechanical calculations, cyclic voltammetry measurements, and chemical reduction experiments. This value is in accord with some, but not the most commonly accepted, previous electrochemical measurements involving NO. Reduction of NO to 1NO− is highly unfavorable, with a predicted reduction potential of about −1.7 (±0.2) V at 1 M versus normal hydrogen electrode. These results represent a substantial revision of the derived and widely cited values of +0.39 V and −0.35 V for the NO/3NO− and NO/1NO− couples, respectively, and provide support for previous measurements obtained by electrochemical and photoelectrochemical means. With such highly negative reduction potentials, NO is inert to reduction compared with physiological events that reduce molecular oxygen to superoxide. From these reduction potentials, the pKa of 3NO− has been reevaluated as 11.6 (±3.4). Thus, nitroxyl exists almost exclusively in its protonated form, HNO, under physiological conditions. The singlet state of nitroxyl anion, 1NO−, is physiologically inaccessible. The significance of these potentials to physiological and pathophysiological processes involving NO and O2 under reductive conditions is discussed.

Journal ArticleDOI
TL;DR: In this paper, the electrochemical behavior and surface chemistry of LiCoO 2 intercalation cathodes as a function of cycling and storage at 25, 45, and 60°C was studied.

Journal ArticleDOI
Jun Li1, Alan M. Cassell1, Lance Delzeit1, Jie Han1, Meyya Meyyappan1 
TL;DR: In this paper, the electrochemical study of three carbon nanotube ensemble electrodes (single-walled nanotubes, as-produced multiwalled nano-tubes towers, and heat-treated multiweled nanotubes) was carried out using cyclic voltammetry.
Abstract: We report on the electrochemical study of three carbon nanotube ensemble electrodes: single-walled nanotube paper, as-produced multiwalled nanotube towers, and heat-treated multiwalled nanotube towers Cyclic voltammetry was used in 010 M KCl containing 50 mM K4Fe(CN)6 to obtain information on both the capacitive background and electron transfer rate from the faradaic reaction of the redox species The capacitance gives insight into the effective surface area (including both the exterior surface and the interior surface within the film) as well as the “pseudocapacitance” due to faradaic reactions of surface bonded oxides We found that a large portion of the carbon nanotube surface of the as-produced multiwalled nanotube tower electrode was blocked by amorphous carbon It can be largely removed by prolonged heat treatment Among the three types of samples, the single-walled nanotube paper electrode presented the largest volume specific capacitance, consistent with its highest carbon nanotube packing de

Journal ArticleDOI
TL;DR: Amorphous nanostructured composite materials with different RuO 2 loadings on carbon were prepared by colloidal method as mentioned in this paper, which was found to be critical in optimizing the electrochemical performance of this material.

Journal ArticleDOI
TL;DR: In this article, six sub-micro-crystalline alloy powders (Sn-Sb, Sn-Ag, Sb-Ag and SnSb) have been synthesized by chemical precipitation with NaBH 4, and their composite electrodes have been electrochemically tested by constant current cycling and cyclic voltammetry.

Journal ArticleDOI
TL;DR: A terthiophene-based quinodimethane, 3.47 and 3.63 A, was synthesized and crystallized in this paper, which is a planar quinoid geometry with dicyanomethylene groups at each end of the molecule.
Abstract: A terthiophene-based quinodimethane, 3‘,4‘-dibutyl-5,5‘ ‘-bis(dicyanomethylene)-5,5‘ ‘-dihydro-2,2‘:5‘,2‘ ‘-terthiophene (1) was synthesized and crystallized. Compound 1 has a planar quinoid geometry that is stabilized by dicyanomethylene groups at each end of the molecule. In the crystal each molecule is part of a dimerized face-to-face π-stack, with intermolecular spacings of 3.47 and 3.63 A, respectively. Cyclic voltammetry showed that 1 could be reversibly reduced and oxidized in methylene chloride solution. Thin film transistors (TFTs) were prepared by vacuum evaporation of 1 onto SiO2(300 nm)/Si substrates, followed by evaporation of Ag source and drain contacts. The doped Si substrate served as the gate electrode. X-ray diffraction and atomic force microscopy indicate the films are polycrystalline, with the long axes of the molecules approximately perpendicular to the substrate. The TFT measurements revealed n-channel conduction in films of 1, with room-temperature electron field effect mobilities ...

Journal ArticleDOI
TL;DR: In this paper, a hybrid capacitor in neutral KCl aqueous electrolyte, which consists of amorphous manganese oxide (a-MnO 2.nH 2 O) as a cathode and activated carbon as an anode, was reported.
Abstract: This study reports a hybrid capacitor in neutral KCI aqueous electrolyte, which consists of amorphous manganese oxide (a-MnO 2 .nH 2 O) as a cathode and activated carbon as an anode. The electrochemical performance of the hybrid capacitor is characterized by cyclic voltammetry and a dc charge/discharge test. The hybrid capacitor shows ideal capacitor behavior with an extended operating voltage of 2 V. The extended operating voltage is preferentially attributed to having asymmetric electrodes with different stable voltage windows and good electrochemical stability in neutral KCl aqueous electrolyte. According to the extended operating voltage, the energy density of the hybrid capacitor at a current density of 0.25 A/g, was found to be 28.8 Wh/kg which is comparable to that of an amorphous ruthenium oxide capacitor (26.7 Wh/kg). The hybrid capacitor also shows no degradation of capacitance during 100 cycles except an initial loss of 7% within a few cycles.

Journal ArticleDOI
TL;DR: In this article, the authors show that only part of these Fe−N4 sites contributes to the activity for the electrochemical reduction of O2 but that they operate according to the well-known redox mechanism.
Abstract: Some FeTPP−Cl/carbon electrocatalysts, heat-treated at temperatures up to 800 °C, have been studied with cyclic voltammetry, x-ray photoelectron spectroscopy, extended X-ray absorption fine structure, and in situ Mossbauer spectroscopy. It appears that the heat treatment induces considerable site heterogeneity in electronic terms, although structurally the Fe−N4 moiety seems persistent. The data indicate that only part of these Fe−N4 sites contributes to the activity for the electrochemical reduction of O2 but that they operate according to the well-known redox mechanism.

Journal ArticleDOI
TL;DR: An integrated bioelectrocatalytic assembly was constructed on the electrode by the covalent attachment of N(6)-(2-aminoethyl)-beta-nicotinamide adenine dinucleotide to the polymer film, and the two-dimensional cross-linking of an affinity complex formed between lactate dehydrogenase and the NAD(+)-cofactor units associated with the polymer using glutaric dialdehyde as a cross-linker.
Abstract: Electropolymerization of aniline in the presence of poly(acrylic acid) on Au electrodes yields a polyaniline/poly(acrylic acid) composite film, exhibiting reversible redox functions in aqueous solutions at pH = 7.0. In situ electrochemical-SPR measurements are used to identify the dynamics of swelling and shrinking of the polymer film upon the oxidation of the polyaniline (PAn) to its oxidized state (PAn(2+)) and the reduction of the oxidized polymer (PAn(2+)) back to its reduced state (PAn), respectively. Covalent attachment of N(6)-(2-aminoethyl)-flavin adenin dinucleotide (amino-FAD, 1) to the carboxylic groups of the composite polyaniline/poly(acrylic acid) film followed by the reconstitution of apoglucose oxidase on the functional polymer yields an electrically contacted glucose oxidase of unprecedented electrical communication efficiency with the electrode: electron-transfer turnover rate approximately 1000 s(-1) at 30 degrees C. In situ electrochemical-SPR analyses are used to characterize the bioelectrocatalytic functions of the biomaterial-polymer interface. The current responses of the bioelectrocatalytic system increase as the glucose concentrations are elevated. Similarly, the SPR spectra of the system are controlled by the concentration of glucose. The glucose concentration controls the steady-state concentration ratio of PAn/PAn(2+) in the film composition. Therefore, the SPR spectrum of the film measured upon its electrochemical oxidation is shifted from the spectrum typical for the oxidized PAn(2+) at low glucose concentration to the spectrum characteristic of the reduced PAn at high glucose concentration. Similarly, the polyaniline/poly(acrylic acid) film acts as an electrocatalyst for the oxidation of NADH. Accordingly, an integrated bioelectrocatalytic assembly was constructed on the electrode by the covalent attachment of N(6)-(2-aminoethyl)-beta-nicotinamide adenine dinucleotide (amino-NAD(+), 2) to the polymer film, and the two-dimensional cross-linking of an affinity complex formed between lactate dehydrogenase and the NAD(+)-cofactor units associated with the polymer using glutaric dialdehyde as a cross-linker. In situ electrochemical-SPR measurements are used to characterize the bioelectrocatalytic functions of the system. The amperometric responses of the system increase as the concentrations of lactate are elevated, and an electron-transfer turnover rate of 350 s(-1) between the biocatalyst and the electrode is estimated. As the PAn(2+) oxidizes the NADH units generated by the biocatalyzed oxidation of lactate, the PAn/PAn(2+) steady-state ratio in the film is controlled by the concentration of lactate. Accordingly, the SPR spectrum measured upon electrochemical oxidation of the film is similar to the spectrum of PAn(2+) at low lactate concentration, whereas the SPR spectrum resembles that of PAn at high concentrations of lactate.

Journal Article
TL;DR: Stamenkovic et al. as discussed by the authors studied the effects of surface segregation on the oxygen reduction reaction (ORR) on polycrystalline Pt Ni alloy in acid electrolyte using ultra high vacuum (UHV) surface sensitive probes and the rotating ring disk electrode (RRDE).
Abstract: Submitted to the Journal of Electroanalytical Chemistry, November 6, 2002 Surface Segregation Effects in Electrocatalysis: Kinetics of Oxygen Reduction Reaction on Polycrystalline Pt Ni Alloy Surfaces** V. Stamenkovic*, T.J. Schmidt - , P.N. Ross and N . M . Markovic Materials Sciences Division, Lawrence Berkeley National Laboratory University of California at Berkeley, CA 94720, USA Abstract Effects of surface segregation on the oxygen reduction reaction (ORR) have been studied on a polycrystalline Pt Ni alloy in acid electrolyte using ultra high vacuum (UHV) surface sensitive probes and the rotating ring disk electrode (RRDE) method. Preparation, modification and Depending on the characterization of alloy surfaces were done in ultra high vacuum (UHV). preparation method, two different surface compositions of the Pt Ni alloy are produced: a sputtered surface with 75 % Pt and an annealed surface (950 K ) with 100 % Pt. The latter surface is designated as the Pt-skin structure, and is a consequence of surface segregation, i.e., replacement of N i with Pt atoms in the first few atomic layers. Definitive surface compositions were established by low energy ion scattering spectroscopy (LEISS). The cyclic voltammetry of the Pt-skin surface as well as the pseudcapacitance in the hydrogen adsorption/desorption potential region is similar to a polycrystalline Pt electrode. Activities of ORR on Pt Ni alloy surfaces were compared to polycrystalline Pt in 0.1M H C l O electrolyte for the observed temperature range of 293 Pt Ni (75% Pt) > Pt with the maximum catalytic enhancement obtained for the Pt-skin being 4 times