Showing papers on "Electrode potential published in 1985"
TL;DR: Essai d'estimation de l'echelle absolue a l'aide d'une methode qui deplace le probleme de la couche dipolaire superficielle hors of l'interface electrolyte-air and le focalise plus sur le solide.
Abstract: Essai d'estimation de l'echelle absolue a l'aide d'une methode qui deplace le probleme de la couche dipolaire superficielle hors de l'interface electrolyte-air et le focalise plus sur le solide
383 citations
TL;DR: In this paper, the electrical conductivity of solvent and electrolyte-wetted poly(pyrrole) films is measured, both statically and dynamically, as a function of the potential applied to an electrode in contact with the film.
Abstract: : The electrical conductivity of solvent and electrolyte-wetted poly(pyrrole) films is measured, both statically and dynamically, as a function of the potential applied to an electrode in contact with the film. The applied potential determines the film oxidation state. Poly(pyrrole) electrical conductivity is ohmic and independent of potential from 0 to +0.4V vs. SSCE, and decreases and becomes less ohmic at more negative potentials. Measurements of the chemically reactive charge stored in poly(pyrrole) as a function of potential were combined with the electrical conductivity results to yield a profile of electrical conductivity vs. average charge per monomer site in the polymer. Electrical conductivity is independent of monomer charge above about 0.15 holes/monomer unit. (Author)
193 citations
TL;DR: In this paper, a transfer system is described which permits the electrochemical preparation of specimens in a purified argon atmosphere and their transport into the UHV for surface analysis, which prevents contamination and oxide formation on semi-noble metals.
65 citations
TL;DR: In this article, the pK/sub a1/1/ of Co/sup III/TMPyP was found to shift from a value of 6.0 for the solution to 2.0 in the adsorbed case.
Abstract: Cobalt(III) tetrakis(N-methyl-4-pyridyl)porphyrin (abbreviated Co/sup III/TMPyP), although water soluble, adsorbs irreversibly on the surface of a highly polished glassy-carbon electrode. This porphyrin readily undergoes a one-electron reduction, either in solution or adsorbed, to produce the cobaltous form, which catalyzes the reduction of oxygen quantitatively to hydrogen peroxide. The pK/sub a1/ of Co/sup III/TMPyP is found to shift from a value of 6.0 for the solution to 2.0 for the adsorbed case. Thus, the electrode potential at which oxygen catalysis occurs is dependent on the pH and on the concentration ratio of the solution cobalt porphyrin to oxygen. However, at a pH of ca. 4 the redox potential of the solution CoTMPyP becomes more positive in value than that of the reversible O/sub 2//H/sub 2/O/sub 2/ potential so that the electrogenerated cobaltous porphyrin no longer catalyzes the reduction of oxygen. The potential of catalysis then shifts negatively to the adsorbed CoTMPyP, which, upon reduction, converts the O/sub 2/ to H/sub 2/O/sub 2/. The addition of thiocyanate ion to the solution can accelerate the rate of electron transfer from the electrode to the cobalt porphyrin. This addition, in low concentrations, can favorably affect the potential at which oxygen is catalytically reacted by decreasingmore » the overpotential for the Co/sup III/TMPyP reduction. 53 references, 9 figures, 3 tables.« less
64 citations
TL;DR: In this paper, it was shown that at high current densities (> 100 mA cm−2, depletion of hydroxide ions occurs at the zinc surface causing a severe deviation in the exponential dependence of the active dissolution current on potential.
61 citations
01 Jan 1985
TL;DR: This paper showed that β-lactoglobulin and ovalbumin adsorbs into a bilayer, with the bottom layer unfolded and attached by strong polar bonds to the surface, so that it is not removed by rinsing.
Abstract: Studies of adsorption of β-lactoglobulin and ovalbumin on plasma cleaned chromium surfaces by ellipsometry show that a thick highly hydrated layer is obtained, which can be partly removed by aqueous buffer rinsing. Changes in the electrode potential during the adsorption and rinsing process were also followed. The results indicate that the protein adsorbs into a bilayer, with the bottom layer unfolded and attached by strong polar bonds to the surface, so that it is not removed by rinsing. On top of that layer, protein molecules are attached by hydrophobic interaction and/or ionic forces. The upper layer results in large electrical changes. For comparison the same measurements were done on chromium surfaces, which were made hydrophobic, and these results are in agreement with the generally accepted model of monolayer adsorption.
56 citations
TL;DR: In this paper, a linear correlation between electrode potential and work function change is observed for the metal as well as for the oxide, and the results confirm known band theory models and provide a fundamental understanding of the electrochromism of anodic iridium oxide films.
56 citations
TL;DR: In this article, the effect of variable space-charge layer on oxygen reduction and xanthate chemisorption was discussed, and it was shown that highly n-type electrodes have a cleavage potential (V /sub FBp/) of approx. =-0.2V (SCE).
Abstract: Electrochemical, interfacial capacitance, and surface photovoltage (SPV) measurements have been used in a study of oxygen reduction and xanthate chemisorption on in situ cleaved natural and synthetic lead sulfide crystals. Electrodes cleaved in nitrogen-sparged 0.1M sodium tetraborate assume the flatband potential, V /sub FBp/ at the instant of cleavage, and thus the cleavage potential decreases with increasing bulk electron concentration. Highly n-type electrodes have a cleavage potential (V /sub FBp/) of approx. =-0.6V (SCE), and highly p-type electrodes have a value of approx. =-0.2V (SCE). The space charge is readily varied by applied potentials in the range -0.2 to -0.6V. This Bureau of Mines, U.S. Department of the Interior, report discusses the effect of the variable space-charge layer on oxygen reduction and xanthate chemisorption.
54 citations
TL;DR: In this article, the transient and ac electrical response of electrochemical systems containing a solid solution electrode was derived using Laplace transform methods for both asymmetrical and symmetrical cell systems.
51 citations
TL;DR: In this article, the behavior of electrode-bound redox material derived from the hydrolysis of the -Si(OEt)/sub 3/ groups of 1,1'-bis(((3-(triethoxysilyl)propyl)amino)carbonyl)cobaltocenium (I) is described.
Abstract: This paper describes the behavior of electrode-bound redox material derived from the hydrolysis of the -Si(OEt)/sub 3/ groups of 1,1'-bis(((3-(triethoxysilyl)propyl)amino)carbonyl)cobaltocenium (I). Surfaces of the conventional electrodes SnO/sub 2/ and Pt derivatized with I have a reversible electrochemical response in H/sub 2/O/electrolyte; the E/sup 0/' is pH independent at -0.62 V vs. SCE. The photoelectrochemical behavior of p-type Si photocathodes derivatized with I reveals that the photoreduction of the cobaltocenium derivative can be effected at an electrode potential approx. 500 mV more positive than on metallic electrodes, consistent with the known behavior of p-type Si photocathodes. When polymer from I is deposited on p-type Si and subsequently coated with a small amount of Rh or Pd (approx. 10/sup -7/ mol/cm/sup 2/), the photoelectrochemical generation of H/sub 2/ is possible with 632.8-nm (approx. 15 mW/cm/sup 2/) radiation and efficiencies in the vicinity of 2%. The polymer derived from I is more optically transparent and more durable at negative potentials than redox polymers derived from vilogen monomers. Potential-step measurements and steady-state-current measurements for mediated redox processes show that the charge-transport rate for the polymer derived from I is about the same as for polymers from viologen monomers. 32 references, 8 figures.
49 citations
TL;DR: A beam of light reflected from a 50-400 μm diameter disk electrode was used to monitor the concentration of an electrogenerated absorber in the submicrosecond time scale.
TL;DR: In this article, the electrochemical oxidation of formaldehyde has been studied by cyclic voltammetry on gold and silver rotating disc electrodes varying the sweep rate, the angular velocity, formaldehyde concentration and pH of the supporting electrolyte.
TL;DR: In this paper, an analytical solution for the current distribution on a wall-jet electrode when the reactant is being destroyed by irreversible electrode kinetics is found. But the Tafel plot obtained from such an electrode is shown to be distorted but a simple modification allows kinetic data to be obtained.
TL;DR: In this article, the reduction of Fe(III) and Fe(CN)3−6 by leucothionine in a thionine modified electrode is studied and a general equation is derived which includes both the surface reaction and the case where the reaction takes place in a thin reaction layer in the firm.
TL;DR: In this paper, the adsorption of carbon monoxide, CO, on a smooth platinum electrode has been studied by in situ UV-visible reflectance spectroscopy, and two kinds of adsorbed CO species are detected, depending on both the electrode potential and the degree of coverage.
TL;DR: In this paper, changes in the interfacial tension of a high surface area graphite electrode could be monitored adopting the moire deflectometry, a new optical technique for ray deflection mapping, by which the resolution in relative length changes of th e electrode was less than 1 microstrain.
TL;DR: In this article, surface-enhanced Raman scattering (SERS) has been used to identify species adsorbed at the electrode surface and to determine the dependence of the Raman intensity from these species on such variables as solvent, concentration, pH, electrode potential and laser exciting wavelength.
Abstract: The discovery of surface-enhanced Raman scattering (SERS) has resulted in a new tool for the elucidation of phenomena occurring at the electrode/solution interface. Our long term objective is to use this technology to identify species adsorbed at the electrode surface and to determine the dependence of the Raman intensity from these species on such variables as solvent, concentration, pH, electrode potential and laser exciting wavelength. The phenomenon is described in the introduction, to provide background for those not familiar with this topic. This is followed by a presentation of recent data from our laboratory, with a focus on nonaqueous solvents. Bands of the solvated Li+ and Na+ cations at the electrode surface are reported. Bands from trace H2O (D2O and HOD) and OH− (OD−) have been observed. At sufficiently negative potentials CN− is generated from acetonitrile. Evidence is presented for the occurrence of photoelectrochemical reduction. Some preliminary results are given for propylene carbonate solvent which support this interpretation.
TL;DR: In this article, the Gibbs Free Energy of the solid solutions and the electrode potential were derived on the basis of the sites available for placement of inserted protons and electrons, the number of possible arrangements of proton and electrons on the sites and the independence of propton and electron arrangements.
TL;DR: In this paper, surface-enhanced Raman scattering (SERS) spectra were measured for 5 m M 2,2′-bipyridine+0.1 M KX (X = CI, Br or I) and the assignments of the bands were discussed by comparing the surface spectra with the Raman and infrared spectra of Ag(I)(bpy)2NO3 and bpy itself.
TL;DR: In this paper, the relation between current density and overpotential for electroreduction of oxygen to hydrogen peroxide in the packed-bed electrode reactor was studied, based on the two-dimensional two-phase model of the particulate electrode.
Abstract: The relation between current density and overpotential for electroreduction of oxygen to hydrogen peroxide in the packed-bed electrode reactor was studied. Theoretical analyses were made on the basis of the two-dimensional two-phase model of the particulate electrode where the distribution of concentration of dissolved oxygen and the overpotential were considered. The kinetics of electrode reactions was determined with a rotating-disk electrode of graphite. The effective specific surface area available for electrode reaction in the packed-bed electrode was determined by analysing the transient current response to a potential step. The observed values of overpotential profile and the polarization curves of the packed-bed electrode agreed with the theoretical ones calculated by use of the kinetic and reactor properties.
01 Sep 1985
TL;DR: In this article, the competition between the anodic decomposition of the semiconductor, anodic oxidation of Fe2+ ions and surface recombination was studied as a function of the light intensity, the electrode potential, and the Fe 2+ concentration by means of the rotating-ring-disc electrode technique.
Abstract: The competition, at the n-GaAs/Fe2+ photoanode, between the anodic decomposition of the semiconductor, the anodic oxidation of Fe2+ ions and surface recombination was studied as a function of the light intensity, the electrode potential, and the Fe2+ concentration by means of the rotating-ring-disc electrode technique. The results are interpreted on the basis of a reaction scheme, in which the competing processes are linked through the intermediates of the decomposition reaction. Numerical calculations, based upon this reaction scheme, of the relationship between the stabilization ratio and the photocurrent density, between the stabilization ratio and the electrode potential, and between the photocurrent density and the electrode potential are in good agreement with the experimental data.
TL;DR: In this article, a theory of hydrogen ion transfer has been evolved, and with its help an estimation of film field strength φ = (1.0-4.6) × 105 V cm−1 has been obtained.
TL;DR: In this article, a simple quantum-mechanical model for electrochemical adsorption is presented; it may explain why the adsorbate charge can change discontinuously at a certain electrode potential.
TL;DR: It is demonstrated that even a small contamination on a single metal electrode produces large fluctuating potentials, which can seriously distort the recording of bioelectric events.
Abstract: This study demonstrates that even a small contamination on a single metal electrode produces large fluctuating potentials. These potentials can seriously distort the recording of bioelectric events. Controlled contaminants were placed on single metal electrodes of copper, zinc, and silver-silver chloride, and recordings were made versus a stable electrode of the same metal. In all cases, the fluctuating potentials recorded with the contaminated electrode were much larger than those when no contaminant was present. Electrolytically clean electrodes produced the smallest fluctuating potentials with all electrode pairs.
TL;DR: Manganese(IV) oxide electrodes formed with a graphite/PTFE substrate are shown to have near-theoretical response to manganese(II) ions in pH-4 acetate medium and a sub-Nernstian response in 0.1M nitric acid medium.
TL;DR: In this article, the cyclic voltammetric dark currents of a series of metallocenes in acetonitrile solutions were monitored by monitoring the capacitance of the space charge region.
Abstract: Electron-transfer processes at highly doped p-InP electrodes were investigated by monitoring the cyclic voltammetric dark currents of a series of metallocenes in acetonitrile solutions. The formal reduction potentials of the metallocenes span the bandgap of InP, allowing a comparison of the cyclic voltammetric response as a function of the formal reduction potential and the energetic condition of the electrode surface. Since the electro transfer of all of the metallocenes was electrochemically reversible on the timescale of cyclic voltammetry at a platinum electrode, differences in the voltammetric responses at p-InP were attributed to processes within the semiconductor or to surface phenomena. The energetic condition of the electrode surface during the cyclic voltammetric experiment was monitored by measurements of the capacitance of the space-charge region. Although a simple chemical etching and electrochemical cycling procedure yielded reproducible surface energetics, the p-InP/oxide/CH/sub 3/CN interface responded ideally to changes in electrode potential over a range of only about 0.8V. Metallocene redox couples with E/sup 0/' located within that range exhibited reversible cyclic voltammetry when the experiment was performed within that range. The couples with E/sup 0/' located outside of the ideal range displayed irreversible cyclic voltammetry. Voltammetric responses for p-InP electrodes with different crystal orientationsmore » and doping densities were compared.« less
TL;DR: In this paper, attenuated total reflection spectroscopy in the 1.2-5-μm spectral region was used to extract vibrational lines from the silicon surface, and the shapes and magnitudes of the various lines were qualitatively well understood.
Abstract: We have investigated the n‐Si/acetonitrile electrolyte interface using attenuated total reflection spectroscopy in the 1.2–5‐μm spectral region. Characteristic information from the surface has been extracted by using modulation of the electrode potential and lock‐in detection of the optical signal. When the modulated potential is kept positive with respect to the flatband potential, vibrational lines can be observed that are characteristic of the Si–H, (Si–)O–H, C–H, and C–N chemical bonds. The shapes and magnitudes of the various lines are qualitatively well understood. Upon electrode aging, the Si–H signal decreases and the (Si–)O–H signal increases, which provides direct in situ evidence for slow oxidation of the silicon surface.
TL;DR: In this article, a general mechanism for the electrode behavior from the experimental data is obtained for two-step electrode reaction, and where comparison is possible agreement is obtained with earlier work.
Abstract: Impedance measurements have been made on a mini electrode disposed between two large (identical) counter electrodes. A general mechanism is obtained for the electrode behaviour from the experimental data. The electrode reaction is two step and complex. Where comparison is possible agreement is obtained with earlier work.
TL;DR: In this article, a silver-silver Cryptate(2, 2) ion electrode (Ag/0.005M AgClO4, 0.05M Et4NClO 4(S)//) was studied with respect to its applicability as the reference electrode in acetonitrile (AN), propylene carbonate (PC), methanol (MeOH), dimethyl sulfoxide (DMSO) and N, N-dimethylformamide (DMF).
Abstract: A silver-silver Cryptate(2, 2) ion electrode (Ag/0.005M AgCryp(2, 2)ClO4, 0.005M Cryp(2, 2), 0.05M Et4NClO4- (S)//0.05M Et4NClO4(S)//) was studied with respect to its applicability as the reference electrode in acetonitrile (AN), propylene carbonate (PC), methanol (MeOH), dimethyl sulfoxide (DMSO) and N, N-dimethylformamide (DMF). The apparent formation constant of AgCryp(2, 2)+ and the potential of the AgCryp(2, 2)+/Ag electrode vs. ferrocene/ferricinium reference system, respectively, were 7.8 and -422mV in AN, 15.5 and -400mV in PC, 9.8 and -253mV in MeOH, 7.3 and -463mV in DMSO, and 9.9 and -466mV in DMF. The exchange current densities of the AgCryp(2, 2)+/Ag electrode were in the range of (3-5)×10-6A cm-2 in all the solvents. The electrode potential was not influenced by the total concentration of (AgCryp(2, 2)++Cryp(2, 2)), provided that the ratio of both species was kept 1:1. The effect of water on the potential was also relatively small. The disadvantages of the silver-silver ion reference electrode especially encountered in PC and DMF were removed with this electrode, and the potential was reproducible and stable enough in all the solvents.