Showing papers on "Overpotential published in 1991"
TL;DR: In this paper, the performance of SnO2 as an anode material with high oxygen gas-evolution overpotential was investigated in view of its application for electrochemical oxidation of bio-refractory organics in waste waters.
Abstract: The electrochemical performance of SnO2 as an anode material with high oxygen gas-evolution overpotential was investigated in view of its application for electrochemical oxidation of bio-refractory organics in waste waters. The influence of the doping agent (Sb, F, Cl) and doping level on the oxygen-evolution reaction was studied in terms of Tafel slope, oxygen-overpotential and exchange current densities for the Ce3+→Ce4+ reaction. Tafel slopes of about 300 mV decade−1 were found and the oxygen evolution overpotential was 600mV higher than that of platinum. While the doping level had no significant influence on Tafel slopes and oxygen overpotentials the stability of the SnO2 electrode increased with charge carrier density. The oxidation of phenol was investigated as a test for the oxidizing power of the new anode material when compared to Pt or PbO2. The rate of phenol removal was much higher for SnO2 than for PbO2 or Pt.
339 citations
TL;DR: In this paper, the formation process and structural properties of nanocrystalline alloys were investigated and the active phase is a metastable solid solution of Mo in fcc Ni whose electrocatalytic activity is associated with the reduction in the size of the crystallites and correlates with the expansion of the Ni lattice.
Abstract: Nanocrystalline fcc Ni x Mo 1−x (x=0.60, 0.85 atom percent) metallic powders prepared by high energy mechanical alloying were found to possess electrocatalytic activities for the hydrogen evolution reaction in 30 weight percent KOH at 70°C equivalent to that of the best electrocatalysts. The formation process and the structural properties of these nanocrystalline alloys were investigated. The active phase is a metastable solid solution of Mo in fcc Ni whose electrocatalytic activity is associated with the reduction in the size of the crystallites and correlates with the expansion of the Ni lattice
111 citations
TL;DR: In this article, the impedance of the Au, O2 (g) / yttria stabilized zirconia interface has been measured as function of the overpotential, temperature and oxygen partial pressure.
80 citations
TL;DR: In this article, three different reaction models are discussed which describe the oxygen exchange reaction at the Au, O2(g)/yytria stabilized zirconia interface, which can predict the apparent Tafel behavior of the current-overpotential curve.
79 citations
TL;DR: In this paper, the authors report work on the preparation of code-posited Ni/WO{sub 3} and Co/WOWO{Sub 3} films which give significantly faster response times and consume less power than traditional WO{ sub 3} film.
Abstract: Tungsten trioxide is being developed as a electrochromic material for smart windows. However, the relatively high electrical resistivity and overpotential for hydrogen evolution and oxidation affect their response time and electrical power consumption. Previous work on Pt/WO{sub 3} indicated that admixing of Pt onto WO{sub 3} significantly reduced the overpotential for hydrogen oxidation and evolution reactions since the formation of hydrogen tungsten bronze results in the spill-over of the hydrogen reaction to the tungsten bronze surface. This paper reports work on the preparation of code-posited Ni/WO{sub 3} and Co/WO{sub 3} films which give significantly faster response times and consumes less power than traditional WO{sub 3} films.
77 citations
TL;DR: In this paper, the electrodeposition and electrodissolution of copper by the potentiostatic method is made with an applied external magnetic induction for both low and high overpotential.
67 citations
TL;DR: In this paper, the effect of benzotriazole in the initial stages of deposition of 7 nm thick Cu deposits was investigated using scanning tunneling microscopy to study the submicron topography of Cu deposits.
Abstract: In this paper, the submicron topography of Cu deposits is studied with scanning tunneling microscopy to investigate the effect of benzotriazole in the initial stages of deposition The presence of benzotriazole results in a marked increase in over-potential for the deposition It is found to eliminate the preferential growth of specific crystallographic planes and the formation of crystal facets The number density of nuclei, determined from Fourier transforms of the surface profiles of 7 nm thick films, is found to increase with increasing overpotential of the deposition but is independent of the presence of the inhibitor
54 citations
TL;DR: In this paper, the electrocatalytic activity of amorphous and crystalline Ni-base alloys with respect to the Hydrogen Evolution Reaction (HER) has been studied.
53 citations
Patent•
09 Jan 1991
TL;DR: In this article, the use of an additive for acid copper plating bath which is chosen based on criteria of creating a shift in the charge transfer overpotential of the bath; or alternatively, creating a differential over-potential between the surface of a high aspect ratio circuit board and the recesses of such boards.
Abstract: The invention discloses the use of an additive for acid copper plating bath which is chosen based on criteria of creating a shift in the charge transfer overpotential of the bath; or alternatively, creating a differential overpotential between the surface of a high aspect ratio circuit board and the recesses of such boards. The additive may be a single or multi-component additive.
47 citations
TL;DR: In this paper, the overpotential normally associated with the electrochemical oxidation of oxalic acid in aqueous solution is greatly reduced at glassy carbon surfaces modified with polymeric metallophthalocyanine films.
44 citations
TL;DR: In this article, it was shown that the catalytic activity and selectivity of polycrystalline Pt for the oxidation of methanol to formaldehyde and Co 2 can be dramatically and reversibly affected when oxygen anions O 2− are electrochemically pumped to or from the Pt catalyst surface.
TL;DR: In this article, the authors showed that some of the iron porphyrin aggregates form a face-to-face structure by the electrostatic interaction and provide the effective sites for the reduction of molecular oxygen.
TL;DR: In this article, the surface of an Au(111) electrode is roughened after a single monolayer of Pb is electro-plated and stripped from the surface in a linear sweep experiment.
TL;DR: In this paper, the behavior of polyaniline (PANI) films as subtrates for metal electrodeposition is investigated and the stationary nucleation rate of silver on PANI is studied as a function of the overpotential and the film thickness.
TL;DR: In this paper, it was shown that improvement in the overpotential and in the exchange current density of the electrodes depends both on the composition of the deposition bath and on deposition time.
Abstract: Nickel was electrodeposited from baths based mainly on dilute aqueous solutions of nickel chloride, sulphate or acetate containing SiW12O404− or SiMo12O404− anions. Each bath contained one of the ions. The other chemical constituents of the solutions were the same in all of the baths. It was shown that improvement in the overpotential (η) and in the exchange current density (i0) of the electrodes depends both on the composition of the deposition bath and on deposition time. The h.e.r. electrocatalytic activity of the electrodeposits was then analysed and related to their chemical composition. The results show that some extremely active electrocatalysts are produced when combinations of nickel-tungsten (Ni−W) or nickel-molybdenum (Ni−Mo) are formed. The discussion is extended to include typical hypo-hyper-d-electronic transition metals, and it is concluded that alloying these metals significantly increases electrocatalytic activity.
TL;DR: In this article, rate-potential data for proton electroreduction on Au(111) and Au(210) in acidic perchlorate electrolyte over the temperature range 0-60°C, and are examined with regard to the temperature dependence of the transfer coefficient α.
TL;DR: In this paper, the electrocatalytic properties of nickel-molybdenum (Ni−Mo) deposits for hydrogen evolution reaction (h.r.) were investigated.
Abstract: Nickel was electrodeposited from dilute aqueous solutions of nickel chloride, containing MoO42− or PMo12O403− ions. It was shown that improvement in the overpotential (η) and in the exchange current density (i0) of the electrodes depends on the composition of the deposition bath. The h.e.r. electrocatalytic activity of the electrodeposits was then analysed and related to their chemical composition. The results show that some extremely active electrocatalysts are produced when combinations of nickel-molybdenum (Ni−Mo) are formed. The influence of the MoO42− or PMo12O403− concentration in the electrode deposition electrolyte on the electrocatalytic properties of these deposits for the hydrogen evolution reaction (h.e.r.) was investigated. The effects of the deposition current density on the electrocatalytic properties of the electrodes were also studied. The best electrocatalytic properties for the h.e.r. were obtained with electrodes electrodeposited with 2 g dm−3 of MoO42− or PMo12O403−. The kinetic parameters for the h.e.r. in H2SO4 1 M were deduced for temperatures ranging from 298 to 378 K.
TL;DR: In this article, the nucleation and growth of silver from dilute aqueous solutions of AgNO3 was studied in the absence and in the presence of potassium sodium tartrate in the electrolyte.
Abstract: The nucleation and growth of silver from dilute aqueous solutions of AgNO3 was studied in the absence and in the presence of potassium sodium tartrate in the electrolyte. In both cases data were obtained for the rate of nucleation and growth of silver crystals at constant overpotential.
TL;DR: In this article, the use of collection efficiency measurements, at the double channel electrode, is considered in the resolution of the ECE-DISP1 problem, where the upstream (generator) electrode is held at a potential in the transport-limited current region, with the downstream (collector) electrode at the potential such that the initial heterogeneous electron transfer is reversed but sufficient overpotential is available to drive the second electron transfer, in the original sense, should it occur.
TL;DR: In this article, the authors investigated the transient events accompanying passivation of active surfaces in aluminum etch tunnels and found that the change in dissolution current is proportional to the cathodic surface overpotential, relative to the critical repassivation potential.
Abstract: Transient events accompanying passivation of active surfaces in aluminum etch tunnels are investigated. Passivation is induced by pulsed reductions of the anodic etching current, of several milliseconds duration. Scanning electron microscopy is used to measure the area passivated. Potential transients are analyzed to identify a possible potential driving force for passivation. For the experimental conditions of this work, at 0.13 ms after the current step, there is a temporary reduction in the metal dissolution current in tunnels. The change in dissolution current is proportional to the cathodic surface overpotential, relative to the critical repassivation potential. The transient reduction in dissolution current is associated with passivation, since no variation in dissolution current with potential is observed during steady tunnel growth. Surface changes resulting in permanent passivation occur later, at times between 3 and 12 ms after the current step.
31 May 1991
TL;DR: In this article, rate-potential data are reported for proton electroreduction on Au(111) and (210) in acidic perchlorate electrolytes over the temperature range 0-60 C, and examined with regard to temperature dependence of the transfer coefficient alpha.
Abstract: : Rate-potential data are reported for proton electroreduction on Au(111) and (210) in acidic perchlorate electrolytes over the temperature range 0-60 C, and examined with regard to temperature dependence of the transfer coefficient alpha Since the Tafel plots exhibit significant curvature the analysis requires information on the temperature-dependent thermodynamics (ie the reaction entropy) for the proton discharge step This was estimated from temperature-dependent voltammetry of reversible proton discharge to form adsorbed hydrogen on platinum When evaluated at a constant overpotential for the proton discharge step, alpha for this reaction on both Au(111) and (210) is independent of temperature An effect of electrocatalysts for proton reduction on Au(111) engendered by prior voltametric oxide formation was also observed This effect is attributed to formation of surface defects on the basis of recently reported scanning tunneling microscopy data Surface structural changes are also evident in the morphology of cyclic voltammograms obtained in the double-layer region Electrochemical effects disappear with time when potential is held in the double layer region, and more rapidly at higher temperatures
TL;DR: In this paper, the nucleation process is assumed to be influenced by compressive strain in the UPD adlayer which arises from a strong substrate-adsorbate interaction, and new information obtained by in situ GIXS (grazing incidence X-ray scattering) is quantitatively interpreted by a new physical model.
TL;DR: In this article, the reduced form of GSH was found to occur at a decreased overpotential at a glassy carbon electrode when 1.2 mol dm-3 of dipotassium hydrogen phosphate were used as the supporting electrolyte.
Abstract: The oxidation of the reduced form of glutathione (GSH) was found to occur at a decreased overpotential at a glassy carbon electrode when 1.2 mol dm–3 of dipotassium hydrogen phosphate were used as the supporting electrolyte. The resulting current for the oxidation peak of GSH varied linearly over the concentration range 0.16–2.4 mmol dm–3 GSH. The reaction between GSH and hydrogen peroxide catalysed by the enzyme GSH-peroxidase (GSH-PX) could be monitored using a glassy carbon electrode with GSH-PX immobilized under a layer of Nafion film.
TL;DR: In this paper, local heat effects caused by electric current in the industrial electrolysis of aluminum are calculated by a non-equilibrium theory, the electric work method, using literature data and assumptions about electrode reactions to obtain the results.
TL;DR: In this article, a poly(2,3-diaminonaphthalene)(PDAN)-filmed glassy carbon electrode, which can be prepared in situ by electropolymerization of the corresponding monomer, shows excellent electrocatalytic activity for O2 reduction to H2O2 in an acidic aqueous solution (pH 1.0), with an activation overpotential which is ca. 300 mV lower than that of the bare electrode.
Abstract: Poly(2,3-diaminonaphthalene)(PDAN)-filmed glassy carbon electrode, which can be prepared in situ by electropolymerization of the corresponding monomer, shows excellent electrocatalytic activity for O2 reduction to H2O2 in an acidic aqueous solution (pH 1.0), with an activation overpotential which is ca. 300 mV lower than that of the bare electrode.
TL;DR: In this paper, the early stages of Ag electrodeposition on columnar structured Pt electrodes were investigated in acid solutions covering the underpotential deposition (upd) and overpotential deposition (opd) ranges.
TL;DR: In this article, the effect of the last parameter on the morphology of electrodeposited metal powder particles on the basis of existing experimental evidence was discussed, and the effect was shown that at one and the same average deposition rate (current density), it is possible to create a number of different deposition conditions in the pulsating regimes.
Abstract: It is well known that the deposition conditions such as bath composition, hydrodynamic regime, temperature, current density, exhibit a strong effect on the grain size and the morphology of electrodeposited metal powder particles [1, 2]. On the other hand it has been shown recently [3] that similar effects can be obtained by changing only the shape of the current overpotential waves in metal powder electrodeposition at a periodically changing rate with other conditions constant. This is in accordance with Ibl's observation [4] that, at one and the same average deposition rate (current density), it is possible to create a number of different deposition conditions in the pulsating regimes. In square-wave pulsating overpotential electrolysis the overpotential amplitude, frequency of pulsation and pause-to-pulse ratio can be varied independently. The purpose of this work is to discuss the effect of the last parameter on the morphology of electrodeposited metal powder particles on the basis of the existing experimental evidence.
Abstract: Studies of the adsorption of the Cl˙ intermediate in anodic Cl2 evolution at a series of four thin-film RuO2 electrodes formed on a Ti substrate have been made by means of potential-relaxation measurements, following interruption of previous steady-state currents, coupled with determination of the current vs. overpotential kinetic relationships.Experiments at rotated RuO2 electrodes show only a small effect, indicating that neither diffusion-controlled supply of Cl– nor effects of Cl2 supersaturation in the boundary region at the electrode materially effect the kinetic behaviour. This behaviour is manifested as continuously curved Tafel relations, which approach limiting currents at overvoltages of 0.2–0.3 V. Therefore, on these thin-film RuO2 materials, kinetic control of Cl2 evolution seems to be by the Cl˙ recombination pathway; this is supported by linearity of Conway–Novak test plots for the recombination mechanism.Analysis of the potential-relaxation transients enables the pseudocapacitance, Cϕ, for adsorbed Cl˙ to be determined. Cϕ shows ascent to large values below 50–100 mV of overpotential, depending on temperature. Some problems arise, however, in reconciling this adsorption behaviour with expectations associated with recombination control.The near-surface composition profiles of the RuO2 films have been determined by means of Rutherford back-scattering and the average compositions, deeper into the films, by energy-dispersive X-ray emission analyses.
TL;DR: In this paper, the formation process and structural properties of nanocrystalline alloys were investigated and the active phase is a metastable solid solution of Mo in fcc Ni whose electrocatalytic activity is associated with the reduction in the size of the crystallites and correlates with the expansion of the Ni lattice.
Abstract: Nanocrystalline fcc Ni x Mo 1−x (x=0.60, 0.85 atom percent) metallic powders prepared by high energy mechanical alloying were found to possess electrocatalytic activities for the hydrogen evolution reaction in 30 weight percent KOH at 70°C equivalent to that of the best electrocatalysts. The formation process and the structural properties of these nanocrystalline alloys were investigated. The active phase is a metastable solid solution of Mo in fcc Ni whose electrocatalytic activity is associated with the reduction in the size of the crystallites and correlates with the expansion of the Ni lattice