Showing papers on "Overpotential published in 1989"
TL;DR: In this paper, it was shown that the catalytic activity of polycrystalline Pt for the oxidation of ethylene to CO 2 and H 2 O can be increased by up to a factor of 50 when oxygen anions O 2− are electrochemically pumped onto the Pt catalyst surface.
193 citations
TL;DR: In this paper, the electrocatalytic properties of composite films containing Pt microparticles dispersed in W(VI,V) oxide supports were described, and the coatings were prepared electrochemically on graphite.
125 citations
TL;DR: In this paper, it is shown how the various components of the overpotential due to an attached bubble on an electrode can be separated and estimated by considering the resistance increments due to the presence on the electrode surface of a bubble, obtained from impedance measurements.
Abstract: It is shown how the various components of the overpotential due to an attached bubble on an electrode can be separated and estimated. By considering the resistance increments due to the presence on the electrode surface of a bubble, obtained from impedance measurements, it is possible to determine the predominant potential distribution which controls the gas evolution. A relationship between the measured overpotential and the diameter of the bubble is established. The time evolution of the overpotential due to a growing bubble is modelled in the case of the limitation of the bubble growth by dissolved gas diffusion in the solution. In agreement with previous experimental results a linear time variation is found.
96 citations
TL;DR: In this article, a new type of oxygen sensor using the electrochemical oxygen pump of a zirconia electrolyte and the artificial oxygen diffusion overpotential behavior has been investigated from the theoretical and practical viewpoints of the "gas polarography", the concept of which is proposed in this paper.
Abstract: A new type of oxygen sensor using the electrochemical oxygen pump of a zirconia electrolyte and the artificial oxygen diffusion overpotential behavior has been investigated from the theoretical and practical viewpoints of the "gas polarography," the concept of which is proposed in this paper. This new oxygen sensor has excellent oxygen sensing characteristics analogous to polarography. As a result of the artificial oxygen diffusion overpotential at the cathode, the reproducible limiting current relating to the oxygen concentration was observed over a wide oxygen concentration range up to 95% and a temperature range of 400°–700°C in gas mixtures. In this paper, the factors influencing the limiting current in the normal diffusion region, that is, the oxygen molar fraction, gaseous diffusion coefficients, the temperature, the pressure, and the two geometric quantities (area and length) of the gas diffusion hole are theoretically considered.
81 citations
TL;DR: The polymer films lower the overpotential of carbon dioxide reduction in DMF by nearly 1,0 V and the four-electron reduction of oxygen in aqueous solution by 300 mV as discussed by the authors.
Abstract: The polymer films lower the overpotential of carbon dioxide reduction in DMF by nearly 1,0 V and the four-electron reduction of oxygen in aqueous solution by 300 mV. The predominant product of carbon dioxide reduction is formic acid. The product distribution (water vs peroxide) in the reduction of oxygen was strongly dependent on the polymer coverage, with water being the predominant product at high coverage (>2,5×10 −9 mol/cm 2 ), whereas at lower coverage, hydrogen peroxide was the main reaction product
67 citations
TL;DR: In this paper, it was shown that the catalytic activity and selectivity of polycrystalline Ag for the dehydrogenation and decomposition of CH 3 OH can be markedly affected by electrochemically pumping oxygen anions from the catalyst surface via stabilized zirconia solid electrolyte cells.
61 citations
TL;DR: In this article, cyclic voltammetry was used to probe the electrooxidation of 2-mercaptoethanol on ordinary pyrolytic graphite modified with adsorbed layers of tetrasulphophthalocyanines (TSPc) of several metals.
43 citations
TL;DR: In this article, a correction factor to the coefficient calculated from available mass transfer equations is proposed, and the effect on the concentration overpotential of disolved gas is discussed, where the effect of the correction factor on the over-potential is discussed.
Abstract: Dissolved gases in the boundary layer of gas-evolving electrodes, in constrast to all other substances generated or consumed at electrodes, undergo two superimposed mass transfer mechanisms. Their interaction results in an increase of the effective mass transfer coefficient of disolved gas. A correction factor to the coefficient calculated from available mass transfer equations is proposed. The effect on the concentration overpotential is discussed.
41 citations
TL;DR: In this article, two new materials recently developed showed a reduction in overpotential of the order of 240 mV at 135 mA cm −2 when compared with mild steel electrodes under long-term operation (1200 h) at 60°C in 28% aqueous KOH.
36 citations
TL;DR: In this article, the deposition of silver on polycrystalline platinum was investigated over a wide range of potentials, covering both underpotential and over-potential regions.
30 citations
TL;DR: In this paper, it was shown that the use of carbon microdisc electrodes allows the study of the nucleation and growth of single centres of α-PbO2 at high overpotentials.
TL;DR: In this article, the geometrical arrangement of Bi ad-atoms affects the electrocatalytic activity for formic acid oxidation as that of Cu ad-atom does for the hydrogen evolution reaction.
TL;DR: In this article, a new activated cathode for chlor-alkali electrolysis is described, which is a composite coating consisting in a first RuO2 thermal layer, on a nickel support, modified by a second layer made of electroless nickel.
TL;DR: In 1989, Fleischmann and Pons as mentioned in this paper reported the production of heat during the electrolysis of D2O at a Pd cathode and Pt anode in excess of that predicted by the electrochemical theory for heat production in cells.
TL;DR: In this article, the photoelectrochemical behavior of both bare and electroplatinized single crystal in and saturated electrolytes has been studied by electrolyte electroreflectance (EER) and photocurrent transient techniques.
Abstract: In order to go further into the mechanisms of water splitting at platinized powder suspensions, the photoelectrochemical behavior of both bare and electroplatinized single crystal in and saturated electrolytes has been studied by electrolyte electroreflectance (EER) and photocurrent transient techniques. EER is shown to be an interesting tool to follow the potential distribution changes occurring at the interface during photo‐ and electrochemical reactions. In particular, reversible shifts of the flatband potential, due to local pH changes associated with evolution, could be detected for the first time by EER. Direct experimental evidence has shown that equilibrium of OH− and H+ ions between the electrolyte and the surface is reached in times no longer than a few seconds. The combined information obtained from EER and photocurrent transient experiments with the platinized single crystal, strongly suggests that the ~1 V Schottky barrier existing at the microjunctions drastically collapses when the electrolyte in the interface with the semiconductor becomes saturated. Evidence is also shown that either dissolved or evolved can be photo‐oxidized with holes trapped at Pt islands. This constitutes an important source of surface recombination, responsible to a great extent for the low water splitting efficiency at platinized suspensions. Finally, it can be inferred from our experimental results that, in colloidal systems, band asymmetry between bare and platinized zones is not a sine qua non condition for water splitting to be a feasible process. Nevertheless, the barrier height diminution at the contact upon interaction of Pt with seems to be decisive for to evolve with an acceptable rate at Pt islands. On the other hand, Pt plays an important role as a catalyst by reducing the overpotential for evolution, which can occur in spite of the small energy difference between the redox level and the conduction bandedge.
TL;DR: In this article, it was shown that the morphology of tin powder particles strongly depends on deposition overpotential and parameters determining the wave of pulsating over-potential, and the possible effect of the overpotency on tin powder morphology was discussed.
TL;DR: In this article, the authors investigated the hydrogen discharge on polished pure pure Co, Cu, Fe, Mo, Nb, Ni, Pd, Pt, V, W and Zr cathodes in 30 wt% KOH at 70°C at a constant current density of 100 mA cm −2.
TL;DR: In this article, the authors examined the relation of growth morphology to the micrometre-scale structure and found that the interface between the growths is a distinctive compact granular deposit, unstable to branching and dendrite growth.
Abstract: The technique of paper-supported copper electrodeposition provides examples of well-presented fractal and dense radial structures. The growths may be developed to reveal concentration gradients around the growths at low cell overpotential. Measurements for current and length scale against time, within a mid-range of cell overpotentials, fit an ohmic model of the growth conditions. To examine the relation of growth morphology to the micrometre-scale structure, we grew first at one overpotential and then continued at a lower overpotential. Electron microscope observations of this growth reveal a distinct change in microstructure from irregular to dentritic microcrystalline from the high to low potential respectively. The interface between the growths is a distinctive compact granular deposit. The granular deposit is unstable to branching and dendrite growth.
TL;DR: In this article, it is shown that cobalt treated lead electrodes work at 1.80 to 1.85 V(NHE) under 500 A/m 2 in 10% w.t. H 2 SO 4 and at 35 to 40°C whereas a thickness decrease of the material no more than 1 to 2 mm per year is observed.
TL;DR: In this article, a systematic investigation comprising the preparative processes, spectral characteristics and the electrochemical behaviour including open circuit potential decay, a.c. impedance, linear sweep cyclic voltammetry and a few simulation experiments to assess its suitability to the process was carried out.
TL;DR: In this article, the anodic dissolution of pure iron in acetonitrile-water solutions with varying concentrations of acetetitrile and varying pH has been investigated, and it was shown that acetite acts as an interface inhibitor for the dissolution of iron at low overpotential, almost entirely inhibiting the I1, reaction.
TL;DR: In this article, a characterization of the electrodes with incorporated Pt particles was carried out, using AC-impedance techniques, and the ohmic resistance was determined as a function of the electrode potential and the Pt loading.
TL;DR: In this article, the growth pattern of staging transition in graphite intercalation compounds (GICs) has been analyzed by time and space-resolved Raman scattering measurements of the electrochemical interalation process in GICs.
TL;DR: In this paper, the hydrogen-sensing capability of a gas polarographic oxygen sensor using a zirconia electrolyte has been investigated at 450°C and 1 atm in H2-N2 gas mixtures.
Abstract: The hydrogen-sensing capability of a gas polarographic oxygen sensor using a zirconia electrolyte has been investigated at 450°C and 1 atm in H2-N2 gas mixtures The limiting current was realized in H2-N2 gas mixtures due to the artificial hydrogen diffusion overpotential behavior at the anode, and is proportional to the hydrogen concentration up to 5% in H2-N2 gas mixtures This result proved that this oxygen sensor can also detect the hydrogen in H2-inert-gas mixtures
TL;DR: In this article, the ionic conductivity of the (ZrO 2 ) 1− x (Y 2 O 3 ) x system, where x is equal to 9, 15 and 25 mol%, has been studi ed.
TL;DR: In this article, the influence of overvoltage on the shapes of cadmium dendrites was investigated by scanning electron microscopy, and it was shown that, in the region of overpotentials where dendritic deposits were obtained, at the lowest overpotential only flat dendris have been recorded.
Abstract: The influence of overvoltage on the shapes of cadmium dendrites was investigated by scanning electron microscopy. It was shown that, in the region of overpotentials where dendritic deposits were obtained, at the lowest overpotential only flat dendrites have been recorded. The initiation of fern-like dendrites was obtained at higher overpotentials and needle-like dendrites were obtained when the overpotential of progressive nucleation was attained. The initiation of fern-like dendrites is discussed in more detail.
TL;DR: The electrochemical behavior of mined iron silicide with a nominal composition of FeSi2 has been examined in KOH solutions over a wide range of cathodic and anodic potentials as mentioned in this paper.
Patent•
24 Nov 1989
TL;DR: A cathode for electrolysis, particularly of a sodium chloride aqueous solution by an ion-exchange membrane method, and a process for producing the same, the cathode comprising a conductive base having a nickel surface and having provided thereon (a) at least one platinum group component selected from the group consisting of a platinum group metal, aatinum group metal oxide, and the platinum group hydroxide, retaining a markedly reduced hydrogen overpotential for an extended period of time and exhibiting excellent resistance to impurities in the electrolytic solution.
Abstract: A cathode for electrolysis, particularly of a sodium chloride aqueous solution by an ion-exchange membrane method, and a process for producing the same, the cathode comprising a conductive base having a nickel surface and having provided thereon (a) at least one platinum group component selected from the group consisting of a platinum group metal, a platinum group metal oxide, and a platinum group metal hydroxide, and (b) at least one cerium component selected from the group consisting of cerium, cerium oxide, and cerium hydroxide, retaining a markedly reduced hydrogen overpotential for an extended period of time and exhibiting excellent resistance to impurities in the electrolytic solution.
TL;DR: In this article, the growth shape of the monolayers is a triangle enclosed by three identical arcs, and a linear dependence of the growth rate of the steps on the overpotential has been established.
TL;DR: In this article, the rate, reaction mechanisms, and the catalysis of the electrochemical reduction of thionyl chloride from anhydrous media, are discussed, where the reduction behaves as though it were diffusion controlled, whether the cathodes are porous carbon electrodes or rotated disc electrodes.