Showing papers on "Overpotential published in 2000"
TL;DR: In this paper, it was shown that at the platinum metals, cathodic H 2 evolution takes place on a surface almost filled by underpotentially deposited H 2 reversible potential, so the binding energy of the H intermediate in the HER is not that to a free Pt surface.
300 citations
TL;DR: In this article, the oxidation of CO adlayers, formed by direct dosing from a CO-saturated solution, and bulk CO has been studied on Pt[ n (111)×(111)] single crystals in 0.5 M H 2 SO 4.
247 citations
TL;DR: In this article, a sensor response model that predicts a linear relationship between response voltage and analyte gas concentration is derived, which is not adequate for describing all types of mixed potential sensor responses.
241 citations
TL;DR: In this paper, the rate constants of the forward and backward reactions of Volmer, Heyrovsky and Tafel steps were estimated by a nonlinear fitting method with ac impedance and dc polarization measurements in 1.0 mol dm−3 NaOH solution at 25°C.
241 citations
TL;DR: In this paper, a mathematical model for polymer electrolyte membrane (PEM) fuel cells is developed and rigorous analytical solutions of the model are obtained, which consists of the cathode gas channel, gas diffuser, catalyst layer, and the membrane.
Abstract: A mathematical model for polymer electrolyte membrane (PEM) fuel cells is developed and rigorous analytical solutions of the model are obtained. The modeling domain consists of the cathode gas channel, gas diffuser, catalyst layer, and the membrane. To account for the composite structure of the gas diffuser and for its gradient in liquid water content, the gas diffuser is modeled as a series of parallel layers with different porosity and tortuosity. Starting from the oxygen transport equations and Ohm's law for proton migration, expressions for the oxygen mass fraction distribution in the gas channel, gas diffuser, and catalyst layer, and current density and membrane phase potential in the catalyst layer and membrane are derived. The solutions are presented in terms of the physical and thermodynamic parameters of the fuel cell. The polarization curve is expressed parametrically as a function of the surface overpotential. Expressions for cathode internal and overall effectiveness factors, active fraction of the catalyst layer, catalyst layer resistance, limiting current density, and the slope of the polarization curve are also presented. Due to the advantage of the closed-form solutions this model can he easily used as a diagnostic tool for a PEM fuel cell operating on H 2 and air.
223 citations
TL;DR: In this paper, a framework for defining charge transfer and non-charge transfer processes in solid state electrochemical systems is presented, and the ALS model for oxygen reduction on a porous mixed-conducting oxygen electrode is examined.
204 citations
TL;DR: In this paper, the effect of liquid velocity on the bubble coverage of gas-evolving electrodes has been investigated, and theoretical analysis and experimental results of the effect has been presented.
201 citations
TL;DR: In this article, a systematic study on the properties of the superior oxide-ion conductor Sr and Mg-doped LaGaO3 (LSGM) and its performance in a single fuel cell is presented.
189 citations
TL;DR: In this article, overpotential and AC impedance spectra were measured to study the reaction model of dense Sm 0.5Sr0.5CoO3 (SSC) as SOFC cathode.
187 citations
TL;DR: In this paper, an ultrafine powder was synthesized from colloidal precursors, and an active electrode for oxygen evolution and reduction was prepared by mixing the powder and Pt black.
Abstract: To improve the water electrolysis performance of unitized regenerative fuel cells, ultrafine powder was synthesized from colloidal precursors, and an active electrode for oxygen evolution and reduction was prepared by mixing the powder and Pt black. Analysis showed that the surface area of the synthesized was higher than that of high‐surface‐area Pt black. During fuel cell operation, increased the overpotential slightly; however during water electrolysis, the mixed electrocatalyst had a considerably higher activity for oxygen evolution. The addition of only a small amount of to the oxygen electrode was sufficient for the unitized regenerative fuel cell. © 2000 The Electrochemical Society. All rights reserved.
165 citations
TL;DR: In this article, the potential distribution of a thin solid electrolyte near active (currentbearing) electrodes is investigated and shown to be approximately equipotential beyond a distance of about three electrolyte thicknesses from the edge of the active electrodes.
TL;DR: In this paper, new electrocatalysts consisting of hydrogen storage alloys, such as MmNi3.6Co0.75Mn0.27 alloy (Mm≡misch metal), LaNi4.9Si0.1 alloy and Ti2Ni alloy and nickel-molybdenum coatings were prepared.
TL;DR: In this article, a Ti substrate for electrocatalysis of the oxygen evolution reaction (OER) in acidic media was obtained from one of three different deposition methods consisting of painting the substrate with the corresponding solutions followed by heat treatment at a temperature range 400-600°C for 1 h.
TL;DR: In this paper, the use of samaria-doped ceria (SDC) interlayer was examined to apply La(Sr)CoO 3 (LSC) as a cathode for medium-temperature solid oxide fuel cells without causing unfavorable solid-state reactions between LSC and yttria-stabilized zirconia electrolyte.
TL;DR: In this article, the formation of spinel NiCo2O4 spinel oxides using the Sol-Gel method on Ni and Ti substrates was described, which showed an oxygen overpotential of nearly 0.3 V, approximately 0.6 V less than that obtained for pure Ni oxide anodes.
TL;DR: In this paper, a mechanism for DME electrooxidation was proposed based on the results of half-cell experiments using cyclic voltammetry combined with gas-chromatographic (GC) analyses of a single direct DME fuel cell.
Abstract: The possibility of using dimethyl ether (DME) as a fuel in direct oxidation polymer‐electrolyte‐membrane (PEM) fuel cells is investigated. A mechanism for DME electro‐oxidation is proposed based on the results of half‐cell experiments using cyclic voltammetry combined with gas‐chromatographic (GC) analyses of a single direct DME fuel cell. It is shown that, as a consequence of this mechanism, there is an additional overpotential at the anode of a direct DME fuel cell which is related to the initial adsorption step on the catalyst surface. DME is typically not oxidized at the cathode of a PEM fuel cell. This minimizes unwanted effects of fuel crossover, leading to improved fuel‐cell efficiencies compared to direct methanol fuel cells, especially at low‐to‐medium current densities. © 2000 The Electrochemical Society. All rights reserved.
TL;DR: The adsorption and incorporation of ruthenium on Pt(110) have been investigated using the techniques of low energy ion scattering spectroscopy (LEISS), X-ray photoelectron spectroscopic (ARXPS) and low energy electron diffraction (LEED).
TL;DR: In this paper, the authors constructed a surface-reaction model to determine the origin of the overpotential, and good agreement was found between their model and experimental results, showing that the interfacial conductivity of the dense LSM electrodes was independent of the oxygen partial pressure and inversely proportional to the thickness of the LSM film.
TL;DR: In this paper, the authors measured the H 2 evolution reaction (HER) potentials at PANI electrodes and analyzed the kinetic parameters of the process, including the coverage of the electrode by H atoms, and the rate constants for the two kinetic steps involved in the process of H2 evolution at Pt nanoparticles incorporated with a thin polyaniline film.
TL;DR: In this paper, the power generation characteristics and the electrode overpotential of the solid oxide fuel cell (SOFC) using doped lanthanum gallate perovskite-type oxide as an electrolyte were measured at temperatures below that of the typical SOFC using yttria-stabilized zirconia (YSZ).
TL;DR: In this article, a fabrication method for the preparation of Ni/3 mol% Y 2 O 3 -ZrO 2 (Ni/TZ3Y) cermet electrodes from various commercial powders has been described.
TL;DR: In this article, the anodic overpotential decreased by mixing Ni with mixed electronic-ionic conductor, in particular, mixing with doped CeO2 is the most effective for decreasing the anode.
TL;DR: In this article, the authors evaluated the performance of copper deposition onto an Au(111) surface from sulfuric acid electrolyte using potentiostatic current transients using a new and nontradi...
Abstract: Kinetics of copper deposition onto an Au(111) surface from sulfuric acid electrolyte, was evaluated using potentiostatic current transients. Measurements were conducted employing a new and nontradi...
TL;DR: In this paper, the mixed potential at the Au electrode was always higher (more negative) than that at the Pt electrode irrespective of the type of reducing gas used, and the polarization curves of the two electrodes during oxygen reduction were also measured.
Abstract: A Pt/Ce{sub 0.8}Gd{sub 0.2}O{sub 1.9}/Au mixed-potential sensor was constructed and its response to reducing gases in an oxygen containing stream was measured at T = 550 and 600 C. The sensor response was maximum for H{sub 2} and negligible for methane; other gases followed the trend methane < propane < CO, propylene < hydrogen. The mixed potentials developed at the Au and Pt electrodes were also independently monitored with respect to Pt air-reference electrodes. The mixed potential at the Au electrode was always higher (more negative) than that at the Pt electrode irrespective of the type of reducing gas used. The polarization curves of the two electrodes during oxygen reduction were also measured. These measurements revealed that the mixed potential at the electrodes was dependent on both the amount of electrochemical oxidation of reducing gas and the overpotential for oxygen reduction. While the response of the Pt electrode was found to be stable at both 600 and 550 C, the Au electrode had stability problems at 600 C due to the changing morphology of the gold film.
TL;DR: In this paper, the effect of non-Faradaic electrochemical modification of catalytic activity (NEMCA effect) or electrochemical promotion (EP) on catalytic performance was investigated.
TL;DR: In this article, the effect of experimental variables, like total Co2++Pb2+ concentration, Co2+/(Co2++pb2+) ratio, potential, pH and angular speed of the anode, on the deposit composition has been investigated.
TL;DR: In this article, composite oxides of Pb and Ru have been anodically deposited on Ti rotating disc electrodes and tested as anode materials for the oxygen evolution reaction (oer) from aqueous sulfuric acid.
TL;DR: In this article, the selective electrodeposition of these heavy metals was studied and the goal was to recover, under potentiostatic conditions, each heavy metal with high purity, yield and reaction rates.
TL;DR: In this article, the thermal and electrochemical behavior of pyrite as an electrode material for rechargeable lithium polymer electrolyte batteries has been investigated, and the performance characteristics, such as Li/Fe ratio, faradaic efficiency and charge-discharge overpotential, were found almost independent of the degree of contamination and, consequently, of the Pyrite source during 30 cycles.
TL;DR: In this paper, the crystallographic structure and morphology of electrodeposited cobalt films on Au(111) is found to be very sensitive on the electrolyte pH value and on the overpotential applied during deposition.
Abstract: The crystallographic structure and morphology of electrodeposited cobalt films on Au(111) is found to be very sensitive on the electrolyte pH value and on the overpotential applied during deposition. The samples, 2 to 500 nm thick, where characterized by nuclear magnetic resonance (NMR), atomic force microscopy (AFM) and electron diffraction. The latter technique shows that the Co films grow in registry with the gold underlayer, reproducing the Au(111) texture. During the first stage of growth and depending on overpotential and pH value, either continuous hcp Co films or hcp Co islands are formed. Only the latter growth mode leads to an out of plane magnetization with 100% of remanence. Increasing the thickness, fcc Co becomes the prevailing phase. Eventually the fcc to hcp ratio saturates at the same value regardless the overpotential. The thickness for which the equilibrium fcc to hcp ratio is obtained as well as the sample structure and morphology before saturation, depend strongly on the overpotential value. In any case, the predominance of the fcc Co phase leads to an in plane magnetization of the thick samples. This study opens up new opportunities of engineering the properties of electrodeposited cobalt films.