Oxide Involvement in Some Anodic Oxidation Reactions

Conway, B. E.; Marinčić, N.; Gilroy, D.; Rudd, E. J.

doi:10.1149/1.2423776

Cited by 43 publications

(15 citation statements)

References 34 publications

(72 reference statements)

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“…In addition to the FA1 process, formic acid oxidation occurs by other mechanisms (15)(16)(17)(18)(19) near 0.9V EH (FAg), as surface oxide formation on Pt commences (31) and also at 1.3V (FA4) on the more highly oxidized "PtO" surface. In the cathodic sweep, facile oxidation occurs ("FC" reaction, Fig.…”

Section: Ehects Of Acetonitrile On Other Formic Acid Oxidation Reactimentioning

confidence: 99%

Origin of Activation Effects of Acetonitrile and Mercury in Electrocatalytic Oxidation of Formic Acid

Angerstein‐Kozlowska

MacDougall

Conway

1973

J. Electrochem. Soc.

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137

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In the presence of catalyst poisons such as acetonitrile or mercury, it is shown that the currents for formic acid oxidation, measured in the potential range +0.4 to ~0.SV EH at Pt can be substantially increased. The effect is shown to originate from blocking of the surface at less positive potentials mainly in the H adsorption/desorption region (-t-0.05 to +0.35V ER) where an inhibitor for the main formic acid oxidation reaction is normally formed in the absence of additive.Under the latter conditions, steady-state oxidation currents are normally small and decrease with time due to build-up of an inhibiting species from the HCOOH or intermediates involved in its oxidation. Increases in the formic acid oxidation peak in the "double-layer" potential region at Pt can also be brought about in potentiodynamic experiments in the absence of additive, by cycling over a restricted potential range which excludes the H adsorption region. The inhibitor for formic acid oxidation is formed at potentials negative to 0.6V E~ by dimerization of COOH groups to give adsorbed formic anhydride. Its formation requires both time and available free surface. The competitive effects of Hg and CHsCN are different insofar as a given extent of surface blocking causes different effects on the formic acid oxidation current. Comparative experiments on the effect of CHaCN on methanol oxidation are described.A general problem in the electro-oxidation of small organic molecules is the progressive decrease of rate (current density) of the reaction at a given potential and temperature, which occurs with time (1). This is usually not due to physical changes of the electrocatalyst structure except at elevated temperatures (2). Build-up of adsorbed species which inhibit (3) the main reaction sequence causes these effects. Periodic activation of the electrode, particularly by pulsing (4) to surface oxide formation potentials (5, 6), or by auto-oscillation (3, 7) regenerates electrode activity.Activating effects in electrode reactions by what would normally be regarded as catalyst poisons were first observed by Monblanova and Kobosev (8);Binder et al. (9) found that partial coverage of the electrode by sulfur from sulfide enhanced the electrocatalytic activity of the surface for formic acid oxidation. Bockris and Conway (10) observed activating effects of traces of As and KCN in the H2 evolution reaction. Satisfactory explanations for these effects have not yet been provided.In the present paper, we report some interesting activating effects which arise in the electro-oxidation of formic acid at platinum electrodes when small concentrations of acetonitrile are present. The behavior is compared with that exhibited with methanol.The present work indicates that the activating effect may be a general one in the case of formic acid oxidation and an account of the behavior may be given in terms of competitive adsorption effects (3) in an electrocatalytic process (11).The electrochemistry of CH3CN in aqueous medium has been described in previous papers (12, 13...

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Section: Ehects Of Acetonitrile On Other Formic Acid Oxidation Reactimentioning

confidence: 99%

Origin of Activation Effects of Acetonitrile and Mercury in Electrocatalytic Oxidation of Formic Acid

Angerstein‐Kozlowska

MacDougall

Conway

1973

J. Electrochem. Soc.

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137

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“…It was suggested tentatively that a chemical reaction of the type (52) with the discharge of OH-ions initially as rate-determining step would give the correct Tafel slope (about 120m V) and a negative reaction order with respect to bCN2H4 at small concentrations in alkaline media. At higher concentrations of N 2H4, a direct oxidation with an adsorbed species at full coverage seems the only possibility [135,138]. (53) In acid solutions, the reaction order is fractional and increases with the hydrazine bulk concentration.…”

Section: Oxidation Of Hydrazinementioning

confidence: 99%

Electrochemical Processes in Fuel Cells

Bréiter¹

1969

Anorganische Und Allgemeine Chemie in Einzeldarstellungen

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All rights reserved. No part of this hook may be translated or reproduced in any form without written permission from Springer-Verlag. «> by Springer-Verlag New York Inc. 1969 PrefaceThe necessity for a better understanding of the basic processes that determine the operation of fuel cells became evident during the development of practical units in the last three decades. The search for efficient electrocatalysts in low-temperature fuel cells intensified the general study of the nature and the role of the electrode material. Research on the complex mechanisms of the anodic oxidation of different fuels and of the reduction of molecular oxygen on solid electrodes was stimulated, and the strong influence of adsorbed species on the electrode reaction in question was investigated. Suitable electrolytes had to be found for the high-temperature fuel cells. The use of electrodes with large internal surface lead to the development of models of porous electrode. structures and to the mathematical analysis of the operation of these models under certain conditions.While the chapters I to III introduce the reader to the general field offuel cells, the progress made in the understanding of the basic problems in the electrochemistry of fuel cells since the end of the second world war is reviewed in chapters IV to XVI of this monograph. In contrast, the technological aspects necessary for the development of practical units are not covered here.The open literature published as books or as papers in scientific journals has been considered up to the time of the writing of the final draft of the specific chapter, at least till the end of 1967.

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“…Hydrazine is one of the most popular reduction agents. Therefore, hydrazine oxidation on platinum [6][7][8][9][10], palladium [11][12][13], nickel [11,[14][15][16], cobalt [13], gold [10], mercury [17][18][19][20], and silver [19] electrodes in alkaline media was investigated intensively from the 1960s to the 1980s. In recent times, the research work in this field has been investigated on of hydrazine oxidation on platinum [21] and Ag/Ti [22] electrodes in alkaline media.…”

Section: Introductionmentioning

confidence: 99%