Chemisorbed intermediates evolution

Chemical system, 32 278-283 Chemisorbed intermediates, 38 1-135 see also Oxide electrocatalysts cathodic hydrogen evolution, 38 58-66 chemical identity, 38 16-23 species from dissociative or associative chemisorption, 38 20-23 species from electrochemical discharge steps, 38 16-20... 

Behavior and Characterization of Kinetically Involved Chemisorbed Intermediates in Electrocatalysis of Gas Evolution Reactions... 

The principal aims of this review are to indicate the role of chemisorbed intermediates in a number of well-known electrocatalytic reactions and how their behavior at electrode surfaces can be experimentally deduced by electrochemical and physicochemical means. Principally, the electrolytic gas evolution reactions will be covered thus, the extensive work on the important reaction of O2 reduction, which has been reviewed recently in other literature, will not be covered. Emphasis will be placed on methods for characterization of the adsorption behavior of the intermediates that are the kinetically involved species in the main pathway of the respective reactions, rather than strongly adsorbed by-products that may, in some cases, importantly inhibit the overall reaction. The latter species are, of course, also important as they can determine, in such cases, the rate of the overall reaction and its kinetic features, even though they are not directly involved in product formation. 

The most important examples from both a fundamental and practical point of view are cathodic evolution from acidic or alkaline water, anodic evolution of O2 from similar solutions, and anodic Clj evolution from Cr ion in melts or in solution. Other related examples are anodic generation of Br2, I2, and (CN)2 from solutions of the corresponding anions, and an interesting case is the Kolbe reaction arising from discharge and decomposition of car-boxylate anions, followed by recombinative coupling of the resulting alkyl radicals. These processes intimately involve chemisorbed intermediates and... 

B.E. Conway and B.V. Tilak, Behavior and Characterization of Kinetically Involved Chemisorbed Intermediates in Electrocatalysis of Gas Evolution Reactions, In D.D. Eley, H. Pines, and P.B. Weisz (eds). Advances in Catalysis, vol. 38, Academic Press, New York (1992). 

The extent to which the electrode surface is covered by chemisorbed hydrogen atoms has been classically demonstrated by cyclic voltammetry and chronopotentiometry, particularly with respect to elucidation of the mechanism of the hydrogen evolution reaction and in the electrochemistry of fuel cells. The involvement of such intermediates is also consistent with the known mechanisms of catalytic hydrogenation, both from the vapor phase and the liquid phase. These results also indicate coadsorption of R species. 

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