Abstract:
The anodic behaviour of water is discussed in terms of a model in which discharge occurs via a cation radical intermediate which rapidly loses a proton to yield potential-determining hydroxyl radicals on the metal surface. Hysteresis in the charging curves in the case of noble metal electrodes is explained in terms of an anodic stage involving the production of these hydroxyl radicals on the surface, and a subsequent cathodic stage involving (largely) the reduction of a layer of chemisorbed oxygen. Coverage of the electrode surface by hydroxide radicals is not at any time regarded as being very large as conversion to an oxide film occurs, possibly via a peroxide intermediate. Oxygen evolution is assumed to occur via a similar mechanism, the adsorbed peroxide intermediate being undetectable under normal conditions as peroxides arc instantaneously oxidized in the potential region in question. An attempt is made to account for the mechanism proposed for oxygen evolution, and other facets of oxygen electrochemistry, in terms of solvent electrostriction at the metalsolution interface at high positive potentials.
