Premonolayer oxidation and its role in electrocatalysis

Abstract Hydrous oxides are considered here as an integral component of noble metal electrochemistry; they are regarded as quite distinct from, and in certain areas more important than, monolayer oxide deposits. The usual polycrystalline metal surface is assumed to be composed of two major components: (i) atoms of high lattice co-ordination number (the vast majority) that oxidize to yield monolayer oxide species, and (ii) atoms of quite low lattice co-ordination number (and of very low coverage) that oxidize to yield incipient hydrous oxide species. Evidence, that is now quite strong in the case of gold, supporting this view is summarized. Data are provided to support the view that in many instances electrocatalytic processes at noble metal electrode/aqueous solution interfaces involve hydrous oxides as mediators and inhibitors in oxidation and reduction processes, respectively. Premonolayer oxidation of metals, in terms of this approach, is considered as an interesting, relevant and challenging area of research.