Incipient hydrous oxide species as inhibitors of reduction processes at noble metal electrode

Evidence is presented to illustrate the important role of hydrous oxide species in noble metal electrocatalysis. It was demonstrated, for instance, that in the case of Au in acid the onset/termination potential, under potential sweep conditions, for hydrazine oxidation and persulfate or iodate reduction occurred at the end of the hydrous oxide reduction peak (recorded for a thick film grown by potential multicycling); there was also a maximum in the faradaic ac response for Au in acid in the same region. Both Au and Pt were investigated in acid and base electrolytes. In some cases a range of potential, rather than a discrete value, was found to be involved, different species react with (or are inhibited by) different types (or coverages) of these submonolayer species. In some, possibly electrocatalytically nondemanding, reduction reactions the hydrous oxide seemed to have little effect. Graphs. 26 ref.--AA