Spontaneous formation of hydrous oxide species at a platinized platinum electrode, held at 0.85 V (RHE), in aqueous H2SO4 solution at 60°C was detected by an electrochemical technique. Such species are assumed to be a source of inhibition of oxygen gas reduction at fuel cell cathodes operating in aqueous media at potentials above ca. 0.6 (RHE); reaction in the latter case may be confined to less active sites where hydrous oxide formation occurs less readily. Reduction of oxygen in the oxide layer region was found to be time dependent and independent of rotation rate. The former effect was attributed to a surface restructuring process and the latter to the fact that oxygen gas was not involved in the rate-determining stage of the reaction.
