The real condition of oxidized pt electrodes: Part III. Kinetic theory of formation and reduction of surface oxides

Abstract

Summary Various reaction mechanisms are considered which can quantitatively, or otherwise, explain the resolvable stages in the formation and reduction of Pt surface oxide demonstrated in Parts I and II. Two of the mechanisms are shown to be unacceptable as they cannot explain the main features of the experimental results. The resolution of three peaks below a monolayer may be quantitatively simulated by a three-stage mechanism of Pt sub-lattice occupation by OH species, followed by their oxidation to O species. Place-exchange rearrangement accounts for the hysteresis between the anodic- and cathodic-going i-V profiles and the experimentally observed single cathodic peak can be represented in terms of the kinetics of a 2-stage reduction of PtO to Pt via PtOH in rearranged states. The experimentally observed dependence of peak potential on log [sweep rate] of ca 40 to 55 mV can be accounted for, as well as other higher values of this slope which arise under certain conditions.