The oxygen evolution reaction on passive oxide covered transition metal electrodes in alkaline solution. Part 2-Cobalt.

Abstract

Details are outlined of an electrochemical investigation of the oxygen evolution reaction (OER) at passive oxide covered polycrystalline Co electrodes in aqueous alkaline solution. Kinetic studies on electrodes subjected to different pre-treatment routines, yielded different values of the Tafel slope and the reaction order with respect to OH- activity. Only one mechanistic pathway could account for all observed values of these kinetic parameters. This pathway is similar, although not identical, to that proposed, in the first paper of this series, for the reaction at oxide covered Ni anodes. Using cyclic voltammetry it was shown that the mechanism for the initial passivation of Co electrodes varies with OH- concentration. This in turn can have an effect on the experimental value of the OER Tafel slope, a phenomenon which can be rationalized in terms of a dual energy barrier model.