On the reduction of platinum oxide layers by hydrogen in aqueous H2SO4 under open circuit conditions

This paper reports investigations on the mechanism of the open circuit (OC) reduction of platinum oxide layers by hydrogen in aqueous sulfuric acid. Special attention was given to the conditions of the oxide layer formation and the anodic oxidation of hydrogen thereupon. A twin-cell technique was developed which allows the instantaneous rate of the OC reduction to be determined. The experimental results show that the dissociative adsorption of hydrogen is the rate-determining step of the process and that the OC reduction follows, an island mechanism. Because of the time-dependent alteration of the oxide layer structure, the formation conditions affect the instantaneous rate of the OC reduction as well as the duration of the total reduction of the oxide layer.