The kinetics of electrode processes. ─Part III. The behaviour of platinum and gold electrodes in sulphuric acid and alkaline solutions containing oxygen

Abstract

The first paper of this series contained a general survey of the reaction of hydrogen and oxygen at platinum electrodes in dilute sulphuric acid solution. We have now investigated in greater detail some of the phenomena which were observed, using mainly small polarizing currents, by means of which they can be more conveniently studied, and extending the scope of the experiments to other metals and solutions. In this paper an account is given of further experiments on platinum electrodes in the presence of oxygen, and of an investigation of the behaviour of gold electrodes in sulphuric acid and alkaline soutions. The experimental arrangements were similar to those previously described. Platinum Electrodes in Oxygen Saturated Solutions . Cathodic Depolarization by Oxygen .—If a platinum electrode in sulphuric acid is anodically polarized until oxygen is liberated and the current is then reversed, a marked depolarization process occurs at about ε H = + 0·05. Bowden's suggestion that this process is the reduction of a platinum oxide was shown in Part I to be untenable, because the length of the arrest of the potential is much reduced even by gentle stirring. The depolarization much be caused by some substance which is formed in the solution during the anodic polarization. Since it appeared that ordinary oxygen in the solution is not very active as a cathodic depolarizer in this region, it was suggested that the discharged oxygen remained for a time in a particularly active condition, but test of the solution failed to reveal any enhanced oxidizing power.