Electrochemical formation and reduction of silver oxides in alkaline media

Abstract

The anodic oxidation of silver electrodes in NaOH solution and the reduction of the silver oxides formed were studied by potential step chronoamperometry. Oxidation of Ag to Ag2O is a diffusion-controlled reaction, the diffusion control being established in the solid phase. Oxidation of Ag2O to AgO proceeds via a nucleation and growth-controlled process. The amount of AgO decreased with increasing step height. The current—time curves for this reaction have been analysed with the Kolmogoroff—Avrami equation. Reduction of AgO to Ag2O occurs initially on the outside of the electrode, and the rate of the reaction is limited by diffusion of ions across the thickening layer of Ag2O. Reduction of Ag2O to Ag proceeds via a nucleation and growth reaction.