Anodic behavior of silver in alkaline solutions

Abstract

Data, covering a range of pH and temperature, were obtained for the anodic oxidation of electropolished silver and the results compared with electrodes which had undergone repeated oxidation and reduction cycles. The behavior of the electrode is, in the main, complex, showing, for example, autopotential cycling under certain galvanostatic conditions (∼3 μA/cm2, 25 °C, 0.7 N NaOH), the period of oscillation being about [Formula: see text]. Several other hitherto unreported phenomena were also observed. The main conclusions reached are (i) that 2 different mechanisms are involved in the anodic formation of Ag2O on silver electrodes in basic electrolytes resulting in 2 types of film, 1 mechanism involves a dissolution–precipitation process, the other possibly a direct interfacial reaction; (ii) that the reduction of anodically formed Ag2O films either electrochemically or in hydrogen at 800 °C leaves behind a highly porous layer of silver metal; and (iii) that the limiting Ag2O film thickness is probably determined by a diffusion process occurring within the film.