The anodic behaviour of silver single crystal electrodes in concentrated chloride solutions

Abstract

The anodic behaviour of <111> single crystal silver electrodes in concentrated hydrochloric acid solutions was examined by the faradaic impedance method. The results show that dissolution of silver as the soluble chloro-complex AgCl 4 3− occurs in 11.52 M HCl at a rate too fast to measure. In less concentrated solutions a mixture of AgCl 4 3− and the other polychloro complexes AgCl 3 2− and AgCl 2 − are formed in the ratio of their individual thermodynamic stabilities. Potentiostatic pulse results confirm these conclusions. No adsorption of Cl − was detected at potentials prior to phase formation. AgCl phase formation took place by progressive nucleation and growth of three-dimensional centres and it is likely that diffusion of Cl − is the rate determining step into the growing edge. Large changes in the real surface area of the silver were observed after the formation and reduction of AgCl nuclei.