Interaction of Aqueous Iodine Species with Ag[sub 2]O∕Ag Surfaces

Abstract

The chemical conversion of Ag2O films on Ag surfaces to AgI in aqueous iodide solutions has been studied electrochemically. Ag2O films were grown potentiostatically and then exposed to I− solutions. The chemical conversion process was followed at open-circuit potential ?EOC? using cathodic stripping voltammetry performed after various exposure periods. The EOC showed a sudden drop at the completion of the conversion of Ag2O to AgI, reaching a steady-state value close to the equilibrium potential for AgI/Ag and the iodide solution. This sudden drop in EOC allowed easy determination of the total reaction time required for complete conversion of Ag2O to AgI. Distinctly separated current peaks were observed for the cathodic reduction of Ag2O and AgI to Ag, and the charges associated with these peaks provided a measure of the amount of Ag2O converted. The conversion reaction was 100% efficient. The total reaction times from the EOC measurements and the cathodic stripping results were used to determine the reaction order and rate constant required for the development of nuclear reactor safety assessment codes.