Considerations of the pH dependence of hydrous oxide films formed on iridium by voltammetric cycling

Abstract

AbstractThe electrochemical behavior and the analytical utility of hydrous oxide films, formed on iridium by voltammetric cycling, have been studied by evaluating the dependence of the apparent Standard Electrode Potential (E°′) and the ratio of protons to electrons (p/e) participating in the potential determining equilibria on the charge storage capacity. A model based on electron exchange involving protons in solution and conductive sites on the hydrous oxide surface is proposed and it is shown that an increase in population of the conductive sites can be correlated with an enhancement in proton exchange capacity. The influence of the pretreatment is shown to be an important factor in determining both E°′ and p/e. The implications of these results for the use of hydrous iridium oxide electrodes as potentiometric pH sensors are considered.