The anodic behaviour of iridium I. The effect of potential cycling

Abstract

The anodic behaviour of iridium in 0.5 M H2SO4 was investigated by cyclic voltammetry and ellipsometry. Voltammograms obtained by continuous cycling between 0 and 1400 mV give oxide peaks which increase with the number of cycles. Ellipsometric measurement, carried out at the reduced surface, after a fixed number of cycles, showed that the substrate changes. The results are interpreted by assuming a pit model for the oxidation process. The oxidation takes place at active sites and penetrates locally, in the pits, into the underlying metal. Calculation showed that 80 cycles can introduce a disturbed layer of about 2.0–3.5 nm.