The potentiodynamic behaviour of iridium electrodes in aqueous 3.7 M H2SO4 in the 293–195 K range

Abstract The effect of temperature on the potentiodynamic behaviour of Ir in 3.7 M H 2 SO 4 was studied in the range 293–195 K. At 293 K, voltammograms are close to those reported for Ir in dilute acids, but no activation for hydrous oxide growth was observed. The H atom potential range exhibits weakly and strongly bound H adatom species. Slow and fast kinetic contributions can be distinguished by applying conventional and triangular modulated voltammetry, respectively. The weakly H adatom electrosorption reactions behave as reversible processes even in the frozen electrolyte while the kinetics of strongly bound species is influenced by a competitive adsorption probably involving sulphate ions. This effect becomes more remarkable as the temperature is diminished. Reversible processes involving H adatom and O-containing species in Ir oxide layers are explained in terms of fast charge transfer accompanied by fast proton motion processes at the interface.