The potentiodynamic behaviour of iridium electrodes in aqueous 3.7 M H2SO4in the 293-195 K range

The effect of temperature on the potentiodynamic behaviour of Ir in 3.7 M H 2SO4 was studied in the range 293-195 K. At 293 K, voltammograms are close to Chose reported for Ir in dilute acids,but no activation for hydrous oxid e growth was observed. The H atom potential range exhibits weakly and stron gly bound H adatom species. Slow and fast kinetic contributions can be dist inguished by applying conventional and triangular modulated voltammetry, re spectively. The weakly H adatom electrosorption reactions behave as reversi ble 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 d iminished, Reversible processes involving H adatom and O-containing Species in Ir oxide layers are explained in terms of fast charge transfer accompan ied by fast proton motion processes at the interface. (C) 1999 Elsevier Sci ence S.A. All rights reserved.