REACTIONS INVOLVING H, OH AND O SPECIES ON RHODIUM IN H2SO4-CENTER-DOT-12H(2)O AND HCLO4-CENTER-DOT-5.5H(2)O IN THE RANGE 198-298 K

The voltammetric behaviour of polycrystalline rhodium in H2SO4 . 12H(2 )O and HClO4 . 5.5H(2)O was investigated by conventional and triangula rly modulated voltammetry in the range 198-298 K. H and OH electrosorp tion reactions and a fast electrochemical process in the potential ran ge preceding the oxygen evolution reaction (OER) were studied. For bot h electrolytes, as the temperature diminished, the H atom reactions an d those reactions related to the O-containing surface species became i ncreasingly irreversible, whereas the fast electrochemical process pre ceding the OER was nearly the same, irrespective of the temperature. E xplanations recently advanced for the behaviour of Rh in more diluted solutions of the same acids at 298 K and the electrochemical behaviour of the different processes are discussed, considering mainly the effe cts of sulphate anion adsorption and perchlorate anion decomposition o n Rh.