THE REVERSIBILITY AND OVERLAPPING OF HYDROGEN AND OXYGEN-ADSORPTION IN THE DOUBLE-LAYER REGION OF RHODIZED ELECTRODES IN H2SO4 SOLUTIONS (THE DECOMPOSITION OF WATER-MOLECULES ON RHODIUM SURFACES)

The voltammetric behaviour of rhodized electrodes (roughness factor va lues, 15-25) was studied in 1 mol dm(-3) H2SO4 solution in the potenti al range from 225 to 500 mV/RHE. It was shown that, at appropriately c hosen sweep rates and at high current-measuring sensitivities, charact eristic voltammograms with a singular point (minimum) could be obtaine d. Addition of strongly adsorbing chloride ions significantly modifies the picture: the singular point disappears and double-layer-like beha viour can be observed. The phenomena observed are treated and explaine d in terms of simultaneous adsorption of H and OH species.