DYNAMICS OF HYDROGEN ADSORPTION ON GAAS ELECTRODES

In situ infrared spectroscopy unravels the dynamics of hydrogen adsorp tion on GaAs(100) electrodes. Hydrogen cathodically adsorbs at arsenic sites only and replaces As-OH groups present in the anodic range, cau sing change in the surface dipole potential. The absolute submonolayer coverages depend on potential and result from a competition between c athodic hydrogenation and anodic or chemical hydroxylation. Surface As -H is identified as the intermediate in hydrogen gas evolution. Its el ectrochemical reduction is the rate-limiting step of the reaction.