Dynamics of hydrogen adsorption on GaAs electrodes

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