HYDROGEN EVOLUTION ON PT SINGLE-CRYSTAL SURFACES - EFFECTS OF IRREVERSIBLY ADSORBED BISMUTH AND ANTIMONY ON HYDROGEN ADSORPTION AND EVOLUTION ON PT(100)

A study of the hydrogen evolution reaction (HER) has been carried out on platinum (111), (100), and (110) oriented electrodes in acidic medi um (H2SO4 0.5 M). No influence of the surface structure of the electro de has been observed. It has been confirmed that H(upd) cannot be the intermediate involved in the hydrogen evolution reaction. A detailed i nvestigation follows concerning the HER on Pt(100) electrodes poisoned by irreversibly adsorbed adatoms. The Bi-Pt(100) and Sb-Pt(100) syste ms have been studied and in both cases the same general behavior has b een observed. The basic HER mechanism does not change with adatom adso rption, while its rate is lowered as a consequence of poisoning. The s imultaneous investigation of the HER and the underpotentially deposite d hydrogen adsorption in such systems can be used to obtain informatio n about the compactness and arrangement of the adlayers. From this inv estigation, a negligible electronic effect of these adatoms on HER has been pointed out.