Hexagonal overlayer of hydroxyl groups on Ni(100) modified by sulfur: effect on the H 2-D 2 isotope exchange reaction

Abstract

The hexagonal overlayer formed by adsorption of H 2, and O 2 on Ni(100) was studied by AES, LEED, TDS and HREELS. This overlayer was generated when H(a) and O 2 coexisted, regardless of the coverage of sulfur. Hydroxyl groups (-OH(a)) were detected by HREEL Spectroscopy. This overlayer was also formed during the H 2+D 2 isotope exchange reaction in the medium-pressure range with O 2 concentrations of ppm. H 2+D 2 isotope exchange reaction was completely arrested by this overlayer. Mechanism of formation of the hexagonal overlayer is discussed.