Abstract
Surface-structure dependence of hydrogen-assisted reduction at oxidized Ni(110) surfaces was studied by metastable-induced electron spectroscopy (MIES) and low-energy electron diffraction (LEED). We prepared three different types of oxidized Ni(110) surfaces: (a) Low oxygen-coverage (3 × 1) surface; (b) moderate oxygen-coverage (2 × 1) surface; (c) high oxygen-coverage (3 × 1) surface. When exposed the surfaces (a) and (b) to hydrogen molecular gas at exposures 10∼100 L, their structures were changed to a hydrogen-adsorbed (1 × 1) structure. MIES clearly demonstrated a progress of hydrogen-assisted reduction by showing intensity decrease of the O2p-induced peak together with recovery in intensity of the Ni3d-induced peak and appearance of hydrogen-induced broad peak. Hydrogenated (1 × 1) surfaces, thus produced, were transformed to oxidized surfaces of the low-coverage (3 × 1) or (2 × 1) structure by being exposed to oxygen, depending on the oxygen exposure. These reduction/oxidation reactions took places reversibly. At the surface (c), however, such reactions were not observed in the range of hydrogen exposure up to 100 L at RT. This fact implies that the density of Ni-O-Ni atomic rows formed on the oxidized Ni(110) surfaces determines the progress of oxygen reduction reaction. [DOI: 10.1380/ejssnt.2006.170]
