Oxygen induced direct hydrogenation of CO on Ni(100) surface

A trace amount of oxygen in H₂ promotes a new type of direct hydrogenation reaction of adsorbed CO on Ni(100) surface. The formation of H_xCO_y was suggested by high resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). HREEL spectra showed the formation of surface hydroxyl (OH) and the C-H bonds of H_iCO_y species but no carbonyl (C=O) loss peak was detected although thermal desorption yielded large amount of CO. The H_xCO_y undergoes the decomposition at 400–450 K on the hex-OH Ni(100) surface, which yielded CO, CO₂, H₂ and H₂CO. It was confirmed that no C-H bond formation occurs on c(2 × 2)-O, p(2 × 2)-O Ni(100) and hex-OH Ni(100) as well as on clean Ni(100) surfaces. This fact indicates that the gas phase oxygen may induce the direct hydrogenation of CO to form H_xCO_y, which is analogous to the hydrogenation of O to form hex-OH onNi(100).