A RAIRS OBSERVATION OF THE LOCAL INTERACTION BETWEEN COADSORBED NO AND CO ON NI(111)

The local interaction between coadsorbed NO and CO on a Ni(111) surface has been investigated using FT-reflection absorption infrared (FT-RAIR) spectroscopy. The adsorption of NO on a CO-predosed Ni(111) surface at 85 K gives rise to the conversion of bridge-CO → terminal-CO. The production of the terminal-CO species could be related to the formation of CO islands upon the post-adsorption of NO. On the other hand, the adsorption of CO on a NO-predosed Ni(111) surface is mainly characterized by the RAIR observation of two NO-induced terminal-CO species with ν(CO) vibrational frequencies observed at ~ 2065 and ~ 2115 cm-1, respectively. These values are higher than that of the terminal ν(CO) mode observed on clean Ni(111) at ~ 2054 cm-1. These results can be explained by the hypothesis that the coadsorbed NO and CO on Ni(111) compete for the surface electron density available for the backdonation into the corresponding 2π* orbitals. © 1990.