Small-Molecule Chemisorption on NiSi₂: Implications for Heterogeneous Catalysis

The chemisorption of O//2, CO, CO//2, H//2, N//2, and CH//3OH on the clean (111) surface of nickel disilicide (NiSi//2) was studied under ultrahigh vacuum conditions. Samples were characterized by high-resolution electron energy loss spectroscopy, low-energy electron diffraction, and Auger electron spectroscopy with experiments carried out between 170 and 300 K. The vibrational spectra clearly indicate that O//2, CO, and CO//2 dissociate on NiSi//2(111) at 170 K. Adsorbed CH//3OH yielded only a methoxide species, even at 300 K. No evidence was found for either molecular H//2 or molecular N//2 adsorption, although atomic hydrogen is strongly bound to the silicide surface. The implications of these unusual findings with respect to both heterogeneous catalysis by supported metal particles and strong metal-support interactions are discussed.