INTERACTION OF HYDROGEN, CARBON MONOXIDE, AND METHANOL WITH Ni( 100)

The chemical nature of the surface species formed either by the interaction of H2 and CO on transition metal surfaces or by the decomposition of molecules composed of hydrogen and CO is vital to the understanding of many current catalytic problems [l-5 1. In a systematic attempt to identify a catalytic interaction between adsorbed-CO and adsorbed-H on a Ni( 100) surface, we have discovered the irreversible formation of a new adsorbate molecular entity. Temperature programmed desorption (TPD) data indicate that H(ads) interacts with CO(ads) to form a significant concentration of interacting species which exhibit new bonding states of CO and H, desorbing simultaneously near 200 K. Ancillary experiments examining the decomposition of methanol were carried out in an attempt to generate, by means of decomposition, a species similar to that observed in the catalytic HZ/CO interaction. The methanol results do suggest the formation of a surface complex; however, no link between the two surface species can be established. TPD evidence is presented for the presence of an adsorbed alcoholic “CO-H” species which decomposes at 500 K into CO and Hz. We have used hydrogen isotopic labeling in methanol to follow upon desorption the chemical behavior of the inequivalent hydrogen in the molecule, viz., CH hydrogen compared to CO-H hydrogen.