The interaction of coadsorbed hydrogen and carbon monoxide on Ni(100)

Abstract

Abstract The coadsorption of H 2 (and D 2 ) with CO on Ru(001) at 100 K has been studied using thermal desorption, work function changes, XPS and UPS. Pre-adsorbed CO strongly blocks H 2 adsorption. Pre-adsorbed H 2 blocks CO adsorption, but less strongly. The desorption of pre-dosed H 2 from a coadsorbed layer shows strong long-range CO-H repulsive interactions. The dipole moment of CO on a H-covered surface appears to be unchanged relative to a clean surface and the sticking coefficient for CO decreases in proportion to the amount of uncovered Ru sites. For CO on Ru(001), with and without coadsorbed hydrogen and H 2 either pre- or post-dosed, the O(ls) XPS are the same whereas He(II) spectra show small changes. These UPS changes are consistent with more extensive crowding of the CO molecules on the surface in the presence of hydrogen. These results are consistent with a model of segregation of H and CO on the surface.