CO Adsorption and Interaction with Oxygen on (110) Nickel

Abstract

The interaction of oxygen and carbon monoxide on the (110) surface of nickel has been studied by LEED. CO is adsorbed with one molecule to each atom of the clean nickel surface. Thus the two‐dimensional surface unit cell of the CO structure has the same dimensions as the nickel substrate. Exposure of clean (110) nickel to O₂ produces a sequence of oxygen—nickel structures terminating with NiO. The intermediate structures which are most easily reproduced have been designated the (1×2) and (1×3), and occur in that order during exposure. Both are quite stable in vacuum. Exposure of the (1×2) structure to CO results in a new structure having the same surface spacings as the (1×3) nickel—oxygen. However, this change was reversible and the surface returned to the (1×2) on standing in vacuum for several hours. CO preadsorbed on the clean (110) surface was readily replaced by oxygen, although the exposure required to produce the (1×2) nickel—oxygen structure was greater than in the corresponding case of the clean surface.