Interaction of carbon monoxide with clean and oxygen covered Cu(111)-Ni surface alloys

Abstract

Cu(lll)-Ni surface alloys were prepared by dissociation of nickel carbonyl on clean Cu(ll1). The adsorption of CO is studied with AES and ellipsometry. At pressures higher than lo-* Pa CO, migration of Ni to surface layers occurs, which makes it impossible to measure adsorption isotherms. The removal of preadsorbed oxygen on Cu(lll)-Ni with CO is also studied with AES and ellipsometry.A reaction scheme is proposed to describe the two different types of reaction curves. At temperatures below 200 o C, the overall apparent activation energy is 40 kJ/mol, at higher crystal temperatures this value drops to 10 kJ/mol. CO is found to react with oxygen on the surface, which is replenished by incorporated (subsurface) oxygen.

Modelling the transient kinetics of heterogeneous catalysts. CO-oxidation over supported Cr and Cu

“…Previous studies over several copper crystal surfaces (Habraken et al, 1979;Mesters et al, 1984;Pruissen et al, 1987) have proven that subsurface oxygen atoms can replenish removed surface oxygen atoms. Based on these results, the observed two-stage reduction mechanism can be explained by a fast reaction of surface oxygen atoms in the first stage, and reaction of subsurface oxygen that has diffused to the surface in the second stage.…”

“…CO~ is formed directly after the step change, therefore CO2 desorption is omitted as a ratedetermining step (Kobayashi, 1982) and ls not included as an individual was also reported in UHV 1979; Mesters et al, 1984; step in Scheme 2. This studies (Habraken et al_, Pruissen et al, 1987).…”