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

Abstract

Cu(111)-Ni surface alloys were prepared by dissociation of nickel carbonyl on clean Cu(111). The adsorption of CO is studied with AES and ellipsometry. At pressures higher than 10-2 Pa CO, migration of Ni to surface layers occurs, which makes it impossible to measure adsorption isotherms. The removal of preadsorbed oxygen on Cu(111)-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°C, the overall apparent activation energy is 40 kJ/mol, at higher crystal temperatures this value drops to 10kJ/mol. CO is found to react with oxygen on the surface, which is replenished by incorporated (subsurface) oxygen.