Chemisorption of Carbon Monoxide on (110) and (100) Nickel Crystal Faces

Abstract

Adsorption equilibria, adsorption rates, and exchange rates of carbon monoxide have been investigated on nickel single-crystal faces of the (110) and (100) orientation using radiotracer techniques. On the clean annealed surfaces, carbon monoxide is uniformly bound, is mobile, and occupies an area of 9 Å2 in the saturated layer. The surface equilibria and the kinetic phenomena are both quantitatively accounted for by a theory utilizing the Stockmayer potential and a cell approximation for describing the lateral interaction of the adsorbed molecules. The ion-bombarded nonannealed surfaces are unstable and heterogeneous. The contaminated surfaces adsorb only minute amounts of carbon monoxide. The chemisorption of CO thus provides a useful criterion for the degree of cleanliness of nickel surfaces.