The surface chemistry of manganese

Abstract

The interaction of carbon monoxide, hydrogen, and oxygen with manganese films has been investigated. Hydrogen is weakly chemisorbed (ΔH≃ 50 kJ mol–1), but both carbon monoxide and oxygen are incorporated into the lattice. The oxide formed is likely to be MnO. Adsorption data suggest that oxygen incorporation occurs even at 78 K and this is confirmed by work function studies; the surface potential of oxygen on manganese at 78 K is ca.–1·6 V. Carbon monoxide is incorporated extensively above 400 K and the kinetics suggest a diffusion-controlled process involving weakly chemisorbed CO. The catalytic oxidation of CO over manganese was first order in CO and only occurred under conditions where oxygen incorporation was slow compared with the catalytic reaction. A surface which had been oxidised to its maximum extent was inactive in catalysis at the temperature of oxidation.