Correlation of the Catalytic Activities of Oxides with their Work-functions

Abstract

The catalytic recombination of oxygen atoms has been studied on powdered samples of Li+ doped (0–1.26 atom %) nickel oxides in the temperature range 20–50°C. It is found that the energy of activation for this reaction is lower, the higher the work function of the surface. This is believed to be due to the fact that the rate determining step of the reaction involves the abstraction of an adsorbed oxygen atom by another atom in the gas phase to give a molecule of oxygen. The energy of activation is, consequently, lower the lower the energy of the bond between an adsorbed oxygen atom and the surface. Since O– ion is the most likely form of an adsorbed oxygen atom on oxides, it follows that if the energy of interaction between O– ion and the different surfaces do not differ appreciably, the energy of the bond between an adsorbed oxygen atom and a surface will be lower, the higher the work function of the surface.