Chemisorption of oxygen and hydrogen on nickel films — reconstitution of the adsorbate-adsorbent interface

Abstract

Considerable detailed information may be obtained about the nature of the adsorbate phase and the changes that take place at the adsorbate-adsorbent interface subsequent to the chemisorption of a gas at a metal surface by measurement of rapid changes of the work function of the metal. Thus, the kinetics of the transformation of a covalently bonded oxygen adatom at the surface of an annealed nickel film to an ionic species within the surface layer have been elucidated; this theory should have general validity for the incorporation of any electronegative element into metal lattices. In systems, where the incorporated state is not ionic, incorporation is not expected although diffusion of the atomic species is still possible. Thus, with hydrogen on nickel, different information, namely, the nature and properties of the adspecies and the rate and activation energy for surface diffusion of one of the adspecies, has been obtained. Greater use of the results of work function changes simultaneously obtained in some LEED studies may therefore prove to be valuable.