CHEMISORPTION AND REACTIONS AT METAL-SURFACES

The late 1950s saw the emergence of two schools of thought, one based on the clean surface concept and the other on the more traditional bulk catalyst approach to surface chemistry. It is the synergistic influence of these two approaches that guided much of the author's research over the last 30 years - an attempt to understand molecular behaviour at well defined metal surfaces but with a view to appreciate the mechanistic subtleties of heterogeneous catalysis. Direct evidence for the atomic nature of solid surfaces and their adsorption behaviour was extremely limited in 1960 and this article attempts to trace how improved experimental methods became available to study relatively simple metal-gas interactions. The limitations of kinetic studies based on indirect measurements (of the gas phase) were recognised and the possible advantages of monitoring the surface work function or photoemission characteristics seen as a possible way forward. The latter resulted in the development of a multi-photon source UHV compatible photoelectron spectrometer and much of this article describes how a detailed understanding was obtained from electron spectroscopy of molecular and dissociative chemisorption, the nature of chemisorbed oxide overlayers at metal surfaces, adsorbate activation and the role of precursor or transient states in the mechanisms of surface reactions.