The role of short-lived oxygen transients and precursor states in the mechanisms of surface reactions; A different view of surface catalysis

It was the search for transients present during the dissociative chemisorption of oxygen and the subsequent formation of the oxide overlayer at single crystal metal surfaces that led to the development of the models for the surface catalysed reactions discussed in this review. The use of probe: molecules enabled transitory complexes (transition states) to be recognised and specific reaction pathways delineated. Examples are discussed where molecular and atomic oxygen transients participate in reaction mechanisms with some emphasis given to the oxygenation reactions of ammonia. A common feature of the chemistry is that highly efficient low-energy reaction pathways can be sustained even though the surface complexes are present at immeasurably small concentrations. Recent independent evidence from both STM and theoretical calculations provides support for the models developed over the last decade and the highly specific reactivity of the oxygen implicated in the reactions.