Promotion of catalytic reactions by depopulation of surface states

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Abstract
Dissociative adsorption is the rate-determining step in many catalytic reactions. However, the promoting mechanisms for dissociative adsorption are not yet fully understood. It is shown here that electronic surface states influence the physisorption potential as well as the dissociation barrier. Additives are able to shift and populate or depopulate surface states. Consequently, dissociation is inhibited or promoted, respectively. The present model provides a consistent explanation for several experimentally observed promoting and poisoning effects in dissociative adsorption of molecules from the gas phase or from a physisorbed precursor state.