Reactivity of Model Inverse Catalysts Prepared by Mass-Selected Cluster Deposition*

Electronic interactions at the interface between supported metals and reducible oxides play an important role in a wide range of catalytic processes, including water-gas-shift for clean hydrogen production and CO/CO₂ hydrogenation for liquid fuels. The enhanced catalytic activity of these systems has been linked to oxygen vacancy formations on the reducible oxide, which act as active sites for reactant binding. In this study, we investigated the electronic and reactivity properties of model “inverse” catalytic systems prepared by the deposition of size-selected metal oxide nanoclusters onto supporting metal surface. Size-selected deposition provides selection of the cluster stoichiometry with atomic precision, which allows for the introduction of oxygen “vacancies”,and variation of metal cation coordination and average oxidation state. Results will be presented for the study of MO_x/Cu(111) surfaces using ambient pressure x-ray photoelectron spectroscopy (AP-XPS) which probe the chemical state of the oxide and metal support, and the formation of surface intermediates under AP conditions.