Elucidating the active phases of CoO films on Au(111) in the CO oxidation reaction.

Noble metals supported on reducible oxides, like CoO and TiO, exhibit superior activity in many chemical reactions, but the origin of the increased activity is not well understood. To answer this question we studied thin films of CoO supported on an Au(111) single crystal surface as a model for the CO oxidation reaction. We show that three reaction regimes exist in response to chemical and topographic restructuring of the CoO catalyst as a function of reactant gas phase CO/O stoichiometry and temperature.