Hydroxyls-Involved Interfacial CO Oxidation Catalyzed by FeO_x(111) Monolayer Islands Supported on Pt(111) and the Unique Role of Oxygen Vacancy

We have comprehensively investigated the reactivity of hydroxyls on FeO x (111) monolayer islands with different amounts of oxygen vacancy concentrations grown on Pt(111) by means of X-ray photoelectron spectroscopy, temperature-programmed desorption/reaction spectroscopy, and low energy electron diffraction. Hydroxyls on FeO x (111) monolayer islands are capable of oxidizing CO(a) on Pt(111) at the FeO x (111)-Pt(111) interface at low temperatures and such an interfacial oxidation of CO by hydroxyls to produce CO 2 is not suppressed by either excess CO(a) or excess H(a) on FeO x (111)/Pt(111) inverse model catalyst surface. However, the reactivity of hydroxyls is controlled by the oxygen vacancy concentration in FeO x (111) monolayer islands. With the increase of oxygen vacancy concentration, reaction pathways of hydroxyls on FeO x (111) monolayer islands to produce H 2 O are thermodynamically suppressed, which thus opens other hydroxyls-involved reaction pathways including the interfacial oxidation of CO to produce CO 2 . These results greatly deepen the fundamental understanding of the reaction mechanism and catalytically active structure for low temperature WGS and PROX reactions catalyzed by oxide supported Pt nanocatalysts.