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

We have comprehensively investigated the reactivity of hydroxyls on FeOx(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 FeOx(111) monolayer islands are capable of oxidizing CO(a) on Pt(111) at the FeOx(111)-Pt(111) interface at low temperatures and such an interfacial oxidation of CO by hydroxyls to produce CO2 is not suppressed by either excess CO(a) or excess H(a) on FeOx(111)/Pt(111) inverse model catalyst surface. However, the reactivity of hydroxyls is controlled by the oxygen vacancy concentration in FeOx(111) monolayer islands. With the increase of oxygen vacancy concentration, reaction pathways of hydroxyls on FeOx(111) monolayer islands to produce H2O are thermodynamically suppressed, which thus opens other hydroxyls-involved reaction pathways including the interfacial oxidation of CO to produce CO2. 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.