Enhanced CO Oxidation on Oxide/Metal Interface: From Ultra-High Vacuum to Near-Atmospheric Pressures

We studied CO oxidation on FeO(1 1 1) films on Pt(1 1 1) at submonolayer oxide coverages at ultrahigh vacuum and near-atmospheric pressure conditions. The FeO(1 1 1) bilayer islands are inert towards CO2 formation. In contrast, the FeO2-x trilayer structure shows substantial CO2 production that reaches a maximum at ≈40 % coverage at both pressure conditions. The results provide compelling evidence that the FeO2-x/Pt(1 1 1) interface is the most active in CO oxidation. Although FeO2-x boundaries possesses weakly bound oxygen species, strong binding of CO to Pt favors the reaction at the FeO2-x/Pt interface as compared to the FeO2-x/FeO one, thus giving a rationale to the reactivity enhancement observed in systems exposing metal/oxide boundaries. In addition, oxygen diffusion from the interior of an FeO2-x island to the active edge sites may be effective for the oxygen replenishment in the CO oxidation catalytic cycle