Oxidation of a Platinum-Tin Alloy Surface during Catalytic CO Oxidation br

We have investigated the surface composition of a well-ordered Pt3Sn(111) surface during CO oxidation with ambient pressureX-ray photoemission spectroscopy. Oxidation of tin in the surfacecoincides with the onset of catalytic conversion, and we observesignificant differences in the oxidation state and morphology of theoxide formed depending on the gas composition, with an oxygen-richmixture leading to formation of 2D wetting layers and a CO-richmixture leading to formation of 3D oxide islands. Spontaneousoscillations in conversion are observed at 300 degrees C in the oxygen-richgas mixture and attributed to the combined effects of site blocking by tinoxides and by CO. The results highlight the importance of gas-surfaceinteractions in determining the nature of oxides formed and thus thetype and number of interfacial sites under reaction conditions.