Formation of surface oxides on Pt(100) during CO oxidation in the millibar pressure range

CO oxidation on Pt(100) at oxygen pressures of 9.0×10−2 mbar was studied. An unusual decrease in catalytic activity with time was observed, which has not been observed at lower pressures. Post-reaction Auger and thermal desorption spectroscopy measurements showed the formation of a surface oxide species, which deactivated the catalyst. The surface oxide is compared to subsurface oxygen and to surface oxide studied previously on low index Pt single crystal surfaces. An adsorbate induced surface reconstruction is proposed as a possible driving force for oxide formation.