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

CO oxidation on Pt(100) at oxygen pressures of 9.0 x 10(-2) mbar was studie d. An unusual decrease in catalytic activity with time was observed, which has not been observed at lower pressures. Post-reaction Auger and thermal d esorption 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 s ingle crystal surfaces. An adsorbate induced surface reconstruction is prop osed as a possible driving force for oxide formation. (C) 2000 Elsevier Sci ence B.V. All rights reserved.