Oxidation of graphitic carbon on a Pt(111) surface

Abstract The interaction of graphitic carbon with dissociatively adsorbed oxygen was investigated by thermal desorption mass spectroscopy (TDS), Auger electron spectroscopy (AES) and measurements of the change Δφ of the work function φ. Carbon coverages on the Pt(111) surface were produced by different C 2 H 4 exposures at 850 K, resulting in immobile graphite islands. The reaction of the carbon atoms at the boundaries of these islands with mobile oxygen adatoms yields the formation and desorption of CO 2 (550–800 K) and CO (700–1100 K). The time t e , for a complete removal of the carbon depends strongly on the initial carbon coverage and is proportional to the reciprocal oxygen partial pressure, whereas for T ≳ 700 K t e does not depend significantly on the surface temperature. The experimental results can be described quantitatively by a model considering the linear decrease of the oxygen sticking coefficient with growing carbon coverage. The comparison of the results with those for the reaction between sulfur and oxygen on a Pt(111) surface [Surface Sci. 136 (1984) 243] demonstrates the different poisoning effects of carbon and sulfur.