Selective modification of reaction sites for carbon monoxide oxidation on a platinum (113) surface

A selective modification of reaction sites is observed in the CO oxidation on a stepped Pt(113)=(s)2(111)x(001) surface through the analysis of the angular distributions of the desorbing product CO2. The desorption of CO2 is sharply collimated either closely along the (111)-terrace or the (001)-step normal. The contribution to the CO2 formation from each microfacet depends on the annealing temperature of oxygen adlayers. The (001) step component is dominant for annealing temperatures below 300 K, whereas after annealing above 350 K, the terrace component becomes major. The (001) step site is proposed to be modified by subsurface oxygen from the correlation between the amount of oxygen and the extent of modification. (C) 1997 Elsevier Science B.V.