Active sites in a two-step catalytic bimolecular reaction on a reconstructed platinum surface

Active sites for a thermally induced bimolecular two-step catalytic reaction (O2-->2O, O + CO-->CO2) that occurs on a Pt(113)(1 x 2) structure at around 160 K were studied by angular distribution measurements of desorbing product CO2. It was found that the intrinsic activity level of two-atom-wide (001) facets is significantly higher than that of two-atom-wide (111) facets, while the activity of (111) facets was also significant when this reaction was induced by irradiation of 193 nm photons. Possible mechanisms for the difference in activities of the two facets are discussed.