Studies on the reaction sites of carbon monoxide oxidation on platinum (113) by angle resolved thermal desorption

The reaction sites for the catalytic oxidation of carbon monoxide on Pt(113) or (s)2(111) x (100) have been studied with angle resolved thermal desorption spectroscopy (ARTDS). A single peak, P-1-CO2, which is mostly formed on step sites, appears at 370 K at small reactant coverages. With increasing CO coverage, the peak temperature shifts to lower values by about 100 K, and reaches a peak position of P-2-CO2. In this shift, the reaction site switches sharply to terrace sites around 10% of CO at saturation. On the other hand, an increase of the oxygen coverage enhances the reaction on the step sites at small CO coverages. A mechanism is proposed for the above site switching.