Site-switching for CO2 formation and structural transformation of (1×2)⇄(1×1) in steady-state CO oxidation on Pt(1 1 0)

The angular and velocity distributions of desorbing product CO2 were studied in steady-state CO oxidation on Pt(1 1 0) by means of cross-correlation time-of-flight techniques. In the active region where the reaction was first order in CO, the angular distribution in the (0 0 1) plane was split into two-directional lobes collimated at ±25° from the surface-normal direction, indicating the CO2 formation on inclined (1 1 1) terraces. The translational temperature was maximized at these collimation angles, reaching about 1820 K. On the other hand, in a limited range of the inhibited region, where CO retarded the reaction, CO2 desorption sharply collimated along the surface-normal direction, suggesting CO2 formation on flat (1×1) domains.