Surface phase transitions of Pt(110) studied by desorption dynamics of product CO2 in steady-state CO oxidation

The transformation of (1×2) into (1×1) on a Pt(110) surface in the course of CO oxidation was studied through the analysis of both angular and velocity distributions of desorbing product CO2 and low-energy electron diffraction (LEED) intensity. The intensity of half-order LEED spots decreased quickly, showing the beginning of the transformation of (1×2)→(1×1) just below the kinetic transition, where the rate-determining step switched from CO adsorption to O2 dissociation. On the other hand, the angular distribution of desorbing CO2 sharply changed at a CO pressure far above the kinetic transition, where (1×2) domains disappeared. Below this approximate CO pressure, CO2 was mostly formed on (1×2) domains regardless of its reduced area.