Structure-sensitivity in the dynamics of CO oxidation over Pd surfaces:: Infrared chemiluminescence of the product CO2

Infrared-chemiluminescence spectra of CO2 molecules formed by steady-state CO oxidation on Pd(111), Pd(110), Pd(100) and polycrystalline-Pd surfaces have been measured to get information on the surface reaction dynamics. In all cases, the product CO2 was vibrationally and rotationally excited. The CO2 molecules desorbed from Pd(100) and Pd(111), which have flat surfaces, were vibrationally more excited than those from Pd(110) (stepped surface) and polycrystalline Pd. These results show that the dynamics of CO oxidation on Pd surfaces are structure-sensitive, i.e. the structure of the activated CO2 complex depends on the surface structures of the reaction sites. Furthermore, the activities of steady-state CO oxidation as a function of surface temperature were different among these Pd surfaces, which indicates that the CO oxidation on Pd is also structure-sensitive in the kinetics.