The infrared chemiluminescence technique was applied to the steady-state CO oxidation by NO on Pd(111) and Pd(110) to measure the internal energy of CO2 desorbed from surfaces. In this paper, on the basis of the results of CO oxidation by O2, we elucidate the CO2 formation mechanism of CO + NO reaction. From the comparison of IR emission spectra of CO2 between CO + NO and CO + O2 reactions, it is found that the vibrational energy states of CO2 in CO + NO reaction are similar to those in CO + O2 reaction. This indicates that the reaction path of CO2 formation in CO + NO is the same as that in CO + O2. The vibrational states are much dependent on the surface structure: the CO2 molecules produced on flat Pd(111) were highly excited (especially bending mode) than those on Pd(110) which has atomically rough surface.
