The internal energy of CO2 produced from catalytic oxidation of CO by NO

Internal energy distributions for CO2 produced in the catalytic oxidation of CO by NO on polycrystalline platinum have been directly measured using a high-resolution tunable diode laser spectrometer. Absorption spectra have been collected for CO2 produced in a flow cell reactor as a function of surface temperature and reactant ratio. Vibrational excitation of the product CO2 is observed for all reaction conditions. The vibrational energy of the asymmetric stretching mode is higher than the bending and symmetric stretching modes. The level of vibrational excitation for all normal modes is sensitive to the NO:CO ratio. The observed internal energy distribution of the product CO2 is compared to that of CO2 produced from CO oxidation by O-2, using the same method. The similarities in the vibrational excitation and its dependence upon oxygen coverage suggest that the transition slate for the CO2 formation step is the same for both the CO+NO and CO+O-2 catalytic oxidation reactions. This similarity of Likely transition states suggests that the CO+NO reaction proceeds by dissociative adsorption of NO, producing adsorbed oxygen atoms which oxidize CO to form CO2. This is the same route to the formation of CO2 which is observed for the CO+O-2 reaction on Pt. (C) 1998 American Institute of Physics.