Comparative study of CO2 formation in CO oxidation by O2, NO and N2O on Pd(110) surface using infrared chemiluminescence

Abstract The infrared (IR) chemiluminescence spectra of CO 2 were measured during steady-state CO oxidation by O 2 , NO and N 2 O over Pd(1 1 0) surface. Kinetics of these reactions were studied using a molecular-beam reaction system, and the order of the activity was as follows: CO + O 2  > CO + NO > CO + N 2 O. From the analysis of the IR emission spectra, it is found that the antisymmetric vibrational mode of CO 2 was more excited in the case of the CO + O 2 and CO + N 2 O reactions, in contrast, the bending vibrational mode was more excited in the case of the CO + NO reaction. These results suggest that the activated complex of CO 2 in the CO + NO reaction has more bent structure than those in the CO + O 2 and CO + N 2 O reactions. The reason of this different behavior of the CO + NO reaction is discussed based on higher structure-sensitivity of the CO + NO reaction than the CO + O 2 and CO + N 2 O reactions.