Investigation of reaction mechanisms of NO with CO on Pd1/MgO and Pd4/MgO catalysts

Abstract

The stepwise and concerted reaction mechanisms of NO with CO on Pd1 atom and Pd4 cluster adsorbed on the MgO surface have been studied by using the DFT/B3LYP method with the embedded cluster model. The reaction barriers have been calculated by using the IMOMO method at the CCSD level. The results suggest that the rate-controlling step barrier of the NO dissociation on the supported Pd4 cluster for the stepwise reaction mechanism is about 57kcal/mol and lower by about 33kcal/mol than that on the single supported Pd atom. However, the concerted reaction pathways on the single supported Pd atom and four supported Pd atoms are energetically unfavorable with the barriers of about 98kcal/mol and 71kcal/mol, respectively. Compared to the concerted reaction mechanism, the stepwise reaction mechanism of NO+CO is a possible pathway of CO2 molecule formation on the supported Pd catalysts.