Theoretical study on the catalytic reduction mechanism of NO by CO on Ag7Au6 cluster

The potential of Ag7Au6 alloy nanocluster to be a catalyst for the reduction of NO by CO has been examined by density functional theory calculations. This reaction is mainly divided into two reaction stages, NO deoxygenation to generate N2O and then the deoxygenenation of N2O with CO to form N2 and CO2. Finally, the product N2 and CO2 desorbs easily from the active Ag7Au6 site, thus avoiding catalyst poisoning. The potential energy surfaces of the doublet- and quartet-states have been systematically elucidated. There is no spin crossing found for the entire reaction and the results show that the reaction preferably follows the doublet state pathway. The main reaction pathways take place on the facet site rather than the edge site of the Ag7Au6 cluster. The crucial reaction step deals with the NO deoxygenation to generate N2O catalyzed by Ag7Au6 cluster, in which the deoxygenation of NO by CO reaction pathway is kinetically more preferable than that in the absence of CO. The results reveal that this catalyzed reaction is both thermodynamically and kinetically favourable. Therefore, the Ag7Au6 nanocluster is predited to be a promising and highly active catalyst for conversion of CO and NO pullutants to non-harmful products under ambient conditions.