Mechanisms in the Catalytic Reduction of N(2)O by CO over the M(13)@Cu(42) Clusters of Aromatic-like Inorganic and Metal Compounds

Metal aromatic substances play a unique and important role in both experimental and theoretical aspects, and they have made tremendous progress in the past few decades. The new aromaticity system has posed a significant challenge and expansion to the concept of aromaticity. From this perspective, based on spin-polarized density functional theory (DFT) calculations, we systematically investigated the doping effects on the reduction reactions of N(2)O catalyzed by CO for M(13)@Cu(42) (M = Cu, Co, Ni, Zn, Ru, Rh, Pd, Pt) core–shell clusters from aromatic-like inorganic and metal compounds. It was found that compared with the pure Cu(55) cluster, the strong M–Cu bonds provide more structural stability for M(13)@Cu(42) clusters. Electrons that transferred from the M(13)@Cu(42) to N(2)O promoted the activation and dissociation of the N–O bond. Two possible reaction modes of co-adsorption (L-H) and stepwise adsorption (E-R) mechanisms over M(13)@Cu(42) clusters were thoroughly discovered. The results showed that the exothermic phenomenon was accompanied with the decomposition process of N(2)O via L-H mechanisms for all of the considered M(13)@Cu(42) clusters and via E-R mechanisms for most of the M(13)@Cu(42) clusters. Furthermore, the rate-limiting step of the whole reactions for the M(13)@Cu(42) clusters were examined as the CO oxidation process. Our numerical calculations suggested that the Ni(13)@Cu(42) cluster and Co(13)@Cu(42) clusters exhibited superior potential in the reduction reactions of N(2)O by CO; especially, Ni(13)@Cu(42) clusters are highly active, with very low free energy barriers of 9.68 kcal/mol under the L-H mechanism. This work demonstrates that the transition metal core encapsulated M(13)@Cu(42) clusters can present superior catalytic activities towards N(2)O reduction by CO.