Density functional theory (DFT) studies of CO oxidation reaction on M13 and Au18M clusters (M Au, Ag, Cu, Pt and Pd) the role of co adsorbed CO molecule
Using the icosahedra M13 (M Au, Ag, Cu, Pt, Pd) and hetero atom doped Au18M (M Ag, Cu, Pt, Pd) clusters as model systems, we have systematically investigated the role of the co adsorbed CO molecule played in the CO oxidation reaction on the basis of density functional theory (DFT) calculations. The results indicate that the co adsorbed CO molecule at a triangular active site can induce the dissociation of the OCOO* intermediate via a tri molecular reaction route. This mechanism is also validated on other larger single doped gold alloy clusters such as AunAg and AunCu (n 32 34, 54) The underlying reason for promoting the oxidation effect of a co adsorbed CO molecule is unraveled. It is found that the relatively weaker d p* back bonding of CO on group 11 elements like Au, Ag and Cu may increase its electrophilic activity, which can facilitate the dissociation of nearby OCOO* intermediates. For the CO molecule that is bounded to the Pd and Pt atoms, it can also induce the dissociation of OCOO* intermediate, but shows weaker electrophilic activity. By explicitly considering the elementary reaction steps in a Kinetic Monte Carlo (KMC) simulation, we have shown that the tri molecular reaction route is an alternative reaction channel of CO oxidation, which is competitive to the conventional bi molecular route on a doped Au18M cluster.