ABSTRACT
The adsorption behaviour of a single O atom on Aunq clusters (n = 1-8, q = 0, ±1) was systematically investigated by DFT calculations. Both hybrid and pure GGA functionals (B3LYP and PBE) were used to provide reliable conclusions. The most stable structures of AunOq clusters were obtained by using global optimizations with a genetic algorithm. Cationic clusters tend to become three-dimensional for large clusters, as for Au8O+. The binding of O in AunOq clusters is quite strong, especially in the anionic clusters. The O atom can be bound to one, two, or three Au atoms, obtaining nearly one electron from gold atoms. Similarities have been found between AunOq and Aun+1q in terms of geometric structures and binding energies. Frontier molecular orbitals and the distribution of unpaired spin density on the O atom were discussed, both of which have a close relationship with the activity of the clusters.
ABSTRACT
The bonding properties between a single atom and its support have a close relationship with the stability and reactivity of single-atom catalysts. As a model system, the structural and electronic properties of bimetallic oxide clusters MV3Oy(q) (M = Au or Ag, q = 0, ±1, and y = 6-8) are systematically studied using density functional theory. The single noble metal atom Au or Ag tends to be adsorbed on the periphery of the V oxide clusters. Au prefers V sites for oxygen-poor clusters and O sites for oxygen-rich clusters, while Ag prefers O sites for most cases. According to natural population analysis, Au may possess positive or negative charges in the bimetallic oxide clusters, while Ag usually possesses positive charges. The bonding between Au and V has relatively high covalent character according to the bond order analysis. This work may provide some clues for understanding the bonding properties of single noble metal atoms on the support in practical single-atom catalysts, and serve as a starting point for further theoretical studies on the reaction mechanisms of related catalytic systems.
