Effect of alloying on the stabilities and catalytic properties of Ag–Au bimetallic subnanoclusters: a theoretical investigation

Density functional theory has been applied to study the geometric and electronic structures and the catalytic properties of Ag and AgAu clusters for CO oxidation. The calculated results suggest that the doping of Au atoms improve the stability of AgAu clusters. Correspondingly, the binding energy (BE) per atom of AgnAu is larger than that of pure Ag_n+1 cluster, due to strong hybridization between the d orbitals of Au and the s orbitals of Ag in Ag_nAu clusters. With the increasing Au concentration, the BE of Ag_13−nAu_n(n = 1–8) clusters increase smoothly, while second-order difference of energies (Δ₂E) and fragmentation energies (ΔE) show an even–odd oscillation. The AgAu clusters containing an odd n umber of gold atoms (Ag_13−nAun, n = 3, 5, 7) are relatively stable compared to their neighbor. The CO and O₂ adsorption properties on the Ag₁₃, Ag₁₀Au3, Ag₈Au₅, and Ag₆Au₇ clusters suggest that O₂ is strongly activated by the clusters, while the activation of CO is much weak. Furthermore, the activation of O₂ on AgAu cluster is stronger than that on pure Ag₁₃ cluster, especially on Ag₈Au₅ cluster, due to the strengthened polarization of O–O bond. Compared to Ag₁₃, Ag₁₀Au₃, and Ag₆Au₇ clusters, the lower energy barriers on Ag₈Au₅ cluster suggest a higher catalytic activity of Ag₈Au₅ cluster for O₂ dissociation and CO oxidation reactions. The calculated results suggest that Ag₈Au₅ cluster could effectively reduce the carbon monoxide poisoning and exhibits the excellent catalytic performance for CO oxidation. Our study provides atomic-scale insights into the nature of the interfacial effects that determine CO oxidation on Ag–Au cluster catalysts.