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

Density functional theory (DFT) has been applied to study the geometrical and electronic structures and the catalytic properties for NO oxidation of pure Pt and PtAu clusters. The calculated results suggest that Pt-10 clusters shows the most stable structure among the pure Pt-n (n = 2-13) clusters with the local maximum Delta E-2 value. The doping of Au atoms reduces the stability of the clusters, and Pt6Au4 cluster has the most stable structure among Pt10-nAun (n = 1-7) clusters, due to the closest band centers between Pt and Au atoms (0.83 eV) and the obvious s-p resonance peaks near the Fermi level. Pt6Au4 cluster displays the strongest activation of O-2 molecules among Pt10-nAun (n = 0-7) clusters, owing to the clear overlap between O 2p and Pt 6 s and Au 6 s near the Fermi level, and the more positive d band center than the others. The interaction between NO and metals changes slightly in NO/Pt10-nAun (n = 2-7) systems, which is weaker than that in NO/Pt9Au system, as a result of the decreasing resonance peaks of sp hybridization near the Fermi level. Compared to pure Pt-10 cluster, the lower energy barriers and larger reaction energies on Pt6Au4 cluster suggest a higher catalytic activity of PtAu cluster for the O-2 dissociation and NO oxidation reactions. Our study provides atomic-scale insights into the nature of the interfacial effect that determines NO oxidation on PtAu cluster catalysts.