Effect of alloying on the catalytic properties of Pt–Ni bimetallic subnanoclusters: a theoretical investigation

Density functional theory has been applied to study the geometrical and electronic structures of Pt13−n Ni n (n = 0–6) clusters, and the catalytic properties for the oxygen reduction reaction (ORR). The calculated results suggest that the doping of Ni atoms improved the stability of the cluster. Correspondingly, Pt10Ni3 and Pt8Ni5 clusters with local maximum Δ2 E are relatively stable compared to their neighbors, owning to the strong interaction between Pt and Ni atoms in the two alloy clusters. The O2 molecule adsorption properties on PtNi clusters suggest that the doping of Ni atoms enhances the ability of metal clusters to activate oxygen molecules, with the larger adsorption energy and bond length of O2 molecule. This is maybe due to the strong hybridization between O 2p and Pt/Ni d orbitals near the Fermi level and the enhanced polarization of adsorbed oxygen molecules. The interaction between O2 and Pt10Ni3 and Pt8Ni5 clusters are stronger than the others, due to the more positive d band center than the others. For the ORR, the energy barriers on Pt10Ni3 are lower than those on pure Pt13 and Pt8Ni5 clusters, suggesting a high catalytic activity of Pt10Ni3 cluster for the ORR. Our study provides atomic-scale insights into the nature of the interfacial effects that determines O2 reduction reaction on PtNi cluster catalysts.