Catalytic activity trends from pure Pd nanoclusters to M@PdPt (M = Co, Ni, and Cu) core-shell nanoclusters for the oxygen reduction reaction: A first-principles analysis

Abstract

The trends of the catalytic activity toward the oxygen reaction reduction (ORR) from Pd44 nanoclusters to M6@Pd30Pt8 (M = Co, Ni, and Cu) core-shell nanoclusters was investigated using auxiliary density functional theory. The adsorption energies of O and OH were computed as predictors of the catalytic activity toward the ORR and the following tendency of the electrocatalytic activity was computed: Pt44 ≈ M6@Pd30Pt8 > M6@Pd38 > Pd44. In addition, the adsorption of O2 on the Ni6@Pd30Pt8 and Pt44 nanoclusters were investigated, finding an elongation of the O–O bond length when O2 is adsorbed on the Ni6@Pd30Pt8 and Pt44 nanoclusters, suggesting that the O2 is activated. Finally, the stabilities of the M6@Pd38 and M6@Pd30Pt8 core-shell nanoclusters were analyzed both in vacuum and in oxidative environment. From the calculated segregation energies for the bimetallic and trimetallic nanoclusters in vacuum, it can be clearly observed that the M atoms prefer to be in the center of the M6@Pd38 and M6@Pd30Pt8 nanoclusters. Nevertheless, it is observed that the segregation energies of M atoms for the M6@Pd38 nanoclusters with an oxidizing environment tend to decrease compared with their M6@Pd38 nanoclusters counterparts in vacuum, which suggests that in an oxidative environment, M atoms may tend to segregate to the surface of the M6@Pd38 nanoclusters.