The trends of the catalytic activity toward the oxygen reaction reduction (ORR) from Pd-44 nanoclusters to M-6@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: Pt-44 approximate to M-6@Pd30Pt8 > M-6@Pd-38 > Pd-44. In addition, the adsorption of O-2 on the Ni-6@Pd30Pt8 and Pt-44 nanoclusters were investigated, finding an elongation of the O-O bond length when O-2 is adsorbed on the Ni-6@Pd30Pt8 and Pt-44 nanoclusters, suggesting that the O-2 is activated. Finally, the stabilities of the M-6@Pd-38 and M-6@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 M-6@Pd-38 and M-6@Pd30Pt8 nanoclusters. Nevertheless, it is observed that the segregation energies of M atoms for the M-6@Pd-38 nanoclusters with an oxidizing environment tend to decrease compared with their M-6@Pd-38 nanoclusters counterparts in vacuum, which suggests that in an oxidative environment, M atoms may tend to segregate to the surface of the M-6@Pd-38 nanoclusters. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.