Density functional theory calculations are performed to investigate O-2 adsorption and dissociation on the icosahedral Pd13-nNinPt42 (n = 0, 1, 12, and 13) tri-metallic nanoparticles. The parallel adsorption of O-2 on Pd13-nNin@Pt-42 (n = 0, 1, 12, and 13) is stronger than the vertical adsorption. The adsorption of O-2 on the bridge site (B1) is favorable in the Pd13-nNin@Pt-42 (n = 0, 1, 12, and 13) nanoparticles, while the adsorption of O atom on the hollow site (H1) is preferred. The adsorption energies of O-2 and O are strongly affected by the coordination number. Low coordination site shows strong adsorption of O-2 and O on the Pd13-nNin@Pt-42 (n = 0, 1, 12, and 13) nanoparticles. The adsorption energies of O-2 and O atoms are found to be correlated well with the d-band center of surface Pt. For the Pd13-nNin@Pt-42 (n = 0, 1, 12, and13) nanoparticles catalysts, the ORR activity follows the order of Ni-13@Pt-42 > Pd-13@Pt-42 > Pd12Ni1 @Pt-42 > Pd-1 Ni-12@Pt-42, illustrating that the Ni-13@Pt-42 is the strongest ORR activity among the Pd13-nNin@Pt-42 (n = 0, 1, 12, and13) nanoparticles catalysts. Our results have important significance to understand the mechanism of O-2 dissociation on the Pd13-nNin@Pt-42 (n = 0, 1, 12, and 13) tri-metallic nanoparticles. (C) 2017 Elsevier B.V. All rights reserved.