The proton exchange membrane fuel cell (PEMFC) is a good source of alternative energy because its main product is water. To increase the catalytic activity and durability of the nanoparticles in the oxygen reduction reaction (ORR), catalysts with a novel core-shell structure were synthesized. The core -shell structure is composed of a singular core, Pd, and a binary alloy shell, PtCo, which exhibits high ORR activity. TEM analysis confirms that the core -shell structure of Pd@Pt3Co/C comprises Pt3Co alloy that is deposited on Pd nanoparticles. In testing of the rotating ring-disk electrode, the ORR activity of Pd@Pt3Co/C is better than that of other samples -Pt/C, Pd/C and Pd@Pt/C. The stability test of Pd@Pt3Co/C shows more decay after 20,000 cycles and then recover during the next 10,000 cycles. The PEMFCs using Pt/C, Pd/C, Pd@Pt/C and Pd@Pt3Co/C in the cathodes show the maximum power densities of 639.3, 382.4, 721.8 and 854.0 mW cm(-2), respectively, indicating that Pd@Pt3Co/C outperforms the others and is suitable for use in the PEMFC. After the stability test, the maximum power density of Pd@Pt3Co/C shows almost no obviously decay, which confirms Pd Pt3Co/C can act as the outstanding catalyst. The improved activity of Pd@Pt3Co/C is associated with the high utilization of Pt3Co shell on the Pd core, the ligand effect, the lattice strain effect and the synergic effect between Pd core and Pt3Co alloy shell. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.