Carbon-supported Pd catalysts (Pd/CBs) for oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs) were modified with transition metals to enhance their catalytic activity. Pd-M/CB(N) (M = Co, Cu, Y, and Ag) was prepared by the reduction of metal precursors with NaBH4 in the presence of ethylene glycol (EG) without heat treatment. Pd-Ag/CB(N) showed the highest catalytic activity for the ORR among all the Pd-based catalysts tested in the present study, and it had twice higher activity than Pd/CB. The Pd-Ag/CB(N) also had the higher ORR activity than the Pd-Ag/CB prepared by a conventional impregnation method (Pd-Ag/CB(I)) due to the formation of smaller Pd-Ag alloy particles with 1-2 nm diameters. Pd-Ag/CB(N) was covered with silica layers (SiO2/Pd-Ag/CB(N)) in order to improve their durability under severe cathode conditions. The SiO2/Pd-AWCB(N) had high catalytic activity for the ORR during the durability test because silica layers prevented the diffusion of metal species from the catalysts. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.