Bimetallic Pt-alloys supported on niobium-doped tin oxide (Nb-SnO2) with a vapor-grown carbon fiber (VGCF) backbone are presented as electrocatalysts for polymer electrolyte membrane fuel cells (PEFCs). These can simultaneously achieve both high catalytic activity and high cycling durability for the oxygen reduction reaction (ORR). This was confirmed both in half-cell and full-cell membrane electrode assembly (MEA) configuration, using 60,000 start-stop potential cycles and 400,000 load potential cycles. In this study, we focus on alloying Pt with Co or Ni, and the best performance is achieved for Pt3Co/Nb-SnO2/VGCF electrocatalysts. The catalyst particles are selectively decorated on the Nb-SnO2, resulting in improved resistance to carbon corrosion. Pt3Co alloying was verified by FE-SEM and high-resolution STEM-EDS. High initial mass activity of 274 A g(-1) at 0.9 VRHE and 1840 A g(-1) at 0.85 VRHE was achieved, with enhanced durability compared to conventional Pt/C electrocatalysts. (C) The Author(s) 2018. Published by ECS.