▎ 摘　　要

A high-efficiency and stable electrocatalyst for oxygen reduction reaction (ORR) is critical for fuel cells. Here we report a new type of ORR catalyst composed of platinum nanocrystals loaded on nitrogen-doped graphene-vanadium carbide (VC) hybrids. This is the first report on using graphene oxide as the carbon source in the synthesis of transition-metal carbides as ORR catalysts; the electrochemical tests and theoretical modeling prove that the N-doping in both VC and graphene could effectively improve the overall catalytic activity. The catalytic performance of the hybrids in alkaline solutions is superior to that of commercial Pt/C catalysts in terms of the oxygen-reduction half-wave potential and the mass activity. The stability study of the catalyst also shows less degradation in catalytic activity after 3000 cycles compared with Pt/C and the hybrid catalyst structure remains virtually unchanged. Therefore, using inexpensive hybrids of high-conductivity nitrogen-doped transition-metal carbides and nanocarbon as the catalyst support presents a new direction to optimize catalyst performance for next-generation fuel cells.