The approaching commercialization of polymer electrolyte membrane fuel cells (PEMFCs) is still hindered by the high cost and limited operational stability of the Pt-based cathode catalysts traditionally utilized. Specifically

the cathode catalyst layer comprises over half of the overall cost of a PEMFC stack and the increasing demands for fuel cell power systems will undoubtedly drive up the already high price of Pt. Developing new catalyst with reduced Pt dependency

improved oxygen reduction reaction (ORR) activity and high stability is an urgent necessity. This paper reviews the recent advancements in the area of Pt-free electrocatalysts for ORR with emphasis on introducing the exciting new research in catalyst synthesis methodologies and the understanding of the mechanism of nitrogen-doped carbon nanomaterials. The integration of these catalysts into fuel cell operations and the resulting performance/durability

are also discussed. Meanwhile

the insights into the remaining challenges and research directions are proposed in order to shed light on the future development of Pt-free catalysts for ORR.