Progress of Pt and iron-group transition metal alloy catalysts with high ORR activity for PEMFCs

The performances of proton exchange membrane fuel cells (PEMFCs) are affected by the cathodic oxygen reduction reaction (ORR). Platinum (Pt)-based catalysts can effectively improve the ORR by reducing the activation energy and substantially increase the reaction rate. However, due to the scarcity and high price of Pt, the exploration of PtM alloy catalysts with low Pt loading, high ORR activity and stability has become the focus of ORR research. Therefore, this paper reviews the recent progresses of Pt and iron-group transition metal alloy catalysts with high ORR activity and stability for PEMFCs. Firstly, the ORR theoretical mechanism is introduced. Then, we discuss several types of PtM (M=Fe, Co, Ni) alloy catalysts, including binary and ternary alloys, especially to understand the effect of particle size, shape (nanostructures, hollow structure, core-shell), structure (intermetallic compounds) and supports (new carbon, MOF derivatives, metal oxides) on the utilization rate of Pt and the ORR catalytic performance, including the ORR catalytic activity and stability. Finally, we analyze the remaining challenges and the future of PtM alloy catalysts.