“…However, among the factors hampering the widespread application of PEMFCs, are the high-cost and low-performance electrocatalysts, which are responsible for accelerating the sluggish oxygen reduction reaction (ORR) at the cathode, and still need to be improved [10,11]. Pt/C, the current state-of-the-art ORR catalyst, suffers from inherent scarcity, insufficient stability, and high cost [12,13]. Although nonprecious metal catalysts, such as Fe-, Co-, Cu-, and Ni-based materials, can lower the cost, activity and metal leaching are the two major issues to be solved [14][15][16].…”