Proton-exchange membrane fuel cells (PEMFCs) are generally regarded as a clean and sustainable energy-conversion technology to replace increasingly scarce fossil fuels due to the high energy conversion efficiency, high energy density, and low or zero pollutant emission. Clearly, platinum (Pt) is a key component of the state-of-the-art electrocatalysts for the oxygen reduction reaction (ORR) at the cathodes by far, which is a determining half reaction to boost the performance of this fuel cell technology. However, the sluggish reaction kinetics of ORR often requires a relatively high load of Pt to achieve a desirable fuel cell performance in the practical applications, which is severely restricted by the high cost and scarcity of Pt.