Proton exchange membrane fuel cells (PEMFCs) suffer severe performance loss in the high current density (HCD) region as Pt‐loading decreases. A smaller electrocatalyst size inducing a higher electrochemically active surface area (ECSA) is critical for solving this issue. However, the poor electrocatalytic activity and stability of sub‐2 nm nanoclusters limit the potential to reduce their size. In this study, 1.69 nm Co‐doped Pt nanoclusters with a large ECSA (116.19 m2 gPt–1) are synthesized. The mass activity (MA) (0.579 A mgPt–1) and stability (9% MA loss after 30k potential cycling) refresh the record of sub‐2 nm nanoclusters. The structural characterization and theoretical calculations reveal that doping reduces the total energy required to stabilize the nanoclusters. Dopant tailoring of the d‐band center and vacancy formation energy account for the activity and stability enhancement, respectively. Due to the larger ECSA and MA induced by doping, HCD voltage loss due to lower Pt‐loading is significantly reduced compared with commercial Pt/C. The peak power density of low‐Pt‐loading PEMFCs (0.075 mgPt cmMEA–2) with a doped nanocluster cathode is 0.811 W cm–2 (H2–air condition), which far exceeds commercial Pt/C (0.5 W cm–2) and that of most reported electrocatalysts.

PEMFCs In article number 2103144, Jia Li, Jianguo Liu and co‐workers demonstrate the underlying mechanism of cobalt doping on the unprecedented activity and durability of sub‐2 nm Pt nanoclusters. With extremely efficient utilization of Pt and superior performance in low‐Pt loading proton exchange membrane fuel cells (PEMFCs), the electrocatalysts contribute significantly to reduce the cost of PEMFCs and mitigate the dependence of hydrogen energy on precious metals.

Morphology regulation induced high stability of ceria in proton exchange membrane.