Disentangling the Activity‐Stability Trade‐Off of Pyrrolic N‐Coordinated Fe─N₄ Catalytic Sites for Long‐Life Oxygen Reduction Reaction in Acidic Medium

Abstract Fe─N─C materials with Fe─N₄ sites are considered as most promising non‐precious metal‐based electrocatalysts for low‐cost proton‐exchange‐membrane fuel cells (PEMFCs). Breaking the trade‐off between activity and stability has been a long‐standing challenge in the field of acidic oxygen reduction reaction (ORR). Herein, a “top‐down” thermally‐driven strategy is developed to achieve highly active pyrrolic N‐coordinated Fe sites in a high spin state with Fe atomic cluster (Fe_n@Fe─N_pyrr─C) and discover that the neighboring Fe_n cluster can synergistically stabilize such vulnerable Fe─N₄ sites by inhibiting their protonation. Consequently, the Fe_n@Fe─N_pyrr─C catalysts exhibit much enhanced ORR activity and stability, endowing PEMFCs with a high power density of 804.6 mW cm⁻² (testing conditions: 80 °C, 100% RH, 2.0 bar) and over 100 h durability (at 0.5 V). These findings open up opportunities for the exploration of durable Fe─N─C ORR electrocatalysts for non‐precious metal‐based PEMFCs and other applications.