Transforming Single‐Atom Site to Dual‐Atom Site in Fe–N–C Catalysts: A Universal Strategy for Enhancing Durability in Proton‐Exchange Membrane Fuel Cells

Abstract Fe–N–C catalyst is the most promising non‐noble metal oxygen reduction catalyst for proton‐exchange membrane fuel cells (PEMFCs); however, their practical applications are still limited by unsatisfactory long‐term stability. This is because the N atoms of the active FeN 4 moiety are easy to protonate, leading to the leaching of Fe atoms, and the H 2 O 2 generated during oxygen reduction reaction (ORR) process triggers the Fenton reaction, further accelerating the dissolution of Fe. To address these critical stability challenge, we developed a general strategy to transform FeN 4 single‐atom sites to Fe 2 N 6 dual‐atom sites in Fe–N–C catalysts with various carbon substrates. This is achieved by treating the presynthesized Fe–N–C catalysts in a H 2 /Ar atmosphere to break the C─N bonds near the FeN 4 sites while introducing Fe and N precursors to form the Fe 2 N 6 sites. Our theoretical calculations and experimental results demonstrate that the newly formed Fe 2 N 6 sites are structurally more stable in acidic ORR and produce negligible H 2 O 2 (<1%). Therefore, the transformed Fe–N–C catalyst exhibits an extremely low Fe demetalation ratio (0.61 at%) in 0.1 M HClO 4 after 80k cycling. More surprisingly, the transformed Fe–N–C catalyst can effectively decompose H 2 O 2 with a high decomposition rate of 15.7 mmol min −1 , approaching that of the state‐of‐the art Pt/C catalyst (17 mmol min −1 ). As a result, the transformed Fe–N–C catalyst assembled PEMFC operates stably for 300 h with only 7% current density attenuation, whereas that of the pristine Fe–N–C catalyst‐based device declines by 84% within 100 h.