Liu, ShengwenLi, ChenzhaoZachman, Michael J.Zeng, YachaoYu, HaoranLi, BoyangWang, MaoyuBraaten, JonathanLiu, JiaweiMeyer, Harry M., IIILucero, MarcosKropf, A. JeremyAlp, Esen E.Gong, QingShi, QiurongFeng, ZhenxingXu, HuiWang, GuofengMyers, Deborah J.Xie, JianCullen, David A.Litster, ShawnWu, Gang2024-05-292024-05-292022Liu S, Li C, Zachman MJ, et al. Atomically dispersed iron sites with a nitrogen–carbon coating as highly active and durable oxygen reduction catalysts for fuel cells. Nat Energy. 2022;7(7):652-663. doi:10.1038/s41560-022-01062-1https://hdl.handle.net/1805/41071Nitrogen-coordinated single atom iron sites (FeN4) embedded in carbon (Fe–N–C) are the most active platinum group metal-free oxygen reduction catalysts for proton-exchange membrane fuel cells. However, current Fe–N–C catalysts lack sufficient long-term durability and are not yet viable for practical applications. Here we report a highly durable and active Fe–N–C catalyst synthesized using heat treatment with ammonia chloride followed by high-temperature deposition of a thin layer of nitrogen-doped carbon on the catalyst surface. We propose that catalyst stability is improved by converting defect-rich pyrrolic N-coordinated FeN4 sites into highly stable pyridinic N-coordinated FeN4 sites. The stability enhancement is demonstrated in membrane electrode assemblies using accelerated stress testing and a long-term steady-state test (>300 h at 0.67 V), approaching a typical Pt/C cathode (0.1 mgPt cm−2). The encouraging stability improvement represents a critical step in developing viable Fe–N–C catalysts to overcome the cost barriers of hydrogen fuel cells for numerous applications.en-USPublisher PolicyElectrocatalysisFuel cellsHydrogen energyArticle