Replacing scarce and expensive platinum (Pt) with metal–nitrogen–carbon (M–N–C) catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells has largely been impeded by the low oxygen reduction reaction activity of M–N–C due to low active site density and site utilization. Herein, we overcome these limits by implementing chemical vapour deposition to synthesize Fe–N–C by flowing iron chloride vapour over a Zn–N–C substrate at 750 °C, leading to high-temperature trans-metalation of Zn–N₄ sites into Fe–N₄ sites. Characterization by multiple techniques shows that all Fe–N₄ sites formed via this approach are gas-phase and electrochemically accessible. As a result, the Fe–N–C catalyst has an active site density of 1.92 × 10²⁰ sites per gram with 100% site utilization. This catalyst delivers an unprecedented oxygen reduction reaction activity of 33 mA cm⁻² at 0.90 V (iR-corrected; i, current; R, resistance) in a H₂–O₂ proton exchange membrane fuel cell at 1.0 bar and 80 °C.

用金属-氮-碳 (M-N-C) 催化剂代替稀有且昂贵的铂 (Pt) 用于质子交换膜燃料电池中的氧还原反应，在很大程度上受到 M-N-C 低氧还原反应活性的阻碍由于低活性位点密度和位点利用率。在此，我们克服了这些限制，通过在 750 °C 下使氯化铁蒸汽流过 Zn-N-C 衬底，实现化学气相沉积合成 Fe-N-C，从而导致 Zn-N ₄位点的高温金属转移进入 Fe–N ₄位点。多种技术的表征表明，通过这种方法形成的所有 Fe-N ₄位点都是气相和电化学可及的。因此，Fe-N-C 催化剂的活性位点密度为 1.92 × 10 ²⁰每克位点，位点利用率为 100%。该催化剂在 1.0 bar 和 80 °C的 H ₂ –O ₂质子交换膜燃料电池中在 0.90 V（iR 校正；i，电流；R，电阻）下提供前所未有的 33 mA cm ⁻²氧还原反应活性.