Atomically dispersed iron-nitrogen-carbon (Fe-N-C) catalysts have emerged as the most promising alternative to the expensive Pt-based catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), however suffer from low site density of active Fe-N₄ moiety and limited mass transport during the catalytic reaction. To address these challenges, we report a three-dimensional (3D) metal-organic frameworks (MOF)-derived Fe-N-C single-atom catalyst. In this well-designed Fe-N-C catalyst, the micro-scale interconnected skeleton, the nano-scale ordered pores and the atomic-scale abundant carbon edge defects inside the skeleton significantly enhance the site density of active Fe-N₄ moiety, thus improving the Fe utilization in the final catalyst. Moreover, the combination of the above mentioned micro- and nano-scale structures greatly facilitates the mass transport in the 3D Fe-N-C catalyst. Therefore, the multiscale engineered Fe-N-C single-atom catalyst achieves excellent ORR performance under acidic condition and affords a significantly enhanced current density and power density in PEMFC. Our findings may open new opportunities for the rational design of Fe-N-C catalysts through multiscale structural engineering.

原子分散的铁-氮-碳（Fe-NC）催化剂已成为质子交换膜燃料电池（PEMFC）中用于氧还原反应（ORR）的昂贵的基于Pt的催化剂的最有前途的替代品，但它的位置低Fe-N ₄活性部分的密度和催化反应过程中的有限质量传递。为了解决这些挑战，我们报告了三维（3D）金属有机骨架（MOF）衍生的Fe-NC单原子催化剂。在这种精心设计的Fe-NC催化剂中，骨架内部的微米级互连骨架，纳米级有序孔隙和原子级丰富的碳边缘缺陷显着提高了活性Fe-N ₄的位点密度。从而提高最终催化剂中的铁利用率。此外，上述微米和纳米级结构的组合极大地促进了3D Fe-NC催化剂中的质量传输。因此，该多级工程化Fe-NC单原子催化剂在酸性条件下可获得出色的ORR性能，并显着提高了PEMFC的电流密度和功率密度。我们的发现可能为通过多尺度结构工程合理设计Fe-NC催化剂提供新的机会。