Implanting Atomically Dispersed Fe Atoms with Dense Active Sites into Carbon Nanospheres for Efficient Oxygen Reduction Electrocatalysis in Anion Exchange Membrane Fuel Cells

Iron single-atom catalysts (SACs) featuring edge-located metal sites have attracted increasing attention as highly effective catalysts for the oxygen reduction reaction (ORR). However, it continues to be a significant challenge that their performance in practical devices, such as anion exchange membrane fuel cells (AEMFCs), is still unsatisfactory due to the sparse distribution of available active sites and prominent electrocatalytic performance. In this work, a facile and scalable SiO2 hard-template approach is elaborately designed to fabricate an Fe SAC immobilized onto N,O-doped carbon nanospheres with highly dense active sites (Fe-N-CNS) for efficient ORR electrocatalysis. Experimental analyses affirm that the constructed Fe active sites are determined as an atomically dispersed FeN4 coordination configuration, where the metal–support interaction between these two components involves electron transfer from FeN4 to a N,O-doped carbon matrix, thereby modulating the electronic redistribution and binding energies of O-related intermediates for the improvement of ORR intrinsic activity. As anticipated, the optimal Fe-N-CNS showcases an exceptional ORR capability, encompassing notable ORR activity and featuring a strikingly higher half-wave potential value (E1/2, 0.85 V), a high density of accessible FeN4 sites (20 μmol g–1), enhanced stability, and an impressive methanol tolerance. More excitingly, this integrated catalyst achieves an outstanding peak power density of 190.5 mW cm–2 under real-world operational conditions of an AEMFC, together with a long cycle life for 30 h, which outperforms those using commercial Pt/C at the cathode. The present work is deemed to offer guiding principles for the fabrication of high-performance AEMFC electrocatalysts in terms of metal-N-C single active site engineering.