Fabricating high-loading Fe-N4 single-atom catalysts for oxygen reduction reaction by carbon-assisted pyrolysis of metal complexes

Iron-based single-atom catalysts with nitrogen-doped carbon as support (Fe-SA/NPC) are considered effective alternatives to replace Pt-group metals for scalable application in fuel cells. However, synthesizing high-loading Fe-SA catalysts by a simple procedure remains challenging. Herein, we report a high-loading (7.5 wt%) Fe-SA/NPC catalyst prepared by carbon-assisted pyrolysis of metal complexes. Both the nitrogen-doped porous carbon (NPC) support with high specific surface area and ο-phenylenediamine (o-PD) play key roles role in the preparation of high-loading Fe-SA/NPC catalysts. The results of X-ray photoelectron spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, and X-ray absorption fine structure spectroscopy experiments show that the Fe atoms are anchored on the carbon carriers in a single-atom site configuration and coordinated with four of the doped nitrogen atoms of the carbon substrates (Fe-N4). The activities of the Fe-SA/NPC catalysts in the oxygen reduction reaction increased with increasing iron loading. The optimized 250Fe-SA/NPC-800 catalyst exhibited an onset potential 0.97 V of and a half-wave potential of 0.85 V. Our study provides a simple approach for the large-scale synthesis of high-loading single-atom catalysts.