A Highly Efficient Fe−N−C Electrocatalyst with Atomically Dispersed FeN4 Sites for the Oxygen Reduction Reaction

Graphical ORR : We fabricated a FeSA/HNPC electrocatalyst with well atomically dispersed FeN 4 species. DFT calculations uncovered that the single-atomic FeN 4 sites within FeSA/HNPC electrocatalyst present in the configurations of pyrrole-N 4 −Fe are more favorable than those of pyridine-N 4 −Fe for boosting ORR performances. Atomically dispersed Fe−N−C electrocatalysts have displayed excellent catalytic performances towards the oxygen reduction reaction (ORR), while the identification of the genuine active sites remains a challenge. Herein, we report a Fe−N−C electrocatalyst of FeSA/HNPC featuring single-atomic FeN 4 sites on hierarchically N-doped porous carbon (HNPC), which shows a very competitive ORR activity in alkaline solution even at a low electrocatalyst loading of 0.2 mg cm −2 on the working electrode. A comparison of energy barriers in ORR reveals that the single-atomic FeN 4 active sites in FeSA/HNPC existing in the form of pyrrole-N 4 −Fe is more favorable than that of pyridine-N 4 −Fe for the enhanced ORR activity. Understanding the nature of FeN 4 active sites will greatly benefit the design of Fe−N−C electrocatalysts with highly effective ORR performances.