NaCl-assisted synthesis of 2D hexagonal FeNC nanosheets as efficient oxygen reduction catalyst for metal-air batteries

Iron coordinated with nitrogen (FeN x ) sites hosted in the micropores of carbon substrate offer excellent performance for the oxygen reduction reaction (ORR). Achieving a highly exposed and dispersed FeN x sites accessible for ORR is still challenging to date. In this work, two-dimensional hexagonal carbon nanosheets supported FeN x moieties (FeNC-NaCl- T ) were synthesized via a molten NaCl-assisted pyrolysis strategy. Benefit from the high specific surface area (1371.635 m 3 ·g −1 ) and highly dispersed FeN x sites, the optimized FeNC-NaCl-900 exhibits superior ORR activity with a high half-wave potential of 0.90 V in alkaline electrolyte. Impressively, with FeNC-NaCl-900 as the cathode catalyst in aqueous zinc–air battery, achieving a remarkable performance with a high peak power density of 177 mW·cm −2 and competitive durability (200 h). Furthermore, the Al-air battery equipped with FeNC-NaCl-900 attained an ultrahigh specific capacity of 2257.48 mAh·g −1 at a large discharge current of 100 mA cm −2 . These findings provide guidance for the development of high performance FeNC catalysts and their applications in metal-air batteries.