Layered Fe–N–C catalysts with axially coordinated single-atom sites induced by molten salts for oxygen reduction reaction

Iron and nitrogen co-doped carbon (Fe–N–C) catalysts with atomically dispersed Fe-N x sites have shown great potential to replace Pt-based catalysts for the oxygen reduction reaction. In this work, a layer-structured Fe–N–C catalyst is synthesised using Fe-doped ZIF-8 precursor via molten salt-assisted pyrolysis with a KCl/ZnCl 2 eutectic mixture, which enables the transformation of bulk three-dimensional structures into two-dimensional layered sheets. The catalyst shows an axially coordinated Fe-N 5 structure, enhancing the surface area and active site exposure. Electrochemical measurement demonstrates superior ORR activity, showing a half-wave potential of 0.874 V vs. RHE in alkaline media. During a zinc–air battery test, a 43% higher peak power density is recorded than that of Pt/C. The structural formation process and catalytic performance enhancement mechanisms are also explored to provide further understanding for the design of highly efficient and scalable non-precious metal ORR catalysts. • Eutectic KCl/ZnCl 2 induces the 3D-to-2D transformation of Fe–N–C catalysts. • Morphological change modulates the coordination environment and forms Fe-N 5 sites. • Layered Fe–N–C shows enhanced ORR activity, with a E 1/2 of 0.874 V vs. RHE in 0.1 M KOH. • The as-prepared catalyst delivers 43% higher peak power density than Pt/C in zinc–air batteries.