Porous nitrogen-doped carbon nanosheets composite Fe₃C synthesized by molten salt-mediated template method as efficient ORR catalyst for zinc-air batteries

Considering the intrinsic activity of non-precious metal oxygen reduction reaction (ORR) catalysts is typically lower than that of precious metal catalysts, it is crucial to focus on the rational design of their micro-morphology and active site. This paper employed a simple molten salt-mediated template method to fabricate a Fe₃C composite N-doped C catalyst with a layered porous framework (Fe₃C@NC). Tannic acid was utilized to form a strong coordination with iron to limit the grain size of Fe₃C nanocrystals generated by high-temperature pyrolysis. Moreover, urea achieved nitrogen doping in tannic acid-derived porous carbon, while the graphite phase nitrogen-doped carbon (g-C₃N₄) formed by its pyrolysis, together with the molten salt-mediated environment, jointly controlled the two-dimensional sheet-like structure of the material. The optimized Fe₃C@NC-800 demonstrated efficient ORR performance, with an ORR half-wave potential of 0.883 V. Its application as a cathode catalyst in a liquid zinc-air battery (ZABs) exhibits a maximum power density of 211.5 mW cm⁻², surpassing that of a Pt/C-based ZAB and indicating the potential practical utility of this material.