Fe₃C@CQD/CNF as a non-precious metal catalyst for enhanced oxygen reduction reaction in lithium-air batteries

The development of efficient non-precious metal cathodes for metal–air batteries is limited by insufficient oxygen reduction reaction (ORR) activity and inadequate electrochemical durability. Although Fe/Fe₃C-based carbon catalysts have demonstrated promising ORR performance, maintaining stable catalytic behaviour under electrochemical conditions remains a key challenge. In this study, we synthesized Fe₃C/Fe nanoparticle-doped CQD/CNF composites using electrospinning and pyrolysis techniques. As a result, the optimized Fe₃C@CQD_0.8/CNF exhibited excellent ORR performance, with a limiting current density of ∼−4.990 mA/cm², a half-wave potential (E_1/2) of 0.851 V, and an onset potential of 0.951 V. A lower Tafel slope (59.7 mV dec^-1) and a near four-electron transfer pathway indicate improved reaction kinetics. Accelerated durability testing shows a small E_1/2 decay of only 8.8 mV after 5,000 cycles. indicating improved electrochemical stability. When employed as a cathode in lithium–air batteries, Fe₃C@CQD_0.8/CNF achieves a high initial discharge capacity of ∼3673.72 mAh g⁻¹ and a reduced discharge–charge voltage gap of only 1.28 V. These results demonstrate that regulating the defect structure and surface chemistry of carbon nanofiber-based Fe-containing catalysts through CQD incorporation is an effective approach to improving ORR activity and electrochemical durability, providing a viable strategy for the design of non-noble metal cathodes in metal–air energy systems.