Synergistic electronic interplay between CoFe single atom and nitrogen on 2D carbon boosts bifunctional oxygen redox in metal-air batteries

Enhancing oxygen redox reactions (ORR and OER) is crucial for improving energy storage and conversion technologies such as fuel cells and metal-air batteries. While single-metal catalysts like Fe-N x and Co-N x are widely used, bi-metallic catalysts offer a synergistic effect that enhances catalytic performance. However, achieving well-defined bi-metallic active sites remains a challenge. In this study, we developed a novel dual-metallic single-atom (DSA) electrocatalyst (CoFe-2DSA) on 2D nitrogen-doped carbon nanosheets, synthesized using a molten salt-assisted pyrolysis approach. The incorporation of zinc acetate and KCl during pyrolysis increased porosity and surface area by preventing structural collapse and facilitating the formation of N-doped carbon sheets. Density Functional Theory (DFT) calculations revealed that Co Fe dual-atom sites and nitrogen dopants synergistically optimize oxygen redox reactions. Graphitic nitrogen enhances charge transfer and metal‑oxygenate bonding, while pyridinic nitrogen introduces sp 3 defects that accumulate charge, reducing further charge transfer and weakening metal‑oxygenate interactions. Coordination between nitrogen and metal sites facilitates electron transfer to Co Fe, tuning d-orbital energy levels and optimizing intermediate adsorption (*O₂, *OH, *OOH). As a result, CoFe-2DSA demonstrated outstanding bifunctional catalytic performance, with an ORR half-wave potential (E 1/2 ) of 0.886 V (vs RHE) and an OER overpotential (η) of 290 mV at 10 mA.cm −2 . As a zinc-air battery cathode, it achieved a power density of 229.6 mW.cm −2 , a specific capacity of 811.5 mA.h.g −1 , and exceptional cycling stability over 74 days (3552 cycles). This study provides a paradigm shift in understanding the synergistic interaction between transition metals and nitrogen-doped carbon in oxygen redox reactions.