Boosting the covalency of FeS via a built-in electric field in FeS/MnS heterojunctions for durable oxygen electrocatalysis in zinc-air batteries

The development of efficient and low-cost non-precious metal bifunctional oxygen electrocatalysts remains a critical challenge for advancing zinc-air batteries. In this study, we designed and synthesized three-dimensional carbon nanofiber catalysts integrated with sulfur- and nitrogen-doped carbon anchoring FeS/MnS heterostructures, leveraging an interfacial engineering approach. Originating from this strategy, the optimized FeS/MnS@CNFs shows a higher half-wave potential (E 1/2 ) of 0.88 V for ORR and a lower overpotential (E j=10 ) of 230 mV at 10 mA cm −2 for OER. The theoretical studies elucidate that the significant work function difference (0.43 eV) between FeS and MnS induces a built-in electric field at their heterointerface. This field drives electron transfer from MnS to FeS, which consequently strengthens the covalency of Fe S bonds and significantly enhances the adsorption capability for the *OOH intermediate species. When employed as the air-cathode catalyst, the FeS/MnS@CNFs-based zinc-air battery achieved a remarkable peak power density of 223 mW cm −2 and maintained stable operation for over 280 h at 10 mA cm −2 . Further theoretical modeling of the heterostructure elucidated that the built-in electric field modulates Fe S bond energies through electronic rearrangement, providing a fundamental explanation for the enhanced oxygen electrocatalytic performance and improved structural stability.