Synergy FeX (X = S, C, P) nanoparticles with Fe-N-C single-atom sites in carbon nanofibers for efficient bifunctional oxygen electrocatalysis in Zn-air batteries

To advance the development of high-performance rechargeable zinc-air batteries (ZABs) with efficient oxygen electrochemistry, significant progress is needed in research on Fe-based nanoparticle/single-atom bifunctional oxygen electrocatalysts. Nevertheless, the structure-activity relationship and synergy mechanism of Fe-based nnoparticle/single-atom hybrid catalysts are not well-known. Herein, Self-supported carbon nanofiber electrocatalysts with in-situ synthesized FeS, Fe 2 P, or Fe 3 C nanoparticles and atomically dispersed Fe-N x sites were prepared in this work by the coaxial electrospinning method. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) simulations showed that there was a significant change in charge distribution, an increase in the adsorption of *O intermediates, and a decrease in the *OH desorption energy barrier at the FeS/FeSA interface. It can be concluded that FeS/FeSA has better electronic and adsorption properties than Fe 2 P/FeSA and Fe 3 C/FeSA. Therefore, FeS/FeSA has an oxygen reduction reaction (ORR) half-wave potential of 0.89 V and an oxygen evolution reaction (OER) overpotential of 240 mV at 10 mA/cm 2 , which is relatively high compared with that of Fe 2 P/FeSA (0.79 V, 260 mV) and Fe 3 C/FeSA (0.77 V, 250 mV), and it has a small potential gap (Δ E ) of 0.58 V. FeS/FeSA can be used as the air cathode in liquid ZABs; it has a high peak power density of 116 mW/cm 2 and is stable for more than 150 hours. The above results have laid the foundation for the construction of high-performance air cathode catalysts by means of effective coupling of atomic nanoparticles and shown the direction for developing high-efficiency, long-life rechargeable zinc-air batteries.