Hierarchically mesoporous Fe-N-C single-atom catalysts for efficient oxygen electrocatalysis in rechargeable zinc-air batteries

Rechargeable zinc-air batteries (ZABs) hold significant promise for next-generation energy storage due to their unique advantages in safety, energy and cost. However, their commercial application remains hindered by the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), necessitating the development of highly efficient and durable electrocatalysts. Herein, we report a hierarchically mesoporous Fe-N-C catalyst (Fe-N/MPC_S500) synthesized via a template-assisted method, which exhibits exceptional bifunctional ORR/OER performance. The Fe-N/MPC_S500 catalyst achieves a positive ORR half-wave potential (0.86 V), along with a low OER over-potential of 510 mV at 10 mA cm⁻², surpassing those of most non-precious metal catalysts. Furthermore, in a liquid-state ZAB, Fe-N/MPC_S500 delivers a high specific capacity of 708 mAh g⁻¹, a peak power density of 409 mW cm⁻², and stable charge-discharge cycling over 470 h, outperforming commercial Pt/C + Ir/C catalysts. The outstanding performance is attributed to the hierarchical porosity, optimized Fe-N coordination, and enhanced electron/mass transport. This work presents a scalable and low-cost strategy for developing high-performance single-atom catalysts, paving the way for practical deployment in energy conversion and storage technologies.