Highly exposed surface pore-edge FeNx sites for enhanced oxygen reduction performance in Zn-air batteries

Abstract

Single Fe atoms with N-coordination (FeN_x sites) in Fe–N–C catalysts are widely recognized as the active centers for catalyzing oxygen reduction reaction (ORR), but attaining superior intrinsic activity and more exposure of the FeN_x sites remains challenging. Herein, the surface pore-edge FeN_x sites anchored on suitable porous carbon (SPE-FeN_x-HPNC) are reported, which could simultaneously enhance the intrinsic activity and more exposed active sites for ORR. Theoretical calculations suggest that pore-edge FeN_x sites are more active than pure FeN_x sites in the rate-determining step, hence promoting the intrinsic ORR activity of active sites. Therefore, due to abundant surface pore-edge FeN_x sites and beneficial pore structures, SPE-FeN_x-HPNC exhibits excellent ORR activity with a half-wave potential (E_1/2) of 0.902 V in an alkaline medium. Moreover, the assembled Zn-air battery with SPE-FeN_x-HPNC delivers a peak power density of 150 mW cm⁻² and a durable charge–discharge cycle over 450 hours. This work provides an effective strategy for preparing a high-performance catalyst for Zn-air batteries.