Integration of Fe Single Atoms to Improve Kinetics and Mass Transport in Oxygen Reduction Reaction for Zinc‐Air Batteries

Abstract

ABSTRACT Simultaneous optimization of intrinsic activity and mass transport to enhance the oxygen reduction reaction (ORR) performance of zinc‐air battery (ZAB) cathodes is crucial yet remains a formidable challenge. In this study, we developed a cross‐scale synergy strategy to embed Fe−N 4 /Fe 3 C active microdomains into a 3D mesopore‐dominated carbon nanoflower framework (Fe SA /Fe 3 C NP @CNF). This approach effectively bridges the microscopic electronic modulation of active sites with the macroscopic regulation of the pore structure of the carbon framework, thus simultaneously improving intrinsic activity and mass transport. The resulting Fe SA /Fe 3 C NP @CNF electrocatalyst exhibits outstanding ORR performance with a half‐wave potential of 0.921 V versus RHE and superior stability. In ZABs, it delivers a high peak power density of 199.1 mW cm −2 and remarkable cycling stability over 500 h. In situ spectroelectrochemical measurements and theoretical calculations reveal that Fe 3 C modulates the electronic structure of Fe−N 4 sites by optimizing Fe 3d orbital occupancy and lowering the energy barrier for oxygen activation. Distribution of relaxation times, zero‐length column chromatography, bubble‐transport dynamics, and finite element simulations collectively demonstrate that the mesopore‐dominated nanoflower architecture promotes rapid oxygen transport and maximizes active‐site accessibility. This study establishes a versatile cross‐scale design principle for developing high‐performance ORR electrocatalysts in practical energy‐conversion devices.