Symbiotic topological defect with atomic Fe sites for enhanced electrocatalytic oxygen reduction

Atomically dispersed Fe–N–C catalysts with highly symmetric FeN₄ structures have emerged as promising candidates for the electrocatalytic oxygen reduction reaction (ORR) and related industrial applications, such as hydrogen fuel cells and zinc–air batteries. However, immobilizing active sites on commonly used carbon supports (e.g., XC-72, activated carbon, and carbon nanotubes) often leads to mass transfer limitations, resulting in reduced efficiency and increased costs. In this work, we achieve the in-situ formation of topological carbon defects around FeN₄ moieties via a multi-step carbonization strategy, yielding a topologically defective N-doped carbon (TDNC)@Fe₁ catalyst with a unique structural configuration. Benefiting from the robust coupling between atomically dispersed Fe–N₄ active sites and TDNC, the resultant TDNC@Fe₁ catalyst exhibits a remarkable half-wave potential of 0.901 V in 0.1 M KOH, outperforming commercial Pt/C (0.857 V) and most reported catalysts in the literature. Through a combination of advanced microstructural characterization techniques and density functional theory (DFT) calculations, we reveal that the symbiotic interaction between topological carbon defects and atomic Fe sites plays a crucial role in enhancing ORR activity and improving zinc–air battery performance.