Atomic Modulation and Structure Design of Fe−N4 Modified Hollow Carbon Fibers with Encapsulated Ni Nanoparticles for Rechargeable Zn–Air Batteries

Excellent bifunctional oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) activity and rapid mass transport capability are two important parameters of electrocatalysts for high‐performance rechargeable Zn–air batteries (ZABs). Herein, an efficient atomic modulation and structure design to promote bifunctional activity and mass transport kinetics of an ORR/OER electrocatalyst are reported. Specifically, atomic Fe−N4 moieties are immobilized on premade hollow carbon fibers with encapsulated Ni nanoparticles (Fe‐N@Ni‐HCFs). Synchrotron X‐ray absorption spectroscopy and spherical aberration‐corrected electron microscope analyses confirm the atomic distribution of the active sites and unique lung bubble‐like hollow architecture of the catalyst, while theoretical investigations reveal that the encapsulated Ni nanoparticles can induce electron distribution of the atomic Fe−N4 moieties to reduce reaction energy barriers. As a result, the prepared catalyst possesses enhanced bifunctional ORR/OER activity and well‐constructed gas–solid–liquid interfaces for improved mass transfer. These synergetic advantages endow the binder‐free Fe‐N@Ni‐HCFs electrode with the remarkable power density and cycling stability for ZABs, outperforming the commercial Pt/C+Ir/C benchmark. This exceptional performance suggests that the proposed strategy can be extended to the design and fabrication of electrocatalysts for energy conversion and storage. Atomic Fe−N4 moieties are immobilized onto lung‐bubble‐like hollow carbon fibers that encapsulate metallic Ni nanoparticles. The electronic coupling between the Fe−N4 moieties and Ni nanoparticles accelerates the oxygen reduction reaction/oxygen evolution reaction kinetics, while the porous hollow structure with inner cavities provides sufficient and stable triple‐phase interfaces to promote mass transfer. The atomic modulation and structure design synergistically boost the electrochemical performance of the assembled Zn–air batteries.