Interfacial Engineering of CoN/Co3O4 Heterostructured Hollow Nanoparticles Embedded in N‐Doped Carbon Nanowires as a Bifunctional Oxygen Electrocatalyst for Rechargeable Liquid and Flexible all‐Solid‐State Zn‐Air Batteries

Abstract The design of economical, efficient, and robust bifunctional oxygen electrocatalysts is greatly imperative for the large‐scale commercialization of rechargeable Zn‐air battery (ZAB) technology. Herein, the neoteric design of an advanced bifunctional electrocatalyst composed of CoN/Co 3 O 4 heterojunction hollow nanoparticles in situ encapsulated in porous N‐doped carbon nanowires (denoted as CoN/Co 3 O 4 HNPs@NCNWs hereafter) is reported. The simultaneous implementation of interfacial engineering, nanoscale hollowing design, and carbon‐support hybridization renders the synthesized CoN/Co 3 O 4 HNPs@NCNWs with modified electronic structure, improved electric conductivity, enriched active sites, and shortened electron/reactant transport pathways. Density functional theory computations further demonstrate that the construction of a CoN/Co 3 O 4 heterojunction can optimize the reaction pathways and reduce the overall reaction barriers. Thanks to the composition and architectural superiorities, the CoN/Co 3 O 4 HNPs@NCNWs exhibit distinguished oxygen reduction reaction and oxygen evolution reaction performance with a low reversible overpotential of 0.725 V and outstanding stability in KOH medium. More encouragingly, the homemade rechargeable liquid and flexible all‐solid‐state ZABs utilizing CoN/Co 3 O 4 HNPs@NCNWs as the air‐cathode deliver higher peak power densities, larger specific capacities, and robust cycling stability, exceeding the commercial Pt/C + RuO 2 benchmark counterparts. The concept of heterostructure‐induced electronic modification herein may shed light on the rational design of advanced electrocatalysts for sustainable energy applications.