Zn Volatilization-Induced Structural Evolution in Lignin-Derived Co/Fe Heterojunction Catalysts Enables Long-Life Zinc-Air Batteries

The development of efficient and robust bifunctional oxygen electrocatalysts is crucial for advancing rechargeable zinc-air batteries. Although bimetallic composites are promising, conventional doping strategies often lack precise structural control. Herein, we report a sustainable synthesis of Co/Fe heterojunction catalysts from biorefinery lignin, incorporating low-cost Zn as a structural regulator. Zn spacers suppress CoFe alloy crystallization and promote Co 5.47 N formation, while Zn volatilization induces in situ carbon nanotube growth to enhance electronic structure and charge transport. The resulting Zn-CoFe@NLC catalyst exhibited favorable bifunctional performance, with a half-wave potential of 0.84   V for the oxygen reduction reactionand a high kinetic current density (17.2   mA   cm -2 at 0.8   V). When implemented in zinc-air batteries, it achieved long cycling stability exceeding 1300   h (at 5   mA   cm -2 ) and 1550   h (at 10   mA   cm -2 ), more than 2.5 times that of noble metal catalyst (600   h at 10   mA   cm -2 ). DFT calculations revealed that the CoFe-Co 5.47 N interface acted as an electron redistribution hub, synergistically enhancing the intrinsic activity of Co/Fe sites. This work underscores the promise of lignin as a sustainable precursor and establishes a generalizable route for rational structural engineering of bimetallic electrocatalysts for energy storage.