Harnessing the Trade‐Off between CoFe/Fe3C Interfacial Junction with Unparalleled Potential Gap of 0.58 V for Reversible Oxygen Electrocatalysis: Application toward Liquid and Solid‐State Zn‐Air Batteries

Abstract Effective integration of multiple active moieties and strategic engineering of coordinated interfacial junctions are crucial for optimizing the reaction kinetics and intrinsic activities of heterogeneous electrocatalysts. Herein, a simple integrated heterostructure of biphasic Co 0.7 Fe 0.3 /Fe 3 C embedded on in situ grown N‐doped carbon sheets is constructed. Rationally designed CoFe/Fe 3 C‐T 2 owns more accessible active sites and interfacial junction effects, cooperatively boosting the electron and mass transfer, needed for multifunctional electrocatalysis. Leveraging the synergistic effect of dual active sites, CoFe/Fe 3 C‐T 2 demonstrates outstanding oxygen electrocatalytic activity in alkaline medium with an ultra‐low potential gap of 0.58 V, surpassing the recently available state‐of‐the‐art catalysts. Moreover, CoFe/Fe 3 C‐T 2 air‐electrode achieves a high peak power density of 249 mW cm −2 , a large specific capacity of 808 mAh g −1 and excellent cycling stability for aqueous Zn‐air batteries. Remarkably, the solid‐state flexible ZAB also exhibits satisfactory performance, showcasing an open‐circuit voltage of 1.43 V and a peak power density of 66 mW cm −2 . These outstanding results push this catalyst to the top of the list of non‐noble metal‐based electrode materials. This work offers a viable method for using the active‐site‐uniting strategy to create double‐active‐site catalysts, which may find real‐time applications in energy conversion/storage devices.