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 Co0.7Fe0.3/Fe3C embedded on in situ grown N-doped carbon sheets is constructed. Rationally designed CoFe/Fe3C-T2 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/Fe3C-T2 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/Fe3C-T2 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.