Built‐in Electric Field Tailored Co‐VN@V 2 O 3 Heterointerface for Hydrazine Oxidation‐Assisted Energy‐Saving Hydrogen Production

Heterointerface engineering with a built‐in electric field enables tailoring of surface electronic structures, bridging electronic modulation with reaction kinetics for efficient energy conversion. Herein, we construct a Co‐doped V 2 O 3 /VN heterointerface (Co‐VN@V 2 O 3 ), wherein the synergistic interfacial effect optimizes water adsorption, dissociation, and hydrogen desorption, thereby conferring high activity for the alkaline hydrogen evolution reaction (HER). The catalyst also exhibits low overpotential and favorable kinetics toward hydrazine oxidation reaction (HzOR), enabling overall hydrazine splitting at a substantially reduced cell voltage. Furthermore, the outstanding HzOR performance allows a direct hydrazine fuel cell to drive the HER‐HzOR electrolyzer, and the system can be further extended to a solar‐driven configuration, underscoring its versatility in sustainable energy conversion. This work establishes heterointerface‐induced electronic modulation as a versatile strategy for bifunctional catalysis, thereby promoting sustainable hydrogen production within a closed‐loop energy cycle.