Efficient Hydrazine Electro‐Oxidation Achieved by Tailored Electron Injection into Fe (III) Sites Activating Dehydrogenation

Abstract Tailoring the d‐orbital electron of Fe (III) in oxyhydroxide is highly expected to realize an efficient hydrazine oxidation reaction (HzOR) for assisting seawater electrolysis. Although interface engineering can effectively change electron states on Fe sites by charge injection or extraction, most interfaces have a directional electric field for inaccessible regulation. Herein, the combination of iron oxyhydroxide and biphasic nickel phosphide is established to obtain a dual built‐in electric field (BEF) with opposite direction, which aims to manipulate the d‐orbital electron configuration of Fe (III) sites, thereby optimizing the binding strength and activating of N₂H₄ intermediates. Both computational and experimental analyses reveal that the moderate Fe─*N₂H₄ binding strength originating from tailored electron injection plays the key role in accelerating dehydrogenation. Impressively, such a promising promotion endows the catalyst with a remarkable HzOR activity, realizing working potentials of −8 and 44 mV for 10 and 100 mA cm⁻² in alkaline seawater, respectively, and achieving outstanding long‐term stability for over 100 h. H₂ production from a hybrid seawater electrolyzer (HSE) requires a dramatically low power consumption of 16.4 Wh L⁻¹ H₂ with ≈100% Faraday efficiency. It is believed that the work sheds new inspiration on d‐orbital regulation for obtaining advanced HzOR electrocatalysts.