Electronic Interaction at Cu–O–Ni Heterointerface Promotes Electrocatalytic Nitrate Reduction to Ammonia and Zinc‐Nitrate Battery

ABSTRACT Electrochemical nitrate‐to‐ammonia conversion powered by sustainable green electricity is a promising supplement to the traditional Haber–Bosch process, but it remains limited by low NH 3 yield and Faradaic efficiency (FE). Herein, we report the synthesis and performance of a Cu 2 O/Cu(OH) 2 @Ni(OH) 2 heterostructure catalyst. The interface exploits strong electronic interactions between Cu and Ni species, promoting efficient NO 3 − adsorption and accelerating in situ water dissociation for hydrogenation steps. In an H‐cell, the catalyst achieved an FE of 99.6 % with an NH 3 yield of 1.14 mmol h −1 mg cat −1 , while a flow electrolyzer maintained 97.9 % efficiency and 17.13 mmol h −1 mg cat −1 at −600 mA cm −2 . Via density functional theory (DFT) calculations and in situ characterization, the interface uses strong Cu–O–Ni electronic interactions to boost efficient NO 3 − adsorption and accelerate in situ water dissociation for hydrogenation steps. When integrated as a cathode into a Zn‐NO 3 − hybrid battery, the material served as a high‐performance cathode. The resulting battery's open‐circuit voltage reached 1.45 V, while its power density peaked at 6.47 mW cm −2 . The integrated device continuously produced 2.78 mg h −1 cm −2 of NH 3 with 93.6 % FE and exhibited robust stability (