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

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 NH₃ yield and Faradaic efficiency (FE). Herein, we report the synthesis and performance of a Cu₂O/Cu(OH)₂@Ni(OH)₂ heterostructure catalyst. The interface exploits strong electronic interactions between Cu and Ni species, promoting efficient NO₃ ^- adsorption and accelerating in situ water dissociation for hydrogenation steps. In an H-cell, the catalyst achieved an FE of 99.6 % with an NH₃ 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 NO₃ ^- adsorption and accelerate in situ water dissociation for hydrogenation steps. When integrated as a cathode into a Zn-NO₃ ^- 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 NH₃ with 93.6 % FE and exhibited robust stability (<2 % voltage decay over 24 h).