Strong metal–support interaction-engineered Cu/LaO x interfaces for selective electrocatalytic nitrate reduction to ammonia

Electrocatalytic nitrate reduction offers a promising route for removing nitrate contaminants from water while recovering nitrogen as ammonia, but its practical efficiency is limited by sluggish nitrate activation and competing hydrogen evolution. Herein, we report a strong metal–support interaction-engineered Cu/LaOx catalyst for selective nitrate-to-ammonia conversion. The optimized Cu/LaOx interface was constructed by regulating the Cu/LaOx ratio, where LaOx partially encapsulates Cu sites and induces interfacial La–O–Cu bonding, oxygen vacancies, and electronic redistribution around Cu centres. These interfacial features enhance nitrate adsorption, accelerate deoxygenation, and facilitate subsequent hydrogenation steps. As a result, the optimized 1:1Cu/LaOx-3DOMC catalyst achieves a high ammonia yield rate of 0.8961 mmol h−1 cm−2 and a Faradaic efficiency of 94.5% at −0.64 V versus reversible hydrogen electrode, markedly outperforming the LaOx-free Cu catalyst. Electrochemical analysis further reveal enhanced nitrate reduction current response, increased electrochemically active surface area, and reduced charge-transfer resistance. In situ Fourier transform infrared spectroscopy and density functional theory calculations confirm that Cu/LaOx interfacial coupling promotes *H-assisted nitrate deoxygenation and *NO hydrogenation while suppressing the competing hydrogen evolution reaction. This work demonstrates that strong metal–support interaction engineering is an effective strategy for coupling electrocatalytic nitrate removal with nitrogen resource recovery from contaminated water.