Copper–nickel–MOF/nickel foam catalysts grown in situ for efficient electrochemical nitrate reduction to ammonia

Reducing nitrate (NO3−) in an aqueous solution to ammonia under ambient conditions can provide a green and sustainable NH3‐synthesis technology and mitigate global energy and pollution issues. In this work, a CuNi0.75–1,3,5‐benzenetricarboxylic acid/nickel foam (CuNi0.75–MOF/NF) catalyst grown in situ was prepared via a one‐pot method as an efficient cathode material for electrocatalytic nitrate reduction reaction (NO3RR). The CuNi0.75–MOF/NF catalyst exhibited excellent electrocatalytic NO3RR performance at −1.0 V versus a reversible hydrogen electrode, achieving an outstanding faradaic efficiency of 95.88 % and an NH3 yield of 51.78 mg h−1 cm−2. The 15N isotope labeling experiments confirmed that the sole source of N in the electrocatalytic NO3RR was the NO3− in the electrolyte. The reaction pathway for the electrocatalytic NO3RR was derived by in situ Fourier transform infrared spectroscopy and in situ differential electrochemical mass spectrometry. Density functional theory calculations revealed that the Ni element in the CuNi0.75–MOF/NF catalyst had excellent O–H activation ability and strong *H adsorption capacity. These *H species were transferred from the Ni sites to the *NO adsorption intermediates located on the Cu sites, providing a continuous supply of *H to Cu, thereby promoting the formation of *NOH intermediates and enhancing the hydrogenation process of the electrocatalytic NO3RR. [Display omitted] •The proposed catalyst serves as an efficient cathode material for the NO3RR.•The reaction pathway for the NO3RR is derived from in situ infrared spectroscopy and electrochemical mass spectrometry.•The synergy of Ni and Cu sites in the catalyst increases *NOH formation and enhances hydrogenation rates in the NO3RR process.