In situ construction of Cu(I)-Cu(II) pairs for efficient electrocatalytic nitrate reduction reaction to ammonia

Electrocatalytic nitrate reduction reaction (NO3-RR) to ammonia under ambient conditions is expected to be a green process for ammonia synthesis and alleviate water pollution issues. We report a CuO nanoparticles incorporated on nitrogen-doped porous carbon (CuO@NC) catalyst for NO3-RR. Part of Cu(II) is reduced to Cu(I) during the NO3-RR process to construct Cu(I)-Cu(II) pairs, confirmed by in situ X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Density functional theory (DFT) calculations indicated that the formation of Cu(I) could provide a reaction path with smaller energy barrier for NO3-RR, while Cu(II) effectively suppressed the competition of hydrogen evolution reaction (HER). As a result, CuO@NC catalyst achieved a Faradaic efficiency of 84.2% at -0.49 V versus reversible hydrogen electrode (RHE), and a NH3 yield rate of 17.2 mg h-1 mgcat.-1 at -0.79 V vs. RHE, higher than the HaberBosch process (<3.4 g h-1 gcat.-1 ). This work may open a new avenue for effective NO3-RR by modulating oxidation states. (c) 2024 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights are reserved, including those for text and data mining, AI training, and similar technologies.