Stabilization of Electron‐Deficient Cu1δ+ Species by Cl–Doped CeO2 Constructed via Electrochemical Reconstruction for Electroreduction of Nitrate to Ammonia Over 2500 Hours

Abstract Copper (Cu)‐based catalysts have been widely used for electrochemical nitrate reduction reaction (NO 3 − RR) to produce ammonia (NH 3 ), but their industrial application is hindered by their inadequate NH 3 yields and long‐term stability. Herein, a novel catalyst is constructed of electron‐deficient single Cu atoms (Cu 1 δ+ (1 <δ <2)) anchored on oxygen vacancy (Ov)‐enriched hierarchical porous Cl–doped CeO 2 matrix hybridized by carbon (Cu 1 /Cl–CeO 2 @C) via electrochemical reconstruction of Cu 1 /CeOCl@C for efficient NO 3 − RR‐to‐NH 3 . The optimized Cu 1 /Cl–CeO 2 @C shows a large NH 3 yield rate of 9.528 ± 0.174 mg NH3 h −1 cm −2 , a high Faraday efficiency (FE) of 98.8 ± 2.13%, and superior cycling stability for 58 h at −0.5 V versus the reversible hydrogen electrode. Impressively, it can maintain a high NH 3 FE of >95% for 2500 h at −300 mA cm −2 , enabling NH 3 production at a 20‐g scale (20.277 g). Combination of experimental studies and theoretical calculations demonstrates that the electronic structure of Cu 1 δ+ species can be regulated and stabilized by Cl dopant and Ce 3+ /Ov in Cu 1 /Cl–CeO 2 @C via their electronic interactions. The Cu 1 δ+ with a moderate electron‐deficient state promotes the adsorption of NO 3 − , the production of active hydrogen, and the hydrogenation of intermediates, thereby lowering reaction energy barriers, suppressing side reactions, and boosting electrocatalytic NO 3 − RR‐to‐NH 3 conversion.