Stabilization of Electron‐Deficient Cu 1 δ+ Species by Cl–Doped CeO 2 Constructed via Electrochemical Reconstruction for Electroreduction of Nitrate to Ammonia Over 2500 Hours

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.