Stabilization of Electron‐Deficient Cu₁^δ+ 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 (NO₃⁻RR) to produce ammonia (NH₃), but their industrial application is hindered by their inadequate NH₃ yields and long‐term stability. Herein, a novel catalyst is constructed of electron‐deficient single Cu atoms (Cu₁^δ+ (1 <δ <2)) anchored on oxygen vacancy (Ov)‐enriched hierarchical porous Cl–doped CeO₂ matrix hybridized by carbon (Cu₁/Cl–CeO₂@C) via electrochemical reconstruction of Cu₁/CeOCl@C for efficient NO₃⁻RR‐to‐NH₃. The optimized Cu₁/Cl–CeO₂@C shows a large NH₃ 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 NH₃ FE of >95% for 2500 h at −300 mA cm⁻², enabling NH₃ production at a 20‐g scale (20.277 g). Combination of experimental studies and theoretical calculations demonstrates that the electronic structure of Cu₁^δ+ species can be regulated and stabilized by Cl dopant and Ce³⁺/Ov in Cu₁/Cl–CeO₂@C via their electronic interactions. The Cu₁^δ+ with a moderate electron‐deficient state promotes the adsorption of NO₃⁻, the production of active hydrogen, and the hydrogenation of intermediates, thereby lowering reaction energy barriers, suppressing side reactions, and boosting electrocatalytic NO₃⁻RR‐to‐NH₃ conversion.