Electrocatalytic nitrate reduction reaction (NitRR) is an efficient route for simultaneous wastewater treatment and ammonia production, but the conversion of NO₃^– to NH₃ involves multiple electron and proton transfer processes and diverse by-products. Therefore, developing ammonia catalysts with superior catalytic activity and selectivity is an urgent task. The distinctive electronic structure of Cu enhances the adsorption of nitrogen-containing intermediates, but the insufficient activation capability of Cu for interfacial water restricts the generation of reactive hydrogen and inhibits the hydrogenation process. In this work, a Ce-doped CuO catalyst (Ce₁₀/CuO) was synthesized by in situ oxidative etching and annealing. The redox of Ce³⁺/Ce⁴⁺ enables the optimization of the electronic structure of the catalyst, and the presence of Ce³⁺ as a defect indicator introduces more oxygen vacancies. The results demonstrate that Ce₁₀/CuO provides an impressive ammonia yield of 3.88 ± 0.14 mmol·cm^–2·h^–1 at 0.4 V vs. reversible hydrogen electrode (RHE) with an increase of 1.04 mmol·cm^–2·h^–1 compared to that of pure CuO, and the Faradaic efficiencies (FE) reaches 93.2% ± 3.4%. In situ characterization confirms the doping of Ce facilitates the activation and dissociation of interfacial water, which promotes the production of active hydrogen and thus enhances the ammonia production efficiency.