Density Functional Theory‐Guided Design and Fabrication of Cu/g‐C ₃ N ₄ Single‐Atom Catalysts for Efficient Nitrate Reduction to Ammonia

The electrocatalytic reduction of nitrate (NO 3 ER) has emerged as a promising strategy for mitigating pollution in wastewater while concurrently producing value‐added ammonia; however, its process is significantly hindered by the lack of highly efficient and low‐cost electrocatalysts. Herein, we proposed several non‐noble single‐atom catalysts (SACs) anchored on graphitic carbon nitride (metal/g‐C 3 N 4 , where M = Mn, Fe, Co, Ni, and Cu) as promising candidates for catalyzing NO 3 ER. Using comprehensive density functional theory (DFT) computations, we identified the Cu/g‐C 3 N 4 candidate as a highly efficient catalyst for the to NH 3 conversion, exhibiting the lowest limiting potential (−0.64 V) among the catalysts examined, attributed to its optimal adsorption of the *NO 3 intermediate. Furthermore, we fabricated the metal‐N 4 catalysts using a facile solution‐based method. Consistent with our DFT results, the Cu/g‐C 3 N 4 exhibits excellent catalytic performance for NH 3 production, achieving a remarkable Faradaic efficiency of 92.4% and an outstanding NH 3 yield of 369.99 mmol g −1 h −1 at −0.6 V RHE, with excellent stability. Our work not only demonstrates a promising catalyst for NH 3 synthesis but also provides fundamental guidance for the future development of efficient SAC‐based electrocatalysts for nitrate reduction.