Ag Single Atoms Boosting Water Dissociation on Cu Nanowires for Efficient H ^* ‐Mediated Nitrate Reduction at Ultra‐Low Concentrations With Ammonia Recovery

Abstract Electrocatalytic nitrate reduction to ammonia (NO ₃ RR) enables sustainable conversion of nitrate into valuable NH ₃ . However, under neutral conditions at low nitrate concentrations (≤50 mg L ⁻¹ ), general‐purpose catalysts suffer from inefficient electron transport and a dominant competing hydrogen evolution reaction (HER). Concurrently, effective ammonia recovery at low nitrate concentrations remains challenging and is critical for preventing secondary environmental contamination. Herein, Cu nanowires uniformly doped with Ag single atoms (Ag _SA ‐Cu NWs) are engineered to enhance low‐concentration NO ₃ ⁻ adsorption and conversion at the electrode surface, leveraging Ag's dual role in accelerating H ₂ O dissociation and strengthening affinity toward key intermediates. The Ag _SA ‐Cu NWs achieve an exceptional Faradaic efficiency for NH ₃ (FE _NH3 ) of 95.45% and a high of 2564.7 µg h ⁻¹ cm ⁻² with 50 mg L ⁻¹ NO ₃ ⁻ . Remarkably, even at ultra‐low concentrations (15 mg L ⁻¹ ), it maintains 86.24% FE _NH3 and 1005.43 µg h ⁻¹ cm ⁻² NH ₃ yield rate. Furthermore, nitrate removal is integrated with in situ ammonia recovery by designing a dual‐loop system. This device achieves near‐complete total nitrogen removal (≈100%) and a 94.77% ammonia recovery rate, successfully yielding high‐purity NH ₄ Cl powder. The corresponding cost is reduced to 0.78 USD kg _N ⁻¹ . This work demonstrated the promising potential of self‐supported electrodes for efficient low‐concentration NO ₃ RR in neutral environments.