A Two‐Step Electrochemical Conversion of Nitric Oxide to Ammonia on Defective Copper Foam Catalyst

Abstract The electrochemical reduction of nitrogen oxides (NO x ) and nitrates (NO 3 − ) to ammonia (NH 3 ) has recently gained interest due to its potential to replace the energy intensive Haber–Bosch process, which requires high temperatures and pressures. In this study, we synthesized a highly porous reduced copper foam enriched with oxygen vacancies and evaluated its performance in both batch (H‐cell) and flow cell configurations for nitrate reduction. The catalyst achieved an impressive NH 3 yield of 162 mg/h cm 2 in the H‐cell and 183 mg/h cm 2 in the flow cell, with a maximum Faradaic efficiency of 95.6% in 0.1 M NO 3 − electrolyte. The enhanced activity is attributed to the increased number of active sites formed via electrochemical reduction of copper oxide. Additionally, we demonstrated a proof‐of‐concept approach for synthesizing nitrate from gaseous NO via chlorine‐ and oxygen‐mediated electrochemical oxidation. The resulting nitrate was subsequently used for ammonia production, completing a two‐step conversion of NO to NH 3 . The synthesized ammonia was effectively recovered by argon stripping and crystallized as ammonium chloride (NH 4 Cl), a stable compound that has direct applications in fertilizers, pharmaceuticals, and battery systems. This work presents a sustainable and scalable strategy for ammonia production from nitrogen oxides, offering a potential pathway toward decentralized, green ammonia synthesis.