Boosting Hydrogenation Activity of Cu ₂ O via Surface Engineering for Efficient Conversion of Nitrate to Ammonia

Abstract Electrochemical reduction of nitrate to ammonia (NO 3 – RR) has recently emerged as a promising strategy for simultaneous nitrate removal and sustainable ammonia production. Copper‐based catalysts are particularly effective for this reaction due to their strong affinity for nitrate. However, their performance is often limited by insufficient hydrogenation activity and the accumulation of nitrite byproducts, which suppresses the ammonia yield. In this work, we employed a surface engineering of polyaniline (PANI) coating to enhance the hydrogenation activity of Cu 2 O. The PANI‐coated Cu 2 O exhibits noticeable higher NO 3 – RR activity than the pristine Cu 2 O, with a nitrate conversion rate of 99.08% at a low applied potential of −0.2 V (versus RHE). Advanced spectroscopy shows that the polyaniline coating promotes the efficient utilization of reactive hydrogen, which accelerates the conversion of nitrite into ammonia and improves reaction kinetics. A techno‐economic assessment confirms the practical potential of this approach, estimating a profit of $0.124/ kilogram of product. This study demonstrates how surface engineering can enhance reaction kinetics and provides valuable insights for other hydrogenation reactions in environmental and energy applications.