In Situ Dynamic Reconstruction of Co ₃ Mo Electrocatalyst for Efficient Nitrate Reduction to Ammonia

ABSTRACT Electrochemical nitrate reduction (NO ₃ RR) provides a promising route for ammonia production, yet its large‐scale application is limited by slow multi‐proton/electron transfer kinetics. In this work, a low‐cost, stable Co ₃ Mo electrocatalyst is engineered through a tandem reconstruction–chemical activation strategy to regulate interfacial NO ₃ ⁻ and H ₂ O behavior, enabling efficient nitrate hydrogenation to ammonia at an ultralow potential. The Co ₃ Mo catalyst achieves an onset potential of only +0.27 V vs. RHE, along with a Faradaic efficiency exceeding 95% and an ammonia yield rate of 5.86 mmol h ⁻¹ cm ⁻² at −0.4 V vs. RHE. In situ experiments and theoretical investigations elucidate the dynamic reconstruction of Co ₃ Mo for enhanced NO ₃ RR performance, where Co sites enhance NO ₃ ⁻ to NO ₂ ⁻ conversion via surface hydroxylation, while Mo sites facilitate active hydrogen ( ^* H) formation on the Co ₃ Mo (200) plane, promoting hydrogenation of nitrogen intermediates. The generated ammonia is upconverted into ammonium formate via integrated electrolysis, coupling cathodic NO ₃ RR with anodic formaldehyde oxidation (FOR). The flow cell achieves current densities of 250 and 500 mA cm ⁻² at ultralow voltages of 0.31 and 0.53 V, respectively, with ammonium formate collection efficiencies above 73.9%. This work presents an effective reconstruction strategy to enhance NO ₃ RR performance and advance its practical commercialization.