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

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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.

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