Ultrathin MOF Nanosheet Catalyzes Spatiotemporal Synchronized Electroreduction of Nitrate‐to‐Ammonia

ABSTRACT The electrochemical nitrate reduction reaction (e‐NO 3 RR) is a green pathway for ammonia synthesis with subsequent recovery of the nitrogen cycle. However, kinetics under neutral pH conditions is challenging since water dissociation becomes slow and inadequate active hydrogen ( * H) species to participate. The study systematically designs an atomically precise dual‐site catalyst by engineering Ru single atoms supported on ultrathin nanosheets of cobalt‐based metal‐organic frameworks (MOFs). According to kinetic isotope effects (KIEs) evaluation, hard‐soft acid‐based (HSAB) poisoning tests, and in situ spectroscopic analysis, Ru single atom sites serve as efficient proton pumps lowering significantly the barrier for water dissociation. The produced * H species are transferred to adjacent oxygen‐bridged cobalt sites, facilitating the hydrogenation as well as deoxygenation processes of N─O. The proximity of these atoms has a combined effect that reduces the gap in rate between nitrate reduction and proton supply, yielding a faradaic efficiency of ca. 97% and an ammonia production rate of 562.44 µmol h −1 cm −2 . This study not only fixes the age‐old “hydrogen lack” problem in neutral e‐NO 3 RR but also gives an atom‐level view into the two‐site electron–proton transfer link, thus setting up a general design model for working active sites in complex many‐electron electrocatalytic steps.