Enzyme‐Inspired Molecular Design Unlocks Efficient and Selective Ammonia Electrosynthesis From Nitrate in Water

Abstract

ABSTRACT Ammonia is a vital feedstock and emerging carbon‐free energy carrier, yet its industrial synthesis via Haber–Bosch process remains highly energy‐ and carbon‐intensive. Electrochemical nitrate reduction (eNO 3 RR) offers a sustainable alternative; however, achieving high selectivity via this pathway necessitates efficient proton management at the catalytic site. Here, we report a family of cobaloxime complexes ( C1–C14 ) incorporating diverse outer coordination sphere (OCS) functionalities that act as enzyme‐inspired proton relays. These electrocatalysts enable complete 8e − /10H + conversion of nitrate () exclusively to ammonium () under near‐neutral aqueous conditions, with the adenosine‐functionalized derivative ( C13 ) achieving a rate of 22.5 mmol.cm −2 .hr −1 . mmol cat − 1 with ∼83% Faradaic efficiency. Mechanistic studies combining in situ Raman spectroscopy, isotopic labelling, 2D NMR, and buffer‐dependent kinetics reveal a stepwise nitrate‐to‐ammonia conversion via metal‐bound intermediates, directed by cooperative intra‐ and intermolecular proton relays. The catalysts operate homogeneously, without electrode deposition or molecular structure decomposition, during eNO 3 RR. These results establish OCS engineering as a powerful strategy for functionally mimicking enzymatic architectures in selective ammonia electrosynthesis via a sustainable eNO 3 RR pathway.