A Cationic Redox‐Active Interface Couples Nitrate Enrichment With Hydroxylamine Release for Cyclohexanone Oxime Electrosynthesis

ABSTRACT

Electrosynthesis of cyclohexanone oxime (CYCO), a key nylon‐6 precursor, is limited by the poor selectivity of nitrate reduction toward hydroxylamine because surface‐bound NH ₂ OH can be over‐reduced to NH ₃ before coupling with cyclohexanone. Herein, we construct a thionine acetate (Th) modified Cu ₂ O interface (Th/Cu ₂ O) that integrates electrostatic steering with redox‐mediated electron transfer. Under weakly acidic conditions, protonated Th creates a positively charged interfacial microenvironment that enriches NO ₃ ⁻ , stabilizes early reduction intermediates, and promotes the release of protonated NH ₂ OH (NH ₃ OH ⁺ ) from the inner Helmholtz layer. Concurrently, the redox activity of Th facilitates electron delivery to Cu active sites and favors the NH ₂ OH‐forming pathway over further reduction to NH ₃ . At −0.35 V vs. RHE, Th/Cu ₂ O achieves a Faradaic efficiency (FE) of 82.14% for NH ₂ OH, with nearly 100% selectivity toward CYCO. In a membrane‐separated flow cell operated at 1.2 A, the CYCO production rate reaches 57.63 g h ⁻¹ g _cat. ⁻¹ , demonstrating the industrial potential of Th/Cu ₂ O for gram‐scale CYCO synthesis. In situ characterization, molecular dynamics simulations, and density functional theory calculations collectively connect interfacial charge regulation, mass transport, and reaction energetics, establishing a molecular‐level interfacial strategy for universal oxime electrochemical synthesis.