Electrocatalytic reduction of nitrate (NO₃⁻) is considered a promising approach for nitrogen recycling and environmental protection, as NO₃⁻ is one of the most prevalent pollutants in surface water and underground aquifers. Currently, significant efforts have been directed toward converting NO₃⁻ into ammonia (NH₃), but NH₃ has relatively low economic value. Therefore, exploring alternative reactions for high-value-added chemical production through electrocatalytic NO₃⁻ reduction is highly desirable. The electroreduction of NO₃⁻ to NH₃ involves an eight-electron process and generates various intermediates such as NO₂⁻, hydroxylamine (NH₂OH), and diamine (N₂H₄). Utilizing these intermediates to produce more valuable organonitrogen compounds through C–N coupling represents a promising approach to expand the range of products and save energy.

Abstract Figure:Electrosynthesis of the Nylon-6 Precursor from Nitrate and Cyclohexanone over a Rutile TiO2 Catalyst

Herein, we present an electrochemical strategy for synthesizing cyclohexanone oxime (CHO), an important feedstock in nylon-6 production through hydrogenative coupling of NO₃⁻ and cyclohexanone (CYC) using a rutile titanium dioxide (R-TiO₂) catalyst under ambient conditions. The CHO productivity achieved 127.3 μmol cm⁻² h⁻¹ with a high Faradaic efficiency (FE) of 68.2% at a current density of 30 mA cm⁻². Moreover, the yield of CHO reached 98.2%.Additionally, we revealed that R-TiO₂ exhibited a superior scaling relation with a high NH₂OH generation rate and excellent CYC adsorption ability, which promoted CHO production. This electrochemical strategy was also effective for the synthesis of different oximes. Finally, we designed a coupling reaction system to realize the simultaneous production of CHO and CYC by combining cathodic NO₃⁻ reduction and anodic cyclohexane oxidation, demonstrating a greener and more economical approach.

 

https://doi.org/10.31635/ccschem.024.202403988