Selective Electrosynthesis of a Nylon-6 Precursor via Facet-Promoted NO*-to-NHO* Conversion

The electrosynthesis of cyclohexanone oxime (CHO) from NO is significant but suffers from low Faradaic efficiency (FE) due to the severe competitive NO*-NO* coupling at high NO concentrations. Here, a facet-regulation strategy is proposed to accelerate the NO hydrogenation process and inhibit NO*-NO* coupling. As a result, the Ag nanocubes with {100} surfaces exhibit an 86.5% FE, a 4.45 mmol h^-1 cm^-2 yield rate, and a 358 mA cm^-2 CHO partial current density, outperforming Ag nanohexahedrons with exposed {111} surfaces. Experimental and theoretical research has shown that stronger NO and H₂O adsorption and lower thermodynamic and kinetic barriers of hydrogenation of NO* to NHO* over the {100} surface promote hydrogenation of NO* to NHO*, the key step that determines the CHO or NO*-NO* coupling products. Thus, NO*-NO* coupling is restrained, and a high CHO FE is achieved on Ag with a {100} surface.