A cyanide-free route towards the electrosynthesis of nitriles.

Abstract

The manufacture of nitriles is critical to various industrial applications, but poor selectivity results in the significant release of pollutive byproducts such as CO₂, NO_x and toxic cyanide. Here, we report the electrochemical conversion of benzaldehyde to benzonitrile at near-unity selectivity, during which Co₃O₄ clusters-decorated Cu_xO electrocatalyst activates the C-N bond of an unstable intermediate species. Operando spectroelectrochemical studies and theoretical calculations reveal that benzaldehyde couples with NH₃ to form the phenylmethanimine intermediate bound atop Cu²⁺ active sites, which facilitates hydrogen transfer from the imine group to nearby surface oxygen. Our electrochemical system can convert aromatic and aliphatic aldehydes to the corresponding nitriles at Faradaic efficiencies of 78-97%. This can be paired with cathodic NO_x reduction, which produces a commensurable amount of NH₃ to that consumed even at a current density of 200 mA cm^-2. Our work offers a clean synthetic route to otherwise-pollutive chemicals, and also expands the repertoire of organonitrogen compounds that can be accessed by electrocatalysis.