Symmetrical Ionic Liquids Effectively Promote the Electrolytic Dimerization of Acrylonitrile to Adiponitrile

The electrochemical dimerization of acrylonitrile (AN) to adiponitrile (ADN) is an essential process for nylon-66 production, but this process still faces many challenges such as low energy conversion efficiency and poor selectivity. Herein, various ionic liquids (ILs) were used as electrolyte additives to evaluate their effects on the electrochemical dimerization of AN. The addition of IL significantly enhanced the performance of the electrolytic reaction and inhibited the hydrogen evolution reaction (HER). The electrolyte containing Tetrabutylphosphonium bromide (TBPB) showed the highest faraday efficiency of adiponitrile (FEADN) of 84.5% and excellent stability at an optimal current density of 200 mA cm–2. Molecular dynamics (MD) simulations revealed that TBPB was uniformly dispersed in the electrolyte and formed a “long brush” hydrophobic layer with appropriate wettability on the electrodes. Moreover, it was observed that ILs with a more symmetrical cationic structure exhibited a better hydrophobic layer effect, favoring the dimerization of AN to ADN.