Efficient and selective electrosynthesis of adiponitrile by electrohydrodimerization of acrylonitrile over a bismuth nanosheet modified electrode

Abstract

Conventional production of adiponitrile (ADN), an important chemical in energy storage devices and the nylon industry, is mainly by hydrocyanation of butadiene, which requires multiple reaction steps, energy-intensive conditions, and the use of toxic hydrogen cyanide. Electrosynthesis of ADN via the electrohydrodimerization of acrylonitrile (EHD-AN) with water as the proton source serves as a less energy-intensive and green synthetic alternative to hydrocyanation of butadiene, but the cathode materials used in the EHD-AN process are limited to highly toxic heavy metals (e.g., Cd, Pb). To mitigate the environmental impact of heavy metal pollution, the exploration of high-performance cathode materials with low toxicity is, therefore, of great importance. Herein, we report on a bismuth-modified electrode, prepared by facile electrochemical deposition, as an efficient and robust electrocatalyst towards the electrosynthesis of ADN. The effects of electrode preparation conditions (e.g., charge passage, use of a nanostructured template) and the electrosynthetic conditions (e.g., concentration of quaternary alkyl ammonium salt, AN concentration, electrolyte pH, applied potential) on the electrocatalytic performance of the bismuth-modified electrodes were thoroughly studied through a series of controlled-potential electrolysis (CPEs). Under optimal conditions, the bismuth nanosheet modified electrode (nanoBi) was demonstrated, for the first time, to exhibit a remarkably high selectivity (81.21 ± 1.96%), ADN generation rate (1.28 ± 0.20 mmol cm⁻² h⁻¹), and activity, in terms of turnover frequency based on the electrochemically accessible amount of metal species (1.65 ± 0.01 s⁻¹) at a moderate potential of −1.03 V vs. RHE, which makes bismuth a promising alternative to the toxic electrode materials currently used in industrial ADN production. Besides, the developed nanoBi electrode is immune to electricity fluctuation, which enables its integration with renewable and green electricity sources for the low-carbon footprint production of ADN. Finally, the scale-up electrosynthesis of ADN at an industrially relevant current density using a divided flow-type electrolyzer was also demonstrated.