Acrylonitrile Conversion on Metal Cathodes: How Surface Adsorption Determines the Reduction Pathways

Electrochemical dimerization of acrylonitrile (AN) on metal cathodes is a simple and green method for manufacturing adiponitrile (ADN), the raw material for nylon 66. However, the current controversial mechanisms hinder the development of more active catalysts. Here, from a combination of experiments and theoretical calculations, we found that the production rate of ADN and byproducts is highly related to the surface adsorption state. High ADN selectivity is obtained only when the surface is mainly covered by AN. Substitution of AN with hydrogen will promote surface hydrogenation to form propionitrile (PN), and a full coverage of hydrogen exclusively leads to hydrogen evolution. An H/D isotopic experiment revealed that the hydrogen adsorbed on an electrode mainly participates in the saturation of AN to PN, while the proton in an aqueous phase contributes to the dimerization of AN to ADN. These results can provide certain guidance for catalyst design of an AN electroreduction reaction.