Spontaneous Chemical Amine Oxidation in Organic Solvents Paired With Electrochemical Hydrogen Production

Benzonitrile (BN) is a versatile chemical building block extensively applied across multiple sectors. Electrochemical benzylamine oxidation reaction (BOR) provides a sustainable method for BN synthesis, simultaneously enabling H₂ fuel generation via hydrogen evolution reaction (HER). Alkaline electrolytes are commonly used to reduce the BOR overpotential but promote the hydrolytic decomposition of benzylimine intermediates and BN products, contributing to significant carbon loss. These side reactions become more pronounced under industrially relevant conditions (>50 mM). In this study, redox reservoirs (RRs) were employed to decouple BOR from HER, allowing their independent operation. Utilizing a highly positive formal potential, RRs facilitated spontaneous BOR in hexane, effectively circumventing hydrolysis issues and simplifying the product purification. Furthermore, NiOOH species within RRs functioned as reactive sites with strong affinity toward benzylamine (BA) and negligible self-reduction, thereby achieving high BN yield and Faradaic efficiency even at BA concentrations exceeding 100 mM. To further demonstrate the versatility, BA derivatives bearing various functional groups were also tested, all of which were successfully converted into their corresponding nitriles. These results highlight the flexibility of RR system to accommodate diverse substrates and meet specific market demands.