Engineering the Electrochemical Interface With Polyborate for High-Selectivity Adiponitrile Electrosynthesis

The electrochemical dimerization of acrylonitrile (AN) to adiponitrile (ADN) offers a sustainable pathway for producing Nylon-66 precursors. However, its efficiency is severely limited by competitive hydrogen evolution, often demanding toxic heavy metals and non-electrochemical hydrolysis induced by local pH changes. Herein, we report that concentrated borate electrolytes dramatically improve the electrosynthesis of ADN, achieving approximately 90% selectivity and 77.9% Faradaic efficiency on non-toxic graphite electrodes. Through a combination of in situ spectroscopies (Raman and ATR-SEIRAS) and ^{1 1}B NMR analysis, we demonstrate that polyborate species formed at high concentrations play a critical role. These species not only act as effective buffers that stabilize the local pH to suppress the formation of 3-hydroxypropionitrile (3-HPN) but also promote the formation of moderately hydrogen-bonded water molecules that serve as efficient proton donors to accelerate the charge transfer required for the AN-to-ADN transition. This poly-borate species not only enables efficient and selective ADN production on low-cost and non-toxic graphite electrodes but also elucidates how electrolyte speciation regulates the interfacial microenvironment toward high-performance organic electrosynthesis.