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

ABSTRACT 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.