Tuning NO coverage promotes ampere-level electrosynthesis of a nylon-6 precursor

The electrocatalytic synthesis of cyclohexanone oxime from NO and cyclohexanone with high Faradaic efficiency at ampere-level current density is highly desirable but highly challenging. Here, theoretical calculations reveal that NO coverage on the Ag catalyst plays a critical role in cyclohexanone oxime electrosynthesis. We then adjust the local NO concentration experimentally by tuning the NO concentration and reaction rate. We find that low NO coverage benefits NH ₃ formation, whereas high coverage delivers cyclohexanone oxime and N-2 (N ₂ O and N ₂ ) products. A mechanistic study indicates that with increasing NO coverage, the active sites transfer from bridge step sites to hollow terrace sites, which results in weaker adsorption of O* species, leading to the stable existence of the NH ₂ OH* intermediate rather than decomposing to form NH₃. However, N‒N coupling also easily occurs at high NO coverage. This mechanistic understanding further inspires us to develop a doping strategy to break the equivalent catalyst surface sites, which can inhibit NO–NO coupling at high NO coverage and thus realize high cyclohexanone oxime Faradaic efficiency at high current density. A Ru-doped Ag catalyst is thus developed, realizing 86% cyclohexanone oxime Faradaic efficiency at a current density of 1.0 A cm ^− 2 , far exceeding the reported performance.