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High-Rate, Selective Electrosynthesis of Cyclohexanone Oxime via In Situ Generation and Release of Hydroxylamine on Bismuth

Year: 2026

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Oxime compounds are key industrial intermediates for nylon precursors and commodity chemicals. However, conventional routes rely on multistep reactions and hydroxylamine (NH 2 OH) salts, raising significant safety and sustainability concerns. Although electrosynthesis offers an alternative, oxime formation on d -block transition metals suffers from poor selectivity, as nitrogen oxyanion intermediates bind strongly to the surface and are readily over-reduced to ammonia. Here, we report morphology-controlled p -block bismuth rhombic dodecahedra (Bi RDs) that promote in situ NH 2 OH generation and its desorption into the electrolyte, enabling an electrochemical-chemical decoupled route for cyclohexanone oxime (CHO) synthesis. Bi RDs deliver nearly 100% Faradaic efficiency (FE) at −0.5 V vs. RHE and a yield of 1.4 mmol h –1 cm –2 at −0.9 V vs. RHE in an H-cell, while maintaining a CHO selectivity of nearly 100% at 100 mA cm –2 in a flow cell. Under identical conditions, d -block electrodes (Cu, Pd, Ag) show FE below 30%. Density functional theory calculations reveal that Bi 6 p orbital-derived surface states weaken intermediate binding and facilitate NH 2 OH desorption, suppressing over-reduction. Kinetic analysis, post-addition trapping experiments, and in situ ATR-FTIR and Raman spectroscopy suggest the following reaction mechanism: NH 2 OH is selectively generated at the electrode surface, released as a freely diffusing intermediate, and undergoes homogeneous condensation with cyclohexanone in the bulk electrolyte, bypassing the surface-confined Langmuir–Hinshelwood pathway. These findings demonstrate that regulating intermediate desorption through p -block orbital chemistry provides a general strategy for achieving high selectivity in electro-organic nitrogen synthesis.

Source: Journal of the American Chemical Society

DOI: 10.1021/jacs.6c05163