Stabilized Bi(III) Sites Direct *NH₂OH Pathway for Efficient Cyclohexanone Oxime Electrosynthesis.

Abstract

Coupling electrocatalytic nitrite reduction reaction (NO₂ ^-RR) with cyclohexanone conversion enables a sustainable route to cyclohexanone oxime (CHO) electrosynthesis, a key feedstock for the nylon-6 industry. However, this approach is fundamentally constrained by the difficulty of sustaining selective *NH₂OH intermediate formation. Here, we reveal for the first time that the Bi(III) sites can enable the catalytic system to efficiently follow the *NH₂OH pathway, avoiding the undesired *N pathway. Accordingly, a BiPO₄/SiO_x interface was designed in which amorphous SiO_x functions as an electron-buffer to stabilize Bi(III) active sites. As a result, the BiPO₄/SiO_x catalyst exhibits a high faradaic efficiency (FE_CHO) of 77.0 ± 3.4% and a CHO yield rate of 0.64 ± 0.01 mmol h^-1 cm^-2, surpassing all previously reported catalysts in H-cellMoreover, the BiPO₄/SiO_x catalyst delivers a nearly 100% carbon and nitrogen selectivity to CHO and retains 91.8% of its initial efficiency after extended cycling, substantially outperforming pristine BiPO₄. Combined experimental and theoretical analyses reveal that the stabilized Bi(III) site suppresses the formation of surface K⁺ H₂O, effectively suppressing competing hydrogen evolution and over hydrogenation, thereby enabling efficient CHO electrosynthesis.