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

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Electrosynthesis of cyclohexanone oxime (CHO) is crucial for nylon-6 production.
• Current methods struggle with selective intermediate formation, limiting efficiency.
• Nitrite reduction coupled with cyclohexanone conversion offers a sustainable pathway.

Purpose of the Study:

• To develop a catalyst enabling efficient and selective electrosynthesis of cyclohexanone oxime (CHO).
• To investigate the role of Bi(III) sites in controlling reaction pathways.
• To design a stable catalyst interface for sustained performance.

Main Methods:

• Design and synthesis of a BiPO4/SiOx catalyst interface.
• Electrocatalytic experiments in an H-cell setup.
• Combined experimental and theoretical analyses (DFT) to elucidate reaction mechanisms.

Main Results:

• The BiPO4/SiOx catalyst achieved a high Faradaic efficiency (FE_CHO) of 77.0 ± 3.4% and a yield rate of 0.64 ± 0.01 mmol h⁻¹ cm⁻².
• Demonstrated nearly 100% carbon and nitrogen selectivity towards CHO.
• The catalyst retained 91.8% of its initial efficiency after extended cycling, outperforming pristine BiPO4.

Conclusions:

• Bi(III) sites are critical for promoting the desired *NH2OH pathway, avoiding undesired side reactions.
• The amorphous SiOx acts as an electron buffer, stabilizing Bi(III) active sites.
• The stabilized Bi(III) site effectively suppresses competing hydrogen evolution and over-hydrogenation, enabling efficient CHO electrosynthesis.