Electrocatalytic synthesis of adipic acid coupled with H₂ production enhanced by a ligand modification strategy

Adipic acid is an important building block of polymers, and is commercially produced by thermo-catalytic oxidation of ketone-alcohol oil (a mixture of cyclohexanol and cyclohexanone). However, this process heavily relies on the use of corrosive nitric acid while releases nitrous oxide as a potent greenhouse gas. Herein, we report an electrocatalytic strategy for the oxidation of cyclohexanone to adipic acid coupled with H₂ production over a nickel hydroxide (Ni(OH)₂) catalyst modified with sodium dodecyl sulfonate (SDS). The intercalated SDS facilitates the enrichment of immiscible cyclohexanone in aqueous medium, thus achieving 3.6-fold greater productivity of adipic acid and higher faradaic efficiency (FE) compared with pure Ni(OH)₂ (93% versus 56%). This strategy is demonstrated effective for a variety of immiscible aldehydes and ketones in aqueous solution. Furthermore, we design a realistic two-electrode flow electrolyzer for electrooxidation of cyclohexanone coupling with H₂ production, attaining adipic acid productivity of 4.7 mmol coupled with H₂ productivity of 8.0 L at 0.8 A (corresponding to 30 mA cm⁻²) in 24 h.

Zhenhua Li, Xiaofan Li, Hua Zhou, Yan Xu, Si-Min Xu, Yue Ren, Yifan Yan, Jiangrong Yang, Kaiyue Ji, Li Li, Ming Xu, Mingfei Shao, Xianggui Kong, Xiaoming Sun, Haohong Duan