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

Adipic acid is an important building block of polymers, although its production relies on harmful reagents. Here, authors examined surfactant-modified nickel hydroxide for adipic acid electrosynthesis coupled with hydrogen gas evolution. 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 H-2 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 H-2 production, attaining adipic acid productivity of 4.7 mmol coupled with H-2 productivity of 8.0 L at 0.8 A (corresponding to 30 mA cm(-2)) in 24 h.

Automated summary

In this study, surfactant-modified nickel hydroxide catalyst was used for electrosynthesis of adipic acid and hydrogen gas. The strategy achieved higher productivity of adipic acid and higher faradaic efficiency compared to pure nickel hydroxide catalyst in aqueous medium, by facilitating enrichment of immiscible cyclohexanone.