Electrifying Adipic Acid Production: Copper‐Promoted Oxidation and C−C Cleavage of Cyclohexanol

• Published in: Angewandte Chemie International Edition 2022-12, Vol.61 (50), p.e202214977-n/a
• Main Authors: Wang, Ran, Kang, Yikun, Wu, Jianxiang, Jiang, Tao, Wang, Yongjie, Gu, Limin, Li, Yefei, Yang, Xuejing, Liu, Zhipan, Gong, Ming
• Format: Article
• Language: English
• Subjects: Acid production; Adipic Acid; Cleavage; Copper; Cyclohexanol; Cyclohexanone; C−C Cleavage; Electrocatalysis; Electroreforming; Hydroxylation; Oxidation; Polymers; Radical; Selectivity; Spectroscopy
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202214977

Adipic acid is a central platform molecule for the polymer industry. Production of adipic acid with electroreforming technology is more sustainable compared to the thermochemical synthesis route. We discovered that incorporation of Cu2+ into a Ni hydroxide lattice significantly improved the electrocatalytic oxidation of cyclohexanol into adipate with a high yield (84 %) and selectivity (87 %). This Cu promotion effect serves as a mechanistic probe that can be combined with product analysis, steady‐state kinetics, and in situ spectroscopy. A two‐electron oxidation into cyclohexanone first occurs, followed by consecutive hydroxylation and C−C cleavage before dione formation. The central role of Cu2+ is to weaken the interaction between the NiOOH and surface‐adsorbed O‐centered radical that facilitates subsequent C−C cleavage. This enables a highly efficient two‐electrode system capable of electroreforming KA oil into adipate and pure H2. Efficient electrocatalytic oxidation of cyclohexanol into adipate was achieved by incorporating copper into a nickel hydroxide electrode. Cu2+ plays a key role in weakening the interaction between the surface‐adsorbed O‐centered radical and the NiOOH surface, thereby facilitating C−C cleavage.