Electrochemical conversion of KA oil by indium tin oxide nanospheres and nanocubes

Abstract

Efficient conversion of KA oil (a mixture of cyclohexanone and cyclohexanol) to adipic acid (AA) holds great significance. Herein, indium tin oxide (ITO) nanospheres and nanocubes were synthesized for electrochemical conversion of KA oil. The catalytic performance of the samples was comparatively evaluated by cyclic voltammetry, linear sweep voltammetry and chronoamperometric tests. The products of KA oil oxidation were analyzed by high performance liquid chromatography (HPLC). Of the two samples, spherical ITO nanoparticles (ITO-ball) exhibited superior electrochemical activity owing to its larger specific surface area while cubic ITO nanoparticles (ITO-cube) showed better intrinsic activity. In addition, ITO-ball exhibited superior oxygen evolution reaction suppression during KA oil oxidation. HPLC results indicated that ITO-ball demonstrated superior AA selectivity (11.6%) and faradaic efficiency (78.5%) after 5-hour electrolysis. Open circuit potential and double layer capacitance measurements demonstrated that the adsorption capacity of KA oil over ITO-ball is greater than that over ITO-cube. Operando electrochemical impedance spectroscopy results suggested that ITO-ball can effectively accelerate the mass transfer process compared with ITO-cube, thereby promoting the catalytic kinetics of KA oil oxidation.