Identifying Mechanisms and Challenges for Electrochemical Oxidation of Cyclohexane to KA Oil

Abstract

Electrochemical oxidation of cyclohexane to KA oil, a mixture of cyclohexanone and cyclohexanol, holds great promise for decarbonized chemical manufacturing based on the value of products and the thermodynamic equilibrium potential. However, fundamental understanding of this reaction is extremely limited. For example, even the number of electrons in this reaction has not yet been identified. In this work, we elucidate the mechanism of electrochemical cyclohexane oxidation to KA oil on fluorine-doped tin oxide (FTO), platinum, and glassy carbon anodes. Using three-electrode electroanalysis, isotopic labeling, and concentration studies, we show that electrochemical cyclohexane oxidation to KA oil is similar to its thermochemical analogue in that O2, not water, is the primary oxygen source. The reaction is initiated through the formation of cyclohexyl or hydroxyl radicals, depending on electrode and electrolyte composition. Additionally, crossover from undivided two-electrode cells is found to impact measurements such that cathodic reaction and reactor design may introduce potential artifacts to anodic activity and selectivity. These findings have significant implications for the technological viability of a theoretically promising electrosynthesis process.