Photoelectrochemical Epoxidation of Cyclohexene on an α-Fe₂O₃ Photoanode Using Water as the Oxygen Source

Abstract

This study developed a safe and sustainable route for the epoxidation of cyclohexene using water as the source of oxygen at room temperature and ambient pressure. Here, we optimized the cyclohexene concentration, volume of solvent/water (CH 3 CN, H 2 O), time, and potential on the photoelectrochemical (PEC) cyclohexene oxidation reaction of the α-Fe 2 O 3 photoanode. The α-Fe 2 O 3 photoanode epoxidized cyclohexene to cyclohexene oxide with a 72.4 ± 3.6% yield and a 35.2 ± 1.6% Faradaic efficiency of 0.37 V vs Fc/Fc + (0.8 V Ag/AgCl ) under 100 mW cm −2 . Furthermore, the irradiation of light (PEC) decreased the applied voltage of the electrochemical cell oxidation process by 0.47 V. This work supplies an energy-saving and environment-benign approach for producing value-added chemicals coupled with solar fuel generation. Epoxidation with green solvents via PEC methods has a high potential for different oxidation reactions of value-added and fine chemicals.

Chlorine-Mediated Electrooxidation of Cyclohexene at High Current Density in a Liquid Diffusion Electrode Reactor

“…Relative thermodynamic equilibria and associated reaction kinetics for each of these reactant/product pairs dictate the selectivity and Faradaic efficiency. The thermodynamic redox potentials for cyclohexene, water, and chloride oxidation are increasingly anodic at ∼0.8, 1.23, and 1.36 V vs the standard hydrogen electrode (V SHE ), respectively. , However, in a system with cyclohexene and water, the sluggish kinetics and large corresponding overpotential required for direct organic oxidation leads to efficiency losses as water oxidation becomes the dominant reaction pathway at high overpotentials. , Because chloride oxidation is a facile, two electron transfer reaction, the relative reaction kinetics allow the selective oxidation of chloride to compete with both water and cyclohexene oxidation when operating in the ∼1.4–1.6 V SHE range explored in this study, despite its higher thermodynamic barrier.…”

The PEC performance of BiVO4 was enhanced by preparing the CoFeBi/BiVO4 photoanode using an ultrafast photoassisted electrodeposition method

“…1,2 Since the early 1970s, when Fujishima and Honda 3 reported the electrochemical photolysis of water hybrid photoanodes for water oxidation combining a molecular photosensitizer with a metal oxide oxygen-evolving catalyst, 4 various semiconductor materials have been widely used as photoanode materials, with narrow-bandgap semiconductors showing excellent performance. 5 Examples include TiO 2 , 6–9 Fe 2 O 3 , 10–13 WO 3 , 14,15 Ta 3 N 5 , 16–18 and BiVO 4 . 19–21 Among these materials, n-type semiconductor bismuth vanadate (BiVO 4 ) is one of the most promising PEC water splitting semiconductors due to its narrow bandgap (2.4 eV) within the visible light range, low cost and non-toxicity.…”