Ti3+ self-doped TiO2 as a photocatalyst for cyclohexane oxidation under visible light irradiation

Most of TiO 2 particles can be used as a photocatalyst for the selective oxidation of cyclohexane under ultraviolet light illumination. In this paper, Ti 3+ self-doped TiO 2 submicron-sized particles (i.e., Ti 3+ /TiO 2 SMP) were used as a catalyst for visible-light driven photocatalytic cyclohexane oxidation. The microstructure and properties of the Ti 3+ /TiO 2 SMP were characterized by X-ray diffraction (XRD), UV–visible diffuse reflection (UV–Vis DRS), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), solid-state photoluminescence spectroscopy (PLS) and X-ray photoelectron spectroscopy (XPS). The Ti 3+ /TiO 2 SMP exhibits good visible-light driven photocatalytic performances for cyclohexane oxidation with cyclohexanone as a dominate product. Effects of solvent, reaction temperature, reaction time and oxygen pressure on the formation of cyclohexanone were investigated. The cyclohexane oxidation over the Ti 3+ /TiO 2 SMP photocatalyst using carbon tetrachloride as a solvent under the optimal conditions presents a greater selectivity to cyclohexane (i.e., 95.1%). Based on the controlled experimental results with different radical scavengers, the hole (h + ) is critical for the activation of cyclohexane.