Photocatalytic oxidation process for treatment of gas phase benzene using Ti³⁺ self-doped TiO₂ microsphere with sea urchin-like structure

Photocatalytic oxidation processes (PCO processes) are a promising technology for controlling the pollution of working environments, namely, the low concentrations of volatile organic compounds (VOCs) generated in industrial processes, and improving the efficiency of this process is an important issue. In this study, the photocatalytic oxidation of gas-phase benzene was carried out with TiO₂ microspheres with a sea-urchin-like structure, and the effect of Ti³⁺ self-doping on the catalytic performance of TiO₂ was investigated in detail. The structures and properties were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV–visible diffuse reflectance spectroscopy, electron spin resonance, scanning electron microscopy, and high-resolution transmission electron microscopy. Ti³⁺ ions were formed in TiO₂ microspheres by heating under vacuum, which improved the catalytic performance of TiO₂ for the complete oxidation of benzene to CO₂ and CO. The photoelectrochemical measurements showed that the incorporation of Ti³⁺ into TiO₂ microspheres reduced electron-hole recombination and increased the light absorption capacity, which contributed to improving the photocatalytic activity. In situ FTIR spectroscopic studies revealed that in the benzene oxidation process, Ti³⁺ self-doped TiO₂ microspheres suppressed the formation of strongly bound byproduct compounds on the TiO₂ surface, which affected the rate of benzene oxidation. Thus, the Ti³⁺ self-doped TiO₂ microspheres are effective catalysts for efficient use of UV light and suppression of catalyst deactivation during benzene oxidation.