Research advancements in the use of TiO2-based materials for the photocatalytic degradation of volatile organic compounds

Abstract

Human health and environmental concerns caused by the massive volatile organic compound (VOC) emission have attracted widespread attention recently. VOCs are toxic and difficult to eliminate; moreover, they come from a wide variety of sources. Efficient and environmentally friendly removal of VOCs has always been one of the primary concerns in the catalytic chemical industry. Presently, the commonly used methods for VOC removal include absorption−adsorption, biodegradation, thermal catalysis, and membrane separation. However, these methods have several drawbacks, such as high initial investment, expensive materials, high energy consumption, low catalyst efficiency, and incomplete treatment. Photocatalytic oxidation (PCO) technology is considered to be one of the effective methods of environmental pollution control. PCO can directly use solar energy to remove various environmental pollutants. Thus, PCO has inherent advantages such as low consumption, environmental protection, no secondary pollution, and convenience. Photocatalyst is a core step in the PCO process, and as aphotocatalyst studied for the longest time, titanium dioxide (TiO2) has the advantages of high cost-effectiveness, good stability, strong photocatalytic degradation capability, and producing no harmful byproducts. However, bottleneck problems such as the inability to utilize visible light and low separation efficiency of photoexcited charge carriers have always restricted its advancement. Thus, the inherent limitations of TiO2 need to be overcome, and its capability to degrade VOCs via PCO needs to be improved. These modifications can improve the PCO performance through the following mechanisms: (1) By introducing electron trapping levels in the bandgap, which will create some defects in the TiO2 lattice and help trap charge carriers, and (2) by slowing down the electron carrier loading rate to increase VOC degradation. Thus, considering the basic principle of TiO2 photocatalytic removal of VOCs, this study focuses on the key factors affecting the photocatalytic reaction. Beginning with aspects such as metal/nonmetal doping, semiconductor recombination, defect engineering, crystal plane engineering, carrier adsorption, and morphology control, the research on the design of TiO2-based materials and their application in the field of photocatalytic degradation of VOCs in recent years are systematically summarized; moreover, a brief introduction of its control parameters and applications in practical engineering and prospects on how to further improve the use of TiO2-based materials for the PCO technology of VOCs is provided. This review will provide parameter support and optimization suggestions for the research on the degradation of VOCs by TiO2-based photocatalytic materials to help researchers lay the foundation for future research.

Keywords

• tio2
• modification
• photocatalysis
• indoor and outdoor pollution
• vocs