TiO₂-based Photocatalvsts For Removing Benzene And Toluene From Indoor Air

Volatile organic compounds (VOCs) are a group of the most abundant organic pollutants in indoor air. Heterogeneous photocatalysis using TiO2 is a promising technology for VOC removal. However, the fast recombination of photogenerated electron-hole pairs and high indoor humidity hinder the photocatalytic degradation of VOCs. Hence, TiO2-based photocatalysts with low recombination of electron-hole pairs and high resistant to humidity were designed. The following results are obtained.(1) Using titanate nanotubes as precursor, anatase/brookite/rutile tricrystalline TiO2 was synthesized. The heterojunction of three polymorphs allowed an easier transfer of photogenerated electrons from one phase to another, hindering the electron-hole pairs recombination. TiO2 with a 1:1:1 ratio of anatase/brookite/rutile exbihted the highest activity. The removal rates of toluene and benzene were 91.6% and 80.1%, respectively.(2) Using HF as morphology controlling agent, (001) facet exposed anatase TiO2 was synthesized. With increasing HF content, the proportion of (001) facet increased from< 6% to 85%. The highest removal rates of benzene and toluene were 84.8% and 93.5%, respectively. This enhancement could be attributed to the synergistic effect of surface fluorination and dominant (001) facet.(3) CNTs/TiO2 reduced the competitive adsorption of water and benzene molecules on the catalyst, increasing the adsorption capacity and removal rate of benzene. At 80% relative humidity, the removal rates of benzene on CNTs/TiO2 were 60.7% and 72.7%, 2.1 and 1.6 times that of tricrystalline TiO2 and (001) facet exposed TiO2, respectively.(4) TiO2 powder photocatalysts were supported onto the surface of glass fibers, forming a model machine of air purifier. The removal rates of BTEX and formaldehyde were more than 96% and 90%, respectively.