Tricrystalline TiO2 with enhanced photocatalytic activity and durability for removing volatile organic compounds from indoor air

It is important to develop efficient and economic techniques for removing volatile organic compounds (VOC_s) in indoor air. Heterogeneous TiO₂-based semiconductors are a promising technology for achieving this goal.Anatase/brookite/rutile tricrystalline TiO₂ withmesoporous structurewas synthesized by a low-temperature hydrothermal route in the presence of HNO₃. The obtained samples were characterized by X-ray diffraction and N₂ adsorption-desorption isotherm. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air under UV light illumination. The results show that tricrystalline TiO₂ exhibited higher photocatalytic activity and durability toward gaseous toluene than bicrystalline TiO₂, due to the synergistic effects of high surface area, uniform mesoporous structure and junctions among mixed phases. The tricrystalline TiO₂ prepared at R_HNO3 = 0.8, containing 80.7% anatase, 15.6% brookite and 3.7% rutile, exhibited the highest photocatalytic activity, about 3.85-fold higher than that of P25. The high activity did not significantly degrade even after five reuse cycles. In conclusion, it is expected that our study regarding gas-phase degradation of toluene over tricrystalline TiO₂ will enrich the chemistry of the TiO₂-based materials as photocatalysts for environmental remediation and stimulate further research interest on this intriguing topic.