Efficient photocatalytic degradation of gaseous toluene over F-doped TiO2/exfoliated bentonite

Abstract

To solve the aggregation problem of TiO2 nanomaterials and improve the catalytic efficiency, F-doped TiO2/exfoliated bentonite (TF/EB) composite was prepared by dispersing F-doped TiO2 (TF) nanoparticles on an exfoliated bentonite (EB) using a facile sol–gel method. The exfoliated bentonite was prepared by liquid-exfoliation method from the natural bentonite (B). The prepared samples were applied for toluene degradation in gas phase under UV and visible light irradiation. The as-prepared TF/EB composite exhibited higher toluene degradation efficiency than that of pure TiO2, F-doped TiO2 and TF/B composite. Results indicated that the calcination temperature and the initial F/Ti atom ratio of reaction precursors greatly affected the photocatalytic activity towards toluene degradation. The best photocatalytic performance was obtained by the sample calcinated at 400 °C with an initial F/Ti atom ratio of 5%. The improved photocatalytic performance is ascribed to a series of benefits introduced by F-doping and exfoliation process. The presence of F- ions increases the percentage of exposedreactive {001} facets on TiO2. Moreover, F- ions incorporated into the TiO2 lattice generate oxygen vacancies and Ti3+ defects, which influence the transfer and migration of the photoinduced charge carriers and induce a visible-light photocatalytic activity. Furthermore, the electrostatic interaction of negatively charged exfoliated bentonite surface leads to a more efficient separation of charge carriers.