Solvothermal syntheses of Si and Zn co-doped TiO2 with enhanced electron-hole separation and efficient photodegradation of gaseous toluene under visible-light

This study investigated the effects of Bi doped and Bi-Zn co-doped TiO2 on photodegradation of gaseous toluene. The doped TiO2 with various concentration of metal was prepared using the solvothermal route and characterized by SEM, XRD, Raman, BET, DRS, XPS, PL and EPR. Their photocatalytic activities under visible-light irradiation were drastically influenced by the dopant content. The results showed that moderate metal doping levels were obviously beneficial for the toluene degradation, while high doping levels suppressed the photocatalytic activity. The photocatalytic degradation of toluene over TiBi1.9%O2 and TiBi1.9%Zn1%O2 can reach to 51% and 93%, respectively, which are much higher than 25% of TiO2. Bi doping into TiO2 lattice generates new intermediate energy level of Bi below the CB edge of TiO2. The electron excitation from the VB to Bi orbitals results in the decreased band gap, extended absorption of visible-light and thus enhances its photocatalytic efficiency. Zn doping not only further enhances the absorption in this visible-light region, but also Zn dopant exists as the form of ZnO crystallites located on the interfaces acts as a mediator of interfacial charge transfer to suppress the electron-hole recombination. These synergistic effects are responsible for the enhanced photocatalytic performance. (C) 2016 Elsevier B.V. All rights reserved.