Facile fabrication of TiO2-SiO2-C composite with anatase/rutile heterostructure via sol-gel process and its enhanced photocatalytic activity in the presence of H2O2

Constructing anatase/rutile heterostructure in TiO₂ based materials is a quite powerful approach to enhance their photocatalytic activities. Herein, by simply annealing the sol-gel derived TiO₂-SiO₂ composite in N₂ atmosphere at 850 °C, TiO₂-SiO₂-C composite (CTS-850) with anatase/rutile heterostructure has been successfully prepared, while the counterpart prepared in air contains only anatase phase. It was proven that the residual organic groups in the sol-gel process were converted into carbon species upon N₂ annealing, during which TiO₂ in the composite was partially reduced, not only leaving lots of oxygen vacancies on its surface but also promoting the phase transformation. By turning the annealing temperature and atmosphere, a series of control products were further synthesized. Among these samples, the CTS-850 showed the best photocatalytic performance toward Rhodamine B degradation in the presence of H₂O₂, which was mainly due to its lowest band gap and the enhanced sensitization of H₂O₂ by oxygen vacancies. Moreover, the photocatalytic activity of CTS-850 remained unchanged after five cycles and a proper mechanism was also proposed.