Hydrothermal in situ synthesis of Rb and S co-doped Ti-based TiO₂ sheet with a thin film showing high photocatalytic activities

TiO₂ is considered as one of the most promising semiconductor photocatalysts used to degrade organic pollutants. Element doping has a good effect on improving the properties of TiO₂. Herein, by using Rb₂SO₄, we explored the in situ synthesis of Ti-based TiO₂ sheets with a thin film through a hydrothermal reaction. Then, the photocatalyst was successfully fabricated by calcination. All samples were characterized by FT-IR, XRD, SEM, XPS, PL and UV-vis DRS measurements. The results indicate that the S doping together with surface hydroxyl groups lead to the band gap narrowing. S and a trace amount of Rb element can enable the formation of uniform microspheres on the surface of the Ti plate and the major phase transformed from titanium to anatase. The band gap absorption extended from 400 nm to 600 nm. The photocatalytic properties were investigated by performing the degradation of methyl orange (MO) and 4-chlorophenol (4-CP) in the aqueous solutions under UV and simulated sunlight. In the series of TiO₂ photocatalysts, Rb/S/TiO₂-48 shows the best photocatalytic efficiency and good photocatalytic performance on recycling. Interestingly, when H₂O₂ was added to the MO aqueous solution, a synergistic effect of the TiO₂ thin film and H₂O₂ on degrading the pollutant was observed.