Solvothermal Treatment of Visible-Light-Responsive TiO2 toward Enhanced Photocatalytic Degradation Activity of Tetracycline

Graphical In this work, the photocatalytic activity of TiO 2 with narrow band gap was successfully improved by a simple solvothermal method. Under visible-light illumination, TiO 2 sample after solvothermal treatment at 180 °C for 24 h (defined as TiO 2 -180-24) can be excited to produce photogenerated electrons and holes. Part of the electrons from the CB move to the catalyst surface and react with dissolved O 2 in solution to form ⋅O 2 − for the degradation of tetracycline (TC). Meanwhile, part of the holes from VB can also move to the catalyst surface and be directly used for the degradation of TC. In addition, the VB potential of TiO 2 -180-24 (E VB =0.56 V vs. NHE) is less positive than the oxidation potential of ⋅OH/OH − (2.38 V vs. NHE), indicating that photogenerated holes cannot oxidize OH − to generate ⋅OH. However, the results of radical capture experiments and ESR measurements indicated the presence of ⋅OH during photocatalytic degradation. Therefore, the further reduction of ⋅O 2 − can be considered as the source of ⋅OH in the photocatalytic degradation process. The generated ⋅O 2 − and ⋅OH together with h + as strong oxidants can react with TC, and finally oxidize TC into small molecular compounds such as CO 2 and H 2 O. Photocatalytic degradation of organic pollutants driven by visible-light is considered as a promising and effective water purification strategy. In this work, solvothermal treatment was carried out on visible-light-responsive TiO 2 samples in isopropyl alcohol to improve the photocatalytic degradation performance. The effects of solvothermal treatment on the microstructure, band structure, optical properties, photoelectrochemical properties and photocatalytic activity of the obtained TiO 2 samples were systematically investigated. The experimental results showed that the photocatalytic degradation performance of the treated TiO 2 samples was significantly improved. The TiO 2 sample treated for 24 h at 180 °C showed the optimal kinetic constant of photocatalytic degradation of tetracycline, which is 4.7 times that of pristine TiO 2 . This work provides some insight into the effect of solvothermal treatment on the photocatalytic properties of semiconductor photocatalysts.