Hydrothermal synthesis of Zn-doped brookite TiO2 for enhanced visible-light-responsive photocatalytic performance

Brookite TiO2 is considered as one of the excellent candidates in photo- or photo-/electro- chemical applications due to its unique crystalline structure and electronic properties. To achieve an enhanced visible-light-responsive brookite TiO2 photocatalyst, Zn-doped brookite TiO2 (ZBT) was in situ synthesized under hydrothermal conditions at 180 & DEG;C for 2 h in this research. X-ray diffraction (XRD) verified that the undoped sample was single-phase brookite TiO2, while the ZBT samples are mixtures of brookite and anatase because the incorporation of Zn caused brookite to anatase phase transformation. The average particle size of the ZBT samples was smaller than pure brookite TiO2 and decreased with the increase of Zn amount, indicating that Zn doping inhibited the growth of crystallite. ZBT samples exhibited better photocatalytic activity for the degradation of methylene blue (MB) than pure brookite TiO2 under visible light irradiation due to the effective separation of electrons and holes by Zn doping. Among the ZBT samples, the 5% ZBT sample exhibited the best photodegradation rate of MB (92.6%) under visible-light irradiation for 2 h, which was attributable to its small particle size (19.78 nm) and the large surface area (67.08 m(-2) g(-1)).