Constructing High-surface-area Anatase/TiO₂（B） Heterojunction From Titanate Nanotubes With Good Thermal Stability And Understanding The Structure-photoactivity Relationship

Heterojunction is an important structure to enhance photocatalytic performance.Recently, Anatase/TiO2(B) heterojunction obtained from titanate nanotube exhibitinghigh photocatalytic activity has been the research hotspot. However, how to fabricateAnatase/TiO2(B) heterojunction with large surface area and good thermal stability isstill a challenge. In this thesis, we fabricated Anatase/TiO2(B) heterojunctionnanotube with good thermal stability via a two-step alkaline hydrothermal technique,hydrogen ion exchange and post-calcination process, and investigated the relationshipbetween phase composition and photocatalytic performance of Anatase/TiO2(B)heterojunction through comparative photocatalytic activity study. Detailed contentsare listed as follows:We employed a two-step alkaline hydrothermal technique and hydrogen ionexchange process to fabricate titanate nanotube with large surface area of322m2/g. Asthe post-annealing temperature increased, titanate nanotube transformed into TiO2(B)nanotube, Anatase/TiO2(B) heterojunction and Anatase nanoparticles. XRDmeasurements indicated that phase transition from TiO2(B) to Anatase located at400-500oC, between which anatase percentage increased from15%to85%, and theAnatase pencentage was50%when the annealing temperature was450oC. SEMcharacterization indicated that samples annealed at450oC inherited the nanotubemorphology, with a large surface area of277m2/g. HRTEM results indicated that theanatase/TiO2(B) heterojunction formed at450oC.Photocatalytic degradation of acetaldehyde test demonstrated that theanatase/TiO2(B) nanotube heterojunction display higher activity than that of pureanatase, TiO2(B), and even Degussa P25for450oC annealed sample. Besides, frommott-schottky and XPS measurements, we demonstrated that the band structure ofanatase/TiO2(B) heterojunction was favorable for photogenerated electron-holeseparation, and proposed the photogenerated charge separation model. Then wedemonstrated the large surface area and high lattice oxygen activity of samplesannealed at and below450oC through oxygen-free photocatalytic test, which isbeneficial to the photocatalytic performance. The study above indicates thatAnatase/TiO2(B) heterojunction nanotube is a promising photocatalyst.