The Preparation, Modification Of Anatase TiO₂ With Exposed（001） Facet And Its Photocatalytic Performance

With the rapid development of social economy, environmental pollution and energy shortage have become increasingly serious, and the elimination of organic pollutants in water is undoubtedly the most important. Recently, the semiconductor photocatalytic technology attracted intense interest. Anatase titanium dioxide（TiO₂） was one of the most widely studied semiconductor catalyst in the field of photocatalysis due to its advantages such as non-toxicity, low-cost, excellent photocatalytic activity and high chemical stability, etc. However, the extensive application of anatase TiO₂ was limited by the activation only under ultraviolet light irradiation and the fast recombination of the photogenerated electron-hole pairs. Thus, the modification of TiO₂ for the improvement of photoelectrochemical and photocatalytic propeties remained an urgent and important research task.In this paper, tuning anatase TiO₂ crystal facets through HF produced in situ by TiF4 hydrolysis, and fabricating composites with other suitable semiconductors was adopted to enhance the photocatalytic quantum efficiency. The crystal phase, morphology, micro-structure and photo-absorption property of the samples were analyzed by field emission scanning electron microscopy（ FE-SEM）, transmission electron microscopy（TEM）, X-ray diffraction（XRD）, Ultraviolet-visible diffuse reflectance spectra（UV-vis DRS）, Fourier Transform infrared spectroscopy（FTIR）, photoluminescence spectroscopy（PL）, N₂ adsorption-desorption isotherms and photoelectrochemical measurement, etc. The main points are listed as following:（1） Preparation of anatase TiO₂ nanocube with exposed（001） facets and its photocatalytic properties. Anatase TiO₂ single crystals with exposed（001） facets have been successfully synthesized by a one-step hydrothermal route. The influences of hydrothermal temperature, time and pH of solution on the morphology and the exposed facets were also investigated. The photocatalytic performance of the catalysts was evaluated by the degradation of Acid Red dye. The experimental results showed that the hydrothermal temperature of 180℃ and the pH of 4⁵ were the optimum conditions for the synthesis of anatase TiO₂ nanocube. The TiO₂ nanocube with（001） facets exhibited enhanced activity under ultraviolet light irradiation, which was 1.6 times as high as that of the common TiO₂.（2） Enhancement of the Visible-Light-driven Photocatalytic Activity of h-In₂O₃/TiO₂ Heteroarchitectures. InOOH-TiO₂ composites have been successfully synthesized through a facile aqueous solvothermal method. h-In₂O₃/TiO₂ heteroarchitectures were obtained via annealing InOOH-TiO₂ precursors at 450℃ for 2 hours. The result showed that the h-In₂O₃ nanoparticles were successfully loaded on the TiO₂ nanocubes to form the heteroarchitecture. The obtained h-In₂O₃/TiO₂ composite photocatalysts exhibited enhanced activity toward the degradation of rhodamine B（RB） under visible-light irradiation, which should result from the efficient the separation of photogenerated electrons and holes between TiO₂ and In₂O₃ heteroarchitectures.Radical trapping experiments demonstrated that ·OH and h+ are the main reactive species in the phtocatalytic degradation process. Furthermore, the h-In₂O₃/TiO₂ had good recycle performance.（3） The preparation and photocatalytic performance of h-In₂O₃-TiO₂-C₃N₄ hybrid material. h-In₂O₃/TiO₂ and g-C₃N₄ were mixed on a mass ratio of 1:5, and annealed at 400℃ for 2 h in a muffle furnace to obtain h-In₂O₃-TiO₂-C₃N₄ hybrid catalyst. The photocatalytic activity of the composite was evaluated via degradation of RhB. It was found that h-In₂O₃-TiO₂-C₃N₄ ternary composites exhibit the highest RhB degradation rate in comparison with pure TiO₂, g-C₃N₄, h-In₂O₃ and their binary composites. The enhanced activities were mainly attributed to the heterojunction formed by h-In₂O₃, TiO₂, and g-C₃N₄, resulting in a strong electronic coupling effect, which led to an effective charge separation in the semiconductor.