| Photocatalysts can degrade most of the organic pollutants into innocuous small molecules or H2O and CO2completely under UV-vis irradiation, which have a wide potential application in air purification and wastewater treatment. TiO2-based nanostructures are especially attended by researchers due to the advantages of low-preparation, no-toxic, and excellent photochemical property. Since the morphology and structure play an important role on the photocatalytic activity of catalysts, we successfully prepared a series of TiO2-based nanostructures with special morphologies and structures by a facile alkaline hydrothermal method. It is found that the adsorption and photocatalytic properties of the nanostructures can be adjusted by controlling their dimensionalities, crystal structures, and surface states. With a proper hydrothermal treatment, the prepared two-dimensional Tio2/trititanate heterostructure exhibits much higher photocatalytic activity than those of three-dimensional TiO2nanoparticles and one-dimensional TiO2-based nanotubes. This kind of heterostructure is beneficial not only to the improvement of separation efficiency of photoinduced carriers, but also to the extension of light response and the enhancement of adsorption capacity of catalysts. Because of the strong adsorption capacity and high photocatalytic activity of TiO2-based nanosheets, we successfully realized the effective removal of organic pollutants in solution with different initial concentrations, especially the pollutants in high-concentration dye systems. Furthermore, we effectively recovered the adsorption and photocatalytic properties of catalysts. After reusing for servral times, the prepared TiO2-based nanosheet and its composites remain large adsorption capacity and high photocatalytic activity. The main points could be summarized as follows:(i) Study on the controlled preparation and adsorption and photocatalytic properties of TiO2-based nanostructures with different dimensionalities. Since the dimensionality, morphology, and surface state of catalysts play an important role on their photocatalytic activities, we successfully prepared TiO2-based nanostructures with various dimensionalities such as nanosheets and nanotubes based on the transformation of TiO2into titanate under hydrothermal treatment conditions. Then, the changes of dimensionality, crystal structure, and specific surface area of the nanostructures were investigated systematically. The results revealed that the morphology and structure of the product can be controlled with a proper alkaline hydrothermal treatment. Combined with the results of photocatalytic degradation of rhodamine B, it is found that the adsorption and photocatalytic activity of the catalysts can be adjusted by the morphological and structural control, and two-dimensional TiO2-based nanosheets exhibit much higher photocatalytic activity than those of three-dimensional TiO2nanoparticles and one-dimensional TiO2-based nanotubes.(ii) Preparation and investigation of the photocatalytic property of sheet-like TiO2/trititanate heterostructure. TiO2/trititanate heterostructure was prepared with alkaline hydrothermal method. It is found that the formation of trititanate on TiO2surface resulted in a larger specific surface area and an increased amount of surface hydroxyl groups, which is beneficial to the enhancement of adsorption capacity of catalyst. Besides, the light response was extended due to the smaller band gap of trititanate than that of TiO2, which is a positive effect to the utilization of light energy. Most important is that the separation efficiency of photoinduced electrons and holes was improved markedly, since the formed trititanate can trap photoinduced electrons from the conduction band of TiO2because of its lower conduction band position. Due to the advantages of enhanced adsorption capacity and separation efficiency of photoinduced carriers, the prepared TiO2/trititanate nanostructure exhibits much higher photocatalytic activity than TiO2during the degradation of rhodamine B.(iii) Effective removal of high-chroma crystal violet by adsorption and photocatalytic degradation over TiO2/trititanate nanosheets. TiO2/trititanate nanosheets with high specific surface area (207mg2/g), plentiful surface hydroxyl groups, and small thickness (ca.5nm) were prepared through an alkaline hydrothermal method. The larger specific surface area may provide much more adsorption sites, and the plentiful surface hydroxyl groups can provide enhanced electrostatic attraction for cationic pollutants. Besides, the smaller thickness will cause the decrease in the migration distance of photoinduced carriers. Thus, the prepared TiO2-based nanosheets exhibit excellent adsorption and photocatalytic properties. However, the photocatalytic activities of TiO2-based nanosheets and commercial P25TiO2were restrained markedly in the high-chroma crystal violet solution, due to the low light transmittance. Depending on the excellent adsorption and photocatalytic properties of TiO2-based nanostructure, we successfully realize the effective removal of organic pollutants in high-chroma crystal violet solution by adsorption-photocatalytic degradation. Besides, it is found that H2O2can produce a synergetic effect with TiO2-based nanosheets during the degradation process, that the addition of a small amount of H2O2can effectively facilitate the recovering of the adsorption capacity and photocatalytic activity of TiO2-based nanosheets.(â…³) Enhanced adsorption and photocatalytic degradation of high concentration methylene blue over Ag2O modified TiO2/trititanate nanosheets. The adsorption capacity of obtained TiO2-based nanosheets is insufficient when treating organic pollutants with high concentration dye solution. Through the modification by Ag2O, the adsorption capacity of TiO2-based nanosheets was enhanced markedly. Compared with the modification by inert adsorbent, the modification by Ag2O not only results in the enhancement of adsorption capacity, but also causes the improvement of photocatalytic activity. It is ascribed to the smaller band gap of Ag2O than that of TiO2-based nanosheets. On the one hand, the loading of Ag2O extended the light response; on the other hand, it facilitates the effective separation of photoinduced electrons and holes. It was found that Ag2O loaded TiO2-based nanosheets can effectively remove the organic pollutants from high concentration methylene blue, which exhibits excellent reusability in the cyclic experiments. |
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