Design, Synthesis And Photocatalytic Activity Of TiO₂Nano-Heterojunction

In recent year, the environmental deterioration and energy shortage have brought a series of problems to the society progress. Rational design and applications of semiconductor photocatalysts is an effective way to solve those problems.Because of its advantages of good stability, high photocatalytic activity and nontoxicity, Titanium dioxide (TiO2) has attracted much attention for its potential use as a solid photocatalyst in environmental purification and hydrogen production from water splitting. However, the major drawback of high recombination rate of photogenerated charge carrier and narrow range of light-response limit the applications of TiO2. Building nano-heterojunction is an effective way to enhance the photocatalytic activities of TiO2due to the inner eleetric field of nano-heterojunction that can provide a driving force for the separation of photogenerated charge carrier and thus effectively inhibit the recombination of photogenerated electronic-hole.In order to enhance the photocatalytic activities of TiO2, we modified the TiO2photocatalyst by constructing TiO2mixed-phase heterojunction and TiO2@MWCNTs core-shell heterostructure. The photocatalytic activity of as-prepared photocatalysts was probed by photocatalytic H2production from water and degradation reaction of Rhodamin B(RhB) and methylene blue (MB) aqueous solution. The main results are as follows:1. Through melamine as mixed medium, a solvent-mixing and calcination method was used to prepare three-dimensional hierarchical TiO2phtocatalysts with mixed-phase heterojunction. The morphology of the photocatalyst is that rutile particles evenly attached on the surface of hierarchical anatase TiO2with nanosheets base structure. In addition, the photocatalyst exhibited enhanced photocatalytic activities than commercial P25and hierarchical anatase TiO2.2. A unique TiO2@MWCNTs nanocomposites showing a one-dimensional heterojunction with TiO2nanoparticles evenly coated on the surface of MWCNTs to form core-shell structure was prepared by a hydrothermal-calcination method and the TiCl4ethanol solution as the precursor. The TiO2coating layers are extremely uniform and its thickness is adjustable in the nanocomposites. The influences of the thickness of TiO2coating layer on the photo-oxidation and reduction reactivity of the TiO2@MWCNTs were studied by degradation of methylene blue and Rhodamine B solution and photocatalytic H2evolution. The photoreactivity of the TiO2@MWCNT nanocomposites is significantly improved.3. Another kind of One Dimensional Heterojunction TiO2@MWCNTs nanophotocatalysts have been successfully synthesized by a one-step hydrothermal process in which the urea as precipitant and the TiCl4aqueous solution as the precursor.. The influencing factors in the growth of the materials was studied, the photocatalytic activity of the nanophotocatalysts was evaluated through the degradation of methylene blue solution.