Structure Design And Performance Regulation Of Titanium Dioxide Based Composite Catalysts

This paper aiming at the existence of low quantum efficiency and relatively wide band gap of TiO2 semiconductor catalyst, combined with surface plasmon resonance of Au nanoparticles (SPR) effect and narrow band gap semiconductor CuO ability to absorb visible light strong, and using the improved sol-gel method and electrostatic spinning method, to design and regulation the structure and performance of titanium dioxide composite catalyst. By combining Au nanoparticles or CuO with TiO2, not only effectively inhibit the recombination of photogenerated electrons and holes, but also widened the spectral response range of the catalyst. This thesis successful preparation of a titanium dioxide based composite catalysts with visible light response ability and high catalytic activity. The main content of the research are as follows:1. Hierarchically porous metal oxide materials including titanium dioxide (TiO2), ferric oxide (Fe2O3), zinc oxide (ZnO), and ceria (CeO2) were prepared on a large scale by an improved sol-gel method assisted with evaporation-induced surfactant self-assembly. The factors influencing the morphology, pore structure and size of these porous metal oxides were studied. Moreover, this method can also be used for one-pot synthesis of hierarchical nanohybrids loaded with noble-metal nanoparticles. The synthesis and catalytic properties of Au/TiO2 nanohybrids with different Au loading (2, 5, and 10 wt.%) were typically demonstrated. Benefiting from the uniform dispersion of Au nanoparticles, the Au/TiO2 nanohybrids show favorable catalytic activity in both the photooxidation of rhodamine B (RhB) under visible light and the catalytic reduction of 4-nitrophenol with sodium borohydride to 4-aminophenol.2. The Au/TiO2 hybrid nanofibers composed of mesoporous TiO2 nanofibers and Au nanoparticles were synchronously fabricated by integrating a facile electrospinning technique and subsequent annealing in air. The Au loading content in the hybrid nanofibers was regulated by varying the dosage of chlorauric acid added in the precursor solution. The compositions, microstructures and optical response properties of the Au/TiO2 hybrid nanofibers were characterized. For the catalytic reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride, the apparent reaction rate constant is raised but TOF value of the catalyst decreases, as the Au loading amount in the hybrid fibers increases. This is because the Au nanoparticles with smaller sizes have higher total surface areas at the same weight and therefore show higher catalytic activity.3. CuO/TiO2 heterostructure nanofibers with high surface area have been successfully prepared by the electrospinning and followed by calcination. The catalytic properties were investigated by photodegradation of rhodamine B (RhB) and the catalytic reduction of nitrophenol with sodium borohydride to aminophenol. According to the results, the modification with CuO nanoparticles induces an increase in the photocatalytic activity under both UV and visible light. More importantly, the green synthesized CuO/TiO2 heterostructure nanofibers presented excellent catalytic activity for reduction of 4-nitrophenol,2-nitrophenol and 3-nitrophenol.