Study On Preparation And Properties Of Porous Metal-oxide Semiconductor

Because of excellent chemical stability, high photoactivity, relatively low cost, and nontoxicity, TiO2has been considered as a promising semiconductor photocatalyst for energy and environment-related applications. However, as a large bandgap semiconductor (3.2eV), TiO2could only be activated by UV light which makes up only4%of the solar spectrum. To more efficiently utilize solar energy, it is highly desired to extend the photoresponse of TiO2-based materials to visible light region. This thesis focuses on developing some efficient visible light photocatalysts including N-dope TiO2inverse opals, CdS sensitized N-TiO2inverse opals and pine cone-like porous Fe3O4@Cu2O/Cu composites.The main contents are summarized as follows:1. The first chapter describes a facile emulsion polymerization approach to synthesize highly monodisperse polystyrene (PS) spheres using potassium persulfate as the initiator and polyvinylpyrrolidone (PVP) as a stabilizer, respectively. The PS colloidal photonic crystals films were fabricated on a microscope slides or FTO glass substrate by using vertical deposition method at45℃. Then a sol-gel process was used to assemble N-TiO2onto the PS photonic crystals films, followed by a calcination process to remove PS templates. The effects of titanium source and concentration on the resulting structure were investigated. Enhanced visible light photocatalytic activity was observed in this unique structure.2. In the second chapter, CdS sensitized nitrogen doped titanium oxide inverse opal structure has been synthesized by an ionic layer adsorption and reaction (SILAR) route. The3D percolated periodical inverse opal structure provides numerous nucleation sites for the following CdS deposition. Also, the high surface area is beneficial for the photocatalysis process. Uv-vis diffuse reflectance spectra indicates that the CdS-N-TiO2inverse opals exhibits a good visible light absorption ability.The photocurrent density is enhanced by8times through CdS QD sensitization in comparison to the pristine TiO2inverse opal photoanodes. The as-obtained film may have potential applications in solar cells, hydrogen generation and so on.3. In the last chapter, novel pine cone-like Fe3O4@Cu2O/Cu nanocomposites (NCs) with photomagnetic difunction were successfully synthesized via a one-pot solvothermal method on Fe3O4without any additional linker or reducer. The products were orderly assembled into many sheets with an average thickness of～100nm, possessing a porous structure. The samples show excellent photocatalytic activity such that MO degradation efficiency is about96%at an irradiation time of20min under visible light. Also, the composites present higher stability than Fe3O4@Cu2O. The above results demonstrate that Cu could improve the photocatalytic activity of NCs and also inhibit the photocorrosion behavior of NCs. These novel Fe3O4@Cu2O/Cu composite materials are ideal candidates in water treatment and environmental cleaning as well as in magnetic applications, etc.