Preparation Of Titanium Dioxide Or Zinc Oxide-based Semiconductors And Study On Their Superhydrophilicity Or Photocatalytic Activities

Titanium dioxide and zinc oxide represented by wide bandgap semiconductor materials are of great importance in the field of photocatalytic and self-cleaning applications. However, these important properties are limited by their wide bandgap. In this dissertation, we aim at improving superhydrophilicity and photocatalysis of titanium dioxide or zinc oxide semiconductor through designing and constructing on the micro-nano structure.Natural superhydrophilicity of Ti O2 thin film can be improved by increasing the surface roughness and hydroxyl content. Zn O/Ti O2 composite sols were prepared from mixing the polycondensation-induced-phase separation Ti O2 sol with Zn O sol in the first part research of this thesis, followed by preparing porous Zn O/Ti O2 thin films by spin-coating. The as-prepared Zn O/Ti O2 thin film exhibit superhydrophilicity under natural conditions. Researching on the mechanism of superhydrophilic suggests that both surface hydroxyl content and porous structure can synergistically enhance superhydrophilicity of Zn O/Ti O2 film.Furthermore, porous Zn O/Ti O2 composite photocatalyst were prepared from calcining the Zn O/Ti O2 composite sol. The study found that the addition of Zn O sol can regulate pore structure, increase the specific surface area of Zn O/Ti O2, enhance light absorption and promote the separation efficiency of photoindued electrons and holes. Thus, photocatalytic performance was enhanced. Regulating microstructure of photocatalyst can improve the photocatalytic performance. Therefore, a simple solvothermal method was successfully used to synthesize multimorphologies nano-Zn Os in the presence of diethylenetriamine in the third part research of this thesis. The results show multimorphologies nano-Zn Os to have excellent photocatalytic activity.In recent years, many research groups have great interest to improve the efficiency of the utilization of sunlight by constructing Ti O2 and Zn O heterojunction photocatalyst under the condition of visible light. The forth and fifth part research of this thesis were focused on constructing Ti O2 and Zn O heterojunction with g-C3N4 to improve visible-light photocatalytic performance. Zn O/oxygen-doped g-C3N4 composite photocatalyst were prepared by adding H2O2 in the forming process of core-shell Zn O/g-C3N4. The results show the addition of H2O2 is in favour of forming uniform and unbroken core-shell Zn O/oxygen doped g-C3N4 and control the size of the particles. The Zn O/oxygen doped g-C3N4 heterojunction can increase light absorption and promote the separation efficiency of photoindued electronic-holes, which result in the enhanced photocatalytic activity. Sum up the disadvantage of low light absorption and separation efficiency of carriers, a novel ternary composite of heterostructured g-C3N4/Ag/Ti O2 microspheres was prepared in the fifth research part of this thesis, and the metallic Ag was photo-deposited as the interlayer between g-C3N4 and Ti O2. The nano-Ag particles deposited on the surface of Ti O2 microspheres in the g-C3N4/Ag/Ti O2 composite play an important role as electron-conduction-bridge, the electrons transfer toward Ti O2 and electron-holes separation in g-C3N4 would be more efficient. Based on the studies of light response, recombination of photoinduced electron-holes and detection of hydroxyl radicals, further studies of photocatalytic mechanism and recyclability of g-C3N4/Ag/Ti O2 were carried on.