Research On The Synthesized Hierarchical Structured Titanium Dioxide Mediated By Amphiphilic Block Copolymer And Its The Photocatalysis

In recent years, the study on titania materials with hierarchical structure has received considerable attention because of their novel or improved properties and potential applications in photocatalysis, solar cells, drug delivery, sensing and self-cleaning coating.In this paper, combining solvothermal methods with soft-template based on amphiphilic copolymers poly(ethylene oxide)-block-polystyrene (PEO-b-PS), a series of TiO2-based photocatalysts with hierarchical structure were successfully synthesized. The compositions, structure, morphologies and photocatalysis activity of the samples were characterized by SEM, TEM,1H NMR, X-ray diffraction, EDS, TG, FT-IR spectrometer and UV-vis spectrophotometer.In this thesis, amphiphilic block copolymers PEO-b-PS were firstly synthesized via atom transfer radical polymerization (ATRP). Their structure was characterized by FTIR,1H NMR and GPC. The results showed that ATRP methods could easily control the block ratio, molecular weight with a narrow molecular weight distribution of PEO-b-PS.Then, the morphology of TiO2microspheres was mediated by the polymersomes soft-template with amphiphilic block copolymers PEO-b-PS. Anatase crystals with uniform microspheres were prepared under low acid concentrations, where rutile crystals were prepared under high acid concentrations. The solvothermal time had influence upon the growing and ripening of crystals. The results of IR, TG and EDS showed the prepared TiO2crystals were covered with organic matrix, which confirmed the role of PEO-b-PS.Furthermore, hollow core-shell structured TiO2microspheres were successfully prepared by a facile one-step solvothermal method using PEO-b-PS as the soft template and urea as structure directing agent. The effect of urea concentration on morphology of TiO2was studied. The structure and size of core and shell could be controlled by solvothermal time and urea concentration. XRD and TEM results showed that the growth of the hierarchical structure TiO2 mechanism was dominanted by Oriented Attachment and the Oswald Ripening. Urea was not only a structured-directing agent which controlled the rod-like crystals but also emitted gas (CO2and NH3) to form the hollow structure between the shell and the core.Finally, the photocatalytic degradation activity of TiO2microspheres was studied using methylene blue as probe. The hollow core-shell structured microspheres showed much higher photocatalytic activity than the ordinary microspheres. The photocatalytic activity of the former was8times as much as one of the latter after60min UV exposure. It is mainly due to that UV light could penetrate and reflect repeatedly between the shell and core. As a result, the photocatalytic ability would improve much more because of the increase of photocatalysis area which includes outer shell area, inner shell area and core area.Based the above studies, we believe this hierarchical stuctured TiO2with hollow core-shell has a wide potential application such as dye-sensitized solar cells and photocatalysis material due to its large specific surface area, special shell-core structure and the resulting high photocatalytic activity.