Preparation And Modification Of TiO₂ Fiber Nanomaterials With Multilevel Structure Via A Novel Template-assisted Solvothermal Method

Energy shortage and environment pollution are two main problems for the sustainable development. The photocatalytic technique provides a new idea and way for development energy and environmental governance. Thus, the exploration of the catalysts with high efficiency has always been a focus of the photocatalytic fields.The application of titanium dioxide photocatalyst is attracting consiferable attention for photocatalytic degradation of pollutants, self-cleaning, hydrogen-production through photochemical water splitting and so on. In this paper, our work is devoted to the preparation, characterization, and modification of TiO₂ photocatalyst and the photodegradation of pollutions on its surface. A novel template-assisted solvothermal method?TA-STM? was developed and employed to prepare TiO₂ fiber nanomaterials with multilevel structure. We modified them by doping rare earth element Ce. The photocatalytic performance of the samples was evaluated by the decolorization of the dye methylene blue?MB? solution as model reaction under light irradiation, and the superior photocatalyst, a multilevel structure fiber nanomaterial, was selected. This thesis mainly consists of three major aspects as follow:1. A novel template-assisted solvothermal method, called as TA-STM, was developed and employed to prepare TiO₂ multilevel structure fiber nanomaterials by using defatted cotton fibers as the template. The degradation of MB was used as the model reaction to investigate the effect of the solvothermal reaction conditions,temperature?160 200 ??, time?2.5 ¹2.5 h?, the pH value of the precursor Ti4+/EtOH, on the photocatalytic activity of the prepared TiO₂ materials. The result showes that as-prepared TiO₂ materials replicated the morphology of original cotton fibers. The effect of the reaction time on the photocatalytic activity of the materials is more remarkable than the reaction temperature in the range of the solvothermal reaction temperature?160 200 ??, time?2.5 ¹2.5 h?. For example, the photocatalytic activity of the sample increase about 20 % in the range of 2.5 to12 h while the activity increases less 10 % in the range of 160 to 200 ?. The pH value ofthe Ti4+/EtOH influences not only the structure and morphology but also the surface charge of the samples and light absorption property. The good photocatalytic activity of the samples, prepared under higher pH value of the precursor solution Ti4+/EtOH,is mainly ascribed to their multi-structure. The as-prepared material is easily removed for repeatedly being used and shows good photocatalytic property and stability.2. TiO₂ nano-particles?TiO₂-NP? and –fibers?TiO₂-NF-1, 2? materials were successfully prepared via three methods, single solvothermal?STM?, template?TM?and template-assisted solvothermal?TA-STM? methods. And the effect of different preparation methods on the structure, morphology and photocatalytic activity of the TiO₂ photocatalytic materials was investigated. The result shows that all of TiO₂ materials are of anatase while their size and crystalline degree and morphology are different. It is important that the nanofiber material TiO₂-NF-2, prepared via TA-STM,possess multilevel structure. The photocatlytic results indicate that the activity order of three TiO₂ photocatalytic materials is TiO₂-NF-2>TiO₂-NF-1>TiO₂-NP. So the multilevel structure of TiO₂-NF-2 plays an important role for enhancing its photocatalytic activity and the enhanced property can be mainly ascribed to fast adsorption/desorption of MB molecules on its surface and high efficiency of absorbing irradiating light, the efficient electrons transfer and separation by interparticles and interparticles to the wall of the fiber.3. With tetrabutyl titanate as titanium source and cerous nitrate as doping agent,Ce/TiO₂ fiber nanomaterials were prepared by TA-STM and the effect of the calcination temperature and time and rare earth element Ce-doped amount on the photocatalytic activity of the TiO₂ materials were investigated. The results indicate that Ce/TiO₂ materials show higher photocatalytic activity than pure TiO₂. Comparing with pure TiO₂, UV-Vis absorption spectrum shows that the absorption band of Ce/TiO₂ obviously shifts to red. Photocatalytic experimental results demonstrate that the sample 0.05 %-Ce/TiO₂, calcinated at 600 oC for 1 h, shows optimal catalytic performance. For example, the decolorizing efficiency of MB solution reached 93 %on the sample 0.05%-Ce/TiO₂ when radiation time was 12 min under the 300 Wmercury lamp.