Synthesis, Characterization And Applications Of TiO₂Based Nanomaterials

As one of the outstanding semiconductors with excellent properties, such as nontoxic, chemically stable, high chemical/surfactants suitable band, high photoelectric conversion efficiency and low cost, titanium dioxide (TiO2) show great potential applications in the fields of energy and environmental protection. Although TiO2has gained extensive success, there are many problems need to be solved, such as ineffective utilization of solar energy, low quantum yield, difficult separation and poor thermal stability of anatase. Modification of TiO2provides the possibility to solve mentioned problems. Present thesis explored modification of TiO2through the fabrication of various functional materials and the characterization of morphology, structure, composition and surface chemistry. In addition, the applications of TiO2based photocatalyst and solid acid in environmental protection and bioenergy is also investigated. The main contents and results are summarized as follows:(1) Carbon nanotubes (CNTs) with modified surface were prepared through oxidation treatment. The morphology, structure and surface property of CNTs is characterized by TEM, XRD, Zeta potential and Raman/FT-IR spectrum. After modification, CNTs become purer than before and have a considerable reduction of impurities as well as cross bundles. Moreover, the sidewall and tube end of CNTs suffered a moderate oxidation with introduced functional groups.(2) CNTs@TiO2composite is prepared through modified sol-gel method. Obtained sample is characterized by SEM, TEM, XRD, Zeta potential and XPS/UV-vis/FT-IR spectrum. Results show that anatase TiO2has a uniform coating on CNTs surface after calcinate at500℃. Spectrum research confirms the interaction between CNTs and TiO2. In addition, the fabrication of CNTs decreases the recombination rate of photoinduced electron-hole pair. Compare with bulk TiO2, CNTs expands the response spectrum of TiO2to visible region. Photodegradation of MO is used to evaluate the photoactivity of CNTs@TiO2. Results show that CNTs@TiO2has a better photoactivity that bulk TiO2and follow the first-order reaction kinetics well. After the illumination of VL/UV with240/100min, MO has a complete photodegradation. Composites with a CNTs loading of5%and calcination temperature of500℃shows the best photoactivity in acidity solution. The decolorization rate of MO with CNTs@TiO2under VL/UV irradiation is89%and95%after four degradation cycles.(3) SiO2nanoparticle with controllable size is prepared by sol-gel method. The influence of preparation parameters on SiO2morphology and structure is investigated, such as the kinds of alcohol, amount of TEOS and ammonia. Obtained sample is further characterized by SEM, TEM, XRD and FT-IR spectrum.(4) SiO2@TiO2composite is prepared and characterized by SEM, TEM, XRD and BET. Photodegradation of methyl orange is used to evaluate the photoactivity of SiO2@TiO2. Obtained anatase TiO2has the diameter of about10nm and uniform distribution on SiO2surface. After calcinate at600℃, the amount of rutile in TiO2is about10.28%. the thickness of TiO2coating increase with the increase of time, which is40nm at6h and160nm at24h. MO Photodegradation is used to evaluate composite photoactivity. Preparation and reaction influence on photoactivity is investigated, which show composites with a CNTs loading of5%and calcinated at500℃have the best photoactivity in acidity solution (ka=0.042min-1).(5) ZrO2particle is prepared by direct hydrolysis method and characterized by SEM, TEM, XRD and XRF.(6) ZrO2@TiO2composite is prepared and characterized by SEM, TEM and XRD. Photodegradation of Rb is used to evaluate the photoactivity of ZrO2@TiO2.(7) Multi-solid acid ZrO2-TiO2is prepared and characterized by FT-IR spectrum, XRD and Hammett indicator. Esterification reaction is used to evaluate the catalytic activity of ZrO2-TiO2. The influence of parameters of preparation and reaction on photoactivity is also investigated. Solid acid with a ZrO2loading of16.1%, calcination temperature of500℃, reaction temperature of130℃, catalyst amount of5%, reaction time of4h and alcohol/oil radio of15has the best catalytic activity. The esterification rate of solid acid is66%after six cycles.