Synthesis Of Mesoporous TiO₂ Micro/Nanometer Structure And Their Photocatalytic Activities In Visible Light

Mesoporous anatase TiO₂micro/nanometer material, as a novel inorganic nanometermaterial, is an ideal efficient catalyst and has received considerable attention due to their wideapplications because of its high chemical stability, good dispersity, high specific surface areaand excellent photocatalytic activity, etc. This thesis focused on the following work: thepreparation of mesoporous TiO₂micro/nanometer structures, formation Mechanism andphotocatalytic activity under simulated sunlight irradiation.1. Mesoporous anatase TiO₂micro/nanometer composite structure was synthesized bysolvothermal method at 180°C for 24 h with triethanolamine as a directing agent andtetrabutyl titanate （TBOT） as a titanium source, followed by calcination at 400°C for 2 h.The as-prepared TiO₂were characterized by XRD, SEM, TEM, HRTEM, XRS and FT-IR.The surface area and pore size were obtained by N2adsorption-desorption experiment.The optoelectric property of the mesoporous TiO₂was studied by UV-Vis absorptionspectra and surface photovoltage spectra （SPS）. The photocatalytic activities wereevaluated by photodegradations of rhodamine B and phenol aqueous solutions undersimulated sunlight irradiation. The experimental results show that the TiO₂compositestructure consists of microspheres （⁰.5-2μm in diameter） and irregular aggregates withsomewhat honeycomb like surface and the primary average particle size of 10.2 nm. Itdemonstrates an N-doped TiO₂with a high specific surface area of 179 m2g-1. Thephotodegradation activities of this mesoporous TiO₂on both rhodamine B and phenolsolutions are higher than those of P25.2. Mesoporous hierarchical TiO₂microspheres were synthesized by a simple solvothermalmethod with polyethyleneimine as a directing agent, alcohol and TBOT as the rawmaterials, followed by heat treatment at 400°C for 2 h. The morphology and crystal phaseof the as-prepared TiO₂were characterized by XRD, SEM and TEM etc. The influence ofthe kind of the templates and dosage, reaction temperature and time on the morphologiesof the products, the formation mechanism and the optimum reaction conditions werestudied. Photocatalytic activities of the products were investigated in terms ofphotodegradations of the organic pollutants and compared with those of commercial TiO₂（P25） under the same conditions. The results demonstrate that the TiO₂was composed ofuniform microspheres （⁰.1-0.4μm in diameter） with mesopores of around 10 nm mainly.The as-prepared TiO₂microspheres exhibit excellent photodegradation activities on phenol and methyl orange, respectively, which are more than twice of degradations over P25.3. TiO₂hollow microspheres were synthesized by alcohol thermal method with oleylamine asa template and TBOT as the raw material. The morphology and crystal phase of theas-prepared TiO₂were characterized by XRD, SEM, TEM and HRTEM. The surfacestructure and the characteristics of chemical bond were studied by FT-IR. Thephotocatalytic activity was evaluated by photodegradations of rhodamine B undersimulated sunlight irradiation. The results show that the products are pure anatase TiO₂with regular shape. The as-prepared TiO₂behaved nice catalytic performance. Thedegradation percentage of the rhodamine B aqueous solution reached up to 72%. Besides,the microspheres with a large size of 2-5μm in diameters can be easily reclaimed after thephotocatalytic experiment.4. The anatase TiO₂nanoparticles were synthesized by solvothermal method with TiCl4as atitanium source. The as-prepared TiO₂was characterized by XRD, SEM, TEM, FI-IR andUV-Vis respectively. The photodegradation percentage of rhodamine B over theas-prepared TiO₂reaches nearly 100% in two hours under simulated sunlight irradiation.The preferential degradation on the coexisting dyes, rhodamine B and methyl orange, inthe aqueous solution was also studied under simulated sunlight irradiation.