Controllable Synthesis And Photocatalytic Properties Of Hierarchical Flower-like TiO₂Nanostructures

Titanium dioxide is one of the most talked about efficient photocatalysts due to itsadvantages of high photocatalytic activity, environment-friendliness, low-cost, and so on. Thehierarchical structure of micro-and nanometer possesses the superiority in structure at bothmicrometer and nanometer levels, and restrains respective structural deficiencies. Therefore, itbecomes a hotspot for materials research. Flower-like TiO₂is a three-dimensional micro-andnanometer material with hierarchical structure, high specific surface area, nicer lightabsorption and refractive index. Usually, a high specific surface area contributes to thegeneration and migration of photo-carrier, adsorption of reactants on the surface, andmeanwhile it is conducive to the absorption and refraction of light. Hence the hierarchicalflower-like TiO₂structure exhibits higher photocatalytical efficiency.In this paper, three-dimension （3D） flower-like TiO₂micro-nanostructures have beensynthesis controlled by a facile and economical route. The impacts of various experimentparameters on the morphology and photocatalytic activity of above materials have beeninvestigated. The main contents of the thesis are listed as follows：1. Ti powder was dissolved in a mixed solution of H₂O₂/HNO3, and reacted with sodiumhydroxide. The hierarchical flower-like anatase TiO₂structure composed of nanosheets wassuccessfully prepared via the hydrothermal method. The morphology, microstructure andspecific surface area of the flower-like TiO₂structure were characterized by scanning electronmicroscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） andsurface area analysis. The results indicated that the radial TiO₂nanosheets emitted from thecenter were assembled into the hierarchical flower-like TiO₂synthesized with diameters ofaround2.5μm. The TiO₂nanosheets were approximately1μm in length,50-200nm in width,and less than10nm in thickness. After the heat treatment, the flower-like TiO₂still has a highspecific surface area （160m2/g）. The morphology of the flower-like TiO₂was influencedsignificantly by the concentrations of H₂O₂, HNO3and NaOH, as well as the reactiontemperature and time. Moreover, these flower-like TiO₂exhibited good photocatalyticalproperties on the degradation of methylene blue.2. Flower-like TiO₂materials, possessing the advantages of high specific surface areaand developed pore structure, high photocatalytic activity, have been widely used in the areasof environmental pollution control, air purification, sterilization, surface self-cleaning and so on. The Novel three-dimension sheet-like TiO₂hierarchical micro-nanostructure weresuccessfully synthesized using a hydrothermal technique of Ti powders with a concentratedNaOH solution. The XRD result suggests that the flowerlike hierarchical structures are typicalanatase TiO₂.3.The Novel three-dimension flower-like TiO₂microspheres were controlled synthesizedusing a hydrothermal technique.The hierarchical flower-like anatase TiO₂structure composedof nanowires was successfully prepared.The obtained hierarchical TiO₂nanospheres had auniform size,good dispersion,high specific surface area.Through the degradation of methyleneblue a catalytic activity evaluation confirmed that the hierarchical flower-like TiO₂microspheres possesses good photocatalytical properties.4. Novel spherical anatase TiO₂nanotube assemblies were successfully synthesized byhydrothermal reaction of Ti powders with a concentrated NaOH solution. The influence of thereaction temperature were investigated. The morphology and microstructure of the sphericalTiO₂nanotube were characterized by scanning electron microscopy （SEM）, transmissionelectron microscopy （TEM）, X-ray diffraction （XRD） and Raman spectroscopy （Raman）.