Syntheis of TiO2-Based Nanostructures by Hydrothermal method and Their Applications
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Titanium oxide (TiO2) is a very useful semiconductor with various promising applications such as, environmental hazard removal, solar energy conversion, electrochromics devices and sensors. A variety of approaches have been utilized to synthesize uniform, well defined TiO2-based nanostructures. Among them, liquid phase hydrothermal (LPH) synthesis is an important method. Although numerous efforts have been devoted to investigating the LPH synthesis of TiO2-based nanostructures, there exist some unclear aspects. For example, in an alkaline LPH synthesis of titanate nanotubes, the actual growth process and intermediate structures are still elusive; in an acid LPH synthesis of TiO2 crystals in fluoride solutions, mechanistic roles that adsorbed fluorine species and pH are playing are still mysterious. To tackle these problems, a delicate strategy has been developed. It was based on comprehensive investigations of material morphologies, structures and corresponding solute concentrations in solutions. Ti metal plates were used as substrates and raw materials. Effects of synthesis parameters such as temperatures, pH (alkalinity and acidity), durations, on crystal growths were studied by comparisons of morphological properties obtained with varied parameters. Comprehensive growth mechanisms have been proposed in order to clarify morphological evolutions and solute concentration variations upon changes of parameters in thermodynamics and crystallographic points of view. After synthesis, photocatalytic and photovoltaic efficiencies of resultant electrodes were evaluated by photoelectrocatalysis and dye-sensitized solar cells (DSSCs). Performance dependences on morphological properties were eventually studied. Based on this methodology, alkaline LPH synthesis of titanate nanotubes on Ti substrate has been investigated. The nanotube formation can be attributed to be an oriented crystal growth process. By using a TiO2 porous film as raw material, 3D titanate nanotube network was obtained. This unique texture was constructed by branching and joining of titanate nanotubes. On a porous Ti substrate, titanate nanotube membrane was fabricated with titanate seed solution. Photoelectrocatalysis, DSSCs and filtration performance of the resultant nanotube structures have been assessed. High surface areas and outstanding mechanic strengths of the resultant nanotubes are beneficial to the high performances.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Item Access Status
Liquid phase hydrothermal synthesis