by Leung Yat-chor, Calvin. / Includes bibliographical references / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984

Leung Cheuk-wan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / Abstract (Chinese) --- p.ii / Acknowledgement --- p.iii / Table of Contents --- p.v / Lists of Tables --- p.ix / Lists of Figures --- p.x / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- TiO2 Photocatalysis --- p.1 / Chapter 1.1.1 --- Mechanisms of TiO2 Photocatalysis --- p.1 / Chapter 1.2 --- Visible Light Photocatalyst --- p.4 / Chapter 1.2.1 --- Preparation of Visible Light Ti02 Photocatalysts --- p.5 / Chapter 1.2.1.1 --- Dye Sensitization --- p.5 / Chapter 1.2.1.2 --- Metal Doping --- p.6 / Chapter 1.2.1.3 --- Coupling of Semiconductors --- p.6 / Chapter 1.2.1.4 --- Nonmetal Doping --- p.7 / Chapter 1.3 --- Enhanced TiO2 Photocatalytic Activity under UV Light --- p.8 / Chapter 1.3.1 --- Preparation of TiO2 Photocatalyst with Enhanced Activity in UV Light --- p.8 / Chapter 1.3.1.1 --- Loading of Metal --- p.8 / Chapter 1.3.1.2 --- Impurity Co-doping --- p.9 / Chapter 1.3.1.3 --- Morphological Control --- p.10 / Chapter 1.3.1.4 --- Increasing Surface Area --- p.10 / Chapter 1.4 --- Summary --- p.11 / Chapter 1.6 --- Aim of This Research and its Significance --- p.12 / Chapter 1.7 --- References --- p.13 / Chapter Chapter 2 --- Preparation of N-doped TiO2 with Enhanced Surface Area: A Detailed Characterization and Mechanism --- p.19 / Chapter 2.1 --- Introduction --- p.19 / Chapter 2.2 --- Experimental --- p.21 / Chapter 2.2.1 --- Materials and Catalyst Preparation --- p.21 / Chapter 2.2.2 --- Characterization --- p.21 / Chapter 2.2.3 --- Photocatalytic Activity --- p.23 / Chapter 2.3 --- Results and Discussion --- p.24 / Chapter 2.3.1 --- XRD Analysis --- p.24 / Chapter 2.3.2 --- UV-Vis Absorption Spectroscopy and Bandgap Energies --- p.27 / Chapter 2.3.3 --- N2 Sorption Analysis --- p.29 / Chapter 2.3.4 --- SEM Analysis --- p.33 / Chapter 2.3.5 --- TEM Analysis --- p.35 / Chapter 2.3.6 --- FT-IR Spectroscopy --- p.36 / Chapter 2.3.7 --- Raman Spectroscopy --- p.39 / Chapter 2.3.8 --- XPS Studies --- p.44 / Chapter 2.3.9 --- PL Measurements --- p.49 / Chapter 2.3.10 --- Photocatalytic Activity Measurements --- p.50 / Chapter 2.3.11 --- Advantages of Using Urea as a N-doping Source --- p.54 / Chapter 2.3.12 --- Mechanisms for N-doping --- p.56 / Chapter 2.4 --- Conclusions --- p.58 / Chapter 2.5 --- References --- p.59 / Chapter Chapter 3 --- Preparation of Nanoporous Interstitial B-doped TiCO2 with Enhanced Photocatalytic Activity --- p.63 / Chapter 3.1 --- Introduction --- p.63 / Chapter 3.2 --- Experimental --- p.65 / Chapter 3.2.1 --- Materials and Catalyst Preparation --- p.65 / Chapter 3.2.2 --- Characterization --- p.66 / Chapter 3.2.3 --- Photocatalytic Activity --- p.67 / Chapter 3.3 --- Results and Discussion --- p.68 / Chapter 3.3.1 --- XRD Analysis --- p.68 / Chapter 3.3.2 --- UV-Vis Absorption Spectroscopy and Bandgap Energies --- p.71 / Chapter 3.3.3 --- N2 Sorption Analysis --- p.73 / Chapter 3.3.4 --- SEM and TEM --- p.76 / Chapter 3.3.5 --- FT-IR Spectroscopy --- p.80 / Chapter 3.3.6 --- Raman Spectroscopy --- p.82 / Chapter 3.3.7 --- PL Measurements --- p.84 / Chapter 3.3.8 --- XPS Studies --- p.85 / Chapter 3.3.9 --- Photocatalytic Activity Measurements --- p.89 / Chapter 3.3.10 --- State and Form of Boron in TiO2 Lattice and its Effects --- p.91 / Chapter 3.4 --- Conclusions --- p.93 / Chapter 3.5 --- References --- p.94 / Chapter Chapter 4 --- Conclusions --- p.97

Anodised titanium dioxide (titania, TiO2) nanotubes have been widely studied over the last few years, following the discovery in 1999 of nanoporous TiO2 films prepared via anodisation in aqueous solution containing small quantities of hydrofluoric acid. The synthesis of nanotubular titania by anodisation, a relatively simple and low cost technique, represents a motivation for scientists, considering the impact that such a material could have on a variety of applications, including gas-sensing, biomedical, photocatalysis, and photovoltaics. This research project has focused on the optimisation of the growth process of anodic titania nanotubes, both in an aqueous (NaF/Na2SO4) and an organic (Glycerol/NaF) electrolyte containing fluorine ions. Reproducibility and the ability to generate anodic films having a thickness of several micrometers are fundamental steps to be achieved before investigating any possible application of the nanotubes. To characterise the anodic specimens and build upon the general lack of information on the growth mechanism, a comprehensive study of the different stages of the process has been performed, using Scanning and Transmission Electronic Microscopy (SEM and TEM). Among the questions to be addressed in this thesis, is to establish whether the anodic film undergoes a transition from pores to tubes or develops a tubular morphology from the beginning of its growth. Additional characterisation of the anodisation process includes the study of current-time curves, and chemical composition analysis of the anodic layers using X-ray Photo-Electron Spectroscopy (XPS). The thermal stability of the nanotubes and structural/morphological changes as a result of heat treatment at different temperatures were also studied, again using SEM, TEM, XPS and Raman spectroscopy. The final part of the thesis is dedicated to preliminary work on the use of anodised TiO2 nanotubes in Dye Sensitized Solar Cells (DSSCs), along with suggestions for future works and general conclusions.

by Lin Jun. / "Nov. 28, 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Another study was to prepare hierarchically mesoporous titania materials with well-defined grape-like morphology in the presence of a triblock copolymer using bubbling-mediated hydrolysis approach. The effects of bubbling time and calcination temperature on both physicochemical and photocatalytic properties were investigated. / Furthermore, thermally stable ordered mesoporous CeO2/TiO 2 visible photocatalysts were prepared by the evaporation-induced self-assembly method. Introducing highly dispersed CeO2 species into the mesoporous TiO2 framework could effectively extend the response of TiO 2 to visible light region and improve the thermal stability of the mesoporous TiO2. / In addition, visible-light-driven mesoporous TiO2-xN x photocatalysts were developed via in-situ pyrolysis of the product from a chelation reaction between TiCl4 and ethylenediamine under sonication. The effects of ultrasound bombardment on the physicochemical properties and photoactivity of mesoporous TiO2-xNx were discussed. / Part I. Ordered and well crystallized cubic Im 3¯ m mesoporous Cr-TiO2 photocatalysts were fabricated through EISA (evaporation induced self assembly) process. The as prepared photoactalysts exhibited very strong photoactivity in the degradation of methylene blue under visible light irradiation owing to the excitation of 3d electron of Cr3+ to the conduction band of TiO2. / Part II. New approaches have been developed for the fabrication of visible light photocatalysts, BiVO4 and Bi 2WO6. In the case of BiVO4, ordered mesoporous bismuth vanadate (BiVO4) crystals were synthesized via nanocasting method. Compared to the conventional BiVO4, the product exhibited superior photocatalytic performance in the photochemical degradation of methylene blue and photocatalytic oxidation of NO gas in air under visible-light irradiation. In addition, hierarchical flower-like Bi2WO6 was synthesized via microwave-assisted route. Compared to the samples prepared by the hydrothermal method, the products exhibited excellent photocatalytic activities of degrading methylene blue and photocatalytic oxidation of NO gas in air under visible light irradiation. The effects of microwave irradiation on both physicochemical and photocatalytic properties of the as prepared products were investigated. / Two different types of porous visible light photocatalysts were studied in this thesis. The first part reports on the improvement of photocatalytic performance of porous TiO2 through metal/nonmetal doping and morphology controlling. The second part describes the fabrication of porous non-TiO2 photocatalysts including BiVO4 and Bi2WO6. / . / Adviser: Jimmy C. Yu. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3527. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

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The photovoltaic energy conversion system (PV cells or solar cells) has been researched over the last few decades, and new technologies have been proposed. At the same time, the synthesis of nano-scale materials has been investigated intensively from the 1990s. These new types of materials encourage the development of new PV technologies with extensive research. Dye-sensitized solar cells (DSSCs) can be a part of these efforts. Since first presented in 1991, DSSCs have become the center of attention due to their great advantages to the traditional silicon solar cells. However, it remains a challenge to develop better performing DSSCs since the efficiency of DSSCs is still much lower than that of high performance solar cells. To meet this challenge, the different types of TiO2 nanostructures in DSSCs have been studied. This thesis presents the synthesis of TiO2 hetero-structures. These structures can achieve two important factors in DSSCs. One is the electron pathway for high electron transport rate, and the other is the large surface area for the dye absorption. TiO2 hetero-structures were successfully synthesized by using a simple thermal annealing method. The synthesis method required neither a high reaction temperature nor complicated reaction processes and produced dense TiO2 nanowires and incorporating TiO2 nanoparticles with relatively short reaction time. The key parameters of growing 1-D TiO2 nanostructures were the Cu eutectic catalyst, the reaction temperatures, and the annealing time. The repetition time and the reaction temperatures were important factors for incorporating TiO2 nanoparticles. The structure and composition of as-grown samples were analyzed using an x-ray diffractometer, a scanning electron microscope, a field emission scanning electron microscope, a transmission electron microscope and an ultraviolet-visible spectroscopy. The results showed they were crystalline structures in rutile phase of TiO2. From this research, we can utilize hetero-structures as an electrode of DSSCs. We also expect that our simple and effective synthesis method can be used for growing other kinds of metal oxide nanostructures, especially for those melting temperature are high.

The mainly research is by adding the rare-earth metal gadolinium salts with sol-gel process to form the gadolinium -doped titanium dioxide, and by forming the liquid crystal template with the non-ionic surfactant to form the mesostructure of titanium dioxide. And the research has aimed at the using different non-ionic surfactant, the different pH value, the different solvent of water/ethanol ratio, the hydrothermal process or not, and the gadolinium content. We discussed these factors how to affect the titanium dioxide in the physical property, the chemical property, or structure influence. Using the XRD to measure the mesostucture of titanium dioxide and the crystallization of titanium dioxide, and we observe the shape and particle size of titanium dioxide with SEM. We use UV-visible spectrum to observe absorption spectrum of titanium dioxide. The result discovers that surfactant effect is using triblock copolymer, poly (ethylene oxide) - poly (propylene oxide) - poly (ethylene oxide), the titanium dioxide has anatase and rutile crystallization, and particle aggregation. The pH affects the partic le size and the shape. In pH is 5.8, the titanium dioxide has anatase and rutile crystallization. In water/ethanol ratio effect, we use solvent including ethanol, the titanium dioxide has anatase and rutile. Through hydrothermal process, titanium dioxide has little brookite crystallization and the few fibrous titanium dioxides. The doping gadolinium effect is the anatase is reducing with gadolinium content increasing, and from the UV-visible spectrum, the doping gadolinium titanium dioxide has the red shift. The titanium dioxide using polyoxyethylene sorbitan monostearate and doping gadolinium has the anatase, and absorbs a longer wavelength, and when the doping content is 1% titanium dioxide has a better absorption.

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