Design, Synthesis and Photocatalytic Activity of Novel Efficient Photocatalysts

Xiao Xia Yan (2011). Design, Synthesis and Photocatalytic Activity of Novel Efficient Photocatalysts PhD Thesis, Aust Institute for Bioengineering & Nanotechnology, The University of Queensland.

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Author Xiao Xia Yan
Thesis Title Design, Synthesis and Photocatalytic Activity of Novel Efficient Photocatalysts
School, Centre or Institute Aust Institute for Bioengineering & Nanotechnology
Institution The University of Queensland
Publication date 2011-03
Thesis type PhD Thesis
Supervisor Max Lu
Lianzhou Wang
Total pages 180
Total colour pages 50
Total black and white pages 130
Subjects 10 Technology
Abstract/Summary Search for renewable energy sources and sustainable environmental technology is one of the foremost challenges for maintaining the quality of human life. Semiconductor photocatalysis is a kind of promising technology converting the solar energy into chemical and/or electric energy. Pioneering work by Honda and Fujishima in the 1970s has opened up great opportunity for the use of photocatalysis in the fields of sustainable energy utilization and environmental remediation. However, photocatalytic applications are still limited due to the low efficiency caused by a number of challenging issues such as narrow light-response range, high recombination rate of charge carriers, and poor material stability, which have hindered the application of photocatlysis. In the photocatalytic reactions, the electronic structure, bulk structure and surface structure of semiconductor photocatalysts play key roles in the excitation, bulk diffusion, and surface transfer of photoinduced charge carriers. In the past decades, tremendous efforts have been made for improving photocatalytic efficiency. The aim of this project is to design and synthesize novel efficient photocatalysts. Based on the fundamental understanding of the heterogeneous photocatalysis, we attempted to design and prepare some promising photocatalysts including TiO2, CdS, WO3, and tantalate by controllable crystal growth, band-gap engineering, and heterostructuring strategy. The first part of this program, nanostructured anatase TiO2 materials with different percentages of active (001) facet were successfully prepared by rationally controlling the hydrothermal synthesis processes. When reducing the exposed (001) facets, their photocatalytic activities in the degradation of dye and phenol pollutants were decreased, suggesting the important role of active (001) facet in photocatalytic organic removal. In the second session of this project, nitrogen-doping were employed to modify the band gap structure of the layered tantalate materials and TiO2 microbelts (TMBs). In the case of the layered tantalate RbTaO3 materials, an exciting band-to-band visible-light response was obtained successfully by homogeneous nitrogen doping. The visible-light-driven photocatalysts exhibit better photo-reactivity by the measurement of OH radicals and photodegradation of organic contaminants. The fundamental understanding of the relationship between crystal size and light absorption property in nitrogen-doped TiO2 micro-belts was further revealed. The experiment results indicate that crystal size of the photocatalysts play a critical role in shifting the visible light absorption. In the last part of this thesis, heterostructured multicomponent semiconductor systems were designed and prepared for improving the photocatalytic performance. Two types of semiconductor systems, CdS/TiO2 and WO3/TiO2, were selected. CdS/TiO2 nanocomposites were obtained by self-assembly of CdS nanoparticles and exfoliated TiO2 nanosheets. The resultant CdS/TiO2 composites exhibited enhanced photocatalytic activity in the oxidation of dye rhodamine B in water under visible light irradiation ( > 420 nm) compared to the pure CdS nanoparticles. More importantly, the photocorrosive problem for CdS particles was weakened obviously due to the outside TiO2 nanosheets. Highly ordered mesoporous WO3/TiO2 (MWT) hybrid materials were prepared by using surfactant as template and WCl6 and Ti(OPr)4 precursors as “acid-base pair’’ through an evaporation-induced self-assembly (EISA) process. This method leads to the better component homogeneity and controllability. Photocatalytic performances of these samples were measured by fluorescence probe for OH radicals and degradation of typical organic pollutants (e.g. rhodamine B and phenol). The assessment of photocatalytic activity indicated that the balance between surface area and crystallinity degree was required by adjusting the calcinations temperatures.
Keyword Photocatalysis
titanium dioxide
controllable synthesis
band-gap engineering
solar energy
organic pollutants
environmental purification
Additional Notes 31,32,34,39,50,53,54,56,59,60, 84,85,88-92, 101-103,105,106,108, 118-122,126,127, 139-142,144, 154,156,157,159-162, 169,173-179

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Created: Wed, 24 Aug 2011, 22:16:33 EST by Ms Xiao Xia Yan on behalf of Library - Information Access Service