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Browsing Thesis by Author "Atanacio, AJ"

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    Effect of indium and niobium segregation on the surface vs. bulk chemistry of titanium dioxide (rutile)
    (University of Western Sydney, 2013-01-01) Atanacio, AJ
    Since the landmark paper in 1972 by Fujishima and Honda [1], TiO2 has become one of the most promising candidates of a new generation of solar energy materials capable of generating clean hydrogen fuel using only sunlight (photo-electrochemically) to dissociate water. TiO2 has both bulk properties and surface properties which contribute to its functional performance. Considering that all of the electrochemical reactions induced by light occur at the surface of TiO2, it becomes clear that understanding the surface properties of TiO2 is of crucial importance for its performance; specifically the conversion of solar energy into chemical energy. The surface phase of TiO2 can be substantially different from that of the bulk phase as a result of a phenomenon known as segregation. Segregation involves the transport of certain lattice species from the bulk phase to the surface, driven by excess surface energy. To date, developments in the understanding of TiO2 solid solutions and related properties have mainly been centred on bulk properties. In comparison, relatively little work has been reported on segregation in TiO2 solid solutions and its influence on functional properties, such as reactivity and photoreactivity. The present work has studied the effect of indium (acceptor-type ion) and niobium (donor-type ion) segregation on the surface chemistry of well-defined In-doped and Nb-doped TiO2 solid solutions. Specifically, examining the relationship between imposed sample processing conditions, such as the gas phase oxygen activity, on segregation-induced surface enrichment. This was achieved using a range of complimentary analysis techniques including X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), Rutherford backscattering (RBS) and proton-induced X-ray emission (PIXE). Copyright © 2013 Western Sydney University