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Characterisation and reactivity of TiO2 based materials for environmental applications; An EPR Investigation

Armstrong, Katherine 2019. Characterisation and reactivity of TiO2 based materials for environmental applications; An EPR Investigation. PhD Thesis, Cardiff University.
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This thesis employs Electron Paramagnetic Resonance Spectroscopy (EPR) Owing to its sensitivity, non-invasive properties and the specificity of the spin Hamiltonian parameters, to study the generation and subsequent behaviour of charge carrier pairs in various TiO2 polycrystalline materials. These charge carriers have been examined via the formation of thermally generated defects (i.e. oxygen deficient environments), with subsequent exposure to different probe molecules i.e. oxygen and VOCs, to understand their stability and reactivity. Studying the photo-dynamics of charge carrier pairs, allows for a greater understanding of the electron transfer mechanism with regards to environmental remediation. Currently, catalysts used for industrial environmental remediation use either expensive catalysts or do not provide the activity to meet current demands, hence a study for an alternative catalyst is imperative. This thesis studies the differences in activity for the various polymorphic forms of TiO2. This allows for further development to improve the efficiency of the TiO2 catalyst. Not only has the phase of TiO2 been demonstrated to influence the catalytic activity, but further modification to the lattices has been indicated to provide an increased activity. This has been demonstrated via the use of incorporation of foreign atoms via aliovalent doping in this thesis. Group VI dopant atoms have been studied, this allows for the use of inexpensive, abundant dopants in an aim to modify the optical properties and the surface chemistry of TiO2. Doping within the lattice matrix has been shown to introduce energy levels within the band gap of the semiconductor and thus reduce the energy or excitation required to produce charge carriers. This will allow for the exploitation of visible light over the current use of UV light which only makes up ~4% of solar energy. Studying both the polymorphic activity and the influence of dopants of the band structure and catalytic activity will allow for more focus on the design of TiO2 based photocatalysts, with particular attention drawn to the ability of alternative transition metal ions to be used as dopants, allowing to move away from using expensive PGMs.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Chemistry
Funders: EPSRC
Date of First Compliant Deposit: 25 February 2020
Last Modified: 26 Mar 2021 16:21

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