Tio2 modifications and their environmental photocatalytic performance: an epr investigation

Salli, Sofia 2024. Tio2 modifications and their environmental photocatalytic performance: an epr investigation. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

This thesis investigates the generation and behaviour of paramagnetic states in various titanium dioxide (TiO2) materials using electron paramagnetic resonance (EPR) spectroscopy. The study focuses on the synthesis of novel co-doped materials, their characterisation and exposure to oxygen under different wavelengths irradiation, highlighting the sensitivity and non-invasive nature of EPR in detecting these states. Additionally, the capabilities of the catalysts were studied via introduction of organic substrates mixtures and formation monitoring of the different radical species. This thesis studies the differences in activity for the various polymorphs of the co-doped TiO2. Thus, allowing for the further development of TiO2 catalysts to be achieved, by improving the efficiency of the materials. It was demonstrated that the photocatalytic activity of the TiO2 materials was influenced by the phase and the variety of lattice modifications. This was achieved via the incorporation of aliovalent dopant atoms via sol-gel synthesis and different calcination methods. The metal dopants selected were tungsten and tantalum, as they are reasonably inexpensive and abundant compared to platinum group metals, while nitrogen was chosen as the non-metal dopant. Doping aimed to modify the optical properties and surface chemistry of TiO2, as it has been demonstrated to introduce energy levels within the band gap of the semiconductor and thus later the charge carriers production. These modifications allow for the catalysis to take place under solar visible light over the current limited UV light, as it only makes up 4% of solar energy. Through this work, it was demonstrated that the polymorphic activity from the different calcinations, the influence of dopants on the band structure and the photocatalytic activity allows for a more targeted design of co-doped TiO2. Though some materials underperformed compared to commercial P25 under UV light, their true potential may lie in visible light-driven processes, such as volatile organic compounds decomposition and glycerol transformation. The insights gained from this thesis provide new directions for designing efficient photocatalysts, with significant implications for industrial applications.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Chemistry
Date of First Compliant Deposit:	4 April 2025
Last Modified:	04 Apr 2025 14:21
URI:	https://orca.cardiff.ac.uk/id/eprint/177419

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