In recent years, publications describing novel photocatalytic systems have abounded, with a particular focus on efficient, stable, and scalable water splitting systems. Despite this, commercial applications of photocatalysis thus far have been dominated by pollutant destruction materials, most of which employ TiO
2. Assessment methods which probe the underlying photocatalytic response as regards the electron/hole generation, separation, migration and subsequent reaction are important for the intentional design of superior photocatalytic systems, as are methods which allow easy assessment and demonstration of photocatalytic activity for commercial purposes. In this thesis, the former need is addressed in two chapters detailing photoinduced absorption spectroscopy (PIAS) studies, and the latter in two chapters pertaining to photocatalytic activity indicator inks (
paiis). A methylene blue
paii is proposed as a superior alternative to the resazurin
paii which forms the basis of an international standard for photocatalytic self-cleaning assessment (Chapter 3), and a highly sensitive Ag based
paii is reported and shown capable of assessing photocatalytic materials which have previously proven too low in activity for assessment by existing ISO standard tests (Chapter 4). PIAS is used in tandem with transient photocurrent (TC) measurements to glean the reaction orders of water and chloride oxidation with respect to surface holes photogenerated on a WO
3 photoanode, and mechanisms which account for these observed orders are proposed; faradaic efficiencies and incident photon to current efficiencies for these reactions are also determined (Chapter 5). Lastly, PIAS is used to probe the photogenerated hole behaviour and oxygen generation mechanism for a P25 TiO
2 film, bypassing the need for electrochemical methods by using a sacrificial electron acceptor (NaIO
4) solution, and a fluorescence based lifetime sensor to monitor the generation of O
2 (Chapter 6). It is hoped that the methods described, and the mechanistic insights to water (and chloride) oxidation on WO
3 and TiO
2 surfaces, will aid in both the current commercial photocatalytic market, and the ongoing development of superior photocatalytic systems for sustainable fuel generation, and pollutant degradation.
| Date of Award | Dec 2024 |
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| Original language | English |
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| Awarding Institution | - Queen's University Belfast
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| Sponsors | Northern Ireland Department for the Economy |
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| Supervisor | Amilra De Silva (Supervisor), Peter Nockemann (Supervisor) & Andrew Mills (Supervisor) |
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