Brlec, Katarina;
(2023)
Mixed Anion Systems for Green Hydrogen Generation.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Hydrogen is the key element behind the global food supply due to its role in nitrogen fixing for ammonia fertiliser production. Currently, over 96% of hydrogen used worldwide is produced in processes associated with substantial carbon footprints like steam methane reforming or coal gasification. In addition to hydrocarbons, another major source of hydrogen on Earth is water. Hydrogen can be sustainably produced using photocatalytic water splitting – a biomimicry of photosynthesis – where water is reduced over a photocatalyst using energy derived from light. This photocatalytic water splitting effect was first characterised on TiO2 in the 1970s and in the 50 years since, TiO2 and other d0 metal oxides have been extensively studied. However, their electronic band structure with band gaps in excess of 3 eV and low-lying oxygen-dominated valence band prevents efficient hydrogen evolution from water under visible light. Mixed anion compounds (ON, OX, OCh) opened a new paradigm in the search for better photocatalysts, as the second anion can be engineered to have a higher-lying p orbital to optimise the band edge positions for water redox. To this effect, in this thesis the optoelectronic and surface properties of three known oxysulphide photocatalysts Y2Ti2O5S2, La5Ti2CuS5O7 and La5Ti2AgS5O7 are investigated using first principles density functional theory (DFT) calculations. As photocatalysis is heavily dictated by surface phenomena, special attention is paid to the simulations of different surfaces by establishing a complete workflow for surface simulations in DFT. The last part of this thesis delves into computational prediction of new oxychalcogenide photocatalysts from the Ln2M2O5Ch2 family, assessing the materials stability and also suitability for applications beyond photocatalysis.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Mixed Anion Systems for Green Hydrogen Generation |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Engineering Science Faculty Office |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10176397 |
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