Design of material for solar fuel production

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Rhatigan, Stephen
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University College Cork
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To harness even a fraction of the solar energy incident at Earth’s surface would meet global demands for clean, environmentally friendly electricity and fuel. Sunlight is an intermittent energy source and a mismatch exists between the peaks of supply and demand. A strategy to overcome this drawback is to convert the solar energy to chemical energy (stored in the bonds of chemical fuels), which allows for storage, transport, and reintroduction to the grid as and where required. Solar-to-fuel technologies will also reduce carbon emissions by providing alternatives to fossil fuels. One avenue for the storage of solar energy in fuel is water splitting, where solar energy is used to decompose water into gases of its constituent elements, O 2 and H 2 gases. Solar driven water splitting can proceed at the surface of a semiconductor photocatalyst. The most widely studied and, to date, the benchmark, photocatalyst material is titanium dioxide (TiO 2 ). TiO 2 is abundant, cheap, non-toxic and stable under operating conditions. However, its large band gap means that TiO 2 is only activated by UV light, which constitutes just 4% of the incident solar energy. Thus, the focus of this thesis is the modification of TiO 2 , through rational design, to enhance its photocatalytic properties. First principles density functional theory (DFT) simulations of modified TiO 2 are performed to assess the performance of the novel materials as photocatalysts for the water splitting half reactions: the oxygen and hydrogen evolution reactions. We adopt a materials descriptor approach, wherein we compute key performance indicators that can be compared across materials to evaluate the impact of the modification on the photocatalytic properties. Our results inform and explain the experimental results from collaborators in Ireland, the Netherlands and Spain.
Photocatalysis , Density functional theory , Titanium Dioxide
Rhatigan, S. 2020. Design of material for solar fuel production. PhD Thesis, University College Cork.