Gupta, Verena Kristin
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Item type:Publication, Modeling TiO2: insights into photocatalytic material properties and reactions(2021-10-07); ; ; Titania is an industrially well known material, which is commonly used as a cost- efficient pigment in sun screens or paints. Additionally to this application, titania is one of the most frequently applied photo-catalysts in water and air purification. However, its utilization in photo-chemistry is up-until date still not satisfactorily ex- plored. Especially the fact, that titania’s three phases, anatase, rutile and brookite, show photo-induced electron-hole pair formation in their pristine form only under ultra violet (UV) irradiation, renders most utilization of titania as a photo-catalyst in- efficient for large-scale applications. Therefore, ways to improve the photo-catalytic activity of Titania are being sought. Despite the discussion of a variety of different approaches to achieve the same, to date no convincing methods have been found that can adequately enhance TiO2s photocatalytic efficiency or are not yet explored satisfactorily. Based on these challenges, the work presented in this thesis set out to explore three different approaches for enhancement, which will be introduced in the following.doctoral thesis270 187 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, NO Degradation on the Anatase TiO2 (001) Surface in the Presence of Water(American Chemical Society, 2022-10-10); ; ; ; Nitric oxide (NO) is known to degrade to nitric acid (HNO3) on anatase TiO2 facets under visible light irradiation in the presence of water. However, the exact role that water plays in this photoreaction is not fully understood. By employing the density functional theory (DFT) and time-dependent density functional tight binding (TD-DFTB), we show the viability of two suggested degradation pathways involving water. Both reaction pathways are triggered by a charge transfer excitation from the NO molecule to the TiO2 surface. In one of them, NO interacts with dissociated water molecules adsorbed on the surface to form HONO+, whereas for the second pathway, NO is oxidized to NO2+ by capturing one oxygen atom from the substrate. Both HONO and NO2 are known byproducts in the photodegradation of NO, which further react with adsorbed water to finally produce HNO3. We also demonstrate by means of nudged elastic band calculations that these reactions are unlikely to happen without illumination.journal articleBand:126Heft:4183 51 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Water Reactions on Reconstructed Rutile TiO2: A Density Functional Theory/Density Functional Tight Binding Approach(American Chemical Society, 2021-06-14); ; ; ; Far from being conclusively understood, the reactive interaction of water with rutile does still present a challenge to atomistic modeling techniques rooted in quantum mechanics. We show that static geometries of stoichiometric TiO2/water interfaces can be described well by density functional tight binding. However, this method needs further improvements to reproduce the low dissociation propensity of H2O after adsorption predicted by density functional theory (DFT). A reliable description of the surface reactivity of water is fundamental to investigate the nonstoichiometric reconstruction of the (001) facet rich in Ti interstitials. Calculations based on DFT predict the transition temperature for the onset of reconstruction in remarkable agreement with experiments and suggest that this surface, in contact with liquid water, can promote spontaneous H2O splitting and formation of H2 molecules.journal articleBand:125Heft:2439 48