TiO2 cement-based materials: Understanding optical properties and electronic band structure of complex matrices

- Combination of TiO2 with cement binders leads to inclusion of energetic disorders.
- Energetic disorders in the TiO2 cement samples leads to energetic tail bands.
- Ti+3 or oxygen vacancies energetic disorders appear in TiO2 cement samples.
- Energetic disorders in TiO2 cement materials can enhance the photoactivity.

Different mortar mixes using TiO2 P25 as photocatalyst have been prepared. The samples were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy and Photoluminiscence spectroscopy. Also, determination of hydroxyl radicals and degradation tests of NOx under visible and UV light have been performed. The results obtained have allowed determining the band edges, Urbach energies and valence band tail sizes, directly related to the energy levels present in the TiO2-cement based materials. Therefore, the schema of the electronic structures of the reference TiO2-photocatalyst and the three TiO2-cement based samples have been constructed. The photocatalytic efficiency has been evaluated according to these energy levels, being able to conclude that in some cases, as the mortar with slags, the chemical composition seems to prevail over the effect of the optical parameter and electronic band structure.

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