Photocatalytic TiO2 nanosheets-SiO2 coatings on concrete and limestone: An enhancement of de-polluting and self-cleaning properties by nanoparticle design

In this study, we develop TiO2-SiO2 nanocomposites that can be employed as photoactive coatings to create surfaces with antipollution and self-cleaning properties in urban buildings. In particular, anatase titanium dioxide with a high percentage of {0 0 1} facets, commonly called titania nanosheet (TNS), was used as active phase. This approach allows us to improve the antipollution properties of similar sols based on P25. The obtained TNS were intensively characterized by UV–Vis diffuse reflectance absorption, X-Ray diffraction and transmission electron microscopy to rationalize the sol synthesis and fully understand the photocatalytic performances. Our results clearly show that after treating the titania nanosheets with NaOH to remove adsorbed residual fluoride from the synthesis, they can be easily dispersed and the photocatalytic activity is dramatically improved. This material has been shown to effectively reduce concentrations of NOx, soot and organic dyes under simulated sun light radiation.