TiO 2 –SiO 2 Self-Standing Materials bearing Hierarchical Porosity: MUB-200(x) Series toward 3D-Efficient VOC Photoabatement Properties
Résumé
3D-photoactive self-standing porous materials have been synthesized through the integration of soft chemistry and colloids (emulsions, lyotrope mesophases and P25 titania nanoparticles). Final multiscale porous ceramics are bearing 700-1000 m 2 g-1 of micro-mesoporosity depending on the P25 nanoparticle contents. The applied thermal treatment is not affecting the P25 anatase/rutile allotropic phase ratio. Photonic investigations correlated with the foams' morphologies suggest that the larger amount of TiO2 is introduced, the larger is the walls' density, the smaller is the mean size of the void macroscopic diameters, both effects inducing a reduction of the photon transport mean free path (lt) with the P25 content increases. A light penetration depth in the range of 6 mm is reached, depicting thus a real 3D-photonic scavenger behavior. The 3D-photocatalytic properties of the MUB-200(x) series, studied in a dynamic 2 "flow through" configuration show that, the highest photo-activity (concentration of acetone ablated and concentration of CO2 formed) is obtained with the highest monolith height (volume), while providing an average of 75 % mineralization. These experimental results validate the fact that these materials, bearing a 3D-photo-activity, are paving the path for air purification operating with self-standing porous monolith-type materials, which are much easier to handle than powders. As such, the photocatalytic systems can be now advantageously miniaturized, offering thereby indoor air-treatment within vehicles/homes while limiting drastically the associated encumbrance. Beyond, this "volumic" counter-intuitive acting mode for lightinduced reactions may find other relevant advanced applications towards photo-induced water splitting, solar fuel, dye sensitized solar cells (DSSC) while both optimizing photons scavenging and opening the path for miniaturization of the processes where encumbrance or footprint penalty would be advantageously circumvented.
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