Three-dimensional
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 bear 700–1000 m2 g–1 of micromesoporosity depending on the P25 nanoparticle
contents. The applied thermal treatment does not affect the P25 anatase/rutile
allotropic phase ratio. Photonic investigations correlated with the
foams’ morphologies suggest that the larger amount of TiO2 that is introduced, the larger the walls’ density
and the smaller the mean size of the void macroscopic diameters, with
both effects inducing a reduction of the photon transport mean free
path (l
t) with the P25 content increase.
A light penetration depth in the range of 6 mm is reached, thus depicting
real 3D photonic scavenger behavior. The 3D photocatalytic properties
of the MUB-200(x) series, studied in a dynamic “flow-through”
configuration, show that the highest photoactivity (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 3D photoactivity, 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 now be advantageously miniaturized,
thereby offering indoor air treatment within vehicles/homes while
drastically limiting the associated encumbrance. This volumetric counterintuitive
acting mode for light-induced reactions may find other relevant advanced
applications for photoinduced water splitting, solar fuel, and dye-sensitized
solar cells while both optimizing photon scavenging and opening the
path for the miniaturization of the processes where encumbrance or
a foot-print penalty would be advantageously circumvented.