The hydrothermal synthesis of titanate nanotubes with different temperatures and
durations and the investigation of their photocatalytic properties for the removal of
methylene blue under UV light irradiation from an aqueous environment was
reported by Liu et al. (Liu et al. 2015) and Subramaniam et al. (2017). Compared
to their P25 TiO 2 nanoparticle precursor, they are mesoporous with larger specific
surface area and present both a higher dye absorption capacity and a better
photocatalytic performance for the dye decomposition under UV light irradiation
in aqueous solutions.
2.4.3 (Nano)composites: TiO 2 Supported on Porous Matrices
Mesoporous TiO 2 are not thermally stable and usually exhibit low porous characteristics, or even a collapse of the mesostructure, after thermal treatment that is
necessary to get highly crystalline anatase walls for good photocatalytic efficiency.
To overcome these drawbacks, silica-embedded titania and/or titania-silica mixed
oxides have been prepared. The introduction of silica is also a way to modulate
surface properties for improving the adsorption of dyes and thus the photocatalytic
performance of the material. Highly ordered 2D hexagonal mesoporous TiO 2 /SiO 2
composite with variable Ti/Si ratios have been prepared by evaporation-induced
co-assembly process using titanium isopropoxide and tetraethyl orthosilicate as
precursors, triblock P123 copolymer as template, and a large amount of HCl to
control co-condensation of precursors (Dong et al. 2007). The obtained TiO 2 /SiO 2
nanocomposites have large regular mesopores (6–8 nm) and are ultra thermally
stable, over 900
C when Ti/Si
80/20, with high specific surface area
(200–300 m
2 /g). Their walls are constituted of anatase nanocrystallites glued by
amorphous silica. The photocatalytic activities of these composites for the degradation of rhodamine B in aqueous solution were found excellent and higher than those
of commercial TiO 2 P25. The study of their photocatalytic properties has been
extended to the degradation of a large variety of anionic and cationic dyes (Dong
et al. 2012). It was demonstrated that the surface properties of these TiO 2 /SiO 2
nanocomposites can be modulated by varying the Ti/Si ratio and the calcination
temperature to adapt them for an optimal adsorption (number of surface hydroxyls)
and efficient photodegradation (size and crystallinity of anatase nanocrystals)
according to the nature of the dye. Recently, it was reported that the extraction of
silica from these TiO 2 /SiO 2 nanocomposites leads to stable and reusable threedimensional interconnected mesoporous anatase photocatalysts. The photocatalytic
activity for the degradation of dyes in aqueous solution under UV light irradiation is
much higher than the TiO 2 /SiO 2 parent materials and commercial P25 (Dong et al.
2017). The departure of silica from the wall has left interlinked mesoporous network
that helps the diffusion of dye molecules. The introduction of silica precursor as a
stabilizer has been also reported for the solvothermal synthesis of silica-embedded
titania rhombic-shaped nanoparticles (Yao et al. 2013). The presence of silica allows
growing well-defined anatase crystals with high specific surface area that increases
56
B. Lebeau et al.
durations and the investigation of their photocatalytic properties for the removal of
methylene blue under UV light irradiation from an aqueous environment was
reported by Liu et al. (Liu et al. 2015) and Subramaniam et al. (2017). Compared
to their P25 TiO 2 nanoparticle precursor, they are mesoporous with larger specific
surface area and present both a higher dye absorption capacity and a better
photocatalytic performance for the dye decomposition under UV light irradiation
in aqueous solutions.
2.4.3 (Nano)composites: TiO 2 Supported on Porous Matrices
Mesoporous TiO 2 are not thermally stable and usually exhibit low porous characteristics, or even a collapse of the mesostructure, after thermal treatment that is
necessary to get highly crystalline anatase walls for good photocatalytic efficiency.
To overcome these drawbacks, silica-embedded titania and/or titania-silica mixed
oxides have been prepared. The introduction of silica is also a way to modulate
surface properties for improving the adsorption of dyes and thus the photocatalytic
performance of the material. Highly ordered 2D hexagonal mesoporous TiO 2 /SiO 2
composite with variable Ti/Si ratios have been prepared by evaporation-induced
co-assembly process using titanium isopropoxide and tetraethyl orthosilicate as
precursors, triblock P123 copolymer as template, and a large amount of HCl to
control co-condensation of precursors (Dong et al. 2007). The obtained TiO 2 /SiO 2
nanocomposites have large regular mesopores (6–8 nm) and are ultra thermally
stable, over 900
C when Ti/Si
80/20, with high specific surface area
(200–300 m
2 /g). Their walls are constituted of anatase nanocrystallites glued by
amorphous silica. The photocatalytic activities of these composites for the degradation of rhodamine B in aqueous solution were found excellent and higher than those
of commercial TiO 2 P25. The study of their photocatalytic properties has been
extended to the degradation of a large variety of anionic and cationic dyes (Dong
et al. 2012). It was demonstrated that the surface properties of these TiO 2 /SiO 2
nanocomposites can be modulated by varying the Ti/Si ratio and the calcination
temperature to adapt them for an optimal adsorption (number of surface hydroxyls)
and efficient photodegradation (size and crystallinity of anatase nanocrystals)
according to the nature of the dye. Recently, it was reported that the extraction of
silica from these TiO 2 /SiO 2 nanocomposites leads to stable and reusable threedimensional interconnected mesoporous anatase photocatalysts. The photocatalytic
activity for the degradation of dyes in aqueous solution under UV light irradiation is
much higher than the TiO 2 /SiO 2 parent materials and commercial P25 (Dong et al.
2017). The departure of silica from the wall has left interlinked mesoporous network
that helps the diffusion of dye molecules. The introduction of silica precursor as a
stabilizer has been also reported for the solvothermal synthesis of silica-embedded
titania rhombic-shaped nanoparticles (Yao et al. 2013). The presence of silica allows
growing well-defined anatase crystals with high specific surface area that increases
56
B. Lebeau et al.