Heterostructural transformation of mesoporous silica–titania hybrids

Abstract

Mesoporous silica (SBA-15 with the BJH pore size of 8 nm) containing anatase nanoparticles in the pore with two different titania contents (28 and 65 mass%), which were prepared by the infiltration of the amorphous precursor derived from tetraisopropyl orthotitanate into the pore, were heat treated in air to investigate the structural changes (both mesostructure of the SBA-15 and the phase and size of the anatase in the pore). The mesostructure of the mesoporous silica and the particle size of anatase unchanged by the heat treatment up to 800 °C. The heat treatment at the temperature higher than 1000 °C resulted in the collapse of the mesostructure and the growth of anatase nanoparticles as well as the transformation to rutile, while the transformation of anatase to rutile was suppressed especially for the sample with the lower titania content (28 mass%). The resulting mesoporous silica-anatase hybrids exhibited higher benzene adsorption capacity (adsorption from water) over those heated at lower temperature, probably due to the dehydroxylation of the silanol group on the pore surface. The photocatalytic decomposition of benzene in water by the present hybrid heated at 1100 °C was efficient as that by P25, a benchmark photocatalyst.

New Insights into Crystal Defects, Oxygen Vacancies, and Phase Transition of Ir-TiO2

“…48 The average crystallite size of the rutile phase is higher than that of anatase, indicating the transformation of anatase crystals into rutile with respect to the increase in temperature and Ir content. 49 The grain size of TiO 2 is less than 10 nm at 400 °C. Then, the crystalline phases started to grow through the reduction of Ti−OH groups at high temperatures.…”

“…According to the XRD results, TiO 2 peaks are broadened at low calcination temperatures (400 and 450 °C), and the intensities are sharper at temperatures above 500 °C, signifying the increase in the degree of crystallization and crystal growth . The average crystallite size of the rutile phase is higher than that of anatase, indicating the transformation of anatase crystals into rutile with respect to the increase in temperature and Ir content . The grain size of TiO 2 is less than 10 nm at 400 °C.…”

Functionalities and modification of sol–gel derived SiO₂–TiO₂ systems for advanced coatings and powders

“…A sample heated at 1100 °C showed efficient photocatalytic decomposition of benzene in water under UV irradiation. 116) Wu et al used a hydrothermal method to prepare powders of a mesoporous carbon-doped SiO 2 TiO 2 nanocomposite (COMS@TiO 2 -x) in the presence of two copolymers employed as surfactants (F127 and P123), 117) where the x in the formula corresponds to the volumetric ratio of TEOS to TBOT. The prepared powder samples were then hydrothermally treated at 180 °C.…”

Quantum Dot-Embedded Hybrid Photocatalytic Nanoreactors for Visible Light Photocatalysis and Dye Degradation

“…Over the last few decades, photocatalytic nanoreactors have gained significant interest because of their unique microenvironment, robust structure, and possibility to accommodate multiple catalytic sites in a confined volume. The porous structures of mesoporous silica NPs and zeolite-based nanoreactors have been utilized as porous hosts for various photocatalytic transformations. − For example, Cazorla-Amorós and co-workers utilized the TiO 2 /zeolite nanocomposite for the photocatalytic oxidation of propene within the nanocomposite . Recently, Ogawa and co-workers fabricated mesoporous silica and titania hybrids for the photocatalytic decomposition of benzene in water .…”

“…The porous structures of mesoporous silica NPs and zeolite-based nanoreactors have been utilized as porous hosts for various photocatalytic transformations. − For example, Cazorla-Amorós and co-workers utilized the TiO 2 /zeolite nanocomposite for the photocatalytic oxidation of propene within the nanocomposite . Recently, Ogawa and co-workers fabricated mesoporous silica and titania hybrids for the photocatalytic decomposition of benzene in water . In recent times, various structurally flexible photocatalytic nanoreactors have been designed to carry out a wide range of visible light-driven chemical transformations such as CO 2 reduction, , pollutant degradation, , hydrogen (H 2 ) production, , oxidation and reduction reactions, − etc.…”