Synthesis of freestanding silica and titania-silica aerogels with ordered and disordered mesopores
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Freestanding blocks of silica and titania-silica aerogels were prepared by the sol-gel method. It is possible to prepare crack-free, titania-silica aerogels with high titanium content by a careful control of the synthesis conditions. Prehydrolysis, complexation and polymer addition were used to adjust the hydrolysis and condensation rates of the silicon and titanium alkoxide precursors. Photoactive anatase TiO2 nanocrystals with a large surface area (i.e., up to 300m2g−1) were crystallized from the gel network by the high-temperature ethanol supercritical drying, and the resulting aerogel blocks were gas permeable and display a transition-regime diffusion behavior. Pore and volume shrinkages were observed in samples prepared by ethanol supercritical drying when the titanium content was increased resulting in a lower flux. Adding Pluronic P123 creates ordered mesopore domains and produces large pore aerogels even at high titanium contents. The photocatalytic oxidation reaction of trichloroethylene was performed by flowing the reactant gas mixture through the UV-irradiated aerogel blocks with excellent results.
KeywordsEnvironmental catalyst Photocatalytic oxidation Anatase TiO2 Volatile organic compound (VOC) Trichloroethylene
The authors would like to thank the financial support from the Hong Kong Research Grant Council and the Hong Kong Innovation and Technology Commission. We also thank the technical help from the Material Preparation and Characterization Facility (MCPF) and the Advanced Engineering Material Facility (AEMF) of the Hong Kong University of Science and Technology.
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