Hydrothermal Synthesis and Morphological Evolution of Mesoporous Titania−Silica

Abstract

Mesoporous titania−silica (TiO2−SiO2) composites have been directly synthesized through a hydrothermal method in weak acidic conditions by using TiCl3 solution as a titanium source and triblock copolymer P123 (EO20PO70EO20) as a template with the assistance of zinc acetate. Characterizations by XRD, TEM, and N2 sorption measurements show that highly ordered mesostructured TiO2−SiO2 with the BET specific area of 882 m2/g was obtained with the Ti/Si molar ratio of 0.1. Morphology of the composites can be controlled by the incorporation of different amounts of titanium species. Highly curved shapes such as winding, worm-like, and wheat grain-like particles were obtained by this direct synthetic method. Acidity and zinc acetate concentration can also affect the morphology of the composites. UV−vis, FTIR and 29Si MAS NMR results display that titanium species exist both in the framework and extra-framework of the mesoporous SiO2. Wide angle XRD, Raman, and HRSEM results show that the outer surface of the SiO2 (probably Ti-doped) is decorated by round anatase nanocrystallites (probably Si-doped), whereas X-ray mapping results reveal that titanium species are highly dispersed on the final mesoporous composites. The formation mechanism of the mesophase was discussed based on characterization results. Photocatalytic results show that the TiO2−SiO2 composites prepared in this way have high catalytic activity in the photodegradation of isopropanol due to both framework and surface titanium species.