Synthesis of Mesoporous Silica-Titania Hollow Spheres and Utilization of Their Bifunctional Catalytic Properties

Abstract

　In this study, mesoporous silica-titania hollow spheres synthesized at Si/Ti molar ratio of 10, 30, and 100 were evaluated the activity for hydrolysis of ammonia borane (NH₃BH₃), adsorption, and photocatalytic activity of methylene blue (MB). These hollow spheres were synthesized via the sol-gel method using polystyrene particles as templates. The uniform hollow spheres structure was observred from the transmission electron microscopy images of the samples synthesized at various Si/Ti molar ratios. Additionally, the result of the pore size distribution suggested the presence of mesopores in shell of the hollow spheres. We measured the avtivity for hydrolysis of NH₃BH₃ in the presence of these hollow spheres. The amount of hydrogen evolution increased in the order of samples synthesized with Si/Ti molar ratios of 100, 10, and 30. We found that the amount of hydrogen evolution was influenced by the number of acid sites from the result of neutralization titration. Meanwhile, the amount of the MB adsorption exhibited a consistent with the amount of hydrogen evolution. The photocatalytic activity of the MB was promoted for samples synthesized at Si/Ti molar ratios of 10 and 30 probaly because these samples might be included to the fine anatase titania particles.