Direct Solvothermal Formation of Nanocrystalline TiO2 on Porous SiO2 Adsorbent and Photocatalytic Removal of Nitrogen Oxides in Air over TiO2–SiO2 Composites

Solvothermal decomposition of titanium(IV) tert-butoxide (TTB) in toluene at 573 K in the presence of silica gel (SiO 2 ) with continuous stirring yielded a titanium(IV) oxide (TiO 2 )–SiO 2 composite in which agglomerates of nanocrystalline TiO 2 were deposited on the surfaces of SiO 2 particles. Various TiO 2 –SiO 2 composites having different TiO 2 contents can be synthesized by changing the ratio of TTB and SiO 2 , and the composites had large surface areas corresponding to porous properties of SiO 2 . These TiO 2 –SiO 2 composites were used for photocatalytic removal of nitrogen oxides in air and their photocatalytic performances were compared with those of other TiO 2 –SiO 2 samples prepared by different methods. Solvothermally synthesized 74 wt.%TiO 2 –SiO 2 composite exhibited excellent photocatalytic performance (almost stoichiometric removal of NO x (98%) and very low NO 2 release (0.3%)) attributable to high photocatalytic activity of TiO 2 and high adsorption property of SiO 2 . Lesser performance of 74 wt.%TiO 2 –SiO 2 composites prepared by other methods suggested that pore-mouth plugging of SiO 2 by TiO 2 and lower level of mixing of TiO 2 and SiO 2 decreased photocatalytic performance of the composites.