Study On Preparation, Modification And Photocatalytic Properties Of Anatase Titania Nanoparticles With High Thermal Stability

The preparation of anatase TiO₂ with high photocatalytic activity and thermal stability has been a hot research and challenge in the field of semiconductor photocatalysis. This thesis aims to synthesize anatase TiO₂ nanoparticles with high photocatalytic activity and thermal stability, and made an attempt on their modification. Here, nanosized anatase TiO₂ particles and its silica-modified composites have been prepared via force hydrolysis, pyrolysis and hydrothermal method using titanium sulfate as starting material, and the properties of catalysts were investigated and compared.(1) Anatase titania nanoparticles with high thermal stability were prepared by force hydrolysis and pyrolysis, respectively. The results of XRD and BET surface areas showed that the catalysts synthesized by the two different methods had similar characteristics. They had the largest specific surface areas and exhibited the highest photocatalytic activity in decomposition of methyl orange when calcined at 700℃. It was suggested that SO₄^2- contributed to the stabilization of the structure of TiO₂, restraining the transformation of antase into rutile and preventing TiO₂ sintering during calcination.(2) Nanosized silica-modified anatase TiO₂ composites with large surface areas were prepared by a hydrothermal method. Ti-O-Si bonds formed. The addition of silica gel could effectively improve the thermal stability of TiO₂ and inhibit the transformation of anatase to rutile phase and the growth of titanium dioxide crystals during the calcination treatment. The silica-modified TiO₂ composites exhibited better photocatalytic activity in comparison with pure TiO₂ and Degussa P-25 in degradation of methylene blue.(3) Silica-modified anatase TiO₂ nanoparticles were synthesized by a direct approach under conventional hydrothermal conditions using urea as template, followed by calcination treatment. The samples treated hydrothermally at 160℃ had a relatively lower specific surface areas and photocatalytic activity than that treated at 100℃. It showed that the urea had a more distinct effect when treated hydrothemally at 100℃.(4) Nanosized silica-modified anatase TiO₂ with mesostructure were synthesized by a direct approach under conventional hydrothermal treatment using poly (ethylene glycol)...