Enhance photocatalysis of TiO2 and ZnO ceramics by addition of fused silica as a UV guiding medium

We report a facile method to prepare porous TiO2 and ZnO photo-catalytic ceramics in which colloidal silica was added to yield nano fused silica (FS). The colloidal silica forms continuous media within the porous ceramic structure, and when calcined at 550 degrees C, it converted to fused silica phase which is an excellent UV wave-guiding material. With light wave guiding effect of FS and capillary effect of reaction solution in the porous channels, the photo-catalytic reactions could occur at the vast active sites at interface inside the porous bulks, as well as at the external surfaces. Photo-catalysis experiments and kinetics were investigated and analyzed. The photo-catalytic efficiencies tested for methylene blue were enhanced by a factor of 4.1 for TiO2/FS system and, astonishingly, by a factor of 34.6 for ZnO/FS system, when compared with pure TiO2 and ZnO under identical testing conditions. A model of UV-waveguide ceramic systems was proposed and discussed. This study proposes a practical approach to construct UV-waveguide porous structures, of which the principle is also potentially applicable to other types of photo-catalytic materials, including visible light active photo-catalysts.