Photocatalytic selective oxidation of anionic compounds on TiO2 photocatalysts modified with quaternary ammonium base groups

Quaternary ammonium base groups were introduced onto surfaces of SiO2-covered TiO2 particles (SiO2–TiO2). Oxidation of p-toluenesulfuric acid on the surface-modified TiO2 powders proceeded more efficiently than that on SiO2-covered TiO2 particles without surface modification. On the other hand, the photocatalytic activity of surface-modified SiO2–TiO2 for oxidation of 1,4-dimethylpyridinium iodide was much lower than that of pure SiO2–TiO2. In addition, no difference in photocatalytic activity for oxidation of toluene was observed between surface-modified SiO2–TiO2 and pure SiO2–TiO2. The enhancement of the photocatalytic activity of surface-modified SiO2–TiO2 is due to electrostatic interaction between the substrate and functional groups introduced on SiO2–TiO2.