Effects of silica coating on photocatalytic reactions of anatase titanium dioxide studied by quantitative detection of reactive oxygen species

[Display omitted] ► Active oxygens were quantitatively detected for UV-irradiated anatase TiO2 suspension. ► H2O2 was produced from both oxidation of water and reduction of O2. ► By silica coating, the photocatalytic formation of H2O2 was significantly suppressed. ► The weather resistance by silica coating may be explained by the suppression of H2O2. The effects of silica coating on the photocatalytic properties of anatase titanium dioxide (TiO2) were studied by quantitative detection of reactive oxygen species under UV-irradiation, because the surface modification with silica has been practically used to suppress the photocatalytic activity in organic supports. For reactive oxygen species such as superoxide radicals (O2−), H2O2, and OH radicals, the detection methods using MCLA chemiluminescence, lucigenin chemiluminescence, and coumarin fluorescence were employed respectively. By comparing silica-coated TiO2 with uncoated TiO2 powders, the amount of H2O2 detected under UV irradiation was significantly decreased by silica coating. Thus the silica modification suppressed the release of H2O2, which may be the nature of the effect of silica coating for suppressing photocatalytic activity against organic supports.