Correlation between photoreactivity and photophysics of sulfated TiO2 photocatalyst

The sulfated TiO2 were prepared by dipping TiO2 in H2SO4 solutions. The reactivity of methylene blue photocatalytic degradation of all SO42−/TiO2 are higher than that of TiO2, and the optimum molar concentration of SO42− on TiO2 is 9%. IR confirmed that the chelating bidentate SO42− and unidentate SO42− coexist in SO42−/TiO2. Methylene blue is cationic dye. Maybe the Lewis acid and Bronsted acid coexist in the SO42−/TiO2 catalyst, the adsorption of methylene blue on the catalyst increases. The high photocatalytic reactivity of SO42−/TiO2 is consistent with the good adsorption. The presence of SO42− enhances the light absorption in the visible region of SO42−/TiO2, and the photocatalytic activity of SO42−/TiO2 correlates with reflectance of the samples in the visible light region. The fluorescence spectra show that weaker the fluorescence intensity the higher the activity. Thus, The enhanced photocatalytic activity of SO42−/TiO2 may be explained by the good adsorption of methylene blue on the catalysts, high light absorption in the visible region, and weak fluorescence intensity.