Development of metal cation compound-loaded S-doped TiO2 photocatalysts having a rutile phase under visible light Original Research Article

We have synthesized S (S4+)-doped TiO2 photocatalysts having a rutile phase. Rutile S-doped TiO2 photocatalysts loaded with metal ion compounds (Fe3+, Rh3+, Cu2+, Co3+, Ni2+, Cr3+) have also been prepared (S-doped TiO2-Mn+). The metal ions were adsorbed on the surfaces of S-doped TiO2 nanoparticles by impregnation methods (IM) or photodeposition methods (PH). The photocatalytic activities of S-doped TiO2 for oxidation of acetaldehyde in gas phase were drastically improved after adsorbing treatment of metal ions under a wide range of incident light wavelengths. Under photoirradiation at wavelengths longer than 350 or 420 nm, S-doped TiO2-Cu2+ (PH) shows the highest level of activity among the metal ions. S-doped TiO2-Fe3+ (IM) shows the highest level of activity for oxidation of acetaldehyde in gas phase compared to the activity levels of S-doped TiO2 with loading of other metal ions such as Rh3+, Cu2+ Co3+, Ni2+, and Cr3+ under a wide range of incident light wavelengths. The optimum amount of metal ion compound nanoparticles adsorbed on S-doped TiO2 was 0.1 wt%. In order to elucidate the role of metal ions adsorbed on the surface of S-doped TiO2, we measured the double beam photoacoustic spectra (DB-PA). The amount of Ti3+ generated as a result of the reaction between Ti4+ and photoexcited electrons was analyzed by this spectroscopy. The relationship between the reaction rate of photocatalytic oxidation of acetaldehyde on S-doped TiO2 adsorbed with metal ions and the charge separation between photoexcited electrons and holes is discussed.