Characterization and photocatalytic activity of noble-metal-supported surface TiO2/SiO2

M-TiO2/SiO2 photocatalysts were prepared by the photodeposition method using noble-metal salts (M: Pt4+, Pd2+, and Ag+) as precursors and the surface bond-conjugated TiO2/SiO2 as supporter in N2 atmosphere. The photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflection spectra (DRS), photoluminescence (PL) spectra, and zeta-potential. Their photocatalytic activities were evaluated using reactive Brilliant Red K-2G (K-2G) and Cationic Blue X-GRL (CBX) that showed different types of adsorption behavior on the oxides. XPS analysis verified that the introduction of noble metal led to the changes of the electronic environmental of Ti cations and the zeta-potential of oxides. As a result, K-2G has higher adsorption on Pt-TiO2/SiO2 than on TiO2/SiO2, while the adsorption of CBX has little change on the modified TiO2/SiO2 catalysts. At the same time, Pt-modified catalyst shows 2.8 times higher photoactivity than TiO2/SiO2 for the photodegradation of K-2G, but has a decrease in activity for CBX degradation. These noble-metal-supported TiO2/SiO2 can efficiently extend the light absorption to the visible region. The PL results demonstrated that the noble metal dopant acted as electron acceptor to hinder the recombination of the photoinduced electron–hole pairs.