Characterization and photocatalytic activity of transition-metal-supported surface bond-conjugated TiO2/SiO2

TM/TiO2/SiO2 photocatalysts were prepared by the photodeposition method using transition metal salts (TM = Fe3+, Co2+, Ni2+ and Cu2+) as precursors and the surface bond-conjugated TiO2/SiO2 as supporter in N-2 atmosphere, and were characterized by XRD, XPS, UV-Vis diffuse reflection and zeta-potential. Their photocatalytic activities were evaluated using reactive brilliant red K-2G (K-2G) and cationic blue X-GRL (CBX) showing different adsorption behavior on the oxides. Fe, Cu supported TiO2/SiO2 can efficiently extend the light absorption to the visible region. XPS analysis verified that the introduction of transition metal lead 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 the modified TiO2/SiO2 than that on the baked one, while the adsorption of CBX has a little change on the both oxides. At the same time, for the photodegradation of K-2G, Fe3+, Co2+, Ni2+-modified catalysts show that their photoactivities are 3.3-2.2 times higher than the bare one. On the contrast, all transition-metal-supported catalysts have no significant activity improvement except that Fe/TiO2/SiO2 shows 1.68 times higher activity for the photodegradation of CBX The results indicate that the photoactivity could be increased in photodegradation of dyes by changing the performances of adsorption to dyes and absorption to light of photocatalyst. (C) 2004 Elsevier B.V. All rights reserved.