Abstract: Two different tin salts, SnCl₂^.2H₂O and SnCl₄^.5H₂O, were employed in the synthesis of Sn-doped TiO₂. And the crystal structures and visible-light photocatalytic activities between Sn2+-doped TiO₂ and Sn⁴⁺-doped TiO₂ were compared. The results show that both the anatase-to-rutile phase transformation temperature and the crystal growth of TiO₂ are remarkably decreased by Sn dopant, and the Sn²⁺ dopant shows the higher efficiency than Sn⁴⁺ dopant. And despite the similar spectra of XRD and FTIR, Sn²⁺-doped TiO₂ displays higher visible-light photocatalytic activities than Sn⁴⁺-doped TiO₂, due to the half-filled d electronic orbit of Sn²⁺. Mesoporous montmorillonite was chosen as the supporting material for Sn²⁺-doped TiO₂, due to its high crystalization and large specific surface area. When Sn²⁺-doped TiO₂ was loaded on mesoporous montmorillonite, the resualtant samples had no significant difference in XRD patterns and FTIR spectra as compared with the supporting material, and no obvious peaks were found related to Sn²⁺-doped TiO₂. While the UV-Vis analysis shows that the adsorption edges of Sn²⁺-doped TiO₂ display red shift after loaded onto mesoporous montmorillonite. As a result, the resultant compound photocatalyst exhibits higher visible-light catalytic activity than unloaded Sn²⁺-doped TiO₂, which is due to the interactions between mesoporous montmorillonite supports and Sn²⁺-doped TiO₂. This might provide a promising way to improve the photocatalytic activity of TiO₂ with minimized cost and widened light-response region.

Key words: Sn-doped TiO₂, visible-light photocatalytic activity, mesoporous montmorillonite, loading