Synthesis and photocatalytic properties of SnO 2-mixed and Sn-doped TiO 2 nanoparticles

Abstract

SnO 2-mixed and Sn-doped TiO 2 nanoparticles were synthesized via a hydrothermal process. SnO 2-mixed TiO 2 nanoparticles prepared in a neutral condition consisted of anatase TiO 2 nanoparticles(diamond shape, ~25 nm) and cassiterite SnO 2 nanoparticles(spherical shape, ~10 nm). On the other hand, Sn-doped TiO 2 nanoparticles obtained under a high acidic condition showed a crystalline phase corresponding to rutile TiO 2. As the Sn content increased, the particle shape changed from rod-like(d~40 nm, l~200 nm) to spherical(18 nm) with a decrease in the particle size. The peak shift in the XRD results and a change of the c-axis lattice parameter with the Sn content demonstrate that the TiO2 in the rutile phase was doped with Sn. The photocatalytic activity of the SnO 2-mixed TiO 2 nanoparticles dramatically increased and then decreased when the SnO 2 content exceeded 4%. The increased photocatalytic activity is mainly attributed to the improved charge separation of the TiO 2 nanoparticles with the SnO 2. In the case of Sn-doped TiO 2 nanoparticles, the photocatalytic activity increased slightly with the Sn content due most likely to the larger energy bandgap caused by Sn-doping and the decrease in the particle size. The SnO 2-mixed TiO 2 nanoparticles generally exhibited higher photocatalytic activity than the Sn-doped TiO 2 nanoparticles. This was caused by the phase difference of TiO 2.