Submicron-sized anatase, TiO2 with high photocatalytic activity, and (Ti, Sn)O2 nanocrystals formed via hydrothermal technique

Abstract

The compositional dependence of the crystalline phase and properties of precipitates (TixSn1−xO2) in the TiO2–SnO2 system, which were hydrothermally formed at 100–200 °C from the precursor solutions of TiCl4 and SnCl4 under weakly basic conditions in the presence of tetramethylammonium hydroxide (TMAH) was investigated. Rutile-type (Ti, Sn)O2 solid solutions with nano-sized crystallite were directly formed at 180 °C in the composition range of x = 0–0.8. Nanoparticles with anatase crystallite around 10 nm as a main crystalline phase of precipitates that were formed in the compositions x = 0.9 and 1.0 showed similar photocatalytic activity. As the hydrothermal treatment temperature rose from 100 to 200 °C, the crystallite size of rutile solid solution, Ti0.5Sn0.5O2, increased from 2.5 to 8.0 nm. The optical band gap of the samples changed in the range of 2.93–3.25 eV depending on their composition in the system. At the composition of x = 1.0, submicron-sized anatase-type pure TiO2 particles (sizes of cuboid sides are around 100–120 nm) with pretty high crystallinity and superior photocatalytic activity were formed from the aqueous solution of TiCl4 under basic hydrothermal condition at 180 °C in the presence of TMAH with concentration as 1.3 times high as the condition in the case of the nano-sized anatase.