Thermally induced phase and photocatalytic activity evolution of polymorphous titania

TiO₂ nano-powders were prepared by hydrolysing titanium tetraisopropoxide at room temperature. The resulting products were dried at 382 K and then annealed at temperatures up to 1172 K for 1 h. Raman analysis showed different titania phase structures depending on the thermal treatment. A mixture of brookite and anatase was observed in the as-prepared sample and after thermal treatment at 472 K and 672 K, a mixture of anatase and rutile was observed at 872 K and 972 K, while a pure rutile phase was identified at 1172 K. Quantitative XRD analysis revealed nano-powders phase composition and crystallite sizes. The photoactivity was assessed by photoinduced degradation of methyl orange. All anatase-brookite compositions have showed high photoactivity while the best values were observed for the sample calcined at 472 K.