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.