Novel modified nonalkoxide sol–gel synthesis of multiphase high surface area TiO2 aerogels for photocatalysis

Multiphase TiO2 aerogels were synthesized through a simple, environment friendly sol–gel route. TiCl3 was used as nonalkoxide precursor with ethanol as solvent. The formed alcogels were converted into aerogels by CO2 supercritical drying. The results revealed that the increase in TiCl3 concentration leads to the decay of the gelation time, possibly due to the availability of Ti+4 ions in the medium that led to the formation of the interconnected gel network more easily. The aerogels produced from 0.75 M TiCl3 and calcined at 450 °C exhibited the three main crystalline phases of titania (anatase, brookite, and rutile) and a specific surface area of 124 m2/g. Through transmission electron microscopy, it was possible to visualize the morphology of the nanostructured aerogels, comprised of a network of nanoparticles with sizes between 5 and 15 nm. The combination of high specific surface area, particle size in nanometer scale, and crystallinity of the material allowed greater photocatalytic reduction of 4-nitrophenol compared with commercial Degussa P-25.