Effect of TiOSO4 hydrothermal hydrolysis conditions on TiO2 morphology and gas-phase oxidative activity

The effect of synthesis conditions on morphology and catalytic activity has been studied for hydrothermal preparation of TiO₂ from acidified aqueous TiOSO₄ solution. It was found that the increase in TiOSO₄ and H₂SO₄ concentration results in the increase of photocatalytic activity of produced TiO₂, as it was revealed by steady-state gas-phase oxidation of acetone and ethanol vapors in a flow-circulating reactor. TiOSO₄ concentration exerts strong influence on the shape of the produced TiO₂ particles. At TiOSO₄ concentration less than 0.1 wt%, hydrolysis gives rise to hedgehog-like agglomerates consisting of spliced-blade TiO₂ nanocrystals. At higher concentration of TiOSO₄, the resultant TiO₂ consists of round agglomerates of 5–10 nm primary particles. The size of secondary particles depends mainly on the H₂SO₄ concentration. The increase of the time of hydrothermal treatment results in the enhancement of TiO₂ photocatalytic activity that reaches a maximum. Among different acids (HCl, HClO₄, HNO₃, H₃PO₄ and CH₃COOH) added during hydrolysis of TiOSO₄, sulfuric and acetic acids had the best effect on photocatalytic activity of TiO₂. The results obtained can help to finely tune this TiO₂ preparation method in order to obtain desirable particles size, shape and activity.