Low-Temperature Sol–Gel Synthesis and Photoactivity of Nanocrystalline TiO2 with the Anatase/Brookite Structure and an Amorphous Component

Nanodispersed TiO 2 consisting of anatase and brookite phases in a ratio of 3 : 1 is obtained by the sol–gel method from titanium(IV) butoxide at a temperature below 100°C. X-ray diffraction, transmission electron microscopy, and Raman spectroscopy are used to show that the size of anatase particles is about 6 nm, and brookite particles consist of a crystal core, 4 nm in diameter, surrounded by an amorphous shell. Compared with the commercial Degussa P25 photocatalyst, which consists of the anatase and rutile phases in the same 3 : 1 ratio, the resulting TiO 2 exhibits an increased photoactivity in hydroquinone oxidation. Quantum chemical modeling of anatase and brookite surfaces as well as their interface does not reveal the specific features of their electronic structure. This fact is indicative of the amorphous phase as an active participant in the transfer of charge carriers in the photocatalytic process.