Preparation and Characterization of Stable Biphase TiO₂ Photocatalyst with High Crystallinity, Large Surface Area, and Enhanced Photoactivity

Stable porous TiO₂ photocatalysts, with higher photocatalytic activity than Degussa P25, were synthesized via a hydrothermal process using cetyltrimethylammonium bromide as the template, followed by a posttreatment in the presence of ethylenediamine. The photocatalysts were characterized by X-ray diffraction, Raman spectroscopy, N₂ adsorption−desorption, transmission electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and UV−vis diffuse reflectance spectra. The posttreatment considerably increases the thermal stability of the porous framework and inhibits the undesirable grain growth and phase transformation during calcination. The prepared TiO₂ photocatalysts have large surface areas of about 205 and 117 m²/g even after calcination at 700 and 800 °C, respectively. The formation mechanism of the stable porous titania was proposed. The high crystallinity, large specific surface area, and heterojunction microstructure between anatase and brookite may be responsible for the high photocatalytic activity in terms of the degradation of organic pollutants such as phenol and rhodamine B under UV irradiation.