Synthesis of self-organized polycrystalline F-doped TiO2 hollow microspheres and their photocatalytic activity under visible light

A wet-chemistry method was used to dope F- ions into crystalline TiO2 by hydrothermal treatment of TiF4 in an HCl solution. Field-emission electron microscope and transmission electron microscope images showed that the products exhibited a flowerlike morphology with a hollow interior. X-ray photoelectron spectroscope data demonstrated the doping of F in the lattice of crystalline TiO2. The flowerlike F-doped TiO2 hollow microspheres synthesized at 180 degrees C showed the highest photocatalytic activity for the degradation of methylene blue under visible light irradiation. Ostwald ripening is the main reason responsible for the formation of the hollow interior of the F-doped TiO2 micropheres, and the HF species generated from the hydrothermal reaction is believed to accelerate the formation of the TiO2 hollow spheres.