Facile synthesis of visible-light-activated f-doped TiO₂ hollow spheres by ultrasonic spray pyrolysis

A fluorine-doped TiO₂ was synthesized using ultrasonic spray pyrolysis process with TiF₄ acidic solution as precursor. The prepared catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), N₂ adsorption-desorption measurement, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of prepared samples were evaluated by the elimination of nitric oxide in the gas phase. The results indicate the hollow submicrospherical TiO₂ with mesoporous structure using ultrasonic spray pyrolysis process. The prepared samples could efficiently eliminate the pollutant in the gas phase under visible light irradiation. The photocatalytic activity of prepared samples was influenced by the air flow rate of pump during the ultrasonic spray pyrolysis. The formation mechanism of hollow spherical structure in the ultrasonic spray pyrolysis process was also discussed.