Rapid synthesis of mesoporous TiO2 with high photocatalytic activity by ultrasound-induced agglomeration

Abstract

Three-dimensional and thermally stable mesoporous TiO₂ was synthesized without the use of any surfactants via treatment with high intensity ultrasound irradiation for a short period of time. Monodispersed TiO₂ sol particles were formed initially by ultrasound-assisted hydrolysis of acetic acid-modified titanium isopropoxide. Then, the mesoporous spherical or globular particles, which have a narrow pore size distribution, were produced by controlled condensation and agglomeration of these sol nanoparticles under high intensity ultrasound irradiation. The mesoporous TiO₂ was characterized by XRD, TEM, nitrogen adsorption, TGA/DTA and FTIR. Low-angle XRD and TEM show the mesoporous TiO₂ has a wormhole-like structure and a lack of long-range order. Nitrogen adsorption results indicate that the mesoporous TiO₂ retains mesoporosity with a narrow pore size distribution and high surface area to at least 673 K. The thermal stability of mesoporous TiO₂ is attributed to its thick inorganic walls, consisting of TiO₂ nanoparticles. TGA study shows that this synthetic method is environmentally friendly. The photocatalytic activity of mesoporous TiO₂ for the oxidation of acetone in air was measured. As-prepared mesoporous TiO₂ has negligible activity due to its amorphous structure. Calcined mesoporous TiO₂ shows better activity than commercial photocatalyst P25. The reasons for the high activity of mesoporous TiO₂ are discussed.