Size controllable synthesis and photocatalytic performance of mesoporous TiO2 hollow spheres

Hollow mesoporous TiO2 spheres (THs) were prepared via template-directed deposition of TiO2 nanoparticles on the surface of carbon spheres. The carbon spheres were used as hard templates. Their diameters were controlled by pH adjustment prior to a hydrothermal process. Physical properties, such as crystallinity, optical characteristics, microstructure and surface morphology of the samples were characterized. The results showed that the diameter of the carbon template could be well controlled in the range of 397–729 nm by adjusting the initial pH value of the dextrose solution from 3 to 10. Hollow TiO2 spheres with average diameters ranging from 171 to 668 nm and shell thicknesses ranging from 28 to 47 nm formed by heat treatment at 450 °C. The photocatalytic performance of hollow TiO2 spheres and TiO2 nanoparticles was examined under UVA irradiation using a methyl orange aqueous solution as an artificial dye. The study revealed that the THs synthesized using a dextrose solution at pH 7 had a higher photocatalytic activity compared to other samples since it had the lowest shell thickness and the proper optical band gap of 3.12 eV with the longest lifetime of electron-hole pair separation.