Template-free synthesis of mesoporous anatase titania hollow spheres and their enhanced photocatalysis

Abstract

Monodispersed mesoporous anatase titania (TiO₂) hollow microspheres with controllable morphology and size are prepared via thioglycolic acid (TGA) chemically induced self-assembly for the first time. The formation process of TiO₂ hollow spheres consists of three steps: hydrolysis of titanium butoxide (TBT) forming Ti-oxo clusters followed by connecting TGA via hydrogen bonding, assembly of the Ti-oxo clusters to solid spheres, and transformation of the TiO₂ solid spheres into hollow spheres through the synergistic effect of thermodynamic (Ostwald ripening process) and kinetic (gas release) factors. TGA molecules firstly provide acidic conditions slowing down the hydrolysis rate of TBT, then control the formation of solid spheres, and finally create hollow structures. The prepared TiO₂ hollow sphere with mesoporous structure has a large specific surface area (292.20 m² g⁻¹). Photocatalytic degradation of methyl orange (MO) by the TiO₂ hollow spheres after reflux treatment improves significantly, owing to removal of TGA molecules from the TiO₂ hollow spheres. Moreover, photocatalytic water splitting of highly crystalline TiO₂ hollow spheres decorated with Pt nanoparticles exhibits an impressive performance for producing H₂ (0.477 mmol h⁻¹).