Fabrication and Characterization of Hierarchical Porous TiO2 Films

Abstract

Hierarchical porous TiO₂ films with macroporous and mesoporous structures are prepared by drop-coating a mixed solution of polystyrene spheres and TiO₂ colloid, followed by sintering to remove polystyrene spheres. XRD shows that crystal phase of TiO₂ particles is major anatase structure with minor brookite structure. AFM displays that particle size distribution of porous TiO₂ films ranges from 20-30 nm. SEM shows that TiO₂ films prepared by drop-coating TiO₂ colloid present mesoporous structure with a size of 8-50 nm. However, TiO₂ films prepared by drop-coating the mixture containing polystyrene spheres and TiO₂ colloid possess hierarchical porous structure with a mesoporous size of 8-50 nm and a macroporous size of about 600 nm. Besides, macropore ratios increase with increase of the ratio of polystyrene spheres to TiO₂ colloid. UV-visible absorption spectra indicate that porous TiO₂ films prepared at a polystyrene spheres/TiO₂ colloid ratio 1, have the highest absorption intensity.