Morphology Control in Anatase TiO2 Mesocrystals Through Hydrofluoride Incorporation for Photocatalytic Application

Mesocrystal is a promising material for improving photocatalytic activity because of its large specific surface area and almost single crystalline structure. In this work, anatase TiO2 mesocrystals were synthesized via a simple hydrothermal process and the morphology and consequent photocatalytic property was controlled through hydrofluoride (HF) addition. The morphology of TiO2 was significantly varied with the amount of HF addition. The pure TiO2 was elliptical mesocrystal, having bipyramidal sub units with high portion of {101} facets, arraying in the [001] direction. Similar mesocrystal morphologies were obtained, but the sub unit size decreased as HF content increased to 0.01 wt%, and the shape of the sub unit then changed to nanosheet with the introduction of further HF (1-2 wt%). The 0.01 wt% sample exhibited superior photocatalytic activity over the pure sample, decomposing similar to 70% and similar to 80% methylene blue in 1 h for the pure sample and 0.01 wt% sample, respectively, resulting from enlarged specific surface area and fluorinated surface. The photocatalytic activity reduced to similar to 20% for the 1-2 wt% particles due to the decrease in surface area and formation of the TiOF2 phase. The present work suggests that the morphology and photocatalytic activity of TiO2 mesocrystal are facilely modified through HF introduction.