TiO2 mesocrystals with exposed {001} facets as efficient photocatalysts

In this work, a fluoride mediated hydrothermal method is proposed for the synthesis of TiO2 mesocrystals (MC) exposed by highly reactive facets. These materials are built of TiO2 nanocrystals with similar crystallographic orientation and the percentage of exposed {001} facet is calculated to be 52%. By adjusting the ratio of fluorine to titanium (R-F), the structure of TiO2 products can be accurately regulated. The low R-F yields the {001} facets unexposed subsphaeroidal mesocrystals (MC), whereas the sheet-like single crystals (SC) were obtained at the high R-F. Owing to the mesocrystalline structure and exposure of highly active facets, MC with {001} facets exhibit superior photocatalytic activity than the {001} unexposed MC and SC in the degradation of methylene blue. The rate constant of the TiO2 mesocrystals with {001} facets nanocrystals is almost 4 times of the TiO2 single crystals, and 1.5 times that of the {001} unexposed TiO2 mesocrystals. The designed fabrication of mesocrystals with exposed reactive facets provides an attractive and effective route for improving the performances of semiconductor photocatalysts. (C) 2016 Elsevier B.V. All rights reserved.