Fabrication, characterization, and photocatalytic properties of anatase TiO₂ nanoplates with exposed {001} facets

Anatase TiO₂ nanoplates, with average side length ranging from 90 to 200 nm and average thickness ranging from 20 to 60 nm, were successfully fabricated by annealing anodized TiO₂ nanotubes with different heating rates. The as-synthesized TiO₂ nanoplates and nanotubes were analyzed by field-emission scanning electron microscopy, X-ray diffraction, X-ray fluorescence spectroscopy, and transmission electron microscopy. To investigate the growth mechanism of the TiO₂ nanoplates dominated by highly reactive {001} facets, different heating rates were applied appropriately during the thermal treatment. The results revealed that the heating rate during thermal treatment is critical in determining the nanostructure of anatase TiO₂. The fast heating rate (samples were annealed when the temperature heated up to 450 °C) and the brittle property are the main reasons for the collapse of the anodized TiO₂ nanotubes. The nanosized TiO₂ species grow into TiO₂ nanoplates with the exposed 60 % of {001} facets because the fluorated surface of TiO₂ species can direct the formation of TiO₂ nanoplates with exposed {001} facets. The photoactivity of the TiO₂ nanoplates is higher than that of TiO₂ nanotubes.