Hierarchical TiO(2) nanospheres with controlled surface morphologies and dominant {001} facets were directly synthesized from Ti powder by a facile, one-pot, hydrothermal method. The obtained hierarchical TiO(2) nanospheres have a uniform size of 400-500 nm and remarkable 78 % fraction of {001} facets. The influence of the reaction temperature, amount of HF, and reaction time on the morphology and the exposed facets was systematically studied. A possible growth mechanism speculates that Ti powder first dissolves in HF solution, and then flowerlike TiO(2) nanostructures are formed by assembly of TiO(2) nanocrystals. Because of the high concentration of HF in the early stage, these TiO(2) nanostructures were etched, and hollow structures formed on the surface. After the F(-) ions were effectively absorbed on the crystal surfaces, {001} facets appear and grow steadily. At the same time, the {101} facets also grow and meet the {101} facets from adjacent truncated tetragonal pyramids, causing coalescence of these facets and formation of nanospheres with dominant {001} facets. With further extension of the reaction time, single-crystal {001} facets of hierarchical TiO(2) nanospheres are dissolved and TiO(2) nanospheres with dominant {101} facets are obtained. The photocatalytic activities of the hierarchical TiO(2) nanospheres were evaluated and found to be closely related to the exposed {001} facets. Owing to the special hierarchical architecture and high percentage of exposed {001} facets, the TiO(2) nanospheres exhibit much enhanced photocatalytic efficiency (almost fourfold) compared to P25 TiO(2) as a benchmark material. This study provides new insight into crystal-facet engineering of anatase TiO(2) nanostructures with high percentage of {001} facets as well as opportunities for controllable synthesis of 3D hierarchical nanostructures.

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Anatase TiO2 single crystals with dominant {001} facets were fabricated in a controlled manner from TiO2 powders through a facile route for the first time. The obtained TiO2 single crystals have a size of approximately 1.5 μm and a remarkable, roughly 65 % fraction of {001} facets. The influence of the reaction temperature, the amount of precursor, and the reaction time on the morphology and the exposed facets was studied systematically. The percentage of {001} facets increased with the temperature and the amount of precursor, as a result of the surface energy reduction effect of F− ions. Further increasing the temperature and the amount of precursor led to serious corrosion of the products because of the enhanced corrosive effect of HF. Owing to the high percentage of exposed {001} facets, the TiO2 single crystals exhibit a much enhanced photocatalytic efficiency (almost fivefold) compared to that of P25 TiO2 as a benchmark material, thus opening a new avenue to prepare highly active TiO2 single crystals with dominant {001} facets from low‐cost TiO2 powders.

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