Double-Shelled TiO₂ Hollow Spheres Assembled with TiO₂ Nanosheets

High-quality double-shelled TiO₂ hollow spheres (DHS-Ti) assembled with TiO₂ nanosheets have been synthesized for the first time through a simple hydrothermal treatment of sSiO₂ @TiO₂ (TiO₂ -coated solid SiO₂ spheres). The double-shelled structure shows a high BET surface area up to 417.6 m²  g^-1 . Anatase DHS-Ti of high crystallinity can be obtained without structural collapse by calcination treatment. The effects of cetyl trimethylammonium bromide (CTAB) concentration, pH, and hydrothermal reaction temperature have also been investigated with a series of contrast experiments. A formation mechanism involving the in situ growth of amorphous TiO₂ nanosheets followed by the redeposition of dissolved silica species is proposed. Lastly, the DHS-Ti forming strategy can be extended as a general strategy to fabricate various morphological hollow nanostructures and double-shelled Pt nanocatalysts by rationally selecting functional sSiO₂ nanoparticles as core materials. This work could open up a new strategy for controllable synthesis of complex hollow structures and other functional materials.