Simultaneous formation of silica-protected and N-doped TiO2 hollow spheres using organic-inorganic silica as self-removed templates

Synthesis of N-doped TiO2 hollow spheres with a small grain size, large surface area and high degree of crystallinity is favorable to achieve an overall high photocatalytic activity. But traditional synthetic approaches generally involve many tedious steps and are time-consuming. Here we present a facile method to synthesize N-doped TiO2 hollow spheres using organic silane-doped silica nanoparticles as templates. The organic-inorganic silica can be simultaneously etched during the deposition of TiO2 shell to create a thin silica layer on the TiO2 surface. Such a thin silica layer can efficiently protect the TiO2 nanocrystals from growing larger during high-temperature calcination. At the same time, the organic silane can serve as a nitrogen source to be doped in the TiO2 shell. The developed silica-protected and N-doped TiO2 hollow spheres can be directly employed as photocatalysts without SiO2 etching and show obvious light utilization in both UV and visible bands.