Mesoporous TiO2 Single-Crystal Polyhedron-Constructed Core-Shell Microspheres: Anisotropic Etching and Photovoltaic Property

A favorable micro-nanostructure is crucial for obtaining superior properties. However, the synthetic techniques for synthesizing the complex morphology still remain a challenge. In this work, we synthesized core-shell-structured submicrometer-sized mesoporous TiO2 microspheres (MTMs) constructed with mesoporous TiO2 polyhedrons through a novel anisotropic etching route. The outer shell of the obtained TiO2 microsphere is constructed by a mesoporous TiO2 single-crystal nanopolyhedron with exposed (101) facets. Hydrogen peroxide was used as the bubble generator, which simultaneously acted as gas templates for the formation of TiO2 microspheres. Fluorine ions facilitate the formation of anatase (001) facets at reaction. The anisotropic etching accrued along the [101] direction with an increase in fluorine ions, leaving mesoporous structures and highly exposed (101) facets. Dye-sensitized solar cells (DSSCs), using the as-prepared product as a light-scatting layer, showed a 29.4% increase in conversion efficiency.