The Design of TiO₂ Nanostructures (Nanoparticle, Nanotube, and Nanosheet) and Their Photocatalytic Activity

Abstract

Density functional theory (DFT) calculation is carried out to access the band structure and density of states (DOS) based on the models of TiO 2 nanoparticle, nanotube, and nanosheet, predicting the order of the photocatalytic activity for three different nanostructures. Sol–gel method and hydrothermal method are used to achieve desired morphologies: nanoparticles, nanotubes, and nanosheets (fragmentized nanotubes). The photocatalytic activity ranks in the order of nanosheets > nanotubes > nanoparticles, which is consistent with theoretical prediction. It was revealed that the enlargement of band gap is caused by the quantum confinement effect; the prolonged lifetime of photogenerated electrons and increased specific surface areas are dependent on the morphology of the nanostructure. All these factors contribute to the improvement of the photocatalytic activity for nanostructures. Our results can guide the design and selection of low-dimensional nanomaterials with desired morphology and improved photoelectric functional properties, which can be used in many fields, such as solar cells, photocatalysis, and photosynthesis.