Comparative study of the mechanical, optoelectronic and photocatalytic properties of the defect-free and oxygen defect induced TiO2 nanosheets under uniaxial strain conditions by DFT simulations

Owing to its excellent mechanical properties, two-dimensional (2D) titanium dioxide (TiO2) nanosheets allow the introduction of huge strain and complex strain fields without fracture. It is confirmed theoretically and experimentally that the strain engineering of 2D TiO2 nanosheets can be used as a rational and effective method to tune the atomic structure, lattice vibration, and optoelectronic properties to improve the performance related to the photocatalytic field. The TiO2 nanosheets with a high exposure ratio of (001) crystal plane have special properties such as high carrier mobility, high optoelectronic activity, excellent chemical stability and so on. In this study, DFT calculation was used to explore the effect of mechanical strain on the anisotropic photoelectric properties of the defect-free and oxygen defect induced TiO2 nanosheet, and the differences between them are compared. The results show that strain engineering can not only change their bandgap, electronic structure, and light absorption range but also produce some novel mechanical phenomena. The systematic study of the effect of strain engineering on the anisotropy of 2D TiO2 nanosheets will help to design and develop new TiO2-based photocatalysts.