Study of the Structure, Electronic and Optical Properties of BiOI/Rutile-TiO Heterojunction by the First-Principle Calculation.

Using the first-principle calculation that is based on the density functional theory (DFT), our group gains some insights of the structural, electronic and optical properties of two brand new types of BiOI/TiO heterojunctions: 1I-terminated BiOI {001} surface/TiO (1I-BiOI/TiO) and BiO-terminated BiOI {001} surface/TiO (BiO-BiOI/TiO). The calculation illustrates that BiOI/TiO heterojunction has excellent mechanical stability, and it shows that there is a great possibility for the BiOI/TiO heterojunction to be used in visible-light range, hence the photocatalytic ability can be enhanced dramatically. Especially, from the calculation, we discovered that there are two specific properties: the band-gap of 1I-BiOI/TiO heterojunction reduces to 0.28 eV, and the BiO-BiOI/TiO semiconductor material changes to n-type. The calculated band offset (BOs) for 1I-BiOI/TiO heterojunction indicates that the interfacial structure contributes a lot to a suitable band alignment which can disperse the photo-generated carriers into the opposite sides of the interface, so this could effectively weaken the electron-hole recombination. Meanwhile, the built-in potential around the interface accelerates the movement of the photo-generated electron-hole pairs. We believe this is the reason that the BiOI/TiO material shows perfect photocatalytic performance. This paper can provide theoretical support for the related research, especially the further research of the BiOI-based material.