Density Functional Theory insights of the Halogen doping on Bi2MoO6 heterogeneous photocatalyst

It is well known that the photocatalytic activity depends on the electronic structure of a semiconductor photocatalyst. To provide a basis for interpretation of experimental optical behavior, the band structure and partial density of states (PDOS) of Halogen-doped Bi2MoO6 were modeled via density functional theory (DFT), using the GGA-PBE method [1]. The calculated band gap, the distance between VBM and CBM, for the pure Bi2MoO6 was 1.89 eV, for F-BMO 1.25 eV, and for Cl-BMO 0.5 eV. In pure Bi2MoO6 Fermi energy level (energy zero) was set at the VB, while in the case of F-BMO VB was located at the top of Fermi level. Meanwhile, after doping of F, CB position shifted to the lower energy, led to decrease the band gap. However, in Cl-doped sample the VB and CB were extremely shifted to the lower energies and the distance between them was reduced to 0.5 eV. This phenomenon was even stronger in Br and I-doped Bi2MoO6, until the band gap was disappeared. It indicates that X-doping can form some sub-levels which facilitate the electron transfer from VB to CB [2].The results from density functional theory calculations revealed in all the X-Bi2MoO6 cases, the valance band maximum and conduction band minimum was mostly composed of O 2p and Mo 4d states, and the gaps decreased with the insertion of halogen atoms, which were in excellent agreement with the previous experimental data. This study may furnish new perspective into the fabrication of a series of photocatalysts with better light-harvesting capacity in a sustainable manner.

Keywords:

Heterogeneous Photocatalyst , Bi2MoO6 , halogen-doping , density of states