Origin of Photocatalytic Activity of BiPO4: the First-principles Calculations

Geometric and electronic structures of three polymorphs of BiPO4 (mMBIP, nMBIP and HBIP) have been investigated by the first-principles calculations. The results show that PO4 tetrahedron in nMBIP is distorted most, and mMBIP possesses minimum effective mass of carriers in three polymorphs of BiPO4. Further, the leading role of inductive effect of dipole moment or effective mass of carries in the separation of electron-hole pairs is analyzed. Based on the fact that nMBIP has higher photocatalytic activity than mMBIP, it can be inferred that the inductive effect of dipole moment deriving from distorted PO4 tetrahedron is the dominant factor affecting the separation efficiency of carries. The calculated results represent that nMBIP has more appropriate redox potential and narrower band gap than others. These findings may provide meaningful guidance for further understanding on the relationship between unique crystal structure and photocatalytic activity of BiPO4.