New insights into photocatalytic mechanism and photoelectrochemical property of bismuth oxybromide heterostructure with DFT investigation

摘要

The BiOBr/Bi24O31Br10 heterostructure was constructed at 500 degrees C by using an in-situ growth method. The results indicated that BiOBr exhibits the strongest adsorption to Rhodamine B (RhB), Tetracycline Hydrochloride (TCh) and Methyl Orange (MO), while no significant difference in adsorption to 4-Chlorophenol (4-CP) can be observed for all the samples. BiOBr shows higher photocatalytic activity for the decomposition of RhB and TCh than the BiOBr/Bi(2)4O(31)Br(10) heterostructure, which might be attributed to its stronger adsorption and more complicated de-alkylation mechanism. However, the BiOBr/Bi24O31Br10 heterostructure exhibits an enhanced visible light photocatalytic activity in degrading MO and 4-CP, which is mainly ascribed to the presence of heterojunction between BiOBr and Bi24O31Br10, thus leading to an improved separation of the photoexcited electron-hole pairs, as evidenced by results of electrochemical impedance spectroscopy, photoluminescence, transient photocurrent, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). It is also noted that the hybridized Bi 6 s and Bi 6p of Bi24O31Br10 cause the valence band maximum to be largely dispersed, and the composition of conduction band maximum contributes to the up-shift of conduction band. Based on Mott-Schottky analysis, band gap energy, VB-XPS results and density functional theory, photocatalytic mechanism of the BiOBr/ Bi24O31Br10 heterostructure is also proposed.