A self-assembly BiOI/Bi4O5Br2 microcluster and its efficiently visible-light-induced photocatalytic degradation of methylparaben

Herein, we developed a self-assembly heterostructured BiOI/Bi4O5Br2 microcluster with the hydrothermal method. Catalysts were mainly characterized by powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscope, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and diffuse reflectance spectra. The results showed that due to charge induction, BiOI nanosheets were successfully self-assembled and deposited on Bi4O5Br2, forming a unique heterojunction and achieving strong transient photocurrent response. Performances of catalysts were tested and effects of different initial concentrations of the Methylparaben (MPB), catalyst dosage, initial pH and total organic carbon (TOC) conversion were studied. Results reveal that catalytic activity increased with lower initial concentration of MPB and the best dosage of catalyst is 0.5 g.L-1. The BiOI/Bi4O5Br2 microcluster exhibits excellent photocatalytic activity under visible-light irradiation, which can degrade 97% MPB in 2 h and the TOC value is only 20% of the original. The catalytic degradation process conforms to pseudo-first-order kinetics with a rate constant of 0.030 min(-1). The results of detailed active species detection indicate that the photogenerated holes and center dot O-2(-) radicals play the main role in the photocatalytic system. In addition, photoelectrochemical measurements reveal that the excellent strengthened photocatalytic activity is due to the high separation and transfer efficiency derived from the heterostructure.