Graphene-analogue h-BN coupled Bi-rich Bi4O5Br2 layered microspheres for enhanced visible-light photocatalytic activity and mechanism insight

The novel boron nitride coupled Bi-rich Bi4O5Br2 layered microspheres (h-BN/Bi4O5Br2-LMs) were successfully synthesized via a facile ionic liquid-in-water (IL/W) microemulsion-mediated route. The physical, chemical and optical properties of these heterojunction photocatalysts were thoroughly characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM) and UV-vis diffuse reflection spectroscopy (DRS). Their photocatalytic activities were primarily evaluated by degradation of 4-tert-butylphenol (PTBP), which found 1.0 wt% h-BN/Bi4O5Br2-LMs to be the best one. The photocurrent experiments showed that the photocurrent density of 1.0 wt% h-BN/Bi4O5Br2-LMs was four times higher than that of pure Bi4O5Br2-LMs due to enhanced charge transfer ability of the former. It revealed that the addition of h-BN was in favor of suppressing the photoinduced electron-hole pair recombination of Bi4O5Br2-LMs, so as to improve the photocatalytic activity of the composite. center dot O-2- and were proved to be the main reactive species in the photocatalytic process by scavenger experiments and electron paramagnetic resonance (EPR) spectra. In addition, the photocatalytic mechanism of h-BN/Bi4O5Br2-LMs was further elaborated in this work. The probable degradation products were identified by GC-MS. The proposed conjugated addition and oxidation reactions were described to be the main pathways by combining the frontier electron density calculation and GC-MS results. (C) 2017 Elsevier B.V. All rights reserved.