Fabrication of multiple hierarchical heterojunction Ag@AgBr/BiPO4/r-GO with enhanced visible-light-driven photocatalytic activities towards dye degradation

Novel hierarchical Z-scheme photocatalyst Ag@AgBr/BiPO4/r-GO was synthesized by in situ deposition of AgBr onto the surface of BiPO4/r-GO precursor and followed by photo-reduction of AgBr into Ag@ AgBr. The as-synthesized photocatalyst was characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), UV-vis diffuse reflectance spectroscopy (DRS) and infrared spectroscopy (IR). The photocatalytic activity of the Ag@AgBr/BiPO4/r-GO was evaluated by degrading reactive blue 19 (RB-19) under visible-light irradiation. The results showed that Ag@AgBr/BiPO4/r-GO composite exhibited much better photocatalytic performance than BiPO4 and Ag@AgBr/BiPO4 due to the efficient visible-light utilization. The construction of Z-scheme kept the photogenerated electrons and holes having high reduction and oxidation capabilities. Ag nanoparticles and r-GO acted as the electron mediators to form the charge transmission bridge for the AgBr/BiPO4 heterojunction, promoting the efficient separation of photo-induced electron-hole pairs and inhibiting the electron-hole recombination. Finally, a possible photocatalytic mechanism for the degradation of RB-19 by Ag@AgBr/BiPO4/r-GO was proposed based on the free radical and hole scavenging experiments. (C) 2018 Elsevier B.V. All rights reserved.