Fabrication of Z-scheme photocatalyst Ag–AgBr@Bi20TiO32 and its visible-light photocatalytic activity for the degradation of isoproturon herbicide

Abstract

A novel hierarchical Z-scheme photocatalyst Ag–AgBr@Bi20TiO32 was synthesized by in situ deposition of AgBr onto the surface of mesoporous metastable Bi20TiO32 template and followed by photoreduction of AgBr to Ag–AgBr. The as-synthesized photocatalyst was characterized by X-ray diffraction spectra (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption–desorption analysis and UV–vis diffuse reflectance spectra (UV–vis DRS). The photocatalytic activity of Ag–AgBr@Bi20TiO32 was evaluated by the degradation of isoproturon herbicide under visible-light irradiation. Results showed that Ag–AgBr@Bi20TiO32 photocatalyst exhibited much better photocatalytic activity than Ag–AgBr, or Bi20TiO32, or the physical mixture of AgBr and Bi20TiO32, due to its efficient visible-light utilization and the construction of Z-scheme keeping photo-generated electrons and holes with high reduction and oxidation capability. A possible catalytic mechanism for Ag–AgBr@Bi20TiO32 photocatalyst was put forward based on band gap structure of AgBr and Bi20TiO32 and free radical and hole scavenging experiments. The degradation pathway of isoproturon herbicide was also proposed according to the intermediates identified in the reaction system.