Fabrication of a Z-scheme AgBr/Bi4O5Br2 nanocomposite and its high efficiency in photocatalytic N2 fixation and dye degradation

Abstract

A AgBr/Bi₄O₅Br₂ nanocomposite (actually a Ag/AgBr/Bi₄O₅Br₂ ternary system) was synthesized by a combination of hydrothermal and ion exchange procedures and applied for the first time in photocatalytic nitrogen fixation. The detailed characterizations indicated that only a small amount of AgBr was formed on the surface of the Bi₄O₅Br₂ nanosheets. Hence, the morphology, BET surface area, and pore size distribution of Bi₄O₅Br₂ changed slightly. However, the charge separation efficiency significantly increased, which was realized via the oriented electron migration between AgBr and Bi₄O₅Br₂ in a Z-scheme mechanism. The Ag nanoparticles formed in situ via the decomposition of AgBr act as the bridge of charge migration. Although improved photoabsorption was also observed, the elevated charge separation was believed to be the dominant factor affecting the photocatalytic performance. Therefore, AgBr/Bi₄O₅Br₂ presented outstanding photocatalytic performance. Under simulated sunlight, the optimal 5.0 wt% AgBr/Bi₄O₅Br₂ composite exhibits a NH₃ production velocity of 179.4 μmol L⁻¹ g⁻¹ h⁻¹, which is three times that of Bi₄O₅Br₂. For methylene blue degradation, the degradation rate under visible light is 0.097 min⁻¹, which is 3.0 and 12 times faster than those of Bi₄O₅Br₂ and AgBr, respectively. This work may provide useful information for the design and synthesis of efficacious catalysts for photocatalytic N₂ fixation.