AgBr quantum dots decorated mesoporous Bi2WO6 architectures with enhanced photocatalytic activities for methylene blue

Abstract

Spherical mesoporous nest-like Bi₂WO₆ nanoarchitectures with scales of 2–4 μm were prepared via a hydrothermal process, and AgBr quantum dots (QDs) were decorated on the surface of Bi₂WO₆ to form a novel p–n AgBr/Bi₂WO₆ heterojunction via a followed facile precipitation–deposition process. Evidence of AgBr QDs decorating mesoporous nest-like Bi₂WO₆ nanoarchitectures was obtained from XRD, XPS, FE-SEM and HR-TEM, which revealed that monodispersed AgBr QDs with an average size of about 10 nm were deposited on the surface of the three-dimensional Bi₂WO₆ nanoarchitectures. The photocatalytic activities of the samples were evaluated by the photodegradation of methylene blue dye (MB) and phenol under visible light irradiation. The results showed that the decoration of AgBr QDs significantly improved the photocatalytic activity of Bi₂WO₆, and the content of deposited AgBr nanodots impacted the catalytic activity of Bi₂WO₆. The 2.0at%AgBr-loaded Bi₂WO₆ sample exhibited the best photocatalytic activity for the decolorization of MB. It is elucidated that AgBr/Bi₂WO₆ generates superoxide radical anions in aqueous aerated solution but no hydroxyl radicals are formed. In addition, the mechanism for the enhancement of photocatalytic activity of AgBr/Bi₂WO₆ was also investigated by a comparison of their PL spectra. The catalytic efficiency enhancement of the p–n AgBr/Bi₂WO₆ heterojunctions relative to pure Bi₂WO₆ can be attributed to the formation of heterojunctions between AgBr QDs and Bi₂WO₆, which suppresses the recombination of photogenerated electron–hole pairs. The test of radical scavengers confirmed that O₂˙⁻ was the main reactive species during the photocatalytic process.