Fabrication of three-dimensional hierarchical BiOBr/Bi2O4 p–n heterojunction with excellent visible light photodegradation performance for 4-chlorophenol

Abstract

Construction of heterojunction and design of its architecture are effective strategies to improve the catalytic performance of photocatalyst. Herein, BiOBr/Bi2O4 p-n heterojunction was fabricated by a co-precipitation method, in which two-dimensional (2D) BiOBr nanosheets sheathed well on the surface of quasi-one-dimensional (1D) Bi2O4 submicrorods, forming a three-dimensional (3D) hierarchical structure. Such structural feature can not only enhance the utilization of incident photons through multi-reflection within the hierarchical structure but also raise the specific surface areas to supply more surface-active sites to participate in photocatalytic reaction. More importantly, BiOBr/Bi2O4 p-n junction could accelerate the interfacial electron-hole pairs transfer and separation via the built-in electric field, extending the lifetime of charge carriers. Thus, as-prepared BiOBr/Bi2O4 heterojunctions exhibit superior visible light catalytic activity for the photodegradation of 4-chlorophenol (4-CP). The catalytic activity of optimal junction is 2.03-fold as high as that of pristine Bi2O4. The trapping experiments demonstrate that hole (h+) and superoxide radical (•O2−) are the major active species during the catalytic photodegradation process of 4-CP. This work presents a unique tactic for the construction of high-performance Bi2O4-based heterojunction for the removal of organic pollutants.