Generation of <sup>•</sup>OH and <sup>•</sup>O<sub>2</sub><sup>–</sup> Radicals by a Bi<sub>2</sub>O<sub>3</sub>-Nanoparticle/Bi<sub>4</sub>O<sub>5</sub>Br<sub>2</sub> Type-II Heterojunction for Photocatalytic Degradation of Organic Molecules
Xiang Yu, Yuwei Mi, Zihan Gong, Yongfang Zhang, Lei Wang, Suyuan Zeng
Abstract
Constructing heterojunctions is an effective strategy for increasing semiconductor photocatalytic activity. Herein, a Bi 2 O 3 /Bi 4 O 5 Br 2 type-II heterojunction was synthesized using a simple one-pot solvothermal route. The 0-dimensional (0D) Bi 2 O 3 nanoparticles are uniformly distributed within the 2D Bi 4 O 5 Br 2 nanosheets with (101̅) facets dominantly exposed. In comparison with pure Bi 2 O 3 and Bi 4 O 5 Br 2, they show higher photocatalytic activity degradation of resorcinol (RO) and Rhodamine B (RhB). The Bi 2 O 3 /Bi 4 O 5 Br 2 composite containing 10% Bi 2 O 3 (BOB4) displays the best photocatalytic activity. For instance, compared with pure Bi 4 O 5 Br 2 and Bi 2 O 3, the k (RO) values of BOB4 (0.58 h –1 ) are 3.1 and 4.8 times higher. The enhanced photocatalytic activity is attributed to the formation of a large heterojunction interface that results from the homogeneous distribution of Bi 2 O 3 nanoparticles in the Bi 4 O 5 Br 2 nanosheet, which effectively enhances the photogenerated charge separation in a type-II mode. Major active species include superoxide radicals ( • O 2 – ), hydroxyl radicals ( • OH), and holes (h + ). In addition, the Bi 2 O 3 /Bi 4 O 5 Br 2 photocatalysts exhibit outstanding resistance to inorganic ions, pH, water matrix, as well as outdoor sunlight and favorable stability and biocompatibility. This work presents a simple method to construct Bi-based heterojunction architectures for photoactivity improvement.