Generation of ^•OH and ^•O₂^– Radicals by a Bi₂O₃-Nanoparticle/Bi₄O₅Br₂ Type-II Heterojunction for Photocatalytic Degradation of Organic Molecules

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.