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 Bi2O3/Bi4O5Br2 type-II heterojunction was synthesized using a simple one-pot solvothermal route. The 0-dimensional (0D) Bi2O3 nanoparticles are uniformly distributed within the 2D Bi4O5Br2 nanosheets with (101̅) facets dominantly exposed. In comparison with pure Bi2O3 and Bi4O5Br2, they show higher photocatalytic activity degradation of resorcinol (RO) and Rhodamine B (RhB). The Bi2O3/Bi4O5Br2 composite containing 10% Bi2O3 (BOB4) displays the best photocatalytic activity. For instance, compared with pure Bi4O5Br2 and Bi2O3, 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 Bi2O3 nanoparticles in the Bi4O5Br2 nanosheet, which effectively enhances the photogenerated charge separation in a type-II mode. Major active species include superoxide radicals (•O2–), hydroxyl radicals (•OH), and holes (h+). In addition, the Bi2O3/Bi4O5Br2 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.