In situ fabrication of type II 3D hierarchical flower-like BiOBr/Bi3O4Br heterojunction with improved photocatalytic activity

A novel 3D hierarchical flower-like BiOBr/Bi3O4Br heterostructure photocatalyst was synthesized by in-situ growth of ultrathin BiOBr on the surface of Bi3O4Br nanosheets through a solvothermal process. The 3D hierarchical heterostructure endows BiOBr/Bi3O4Br heterojunction with a large specific surface area and tight interfacial contact, which can provide sufficient channels for carrier migration. The introduction of Bi3O4Br can enhance the light absorption ability of BiOBr/Bi3O4Br photocatalysts. Furthermore, the staggered type II heterostructure energy band alignment formed between BiOBr and Bi3O4Br can promote the separation of photo-excited carriers. The improved performance of carrier migration and light absorption ability was evaluated by SEM, TEM, BET, EIS, and DRS tests. The results of transient photocurrent response and photoluminescence tests confirmed the improvement for separating photoexcited carriers. The optimal 20% BiOBr/Bi3O4Br sample exhibited the greatest photocatalytic degradation rate of 97.1% for RhB and 89.4% for TC, under 90 min of simulated solar light irradiation. Its apparent rate constant k values are 0.03378 and 0.02013 min−1, being 9.44 and 2.18 folds than that of Bi3O4Br, 2.76 and 1.47 folds than that of BiOBr. The free radical scavenging experiment results showed that h+ and •O2- are the prime active species during the photodegradation process. Hence, a possible photocatalytic mechanism of type II BiOBr/Bi3O4Br heterojunction was proposed.