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

A novel 3D hierarchical flower-like BiOBr/Bi 3 O 4 Br heterostructure photocatalyst was synthesized by in-situ growth of ultrathin BiOBr on the surface of Bi 3 O 4 Br nanosheets through a solvothermal process. The 3D hierarchical heterostructure endows BiOBr/Bi 3 O 4 Br heterojunction with a large specific surface area and tight interfacial contact, which can provide sufficient channels for carrier migration. The introduction of Bi 3 O 4 Br can enhance the light absorption ability of BiOBr/Bi 3 O 4 Br photocatalysts. Furthermore, the staggered type II heterostructure energy band alignment formed between BiOBr and Bi 3 O 4 Br 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/Bi 3 O 4 Br 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 Bi 3 O 4 Br, 2.76 and 1.47 folds than that of BiOBr. The free radical scavenging experiment results showed that h + and •O 2 - are the prime active species during the photodegradation process. Hence, a possible photocatalytic mechanism of type II BiOBr/Bi 3 O 4 Br heterojunction was proposed.