Room-temperature one-step synthesis of tube-like S-scheme BiOBr/BiO (HCOO)Br-x heterojunction with excellent visible-light photocatalytic performance

Ultrathin-nanosheet-based bismuth oxide formate (BiOHCOO, denoted as BiOR) tubular hierarchitecture was prepared by a facile room-temperature precipitation route. In order to enlarge its visible-light absorption, tubular solid solutions BiO(HCOO)Br-x (BiORBr-x, x referring to the feeding molar ratio of Br/Bi) were obtained by using similar method through simultaneously adding KBr and HCOONa into Bi(NO3)3 aqueous solution. By controlling the x value at 0.6, the heterojunction BiOBr/BiORBr-0.6 was obtained, which exhibited greatly enhanced visible-light photocatalytic activity and malachite green (MG) could be completely decomposed within 60 min of visible light irradiation, whereas the degradation efficiency of MG on BiOR, BiOBr, the solid solution BiORBr-0.4 and BiOBr/BiOR was only 7%, 50%, 49%, 60%, respectively. In addition, BiOBr/BiORBr-0.6 exhibited excellent removal rate to rhodamine B (RhB, 98%) and antibiotic tetracycline (TC, 80%) within 120 min of the irradiation. The detailed characterization indicates that good photocatalytic performance of BiOBr/BiORBr-0.6 could be attributed to the construction of interfacial-close-contacted step-scheme (S-scheme) heterojunction between BiOBr and the solid solution BiORBr-0.4, which could preserve electrons and holes with higher redox ability. And also, tube-like microstructure of BiOBr/BiORBr-0.6 facilitated highly efficient and directional transfer of charge carriers and transportation of chemical substances.