Rod-like Bi4O5I2/Bi4O5Br2 step-scheme heterostructure with oxygen vacancies synthesized by calcining the solid solution containing organic group

Abstract

To improve separation efficiency of the photogenerated electron-hole pairs, constructing a heterojunction is considered to be a promising strategy. However, the fabrication of heterojunction via a facile route to achieve a substantial improvement in photocatalytic performance is still challenging. In this work, a well-designed nanosheet-based rodlike step-scheme (S-scheme) heterojunction Bi4O5I2/Bi4O5Br2 with rich oxygen vacancies (OVs) (Bi4O5I2/Bi4O5Br2-OV) was easily synthesized by calcining BiOAc0.6Br0.2I0.2 (Ac− = CH3COO−) precursor. The as-prepared Bi4O5I2/Bi4O5Br2-OV exhibited excellent visible light photocatalytic performance towards antibiotic tetracycline (TC) and dye rhodamine B (RhB) degradation and removal rate reached 90.2% and 97.0% within 120 min, respectively, which was higher than those of Bi4O5I2-OV (56.8% and 71.8%), Bi4O5Br2-OV (47.4% and 68.4%), solid solution BiOAc0.6Br0.2I0.2 (67.0% and 84.0%) and Bi4O5I2/Bi4O5Br2 with poor oxygen vacancies (Bi4O5I2/Bi4O5Br2-P) (30.6% and 40.4%). Owing to the release of heat and generation of reducing carbon during calcining the precursor with Ac−, it could not only reduce the generation temperature of Bi-rich bismuth oxyhalides, which thus decreased particle size and increased surface areas, but also introduce surface OVs, which could trap photoelectrons and inhibit the recombination of carriers. In addition, the calcination of single solid solution precursor benefited to the formation of well-alloyed interfaces with larger contact areas between 2D/2D nanosheet-like materials, which facilitates charge carriers transfer at the interfaces. The Bi4O5I2/Bi4O5Br2-OV also shows the desirable removal rate for TC and RhB in actual wastewater or in the presence of some electrolytes. This study provides an effective and simple strategy for designing OVs modified Bi-rich oxyhalides heterojunctions.