Fabrication of n-n isotype BiOBr-Bi2WO6 heterojunctions by inserting Bi2WO6 nanosheets onto BiOBr microsphere for the superior photocatalytic degradation of Ciprofloxacin and tetracycline

Ciprofloxacin (CIP) and tetracycline (TC) are emerging contaminants which seriously threaten the survival of aquatic life and human health. In this study, we report a facile and energy-efficient one-step hydrothermal strategy for the fabrication of n-n isotype BiOBr-Bi2WO6 heterojunctions with nanosheet-insertion-microsphere morphology. Morphological characterizations indicated that two-dimensional (2D) n-Bi2WO6 nanosheets were inserted or covered upon n-type three-dimensional (3D) BiOBr microspheres which acted as the support successfully restricted the aggregation of Bi2WO6 nanosheets and supplied more active sites. The 2D Bi2WO6 nanosheets enhanced the interfacial contact and improved visible-light absorption efficiency. Photocatalytic degradation experiments revealed that BiOBr-Bi2WO6 = 8:1 exhibited superior CIP and TC degradation (90%and 96%, respectively) within 120 min as compared to that of the pristine BiOBr and Bi2WO6. Moreover, BiOBrBi2WO6 = 8:1 also realized efficient photocatalytic degradation of Rhodamine B (100%) and Methylene blue (94%). Excellent stability and recyclability remained in BiOBr-Bi2WO6 = 8:1 composite after five consecutive cycles. Based on the band structure analyses, and radical trapping and electron spin resonance characterization results, a possible Z-scheme path of charger transfer was proposed to elucidate the enhanced photocatalytic mechanism. This study offers a novel avenue to design efficient n-n isotype heterojunction with superior visiblelight response for refractory antibiotics degradation.

Automated summary

A facile and energy-efficient one-step hydrothermal strategy was used to fabricate n-n isotype BiOBr-Bi2WO6 heterojunctions, which showed superior degradation efficiency towards CIP and TC in water. The BiOBr-Bi2WO6 = 8:1 composite also exhibited efficient photocatalytic degradation towards Rhodamine B and Methylene blue. Band structure analyses and radical trapping results suggested a possible Z-scheme path of charger transfer to enhance the photocatalytic mechanism.