A novel 0D/2D WS2/BiOBr heterostructure with rich oxygen vacancies for enhanced broad-spectrum photocatalytic performance.

ABSTRACT

In this study, a novel 0D/2D WS2/BiOBr heterostructured photocatalyst with rich oxygen vacancies was fabricated by a hydrothermal method. The WS2 QDs/BiOBr-10 heterostructures exhibited a maximum removal rate of 92% towards ciprofloxacin (CIP) within 100 min under visible-light irradiation, which was 2.63- and 2.02- folds higher activity than that of pristine BiOBr and WS2 QDs/BiOBr-10 with poor oxygen vacancies, respectively. In addition, the removal efficiencies of this photocatalyst towards various pollutants were 99% (Lanasol Red 5B), 95% (Rhodamine B), 85% (metronidazole), 96% (tetracycline) and 41% (Bisphenol A), respectively. Besides, the simultaneous photocatalytic degradation showed the competitive interactions between these organic contaminants for the active species, decreasing the removal efficiency for CIP. However, the simultaneous photocatalytic oxidation of CIP and reduction of Cr(VI) improved the utilization efficiency of photo-induced electrons and holes, resulting in high removal efficiencies for both CIP and Cr(VI). Three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs) were used to investigate the degradation of CIP molecules. The synergistic effect of heterostructure and oxygen vacancies greatly assisted in the removal of organic pollutants, attributing to the enhanced visible-light harvesting and effective separation of photo-induced electron-hole pairs. Furthermore, trapping experiments and ESR results demonstrated that the CIP removal was dominated by the direct oxidation of holes (h+), whereas the hydroxyl radicals (OH) and superoxide radicals (O2-) acted as auxiliary active species. This study provides a new way to rationally design and construct active 0D/2D pattern heterojunction photocatalysts for environmental remediation.