Construction of direct Z-scheme WO3/ZnS heterojunction to enhance the photocatalytic degradation of tetracycline antibiotic

Abstract

Heterogeneous photocatalysis has been considered as a green and sustainable alternative for water decontamination where the key step is the nanomaterials design to enhance the photocatalytic process. Therefore, in this study the photocatalytic degradation of an emerging contaminant as the tetracycline antibiotic in aqueous solution, was investigated under UV–Vis irradiation by using the WO3/ZnS photocatalyst. The coupled catalyst was synthesized by hydrothermal method and by varying the WO3 weight ratio (5, 10 and 20 wt%) with respect to the ZnS. The WO3/ZnS photoactivity for tetracycline degradation was greatly enhanced when both semiconductors were coupled to form a highly efficient direct Z-scheme. The highest degradation percentage was reached using the catalyst t WO3(5%)/ZnS, which completely degraded the pollutant within 90 min, and the determination of total organic carbon (TOC) removal indicated a high mineralization degree. Photoelectrochemical studies showed that WO3(5%)/ZnS exhibited the highest separation of e−/h+ pairs and the highest transfer efficiency. The improvement of the electron-hole separation in combination with the band alignment analysis, explained the intrinsic mechanism which corresponded to the direct Z-scheme photocatalytic system.