Zinc sulfide quantum dots/zinc oxide nanospheres/bismuth-enriched bismuth oxyiodides as Z-scheme/type-II tandem heterojunctions for an efficient charge separation and boost solar-driven photocatalytic performance.

ABSTRACT

A novel zinc sulfide quantum dot (ZnS QD)/zinc oxide (ZnO) nanosphere/bismuth-enriched bismuth oxyiodide (Bi4O5I2) tandem heterojunction photocatalyst is fabricated through two-step solvothermal, calcination and one-step hydrothermal strategies. The successfully constructed core-shell nanostructure can increase the interface area and the active sites of the composite photocatalysts. The formation of a Z-scheme/Type-II tandem heterojunction favors the transfer and spatial separation of charge carriers, in which Bi4O5I2 plays a bridging role to connect ZnO and ZnS. Simultaneously, the participation of Bi4O5I2 significantly shortens the band gap of the composite photocatalyst. This dual functional ZnO@Bi4O5I2/ZnS composite photocatalyst has a high photocatalytic hydrogen evolution rate of 578.4 µmol g-1h-1 and an excellent photocatalytic degradation efficiency for bisphenol A (BPA) and 2,4,5-trichlorophenol (TCP). In addition, cycling tests show that ZnO@Bi4O5I2/ZnS has a high stability, which is favorable for practical applications. This novel ZnO@Bi4O5I2/ZnS Z-scheme/Type-II tandem heterojunction photocatalyst will provide new ideas for the multichannel charge transfer of other highly efficient heterojunction photocatalysts.