CdS nanoparticles grown in situ on oxygen deficiency-rich WO3−x nanosheets: direct Z-scheme heterojunction towards enhancing visible light-driven hydrogen evolution

Abstract

The rapid separation and transport of photogenerated carriers are pivotal toward enhancing the photocatalytic performance. Herein, CdS nanoparticles are grown in situ on oxygen deficiency-rich WO_3−x nanosheets, successfully providing a direct Z-scheme CdS/WO_3−x heterojunction to enhance photocatalytic hydrogen production. We demonstrate an effective electron collection in the Z-scheme CdS/WO_3−x heterojunction by regulating the relative content of WO_3−x. The optimized CdS/20 wt% WO_3−x (CW20) affords a high photocatalytic hydrogen production rate of 6545.3 μmol g⁻¹ h⁻¹ in lactic acid aqueous solution under visible light (400–800 nm), which is about 54.1 times that of pure CdS (121.0 μmol g⁻¹ h⁻¹). In addition, CW20 also provides a considerable external quantum efficiency (EQE) of 10.03% at λ = 420 nm. The best-performing CW20 sample is explored by cyclic stability experiment and XRD characterization after hydrogen production, which reveals the robust stability of CW20. The excellent photocatalytic activity can be attributed to the formation of a Z-scheme CdS/WO_3−x heterojunction, resulting in an efficient spatial separation of photogenerated carriers. Electron and hole catalytic centers are maintained in two separate components to minimize the adverse products of photocatalytic hydrogen production. This study uncovers the role of oxygen deficiency based on the Z-scheme heterojunction in affecting electron transfer and reaction sites, opening new opportunities for achieving efficient hydrogen production.