Unique CdZnS/WO direct -scheme heterojunction with S, O vacancies and twinning superlattices for efficient photocatalytic water-splitting.

Photocatalytic water-splitting employing the -scheme semiconductor systems mimicking natural photosynthesis is regarded as a promising way to achieve efficient soalr-to-H conversion. Nevertheless, it still remains a big challenge to design high-performance direct -scheme photocatalysts without the use of noble metals as electron mediators. Herein, a unique CdZnS/WO direct -scheme heterojunction was constructed for the first time, which consisted of smaller O-vacancy-decorated WO nanocrystals anchoring on CdZnS nanocrystals with S vacancies and zinc blende/wurtzite (ZB/WZ) twinning superlattices. Under visible-light ( > 420 nm) irradiation, the CdZnS/WO composites exhibited an outstanding H evolution reaction (HER) activity of 20.50 mmol h g (corresponding to the apparent quantum efficiency of 18.0% at 420 nm), which is much superior to that of WO, CdZnS, and CdZnS loaded with Pt. Interestingly, the introduced O and S vacancies contributed to improving the HER activity of CdZnS/WO significantly. Moreover, the cycling and long-term HER measurements confirmed the robust photocatalytic stability of CdZnS/WO for H production. The excellent light harvesting and efficient spatial charge separation induced by the ZB/WZ twinning homojunctions and defect-promoted direct -scheme charge-transfer pathway are responsible for the exceptional HER capability. Our study could enlighten the rational engineering and optimization of semiconductor nanostructures for energy and environmental applications.