Enhanced Light-Driven Charge Separation and H Generation Efficiency in WSe Nanosheet-Semiconductor Nanocrystal Heterostructures.

Semiconductor-catalyst heterostructures have shown promising performances for light-driven H generation, although further development of these materials is hindered by the lack of cost-effective and efficient catalysts. In this paper, we adopt a colloidal method to prepare few-layer WSe nanosheets without exfoliation and apply them as catalysts for forming heterostructures with a wide range of semiconductor absorbers (CdS nanorods, CdSe/CdS dot-in-rods, TiO nanoparticles, g-CN nanosheets). These WSe-semiconductor heterostructures show enhanced solar-to-hydrogen conversion efficiencies compared to semiconductors without WSe. The detailed mechanism of this enhancement has been investigated using WSe nanosheet-decorated CdSe/CdS dot-in-rods as a model system, which display ∼5.5-fold higher hydrogen generation apparent quantum efficiency compared to free CdSe/CdS dot-in-rods. Transient absorption spectroscopic studies reveal efficient charge separation in WSe-decorated CdSe/CdS dot-in-rods, suggesting its key role in enhancing the H generation efficiency of WSe-semiconductor heterostructures. This work demonstrates the great potentials of WSe nanosheets as catalysts for light-driven hydrogen production and the important effect of forming WSe-semiconductor heterostructures in facilitating charge separation and photocatalysis.