Enhanced Light-Driven Charge Separation and H2 Generation Efficiency in WSe2 Nanosheet-Semiconductor Nanocrystal Heterostructures.

Semiconductor-catalyst heterostructures have shown promising performances for light-driven H2 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 WSe2 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, TiO2 nanoparticles, g-C3N4 nanosheets). These WSe2-semiconductor heterostructures show enhanced solar-to-hydrogen conversion efficiencies compared to semiconductors without WSe2. The detailed mechanism of this enhancement has been investigated using WSe2 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 WSe2-decorated CdSe/CdS dot-in-rods, suggesting its key role in enhancing the H2 generation efficiency of WSe2-semiconductor heterostructures. This work demonstrates the great potentials of WSe2 nanosheets as catalysts for light-driven hydrogen production and the important effect of forming WSe2-semiconductor heterostructures in facilitating charge separation and photocatalysis.