In situ construction of a heterojunction over the surface of a sandwich structure semiconductor for highly efficient photocatalytic H evolution under visible light irradiation.

Developing a heterostructure on the surface of a "sandwich" structure semiconductor is essential for full utilization of its heterojunction function and hence for designing efficient solar energy conversion systems. Here, we show that 2D-2D MoS/MnSbS heterostructure composites are designed for the first time and successfully synthesized by a simple in situ calcination pathway. Under visible light irradiation, the ca. 3.3 wt% MoS/MnSbS samples exhibited the highest activity for H evolution, which was 7.7 times higher than that of the pristine MnSbS monolayer. The outstanding photocatalytic performance was attributed to the MoS nanosheets intimately growing on the surface [SbS] layers of monolayer MnSbS nanosheets with the [SbS]-[MnS]-[SbS] sandwich substructure to form the 2D-2D MoS/MnSbS heterojunction structure. More importantly, we prove that this specific heterojunction structure can lead to more weakening of the constraint of the valence electrons in the composited photocatalysts, which can promote the transfer of photogenerated electrons from MnSbS to MoS. The present study provides a new design strategy for the construction of a heterostructure to improve the photocatalytic H production activity highly efficiently.