A hierarchical SnS@ZnIn 2 S 4 marigold flower-like 2D nano-heterostructure as an efficient photocatalyst for sunlight-driven hydrogen generation.

Herein, we report the in situ single-step hydrothermal synthesis of hierarchical 2D SnS@ZnIn 2 S 4 nano-heterostructures and the examination of their photocatalytic activity towards hydrogen generation from H 2 S and water under sunlight. The photoactive sulfides rationally integrate via strong electrostatic interactions between ZnIn 2 S 4 and SnS with two-dimensional ultrathin subunits, i.e. nanopetals. The morphological study of nano-heterostructures revealed that the hierarchical marigold flower-like structure is self-assembled via the nanopetals of ZnIn 2 S 4 with few layers of SnS nanopetals. Surprisingly, it also showed that the SnS nanopetals with a thickness of ∼25 nm couple in situ with the nanopetals of ZnIn 2 S 4 with a thickness of ∼25 nm to form a marigold flower-like assembly with intimate contact. Considering the unique band gap (2.0-2.4 eV) of this SnS@ZnIn 2 S 4 , photocatalytic hydrogen generation from water and H 2 S was performed under sunlight. SnS@ZnIn 2 S 4 exhibits enhanced hydrogen evolution, i.e. 650 μmol h -1 g -1 from water and 6429 μmol h -1 g -1 from H 2 S, which is much higher compared to that of pure ZnIn 2 S 4 and SnS. More significantly, the enhancement in hydrogen generation is 1.6-2 times more for H 2 S splitting and 6 times more for water splitting. SnS@ZnIn 2 S 4 forms type I band alignment, which accelerates charge separation during the surface reaction. Additionally, this has been provoked by the nanostructuring of the materials. Due to the nano-heterostructure with hierarchical morphology, the surface defects increased which ultimately suppresses the recombination of the electron-hole pair. The above-mentioned facts demonstrate a significant improvement in the interface electron transfer kinetics due to such a unique 2D nano-heterostructure semiconductor which is responsible for a higher photocatalytic activity.