Hierarchical SnS@ZnIn2S4 marigold flower 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@ZnIn2S4 nanoheterostructure and their photocatalytic activity towards hydrogen generation from H2S and water under sunlight. The photoactive sulfides rationally integrated by strong electrostatic interaction between ZnIn2S4 and SnS with two-dimensional ultrathin subunits i.e nanopetals. The morphological study of nanoheterostructure reveals that the hierarchical marigold flower-like assembly is self-assembled by nanopetals of ZnIn2S4 with few layers of SnS nanopetals. Surprisingly, it also shows the SnS nanopetals of the thickness (~25 nm) in-situ coupled with the nanopetals of ZnIn2S4 having thickness (~25 nm) marigold flower with intimate contact. Considering the unique band gap (2.0-2.4 eV) of this nano-heterostructure, the photocatalytic hydrogen generation from water and H2S was performed under sunlight. The nanoheterostructures exhibit enhanced hydrogen evolution i.e. 650 μmol h–1g–1 from water and 6429 μmol h–1g–1 from H2S which is much higher compared to pure ZnIn2S4 and SnS. More significantly, the enhancement in hydrogen generation is 1.6-2 times more for H2S splitting and 6 times for water splitting. The nanoheterostructure exhibits the formation of type II band alignment which accelerates better charge separation to the surface reaction. Additionally, this has been provoked by the nanostructuring of the materials. Due to the nanoheterostructure with hierarchical morphology, the surface defects have been increased which ultimately suppresses the recombination of the electron-hole pair. The above facts demonstrate significant improvement of the interface electron transfer kinetics due to such a unique 2D nano-heterostructure semiconductor which is responsible for higher photocatalytic activity.