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.