Co-catalyst-free ZnS-SnS2 porous nanosheets for clean and recyclable photocatalytic H2 generation

Highlights: • ZnS-SnS₂ porous nanosheets were synthesized as a cost-effective photocatalyst for H₂ evolution. • The special porous structure ensured a lots of chemical reaction sites. • The unique quasi-type II heterojunction improved the carriers' separation rate. • The composites exhibited a hydrogen evolution rate that was 17 times higher than SnS₂ and 10 times than ZnS. • The composites are photostable and can be reused for at least five runs without obvious changes in activity. Two-dimensional (2D) ZnS-SnS₂ porous nanosheets are designed as clean and low cost photocatalysts for water splitting. The composites successfully combine high photoelectron reduction potential of ZnS with the sufficient sunlight harvesting ability of SnS₂. Moreover, SnS₂ acts as an effective electron transfer medium from ZnS to SnS₂ due to the construction of quasi-type II structure. This greatly promotes the transfer of electron-hole pairs and effectively inhibits their recombination. Especially, the unique porous nanosheets structure maintains them high specific surface area and countless reactive sites, which increases the reactants' contact area and facilitates the migration of carriers upon photocatalysis. This further suppresses the charge recombination and improves the photocatalysts' stability. As a result, an optimized specific surface area of 246.7 m² g⁻¹ and photocatalytic H₂ generation rate of 536 μmol h⁻¹ g⁻¹ are achieved in the absence of a surfactant and co-catalyst, which is 10 times higher than ZnS and 17 times higher than SnS₂. In addition, the porous nanosheets have fairly good photocatalytic stability and can be reused at least five cycles without obvious changes in activity and structure. This work successfully presents the potential of ZnS and SnS₂-based photocatalyst for clean and low cost hydrogen production from water splitting.