One-step hydrothermal synthesis of high-performance visible-light-driven SnS2/SnO2 nanoheterojunction photocatalyst for the reduction of aqueous Cr(VI)

Abstract

A simple and cost-effective one-step hydrothermal method, which was based on the reactions of tin(IV) chloride pentahydrate and different dosages of thioacetamide in water at 190°C for 6h, was employed for the synthesis of composition-tunable SnS2/SnO2 nanoheterojunctions (e.g., SnS2/SnO2-A, SnS2/SnO2-B and SnS2/SnO2-C). The photocatalytic properties of the as-synthesized SnS2/SnO2 nanoheterojunctions were tested by the reduction of aqueous Cr(VI) under visible-light (λ>420nm) irradiation. Furthermore, the photocatalytic efficiency of SnS2/SnO2-B was compared with those of PM-SnS2/SnO2 (which denotes the physically mixed SnS2/SnO2 nanocomposite with the same composition as SnS2/SnO2-B) and SnS2 nanoflakes at different dosages of photocatalysts. It was observed that (i) the photocatalytic activities of the as-synthesized SnS2/SnO2 nanoheterojunctions depended on their compositions, and SnS2/SnO2-B with 70mol% SnS2 displayed the highest photocatalytic activity; (ii) SnS2/SnO2-B invariably exhibited higher photocatalytic efficiencies than PM-SnS2/SnO2 and SnS2 nanoflakes at different dosages of photocatalysts; (iii) the washing with 1mol/L HNO3 can effectively regenerate the used photocatalyst; (iv) SnS2/SnO2-B exhibited good photocatalytic stability in reuses, with regeneration by 1mol/L HNO3-washing after each cycle of photocatalytic use; and (v) Cr(VI) was reduced to Cr(III). The possible formation mechanism of SnS2/SnO2 nanoheterojunctions and the reasons accounting for the photocatalytic results were also discussed.