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

• One-step hydrothermal synthesis of composition-tunable SnS2/SnO2 nanoheterojunctions.
• Composition dominates the photocatalytic activity of SnS2/SnO2 nanoheterojunction.
• Higher photocatalytic efficiencies than PM-SnS2/SnO2 and SnS2 at different dosages.
• The washing with 1 mol/L HNO3 can effectively regenerate the used photocatalyst.
• High activity and good stability in photocatalytic reduction of aqueous Cr(VI).

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 6 h, 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 > 420 nm) 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 70 mol% 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 1 mol/L HNO3 can effectively regenerate the used photocatalyst; (iv) SnS2/SnO2-B exhibited good photocatalytic stability in reuses, with regeneration by 1 mol/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.

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