| Currently, there is an increasing interest in the application of semiconductors as photocatalysts to degrade organic pollutants. In this paper, SnS2and SnS2/SnO2nanopowders with high visible light photocatalytic activity were synthesized via liquid-solid state method or hydrothermal method. The as-prepared products were characterized by X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, Brumauer-Emmett-Teller (BET) surface area analysis, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectra and UV-vis diffuse reflectance spectra. Furthermore, their photocatalytic properties of the as-prepared products were tested by degrading methyl orange in water under visible light (λ>420nm) or natural sunlight irradiation. The main works achieved are summed up as following:1. Bulk-pure hexagonal phase SnS2nanoflakes were synthesized by heating the mixture of SnCl2·2H2O and excess S powders in air at200-240℃for0-10h (t=0h, that is, the heating of the reactants was stopped immediately once temperature reached the designed degree), coupled with a subsequent washing treatment. Besides, degradation of methyl orange in deionized water was carried out with the as-synthesized SnS2nanoflakes as photocatalysts under both the visible light (λ>420nm) and natural sunlight irradiation. The results demonstrated that all the SnS2products had high visible light photocatalytic activity, and the most efficient photocatalyst among them was the one synthesized at200℃for0h. Moreover, the best sample also possessed much higher photocatalytic activity than the commercial Degussa P25TiO2photocatalyst under the natural sunlight irradiation, and can be easily recovered from the suspension by filtration after the photocatalysis.2. Tetragonal phase SnO2nanopowders were synthesized via hydrothermal treatment of SnCl2·2H2O and6%H2O2aqueous solution at180℃for12h, and subsequently SnO2/SnS2nanocomposites with different SnO2contents were prepared via ion exchange process between the as-synthesized SnO2nanoparticles and different amount thioacetamide in5%acetic acid aqueous solution at150℃for0-24h. In addition, the photocatalytic properties of the obtained products were evaluated by degradation methyl orange in deionized water under the visible light (λ>420nm) irradiation. All the as-prepared SnO2/SnS2nanocomposites showed superior photocatalytic activity to SnS2nanoflakes and physically mixed SnO2/SnS2nanocomposites. It was believed that heterojunction structure of the synthesized SnO2/SnS2nanocomposites, which can facilitate interfacial electron transfer and reduce the self-agglomeration of two components, was considered to play an important role in achieving its higher photocatalytic activity.3. Hexagonal phase SnS2nanopowders were synthesized via hydrothermal reaction between SnCl4·5H2O and different amounts of thioacetamide in5%acetic acid aqueous solution at120-180℃for12h. Besides, the photocatalytic properties of the obtained products were evaluated by degradation methyl orange in deionized water under the visible light (λ>420nm) irradiation. It was found that the synthesis conditions of SnS2nanoflakes affect their photocatalytic activities in degrading MO, and the product synthesized at200℃for0h has the highest photocatalytic activity under the visible light irradiation. Moreover, all the SnS2products showed higher photocatalytic efficiencies than Degussa P25TiO2and flowerlike CdS under the visible light irradiation.Subsequently SnS2/SnO2nanopowders with tunable SnO2contents were prepared via in-situ hydrothermal oxidation of the as-synthesized SnS2nanopowders in0.375-4.5 %of H2O2aqueous solutions at180℃for0-12h. Besides, the photocatalytic properties of the obtained products were evaluated by degradation methyl orange (MO: in deionized water under the visible light (λ>420nm) irradiation. It was found that the as-prepared SnS2/SnO2nanocomposites with suitable SnO2content demonstrated superior photocatalytic activity to both SnS2nanoparticles and physically mixed SnS2/SnO2composite nanoparticles. Moreover, the as-synthesized SnS2/SnO2nanoparticles had remarkable photocatalytic stability. It was found that the tight attachment of SnO2nanoparticles to SnS2nanoparticles, which can facilitate interfacial electron transfer and reduce the self-agglomeration of two components, was considered to play an important role in achieving the high photocatalytic performances exhibited by the as-prepared SnS2/SnO2nanocomposites. |
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