Exceptional synergistic enhancement of the photocatalytic activity of SnS2 by coupling with polyaniline and N-doped reduced graphene oxide

Abstract

Effective enhancement of the separation and transfer of photogenerated electrons and holes of semiconductor photocatalysts is key to increase their photocatalytic efficiency. This study aims at improving the photocatalytic performance of visible-light-responsive, CdI2-type layered SnS2 by employing good conductivity N-doped reduced graphene oxide (NRG) and polyaniline (PANI) as the receptors and transporters of photogenerated electrons and holes, respectively. PANI/SnS2/NRG ternary composites were prepared by a three-step method, and the optimum conditions for preparing the most efficient product were explored. The photocatalytic experiments demonstrated that the PANI/SnS2/NRG ternary composite prepared under the optimum conditions (PANI/SnS2/NRG-2%) had markedly higher photocatalytic activity than SnS2 nanoplates, SnS2/PANI and SnS2/NRG binary composites in the reduction of aqueous Cr(VI) under the irradiation of visible-light (λ > 420 nm). Based on comparison of the photoabsorption, photoluminescence and electrochemical impedance properties of PANI/SnS2/NRG, SnS2/PANI and SnS2, it was thought that the coupling of SnS2 with both PANI and NRG had synergistic effects in increasing the absorption of visible-light as well as the separation and transfer of photogenerated electrons and holes, which contributed to the exceptionally high photocatalytic activity of PANI/SnS2/NRG ternary composite. Moreover, it was discovered that the photocatalytic reduction of Cr(VI) over PANI/SnS2/NRG-2% was dominantly through the reduction by photogenerated electrons, whereas both photogenerated electron and superoxide anion radical (O2–) reduction played important roles in the photocatalytic reduction of Cr(VI) over SnS2. Besides, the influences of photocatalytic testing conditions (including starting pH and concentration of Cr(VI) solution, and dosage of photocatalyst) on the efficiency of PANI/SnS2/NRG-2% in treatment of aqueous Cr(VI) were also examined.