Efficient visible-light-driven photocatalytic reduction of hexavalent chromium by three-dimensional heterostructure PANI@SnS2@carbon sphere

Tin sulfide (SnS2) is an excellent photocatalyst, which is widely used in reduction of heavy metal pollutants. However, its application is hindered by the rapid recombination of photogenerated carriers. In this study, a heterostructure composite composed of PANI, SnS2 and carbon sphere (PANI@SnS2@Cs) was prepared by a hydrothermal approach combined with in-situ oxidative polymerization to release the fast recombination of photogenerated carriers and improve the photoreduction performance. Compared with bare SnS2 and SnS2@Cs, PANI@SnS2@Cs not only provides more efficient photoreduction performance, but also possesses stronger adsorption capability. In neutral solution, 60 mg PANI@SnS2@Cs is capable of reducing 60 mL contaminated water with a concentration of 100 mg/L Cr(VI) within 30 min of solar light. Characterizations including transmission electron microscope and UV-Vis-NIR diffusive reflectance spectra were applied to provide evidences to confirm the heterostructure and the excellent optical performance of PANI@SnS2@Cs. Besides, the mechanism behind PANI@SnS2@Cs was investigated that the photogenerated e- in the lowest unoccupied molecular orbital (LUMO) of PANI can be transferred into the conduction band of SnS2 while h+ in valence band of SnS2 can be transferred into the highest occupied molecular orbital (HOMO) of PANI.