Preparation And Photocatalytic Properties Of Bi₂S₃ Nanocomposites

Bi₂S₃ has wide band gaps,abundant active sites,and stable physicochemical properties in the visible light region.Therefore,it has been extensively studied in photocatalytic removal of pollutants.However,the single Bi₂S₃ photogenerated hole recombination rate is high,which results in a certain limitation of its photocatalytic efficiency.In this paper,Bi₂S₃ is compounded with three different materials to improve the photocatalytic performance of Bi₂S₃ composites.The main research contents are as follows:(1)Heterojunctioned ZnO/Bi₂S₃ nanocomposites were prepared via a facile solvothermal method.The obtained samples were characterized by XRD,SEM,HRTEM,XPS,UV-Vis DRS,Photoelectrochemical and PL,respectively.The results showed that ZnO/Bi₂S₃ composites exhibited the sandwiched-like structure,where ZnO nanoparticles were randomly embedded between Bi₂S₃ nanoflakes.The performance of photocatalytic Cr(VI)reduction under visible light indicated that ZnO/Bi₂S₃ composites exhibited high-efficiency photocatalytic activity in comparison with either Bi₂S₃ or ZnO.The 5%-ZnO/Bi₂S₃ photocatalyst removed 96%of Cr(VI)within 120 min at 20mg/L initial concentration of Cr(VI).The enhanced performance of ZnO/Bi₂S₃photocatalysts could be ascribed to the increased light harvesting and the effectiveseparation and transfer of the photogenerated charge carriers across the heterojunction interface of the ZnO/Bi₂S₃ composite.(2)Different percentages of Bi/Bi₂S₃ nanocomposites were synthesized via solvothermal method by adjusting the dosage of Bi(NO₃)₃·5H₂O.The obtained samples were characterized by XRD,SEM,HRTEM,XPS,UV-Vis DRS,Photoelectrochemical and PL,respectively.The results showed that Bi nanoparticles were deposited on the surface of Bi₂S₃ rods.The performance of visible light photocatalytic reduction of Cr(VI)shows that,compared with pure Bi₂S₃,the deposition of a proper amount of particulate Bi can promote the photocatalytic activity of Bi/Bi₂S₃ composites.Under120min visible light irradiation,20%-Bi/Bi₂S₃ composite of the removal rate of Cr(VI)was 90.8%.The enhanced photocatalytic performance of the Bi/Bi₂S₃ nanocomposites could be attributed to the SPR effect of Bi.The photo-generated carriers are effectively separated and electrons are more easily transferred at the interface.(3)RGO/Bi₂S₃ composites were prepared by solvothermal method.Photocatalysis experiments show that:the RGO/Bi₂S₃ composites had higher photocatalytic activity in the mixing system of Cr(VI)and MO instead of the single removal of Cr(VI)or MO,which proved that there was a synergy between the reduction of Cr(VI)and MO oxidation.Under the visible light irradiation for 3h,the efficiency of photo-reduction of Cr(VI)and photo-oxidation of MO was higher than that of pure Bi₂S₃ in RGO/Bi₂S₃ composite material.It shows that the introduction of RGO has a positive effect on the photocatalytic performance of composite materials.This is because the?-?conjugate structure of RGO is conducive to the transmission of e^–,thereby promoting the separation of photo-generated e^–/h⁺pairs in Bi₂S₃ and enhancing the photocatalytic performance of RGO/Bi₂S₃ composites.In the cooperative reaction of the mixed solution of Cr(VI)and MO,Cr(VI)acted as a trapping agent for e^–,and MO acted as a trapping agent for h+,thereby significantly improving the photocatalytic efficiency.