Preparation Of Novel Molybdenum Disulfide-based Nanocomposites And Their Application In Environmental Field

With the rapid development of modern industrialization and population,people pay more and more attention to the problem of environmental pollution.In recent years,the new two-dimensional transition metal sulfide,such as molybdenum disulfide（MoS₂）,has gained widespread attention due to their unique optical and electrical properties.MoS₂ is a layered compound similar to graphene,whose structure exhibits a sandwich structure of S-Mo-S.The overlapping layers and layers are held together by the weak van der Waals forces.In addition,MoS₂ has an adjustable bandgap structure,which means that as the number of layers decreases,the band gap increases.MoS₂ has two common phases,namely semiconducting 2H and metallic1T.In view of these unique properties,MoS₂ can be used in the field of photocatalysis to solve some of the current pollution problems in the environment.In our research,by adopting the concept of solvent engineering,we retional design a simple and controllable method to prepare a series of novel MoS₂-based nanocomposites.Under the synergistic effect of the solvent 1-methyl-2-pyrrolidone（NMP）and the surfactant cetyltrimethylammonium bromide（CTAB）,we have prepared GO/g-C₃N₄/MoS₂ with a flower-like heterostructures,which is applied to photocatalytic degradation of dye wastewater.The crystal structure and morphology of materials were characterized by scanning electronic microscopy（SEM）,transmission electron microscope（TEM）,X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）.Graphene（GO）,graphitic phase carbon nitride（g-C₃N₄）and MoS₂ are intimately bonded together to form a flower-like heterogeneous nanojunction.Under visible light irradiation,GO/g-C₃N₄/MoS₂composites have excellent photocatalytic degradation performance for organic dye wastewaters,such as methylene blue(MB,20 mg L^-1),rhodamine B(RhB,20 mg L^-1)and crystal violet(CV,20 mg L^-1).In the meantime,the photocatalytic elimination of toxic heavy metal Cr（VI）is also carried out by the hybrids.Meanwhile,the nanocomposites exhibit good reproducibility and stability during the cycle of the experiment.The design of the flower-like GO/g-C₃N₄/MoS₂heterojunction has the potential to be applied to the actual dye wastewater water remediation.The 2H phase MoS₂ still has the disadvantages of poor electrical conductivity,small specific surface area and relatively less photocatalytic active sites.Therefore,we use a typical zeolitic imidazolate framework-8（ZIF-8）and a mixed phase MoS₂（1T/2H-MoS₂）composite（1T/2H-MoS₂/ZIF-8）to enhance the photocatalytic degradation performance.In the solvothermal process,1T/2H-MoS₂/ZIF-8composites were successfully synthesized.Under the characterizations of SEM,TEM and XRD,the composites presented an ultrathin tubular structure with ZIF-8firmly attached to 1T/2H-MoS₂.The composites have excellent photocatalytic degradation properties for tetracycline hydrochloride(TC,20 mg L^-1)and ciprofloxacin(CIP,20 mg L^-1).The decisive factor for a significant increase in the photocatalytic performance of composites may be the unique ultrathin tubular structure,dense uniform interface contact and more adsorption and catalytic reaction sites.Besides,1T-MoS₂ improves the electrical conductivity of the composite,whereas 2H-MoS₂ provides more active edges.Based on these advantages,1T/2H-MoS₂/ZIF-8 can better photocatalytically degrade antibiotic.