Synthesis And Piezocatalytic Research Of MoS₂ Hollow Microspheres

As an emerging sewage treatment and environmental purification technology,piezocatalysis has broad application prospects due to its advantages of high catalytic efficiency and wide source of driving force.Among many piezocatalytic materials,MoS2 has been studying due to its simple preparation process and great piezocatalytic performance.At present,MoS2 piezocatalysts with various shapes such as nanosheets and nanoflowers show good piezocatalytic properties.However,there have been few reports on using MoS2 hollow microspheres as piezocatalyst.Therefore,in this paper,MoS2 hollow microsphere catalysts were prepared by soft template method and template-free method,respectively,and their piezocatalytic properties were studied.Based on the research of MoS2 hollow microspheres,it was modified by Co doping,and the piezocatalytic performance of the catalysts was further discussed.The specific results of studies are as follows:(1)Using cetyltrimethylammonium bromide(CTAB)and tetrabutylammonium bromide(TBAB)as template agents,NaMoO4·2H2O and CN2H4S as molybdenum sources and sulfur sources,respectively,MoS2 hollow microspheres were prepared by soft template method.They were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM).Energy diffraction spectrum(EDS),X-ray photoelectron spectroscopy(XPS)and N2 adsorptiondesorption isotherm(BET).And the formation mechanism of MoS2 hollow microspheres was discussed.The piezocatalytic properties of MoS2 hollow microspheres was investigated by piezocatalytic degradation of methylene blue(MB),which were used as the degradation models.Furthermore,the catalyst was applied to the piezocatalytic degradation of Rhodamine B(RhB),Ciprofloxacin(CIP),Tetracycline(TC)and Oxytctracycline(OTC),and the piezocatalytic performance of MoS2 hollow microspheres to other dyes and antibiotic organic pollutants was discussed.The results show that the crystal phase of the MoS2 hollow microspheres is 2H phase,which were prepared when the hydrothermal temperature at 240℃,the hydrothermal reaction time for 24 h and the TBAB concentration at 8 g/L.In addition,the particle size of the microspheres is about 2-4 μm,and the particle size distribution is uniform,and the specific surface area is 41.75 m2/g.The MoS2 hollow microspheres prepared under these conditions have the best piezocatalytic performance.Under the ultrasonic driving,the degradation rates of MB,RhB,CIP,TC and OTC reached 98.0%,84.6%,88.9%,72.9%,80.3%within 150 s,150 s,300 s,600 s and 600 s,respectively.(2)MoS2 hollow microspheres were prepared successfully with template-free process by using MoO3,KSCN and NaF as raw materials.XRD,SEM,EDS,XPS and BET were used to analyze the crystal properties,micro-morphology and specific surface area of the samples,and the growth mechanism of MoS2 hollow microspheres during template-free process was discussed.And the piezocatalytic performance of MoS2 hollow microspheres prepared by template-free method was investigated by degrading MB.The degradation activity of the MoS2 hollow microspheres to other dyes and antibiotic organic pollutants was further investigated by using RhB and CIP as degradation models and its practical value was discussed.The results show that MoS2 hollow microspheres with wrinkles on the surface were obtained when the hydrothermal temperature is 220℃,the hydrothermal time last for 16 h,and the amount of NaF added is 12 mmol.The crystal phase of the samples prepared is 1T phase,and the particle size of it is about 0.5-1 μm,the specific surface area is 57.67 m2/g.The results of degradation experiments show that the MoS2 hollow microspheres prepared under this condition have excellent piezoelectric catalytic performance.The degradation rate of MB and RhB is as high as 89.3%and 98.9%within 60 s,respectively.And the degradation rate of CIP reached 94.7%within 120 s.(3)Based on the study of the piezocatalytic properties of MoS2 hollow microspheres,CoCl2·6H2O was selected as the cobalt source and a series of Co doped MoS2 hollow microspheres with different doping amounts were prepared by the soft template method and the template-free method.The samples prepared were characterized by XRD,SEM,EDS,XPS and BET.The piezocatalytic activity of Co doped MoS2 hollow microspheres prepared by the soft template method on dyes and antibiotics contaminants was investigated through the degradation of MB and TC.The piezocatalytic properties of Co doped MoS2 hollow microspheres prepared by the template-free method was studied by using CIP as degradation models.The results show that the amount of Co doping has no significant effect on the crystallinity and microscopic morphology of the samples prepared by either the soft template method or the template-free method.XPS spectrum shows that the binding energies of Mo 3d5/2 and Mo 3d3/2 shift to higher values after doping with Co and the specific surface area of Co doped MoS2 hollow microspheres is 38.47 m2/g,slightly lower than pure MoS2.When the doping amount of Co reaches 15%,Co doped MoS2 hollow microspheres prepared by both methods have the best piezocatalytic performance.Under the ultrasonic driving,the Co doped MoS2 hollow microspheres prepared by the soft template method achieved a MB degradation rate of 94.8%within 90 s and a TC degradation rate of 84.3%within 600 s,which is 13.1%and 11.4%higher than that of pure MoS2 hollow microspheres prepared by soft template method,respectively.Similarly,the degradation rate of Co doped MoS2 hollow microspheres prepared by the template-free method to MB is as high as 98.3%in 40 s and it to CIP reached 94.5%within 80 s,which is an increase of 17.7%and 14.6%compared to pure MoS2 hollow microspheres prepared by template-free method,respectively.