Preparation And Properties Of MoS₂-based Nanocomposites

This paper focuses on the two-dimensional transition metal sulfide MoS2.The properties of MoS₂ are improved mainly by constructing the composite of MoS₂ with other materials and the doping of MoS2 itself.The heterogeneous structure of MoS2/Bi2S3 was designed and synthesized,and its formation mechanism was studied.The change of its hydrogen evolution reaction was discussed.Based on the heterostructure of MoS₂/Bi₂S₃,P-doped MoS₂ was used to study the change of its hydrogen evolution reaction.Bi2S3 was used as the substrate to load MoSe_2xS_2?1-x?with different ratio Se/S and to investigate the change of hydrogen evolution reaction.MoS₂ was loaded onto a hollow Fe₂O₃ cubic box,and its Photo-Fenton and adsorption properties were studied by adjusting the load.Specific research contents are as follows:1.In order to improve the electrocatalytic hydrogen evolution reaction?HER?,semiconductor heterojunctions must be further developed.In the present investigation,three-dimensional scaffold-like networks,consisting of gold?Au?,bismuth sulfide?Bi₂S₃?,and molybdenum disulfide?MoS2?,have been developed and constructed.The main purpose was to improve the HER performances of a MoS2-based material.A MoS2/Bi2S3heterostructure was,at first,prepared by using a hydrothermal synthesis technique and a Bi₂WO₆ precursor.The resulting MoS₂/Bi₂S₃ network was found to exhibit a disk-like morphology with a homogeneous scaffold structure.The Au@MoS2/Bi2S3 ternary composite structure was,thereafter,synthesized by depositing Au nanoparticles on the MoS2/Bi2S3heterostructure.As a result of the following HER measurement,the onset overpotential of Au@MoS2/Bi2S3 was observed to decrease to 72 mV,and the Tafel slope decreased to 40m V/dec.The three different materials?within Au@MoS2/Bi2S3?was found to contribute to these positive results.The Bi2S3 structure promoted the electronic charge transport,while the dispersed MoS₂ structure exposed more active sites.Furthermore,the deposited Au nanoparticles promoted the conduction of electrons from the nanoparticles to the hydrogen carriers and was also found to accelerate the complete HER process?by reducing the activation energy of HER?.Owing to these excellent catalytic performances,the here presented results will aid in the construction of a composite semiconducting material with improved electrocatalytic performances.2.Hydro-catalytic hydrogen production is considered to be a promising and sustainable strategy.In this study,we successfully prepared the scaffolded P-MoS2/Bi2S3 heterostructure,providing stable and efficient electrocatalysis.When the current density is 10mA cm^-2,P-MoS₂/Bi₂S₃ showed an overpotential of 155 m V in 0.5 M H₂SO₄,and the Tafel slope was44 mV dec^-1,which was better than pure MoS₂,P-MoS₂ and MoS₂/Bi₂S₃ composite structure.Detailed characterization shows that the performance improvement is closely related to P doping and scaffold-like nanostructures.P doping increases the density of active sites for hydrogen evolution of MoS₂ material,and more active sites are exposed in scaffold composite structure.Accelerate the process of electrocatalytic hydrogen evolution.Moreover,by changing the temperature and time of hydrothermal reaction,the disorder degree of P-MoS₂nanosheets was optimized to produce denser active sites,which greatly improved the overall catalytic performance of P-MoS2/Bi2S3 heterostructure.This work not only provides a simple and low-cost selective method for HER,but also provides guidance for optimizing the composition and structure of nanocomposites.3.In this part,the catalytic materials of MoX₂?X=S,Se?were studied.MoSe_2xS_2?1-x?nanosheets was synthesized using hydrothermal process.By changing the proportion of the element Se and S to adjust the structure of electronic materials promoted MoSe_2xS_2?1-x?conductive performance,reduce the power consumption required for catalytic reaction.And by changing the temperature and time of hydrothermal,optimize MoSe_2xS_2?1-x?nanosheets disorder produced more effective active site,improve the internal electron mobility of the material,greatly improved the MoSe_2xS_2?1-x?nanosheets catalytic performance.The scaffold-like Bi₂S₃ as the substrate greatly dispersed the MoSe_2xS_2?1-x?nanosheets,effectively exposing more active sites.The overpotential of MoSe_1.9S_0.1/Bi₂S₃ was reduced to 162 m V and the slope of Tafel was reduced to 40 mV dec^-1.It is further proved that the design and synthesis of the structure can effectively improve the catalytic performance.4.Photo-Fenton catalysts enable to completely remove contaminants from water with its advanced oxidation technology.In this part,a layered hollow Fe₃O₄/Fe_1-x-x S@MoS₂ composite as photo-Fenton catalyst and adsorbent was reported to remove organic dyes and antibiotics from water.First,Prussian blue is subjected to ion exchange and subsequent calcination to synthesize hollow Fe₂O₃.Then,a layered hollow composite material Fe₃O₄/Fe_1-xS@MoS₂ was synthesized by simple in situ hydrothermal growth of MoS₂ with Fe₂O₃ as the substrate.The synthesized sample exhibited excellent photo-Fenton degradation performance and high adsorption capacity.Under the condition of unregulated pH,the degradation of 20 mg/L RhB solution just carried out within 4 min using 0.2 g/L of Fe₃O₄/Fe_1-xS@MoS₂-50%.The result indicates that strong oxidizing of OH·is the main active species.In addition,the maximum adsorption capacity of Fe₃O₄/Fe_1-xS@MoS₂-50%sample adsorbed tetracycline hydrochloride reached 748.9 mg/L.The adsorption process follows pseudo-second-order kinetics model and Freundlich isotherm model.It is confirmed that the sample revealed fine cycle stability in both the photo-Fenton and the adsorption process.Moreover,the material has ferromagnetism for easy recycling.The layered hollow composite Fe₃O₄/Fe_1-x-x S@MoS₂ can be used as an excellent catalyst and adsorbent for environmental treatment.