The Application Of Molybdenum Disulfide-based Heterostructures In Photocatalysis

Recent years,photocatalytic technology with the advantages of low cost,high efficiency,no toxicity sustainability,has become the research hotspots to address the environmental problem especially the contaminated water problem.It is acknowledged that photocatalysts are the key factors to determine the photocatalytic performance.However,the traditional photocatalysts like Ti O₂,Zn O,used nowadays,is not able to satisfy human's usual requirements.Therefore,scientists begin to explore novel effective photocatalysts to promote the further application for photocatalysis.Transitional metal dichalcogenides,due to layered two dimensional structures similar to graphene,have aroused people's research interests.Among them,molybdenum disulfide?MoS₂?is a typical transitional metal dichalcogenide,which has been applied in various fields,such as energy storage,biochemistry,sensors,gas sensing and catalysis.Owing to the unique electronic structure and excellent catalytic properties,MoS₂performs an excited photocatalytic activity.Many researches have demonstrated that MoS₂is not only an outstanding photocatalysts,but a co-catalyst to improve the catalysis.In our work,we have synthesized kinds of MoS₂-based heterostructures as photocatalysts,displaying excellent photocatalytic performance.Additionally,we have also investigate the factors having influence on their properties.The main research finding are depicted as follows:?1?The products transformed from 2H-MoS₂to?-Mo O₃have been synthesized by calcined the MoS₂nanoflakes in air,which were synthesized by a hydrothermal method.The results demonstrated that the calcination temperature is the key factor to influence the morphologies and composition of the products.When the temperature is 200°C,the2H-MoS₂changes nothing.When the temperature is up to 300°C,2H-MoS₂starts to oxides and forms the Mo O₃finally.When the temperature rised to 400°C,the products transformed into?-Mo O₃completely.From the absorption and photocatalysis experiments,we have concluded that all the three products preform the absorption properties for methylene blue,and the?-Mo O₃perform the best due to the strong electrostatic effects on the surface of?-Mo O₃and methlyene blue.And Mo O₃/MoS₂composition performs the best photocatalytic activity for Rhodamine B,which may be attributed to the heterojunction,promoting the separation of photo-electrons and photo-holes.?2?The CC@MoS₂-Ag₃PO₄heterostructure is successfully prepared by hydrothermal method and successive ion layer absorption reaction,and the growth process is also investigated.The MoS₂crystals grow from the nanoparticles to nanoflakes as the time go on.Furthermore,the size and dispersity of Ag₃PO₄nanoparticles are influenced by the concentration of precursor solution and the reaction times.When the concentration and times increase,the size and dispersity tend to increase,too.The photocatalytic properties of CC@MoS₂-Ag₃PO₄is enhanced very much,which is more than 10 times higher than that of single MoS₂and Ag₃PO₄,and five times higher than that of CC@MoS₂.Moreover,it also displays an enhanced stability under light irradiation and a satisfactory photoactivity under visible light.In addition,the investigations on the DRS and CV reveal that the improved photocatalytic properties come from the synergistic effect among CC,MoS₂and Ag₃PO₄,which can not only broaden the photo-absorption range but also enhance the electronic conductivity,thus leading to an optimized electron transport channels and promoting the separation efficiency.