Preparation Of Molybdenum-based Sulphide Nanocomposite Materials And Study Of Their Photocatalytic And Electrochemical Performance

MoS₂,as a typical semiconductor material,owns high research and application value due to its unique structures and excellent properties.At the same time,MoS₂ possesses a layered structure analogue of graphene,which is composed of three atomic layers?S-Mo-S?stacked together and bonded through van der Waals interactions.On the one hand,this 2D nanosheets can provide high specific areal and space for ion intercalation,as well as the higher ionic conductivity than metal oxide and larger specific than graphene,therefore it turns to be the candidate electrode for supercapacitor with wide application future;on the other hand,MoS₂ shows enhanced visible light absorption,nice adsorption capacity for organic matters,proper band edge,higher reaction activity,making it an ideal photocatalysts.However,pure MoS₂ nanosheets own several disadvantages of easy to get stacked and reunion,relativity large conduction resistance,and relativity small capacitance and unstable in the cyclic process,constraints on its development.Therefore,the study of MoS₂ nanomaterials means a lot.Based on all of these,we successfully synthesized the MoS₂ nanocomposite with other nanomaterials and through the addition of promote phase or the formation of ternary molybdenum sulfide nanocomposite,taking full use of the large specific surface area to improve the conductivity and specific capacitance,achieving the new type of composite materials as catalyst and supercapacitor electrode.In this paper,we realized the controllable synthesis of materials,meanwhile their structures are characterized,also study the photocatalytic and supercpacitors performance.The main contents are summarized as follows:1.How to controllable synthesis of the compound of MoS₂ nanosheets with Fe₂O₃ nanocubes was studied in this work.Firstly,nanoscaled and good dispersion of Fe₂O₃ nanocubes are synthesized through the facile one-step hydrothermal treatment.The Fe₂O₃ nanoparticles guide the growth of 2D MoS₂ in the hydrothermal treatment,and construct the unique 3D hierarchical nanoheterostructures with Fe₂O₃ nanoparticles uniformly loaded on 2D MoS₂ sheets.Meanwhile,in the reaction process,Fe₂O₃ nanoparticles formed the porous structures and abundant oxygen vacancies on the interface with MoS₂.The Fe₂O₃/MoS₂ hybrid shows excellent photo-Fenton catalytic activity with 99% of MO?30 m L,20 mg/L?degraded within 10 min,even after 6 successive cycles,the 3.0MF still retains 97% degradation degree of MO within 20 min.Besides,the catalyst also presents good generalizability,and shows nice ability for degradation of Congo red(CR,50 mg L^-1)and Rhodamine B(Rh B,20 mg L^-1).While,in this work,we collected the materials after 6 cycles' catalysis and applied as the electrode for supercapacitors.It was found that,the materials reusing as supercapacitor electrode after catalysis shows nice electrochemical performance.At the density of 0.5 A g^-1,the specific capacitances of the recycled 3.0MF were calculated to be 266 F g^-1,higher than the fresh materials,meanwhile possesses good stability with 84% of the initial capacitance remaining after 2000 cycles.These results mainly attributed to the porous structures of the Fe₂O₃ nanoparticles,which facilitate electrochemical sites;short ion diffusion path lengths and more paths for insertion and extraction ions.Meanwhile,the rich oxygen vacancies formed on the interface of Fe₂O₃/MoS₂ enable remarkably improved conductivity,increased active sites and highly reversible,faster charge transfer kinetics,therefore,contribute to the high electrochemcal performance.2.We studied the preparation method of ternary sulfides Co Mo₂S₄,and through a facile one-step hydrothermal method,vertically aligned Co₃S₄/Co Mo₂S₄?CMS?ultrathin nanosheets on reduced graphene oxide?r GO?are first prepared.As the Co is a promoted phase for MoS₂,so the introduction of Co can accelerate the charge transfer on the interfaces between Co₃S₄/Co Mo₂S₄.Interestingly,through simulated the nanointerfaces of the hybrid,it was found that the Co₃S₄?111?surfaces exhibits good match with that of Co Mo₂S₄?200?surfaces and connected by the S atoms in the Co₃S₄ layer and Co atoms in the Co Mo₂S₄ layer,therefore,generating strong electron transfer through S-Co on the interface.However,not all the S atoms in the Co₃S₄ layer bonded with Co atoms in the Co Mo₂S₄ layer,implying the nanointerfaces of the hybrid are semicoherent interfaces.Thus,the nanointerfaces are abundant with defects,which may provide some void space for easier ions transfer,also to endure the volume expansion during the charge-discharge process.Furthermore,the direct growth of CMS hybrid on the r GO helps the dispersion of the CMS hybrid,and provides good electrical conducting pathways for ion and electron transportiation between CMS and r GO.On one hand,the as-prepared CMS-RGO hybrid system favors a synergetic effect through the nanointerfaces of the CMS hybrid,which contribute to the high electrochemical performance.On the other hand,the ultrathin characteristic of the nanosheets and the defects abundant nanointerfaces allow easy electrolyte penetration and provide a large void space to endure the volume expansion.Hence,a three-electrode system was used to investigate the electrochemical performance of the CMS-r GO.The specific capacitance can achieve a maximum of 1457.8 F g^-1 at a current density of 1 A g^-1.As the current density increases to 10 and 20 A g^-1,the electrode still retians high capacitance of 833.3 and 657.8 Fg^-1 respectively,indicating its high-rate capability for high-power delivery.Meanwhile,the specific capacitance of the electrode still maintian 97% capacitance after 2000 cycles at 10 A g^-1,and the morphologies stay intact.Furthermore,an asymmetric supercapacitor device fabricated by using the CMS-r GO as the positive electrode and activated carbon?AC?as the negative electrode to evaluate its application value.The device presents good specific capacitance of 82.4 F g^-1 at 1 A g^-1,and high energy density of 33.1 Wh kg^-1 at a power density of 0.85 k W kg^-1 with excellent cycle stability?93.8%?even after 5000 times cycles.3.We studied the preparation method for one-dimensional?1D?hierarchical structures composed of nickel sulfides/MoS₂?NMS?supported on carbon nanotube?CNT?-?NMS/CNT?,and proposed an efficient one-step facile glucose-assisted hydrothermal method.The carbon derived from glucose providing close connection between the MoS₂ layers with the CNT backbones,as well as the formation of metallic 1T-2H hybridized MoS₂ both give rise to better electrical conductivity.Meanwhile,the active phase of NS on MoS₂ promotes the ions diffusion on the interfaces between them and the void space between the NMS layers can endure the volume change in the long-term cycling.What's more,the curled and tangled one-dimensional?1D?hierarchical structure is intertwined with each other and constructs three-dimensional?3D?porous conducting networks,facilitating electrolyte diffusion and providing fast electron pathways.This design has the advantage of synergy for transition metal sulfides?pseudocapacitive capability due to nickel sulfides and MoS₂?and CNT?EDLC due to CNTs?.Therefore,the materials show good electrochemical performance,and the obtained specific capacity for NMS/CNT is 757 F g^-1 at the current density of 0.5 A g^-1.Remarkably,the NMS/CNT can almost maintain the 100% of the initial capacity even after 2000 cycles,confirming the remarkable stability and nice reversibility performance of this cross-linked network.Besides,we assembled the NMS/CNT//AC asymmetric supercapacitor device to further evaluate its pratical application value,which manifests favorable specific capacitance of 108 F g^-1 at 0.5 A g^-1 meanwhile possesses high energy density of 40 Wh kg^-1 at 0.4 k W kg^-1,along with good cycling stability of almost 100% capacity maintained even after 10000 cycles.Finally,two NMS/CNT//AC asymmetric supercapacitors were further assembled in series to intuitively display their practical application,which own the power to light up four red light-emitting diodes,indicating its high potential for application in energy storage.