Molybdenum Disulfide-Based Nanohybrids For Energy Storage And Conversion

Molybdenum disulfide(MoS2),one of the transitional metals dichalchogenides,is a layered material,in which the Mo layer is sandwiched by two S layers,and such triple layers are arranged and detained together by weak van der Waals forces.The MoS2 is receiving worldwide attractions because of its distinctive electronic properties,optical properties,and mechanical properties,which are closely related to the inherent fast ionic conductivity,higher theoretical capacity,and acidic stability.For the preparation of MoS2 nanomaterials,various methods have been developed,including mechanical exfoliation,liquid exfoliation,chemical vapor deposition,atomic layer deposition,high-temperature annealing,and hydrothermal or solvothermal method.MoS2 nanosheets compromise the great potential for the preparation of composite nanomaterials with several materials including metals,metal oxides,transitional metal chalcogenides,carbon-based materials,and MOFs.Significantly,the MoS2 nanosheets and their composite materials show in numerous applications,such as energy storage and conversion,sensing,electronic,and bio-applications.Chapter 1 reports the summary of transitional metal dichalcogenides,molybdenum disulfide(MoS2)nanomaterials structure,properties,synthesis methods,and applicationChapter 2 describes the strategy of positively charged PDDA effectively connect two negatively charged of CNT@MoS2 and PMo12 via electrostatic interactions and significantly improve the synergistic effects of the component materials.The successful synthesis of CNT@MoS2/PDDA/PMo12 symmetric SC exhibits a high specific capacitance of 110 F g-1,the high energy density of 25.83 W h kg-1,the high power density of 250 W kg-1 and excellent long life with capacitance retention of 92%after 10000 cycles in 1M H2SO4Chapter 3 studies the synthesis of Bi2WO6/MoS2/rGO ternary composite material by a facile hydrothermal method.In this process,Bi2W06 nanoparticles are attached to MoS2/rGO nanosheets to construct Bi2WO6/MoS2/rGO composite.The maximum specific capacitance of Bi2WO6/MoS2/rGO composite is 655 F g-1 at a discharge current density of 1 A g-1 compared to 305 F g-1 for Bi2WO6 and 345 F g-1 for MoS2/rGO.Furthermore,the capacitance retention is still over 89%of initial capacitance after 4000 cycles.The Bi2WO6/MoS2/rGO shows excellent electrochemical performance and high cycling stability,making that potentially suitable for highly efficient supercapacitors.Chapter 4 designs a new nanocomposite material of MoS2/rGO/PDDA/PMo12 via two-step process,in which the MoS2/rGO was synthesized by the hydrothermal method,followed by electrostatically attaching the PDDA and PMo 12 onto the MoS2/rGO nanosheets.The new nanocomposite proves to be excellent HER electrocatalysts with a low overpotential of 54 mV at 10 mA cm-2 and a Tafel slope of 48 mV dec-1.Furthermore,this catalyst shows the higher double-layer capacitance(Cd1)27 mF cm-2 and long-time durability(10 h)in 0.5 M H2SO4.Chapter 5 analyses a general and effective strategy of assembling Co-Ni@MoS2/CC heterostructures for highly efficient bi-functional electrocatalytic water splitting via a two-step procedure.Firstly,MoS2/CC sheet arrays were prepared by the hydrothermal and then electrodeposited Co-Ni LDH nanosheets on the MoS2/CC.Besides,the hybrid catalyst exhibits low overpotentials of 98 and 269 mV at 10 mA cm-2 in 1 M KOH for HER and OER,with the corresponding Tafel slopes of 59 mV dec-1 and 57 mV dec-1,respectively.For overall water splitting,the cell voltage was only 1.59 V to achieve 10 mA cm-1.The resultant Co-Ni@MoS2/CC composite displays a promising candidate for high-efficiency overall water splitting.In this work,MoS2-based composite materials were fabricated successfully and it showed good performance when applied as supercapacitor and HER catalyst,respectively It was demonstrated that the synergistic effect among each component in these designed composite materials played significant roles.These approaches of fabricating MoS2-based composite materials can be considered as a new pathway for the development of MoS2-based advanced functional materials.