ZIF-67 Derived Sulfide Composite Nanomaterials:Preparation And Properties In Electrocatalytic Hydrogen Evolution And Supercapacitors

Transition metal sulfide is an ideal energy material because of its high conductivity,abundant redox active sites,low cost and simple synthesis method.In this paper,the synthesis,structural control,electrocatalytic hydrogen evolution performance and supercapacitor performance of transition metal sulfide nanocomposites were systematically studied.The details are as follows:(1)Synthesis of hollow heterostructure NiCo2S4@MOS2 and applications in electrocatalytic hydrogen evolution and supercapacitors.We designed and synthesized a kind of hollow heterostructure NiCo2S4@MoS2 nanocomposites,first by ion exchange with ZIF-67 preparated double metal compounds,Then,the hollow structure was sulfided by hydrothermal method,and the composite heterostructure was formed by combining with MoS2,explored the influence of the hollow heterostructure and the change of material composition on the electrochemical properties.The results of research show that:the NiCo2S4@MoS2 heterostructures show high specific capacity,the specific capacitance of NiCo2S4@MoS2 can reach 860 F·g-1 at the current density of 1 A·g-1.In addition,the NiCo2S4@MoS2 electrode has good cycling stability,71.9%capacitance is maintained after 1000 charging and discharging cycles at 20 A·g-1 current density.The NiCo2S4@MoS2 heterostructure also efficiently electrocatalyzes HER in alkaline(1 M)electrolyte with a lower overpotential of 194 mV at the current density of 10 mA·cm-2.After 1000 times continuous hydrogen evolution cycle,its overpotential remained almost unchanged,showing good stability The results of these two tests show that the electrochemical properties of the materials with hollow heterostructure are better than the corresponding single materials.(2)To investigate the design and synthesis of 3D NiCo2S4/Ni3S2/MoS2@NF nanocolumn array composites and their electrocatalytic hydrogen evolution propertiesZIF-67 nanocolumns were grown on a three dimensional nickel foam(NF)substrate with high specific surface area and porous structure.Based on the results of the previous part,nanocomposites with heterostructure have better catalytic performance in catalytic hydrogen evolution.This part continues to take advantage of the advantages of nanocomposites with heterogeneous structures to prepare 3d nanocomposites with nickel foam as the substrate,and control the structure and morphology of the materials by adjusting the reaction time and temperature.The results show that when the curing time is 8 h the material performance is the best;the required overpotential of the active material at the current density of 10 mA·cm-2 was 159 mV.After 12 h continuous hydrogen evolution cycle,the overpotential remained almost unchanged.