Preparation And Electrochemical Performance Of Graphene Hydrogel/MnO₂ Composite

Graphene-based composite attracted widespread attention in the supercapacitor electrode material,because of its many excellent physical and chemical properties.Using reducing agent,graphene hydrogel with the three-dimensional structure could be prepared by self-assembling.In our study,we designed two schemes of preparing manganese dioxide graphene hydrogel composites,by XRD,BET,SEM and TEM,we analyzed the composition and microstructure of the composites we prepared,and tested its electrochemical properties.Graphene hydrogel/ MnO2 composite was prepared by electrochemical deposition.MnO2 nanoparticles with sizes of 20 ~ 50 nm supported on graphene sheets.By controlling the deposition time to obtain different MnO2 loadings composites,capacitance decreases with MnO2 after loading to increase.When the MnO2 content is 44 %,the specific capacitance reach the highest point,84.85 F/g.Another Graphene hydrogel/ MnO2 composite was prepared by chemical synthesis method in isopropanol-water biphasic system.MnO2 nanorods(diameter 5 ~ 10 nm,length 100 ~ 500 nm)with uniform distribution in the form of three-dimensional network structure of graphene.Characterization tests show that manganese dioxide was well crystallized as a single crystal of α-MnO2.Three-dimensional network graphene hydrogel own a high degree of disorder,with specific surface area of up to 115.87 m2 /g.With the increase in the composite material feed ratio of manganese,the capacitance increases.when the feed ratio of 1:1,the maximum capacitance reached 164.6 F/g.Galvanostatic charge-discharge tests showed good reversibility.in 1 A/g constant current charging and discharging,the specific capacitance reaches 209.3 F/g.At the same time has been calculated,the energy density E = 49.13 Wh·kg-1,the power density P = 0.6496 W·kg-1.After 1000 cycles,the specific capacitance retention rate is still as high as 93%.