Study On The Preparation And Electrochemical Properties Of Manganese Oxide/graphene Hydrogel

As a new energy storage device between batteries and conventional capacitors,supercapacitors have attracted wide attention.Graphene has many excellent properties,and it is expected to be a high performance electrode material for supercapacitors.However,the molecular layers of two-dimensional graphene are easily stacked,which makes it lose its excellent performance in practical application.In addition,its specific capacitance is relatively small,these shortcomings greatly limit its application in supercapacitors.In order to remedy this shortcoming,we should consider making graphene into three dimensional structure graphene hydrogel,which can greatly reduce the stacking phenomenon.Manganese oxides,which are the most commonly used transition metal oxide in supercapacitor electrode materials,are rich in resources,low in price and environmentally friendly in nature.More importantly,their electrochemical performance is stable and their theoretical specific capacitance(about 1400 F/g)is very high.But their electrical conductivities are poor,so it is a good choice to combine it with graphene hydrogel.In this paper,in order to obtain high performance electrode materials,MnGH composite electrode materials were synthesized by electrochemical deposition of manganese oxide on the substrate of graphene hydrogel.The main research contents are as follows:(1)SEM and TEM revealed that after electrochemical deposition,the RGO layer was covered by MnOx,which became rougher and rougher,but still retained the characteristics of porous frame,and the micro-morphology of the electrode after deposition was closely related to the electrodeposition condition.XRD and EDS show that manganese oxide has been uniformly deposited on GH,and it is a kind of manganese dioxide.On the basis of XPS,FT-IR and Raman surface chemical information.It is proved that the oxygen functional groups have been reduced at the same time of manganese oxide deposition.(2)The electrochemical performance of MnGH was measured by cyclic voltammetry and constant current charge-discharge method.It was found that when the amount of deposition is 200 mC,the deposition current was 20 mA/cm2 and the deposition temperature was 40?,the measured specific capacitance value was 409 F/g under the discharge current density of 1 A/g,which is far greater than pure GH(118.3 F/g).After 10000 charge-discharge cycles,the specific capacitance decreased to 328.5 F/g,and the specific capacitance retention rate was 80.2%,showing excellent cycle stability.(3)On application,MnGH and GH were combined with activated carbon respectively to assemble asymmetric supercapacitor MnGH//AC and GH/AC for comparison.Experimental results show that the r MnGH//AC delivered 41.8 Wh·kg-1 at 0.2 kW kg-1,which is better than the reported graphene or MnOx supercapacitors in the literatures.