Effect Of Surface Modified And Doping On The Supercapacitor Performance Of MnO₂/C Compound

MnO₂ has high specific capacity,low cost,abundant in nature and environment friendly,which was widely used in chemical power source.MnO₂ has extremely high theoretical capacitance but very low actual capacitance because of its low electronic conductivity.Composite MnO₂ and carbon materials have the chemical stability of carbon and high capacitance of MnO₂ But research shows that composed of graphite layers of carbon materials（such as graphite nanometer slices,graphene）making its surface show chemical inertness to some extent,beacause of the integrity of carbon six-member ring in the two-dimensional structure.When MnO₂ particles load in the graphite layers without any modification,MnO₂ and carbon will exist physical adsorption phenomenon.The phenomenon make the electronic conduction and MnO₂adsorption more difficult.Surface modification of the graphite layers is a way to solve the problem.In this paper,modify graphite layers by PTCDI、Amin、CTAB、PCA and anthraquinone.By physical test（SEM、TEM、XRD、XPS、Raman spectroscopy）and electrochemical test（CV、EIS、CA）,their physical and chemical properties were investigated.Physical characterization and electrochemical performance analysis indicated that the different reducing agents and technical methods,different organic small molecules significantly influenced the precipitation of MnO₂.In vitamin C（VC）reducing graphite oxide at room temperature when the organic small molecule was CTAB,MnO₂/C composite material had the best electochemical performance;In hydrothermal reactions when the organic small molecule was PCA,G/MnO₂composite material had the best electochemical capacity and stability.When PCA act as the organic molecule,hydrothermal reaction had best electochemical performance.PCA can peel graphite layers to the monolayer graphene and it will not affect the MnO₂ crystal structure;MnO₂/C composite had good cycle stability,but the change of crystal about MnO₂ was different from pure MnO₂ in the circulation.The reason is that PCA can enhance the interaction between MnO₂ and flake graphite layer.When the graphite layers was mixed with potassium hydroxide directly at a certain percentage,and was soaked at 80℃,the chemical capacity had not changed for MnO₂/C composite material.The heteroatoms（N and S）lead to the generation of a large number of active sites with porous nature.It was found the electrochemical performance significantly improved from 106F/g to 189F/g compared with the pristine MnO₂/C composite material.