Preparation And Properties Of Graphene Based Supercapacitor Electrode

With the depletion of oil resources and the deterioration of the environment,more and more attention has been paid to the development and utilization of clean energy.The key issue of the utilization of clean energy is energy storage.As one of the most important vehicles among the energy storage devices,supercapacitors have been widely used in electric vehicles,mobile communications,information technology,aerospace and defense science and technology.This paper mainly studies the preparation and properties of graphene based supercapacitor electrode.This thesis mainly contains the following contents:First,we prepare chemical reduced graphene oxide by using the sodium borohydride to reduce graphene oxide,and the graphene was confirmed by transmission electron microscope.Besides,we prepare hydrothermal reduced graphene oxide by using 180 ? hydrothermal reduction of graphene oxide.When used as a supercapacitor electrode,the chemical reduced graphene oxide holds a specific capacitance of 136 F g-1,while hydrothermal reduced graphene oxide holds a specific capacitance of 187 F g-1 at a current density of 1 A g-1.It is consistent with other's data reported in the literature.We confirmed the reduced graphene oxide is a kind of excellent supercapacitor electrode materials.Then,porous graphene has been easily synthesized by hydrothermal treating reduced graphene oxide in alkaline solution,and the porous structure was confirmed by transmission electron microscope.When used as supercapacitor electrode,the porous graphene holds a specific capacitance of 88 F g-1 at an ultra-high current density of 50 A g-1,an increase of about 83% compared with that for the pristine graphene sheets.The reason is that the porous graphene opens a new and short way for ion transportation.Besides,we utilize pseudo-second-order kinetic equation to evaluate the adsorption rate constant k;the k of pristine graphene sheets was 9.6 while that of porous graphene was 15.9.At last,we prepared porous graphene by alkaline-mediated hydrothermal treating graphene oxide.We studied the effect of the preparation temperature on the microscopic structure of porous graphene and its properties as supercapacitor electrode.We find that the higher temperature the hydrothermal process,the smaller the specific surface area,the bigger pore and the higher specific capacitance.The specific capacitance of porous grapheme prepared under 180 ?,220 ?,260 ? are 205 F g-1?237 F g-1?264 F g-1 at a current density of 1 A g-1,respectively.The specific capacitance decreases with the increasing charge-discharge current density.At a current density of 50 A g-1,the sample prepared at 180 ? can only have a specific capacitance of 19 F g-1,while the sample prepared at 220 ? and 260 ? are 66 F g-1and 123 F g-1,respectively.