Preparation And Electrochemical Performances Study Of Graphene Aerogel(Powders)

In this thesis,we prepared graphene oxide?GO?by modified Hummers method using natural graphite powders as original materials.Then we used GO as precursor to preapre graphene aerogel?powders??GA?Ps??and studied their electrochemical properties for supercapacitor electrode.The main findings are as follows.For GAPs,GO were prepared using graphite of 325,2000 and 3500 mesh as original materials.Then GAPs were prepared from GO aqueous dispersion via hydrothermal reduction,freeze-drying and pulverizing process and named GAPs-325,GAPs-2000 and GAPs-3500.It can be observed that the size of macropores in GAPs-325,GAPs-2000 and GAPs-3500 is about 5,3,2?m.GAPs-2000 show uniform and compact macroporous structure.All the GAPs present hierarchical mesopores structure.At 0.5 A g^-1,the specific capacitance of GAPs-325,GAPs-2000 and GAPs-3500 in potassium hydroxide solution is seperately 234.1,306.5 and 277.2 F g^-1.It can be seen the specific capacitance of GAPs-2000 is higher than the others.Furthermore,GAPs-2000 present good cycling stability,its capacitance ratention rate is 89.1%after 20000 cycles at 10 A g^-1.For GA,GO were synthesized with natural graphite powders of 2000 and 5000 mesh.Then three kinds of GA were prepared by low-temperature chemical reduction process using ascorbic acid as reducing agent with two kinds of GO seperately and their mixture as precursor and named GA-2,GA-5 and GA-25.It was found that GA-2 and GA-5showed macroporous structure with a trend of orientation arrange of reduced graphene oxide.While the macroporous structure of GA-25 is obviously disordered and many large holes about 10?m in diameter with uniform distribution can be seen and uniform small pores can be seen on the wall of the large holes.All the GA have hierarchical structure.There are not many mesopores for GA-2 and their distrubution range is 5²0 nm,but GA-25 have mesopores of 2³0 nm as rich as GA-5's of 2⁵0 nm.The specific capacitance of GA-2,GA-5 and GA-25 is 234.3,212.7 and 274.2 F g^-1 at 0.5 A g^-1,when the current density increased to 10 A g^-1,the capacitance retention is 64.6,66.3 and 79.9%,respectively.Furthermore,the cycling stability of GA-2,GA-5 and GA-25 is 98.6,97.8and 97.2%after 20000 cycles at 10 A g^-1.It can be concluded that when GA were prepared with GO mixture,micro-structure optimization probably can be achieved and thus resulted in synergistic effect in electrochemical performances.