Synthesis And Application In Supercapacitor Of Graphite Nanosheets

Mechanochemistry is a physical method of breaking and stripping of nano material effectively,this article used a new Mechanochemieal process—magentic grinding method to strip graphite.We produced low-oxidized graphite nanosheets?GNS?with oxygen-containing functional group of hydroxyl and carboxyl,resulting from mechanochemical effects in procressing.The stripped graphite nanosheets have large specific surface area and oxygen-containing group,so it has a good applying prospect in supercapacitor.The thesis mainly contains the following contents:Preparation of graphite nanosheets:with the friction,collision,and shear forces created by the needles rotating at high speed,natural flake graphite could be exfoliated into nano scale with extremely high efficiency through magnetic grinding method.The sample were tested by SEM,TEM,Nitrogen-sorption measurements,XRD and Raman,the results show magentic grinding method could strip graphite quickly.In addition,grinding praphite is a process of stripped GNS broke and aggregated,according to the aggregated degree,we can divide grinding process into three part,as follow:stripping stage?T<8 h?,the balance of stripping and aggregating stage?8 h<T<12 h?and aggregating stage?T<12 h?.The specific surface area of GNS after ground chould reach 803.7 m²·g^-1,meanwhile those GNS could keep crystal structure.The surface functional group was characterized by FT-IR?XPS,TGA and element analysis,the results show the GNS has numbers of oxygen-containing functional group of hydroxyl and carboxyl,and the most oxygen-content is 19.35 wt%.The electrochemical properties of graphite nanosheets:the GNS is good material for electrical doule-layer capacitor?EDLC?because of its'big specific surface area,and the oxygen-containing functional groups on the surface of GNS could offer pseudocapacitance,the electrochemical test used three electrodes and in 1M H₂SO₄ electrolyte.All of GNS show properties of EDLC-pseudocapacitance,and the specific capacitance of GNS-12 is266.8 F·g^-1 at current density 0.1 A·g^-1.Then we studied influencing factors about electrochemical properties of GNS,as follow:size of pristine graphite;specific surface area of GNS;Mechanochemical effects.The results prove that the bigger size of pristine graphite,the more time used to reach its'biggest specific capacitance;Amorphous structure of carbon will became more and more with the grinding time increasing,result in the specific capacitance declining,so it could reach its'biggest effective specific surface area and specific capacitance at 8 h;Mechanochemical effects of GNS depend on Grinding atmosphere,and H₂O in atmosphere is not the mainly factor.In the process of studying the effect of oxygen,we found it could enhance oxygen-content of GNS in the condition of oxygen,and keeping the crystal structure of GNS integrity.Magentic grinding method is a efficient?environmental?low-costing and easy-operating way to produce GNS,it deserved to pay more attention on the Mechanochemical effects of GNS,the GNS that low-oxided and have big specific surface area has a good prospect in supercapacitor.