Ordered Mesoporous Carbons: Preparation And Capacitance Properties

Asphaltene(A),preasphaltene(P),and the mixture of asphaltene and preasphaltene(M) extracted from coal liquefaction residue were taken as carbon precursors to synthesize ordered mesoporous carbons(OMCs).The OMCs of OMC-A,OMC-P and OMC-M were synthesized by template method,using SBA-15 as template.The microstructures of the carbons were studied by X-ray diffraction(XRD),transmission electron microscopy(TEM), and N₂ adsorption.Electrochemical workstation was used to analyse the electrochemical characteristics of the capacitors assembled from the OMCs.The effect of pore structure on capacitance properties was discussed.The results show that the OMCs are all reverse replications of the template,and have highly ordered pore structures.The carbons have high specific surface areas and pore volumes,which range from 542～843m²Â·g^-1 and 0.5～0.7cm³Â·g^-1,respectively.The electrochemical characteristics of the capacitors from the OMCs were studied with 6mol·L^-1 KOH as electrolyte in three-electrode system.The results indicate the excellent capacitance properties of the OMCs,of which the specific capacitances are above 300F·g^-1 at the current intensity of 1mA.Among them OMC-M is as high as 413F·g^-1.Ordered mesoporous carbons with different pore diameters were prepared by taking templates with various pore sizes,and the effect of pore size on capacitance properties was studied.Ordered mesoporous carbons with different graphitization degrees were produced by adjusting carbonization temperature and the impact of graphitization degree on capacitance properties was investigated.The results show all the specific surface areas,orderliness of pores,graphitization degrees,and pore sizes of the carbons have significant influence on their electrochemical characteristics:the specific capacitances were incrseased with the increase of the specific surface area;highly ordered pore structure leads to increasing utilizationon of specific surface area,which is benefical to improve specific capacitance;the increase of the graphitization degree results in the ideal electric double layer behavior;under the research conditions in this paper,the OMCs with pore diameter of 4nm have higher capacitances.