Preparation And Supercapacitor Performance Of Mesoporous Composite Of C@SiC By Magnesium Reduction Method

Supercapacitors have received widely attention as a chemical power source because of the advantages of high power density and environmental friendly.In the research of supercapacitor,it is of great value and theoretical significance to develop the electrode materials with high specific capacity.As a semiconductor material,silicon carbide has the advantages of wide band-gap,corrosion resistance,good chemical stability and high thermal conductivity.It can be used as an electrode material for supercapacitor.Ordered mesoporous carbons(OMCs)are one of particularly attractive carbon material due to their high specific surface areas and inherent structural characteristics that include developed porosity structure and uniform pore size distribution.In this paper,we use this characteristic to deposit carbon layer on silicon dioxide template by CVD technology and prepare mesoporous carbon-containing silica(C@SiO2).Silicon carbide was synthesized by magnesium reduction by using C@SiO2 as the precursor.Then,SiO2 template was removed by chemical etching to obtain mesoporous silicon carbide and carbon composite material(C@SiC).The effects of C@SiO2 and magnesium reduction temperature on the microstructure,morphology,pore structure and distribution of C@SiC were investigated by using XRD,Raman,TG,SEM,TEM and BET.The performance of mesoporous C@SiC as the electrode material of supercapacitor is studied by cyclic voltammetry,constant current charge/discharge,and AC impedance.The main results are as follows:C@SiC is successfully prepared by the above method.C@SiC preserves the ordered mesoporous structure of the silicon dioxide template,and the pore is composed of ordered mesoporous and micropore.It has high specific surface area(389-644m2?g-1).The pore volume,specific surface area and carbon content of C@SiC can be controlled by controlling the carbon coating of C@SiO2 precursor and the temperature of magnesium reduction.Thus,the performance of C@SiC as supercapacitor material is regulated.Because of the high specific surface area and ordered mesoporous structure for ionic transmission of C@SiC,it shows excellent specific capacitance and specific power as supercapacitor material.Three hours of carbon deposition of C@SiC-700℃ has the largest specific capacitance.It obtains the specific capacitance of 282 F ? g-1 from at the current density of 100 m A?g-1.But the specific capacitance only keeps 69.9% after 10000 consecutive cycles because the carbon deposition time is short,and the structure of the carbon layer is unstable.It obtains the energy density of 39.7Wh·kg-1 and 22.6Wh·kg-1 at the power density of 35.1W·kg-1 and 227.9W·kg-1,respectively.Five hours of carbon deposition of C@SiC-650℃ possesses ordered mesostruture.And its internal resistance is only 0.24Ω.The ordered mesoporous structure improves the cycle stability of the supercapacitor by improving the ability of electron transfer.It obtains the specific capacitance of 169F?g-1 from at the current density of 100 m A?g-1.the specific capacitancekeeps 90.4% after 10000 consecutive cycles.It obtains the energy density of 25.8Wh·kg-1and 16.7Wh·kg-1 at the power density of 32.2W·kg-1 and 289.9W·kg-1,respectively.The energy density of the supercapacitor using both of them as electrode are larger than that of activated carbon(15-20Wh·kg-1).