Preparation And Application As Electrode Of Supercapacitors Of Carbon Aerogel

RF organic aerogels were prepared by sol-gel process, ambient drying and then to gain carbon aerogels by pyrolysis of RF organic aerogels. The microstructure of the carbon aerogels was investigated by means of low-temperature N₂ adsorption, SEM, TG etc. The pore structure of carbon aerogels was adjusted via two approaches: one was activation of it with carbon dioxide, another was to use ethanol (A) as an additive in the sol-gel process. The modified carbon aerogels were investigated as electrode materials in electric double-layer capacitors, and the electrochemical behaviors were characterized by the constant current charge-discharge experiment and cyclic voltammetry (CV) in electrolyte of 6M KOH aqueous solution.The results showed that the BET specific surface area( Sbet) and total pore volume of carbon aerogel reached the most when the carbon aerogel was activated with CO₂ at 900℃ for 3h. And the corresponding specific capacitance increased from 81 F/g to 172 F/g at current density of 1 mA/cm², and the charging-discharging curve showed a good symmetry, which indicated that the sample possessed excellent power property. The CV analysis curves showed the pseudo-rectangular shape at different potential scan rate, revealing a good capacitive propertiy. There was no redox peak in the CV curve, that is to say, the capacitance was totally offered by the electrical double-layer capacitance. When the activation time prolonged to 4h, the total pore volume and Sbet have decreased, indicating that 3h was the best activation time at 900 °C for carbon aerogel.The specific capacitance of activated C_mRF carbon aerogels reached 160 F/g when the mass ratio of cresol was 20%. And it also showed a good CV property. Since cresol is much cheaper than resorcinol, this can be considered as an alternative economic route to the classic RF gels when it was used as electrode materials in supercapacitors.The N₂ adsorption results indicated that the specific surface area of mesopores (S_meso) and its proportion in total specific surface area (Sbet) of carbon aerogel increased with the increasing amount of ethanol in sol-gel solution, with the average pore diameter around 10 nm. When the atomic ratio of R/A was 1.5, the specific capacitance of the corresponding carbon aerogel reached 134 F/g at current density of 1 mA/cm².