Characterization of carbon cryogels synthesized by sol-gel polycondensation

Resorcinol-formaldehyde (RF) cryogels were synthesized by the sol-gel polycondensation of resorcinol (R) with formaldehyde (F) and freeze-drying was carried out with t-butanol. Carbon cryogels were obtained by pyrolyzing RF cryogels in an inert atmosphere. Characterization by nitrogen adsorption showed that the carbon cryogels were micro and mesoporous materials with high specific surface areas (S-BET approximate to 550 m(2)/g). Cyclic voltammetry experiments at various scan rates (2 to 200 mV s(-1)) were performed to study the electrical double-layer charging of carbon cryogel electrodes in 0.5 mol dm(-3) HClO4 solution. It has been demonstrated that it is possible to sub-divide the total specific capacitance into the mesoporous and the microporous specific capacitance by analyzing the linear dependence of the charge (q) on the reciprocal of the square root of the potential scan rate (v(-1/2)), and the linear dependence of the reciprocal charge (l/q) on the square root of the potential scan rate (v(-1/2)). The specific capacitance was found to be constant over a wide range of sample weight (12.5 to 50.0 mug) and a very promising specific capacitance value of 150 F/g, was found for this material operating in an acidic 0.5 mol dm(-3) HClO4 solution at room temperature.