Pore structure and electrochemical performances of tannin-based carbon cryogels

Carbon cryogels have been obtained by freeze-drying and pyrolysis of a family of tannin – formaldehyde organic gels prepared at different pHs. Such new materials, cheap and derived from biomass at a mass fraction of 0.8, were completely characterised in terms of pore structure and density. Samples obtained at pH higher than 6 were extremely lightweight and presented surface areas higher than 1200 m2 g−1. Tested as electrodes for electric double-layer capacitors, specific capacitances as high as 100 F g−1 were obtained and an ideal, purely capacitive, behaviour was always evidenced. Correlations have been observed between capacitance and micropore volumes, unambiguously suggesting that the latter mainly contribute to the capacitance.