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 light-weight and presented surface areas higher than 1200 m(2) 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. (C) 2012 Elsevier Ltd. All rights reserved.