The electrical double-layer and electrochemical characteristics at the nanoporous carbon I acetone, acetonitrile, gamma-butyrolactone and propylene carbonate interfaces with addition of (C2H5)(3)CH3NBF4 electrolyte have been studied by cyclic voltammetry and electrochemical impedance spectroscopy methods. The region of ideal polarizability, values of series and parallel capacitances, pore resistance and other characteristics have been established. Analysis of complex impedance plane plots shows that the nanoporous carbon\1 M (C2H5)(3)CH3NBF4 electrolyte interface can be simulated by an equivalent circuit, in which the two parallel conduction parts in the solid and liquid phases are interconnected by the double-layer capacitance in parallel with the complex admittance of hindered reaction of the charge transfer process or of the partial charge transfer (i.e., adsorption stage limited) process. The values of the characteristic frequency depend on the electrolyte composition (i.e., on the solvent viscosity and dielectric constant) and on the electrode potential (i.e., on the Gibbs adsorption energy of the solvent molecules and ions at the surface of the nanoporous carbon electrode dependent on the electrode potential). The modified combined Frumkin-Melik-Gaikazyan and Randles-like equivalent circuit, combined Voigt and Frumkin-Melik-Gaikazyan and Newman et al. models have been used for the simulation of the complex impedance plane plots. (C) 2004 Elsevier B.V. All rights reserved.