Electrical double layer and electrochemical characteristics at the nanoporous carbon | (C 2 H 5 ) 4 NBF 4 + acetonitrile interface have been studied by the cyclic voltammetry and impedance spectroscopy methods. The value of zero charge potential (0.23 V vs. SCE in H 2 O), the region of ideal polarizability and other characteristics have been established. Analysis of complex plane plots shows that the nanoporous carbon | x M (C 2 H 5 ) 4 NBF 4 + acetonitrile interface can be simulated by the 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. The values of the characteristic frequency depend on the electrolyte concentration and on the electrode potential, i.e. on the nature of ions adsorbed at the surface of nanoporous carbon electrode.