Analysis of electric double layer in aqueous solutions of sodium chloride

Electric double layer capacitor (EDLC) is an electric capacitor which uses electric double layer (EDL) in electrolytic solution. The purpose of the present study is seeking out electrolytic solution with higher decomposition voltage. For this purpose, behavior of ions in electrolytic solution was analyzed. We selected an electrolytic solution of simple structure, NaCl aqueous solution. The capacitance between two electrodes in the NaCl aqueous solution was measured to be about 10.6μF. This value was obtained at DC voltage of 0.3~0.5V, at which the electric current was negligibly small. The geometrical capacitance was calculated to be 7.08pF providing the dielectric constant of water to be 80. It means that the EDL was formed at the electrodes in the NaCl aqueous solutions. When 1.3V was applied, electric current flowed through the system, and corrosion was found at the electrodes.