Generalized Langmuir kinetic equation for ions adsorption model applied to electrical double layer capacitor

The electric response of an electrical double layer capacitor is analyzed by means of the impedance spectroscopy technique. From the spectrum of the imaginary part of the electric impedance of the cell, in the low frequency region, it follows that the electrodes are blocking. To interpret the experimental data we assume that the electrodes are adsorbing. The kinetic equation describing the adsorption phenomenon used in our analysis is a generalization of Langmuir isotherm, where the effective adsorption coefficient and desorption time are frequency dependent. Their frequency dependence is deduced considering the adsorption as a linear phenomenon relating the bulk density of particles to the surface density of particles, characterized by a distribution of relaxation times. The agreement between the experimental data and the theoretical predictions is very good within explored frequency range.