ABSTRACT
In this chapter, the role of the diffuse layer of the ionic cloud on the impedance spectroscopy measurements of a cell of a liquid is discussed. The analysis is performed, firstly, by assuming that the ions have the same mobility, the electrodes are perfectly blocking and the adsorption phenomenon can be neglected. It is shown that the dielectric permittivity, in the limit of large frequency ω, tends to the dielectric permittivity of the pure liquid as ω−3/2. The connection between the detected equivalent permittivity and chemical potential of the cell with the real and imaginary parts of the complex dielectric constant is discussed. It is shown also that the presence of the ions is responsible for a distribution of relaxation times. Subsequently, a generalization of the obtained results to the case in which the mobility of the positive ions is different from that of the negative ones is presented. It is shown that the difference between the mobilities of the positive and negative ions gives rise, in the low frequency region, to a new plateau of the real part of the electric impedance of the cell. Furthermore, it is responsible for a deviation from the ideal Cole-Cole diagram relevant to the real and imaginary parts of the complex dielectric constant. Finally, the influence of the adsorption phenomenon on the impedance spectroscopy measurements is considered. The analysis is performed by assuming that the ions have the same mobility and the electrodes are perfectly blocking. We find that in the low frequency range the presence of the adsorption phenomenon is responsible for an increasing of the real part of the impedance of the cell, similar to the one usually described by means of the impedance of the metal-electrolyte interface.
