Electrical impedance spectroscopy of the water/nitrobenzene interface

Abstract

The electrical impedance spectrum of the water/nitrobenzene interface was studied using a specially designed impedance cell. The main goal of the project was to determine the capacitance of the double layer that exist at the interface between water and nitrobenzene. The interfacial capacitance of the water/nitrobenzene interface is the ability to store electrical charge. The interface will be described by the Gouy-Chapman theory for a flat double layer. During the experiments the interfacial capacitance will be examined as a function of the area of contact between the phases and as an applied DC potential. To extract data from the impedance spectrum an equivalent circuit is fitted to the measured data. From our results, there are two clear indications that the impedance spectrum of the water/nitrobenzene was measured. First, the Warburg coefficient scales with the neck of the center part of the impedance cell. The Warburg coefficient gives information about the diffusion of the ions in the electrolyte, with an increase in area of the neck, more diffusion is possible to the interface. Second, the interfacial capacitance scale with the area of the neck and is in the same order of magnitude as expected from the theory of Gouy-Chapman, the characteristic shape however is not observed.