Classical Models of the Interface Between an Electrode and an Electrolyte

E. Gongadze[1], S. Petersen[1], U. Beck[2], and U. van Rienen[1]
[1]Institute of General Electrical Engineering, University of Rostock, Rostock, Germany
[2]Institute of Electronic Appliances and Circuits, University of Rostock,
Rostock, Germany

The Electrical Double Layer (EDL) plays a major role in understanding the interface between a charged surface (e.g. an implant) and ionic liquids (e.g. body fluids). The three classical models of the EDL (Helmholtz, Gouy, and Chapman-Stern) are numerically solved for a flat surface electrode in the 3D Electrostatics application mode of COMSOL Multiphysics® 3.5a. The values of the electric potential drop near the electrode’s surface are compared and their area of validity is shown. The double layer capacitance is computed analytically, numerically and measured by Electrochemical Impedance Spectroscopy (EIS) and it has been shown that the classical models do not agree with the experimental measurements.