Simulating the Electrical Double Layer Capacitance
When a solid surface makes contact with a liquid medium, an electrical double layer (EDL) structure forms spontaneously through thermodynamic interaction between electrons and ions. In this study, we developed a computational model using commercial finite element analysis package COMSOL Multiphysics to simulate the double layer structure and quantify the EDL capacitance for the first time. In the modeling we considered the electrochemical processes at an EDL structure by solving the Poisson, Nernst-Plank and Butler-Volmer equations without applying electroneutrality and Boltzmann distributions. Moreover, to consider the effect of charge transfer on the EDL capacitance, we modeled the cases with and without redox reactions. To take advantage of the computational equation solving capability, we allowed the dielectric constant inside the compact layer to vary smoothly and continuously.