Discussion Forum

Hello,

I'm a beginner with COMSOL and appreciate any guidance that could assist me learn more about this powerful tool.

I have a question about modeling the voltage drop across the electrode-solution interface inside an electrolyte solution. My configuration is shown in the attached image (adapted from an image by Mr. Trivedi) : i basically have an two insulated electrodes which i place inside a solution and apply a known AC voltage on the v+ electrode while grounding the other electrode.

I would like to model the magnitudes of electric fields inside the bulk electrolyte as well as on the interface with the electrode. What i've done so far was defining this geometry and solving using the electrostatics module, completely
ignoring the voltage drop across the interface layer.

I have been exploring the electro-chemistry necessary for my problem and i was thinking of using the boltzmann-poisson equation to prescribe charge density at a given location in the electrolyte.

I have a few key questions about the approach:

1. Most of the literature i've reviewed deals with electrolysis-like configurations i.e. the current is DC current, and the double layer is discussed in this framework is between the typically metal electrode and the fluid, i.e. faradaic currents. My case is somewhat different, since the metal doesn't directly touch the liquid, so no faradaic currents take place. I think that fundamentally there is still capacitance since the thin insulating layer of silicon-dioxide
separates between the two plates : metal & fluid, but i am not if this is the way to go and i am missing some other effect. Would appreciate an expert's opinion on this.

2. In terms of approaching this inside comsol - can i use the secondary current distribution model from the electrochemistry module, i believe it should account for voltage drops on the electrodes, or would i do better "rolling my own" with one large poisson equation for the all the domains + prescribed charge densities from Boltzman-Poisson ?


Thanks for your advice,
Lenny