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Electrode- Electrolyte Interface / Double Layer Help

Posted May 20, 2013, 5:13 p.m. EDT Low-Frequency Electromagnetics, Battery Design, Chemical Reaction Engineering Version 4.3a 3 Replies

Duncan Harris
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Hello Guys

I was wondering if anyone here has any experience modelling the electrode- electrolyte interface?

To start with Im attempting to create a 2d two electrode model measuring the potential difference between the two electrodes when stimulated with biphasic current waveforms (possibly monophasic to start with).

There are so many ways to model the electrode- electrolyte interface so it would be great to hear off someone who has attempted it and what method they found to be simplest and what problems they had with it.

any guidance would be great.

Thanks

Duncan
3 Replies Last Post May 22, 2013, 7:42 a.m. EDT
Eric Lämmel
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Posted: 1 decade ago May 21, 2013, 3:21 a.m. EDT
Hey,

I wanted to model this as well, but didn't succeed so far. I guess you will have to incorporate more than the AC/DC module, maybe an electrochemical module if you don't want to implement the equations manually.

I suggest to start with one electrode and a stationary analysis for simplicity. If this model solves well, you may go further.

I found a useful paper of some researchers who modeled the double layer at a spheric nano-sized electrode in 2D. They even considered the varying permittivity inside the double layer! Its title is "Simulating the Electrical Double Layer Capacitance" (G. Zhang, Clemson University, COMSOL Conference 2010).

Another publication, which I didn't review in detail yet, is "Accurate Simulations of Electric Double Layer Capacitance of Ultramicroelectrodes" (Wang and Pilon, University of California, Journal of Physical Chemistry 2011).

I wish you good luck with your problem and keep us updated!

Bye
Hey, I wanted to model this as well, but didn't succeed so far. I guess you will have to incorporate more than the AC/DC module, maybe an electrochemical module if you don't want to implement the equations manually. I suggest to start with one electrode and a stationary analysis for simplicity. If this model solves well, you may go further. I found a useful paper of some researchers who modeled the double layer at a spheric nano-sized electrode in 2D. They even considered the varying permittivity inside the double layer! Its title is "Simulating the Electrical Double Layer Capacitance" (G. Zhang, Clemson University, COMSOL Conference 2010). Another publication, which I didn't review in detail yet, is "Accurate Simulations of Electric Double Layer Capacitance of Ultramicroelectrodes" (Wang and Pilon, University of California, Journal of Physical Chemistry 2011). I wish you good luck with your problem and keep us updated! Bye
Duncan Harris
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Posted: 1 decade ago May 21, 2013, 3:44 p.m. EDT
Hi Eric

Thanks for getting back to me

It seems that this is quite a complex problem.
I have been researching for a while to gather all the equations that explain the behaviour of the interface.

I have started by creating a simple 1d model of the behaviour of the double layer with a single initial voltage. I used Nernst- Plancks equation. My next step would be to translate this into 2d which i am struggling with as my grasp of comsol is limited. Im not sure where to place my boundaries.
Once ive manage to do that then i will think about introducing more complex equations used to describe the interface.
Then stimulating it with current waveforms. Then introducing a second electrode etc.
Im just getting lost thinking about it. It is so multidisciplinary.
ill get back to you with my progress.

thanks again
Duncan
Hi Eric Thanks for getting back to me It seems that this is quite a complex problem. I have been researching for a while to gather all the equations that explain the behaviour of the interface. I have started by creating a simple 1d model of the behaviour of the double layer with a single initial voltage. I used Nernst- Plancks equation. My next step would be to translate this into 2d which i am struggling with as my grasp of comsol is limited. Im not sure where to place my boundaries. Once ive manage to do that then i will think about introducing more complex equations used to describe the interface. Then stimulating it with current waveforms. Then introducing a second electrode etc. Im just getting lost thinking about it. It is so multidisciplinary. ill get back to you with my progress. thanks again Duncan
Eric Lämmel
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Posted: 1 decade ago May 22, 2013, 7:42 a.m. EDT
Hello Duncan,

as in the first paper that I mentioned, inside the compact layer a Nernst-Planck approach is not suitable, I guess. This is because in theory there is no free electrolyte in there. But this layer is mostly responsible for the double layer capacitance. In the paper a Poisson equation inside the compact layer and a combined Poisson and Nernst-Planck problem outside the compact layer is solved. Neglecting the electrostatic governed region inside the compact layer must result in a not useful solution, I assume.

That's just my opinion and I didn't succeed in modeling the whole problem, as mentioned before. But maybe you can benefit from my input in a way...

Ciao
Eric
Hello Duncan, as in the first paper that I mentioned, inside the compact layer a Nernst-Planck approach is not suitable, I guess. This is because in theory there is no free electrolyte in there. But this layer is mostly responsible for the double layer capacitance. In the paper a Poisson equation inside the compact layer and a combined Poisson and Nernst-Planck problem outside the compact layer is solved. Neglecting the electrostatic governed region inside the compact layer must result in a not useful solution, I assume. That's just my opinion and I didn't succeed in modeling the whole problem, as mentioned before. But maybe you can benefit from my input in a way... Ciao Eric

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