Hi! I am doing a stationary study of a 1D model in COMSOL 5.4 and I am interested in how I can model the charge transfer between the semiconductor electrode and the electrolyte. I'm using the semiconductor interface for the electrode and a coupling between Electrostatics and Transport of Dilute Species for the electrolyte.
I have defined a variable R over the boundary to represent the charge transfer rate across the interface. My question is how do I link this calculated rate to the current flowing across the interface.
On the electrolyte domain I have define a surface reaction with the rate same as R. But it's more complicated for the semiconductor domain. The semiconductor domain boundary condition is a "Metal Contact" with the workfunction given by the redox level in the electrolyte. Setting a very low value for the Richardson's coefficient allows me to cancel the unwanted thermionic current.
To account for the charge carriers involved in the transfer, I can define a recombination process. My problem is that the way COMSOL is built, recombination is defined over a domain, not a boundary. Therefore if I try to restrict my recombination rate to R I get an error.
Applying a boundary pointwise constraint to the expression "Recomb_rate - R = 0" doesn't seem to work. Does anyone have any ideas?
Hi Radu,
I assume that you're using(?) a Poisson-Nernst-Planck model for the electrolyte and a semiconductor model for the solid. At the interface the current density coming from the electrolyte must be the same as the current flowing into the semiconductor. So I assume, again, that you do not have any charge accumulation at the physical interface. There could be a charge unbalancing in the electrolyte side due to the diffuse layer.
Then it would be nice if you attach at least a sketch of the problem you want to solve and the hypothesis you want to keep. I think that more than a problem related with Comsol the question is what model you want to assume.
Best,
Fabio
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