Campbell:
As far as I can infer, your 1-D model has a point (A) for the anode (which is grounded) then a "line (A-B)" representing the electrolyte region and then another "line (B-C)" where C is the current collector side of the porous cathode.
1) Could you explain how you have set up the boundary conditions for the Darcy-flow equation at each of these points?
2) From what I understand, point A is grounded, point C is where a fixed current density BC is used and the line (B-C) is where the reaction occurs. You have species P+, Q- and R in your solution. In the porous electrode, P+ and R electrochemically form an insoluble species. The deposit starts at C and then slowly increases in thickness going towards B. Is the deposit conductive? Does it change the overall electronic conductivity of the porous electrode?
From what I can infer, when you reduce the porosity of the electrode, you are somehow effectively decreasing the volume available but the number of moles of your anion are not correspondingly reducing causing an increase in anion concentration. Have you checked to see if your cation and neutral species concentration are also increasing? If they are decreasing, are they decreasing by an amount that you expect?
Sri Puranam
As far as I can infer, your 1-D model has a point (A) for the anode (which is grounded) then a "line (A-B)" representing the electrolyte region and then another "line (B-C)" where C is the current collector side of the porous cathode.
1) Could you explain how you have set up the boundary conditions for the Darcy-flow equation at each of these points?
2) From what I understand, point A is grounded, point C is where a fixed current density BC is used and the line (B-C) is where the reaction occurs. You have species P+, Q- and R in your solution. In the porous electrode, P+ and R electrochemically form an insoluble species. The deposit starts at C and then slowly increases in thickness going towards B. Is the deposit conductive? Does it change the overall electronic conductivity of the porous electrode?
From what I can infer, when you reduce the porosity of the electrode, you are somehow effectively decreasing the volume available but the number of moles of your anion are not correspondingly reducing causing an increase in anion concentration. Have you checked to see if your cation and neutral species concentration are also increasing? If they are decreasing, are they decreasing by an amount that you expect?
Sri Puranam