Use the Ion-Exchange Membrane Boundary node to specify an exterior boundary over which the flux of a charge-carrying species is continuous but the electrolyte potential shifts with a specified value. This condition is typically used in electrochemical cells containing both free electrolytes and ion-exchange membranes, for instance in dialysis or flow-battery problems. The node is typically used to couple two separate current distribution interfaces, where one of the interfaces models a free-electrolyte domain and the other models the ion-exchange membrane domain.

Note that using the Ion-Exchange Membrane domain node often is a more convenient modeling approach if the transported species in the free electrolyte and ion-exchange membrane are the same.

The node is applicable to exterior boundaries to electrolyte domains. For defining ion-exchange membranes on an interior boundary between two electrolyte domains, use the Thin Electrolyte Layer node.

The choice of Charge-carrying species concentration species specifies that the current flowing over the boundary will be carried by this species (which must have a nonzero charge number). Use the Membrane potential setting to set the electrolyte potential on the membrane side of the boundary. Note that if this potential is set to the electrolyte potential of a Primary Current Distribution or a Secondary Current Distribution interface, no additional settings are needed in that interface to set up the correct boundary condition.

The potential condition may be either Donnan, which will calculate the potential shift over the boundary based on the membrane charge carrying species concentration, or can be User defined.