Use the Periodic Condition to define a periodic relation between two boundaries — for instance, in a model describing a repetitive unit cell.

Use the Apply for electrolyte phase and Apply for electronic conducting phase checkboxes to enable the periodic condition for the electrolyte and electrode phase potentials, respectively. Additionally, the periodic condition for the chemical potential is enabled when Electroosmotic water drag checkbox is selected under Membrane Transport section.

By specifying a Potential difference, an offset in potential (typically per unit cell) can be prescribed.

For more information, see Periodic Boundary Conditions in the COMSOL Multiphysics Reference Manual.