To move towards practical implementations, advanced eCO 2 R electrolyzers, such as Membrane Electrode Assemblies (MEAs) , employ microenvironments based on stabilized cationic polyelectrolytes (ionomers) on the electrodes . Cross-linking the ionomer on Ag electrode supports prolonged high CO Faradaic efficiencies in acidic electrolytes, avoiding carbonate precipitation . Considering these interfaces in the modeling efforts requires including activity and transport of water in the continuum model .