Lawrence Berkeley National Laboratory

Transport phenomena in an ion-exchange membrane containing both H+ and K+ are described using multicomponent diffusion equations (Stefan-Maxwell). A model is developed for transport through a Nafion 112 membrane in a hydrogen-pump setup. The model results are analyzed to quantify the impact of cation contamination on cell potential. It is shown that limiting current densities can result due to a decrease in proton concentration caused by the build-up of contaminant ions. An average cation concentration of 30 to 40 percent is required for appreciable effects to be noticed under typical steady-state operating conditions.