Transport Phenomena in Perfluorosulfonic Acid Membranes during the Passage of Current

A membrane transport model is developed and applied to analyze electrochemical and radiotracer data obtained during the passage of current. The results of this work provide insight into the processes promoting proton and water transport in perfluorosulfonic acid membranes. Specifically, a 1.0 M sulfuric acid concentration is shown to yield the lowest water‐transport rates and ohmic losses for the sulfuric‐acid, Nafion‐117 system. The transport of tritiated radiotracer species , which are present upon the addition of tritiated water to the system, are treated. The analysis allows for the accurate description of the number of water molecules associated with each proton transported across a membrane, the knowledge of which is required for the design of a fuel‐cell system. The diffusion coefficients of all mobile ions are related to their free‐solution values, and the membrane permeability can be predicted from published structure theories and x‐ray data.