The Membrane-Electrode Interface in PEFCs: IV. The Origin and Implications of Interfacial Resistance

Membrane-electrode interfacial resistance and deterioration over time was investigated using a series of sulfonated poly(arylene ether) membranes and Nafion. Dimensional mismatch due to swelling/deswelling, wetting/adhesion, and water transport mismatch between the electrodes and the polymer electrolyte membrane were all investigated as potential root causes of membrane-electrode interfacial resistance and durability. The data presented from a large number of diverse polymers strongly support dimensional mismatch as the primary cause of interfacial failure. Extended direct methanol fuel cell life tests, up to 3000 h, showed high performance and good durability for membranes with low water uptake. Polymer electrolyte membranes with ∼35 vol % water uptake were the best in this study. However, a low water uptake coating layer greatly improved the performance and durability of a higher water uptake polymer electrolyte membrane. This study demonstrates the potential importance of the membrane-electrode interface on fuel cell performance and durability and provides a basis for implementing polymer electrolyte membranes effectively in high performance polymer electrolyte fuel cells (PEFCs).