AC-Impedance investigation of different MEA configurations for Passive-Mode DMFC mini-stack applications

Membrane-electrode assemblies (MEAs) characterised by different hydrophobic-hydrophilic properties were investigated in a passive Direct methanol fuel cell (DMFC) monopolar mini-stack at room temperature. These properties were modulated by varying the amount of Nafion or replacing the ionomer in the catalytic layer with polytetrafluoroethylene (PTFE). Impedance spectroscopy provided valuable information with respect to the limiting processes occurring during fuel cell operation. Methanol crossover, especially in the presence of high methanol concentration, played a major role in determining the overall performance. The development of a methanol impermeable membrane appears crucial for increasing the performance of DMFC devices for portable applications.