Performance analysis of polymer electrolyte membranes for direct methanol fuel cells

The status of research and development of polymer electrolyte membranes (PEMs) for direct methanol fuel cells (DMFCs) is described. Perfluorosulfonic acid membranes, e.g. Nafion, are widely used in fuel cell technology; but, despite their success, they show some drawbacks such as high cost, limited operating temperature range and high methanol crossover. These limit their widespread commercial application in DMFCs. Such disadvantages are inspiring worldwide research activities for developing new PEM materials based on non-perfluorinated polymers as alternative to Nafion for DMFCs. A review of membrane properties is carried out on the basis of thermal stability, methanol crossover and proton conductivity. The analysis of DMFC performance covers perfluorosulfonic acid membranes (PFSA), sulfonated aromatic polymers (SAPs) and composite membranes. PFSA membranes are suitable materials in terms of power density, SAPs are more advantageous regarding the low methanol permeability and cost, whereas composite membranes are more appropriate for operation above 100 °C. DMFC power density values reported in literature show that, although there are remarkable research efforts on this subject, the achieved results are not yet satisfying. Further work is especially necessary on non-perfluorinated polymers to improve performance and durability for an effective application in practical DMFC devices.