Direct oxidation.methanol fuel cell (DMFC)

DMFCs have lower weight and volume compared with indirect fuel cells. In this kind of fuel cells, solid polymers have been shown as an attractive alternative to the traditional liquid electrolytes. Nafion perfluorosulfonic acid polymers are the most commonly used fuel cell membranes. Although it would be desirable methanol could be spontaneously oxidized at the cathode methanol transport takes place across the membrane causing depolarization losses at the cathode and conversion losses in terms of lost fuel.In order to improve the performance of the DMFC, it is necessary to eliminate or reduce the loss of fuel across the cell, usually termed as methanol crossover. This is a major limitation at present for DMFCs to become a commercially viable alternative. Although nafion membranes are the most usually used as solid polymer electrolyte in DMFCs, methanol readily transports across perfluorosulfonic acid membranes and minimises the effects of methanol crossover. Materials such as acid doped PBI membranes seems to have a lower methanol permeability than nafion membranes.