Blended Polyphosphazene/Polyacrylonitrile Membranes for Direct Methanol Fuel Cells

Direct liquid methanol fuel cell tests were performed with membrane electrode assemblies (MEAs) fabricated with polyphosphazene-based proton-exchange membranes. The membranes were prepared from sulfonated poly[bis(3-methylphenoxy)phosphazene] that was blended with polyacrylonitrile and then UV cross-linked using benzophenone as the photoinitiator. MEAs worked best when a high ion-exchange capacity (high conductivity) polyphosphazene membrane contacted the electrodes, in which case the fuel cell power output was nearly the same as that with Nafion 117 (for current densities ⩽ 0.15 A / cm 2 ) , but the methanol crossover was three times lower than that of Nafion. With a three-membrane composite MEA (a methanol-blocking film sandwiched between two high conductivity membranes), there was a significant decrease in crossover (ten times lower than that of Nafion 117) with a modest decrease in current-voltage behavior.