The membranes in direct methanol fuel cells must both conduct protons and serve as a barrier for methanol. Nafion, the most common fuel cell membrane, is an excellent conductor but a poor barrier. Polyvinyl alcohol pervaporation membranes are good methanol barriers but poor conductors. These and most other pervaporation membranes offer no significant advantages over Nafion in methanol fuel cell applications. However, polybenzimidazole membranes have demonstrated characteristics that suggest up to a 15-fold improvement in direct methanol fuel cells. This improvement may be due to an alternate form of proton conduction in which protons travel via a Grotthus or "hopping" mechanism.

Sulfonated poly (ether ether ketone) (SPEEK) membranes with various degrees of sulfonation (DS) were prepared. Their proton conductivity and methanol permeability as a function of temperature were investigated. It was found that the proton conductivity of SPEEK membranes exceeded 10-2S/cm above 80℃, which is close to that of Nafion® 115 membrane under the same condition. The methanol permeability of SPEEK membranes was about an order of magnitude lower than that of Nafion® 115 membrane. The direct methanol fuel cell (DMFC) performance of the SPEEK membranes was better than that of Nafion® 115 membrane at 80℃

A highly ionic conductive solid-gel membrane based on polyacrylamide hydrogels with a K2CO3 additive was investigated. The polymer-based gel was prepared by adding ionic species K2CO3 to a monomer solution followed by polymerization. After polymerization, the ionic species was embedded in the polymer-based gel, where it remained. The ionic species behaved like a liquid electrolyte, whereas the polymer-based solid-gel membrane provided a smooth impenetrable surface that allowed for the exchange of ions. The gel membranes were obtained in the form of thin films of reasonable mechanical strength. Their ambient temperature conductivities were in the range 10-2 to 10-1S/cm. The effect of K2CO3 concentration on the conductivity of the gels prepared was examined in the temperature range from 0 to 100℃. The microstructure and chemical composition of the gels studied were characterized by environmental scanning electron microscopy and FTIR, respectively.

A novel composite membrane based on poly (vinyl alcohol) (PVA) with embedded phosphotungstic acid (PWA) were prepared and their proton conductivity and methanol permeability were studied. Infrared (IR) and UV spectrographic measurement indicates that the Keggin structure characteristic of the PW12O403- anion presents in the PVA membranes. Highest proton conductivity of 6.27