Electrospun nanofibrous blend membranes for fuel cell electrolytes

We have synthesized the novel blend membranes composed of sulfonated polyimide nanofibers and sulfonated polyimide for proton exchange membrane fuel cell. The proton conductivities of the blend membrane containing nanofibers were measured as functions of the relative humidity and temperature using electrochemical impedance spectroscopy. The proton conductivity of the blend membrane indicated a higher value when compared to that determined for the blend membrane without nanofibers prepared with conventional solvent-casting method. In addition, the membrane stability, such as oxidative and hydrolytic stabilities, of the blend membrane containing nanofibers strongly depended on the amount of nanofiber and was significantly improved with an increase in nanofiber. Oxygen permeability of the membrane was also investigated under dry condition at 35 °C and 760 mm Hg. Oxygen permeability coefficient of the blend membrane slightly decreased when compared to that determined in the blend membrane without nanofibers. Consequently, nanofibers proved to be promising materials as a proton exchange membrane and the blend membrane containing nanofibers may have potential application for use in fuel cells.