Aligned electrospun nanofiber composite membranes for fuel cell electrolytes.

We have synthesized the novel composite membranes composed of sulfonated polyimide nanofibers and sulfonated polyimide for proton exchange membrane fuel cell. It was clear that the polyimides within nanofiber were significantly oriented or aggregated when electrospun; as the result, the membrane stability, such as oxidative and hydrolytic stabilities, of the composite membrane was significantly improved with an increase in nanofiber, and oxygen permeability of the composite membrane also decreased when compared to that determined in the membrane without nanofibers. In addition, the proton conductivity of the membrane in the parallel direction indicated a significantly higher value when compared to that determined for the membrane in the perpendicular direction or for the membrane without nanofibers prepared with conventional solvent-casting method. Consequently, nanofibers proved to be promising materials as a proton exchange membrane and the composite membrane containing nanofibers may have potential application for use in fuel cells.