Enhanced performance of a Nafion membrane through ionomer self-organization in the casting solution

A Nafion membrane with enhanced performance has been prepared by using a novel casting solution containing low-polarity nonsolvent tetrachloroethylene (TCE). TCE induces self-organization of the ionomer and turns the originally transparent Nafion in dimethylformamide (DMF) solution into opaque. The Nafion membrane cast from such opaque solution remains mechanically robust and shows a proton conductivity of 0.07 S cm−1 at room temperature, and 0.21 S cm−1 at 80 °C under saturated humidity, which is an increase of 62% and 103% respectively over the membrane without TCE involvement. Besides, water content and water permeability of the new membrane become higher. The enhanced membrane performance is attributed to larger clusters of sulfonate groups in Nafion, which is revealed by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM).

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► Nonsolvent tetrachloroethylene leads to self-organization of ionomer in casting solution.
► Such casting solution results in Nafion membranes with greatly improved proton conductivity.
► Higher water content and water permeability of the membrane were also observed.
► The membranes were mechanically robust despite of polymer aggregation in casting solution.
► Larger clusters of sulfonate groups in the membranes were detected via SAXS and TEM.