Ion exchange resin/polystyrene sulfonate composite membranes for PEM fuel cells

A new composite proton exchange membrane was made by casting a polystyrene sulfonate (PSS) solution with suspended micron sized particles of a crosslinked PSS ion exchange resin. The chemical compatibility of the resin and the PSS allow stable composites with up to 50 wt.% resin. The resin/PSS composite membranes have greater ion exchange capacity than PSS membranes, but the ion conductivity is similar to that of PSS. Swelling of the composite membranes as a function of water uptake is lower than that of PSS. The composite membranes are mechanically more robust and display greater chemical stability in a fuel cell than the PSS membranes. The polarization curves show long-term degradation of the membranes; the cell potential decreased by 60% in 55 h for a PSS membrane, and in 340 h for a composite membrane. The reduced rate of degradation of the composite membranes suggests that with further refinement they may have potential as an inexpensive alternative for PEM fuel cells.