Performance analysis of sulfonated PPTA polymers as potential fuel cell membranes

In this paper, preliminary fuel cell tests on sulfonated poly(p-phenylene terephthalamide)s (PPTAs) are reported. Two polymers with differing degrees of sulfonation were imbibed into a porous support matrix (Solupor® (DSM) with proton conductivities ranging from 10−3 to 10−2 S cm−1. Under fuel cell conditions, the fully sulfonated PPTA demonstrated longer lifetime. Furthermore, the same polymer exhibited a higher open circuit voltage and constant current value under constant voltage conditions. The partially sulfonated PPTA failed after approximately 250 h. SEM analysis indicated a less uniform integration of the partially sulfonated PPTA into the Solupor® matrix, which could account for the premature failure of the membrane. Initial polarisation measurements showed slightly poorer performance for the partially sulfonated PPTA but after 230 h, the polarisation curves for the two membranes were very similar. Under similar conditions, Nafion® 112 is a far superior membrane. However, if the incomplete filling of the Solupor® with PPTA in the present materials is taken into consideration, the performance of the sulfonated PPTAs becomes more competitive.