Enhanced stability of PFSA membranes for fuel cells: Combined effect between supercritical carbon dioxide treatment and radical scavenger incorporation

Perfluorosulfonic acid (PFSA) membrane is the core component in fuel cell system. However, it is susceptible to degradation due to radical attack on the polymer chains. Thus, improvement of the membrane stability is of significant importance for fuel cell applications. In this work, terephthalic acid (TPA), an effective hydroxyl radical (OH) scavenger, was incorporated into PFSA membranes with varying fractions. The pristine and composite membranes were further treated in supercritical carbon dioxide (Sc-CO2), resulting in membranes with increased crystallinity and thus improved dimensional and physical stability. Fenton acceleration test was conducted to evaluate the chemical durability of the membranes. It is found that Sc-CO2 treated membranes show better stability than those without treatment. Moreover, incorporation of appropriate fraction of TPA (0.5-1 wt%) can further mitigate chemical degradation of the membranes owing to its radical trapping capacity. Such combined effect between TPA and Sc-CO2 treatment affords highly stable PFSA membranes, which are promising for fuel cell applications.