Double Filler Reinforced Ionomer: A New Approach to the Design of Composite Membranes for Fuel Cell Applications

A novel approach to mechanically reinforce polymer electrolyte membranes for fuel cells was developed by using hydrophilic zirconium phosphate (ZP) and hydrophobic fluoroalkyl zirconium phosphate (ZF) as a two-component mixed filler of a short-side-chain perfluorosulfonic acid (PFSA) membrane. Composite membranes filled with 10 wt% ZF and 5 wt% ZP have a strongly enhanced elastic modulus (E) and yield stress (sY) with respect to the unmodified PFSA (DE/E 300%, DsY/sY 95% at 70 C and 80% relative humidity (RH)) and to the single filler membranes with optimized ZP or ZF loadings. In the RH range 50- 95%, the in-plane conductivity of the mixed filler membrane is comparable with that of the unmodified PFSA, both at 80 and 110 C, in spite of a lower water content. At 50% RH, the mixed filler membrane shows better fuel cell performance in H2/air than the neat PFSA in terms of higher OCV, lower H2 crossover and greater power density, with peaks of 0.82 W cm2 at 80 C, and 0.70 W cm2 at 110 C.