Physically reinforced
short-side-chain perfluorinated sulfonic
acid electrolyte membranes were fabricated by annealing and using
a porous support. Five types of solution-cast membranes were produced
from commercial perfluorinated ionomers (3M and Aquivion (AQ)) with
different equivalent weights, annealed at different temperatures,
and characterized in terms of ion conductivity, water uptake, and
in-plane/through-plane swelling, while the effect of annealing on
physical structure of membranes was evaluated by small-angle X-ray
scattering and dynamic mechanical analysis. To create a reinforced
composite membrane (RCM), we impregnated a polytetrafluoroethylene
porous support with 3M 729 and AQ 720 electrolytes exhibiting excellent
proton conductivity and water uptake. The electrolyte impregnation
stability for the porous support was evaluated using a solvent resistance
test, and the best performance was observed for the 3M 729 RCM annealed
at 200 °C. Both annealed and nonannealed 3M 729 RCMs were used
to produce membrane electrode assemblies, the durability of which
was evaluated by open-circuit voltage combined wet–dry cycling
tests. The nonannealed 3M 729 RCM survived 5800 cycles, while the
3M 729 RCM annealed at 200 °C survived 16 600 cycles and
thus exhibited improved mechanical durability.