Mechanical degradation behavior of recast composite PFSA membrane and Nafion® N-112 membrane under OCV condition

The authors report the mechanical degradation behavior of perfluorosulfonic acid (PFSA) membranes under open circuit voltage hold condition. The degradation behavior of an ePTFE reinforced PFSA membrane impregnated with phosphotungstic acid (PTA) in cesium form was compared with that of an extruded Nafion® N-112 membrane. Membrane electrode assemblies were fabricated by spraying carbon supported platinum catalysts on either side of the membrane. Diagnostic tests were conducted before and after 100 hours of OCV hold period. Mechanical tests were performed on as-fabricated MEAs and MEAs after OCV hold test. The PTA additive was found to be very effective in reducing fluoride emission rates. However, the mechanical strength decay for both type of membranes remains significant. The composite membrane retained a comparatively higher level of residual toughness than the N112 membrane. SEM analysis revealed localized cracks form inside the membranes as a result of OCV hold. ©The Electrochemical Society.