Durability of Radiation-Grafted Fuel Cell Membranes

Partially fluorinated proton exchange membranes prepared via radiation-induced graft copolymerization (“radiation grafting”) offer the prospect of cost-effective and tailor-made membranes for the polymer electrolyte fuel cell. The composition and structure of radiation-grafted membranes can be adjusted in a broad range to balance the different requirements of proton transport and mechanical robustness. Styrene, which is readily sulfonated, is predominantly used as grafting monomer. Crosslinking of the structure is a key design parameter, which, if optimized, yields membranes with durability of several thousand hours. Nevertheless, there is potential for improving chemical durability through the use of advanced styrene-derived grafting monomers, such as α-methylstyrene, with enhanced stability against radical attack.

Post mortem

investigations of aged membranes yield important insights into the extent of degradation, in particular locally resolved analysis on the scale of flow field channels and lands. An asset of crosslinked radiation-grafted membranes is their dimensional stability between dry and wet states, which is a key parameter in the context of the mechanical functionality as a separator in the cell. Yet still, the understanding of chemically and mechanically induced degradation, in particular their interplay, is limited, and meaningful accelerated aging test methods have started to be implemented to yield detailed understanding of prevailing degradation mechanisms.