Modification of hydrocarbon structure for polymer electrolyte membrane fuel cell binder application

The development of novel hydrocarbon polymer membranes needs to be accompanied by catalyst layer hydrocarbon binder research so that the resultant membrane electrode assembly (MEA) can be durable. Hydrocarbon polymers which show high performance levels as membranes, however, are inadequate as catalyst layer binders as they are designed for low fuel penetration. Modification to the hydrocarbon polymer structure of high performing hydrocarbon polymers such as Sulfonated poly(arylene ether sulfone) (SPAES) can take advantage of its high conductivity while increasing gas permeability and maintaining interfacial compatibility with the membrane. The incorporation of a biphenyl fluorene group into the polymer backbone of SPAES successfully increased d-spacing which led to an increase in gas crossover. In the catalyst layer, the modified polymer ionomer showed higher penetration into primary pore volume thus increasing ESA. Higher catalyst utilization due to easier fuel access and ionomer coverage led to higher fuel cell performance. Durability tests revealed that structural modification did not hinder interfacial compatibility as well as performance.

► Modification of hydrocarbon structure enhanced catalyst layer performance. ► Structural modification causes no increase in interfacial charge transfer resistance. ► Performance at 80 °C 100 R.H.% is increased by 28% at 0.6 V. ► Modified ionomer maintains greater performance after durability testing.