High-temperature proton-exchange membrane fuel cells (HT-PEMFCs) have the potential to resolve the heat rejection issue of fuel cells for automotive applications. However, phosphoric acid-doped polybenzimidazole (PA-PBI)-based HT-PEMFCs are not stable under dynamic automotive operating conditions because of acid loss from the membrane electrode assembly (MEA). In 2016, Los Alamos National Laboratory developed ion-pair membranes for HT-PEMFCs, which have improved acid retention under dynamic operating conditions. The ion-pair HT-PEMFCs have 3-6 times lower amounts of phosphoric acids in the MEAs than PA-PBI-based HT-PEMFCs. High ion-pair interaction in the ion-pair MEA helps retain phosphoric acid in the presence of water or under dynamic operating conditions. In addition, the low amounts of phosphoric acids in the ion-pair MEA reduce electrode flooding that allows using ionomers at the electrodes instead of polytetrafluoroethylene (PTFE) binder for PA-PBI-based HT-PEMFCs. The use of ionomeric binder (charged polymers) in the fuel cell electrode has benefits over non-charged polymers. Here, we present our six years of efforts to develop ionomeric materials for ion-pair HT-PEMFCs (Figure 1).

Ionomers for ion-pair high-temperature proton exchange membrane fuel cells

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