Dimeric ionic liquid for improving performance and durability of PEMFCs

A dimeric ionic liquid (1,1'-(butane-1,4-diyl)bis9-methylpyrimido[1,2-a]pyrimidinium) di-nonafluorobutanesulfonate (D-MTBD) is investigated for surface modification to a PtCo/C catalyst for improving performance and durability of the catalyst in a fuel cell membrane electrode assembly (MEA). Compared to the PtCo/C catalyst without modification, the addition of the dimeric ionic liquid (IL) improves the mass activity (MA) of the PtCo/C catalyst in the MEA, as well as fuel cell performance. Moreover, the dimeric IL also improves the durability of the PtCo/C catalyst. Thermogravimetry and differential scanning calorimetry were used to evaluate the IL's thermal stability and melting point. The viscosity of the catalyst inks with and without IL were compared. Electrochemically active surface area, impedance, and gas diffusion resistance were evaluated and compared with the PtCo/C catalyst without IL modification. Owing to its higher molecular weight and melting point, the dimeric IL shows potential as a highly stable catalyst modifier. This work shows that the dimeric IL may serve as a replacement to regular monomeric ILs for catalyst surface modification.