Nitrogen heterocyclic polymers with different acidophilic properties as proton exchange membranes and binders for high-temperature fuel cells

Abstract

For high-temperature proton exchange membrane fuel cells (HT-PEMFCs), the PA amount in membrane electrode assembly (MEA), which can be tuned by the membrane and binder materials, has a vital influence on cell performance. Herein, to control the PA uptake ability of the MEA, a series of membrane and binder materials functionalized by nitrogen heterocyclic groups with different acidophilic properties were synthesized via superacid-catalyzed copolymerization of p-terphenyl and functional aldehydes. As expected, the PA-doped TP-2-IM membrane exhibits the highest proton conductivity of 66 mS/cm due to the largest PA uptake, and the corresponding MEA using TP-2-IM membrane displays the highest PPD of 621 mW/cm2 at 160 °C. However, the MEA using TP-2-IM as binder demonstrates the poorest cell performance mainly attributed to the limited mass transport resulted from the too strong PA interplay. Notably, owing to the suitable PA uptake ability of TP-4-IM binder, a good balance between the proton conductivity and fuel diffusion in the MEA has been achieved. Thus, the corresponding MEA illustrates the largest electrochemical surface area (ECSA) of 159 cm2/mgPt and exhibits the highest PPD of 821 mW/cm2 at 160 °C and 1004 mW/cm2 at 200 °C with H2 and O2 as fuel.