Membrane electrode assemblies doped with H3PO4 for high temperature proton exchange membrane fuel cells

H3PO4 content plays a critical role in high temperature proton exchange membrane fuel cells (HT-PEMFC), as it is responsible for the majority of the conductivity of the key components under high temperature operation. The conductivities of commercial AB-PBI membranes doped by immersing in 85 wt.% H3PO4 for different times and temperatures are investigated. The effect of H3PO4 loading in electrodes, including the AB-PBI polymer and a Pt/C catalyst, is also studied. The as-prepared electrodes and membranes are combined to fabricate a membrane electrode assembly for HT-PEMFCs. The results reveal that AB-PBI membranes doped with 85 wt.% H3PO4 at 90 °C for 9 h display a maximum conductivity of 33 mS cm−1. This membrane was selected and combined with electrodes including 15 wt.% AB-PBI and 0.75 mg cm−2 Pt with different H3PO4 loadings. A maximum current density of 260 mA cm−2 was achieved in the as-prepared MEA (with 5 mg cm−2 H3PO4 in electrodes) operating at 0.6 V and 160 °C, using oxygen and hydrogen.

► Increase in immersion temp/hour is beneficial for H3PO4 uptake in membranes.
► Optimization of H3PO4 in the electrode is 5 mg cm−2.
► Impedance of MEA with H3PO4 (15 mg cm−2) doped electrode lowers during activation.