In order to classify membrane behavior as a function of weight percent polyHPA (reference figure 1), membranes were synthesized in 0 wt%, 25 wt%, 50 wt%, 75 wt%, and 100 wt% polyHPA and the balance PFSA. Electrochemical impedance spectroscopy (EIS) was used to characterize conductivity of the membranes at 80 ºC with a relative humidity sweep (50 - 90 %RH). Additionally, small-angle x-ray scattering (SAXS) was performed at 80 °C with a relative humidity sweep from 0 - 95 %RH, and FTIR was performed at 80 °C at 0 %RH and 100 %RH. These conditions were chosen specifically for the typical operating region for PEMFC applications. In this blend study, the addition of polyHPA was found to categorically decrease performance (conductivity) of standard 3M© 825EW PFSA membrane. Though improvement of the PFSA membrane was not achieved, this research will provide valuable information regarding the morphology of blended membranes, particularly in membranes exhibiting two-phase behavior; furthermore, results will provide some insight into choosing other viable additives for improved conductivity of PEMFCs.
Figure 1. Chemical structure of polyHPA, 60 wt% HPA (K8SiW11O39)
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