Study on the characteristics of semi-IPN membrane for long-term operation of polymer electrolyte membrane fuel cell

Abstract

The most attention alternative membranes are based on non-fluorinated hydrocarbon polymers, and one of the typical membrane is made of sPEEK. It has many advantages, such as low cost, easy sulfonation process, and high proton conductivity at a high degree of sulfonation. But there is critical problem that must be solved for successful commercialization. The volume change during the hydration-dehydration cycle process of fuel cell operation can lead to poor long-term operation. In this study, semi-IPN membrane system has been applied to enhance the dimensional stability of membrane associated with the long-term stability. sPEEK/polyimide(sPPI), sPEEK/poly(AMPS)(sPAMPS) semi-IPN membrane was synthesized to overcome the problem of bare sPEEK membrane. The synthesized semi-IPN membrane has higher dimensional stability than bare sPEEK membrane. And sPAMPS30 membrane shows relatively narrow hydrophilic channel (13.1nm). Due to the high dimensional stability and proton conductivity, sPAMPS30 was chosen as a representative membrane for long-term operation. Current density change of sPEEK ($600mA cm^{-2} -> 331mA cm^{-2}$) membrane at 0.6V was higher than that of Nafion ($607mA cm^{-2} -> 472mA cm^{-2}$) membrane as well as sPAMPS30($703mA cm^{-2} -> 596mA cm^{-2}$) membrane during accelerated durability test(ADT). During the accelerated durability test, open circuit voltage (OCV), which is a good measure of the reactant permeation through the membrane, has taken as a function of the operation time. These OCVs were measured before the polarization. Both cells using Nafion and sPAMPS30 membrane maintained the OCV for 23 day of fuel cell operation. However, the OCV of sPEEK membrane decreased during accelerated durability test.