Application of small-angle X-ray scattering to evaluete the impact of electron density fluctuation on the micro structures of proton exchange membrane in fuel cell

Abstract

The electron density fluctuation is present everywhere in the small-angle X-ray scattering (SAXS) profiles, but it affects more strongly on the structures located in the high q-range because of its contribution more than 90% of total scattering intensity. Poly(styrenesulfonic acid)-grafted poly(ethylene-co-tetrafluoroethylene) polymer electrolyte membranes (ETFE-PEMs) have hierarchical structures at different scale ranges, including lamellar structure, interfacial boundary, and conducting layer. These structures have a close relationship with the properties that the membranes express such as proton conductivity, water uptake, mechanical strength, chemical strength, thermal stability and other properties related to the efficiency and performance of the fuel cell. In this article, we used the Vonk grade 6 model (Vonk 6) to evaluate the effect of electron density fluctuation on the structures mentioned above. The result showed that the electron density fluctuation strongly affected the sizes of interfacial boundary and conducting layer but had an insignificantly effect on the lamellar structure.