Mechanical Properties and Chemical Durability of Nafion/Sulfonated Graphene Oxide/Cerium Oxide Composite Membranes for Fuel-Cell Applications.

Dong Chan Seo,Jae Young Jho,Ikseong Jeon,Eun Suk Jeong

doi:10.3390/polym12061375

Abstract

To improve both the mechanical and chemical durability of Nafion membranes for polymer electrolyte membrane fuel-cells (PEMFCs), Nafion composite membranes containing sulfonated graphene oxide (SGO) and cerium oxide (CeO2; ceria) were prepared by solution casting. The structure and chemical composition of SGO were investigated by FT-IR and XPS. The effect of the sulfonation, addition of SGO and ceria on the mechanical properties, proton conductivity, and chemical stability were evaluated. The addition of SGO gave rise to an increase in the number of sulfonic acid groups in Nafion, resulting in a higher tensile strength and proton conductivity compared to that of graphene oxide (GO). Although the addition of ceria was found to decrease the tensile strength and proton conductivity, Nafion/SGO/ceria composite membranes exhibited a higher tensile strength and proton conductivity than recast Nafion. Measurement of the weight loss and SEM observations of the composite membranes after immersing in Fenton’s reagent indicate an excellent radical scavenging ability of ceria under radical degradation conditions.

Highlights

Polymer electrolyte membrane fuel-cells (PEMFCs) are attracting attention as a clean and efficient source of energy due to their advantages of a high energy density, low emission of pollutants, and low corrosion
XPS spectroscopy indicated that the hydroxyl groups of graphene oxide (GO) were substituted with a new functional group containing a sulfonic acid group from the sulfonation reaction
Fourier transform infrared spectroscopy (FT-IR) and XPS spectroscopy indicated that the hydroxyl groups of GO were substituted with a new functional group containing a sulfonic acid group from the sulfonation reaction

Summary

Introduction

Polymer electrolyte membrane fuel-cells (PEMFCs) are attracting attention as a clean and efficient source of energy due to their advantages of a high energy density, low emission of pollutants, and low corrosion. A perfluorosulfonic acid polymer, is widely used as a polymer electrolyte membrane because of its high proton conductivity [1,2]. As the major causes that determine the durability of Nafion are its mechanical property and chemical stability, enhancing them is highly desirable for applications as a fuel-cell membrane. Various organic or inorganic fillers, used as reinforcement materials, have been widely applied to enhance the mechanical properties of Nafion [6,7,8,9]. The incorporation of multi-walled carbon nanotubes (MWCNTs) into Nafion resulted in an increase in tensile strength, but due to the high electrical conductivity of the MWCNTs, it caused an electronic crossover which is detrimental to a fuel-cell membrane. The addition of inorganic fillers such as zirconium phosphate and titania into

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Conclusion