The physical and chemical degradations of a state-of-the-art proton exchange membrane (PEM) composed of a perfluorinated sulfonic acid (PFSA) ionomer and polytetrafluoroethylene (PTFE) reinforcement are induced through the repeated expansion/shrinkage of the ionomer and free radical attacks. Such degradations essentially originate from the loose structure of the materials and the low interactive binding force among the PEM constituents. In this study, the need for simplified design principles of adhesives led to the use of mussel-inspired polydopamine (PD) as an interfacial modifier for the fabrication of highly durable PEM. Indeed, a self-polymerized dopamine layer acts as an interfacial glue, and enables efficient impregnation of a hydrophilic PFSA ionomer into porous hydrophobic PTFE with high packing density, resulting in strong adhesion between the PTFE and the PFSA polymers in the membrane. In addition, the redox property of the PD end groups spontaneously reduces the partial Ce salts in the ionomer solution and anchors them to the PD@PTFE substrate as defective cerium oxide (CeO x ) nanoparticles, reducing the dissolution and subsequent migration under cell operations. Finally, a CePD@PTFE membrane shows outstanding durability in fuel cells under an accelerated humidity cycling test with a reduction in the degree of physical and chemical failures.
Improving the durability of the membrane electrode assembly (MEA) while obtaining high performance is required to further commercialize polymer electrolyte membrane fuel cells (PEMFCs). The durability of PEMFCs is improved by incorporating radical scavengers, such as CeO 2 (ceria), into the MEA, especially the membrane. However, nanosized ceria particles are generally mixed with ionomers and are cast on substrates to fabricate composite membranes. Inchemical degradation, durability, membrane electrode assembly, polymer electrolyte membrane fuel cell, radical scavenger Yun Sik Kang and Segeun Jang contributed equally to this study.
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