Résumé
Proton exchange membrane fuel cell durability and efficiency strongly depend on membrane properties, such as low electrical resistance, high mechanical and chemical stability. However, free radical attack, thermal stress, dimensional changes and microcracks are the various challenges that affect membrane lifetime on operation. Recent developments have been geared towards the use of thinner membranes due to their advantages such as lower membrane protonic resistance and improved water transport, although less resilience due to poorer mechanical properties. Conventionally, expanded polytetrafluorethylene is used as a membrane reinforcement, however a major drawback is the loss in mechanical properties as the temperature is increased. The objective of this presentation is to discuss the results on composite proton exchange membranes prepared using PFSA with an alternative reinforcement type1-3 developed using electrospinning. Poly(oxy-2,6-dimethyl-1,4-phenylene) (PPO) was chemically modified by sequential bromination, azidation, and copper-catalysed azide–alkyne cycloaddition click chemistry4 to afford 4-propyl-1,2,3-triazole-functionalized PPO with a range of substitution degrees and electrospun into nanofibers. For the preparation of composite membranes, 4-propyl-1,2,3-triazole-functionalized PPO nanofiber webs were embedded into Aquivion ionomer during the casting process, which resulted in a final membrane of controlled thickness and superior nanocomposite structure. The composite membrane morphology and fiber web incorporation, and interaction with the ionomer matrix, were examined using SEM and TEM/EDX, respectively. The strain-stress mechanical properties of the membrane indicate an increase in the Young’s modulus of the 4-propyl-1,2,3-triazole-functionalized PPO reinforced membrane compared to non-modified membrane, while the proton conductivity was maintained and the hydrogen permeation reduced. The fluoride emission rate is significantly lower during an accelerated stress test combining open circuit voltage hold at 90 °C and relative humidity cycling (fully wet/fully dry gases). The beneficial properties and application of these membranes in fuel cell membrane electrode assemblies will be discussed. Acknowledgements: Financial support under the ANR PEPR Hydrogène contract 22-PEHY-0005 PEMFC95 is acknowledged.References: WO2016020668A1 D. Jones, J. Rozière, S. Cavaliere, S. Subianto, S. Burton, Assigned to CNRS-University of Montpellier-Johnson Matthey. R. Sood, S. Cavaliere, D. J. Jones, J. Rozière, “Electrospun nanofiber composite polymer electrolyte fuel cell and electrolysis membranes”, Nano Energy 2016, 26, 179. R. Sood, S. Giancola, A. Donnadio, M. Zaton, N. Donzel, J. Rozière, D. J. Jones, S. Cavaliere. « Active electrospun nanofibers as an effective reinforcement for highly conducting and durable proton exchange membranes”, Journal Membrane Science 2021, 622, 119037. L. Liang, D. Astruc, “The copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) “click” reaction and its applications. An overview”, 2011, 2933.