Proton Exchange Membrane Fuel Cell (PEMFC) is a promising device to convert hydrogen into electricity. At the center of PEMFC, it can be find a Membrane Electrode Assembly (MEA) composed of a Proton Exchange Membrane (PEM) sandwiched between two catalytic layers. Recently, specific performances are being targeted to ensure the industrialization of this technology:

1) Operation at 100-150°C and thus at low RH (10-50%) to improve electrochemical kinetics and limit the catalyst pollution [1].

2) Performance lifetime of 8000h (transportation application) and 50 000h (stationary application).

Current polymers used (perfluorinated like Nafion®), in addition to the environmental risk that they represent, are unsuitable for the high-temperature range (loss of mechanical properties, loss of performance at low RH). To overcome this issue, sulfonated polyaromatic polymers appear to be a good alternative since they have very good thermomechanical properties. However, their proton conductivity and chemical stability (oxidative resistance to H2O2 formed during fuel cell (FC) operation) are very low. In our team, we patented an original concept of hybrid membranes able to fulfill the specific requirements for PEMFC [2]. This idea is based on the sol-gel (SG) hybridization (with judicious chemical functions) of a commercial host polymer membrane. This strategy is thus breaking up with traditional approaches (design of new copolymers, use of inorganic charges/additives). In 2020, we presented the elaboration and functional properties of hybrid membranes with promising performance and durability thanks to the thiol chemical function as a “sacrificial function” reacting with H2O2 [3]. The latter were made by self-condensing 3(mercaptopropyl)trimethoxysilane (MPTMS) into a commercial sPEEK host membrane. It was highlighted that both SG phase morphology and its localisation in the host membrane have a huge impact on the PEM functional properties [4].

We are now working on a new generation of hybridized membranes with both “sacrificial” and “regenerative” chemical functions (with redox properties). These hybrid membranes are expected to mitigate the chemical aging of sPEEK more efficiently. To do so, we synthetized specific SG precursors with a wide range of chemical functions. Then, these functions were successfully integrated into the sPEEK host membranes by impregnation/self-condensation of the new SG precursors. Accelerating chemical aging tests (exposure to H2O2 solutions) are under study to assess their durability. Finally, the morphology (distribution of the SG phase) will be studied in both direct space analysis (co-localized Raman-AFM, TEM, SEM-EDS) and indirect space analysis (SANS, SAXS).

[1] Y. Matsuda et al., J. Electrochem. Soc., 2020, vol. 167, no 4, p. 044509

[2] L. Gonon & V. Mareau, 10 septembre 2014, EP2774946A1

[3] N. Huynh et al., Journal of Power Sources, 2020, vol. 462, p. 228164

[4] N. Huynh et al., Nanoscale Adv., 2021, vol. 3, no 9, Art. no 9