Modification of Nafion Thermoplastic Precursor to Enhance Durability and Recyclability of Ionomer Membranes for Fuel Cells and Electrolyzers

To meet national clean hydrogen goals by 2050, hydrogen energy technologies like fuel cells and electrolyzers need to scale up while reducing costs. These technologies depend on proton exchange membranes (PEMs) made from polyfluorinated sulfonic acid (PFSA) ionomers such as Nafion® and Aquivion®, which are costly, hazardous to produce, and non-recyclable. This results in significant hazardous fluorinated waste from unused manufacturing scraps and end-of-life (EOL) membranes. Developing new methods to recycle and reuse scraps and end-of-life PFSA-PEM can reduce emissions and hazards from conventional disposal and decrease manufacturing impacts. We will explore two approaches to develop circular PFSA-PEMs, focusing on modifying the material at the thermoplastic precursor stage using modern click chemistry. The first approach involves creating a covalent adaptable network (CAN) with dynamic crosslinks that exchange during heating, a core technology of RockyTech, Ltd. This will endow conventional non-processable materials with thermal processability, allowing the PFSA-PEM to be thermally reprocessable (self-healing) for additional lifecycles. The second approach aims to enhance solvent reprocessability by introducing hydrophilic modifications to the precursor, increasing the PFSA-PEMĺs dispersibility in water-alcohol mixtures under mild conditions, offering a more industry-acceptable recycling method. We have successfully developed a method for chemically modifying the thermoplastic precursor by either crosslinking with dynamic covalent crosslinkers or grafting tethering groups. This modified precursor was then converted into a new form of reprocessible Nafion ionomers, which show reduced swelling and enhanced proton conductivity (approximately 40% increase) at 70°C compared to commercially available Nafion 115. will further refine membrane properties by varying crosslinkers and tethers and investigate their properties in both ex-situ and in-situ fuel cell settings. We will also explore their durability, self-healing capabilities, and end-of-life recycling, along with feasibility testing for integration into the current manufacturing process. Realizing circular PFSA-PEMs will not only reduce hazardous fluorinated waste issues, but also reduce the costs, hazards, and emissions of new manufacturing. Our chemical modification approaches are simple and will not impair membrane performance. Thus, our technology can be feasibly integrated into current PFSA-PEM manufacturing processes, promoting commercial adoption by producers such as Chemours and Solvay.