Recycling of Ionomer Membranes in End-of-Life PEM Fuel Cells: Study of Membrane-Electrodes Separation Processes

With the increasing development of Proton Exchange Membrane Fuel Cell (PEMFC) technology in recent years, the recyclability of aged Membrane Electrode Assemblies (MEAs), is becoming an important issue to address. Up to now, the main studies dealing with PEMFCs recycling have mainly focused on the recovery of rare and precious materials (e.g. platinum (Pt)) contained in the catalyst layers (CL). However, the PFSA (Perfluorinated Sulfonic Acid) ionomer membrane is another essential and value-added PEMFCs component that must be included in the recycling process in order to both reduce its manufacturing costs (related to the complex fluorine chemistry) and its environmental impacts at the end of their life (EoL). Current EoL technologies for platinum recovery from MEAs are either based on hydrometallurgical or pyro-hydrometallurgical processes, and offer high recovery yields. However, they have two major drawbacks: they do not allow direct recovery of the ionomer membrane and, in the case of pyrometallurgy, they involve the release of a significant quantity of highly corrosive and toxic hydrogen fluoride (HF) gas due to the membrane incinerationWith this in mind, different routes for the separation of membrane electrodes from end-of-life MEAs, which constitutes the first step in the recycling of ionomer membrane, is investigated in this study 1 (Figure1). To monitor the process of membrane-electrodes separation, a specific methodology based on ultraviolet (UV-Vis) spectroscopy and optical microscopy is first set up.. Subsequently, the quality of the components separation is monitored through the establishment of a material balance thanks to thermogravimetric analysis (TGA). A two-step process, based on the use of diluted isopropyl alcohol (IPA) solutions under stirring, is proposed as an efficient and environmentally friendly method for the effective separation of the electrodes from the ionomer membrane. This process offers a high yield recovery (up to 95 % for PFSA), a low energy consumption and the avoidance of harmful gases emission. At a first stage, the physical separation of membrane and electrodes is carried out under mild temperature (40 °C), allowing to recover carbon, Pt and ionomer binder on one side and the PFSA ionomer membrane on the other side. The further dissolution of the PFSA ionomer membrane at a higher temperature (75 °C) in a second stage enables the recovery of a PFSA ionomer dispersion. The most promising processes are tested on both pristine and various samples of aged MEAs to demonstrate the robustness of the methodology regardless of the ionomer membrane type and aging state. The hydroalcoholic ionomer solutions resulting from EoL MEAs recycling have interesting potential for reuse in a variety of applications, such as in purification technologies (e.g. pervaporation, ultrafiltration). Reference: (1) M.Robert et al., Energy Fuels 2025, 39, 5, 2758–2771 Figure 1