Cation Contamination Redistribution throughout the PEMFC MEA: Towards the Establishment of Regeneration Protocols

Proton exchange membrane fuel cells (PEMFCs) are a promising technology for automotive applications. The membrane electrode assembly (MEA) remains the most vulnerable element in fuel cells due to its membrane composed of perfluorosulfonic acids. Over the lifetime of the PEMFC, cation contamination occurs from corrosion of fuel cell stack components such as bipolar plates and could be concentrated at particular locations. These cations can migrate from the bipolar plate into the electrode and the membrane. Indeed, due to their affinity toward sulfonic groups, they tend to replace protons affecting membrane conductivity. In addition, some ionic species such as iron cations are commonly known as catalysts for the Fenton reaction responsible for the chemical degradation of the membrane. In this work, we investigate the local effect of ferric contamination and its diffusion through electrochemical tests and post-mortem analyses. A membrane is strategically contaminated by Fe 3+ ions, then assembled into MEA using a hot-pressing method. A segmented cell monitors the ferric ion impact on local cell performance and impedance parameters at different operating conditions. After in-situ tests, MEA’s membrane and gas diffusion electrodes (GDE) are separated for analysis. Then, iron species are quantified to visualize the migration of Fe 3+ in both in- and through-plane directions. Post-mortem analysis suggests that at high local contamination, a part of cations is leached from the contaminated regions of the membrane after a PEMFC operating (Figure 1). In terms of cation distribution, post-mortem analyses reveal a preferential diffusion of Fe 3+ perpendicular to the gas diffusion channels and in the flow direction of H 2 . On a local scale, performances of contaminated channels are affected especially at low hydration levels Besides the in-plane diffusion the propagation of cations from the membrane to electrodes has been detected, at rates approaching 25% of total contamination. The impact of the Fe 3+ migration on radical scavenger diffusion is discussed. Our results provide useful information about cation diffusion in complex systems such as MEAs and gives us some hints on recovery protocols to extend lifetime of fuel cells. Figure 1