Inhibiting the Swelling Behavior of Nafion Membranes for PEM Water Electrolysis

Nafion is a commercially available perfluorosulphonate (PFSA) polymer electrolyte membrane (PEM) commonly used in both PEM fuel cells and electrolyzers. Catalyst coated membranes (CCMs) are prepared by hot-pressing the catalyst layers on a hot and dry Nafion film[1]. In the electrolyser, the dry CCMs get in contact with liquid water, which swells the membrane. Because the CCM is clamped in the cell, this leads to formation of folds and wrinkles. Furthermore, when the membrane shows stronger in-plane swelling than the catalyst layer, this swelling can also lead to membrane-electrode delamination and formation of electrode cracks. Therefore, the large in-plane swelling of Nafion membranes is an unwanted feature.

 In this work, a facile and economical approach was developed to inhibit the in-plane swelling behavior of Nafion membranes. When first swollen on a fixed metal frame and afterwards dried in a fixed geometry, the Nafion film will memorize the wet shape and show reduced area swelling upon rehydration, providing outstanding benefits for CCM fabrication[2]. We expect that when using Nafion membranes with inhibited swelling behavior for CCM fabrication, the life time of PEM water electrolyzers shall be remarkably increased.

[1] M. Carmo, D. Fritz, J. Mergel and D. Stolten, International Journal of Hydrogen Energy, 38, 4901-4934 (2013) 

[2] S. Hink, D. Henkensmeier, J. H. Jang, H.‐J. Kim, J. Han, S.‐W. Nam, Macromol. Chem. Phys. 2015, DOI: 10.1002/macp.201500063.