One of the key issues to resolve for the wide spread commercialization of fuel cells in automobiles is their durability.¹ It is known that when a fuel cell cathode undergoes electrical potential swings, between low and high cell voltages, fuel cell degradation increases. While most studies on fuel cell cathode degradation have examined catalyst particle dissolution/agglomeration², the impact of the interaction between catalysts and polymer electrolytes should not be overlooked.

In this presentation, we will report our approach to forming a robust interface between the catalyst and the ionomer by controlling ionomer relaxation under fuel cell operating conditions. In the first part of the presentation, we will examine the non-equilibrium thermodynamics of Nafion in liquid media by using small angle neutron scattering analysis.³ The impact of the dispersing media on electrochemical reactions in fuel cell cathodes is explored by comparing the fuel cell beginning of life performance and the performance after potential cycling.⁴ In the second part, we will discuss a rejuvenation process which can control ionomer relaxation, improving fuel cell durability. The rejuvenation process was accomplished by the periodic exposure of a membrane electrode assembly to a dry-N₂ gas stream, thus suppressing ionomer relaxation during potential cycling accelerated stress tests.⁵ We will demonstrate how this technique can effectively extend the lifetime of a fuel cell by over a factor of five. The impact of the rejuvenation process conditions will also be reported.

References

1. Borup, J. Meyers, B. Pivovar, Y.S. Kim, R. Mukundan, N. Garland, D. Myers, M. Wilson, F. Garzon, D. Wood, P. Zelenay, J. More, K. Stroh, T. Zawodzinski, J. Boncella, J.E. McGrath, M. Inaba, K. Miyatake, M. Hori, K. Ota, Z. Ogumi, S. Miyata, A. Mishikata, Z. Siroma, Y. Uchimoto, K. Yasuda, K. Kimijima and N. Iwashita, Chem. Rev., 107, 3904 (2007).
2. K. Ahluwalia, S. Arisetty, J.-K. Peng, R. Subbaraman, X. Wang, N. Kariuki, D. J. Myers, R. Mukundan, R. Borup, and O. Polevaya, J. Electrochem. Soc., 161, F291 (2014)
3. S. Kim, C.F. Welch, R.P. Hjelm, N.H. Mack, A. Labouriau and E.B. Orler, Macromolecules, 48, 2161 (2015).
4. S. Kim, C.F. Welch, N.H. Mack, R.P. Hjelm, E.B. Orler, M.E. Hawley, K.S. Lee, S.-D. Yim and C.M. Johnston, Phys. Chem. Chem. Phys., 16, 5927 (2014).
5. S. Kim and D. Langlois, US Patent 9425461 (2016).