Enabling Low-PGM Anode Electrodes for Improved Cell Performance and Durability in Alkaline Exchange Membrane Fuel Cells

Anion exchange membrane fuel cells (AEMFCs) have gained great interest due to their potential to reduce cost relative to proton exchange membrane fuel cells (PEMFCs) as the alkaline working environment allows the reduction of precious metals and the use of non-precious metals as the oxygen reduction reaction catalysts. Significant progress in highly conductive and base stable anion exchange membranes has advanced the direction of research towards device level fuel cell performance and durability.^1,2 High performing alkaline electrodes further improved AEMFC performance reaching to 3.4 W cm^-2 and durability test over 2000 h at 0.6 A cm^-2.^3,4 In addition, maneuvering the operating window such as varied relative humidity of anode and cathode, gas flow rates, and operating temperature can further enable efficiency in fuel cell performance.^5,6

Despite the significant improvements in AEMFC, the advanced performance is limited under certain conditions (e.g. H₂/O₂ operation, high gas stoichiometry and high PGM loading).⁷ Many of the fundamental performance and durability mechanisms remain poorly understood. Therefore, it is important to gain a better understanding of AEMFC electrode structures, catalyst-ionomer interactions, and degradation factors to further advance AEMFC towards commercially available.

This talk will focus on MEA development emphasized in reducing anode PGM loading, using a perfluorinated AEM polymer (PFAEM) (jointly developed by 3M and the National Renewable Energy Lab)⁸ based MEA, in which PFAEM polymer is used as the membrane as well as the electrode ionomer. A combination of in-situ and ex-situ techniques are applied to understand structure-property relationships of the electrodes. Systematic study demonstrating our approach towards decreasing anode PGM loading will be presented. The results indicate that despite an 85% reduction in anode electrode's PGM loading (0.7 mg_PGM cm^-2 to 0.1 mg_PGM cm^-2), peak power is able to be maintained by 70%, ~ 1.15 W cm^-2 and with reasonable in-situ stability performance. This is accomplished by incorporating anode electrode's electrocatalyst/ionomer integration and improving the electrode's structure, leading for better water balance. This work is intended to provide practical methods and direction for improving AEMFC electrode's structure and subsequently their fuel cell performance and durability.

References

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2. S. Gottesfeld, D. R. Dekel, M. Page, C. Bae, Y. Yan, P. Zelenay, and Y. S. Kim, Journal of Power Sources, 375, 170–184 (2018).

3. G. Huang, M. Mandal, X. Peng, A. C. Yang-Neyerlin, B. S. Pivovar, W. E. Mustain, and P. A. Kohl, J. Electrochem. Soc., 166, F637–F644 (2019).

4. N. U. Hassan, M. Mandal, G. Huang, H. A. Firouzjaie, P. A. Kohl, and W. E. Mustain, Advanced Energy Materials, 10, 2001986 (2020).

5. T. J. Omasta, A. M. Park, J. M. LaManna, Y. Zhang, X. Peng, L. Wang, D. L. Jacobson, J. R. Varcoe, D. S. Hussey, B. S. Pivovar, and W. E. Mustain, Energy Environ. Sci., 11, 551–558 (2018).

6. A. C. Yang-Neyerlin, S. Medina, K. M. Meek, D. J. Strasser, C. He, D. M. Knauss, W. E. Mustain, S. Pylypenko, and B. Pivovar, J. Electrochem. Soc. (2021) http://iopscience.iop.org/article/10.1149/1945-7111/abf77f.

7. S. T. Thompson, D. Peterson, D. Ho, and D. Papageorgopoulos, J. Electrochem. Soc., 167, 084514 (2020).

8. A. M. Park, Z. R. Owczarczyk, L. E. Garner, A. C. Yang-Neyerlin, H. Long, C. M. Antunes, M. R. Sturgeon, M. J. Lindell, S. J. Hamrock, M. Yandrasits, and B. S. Pivovar, ECS Trans., 80, 957–966 (2017).