Durable Ion-Pair High-Temperature Proton Exchange Membrane Fuel Cells with a Low Platinum Loading Intermetallic Catalyst
Authors: Kim Youngkwang , Zhao Xueru , Maurya Sandip , De Castro Emory S. , Sasaki Kotaro , Kim Yu Seung 
Published: December 2024

Conventional high-temperature proton exchange membrane fuel cells (HT-PEMFCs) often necessitate a relatively high platinum cathode loading, primarily due to the undesirable issue of phosphate poisoning. Previous research has suggested that employing ordered Pt-alloy catalysts could mitigate this problem [1, 2]. Our study demonstrates that an ion-pair proton exchange membrane (PEM) based on quaternary ammonium functionalized membrane can further alleviate phosphate poisoning by reducing the concentration of phosphoric acid in the electrode [3, 4].
In this study, we integrate two strategies: the utilization of intermetallic catalysts and the ion-pair PEM platform, aiming to decrease the Pt loading of the catalyst without compromising performance and durability. Carbon-supported intermetallic PtCoNiCrN catalysts were synthesized via a single thermal annealing process [5, 6]. Their crystallographic structure was confirmed through X-ray diffraction, atomic-resolution transmission electron microscopy, and in-/ex-situ X-ray absorption spectroscopy.
Rotating disk electrode (RDE) experiments revealed that the half-wave potential of ORR of the intermetallic PtCoNiCrN/C in 0.1 M H3PO4 with 0.1 M HClO4 was 876 mV, surpassing that of disordered PtCoNiCrN/C (829 mV) and commercial Pt/C (TEC10E20E) catalysts (769 mV). In membrane electrode assembly (MEA), the MEA utilizing the intermetallic catalyst with a platinum loading of 0.3 mg cm-2 exhibited a current density of 0.212 A cm-2 at 0.7 V and the peak power density (PPD) of 713 mW cm-2 under H2/air conditions, significantly outperforming the MEA employing the commercial Pt/C catalyst with optimized electrode composition (0.103 A cm-2 at 0.7 V and PPD of 625 mW cm-2).
Remarkably, the intermetallic catalyst demonstrated stable operation for 1,000 hours at 160 °C under anhydrous conditions without notable performance degradation. This study presents a pathway to reduce the catalyst loading of HT-PEMFCs, emphasizing the crucial role of the crystallographic structure of nanoparticles in enhancing the performance of HT-PEMFCs.

Acknowledgments

This work was supported by the US Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (L’Innovator program).

References:
[1] Hu, Y.; Shen, T.; Zhao, X.; Zhang, J.; Lu, Y.; Shen, J.; Lu, S.; Tu, Z.; Xin, H.L.; Wang, D. Combining structurally ordered intermetallics with N-doped carbon confinement for efficient and anti-poisoning electrocatalysis, Applied Catalysis B: Environmental, 279, 119370 (2020).
[2] Zhang, W.; Xu, S.; Yang, Y.; Gao, Q.; Zhu, S.; Ding, K.; Li, Q.; Shi, P.; Min, Y. Rhombohedral platinum-copper intermetallic compound: A high phosphate tolerance electrocatalyst for HT-PEMFC, Chemical Engineering Journal, 487, 150348 (2024)
[3] Lee, KS.; Spendelow, J. S.; Choe, YK.; Fujimoto, C.; Kim, Y. S.; An operationally flexible fuel cell based on quaternary ammonium-biphosphate ion pairs. Nature Energy 1, 16120 (2016)
[4] Lim, K, H; Matanovic, I; Maurya, S; Kim Y; De Castro E. S; Jang, J-H; Park, H; Kim, Y.S. High Temperature Polymer Electrolyte Membrane Fuel Cells with High Phosphoric Acid Retention. ACS Energy Lett., 8, 1, 529–536 (2023).
[5] Song, L.; Cai, Y.; Liu, Y.; Zhao, X.; Kuttiyiel, K. A.; Marinkovic, N.; Frenkel, A. I.; Kongkanand, A.; Choi, YM.; Adzic R. R.; Sasaki, K.; One-step facile synthesis of high-activity nitrogen-doped PtNiN oxygen reduction catalyst, ACS Appl
ied
Energ
y
Mater
ials, 5, 5245-5255 (2022).
[6] Zhao, X. R.; Xi, C.; Zhang, R.; Song, L.; Wang, C. Y.; Spendelow, J. S.; Frenkel, A. I.; Yang, J.; Xin H. L. Sasaki, K.; High-performance nitrogen-doped intermetallic PtNi catalyst for the oxygen reduction reaction, ACS Catal
ysis, 10, 10637-10645 (2020).