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:

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