During high current density operation, water production in the polymer electrolyte membrane fuel cell (PEMFC) cathode
catalyst layer can negatively affect performance by lowering mass transport of oxygen into the cathode. In this paper, a novel
heat treatment process for controlling the ionic polymer/gas interface property of the fuel cell catalyst layer is investigated
and then incorporated into the membrane electrode assembly (MEA) fabrication process. XPS characterization of the catalyst
layer’s ionomer-gas interface at its outer surface and its sublayers’ surfaces obtained by scraping off successive layers of the
catalyst layers confirms that a hydrophobic ionomer interface can be achieved across the catalyst layer using a specific heat
treatment condition. Based on the results of the catalyst layer study, the MEA fabrication process is modified to identify heat
treatment configuration and conditions that will create an optimal hydrophobic ionomer-gas interface inside the cathode
catalyst layer. Finally, fuel cell tests conducted on the conventional and new MEAs under different operating temperatures
show the performance of the fuel cells with the treated MEAs was > 130% higher than that with the conventional MEA at
25 °C and 70 °C with humidified air and > 45% higher at 70 °C with dry air. The durability of the hydrophobic treatment on
the cathode catalyst layer ionomer is also confirmed by the accelerated stress test.
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Degradation Effects at the Porous Transport Layer/Catalyst Layer Interface in Polymer Electrolyte Membrane Water Electrolyzer
The porous transport layer (PTL)/catalyst layer (CL) interface plays a crucial role in the achievement of high performance and efficiency in polymer electrolyte membrane water electrolyzers (PEMWEs). This study investigated the effects of the PTL/CL interface on the degradation of membrane electrode assemblies (MEAs) during a 4000 h test, comparing the MEAs assembled with uncoated and Ir-coated Ti PTLs. Our results show that compared to an uncoated PTL/CL interface, an optimized interface formed when using a platinum group metal (PGM) coating, i.e., an iridium layer at the PTL/CL interface, and reduced the degradation of the MEA. The agglomeration and formation of voids and cracks could be found for both MEAs after the long-term test, but the incorporation of an Ir coating on the PTL did not affect the morphology change or oxidation of IrOxin the catalyst layer. In addition, our studies suggest that the ionomer loss and restructuring of the anodic MEA can also be reduced by Ir coating of the PTL/CL interface. Optimization of the PTL/CL interface improves the performance and durability of a PEMWE.
more » « less- NSF-PAR ID:
- 10403692
- Publisher / Repository:
- The Electrochemical Society
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 170
- Issue:
- 3
- ISSN:
- 0013-4651
- Page Range / eLocation ID:
- Article No. 034508
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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