Abstract
Hydrogen crossover in proton exchange membrane water electrolyzers (PEMWEs) poses a safety hazard, reduces the overall efficiency, and limits the operational differential pressure range. In this study, a membrane electrode assembly (MEA) with innovative Pt duo-recombination layer (DRL) design is developed by the unique reactive spray deposition technology (RSDT). The novel design comprises two thin RLs integrated within the volume of the membrane and has a total Pt loading of only 0.04 mgPt cm−2. Long-term durability test for over 3000 h is performed with as-fabricated MEA at steady-state conditions typical for an industrial hydrogen production system. The results from the durability test show that the newly developed DRL design effectively suppresses the H2 crossover to below 0.5 vol%. Furthermore, comprehensive post-test characterization of the MEA is performed and potential failure mechanisms in the Pt RLs observed during the durability test are identified and discussed in detail for the first time.
| Original language | English |
|---|---|
| Pages (from-to) | 534-544 |
| Number of pages | 11 |
| Journal | International Journal of Hydrogen Energy |
| Volume | 114 |
| DOIs | |
| State | Published - Mar 31 2025 |
Funding
A detailed description of the fabrication procedures for the RSDT-fabricated cathode and anode catalyst layers can be found in our previous publications [52,53]. A 10 mM platinum solution was prepared by dissolution of a pre-weighed amount of the platinum acetylacetonate precursor (Colonial Metal, Inc.) in a mixture of 75% xylene and 25% acetone (Sigma Aldrich HPLC 99.9%). Similarly, a 12.5 mM iridium solution was prepared by dissolving iridium acetylacetonate precursor (Colonial Metal, Inc.) in a 1:1:2 vol ratio solution of diethylene glycol monobutyl ether (Fisher Scientific, laboratory-grade), ethanol (Fisher Scientific, anhydrous histological grade), and xylene (Sigma Aldrich, ACS reagent 98.5%). In addition, 16 wt% of liquid propane (Airgas, Inc., 90%) was added to both solutions to improve the nebulization and increase the combustion temperature in the RSDT flame [41,42]. As-prepared solutions were sprayed through the primary nozzle into the flame of the RSDT apparatus, and the resulting Pt or Ir nanoparticles were deposited directly on the Nafion® membrane. After the flame, an air quench was used to reduce the temperature of the synthesized nanoparticles to prevent the membrane from overheating. In addition, a solution of Nafion® ionomer or a slurry of carbon and ionomer were sprayed through the secondary nozzles located after the air quench of the RSDT. Vulcan XC-72R carbon black (Cabot Corp.) was used as the catalyst support for the cathode. The carbon black was dispersed at a concentration of 2.5 mg mL−1 in methanol, and Nafion®D521 solution was used as an ionomer. The weight ratio of Nafion® to carbon was maintained at 0.15. Before use, the slurry was sonicated in an ice bath (Misonix S-4000, QSonica, LLC, Newtown, CT) for 180 min. The ionomer solution for the anode was prepared by mixing a pre-determined Nafion® solution with methanol (Fisher Chemical, certified ACS, 99.8%) and stirring the mixture for 30 min before spraying.After the RSDT fabrication, the MEA with DRL design was subjected to pre-test analysis, including cross-sectional imaging and catalyst loading assessment. Fig. 2 illustrates the structure of the as-fabricated MEA, along with the thickness and loadings of the catalyst layers. The anode catalyst layer is ∼2 μm thick, with a targeted Ir loading of 0.3 mgIr cm−2 and is composed of IrOx nanoparticles after deposition. The RSDT-fabricated cathode catalyst layer is ∼15 μm thick, with a targeted Pt loading of 0.2 mgPt cm−2 and is comprised of Pt nanoparticles supported on carbon (Vulcan XC-72R) and Nafion® ionomer.The authors would like to acknowledge the U.S. Department of Energy, Office of Energy Efficiency and Renewable Sources, Hydrogen and Fuel Cell Technologies Office for the financial support of this work (award number: DE-EE0008427). The content is solely the responsibility of the authors and does not necessarily represent the official views of the U.S. Department of Energy. The authors also acknowledge the University of Connecticut and Nel Hydrogen for providing the research facilities. Electron microscopy research was conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors would like to thank Kimberly S. Reeves at ORNL for preparing SEM and TEM specimens. The authors would like to acknowledge the U.S. Department of Energy, Office of Energy Efficiency and Renewable Sources, Hydrogen and Fuel Cell Technologies Office for the financial support of this work (award number: DE-EE0008427). The content is solely the responsibility of the authors and does not necessarily represent the official views of the U.S. Department of Energy. The authors also acknowledge the University of Connecticut and Nel Hydrogen for providing the research facilities. Electron microscopy research was conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The authors would like to thank Kimberly S. Reeves at ORNL for preparing SEM and TEM specimens.
Keywords
- Degradation mechanisms
- Hydrogen crossover mitigation
- Membrane electrode assemblies
- PEM water electrolyzers
- Recombination layers