Advanced Porous Transport Layers for PEM Water Electrolyzers: Impact of the Interfacial and Bulk Properties of the PTLs on the Electrolyzers Performance

Proton exchange membrane water electrolyzers (PEMWEs) are widely seen as a crucial technology for integration with renewable energy sources to convert the generated electricity to green hydrogen, which is a clean and sustainable energy carrier. 1 However, their high capital cost and operational expenditures increase the production cost of green H 2 . 2 To make the technology economically competitive and boost its market penetration, DOE implemented targets of $2 kg -1 by 2025 and $1 kg -1 hydrogen by 2030. 3 The interfacial and bulk properties of the porous transport layer (PTL) are vital to the PEMWEs performance. 4–6 The optimal bulk properties of PTL improve cell performance mainly by improving the mass transport, while the reduced interfacial contact resistance between the anode catalyst layer and PTL, also enhances the catalyst utilization, allowing for a reduction of the precious metal loading. Further reduction of the interfacial contact resistance between the PTL and the catalyst layer is of crucial importance for increasing the efficiency of the PEMWEs, as well as for decreasing the production cost of green H 2 . In this study, an innovative reactive spray deposition technology (RSDT) is used to fabricate catalyst-coated membranes (CCMs) and catalyst-coated electrodes (CCEs) with ultra-low PGM loading (0.2 - 0.3 mg PGM cm -2 ) in both catalyst layers. The RSDT is a flame-based method that combines the synthesis and deposition of the catalyst in a single step, which results in a significant reduction of the MEA fabrication time and cost, respectively. 7–9 A set of commercially available Ti PTLs with various thicknesses and porosities have been used to assemble single cells as fabricated MEAs, and their performance has been assessed and compared to the state-of-the-art MEAs for PEMWEs. In addition, the impact of the thickness and porosity of the PTL, as well as the interfacial contact resistance between the PTL and catalyst layer for both single-cell PEMWE configurations (CCMs and CCEs) have been investigated. The performance loss in each cell configuration has been identified and discussed in detail. Furthermore, a standard accelerated stress test (AST) protocol has been applied to assess the durability of the RSDT-fabricated MEAs, with one order of magnitude lower PGM loading in their catalyst layers in comparison to the best reported in the literature MEAs for PEMWEs. Reference 1. Carmo, M. et al. A comprehensive review on PEM water electrolysis. Int. J. Hydrogen Energy 38, 4901–4934 (2013). 2. Babic, U. et al. Critical Review — Identifying Critical Gaps for Polymer Electrolyte Water Electrolysis Development Review — Identifying Critical Gaps for Polymer Electrolyte Water. (2017) doi:10.1149/2.1441704jes. 3. https://www.energy.gov/eere/fuelcells/hydrogen-shot 4. Peng, X. et al. Insights into Interfacial and Bulk Transport Phenomena Affecting Proton Exchange Membrane Water Electrolyzer Performance at Ultra-Low Iridium Loadings. Adv. Sci. 8, 1–9 (2021). 5. Bühler, M. et al. Optimization of anodic porous transport electrodes for proton exchange membrane water electrolyzers. J. Mater. Chem. A 7, 26984–26995 (2019). 6. Kulkarni, D. et al. Elucidating effects of catalyst loadings and porous transport layer morphologies on the operation of proton exchange membrane water electrolyzers. Appl. Catal. B Environ. 308, 121213 (2022). 7. Zeng, Z. et al. Degradation Mechanisms in Advanced MEAs for PEM Water Electrolyzers Fabricated by Reactive Spray Deposition Technology. J. Electrochem. Soc. 169, 054536 (2022). 8. Mirshekari, G. et al. High-performance and cost-effective membrane electrode assemblies for advanced proton exchange membrane water electrolyzers: Long-term durability assessment. Int. J. Hydrogen Energy 46, 1526–1539 (2021). 9. Yu, H. et al. Nano-size IrOx catalyst of high activity and stability in PEM water electrolyzer with ultra-low iridium loading. Appl. Catal. B Environ. 239, 133–146 (2018).