Development and Characterization of Commercial-Scale Microporous Layers on Porous Transport Layers for Proton Exchange Membrane Water Electrolyzers
Authors: Ouimet Ryan J. , Soucie Hanna , Fortiner Serafina , Kulkarni Devashish , Lang Jack Todd , Zenyuk Iryna , Erb Bryan , Smeltz Andrew , Capuano Christopher B. , Ayers Katherine E. 
Published: December 2024

One of the critical components of a proton exchange membrane (PEM) water electrolyzer is the porous transport layer (PTL). PTLs help control the water and gas flow to and from the cell and provide an electrical interface between the system and the anode electrode which is required for electrolysis. By adjusting the PTL properties (thickness, porosity, etc.) fluid transport can be greatly impacted which could improve or worsen mass transport effects to the stack [1]. Additionally, the anode/PTL interface will greatly impact the cell performance as the anode catalyst utilization is greatest where the PTL is in contact with the anode catalyst. Despite these critical features, there has not been significant effort to improve the design of existing PTLs to optimize the overall design to best suit PEM water electrolyzer operation.
When examining potential pathways for improving the anode/PTL interface, one pathway can be to incorporate a microporous layer (MPL) onto the PTL. By adding a metal MPL with finer surface pore sizes compared to the bulk PTL, it is possible to create a smoother interface where the PTL can better interact with the anode catalyst. By maximizing the contact between the MPL/PTL and the anode surface, the catalyst utilization can be maximized which can improve cell performance [2]. Additionally, improved catalyst utilization may allow PEM electrolyzer manufacturers to be able to reduce anode catalyst loadings while maintaining existing performance which will ultimately lower overall electrolyzer capital expenses [3]. While an MPL can improve cell performance, the MPLs must be designed in a way to prevent any mass transport limitations with the smaller surface pores. To prevent any negative mass transport effects, the MPL and PTL must have an optimized porosity, pore size, tortuosity, and thickness which allows for the cells to continue operation with high performance.
This work highlights ongoing efforts to develop PTLs that have MPLs for PEM water electrolyzers. Based on the PTL and MPL properties (thickness porosity, tortuosity, etc.) characterized at the prototype scale, parts have been fabricated and tested at a scale that can be utilized in a megawatt capacity stack. The electrochemical test data shows the ability of these PTLs with MPLs to allow for a significant reduction in anode catalyst loading compared to baseline PTLs.

References

[1] X. Peng, P. Satjaritanun, Z. Taie, L. Wiles, A. Keane, C. Capuano, I. V. Zenyuk, N. Danilovic. Insights into Interfacial and Bulk Transport Phenomena Affecting Proton Exchange Membrane Water Electrolyzer Performance at Ultra-Low Iridium Loadings. Advanced Science, 8, (2021), 2102950.
[2] D. Kulkarni, R. Ouimet, B. Erb, D. Y. Parkinson, H.-M. Chang, C. Wang, A. Smeltz, C. Capuano, I.V. Zenyuk. Influence of Microporous Layers on Interfacial Properties, Oxygen Flow Distribution, and Durability of Proton Exchange Membrane Water Electrolyzers. ACS Applied Materials & Interfaces, 15, (2023), 48060-48071.
[3] T. Schuler, J.M. Ciccone, B. Krentcher, F. Marone, C. Peter, T.J. Schmidt, F.N. Büchi. Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis. Advanced Energy Materials, 10, (2019), 1903216.