Low Iridium Catalyst Loading in PEM Water Electrolysis Anodes Via Smoltek Nanofiber Integration in Porous Transport Electrodes

A major key to successful decarbonization of industrial processes is fossil-free hydrogen produced via Proton Exchange Membrane Water Electrolyzers (PEMWE), which has the potential to reduce CO 2 emissions by at least 10% of the total abatement needed by 2050 [1]. However, as this method relies on scarce and expensive materials, it is critical to reduce the loading of Ir-based Oxygen Evolution Reaction (OER) catalyst on the anode side without compromising the overall performance and durability of the cell. For example, the U.S. Department of Energy (DOE) put the target on Ir content in electrodes at less than 0.4 mg/cm 2 by 2026 [2]. Smoltek Hydrogen developed a unique Porous Transport Electrode (PTE) using its patented Carbon NanoFiber (CNFs) structure [3], grown vertically on the Porous Transport Layers (PTLs), to significantly enhance the available surface area. The CNFs are then protected with a corrosion-resistant and conductive layer and electrodeposited with OER catalyst (Fig. 1a). By electrodeposition, the Ir catalyst forms a thin and conformal layer along the nanostructure, maximizing the catalyst utilization, achieving loading levels as low as 0.1 mg/cm 2 and reducing contact resistance between the catalyst layer and the PTL substrate. The performance of the PEMWE cell will depend mainly on the interfaces between the materials used in the different layers. In order to avoid mass transport limitations, it is key to create a durable interfacial contact [4] between the PTE and the proton-conducting membrane. The MicroPorous Layers (MPLs), sintered Ti multilayer structures with advanced interface properties, lower the roughness of the substrate’s surface and provide homogeneous contact pressure distribution, resulting in high catalyst utilization and low mass transport losses [5]. This study aims to test the performance and durability of a combination of Smoltek’s solution and this low-roughness substrate by growing corrosion-protected CNFs with low-loading Ir on top of the MPL, giving a special PTE tested in full-cell under different conditions. References IEA (2021), Net Zero by 2050, IEA, Paris, https:/www.iea.org/reports/net-zero-by-2050 https://www.energy.gov/eere/fuelcells/technical-targets-proton-exchange-membrane-electrolysis Xin Wen. Enhancing Efficiency and Durability of PEM Water Electrolysis with Low Iridium Loading through Nanofiber-Modified Porous Transport Electrodes , 2024, ECS Meeting Abstracts. MA2024-01 Katherine Ayers. Current Opinion in Chemical Engineering , 2021, 33, 100719. Tobias Schuler. Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis , 2020, 1903216 https://publications.jrc.ec.europa.eu/repository/handle/JRC104045 Figure 1