Reducing Iridium Loading on the Anode Using a 3D Nanostructured Catalyst-Coated Substrate in PEM Water Electrolysis

Proton Exchange Membrane Water Electrolysis (PEMWE) is considered one of the most promising form of green hydrogen production that could lead to a successful decarbonization of industrial processes, with a potential of at least 10% reduction of CO 2 emissions of the total abatement needed by 2050 [1]. Since the oxygen evolution reaction (OER) catalyst on the anode side is dominated by Iridium (Ir)-based materials, scarce and expensive, reducing the loading to 0.1 - 0.2 mg Ir /cm 2 is critical to ensure cost-effectiveness in large-scale PEMWE deployment for hydrogen production. As outlined by the U.S. Department of Energy (DOE), the target Ir content in electrodes should be reduced to less than 0.5 mg/cm 2 by 2026 [2]. To achieve low Ir loadings, Smoltek Hydrogen’s aim is to significantly increase the available surface area of the Porous Transport Layers (PTLs) by growing vertically its patented Carbon NanoFiber (CNFs) structure [3], protected with a corrosion-resistant and conductive layer and electrodeposited with OER catalyst (Fig. 1a), creating a unique Porous Transport Electrode (PTE). With this electrodeposition method, we obtain a thin continuous Ir layer with a strong adhesion along the nanostructures, a high electrical conductivity [4] reducing contact resistance between the catalyst layer and PTL substrates, and a maximum utilization of the catalyst. This work will concentrate on the successful reduction of Ir loading to 0.1 mg/cm 2 in the PTE, demonstrating excellent mass activity in Half-Cell tests (Fig. 1c). The polarization curves of electrodes with low Ir loading obtained in Full-Cell exhibited superior performance compared to cells with significantly higher Ir loading. The aim is now to reach constant current durability tests (Fig. 1d) for 2000 hours or more on PEMWE operation using 0.1 mg/cm 2 Ir loaded PTEs, with minimum degradation and overcoming mass transport limitations, particularly at higher current densities. 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 Krivina et al. Adv.Mater., 2022, 34, 2203033. Figure 1