Recent advancements have explored the direct growth of self-supported nanostructured catalysts onto conductive substrates such as foams, meshes and fibers made from Ni and Fe alloys. These binder-free electrodes provide a high surface area and improved gas transport while eliminating the need for ionomer/binder coating. However, most studies demonstrating these structures as effective HER catalysts have been performed in simplified two-electrode configurations, often in a beaker type or H-Cell set-ups under conditions that do not represent the operational constraints of real AEMWE systems. Such configurations lack essential design features including compressive sealing, through-plane transport resistances, and water/gas flow management, all of which are critical in determining full-cell performance. Moreover, substrates like Ni foam, while ideal for nanostructure growth due to their high surface porosity and large surface area, pose practical challenges in MEA configurations [3, 4].
To address this gap, our study investigates the influence of substrate characteristics on the growth and functionality of various catalyst nanostructures using a range of porous transport layers (PTLs) compatible with commercial AEMWEs. Variations in surface roughness, porosity, and metallic fiber morphology were found to strongly affect catalyst nucleation, growth orientation, and mechanical anchoring. Electrochemical testing revealed that excessive nanorod growth, though beneficial for enhancing catalytic activity, can introduce resistive losses and poor interfacial contact when integrated into MEA-based electrolyzers. Strategies to optimize the resistive losses in such systems were explored. These findings emphasize the critical role of substrate-engineering in enabling the practical development of advanced catalyst architectures and provide actionable insights for the design of scalable, fully PGM-free AEMWE systems.
References: