Impact of Catalyst Layer Architecture on AEMWE Performance: A Comparative Study of Carbon-Supported and Carbon-Free Catalysts

The development of high-performance anion exchange membrane water electrolyzers (AEMWEs) requires precise control over catalyst layer (CL) structure and composition to balance ionic, electronic, and mass transport within the electrode. This study systematically investigates the effects of ionomer content, catalyst loading, and catalyst formulation on the performance of conventional powder-type porous transport electrodes (PTEs) for AEMWE. For cathodes utilizing carbon-supported Pt-based catalysts (Pt/C and PtRu/C), increasing catalyst loading improved reaction kinetics, but performance declined beyond a critical catalyst layer thickness of ~ 10 µm due to mass transport limitations. Within this thickness threshold, maximizing roughness factor and enhancing intrinsic hydrogen evolution reaction (HER) activity were essential for optimal performance. The high electronic conductivity of carbon supports enabled structural flexibility without significantly affecting high-frequency resistance (HFR). In contrast, carbon-free NiFe alloy-based anodes showed strong sensitivity to electrode architecture due to their inherently low electrical conductivity. Optimal anode performance was achieved at a lower ionomer content and thinner catalyst layers, beyond which both HFR and reaction kinetics deteriorated. Unlike cathodes, increases in loading or ionomer content in anodes directly led to increased internal resistance and decreased catalyst utilization. These findings provide design guidelines for advancing carbon-free anode materials in AEMWEs.