From kinetics to cathode layer design: establishing targets for cathodes in anion-exchange membrane electrolyzers

Abstract

While non-platinum-based anodes are common in anion-exchange membrane water electrolyzers (AEMWEs), the cathode still requires Pt to achieve sufficient performance and durability. While critical for the technology, little work has been performed determing Pt loading targets, or generlized hydrogen evoltuion reaction (HER) activity targets. Here, we analyzed a low surface area catalyst (LSAC) and developed a performance model. The data reveals cathode kinetics transition from a low-field approximation (LFA) to a high-field approximation (HFA) as the loading is steadily decreased from 1 to 0.1 mg_Pt cm⁻². This transition point is catalyst-specific, but when expressed as a roughness factor (RF), a universal kinetic transition is identified at ∼100 cm_Pt² cm_MEA⁻² for Pt-based catalysts, and this is further extended to activity targets for non-Pt catalysts. This provides essential guidance for catalyst development and modeling low-loading cathodes.