Recent progress in understanding the catalyst layer in anion exchange membrane electrolyzers - durability, utilization, and integration

Anion exchange membrane water electrolyzers (AEMWEs) are poised to play a key role in reducing capital cost and materials criticality concerns associated with traditional low-temperature electrolysis technologies. To accelerate the development and deployment of this technology, an in-depth understanding of cell materials integration is essential. Notably, the complex chemistries and interactions within the catalyst layer (consisting of the anode/cathode catalyst, anion exchange ionomer, and their interfaces with the transport layers and membrane) collectively influence overall cell performances, lifetimes, and costs. This review outlines recent advances in understanding the catalyst layer in AEMWEs. Specifically, electrode development strategies (including catalyst deposition techniques and configurations as well as transport layer design strategies) and our current understanding of catalyst-ionomer interactions are discussed. Effects of cell assembly and operational variables (including compression, temperature, pressure, and electrolyte conditions) on cell performance are also discussed. Lastly, we consider cutting-edge in situ and ex situ diagnostic techniques to study the complex chemistries within the catalyst layer as well as discuss degradation mechanisms that arise due to the integration of cell components. Simultaneously, comparisons are made to proton exchange membrane water electrolyzers (PEMWEs) and liquid alkaline water electrolyzers (LAWE) throughout the review to provide context to researchers transitioning into the AEMWE space. We also include recommendations for standard operating procedures, configurations, and metrics for comparing activity and stability. This review discusses recent insights in catalyst layer design strategies for anion exchange membrane water electrolyzers, including electrode design, catalyst/ionomer integration, operational variables, in situ diagnostics, and cell durability.