Recent advances in understanding catalyst coated membranes vs catalyst coated substrates for AEM electrolysers

There is growing interest in anion exchange membrane water electrolysers (AEMWE) as the need for lower-cost, green H 2 production technologies compatible with intermittent variable renewable energy sources grows. Especially given their unique ability to utilise low-cost, non-PGM materials in the alkaline environment, enabling them to readily lower system capital cost and avoid problems from material criticality. This review outlines recent advances in understanding the membrane electrode assembly (MEA) in AEMWEs, specifically the influence of catalyst-coated substrate (CCS) and catalyst-coated membrane (CCM) assembly methods on cell performance and durability. The aim of this review is to identify the current level of material and cell assembly development and highlight aspects that would benefit from further work in order to demonstrate the technological and cost feasibility of AEMWE and direct them toward commercial viability. • Structure engineering: Hierarchical structures show potential to improve performance. • Interface engineering: Anode passivation layers effectively improve stability. • Morphology engineering: Patterned membranes increase the ECSA and cell performance. • Morphology engineering: 3D printed PTLs can optimise gas transport and conductivity. • Membrane electrode assemblies: Results do not indicate whether CCS or CCM is preferable.