Scalable Implementation of Recombination Catalyst Layers to Mitigate Gas Crossover in PEM Water Electrolyzers

Abstract

Hydrogen permeation across the membrane is a critical safety hurdle within polymer electrolyte membrane (PEM) water electrolysis (WE). It is crucial to implement recombination catalysts into the membrane electrode assemblies (MEAs) for reducing hydrogen concentrations and allow the use of much thinner membrane architectures that allow high efficiency operation. Here we show how recombination catalyst layers can be fabricated into MEAs by using a scalable method. In subsequent slot-die coating steps, an electrically insulating and then a recombination layer (both 5 μm thick) are applied directly to the anode. This three-layer system is then processed into a 5-layer MEA with a cathode and membrane using the decal process. The 5-layer MEA shows a reliable hydrogen reduction in the anode product gas for a wide-range of membrane thicknesses. The long-term stability of the recombination layer is shown for a 5-layer Nafion™ HP-MEA in comparison to a 3-layer MEA. Even after long-term operation, the MEA shows a safe hydrogen concentration reduction on the anode. Finally, the presented technique is used to produce 5-layer MEAs with active areas of 1056 cm2 and 60 μm membrane thicknesses. Measurements on reference MEAs show a successful scale-up, proving the technique to be applicable to all scales.