In Search of Lost Iridium: Quantification of Anode Catalyst Layer Dissolution in Proton Exchange Membrane Water Electrolyzers

Understanding catalyst dissolution pathways in protonexchangemembrane water electrolyzers is paramount for developing mitigationstrategies aiming toward higher durability and lower catalyst loadings.To this end, Ir dissolution has been extensively studied using aqueousmodel systems but not in real devices. Aiming to bridge this knowledgegap, we use a metal-free water electrolysis setup to determine themass balance of the dissolved Ir in an electrolyzer when applyinga protocol mimicking intermittent operation. We find that the mainIr sinks are the cathode catalyst layer and the membrane, while Irdissolution into the water lines is significantly lower. Althoughreproducible estimation of Ir present in the membrane is challenging,quantification of Ir within the cathode is reliable and efficient.This new finding implies that tracking Ir present in the cathode canbe used to estimate anode catalyst stability, thus accelerating catalystdevelopment and operational parameters optimization.