Tracing Iridium Dissolution Pathways in Proton Exchange Membrane Water Electrolyzers at Relevant Current Densities in Real Time

Catalyst dissolution is one of the key challenges in achieving long-term performance in proton exchange membrane water electrolysis with low iridium loading. However, most of the dissolved catalyst remains in the catalyst-coated membrane, inaccessible for operando quantification. While simpler aqueous model systems improve mechanistic understanding, dissolution rates are significantly overestimated compared to the device level. To bridge this gap, herein, an electrochemical half-cell setup that mimics the anode catalyst layer environment to enable operation at relevant current densities (>1 $$) is presented. Dissolved catalyst species transported through the porous transport layer or through the membrane are separately detected operando by coupling to inductively coupled plasma-mass spectrometry. The results demonstrate a strong preference for the transport of dissolved iridium through the membrane (99.9%) and a decrease in catalyst stability by factor 10 at high current densities. Discrepancies with so far reported findings from full-cell and half-cell experiments highlight a lack of understanding of catalyst dissolution and the transportation of dissolved species in different systems. The presented method offers unique insights which will help to study and optimize catalyst dissolution by means of various manufacturing and operation parameters to ultimately improve the stability of catalyst layers for water electrolysis.