Recent research indicates a severe discrepancy between oxygen evolution reaction catalysts dissolution in aqueous model systems and membrane electrode assemblies. This questions the relevance of the widespread aqueous testing for real world application. In this study, we aim to determine the processes responsible for the dissolution discrepancy. Experimental parameters known to diverge in both systems are individually tested for their influence on dissolution of an Ir-based catalyst. Ir dissolution is studied in an aqueous model system, a scanning flow cell coupled to an inductively coupled plasma mass spectrometer. Real dissolution rates of the Ir OER catalyst in membrane electrode assemblies are measured with a specifically developed, dedicated setup. Overestimated acidity in the anode catalyst layer and stabilization over time in real devices are proposed as main contributors to the dissolution discrepancy. The results shown here lead to clear guidelines for anode electrocatalyst testing parameters to resemble realistic electrolyzer operating conditions.

Pt dissolution has already been intensively studied in aqueous model systems and many mechanistic insights have been gained. Nevertheless,t ransfer of new knowledge to realworld fuel cell systems is still as ignificant challenge.T oc lose this gap,w ep resent an ovel in situ method combining ag as diffusion electrode (GDE) half-cell with inductively coupled plasma mass spectrometry (ICP-MS). With this setup,P t dissolution in realistic catalyst layers and the transport of dissolved Pt species through Nafion membranes were evaluated directly.W eo bserved that 1) specific Pt dissolution increased significantly with decreasing Pt loading, 2) in comparison to experiments on aqueous model systems with flowc ells,t he measured dissolution in GDE experiments was considerably lower,a nd 3) by adding am embrane onto the catalyst layer,Ptdissolution was reduced even further.All these phenomena are attributed to the varying mass transport conditions of dissolved Pt species,i nfluencing re-deposition and equilibrium potential.