On the limitations in assessing stability of oxygen evolution catalysts using aqueous model electrochemical cells

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. Dissolution of Ir catalysts varies widely between PEM water electrolysers and aqueous electrolytes. Here, we systematically investigate this finding and propose that stabilization of the catalysts over time and overestimated ionomer acidity are the main contributors to the dissolution discrepancy.

Automated summary

Recent research shows a severe difference in the dissolution of oxygen evolution reaction catalysts in aqueous model systems and membrane electrode assemblies. The main contributors to this dissolution discrepancy are identified as the overestimated acidity in the anode catalyst layer and the stabilization of catalysts over time in real devices.