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

Abstract

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.

The low overpotential regime of acidic water oxidation part II: trends in metal and oxygen stability numbers

“…Samples were tested at constant current in the chip EC-MS setup modified to collect electrolyte samples for ICP-MS measurements of metal dissolution before post-reaction LEIS characterization. The dissolution of OER catalysts is known to be dependent on the flow characteristics of the setup 32 – in this regard, the stagnant thin layer of electrolyte in the EC-MS setup resembles more the environment experienced by an OER catalyst in a PEMEC than do most aqueous model systems.…”

On the Durability of Iridium‐Based Electrocatalysts toward the Oxygen Evolution Reaction under Acid Environment

“…Reproduced under the terms of the Creative Commons CC BY license. [ 60 ] Copyright 2021, The Authors, published by Springer Nature.…”

“…Later, Cherevko and co‐workers studied the dissolution of Ir‐based electrocatalysts using both aqueous electrochemical cells (AECs) and membrane electrode assemblies (MEAs) to explore the limitations of using the AEC model for evaluating the durability of OER electrocatalysts. [ 60 ] They compared the S‐number of IrO x electrocatalysts working under different conditions, and the results demonstrated that IrO x possesses a much larger S‐number under MEA conditions as compared with AECs (Figure 4c). Further, by varying the catalyst loading, the flow rates in SFCs, the concentration of dissolved Ir species, the Nafion content, and the pH of the working electrolyte, the authors discovered two major reasons for such differences.…”

“…The red dashed line indicates the S-number of the AMS system (0.1 m H 2 SO 4). Reproduced under the terms of the Creative Commons CC BY license [60]. Copyright 2021, The Authors, published by Springer Nature.…”

Corrosion-resistant and high-entropic non-noble metal bifunctional electrodes for PEM-type water electrolyser

“…the reaction environment (ex. severe oxidation conditions under a high operation voltage) wherein even noble metals can be dissolved (1.5 ng cm -2 h -1 dissolution rate for Pt and 0.1 ng cm -2 h -1 dissolution rate for Ir) 12,13 . Thus, a key challenge is to develop highly corrosionresistant non-noble metal electrodes with the performance comparable to noble metal electrodes.…”