The Effect of Material Properties on Oxygen Evolution Activity and Assessing Half-Cell Screening as a Predictive Tool in Electrolysis

Iridium-based oxygen evolution catalysts are screened in this study for activity and stability in rotating disk electrode (RDE) half-cells. Characterization is completed with no knowledge of composition or synthesis conditions. Study findings focus on the RDE methodologies and data interpretation, detailing the difficulties of comparing catalysts across materials sets with different elemental and oxide compositions, and the difficulties of linking RDE activity to device-level performance. At the surface, the catalysts are a mixture of oxides and metals, and several methods are used to quantify metal content, qualitatively assess oxide content, and determine surface area. Oxygen evolution activities are further compared kinetically, and stability assessed with a 2 V potential hold, where a wide range of results are reported. In general, higher RDE performances are found for catalysts that contained larger amounts of ruthenium and metals. Higher durability, however, is found for catalysts that only contained iridium and a higher proportion of oxides. Additionally, catalysts are evaluated for performance in membrane electrode assemblies to assess RDE as a predictive tool in electrolysis. While activity trends within individual material sets generally held between ex- and in-situ testing, RDE tends to overestimate the activity of more metallic catalysts when compared to device-level performance.