Iridium Oxygen Evolution Activity and Durability Baselines in Rotating Disk Electrode Half-Cells

This paper evaluates iridium (Ir) and Ir oxide nanoparticles for baseline oxygen evolution performance and durability in rotating disk electrode (RDE) half-cells. These efforts address a literature gap, developing best practices for RDE testing by focusing on ink preparation and test protocols that affect measured activities. While Ir nanoparticles produce double the mass activity of Ir oxide in half-cells, the benefit is not observed in single-cells due to near-surface oxidation during conditioning. Ir oxide nanoparticle durability, however, is improved in both RDE and membrane electrode assemblies (MEAs) due to slower dissolution kinetics. Establishing separate Ir and Ir oxide baselines are critical since RDE may overestimate Ir performance and underestimate Ir durability when compared to Ir oxide in MEAs. While half-cells may be a reasonable gauge for oxygen evolution performance, the technique is limited in approximating long-term durability since dissolution dominates loss at electrolysis-relevant potentials. (C) The Author(s) 2019. Published by ECS.