(510b) Stabilizing Active Motifs of Iridium Oxide for the Oxygen Evolution Reaction through Secondary Cation Tuning

Electrocatalyst materials undergo extreme transformations upon exposure to reaction conditions, thereby creating unique and often poorly defined interfacial structures. Improved understanding of catalyst dynamics for the oxygen evolution reaction (OER) in acid is critical for informing the development of highly efficient, stable, and cost-effective OER catalysts for proton exchange membrane water electrolysis (PEMWE) applications. In this work we leverage the incorporation and controlled dissolution of secondary cations in complex iridium oxide catalysts to tune the electronic structure, coordination, and stability of iridium active sites which directly impacts the resulting activity and stability performance of these materials. Insightful trends are presented using a highly tunable, active, and dynamic set of Ir 5+ materials, Ln₃IrO₇ (Ln = Pr, Nd, Sm, and Eu). A combination of in situ and ex situ characterization, as well as advanced electrochemical methods for Ir surface site quantification, reveals that maintaining excellent OER activity throughout performance testing is correlated to a catalysts’ ability to preserve a high degree of Ir enrichment, with heightened stability of Ir sites and reduced stability of Ln sites throughout testing. Finally, we draw comparisons to a paracrystalline iridium oxide material that has been formed via complete, controlled leaching of its secondary cation to reveal short-range order active motifs that contribute most to activity and stability of these ubiquitously restructured iridium oxide catalysts used for OER. This talk will provide novel insights that elucidate and characterize key processes involved in the evolution of dynamic catalysts and seek to inform future work leveraging the incredible activity of dynamic Ir-based materials for the OER in acidic conditions.