Direct Observation of Collective Dissolution Mechanisms in Iridium Oxide Nanocrystals

Iridium oxide (IrO 2 ) is the state-of-the-art electrocatalyst for water oxidation in electrolyzers, yet it suffers from instability under operating conditions. Here, we combine first-principles modeling with in situ liquid-phase transmission electron microscopy and device-scale characterization to resolve the atomic-scale morphology and dissolution dynamics of IrO 2 nanocrystals. Our computational Wulff constructions uniquely incorporate high-index facets, providing new insights into thermodynamic facet-dependent stability under operating conditions. Atomically resolved studies reveal multiple distinct collective dissolution pathways, including high-index facet formation, monolayer reconstruction, step-edge formation, and monolayer delamination on {110} surfaces. Device-scale studies confirm that electrochemical operation results in high-index facet formation. Ab initio molecular dynamics simulations further show that initial dissolution kinetics are facet-dependent. These findings highlight how combining in situ imaging with first-principles modeling reveals atomic-scale dynamics that influence material performance.