CCE Special Seminar

Iridium oxide is the state-of-the-art electrocatalyst for water oxidation in acidic environments. Although it is widely used in proton exchange membrane (PEM) electrolyzers for green hydrogen production, the mechanisms of water oxidation on iridium oxide—particularly how different oxidizing species influence this process—are not well understood.

In this talk, I will discuss our recent work using time-resolved optical and X-ray spectroscopies to probe both high-valence metal oxidizing species and oxygenated species on iridium-based catalysts. We have quantified these species as functions of both potential and time, and have assessed their energetics. We found that the densities and energetics of the oxygenated species control the intrinsic reaction kinetics of water oxidation. Building on these insights, I will compare two common structures of iridium oxide—amorphous IrOx and crystalline rutile IrO2—to understand how their different catalytic activities are influenced by these mechanisms. The effect of the electrolyte pH on tunning the energetics of oxygenated species, and thus on tuning the intrinsic kinetics of water oxidations will also be discussed.

Finally, I will present a new volcano-type model that explains the activity of various water oxidation catalysts. This model incorporates the effects of adsorbate-adsorbate interactions on the energetics of oxygenated species, unveiling essential design principles for enhancing catalytic activity.