Self-Coordinating Electronic Metal-Support Interaction Stabilizes Ultralow-Loading Ir Single Atoms for Durable Acidic Oxygen Evolution.

Engineering electronic metal-support interactions (EMSI) enables scalable proton exchange membrane water electrolysis (PEMWE) at ultralow Ir loadings by buffering Ir against overoxidation and dissolution under acidic oxygen evolution conditions (OER). However, a seemingly disparate interpretation has persisted: high-valent Ir is often associated with optimal intermediate adsorption, whereas low-valent Ir correlates with improved corrosion resistance, suggesting that static EMSI fails to rationalize the activity-stability trade-off. Here, we construct an atomically dispersed Ir-O-Co interface by anchoring isolated Ir single atoms on spinel Co3O4, providing a new perspective on a dynamic charge-compensation mechanism: at low bias, the Ir site is progressively oxidized to enhance water activation and intermediate turnover; at high bias, the Co3O4 compensates charge back to the Ir site, thereby suppressing overoxidation-driven dissolution. Such self-coordinating EMSI breaks the conventional activity-stability trade-off in acidic OER. In an integrated PEM electrolyzer, the Ir single-atom catalyst sustains operation for >1500 h at 1.0 A cm-2 with an ultralow Ir loading of 0.1 mg cm-2, highlighting the importance of self-coordinating EMSI for durable, precious-metal-minimized PEMWE anodes.