Understanding the dynamic structural and chemical evolutions at the catalyst–electrolyte interfaces is crucial for the development of active and stable electrocatalysts. In this work, β-Li₂IrO₃ is employed as a model catalyst for the oxygen evolution reaction (OER). Its elastic three-dimensional Ir-O framework enables us to investigate the Li⁺ cation dissolution-induced structure evolutions and the formation mechanism of amorphous IrO_x species. Electrochemical measurements by rotating ring disk electrode (RRDE) reveal that up to 60% of the measured OER current can be ascribed to catalyst degradation. A series of in-situ X-ray diffraction spectroscopy (XRD), X-ray absorption spectroscopy (XAS), and Raman spectroscopy are conducted. Structure vibration is observed with oxidation states of Ir being reduced abnormally during OER at high potentials. It’s hypothesized that the reversible proton intercalations are responsible for the Ir turn-over mechanism. Results of this work demonstrate a stable and elastic iridate structure and reveal the initial catalyst degradation behaviors during OER in acid media.