Amorphous ZrO x ‐Mediated *OH Enrichment Enables Dynamic Oxygen Replenishment for Stable Acidic Water Oxidation

While triggering the lattice oxygen mechanism (LOM) represents an efficient approach to enhancing the intrinsic activity of iridium‐based catalysts for proton exchange membrane water electrolysis (PEMWE), the irreversible lattice oxygen loss and subsequent Ir dissolution induce structural collapse, constituting the fundamental activity‐stability trade‐off. To address this challenge, we propose an amorphous support‐mediated *OH enrichment strategy that dynamically replenishes oxygen vacancies (O v ) to stabilize and optimize the LOM pathway. This concept is exemplified by engineering IrO x nanoparticles supported on amorphous zirconia (ZrO x ). In addition to anchoring Ir sites and mitigating their over‐oxidation‐induced dissolution, the ZrO x support efficiently facilitates water dissociation, leading to the in situ accumulation of reactive *OH intermediates. This enrichment process dynamically replenishes the O v generated during the oxygen evolution reaction (OER), thereby accelerating the LOM rate‐determining step and simultaneously preserving the catalyst's structural integrity and boosting the intrinsic activity, as evidenced by in situ spectroscopic analysis and theoretical calculations. In PEMWE tests, the catalyst achieves a low voltage of 1.75 V at 2 A cm −2 and demonstrates stable operation for 1000 h. This work establishes a new design principle for developing highly efficient and durable Ir‐based OER catalysts for PEMWE applications.