Tailoring Oxygen Evolution Reaction Pathway in Layered Perovskite Oxide via Defect Engineering

Regulating the electrocatalytic pathway is an efficient strategy to enhance oxygen evolution reaction (OER) activity. The lattice-oxygen-mediated mechanism (LOM) offers superior performance to the adsorbate evolution mechanism (AEM) by circumventing scaling relationships. Nevertheless, precise control over the reaction pathway remains challenging. Herein, we demonstrate that precise regulation of oxygen vacancy concentration alone can directly dictate the OER pathway. Highly textured Ruddlesden–Popper-phase La 1.5 Sr 0.5 CoO 4−δ (LSC) thin films, with controllable oxygen vacancies introduced via Ar + ion irradiation, are taken as a model system. The film with moderate vacancy concentration exhibits dramatically enhanced OER activity, achieving a turnover frequency of 1.154 s –1 at 0.5 V overpotential, a 17-fold increase over pristine LSC. This enhancement is driven by a weakened metal–oxygen bond, reduced vacancy formation energy, and optimized *OH adsorption, which collectively promote a shift from the AEM to the LOM pathway. Conversely, excessive vacancies induce a reversion to the less active AEM. This work provides critical insight into the determining role of oxygen vacancy for governing both the intrinsic activity and the operative reaction pathway, providing a design principle for advanced electrocatalysts in energy and environmental applications.