Tailoring Pyrochlore Electrocatalyst via Bias‐Induced Enhancement for Acidic Oxygen Evolution

Abstract Proton exchange membrane water electrolysis offers a promising pathway for green hydrogen production. However, its practical application is hindered by the sluggish oxygen evolution reaction (OER). Here, the findings in bias‐induced enhancement in a ruthenium‐based pyrochlore oxide (Y₂Ru₂O₇) model electrocatalyst are demonstrated. Applying a negative bias generates oxygen vacancies, which induce slight lattice distortions and enrich surface oxygen species. These modifications ultimately result in significantly enhanced OER activity. Density functional theory calculations reveal that these oxygen vacancies drive a transition from the adsorbate evolution mechanism to the oxide path mechanism (OPM). The vacancies regulate charge transfer within Ru‒O bonds, shorten the distance between neighboring *O species, and promote the *O‒*O coupling, thereby optimizing the adsorption energies associated with the OPM. Furthermore, the stabilization of the bias‐induced oxygen‐vacancy‐rich structure is further achieved by Na doping at the Y‐site, which improves OER durability. The optimized catalyst, Y_1.85Na_0.15Ru₂O_7‒δ after electrochemical reduction, exhibits a low overpotential of 220 mV at 10 mA cm⁻², and reaches a stable durability for 250 h. This bias‐driven oxygen vacancy engineering strategy provides an effective approach for achieving highly efficient OER in acidic environments. This work highlights the potential of dynamic defect formation for designing high‐performance catalysts.