Stabilizing RuO ₂ in Acidic Oxygen Evolution via Controlled Lattice Oxygen Hydroxylation

RuO2 is one of the most active electrocatalysts for the acidic oxygen evolution reaction (OER), yet its poor structural stability severely restricts long-term operation in water electrolysis technique. Herein, we report a simple yet highly effective hydroxylation strategy that fundamentally enhances the stability of RuO2 through controlled lattice oxygen hydroxylation. Comprehensive in situ/ex-situ spectroscopic characterizations reveal that lattice oxygen remains largely inert during the OER, while hydroxyl incorporation predominantly regulates the Ru active centers. An optimal hydroxyl concentration yields increase in durability from 21 to 1200 h, forming a volcano-type dependence between hydroxyl content and stability. Theoretical simulations unveil that hydrogen incorporation disrupts the Ru-O octahedral symmetry and broadens the Ru eg orbital, strengthening electron back-donation and mitigating Ru oxidation-state fluctuations during the OER. Excessive hydroxylation, however, destabilizes the lattice by facilitating Ru dissolution. This work establishes hydroxylation as a facile electronic-structure modulation strategy to stabilize Ru-based catalysts, providing mechanistic insights and design principles for durable acidic OER catalysts.