Strategic Modulation of *OH Characteristics via Metal‐Support Interactions and Charge Gradient in RuMo@RuMoOx for Enhanced Water Oxidation

Tailoring the characteristics of hydroxyl intermediates ( * OH) on Ru‐based catalysts is vital for modulating catalytic pathways and optimizing their performance for water oxidation (OER); however, their modulation mechanisms and roles remain a significant challenge. Here, a strategy is proposed to regulate the * OH adsorption behavior of Ru‐based catalysts by designing RuMo@RuMoO x electrocatalysts with strong metal‐support interactions and built‐in charge gradients. Quasi‐in‐situ/operando characterization and theoretical calculations reveal that this design effectively promotes the adsorption of * OH at Ru sites, optimizes the orientation of * OH, and facilitates * OH spillover to the adjacent Mo sites via charge gradients between the Ru and Mo sites. This process initiates a hydroxyl migration‐coupled mechanism (HMCM), which breaks the * OH‐ * OOH scaling relation, alters the rate‐determining step (RDS), and stabilizes OER intermediates, thereby boosting the OER performance. The RuMo@RuMoO x catalyst exhibits low overpotentials of 166, 200, and 199 mV in 0.5 M H 2 SO 4 , 1 M KOH, and 1 M PBS, respectively, at 10 mA cm −2 , along with an outstanding stability of over 1000 h of operation. Furthermore, the RuMo@RuMoO x catalyst demonstrates a lower overpotential than RuO 2 and maintains stable operation for over 1000 h in a PEM water electrolyzer at 1 A cm −2 .