Role of MoOx Surficial Modification in Enhancing the OER Performance of Ru–Pyrochlore

Abstract Pyrochlore ruthenate (Y 2 Ru 2 O 7–δ ) is highlighted as a promising oxygen evolution reaction (OER) catalyst for water splitting in polymer electrolyte membrane electrolyzers. However, an efficient electronic modulation strategy for Y 2 Ru 2 O 7–δ is required to overcome its electrochemical inertness. Herein, a surface manipulation strategy involving implanting MoO x moieties on nano Y 2 Ru 2 O 7–δ (Mo–YRO) using wet chemical peroxone method is demonstrated. In contrast to electronic structure regulation by intramolecular charge transfer (i.e., substitutional strategies), the heterogeneous Mo−O−Ru micro‐interfaces facilitate efficient intermolecular electron transfer from [RuO 6 ] to MoO x . This eliminates the bandgap by inducing Ru 4 d delocalization and band alignment rearrangement. The MoO x modifiers also alleviate distortion of [RuO 6 ] by shortening Ru−O bond and enlarging Ru−O−Ru bond angle. This electronic and geometric structure tailoring enhances the OER performance, showing a small overpotential of 240 mV at 10 mA cm −2 . Moreover, the electron‐accepting MoO x moieties provide more electronegative surfaces, which serve as a protective “fence” to inhibit the dissolution of metal ions, thereby stabilizing the electrochemical activity. This study offers fresh insights into the design of new‐based pyrochlore electrocatalysts, and also highlights the versatility of surface engineering as a way of optimizing electronic structure and catalytic performance of other related materials.