Role of MoO_x Surficial Modification in Enhancing the OER Performance of Ru-Pyrochlore

Pyrochlore ruthenate (Y₂ Ru₂ 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 Y₂ Ru₂ O_7-δ is required to overcome its electrochemical inertness. Herein, a surface manipulation strategy involving implanting MoO_x moieties on nano Y₂ Ru₂ 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 [RuO₆ ] to MoO_x . This eliminates the bandgap by inducing Ru 4d delocalization and band alignment rearrangement. The MoO_x modifiers also alleviate distortion of [RuO₆ ] 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.