Stabilizing Ru Atomic Clusters and Activating Interfacial Water Structure via Bridged p-Block In-N₃O₁ Single Sites...

Ru atomic clusters (AC) are promising cost-effective platinum-group-metal anode catalysts for the alkaline hydrogen oxidation reaction (HOR) in anion-exchange-membrane fuel cells (AEMFCs), yet their practical application remains limited by insufficient structural robustness and sluggish proton transport across the electrolyte/electrode interface. Herein, we report a design concept that leverages p-block indium single atoms with In-N₃O₁ coordination as electronic bridges to stabilize Ru AC and reconstruct a proton-conductive interfacial hydrogen-bond network for efficient and durable HOR catalysis in practical AEMFCs. We find that the bridged In-N₃O₁ sites establish strong covalent Ru-In anchoring interactions through pronounced d-p orbital hybridization, stabilizing Ru AC against coalescence and detachment for markedly improved operational durability. Meanwhile, electronic coupling between Ru AC and bridged In-N₃O₁ sites tunes surface oxophilicity of Ru to promote higher coverage of hydroxyl adsorbate species and drive dynamic reorientation of interfacial water from cation-bound states toward free water in the gap region, thereby reinforcing hydrogen-bond connectivity and enabling more efficient interfacial proton transport. The resulting Ru AC/In₁@CNO delivers a mass activity of 7.17 A mg_Ru ^-1, surpassing Pt/C by 9.0-fold. Particularly, Ru AC/In₁@CNO-based AEMFCs achieve a high peak power density of 1.33 W cm^-2 and maintain stable operation for over 50 h at 500 mA cm^-2.