Engineering ionic Ru–F bonds in amorphous RuO₂ nanosheets for enhanced alkaline hydrogen electrocatalysis

Overcoming the mismatched adsorption energies is critical for efficient alkaline hydrogen electrocatalysis, yet modulating the strong Ru–O covalency without compromising structural integrity remains a key challenge. Herein, we address this by introducing ionic Ru–F bonds into selected regions of RuO₂ via tailored chemical bond engineering for enhanced hydrogen evolution and oxidation reactions (HER/HOR). Using fluorine-doped amorphous RuO₂ (F-RuO₂) nanosheets as a model catalyst, we find that electrons around fluorine atoms can become highly localized, forming ionic-character Ru–F bonds. This design results in a low HER overpotential of 32 mV at 100 mA cm⁻² and delivers a high HOR diffusion-limiting current density of 2.98 mA cm⁻², positioning F-RuO₂ among the best-performing Ru-based electrocatalysts yet reported. Moreover, the anion-exchange-membrane water electrolyzer with F-RuO₂ can maintain a cell voltage of 1.60 V at 100 mA cm⁻² for over 300 h with negligible degradation. In-situ spectroscopic analysis and density functional theory calculations reveal that the formed Ru–F bonds weaken Ru–O covalency and moderately lower the Ru oxidation states, optimizing hydrogen-intermediate adsorption toward the ideal range and enhancing both HER and HOR electrocatalysis. This work offers fundamental insights into covalent-bond modulation in amorphous oxides and establishes a generalizable design paradigm for high-performance electrocatalysts in sustainable energy conversion.