Dual-Scale Electronic Regulation via Ru–O–Fe Coupling Enables Decoupling of Activity and Stability in Acidic Oxygen Evolution

Abstract Ruthenium-based catalysts are promising alternatives to iridium for proton exchange membrane water electrolysis (PEMWE), yet their practical application is limited by the intrinsic trade-off between high activity and poor stability in acidic oxygen evolution reaction (OER). Here, we report a RuFeOx superstructure that establishes a dual-scale electronic regulation framework to overcome this limitation. The Fe 2 O 3 @RuO 2 core–shell architecture introduces two synergistic Ru–O–Fe coupling motifs with distinct but hierarchical roles. At the heterointerface, energy-level alignment enables continuous electron donation from Fe to Ru, suppressing excessive oxidation of Ru active sites. Within the RuO 2 lattice, the coupling motif induces orbital redistribution by increasing the filling of the Ru d z ² orbital, which weakens Ru–O covalency, optimizes oxygen adsorption energetics, and promotes direct O–O coupling with reduced lattice oxygen participation. As a result, the catalyst simultaneously achieves high activity and durability, delivering an overpotential of 208 mV at 10 mA cm − 2 in 0.5 M H 2 SO 4 and stable operation for over 300 h. In a PEM water electrolyzer, it enables continuous operation at 1 A cm − 2 for 200 h with a low Ru loading of 0.85 mg cm − 2 . Combined experimental and theoretical analyses reveal that interfacial charge transfer and lattice-confined orbital modulation operate in a hierarchical manner to govern catalytic behavior across multiple scales. This work provides a generalizable strategy for decoupling activity and stability through multi-scale electronic regulation in acidic OER catalysis.