biostudies-literatureUnknownTan LProton exchange membrane water electrolysis (PEMWE) is a cornerstone technology for carbon-neutral hydrogen production, yet its scalability is constrained by the intrinsic activity-stability trade-off of oxygen evolution reaction (OER) electrocatalysts. To overcome this challenge, we design a Ru/RuO<sub>2</sub> heterostructure by integrating metallic Ru to modulate the d-orbital electron density of RuO<sub>2</sub>. The metallic Ru domains suppress lattice oxygen migration (LOM) while enhancing electron delocalization. The e<sub>g</sub> orbital filling shifts the Ru 4d-band center downward, reducing the adsorption strength of reaction intermediates (*OH, *O, and *OOH). The optimized Ru/RuO<sub>2</sub> electrocatalyst achieves an overpotential of 181 mV at 10 mA cm<sup>-2</sup> in 0.5 M H<suChemical sciencehttps://www.ebi.ac.uk/biostudies/studies/S-EPMC12822733biostudies-literatureDopant-free stabilization of ruthenium oxide <i>via</i> metallic Ru-induced d-orbital modulation for acidic water electrolysis.PMC12822733Tan LTian JSu TLi XLin CZhu LFaiza MLuo WZhang QXu JWu XSong YfalseDopant-free stabilization of ruthenium oxide <i>via</i> metallic Ru-induced d-orbital modulation for acidic water electrolysis.Proton exchange membrane water electrolysis (PEMWE) is a cornerstone technology for carbon-neutral hydrogen production, yet its scalability is constrained by the intrinsic activity-stability trade-off of oxygen evolution reaction (OER) electrocatalysts. To overcome this challenge, we design a Ru/RuO<sub>2</sub> heterostructure by integrating metallic Ru to modulate the d-orbital electron density of RuO<sub>2</sub>. The metallic Ru domains suppress lattice oxygen migration (LOM) while enhancing electron delocalization. The e<sub>g</sub> orbital filling shifts the Ru 4d-band center downward, reducing the adsorption strength of reaction intermediates (*OH, *O, and *OOH). The optimized Ru/RuO<sub>2</sub> electrocatalyst achieves an overpotential of 181 mV at 10 mA cm<sup>-2</sup> in 0.5 M H<su2026-01-01T00:00:00Z2026 Jan2026-06-06T21:36:28.895Z2026-06-05T03:11:24.738ZS-EPMC128227334157312010.1039/d5sc08602g