Tailoring electron-rich Ru/Mo-RuO₂ heterointerface triggers ultrastable proton-inert oxygen evolution reaction

Water electrolysis is prospected to integrate the electricity harvested from renewable energy sources for clean hydrogen production. However, Ir/Ru-based benchmark catalysts are high-cost and subject to serious inactivation in harsh environments for oxygen evolution reaction (OER). Herein, we proposed a delicate Mo-doped Ru/RuO₂ heterojunction catalyst (denoted as Ru/Mo-RuO₂) using a cost-effective hydrothermal-calcination strategy. The Ru/RuO₂ hetero-interface promotes charge transfer and accelerates the reaction kinetics, while the doped Mo atoms optimize the unstable pristine RuO₂ crystalline, inhibiting the reaction over-oxidation. Consequently, the Ru/Mo-RuO₂ nanocomposites demonstrate excellent OER catalytic activity in alkaline and acidic environments, yielding ultra-low overpotentials of 212 mV and 218 mV to reach 10 mA cm⁻², as well as excellent non-degradation operation for 200 h and 100 h in 1.0 M KOH and 0.5 M H₂SO₄ electrolytes, respectively. Density functional theory calculations disclose that architecting the Ru/RuO₂ heterostructure with Mo dopants can regulate the electronic structure of the Ru active sites, tune the adsorption/desorption energies of O-related intermediates, and reduce the kinetic barriers. Moreover, Mo-doping contributes to forming electron-abundant Ru species in RuO₂ and critically strengthens the Ru–O bonding to confer proton-inert character, effectively suppressing demetallation-driven collapse. This work provides a paradigm for designing acid/alkali-durable OER catalysts via electronic hetero-dopant/interface engineering. © 2025 The Authors