Dopant-free stabilization of ruthenium oxide via metallic Ru-induced d-orbital modulation for acidic water electrolysis

Abstract

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/RuO₂ heterostructure by integrating metallic Ru to modulate the d-orbital electron density of RuO₂. The metallic Ru domains suppress lattice oxygen migration (LOM) while enhancing electron delocalization. The e_g orbital filling shifts the Ru 4d-band center downward, reducing the adsorption strength of reaction intermediates (*OH, *O, and *OOH). The optimized Ru/RuO₂ electrocatalyst achieves an overpotential of 181 mV at 10 mA cm⁻² in 0.5 M H₂SO₄ and exhibits stable performance for 260 hours with minimal degradation rate (0.065 mV h⁻¹). In the PEMWE device, it lowers the cell voltage from 1.88 V (RuO₂) to 1.68 V (Ru/RuO₂) at 1 A cm⁻², exhibiting negligible performance loss over 120 hours. This work introduces a dopant-free electronic engineering strategy that advances the design of stable, high performance pure Ru-based anodic catalysts for energy conversion technologies.