Molybdenum‐Enriched Mo _0.5 Ru _0.5 O ₂ Nanoparticles for Efficient and Stable Oxygen Evolution Reaction

Ruthenium dioxide (RuO₂) shows excellent activity toward the acidic oxygen evolution reaction (OER); however, its practical application is limited by poor long-term stability. Herein, a single-phase Mo_0.5Ru_0.5O₂ nanoparticle catalyst is reported with a high Mo content, synthesized via high-temperature thermal shock treatment under an oxygen atmosphere (HTSO), exhibiting high activity and stability in OER. The HTSO technique involves rapidly heating the precursor to ≈1200 °C for ≈0.05 s in oxygen, followed by immediate quenching at a rate of ≈10⁴ °C s^-1. The resulting nanoparticles exhibit a uniform size of ≈10 nm and homogeneous elemental mixing, overcoming the thermodynamic barriers that typically lead to phase separation in conventional synthesis methods. The Mo_0.5Ru_0.5O₂ catalyst achieves an overpotential of 210 mV at 10 mA cm^-2 and maintains stable performance over 300 h at 50 mA cm^-2 in OER, significantly surpassing the stability of RuO₂ and other reported high-metal-content doped RuO₂ catalysts. High-valence Mo, with its multiple accessible oxidation states and compatible ionic radius, serves as an ideal dopant for RuO₂, enabling stable lattice substitution, effective electron donation, and ultimately suppressing Ru over-oxidation while enhancing stability. This approach enhances catalyst stability and Ru utilization, providing a versatile platform for synthesizing other metal-doped RuO₂ systems toward cost-effective and stable OER catalysts.