Molybdenum‐Enriched Mo 0.5 Ru 0.5 O 2 Nanoparticles for Efficient and Stable Oxygen Evolution Reaction

Abstract Ruthenium dioxide (RuO 2 ) 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 0.5 Ru 0.5 O 2 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 ≈10 4 °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 0.5 Ru 0.5 O 2 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 RuO 2 and other reported high‐metal‐content doped RuO 2 catalysts. High‐valence Mo, with its multiple accessible oxidation states and compatible ionic radius, serves as an ideal dopant for RuO 2 , 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 RuO 2 systems toward cost‐effective and stable OER catalysts.