Solving the Limitation in the Slow Synthesis Method to Minimize Reaction Time Differences for Synthesizing Au_xOs_1-x...

The syntheses of solid-solution alloys consisting of elements with large redox-potential differences remain significant challenges. In this work, by a slow synthesis method, we precisely controlled the reduction, nucleation, and growth processes of Au and Os and successfully synthesized homogeneous Au_xOs_1-x solid-solution NPs for the first time, which cannot mix with each other over most composition ranges up to 3000 °C. The reaction-area confinement effect in the spray method was proved to be favorable for preventing Au phase segregation. In NO_x reduction tests, Au_0.1Os_0.9 NPs showed much higher activity with a temperature at 50% conversion (T₅₀) of 239 °C than the state-of-the-art monometallic Rh catalysts (T₅₀ of 267 °C). Based on in situ Fourier transform infrared measurements and density functional theory calculations, the modifications of Os electronic states via Au alloying significantly enhanced CO and NO activation at Os sites, leading to the excellent NO_x reduction catalytic activities for Au_xOs_1-x solid-solution NPs.