Denary High-Entropy Oxide Nanoparticles Synthesized by a Continuous Supercritical Hydrothermal Flow Process.

Area of Science:

• Materials Science
• Nanotechnology
• Catalysis

Background:

• High-entropy oxide nanoparticles (HEO NPs) are recognized for their exceptional stability and catalytic performance.
• Traditional synthesis methods for HEO NPs often require high temperatures and lengthy processes, limiting their scalability and application.

Purpose of the Study:

• To develop a novel, rapid, and low-temperature synthesis method for denary high-entropy oxide nanoparticles (HEO NPs).
• To characterize the structure and elemental composition of the synthesized HEO NPs.
• To evaluate the catalytic activity of the HEO NPs in CO oxidation.

Main Methods:

• Synthesis of denary HEO NPs using a continuous supercritical hydrothermal flow process.
• Characterization using atomic-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).
• Elemental analysis via energy-dispersive X-ray spectroscopy (EDS).

Main Results:

• Successfully synthesized denary HEO NPs containing 10 metal elements (La, Ca, Sr, Ba, Fe, Mn, Co, Ru, Pd, Ir) with a perovskite-type structure.
• The continuous supercritical hydrothermal flow process enabled rapid NP formation (seconds) at a relatively lower temperature without calcination.
• HAADF-STEM and EDS confirmed the homogeneous dispersion of all 10 metal elements within the nanoparticles.
• The synthesized HEO NPs exhibited significantly higher catalytic activity for CO oxidation compared to LaFeO₃ NPs.

Conclusions:

• The continuous supercritical hydrothermal flow process is a highly efficient method for synthesizing complex denary HEO NPs.
• The resulting HEO NPs possess a unique composition and structure, leading to enhanced catalytic properties.
• This advancement opens new avenues for the development of advanced catalytic materials.