Atomic-scale elucidation of formation and structure in high-performance Re-Ge nanocatalysts

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Rational design of high-performance bimetallic nanocatalysts is crucial.
• Understanding the atomic structures governing catalyst performance is essential.
• The Re-Ge/TiO2 catalyst shows high performance for carboxylic acid hydrogenation.

Purpose of the Study:

• To analyze structural and electronic state changes during the preparation of Re-Ge/TiO2.
• To elucidate key structural factors responsible for the catalyst's high performance.
• To establish a correlative methodology for identifying performance-determining factors in nanomaterials.

Main Methods:

• Complementary approach combining in situ X-ray absorption fine structure (XAFS) analysis and ex situ scanning transmission electron microscopy (STEM).
• STEM measurements utilized an air-free transfer holder to track individual nanoparticles throughout preparation.
• Density functional theory (DFT) calculations verified the nanoparticle crystal structure.

Main Results:

• The highly active catalytic state is associated with approximately 1 nm crystalline Re-Ge alloy nanoparticles.
• The nanoparticle crystal structure is a unique, low-energy, face-centered cubic fragment.
• Quantitative STEM analysis demonstrated a Re-Ge random alloy, stabilizing the metallic Re(0) state and making Re electron-rich.

Conclusions:

• Atomic-level mixing in Re-Ge random alloy nanoparticles stabilizes the metallic Re(0) state, enhancing catalytic activity.
• A unique, low-energy, face-centered cubic fragment structure of 1 nm Re-Ge alloy nanoparticles is responsible for high performance.
• The findings offer a new strategy for designing high-performance nanocatalysts and establish a valuable correlative methodology.