Structural Disorder Reveals New Insights into Nanocatalyst Behavior

Researchers from Skolkovo Institute of Science and Technology (Skoltech) and Khakassian State University have uncovered how structural changes in iridium and palladium nanoparticles—specifically the transition to an amorphous state—impact their catalytic behavior. The study, led by Professor Alexander Kvashnin, a Doctor of Sciences in Physics and Mathematics, was recently published in the Journal of Catalysis and provides new perspectives on the catalytic potential of these nanostructures.

The research focuses on how slight degradation and structural disorder can alter the efficiency of catalysts, particularly for reactions crucial to sustainable energy processes such as oxygen evolution, hydrogen evolution, and oxygen reduction.

At the nanoscale, materials behave differently from their bulk counterparts. When particles shrink to just a few nanometers in size, the proportion of surface atoms becomes nearly equivalent to the total number of atoms, resulting in a significant shift in both physical and chemical properties. This size-dependent behavior is heavily influenced by quantum effects—phenomena governed by the principles of quantum mechanics.

“Palladium and iridium nanoalloys serve as critical catalysts in a wide range of organic and oxidation reactions, including carbon monoxide conversion,” explained Professor Kvashnin of the Skoltech Energy Transition Center. “To optimize these materials, it’s essential to understand what occurs at the atomic level, especially since real-world experiments struggle to determine exact surface compositions or the energetics of different shell configurations.”

To investigate this, the researchers studied 2-nanometer core-shell nanoparticles composed of iridium and palladium with varying chemical orders—such as iridium-core with a palladium shell and the reverse configuration—alongside alloyed forms. Their objective was to examine how structural order (crystalline vs. amorphous), chemical makeup, and atomic surroundings influence the nanoparticles’ electronic characteristics and surface charge distribution.

A key finding revealed that nanoparticles with an iridium core and a single-atom-thick palladium shell showed a notable charge redistribution. In these structures, electrons transferred from the iridium core to the palladium surface, creating a negatively charged outer layer. Interestingly, the nature of the nanoparticle—whether crystalline or amorphous—did not significantly impact this surface charge effect.

Lead author Ilya Chepkasov, a senior research scientist at Skoltech, pointed out the significance of temperature in practical applications: “Nanoparticles have much lower melting points than bulk metals. During high-temperature catalytic reactions, they can lose their crystalline form and become amorphous. Most existing research focuses on crystalline structures, but we wanted to explore what happens when that order is lost.”

The findings emphasize that while the structural form (crystalline or amorphous) has limited effect on charge behavior, the chemical arrangement and shell thickness play a dominant role in determining catalytic performance. This knowledge could guide the design of more efficient nanocatalysts for use across energy, environmental, and industrial applications.

Source: https://phys.org/news/2025-04-amorphization-nanocatalyst-properties-impact-disorder.html

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