Structural characterization of Pt-Pd and Pd-Pt core-shell nanoclusters at atomic resolution

Area of Science:

• Materials Science
• Nanotechnology
• Catalysis

Background:

• Polymer-capped monometallic and bimetallic platinum (Pt) and palladium (Pd) nanoclusters serve as model systems for nanoscale electrocatalysts.
• Understanding their atomic structures is critical for optimizing catalytic performance and designing advanced materials.

Purpose of the Study:

• To investigate the atomic structures and elemental speciation of Pt and Pd within nanoclusters at unprecedented resolution.
• To elucidate the factors influencing nanocluster stability, including quenched states and structural nonidealities.
• To validate theoretical models by comparing experimental data with simulations.

Main Methods:

• Utilized aberration-corrected scanning transmission electron microscopy (STEM) with sub-nanometer resolution and Z-contrast measurements.
• Employed theory-directed modeling to compare experimental intensity profiles with simulated profiles from predicted cluster geometries.
• Analyzed atomic structures, elemental distribution, twinning, and segregation within the nanoclusters.

Main Results:

• Achieved atomic-resolution insights into the structures and elemental distribution (Pt/Pd speciation) of the nanoclusters.
• Identified deeply quenched states hindering alloy formation and revealed nonidealities like twinning and atomic segregation.
• Demonstrated strong agreement between experimental STEM data and theoretical models, highlighting composition-sensitive structural complexities.

Conclusions:

• Aberration-corrected STEM is a powerful tool for atomic-scale characterization of nanomaterials and catalysts.
• The study provides a fundamental understanding of nanocluster structures, informing the development of next-generation electrocatalysts.
• Structural complexities are composition-dependent and can be amplified during cluster growth.