Phase Control of Solid-Solution Nanoparticles beyond the Phase Diagram for Enhanced Catalytic Properties

Area of Science:

• Materials Science
• Nanotechnology
• Catalysis

Background:

• Crystal structure fundamentally influences solid-state properties.
• Controlling crystal structures is limited by thermodynamic constraints and phase diagrams.
• Nanoparticles (NPs) offer unique properties due to their high surface area-to-volume ratio.

Purpose of the Study:

• To demonstrate the first instance of controlling crystal structure in solid-solution nanoparticles (NPs) without changing composition or size.
• To investigate the impact of controlled crystal structures on catalytic performance, specifically for the oxygen evolution reaction (OER).

Main Methods:

• Synthesis of face-centered cubic (fcc) and hexagonal close-packed (hcp) structured palladium-ruthenium (PdRu) NPs with varying compositions (x=0.4, 0.5, 0.6).
• Characterization using synchrotron X-ray-based spectroscopy and atomic-resolution electron microscopy.
• Theoretical analysis using density functional theory (DFT) calculations.

Main Results:

• Successfully synthesized fcc or hcp structured PdRu NPs, structures not achievable in bulk materials.
• Demonstrated significantly improved OER catalytic properties in hcp-PdRu NPs compared to their fcc counterparts in corrosive acid.
• Achieved an overpotential (η) of 200 mV at 10 mA cm⁻² for hcp-PdRu NPs, with sustained activity over 20 hours, outperforming fcc-PdRu NPs (η = 280 mV, 9 min).

Conclusions:

• Crystal structure control in PdRu NPs, achieved without altering composition, enhances catalytic efficiency for the oxygen evolution reaction.
• The superior performance of hcp-PdRu NPs is attributed to their enhanced stability against oxidative dissolution.
• This study presents a novel approach for designing advanced catalysts with tailored crystal structures for demanding applications.