Σ3(111) Grain Boundaries Accelerate Hydrogen Insertion into Palladium Nanostructures

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Grain boundaries (GBs) are critical defect sites in nanomaterials.
• Their role in metal hydride formation, particularly in palladium (Pd), is not fully understood.
• Understanding GBs is crucial for developing advanced functional materials.

Purpose of the Study:

• To investigate the influence of well-defined Σ3(111) grain boundaries (GBs) on hydrogen insertion in Pd nanostructures.
• To elucidate the mechanisms governing hydrogen kinetics at GBs.
• To explore GB-engineered Pd-based materials for enhanced hydride formation.

Main Methods:

• Synthesis of Pd nanostructures enriched with Σ3(111) GBs using electrolysis-driven nanoparticle assembly.
• In situ synchrotron X-ray diffraction to study hydriding/dehydriding kinetics.
• Environmental transmission electron microscopy for strain mapping.
• Density functional theory (DFT) calculations for mechanistic insights.

Main Results:

• Pd nanostructures with GBs (Pd_GB) showed significantly faster hydriding and dehydriding kinetics.
• Strain was localized at GBs and intensified upon hydrogen exposure, indicating preferential hydrogen insertion.
• DFT calculations confirmed energetically favorable hydrogen insertion near GBs and the effect of tensile strain.

Conclusions:

• Grain boundaries act as preferential sites for hydrogen insertion in palladium nanostructures.
• GBs dramatically accelerate metal hydride formation and decomposition kinetics.
• GB engineering offers a promising strategy for designing advanced Pd-based functional materials.