$\Sigma$3(111) Grain Boundaries Accelerate Hydrogen Insertion into Palladium Nanostructures

TL;DR

This study demonstrates that $$(111) grain boundaries in palladium nanostructures significantly accelerate hydrogen insertion and release, with strain localized at GBs facilitating this process, supported by experimental and computational evidence.

Contribution

The paper reveals that well-defined $$(111) grain boundaries in Pd nanostructures enhance hydrogen kinetics, providing atomic-level insights into their role in hydride formation and guiding GB-engineered material design.

Findings

$$(111) GBs accelerate hydriding/dehydriding kinetics.

Strain localizes at GBs and increases with hydrogen exposure.

Hydrogen insertion is energetically more favorable near GBs.

Abstract

Grain boundaries (GBs) are frequently implicated as key defect structures facilitating metal hydride formation, yet their specific role remains poorly understood due to their structural complexity. Here, we investigate hydrogen insertion in Pd nanostructures enriched with well-defined $\Sigma$3(111) GBs (Pd GB) synthesized via electrolysis-driven nanoparticle assembly. In situ synchrotron X-ray diffraction reveals that Pd GB exhibits dramatically accelerated hydriding and dehydriding kinetics compared to ligand-free and ligand-capped Pd nanoparticles with similar crystallite sizes. Strain mapping using environmental transmission electron microscopy shows that strain is highly localized at GBs and intensifies upon hydrogen exposure, indicating preferential hydrogen insertion along GB sites. Density functional theory calculations support these findings, showing that hydrogen insertion near $\Sigma$3(111) GBs is energetically more favorable and that tensile strain lowers insertion barriers. These results provide atomic-level insights into the role of GBs in hydride formation and suggest new design strategies for GB-engineered Pd-based functional materials. Keywords: Hydrogen Insertion; Tensile Strain; Grain Boundaries; Palladium Nanostructures.