Effect of oxygen adsorption and oxidation on the strain state of Pd nanocrystals

TL;DR

This study investigates how oxygen adsorption and oxidation alter the morphology and strain distribution in Palladium nanocrystals, revealing complex surface-dependent effects through experimental and computational analyses.

Contribution

It combines synchrotron X-ray diffraction and multiscale modeling to elucidate the effects of oxidation on strain and morphology in Pd nanocrystals, highlighting surface facet influences.

Findings

Oxidation increases short-range surface strain in Pd nanocrystals.

Long-range strain decreases due to increased truncation of nanocubes.

Surface disorder varies across facets, affecting oxygen activation.

Abstract

X-ray powder diffraction using a synchrotron light source reveals significant modifications to both morphology and strain state in Palladium nanocubes after oxidation. Short-range strain measured by the static component of the Debye-Waller coefficient is observed to be higher in the oxidized nanoparticles; while long-range strain related to the line broadening of the diffraction peaks is seen to decrease. Using multiscale modelling with classical molecular dynamics and density functional theory, we connect the decrease in long-range strain to the increased truncation of the oxidized nanocubes, while the higher short-range strain is shown to be due to surface softening from oxygen adsorption. Different surface disorder on different crystallographic facets lead to opposing trends for oxygen activation on the different exposed surfaces of the truncated nanoparticles.