First principles studies of the size and shape effects on reactivity of the Se modified Ru nanoparticles

TL;DR

This study uses density functional theory to analyze how size and shape influence the reactivity of Se-modified Ru nanoparticles, revealing insights into their electronic structure and potential catalytic performance for oxygen reduction.

Contribution

It provides the first detailed theoretical analysis of Se and O adsorption on Ru nanoparticles of different sizes and shapes, highlighting how these factors affect catalytic activity.

Findings

Se bonding on flat facets is ionic, while on low-coordinated sites it shows covalent character.

Se modification weakens oxygen binding to Ru nanoparticles.

Larger, flat-faceted particles are predicted to be more effective ORR catalysts.

Abstract

We present here the results of our density-functional-theory-based calculations of the electronic and geometric structures and energetics of Se and O adsorption on Ru 93- and 105-atom nanoparticles. These studies have been inspired by the fact that Se/Ru nanoparticles are considered promising electrocatalysts for the oxygen reduction reaction (ORR) on the direct methanol fuel cell cathodes and the oxygen binding energy is a descriptor for the catalyst activity towards this reaction. We find the character of chemical bonding of Se on a flat nanoparticle facet to be ionic, similar to that obtained earlier for the Se/Ru(0001) surface, while in the case of a low coordinated Ru configuration there is an indication of some covalent contribution to the bonding leading to an increase in Se binding energy. Se and O co-adsorbed on the flat facet, both accept electronic charge from Ru, whereas the adsorption on low-coordinated sites causes more complicated valence charge redistribution. The Se modification of the Ru particles leads to weakening of the oxygen bonding to the particle. However, overall, O binding energies are found to be higher for the particles than for Se/Ru(0001). High reactivity of the Se/Ru nanoparticles found in this work is not favorable for ORR. We thus expect that larger particles with well-developed flat facets are more efficient ORR catalysts than small nanoparticles with a large fraction of under-coordinated adsorption sites.