Adsorption and dissociation of H$_{2}$O monomer on ceria(111): Density functional theory calculations

TL;DR

This study uses density functional theory and molecular dynamics to explore how water molecules adsorb, diffuse, and dissociate on ceria(111) surfaces, revealing the effects of oxygen vacancies on these processes.

Contribution

It provides detailed insights into water adsorption configurations, diffusion barriers, and dissociation mechanisms on both stoichiometric and reduced ceria(111) surfaces, highlighting the role of oxygen vacancies.

Findings

Water forms two hydrogen bonds with ceria(111) surfaces.

Diffusion barrier of water on stoichiometric surface is 0.51 eV.

Oxygen vacancies promote water dissociation into H and OH.

Abstract

The adsorption properties of isolated H$_{2}$O molecule on stoichiometric and reduced (with on-surface oxygen vacancy) ceria(1111) surfaces at low coverage are theoretically investigated by using density-functional-theory+\emph{U} calculations and \textit{ab initio} molecular dynamics simulations. We identify the most stable adsorption configurations on these two kinds of surfaces, which form two hydrogen bonds between the water molecule and the oxide surface. The electronic structures indicate that the hybridization of the molecular orbitals of water and surface-layer O-2\emph{p} states dominates the interactions between adsorbate and substrate. The barrier of 0.51 eV for water diffusion on the stoichiometric surface implies the inertia of water unless up to a high temperature of 600 K, which is confirmed by the molecular dynamics simulations. For the reduced surface, we find that the oxygen vacancy obviously enhances the interaction. Moreover, it is facilitated for water to dissociate into H and OH species with a hydroxyl surface formed, instead of oxidizing the reduced surface with the production of hydrogen gas. In addition, the molecular dynamics simulations at low temperature 100 K confirm the dissociation process.