First principles modeling of oxygen adsorption on LaMnO3 (001) surface

TL;DR

This study uses first-principles DFT calculations to analyze oxygen adsorption and diffusion on LaMnO3 (001) surfaces, relevant for solid oxide fuel cell cathodes, revealing adsorption energetics, migration barriers, and stability conditions.

Contribution

It provides detailed atomic-level insights into oxygen behavior on LaMnO3 surfaces, a novel application of ab initio thermodynamics for SOFC materials.

Findings

Dissociative O2 adsorption is energetically favorable on Mn ions.

Surface migration energy for O ions is approximately 1.6 eV.

Adsorbed O atoms can penetrate into the electrode with mobile oxygen vacancies.

Abstract

We present and discuss the results of ab initio DFT plane-wave supercell calculations of the atomic and molecular oxygen adsorption and diffusion on the LaMnO3 (001) surface which serves as a model material for a cathode of solid oxide fuel cells. The dissociative adsorption of O2 molecules from the gas phase is energetically favorable on surface Mn ions even on a defect-free surface. The surface migration energy for adsorbed O ions is found to be quite high, 1.6 eV. We predict that the adsorbed O atoms could penetrate into electrode first plane when much more mobile surface oxygen vacancies (migration energy of 0.69 eV) approach the O ions strongly bound to the surface Mn ions. Ab initio thermodynamics predicts that at typical SOFC operation temperatures (~1200 K) the MnO2 (001) surface with adsorbed O atoms is the most stable in a very wide range of oxygen gas pressures (above 10^2 atm).