Fermi level dependence of gas-solid oxygen defect exchange mechanism on TiO2 (110) by first-principles calculations

Heonjae Jeong; Edmund G Seebauer; Elif Ertekin

doi:10.1063/5.0023180

Fermi level dependence of gas-solid oxygen defect exchange mechanism on TiO₂ (110) by first-principles calculations

J Chem Phys. 2020 Sep 28;153(12):124710. doi: 10.1063/5.0023180.

Authors

Heonjae Jeong¹, Edmund G Seebauer², Elif Ertekin¹

Affiliations

¹ Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
² Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.

PMID: 33003753
DOI: 10.1063/5.0023180

Abstract

In the same way that gases interact with oxide semiconductor surfaces from above, point defects interact from below. Previous experiments have described defect-surface reactions for TiO₂(110), but an atomistic picture of the mechanism remains unknown. The present work employs computations by density functional theory of the thermodynamic stabilities of metastable states to elucidate possible reaction pathways for oxygen interstitial atoms at TiO₂(110). The simulations uncover unexpected metastable states including dumbbell and split configurations in the surface plane that resemble analogous interstitial species in the deep bulk. Comparison of the energy landscapes involving neutral (unionized) and charged intermediates shows that the Fermi energy E_F exerts a strong influence on the identity of the most likely pathway. The largest elementary-step thermodynamic barrier for interstitial injection trends mostly downward by 2.1 eV as E_F increases between the valence and conduction band edges, while that for annihilation trends upward by 2.1 eV. Several charged intermediates become stabilized for most values of E_F upon receiving conduction band electrons from TiO₂, and the behavior of these species governs much of the overall energy landscape.