Influences of stoichiometry deviations on geometry and electronic structures of TiO2 anatase (101)

TL;DR

This study explores how deviations in stoichiometry affect the structure and electronic properties of TiO2 anatase (101), revealing their impact on photocatalytic activity and defect configurations.

Contribution

It provides the first systematic analysis of native defects and reconstructions in TiO2 anatase (101) using computational methods, linking stoichiometry to electronic and structural changes.

Findings

O vacancies depend on bulk concentration in lightly reduced samples.

Ti interstitials prefer to dissolve in the bulk.

O interstitials induce bandgap narrowing and transition to direct bandgap.

Abstract

We systematically investigated native defects and reconstructions of TiO2 anatase (101) using USPEX and VASP codes. For lightly reduced samples, the coverage of O vacancies at surface depends on its concentration in bulk, while Ti interstitials prefer to dissolve in bulk. Atomic configurations of reconstructed TiO2 anatase (101) structures were given for severe reduced samples at the first time. Increasing the reduction degree, the Fermi level can be modulated in the whole bandgap. For O-rich samples, due to the indirect-to-direct bandgap transition and bandgap narrowing, O interstitials are responsible for visible light photoactivity. In a word, stoichiometry deviations of TiO2 anatase (101) have broad implications for photocatalytic reactions.