Subsurface Polaron Concentration As a Factor in the Chemistry of Reduced TiO2 (110) Surfaces

Taizo Shibuya, Kenji Yasuoka, Susanne Mirbt, Biplab Sanyal

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Surface reactivity of rutile TiO2 (110) surfaces has long been ascribed to bridging oxygen vacancies (VO), but recently, excess electrons introduced by donor defects are being considered as the main players. However, the spatial distribution of them is not yet clear due to difficulties in interpreting filled state images of scanning tunneling microscopy (STM). In this study, several different images available in the literature are consistently interpreted using density functional theory (DFT). The key factors are polarons in the second layer below Ti5c row (Ti5c-2nd polarons) and a temperature dependence of their concentration. Bright blobs in the experimental images are interpreted as Ti5c-2nd polarons. At 78 K, their concentration reaches 33.3% ML, where 1 ML is defined as the density of (1 × 1) unit cells, regardless of VO coverage. In contrast, at 5 K, it is twice the VO coverage. This discrepancy is understood by the ionization of donor defects other than VO, most probably subsurface Ti interstitials, and subsequent diffusion of polarons to Ti5c-2nd sites at high temperature. This mechanism explains seemingly contradicting reports on oxygen chemisorption on this surface, which suggests that the so-called oxygen-vacancy model needs to be modified at temperature above at least 78 K.

Original languageEnglish
Pages (from-to)11325-11334
Number of pages10
JournalJournal of Physical Chemistry C
Volume121
Issue number21
DOIs
Publication statusPublished - 2017 Jun 1

Fingerprint

Gene Conversion
Polarons
polarons
chemistry
Oxygen vacancies
oxygen
Defects
defects
Scanning tunneling microscopy
Chemisorption
rutile
Temperature
chemisorption
Spatial distribution
Ionization
Density functional theory
scanning tunneling microscopy
spatial distribution
interstitials
reactivity

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry

Cite this

Subsurface Polaron Concentration As a Factor in the Chemistry of Reduced TiO2 (110) Surfaces. / Shibuya, Taizo; Yasuoka, Kenji; Mirbt, Susanne; Sanyal, Biplab.

In: Journal of Physical Chemistry C, Vol. 121, No. 21, 01.06.2017, p. 11325-11334.

Research output: Contribution to journalArticle

Shibuya, Taizo ; Yasuoka, Kenji ; Mirbt, Susanne ; Sanyal, Biplab. / Subsurface Polaron Concentration As a Factor in the Chemistry of Reduced TiO2 (110) Surfaces. In: Journal of Physical Chemistry C. 2017 ; Vol. 121, No. 21. pp. 11325-11334.
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