The Distribution of Ti3+ Surface Sites in Reduced TiO2
We describe a DFT+U study of the (110) rutile surface with oxygen vacancies (Ov). Oxygen vacancies leave behind two excess unpaired electrons per Ov the formation of two Ti3+ ions. We investigate the location of the Ti3+ ions within the first three surface layers. In total we obtained 49 unique solutions of possible Ti3+ pairs, to examine the stability of all Ti types (e.g. five-coordinated surface Ti, six-coordinated surface Ti, sub-surface sites, etc.). Our results show that sub-surface sites are preferred, but that many configurations are close in energy, up to 0.3-0.4 eV of each other. In contrast to findings in previous work, we show that sites directly adjacent to the Ov are unstable. Analysis of our results show that the two Ti3+ ions within a pair behave independent of each other, as there are little electronic interactions between the excess electrons associated with these sites. We also examined the migration of Ti3+ sites from the surface into the bulk and find the surface locations to be preferred by ~ 0.5 eV relative to the bulk. Our systematic results provide a comprehensive picture of excess electrons that indicates that they are not trapped or localized at specific sites, but are distributed across several sites due to nearly degenerate Ti3+ states. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1012843
- Report Number(s):
- PNNL-SA-77079; 35193; KC0302010; TRN: US201110%%373
- Journal Information:
- Journal of Physical Chemistry C, 115(15):7562-7572, Vol. 115, Issue 15; ISSN 1932--7447
- Country of Publication:
- United States
- Language:
- English
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