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Water Interaction with native defects on rutile TiO2 nanowire: Ab initio calculations
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 8, 083115- p.Article in journal (Refereed) Published
Abstract [en]

Adsorption of water molecules on stoichiometric and defective surfaces of rutile TiO2 nanowire oriented along the [(1) over bar 10] direction is investigated using density function theory calculations. We have investigated, in particular, O and Ti vacancies where energetic, structural, and electronic properties were evaluated. It was found that the water molecules interacting with O-vacancy undergo spontaneous dissociation, forming hydroxyl groups bound to Ti atoms and other OH groups formed by surface O and H-water. The same is not found in the case of perfect and Ti-vacancy containing nanowire. This dissociation of water molecules is due to charge transfer from neighboring Ti atom, which is polarized due to the O-vacancy.

Place, publisher, year, edition, pages
2011. Vol. 98, no 8, 083115- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-149060DOI: 10.1063/1.3556276ISI: 000287764300079OAI: oai:DiVA.org:uu-149060DiVA: diva2:403778
Available from: 2011-03-15 Created: 2011-03-15 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Atomic Scale Design of Clean Energy Materials: Efficient Solar Energy Conversion and Gas Sensing
Open this publication in new window or tab >>Atomic Scale Design of Clean Energy Materials: Efficient Solar Energy Conversion and Gas Sensing
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The focus of this doctoral thesis is the atomic level design of photocatalysts and gas sensing materials. The band gap narrowing in the metal oxides for the visible-light driven photocatalyst as well as the interaction of water and gas molecules on the reactive surfaces of metal oxides and the electronic structure of kaolinite has been studied by the state-of-art calculations. Present thesis is organized into three sections.

The first section discusses the possibility of converting UV active photocatalysts (such as Sr2Nb2O7, NaTaO3, SrTiO3, BiTaO4 and BiNbO4) into a visible active photocatalysts by their band gap engineering. Foreign elements doping in wide band gap semiconductors is an important strategy to reduce their band gap. Therefore, we have investigated the importance of mono- and co-anionic/cationic doping on UV active photocatalysts. The semiconductor's band edge position is calculated with respect to the water oxidation/reduction potential for various doping. Moreover, the tuning of valence and conduction band edge position is discussed on the basis of dopant's p/d orbital energy.

In the second section of thesis the energetic, electronic and optical properties of TiO2, NiO and β-Si3N4 have been discussed to describe the adsorption mechanism of gas molecules at the surfaces. The dissociation of water into H+ or OH- occurs on the O-vacancy site of the (001)-surface of rutile TiO2 nanowire, which is due to the charge transfer from Ti atom to water molecule. The dissociation of water into OH- and imino (NH) groups is also observed on the β-Si3N4 (0001)-surface due to the dangling bonds of the lower coordinated N and Si surface atoms. Fixation of the SO2 molecules on the anatase TiO2 surfaces with O-deficiency have been investigated by Density Functional Theory (DFT) simulation and Fourier Transform Infrared (FTIR) spectroscopy. DFT calculations have been employed to explore the gas-sensing mechanism of NiO (100)-surface on the basis of energetic and electronic properties.

In the final section the focus is to describe the optical band gap of pristine kaolinite using the hybrid functional method and GW approach. Different possible intrinsic defects in the kaolinite (001) basal surface have been studied and their effect on the electronic structure has been explained. The detailed electronic structure of natural kaolinite has been determined by the combined efforts of first principles calculations and Near Edge X-ray Absorption Fine Structure (NEXAFS).

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 68 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 958
Keyword
Photocatalysts, Band gap narrowing, Water dissociation, Density functional theory, Gas sensing, Kaolinite
National Category
Condensed Matter Physics Nano Technology Atom and Molecular Physics and Optics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-179372 (URN)978-91-554-8436-1 (ISBN)
Public defence
2012-09-28, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2012-09-06 Created: 2012-08-14 Last updated: 2013-01-22

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Ahuja, Rajeev

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