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Molecular simulation for gas adsorption at NiO (100) surface
Department of Materials and Engineering, The Royal Institute of Technology (KTH). (Applied Materials Physics)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. (Condense Matter Theory Group)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. (Condense Matter Theory Group)
2012 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 4, no 10, 5691-5697 p.Article in journal (Refereed) Published
Abstract [en]

Density functional theory (DFT) calculations have been employed to explore the gas-sensing mechanisms of NiO (100) surface on the basis of energetic and electronic properties. We have calculated the adsorption energies of NO 2, H 2S, and NH 3 molecules on NiO (100) surface using GGA+U method. The calculated results suggest that the interaction of NO 2 molecule with NiO surface becomes stronger and contributes more extra peaks within the band gap as the coverage increases. The band gap of H 2S-adsorbed systems decrease with the increase in coverage up to 0.5 ML and the band gap does not change at 1 ML because H 2S molecules are repelled from the surface. In case of NH 3 molecular adsorption, the adsorption energy has been increased with the increase in coverage and the band gap is directly related to the adsorption energy. Charge transfer mechanism between the gas molecule and the NiO surface has been illustrated by the Bader analysis and plotting isosurface charge distribution. It is also found that that work function of the surfaces shows different behavior with different adsorbed gases and their coverage. The work function of NO 2 gas adsorption has a hill-shaped behavior, whereas H 2S adsorption has a valley-shaped behavior. The work function of NH 3 adsorption decreases with the increase in coverage. On the basis of our calculations, we can have a better understanding of the gas-sensing mechanism of NiO (100) surface toward NO 2, H 2S, and NH 3 gases

Place, publisher, year, edition, pages
2012. Vol. 4, no 10, 5691-5697 p.
Keyword [en]
conductivity, density functional theory (DFT), gas sensing, NiO (100) surface
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-179340DOI: 10.1021/am3016894ISI: 000310109000084OAI: oai:DiVA.org:uu-179340DiVA: diva2:544224
Funder
Swedish Research Council
Available from: 2012-08-13 Created: 2012-08-13 Last updated: 2017-12-07Bibliographically 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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Nisar, JawadAhuja, Rajeev

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