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Band gap engineering by anion doping in the photocatalyst BiTaO4: First principle calculations
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
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2012 (Engelska)Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, nr 4, s. 3014-3018Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We have shown the effect of mono and co-doping of non-metallic anion atoms on the electronic structure in BiTaO4 using the first-principles method. It can improve the photocatalytic efficiency for hydrogen production in the presence of visible sunlight. It is found that the band gap of BiTaO4 has been reduced significantly up to 54% with different nonmetallic doping. Electronic structure analysis shows that the doping of nitrogen is able to reduce the band gap of BiTaO4 due to the impurity N 2p state at the upper edge of the valence band. In case of C or C-S doped BiTaO4, double occupied (filled) states have been observed deep inside the band gap of BiTaO4. The large reduction of band gap has been achieved, which increases the visible light absorption. These results indicate that the doping of non-metallic element in BiTaO4 is a promising candidate for the photocatalyst due to its reasonable band gap.

Ort, förlag, år, upplaga, sidor
2012. Vol. 37, nr 4, s. 3014-3018
Nyckelord [en]
Band gap engineering, Photocatalysis, Anionic doping in BiTaO4
Nationell ämneskategori
Fysik
Identifikatorer
URN: urn:nbn:se:uu:diva-173827DOI: 10.1016/j.ijhydene.2011.11.068ISI: 000301615100004OAI: oai:DiVA.org:uu-173827DiVA, id: diva2:525777
Konferens
International Conference on Renewable Energy (ICRE 2011)
Tillgänglig från: 2012-05-09 Skapad: 2012-05-07 Senast uppdaterad: 2017-12-07Bibliografiskt granskad
Ingår i avhandling
1. Atomic Scale Design of Clean Energy Materials: Efficient Solar Energy Conversion and Gas Sensing
Öppna denna publikation i ny flik eller fönster >>Atomic Scale Design of Clean Energy Materials: Efficient Solar Energy Conversion and Gas Sensing
2012 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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).

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2012. s. 68
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 958
Nyckelord
Photocatalysts, Band gap narrowing, Water dissociation, Density functional theory, Gas sensing, Kaolinite
Nationell ämneskategori
Den kondenserade materiens fysik Nanoteknik Atom- och molekylfysik och optik
Forskningsämne
Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik
Identifikatorer
urn:nbn:se:uu:diva-179372 (URN)978-91-554-8436-1 (ISBN)
Disputation
2012-09-28, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2012-09-06 Skapad: 2012-08-14 Senast uppdaterad: 2013-01-22

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