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Mo- and N-doped BiNbO(4) for photocatalysis applications
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.ORCID iD: 0000-0001-7321-8594
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2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 5, 051909- p.Article in journal (Refereed) Published
Abstract [en]

The electronic structure of pure BiNbO(4) has been calculated and their electronic band positions have been aligned with respect to the water oxidation/reduction potential. The effect of cationic (Mo), anionic (N), and co-doping (Mo-N) on BiNbO(4) has been studied and discussed with respect to the standard redox potential levels. Our results show that co-doping of Mo and N in BiNbO(4) reduces the band gap up to 31.8%, thus making it a potential candidate for the photocatalysis of water for hydrogen production. The relative stability between the mono-and co-doped BiNbO(4) materials show that co-doped material is more stable and feasible in comparison to the mono-doped materials.

Place, publisher, year, edition, pages
2011. Vol. 99, no 5, 051909- p.
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-40668DOI: 10.1063/1.3622659ISI: 000293617300023Scopus ID: 2-s2.0-80051584758OAI: oai:DiVA.org:kth-40668DiVA: diva2:443591
Funder
Swedish Research Council
Note
QC 20110926Available from: 2011-09-26 Created: 2011-09-20 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Electronic Structure and Optical Properties of Solar Energy Materials
Open this publication in new window or tab >>Electronic Structure and Optical Properties of Solar Energy Materials
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, we have studied the electronic and optical properties of solar energy m-terials. The studies are performed in the framework of density functional theory (DFT), GW, Bethe-Salpeter equation (BSE) approaches and Kinetic Monte Carlo (KMC). We present four sets of results. In the first part, we report our results on the band gap engineering issues for BiNbO4and NaTaO3, both of which are good photocatalysts. The band gap tuning is required for these materials in order to achieve the maximum solar to hydrogen conversion efficiency. The most common method for the band gap reduction is an introduction of foreign elements. The mono-doping in the system generates electrons or holes states near band edges, which reduce the efficiency of photocatalytic process. Co-doping with anion and cation or anion and anion can provide a clean band gap. We have shown that further band gap reduction can be achieved by double-hole mediated coupling between two anionic dopants. In the second part, the structure and optical properties of (CdSxSe1x)42nanoclusters have been studied. Within this study, the structures of the (CdS)42, (CdSe)42, Cd42Se32S10, Cd42Se22S20, and Cd42Se10S32 clusters have been determined using the simulated annealing method. Factors influencing the band gap value have been analyzed. We show that the gap is most significantly reduced when strongly under coordinated atoms are present on the surface of the nanoclusters. In addition, the band gap depends on the S concentration as well as on the distribution of the S and Se atoms in the clusters. We present the optical absorption spectra calculated with BSE and random phase approximation (RPA) methods based on the GW corrected quasiparticle energies. In the third part, we have employed the state-of-art computational methods to investigate the electronic structure and optical properties of TiO2high pressure polymorphs. GW and BSE methods have been used in these calculations. Our calculations suggest that the band gap of fluorite and pyrite phases have optimal values for the photocatalytic process of decomposing water in the visible light range. In the fourth part we have built a kinetic model of the first water monolayer growth on TiO2(110) using the kinetic Monte Carlo (KMC) method based on parameters describing water diffusion and dissociation obtained from first principle calculations. Our simulations reproduce the experimental trends and rationalize these observations in terms of a competition between different elementary processes. At high temperatures our simulation shows that the structure is well equilibrated, while at lower temperatures adsorbed water molecules are trapped in hydrogen-bonded chains around pairs of hydroxyl groups, causing the observed higher number of molecularly adsorbed species at lower temperature.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. viii, 82 p.
Keyword
GW, Bethe-Salpeter equation, Kinetic Monte Carlo, Density Functional Theory
National Category
Condensed Matter Physics
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-145625 (URN)978-91-7595-190-4 (ISBN)
Public defence
2014-06-13, FB53, AlbaNova, Roslagstullsbacken, Stockholm, 10:00 (English)
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Note

QC 20140603

Available from: 2014-06-03 Created: 2014-05-23 Last updated: 2014-06-03Bibliographically approved

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Wang, B. C.

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