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Kim, Kwang S.
Center for Superfunctional Materials (CSM)
Research Interests
  • Theoretical/experimental nanosciences, molecular electronics spectroscopy, energy materials

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Band Gap Narrowing of Zinc Orthogermanate by Dimensional and Defect Modification

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Title
Band Gap Narrowing of Zinc Orthogermanate by Dimensional and Defect Modification
Author
Kim, Dong YeonYoon, TaeseungJang, Youn JeongLee, Jin HoNa, YounghoonLee, Byeong JunLee, Jae SungKim, Kwang S.
Issue Date
2019-06
Publisher
American Chemical Society
Citation
JOURNAL OF PHYSICAL CHEMISTRY C, v.123, no.23, pp.14573 - 14581
Abstract
Dimensional reduction and defect control are powerful techniques for enhancing the physical and chemical properties of raw materials. Herein, we report the new type of sheetlike or two-dimensional-like zinc orthogermanate (Zn2GeO4, denoted as S-ZGO) with a one-step hydrothermal reaction and its application to photocatalytic water splitting. S-ZGO is directly grown along the surface of the Zn foil, since the growth rate of a crystal facet can be modified through the restricted reaction of dissolved precursor (GeO2) with a solid precursor (Zn foil) during the hydrothermal reaction. For further modification, the oxygen vacancies are introduced on the surface of S-ZGO using thermal hydrogen treatment and photodeposition-driven low amount of Pt/RuO2 co-catalysts loading. Notably, this reduced dimension decreases the band gap to 4.09 eV for S-ZGO (from 4.5 eV for the bulk), and the hydrogenation of S-ZGO further decreases the band gap to 3.88 eV. The origin of band gap narrowing is demonstrated with the density functional theory showing increased density of states at the edge of the conduction band (CB) and valence band (VB), and a new defect level between the CB minimum and VB maximum. As a possible application, we demonstrate that S-ZGO/H2 loaded with Pt/RuO2 exhibits the H2 rate of 167.0 μmol h-1 g-1 and the O2 rate of 83.0 μmol h-1 g-1, a8 times those of the rodlike ZGO photocatalysts.
URI
https://scholarworks.unist.ac.kr/handle/201301/27027
URL
https://pubs.acs.org/doi/10.1021/acs.jpcc.9b03728
DOI
10.1021/acs.jpcc.9b03728
ISSN
1932-7447
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ECHE_Journal Papers
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