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Mixed valence Zn-Co-layered double hydroxides and their exfoliated nanosheets with electrode functionality

Title
Mixed valence Zn-Co-layered double hydroxides and their exfoliated nanosheets with electrode functionality
Authors
Woo M.A.Song M.-S.Kim T.W.Kim I.Y.Ju J.-Y.Lee Y.S.Kim S.J.Choy J.-H.Hwang S.-J.
Ewha Authors
최진호황성주
SCOPUS Author ID
최진호scopus; 황성주scopus
Issue Date
2011
Journal Title
Journal of Materials Chemistry
ISSN
0959-9428JCR Link
Citation
vol. 21, no. 12, pp. 4286 - 4292
Indexed
SCOPUS WOS scopus
Abstract
New phases of Zn-Co-layered double hydroxides (Zn-Co-LDHs) were synthesized for the first time via a co-precipitation reaction using hydrogen peroxide as an oxidant. According to powder X-ray diffraction and field emission-scanning electron microscopy, both nitrate- and sulfate-forms of the Zn-Co-LDHs crystallized with the brucite-type layer structure having interlayer nitrate and sulfate anions, respectively, and commonly showed plate-like morphology with a crystal size of several hundred nanometers. dc magnetic susceptibility measurements revealed that the Zn-Co-LDHs displayed ferromagnetic/ antiferromagnetic transitions below 15 K and the magnetic moment calculated from the paramagnetic region (30-300 K) indicated the co-existence of weak field Co 2+ and strong field Co 3+ ions. The mixed oxidation state of Co 2+/Co 3+ was confirmed by the results of iodometry and X-ray absorption near-edge structure spectroscopy. The heat-treatment for the Zn-Co-LDHs at elevated temperatures produced mixed metal oxide nanocomposites composed of spinel ZnCo 2O 4 and wurzite ZnO phases. The colloidal suspension of exfoliated Zn-Co-LDH nanosheets could be synthesized by dispersion of the pristine LDH materials in formamide, which was confirmed by the Tyndall phenomenon, high resolution-transmission electron microscopy/selected area electron diffraction, and UV-vis spectroscopy. The Zn-Co-LDH film fabricated with the restacked nanosheets exhibited pseudocapacitive behavior with a large specific capacitance and a good capacitance retention. The present findings underscore that the newly synthesized mixed valence Zn-Co-LDH phases showed promising functionality as a supercapacitor electrode material and also showed interesting magnetic coupling behavior. © 2011 The Royal Society of Chemistry.
DOI
10.1039/c0jm03430d
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자연과학대학 > 화학·나노과학전공 > Journal papers
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