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

Myong A. Woo, Min Sun Song, Tae Woo Kim, In Young Kim, Ji Yun Ju, Young Soo Lee, Seung Joo Kim, Jin Ho Choy, Seong Ju Hwang

Research output: Contribution to journalArticle

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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 2 O 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.

Original languageEnglish
Pages (from-to)4286-4292
Number of pages7
JournalJournal of Materials Chemistry
Volume21
Issue number12
DOIs
Publication statusPublished - 2011 Mar 28

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Hydroxides
Nanosheets
Nitrates
Capacitance
X ray absorption near edge structure spectroscopy
Magnetic couplings
Electrodes
Coprecipitation
High resolution transmission electron microscopy
Magnetic moments
Ultraviolet spectroscopy
Magnetic susceptibility
Oxidants
Hydrogen peroxide
Electron diffraction
Field emission
X ray powder diffraction
Sulfates
Nanocomposites
Negative ions

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Chemistry

Cite this

Woo, Myong A. ; Song, Min Sun ; Kim, Tae Woo ; Kim, In Young ; Ju, Ji Yun ; Lee, Young Soo ; Kim, Seung Joo ; Choy, Jin Ho ; Hwang, Seong Ju. / Mixed valence Zn-Co-layered double hydroxides and their exfoliated nanosheets with electrode functionality. In: Journal of Materials Chemistry. 2011 ; Vol. 21, No. 12. pp. 4286-4292.
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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 2 O 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.",
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Mixed valence Zn-Co-layered double hydroxides and their exfoliated nanosheets with electrode functionality. / Woo, Myong A.; Song, Min Sun; Kim, Tae Woo; Kim, In Young; Ju, Ji Yun; Lee, Young Soo; Kim, Seung Joo; Choy, Jin Ho; Hwang, Seong Ju.

In: Journal of Materials Chemistry, Vol. 21, No. 12, 28.03.2011, p. 4286-4292.

Research output: Contribution to journalArticle

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AU - Woo, Myong A.

AU - Song, Min Sun

AU - Kim, Tae Woo

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AU - Ju, Ji Yun

AU - Lee, Young Soo

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AU - Choy, Jin Ho

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AB - 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 2 O 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.

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