Origin of improved electrochemical activity of β-MnO 2 nanorods: Effect of the Mn valence in the precursor on the crystal structure and electrode activity of manganates

In Young Kim, Hyung Wook Ha, Tae Woo Kim, Younkee Paik, Jin Ho Choy, Seong Ju Hwang

Research output: Contribution to journalArticle

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Abstract

1D nanorods/nanowires of manganese oxides with different crystal structures and morphologies were prepared and characterized to understand the influence of the Mn valence in the solid-state precursor on the electrochemical activity of these nanomaterials and to elucidate the mechanism responsible for the excellent activity of β-MnO 2 nanorods as well. According to powder X-ray diffraction analyses, treating manganese oxide precursors that have an oxidation state of ≤+3 with persulfate ions under hydrothermal conditions yields manganese oxides with the β-MnO 2 structure. In contrast, the use of a LiMn 2 O 4 precursor with a higher Mn valence leads to the formation of the α-MnO 2 -structured manganese oxide. Electron microscopic studies clearly show a 1D nanorod-type morphology for the β-MnO 2 material, whereas a 1D nanowire-type morphology with a higher aspect ratio is observed for the α-MnO 2 material. The diameter of the β-MnO 2 nanorods decreases as the Mn valence in the precursors becomes smaller. According to electrochemical measurements, the formation of nanorods dramatically improves the electrode performance of the β-MnO 2 phase. This compares with a relatively weak performance enhancement for the α- and δ-MnO 2 phases upon the nanowire formation. The optimum electrode property results from the smaller β-MnO 2 nanorods prepared with the MnO precursor. 7 Li magic angle spinning nuclear magnetic resonance spectroscopy clearly demonstrates that Li + ions in the lithiated β-MnO 2 phase are adsorbed mainly on the sample surface. On the basis of this finding, we attribute the improved electrode performance of the β-MnO 2 nanorods to their expanded surface area.

Original languageEnglish
Pages (from-to)21274-21282
Number of pages9
JournalJournal of Physical Chemistry C
Volume113
Issue number51
DOIs
Publication statusPublished - 2009 Dec 1

Fingerprint

Nanorods
nanorods
Crystal structure
Manganese oxide
valence
manganese oxides
Electrodes
crystal structure
electrodes
Nanowires
nanowires
Ions
Magic angle spinning
crystal morphology
magnetic resonance spectroscopy
high aspect ratio
Nanostructured materials
X ray powder diffraction
metal spinning
Nuclear magnetic resonance spectroscopy

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Cite this

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title = "Origin of improved electrochemical activity of β-MnO 2 nanorods: Effect of the Mn valence in the precursor on the crystal structure and electrode activity of manganates",
abstract = "1D nanorods/nanowires of manganese oxides with different crystal structures and morphologies were prepared and characterized to understand the influence of the Mn valence in the solid-state precursor on the electrochemical activity of these nanomaterials and to elucidate the mechanism responsible for the excellent activity of β-MnO 2 nanorods as well. According to powder X-ray diffraction analyses, treating manganese oxide precursors that have an oxidation state of ≤+3 with persulfate ions under hydrothermal conditions yields manganese oxides with the β-MnO 2 structure. In contrast, the use of a LiMn 2 O 4 precursor with a higher Mn valence leads to the formation of the α-MnO 2 -structured manganese oxide. Electron microscopic studies clearly show a 1D nanorod-type morphology for the β-MnO 2 material, whereas a 1D nanowire-type morphology with a higher aspect ratio is observed for the α-MnO 2 material. The diameter of the β-MnO 2 nanorods decreases as the Mn valence in the precursors becomes smaller. According to electrochemical measurements, the formation of nanorods dramatically improves the electrode performance of the β-MnO 2 phase. This compares with a relatively weak performance enhancement for the α- and δ-MnO 2 phases upon the nanowire formation. The optimum electrode property results from the smaller β-MnO 2 nanorods prepared with the MnO precursor. 7 Li magic angle spinning nuclear magnetic resonance spectroscopy clearly demonstrates that Li + ions in the lithiated β-MnO 2 phase are adsorbed mainly on the sample surface. On the basis of this finding, we attribute the improved electrode performance of the β-MnO 2 nanorods to their expanded surface area.",
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Origin of improved electrochemical activity of β-MnO 2 nanorods : Effect of the Mn valence in the precursor on the crystal structure and electrode activity of manganates. / Kim, In Young; Ha, Hyung Wook; Kim, Tae Woo; Paik, Younkee; Choy, Jin Ho; Hwang, Seong Ju.

In: Journal of Physical Chemistry C, Vol. 113, No. 51, 01.12.2009, p. 21274-21282.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Origin of improved electrochemical activity of β-MnO 2 nanorods

T2 - Effect of the Mn valence in the precursor on the crystal structure and electrode activity of manganates

AU - Kim, In Young

AU - Ha, Hyung Wook

AU - Kim, Tae Woo

AU - Paik, Younkee

AU - Choy, Jin Ho

AU - Hwang, Seong Ju

PY - 2009/12/1

Y1 - 2009/12/1

N2 - 1D nanorods/nanowires of manganese oxides with different crystal structures and morphologies were prepared and characterized to understand the influence of the Mn valence in the solid-state precursor on the electrochemical activity of these nanomaterials and to elucidate the mechanism responsible for the excellent activity of β-MnO 2 nanorods as well. According to powder X-ray diffraction analyses, treating manganese oxide precursors that have an oxidation state of ≤+3 with persulfate ions under hydrothermal conditions yields manganese oxides with the β-MnO 2 structure. In contrast, the use of a LiMn 2 O 4 precursor with a higher Mn valence leads to the formation of the α-MnO 2 -structured manganese oxide. Electron microscopic studies clearly show a 1D nanorod-type morphology for the β-MnO 2 material, whereas a 1D nanowire-type morphology with a higher aspect ratio is observed for the α-MnO 2 material. The diameter of the β-MnO 2 nanorods decreases as the Mn valence in the precursors becomes smaller. According to electrochemical measurements, the formation of nanorods dramatically improves the electrode performance of the β-MnO 2 phase. This compares with a relatively weak performance enhancement for the α- and δ-MnO 2 phases upon the nanowire formation. The optimum electrode property results from the smaller β-MnO 2 nanorods prepared with the MnO precursor. 7 Li magic angle spinning nuclear magnetic resonance spectroscopy clearly demonstrates that Li + ions in the lithiated β-MnO 2 phase are adsorbed mainly on the sample surface. On the basis of this finding, we attribute the improved electrode performance of the β-MnO 2 nanorods to their expanded surface area.

AB - 1D nanorods/nanowires of manganese oxides with different crystal structures and morphologies were prepared and characterized to understand the influence of the Mn valence in the solid-state precursor on the electrochemical activity of these nanomaterials and to elucidate the mechanism responsible for the excellent activity of β-MnO 2 nanorods as well. According to powder X-ray diffraction analyses, treating manganese oxide precursors that have an oxidation state of ≤+3 with persulfate ions under hydrothermal conditions yields manganese oxides with the β-MnO 2 structure. In contrast, the use of a LiMn 2 O 4 precursor with a higher Mn valence leads to the formation of the α-MnO 2 -structured manganese oxide. Electron microscopic studies clearly show a 1D nanorod-type morphology for the β-MnO 2 material, whereas a 1D nanowire-type morphology with a higher aspect ratio is observed for the α-MnO 2 material. The diameter of the β-MnO 2 nanorods decreases as the Mn valence in the precursors becomes smaller. According to electrochemical measurements, the formation of nanorods dramatically improves the electrode performance of the β-MnO 2 phase. This compares with a relatively weak performance enhancement for the α- and δ-MnO 2 phases upon the nanowire formation. The optimum electrode property results from the smaller β-MnO 2 nanorods prepared with the MnO precursor. 7 Li magic angle spinning nuclear magnetic resonance spectroscopy clearly demonstrates that Li + ions in the lithiated β-MnO 2 phase are adsorbed mainly on the sample surface. On the basis of this finding, we attribute the improved electrode performance of the β-MnO 2 nanorods to their expanded surface area.

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