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Control of H-Related Defects in γ-MnO2 in a Hydrothermal Synthesis

Magnard, Nicolas P.L. ; Kirsch, Andrea ; Jørgensen, Mads R.V. LU orcid ; Kantor, Innokenty LU ; Sørensen, Daniel R. LU orcid ; Huotari, Simo ; Rudić, Svemir ; Bordallo, Heloisa N. and Jensen, Kirsten M.Ø. (2023) In Inorganic Chemistry 62(32). p.13021-13029
Abstract

Manganese dioxide is a good candidate for effective energy storage and conversion as it possesses rich electrochemistry. The compound also shows a wide polymorphism. The γ-variety, an intergrowth of β- and R-MnO2, has been extensively studied in several types of batteries (e.g., Zn/MnO2, Li-ion) and is a common electrode material for commercial batteries. It is well known that the insertion of protons thermodynamically stabilizes γ-MnO2 with respect to β-MnO2. Protons can enter the structure either by forming groups of 4 hydroxyls around a Mn4+ vacancy, called a Ruetschi defect, or by forming a hydroxyl group near a Mn3+ ion, called a Coleman defect. These defects... (More)

Manganese dioxide is a good candidate for effective energy storage and conversion as it possesses rich electrochemistry. The compound also shows a wide polymorphism. The γ-variety, an intergrowth of β- and R-MnO2, has been extensively studied in several types of batteries (e.g., Zn/MnO2, Li-ion) and is a common electrode material for commercial batteries. It is well known that the insertion of protons thermodynamically stabilizes γ-MnO2 with respect to β-MnO2. Protons can enter the structure either by forming groups of 4 hydroxyls around a Mn4+ vacancy, called a Ruetschi defect, or by forming a hydroxyl group near a Mn3+ ion, called a Coleman defect. These defects differently affect the electrochemistry of manganese oxide, and tailoring their amount in the structure can be used to tune the material properties. Previous studies have addressed the proton insertion process, but the role of the synthesis pathway on the amount of defects created is not well understood. We here investigate how the parameters in a hydrothermal synthesis of γ-MnO2 nanoparticles influence the amount and type of H-related defects. Structural investigations are carried out using Pair Distribution Function analysis, X-ray absorption spectroscopy, thermogravimetric analysis, and inelastic neutron scattering. We demonstrate the possibility to control the amount and type of defects introduced during the synthesis. While the amount of Ruetschi defects increases with synthesis temperature, it decreases with extended synthesis time, along with the amount of Coleman defects. Moreover, we discuss the arrangement of the defects in the γ-MnO2 nanoparticles.

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author
; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Inorganic Chemistry
volume
62
issue
32
pages
9 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • pmid:37537143
  • scopus:85168336745
ISSN
0020-1669
DOI
10.1021/acs.inorgchem.3c01815
language
English
LU publication?
yes
id
8528881c-7483-4dda-8cab-ed76d8f970b8
date added to LUP
2023-12-08 09:44:46
date last changed
2024-04-21 03:43:04
@article{8528881c-7483-4dda-8cab-ed76d8f970b8,
  abstract     = {{<p>Manganese dioxide is a good candidate for effective energy storage and conversion as it possesses rich electrochemistry. The compound also shows a wide polymorphism. The γ-variety, an intergrowth of β- and R-MnO<sub>2</sub>, has been extensively studied in several types of batteries (e.g., Zn/MnO<sub>2</sub>, Li-ion) and is a common electrode material for commercial batteries. It is well known that the insertion of protons thermodynamically stabilizes γ-MnO<sub>2</sub> with respect to β-MnO<sub>2</sub>. Protons can enter the structure either by forming groups of 4 hydroxyls around a Mn<sup>4+</sup> vacancy, called a Ruetschi defect, or by forming a hydroxyl group near a Mn<sup>3+</sup> ion, called a Coleman defect. These defects differently affect the electrochemistry of manganese oxide, and tailoring their amount in the structure can be used to tune the material properties. Previous studies have addressed the proton insertion process, but the role of the synthesis pathway on the amount of defects created is not well understood. We here investigate how the parameters in a hydrothermal synthesis of γ-MnO<sub>2</sub> nanoparticles influence the amount and type of H-related defects. Structural investigations are carried out using Pair Distribution Function analysis, X-ray absorption spectroscopy, thermogravimetric analysis, and inelastic neutron scattering. We demonstrate the possibility to control the amount and type of defects introduced during the synthesis. While the amount of Ruetschi defects increases with synthesis temperature, it decreases with extended synthesis time, along with the amount of Coleman defects. Moreover, we discuss the arrangement of the defects in the γ-MnO<sub>2</sub> nanoparticles.</p>}},
  author       = {{Magnard, Nicolas P.L. and Kirsch, Andrea and Jørgensen, Mads R.V. and Kantor, Innokenty and Sørensen, Daniel R. and Huotari, Simo and Rudić, Svemir and Bordallo, Heloisa N. and Jensen, Kirsten M.Ø.}},
  issn         = {{0020-1669}},
  language     = {{eng}},
  month        = {{08}},
  number       = {{32}},
  pages        = {{13021--13029}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Inorganic Chemistry}},
  title        = {{Control of H-Related Defects in γ-MnO<sub>2</sub> in a Hydrothermal Synthesis}},
  url          = {{http://dx.doi.org/10.1021/acs.inorgchem.3c01815}},
  doi          = {{10.1021/acs.inorgchem.3c01815}},
  volume       = {{62}},
  year         = {{2023}},
}