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Structures of mixed manganese ruthenium oxides (Mn1−xRux)O2 crystallised under acidic hydrothermal conditions
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McLeod, Lucy, Spikes, Geoffrey H., Kashtiban, Reza J., Walker, Marc, Chadwick, Alan V., Sharman, Jonathan D. B. and Walton, Richard I. (2020) Structures of mixed manganese ruthenium oxides (Mn1−xRux)O2 crystallised under acidic hydrothermal conditions. Dalton Transactions, 49 (8). pp. 2661-2670. doi:10.1039/C9DT04156G ISSN 1477-9226.
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Official URL: https://doi.org/10.1039/C9DT04156G
Abstract
A synthesis method for the preparation of mixed manganese–ruthenium oxides is presented along with a detailed characterisation of the solids produced. The use of 1 M aqueous sulfuric acid mediates the redox reaction between KRuO4, KMnO4 and Mn2+ to form ternary oxides. At reaction temperature of 100 °C the products are mixtures of α-MnO2 (hollandite-type) and β-MnO2 (rutile-type), with some evidence of Ru incorporation in each from their expanded unit cell volumes. At reaction temperature of 200 °C solid-solutions β-Mn1−xRuxO2 are formed and materials with x ≤ 0.6 have been studied. The amount of Ru included in the oxide is greater than expected from the ratio of metals used in the synthesis, as determined by elemental analysis, implying that some Mn remains unreacted in solution. Powder X-ray diffraction (XRD) shows that while the unit cell volume expands in a linear manner, following Vegard's law, the tetragonal lattice parameters, and the a/c ratio, do not follow the extrapolated trends: this anisotropic behaviour is consistent with the different local coordination of the metals in the end members. Powder XRD patterns show increased peak broadening with increasing ruthenium content, which is corroborated by electron microscopy that shows nanocrystalline material. X-ray absorption near-edge spectra show that the average oxidation state of Mn in the solid solutions is reduced below +4 while that of Ru is increased above +4, suggesting some redistribution of charge. Analysis of the extended X-ray absorption fine structure provides complementary local structural information, confirming the formation of a solid solution, while X-ray photoelectron spectroscopy shows that the surface oxidation states of both Ru and Mn are on average lower than +4, suggesting a disordered surface layer may be present in the materials.
Item Type: | Journal Article | ||||||||
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Subjects: | Q Science > QC Physics Q Science > QP Physiology T Technology > TA Engineering (General). Civil engineering (General) T Technology > TN Mining engineering. Metallurgy |
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry Faculty of Science, Engineering and Medicine > Science > Physics |
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Library of Congress Subject Headings (LCSH): | Manganese oxides, Ruthenium oxides, Manganese oxides -- Synthesis, Ruthenium oxides -- Synthesis, X-ray diffraction imaging | ||||||||
Journal or Publication Title: | Dalton Transactions | ||||||||
Publisher: | Royal Society of Chemistry | ||||||||
ISSN: | 1477-9226 | ||||||||
Official Date: | 28 February 2020 | ||||||||
Dates: |
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Volume: | 49 | ||||||||
Number: | 8 | ||||||||
Page Range: | pp. 2661-2670 | ||||||||
DOI: | 10.1039/C9DT04156G | ||||||||
Status: | Peer Reviewed | ||||||||
Publication Status: | Published | ||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||
Date of first compliant deposit: | 4 March 2020 | ||||||||
Date of first compliant Open Access: | 6 March 2020 | ||||||||
RIOXX Funder/Project Grant: |
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