The relationship between Mn oxidation state and structure in triclinic and hexagonal birnessites

Ling, Florence T.; Post, Jeffrey E.; Heaney, Peter J.; Ilton, Eugene S.

doi:10.1016/j.chemgeo.2018.01.011

Cited by 36 publications

(28 citation statements)

References 54 publications

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“…It is proposed that a higher amount of Mn 3+ in the structure (>25 at%; 32% for MnO x ‐3) favors Jahn–Taller distortion, which deforms the octahedra compared to those containing Mn 4+ , and increases the extent of triclinic symmetry in the structure. On the other hand, insufficient concentration of Mn 3+ (<25 at%, 21% for MnO x ‐0.5) does not generate enough strain in the octahedra, and hence, the oxide structure tends to be more hexagonal . In general, the oxide chemistry and its structure are strongly linked to electrochemical activity and therefore can influence the material response.…”

Section: Resultsmentioning

confidence: 99%

Electrodeposited Manganese Oxide on Tailored 3D Bimetallic Nanofoams for Energy Storage Applications

et al. 2019

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Three‐dimensional (3D) electrode design has great advantages over its two‐dimensional (2D) counterparts, including higher mass loading of active material, enhanced ion diffusion, and electron charge transfer. Commercial 3D porous structures (i.e., Ni foams) do not fit the purpose of the ideal 3D electrode for supercapacitors, in which surface area (per cm2) is more important than large pore volume. These characteristics, however, can be tuned by the dynamic hydrogen bubble template (DHBT) electrodeposition, a route that is used to tailor 3D nanostructured (multi‐) metallic porous surfaces. In addition to the higher surface area and tailored porosity, these 3D nanostructures can be subsequently functionalized with different species such as metal oxides or other compounds. Therefore, a facile two‐step electrochemical fabrication of 3D composite electrode composed of a bimetallic foam functionalized with manganese (Mn) oxide is proposed. The effect of applied current densities on the distribution and structure of Mn oxide (MnOx) electrodeposited over the bare foam is discussed. The results demonstrate that this route paves the way to design high‐surface‐area architectures for charge storage electrodes with enhanced electrochemical performance (194 F g−1 mg−1 of electrodeposited MnOx at 0.5 A g−1) and high charge–discharge rate capabilities (91% capacitance retention at 20 A g−1) for supercapacitor applications.

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Section: Resultsmentioning

confidence: 99%

Electrodeposited Manganese Oxide on Tailored 3D Bimetallic Nanofoams for Energy Storage Applications

et al. 2019

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“…The manganese oxide mineral phase in varnish has been described as poorly crystalline birnessite (2)-a phase composed of manganese octahedra organized in layers (35); it is formally Mn 4+ O 2 , but can incorporate a substantial fraction of Mn 3+ instead of Mn 4+ when accompanied by charge balance with heteroatoms (Na + , K + , Ba 2+ , etc.) between the layers (36). Using synchrotron X-ray absorption near-edge structure (XANES) spectroscopy and multiple-energy "redox" mapping at the manganese K-edge, we found that varnish birnessite is not homogenous in its redox properties.…”

Section: Significancementioning

confidence: 94%

An ecophysiological explanation for manganese enrichment in rock varnish

Lingappa

Yeager

Sharma

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Desert varnish is a dark rock coating that forms in arid environments worldwide. It is highly and selectively enriched in manganese, the mechanism for which has been a long-standing geological mystery. We collected varnish samples from diverse sites across the western United States, examined them in petrographic thin section using microscale chemical imaging techniques, and investigated the associated microbial communities using 16S amplicon and shotgun metagenomic DNA sequencing. Our analyses described a material governed by sunlight, water, and manganese redox cycling that hosts an unusually aerobic microbial ecosystem characterized by a remarkable abundance of photosynthetic Cyanobacteria in the genus Chroococcidiopsis as the major autotrophic constituent. We then showed that diverse Cyanobacteria, including the relevant Chroococcidiopsis taxon, accumulate extraordinary amounts of intracellular manganese—over two orders of magnitude higher manganese content than other cells. The speciation of this manganese determined by advanced paramagnetic resonance techniques suggested that the Cyanobacteria use it as a catalytic antioxidant—a valuable adaptation for coping with the substantial oxidative stress present in this environment. Taken together, these results indicated that the manganese enrichment in varnish is related to its specific uptake and use by likely founding members of varnish microbial communities.

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“…Nevertheless, the birnessite group of minerals has a wide structural and compositional complexity such that there remains uncertainty as to the level of accuracy in modeling this group using mechanical mixtures of end members (Ling et al., 2018). We pose that combining bulk‐ and micro‐scale analysis for linear combination EXAFS alleviates some uncertainty and provide confirmation of bulk modeling trends.…”

Section: Discussionmentioning

confidence: 99%

Spectroscopic Insights Into Ferromanganese Crust Formation and Diagenesis

Sutherland

Wankel

Hein

et al. 2020

Geochem Geophys Geosyst

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Marine ferromanganese deposits, including both crusts and nodules, form in all five global ocean basins at almost every latitude (Cronan, 1977; Hein et al., 1997, 2000). Ferromanganese deposits have classically been categorized into one of three groups based on mode of formation and trace element associations: hydrogenetic deposits, diagenetic deposits, and hydrothermal deposits. Hydrogenetic ferromanganese deposits precipitate in direct contact with the water column on the surface of a substrate rock or existing crust or nodule

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The relationship between Mn oxidation state and structure in triclinic and hexagonal birnessites

Cited by 36 publications

References 54 publications

Electrodeposited Manganese Oxide on Tailored 3D Bimetallic Nanofoams for Energy Storage Applications

Electrodeposited Manganese Oxide on Tailored 3D Bimetallic Nanofoams for Energy Storage Applications

An ecophysiological explanation for manganese enrichment in rock varnish

Spectroscopic Insights Into Ferromanganese Crust Formation and Diagenesis

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