Porous manganese oxide spheres form readily from a reaction between KMnO4 and n-butanol in aqueous butyric acid under ambient conditions. Spheres have uniform size, tuneable diameters and high surface areas. The material is an active catalyst for the oxidation of isopropanol to acetone.

Manganese oxide hollow spheres have been prepared by a facile, self-assembly synthesis and doped with Fe, Cu, V, and Ce. The materials have high surface areas and shells consisting of nanoplatelets. Two different sets of reactions were carried out: (1) with constant butyric acid concentration using 10:1 BA: Mn and (2) with adjusted butyric acid concentration using 10:1 BA:total metal (Mn + dopant). Dopants promote the formation of yolk structures within the hollow spheres, and at higher dopant:Mn ratios cause the spheres to fill. Increasing the butyric acid concentration likewise promotes yolk formation and sphere filing, as well as larger sphere size and loss of monodispersity. Manganese oxide hollow spheres are active catalysts in converting isopropanol to acetone, although doping does not improve catalyst performance except in the case of Cu. (C) 2015 Elsevier Ltd. All rights reserved.

The synthesis of a tunneled hollandite-type manganese oxide with interstitial and framework Cr3+ is described. This unique material is prepared from a layered buserite precursor under conditions previously believed to only yield todorokite-type manganese oxides with larger tunnels. The influence of Cr3+ in promoting the hollandite structure has been investigated by selectively placing the cation either in interstitial or framework sites. The use of framework Cr3+ in combination with other interstitial cations generates related hollandite and todorokite derivatives. Catalytic oxidation reactions with benzyl alcohol and carbon monoxide have also been examined. (C) 2012 Elsevier Ltd. All rights reserved.

Reactions between MnSO4 and KMnO4 in the presence of carboxylic acids provide a facile, one-pot route to nanostructured manganese oxides with high surface areas. Acetic and propionic acid induce formation of hierarchical nanosphere morphologies whereas butyric acid promotes assembly of hollow spheres. The materials are active catalysts for CO oxidation.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and Characterization of a Layered Manganese Oxide: Materials Chemistry for the Inorganic or Instrumental Methods LabStanton Ching , Ram P. Neupane , and Timothy P. Gray View Author Information Department of Chemistry, Connecticut College, New London, CT 06320Cite this: J. Chem. Educ. 2006, 83, 11, 1674Publication Date (Web):November 1, 2006Publication History Received3 August 2009Published online1 November 2006Published inissue 1 November 2006https://pubs.acs.org/doi/10.1021/ed083p1674https://doi.org/10.1021/ed083p1674research-articleACS PublicationsRequest reuse permissionsArticle Views1273Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Hydration,Layered materials,Morphology,Oxides,Physical and chemical processes Get e-Alerts

High quality manganese oxide thin films with smooth surfaces and even thicknesses have been prepared with a nonaqueous sol–gel process involving reduction of tetraethylammonium permanganate in methanol. Spin-coated films have been cast onto soft glass, quartz, and Ni foil substrates, with two coats being applied for optimum crystallization. The addition of alkali metal cations as dopants results in exclusive formation of the layered birnessite phase. By contrast, analogous reactions in bulk sol–gel reactions yield birnessite, tunneled, and spinel phases depending on the dopant cation. XRD patterns confirm the formation of well-crystallized birnessite. SEM images of Li-, Na-, and K–birnessite reveal extremely smooth films having uniform thickness of less than 0.5μm. Thin films of Rb– and Cs–birnessite have more fractured and uneven surfaces as a result of some precipitation during the sol–gel transformation. All films consist of densely packed particles of about 0.1μm. When tetrabutylammonium permanganate is used instead of tetraethylammonium permanganate, the sol–gel reaction yields amorphous manganese oxide as the result of diluted Mn sites in the xerogel film. Bilayer films have been prepared by casting an overcoat of K–birnessite onto an Na–birnessite film. However, Auger depth profiling indicates considerable mixing between the adjacent layers.

Microporous manganese oxides have been prepared by nonaqueous sol-gel reactions involving tetrabutylammonium. (TBA) or tetraethylammonium (TEA) permanganate and methanol in the presence of alkali cation dopants. Layered birnessite-type materials were obtained for Na+ and K+ dopants in a 0.5:1 reactant ratio with manganese. Na-birnessite was isolated in hydrated and dehydrated forms (7 vs 5.6 Angstrom interlayer spacing) whereas only the hydrated K-birnessite was observed. Cryptomelane was generated with a K:Mn ratio of 0.25:1. Spinel manganese oxides were formed with Li+ dopants using 0.5:1 and 0.75:1 Li:Nin ratios. The materials were characterized by powder X-ray diffraction (XRD), elemental analyses, Mn oxidation state determination, thermogravimetric analysis, and scanning electron microscopy. Thin films of manganese oxides were prepared by spin coating TEAMnO(4)-derived sols onto glass slides. Unlike the bulk gel syntheses, only layered birnessite phases were obtained for thin films with Li+, Na+, and K+ dopants. Aerogels of K-birnessite and cryptomelane were prepared by supercritical fluid extraction of bulk gels with carbon dioxide. Surface areas were increased over the conventional sol-gel workup, but overall the values were not exceptional in these preliminary experiments.

Hollandite with Cr(III) in both tunnel and framework sites has been prepared hydrothermally from layered manganese oxide precursors.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTManganese Oxide Thin Films with Fast Ion-Exchange PropertiesOscar Giraldo, Stephanie L. Brock, William S. Willis, Manuel Marquez, Steven L. Suib, and Stanton ChingView Author Information Department of Chemistry, University of Connecticut, U-60 55 North Eagleville Rd., Storrs, Connecticut 06269-3060 Department of Chemical Engineering and Institute of Materials Sciences University of Connecticut, Storrs, Connecticut 06269 Department of Chemistry, Connecticut College 270 Mohegan Av., New London, Connecticut 06320 Cite this: J. Am. Chem. Soc. 2000, 122, 38, 9330–9331Publication Date (Web):September 8, 2000Publication History Received30 May 2000Published online8 September 2000Published inissue 1 September 2000https://doi.org/10.1021/ja001860iCopyright © 2000 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1100Altmetric-Citations100LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (38 KB) Get e-AlertsSUBJECTS:Cations,Oxides,Thin films,Transition metals,X-ray photoelectron spectroscopy Get e-Alerts

Microporous todorokite-type manganese oxides have been synthesized by a new route in which the key Na-birnessite precursor is prepared by oxidation of Mn(OH)2 with K2S2O8 in aqueous NaOH. The reaction is promoted by foreign metal cations such as Mg2+, Co2+, Ni2+, and Cu2+, which are incorporated into the manganese oxide layer framework. These same divalent cations are used in a subsequent ion-exchange reaction that converts the Na-birnessite into a related layered material, buserite. Hydrothermal treatment of the buserite ultimately yields Mg-, Co-, Ni-, or Cu-todorokite. The todorokites have been characterized by powder X-ray diffraction, elemental analysis, Mn oxidation state determination, scanning electron microscopy, and cyclic voltammetry. The composition of Mg-doped Na-birnessite is Na0.26Mg0.13MnO2.04(H2O)1.26, with the average Mn oxidation state being 3.55. Mg-todorokite has a composition of Mg0.33MnO2.14(H2O)0.97, with a Mn oxidation state of 3.62. A mixed Co/Ni-todorokite has been synthesized to assess the distribution of foreign cation in framework and tunnel sites. For Co-todorokite, 42% of the Co is in the manganese oxide framework and 58% is in the interlayer galleries, which gives the formula Co0.21(Co0.16Mn)O2.21(H2O)0.97. If the Co percentages are applied to Mg-todorokite, a formula of Mg0.19(Mg0.14Mn)O2.14(H2O)0.97 is obtained. Thermal stability experiments reveal that Mg-todorokite is more robust compared to the other todorokites and remains intact up to 400°C. The Co, Ni, and Cu-todorokites have similar thermal stabilities and their structures collapse at about 300°C. Na-birnessite prepared by the Mn(OH)2/K2S2O8 route can further be used to generate other birnessite derivatives such as H-birnessite and alkylammonium-birnessites. These derivatives can be synthesized both with and without Mg2+, Co2+, Ni2+, and Cu2+ as isomorphous framework dopants.