Structural Chemistry of Manganese Dioxide and Related Compounds

Albering, Jörg

doi:10.1002/9783527611676.ch4

Cited by 13 publications

(27 citation statements)

References 66 publications

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“…Of the several phases formed by manganese when combined with oxygen, Mn 3 O 4 , Mn 2 O 3 and MnO 2 are of particular interest here. The last one has been reported to feature about 14 different crystallographic phases [34][35][36], which explains the difficulty in understanding the catalytic mechanisms. However, the catalytic properties of Mn oxides are of remarkable interest for possible sensing applications due to the broad range of VOCs that can be oxidized.…”

Section: Manganese Oxidesmentioning

confidence: 99%

How Chemoresistive Sensors Can Learn from Heterogeneous Catalysis. Hints, Issues, and Perspectives

et al. 2021

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The connection between heterogeneous catalysis and chemoresistive sensors is emerging more and more clearly, as concerns the well-known case of supported noble metals nanoparticles. On the other hand, it appears that a clear connection has not been set up yet for metal oxide catalysts. In particular, the catalytic properties of several different oxides hold the promise for specifically designed gas sensors in terms of selectivity towards given classes of analytes. In this review, several well-known metal oxide catalysts will be considered by first exposing solidly established catalytic properties that emerge from related literature perusal. On this basis, existing gas-sensing applications will be discussed and related, when possible, with the obtained catalysis results. Then, further potential sensing applications will be proposed based on the affinity of the catalytic pathways and possible sensing pathways. It will appear that dialogue with heterogeneous catalysis may help workers in chemoresistive sensors to design new systems and to gain remarkable insight into the existing sensing properties, in particular by applying the approaches and techniques typical of catalysis. However, several divergence points will appear between metal oxide catalysis and gas-sensing. Nevertheless, it will be pointed out how such divergences just push to a closer exchange between the two fields by using the catalysis knowledge as a toolbox for investigating the sensing mechanisms.

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Section: Manganese Oxidesmentioning

confidence: 99%

How Chemoresistive Sensors Can Learn from Heterogeneous Catalysis. Hints, Issues, and Perspectives

et al. 2021

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“…The structure of α-MnO2 consists of double chains of edge-sharing MnO6 octahedra to form [2 × 2] tunnels of ca 0.46 nm × 0.46 nm. 16 The morphology of α-MnO2 was nanorod-shaped as shown in Fig.2d. Wang et al 11 proposed that α-MnO2 nanorods grew along a (001) axis direction and exposed the most stable (110) crystal planes (Fig.2(c, cʹ)).…”

Section: Scr Catalytic Activitymentioning

confidence: 93%

“…The crystal structure of δ-MnO2 is built up from layers of edge-sharing MnO6 octahedra with a certain number of water molecules and foreign cations between them. The spacing between the two layers is about 0.713 nm, 16 larger than the tunnel size of α-MnO2, so δ-MnO2 needs more H2O or other foreign cations to stabilize the structure. According to Braggʹs equation, the interplanar spacing for (001) plane of δ-MnO2 was calculated to be 0.719 nm, close to the interlayer spacing of 0.713 nm, which was in agreement with the schematic structures of δ-MnO2 (Fig.2bʹ).…”

Section: Scr Catalytic Activitymentioning

confidence: 99%

“…11 The average Mn-O bond lengths of α-and δ-MnO2 are 0.198 and 0.194 nm, respectively. 16 It suggests that the Mn cations of α-MnO2 are more active than those of δ-MnO2, beneficial to the NH3 adsorption on Mn sites. Furthermore, α-MnO2 owns the [2×2] tunnels as shown in Fig.2b, of which the effective pore opening for gas adsorption is close to 0.265 nm, so that NH3 and H2O molecules with diameters below 0.265 nm can be inserted into the tunnels.…”

Section: Aciditymentioning

confidence: 99%

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Effects of MnO<sub>2</sub> Crystal Structure and Surface Property on the NH<sub>3</sub>-SCR Reaction at Low Temperature

Dai¹,

Li²,

Peng³

et al. 2012

Acta Physico-Chimica Sinica

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察其低温 NH3选择性催化还原 NOx (NH3-SCR)的性能. 结果表明 MnO2纳米棒的比表面积不是影响活性的主要因素, 催化剂的晶相结构和表面性质对催化活性有很大影响, 隧道状α-MnO2纳米棒的低温 NH3-SCR 活性明显高于层状δ-MnO2纳米棒. 结构分析和 NH3程序升温脱附(NH3-TPD)实验表明, α-MnO2纳米棒的暴露晶面(110) 面存在大量的配位不饱和 Mn 离子, 形成较多的 Lewis 酸性位点, 而且α-MnO2较弱的 Mn-O 键和隧道结构都有利于 NH3的吸附; 而δ-MnO2纳米棒的暴露晶面(001)面上的 Mn 离子已达到配位饱和, 所以其表面 Lewis 酸性位点较少. X 射线光电子能谱(XPS)和热重(TG)分析表明α-MnO2纳米棒的表面更有利于 NH3和 NOx的活化. 具有有利于吸附 NH3和活化 NH3和 NOx的表面性质和晶型结构, 是α-MnO2纳米棒活性高的主要原因.

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“…Диоксид марганца способен образовывать ряд полиморфных модификаций: криптомелан (α-MnO 2 ), пиролюзит (β-MnO 2 ), нсутит (γ-MnO 2 ), бирнессит (δ-MnO 2 ), рамсделлит (R-MnO 2 ) и др. [1][2][3]. Структурными единицами всех модификаций диоксида марганца являются октаэдры [MnO 6 ], различное сочленение которых обеспечивает существование структур со сквозными каналами (тодорокит, рамсделлит, криптомелан), слоистых структур (бернессит и бузерит) или структур срастания пиролюзита и рамсделлита (нсутит) [4].…”

Section: Introductionunclassified

MICROWAVE-HYDROTHERMAL HEXAMETHYLENETETRAMINE-MEDIATED SYNTHESIS OF NANOCRYSTALLINE MnO2

2018

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В статье рассмотрен нетрадиционный подход к синтезу различных полиморфных модификаций диоксида марганца, заключающийся в гидротермально-микроволновой обработке реакционной смеси, содержащей перманганат калия и гексаметилентетрамин. Подчеркнута актуальность работы, обусловленная такими свойствами MnO 2 , как каталитическая и фотокаталитическая активность, его применением в аккумуляторах, суперконденсаторах, в биохимических приложениях. Подробно проанализировано влияние температуры и продолжительности гидротермально-микроволновой обработки, pH среды и типа добавляемой кислоты на фазовый состав и морфологию диоксида марганца. Показано, что фазовый состав диоксида марганца в значительной степени определяется не только температурой, продолжительностью синтеза и pH среды, но и типом добавляемой в реакционную смесь кислоты -азотной или серной. В частности, присутствие серной кислоты, по-видимому, приводит к стабилизации α-MnO 2 . Отмечено, что тип используемой в ходе синтеза кислоты, а также другие условия синтеза не оказывают существенного влияния ни на форму, ни на размер частиц α-, γ-и δ-MnO 2 . Напротив, морфология β-MnO 2 оказалась крайне чувствительной к условиям синтеза: в условиях продолжительной (24 ч) гидротермальной обработки реакционных смесей в диапазоне рН 0.5-1 происходит формирование однофазного пиролюзита, микроструктура которого определяется составом реакционной смеси.Ключевые слова: гидротермально-микроволновой синтез, MnO 2 , гексаметилентетрамин.The article considers a non-conventional approach to the synthesis of various polymorphic modifications of manganese dioxide. The approach consists in hydrothermal microwave processing of a reaction mixture containing potassium permanganate and hexamethylenetetramine. We emphasize the relevance of the work due to such MnO 2 properties as catalytic and photocatalytic activity, its application in accumulators, supercondensers and biochemistry. We report on the first detailed study on the role of temperature, synthesis duration and pH value on the phase composition and morphology of nanocrystalline MnO 2 . We show that the phase composition of manganese dioxide is largely determined not only by temperature, synthesis duration and pH value, but also by the acid added to the reaction mixture (nitric or sulphuric). In particular, the presence of sulfuric acid apparently results in α-MnO 2 stabilization. It is noted that the type of the acid used in the course of the synthesis,

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Structural Chemistry of Manganese Dioxide and Related Compounds

Cited by 13 publications

References 66 publications

How Chemoresistive Sensors Can Learn from Heterogeneous Catalysis. Hints, Issues, and Perspectives

How Chemoresistive Sensors Can Learn from Heterogeneous Catalysis. Hints, Issues, and Perspectives

Effects of MnO<sub>2</sub> Crystal Structure and Surface Property on the NH<sub>3</sub>-SCR Reaction at Low Temperature

MICROWAVE-HYDROTHERMAL HEXAMETHYLENETETRAMINE-MEDIATED SYNTHESIS OF NANOCRYSTALLINE MnO2

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