Amorphous Metal Fluorides with Extraordinary High Surface Areas

Kemnitz, Erhard; Groß, U.; Rüdiger, Stephan; Shekar, Chandra S.

doi:10.1002/anie.200351278

Cited by 229 publications

(292 citation statements)

References 8 publications

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“…6B). Two very weak n(OD) bands are detected at 2629 and 2540 cm 1 , showing that Zn OH groups are not accessible to D 2 O and hence are located in the bulk. This location is confirmed by the following infrared experiments performed with different probe molecules, since no n(OH) band perturba tion has been observed whatever the probe used.…”

Section: 26mentioning

confidence: 99%

“…Therefore, we conclude the existence of Zn OH bindings. The assignment of these species is not straightforward, since previous studies reported the presence of OH groups on zinc oxide at 3670, 3625 and 3445 cm 1 . 28 Recently, a FTIR investigation performed under UHV conditions combining single crystal HREELS results showed that OH groups formed on defects exhibit IR bands at 3564 and 3448 cm 1 , which is closer to our positions.…”

Section: 26mentioning

confidence: 99%

“…Although this new approach for high surface area metal fluorides was devel oped just a few years ago, the already achieved results have given access to fundamental research insights and opened a very broad range of practical applications. 1,2 Since the early days of this approach, we have continuously worked on the fluorolytic sol gel synthesis of novel nanoscopic fluoride materials and on the evaluation of their properties. The latter is essential for a targeted application of the resulting fluorides in fields such as anti reflective coatings, 3 high performance ceramics 4 and heteroge neous catalysis.…”

Section: Introductionmentioning

confidence: 99%

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Novel sol–gel prepared zinc fluoride: synthesis, characterisation and acid–base sites analysis

et al. 2012

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The fluorolytic sol-gel route sets a milestone in the development of synthesis methods for nanoscopic fluoride materials. They exhibit fundamentally distinct properties in comparison to classically prepared metal fluorides. To broaden this area, we report in this paper the first fluorolytic sol-gel synthesis of ZnF 2 . The obtained sol was studied with dynamic light scattering (DLS). The dried ZnF 2 xerogel was investigated with elemental analysis, thermal analysis, powder X-ray diffraction (XRD), solid-state MAS NMR, and N 2 adsorption-desorption measurements. The characterisations revealed a remarkably high surface area of the sol-gel prepared ZnF 2 . To determine key parameters deciding its prospects in future catalytic applications, we studied the surface acidity-basicity by using in situ FTIR with different probe molecules. Compared to the previously established MgF 2 , weaker Lewis acid sites are predominant on the surface of ZnF 2 with some base sites, indicating its potential as a heterogeneous catalyst component. In short, we believe that the successful synthesis and detailed characterisation of nanoscopic ZnF 2 allow follow-up work exploring its applications, and will lead to studies of more metal fluorides with similar methods.

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Section: 26mentioning

confidence: 99%

Section: 26mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Novel sol–gel prepared zinc fluoride: synthesis, characterisation and acid–base sites analysis

et al. 2012

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“…In order to improve the performances for the conversion reaction, it is favorable to shorten and increase the lithium insertion pathways and to create the abundant active reaction area for FeF 3 and lithium. Thus, the authors focused on the fluorolysis method to prepare metal fluorides with high surface area [27].…”

Section: Introductionmentioning

confidence: 99%

“…In the first step, a precursor of metal fluoride is prepared by mixing organic solutions of anhydrous hydrogen fluoride (HF) and a metal salt (alkoxides, nitrates, or chlorides) followed by removal of organics in vacuo. In the second step, the obtained precursor is fluorinated by a fluorine containing gas at elevated temperatures to form metal fluoride [27][28][29][30][31][32]. Several studies reported the effects of synthetic conditions on the structural properties of AlF 3 [29] and MgF 2 [30].…”

Section: Introductionmentioning

confidence: 99%

Iron(III) fluoride synthesized by a fluorolysis method and its electrochemical properties as a positive electrode material for lithium secondary batteries

Tawa

Yamamoto

Matsumoto

et al. 2016

Journal of Fluorine Chemistry

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Iron(III) fluoride (FeF 3 ) with low crystallinity and high surface area has been synthesized by a fluorolysis method, and applied as a positive electrode material for lithium secondary batteries. The FeF 3 prepared with a high molar ratio of hydrogen fluoride exhibits a high surface area and crystallinity. The FeF 3 sample treated at 300 °C under a F 2 /Ar atmosphere exhibits the highest surface area and was selected for further electrochemical test in view of improvement of performance in the potential region of conversion reactions. The initial discharge (lithiation) capacity was 676 mAh g −1 that was close to the theoretical capacity of FeF 3 (712 mAh g −1 ).Compared to the highly crystalline FeF 3 commercially available, the synthesized FeF 3 in the present study exhibited a low discharge capacity attributed to the insertion reaction because of the low crystallinity, and showed a low overpotential and larger capacity corresponding to the conversion reaction owing to the higher surface area of the fluorides.

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Fluorides: Solid‐State Chemistry

Massa

2005

Encyclopedia of Inorganic Chemistry

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Inorganic solid fluorides and fluorometalates play a unique role in inorganic chemistry. The preparation, mostly using aqueous or anhydrous HF or even elemental F 2 , requires special conditions: no glass or silicate containing vessels can be used. Their structural chemistry is governed by the outsider role of the fluoride anion. It is the smallest and least polarizable anion and its mainly ionic compounds follow the rules of hard spheres packing better than any other class of substances. Nearly all metal ions except those with the largest ionic radii form fluoride structures with octahedral [M n + F 6 ] (6− n )– units. If the metal:fluorine ratio is less than 6, these octahedra share common vertices or, in rare cases, edges or even faces to account for electroneutrality, the more the lower the oxidation state of the metal. In this way, a variety of 1D chain, 2D net, and 3D framework structures is formed that can be classified into a few large structure families. In binary fluorides, for example, VF 5 has an octahedral cis‐chain structure, VF 4 a layer structure based on a square net of corner‐connected octahedra, VF 3 has a ReO 3 ‐related 3D structure with all corners of octahedra connected, and VF 2 has the rutile‐type structure with partial edge‐sharing of octahedra. In ternary or quaternary compounds, for example, alkali or alkaline earth fluorometalates, the same principles are valid for the anionic substructure while the counter cations fill interstices and stabilize at the same time the structure. The main structure families are grouped according to the basic principles of octahedral nets. These are the ReO 3 ‐related trifluorides, the fluoride perovskites AMF 3 , their relatives elpasolites A 2 A′MF 6 , and cryolites A 3 MF 6 , as well as some layer structures with square nets. A second large family is based on mixed octahedral nets including triple units: it includes for example, the pyrochlores, the weberites, the hexagonal and tetragonal tungsten bronze structures, and some derivable layer structures. Recent developments deal with ‘tailoring’ of low‐dimensional or framework structures using ‘soft‐chemistry’ methods. The relatively simple structural chemistry of fluorides invoked their use as model systems, for instance, for the investigation of electronic effects like Jahn–Teller ordering, or for magnetic investigations. Besides the cryolite Na 3 AlF 6 used in Al production, some fluorides are of technical interest owing to their special optical properties (e.g. laser optics, fluoride glasses), their ability for fluoride ion conductivity, or their role as catalysts for fluorinations or halogene exchange in organic systems.

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Amorphous Metal Fluorides with Extraordinary High Surface Areas

Cited by 229 publications

References 8 publications

Novel sol–gel prepared zinc fluoride: synthesis, characterisation and acid–base sites analysis

Novel sol–gel prepared zinc fluoride: synthesis, characterisation and acid–base sites analysis

Iron(III) fluoride synthesized by a fluorolysis method and its electrochemical properties as a positive electrode material for lithium secondary batteries

Fluorides: Solid‐State Chemistry

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