A Computational Study of AlF3 and ACF Surfaces

Pandharkar, Riddhish; Becker, Christian F. W.; Budau, Johannes Horst; Kaawar, Zeinab; Paulus, Beate

doi:10.3390/inorganics6040124

Cited by 5 publications

(16 citation statements)

References 84 publications

(94 reference statements)

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“…Locally, the structural motifs found by Bailey [20] and ours agree well, as proven by similar frequency shift obtained for CO. Contrary to the model of Bailey et al, the (0001) surface model used in this work shows threefold coordinated aluminium centers due to the usage of a different theoretical set-up and no additional fluorides [21].…”

Section: Introductioncontrasting

confidence: 67%

“…For both surface models, the theoretical results are in the range of the experimental data [20]. Our previous investigations [21] have shown that the (01 12) surface is quite high in energy and only another layer of fluorides and surface reconstruction stabilizes the α-AlF 3 -(01 12) surface. Locally, the structural motifs found by Bailey [20] and ours agree well, as proven by similar frequency shift obtained for CO.…”

Section: Introductionmentioning

confidence: 73%

“…VESTA [42] was used for visualization. The same settings were used for the evaluation of our surface models [21].…”

Section: Computational Detailsmentioning

confidence: 99%

“…The most stable α-AlF 3 (space group R 3c) surfaces from our previous investigation [21] and their chlorinated variants were used as model surfaces to adsorb CO and NH 3 . For the structure optimization, the probe molecules were placed at the fractional coordinates x = 0.5 and y = 0.5 of the 1 × 1 super cell of the selected surface with a distance of 3 Å to the highest surface atom, regardless of whether it was a fluoride or an aluminium ion.…”

Section: Modelmentioning

confidence: 99%

“…This paper covers studies on the adsorption of CO and NH 3 on different surface models of α-AlF 3 and Cl-doped α-AlF 3 under the usage of periodic DFT calculations, applying the PBE functional with D3-BJ dispersion correction. In earlier studies [21], different surfaces, which appear in the nano-crystal of the α-AlF 3 , were characterized in detail and stable chloride-doped variants were proposed. The structural changes due to adsorption and the frequency shifts of the probe molecules are compared with the experimental results [3,17,18] of the corresponding fluorides.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Study on the Lewis Acidity of the Pristine AlF3 and Cl-Doped α-AlF3 Surfaces

2021

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In the past two decades, metal fluorides have gained importance in the field of heterogenous catalysis of bond activation reaction, e.g., hydrofluorination. One of the most investigated metal fluorides is AlF3. Together with its chlorine-doped analogon aluminiumchlorofluoride (AlClxF3−x, x = 0.05–0.3; abbreviated ACF), it has attracted much attention due to its application in catalysis. Various surface models for α-AlF3 and their chlorinated analogues (as representatives of amorphous ACF) are investigated with respect to their Lewis acidity of the active centres. First-principle density functional theory (DFT) methods with dispersion correction are used to determine the adsorption structure and energy of the probe molecules CO and NH3. The corresponding vibrational frequency shift agrees well with the measured values. With this insight we predict the local structure of the active sites and can clarify the importance of secondary interactions to the local anionic surrounding of the catalytic site.

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Section: Introductioncontrasting

confidence: 67%

Section: Introductionmentioning

confidence: 73%

“…VESTA [42] was used for visualization. The same settings were used for the evaluation of our surface models [21].…”

Section: Computational Detailsmentioning

confidence: 99%

Section: Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Theoretical Study on the Lewis Acidity of the Pristine AlF3 and Cl-Doped α-AlF3 Surfaces

2021

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Multifunctional Separator Allows Stable Cycling of Potassium Metal Anodes and of Potassium Metal Batteries

et al. 2021

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This is the first report of a multifunctional separator for potassium‐metal batteries (KMBs). Double‐coated tape‐cast microscale AlF3 on polypropylene (AlF3@PP) yields state‐of‐the‐art electrochemical performance: symmetric cells are stable after 1000 cycles (2000 h) at 0.5 mA cm−2 and 0.5 mAh cm−2, with 0.042 V overpotential. Stability is maintained at 5.0 mA cm−2 for 600 cycles (240 h), with 0.138 V overpotential. Postcycled plated surface is dendrite‐free, while stripped surface contains smooth solid electrolyte interphase (SEI). Conventional PP cells fail rapidly, with dendrites at plating, and “dead metal” and SEI clumps at stripping. Potassium hexacyanoferrate(III) cathode KMBs with AlF3@PP display enhanced capacity retention (91% at 100 cycles vs 58%). AlF3 partially reacts with K to form an artificial SEI containing KF, AlF3, and Al2O3 phases. The AlF3@PP promotes complete electrolyte wetting and enhances uptake, improves ion conductivity, and increases ion transference number. The higher of K+ transference number is ascribed to the strong interaction between AlF3 and FSI− anions, as revealed through 19F NMR. The enhancement in wetting and performance is general, being demonstrated with ester‐ and ether‐based solvents, with K‐, Na‐, or Li‐ salts, and with different commercial separators. In full batteries, AlF3 prevents Fe crossover and cycling‐induced cathode pulverization.

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Strong Mesoscopic Prismatic Face Growth Suppression in High-Speed Unidirectional Growth of KDP Single Crystals

Fang

Zhu

Zhao

et al. 2020

Crystal Growth & Design

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We show strong mesoscopic prismatic face growth arrest that coexists with high-speed pyramidal face growth in single-crystalline KDP crystals with large aspect ratios. To explain this unique growth morphology, which cannot be explained by any current theories, we introduce a new set of surface concentration rate equations and demonstrate a molecular-orientation-selective surface-self-shielding and channeling mechanism. We numerically solve full diffusion equations with time-dependent surface boundary conditions for the crystal growth driving force and growth rate, demonstrating the quick arrest of both quantities as the result of molecule-orientation selectivity based self-shielding and channeling effects. The growth dynamics thus derived can satisfactorily explain all experimental observations in single-crystalline KDP crystal growth reported here.

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A Computational Study of AlF3 and ACF Surfaces

Cited by 5 publications

References 84 publications

Theoretical Study on the Lewis Acidity of the Pristine AlF3 and Cl-Doped α-AlF3 Surfaces

Theoretical Study on the Lewis Acidity of the Pristine AlF3 and Cl-Doped α-AlF3 Surfaces

Multifunctional Separator Allows Stable Cycling of Potassium Metal Anodes and of Potassium Metal Batteries

Strong Mesoscopic Prismatic Face Growth Suppression in High-Speed Unidirectional Growth of KDP Single Crystals

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