Monatshefte für Chemie / Chemical Monthly最新文献

This paper investigates the effect of water content on lithium-ion battery electrolytes with particular emphasis on the degradation of lithium hexafluorophosphate, a commonly used salt in commercial electrolytes. The study addresses various degradation mechanisms caused by water in a battery system. In addition, the research utilizes electrochemical techniques to detect water and associated changes in electrochemical performance of the cell. The electrochemical water detection method investigated is very fast. The lower detection limit was not tested, but contamination of 250 ppm can be reliably detected. It can be used, for example, in experimental research to determine the purity and quality of the electrolyte used.

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Fe-doped lithium-manganese spinel of the composition LiFe_0.05Mn_1.95O₄ was synthesized by means of a citric acid-aided route. The influence of annealing temperature on structural and morphological characteristics LiFe_0.05Mn_1.95O₄ is investigated by XRD and SEM methods. Specific and kinetic electrochemical characteristics of LiFe_0.05Mn_1.95O₄ in organic and aqueous electrolyte solutions were studied by galvanostatic cycling method and cyclic voltammetry. LiFe_0.05Mn_1.95O₄ samples annealed at temperatures of 700, 750, and 800 °C demonstrate specific capacity of 114, 102, and 109 mAh g⁻¹ at the cycling current density of 0.5 C, respectively. The best cycling stability and rate performance with discharge currents up to 50 C were obtained in a case of the sample annealed at 750 °C.

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This work describes the modification of organic–inorganic nanofibrous templates for advanced electrotechnical applications and their filling with active particles from various materials, according to their intended use. The organic component of the templates consists of high molecular polyvinylpyrrolidone. The inorganic part is colloidal SiO₂. The organic–inorganic templates produce by electrospinning can be filled with inorganic particles with diameter below 50 µm (for example, different types of spinels or electroactive nanopowders). The idea is to create a modifiable and flexible material for use as a template for electrodes or a solid electrolyte in a safe solid-state battery. The quality and properties of nanofibers are very important for advanced applications, and therefore, the optimization of the manufacturing process is needed. The most important property is the viscosity of the organic–inorganic solution for electrospinning. The influence of viscosity on the quality of nanofibrous layers was observed even with very subtle differences in viscosity. The age of the precursors and the resulting workability time also plays a significant role.

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This study describes a simple, highly sensitive, and cost-effective electrochemical determination of salbutamol (SBT) at a disposable pencil graphite electrode modified with Nafion/functionalized multi-walled carbon nanotubes composite material (Nf/f-MWCNTs/PGE). The electrochemical response of SBT at this modified electrode was investigated by both differential pulse voltammetry (DPV) and cyclic voltammetry techniques. The voltammetric measurements confirmed that the combination of f-MWCNTs with Nafion shows remarkable electrocatalytic activity on the oxidation of SBT due to a synergistic effect of Nafion via electrostatic interaction and f-MWCNTs via excellent conductivity and large specific surface area. Differential pulse voltammetry results show that the composite electrode gives two linear ranges of 0.10–17.5 µM and 17.5–100 µM with a detection limit (LOD) of 0.027 µM SBT. Moreover, the studies of some potential interferants show that there is no significant interference in the determination of SBT. The proposed procedure was successfully applied to determine SBT in tube- and syrup-type pharmaceutical formulations, animal feed, and beef meat samples, and acceptable results were obtained with high accuracy and precision. Moreover, the proposed sensor displays good intra-day and inter-day precisions for the voltammetric determination of SBT.

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The porous structure of three different, commercially available porous carbonaceous materials is investigated by the α_S-plot method and by the t-plot method. Subsequently, the electrochemical properties of sulfur-free porous carbon electrodes from inspected materials are studied by cyclic voltammetry. The comparison of double-layer capacitances with the corresponding adsorption isotherms of N₂ reveals the role of micropores during the capacitive charging of carbons by Li⁺. The studied carbons are added to the sulfur cathodes and evaluated. The cyclic voltammograms show no contribution of micropores in the carbon structure to the electrochemical processes taking place in the lithium–sulfur coin cell. The highest specific capacity of 816 mAh/g is observed for material with the lowest content of micropores in the structure (14%). The partially mesoporous and partially microporous (65%) sample and the predominantly microporous one (87%), show specific capacities of 664 mAh/g and 560 mAh/g, respectively. The galvanostatic cycling of lithium–sulfur coin cells with carbonaceous additives reveals that the mesopores and macropores in the carbon structure increase the specific charge capacity of the lithium–sulfur batteries and that the micropores improve the cycling stability of these batteries.

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An efficient protocol providing easy access to chiral 2-(N-Boc-azetidin-3-yl)-2-alkylpropanoic acids as novel GABA derivatives is described. In the first stage of the synthesis, alkylated phosphonates and N-Boc-azetidin-3-one were converted to the corresponding N-Boc-azetidine-3-ylidenes via a Horner–Wadsworth–Emmons reaction; these were then subjected to a standard hydrogenation procedure. The subsequent reaction of racemic amino esters with sodium hydroxide in methanol afforded the target racemic N-Boc-amino acids as major products. The optically active enantiomers of 2-(N-Boc-azetidin-3-yl)-2-alkylpropanoic acids were prepared via optical resolution of the racemates using (S)-4-benzyl-2-oxazolidinone as the resolving agent to obtain the diastereomeric pairs. After isolation of the pure diastereomers, they were treated with lithium hydroxide and hydrogen peroxide to give the corresponding enantiomerically pure 2-(N-Boc-azetidin-3-yl)-2-alkylpropanoic acids, respectively. Unambiguous structural assignments were based on ¹H, ¹³C, ¹⁵N, and ³¹P NMR spectroscopy; HRMS; and single-crystal X-ray diffraction data.

In recent years, heterogeneous catalysts have been developed due to their inherent activity, easily recoverable and reusable nature, and eco-friendly nature. The palladium nanoparticles have excellent catalytic activity due to their outstanding performance as catalysts for various chemical reactions. Palladium nanoparticle-incorporated clay-supported heterogeneous composites have been developed recently and possess excellent activity as catalysts for various organic transformations. Palladium nanoparticle-supported clay materials have a high surface area, porosity, ion exchangeability, and binding nature. Due to these criteria, clay-palladium composites act as better catalysts. This review has tried to accentuate the potential advantages of the clay-based heterogeneous catalyst in various carbon–carbon coupling reactions. This review detailed the clay-supported palladium nanoparticles used as catalysts for the construction of C–C moieties, like Suzuki–Miyaura cross-coupling, Sonogashira coupling, Ullmann coupling, and Heck coupling reactions. The advantages and merits of clay-supported palladium catalysts compared with normal conventional methods are easily recovered and reused, reduced palladium metal leaching, and reduced byproduct formation.

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The research of the batteries is still going forward and there are lots of challenges which should be solved. This text examines the effect of external pressure on different types of batteries and explores their potential for improving performance and lifetime. The studies reviewed in the text show interesting results where external pressure affects capacity, internal resistance, stability or other parameters of modern battery systems as Li-ion, solid-state, or Li–S batteries. Despite the challenges, the benefits for next-generation batteries seem promising and show its role in battery development and manufacturing.

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This work deals with the development of new anode materials for sodium-ion cells. Unlike lithium-ion batteries, where graphite is commonly used, it is not suitable for sodium-ion technology. Therefore, the aim is to identify an alternative material. Anthracite appears to be a promising candidate due to its affordability and geopolitical availability compared to graphite. The experimental part of the research involves the characterization of calcined anthracite, and its processing for the preparation of negative electrodes. This is followed by electrochemical characterization of the prepared electrodes.

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Equilibrium vapour pressure measurements were carried out over the neodymium–tellurium samples using the non-isothermal isopiestic method. The samples were equilibrated in the temperature range from 821 to 1100 K. Using vapour pressure data obtained for the composition range ~ 64.0–74.5 at% Te, the thermodynamic activities of Te were determined. Non-stoichiometry in the NdTe₂ phase has been precisely determined under experimental conditions reported.

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