Alkali Metal Salts Research Articles

Long-Range Surface Forces in Salt-in-Ionic Liquids.

Ionic liquids (ILs) are a promising class of electrolytes with a unique combination of properties, such as extremely low vapor pressures and nonflammability. Doping ILs with alkali metal salts creates an electrolyte that is of interest for battery technology. These salt-in-ionic liquids (SiILs) are a class of superconcentrated, strongly correlated, and asymmetric electrolytes. Notably, the transference numbers of the alkali metal cations have been found to be negative. Here, we investigate Na-based SiILs with a surface force apparatus, X-ray scattering, and atomic force microscopy. We find evidence of confinement-induced structural changes, giving rise to long-range interactions. Force curves also reveal an electrolyte structure consistent with our predictions from theory and simulations. The long-range steric interactions in SiILs reflect the high aspect ratio of compressible aggregates at the interfaces rather than the purely electrostatic origin predicted by the classical electrolyte theory. This conclusion is supported by the reported anomalous negative transference numbers, which can be explained within the same aggregation framework. The interfacial nanostructure should impact the formation of the solid electrolyte interphase in SiILs.

Double alkali metal salts synergistic activation coupled with S-doped cotton derived honeycomb porous carbon for enhanced zinc ion storage capability

Biomass-derived carbon materials are ideal electrode materials due to their inherent eco-friendliness, easily available and unique micro-morphology. Herein, zinc ion capacitors (ZICs) are designed utilizing S doped honeycomb porous carbon nanosheet cathode, which is obtained via synergistic activation from sodium thiosulfate and potassium carbonate. The honeycomb microstructure is result from the pore-forming effect of double alkali metal salts, which can promote the electrolyte ion fast migration in the cathode. Besides, the S doping in carbon array can regulate the electron distribution within the carbon framework and lower the energy barrier for the chemical absorption of Zn2+/H+, which is demonstrated by density functional theory calculation and expected to produce additional capacitance. Further, the ex-situ X-ray photoelectron spectroscopy reveals the consistent changes in C-O-H and C-O-Zn throughout the charging and discharging cycles, which demonstrate the S doping can promote the reversible chemical adsorption and desorption reaction of Zn2+/H+. As a result, the S doping honeycomb porous carbon nanosheet cathode can achieves a high discharge capacity of 147.2 mAh g−1 and high energy density of 92.7 Wh kg−1. Additionally, the obtained material exhibits good cycling stability at 20 A g−1, retaining 99.9 % of its initial capacity after 2000 cycles. This research presents a versatile approach to synthesizing heteroatom-doped carbon materials from biomass waste for ZICs.

Pop the bubbles and let the current flow: mechanochemistry of micron and nano-sized openings in dielectric layers

Thin or ultra-thin dielectric layers have been widely used in various applications such as capacitors, piezo-electrics, and solar cells. This study explains the mechanism and chemistry of creating nano- and micron-sized openings in atomic-layer-deposited aluminum oxide-based dielectric layers using the alkali metal salt selenization technique. The necessary components for this mechanism are excess methyl groups present in the dielectric layer, supply of selenium and alkali metals, and a minimum annealing temperature. It is shown and explained that to create openings in the dielectric layer, heavier alkali halide metal salts require less energy, or - in other words - a lower annealing temperature. The overall hypothesis is explained via a thermodynamic approach with supportive thermochemical reactions. Thus, an easy way to engineer the dielectric layer to form openings at low temperatures is presented, beneficial for various applications like photovoltaics, optoelectronics, or micro-electro-mechanical systems (MEMS).

Cholesterol modulates the interaction of sodium salt with negatively charged phospholipid membrane

We present a systematic study on how alkali metal salts, like NaCl and NaI, affect negatively charged phospholipid vesicles using a range of experimental methods. Our goal was to find out how chain saturation and cholesterol affect the interaction between the ions and the membrane. An isothermal titration calorimetry study on large unilamellar vesicles made from dimyristoyl phosphatidylcholine (DMPC) revealed that Na+ shows higher binding affinity to the gel phase at 15 °C compared to the fluid phase at 30 °C. Further, cations also show stronger affinity to the membrane in the fluid composed of saturated lipids than that of unsaturated lipids. The binding affinity of Na + with anionic vesicles prepared from a mixture of DMPC and DMPG was found to decrease significantly with increasing cholesterol as well as salt concentrations, as revealed by the zeta potential study. Besides the binding constant, the Gouy Chapman theory based on the electrostatic double layer shows that cholesterol reduces the surface charge density without altering the significant area per molecule. Further, the effect of counterions was investigated using fluorescence spectroscopy of an environment-sensitive lipophilic dye, nile red. Although cholesterol alters the emission properties of nile red significantly, there is no significant change in the presence of ions. This result suggests that anions do not bind significantly to anionic vesicles. The main striking feature of the ion-membrane interaction in the presence of cholesterol is that membranes with saturated lipids exhibit a completely opposite trend from membranes with unsaturated lipids.

Preparation of the porous spherical propellant by using the additives of alkali-metal salt

This article presents the research results on using some alkali-metal salts as additives in the technological process of making porous spherical propellants and the effects of some of these additives on the porosity and some characteristics of the propellant. The porous spherical propellants are prepared using the emulsion method with additive concentrations of Na2SO4, K2SO4, and KNO3 from 0% to 3%. The important characteristics of the sample were determined, such as heat of combustion (Qv), bulk density (ω), temperature of ignition (Tig), and chemical stability. The porosity is calculated and converted through bulk density and theoretical density. The results show that the sample with the Na2SO4 salt has the best porosity (51÷53%) at concentrations over 2%. The important characteristics of the porous propellant do not change significantly compared to the no-additive spherical propellant.

Experimental and theoretical investigation on pre-deposited precursor as growth sites for monolayer MoS2 growth by supercritical fluid deposition

The assistance of promoters, Molybdates or alkali metal salts can regulate the nucleation site of MoS2 in chemical vapor deposition. However, the introduction of impurities inevitably reduces the MoS2 quality. Here, we present the growth of monolayer MoS2 by supercritical fluid deposition to pre-deposit Mo(CO)6 precursors as nucleation sites, replacing difficult to clean conventional promoters. Domain-limited homogeneous and heterogeneous reactions occur at nucleation sites, and through optimization of sulfurization parameters, high-quality monolayer MoS2 with about 20 μm domain size can be obtained by growing at 760 °C and 40 sccm argon for 20 min. Monolayer MoS2 coverage ranged from 2.6 % to 39.1 % by regulating dissolution mass in range of 100–400 mg, utilizing the highly soluble Mo(CO)6 in supercritical CO2. Density functional theory calculations show that decarbonylated Mo(CO)6 possesses higher sulfide reactivity. This study provides new insights into the impurity-free controlled site growth of two-dimensional materials.

The effect of the isocyanate trimerisation catalyst on the chemical composition and strength characteristics of polyurethane-polyisocyanate foams

Nowadays polyurethane-polyisocyanurate (PIR) foams are in a wide use as structural and thermal insulation materials. Isocyanate trimerisation catalysts for foams synthesis have low selectivity in terms of isocyanurate formation. As a consequence, a significant number of target (primary) and (secondary) chemical processes occur during the synthesis of PIR foams. We estimated the dependence of isocyanate group consumption for the formation of the main primary and secondary products on composition isocyanate index by methods based on the internal standard. Indeed, with an increase in the isocyanate index, the conversion of isocyanate to isocyanurate decreases significantly. The paper examines the influence of trimerisation catalyst type on chemical composition and strength characteristics of PIR foams. Hence, catalysts based on organic salts of alkali metals are more selective to the isocyanate trimerisation process than tertiary amines and derivatives of quaternary ammonium bases.

Dibenzodioxin-Based Polymers of Intrinsic Microporosity with Enhanced Transport Properties for Lithium Ions in Aqueous Media.

Boosting the transport and selectivity properties of membranes based on polymers of intrinsic microporosity (PIMs) toward one specific working analyte of interest is challenging. In this work, a novel family of PIM membranes, prepared by casting and exhibiting optima mechanical properties and high thermal stability, was synthesized from 4,4'-(2,2,2-trifluoro-1-phenylethane-1,1-diyl) bis(benzene-1,2-diol) and two tetrafluoro-nitrile derivatives. Gas permeability measurements evidenced a CO2/CH4 selectivity up to 170% relative to the reference polymer, PIM-1, in agreement with their calculated fractional free volume and the analysis of the textural properties by N2 and CO2 gas adsorption. Besides, the chemical modification by acid hydrolysis of the PIM membranes favored the permeability for lithium ions (LiCl 2M, 6 × 10-9 cm2·s-1) compared to other alkali metal analogs such as sodium (NaCl 2M, 7.38 × 10-10 cm2·s-1) and potassium (KCl 2M, 1.05 × 10-9 cm2·s-1). Moreover, the complete mitigation of the crossover of redox species with higher molecular sizes than the ions from alkali metal salts was confirmed by using in-line benchtop NMR methods. Additionally, the modified PIM membranes were measured in a symmetric electrochemical flow cell using an aqueous electrolyte by combining lithium ferro/ferricyanide redox compounds and lithium chloride. The electrochemical tests showed low polarization, high-rate capability, and capacity retention values of 99% when cycled at 10 mA·cm-2 for over 50 cycles. Based on these results, these polymers could be used as highly selective and conducting membranes in electrodialysis for lithium separation and lithium-based redox flow batteries and as a protective layer in high-energy density lithium metal batteries.

Structural Expansion and Enhanced Photocurrent Conversion of Selenido Stannates with Cu+ Ions.

As a means of tuning the electronic properties of tin-chalcogenide-based compounds, we present a strategy for the compositional and structural expansion of selenido stannate frameworks under mild conditions by introducing Cu+ ions into binary anionic Sn/Se aggregates in ionothermal reactions. The variable coordination modes of Cu+-contrasting with tetrahedral {SnSe4} or trigonal bipyramidal {SnSe5} units-and corresponding expansion toward ternary Cu/Sn/Se substructures helped to add another degree of freedom to the nanoarchitectures. As desired, the variation of the structural features was accompanied by concomitant changes of the physical properties. Upon treatment of alkali metal salts of the [SnSe4]4- anion at slightly elevated temperatures (120 or 150 °C) in ionic liquids, we isolated a series of compounds comprising ternary or quaternary cluster molecules or networks of cluster units, (C2C2Im)9Li[Cu10Sn6Se22] (1), (C2C2Im)4[Cu8Sn6Se18] (2), (C2C1Im)3[Cu5Sn3Se10] (3), and (C2C2Im)5[Cu8Sn6Se18F]·(C2C2Im)[BF4] (4; C2C2Im = 1,3-diethyl-imidazolium, C2C1Im = 1-ethyl-3-methyl-imidazolium), which were investigated in terms of their optical gaps and photocurrent conversion properties. As illustrated by the synthesis and characterization of an additional salt that does not include Cu+, {(C2C2Im)2[Sn3Se7]}4·{(C2C2Im)[BF4]}2 (5), the significant role of Cu+ in this system was shown to be 3-fold: (a) structural expansion, (b) narrowing of the optical gap, and (c) photocurrent enhancement. By this three-in-one effect, the work offers an in-depth understanding of chalcogenido metalate chemistry with atomic precision.

Osmolyte-Induced Modulation of Hofmeister Series.

Natural selection has driven the convergence toward a selected set of osmolytes, endowing them with the necessary efficiency to manage stress arising from salt diversity. This study combines atomistic simulations and experiments to investigate how two osmolytes, glycine and betaine, individually modulate the Hofmeister ion ordering of alkali metal salts (LiCl, KCl, and CsCl) near a charged silica interface. Both osmolytes are found to prevent salt-induced aggregation of the charged entities, yet their mode and degree of relative modulation depend on their intricate interplay with specific salt cations. Betaine's ion-mediated surface interaction maintains Hofmeister ion ordering, whereas glycine alters the relative Hofmeister order of the cation by salt-specific ion desorption from the surface. Experimental validation through surface-enhanced Raman spectroscopy supports these findings, elucidating osmolyte-mediated alterations in interfacial water structures. These observations based on an inorganic interface are reciprocated in amyloid beta 40 dimerization dynamics, highlighting osmolytes' efficacy in mitigating salt-induced aggregation. A molecular analysis suggests that the differential modes of interaction, as found here for glycine and betaine, are prevalent across classes of zwitterionic osmolytes.

Lightweight, compressible, elastic resorcinol-formaldehyde aerogels with cobalt-ligand-enhanced cross-linked skeletons

Resorcinol-formaldehyde (RF) aerogel materials exhibit remarkable properties such as low density, ablation resistance (high residual carbon rate), easily regulated pore structure and low thermal conductivity, making them promising for applications in adsorption, medicine and aerospace, among others. However, since their inception, RF aerogels have suffered from disadvantages such as brittleness and long preparation cycles, which have severely limited their widespread use. In order to improve the mechanical properties of RF aerogels, this paper presents a new synthetic route for obtaining strong elastic properties without introducing additional fiber reinforcement. Here, a lightweight, compressible, elastic resorcinol-formaldehyde aerogel with cobalt-ligand-enhanced cross-linked skeletons was prepared by sol-gel and freeze-drying methods using an alkali metal salt (cobalt (II) acetate) as a cross-linking agent and sodium acetate as a catalyst. The coordination of metal ions (Co2+) with resorcinol resulted in the formation of a structure analogous to a metal-phenolic network (MPN), which altered the crosslinking mode and degree of crosslinking of the RF aerogel. This process led to the thickening of the skeletal structure of the sample. Concurrently, a multilayered pore structure was generated within the interior under the appropriate pH conditions, which contributed to the strengthening of the skeleton of the samples and a reduction in thermal conductivity. The obtained RF-Co aerogel can withstand 68.6 % compression change without fracture and shows good elastic deformation at 35 % compression rate, while the aerogel exhibits low thermal conductivity (0.039 W (m K)−1) and low density (0.09 g cm−3).

Visible‐Light‐Induced Diastereoselective Cascade Cyclization to Construct Polycyclic Spiroindolines

AbstractWe herein reported, a visible‐light‐induced K2S2O8 mediated cascade reaction of 3‐(2‐isocyanoethyl)indoles with α‐oxocarboxylic acids leading to diastereoselective synthesis of polycyclic spiroindolines bearing an N‐formyl unit derivative utilising the alkali metal salt K2S2O8 as a mediator under mild reaction conditions. This study offers an illustration of α‐oxocarboxylic acids and 3‐(2‐isocyanoethyl)indoles‐based reactions as it shows the involvement of glyoxolate ions without decarboxylation to access polycyclic spiroindolines bearing an N‐formyl unit analogue. The batch process can be extended to a continuous flow system using a glass tube loaded with K2S2O8 placed between the PFA capillary reactor, which can greatly advance the reaction efficiency and can even be promoted to gram‐scale synthesis.

The influence of multi-step modification method on the adsorption effect of alkali metal adsorbent in high temperature corrosive environment

In order to mitigate the serious high-temperature corrosion problem caused by gaseous alkali metal salts on the heating surface of boilers, the adsorption effect of kaolinite for alkali metal vapor stood out among many silicon-aluminum-based adsorbents. To improve the adsorption capacity of kaolinite for alkali metal vapor, a novel multi-step modification method was proposed in this reported work. The multi-step modification method consisted of the following four steps, which were pre-intercalation, replacement intercalation, multiple intercalation, and exfoliation, and it was found that the multi-step modification method resulted in the increase of the particle size, the expansion of the interlayer spacing, and the expansion of the porosity structure of kaolinite. The physicochemical analyses showed that the multi-step modification method made it easier to dehydrate kaolinite to produce metakaolinite. In addition, it was found that the multi-step modification method led to the generation of a new crystalline phase of kaolinite, which was formed by the dehydration and condensation of methanol and AlOH groups. It also led to the pre-removal of some of the hydroxyl groups in kaolinite. The insoluble sodium loading capacity of the multi-step modified kaolinite was enhanced by 64.47% and the insoluble potassium loading capacity was enhanced by 29.68% under the adsorption condition of 850 °C for 45 min. Therefore, the multi-step modification method enhanced the alkali metal vapor adsorption capacity of raw kaolinite under high-temperature environment, which laid a certain foundation for subsequent research in this field.

Recent developments in metal-catalysed transamidation of quiescent amides

Amides played a vital role in the development of organic synthesis in recent years. These structural motifs are found in several biologically important synthetic and naturally occurring compounds. Developing efficient methods for their synthesis is crucial for drug discovery. Transamidation is a prominent tool in organic and medicinal chemistry, enabling the replacement of the amine group in an existing amide with new functionalised amines. Additionally, Transamidation process is used significantly in the total synthesis of few naturally occurring compounds. Transamidation reaction has been achieved significantly by using metal catalysis but there are several metal-free approaches have been employed to achieve the same reaction. This review focuses on recent literature concerning metal-catalysed transamidation reactions, highlighting the use of alkaline earth metals, transition metals, lanthanides, actinides, alkali metal salts or complexes, and metalloids. Both catalytic and stoichiometric quantities of catalysts are discussed for their roles in enhancing reaction efficiency.

Electronic and Molecular Structures of a Series of Nickel Bis-1,1-Dithiolates.

A series of homoleptic Ni bis-1,1-dithiolates, [Ni(S2C2RR')2]2- (R=CN, R'=CN, CO2Et, CONH2, Ph, Ph-4-Cl, Ph-4-OMe, Ph-4-NO2, Ph-3-CF3, Ph-4-CF3, Ph-4-CN; R=NO2, R'=H; R=R'=CO2Et) have been synthesized from the reaction of the alkali metal salt of the ligand and nickel chloride, and isolated as tetraphenylphosphonium or tetrabutylammonium salts. The complexes were characterized by X-ray crystallography, high-resolution mass spectrometry, and infrared (IR), nuclear magnetic resonance (NMR) and electronic absorption spectroscopies. The molecular structures show a rigidly square planar Ni(II) center linking two four-membered chelate rings whose dimensions are constant across the series. The electronic effect of the ligand substituent is revealed in the 13C NMR and electronic spectra, and corroborated by density functional calculations. Electron withdrawing groups deshield the low-field CS2 resonance, and the signature charge transfer band in the visible region is red-shifted. These observables have been accurately reproduced computationally, and revealed the Ni contribution to the ground state diminishes with decreasing electron withdrawing capacity of the ligand substituent. In contrast to 1,2-dithiolates, the redox inactivity afforded by 1,1-dithiolates stems from the smaller chelate ring and substantially reduced sulfur content that is key to stabilizing the radical form.

Insight into catalytic effects of alkali metal salts addition on bamboo and cellulose pyrolysis

Alkali metal compounds have vital influence on biomass pyrolysis conversion. In this study, cellulose, and bamboo catalytic pyrolysis with different alkali metal salts catalysts (KCl, K2SO4, K2CO3, NaCl, Na2SO4, and Na2CO3) were investigated in the fixed-bed reaction system. The effects of cations (K+ and Na+) and anions (Cl-, SO42−, and CO32-) on the evolution properties of biochar, bio-oil, and gas products were explored under both in-situ and ex-situ catalytic pyrolysis. Results showed that alkali metal salts facilitated the yields of biochar and gases at the expense of that of bio-oil. Alkali metal chloride and sulfate showed a weaker catalytic effect, while alkali metal carbonate greatly promoted the generation of gas products and increased the condensation degree of biochar. With the addition of K2CO3 and Na2CO3, cyclopentanones content was over 50% from cellulose catalytic pyrolysis, and phenols content (mainly alkylphenols) reached over 80% from bamboo catalytic pyrolysis. Moreover, solid-solid catalytic reactions with K2CO3 and Na2CO3 catalysts had an important role in strikingly promoting conversion of pyrolysis products, and the solid-solid and gas-solid catalytic reactions with alkali metal carbonate catalysts were stronger than those with alkali metal chloride and sulfate catalysts. Furthermore, the possible catalytic pyrolysis mechanism of alkali metal salts on biomass pyrolysis was proposed, which is important to the high-value utilization of biomass.

Enhanced CO2 capture and stability of MgO modified with alkali metal nitrates and carbonates at moderate temperature

AbstractBACKGROUNDMagnesium oxide (MgO) is favored for solid‐state carbon dioxide (CO2) capture due to its high theoretical adsorption capacity, abundant reserves, low cost, and environmental friendliness. However, its practical application in industry is hindered by low CO2 adsorption capacity under moderate operating conditions. In this work, MgO was modified by a deposition method using LiNO3, NaNO3, KNO3, Na2CO3 and K2CO3 as additives.RESULTSThe study determines optimal ratios within the [(Li, Na, K)x − (Na, K)]y/MgO system, specifically identifying x = 0.5 and y = 0.15 as most effective. At 275 °C under pure CO2 conditions, the adsorption capacity peaks at 0.631 g CO2 g−1 adsorbent. Effective regeneration of the adsorbent occurs at 400 °C under 100% N2 for 15 min. Under Integrated Gasification Combined Cycle (IGCC) conditions, the adsorption capacity stabilizes at 0.462 g g−1 after 20 cycles, representing a 25% decrease from initial capacity.CONCLUSIONExperimental findings demonstrate that the inclusion of alkali metal salts in MgO precursors enhances the adsorbent's microstructure, thereby improving its CO2 capture efficiency and bolstering cycling stability. This research enhances our understanding of the factors influencing CO2 adsorption and cyclic stability in alkali metal salt‐promoted MgO, providing valuable insights for further refinement in the formulation and synthesis protocols of MgO‐based CO2 adsorbents. © 2024 Society of Chemical Industry (SCI).

Salt promoted metallic Pt photodeposition on graphitic carbon nitride towards efficiently photocatalytic hydrogen evolution

The photocatalytic hydrogen evolution (PHE) activity of pristine graphitic carbon nitride (GCN) and highly crystalline K+-doped GCN can significantly be enhanced under visible light irradiation via adding alkali metal salt into their PHE reaction solution. As manifested in XRD, UVDRS, TEM and XPS measurements, the loading amount of Pt cocatalyst on both GCN and K+-doped GCN, as well as the content of metallic Pt were greatly increased in the presence of 1.0 M KCl solution in the photoreduction solution. More significantly, the proportion of metallic Pt reached around 75 %. As a result, the PHE rate of K+-doped GCN was even as high as 11 mmol h–1g−1 under visible light irradiation. The current work offers a simple and cost-efficient strategy to promote the low depositing efficiency of Pt cocatalyst by traditional photoreduction method, thereby increasing the PHE activity of GCN and GCN based materials.

Synthesis and Characterization of Bulky 1,3-Diamidopropane Complexes of Group 2 Metals (Be-Sr).

Reaction of lithium 1,3-diamidopropane Li2(TripNCN) (TripNCN=[{(Trip)NCH2}2CH2]2-, Trip=2,4,6-triisopropylphenyl) with BeBr2(OEt2)2 gave the diamido beryllium complex, [(TripNCN)Be(OEt2)]. Deprotonation reactions between the bulkier 1,3-diaminopropane (TCHPNCN)H2 (TCHPNCN=[{(TCHP)NCH2}2CH2]2-, TCHP=2,4,6-tricyclohexylphenyl) and magnesium alkyls afforded the adduct complexes [(TCHPNCN)Mg(OEt2)] and [(TCHPNCN)Mg(THF)2], depending on the reaction conditions employed. Treating [(TCHPNCN)Mg(THF)2] with the N-heterocyclic carbene :C{(MeNCMe)2} (TMC) gave [(TCHPNCN)Mg(TMC)2] via substitution of the THF ligands. Reactions of (ArNCN)H2 (Ar=Trip or TCHP) with Mg{CH2(SiMe3)}2, in the absence of Lewis bases, yielded the N-bridged dimers [{(ArNCN)Mg}2]. Salt metathesis reactions between alkali metal salts M2(TCHPNCN) (M=Li or K) and CaI2 or SrI2 led to the THF adduct compounds [(TCHPNCN)Ca(THF)3] and [(TCHPNCN)Sr(THF)4], the differing number of THF ligands in which is a result of the different sizes of the metals involved. The described complexes hold potential as precursors to kinetically protected, low oxidation state group 2 metal species.

Study of oxidation of cellulose by Fenton-type reactions using alkali metal salts as swelling agents

Study of oxidation of cellulose by Fenton-type reactions using alkali metal salts as swelling agents