Influence Of Alkali Metal Cations Research Articles

Influence of alkali metal cation modifications on physical characteristics of double perovskites Rb2XTlBr6 (X=Li, Na, K): First-principles study for solar energy and thermoelectric applications

In the present work, we used a first-principles method to examine novel direct band gap combinations of double perovskites Rb2XTlBr6 (X = Li, Na, K) and provide a thorough description of their structural, electronic, optical, thermoelectric, and elastic properties. The materials that are being studied have attractive optical and thermoelectric qualities and are proven to be stable, inexpensive, and efficient. The influence of alkali metal cations (Li–K) substitutions on stability and physical characteristics has also been investigated. These materials remain stable in cubic structure as evidenced by the tolerance factor. The electronic characteristics reveal that these combinations are direct band gap semiconductors and alkali metal cations substitutions modify the band gap. The band gap is 1.92 eV for Rb2LiTlBr6, which decreases to 1.87 eV for Rb2NaTlBr6 and 1.78 eV for Rb2KTlBr6. The optical analysis has noticed the absorption edge redshifted, improved upon the cation modification, and has the ability to absorb a broad spectrum. Thermoelectric parameters suggest that an increase in the Seebeck coefficient and reduction in thermal conductivity improves thermoelectric response upon cation substitutions. The anticipated ZT values for Rb2LiTlBr6, Rb2NaTlBr6, and Rb2KTlBr6 are 0.70, 0.72, and 0.74, respectively, increasing with cation modification. The exploration of elastic parameters suggests Rb2LiTlBr6 is stronger than Rb2NaTlBr6 and Rb2KTlBr6, and these combinations are anisotropic and ductile. The findings of this study reveal the importance of alkali metal cation modification for enhancing photovoltaic and thermoelectric capabilities.

Influence of alkali metal cations on the formation of the heterobimetallic actinide tert-butoxides [AnM3(OtBu)7] and [AnM2(OtBu)6] (AnIV = Th, U; MI = Li, Na, K, Rb, Cs).

Heterobimetallic tert-butoxides of alkali metal cations with tetravalent actinide centers exhibit two distinctive structural motifs, [AnM2(OtBu)6] and [AnM3(OtBu)7] (AnIV = Th, U and MI = Li, Na, K, Rb, Cs), evidently governed by the size of the alkali metal ions. Both [AnM3(OtBu)7] AnM3 (AnIV = U, MI = Li; AnIV = Th, MI = Li, Na) and [AnM2(OtBu)6] AnM2 (AnIV = U, MI = Na-Cs; AnIV = Th, MI = K-Cs) compounds are obtained in nearly quantitative yields by reacting actinide and alkali metal silyl amides with an excess of tert-butyl alcohol. The AnM3 complexes form a cubane-type coordination motif, whereas the AnM2 complexes display a geometry resembling two face-shared bipyramids. The sodium derivatives of thorium and uranium (ThNa3 and UNa2) allow the determination of the structural transition threshold as a function of the ratio of the ionic radii ri(AnIV)/ri(MI). The AnM3 complexes are formed for ratios above 0.92 and the AnM2 type is formed for ratios below 0.87. All compounds are unambiguously characterized in both solution and solid states by NMR and IR spectroscopic studies and single crystal X-ray diffraction analyses, respectively.

(Digital Presentation) The Influence of Alkali Metal Cations on the Redox Processes of Copper Hexacyanoferrate in Rechargeable Aqueous Zinc-Ion Batteries

Rechargeable aqueous batteries are of high interest for future stationary grid-scale energy storage applications where high safety is needed (1). Copper hexacyanoferrate (CuHCF), a Prussian Blue Analogue (PBA) material, has recently gained interest as positive electrode for aqueous Zn-ion batteries (ZIBs) (2,3). Reversible Zn2+ ion insertion is facilitated by its open-framework with large channels that can host a variety of monovalent and divalent cations. Recent studies have shown that the charge compensation process takes place via Zn2+ ions swapping position between tunnel sites and vacancy sites (4).Among aqueous ZIBs, the Zn/CuHCF cell has attracted noticeable attention, as it can combine abundant and inexpensive materials with a good trade-off between capacity and performance. Zinc can supply a high capacity (820 mAh g-1), while CuHCF typically provides a moderate capacity of ca. 60-80 mAh g-1.However, it exhibits one of the highest operating voltages among PBA-type cathodes (1.7 V vs. Zn2+/Zn) and exhibits a cubic-type structure with wide channels. In comparison to many other materials, CuHCF undergoes minimal volume and structural changes during ion insertion/de-insertion, exhibits a high Coulombic efficiency of ca. 99%, and can be cycled at high rates without compromising the capacity, which makes it an interesting material for high-power applications.Nevertheless, CuHCF suffers from capacity fade owing to instabilities of Cu, which we have demonstrated in details in a recent investigation (5). In that study, we also highlighted that the characteristic aging effect, observed as a growth of a two-phase plateau in the charge/discharge profiles and associated with capacity loss (6), can be explained by Cu dissolution and thereby a displacement of the two Cu2+/Cu+ and Fe3+/Fe2+ redox-couples (5). Alkali metal cations (Li+, Na+, K+, Rb+, Cs+) have recently been shown to impact the capacity of the Zn/CuHCF cell along with a modulation of the characteristic redox-features in the voltammetric profiles (7). Cycling of large cations (Rb+, Cs+) was linked to a reduced capacity, while moderately sized cations (K+) resulted in optimal capacity and higher charge retention. This has motivated us to investigate the effect of the alkali metal cations on the charge compensation and redox processes in CuHCF in more detail in this study.By employing X-ray photoelectron spectroscopy (XPS), we show that small cations (Li+) have negligible impact on the Cu and Fe redox processes, while moderately sized cations (K+) suppress Cu redox and enhance Fe redox, which optimizes the capacity and improves the cycling stability, accordingly. Large cations (Cs+), on the other hand, prevent reversible redox and lock both metal centers in their most reduced states (Cu+, Fe2+), which impedes the charge compensation process and reduces the capacity. Our study unveils how alkali metal cations influence the performance of ZIBs by affecting the synergy of the Cu2+/Cu+ and Fe3+/Fe2+ redox couples in CuHCF and demonstrates how tailoring the electrolyte formulation can conveniently impact the capacity retention of this compound in PBA-type ZIBs. Figure 1. The aqueous Zn/CuHCF cell. (a) Schematic figures illustrating the structure of the CuHCF cathode and its wide channels that can host ions. (b) Cyclic voltammograms (CV) of the Zn/CuHCF cell in pure 1M ZnSO4 and in presence of 0.2 M alkali metal cation additives (Li+, K+, Cs+). (c) X-ray photoelectron spectroscopy (XPS) showing the Cu 2p3/2 and Fe 2p3/2 spectra of the same electrolytes as shown in (b). References J. Shin, and J. W. Choi, Advanced Energy Materials, 10, 2001386–2001386 (2020).R. Trócoli, and F. La Mantia, ChemSusChem, 8, 481–485 (2015).Z. Jia, B. Wang, and Y. Wang, Materials Chemistry and Physics, 149–150, 601–606 (2015).V. Renman, D. O. Ojwang, M. Valvo, C. P. Gómez, T. Gustafsson, G. Svensson, Journal of Power Sources, 369, 146–153 (2017).M. Görlin, D. O., Ojwang, M.-T. Lee, V. Renman, C.-W. Tai, and M. Valvo, ACS Applied Materials & Interfaces, 13, 59962–59974 (2021)R. Trócoli, G. Kasiri, and F. La Mantia, Journal of Power Sources, 400, 167–171 (2018).D. Phadke, R. Mysyk, and M. Anouti, Journal of Energy Chemistry 40, 31–38 (2020). Figure 1

Influence of alkali metal cations on the photoactivity of crystalline and exfoliated amorphous WO3 – photointercalation phenomenon

In order to investigate the effect of photointercalation on photoelectrochemical properties, two types of WO3-based photoanodes, bulk and exfoliated have been prepared and investigated. An aqueous exfoliation method is introduced for the simple fabrication of amorphous and hydrated WO3 nanomaterial using commercial bulk WO3 precursor. The comparison of obtained material with bulk WO3 was performed using Raman, UV–vis, and XPS as well as scanning and transmission electron microscopies. The photoelectrochemical and photocatalytic performances of bulk and exfoliated WO3 were compared. Generally, the proposed exfoliation procedure led to the preparation of photo(electro)catalyst characterized by better performance measured as a photocurrent of water oxidation and rate of methylene blue photodecomposition. The main aim of this research was to investigate the influence of alkali metal cations (Li+,Na+,K+,Cs+) presence in electrolyte on the photocatalytic and photo(electro)catalytic activity of the samples in a form of suspended powder and thin layer on transparent-conductive substrate (FTO), respectively.

Influence of Alkali Metal Cations on the Photodimerization of Bromo Cinnamates Studied by Solid-State NMR

The alkali metal salts of m-bromocinnamic acid and their photodimerization products are analyzed by solid-state NMR. Cesium, rubidium, and potassium salts show well-resolved signals in the 13C CPMA...

How the Nature of the Alkali Metal Cations Influences the Double-Layer Capacitance of Cu, Au, and Pt Single-Crystal Electrodes

In this work, we have investigated the influence of alkali metal cations on the electrical double-layer (EDL) properties for various metal electrodes. Using electrochemical impedance spectroscopy, ...

Influence of Alkali Metal Cations on the Hydrogen Evolution Reaction Activity of Pt, Ir, Au, and Ag Electrodes in Alkaline Electrolytes

AbstractFundamental understanding of the influence of so‐called spectator electrolyte species on the catalytic activity of electrodes is considered as a relatively novel direction in electrocatalysis. Numerous recent examples show that seemingly inert electrolyte components drastically influence the performance of catalytic centers. Even alkali metal cations in aqueous electrolytes at high pH values can change the reaction turnover frequency by orders of magnitude, depending on their nature, from Li+ to Cs+. Here, we use several electrodes, namely Pt(polycrystalline), Pt(111), Pt(221), Ir(111), Au(111), and Ag(polycrystalline), in different alkali metal cation‐containing electrolytes to reveal their role in the hydrogen evolution reaction (HER). The HER activity trends of various Pt electrodes, irrespective of their surface structure, correlate with the hydration energy of the corresponding alkali metal cations present in the electrolyte (Li+>Na+>K+>Rb+>Cs+). The trend remains the same for the Ir(111), however, it is reversed for Au(111) and Ag(pc) electrocatalysts.

Anionic polymer as a quasi-neutral medium for low-cost synthesis of titanosilicate molecular sieves in the presence of high-concentration alkali metal ions

Titanosilicate molecular sieve (TS-1) is an important commercial catalyst for green production of oxyfunctionalized chemicals such as alcohols, ketones, epoxides, and oximes. Active TS-1 can normally be achieved in the synthetic media strictly free of alkali metal cations (e.g., Na+ and K+). This condition severely raises the purity demands of starting reagents, which greatly increases the production cost. Herein, we developed a method to achieve highly active titanosilicates in the presence of high-concentration alkali metal cations using anionic polymer-based quasi-neutral media. This synthetic route could effectively inhibit the adverse influence of alkali metal cations on the incorporation of active titanium(IV) sites into the framework of titanosilicate, directly affording the maximal framework titanium content (2.0wt.%) with almost 100% yield. This development shows a great commercial potential and opens the possibility of preparing silica-based molecular sieves/zeolites in non-fluoride neutral media.

Influence of alkali metal cations on mixed tetramer formed by guanosine and cytidine – GCGC

By using electrospray ionization mass spectrometry, it was found that larger alkali metal cations (K+, Rb+, Cs+) favor formation of mixed tetramer GCGC. This tetramer, cationized by these cations (ions [2C+2G+K]+, [2C+2G+Rb]+ and [2C+2G+Cs]+), was more abundant than other tetramers cationized by these cations (e.g. [2C+2G+K]+>[C+3G+K]+). The observed influence of K+, Rb+ and Cs+ on mixed GCGC tetramer is different from their influence on mixed dimer GC, since K+, Rb+ and Cs+ disfavor formation of mixed dimer GC (e.g. [2C+Rb]+>[C+G+Rb]+<[2G+Rb]+). As demonstrated by CID MS/MS spectra, gas phase decomposition of cationized GCGC is dominated by loss of cytidine molecule.

RETRACTED: Influence of alkali metal cations on the thermal, mechanical and morphological properties of rectorite/chitosan bio-nanocomposite films

The main theme of this work is to study the influence of ion-exchangeable alkali metal cations, such as: Li(+), Na(+), K(+), and Cs(+) on the thermal, mechanical and morphological properties. In this regard, a set of rectorite/chitosan (REC-CS) bio-nanocomposite films (BNCFs) was prepared by facile reaction of chitosan with ion-exchanged REC clay. The microstructure and morphology of BNCFs were investigated with XRD, TEM, SEM and AFM. Thermal and tensile properties of BNCFs were also investigated. As revealed from TEM and XRD results, the BNCFs featured a mixed morphology. Some intercalated clay sheets, together with nano-sized clay tactoids were obtained in LiREC/CS, NaREC/CS and KREC/CS of the BNCFs. From fractured surface study, via SEM, it was observed that the dispersion of chitosan polymer attaches to (and covers) the clay platelets. FTIR confirmed strong hydrogen bonds between clay and chitosan polymer. In addition, the thermal stabilities significantly varied when alkali metal cations varied from Li(+) to Cs(+). The BNCFs featured high tensile strengths (up to 84 MPa) and tensile moduli (up to 45 GPa). After evaluating these properties of BNCFs, we came to conclusion that these bio-nano composites can be used for packaging applications.

Influence of alkali metal cations on the formation of zeolites under hydrothermal conditions with no organic structure directing agents

Alkali metal cations play an important role in directing formation of zeolite frameworks in the absence of organic structure directing agents.

Cation assisted complexation of octacarbazolylphenyl substituted Zn(ii)-tetraphenylporphyrin with [2,2,2]cryptand

Supramolecular complex formed from a carbazolylphenyl-porphyrin first generation dendrimer and [2,2,2]cryptand was prepared and investigated the influence of alkali metal cations on its formation and properties.

A database of alkali metal-containing peptide cross sections: Influence of metals on size parameters for specific amino acids

Ion mobility/mass spectrometry techniques have been used to generate a cross section database containing 1772 entries (147 singly-, 1325 doubly-, and 300 triply-charged) for protonated and alkalated tryptic peptide ions. Such a large number of values make it possible to assess the influence of alkali metal cations [where the cation (M+) corresponds to Li+, Na+, K+, or Cs+] on peptide ion conformation. Peptide ion sizes generally increase with increasing cation size relative to the respective singly- or doubly-protonated species. Intrinsic size parameters for individual amino acid residues for alkali [Pep+M+H]2+ and [Pep+2M]2+ ions are similar to those obtained from the [Pep+2H]2+ ions. However, polar residues (Asp, Glu, Asn, Gln, His, and carboxyamidomethylated Cys), as well as Met, appear to be substantially smaller for metal-containing [Pep+M+H]2+ species compared with [Pep+2H]2+ species. This suggests these residues form tight binding interactions with these metals. A discussion of these results and the implications regarding structure are provided.

Spectroscopic (FT-IR, FT-Raman,1H and13C NMR) and theoretical studies ofp-coumaric acid and alkali metalp-coumarates

The evaluation of the electronic charge distribution in metal complexes enables more precise interpretation of mechanism by which particular metal ions affect biochemical properties of ligands [J. Inorg. Biochem. 99 (2005), 1407–1423, J. Mol. Struct. 919 (2009), 284–289]. In this paper we investigated the influence of alkali metal cations (lithium, sodium, potassium, rubidium and cesium) on the electronic structure ofp-coumaric acid (p-CA). It allowed to observe the systematic changes in the spectra of investigated complexes depending on the position of the element in the periodic table.p-Coumaric acid is a derivative of cinnamic acid that occurs in several plant species. Li, Na, K, Rb and Csp-coumarates were synthesized and the experimental and theoretical FT-IR, FT-Raman,1H and13C NMR spectra ofp-coumaric acid and its salts were registered and analyzed. The structures, atomic charges, infrared and NMR spectra ofp-coumaric acid and Li, Na, K salts were calculated by B3LYP/6-311++G**method.

Spectroscopic (FT-IR, FT-Raman, 1H and 13C NMR) and theoretical studies of p-coumaric acid and alkali metal p-coumarates

The evaluation of the electronic charge distribution in metal complexes enables more precise interpretation of mechanism by which particular metal ions affect biochemical properties of ligands [J. Inorg. Biochem. 99 (2005), 1407–1423, J. Mol. Struct. 919 (2009), 284–289]. In this paper we investigated the influence of alkali metal cations (lithium, sodium, potassium, rubidium and cesium) on the electronic structure of p-coumaric acid (p-CA). It allowed to observe the systematic changes in the spectra of investigated complexes depending on the position of the element in the periodic table. p-Coumaric acid is a derivative of cinnamic acid that occurs in several plant species. Li, Na, K, Rb and Cs p-coumarates were synthesized and the experimental and theoretical FT-IR, FT-Raman, 1H and 13C NMR spectra of p-coumaric acid and its salts were registered and analyzed. The structures, atomic charges, infrared and NMR spectra of p-coumaric acid and Li, Na, K salts were calculated by B3LYP/6-311

The influence of alkali metal cations in substituted nanostructured LaCoO3 on oxidation catalytic activity

Perovskite-type oxides La 0.9 M 0.1 CoO 3 (M=K/Na/Li) were prepared by a citrate sol–gel method. These oxides were characterized by x-ray diffraction analysis (XRD), a scanning electron microscope (SEM) and the N 2 physisorption Brunauer–Emmitt–Teller (BET) method. Their catalytic activity was studied by a constant microflow method for CO- and C 3 H 6-oxidation and by thermal decomposition of diesel soot. The results show that the obtained perovskite materials have a sphere shape, particles size of about 40–50 nm and surface area from 12.0 to 14.9 m 2 g −1. They have high catalytic activities decreasing in the sequence K > Na > Li on conversion CO, C 3 H 6 and diesel soot. The total conversion temperature of CO, C3H6 and diesel soot is 325 °C, 340 °C and 430 °C, respectively. Thus, these catalysts have high applicability in the removal of exhaust gas, especially from diesel engines.

N2 Activation in NiI–NN–NiI Units: The Influence of Alkali Metal Cations and CO Reactivity

AbstractAfter single electron reduction of the dinitrogen complex [LtBuNi(μ‐η1:η1‐N2)NiLtBu] (I) with KC8, reaction of the resulting compound K[LtBuNi(μ‐η1:η1‐N2)NiLtBu] (II) with sodium sand yields KNa[LtBuNi(μ‐η1:η1‐N2)NiLtBu] (1), which contains two different alkali metal ions. Treatment of I with two equivalents of sodium sand leads to the symmetric complex Na2[LtBuNi(μ‐η1:η1‐N2)NiLtBu] (2). Complexes 1 and 2 were investigated by single crystal X‐ray diffraction analysis as well as by Raman spectroscopy, and the results were compared with the data of K2[LtBuNi(μ‐η1:η1‐N2)NiLtBu] (III), which contains two K+ ions. Thus, it became obvious that the nature of the alkali metal ion M in compounds M2[LtBuNi(μ‐η1:η1‐N2)NiLtBu] has hardly any influence on the degree of NN bond activation. Furthermore, it was shown that treatment of the dinickel(I) complex III with CO leads to the dinickel(0) compound K2[LtBuNi(CO)]2 (4) and N2. Reaction of the unreduced dinickel(I) complex I with CO leads to a more simple replacement of the N2 ligand and formation of [LtBuNi(CO)] (3).

Synthesis and adsorption investigations of zeolites MCM-22 and MCM-49 modified by alkali metal cations

Ion exchange was made on MCM-22 and MCM-49 zeolites with different Si/Al molar ratios, with Li+, Na+, K+, and Cs+ ions and the study of the influence of alkali metal cations on CO2 adsorption properties was performed. The degree of ion-exchange decreased for larger cations (Cs+) apparently due to steric hindrances. The exchange with different cations led to a decrease in the surface area and the micropore volume. Our study shows that the adsorption capacity of the tested zeolites depends significantly on the nature and the concentration of the charge-compensating cations. The highest CO2 adsorption capacity was obtained on the MWW zeolites with the lowest Si/Al molar ratio and the Li+ or K+ cations.

Influence of the exchanged cation in Pd/BEA and Pd/FAU zeolites for catalytic oxidation of VOCs

0.5wt% palladium supported on exchanged BEA and FAU zeolites were prepared, characterized and tested in the total oxidation of volatile organic compounds (VOCs). The BEA and FAU zeolites were exchanged with different cations to study the influence of alkali metal cations (Na+, Cs+) and H+ in Pd-based catalysts on propene and toluene total oxidation. The exchange with different cations (Na+, Cs+) and H+ led to a decrease of the surface area and the micropore volume. All Pd/BEA and Pd/FAU zeolites were found to be powerful catalysts for the total oxidation of VOCs. They were active at low temperature and totally selective for CO2 and H2O. However, their activity depends significantly on the type of zeolite and on the nature of the charge-compensating cation. The activity order for propene and toluene oxidation on FAU catalysts, Pd/CsFAU>Pd/NaFAU>Pd/HFAU, is the reverse of the activity order on BEA catalysts: Pd/HBEA>Pd/NaBEA>Pd/CsBEA. The catalytic activities can be rationalized in terms of the influence of the electronegativity of the charge-compensating cation on the Pd particles, the Pd dispersion, the PdO reducibility and the adsorption energies for VOCs.

Influence of Alkali Metal Cations on the Rate of Oxygen Evolution from a Mixed Mg−LiCoO2 Oxide

O2 evolution from a mixed Mg−LiCoO2 oxide is investigated in base solutions of alkali metal cations (0.1−2 M LiOH, KOH, or CsOH) without added supporting electrolytes. Tafel slopes range 30−50 mV/decade, scarcely related to the used alkali. However, Tafel lines are displaced to more positive potentials in passing from CsOH to KOH and LiOH at the same concentration, and moreover, reaction orders with respect to OH- decrease from ∼3 to ∼1 along the same alkali sequence with fractional rather than integer values. The reaction mechanism is examined on the assumption that Temkin-type adsorption conditions apply to the many reacting intermediates possibly involved. Analytical equations representing Tafel slope and reaction order in Temkin conditions are derived and reported for many frequently adopted O2 evolution pathways, most of them for the first time. From these equations, the experimental behavior is reconciled with a constant mechanism (Kobussen's path) in which the rate-determining step varies depending on the alkali cation, shifting forward in the sequence of elementary steps from early positions in CsOH and KOH to the last one in which molecular O2 is released in LiOH. Cation interactions with reacting surface sites apparently intervene to modify the reaction activation free energy profile, stronger for Li+ than K+ and Cs+. Structural relations with Li+ (and Mg2+) sites in the oxide lattice may be involved. However, the interaction sequence, Li+ > K+ > Cs+, is similar to that observed at the interface of many structurally and chemically unrelated oxides suspended in water and is attributed to entropic contributions from interactions of water molecules bonded in the hydration ion cosphere and at the oxide−solution interface.