Alkali Metal Research Articles

Insight into the Pyrolysis Mechanism of α-O-4 Linked Lignin: The Role of Alkali Metal Potassium

Insight into the Pyrolysis Mechanism of α-O-4 Linked Lignin: The Role of Alkali Metal Potassium

Pollution of the Main Components of the Natural Environment of the Most Developed Part of the Southwestern Coast of Lake Baikal (within the Baikal Municipal Formation)

The data of landscape-geochemical studies of the main components of the environment (snow, surface water, soils and vegetation) near the sedimentation ponds of the industrial site of the former Baikal pulp and paper mill, Baikalsk, at the mouth of the Kharlakta and Babkha rivers on the southwestern coast of Lake Baikal are presented. Increased content of heavy (HM) and alkaline-earth metals, SO42–, NO3–, NH4+, PO43– was detected in the snow near the Baikalsk town, exceeding background readings. Concentrations of F–, NO3–, NH4+, Pb, Mo, Mn, Zn, Sr and V in surface waters of local lake shore sites exceed sanitary and hygienic norms. Soil contamination with HM in the recreational and industrial zone located on the shore of Lake Baikal has been revealed. Correlations between the concentrations of macro- and microelements in soils and their indicators such as the content of organic carbon and physical clay fraction have been established, which indicates the presence of biogeochemical barriers on which Na, Ni, Cu, Zn, Sr, Co accumulate in values above the background readings and MAC.

Characteristics of Ash Accumulation and Alkali Metal Migration in Coal-Fired Power Station Boilers Under Low-Load Combustion

This study aims to investigate the characteristics of ash accumulation and slagging in boilers during low- and medium-load operation and to analyse the migration pattern of alkali metals in high-alkali coal. In this paper, the ash accumulation characteristics and slagging trend of the furnace interior under a 500 MW load were investigated using numerical simulation by comparing the ash accumulation and slagging characteristics under two different burner configurations, and analysing the slagging trend of the furnace with upper burner arrangement and lower burner arrangement by taking the deposition location on the furnace wall and the deposition rate and the temperature of the furnace wall as the indices. The existing formation of sodium in Jundong coal at different temperatures was investigated using computational methods; SiO2, Al2O3, and kaolin were doped separately; and the migration and transformation characteristics of their different additives on the sodium-based compounds in Jundong coal were explored. The results showed that, under a 500 MW load, the size of the tangent circle formed in the furnace by commissioning the upper burner condition was larger than the lower burner, and the main combustion zone was larger than the lower burner. The ash accumulation of coal ash particles in the boiler was mainly concentrated in the hearth region, and the deposition rate was higher at the height regions of 10 m and 25 m in the hearth. The solid-phase NaCl transition temperature was reduced to 350 °C after the doping of SiO2 in Jundong coal, and the doping of Al2O3 inhibited the transition of solid-phase NaCl, promoted the generation of gas-phase NaCl, and had certain inhibitory effects on the generation of sodium-based silica–aluminium compounds, the content of which at all temperatures was inversely proportional to the proportion of doping. The doping of kaolin promotes the transformation of solid-phase NaCl and inhibits the generation of gas-phase NaCl.

Stabilizing Contorted Doubly‐Reduced Tetraphenylene with Heavy Alkali Metal Complexation: Crystallographic and Theoretical Evidence

AbstractThe two‐fold reduction of tetrabenzo[a,c,e,g]cyclooctatetraene (TBCOT, or tetraphenylene, 1) with K, Rb, and Cs metals reveals a distinctive core transformation pathway: a newly formed C−C bond converts the central eight‐membered ring into a twisted core with two fused five‐membered rings. This C−C bond of 1.589(3)–1.606(6) Å falls into a single σ‐bond range and generates two perpendicular π‐surfaces with dihedral angles of 110.3(9)°–117.4(1)° in the 1TR2− dianions. As a result, the highly contorted 1TR2− ligand exhibits a “butterfly” shape and could provide different coordination sites for metal‐ion binding. The K‐induced reduction of 1 in THF affords a polymeric product with low solubility, namely [{K+(THF)}2(1TR2−)] (K2‐1TR2−). The use of a secondary ligand facilitates the isolation of discrete complexes with heavy alkali metals, [Rb+(18‐crown‐6)]2[1TR2−] (Rb2‐1TR2−) and [Cs+(18‐crown‐6)]2[1TR2−] (Cs2‐1TR2−). Both internal and external coordination are observed in K2‐1TR2−, while the bulky 18‐crown‐6 ligand only allows external metal binding in Rb2‐1TR2− and Cs2‐1TR2−. The reversibility of the two‐fold reduction and bond rearrangement is demonstrated by NMR spectroscopy. Computational analysis shows that the heavier alkali metals enable effective charge transfer from the 1TR2−TBCOT dianion, however, the aromaticity of the polycyclic ligand remains largely unaffected.

Electrospun Carbon Nanofibers with Numerous Miniature Carbon Nanofibers for Free‐Standing, Binder/Conductive Additive‐Free Lithium‐Ion Battery Anodes

Among their several unique properties, the high electrical conductivity and mechanical strength of carbon nanofibers make them suitable for applications such as catalyst support for fuel cells, flexible electrode materials for secondary batteries, and sensors. However, their performance requires improvement for practical applications. Several methods have been pursued to achieve this, such as growing carbon nanotubes from carbon nanofibers; however, the transition metal catalyst used to grow carbon nanotubes causes problems, including side reactions. This study attempts to address this issue by growing numerous branched carbon nanofibers from the main carbon nanofibers using alkali metals. Excellent electrical conductivity is achieved by growing densely branched carbon nanofibers. Consequently, a current collector, binder, and conductive material‐free anode material is realized, exhibiting excellent electrochemical performance compared with existing carbon nanofibers. The proposed method is expected to be a powerful tool for secondary batteries and have broad applicability to various fields.

BaFS: Birefringence Enhanced by the Transformation from Optical Isotropy to Anisotropy via Interlayer Anion Substitution.

Improved birefringence, given its capacity to modulate polarized light, holds a lively role in the optoelectronic industry. Traditionally, alkaline-earth metal halides have possessed low birefringence due to their nearly optical isotropic properties. Herein, the substitution of interlayer anion with linear S─S unit that meticulously engineered by reduced valence state and strong covalent bond is integrated into the optically isotropic BaF2, offering the new salt-inclusion chalcogenide BaFS. Notably, it has dramatically enhanced optical anisotropy, thereby significantly boosting birefringence of 0.238@546nm, achieved by overall considering experimental observations with theoretical analysis. Theoretical investigation has established the significant effect of the covalent S─S bond on the birefringence index. Additionally, BaFS demonstrates a remarkable laser-induced damage threshold (LIDT, 12.0×AgGaS2@1064nm), illuminating a promising pathway for designing materials with significant birefringence properties in laser applications.

Ultrafast Synthesis of Nanoscale Metal Borides for Efficient Hydrogen Evolution.

Nanoscale metal borides, with exceptional physicochemical properties, have been attracted widespread attention. However, traditional synthesis methods of metal borides often lead to surface coking and large particle sizes. Herein, we have employed a flash Joule heating (FJH) technique to enable the ultrafast synthesis of metal boride nanomaterials. The synthesized materials encompass a wide range of diverse categories, including alkaline-earth metal borides (CaB6), transition metal borides (TiB2, VB2, CrB2, MoB, MoB2, MnB2, MnB4, FeB, CoB, NiB), noble-metal borides (RuB2, RuB1.1), and rare-earth metal borides (LaB6, CeB6). As an example, the RuB2 demonstrates highly desirable electrocatalytic performance for all-pH hydrogen evolution reaction (HER). Especially, under the acidic condition, it exhibits an overpotential as low as 15 mV at a current density of 10 mA cm-2, with a nearly 100% faradic efficiency. Additionally, in situ Raman spectra confirm that both Ru and B sites serve as active sites for the HER. Moreover, the stability of RuB2 can be further enhanced by optimizing the microenvironments of the anolyte composition (H+, K+). More importantly, the experimental and density functional theory (DFT) calculations reveal that the co-existence of H+ and K+ localized around the RuB2 plays a crucial role in further enhancing the stability.

Multiple Electron Transfers Enable High-Capacity Cathode Through Stable Anionic Redox.

Single-electron transfer, low alkali metal contents, and large-molecular masses limit the capacity of cathodes. This study uses a cost-effective and light-molecular-mass orthosilicate material, K2FeSiO4, with a high initial potassium content, as a cathode for potassium-ion batteries to enable the transfer of more than one electron. Despite the limited valence change of Fe ions during cycling, K2FeSiO4 can undergo multiple electron transfers via successive oxygen anionic redox reactions to generate a high reversible capacity. Although the formation of O‒O dimers in K2FeSiO4 occur upon removing large amounts of potassium, the strong binding effect of Si on O mitigates irreversible oxygen release and voltage degradation during cycling. K2FeSiO4 achieves 236 mAh g-1 at 50mA g-1, with an energy density of 520Wh kg-1, which can be comparable with commercial LiFePO4 materials. Moreover, it also exhibits 1400 stable cycles under high-current conditions. These findings enhance the potential commercialization prospects for potassium-ion batteries.

Alkaline earth metal enhancement of cerium‐manganese‐based three‐dimensional ordered macroporous catalysts for NO oxidation

Nitrogen oxides are an industrial and domestic waste gas, which pollutes the air and affects health. In this paper, we use the template method to achieve the doping of alkaline earth metals, and the alkaline earth metals are doped into cerium‐manganese‐based three‐dimensional ordered macroporous (3DOM) catalysts to detect NO oxidation. The introduction of alkaline earth metals can improve the stability and thickness of macroporous results, which increases the contact area between the catalyst and reactant gases. At the same time, alkaline earth metal doping can promote the formation of more oxygen vacancies and unsaturated structures, and improve the catalytic activity of NO oxidation. The NO conversion rate of CM‐3Mg doped with 3% Mg was 61.25% at 250°C, and the NO conversion rate was the highest at 303°C, which was 79.2%. This study provides a promising catalyst candidate for NO oxidation in practical applications.

Light-Enabled Reversible Hydrogen Storage of Borohydrides Activated by Photogenerated Vacancies.

Borohydrides, known for ultrahigh hydrogen density, are promising hydrogen storage materials but typically require high operating temperatures due to their strong thermodynamic stability. Here we introduce a novel light-induced destabilization mechanism for hydrogen storage reaction of borohydrides under ambient conditions via photogenerated vacancies in LiH. These vacancies thermodynamically destabilize B-H bonds through the spontaneous "strong adsorption" of BH4 groups, which trigger an asymmetric redistribution of electrons, enabling hydrogen release at near room temperature, approximately 300 °C lower than the corresponding thermal process. By utilizing specially designed "nano-photothermal reactors", which optimize thermodynamic destabilization effect with nanoscale dispersed LiH and create space-confined "hotspots" to enhance hydrogen storage kinetics, we achieve an ultrahigh hydrogen storage capacity of 11.02 wt % H2 in LiBH4 using only light irradiation. This light-induced destabilization mechanism can also be extended to other alkali metal borohydrides, offering insights for developing solid-state hydrogen storage materials under mild conditions.

Recovery of Li Through Selective Adsorption on Two Types of Calix[4]arene Derived Adsorbents

ABSTRACT Recovery of Li is one of urgent issues owing to exponential increase of Li demand of Li-ion battery. More efficient and selective reagents for Li recovery have been required. Calixarene as a host oligomer was focused on this purpose, and it was applied to adsorptive reagents. Two types of adsorbents incorporating trialkyl monoacetic acid derivatives of calix[4]arene through either impregnation or crosslinking were synthesized. The impregnated adsorbents were synthesized by impregnation of four trialkyl monoacetic acid derivatives of calix[4]arene into macroporous Ambelite XAD-7. The crosslinked adsorbents were synthesized by crosslinking of three trialkyl monoacetic acid derivatives of debutylated calix[4]arene each other using sym-trioxane under an acidic condition. Their adsorption behaviors and Li+ selectivities over other alkali metal ions were investigated. Incorporation of the ligand into the adsorbents had a negligible effect on the time required to reach equilibrium. The impregnated adsorbents exhibited extremely high Li+ selectivity over other alkali metal ions that reflected those of the incorporated ligand, whereas the crosslinked adsorbents exhibited Cs+ selectivity and mixed effects arising from incomplete dehydration and ion discrimination. The adsorption of alkali metal ions was driven by ion-exchange mechanism. The apparent adsorption equilibrium constants for alkali metal ions on both adsorbents and the separation factors between the metal ions were estimated. It was found that three alkyl branches affected the adsorption efficiency, together with separation efficiency.

Quadrupole-Central-Transition 23Na, 39K, 87Rb NMR Studies of Alkali Metal Ions under Different Molecular Tumbling Conditions: A Simple Model to Treat Chemical Exchange Involving Quadrupolar Nuclei.

We report a new NMR method for treating two-site chemical exchange involving half-integer quadrupolar nuclei in a solution. The new method was experimentally verified with extensive 23Na (I = 3/2), 39K (I = 3/2), and 87Rb (I = 3/2) NMR results from alkali metal ions (Na+, K+, and Rb+) in a solution over a wide range of molecular tumbling conditions. In the fast-motion limit, all allowed single-quantum NMR transitions for a particular quadrupolar nucleus are degenerate giving rise to one Lorentzian signal. In the slow-motion regime, although the NMR signal from quadrupolar nuclei should in principle exhibit a multi-Lorentzian line shape, only the quadrupole central transition (QCT) is often detectable in practice. In all the cases studied in this work, we found that alkali metal ions undergo fast exchange between free and bound states. Using the new theoretical method, we were able to interpret the experimental transverse relaxation data (i.e., line widths) obtained for 23Na, 39K, and 87Rb NMR signals including QCT signals over a large temperature range and extract information about ion-binding dynamics in different chemical environments. This work fills a gap in the literature where a unified approach for treating NMR transverse relaxation data for quadrupolar nuclei over the entire range of motion has been lacking. Our results suggest that the new approach is applicable in the study of alkali metal ion binding to biological macromolecules.

The Missing Link in the Monogermanide Series: YbGe.

High-pressure, high-temperature synthesis at 12 GPa between 750 and 1000 °C for 30 to 300 min yields the last missing rare-earth metal monogermanide, YbGe. Powder and single-crystal X-ray diffraction measurements reveal that the compound crystallizes in a FeB-type structure (space group Pnma, a=7.901(2) Å, b=3.8981(9) Å, and c=5.873(2) Å). The results of the chemical bonding study, while supporting the presence of polyanionic Ge chains interacting with the surrounding Yb through multi-atomic polar bonds, suggest a transitional scenario between the monogermanides formed by alkaline-earth elements and those formed by trivalent rare-earth metals.

Atomic Manipulation on 2D Sumanene for Precise Fermi Level Positioning in Ultrafast High-Capacity Alkali Metal Batteries.

A sumanene monolayer, with a Kagome-like lattice and two flat bands and two Dirac cones in the band structures, can be atomically assembled by C21 clusters. In this paper, first-principles simulations indicate surface charge doping can purposely shift the Fermi level between Dirac cones and flat bands. Interestingly, Li/Na/K atoms can be well distributed in bowl-like structures, transforming the semiconducting sumanene monolayer into a semimetal by shifting the Fermi energy exactly to the Dirac cone. As a natural hosting platform, sumanene shows a high theoretical storage capacity (1115.7 mAh/g for Na/K). Additionally, the moderate adsorption and very low diffusion barrier (≤0.24 eV) imply a suitable open-circuit voltage and ultrafast charge. Besides, the naturally curved and flexural configuration of sumanene effectively releases the lattice expansion during charging and discharging. Therefore, doped sumanene is a compelling anode material for alkali-metal batteries with high capacity, ultrafast charge, and high structural stability.

Research on the Application of Silver Nanowire-Based Non-Magnetic Transparent Heating Films in SERF Magnetometers.

We propose a non-magnetic transparent heating film based on silver nanowires (Ag-NWs) for application in spin-exchange relaxation-free (SERF) magnetic field measurement devices. To achieve ultra-high sensitivity in atomic magnetometers, the atoms within the alkali metal vapor cell must be maintained in a stable and uniform high-temperature environment. Ag-NWs, as a transparent conductive material with exceptional electrical conductivity, are well suited for this application. By employing high-frequency AC heating, we effectively minimize associated magnetic noise. The experimental results demonstrate that the proposed heating film, utilizing a surface heating method, can achieve temperatures exceeding 140 °C, which is sufficient to vaporize alkali metal atoms. The average magnetic flux coefficient of the heating film is 0.1143 nT/mA. Typically, as the current increases, a larger magnetic field is generated. When integrated with the heating system discussed in this paper, this characteristic can effectively mitigate low-frequency magnetic interference. In comparison with traditional flexible printed circuits (FPC), the Ag-NWs heating film exhibits a more uniform temperature distribution. This magnetically transparent heating film, leveraging Ag-NWs, enhances atomic magnetometry and presents opportunities for use in chip-level gyroscopes, atomic clocks, and various other atomic devices.

Temperature-dependent elastic, mechanical, thermal, and acoustic behavior in alkaline earth semiconductors

Temperature-dependent elastic, mechanical, thermal, and acoustic behavior in alkaline earth semiconductors

Association between alkali and alkaline earth elements in chorionic villus and risk for spontaneous abortion.

Exposure to specific alkali and alkaline earth elements(AEs/AEEs) has been reported that are linked to an increased risk of spontaneous abortion. However, the direct evidence of exposure in the uterus are absent. Therefore, we collected chorionic villi after spontaneous abortion or induced abortion in Peking University Third Hospital. The concentrations of six alkali and alkaline earth elements in chorionic villi were measured using inductively coupled plasma mass spectrometry (ICP-MS). Through using logistic regression, Bayesian kernel machine regression (BKMR) and Weighted quantile sum regression (WQS) model, we assessed single and mixed exposure effects of alkali and alkaline earth elements on spontaneous abortion. In terms of the individual effect, high concentration group of barium (Ba) increased the risk of spontaneous abortion by 150 % (95 % CI: 1.38-4.51), whereas rubidium (Rb), cesium (Cs) and Magnesium (Mg) all clearly demonstrated dose dependency in reducing the incidence of spontaneous abortion. The BKMR model demonstrated that as the mixed exposure percentile increased, the likelihood of spontaneous abortion decreased almost linearly. For every quartile increasing in the WQS index, the risk of spontaneous abortion decreased (OR: 0.21, 95 % CI: 0.13-0.33), with Mg and Rb having the highest weights at 0.587 and 0.367, respectively. According to our findings, there were negative dose-response relationships between Mg and Rb levels and risk for spontaneous abortion, but exposure to higher concentration of Ba in the chorionic villi was positively associated with the risk of it.

Pristine and Alkaline Earth Metal‐Decorated C24N24 Fullerenes as Potential Sensors for Halomethanes: A Comparative DFT Investigation

AbstractIn this paper, attempts were made to investigate the adsorption potential of pristine and alkaline earth metal (AEM)‐decorated C24N24 fullerenes toward the halomethanes (XCH3, where X═F, Cl, and Br). By means of DFT calculations, the XCH3⋯C24N24 and ⋯AEM@C24N24 complexes (AEM═Be and Mg) were adequately examined. Upon energetic features, the FCH3⋯Mg@C24N24 complex exhibited the most negative adsorption and interaction energies with values of −21.01 and −22.61 kcal/mol, respectively. From thermodynamic analysis, spontaneous and exothermic natures of XCH3⋯Mg@C24N24 interactions were affirmed, unveiling favorable role of Mg decoration in enhancing the adsorption process. From SAPT analysis, the electrostatic forces dominated the interactions within the XCH3⋯C24N24 and ⋯Be/Mg@C24N24 complexes. Upon FMOs analysis, notable alterations in the distribution of molecular orbitals of studied fullerenes were noticed, indicating the effect of XCH3 adsorption on the electronic features of the studied fullerenes. Further, the Egap values were decreased after the adsorption process which enhanced electrical conductivity of studied fullerens. From DOS plots, the capacity of the C24N24 and Be/Mg@C24N24 to adsorb the XCH3 molecules was affirmed. Solvation energies demonstrated the favorability of the studied adsorption process in the water phase. The present findings established C24N24 and AEM@C24N24 fullerenes as potential effective candidates for detecting halomethanes.

Several energetic MOFs based on the N-rich energetic materials and alkali metals: towards high detonation performances and good stabilities

This study involves the design and synthesis of a series of novel E-MOFs derived from the N-rich energetic material ATDT and various alkali metals, ranging from ATDT-Li to ATDT-Cs.

Selective adsorption of copper by amidoxime modified low-temperature biochar: Performance and mechanism.

Biochars prepared at 300-700°C were functionalized with amidoxime groups to evaluate their selective adsorptive removal capabilities towards Cu(II), Cd(II), and Pb(II). The results show that the amidoxime modification significantly enhanced the the Cu(II) adsorption capacity of the biochar prepared at 300°C (AOBC300) by 1.6 times, reaching 0.61mmol/g. In binary and ternary heavy metal solutions, AOBC300 exhibited preferential adsorption of Cu(II), followed by Pb(II) and Cd(II). High salinity, alkaline earth metal ions, humic substances, and other metal cations had minimal interference on the adsorption of heavy metals by AOBC300. Sample characterization revealed that amidoxime modification reduced the zeta potential and increased the hydrophilicity of the biochar. XPS analysis demonstrated that both N and O atoms of the amidoxime group are involved in the adsorption process, contributing to AOBC300's strong affinity for heavy metal ions. DFT calculations further confirmed the adsorption preference of different heavy metals on AOBC300. This study demonstrates that amidoxime grafting is an effective protocol for refining low-temperature biochar, aimed at efficiently eliminating heavy metals from waste streams.