Alkali Metal Research Articles

Ultrasmall Fe3O4 Nanoparticles on ZrO2 as Catalysts for CO2 Hydrogenation to Lower Olefins

AbstractOrganic synthesis presents significant opportunities for converting the abundant and hazardous carbon dioxide (CO2) in the atmosphere into a more sustainable carbon source. To reduce the carbon footprint, we explored the direct hydrogenation of CO2 to lower (C2‐4=) olefins using various catalysts composed of ZrO2‐supported alkali‐metal‐promoted superparamagnetic iron oxide nanoparticles (SPIONs; Fe3O4). These catalysts are notable for their straightforward preparation; we employed a cost‐effective dry‐mixing method to create a range of alkali metal‐doped SPIONs supported on ZrO2. Results showed that the strong interactions between Fe3O4 and the ZrO2 support enhanced CO2 hydrogenation performance compared to other forms.. Under optimal conditions – using a gas hourly space velocity (GHSV) of 4500 mL/h/gcat. and a feed ratio of H2:CO2=3 : 1 – this catalyst achieved over 22 % CO2 conversion and high selectivity for light (C2–4=) olefins at 30 bar and 375 °C, with 30 wt% Fe3O4 loading on ZrO2 and 2 wt% K promoter. We also investigated several variables, including alkali metal concentration, iron content, reaction conditions, and catalyst stability over 96 hours.

CO2 reduction by borohydride over modified biochar-loaded nickel-copper alloy at ambient temperature and atmospheric pressure

CO2 reduction with sodium borohydride (NaBH4) at ambient temperature and atmospheric pressure is considered as a low-energy technology that contributes to carbon neutrality. However, the hydrolysis of NaBH4 as the hydrogen donor leads to a decrease in formate production from CO2 reduction. In order to address this issue, nickel-copper bimetallic alloy supported on biochar modified with sodium hydroxide (NC/BS) was prepared by a modified liquid-phase reduction method as a cost-effective catalyst to enhance CO2 reduction for the first time. The nickel-copper loading and the molar ratio of copper to nickel of NC/BS were optimized to 10 wt% and 2:3, respectively. The NC/BS with 10 wt% nickel-copper loading (10 % NC/BS) was characterized by TEM, EDS mapping, XRD, XPS, FTIR, ICP and EA, and the results showed that nickel-copper nanoparticles were uniformly distributed on the catalyst surface and that -OH groups were present on the 10 % NC/BS. The optimal experimental conditions for the catalytic reduction of CO2 were determined to be that the 10 % NC/BS dosage was 20 mg, NaBH4 concentration was 100 mmol/L, and reaction temperature was 20°C. By using 10 % NC/BS, the formate production from CO2 reduction was increased by 42 % and the hydrogen production from NaBH4 hydrolysis was decreased by 29 %. The use of 10 % NC/BS improved the effective utilization of borohydride for CO2 reduction from 29 % to 50 %. Based on density functional theory (DFT) calculations, it was demonstrated that the alkali metals and -OH groups of 10 % NC/BS had strong adsorption capacity for CO2, which favored the activation of CO2 and lowered the thermodynamic barrier of CO2 reduction. In addition, the presence of nickel-copper bimetallic alloy was conducive to improving the reactivity of NaBH4, which could also promote the conversion of CO2 to formate.

Characterization of Physical and Chemical Properties of Multi-Source Metallurgical Dust and Analysis of Resource Utilization Pathways

Steel metallurgical dust, characterized by a substantial output, minute particle size, and intricate composition, poses a considerable risk of environmental contamination while simultaneously embodying an exceptionally high potential for recycling. To achieve its resource utilization, chemical analysis, particle size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), Mössbauer spectroscopy, and water leaching methods were employed to investigate the chemical compositions, particle size distributions, phase compositions, and microscopic morphologies of blast furnace bag dust, sintering dust, converter fine dust, and electric arc furnace dust from steel plants. The results indicate that the four types of dust have extremely fine particle sizes, with the main distribution range of particle size being less than 100 μm. The main constituent element is Fe (19–56%), and it also contains Zn (1.4–33.5%), Pb, K, C, and other valuable elements. Alkali metals in blast furnace bag dust and sintering machine head dust existed mainly in the form of chloride. The zinc phases in sintering machine head dust and converter fine dust were ZnFe2O4, and the zinc phases in blast furnace bag dust were ZnCl2 and ZnFe2O4. Zinc in electric furnace dust was composed of ZnO and ZnFe2O4, accounting for 70.31% and 23.12%, respectively. There are significant differences in the types and contents of valuable elements among various dusts, making it difficult to achieve full-scale recovery through a single process. In view of this, a process of “in-plant recycling of harmless dusts—collaborative treatment of harmful dusts” has been proposed. Based on the characteristics of metallurgical dusts, multiple processes are used for collaborative treatment (using hydrometallurgical and pyrometallurgical methods), which can not only directly recover iron resources from dusts within the plant, but also avoid the waste of valuable elements such as Zn, Pb, K, Na, etc. It is hoped that the above work can provide a reference for steel enterprises to achieve full-scale and high value-added treatment of metallurgical dusts.

Hydridostannylene Derivatives of Magnesium and Calcium.

Reactions of a m-terphenylhydridostannylene with β-diketiminato magnesium and calcium hydrides provide bis-μ2-hydrido species, the heterobimetallic constitutions of which are maintained after the addition of THF donor solvent. In both cases, reactions with hex-1-ene result in the formation of tetravalent organostannyl alkaline earth derivatives. Whereas the magnesium reagent undergoes facile twofold addition, the calcium-centered process is arrested after a single alkene reduction event. This contrasting behavior is assessed to result from the heavier alkaline earth element's ability to form a persistent polyhapto interaction with an arene substituent of the m-terphenyl ligand.

BaPb2(CO3)2F2: Enhancing Birefringence by a Multiunit Synergy Effect.

Carbonates are ideal birefringent materials because their π-conjugated [CO3] groups are beneficial for large anisotropy. How to maximize the birefringence and maintain a wide transmittance simultaneously in carbonates is a great challenge. Adopting a multiple-functional group synergy strategy by combining alkaline-earth metal Ba2+ with large ion radius, PbO6F distorted hexagonal pyramid, and paralleled π-conjugated CO3 triangles together, we synthesized a new metal carbonate crystal, BaPb2(CO3)2F2. BaPb2(CO3)2F2 features a typical two-dimensional layered structure, which consists of a PbCO3F monolayer parallel to the ab plane and Ba2+ cations filled between the monolayers. BaPb2(CO3)2F2 exhibits a large experimental birefringence of approximately 0.245@546 nm and a short ultraviolet absorption edge down to 264 nm (Eg = 4.70 eV), indicating that it is a promising ultraviolet birefringent material. The reported highest experimental birefringence index among carbonate crystals is surpassed by BaPb2(CO3)2F2. The theoretical calculation shows that the contribution percentages for total birefringence are 57 and 43% for the CO3 group and PbO3F group, respectively. Our work offers a new route for designing new birefringent materials with excellent comprehensive performance.

Alkali Metal Amide-Catalyzed α-Deuteration of Sulfides.

The catalytic α-deuteration of sulfides was developed under mild conditions by using alkali metal amides [KN(SiMe3)2 and CsN(SiMe3)2] as the catalyst. This approach successfully achieves a selective and efficient H/D exchange reaction of sulfides with D2 without using transition metal catalysts. A series of deuterium-labeled thioanisoles and alkyl methyl sulfides were obtained in good to high levels of deuterium incorporation.

Enabling controllable time‐dependent phosphorescence in carbonized polymer dots based on chromophore excited triplet energy level modulation by ionic bonding

Time‐dependent phosphorescence color (TDPC) materials are highly attractive for realizing multitiered dynamic information encryption and anti‐counterfeiting. It’s extremely challenging to modulate puzzle of multiple luminescence species and understand the intrinsic mechanism. Herein, we demonstrate a novel and synthesize‐friendly strategy to develop a high contrast TDPC carbonized polymer dots (CPDs) with adjustable lifetime and quantum yields. The ionic bonding is introduced in self‐protected CPDs to effectively tune the excited triplet energy level of chromophores, and promote the stable existence of L‐aspartic (AA) with green phosphorescence at 545 nm, and alkali metal aspartates (AA‐M) with red phosphorescence at 665 nm. The precise regulation for TDPC lifetime can be achieved based on heavy atom effort and crosslink‐enhanced emission (CEE) effect. And, the efficient radiative energy transfer could be proven as an intrinsic mechanism for better understanding the TDPC materials. These results further expand on the fundamental principle to design high‐quality TDPC materials with more flexible regulation for luminescence properties, providing a major step forward in broadening the scope of smart phosphorescence applications.

Enabling controllable time‐dependent phosphorescence in carbonized polymer dots based on chromophore excited triplet energy level modulation by ionic bonding

Time‐dependent phosphorescence color (TDPC) materials are highly attractive for realizing multitiered dynamic information encryption and anti‐counterfeiting. It’s extremely challenging to modulate puzzle of multiple luminescence species and understand the intrinsic mechanism. Herein, we demonstrate a novel and synthesize‐friendly strategy to develop a high contrast TDPC carbonized polymer dots (CPDs) with adjustable lifetime and quantum yields. The ionic bonding is introduced in self‐protected CPDs to effectively tune the excited triplet energy level of chromophores, and promote the stable existence of L‐aspartic (AA) with green phosphorescence at 545 nm, and alkali metal aspartates (AA‐M) with red phosphorescence at 665 nm. The precise regulation for TDPC lifetime can be achieved based on heavy atom effort and crosslink‐enhanced emission (CEE) effect. And, the efficient radiative energy transfer could be proven as an intrinsic mechanism for better understanding the TDPC materials. These results further expand on the fundamental principle to design high‐quality TDPC materials with more flexible regulation for luminescence properties, providing a major step forward in broadening the scope of smart phosphorescence applications.

Insights into Structural Diversity and Morphotropic Evolution in A4Th(WO4)4 (A = Li, Na, K, Rb and Cs) Family

A series of four new thorium tungstates, A4Th(WO4)4 (A = Li, K, Rb, Cs), were synthesized using high‐temperature solid‐state method. Structural studies of the materials reveal distinct structural changes with underlying similarities influenced by the nature of A‐site cations. Li4Th(WO4)4 exhibits a two‐dimensional corrugated sheet structure stabilized by Li+ cations, crystallizing in P space group. K4Th(WO4)4 crystallizes in I41/a space group and exhibits a three‐dimensional framework consisting of ThO8 antiprisms and WO4 tetrahedra. Rb4Th(WO4)4 forms in C2/c space group, showcasing a framework with two‐dimensional sheet structure. Cs4Th(WO4)4 is isostructural to Rb4Th(WO4)4 but displays increased interlayer spacing due to the larger ionic radius of Cs. Raman spectroscopy confirms the structural data, revealing distinct vibrational modes that correlate with tungsten coordination changes from WO6 in Li4Th(WO4)4 to WO4 in the Cs4Th(WO4)4. This study demonstrates how variation of alkali metals affects the structural properties of thorium tungstates series, showing a morphotropic evolution as a factor of the ionic radii of the alkali metals.

All-solid-waste cementitious materials for grouting: Effects of alkali content and elemental ratios on performance and sustainability

The use of all-solid waste cementitious materials (ACM) in coal mine grouting backfill offers substantial green, low-carbon, and energy-saving benefits. This study systematically examines the effects of combining carbide slag (CS), fly ash (FA), and ground granulated blast furnace slag (GGBS) on the strength, workability, hydration characteristics, and microstructure of ACM. The utilization of sulfur-containing CS was achieved. The detrimental effects of delayed FA reaction and prolonged setting time can be mitigated by the introduction of high alkalinity or an increase in the Ca/Si ratio. The compressive strength may also be enhanced. The addition of excessive alkalinity (10 %) will result in a prolongation of the setting time. The primary hydration products include calcium aluminum silicate hydrate and magnesium-aluminum layered double hydroxide. Low Ca/Si ratios favor alkali metal ion charge balance, facilitating the transformation of silicate gels from single to double chains, while excessively high ratios reduce polymerization. Gmelinite forms when the (Ca+Na)/(Al+Si) ratio exceeds 1.6, and high NaOH concentrations inhibit ettringite formation. Validation shows that a GGBS:FA:CS= 3:1:3 mix with 4 % alkali binder (Group A2) meets mine grouting backfill criteria, with 80 % lower carbon emissions, 68 % lower energy intensity, and 50 % lower cost than cement. This research offers a viable pathway for the comprehensive utilization of multi-solid waste in mining applications.

Effect of sludge-based additive on particulate matter emission during the combustion of agricultural biomass pellet

In this study, the effects of a sludge-based additive on particulate matter emission during the cornstalk pellet combustion were investigated using a vertical fixed bed reactor combined with a Dekati low pressure impactor (DLPI). It was found that the PM1 and total PM10 yields from the cornstalk pellet combustion were much higher than those from the individual combustion of sludge-based additive. With the addition of sludge-based additive, the alkali and alkaline earth metals (AAEMs) in biomass would react with the Al/Si-containing and P-containing inorganic minerals in sludge-based additive to form various aluminosilicates, silicates, and K-Ca-P compounds, which could enhance the potassium fixation and retain it in the coarse particles, such as fly ash and residual ash. The PM1 and total PM10 yields from the composite pellet combustion could be effectively reduced by 62%, with the mixing ratio of sludge-based additive increasing to 75%. The mixing ratio of sludge-based additive showed a positive synergistic effect in reducing the emission of PM and a mixing ratio of <30% was recommended based on comprehensive considerations to produce relatively high-quality pellet fuel with respect to good heating value and low ash content and PM emission in later combustion application.

[formula omitted] phase diagram of Na[formula omitted]C[formula omitted]O[formula omitted] at pressures up to 100 GPa

In this work, a detailed search for stable structures of the Na2C2O5 composition was carried out using first-principles calculations and modern crystal structure prediction approaches. It was found that the Na2C2O5 compound is formed as a result of the reaction Na2CO3 + CO2 at a pressure of 4.5 GPa at 0 K and is stable in the P21 structure. This structure is consistent with recent experiments on the synthesis of Na2C2O5. The structure of Na2C2O5-P21 belongs to a new class of compounds, namely pyrocarbonates, and is characterized by the presence of [C2O5] pyro-groups formed by [CO3] triangles bonded through a common oxygen atom. Unlike alkaline earth metals, stable structures characterized by the presence of [CO4] tetrahedra have not been found for Na2C2O5. The calculated P–T phase diagram indicates the stability of Na-pyrocarbonate relative to the decomposition reaction in the pressure range 4.5–52.7 GPa at 0 K (6–58.2 GPa at 1000 K). Thus, for the first time, the lower limit of stability of Na-pyrocarbonate has been determined, which at 0 K is the same as that of the recently discovered Li-pyrocarbonate. Calculations of the phonon spectrum indicate that Na-pyrocarbonate is dynamically stable at atmospheric pressure.

A novel photoluminescence theory and design rule based on solution entropy for rare earth ion doped alkaline metal silicates

This paper introduces an innovative theory for customizing photoluminescence (PL) emission wavelengths in rare earth ion (Eu2+) doped alkaline earth metals (Ca, Mg) silicates, rooted in the entropy of fusion and configurational entropy of congruent and incongruent silicates, respectively, aiming to reveal dynamic deformation of the tetrahedral SiO4 ligand within these materials. Using FactSage, we computationally calculate the fusion entropy of congruent silicates in the CaO-MgO-SiO2 system. Synthesized ternary silicates confirm our theory by highlighting correlations between lower/higher fusion entropy (for congruent) and configurational entropy (for incongruent) silicates, leading to red/blue shifts in PL emission wavelengths. In binary silicate systems, we observe an inverse correlation between PL emission wavelengths and fusion entropy of congruent silicates or pseudo-congruent silicates like MgSiO3, whose solid-liquid decomposition temperature is close to its melting point. Furthermore, the non-ideal liquid phase entropy of incongruent silicates positioned between congruent CaMgSi2O6 (Pyroxene) and congruent Ca2MgSi2O7 (Akermanite) in the MgO-CaO-SiO2 ternary phase diagram comprehensively explains diverse PL emission wavelengths. Beyond its scholarly impact, this work expands perspectives in lighting and photonic research, opening an exciting frontier in entropy-lighting research and enabling predictions of host chemical composition and tunable PL emission wavelengths, particularly relevant to LED technologies.

Syntheses and Crystal Structures of Alkaline Earth Metal Hydrogen Acetylides AE(C2H)2 with AE = Ca, Sr, Ba.

Crystalline Ba(C2H)2 was obtained by the reaction of elemental barium dissolved in liquid ammonia, forming a blue electride, and acetylene (C2H2) injected into the reaction vial with the electride solution. From the colorless precipitate that was obtained after evaporation of the ammonia, the crystal structure of Ba(C2H)2 was solved and refined using synchrotron powder diffraction data. It crystallizes in the trigonal space group P3̅m1 (no. 164) with Z = 1, all HC2- anions are aligned along [001]. It is the first crystal structure of an alkaline earth metal hydrogen acetylide published up to now, showing a close similarity with the brucite (Mg(OH)2) and CdI2-type structures. For Sr(C2H)2, a product with a significantly reduced crystallinity was obtained, but its powder diffraction pattern makes an isotypic crystal structure very likely. IR/Raman spectroscopic investigations as well as GC analysis of the gases released upon hydrolysis unambiguously confirm the existence of HC2- anions in these compounds. Similar results were obtained for Ca(C2H)2, however this compound is almost completely amorphous. Upon heating Ba(C2H)2 with additional elemental barium to 200 °C in vacuum, highly crystalline BaC2 (I4/mmm, Z = 2) was obtained.

New NASICON-type phosphates, KNbM(PO4)3 (M = Ti, V), exhibiting a reversible alkali metal intercalation

The NASICON framework is an attractive object for designing polyanion electrode materials for metal-ion batteries. Two new NASICON-structured (S.G. R-3c) niobium phosphates KNbTi(PO4)3 (a = 8.4307(1) Å, c = 23.3955(4) Å, V = 1440.11(5) Å3) and KNbV(PO4)3 (a = 8.4892(1) Å, c = 23.3042(4) Å, V = 1454.45(3) Å3) were synthesized by the Pechini sol–gel method. Rietveld refinement revealed the potassium atoms occupy only the A(1) 6-fold antiprismatic site in both structures. Nb K-edge XANES measurements confirmed the presence of Nb5+ in KNbV(PO4)3 and the mixed-valent Nb5+/4+ in KNbTi(PO4)3 phosphates. Electrochemical measurements showed that both compounds deliver the initial discharge capacity of 110–120 mAh g−1 at a C/10 rate in the Na-half cell. KNbV(PO4)3 also maintains a reversible K+ intercalation at about 1.5 V vs. K+/K with a significant hysteresis (∼0.35 V at a C/10 rate) indicating a sluggish K+ diffusion. The mobility of alkali metal ions within the framework of new phosphates is discussed in terms of bond valence site energy calculations.

Construction of low-vacancy hexagonal Prussian blue analogues for efficient rubidium recovery

Prussian blue analogues (PBAs) are considered a promising adsorbent for rubidium recovery due to their high ion exchange capacity and selectivity. However, the development of PBAs-based rubidium adsorbents with excellent stability and adsorption capacity is still hindered by the inevitable CN ligand vacancies. Herein, a synthetic strategy is proposed to slow down crystal nucleation and promote the self-repair of crystal defects by incorporating N-doped porous carbon (NPC) as a solid modifier during the synthesis process. As a result, the vacancy content of Zn-PBA-NPC is significantly decreased and large size twinned crystals are produced, which remarkably improves the thermal and acid-base stability. Benefiting from the high content of K+ in the low-vacancy Zn-PBA-NPC, it achieves a high adsorption amount of 199.1 mg/g and rapid adsorption kinetics of just 5 min for Rb+. In addition, it shows good selectivity in the presence of other alkali metal ions. This work not only prepares a high-performance adsorbent for efficient recovery of Rb+, but also facilitates insights into the design and construction of low-vacancy PBAs.

Design of alkali metal oxide adsorbent for direct air capture: Identification of physicochemical adsorption and analysis of regeneration mechanism

Direct air capture (DAC) represents an advanced negative carbon emission technology, with the key being high-performance CO2 adsorbents. First, this work carefully identifies CO2 physisorption and chemisorption by CaO/HcATP (CaO loaded on acid-modified attapulgite) as DAC adsorbent. The chemisorption of amorphous "CaO" plays a crucial role in both the adsorption capacity and rate, with contributions of 66.8 % and 50.85 %, respectively. The adsorption capacity of CaO/HcATP is only 212.4 ± 25.7 µmol/g via the simple CO2 physisorption and improved by 426.7 µmol/g owning to the chemisorption of amorphous CaO. Second, the concentration of silanol groups on CaO/HcATP plays a pivotal role in the adsorption process. The concentration of silanol groups decreases to 3.85 OH/nm2 after undergoing 30 cycles of adsorption-desorption. Then it increases to 9.54 OH/nm2 by adsorbing the moisture in the air, resulting in a recovered adsorption capacity of 90.7 %. Furthermore, the pseudo-first-order adsorption kinetics model effectively predicted the experimental results. Finally, the dual loop of CO2 capture and regeneration is summarized using the CaO/HcATP as DAC adsorbent. The amorphous "CaO" interacts with the surface silanol of HcATP, synergistically capturing CO2 in the form of "CaO···CO2", which reduces desorption energy consumption. The wetting property of HcATP contributes to the regeneration of CaO/HcATP. This work contributes to establishing fundamental principles for designing cost-effective DAC adsorbents.

Tunable electronic structure and enhanced optical properties of blue phosphorene via adsorption of alkali metal atoms

Tunable electronic structure and enhanced optical properties of blue phosphorene via adsorption of alkali metal atoms

Recent advances in heteroatom doped transition metal sulfides for high-performance supercapacitors

Supercapacitors have been well focused on, due to the advantages of fast charging/discharging, high power density, long service time and safety. Electrode materials determine the performance of supercapacitors. Serving as a kind of battery-type materials, transition metal sulfides have been received more attentions for high redox activity and high specific capacity. Controllable synthesis of metal sulfides determines their microstructure and composition, which is the basis for developing new materials. Therefore, this review firstly introduces existing synthetic methods of transition metal sulfides, including hydrothermal/solvothermal method, template method, electrodeposition method, sol-gel method, co-precipitation method, exfoliation/intercalation method and solid state method. The preparation process, principle, advantages/shortages of each method and related examples are highlighted. Taking controllable synthesis as the main line, recent advances of heteroatom doped metal sulfides and their application in supercapacitors are introduced in the second section. According to the type of dopants, all doped metal sulfides are divided into two parts: nonmetal doped metal sulfides, including B, N, F, O, P and Se, and metal doped sulfides, including alkali metal, precious metal, rare earth metal and transition metal. The research progresses about materials preparation, structure feature and supercapacitance performance are summarized. At last, current issues and future prospects in the field of heteroatom doped metal sulfides are proposed. It is anticipated that the review will provide guiding ideas or strategies for developing high-performance metal sulfides electrode materials.

Machine learning model with a novel self–adjustment method: A powerful tool for predicting biomass ash fusibility and enhancing its potential applications

Biomass ash has been extensively studied for its potential applications, owing to its high content of alkali and alkaline earth metallic species (AAEMs). These AAEMs can act as catalysts in biomass thermochemical conversion and other industrial processes. However, AAEMs can also cause slagging and agglomeration, which can significantly impact system operations. To better understand these effects, we investigated the relationship between ash melting behavior and the chemical composition of biomass ash using a machine learning (ML) model. To enhance the model's performance, we employed a self-adjustment (SA) method, which significantly improved predictive accuracy. The SA-ETR model achieved an R2 value greater than 0.93, based on a dataset of 268 data points. We provided a detailed explanation of the SA-optimized ML model using Python's Shapley Additive Explanations (SHAP) library, which included global and local feature importance analysis, investigation of simultaneous effects between two features, and individual data point prediction analysis. The contents of K2O, SiO2, CaO, and Al2O3 were considered as the most significant factors affecting biomass ash's initial deformation temperature (IDT). The insights gained from this study can help investors and researchers reduce experimental complexity and improve system operation.