Metal Sites Research Articles

Spatial Structure of Electron Interactions in High-entropy Oxide Nanoparticles for Active Electrocatalysis of Carbon Dioxide Reduction.

High-entropy oxides (HEOs) exhibit distinctive catalytic properties owing to their diverse elemental compositions, garnering considerable attention across various applications. However, the preparation of HEO nanoparticles with different spatial structures remains challenging due to their inherent structural instability. Herein, ultrasmall high-entropy oxide nanoparticles (less than 5nm) with different spatial structures are synthesized on carbon supports via the rapid thermal shock treatment. The low-symmetry HEO, BiSbInCdSn-O4, demonstrates exceptional performance for electrocatalytic carbon dioxide reaction (eCO2RR), including a lower overpotential, high Faraday efficiency across a wide electrochemical range (-0.3 to -1.6V), and sustained stability for over100h. In the membrane electrode assembly electrolyzer, BiSbInCdSn-O4 achieves a current density of 350mAcm-2 while maintaining good stability for 24h. Both experimental observations and theoretical calculations reveal that the electron donor-acceptor interactions between bismuth and indium sites in BiSbInCdSn-O4 enable the electron delocalization to facilitate the efficient adsorption of CO2 and hydrogenation reactions. Thus, the energy barrier of the rate-determining step is reduced to enhance the electrocatalytic activity and stability. This study elucidates that the spatial structure of metal sites in HEOs is able to regulate CO2 adsorption status for eCO2RR, paving the way for the rational design of efficient HEO catalysts.

Half-metallization Atom-Fingerprints Achieved at Ultrafast Oxygen-Evaporated Pyrochlores for Acidic Water Oxidation.

The stability and catalytic activity of acidic oxygen evolution reaction (OER) are strongly determined by the coordination states and spatial symmetry among metal sites at catalysts. Herein, an ultrafast oxygen evaporation technology to rapidly soften the intrinsic covalent bonds using ultrahigh electrical pulses is suggested, in which prospective charged excited states at this extreme avalanche condition can generate a strong electron-phonon coupling to rapidly evaporate some coordinated oxygen (O) atoms, finally leading to a controllable half-metallization feature. Simultaneously, the relative metal (M) site arrays can be orderly locked to delineate some intriguing atom-fingerprints at pyrochlore catalysts, where the coexistence of metallic bonds (M─M) and covalent bonds (M─O) at this symmetry-breaking configuration can partially restrain crystal field effect to generate a particular high-spin occupied state. This half-metallization catalyst can effectively optimize the spin-related reaction kinetics in acidic OER, giving rise to 10.3 times (at 188mV overpotential) reactive activity than pristine pyrochlores. This work provides a new understanding of half-metallization atom-fingerprints at catalyst surfaces to accelerate acidic water oxidation.

Base-metal exploration by using remote sensing, geological, geophysical, and geochemical datasets with clues from ancient mining: A comprehensive review on Aravalli-Delhi Fold Belt, Rajasthan, India

Base metal deposits are present in different continents with evidences of their mining activities during ancient times as mentioned in the historical literature. Aravalli – Delhi Fold Belt (ADFB) in Rajasthan, India is having numerous base metal prospects where ancient mining signages are recorded. Modern-day mining has commenced taking clues from these evidences. Present-day techniques such as remote sensing, geological mapping, geophysical survey, geochemical survey, and exploration/drilling are utilized for the identification of surficial ancient mining features and identification of the mineralized zones. These techniques utilize their unique criteria to get an idea of the mineral association. The integration of all the unique characteristics of modern techniques with the help of weighted overlay analysis, fuzzy logic, multi-criteria overlay analysis, etc. helps to identify the mineral potential zones from the ancient working sites. Their integrated results provide the surficial as well as sub-surficial information of the region that gives a better revelation about the region and helps in decision-making towards the mineralization status of the region. World-over surficial ancient features have been recorded in exploratory sites for base metals, and the case histories where integrated techniques were used for mineral exploration are discussed. Zawar – Dungarpur belt also has the potential for base metals therefore, the boolean approach, weighted overlay, and multi-criteria overlay analysis were performed using remote sensing, structural, and geochemical datasets. The integrated results showed that the head zone and southern broader part near Keekawat have the potential for base metals.

Electrochemical Synthesis of Metal‐Organic Frameworks Based on Zinc(II) and Mixed Ligands Benzene‐1,4‐Dicarboxylate (BDC) and 4,4′‐Bipyridine (Bpy) and its Preliminary Study on CO2 Adsorption Capacities

AbstractEfficient and environmentally friendly synthesis methods for metal‐organic frameworks (MOFs) have emerged as a compelling topic in the organometallic field. In this study, we successfully electro‐synthesized a MOF based on mixed ligands, benzene‐1,4‐dicarboxylate (BDC) and 4,4′‐bipyridine (Bpy), denoted as MOF‐508b, and investigated its CO2 adsorption capacity, comparing it with that of Zn‐BDC and Zn‐Bpy coordination polymers. Unlike the circular shapes of Zn‐BDC and Zn‐Bpy, MOF‐508 adopts a three‐dimensional structure upon binding with the pillar ligand, featuring mesoporous pore sizes. MOF‐508b demonstrates superior stability at room temperature, exhibiting a thermal stability of 400 °C. The CO2 capture potential of the materials was assessed under low‐pressure conditions at room temperature. The pillared layer of MOF‐508b results in the reduction of open metal sites, facilitating the binding of active CO2 through coordination, thereby influencing its optimum CO2 adsorption capacity (2.51 mmol g−1), which was found to be lower than that of Zn‐Bpy (3.83 mmol g−1) and Zn‐BDC (4.46 mmol g−1). The adsorption mechanism on MOF‐508b follows the Weber‐Morris model, emphasizing diffusion within particles over direct attachment to the material surface.

Boosting hydrogen production via alkaline water splitting: Impact of Ag doping in Gd2O3 nanosheet arrays

Hydrogen is a preferable renewable energy carrier in decarbonization efforts to develop sustainable and carbon-free economies due to its high energy density and absence of pollutant emissions during combustion. Among others, electrochemical water splitting (EWS) is a sustainable and eco-friendly technology for producing green hydrogen, representing an essential initial step towards achieving carbon neutrality. In this study, we synthesized a bifunctional electrocatalyst by vertically anchoring Ag-doped Gd2O3 nanosheet arrays onto a three-dimensional nickel foam (NF) substrate. The developed materials were thoroughly investigated using various analytical techniques. Furthermore, the electrocatalyst effectively performed oxygen evolution reactions (OER) and hydrogen evolution reactions (HER). The Ag4%-Gd2O3/NF exhibited boosted HER activity, achieving higher current densities ranging from 10 to 400 mA cm−2 at an overpotential between 14 and 122 mV. This study also highlights the considerable impact of metal sites in both Ag4%-Gd2O3/NF and Gd2O3/NF on the HER catalytic process. Similarly, the Ag4%-Gd2O3 electrocatalyst exhibited superior OER activity, with an overpotential of 209 mV at 10 mA cm−2. The optimized composition also shows Tafel slope of 25 and 20 mVdec−1. Furthermore, Ag4%-Gd2O3 demonstrated the ability to generate oxygen gas bubbles in approximately 20 h for OER, making it an attractive material for energy conversion and storage devices.

Complementary Multisite Turnover Catalysis toward Superefficient Bifunctional Seawater Splitting at Ampere-Level Current Density.

The utilization of seawater for hydrogen production via water splitting is increasingly recognized as a promising avenue for the future. The key dilemma for seawater electrolysis is the incompatibility of superior hydrogen- and oxygen-evolving activities at ampere-scale current densities for both cathodic and anodic catalysts, thus leading to large electric power consumption of overall seawater splitting. Here, in situ construction of Fe4N/Co3N/MoO2 heterostructure arrays anchoring on metallic nickel nitride surface with multilevel collaborative catalytic interfaces and abundant multifunctional metal sites is reported, which serves as a robust bifunctional catalyst for alkaline freshwater/seawater splitting at ampere-level current density. Operando Raman and X-ray photoelectron spectroscopic studies combined with density functional theory calculations corroborate that Mo and Co/Fe sites situated on the Fe4N/Co3N/MoO2 multilevel interfaces optimize the reaction pathway and coordination environment to enhance water adsorption/dissociation, hydrogen adsorption, and oxygen-containing intermediate adsorption, thus cooperatively expediting hydrogen/oxygen evolution reactions in base. Inspiringly, this electrocatalyst can substantially ameliorate overall freshwater/seawater splitting at 1000mA cm-2 with low cell voltages of 1.65/1.69V, along with superb long-term stability at 500-1500mA cm-2 for over 200 h, outperforming nearly all the ever-reported non-noble electrocatalysts for freshwater/seawater electrolysis. This work offers a viable approach to design high-performance bifunctional catalysts for seawater splitting.

Glass fiber-based metal organic gel composite electrolytes for solid-state lithium batteries

Abstract Quasi-solid-state electrolytes encounter great obstacles in structural stability due to their inherent heterogeneity. Here, we introduce a new composite structure of glass-fiber-based metal-organic gel as a solid-state electrolyte and explore its electrochemical properties in lithium-metal batteries. We use a straightforward in-situ sol-gel method to synthesize this composite electrolyte, where glass fiber acts as matrices, ferric nitrate reacts with trimeric acid to form interconnected channels with abundant unsaturated metal sites, while ionic liquid electrolyte is in-situ confined into interconnected channels. The as-prepared composite electrolyte membrane has a uniform structure and composition, exhibiting a high room-temperature ionic conductivity of 1.79×10−3 S cm−1 and a high electrochemical oxidation potential of 4.76 V vs Li/Li+. This composite has excellent cycling performance in LiFePO4//Li (99.5% after 100 cycles) and NCM811//Li (86.6% after 200 cycles) batteries.

Improvement of ionic conductivity of solid polymer electrolyte based on Cu−Al bimetallic metal-organic framework fabricated through molecular grafting

A composite solid electrolyte comprising a Cu−Al bimetallic metal-organic framework (CAB), lithium salt (LiTFSI) and polyethylene oxide (PEO) was fabricated through molecular grafting to enhance the ionic conductivity of the PEO-based electrolytes. Experimental and molecular dynamics simulation results indicated that the electrolyte with 10 wt.% CAB (PL-CAB-10%) exhibits high ionic conductivity (8.42×10−4 S/cm at 60 °C), high Li+ transference number (0.46), wide electrochemical window (4.91 V), good thermal stability, and outstanding mechanical properties. Furthermore, PL-CAB-10% exhibits excellent cycle stability in both Li−Li symmetric battery and Li/PL-CAB- 10%/LiFePO4 asymmetric battery setups. These enhanced performances are primarily attributable to the introduction of the versatile CAB. The abundant metal sites in CAB can react with TFSI− and PEO through Lewis acid–base interactions, promoting LiTFSI dissociation and improving ionic conductivity. Additionally, regular pores in CAB provide uniformly distributed sites for cation plating during cycling.

Precise fine-tuning of the defect degree in FeNi-TDC nanoarrays via fluorinated acetic acid for rapid urea-assisted hydrogen production in seawater

Precisely regulating the defect degree in metal-organic framework (MOF) crystals and exploring the structure-activity relationship is of great significance for urea-assisted seawater electrolysis to produce green hydrogen. Herein, a series of X-FeNi-TDC nanoarrays with various defects are successfully constructed through the competitive coordination of ligand 2,5-thiophenedicarboxylic acid (H2TDC) and fluorinated acetic acid modulators with different pKa and coordination ability of -COO. The 20D-FeNi-TDC nanosheets containing more unsaturated sites and moderate electron delocalization exhibit multifunctional activity with an overpotential of 194 mV in OER, 116 mV in HER and an applied voltage of 1.326 V in UOR at 10 mA cm-2. In addition, small angle X-ray scattering (SAXS), small angle neutron scattering (SANS), X-ray absorption near-edge structure (XANES) and density functional theory (DFT) calculation further elucidate alterations in pore structure and electronic arrangement of metal sites. This study provides insight into the mechanism by which modulators regulate defects in MOF-based electrocatalyst.

Efficient hydrodeoxygenation of cresol by hierarchical porous FLRC-TiO2 nanoflower

The construction of highly efficient and selective hydrodeoxygenation (HDO) catalysts is of great significance for upgrading pyrolysis oil. In this work, nickel and iron-based NiFe(x)/FLRC-TiO2 catalysts with a flower-like radial channel structure were successfully fabricated with a facile strategy. The effects of Ni/Fe molar ratios and operation conditions on the structure, morphology and HDO performance were investigated using p-cresol as model compound. Impressively, the NiFe(x)/FLRC-TiO2 catalysts exhibit a well-defined radial channel structure with an average pore diameter of 27.4 nm and the NiFe(5)/FLRC-TiO2 with appropriate Ni/Fe ratio of 5 exhibits the best HDO performance. Under the conditions of T=275 °C, p=3 MPa, and t=2.5, the conversion rate of p-cresol and the selectivity to the target product MCH reaches 100 % and 97.8 %, respectively, which supresses most of the reported Ni based catalysts. Combining with the structure and morphology charateriazation results, this excellent HDO performance could be ascribed to: (a) the unique flower-like radial channel structure of the catalysts stemmed from FLRC-TiO2 provides more exposed active sites for HDO and fast mass transfer; (b) an appropriate Ni/Fe ratio contributes to the increase of specific surface area and pore volume of the catalyst, which boots the higher catalytic HDO activity; (c) the addition of Fe enhances acidity of catalyst and promotes the hydrodehydration of C–OH to target product MCH, together with the synergistic effect of FeNi metal sites, favoring the higher catalytic HDO activity. The proposed strategy for the preparation of radial channel structure FLRC-TiO2 support can be extended to various other reactions.

Cerium-optimized platinum-free high-entropy alloy nanoclusters for enhanced ampere-level sustainable hydrogen generation

The incorporation of rare earth (RE) elements into high-entropy alloys (HEAs) as electrocatalysts for hydrogen evolution reaction (HER) shows great potential in addressing the energy crisis. Here, we successfully synthesized cerium (Ce)-tailored PdCeMoCuRu HEA with chemical homogeneity and stability using a facile wet-chemical synthesis strategy. The obtained PdCeMoCuRu HEA provides abundant active metal sites, resulting in superior HER performance compared to state-of-the-art Pt/C. It only requires 12.8 mV to achieve a current density of 10 mA cm−2, which is nearly half that required for Pt/C (24.8 mV). Importantly, it exhibits excellent electrocatalytic durability for 100 hours even under a high current density of 1.0 A cm−2 at the ampere level. Density functional theory (DFT) calculations confirm that the introduction of Ce can modify the electronic configuration and generate synergistic effects around Pd, Cu, and Ru active sites. This work establishes a novel approach for designing efficient RE-tailored HEA electrocatalysts.

Investigating the Structure of Defects in Heterometallic Zeolitic Imidazolate Frameworks ZIF-8(Zn/Cd) and Its Interaction with CO2 Using First-Principle Calculations

Inducing defect in metal-organic frameworks (MOFs) is one of the strategies to modify the structure and properties of this functional material. Defect may occur in a pristine MOF due to missing organic linkers, metal centres and/or other structural behaviours. In this study, the structure of defects in multicomponent MOFs especially heterometallic MOFs of zeolitic imidazolate framework (ZIF-8(Zn/Cd)) was examined to unveil the possible preference defect formation due to missing 2-methylimidazolate (MeIm) and metal centres of Cd2+ and Zn2+. Assuming defect formation due to the reaction between ZIF-8(Zn/Cd) and water, MeIm linker removal is energetically lower than removing metal centres of either Cd2+ or Zn2+. But, the MeIm linker is easier to be removed when it is connected to Cd2+ (Cd-MeIm-Cd) than when it is connected to Zn2+ (Zn-MeIm-Zn). Defect in ZIF-8(Zn/Cd) affects the band gap energy to give slightly lower value than it in pristine ZIF-8(Zn/Cd). Non-covalent interaction (NCI) and interaction region indicator (IRI) analyses were also performed to indicate possible intermolecular forces such as van der Waals and attractive forces present in non-defective and defective ZIF-8(Zn/Cd). The presence of defects in mixed-metal ZIF-8(Zn/Cd) was also tested for its potential use on CO2 adsorption. The interaction energy of CO2 inside defective ZIF-8(Zn/Cd) indicates an exothermic behaviour where CO2 molecule has a preference to be adsorbed inside the framework. This is especially when the capping agents at the defective ZIF-8(Zn/Cd) sites are removed to give open metal sites. This study provides insight how defects in multicomponent MOFs might presence affecting the structural and properties changes. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Constructing binuclear sites to modulate the charge distribution of MIL-101 for enhanced toluene adsorption performance: experimental and theoretical studies

Toluene is a class of volatile organic compounds (VOCs) in the air that harm environmental quality and human health. To enhance the adsorption performance of adsorbents for toluene, based on the principle that unsaturated metal sites in MOFs can be replaced, nanoscale M@MIL-101(M represents Mg, Ca, Sr) with binuclear sites was prepared by a one-step solvothermal method. The second metal was successfully introduced into the topology of MIL-101 by partially substituting Cr sites. The results of the dynamic adsorption experiments showed that 20%Sr@MIL-101 exhibited the highest toluene adsorption capacity, which was about 60% higher than that of the undoped MIL-101. Analysis using a monolayer and multilayer model based on statistical physics theory indicated that the Sr/Cr binuclear sites could enhance the interaction strength of the adsorption system, promoting the adsorption of more layers of toluene molecules on the surface of MIL-101. Characterization and simulation together confirmed that constructing Sr/Cr binuclear sites in MIL-101 can cause significant redistribution of charge within the pores, enhancing the van der Waals interactions, π-π stacking interactions, hydrogen bonding, and Lewis acid-base interactions between the pore interior and the adsorbate molecules. Additionally, density functional theory (DFT) revealed that the adsorption sites of toluene in MIL-101 were distributed in a trigonal prism arrangement and were symmetrically aligned with a 180° rotation of the MIL-101 triangular cage.

Missing-Linker Defect Functionalized Metal-Organic Frameworks Accelerating Zinc Ion Conduction for Ultrastable All-Solid-State Zinc Metal Batteries.

Solid-state polymer electrolytes (SPEs) are promising for high-performance zinc metal batteries (ZMBs), but they encounter critical challenges of low ionic conductivity, limited Zn2+ transference number (tZn2+), and an unstable electrolyte-electrode interface. Here, we present an effective approach involving a missing-linker metallic organic framework (MOF)-catalyzed poly(ethylene glycol) diacrylate (PEGDA)/polyacrylamide (PAM) copolymer SPE for single Zn2+ conduction and seamless electrolyte-electrode contact. The single-Zn2+ conduction is facilitated by the anchoring of the OTF- anions onto the unsaturated metal sites of missing-linker MOF, while the PEGDA and PAM chains in competitive coordination with Zn2+ ions promote rapid Zn ion transport. Our all-solid-state electrolyte simultaneously achieves a superior ionic conductivity of 1.52 mS cm-1 and a high tZn2+ of 0.83 at room temperature, alongside uniform Zn metal deposition (1000 cycles in symmetric cells) and high Zn plating/striping efficiencies (>99% after 600 cycles in asymmetric cells). Applications of our SPE in Zn//VO2 full cells are further demonstrated with a long lifespan of 2000 cycles and an extremely low-capacity degradation rate of 0.012% per cycle. This work provides an effective strategy for using a missing-linker MOF to catalyze competitively coordinating copolymers for accelerating Zn2+ ion conduction, assisting the future design of all-solid-state ZMBs.

In situ anchoring of bimetal (Cu, Fe) sulfides featured by sulfur vacancy and phosphorus doping within porous carbon nanocubes derived from Prussian blue analogs to activate peroxymonosulfate for the efficient degradation of organic pollutants

In this work, Prussian blue analogues (CuFe-PBA) derived copper-iron sulfides/N-doped porous carbon composite (CuFe-NC-SP-x) was prepared as an effective peroxymonosulfate (PMS) activator to degrade sulfadiazine (SDZ). A strategy that kills two birds with one stone was proposed to construct CuFe-NC-SP-x, i.e., S-etched CuFe-PBA (CuFe-PBA-S) was annealed with NaH2PO2 in N2 atmosphere to simultaneously introduce sulfur vacancy (Sv) and phosphorus doping. 40 μM SDZ was completely removed by CuFe-NC-SP-2/PMS in 20 min (0.2 g/L catalyst and 0.5 mM PMS). The kobs value obtained by CuFe-NC-SP-2 (0.48 min−1) was nearly 33 and 17 times higher than that of CuFe-PBA (0.014 min−1) and CuFe-PBA-S (0.028 min−1), respectively. Quenching tests, electron paramagnetic resonance (EPR) analysis indicated that PMS activation in the system involved radical pathway (26.1 % OH and 22.7 % SO4–) and non-radical pathway (17.8 % 1O2 and 33.4 % electron transfer process). OH, SO4– and 1O2 were mainly produced by S enhanced metal sites for PMS activation. The synergistic effect of Sv and P doping enabled the powerful electron transfer mechanism. Electrochemical tests and DFT calculations demonstrated that Sv existing in CuFe-NC-SP-x improved the electron donor ability and increased the adsorption energy toward PMS, and phosphorus doping accelerated the electron transport from SDZ to PMS. This work not only provides a novel strategy to synthesize a high effective PMS activator by introducing Sv and phosphorous doing in one step, but also manages to comprehensively understand the electron transfer activation mechanisms of PMS facilitated by Sv and phosphorous doping.

In-situ synthesis to promote surface reconstruction of metal–organic frameworks for high-performance water/seawater oxidation

Metal-organic frameworks (MOFs) have gained tremendous notice for the application in alkaline water/seawater oxidation due to their tunable structures and abundant accessible metal sites. However, exploring cost-effective oxygen evolution reaction (OER) electrocatalysts with high catalytic activity and excellent stability remains a great challenge. In this work, a promising strategy is proposed to regulate the crystalline structures and electronic properties of NiFe-metal-organic frameworks (NiFe-MOFs) by altering the organic ligands. As a representative sample, NiFe-BDC (BDC: C8H6O4) synthesized on nickel foam (NF) shows extraordinary OER activity in alkaline condition, delivering ultralow overpotentials of 204, 234 and 273 mV at 10, 100, and 300 mA cm−2, respectively, with a small Tafel slope of 21.6 mV dec−1. Only a slight decrease is observed when operating in alkaline seawater. The potential attenuation is barely identified at 200 mA cm−2 over 200 h continuous test, indicating the remarkable stability and corrosion resistance. In-situ measurements indicate that initial Ni2+/Fe2+ goes through oxidation process into Ni3+/Fe3+ during OER, and eventually presents in the form of NiFeOOH/NiFe-BDC heterojunction. The unique self-reconstructed surface is responsible for the low reaction barrier and fast reaction kinetics. This work provides an effective strategy to develop efficient MOF-based electrocatalysts and an insightful view on the dynamic structural evolution during OER.

Local Coordination Environment of Lanthanides Adsorbed onto Cr- and Zr-based Metal-Organic Frameworks.

Separating individual lanthanide (Ln) elements in aqueous mixtures is challenging. Ion-selective capture by porous materials, such as metal-organic frameworks (MOFs), is a promising approach. To design ion-selective MOFs, molecular details of the Ln adsorption complexes within the MOFs must be understood. We determine the local coordination environment of lanthanides Nd(III), Gd(III), and Lu(III) adsorbed onto Cr(III)-based terephthalate MOF (Cr-MIL-101) and Zr(IV)-based Universitet in Oslo MOFs (UiO-66 and UiO-68) and their derivatives. In the Cr(III)- and Zr(IV)-based MOFs, Ln adsorb as inner-sphere complexes at the metal oxo clusters, regardless of whether the organic linkers are decorated with amino groups. Missing linkers result in favorable Ln binding sites at oxo clusters; however, Ln can coordinate to metal sites even with linkers in place. MOF functionalization with phosphonate groups led to Ln chemisorption onto these groups, which out-compete metal cluster sites. Ln form monodentate and bidentate and mononuclear and binuclear surface complexes. We conclude that MOFs for ion-selective Ln capture can be designed by a combination of (1) maximizing metal-lanthanide interactions via shared O atoms at the metal oxo cluster sites, where mixed oxo clusters can lead to ion-selective Ln adsorption, and (2) functionalizing MOFs with Ln-selective groups capable of out-completing the metal oxo cluster sites.

Structure and physical properties of a new telluride Mg1.2(1)In1.2(1)Si2Te6

A new Mg-containing disordered quaternary telluride Mg1.2(1)In1.2(1)Si2Te6 is prepared at 1223 K by direct fusion of elements. This mixed metal telluride adopts a trigonal (P3‾1m space group) structure having refined cell constants of a = b = 7.0603(3) Å and c = 7.1681(4) Å. Four unique crystallographic sites are filled in the structure: one disordered metal site (In1/Mg1), one partially filled Mg2, one Si1, and one Te1. Each metal ion (In and Mg) in the structure sits at the center of a distorted octahedron of Te1 atoms. Two Si atoms are involved in forming an ethane-like Si2Te6 unit with the help of a Si−Si bond. The local coordination environment around each Si atom can be described as a distorted tetrahedron comprising one Si1 and three Te1 atoms. A polycrystalline sample with the loaded composition of Mg1.2In1.2Si2Te6 shows an optical bandgap of 1.02(2) eV. The p-type semiconducting nature of the Mg1.2In1.2Si2Te6 sample was established from the positive values of the Seebeck coefficient (S) and resistivity studies. The complex structure of the Mg1.2In1.2Si2Te6 phase, which features heavy elements (In and Te), helps to achieve ultralow total thermal conductivity (ktot) of 0.33 W/mK at 773 K.

Hollow microspheres of layered double hydroxides through surfactant-free method enhanced heavy metals removal from soil

A three-dimensional MgAl layered double hydroxides hollow microsphere (HMS-LDH) is fabricated by surfactant-free method. The microstructure and the formation mechanism of HMS-LDH are investigated by XRD (X-ray diffraction), SEM (Scanning Electron Microscope), EDS (Energy dispersive Spectrometer) and XPS (X-ray photoelectron spectrometer). The morphology of LDHs could be varied by changing the ratio of metal cations to urea. The adsorption properties of HMS-LDH for heavy metals from soil are investigated. The results of experiments demonstrates that the adsorption kinetics of Cu(Ⅱ), Pb(Ⅱ), As(Ⅴ), Cr(Ⅵ) are in good agreement with the pseudo-second-order kinetic and intraparticle diffusion model. The adsorption isotherm data of Cu(Ⅱ)/Pb(Ⅱ) is accordance with the Langmuir-Freundlich model, while the equilibrium adsorption of As(Ⅴ)/Cr(Ⅵ) follow the Generalized-Langmuir isotherm model well. Site energy distribution theory denotes the hollow microsphere structure increases the adsorption sites of heavy metals, which is conducive to the adsorption process. The different mechanisms of precipitation for Cu(Ⅱ)/Pb(Ⅱ) removal and interlayer adsorption for As(Ⅴ)/Cr(Ⅵ) removal are proposed. The effects of coexisting cations and column leaching experiments on the performance evaluation are also investigated, which indicate most the ions have no effect on the adsorption of Cu (Ⅱ)/Pb(Ⅱ) and As(Ⅴ)/Cr(Ⅵ). This work proposes a simple approach to prepare LDHs hollow microspheres and demonstrates their excellent properties for the remediation of heavy metal polluted soil.

Chelated Metal-Organic Frameworks for Improved the Performance of High-Nickel Cathodes in Lithium-Ion Batteries.

Lithium-ion batteries have gained widespread use in various applications, including portable devices, electric vehicles, and energy storage systems. High Ni cathode, LiNixCoyMnzO2 (NCM, x ≥ 0.8, x + y + z = 1), have garnered significant attention owing to their high energy density. However, the limited lithium-ion transfer rate and transition metal cross-talk to anode pose obstacles to further improvement of electrochemical performance. To tackle these challenges, metal-organic frameworks (MOFs) with chelating agents are employed as additive materials for electrode. MOFs with chelating agents offer three key attributes: (1) Effective mitigation of transition metal cross-talk to the anode, (2) Partial desolvation of Li+ ions through MOF pores, and (3) Immobilization of anions via metal sites in the MOF. Leveraging these advantages, the chelating MOF-modified NCM cathode demonstrates reduced charge transfer resistance, both in their pristine and cycled states. In addition, they exhibit significantly improved lithium-ion diffusion coefficients after 100 cycles. These findings underscore the potential of MOFs with chelating agents as promising additive materials for enhancing the performance of LIBs.