Original Layered Structure Research Articles

Electrochemical properties of tungsten doped LiNi0.9Co0.1O2 lithium-ion battery cathode materials

High-nickel layered cathode materials for lithium-ion batteries have received widespread attention in new energy vehicles for their excellent specific energy and cost advantages, and are considered to be the most promising cathode materials for high-energy density lithium-ion batteries. Despite its many advantages, poor thermal stability and rapid capacity degradation have greatly limited its large-scale application. Ion doping is considered to be an effective way to improve its drawbacks, and in this paper, a series of W-doped LiNi0.9Co0.1O2 cathode materials were prepared using WO3 as a tungsten source. Among them, 1 mol% W doping was the most effective, and its reversible capacity of 204.44 mA g −1 still had 93.25 % capacity retention after 100 this cycles at 1C. Combined with DFT calculations, it is found that the introduction of W does not change the original layered structure and the material transitions from semi-metallic to metallic at lower doping concentrations, resulting in more electrons occupying the Fermi energy levels to enhance its electrical conductivity and leading to an elevated spin state and a lower oxidation state of Ni.

Sustainable Electrochemical Recycling of Spent Lithium-Ion Batteries: Selective Extraction of Lithium and Direct Regeneration of De-Lithiated Material

The recycling of spent lithium-ion batteries has become an urgent imperative. In recent years, the rising demand for lithium has sparked interest in the selective extraction of lithium from spent LIBs cathode materials. This process is of interest as it can streamline processes, improve lithium recovery efficiency, and reduce processing costs. Electrochemical methods for selectively extracting lithium from spent cathode materials have gained significant attention among various selective extraction methods due to their advantages, such as low energy consumption and environmental friendliness. Despite substantial progress in improving the efficiency of lithium recovery through electrochemical methods, the economic returns from lithium salt products, to some extent, are still insufficient to offset the processing costs of the entire process, thereby limiting the further development of this technology. Therefore, it is necessary to develop reasonable strategies for the utilization of such de-lithiated materials to further enhance product yields. One promising strategy among these approaches is direct regeneration of fresh cathode materials from the de-lithiated material. However, due to a lack of clear understanding of the structural evolution of transition metal oxides during the lithium extraction process, and the lithiation mechanisms of lithium-depleted materials, there is currently no research report on the direct regeneration of such de-lithiated materials into battery materials.Herein, an electrochemical method using LiCl aqueous as electrolyte is developed to realize the selective extraction of lithium from spent polycrystal LiNi0.55Co0.15Mn0.3O2 (NCM) cathode materials, with a maximum de-lithiation rate approaching 90%. Thorough characterizations were conducted to monitor the morphological, structural, and compositional evolution of NCM during the electrochemical de-lithiation process. These findings contribute to a profound understanding of the characteristics of the de-lithiated material and inform the rational design of regeneration pathways tailored to such materials. The results reveal that the deep de-lithiation of NCM in lithium-aqueous electrolyte triggers water-molecule intercalation, leading to an unusual phase transformation beyond H1→H2→H3. This phase transformation causes substantial lattice expansion along c-axis and introduces severe lattice distortion in de-lithiated material. The over-expanded lattice and the presence of bulk defects resulted in an unstable structure, posing huge challenge for the subsequent direct regeneration of de-lithiated material using conventional calcination methods. To address this, we employ a hydrothermal re-lithiation process, characterized by a milder, lithium-rich and water-based environment. This process is able to create a “lithium-water-balance” structure for de-lithiated materials by promoting the lithium diffusion into the lithium-deficiency structure and facilitating the exchange between lithium ions and water molecules. This process effectively enhances structural stability of the de-lithiated material. As a result, subsequent calcination successfully converts the degraded structure back into the original lithium-conductive layer structure by further eliminating the remaining lattice defects in material and promoting the cation rearrangement. The regenerated material exhibits decent electrochemical performances, which delivers a capacity of 153.2 mAh g−1 at 1C and 132.5 mAh g− 1 at 5C. This work provides insights into the electrochemical de-lithiation method and fills a gap in the utilization of de-lithiated NCM, paving the way for the sustainable recycling of spent LIBs.

γ-Radiation-induced in-situ formation of TiC/MXene nanocomposites for superior electromagnetic wave absorption

The layered structure of two-dimensional transition metal carbides/nitrides (MXenes) is potentially conducive to efficient electromagnetic wave absorption (EWA). However, Ti3C2Tx MXene typically encounters challenges with a narrow effective absorption bandwidth (EAB) due to impedance mismatch caused by its inherent high conductivity. This study employed γ-radiation to induce the in-situ formation of TiC/MXene nanocomposites for EWA. The radiation preparation process is carried out under reducing conditions at ambient temperature and pressure, effectively minimizing the risk of MXene oxidation while preserving its original layered structure. The resultant intercalated structure, featuring in-situ formed TiC nanoparticles embedded within the Ti3C2Tx MXene layers, facilitates the integration of layered conductive networks with abundant spatial gaps and multiple heterojunction interfaces. Leveraging these structural and chemical advantages, the composite demonstrates enhanced EWA capabilities. At a 50 wt% irradiated MXene loading, the material achieves an EAB of 6.08 GHz at 1.55 mm thickness and a minimum reflection loss (RLmin) of −51.1 dB at 3.95 mm. Compared to conventional composite fabrication methods, γ-radiation offers a more environmentally sustainable, efficient, and scalable approach. This research opens up a new avenue for exploiting the MXene family in EWA applications.

Scalable direct recycling of spent LiNi1/3Co1/3Mn1/3O2 via in-situ elements replenishment and structural restoration

The proliferation of vehicles and portable devices has led to a significant increase in the number of spent lithium-ion batteries (LIBs). Recycling these spent LIBs is crucial to prevent negative environmental impacts and resource wastage. However, traditional pyrometallurgical and hydrometallurgical methods suffer from inherent drawbacks as being time-consuming, energy-intensive and causing secondary pollution. Herein, an innovative approach is proposed to direct regenerate degraded LiNi1/3Co1/3Mn1/3O2 (NCM111) in-situ by combining hydrothermal treatment with solid-state sintering. Structural and morphology characterizations reveal that the amorphous layer near the surface of degraded NCM111 (D-NCM111) are dissolved after the hydrothermal treatment, restoring the original layered structure due to the relithiation reaction, whereas the target stoichiometric ratios of transition metal elements are achieved through the solid-state sintering process. The regenerated NCM111 (R-NCM111) exhibits a high discharge specific capacity of 152.3 mAh/g at 0.1 C and a capacity retention of 96.1% at 1 C after 300 cycles. The recycling method presented in this work is not only facile but also scalable, potentially opening a new pathway to address the environmental challenges posed by massive spent LIBs.

Development, Analytical Characterization, and Bioactivity Evaluation of Boswellia serrata Extract-Layered Double Hydroxide Hybrid Composites.

Boswellia serrata Roxb. extract (BSE), rich in boswellic acids, is well known as a potent anti-inflammatory natural drug. However, due to its limited aqueous solubility, BSE inclusion into an appropriate carrier, capable of improving its release in the biological target, would be highly desirable. Starting with this requirement, new hybrid composites based on the inclusion of BSE in a lamellar solid layered double hydroxide (LDH), i.e., magnesium aluminum carbonate, were developed and characterized in the present work. The adopted LDH exhibited a layered crystal structure, comprising positively charged hydroxide layers and interlayers composed of carbonate anions and water molecules; thus, it was expected to embed negatively charged boswellic acids. In the present case, a calcination process was also adopted on the LDH to increase organic acid loading, based on the replacement of the original inorganic anions. An accurate investigation was carried out by TGA, PXRD, FT-IR/ATR, XPS, SEM, and LC-MS to ascertain the nature, interaction, and quantification of the active molecules of the vegetal extract loaded in the developed hybrid materials. As a result, the significant disruption of the original layered structure was observed in the LDH subjected to calcination (LDHc), and this material was able to include a higher amount of organic acids when its composite with BSE was prepared. However, in vitro tests on the composites' bioactivity, expressed in terms of antimicrobial and anti-inflammatory activity, evidenced LDH-BSE as a better material compared to BSE and to LDHc-BSE, thus suggesting that, although the embedded organic acid amount was lower, they could be more available since they were not firmly bound to the clay. The composite was able to significantly decrease the number of viable pathogens such as Escherichia coli and Staphylococcus aureus, as well as the internalization of toxic active species into human cells imposing oxidative stress, in comparison to the BSE.

Tuning the CO2 hydrogenation path by moderately phosphating the Co-Al catalyst toward methanol synthesis

Regulating diversified reaction paths is one of the key challenges for commercial CO2 hydrogenation. Herein, a phosphating strategy is proposed to modify the surface structure of a layered double hydroxide-derived Co-Al catalyst for CO2 hydrogenation to CH3OH. It is shown that moderate phosphating can achieve a uniform incorporation of P without damaging the original layered morphology and crystal structure. Experiments and density functional theory calculations demonstrate that a significant electron transfer occurs in the surface oxygen vacancies after phosphating, which promotes the direct hydrogenation of key intermediate H3CO* to CH3OH by constraining the cleavage of the C-O bond in H3CO*. The CH3OH selectivity and space-time yield are, therefore, substantially boosted after moderate phosphating, far superior to those on conventional Cu-, In2O3- and noble metal-based catalysts. This work provides valuable insights into the manipulation of reaction paths through the design and rational modification of catalytic materials.

How to effectively and greenly prepare multi-scale structural starch nanoparticles for strengthening gelatin film (ultrasound-Fenton system)

Ultrasound (US) assisted with Fenton (US-Fenton) reaction was developed to efficiently and greenly prepare starch nanoparticles (SNPs) that were employed as nanofillers to enhance gelatin (G) film properties. Compared to Fenton reaction alone, US-Fenton reaction significantly improved preparation efficiency and dispersion of SNPs (p < 0.05). An optimal US-Fenton reaction parameter (300 mM H2O2, ascorbic acid 55 mM, US 45 min) was found to prepare SNPs with uniform sizes (50–90 nm) and low molecular weight (Mn 7.91 × 105 Da). The XRD, FT-IR, and SAXS analysis revealed that the US-Fenton reaction degraded the amorphous and crystalline zones of starch from top to down, leading to the collapse of the original layered structure starch and the progressive formation of SNPs. The different sizes of SNPs were selected to prepare the composite films. The G-SNP3 film (with 50–90 nm SNPs) showed the most outstanding UV blocking, tensile, and barrier properties. Especially, the tensile strength of G-5%SNP3 film (containing 5 % SNPs) increased by 156 % and 6 % over that of G film and G-5%SNP2 film (containing 5%SNPs with 100–180 nm), respectively. Therefore, the nanomaterial was promisingly prepared by the US-Fenton system and provided a strategy for designing and producing nanocomposite films.

Optimization of deconvoluted parameter for the quantification of high-resolution SIMS depth profiles

It is demonstrated in this paper that the searching step τ in the TV-Tikhonov algorithm plays an important role for determining the original layer structure directly from measured high-resolution depth profiling data. The optimization of τ is very necessary for obtaining a reliable deconvoluted result. Considering a large increase of simulated data points by decreasing the depth interval for quantification of high-resolution depth profiling data, the optimization of τ is performed simply by one-dimensional search algorithm. Furthermore, the noise effects from “measured” depth profiling data on the deconvoluted profile with different optimal τ values are also quantitatively evaluated. Finally, as examples, the measured SIMS depth profiling data of the two In nano-layers embedded in InGaAs thin films and the 28Si/30Si isotope nano-superlattices are deconvoluted directly and the respective original layer structures are obtained accordingly.

Interlayer Nano-Dots Induced High-Rate Supercapacitors.

The fast OH- transfer between hydroxide layers is the key to enhancing the charge storage efficiency of layered double hydroxides (LDH)-based supercapacitors (SCs). Constructing interlayer reactive sites in LDH is much expected but still a huge challenge. In this work, CdS nano-dots (NDs) are introduced to interlayers of ultra-thin NiFe-LDH (denoted CdSinter. -NiFe-LDH), promoting the interlayer ions flow for higher redox activity. The excellent performance is not only due to the enlarged layer spacing (from 0.70 to 0.81nm) but also stems from anchored interlayer reactive units and the undamaged original layered structure of LDH, which contribute to the improvement of OH- diffusion coefficient (1.6×10-8 cm2 s-1 ) and electrochemical active area (601mFcm-2 ) better than that of CdS NDs on the surface of NiFe-LDH (2.1×10-9 cm2 s-1 and 350mFcm-2 ). The champion CdSinter. -NiFe-LDH electrode displays high capacitance of 3330.0Fg-1 at 1Ag-1 and excellent retention capacitance of 90.9% at 10Ag-1 , which is better than the NiFe-LDH with CdS NDs on the surface (1966.6Fg-1 ). Moreover, the assembled asymmetric SCs (ASC)device demonstrate an outstanding energy density/power density (121.56Whkg-1 /754.5Wkg-1 ).

The in-situ construction of 2D electronic channel for C/TiO2 via Ti3C2 and its H2-production performance

The extending of electronic transmission channel is very beneficial to accelerating the electronic transmission efficiency. Herein, the two-dimensional C/TiO2 composites with an extended electron transmission space were constructed by boric acid-induced hydrothermal method with Ti3C2 as template. The electron microscope shows that the C layer in C/TiO2 retains the original layered structure of Ti3C2. Heterogeneous interface formed between the titanium dioxide particles and the C layer, which is confirmed by HRTEM and XRD. The EPR proves that massive oxygen vacancies formed on the appearance of the heterogeneous. The results of PL spectrum, EIS and I-t transient photocurrent show that the C layer acted as electron transport path to improve the transmission efficiency of electrons. The cooperative effect of the conductive layer (C layer) and the electron trap (oxygen vacancy) accelerated the migration of photo-generated electrons, boosting an enhanced photocatalytic hydrogen production performance with about 3622.7 ( ± 108.2) μmol·g−1·h−1 on the BCT sample. As a result, the designed structure showed an enhanced photocatalytic hydrogen production performance with about 3622.7 ( ± 108.2) μmol·g−1·h−1 on the BCT sample compared with 0 μmol g−1 h−1 on the Ti3C2 sample. The BCT sample displayed a stable photocatalytic performance during the experimental process. It is wish that this research can supply a valuable idea for the application of the two-dimensional substances in photocatalysis.

Intermetallic Compound TiM (M=Co, Fe) with a Layered Structure Prepared by Deoxidizing Ilmenite-type Oxides in Molten LiCl-CaH2 Mixtures.

CsCl-type intermetallic compounds TiM (M=Co, Fe) were obtained by deoxidizing trigonal ilmenite-type MTiO3 with a reducing agent CaH2 in molten LiCl at 600 °C. X-ray diffraction, nitrogen adsorption, scanning electron microscopy, and transmission electron microscopy with energy-dispersive X-ray, and X-ray photoelectron spectroscopy analyses revealed the formation of nanoscale layered structures, which enhanced specific surface areas (approximately 20 m2 /g) in the intermetallic compounds. In the initial deoxidation stage, Li2 TiO3 -like compounds were observed as an intermediate, suggesting the substitution of M in MTiO3 by Li from the molten LiCl. Compound MTiO3 has a layered structure perpendicular to the c axis of the trigonal structure, suggesting that the layered structures may originate from the crystal structure of the precursors. Formation of the Li2 TiO3 -like intermediate may help maintain the original layered structure during deoxidation and the subsequent alloying at temperatures as low as 600 °C.

Enhance and balance AVT and PCE of the semi-transparent perovskite solar cells for BIPV via grating-based photonic crystals

Semi-transparent perovskite solar cells attract significant attention in building-integrated photovoltaics, especially for solar window application. However, thinning the perovskite photoactive layer, setting up nanostructures in the perovskite layer, and improving the functional layer transparent can neither effectively balance the power conversion efficiency (PCE) and average visible transmittance (AVT), nor can it effectively resolve the issue of colorful transmitted light. Here, based on the light polarization-selective absorption characteristics of photonic crystals, a semi-transparent perovskite solar cell with the grating-based photonic crystals is presented. It can apply the original layer structure of high efficiency perovskite solar cells without any transparent replacement, including the retention of opaque electrodes. Through the developed multiphysics and multi-objective mathematical model, the semi-transparent FAPbI3 solar cells can be optimized with PCE of 10% and AVT of 60.3%. When PCE increases to 12%, 15%, and 17%, the corresponding AVTs are 52.6%, 41.1%, and 33.4%, respectively. The performance far exceeds the benchmark of PCE (10%) and AVT (25%) for solar window application. Also, the transmitted light remains white regardless of the values of AVT and PCE. Furthermore, the semi-transparent perovskite solar cells with the grating-based photonic crystals can exhibit stable high-performance when the dimension tolerance varies from 1% to 20%, which reduces the requirement of processing technology. In the end, a design and optimization guideline for the semi-transparent perovskite solar cells is proposed through the analyses on the effect of a broad incident angle. These findings provide effective design strategies for the semi-transparent perovskite solar cells in the context of building-integrated photovoltaics.

Synthesis and Crystal Structure of a New RTH-Type Precursor and Its Interlayer Expanded Zeolite.

Two dimensional zeolites have drawn a lot of attention due to their structural diversity and chemical composition, which can be used to obtain 3D zeolites, for which there is no direct synthesis. Here, a new layer silicate zeolite L was synthesized using the N, N-dimethyl-(2-methyl)-benzimidazolium as the organic structure-directing agent (OSDA) in the presence of fluoride. Structure determination by single-crystal X-ray diffraction reveals that the pure silica precursor with five-ring pores in the crystalline sheets is composed of the rth layer stacking along the (001) direction in an …AAAA… sequence with SDA+ cations and F- residing within the interlayer spaces. Variable temperature powder X-ray diffraction (PXRD) results showed that the new layer could transform into a 3D RTH topology structure at 350 °C via 2D-3D topotactic transformation. Furthermore, a new 3D zeolite material is obtained by treating the original layer with a diethoxydimethylsilane agent under hydrochloric acid condition (HCl-DEDMS). Based on the PXRD results and the original layer structure, the new 3D zeolite structure expanding the rth layer with another Si atom is constructed, which possesses a 10×8×6 channel system. It displays a high BET surface area of 188 cm3 /g with an external surface area of 130 cm3 /g. The structure and textural properties pave a way for potential catalytic applications. The research not only provides a new layered zeolite, broadening the 2D zeolite framework types, but also allows for the discovery of a new stable 3D zeolite expanding the RTH structure with Si atom, which hasn't been reported yet.

Oxygen-rich vacancies CuCoLDH with 1D/2D nanoarray structure for high performance asymmetric supercapacitor

The performance of optimization layered double hydroxide (LDH) electrodes via oxygen vacancy engineering is of great significance for high-performance hybrid supercapacitors. Herein, we obtain oxygen-rich CuCoLDH (Ov-CuCoLDH) nanoarray structure by in-situ etching of Co-MOF nanorods and subsequent NaBH4 reduction. The addition of oxygen vacancy does not affect the original unique layered structure and creates more active centers, promoting faster electron transfer and ion conversion. Moreover, this method maximizes the synergistic effect between copper and cobalt ions. The as-assembled Ov-CuCoLDH electrode shows an outstanding specific capacity of 1392.4 F g−1. Furthermore, forming the Ov-CuCoLDH and AC electrodes possesses 58.2 W h kg−1 of energy density (at a power density of 850 W kg−1). At the end of 10,000 cycles, the CF@Ov-CuCoLDH//AC device keeps 86.7 % of the original capacitance, indicating a high degree of stability. The results show that the strategy of introducing oxygen vacancy by a mild and effective method to improve the capacity of LDH has a certain guiding significance for designing higher-performance electrode materials.

Dense Platinum/Nickel Oxide Heterointerfaces with Abundant Oxygen Vacancies Enable Ampere‐Level Current Density Ultrastable Hydrogen Evolution in Alkaline

AbstractPlatinum (Pt) remains the benchmark electrocatalyst for alkaline hydrogen evolution reaction (HER), but its industry‐scale hydrogen production is severely hampered by the lack of well‐designed durable Pt‐based materials that can operate at ampere‐level current densities. Herein, based on the original oxide layer and parallel convex structure on the surface of nickel foam (NF), a 3D quasi‐parallel architecture consisting of dense Pt nanoparticles (NPs) immobilized oxygen vacancy‐rich NiOx heterojunctions (Pt/NiOx‐OV) as an alkaline HER catalyst is developed. A combined experimental and theoretical studies manifest that anchoring Pt NPs on NiOx‐OV leads to electron‐rich Pt species with altered density of states (DOS) distribution, which can efficiently optimize the d‐band center and the adsorption of reaction intermediates as well as enhance the water dissociation ability. The as‐prepared catalyst exhibits extraordinary HER performance with a low overpotential of 19.4 mV at 10 mA cm−2, a mass activity 16.3‐fold higher than that of 20% Pt/C, and a long durability of more than 100 h at 1000 mA cm−2. Furthermore, the assembled alkaline electrolyzer combined with NiFe‐layered double hydroxide requires extremely low voltage of 1.776 V to attain 1000 mA cm−2, and can operate stably for more than 400 h, which is rarely achieved.

Adsorption of nitrate from interflow by the Mg/Fe calcined layered double hydroxides.

Nitrate loss in interflow caused serious nitrate pollution of neighboring water bodies in the purple soil region of China's Sichuan Province. In this study, Mg/Fe(Al)-calcined layered double hydroxides (Mg/Fe(Al)-CLDHs) with varied Mg/Fe(Al) ratios were synthesized for nitrate removal from interflow, and 3:1 Mg/Fe CLDH exhibited the best adsorption performance. The effects of initial pH, adsorbent dosage and co-existing anions on the adsorption performance were investigated by batch experiments. The best-fitting kinetic and isothermal models for nitrate adsorption were the pseudo-second-order model and Freundlich model, respectively, indicating that the adsorption process was a physical-chemical multilayer process. The maximum adsorption capacity of nitrate was 73.36 mg/g, which was higher than that of many other commonly used adsorbents. The adsorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) techniques, and the XRD and FT-IR results revealed that the adsorption mechanism involved original layered structure reconstruction and ion-exchange interaction. Under the coexistence of SO42- and Cl-, 75.63% nitrate in interflow could be removed after 6 h of adsorption. Overall, the synthesized Mg/Fe CLDH is an effective and low-cost nitrate adsorbent for in-situ nitrate removal.

Efficient and Fast Removal of Aqueous Tungstate by an Iron-Based LDH Delaminated in L-Asparagine.

High concentrations of tungstate in aqueous systems pose a severe threat to the environment and human health. This study explored the potential of iron-based LDHs to remove tungstate from water. To improve its tungstate uptake capacity, environment-friendly L-asparagine was used to delaminate iron-based LDH synthesized via a coprecipitation method. The successful delamination was proved by AFM, revealing that the thickness of the obtained nanoparticles was approximately 1–2 times that of a single LDH layer. XRD, TEM, and XPS analyses confirmed that the delaminated LDHs were amorphous and ultrathin and had surface defects within their nanosheets that acted as active sites, leading to a very fast tungstate sorption rate and superior tungstate uptake capacity. Notably, the original layered structure of the L-asparagine-treated LDH was recovered upon its reaction with tungstate-bearing solutions, and therefore, the high availability of aqueous tungstate to the interlayer regions during the structural restoration of the delaminated iron-based LDH contributed to its excellent capability of tungstate removal as well. In addition, the tungstate uptake by the delaminated iron-based LDH was not affected substantially by the presence of coexisting anions, implying that the strong inner-sphere complexation between the tungstate and LDH layers with defects (i.e., Fe-O bonds) was the primary mechanism responsible for the tungstate removal. The delamination process described in this paper was validated to be an effective way to enhance the immobilization of tungstate by iron-based LDHs without inducing secondary pollutions, and delaminated iron-based LDHs are promising to be used extensively in the practice of treating tungstate-rich waters.

Dimensionality switching and superconductivity transition in dense 1T−HfSe2

The quest for new transition metal dichalcogenides (TMDs) with outstanding electronic properties is a particularly significant and interesting subject. The use of nonconventional methods of materials synthesis, especially pressure engineering, shows great potential for breakthrough discoveries in TMDs. Here, we employ the high-pressure techniques to successfully realize the transformation of two-dimensional semiconductor into three-dimensional superconducting states in $1T\text{\ensuremath{-}}{\mathrm{HfSe}}_{2}$. We unambiguously demonstrate that the enhancement of the interlayer coupling and the bonding between interlayer Se-Se atoms contribute to the emergence of nonlayered $C2/m$ and $I4/mmm$ phases. The discovered three-dimensional (3D) structures present excellent superconductivity compared to the original layered structure, and the superconducting critical temperature reaches a maximum of 5.8 K at around 50 GPa. Theoretical calculations reveal that the realization of superconductivity in these two 3D structures is related to the increase in the density of states at the Fermi surface $[N({\ensuremath{\varepsilon}}_{f})]$. The present results in ${\mathrm{HfSe}}_{2}$ may provide a platform for our deep understanding of the relationship among dimensionality, structure, and superconductivity phenomena in TMDs.

Single-step removal of arsenite ions from water through oxidation-coupled adsorption using Mn/Mg/Fe layered double hydroxide as catalyst and adsorbent

This study developed a layered double hydroxides (Mn/Mg/Fe-LDH) material through a simple co-precipitation method. The Mn/Mg/Fe-LDH oxidized arsenite [As(III)] ions into arsenate [As(V)] anions. The As(III) and oxidized As(V) were then adsorbed onto Mn/Mg/Fe-LDH. The adsorption process of arseniate [As(V)] oxyanions by Mn/Mg/Fe-LDH was simultaneously conducted for comparison. Characterization results indicated that (i) the best Mg/Mn/Fe molar ratio was 1/1/1, (ii) Mn/Mg/Fe-LDH structure was similar to that of hydrotalcite, (iii) Mn/Mg/Fe-LDH possessed a positively charged surface (pHIEP of 10.15) and low Brunauer–Emmett–Teller surface area (SBET = 75.2 m2/g), and (iv) Fe2+/Fe3+ and Mn2+/Mn3+/Mn4+ coexisted in Mn/Mg/Fe-LDH. The As(III) adsorption process by Mn/Mg/Fe-LDH was similar to that of As(V) under different experimental conditions (initial solutions pH, coexisting foreign anions, contact times, initial As concentrations, temperatures, and desorbing agents). The Langmuir maximum adsorption capacity of Mn/Mg/Fe-LDH to As(III) (56.1 mg/g) was higher than that of As(V) (32.2 mg/g) at pH 7.0 and 25 °C. X-ray photoelectron spectroscopy was applied to identify the oxidation states of As in laden Mn/Mg/Fe-LDH. The key removal mechanism of As(III) by Mn/Mg/Fe-LDH was oxidation-coupled adsorption, and that of As(V) was reduction-coupled adsorption. The As(V) mechanism adsorption mainly involved: (1) the inner-sphere and outer-sphere complexation with OH groups of Mn/Mg/Fe-LDH and (2) anion exchange with host anions (NO3−) in its interlayer. The primary mechanism adsorption of As(III) was the inner-sphere complexation. The redox reactions made Mn/Mg/Fe-LDH lose its original layer structure after adsorbing As(V) or As(III). The adsorption process was highly irreversible. Mn/Mg/Fe-LDH can decontaminate As from real groundwater samples from 45–92 ppb to 0.35–7.9 ppb (using 1.0 g/L). Therefore, Mn/Mg/Fe-LDH has great potential as a material for removing As.

Restoring Surface Defect Crystal of Li-Lacking LiNi0.6Co0.2Mn0.2O2 Material Particles toward More Efficient Recycling of Lithium-Ion Batteries

Lithium-ion batteries are the core components of new energy vehicles. Recycling of spent lithium-ion batteries resources is beneficial for the sustainable development of new energy vehicles. However, the current traditional recycling strategy has the disadvantages of high energy consumption and complex treatment process, which do not meet the requirements of green and energy saving. Here, we report a simpler and greener approach to regenerate spent cathode materials by preoxidation followed by a short annealing approach. The generated cathode material has a good crystal structure and lower Li/Ni mixing. Owing to the stable structure, the generated cathode material exhibits a capacity of 153.82 mA h g–1 at 1C over 2.8–4.3 V with retention reaching 94.74% after 100 cycles. β-NiOOH obtained by preoxidation is beneficial for transformation of the original layered structure in the subsequent short annealing process. The novel approach provides efficient and green ideas for efficient direct regeneration of spent cathode materials.