Unique Layered Structure Research Articles

Sputter Grown Hexagonal WSe2@Graphite Nanoflakes for Electrochemical Energy Storage

In the pursuit of sustainable and efficient energy storage solutions, researchers have continuously explored novel materials and technologies to enhance the performance of energy storage devices. Recently, transition metal dichalcogenide (TMDCs) such as molybdenum disulfide (MoS2), molybdenum diselenides (MoSe2), and tungsten disulfide (WS2) with a honeycomb-like structure has sparked considerable interest in utilization as electrode material for supercapacitor (SCs) applications due to their unique layered structures. Generally, the small surface area of TMDCs in their bulk form restricts their practical usage in the SCs applications. Whereas TMDC in thin 2D form exhibits high surface area and flexibility to the electrode material which allows more charge storage and results in high capacitance and energy density. In the present work, high-quality tungsten diselenide (WSe2) thin film electrodes were deposited over graphite sheets (WSe2@Graphite) using DC magnetron sputtering technique at an elevated temperature of around 200 0C under the controlled argon atmosphere. The electrochemical properties of these WSe2@Graphite electrode were investigated in three electrodes configuration using 1M Na2SO4 aqueous electrolyte by recording CV, GCD, and EIS spectra. The hexagonal WSe2@graphite nanoflakes were found to exhibit an exceptionally high areal capacitance of 88.05 mF/cm2 and energy density of 7.83 µWh/cm2 at a scan rate of 5 mV/s. Further, GCD was performed, and the WSe2@graphite electrode exhibits a high areal capacitance of 37.5 mF/cm2 at the current density of 0.5 mA/cm2. The WSe2 thin film electrode shows a high energy density of 3.3 µWh/cm2 at a power density of 199.98 µW/cm2. Additionally, the WSe2@graphite thin film electrode demonstrates high cyclic stability with retaining ~ 90.33% capacitance even after 2000 consecutive GCD cycles. The obtained hexagonal nanoflakes-like morphology provides a high surface area and porous structure that helps to improve the electrochemical performance of the WSe2 thin film. The obtained results demonstrate that the WSe2@graphite thin film exhibit excellent electrochemical performance and can be utilized as a potential material for supercapacitor electrodes. Keywords- Transition metal dichalcogenide (TMDCs), tungsten diselenide (WSe2), DC magnetron sputtering, supercapacitor, and nanoflakes Figure 1

Silicon Oxycarbide-Coated Bismuth for Enhanced Anode Stability in Lithium-Ion Batteries

The current state-of-the-art lithium-ion batteries (LIBs) with graphite as an anode foresees shortcomings to demands in energy storage and supplies with high energy and power densities for large-scale applications such as electric vehicles. Metallic Bi alloy is among the promising alternative alloy candidates to replace the graphitic anode owing to its high volumetric capacity (3765 mAh cm−3), relatively small volume expansion (~215%), and unique layered crystalline structure with large interlayer spacing along the c-axis (d 003 = 3.95 Å). Nevertheless, inevitable volume expansion during repetitive Li+-ion insertion/extraction build-ups localized mechanical strain, causing particle pulverization, cracking, and isolations, eventually leading to cell failure. Herein, to achieve decent reversibility of alloys, we introduce a polymer-derived ceramic silicon oxycarbide (SiOC) coating onto Bi nanoparticles (NPs) via facile dispersion of bismuth hydroxide in silicone oil and consecutive heat treatment. The SiOC coating layer alone is an active conversion material with a higher specific capacity but lower volumetric capacity than Bi. To promote the fabrication of high volumetric capacity Bi-based composites using higher tap density materials with a well-balanced specific capacity, the content of the metal precursor and silicone oil were varied. The sturdy SiOC matrix embedded with the Bi NPs cushions the stress cultivated upon (de)lithiation reactions, achieving stable capacity (507 mAh g−1 at 0.05 A g−1 after 150 cycles), high volumetric capacity (872 mAh cm−3), superb cyclic stability (380 mAh g−1 at 0.5 A g−1 after 500 cycles), and adequate cell integrity when tested as an anode in a half cell. In a full cell configuration coupled with a LiNi0.5Co0.2Mn0.3O2 cathode, high gravimetric and volumetric energy densities of 343 Wh kg−1 and 607 Wh L−1 can be estimated, respectively. The conducted kinetic and postmortem analyses provide additional insights into the effectiveness of amorphous SiOC as a protective layer in preventing excess solid electrolyte interface passivation and preserving the electrically conductive network for continuous transport of ions and electrons. Figure 1

Electrochemical Synthesis of Molybdenum Ditelluride (MoTe2) and Its Potential Application as Negative Electrode Material for Sodium Ion Battery

With the rapid expansion in energy demands and depletion of fossil fuel reservoirs, the importance of clean energy production and storage has increased drastically. The renewable energy recourses are cost effective, sustainable and carbon dioxide emission free alternatives. Nevertheless, this energy is not always available and needs to be stored. Lithium-ion batteries (LIBs) are rapidly used in various applications such as powering electronics, electric vehicles and grid energy storage. However, the source of lithium is extremely limited in earth crust, during mining it pollutes the environment and it is costly. Therefore, attention has been shifted towards development of sodium ion batteries (SIBs) which have wide reserves and low precursor cost and thus is considered as an appropriate choice for solar and wind energy development. The prime problem encountered in development of large-scale SIBs is the low effectiveness of appropriate anode material because of large size and sluggish kinetics of Na ions which limits the specific capacity as well as energy density.Metal tellurides have emerged as a promising material for use as negative electrode in sodium-ion batteries due to its unique layered crystal structure, high intrinsic conductivity, and high trap density. Molybdenum ditelluride has more electric conductivity than selenides and sulfides. Other metals except molybdenum in the group takes part in alloying mechanism that leads to higher volume expansion and poor cycling stability.In this study, we describe the synthesis of MoTe2 on copper and aluminium substrate by using predeposited molybdenum and electrodeposited tellurium at relatively low temperature of 450°C. Further we characterized the samples by X-Ray Diffraction, Raman Spectroscopy and Field Emission Scanning Electron Microscope for structural, elemental, and morphological properties, respectively. The synthesized material was used as negative electrode in sodium ion coin cell. The electrochemical performance of the coin cell will be correlated with the structural and electronic property of MoTe2.

Cetyl alcohol surface functionalization: a strategy for modulating electronic characteristics of boron nitride nanosheets

Hexagonal boron nitride (h-BN) is a two-dimensional material with a unique layered structure akin to Graphene. Cetyl alcohol (CH₃(CH₂)₁₅OH) denoted as CA, a fatty alcohol derived from natural sources like palm oil and coconut oil, holds a significant place in various industries due to its versatile properties. Cetyl alcohol's has a potential in forming stable nanostructures and its interactions with other compounds, shedding light on its utility in nanotechnology and materials science. In this work exfoliation of BNNS and subsequent functionalization using Cetyl alcohol is investigated. The functionalization of boron nitride nanosheets (BNNS) using CA is investigated in this study. The modification process aims to enhance the properties and applications of BNNS. OH groups are functionalized and bring about beneficial changes to its properties, enabling enhanced interactions with other compounds. This modification can lead to improved solubility, emulsification, and lubrication capabilities, expanding its utility in various applications such as cosmetics, pharmaceuticals, and industrial processes. Characterization techniques, including Thermogravimetric analysis(TG/DTA), UV-Visible spectroscopy, Photoluminescence, X- ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) are employed to analyze the efficacy of the functionalization process. Thermogravimetric-differential thermal analysis (TG-DTA) was utilized to investigate the thermal characteristics of the functionalized samples.

Structure, Properties, Preparation, and Application of Layered Titanates.

As a typical cation-exchangeable layered compound, layered titanate has a unique open layered structure. Its excellent physical and chemical properties allow its wide use in the energy, environmental protection, electronics, biology, and other fields. This paper reviews the recent progress in the research on the structure, synthesis, properties, and application of layered titanates. Various reactivities, as well as the advantages and disadvantages, of different synthetic methods are discussed. The reaction mechanism and influencing factors of the ion exchange reaction, intercalation reaction, and exfoliation reaction are analyzed. The latest research progress on layered titanates and their modified products in the fields of photocatalysis, adsorption, electrochemistry, and other applications is summarized. Finally, the future development of layered titanate and its exfoliated product two-dimensional nanosheets is proposed.

MXene-based anode materials for high performance sodium-ion batteries

As an emerging class of layered transition metal carbides/nitrides/carbon-nitrides, MXenes have been one of the most investigated anode subcategories for sodium ion batteries (SIBs), due to their unique layered structure, metal-like conductivity, large specific surface area and tunable surface groups. In particular, different MAX precursors and synthetic routes will lead to MXenes with different structural and electrochemical properties, which actually gives MXenes unlimited scope for development. In this feature article, we systematically present the recent advances in the methods and synthetic routes of MXenes, together with their impact on the properties of MXenes and also the advantages and disadvantages. Subsequently, the sodium storage mechanisms of MXenes are summarized, as well as the recent research progress and strategies to improve the sodium storage performance. Finally, the main challenges currently facing MXenes and the opportunities in improving the performance of SIBs are pointed out.

The effect of coarse and fine Ti3SiC2 particle reinforcement in aluminum matrix composites

Metal matrix composites (MMCs) reinforced by MAX phases are a promising class of advanced materials that exhibit high mechanical strength, wear resistance, and fracture toughness. Compared to MMCs reinforced with conventional ceramic particles, MAX phases do not hinder machinability or electrical and thermal conductivity of the metal matrix. This study investigated the effect of adding 3, 9 and 18 wt% coarse- and fine-sized Ti3SiC2 particles to pure Al. The Ti3SiC2/Al composites were fabricated by spark plasma sintering at a relatively low temperature of 540 °C, preventing the decomposition of the MAX phase and retaining its unique layered structure. It was found that the fine MAX particles hindered the sintering process. A high fraction of fine particles resulted in abundant porosity, weak interfaces and deteriorated mechanical properties. The microstructural analysis revealed a homogenous microstructure with the residual porosity being located mostly at grain boundaries near Ti3SiC2–Al interfaces. In addition, thin oxide layers could be observed at some of the Ti3SiC2–Al interfaces, which can aid in facilitating bonding between Al and Ti3SiC2. The composites with mostly coarse particles exhibited superior mechanical properties. The hardness increased with the addition of MAX particles and was shown to be slightly anisotropic, and the highest bending strength was achieved for the 3 wt% Ti3SiC2/Al. Nanoindentation hardness mapping analysis shed some light on the strengthening mechanism. The results of this study can serve as a basis for further research utilizing MAX-phase particle reinforcements in MMCs.

Semiconductor-to-metal transition renders intrinsic pseudocapacitance and high volumetric capacity for iron chalcogenide anode

There is a burgeoning need for high-power-density sodium-ion batteries (SIBs) with compressed size, whereas it is very challenging to integrate fast kinetics and high volumetric capacity into one material. Herein, we demonstrate an effective strategy to jointly promote the power and volumetric energy densities from the perspective of materials’ electronic conductivity. Via semiconductor-to-metal transition, we successfully develop the first intrinsic pseudocapacitive chalcogenide material, metallic FeS1-xSex(x ≥ 0.5), which shows inherent capacitor-like faradic charge storage, even when crystallizes in micrometer bulk material and operates in the absence of conducting additives. Therefore, it enables conducting-additive-free (CA-free) electrodes with high volumetric capacities of 965 mA h cm−3, which also delivers exceptional rate capability with a capacity above 392 mA h cm−3 at 50C-rate, among the best state-of-the-art SIB anodes. These superior performances can be attributed to a rare intrinsic intercalation pseudocapacitive mechanism, which is related to the nature of metallic behavior and unique layered structure. This discovery not only provides a valuable complement to our understanding of pseudocapacitive processes, but also facilitates the design of high-rate electrode materials with compressed sizes in the future.

Constructing 1D/2D NiCo‐LDH Nanowire/MXene Composites for Efficient And Stable Lithium Storage

AbstractBimetallic layered double hydroxide (LDH) delivers competitive performance in lithium‐ion battery (LIB) because of the unique layered structure. However, the electrochemical performance of LDH is hindered by the low conductivity and the huge structure change upon cycling. To face this challenge, the 1D/2D NiCo‐LDH nanowire/MXene composites (NiCo‐LDH/MXene) are dedicatedly constructed via a simple one‐step hydrothermal method. Owing to the robust conductive skeleton is enabled by MXene nanosheets and abundant electroactive sites provided by NiCo‐LDH nanowires, the NiCo‐LDH/MXene anode exhibits rapid ion diffusion, exceptional redox reaction, and superior structural stability. Consequently, it offers a high specific capacitance of 1081 mAh g−1 after 100 cycles at the current density of 100 mA g−1 and impressive rate performance, i.e., 439 mAh g−1 at the current density of 1000 mA g−1. These results will motivate the exploration of advanced electrode materials for application in energy storage devices.

Two-dimensional graphene oxide/MXene lamellar membrane cross-linked by urea with adjustable interlayer spacing for efficient dye rejection and ion sieving

Two-dimensional (2D) membranes demonstrate good performance in molecular and ion separation due to their unique layer structure. However, the sieving performance of 2D membranes is severely limited by drawbacks such as poor stability and low mass transfer rates. Here, we propose a design strategy using urea as a cross-linking agent to construct stable and regular nanochannels inside the graphene oxide/MXene (GO/MXene) composite membranes. More importantly, by changing the composition, the effective interlayer spacing of the membrane can be easily adjusted within 4.47–8.92 Å with angstrom-level precision for tunable ion sieving. The composite membrane exhibits high water permeance (79.58 L m−2 h−1 bar−1) and excellent small molecule dye rejection (>99 %). Moreover, depending on the ionic valence state, the membrane exhibits significant ion sieving. The good Cl−/SO42− selectivity (11.64) makes it a promising alternative to conventional ion exchange membranes. This study demonstrates an innovative and facile way to construct 2D lamellar membranes with stable structures for efficient and precise separation.

Highly dispersed ultrasmall BiOCl nanoclusters on graphene sheets as high-performance anion-capture electrode for hybrid capacitive deionization

BiOCl nanomaterials, because of their unique layered structure and fascinating physicochemical properties, have attracted enormous attention as anode material for capacitive deionization (CDI) towards the relief of global freshwater scarcity. However, the synthesis of ultrasmall BiOCl nanoclusters remains a considerable challenge, while the effect of crystalline surfaces on the Cl− ion intercalation/deintercalation has not yet been explored so far. In this work, highly dispersed BiOCl nanoclusters with the predominant exposure of (110) and (101) planes on graphene sheets (BiOCl@G) are fabricated by nanoconfinement and air-plasma strategy. On one hand, the ultrasmall BiOCl nanoclusters with size of ∼3 nm significantly increased their atomic utilization and electrochemical active sites, whereas the preferred crystalline planes of (110) and (101) favored the Cl− intercalation/deintercalation process within BiOCl. On the other hand, the dominant mesopores, along with a large interlayer distance (∼0.4 nm) between exfoliated graphene sheets, ensured the fast ion transport-adsorption at BiOCl/solution interface. With these novel structural features, the BiOCl@G possesses excellent figure-of-merits in terms of the Cl−-adsorption capacity (109.8 mg g−1), adsorption rate (0.110 mg g−1 s−1), energy consumption, and CDI cycling stability. These results provide new fundamental insights for developing high performance BiOCl-graphene nanocomposites used in CDI desalination and beyond.

Insight into the effect of Ti substitutions on the static oxidation behavior of (Hf,Ti)C at 2500 ​°C

Hf-based carbides are highly desirable candidate materials for oxidizing environments above 2000 ​°C. However, the static oxidation behavior at their potential service temperatures remains unclear. To fill this gap, the static oxidation behavior of (Hf, Ti)C and the effect of Ti substitutions were investigated in air at 2500 ​°C under an oxygen partial pressure of 4.2 ​kPa. After oxidation for 2000 ​s, the thickness of the oxide layer on the surface of (Hf, Ti)C bulk ceramic is reduced by 62.29 ​% compared with that on the HfC monocarbide surface. The dramatic improvement in oxidation resistance is attributed to the unique oxide layer structure consisting of various crystalline oxycarbides, HfO2, and carbon. The Ti-rich oxycarbide ((Ti, Hf)CxOy) dispersed within HfO2 formed the major structure of the oxide layer. A coherent boundary with lattice distortion existed at the HfO2/(Ti, Hf)CxOy interface along the (111) crystal plane direction, which served as an effective oxygen diffusion barrier. The Hf-rich oxycarbide ((Hf, Ti)CxOy) together with (Ti, Hf)CxOy, HfO2, and precipitated carbon constituted a dense transition layer, ensuring favorable bonding between the oxide layer and the matrix. The Ti content affects the oxidation resistance of (Hf, Ti)C by determining the oxide layer's phase distribution and integrity.

Constructing a Functionalized Electrocatalyst of a Transition Metal Chalcogenide on Accordion-Like MXene to Boost the Hydrogen Evolution Reaction.

MXenes exhibit unique layered structures and excellent electrical conductivity, and their multiple surface termination groups are favorable for hosting impressive performance for electrochemical reactions. Therefore, a two-dimensional (2D) layered MXene-based catalyst may become a novel high-efficiency electrocatalyst to replace traditional noble metal electrocatalysts. In this work, a transition metal chalcogenide (MoS2/CuS) and MXene are combined to prepare a 2D electrocatalyst (MoS2/CuS/MXene) for the hydrogen evolution reaction (HER). MXene exhibited a large specific surface area in the shape of an accordion, which was very beneficial for the growth of nanomaterials. CuS/MXene promoted electron transfer and improved the exposed active site for HER. The exposed MoS2 edges exhibited a high chemical adsorption capacity, which is conducive to HER. Electrochemical tests reveal that the MoS2/CuS/MXene electrocatalyst can reduce the charge transfer resistance toward the HER and increase active sites for HER, leading to enhancing the catalytic performance. The MoS2/CuS/MXene electrocatalyst affords an efficient HER with a low overpotential (115 mV@10 mA cm-2). This work offers a new idea to create layered transition metal chalcogenide- and MXene-based electrocatalysts for HER.

Fabrication of the hollow dodecahedral NiCoZn layered double hydroxide for high-performance flexible asymmetric supercapacitor

Layered double hydroxides (LDHs) with unique layered structure have excellent theoretical capacitance. Nevertheless, the constrained availability of electrically active sites and cationic species curtails their feasibility for practical implementation within supercapacitors. Most of the reported materials are bimetallic hydroxides, and fewer studies are on trimetallic hydroxides. In here, the hollow dodecahedron NiCoZn-LDH is synthesized using CoZn metal–organic frameworks (CoZn-MOFs) as template. Its morphology and composition are studied in detail. Concurrently, the effect of the amount of third component on the resulting structure of NiCoZn-LDH is also researched. Benefiting from its favorable structural and compositional attributes to efficient transfer of ions and electrons, NiCoZn-LDH-200 demonstrates outstanding specific capacitance of 1003.3F g−1 at 0.5 A/g. Furthermore, flexible asymmetric supercapacitor utilizing NiCoZn-LDH-200 as the positive electrode and activated carbon (AC) as the negative electrode reveals favorable electrochemical performances, including a notable specific capacitance of 184.7F g−1 at 0.5 A/g, a power density of 368.21 W kg−1 at a high energy density of 65.66 Wh kg−1, an energy density of 31.78 Wh kg−1 at a high power density of 3985.97 W kg−1, a capacitance retention of 92 % after 8000 cycles at 5 A/g, and a good capacitance retention of 90 % after 500 cycles of bending. The template method presented herein can effectively solve the problem of easy accumulation and improve the electrochemical properties of the materials, which exhibits a broad research prospect.

The core-shell structure of nitrogen-doped carbon coated Fe3O4 decorated MXene for broadband and efficient microwave absorption

In recent years, MXene has gained widespread attention in the field of microwave absorption (MA) due to its unique two-dimensional layered structure, excellent electrical conductivity, and chemically active surface. However, the MA mechanism of MXene is limited to dielectric loss alone, which poses a challenge in meeting the performance requirements of new absorbers. Therefore, to enhance the performance of MXene in MA, this paper successfully prepared Fe3O4/NC@MXene (FNCM) composites by modifying core-shell magnetic nanoparticles of nitrogen-doped carbon coated Fe3O4 (Fe3O4/NC) on MXene. By adjusting the dose of Fe3O4/PDA precursor, the impedance matching is further optimized. FNCM-2 demonstrates superior MA performance with a thickness of 2mm, achieving a minimum reflection loss (RLmin) of −54.41 dB and an effective absorption bandwidth (EAB) of 7.32 GHz. Meanwhile, the RLmin of the FNCM-1 sample at a thickness of 2 mm can reach −55.65 dB. The remarkable improvement in MA performance can be attributed to the synergistic effect of dielectric and magnetic losses, which optimizes impedance matching. This study is expected to provide insights for the development of efficient and broadband MXene-based MA materials.

Magnetic field-assisted microbial corrosion construction iron sulfides incorporated nickel-iron hydroxide towards efficient oxygen evolution

Nickel iron (hydroxyl) hydroxide with unique layered structure and controllable composition is widely regarded as typical oxygen evolution reaction (OER) catalysts. Recently, developing top-down approaches to realize the facile preparation of transition metal hydroxide catalyst has received wide attention. Based on the natural microorganism corrosion behavior, this work demonstrates the external magnetic field-assisted microbial corrosion strategy to construct advanced transition metal hydroxide OER catalyst, and the prepared biofilm electrode presents superior OER performance in the existence of magnetic field, which needs an overpotential of 287 ​mV at 100 ​mA ​cm−2. Experimental and theoretical calculations show the applied magnetic field can accelerate sulfate reducing bacteria (SRB) corrosion and chemical corrosion. The additional magnetic field can promote SRB corrosion to produce FeS, which can facilitate the optimization of O intermediate desorption from the NiOOH catalyst during OER process, reducing the reaction energy barrier for O→OOH. The synergistic effect between the nickel-iron oxyhydroxides originated from the accelerated chemical corrosion and FeS produced from the accelerated SRB corrosion interprets the improved OER activity. This work explores the influence of magnetic field on the construction of advanced OER materials, which can provide an effective magnetic field-assisted corrosion engineering strategy, and promote the development of multidisciplinary fields of physics, biology, and emerging energy conversion technologies.

Enhancing Zn2+ diffusion for dendrite-free zinc anodes via a robust zincophilic clay mineral coating

Clay minerals as artificial solid electrolyte interphase (SEI) layers have played a crucial role in protecting zinc metal anodes for aqueous Zn-ion batteries (AZIBs) due to their unique layered structure, negatively charged lamellas, ion exchange ability, and electronic insulation. However, the clay mineral layers exhibit limited ability to suppress dendrites and side reactions on the Zn anode in the water-based working environment. This limitation is attributed to the severe volumetric expansion, poor mechanical performance, and inferior zinc ion conductivity. To address these issues, montmorillonite (MMT) is intercalated with urea in this study. The resulting dense and robust UMMT coating layer enhances the diffusion of Zn2+ and increases the Zn2+ concentration at the Zn deposition surface through strong absorption of Zn2+ at −C=O and −NH2 active sites. As a result, it facilitates the uniform deposition of Zn2+ and inhibits dendrite growth. Additionally, the UMMT coating layer acts as a desolvation layer, mitigating parasitic reactions originated from active water. Consequently, the UMMT coating layer enables stable Zn plating/stripping compared to MMT layer. In symmetric cells, MMT@Zn electrode exhibits a significantly longer lifespan of over 1300 h at 6 mA cm−2 with a capacity of 3 mAh cm−2. Furthermore, it demonstrates enhanced cyclic performance of 254 mAh g−1 at 10 A g−1 after 4000 cycles in Zn//V2O5 full cells. This present work presents a strategy to intercalate small-molecule organics into clay minerals, enhancing their protective capacity and expanding their application as SEI layers in AZIBs.

Roles of MXenes in Photocatalysis

Artificial photocatalysis is beneficial to carbon neutrality, renewable resources generation, and sustainable society development. Due to the unique layered structure, abundant surface functional groups, and tunable electronic properties, MXene is emerging as a promising contender to improve the comprehensive performance of photocatalysts. Much progress has been made in the study of MXene‐based nanomaterials over the past years, and state‐of‐the‐art advances in the rational design, controllable synthesis, characterization techniques, and diverse applications of MXene‐based photocatalysts have been reviewed. However, the roles and perspectives of MXenes in photocatalysis have been less summarized. Based on the analysis of the physical/chemical properties of MXenes and the latest research progress, herein, the multiple roles of MXenes are discussed in promoting photocatalysis, including carrier for active site anchoring, light‐transmitting media, mass transfer medium, cocatalyst, and heat conductor. In addition, the current status and challenges of MXenes in photocatalysis are summarized, and the future directions as well as the bottleneck of development that need to be broken through for MXenes in photocatalysis are also proposed. This review provides a clear and in‐depth understanding of the physical/chemical properties of MXene‐based photocatalysts and their contributions to photocatalysis.

Interfacial Engineering of MoS2/V2O3@C-rGO Composites with Pseudocapacitance-Enhanced Li/Na-Ion Storage Kinetics.

Molybdenum sulfide has been widely investigated as a prospective anode material for Li+/Na+ storage because of its unique layered structure and high theoretical capacity. However, the enormous volume variation and poor conductivity limit the development of molybdenum sulfide. The rational design of a heterogeneous interface is of great importance to improve the structure stability and electrical conductivity of electrode materials. Herein, a high-temperature mixing method is implemented in the hydrothermal process to synthesize the hybrid structure of MoS2/V2O3@carbon-graphene (MoS2/V2O3@C-rGO). The MoS2/V2O3@C-rGO composites exhibit superior Li+/Na+ storage performance due to the construction of the interface between the MoS2 and V2O3 components and the introduction of carbon materials, delivering a prominent reversible capacity of 564 mAh g-1 at 1 A g-1 after 600 cycles for lithium-ion batteries and 376.3 mAh g-1 at 1 A g-1 after 450 cycles for sodium-ion batteries. Theoretical calculations confirm that the construction of the interface between the MoS2 and V2O3 components can accelerate the reaction kinetics and enhance the charge-ionic transport of molybdenum sulfide. The results illustrate that interfacial engineering may be an effective guide to obtain high-performance electrode materials for Li+/Na+ storage.

Polyaniline spaced MoS2 nanosheets with increased interlayer distances for constructing high-rate dual-ion batteries

Dual-ion batteries (DIBs) have attracted great attention due to their affordable prices, environmental friendliness, and high operating voltage. However, the conventional graphite anode in DIBs has drawbacks such as unsatisfactory capacity and worrying safety. MoS2 is considered to be a competitive anode material that exhibits large capacity due to its unique layered structure for cation insertion/extraction. Nevertheless, the sluggish reaction kinetics of MoS2 does not match the cathode side, which makes the constructed full DIBs show poor rate ability. Here, a flower-like MoS2/ polyaniline composite electrode (MoS2-PANI) where PANI was grown in situ between layers of MoS2 nanosheets was designed. In this design, the inserted PANI can broaden the layer distance of MoS2 to facilitate cation diffusion and prevent the restacking of nanosheets. Furthermore, PANI is also expected to increase the conductivity and relieve the volume changes during repeated charge/discharge cycles. Benefiting from that, the MoS2-PANI electrode delivered a reversible capacity of 561.91 mA h g–1 at 5 A g–1 in half-cell test. Moreover, when coupled with a mildly expanded graphite (MEG) cathode, the obtained MEG//MoS2-PANI DIB shows excellent rate ability with a reversible discharge capacity of 86.62 mA h g–1 and a desirable energy density of 308.83 W h kg–1 at 20 C. These results provide some inspiration for the design of high-rate DIBs.