Three‐Dimensional MoS2 Hierarchical Nanoarchitectures Anchored into a Carbon Layer as Graphene Analogues with Improved Lithium Ion Storage Performance

Much attention has recently been focused on the synthesis and application of graphene analogues of layered nanomaterials owing to their better electrochemical performance than the bulk counterparts. We synthesized graphene analogue of 3D MoS₂ hierarchical nanoarchitectures through a facile hydrothermal route. The graphene‐like MoS₂ nanosheets are uniformly dispersed in an amorphous carbon matrix produced in situ by hydrothermal carbonization. The interlaminar distance between the MoS₂ nanosheets is about 1.38 nm, which is far larger than that of bulk MoS₂ (0.62 nm). Such a layered architecture is especially beneficial for the intercalation and deintercalation of Li⁺. When tested as a lithium‐storage anode material, the graphene‐like MoS₂ hierarchical nanoarchitectures exhibit high specific capacity, superior rate capability, and enhanced cycling performance. This material shows a high reversible capacity of 813.5 mAh g^?1 at a current density of 1000 mA g^?1 after 100 cycles and a specific capacity as high as 600 mAh g^?1 could be retained even at a current density of 4000 mA g^?1. The results further demonstrate that constructing 3D graphene‐like hierarchical nanoarchitectures can effectively improve the electrochemical performance of electrode materials.     

Few-Layer MoS2 Nanosheets Encapsulated in N-Doped Carbon Hollow Spheres as Long-Life Anode Materials for Lithium-Ion Batteries

Two-dimensional molybdenum disulfide (MoS₂) has been recognized as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity, but its rapid capacity decay owing to poor conductivity, structure pulverization, and polysulfide dissolution presents significant challenges in practical applications. Herein, triple-layered hollow spheres in which MoS₂ nanosheets are fully encapsulated between inner carbon and outer nitrogen-doped carbon (NC) were fabricated. Such an architecture provides high conductivity and efficient lithium-ion transfer. Moreover, the NC shell prevents aggregation and exfoliation of MoS₂ nanosheets and thus maintains the integrity of the nanostructure during the charge/discharge process. As anode materials for LIBs, the C@MoS₂@NC hollow spheres deliver a high reversible capacity (747 mA h g⁻¹ after 100 cycles at 100 mA g⁻¹) and excellent long-cycle performance (650 mA h g⁻¹ after 1000 cycles at 1.0 A g⁻¹), which confirm its potential for high-performance LIBs.     

Hierarchical MoS2@Carbon Microspheres as Advanced Anodes for Li‐Ion Batteries

Hierarchical hybridized nanocomposites with rationally constructed compositions and structures have been considered key for achieving superior Li‐ion battery performance owing to their enhanced properties, such as fast lithium ion diffusion, good collection and transport of electrons, and a buffer zone for relieving the large volume variations during cycling processes. Hierarchical MoS₂@carbon microspheres (HMCM) have been synthesized in a facile hydrothermal treatment. The structure analyses reveal that ultrathin MoS₂ nanoflakes (ca. 2–5 nm) are vertically supported on the surface of carbon nanospheres. The reversible capacity of the HMCM nanocomposite is maintained at 650 mA h g^?1 after 300 cycles at 1 A g^?1. Furthermore, the capacity can reach 477 mA h g^?1 even at a high current density of 4 A g^?1. The outstanding electrochemical performance of HMCM is attributed to the synergetic effect between the carbon spheres and the ultrathin MoS₂ nanoflakes. Additionally, the carbon matrix can supply conductive networks and prevent the aggregation of layered MoS₂ during the charge/discharge process; and ultrathin MoS₂ nanoflakes with enlarged surface areas, which can guarantee the flow of the electrolyte, provide more active sites and reduce the diffusion energy barrier of Li⁺ ions.     

TiO2–B Nanosheets/Anatase Nanocrystals Co‐Anchored on Nanoporous Graphene: In Situ Reduction–Hydrolysis Synthesis and Their Superior Rate Performance as an Anode Material

A unique hybrid, TiO₂–B nanosheets/anatase nanocrystals co‐anchored on nanoporous graphene sheets, can be synthesized by a facile microwave‐induced in situ reduction–hydrolysis route. The as‐formed nanohybrid has a hierarchically porous structure, involving both mesopores of approximately 4 nm and meso‐/macropores of 30–60 nm in the graphene sheets, and a large surface area. Importantly, electrodes composed of the nanohybrid exhibit superior rate capability (160 mA h g^?1 at ca. 36 C; 154 mA h g^?1 at ca. 72 C) and excellent cyclability. The synergistic effects of conductive graphene with numerous nanopores and the pseudocapacitive effect of ultrafine TiO₂–B nanosheets and anatase nanocrystals endow the hybrid a superior rate capability.     

A Microwave Synthesis of Mesoporous NiCo2O4 Nanosheets as Electrode Materials for Lithium‐Ion Batteries and Supercapacitors

A facile microwave method was employed to synthesize NiCo₂O₄ nanosheets as electrode materials for lithium‐ion batteries and supercapacitors. The structure and morphology of the materials were characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller methods. Owing to the porous nanosheet structure, the NiCo₂O₄ electrodes exhibited a high reversible capacity of 891 mA h g^?1 at a current density of 100 mA g^?1, good rate capability and stable cycling performance. When used as electrode materials for supercapacitors, NiCo₂O₄ nanosheets demonstrated a specific capacitance of 400 F g^?1 at a current density of 20 A g^?1 and superior cycling stability over 5000 cycles. The excellent electrochemical performance could be ascribed to the thin porous structure of the nanosheets, which provides a high specific surface area to increase the electrode–electrolyte contact area and facilitate rapid ion transport.     

Ultrathin MoS2 Nanosheets Supported on N‐doped Carbon Nanoboxes with Enhanced Lithium Storage and Electrocatalytic Properties

Molybdenum disulfide (MoS₂) has received considerable interest for electrochemical energy storage and conversion. In this work, we have designed and synthesized a unique hybrid hollow structure by growing ultrathin MoS₂ nanosheets on N‐doped carbon shells (denoted as C@MoS₂ nanoboxes). The N‐doped carbon shells can greatly improve the conductivity of the hybrid structure and effectively prevent the aggregation of MoS₂ nanosheets. The ultrathin MoS₂ nanosheets could provide more active sites for electrochemical reactions. When evaluated as an anode material for lithium‐ion batteries, these C@MoS₂ nanoboxes show high specific capacity of around 1000 mAh g^?1, excellent cycling stability up to 200 cycles, and superior rate performance. Moreover, they also show enhanced electrocatalytic activity for the electrochemical hydrogen evolution.     

Boron‐Doped,Carbon‐Coated SnO2/Graphene Nanosheets for Enhanced Lithium Storage

Heteroatom doping is an effective method to adjust the electrochemical behavior of carbonaceous materials. In this work, boron‐doped, carbon‐coated SnO₂/graphene hybrids (BCTGs) were fabricated by hydrothermal carbonization of sucrose in the presence of SnO₂/graphene nanosheets and phenylboronic acid or boric acid as dopant source and subsequent thermal treatment. Owing to their unique 2D core–shell architecture and B‐doped carbon shells, BCTGs have enhanced conductivity and extra active sites for lithium storage. With phenylboronic acid as B source, the resulting hybrid shows outstanding electrochemical performance as the anode in lithium‐ion batteries with a highly stable capacity of 1165 mA h g^?1 at 0.1 A g^?1 after 360 cycles and an excellent rate capability of 600 mA h g^?1 at 3.2 A g^?1, and thus outperforms most of the previously reported SnO₂‐based anode materials.     

Reduced Graphene Oxide‐Supported TiO2 Fiber Bundles with Mesostructures as Anode Materials for Lithium‐Ion Batteries

Although the synthesis of mesoporous materials is well established, the preparation of TiO₂ fiber bundles with mesostructures, highly crystalline walls, and good thermal stability on the RGO nanosheets remains a challenge. Herein, a low‐cost and environmentally friendly hydrothermal route for the synthesis of RGO nanosheet‐supported anatase TiO₂ fiber bundles with dense mesostructures is used. These mesostructured TiO₂‐RGO materials are used for investigation of Li‐ion insertion properties, which show a reversible capacity of 235 mA h g^?1 at 200 mA g^?1 and 150 mA h g^?1 at 1000 mA g^?1 after 1000 cycles. The higher specific surface area of the new mesostructures and high conductive substrate (RGO nanosheets) result in excellent lithium storage performance, high‐rate performance, and strong cycling stability of the TiO₂‐RGO composites.     

Interlayer-expanded MoS<Subscript>2</Subscript>/graphene composites as anode materials for high-performance lithium-ion batteries

A facile strategy was developed to prepare interlayer-expanded MoS₂/graphene composites through a one-step hydrothermal reaction method. MoS₂ nanosheets with several-layer thickness were observed to uniformly grow on the surface of graphene sheets. And the interlayer spacing of MoS₂ in the composites was determined to expand to 0.95 nm by ammonium ions intercalation. The MoS₂/graphene composites show excellent lithium storage performance as anode materials for Li-ion batteries. Through gathering advantages including expanded interlayers, several-layer thickness, and composited graphene, the composites exhibit reversible capacity of 1030.6 mAh g^?1 at the current density of 100 mA g^?1 and still retain a high specific capacity of 725.7 mAh g^?1 at a higher current density of 1000 mA g^?1 after 50 cycles.     

Two‐Dimensional Cobalt‐/Nickel‐Based Oxide Nanosheets for High‐Performance Sodium and Lithium Storage

Two‐dimensional (2D) nanomaterials are one of the most promising types of candidates for energy‐storage applications due to confined thicknesses and high surface areas, which would play an essential role in enhanced reaction kinetics. Herein, a universal process that can be extended for scale up is developed to synthesise ultrathin cobalt‐/nickel‐based hydroxides and oxides. The sodium and lithium storage capabilities of Co₃O₄ nanosheets are evaluated in detail. For sodium storage, the Co₃O₄ nanosheets exhibit excellent rate capability (e.g., 179 mA h g^?1 at 7.0 A g^?1 and 150 mA h g^?1 at 10.0 A g^?1) and promising cycling performance (404 mA h g^?1 after 100 cycles at 0.1 A g^?1). Meanwhile, very impressive lithium storage performance is also achieved, which is maintained at 1029 mA h g^?1 after 100 cycles at 0.2 A g^?1. NiO and NiCo₂O₄ nanosheets are also successfully prepared through the same synthetic approach, and both deliver very encouraging lithium storage performances. In addition to rechargeable batteries, 2D cobalt‐/nickel‐based hydroxides and oxides are also anticipated to have great potential applications in supercapacitors, electrocatalysis and other energy‐storage‐/‐conversion‐related fields.     

Hydrothermal exfoliated molybdenum disulfide nanosheets as anode material for lithium ion batteries

Ultrathin MoS2nanosheets were prepared in high yield using a facile and effective hydrothermal intercalation and exfoliation route. The products were characterized in detail using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The results show that the high yield of MoS2nanosheets with good quality was successfully achieved and the dimensions of the immense nanosheets reached 1 μm–2 μm. As anode material for Li-ion batteries, the as-prepared MoS2nanosheets electrodes exhibited a good initial capacity of 1190 mAh g-1and excellent cyclic stability at constant current density of 50 mA g-1. After 50 cycles, it still delivered reversibly sustained high capacities of 750 mAh g-1.     

Enhanced specific energy of silver-doped MnO2/graphene oxide electrodes as facile fabrication symmetric supercapacitor device

The present work is about the preparation of silver (Ag)-doped manganese oxide (MnO₂)/graphene oxide (GO) composite thin films are deposited by a facile and binder-free successive ionic layer adsorption and reaction (SILAR) method for the first time. The Brunauer-Emmett-Teller (BET) study revealed the nanosheets of MnO₂–Ag3/GO exhibit high specific surface area of 192 m² g^?1. The tailored flower-like morphology and interconnected nanosheets of MnO₂–Ag3/GO electrodes achieved high electrochemical performance. The maximum specific capacitance (Cs) of 877 F g^?1 at the scan rate of 5 mV s^?1 is obtained for MnO₂–Ag3/GO electrode tested in 1 M sodium sulfate (Na₂SO₄) electrolyte with capacity retention of 94.57% after 5000 cycling stability. The MnO₂–Ag3/GO composite-based flexible solid state symmetric supercapacitor (FSS-SSC) device delivered Cs as 164 F g^?1 with specific energy of 57 Wh kg^?1 at specific power of 1.6 kW kg^?1 and capacitive retention of 94% after 10,000 cycles.     

Hierarchical Nanotubes Constructed by Co9S8/MoS2 Ultrathin Nanosheets Wrapped with Reduced Graphene Oxide for Advanced Lithium Storage

Nanostructured hybrid metal sulfides have attracted intensive attention due to their fascinating properties that are unattainable by the single‐phased counterpart. Herein, we report an efficient approach to construct cobalt sulfide/molybdenum disulfide (Co₉S₈/MoS₂) wrapped with reduced graphene oxide (rGO). The unique structures constructed by ultrathin nanosheets and synergetic effects benefitting from bimetallic sulfides provide improved lithium ions reaction kinetics, and they retain good structural integrity. Interestingly, the conductive rGO can facilitate electron transfer, increase the electronic conductivity and accommodate the strain during cycling. When evaluated as anode materials for lithium‐ion batteries (LIBs), the resultant reduced graphene oxide‐coated cobalt sulfide/molybdenum disulfide (Co₉S₈/MoS₂@rGO) nanotubes deliver high specific capacities of 1140, 948, 897, 852, 820, 798 and 784 mAh g^?1 at the various discharging current densities of 0.2, 0.5, 1, 2, 3, 4 and 5 A g^?1, respectively. In addition, they can maintain an excellent cycle stability with a discharge capacity of 807 mAh g^?1 at 0.2 A g^?1 after 70 cycles, 787 mAh g^?1 at 1 A g^?1 after 180 cycles and 541 mAh g^?1 at 2 A g^?1 after 200 cycles. The proposed method may offer fundamental understanding for the rational design of other hybrid functional composites with high Li‐storage properties.     

Mesoporous Carbon Nanofibers Embedded with MoS2 Nanocrystals for Extraordinary Li‐Ion Storage

MoS₂ nanocrystals embedded in mesoporous carbon nanofibers are synthesized through an electrospinning process followed by calcination. The resultant nanofibers are 100–150 nm in diameter and constructed from MoS₂ nanocrystals with a lateral diameter of around 7 nm with specific surface areas of 135.9 m² g^?1. The MoS₂@C nanofibers are treated at 450 °C in H₂ and comparison samples annealed at 800 °C in N₂. The heat treatments are designed to achieve good crystallinity and desired mesoporous microstructure, resulting in enhanced electrochemical performance. The small amount of oxygen in the nanofibers annealed in H₂ contributes to obtaining a lower internal resistance, and thus, improving the conductivity. The results show that the nanofibers obtained at 450 °C in H₂ deliver an extraordinary capacity of 1022 mA h g^?1 and improved cyclic stability, with only 2.3 % capacity loss after 165 cycles at a current density of 100 mA g^?1, as well as an outstanding rate capability. The greatly improved kinetics and cycling stability of the mesoporous MoS₂@C nanofibers can be attributed to the crosslinked conductive carbon nanofibers, the large specific surface area, the good crystallinity of MoS₂, and the robust mesoporous microstructure. The resulting nanofiber electrodes, with short mass‐ and charge‐transport pathways, improved electrical conductivity, and large contact area exposed to electrolyte, permitting fast diffusional flux of Li ions, explains the improved kinetics of the interfacial charge‐transfer reaction and the diffusivity of the MoS₂@C mesoporous nanofibers. It is believed that the integration of MoS₂ nanocrystals and mesoporous carbon nanofibers may have a synergistic effect, giving a promising anode, and widening the applicability range into high performance and mass production in the Li‐ion battery market.     

High-performance supercapacitor electrode based on a nanocomposite of polyaniline and chemically exfoliated MoS<Subscript>2</Subscript> nanosheets

In this study, MoS₂ nanosheets were first prepared by exfoliating its bulk material in HCl/LiNO₃ solution with a yield of 45%, and then a facile strategy was developed to synthesize polyaniline/MoS₂ (PANI/MoS₂) nanocomposite via in situ polymerization. Structural and morphological characterizations of MoS₂ nanosheets and the nanocomposite were investigated by scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray powder diffraction. The results of SEM illustrated that orderly sawtooth polyaniline (PANI) nanoarrays were formed on the surface of MoS₂ nanosheets. The nanocomposite displayed good electrochemical performance as a supercapacitor electrode material. The specific capacitance reached 560 F/g at a current density of 1.0 A g^?1 in 1.0 M H₂SO₄ solution. Such good performance is because that the MoS₂ nanosheets provided a highly electrolytic accessible surface area for redox-active PANI and a direct path for electrons.     

Sucrose assisted hydrothermal synthesis of SnO2/graphene nanocomposites with improved lithium storage properties

SnO₂/graphene nanocomposites are synthesized by a new hydrothermal treatment strategy under the assistance of sucrose. From the images of the scanning electron microscope (SEM) and transmission electron microscope (TEM), it can be observed that SnO₂ nanoparticles with the size of 4~5 nm uniformly distribute on the graphene nanosheets. The result demonstrates that sucrose can effectively prevent graphene nanosheets from restacking during hydrothermal treatment and subsequently treatment. The charging/discharging test result indicates that the SnO₂/graphene nanocomposites exhibit high specific capacity and excellent cycleability. The first reversible specific capacity is 729 mAh.g^?1 at the current density of 50 mA.g^?1, and remains 646 mAh.g^?1 after 30 cycles at the current density of 100 mA.g^?1, 30 cycles at the current density of 200 mA.g^?1, 30 cycles at the current density of 400 mA.g^?1, 30 cycles at the current density of 800 mA.g^?1, and 30 cycles at the current density of 50 mA.g^?1.     

High‐Loading Nano‐SnO2 Encapsulated in situ in Three‐Dimensional Rigid Porous Carbon for Superior Lithium‐Ion Batteries

Tin oxide nanoparticles (SnO₂ NPs) have been encapsulated in situ in a three‐dimensional ordered space structure. Within this composite, ordered mesoporous carbon (OMC) acts as a carbon framework showing a desirable ordered mesoporous structure with an average pore size (≈6 nm) and a high surface area (470.3 m² g^?1), and the SnO₂ NPs (≈10 nm) are highly loaded (up to 80 wt %) and homogeneously distributed within the OMC matrix. As an anode material for lithium‐ion batteries, a SnO₂@OMC composite material can deliver an initial charge capacity of 943 mAh g^?1 and retain 68.9 % of the initial capacity after 50 cycles at a current density of 50 mA g^?1, even exhibit a capacity of 503 mA h g^?1 after 100 cycles at 160 mA g^?1. In situ encapsulation of the SnO₂ NPs within an OMC framework contributes to a higher capacity and a better cycling stability and rate capability in comparison with bare OMC and OMC ex situ loaded with SnO₂ particles (SnO₂/OMC). The significantly improved electrochemical performance of the SnO₂@OMC composite can be attributed to the multifunctional OMC matrix, which can facilitate electrolyte infiltration, accelerate charge transfer, and lithium‐ion diffusion, and act as a favorable buffer to release reaction strains for lithiation/delithiation of the SnO₂ NPs.     

Facile synthesis of Fe3O4/MoS2 nanohybrid for solid phase extraction of Ag(I) and Pb(II): kinetic,isotherm and thermodynamic studies

Recently, MoS₂ with abundant electron density in its structure attracted more attention as an adsorbent for environmental remediation. However, hard manipulation of target solution owing to high dispersibility in aqueous media restricts its application as adsorbent. Preparation of Fe₃O₄/MoS₂ nanohybrid can solve this problem. Also, this nanohybrid improves adsorption capacities of target ions. In this work, Fe₃O₄ nanoparticles, MoS₂ nanosheets and hybrid of these two were synthesised and then characterised by X-ray diffraction, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, Fourier transforms infrared spectra, Brunauer–Emmett–Teller surface area and vibrating sample magnetometer. Subsequently, adsorption of Ag(I) and Pb(II) ions from aqueous solution by these three adsorbents was examined in detail and compared with each other while the adsorption conditions including the pH value, contact time, dosage of sorbent, elution conditions and interfering ions have been optimised. According to obtained results, prepared nanohybrid showed enhanced adsorption capacities for both ions relative to naked Fe₃O₄ and MoS₂. The limits of detection for Ag(I) and Pb(II) were calculated as 0.49 µg L^?1 and 2.7 µg L^?1, respectively, and the relative standard deviation percentages (n = 5) for Ag(I) and Pb(II) were 2.8%, and 3.0%, respectively. Furthermore, the preconcentration factors were 300 and 75 for Ag(I) and Pb(II) ions, respectively. Moreover, kinetic studies showed that pseudo-second-order model can better describe target analytes adsorption properties by every three adsorbents. Regeneration of the adsorbents was performed with HCl/thiourea mixture.     

A Hybrid Assembly of MXene with NH2−Si Nanoparticles Boosting Lithium Storage Performance

A facile hybrid assembly between Ti₃C₂T_x MXene nanosheets and (3‐aminopropyl) triethoxylsilane‐modified Si nanoparticles (NH₂?Si NPs) was developed to construct multilayer stacking of Ti₃C₂T_x nanosheets with NH₂?Si NPs assembling together (NH₂?Si/Ti₃C₂T_x). NH₂?Si/Ti₃C₂T_x exhibits a significantly enhanced lithium storage performance compared to pristine Si, which is attributed to the robust crosslinking architecture and considerably improved electrical conductivity as well as shorter Li⁺ diffusion pathways. The optimized NH₂?Si/Ti₃C₂T_x anode with Ti₃C₂T_x: NH₂?Si mass ratio of 4 : 1 displays an enhanced capacity (864 mAh g^?1 at 0.1 C) with robust capacity retention, which is significantly higher than those of NH₂?Si NPs and Ti₃C₂T_x anodes. Furthermore, this work demonstrates the important effect of the MXene‐based electrode architecture on the electrochemical performance and can guide future work on designing high‐performance Si/MXene hybrids for energy storage applications.     

Compositing Amorphous TiO2 with N‐Doped Carbon as High‐Rate Anode Materials for Lithium‐Ion Batteries

Compositing amorphous TiO₂ with nitrogen‐doped carbon through Ti? N bonding to form an amorphous TiO₂/N‐doped carbon hybrid (denoted a‐TiO₂/C? N) has been achieved by a two‐step hydrothermal–calcining method with hydrazine hydrate as an inhibitor and nitrogen source. The resultant a‐TiO₂/C? N hybrid has a surface area as high as 108 m² g^?1 and, when used as an anode material, exhibits a capacity as high as 290.0 mA h g^?1 at a current rate of 1 C and a reversible capacity over 156 mA h g^?1 at a current rate of 10 C after 100 cycles; these results are better than those found in most reports on crystalline TiO₂. This superior electrochemical performance could be ascribed to a combined effect of several factors, including the amorphous nature, porous structure, high surface area, and N‐doped carbon.