Ultrathin MoS2 Nanosheets Research Articles

TEMPO-Oxidized Nanofibrillated Cellulose Assisted Exfoliation of MoS2 /Graphene Composites for Flexible Paper-Anodes.

TEMPO-oxidized nanofibrillated cellulose (ONFC) with charged carboxyl groups is introduced for the efficient exfoliation of two-dimensional (2D) MoS2 /graphene composites. As an effective dispersant agent, ONFC can be easily absorbed between the adjacent layers, so as to prevent the accumulation of the exfoliated nanosheets. With the assistance of charged ONFC, the exfoliated MoS2 /graphene is gradually increased in the aqueous dispersions with the elongated sonication time. After dewatering, self-standing MoS2 /Graphene/ONFC/CNTs composite films are rationally constructed using ONFC as flexible fibrous skeleton, and CNTs/graphene as 1D/2D interpenetrating electrical networks. Ultrathin MoS2 nanosheets anchored on the 1D/2D heterogeneous networks is directly acted as an ideal paper-anode for lithium-ion batteries (LIBs) without using traditional metallic current collector. The self-standing flexible electrode materials based on natural cellulose will promote the future green electronics with high flexibility, miniaturization, and increased portability.

Covalent-anion-driven self-assembled cadmium/ molybdenum sulfide hybrids for efficient nitenpyram degradation

Photocatalytic technology is an attractive and promising approach for nitenpyram degradation; however, how to ensure the carrier separation efficiency and catalytic sites exposure is still great challenges. In this study, we construct CdS@MoS2 (CM) nanohybrids with a 3D hierarchical configuration to enhance the separation and transfer efficiency of the photo-induced electron by a covalent-anion-driven self-assembly method. The vertical orientation of MoS2 ultrathin nanosheets not only provides a large specific surface area for the oxidation and reduction reactions but also enables the active edge sites of MoS2 to be maximally exposed. As a result, this structure drastically facilitates the exposure of the catalytic active region and the performance of the carrier transfer and injection into photocatalytic degradation for nitenpyram (NTP). The optimal CdS–MoS2 has an impressive and stable NTP removal efficiency with a high reaction rate constant up to 0.078 min−1, which is 3.25 times higher than that of pure cadmium sulfide. The photocatalytic degradation mechanism and degradation pathway of NTP were presented by synthesizing the results of experimental analysis and density flooding theory (DFT) calculations. In further, for the first time, the cytotoxicity and genotoxicity of NTP on moving bed biofilm reactors (MBBRs) was disclosed and a continuous photocatalytic wastewater pretreatment device based on the CM is proposed for the stable biological nitrogen removal activity of MBBRs, which can degrade more than 80% NTP per hour.

Ionic Liquid Crystals Confining Ultrathin MoS2 Nanosheets: A High-Concentration and Stable Aqueous Dispersion

To realize the application potential of molybdenum disulfide (MoS2) in aqueous environments, scalable and efficient methods for the preparation of high-concentration and stable dispersions need to be developed. In this paper, ultrathin MoS2 successfully was synthesized using an in situ-exfoliated bulk MoS2 method in water using ionic liquid crystals (ILCs) as green exfoliating/dispersing agents. The ILCs containing hydrophobic cations and hydrophilic anions not only help to exfoliate bulk MoS2 into ultrathin MoS2 nanosheets but also prevent the re-agglomeration of the ultrathin MoS2 nanosheets in water. MoS2 nanosheets were confined by the ILCs through π–π and C–H···π interactions, preventing direct contact of MoS2 with water. The ILC–MoS2 dispersion exhibited remarkable dispersion stability exceeding 8 months at room temperature. Moreover, the ILC–MoS2 dispersion has been successfully proven to be an excellent water-based lubricant, where the ILCs form a lubricant film on the friction surface through electrostatic interactions and MoS2 increases the load-bearing capacity of the lubricant film due to its high modulus, resulting in an 84.9% reduction in the coefficient of friction compared to pure water. The method is expected to provide a new idea for the preparation and application of MoS2.

Ultrathin layered Zn-doped MoS2 nanosheets deposited onto CdS nanorods for spectacular photocatalytic hydrogen evolution

The utilization of non-precious and noble-metal free catalysts for the photo conversion of water into hydrogen is of significant interest. In particular, the typical layered MoS2 has attracted interest as a low-cost alternative to platinum in the photocatalytic hydrogen evolution system. However, theoretical studies have suggested that the activity of the MoS2 co-catalyst arises only at the S sites on the edges of grains, and not on the basal planes. In this respect, the doping of a foreign metal into the MoS2 system is an interesting method for boosting the hydrogen production rate by increasing the conductivity and number of active sites. Herein, simple methods are used to decorate CdS nanorods with earth-abundant, few-layered zinc-doped MoS2 nanosheets (Zn-MoS2/CdS), and the so-obtained Zn-MoS2/CdS composite is used for the photocatalytic hydrogen evolution reaction under solar irradiation in the presence of lactic acid as a hole scavenger. Thus, the catalyst is shown to provide significant hydrogen generation activity, along with excellent and continuous photo stability for more than 60 h under optimal conditions. Moreover, the hydrogen evolution rate of the Zn-MoS2/CdS composite is up to ~75-fold greater than that of the pure CdS. The loading of Zn-MoS2 is shown to increase the synergistic effects of the photocatalyst due to the effective separation of charge carriers, extensive exposure of catalytic sites, and high dispersion of the few-layered Zn-MoS2. In addition, the stability of the optimized material is enhanced by the doping of Zn metal into the MoS2. To the best of our knowledge, the hydrogen evolution activity of the as-prepared composite is the highest ever reported for the CdS and single metal-doped MoS2-based catalysts. Hence, this type of Zn-MoS2/CdS composite is strongly believed to have great potential as a low-cost, highly-efficient, noble-metal free catalyst for the photocatalytic reduction of water.

Carbon-coated MoS2 nanosheets@CNTs-Ti3C2 MXene quaternary composite with the superior rate performance for sodium-ion batteries

The exploration of advanced MoS2-based electrode materials overcoming their inherent low conductivity and large volume changes is of importance for next-generation energy storage. In this work, we report a simple and high-efficient one-pot hydrothermal approach to prepare a unique and stable 1D/2D heterostructure. In the architecture, ultrathin carbon layer-coated MoS2 nanosheets with large expanded interlayer of 1.02 nm are vertically grown onto the Ti3C2 MXene and cross-linked carbon nanotubes (CNTs), giving rise to a highly conductive 3D network. The interlayer expanded MoS2 nanosheets can greatly facilitate the Na ions/electrons transmission. Meanwhile, the N-doped 1D/2D CNTs-Ti3C2 matrix can be used as a strong mechanical support to well relieve the large volume expansion upon cycles. As a combination result of several advantages, the developed quaternary C-MoS2/CNTs-Ti3C2 composite anode shows an excellent sodium storage performance (562 mA h g−1 at 100 mA g−1 after 200 cycles) and rate capability (475 mA h g−1 at 2000 mA g−1). The density functional theory calculations further prove that the full combination of layer-expanded MoS2 nanosheets and N-doped Ti3C2 matrix can significantly enhance the adsorption energy of Na ions, further resulting in the enhancement of sodium storage capabilities.

Ultrathin metallic phase MoS2 nanosheets decorated hollow carbon spheres for sodium and potassium ions storage

Molybdenum disulfide (MoS2) has become a very promising anode material due to its expandable interlayer spacing and high theoretical capacity. Herein, metallic phase MoS2 ultrathin nanosheets in-situ grown on chemically activated hollow carbon spheres (HCS) are synthesized. The 3D conductive structures not only improve the conductivity and shorten the ion diffusion path, but also buffer the volume expansion and avoid the agglomeration of the MoS2 nanosheets. Due to the above advantages, this composite electrode shows considerable storage characteristics. When used as the anode for SIBs, the discharge capacity is 296.2 mA h g−1 at a current density of 0.1 A g−1 after 50 cycles. When used as the anode for PIBs, the discharge capacity reaches 287.8 mA h g−1 after 50 cycles at a current density of 0.1 A g−1. The current synthesis strategy provides an alternative route to develop high performance electrodes for sodium and potassium ions storage.

Two-dimentional MoSe2/chitosan-derived nitrogen-doped carbon composite enabling stable sodium/potassium storage

The large ionic size of Na+ and K+ leads to severe volume variation and sluggish reaction kinetics, hindering the cycle stability and specific capacity of sodium/potassium-ion batteries (SIBs/PIBs). It is of great importance to develop high-performance anodes for SIBs/PIBs with superior stability, high capacity, and low cost. Herein, we elaborately designed MoSe2 encapsulated in biomass-derived nitrogen (N)-doped carbon (MoSe2/N–C) composite, where chitosan acts as an adsorbent and carbon precursor. In the composite, the ultra-thin MoSe2 nanosheets compose of (size of ca. 10 nm) nanocrystals embed on the chitosan derived N-doped carbon. The resultant MoSe2/N–C electrode exhibits admirable electrochemical performance for SIBs and PIBs. It displays a Na storage capacity of 505 mAh g−1 at 0.1 A g−1 for 100 cycles. More importantly, the composite anode also exhibits impressive long-term cycling performance, which retains 266 mAh g−1 at 1 A g−1 over 1200 cycles. When employed as an anode of PIBs, it also displays an impressive storage capacity of 240 mAh g−1 at 0.1 A g−1 after 100 cycles. This finding is expected to be of immediate benefit to researchers in using biomass to fabricate energy storage applications.

Porous MoS2 nanosheets for the fast decomposition of energetic compounds.

The energy release performance of energetic compounds like 3-nitro-1,2,4-trizole-5-one (NTO) and 5,5'-bistetrazole-1,1'-diolate (TKX-50) are indispensable in propellent formulations. However, thermal decomposition behavior is impeded by unfavorable catalysts. Presently, ultrathin porous MoS2 nanosheets (pMoS2) are considered as high-performance catalysts for NTO and TKX-50 decomposition. The pMoS2 in 5 wt% content could decrease the decomposition temperature of NTO and TKX-50 by 13.5 °C and 37.1 °C, respectively. Furthermore, the exothermic heat-release for pMoS2@NTO and pMoS2@TKX-50 were increased almost by a factor of two. The porous structure combined with large specific area of pMoS2 could mostly trigger the catalytic effect towards energetic compound decomposition. Additionally, the as-obtained MoS2 endowed advances in safety performance of NTO and TKX-50, with remarkably reduced impact and friction sensitivity. The as-proposed strategy may stimulate a different perspective towards the fast decomposition of energetic materials in propellants.

Tribological performance of ultrathin MoS2 nanosheets in formulated engine oil and possible friction mechanism at elevated temperatures

MoS2 nanoparticles have been extensively applied as lubricating additives enhancing tribological behavior of base oils over the past decades. But how MoS2 nanoparticles specially behave in formulated engine oil is still poorly understood, and even some contradictory conclusions have been obtained. Herein, ultrathin MoS2 nanosheets were synthesized through a chemical method and their friction-reducing and antiwear capabilities in formulated engine oil was investigated. In addition, the tribofilm formation, interface structure and friction mechanism were studied in terms of the surface characterization and chemical analysis. The research contributed to comprehending the lubrication mechanism of MoS2 nanoparticles within formulated engine oil.

Two-dimensional ultrathin MoS2 modified hydrogenated TiO2 nanoparticles for superior photocatalytic degradation under simulated sunlight

Photocatalysis is an effective technology for degradation of organic contaminants. Herein, we firstly synthesized hydrogenated TiO2 (HT) nanoparticles by calcining P25, and on the basis of HT, two-dimensional ultrathin MoS2/HT binary composites with different component ratios (MHT-20%, MHT-30% and MHT-35%) were controlled prepared. UV–vis diffuse reflectance spectra (DRS) showed that the HT nanoparticles exhibited stronger absorption towards visible light in the range of 550–800 nm compared to P25, and the introduction of two-dimensional ultrathin MoS2 nanosheets further enhanced the visible light absorption ability of MHT composites. Under simulated sunlight irradiation, the removal test of methylene blue (MB) in the present of various photocatalysts indicated that the catalytic performance of HT sample was better than that of P25, and MHT binary composites displayed more excellent photocatalytic performance. A maximum removal efficiency of MB reached 95% within 4 h over MHT-30% photocatalyst. Moreover, the kinetic constant of MHT-30% catalyst is 5.6, 3.6 and 2.5 times as much as that of P25, MoS2 and HT, respectively. In addition, the repeated degradation study and composition analysis of MHT-30% before and after photocatalytic reaction showed that MHT-30% photocatalyst exhibited good stability, and the removal rate of MB still reached 88% in four cycles. The improved and stable photocatalytic performance of MHT-30% can be attributed to band matching and tight interface bonding between MoS2 and HT, which accelerated the electron transfer and broaden the visible-light response range.

In-situ N-doped ultrathin MoS2 anchored on N-doped carbon nanotubes skeleton by Mo-N bonds for fast pseudocapacitive sodium storage

As one of the most promising anode materials in sodium ion batteries (SIBs), MoS2 has been severely hindered its wide application in the field of energy storage due to the low electronic conductivity and severe volume variation during charge/discharge. Herein, we propose and synthesize an innovative structure of ultrathin N-doped MoS2 nanosheets anchored on hollow N-doped carbon nanotube skeleton by Mo-N bonds (N-MoS2@NCNT). It is demonstrated that the N atoms decomposed from NH4+ ions after annealing in-situ substitute the basal S atoms in MoS2 structure to form N-doped MoS2 (N-MoS2), which improves the conductivity of the materials. Moreover, the stable Mo-N bonds between N-MoS2 and carbon skeleton keep the structural integrity of the electrode. With these merits, the N-MoS2@NCNT electrode shows high reversible capacity of 504.1 mAh g–1 with the ultrahigh capacity retention of 104.4 % after 100 cycles at 0.1 A g–1. The structural engineering of in-situ nitrogen doping combined with the tight chemical bonds between active material and carbon can significantly increase the electrochemical performance of MoS2. This strategy also provides an original idea for the next step of designing high-performance transition metal sulfide/carbon-based composites anodes for SIBs.

Triangle nanowall arrays of ultrathin MoS2 nanosheets vertically grown on Co-Fe bimetallic disulfide as highly efficient electrocatalysts for hydrogen evolution reaction

Hydrogen evolution reaction (HER) in water splitting normally requires efficient and durable electrocatalysts. Herein, we demonstrate Fe-CoS2@MoS2 triangle nanowall arrays grown on carbon cloth (CC) exhibiting superior electrocatalytic performance for HER. In this strategy, CC acts as conductive substrate to generate Co-MOF and Fe is introduced through ligand exchange of [Fe(CN)6]4−, and sulfidation treatment produces the Co-Fe bimetallic disulfide (noted as Fe-CoS2) nanowall arrays, on which vertically oriented MoS2 nanosheets grow via hydrothermal reaction. The as-obtained CC@Fe-CoS2@MoS2 catalyst shows an extremely low overpotential of 68 mV to deliver 10 mA cm−2 current density (η10 = 68 mV) and high stability (24 h) in acid media (0.5 M H2SO4). The vertically growing MoS2 ultrathin nanosheets expose more catalytic active sites. Meanwhile, electron transfer from Co to Mo may result in increased electron density of MoS2 thus enhancing the conductivity. The DFT calculations reveal that the hybridization of MoS2 and Fe-CoS2 dramatically reduces the Gibbs free energy of H adsorption and speeds up HER process. All the above merits contribute to the improved HER performance. This study will provide an inspiration for the design of novel electrocatalysts via interface engineering for scalable hydrogen generation.

Ultrathin MoS2 nanosheets anchored on carbon nanofibers as free-standing flexible anode with stable lithium storage performance

Lithium-ion batteries have high potential to be used as energy storage devices for wearable electronics due to their high energy density, high output voltage and environmental benignity. The increasing demand to develop wearable electronics has aroused great interests for flexible anode of lithium-ion batteries. However, the traditional rigid anode severely hiders further development of lithium-ion batteries in flexible wearable devices. Herein, we demonstrated a flower-like architecture material, in which the layered MoS2 nanosheets are anchoring on 3D porous carbon nanofibers (CNFs), serving as free-standing anode for LIBs, and this material can be wound at will. The free-standing CNFs were prepared through a facile electrospinning and carbonization process, the MoS2 nanosheets consist of few MoS2 ≤ 5 layers and were prepared through a hydrothermal process. Time-dependent experiment illustrated that the flower-like architecture was transformed from bare fibers and tiny particles. Although the polymers were stretched, shrank and covered by MoS2 nanosheets in the fabrication proess, the membrane still retained excellent flexible from beginning to end. Benefiting from the coaxial structure and synergistic effect, the flexible anode delivered an initial high discharge capacity (938.8 mAh g−1, 0.2 A g−1) and outstanding capacity retention rate at high current density (457.2 mAh g−1, 2 A g−1, 276.3 mAh g−1 after 1000 cycles). Its stability can surpass other flexible MoS2-based anodes. Furthermore, the hybrid electrode can maintain superior flexibility and mechanical stability after experiments, guaranteeing a promising future in wearable electronics. This work indicates that the flexible MoS2 @CNFs can be used as anode for flexible batteries, flexible capacitors and other wearable applications.

Enhancing Mg2+ and Mg2+/Li+ Storage by Introducing Active Defect Sites and Edge Surfaces in MoSe2

AbstractRecently, Mg‐ion batteries (MIBs) and Mg−Li hybrid ion batteries (MLIBs) are deemed as potential energy‐storage devices. However, due to the insufficient storage sites of Mg2 + in the cathode, MIBs show a low reversible capacity. For MLIBs, the property is also seriously restricted due to the main Li+ intercalation reaction and less Mg2+ intercalation reaction. Herein, ultrathin MoSe2 nanosheets with enriched atomic defects and exposed edge surfaces are prepared by the hydrothermal method and subsequent hydrogen treatment. It is found that the Mg2+ storage performance is markedly enhanced, and Mg2+/Li+ co‐intercalation can be achieved. Density functional theory (DFT) calculation shows that, by introducing a large number of atomic defects and edge exposed surfaces in the ultrathin MoSe2 nanosheets, the Mg2+ storage sites are increased, and the diffusion and migration ability of Mg2+ and Li+ are improved, resulting in a significant property improvement. Further, the Mg2+ intercalation in MIBs and Mg2+/Li+ co‐intercalation in MLIBs are confirmed. The discharge‐charge mechanisms only based on the intercalation reactions for both MIBs and MLIBs are also revealed.

A PCR-free genosensing platform for detection of Shigella dysenteriae in human plasma samples by porous and honeycomb-like biochar decorated with ultrathin flower-like MoS2 nanosheets incorporated with Au nanoparticles

Shigella dysenteriae, a gram-negative bacterium, which results in the most infectious of bacterial shigellosis and dysenteries. In this study, an innovative gene detection platform based on label-free DNA sequences was developed to detect Shigella dysenteriae in human plasma samples. The porous and honeycomb-like structure of biochar (BC) was first synthesized through a pyrolysis process. Then, the produced biochar was effectively decorated with flower-like MoS2 nanosheets (MoS2/BC). The resulting nanocomposite was incorporated with Au nanoparticles (AuNPs) by applying chronoamperometry technique, and then the subsequent product including MoS2 nanosheets, biochar and AuNPs were immobilized on the Au electrode surface and used for modifier agent in electrochemical bio-assays. Structural and morphological study of the synthesized compounds were investigated using various characterization methods such as FE-SEM, TEM, EDS, FTIR, and XRD. Various electrochemical techniques including cyclic voltammetry (CV) and Differential pulse anodic stripping voltammetry (DPASV) have been used to investigate the applicability of the fabricated genosensing bio-assay. Under optimal conditions, LOD and LOQ were calculated 9.14 fM and 0.018 pM respectively. In addition, a linear range from 0.01 to 100 pM was obtained for single stranded-target DNA (ss-tDNA), with R2 of 0.9992. The recoveries ranged from 98.0 to 101.3%. The fabricated bio-detection assay demonstrated high selectivity for 1, 2, and 3 base mismatch sequences. In addition, a negative control of the gene detection platform which was performed to study selectivity was provided by ss-tDNA from Haemophilusinfluenzae, and Salmonella typhimurium. Moreover, it is important to mention that the organized bioassay is simply reusable and reproducible with the RSD% (relative standard deviation) ˂ 5 to next detection assays.

Ultrathin MoS2 nanosheet as co-catalyst coupling on graphitic g-C3N4 in suspension system for boosting photocatalytic activity under visible-light irradiation

In this study, ultrathin molybdenum disulfide (MoS2) nanosheets with thickness of 1.6–8.8 nm were obtained by liquid-phase exfoliating bulk MoS2. Then, they were employed as cocatalyst to build ultrathin MoS2/g-C3N4 heterojunction by self-assembly method. The degradation reaction of chlorimuron-methyl herbicide and tetracycline antibiotics under visible light was used to evaluate the photocatalytic properties of ultrathin MoS2/g-C3N4. The results showed that ultrathin MoS2/g-C3N4 composite exhibit superior photocatalytic performance. The MoS2/g-C3N4 composite with 15 wt% of ultrathin MoS2 nanosheet exhibited the highest degradation efficiency with 90.4% for chlorimuron-ethyl and 91.7% for tetracycline in 45 min under simulated sunlight, which was 8.8 times and 13.4 times than that of bare g-C3N4, respectively. The outstanding photocatalytic activity of ultrathin MoS2/g-C3N4 heterojunction thanks to the unique features of ultrathin MoS2 nanosheet that it harvesting the entire visible light, increasing the contact surface area with the support and shortened the electron and ion migration length, as well as more exposed edge sulfur atoms as redox centers. The radical scavenger experiments showed that •OH and •O2- plays a key role in the photocatalytic degradation process. This study provides a new idea for the design of high-activity a co-catalyst, that is, ultrathin MoS2 nanosheet has a significant influence on the photocatalytic performance of MoS2/g-C3N4 heterostructure photocatalyst.

Vertically Aligned MoS2 Nanosheets on Nitrogen‐Doped Carbon Sheets for Enhanced Electrocatalytic Hydrogen Evolution

AbstractFabrication of two‐dimensional electrocatalysts with low cost and high efficiency is of great significance for electrochemical hydrogen evolution reaction (HER). Molybdenum disulfide (MoS2) is one of the most promising alternatives to Pt‐based HER catalysts, however its electrocatalytic performance is greatly limited by insufficient active edge sites and poor conductivity. Herein, ZIF‐8‐derived nitrogen‐doped carbon sheet (NCS) is utilized as the support, and the heterostructure of NCS@MoS2 is assembled by a facile hydrothermal reaction between MoS2 precursor and NCS. This is the first example of NCS‐supported MoS2 structures for HER application. The results show that defect‐rich MoS2 ultrathin nanosheets are uniformly and vertically aligned on NCS, and the dispersion degree of MoS2 can be well controlled by adjusting the surface modification of NCS. As expected, the optimized catalyst possesses a superior catalytic performance to pristine MoS2 evidenced by a low overpotential (250 mV) to afford 10 mA cm−2, and a small Tafel slope (74 mV dec−1) with good stability in acidic media. The intriguing HER activity is attributed to the synergistic effect of abundantly exposed active sites and high conductivity.

Ultrathin MoSe2 nanosheets decorated on carbon aerogel microspheres for high-capacity supercapacitor electrodes

A new MoSe 2 /CRF electrode was successfully constructed, which possessed enhanced specific capacitance and high cycling stability via the synergistic effect of MoSe 2 nanosheets and carbon aerogel microspheres. • MoSe 2 nanosheets and carbon aerogel microspheres hybrid via solvent-thermal method was prepared. • MoSe 2 NSs/CRF electrode exhibits an excellent specific capacitance and a high cycling stability. • Porous carbon aerogel microspheres restrict the aggregation of MoSe 2 nanosheets. • MoSe 2 NSs/CRF has potential as an electrode material in supercapacitor fields. Two-dimensional layered molybdenum selenide nanosheets have been a promising electrode material for electrochemical energy storage because of their high theoretical capacitance. However, the intrinsic low electrical conductivity and inferior structural stability impede its real application. Herein, MoSe 2 nanosheets are incorporated into carbon aerogel microspheres (MoSe 2 NSs/CRF) via a facile solvent-thermal method. The specific surface area and electric conductivity of the MoSe 2 NSs/CRF electrode were increased simultaneously because of its incorporation with porous carbon aerogel microspheres. As a result, the MoSe 2 NSs/CRF electrode exhibits an excellent specific capacitance of 498F g −1 at a current density of 1 A g −1 , which is 3 times higher than that (136F g −1 ) of the pristine MoSe 2 nanosheets. With a 5-fold increase to 5 A g −1 , it still retains 278F g -1 and high cycling stability of 127.2% of the initial retention after 2500 cycles at 100 mV s −1 . Moreover, we fabricated a symmetric supercapacitor (SC) using a composite composed of MoSe 2 NSs/CRF. The symmetric supercapacitor showed capacitance of 124F g −1 with an energy density of 8.5 W h Kg −1 at a power density of 264.8 W Kg −1 at a current density of 1 A g −1 . The superior electrochemical performances demonstrating that the MoSe 2 NSs/CRF has potential as an electrode material for energy storage application in high-performance supercapacitor fields.

Construction of N-doped C@MoS2 heteroshell with the yolk of Sn nanoparticles as high-performance anodes for sodium-ion batteries

Herein, we demonstrate the reasonable design and preparation of yolk-heteroshell Sn@N-doped C@MoS2 nanospheres as anode materials in sodium-ion battery. Through an effective multi-step strategy, Sn nanoparticles are encapsulated in N-doped C nanocage surrounded by ultra-thin MoS2 nanosheets to form Sn@N-doped C@MoS2 nanospheres. In this novel structure, Sn nanoparticles with high theoretical capacity improve the space utilization inside the heteroshell; the N-doped carbon nanocage as the skeleton not only inhibits the mutual accumulation of Sn and MoS2, but also improves conductivity; the outer MoS2 ultra-thin sheets can consolidate C@MoS2 heteroshell, provide numerous active sites and favor the fast diffusion of Na+/e-. Notably, the combination of carbon nanocage and MoS2 sheets in the yolk-heteroshell structure can effectually buffer the volume expansion of Sn nanoyolks and reinforce C@MoS2 heteroshell while reducing the carbon content. Therefore, the yolk-heteroshell structure plays a crucial role in enhanced reversible capacity and cyclic stability of Sn@N-doped C@MoS2 nanospheres, which activates their sodium storage potential. The yolk-heteroshell Sn@N-doped C@MoS2 nanospheres exhibit high reversible capacity of 488.4 mAh g−1 at 0.1 A g−1 after 300 cycles and long-cycle stability of 350.6 mAh g−1 at 0.5 A g−1 after 500 cycles. Moreover, their full cell delivers a stable reversible discharge capacity of about 80.1 mAh g−1 after 30 cycles at 0.5 C. This work provides a feasible yolk-heteroshell strategy for Sn-based composite nanomaterials.

Porous cobalt ferrite microspheres decorated two-dimensional MoS2 as an efficient and wideband microwave absorber

In this article, the CoFe2O4/MoS2 composites have been well constructed via a facial hydrothermal method, from which the porous CoFe2O4 microspheres were embedded into MoS2 ultrathin nanosheets. As a typical two-dimensional transition metal sulfide, MoS2 with high electrical conductivity and flexible properties is expected to exhibit high dielectric loss and magnetic loss when combined with magnetic material CoFe2O4. Meanwhile, the unique hierarchical structure of as-synthesized MoS2 nanoflowers is conducive to scattering and reflection of electromagnetic waves, and endows designed composites with competitive microwave absorption properties. Notably, although the saturation magnetization of MoS2/CoFe2O4 composites is significantly decreased compared to pure CoFe2O4 microspheres, the coercivity still maintains a high value of 626.1 Oe. As expected, the results demonstrate that as-fabricated MoS2/CoFe2O4 composites do have superior microwave absorption properties in comparison with CoFe2O4 and MoS2. It is found that the complex permittivity is enhanced with increasing filling ratio from 45 wt% to 60 wt%, which is helpful for obtaining a moderate permittivity value. When the filling ratio is 50 wt%, the MoS2/CoFe2O4 composites exhibit a minimum reflection loss (RLmin) of − 53.1 dB at 12.08 GHz when the thickness is 2.5 mm. An effective absorption bandwidth less than − 10 dB of 6.61 GHz from 11.28 to 17.89 GHz is achieved with a thin thickness of 2.2 mm, almost covering the whole Ku-band. The improvement in microwave absorption properties can be ascribed to the synergistic effect of the magnetic CoFe2O4 and dielectric MoS2. The impedance matching characteristic and interfacial polarization are significantly optimized by inserting CoFe2O4 spheres onto the surface of MoS2 nanosheets. Considering the excellent performance of as-fabricated MoS2/CoFe2O4 composites, it is believed that the MoS2-based composites can be applied as a promising candidate of highly effective microwave absorbers with strong absorption intensity and broad absorption frequency.