Space-Confined Growth of Defect-Rich Molybdenum Disulfide Nanosheets Within Graphene: Application in The Removal of Smoke Particles and Toxic Volatiles

Recent Progress on Graphene-Based Nanocomposites for Electrochemical Sodium-Ion Storage

In advancing battery technologies, primary attention is paid to developing and optimizing low-cost electrode materials capable of fast reversible ion insertion and extraction with good cycling ability. Sodium-ion batteries stand out due to their inexpensive price and comparable operating principle to lithium-ion batteries. To achieve this target, various graphene-based nanocomposites fabricate strategies have been proposed to help realize the nanostructured electrode for high electrochemical performance sodium-ion batteries. In this review, the graphene-based nanocomposites were introduced according to the following main categories: graphene surface modification and doping, three-dimensional structured graphene, graphene coated on the surface of active materials, and the intercalation layer stacked graphene. Through one or more of the above strategies, graphene is compounded with active substances to prepare the nanocomposite electrode, which is applied as the anode or cathode to sodium-ion batteries. The recent research progress of graphene-based nanocomposites for SIBs is also summarized in this study based on the above categories, especially for nanocomposite fabricate methods, the structural characteristics of electrodes as well as the influence of graphene on the performance of the SIBs. In addition, the relevant mechanism is also within the scope of this discussion, such as synergistic effect of graphene with active substances, the insertion/deintercalation process of sodium ions in different kinds of nanocomposites, and electrochemical reaction mechanism in the energy storage. At the end of this study, a series of strategies are summarized to address the challenges of graphene-based nanocomposites and several critical research prospects of SIBs that provide insights for future investigations.

MoS2 Decorated Silver Nanowire-Reduced Graphene Oxide Aerogel Micro-Particle for Thermally Conductive Polymer Composites with Enhanced Flame Retardancy

Multifunctional polymer composites with efficient heat dissipation and flame retardancy are highly desirable in the electronic industry. Here, by the combination of hydrothermal reaction and in-situ fragmentation, molybdenum disulfide (MoS₂ ) decorated silver nanowire (AgNW) and 3D reduced graphene oxide (RGO) (AgNW-RGO@MoS₂ ) aerogel micro-particle (AMP) is successfully prepared. When the above AMP is introduced to epoxy (EP) resin by the simple blending method, polymer composite with continuous thermally conductive pathways and flame barrier layers is achieved. With AMP loading of 4.0 vol%, the polymer composite displays superior enhancement in thermal conductivity up to 420%. Compared to neat EP, the peak heat release rate and total heat release decrease 61.1% and 58.8%, respectively. This work provides new insights into the design and large-scale fabrication of multifunctional polymer composites for efficient thermal management materials. This article is protected by copyright. All rights reserved.

Synergistic Flame Retardant Effect of Barium Phytate and Intumescent Flame Retardant for Epoxy Resin

Recently, widespread concern has been aroused on environmentally friendly materials. In this article, barium phytate (Pa-Ba) was prepared by the reaction of phytic acid with barium carbonate in deionized water, which was used to blend with intumescent flame retardant (IFR) as a flame retardant and was added to epoxy resin (EP). Afterward, the chemical structure and thermal stability of Pa-Ba were characterized by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA), respectively. On this basis, the flammability and flame retardancy of EP composites were researched. It is shown that EP/14IFR/2Ba composite has the highest limiting oxygen index (LOI) value of 30.7%. Moreover, the peak heat release rate (PHRR) of EP/14IFR/2Ba decreases by 69.13% compared with pure EP. SEM and Raman spectra reveal the carbonization quality of EP/14IFR/2Ba is better than that of other composites. The results prove that Pa-Ba can cooperate with IFR to improve the flame retardancy of EP, reducing the addition amount of IFR in EP, thus expanding the application range of EP. In conclusion, adding Pa-Ba to IFR is a more environmentally friendly and efficient method compared with others.

Reversible Phase Transition of Porous Coordination Polymers

Porous coordination polymers or metal-organic frameworks with reversible phase-transition behavior possess some attractive properties, and can respond to external stimuli, including physical and chemical stimuli, in a dynamic fashion. Their phase transitions can be triggered by adsorption/desorption of guest molecules, temperature changes, high pressure, light irradiation, and electric fields; these mainly include two types of transitions: crystal-amorphous and crystal-crystal transitions. These types of porous coordination polymers have received much attention because of their interesting properties and potential applications. Herein, reversible phase transition porous coordination polymers are summarized and classified based on different stimuli sources. Corresponding typical examples are then introduced. Finally, examples of their applications in gas separation, chemical sensors, guest molecule encapsulation, and energy storage are also presented.

Novel MoS2-DOPO Hybrid for Effective Enhancements on Flame Retardancy and Smoke Suppression of Flexible Polyurethane Foams

A novel MoS₂-DOPO hybrid has been successfully synthesized through the grafting of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) on the surface of MoS₂ nanosheets using allyl mercaptan as an intermediate. MoS₂-DOPO was used as a flame retardant additive to prepare flame-retardant flexible polyurethane foam (FPUF). The influence of MoS₂-DOPO on the mechanical, thermal stability, and flame retardancy properties of FPUF composites were systematically investigated. The incorporation of MoS₂-DOPO could not deteriorate greatly the tensile strength and 50% compression set of FPUF composites, but effectively improves the char residue. The cone calorimeter and smoke density tests results revealed that the peak heat release rate, total heat release, and the maximum smoke density of the MoS₂-DOPO/FPUF composite were reduced by 41.3, 27.7, and 40.5%, respectively, compared with those of pure FPUF. Furthermore, the char residue after cone calorimeter tests and pyrolysis gaseous products of the MoS₂-DOPO/FPUF composite were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and thermogravimetric analysis/infrared spectrometry. The results suggested that the MoS₂-DOPO hybrid played a synergistic flame retardant effect of gas and condensed bi-phase action. In addition, a possible flame retardancy and smoke suppression mechanism of the MoS₂-DOPO/FPUF composite were proposed. This study provides a facile and promising strategy for the fabrication of polymer materials with excellent flame retardancy and smoke suppression properties.

Enhanced thermal properties of poly(lactic acid)/MoS2/carbon nanotubes composites

In this work, few-layered molybdenum disulfide (MoS₂) was functionalized with metal oxide (M_xO_y) nanoparticles which served as a catalyst for carbon nanotubes (CNT) growth in the chemical vapour deposition (CVD) process. The resulting MoS₂/M_xO_y/CNT functionalized nanomaterials were used for flame retarding application in poly(lactic acid) (PLA). The composites were extruded with a twin-screw extruder with different wt% loading of the nanomaterial. Full morphology characterization was performed, as well as detailed analysis of fire performance of the obtained composites in relation to pristine PLA and PLA containing an addition of the composites. The samples containing the addition of MoS₂/M_xO_y/CNT displayed up to over 90% decrease in carbon oxide (CO) emission during pyrolysis in respect to pristine PLA. Microscale combustion calorimetry testing revealed reduction of key parameters in comparison to pristine PLA. Laser flash analysis revealed an increase in thermal conductivity of composite samples reaching up to 65% over pristine PLA. These results prove that few-layered 2D nanomaterials such as MoS₂ functionalized with CNT can be effectively used as flame retardance of PLA.

A comparative study of mechanisms of the adsorption of CO2 confined within graphene-MoS2 nanosheets: a DFT trend study

The space within the interlayer of 2-dimensional (2D) nanosheets provides new and intriguing confined environments for molecular interactions. However, atomic level understanding of the adsorption mechanism of CO₂ confined within the interlayer of 2D nanosheets is still limited. Herein, we present a comparative study of the adsorption mechanisms of CO₂ confined within graphene-molybdenum disulfide (MoS₂) nanosheets using density functional theory (DFT). A comprehensive analysis of CO₂ adsorption energies (E _AE) at various interlayer spacings of different multilayer structures comprising graphene/graphene (GrapheneB) and MoS₂/MoS₂ (MoS₂B) bilayers as well as graphene/MoS₂ (GMoS₂) and MoS₂/graphene (MoS₂G) hybrids is performed to obtain the most stable adsorption configurations. It was found that 7.5 Å and 8.5 Å interlayer spacings are the most stable conformations for CO₂ adsorption on the bilayer and hybrid structures, respectively. Adsorption energies of the multilayer structures decreased in the following trend: MoS₂B > GrapheneB > MoS₂G > GMoS₂. By incorporating van der Waals (vdW) interactions between the CO₂ molecule and the surfaces, we find that CO₂ binds more strongly on these multilayer structures. Furthermore, there is a slight discrepancy in the binding energies of CO₂ adsorption on the heterostructures (GMoS₂, MoS₂G) due to the modality of the atom arrangement (C-Mo-S-O and Mo-S-O-C) in both structures, indicating that conformational anisotropy determines to a certain degree its CO₂ adsorption energy. Meanwhile, Bader charge analysis shows that the interaction between CO₂ and these surfaces causes charge transfer and redistributions. By contrast, the density of states (DOS) plots show that CO₂ physisorption does not have a substantial effect on the electronic properties of graphene and MoS₂. In summary, the results obtained in this study could serve as useful guidance in the preparation of graphene-MoS₂ nanosheets for the improved adsorption efficiency of CO₂.

Facile synthesis of a novel magnesium amino-tris-(methylenephosphonate)-reduced graphene oxide hybrid and its high performance in mechanical strength, thermal stability, smoke suppression and flame retardancy in phenolic foam

This study presents a one-step synthesis of a magnesium amino-tris-(methylenephosphonate) (Mg-AMP)-reduced graphene oxide (Mg-rGO) hybrid involving graphene oxide (GO) reduction and growth in situ of Mg-AMP nanoparticles in the absence of a reducing agent. Mg-rGO was characterized by X-ray diffraction, X-ray photoelectron and Fourier-transform infrared spectroscopies, transmission electronic microscopy, and thermogravimetric analysis (TGA). Mg-rGO was then used to prepare flame-retardant and toughened phenolic (PF) foam. This additive was found to enhance the compressive and flexural strengths of PF foam as well as to reduce its high friability and brittleness. The limiting oxygen index of the foam with 4 phr Mg-rGO (sample PF/4Mg-rGO) increased to 41.5%, compared with the 38% of untreated foam; the peak heat release rate and total heat release of sample PF/4Mg-rGO were decreased by 28.7 and 18.4%, respectively. Also, the total smoke release and peak CO production rate of PF/4Mg-rGO were reduced by 52.5 and 38.1%, respectively. TGA results indicated that Mg-rGO clearly improved the thermal stability of PF foam.

The flame retardancy and smoke suppression effect of a hybrid containing CuMoO4 modified reduced graphene oxide/layered double hydroxide on epoxy resin

The co-precipitation method was used to synthesize a hybrid with MgAl-layered double hydroxide loaded graphene (RGO-LDH). CuMoO₄ was then introduced onto the surface of RGO-LDH to prepare a hybrid with CuMoO₄ modified RGO-LDH (RGO-LDH/CuMoO₄). The composition, structure and morphology of RGO-LDH/CuMoO₄ were characterized by X-ray diffraction, Laser raman spectroscopy and Transmission electron microscope-energy-dispersive X-ray spectroscopy. It was found that the hybrid of RGO-LDH/CuMoO₄ had been successfully prepared. The effects of flame retardancy and smoke suppression of epoxy resin were studied with added RGO-LDH/CuMoO₄. Results showed that the PHRR and THR of the EP composite with RGO-LDH/CuMoO₄ added were decreased dramatically. The char yield, LOI and UL-94 vertical burning rating of the EP composite were increased, with improved flame ratardancy. In addition, the SPR, TSP, and D_s,max of the EP composite were decreased drastically with added RGO-LDH/CuMoO₄. Its improved flame retardancy and smoke suppression performance were due mainly to the physical barrier of graphene and LDH, and the catalytic carbonization function of LDH. Meanwhile, Cu₂O and MoO₃ generated from RGO-LDH/CuMoO₄ in the combustion process helped enhance the production of char residue and raised the compactness of the char layer.