Graphene Nanosheet Composites Research Articles

Enhancing Electron/Ion Transport in SnO2 Quantum Dots Decorated Polyaniline/Graphene Hybrid Fibers for Wearable Supercapacitors with High Energy Density.

Fiber-based supercapacitors are the potential power sources in the field of wearable electronics and energy storage textiles due to their unique advantages of electrochemical properties and mechanical flexibility, but achieving high energy density and practical energy supply still presents some challenges. In this study, we reported an approach of microfluidic assisted wet-spinning to fabricate SnO2 quantum dots encapsulated polyaniline/graphene hybrid fibers (SnO2 QDs@PGF) by incorporating uniformly polyaniline into graphene fibers and covalently bridging SnO2 quantum dots. The assembled SnO2 QDs@PGF fiber-typed flexible supercapacitors exhibit an ultralarge specific areal capacitance of 925 mF cm-2 in PVA/H2SO4, superior rate capabilities, and capacitance retention of 88% after 8000 cycles, indicating that the SnO2 QDs@PGF possess near-ideal capacitance properties, efficient ion transfer rate, and good cycling stability. In the EMITFSI/PVDF-HFP electrolyte system, SnO2 QDs@PGF realize a wide operating potential window of 2.5 V, a specific areal capacitance of 678.4 mF cm-2, and an energy density of 147.2 μWh cm-2 at 500 μW cm-2, which can be utilized to power an alarm clock, an electronic timer, and a desk lamp with a requirement of a 3 V battery. The exceptional performance of the SnO2 QDs@PGF can be attributed to the molecular-level homogeneous composite of granular polyaniline and graphene nanosheets and the interfacial C-O-Sn covalent coupling strategy employed between SnO2 QDs and PGF. These avenues not only effectively prevent the undesirable restacking of graphene nanosheets but also increase the interlayer electroactive sites, ordered ion diffusion channels, and strong interfacial charge transfer.

Preparation of Co-nanocluster graphene composite by asymmetric domain-limited electrochemical exfoliation for functionalized lithium-sulfur battery separator applications

Transition metal nanocluster graphene composite exhibits better performance in energy storage materials than heteroatom graphene composite. In catalytic function separator materials for lithium-sulfur batteries, the introduction of functionalized graphene into asymmetric separators effectively seals and anchors soluble polysulfides, largely mitigating the notorious “shuttle effect”. Here, we report the development of a novel asymmetric domain-limited electrochemical (ALE) exfoliation of graphite foils (natural-scaled graphite) to prepare Co-nanocluster graphene composite nanosheets (labeled as Co-G). Co-G has a large lateral size, many surface folds, and few intrinsic defects (ID/IG = 0.38). Co-nanocluster graphene composite promotes redox kinetic conversion, and its high electronic conductivity allows it to act as a second collector, accelerating charge transfer, improving the utilization of active material, and increasing cyclic stability. A lithium-sulfur battery incorporating a Co-G modified separator achieved an initial discharge capacity of 1315.5 mAh/g at 0.5 C with excellent multiplicity performance (932.3 mAh/g specific capacity at 2 C multiplicity) and cycling stability (848.4 mAh/g after 400 cycles). The asymmetric domain-limited electrochemical (ALE) method is a viable approach to the preparation of catalytic function separator materials for lithium-sulfur batteries that will have high magnification and high cyclic stability.

The cocontinuous morphology induced from the graphene nanosheets percolation network structures in the immiscible high density polyethylene/polyamide 6/graphene nanosheets composites

AbstractThe addition of graphene nanosheets (GNSs) into immiscible polymer composites to induce the cocontinuous morphologies shows potential application in reinforced nanocomposites and conductive polymer nanocomposites. In this work, immiscible high density polyethylene (HDPE)/polyamide 6 (PA6)/GNS composites were prepared via melt mixing. The electrical and rheological property of HDPE/PA6 composites filled with various GNS contents according to different viscosity ratios and mixing orders were investigated to reveal the double percolation effect via percolation scaling laws, and compared with those of HDPE/GNS and PA6/GNS composites. The morphology and GNS dispersion state of HDPE/PA6/GNS composites were examined via transmission electron microscopy and scanning electron microscope. Most of the GNS were selectively located in the PA6 phase of HDPE/PA6/GNS composites. The GNS‐related network and mixing order played important roles in the cocontinuous morphology formation and performance of HDPE/PA6/GNS conductive composites. Moreover, the addition of GNS also affected the crystallization kinetics and mechanical property of HDPE/PA6/GNS composites.

Graphene nanosheet stabilized Pickering emulsion and its polystyrene nanocomposites

AbstractHigh thermal conductivity and electrical insulation materials are necessary for packaging materials of miniaturized electronic equipment at present. Graphene nanosheets (GNs) have great potential in polymer composites due to its excellent thermal conductivity. However, the ultra‐high conductivity of GNs will reduce the insulation of polymer composites, so that the GN composites have good thermal conductivity and electrical insulation has become the focus of research. Herein, the closed cell polystyrene nanocomposites are polymerized by using a Pickering emulsion route. Based on the exfoliating effect of pristine graphite at the oil–water interface and the amphiphilic properties of GNs during the preparation of emulsion, the resulting graphite can achieve good dispersion in the polystyrene resin. Furthermore, the high heat transfer rate of the resulting graphite makes the temperature of polystyrene resin increase by 60.2°C at room temperature within 1 min. Meanwhile, the high volume electrical resistivity (3.63 × 109 Ω·m) and breakdown strength (33.8 kV·mm−1) confirms the PNGL0.610%/PS composite keep excellent electrical insulation at 10.0 wt% filler loading.

Composites of an Epoxy Resin (EP)/PVDF/NiCo-Graphene Nanosheet (GNS) for Electromagnetic Shielding

In this study, a series of three-dimensional (3D) epoxy resin/poly(vinylidene fluoride)/nickel–cobalt alloy–graphene nanosheet (EP/PVDF/NiCo-GNS) composites with high thermal conductivity and electromagnetic interference shielding effectiveness (EMI SE) were successfully prepared using a salt template-assisted strategy. X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses jointly presented the successful modification of GNS and in situ growth of NiCo alloy. The cross-sectional morphological observations on the PVDF/NiCo-GNS skeleton and epoxy-based composites clearly showed the successful construction of a honeycomb-like heat conduction network. At a NiCo-GNS loading of 15 wt %, the prepared composites’ EMI SE could reach a value of 34.62 dB. The special structures not only perfected the interconnected thermally and electrically conductive network but also facilitated the multiple internal reflections of electromagnetic waves inside the composites. The present work provides an insight into the design of multifunctional polymer-based composites for electronic 3D encapsulation applications.

Highly effective electromagnetic interference shielding composites with solvent-dispersed uniformly aligned graphene nanosheets enabled by strong intrinsic diamagnetism under magnetic field

Graphene nanosheets (GNS) have been regarded as one of the best fillers in polymers for electromagnetic interference (EMI) shielding composites, but it remains a challenge to prepare well-dispersed and highly aligned GNS for optimal EMI shielding despite many recently developed methods. Here we demonstrate a new technology that not only enables uniform alignment of GNS in polymer composites in any direction but also allows us to systematically tune the composites for optimal EMI performance. The technique makes use of graphene's strong intrinsic and anisotropic diamagnetic susceptibility. Unlike paramagnetism and ferromagnetism, diamagnetism allows us to fully control the orientation of GNS by a rotating magnetic field without causing any aggregation or introducing unwanted magnetic particles due to the repulsive force between GNS. This process for GNS composites further enables us to systematically modify GNS concentration and polymer matrix besides GNS orientations. A record-high shielding effectiveness (SE) of 95 dB is achieved with industrially mass-produced multilayer GNS aligned parallel to the surface of a mixed polyvinylidene fluoride-epoxy composite, and a 50% higher SE is further achieved with few-layer GNS. This technique is scalable, thus opening the practical applications of graphene in EMI shielding.

Synthesis of SiC/ graphene nanosheet composites by helicon wave plasma* *Project supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) and Postgraduate Research & Practice Innovation Program of Jiangsu Province, China (Grant No. KYCX20 2649).

We report an approach to the rapid, one-step, preparation of a variety of wide-bandgap silicon carbide/graphene nanosheet (SiC/GNSs) composites by using a high-density helicon wave plasma (HWP) source. The microstructure and morphology of the SiC/GNSs are characterized by using scanning electron microscopy (SEM), Raman spectroscopy, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and fluorescence (PL). The nucleation mechanism and the growth model are discussed. The existence of SiC and graphene structure are confirmed by XRD and Raman spectra. The electron excitation temperature is calculated by the intensity ratio method of optical emission spectroscopy. The main peak in the PL test is observed at 420 nm, with a corresponding bandgap of 2.95 eV that indicates the potential for broad application in blue light emission and ultraviolet light emission, field electron emission, and display devices.

Nitrogen and Sulfur Quantum Dot Co-Modified Graphene Nanosheet with Enhanced Photocatalytic Activity for Methyl Orange Degradation

Nitrogen-sulfur quantum dot co-modified graphene nanosheets composites (NSG) were fabricated via a facile hydrothermal method as a high performance metal-free catalyst for methyl orange (MO) degradation. Physical-chemical properties of the obtained samples were characterized by XRD, FTIR, SEM, TEM, EDX, TGA, BET, and UV–Vis DRS technologies. Compared with RGO, NSG exhibited much better photocatalytic performance for MO degradation under visible light, especially, NSG(30) showed the best photocatalytic degradation rate of 100% within 180 min. XRD, TG, and UV–Vis DRS results demonstrated that the addition of N and S can enhance the stability of oxygen containing functional groups to supply more adsorption active centers for organic contaminant molecular, adjust the band gap to a certain extent and increase the number of photogenerated electrons, improve the visible light utilization rate of the material and thus improve the photocatalytic degradation performance of the NSG composites. The degradation activity of the catalyst remained above 90% after 3 recycles. Finally, a possible photodegradation mechanism of MO on the obtained NSG sample was proposed.

Layered mesoporous CoO/reduced graphene oxide with strong interfacial coupling as a high-performance anode for lithium-ion batteries

Composites of few-layer transition metal oxides and graphene nanosheets with strong interfacial connection hold great promise as high-performance anodes for lithium-ion batteries, but it is highly challenging to realize full interfacial properties. Herein, we report an ultra-refined layer-by-layer mesoporous CoO/reduced graphene oxide (CoO/RGO) architecture synthesized via a facile method. The CoO/RGO has stacked interfaces between the CoO nanosheets and the graphene nanosheets via Co–O–C bonds, which has been proposed to have an important role in achieving excellent performance in lithium ion batteries with high initial capacity and good rate capability. It is shown that the CoO/RGO exhibits a high initial discharge capacity of 2189.4 mAh g−1 at a current density of 100 mA g−1. Furthermore, the CoO/RGO exhibits a high reversible capacity retention of 70% after prolonged 300 cycles at a high rate of 2 A g−1. Significantly, it delivers an ultrahigh reversible capacity of 1167 mAh g−1 at 5 A g−1 with an excellent reversible capacity retention of 76% over 40 cycles.

Hydrophobic-Superoleophilic Fluorinated Graphene Nanosheet Composites with Metal–Organic Framework HKUST-1 for Oil–Water Separation

The spills of oils and petroleum byproducts into water bodies cause severe damage to aquatic species and humans along with massive loss to economy. Efficient methods using state of art sorbent mate...

Synthesis and electrochemical performances of platinum decorated polydopamine-coated carbon nanotubes/graphene composites as fuel cell catalysts

The electrochemical analysis of platinum catalyst which is deposited on polydopamine-coated multi-walled carbon nanotubes (PCNT) and graphene nanosheet (GNS) composites is investigated. The Pt-PCNT/GNS composites are prepared via a facile one-step synthesis process in a Teflon-lined autoclave. Cyclic voltammetry, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy are utilized to analyze the characteristics of the Pt-PCNT/GNS composites. The electrochemical surface area and methanol oxidation reaction is changed depending on the weight ratio of PCNT:GNS compounds, which affects the dispersion of the Pt nanoparticles. The Pt-PCNT/GNS composites exhibit superior properties compared to those of Pt-GNS and Pt-PCNT, which demonstrate that the PCNT/GNS could be used as promising catalyst supports for direct methanol fuel cells.

Controllable synthesis of intercalated γ-Bi2MoO6/graphene nanosheet composites for high performance NO2 gas sensor at room temperature

Intercalated γ-Bi2MoO6/graphene nanosheet composites (BMO/GNCs) were prepared by vacuum-assistant and solvothermal technique. In BMO/GNCs, BMO nanoparticles (NPs) were uniformly distributed on the surface and interlayer of graphene nanosheets (GNs), simultaneously along with a large number of defects and interface on GNs and BMO NPs. As synthesized with solvothermal temperature at 160 °C and graphite content of 80 mg, BMO/GNCs-8-160 sample exhibits the remarkable gas sensitivity, reversibility and selectivity to NO2 at room temperature (RT, 22 °C). The relative response rate of the sensor toward 100 ppm NO2 is 96.73, which is about 6.41 times of pure BMO NPs. Furthermore, the response time and recovery time is merely 2.5 and 34.1 s, respectively. The detection limit can reach 10 ppb with response value of 1.51. The improved NO2 sensing performance is attributed to the effective electron transfer between BMO NPs and GNs and typical structure characteristics of BMO/GNCs, which is rarely reported in the room temperature type of Bi2MoO6 sensor.

Highly Dispersed MgH2 Nanoparticle–Graphene Nanosheet Composites for Hydrogen Storage

We report a facile solid state method to in situ synthesize highly dispersed MgH2 nanoparticle–graphene nanosheet composites and their improved dehydrogenation/hydrogenation properties. The graphen...

Flower-like structured Fe3O4−MQDs/Bi2WO6/GNs heterojunction with high-efficiently charge transfer for organic contaminants degradation

Abstract A novel flower-like ternary Fe3O4-magnetic quantum dots / Bi2WO6/ Graphene nanosheet (Fe3O4−MQDs/Bi2WO6/GNs) composite was successfully prepared by a facile one-pot hydrothermal method. The prepared samples were characterized by XRD, FTIR, UV–vis, SEM, HRTEM, EDS, BET and VSM technologies. Compared with the Bi2WO6 and Fe3O4/Bi2WO6, the Fe3O4/Bi2WO6/GNs catalyst exhibited higher photodegradation ratio of 98.2% for methylene blue (MB) and 90% for Tetracycline hydrochloride (TC) within 210 min irradiation at pH 7, and stability over 80% even after six cycles. Characterization results showed that the enhanced photocatalytic activity was mainly due to the strong interactions of MQDs/Bi2WO6 heterojunction and high specific surface area. A possible photocatalytic degradation mechanism was proposed on the basis of the identified intermediates. Furthermore, the Fe3O4/Bi2WO6/GNs composite could be easily recovered from the reaction system under an external magnetic field owing to its sufficient magnetism, therefore which has certain potential applications in water treatment process.

Effect of Graphene Nanosheets Content on Microstructure and Mechanical Properties of Titanium Matrix Composite Produced by Cold Pressing and Sintering.

The effect of graphene nanosheet (GNS) reinforcement on the microstructure and mechanical properties of the titanium matrix composite has been discussed. For this purpose, composites with various GNS contents were prepared by cold pressing and sintering at various time periods. Density calculation by Archimedes’ principle revealed that Ti/GNSs composites with reasonable high density (more than 99.5% of theoretical density) were produced after sintering for 5 h. Microstructural analysis by X-ray diffraction (XRD) and a field emission scanning electron microscope (FESEM) showed that TiC particles were formed in the matrix during the sintering process as a result of a titanium reaction with carbon. Higher GNS content as well as sintering time resulted in an increase in TiC particle size and volume fraction. Microhardness and shear punch tests demonstrated considerable improvement of the specimens’ mechanical properties with the increment of sintering time and GNS content up to 1 wt. %. The microhardness and shear strength of 1 wt. % GNS composites were enhanced from 316 HV and 610 MPa to 613 HV and 754 MPa, respectively, when composites sintered for 5 h. It is worth mentioning that the formation of the agglomerates of unreacted GNSs in 1.5 wt. % GNS composites resulted in a dramatic decrease in mechanical properties.

Restricting Growth of Ni3Fe Nanoparticles on Heteroatom-Doped Carbon Nanotube/Graphene Nanosheets as Air-Electrode Electrocatalyst for Zn-Air Battery.

Exploring bifunctional oxygen electrode catalysts with efficient and stable oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) performance is one of the limitations for high-performance zinc-air battery. In this work, Ni3Fe alloy nanoparticles incorporated in three-dimensional (3D) carbon nanotube (CNT)/graphene nanosheet composites with N and S codoping (Ni3Fe/N-S-CNTs) as bifunctional oxygen electrode electrocatalysts for zinc-air battery. The main particle size of Ni3Fe nanoparticles could be well restricted because of the unique 3D structure of carbon nanotube/graphene nanosheet composites (N-S-CNTs). The large specific area of N-S-CNTs is conducive to the uniform dispersion of Ni3Fe nanoparticles. On the basis of the synergistic effect of Ni3Fe nanoparticles with N-S-CNTs, and the sufficient exposure of reactive sites, the synthesized Ni3Fe/N-S-CNTs catalyst exhibits excellent OER performance with a low overpotential of 215 mV at 10 mA cm-2, and efficient ORR activity with a half-wave potential of 0.877 V. When used as an electrocatalyst in zinc-air battery, the device exhibits a power density of 180.0 mW cm-2 and long term durability for 500 h.

Facile synthesis of NiSnO3/graphene nanocomposite for high-performance electrode towards asymmetric supercapacitor device

Potentially, active nickel stannate (NiSnO3)/graphene nanosheets (GNS) composite was prepared using facile hydrothermal method. From XRD analysis, the average crystallite size of NiSnO3 nanoparticles and NiSnO3/GNS nanocomposite was found to be 5 and 3 nm, respectively. XPS analysis revealed chemical species and oxidation state of elements present on the surface of the samples. HRSEM analysis showed the formation of elongated shape of NiSnO3/graphene nanocomposite with size of ~ 6 nm. Moreover, the internal structure and interactions between stannate and graphene were examined using transmission electron microscope analysis. BET analysis revealed the significant increase in surface area of 162 m2/g in NiSnO3/GNS nanocomposite, whereas bare NiSnO3 nanoparticles showed 101 m2/g. Electrochemical performance of bare NiSnO3 and NiSnO3/GNS nanocomposite was studied using cyclic voltammetry and charge–discharge techniques. Cyclic voltammetry of NiSnO3/GNS resulted in maximum specific capacitance of 891 F/g at a scan rate of 5 mV/s which is higher than that of NiSnO3 alone 570 F/g at same scan rate. Electrochemical impedance spectra show negligible charge transfer resistance of 1.6 and 1.5 Ω for NiSnO3 and NiSnO3/GNS, respectively. Enhancement in the electrochemical performance of NiSnO3/GNS is mainly due to graphene incorporation which provided high surface area, thereby offering high interfacial sites, electrical conductivity and improved redox activity. Further, an asymmetric supercapacitor was constructed using NiSnO3/GNS nanocomposite and activated carbon acted as positive and negative electrodes within an operating potential window of 0–0.8 V. Fabricated asymmetric device delivered a high energy density of 42.54 Wh/kg at a power density of 0.34 kW/kg. Moreover, this device exhibited excellent charge–discharge cycling stability with 88.3% capacitance retention even after 4000 cycles.

One-step synthesis of TiC/multilayer graphene composite by thermal plasma

Graphene hybrid materials have been attracting a great deal of attention due to their superior properties. Nevertheless, problems such as expensive and complicated production processes have limited their application to industrial fields. Here, we introduce a one-step synthesis of titanium carbide (TiC) nanoparticles on multilayer graphene nanosheet (TiC/multilayer graphene) composites using thermal plasma. Although there are three types of titanium alkoxides (titanium ethoxide, titanium isopropoxide and titanium n-butoxide), the TiC/multilayer graphene was synthesized from only titanium isopropoxide. The injection temperature of the precursor was varied to investigate the effects of the precursor concentration in the plasma region. A TiC/multilayer graphene hybrid material with crystalline TiC nanoparticles below 50 nm on graphene nanosheets was observed. The number of graphene nanosheet layers varied from one to over 10 according to the injection temperature. When titanium ethoxide and titanium butoxide were injected, TiC with amorphous carbon and graphite were synthesized. The formation of graphene is considered to be affected by the structure of the carbon chain in the precursors and the concentration in the plasma region.

The self-aligning behaviour of graphene nanosheets in the styrene butadiene rubber by controlling curing temperature

ABSTRACTThis paper presents a simple strategy that utilizes the regulation of curing temperature to control the orientation of the aligned graphene nanosheets (GNSs) in styrene butadiene rubber (SBR). GNSs would settle from the well-dispersed GNSs suspensions with the styrene butadiene latex (SBL) mixture under the field of gravity to form parallel-aligned GNSs composites with enough standing time at a lower curing temperature. The vertical-aligned GNSs composites were formed by the combined effect of gravity and steam inductive force within a higher curing temperature. The detail forming mechanisms were discussed in the investigation. The parallel-aligned GNSs/SBR composites demonstrated anisotropic conductivity between the parallel and the perpendicular directions. Along with parallel direction, a percolation threshold value of the GNSs was 0.13 wt%, and 0.58 S/cm and of electric conductivity was attained when the GNSs content was 3 wt%. Along with vertical direction, it the GNSs showed insulating property.

Enhanced Reversible Sodium‐Ion Intercalation by Synergistic Coupling of Few‐Layered MoS2 and S‐Doped Graphene

AbstractSodium‐ion batteries (SIBs) are regarded as the best alternative to lithium‐ion batteries due to their low cost and similar Na+ insertion chemistry. It is still challenging but greatly desired to design and develop novel electrode materials with high reversible capacity, long cycling life, and good rate capability toward high‐performance SIBs. This work demonstrates an innovative design strategy and a development of few‐layered molybdenum disulfide/sulfur‐doped graphene nanosheets (MoS2/SG) composites as the SIB anode material providing a high specific capacity of 587 mA h g−1 calculated based on the total composite mass and an extremely long cycling stability over 1000 cycles at a current density of 1.0 A g−1 with a high capacity retention of ≈85%. Systematic characterizations reveal that the outstanding performance is mainly attributed to the unique and robust composite architecture where few‐layered MoS2 and S‐doped graphene are intimately bridged at the hetero‐interface through a synergistic coupling effect via the covalently doped S atoms. The design strategy and mechanism understanding at the molecular level outlined here can be readily applied to other layered transition metal oxides for SIBs anode and play a key role in contributing to the development of high‐performance SIBs.