Graphite Nanocomposites Research Articles

MnO2/CdS/N-doped Graphite Nanocomposite for High-Performance Supercapacitors

MnO2/CdS/N-doped Graphite Nanocomposite for High-Performance Supercapacitors

Synergism of Rare Earth Trihydrides and Graphite in Lithium Storage: Evidence of Hydrogen-Enhanced Lithiation.

The lithium storage capacity of graphite can be significantly promoted by rare earth trihydrides (REH3 , RE = Y, La, and Gd) through a synergetic mechanism. High reversible capacity of 720 mA h g-1 after 250 cycles is achieved in YH3 -graphite nanocomposite, far exceeding the total contribution from the individual components and the effect of ball milling. Comparative study on LaH3 -graphite and GdH3 -graphite composites suggests that the enhancement factor is 3.1-3.4 Li per active H in REH3 , almost independent of the RE metal, which is evident of a hydrogen-enhanced lithium storage mechanism. Theoretical calculation suggests that the active H from REH3 can enhance the Li+ binding to the graphene layer by introducing negatively charged sites, leading to energetically favorable lithiation up to a composition Li5 C16 H instead of LiC6 for conventional graphite anode.

Photocatalytic application of Pd-ZnO-exfoliated graphite nanocomposite for the enhanced removal of acid orange 7 dye in water

In this work, a nanocomposite photocatalyst which consists of palladium (Pd), zinc oxide (ZnO) as well as exfoliated graphite (EG) was synthesised, characterised and applied to the removal of acid orange 7 dye as a model organic pollutant. The Pd-ZnO-EG nanocomposite was synthesised by a one-pot hydrothermal technique in a Teflon-lined stainless steel autoclave at 160 °C for a period of 12 h, cooled, washed and dried. The nanocomposite was characterised by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), scanning electronic microscopy (SEM) as well as energy dispersive X-ray spectrometry (EDX). The as-prepared materials were further applied for the degradation of acid orange 7 dye photocatalytically. Results obtained showed that Pd-ZnO-EG composite displayed a better photocatalytic performance, giving better removal efficiency of 87% in comparison with ZnO and Pd-ZnO which gave 3 and 25% percentage removal respectively.

Molecular dynamics simulation study of parallel orientation structure and gas transport in graphite-nanoplatelet/polyethylene composites

Molecular dynamics simulations of graphite-nanoplatelet/polyethylene composites have been implemented to investigate the morphological structure and gas transport property by calculations of dynamical energy, structural parameter, X-ray scattering spectrum and gas diffusion coefficient, analyzing their relationship with nanofiller concentration and temperature. The graphite-nanoplatelet/polyethylene composites represent as two-dimensional anisotropic structures with the graphite-nanoplatelets orientating in parallel to each other and composite with polyethylene matrix by intense Van der Waals force and CH-π bonding on nanoplatelet surface, causing a few ordered atomic layers of polyethylene at interface while the internal polyethylene matrix retaining isotropic amorphous morphology. Due to the nanocomposite effect, gas transport in graphite-nanoplatelet/polyethylene composites is significantly affected by the nano-interfaces and orientation of graphite-nanoplatelets without gas selectivity for percolation. The graphite nanocomposites present two-dimensional anisotropic permeation of nitrogen, oxygen and carbon dioxide molecules that the diffusion coefficients are 4 and 7 times higher along orientation plane than in perpendicular direction of graphite-nanoplatelets for 10.4% and 20.4% filler concentrations respectively, suggesting reasonable material application to the gas barrier and percolation control.

Hybrid magnetic graphitic nanocomposites towards catalytic wet peroxide oxidation of the liquid effluent from a mechanical biological treatment plant for municipal solid waste

Magnetite, nickel and cobalt ferrites were prepared and encapsulated within graphitic shells, resulting in three hybrid magnetic graphitic nanocomposites. Screening experiments with a 4-nitrophenol aqueous model system (5gL−1) allowed to select the best performing catalyst, which was object of additional studies with the liquid effluent resulting from a mechanical biological treatment plant for municipal solid waste. Due to its high content in bicarbonates (14350mgL−1) and chlorides (2833mgL−1), controlling the initial pH was a crucial step to maximize the performance of the catalytic wet peroxide oxidation (CWPO) treatment. The catalyst load was 0.5gL−1, a very low dosage when compared to the high chemical oxygen demand (COD) of the effluent − 9206mgL−1. At the optimum operating pH (i.e., pH=6), ca. 95% of the aromaticity was converted and ca. 55% of COD and total organic carbon (TOC) of the liquid effluent was removed. The biodegradability of the liquid effluent was enhanced during the treatment by CWPO, as reflected by the 2-fold increase of the five-day biochemical oxygen demand (BOD5) to COD ratio (BOD5/COD), namely from 0.21 (indicating non-biodegradability) to 0.42 (suggesting biodegradability of the treated wastewater). In addition, the treated water revealed no toxicity against selected bacteria.Lastly, a magnetic separation system was designed for in-situ catalyst recovery after the CWPO reaction stage. The high catalyst stability was demonstrated through five reaction/separation sequential experiments in the same vessel with consecutive catalyst reuse.

Rotomolded antistatic and flame-retarded graphite nanocomposites

Graphite nanoplatelets with an average particle size of 13 μm and an estimated flake thickness of about 76 nm were prepared by microwave exfoliation, followed by ultrasonication-assisted liquid-phase delamination, of an expandable graphite. This nanoadditive was used to fabricate linear low-density polyethylene (LLDPE) and poly(ethylene-co-vinyl acetate) (EVA)-based nanocomposite sheets using rotational molding. The dry blending approach yielded surface resistivities within the static dissipation range at filler loadings as low as 0.25 wt.% (0.1 vol.%). However, even at this low graphite content, impact properties were significantly reduced compared to the neat polymers. Bilayer moldings via the double dumping method proved to be a feasible approach to achieve both acceptable mechanical properties and antistatic properties. This was achieved by rotomolding nanocomposite sheets with a 1-mm outer layer containing the filler and a 2-mm inner layer of neat LLDPE. Excellent fire resistance, in terms of cone calorimeter testing, was achieved when the outer layer also contained 10 wt.% expandable graphite.

Graphite nanocomposites sensor for multiplex detection of antioxidants in food

Butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tert-butylhydroquinone (TBHQ) are synthetic antioxidants used in the food industry. Herein, we describe the development of a novel graphite nanocomposite-based electrochemical sensor for the multiplex detection and measurement of BHA, BHT, and TBHQ levels in complex food samples using a linear sweep voltammetry technique. Moreover, our newly established analytical method exhibited good sensitivity, limit of detection, limit of quantitation, and selectivity. The accuracy and reliability of analytical results were challenged by method validation and comparison with the results of the liquid chromatography method, where a linear correlation of more than 0.99 was achieved. The addition of sodium dodecyl sulfate as supporting additive further enhanced the LSV response (anodic peak current, Ipa) of BHA and BHT by 2- and 20-times, respectively.

Preparation and characterization of polytetrafluoroethylene (PTFE)/Thermally Expanded Graphite (TEG) nanocomposites

In this study, TEG-reinforced polytetrafluoroethylene (PTFE) nanocomposites were prepared. The structural properties of the PTFE/TEG composites were then investigated using X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). Subsequently, the thermal stability, thermal resistance of the composites were studied through differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). The XRD results allowed to report a high degree of dispersion of the TEG inside of the PTFE matrix. Moreover, milling at high temperature was found to enhance the dispersion of the TEG inside of the polymer matrix. Furthermore, the results revealed an increase of the glass-transition temperature when using an increased concentration of TEG. This result confirms that the degradation of the TEG/PTFE nanocomposite occurs at a higher temperature with a greater TEG loading. These finds give an indication of the potential of TEG to improve the thermal properties and durability of PTFE, for instance with application in the field of aeronautics.

Ge/GeO<sub>2</sub>/multi-layer graphite nanocomposites as anode materials for lithium-ion batteries

Germanium (Ge) has been considered as a promising material applied in lithium-ion batteries due to its unique properties, e.g. high capacity, fast lithium-ion diffusivity, and high electrical conductivity. In this work, Ge/GeO2/multi-layer graphite (Ge/GeO2/MLG) nanocomposites have been synthesized using a solution process from graphite oxide and GeO2 precursors. The electrochemical performances of the prepared Ge/GeO2/MLG nanocomposites were then investigated. The experimental results indicated that in the first cycle, the electrode delivered discharge and charge capacities of 2046 and 1146 mA h g−1, giving the Coulombic efficiency of 56.0%. After 50 cycles, the electrode capacity was still maintained at 1008 mA h g−1 at 100 mA g−1 in the potential range from 0.01 to 1.5 V, and it reached high capacities of 790 and 700 mA h g−1 at the high rates of 1 and 2 A g−1.

Efficient photocatalysis of organic vapors using graphitic carbon nitride and iron dual-coupled ZnO nanocomposites

Abstract This study assessed the performance of graphitic carbon nitride (g-C 3 N 4 ) and iron (Fe) dual-coupled zinc oxide (ZnO) nanocomposites (FCZs) in the photocatalytic degradation of vaporous β -pinene and o -xylene via a continuous system. The properties of the synthesized photocatalysts were examined by various spectral analyses. The adsorption efficiencies of g-C 3 N 4 -coupled ZnO composites (CZs) determined in the dark were lower than those of ZnO. In contrast, the CZ samples exhibited higher photocatalytic degradation than ZnO. Moreover, the photocatalytic degradation efficiencies of the FCZ photocatalysts were higher than those of the CZ, Fe-modified ZnO, and bare ZnO samples, likely due to the greater charge separation efficiency in FCZ. The optimal g-C 3 N 4 /ZnO and Fe/CZ ratios for the synthesis of the CZ and FCZ samples, respectively, were determined. Under certain conditions, mineralization efficiencies of β -pinene (37.0%) and o -xylene (46.6%) over an FCZ sample with the Fe/CZ ratio of 0.05 were lower than the corresponding photocatalytic degradation efficiencies (67.5% and 72.4%, respectively). CO and organic vapors were identified as the major gaseous intermediates, while chemicals adsorbed onto the catalyst surface inside the reactor were not detectable. Super oxide ion radicals, hydroxyl radicals, and positive holes appeared to be responsible for vapor degradation over the FCZ photocatalysts, and a heterojunction-type mechanism is proposed.

TiP2O7 and Expanded Graphite Nanocomposite as Anode Material for Aqueous Lithium-Ion Batteries

This paper reports a facile sol-gel synthesis method to successfully prepare the TiP2O7/expanded graphite (EG) nanocomposite as an advanced anode material for aqueous lithium-ion batteries. The constructed TiP2O7 nanocomposites (50-100 nm) are in situ encapsulated in the pore and layer structure of expanded graphite with good conductivity and high specific surface area. As a consequence, the resulting TiP2O7/EG electrode exhibits a reversible capacity of 66 mAh g-1 at 0.1 A g-1 with an appropriate potential of -0.6 V before hydrogen evolution in aqueous electrolytes, and also demonstrates greatly enhanced cycling stability with 75% capacity retention after 1000 cycles at the current density of 0.5 A g-1. A full cell consisting of TiP2O7/EG anode, LiMn2O4 cathode, and 1 M Li2SO4 electrolyte delivers a specific energy of 60 Wh kg-1 calculated on the weight of both cathode and anode materials with an operational voltage of 1.4 V. It also exhibits superior rate capability and remarkable cycling performance with a capacity maintenance of 66% over 500 cycles at 0.2 A g-1 and 61% at 1 A g-1 over 2000 cycles.

Formation of NiFe2O4/Expanded Graphite Nanocomposites with Superior Lithium Storage Properties

A NiFe2O4/expanded graphite (NiFe2O4/EG) nanocomposite was prepared via a simple and inexpensive synthesis method. Its lithium storage properties were studied with the goal of applying it as an anode in a lithium-ion battery. The obtained nanocomposite exhibited a good cycle performance, with a capacity of 601 mAh g−1 at a current of 1 A g−1 after 800 cycles. This good performance may be attributed to the enhanced electrical conductivity and layered structure of the EG. Its high mechanical strength could postpone the disintegration of the nanocomposite structure, efficiently accommodate volume changes in the NiFe2O4-based anodes, and alleviate aggregation of NiFe2O4 nanoparticles.

High‐density polyethylene/expanded graphite nanocomposites produced by polymerization‐filling technique using an industrial heterogeneous catalyst

ABSTRACTHigh‐density polyethylene nanocomposites with different expanded graphite (EG) contents (0.34–1.80 wt %) were prepared by polymerization‐filling technique using an industrial heterogeneous catalyst (cat K), and characterized using a range techniques: melting flow index (MFI), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM). The MFI data showed that EG acts as a plasticizer decreasing melt viscosity in comparison to neat HDPE produced exclusively by cat K. DSC results showed that EG nucleated the HDPE crystallization as established by the increased crystallization temperature, and the degree of crystallinity. HDPE/EG nanocomposites displayed a significant improvement in the flexural (increased from 1458 to 1831 MPa), and storage modulus (increased from 122 to 1627 MPa) at only 1.80 wt % EG content. TEM images confirmed a homogeneous distribution of EG into the polymer matrix with the presence of dispersed, intercalated and aggregated EG nanofillers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 55, 1260–1267

Synthesis of OMS-2/graphite nanocomposites with enhanced activity for pollutants degradation in the presence of peroxymonosulfate

The octahedral molecular sieve manganese oxide (OMS-2) and graphite (Gt) composites (OMS-2/Gt) were prepared by a facile refluxing approach. The structure and morphology of the obtained materials were systematically investigated. The results reveal that OMS-2 nanofibers are uniformly dispersed on the surface of Gt, and the ratio of Mn3+ species in OMS-2 increases lineally with the increase of Gt dosage. The catalytic activity of OMS-2/Gt was evaluated by the degradation of Acid Orange 7 (AO7) in the presence of peroxymonosulfate (PMS). It is found that the OMS-2/Gt composites show enhanced catalytic performance with the degradation rate lineally correlated with the content of OMS-2 in the catalyst, and even with the ratio of Mn3+/Mn4+. XPS and radical scavenger experiments further indicated that the oxidation of Mn3+ by PMS system occurs in the system with the formation of hydroxyl radicals contributed to the dye degradation. The catalysts also exhibit good stability and reusability during consecutive cycles. Thus, the environmental friendly OMS-2/Gt composites with low cost, facile synthesis process and high efficiency are very promising catalysts for PMS activation and pollutants degradation.

ZnO Doped Graphite Nanocomposite via Agathosma Betulina Natural Extract with Improved Bandgap and Electrical Conductivity

ZnO Doped Graphite Nanocomposite via Agathosma Betulina Natural Extract with Improved Bandgap and Electrical Conductivity

Hybrid magnetic graphitic nanocomposites for catalytic wet peroxide oxidation applications

Fe3O4, with a lattice parameter a=8.357Å and average particle size of 12.5±3.6 nm, was successfully encapsulated within a graphitic structure by a hierarchical co-assembly approach, followed by thermal annealing. The resulting material was denoted as MGNC—magnetic graphitic nanocomposite. MGNC possesses average core size of 109±35nm (mainly composed by agglomerates of magnetic nanoparticles), stability up to 400°C under oxidizing atmosphere, a micro-mesoporous structure with a fairly developed specific surface area (SBET=330m2g−1) and neutral character (pHPZC=7.1).Catalytic wet peroxide oxidation (CWPO) experiments performed with a 4‐nitrophenol (4-NP)/Fe3O4 mass ratio fixed at 36.6, allowed to achieve high efficiency of catalyst usage throughout the wide range of 4-NP concentration considered (200mg L−1–5gL−1). The inclusion of Fe3O4 nanoparticles in a graphitic structure during the synthesis of MGNC was found to (i) enhance the catalytic activity in CWPO when compared to Fe3O4, due to increased adsorptive interactions between the surface of the catalyst and the pollutant molecules, while (ii) strongly limiting the leaching of Fe species from Fe3O4 to the treated water, due to the confinement effect caused by the carbon shell.As a result of these effects, unprecedented pollutant mass removals were obtained − ranging from 5000mgg−1h−1, when the CWPO process is performed with [4‐NP]0=200mgL−1 at pH=3, to 1250mgg−1h−1, when [4-NP]0=5gL−1. High efficiency of H2O2 consumption is obtained when MGNC is applied in the CWPO of 4‐NP solutions at pH=3, with TOC removals per unit of H2O2 decomposed (ɳH2O2) in the range 64–100%. In addition, the MGNC catalyst is also active at pH=6; in this case a pollutant mass removal of 2090mgg−1h−1 was obtained.Although MGNC partially deactivates through successive reusability cycles, the pollutant mass removal obtained at the end of the fourth cycle is still very high when 200mgL−1 4-NP solutions are considered (4808mg g−1h−1, representing only a ca. 4% decrease when compared to the first cycle). A higher deactivation of the MGNC catalyst is observed when 5gL−1 4-NP solutions are employed. Nevertheless, the pollutant mass removal obtained at the end of the third cycle is still high (551mgg−1h−1).

Graphene Nanocomposites with High Molecular Weight Poly(ε-caprolactone) Grafts: Controlled Synthesis and Accelerated Crystallization.

Grafting of high molecular weight polymers to graphitic nanoplatelets is a critical step toward the development of high performance graphene nanocomposites. However, designing such a grafting route has remained a major impediment. Herein, we report a "grafting to" synthetic pathway by which high molecular weight polymer, poly(ε-caprolactone) (PCL), is tethered, at high grafting density, to highly anisotropic graphitic nanoplatelets. The efficacy of this tethering route and the resultant structural arrangements within the composite are confirmed by neutron and X-ray scattering measurements in the melt and solution phase. In the semicrystalline state, X-ray analysis indicates that chain tethering onto the graphitic nanoplatelets results in conformational changes of the polymer chains, which enhance the nucleation process and aid formation of PCL crystallites. This is corroborated by the superior thermal properties of the composite, manifested in accelerated crystallization kinetics and a significant increase in the thermal degradation temperature. In principle, this synthesis route can be extended to a variety of high molecular weight polymers, which can open new avenues to solution-based processing of graphitic nanomaterials and the fabrication of complex 3D patterned graphitic nanocomposites.

Enhancement of plasma illumination characteristics via typical engineering of diamond–graphite nanocomposite films

Microstructural engineering of a diamond–graphite nanocomposite (DGC) with requisite properties in order to enhance the plasma illumination characteristics is being established via bias enhanced nucleation and growth of the nanocomposite material on silicon substrates using a microwave plasma (CH4/N2/H2) enhanced chemical vapor deposition method. Inspired by the concept of structure–property relationship, the microstructure of the DGC films is altered via varying the %H2 gas inclusion in the plasma. Consequently, the electrical conductivity, field emission (FE) properties and the plasma illumination characteristics of the DGC films are optimized depending upon their microstructure as well as morphological characteristics. The films grown using the optimum level of H2 (0.01%) encompass a diamond core with a needle-like morphology encased in layers of an sp2-bonded graphitic phase exhibiting an onion-like hierarchical structure forming a continuous network throughout the film and act as a matrix. The nano-sized diamond grains with needle-like morphology encased in graphitic layers is an exclusive choice of cathode material for plasma device applications as the Ar plasma of the DGC device can be triggered by a voltage as low as 310 V and possesses a better lifetime (14 h). The underlying mechanism of the microstructural engineering of the diamond–graphite nanocomposite is being proposed.

Electrocatalytic Properties of Vanadyl Complex in Graphite Nanocomposite and its Enhanced Electrochemical Catalysis Properties for Levodopa Oxidation

In the present paper, the use of a nanocomposite system based on bis(2-hydroxy-acetophenone)ethylenediimine vanadyl and carbon nanotubes prepared by a simple and rapid method for the catalysis oxidation of levodopa (LD) was described. Cyclic voltammetry was used to investigate the redox properties of this composite. A pair of well-defined quasi reversible redox peaks of vanadyl complex was obtained at the modified carbon paste electrode by direct electron transfer between the vanadyl complex and the electrode. Dramatically enhanced electrocatalytic activity was exemplified at the modified electrode, as an electrochemical sensor to study the electro oxidation of LD. At the optimum pH of 7.0, the oxidation of LD occurs at a potential about 300 mV less positive than that of an unmodified electrode. Based on differential pulse voltammetry, the oxidation of LD exhibited a dynamic range between 0.8 and 1000 µM and a detection limit (3σ) of 0.43 µM.

Direct Electron Transfer of Glucose Oxidase and Electrocatalysis of Glucose Based on Gold Nanoparticles/Electroactivated Graphite Nanocomposite

Direct Electron Transfer of Glucose Oxidase and Electrocatalysis of Glucose Based on Gold Nanoparticles/Electroactivated Graphite Nanocomposite