Three-dimensional Graphene Nanosheets Research Articles

Enhanced stability of a three-dimensional graphene nanosheets networks modified asphalt mixture

To date, several concepts have been developed to enhance the mechanical and service life of asphalt pavements. Additives such as graphene, carbon nanotubes, carbon fibers and carbon black are used in the hot mix asphalt (HMA) or the asphalt binder (i.e., bitumen) for higher resistance to permanent deformations such as rutting, and transverse thermal cracking due to increased traffic volumes, vehicle mass and axle loads. In this study, graphene nanosheets (GNs) were used as potential modifier of bitumen binder in the HMA. The objective of this work is to investigate the impact of GNs modified bitumen on the Marshall stability and flow of the asphalt mixture using laboratory-compacted samples. The X-ray diffraction (XRD) study revealed a diffraction peak of GNs (002) at 2θ =26.5° along the bitumen’s γ-band and 10-band, which confirm a successful dispersion of GNs into bitumen binder. Furthermore, morphological analysis showed formation of a three dimensional (3d) interconnected networks of GNs between the bitumen micro-structures which could act as bridges for increased flexural strength of the binder. The Marshall stability and flow test results indicate that the mechanical properties of asphalt mixture were influenced by the addition of GNs to the bitumen binder. At 5% by weight of GNs modified bitumen (GNs-B), the compacted hot-mix Asphalt sample showed a higher Marshall stability of 11.7 kN recording 13.6% enhancement in comparison with the asphalt mixture with pure bitumen (P-B). In addition, when GNs-B was used, a lower flow of 1.4 mm was recorded which is desirable to prevent rutting and other forms of failure in asphalt pavements. This study underlines that adding GNs into asphalt binders such as bitumen could play a key role in enhancing the performance of asphalt pavements, which in turn extends their service life and saves maintenance expenses.

Preparation of wavy three-dimensional graphene-like biochar and its adsorption mechanism of embedded separation for dimethoate

In this study, graphene-like biochar (IZBC) was prepared by pyrolysis of wheat straw in the presence of catalyst and activator. The formation of graphene in IZBC could be divided into three stages: shell core generation, carburization, and carbon precipitation. When the pyrolysis temperatures were in the ranges of 500–600 ℃, 600–700 ℃, 700–800 ℃ and 800–900 ℃, 17%, 32%, 13% and 38% of graphene were produced, respectively. The contribution ratios of graphene by FeCl3, ZnCl2 and HCl were 64%, 23% and 13%, respectively. Moreover, IZBC was filled with porous wavy three-dimensional graphene nanosheets that enabled self-aggregation to be effectively prevented, which was superior to the striped two-dimensional structure. The adsorption of IZBC for dimethoate was a spontaneous exothermic reaction with the adsorption capacity of 980 μmol/g, which was consistent with the pseudo-second-order and intraparticle diffusion models. The adsorption was inhibited by coexisting cations, anions, and humic acid in water. Dimethoate was adsorbed on graphene through embedded separation, with pore filling, cation-π and electrostatic attraction as the key driving forces. In addition, the adsorbed saturated IZBC could be effectively regenerated for many times by 2 mol/L HCl solution.

Tribological and Friction-Induced Vibration Behaviors of Inorganic Fullerene-Like Tungsten Disulfide and Three-Dimensional Graphene as Lubricant Additives

Abstract Friction and friction-induced vibration have a great impact on the service life of mechanical systems. In this study, the tribological performances and vibration characteristics of three-dimensional graphene nanosheets (3D GNS), inorganic fullerene-like tungsten disulfide (IF-WS2), and their mixed additive lubricants are investigated by experiments. The results show that IF-WS2/3D GNS (1:1) mixed additive can improve the friction-reduction and anti-wear of base oil by 62.9% and 71.4%, respectively. In terms of vibration damping, the mixed additive has an extremely strong dampening effect on vibration acceleration in all directions, especially in the Z-axis direction, where the amplitude is reduced by about 90%. The vibration damping should be attributed to the filling effect of 3D GNS and IF-WS2, which greatly flattens the friction surface, thus reducing the number of collision micro-bumps in the relative movement of the friction pair and suppressing the vibration. In addition, the unique ductile deformation of IF-WS2 makes the two additives form a flexible ball-bearing damper between the two contact surfaces, thus greatly reducing the vibration.

3D-graphene nanosheets as efficient antibacterial agent

This paper reports on the antibacterial performance (AP) of free standing three-dimensional graphene nanosheets (3D-GNS) with a high density of graphene edges, prepared by the electrochemical exfoliation of graphite. The 3D-GNS exhibits an outstanding AP against E. coli, reaching ∼100% at a low concentration of 40 mg/L after 4 h of exposure, while the AP of the graphite mother is measure to be ∼10% under same conditions. Electron microscopy reveals that sharp nanoedges in 3D-GNS can efficiently cut bacterial cells into fragments.

Shielded SnS2/SnS heterostructures on three-dimensional graphene framework for high-rate and stable sodium-ion storage

Tin sulfides are promising anode materials for sodium-ion batteries (SIBs) for their high theoretical capacity and fast kinetics for Na storage. However, the severe volume expansion and intrinsically low charge conductivity fundamentally compromise their electrochemical performance. Addressing at the issue, SnS2/SnS heterostructures are decorated on three-dimensional graphene nanosheets (3D GNS) framework, which is then shielded with a nanocarbon layer. In this nanocomposite, the SnS2/SnS p-n heterostructures induce an internal electric field on the heterointerfaces to promote the charge transfer inside the material, which effectively ensures the rate capability of the material. Moreover, the 3D GNS provides a porous conductive network to accelerate the long-range transport of electron further enhancing its rate performance. Meanwhile, the dual-carbon structure would alleviate the volume expansion of SnS2/SnS during cycling, ensuring improved stability. The integration of these merits leads to excellent battery performance for the material, including high reversible capacity, rate capability, and cycling stability. This concept of simultaneously enhancing the ionic, electronic, and mass conductivity as well as the structural stability by combining heterogeneous structures, 3D conductive networks, and protective shields can further shed light on not only SIB materials but also other energy storage materials or devices.

Three-dimensional graphene nanosheet films towards high performance solid lubricants

Graphene nanosheet films (GNSF) show great potential as solid lubricants. They, however, usually suffer from short lifetime and low load capability, limiting their further engineering application. In this work, we try to address these crucial challenges, for the first time, by inducing a unique three-dimensional microstructure into the GNSF. The as-prepared three-dimensional graphene nanosheet films (3D-GNSF) are composed of many crumpled and partially standing graphene nanosheets (GNS) that overlap with each other and form a three-dimensional interconnected network. The morphology, composition and structure of the 3D-GNSF are investigated in detail using scanning electron microscope, X-ray diffractometer, transmission electron microscope and X-ray photoelectron spectroscopy to deduce their possible formation mechanism. Tribological tests are conducted in air as a function of contact pressure that is up to about 1GPa. The results suggest it is the unique architecture of the 3D-GNSF that quickly produces a compact and stable sliding interface consisting of GNS against GNS, enabling 3D-GNSF as promising solid lubricants with low friction, excellent anti-wear ability, good durability and high load capability.

Surface-modified three-dimensional graphene nanosheets as a stationary phase for chromatographic separation of chiral drugs

Carbon-based stationary phases for chromatographic separation have been commercially available since the 1980s. Porous graphitic carbon liquid chromatography columns are known to be highly resistant to aggressive mobile phases and extreme pH values of solvents and eluents, an important advantage compared to conventional silica-based alternatives. In our work, we demonstrate a new variant of carbon-based stationary phases for liquid chromatography, specifically developed for chiral separation. Mesoporous three-dimensional graphene nanosheets (3D GNS), functionalized with tetracyanoethylene oxide (TCNEO) and (S)-(+)-2-pyrrolidinemethanol, demonstrate pharmaceutical-grade chiral separation of model ibuprofen and thalidomide racemic mixtures when used as Chiral Stationary Phases (CSPs), with performance parameters comparable to currently commercially available CSPs. Simple covalent attachment of functionalization groups to the surface of mesoporous three-dimensional graphene nanosheets makes these carbon-based CSPs chemically stable and up to an order of magnitude less expensive than standard silica-based analogues.

Flower-like MoS2 supported on three-dimensional graphene aerogels as high-performance anode materials for sodium-ion batteries

Flower-like MoS2 supported on three-dimensional graphene aerogel (MoS2/GA) composite has been prepared by a facile hydrothermal method followed by subsequent heat-treatment process. Each of MoS2 microflowers is surrounded by the three-dimensional graphene nanosheets. The MoS2/GA composite is applied as an anode material of sodium-ion batteries (SIBs) and it exhibits high initial discharge/charge capacities of 562.7 and 460 mAh g−1 at a current density of 0.1 A g−1 and good cycling performance (348.6 mAh g−1 after 30 cycles at 0.1 A g−1). The good Na+ storage properties of the MoS2/GA composite could be attributed to the unique structure which flower-like MoS2 are homogeneously and tightly decorated on the surface of three-dimensional graphene aerogel. Our results demonstrate that as-prepared MoS2/GA composite has a great potential prospect as anodes for SIBs.

Three-dimensional graphene nanosheet doped with gold nanoparticles as electrochemical DNA biosensor for bacterial detection

Corrosion induced by sulfate-reducing bacteria (SRB) occurs in a wide variety of industry sectors. It is urgent to develop effective techniques for convenient detection of SRB in service environments and early diagnosis of the potential of microbial corrosion. Herein, a novel electrochemical DNA biosensor based on 3-dimensional graphene (3D G) hierarchical structure functionalized with Au nanoparticles (Au NPs) is developed, enabling detection of the dissimilatory sulfite reductase (DsrAB) gene from SRB with a good sensitivity and reliability, and proper selectivity. Various surface analysis techniques are used to characterize the morphology and composition of the 3D G-Au NP nanocomposite, and cyclic voltammetry is used to measure the electrochemical response of the nanocomposite biosensor to hybridization of a target DNA (TD). The improved performance of the developed biosensor is attributed to the large surface/volume ratio and good conductivity of the 3D G-Au NP hierarchical structure. Under optimized conditions, the biosensor shows a high sensitivity, with the detection limit up to 9.41×10−15 M of the TD. Moreover, the biosensor successfully detects the DsrAB DNA in the fluid collected from an oilfield, and shows an improved detection limit than both gel electrophoresis and the quantitative reverse transcription polymerase chain reaction methods.

Three-dimensional graphene nanosheets as cathode catalysts in standard and supercapacitive microbial fuel cell.

Three-dimensional graphene nanosheets (3D-GNS) were used as cathode catalysts for microbial fuel cells (MFCs) operating in neutral conditions. 3D-GNS catalysts showed high performance towards oxygen electroreduction in neutral media with high current densities and low hydrogen peroxide generation compared to activated carbon (AC). 3D-GNS was incorporated into air-breathing cathodes based on AC with three different loadings (2, 6 and 10 mgcm−2). Performances in MFCs showed that 3D-GNS had the highest performances with power densities of 2.059 ± 0.003 Wm-2, 1.855 ± 0.007 Wm-2 and 1.503 ± 0.005 Wm-2 for loading of 10, 6 and 2 mgcm−2 respectively. Plain AC had the lowest performances (1.017 ± 0.009 Wm-2). The different cathodes were also investigated in supercapacitive MFCs (SC-MFCs). The addition of 3D-GNS decreased the ohmic losses by 14–25%. The decrease in ohmic losses allowed the SC-MFC with 3D-GNS (loading 10 mgcm−2) to have the maximum power (Pmax) of 5.746 ± 0.186 Wm-2. At 5 mA, the SC-MFC featured an “apparent” capacitive response that increased from 0.027 ± 0.007 F with AC to 0.213 ± 0.026 F with 3D-GNS (loading 2 mgcm−2) and further to 1.817 ± 0.040 F with 3D-GNS (loading 10 mgcm−2).

Three-dimensional graphene nanosheets supported by NiO/Si-MCP as electrode materials for high-performance supercapacitors

A three-dimensional (3D) graphene/NiO/Si-microchannel (MCP) composite electrode is synthesized by the conventional microelectronic machining process and electrochemical exfoliation technology for electrochemical capacitors. SEM, AFM, and Raman scattering are used to investigate the morphology and structure, and electrochemical characterization reveals that the 3D graphene/NiO/Si-MCP has a high specific capacitance of 833 Fg−1 at a current density of 5 Ag−1 in 6 mol L−1 KOH. Moreover, good cycling performance with 92% capacitance retention after 1000 cycles is observed indicating the novel electrode has large potential in high-performance supercapacitors.

Performance of Pd/Graphene Nanocomposite Catalysts in H2/O2 Anion Exchange Membrane Fuel Cells

With the recent developments of high-performance anion-exchange membranes (AEM), there has been an increased interest towards studying various electrochemical reactions such as ethanol electrooxidation, hydrogen oxidation reactions and oxygen reduction reactions in AEM fuel cells (AEMFC). This increased attention has been attributed to the faster electro oxidation kinetics, increased stability and lower poisoning of the catalysts in alkaline media. And since AEMFCs are not limited to platinum - unlike in proton exchange membrane fuel cells (PEMFCs) with highly acidic environments - intensive efforts towards developing alternatives such as palladium (Pd) and Pd-based alloys are currently underway.1 , 2 Various studies have shown the enhanced stability and higher activities of Pd-based catalysts compared to Pt in alkaline medium using potentiodynamic and potentiostatic techniques. However, there are only a limited number of studies that have investigated the performance of Pd-based electrocatalysts in AEMFCs. Also, majority of these studies have demonstrated relatively low performances in AEMFCs, mainly due the complications associated with forming the triple-phase boundary (TPB) structure in the membrane layer, where reactions are taking place in the electrolyte, gaseous fuel and electrode interface. The density of the TPB, along with the intrinsic activities of the catalysts can play an important role in determining the overall performance of AEMFCs. Moreover, Pd-based are usually synthesized using surfactants, organic stabilizers or reducing agents, that can get adsorbed onto the surface of Pd and inhibit ionomer-catalyst-fuel interactions in the TPB. To mitigate the limitations associated with TPB structure and subpar catalyst activities, macroporous three-dimensional Graphene nanosheet (3D-GNS) supports with controlled morphologies and porosities were fabricated by utilizing silica sacrificial templates.3 The sacrificial templates were then etched to leave a network of porous channels within its matrix, and utilized as supports for Pd nanoparticles. The porous structure of these highly graphitized 3D-GNS supports can facilitate mass-transport kinetics by enabling the ionomer and polymer electrolyte getting the reactants to get catalyzed by Pd nanoparticles. Also, to enhance ionomer-nanoparticle interactions, the Pd nanoparticles of an average size of 3-5 nm were synthesized using a previously established surfactant-free soft alcohol reduction method.4 In this study, anion exchange catalyst-coated membranes (CCMs) were prepared using Pd nanoparticles supported on both commercial carbon blacks (Vulcan) and 3D-Graphene supports as both cathode and anode catalyst in H2/O2 fed AEMFCs. The Pd catalyst inks were prepared by mixing the dispersed Pd-catalyst in an optimized solution of isopropyl alcohol and quaternary ammonium-functionalized AS4 ionomer. The inks were then applied onto an anion exchange membrane (A201, Tokuyama) with an active area of 5 cm2. The CCMs was then hydrated in 0.5 M KOH for 24 hours, followed by rinsing in de-ionized water for 24 hours. It was then sandwiched between gas diffusion layers and annealed with gaskets by pressing under 500 psi for 5 minutes. The cell was then assembled and activated by operating at 0.3V at 60ºC for 10 minutes under humidified O2 and H2, followed by the measuring the polarization curves. Preliminary results show that Pd nanoparticles synthesized using surfactant-free method SARM and deposited on commercial carbon supports have and OCV of 0.95 V and a peak power output of 200 mWcm-2. These results already show the promising potential of using surfactant-free non-alloyed monometallic Pd nanoparticles. Further tests will also be performed to show the effect of porous 3D-Graphene supports towards modifying the TPB interphase and its effects on MEA performance in both Ethanol/O2 and H2/O2 fed AEMFCs. The results from this study will not only contribute towards the development of Pt-free oxidative and reductive electrocatalysts, but also lead to further advancements in AEMFC technology that will enable it to operate with other fuels such as methanol and hydrazine.

Three-dimensional graphene nanosheets loaded with Si nanoparticles by in situ reduction of SiO2 for lithium ion batteries

The utilization of silicon based anode materials for lithium-ion batteries is hindered by their low intrinsic electronic conductivity, unstable cycling behavior and complex scalable synthesis of nano silicon. Herein, we propose a step-by-step synthesis route to fabricate three-dimensional (3D) graphene nanosheets loaded with Si nanoparticles for lithium ion batteries. For this purpose, silica is deposited on the surface of graphene oxide firstly through a hydrolysis process. After that, a further in situ magnesiothermic reduction is carried out. In an attempt to fine-tune the mass ratio of graphene and Si, different amount of tetraethyl orthosilicate was applied during the hydrolysis process. The 3D graphene as supporting sheets could not only provide position for the firmly attached Si nanoparticles but also enhance the electronic conductivity and accommodate large volume changes of Si nanoparticles. As a result, the properly designed Si@G-2 exhibits an excellent electrochemical performance and rate capability, showing capacity retention of 90.9% after 100 cycles at 1Ag−1 and specific capacity around 500mAhg−1 at 20Ag−1. This synthetic route demonstrates an efficient method for the controlled synthesis of graphene nanosheets loaded with Si nanoparticles with excellent electrochemical performance, which may facilitate its commercial applications.

Three-dimensional graphene nanosheet encrusted carbon micropillar arrays for electrochemical sensing

Integrating graphene onto three-dimensional (3D) microelectrodes is a plausible technique to significantly improve the sensitivity of electrochemical devices. However, the construction of graphene coated 3D microstructures has been a considerable challenge. In this paper, we present a simple methodology using electrostatic spray deposition (ESD) to conformally coat graphene onto 3D carbon micropillars that are fabricated by pyrolyzing finely patterned photoresist. During the ESD, changes in the critical parameters such as substrate temperature, deposition time, and nozzle to substrate distance have shown a significant effect on the morphology of the deposited graphene film. The amperometric response of graphene/carbon micropillar electrode arrays exhibited higher electrochemical activity, improved charge transfer and a linear response towards H(2)O(2) detection between 250 μM and 5.5 mM. The ESD technique, with the flexibility of integrating a wide variety of functional nanomaterials onto complex 3D microstructures, is attractive in the field of electrochemistry and biotechnology.