Three-dimensional Graphene Foam Research Articles

Energy Harvesting from the Mixture of Water and Ethanol Flowing through Three-Dimensional Graphene Foam

In this work, the electrical conductance and induced current of three-dimensional graphene foam (GF) are investigated when the mixture of water and ethanol flows through it. When different mixing ratios of ethanol:water (ethanol:water = 25:75, 50:50, 75:25, and 100:0 by volume) flow through the GFs, their electrical conductance is almost the same as that of the original GF. Meanwhile, the induced current can be obtained when the mixture flows through the GF. The direction of induced current depends on that of the flow of the mixture, the value of induced current has no dependence on the flow direction of the mixture but is closely related to the flow velocity and polarity of the mixture. The mechanism of the induced electricity is discussed, which is attributed to the coupling of flowing solution molecules with the charge carriers of graphene at the solid/liquid interface. These results indicate that GFs have a bright potential application in realizing the self-powered function of nano/micro electromechanical systems (N/MEMS) in many special environments.

Porous CoO nanostructures grown on three-dimension graphene foams for supercapacitors electrodes

Abstract Three-dimensional graphene foams with good conductivity, light weight and chemical stability were produced by chemical vapor deposition. Then porous CoO nanowalls were deposited on graphene foam by a simple hydrothermal process and subsequent thermal treatment. This hybrid structures possessing large surface area in which the CoO nanowalls are separated by graphene foam with robust adhesion can directly serve as supercapacitor electrode including current collector without the need of any other binder materials and conductive agents. Electrochemical tests manifest a high specific capacitance of 231.87 F/g scaled to the mass of CoO (139.47 F/g for total mass of electrodes) at 1 A/g current, good rate capability and excellent cycling performance of >98% capacitance retention over 1000 cycles at 7 A/g current. The high conductivity, light weight and rational architectures, which provide fast electron pathway and the low diffusion resistance of ions, are responsible for the high performance of the electrodes.

Dynamic surface wettability of three-dimensional graphene foam

In this work, three-dimensional graphene foams (GFs) are synthesized and characterized by scanning electron microscope (SEM) and Raman spectroscopy. The SEM images indicate that after the growth of graphene, the graphene covers the surface of nickel (Ni) foam uniformly. Raman spectra show that the percentages of monolayer, bilayer, trilayer, and multilayer graphenes are ∼ 58%, ∼ 32%, ∼ 8%, and ∼ 2%, respectively. The contact angle (CA) (∼ 12°) of water droplet (3 μL) on GF is found to be larger than that on Ni foam (∼ 107°), indicating that graphenes have changed the surface wettability of the Ni foam. Meanwhile, the dynamic characteristics of CA of water droplet on GF are different from those on Ni foam. The mechanisms for different behaviors are discussed, which are attributed to volatilization and seepage of water droplets.

Enhanced Supercapacitive Performance of Chemically Grown Cobalt–Nickel Hydroxides on Three-Dimensional Graphene Foam Electrodes

Chemical growth of mixed cobalt-nickel hydroxides (CoxNi1-x(OH)2), decorated on graphene foam (GF) with desirable three-dimensional (3D) interconnected porous structure as electrode and its potential energy storage application is discussed. The nanostructured CoxNi1-x(OH)2 films with different Ni:Co (x) compositions on GF are prepared by using the chemical bath deposition (CBD) method. The structural studies (X-ray diffraction and X-ray photoelectron spectroscopy) of electrodes confirm crystalline nature of CoxNi1-x(OH)2/GF and crystal structure consists of Ni(OH)2 and Co(OH)2. The morphological properties reveal that nanorods of Co(OH)2 reduce in size with increases in nickel content and are converted into Ni(OH)2 nanoparticles. The electrochemical performance reveals that the Co0.66Ni0.33(OH)2/GF electrode has maximum specific capacitance of ∼1847 F g(-1) in 1 M KOH within a potential window 0 to 0.5 V vs Ag/AgCl at a discharge current density of 5 A g(-1). The superior pseudoelectrochemical properties of cobalt and nickel are combined and synergistically reinforced with high surface area offered by a conducting, porous 3D graphene framework, which stimulates effective utilization of redox characteristics and communally improves electrochemical performance with charge transport and storage.

Power generation from water flowing through three-dimensional graphene foam

Three-dimensional graphene foam (GF) is synthesized by CVD. When water flows through GF, electricity is induced. The direction of the induced current is dominated by the flow direction of water; the value of induced current is related to the flow velocity but has no relationship with the flow direction and external bias voltage.

Free-standing three-dimensional graphene and polyaniline nanowire arrays hybrid foams for high-performance flexible and lightweight supercapacitors

Free-standing three-dimensional hierarchical porous reduced graphene oxide foam (RGO-F) was first fabricated by a “dipping and dry” method using nickel foam as a template.

Preparation of multifunctional microchannel-network graphene foams

A three-dimensional microchannel-network graphene foams with high performance supercapacitors and excellent adsorption function was fabricated.

High-Yield Assembly of Graphene Field-Effect Transistors under a Non-Uniform Electric Field

Intriguing properties of graphene such as high carrier mobility, large surface area, and high thermal conductivity, and superior optical transmittance make it very promising for a lot of applications including field-effect transistors (FETs), chemical sensors, solar-cells and light-emitting diodes, 1‐4 where a large quantity production of high quality graphene is very important for its implementation. Graphene canbeobtainedbymanymethodsincludingthemechanical/chemical exfoliation, epitaxial growth on SiC or Cu foil, reduction of graphene oxide (GO). 5 Among them, reduced graphene oxide (rGO) has been intensivelyinvestigatedbecausealargeamountofgrapheneflakescan be produced. 6‐8 Also, a method for high-yield production of graphene dispersions has been demonstrated by exfoliating the graphite in organic solvents. 8,9 However, the properties of rGO are still not as good as those of the pristine graphene due to the functional groups, insufficient reduction, and point defects created during the chemical processes. 10,11 In our experiments, graphene flakes were obtained by sonicating three-dimensional (3-D) graphene foam because a large amount of graphene flakes with good conductivity and carrier mobility can be produced without complex chemical processes. 3-D graphene foam, which is grown by the chemical vapor deposition (CVD) method, is a fascinating material due to its superior properties such as large surface-to-volume ratio, high conductivity and carrier mobility. Therefore, the graphene flakes which are obtained from 3-D graphene foam have a great potential for graphene-based electronic

Powder, Paper and Foam of Few‐Layer Graphene Prepared in High Yield by Electrochemical Intercalation Exfoliation of Expanded Graphite

A facile and high-yield approach to the preparation of few-layer graphene (FLG) by electrochemical intercalation exfoliation (EIE) of expanded graphite in sulfuric acid electrolyte is reported. Stage-1 H2SO4-graphite intercalation compound is used as a key intermediate in EIE to realize the efficient exfoliation. The yield of the FLG sheets (<7 layers) with large lateral sizes (tens of microns) is more than 75% relative to the total amount of starting expanded graphite. A low degree of oxygen functionalization existing in the prepared FLG flakes enables them to disperse effectively, which contributes to the film-forming characteristics of the FLG flakes. These electrochemically exfoliated FLG flakes are integrated into several kinds of macroscopic graphene structures. Flexible and freestanding graphene papers made of the FLG flakes retain excellent conductivity (≈24,500 S m(-1)). Three-dimensional (3D) graphene foams with light weight are fabricated from the FLG flakes by the use of Ni foams as self-sacrifice templates. Furthermore, 3D graphene/Ni foams without any binders, which are used as supercapacitor electrodes in aqueous electrolyte, provide the specific capacitance of 113.2 F g(-1) at a current density of 0.5 A g(-1), retaining 90% capacitance after 1000 cycles.

Three-Dimensional Graphene Foam Supported Fe3O4 Lithium Battery Anodes with Long Cycle Life and High Rate Capability

Fe3O4 has long been regarded as a promising anode material for lithium ion battery due to its high theoretical capacity, earth abundance, low cost, and nontoxic properties. However, up to now no effective and scalable method has been realized to overcome the bottleneck of poor cyclability and low rate capability. In this article, we report a bottom-up strategy assisted by atomic layer deposition to graft bicontinuous mesoporous nanostructure Fe3O4 onto three-dimensional graphene foams and directly use the composite as the lithium ion battery anode. This electrode exhibits high reversible capacity and fast charging and discharging capability. A high capacity of 785 mAh/g is achieved at 1C rate and is maintained without decay up to 500 cycles. Moreover, the rate of up to 60C is also demonstrated, rendering a fast discharge potential. To our knowledge, this is the best reported rate performance for Fe3O4 in lithium ion battery to date.

Direct Synthesis and Characterization of Three-Dimensional Graphene Foam

Three-dimensional graphene foam (GF) is synthesized by chemical vapor deposition (CVD) at ~1000°C under ambient pressure. Then it is characterized by scanning electron microscopy (SEM) and laser Raman spectroscopy, the results indicate that GF has changed the surface morphology of Ni foam, and ~ 98% of the GF are fewlayer. At last, the surface wettability of GF is investigated, which shows that it is hydrophobic. The special three-dimensional structure and excellent properties of GF make it a candidate for a range of applications.

Exceptional thermal interface properties of a three-dimensional graphene foam

We have uncovered some unusual thermal interface properties of a three-dimensional, flexible and interconnected graphene foam (GF). The thermal interfacial resistance of GF at Si–Al interface is as low as 0.04cm2KW−1, which is one order of magnitude lower than conventional thermal grease and thermal paste-based thermal interfacial material (TIM). The thermal contact resistance was found to dominate the overall interfacial resistance of GF-based TIM, in as much as the bulk thermal conductivity of GF is rather high. The contact pressure-dependent thermal interfacial resistance of GF exhibits an asymptotic behavior, which converges into a plateau value at an ultralow contact pressure (∼0.1MPa). Significantly, the GF-based TIM has shown a superior performance to vertically aligned carbon nanotubes currently held as the gold standard (at least ∼75% improvement in thermal interfacial resistance at Si–Al interface), thus providing a strong candidate for the next generation of high-performance carbon-based TIM.

Three-dimensional graphene foam as a biocompatible and conductive scaffold for neural stem cells

Neural stem cell (NSC) based therapy provides a promising approach for neural regeneration. For the success of NSC clinical application, a scaffold is required to provide three-dimensional (3D) cell growth microenvironments and appropriate synergistic cell guidance cues. Here, we report the first utilization of graphene foam, a 3D porous structure, as a novel scaffold for NSCs in vitro. It was found that three-dimensional graphene foams (3D-GFs) can not only support NSC growth, but also keep cell at an active proliferation state with upregulation of Ki67 expression than that of two-dimensional graphene films. Meanwhile, phenotypic analysis indicated that 3D-GFs can enhance the NSC differentiation towards astrocytes and especially neurons. Furthermore, a good electrical coupling of 3D-GFs with differentiated NSCs for efficient electrical stimulation was observed. Our findings implicate 3D-GFs could offer a powerful platform for NSC research, neural tissue engineering and neural prostheses.

A hierarchically structured composite of Mn3O4/3D graphene foam for flexible nonenzymatic biosensors.

We report a novel composite material of hierarchically structured Mn3O4 grown on three-dimensional graphene foam (3DGF). This hierarchical Mn3O4/3DGF composite was fabricated as a flexible and freestanding biosensor for nonenzymatic determination of glucose and H2O2, significant analytes in health care and food industry. The Mn3O4/3DGF-based biosensor achieved high sensitivity, large linear range and low detection limit for the detection of both analytes, due to the synergistic effects of the two materials, which combines the high electrocatalytic activity of the nanostructured Mn3O4 network, and high conductivity and large surface area of 3DGF. This enzymeless biosensor also exhibited excellent performance for real-time detection of glucose and H2O2 in serum and food samples.

Freestanding three-dimensional graphene foam gives rise to beneficial electrochemical signatures within non-aqueous media

Freestanding three-dimensional (3D) graphene foam has been fabricated via a Chemical Vapour Deposition (CVD) methodology which has a macroscopic structure with microscopic (graphene) features. The 3D graphene macrostructure is characterised with SEM, EDX, XPS and Raman spectroscopy and is found to comprise pristine graphene (O/C of 0.05) which is in the range of mono- to few-layered graphene sheets and is thus termed quasi-graphene. This unique 3D graphene foam is electrochemically explored in both aqueous and non-aqueous solutions and compared to a freestanding 3D reticulated vitreous carbon (RVC) foam alternative. In aqueous solutions, the 3D graphene foam exhibits poor voltammetric responses. Contact angle measurements reveal the 3D graphene to exhibit a value of 120° representing quasi-super-hydrophobicity. Consequently the freestanding 3D graphene foam is found to give rise to significantly improved voltammetric signatures in non-aqueous media (ionic liquids) over that of a freestanding 3D RVC alternative. The 3D graphene foam provides a promising and beneficial architecture over 2D pristine graphene due to its ease of use and macroscopic/microscopic structure, which will have wide implementation in the field of electrochemistry.

Three-dimensional graphene foams promote osteogenic differentiation of human mesenchymal stem cells

Graphene is a novel material whose application in biomedical sciences has only begun to be realized. In the present study, we have employed three-dimensional graphene foams as culture substrates for human mesenchymal stem cells and provide evidence that these materials can maintain stem cell viability and promote osteogenic differentiation.

3D Graphene Foam as a Monolithic and Macroporous Carbon Electrode for Electrochemical Sensing

Graphene, a single-atom-thick monolayer of sp(2) carbon atoms perfectly arranged in a honeycomb lattice, is an emerging sensing material because of its extraordinary properties, such as exceptionally high specific surface area, electrical conductivity, and electrochemical potential window. In this study, we demonstrate that three-dimensional (3D), macroporous, highly conductive, and monolithic graphene foam synthesized by chemical vapor deposition represents a novel architecture for electrochemical electrodes. Being employed as an electrochemical sensor for detection of dopamine, 3D graphene electrode exhibits remarkable sensitivity (619.6 μA mM(-1) cm(-2)) and lower detection limit (25 nM at a signal-to-noise ratio of 5.6), with linear response up to ∼25 μM. And the oxidation peak of dopamine can be easily distinguished from that of uric acid - a common interferent to dopamine detection. We envision that the graphene foam provides a promising platform for the development of electrochemical sensors as well as other applications, such as energy storage and conversion.

3D Graphene–Cobalt Oxide Electrode for High-Performance Supercapacitor and Enzymeless Glucose Detection

Using a simple hydrothermal procedure, cobalt oxide (Co(3)O(4)) nanowires were in situ synthesized on three-dimensional (3D) graphene foam grown by chemical vapor deposition. The structure and morphology of the resulting 3D graphene/Co(3)O(4) composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The 3D graphene/Co(3)O(4) composite was used as the monolithic free-standing electrode for supercapacitor application and for enzymeless electrochemical detection of glucose. We demonstrate that it is capable of delivering high specific capacitance of ∼1100 F g(-1) at a current density of 10 A g(-1) with excellent cycling stability, and it can detect glucose with a ultrahigh sensitivity of 3.39 mA mM(-1) cm(-2) and a remarkable lower detection limit of <25 nM (S/N = 8.5).

High Sensitivity Gas Detection Using a Macroscopic Three-Dimensional Graphene Foam Network

Nanostructures are known to be exquisitely sensitive to the chemical environment and offer ultra-high sensitivity for gas-sensing. However, the fabrication and operation of devices that use individual nanostructures for sensing is complex, expensive and suffers from poor reliability due to contamination and large variability from sample-to-sample. By contrast, conventional solid-state and conducting-polymer sensors offer excellent reliability but suffer from reduced sensitivity at room-temperature. Here we report a macro graphene foam-like three-dimensional network which combines the best of both worlds. The walls of the foam are comprised of few-layer graphene sheets resulting in high sensitivity; we demonstrate parts-per-million level detection of NH3 and NO2 in air at room-temperature. Further, the foam is a mechanically robust and flexible macro-scale network that is easy to contact (without Lithography) and can rival the durability and affordability of traditional sensors. Moreover, Joule-heating expels chemisorbed molecules from the foam's surface leading to fully-reversible and low-power operation.