Porous Graphene Foam Research Articles

Mineral-Templated 3D Graphene Architectures for Energy-Efficient Electrodes.

3D graphene networks have shown extraordinary promise for high-performance electrochemical devices. Herein, the chemical vapor deposition synthesis of a highly porous 3D graphene foam (3D-GF) using naturally abundant calcined Iceland crystal as the template is reported. Intriguingly, the Iceland crystal transforms to CaO monolith with evenly distributed micro/meso/macropores through the releasing of CO2 at high temperature. Meanwhile, the hierarchical structure of the calcined template could be easily tuned under different calcination conditions. By precisely inheriting fine structure from the templates, the as-prepared 3D-GF possesses a tunable hierarchical porosity and low density. Thus, the hierarchical pores offer space for guest hybridization and provide an efficient pathway for ion/charge transport in typical energy conversion/storage systems. The 3D-GF skeleton electrode hybridized with Ni(OH)2 /Co(OH)2 through an optimal electrodeposition condition exhibits a high specific capacitance of 2922.2 F g-1 at a scan rate of 10 mV s-1 , and 2138.4 F g-1 at a discharge current density of 3.1 A g-1 . The hybrid 3D-GF symmetry supercapacitor shows a high energy density of 83.0 Wh kg-1 at a power density of 1011.3 W kg-1 and 31.4 Wh kg-1 at a high power density of 18 845.2 W kg-1 . The facile fabrication process enables the mass production of hierarchical porous 3D-GF for high-performance supercapacitors.

Scalable Self-Supported Graphene Foam for High-Performance Electrocatalytic Oxygen Evolution.

Developing efficient electrocatalysts consisting of earth-abundant elements for oxygen evolution reaction (OER) is crucial for energy devices and technologies. Herein, we report self-supported highly porous nitrogen-doped graphene foam synthesized through the electrochemical expansion of carbon-fiber paper and subsequent nitrogen plasma treatment. A thorough characterization, such as electron microscopy and synchrotron-based near-edge X-ray absorption fine structure, indicates the well-developed porous structures featuring homogeneously doped nitrogen heteroatoms. These merits ensure enriched active sites, an enlarged active surface area, and improved mass/electron transport within the continuous graphene framework, thus leading to an outstanding capability toward electrocatalyzing OER in alkaline media, even competitive with the state-of-the-art noble-/transition-metal and nonmetal electrocatalysts reported to date, from the perspectives of the sharp onset potential, a small Tafel slope, and remarkable durability. Furthermore, a rechargeable Zn-air battery with this self-supported electrocatalyst directly used as the air cathode renders a low charge/discharge overpotential and considerable life span. The finding herein suggests that a rational methodology to synthesize graphene-based materials can significantly enhance the oxygen electrocatalysis, thereby promoting the overall performance of the energy-related system.

Superelastic air-bubbled graphene foam monoliths as structural buffer for compressible high-capacity anode materials in lithium-ion batteries

Superelastic porous graphene foam monoliths (GFMs) constraining high-capacity anode electrode materials of GeO2 nanoparticles (NPs) have been prepared by simple solution-processed approach and studied in lithium-ion batteries (LIBs). Through an optimization of GeO2 content in the composite as 40% by weight, the GeO2-NPs@GFM-2 anode shows a constant compressive stress of 14kPa at a high strain of 90% for 200 cycles and simultaneously features a high specific capacity of 900mAhg−1 for at least 350 cycles. Based on its excellent flexibility and electrochemical properties, a compressible LIB is fabricated as a proof-of-concept when the GeO2-NPs@GFM-2 is directly used as the binder-free anode and paired with a lithium metal. This compressive half cell is capable to deliver pressure-sensible power output under a range of compressive strains up to 90%, setting a new benchmark in area-specific capacity (5.76mAhcm−2) for compressible/flexible LIBs with an energy density of 224.7Whkg−1. Furthermore, we demonstrate the universality of this approach by replacing GeO2 with Si nanoparticles to prepare compressible Si-NPs@GFM anode materials with high capacity and stability, validating GFMs asa general and efficient structure buffer for high-capacity anode materials in LIBs.

High-Capacity and Ultrafast Na-Ion Storage of a Self-Supported 3D Porous Antimony Persulfide-Graphene Foam Architecture.

The key challenge for high-performance sodium-ion batteries is the exploitation of appropriate electrode materials with a long cycling stability and high rate capability. Here, we report Sb2S5 nanoparticles (∼5 nm) uniformly encapsulated in three-dimensional (3D) porous graphene foam, which were fabricated by a facile hydrothermal coassembly strategy, as a high-performance anode material for sodium-ion batteries. The as-prepared composite can be directly used as electrodes without adding a binder or current collector, exhibiting outstanding electrochemical performance with a high reversible capacity (845 mA h g-1 at 0.1 A g-1), ultralong cycling life (91.6% capacity retention after 300 cycles at 0.2 A g-1), and exceptional rate capability (525 mA h g-1 at 10.0 A g-1). This is attributed to fast Na+ ion diffusion from the ultrasmall nanoparticles and excellent electric transport between the active material and 3D porous graphene, which also provide an effective strategy for anchoring the nanoparticles. Experimental results show that the Sb2S5 undergoes a reversible reaction of Sb2S5 + 16Na ↔ 5Na2S + 2Na3Sb during sodiation/desodiation. Moreover, a full cell with Na3(VO0.5)2(PO4)2F2/C cathode and the as-prepared composite anode was assembled, displaying high output voltage (∼2.2 V) with a stable capacity of 828 mA h g-1 for anode material (with 100 cycles at 0.1 A g-1), showing the potential for practical application.

Octahedron Fe3O4 particles supported on 3D MWCNT/graphene foam: In-situ method and application as a comprehensive microwave absorption material

In this work, we used in-situ method to directly prepare a novel structure consisting of well-distributed octahedron Fe3O4 particles, porous graphene foam (GF) and fibrous multiwalled carbon nanotube (MWCNT): started with an intense stir to anchor Fe3+ on the surfaces of graphene oxide and oxided MWCNT, followed by solvothermal reaction to synthesize 3D lightweight Fe3O4/MWCNT/GF hybrids with high performance microwave absorption (MA). The maximum Reflection Loss (RL) value of −35.30dB and 9.01GHz bandwidth with RL below −10dB detected with the thickness of 3.0mm are achieved by Fe3O4/MWCNT/GF with an ultralow bulk density of 5.0mgcm−3, of which the Specific Microwave Absorption Performance is much higher than most available MA materials reported. Impedance matching, high loss characteristic, interfacial polarization and polarization relaxation significantly improve MA properties, which serves as a guide for fabricating comprehensive MA materials enjoying numerous advantages of high RL value, broad bandwidth, low density and thin thickness.

Simple and Large-Scale Strategy to Prepare Flexible Graphene Tape Electrode.

A simple and large-scale strategy to prepare flexible graphene tape electrode (GTE) was proposed. The flexible GTE was prepared by a facile peeling method in which a piece of commercial graphite foil was first covered by a commercial acrylic transparent tape and then the transparent adhesive tape was quickly torn off from the graphite foil. Scanning electron microscopy results showed that some folded and wrinkled graphene layers stood up on the GTE surface to form three-dimensional (3D) porous graphene foam. The 3D porous flexible GTE was proposed as a novel supporting matrix to load Ni-Co nanoparticles (Ni-CoNPs) and glucose oxidase (GOD) as examples to test its applications for electrochemical glucose sensing. The Ni-CoNPs/GTE showed the linear range of 0.6 μM-0.26 mM and 1.360-5.464 mM with a detection limit of 0.16 μM. The GOD/AuNPs-CHIT/GTE had a linear range of 0.616-14.0 mM and a detection limit of 0.202 mM. These results were similar or superior to the printable electrodes by nanocarbon and electrodes modified with graphene, carbon nanotubes, or porous carbon materials, but the flexible GTE was more easier to prepare in large-scale and the 3D porous graphene foam were not easy to drop off from the tape because they were glued on acrylic transparent tape firmly. Therefore, the 3D porous flexible GTE should be promising candidates for electrochemical sensors and other electrochemical applications.

Well-Ordered Oxygen-Deficient CoMoO4 and Fe2O3 Nanoplate Arrays on 3D Graphene Foam: Toward Flexible Asymmetric Supercapacitors with Enhanced Capacitive Properties.

In this work, we report the development of well-ordered hydrogenated CoMoO4 (H-CoMoO4) and hydrogenated Fe2O3 (H-Fe2O3) nanoplate arrays on 3D graphene foam (GF) and explore their practice application as binder-free electrodes in assembling flexible all-solid-state asymmetric supercapacitor (ASC) devices. Our results show that the monolithic 3D porous GF prepared by solution casting method using Ni foam template possesses large surface area, superior electrical conductivity, and sufficient surface functional groups, which not only facilitate in situ growth of CoMoO4 and Fe2O3 nanoplates but also contribute the double-layer capacitance of the resultant supercapacitor. The well-ordered pseudocapacitive metal oxide nanoplate arrays standing up on 3D GF scaffold can provide efficient space and shorten the length for electrolyte diffusion from the outer to the inner region of the electrode material for Faradaic energy storage. Furthermore, one of our major findings is that the introduction of oxygen vacancies in CoMoO4 and Fe2O3 nanoplates by hydrogenation treatment can increase their electronic conductivity as well as improve their donor density and surface properties, which gives rise to a substantially improved electrochemical performance. Benefiting from the synergistic contributions of different components in the nanohybrid electrode, the resultant flexible ASC device with GF/H-CoMoO4 as the positive electrode and GF/H-Fe2O3 as the negative electrode achieves a wide operation voltage of 1.5 V and a maximum volumetric specific capacitance of 3.6 F cm-3, which is two times larger than that of the Ni/GF/CoMoO4//Ni/GF/Fe2O3 device (1.8 F cm-3), and the rate capability is up to 70% as the current density increases from 2 to 200 mA cm-3. Moreover, the Ni/GF/H-CoMoO4//Ni/GF/H-Fe2O3 device also exhibits a high energy density of 1.13 mWh cm-3 and a high power density of 150 mW cm-3, good mechanical flexibility with the decrease in capacitance of less than 4% after being bent inward to different angles and inward to 90° 200 times, and good cycling stability of 93.1% capacitance retention after 5000 cycles.

Laser induced white lighting of graphene foam

Laser induced white light emission was observed from porous graphene foam irradiated with a focused continuous wave beam of the infrared laser diode. It was found that the intensity of the emission increases exponentially with increasing laser power density, having a saturation level at ca. 1.5 W and being characterized by stable emission conditions. It was also observed that the white light emission is spatially confined to the focal point dimensions of the illuminating laser light. Several other features of the laser induced white light emission were also discussed. It was observed that the white light emission is highly dependent on the electric field intensity, allowing one to modulate the emission intensity. The electric field intensity ca. 0.5 V/μm was able to decrease the white light intensity by half. Origins of the laser-induced white light emission along with its characteristic features were discussed in terms of avalanche multiphoton ionization, inter-valence charge transfer and possible plasma build-up processes. It is shown that the laser-induced white light emission may be well utilized in new types of white light sources.

3D nitrogen-doped graphene foam with encapsulated germanium/nitrogen-doped graphene yolk-shell nanoarchitecture for high-performance flexible Li-ion battery

Flexible electrochemical energy storage devices have attracted extensive attention as promising power sources for the ever-growing field of flexible and wearable electronic products. However, the rational design of a novel electrode structure with a good flexibility, high capacity, fast charge–discharge rate and long cycling lifetimes remains a long-standing challenge for developing next-generation flexible energy-storage materials. Herein, we develop a facile and general approach to three-dimensional (3D) interconnected porous nitrogen-doped graphene foam with encapsulated Ge quantum dot/nitrogen-doped graphene yolk-shell nano architecture for high specific reversible capacity (1,220 mAh g−1), long cycling capability (over 96% reversible capacity retention from the second to 1,000 cycles) and ultra-high rate performance (over 800 mAh g−1 at 40 C). This work paves a way to develop the 3D interconnected graphene-based high-capacity electrode material systems, particularly those that suffer from huge volume expansion, for the future development of high-performance flexible energy storage systems.

Strong contribution ofin situgrown nanowires to enhance the thermostabilities and microwave absorption properties of porous graphene foams under different atmospheres

Enhanced thermostabilities and microwave absorption properties of porous graphene foams modified within situgrown nanowires under different atmospheres.

Graphene Nanoribbons on Highly Porous 3D Graphene for High-Capacity and Ultrastable Al-Ion Batteries.

Graphene nanoribbons on highly porous 3D graphene foam as the binder-free cathode for flexible Al-ion batteries exhibit low charge voltage, high capacity, excellent cycling ability (even after 10 000 cycles there is no capacity decay), and fast charging and slow discharging performance (the battery can be fully charged in 80 s and discharged in more than 3100 s).

Microfluidic Immuno-Biochip for Detection of Breast Cancer Biomarkers Using Hierarchical Composite of Porous Graphene and Titanium Dioxide Nanofibers

We report on a label-free microfluidic immunosensor with femtomolar sensitivity and high selectivity for early detection of epidermal growth factor receptor 2 (EGFR2 or ErbB2) proteins. This sensor utilizes a uniquely structured immunoelectrode made of porous hierarchical graphene foam (GF) modified with electrospun carbon-doped titanium dioxide nanofibers (nTiO2) as an electrochemical working electrode. Due to excellent biocompatibility, intrinsic surface defects, high reaction kinetics, and good stability for proteins, anatase nTiO2 are ideal for electrochemical sensor applications. The three-dimensional and porous features of GF allow nTiO2 to penetrate and attach to the surface of the GF by physical adsorption. Combining GF with functional nTiO2 yields high charge transfer resistance, large surface area, and porous access to the sensing surface by the analyte, resulting in new possibilities for the development of electrochemical immunosensors. Here, the enabling of EDC-NHS chemistry covalently immobilized the antibody of ErbB2 (anti-ErbB2) on the GF-nTiO2 composite. To obtain a compact sensor architecture, the composite working electrode was designed to hang above the gold counter electrode in a microfluidic channel. The sensor underwent differential pulse voltammetry and electrochemical impedance spectroscopy to quantify breast cancer biomarkers. The two methods had high sensitivities of 0.585 μA μM(-1) cm(-2) and 43.7 kΩ μM(-1) cm(-2) in a wide concentration range of target ErbB2 antigen from 1 × 10(-15) M (1.0 fM) to 0.1 × 10(-6) M (0.1 μM) and from 1 × 10(-13) M (0.1 pM) to 0.1 × 10(-6) M (0.1 μM), respectively. Utilization of the specific recognition element, i.e., anti-ErbB2, results in high specificity, even in the presence of identical members of the EGFR family of receptor tyrosine kinases, such as ErbB3 and ErbB4. Many promising applications in the field of electrochemical detection of chemical and biological species will derive from the integration of the porous GF-nTiO2 composite into microfluidic devices.

Rapid one-step synthesis of conductive and porous MnO2/graphene nanocomposite for high performance supercapacitors

Herein, we report a rapid and simultaneous synthesis of manganese oxide (MnO2) nanoparticles deposited on porous graphene foam by microwave-assisted method. The microwave irradiation enables simultaneously reduction and porous structure of graphene oxide and deposition of MnO2. As-synthesized MnO2/graphene nanocomposites are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The resultant MnO2/graphene nanocomposite electrodes exhibit as high as specific capacitance of 372Fg−1 at 0.5Ag−1, high rate capability (82% retention at 5Ag−1), and good long-term stability (98.5% retention during 3000cycles). This synthetic method could be applicable to the mass production of porous nanocomposites as energy storage materials for supercapacitors and lithium-ion batteries.

Hierarchical porous N-doped graphene foams with superior oxygen reduction reactivity for polymer electrolyte membrane fuel cells

Oxygen reduction reaction (ORR) is one of the most important processes in energy conversion and conservation such as in fuel cells, metal–air batteries and water-splitting devices. In this work, hierarchical porous N-doped graphene foams (HPGFs) functioned by a transition metal were successfully prepared using silica nanoparticles as a template. The introduction of a silica template and a transition metal provided HPGFs with a large specific surface area (918.7m2/g) and abundant active sites. By selecting proper nitrogen precursors (cyanamide, melamine and urea), HPGFs exhibit excellent ORR catalytic activity in 0.1M KOH with a high onset potential of 1.03V and a limiting current of ∼9mAcm−2, even better than that of commercial Pt/C catalysts at the same loading. Surprisingly, they show superior catalytic activity in an acidic medium with an onset potential of 0.81V and a limiting current reaching ∼10mAcm−2. Furthermore, the catalysts deliver good methanol tolerance and excellent long term durability after 5000 cycles of accelerated durability tests in both acidic and alkaline solutions, much better than that of a commercial Pt/C catalyst. Very inspiring cell performance was observed with HPGF-1 catalyst upon integration into a zinc–air battery. Our study presents an experimental realization of rationally designing a highly efficient ORR electrocatalyst for electrochemical energy conversion systems particular to fuel cells and metal–air batteries.

Microcellular graphene foam for improved broadband electromagnetic interference shielding

As reported, the foaming of layered graphene films into porous graphene foams could improve their performance for absorbents, catalysis and supercapacitors. Herein, to emphasize the impact of porous structure on electromagnetic interference (EMI) shielding, the direct comparison between graphene film (G-film) and corresponding microcellular graphene foam (G-foam) in terms of EMI shielding efficiency has been investigated in a broadband frequency range of 8.2–59.6 GHz, including X-band, Ku-band, K-band, Ka-band, and U-band. Consequently, despite the lower electrical conductivity of the as-prepared G-foam, it exhibited an improved average shielding effectiveness (SE) of ∼26.3 dB over the entire frequency range in comparison with that of G-film (∼20.1 dB). Implication of the results suggested that the foaming of layered graphene films into porous graphene foams could lead to an improvement in EMI shielding, which should be ascribed to the formation of improved internal multiple reflections at the large cell–matrix interfaces owing to the existence of microcellular structure in G-foam. We believe that this research would open up new opportunity for the development of graphene foams in the field of EMI shielding.

Green Synthesis of Porous Three-Dimensional Nitrogen-Doped Graphene Foam for Electrochemical Applications.

A facile and green approach was developed for the production of porous three-dimensional (3D) nitrogen-doped graphene with a foam structure. In comparison with conventional methods, this green approach uses environmental precursors in the preparation of graphene products. The resulting crystalline graphene foam product exhibited a uniform structure with large surface area. These appealing features render the prepared graphene foam product a prospective backbone for producing 3D charge-transport networks. The 3D graphene foam products were employed as the skeleton with an interconnected network for lithium-ion batteries. The lithium-ion batteries with the 3D porous foam structure exhibit superior cycling stability and good rate capability. There is no capacity loss after 800 cycles because the capacity stabilized for the first few cycles, and the lithium-ion batteries with 3D graphene foam showed a discharge capacity of 180 mA h g(-1) at a current density of 1000 mA g(-1). This superior cycling stability and good rate capability was ascribed to the 3D structure with an interconnected porous network and the nitrogen-doping strategy for improved conductive properties of graphene foam, which produces an efficient 3D charge-transport network. The configuration of this 3D transport network in lithium-ion cells not only can improve the electron-transport efficiency but also can suppress the volume effect during charge/discharge cycling. Besides, nitrogen doping could enhance the formation of chemical bonding between carbon and the nearby nitrogen atoms, which could accelerate the diffusion of lithium ions through the whole graphene network.

Copper Hydroxide Nanorods Decorated Porous Graphene Foam Electrodes for Non-enzymatic Glucose Sensing

For the first time, we are reporting the flower-like structure of copper hydroxide (Cu(OH)2) on freestanding 3D porous graphene foam (PGF). The Cu(OH)2 flowerlike structure fabricated via a simple and cost-effective chemical bath deposition (CBD) method. The CBD is a facile method which provide relatively inexpensive, simple and convenient route for large area deposition. The structural and morphological characterization of Cu(OH)2 reveals that, Cu(OH)2 flower-like structure, consists of nanorods (diameter ∼100nm), are well covered over the porous graphene framework. The flower-like structure of copper hydroxide on PGF provides large surface area (Effective surface area=9.44cm2), which leads to enhancement of electrochemical activity. Significantly, Cu(OH)2/PGF electrode showed the excellent sensitivity (up to 3.36mAmM−1cm−2), low detection limit (1.2μM), wide linear range (1.2μM ∼ 6mM). The Cu(OH)2/PGF exhibited good reproducibility and excellent selectivity toward usual interfering materials such as lactose, fructose, Acetaminophen, ascorbic acid, dopamine and urea in 1M KOH aqueous electrolyte.

Flame treatment of graphene oxides: cost-effective production of nanoporous graphene electrode for Lithium-ion batteries.

A facile production of highly porous graphene foam by using flame treatment of graphene oxide (GO) is proposed. Highly porous architectures with randomly distributed micro-crack and micro-slit were produced due to the high temperature induced ruinous reduction and rapid expansion of GO. Synchronously, abundant oxygen-containing groups (OCGs) on GO sheets could be effectively removed after flame treatment, which renders significantly increased conductivity to the resultant flame reduced GO (FR-GO). The synergistic effect of micro/nanostructuring and the OCGs removal makes FR-GO a promising candidate for electrode materials. Compared with chemically reduced GO (CR-GO), FR-GO delivers much higher specific capacity. It gives us some hints that flame treatment of graphene-based material is a smart strategy for cost-effective production of anode materials for commercial application.

Binder Free Graphene- Based Electrodes with Excellent Pseudocapacitive Performance

Owing to the high impact of the electrode’s architecture on the energy storage and power performance, it is very important to create optimum structures that provide efficient short paths for ion and charge transportation. Given excellent advantages of graphene, e.g. very high surface area, and excellent mechanical properties, this material is an ideal candidate to serve as an electrode matrix to stabilise electroactive materials for the charge-discharge process [1]. In this study, three dimensional (3D) binder free graphene composites have been synthesised by a two-step process, a chemical vapour deposition of the graphene followed by a chemical or electrochemical deposition of the redox counterpart. Pure graphene (GN), Polyaniline-graphene (PANI-GN), Polypyrrole-graphene (PPY-GN) and some other electrodes will be described in this work, and their electrochemical performance will be studied by using combined cyclic voltammetry, impedance spectroscopy and galvanostatic charge discharge techniques. Effects of the electrode dimensionality (3D vs 2D) and the binder on the performance will be investigated and explained. Figure 1 (a) is a SEM image of 3D graphene foam. The open porosity feature of the foam facilitates effectively the ion intercalation and extraction. Figures 1 (b) and 1 (c) are the cyclic voltammetry and Nyquist curve of the 3D PANI-GN. In contrast to the pure graphene and PANI, the composite electrode showed a much better electron conductivity and higher performance. The performance data have also revealed that using the porous 3D graphene foam as the electrode matrix and eliminating the insulating binder from the electrode structures result in an improved conductivity of the electrode, with excellent cycle life. The improved electrochemical performance efficiency is due to the dual energy storage mechanism and the synergetic effect of the graphene foam and redox counterpart. Reference: 1. Chabi, S., et al., Ideal Three‐Dimensional Electrode Structures for Electrochemical Energy Storage. Advanced Materials, 2014. 26(15): p. 2440-2445. Figure caption Figure 1: SEM image of graphene foam (a) cyclic voltammetry of 3D PANI-GN (b) and Nyquist curve of 3D PANI-GN in 0.5 M H2SO4. Figure 1

High temperature dependence of thermal transport in graphene foam

In contrast to the decreased thermal property of carbon materials with temperature according to the Umklapp phonon scattering theory, highly porous free-standing graphene foam (GF) exhibits an abnormal characteristic that its thermal property increases with temperature above room temperature. In this work, the temperature dependence of thermal properties of free-standing GF is investigated by using the transient electro-thermal technique. Significant increase for thermal conductivity and thermal diffusivity from ∼0.3 to 1.5 W m−1 K−1 and ∼4 × 10−5 to ∼2 × 10−4 m2 s−1 respectively is observed with temperature from 310 K to 440 K for three GF samples. The quantitative analysis based on a physical model for porous media of Schuetz confirms that the thermal conductance across graphene contacts rather than the heat conductance inside graphene dominates thermal transport of our GFs. The thermal expansion effect at an elevated temperature makes the highly porous structure much tighter is responsible for the reduction in thermal contact resistance. Besides, the radiation heat exchange inside the pores of GFs improves the thermal transport at high temperatures. Since free-standing GF has great potential for being used as supercapacitor and battery electrode where the working temperature is always above room temperature, this finding is beneficial for thermal design of GF-based energy applications.