The surface area of a single graphene sheet is 2630 m2/g, substantially higher than values derived from BET surface area measurements of activated carbons used in current electrochemical double layer ...capacitors. Our group has pioneered a new carbon material that we call chemically modified graphene (CMG). CMG materials are made from 1-atom thick sheets of carbon, functionalized as needed, and here we demonstrate in an ultracapacitor cell their performance. Specific capacitances of 135 and 99 F/g in aqueous and organic electrolytes, respectively, have been measured. In addition, high electrical conductivity gives these materials consistently good performance over a wide range of voltage scan rates. These encouraging results illustrate the exciting potential for high performance, electrical energy storage devices based on this new class of carbon material.
Graphene-like nanosheets have been synthesized by the reduction of a colloidal suspension of exfoliated graphite oxide. The morphology and structure of the graphene powder sample was studied using ...scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The graphene sheets are found to be in a highly agglomerated state, with many wrinkles. The sample has a BET surface area of 640
m
2/g as measured by nitrogen adsorption at 77
K. Hydrogen adsorption–desorption isotherms were measured in the temperature range 77–298
K and at pressures of up to 10
bar. This gives hydrogen adsorption capacities of about 1.2 wt.% and 0.1 wt.% at 77
K and 298
K, respectively. The isosteric heat of adsorption is in the range of 5.9–4
kJ/mol, indicating a favourable interaction between hydrogen and surface of the graphene sheets. The estimated room temperature H
2 uptake capacity of 0.72 wt.% at 100
bar and the isosteric heat of adsorption of our sample are comparable to those of high surface area activated carbons, however significantly better than the recently reported values for graphene and a range of other carbon and nanoporous materials; single and multi walled carbon nanotubes, nanofibers, graphites and zeolites.
Carbon nanomaterials are perceived to be ideally suited candidates for high‐end energy applications, owing to their unparalleled advantages including superior electric and thermal conductivity, ...excellent mechanical properties, and high specific surface areas. It has been demonstrated through several research contributions that the electrochemical performance of carbon nanomaterials significantly depends upon their versatile electronic structures and microstructures. These can be precisely tailored by rational defect engineering, heteroatom doping, heterostructure coupling, and pore fabrication, which largely affect the intrinsic nature of active sites and facilitate the ion/electron transfer. Herein, the recent progress in tailoring carbon nanostructures toward high‐end electrocatalysis and supercapacitor applications is summarized, with an emphasis on synthesis strategies, advanced characterizations, and specific elucidation of structure–performance relationship. The challenges and opportunities for the rational design and detection of variously tailored carbon nanomaterials that can further improve the fundamental understanding and practical applications in the field of energy storage and conversion are also discussed.
The recent advances in tailoring carbon nanomaterials from the aspects of defect engineering, heteroatom doping, heterostructure coupling, and microstructure modulation are briefly summarized. An overview of the synthesis strategies and advanced characterization methods is presented, with an emphasis on the elucidation of the structure–performance relationship for electrocatalysis and supercapacitors. Finally, possible solutions to the challenges that still remain unresolved in the mentioned energy‐related applications are discussed.
Reduced graphene oxide/Fe2O3 composite was prepared using a facile two-step synthesis by homogeneous precipitation and subsequent reduction of the G-O with hydrazine under microwave irradiation to ...yield reduced graphene oxide (RG-O) platelets decorated with Fe2O3 nanoparticles. As an anode material for Li-ion batteries, the RG-O/Fe2O3 composite exhibited discharge and charge capacities of 1693 and 1227 mAh/g, respectively, normalized to the mass of Fe2O3 in the composite (and ∼1355 and 982 mAh/g, respectively, based on the total mass of the composite), with good cycling performance and rate capability. Characterization shows that the Fe2O3 nanoparticles are uniformly distributed on the surface of the RG-O platelets in the composite. The total specific capacity of RG-O/Fe2O3 is higher than the sum of pure RG-O and nanoparticle Fe2O3, indicating a positive synergistic effect of RG-O and Fe2O3 on the improvement of electrochemical performance. The synthesis approach presents a promising route for a large-scale production of RG-O platelet/metal oxide nanoparticle composites as electrode materials for Li-ion batteries.
There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and ...potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.
The synthesis, properties, and applications of graphene and graphene oxide‐based materials are reviewed in this article. Graphene can be synthesized by chemical vapor deposition (e.g., on Cu, Figure a) and graphene oxide is a precursor for other graphene‐based materials (e.g., “paper”, Figure b). Graphene shows exceptional physical properties (e.g., high thermal conductivity, as measured by using the device in Figure c) and may be used in future high‐performance electronic devices (e.g., single electron transistor, Figure d), among other possible applications.
Lithium metal is an attractive anode material for rechargeable batteries because of its high theoretical specific capacity of 3860 mA h g−1 and the lowest negative electrochemical potential of −3.040 ...V versus standard hydrogen electrode. Despite extensive research efforts on tackling the safety concern raised by Li dendrites, inhibited Li dendrite growth is accompanied with decreased areal capacity and Li utilization, which are still lower than expectation for practical use. A scaffold made of covalently connected graphite microtubes is reported, which provides a firm and conductive framework with moderate specific surface area to accommodate Li metal for anodes of Li batteries. The anode presents an areal capacity of 10 mA h cm−2 (practical gravimetric capacity of 913 mA h g−1) at a current density of 10 mA cm−2, with Li utilization of 91%, Coulombic efficiencies of ≈97%, and long lifespan of up to 3000 h. The analysis of structure evolution during charge/discharge shows inhibited lithium dendrite growth and a reversible electrode volume change of ≈9%. It is suggested that an optimized microstructure with moderate electrode/electrolyte interface area is critical to accommodate volume change and inhibit the risks of irreversible Li consumption by side reactions and Li dendrite growth for high‐performance Li‐metal anodes.
A scaffold made of covalently connected graphite microtubes provides a firm and conductive framework with moderate specific surface area to accommodate Li metal, yielding an anode for Li batteries capable of delivering an areal capacity of 10 mA h cm−2 at a current density of 10 mA cm−2, with Coulombic efficiencies of ≈97%, Li utilization of 91%, and long lifespan of up to 3000 h.
A hierarchical porous carbon is fabricated by introducing a polyurethane sponge to a template graphene oxide into a 3D interconnected structure, while KOH activation generates abundant micropores in ...its backbone. Supercapacitors assembled with this carbon achieve a high energy density of 89 W h kg−1 (64 W h L−1) and outstanding power density due to the shortened ion‐transport distance in 3D.
Developing multicomponent transition-metal phosphides has become an efficient way to improve the capacitive performance of single-component transition-metal phosphides. However, reports on quaternary ...phosphides for supercapacitor applications are still scarce. Here, we report high capacity and energy density of Zn–Ni–Co–P quaternary phosphide nanowire arrays on nickel foam (ZNCP-NF) composed of highly conductive metal-rich phosphides as an advanced binder-free electrode in aqueous asymmetric supercapacitors. In a three-electrode system using the new electrode, a high specific capacity of 1111 C g–1 was obtained at a current density of 10 A g–1. Analysis of this aqueous asymmetric supercapacitor with ZNCP-NF as the positive electrode and commercial activated carbon as the negative electrode reveals a high energy density (37.59 Wh kg–1 at a power density of 856.52 W kg–1) and an outstanding cycling performance (capacity retention of 92.68% after 10 000 cycles at 2 A g–1). Our results open a path for a new design of advanced electrode material for supercapacitors.
Graphene monolayer has been grown by chemical vapor deposition on copper and then suspended over a hole. By measuring the laser heating and monitoring the Raman G peak, we obtain room-temperature ...thermal conductivity and interface conductance of (370 + 650/−320) W/m K and (28 + 16/−9.2) MW/m2 K for the supported graphene. The thermal conductivity of the suspended graphene exceeds (2500 + 1100/−1050) W/m K near 350 K and becomes (1400 + 500/−480) W/m K at about 500 K.
Abstract
Graphene is considered a promising material for industrial application based on the intensive laboratory-scale research in the fields of physics, chemistry, materials science and ...engineering, and biology over the last decade. Many companies have thus started to pursue graphene materials on a scale of tons (for the flake material) or hundreds of thousands of square meters (for the film material) for industrial applications. Though the graphene industry is still in its early stages, very significant progress in mass production and certain industrial applications has become obvious. In this report, we aim to give a brief review of the mass production of graphene materials for some industrial applications and summarize some features or challenges for graphene in the marketplace.
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