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.

/pdf/graphene-and-graphene-oxide-synthesis-properties-and-2q80uaujok.pdf

Graphene and Graphene Oxide: Synthesis, Properties, and Applications

Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp 2 -bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.

/pdf/carbon-based-supercapacitors-produced-by-activation-of-1wqrpq3luo.pdf

Carbon-based Supercapacitors Produced by Activation of Graphene

Although electrochemical capacitors (ECs), also known as supercapacitors or ultracapacitors, charge and discharge faster than batteries, they are still limited by low energy densities and slow rate capabilities. We used a standard LightScribe DVD optical drive to do the direct laser reduction of graphite oxide films to graphene. The produced films are mechanically robust, show high electrical conductivity (1738 siemens per meter) and specific surface area (1520 square meters per gram), and can thus be used directly as EC electrodes without the need for binders or current collectors, as is the case for conventional ECs. Devices made with these electrodes exhibit ultrahigh energy density values in different electrolytes while maintaining the high power density and excellent cycle stability of ECs. Moreover, these ECs maintain excellent electrochemical attributes under high mechanical stress and thus hold promise for high-power, flexible electronics.

/pdf/laser-scribing-of-high-performance-and-flexible-graphene-2b5d3mxb2h.pdf

Laser Scribing of High-Performance and Flexible Graphene-Based Electrochemical Capacitors

Graphene has attracted tremendous research interest in recent years, owing to its exceptional properties. The scaled-up and reliable production of graphene derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO), offers a wide range of possibilities to synthesize graphene-based functional materials for various applications. This critical review presents and discusses the current development of graphene-based composites. After introduction of the synthesis methods for graphene and its derivatives as well as their properties, we focus on the description of various methods to synthesize graphene-based composites, especially those with functional polymers and inorganic nanostructures. Particular emphasis is placed on strategies for the optimization of composite properties. Lastly, the advantages of graphene-based composites in applications such as the Li-ion batteries, supercapacitors, fuel cells, photovoltaic devices, photocatalysis, as well as Raman enhancement are described (279 references).

/pdf/graphene-based-composites-540z2xd3o0.pdf

Graphene-based composites

Graphene based materials: Past, present and future

Hierarchical porous carbon microspheres derived from porous starch for use in high-rate electrochemical double-layer capacitors

High performance transition metal oxide composite cathode for low temperature solid oxide fuel cells

To address the issues of low electrical conductivity, sluggish lithiation kinetics and dramatic volume variation in Fe3O4 anodes of lithium ion battery, herein, a double carbon-confined three-dimensional (3D) nanocomposite architecture was synthesized by an electrostatically assisted self-assembly strategy. In the constructed architecture, the ultrafine Fe3O4 subunits (∼10 nm) self-organize to form nanospheres (NSs) that are fully coated by amorphous carbon (AC), formatting core–shell structural Fe3O4/AC NSs. By further encapsulation by reduced graphene oxide (rGO) layers, a constructed 3D architecture was built as dual carbon-confined rGO/Fe3O4/AC. Such structure restrains the adverse reaction of the electrolyte, improves the electronic conductivity and buffers the mechanical stress of the entire electrode, thus performing excellent long-term cycling stability (99.4% capacity retention after 465 cycles relevant to the second cycle at 5 A g–1). Kinetic analysis reveals that a dual lithium storage mechanis...

N-Doped Dual Carbon-Confined 3D Architecture rGO/Fe3O4/AC Nanocomposite for High-Performance Lithium-Ion Batteries

Nanoporous carbon was prepared by the oxidation of coal tar pitch in a mixture of HNO3–H2SO4 and simultaneous KOH activation with carbonisation at 800 °C. Its capacitive performance was studied by constructing symmetric and asymmetric capacitors. In symmetric supercapacitors in which a 6 M KOH solution was used as an aqueous electrolyte, the synthesised nanoporous carbon possessed a capacitance of more than 160 F g−1 when operating at a current density of up to 100 A g−1. The present process via oxidation from the pitch produced minute particles with a size of approximately 250 nm × 10 nm and abundant oxygen content, which could be efficiently activated using relatively small amounts of KOH. The use of KOH at a concentration of 1.5 times that of the carbon precursor resulted in a high BET surface area of 2600 m2 g−1 and a micro- and meso-pore network that was most likely to be highly connected. The asymmetric capacitor of the synthesised nanoporous carbon and hollow MnO2 microcubes could be charged and discharged reversibly within a potential range of 0.0–2.0 V when a 1 M Na2SO4 solution was used as the aqueous electrolyte, delivering an energy density of 30 W h kg−1 at a power density of 0.15 kW kg−1 and preserving an energy density of 13 W h kg−1 even at a higher power density of 30 kW kg−1.

Mingming Chen

Papers

Hierarchical porous carbon microspheres derived from porous starch for use in high-rate electrochemical double-layer capacitors

High performance transition metal oxide composite cathode for low temperature solid oxide fuel cells

N-Doped Dual Carbon-Confined 3D Architecture rGO/Fe3O4/AC Nanocomposite for High-Performance Lithium-Ion Batteries

Nanoporous carbon synthesised with coal tar pitch and its capacitive performance

Potential low-temperature application and hybrid-ionic conducting property of ceria-carbonate composite electrolytes for solid oxide fuel cells