The chemistry of graphene oxide is discussed in this critical review Particular emphasis is directed toward the synthesis of graphene oxide, as well as its structure Graphene oxide as a substrate for a variety of chemical transformations, including its reduction to graphene-like materials, is also discussed This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material (91 references)

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The chemistry of graphene oxide

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.

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Graphene and Graphene Oxide: Synthesis, Properties, and Applications

Electrochemical energy storage technology is based on devices capable of exhibiting high energy density (batteries) or high power density (electrochemical capacitors). There is a growing need, for current and near-future applications, where both high energy and high power densities are required in the same material. Pseudocapacitance, a faradaic process involving surface or near surface redox reactions, offers a means of achieving high energy density at high charge–discharge rates. Here, we focus on the pseudocapacitive properties of transition metal oxides. First, we introduce pseudocapacitance and describe its electrochemical features. Then, we review the most relevant pseudocapacitive materials in aqueous and non-aqueous electrolytes. The major challenges for pseudocapacitive materials along with a future outlook are detailed at the end.

https://hal.archives-ouvertes.fr/hal-01171774/document

Pseudocapacitive oxide materials for high-rate electrochemical energy storage

Every few years, a new material with unique properties emerges and fascinates the scientific community, typical recent examples being high-temperature superconductors and carbon nanotubes. Graphene is the latest sensation with unusual properties, such as half-integer quantum Hall effect and ballistic electron transport. This two-dimensional material which is the parent of all graphitic carbon forms is strictly expected to comprise a single layer, but there is considerable interest in investigating two-layer and few-layer graphenes as well. Synthesis and characterization of graphenes pose challenges, but there has been considerable progress in the last year or so. Herein, we present the status of graphene research which includes aspects related to synthesis, characterization, structure, and properties.

Graphene: The New Two-Dimensional Nanomaterial

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).

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Graphene-based composites

The invention relates to a composite material of monolayer graphite and polymers, as well as a preparation method thereof. The composite material takes the monolayer graphite and the polymers as raw materials which are well mixed, wherein the weight portions of the raw materials are: 0.1 to 100 portions of the monolayer graphite and 0.1 to 100 portions of the polymers or other matrix materials. The preparation method is characterized by utilizing the excellent conductivity and large length-diameter ratio of the monolayer graphite to prepare conducting composite materials. Micro analysis proves that the monolayer graphite evenly disperses in the matrix materials, and a conducting network can be formed only by adding a small amount of the monolayer graphite, so as to obtain the conducting composite material with a plurality of forms. The composite material simultaneously has high strength and modulus, and is used in building, mechanical, aerospace and other special environments. In addition, as the monolayer graphite has excellent heat-conducting property, the composite material has the advantages of heat dissipation convenience and the like, and is expected to be applied to the precision instrument, microelectronic and other fields.

Mono-layer graphite and polymer compound material and preparation and application thereof

An auxetic cellular structure as a universal design for enhanced piezoresistive sensitivity

Strong chemical interactions between the oxygen-containing functional groups on graphene oxide (GO) sheets and the ions of divalent metals were exploited for the softening of hard water. GO membranes were prepared and evaluated for their ability to absorb Ca2+ and Mg2+ ions. These GO membranes can effectively absorb Ca2+ ions from hard water; a 1 mg GO membrane can remove as much as 0.05 mg Ca2+ ions. These GO membranes can be regenerated and used repeatedly.

The use of graphene oxide membranes for the softening of hard water

DOI: 10.1002/aenm.202003771 of chip operating temperature to avoid overheating is an important guarantee to maintain the normal operation of electronic devices. The traditional refrigeration technology based on the vapor compression cycle is difficult to meet the refrigeration requirements of highly integrated microelectronic devices due to the existence of the compressor.[2] Moreover, the extensive use of chlorofluorocarbons and other refrigerants bring about new problems such as ozone layer destruction and greenhouse effect, and the relatively low coefficient of performance (COP) also limits its application in cooling systems for electronic devices.[3] Therefore, it is necessary to develop a new type of refrigeration technology that can be miniaturized, high efficiency, and environment-friendly. Solid-state refrigeration technology as an alternative has the properties of no heat transfer media of liquid refrigerants, rapid cooling, safety, and environmental protection.[2] The existing solid-state refrigeration technologies include thermoelectric, magnetocaloric, elastocaloric, and electrocaloric (EC) refrigeration technologies. Thermoelectric refrigerators fabricated by bismuth antimony telluride ceramics have a variety of applications.[4–6] However, their COP is lower than that of vapor compression coolers.[7] Magnetocaloric and elastocaloric coolers require a strong magnetic field and high load to achieve the entropy change of the refrigeration material, respectively, which limits their miniaturization.[8,9] The EC cooling technology has been considered to be a more effective alternative and can also be used to realize compact and low-profile devices. The EC effect is the change of internal polarization state caused by the change of external electric field under adiabatic condition, which leads to the change of entropy and temperature.[10] The current generated in the cooling process is quite small and energy consumption is very low due to the insulation of materials. Therefore, compared with other solid-state refrigeration technologies, EC refrigeration is not only environmentally friendly and efficient, but also has an important application prospect in the temperature regulation of microelectronic devices. Current EC materials of relaxor ferroelectric ceramics have promising performance. However, EC refrigeration devices based on ferroelectric ceramics are limited by the inherent Compact solid-state refrigeration systems that offer a high specific cooling power and a high coefficient of performance (COP) are desirable in a wide range of applications where efficient and localized heat transfer is required. Here, a double-unit electrocaloric (EC) polymer-based refrigeration device with high intrinsic thermodynamic efficiency is demonstrated using a flexible EC polymer film with improved performance by doping plasticizer and an electrostatic actuation mechanism. The double-unit refrigeration device achieves a large temperature span of 4.8 K, which is 71% higher than that of the single-unit device. A specific cooling power of 3.6 W g−1 and a maximum COP of 8.3 for the cooling device are produced. The surface temperature of a central processing unit (CPU) cooled by an active EC device is 22.4 K lower than that of the CPU cooled in air. The highly efficient and compact EC cooling device demonstrated here not only leapfrogs the performance of existing solid-state cooling technologies, but also brings solid state cooling closer to reality for a variety of practical applications that require compact or mechanically flexible refrigeration.

Electrostatic Actuating Double‐Unit Electrocaloric Cooling Device with High Efficiency

Polymer nanocomposite dielectrics possess exceptional electric properties that are absent in the pristine dielectric polymers. The matrix/particle interface in polymer nanocomposite dielectrics is suggested to play decisive roles on the bulk material performance. Herein, we present a critical overview of recent research advances and important insights in understanding the matrix/particle interfacial characteristics in polymer nanocomposite dielectrics. The primary experimental strategies and state-of-the-art characterization techniques for resolving the local property-structure correlation of the matrix/particle interface are dissected in depth, with a focus on the characterization capabilities of each strategy or technique that other approaches cannot compete with. Limitations to each of the experimental strategy are evaluated as well. In the last section of this Review, we summarize and compare the three experimental strategies from multiple aspects and point out their advantages and disadvantages, critical issues, and possible experimental schemes to be established. Finally, the authors' personal viewpoints regarding the challenges of the existing experimental strategies are presented, and potential directions for the interface study are proposed for future research.

Jiajie Liang

Papers

Mono-layer graphite and polymer compound material and preparation and application thereof

An auxetic cellular structure as a universal design for enhanced piezoresistive sensitivity

The use of graphene oxide membranes for the softening of hard water

Electrostatic Actuating Double‐Unit Electrocaloric Cooling Device with High Efficiency

Polymer Nanocomposite Dielectrics: Understanding the Matrix/Particle Interface.