Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

https://hal.archives-ouvertes.fr/hal-02417326/document

Materials for electrochemical capacitors

4.3. Reaction Mechanism 2373 4.4. Asymmetric Synthesis 2374 4.5. Outlook 2374 5. Alternating Polymerization of Oxiranes and CO2 2374 5.1. Reaction Outlines 2374 5.2. Catalyst 2376 5.3. Asymmetric Polymerization 2377 5.4. Immobilized Catalysts 2377 6. Synthesis of Urea and Urethane Derivatives 2378 7. Synthesis of Carboxylic Acid 2379 8. Synthesis of Esters and Lactones 2380 9. Synthesis of Isocyanates 2382 10. Hydrogenation and Hydroformylation, and Alcohol Homologation 2382

Transformation of carbon dioxide.

Background Since at least 400 C.E., when the Mayans first used layered clays to make dyes, people have been harnessing the properties of layered materials. This gradually developed into scientific research, leading to the elucidation of the laminar structure of layered materials, detailed understanding of their properties, and eventually experiments to exfoliate or delaminate them into individual, atomically thin nanosheets. This culminated in the discovery of graphene, resulting in a new explosion of interest in two-dimensional materials. Layered materials consist of two-dimensional platelets weakly stacked to form three-dimensional structures. The archetypal example is graphite, which consists of stacked graphene monolayers. However, there are many others: from MoS 2 and layered clays to more exotic examples such as MoO 3 , GaTe, and Bi 2 Se 3 . These materials display a wide range of electronic, optical, mechanical, and electrochemical properties. Over the past decade, a number of methods have been developed to exfoliate layered materials in order to produce monolayer nanosheets. Such exfoliation creates extremely high-aspect-ratio nanosheets with enormous surface area, which are ideal for applications that require surface activity. More importantly, however, the two-dimensional confinement of electrons upon exfoliation leads to unprecedented optical and electrical properties. Liquid exfoliation of layered crystals allows the production of suspensions of two-dimensional nanosheets, which can be formed into a range of structures. (A) MoS 2 powder. (B) WS 2 dispersed in surfactant solution. (C) An exfoliated MoS 2 nanosheet. (D) A hybrid material consisting of WS 2 nanosheets embedded in a network of carbon nanotubes. Advances An important advance has been the discovery that layered crystals can be exfoliated in liquids. There are a number of methods to do this that involve oxidation, ion intercalation/exchange, or surface passivation by solvents. However, all result in liquid dispersions containing large quantities of nanosheets. This brings considerable advantages: Liquid exfoliation allows the formation of thin films and composites, is potentially scaleable, and may facilitate processing by using standard technologies such as reel-to-reel manufacturing. Although much work has focused on liquid exfoliation of graphene, such processes have also been demonstrated for a host of other materials, including MoS 2 and related structures, layered oxides, and clays. The resultant liquid dispersions have been formed into films, hybrids, and composites for a range of applications. Outlook There is little doubt that the main advances are in the future. Multifunctional composites based on metal and polymer matrices will be developed that will result in enhanced mechanical, electrical, and barrier properties. Applications in energy generation and storage will abound, with layered materials appearing as electrodes or active elements in devices such as displays, solar cells, and batteries. Particularly important will be the use of MoS 2 for water splitting and metal oxides as hydrogen evolution catalysts. In addition, two-dimensional materials will find important roles in printed electronics as dielectrics, optoelectronic devices, and transistors. To achieve this, much needs to be done. Production rates need to be increased dramatically, the degree of exfoliation improved, and methods to control nanosheet properties developed. The range of layered materials that can be exfoliated must be expanded, even as methods for chemical modification must be developed. Success in these areas will lead to a family of materials that will dominate nanomaterials science in the 21st century.

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Liquid Exfoliation of Layered Materials

Due to their abundance, high strength and stiffness, low weight and biodegradability, nano-scale cellulose fiber materials (e.g., microfibrillated cellulose and bacterial cellulose) serve as promising candidates for bio-nanocomposite production. Such new high-value materials are the subject of continuing research and are commercially interesting in terms of new products from the pulp and paper industry and the agricultural sector. Cellulose nanofibers can be extracted from various plant sources and, although the mechanical separation of plant fibers into smaller elementary constituents has typically required high energy input, chemical and/or enzymatic fiber pre-treatments have been developed to overcome this problem. A challenge associated with using nanocellulose in composites is the lack of compatibility with hydrophobic polymers and various chemical modification methods have been explored in order to address this hurdle. This review summarizes progress in nanocellulose preparation with a particular focus on microfibrillated cellulose and also discusses recent developments in bio-nanocomposite fabrication based on nanocellulose.

Microfibrillated cellulose and new nanocomposite materials: a review

Hyperbranched polymers: from synthesis to applications

Formation of an amylose-polyester inclusion complex by means of phosphorylase-catalyzed enzymatic polymerization of α-d-glucose 1-phosphate monomer in the presence of poly(∈-caprolactone)

Facile production of chitin from crab shells using ionic liquid and citric acid.

In this paper, we describe a new polymerization manner termed as "vine-twining polymerization" to produce amylose-polymer inclusion complexes. The polymerization was achieved by an enzymatic polymerization of alpha-D-glucose-1-phosphate monomer catalyzed by phosphorylase in the presence of polyTHF as a guest polymer. The structure of the product was determined by X-ray powder diffraction and (1)H NMR measurements to be the inclusion complex. The formation process of the inclusion complexes during the polymerization was also evaluated. Furthermore, the formation of the inclusion complexes by this polymerization method by using polyTHFs with various M(n)s and end groups, as well as other polyethers as the guest polymers, was examined.

Vine-twining polymerization: amylose twines around polyethers to form amylose-polyether inclusion complexes.

In this paper, we describe a detailed study on preparation and characterizations of functional ionic liquid-gels and hydrogels of xanthan gum. When the 9.1–50.0 wt% solutions of xanthan gum in an ionic liquid, 1-butyl-3-methylimidazolium chloride (BMIMCl), were left standing at room temperature, they completely turned into gel forms. The obtained xanthan gum/BMIMCl gels showed good mechanical properties and thermally induced shape-memory effect. The formation of specific association of BMIMCl in the gels, which was constructed on the basis of the regularly ordered interaction of the imidazolium counter cations of xanthan gum with other BMIMCl molecules because of the rigidity of its main-chain, was suggested as a reason for the production of such unique gels. Furthermore, the 9.1 wt% xanthan gum/BMIMCl gel was converted into the xanthan gum hydrogel by soaking it in water, which showed good elasticity under compression. Moreover, ion-exchanged xanthan gum hydrogels with Na+, Ca2+, and Fe3+ were prepared. The ion-exchanged hydrogel with Ca2+ exhibited better mechanical properties both under compressive and tensile modes compared with the hydrogel with Na+, probably due to ionic cross-linking. However, the hydrogel with Fe3+ showed hard and brittle natures. Moreover, the reversible swelling–shrinking behaviors of the ion-exchanged hydrogels with Na+ and Ca2+ were clearly demonstrated to reveal their salt concentration-induced responsive properties.

Preparation and characterizations of functional ionic liquid-gel and hydrogel materials of xanthan gum

This paper reports the preparation of inclusion complexes of amylose with synthetic polymers by means of enzymatic polymerization of α-D-glucose 1-phosphate monomer (Glc-1-P). The synthetic polymers, employed as the guests, are poly(e-caprolactone), poly(δ-valerolactone), and poly(ester-ether), containing ester groups in the main chains. The formation of the inclusion complexes was carried out by the enzymatic polymerization of Glc-1-P catalyzed by phosphorylase in the presence of the guest polymers.

Jun-ichi Kadokawa

Papers

Formation of an amylose-polyester inclusion complex by means of phosphorylase-catalyzed enzymatic polymerization of α-d-glucose 1-phosphate monomer in the presence of poly(∈-caprolactone)

Facile production of chitin from crab shells using ionic liquid and citric acid.

Vine-twining polymerization: amylose twines around polyethers to form amylose-polyether inclusion complexes.

Preparation and characterizations of functional ionic liquid-gel and hydrogel materials of xanthan gum

Preparation of Inclusion Complexes between Amylose and Ester‐Containing Polymers by Means of Vine‐Twining Polymerization