Carbon nanostructured

Jurewicz K, Frackowiak E, Beguin F. Towards the mechanism of electrochemical hydrogen storage in nanostructured carbon materials. Appl. Phys. A 2003 in press. 

MECHANISMS OF REVERSIBLE AND IRREVERSIBLE INSERTION IN NANOSTRUCTURED CARBONS USED FOR Li-ION BATTERIES... 

In this paper, new highlights are proposed to interpret the reversible and irreversible capacities of nanostructured carbons in lithium batteries. A proportional dependence between the irreversible capacity and the active surface area (ASA) of carbon materials will be demonstrated, showing the ASA concept more universal than any of the other parameters which were previously considered. In-situ 7Li NMR will be also presented as a means to... 

Although some nanostructured carbons are able to store reversibly higher amounts of lithium than graphite [2], they generally demonstrate a high hysteresis (see for example Figure 2) that still precludes their use in lithium-ion batteries. In order to improve their electrochemical properties as electrode materials, a current effort is made to better understand the... 

Frackowiak E., Beguin F. Electrochemical storage of energy in carbon nanotubes and nanostructured carbons. Carbon 2002 40 1775-87. 

Zuttel, A., P. Wenger, P. Sudan, P. Maurona, S.-i. Orimob, Hydrogen density in nanostructured carbon, metals and complex materials. Mater. Sci. Eng. B108, 9-18, 2004. 

Panella, B., M. Hirscher, S. Roth, Hydrogen adsorption in different carbon nanostructures. Carbon 43,2209-2214,2005. 

Carbon nanotubes (CNTs) constitute a nanostructured carbon material that consists of rolled up layers of sp2 hybridized carbon atoms forming a honeycomb lattice. After diamond, graphite and fullerenes, the one-dimensional tubular structure of CNTs is considered the 4th allotrope of carbon (graphene is the 5th). 

Until recently, synthesis of nanostructured carbon materials was usually based on very harsh conditions such as electric arc discharge techniques [1], chemical vapor deposition [2], or catalytic pyrolysis of organic compounds [3]. In addition (excluding activated carbons), only little research has been done to synthesize and recognize the structure of carbon materials based on natural resources. This is somewhat hard to understand, as carbon structure synthesis has been practiced from the beginning of civilization on the base of biomass, with the petrochemical age only being a late deviation. A refined approach towards advanced carbon synthesis based on renewable resources would be significant, as the final products provide an important perspective for modern material systems and devices. 

Modifying the surface characteristics to enhance the charge storage. There is a broad protocol to modify the surface characteristics of carbon materials, especially the nanostructured carbon materials, to have excellent adsorption/desorp-tion behavior ... 

Besides the practical application, the diversity of nanostructured carbon allotropes makes nanocarbon also an ideal model system for the investigation of structure-function correlations in heterogeneous catalysis. Nanocarbons can be tailored in terms of their hybridization state, curvature, and aspect ratio, i.e., dimensions of stacks of basic structural units (BSU), Chapters 1 and 2. The preferred exposition of two types of surfaces, which strongly differ in their physico-chemical behavior, i.e., the basal plane and prismatic edges, can be controlled. Such controlled diversity is seldom found for other materials giving carbon a unique role in this field of basic research. The focus of this chapter is set on the most prominent representatives of the... 

Fig. 15.1 Classification of sp2- and sp3-hybridized nanostructured carbon materials. CNTs are considered as open-end tubes, thus also exposing prismatic edge surfaces.

The activity of elemental carbon as a metal-free catalyst is well established for a couple of reactions, however, most literature still deals with the support properties of this material. The discovery of nanostructured carbons in most cases led to an increased performance for the abovementioned reasons, thus these systems attracted remarkable research interest within the last years. The most prominent reaction is the oxidative dehydrogenation (ODH) of ethylbenzene and other hydrocarbons in the gas phase, which will be introduced in a separate chapter. The conversion of alcohols as well as the catalytic properties of graphene oxide for liquid phase selective oxidations will also be discussed in more detail. The third section reviews individually reported catalytic effects of nanocarbons in organic reactions, as well as selected inorganic reactions. 

Besides ODH processes, a few reports about non-oxidative dehydrogenation (DH) over carbon catalysts also exist. At the reaction temperature of 823-873 K, propane is reported to react to propylene and hydrogen in high yield (30-40 %) over ordered mesoporous carbon, which was shown to be much more active than graphitic and/or nanostructured carbon (CNTs) [66], On the other hand, a hybrid catalyst system for... 

Centi, G. Perathoner, S., Problems and perspectives in nanostructured carbon-based electrodes for clean and sustainable energy. Catat. Today 2010,150 151-162. 

Su, D.S. Schlogl, R., Nanostructured Carbon and Carbon Nanocomposites for Electrochemical Energy Storage. ChemSusChem 2010,3 136-168. 

The hydrogen storage capacities for disordered graphites, nanographites, and activated carbons are collected in Table 4.1. One can conclude that activated carbons are better storage materials than CNTs and most experimentally investigated carbon nanophases (like GNFs). Yet, if one applies a broader definition of nanomaterials, the activated carbon phases are, indeed, the disordered and nanostructured carbons. 

A. Zuttel, S. Orimo, Hydrogen in nanostructured, carbon-related, and metastable materials. MRS BuU. (Special Issue on Hydrogen Storage), (2002) 705. 

The low-temperature physisorption (type I isotherm) of hydrogen in zeolites is in good agreement with the adsorption model mentioned above for nanostructured carbon. The desorption isotherm followed the same path as the adsorption, which indicates that no pore condensation occurred. The hydrogen adsorption in zeolites depends linearly on the specific surface areas of the materials and is in very good agreement with the results on carbon nanostructures [24]. 

Goel A, Hebgen P, Vander Sande JB et al (2002) Combustion synthesis of fullerenes and fullerenic nanostructures. Carbon 40 177-182... 

The synthesis of nanostructured carbon using aliphatic alcohols as selfassembling molecules has demonstrated that this strategy can be extended beyond metal oxide-based materials [38]. Recently, we have reported the synthesis of a novel carbon material with tunable porosity by using a liquid-crystalline precursor containing a surfactant and a carbon-yielding chemical, furfuryl alcohol. The carbonization of the cured self-assembled carbon precursor produces a new carbon material with both controlled porosity and electrical conductivity. The unique combination of both features is advantageous for many relevant applications. For example, when tested as a supercapacitor electrode, specific capacitances over 120 F/g were obtained without the need to use binders, additives, or activation to increase surface area [38]. The proposed synthesis method is versatile and economically attractive, and allows for the precise control of the structure. 

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