Porous carbons nanotexture

Oberlin and coworkers [42, 90] (Fig. 2.7c) used a crumpled sheets of paper model to describe the nanotexture of porous carbons. Figure 2.19 depicts this model and includes an enlarged sketch of pores in sucrose-based carbons [91]. In Fig. 2.19a, each zone of molecular orientation is represented by a shaded area inside of which each individual stack is shown either as a rectangular unit or as two parallel segments depending on whether they are observed in perspective... 

We will not discuss here models for pores in carbons, as this topic is treated in Chapter 5, and elsewhere in specialist [15] or general reviews [106, 107]. For similar reasons, we will not discuss porosity control [44, 108] in detail. However, porous carbons prepared by the template technique, especially the ordered ones, deserve special attention. Ordered mesoporous carbons have been known to scientists since 1989 when two Korean groups independendy reported their synthesis using mesoporous silicas as templates [109, 110]. Further achievements have been described in more recent reports [111, 112]. One might have expected that the nanotexture of these materials would merely reflect the nature of the precursor used, namely phenol-formaldehyde [109] or sucrose [110] in the two first ordered mesoporous carbon syntheses (as is well known, these two precursors would have yielded randomly oriented, isotropic carbon had they been pyrolyzed/activated under more conventional conditions). However, the mesopore walls in some ordered mesoporous carbons exhibited a graphite-like, polyaromatic character [113, 114], as described in Chapter 18. This information was obtained by nitrogen adsorption at low relative pressures, as in classical... 

The most used materials for electrochemical double layer capacitors are activated carbons, because they are commercially available and cheap, and they can be produced with large specific surface area. In addition to the nanotextural properties, the chemical properties of carbons will determine their efficiency as electrodes. In the present section, an overview of the influence of the porous texture and surface chemistry of carbons on their electrochemical parameters, as capacitance or power density, is presented. 

Assuming that the part of hydrogen which can be reversibly recovered is in a state close to physisorption, the adsorption capacity should be influenced by the porous nanotexture of the carbon material. Therefore, by analogy with the experiments in the gas phase and in order to find possible directions of optimization, some correlations were tentatively established with the nanotextural parameters of carbons. 

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