Ordered nanoporous carbons

Lee J. S., Joo S. H. and Ryoo R., Synthesis of mesoporous silicas of controlled pore wall thickness and their replication to ordered nanoporous carbons with various pore diameters. J. Am. Chem. Soc. 124 (2001) pp. 11S6-1157. 

J.S. Lee, S.H. Joo, and R. Ryoo, Synthesis of Mesoporous Silicas of Controlled Pore Wall Thickness and their Replication to Ordered Nanoporous Carbons with Various Pore Diameters. J. Am. Chem. Soc., 2002, 124, 1156-1157. 

S.B. Yoon, J.Y. Kim, and J.S. Yu, Synthesis of Highly Ordered Nanoporous Carbon Molecular Sieves from Silylated MCM-48 using Divinylbenzene as Precursor. Chem. Commun., 2001, 559-560. 

Fig. 36. TEM image and corresponding Fourier diftractogram (a), and schematic model for CMK-5 carbon (b). The TEM im is viewed along the direction of the ordered nanoporous carbon. Reprinted with permission fiom Ref. [118]. Copyright 2001 Macmillan Magazines Ltd.

Carbonaceous materials such as porous carbons (e.g., active carbons and ordered nanoporous carbons) and nonporous carbons (e.g., carbon blacks) are a non-graphitic form of carbon characterized by internal surface areas ranging from lO-AO m g (nonporous or macroporous carbon blacks) to 500-3000 g" (active carbons). X-ray analysis shows that... 

Besides the investigation of monolithic carbons with well-ordered mesoporosity as CO2 sorbents, the synthesis of ordered mesoporous carbon films for CO2 capture (membrane gas separation) also attracts much interest. Noticeably, highly ordered mesoporous carbon with cubic Im3m symmetry has been synthesized successfully via a direct carbonization of self-assembled F108 (EOi32P05oEOi32) and RE composites obtained in a basic medium of non-aqueous solution [66]. Dai et al. [49] demonstrated a stepwise self-assembly approach to the preparation of large-scale, highly ordered nanoporous carbon films (Eig. 2.14). 

Fig. 24.11 TEM image of ordered nanoporous carbon (ONC) and its Fourier diffraction (a), schematic of ONC (b), mass activities of Pt on ONC and carbon black depending on the Pt loading (c), and ORR polarization curves measured in 02-saturated 0.1 M HCIO4 at 10,000 RPM (d) [70]...

Selvam, R, Murthy, P.R., Krishna, N.V Viswanathan, B. Ordered nanoporous carbons (NCCR-56) Synthesis, characterization and applications. Srdint. Conf. onAdv. Mater. Sys. (ICAMS-20I0), Bucharest, Romania, 2010b, pp. 125-130. 

Figure 3.2 Ordered nanoporous carbon obtained by template synthesis using ordered meso-porous silica SBA-15 [8].

In order to satisfy the industrial demand, the performance of supercapacitors must be improved and new solutions should be proposed. The development of new materials and new concepts has enabled important breakthroughs during the last years. In this forecast, carbon plays a central role. Due to its low cost, versatility of nanotextural and structural properties, high electrical conductivity, it is the main electrode component. Nanoporous carbons are the active electrode material, whereas carbon blacks or nanotubes can be used for improving the conductivity of electrodes or as support of other active materials, e.g., oxides or electrically conducting polymers. 

As d is of the order of lnm, the specific capacity is very high, e.g., 0.1 F nr2. Nanoporous carbons are ideal materials for supercapacitor electrodes [8], because of their low cost, good electrical conductivity, and very high specific surface area (between 1000 and 2500 m2 g-1). The values of capacity are generally ranging from 100 to 200 F g 1. 

Nanoporous materials like zeolites and related materials, mesoporous molecular sieves, clays, pillared clays, the majority of silica, alumina, active carbons, titanium dioxides, magnesium oxides, carbon nanotubes and metal-organic frameworks are the most widely studied and applied adsorbents. In the case of crystalline and ordered nanoporous materials such as zeolites and related materials, and mesoporous molecular sieves, their categorization as nanoporous materials are not debated. However, in the case of amorphous porous materials, they possess bigger pores together with pores sized less than 100 nm. Nevertheless, in the majority of cases, the nanoporous component is the most important part of the porosity. 

In addition to zeolites and MMS which are crystalline, ordered nanoporous materials and amorphous adsorbents, such as silica and active carbon, have been used in gas cleaning. The silica gel surface is generally terminated with OH groups bonded with a silicon atom, SiOH units, that is, silanols (see Figure 2.30). The concentration of OH groups at the surface is... 

S.H. Joo, S.J. Choi, I. Oh, J. Kwak, Z. Liu, O. Terasaki, and R. Ryoo, Ordered Nanoporous Arrays of Carbon Supporting High Dispersions of Platinum Nanoparticles. Nature London), 2001, 412, 169-172. 

Ordered mesoporous carbons (OMCs) are new carbon materials that were developed over the last ten years. Their mesopores have a defined width with a very narrow pore size distribution. This sets them aside from older nanoporous carbons, such as activated carbons or activated carbon fibers. The last two classes of carbons are produced from various carbon-containing materials by carbonization followed by partial oxidation (activation). To a certain degree, the pore structure of these materials can be controlled by the carbonization and activation conditions. However, it is not possible to produce purely mesoporous activated carbons or activated carbon fibers. Furthermore, these materials generally exhibit a broad pore size distribution [1, 2]. 

Ordered mesoporous carbons (OMC) of various structures, designated as CMK-1 5, have been synthesized by carbonization of sucrose, furfuryl alcohol or other carbon sources inside silica or aluminosilicate mesopores that are interconnected into three-dimensional networks such as in MCM-48, SBA-1 and SBA-15. The mesoporous carbon molecular sieves, obtained after template removal, show TEM images and patterns characteristic of the ordered arrangement of uniform mesopores. The OMC, which are opening up a new area of the nanoporous materials, exhibit high BET specific surface areas, excellent thermal stability in inert atmospheres and strong resistance to attack by acids and bases. 

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