Macroporous carbon colloidal-crystal-templated

Theoretically, colloidal-crystal-templated macroporous structures should have a relatively low surface area because of the dominant presence of large pores. However, macroporous carbons prepared by this mechanism can possess a high surface area because a considerable number of micropores may be present as... 

In this chapter, we provide an overview of the recent research and development in the preparation, characterization, and application of novel porous carbons using both the endotemplate and the exotemplate methods. A discussion of zeolite templates for microporous carbons is followed by that of ordered mesoporous silica templates for OMCs, nanoparticle templates for mesoporous carbons, sol-gel processed porous carbons, self-assembled colloidal crystal templates for ordered macroporous carbons, and colloidal sphere templates for hollow carbon spheres, as well as other templating approaches to preparing carbon nanostructures. Then,... 

The colloidal-crystal-templating approach offers yet another new approach to preparing 3-D macroporous solid materials [6,17]. Spherical colloidal particles of submicrometer size can self-organize themselves into a colloidal crystal, the so-called opal [64], which can be utilized as an endotemplate to fabricate ordered macroporous carbons of two types volume-templated carbon, which is an exact inverse replica of the opal template, and surface-templated carbon, which is formed by coating the colloidal spheres. Zakhidov et al. [64] were the first to use colloidal crystals as templates to prepare highly ordered 3-D macroporous carbon of both types. As schematically illustrated in Figure 2.39, for the volume-templat-ing approach, a carbon precursor is infiltrated into interstitial spaces between colloidal spheres. Carbonization and removal of the opal template leave behind a 3-D periodic carbon structure (i.e., an inverse carbon). With this approach, macroporous carbon structures with a wide range of pore sizes have been produced. 

Instead of infiltration with neat metal nanoparticles, the interstitial voids of the template opal can also be filled wifh a mefal precursor. The impregnation of the preformed colloidal crystals with the metal precursor, followed by transformation of the precursor to the neat metal and removal of the template, results in metallic inverse opals. For example, nickel oxalate was precipitated in a PS opal and converted into a NiO macroporous network by calcination of the metal salt and combustion of the polymer. In a subsequent step, the nickel oxide was reduced to neat Ni in a hydrogen atmosphere to yield a macroporous metal network [82]. It was further suggested by the authors that by the same technique other metal networks (e.g.. Mg, Mn, Fe, Zn from their oxides and Ca, Sr, Ba etc. from their carbonates) should be accessible. 

Sen T, Tiddy GJT, Casci JL, Anderson MW (2004) Synthesis and characterization of hierarchically ordered porous silica materials. Chem Mater 16 2044 Deng Y, Liu C, Yu T, Liu F, Zhang F, Wan Y, Zhang L, Wang C, Tu B, Webley PA, Wang H, Zhao D (2007) Facile synthesis of hierarchically porous carbons from dual colloidal crystal/block copolymer template approach. Chem Mater 19 3271 Luo Q, Li L, Yang B, Zhao D (2000) Three-dimensional ordered macroporous structures with mesoporous silica walls. Chem Lett 29 378... 

In principle, the morphology of macroporous carbon materials is largely dependent on the degree of void infiltration of the opal template. In order to maximise the filling of the interstitial voids of the colloid crystal with carbon precursors, liquid phase carbon precursors such as phenolic resin and sucrose solution are usually used to achieve better replication.1 2 -194] variety of carbon precursors, including propylene gas, benzene and divinylbenzene can also be successfully utilised to make three-dimensional macroporous carbon materials using colloid crystals as hard templates. The... 

FIGURE 2.42 Schematic illustration of fabrication of 3-D macroporous carbon nsing the surface-templating approach (a) PS colloidal crystal, (b) silica-infiltrated PS colloidal crystal, (c) an inverse silica opal after removal of PS spheres, (d) carbon-coated inverse silica opal, and (e) 3-D macroporous carbon after removal of sdica. 

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