Templating method macroporous carbons

The meso/macroporous carbons have attracted much attention in their application as electrode materials in EDLCs, since the meso/macropores promote the formation of an effective doublelayer or the transfer of ions into the pores, resulting in the increases in the electrolyte wettability and the rate capability.67,68 In this regard, there has been considerable research targeted towards developing the synthetic methods of novel meso/macroporous carbons.17,36"55,69 72 Various types of such inorganic templates as silica materials and zeolites are widely used for the synthesis of the meso/macroporous carbons, since it was revealed17,36"55 that these inorganic templates contribute to the formation of the meso/macropores with various pore structures and broad PSD. 

The present article first provided the brief overview of the synthetic methods of the porous carbons. In order to prepare the microporous carbons with high surface area, the physical/chemical activation methods have been widely used for a long time.18"35 Recently, the meso/macroporous carbons with various pore structures are prepared by templating methods by using various templates and changing sol-gel reaction conditions, e.g., pH, amount of template, and gelation temperature.17,36 55... 

Indeed, the past ten years have witnessed rapid advances in using template carbonisation to produce ordered porous carbon materials, ranging from microporous to mesoporous and macroporous carbons. The template carbonisation method has thus been regarded as one of the most effective approaches to prepare porous carbon materials with desirable physical and chemical properties. It has, therefore, opened up new opportunities in making novel porous materials for a wide range of applications. 

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,... 

Recently, a dual template method using both polystyrene spheres and silica particles as templates was reported to result in the preparation of ordered, uniform, macroporous carbons with mesoporous walls [254], Figure 2.41a shows the... 

Preparing carbons with hierarchical pore structure is done by impregnation of preformed macropo-rous structures, such as silica colloids, with the carbon precursor gels, followed by precursor carbonization and macropore template dissolution. Although in hard-templated carbons, two particle sizes of the hard template are simultaneously required for the colloidal imprinting method the soft-templating method makes this procedure much simpler and broadens the selection of templates for the larger mesopores and macropores. 

Hu et al. have synthesised ordered mesoporous and macroporous carbon monoliths by template method using silica monoliths as template. In this preparation, the mesophase pitch was used as the carbon precursor [54]. The silica monolith templates were filled with a 10 wt.% solution of mesophase pitch in tetrahydrofuran solvent and then carbonised at different temperatures. The physical characteristics of these various mesoporous and macro-porous carbon are presented in Table 7.8, which demonstrates these carbons have more prominent graphitic structures as the carbonisation temperature increases. SEM images of the carbon monoliths obtained at carbonisation temperature of 700°C and 2500°C are shown in Figure 7.59. 

Kim et al. [64] analyzed porous carbon by using colloidal sUica particles as templates. Carbon with micro, meso and macropores were obtained modifying the initial pH of the carbon precursor solutions. This fabrication method produces materials with narrow pore size distribution in a broad range of pore size. The fuel cell test showed better DMFC performance for carbons with high meso-macropore area with large pore than that with micropores. Again, this effect was attributed to the fact that meso and macropores produce a favorable dispersion of PtRu metal species and allow the access of perfluorosulfonate ionomer for the formation of the triple phase boundary. 

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