Macroporous carbon materials synthesis

The synthesis of macroporous carbon materials was first realised by Zakhidov et al. in 1998. Macroporous carbon materials with inverse opal structures, as shown in Figure 4.14, were obtained using silica opals as hard templates and phenol resin and/or propylene gas as carbon precursor. The macroporous carbons had different structures depending... 

The physical and chemical activation processes have been generally employed to prepare the porous carbons.18"35 However, the pore structures are not easily controlled by the activation processes and the size of the pores generated by the activation processes is limited to the micropore range only. Recently, much attention has been paid to the synthesis of meso/macroporous carbons with various pore structures and pore size distributions (PSD) by using various types of such inorganic templates as silica materials and zeolites.17,36 55... 

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. 

Since the texture of the final material obtained after drying and pyrolysis is strongly influenced by the reaction mechanism which is itself influenced by pH, the latter is a key variable for controlling texture. Indeed, depending on the pH interval used for synthesis, micro-macroporous, micro-mesoporous, only microporous or totally non-porous carbon materials can be obtained [54, 59, 66]. 

To overcome the stability problem, it is obvious that an alternative approach to material synthesis would be needed. In this respect a recent report suggested that iron oxide encapsulated in meso- and macroporous carbon can be used as anode in Li batteries and reaches a greatly improved reversibility and rate performance. At the same time, a similar structure for a cathode material based on iron and lithium fluoride was synthesized and investigated. It was demonstrated that encapsulation of transition metal-metal fluoride in nanocarbon might be an effective strategy to improve the cycling performance of such a cathode material. ... 

Zeolites are widely used as acid catalysts, especially in the petrochemical industry. Zeolites have several attractive properties such as high surface area, adjustable pore size, hydrophilicity, acidity, and high thermal and chemical stability. In order to fully benefit from the unique sorption and shape-selectivity effects in zeolite micropores in absence of diffusion limitation, the diffusion path length inside the zeolite particle should be very short, such as, e.g., in zeolite nanocrystals. An advantageous pore architecture for catalytic conversion consists of short micropores connected by meso- or macropore network [1]. Reported mesoporous materials obtained from zeolite precursor units as building blocks present a better thermal and hydrothermal stability but also a higher acidity when compared with amorphous mesoporous analogues [2-6]. Alternative approaches to introduce microporosity in walls of mesoporous materials are zeolitization of the walls under hydrothermal conditions and zeolite synthesis in the presence of carbon nanoparticles as templates to create mesopores inside the zeolite bodies [7,8]. 

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... 

The carbon support chosen for this study was a micro-macroporous caibon xerogel with a macropore size ranging from 50 to 85 nm, a specific surface area of 640 m g and a total pore volume of about 2.1 cm g (including 0.26 cm g of micropores, i.e. pores smaller than 2 nm). Carbon xerogels are materials composed of intereonnected spherical-like microporous nodnles. So, they classically display a bimodal pore size distribntion micropores inside the carbon nodules, and larger pores identified as the voids located between the nodnles [6], The size of the nodules and that of the voids in-between is controlled by the synthesis conditions of the material [6, 7],... 

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