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Journal ArticleDOI

Novel synthesis of porous carbons with tunable pore size by surfactant-templated sol-gel process and carbonisation.

04 Nov 2002-Chemical Communications (The Royal Society of Chemistry)-Iss: 22, pp 2722-2723
TL;DR: Surfactant-templated sol-gel polymerisation was explored to synthesize the resorcinol-formaldehyde gels without supercritical drying step, which were further carbonised to obtain porous carbons of a tunable pore size.
About: This article is published in Chemical Communications.The article was published on 2002-11-04 and is currently open access. It has received 77 citations till now. The article focuses on the topics: Supercritical drying.

Summary (1 min read)

T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f

  • The pore size is primarily determined by the size of gel clusters, which is in turn controlled by the monomer/surfactant concentration.
  • It is thus very likely that, in acidic conditions, the cross-linking between gel clusters becomes more facilitated to produce a more rigid gel network, and the pore collapse or shrinking at both the drying step and subsequent carbonisation step is suppressed.
  • To test this possibility, the sol-gel polymerisation was performed at different pH by varying the R/F ratio in this work (samples C5-C7).
  • When the pore properties are compared for samples C5-C7, there appears a strong correlation between the porosity and pH of the sol-gel medium even if the carbon cluster size is comparable for the three because the monomer/surfactant concentration is the same.
  • Fig. 3(b) shows the pore size distribution of samples C3-C7 as calculated by the Barrett-Joyner-Halenda (BJH) method from the desorption branch of the isotherm.

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Citations
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Journal ArticleDOI
TL;DR: Organic porous materials—a class of advanced materials— possess enormous potential for many high-tech applications, such as bioreactors, dielectrics, sensors, microelectrophoresis, thermal insulation, and catalysts, but large porosity has rarely been reported.
Abstract: Organic porous materials—a class of advanced materials— possess enormous potential for many high-tech applications, such as bioreactors, dielectrics, sensors, microelectrophoresis, thermal insulation, and catalysts. In general, they can be prepared by phase separation, and a hard templating approach, such as those employing colloidal particles. Phase separation can be derived from organic– organic phases, while the pore structures can be formed after etching, or by dissolving one block (A) from the assembled block copolymer (A–B). However, most of the resulting porous polymer structures are disordered with wide pore size distributions because of the contraction and swelling from changes in volume, as well as the structured defects formed during template removal. Large porosities have rarely been reported. Furthermore, the resistance of the pore structure to heat and solvents is rather low because the materials are formed by weak van der Waals forces and physical twists between polymer chains, which means that the framework is not connected by covalent bonds. Recently, a procedure for cross-linking lyotropic liquid crystals (LLC) in water was introduced to prepare periodic porous organic mesostructures. Unfortunately, polymerization only occurs between nearest neighboring head groups, and the mesostructured channels are fully occupied with solution. Therefore, it is not surprising that porosity has yet to be reported. Carbon materials, including nanotubes and fullerenes, have attracted considerable attention because of their remarkable properties. The traditional carbonization process for active carbon and related materials can only generate

1,272 citations

Journal ArticleDOI
TL;DR: In this paper, the synthesis of mesoporous polymers and carbon frameworks from organic−organic assembly of triblock copolymers with soluble, low-molecular-weight phenolic resin precursors (resols) by an evaporation induced self-assembly strategy has been reported.
Abstract: The syntheses of a family of highly ordered mesoporous polymers and carbon frameworks from organic−organic assembly of triblock copolymers with soluble, low-molecular-weight phenolic resin precursors (resols) by an evaporation induced self-assembly strategy have been reported in detail. The family members include two-dimensional hexagonal (space group, p6m), three-dimensional bicontinuous (Ia3d), body-centered cubic (Im3m), and lamellar mesostructures, which are controlled by simply adjusting the ratio of phenol/template or poly(ethylene oxide)/poly(propylene oxide) in the templates. A five-step mechanism from organic−organic assembly has been demonstrated. Cubic FDU-14 with a gyroidal mesostructure of polymer resin or carbon has been synthesized for the first time by using the copolymer Pluronic P123 as a template in a relatively narrow range. Upon calcination at 350 °C, the templates should be removed to obtain mesoporous polymers, and further heating at above a critical temperature of 600 °C transfor...

1,013 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present the state-of-the-art of adsorption characterization of mesoporous and microporous materials by using the density functional theory (DFT) methods.

903 citations

Journal ArticleDOI
TL;DR: In this article, a review examines methods of functionalizing porous carbon through direct incorporation of heteroatoms in the carbon synthesis, surface oxidation and activation, halogenation, sulfonation, grafting, attachment of nanoparticles and surface coating with polymers.
Abstract: Recent progress in syntheses of porous carbons with designed pore architecture has rejuvenated the field of carbon chemistry and promises to provide new advanced materials. In order to reap the full benefit of designer carbons, it is necessary to develop chemistries for functionalizing the porous carbon surfaces. This Review examines methods of functionalizing porous carbon through direct incorporation of heteroatoms in the carbon synthesis, surface oxidation and activation, halogenation, sulfonation, grafting, attachment of nanoparticles and surface coating with polymers. Methods of characterizing the functionalized carbon materials and applications that benefit from functionalized nanoporous carbons with designed architecture are also highlighted.

781 citations

Journal ArticleDOI
TL;DR: In this article, the synthesis of carbon aerogels with hierarchical porosities for energy applications, including carbon nanotube and graphene composite carbon aeroglobels, as well as their functionalization by surface engineering are discussed.
Abstract: Carbon aerogels are a unique class of high-surface-area materials derived by sol–gel chemistry. Their high mass-specific surface area and electrical conductivity, environmental compatibility and chemical inertness make them very promising materials for many energy related applications, specifically in view of recent developments in controlling their morphology. In this perspective we will review the synthesis of monolithic resorcinol–formaldehyde based carbon aerogels with hierarchical porosities for energy applications, including carbon nanotube and graphene composite carbon aerogels, as well as their functionalization by surface engineering. Applications that we will discuss include hydrogen and electrical energy storage, desalination and catalysis.

576 citations

References
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Journal ArticleDOI
TL;DR: In this article, a simple preparation method for mesoporous carbons with high pore volumes using surfactant stabilized silica particles as templates is reported, and a simple template template template is used for each mesopore.

171 citations

Journal ArticleDOI
TL;DR: In this paper, aqueous polycondensation of resorcinol with formaldehyde leads to organic gels the structure of which can be controlled by the reaction parameters, such as the amount of catalyst and the size of the particles constituting the gel network.
Abstract: Aqueous polycondensation of resorcinol with formaldehyde leads to organic gels the structure of which can be controlled by the reaction parameters. The amount of catalyst controls the size of the particles constituting the gel network. We could show that for very low catalyst concentrations in a high dilution of reactants, the particle growth can be further enhanced if the reaction temperature is kept low, and the gel time is prolonged. The resultant structure is largely affected by this treatment, producing particles with sizes of about 2 μm and average pore sizes of up to 7 μm. Due to these coarse structures it is possible to dry these RF gels subcritically with very little shrinkage. The structure has been studied by nitrogen sorption, small angle X-ray scattering and acoustic sound propagation. The change of the elastic modulus caused by pyrolysis at around 1000°C has been investigated. Mechanical properties of carbon aerogels are correlated with their electrical properties. The derived carbon aerogels have large specific surface areas, very little mesopore volume however, micron-sized macropores.

120 citations

Journal ArticleDOI
TL;DR: In this paper, the temperature dependence of dc electrical resistivity and magnetic susceptibility (χ) from 4 K to room temperature, magnetoresistance (MR) in a magnetic field up to 15 T, and Raman scattering were measured as a function of aerogel density.
Abstract: Carbon aerogels are a special class of low-density microcellular foams. These materials are composed of interconnected carbon particles with diameters of approximately 10 nm. The temperature dependence of the dc electrical resistivity and magnetic susceptibility (χ) from 4 K to room temperature, magnetoresistance (MR) in a magnetic field up to 15 T, and Raman scattering were measured as a function of aerogel density. While Raman scattering measurements are not sensitive to variations in density, the χ data show that there are more free carriers in samples of higher density. Aerogel samples with different densities all show a negative temperature coefficient of resistivity and a positive MR. The less dense samples exhibit a stronger temperature dependence of resistivity and a stronger field dependence of the MR, indicating that with decreasing density and increasing porosity, charge carriers are more localized. Data analysis precludes variable-range hopping in favor of nearest-neighbor hopping and fluctuation-induced tunneling as the most likely conduction mechanisms for carbon aerogels.

64 citations

Frequently Asked Questions (1)
Q1. What have the authors contributed in "Novel synthesis of porous carbons with tunable pore size by surfactant-templated sol–gel process and carbonisation" ?

Here, the authors report another low-cost preparation method for RF xerogels, where a normal drying is still applicable because the pore collapse can be minimized during the water evaporation. The microto nanosized spherical gel clusters are formed within the micelles, which are further three-dimensionally connected via a crosslinking reaction. The resulting RF gels are dried at 85 °C and further heat-treated at 1000 °C for 3 h under argon atmosphere to obtain porous carbons in monolithic shape.