Mesoporous Carbon Monoliths Research Articles

Aromatic sulfide, sulfoxide, and sulfone mediated mesoporous carbon monolith for use in supercapacitor

Monoliths of aromatic sulfur mediated mesoporous carbon were fabricated via an aqueous self-assembly strategy and the species of sulfide, sulfoxide, and sulfone on the surface can be tuned rationally. The resultant S-doped mesoporous carbon exhibited superior performance as supercapacitor electrodes. The controllable modulation of sulfur species provided a possibility to clearly understand the role sulfur playing and allowed mechanistic insight into material requirements for high performance capacitors.

Formation Mechanism of Cubic Mesoporous Carbon Monolith Synthesized by Evaporation-Induced Self-assembly

The formation mechanism of the cubic mesoporous carbon, FDU-16, synthesized by evaporation-induced self-assembly (EISA) was investigated at the molecular level by electron paramagnetic resonance (EPR) spectroscopic techniques. This material is synthesized using F127 pluronic block copolymer [poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO106-PPO70-PEO106)] as a structure-directing agent (template) and phenolic resol as a carbon precursor. Using two spin probes derived from pluronics with PEO and PPO chains of different lengths that are designed to sense different regions of the system, we followed the evaporation and thermopolymerization stages of the synthesis in situ. To make such studies possible, we have used a polyurethane foam support, placed in the EPR tube, which allows for the efficient solvent evaporation as required for EISA. We focused on the evolution of the dynamics of the template and its interactions with the resol during the reaction. We observed that during the evaporation stage the resol is distributed throughout the entire PEO blocks, all the way to the PPO–PEO interface, interacting with them via H-bonds, thus hindering the local motion of the PEO chains. At the end of this stage there is no polarity gradient along the PEO blocks, as found for traditional F127 micelles in water or during the synthesis of silica materials, and the mesostructure is not well-defined. A polarity and a resol gradient developed during the thermopolymerization stage where the polymerizing resol is driven out to the outer region of the PEO corona. This produces a corona of resin-pluronic composite and a resol-free PPO core with high mobility of the PEO segments close to the PPO–PEO interface and restricted mobility in the composite corona. During this stage the final structure sets in.

Facile Synthesis of Transparent Mesostructured Composites and Corresponding Crack-free Mesoporous Carbon/Silica Monoliths

Transparent ordered mesostructured resin-silica composite monoliths with uniform rectangular shape which fully copies the inner-shape of vessels and size (5 × 3 × 0.3 cm3) are prepared via a facile approach of evaporation induced self-assembly (EISA) without adding any protecting agent by using triblock copolymer Pluronic F127 as a template. Ordered mesoporous carbon-silica composite monoliths can be obtained in a wide range of silica content (34–82 wt %) after calcination in N2. Monolithic shape can be maintained with shrinkage (∼20%) in sizes. Furthermore, each component of the composites can be easily removed after the simple post treatments. After etching silica, mesoporous carbon monoliths retain the same in shape and sizes, but show much larger pore volume (∼2.65 cm3/g) and higher surface area (∼1800 m2/g) than the carbon–silica composites. Besides, mesoporous silica monoliths with large pore size (∼14.6 nm) show an integral and uniform shape after air combustion. The obtained mesoporous carbon monoliths show high capacitance (186 F/g) and high cycling stability (8% capacitance loss after 1000 cycles), exhibiting an excellent potential in capacitor applications.

Fabrication of Complex-Shaped SiC Parts Based on Polymerization -Induced Phase Separation and Pyrolysis Technique

A route based on a technique of polymerization - induced phase separation and pyrolysis (PIPSP) has been developed to fabricate complex-shaped SiC parts. The capability of this process to produce complex component shapes has been demonstrated, and corresponding reactive mechanisms have been also discussed. Three types of porous carbon preforms, i.e. mesoporous carbon monoliths (MCMs), hierarchical porous carbon monoliths (HCMs) and porous carbon foam (PCFs) were obtained, which has different pore size distributions. The pore structures of the preforms can be controlled through changing starting mixture composition and polymerizing conditions. The apparent porosity of the preform was changed from 19.9 to 60%, which was a key parameter to obtain dense SiC parts. After reactive infiltration of the preform with Si, the SiC parts were obtained. Geometry of SiC parts were controlled by molds. The dimension shrinkage of SiC parts was less than 3% before/after siliconization and no distortion occurred. Compared with other molds assistance route, the wax mold assistance route was a most potential technique to fabricate SiC parts industrially because of its suitable forming precision, recycled mold materials and low-cost. The mechanism of the reactive infiltration of MCMs was different from that of the reactive infiltration of preforms with bigger pore size, i.e. the pore channels of MCMs were restructured at transitional stage of reaction.

A low-temperature autoclaving route to synthesize monolithic carbon materials with an ordered mesostructure

Low-temperature autoclaving has been demonstrated to synthesize monolithic carbon materials with an ordered mesostructure by using triblock copolymer F127 as template, and resorcinol/formaldehyde resol as carbon precursor under acidic conditions. Transmission electron microscopy, small angle X-ray scattering, Fourier transform infrared spectroscopy and nitrogen adsorption measurements show that the crack-free carbon monoliths have a 2-D hexagonal pore system, a uniform pore size of ∼5.0nm and a high surface area of ∼675m2g−1. The macroscopic morphology can be tuned by changing the diameter of the autoclave. The influence of the synthesis conditions including the autoclaving treatment time and the molar ratio of formaldehyde (F) to resorcinol (R) are discussed. It is found that while the F/R molar ratio ⩽2 and the autoclaving treatment time ⩾2d, highly ordered mesoporous carbon monoliths can be obtained. In comparison, monolithic mesoporous carbon materials prepared through an evaporation-induced self-assembly strategy are partly cracked with a disordered wormhole-like mesostructure, suggesting that low-temperature autoclaving is an efficient way to prepare crack-free monolithic carbon materials with an ordered mesostructure.

Pore structure control of mesoporous carbon monoliths derived from mixtures of phenolic resin and ethylene glycol

Mesoporous carbon monoliths derived from phenolic resin mixtures have been prepared in the process based on polymerization-induced phase separation. The effect of the composition of resin mixtures and the resin curing temperature on the pore structure of carbon monoliths has been systematically investigated, with emphasis on controlling the apparent porosity and pore size distribution. Fractal dimensions have been introduced to evaluate the morphologies of the carbon monoliths. The results showed that mesoporous carbon monoliths with narrow pore size distribution were obtained. The pore structure of carbon monoliths could be controlled by changing the resin curing temperature and the content of ethylene glycol, curing catalyst and water in the resin mixtures. The apparent porosity of carbon monoliths varied from 54.27% to 26.83%. Carbon monoliths had narrower pore size distribution when more ethylene glycol and higher resin curing temperature were employed. The pore structure of carbon monoliths would be changed radically when the initial resin samples were prepared with excess water (9.8 wt%), i.e. porous carbon foams with sponge structure were obtained. Carbon monoliths inherit their porosity from precursing cured resins where it was formed as a result of phase separation of resin-rich and glycol-rich phases. Volume contraction had certain effect on the pore structure of carbon monoliths.

Porous Carbon/Tin (IV) Oxide Monoliths as Anodes for Lithium-Ion Batteries

A monolithic, three-dimensionally ordered macroporous/mesoporous carbon/tin (IV) oxide (3DOM/m ) nanocomposite was prepared and tested as an anode material for lithium-ion batteries. A macro-/mesoporous glassy carbon (3DOM/m C) monolith was first synthesized from a triconstituent precursor, using a polymer colloidal crystal and a nonionic surfactant as the templates for macropores and mesopores, respectively. Tin (IV) oxide nanocrystals were then introduced into the mesopores of the carbon monolith via an infiltration-hydrolysis process while maintaining connections between macropores. The composite electrode exhibited superior reversible lithium capacity over a carbon/tin dioxide electrode without any designed mesostructure and also over similarly templated glassy carbon electrodes lacking the tin oxide component. The initial discharge capacity was and remained above for at . The formation of stable solid-electrolyte interphase layers contributed to the good cycleability of 3DOM/m . The structural and morphological changes of the electrode after cycling were evaluated by scanning and transmission electron microscopy and by X-ray diffraction.

Incorporation of Inorganic Nanoparticles into Mesoporous Carbons Synthesized by Soft Templating

Mesoporous carbon monoliths with embedded alumina and silica nanoparticles were synthesized using phloroglucinol and formaldehyde as carbon precursors and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer as a soft template. While the carbon mesostructure was not significantly affected by embedding silica nanoparticles (∼20 nm), this was not the case for the incorporation of alumina nanoparticles (∼50 nm). In the latter case a gradual reduction in the carbon mesoporosity was observed with increasing loading of alumina nanoparticles. Since various inorganic nanoparticles of different sizes and shapes are available commercially, the soft-templating synthesis route is a very promising way for the design of carbon-based materials with embedded nanoparticles of desired properties.

Colloidal Silica Templating Synthesis of Carbonaceous Monoliths Assuring Formation of Uniform Spherical Mesopores and Incorporation of Inorganic Nanoparticles

Colloidal silica templating synthesis was successfully used to prepare carbon monoliths with uniform spherical pores. Uniformity of the mesopores was assured by formation of a phenolic resin-type carbon precursor on the entire surface of a monolithic colloidal silica template pretreated with oxalic acid as a catalyst. Carbonization of the phenolic resin present in the pores of the colloidal silica template followed by silica dissolution afforded monolithic carbons with tailorable pore sizes reflecting the sizes of the silica colloids used. This synthesis strategy is also convenient for the introduction of metal and metal oxide nanoparticles into mesoporous carbon monoliths. Additional activation of the aforementioned carbon monoliths with KOH introduced substantial microporosity, which makes these materials attractive for a variety of applications, including adsorption and catalysis.

Ordered Mesoporous Carbon Monoliths: CVD Nanocasting and Hydrogen Storage Properties

We report on the use of a chemical vapor deposition to nanocast ordered mesoporous carbon monoliths using mesoporous silica monoliths as template. The size and shape of the silica monolith template are well retained in the carbon resulting in a mechanically robust mesoporous carbon monolith. A relatively high level of mesostructural ordering is observed in the carbon monolith, which has surface area and pore volume of 1090 m2/g and 0.75 cm3/g, respectively. The carbon monolith exhibits limited microporosity (micropore surface area of 156 m2/g). The surface area and pore volume of the carbon monolith was higher than that of the silica template (553 m2/g and 0.5 cm3/g). The carbon in the monolith is mainly amorphous with a small proportion of graphitic carbon. As far as we are aware, this is the first successful attempt to generate ordered mesoporous carbon monoliths via chemical vapor nanocasting. The chemical vapor nanocasting route offers the advantage of improved mesostructural ordering in the carbon mo...

Several ways to produce porous carbon monoliths by template assisted routes

Several ways to produce microporous and mesoporous carbon monoliths by template assisted synthesis routes are described. Pressed zeolite (HY) and silica powder tablets have been used as templates. Sucrose acts as a carbon precursor and as a binder between the carbon particles as well. In the case of zeolite template, the carbon porosity could be increased by additional loading of the template with ethene. Due to the balance between mechanic stability and porosity of the carbon monolith, an optimal amount of sucrose is required. The final products were characterized by low temperature nitrogen adsorption.

A facile synthesis of highly ordered mesoporous carbon monolith with mechanically stable mesostructure and superior conductivity from SBA-15 powder

A highly ordered mesoporous carbon monolith has been successfully synthesized from the template of SBA-15 powder. Interestingly, not only the size and shape of the mesoporous carbon monolith could be simply tailored by controlling the size and shape of a vessel, but also macrocracks on the carbon monolith could be avoided. X-ray diffraction (XRD), nitrogen sorption, transmission electron microscopy (TEM), Scanning electron microscopy (SEM), mechanical stability test, and conductivity test were used to characterize the mesoporous carbon monolith, which exhibits the improved long-range mesostructured order, higher mechanically stable mesostructure, and superior conductivity, compared with mesoporous carbon monolith synthesized from SBA-15 monolith.

Synthesis of ordered mesoporous carbon monoliths with bicontinuous cubic pore structure of Ia3d symmetry.

Large-diameter-sized mesoporous carbon monoliths with bicontinuous cubic structure of Ia3d symmetry have been synthesized by using mesoporous silica monoliths as hard templates; such carbon monoliths show potential application of advanced electrodes and electrochemical double layer capacitors.