Large Mesopore Volume Research Articles

High-performance carbon-based supercapacitors using Al current-collector with conformal carbon coating

Al current-collector with porous surface is coated with a conformal carbon (C) layer via a chemical vapor deposition process in CH 4 at 600 °C. X-ray photoelectron spectroscopy analysis indicates that the coating process leads to the replacement of native aluminum oxide with a composite coating consisting of an Al 4C 3 interfacial layer and a C top layer. Activated C-based supercapacitors employing the resulting C-coated Al current-collectors have exhibited remarkably enhanced high-rate performance, and the enhancement can be attributed to two accounts. Firstly, the current-collector/active-layer interface resistance is reduced due to removal of the insulating oxide layer and improved adhesion of the active-layer on the current-collector. Secondly, the presence of the conducting C layer shortens the effective current conduction distance from the solid-electrolyte interface to the current-collector, leading to reduced charge-transfer resistance within the active-layer. Combining the C-coated Al current-collector with a C fiber active-layer that contains a large mesoporous pore volume (0.4 cm 3 g −1) has resulted in high-performance supercapacitors that exhibit, for instance, a cell specific energy of 18 Wh Kg −1 at 25 °C or 7 Wh Kg −1 at −10 °C under a cell specific power of 25 KW Kg −1.

Hollow spherical carbon with mesoporous shell as a superb anode catalyst support in proton exchange membrane fuel cell

Hollow core mesoporous shell carbon (HCMSC) has been explored for the first time as an anode catalyst support in proton exchange membrane fuel cell (PEMFC). The fantastic structural characteristics of the HCMSC such as large specific surface area and mesoporous volume and well-developed three-dimensionally interconnected bimodal porosity make it an excellent catalyst support in PEMFC. The supported PtRu nanoparticles have shown smaller particle size and better dispersion on the HCMSC than on commercial carbon black Vulcan XC-72. Considerable improvements in the electrocatalytic activity toward H 2 oxidation and fuel cell performance have been demonstrated by the HCMSC-supported PtRu nanoparticles compared with Vulcan XC-72 supported ones (i.e., corresponding to an enhancement of more than 60% in power density compared with that of PtRu/Vulcan), implying that HCMSC is a superb anode catalyst support in PEMFC.

Preparation of mesopore-rich carbons using attapulgite as templates and furfuryl alcohol as carbon source through a vapor deposition polymerization method

Mesoporous carbons with specific surface areas in the range of 409–937 m 2 g −1, mesopore volumes in the range of 0.55–2.26 cm 3 g −1 and mesopore volume fraction higher than 86% are prepared by using crude attapulgite, calcined attapulgite and HCl-treated attapulgite as inorganic templates and furfuryl alcohol as the carbon source through a vapor deposition polymerization (VDP) method at 130 °C. The influences of VDP time, the calcination temperature and HCl concentration on the pore structure of the resultant carbons are investigated. The results indicate that the optimized VDP time, the calcination temperature and the HCl concentration are 6 h, 800 °C and 5 M, respectively, and the corresponding carbons have the maximum surface areas and mesopore volumes. Adsorption of tannic acid on the mesoporous carbons in tannic acid aqueous solution with an initial concentration of 200 mg l −1 at 20 °C reveals that the equilibrium adsorption capacities ( q e) are in the range of 111–464 mg g −1. The mesoporous carbon prepared from attapulgite calcined at 800 °C (C– T 800-6) exhibits the highest specific surface area (937 m 2 g −1), the largest mesopore volume (2.26 cm 3 g −1) and the highest q e (464 mg g −1) among all the resultant carbons.

Enhanced electrochemical and structural properties of carbon cryogels by surface chemistry alteration with boron and nitrogen

Resorcinol–formaldehyde (RF) derived carbon cryogels (CCs) with narrow pore size distribution were obtained via chemical modification using ammonia borane (AB). This chemical modification was achieved by adding AB to the hydrogels during the solvent exchange stage. Nitrogen sorption analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy are used to investigate the pore structure, morphology, and electrochemical properties of the modified CCs. After pyrolysis, the AB modified CCs show an increased surface area and larger mesopore volume in comparison to the untreated precursor. In addition, a uniform porous structure with a narrow pore size distribution is produced with a mesopore diameter that does not change significantly during pyrolysis. Moreover, electric double-layer supercapacitors (EDLS) used to characterize the AB modified samples shows pseudocapacitive behavior, higher current density and capacitance.

Cyclic diquaternary ammoniums for nanocrystalline BEA, MTW and MFI zeolites with intercrystalline mesoporosity

3,10-Diazoniabicyclo[10.2.2]hexadeca-12,14,15-triene-3,3,10,10-tetramethyl-dichloride is an effective structure-directing agent for BEA zeolite under a high concentration of Na+. The pseudomorphic crystallization process led to nanocrystalline BEA particles possessing a large volume of intercrystalline mesopores. The synthesis of nanocrystalline zeolite has been extended to other cyclic diammonium compounds that can generate BEA, MTW and MFI zeolite structures. Phase diagrams for these nanocrystalline zeolites have been constructed using sodium silicate as a silica source. The nanocrystalline morphologies and intercrystalline mesoporosity have been characterized by electron microscopy and N2 adsorption. The result indicates that the pseudomorphic crystallization process is limited to BEA, and not MTW or MFI despite their nanocrystalline morphologies.

Hierarchical nanostructured hollow spherical carbon with mesoporous shell as a unique cathode catalyst support in proton exchange membrane fuel cell

Hierarchical nanostructured spherical carbon with hollow macroporous core in combination with mesoporous shell has been explored to support Pt cathode catalyst with high metal loading in proton exchange membrane fuel cell (PEMFC). The hollow core-mesoporous shell carbon (HCMSC) has unique structural characteristics such as large specific surface area and mesoporous volume, ensuring uniform dispersion of the supported high loading (60 wt%) Pt nanoparticles with small particle size, and well-developed three-dimensionally interconnected hierarchical porosity network, facilitating fast mass transport. The HCMSC-supported Pt(60 wt%) cathode catalyst has demonstrated markedly enhanced catalytic activity toward oxygen reduction and greatly improved PEMFC polarization performance compared with carbon black Vulcan XC-72 (VC)-supported ones. Furthermore, the HCMSC-supported Pt(40 wt%) or Pt(60 wt%) outperforms the HCMSC-supported Pt(20 wt%) even at a low catalyst loading of 0.2 mg Pt cm(-2) in the cathode, which is completely different from the VC-supported Pt catalysts. The capability of supporting high loading Pt is supposed to accelerate the commercialization of PEMFC due to the anticipated significant reduction in the amount of catalyst support required, diffusion layer thickness and fabricating cost of the supported Pt catalyst electrode.

Hollow core/mesoporous shell carbon capsule as an unique cathode catalyst support in direct methanol fuel cell

Hollow core mesoporous shell (HCMS) carbon has been explored for the first time as a cathode catalyst support in direct methanol fuel cells (DMFCs). The HCMS carbon consisting of discrete spherical particles possesses unique structural characteristics including large specific surface area and mesoporous volume and well-developed interconnected void structure, which are highly desired for a cathode catalyst support in low temperature fuel cells. Significant enhancement in the electrocatalytic activity toward oxygen reduction reaction has been achieved by the HCMS carbon-supported Pt nanoparticles compared with carbon black Vulcan XC-72-supported ones in the DMFC. In addition, much higher power was delivered by the Pt/HCMS catalysts (i.e., corresponding to an enhancement of ca. 91–128% in power density compared with that of Pt/Vulcan), suggesting that HCMS carbon is a unique cathode catalyst support in direct methanol fuel cell.

Direct fabrication of bimodal mesoporous carbon by nanocasting

Bimodal mesoporous carbons were successfully prepared by a simple one-step templating method. The template of large mesopores in our method is the in situ formed silica nano-agglomerate from the drying-induced collapse of superfluous silica frameworks. Moreover, the diameter of large mesopores can be easily tailored by the ratio of methylated β-cyclodextrin to tetramethyl orthosilicate (CD/TMOS), increasing with decreasing the CD/TMOS. The typical bimodal mesoporous carbons with 2.4 nm and ca. 24 nm diameter mesopores have great Brunauer–Emmett–Teller surface areas (e.g. 783 m 2/g) and large mesopore volumes (e.g. 2.18 cm 3/g).

The pore structure evolution and stability of mesoporous carbon FDU-15 under CO 2, O 2 or water vapor atmospheres

Mesoporous carbons FDU-15 with ordered hexagonal structure were prepared by using triblock copolymer Pluronic F127 as a template and resol as a carbon precursor via evaporation induced organic–organic assembly method. The pore structure evolution and stability of FDU-15 functioned with the treatment temperature and time were systematically investigated in CO 2, O 2 or water vapor atmospheres. A variety of techniques such as powder X-ray diffraction (XRD), nitrogen sorption and transmission electron microscopy (TEM) were used to characterize the thermal stability of the carbon mesostructure. N 2 sorption measurements show that the activation process can simply increase the specific surface area and pore volume of the mesoporous carbons. The effect of structural regularity, pore size, meso- or microporosity, and wall thickness on the thermal stability at different treatment temperature and time was discussed. The results show that mesoporous carbon FDU-15 materials after the carbonization at 900 °C have a good thermal stability under CO 2 at 750 °C, O 2 at 350 °C and water vapor at 800 °C for at least 3 h. Nevertheless, CO 2, O 2 or water vapor develops the pore system through different ways. For CO 2, the thermal treatment leads to large mesopore volumes while the micropores are slightly increased during the carbon burn-off. Different from CO 2, water vapor activation renders a continuous increase of micropore volumes as well as the total pore volumes with increasing the carbon burn-off. Under O 2-treatment at 350 °C, the ordered mesostructures can be rapidly destroyed due to the fast burning reactions of oxygen with mesoporous carbons.

Micro and mesoporosity of carbon derived from ternary and binary metal carbides

In this work we systematically characterized both the micro- and mesoporosity that develops when Ti 3SiC 2, Ti 3AlC 2, Ti 2AlC, Ti 2AlC 0.5N 0.5, Ta 2AlC, Ta 2C, and TaC are chlorinated at different temperatures. The porosity of the carbide-derived carbon varied based on the initial carbide’s structure and chemistry. The carbides with anisotropic structures, such as the layered ternary carbides, result in larger mesopore volumes as compared to more isotropic carbides such as TaC. Furthermore, the carbon pore structure can collapse, resulting in low pore volumes for materials with low molar fractions of carbon, as was the case with Ti 2AlC 0.5N 0.5.

Textural and surface chemical characteristics of activated carbons prepared from cattle manure compost

Two activated carbons (ACs) prepared from cattle manure compost (CMC) by ZnCl(2) activation were selected and out-gassed in a helium flow at various temperatures for 2h. The pore structure and surface chemical properties of the two selected ACs and their out-gassing treated ACs were characterized using N(2) adsorption-desorption, elements analysis, SEM and Boehm titration. A basic dye, methylene blue (MB), was chosen as an adsorbate to investigate the adsorption capacity for organic contaminant onto the activated carbons. It was found that the out-gassing treatment at 400 degrees C had little effect on the textural characteristics of the carbons but significantly changed the surface chemical properties such as surface functional groups concentration, pH and pH(PZC). The CMC-based activated carbons exhibited excellent performance for MB adsorption due to their high surface area, large mesopore volume and high nitrogen content. The kinetics of MB adsorption onto the activated carbons followed a pseudo-second-order equation, and the equilibrium data agreed well with the Langmuir model under the experimental conditions. The highest adsorption rate constant of k(ad) and the largest adsorption capacity of q(m) were found be 1.44x10(-4)g/mgmin and 519mg/g, respectively. The results suggested that the CMC-based activated carbons were effective adsorbents for the removal of methylene blue from aqueous solution.

Removal of diuron and amitrole from water under static and dynamic conditions using activated carbons in form of fibers, cloth, and grains

This study investigated the removal of the herbicides diuron and amitrole from water under static and dynamic conditions using different activated carbons in the form of fibers, cloth, and grains. In all cases, there was much greater adsorption of diuron than of amitrole due to the lower solubility, greater hydrophobicity, and larger dipolar moment of the former. The activated carbon cloth was the best adsorbent for diuron under dynamic conditions because it had the largest mesopore volume, water-accessible pore volume, and surface area. However, the best adsorbent for amitrole under dynamic conditions was the granular activated carbon due to its higher surface basicity. Comparisons using the best adsorbent for each herbicide showed that diuron was removed by the activated carbon more efficiently compared with amitrole under both dynamic and static conditions.

Preparation of carbon cryogels from wattle tannin and furfural

Wattle tannin-furfural (TFu) hydrogels were synthesized by the sol–gel polycondensation of wattle tannin with furfural by using three types of base catalysts (NaOH, Na 2CO 3 and NaHCO 3). TFu cryogels were prepared by freeze drying of the hydrogels and TFu carbon cryogels were obtained by pyrolysis of the cryogels in an inert atmosphere. The TFu and carbon cryogels were characterized by N 2 adsorption and scanning electron microscope (SEM). The effect of catalysts on porous properties of carbon cryogels resulted in different ways: (1) NaOH enhances increasing mesopore volumes and surface area of carbon cryogels and (2) Na 2CO 3 and NaHCO 3 cause decreasing those of carbon cryogels. The TFu and carbon cryogels prepared by using NaOH as a catalyst possessed large mesopore volumes comparing with micropore volumes. Even though the TFu cryogels have surface area and mesopore volumes smaller than the resorcinol-formaldehyde (RF) cryogels, the carbon cryogels have unique porous properties differed from the RF carbon gels. The properties are summarized as follows: (1) the mesopore volume changes insignificantly after pyrolysis, (2) the pore radius is increased after pyrolysis and (3) micropores are not greatly developed during pyrolysis.

Mesoporous carbide-derived carbon with porosity tuned for efficient adsorption of cytokines

Porous carbons can be used for the purification of various bio-fluids, including the cleansing blood of inflammatory mediators in conditions such as sepsis or auto-immune diseases. Here we show that the control of pore size in carbons is a key factor to achieving efficient removal of cytokines. In particular, the surface area accessible by the protein governs the rate and effectiveness of the adsorption process. We demonstrate that novel mesoporous carbon materials synthesized from ternary MAX-phase carbides can be optimized for efficient adsorption of large inflammatory proteins. The synthesized carbons, having tunable pore size with a large volume of slit-shaped mesopores, outperformed all other materials or methods in terms of efficiency of TNF-alpha removal and the results are comparable only with highly specific antibody-antigen interactions.

Carbons with Extremely Large Volume of Uniform Mesopores Synthesized by Carbonization of Phenolic Resin Film Formed on Colloidal Silica Template

Mesoporous carbons with extremely large pore volume ( approximately 6 cm3/g) and narrow bimodal pore size distribution were synthesized by using 24 nm silica colloids as template.

Highly dispersed platinum catalysts prepared by impregnation of texture-tailored carbon xerogels

Pt/C catalysts were prepared by impregnation of carbon xerogels with H 2PtCl 6 aqueous solutions. Three supports with various pore textures were used: two micro-mesoporous (maximum pore size = 10 and 40 nm, respectively) and one micro-macroporous (maximum pore size = 70 nm). After impregnation, drying and reduction, the metal particles were at most 1–1.5 nm in diameter. The Pt dispersion was close to 100% in the case of the xerogel with large mesopores. For the two other supports, a small fraction of Pt was trapped in blocked micropores. The specific catalytic activity obtained for benzene hydrogenation was 4–10 times higher than that obtained with active charcoal-supported catalysts prepared by a similar method. The high dispersion of Pt was attributed to the presence in the xerogel of large mesopore or macropore volumes, which facilitates impregnation, and a low amount of oxygenated surface groups.

Role of Nanosized Zirconia on the Properties of Cu/Ga2O3/ZrO2 Catalysts for Methanol Synthesis

AbstractThe introduction of mesoporous nanosize zirconia to the catalyst for methanol synthesis dedicates the nanosized catalyst and mesoporous duplicated properties. The catalyst bears the larger surface area, larger mesoporous volume and more uniform diameter, more surface metal atoms and oxygen vacancies than the catalyst prepared with the conventional coprecipitation method. The modification of microstructure and electronic effect could result in the change of the reduced chemical state and decrease of reducuction temperature of copper, donating the higher activity and methanol selectivity to the catalyst. The results of methanol synthesis demonstrate that the Cu+ is the optimum active site. Also, the interaction between the copper and zirconia shows the synergistic effect to fulfil the methanol synthesis.

Fabrication and Physical Properties of Organic and Carbon Aerogel Derived from Phenol and Furfural

Phenol can be used as a cheap raw material to prepare organic and carbon aerogels based upon the gelation and supercritical drying in ethanol. In addition, organic and carbon aerogels could also be obtained by directly drying phenol-furfural alco-gels at ambient pressure under proper preparation conditions. The effect of the preparation conditions, such as the phenol-furfural (PF) concentration, the mass ratio of HCl to phenol (HCl/P), the mole ratio of phenol to furfural (P/F) and the gelation temperature, on the gelation ability and the bulk density was studied. The aerogels obtained have a three-dimensional network that consists of approximately 20 nm particles, which define numerous mesopores with diameter less than 50 nm. Organic aerogels obtained have high BET surface areas of 267–503 m/g and large mesopore volumes of 0.657–2.734 cm/g. Carbonization generates numerous micropores of ca. 0.45 nm in diameters but impairs to some extent the mesopore structure. As a result, carbon aerogels have high BET surface areas of 507–561 m/g, large micropore volumes of 0.106–0.168 cm/g and small mesopore volumes of 0.505–0.710 cm/g relative to their organic aerogel precursors. XRD characterization indicates that carbon aerogels are more crystalline than activated carbon but less than graphite.

Organic and carbon aerogels from the NaOH‐catalyzed polycondensation of resorcinol–furfural and supercritical drying in ethanol

AbstractOrganic aerogels and related carbon aerogels were prepared from the NaOH‐catalyzed polycondensation of resorcinol–furfural (RF) and supercritical drying in ethanol. The effect of the preparation conditions, including the RF concentration, molar ratio of resorcinol (R) to NaOH, and molar ratio of R to furfural, on the gelation time and bulk density was studied. The chemical structure of the organic aerogel was revealed by IR spectroscopy. The pyrolysis process of the organic aerogel was investigated by thermogravimetric analysis. According to characterizations of transmission electron microscopy and nitrogen adsorption, the organic and carbon aerogels we obtained had a three‐dimensional network that consisted of around 30‐nm particles, which defined numerous mesopores of less than 30 nm. As a result, the aerogels had high Brunauer–Emmett–Teller surface areas (698–753 m2/g) and large mesopore volumes (1.09–1.64 cm3/g). X‐ray diffraction characterization indicated that the carbon aerogel was more crystalline than activated carbon but less activated than graphite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1429–1435, 2005

Effect of metal oxides on the pyrolysis residues of poly(ethylene terephthalate): Formation of carbonaceous submicron, nano-scale filaments and mesoporous compounds

Thermal decomposition of mixture of poly(ethylene terephthalate) (PET) and metal oxide has been investigated. Morphology of pyrolysis residues has been observed by using scanning electron microscopy. Among various oxides examined the addition of zinc oxide or trivalent rare earth oxide (Ln 2O 3) resulted in the formation of porous fibre-like structures with the diameter of ∼1 μm for ZnO and ∼100 nm (or thinner) for Ln 2O 3. The formation process as well as thermal decomposition behaviour has been studied by various analytical methods. The thermal decomposition of PET on single crystal ZnO indicated that the unique morphology was due to the oxygen-terminated surface of the metal oxide. Furthermore, pore structures of the carbonaceous compounds from various PET–metal oxide mixtures have been determined by nitrogen adsorption isotherm at −196 °C. It was found that the carbonaceous compounds obtained from PET–Fe 2O 3 and PET–Ln 2O 3 had large mesopore volumes. This was confirmed also by the adsorption study of large molecules such as humic acid (HA).