Hierarchical Porous Carbon Monoliths Research Articles

Mesoporosity enhancement in carbon monoliths through incorporation of a nonpolar solvent with a templating source for fast adsorption of organic dyes

Obtaining hierarchical porous carbon monoliths with bigger and controlled pore sizes through soft templating and without macroscopic phase separation remains a challenge for the synthesis. In this study, we tried to introduce nonpolar solvents (benzene or toluene) together with a pluronic template in the sol-gel polycondensation route of polymer precursors to obtain carbons in the monolithic form without macroscopic phase separation during the polymerization stage. The porosity results show that carbon monoliths vary solely with mesopore features while retaining macropores, compared to carbon monoliths obtained with pluronic template alone. The mesopore volumes almost double with an increase in pore sizes by 1 nm at maxima, and the pore sizes extend to 30 nm from the addition of nonpolar solvent. This is possible due to the interaction of the nonpolar solvent with the hydrophobic core of the pluronic template, which causes swelling of micelles during the polymerization stage, and thus finally, retention of larger pore sizes and pore volumes within carbon monoliths. The structural and surface chemistry characterizations ensure a similar behaviour of the resulting carbon monoliths that are further investigated for the adsorption kinetics of different types of organic dyes (methylene blue, methyl orange, and congo red) to understand the sole role of mesoporosity. The adsorption kinetics follows the trend of mesopore volumes with fast adsorption vis-à-vis the sizes and molar masses of organic dyes.

Self-supporting composited electrocatalysts of ultrafine Mo2C on 3D-hierarchical porous carbon monoliths for efficient hydrogen evolution

A self-supporting binder-free electrocatalyst with ultrafine Mo2C particles anchored on a hierarchical porous carbon monolith exhibits superior HER performance.

Texture Tailorable Hierarchical Porous Carbon Monolith with Large Mass Loading for High Performance Supercapacitor

In this research, texture tailorable 3-dimension (3D) interconnected hierarchical porous carbon (HPC) monoliths were prepared by a simple method. By regulation of the polymerization rate of furfural alcohol in solvent, 3D HPC monoliths with various textures are obtained. The optimum HPC monolith shows high specific surface area of ∼580 m2 g-1 and desired morphology, texture and pore structure. The HPC monolith with ∼15 mg cm-2 mass loading delivers a high capacitance of 129.1 F g-1 at 0.1 A g-1 and shows high rate capability of 76.9% capacitance retention when the current density increased 50-fold to 5 A g-1. The assembled supercapacitor can drive a toy fan for more than 30 min.

Nanocrystalline celluloses-assisted preparation of hierarchical carbon monoliths for hexavalent chromium removal

Hierarchical porous carbon monoliths with a 3D framework were synthesized through a facile sol–gel process using resorcinol-melamine–formaldehyde (RMF) as carbon precursors, and nanocrystalline celluloses (NCCs) as the structural inducing agent, followed by ambient pressure drying and carbonization. Polymerization of the RMF resin occurs around the nanorod-like NCCs dispersed homogeneously in water, which is quite beneficial for the formation of an interconnected network and supports the rigid macroporous structure. A hierarchical porous carbon monolith with modest micropores and well-developed macropores was prepared after CO2 activation at 950°C. The microporous structure was generated from the network of RMF polymer chains, while the macroporous structure was formed from the interconnection of polymer networks induced by NCCs. The obtained carbon monolith has a large specific surface area of 1808m2g−1 and shows a high adsorption capacity of 463mgg−1 for toxic Cr(VI) ions. Moreover, the activated carbon monolith exhibits a high selectivity for Cr(VI) in the coexistence of several other metal ions. These outstanding advantages of carbon monoliths, including their micro/macroporous structures, rich functional groups, low cost and easy synthesis, endow them with potential for use in a wide range of applications.

Synthesis and characterization of lignosulfonate-derived hierarchical porous graphitic carbons for electrochemical performances

Porous carbon can be widely applied in energy ranging from lithium-ion batteries to supercapacitors. We here propose a novel hierarchical porous graphitic carbon (HPGC) monolith to replace conventional activated carbon for achieving excellent electrochemical performance. In this monolith structure made from the cross-linking of lignosulfonate without any templating agent, the nanoscale core is composed of porous amorphous carbon, while the microscale shell is formed by graphitic carbon and generated within mesoporous wall of HPGC. As evidenced by cyclic voltammetry, the abundant porosity and the high surface area not only offer sufficient reaction sites to store electrical charge physically, but also accelerate the liquid electrolyte to penetrate the electrode and the ions to reach the reacting sites. Of special interest is the fact that HPGC monolith maintains mesoporous without extrinsic template agent.

Hierarchical porous nitrogen-doped partial graphitized carbon monoliths for supercapacitor

Porous carbon monoliths have attracted great interest in many fields due to their easy availability, large specific surface area, desirable electronic conductivity, and tunable pore structure. In this work, hierarchical porous nitrogen-doped partial graphitized carbon monoliths (N–MC–Fe) with ordered mesoporous have been successfully synthesized by using resorcinol-formaldehyde as precursors, iron salts as catalyst, and mixed triblock copolymers as templates via a one-step hydrothermal method. In the reactant system, hexamethylenetetramine (HMT) is used as nitrogen source and one of the carbon precursors under hydrothermal conditions instead of using toxic formaldehyde. The N–MC–Fe show hierarchically porous structures, with interconnected macroporous and ordered hexagonally arranged mesoporous. Nitrogen element is in situ doped into carbon through decomposition of HMT. Iron catalyst is helpful to improve the graphitization degree and pore volume of N–MC–Fe. The synthesis strategy is user-friendly, cost-effective, and can be easily scaled up for production. As supercapacitors, the N–MC–Fe show good capacity with high specific capacitance and good electrochemical stability.

One-pot hydrothermal synthesis and supercapacitive performance of nitrogen and MnO co-doped hierarchical porous carbon monoliths

Nitrogen and MnO co-doped hierarchical porous carbon monolith (N-MnO-HPCM) materials were synthesized through a facile one-pot hydrothermal method. The resulting N-MnO-HPCM materials had hierarchical porous structure, high BET surface area (606m2/g), large pore volume (0.33cm3/g), and contained evenly dispersed MnO nanoparticles of about 6nm in the carbon matrix. Their electrochemical performances as electrodes for supercapacitors were investigated. N-MnO-HPCM material exhibited an excellent electrochemical performance with a specific capacitance of 261.7F/g at a current density of 1A/g. It also showed a good rate capability with 74% capacity retention at high current density (5A/g), indicating its potential applications in supercapacitors.

Facile Synthesis of Hierarchical Porous Carbon Monolith: A Free-Standing Anode for Li-Ion Battery with Enhanced Electrochemical Performance

Hierarchical porous carbon aerogel with a continuous three-dimensional framework has been synthesized via evaporation induced, coassembly based sol–gel polymerization of organic and inorganic precursors, for application as the anode in a Li-ion battery. A combination of resorcinol (R) and formaldehyde (F) as organic precursors and hybrid silica sources composed of TEOS (tetraethyl orthosilicate), APTES (3-aminopropyl triethoxysilane) and APTEMS (3-aminopropyl trimethoxysilane) as inorganic precursors has been used to obtain the porous carbon monolith. The porosity of the carbon aerogel has been tuned by varying the ratio of APTES/APTEMS. Postpyrolysis, the etching of the composite to remove silica network resulted in the formation of a high specific surface area (BET ∼ 2600 m2 g–1) carbon containing the distribution of micro-, meso- and macroporous domains. The electrode exhibits a high reversible capacity of 890 mAh g–1 after 100 cycles at a current density of 50 mA g–1.

Lignin-derived interconnected hierarchical porous carbon monolith with large areal/volumetric capacitances for supercapacitor

A large scale 3D interconnected hierarchical porous carbon monolith was developed by a novel synthetic approach from the 2nd most abundant natural polymer, lignin. This newly derived carbon monolith possess desirable microstructure and high conductivity that enables the fabrication of a binder-/conductive additive-free thick electrode. The carbon monolith delivered simultaneously excellent areal/volumetric capacitances of 3.0 F cm−2/97.1 F cm−3, at a high mass loading of 14.4 mg cm−2. The areal capacitances obtained in our work are the highest among the reported carbon-based electrodes. The carbon monolith based symmetric supercapacitor achieved a high areal energy density of 0.16 mWh cm−2 at 1.75 mW cm−2, with excellent cycling performance (∼95% retention after 10,000 cycles). Our work demonstrates the successful conversion of biomass waste into high-performance eletrode, and the promising areal/volumetric performances further suggest the developed approach may provide a positive route to improving the energy density of supercapacitor.

Facile one-step synthesis of hierarchical porous carbon monoliths as superior supports of Fe-based catalysts for CO2 hydrogenation

A versatile strategy involving one-step desilication of coke-deposited spent zeolite catalyst was successfully developed to prepare hierarchical porous carbon monoliths (HPCMs).

Ionothermal synthesis of microporous and mesoporous carbon aerogels from fructose as electrode materials for supercapacitors

In the present work, a series of hierarchical porous carbon monoliths were prepared from fructoseviaa one-step ionothermal carbonization approach using an iron-based ionic liquid as solvent, and a porogenic agent.

Hierarchical porous graphitic carbon monoliths with detonation nanodiamonds: synthesis, characterisation and adsorptive properties

The addition of nano-carbons to composite materials is an area of significant research interest, when their addition results in improved properties. This work reports on the use of detonation nanodiamond (DND) in the preparation of porous carbon monoliths and an investigation of the properties of the final carbon–nanocarbon composite material. Porous carbon–nanodiamond (CND) monoliths, with macro-, meso- and micropores were prepared by carbonisation of a resorcinol-formaldehyde (RF) polymeric rod with an Fe(III) catalyst and spherical silica template. Pore characteristics and BET surface areas were determined from N2 isotherms, with surface areas in the range of 214–461 m2 g−1, depending on DND content. SEM imaging further confirmed the hierarchical pore structure present, where there was a trimodal structure for monoliths containing nanodiamond following pyrolysis up to 900 °C. Thermogravimetric analysis, TEM imaging, energy dispersive X-ray electron spectroscopy and Raman spectroscopy were employed to evaluate the properties of this new composite material. The adsorptions of methylene blue (MB) and neutral red (NR) dyes from water onto the composite monoliths were investigated and compared with activated carbon in order to further evaluate their physical and adsorptive properties. CND materials adsorb these two cationic dyes more effectively than activated carbon, due to a more accessible pore network, and DND content had a direct effect on adsorption capacities for the dyes. The adsorption isotherms coincided with Langmuir and Freundlich adsorption models. Maximum adsorption capacities of 599 and 284 mg g−1 were achieved for NR and MB, respectively, on the CND composites.

Producing hierarchical porous carbon monoliths from hydrometallurgical recycling of spent lead acid battery for application in lithium ion batteries

An environmentally clean process to recycle the paste from a spent lead acid battery (LAB) is further developed to produce a porous carbon anode material for a lithium ion battery (LIB) which is under increasing focus as the solution for future energy storage and distribution networks.

Increasing the dissolution rate and oral bioavailability of the poorly water-soluble drug valsartan using novel hierarchical porous carbon monoliths

In the present study, a novel hierarchical porous carbon monolith (HPCM) with three-dimensionally (3D) ordered macropores (∼400nm) and uniform accessible mesopores (∼5.2nm) was synthesized via a facile dual-templating technique using colloidal silica nanospheres and Poloxamer 407 as templates. The feasibility of the prepared HPCM for oral drug delivery was studied. Valsartan (VAL) was chosen as a poorly water-soluble model drug and loaded into the HPCM matrix using the solvent evaporation method. Scanning electron microscopy (SEM) and specific surface area analysis were employed to characterize the drug-loaded HPCM-based formulation, confirming the successful inclusion of VAL into the nanopores of HPCM. Powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) demonstrated that the incorporated drug in the HPCM matrix was in an amorphous state and the VAL formulation exhibited good physical stability for up to 6 months. In vitro tests showed that the dissolution rate of HPCM-based formulation was increased significantly compared with that of crystalline VAL or VAL-loaded 3D ordered macroporous carbon monoliths (OMCMs). Furthermore, a pharmacokinetic study in rats demonstrated about 2.4-fold increase in oral bioavailability of VAL in the case of HPCM-based formulation compared with the commercially available VAL preparation (Valzaar®). These results therefore suggest that HPCM is a promising carrier able to improve the dissolution rate and oral bioavailability of the poorly water-soluble drug VAL.

Hierarchical porous nitrogen-rich carbon monoliths via ice-templating: high capacity and high-rate performance as lithium-ion battery anode materials

Ice-templating is utilized to prepare hierarchically porous carbon monolith with aligned macropores. N-doped and graphene-incorporated carbon composite can be easily produced, demonstrating a reversible capacity of about 300 mA h g−1 at a high current density of 10 A g−1.

Synthesis of Hierarchical Porous Carbon Monoliths with Incorporated Metal–Organic Frameworks for Enhancing Volumetric Based CO2 Capture Capability

This work aims to optimize the structural features of hierarchical porous carbon monolith (HCM) by incorporating the advantages of metal-organic frameworks (MOFs) (Cu₃(BTC)₂) to maximize the volumetric based CO₂ capture capability (CO₂ capacity in cm³ per cm³ adsorbent), which is seriously required for the practical application of CO₂ capture. The monolithic HCM was used as a matrix, in which Cu₃(BTC)₂ was in situ synthesized, to form HCM-Cu₃(BTC)₂ composites by a step-by-step impregnation and crystallization method. The resulted HCM-Cu₃(BTC)₂ composites, which retain the monolithic shape and exhibit unique hybrid structure features of both HCM and Cu₃(BTC)₂, show high CO₂ uptake of 22.7 cm³ cm⁻³ on a volumetric basis. This value is nearly as twice as the uptake of original HCM. The dynamic gas separation measurement of HCM-Cu₃(BTC)₂, using 16% (v/v) CO₂ in N₂ as feedstock, illustrates that CO₂ can be easily separated from N₂ under the ambient conditions and achieves a high separation factor for CO₂ over N₂, ranging from 67 to 100, reflecting a strongly competitive CO₂ adsorption by the composite. A facile CO₂ release can be realized by purging an argon flow through the fixed-bed adsorber at 25 °C, indicating the good regeneration ability.

One-pot synthesis, characterization and properties of acid-catalyzed resorcinol/formaldehyde cross-linked silica aerogels and their conversion to hierarchical porous carbon monoliths

A rapid and facile synthesis of resorcinol/formaldehyde cross-linked silica (RF/SiO2) aerogels was carried out in one pot based on an acid-catalyzed route, instead of the previously reported base-catalyzed ones. The gelation time was reduced to several hours at room temperature while it took several days even under heating conditions in the base-catalyzed ones. The interpenetrating network of RF/SiO2 aerogels showed similar porous structures with those of silica aerogels or RF aerogels. Their thermal conductivity was as low as that of the typical glass wool materials. The mechanical properties are characterized by dynamic mechanical analysis and compression testing. At room temperature, the results of compression testing show that the compressive Young’s modulus or ultimate failure strength of RF/SiO2 aerogel specimen is higher than that of native SiO2 aerogels with a similar density. The one-pot method improves the efficiency and reduces the cost of RF/SiO2 aerogels. The hierarchical porous carbon monoliths are also converted from carbonized RF/SiO2 aerogels by an additional HF treatment. Hence, they could be further explored as multifunctional candidate materials for thermal, mechanical, and electrochemical applications.

On the use of mesophase pitch for the preparation of hierarchical porous carbon monoliths by nanocasting

A detailed study is given on the synthesis of a hierarchical porous carbon, possessing both meso- and macropores, using a mesophase pitch (MP) as the carbon precursor. This carbon material is prepared by the nanocasting approach involving the replication of a porous silica monolith (hard templating). While this carbon material has already been tested in energy storage applications, various detailed aspects of its formation and structure are addressed in this study. Scanning electron microscopy (SEM), Hg porosimetry and N2 physisorption are used to characterize the morphology and porosity of the carbon replica. A novel approach for the detailed analysis of wide-angle x-ray scattering (WAXS) from non-graphitic carbons is applied to quantitatively compare the graphene microstructures of carbons prepared using MP and furfuryl alcohol (FA). This WAXS analysis underlines the importance of the carbon precursor in the synthesis of templated porous carbon materials via the nanocasting route. Our study demonstrates that a mesophase pitch is a superior precursor whenever a high-purity, low-micropore-content and well-developed graphene structure is desired.

Synthesis, characterization, and hydrogen storage capacities of hierarchical porous carbide derived carbon monolith

Hierarchical porous carbide-derived carbon monoliths (HPCDCM) were prepared by selective extraction of silicon from ordered mesoporous silicon carbide monoliths (OMSCM) through chlorination at high temperature. The OMSCM was firstly synthesized by pressure-assisted nanocasting procedure using KIT-6 silica as the hard template and polycarbosilane (PCS-800) as the preceramic precursor. The OMSCM showed cubic ordered mesoporous structure with specific surface area of over 600 m2 g−1. After the chlorination, the resulting HPCDCM demonstrated very high specific surface area (2933 m2 g−1), large pore volume (2.101 cm3 g−1) with large volume of micropores (0.981 cm3 g−1), and narrow dual pore size distributions (micropore: 0.9 nm, and mesopore: 3.1 nm). Macropores in the micron range were observed in the HPCDCM. The mesostructural ordering was not maintained in the HPCDCM and the volume of the HPCDCM had greatly shrunk, by 21.2% compared to that of the OMSCM, but the tablet-like appearance was well retained in the HPCDCM. At −196 °C, the HPCDCM shows good hydrogen uptakes of 2.4 wt% and 4.4 wt% at 1 bar and 36 bar, respectively. The calculated volumetric hydrogen storage capacity is 11.6 g L−1 at 36 bar. The gravimetric hydrogen uptake capacity of the HPCDCM is comparable to, or higher than, those of previously reported ordered mesoporous carbide-derived carbon (CDC) powder and microporous CDC powder.

Flow-through immobilization of Candida rugosa lipase on hierarchical micro-/macroporous carbon monolith

► Hierarchical porous carbon monolith shows great potential for enzyme immobilization support. ► Oxygenated micro-/macroporous carbon monolith can also be used as a good candidate for lipase support in continuous process. ► Flow-through immobilization is introduced as an interesting technique to improve enzyme properties and enzyme catalyzed reaction. Hierarchical micro-/macroporous carbon monoliths are prepared as enzyme carriers for flow-through process. The immobilization of Candida rugosa lipase on micro-/macroporous carbon monoliths is studied. Lipase is immobilized by physical adsorption which lipase solution is circulated through the micro-/macroporous carbon monolith. An accessibility of lipase to the surface inside the micro-/macroporous carbon monolith is enhanced by flow-through method which promotes enzyme–surface interaction and finally leads to rapid enzyme immobilization. After immobilization is conducted for 10 min, the maximum protein binding can be measured. In terms of substrate-immobilized lipase reactions, flowing of substrate through lipase immobilized micro-/macroporous carbon monolith promotes high efficiency in both reaction and product withdrawal. Moreover, at high flow rates of lipase solution in immobilization step, the lipase activity increases. Oxygenated surface of micro-/macroporous carbon monoliths support also demonstrates an interesting effect on lipase immobilization and biocatalyst activity. The initial reaction rate of lipase immobilized on oxygenated surface carbon monolith support has higher activity compared with normal surface.