Mesoporous Carbon Monoliths Research Articles

Electric Field-Assisted Uptake of Hexavalent Chromium Ions with In Situ Regeneration of Carbon Monolith Adsorbents.

The uptake of hexavalent chromium (Cr(VI)) ions from wastewater is of great significance for environmental remediation and resource utilization. In this study, a self-designed instrument equipped with an oxidized mesoporous carbon monolith (o-MCM) as an electro-adsorbent is developed. o-MCM with a super hydrophilic surface displayed a high specific surface area (up to 686.5m2 g-1 ). With the assistance of an electric field (0.5V), the removal capacity of Cr(VI) ions is as high as 126.6mgg-1 , much higher than that without an electric field (49.5mgg-1 ). During this process, no reduction reaction of Cr(VI) to Cr(III) ions is observed. After adsorption, the reverse electrode with 10V is used to efficiently desorb the ions on the carbon surface. Meanwhile, the in situ regeneration of carbon adsorbents can be obtained even after ten recycles. On this basis, the enrichment of Cr(VI) ions in a special solution is achieved with the assistance of an electric field. This work lays a foundation for the uptake of heavy metal ions from wastewater with the assistance of the electric field.

In-situ regeneration of carbon monoliths as an environmental-benign adsorbent for environmental remediation via a flow-through model

Electro-adsorption is considered an attractive and efficient technology for wastewater treatment, which still faces challenges for practical applications. Mesoporous carbon monolith (MCM) as an adsorbent with the aid of an electric field in a self-designed device via a flow-through model was developed. The high removal performances for organic (242.72 and 195.31 mg g−1 for methylene blue and ofloxacin, respectively) and inorganic (33.34 mg g−1 for Cu2+) contaminants with the aid of an electric field were obtained, higher than those without an electric field. The low resistance, high specific capacitance, and specific surface area of MCM were found to be beneficial for the transportation and storage of contaminants, thus improving the removal performance. The high recyclability of MCM with eight runs was also observed through the efficient electro-desorption process, which was helpful for the in-situ regeneration of the carbon adsorbent. Furthermore, the efficient electro-desorption of Cu2+ ions from the MCM surface could enrich Cu2+ in the defined solution with a concentration of 36.23 mg L-1 after ten times electro-adsorption/desorption recycles.

High-Performance Heat Storage Phase Change Composite by Highly Aligned N-Doped Mesoporous Carbon for Efficient Battery Thermal Management

Limited by leakage from inherent liquid to solid phase transition and inferior heat transfer, pristine organic phase change materials (PCMs) possess extremely low thermal storage performance. Thus, establishing shape-stable PCM composites with enhanced thermal conductivity and latent heat is a key task for practical application. Herein, we constructed N-doped mesoporous carbon monoliths with a highly aligned structure by directional freeze-drying to encapsulate polyethylene glycol. Benefiting from the mesoporous carbon matrix and pyridinic N from N-doping, the PCM composite possessed large latent heat (140 J·g–1) and leakage proof at 80 °C. Meanwhile, the highly aligned structure created a fast heat transfer pathway that improved thermal conductivity of the PCM composite by 1500%. Being different from most research studies, highly aligned carbon was utilized as the support directly without skeletons, which could increase PCM loading capacity and thermal conductivity as well. The PCM composite can be employed as promising candidates for thermal management working efficiently to decrease battery pack temperature by 13 °C and improve discharge capacity by 28%.

A Simple Method for the Synthesis of High Surface Area Mesoporous Carbon Monolith via Soft Template Technique

The aim of this work was the synthesis and characterization of a mesoporous carbon monolith (MC). The MC was prepared using the soft template method. Resorcinol and formaldehyde were used as the carbon precursor and triblock copolymer Pluronic F127 as the templating agent under acidic conditions. Several techniques were used to characterize the synthesized material such as Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller nitrogen sorption measurements (BET), Powder X-Ray Diffraction (PXRD), Fourier Transform Infrared spectroscopy (FTIR), and Thermogravimetric Analysis (TGA). The work characterized the changes due to the decomposition of the template during the carbonization process to form the pores in the carbon material. The result confirmed that the mesoporous monolithic carbon prepared had a high surface area and a narrow pore size in the mesometer range.

Facile synthesis of ordered mesoporous carbon monolith with close-packed microspheres structure through emulsion templating

Abstract Carbonaceous monoliths with captivating interior compartmentalized structure hold a great potential for numerous applications, but their synthesis is extremely challenging due to lack of viable synthesis approaches. To address this challenge, herein, we report a method for access to an unprecedented carbonaceous monolith with compartment structure by taking advantage of the interface and the limited coalescence phenomenon occurring in emulsions stabilized by solid particles. The developed monolith consists of three dimensionally close-packed ordered mesoporous carbon microspheres with excellent mechanical strength, high specific surface area and homogeneous nitrogen doping. The unique structure is unattainable for the conventional bulk synthesis even at exactly the same conditions. Moreover, the strategy makes it possible to tailor the interior structure of the monolith through precisely controlling synthesis conditions. More importantly, we envision that the Pickering droplet-based synthesis strategy along with its synthesis mechanism may open up a new avenue to preparation of various macroscopic materials with interior compartment structures in view of its high degree of flexibility and control, and further brings great opportunity for fascinating practical applications.

Reply to “Comments on ‘Electrochemical study of tetraalkylammonium tetrafluoroborate electrolytes in combination with microporous and mesoporous carbon monoliths’ [Electrochimica Acta 268 (2018) 121–130]” by Teresa A.A. Centeno [Electrochim. Acta 296 (2019) 1163–1165

Reply to “Comments on ‘Electrochemical study of tetraalkylammonium tetrafluoroborate electrolytes in combination with microporous and mesoporous carbon monoliths’ [Electrochimica Acta 268 (2018) 121–130]” by Teresa A.A. Centeno [Electrochim. Acta 296 (2019) 1163–1165

Salt-template synthesis of mesoporous carbon monolith for ionogel-based supercapacitors

Mesoporous carbon monoliths (MCM) were prepared by using soluble salt as templates. During the synthesis, a freeze-drying process enables a surface coating of self-assembled Na2SiO3 salt particles with sucrose, which is further transformed into carbon by heat treatment. After removal of the salt templates by washing, MCM were obtained. MCM samples exhibit high specific surface area together with high mesoporous volume, whose pore sizes can be tuned from 10 to 30 nm by adjusting the ratio between salt and carbon sources. MCM materials were further used as electrodes in combination with ionogel electrolyte to assemble a solid-state supercapacitor. In this configuration, MCM electrodes show capacitance as high as 75 F g−1 and good rate performance thanks to the carbon monolith pore size selected.

Multifunctional, Self-Activating Oxygen-Rich Holey Carbon Monolith Derived from Agarose Biopolymer

Agarose, a natural biopolymer, is carbonized to synthesize an economical lightweight (0.05 g cm–3) mesoporous carbon monolith with large BET surface area (625 m2 g–1). The monolith prepared at different temperatures (700, 800, 900 °C) exhibits interesting morphologies without using any activating agent. The holey pattern appearing at 900 °C, besides increasing the meso/microporosity, confirms the self-activation at higher temperature. Most interestingly, the thick sheet-like morphology obtained at 700 °C is changed to nanoporous carbon flakes as the synthesizing temperature is increased to 800 and 900 °C. This synthesis approach affords an oxygen-enriched meso/microporous carbon monolith that constitutes high pseudocapacitance in addition to electric double layer charge. Lightweight carbon monolith exhibits excellent thermal and mechanical characteristics having a weight bearing capacity of ∼5900 times compared to its weight without developing any deformity. The electrochemical performance of carbonized agarose (CAR) tested in 1 M H2SO4 exhibits superior charge storage capacity in CAR 900 (302 F g–1 at 5 mV s–1) compared to that of CAR 800 (124 F g–1) and CAR 700 (107 F g–1). The symmetric cell (1 × 1 cm2 area) fabricated using CAR 900 as electrodes exhibits excellent cell performance over 5000 charge/discharge cycles with ∼98% capacity retention. Three symmetric CAR 900 cells connected in series enable powering a red LED bulb (3 V) that indicates excellent sustainability of agarose-derived carbon in energy storage devices.

Porous carbon monoliths with pore sizes adjustable between 10 nm and 2 μm prepared by phase separation – New insights in the relation between synthesis composition and resulting structure

Porous carbon monoliths with tunable porosity are promising materials for a variety of applications like energy storage and adsorption. But the synthesis of carbons with monolithic shape and controlled porosity is often time-consuming and expensive. Here, micro-/macroporous and micro-/mesoporous carbon monoliths were synthesized via a simple process of polymerization induced phase separation of resorcinol and formaldehyde followed by drying at ambient pressure and carbonization. The carbon monoliths are mechanically stable and exhibit specific surface areas between 390 and 1100 m2·g−1. The size of the macro- and mesopores can be tailored over a wide range from approximately 10 nm to 2 μm by simply altering the solvent composition during the synthesis of the organic monoliths. The influence of solvent composition and resorcinol concentration on the pore size in the carbon monoliths was investigated with a focus on the smaller pore sizes and an exponential relation was observed. Finally, selected monoliths were activated in a stream of CO2 to produce hierarchically porous monoliths with specific surface areas between 1000 and 2400 m2·g−1. The activated monoliths were characterized in terms of their CO2 adsorption and showed adsorption capacities of up to 3.10 mmol·g−1 at 298 K.

Worm-hole structured mesoporous carbon monoliths synthesized with amphiphilic triblock copolymer

In the present work, mesoporous carbon monoliths with worm-hole structure had been synthesized through hydrothermal reaction by using amphiphilic triblock copolymer F127 and P123 as templates and resole as carbon precursor. Synthesis conditions, carbonization temperature and pore structure were studied by Fourier transform infrared, thermogravimetric analysis, transmission electron microscopy and N2 adsorption–desorption. The results indicated that the ideal pyrolysis temperature of the template is 450 °C. The organic ingredients were almost removed after further carbonized at 600 °C and the mesoporous carbon monoliths with worm-hole structure were obtained. The mesoporous carbon synthesized with P123 as single template exhibited larger pore size (6.6 nm), higher specific surface area (747 m2 g−1), lower pore ratio (45.9 %) in comparison with the mesoporous carbon synthesized with F127 as single template (with the corresponding value of 4.9 nm, 681 m2 g−1, 49.6 %, respectively), and also exhibited wider pore size distribution and lower structure regularity. Moreover, the higher mass ratio of template P123/resole induced similar pore size, larger specific surface area and lower pore ratio at the same synthesizing condition. It was also found that the textural structure of mesoporous carbon was affect by calcination atmosphere.

Bio-sourced mesoporous carbon doped with heteroatoms (N,S) synthesised using one-step hydrothermal process for water remediation

Mesoporous carbon monoliths doped with nitrogen, sulphur or both have been prepared in one step hydrothermal carbonization from bio-based precursors. Glucose and pyrrole carboxaldehyde or glucose and thiophene carboxaldehyde aqueous solutions have been used as precursors for nitrogen and sulphur doped carbon materials, respectively. In the same hydrothermal process, a salt-templating approach was used to endow the material with mesoporosity. Additionally, the materials were also pyrolysed in N2 at 973 K. The average mesopore size of resulting xerogels is tuned by the used dopant. Both the doping and mesoporosity enhanced substantially the adsorption of large dye molecules. Accordingly, these metal-free, cost-effective and sustainable materials are excellent candidates for liquid phase environmental and energy applications where the dopant may play a role as catalytic active phase or electronic modulator.

Enhancement of phenol adsorption on mesoporous carbon monolith modified by NaOH and NH3: equilibrium and kinetic studies

Carbon-coated monoliths (CCMs) were chemically modified by sodium hydroxide (NaOH) and ammonia aqueous solution (NH3) in order to enhance phenol adsorption. The adsorptive performance of phenol onto CCM-NaOH and CCM-NH3 was comparatively evaluated by batch mode. Experiments were carried out by varying pH, contact time, and initial adsorbate concentration. The optimum molarities for modification were 1.5M NaOH and 2M NH3 solutions. The basicity groups of modified CCM were 0.198 and 0.339 mmol g−1 for CCM-NaOH and CCM-NH3 by Boehm titration method, respectively. The presence of basic groups (O–H and NH3) was also confirmed by FT-IR. The studies showed optimum phenol adsorption, at pH 4 for both adsorbents. As compared to unmodified CCM, the CCM-NH3 and CCM-NaOH enhanced phenol uptake by 16.5 and 9.7%, respectively. The maximum equilibrium adsorption capacities were 51.29±0.7 mg g−1 for CCM-NaOH and 54.45±0.7 mg g−1 for CCM-NH3 in the range of concentration 50–350 mg L−1. The equilibrium adsorption data for CCM-NaOH and CCM-NH3 was fitted to both Langmuir and Freundlich models. Kinetic studies of both modified CCMs showed better applicability of pseudo-second-order kinetics model. The regeneration studies showed a 26% drop in adsorption capacity after four cycles for CCM-NH3.

A facile nanocasting strategy to nitrogen-doped porous carbon monolith by treatment with ammonia for efficient oxygen reduction

A series of three-dimensional N-doped hierarchical macro- and meso-porous carbon monoliths (NCMs), which were prepared successfully using a facile nanocasting strategy in combination with pyrolysis in NH3, showed comparable catalytic activity but superior durability and methanol tolerance to Pt/C for the oxygen reduction reaction.

Facile synthesis of gradient mesoporous carbon monolith based on polymerization-induced phase separation

In this paper, a gradient mesoporous carbon (GMC) monolith derived from the mixtures of phenolic resin (PF) and ethylene glycol (EG) was prepared by a facile route based on polymerization-induced phase separation under temperature gradient (TG). A graded biphasic structure of PF-rich and EG-rich phases was first formed in preform under a TG, and then the preform was pyrolyzed to obtain the GMC monolith. The TG is mainly induced by the thermal resistance of the preferential phase separation layer at high temperature region. The pore structure of the monolith changes gradually along the TG direction. When the TG varies from 58°C to 29°C, the pore size, apparent porosity and specific surface area of the monolith range respectively from 18 nm to 83 nm, from 32% to 39% and from 140.5 m2/g to 515.3 m2/g. The gradient porous structure of the monolith is inherited from that of the preform, which depends on phase separation under TG in the resin mixtures. The pyrolysis mainly brings about the contraction of the pore size and wall thickness as well as the transformation of polymerized PF into glassy carbon.

Synthesis and Characterization of Gyroidal Mesoporous Carbons and Carbon Monoliths with Tunable Ultralarge Pore Size

Ordered mesoporous carbons with high pore accessibility are of great interest as electrodes in energy conversion and storage applications due to their high electric and thermal conductivity, chemical inertness, and low density. The metal- and halogen-free synthesis of gyroidal bicontinuous mesoporous carbon materials with uniform and tunable pore sizes through bottom-up self-assembly of block copolymers thus poses an interesting challenge. Four double gyroidal mesoporous carbons with pore sizes of 12, 15, 20, and 39 nm were synthesized using poly(isoprene)-block-poly(styrene)-block-poly(ethylene oxide) (ISO) as structure-directing triblock terpolymer and phenol-formaldehyde resols as carbon precursors. The highly ordered materials were thermally stable to at least 1600 °C with pore volumes of up to 1.56 cm(3) g(-1). Treatment at this temperature induced a high degree of sp(2)-hybridization and low microporosity. Increasing the resols/ISO ratio led to hexagonally packed cylinders with lower porosity. A single gyroid carbon network with high porosity of 80 vol % was obtained using a similar synthesis strategy. Furthermore, we present a method to fabricate monolithic materials of the gyroidal carbons with macroscopic shape and thickness control that exhibit an open and structured surface with gyroidal features. The gyroidal materials are ideally suited as electrode materials in fuel cells, batteries, and supercapacitors as their high, three-dimensionally connected porosity is expected to allow for good fuel or electrolyte accessibility and to prevent total pore blockage.

Biomass derived mesoporous carbon monoliths via an evaporation-induced self-assembly

Evaporation-induced self-assembly has been applied in the synthesis of crack-free mesoporous carbon monolith with good mechanical stability using a waste plant material as carbon precursor and triblock copolymer F127 as template. The carbon monolith was characterized using transmission electron microscopy, scanning electron microscopy, nitrogen adsorption–desorption measurement, X-ray diffraction and Fourier transform infrared spectroscopy. The results showed that the carbon monolith is mesoporous, has a surface area of 219m2/g, and a narrow pore size distribution of 6.5nm.

Fabrication of Hierarchical Macroporous/Mesoporous Carbons via the Dual-Template Method and the Restriction Effect of Hard Template on Shrinkage of Mesoporous Polymers

A series of hierarchically ordered macro-/mesoporous polymer resins and macro-/mesoporous carbon monoliths were synthesized using SiO2 opal as a hard template for the macropore, amphiphilic triblock copolymer PEO–PPO–PEO as a soft template for the mesopore, and phenolic resin as a precursor for the polymer or carbon. The obtained hierarchical macro-/mesoporous frameworks had highly periodic arrays of uniform macropores that were surrounded by walls containing the mesoporous structures. The mesoporous structure of the walls was adjusted using different precursors for the synthesis of FDU-14, FDU-15, and FDU-16. Results of the N2 adsorption–desorption analysis showed that the Brunauer–Emmett–Teller surface areas, the pore volumes, and the mesopore sizes of the macro-/mesoporous carbons were much larger than those of the FDU-14, FDU-15, and FDU-16 carbon materials. The mesopore size of the samples clearly increased with the increasing heat-treatment temperature when the temperature was below 700 °C. The resu...

High-temperature hydrothermal synthesis of magnetically active, ordered mesoporous resin and carbon monoliths with reusable adsorption for organic dye

Magnetically active, thermally stable, and ordered mesoporous resin (MOMR-200) and carbon (MOMC-200) monoliths were prepared by one-pot hydrothermal synthesis from resol, copolymer surfactant, and iron cations at high-temperature (200 ∘C), followed by calcination at 360 ∘C and carbonization at 600 ∘C. X-ray diffraction results show that both MOMR-200 and MOMC-200 have ordered hexagonal mesoporous symmetry, and N2 isotherms indicate that these samples have uniform mesopores (3.71, 3.45 nm), high surface area (328, 621 m2/g) and large pore volume (0.31, 0.43 cm3/g). Transmission electron microscopy shows that iron nanoparticles, which are superparamagnetic in nature, are dispersed in the network. More importantly, the high temperature (200 ∘C) products exhibit much better stability than the samples synthesized at low temperature (100 ∘C). Interestingly, MOMC-200 has higher adsorption capacity for organic dyes when compared with commercial adsorbents (activated carbon and macroporous resin: XAD-4). Combining the advantages such as magnetically active, thermally stable networks, ordered and open mesopores, high surface area, large pore volume, adsorption of pollutants in water and desorption in ethanol solvent, MOMC-200 is potentially important for water treatments.

Preparation of Monolithic Transparent Mesoporous Silica and Mesoporous Onion-Like Carbon

Large-sized, crack-free silica monoliths have been fabricated by a fast and convenient way via EISA method using P123 as soft template and 1-hexadecyl-3-methylimidazolium bromide (［C16mim］Br) as additive. The hydrogen bonds formed between ILs and the silano groups of silica gel play crucial roles in the form of the bulk, transparent silica monolith. The mesoporous structure onion-like carbon monoliths were prepared with the transparent silica monolith as template via the nanocasting technique. The mesoporous silica and carbon monoliths have been characterized by the XRD, HRTEM, N2sorption and elemental analysis. The results reveal that pore diameter of the mesoporous carbon about 3.47nm, and the specific surface area of carbon with a nitrogen content of 4.2%, can be tuned from 408.2-629.0m2/g. HRTEM shows that this carbon material with nanoonions structure.

Preparation and Mechanism of Interconnected Mesoporous Carbon Monoliths from Phenolic Resin/Ethylene Glycol Mixtures

The preparation of interconnected mesoporous carbon monoliths (MCMs) derived from phenolic resin/ethylene glycol mixtures based on polymerization-induced phase separation have been investigated for fabrication of complex-shape SiC ceramics. The effect of the ethylene glycol content, curing catalyst and the curing temperature on the pore structure and pore distribution of carbon monoliths has also been studied, with emphasis on controlling the apparent porosity and pore size distribution. Fractal dimensions (DF) was proposed to evaluate the morphologies of carbon monoliths by using the box counting method. The results show that interconnected mesoporous carbon monoliths with narrow pore size distribution were obtained by changing the curing temperature and the content of ethylene glycol, curing catalyst in the resin mixtures and its mechanism was discussed in this paper. In this paper, interconnected mesoporous structure was attributed to the mechanism of spinodal decomposition (SD), which was discussed in detail. Carbon monoliths inherit their porosity from cured resins where it was formed as a result of phase separation of resin-rich and glycol- rich phases.