Porous Carbon Monoliths Research Articles

Synthesis of pegylated metal phthalocyanines, incorporation in hierarchically porous carbon monoliths and evaluation as heterogeneous catalysts

Synthesis of pegylated metal phthalocyanines, incorporation in hierarchically porous carbon monoliths and evaluation as heterogeneous catalysts

Facile synthesis of hierarchically porous carbon monolith without templating agent for various applications in energy and catalysis

Monolithic carbon with hierarchically porous structure has a promising prospect for a wide range of applications in the fields of energy, environment, catalysis, etc. Due to the reliance on the utilization of templating agents, conventional preparation approaches often suffer from time-consuming preparation, complex post-processing, and uneconomical cost. Herein, we develop a novel strategy to match the sol-gel transition with the phase separation process for the direct preparation of hierarchically porous carbon monolith (HPCM) without templating agent. Resorcinol and resol are employed as carbon sources to adjust the polymerization for the formation of bi-continuous microstructure. Well-defined hierarchical pores and large specific surface area for fast mass diffusion enable the HPCM to be a prospective kind of electrode material in supercapacitor with an outstanding specific capacitance over 350 F g−1 (1.0 A g−1). After facile sulfonation, the modified HPCM can act as solid acid catalyst to realize a high-performance production of 5-hydroxymethylfurfural (5-HMF) in a 90 % yield with turnover frequency (TOF) value up to 155.9 h−1. Additionally, HPCM also exhibits an excellent Joule heating effect, which can be applied to the thermal management after compounding with phase change materials. The desirable integrated performance enables HPCM to be a valuable material suitable for various applications.

Efficient Preparation and Optimization of Activated Carbon Monoliths from Resorcinol-Formaldehyde Resins for CO2 Capture

Activated carbon monoliths with developed porosity, high surface area and excellent adsorption properties were successfully prepared from resorcinol-formaldehyde resins using a physical activation method. The primary objective of this study was to examine the impact of key parameters, namely hexamethylenetetramine content (0.08–0.2 g), pyrolysis heating rate (5–20 °C/min) and activation time (1–7 h), on the final characteristics of the activated carbon in order to identify the optimal operating conditions to achieve the desired properties. All the cured resin samples were pyrolyzed at 900 °C under a nitrogen atmosphere, while the activation process took place in the presence of CO2. The evaluation of the activated carbon materials was based on the CO2 adsorption capacity and BET surface area, micropore area and total pore volume, which were employed as the criteria for selecting the optimal activated carbon. The synthesized porous carbon monoliths exhibited good properties: high BET surface area (900 m2/g), high CO2 adsorption capacity (5.33 mmol/g at 0 °C and 1 bar, 3.8 mmol/g at 25 °C and 1 bar) and good CO2 selectivity for CO2/N2 and CO2/CH4 mixtures. These results were obtained with a pyrolysis heating rate of 5 °C/min and a 3 h activation period.

Phenolic resin filled wood-derived hierarchically porous carbon monolith for high areal capacitance supercapacitors

Wood-based electrodes are widely used in supercapacitors due to their renewable and three-dimensional self-supported properties. Low space utilization of wood-based electrodes seriously restricts its practical applications. In this paper, a wood/phenolic resin composite was designed, which can effectively enhance the space utilization of wood and ensure a hierarchical porous structure. The prepared balsa wood/phenolic resin composite-derived electrode obtained a high areal capacitance (8169 mF cm–2), which is 954 % of pure balsa wood-based electrode. Moreover, the assembled symmetrical supercapacitor device exhibits outstanding electrochemical performance, displaying a high areal capacitance of 3.3 F cm–2, and a competitive volumetric energy density of 2.88 mWh cm–3. More importantly, this design has been successfully used to prepare various species wood-derived electrodes. Therefore, as a general strategy, which gives a novel idea for the design of wood-derived electrodes and may affect other fields using wood-based materials.

Monolithic metal-based/porous carbon nanocomposites made from dissolved cellulose for use in electrochemical capacitor

Porous metal-based carbon nanocomposites, with a monolithic shape, were prepared by a one-pot synthesis from dissolved cellulose and metallic salts using a simple, cheap, and environmentally friendly route. Their potential performances as electrochemical capacitors were tested with three metal precursors (M = Cu, Mn, and Fe) with two loadings and in an asymmetric cell for the Fe-based carbon material. Interestingly, here soluble metal precursors were not deposited on a hard cellulose template but mixed in a precooled concentrated NaOH solution where cellulose was previously dissolved, allowing for a good dispersion of the metallic species. After a freezing step where concomitant cellulose regeneration and pore ice-templating phenomena took place, followed by a carbonization step, the mixture led to a porous carbon monolith embedding well-dispersed metal-based nanoparticles having a diameter below 20 nm and present as metallic, oxide, or carbide phase(s) according to the element M. These materials were characterized by different physicochemical techniques and electrochemical tests. Their performances as supercapacitors are discussed in light of the specific behaviour of the metal-based phase and its influence on the carbon matrix properties such as mesopore formation and carbon graphitization. An asymmetric energy storage cell assembled with a Fe-based carbon electrode against a carbon xerogel electrode derived from a phenolic resin shows specific energy and power of 18.3 Wh kg−1 at 5 mA cm−2 and 1.6 kW kg−1 at 25 mA cm−2, respectively.

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.

Treatment of Wastewater Containing Pharmaceutical Micropollutants by Adsorption under Flow in Highly Porous Carbon Monoliths

Treatment of Wastewater Containing Pharmaceutical Micropollutants by Adsorption under Flow in Highly Porous Carbon Monoliths

3D porous alumina/graphene hybrids prepared by atomic layer deposition and their performance for water treatment

Metal / carbon hybrids have impressive potential of applications in many fields: catalysis, energy conversion and storage, environmental. However, further efforts are needed to achieve a better control of homogeneity of the metal oxide deposit on the carbon surface to provide reliable synthesis approaches of metal / carbon hybrids. In this work, atomic layer deposition is used to prepare 3D porous alumina / reduced graphene oxide hybrid monoliths. We show that atomic layer deposition, even though rarely reported to prepare metal oxide / carbon hybrids, allows a conformal coating onto the graphene nanosheet surface. In-depth advanced characterization have been performed thanks to a coupled approach consisting of the preparation of lamellas of the porous hybrid by means of focused ion beam and their analysis by transmission electron microscopy. A good accessibility of the alumina precursors to the internal surface of the prepared 3D porous carbon monoliths was evidenced. The alumina / graphene hybrid prepared with 50 cycles of ALD deposit has a surface as high as 284 m2/g. As a proof-of-concept for the interest of the designed hybrids, they are tested for the removal of Congo red, a standard organic dye pollutant. 87 and 98 % of Congo red removal were reached at the first and the second step of adsorption proving the good adsorption performance and reusability ability of the de designed hybrid adsorbents. We believe that such multi-porous 3D alumina / graphene macrostructures that offers a favorable accessibility to the adsorption sites open interesting potentialities for pollution remediation applications.

Enhanced electro-Fenton activity with Fe/Sm2O3 monoliths as novel and efficient heterojunction for glyphosate degradation

Excessive utilization of herbicide has posed irreversible effect on aquatic organisms and human being. FexSmy@PCMs have been synthesized as efficient heterogeneous electro-Fenton catalysts for herbicide degradation, in which H2O2 is in situ generated by the porous carbon monolith (PCM) ground and then H2O2 is activated into •OH by the anchored Fe/Sm2O3. Fe nanocrystals are intimately embedded into the Sm2O3 nanoblocks in Fe0.3Sm0.7@PCM, which can promote the electron transfer and induce synergistic redox cycle. Fe0.3Sm0.7@PCM achieves over 95% glyphosate (GLP) degradation within one hour in neutral condition, which is 30% better than Fe@PCM. Thanks to high efficiency and exceptional stability, Fe0.3Sm0.7@PCM maintains over 94% GLP removal after six consecutive batches.

Separation of alkane isomers in a hierarchically structured 3D-printed porous carbon monolith

Hierarchically structured 3D printed porous carbons monoliths, exhibiting cylinder structures composed of tetragonal cubic centered unit cells, were studied for their applicability in adsorptive pentane (C5) and hexane (C6) alkane isomers separation (linear/branched). Three materials of the same macroscopic shape were employed in the study, which varied in the micro- and mesoporosity by changing the final CO2 activation step: non-activated and activated at 1133 K for 6 and 12 h, respectively. Fixed bed breakthrough experiments were conducted for C5/C6 isomer feed mixtures, covering 373, 423, and 473 K temperatures and total alkane partial pressure up to 50.0 kPa. Results demonstrated that the initial porosity for the non-activated monolith enables the complete separation of linear from their respective branched isomers (slightly adsorbed) via a near molecular sieving effect, showing the following sorption hierarchy order (nC6 > nC5) ≫>≫ (2MP > 3MP > 23DMB ≈ iC5 > 22DMB). Regarding the CO2-activated monoliths, both showed a completely different picture, being all the alkane isomers adsorbed (much higher loadings) following the sorption hierarchy order: nC6 > 3MP > 2MP > 23DMB > 22DMB > nC5 > iC5. These results indicate that besides enhancing the microporosity and available specific surface area, the pore sieving effect of branched alkanes is lost due to the pore widening during the CO2 activation. The breakthrough data for the non-activated monolith is also numerically fitted with a convenient, dynamic adsorption model.

Magnetically Guided Synthesis of Anisotropic Porous Carbons toward Efficient CO2 Capture and Magnetic Separation of Oil

Conventional synthetic strategies do not allow one to impart structural anisotropy into porous carbons, thus leading to limited control over their textural properties. While structural anisotropy alters the mechanical properties of materials, it also introduces an additional degree of directionality to increase the pore connectivity and thus the flux in the designed direction. Accordingly, in this work the structure of porous carbons prepared from resorcinol-formaldehyde gels has been rendered anisotropic by integrating superparamagnetic colloids to the sol-gel precursor solution and by applying a uniform magnetic field during the sol-gel transition, which enables the self-assembly of magnetic colloids into chainlike structures to template the growth of the gel phase. Notably, the anisotropic pore structure is maintained upon pyrolysis of the gel, leading to hierarchically porous carbon monoliths with tunable structure and porosities. With an advantage granted to anisotropic materials, these porous carbons showed higher porosity, a higher CO2 uptake capacity of 3.45 mmol g-1 at 273 K at 1.1 bar, and faster adsorption kinetics compared to the ones synthesized in the absence of magnetic field. Moreover, these materials were also used as magnetic sorbents with fast adsorption kinetics for efficient oil-spill cleanup and retrieved easily by using an external magnetic field.

Solar thermal swing adsorption on porous carbon monoliths for high-performance CO2 capture

Solar thermal swing adsorption on porous carbon monoliths for high-performance CO2 capture

Dual synergistic effects assisting Cu-SeS2 electrochemistry for energy storage

Selenium sulfide (SeS2) features higher electronic conductivity than sulfur and higher theoretical capacity and lower cost than selenium, attracting considerable interest in energy storage field. Although nonaqueous Li/Na/K-SeS2 batteries are attractive for their high energy density, the notorious shuttle effect of polysulfides/polyselenides and the intrinsic limitations of organic electrolyte have hindered the deployment of this technology. To circumvent these issues, here we design an aqueous Cu-SeS2 battery by encapsulating SeS2 in a defect-enriched nitrogen-doped porous carbon monolith. Except the intrinsic synergistic effect between Se and S in SeS2, the porous structure of carbon matrix has sufficient internal voids to buffer the volume change of SeS2 and provides abundant pathways for both electrons and ions. In addition, the synergistic effect of nitrogen doping and topological defect not only enhances the chemical affinity between reactants and carbon matrix but also offers catalytic active sites for electrochemical reactions. Benefiting from these merits, the Cu-SeS2 battery delivers superior initial reversible capacity of 1,905.1 mAh g-1 at 0.2 A g-1 and outstanding long-span cycling performance over 1,000 cycles at 5 A g-1. This work applies variable valence charge carriers to aqueous metal-SeS2 batteries, providing valuable inspiration for the construction of metal-chalcogen batteries.

High Value Utilization of Waste Wood toward Porous and Lightweight Carbon Monolith with EMI Shielding, Heat Insulation and Mechanical Properties.

With the increasing pollution of electromagnetic (EM) radiation, it is necessary to develop low-cost, renewable electromagnetic interference (EMI) shielding materials. Herein, wood-derived carbon (WC) materials for EMI shielding are prepared by one-step carbonization of renewable wood. With the increase in carbonization temperature, the conductivity and EMI performance of WC increase gradually. At the same carbonization temperature, the denser WC has better conductivity and higher EMI performance. In addition, due to the layered superimposed conductive channel structure, the WC in the vertical-section shows better EMI shielding performance than that in the cross-section. After excluding the influence of thickness and density, the specific EMI shielding effectiveness (SSE/t) value can be calculated to further optimize tree species. We further discuss the mechanism of the influence of the microstructure of WC on its EMI shielding properties. In addition, the lightweight WC EMI material also has good hydrophobicity and heat insulation properties, as well as good mechanical properties.

Nano-Fe3O4 coated on carbon monolith for anode enhancement in microbial fuel cells

Anode materials were vital for power production in microbial fuel cells (MFCs). By freeze-drying and carbonization, porous carbon monolith derived from wax gourd (WGCM) was prepared. WGCM was then coated by nano-Fe3O4 to obtain the nano-Fe3O4/WGCM anode. WGCM anode increased the maximum power density of the MFCs from 430.6 mW/m2 to 906.6 mW/m2, while nano-Fe3O4/WGCM anode further promoted it to 1438.8 mW/m2. WGCM had a three-dimensional (3D) microporous network structure, a hydrophilic surface and good conductivity, which enhanced biofilm formation and reduced internal resistance. Fe3O4 increased Geobacter enrichment on anode surface, a popular electricigen in MFCs. Calculated from anode surface microbial cell density and the relative abundance, Geobacter on the nano-Fe3O4/WGCM increased by 41.4% compared with the WGCM anode. The results demonstrated that the preparation of carbon monolith coated with nano-Fe3O4 was a promising method for anode enhancement in MFCs.

Three-Dimensional Carbon Monolith Coated by Nano-TiO2 for Anode Enhancement in Microbial Fuel Cells.

A three-dimensional (3D) anode is essential for high-performance microbial fuel cells (MFCs). In this study, 3D porous carbon monoliths from a wax gourd (WGCM) were obtained by freeze-drying and carbonization. Nano-TiO2 was further coated onto the surface of WGCM to obtain a nano-TiO2/WGCM anode. The WGCM anode enhanced the maximum power density of MFCs by 167.9% compared with the carbon felt anode, while nano-TiO2/WGCM anode additionally increased the value by 45.8% to achieve 1396.2 mW/m2. WGCM enhancement was due to the 3D porous structure, the good conductivity and the surface hydrophilicity, which enhanced electroactive biofilm formation and anodic electron transfer. In addition, nano-TiO2 modification enhanced the enrichment of Acinetobacter, an electricigen, by 31.0% on the anode to further improve the power production. The results demonstrated that the nano-TiO2/WGCM was an effective anode for power enhancement in MFCs.

Enhancement of supercapacitive performance of carboxymethyl cellulose-derived porous carbon monoliths by the addition of carbon nanotubes

In this study, a simple and eco-friendly fabrication strategy for the preparation of porous carbon monoliths with 3-dimensional conductive networks was demonstrated. Porous carbon/carbon nanotube composite monoliths (PCCMs) with large specific surface area and hierarchical pore structures were prepared via eco-friendly ice-templating followed by carbonization. The resulting PCCMs showed excellent electrochemical performance due to their well-developed hierarchical porosity and high electrical conductivity following the addition of 1-D carbon nanotubes. In a 3-electrode configuration, the PCCM-derived electrode delivered a specific capacitance of 240 F g−1 at 1 A g−1. In a practical application, the PCCM-based symmetric capacitor exhibited the specific capacitance of 47.0 F g−1, rate capability of 72.7%, power density of 9.5 kW kg−1 and a cycling stability of ∼100% after 20,000 cycles, respectively. These results suggested that the PCCMs can be applied as an active material for high-performance electrical double-layer capacitors.

Graphene as a promising additive to hierarchically porous carbon monoliths for enhanced H2 and CO2 sorption

This study aimed to examine a synthesis of hierarchically porous carbon monoliths (HPCM) doped with graphene oxide (GO) for H2 and CO2 sorption applications. The synthesis procedure combining the sol-gel process with soft-templating was tuned by adding different quantities of GO (0.5; 2 and 10 wt% of the total amount of polycondensation mixture), as well as different carbonization temperatures (500 °C, 900 °C) of the composite materials during which the reduction of GO to graphene occurs. The degree of GO reduction to graphene and its incorporation into the HPCM matrix of prepared materials were characterized by Raman, FTIR, SEM, TEM, and elemental analysis. Although incorporation was successful, the higher pyrolysis temperature of 900 °C promotes the reduction of GO to graphene, which enhances the (ultra)microporosity (proven by gas physisorption experiments) of the samples, especially of the one with 10% GO addition. The effectivity of materials towards H2 and CO2 sorption was examined by sorption of H2 (77 K, up 1 bar) and CO2 (273 K, up 1 bar), respectively. Addition of any amount of GO together with the used lower pyrolysis temperature of 500 °C reduced the adsorption capacity of the samples for CO2 (from 2.4 to 1.8 mmol g−1) and H2 (from 5.8 to 3.6 mmol g−1) compared to the original HPCM. On the bright side, a 10% addition of GO in combination with a pyrolysis temperature of 900 °C results in industrially perspective material with an H2 and CO2 adsorption capacity of 9.6 mmol g−1 and 4.6 mmol g−1, respectively.

PHP-graphene nanoribbon-assembled porous metallic carbon for sodium-ion battery anode with high specific capacity

In recent years, a number of three-dimensional (3D) porous metallic carbon allotropes have been proposed to be used as anode materials for metal-ion batteries by assembling graphene or penta-graphene nanoribbons. Here, based on density functional theory and tight-binding model, we design a new 3D porous metallic carbon monolith (termed Hex-C568) consisting of PHP-graphene nanoribbons which contain pentagonal, hexagonal and octagonal rings. It is thermally, dynamically and mechanically stable. We find that its metallicity is attributed to the delocalized electrons in the p-orbitals of the sp2 hybridized carbon atoms, and Hex-C568 is a promising anode material for Na-ion batteries with high performance. Its reversible gravimetric and volumetric capacities are 787.53 mAhg−1 and 718.10 mAhcm−3, respectively, with low diffusion energy barrier (0.04–0.30 eV), low average open-circuit voltage (0.26 V), and small volume change during the charging/discharging process (3.71%). These electrochemical properties are superior to those of most recently reported anode materials, suggesting that PHP-graphene nanoribbon is a promising building unit for the design of novel carbon anode materials going beyond graphene and penta-graphene.

Direct Ink 3D Printing of Porous Carbon Monoliths for Gas Separations.

Additive manufacturing or 3D printing is the advanced method of manufacturing monolithic adsorbent materials. Unlike beads or pellets, 3D monolithic adsorbents possess the advantages of widespread structural varieties, low heat and mass transfer resistance, and low channeling of fluids. Despite a large volume of research on 3D printing of adsorbents having been reported, such studies on porous carbons are highly limited. In this work, we have reported direct ink 3D printing of porous carbon; the ink consisted of commercial activated carbon, a gel of poly(4-vinylphenol) and Pluronic F127 as plasticizer, and bentonite as the binder. The 3D printing was performed in a commercial 3D printer that has been extensively modified in the lab. Upon 3D printing and carbonization, the resultant 3D printed porous carbon demonstrated a stable structure with a BET area of 400 m2/g and a total pore volume of 0.27 cm3/g. The isotherms of six pure-component gases, CO2, CH4, C2H6, N2, CO, and H2, were measured on this carbon monolith at 298 K and pressure up to 1 bar. The selectivity of four gas pairs, C2H6/CH4, CH4/N2, CO/H2, and CO2/N2, was calculated by Ideally Adsorbed Solution Theory (IAST) and reported. Ten continuous cycles of adsorption and desorption of CO2 on this carbon confirmed no loss of working capacity of the adsorbent.