Cellulose-based Carbon Aerogels Research Articles

One-Pot Synthesis of Cellulose-Based Carbon Aerogel Loaded with TiO2 and g-C3N4 and Its Photocatalytic Degradation of Rhodamine B.

A cellulose-based carbon aerogel (CTN) loaded with titanium dioxide (TiO2) and graphitic carbon nitride (g-C3N4) was prepared using sol-gel, freeze-drying, and high-temperature carbonization methods. The formation of the sol-gel was carried out through a one-pot method using refining papermaking pulp, tetrabutyl titanate, and urea as raw materials and hectorite as a cross-linking and reinforcing agent. Due to the cross-linking ability of hectorite, the carbonized aerogel maintained a porous structure and had a large specific surface area with low density (0.0209 g/cm3). The analysis of XRD, XPS, and Raman spectra revealed that the titanium dioxide (TiO2) and graphitic carbon nitride (g-C3N4) were uniformly distributed in the CTN, while TEM and SEM observations demonstrated the uniformly distributed three-dimensional porous structure of CTN. The photocatalytic activity of the CTN was determined according to its ability to degrade rhodamine B. The removal rate reached 89% under visible light after 120 min. In addition, the CTN was still stable after five reuse cycles. The proposed catalyst exhibits excellent photocatalytic performance under visible light conditions.

Enhanced hydrogen storage and CO2 capture capacities on carbon aerogels from Ni-N co-doping

Carbon aerogels (CAs) has been a promising candidate for gas adsorption due to their unique attributes, but the poor surface properties and temperature reliance limit the application range. Investigations have proven that surface modification can enhance the adsorption performance. Thus, nickel and nitrogen co-doped cellulose-based carbon aerogels were synthesized by introducing nanoparticles. The outcomes demonstrate the excellent adsorption capacity and reversible adsorption/desorption features. Nickel particles improved the dissociation of hydrogen by “hydrogen spillover” effect, and interacted electrostatically with CO2 enhanced the capture performance. Nitrogen particles enhanced the unsaturation of Ni active sites and the surface basicity, resulting a stronger interaction force with adsorbed gases. Ultimately, despite a slightly decrease in specific surface area and micropore volume, the sample exhibit the hydrogen storage capacity of 0.79 wt.% (298 K) and 7.4 wt.% (77 K), and the CO2 capture of 17.1 mmol/g (298 K). Unique design strategy of co-doping reduced the reliance on surface area and temperature changes, and is expected to be a regular means of industrial modification of carbon materials.

A novel cost-effective kapok fibers and regenerated cellulose-based carbon aerogel for continuous oil/water separation

The development of cost-effective, environmentally friendly, and reusable superabsorbent materials for removing oil spills from water presents significant challenges. Herein, a novel, cost-effective, environmentally friendly, and reusable carbon aerogel (KRxCA) was synthesized by combining kapok fibers (KF) with hardwood pulp regenerated cellulose, dissolving in a mixture of N-methyl morpholine-N-oxide monohydrate (NMMO) and deep eutectic solvent (DES), which is named co-solvent DNS. This carbon aerogel presents remarkable compressibility, elasticity, and fatigue resistance, maintaining maximum stress after 100 cycles at 50 % strain due to its three-dimensional network of carbonized hollow tubular KF fixed by carbonized regenerated cellulose. The water contact angle (144.7°) indicates the excellent hydrophobicity of the KR10CA, demonstrating the potential for efficient oil/water separation. The resulting ultra-light (3.78 mg cm−3) and high porous (98.9 %) KR10CA exhibits exceptional oil sorption capacity (137.5–371.7 g⋅g−1) and retains 89.3 % of its sorption capacity after ten extrusion cycles. Additionally, as a filter membrane, the KR10CA effectively separates n-hexane from water with a high flux rate (21972.7 L m-2h−1). Therefore, the carbon aerogel derived from renewable resources presents itself as a cost-effective and environmentally friendly oil/water separator for practical application.

Decoration on the inner surface of low-tortuosity microchannels derived from wood plate for highly stable lithium sulfur batteries

The low-tortuosity microchannels of wood-based carbon matrix in free-standing cathodes for lithium sulfur batteries (LSBs) were a double-edged sword, which brought in both a high energy density due to a high sulfur loading and severe shuttle effect for poor cycling stability. Herein, a layer of cellulose aerogel extracted from the wood wall was coated on the inner surface of the low-tortuosity microchannels of the wood plate, which was further transformed into a hierarchical carbon matrix using in free-standing cathode for LSBs. The decorated cathode exhibited a maximal specific capacity of 1377.2 mAh g−1 due to the enhanced utilizing ratio of active materials and exceptional cycling stability even under a high current density (1 C) for more than 500 cycles. Furthermore, the decorated cathode maintained good cycling stability with a higher sulfur areal loading (6.3 mg cm−2). The cellulose-based carbon aerogel coated on the inner surface of low-tortuosity microchannels provided a large specific surface area. This decoration strategy not only provided physical restriction on polysulfides but also increased conversion sites for polysulfides, improving the cycling performance of the wood-based free-standing cathode of LSBs. This work provided a potential structural design strategy for the advanced free-standing cathode of LSBs.

Hierarchically porous cellulose-based carbon aerogels with N-doped skeletons and encapsulated iron-based catalysts for efficient tetracycline catalytic degradation

Three-dimensional interpenetrating and hierarchically porous carbon material is an efficient catalyst support in water remediation and it is still a daunting challenge to establish the relationship between hierarchically porous structure and catalytic degradation performance. Herein, a highly porous silica (SiO2)/cellulose-based carbon aerogel with iron-based catalyst (FexOy) was fabricated by in-situ synthesis, freeze-drying and pyrolysis, where the addition of SiO2 induced the hierarchically porous morphology and three-dimensional interpenetrating sheet-like network with nitrogen doping. The destruction of cellulose crystalline structure by SiO2 and the iron-catalyzed breakdown of glycosidic bonds synergistically facilitated the formation of electron-rich graphite-like carbon skeleton. The unique microstructure is confirmed to be favorable for the diffusion of reactants and electron transport during catalytic process, thus boosting the catalytic degradation performance of carbon aerogels. As a result, the catalytic degradation efficiency of tetracycline under light irradiation by adding only 5 mg of FexOy/SiO2 cellulose carbon aerogels was as high as 90 % within 60 min, demonstrating the synergistic effect of photocatalysis and Fenton reaction. This ingenious structure design provides new insight into the relationship between hierarchically porous structure of carbon aerogels and their catalytic degradation performance, and opens a new avenue to develop cellulose-based carbon aerogel catalysts with efficient catalytic performance.

Cuprous oxide/copper oxide interpenetrated into ordered mesoporous cellulose-based carbon aerogels for efficient photocatalytic degradation of methylene blue

Cuprous oxide/copper oxide interpenetrated into ordered mesoporous cellulose-based carbon aerogels for efficient photocatalytic degradation of methylene blue

Natural microfibrils/regenerated cellulose-based carbon aerogel for highly efficient oil/water separation

Cellulose-based carbon aerogels as biodegradable and renewable biomass materials have presented potential applications in oil/water separation. Herein, a novel carbon aerogel composed of natural microfibrils/regenerated cellulose (NM/RCA) was directly prepared by economical hardwood pulp as raw material using a novel co-solvent composed of deep eutectic solvent (DES) and N-methyl morpholine-N-oxide monohydrate (NMMO·H2O). In addition, the morphology and structure of the filiform natural microfibers could be remained after carbonized at 400 ℃, which resulted in a low density (8–10 mg cm−3), high specific surface area (768.89 m2 g−1) and high sorption capability. In addition, the aerogel exhibited high compressibility, outstanding elasticity, excellent fatigue resistance, and recyclability (80.5% height recovery after repeating 100 cycles at the strain of 80%). Due to the morphology and composition of the carbonized microfiber surface, the superhydrophobic materials with a water contact angle of 151.5°, could sorb various oils and organic solvents with 65–133 times its own weight and maintain 91.9% sorption capacity after 25 cycles. In addition, the aerogels could achieve the continuous separation of carbon tetrachloride (CCl4) from water with a high flux rate of 11,718.8 L m−2 h−1. Therefore, our prepared NM/RCA aerogels are anticipated to have broad potential applications in oil purification and contaminant remediation.

Deep eutectic solvents promote the formation of ultradispersed ZrO2 in cellulose-based carbon aerogel for the transfer hydrogenation of biomass aldehydes

Zr-carbon aerogel (Zr-DCCA) was prepared by using renewable deep eutectic solvents (DESs) and cellulose nanofiber as sacrifice templates. The Zr-DCCA shows high conversion, selectivity and stability for the transfer hydrogenation of various biomass aldehydes to alcohols. While lower catalytic performance was obtained using Zr-based carbon aerogel (Zr-CCA) prepared without DESs in precursors. A series of characterizations showed that Zr-DCCA possesses the higher dispersion and smaller size of ZrO2 nanoparticles and thus shows stronger acid/base properties than Zr-CCA. In addition, traditional stirring for the reaction and centrifugation for recycling are not required, which simplifies equipment and operations, making the process more valuable to practice.

A novel adsorptive and photocatalytic system for dye degradation using ZIF-8 derived carbon (ZIF-C)-modified graphene oxide nanosheets

BackgroundAerogels have attracted widespread interest in adsorption and photocatalysis. The effect of single aerogel material cannot meet the demand and we can enhance the adsorption and photocatalysis efficiency via adding other materials such as ZIF-8 and graphene oxide (GO). MethodsWe developed an adsorptive and photocatalytic system of ZIF-GO/CCA using a cellulose-based carbon aerogel (CCA) for the fabrication of GO nanosheets modified with ZIF-8-derived carbon (ZIF-C), followed by pyrolysis. The characteristics were evaluated using SEM, HRTEM, BET, XRD, XPS, UV–vis DRS, ESR, PL, EIS and LC-MS analysis. Significant findingsCCA exhibit hierarchical porosity and conductive network, which provides abundant active sites for dye adsorption and degradation. ZnO and g-C3N4 were formed after the incorporation of ZIF-C into GO to, promote charge separation. In the presence of 1ZIF-GO/CCA and at an initial concentration of 300 mg·L−1 MG, the removal of MG exceeded 96%. The removal capacity reached 1152 mg·g−1 after adsorption-photocatalysis for 120 min. 1ZIF-GO/CCA showed the largest specific surface area (375.059 m2·g−1). GO served as an excellent electron accepter to enable fast electron transfer from the ZIF-C to the conduction band of GO. The narrower bandgap (2.06 eV) and lower resistance during charge transfer promoted the separation of e−/h+ and contributed to the higher photocatalytic activity of ZIF-GO/CCA. Further, ZIF-GO/CCA showed increased recyclability. The plausible photocatalytic mechanism for the 1ZIF-GO/CCA was discussed.

Three-dimensional directional cellulose-based carbon aerogels composite phase change materials with enhanced broadband absorption for light-thermal-electric conversion

Energy shortage, environmental and ecological issues have prompted a focus on effective solar energy utilization. Using composite phase change materials (PCMs) as an energy storage medium is an important method to achieve efficient solar energy conversion. Biomass materials are highly desirable for solar applications due to their wide range of sources, low cost, environment-friendly, and natural porous structure. In this study, cellulose is selected as a carbon source precursor. Three-dimensional (3D) directional cellulose-based carbon aerogels (CBCA) are constructed through an immersion expansion, orientation, freeze-drying, and carbonization process. Taking tert-butanol/ deionized water as co-solvent, the aerogel shows high specific surface and productivity as well as low structural shrinkage. 3D directional graphitized porous network and graphene guarantee excellent broadband absorption, efficient heat transfer pathways, and effective thermal storage ability. Stearic acid (SA) and graphene are melt blending, followed by a vacuum-impregnating process for the formation of 3D composite PCMs. The thermal storage capability of PCMs is greater than 96%, accompanied by the highest thermal conductivity of 1.17 W/(m·K) with 0.5 wt% graphene. Moreover, the highest light-thermal conversion efficiency can reach 90.3%. It also has a maximum light-thermal-electric energy conversion output power of 1.80 mW. This work provides a feasible, economical strategy for highly efficient solar energy storage and thermal energy utilization.

FeCo alloy nanoparticle decorated cellulose based carbon aerogel as a low-cost and efficient electromagnetic microwave absorber

Magnetic FeCo alloy nanoparticle decorated cellulose-based carbon aerogel (FeCo@CCA) exhibits efficient electromagnetic microwave absorption performance with a RLmin of −49.5 dB and an EAB of 10.88 GHz.

N-doped cellulose-based carbon aerogels with a honeycomb-like structure for high-performance supercapacitors

Derived from abundant biomass, porous carbon materials that have a unique structure, a high specific surface area, and heteroatom doping are promising electrodes for supercapacitors. In this work, using cellulose as the raw material and polypyrrole as the nitrogen source, a porous N-doped carbon aerogel with an interconnected honeycomb-like structure is synthesized by using ice crystals as a template, along with a facile CO2 activation treatment. The carbon aerogels possess a three-dimensional percolation network with a high specific surface area (1196 m2g − 1) and numerous micropores (0.58 cm3g − 1), which aid electrolyte penetration and ion storage. In addition, the doped N heteroatoms contribute to a pseudo-capacitance. As a result, the supercapacitor based on the prepared carbon aerogel exhibits a high specific capacitance (160 F g − 1), good charging/discharging rates, and an excellent cycling stability (only 0.18% loss after 3000 cycles). A specific energy up to 21.9 Wh kg−1 is achieved at a specific power of 145 W kg−1 when using a 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte. This work demonstrates that a N-doped, cellulose-based carbon aerogel with an interconnected honeycomb-like percolation structure is a promising electrode material for high-performance supercapacitors.

Compressible, anisotropic lamellar cellulose-based carbon aerogels enhanced by carbon dots for superior energy storage and water deionization

Heteroatom-doped carbon materials have received great attention for applications in electrode materials. However, conventional heteroatom-doping methods sacrifice conductivity, stability, and specific surface area (SSA). Here, the carbon quantum dots (CDs) are used as carriers of N, P, O to form electron-rich regions promoting electron transport without decreasing stability and SSA. The CDs promote the formation of graphitic nitrogen in the composite, which effectively reduces their internal resistance by increasing the dielectric constant. Moreover, the orderly growth of ice crystals generates a unique bridged layer structure under bidirectional freeze-casting in a mixture of GO/CDs/microfibrillated cellulose, which gives the composite super-compressibility. Notably, the optimal sample has a 117% increase in specific capacitance. The CDs also improve wettability and thus reduce the charge transfer resistance giving a large desalination capacity of 32.59 mg g−1 (504 mg L−1 NaCl). This work illustrates the unique role of CDs in improving the electrochemical performance of composites.

High-performance asymmetric supercapacitor made of NiMoO4 nanorods@Co3O4 on a cellulose-based carbon aerogel.

In this study, a new nanoporous material comprising NiMoO4 nanorods and Co3O4 nanoparticles derived from ZIF-67 supported by a cellulose-based carbon aerogel (CA) has been successfully synthesized using a two-step hydrothermal method. Due to its chemical composition, the large specific surface and the hierarchical porous structure, the NiMoO4@Co3O4/CA ternary composite yields electrodes with an enhanced specific capacitance of 436.9 C/g at a current density of 0.5 A/g and an excellent rate capability of 70.7% capacitance retention at 5.0 A/g. Moreover, an advanced asymmetric supercapacitor (ASC) is assembled using the NiMoO4@Co3O4/CA ternary composite as the positive electrode and activated carbon as the negative electrode. The ASC device exhibits a large capacitance of 125.4 F/g at 0.5 A/g, a maximum energy density of 34.1 Wh/kg at a power density of 208.8 W/kg as well as a good cyclic stability (84% after 2000 cycles), indicating its wide applicability in energy storage. Finally, our results provide a general approach to the construction of CA and MOF-based composite materials with hierarchical porous structure for potential applications in supercapacitors.

Directional preparation of superhydrophobic magnetic CNF/PVA/MWCNT carbon aerogel.

Carbon aerogels have attracted considerable attention in basic research and for their potential applications in many fields. Here, the fabrication of a magnetic cellulose nanofibre (CNF)/poly(vinyl alcohol) (PVA)/multiwalled carbon nanotubes (MWCNT) carbon aerogel (m-CPMCA) is reported using a simple freeze-drying followed by a carbonisation process, and direct immobilisation of Fe3O4 nanoparticle on the surface of aerogels. The obtained target aerogel has the characteristics of low density (0.098 g/cm3), high porosity (>90%) and 3D interpenetrating porous structures. Furthermore, m-CPMCA has a surprising compressive strength (about 0.35 MPa) which is obviously higher than many other cellulose-based carbon aerogels. After Carbonization, m-CPMCA exhibits superhydrophobicity, selective absorption for organic solvents and fire-resistance. The m-CPMCA also exhibited a magnetic response and can absorb oil on the water surface and can be actuated by a small magnet. More importantly, the m-CPMCA could be recycled many times by combustion, which showed economic significance. To sum up, the authors believe that m-CPMCA will become a very potential adsorbent for dealing with the increasingly serious problem of organic pollution.

Carbon Aerogel-Supported Nickel and Iron for Gasification Gas Cleaning. Part I: Ammonia Adsorption

Biomass gasification is a promising way to obtain “green energy”, but the gas composition makes it unsuitable for use in traditional technologies (i.e., IC engine). Gas purification over nickel and/or iron catalysts is an attractive alternative. Cellulose-based carbon aerogels (CAGs) have shown suitable physical chemical properties for use as catalyst supports. In this work, nickel and iron catalysts are supported on CAG made from cellulose microfibers. Microfibers were impregnated with (NH4)2SO4 to increase the mass yield. Carbonization was evaluated at different heating rates, maximum temperatures, and dwell times to generate CAGs. Resulting chars were characterized by N2 adsorption, X-ray diffraction (XRD), and Raman spectroscopy. The CAG with better properties (specific surface, pore size, thermal resistance) was impregnated with the metal precursor salt via incipient wetness and treated with H2. Catalysts were characterized by transmission electron microscopy (TEM), XRD, N2 adsorption, and inductively coupled plasma optical emission spectrometry (ICP-OES). Ammonia adsorption was studied over CAG and catalysts to estimate the thermodynamic parameters. The impregnation with ((NH4)2SO4 improves thermal resistance of the char obtained from carbonization. The catalysts exhibit higher adsorption capacity than CAG (without metal), indicating chemical interaction between ammonia and metals. The metal-ammonia interaction is stronger on Fe than on Ni catalyst, which is consistent with reported theoretical calculations.

A novel carbon aerogel prepared for adsorption of copper(II) ion in water

A novel carbon aerogel with network pore and surface group of hydroxyl was prepared from cellulose colloid, through sol-gel reaction, freeze-drying and carbonization. Surfactant like isooctyl alcohol ether phosphate was taken as structure inducer in sol-gel reaction, for construction of porous network in the prepared samples. Characteristic of a specific area about 725.12 m2/g and total pore volume about 0.64 cm3/g, the prepared cellulose-based carbon aerogel of CCA2, has a maximum capacity about 55.25 mg/g for Cu2+ in neutral aqueous solution. Its adsorption equilibrium can be reached within 10 min in an aqueous solution of pH7.0 at 25 °C, while desorption of Cu2+ need about 1 h eluted by HCl or HNO3 solution of 0.01 M. And regeneration of the carbon aerogel in adsorption of Cu2+ can be repeated for five times, remaining 96% adsorption capacity. It is also found in adsorption process the kinetics nicely follows pseudo-second-order rate expression, and the isotherm fits Langmuir model.

Versatile Cellulose-Based Carbon Aerogel for the Removal of Both Cationic and Anionic Metal Contaminants from Water.

Hydrothermal carbonization of cellulose in the presence of the globular protein ovalbumin leads to the formation of nitrogen-doped carbon aerogel with a fibrillar continuous carbon network. The protein plays here a double role: (i) a natural source of nitrogen functionalities (2.1 wt %) and (ii) structural directing agent (S(BET) = 38 m(2)/g). The applicability in wastewater treatment, namely, for heavy metal removal, was examined through adsorption of Cr(VI) and Pb(II) ion solely and in a mixed bicomponent aqueous solutions. This cellulose-based carbogel shows an enhanced ability to remove both Cr(VI) (∼68 mg/g) and Pb(II) (∼240 mg/g) from the targeted solutions in comparison to other carbon materials reported in the literature. The presence of competing ions showed little effect on the adsorption efficiency toward Cr(VI) and Pb(II).

Synthesis and Properties of Platinum Nanocatalyst Supported on Cellulose-Based Carbon Aerogel for Applications in PEMFCs

Platinum nanoparticles supported on nanostructured cellulose-based carbon aerogels (carbonized aerocellulose, CAC) were evaluated in proton exchange membrane fuel cell (PEMFC). The CAC substrate was synthesized through the dissolution, gelation, regeneration, supercritical CO2 drying and pyrolysis of cellulose. The Pt nanoparticles deposition was performed by impregnation of the CAC with H2PtCl6, followed by Ptz+ species reduction either under H2 at 300–400°C or in basic NaBH4 solution. While H2 reduction leads to uniform Pt nanoparticles well-dispersed over the CAC surface, larger agglomerates form with NaBH4 reduction, as revealed by transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). The reduction methods influences the quantity of platinum deposited, which may be increased by using multiple impregnation/reduction steps. The specific surface area of Pt and specific/mass activities towards oxygen reduction of the Pt/CAC materials, investigated using the rotating disk electrode setup, are similar to those of commercial Pt/Carbon Black (CB). Finally, PEMFC unit cell testing demonstrates that a Pt/CAC sample synthesized using three successive impregnation/reduction steps, loaded at ca. 14 wt % Pt/(Pt + C), competes with state-of-the-art Pt/CB electrocatalysts of comparable Pt loading.

Elaboration and Characterizations of Platinum Nanoparticles Supported on Cellulose-Based Carbon Aerogel

This work investigates the deposition of Pt nanoparticles onto carbonized aerocellulose (CAC), via impregnation of the CAC with H2PtCl6 followed by reduction either under H2 at 300-400{degree sign}C or in a basic NaBH4 solution. H2 reduction yields uniform Pt nanoparticles (average diameter < 2 nm) dispersed over the CAC surface, as revealed by transmission electron microscopy (TEM). Larger agglomerates can be seen in TEM images for NaBH4 reduced samples, which is confirmed by powder X-ray diffraction (XRD). A rotating disk electrode was employed to analyze the electrochemical properties of the Pt/CAC materials. The active area of the platinum nanoparticles was evaluated using hydrogen adsorption/desorption cyclic voltammetry and CO-stripping measurements. The oxygen reduction reaction kinetic parameters of the Pt/CAC materials compare well with those of commercial Pt/Carbon Black (CB). Finally, PEMFC unit cell testing demonstrates that a Pt/CAC electrocatalyst synthesized using 3 successive impregnation/reduction steps can compete with state-of-the-art Pt/CB electrocatalysts.