Carbon Nanofiber Aerogels Research Articles

Nanoporous Magnetic Carbon Nanofiber Aerogels with Embedded α-Fe/γ-Fe Core–Shell Nanoparticles for Oil Sorption and Recovery

Biomass-based carbon aerogels have received a lot of attention as oil sorbents or oil/water separators due to their effectiveness, low cost, and vast availability of natural resources as their precursors. Magnetically functionalizing the carbon aerogel improves its reusability by magnetic recovery after oil sorption. This work fabricated magnetic carbon nanofibers (MCF) aerogels from the pyrolysis of magnetic bacterial cellulose (MBC) aerogels. The effect of the pyrolysis temperature on the phase transformation and functionalities of the MCF aerogel was investigated. The combined characterization techniques concluded that the MBC aerogel consists of the BC nanofiber matrix decorated with nonmagnetic FeC4H2O4 and magnetic Fe3O4 nanoparticles, which transformed into amorphous carbon nanofibers anchored with the α-Fe/Fe3O4 core–shell structured nanoparticles after pyrolysis at 700 °C. Increasing the pyrolysis temperature to 800–900 °C led to the formation of purer amorphous carbon nanofibers, whereas the nanoparticles turned into the α-Fe/γ-Fe core–shell structure. At 1000 °C, the amorphous carbon structure is better developed and coated on the α-Fe/γ-Fe core–shell nanoparticles. The interpretation explains the results from the magnetic measurement very well and fits perfectly on the Fe–C phase diagram. Furthermore, the MCF aerogels show excellent properties as an efficient oil sorbent, such as large surface area, low density, and hydrophobic properties. Among the samples, the MCF aerogel pyrolyzed at 700 °C (MCF700) exhibits the most desirable properties while requiring the lowest pyrolysis temperature. It could adsorb various oils and organic solvents with high sorption capacity and could be recycled several times. With its magnetic attraction ability, the MCF700 could be magnetically manipulated toward oil, and it could be retrieved after use without direct human contact. These synergistic functionalities make it practically helpful for oil-spill remedies over a large-scale area.

Tailoring pore structures and hydrophobicity of monolithic carbon nanofiber aerogels for optimized adsorption performance

Tailoring pore structures and hydrophobicity of monolithic carbon nanofiber aerogels for optimized adsorption performance

An ultralight, elastic carbon nanofiber aerogel with efficient energy storage and sorption properties.

The fabrication of ultralight strong carbon nanofiber aerogels with excellent elasticity is still a challenge. Herein, 3D mesoporous graphene/carbon nanofibers (G/CNF) were prepared for the first time from polyacrylonitrile/poly(4-vinyl phenol) (PAN/PVPh) electrospun fibers. Through hydrogen bonding interactions between PAN and PVPh polymer chains, traditional soft carbon nanofibers can be converted to form hard nanofiber aerogels with excellent mechanical, electrical, and sorption properties. The specific interactions among PAN/PVPh led to the formation of porous features on carbonized nanofiber foams. The 3D carbon foams are extremely elastic, strong, and light in weight, and they exhibited super oleophilic and fire-resistance properties. Electrochemical studies indicate that the G/CNF foam achieves a capacitance of up to 267 F g-1 (at a scan rate of 1 mV s-1), with an energy density of 37.04 W h kg-1, exhibiting better electrochemical performance than other reported porous carbon devices. In addition, the G/CNF foam also exhibits sorption capacity towards various organic solvents and oils. This study paves the way toward a new class of lightweight and robust porous carbon nanocomposites for application in electrochemical energy storage systems and oil sorption devices.

Engineering bacteria for high-performance three-dimensional carbon nanofiber aerogel

Compared with carbon nanotube (CNT) and graphene (GE) aerogels, the synthesis of three-dimensional (3D) carbon nanofiber (CNF) aerogels that are highly compressible, resilient under cyclic strains, and creep and fatigue resistant remains extremely challenging. Herein, a revolutionary green and scalable biosynthesis is presented, by which a novel 3D CNF aerogel derived from natural bacterial cellulose (BC) decorated with its mother bacteria is created. The as-prepared CNF aerogel possesses excellent mechanical resilience, ultra-low energy loss coefficient, and outstanding cycling stability, which are by far among the best performances for CNT and GE aerogels reported thus far. Furthermore, the CNF aerogel exhibits excellent creep and fatigue resistance and sensitive electrical conductivity change upon compression. Surprisingly, the as-prepared 3D CNF aerogel exhibits superhydrophilicity. These superb properties are attributed to the existing carbonized bacteria in the carbonized BC matrix that serve as crosslinks to strengthen the aerogel and buffers to store deformation energy. This study presents a breakthrough method for the construction of superb and cost-effective 3D CNF aerogel from natural biomass material.

Carbon Nanofiber Aerogel Fabricated by Supercritical Drying and Application in Li–O<sub>2</sub>/CO<sub>2</sub> Battery

Carbon Nanofiber Aerogel Fabricated by Supercritical Drying and Application in Li–O<sub>2</sub>/CO<sub>2</sub> Battery

Cover Feature: Mono‐Doped Carbon Nanofiber Aerogel as a High‐Performance Electrode Material for Rechargeable Zinc‐Air Batteries (5/2021)

Cover Feature: Mono‐Doped Carbon Nanofiber Aerogel as a High‐Performance Electrode Material for Rechargeable Zinc‐Air Batteries (5/2021)

Mono‐Doped Carbon Nanofiber Aerogel as a High‐Performance Electrode Material for Rechargeable Zinc‐Air Batteries

AbstractNitrogen‐doped porous carbon (NPC) materials have attracted increased attention for zinc‐air battery (ZAB) applications because of their comparable electrocatalytic activity to precious metals. However, few metal‐free NPC catalysts exhibit an oxygen reduction reaction performance better than Pt catalysts, together with high oxygen evolution reaction catalytic activity. Herein, an efficient oxygen electrocatalyst based on highly integrated carbon nanofiber (CNF) and NPC aerogels, with CNF as the core and NPC as the shell, is demonstrated. The NPC@CNF aerogels are prepared through a large‐scale, direct pyrolysis of metal‐organic frameworks and bacterial cellulose hybrids. This mono‐doped carbon material with nitrogen heteroatoms displays outstanding bifunctional performance compared to the individual counterparts, which demonstrates the effectiveness of morphological and structural engineering. Density functional theory calculations reveal that the active sites with the participation of multi‐electrons weaken the O−O bond and facilitate the four‐electron oxygen reduction in the dissociation pathway. The ZAB based on the NPC@CNF air electrode exhibits a peak density of 96 mW cm−2 and a stable charge–discharge durability of over 420 cycles with an overpotential increase of only 0.10 V, indicating that the mono‐doped NPC@CNF performs as one of the best bifunctional catalysts among those recently reported metal‐based and metal‐free catalysts.

Ultralight and robust carbon nanofiber aerogels for advanced energy storage

Ultralight and robust carbon aerogels with a spider-web-like 3D network based on the nanofiber welding effect were reported. Their solid-state supercapacitors had a great potential to be applied in flexible energy storage.

Novel synthesis of carbon nanofiber aerogels from coconut matrix for the electrochemical detection of glucose

Bacterial cellulose aerogels (BCAs) were obtained from a delicious food grade coconut. Following with a simple process of carbonized calcination (700 °C~1100 °C). The obtained coconut matrix carbon nanofiber aerogels (CMCNFs) exhibit low density (≤3.47 mg/cm3), high surface area (≥1102 m2/g), and high porosity (≈99.6%), which are much higher than those of common BCAs owing to the removal of hydrogen, oxygen and other elements along with only small volume changes. Due to the flexibility of the nanofiber matrix of our presoma, the three-dimensional network micro-structure is preserved during high temperature carbonization process. The obtained CMCNFs show an excellent conductivity bearing a direct electron transfer process between glucose oxidase (GOx) and electrode surface in the electrochemical processes. It was discovered that CMCNFs can achieve a fast direct electron transfer (DET) of GOx to the rapid detection of glucose. This character should be related to the three-dimensional pore structure determined by carbonization temperature, which has been proved that the CMCNFs calcined at 1000 °C possesses the best capabilities. With merits above, a highly sensitive glucose sensor is successfully prepared by the simple carbonization of coconut cellulose matrix, which expands the application scope of bacterial cellulose aerogels. This work also offers insights for the future develop of protein-based electrochemical devices.

Carbon nanofibril composites with high sulfur loading fabricated from nanocellulose for high-performance lithium-sulfur batteries

Owing to the low cost, high theoretical specific energy density and environmentally friendly, Lithium-sulfur (Li-S) batteries have become one of the most promising candidates for electrical energy storage systems. However, some technical obstacles of lithium sulfur batteries are still addressed, such as the volume expansion, non-conductivity and shuttle effect of polysulfides. Herein, we have described a simple method for preparing carbon nanofiber aerogel (CNFA) via carbonization of the 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TOCN) aerogel. Special three-dimensional (3D) net-like carbon@sulfur (C@S) composite was then successfully fabricated based on CNFA with high porosity, which dramatically alleviates the volume expansion during charging and discharging process of lithium-sulfur battery, improves the conductivity of polysulfide and suppresses the diffusion and dissolution of polysulfide generated during the charge and discharge process. The results showed that the composite material exhibited an extremely high reversible capacity of 590 mA h g−1 and had a great loaded performance of 390 mA h g−1 with high load 2.9 mg/cm2 over 200 cycles at 0.5 C. Compared with other biomass carbon materials, we have omitted the complicated high-temperature activation pore-forming process. In addition, the high sulfur loading carbon nanofibril composite aerogel also provides a way for the high-quality needs of electronic products.

Conjugated polyimide-coated carbon nanofiber aerogels in a redox electrolyte for binder-free supercapacitors

Boosting the energy density of supercapacitors without sacrificing power density and lifespan, requires ingenious electrode materials outfitting both sufficient assessable surface area and fast electrochemical reaction kinetics. Herein, hierarchically porous core-sheath nanoarchitecture was elaborately designed, via a robust support-coating strategy using a cellulose-derived porous carbon aerogel as the conductive 3D skeleton to support a uniform coating of conjugated polyimide. The inner carbon aerogel skeleton ensures a fast electron transfer and the outer conjugated polyimide layer affords abundant micropores and sufficient active sites, hence enriching the charge storage in such a porous core-sheath nanoarchitecture. The as-designed electrode was then applied to a redox electrolyte-assisted supercapacitor (RESC) with the KI-doped H2SO4 redox electrolyte. Due to the redox electrolyte further expediting the electrochemical reaction kinetics, the as-fabricated RESC delivers an ultrahigh electrode specific capacitance of 1139F g−1 at 5 A g−1, high energy density of 94 Wh kg−1 at a well-maintained power density, and long-term capability with 90% capacitance retention after 10,000 cycles at 100 A g−1. The successful construction of high-performance electrode materials and RESC in this work opens a new insight into the development of the state-of-the-art energy storage systems.

Advances in Manufacturing Composite Carbon Nanofiber-Based Aerogels

This article provides an overview on manufacturing composite carbon nanofiber-based aerogels through freeze casting technology. As known, freeze casting is a relatively new manufacturing technique for generating highly porous structures. During the process, deep cooling is used first to rapidly solidify a well-dispersed slurry. Then, vacuum drying is conducted to sublimate the solvent. This allows the creation of highly porous materials. Although the freeze casting technique was initially developed for porous ceramics processing, it has found various applications, especially for making aerogels. Aerogels are highly porous materials with extremely high volume of free spaces, which contributes to the characteristics of high porosity, ultralight, large specific surface area, huge interface area, and in addition, super low thermal conductivity. Recently, carbon nanofiber aerogels have been studied to achieve exceptional properties of high stiffness, flame-retardant and thermal-insulating. The freeze casting technology has been reported for preparing carbon nanofiber composite aerogels for energy storage, energy conversion, water purification, catalysis, fire prevention etc. This review deals with freeze casting carbon nanofiber composite materials consisting of functional nanoparticles with exceptional properties. The content of this review article is organized as follows. The first part will introduce the general freeze casting manufacturing technology of aerogels with the emphasis on how to use the technology to make nanoparticle-containing composite carbon nanofiber aerogels. Then, modeling and characterization of the freeze cast particle-containing carbon nanofibers will be presented with an emphasis on modeling the thermal conductivity and electrical conductivity of the carbon nanofiber network aerogels. After that, the applications of the carbon nanofiber aerogels will be described. Examples of energy converters, supercapacitors, secondary battery electrodes, dye absorbents, sensors, and catalysts made from composite carbon nanofiber aerogels will be shown. Finally, the perspectives to future work will be presented.

Unique carbon nanofiber@ Co/C aerogel derived bacterial cellulose embedded zeolitic imidazolate frameworks for high-performance electromagnetic interference shielding

Recently, lightweight and highly efficient electromagnetic interference (EMI) shielding composites are crucial but changing for the development of modern electronics and telecommunication. Here, a novel polyhedral Co/C particle embedded carbon nanofiber (CNF@Co/C) aerogels were synthesized via pyrolysis of bacterial cellulose wired zeolitic imidazolate frameworks-67 (ZIF-67) aerogel under argon. The flexible CNF@Co/C aerogels exhibit a high EMI shielding effectiveness (SE) is approaching 56.07 dB at a density of only 0.023 g cm−3 in the X band, and the average absorption coefficient is as high as 0.79, indicating 79% of electromagnetic (EM) waves are absorbed in shielding process. The remarkable performance results from the three-dimensional (3D) CNF-threaded porous structure with interconnected network and the magnetic Co/C particle strung by CNF, which contribute to a conduction loss and optimal impedance matching along with multiple polarization and strong magnetic loss. This work paves a promising way for the new generation of electronic device with lightweight and efficient EMI shielding.

Design of compressible and elastic N-doped porous carbon nanofiber aerogels as binder-free supercapacitor electrodes

Compressible and elastic N-doped porous carbon nanofiber aerogels are designed and used as binder-free supercapacitor electrodes.

Rocking-chair capacitive deionization with flow-through electrodes

Flow-through Rocking-chair Capacitive Deionization system with ultrahigh desalination rate is built for the first-time, in which sodium-pre-intercalated MnO2 coated carbon nanofiber aerogels are employed as the flow-through electrode.

MoC nanoparticle-embedded carbon nanofiber aerogels as flow-through electrodes for highly efficient pseudocapacitive deionization

Highly efficient pseudo-capacitive deionization systems equipped with flow-through electrodes are developed for the first time based on the utilization of MoC nanoparticle-embedded carbon nanofiber aerogels as electrode materials.

Magnetic bacterial cellulose and carbon nanofiber aerogel by simple immersion and pyrolysis

Bacterial cellulose (BC)/Fe3O4 aerogels were fabricated by a simple immersion of BC hydrogels in commercially available ferrofluid solution followed by freeze-drying. The BC/Fe3O4 aerogels were converted into carbon nanofiber (CNF)/Fe3O4 aerogels by pyrolysis at 600 °C. With our fabrication methods, the Fe3O4 nanoparticles (NPs) were effectively impregnated and homogeneously distributed in the nanostructures of BC and CNF. The average diameters of the BC and CNF nanofibers were found to be about 79.3 ± 14.1 nm and 56.7 ± 13.6 nm, respectively. Increasing the ferrofluid concentration resulted in a nonlinear increase of Fe3O4 NPs loaded into the BC and CNF structure, but the functional groups were not affected. The saturation magnetization (Ms) of CNF/Fe3O4 was larger than those of BC/Fe3O4 and increased with the amount of impregnated Fe3O4 NPs. The maximum magnetization in our work was larger than literature values, with the highest Ms of 82.9 emu/g approaching the bulk value of Fe3O4. The materials presented could be used as pollutant absorbers for wastewater treatment. We have demonstrated the capability of using magnetic CNF aerogels in absorbing a common dye pollutant from water. The dye was absorbed efficiently, and the aerogels were easily magnetically removed from the solution and are reusable.

Scalable syntheses of three-dimensional graphene nanoribbon aerogels from bacterial cellulose for supercapacitors

Three-dimensional (3D) carbon aerogels with well-defined structures, e.g. high specific surface area (SSA), appropriate pore size distribution, good electrical conductivity and ideal building blocks, have been regarded as promising electrode materials or substrates for incorporation with pseudocapacitive materials for energy storage and conversion applications. Herein, we report a simple and scalable sonochemical method followed by a chemical activation process to transform bacterial cellulose-derived carbon nanofiber aerogels (CNFAs) into 3D graphene nanoribbon aerogels (GNRAs) for supercapacitors. Benefiting from a high SSA, reasonable pore size distribution and good conductivity, the GNRA electrode demonstrates a long cyclability, good rate capability and high charge storage performance for supercapacitors, yielding more than 1.5 times (three-electrode cell) and 2.6 times (two-electrode cell) the gravimetric capacitance of the CNFA electrode. In addition, a hybrid Ni–Co layered double hydroxides (LDHs)@GNRAs electrode achieves an impressive gravimetric capacitance of 968 F g−1 (based on the mass of the active material) at a current density of 1 A g−1. Moreover, an asymmetric supercapacitor device with a remarkable energy density of 29.87 Wh kg−1, wide working voltage windows of 1.6 V and good cycling stability (63.5% retention after 10 000 cycles) is achieved by using the GNRA as an anode and the Ni–Co LDHs@GNRAs as a cathode.

Temperature-Invariant Superelastic and Fatigue Resistant Carbon Nanofiber Aerogels.

Superelastic and fatigue-resistant materials that can work over a wide temperature range are highly desired for diverse applications. A morphology-retained and scalable carbonization method is reported to thermally convert a structural biological material (i.e., bacterial cellulose) into graphitic carbon nanofiber aerogel by engineering the pyrolysis chemistry. The prepared carbon aerogel perfectly inherits the hierarchical structures of bacterial cellulose from macroscopic to microscopic scales, resulting in remarkable thermomechanical properties. In particular, it maintains superelasticity without plastic deformation even after 2 × 106 compressive cycles and exhibits exceptional temperature-invariant superelasticity and fatigue resistance over a wide temperature range at least from -100 to 500 °C. This aerogel shows unique advantages over polymeric foams, metallic foams, and ceramic foams in terms of thermomechanical stability and fatigue resistance, with the realization of scalable synthesis and the economic advantage of biological materials.

Elastic and hierarchical carbon nanofiber aerogels and their hybrids with carbon nanotubes and cobalt oxide nanoparticles for high-performance asymmetric supercapacitors

Although lightweight and elastic carbon nanofiber (CNF)-based aerogels are promising in wearable supercapacitors, it is still a serious issue to produce CNF-based aerogels with satisfactory integrated properties of mechanical strength, compression resilience, conductivity, and electrochemical performances. Herein, elastic aerogel anode materials with welded CNFs are fabricated by electrospining polyacrylonitrile nanofibers with polyvinylpyrrolidone as a solder to weld adjacent nanofibers followed by freeze-drying, carbonization, and CO2 activation, exhibiting remarkable electrical conductivity, excellent reversible compressibility, and a high specific capacitance of 300 F g−1 at 0.3 A g−1. Furthermore, carbon nanotubes (CNTs) are uniformly grown on the CNF surface of the aerogels with the catalysis of metallic Co, while the Co nanoparticles at the CNT tips are oxidized in situ to Co3O4 nanoparticles. The CNF-CNT-Co3O4 hybrid aerogel as a hierarchical cathode exhibits a high specific capacitance of 2376 F g−1 at 1 A g−1. An assembled asymmetric supercapacitor with the activated CNF aerogel as its anode and the hybrid aerogel as its cathode exhibits a considerably high energy density of 48.1 W h kg−1 at 780.2 W kg−1. This study provides a new strategy for constructing lightweight and elastic electrode materials for highly efficient energy-storage application.