As-prepared Carbon Aerogels Research Articles

Sustainable chitosan derived 3D hierarchically porous carbon aerogel toward advanced infrared-radar compatibility

Simultaneously achieving infrared-radar compatibility in one material is an important challenge for multi-spectral compatible stealth technology. Chitosan-derived three-dimensional (3D) hierarchically porous carbon aerogel can effectively solve the problem. Inspired by floors-pillars concept, this work elaborately designed and successfully fabricated 3D skeletons consisted of two-dimensional (2D) sheets and one-dimensional (1D) struts. Benefiting from esterification and directional freeze drying method, the entire network could provide sufficient space for reducing thermal conductivity and motivating dipole polarization sites. Thanks to the facile calcination process, conductive components could be obtained, which guarantee low infrared (IR) emissivity and high conduction loss performance. In this work, the as-prepared carbon aerogel with ultra-low density of 0.005 g cm−3 exhibits superb infrared stealth property. It shows a low thermal conductivity coefficient of only 0.0933 W m−1 K−1. In addition, the heating rate of the upper surface is slow when placed on a heating platform of 60 °C. The relevant IR emissivity value is as low as 0.563 in 3–5 μm band and 0.432 in 8–14 μm band. Under relatively thin thicknesses, the prominent radar stealth performance including the optimum reflection loss value of −75.90 dB, the maximum effective bandwidth of 3.93 GHz, and the simulated radar cross section reduction value of 27.66 dB m2, can be obtained. This study not only introduces innovative design ideas but also offers technical approaches, facilitating further development in the realm of infrared-radar compatible stealth.

Facile Synthesis of Fe-Doped, Algae Residue-Derived Carbon Aerogels for Electrochemical Dopamine Biosensors.

An abnormal level of dopamine (DA), a kind of neurotransmitter, correlates with a series of diseases, including Parkinson's disease, Willis-Ekbom disease, attention deficit hyperactivity disorder, and schizophrenia. Hence, it is imperative to achieve a precise, rapid detection method in clinical medicine. In this study, we synthesized nanocomposite carbon aerogels (CAs) doped with iron and iron carbide, based on algae residue-derived biomass materials, using Fe(NO3)3 as the iron source. The modified glassy carbon electrode (GCE) for DA detection, denoted as CAs-Fe/GCE, was prepared through surface modification with this composite material. X-ray photoelectron spectroscopy and X-ray diffraction characterization confirmed the successful doping of iron into the as-prepared CAs. Additionally, the electrochemical behavior of DA on the modified electrode surface was investigated and the results demonstrate that the addition of the CAs-Fe promoted the electron transfer rate, thereby enhancing their sensing performance. The fabricated electrochemical DA biosensor exhibits an accurate detection of DA in the concentration within the range of 0.01~200 µM, with a detection limit of 0.0033 µM. Furthermore, the proposed biosensor is validated in real samples, showing its high applicability for the detection of DA in beverages.

Tunable high-performance electromagnetic interference shielding of intrinsic N-doped chitin-based carbon aerogel

Heteroatom doping of carbon aerogels is a promising strategy to dissipate electromagnetic waves (EMWs) and it is still a daunting challenge to establish the relationship between heteroatomic structure and EMI shielding performance. In our work, intrinsic N-doped biomass-based carbon aerogel was successfully prepared by freeze-drying and a specific two-stage pyrolysis using chitin and chitosan as carbon and nitrogen source. The content and type of doping elements and electrical conductivity could be accurately manipulated by controlling the content of precursors and carbonization temperature. The intrinsic N-doped induced a dipole polarization, and the unique three-dimensional porous architecture of biomass-based carbon aerogel was conducive to multiple reflection/scattering of EMWs. The as-prepared biomass-based carbon aerogel at 1300 °C exhibited an optimal EMI performance of 82 dB, and the absorption coefficients could be tuned in the range of 0.31–0.88. The excellent EMI performance originated from a variety of mechanisms involving conduction loss, dipole polarization loss, and interface polarization loss. The novel heteroatomic doping strategy not only provides new insight into the contribution of heteroatomic structure to EMI shielding performance, but also opens a new avenue to develop biomass-based carbon aerogels with tunable EMI shielding performances.

Three-dimensional macroporous hybrid carbon aerogel with heterogeneous structure derived from MXene/cellulose aerogel for absorption-dominant electromagnetic interference shielding and excellent thermal insulation performance

The development of electromagnetic interference (EMI) shielding materials with excellent absorption coefficient (A) is vital to completely eliminate the pollution of the ever-increasing electromagnetic waves (EMWs). In this regard, a TiC/carbon hybrid aerogel, derived from MXene/cellulose aerogel, was successfully fabricated via freeze-drying and subsequent pyrolysis process. Profiting from the open, loose three-dimensional (3D) macro pores with sheet-like morphology and high porosity, as well as the rich heterogeneous interfaces between TiC and cellulose-derived carbon, the as-prepared hybrid carbon aerogel achieves ultra-efficient EMI shielding effectiveness of 72.9 dB in conjunction with a superior A value of 0.76 and low thermal conductivity. These properties endow the as-prepared aerogel with strong absorption-dominant ultra-efficient EMI shielding and thermal insulation performance to meet the complex practical requirements. This work provides a promising strategy for achieving ultra-efficient multifunctional EMI shielding performance and superior A simultaneously.

Porous carbon aerogel derived from bacterial cellulose with prominent potential for efficient removal of antibiotics from the aquatic matrix.

The development of adsorption methods for the remediation of antibiotics pollution in water is hindered by the lack of high-performance sorbents. In this study, a nanofiber carbon aerogel was prepared using bacterial cellulose and its adsorption performances for three common antibiotics (norfloxacin, sulfamethoxazole, and chloramphenicol) in water were evaluated. The as-prepared nanofiber carbon aerogel showed a higher adsorption capacity toward target antibiotics compared to other adsorbents reported in the literature. The maximum adsorption capacities for norfloxacin, sulfamethoxazole, and chloramphenicol were 1,926, 1,264, and 525 mg/g, respectively at 298 K. Notably, the nanofiber carbon aerogel was able to adsorb 80% of the equilibrium adsorption capacity within 1 min and reach equilibrium within 15 min. After five regeneration cycles, the adsorption capacity still reached 1,166, 847, and 428 mg/g for norfloxacin, sulfamethoxazole, and chloramphenicol, respectively. The characterization results showed that the carbon aerogel exhibited a high specific surface area (1,505 m2/g) and a layered porous network structure. Furthermore, the mechanistic study reveals that the enhanced antibiotic adsorption by the as-prepared nanofiber carbon aerogel was attributed to the pore filling effect, hydrogen bonding, hydrophobic effect, electrostatic interaction, and π-π interactions. Overall, these results imply that low-cost and green nanofiber carbon aerogels may be promising adsorbents for the remediation of antibiotic-contaminated wastewater. The materials prepared from natural and readily available bacterial cellulose can adsorb antibiotics efficiently, which provides a reference for the development of adsorbent materials using natural substances.

Environmentally Friendly and Multifunctional Shaddock Peel-Based Carbon Aerogel for Thermal-Insulation and Microwave Absorption

HighlightsThe eco-friendly shaddock peel-derived carbon aerogels were prepared by a freeze-drying method.Multiple functions such as thermal insulation, compression resistance and microwave absorption can be integrated into one material-carbon aerogel.Novel computer simulation technology strategy was selected to simulate significant radar cross-sectional reduction values under real far field condition..Eco-friendly electromagnetic wave absorbing materials with excellent thermal infrared stealth property, heat-insulating ability and compression resistance are highly attractive in practical applications. Meeting the aforesaid requirements simultaneously is a formidable challenge. Herein, ultra-light carbon aerogels were fabricated via fresh shaddock peel by facile freeze-drying method and calcination process, forming porous network architecture. With the heating platform temperature of 70 °C, the upper surface temperatures of the as-prepared carbon aerogel present a slow upward trend. The color of the sample surface in thermal infrared images is similar to that of the surroundings. With the maximum compressive stress of 2.435 kPa, the carbon aerogels can provide favorable endurance. The shaddock peel-based carbon aerogels possess the minimum reflection loss value (RLmin) of − 29.50 dB in X band. Meanwhile, the effective absorption bandwidth covers 5.80 GHz at a relatively thin thickness of only 1.7 mm. With the detection theta of 0°, the maximum radar cross-sectional (RCS) reduction values of 16.28 dB m2 can be achieved. Theoretical simulations of RCS have aroused extensive interest owing to their ingenious design and time-saving feature. This work paves the way for preparing multi-functional microwave absorbers derived from biomass raw materials under the guidance of RCS simulations.

Construction and Transition Metal Oxide Loading of Hierarchically Porous Carbon Aerogels.

Hierarchically porous carbon aerogels (CAs) were prepared by organic condensation gelation method combined with atmospheric drying and pore-formation technology, followed by a carbonization process. With as-prepared CAs as substrate, the transition metal oxide nanoparticles loaded CAs composites (MnO2/Mn2O3@CA and Ni/NiO@CA) were achieved by means of liquid etching method combined with heat treatment, respectively. The catalyst, pore-forming agent and etching have important roles on the apparent density and pore structure of CAs. The hydrochloric acid (catalyst) significantly accelerates the gelation process and influences the size and distribution of macropores, whereas the addition of PEG2000 (pore-forming agent) and the etching of liquid solution leads to the formation of mesopore structure in CAs. Appropriate amounts of hydrochloric acid and PEG2000 allow the formation of hierarchically porous CAs with a BET surface area of 482.9 m2·g−1 and a macropore size of 11.3 μm. After etching and loading, the framework of CAs is etched to become a mesoporous structure, and the transition metal oxide nanoparticles can be uniformly loaded in CAs. These resultant composites have promising application in super capacitor, electrocatalysis, batteries and other fields.

Renewable and robust biomass carbon aerogel derived from deep eutectic solvents modified cellulose nanofiber under a low carbonization temperature for oil-water separation

Carbon aerogels are potential materials in oil/water separation. However, the key challenges of the scare/toxic precursor, metals employment, unsatisfied reuse, and high calcination temperature still remain. Here, we fabricated a novel, robust and hydrophobic carbon aerogel (DCCA-350) derived from deep eutectic solvents (DESs, formed by glucose and choline chloride) modified cellulose nanofiber (CNF) under low carbonization temperature of 350 °C. The raw materials are renewable and abundant, and the as-prepared carbon aerogel possesses the high volume absorption capability for organic pollutants and oils range from 74% to 95%. Due to its excellent thermostability and mechanical properties, methods of combustion and distillation can be applied for the recycling of the DCCA-350 carbon aerogel up to 100 cycles. The effective oils/water separation is mainly attributed to the presence of roughness surface and reduced hydrophilic groups in the carbon aerogel. This is also the first development of carbon aerogel derived from DESs modified CNF, with a promising application on oil/water separation.

Carbon aerogels derived from sodium lignin sulfonate embedded in carrageenan skeleton for methylene-blue removal

We reported an ecofriendly and cost-effective way to prepare carbon aerogels that were derived from sodium lignin sulfonate using κ-carrageenan as a skeleton for efficient dye adsorption. The scanning electron microscopy, nitrogen adsorption and desorption methods were used to analyze the surface configuration and porous structure of the samples. The specific surface area of the as-prepared carbon aerogels based on the Brunauer–Emmet–Teller method reached 594.6 m2/g and the average pore diameter based on the Barrett–Joyner–Halenda method was 2.2118 nm. X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy were used to analyze the elements and functional groups in the samples. The interaction between the as-prepared carbon aerogels and methylene blue (MB) involved π–π electron–donor–acceptor interaction, hydrogen bonding, and electrostatic interaction. The adsorption data at different conditions fitted the pseudo-second-order and Freundlich models well. ∆S° data demonstrated the increased randomness during adsorption. ∆H° and ∆G° data indicated that the interaction between MB and carbon aerogel was endothermic and spontaneous. The adsorption capacity of the as-prepared carbon aerogels for MB removal reached 421.94 mg/g. This work is promising for multi-valued use of lignin sulfonate from pulping wastewater and MB dye wastewater treatment.

N-Doped Carbon Aerogel Derived from a Metal-Organic Framework Foam as an Efficient Electrocatalyst for Oxygen Reduction.

Metal-organic frameworks (MOFs) are promising alternative precursors for the fabrication of heteroatom-doped carbon materials for energy storage and conversion. However, the direct pyrolysis of bulk MOFs usually gives microporous carbonaceous materials, which significantly hinder the mass transportation and the accessibility of active sites. Herein, N-doped carbon aerogels with hierarchical micro-, meso-, and macropores were fabricated through one-step pyrolysis of zeolitic imidazolate framework-8/carboxymethylcellulose composite gel. Owing to the hierarchical porosity, high specific surface area, favorable conductivity, excellent thermal and chemical stability, the as-prepared N-doped carbon aerogel exhibits excellent oxygen reduction reaction (ORR) activity, long-term durability, and good methanol tolerance in alkaline medium. This work thus provides a new way to fabricate new types of MOF-derived carbon aerogels for various applications.

Carbon aerogels with oxygen-containing surface groups for use in supercapacitors

We prepared a series of modified carbon aerogels with oxygen-containing functional groups through a sol–gel process by polycondensation of phloroglucinol, resorcinol and formaldehyde using starch addition. The effect of starch addition on the pore structure and electrochemical performance of the carbon aerogels was investigated. Carbon aerogels were characterized by scanning-electron microscopy, transmission-electron microscopy, surface-area analysis, X-ray diffractometry, Raman spectrometry and X-ray photoelectron spectroscopy. The electrochemical properties were studied by using cyclic voltammetry, galvanostatic charge–discharge measurements and electrochemical impedance spectroscopy. When the starch addition was 25 wt%, the as-prepared sample had a specific surface area of 734 m2 g−1 and an outstanding specific capacitance of 147 F g−1 at 1.0 A g−1. The as-prepared carbon aerogels exhibited a high coulombic efficiency and a stable cycle life at a current density of 1.0 A g−1 over 1000 cycles. This ideal performance was attributed to the addition of starch, which was beneficial for the application of carbon aerogels in supercapacitors.

Structuring dense three-dimensional sheet-like skeleton networks in biomass-derived carbon aerogels for efficient electromagnetic interference shielding

Developing ultralight, highly conductive carbon aerogels with facilely tunable microscopic structure is still a long-standing issue to effectively shield the electromagnetic interference (EMI). Here, highly porous and conductive all biomass-derived carbon aerogels were first successfully achieved by carbonizing cellulose aerogels, which held excellent structure designability by controlling cellulose content in lithium hydroxide/urea aqueous solution, porogen composition in solvent exchange process, as well as freezing rate during freeze-drying. The as-prepared cellulose-derived carbon aerogels with optimized structure of small pore size and dense three-dimensional sheet-like skeleton network were demonstrated to be highly efficient to greatly prolong the propagation path of electromagnetic waves (EMWs) and dissipate incident EMWs into heat energy, exhibiting the dominant EMI shielding mechanism of EMW absorption. As a result, an impressive EMI shielding effectiveness of as high as 93.1 dB in the X band frequency range at a density of as low as 0.079 g cm−3 was achieved. Of more practical significance is that the new insight into the relationship between microscopic pore structure of carbon aerogels and their EMI shielding performance provides a valuable clue in developing highly efficient EMI shielding carbon aerogels in the application of microelectronics, aircraft and spacecraft.

A Pt-free pristine monolithic carbon aerogel counter electrode for dye-sensitized solar cells: up to 20% under dim light illumination.

In this work, pristine carbon aerogels (CAs) were used as Pt-free counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) by varying the molar ratio of their precursors. Pristine mesoporous CAs with controlled resorcinol (R)/formaldehyde (F) and resorcinol (R)/sodium carbonate (C) molar ratios were successfully prepared. The as-prepared CAs were synthesized via a polymeric sol-gel reaction and were labeled as CA-O, CA-Q, CA-F, CA-C, and CA-G. The DSSCs using the as-prepared CA-C CE gave the best power conversion efficiency (PCE, η), 9.08 ± 0.01%, among all the CA CEs. The CA-C CE is further applied to an indoor T5 light source system with an impressive η value of 20.1 ± 0.60% at 2.18 mW cm-2 (T5 lamp with 7000 lux). Moreover, the hardness of CA-C CE is 3.01 GPa (Brinell hardness test), which is comparable to that of the FTO/glass substrate. As a result, the CA-C CE shows great potential to replace traditional CEs based on the Pt/FTO/glass in DSSCs.

Superelastic Carbon Aerogel with Ultrahigh and Wide-Range Linear Sensitivity.

Compressible and elastic carbon materials offer many advantages and have promising applications in various electronic devices. However, fabricating carbon materials with super elasticity, fatigue resistance, and high and wide-range linear sensitivity for pressure or strain remains a great challenge. Herein, a facile and sustainable route is developed to fabricate a carbon aerogel with not only superior mechanical performances but also exceptionally high and wide-range linear sensitivity by using chitosan as a renewable carbon source and cellulose nanocrystal as a nanoreinforcement or support. The as-prepared carbon aerogel with wave-shaped layers shows high compressibility, super elasticity, stable strain-current response, and excellent fatigue resistance (94% height retention after 50 000 cycles). More importantly, it demonstrates both an ultrahigh sensitivity of 103.5 kPa-1 and a very wide linear range of 0-18 kPa. In addition, the carbon aerogel has a very low detection limit (1.0 Pa for pressure and 0.05% for strain). The carbon aerogel also can be bended to detect a small angle change. These superiorities render its applications in various wearable devices.

A Supercompressible, Elastic, and Bendable Carbon Aerogel with Ultrasensitive Detection Limits for Compression Strain, Pressure, and Bending Angle.

Ultralight and compressible carbon materials have promising applications in strain and pressure detection. However, it is still difficult to prepare carbon materials with supercompressibility, elasticity, stable strain-electrical signal response, and ultrasensitive detection limits, due to the challenge in structural regulation. Herein, a new strategy to prepare a reduced graphene oxide (rGO)-based lamellar carbon aerogels with unexpected and integrated performances by designing wave-shape rGO layers and enhancing the interaction among the rGO layers is demonstrated. Addition of cellulose nanocrystalline and low-molecular-weight carbon precursors enhances the interaction among rGO layers and thus produces an ultralight, flexible, and superstable structure. The as-prepared carbon aerogel displays a supercompressibility (undergoing an extreme strain of 99%) and elasticity (100% height retention after 10 000 cycles at a strain of 30%), as well as stable strain-current response (at least 10 000 cycles). Particularly, the carbon aerogel is ultrasensitive for detecting tiny change in strain (0.012%) and pressure (0.25 Pa), which are the lowest detection limits for compressible carbon materials reported in the literature. Moreover, the carbon aerogel exhibits excellent bendable performance and can detect an ultralow bending angle of 0.052°. Additionally, the carbon aerogel also demonstrates its promising application as wearable devices.

Fabrication of nitrogen-doped porous electrically conductive carbon aerogel from waste cabbage for supercapacitors and oil/water separation

Nitrogen-doped porous carbon aerogels were prepared by using low-cost and high yield cabbages as carbon source via a mild method, including hydrothermal, freeze-drying, and carbonization processes. Owing to natural structure and nitrogen-containing features, the as-prepared carbon aerogels exhibited hierarchical 3D network porous structure with suitable nitrogen-doped and high conductivity. With such unique structural characteristics, these carbon aerogels displayed a superior performance, such as superior capacitance of 291 F g−1 with high large capacitance retention of 96.76% after 10,000 cycles in 6 M KOH electrolyte, as well as high energy density of 97.1 Wh kg−1 with and long cycling stability of 92.87% after 10,000 cycles in ionic liquid. Moreover, these superoleophilic carbon aerogels exhibited excellent adsorption capacity and recyclability for various oils and organic solvents. This work fully utilized the advantages of the cabbage leaves derived porous carbon aerogels as a promising “green” candidate to apply in low-prices and high-performance energy storage devices and adsorbent materials.

High Performance Lithium–Sulfur Batteries with a Sustainable and Environmentally Friendly Carbon Aerogel Modified Separator

Carbon-based aerogel prepared via direct conversion of natural biomass has wide application prospects in the environment and energy field. Herein, the sustainable and environmentally friendly porous carbon aerogel is prepared through hydrothermal treatment, freeze-drying, and postpyrolysis using sweet potato as the precursor. The as-prepared carbon aerogel is used to modify the commercial separator of lithium–sulfur batteries to solve the problems of poor cycle life and low utilization rate of active substances. The carbon aerogel coating can not only suppress the shuttle effect of the polysulfide intermediates during cycling and reduce the cell resistance but also act as an upper current collector to increase the utilization rate of sulfur. The cell with carbon aerogel modified separator exhibits high electrochemical performance. The results show that the initial discharge capacity is 1216 mAh/g at 0.1 C and the reversible discharge capacity retains 431 mAh/g after 1000 cycles at 1 C with the Coulombic e...

Adsorption of methylene blue on natural cotton based flexible carbon fiber aerogels activated by novel air-limited carbonization method

A flexible carbon fiber aerogel material was synthesized from abandoned cotton by using air-limited calcination method. The activity of carbon fiber aerogel can be controlled by the calcination temperature and the loading weight of cotton (Lcotton) in the sealed container. The obtained material was characterized using SEM, FT-IR, BET and XPS. The results showed that the as-prepared carbon aerogels were fibrous and the surface of carbon aerogels can effectively form active groups after the calcination under air-limited condition. Samples with bigger specific area (457.73m2g−1) and more active groups can be obtained at 600°C and Lcotton=0.25. Adsorption isotherm and kinetics of methylene blue on carbon fiber aerogels were determined from batch tests. The effects of contact time (1–100min) and solution temperature (298K–328K) were investigated. The equilibrium data were best represented by Langmuir isotherm model, showing maximum monolayer adsorption capacity of 102.23mgg−1, and the kinetic data was found to follow closely the pseudo-second-order kinetic model. Furthermore, the calculation of thermodynamic parameters demonstrated that the adsorption process of methylene blue onto the carbon fiber aerogels was spontaneous, endothermic and random. These results proved that the carbon fiber aerogels could be a promising candidate for the treatment of dye wastewater.

Magnetic carbon aerogel pyrolysis from sodium carboxymethyl cellulose/sodium montmorillonite composite aerogel for removal of organic contamination

In this paper, we present a facile approach for the synthesis of polysaccharide-based carbon aerogel by sol–gel processing, freeze-drying, and pyrolysis of a sodium carboxymethyl cellulose/sodium montmorillonite composite aerogel. The as-prepared carbon aerogel was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, nitrogen adsorption measurements, and vibrating sample magnetometry. The carbon aerogel obtained in this study possessed low density (0.064 ± 0.0029 g/cm3), a high surface area (185 m2/g), and flame retardance. Measurements of the magnetic properties indicated that the carbon aerogel exhibited typical ferromagnetic characteristic at room temperature. The absorption capacity of the carbon aerogel for oils and organic solvents is as much as 10–20 times its own weight. Moreover, a method of combustion could be employed to recycle the carbon aerogel. The results imply that the carbon aerogel is a potential cost-effective adsorbent for oil and organic pollutants from aqueous solutions in environmental pollution cleanup.

KOH-activated carbon aerogels derived from sodium carboxymethyl cellulose for high-performance supercapacitors and dye adsorption

In this paper, we present a facile and eco-friendly approach for the synthesis of porous carbon aerogels by sol–gel processing, freeze-drying, and pyrolysis of sodium carboxymethyl cellulose aerogels. The obtained carbon aerogels were further treated via a KOH activation process. The results showed that the as-prepared carbon aerogels exhibited a high specific surface area of 428m2/g after KOH activation for 3h. The highly porous and interconnected three-dimensional nanostructure provided efficient migration of electrolyte ions and electrons, and thus the activated carbon aerogels exhibited excellent electrochemical performance for supercapacitors. The specific capacitances reached 152.6F/g at a current density of 0.5A/g within a potential window of −1.0 to 0V in a 6M KOH solution. In addition, the carbon aerogels showed excellent adsorption capacity for methylene blue and malachite green, which reached 249.6mg/g and 245.3mg/g, respectively. The excellent electrochemical performance and adsorption capacities showed the carbon aerogels to be a high-performance and promising material for supercapacitors and adsorbents.