With the rapid advancement of telecommunications and the extensive usage of electronic products, electromagnetic wave (EMW) radiation pollution has become an environmental concern or safety threat in personal healthcare, information security, and military stealth. Nevertheless, it is highly desired but challenging to develop lightweight, flexible, and high-efficiency EMW absorption materials that can alleviate the adverse interference in wide-range frequency. Numerous magnetic and conductive materials including carbon, metal, and intrinsically conductive polymers can be used for EMW absorption materials. Among them, electrospun carbon nanofibers (CNFs) are regarded as promising candidates for high-performance EMW absorption materials owing to the advantages of soft texture, porous fiber structure, high surface area, and tunable compositions. In this review, we have systematically summarized the recent progress in carbon nanofibrous membranes with different nanostructures via electrospinning method. The EMW absorption mechanism, fabrication processes, performance characterizations, practical applications, existing problems, and future prospects are logically described at great length. This comprehensive review may provide useful and instructive information to enlighten potential readers in relevant research fields.

This work uses a one-step KOH activation for lignin precursors to produce ultra-high mesoporous activated carbons (ACs) with an unprecedented combination of the surface area of 3207 m2 g−1 and mesopore ratio of 76%. The ACs are applied for supercapacitors (SCs) and methylene blue (MB) adsorption. The capacitance of the SCs in the three-electrode system reaches 812.3 F g−1 and demonstrates a remarkable maximum MB adsorption capacity of 1250 mg g−1. By modifying the process conditions, the mesopore ratio of ACs could be controlled from 10% to 80%. Compared with one-step activation, a two-step method produced microporous carbons with a lower surface area of 1227 m2 g−1 and a high micropore ratio of 73%. The capacitance of SCs with two-step ACs reached 228.1 F g−1 and the maximum adsorption capacity of 476.19 mg g−1 for MB adsorption. The two-step method limited the surface area but had a higher oxygen surface functionality, benefiting its electrochemical performance. A techno-economic analysis reveals that the one-step KOH activation-based process develops ACs with a minimum selling price of $7648/ton. This work demonstrates tuning the processing-structure-property-performance relationship of lignin-based ACs to make an economically viable domestic carbon source.

Kite growth is a process that utilizes laminar gas flow in chemical vapor deposition to grow long, well-aligned carbon nanotubes (CNTs) for electronic application. This process uses metal nanoparticles (NPs) as catalytic seeds for CNT growth. However, these NPs remain as impurities in the grown CNT. In this study, nanodiamonds (NDs) with negligible catalytic activity were utilized as nonmetallic seeds instead of metal catalysts because they are stable at high temperatures and facilitate the growth of low-defect CNTs without residual metal impurities. Results demonstrate the successful growth of over 100-μm-long CNTs by carefully controlling the growth conditions. Importantly, we developed an analysis method that utilizes secondary electron (SE) yield to distinguish whether or not CNTs grown from metal impurities. The absence of metallic NPs at the CNT tips was revealed by the SE yield mapping, whereas the presence of some kind of NPs at the same locations was confirmed by atomic force microscopy (AFM). These results suggest that most of the aligned CNTs were grown from nonmetallic seeds, most likely ND-derived NPs, via the tip-growth mode. Structural characterizations revealed the high crystallinity of CNTs, with relatively small diameters. This study presents the first successful use of nonmetallic seeds for kite growth and provides a convincing alternative for starting materials to prepare long, aligned CNTs without metal impurities. The findings of this study pave the way for more convenient fabrication of aligned CNT-based devices, potentially simplifying the production process by avoiding the need for the removal of metal impurities.

The effects of water and CO2 exposure on the performance of epoxy-based coatings under conditions commonly found in pipeline applications are investigated. The permeability of fusion bonded epoxy (FBE) decreases as CO2 pressure increases and the presence of water facilitates gas transport through the coating. The latter is in conflict with theories of competitive transport in gas/vapor systems, in which water is the predominant permeant for its lower kinetic diameter and higher condensability. Our results show that this anomaly was due to the dynamic transformation of permeable channels in the coating structure. Microstructural characterization of FBE after exposure to CO2/H2O mixtures showed that carbonation of wollastonite fillers results in a change in shape and chemical composition of these filler particles. To verify these findings for the coating in the presence of adhesion forces, electrochemical impedance spectroscopy (EIS) was also used. Initially, the carbonation of fillers led to an increase in the pore resistance of the coating, which was attributed to the plugging of micropore channels on the coating surface. However, the subsequent decreasing trend of this parameter suggested that water infiltration into the coating had increased due to this degradation. This transformation facilitates the easier penetration of water and dissolved gas to the underlying substrate. Consequently, the accumulation of water inside the coating increases the dielectric constant, resulting in a higher capacitance of the coating. It appears that high concentrations of CO2 in wet conditions, even at low pressures, can have negative impacts on the barrier performance of the coating.

With the advancements in military detection technology, stealth materials that only operate in a single frequency band are no longer efficient in dealing with detection weapon interference. Hence, there is an urgent need to develop multifunctional material to achieve multi-band compatible stealth. In this study, a composite porous aerogel was synthesized utilizing a chitosan-derived carbon aerogel as the scaffold loaded with VO2 (VO2/CA), which demonstrated exceptional radar/infrared compatible stealth performance. Under the action of loss mechanisms conductivity loss, dipole polarization and interface polarization, the composite material can reach the minimum RL of −52.0 dB at a thickness of 2.4 mm, and the EAB at 1.6 mm is 5.2 GHz, covering almost the whole Ku band. Meantime, VO2/CA achieves excellent thermal stealth characteristic. In terms of infrared stealth, after the bottom is heated to 120 °C for 180 s, the surface temperature of the sample is only 2.6 °C. This work provides a feasible idea and scheme for the research of radar infrared stealth compatibility materials.

Individual carbon nanotubes (CNTs) have gained popularity as lightweight wire materials due to their high electrical conductivity and low density than that of copper wires. Despite intensive research on light-weight and highly conductive CNT fibers, the bulk properties of CNT assemblies are inferior to those of metal wires in terms of electrical conductivity. Herein, we propose a method to increase the specific electrical conductivity of CNT fibers with polyaniline (PANI). The structure and physical properties of the CNT fibers are precisely controlled by optimizing the PANI content through a simple and effective solution process. PANI is considered to enhance CNT orientation, decrease voids, and dope the CNT fibers, resulting in a better electron flow in the fibers. The developed composite fiber with 5 wt% PANI demonstrated remarkable specific electrical conductivity of 6,200 ± 160 S m2/kg (11.9 MS/m) (max: 6,360 S m2/kg), an improvement of 16% above as-spun CNT fiber. Simultaneously, the mechanical properties increased by 27%, yielding a high specific tensile strength of 2.63 ± 0.10 N/tex (5.05 GPa). Furthermore, the toughness improved to 79.5 J/g, approximately a 1.8 times improvement over that of the CNT fiber. The addition of a small amount of PANI to CNT fibers has led to significant improvements in electrical and mechanical properties, which can provide insights into research on the CNT fiber field.

Energy storage materials for electric vehicles and energy storage systems must be able to supply high capacity quickly, which requires efficient Li-ion transport within the anode active material. The transport of Li ions through a battery system can lead to concentration polarization and subsequent overpotential, which can limit the electrochemical performance, especially under fast charging conditions. To overcome these limitations, it is important to control solvated Li-ion transport and design an anode material with a rational approach. One way to achieve this is by controlling the morphology of carbon nanofibers (CNFs) to create ion transport channels. A facile method for this was investigated using an immiscible polymer blend electrospinning system and interpreting a ternary phase diagram. The effects of the morphology and space characteristics of each CNF on the electrochemical performance were studied, particularly the rate capability and cycle stability under fast charging conditions. These characteristics were analyzed in terms of the transport properties of the electrochemical species in different types of ion channels.

Morphological and functional modifications allow graphene to be applied as promising electrode support for improved electrochemical cell performance. Typically, however, modification requires complicated steps with various organic additives, such as binders, which causes low electrochemical stability, especially under harsh pH conditions. Herein, we introduce self-supported and long-term stable water splitting electrodes based on nanoparticles (NPs) decoration on three-dimensional porous laser-induced graphene (3D-LIG). A binder-free, single-step electrochemical process homogeneously decorates the 3D-LIG electrodes with CuO and Pt NPs, referred to CuO-3D-LIG and Pt-3D-LIG electrodes, respectively. These electrodes are individually analyzed for enduring oxygen evolution (OER) and hydrogen evolution (HER) activities. The porous wrinkled morphology of the 3D-LIG offers a large surface area and facilitates electrolyte influx within channels. Whereas strongly anchored CuO and Pt NPs enable highly stable electrochemical performances of the CuO-3D-LIG and the Pt-3D-LIG electrodes. The corresponding OER and HER overpotentials at 10 mA cm−2 (η10) are observed at 251 mV and 455 mV. These electrodes offer excellent electrochemical robustness in operationally challenging alkaline conditions (1 M KOH, pH ∼ 14) for extensive periods. In addition, we confirm the workable electrostatic interactions NPs – graphene via Becke-3-parameter Lee–Yang–Parr (B3LYP) model with 6-31G (d,p) and Stuttgart-Dresden (SDD) basis, which is supposed to be responsible for electrochemical durability and high current density yield of CuO-3D-LIG and Pt-3D-LIG electrodes. This study offers one of a few experiments to utilize decorated 3D-LIG for both OER and HER processes, assuming their substantial industrial potential in overall water splitting.

To maximize the performance of a supercapacitor at a device level, it is essential to increase the volumetric capacitance of electrodes and decrease the fraction of inactive components. However, it is still a challenge to achieve these two goals. Here, we prepared surface-oxidized multi-layer graphene (SMG) by a facile electrochemical method. The unique thickness and oxygen groups facilitate the balance of the porosity and density and benefit the preparation of free-standing graphene electrodes. The preparation method of free-standing SMG electrode exhibits all-sided superiorities, including simple, environmental, energy-saving, high-stability, etc. Furthermore, SMG can achieve a high capacitance of 217.6 F cm−3 and landmark energy density of 120.27 Wh L−1, which provides a potential perspective for practical applications in energy storage.

The urgent needs of information security and the target stealth has led to an increasing demand for lightweight, high-performance electromagnetic wave absorbing materials. Recently, one-dimensional (1D) carbon-based materials based on their specific electrical conductivity and aspect ratios exhibits distinctive microstructural orientation, structural design, impedance matching, component modulation and surface modification. First, the high aspect ratio of the 1D dimensional material is much easier to construct effective conductive absorption networks. Second, the distinct voids in the networks built from 1D materials is facilitate to optimize the degree of impedance matching. In this paper, we review the recent research progress of 1D carbon-based microwave absorbing materials, including the types of 1D carbon-based composites, design strategies, synthesis methods, and the structure-function relationship of microwave absorbing materials. Finally, the challenges and prospects of 1D carbon-based materials for future applications are discussed. This critical review is timely and aims to provide researchers with a comprehensive understanding of the state-of-the-art in the design of 1D carbon-based material assemblies for lightweight microwave absorption, and to stimulate further innovation for ultralight carbon-based electromagnetic absorption material.

Constructing conductive network and adjusting impedance matching are effective ways to enhance the microwave absorption capacity of absorbers. However, the experimental procedures for preparing three-dimensional porous network are complex and often involve the use of hazardous agents. We proposed a simple and safe strategy to prepare porous three-dimensional network Mo2C/C composites. The salting-out method can change the aggregation state of chitosan macromolecules and make the free chitosan molecules form a porous three-dimensional network structure autonomously. In addition, the plus-charged amino on chitosan is able to attract minus-charged molybdate ions, which makes the surface of the 3D structured chitosan precursor covered with molybdenum-containing species. The result shows that the porous mesh structure and the heterogeneous interfaces combine to achieve excellent absorption performance of Mo2C/C with effective absorption bandwidth of 5.04 GHz at 1.8 mm. This work demonstrates that salting-out method broadens the idea of porous three-dimensional network electromagnetic wave absorbing materials.

Carbon-based materials are considered as promising anode candidates for potassium-ion storage with the key bottlenecks lying in the slow kinetics and huge volume expansion caused by the large size of K+. Herein, nitrogen-doped hollow carbon nanoparticles (NHCP) with optimized multiscale nanostructures are synthesized by a natural template-assisted chemical vapor deposition process. Benefiting from the stacking nanoparticles structure with hierarchical pores, high level of pyridinic-/pyrrolic-N, and enlarged interlayer spacing, the constructed NHCP anode delivers superior K+ storage properties in terms of high reversible capacity (412.7 mAh g−1 at 0.03 A g−1), favorable rate capability, and long cyclic stability. The detailed experimental and computational studies reveal the combined storage mechanism of K+ adsorption and insertion in the multiscale nanostructure of NHCP. To achieve high areal capacities, self-supported NHCP electrodes with high mass loadings (3.41 and 6.23 mg cm−2) were constructed by a vacuum-assisted infiltration process which exhibits greatly improved areal capacities as compared with the traditional slurry coating electrode. The assembled full-carbon potassium-ion capacitor based on NHCP anode exhibits high energy and power densities (168 Wh kg−1 and 9.4 kW kg−1) and a long cycling lifespan (83.9% capacity retention after 10000 cycles at 1.0 A g−1). This work provides a facile fabrication method for porous carbon electrodes with high mass loadings and capacities, which holds the potential for practical application.

We have discovered Raman peculiarities of sp3-bonded carbon nanoclusters forming ultrahard fullerite synthesized at pressure up to 85 GPa. The nanoclusters differ in the values of bulk modulus B0 ranging from 580 to 730 GPa. We found that the Raman frequency, corresponding to the C-C stretching mode of the nanoclusters, varies linearly from 1485 to 1640 cm−1, depending on the excitation wavelength used, which ranges from 785 nm to 257 nm. In particular, the nanoclusters with higher B0 have a higher Raman frequency. We also observed a resonant Raman spectrum when excited at a wavelength of 1064 nm. This showed a plateau from 1400 to 1720 cm−1, covering all Raman band positions of the nanoclusters from 1485 to 1640 cm−1. In addition, two Raman bands at 1285 and 1600 cm−1 appear at the resonance. The presence of several types of carbon sp3-bonded nanoclusters is confirmed by high-resolution transmission electron microscopy. Using moment tensor potentials, a class of machine learning interatomic potentials, we calculated the phonon density of states of the nanoclusters formed during the 3D polymerization of C60. The presence of high frequency modes in the resonant Raman spectra suggests the existence of bonds with force constants higher than those in a single crystal diamond. In addition, we observed a stiffening effect when analyzing the dependence of the mechanical stiffness on the cluster size, with smaller clusters exhibiting a more rigid structure.

Edge-N (pyridinic/pyrrolic-N) functionalized carbon is a promising anode for potassium-ion batteries, while micropores have been proven to be effective in increasing capacity and cyclability. However, the obtained carbon materials usually exhibit a low N-doping level and edge-N species based on the conventional pyrolysis method, and the exploration of the synergistic effect of edge-N doping and micropores on the potassium-storage performance is still lacking. Herein, a novel strategy is proposed to prepare edge-N doped carbon (ENC-850) by directly pyrolyzing supermolecule precursors self-assembled by terephthalic acid (BDC) and melamine (MA). Because the s-triazine structure in MA is more stable than BDC, which can easily ensure a higher N-doping content in carbon, and the decomposition of s-triazine structure is accompanied by the release of NCNH2 gas, which enables most doped N-atoms to be of edge-N configurations, favoring the adsorption storage of K-ions. Besides, the released small molecules can create numerous micropores, not only providing active sites, but accommodating volume fluctuation. Therefore, the optimized ENC-850 with the most suitable edge-N content of 60.6% (7.73 at% of total 11.71 at% N-doping) and micropores delivers a high capacity (280 mAh g−1 at 0.5 A g−1) and superior cycling stability (over 2000 cycles).

To optimize the electromagnetic wave performance for absorbers, it is crucial to implement rational structural designs and integrate multiple loss modes in a coordinated manner. Here, three-dimensional (3D) porous macroscopic coral-like Co/CoO/reduced graphene oxide aerogels (Co/CoO/RGO), are successfully fabricated by an ice-templated freeze-drying and thermal reduction techniques, and their pore structures, involving aperture and total pore volume, are availably regulated by manipulating the water addition. The electromagnetic parameters and electromagnetic wave performance appear strong response toward the variation of pore structure. By controlling the pore structure, these parameters can be efficaciously tunned, thus manipulating the performance. The optimized absorption performance is obtained when the water addition is 1 ml, the minimum reflection loss reaches to −61.8 dB and the effective bandwidth is 4.2 GHz. Such good performance is inseparable with the 3D crosslinked conductive framework, the hybrid of magnetic and dielectric units, numerous heterointerfaces and countless pores walls in aerogels, which brings multiple electromagnetic wave loss mechanism. Moreover, it is very important that Co/CoO/RGO aerogels also integrate good hydrophobicity and heat insulation properties, allowing their application in harsh conditions. This work shows the potential of pore structural control engineering for producing multifunctional aerogels.

An ultra-broadband and lightweight structural absorber based on a mixture absorbent composed of carbon nanotubes (CNTs) and carbon black has been proposed here. The absorber adopts a low surface density double frame structure design. In order to improve the microwave absorption performance to cope with the increasingly complex electromagnetic environment, the multi-layer structure design was used here. The simulation results show that the double-frame microwave absorber (DFMA) with a matching layer has a better absorption effect and wide-angle absorption property. The simulation results were verified by related experiments. The experimental results show the DFMA with inner and outer frame matching layers can reach more than 90% absorption within 5.8–18 GHz, with a bandwidth of 12.2 GHz. And over the 90% range of absorption bandwidth, the absorptivity is greater than 96.3% (the reflection loss is less than - 15dB). The absorber which has the advantages of high absorption gain, wide-angle absorption performance, low cost, and low surface density meets the application requirements in the current complex electromagnetic environment. Meanwhile, the design of the absorber also provides new ideas for improving the microwave absorption performance of traditional carbon-based absorbents.

Low-density fire-resistant materials with high EMI shielding effectiveness and low thermal conductivity are extremely important in aerospace and defence applications. Utilization of agricultural residues for achieving this reduces CO2 emission as well as produces wealth for the farmers. Herein, a fibre extracted from the wasted matured banana leaf by a simple chopping and grinding using a mixture-grinder is used for the preparation of carbon composite foams. The banana leaf fibres dispersed in sucrose solution are consolidated by filter-pressing followed by freeze drying to produce banana leaf fibre-sucrose composites. The carbon produced from sucrose during carbonization binds the carbonized banana leaf fibre to produce the carbon composite foams. The XRD pattern and Raman analysis indicated the turbostratic nature of the carbon, and XPS analysis shows the presence of oxygen-containing functional groups. The textural property measurement and TEM analysis indicated the presence of micro and meso pores in the carbon composite foams. The foam density (0.14–0.28 g cm−3), compressive strength (0.14–0.88 MPa), electrical conductivity (3.7–8.7 S m−1), and thermal conductivity (0.095–0.144 W m-1 K−1) of the carbon composite foams increases with an increase in sucrose solution concentration (300–700 g L−1). The carbon composite foams exhibit a reflection-dominated EMI shielding with high total shielding effectiveness in the range of 48.3–77.5 dB. The multiple internal reflections within a range of macropores available in the carbon composite foams, leading to enhanced absorption, are responsible for the excellent EMI shielding characteristics.

The chemical composition of reduced magnetic particles strongly correlates with the reduction potential of their metal species. However, this phenomenon rarely has been investigated in magnetic-dielectric absorbers. In this manuscript, a formaldehyde-assisted metal-ligand crosslinking strategy is employed to incorporate different metal species (Fe3+, Co2+, Co2+-Ni2+) into the colloidal frameworks by the chelating coordination. Because of their different reduction potentials, porous magnetic carbon spheres (PMCSs) with adjustable magnetic-composition and micro-mesoporous characteristics are constructed via the subsequent annealing process. Compared with self-assembly polyphenol derived porous carbon spheres (PCSs), these PMCSs, including Fe3O4-PMCSs, Co-PMCSs and CoNi-PMCSs, exhibit promoted impedance matching and superior microwave absorption attenuation owing to the additional magnetic resonance and synergistic effect. As results, the optimal reflection loss and corresponding bandwidth are −48.6 dB and 7.8 GHz, −45 dB and 8.6 GHz, −53.2 dB and 5.1 GHz for Fe3O4-PMCSs, Co-PMCSs and CoNi-PMCSs with only 15 wt% filler loading, both are higher than PCSs (−39.3 dB and 4.8 GHz). This study inspires us a novel inspiration in constructing of adjustable magnetic-composition and the fabricated PMCSs can be used as lightweight microwave absorbers in the application of electromagnetic protection.

Delaminating Van der Waals-based three-dimensional (3D) solid precursors into ultra-thin sheets of layered materials using liquid-phase exfoliation gained global interest due to the process' simplicity and industrial applicability. The characteristics of exfoliated graphene depend on the processing technique and starting precursor materials' properties. In this work, graphene is stabilized after exfoliation in a water/surfactant medium where 3D graphite of various sizes, including large flakes (∼700 μm) to fine powders (∼8 μm) are used as initial precursors in ultrasonication (bath and probe). The graphene concentration exhibited a peak-like and flat trend in these processes. After exfoliating from different-sized graphite, the nanosheet's morphology is assessed extensively by electron microscopy, and defects are probed by Raman spectroscopy. Large graphite flakes (∼700 μm and 17000) produced nanosheets with high aspect ratios (∼700) with average lateral size of ∼1 μm and 4 ± 1. Surprisingly, graphite with the size of 8 μm and 1235 also produced graphene with lateral size of ∼1 μm and 8 ± 5. Graphite with a large particle size undergoes significant fragmentation and then exfoliation. In contrast, fragmentation is less when the small-sized graphite undergo exfoliation. This study provides insights into the role of initial 3D precursors in creating 2D materials.

Recent discoveries using polyethylene-derived carbon dots (CD) not only offer tangible ways of mitigating plastics pollution but also open tremendous application prospects. Using their massive aerial-oxygen-harvesting properties, oxidation reactions can be accomplished with equal efficiencies in air and in oxygen, enabling the use of free air as oxidants, while their ability to self-eliminate or ‘autophagy’ enables easy disposal. Light-induced ‘hypoxia’ in them can provide for programmable oxygen concentrations within a solution. However, utilizing different waste plastics as feedstock and the tunability of the emergent properties has remained unexplored. Herein, we show that CDs can be obtained from ten of the most abundant plastic wastes with 100% conversion efficiencies, and recovered as powders for easy transportation and storage. We further establish that O2 harvesting ability and the magnitude of hypoxia in CDs are highly structure-dependent and rationally controllable. O2 enrichment can be tremendously modulated in the as-synthesized CDs within a 405–830 μM range where the ratios of strongly and weakly bound oxygen molecules vary between 1.46 and 3.14. Moreover, hypoxia can be adjusted in the 82–266 μM range with 30 min of light exposure while autophagy follows a pseudo-first-order kinetics with effective disappearances from a solution spanning from two days to months.