Construction of layer-by-layer sandwiched graphene/polyaniline nanorods/carbon nanotubes heterostructures for high performance supercapacitors

Progress, Challenges and Prospects of Biomass-Derived Lightweight Carbon-Based Microwave-Absorbing Materials

The widespread use of electronic devices in daily life, industry and military has led to a large amount of electromagnetic pollution, which has become an increasingly serious security issue. To eliminate or mitigate such risks and hazards, various advanced microwave absorption technologies and materials have been reported. As a new type of microwave absorber, biomass-derived carbon-based materials have received extensive attention. They have the characteristics of low cost, easy preparation, high porosity and environmental friendliness while retaining the advantageous adjustable dielectric properties, high conductivity and good stability of traditional carbon materials. The development of biomass microwave-absorbing materials not only provides a new idea for solving electromagnetic radiation but also helps to create an environmentally friendly and harmonious environment. Herein, various biomass-derived carbon-based microwave-absorbing materials (MAMs) including plant shells, plant fibers and other potential biomass materials are generalized and discussed including their preparation technology, microstructure design and so on. The two critical factors affecting microwave absorption properties, impedance matching and attenuation characteristics, are analyzed in detail. Finally, the confronting challenges and future development prospects of biomass-based microwave-absorbing materials are pointed out.

3D-Printed Nanocarbon Polymer Conductive Structures for Electromagnetic Interference Shielding

Electromagnetic interference (EMI) significantly affects the performance and reliability of electronic devices. Although current metallic shielding materials are effective, they have drawbacks such as high density, limited flexibility, and poor corrosion resistance that limit their wider application in modern electronics. This study investigates the EMI shielding properties of 3D-printed conductive structures made from polylactic acid (PLA) infused with 0D carbon black (CB) and 1D carbon nanotube (CNT) fillers. This study demonstrates that CNT/PLA composites exhibit superior EMI shielding effectiveness (SE), achieving 43 dB at 10 GHz, compared to 22 dB for CB/PLA structures. Further, conductive coating of polyaniline (PANI) electrodeposition onto the CNT/PLA structures improves the SE to 54.5 dB at 10 GHz. This strategy allows fine control of PANI loading and relevant tuning of SE. Additionally, the 3D-printed PLA-based composites offer several advantages, including lightweight construction and enhanced corrosion resistance, positioning them as a sustainable alternative to traditional metal-based EMI shielding materials. These findings indicate that the SE of 3D-printed materials can be substantially improved through low-cost and straightforward PANI electrodeposition, enabling the production of customized EMI shielding materials with enhanced performance. This novel fabrication method offers promising potential for developing advanced shielding solutions in electronic devices.

Synergistic Remediation of Cadmium Pollution in Saline-Alkali Soil by Hydrogel and Suaeda salsa

The cadmium (Cd) in saline-alkali soil poses a serious threat to the ecological environment and human health. Suaeda salsa, as a hyperaccumulator plant, can remediate Cd in saline-alkali soil, but the efficiency of phytoremediation is low. To improve the remediation effect of Cd pollution in saline-alkali soil, this study for the first time uses the synergy of hydrogel and Suaeda salsa for the remediation of Cd in saline-alkali soil. Hydrogel possesses excellent mechanical properties and outstanding adsorption properties. In addition, the hydrogel increases the content of some nutrient elements in the soil and improves the physicochemical properties of the soil. The water retention capacity of the hydrogel and the improvement of the physicochemical properties of the soil further promote the growth of Suaeda salsa. Meanwhile, both the hydrogel and Suaeda salsa have a positive impact on microorganisms. Our experiment provides a brand-new way for the remediation of Cd pollution in saline-alkali soil and is of great significance for soil health and ecological protection.

An environmentally sustainable ultrasonic-assisted exfoliation approach to graphene and its nanocompositing with polyaniline for supercapacitor applications

In the present work, a green high-yielding method for the preparation of graphene is introduced via ultrasonic-assisted liquid phase exfoliation (LPE) of graphite in a green solvent medium, since the common preparation method of graphene via graphite oxide is hazardous. A high concentration of 3.2 mg/ml graphene is achieved here in a comparatively short duration of 3 h ultrasonication. By using a mixed solvents strategy (acetophenone and isopropyl alcohol, 1:19 V/V), surface energy requirements needed for the exfoliation of graphite are satisfied here with acetophenone, where isopropyl alcohol further facilitated the exfoliation via non-conventional CH-π and OH-π interactions. Turbostratic graphene in high-yield (16 %) in a simple means of ultrasonic assisted LPE is the added attraction of the present procedure. The less-defective structure of graphene, its few-layered turbostratic nature, and edge functionalization of the sheets are evident from the material characterization via Raman spectroscopy, XRD, TEM-SAED, and XPS analyses. Here, we report a combination of the attractive conducting polymer polyaniline (PANI) with the as-prepared graphene for supercapacitor applications, where the PANI/graphene nanocomposites with different aniline concentrations (PANI1.125/G, PANI4.5/G, and PANI9/G) have been prepared via in-situ polymerization of aniline in the graphene dispersion. The structure and morphology of the nanocomposites are investigated using different characterization techniques which revealed that the molecular structure of the PANI is retained in the nanocomposites even with a strong interaction with graphene. FESEM and TEM images revealed the good coverage of graphene sheets with PANI that limit the volume change of PANI during the repeated charge-discharge processes. Electrochemical studies showed that PANI4.5/G has the highest specific capacitance of 126.16 mF/cm2 at a current density of 1 mA/cm2, resulting from the perfect combination of the pseudocapacitance behavior of the PANI along with the electrical double layer capacitance of graphene. A symmetric supercapacitor device is also fabricated with PANI4.5/G, which showed the highest areal capacitance of 116.38 mF/cm2 similar to that with three-electrode studies and also good cycling stability with 87 % capacitance retention in the specific capacitance after 6000 cycles. It also exhibited an energy density of 16 µWh/cm2 (0.29 Wh/kg) and a power density of 3.99 mW/cm2 (72.72 W/kg).

Synthesis, Electrical Conductivity, and Wave-Absorption Performances of Bamboo-Based Composites Co-Doped with Graphene Oxide and Polyaniline

Bamboo was carbonized and further modified via co-doping with graphene oxide (GO) and polyaniline (PANI) to prepare microwave absorption composites (GO/PANI/CB) by in situ polymerization of 1R-(-)-Camphorsulfonic acid (L-CSA). The conductivity of GO/PANI/CB reached 2.17 ± 0.05 S/cm under the optimized process conditions. The oxygen-containing group of GO reacts with PANI to form hydrogen bonds and thus polymerize. The GO and PANI particles covered the carbonized bamboo (CB) surface in a disordered aggregation form. Based on the measuring method of the vector network analyzer (VNA), the microwave-absorption performance of GO/PANI/CB was investigated. With 30% addition of GO/PANI/CB, the minimum reflection loss (RLmin) at 7.12 GHz with a thickness of 3.5 mm of samples reached -49.83 dB. The effective absorption bandwidth (<-10 dB) is as high as 4.72 GHz with a frequency range of 11.68-16.40 GHz and a thickness of 2 mm. Compared with many PANI based electromagnetic wave absorbing materials reported in recent years, GO/PANI/CB provides improved microwave-absorption performance while maintaining high absorption bandwidth. GO/PANI/CB exhibited the advantages of simple preparation, low cost, renewability, light texture, thinness, wide absorption bandwidth, and strong absorption ability, and can be used for new microwave absorption materials.

Carbon Dot-Stabilized Hydrogel Composite: A New Adsorbent for Efficient and Sustainable Pb(II) Removal

In this paper, a carbon dot hydrogel composite (CDs-Hy) capable of efficiently removing Pb(II) was prepared by hydrogen bonding self-assembly in combination with carbon dots and a hydrogel. CDs-Hy was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), and the effect of the adsorption conditions on the adsorption efficiency of CDs-Hy was studied. The results of the study showed that the incorporation of carbon dots, on the one hand, significantly increased the adsorption capacity of the material. On the other hand, it can increase the stability of hydrogels in aqueous solution. The possible adsorption mechanisms were further verified as ion exchange and coordination. CDs-Hy is a novel adsorbent material capable of removing Pb2+ efficiently, which can be reused several times with high stability.

Recent Advances in Carbon-Based Electrodes for Energy Storage and Conversion

Carbon-based nanomaterials, including graphene, fullerenes, and carbon nanotubes, are attracting significant attention as promising materials for next-generation energy storage and conversion applications. They possess unique physicochemical properties, such as structural stability and flexibility, high porosity, and tunable physicochemical features, which render them well suited in these hot research fields. Technological advances at atomic and electronic levels are crucial for developing more efficient and durable devices. This comprehensive review provides a state-of-the-art overview of these advanced carbon-based nanomaterials for various energy storage and conversion applications, focusing on supercapacitors, lithium as well as sodium-ion batteries, and hydrogen evolution reactions. Particular emphasis is placed on the strategies employed to enhance performance through nonmetallic elemental doping of N, B, S, and P in either individual doping or codoping, as well as structural modifications such as the creation of defect sites, edge functionalization, and inter-layer distance manipulation, aiming to provide the general guidelines for designing these devices by the above approaches to achieve optimal performance. Furthermore, this review delves into the challenges and future prospects for the advancement of carbon-based electrodes in energy storage and conversion.

Nanostructured Conducting Polymers and Their Applications in Energy Storage Devices

Due to the energy requirements for various human activities, and the need for a substantial change in the energy matrix, it is important to research and design new materials that allow the availability of appropriate technologies. In this sense, together with proposals that advocate a reduction in the conversion, storage, and feeding of clean energies, such as fuel cells and electrochemical capacitors energy consumption, there is an approach that is based on the development of better applications for and batteries. An alternative to commonly used inorganic materials is conducting polymers (CP). Strategies based on the formation of composite materials and nanostructures allow outstanding performances in electrochemical energy storage devices such as those mentioned. Particularly, the nanostructuring of CP stands out because, in the last two decades, there has been an important evolution in the design of various types of nanostructures, with a strong focus on their synergistic combination with other types of materials. This bibliographic compilation reviews state of the art in this area, with a special focus on how nanostructured CP would contribute to the search for new materials for the development of energy storage devices, based mainly on the morphology they present and on their versatility to be combined with other materials, which allows notable improvements in aspects such as reduction in ionic diffusion trajectories and electronic transport, optimization of spaces for ion penetration, a greater number of electrochemically active sites and better stability in charge/discharge cycles.

Emerging of Heterostructure Materials in Energy Storage: A Review

With the ever-increasing adaption of large-scale energy storage systems and electric devices, the energy storage capability of batteries and supercapacitors has faced increased demand and challenges. The electrodes of these devices have experienced radical change with the introduction of nano-scale materials. As new generation materials, heterostructure materials have attracted increasing attention due to their unique interfaces, robust architectures, and synergistic effects, and thus, the ability to enhance the energy/power outputs as well as the lifespan of batteries. In this review, the recent progress in heterostructure from energy storage fields is summarized. Specifically, the fundamental natures of heterostructures, including charge redistribution, built-in electric field, and associated energy storage mechanisms, are summarized and discussed in detail. Furthermore, various synthesis routes for heterostructures in energy storage fields are roundly reviewed, and their advantages and drawbacks are analyzed. The superiorities and current achievements of heterostructure materials in lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), lithium-sulfur batteries (Li-S batteries), supercapacitors, and other energy storage devices are discussed. Finally, the authors conclude with the current challenges and perspectives of the heterostructure materials for the fields of energy storage.

Enhanced tensile and electrochemical performance of MXene/CNT hierarchical film

Nowadays, it is highly desirable to achieve high strength, flexibility and electrochemical performance for supercapacitor electrodes simultaneously. Herein, few-layer MXene flakes are assembled into free-standing films by facile vacuum-filtration method, in which hydrophilic-functionalized carbon nanotubes (CNTs) are further incorporated. The morphology of MXene/CNT composite films evolves from compact to 'CNT in MXene' to laminar to 'MXene in CNT' and finally to separate structures when increasing the CNT weight percentage. Among them, the laminar structure in which thin MXene and CNT layers are stacked alternately is demonstrated to be the best. The laminar MXene/CNT film possesses much higher strength, elongation and specific capacitance than MXene film due to the engineered porosity, good interaction between MXene flakes and CNTs, and proper CNTs' distribution. As a result, high specific capacitance of 423.4 F g^-1at 1 A g^-1and capacitance retention of nearly 60% at 10 A g^-1are accomplished. Moreover, the composite film is flexible and withstands bending up to 180°, indicating that the proposed laminar MXene/CNT composite film is a superb candidate for flexible supercapacitors.

Graphene/Reduced Graphene Oxide-Carbon Nanotubes Composite Electrodes: From Capacitive to Battery-Type Behaviour

Thanks to the advanced technologies for energy generation such as solar cells and thermo- or piezo-generators the amount of electricity transformed from light, heat or mechanical pressure sources can be significantly enhanced. However, there is still a demand for effective storage devices to conserve electrical energy which addresses the wide range of large stationary applications from electric vehicles to small portable devices. Among the large variety of energy-storage systems available today, electrochemical energy sources and, in particular, supercapacitors (SC), are rather promising in terms of cost, scaling, power management, life cycle and safety. Therefore, this review surveys recent achievements in the development of SC based on composites of such carbon-derived materials as graphene (G) and reduced graphene oxide (rGO) with carbon nanotubes (CNT). Various factors influencing the specific capacitance are discussed, while specific energy and power as well as cycling stability of SC with G/rGO-CNT composite electrode materials are overviewed.

Preparation of nitrogen self-doped hierarchical porous carbon with rapid-freezing support for cooperative pollutant adsorption and catalytic oxidation of persulfate

Herein, we report a method to synthesize nitrogen self-doped hierarchical porous carbon materials derived from chitosan. This method uses potassium hydroxide (KOH) activation and rapid-freezing technology. The catalyst (CA-900Q 1-1) obtained after rapid-freezing and KOH activation treatment show excellent persulfate activation ability. It can remove 20 mg bisphenol A (BPA) within 10 min better than traditional metal oxidate and nanomaterials. In the aquatic environment, CA-900Q 1-1 has a high resistance to inorganic anions. CA-900Q 1-1, possessing a high proportion of graphitic nitrogen, provides a sufficient number of active sites for persulfate activation. In addition, the catalyst yielded sizeable specific surface areas (SSAs) (1756.1 m²/g) and a hierarchical pore structure, which helps to improve the mass transfer in the carbon framework. The efficient adsorption of pollutants by the catalyst shortens the time required for target organic molecules to migrate to the catalyst surface and hierarchical pore structure. Furthermore, the catalyst has excellent electrical conductivity (R = 1.73 Ω), which enables pollutants adsorbed on the catalyst surface to transfer electrons to the persulfate through the N-doped sp²-hybrid carbon network faster.

In Situ Growth of Oriented Polyaniline Nanorod Arrays on the Graphite Flake for High-Performance Supercapacitors

Polyaniline with oriented nanorod arrays could provide high surface area and relaxed nanostructure to optimize ion diffusion paths, thus enhancing the performance of the device. In this paper, we designed an all-solid symmetrical supercapacitor with good performance based on polyaniline nanorod arrays in situ-grown on a graphite flake free-standing substrate. The specific capacitance, cycle stability, and energy density of the prepared supercapacitor device were 135 F/g, 75.4% retention after 1500 cycles, and the energy density is 18.75 W h/kg at a power density of 500 W/kg. The good performance of the supercapacitor device was obviously related to the oriented nanorod arrays of polyaniline/graphite flakes. In order to find the application of the prepared supercapacitor device, the tandem device consisting of three single supercapacitor devices connected in series had been used to drive small electronic equipment. The red light-emitting diode and chronograph could be easily driven by the 3-series supercapacitor devices. These results indicated that the prepared supercapacitor device based on the polyaniline/graphite flake electrode had potential applications in energy storage devices.

Construction of mesoporous carbon microsphere/polyaniline composites as high performance pseudocapacitive electrodes

Mesoporous carbon microspheres (MCMs), as a supercapacitor electrode material, have good gravimetric capacitance and rate performance; however, their low volumetric capacitance, which results from their low density, restricts their application as a micro power source. Herein, polyaniline was introduced into the channels of MCMs to achieve a synergistic effect and significantly increase the volumetric capacitance. MCMs with a high surface area and pore volume allowed the uniform dispersion of PANI within their channels in nanoscale dimensions. The interconnected carbon framework could provide excellent electrical conductivity and alleviate the structural collapse of PANI. Moreover, PANI could function not only as an active pseudocapacitive material that facilitated energy storage but also as a proton transport media that promoted a rapid protonation/deprotonation process during the redox reaction in the internal channels. As a result, PANI/MCM composites, even with a poor pore structure, delivered a high volumetric capacitance of 539F cm^-3 at 1 A g^-1 and an excellent rate performance of 83% at current densities ranging from 0.5 to 20 A g^-1. In addition, PANI/MCM composites exhibited good cycling stability, retaining 84% of the capacitance after 1000 charge/discharge cycles at 1 A g^-1, owing to the high mechanical strength of the MCMs. Therefore, this synthesis strategy could provide an efficient and scalable solution for the development of supercapacitor electrode materials.

Polypyrrole Chains Decorated on CoS Spheres: A Core-Shell Like Heterostructure for High-Performance Microwave Absorption

Cobalt sulfide composites have exhibited great potential in terms of microwave absorption, owing to their low price, relatively high capacitance, and excellent electrocatalytic activity. Thus, a novel core-shell like structure comprising cobalt sulfide@polypyrrole (CoS@PPy) composite was synthesized by a facile solvothermal synthesis method and in situ polymerization. When coated by the heterostructure polypyrrole aerogel, CoS@PPy composite exhibited excellent microwave absorption properties with an optimal reflection loss (RL) of -41.8 dB at 6.96 GHz. Furthermore, the absorption bandwidth (RL < -10 dB) of 5.4 GHz could be reached at a coating thickness of 2.05 mm, probably attributing to the synergistic effect of good impedance matching, interfacial polarization, dipole polarization, and conductivity loss. Moreover, this work proposed a loss mechanism mode which probably occurred in the CoS@PPy composites. It was demonstrated that the CoS@PPy composite is a promising material in the field of electromagnetic wave absorption.

3D Hollow Quasi-Graphite Capsules/Polyaniline Hybrid with a High Performance for Room-Temperature Ammonia Gas Sensors

Designing sensing materials with novel morphologies and compositions is eminently challenging to achieve high-performance gas sensor devices. Herein, an in situ oxidative polymerization approach is developed to construct three-dimensional (3D) hollow quasi-graphite capsules/polyaniline (GCs/PANI) hierarchical hybrids by decorating protonated PANI on the surface of GCs; as a result, an immensely active and sensitive material was developed for sensing ammonia gas at room temperature. Moreover, the GCs possessed a capsule-like hollow/open structure with partially graphitized walls, and PANI nanospheres were uniformly decorated on the GC surfaces. Furthermore, the inflexible and rigid 3D ordered chemistry of these materials provides the resulting hybrids with a large interfacial surface area, which not only allows for rapid adsorption and charge transfer but also provides the necessary structural stability. The 3D hollow GCs/PANI hybrids exhibit excellent performance; the GCs/PANI-3 hybrid is highly sensitive (with a response value of 1.30) toward 10 ppm NH₃ gas and has short response and recovery times of 34 and 42 s, respectively. The GCs/PANI-3 hybrid also demonstrates a good selectivity, repeatability, and long-term stability, which are attributed to the substantial synergistic effect of the GCs and PANI. The design of such a unique 3D ordered framework provides a promising pathway to achieve room-temperature gas sensors for commercial applications.

Novel three-dimensional polyaniline nanothorns vertically grown on buckypaper as high-performance supercapacitor electrode

Combining polyaniline (PANI) with different dimensional carbon materials is an effective way to solve the disadvantages of poor rate performance and cycling stability induced by the structure destruction of conductive polymer materials over long-term charge/discharge cycles. In this work, novel three-dimensional (3D) conical PANI nanothorns are synthesized on a buckypaper substrate via a controlled electropolymerization process. Benefiting from the synergistic effect of the vertical growth of PANI nanothorns and the excellent mechanical elasticity of multi-wall carbon nanotubes, it can effectively alleviate the volume change during the charging and discharging process of the electrode material and ensure the rapid transmission of electrons. The morphology and structure of the composite have been characterized by scanning electron microscopy, x-ray diffraction, and Fourier transform infrared spectroscopy. The results show that the electrode exhibits a high specific capacitance of 742 F g^-1 at 1 A g^-1 in 1 M of H₂SO₄ electrolyte and a capacitance retention of 76% after 2000 cycles. The novel 3D PANI nanothorn/buckypaper composite has significant potential as practical for use as electrode materials of supercapacitors due to its easy synthesis, low cost, and high specific capacitance.

Core-Shell CoNi@Graphitic Carbon Decorated on B,N-Codoped Hollow Carbon Polyhedrons toward Lightweight and High-Efficiency Microwave Attenuation

Lightweight and high-efficiency microwave attenuation are two major challenges in the exploration of carbon-based absorbers, which can be achieved simultaneously by manipulating their chemical composition, microstructure, or impedance matching. In this work, core-shell CoNi@graphitic carbon decorated on B,N-codoped hollow carbon polyhedrons has been constructed by a facile pyrolysis process using metal-organic frameworks as precursors. The B,N-codoped hollow carbon polyhedrons, originated from the calcination of Co-Ni-ZIF-67, are composed of carbon nanocages and BN domains, and CoNi alloy is encapsulated by graphitic carbon layers. With a filling loading of 30 wt %, the absorber exhibits a maximum R_L of -62.8 dB at 7.2 GHz with 3 mm and the effective absorption bandwidth below -10 dB remarkably reaches as strong as 8 GHz when the thickness is only 2 mm. The outstanding microwave absorption performance stems from the hollow carbon polyhedrons and carbon nanocages with interior cavities, the synergistic coupling effect between the abundant B-C-N heteroatoms, the strong dipolar/interfacial polarizations, the multiple scatterings, and the improved impedance matching. This study demonstrates that the codoped strategy provides a new way for the rational design of carbon-based absorbers with lightweight and superior microwave attenuation.

Permittivity-Regulating Strategy Enabling Superior Electromagnetic Wave Absorption of Lithium Aluminum Silicate/rGO Nanocomposites

Lithium aluminum silicate (LAS) nanoparticles have been successfully loaded on graphene nanosheets by adding a silane coupling agent KH-550 by sol-gel process, hydrothermal reaction, and heat treatment process. By regulating the complex permittivity of reduced graphene oxide (rGO) by LAS nanoparticles and KH-550, LAS/rGO-KH-550 possesses excellent microwave absorption performance. The maximum reflection loss of LAS/rGO-KH-550 reaches -62.25 dB at 16.48 GHz with thickness of only 2.7 mm, and the widest bandwidth is up to 6.64 GHz below -10 dB. The LAS/rGO-KH-550 has effective absorption (99.9%) below -20 dB at all X and Ku bands (8-18 GHz). Also, the added quantity of composites in the paraffin matrix is only 20 wt %. The results demonstrate that the interfacial polarization, the Debye dipolar relaxation, the well-matched characteristic impedance, and the quarter-wavelength matching all play important roles in improving the microwave absorption properties of LAS/rGO-KH-550 nanocomposites. Consequently, the LAS/rGO-KH-550 nanocomposites can be readily applied as an ultra-wide-band, light weight, and ultra-high-performance microwave-absorbing material.

Enhanced microwave-absorption with carbon-encapsulated Fe-Co particles on reduced graphene oxide nanosheets with nanoscale-holes in the basal plane

In this study, an Fe-Co alloy is coated with carbon and decorated on a holey reduced graphene oxide nanosheet (FeCo@C/HRGO) composite. The structure is synthesized using liquid-phase reduction and hydrothermal processes followed by high-temperature calcination. The FeCo@C/HRGO composite is identified and characterized using XRD, XPS, Raman spectroscopy, TEM, and SEM. This novel composite exhibits excellent electromagnetic-wave absorption properties. The maximum reflection loss for FeCo@C/HRGO reaches -76.6 dB at 16.64 GHz with a thickness of 1.7 mm. The R_L below -10 dB reaches 14.32 GHz for a thickness of 1.7-5.0 mm. This confirms that microwave absorption of FeCo@C can be substantially improved upon decoration with HRGO nanosheets.

Hybridization-Induced Polarization of Graphene Sheets by Intercalation-Polymerized Polyaniline toward High Performance of Microwave Absorption

An intercalation polymerization is applied to regulate the hybridizing structures of polyaniline@graphene (PANI@GE). Polarization of GE sheets is realized, which is attributed to the hybridization by the in situ intercalation-polymerized PANI molecules. The polarizing effect on GE is confirmed by characterizations and density functional theory calculations, and the results indicate that distinct p-π and π-π interactions exist between the PANI molecules and the GE sheets. As a result, this new structural hybrid leads to a high performance of microwave absorption. The minimum reflection loss (RL) of the optimized PANI@GE hybrid can be as low as -64.3 dB at 10.1 GHz with the RL bandwidth of -10 dB being 5.1 GHz (from 8.6 to 13.7 GHz). A further study reveals a special mechanism for the electromagnetic energy consumptions by the structural resonance of the polarized GE-based hybrids, a complex macromolecule. In addition, the fully separated GE provides a good impedance matching, together with the widely held multiscaled relaxations of the interfacial polarization.

Dopamine-derived cavities/Fe3O4 nanoparticles-encapsulated carbonaceous composites with self-generated three-dimensional network structure as an excellent microwave absorber

Dopamine-derived cavities/Fe₃O₄ nanoparticles-encapsulated carbonaceous composites with self-generating three-dimensional (3D) network structure were successfully fabricated by a facile synthetic method, in which sodium alginate provided carbon matrix pores and excellent microwave absorption performance was established. The hollow cavities derived from the core–shell-like CaCO₃@polydopamine were creatively introduced into the 3D absorber to significantly improve the absorption performance. The sample calcined at 700 °C exhibited the most outstanding microwave absorption performance, with minimal reflection loss up to −50.80 dB at 17.52 GHz with a rare thickness of only 1.5 mm when filler loading was 35% in paraffin matrix. The effective absorption bandwidth of reflection loss < −10 dB reached 3.52 GHz from 14.48 GHz to 18 GHz, corresponding to the same thickness of 1.5 mm. In contrast, the sample without hollow dopamine-derived cavities showed poor performance due to poor impedance matching, and this highlights the role of hollow cavities brought into the 3D structure, which led to a difference in interfacial polarization, multiple reflections and scattering. The novel dopamine-derived cavities/Fe₃O₄ nanoparticles-encapsulated carbonaceous composites with 3D network structure can be regarded as a promising candidate for application as a microwave absorber with strong absorption.

Hollow dopamine-derived cavities/Fe₃O₄ nanoparticles-encapsulated carbonaceous composites with self-generating 3D network structure were fabricated for potential application as excellent microwave absorbers.

Functionalized Carbon Nanofibers Enabling Stable and Flexible Absorbers with Effective Microwave Response at Low Thickness

Lots of work has been done to develop microwave absorbing materials (MAM) utilized as flexible electronic devices and communication instruments. Conventionally developed powder MAM are often limited in practical applications because of the bad stability and poor durability, which is out of the scope for exploiting flexible and long-term microwave absorbers. To overcome such limitations, a facile and binder-free technique from a Co-based zeolitic imidazolate framework (ZIF-67, a member of metal-organic frameworks)-coated carbon fiber precursor is developed for the in situ horizontal growth of Co₃O₄ nanoparticles, which embedded nitrogen-doped carbon array (triangular nanoplates) on the surface of carbon fibers in the carbon paper (NC-Co₃O₄/CP) as low-thickness MAM. The maximum reflection loss (RL) values reaches -16.12 and -34.34 dB when the thickness is 1.1 and 1.5 mm, respectively. As the thickness increases, the absorbing performance at low frequency performs well (RL < -20 dB). The hierarchical architecture is facilely originated from a metal-organic framework precursor. In view of the simple preparation technique, NC-Co₃O₄/CP exhibit huge potential in large-scale production of portable microwave absorbing electronic devices with strong microwave response at low thickness.