Search

The accurate heterojunction engineering in MXene-based composites unprecedentedly boosts their electromagnetic (EM) wave absorption and shielding performance. However, the flocculation of MXene caused by abundant termination groups severely restricts the regulation of heterojunction, which hankers for a revolutionary compositing strategy against unmanageable self-aggregation. Herein, electrically neutral coordination compound with large molecular volume is decorated on Ti3C2Tx lamellas to protect them from self-precipitation. A rapid polymerization reaction then controllably assembles them into a hierarchical microsphere composed of superlattice-like 2D/2D polymer/MXene building blocks. In the carbonized Ti3C2Tx/C/MoO2 microspheres, 2D/2D/0D heterojunctions can be precisely tuned to regulate electric/dielectric properties. These heterojunctions simultaneously trigger the intensive interfacial polarization and out-plane electron flowing to exhaust the EM energy as much as possible, confirmed by electron holography. Therefore, our products achieve the first-rate EM wave absorption with an ultrabroad absorption bandwidth of 7.7 GHz at the thickness of 2.5 mm. By altering the heterojunction, the composite acquires excellent EM interference shielding performance with an average shielding effectiveness of 35.9 dB. These accomplishments light a new way to microstructure construction and heterojunction design of MXene-based composites and lay out a profound insight into their EM wave absorption mechanism.

As a hot two-dimensional (2D) material, molybdenum disulfide has been attracting extensive attention for electromagnetic wave response applications because of its unique structure. However, the electronic conductivity of nanostructured MoS2 needs to be optimized urgently. Here, nitrogen-doped 1T@2H-MoS2/reduced graphene oxide (RGO) composites are effectively constructed by hydrothermal reaction and consecutive calcination under an NH3 atmosphere. The prepared composites possess great microwave absorption (MA) performance with an expected absorption bandwidth (4.00 GHz) at the Ku band and a maximum reflection loss value (-67.77 dB), which is much better than the performance of conventional 2H-MoS2 or 2H-MoS2/RGO. The prominent absorption property is ascribed to the (i) unique self-assemble morphology of rose-like MoS2 supported on 2D RGO; (ii) controllable crystalline phase switch between 2H and 1T; and (iii) brilliant energy attenuation caused by the intense multipolarization. Furthermore, the dominant MA mechanism is described as the local polarization motivated by the interaction between RGO and MoS2. Thus, our novel structure design provides a necessary reference to achieve optimized absorption performance based on 2D materials.

Hierarchically porous carbon/magnetic particle composites have been successfully prepared via drying the gels of gelatin/metal nitrates and subsequent carbonization process. The micro-scale pores are formed due to the self-foaming of the gels during the drying process. At the early stage of carbonization process, metal nitrates are converted into metal oxides rapidly. Then the nano-scale pores are generated via the etching reaction between the gelatin-derived carbon and the nucleated metal oxides induced by gelatin with the elongation of carbonization process. Eventually, the nucleated metal oxides are further reduced by gelatin-derived carbon to form carbon/magnetic particle composites. The superimposed effects between heterogeneous chemical components and hierarchical porosity endow the absorbent with excellent microwave absorption (MA) performance. A maximum reflection loss (RL) of −57.1 dB and a broad effective absorption bandwidth (EAB) of 8.16 GHz are achieved in the hierarchically porous C/Fe3C composites. Similarly, the broad EABs of 6.32 and 8.80 GHz can be gained by drying and carbonization of gelatin/cobalt nitrate and gelatin/nickel nitrate gels, respectively. All the results demonstrate that the combination of hierarchically porous structures and dual loss components is a promising strategy for the preparation of high-performance MA materials with broad EAB.

1D structures have been gaining traction in the microwave absorption (MA) field benefiting from their electromagnetic (EM) anisotropy. However, there remain considerable challenges in adjusting EM properties by structural design. Herein, using the coaxial electrospinning and solvothermal method, the EM gradient has been achieved in TiO2@Co/C@Co/Ni multilayered microtubes. From the outer layer to the inner one, the impedance matching is gradually worsened, while the EM loss capacity is continuously enhanced, facilitating both the incidence and attenuation of microwave. Besides, 1D structural anisotropy simultaneously realizes multilevel magnetic interaction and 3D conductive double network. Therefore, the 1D EM-gradient hierarchical TiO2@Co/C@Co/Ni carbon microtube composite exhibits excellent MA performance. Its maximum reflection loss (RL) value reaches -53.99 dB at 2.0 mm and effective absorption bandwidth (EAB, RL ≤ -10 dB) is as wide as 6.0 GHz, covering most of the Ku band with only 15% filling. The unique design of 1D EM-gradient hierarchical composites promises great potential in the construction of advanced MA materials.

A hierarchical carbon/reduced graphene oxide (rGO)/FeOx (CGF) composite has been successfully prepared utilizing a sequential process of immersion and carbonization. During the immersion of melamine foam in a liquid precursor, graphene oxide (GO) is covered on the interconnected framework of the foam and is decorated by metallic ions simultaneously. Therefore, the hierarchical structure is constructed in one step. The CGF composite exhibits a maximum reflection loss of as much as −51.2 dB and an ultrawide effective absorption bandwidth of 8.2 GHz. Detailed investigation suggests that the hierarchical structure contributes to the superb microwave absorption performance significantly through enhancing the interfacial polarization and inducing multireflection of microwave. The simple and cost-effective fabrication process together with the excellent microwave absorption performance endows the CGF composite with great potential for practical application.

Hyper-crosslinked polymers (HCPs) are promising materials for gas capture and storage because of their low cost and easy preparation. In this work, we report the massive preparation of coumarone-indene resin-based hyper-crosslinked polymers via one-step Friedel-Crafts alkylation. Low-cost coumarone-indene resin serves as the new building block and chloroform is employed as both solvent and external crosslinker. A maximum surface area of 966 m2·g−1 is achieved, which is comparable with that of previously-reported coal tar-based porous organic polymers. Most importantly, a large number of heteroatoms including inherent oxygen atoms and introduced chlorine atoms in obtianed HCPs further enhance the interaction between specific sorbate molecule and adsorbent. Therefore, optimal structural and chemical property endow the new coumarone-indene resin-based HCPs with decent gas storage capacity (14.60 wt% at 273 K and 0.1 MPa for CO2; 1.18 wt% at 77.3 K and 0.1 MPa for H2). These results demonstrate that new HCPs are potential candidates for applications in CO2 and H2 capture.

Mechanically flexible supercapacitors with fast charge-discharge capacity, high stability and good mechanical properties are essential for powering flexible electronics devices. In this paper, we report a simple process to obtain composite electrode consisting of graphene and polyaniline on stainless steel fabric. The all solid-state flexible supercapacitors based on the composite electrode exhibit a maximal specific capacitance of 1506.6 mF/cm2, and capacitance retention of 92% after 5000 charge-discharge cycles. Furthermore, the bending test shows that the flexible supercapacitor maintains 95.8% of the original capacitance after 1000 bending cycles. The high capacitive performance and anti-bending property of the supercapacitor are ascribed to the favourable microstructure of graphene/polyaniline composite and high flexibility of stainless steel fabric. Our work demonstrates a novel type of high-performance flexible electrode, which will boost the development of flexible and wearable electronics and integrated fabric power devices.

To probe the influence of the porous morphology of carbon materials on their microwave absorption performance, hierarchically porous carbons (HPCs) with designed structures have been successfully prepared starting from poly(divinylbenzene) by emulsion template polymerization. There exist two levels of pores in the obtained HPCs. One level of micro-scale pores templates from the water drops, and the other level of nano-scale pores is created during KOH activation in the subsequent carbonization process. By adjusting the water volume fraction during polymerization and the KOH dosage, both micro- and nano-scale porous structures can be accurately tuned. The influences of pores with diverse scales on microwave adsorption capacity are investigated in detail. Eventually, the maximum reflection loss of −56.4 dB and an effective adsorption bandwidth of 6.0 GHz are achieved. The superior microwave absorption performance of HPCs is attributed to the superimposed contributions of the two-level pores to the enhancement of polarization abilities and the multiple reflections of the microwave.

Hierarchically porous carbon (HPC) materials with interconnected pore texture are produced from porous poly(divinylbenzene) precursor, synthesized by polymerizing high internal phase emulsion. After carbonation, the macroporous structures of the poly(divinylbenzene) precursor are preserved and enormous micro/mesopores via carbonation with KOH are produced, resulting in interconnected hierarchical pore network. The prepared HPC has a maximum specific surface area of 2189 m2 g-1. The electrode materials for supercapacitor and capacitive deionization (CDI) device employing the formed HPC exhibit high specific capacity of 88 mAh g-1 through a voltage range of 1V (319 F g-1 at 1 A g-1) and superior electrosorption capacity of 21.3 mg g-1 in 500 mg L-1 NaCl solution, respectively. The excellent capacitive performance could be ascribed to the combination of high specific surface area and favorable hierarchical porous structure.

A series of N-doped porous carbon materials have been successfully prepared by using nitrogen-rich triarylisocyanurate-cored polymers as carbon precursor. The cross-linked networks explain the precursor with high carbonaceous residues in the following carbonization. The influence of KOH dosage and activation temperature on the specific surface area and nitrogen content of the resultant carbon materials is investigated in detail. Eventually, a maximum specific surface area of 2341 m2 g–1 and nitrogen content of 1.7 wt % are achieved in the resultant carbon materials. High CO2 capacity (30.2 wt % at 273 K/1 bar and 17.2 wt % at 298 K/1 bar) is attributed to abundant microporous structures and basic sites, superior to that of the most porous carbon materials reported in the previous literature. In addition, the carbon materials also demonstrate high H2 and CH4 uptake (2.7 wt % at 77.3 K/1.13 bar and 3.8 wt % at 273 K/1.13 bar, respectively). The characters of easy preparation and high gas uptake capacity end...

Core–shell Fe3O4@polypyrrole (PPy) composites with excellent electromagnetic wave absorption properties have been prepared by a sequential process of etching, polymerization, and replication. Templating from pre-prepared Fe3O4 microspheres, ferric ions were released from the skin layer of the microspheres by acid etching and initiated the oxidative polymerization of pyrrole in suit. The morphological and textural evolution of core–shell Fe3O4@PPy composites depending on etching time was investigated by scanning and transmission electron microscope. A maximum reflection loss of as much as −41.9 dB (>99.99% absorption) at 13.3 GHz with a matching layer thickness of 2.0 mm was achieved when the etching time was 5 min. In comparison with other conductive polymer-based core–shell composites reported previously, the Fe3O4@PPy composites in this study not only possess better reflection loss performance but also demonstrate a wider effective absorption bandwidth (

Metal-organic framework (MOF) is highly desirable as a functional material owing to its low density, tunable pore size, and diversity of coordination formation, but limited by the poor dielectric properties. Herein, by controlling the solvent and mole ratio of cobalt/linker, multidimension-controllable MOF-derived nitrogen-doped carbon materials exhibit tunable morphology from sheet-, flower-, cube-, dodecahedron- to octahedron-like. Tunable electromagnetic parameters of Co@N-doped carbon composites (Co@NC) can be obtained and the initial MOF precursor determines the distribution of carbon framework and magnetic cobalt nanoparticles. Carbonized Co@NC composites possess the following advantages: i) controllable dimension and morphology to balance the electromagnetic properties with evenly charged density distribution; ii) magnetic-carbon composites offer plenty of interfacial polarization and strong magnetic coupling network; iii) a MOF-derived dielectric carbon skeleton provides electronic transportation paths and enhances conductive dissipation. Surface-mediated magnetic coupling reflects the stray magnetic flux field, which is corroborated by the off-axis electron holography and micro-magnetic simulation. Optimized octadecahedral Co@NC sample exhibits the best microwave absorption (MA) of -53.0 dB at the thickness of 1.8 mm and broad effective frequency from 11.4 to 17.6 GHz (Ku-band). These results pave the way to fabricate high-performance MA materials with balanced electromagnetic distribution and controlled morphology.

Multilayered microwave absorbers which can provide massive interfaces are highly needed for electromagnetic-wave absorption property enhancement. Meanwhile, how to effectively avoid agglomeration and further widen the absorption band is still a challenge. Herein, accordion-like magnetized MXene/Ni composites were fabricated by the electrostatic self-assembly interaction between multilayer MXene and Ni(OH)

1D tubular micro-nano structural materials have been attracting extensive attention in the microwave absorption (MA) field for their anisotropy feature, outstanding impedance matching, and electromagnetic energy loss capability. Herein, unique double-shelled Sn@Mo2 C/C tubes with porous Sn inner layer and 2D Mo2 C/C outer layer are successfully designed and synthesized via a dual-template method. The composites possess favorable MA performance with an effective absorption bandwidth of 6.76 GHz and a maximum reflection loss value of -52.1 dB. Specifically, the rational and appropriate construction of Sn@Mo2 C/C tubes promotes the multi-path electron transfer in the composites to optimize the dielectric constant and consequently to enhance the capacity of electromagnetic wave energy dissipation. Three mechanisms dominate the MA process: i) the conductive loss resulted from the rapid electron transmission due to the novel 1D hollow coaxial multi-shelled structure, especially the metallic Sn inner layer; ii) the polarization loss caused by abundant heterogeneous interfaces of Sn-Mo2 C/C and Mo2 CC from the precise double-shelled structure; iii) the capacitor-like loss by the potential difference between Mo2 C/C nanosheets. This work hereby sheds light on the design of the 1D hierarchical structure and lays out a profound insight into the MA mechanism.

The poor penetration ability of light in tissues makes phototherapy be difficult to treat bacteria-induced osteomyelitis effectively. Herein, we developed a rapid and noninvasive therapeutic strategy by employing Prussian blue (PB) as a microwave-responsive material. The PB was excited by microwave through dielectric loss of PB and the changed spin state of iron ions, which led to the heat generation and then weakened the bond energy of Fe II‒(CN) and Fe III‒(NC) in physiological saline. At the same time, the insertion of Na+ in PB made the bond energy become irreversible, which accelerated the release of Fe2+ and Fe3+ from PB. The released Fe2+ and Fe3+ could be easy to penetrate bacterial membrane with reduced permeability by microwave to react with H2O2 and GSH in the inside of bacteria, leading to the final death of the bacteria due to the synergistic action of microwave, microwave thermal effect and Fe2+/Fe3+ induced Fenton reaction/GSH consumption. This study will provide novel insight for designing remote and noninvasive antibacterial systems for treating deep bacteria-infected diseases.

To circumvent the intractable disadvantages of a hyper-cross-linked strategy based on the Friedel–Crafts reaction, a new type of microporous organic polymer (MOP) has been successfully prepared using fumaronitrile and divinylbenzene via alternating radical polymerization. The obtained MOPs exhibit a maximum surface area of 805 m2 g−1 and excellent thermochemical stability. By pyrolyzing the copolymer precursor, a rich nitrogen-doped porous carbon material can be produced, which possesses a specific surface area of 1450 m2 g−1 with a CO2 uptake of 30 wt% at 273 K. The porous carbon also shows a high specific capacitance of 330 F g−1 at a current density of 1.0 A g−1 and a good cycling stability of 96.8% retention after 8000 cycles in a three electrode system. The unique synthesis strategy inspires researchers to seek novel building blocks for the scaled-up preparation of MOPs and the resulting porous carbon has promising application for gas adsorption and energy storage.

The powdery electromagnetic functional materials severely suffer from the intricate post-compositing/coating process and high weight loading in the ultimate production, which desires a significant revolution of the manufacture technology. Herein, a facile and scalable drawing method is developed for manufacturing a series of flexible, repairable, and high-performance electromagnetic functional coatings with merely ultra-low filler contents. The holography and simulation demonstrate that the drawing process can simultaneously enhance the structural anisotropy and confine the distribution of the filler, thereby significantly reducing the filler content. For instance, the pencil drawing with high dielectric constant holds a record-low graphite content of 4.7 wt%, which sharply reduces by 89.6% compared to traditional polymer/graphite composite. Other six kinds of materials with different dimensions are further employed to prove the universality of the unique drawing method. All these drawings acquire the first-rate electromagnetic stealth and interference shielding performance within a wide effective operating bandwidth of 12 GHz with slight filler weight fractions. Eventually, the as-drawn composites with excellent flexibility and repairability can be easily coated on the equipment without any post-processing. The above achievements endow the drawing method with broad application prospects, such as wearable electromagnetic functional textiles and renewable devices.

A variety of biomass-based carbon materials with two-level porous structure have been successfully prepared by one-step carbonization process. The first level of microscale pores templates from the inherent porous tissues, while the second one of nanopores is produced by the in situ etching by the embedded alkaline metal elements. The superimposed effect of nano and microscale pores endows the hierarchically porous carbons (HPCs) with excellent microwave absorption (MA) performance. Among them, the spinach-derived HPC exhibits a maximum reflection loss of −62.2 dB and a broad effective absorption bandwidth of 7.3 GHz. Particularly, this excellent MA performance can be reproduced using the biomass materials belonging to different families, harvested seasons, and origins, indicating a green and sustainable process. These encouraging findings shed the insights on the preparation of biomass-derived microwave absorbents with promising practical applications.

Layered transition metal dichalcogenide (TMD) such as MoS2 are becoming promising microwave absorbers due to their large surface area, good flexibility, and well electrical and mechanical properties. However, it still remains a great challenge to optimize local microstructure in nanoscale so that contribute to more excellent performance 2D material-based microwave absorbers. Herein, a three-dimensional (3D) hierarchical MoS2/FeS2 composite with local face-to-face connected heterojunction was developed via a facile hydrothermal method. Electron holography convincingly confirmed that both the compact ohmic contact and local electric field were formed in the region of MoS2/FeS2 heterojunction, which contributed to the interface polarization loss capacity greatly. Therefore, a maximum reflection loss value of 60.2 dB at 8.08 GHz and effective absorption bandwidth up to 6.48 GHz (from 11.52 to 18 GHz) were successfully achieved with the thickness of only 2 mm. These encouraging accomplishments offer an avenue for the rational design of high-performance microwave absorbers based on 2D materials.