Fixed-Point Atomic Regulation Engineered Low-Thickness Wideband Microwave Absorption.

Atomic doping is widely employed to fine-tune crystal structures, energy band structures, and the corresponding electrical properties. However, due to the difficulty in precisely regulating doping sites and concentrations, establishing a relationship between electricity properties and doping becomes a huge challenge. In this work, a modulation strategy on A-site cation dopant into spinel-phase metal sulfide Co9S8 lattice via Fe and Ni elements is developed to improve the microwave absorption (MA) properties. At the atomic scale, accurately controlling doped sites can introduce local lattice distortions and strain concentration. Tunned electron energy redistribution of the doped Co9S8 strengthens electron interactions, ultimately enhancing the high-frequency dielectric polarization (ɛ' from 10.5 to 12.5 at 12 GHz). For the Fe-doped Co9S8, the effective absorption bandwidth (EAB) at 1.7 mm increases by 5%, and the minimum reflection loss (RLmin) improves by 26% (EAB = 5.8 GHz, RLmin = -46 dB). The methodology of atomic-scale fixed-point doping presents a promising avenue for customizing the dielectric properties of nanomaterials, imparting invaluable insights for the design of cutting-edge high-performance microwave absorption materials.

Controllable Synthesis of Highly Symmetrical Streamlined Structure for Wideband Microwave Absorption.

Highly symmetrical and streamlined nanostructures possessing unique electron scattering, electron-phonon coupling, and electron confinement characteristics have attracted a lot of attention. However, the controllable synthesis of such a nanostructure with regulated shapes and sizes remains a huge challenge. In this work, a peanut-like MnO@C structure, assembled by two core-shell nanosphere is developed via a facile hydrogen ion concentration regulation strategy. Off-axis electron holography technique, charge reconstruction, and COMSOL Multiphysics simulation jointly reveal the unique electronic distribution and confirm its higher dielectric sensitive ability, which can be used as microwave absorption to deal with currently electromagnetic pollution. The results reveal that the peanut-like core-shell MnO@C exhibits great wideband properties with effective absorption bandwidth of 6.6 GHz, covering 10.8-17.2 GHz band. Inspired by this structure-induced sensitively dielectric behavior, promoting the development of symmetrical and streamlined nanostructure would be attractive for many other promising applications in the future, such as piezoelectric material and supercapacitor and electromagnetic shielding.

Engineering Phase to Reinforce Dielectric Polarization in Nickel Sulfide Heterostructure for Electromagnetic Wave Absorption.

Engineering phase transition in micro-nanomaterials to optimize the dielectric properties and further enhance the electromagnetic microwave absorption (EMA) performance is highly desirable. However, the severe synthesis conditions restrict the design of EMA materials featuring controllable phases, which hinders the tunability of effective absorption bandwidth (EAB) and leads to an unclear loss mechanism. Herein, a seed phase decomposition-controlled strategy is proposed to induct nickel sulfide (NiSx ) absorbers with controllable phases and hollow sphere nature. Transmission electron microscopy holography and theoretical calculations evidence that the reconstruction of atoms in phase transition induces numerous heterogeneous interfaces and lattice defects/sulfur vacancies to cause varied work functions and local electronic redistribution, which contributes to reinforced dielectric polarization. As a result, the optimized NiS2 /NiS heterostructure enables enhanced EM attenuation capability with a wide EAB of 5.04 GHz at only 1.6 mm, compared to that of NiS2 and NiS. Moreover, the correlation between EAB and NiS phase content is demonstrated as the "volcano" feature. This study on the concept of phase transition of micro-nanomaterials can offer a novel approach to constructing highly efficient absorbers for EMA and other functionalities.

Hierarchical Ti3 C2 Tx MXene/Carbon Nanotubes Hollow Microsphere with Confined Magnetic Nanospheres for Broadband Microwave Absorption.

Hierarchical hollow structure with unique interfacial properties holds great potential for microwave absorption (MA). Ti3 C2 Tx MXene has been a hot topic due to rich interface structure, abundant defects, and functional groups. However, its overhigh permittivity and poor aggregation-resistance limit the further application. Herein, a hierarchical MXene-based hollow microsphere is prepared via a facile spray drying strategy. Within the microsphere, few-layered MXene nanosheets are separated by dispersed carbon nanotubes (CNTs), exposing abundant dielectric polarization interfaces. Besides, numerous magnetic Fe3 O4 nanospheres are uniformly dispersed and confined within nano-cavities between 1D network and 2D framework. Such a novel structure simultaneously promotes interfacial polarization by ternary MXene/CNTs/Fe3 O4 interfaces, enhances magnetic loss by microscale and nanoscale coupling network, enlarges conduction loss by MXene/CNTs dual-network, and optimizes impedance matching by hierarchical porous structure. Therefore, Fe3 O4 @Ti3 C2 Tx /CNTs composite achieves excellent MA property with a maximum reflection loss of -40.1 dB and an effective bandwidth of 5.8 GHz at the thickness of only 2 mm. This work demonstrates a feasible hierarchical structure design strategy for multi-dimension MXene composite to realize the high-efficiency MA performance.

Magnetic Interacted Interaction Effect in MXene Skeleton: Enhanced Thermal-Generation for Electromagnetic Interference Shielding.

With the rapid advancements of portable and wearable equipment, high-efficiency electromagnetic interference (EMI) shielding materials are highly entailed to eliminate radiated electromagnetic pollution. Herein, by assembling hexagonal SrFe12 O19 flakes into a Ti3 C2 Tx MXene/MWCNT substrate, a magnetized Ti3 C2 Tx -based film is successfully fabricated by a facile filtration approach. Carbon nanotubes are used as isolation agents to realize the submicroscopic dispersion of MXene and SrFe12 O19 . The obtained MXene/MWCNTs/SrFe12 O19 film shows a high electrical conductivity of 438 S cm-1 and an excellent EMI shielding effectiveness of 62.9 dB in X-band at a thickness of only 40 µm. Benefiting from a strong magnetic response ability and an expanded magnetic coupling space, hexagonal SrFe12 O19 sheets can efficiently consume incident magnetic field energy by domain wall migration and the ferromagnetic resonance effect. Boosted EMI shielding performance can be achieved by improving the magnetic loss in the Ti3 C2 Tx MXene/MWCNTs/SrFe12 O19 film, preventing the secondary reflection of electromagnetic waves. Meanwhile, magnetized MXene-based films display the freestanding and flexible features and are suitable for installation in electric devices. It is anticipated that this strategy offers new ideas for designing EMI shielding films and in broadening potential utility of MXene-based materials.

Multi-Path Electron Transfer in 1D Double-Shelled Sn@Mo2 C/C Tubes with Enhanced Dielectric Loss for Boosting Microwave Absorption Performance.

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.

Multidimension-Controllable Synthesis of MOF-Derived Co@N-Doped Carbon Composite with Magnetic-Dielectric Synergy toward Strong Microwave Absorption.

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.

Facile Preparation of a Hierarchical C/rGO/FeO x Composite with Superior Microwave Absorption Performance.

A hierarchical carbon/reduced graphene oxide (rGO)/FeO x (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.

Hierarchically Porous Carbon Derived from PolyHIPE for Supercapacitor and Deionization Applications.

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

Recent progress in TiO2-based microwave absorption materials.

It is particularly important to develop high-performance microwave absorption (MA) materials to remediate the increasingly serious electromagnetic pollution. Recently, titanium dioxide-based (TiO2-based) composites have become a research hotspot owing to their light weight and synergy loss mechanism. In this study, significant research progress in TiO2-based complex-phase microwave absorption materials is reviewed, which involves carbon components, magnetic materials, polymers and so on. First, the research background and limitations of TiO2-based composites are discussed. The design principles for microwave absorption materials are elaborated in the next section. More importantly, TiO2-based complex-phase materials with multi-loss mechanisms are analyzed and summarized in this review. Finally, the conclusions and prospectives are presented, which provide a reference for the understanding of TiO2-based MA materials.

Dopant Engineering of Flexible MNPs/TPU/PPy Core-Shell Films for Controllable Electromagnetic Interference Shielding.

Intrinsically conductive polymers have attracted much attention in the electromagnetic interference (EMI) shielding field because of their high conductivity and favorable flexibility. Delocalized π-electrons migrating along the conjugated long-chain structures can form a current. Based on this special conductive mechanism, the doping process significantly influences the conductivity and EMI shielding efficiency (SE). However, it is challenging to investigate the influence of the doping process on EMI shielding performance, which would enable the optimization of dopant selection. In this study, dopant engineering was explored for controllable conductivity, EMI SE, and mechanical properties. Polypyrrole (PPy) doped with various dopants serves as a conductive coating owing to its adjustable conductivity and abundant functional groups. Elastic thermoplastic polyurethane was chosen as the porous framework because of its high tensile strength, and magnetic nanoparticles supplied the magnetic loss in the 3D network. Eventually, the composite film showed the best properties when PPy was doped with sodium p-toluenesulfonate. The film exhibited an average SE of 26.3 dB in the X band and a specific SE of 1563.17 dB cm2 g-1 with a thickness of merely 0.2 mm. This film withstood a tensile stress of 16.0 MPa, while the breaking elongation ratio reached 538.0%. After 10,000 cyclic bending, 92.3% of the EMI shielding property was retained. In summary, this study highlights the most suitable dopant for EMI shielding applications and provides a prospective alternative for advanced, flexible, and smart devices.

Self-Assembly MXene-rGO/CoNi Film with Massive Continuous Heterointerfaces and Enhanced Magnetic Coupling for Superior Microwave Absorber.

MXene, as a rising star of two-dimensional (2D) materials, has been widely applied in fields of microwave absorption and electromagnetic shielding to cope with the arrival of the 5G era. However, challenges arise due to the excessively high permittivity and the difficulty of surface modification of few-layered MXenes severely, which infect the microwave absorption performance. Herein, for the first time, a carefully designed and optimized electrostatic self-assembly strategy to fabricate magnetized MXene-rGO/CoNi film was reported. Inside the synthesized composite film, rGO nanosheets decorated with highly dispersed CoNi nanoparticles are interclacted into MXene layers, which effectively suppresses the originally self-restacked of MXene nanosheets, resulting in a reduction of high permittivity. In addition, owing to the strong magnetic coupling between the magnetic FeCo alloy nanoparticles on the rGO substrate, the entire MXene-rGO/CoNi film exhibits a strong magnetic loss capability. Moreover, the local dielectric polarized fields exist at the continuous hetero-interfaces between 2D MXene and rGO further improve the capacity of microwave loss. Hence, the synthesized composite film exhibits excellent microwave absorption property with a maximum reflection loss value of - 54.1 dB at 13.28 GHz. The electromagnetic synergy strategy is expected to guide future exploration of high-efficiency MXene-based microwave absorption materials.

Enhanced electrocatalytic hydrogen evolution by molybdenum disulfide nanodots anchored on MXene under alkaline conditions.

Efficient hydrogen production through electrocatalysis represents a promising path for the future clean energy. Molybdenum disulfide (MoS2) is a good substitute for platinum-based catalysts, due to its low cost and high activity. However, the limited active sites and low electrical conductivity of MoS2 hinder its large-scale industrial application under alkaline conditions. Herein, we constructed MoS2 nanodots anchored on an MXene/nickel foam (MoS2 NDs/MXene/NF) heterostructure by a cascade polymerization synthesis and in situ vulcanization. The prepared heterostructure displays an ultralow overpotential of 94 mV at a current density of 10 mA cm-2 with a Tafel slope of only 59 mV dec-1 in alkaline (1 M KOH) hydrogen evolution reaction (HER), and is better than conventional MoS2 electrocatalysts reported so far. Fine structural analysis indicates that MoS2 NDs are dispersed uniformly on the surface of the heterostructure with consistent orientation, leading to the improvement of MoS2 conductivity with more paths for electron transfer. Moreover, the orientation of the synthesized MoS2 NDs was verified to expose the more (002) crystal plane, which exhibits higher activity than other planes. Our results demonstrate that MoS2 NDs with heterostructure design and preferential growth can serve as high-efficiency noble-metal free electrocatalysts for the HER in alkaline solution.

Morphology-Evolved Succulent-like FeCo Microarchitectures with Magnetic Configuration Regulation for Enhanced Microwave Absorption.

The regulation of magnetic configuration through diverse morphologies to achieve a rapid magnetic response has attracted considerable academic favor on account of the unique application prospects in various fields. Herein, porous FeCo alloys with morphology evolved from spheres to succulent-like microstructures are successfully constructed via a facile hydrothermal reaction-hydrogen reduction synthetic strategy. A multiple balance/competition mechanism is proposed, including the coexistence of the dissolution-precipitation balance of hydroxides and the dissociation-stability balance of coordination compounds, the Fe3+-Co2+ competition, and the precipitation-coordination reaction contest. As the morphology evolves to a succulent-like assembly, the multidomain features with a stable combination of vortex states and the violent motion of magnetic vectors contribute to the improvement of magnetic storage capacity and loss capability, which are evidenced by the off-axis electron holography and micromagnetic simulation. Consequently, the succulent-like FeCo exhibits enhanced permeability and microwave absorption performance. The effective absorption bandwidth reaches 5.68 GHz, and the maximum reflection loss is elevated to -53.81 dB. This work sheds considerable insight into the microstructure regulation with an application in microwave absorption and offers guidance in research for the topological magnetic configuration and dynamic response mechanism of magnetic alloys.

Dimensional Design and Core-Shell Engineering of Nanomaterials for Electromagnetic Wave Absorption.

Electromagnetic (EM) wave absorption materials possess exceptionally high EM energy loss efficiency. With vigorous developments in nanotechnology, such materials have exhibited numerous advanced EM functions, including radiation prevention and antiradar stealth. To achieve improved EM performance and multifunctionality, the elaborate control of microstructures has become an attractive research direction. By designing them as core-shell structures with different dimensions, the combined effects, such as interfacial polarization, conduction networks, magnetic coupling, and magnetic-dielectric synergy, can significantly enhance the EM wave absorption performance. Herein, the advances in low-dimensional core-shell EM wave absorption materials are outlined and a selection of the most remarkable examples is discussed. The derived key information regarding dimensional design, structural engineering, performance, and structure-function relationship are comprehensively summarized. Moreover, the investigation of the cutting-edge mechanisms is given particular attention. Additional applications, such as oxidation resistance and self-cleaning functions, are also introduced. Finally, insight into what may be expected from this rapidly expanding field and future challenges are presented.

Customizing Heterointerfaces in Multilevel Hollow Architecture Constructed by Magnetic Spindle Arrays Using the Polymerizing-Etching Strategy for Boosting Microwave Absorption.

Heterointerface engineering is evolving as an effective approach to tune electromagnetic functional materials, but the mechanisms of heterointerfaces on microwave absorption (MA) remain unclear. In this work, abundant electromagnetic heterointerfaces are customized in multilevel hollow architecture via a one-step synergistic polymerizing-etching strategy. Fe/Fe3 O4 @C spindle-on-tube structures are transformed from FeOOH@polydopamine precursors by a controllable reduction process. The impressive electromagnetic heterostructures are realized on the Fe/Fe3 O4 @C hollow spindle arrays and induce strong interfacial polarization. The highly dispersive Fe/Fe3 O4 nanoparticles within spindles build multi-dimension magnetic networks, which enhance the interaction with incident microwaves and reinforce magnetic loss capacity. Moreover, the hierarchically hollow structure and electromagnetic synergistic components are conducive to the impedance matching between absorbing materials and air medium. Furthermore, the mechanisms of electromagnetic heterointerfaces on the MA are systematically investigated. Accordingly, the as-prepared hierarchical Fe/Fe3 O4 @C microtubes exhibit remarkable MA performance with a maximum refection loss of -55.4 dB and an absorption bandwidth of 4.2 GHz. Therefore, in this study, the authors not only demonstrate a synergistic strategy to design multilevel hollow architecture, but also provide a fundamental guide in heterointerface engineering of highly efficient electromagnetic functional materials.

Accurately Engineering 2D/2D/0D Heterojunction In Hierarchical Ti3C2Tx MXene Nanoarchitectures for Electromagnetic Wave Absorption and Shielding.

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.

1D Electromagnetic-Gradient Hierarchical Carbon Microtube via Coaxial Electrospinning Design for Enhanced Microwave Absorption.

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.

Compressible and flexible PPy@MoS2/C microwave absorption foam with strong dielectric polarization from 2D semiconductor intermediate sandwich structure.

Structural engineering represents a major trend in the field of two-dimensional (2D) materials regarding microscopic interfacial electric/dielectric properties and macroscopic device strategies. 2D molybdenum disulfide (MoS2) with semiconductive features and lamellar architecture has been widely applied in the microwave absorption (MA) field. However, due to its limitations of weak dielectric loss capacity and poor intrinsic mechanical property, MoS2-based MA devices are a considerable design challenge for practical applications with the peculiarities of light weight, high absorption performance, flexibility, and compressibility. Herein, 2D MoS2 was riveted on carbonized melamine foam (CMF) templated from a commercial foam skeleton, which was cladded with the conductive polymer polypyrrole (PPy). The as-prepared PPy@MoS2/CMF was integrated to simultaneously achieve an excellent MA performance including a maximum reflection loss (RL) value of -45.40 dB and a wide absorption bandwidth of 3.8 GHz, together with mechanical practicability including a high compression ratio of over 45.6% in volume and a bending angle of over 43.2°. This excellent MA performance is attributed to the synergetic effect from its sandwiched multi-layered skeleton, consisting of a conductive/semiconductive/conductive ternary conductive network, and multiple polarizations from the 2D MoS2 interlayer. Our strategy sheds novel insight into the construction of advanced carbon-supported composites and 2D materials for use in devices, which can be further extended to energy storage and conversion applications.

Hierarchical Magnetic Network Constructed by CoFe Nanoparticles Suspended Within "Tubes on Rods" Matrix Toward Enhanced Microwave Absorption.

Hierarchical magnetic-dielectric composites are promising functional materials with prospective applications in microwave absorption (MA) field. Herein, a three-dimension hierarchical "nanotubes on microrods," core-shell magnetic metal-carbon composite is rationally constructed for the first time via a fast metal-organic frameworks-based ligand exchange strategy followed by a carbonization treatment with melamine. Abundant magnetic CoFe nanoparticles are embedded within one-dimensional graphitized carbon/carbon nanotubes supported on micro-scale Mo2N rod (Mo2N@CoFe@C/CNT), constructing a special multi-dimension hierarchical MA material. Ligand exchange reaction is found to determine the formation of hierarchical magnetic-dielectric composite, which is assembled by dielectric Mo2N as core and spatially dispersed CoFe nanoparticles within C/CNTs as shell. Mo2N@CoFe@C/CNT composites exhibit superior MA performance with maximum reflection loss of - 53.5 dB at 2 mm thickness and show a broad effective absorption bandwidth of 5.0 GHz. The Mo2N@CoFe@C/CNT composites hold the following advantages: (1) hierarchical core-shell structure offers plentiful of heterojunction interfaces and triggers interfacial polarization, (2) unique electronic migration/hop paths in the graphitized C/CNTs and Mo2N rod facilitate conductive loss, (3) highly dispersed magnetic CoFe nanoparticles within "tubes on rods" matrix build multi-scale magnetic coupling network and reinforce magnetic response capability, confirmed by the off-axis electron holography.