3D Porous Network Research Articles

Fabrication of paper based carbon/graphene/ZnO aerogel composite decorated by polyaniline nanostructure: Investigation of electrochemical properties

The cellulose derived carbon/graphene/ZnO aerogel composite was prepared as an electrode in order to investigate the electrochemical properties. Carbon aerogel was synthesized using paper as an available cellulose source, and the composite was obtained through a new and simple preparation method including the immersion of monolithic carbon aerogel in graphene oxide/Zn2+ suspension and subsequent chemical reduction and freeze drying. The morphology, functional groups and crystalline structure of the samples were studied with Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction Spectroscopy (XRD), respectively. Electrochemical performance of the prepared binder free electrodes was examined using Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS). The data revealed that flexible carbon/graphene/ZnO composite resulted in a low density (0.035 g cm−3) electrode with the capacitance of 900 mF cm−2 at a high current density of 10 mA cm−2, lower IR drop and high cyclic stability (capacitance retention of 96%) after 1000 cycles, at 10 mA cm−2. These features were due to the presence of 3D porous conductive network, highly reduced graphene oxide, and the formation of ZnO nanoparticles on graphene sheets. Moreover, polyaniline (PANI) was introduced to carbon/graphene/ZnO composite electrode using electro-oxidation method at different reaction time and aniline concentration in order to achieve remarkably improved capacitance of 2500 mF cm−2 (at 10 mA cm−2) and low charge transfer resistance. Also, after the supercapacitor device assembly, the capacitance was retained. Based on the results, the synthesized composite is a promising material for new generation of lightweight freestanding electrodes with the high electrochemical performance.

Confining nano FeSb2S4 in carbon nanotube/oxide graphene 3D porous networks for high-capacity sodium ion battery anode

Sodium ion batteries (SIBs) are promising alternative for lithium ion batteries (LIBs) due to the abundant reserve of Na compared to Li. Although the three-dimensional (3D) thick electrodes for LIBs have been widely studied, corresponding researches are seldom reported for SIBs anode. Herein, a high theoretical capacity binary metal sulfide (FeSb2S4) on reduced oxide graphene (rGO) was used as active component to prepare the light-weight, current collector-free, 3D thick anode (FeSb2S4/CNTs/rGO/GO) for SIBs. The as-prepared 3D discs can keep its integral structure under the pressure from the battery assembly, as the interconnected macropores are formed during the freeze-drying process. The macropores can also act as the electrolyte channel to facilitate the mass transfer, thus enabling the low Na+ diffusion resistance when the thickness of the electrodes increased from 150 µm to 540 µm. Based on the capacity calculation of the active components (FeSb2S4/rGO), the as-prepared 3D discs with a thickness of 540 µm can achieve a mass capacity of 391.7 mAh g–1 under 0.1 A g–1, corresponding to 3.11 mAh cm–2 of area-capacity and 57.64 mAh cm–3 of volume-capacity, respectively.

Syntheses, Structures and Luminescent Properties of Eu- and Tb-MOFs with 3,5-Pyridinedicarboxylate and 1,2-Benzenedicarboxylate.

Two lanthanide-based MOFs (Ln-MOFs) were synthesized by reaction of Eu(III) or Tb(III) perchlorates with mixed dicarboxylates of 3,5-pdc and 1,2-bdc (3,5-H2pdc = 3,5-pyridinedicarboxylic acid; 1,2-H2bdc = 1,2-benzenedicarboxylic acid) by hydrothermal method. The chemical formulas of the two complexes were [Eu2(3,5-pdc)(1,2-bdc)2(H2O)4]n (1) and {[Tb2(3,5-pdc)(1,2-bdc)2(H2O)4]·2H2O}n (2). IR spectra and element analyses were tested to characterize the two compounds. The crystal structures were determined by X-ray single crystal diffraction. MOF 1 was 3D porous network structure but MOF 2 was 2D layered structure. The two MOFs emitted the characteristic fluorescence of Eu(III) or Tb(III) ion with the excitations of UV-rays. Their lifetimes of excited states for Eu(III) (5D0) and Tb(III) (5D4) were 0.31 and 0.82ms. The absolute quantum yields (Фa) of MOF1 and 2 were also tested and the Фa(1) (λex = 320nm) and Фa(2) (λex = 296nm) were 15% and 48%, respectively.

Fabrication of three-dimensional nitrogen-doped reduced graphene oxide/tin oxide composite aerogels as high-performance electromagnetic wave absorbers

Developing light-weight and high-efficiency electromagnetic wave (EMW) absorbers has been considered as an effective strategy to resolve the electromagnetic radiation pollution problem. Herein, nitrogen-doped reduced graphene oxide/tin oxide (NRGO/SnO2) composite aerogels were facilely prepared through the hydrothermal process and subsequent lyophilization treatment. Morphological characterization results manifested that the attained NRGO/SnO2 composite aerogels possessed unique three-dimensional (3D) porous network structure constituted by the tiny SnO2 nanoparticles decorated wrinkled surfaces of flake-like NRGO. Moreover, excellent EMW absorption performance could be achieved through facilely regulating the additive volumes of ethylenediamine and filler contents. Impressively, the composite aerogel with a doped nitrogen concentration of 6.5 wt% displayed the optimal minimum reflection loss of −62.3 dB at a matching thickness of 3.5 mm and the broadest effective absorption bandwidth of 5.1 GHz under an ultrathin thickness of merely 1.6 mm. Furthermore, the as-synthesized composite aerogels showed a light-weight characteristic with the low bulk density of 19.9–25.7 mg·cm−3. Additionally, the potential EMW absorption mechanisms of obtained composite aerogels were revealed, which were mainly ascribed to the unique 3D porous network structure, synergistic effects between conduction loss and polarization loss, as well as the balanced attenuation loss and impedance matching. This work could be valuable for the structural design and fabrication of 3D graphene-based dielectric composites as light-weight and high-efficiency EMW absorbers.

Operando Investigation of Structural and Chemical Origin of Co3O4 Stability in Acid under Oxygen Evolution Reaction

Replacement of an expensive anode electrocatalyst in proton exchange membrane water electrolysis is of great importance. Recently explored Co3O4 shows good activity and stability toward oxygen evolution reaction (OER) in acid; however, the stability is not adequately explained. Lack of such information delays the design of an acid-stable OER electrocatalyst. Here, we investigate the structural origin of cobalt dissolution by various local atomic configurations of Co3O4. Operando Raman studies and voltammetric data reveal that chemical reduction of the CoO2 intermediate accompanied by lattice oxygen loss leads to undercoordinated CoO sites, which then react with water and form an amorphous three-dimensional (3D) porous network of CoO(OH)x, called the hydrous oxide layer (HOL). Growth of HOL mainly depends on the oxygen vacancies and near-surface OI- that impair the crystalline integrity and favor dissolution. These insights provide a fundamental relation between OER activity and stability and offer a specific guideline for the electrocatalyst design.

Electrodeposition Polyaniline Nanofiber on the PEDOT:PSS-Coated SiNWs for High Performance Supercapacitors

In this article, a novel silicon-based electrode was designed with the facile solution methods. With the modification of highly conductive PEDOT:PSS layer on the SiNWs by the spin-coated method (SiNWs-PSS), three-dimensional (3D) porous network polyaniline nanofibers (PANI) film was uniformly electrodeposited on the silicon surface (SiNWs-PSS@PANI). The sheet resistances of the PEDOT:PSS layer with different surfactants as well as the deposition time of the PANI were investigated. After optimization, the fabricated SiNWs-PSS@PANI electrode displayed high capacitance about 301.71 mF cm−2 at the current density of 1 mA cm−2, which enhanced ~ 29 fold comparing to 10.18 mF cm−2 of electrode without the PEDOT:PSS layer between the SiNWs and PANI (SiNWs@PANI), outperforming most values of the reported silicon-based electrodes. The electrode designed in this paper provides a new idea to fabricate high-performance of silicon-based micro-supercapacitors with the simple and low-temperature method.

A nanotubular TiO2/SiOx/Si composite derived from cellulosic cotton as an anode material for lithium-ion batteries with enhanced electrochemical performance

A TiO2/SiOx/Si composite derived from cellulosic cotton as the structural template was biomimetically synthesized. Modified sol–gel deposition processes were performed to coat each cellulose nanofiber with a SiO2 thin gel layer, followed by layer-by-layer self-assembly processes to form an external TiO2 coating with controllable thickness. The resulted matter was calcined in air to obtain the TiO2/SiO2 composite, which was successively put in N2 atmosphere and treated with magnesiothermic reduction reaction, resulting in the final TiO2/SiOx/Si composite. The composite possessed a typical hierarchical three-dimensional (3D) nanotubular network microstructure precisely inherited from the cellulosic cotton template, and each nanotube had a core-shell nanostructure with Si-based matters as the core and TiO2 coating as the shell. Compared with the bare nanotubular SiOx/Si material, the TiO2/SiOx/Si composite showed a highly enhanced electrochemical performance as an anode material for lithium-ion batteries (LIBs), delivering an initial discharge capacity of 2370 mAh g−1 at a current density of 0.2 A g−1 (an initial Coulombic efficiency of 56.4%), a reversible capacity of 682 mAh g−1 after 100 discharge/charge cycles, and a discharge capacity of 241 mAh g−1 at a high current density of 2.0 A g−1. The excellent specific capacity, cycling stability and rate capability are ascribed to the synergistic effect of the unique 3D porous nanotubular network structure and the uniform TiO2 coating layer, which accommodates the volume variation of Si-based components during cycling, offers sufficient ion transport pathways and improves the electron transfer efficiency. This work provides a facile biomass-based strategy for fabrication of metal oxide/Si composites with well-defined microstructures that exhibit significant potential as anode materials for LIBs.

Synthesis of 3D Porous Network Nanostructure of Nitrated Bacterial Cellulose Gel with Eminent Heat‐Release, Thermal Decomposition Behaviour and Mechanism

AbstractIn this study, a novel three‐dimensional (3D) porous cross‐link network structure of nitrated bacterial cellulose (NBC) nano‐gel, as an energetic gel matrix for fabrication of nanocomposite energetic materials, (nEMs) was synthesized by sol‐gel synthetic and the freeze‐drying technology. The analysis results revealed that the unique network structure with abundant of nano‐porous, which made the thermal behaviour of the NBC gel different from that of raw NBC. The thermal decomposition kinetic and mechanism of the NBC gel indicated that the exothermic peak temperature of the gel matrix decreased at low concentration, and the activation energy (Ea) of the gel0.5 (150000 J ⋅ mol−1) was much lower than that of raw NBC (223510 J ⋅ mol−1). However, the decomposition kinetic parameters of this study were not enough to illustrate the thermal properties, and which needs more effort to study them and complete. Furthermore, the initial reaction of gel decomposition was the splitting of urethane bond, and then the scission of −O−NO2 bonds happened, and the macromolecular chains’ breakage site of gel first occurred at −C−O−C− in the ring. After then, the chains of NBC break at −C−O−C− between the rings; notably, the heat‐release of gel was several times than that of raw NBC, which was liberated during the process of thermal decomposition. This promising research may provide potential application in preparing binder‐based nEMs and the basic theory of thermo‐analysis used in propellants and explosives.

Precise tuning of low-crystalline Sb@Sb2O3 confined in 3D porous carbon network for fast and stable potassium ion storage

Metal antimony (Sb) is a promising anode material of potassium-ion batteries (PIBs) for its high theoretical capacity but limited by its inferior cycle stability due to the serious volume expansion during cycling. Herein, we design and construct a kind of low-crystalline Sb nanoparticles coated with amorphous Sb2O3 and dispersed into three-dimensional porous carbon via a strategy involving NaCl template-assisted in-situ pyrolysis and subsequent low-temperature heat-treated in air. Significantly, the crystallinity and ratio of Sb/Sb2O3 have been precisely tuned and controlled, and the optimized sample of [email protected]2O3@C-4 displays a high reversible specific capacity of 543.9 mAh g−1 at 0.1 A g−1, superior rate capability and excellent cycle stability (~273 mAh g−1 at 2 A g−1 after 2000 cycles) as an anode of PIBs. The outstanding potassium-ion storage performance can be ascribed to the appropriate crystallinity and the multiple-buffer-matrix structure comprising an interconnected porous conductive carbon to relieve the volume changes and suppress the aggregation of Sb, a Sb nanoparticle core to shorten the ion transport pathways and decrease the mechanical stress, and a low-crystalline Sb2O3 as the shell to consolidate the interface between Sb and carbon as well as facilitate the rapid electron transport. The dynamic analysis shows that the composite is mainly controlled by pseudocapacitance mechanism. This work provides a novel thought to design high-performance composite electrode in energy storage devices.

Preparation of g-C3N4/TiO2 by template method and its photocatalytic performance

A method for preparing TiO2 supported on g-C3N4 by freeze-drying was proposed using NaCl as template as well as TiO2 dispersion and melamine as raw materials. This method solves the problems of low specific surface area and fast electron-hole recombination rate of traditional g-C3N4. During the calcination process, the generated g-C3N4 and TiO2 formed a heterojunction, which reduced the rate of electron-hole combination. After removing the template, a 3D porous g-C3N4 network supporting TiO2 was obtained. In this study, XRD, FT-IR, TG-DSC, XPS, TEM and SEM were used to explore the microstructure evolution of g-C3N4/ TiO2 at different stages. And then the band structures of different samples were analyzed by UV-Vis. Finally, the photocatalytic activity of different samples was studied by photolytic water experiment. The results showed that the TiO2 nanoparticles were successfully supported on the surface of the 3D porous g-C3N4 network, and the photocatalytic activity of g-C3N4 was significantly improved. When g-C3N4: TiO2 = 2.5: 1, the sample had the highest photocatalytic efficiency, and the hydrogen production rate reached 200.806 μmol/g/h.

Two-Dimensional Molecular Network Built from Hierarchy Self-Assembly of Perylene Bisimide Derivatives.

The structures of two-dimensional (2D) self-assembled molecular networks formed by a series of perylene bisimide (PBI) derivatives were investigated by scanning tunneling microscopy (STM). By introducing different functional groups to the PBI rings, we successfully built a different self-assembled molecular network on the liquid-solid interface. When the substituent is propanol, PBI is aligned in lines. When we introduced either an ester group or an amide group to the PBI compounds, they tended to form dimers and trimers. Especially, the PBI with the amide groups can form a 2D porous molecular network by hierarchy self-assembly. The 2D porous molecular network has a great potential to be the host molecule for the accommodation of a guest molecule, coronene (COR), and the structure of the 2D porous molecular network can be tuned by varying the concentration. The density functional theory calculations were also performed to disclose the mechanisms involved.

Atomic iridium species anchored on porous carbon network support: An outstanding electrocatalyst for CO2 conversion to CO

Converting CO2 into valuable chemicals using electrocatalysis is an attractive approach for sustainable energy storage and artificial carbon cycle. In this study, atomically dispersed Ir species (Ad-Ir) that are supported on three-dimensional (3D) porous carbon networks are proposed as electrocatalysts for highly efficient CO2 conversion. The resulting catalysts can preferentially and rapidly produce CO with a high Faradaic efficiency of 95.6 % and a very high turnover frequency (TOF) value of 33,365 h−1. Furthermore, it shows no obvious decay in both FE for CO and current density over 20 h of continuous operation. Based on detailed experimental studies and density functional theory (DFT) calculations, such outstanding catalytic performance for CO2 conversion to CO production can be attributed to the structural advantages of 3D network of porous carbon and atomically dispersed Ir species on the 3D carbon support.

Novel insight into the adsorption of Cr(VI) and Pb(II) ions by MOF derived Co-Al layered double hydroxide @hematite nanorods on 3D porous carbon nanofiber network

• A novel MOF derived Co-Al-LDH@Fe 2 O 3 /3DPCNF adsorbents was synthesized. • The hybrid nanocomposites showed excellent adsorption capacities on Cr(VI) and Pb(II). • The adsorption isotherm, kinetics, thermodynamics, and mechanism were discussed in detail. • The composite can be easily recovered by magnet after adsorption process. Metal organic framework (MOF) derived layered double hydroxide (LDHs) are not properly probed in the field of the heavy metal ions adsorption from its aqueous solution, although they demonstrated a high possibility in adsorption. In this report, a Co-Al layered double hydroxide loaded with hematite (α-Fe 2 O 3 )@3D porous carbon nanofiber (Co-Al-LDH@Fe 2 O 3 /3DPCNF) was synthesized by a sequential hydrothermal process. The Co-Al LDH was derived from a Co-metal organic framework. FE-SEM, TEM, FTIR, XPS, and BET characterizations and Cr(VI) and Pb(II) adsorption capacities of the composites were investigated in detail. The super hydrophilic Co-Al-LDH@Fe 2 O 3 /3DPCNF exhibited superfast removal efficiencies for Cr(VI) and Pb(II) with maximum adsorption capacities of 400.40 mg g −1 and 426.76 mg g −1 , respectively. Precipitation, surface complexation, isomorphic substitution, and electron transfer were considered to be the main adsorption mechanisms. Adsorption isotherms were well fitted using the Sips model, and the adsorption thermodynamics demonstrated that the adsorption process is endothermic and spontaneous. The Co-Al-LDH@Fe 2 O 3 /3DPCNF maintained excellent adsorption capacity after ten cycles. The present study provides a new pathway to significantly improve the adsorption performance and stability of LDHs with easy separation from water body.

Balsa‐Wood‐Derived Binder–Free Freestanding Carbon Foam as High‐Performance Potassium Anode

The binder‐free freestanding electrode is assumed as a proven and effective method of increasing the energy density of potassium‐ion batteries (PIBs) because of the addition of binder and conductor. However, an expensive and complex synthesis process hampers its development, Herein, a binder‐free freestanding biomass hard carbon (BHC) foam with balsa wood as the precursor is put forward. The prepared BHC foam maintains a highly hierarchical structure, in which the channels are interconnected and the pipe walls form an extremely stable 3D structure. This 3D porous network is synthesized in one step by a simple, environmentally friendly method, which ensures efficient ion and electrolyte transfer without structure collapse during the electrochemical cycle. When used as PIB anodes, the binder‐free freestanding carbon foam delivers a high reversible capacity of 252.7 mAh g−1 at 100 mA g−1 with a high initial coulombic efficiency of 63.7%, excellent long cycle stability (95.1% capacity retention after 500 cycles, and the average decay rate per cycle is 0.012% over 2500 cycles), and superior rate capability (the capacity of 165 mAh g−1 reserved at 2000 mA g−1). This strategy provides a simple and fast way to fabricate a stable and high‐performance anode for PIBs.

Porous network carbon nanotubes/chitosan 3D printed composites based on ball milling for electromagnetic shielding

Carbon nanotubes (CNTs) are easy to agglomerate, which results in poor structure reproducibility, and seriously restricts the improvement of conductivity and electromagnetic interference (EMI) shielding properties of CNTs composites. In this study, CNTs were evenly dispersed in the chitosan (CS) matrix by a high energy mechanical ball milling method, and three-dimensional (3D) printing ink of CNTs/CS was obtained. The CNTs/CS composites with porous network structures are prepared by the 3D printing technology. The results show that the 3D porous network CNTs/CS composites can effectively absorb electromagnetic waves. The 3D printed CNTs/CS composites with porous networks show an exceptional EMI shielding effectiveness of 25.07 dB at a low density of 72 mg/cm3. According to the square hole grid structure of 3D printed products, the influence of pore size and conductivity of the composites on the EMI shielding performance is simulated and analyzed, which are consistent with the experimental results. For non-magnetic materials, conductivity has a greater influence on the EMI shielding performance than that of pore size. This study provides a new idea and method for the rapid and accurate preparation of polymer matrix composites with excellent EMI shielding properties as surface of electronic components.

Fibrin biopolymer hydrogel-templated 3D interconnected Si@C framework for lithium ion battery anodes

Silicon is considered a promising candidate for lithium-ion battery anodes because of its exceptionally high capacity. However, employing Si in real applications remains a challenge, owing to dramatic reduction in the capacity after a few cycles. Redesigning the advanced electrode structure, including the available free volume and continuous conductive scaffold, may potentially circumvent this problem. Here, we demonstrate a new method of creating binder- and conductive additive-free three-dimensional (3D) porous network Si@C electrodes via fibrin hydrogel templating followed by pyrolysis. Hydrogen bonds between hydroxyl groups on Si and amides of fibrin enable the hierarchical 3D structures. These comprise well-distributed Si nanoparticles (SiNPs) in carbon frameworks, with each particle conformally encapsulated by the carbon layer. We confirm that carbon is doped with nitrogen and that pyridinic N and pyrrolic N are the predominant configurations. The 3D Si@C electrode exhibits a good rate performance (capacity of 730 mAh g−1 at 1000 mA g−1 (0.5C, Si + C basis)) and also a stable cycling property (54% capacity retention after 500 cycles at 500 mA g−1). Compared to a conventional mixture (SiNPs/alginate/Super P), the 3D Si@C electrode exhibits significantly improved electrochemical properties.

Solar-driven hydrogen generation coupled with urea electrolysis by an oxygen vacancy-rich catalyst

Urea, an environmental pollutant for both soil and water, is widely present in wastewater. On the other hand, a strategy utilizing renewable electricity to decrease the cost of green hydrogen, which holds the key to a sustainable energy future, is promising but challenging. Gas crossover that generates explosive hydrogen–oxygen mixture becomes very serious with intermittent renewable power source (partial load issue). Herein, we address these issues in one device, i.e., a hybrid electrolyzer where water oxidation that produces oxygen is replaced by urea oxidation which generates inert gases. A self-supported electrocatalyst of nitrogen-doped nickel-iron oxyhydroxide derived from waste rusty iron foam is synthesized via an in situ ‘waste-to-value’ synthetic route followed by an ammonia/argon plasma treatment, which reconstructs the surface of the catalyst to a 3D nanosheet-like porous network with abundant oxygen vacancies. The as-prepared catalyst shows a small potential of 1.45 V vs. RHE at 500 mA cm−2 for urea oxidation. Overall water-urea electrolysis only requires 1.58 V to deliver 100 mA cm−2, which is 0.33 V less than that in urea-free water splitting, and thus lowers the overall energy consumption by 17.3%. Without oxygen evolution, the hybrid electrolysis does not suffer from the safety hazard caused by explosive hydrogen–oxygen mixture. We demonstrate the safe production of green hydrogen (3.1% oxygen in the gaseous product) in the hybrid electrolysis powered by solar energy via a photovoltaic panel. Our work provides a method to address the urea-caused environmental issues and simultaneously generate green hydrogen safely using solar energy.

Hierarchically Ordinated Two-Dimensional MoS2 Nanosheets on Three-Dimensional Reduced Graphene Oxide Aerogels as Highly Active and Stable Catalysts for Hydrogen Evolution Reaction

Hydrogen gas (H2) is being intensively proposed as a next-generation clean energy owing to the depletion of fossil fuels. Electrochemical water splitting is one of the most promising processes for hydrogen production. Furthermore, many efforts focusing on electrochemical water splitting have been made to develop low-cost, electrochemically active, and stable catalysts for efficient hydrogen production. MoS2 has emerged as an attractive material for developing catalysts for the hydrogen evolution reaction (HER). Hence, in this study, we design hierarchically ordinated two-dimensional (2D) MoS2 nanosheets on three-dimensional (3D) reduced graphene oxide (rGO) (H-2D/3D-MoS2-rGO) aerogel structures as a new class of electrocatalysts for the HER. We use the one-pot hydrothermal synthesis route for developing high-performance electroactive materials for the HER. The as-prepared H-2D/3D-MoS2-rGO contains a unique 3D hierarchical structure providing large surface areas owing to the 3D porous networks of rGO and more active sites owing to the many edge sites in the MoS2 nanosheets. In addition, the H-2D/3D-MoS2-rGO structure exhibits remarkable electrochemical properties during the HER. It shows a lower overpotential than pure MoS2 and excellent electrochemical stability owing to the large number of active sites (highly exposed edge sites) and high electrical conductivity from the rGO structure.

3D Hierarchical NiCo2S4 Nanoparticles/Carbon Nanotube Sponge Cathode for Highly Compressible Asymmetric Supercapacitors

By employing a carbon nanotube (CNT) sponge with a 3D porous network as a compressible substrate and NiCo2S4 nanoparticles as active materials, a NiCo2S4/CNT sponge electrode with high compression ...

Achieving super-broad effective absorption bandwidth with low filler loading for graphene aerogels/raspberry-like CoFe2O4 clusters by N doping

A unique three-dimension (3D) porous network structure where N-doped reduced graphene oxide aerogels (N-rGA) are decorated by raspberry-like CoFe2O4 (CFO) clusters. Super-broad effective microwave absorption bandwidth (7.28 GHz) of the CFO/N-rGA composite is obtained at 2.53 mm by changing N contents. Here, the dipolar relaxation loss and conduction loss are highly sensitive to the presence of pyridinic, pyrrolic and graphitic N in the CFO/N-rGA composites. A minimum reflection loss of the CFO/N-rGA composites reaches up to −55.43 dB at 15.36 GHz with a matching thickness (2.3 mm) and low filler loading (10 wt%). Its effective absorption bandwidth completely covers X-band from 7.76 to 12.72 GHz at 3.3 mm. The high-efficiency microwave absorption of the composites mainly results from the enhanced polarization relaxation, the specific design of conductive network and the superior impedance matching. This study offers a promising technical route to explore new N-doped magnetic/dielectric composites as ideal microwave absorbers.