Magnetic metal nanoparticle-loaded MXene-based lignocellulose-derived carbon aerogel wave-absorbing material and method

Abstract

The method comprises the following steps: step 1, etching an Al layer in a Ti2AlC3 MAX phase by using a LiF / HCl system, so as to obtain an Mxene colloidal solution; 2, the TEMPO-oxidized cellulose nanofibril CNF dispersion liquid, the Mxene colloidal solution, calcium lignosulphonate and ferric acetate are sequentially mixed, stirred and subjected to ultrasonic treatment till a uniform mixed suspension is formed, then freeze drying is conducted, and MXene-based lignocellulose aerogel loaded with metal ions is obtained; 3, the MXene-based lignocellulose aerogel loaded with the metal ions is subjected to high-temperature carbonization treatment in inert gas, and the MXene-based lignocellulose derived carbon aerogel wave-absorbing material loaded with the metal nanoparticles is obtained. Multiple scattering of electromagnetic waves is effectively promoted, a rich heterogeneous interface is formed, and the synergistic effect of a dielectric-magnetic loss mechanism is further achieved through introduction of the magnetic metal. Therefore, the problems of poor impedance matching, single component and the like in the preparation process of the wave-absorbing material are solved.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to an MXene-based lignocellulose-derived carbon aerogel wave absorbing material and method supported by magnetic metal nanoparticles. Background Technology

[0002] With the rapid development of high-frequency electronic devices, wireless communication, and radar detection technologies, electromagnetic radiation pollution and target detectability issues are becoming increasingly prominent, necessitating the development of absorbing materials with broadband absorption characteristics and high attenuation efficiency. Carbon aerogel materials, due to their tunable three-dimensional porous conductive network structure, significant low-density characteristics, and excellent surface chemical modifiability, are considered an innovative solution for achieving high-performance electromagnetic wave absorption.

[0003] As a novel two-dimensional material, transition metal carbides / nitrides (MXenes) exhibit unique advantages in constructing carbon aerogel microwave absorbing materials due to their layered structure, high electrical conductivity, and abundant surface end groups (-O, -OH, etc.). However, existing carbon aerogel microwave absorbing materials based on single MXenes have significant technical drawbacks. Due to their excessively high intrinsic conductivity, there is a severe mismatch between the material surface and free-space wave impedance, resulting in strong reflection of incident electromagnetic waves at the material interface, making it difficult for them to penetrate and be effectively dissipated. This phenomenon is particularly prominent in the low-frequency band, greatly limiting the material's actual absorption efficiency. Furthermore, these materials rely entirely on dielectric loss mechanisms for electromagnetic energy conversion, essentially lacking the synergistic effect of magnetic loss capabilities. This leads to severely insufficient attenuation of low-frequency electromagnetic waves, ultimately resulting in a narrow absorption bandwidth and poor low-frequency absorption performance. Summary of the Invention

[0004] To overcome the problems existing in the prior art, the present invention aims to provide an MXene-based lignocellulose-derived carbon aerogel microwave absorbing material and method supported by magnetic metal nanoparticles. The three-dimensional interpenetrating network structure constructed by the lignocellulose-derived carbon skeleton and MXene conductive sheets effectively promotes multiple scattering of electromagnetic waves and forms abundant heterogeneous interfaces. The introduction of magnetic metal further realizes the synergistic effect of the dielectric-magnetic loss mechanism. This solves the problems of poor impedance matching and single composition in the preparation of microwave absorbing materials.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported by magnetic metal nanoparticles includes the following steps;

[0007] Step 1: Etch the Al layer in the Ti2AlC3 MAX phase using the LiF / HCl system to obtain the Mxene colloidal solution;

[0008] Step 2: The TEMPO-oxidized cellulose nanofiber CNF dispersion, Mxene colloidal solution, calcium lignosulfonate and ferric acetate were mixed and stirred sequentially and ultrasonically treated until a uniform mixed suspension was formed. Then, the mixture was freeze-dried to obtain MXene-based lignocellulose aerogel loaded with metal ions.

[0009] Step 3: The MXene-based lignocellulose aerogel loaded with metal ions is carbonized at high temperature in an inert gas to obtain an MXene-based lignocellulose-derived carbon aerogel microwave absorbing material loaded with metal nanoparticles.

[0010] In step 1, the concentration of the obtained MXene colloidal solution is 10~12 mg / mL.

[0011] In step 1, the specific preparation process of the MXene colloidal solution is as follows:

[0012] Dissolve 0.8–1.2 g of LiF powder in 15–25 mL of 8–10 mol / L HCl until completely dissolved to form an etching solution. Then, add 0.8–1.2 g of Ti3AlC2 powder in batches to the etching solution and stir magnetically at a constant temperature for 46–48 h to obtain a uniform suspension. Centrifuge and wash repeatedly with deionized water until the pH of the supernatant is approximately 6. Then, sonicate for 30–35 min to achieve separation. Finally, centrifuge the dispersion and collect the upper suspension.

[0013] In step 2, the suspension is poured into a polytetrafluoroethylene mold with a copper substrate and then directionally cryogenically cast in a liquid nitrogen environment.

[0014] In step 2, the freeze-drying is carried out at a temperature of -55 to -60°C and a pressure of 3 Pa for 46 to 48 hours.

[0015] In step 2, the mass ratios of CNF, Mxene colloidal solution, calcium lignosulfonate, and ferric acetate are (18~20):(1~2):(3~4):(4~5), respectively. This constructs a multi-component synergistic attenuation system, achieving electromagnetic synergy and thus realizing excellent wave absorption performance.

[0016] In step 3, the inert gas is argon / hydrogen, with hydrogen accounting for 2-10%.

[0017] In step 3, the carbonization temperature is 900~1000 ℃, the heating rate is 4~6 ℃ / min, and the carbonization time is 2~3 hours. This promotes the high carbonization and graphitization of the carbon matrix, constructs a highly conductive network structure, and enhances dielectric loss.

[0018] The MXene-based lignocellulose-derived carbon aerogel composite material supported by magnetic metal nanoparticles is applied in the field of electromagnetic wave absorption.

[0019] The MXene-based lignocellulose-derived carbon aerogel absorbing material supported on magnetic metal nanoparticles exhibits an interconnected porous structure with stacked sheets and pore sizes ranging from 50 to 60 μm. This is a three-dimensional conductive network constructed from a lignocellulose-derived carbon skeleton and MXene sheets, with a large number of magnetic metal particles loaded on the surface, the size of which is between 150 and 200 nm. The carbon fibers of lignocellulose form the macroscopic porous skeleton, while the MXene nanosheets are uniformly embedded and bridged on the carbon skeleton. Together, they construct a continuous and efficient conductive network.

[0020] Among them, the MXene-based lignocellulose-derived carbon aerogel absorbing material loaded with magnetic metal nanoparticles achieved a maximum absorption intensity of -51.2 dB and an effective absorption bandwidth of 4.12 GHz when the thickness was 1.4 mm; the MXene-based lignocellulose-derived carbon aerogel absorbing material without magnetic metal nanoparticles achieved a maximum absorption intensity of -46.2 dB and an effective absorption bandwidth of 2.53 GHz when the thickness was 3.0 mm; and the lignocellulose-derived carbon aerogel absorbing material loaded with magnetic metal nanoparticles achieved a maximum absorption intensity of -43.2 dB and an effective absorption bandwidth of 3.96 GHz when the thickness was 2.2 mm.

[0021] The beneficial effects of this invention are:

[0022] This invention provides a strategy for preparing carbon-based magnetic composite microwave absorbing materials, using a directional freeze-drying method and carbonization to prepare an electromagnetically dual-component porous carbon aerogel. A three-dimensional conductive network constructed from a lignocellulose-derived carbon framework and MXene sheets has magnetic iron particles distributed on its surface. Directional freeze-drying, as a key structural shaping step, endows the material with an anisotropic hierarchical porous structure. Carbonization, as a key functional activation step, successfully transforms the precursor into a highly conductive carbon / MXene network and stable magnetic nanoparticles. The conductivity of MXene and the magnetism of iron synergistically introduce electromagnetic losses, optimizing impedance matching. Furthermore, the porous structure of this network promotes multiple scattering paths for incident waves, significantly improving energy dissipation efficiency. The high conductivity of MXene promotes electron migration, thereby inducing conduction losses. The abundant heterogeneous interfaces within the aerogel induce charge accumulation, resulting in interfacial polarization effects, further enhancing the polarization loss capability of the composite aerogel. Due to the introduction of magnetic iron, natural resonance and eddy current losses dominate the magnetic loss process, effectively promoting the efficient conversion of magnetic energy. Based on the study of the interaction mechanism of electromagnetic dual components in aerogels, effective control of electromagnetic parameters and impedance matching was achieved through reasonable material composition and good structural design. Based on this, MXene carbon aerogel absorbing materials supported by magnetic metal nanoparticles exhibit excellent electromagnetic wave absorption performance. Among them, the MXene-based lignocellulose-derived carbon aerogel absorbing material supported by magnetic metal nanoparticles achieves an optimal reflection loss of -51.2 dB with a thickness of 1.4 mm and has an effective absorption bandwidth of 4.12 GHz. Attached Figure Description

[0023] Figure 1 These are photographs and scanning electron microscope (SEM) images of the MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported by magnetic metal nanoparticles obtained in Example 1 of this invention.

[0024] Figure 2 This is a transmission electron microscope (TEM) image of the MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles obtained in Example 1 of this invention.

[0025] Figure 3 This is the X-ray diffraction (XRD) pattern of the MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported by magnetic metal nanoparticles obtained in Example 1 of this invention.

[0026] Figure 4 These are SEM magnified images and hysteresis loop diagrams of the MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported by magnetic metal nanoparticles obtained in Example 1 of this invention.

[0027] Figure 5 This is a graph showing the reflection loss of the coaxial sample of the MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported by magnetic metal nanoparticles obtained in Example 1 of this invention as a function of frequency.

[0028] Figure 6 This is a graph showing the reflection loss of the coaxial sample of the MXene-based lignocellulose-derived carbon aerogel absorbing material without magnetic metal nanoparticles obtained in Comparative Example 1 of this invention as a function of frequency.

[0029] Figure 7 This is a graph showing the change in reflection loss as a function of frequency for the coaxial sample of carbon aerogel absorbing material supported by magnetic metal nanoparticles obtained in Comparative Example 2 of this invention. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings.

[0031] Example 1:

[0032] Step 1: Dissolve 1 g of LiF powder in 20 mL of 9 mol / L HCl and stir magnetically for 10 min until completely dissolved. Then, add 1 g of Ti3AlC2 powder in batches to the above etching solution, and maintain the system at a constant temperature of 35℃ with magnetic stirring for 48 h to obtain a homogeneous suspension. Centrifuge (3500 rpm, 5 min) and wash repeatedly with deionized water until the pH of the supernatant is approximately 6, followed by sonication for 30 min to achieve separation. Finally, centrifuge the dispersion (3500 rpm, 1 h), collect the supernatant, and obtain an MXene colloidal solution with a concentration of 10 mg / mL.

[0033] Step 2: Add 20 mL of CNF dispersion (10 mg / mL) to a 100 mL beaker, then add 2 mL of MXene (10 mg / mL) solution, 2 g of calcium lignosulfonate, and 2.5 g of ferric acetate sequentially. Mix, stir, and sonicate until a homogeneous suspension is formed. Pour the suspension into a copper-based polytetrafluoroethylene mold and directionally freeze-cast in liquid nitrogen. Subsequently, freeze-dry (-60℃, 3 Pa) for 48 hours to obtain MXene-based lignocellulose aerogel loaded with magnetic metal.

[0034] Step 3: Place the MXene-based lignocellulose aerogel loaded with magnetic metal obtained in Step 2 into an alumina crucible and then into a tube furnace. In an argon / hydrogen (10% hydrogen) atmosphere, heat to 900°C at a heating rate of 5°C / min and hold for 2 hours to finally obtain MXene-based lignocellulose-derived carbon aerogel loaded with magnetic metal nanoparticles.

[0035] Example 2:

[0036] Step 1: The basic operation of preparing the MXene colloidal solution in Step 1 of this embodiment is basically the same as the process in Step 1 of Example 1, and will not be repeated here.

[0037] Step 2: Add 20 mL of CNF dispersion (10 mg / mL) to a 100 mL beaker, then add 1 mL of MXene (10 mg / mL) solution, 2 g of calcium lignosulfonate, and 3 g of ferric acetate. Mix, stir, and sonicate until a homogeneous suspension is formed. Pour the suspension into a copper-based polytetrafluoroethylene mold and directionally freeze-cast in liquid nitrogen. Subsequently, freeze-dry (-60℃, 3 Pa) for 48 hours to obtain MXene-based lignocellulose aerogel loaded with magnetic metal.

[0038] Step 3: Place the MXene-based lignocellulose aerogel loaded with magnetic metal obtained in Step 2 into an alumina crucible and then into a tube furnace. In an argon / hydrogen (5% hydrogen) atmosphere, heat to 900°C at a heating rate of 5°C / min and hold for 2 hours to finally obtain MXene-based lignocellulose-derived carbon aerogel loaded with magnetic metal nanoparticles.

[0039] Example 3:

[0040] Step 1: The basic operation of preparing the MXene colloidal solution in Step 1 of this embodiment is basically the same as the process in Step 1 of Example 1, and will not be repeated here.

[0041] Step 2: Add 20 mL of CNF dispersion (10 mg / mL) to a 100 mL beaker, then add 3 mL of MXene (10 mg / mL) solution, 2 g of calcium lignosulfonate, and 4 g of ferric acetate. Mix, stir, and sonicate until a homogeneous suspension is formed. Pour the suspension into a copper-based polytetrafluoroethylene mold and directionally freeze-cast in liquid nitrogen. Subsequently, freeze-dry (-60℃, 3 Pa) for 48 hours to obtain MXene-based lignocellulose aerogel loaded with magnetic metal.

[0042] Step 3: Place the MXene-based lignocellulose aerogel loaded with magnetic metal obtained in Step 2 into an alumina crucible and place it in a tube furnace. In an argon / hydrogen (2% hydrogen) atmosphere, heat it to 900℃ at a heating rate of 5℃ / min and hold it for 2 hours to finally obtain MXene-based lignocellulose-derived carbon aerogel loaded with magnetic metal nanoparticles.

[0043] Comparative Example 1:

[0044] Step 1: The basic operation of preparing the MXene colloidal solution in step 1 of this comparative example is basically the same as the process in step 1 of Example 1, and will not be repeated here.

[0045] Step 2: Add 20 mL of CNF dispersion (10 mg / mL) to a 100 mL beaker, then add 2 mL of MXene (10 mg / mL) solution and 2 g of calcium lignosulfonate. Mix, stir, and sonicate until a homogeneous suspension is formed. Pour the suspension into a copper-based polytetrafluoroethylene mold and perform directional freeze casting in liquid nitrogen. Subsequently, freeze-dry (-60℃, 3 Pa) for 48 hours to obtain MXene-based lignocellulose aerogel without magnetic metal loading.

[0046] Step 3: Place the MXene-based lignocellulose aerogel obtained in Step 2 in an alumina crucible and place it in a tube furnace. In an argon / hydrogen (10% hydrogen) atmosphere, heat it to 900°C at a heating rate of 5°C / min and hold it for 2 hours to finally obtain MXene-based lignocellulose-derived carbon aerogel without magnetic metal nanoparticles.

[0047] Comparative Example 2:

[0048] Step 1: The basic operation of preparing the MXene colloidal solution in step 1 of this comparative example is basically the same as the process in step 1 of Example 1, and will not be repeated here.

[0049] Step 2: Add 20 mL of CNF dispersion (10 mg / mL) to a 100 mL beaker, then add 2 g of calcium lignosulfonate and 2.5 g of ferric acetate sequentially. Mix, stir, and sonicate until a homogeneous suspension is formed. Pour the suspension into a copper-based polytetrafluoroethylene mold and directionally freeze-cast in liquid nitrogen. Subsequently, freeze-dry (-60℃, 3 Pa) for 48 hours to obtain lignocellulose aerogel loaded with magnetic metal.

[0050] Step 3: Place the lignocellulose aerogel loaded with magnetic metal obtained in Step 2 into an alumina crucible and put it into a tube furnace. In an argon / hydrogen (10% hydrogen) atmosphere, heat it to 900℃ at a heating rate of 5℃ / min and hold it for 2 hours to finally obtain lignocellulose-derived carbon aerogel loaded with magnetic metal nanoparticles.

[0051] Figure 1 The images shown are digital photographs and SEM images of Example 1. Macroscopically, the absorbing material can support the dandelion fluff without deformation, exhibiting an ultra-low density. Microscopically, the absorbing material displays an interconnected porous structure of stacked sheets, a three-dimensional conductive network constructed from a cellulose-derived carbon skeleton and MXene sheets. Figure 2TEM characterization of Example 1 is given, revealing that Fe particles are randomly modified on the MXene / lignocellulose carbon skeleton or encapsulated in nanosheets, and the lattice spacings of 0.20 nm and 0.26 nm correspond to the interlayer spacing of the (110) plane of Fe particles and the (1010) plane of MXene, respectively.

[0052] Figure 3 XRD patterns of the carbon aerogel absorbing materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 are presented. For Example 1 and Comparative Example 2, the two diffraction peaks at 44.6° and 65.0° correspond to the (111) and (200) crystal phases of metallic iron (Fe #PDF06 - 0696), respectively, consistent with TEM characterization. For Example 1 and Comparative Example 1, the peak at 28.5° is related to the (006) crystal plane of MXene. The presence of metallic Fe in the carbon aerogels of Example 1 and Comparative Example 2 is confirmed. MXene is present in the carbon aerogels of Example 1 and Comparative Example 1.

[0053] Figure 4 SEM images and hysteresis loops of the MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles prepared in Example 1 are presented at magnification. It can be seen that a large number of magnetic iron particles are attached to the layered dendritic structure; these particles have a density of 16.83 emu g. -1 The strong saturation magnetization intensity ensures electromagnetic wave absorption and other magnetically related applications.

[0054] The MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles prepared in Example 1 was used for microwave absorption performance testing. The testing method for electromagnetic wave absorption performance was as follows: The powder of the metal-supported MXene-based carbon aerogel microwave absorbing material and paraffin were mixed at a mass ratio of 1.5:8.5 (i.e., a filling ratio of 15%) and pressed into a coaxial sample with an outer diameter of 7.00 mm, an inner diameter of 3.04 mm, and a thickness of approximately 2 mm in a special mold. The electromagnetic parameters of the sample from 2 to 18 GHz were tested using a vector network analyzer, and the microwave absorption performance was calculated. The reflection loss curve of the sample as a function of frequency is shown below. Figure 5 As shown, when the matching thickness is 1.4 mm, the maximum absorption intensity reaches -51.2 dB, with a maximum effective absorption band (less than -10 dB) width of 4.12 GHz. It is evident that the MXene-based carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles prepared in Example 1 exhibits strong microwave absorption performance.

[0055] The MXene lignocellulose-derived carbon aerogel microwave absorbing material without metallic magnetic nanoparticles prepared in Comparative Example 1 was subjected to the same microwave absorption performance tests as in Example 1. The reflection loss of the sample as a function of frequency is shown in the figure below. Figure 6As shown, when the matching thickness is 3.0 mm, the maximum absorption intensity reaches -46.2 dB, with a maximum effective absorption band (less than -10 dB) width of 2.53 GHz. It is evident that the MXene carbon aerogel absorbing material without loaded metallic magnetic nanoparticles prepared in Comparative Example 1 exhibits strong microwave absorption performance.

[0056] The carbon aerogel absorbing material supported on magnetic metal nanoparticles prepared in Comparative Example 2 was subjected to the same microwave absorption performance test as in Example 1. The reflection loss of the sample as a function of frequency is shown in the figure below. Figure 7 As shown, when the matching thickness is 2.2 mm, the maximum absorption intensity reaches -43.2 dB, with a maximum effective absorption band (less than -10 dB) width of 3.96 GHz. It is evident that the carbon aerogel absorbing material supported on metallic magnetic nanoparticles prepared in Comparative Example 2 exhibits strong microwave absorption performance.

Claims

1. A method for preparing MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles, characterized in that, Includes the following steps; Step 1: Etch the Al layer in the Ti2AlC3 MAX phase using the LiF / HCl system to obtain the Mxene colloidal solution; Step 2: The TEMPO-oxidized cellulose nanofiber CNF dispersion, Mxene colloidal solution, calcium lignosulfonate and ferric acetate were mixed and stirred sequentially and ultrasonically treated until a uniform mixed suspension was formed. Then, the mixture was freeze-dried to obtain MXene-based lignocellulose aerogel loaded with metal ions. Step 3: The MXene-based lignocellulose aerogel loaded with metal ions is carbonized at high temperature in an inert gas to obtain an MXene-based lignocellulose-derived carbon aerogel microwave absorbing material loaded with metal nanoparticles.

2. The method for preparing MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles according to claim 1, characterized in that, In step 1, the concentration of the obtained MXene colloidal solution is 10~12 mg / mL.

3. The method for preparing MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles according to claim 1, characterized in that, In step 1, the specific preparation process of the MXene colloidal solution is as follows: Dissolve 0.8–1.2 g of LiF powder in 15–25 mL of 8–10 mol / L HCl until completely dissolved to form an etching solution. Then, add 0.8–1.2 g of Ti3AlC2 powder in batches to the etching solution and stir magnetically at a constant temperature for 46–48 h to obtain a uniform suspension. Centrifuge and wash repeatedly with deionized water until the pH of the supernatant is 6. Then, sonicate for 30–35 min to achieve separation. Finally, centrifuge the dispersion and collect the upper suspension, i.e., the Mxene colloidal solution.

4. The method for preparing the MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles according to claim 3, characterized in that, In step 2, the suspension is poured into a polytetrafluoroethylene mold with a copper substrate and then directionally cryogenically cast in a liquid nitrogen environment. In step 2, the freeze-drying is carried out at a temperature of -55 to -60°C and a pressure of 3 Pa for 46 to 48 hours.

5. The method for preparing the MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles according to claim 4, characterized in that, In step 2, the mass ratio of CNF, Mxene colloidal solution, calcium lignosulfonate, and ferric acetate is (18~20): (1~2): (3~4): (4~5).

6. The method for preparing the MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles according to claim 1, characterized in that, In step 3, the inert gas is argon / hydrogen, with hydrogen accounting for 2-10%.

7. The method for preparing the MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported on magnetic metal nanoparticles according to claim 1, characterized in that, In step 3, the carbonization temperature is 900~1000 ℃, the heating rate is 4~6 ℃ / min, and the carbonization time is 2~3 hours.

8. The application of the MXene-based lignocellulose-derived carbon aerogel composite material supported on magnetic metal nanoparticles prepared by the method according to any one of claims 1-7, characterized in that, Composite materials are used in the field of electromagnetic wave absorption.

9. The MXene-based lignocellulose-derived carbon aerogel composite material supported on magnetic metal nanoparticles prepared by the method according to any one of claims 1-7, characterized in that, The MXene-based lignocellulose-derived carbon aerogel microwave absorbing material supported by magnetic metal nanoparticles exhibits a sheet-like stacked interconnected porous structure with pore sizes ranging from 50 to 60 μm. The three-dimensional conductive network constructed by the lignocellulose-derived carbon skeleton and MXene sheets is also loaded with a large number of magnetic metal particles with sizes ranging from 150 to 200 nm. The carbon fibers of lignocellulose form a macroscopic porous skeleton, while the MXene nanosheets are uniformly embedded and bridged on the carbon skeleton. Together, they construct a continuous and efficient conductive network.

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