A single atom modified carbon composite absorbing material and preparation method thereof

Abstract

The invention belongs to the technical field of absorbing materials, and specifically relates to a single-atom-modified carbon composite absorbing material and a preparation method thereof; the method specifically comprises: S1. uniformly dispersing a pyrrole monomer and hydrogenated molybdenum trioxide by using a solvent, and reacting them at room temperature for 3 to 6 hours to obtain an HM@PPy composite; S2. adding metal porphyrin and thionyl chloride to N,N-dimethylformamide and mixing them uniformly, and then adding 4-dimethylaminopyridine to obtain a raw material solution; S3. dispersing the HM@PPy composite into an N,N-dimethylformamide solution containing triethylamine to obtain a suspension; S4. dropping the raw material solution into the suspension, stirring and reacting at room temperature for 20 to 25 hours to obtain HM@PPy-MPor; S5. pyrolyzing HM@PPy-MPor to obtain the single-atom-modified carbon composite absorbing material.

Description

Technical Field

[0001] The invention belongs to the technical field of wave-absorbing materials, and in particular relates to a single-atom-modified carbon composite wave-absorbing material and a preparation method thereof. Background Art

[0002] In the 5G electronic information age, smart electronic devices bring convenience to people's lives, but also cause serious electromagnetic interference and pollution problems. In order to solve these problems, it is particularly important to develop high-performance electromagnetic wave absorbing materials.

[0003] In recent years, carbon nanostructures anchored by metal single atoms have received extensive research attention. Such structures are known for their extremely high surface free energy and nearly 100% atomic utilization. However, most single-atom materials are experimentally synthesized at high temperatures, and there is a challenge here: metal atoms tend to aggregate at high temperatures to form metal clusters or nanoparticles instead of the expected single atomic sites. The main problem is that traditional precursors lack effective constraints to pre-disperse metal single atoms or prevent them from aggregating under high temperature conditions. For example, a precursor composed of graphene and cobalt-coordinated porphyrin undergoes high-temperature pyrolysis to form metal cobalt particles instead of cobalt single atomic sites. Therefore, the rationality of precursor design, especially the effective confinement of metal single atoms, becomes a key factor in the preparation of single-atom adsorbents.

[0004] Therefore, it is of great significance to develop a new single-atom modified carbon composite absorbing material and its preparation method. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a single-atom-modified carbon composite absorbing material and a preparation method thereof in view of the deficiencies of the prior art. The present invention is the first to use the click restriction strategy to construct a single-atom absorbing material and has achieved significant results. The single-atom-modified carbon composite absorbing material has excellent electromagnetic wave absorption performance.

[0006] Specifically, the click confinement strategy, as a new synthetic method, confines transition metal atoms in the precursor to prepare single-atom-modified carbon composite absorbers. Specifically, click confinement refers to the pre-construction of a stable coordinate environment, and then the obtained molecules are further anchored to the substrate through covalent bond connection according to the principle of click chemistry. On the one hand, the inherent directionality and saturation of covalent bonds ensure the monodispersity of the grafted transition metal-containing molecules. On the other hand, compared with van der Waals forces, the covalent bond interaction is relatively strong, which prevents the transition metal atoms from undesirable aggregation tendency during pyrolysis (Chang-Xin Zhao, Jia-Ning Liu, et al. A clicking confinementstrategy to fabricate transition metal single-atom sites for bifunctionaloxygen electrocatalysis. Science Advances. 2022, 8, 11). The click confinement strategy not only has no strict requirements on molecular size or symmetry, thereby broadening the synthetic route, but also the inherent advantages of click chemistry give this strategy great specificity.

[0007] In order to solve the above technical problems, the present invention discloses a method for preparing a single-atom modified carbon composite absorbing material, the specific steps of which are:

[0008] S1. Pyrrole monomer and hydrogenated molybdenum trioxide are dispersed evenly by solvent, and reacted at room temperature for 3-6 h to obtain HM@PPy composite;

[0009] S2. The metal porphyrin and thionyl chloride are added to N, N-dimethylformamide and mixed evenly, and then 4-dimethylaminopyridine is added to obtain a raw material solution;

[0010] S3. Dispersing the HM@PPy complex obtained in S1 into an N,N-dimethylformamide solution containing triethylamine to obtain a suspension of the HM@PPy complex;

[0011] S4. The raw material solution obtained in S2 is added dropwise to the suspension of the HM@PPy complex obtained in S3, and the mixture is stirred at room temperature for 20 to 25 h to obtain HM@PPy-MPor.

[0012] S5. Pyrolyze the HM@PPy-MPor obtained in S4 to obtain a single-atom modified carbon composite absorbing material.

[0013] Wherein, in S1, the mass ratio of the pyrrole monomer to hydrogenated molybdenum trioxide is (0.2-5): 1

[0014] Among them, in S1, the mass ratio of the pyrrole monomer to the solvent is 1:(200~400), and the solvent is a mixed solvent composed of ethanol and water, wherein the volume ratio of ethanol to water is (0.5~2):1.

[0015] Wherein, in S2, the mass volume ratio of the metal porphyrin to N,N-dimethylformamide is (10-15):1; the volume ratio of the thionyl chloride to N,N-dimethylformamide is 1:(200-250); the mass ratio of the metal porphyrin to 4-dimethylaminopyridine is (1.5-2):1;

[0016] Preferably, the metal porphyrin includes one or a mixture of nickel porphyrin, copper porphyrin, cobalt porphyrin, manganese porphyrin, iron porphyrin, zinc porphyrin, molybdenum porphyrin, vanadium porphyrin, silver porphyrin, iridium porphyrin, rhodium porphyrin and platinum porphyrin.

[0017] Among them, in S3, the volume ratio of triethylamine and N,N-dimethylformamide in the solution of N,N-dimethylformamide containing triethylamine is 1:(80~90); the mass volume ratio of the HM@PPy composite and the N,N-dimethylformamide solution containing triethylamine is (5~7):1.

[0018] Wherein, in S4, the volume ratio of the raw material solution to the suspension of the HM@PPy complex is 1:(1-3).

[0019] Among them, in S5, the pyrolysis conditions are: heating to 600-900°C at a rate of 5-10°C / min in an argon atmosphere and keeping the temperature for 2-8 hours.

[0020] Specifically, in some embodiments of the present invention, by testing the conductivity, conduction loss, polarization loss and electromagnetic parameters of the single-atom-modified carbon composite absorbing material prepared by the present invention, the application prospect of the single-atom-modified carbon composite absorbing material prepared by the present invention in the field of electromagnetic wave absorption is verified.

[0021] Beneficial effects: The present invention further anchors the single atom to the substrate through covalent bonding. The modified single atom is constrained by porphyrin, so the metal atoms are not easy to agglomerate during high-temperature pyrolysis and exist in the form of stable single atom sites. By changing the coordinated metal of metal porphyrin, different metal single atoms can be modified on the surface of the material. And because only the surface of the material is modified, this method will not affect the intrinsic morphology of the material, which is more gentle, more efficient, easier to control, and has universal applicability. And only a small amount of metal single atom modification can significantly improve the electromagnetic wave absorption performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0023] Figure 1 Transmission electron microscope images and element distribution diagrams of the single-atom modified carbon composite absorbing materials prepared in Examples 1-4 of the present invention;

[0024] Figure 2 Inductively coupled plasma mass spectrometry of the single atom modified carbon composite absorbing material prepared in Examples 1-4 of the present invention;

[0025] Figure 3 The electrical conductivity of the single-atom modified carbon composite absorbing materials prepared in Examples 1-4 of the present invention and the HM@NC prepared in Comparative Example 1;

[0026] Figure 4 The conduction loss and polarization loss of the single-atom modified carbon composite absorbing materials prepared in Examples 1-4 of the present invention and the HM@NC prepared in Comparative Example 1;

[0027] Figure 5 This is a diagram of the microwave absorption performance of HM@NC-Ni prepared in Example 1 of the present invention;

[0028] Figure 6 This is a diagram of the microwave absorption performance of HM@NC-Ni-60 prepared in Example 2 of the present invention;

[0029] Figure 7 This is a diagram of the microwave absorption performance of HM@NC-Ni-80 prepared in Example 3 of the present invention;

[0030] Figure 8 This is a diagram of the microwave absorption performance of HM@NC-Ni-100 prepared in Example 4 of the present invention;

[0031] Fig. 9 The electrical conductivity of the single-atom modified carbon composite absorbing material prepared in Examples 5-7 of the present invention;

[0032] Fig.10 The conduction loss of the single-atom modified carbon composite absorbing material prepared in Examples 5-7 of the present invention;

[0033] Fig.11 The polarization loss of the single-atom modified carbon composite absorbing material prepared in Examples 5-7 of the present invention;

[0034] Fig.12 This is a diagram of the microwave absorption performance of HM@NC-Co prepared in Example 5 of the present invention;

[0035] Fig.13 This is a diagram of the microwave absorption performance of HM@NC-Cu prepared in Example 6 of the present invention;

[0036] Fig.14 This is a diagram of the microwave absorption performance of HM@NC-Ni / Cu prepared in Example 7 of the present invention;

[0037] Fig.15 This is a diagram of the wave absorption performance of HM@NC prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The experimental methods described in the following examples are all conventional methods unless otherwise specified; the methods for material characterization described in the following examples are all conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0039] Example 1: 0.854 g of tetrakis(4-carboxyphenyl)porphyrin (purchased from MacLean) and 3.1 g of nickel chloride hexahydrate were dissolved in 100 mL of N,N-dimethylformamide, and the solution was heated to reflux at 140°C for 6 h. Then, 150 mL of deionized water was added to the above solution and filtered to obtain a solid. The solid was first washed three times with 1 mol / L hydrochloric acid solution and then washed three times with deionized water. The purple solid was collected by filtration and dried overnight in vacuo.

[0040] 0.75 g of the purple solid was dissolved in a mixture of 25 mL of tetrahydrofuran and 25 mL of methanol, and then 25 mL of KOH solution (the mass of KOH was 2.63 g) was slowly added. The mixture was heated to reflux at 85 °C for 24 h. After the reaction was completed and cooled to room temperature, enough deionized water was added to completely dissolve the solid. The reaction solution was then acidified by slowly adding 1 mol / L hydrochloric acid solution until no excess precipitation was produced in the system. After filtering and washing with a large amount of water, a red solid was obtained. The product was labeled as nickel-coordinated porphyrin (NiPor-carboxy).

[0041] The preparation methods of copper coordinated porphyrin (CuPor-carboxy) and cobalt coordinated porphyrin (CoPor-carboxy) are similar to this, except that nickel chloride hexahydrate is replaced by copper chloride dihydrate and cobalt chloride tetrahydrate, respectively.

[0042] Example 2: Pyrrole monomer and hydrogenated molybdenum trioxide were added to a mixed solvent of ethanol and water with a volume ratio of (0.5-2):1 in a mass ratio of 1:1 (the mass ratio of pyrrole to the mixed solvent was 1:200-400), stirred at room temperature for 3-6 h, filtered, washed, and dried to obtain the HM@PPy complex; NiPor-carboxy (200 mg) and SOCl2 (68 µl) were then dissolved in 15 mL DMF by ultrasound for 10 min, and the carboxyl group was subsequently converted into acyl chloride, and then the catalyst 4-dimethylaminopyridine (115 mg) was added to the above solution for further amidation to form a raw material solution; HM@PPy (200 mg) was dispersed in a DMF (30 mL) solution containing 346 μL triethylamine, and ultrasound was performed for 45 min to form a uniform suspension. Finally, the raw material solution was added dropwise to the uniformly dispersed HM@PPy suspension. After stirring at 30 °C for 24 h and cooling to room temperature, black particles were obtained by filtration and washed alternately with DMF and ethanol for 6 times. The obtained sample was vacuum dried at 60 °C for 12 h to obtain HM@PPy-NiPor; then, the temperature was increased to 700 °C in an Ar atmosphere at a heating rate of 5 °C / min and pyrolyzed for 3 h to obtain the single atom modified carbon composite absorbing material HM@NC-Ni.

[0043] Example 3: Pyrrole monomer and hydrogenated molybdenum trioxide were added to a mixed solvent of ethanol and water with a volume ratio of (0.5-2):1 in a mass ratio of 1:1 (the mass ratio of pyrrole used to the mixed solvent was 1:200-400), stirred at room temperature for 3-6 h, and after the reaction, filtered, washed, and dried to obtain the HM@PPy complex; then NiPor-carboxy (200 mg) and SOCl2 (68 µl) were dissolved in 15 mL DMF by ultrasound for 10 min, and the carboxyl group was subsequently converted into acyl chloride, and then the catalyst 4-dimethylaminopyridine (115 mg) for further amidation was added to the above solution to form a raw material solution; HM@PPy (200 mg) was dispersed in a DMF (30 mL) solution containing 346 μL triethylamine, and ultrasound was applied for 45 min to form a uniform suspension. Finally, the raw material solution was added dropwise to the uniformly dispersed HM@PPy suspension. After stirring at 60 °C for 24 h and cooling to room temperature, the black particles were filtered and washed alternately with DMF and ethanol for 6 times. The obtained sample was vacuum dried at 60 °C for 12 h to obtain HM@PPy-NiPor-60; then, it was heated to 700 °C in an Ar atmosphere at a heating rate of 5 °C / min and pyrolyzed for 3 h to obtain the single atom modified carbon composite absorbing material HM@NC-Ni-60.

[0044] Example 4: Pyrrole monomer and hydrogenated molybdenum trioxide were added to a mixed solvent of ethanol and water with a volume ratio of (0.5~2):1 in a mass ratio of 1:1 (the mass ratio of pyrrole used to the mixed solvent was 1:200~400), stirred at room temperature for 3~6 h, and after the reaction, filtered, washed, and dried to obtain the HM@PPy complex; then NiPor-carboxy (200 mg) and SOCl2 (68µl) were dissolved in 15 mL DMF by ultrasound for 10 min, and the carboxyl group was subsequently converted into acyl chloride, and then the catalyst 4-dimethylaminopyridine (115 mg) for further amidation was added to the above solution to form a raw material solution; HM@PPy (200 mg) was dispersed in a DMF (30 mL) solution containing 346 μL triethylamine, and ultrasonicated for 45 min to form a uniform suspension. Finally, the raw material solution was added dropwise to the uniformly dispersed HM@PPy suspension. Stir at 80 °C for 24 h. After cooling to room temperature, black particles were filtered out and washed alternately with DMF and ethanol for 6 times. The obtained sample was vacuum dried at 60 °C for 12 h to obtain HM@PPy-NiPor-80. Then, it was pyrolyzed at 700 °C in an Ar atmosphere at a heating rate of 5 °C / min for 3 h to obtain the single atom modified carbon composite absorbing material HM@NC-Ni-80.

[0045] Example 5: Pyrrole monomer and hydrogenated molybdenum trioxide were added to a mixed solvent of ethanol and water with a volume ratio of (0.5-2):1 in a mass ratio of 1:1 (the mass ratio of pyrrole used to the mixed solvent was 1:200-400), stirred at room temperature for 3-6 h, and after the reaction, filtered, washed, and dried to obtain the HM@PPy complex; then NiPor-carboxy (200 mg) and SOCl2 (68 µl) were dissolved in 15 mL DMF by ultrasound for 10 min, and the carboxyl group was subsequently converted into acyl chloride, and then the catalyst 4-dimethylaminopyridine (115 mg) for further amidation was added to the above solution to form a raw material solution; HM@PPy (200 mg) was dispersed in a DMF (30 mL) solution containing 346 μL triethylamine, and ultrasound was performed for 45 min to form a uniform suspension. Finally, the raw material solution was added dropwise to the uniformly dispersed HM@PPy suspension. After stirring at 100 °C for 24 h and cooling to room temperature, the black particles were filtered and washed alternately with DMF and ethanol for 6 times. The obtained sample was vacuum dried at 60 °C for 12 h to obtain HM@PPy-NiPor-100; then, it was heated to 700 °C in an Ar atmosphere at a heating rate of 5 °C / min and pyrolyzed for 3 h to obtain the single atom modified carbon composite absorbing material HM@NC-Ni-100.

[0046] Example 6: Pyrrole monomer and hydrogenated molybdenum trioxide were added to a mixed solvent of ethanol and water with a volume ratio of (0.5~2):1 in a mass ratio of 1:1 (the mass ratio of pyrrole used to the mixed solvent was 1:200~400), stirred at room temperature for 3~6 h, and after the reaction, filtered, washed, and dried to obtain HM@PPy complex; then CoPor-carboxy (200 mg) and SOCl2 (68µl) were dissolved in 15 mL DMF by ultrasound for 10 minutes, and the carboxyl group was subsequently converted into acyl chloride, and then the catalyst 4-dimethylaminopyridine (115 mg) for further amidation was added to the above solution to form a raw material solution; HM@PPy (200 mg) was dispersed in a DMF (30 mL) solution containing 346 μL triethylamine, and ultrasound was performed for 45 min to form a uniform suspension. Finally, the raw material solution was added dropwise to the uniformly dispersed HM@PPy suspension. After stirring at 30 °C for 24 h and cooling to room temperature, the black particles were filtered and washed alternately with DMF and ethanol for 6 times. The obtained sample was vacuum dried at 60 °C for 12 h to obtain HM@PPy-CoPor; then, the temperature was increased to 700 °C in an Ar atmosphere at a heating rate of 5 °C / min and pyrolyzed for 3 h to obtain the single atom modified carbon composite absorbing material HM@NC-Co.

[0047] Example 7: Pyrrole monomer and hydrogenated molybdenum trioxide were added to a mixed solvent of ethanol and water with a volume ratio of (0.5-2):1 in a mass ratio of 1:1 (the mass ratio of pyrrole to the mixed solvent was 1:200-400), stirred at room temperature for 3-6 h, filtered, washed, and dried to obtain the HM@PPy complex, and then CuPor-carboxy (200 mg) and SOCl2 (68 µl) were dissolved in 15 mL DMF by ultrasound for 10 minutes, and the carboxyl group was subsequently converted into acyl chloride, and then the catalyst 4-dimethylaminopyridine (115 mg) was added to the above solution for further amidation to form a raw material solution; HM@PPy (200 mg) was dispersed in a DMF (30 mL) solution containing 346 μL triethylamine, and ultrasound was performed for 45 min to form a uniform suspension. Finally, the raw material solution was added dropwise to the uniformly dispersed HM@PPy suspension. After stirring at 30 °C for 24 h and cooling to room temperature, the black particles were filtered and washed alternately with DMF and ethanol for 6 times. The obtained sample was vacuum dried at 60 °C for 12 h to obtain HM@PPy-CuPor; then, it was heated to 700 °C in an Ar atmosphere at a heating rate of 5 °C / min and pyrolyzed for 3 h to obtain the single atom modified carbon composite absorber HM@NC-Cu.

[0048] Example 8: Pyrrole monomer and hydrogenated molybdenum trioxide were added to a mixed solvent of ethanol and water with a volume ratio of (0.5-2):1 in a mass ratio of 1:1 (the mass ratio of pyrrole used to the mixed solvent was 1:200-400), stirred at room temperature for 3-6 h, filtered, washed, and dried after the reaction to obtain the HM@PPy complex, and then NiPor-carboxy (100 mg), CuPor-carboxy (100 mg) and SOCl2 (68µl) were dissolved in 15 mL DMF by ultrasound for 10 minutes, and the carboxyl group was subsequently converted into acyl chloride, and then the catalyst 4-dimethylaminopyridine (115 mg) for further amidation was added to the above solution to form a raw material solution; HM@PPy (200 mg) was dispersed in a DMF (30 mL) solution containing 346 μL triethylamine, and ultrasound was performed for 45 min to form a uniform suspension. Finally, the raw material solution was added dropwise to the uniformly dispersed HM@PPy suspension. After stirring at 30 °C for 24 h and cooling to room temperature, the black particles were filtered and washed alternately with DMF and ethanol for 6 times. The obtained sample was vacuum dried at 60 °C for 12 h to obtain HM@PPy-NiPor / CuPor; then, it was heated to 700 °C in an Ar atmosphere at a heating rate of 5 °C / min and pyrolyzed for 3 h to obtain the single atom modified carbon composite absorbing material HM@NC-Ni / Cu.

[0049] Comparative Example 1: Pyrrole monomer and hydrogenated molybdenum trioxide (HM) were added to a mixed solvent consisting of ethanol and water with a volume ratio of (0.5-2):1 in a mass ratio of 5:1-1:5 (the mass ratio of pyrrole to the mixed solvent was 1:200-400), stirred for 3-6 h at room temperature, and after the reaction, filtered, washed, and dried to obtain a HM@PPy composite. The HM@PPy composite was placed in a tubular furnace in an argon atmosphere, and heated to 700 °C at a heating rate of 5 °C / min and maintained for 3 h to obtain a carbon-coated hydrogenated molybdenum trioxide nanocomposite material HM@NC.

[0050] The properties of the materials prepared in Examples 1 to 8 and Comparative Example 1 are as follows:

[0051] 1. TEM (FEI Tecnai F20) and STEM-EDS (Hitachi Regulus8100) were used to observe the morphological changes of the single-atom modified carbon composite absorbing materials prepared in Examples 2 to 5:

[0052] Figure 1Transmission electron microscope images and element distribution diagrams of HM@NC-Ni, HM@NC-Ni-60, HM@NC-Ni-80 and HM@NC-Ni-100 prepared in Examples 2 to 5; From the HAADF-STEM image and the corresponding energy dispersive spectrum STEM-EDS image, it can be observed that in HM@NC-Ni, HM@NC-Ni-60, HM@NC-Ni-80 and HM@NC-Ni-100, Mo, N and Ni elements are evenly distributed on HM. Due to the low content of Ni atoms, Ni elements do not appear on the surface of carbon materials in the form of clusters or nanoparticles. These results clearly show that the click constraint strategy effectively disperses the metal single atoms in the precursor and solves the problem of metal atom aggregation during pyrolysis.

[0053] 2. The single-atom modified carbon composite absorbing materials prepared in Examples 2 to 5 were subjected to mass spectrometry analysis using an inductively coupled plasma mass spectrometer (NEXSA, iCAPRQ):

[0054] Figure 2 The single-atom content of nickel in HM@NC-Ni, HM@NC-Ni-60, HM@NC-Ni-80 and HM@NC-Ni-100 prepared in Examples 2 to 5 is as follows: Figure 2 It can be seen that the nickel single atom contents of HM@NC-Ni, HM@NC-Ni-60, HM@NC-Ni-80 and HM@NC-Ni-100 are 0.17 wt.%, 0.19 wt.%, 0.23 wt.% and 0.28 wt.%, respectively. The nickel single atom content gradually increases with the increase of stirring temperature after the raw material solution is added dropwise to the uniformly dispersed HM@PPy suspension.

[0055] 3. Test the conductivity (RTS-8), conduction loss and polarization loss (based on the formula: ε c ״= σ / ωε 0, ε p ״= ε ״ – ε c ״ Calculate the conduction loss ε c ״ and polarization losses ε p ״):

[0056] Figure 3The conductivity diagram of the single-atom modified carbon composite absorbing material prepared in Examples 2 to 5 of the present invention and the HM@NC prepared in Comparative Example 1 is shown in FIG. Figure 3 It can be observed that the electrical conductivities of HM@NC, HM@NC-Ni, HM@NC-Ni-60, HM@NC-Ni-80 and HM@NC-Ni-100 are 0.129 S / m, 0.134 S / m, 0.16 S / m, 0.151 S / m and 0.195 S / m, respectively. Modifying a small amount of metal atoms on the surface by click reaction does not significantly improve the electrical conductivity of the material. Figure 4 It can be found that the improved electromagnetic wave absorption ability of single-atom modified carbon composite absorber materials mainly comes from the enhanced polarization loss rather than the conduction loss.

[0057] 4. Test the electromagnetic parameters of the single-atom modified carbon composite absorbing materials prepared in Examples 2 to 5:

[0058] The electromagnetic parameters of the single-atom-modified carbon composite absorbers prepared in Examples 2 to 5 were tested in the 2 to 8 GHz frequency band using a network analyzer (VNA, N5245A, Agilent, USA). The mass ratio of the single-atom-modified carbon composite absorbers (HM@NC-Ni, HM@NC-Ni-60, HM@NC-Ni-80 and HM@NC-Ni-100) prepared in Examples 2 to 5 to paraffin was 4:6. All samples were pressed into a standard annulus ( f in : 3.04 mm, f out : 7.00 mm) to maintain geometrical certainty. The thickness of all annuli was kept at 2.5 mm. Agilent PNA software automatically outputs relevant electromagnetic parameters based on the Nicolson and Rossand Weir algorithm. Figure 5~Figure 8 The electromagnetic wave absorption properties of the materials prepared in Examples 2 to 5 are shown. The minimum reflection losses of HM@NC-Ni, HM@NC-Ni-60, HM@NC-Ni-80 and HM@NC-Ni-100 are -17.8 dB, -36.3 dB, -54 dB and -26.9 dB, respectively, and the maximum effective absorption bandwidths are 4.7, 5.6, 5.9 and 5.3 GHz, respectively. The results show that the surface nickel single atom modification completely changes the electromagnetic wave absorption capacity of the HM@NC material, transforming it from no absorption to high absorption.

[0059] 5. Test the conductivity, conduction loss, polarization loss and electromagnetic parameters of the single-atom modified carbon composite absorbing materials prepared in Examples 6 to 8:

[0060] Fig. 9It can be observed that the electrical conductivities of HM@NC-Cu, HM@NC-Co and HM@NC-Ni / Cu are 0.198 S / m, 0.234 S / m and 0.251 S / m, respectively. Fig.10 and Fig.11 It can be found that the enhanced electromagnetic wave absorption capacity of carbon composite absorbers modified with different metal single atoms still mainly comes from the enhanced polarization loss, which indicates that the polarization capacity induced by different metal single atoms is different. This conclusion can be found in Figure 12~Figure 15 It has been verified that the minimum reflection losses of HM@NC-Cu, HM@NC-Co and HM@NC-Ni / Cu are -38.6, -55.9 and -51.7 dB respectively; the maximum absorption bandwidths are 4.6, 4.8 and 6.44 GHz respectively. Therefore, among the modified metal single atoms, Co has the strongest polarization loss ability, followed by Cu, and Ni is the weakest. In short, the present invention can significantly improve the electromagnetic wave absorption performance of the material by modifying a small amount of metal single atoms on the surface of the material.

[0061] The present invention provides a single-atom modified carbon composite absorbing material and a preparation method thereof. There are many methods and approaches to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A method for preparing a single-atom modified carbon composite absorbing material, characterized in that: The specific steps are: S1. Pyrrole monomer and hydrogenated molybdenum trioxide are dispersed evenly by solvent, and reacted at room temperature for 3-6 h to obtain HM@PPy composite; S2. The metal porphyrin and thionyl chloride are added to N, N-dimethylformamide and mixed evenly, and then 4-dimethylaminopyridine is added to obtain a raw material solution; S3. Dispersing the HM@PPy complex obtained in S1 into an N,N-dimethylformamide solution containing triethylamine to obtain a suspension of the HM@PPy complex; S4. The raw material solution obtained in S2 is added dropwise to the suspension of the HM@PPy complex obtained in S3, and the mixture is stirred at room temperature for 20 to 25 h to obtain HM@PPy-MPor. S5. Pyrolyze the HM@PPy-MPor obtained in S4 to obtain a single-atom modified carbon composite absorbing material.

2. The preparation method according to claim 1, characterized in that: In S1, the mass ratio of the pyrrole monomer to hydrogenated molybdenum trioxide is (0.2~5):

1.

3. The preparation method according to claim 1, characterized in that: In S1, the mass ratio of the pyrrole monomer to the solvent is 1:(200-400), and the solvent is a mixed solvent consisting of ethanol and water, wherein the volume ratio of ethanol to water is (0.5-2):

1.

4. The preparation method according to claim 1, characterized in that: In S2, the mass volume ratio of the metal porphyrin to N,N-dimethylformamide is (10-15):1; the volume ratio of the thionyl chloride to N,N-dimethylformamide is 1:(200-250); and the mass ratio of the metal porphyrin to 4-dimethylaminopyridine is (1.5-2):

1.

5. The preparation method according to claim 4, characterized in that: The metal porphyrin includes one or a mixture of nickel porphyrin, copper porphyrin, cobalt porphyrin, manganese porphyrin, iron porphyrin, zinc porphyrin, molybdenum porphyrin, vanadium porphyrin, silver porphyrin, iridium porphyrin, rhodium porphyrin and platinum porphyrin.

6. The preparation method according to claim 1, characterized in that: In S3, the volume ratio of triethylamine to N,N-dimethylformamide in the N,N-dimethylformamide solution containing triethylamine is 1:(80-90); the mass volume ratio of the HM@PPy composite to the N,N-dimethylformamide solution containing triethylamine is (5-7):

1.

7. The preparation method according to claim 1, characterized in that: In S4, the volume ratio of the raw material solution to the suspension of the HM@PPy composite is 1:(1-3).

8. The preparation method according to claim 1, characterized in that: In S5, the pyrolysis conditions are: heating to 600-900°C at a rate of 5-10°C / min in an argon atmosphere and keeping the temperature for 2-8 hours.

9. A single atom modified carbon composite absorbing material prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the single atom modified carbon composite absorbing material according to claim 9 in the field of electromagnetic wave absorption.

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