A method for efficiently growing carbon nanotubes

Abstract

The application discloses a method for growing carbon nanotubes with high growth rate, and relates to the technical field of new carbon materials.The metal ions are chelated and fixed in the block-shaped graphene aerogel or graphene aerogel microspheres by the action of metal ligands, the metal ions are in-situ reduced into nano metal particles by high-temperature thermal reduction, the graphene aerogel microspheres or block-shaped graphene aerogel loaded with metal nano particles are obtained, and high-purity carbon nanotubes are further prepared by high-temperature catalytic cracking of organic gas.The metal nano particles are uniformly dispersed in the porous structure of the graphene aerogel, the catalytic activity is greatly improved, the growth rate of the carbon nanotubes is more than 100, and the carbon nanotubes are high in purity and do not need to be further acidified and purified.

Description

Technical Field

[0001] This invention relates to the field of novel carbon materials technology, and in particular to a method for efficiently growing carbon nanotubes. Background Technology

[0002] Carbon nanotubes are isotopic forms of crystalline carbon, structurally appearing as honeycomb-like one-dimensional hollow nanotubes, in which C and C atoms are arranged in sp... 2 Hybridization forms covalent bonds, and the hexagonal structure is perfectly connected, resulting in excellent mechanical, electrical, and chemical properties, with an electrical conductivity reaching 10⁻⁶. 8 S m -1 Thermal conductivity is higher than 3000 W·(m·K). -1 Carbon nanotubes possess a tensile strength of up to 200 GPa, an elastic modulus of 1.34 TPa, and a density only one-sixth that of steel. Furthermore, they exhibit high elasticity, large specific surface area, good stability, and fatigue resistance. In recent years, with in-depth research into carbon nanotubes, their broad application prospects have become increasingly apparent. Currently, significant progress has been made in the research of the properties and preparation methods of carbon nanotubes, with the focus shifting towards research on their large-scale production and application.

[0003] High-rate growth of carbon nanotubes can overcome two main challenges: 1. reducing production costs; 2. increasing purity and reducing subsequent purification processes. When the growth rate exceeds 100, the purity of the carbon nanotubes obtained can exceed 99%. Carbon nanotubes grown at even higher rates can be used directly without purification after growth, offering significant convenience. Current chemical vapor deposition technology can achieve carbon nanotube production rates of 10 to 60 times, but further improvements in growth rate are needed. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of low growth rate of carbon nanotubes in the prior art and to provide a method for efficient growth of carbon nanotubes.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for efficiently growing carbon nanotubes, comprising the following steps:

[0006] S1. Prepare an aqueous dispersion of graphene oxide with a concentration of 2-10 mg / mL and an aqueous solution of sodium alginate with a concentration of 10-30 mg / mL. Then, add the aqueous solution of sodium alginate to the aqueous dispersion of graphene oxide to obtain a mixed dispersion system. The final concentration of sodium alginate in the system is 3-9 mg / mL.

[0007] S2. The mixed dispersion in S1 and the polyvalent metal ion salt solution are reacted to form a hydrogel, wherein the concentration of the polyvalent metal ion salt solution is 15%-30%.

[0008] S3. Filter and wash the hydrogel in S2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel.

[0009] S4. The aerogel in S3 is thermally reduced at high temperature in an inert atmosphere in a tube furnace to obtain aerogel supported by nano-metal particles.

[0010] S5. Switch the atmosphere of the tubular furnace in S4, heat it at high temperature in a mixed atmosphere of carbon-containing gas and inert gas, then close the carbon-containing gas valve and cool it to room temperature.

[0011] Preferably, the polyvalent metal ion in the polyvalent metal ion salt solution is one or more of ferrous ions, ferric ions, cobalt ions, nickel ions, and lanthanum ions; and the salt of the polyvalent metal ion is one or more of hydrochloride, acetate, sulfate, and nitrate.

[0012] Preferably, the hydrogel in S2 is prepared by adding a multivalent ion salt solution to the mixed dispersion in S1 for cross-linking and fixation to form a hydrogel.

[0013] Preferably, the preparation method of the hydrogel in S2 is as follows: the mixed dispersion in S1 is loaded into a syringe and placed on an electrostatic spraying device, and a paperclip is installed. A voltage of 7-17kV is applied. An organic solvent is added to a polyvalent metal ion salt solution to prepare a two-phase mixture and placed directly below the paperclip. A stir bar is added and stirred. The mixture is electrostatically sprayed and collected to obtain microsphere-shaped hydrogels.

[0014] Preferably, the organic solvent is one or more of n-hexane, n-heptane, n-octane, cyclohexane, liquid paraffin, toluene, and petroleum ether.

[0015] Preferably, in step S4, the high-temperature thermal reduction equipment is a tube furnace with a temperature of 600-1100℃, and the inert gas is one or both of N2 and Ar.

[0016] Further preferably, in step S5, the carbon-containing gas is one or more of methane, acetylene, ethylene, propyne, propylene, carbon monoxide, and carbon dioxide; the inert gas is one or two of N2 and Ar; and the volume flow ratio of the carbon-containing gas to the inert gas is carbon-containing gas:inert gas = 1:5-5:1.

[0017] Further preferably, in S5, the high-temperature heating temperature is 600℃-900℃, and the heating time is 0.1h-3h.

[0018] The beneficial effects of this invention are as follows: By loading the catalyst metal in the form of nanoparticles into graphene block aerogel and aerogel microspheres, this invention greatly exposes its active sites, thereby enabling the rapid and efficient preparation of high-purity carbon nanotubes. This solves the technical problems of insufficient purity of carbon nanotubes prepared in the prior art, the need for purification, and the complexity of catalyst formulations. Attached Figure Description

[0019] Figure 1 The images show the morphology of aerogels supported on nano-metal particles grown from carbon nanotubes; where (a) is the surface morphology, (b) is the cross-sectional morphology, and (c) is a magnified schematic diagram of a local area. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0021] Characterization parameters in this invention: Carbon nanotube growth ratio = total mass after growth / mass of aerogel added before growth;

[0022] Carbon nanotube catalyst growth rate = total mass after growth / mass of metal nanoparticles added to the aerogel before growth.

[0023] Example 1

[0024] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0025] Step 2. Load the mixed dispersion from Step 1 into a syringe and onto an electrostatic spraying device, attaching a paperclip needle. Apply a voltage of 10kV. Prepare a 15% nickel acetate to cobalt acetate solution with a mass ratio of 1:1, and add n-hexane to prepare a two-phase mixture. Place the mixture directly below the paperclip needle and add a stir bar to stir. Electrostatically spray and collect the mixture to obtain microspherical hydrogels.

[0026] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0027] Step 4. The above aerogel is thermally reduced at 800°C in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0028] Step 5. Switch the atmosphere of the tubular furnace in Step 4, heat at 660°C for 1 hour in a mixed atmosphere with a volume flow ratio of propylene:N2 = 3:2, then close the carbon-containing gas valve, cool to room temperature and remove it.

[0029] Carbon nanotube growth ratio = 135.3;

[0030] The loading of NiCo metal nanoparticles in the aerogel was 25 wt%, therefore, the carbon nanotube catalyst growth ratio was 541.3; its morphology was as follows. Figure 1 As shown.

[0031] Example 2

[0032] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0033] Step 2. Load the mixed dispersion from Step 1 into a syringe and onto an electrostatic spraying device, attaching a paperclip needle. Apply a voltage of 10kV. Prepare a 15% nickel acetate to lanthanum nitrate solution with a mass ratio of 1:1, and add n-hexane to prepare a two-phase mixture. Place the mixture directly below the paperclip needle and add a stir bar to stir. Electrostatically spray and collect the mixture to obtain microspherical hydrogels.

[0034] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0035] Step 4. The above aerogel is thermally reduced at 800°C in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0036] Step 5. Switch the atmosphere of the tubular furnace in Step 4, heat at 600°C for 1.2 hours in a mixed atmosphere with a volume flow ratio of propylene:N2 = 2:1, then close the carbon-containing gas valve, cool to room temperature and remove it.

[0037] Carbon nanotube growth ratio = 165.6;

[0038] The loading of NiLa metal nanoparticles in the aerogel is 28wt%, therefore, the growth rate of the carbon nanotube catalyst is 591.4.

[0039] Example 3

[0040] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0041] Step 2. Load the mixed dispersion from Step 1 into a syringe and onto an electrostatic spraying device, attaching a paperclip needle. Apply a voltage of 10kV. Prepare a 15% cobalt acetate to ferric chloride solution with a mass ratio of 2:1, and add n-hexane to prepare a two-phase mixture. Place the mixture directly below the paperclip needle and add a stir bar to stir. Electrostatically spray and collect the mixture to obtain microspherical hydrogels.

[0042] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0043] Step 4. The above aerogel is thermally reduced at 900°C in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0044] Step 5. Switch the atmosphere of the tubular furnace in Step 4, heat at 700°C for 1 hour in a mixed atmosphere with a volume flow ratio of methane:N2 = 5:2, then close the carbon-containing gas valve, cool to room temperature and remove it.

[0045] Carbon nanotube growth ratio = 145.4;

[0046] The loading of FeCo metal nanoparticles in the aerogel is 24wt%, therefore, the growth rate of the carbon nanotube catalyst is 605.8.

[0047] Example 4:

[0048] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0049] Step 2. Load the mixed dispersion from Step 1 into a syringe and onto an electrostatic spraying device, and install a paperclip needle. Apply a voltage of 10kV. Prepare a 15% nickel acetate solution and add n-hexane to it to prepare a two-phase mixture. Place the mixture directly below the paperclip needle and add a stir bar to stir. Electrostatically spray and collect the mixture to obtain microspherical hydrogels.

[0050] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0051] Step 4. The above aerogel is thermally reduced at 700°C in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0052] Step 5. Switch the atmosphere of the tubular furnace in Step 4, and heat it at 800°C for 2 hours in a mixed atmosphere of ethylene and N2 with a volume flow ratio of ethylene:N2 = 5:1. Then close the carbon-containing gas valve, cool it to room temperature, and take it out.

[0053] Carbon nanotube growth ratio = 190.6

[0054] The loading of Ni nanoparticles in the aerogel is 25 wt%, therefore, the growth rate of the carbon nanotube catalyst is 762.4.

[0055] Example 5

[0056] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0057] Step 2. Load the mixed dispersion from Step 1 into a syringe and onto an electrostatic spraying device, attaching a paperclip needle. Apply a voltage of 10kV. Prepare a solution with a total concentration of 15% nickel acetate and a mass ratio of 1:1 ferric acetate, and add n-hexane to prepare a two-phase mixture. Place the mixture directly below the paperclip needle and add a stir bar to stir. Electrostatically spray and collect the mixture to obtain microspherical hydrogels.

[0058] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0059] Step 4. The above aerogel is thermally reduced at 900°C in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0060] Step 5. Switch the atmosphere of the tubular furnace in Step 4, heat at 900°C for 0.1 h in a mixed atmosphere with a volume flow ratio of propylene:N2 = 1:5, then close the carbon-containing gas valve, cool to room temperature and remove it.

[0061] Carbon nanotube growth ratio = 108.3;

[0062] The loading of NiFe metal nanoparticles in the aerogel is 21 wt%, therefore, the growth rate of the carbon nanotube catalyst is 515.7.

[0063] Example 6:

[0064] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0065] Step 2. Load the mixed dispersion from Step 1 into a syringe and onto an electrostatic spraying device, attaching a paperclip needle. Apply a voltage of 10kV. Prepare a solution of lanthanum nitrate and ferric sulfate with a total concentration of 15% and a mass ratio of 2:1, and add n-hexane to prepare a two-phase mixture. Place the mixture directly below the paperclip needle and add a stir bar to stir. Electrostatically spray and collect the mixture to obtain microspherical hydrogels.

[0066] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0067] Step 4. The above aerogel is thermally reduced at 1000℃ in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0068] Step 5. Switch the atmosphere of the tubular furnace in Step 4, heat at 760°C for 1.2 hours in a mixed atmosphere with a volume flow ratio of ethylene:N2 = 3:5, then close the carbon-containing gas valve, cool to room temperature and remove it.

[0069] Carbon nanotube growth ratio = 132.7;

[0070] The loading of LaFe metal nanoparticles in the aerogel is 19wt%, therefore, the growth rate of the carbon nanotube catalyst is 698.4.

[0071] Example 7

[0072] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0073] Step 2. Add 15% of a nickel acetate to cobalt acetate solution with a mass ratio of 1:1 to the mixed dispersion in Step 1 for cross-linking and fixation to form a hydrogel of a certain shape;

[0074] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0075] Step 4. The above aerogel is thermally reduced at 800°C in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0076] Step 5. Switch the atmosphere of the tubular furnace in Step 4, heat at 660°C for 1 hour in a mixed atmosphere with a volume flow ratio of propylene:N2 = 3:2, then close the carbon-containing gas valve, cool to room temperature and remove it.

[0077] Carbon nanotube growth ratio = 124.3;

[0078] The loading of NiCo metal nanoparticles in the aerogel is 30wt%, therefore, the growth rate of the carbon nanotube catalyst is 414.3.

[0079] Example 8

[0080] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0081] Step 2. Add a 15% nickel acetate to lanthanum nitrate solution with a mass ratio of 1:1 to the mixed dispersion in Step 1 for cross-linking and fixation to form a hydrogel of a certain shape;

[0082] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0083] Step 4. The above aerogel is thermally reduced at 800°C in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0084] Step 5. Switch the atmosphere of the tubular furnace in Step 4, heat at 600°C for 1.2 hours in a mixed atmosphere with a volume flow ratio of propylene:N2 = 2:1, then close the carbon-containing gas valve, cool to room temperature and remove it.

[0085] Carbon nanotube growth ratio = 143.2;

[0086] The loading of NiLa metal nanoparticles in the aerogel is 32wt%, therefore, the growth rate of the carbon nanotube catalyst is 447.5.

[0087] Example 9

[0088] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0089] Step 2. Add a 15% cobalt acetate to ferric chloride solution with a mass ratio of 2:1 to the mixed dispersion in Step 1 for cross-linking and fixation to form a hydrogel of a certain shape;

[0090] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0091] Step 4. The above aerogel is thermally reduced at 900°C in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0092] Step 5. Switch the atmosphere of the tubular furnace in Step 4, heat at 700°C for 1 hour in a mixed atmosphere of methane and N2 with a volume flow ratio of methane:N2 = 5:2, then close the carbon-containing gas valve, cool to room temperature and remove it.

[0093] Carbon nanotube growth ratio = 133.3;

[0094] The loading of FeCo metal nanoparticles in the aerogel is 29 wt%, therefore, the growth rate of the carbon nanotube catalyst is 459.7.

[0095] Example 10

[0096] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0097] Step 2. Add 15% nickel acetate solution to the mixed dispersion in Step 1 for cross-linking and fixation to form a hydrogel of a certain shape;

[0098] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0099] Step 4. The above aerogel is thermally reduced at 700°C in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0100] Step 5. Switch the atmosphere of the tubular furnace in Step 4, and heat it at 800°C for 2 hours in a mixed atmosphere of ethylene and N2 with a volume flow ratio of ethylene:N2 = 5:1. Then close the carbon-containing gas valve, cool it to room temperature, and take it out.

[0101] Carbon nanotube growth ratio = 162.8;

[0102] The loading of Ni nanoparticles in the aerogel is 29 wt%, therefore, the growth rate of the carbon nanotube catalyst is 561.4.

[0103] Example 11

[0104] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0105] Step 2. Add nickel acetate (total concentration 15%) and ferric acetate (mass ratio 1:1) to the mixed dispersion in Step 1 for cross-linking and fixation to form a hydrogel of a certain shape.

[0106] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0107] Step 4. The above aerogel is thermally reduced at 900°C in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0108] Step 5. Switch the atmosphere of the tubular furnace in Step 4, heat at 900°C for 0.1 h in a mixed atmosphere with a volume flow ratio of propylene:N2 = 1:5, then close the carbon-containing gas valve, cool to room temperature and remove it.

[0109] Carbon nanotube growth ratio = 96.5;

[0110] The loading of NiFe metal nanoparticles in the aerogel is 25wt%, therefore, the growth rate of the carbon nanotube catalyst is 386.

[0111] Example 12

[0112] Step 1. Prepare a graphene oxide aqueous dispersion with a concentration of 6 mg / mL and a sodium alginate aqueous solution with a concentration of 20 mg / mL. Add the prepared sodium alginate aqueous solution to the graphene oxide aqueous dispersion in a certain proportion so that its final concentration in the system is 4 mg / mL.

[0113] Step 2. Add a solution of lanthanum nitrate and ferric sulfate with a total concentration of 15% and a mass ratio of 2:1 to the mixed dispersion in Step 1 to crosslink and fix it, forming a hydrogel of a certain shape.

[0114] Step 3. Filter and wash the hydrogel obtained in Step 2; freeze-dry it after liquid nitrogen blasting to obtain the corresponding aerogel;

[0115] Step 4. The above aerogel is thermally reduced at 1000℃ in a tube furnace under N2 atmosphere to obtain aerogel supported by nano-metal particles.

[0116] Step 5. Switch the atmosphere of the tubular furnace in Step 4, heat at 760°C for 1.2 hours in a mixed atmosphere with a volume flow ratio of ethylene:N2 = 3:5, then close the carbon-containing gas valve, cool to room temperature and remove it.

[0117] Carbon nanotube growth ratio = 126.2;

[0118] The loading of LaFe metal nanoparticles in the aerogel is 23 wt%, therefore, the growth rate of the carbon nanotube catalyst is 548.7.

[0119] The specification and drawings of this invention are intended to be illustrative rather than restrictive. Based on this invention, those skilled in the art can make substitutions and modifications to some of the technical features without creative effort, and all such modifications are within the scope of protection of this invention.

Claims

1. A method for efficient growth of carbon nanotubes, characterized by, The method comprises the following steps: S1, preparing a graphene oxide water dispersion with a concentration of 2-10 mg / mL and a sodium alginate water solution with a concentration of 10-30 mg / mL, then adding the sodium alginate water solution into the graphene oxide water dispersion to obtain a mixed dispersion system; the final concentration of the sodium alginate in the system is 3-9 mg / mL; S2, loading the mixed dispersion in S1 into a syringe and onto an electrostatic spraying device, then installing a back-shaped needle, applying a voltage of 7-17 kV; adding an organic solvent into a polyvalent metal ion salt solution to prepare a two-phase mixed solution and placing it directly below the back-shaped needle, adding a stirring rod for stirring; electrostatic spraying and collection to obtain a microspherical hydrogel; The concentration of the polyvalent metal ion salt solution is 15%-30%. S3, filtering and washing the hydrogel in S2; freezing with liquid nitrogen and then performing freeze drying to obtain a corresponding aerogel; S4, high-temperature thermal reduction of the aerogel in S3 in a tube furnace in an inert atmosphere to obtain a nano metal particle loaded aerogel; S5, switching the atmosphere of the tube furnace in S4, high-temperature heating in a mixed atmosphere containing a carbon-containing gas and an inert gas, then closing the carbon-containing gas valve and cooling to room temperature.

2. The method of claim 1, wherein, The polyvalent metal ion in the polyvalent metal ion salt solution is one or more of ferrous ion, ferric ion, cobalt ion, nickel ion and lanthanum ion; the salt of the polyvalent metal ion is one or more of hydrochloride, acetate, sulfate and nitrate.

3. The method of claim 1, wherein, The preparation method of the hydrogel in S2 is adding a polyvalent ion salt solution into the mixed dispersion in S1 for cross-linking and fixing to form a hydrogel.

4. The method of claim 1, wherein, The organic solvent is one or more of n-hexane, n-heptane, n-octane, cyclohexane, liquid paraffin, toluene and petroleum ether.

5. The method of claim 1, wherein, In S4, the high-temperature thermal reduction device is a tube furnace, the temperature is 600-1100°C, and the inert gas is one or both of N2 and Ar.

6. The method of claim 1, wherein, In S5, the carbon-containing gas is one or more of methane, acetylene, ethylene, propyne, propylene, carbon monoxide and carbon dioxide; the inert gas is one or both of N2 and Ar; the volume flow ratio of the carbon-containing gas to the inert gas is carbon-containing gas: inert gas = 1:5-5:

1.

7. The method of claim 1, wherein, In S5, the high-temperature heating temperature is 600-900°C, and the heating time is 0.1-3 h.

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