A seaweed-based foam carbon material, its preparation method and application

Abstract

The present invention belongs to the technical field of carbon foams, and provides a seaweed-based carbon foam material, a preparation method thereof and an application. In the present invention, seaweed powder, phenol and concentrated sulfuric acid are liquefied to obtain a liquefied product; the liquefied product, sodium hydroxide and formaldehyde aqueous solution are self-assembled to obtain a phenolic resin-like substance; foaming is carried out in the presence of a surfactant, a transplanted nucleus and a curing agent to obtain a foamed material; the foamed material and an activator are mixed and subjected to carbonization treatment and graphitization treatment in sequence to obtain a foam precursor, and the foam precursor is modified to obtain a seaweed-based carbon foam material. The presence of the transplanted nucleus can optimize the pore structure, make the pore size more uniform, and can also increase the ligament node thickness and improve the mechanical strength of the seaweed-based carbon foam material; the surfactant can promote the uniform mixing of the curing agent, the phenolic resin-like substance and the transplanted nucleus, make the foaming process more stable, and the obtained foam more uniform; the curing agent can solidify the foam and prevent it from collapsing easily.

Description

Technical Field

[0001] The present invention relates to the technical field of foamed carbon, and in particular to a seaweed-based foamed carbon material and a preparation method and application thereof. Background Art

[0002] Carbon foam refers to a foamy porous carbon material. Carbon foam is a lightweight porous material with a three-dimensional network structure consisting of pores and interconnected pore walls. It has the characteristics of low density, high strength, thermal shock resistance, easy processing, and good physical and chemical properties such as electrical conductivity, thermal conductivity, and wave absorption. These excellent properties make carbon foam have great application potential in many technical fields such as chemical industry, aerospace, and electronics.

[0003] The related prior art discloses a lignin-based foamed carbon, wherein lignin is dissolved in dilute acid, vigorously stirred, filtered, and dried to obtain ash-free lignin; the lignin is directly loaded into a crucible and sealed with a sealing cover, and holes are punched in the sealing cover; the crucible containing the lignin is heat-treated to obtain a lignin foam block; the lignin foam block is subjected to high-temperature carbonization treatment to obtain the lignin-based foamed carbon. However, the pore size of the obtained lignin-based foamed carbon is disordered and uneven. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a seaweed-based foamed carbon material and a preparation method and application thereof. The seaweed-based foamed carbon material prepared by the preparation method provided by the present invention has uniform pore size.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a seaweed-based foamed carbon material, comprising the following steps:

[0007] The seaweed powder, phenol and concentrated sulfuric acid are mixed and liquefied to obtain a liquefied product;

[0008] The liquefied product, sodium hydroxide and formaldehyde aqueous solution are mixed and self-assembled to obtain a phenolic resin;

[0009] The phenolic resin, surfactant, transplant core and curing agent are mixed and foamed to obtain a foamed material;

[0010] The foaming material and the activator are mixed, and carbonization and graphitization are performed in sequence to obtain a foam precursor;

[0011] Modifying the foam precursor to obtain the seaweed-based foam carbon material;

[0012] The transplant core is prepared by heating seaweed biochar and normal hexane.

[0013] Preferably, the mass fraction of the concentrated sulfuric acid is 94 - 96%, the mass ratio of the seaweed powder to phenol is 5 - 10:10 - 20, and the dosage ratio of the seaweed powder to the concentrated sulfuric acid is 5 - 10 g:0.3 - 1 mL;

[0014] The temperature of the liquefaction is 120 - 180 °C, the time is 1 - 3 h, and the liquefaction is carried out under the condition of an oil bath.

[0015] Preferably, the mass fraction of the formaldehyde aqueous solution is 36 - 38%, the mass ratio of the seaweed powder to sodium hydroxide is 5 - 10:0.5 - 1, and the dosage ratio of sodium hydroxide to the formaldehyde aqueous solution is 0.5 - 1 g:15 - 20 mL;

[0016] The temperature of the self-assembly is 60 - 80 °C, and the time is 1 - 3 h;

[0017] After the self-assembly, it further includes: after cooling the obtained self-assembly liquid to room temperature, adjusting the pH value to 7 - 8, and performing rotary evaporation to obtain the phenolic resin-like product.

[0018] Preferably, the preparation method of the seaweed biochar includes the following steps: acid-leaching the seaweed to obtain acid-leached seaweed; performing a first heat treatment on the acid-leached seaweed to obtain a precursor; mixing the precursor and an active agent and performing a second heat treatment to obtain the seaweed biochar;

[0019] The reagent for the acid-leaching is a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 0.1 - 0.5 mol / L, and the time for the acid-leaching is 12 - 24 h;

[0020] The temperature of the first heat treatment is 600 - 1000 °C, and the time is 1 - 3 h;

[0021] The active agent includes potassium hydroxide and / or sodium hydroxide, and the mass ratio of the precursor to the active agent is 1:3 - 5;

[0022] The temperature of the second heat treatment is 700 - 1000 °C, and the time is 1 - 5 h.

[0023] Preferably, the preparation method of the transplanted nucleus includes the following steps: mixing the seaweed biochar and n-hexane and heating to obtain the transplanted nucleus; the mass of the n-hexane is 20 - 60% of the mass of the seaweed biochar; the temperature of the heating is 130 - 150 °C, and the time is 1 - 3 h;

[0024] After the heating, it further includes: naturally cooling the obtained heated liquid to room temperature to obtain the transplanted nucleus.

[0025] Preferably, the surfactant includes one or more of Tween-80, sodium dodecyl sulfate, isomeric alcohol polyoxyethylene ether, and sodium alcohol polyoxyethylene ether sulfate;

[0026] The curing agent includes hydrochloric acid, and the mass fraction of the hydrochloric acid is 36-38%;

[0027] The mass of the surfactant is 1-10% of the mass of the phenolic resin-like resin;

[0028] The mass of the grafted nucleus is 2-10% of the mass of the phenolic resin-like resin;

[0029] The mass of the curing agent is 1-10% of the mass of the phenolic resin-like resin;

[0030] The foaming pressure is 0.05-0.3 MPa, and the time is 30-120 min. The foaming is carried out in a high-temperature and high-pressure reaction device.

[0031] Preferably, the activator includes zinc chloride; the mass ratio of the foaming material to the activator is 1-5:1-5;

[0032] The temperature of the carbonization treatment is 500-1000 °C, the heat preservation time is 1-3 h, the heating rate from room temperature to the temperature of the carbonization treatment is 5-15 °C / min, and the atmosphere of the carbonization treatment is nitrogen;

[0033] The temperature of the graphitization treatment is 2000-2800 °C, the heat preservation time is 1-3 h, and the heating rate from room temperature to the temperature of the graphitization treatment is 5-10 °C / min.

[0034] Preferably, the modifier used for the modification includes an inorganic base solution or an inorganic acid solution;

[0035] The inorganic base solution is an aqueous potassium hydroxide solution, and the concentration of the aqueous potassium hydroxide solution is 2-4 mo1 / L;

[0036] The inorganic acid solution is sulfuric acid, and the mass fraction of the sulfuric acid is 8-12%;

[0037] The time of the modification is 30-120 min.

[0038] The present invention also provides a seaweed-based foam carbon material prepared by the preparation method described in the above technical solution.

[0039] The present invention also provides the application of the seaweed-based foam carbon material described in the above technical solution in the fields of chemical engineering, aerospace, or electronics.

[0040] The present invention provides a preparation method of a seaweed-based foam carbon material.

[0041] The present invention liquefies seaweed powder, phenol and concentrated sulfuric acid to obtain a liquefied product; the liquefied product, sodium hydroxide and aqueous formaldehyde solution are mixed and self-assembled to obtain a phenolic resin-like substance; the phenolic resin-like substance is foamed in the presence of a surfactant, a grafting core and a curing agent to obtain a foamed material; the foamed material and an activator are mixed and subjected to carbonization treatment and graphitization treatment in sequence to obtain a foam precursor, and then the foam precursor is modified to obtain a seaweed-based foam carbon material. The present invention uses waste seaweed powder as a raw material, realizing the resource recycling of waste seaweed powder; at the same time, the foam carbon material prepared from seaweed powder is light in weight. Meanwhile, foaming can generate pores inside the material. The presence of the grafting core can optimize the pore structure, make the pore size more uniform, and can also increase the ligament node thickness, improving the mechanical strength of the seaweed-based foam carbon material; the surfactant promotes the uniform mixing of the curing agent, the phenolic resin-like substance and the grafting core by changing the surface tension of the system, making the foaming process more stable and the obtained foam more uniform; the curing agent cures the foam by changing the curing rate of the resin matrix, making it not easy to collapse and ensuring the porosity and bulk density of the material; the graphitization treatment can further improve the mechanical properties of the material.

[0042] The data of the examples show that: the compressive strength of the seaweed-based foam carbon material provided by the present invention is 6.3 - 8.9 MPa, and the bulk density is 0.19 - 0.65 g / cm 3 , and the specific surface area is 752 - 987 m 2 / g. Description of the Drawings

[0043] Figure 1 It is a physical appearance photo of Enteromorpha prolifera as the seaweed raw material and the seaweed powder obtained from the seaweed raw material;

[0044] Figure 2 It is the SEM pattern of the seaweed powder (Enteromorpha prolifera) at different magnifications;

[0045] Figure 3 It is the thermogravimetric curve of the seaweed powder (Enteromorpha prolifera) under nitrogen;

[0046] Figure 4 It is the physical appearance photo of the materials obtained in the examples and the comparative examples;

[0047] Figure 5 It is the SEM pattern of the seaweed-based foam carbon material obtained in Comparative Example 2;

[0048] Figure 6 It is the SEM pattern of the seaweed-based foam carbon material A1 obtained in Example 1 at different magnifications. Detailed Embodiments

[0049] The present invention provides a preparation method of a seaweed-based foam carbon material, comprising the following steps:

[0050] Mix seaweed powder, phenol, and concentrated sulfuric acid, and perform liquefaction to obtain a liquefied product;

[0051] Mix the liquefied product, sodium hydroxide, and aqueous formaldehyde solution, and perform self-assembly to obtain a phenolic resin-like material;

[0052] Mix the phenolic resin-like material, surfactant, grafted nucleus, and curing agent, and perform foaming to obtain a foamed material;

[0053] Mix the foamed material and activator, and perform carbonization treatment and graphitization treatment in sequence to obtain a foam precursor;

[0054] Modify the foam precursor to obtain the seaweed-based foam carbon material;

[0055] The grafted nucleus is prepared by heating reaction of seaweed biochar and n-hexane.

[0056] Unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0057] In the present invention, seaweed powder, phenol, and concentrated sulfuric acid are mixed and liquefied to obtain a liquefied product.

[0058] In the present invention, the particle size of the seaweed powder is preferably 20 - 100 mesh. In the present invention, the seaweed powder is preferably prepared from seaweed raw materials, and the seaweed raw materials preferably include one or more of Enteromorpha prolifera, Laminaria japonica, Porphyra yezoensis, Undaria pinnatifida, Gelidium amansii, and Sargassum thunbergii. In the present invention, the preparation method of the seaweed powder preferably includes the following steps: wash, dry, and ball-mill the seaweed raw materials in sequence to obtain the seaweed powder; the present invention does not make specific limitations on the reagents and times of the washing, as long as the impurities on the surface of the seaweed raw materials can be completely removed. The present invention does not make specific limitations on the parameters of the ball-milling, as long as the seaweed powder with a particle size of 20 - 100 mesh can be obtained. In the present invention, compared with the seaweed raw materials, the seaweed powder can better contact with phenol and concentrated sulfuric acid and perform liquefaction, ultimately improving the mechanical properties of the seaweed-based foam carbon material and reducing the bulk density.

[0059] In the present invention, the mass ratio of the seaweed powder to phenol is preferably 5 - 10:10 - 20, specifically preferably 5:15. In the present invention, the mass fraction of the concentrated sulfuric acid is preferably 94 - 96%, specifically preferably 95%; the dosage ratio of the seaweed powder to the concentrated sulfuric acid is preferably 5 - 10 g:0.3 - 1 mL, specifically preferably 5 g:0.5 mL.

[0060] In the present invention, the temperature of the liquefaction is preferably 120 - 180°C, specifically it can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C; the time is preferably 1 - 3 h, specifically preferably 1 h, 2 h or 3 h. In the present invention, the liquefaction is preferably carried out under the condition of an oil bath. In the present invention, the liquefaction is preferably carried out under the conditions of stirring and refluxing.

[0061] In the present invention, the mixing of the seaweed powder, phenol and concentrated sulfuric acid for liquefaction preferably includes the following steps: mixing the seaweed powder and phenol, heating to the temperature of the liquefaction, adding concentrated sulfuric acid, and carrying out liquefaction; the addition method of the concentrated sulfuric acid is preferably dropwise addition; the liquefaction time preferably starts to be timed after the addition of the concentrated sulfuric acid is completed.

[0062] After the liquefaction, the present invention preferably further includes cooling to room temperature to obtain the liquefied product.

[0063] After obtaining the liquefied product, the present invention mixes the liquefied product, sodium hydroxide and aqueous formaldehyde solution for self-assembly to obtain a phenolic resin-like product.

[0064] In the present invention, the mass ratio of the seaweed powder to sodium hydroxide is preferably 5 - 10:0.5 - 1, specifically preferably 5:0.72. In the present invention, the mass fraction of the aqueous formaldehyde solution is preferably 36 - 38%, specifically preferably 37%, and the dosage ratio of sodium hydroxide to the aqueous formaldehyde solution is 0.5 - 1 g:15 - 20 mL, specifically preferably 0.72 g:17 mL.

[0065] In the present invention, the temperature of the self-assembly is preferably 60 - 80°C, specifically preferably 60°C, 65°C, 70°C, 75°C or 80°C; the time is preferably 1 - 3 h, specifically preferably 1 h, 2 h or 3 h. In the present invention, the self-assembly is preferably carried out under the condition of a water bath.

[0066] After the self-assembly, the present invention further includes: after cooling the obtained self-assembly liquid to room temperature, adjusting the pH value to 7 - 8, and carrying out rotary evaporation to obtain the phenolic resin-like product. In the present invention, the temperature of the rotary evaporation is preferably 50°C, and the vacuum degree is preferably 0.07 MPa.

[0067] After obtaining the phenolic resin-like product, the present invention mixes the phenolic resin-like product, surfactant, transplantation core and curing agent for foaming to obtain a foamed material; the transplantation core is prepared by heating reaction of seaweed biochar and n-hexane.

[0068] In the present invention, the preparation method of the seaweed biochar preferably comprises the following steps: acid-leaching seaweed to obtain acid-leached seaweed; performing a first heat treatment on the acid-leached seaweed to obtain a precursor; mixing the precursor and an active agent and performing a second heat treatment to obtain the seaweed biochar. In the present invention, the reagent for acid-leaching is preferably a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is preferably 0.1 - 0.5 mol / L, specifically preferably 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L; the temperature for acid-leaching is preferably room temperature, and the time is preferably 12 - 24 h, specifically preferably 12 h, 16 h, 20 h or 24 h; the acid-leaching can remove metal elements in the seaweed. In the present invention, the temperature for the first heat treatment is preferably 600 - 1000 °C, specifically preferably 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 950 °C or 1000 °C; the time is preferably 1 - 3 h, specifically preferably 1 h, 2 h or 3 h; the atmosphere for the first heat treatment is preferably nitrogen; after the first heat treatment, the present invention preferably naturally cools down to room temperature. In the present invention, the first heat treatment can obtain a preliminary carbonized product. In the present invention, the active agent preferably comprises potassium hydroxide and / or sodium hydroxide, and the mass ratio of the precursor to the active agent is preferably 1:3 - 5, specifically preferably 1:3, 1:4 or 1:5; the temperature for the second heat treatment is preferably 700 - 1000 °C, specifically preferably 700 °C, 800 °C, 900 °C or 1000 °C; the time is preferably 1 - 5 h, specifically preferably 1 h, 2 h, 3 h, 4 h or 5 h; the atmosphere for the second heat treatment is preferably nitrogen; after the second heat treatment, it is preferably naturally cooled down to room temperature to obtain the seaweed biochar. In the present invention, the second heat treatment can obtain a seaweed biochar with stable performance and rich pore structure.

[0069] In the present invention, the preparation method of the transplanted core preferably includes the following steps: mixing seaweed biochar and n-hexane, and heating to obtain the transplanted core. In the present invention, the seaweed biochar is preferably dried before use, the drying temperature is preferably 60-100°C, more preferably 80°C; the time is preferably 1-3h, more preferably 2h; the mass of the n-hexane is preferably 20-60% of the mass of the seaweed biochar, specifically preferably 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%; the heating temperature is preferably 130-150°C, more preferably 140°C; the time is preferably 1-3h, more preferably 2h; the heating is preferably carried out under closed conditions, and the heating is preferably carried out in a high-pressure reactor. After the heating, it preferably further includes: naturally cooling the obtained heated liquid to room temperature to obtain the transplanted core. In the present invention, the transplanted core can optimize the pore structure and improve the uniformity of the pore size; at the same time, the transplanted core can also increase the ligament node thickness and improve the mechanical strength of the seaweed-based foam carbon material.

[0070] In the present invention, the mass of the transplanted core is preferably 2-10% of the mass of the phenolic resin-like, specifically preferably 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0071] In the present invention, the surfactant preferably includes one or more of Tween-80, sodium dodecyl sulfate, isomeric alcohol polyoxyethylene ether and sodium fatty alcohol polyoxyethylene ether sulfate, more preferably Tween-80; the mass of the surfactant is preferably 1-10% of the mass of the phenolic resin-like, specifically preferably 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%. In the present invention, the surfactant can promote the uniform mixing of the curing agent, phenolic resin-like and transplanted core, make the foaming process more stable, and the obtained foam more uniform.

[0072] In the present invention, the curing agent preferably includes hydrochloric acid, and the mass fraction of the hydrochloric acid is preferably 36-38%, specifically preferably 37%. In the present invention, the mass of the curing agent is preferably 1-10% of the mass of the phenolic resin-like, specifically preferably 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%. In the present invention, the curing agent can fix the foam generated by foaming, making it not easy to collapse, and achieving the effect of reducing the volume density of the material.

[0073] In the present invention, the pressure for foaming is preferably 0.05 - 0.3 MPa, specifically preferably 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa or 0.3 MPa; the time is preferably 30 - 120 min, specifically preferably 30 min, 60 min, 90 min or 120 min, and the foaming is preferably carried out in a high-temperature and high-pressure reaction device. In the present invention, the foaming can generate pores in the material and reduce the volume density of the material; at the same time, the addition of the transplantation nuclei can make the pore sizes uniform.

[0074] After obtaining the foamed material, in the present invention, the foamed material and the activator are mixed, and carbonization treatment and graphitization treatment are carried out in sequence to obtain a foam precursor.

[0075] In the present invention, the activator preferably includes zinc chloride, and the mass ratio of the foamed material to the activator is preferably 1 - 5:1 - 5, specifically preferably 1:3. In the present invention, the activator can expand pores, improve the degree of pore development, and increase the specific surface area.

[0076] In the present invention, the temperature of the carbonization treatment is preferably 500 - 1000 °C, specifically preferably 500 °C, 600 °C, 700 °C, 800 °C, 900 °C or 1000 °C; the heat preservation time is preferably 1 - 3 h, specifically preferably 1 h, 2 h or 3 h, and the heating rate from room temperature to the temperature of the carbonization treatment is preferably 5 - 15 °C / min, specifically preferably 5 °C / min, 10 °C / min or 15 °C / min; the atmosphere of the carbonization treatment is preferably nitrogen; after the carbonization treatment, the present invention preferably further includes natural cooling to room temperature. In the present invention, the carbonization treatment can improve the structural stability performance of the foam carbon.

[0077] In the present invention, the temperature of the graphitization treatment is preferably 2000 - 2800 °C, specifically preferably 2000 °C, 2100 °C, 2200 °C, 2300 °C, 2400 °C, 2500 °C, 2600 °C, 2700 °C or 2800 °C; the heat preservation time is 1 - 3 h, specifically preferably 1 h, 2 h or 3 h, and the heating rate from room temperature to the temperature of the graphitization treatment is preferably 5 - 10 °C / min, specifically preferably 5 °C / min or 10 °C / min; the atmosphere of the graphitization treatment is preferably nitrogen. After the graphitization treatment, the present invention preferably further includes natural cooling to room temperature. In the present invention, the graphitization treatment is preferably carried out in a high-temperature graphitization furnace. In the present invention, the graphitization treatment can further enhance the mechanical properties of the material.

[0078] After obtaining the foam precursor, in the present invention, the foam precursor is modified to obtain the seaweed-based foam carbon material.

[0079] In the present invention, the modifier used for the modification preferably includes an inorganic base solution or an inorganic acid solution, and more preferably an inorganic acid solution. In the present invention, the inorganic base solution is preferably an aqueous potassium hydroxide solution, and the concentration of the aqueous potassium hydroxide solution is preferably 2 - 4 mol / L, specifically preferably 3 mol / L.

[0080] In the present invention, the inorganic acid solution is preferably sulfuric acid, and the mass fraction of the sulfuric acid is preferably 8 - 12%, specifically preferably 10%.

[0081] In the present invention, the temperature of the modification is preferably room temperature, and the time of the modification is preferably 30 - 120 min, specifically preferably 30 min, 60 min, 90 min or 120 min. After the modification, the present invention preferably further includes: taking out the modified precursor, washing and drying it in sequence to obtain the seaweed-based foam carbon material. In the present invention, the washing reagent is preferably water, and the water is preferably distilled water. The present invention does not specifically limit the number of washing times, as long as the pH value of the obtained washing solution no longer changes. The present invention does not specifically limit the drying parameters.

[0082] In the present invention, the modification can improve the surface functional group structure of the foam carbon and directionally prepare a carbon-based material rich in active groups.

[0083] The present invention also provides a seaweed-based foam carbon material prepared by the preparation method described in the above technical solution. In the present invention, the pore sizes of the seaweed-based foam carbon material are uniform and the structure is homogeneous.

[0084] The present invention also provides the application of the seaweed-based foam carbon material described in the above technical solution in the fields of chemical engineering, aerospace or electronics.

[0085] The present invention does not specifically limit the specific implementation manners of the application, and those skilled in the art can set them according to actual needs.

[0086] The following combines examples to elaborate in detail on the seaweed-based foam carbon material provided by the present invention, its preparation method and application, but they cannot be understood as limiting the protection scope of the present invention.

[0087] Example 1

[0088] A preparation method of a seaweed-based foam carbon material includes the following steps:

[0089] (1) Pretreatment process: The seaweed raw material (Enteromorpha prolifera) is cleaned, impurity-removed, dried and ball-milled, and then passed through an 80-mesh sieve to obtain seaweed powder.

[0090] (2) Liquefaction process: Weigh 5 g of seaweed powder and 15 g of phenol and place them in an oil bath equipped with a mechanical stirrer and a reflux condenser. While heating and stirring in the 150 °C oil bath, gradually add 0.5 mL of 95 wt% concentrated sulfuric acid as a catalyst. After the addition of concentrated sulfuric acid is complete, carry out liquefaction for 2 h. After the product is cooled to room temperature, the liquefied product is obtained.

[0091] (3) Self-assembly process: Place the above liquefied product, 0.72 g of NaOH, and 17 mL of 37 wt% formaldehyde aqueous solution in a 70 °C water bath for self-assembly for 2 h. After self-assembly is complete, cool to room temperature, adjust the pH value of the system to 7.5 with hydrochloric acid, and then carry out rotary evaporation at 50 °C and a vacuum degree of 0.07 MPa to obtain a phenolic resin-like product.

[0092] (4) Preparation of the transplantation nucleus: Dry the seaweed biochar at 80 °C for 2 h, then weigh the seaweed biochar and n-hexane, where the mass of n-hexane is 40% of the mass of the seaweed biochar. Place the two in a high-pressure reactor, seal it, and put it in an oven to heat at 140 °C for 2 h, and then naturally cool to room temperature to obtain the transplantation nucleus. Among them, the preparation method of the seaweed biochar includes the following steps: Immerse the seaweed in a hydrochloric acid solution with a concentration of 0.5 mol / L for acid leaching for 12 h; take out the acid-leached seaweed, wash it to neutrality, and then dry it to obtain acid-leached seaweed; carry out the first heat treatment of the acid-leached seaweed at 700 °C in a nitrogen atmosphere for 2 h, and then naturally cool to obtain a precursor; mix the precursor and the activator KOH according to a mass ratio of 1:3, and then carry out the second heat treatment at 800 °C in a nitrogen atmosphere for 2 h, and then naturally cool to obtain the seaweed biochar.

[0093] (5) Foaming process: Put the phenolic resin-like product, the surfactant Tween-80, the transplantation nucleus, and the curing agent (hydrochloric acid with a mass fraction of 37%) into a high-pressure autoclave for foaming, and maintain the foaming pressure at 0.05 MPa for 0.5 h to obtain a foamed material; among them, the mass of the curing agent is 5% of the mass of the phenolic resin-like product, the mass of the surfactant is 8% of the mass of the phenolic resin-like product, and the mass of the transplantation nucleus is 5% of the mass of the phenolic resin-like product. To maintain the constant pressure during the foaming process, the micro high-pressure reactor is improved. During operation, pure N2 is introduced through the inlet, and the exhaust port is slightly opened, and the internal pressure of the equipment is indicated by a pressure gauge.

[0094] (6) Carbonization treatment and graphitization treatment: Mix the foamed material and ZnCl2 according to a mass ratio of 1:3, and under N2 protection, heat it at a heating rate of 5 °C / min to a final temperature of 800 °C for carbonization treatment for 2 h, and then naturally cool to room temperature to obtain a carbonization treatment product. Then put the carbonization treatment product into a high-temperature graphitization furnace, and under N2 protection, heat it at a heating rate of 10 °C / min to 2500 °C, hold for 1 h, and after the holding is over, naturally cool to room temperature to obtain a foam precursor.

[0095] (7) Add the foam precursor to 10 wt% sulfuric acid for modification for 1 h. Take out the modified foam precursor, wash it with distilled water until the pH of the obtained washing liquid remains unchanged, and then dry it to obtain the seaweed-based foam carbon material A1.

[0096] Example 2

[0097] A preparation method of a seaweed-based foam carbon material, comprising the following steps:

[0098] (1) Pretreatment process: The seaweed raw material (Enteromorpha prolifera) is washed to remove impurities, dried and ball-milled, and then passed through an 80-mesh sieve to obtain seaweed powder.

[0099] (2) Liquefaction process: Weigh 5 g of seaweed powder and 15 g of phenol and place them in an oil bath equipped with a mechanical stirrer and a reflux condenser. While stirring and heating in an oil bath at 150 °C, gradually add 0.5 mL of 95 wt% sulfuric acid as a catalyst. After the addition of sulfuric acid is completed, carry out liquefaction for 2 h. After the product is cooled to room temperature, a liquefied product is obtained.

[0100] (3) Self-assembly process: Place the above liquefied product, 0.72 g of NaOH, and 17 mL of 37 wt% formaldehyde aqueous solution in a 60 °C water bath for self-assembly for 2 h. After self-assembly is completed, cool to room temperature, adjust the pH value of the system to 7.5 with hydrochloric acid, and then carry out rotary evaporation at 50 °C and a vacuum degree of 0.07 MPa to obtain a phenolic resin-like product.

[0101] (4) Preparation of the grafting core: Dry the seaweed biochar at 80 °C for 2 h, and then weigh the seaweed biochar and n-hexane, where the mass of n-hexane is 30% of the mass of the seaweed biochar. Place the two in a high-pressure reaction kettle, seal it, and then put it into an oven and heat it at 140 °C for 2 h, and naturally cool to room temperature to obtain the grafting core. Among them, the preparation method of the seaweed biochar is the same as that in Example 1.

[0102] (5) Foaming process: Put the phenolic resin-like product, the surfactant Tween-80, the grafting core, and the curing agent (hydrochloric acid with a mass fraction of 37%) into a high-pressure kettle for foaming, and maintain the foaming pressure at 0.2 MPa for 0.5 h to obtain a foamed material; among them, the mass of the curing agent is 5% of the mass of the phenolic resin-like product, the mass of the surfactant is 8% of the mass of the phenolic resin-like product, and the mass of the grafting core is 5% of the mass of the phenolic resin-like product. To maintain the pressure constant during the foaming process, the micro high-pressure reaction kettle is improved. During operation, pure N2 is introduced through the inlet, and the exhaust port is slightly opened, and the internal pressure of the equipment is indicated by a pressure gauge.

[0103] (6) Carbonization treatment and graphitization treatment: Mix the foaming material with ZnCl2 at a mass ratio of 1:3. Under N2 protection, heat it at a heating rate of 5 °C / min to a final temperature of 800 °C for 2 h of carbonization treatment, and then cool it naturally to room temperature to obtain the carbonization treatment product. Then put the carbonization treatment product into a high-temperature graphitization furnace. Under N2 protection, heat it at a heating rate of 10 °C / min to 2500 °C, hold for 1 h, and after the holding ends, cool it naturally to room temperature to obtain the foam precursor.

[0104] (7) Add the foam precursor to sulfuric acid with a concentration of 10 wt%, carry out modification for 1 h, take out the modified foam precursor, wash it with distilled water until the pH of the obtained washing liquid remains unchanged, and then dry it to obtain the seaweed-based foam carbon material A2.

[0105] Example 3

[0106] A preparation method of a seaweed-based foam carbon material, comprising the following steps:

[0107] (1) Pretreatment process: The seaweed raw material (Enteromorpha prolifera) is washed, decontaminated, dried and ball-milled, and then passed through an 80-mesh sieve to obtain seaweed powder.

[0108] (2) Liquefaction process: Weigh 5 g of seaweed powder and 15 g of phenol and place them in an oil bath equipped with a mechanical stirrer and a reflux condenser. Under stirring and heating in an oil bath at 170 °C, gradually add 0.5 mL of 95 wt% concentrated sulfuric acid as a catalyst. After the addition of concentrated sulfuric acid is completed, carry out liquefaction for 2 h. After the product cools to room temperature, obtain the liquefaction product.

[0109] (3) Self-assembly process: Place the above liquefaction product, 0.72 g of NaOH and 17 mL of 37 wt% formaldehyde aqueous solution in a 60 °C water bath for self-assembly for 1 h. After self-assembly is completed, cool to room temperature, adjust the pH value of the system to 7.5 with hydrochloric acid, and then carry out rotary evaporation at 50 °C and a vacuum degree of 0.07 MPa to obtain a phenolic resin-like product.

[0110] (4) Preparation of the transplantation nucleus: Dry the seaweed biochar at 80 °C for 2 h, and then weigh the seaweed biochar and n-hexane, where the mass of n-hexane is 40% of the mass of the seaweed biochar. Place the two in a high-pressure reaction kettle, seal it and put it into an oven to heat at 140 °C for 2 h, and then naturally cool to room temperature to obtain the transplantation nucleus. The preparation method of the seaweed biochar is the same as that in Example 1.

[0111] (5) Foaming process: Put phenolic resin-like, surfactant Tween-80, grafted nuclei, and curing agent (hydrochloric acid with a mass fraction of 37%) into an autoclave for foaming, and maintain the foaming pressure at 0.1 MPa for 0.5 h to obtain the foamed material; among them, the mass of the curing agent is 3% of the mass of the phenolic resin-like, the mass of the surfactant is 4% of the mass of the phenolic resin-like, and the mass of the grafted nuclei is 5% of the mass of the phenolic resin-like. To maintain a constant pressure during the foaming process, the micro autoclave reactor is improved. During operation, pure N2 is introduced through the inlet, and the exhaust port is slightly opened, and the internal pressure of the equipment is indicated by a pressure gauge.

[0112] (6) Carbonization treatment and graphitization treatment: Mix the foamed material with ZnCl2 at a mass ratio of 1:3, and under N2 protection, heat it at a heating rate of 5 °C / min to a final temperature of 800 °C for carbonization treatment for 2 h, and then cool it naturally to room temperature to obtain the carbonized treatment product. Then put the carbonized treatment product into a high-temperature graphitization furnace, and under N2 protection, heat it at a heating rate of 10 °C / min to 2500 °C, hold for 1 h, and after the holding is completed, cool it naturally to room temperature to obtain the foam precursor.

[0113] (7) Add the foam precursor to sulfuric acid with a concentration of 10 wt% for modification for 1 h. Take out the modified foam precursor, wash it with distilled water until the pH of the obtained washing liquid remains unchanged, and then dry it to obtain the seaweed-based foam carbon material A3.

[0114] Example 4

[0115] A preparation method of a seaweed-based foam carbon material, comprising the following steps:

[0116] (1) Pretreatment process: The seaweed raw material (Enteromorpha prolifera) is washed, impurity-removed, dried, and ball-milled, and then passed through an 80-mesh sieve to obtain seaweed powder.

[0117] (2) Liquefaction process: Weigh 5 g of seaweed powder and 15 g of phenol and place them in an oil bath equipped with a mechanical stirrer and a reflux condenser. Under stirring and heating in an oil bath at 120 °C, gradually add 0.5 mL of 95 wt% sulfuric acid as a catalyst. After the addition of sulfuric acid is completed, carry out liquefaction for 2 h. After the product is cooled to room temperature, the liquefied product is obtained.

[0118] (3) Self-assembly process: Put the above liquefied product, 0.72 g of NaOH, and 17 mL of 37 wt% formaldehyde aqueous solution in a 70 °C water bath for self-assembly for 1 h. After self-assembly is completed, cool it to room temperature, adjust the pH value of the system to 7.5 with hydrochloric acid, and then carry out rotary evaporation at 50 °C and a vacuum degree of 0.07 MPa to obtain phenolic resin-like.

[0119] (4) Preparation of the grafted core: The seaweed biochar was dried at 80 °C for 2 h, and then the seaweed biochar and n - hexane were weighed. The mass of n - hexane was 50% of the mass of the seaweed biochar. The two were placed in a high - pressure reactor, sealed and then put into an oven and heated at 140 °C for 2 h, and then cooled naturally to room temperature to obtain the grafted core. The preparation method of the seaweed biochar was the same as that in Example 1.

[0120] (5) Foaming process: The phenolic - resin - like resin, the surfactant Tween - 80, the grafted core, and the curing agent (hydrochloric acid with a mass fraction of 37%) were put into a high - pressure autoclave for foaming, and the foaming pressure was maintained at 0.15 MPa for 0.5 h to obtain the foamed material. Among them, the mass of the curing agent was 7% of the mass of the phenolic - resin - like resin, the mass of the surfactant was 6% of the mass of the phenolic - resin - like resin, and the mass of the grafted core was 5% of the mass of the phenolic - resin - like resin. To maintain a constant pressure during the foaming process, the micro - high - pressure reactor was improved. During operation, pure N2 was introduced through the inlet, and the exhaust port was slightly opened, and the internal pressure of the equipment was indicated by a pressure gauge.

[0121] (6) Carbonization treatment and graphitization treatment: The foamed material was mixed with ZnCl2 at a mass ratio of 1:3. Under N2 protection, it was heated at a heating rate of 10 °C / min to a final temperature of 900 °C for carbonization treatment for 2 h, and then cooled naturally to room temperature to obtain the carbonization treatment product. Then the carbonization treatment product was put into a high - temperature graphitization furnace. Under N2 protection, it was heated at a heating rate of 10 °C / min to 2500 °C, held for 1 h, and then cooled naturally to room temperature after the holding was completed to obtain the foam precursor.

[0122] (7) The foam precursor was added to sulfuric acid with a concentration of 10 wt% for modification for 1 h. The modified foam precursor was taken out, washed with distilled water until the pH of the obtained washing solution remained unchanged, and then dried to obtain the seaweed - based foam carbon material A4.

[0123] Example 5

[0124] A preparation method of a seaweed - based foam carbon material, comprising the following steps:

[0125] (1) Pretreatment process: The seaweed raw material (Enteromorpha prolifera) was washed, de - impurities, dried and ball - milled, and then passed through an 80 - mesh sieve to obtain seaweed powder.

[0126] (2) Liquefaction process: 5 g of seaweed powder and 15 g of phenol were weighed and placed in an oil bath equipped with a mechanical stirrer and a reflux condenser. Under stirring and heating in an oil bath at 150 °C, 0.5 mL of 95 wt% concentrated sulfuric acid was added dropwise as a catalyst. After the addition of the concentrated sulfuric acid was completed, liquefaction was carried out for 2 h. After the product was cooled to room temperature, the liquefaction product was obtained.

[0127] (3) Self-assembly process: The above-mentioned liquefied product, 0.72 g of NaOH, and 17 mL of 37 wt% formaldehyde aqueous solution were placed in a 70 °C water bath for self-assembly for 2 h. After self-assembly was completed, it was cooled to room temperature, the pH value of the system was adjusted to 7.5 with hydrochloric acid, and then rotary evaporation was carried out at 50 °C under a vacuum of 0.07 MPa to obtain phenolic resin-like resin.

[0128] (4) Preparation of grafted nuclei: The seaweed biochar was dried at 80 °C for 2 h, and then the seaweed biochar and n-hexane were weighed. The mass of n-hexane was 40% of the mass of the seaweed biochar. The two were placed in a high-pressure reactor, sealed, and then placed in an oven and heated at 140 °C for 2 h, and naturally cooled to room temperature to obtain grafted nuclei. The preparation method of the seaweed biochar was the same as that in Example 1.

[0129] (5) Foaming process: The phenolic resin-like resin, surfactant Tween-80, grafted nuclei, and curing agent (hydrochloric acid with a mass fraction of 37%) were put into a high-pressure autoclave for foaming, and the foaming pressure was maintained at 0.2 MPa for 0.5 h to obtain a foamed material; among them, the mass of the curing agent was 5% of the mass of the phenolic resin-like resin, the mass of the surfactant was 4% of the mass of the phenolic resin-like resin, and the mass of the grafted nuclei was 5% of the mass of the phenolic resin-like resin. To maintain the constant pressure during the foaming process, the micro high-pressure reactor was improved. During operation, pure N2 was introduced through the inlet, and the exhaust port was slightly opened, and the internal pressure of the equipment was indicated by a pressure gauge.

[0130] (6) Carbonization treatment and graphitization treatment: The foamed material was mixed with ZnCl2 at a mass ratio of 1:3, and under N2 protection, it was heated at a heating rate of 10 °C / min to a final temperature of 700 °C for carbonization treatment for 2 h, and then naturally cooled to room temperature to obtain a carbonization treatment product. Then the carbonization treatment product was put into a high-temperature graphitization furnace, and under N2 protection, it was heated at a heating rate of 10 °C / min to 2500 °C, and held for 1 h. After holding, it was naturally cooled to room temperature to obtain a foam precursor.

[0131] (7) The foam precursor was added to sulfuric acid with a concentration of 10 wt% for modification for 1 h. The modified foam precursor was taken out, washed with distilled water until the pH of the obtained washing liquid remained unchanged, and then dried to obtain the seaweed-based foam carbon material A5.

[0132] Comparative Example 1

[0133] A preparation method of a seaweed-based foam carbon material, comprising the following steps:

[0134] (1)Liquefaction process: 5 g of unpretreated seaweed raw material and 15 g of phenol were placed in an oil bath equipped with a mechanical stirrer and a reflux condenser. While stirring and heating in the oil bath at 150 °C, 0.5 mL of 95 wt% concentrated sulfuric acid was added dropwise as a catalyst. After the addition of concentrated sulfuric acid was completed, liquefaction was carried out for 2 h. After the product was cooled to room temperature, the liquefied product was obtained.

[0135] (2)Self-assembly process: The above liquefied product, 0.72 g of NaOH, and 17 mL of 37 wt% formaldehyde aqueous solution were placed in a 70 °C water bath for self-assembly for 2 h. After self-assembly was completed, it was cooled to room temperature, and the pH value of the system was adjusted to 7.5 with hydrochloric acid. Then, rotary evaporation was carried out at 50 °C under a vacuum of 0.07 MPa to obtain a phenolic resin-like product.

[0136] (3)Preparation of transplantation nuclei: The seaweed biochar was dried at 80 °C for 2 h. Then, seaweed biochar and n-hexane were weighed, where the mass of n-hexane was 40% of the mass of seaweed biochar. The two were placed in a high-pressure reactor, sealed, and then placed in an oven and heated at 140 °C for 2 h, and then naturally cooled to room temperature to obtain transplantation nuclei. The preparation method of seaweed biochar was the same as that in Example 1.

[0137] (4)Foaming process: The phenolic resin-like product, surfactant Tween-80, transplantation nuclei, and curing agent (37% hydrochloric acid by mass fraction) were put into a high-pressure kettle for foaming, and the foaming pressure was maintained at 0.05 MPa for 0.5 h to obtain a foamed material. Among them, the mass of the curing agent was 5% of the mass of the phenolic resin-like product, the mass of the surfactant was 4% of the mass of the phenolic resin-like product, and the mass of the transplantation nuclei was 5% of the mass of the phenolic resin-like product. To maintain a constant pressure during the foaming process, the micro high-pressure reactor was improved. During operation, pure N2 was introduced through the inlet, and the exhaust port was slightly opened, and the internal pressure of the equipment was indicated by a pressure gauge.

[0138] (5)Carbonization treatment and graphitization treatment: The foamed material and ZnCl2 were mixed at a mass ratio of 1:3. Under N2 protection, it was heated at a heating rate of 5 °C / min to a final temperature of 800 °C for carbonization treatment for 2 h, and then naturally cooled to room temperature to obtain a carbonization treatment product. Then, the carbonization treatment product was put into a high-temperature graphitization furnace. Under N2 protection, it was heated at a heating rate of 10 °C / min to 2500 °C, and held for 1 h. After the holding was completed, it was naturally cooled to room temperature to obtain a foam precursor.

[0139] (6)The foam precursor was added to sulfuric acid with a concentration of 10 wt% for modification for 1 h. The modified foam precursor was taken out and washed with distilled water until the pH of the obtained washing solution remained unchanged, and then dried to obtain the seaweed-based foam carbon material D1.

[0140] Comparative Example 2

[0141] A preparation method of a seaweed-based foam carbon material, comprising the following steps:

[0142] (1) Pretreatment process: After the seaweed raw material (Enteromorpha prolifera) is cleaned, impurity-removed, dried and ball-milled, it is sieved through a 80-mesh sieve to obtain seaweed powder.

[0143] (2) Liquefaction process: Weigh 5 g of seaweed powder and 15 g of phenol and place them in an oil bath equipped with a mechanical stirrer and a reflux condenser. While heating and stirring in an oil bath at 150 °C, gradually add 0.5 mL of 95 wt% concentrated sulfuric acid as a catalyst. After the addition of the concentrated sulfuric acid is completed, carry out liquefaction for 2 h. After the product is cooled to room temperature, a liquefied product is obtained.

[0144] (3) Self-assembly process: Place the above liquefied product, 0.72 g of NaOH and 17 mL of 37 wt% formaldehyde aqueous solution in a 70 °C water bath for self-assembly for 2 h. After self-assembly is completed, cool to room temperature, adjust the pH value of the system to 7.5 with hydrochloric acid, and then carry out rotary evaporation at 50 °C under a vacuum of 0.07 MPa to obtain a phenolic resin-like product.

[0145] (4) Foaming process: Put the phenolic resin-like product, surfactant Tween-80, and curing agent (37% by mass of hydrochloric acid) into an autoclave for foaming, and maintain the foaming pressure at 0.05 MPa for 0.5 h to obtain a foamed material; among them, the mass of the curing agent is 5% of the mass of the phenolic resin-like product, and the mass of the surfactant is 4% of the mass of the phenolic resin-like product. To maintain the pressure constant during the foaming process, the micro high-pressure reaction kettle is improved. During operation, pure N2 is introduced through the inlet, and the exhaust port is slightly opened, and the internal pressure of the equipment is indicated by a pressure gauge.

[0146] (5) Carbonization treatment and graphitization treatment: Mix the foamed material and ZnCl2 in a mass ratio of 1:3, and under N2 protection, heat it at a heating rate of 5 °C / min to a final temperature of 800 °C for carbonization treatment for 2 h, and then naturally cool to room temperature to obtain a carbonization treatment product. Then put the carbonization treatment product into a high-temperature graphitization furnace, and under N2 protection, heat it at a heating rate of 10 °C / min to 2500 °C, hold for 1 h, and after the holding is completed, naturally cool to room temperature to obtain a foam precursor.

[0147] (6) Add the foam precursor to sulfuric acid with a concentration of 10 wt% for modification for 1 h. Take out the modified foam precursor, wash it with distilled water until the pH of the obtained washing liquid remains unchanged, and then dry it to obtain the seaweed-based foam carbon material D2.

[0148] Comparative Example 3

[0149] A preparation method of a seaweed-based foam carbon material, comprising the following steps:

[0150] (1) Pretreatment process: The seaweed raw material (Enteromorpha prolifera) is washed to remove impurities, dried, and ball-milled, then passed through an 80-mesh sieve to obtain seaweed powder.

[0151] (2) Liquefaction process: Weigh 5 g of seaweed powder and 15 g of phenol, place them in an oil bath equipped with a mechanical stirrer and a reflux condenser, add 0.5 mL of 95 wt% concentrated sulfuric acid dropwise under stirring with heating in the 160 °C oil bath. After the addition of concentrated sulfuric acid is complete, carry out liquefaction for 2 h. After the product is cooled to room temperature, the liquefied product is obtained.

[0152] (3) Self-assembly process: Place the above liquefied product, 0.72 g of NaOH, and 17 mL of 37 wt% formaldehyde aqueous solution in a 70 °C water bath for self-assembly for 2 h. After self-assembly is completed, cool to room temperature, adjust the pH value of the system to 7.5 with hydrochloric acid, and then carry out rotary evaporation at 50 °C and a vacuum degree of 0.07 MPa to obtain phenolic resin-like.

[0153] (4) Preparation of transplantation nuclei: The seaweed biochar is dried at 80 °C for 2 h, then weigh the seaweed biochar and n-hexane, where the mass of n-hexane is 40% of the mass of the seaweed biochar. Place the two in a high-pressure reaction kettle, seal it, and put it into an oven to heat at 140 °C for 2 h, and naturally cool to room temperature to obtain transplantation nuclei. The preparation method of the seaweed biochar is the same as that in Example 1.

[0154] (5) Foaming process: Put the phenolic resin-like, surfactant Tween-80, transplantation nuclei, and curing agent (hydrochloric acid with a mass fraction of 37%) into a high-pressure kettle for foaming, and maintain the foaming pressure at 0.05 MPa for 0.5 h to obtain a foamed material; among them, the mass of the curing agent is 5% of the mass of the phenolic resin-like, the mass of the surfactant is 4% of the mass of the phenolic resin-like, and the mass of the transplantation nuclei is 5% of the mass of the phenolic resin-like. To maintain the constant pressure during the foaming process, the micro high-pressure reaction kettle is improved. During operation, pure N2 is introduced through the air inlet, and the exhaust port is slightly opened, and the internal pressure of the equipment is indicated by a pressure gauge.

[0155] (6) Carbonization treatment and graphitization treatment: Mix the foamed material and ZnCl2 in a mass ratio of 1:3, under N2 protection, heat at a heating rate of 5 °C / min to a final temperature of 800 °C for carbonization treatment for 2 h, and naturally cool to room temperature to obtain a carbonization treatment product. Then put the carbonization treatment product into a high-temperature graphitization furnace, under N2 protection, heat at a heating rate of 10 °C / min to 2500 °C, keep it warm for 1 h, and after the heat preservation is completed, naturally cool to room temperature to obtain the seaweed-based foam carbon material D3.

[0156] Comparative Example 4

[0157] The differences from Example 1 are as follows: In (6), only carbonization treatment is carried out, and the obtained carbonized product is directly subjected to step (7), and other operations are the same as those in Example 1.

[0158] Comparative Example 5

[0159] The differences from Example 1 are as follows: In (6), ZnCl2 is not added, and carbonization treatment is directly carried out, and other operations are the same as those in Example 1.

[0160] Comparative Example 6

[0161] The differences from Example 1 are as follows: In (6), carbonization treatment is not carried out, and the temperature is directly raised to 2500 °C for graphitization treatment, and other operations are the same as those in Example 1.

[0162] Performance Test

[0163] Figure 1 They are physical appearance photos of the seaweed raw material Enteromorpha prolifera and the seaweed powder obtained from the seaweed raw material.

[0164] Figure 2 They are SEM maps of the seaweed powder (Enteromorpha prolifera) at different magnifications. It can be seen from Figure 2 that the surface is relatively flat and there is no pore structure.

[0165] Figure 3 They are the thermogravimetric curves of the seaweed powder (Enteromorpha prolifera) under nitrogen. It can be seen from Figure 3 that when the carbonization temperature exceeds 600 °C, the mass basically remains unchanged, and the sample has reached a thermally stable state. The range of 600 - 1000 °C can be used as an appropriate carbonization temperature range.

[0166] Figure 4 They are physical appearance photos of the materials obtained in the examples and comparative examples. Among them, a - l are the physical appearance photos of the materials obtained in Examples 1 - 5 and Comparative Examples 1 - 7 respectively. It can be seen from Figure 4 that through the above experimental steps, the successful preparation of macroscopic three - dimensional seaweed foam carbon materials can be achieved in Examples 1 - 5. However, there are problems such as poor foam carbon formability in the samples prepared in the comparative examples. In particular, the sample synthesized in Comparative Example 7 has a loose and fragile structure and cannot be cut into shape.

[0167] Figure 5 They are the SEM maps of the seaweed - based foam carbon material obtained in Comparative Example 2. It can be seen from Figure 5 that the microscopic pore structure of the seaweed foam carbon is non - uniform, and the pore structure is poorly developed, which may be due to uneven foaming caused by the absence of a nucleation site during the foaming process.

[0168] Figure 6 They are the SEM maps of the seaweed - based foam carbon material A1 obtained in Example 1 at different magnifications. It can be seen from Figure 6It can be seen that the carbon foam prepared under this condition has a rich and uniform pore structure.

[0169] The compressive strength of the materials obtained in the examples and comparative examples was measured according to the test method for the cold crushing strength of refractories in GB / T 5072-2008, and the results are shown in Table 1. The bulk density of the materials obtained in the examples and comparative examples was measured according to the method for measuring the bulk density of carbon materials in GB / T 24528-2009, and the results are shown in Table 1. The specific surface area of the materials obtained in the examples and comparative examples was measured by the BET method, and the results are shown in Table 1.

[0170] Table 1 Performance test results of the materials obtained in the examples and comparative examples

[0171]

[0172] It can be seen from Table 1 that the seaweed-based carbon foam materials obtained in the examples are light in weight but have relatively high compressive strength. Among them, the seaweed-based carbon foam material A1 obtained in Example 1 has the highest compressive strength and the smallest bulk density, combining the dual advantages of light weight and strong mechanical properties. The compressive strength and bulk density of the materials prepared in the comparative examples are slightly worse.

[0173] The above results show that the seaweed-based carbon foam materials prepared by the preparation method provided by the present invention have many excellent properties such as nanoporosity, low density, and high compressive strength. Moreover, the raw materials are widely sourced, green and safe. The prepared products have high mechanical strength and recyclability, and have good application prospects and can be industrially promoted.

[0174] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a seaweed-based foamed carbon material, characterized in that: The following steps are involved: Mixing seaweed powder, phenol and concentrated sulfuric acid, and liquefying them to obtain a liquefied product; the seaweed is Enteromorpha; The liquefied product, sodium hydroxide and formaldehyde aqueous solution are mixed and self-assembled to obtain a phenolic resin; The phenolic resin, surfactant, transplant core and curing agent are mixed and foamed to obtain a foamed material; The foaming material and the activator are mixed, and carbonization and graphitization are performed in sequence to obtain a foam precursor; Modifying the foam precursor to obtain the seaweed-based foam carbon material; The transplant core is prepared by heating seaweed biochar and n-hexane; The method for preparing the transplant core comprises the following steps: mixing seaweed biochar and n-hexane, and heating to obtain the transplant core; the mass of the n-hexane is 20-60% of the mass of the seaweed biochar; the heating temperature is 130-150° C., and the heating time is 1-3 hours; The activator includes zinc chloride; the mass ratio of the foaming material to the activator is 1-5:1-5; The modifying agent used in the modification is an inorganic acid solution; The method for preparing seaweed biochar comprises the following steps: subjecting seaweed to acid leaching to obtain acid leached seaweed; subjecting the acid leached seaweed to a first heating treatment to obtain a precursor; mixing the precursor with an active agent and subjecting the precursor to a second heating treatment to obtain the seaweed biochar; the acid leaching reagent is a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 0.1-0.5 mol / L, and the acid leaching time is 12-24 hours; the temperature of the first heating treatment is 600-1000° C., and the time is 1-3 hours; the active agent comprises potassium hydroxide and / or sodium hydroxide, and the mass ratio of the precursor to the active agent is 1:3-5; the temperature of the second heating treatment is 700-1000° C., and the time is 1-5 hours; The liquefaction temperature is 120-180° C., the time is 1-3 hours, and the liquefaction is carried out under oil bath conditions.

2. The preparation method according to claim 1, characterized in that: The mass fraction of the concentrated sulfuric acid is 94-96%, the mass ratio of the seaweed powder to phenol is 5-10:10-20, and the dosage ratio of the seaweed powder to concentrated sulfuric acid is 5-10g:0.3-1mL.

3. The preparation method according to claim 1, characterized in that: The mass fraction of the formaldehyde aqueous solution is 36-38%, the mass ratio of the seaweed powder to sodium hydroxide is 5-10:0.5-1, and the dosage ratio of the sodium hydroxide to the formaldehyde aqueous solution is 0.5-1g:15-20mL; The self-assembly temperature is 60-80°C and the time is 1-3h; After the self-assembly, the method further comprises: cooling the obtained self-assembly liquid to room temperature, adjusting the pH value to 7-8, and performing rotary evaporation to obtain the phenolic resin.

4. The preparation method according to claim 1, characterized in that: After the heating, the method further includes: naturally cooling the obtained heated liquid to room temperature to obtain the transplanted nucleus.

5. The preparation method according to claim 1 or 4, characterized in that: The surfactant includes one or more of Tween-80, sodium lauryl sulfate, isomeric alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate; The curing agent includes hydrochloric acid, and the mass fraction of the hydrochloric acid is 36-38%; The mass of the surfactant is 1-10% of the mass of the phenolic resin; The mass of the transplant core is 2-10% of the mass of the phenolic resin; The mass of the curing agent is 1-10% of the mass of the phenolic resin; The foaming pressure is 0.05-0.3 MPa, the time is 30-120 min, and the foaming is carried out in a high temperature and high pressure reaction device.

6. The preparation method according to claim 1, characterized in that: The temperature of the carbonization treatment is 500-1000°C, the holding time is 1-3h, the heating rate from room temperature to the temperature of the carbonization treatment is 5-15°C / min, and the atmosphere of the carbonization treatment is nitrogen; The temperature of the graphitization treatment is 2000-2800° C., the insulation time is 1-3 hours, and the heating rate from room temperature to the temperature of the graphitization treatment is 5-10° C. / min.

7. The preparation method according to claim 1, characterized in that: The inorganic acid solution is sulfuric acid, and the mass fraction of the sulfuric acid is 8-12%; The modification time is 30 to 120 minutes.

8. A seaweed-based foamed carbon material obtained by the preparation method according to any one of claims 1 to 7.

9. Application of the seaweed-based foamed carbon material according to claim 8 in the fields of chemical industry, aerospace or electronics.

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