MXene-based supercapacitor material and preparation method thereof

Abstract

The application discloses a kind of MXene-based supercapacitor materials and preparation method thereof, belong to supercapacitor electrode material technical field, by directional growth cobalt-based nanoarray on the surface of porous carbon foam, then utilize polyaniline and polymerize on the surface of MXene powder, again utilize electrostatic self-assembly and form multilayer three-dimensional network composite structure, porous carbon foam is rigid skeleton, cobalt-based nanoarray is active array unit, polyaniline / MXene core-shell nanosheet is functional coating, three synergies play a role, relieve volume expansion effect;The porous carbon foam of the application is as primary buffer unit, accommodate the overall volume expansion of cobalt-based nanoarray, avoid structure collapse, the gap between cobalt-based nanoarray each other, as secondary buffer unit, disperse the expansion stress of cobalt-based particle, MXene interlayer gap can be as tertiary buffer unit, accommodate the volume change caused in polyaniline redox process, simultaneously release stress by interlayer sliding.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor electrode material technology, specifically an MXene-based supercapacitor material and its preparation method. Background Technology

[0002] Supercapacitors play a crucial role in new energy storage and electric vehicles due to their high power density, rapid charge-discharge, and long cycle life; however, their relatively low energy density limits their large-scale application. Developing high-performance electrode materials to overcome energy storage performance bottlenecks is of significant research value for improving the energy density of supercapacitors, promoting energy structure transformation, and achieving dual-carbon goals. Nickel-cobalt based oxides and sulfides have attracted considerable attention due to their high theoretical specific capacity, tunable structure, and redox reaction capabilities. However, they also suffer from poor conductivity and structural collapse under long-cycle charge-discharge, leading to poor cycle stability. Two-dimensional material MXene exhibits excellent conductivity, mechanical flexibility, and hydrophilicity, but it also faces challenges, such as the tendency for MXene layers to stack and aggregate, resulting in low capacitance and hindering its development as an energy storage material.

[0003] Chinese patent application CN114864297A discloses a method for preparing an MXene / zinc oxide / graphene composite material. In this method, MXene and graphene are added to form a three-dimensional network structure on zinc oxide. The excess space between zinc oxide, MXene, and graphene forms a buffer region to temporarily store excess electrolyte ions, preventing volume expansion during charging and discharging. However, zinc oxide itself undergoes volume changes during ion insertion / extraction. The buffer region can only temporarily accommodate some of the expansion stress. As the number of cycles increases, this suppression effect cannot cope with the volume changes under long cycles, resulting in the cycle life of the capacitor material failing to meet the requirements of practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide an MXene-based supercapacitor material and its preparation method. A porous carbon nanoarray is obtained by directionally growing a cobalt-based nanoarray on the surface of porous carbon foam. Then, polyaniline is polymerized on the surface of MXene powder to obtain polyaniline MXene. Finally, polyaniline MXene and the porous carbon nanoarray are electrostatically self-assembled to form a multilayer three-dimensional interconnected network composite structure. The essence of this structure is that the porous carbon foam serves as a rigid framework, the cobalt-based nanoarray as an active array unit, and the polyaniline / MXene core-shell nanosheets as a functional coating layer. These three elements work synergistically as buffer units to alleviate the volume expansion effect.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing an MXene-based supercapacitor material includes the following steps: Step 1: Using formaldehyde and phenol as raw materials and ammonium dihydrogen phosphate as a modifier, the carbon is obtained by polycondensation followed by calcination and carbonization to obtain porous foamed carbon.

[0006] Step 2: Using urea as the nitrogen source, cobalt nitrate hexahydrate as the cobalt source, and ammonium fluoride as the regulator, a cobalt-based precursor is grown on the surface of porous foam carbon by hydrothermal method, and then annealing is used to form a cobalt-based nanoarray to obtain cobalt composite porous foam carbon.

[0007] Step 3: Using MXene powder as a carrier, aniline and 3-aminophenylboronic acid are copolymerized under acidic conditions to covalently bond boric acid groups onto polyaniline, forming polyaniline-coated MXene powder. Then, the boric acid-containing polyaniline and p-hydroxybenzenesulfonic acid are bonded through dynamic borate ester bonds, allowing sulfonic acid groups to be grafted onto the polyaniline backbone, resulting in polyaniline / MXene core-shell nanosheets.

[0008] Step 4: MXene-based supercapacitor materials are obtained by electrostatic self-assembly of cobalt composite porous carbon foam with the abundant functional groups on the surface of polyaniline / MXene core-shell nanosheets.

[0009] Furthermore, the specific preparation steps for porous foamed carbon are as follows: A 20-22% (w / w) formaldehyde solution, ammonium dihydrogen phosphate, phenol, and deionized water are added to a reaction vessel and stirred for 1-2 hours at 50-60℃ and 500-600 rpm. Then, a 1-2% (w / w) sodium hydroxide solution is added, and the reaction continues for 1-2 hours. The mixture is then heated at 90-95℃ for 1-2 hours. The product is cooled to 60-70℃, and the pH is adjusted to neutral with a 1-2 mol / L hydrochloric acid solution. The product is then dehydrated by vacuum distillation at 0.092 MPa. The product is then mixed with Tween 80, n-pentane, and concentrated sulfuric acid and stirred at 2000-2200 rpm for 15-20 minutes. The mixture is placed in a mold, foamed, and cured at 60-70℃ for 20-24 hours. Finally, it is transferred to a muffle furnace and calcined at 700-800℃ for 2-3 hours under a nitrogen atmosphere to obtain porous foamed carbon.

[0010] Furthermore, the ratio of formaldehyde solution, ammonium dihydrogen phosphate, phenol, deionized water, sodium hydroxide solution, Tween 80, n-pentane, and concentrated sulfuric acid is 280-290mL: 52-54g: 260-270g: 2-3L: 50-52mL: 5-7mL: 200-250mL: 20-22mL.

[0011] Furthermore, the specific preparation steps of cobalt composite porous foam carbon are as follows: Urea, ammonium fluoride, cobalt nitrate hexahydrate, and deionized water were added to a polytetrafluoroethylene high-pressure reactor and stirred for 20-30 minutes at 20-25℃ and 500-600 r / min. Then, porous foamed carbon was added, and the mixture was heated to 120-130℃ for hydrothermal reaction for 6-8 hours. After natural cooling to room temperature, the mixture was filtered, and the precipitate was washed 2-4 times with deionized water and ethanol, respectively. The precipitate was then vacuum dried at 60-80℃ for 1-2 hours and transferred to a muffle furnace. Under an argon atmosphere, the mixture was heated to 350-360℃ and held for 2-2.5 hours to obtain cobalt composite porous foamed carbon.

[0012] Furthermore, the ratio of urea, ammonium fluoride, cobalt nitrate hexahydrate, deionized water, and porous foamed carbon is 60-70g: 40-50g: 15-20g: 300-400mL: 50-60g.

[0013] Furthermore, the specific preparation steps of polyaniline / MXene core-shell nanosheets are as follows: Aniline, 3-aminophenylboronic acid, p-hydroxybenzenesulfonic acid, and a 1 mol / L hydrochloric acid solution were added to a reaction vessel and stirred for 20-30 min at 20-25℃ and 500-600 r / min. Then, ammonium persulfate and MXene powder were added, the temperature was lowered to 0-4℃, and stirring was continued for 8-10 h. The mixture was filtered, and the precipitate was washed 2-4 times with deionized water and ethanol, respectively. The precipitate was then vacuum dried at 60-80℃ for 1-2 h to obtain polyaniline / MXene core-shell nanosheets.

[0014] Furthermore, the ratio of aniline, 3-aminophenylboronic acid, p-hydroxybenzenesulfonic acid, hydrochloric acid solution, ammonium persulfate and MXene powder is 100-200mL: 5-6g: 500-600mL: 600-700mL: 2-4g: 5-7g.

[0015] Furthermore, the specific preparation steps of MXene-based supercapacitor materials are as follows: Polyaniline / MXene core-shell nanosheets and deionized water were added to a reaction vessel and stirred for 20-30 minutes at 20-25℃ and 500-600 rpm. Then, cobalt composite porous carbon foam was added, and stirring was continued for 10-12 minutes. The mixture was then vacuum dried at 60-80℃ for 15-20 minutes, stirred again, and dried until the loading was 2-3 mg / cm³. 2 MXene-based supercapacitor materials containing a multilayer three-dimensional interconnect network composite structure were obtained.

[0016] Furthermore, the ratio of polyaniline / MXene core-shell nanosheets, deionized water, and cobalt composite porous foam carbon is 23-25g: 1-2L: 10-12g.

[0017] The beneficial effects of this invention are: 1. The MXene-based supercapacitor material prepared in this invention is obtained by directionally growing a cobalt-based nanoarray on the surface of porous carbon foam to obtain a porous carbon nanoarray, then using polyaniline to polymerize on the surface of MXene powder to obtain polyaniline MXene, and then using polyaniline MXene and porous carbon nanoarray to electrostatically self-assemble to form a multilayer three-dimensional interconnected network composite structure. The essence of this structure is that porous carbon foam is a rigid framework, cobalt-based nanoarray is an active array unit, and polyaniline / MXene core-shell nanosheets are a functional coating layer. The three act as buffer units and work together to alleviate the volume expansion effect.

[0018] 2. The porous carbon nanoarray of the present invention has a continuous pore structure, which can serve as a growth substrate for cobalt-based nanoarrays. The porous structure not only ensures the high specific surface area and electron transport channels of the material, but also provides sufficient loading space for subsequent electrostatic self-assembly. The cobalt-based nanoarrays are oriented vertically, which promotes good dispersion of cobalt metal, exposes more active sites, and forms a strong interfacial bond with porous foam carbon, thus preventing detachment.

[0019] 3. The polyaniline MXene of the present invention utilizes MXene with a large specific surface area as a carrier, and fixes sulfonic acid groups onto the polyaniline backbone through grafting and copolymerization. The presence of sulfonic acid groups helps to promote the redox reaction of polyaniline and enhance its pseudocapacitive properties. Furthermore, the cobalt-based nanoarray can provide abundant redox active sites. The high conductivity and two-dimensional layered structure of MXene accelerate charge transport, and the two can synergistically improve the reversibility of electrode reactions and structural stability. The large surface area and electron transport properties of MXene can alleviate the entanglement and aggregation of one-dimensional molecular chains of polyaniline and provide double-layer capacitance.

[0020] 4. The MXene-based supercapacitor material prepared by this invention contains a multilayer three-dimensional interconnected network composite structure in which porous foamed carbon can serve as a primary buffer unit to accommodate the overall volume expansion of the cobalt-based nanoarray and prevent macroscopic structural collapse. The gaps between the cobalt-based nanoarrays can serve as secondary buffer units to disperse the expansion stress of the cobalt-based particles. The MXene interlayer voids in polyaniline MXene can serve as tertiary buffer units to accommodate the volume changes caused by the oxidation-reduction process of polyaniline and release stress through interlayer sliding. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1: A method for preparing an MXene-based supercapacitor material, comprising the following steps: S1: Add 280-290 mL of 20-22% formaldehyde solution, 52-54 g of ammonium dihydrogen phosphate, 260-270 g of phenol, and 2-3 L of deionized water to a reaction vessel. Stir for 1-2 h at 50-60℃ and 500-600 r / min. Then add 50-52 mL of 1-2% sodium hydroxide solution and continue the reaction for 1-2 h. Heat at 90-95℃ for 1-2 h. Cool the product to 60-70℃ and then react with 1-2 mol / L hydrochloric acid solution. Adjust the pH to neutral and distill under reduced pressure at 0.092 MPa to remove water. Mix the product with 5-7 mL Tween 80, 200-250 mL n-pentane and 20-22 mL concentrated sulfuric acid. Stir at 2000-2200 r / min for 15-20 min. Place the mixture in a mold and foam and solidify at 60-70℃ for 20-24 h. Then transfer it to a muffle furnace and calcine at 700-800℃ for 2-3 h under a nitrogen atmosphere to obtain porous foamed carbon with an average particle size of 400 μm.

[0023] S2: Add 60-70g urea, 40-50g ammonium fluoride, 15-20g cobalt nitrate hexahydrate and 300-400mL deionized water to a polytetrafluoroethylene high-pressure reactor. Stir for 20-30min at 20-25℃ and 500-600r / min. Then add 50-60g porous foamed carbon, heat to 120-130℃, and perform hydrothermal reaction for 6-8h. Allow to cool naturally to room temperature, filter, and wash the precipitate 2-4 times with deionized water and ethanol respectively. Vacuum dry at 60-80℃ for 1-2h, transfer to a muffle furnace, and heat to 350-360℃ under argon atmosphere for 2-2.5h to obtain cobalt composite porous foamed carbon with cobalt-based nanoarrays on the surface.

[0024] Fluoride ions in ammonium fluoride can be selectively adsorbed on porous carbon foam. During the formation of cobalt-based nanoarrays, they can suppress the random growth of crystals and induce them to grow into an array along a direction perpendicular to the surface of the porous carbon foam.

[0025] S3: Add 100-200 mL of aniline, 5-6 g of 3-aminophenylboronic acid, 500-600 mL of p-hydroxybenzenesulfonic acid, and 600-700 mL of 1 mol / L hydrochloric acid solution to a reaction vessel. Stir for 20-30 min at 20-25℃ and 500-600 r / min. Then add 2-4 g of ammonium persulfate and 5-7 g of MXene powder. Cool to 0-4℃ and continue stirring for 8-10 h. Filter and wash the precipitate 2-4 times with deionized water and ethanol, respectively. Vacuum dry at 60-80℃ for 1-2 h to obtain polyaniline / MXene core-shell nanosheets with an average particle size of 10 μm.

[0026] S4: Add 23-25g of polyaniline / MXene core-shell nanosheets and 1-2L of deionized water to a reactor. Stir for 20-30min at 20-25℃ and 500-600r / min. Then add 10-12g of cobalt composite porous carbon foam and continue stirring for 10-12min. Vacuum dry at 60-80℃ for 15-20min, stir again, and dry until the loading is 2-3mg / cm³. 2 MXene-based supercapacitor materials containing a multilayer three-dimensional interconnect network composite structure were obtained.

[0027] Example 2: A method for preparing an MXene-based supercapacitor material, comprising the following steps: S1: Add 285 mL of 21% formaldehyde solution, 53 g of ammonium dihydrogen phosphate, 265 g of phenol, and 2.5 L of deionized water to a reaction vessel. Stir for 1.5 h at 55 °C and 550 r / min. Then add 51 mL of 1.5% sodium hydroxide solution and continue the reaction for 1.5 h. Heat at 92.5 °C for 1.5 h. Cool the product to 65 °C and adjust the temperature with 1.5 mol / L hydrochloric acid solution. The pH was adjusted to neutral, and the mixture was dehydrated by vacuum distillation at a vacuum degree of 0.092 MPa. The product was then mixed with 6 mL of Tween 80, 225 mL of n-pentane, and 21 mL of concentrated sulfuric acid. The mixture was stirred at 2100 r / min for 17.5 min, placed in a mold, foamed and cured at 65 °C for 22 h, and then transferred to a muffle furnace and calcined at 750 °C for 2.5 h under a nitrogen atmosphere to obtain porous foamed carbon with an average particle size of 400 μm.

[0028] S2: Add 65g urea, 45g ammonium fluoride, 17.5g cobalt nitrate hexahydrate and 350mL deionized water to a polytetrafluoroethylene high-pressure reactor. Stir for 25min at 22.5℃ and 550r / min. Then add 55g porous foamed carbon, heat to 125℃, and hydrothermally react for 7h. Cool naturally to room temperature, filter, wash the precipitate three times with deionized water and ethanol respectively, dry under vacuum at 70℃ for 1.5h, transfer to a muffle furnace, and heat to 355℃ and hold for 2.25h under an argon atmosphere to obtain cobalt composite porous foamed carbon with cobalt-based nanoarrays on the surface.

[0029] S3: Add 150 mL of aniline, 5.5 g of 3-aminophenylboronic acid, 550 mL of p-hydroxybenzenesulfonic acid, and 650 mL of 1 mol / L hydrochloric acid solution to a reaction vessel. Stir for 25 min at 22.5 °C and 550 r / min. Then add 3 g of ammonium persulfate and 6 g of MXene powder. Cool to 2 °C and continue stirring for 9 h. Filter and wash the precipitate three times with deionized water and ethanol, respectively. Dry under vacuum at 70 °C for 1.5 h to obtain polyaniline / MXene core-shell nanosheets with an average particle size of 10 μm.

[0030] S4: Add 24g of polyaniline / MXene core-shell nanosheets and 1.5L of deionized water to a reactor, stir for 25min at 22.5℃ and 550r / min, then add 11g of cobalt composite porous carbon foam, continue stirring for 11min, and vacuum dry at 70℃ for 17.5min. Stir again and dry until the loading is 2.5mg / cm³. 2 MXene-based supercapacitor materials containing a multilayer three-dimensional interconnect network composite structure were obtained.

[0031] Example 3: A method for preparing an MXene-based supercapacitor material, comprising the following steps: S1: 290 mL of 22% formaldehyde solution, 54 g of ammonium dihydrogen phosphate, 270 g of phenol and 3 L of deionized water were added to a reaction vessel and stirred at 60 °C and 600 r / min for 2 h. Then, 52 mL of 2% sodium hydroxide solution was added and the reaction was continued for 2 h. The mixture was heated at 95 °C for 2 h and cooled to 70 °C. The pH was adjusted to neutral with 2 mol / L hydrochloric acid solution and then distilled under reduced pressure at 0.092 MPa to remove water. The product was mixed with 7 mL of Tween 80, 250 mL of n-pentane and 22 mL of concentrated sulfuric acid and stirred at 2200 r / min for 20 min. The mixture was placed in a mold, foamed and cured at 70 °C for 24 h, and then transferred to a muffle furnace and calcined at 800 °C for 3 h under a nitrogen atmosphere to obtain porous foamed carbon with an average particle size of 400 μm.

[0032] S2: Add 70g urea, 50g ammonium fluoride, 20g cobalt nitrate hexahydrate and 400mL deionized water to a polytetrafluoroethylene high-pressure reactor. Stir for 30min at 25℃ and 600r / min. Then add 60g porous foamed carbon, heat to 130℃, and hydrothermally react for 8h. Cool naturally to room temperature, filter, wash the precipitate four times with deionized water and ethanol respectively, dry under vacuum at 80℃ for 2h, transfer to a muffle furnace, and heat to 360℃ for 2.5h under argon atmosphere to obtain cobalt composite porous foamed carbon with cobalt-based nanoarrays on the surface.

[0033] S3: Add 200 mL of aniline, 6 g of 3-aminophenylboronic acid, 600 mL of p-hydroxybenzenesulfonic acid, and 700 mL of 1 mol / L hydrochloric acid solution to a reaction vessel. Stir for 30 min at 25 °C and 600 r / min. Then add 4 g of ammonium persulfate and 7 g of MXene powder. Cool to 4 °C and continue stirring for 10 h. Filter and wash the precipitate four times with deionized water and ethanol, respectively. Dry under vacuum at 80 °C for 2 h to obtain polyaniline / MXene core-shell nanosheets with an average particle size of 10 μm.

[0034] S4: Add 25g of polyaniline / MXene core-shell nanosheets and 2L of deionized water to a reactor, stir for 30min at 25℃ and 600r / min, then add 12g of cobalt composite porous carbon foam, continue stirring for 12min, vacuum dry at 80℃ for 20min, stir again and dry until the loading is 3mg / cm³. 2 MXene-based supercapacitor materials containing a multilayer three-dimensional interconnect network composite structure were obtained.

[0035] Comparative Example 1: Based on Example 3, the ammonium fluoride in step S2 was omitted, while the other steps remained unchanged, and MXene-based supercapacitor materials were prepared.

[0036] Comparative Example 2: Based on Example 3, the polyaniline / MXene core-shell nanosheets in step S4 were replaced with commercially available polyaniline, while the other steps remained unchanged, to prepare MXene-based supercapacitor materials.

[0037] Comparative Example 3: Based on Example 3, polyaniline / MXene core-shell nanosheets and cobalt composite porous carbon foam from step S4 were mixed at a mass ratio of 1:3 to prepare MXene-based supercapacitor materials.

[0038] In the examples and comparative examples: The MXene powder is specifically Ti3C2 titanium dicarbide MXene (all-hydroxyl MXene powder), purchased from Xi'an Qiyue Biotechnology Co., Ltd., item number: 52352.

[0039] The MXene-based supercapacitor materials obtained in Examples 1-3 and Comparative Examples 1-3 were cut into 1×1cm pieces as working electrodes, silver / silver chloride as reference electrodes, and platinum sheet electrodes as counter electrodes. 1M sulfuric acid was used as the electrolyte solution. The tests were conducted using an electrochemical workstation, cycling 8000 times at a current of 2A to test the capacitance retention rate. The results are shown in Table 1. Table 1 As shown in Table 1, ammonium fluoride in Comparative Example 1 is a regulator of cobalt-based nanoarrays. It can selectively adsorb onto specific crystal faces of cobalt-based crystals, inhibiting random growth and inducing crystals to align vertically along the surface of porous carbon foam into an array. Without ammonium fluoride, the cobalt-based precursor loses the constraint of crystal face growth during hydrothermal processes and cannot form an ordered nanoarray. Instead, it is deposited on the surface of porous carbon foam as random particle agglomerates, directly resulting in poor dispersion of cobalt-based particles and insufficient exposure of active sites. Without the array gaps as secondary volume expansion buffer units, the particle expansion stress cannot be dispersed.

[0040] In Comparative Example 2, the two-dimensional layered structure of MXene provides high conductivity and interlayer buffer units, while polyaniline provides pseudocapacitive active sites. Furthermore, MXene can alleviate the entanglement and aggregation of polyaniline molecular chains. When replaced with pure polyaniline, the material loses the support of MXene, and the polyaniline molecular chains undergo severe aggregation, forming a dense blocky structure. At the same time, it lacks the two-dimensional interlayer channels of MXene as three-dimensional volume expansion buffer units.

[0041] In Comparative Example 3, physical mixing alone could not achieve uniform coating of cobalt composite porous carbon foam with polyaniline / MXene core-shell nanosheets, resulting in only discontinuous local coating layers. The synergistic effect could not be fully utilized, and the uncoated cobalt-based nanoarrays were directly exposed, so the expansion stress could not be relieved, and the ability to act as a tertiary buffer unit was reduced.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing an MXene-based supercapacitor material, characterized in that, Includes the following steps: Step 1: Using urea as nitrogen source, cobalt nitrate hexahydrate as cobalt source, and ammonium fluoride as regulator, a cobalt-based precursor is grown on the surface of porous foam carbon by hydrothermal method, and then annealing is used to form a cobalt-based nanoarray to obtain cobalt composite porous foam carbon. Step 2: Using MXene powder as a carrier, aniline and 3-aminophenylboronic acid are copolymerized under acidic conditions to covalently bond boric acid groups onto polyaniline, forming polyaniline-coated MXene powder. Then, the boric acid-containing polyaniline and p-hydroxybenzenesulfonic acid are bonded through dynamic borate ester bonds, allowing sulfonic acid groups to be grafted onto the polyaniline backbone, resulting in polyaniline / MXene core-shell nanosheets. Step 3: MXene-based supercapacitor materials are obtained by electrostatic self-assembly of cobalt composite porous carbon foam with the abundant functional groups on the surface of polyaniline / MXene core-shell nanosheets.

2. The method for preparing an MXene-based supercapacitor material according to claim 1, characterized in that, The specific preparation steps for the porous foamed carbon are as follows: Add 20-22 wt% formaldehyde solution, ammonium dihydrogen phosphate, phenol, and deionized water to a reaction vessel, stir at 50-60℃ and 500-600 r / min for 1-2 h, then add 1-2 wt% sodium hydroxide solution, continue the reaction for 1-2 h, heat at 90-95℃ for 1-2 h, cool to 60-70℃, adjust the pH to neutral with 1-2 mol / L hydrochloric acid solution, and dehydrate by vacuum distillation at 0.092 MPa. Mix the product with Tween 80, n-pentane, and concentrated sulfuric acid, stir at 2000-2200 r / min for 15-20 min, place in a mold, foam and cure at 60-70℃ for 20-24 h, then transfer to a muffle furnace and calcine at 700-800℃ for 2-3 h under a nitrogen atmosphere to obtain porous foamed carbon.

3. The method for preparing an MXene-based supercapacitor material according to claim 2, characterized in that, The ratio of formaldehyde solution, ammonium dihydrogen phosphate, phenol, deionized water, sodium hydroxide solution, Tween 80, n-pentane, and concentrated sulfuric acid is 280-290mL: 52-54g: 260-270g: 2-3L: 50-52mL: 5-7mL: 200-250mL: 20-22mL.

4. The method for preparing an MXene-based supercapacitor material according to claim 1, characterized in that, The specific preparation steps of the cobalt composite porous foam carbon are as follows: Urea, ammonium fluoride, cobalt nitrate hexahydrate, and deionized water are added to a polytetrafluoroethylene high-pressure reactor and stirred at 20-25℃ and 500-600 r / min for 20-30 min. Then, porous foamed carbon is added, and the mixture is heated to 120-130℃ for hydrothermal reaction for 6-8 h. After naturally cooling to room temperature, the mixture is filtered, washed, vacuum dried, and transferred to a muffle furnace. Under an argon atmosphere, it is heated to 350-360℃ and held for 2-2.5 h to obtain cobalt composite porous foamed carbon.

5. The method for preparing an MXene-based supercapacitor material according to claim 4, characterized in that, The ratio of urea, ammonium fluoride, cobalt nitrate hexahydrate, deionized water, and porous foam carbon is 60-70g: 40-50g: 15-20g: 300-400mL: 50-60g.

6. The method for preparing an MXene-based supercapacitor material according to claim 1, characterized in that, The specific preparation steps of the polyaniline / MXene core-shell nanosheets are as follows: Aniline, 3-aminophenylboronic acid, p-hydroxybenzenesulfonic acid, and a 1 mol / L hydrochloric acid solution were added to a reaction vessel and stirred at 20-25°C and 500-600 r / min for 20-30 min. Then, ammonium persulfate and MXene powder were added, the temperature was lowered to 0-4°C, and stirring was continued for 8-10 h. The mixture was then filtered, washed, and vacuum dried to obtain polyaniline / MXene core-shell nanosheets.

7. The method for preparing an MXene-based supercapacitor material according to claim 6, characterized in that, The ratio of aniline, 3-aminophenylboronic acid, p-hydroxybenzenesulfonic acid, hydrochloric acid solution, ammonium persulfate and MXene powder is 100-200mL: 5-6g: 500-600mL: 600-700mL: 2-4g: 5-7g.

8. The method for preparing an MXene-based supercapacitor material according to claim 1, characterized in that, The specific preparation steps of the MXene-based supercapacitor material are as follows: Polyaniline / MXene core-shell nanosheets and deionized water were added to a reaction vessel and stirred at 20-25℃ and 500-600 rpm for 20-30 min. Then, cobalt composite porous carbon foam was added, and stirring was continued for 10-12 min. The mixture was then vacuum dried at 60-80℃ for 15-20 min, stirred again, and dried to obtain a loading of 2-3 mg / cm³. 2 MXene-based supercapacitor materials.

9. The method for preparing an MXene-based supercapacitor material according to claim 8, characterized in that, The ratio of polyaniline / MXene core-shell nanosheets, deionized water, and cobalt composite porous foam carbon is 23-25g: 1-2L: 10-12g.

10. An MXene-based supercapacitor material, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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