Three-dimensional interconnected porous skeleton structure carbon aerogel as well as preparation method and application thereof

Abstract

The invention provides three-dimensional interconnected porous skeleton structure carbon aerogel as well as a preparation method and application thereof, and belongs to the technical field of electrode materials. The green deep eutectic solvent is used for cellulose modification, and efficient carboxylation can be realized under the condition that a crystal structure is not damaged, so that the dispersity and the compatibility with conductive components are improved. The MOF template is used as a sacrificial template, a porous structure is formed through induction in carbonization, and the conductivity of the material is improved through the metal center effect; a three-dimensional network is constructed by using a gelatinizing agent, so that the gel strength is improved, and the aerogel skeleton forming is ensured. According to the method, the carbon aerogel is prepared by combining carboxylation of the deep eutectic solvent, doping of the natural polymer gelatinizing agent and regulation and control of the MOF soft template, and the structure of the carbon aerogel and the electrochemical performance of the carbon aerogel in a three-electrode system are remarkably improved by utilizing the synergistic effect of the three components.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and in particular to a three-dimensional interconnected porous framework carbon aerogel, its preparation method, and its application. Background Technology

[0002] With the rapid growth in energy storage demand, supercapacitors have attracted widespread attention due to their high power density, fast charge-discharge, and long cycle life. However, there is still room for improvement in their energy density, and the evaluation of material performance usually relies on preliminary electrochemical tests using a three-electrode system. Although existing carbon aerogel materials possess large specific surface areas and porous structures, they still have significant shortcomings in terms of conductivity, pore distribution, and cycle stability.

[0003] To improve performance, researchers are exploring the use of biomass resources as precursors for carbon materials. Cellulose nanofibers (CNFs) have become important candidate materials due to their wide availability, low cost, high crystallinity, and good mechanical properties. However, their low intrinsic electrical conductivity and simple pore structure limit their application in electrochemical energy storage. Traditional oxidation modification methods (such as TEMPO oxidation and esterification reactions) can introduce functional groups, but they often lead to cellulose degradation and are difficult to scale up. Summary of the Invention

[0004] The purpose of this invention is to provide a three-dimensional interconnected porous framework carbon aerogel, its preparation method, and its application. The obtained three-dimensional interconnected porous framework carbon aerogel has a high specific surface area, abundant pore structure, and good electrochemical activity. It can avoid cellulose degradation and is suitable for large-scale preparation of high-performance supercapacitor electrode materials.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a three-dimensional interconnected porous framework carbon aerogel, comprising the following steps: Cellulose raw materials are mixed with a deep eutectic solvent and carboxylated to obtain carboxylated cellulose; The carboxylated cellulose, MOF template and gelling agent were mixed and freeze-dried to obtain an aerogel precursor; The aerogel precursor was carbonized in a protective atmosphere to obtain a three-dimensional interconnected porous framework carbon aerogel.

[0006] Preferably, the deep eutectic solvent is composed of citric acid, choline chloride and water, and the mass ratio of citric acid, choline chloride and water is 2.5~3.5:0.8~1.2:0.8~1.2.

[0007] Preferably, the cellulose raw material is a cellulose-based slurry derived from plants; the mass ratio of the cellulose raw material to the deep eutectic solvent is 1:(25~35).

[0008] Preferably, the carboxylation treatment is performed at a temperature of 120-140°C for 2-4 hours.

[0009] Preferably, the MOF template includes Zn-BTC, ZIF-8, or ZIF-67; the gelling agent includes gelatin, polyvinyl alcohol, sodium alginate, or chitosan. The method for preparing Zn-BTC includes the following steps: Zinc nitrate hexahydrate, 1,3,5-benzenetricarboxylic acid, and an organic solvent were mixed and subjected to a solvothermal reaction to obtain Zn-BTC; the temperature of the solvothermal reaction was 100~140℃ and the time was 8~24h.

[0010] Preferably, the mass ratio of the carboxylated cellulose, MOF template and gelling agent is 1:(0.5~2):(0.5~2).

[0011] Preferably, the freeze-drying temperature is -50 to -40°C and the time is 40 to 60 hours.

[0012] Preferably, the carbonization temperature is 800~1000℃ and the time is 2~4h; the protective atmosphere includes argon or nitrogen.

[0013] This invention provides a three-dimensional interconnected porous framework carbon aerogel prepared by the preparation method described above, which has a porous structure and a specific surface area of ​​600~900 m². 2 / g, with a pore size range of 1~40 nm.

[0014] This invention provides the application of the three-dimensional interconnected porous framework carbon aerogel described above as an electrode material in the field of supercapacitors.

[0015] This invention provides a method for preparing a three-dimensional interconnected porous framework carbon aerogel. The method involves carboxylating cellulose raw materials with a deep eutectic solvent (H-DES), combining a gelling agent with a metal-organic framework template, and then freeze-drying and carbonizing to obtain a three-dimensional interconnected porous carbon aerogel. This invention utilizes a green deep eutectic solvent for cellulose modification, enabling efficient carboxylation without damaging the crystal structure, thereby improving dispersibility and compatibility with conductive components. The MOF template acts as a sacrificial template, inducing the formation of a porous structure during carbonization and improving the material's conductivity through the metal center effect. The gelling agent is used to construct a three-dimensional network, improve gel strength, and ensure the formation of the aerogel framework. This invention combines deep eutectic solvent carboxylation, natural polymer gelling agent doping, and soft template control to prepare carbon aerogels. This method utilizes the synergistic effect of these three types of components to significantly improve the structure of the carbon aerogel and its electrochemical performance in a three-electrode system.

[0016] The beneficial effects of this invention are: Green modification: Carboxylation of cellulose raw materials is carried out using deep eutectic solvent (H-DES), which introduces abundant carboxyl groups under mild conditions, improves its dispersibility and compatibility with other components, and avoids the structural degradation and environmental pollution problems caused by traditional strong oxidants.

[0017] Co-assembly: A gelling agent is used as a structural crosslinking agent, mixed with carboxylated cellulose and MOF templates to construct a stable three-dimensional network structure. Moreover, when gelatin is used, it can provide nitrogen doping during carbonization, which helps to improve the electrochemical activity and pseudocapacitive contribution of the material in the three-electrode system, while enhancing the stability of the framework.

[0018] Template regulation: During carbonization, the MOF template decomposes as a sacrificial template, inducing the formation of a porous structure, increasing the specific surface area and optimizing ion transport channels. At the same time, its metal center has a catalytic effect, which helps to improve the conductivity and electrochemical performance of the material in a three-electrode system.

[0019] This invention organically combines green modification of cellulose, gelling agents, and porous structure construction to achieve the preparation of low-cost, scalable supercapacitor electrode materials with both high energy density and long lifespan. Through testing with a three-electrode system, the three-dimensional interconnected porous framework carbon aerogel prepared in this invention exhibits excellent electrochemical activity in a three-electrode system, while also possessing a reasonable pore structure and a high specific surface area.

[0020] The green deep eutectic solvent (H-DES) used in this invention is inexpensive and environmentally friendly, with mild reaction conditions, simple and environmentally friendly process, low cost and green sustainability. The resulting material has a high specific surface area, rich pore structure and good electrochemical activity, and is suitable as a precursor for supercapacitor electrode materials, enabling the large-scale preparation of high-performance supercapacitor electrode materials. Attached Figure Description

[0021] Figure 1 GZBTC in Example 1 0.2 Typical scanning electron microscope (SEM) images at different magnifications: -900 nm, where (a) is 2 μm and (b) is 500 nm. Figure 2 For C-CNFs-900, ZBC-900 and GZBTC 0.2 Raman spectrum at -900; Figure 3 For C-CNFs-900, ZBC-900 and GZBTC 0.2 -900 XPS full spectrum; Figure 4For C-CNFs-900, ZBC-900 and GZBTC 0.2 -900 nitrogen adsorption-desorption isotherm (a) and pore size distribution curve (b); Figure 5 For C-CNFs-900, ZBC-900 and GZBTC 0.2 The constant current charge-discharge curve (GCD) of the -900 sample, with a current density of 0.5 A. ¹; Figure 6 The graphs show the constant current charge-discharge (GCD) curves of samples from Examples 1-5, with a current density of 0.5 A. ¹; Figure 7 For C-CNFs-900, ZBC-900 and GZBTC 0.2 Cyclic voltammetry (CV) curves of the -900 sample, scan rate 5 mV· ¹; Figure 8 The cyclic voltammetry (CV) curves for the samples in Examples 1-5 are shown, with a scan rate of 5 mV. ¹; Figure 9 For C-CNFs-900, ZBC-900 and GZBTC 0.2 -900 Specific capacitance variation under different current densities. Detailed Implementation

[0022] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0023] This invention provides a method for preparing a three-dimensional interconnected porous framework carbon aerogel, comprising the following steps: Cellulose raw materials are mixed with a deep eutectic solvent and carboxylated to obtain carboxylated cellulose; The carboxylated cellulose, MOF template and gelling agent were mixed and freeze-dried to obtain an aerogel precursor; The aerogel precursor was carbonized in a protective atmosphere to obtain a three-dimensional interconnected porous framework carbon aerogel.

[0024] This invention involves mixing cellulose raw materials with a deep eutectic solvent and then performing a carboxylation treatment to obtain carboxylated cellulose.

[0025] In this invention, the cellulose raw material is preferably a cellulose-based pulp derived from plants; the cellulose-based pulp preferably includes bleached or unbleached wood pulp, bamboo pulp, sugarcane pulp, wheat straw pulp, rice straw pulp, reed pulp, or crop straw pulp.

[0026] The present invention does not have any particular limitation on the source of the cellulose-based pulp, and commercially available products well known in the art or obtained in a well-known manner are acceptable; in the embodiments of the present invention, the cellulose raw material is preferably bleached sugarcane pulp.

[0027] In this invention, the deep eutectic solvent is preferably composed of citric acid, choline chloride, and water, and the mass ratio of citric acid, choline chloride, and water is preferably 2.5~3.5:0.8~1.2:0.8~1.2, more preferably 2.8~3.2:0.9~1.1:0.9~1.1, and even more preferably 3:1:1. This invention does not impose any particular limitation on the preparation method of the deep eutectic solvent; the reagents can be mixed according to methods well known in the art, and stirred at 80°C for 30 min.

[0028] In this invention, the mass ratio of the cellulose raw material to the deep eutectic solvent is preferably 1:(25~35), more preferably 1:(28~32), and even more preferably 1:30.

[0029] The present invention preferably involves mixing cellulose raw materials with water and stirring at high speed for 30 minutes at room temperature to allow the fibers to fully absorb water, swell, and disperse evenly. The resulting slurry is then filtered to form a wet cake, which is then added to a deep eutectic solvent for carboxylation treatment.

[0030] In this invention, the temperature of the carboxylation treatment is preferably 120~140℃, more preferably 130℃, and the time is preferably 2~4h, more preferably 3h.

[0031] After the carboxylation treatment is completed, the reaction product is preferably filtered and washed multiple times with deionized water until the filtrate is pH neutral to remove residual eutectic solvent and byproducts. The filtrate is then redispersed in deionized water and sonicated to obtain a carboxylated cellulose suspension. After freeze-drying at -50°C, carboxylated cellulose is obtained. The present invention does not have a special limitation on the concentration of the above suspension, which can be adjusted according to the requirements.

[0032] After obtaining carboxylated cellulose, the present invention mixes the carboxylated cellulose, MOF template and gelling agent, and freeze-dries them to obtain an aerogel precursor.

[0033] In this invention, the MOF template preferably includes Zn-BTC, ZIF-8, or ZIF-67.

[0034] In this invention, the method for preparing Zn-BTC preferably includes the following steps: Zinc nitrate hexahydrate, 1,3,5-benzenetricarboxylic acid (H3BTC), and an organic solvent were mixed and subjected to a solvothermal reaction to obtain Zn-BTC.

[0035] In this invention, the molar ratio of zinc nitrate hexahydrate to 1,3,5-benzenetricarboxylic acid is preferably 2:1; the organic solvent is preferably one or more of ethanol, methanol, ethanol, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), or a mixture thereof with water; this invention does not impose any special limitation on the amount of the organic solvent used, and it can be adjusted according to requirements.

[0036] In this invention, the temperature of the solvothermal reaction is preferably 100~140℃, more preferably 120~130℃, and the time is preferably 8~24h, more preferably 12h. After the solvothermal reaction is completed, the mixture is naturally cooled to room temperature, Zn-BTC crystals are collected, and the crystals are repeatedly washed with ethanol and deionized water until neutral. After drying, Zn-BTC is obtained.

[0037] When the MOF template is ZIF-8 or ZIF-67, the present invention does not impose any special limitations on the preparation process of ZIF-8 or ZIF-67, and it can be prepared according to methods well known in the art.

[0038] In this invention, the gelling agent preferably includes gelatin, polyvinyl alcohol (PVA), sodium alginate, or chitosan; when the gelling agent is gelatin, it is preferably used in the form of an aqueous gelatin solution; the concentration of the aqueous gelatin solution is preferably 5 mg / mL. -1 The present invention preferably uses gelatin dissolved in deionized water and magnetically stirred at 50°C to obtain a gelatin solution.

[0039] When gelatin is used as the gelling agent, natural polymeric gelatin serves as an inexpensive nitrogen source, enabling nitrogen doping and enhancing structural stability during the carbonization process.

[0040] In this invention, the mass ratio of carboxylated cellulose, MOF template and gelling agent is preferably 1:(0.5~2):(0.5~2), more preferably 1:(0.8~1.5):(0.5~1.5), and even more preferably 1:1:0.5.

[0041] In this invention, the mixing temperature of the carboxylated cellulose, MOF template and gelling agent is preferably 40°C, and the mixing time is preferably 2~8 h, more preferably 4~6 h; the mixing is preferably carried out under stirring conditions to promote coordination and electrostatic interaction between MOF template and carboxylated cellulose / gelling agent network to form a stable composite sol.

[0042] In this invention, the freeze-drying temperature is preferably -50 to -40°C, more preferably -50°C, and the freeze-drying time is preferably 40 to 60 hours, more preferably 36 to 48 hours.

[0043] After obtaining the aerogel precursor, the present invention carbonizes the aerogel precursor in a protective atmosphere to obtain a three-dimensional interconnected porous framework structure carbon aerogel.

[0044] In this invention, the carbonization temperature is preferably 800~1000℃, more preferably 900℃, and the time is preferably 2~4h, more preferably 2~3h; the protective atmosphere preferably includes argon or nitrogen; and the heating rate is preferably 2℃ / min.

[0045] This invention provides a three-dimensional interconnected porous framework carbon aerogel prepared by the preparation method described above, which has a porous structure and a specific surface area of ​​600~900 m². 2 / g, with a pore size range of 1~40 nm.

[0046] This invention provides the application of the three-dimensional interconnected porous framework structure carbon aerogel described above as an electrode material in the field of supercapacitors. This invention does not impose any particular limitation on the method of application; any method well-known in the art can be used.

[0047] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0048] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the reagents and raw materials described below are all commercially available.

[0049] The bleached sugarcane pulp used in the following examples was purchased from Dalian Yangrun Trading Co., Ltd., product number YR004.

[0050] Example 1

[0051] (1) Preparation of deep eutectic solvent (H-DES): Citric acid, choline chloride and deionized water were mixed in a mass ratio of 3:1:1 and stirred at 80℃ for 30 min to obtain a uniform and transparent deep eutectic solvent H-DES. (2) Preparation of carboxylated cellulose Add 4.0g of bleached sugarcane pulp to 500mL of deionized water and stir at high speed for 30min at room temperature. Filter the resulting pulp to form a wet cake. Add the wet cake to 120g of H-DES prepared in step (1) and reflux at 130℃ for 3h for carboxylation treatment. After the reaction, filter and wash with deionized water until the filtrate is nearly neutral. Then disperse it in deionized water with a solid content of 1wt% and sonicate for 20min to obtain a uniform carboxylated cellulose suspension. Freeze-dry the suspension at -50℃ to obtain C-CNFs solid powder. (3) Preparation of Zn-BTC template: 6 mmol Zn(NO3)2·6H2O and 3 mmol 1,3,5-benzenetricarboxylic acid (H3BTC) were dissolved in 60 mL of ethanol. After stirring for 20 min, the mixture was transferred to a 250 mL high-pressure reactor and subjected to a solvothermal reaction at 120 °C for 12 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. Zn-BTC crystals were collected, washed repeatedly with ethanol and deionized water until neutral, and dried at 60 °C for 3 h to obtain Zn-BTC. (4) Preparation of aerogel precursors: Gelatin was dissolved in deionized water and magnetically stirred at 50°C to obtain a gelatin solution with a mass concentration of 5 mg / mL. 20 mL of the gelatin solution (0.10 g gelatin) was taken, and 0.2 g of carboxylated cellulose (C-CNFs) was added. The mixture was ultrasonically dispersed for 5 min to obtain a uniform suspension. Subsequently, 0.2 g of Zn-BTC powder was gradually added, and the mixture was continuously stirred at 40°C for 8 h. The resulting uniform suspension was poured into a mold, frozen at -50°C, and freeze-dried under vacuum for 48 h to obtain the aerogel precursor. (5) Preparation of carbon aerogel: The precursor was heated to 900°C in an Ar atmosphere at a heating rate of 2°C / min and held at that temperature for 2 hours to complete carbonization. After cooling to room temperature, a carbon aerogel was obtained, denoted as GZBTC. 0.2 -900.

[0052] Example 2

[0053] The only difference from Example 1 is that in step (5), the carbonization temperature is 800°C, and the resulting carbon aerogel is denoted as GZBTC. 0.2 -800.

[0054] Example 3

[0055] The only difference from Example 1 is that in step (5), the carbonization temperature is 1000℃, and the resulting carbon aerogel is denoted as GZBTC. 0.2 -1000.

[0056] Example 4

[0057] The only difference from Example 1 is that in step (4), 0.3g of Zn-BTC is added, and the resulting carbon aerogel is denoted as GZBTC. 0.3 -900.

[0058] Example 5

[0059] The only difference from Example 1 is that in step (4), 0.4g of Zn-BTC is added, and the resulting carbon aerogel is denoted as GZBTC. 0.4 -900.

[0060] Comparative Example 1

[0061] The carboxylated cellulose (C-CNFs) prepared in Example 1 was dried and used as a carbon precursor. It was placed in a tube furnace and heated to 900°C at a heating rate of 2°C / min in an Ar atmosphere. The temperature was held for 2 hours and then naturally cooled to room temperature. The resulting sample was named C-CNFs-900.

[0062] Comparative Example 2

[0063] The Zn-BTC crystal powder obtained in Example 1 was placed directly in a tube furnace and heated to 900°C at a heating rate of 2°C / min under an argon atmosphere. After holding at this temperature for 2 hours, it was naturally cooled to obtain the ZBC-900 sample.

[0064] Structural characterization

[0065] Figure 1 GZBTC in Example 1 0.2 Typical scanning electron microscope (SEM) images at different magnifications: -900 nm, where (a) is 2 μm and (b) is 500 nm. like Figure 1 As shown, GZBTC 0.2 The -900 sample exhibits a typical three-dimensional interconnected network framework morphology, with numerous interwoven frameworks forming a continuous spatial network structure. Open pores ranging in size from hundreds of nanometers to several micrometers are distributed between the frameworks, demonstrating high porosity and open-pore characteristics, reflecting a typical open-pore aerogel structure; this is beneficial for rapid electrolyte wetting and long-range ion transport. In contrast, the framework connectivity and pore richness of C-CNFs-900 and ZBC-900 are inferior to those of the sample of this invention.

[0066] Figure 2 For C-CNFs-900, ZBC-900 and GZBTC 0.2 Raman spectrum at -900; Figure 2 The data shows that the three samples are located at approximately 1350 cm. -1 and 1590cm -1 D and G peaks appeared at all locations, with GZBTC showing the highest peak.0.2 -900 of I D / I G The intensity ratio is 1.45, which is higher than that of C-CNFs-900 (1.12) and ZBC-900 (1.09), indicating that it has more defect carbon sites and amorphous regions.

[0067] Figure 3 For C-CNFs-900, ZBC-900 and GZBTC 0.2 -900 XPS full spectrum; Figure 3 The results show that GZBTC 0.2 -900 is mainly composed of C and O elements, with only a weak Zn signal observed, indicating that most of the Zn has been effectively volatilized during the pyrolysis process, leaving only a small number of Zn-related active centers, which is beneficial to improving the wettability of the electrode surface and the interfacial charge transfer behavior.

[0068] In addition, by Figures 2-3 It can be seen that GZBTC 0.2 -900 of I D / I G The highest ratio indicates the abundance of defective carbon sites, which is beneficial for providing more electrochemical active sites. Simultaneously, its surface oxygen-containing functional groups and a small number of Zn-related active centers help improve electrolyte wettability and promote interfacial charge transfer. In contrast, although C-CNFs-900 possesses a certain porous structure and oxygen-containing functional groups, its defect degree and pore volume are lower than those of GZBTC. 0.2 -900; ZBC-900 has the lowest specific surface area and pore volume, more Zn residue, and limited overall electrochemical activity.

[0069] Figure 4 For C-CNFs-900, ZBC-900 and GZBTC 0.2 The nitrogen adsorption-desorption isotherm (a) and pore size distribution curve (b) at -900°C show that all three samples exhibit a type IV isotherm with a hysteresis loop, indicating that they are predominantly mesoporous porous materials. GZBTC 0.2 The specific surface area at -900°C is 849.3 m². 2 / g, pore volume is 1.27cm³ 3 / g, with a main pore size distribution in the range of 1~40nm, significantly higher than C-CNFs-900 and ZBC-900, and moreover, GZBTC 0.2The overall adsorption capacity, specific surface area, and pore volume of GZBTC-900 are significantly higher than those of C-CNFs-900 and ZBC-900. It exhibits a distinct micropore or narrow mesopore peak at approximately 2 nm, a broad mesopore distribution in the 10-40 nm range, and maintains a high pore volume even across a larger pore size range. This indicates that the synergistic regulation of the Zn-BTC template and C-CNFs / gelatin significantly enhances the pore volume and accessible surface area of ​​the material. Combined with the macropore / channel structure shown in SEM images, it can be concluded that GZBTC... 0.2 -900 simultaneously possesses micropores, mesopores, and larger-sized channels, forming a hierarchical porous structure with micro / mesopore / macropore synergy. This is beneficial for providing a fast and continuous transport channel for electrolyte ions while ensuring a high specific surface area.

[0070] Electrochemical performance testing: Electrochemical testing was conducted using a three-electrode system: Carbon aerogel electrodes prepared in different cases were used as the working electrodes. A uniform slurry was prepared by dispersing the active material, carbon black, and polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP) at a mass ratio of 8:1:1. This slurry was then coated onto a 1 cm × 1 cm nickel foam substrate, dried at 80 °C for 8 h, and pressed into a pellet at 10 MPa for 30 s. A platinum sheet was used as the counter electrode, and an Hg / HgO electrode was used as the reference electrode. The electrochemical tests were conducted at 6 mol·L⁻¹. -1 Using KOH aqueous solution as the electrolyte and at room temperature, cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests were performed sequentially using an electrochemical workstation. The results are shown in [Figure number missing]. Figures 5-9 .

[0071] The results showed that at 6 mol·L -1 In the KOH three-electrode system, GZBTC 0.2 -900 cyclic voltammetry curve ( Figure 7 The area is the largest and the shape is close to an ideal rectangle, with a constant current charge-discharge curve ( Figure 5 It has a nearly isosceles triangle shape and the longest discharge time. At a current density of 0.5 A / g, its specific capacitance can reach 250 F / g, and it can still maintain 172 F / g at a high current density of 20 A / g, with a specific capacitance retention rate of approximately 69%. Figure 9 The GZBTC exhibits excellent specific capacitance and rate performance, indicating that... 0.2 -900 materials exhibit good double-layer capacitance characteristics and low polarization; while C-CNFs-900 and ZBC-900 show smaller CV curve areas, significant shape distortion, and more pronounced specific capacitance decay at high rates. Furthermore, compared to the two control samples C-CNFs-900 and ZBC-900, GZBTC... 0.2 -900 exhibits the highest specific capacitance at the same current density and the best capacity retention at high current densities, demonstrating significant superiority over the two control samples in terms of specific capacitance, rate performance, and polarization.

[0072] Examples 2-5 prepared carbon aerogels at different carbonization temperatures (800℃, 1000℃) and different Zn-BTC addition amounts (0.3g, 0.4g), and compared their cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) performance. The results are as follows: Figure 6 and Figure 8 As shown: GZBTC 0.2 The discharge time of GCD at -800 is significantly shorter than that of GZBTC. 0.2 -900, its CV curve has poor rectangularity, indicating insufficient carbonization at 800℃, low conductivity, and the pore structure is not fully opened; GZBTC 0.2 The current response of the CV curve at -1000 is slightly lower than that of GZBTC. 0.2 -900℃ and the GCD discharge time is also slightly shorter, indicating that excessively high carbonization temperature causes some pore structures to shrink, thereby reducing the effective specific surface area. Therefore, 900℃ is the optimal carbonization temperature.

[0073] The electrochemical performance of samples with different Zn-BTC addition amounts also showed significant differences: as the Zn-BTC addition amount increased from 0.2 g to 0.3 g and then to 0.4 g, the GCD discharge time gradually shortened, the current response of the CV curve decreased, and the rectangularity weakened. This indicates that excessive Zn-BTC addition can lead to pore structure collapse or excessive foaming during carbonization, thereby damaging the conductive network and reducing the specific surface area. Therefore, 0.2 g is the optimal Zn-BTC addition amount, achieving the best balance between pore structure formation and conductive network.

[0074] Based on the comparison results of different temperatures and dosages, it can be seen that GZBTC 0.2 -900 exhibits the best specific capacitance, highest current response, and longest discharge time in the three-electrode system, and its electrochemical performance is significantly better than that of other embodiments.

[0075] Structure and electrochemical performance of C-CNFs-900 in Comparative Example 1: Nitrogen adsorption-desorption tests showed that the specific surface area of ​​C-CNFs-900 was 692.5 m². 2 / g, average pore size approximately 3.91nm ( Figure 4 This indicates that the sample also has a porous structure, but its specific surface area and pore volume are both lower than those of GZBTC. 0.2 -900. I in the Raman spectrum D / I G The ratio is approximately 1.12 ( Figure 2 The defect level is lower than that of GZBTC. 0.2 -900; XPS full spectrum display mainly shows C and O element signals ( Figure 3This indicates that the sample surface contains a certain amount of oxygen-containing functional groups, but the overall number of active sites is relatively small. Under the same three-electrode testing conditions, the specific capacitance of C-CNFs-900 at a current density of 0.5 A / g is approximately 149 F / g. Figure 9 ), significantly lower than GZBTC 0.2 -900.

[0076] Structure and electrochemical performance of ZBC-900 sample in Comparative Example 2: Nitrogen adsorption-desorption results showed that the specific surface area of ​​ZBC-900 was 263.7 m². 2 / g, pore volume approximately 0.44cm³ 3 / g ( Figure 4 ), significantly lower than GZBTC 0.2 -900 and C-CNFs-900 indicate that the pore structure of carbon materials obtained solely by Zn-BTC carbonization is relatively limited. Its Raman spectrum shows I... D / I G The ratio is approximately 1.09 ( Figure 2 The defect level is the lowest; C, O, and relatively obvious Zn-related signals are visible in the XPS full spectrum. Figure 3 This indicates that there are many Zn species remaining, and the types of surface active sites are relatively simple. Under three-electrode testing conditions, the specific capacitance of ZBC-900 at a current density of 0.5 A / g is approximately 81 F / g. Figure 9 (), which is the lowest among the three.

[0077] Results and Analysis: Comprehensive analysis of morphology, pore structure, surface chemical and electrochemical properties shows that this invention, through H-DES carboxylation of cellulose, introduction of gelatin, and synergistic regulation using a Zn-BTC template, achieves [the desired effect] in GZBTC [a specific application]. 0.2 The -900 medium is constructed with porous channels and abundant active sites, which significantly improves the specific surface area, pore volume and interfacial reactivity of the material, thereby achieving excellent charge storage capacity and fast charge and discharge characteristics.

[0078] As can be seen from the above examples and comparative examples, compared with the control materials C-CNFs-900 and ZBC-900, the GZBTC prepared by the present invention has better performance. 0.2 -900 carbon aerogels exhibit significant advantages in both pore structure and electrochemical conductivity: their specific surface area ranges from 263.7 to 692.5 m². 2 / g increased to 849.3m 2 / g, pore volume increased from 0.44cm³ 3 / g increased to 1.27cm 3At 0.5 A / g, the specific capacitance increased from 81 F / g and 149 F / g to 250 F / g, while maintaining 172 F / g at a high current density of 20 A / g, demonstrating excellent rate performance and cycle stability. The H-DES carboxylation process employed in this invention is environmentally friendly, with widely available and inexpensive raw materials. The preparation process is simple and mild, possessing good potential for scale-up and industrialization. The resulting carbon aerogel is suitable as an electrode material for supercapacitors and can also be applied to other electrochemical energy storage and catalysis fields, exhibiting excellent electrochemical performance in both three-electrode systems and practical devices.

[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a three-dimensional interconnected porous framework carbon aerogel, characterized in that, Includes the following steps: Cellulose raw materials are mixed with a deep eutectic solvent and carboxylated to obtain carboxylated cellulose; The carboxylated cellulose, MOF template and gelling agent were mixed and freeze-dried to obtain an aerogel precursor; The aerogel precursor was carbonized in a protective atmosphere to obtain a three-dimensional interconnected porous framework carbon aerogel.

2. The preparation method according to claim 1, characterized in that, The deep eutectic solvent is composed of citric acid, choline chloride and water, and the mass ratio of citric acid, choline chloride and water is 2.5~3.5:0.8~1.2:0.8~1.

2.

3. The preparation method according to claim 1 or 2, characterized in that, The cellulose raw material is a cellulose-based slurry derived from plants; the mass ratio of the cellulose raw material to the deep eutectic solvent is 1:(25~35).

4. The preparation method according to claim 3, characterized in that, The carboxylation treatment is performed at a temperature of 120-140°C for 2-4 hours.

5. The preparation method according to claim 1, characterized in that, The MOF template includes Zn-BTC, ZIF-8, or ZIF-67; the gelling agent includes gelatin, polyvinyl alcohol, sodium alginate, or chitosan. The method for preparing Zn-BTC includes the following steps: Zinc nitrate hexahydrate, 1,3,5-benzenetricarboxylic acid, and an organic solvent were mixed and subjected to a solvothermal reaction to obtain Zn-BTC; the temperature of the solvothermal reaction was 100~140℃ and the time was 8~24h.

6. The preparation method according to claim 1 or 5, characterized in that, The mass ratio of carboxylated cellulose, MOF template and gelling agent is 1:(0.5~2):(0.5~2).

7. The preparation method according to claim 1, characterized in that, The freeze-drying temperature is -50 to -40°C, and the time is 40 to 60 hours.

8. The preparation method according to claim 1, characterized in that, The carbonization temperature is 800~1000℃, and the time is 2~4h; the protective atmosphere includes argon or nitrogen.

9. The three-dimensional interconnected porous framework carbon aerogel prepared by the preparation method according to any one of claims 1 to 8, characterized in that, It has a porous structure and a specific surface area of ​​600~900 m². 2 / g, with a pore size range of 1~40 nm.

10. The application of the three-dimensional interconnected porous framework carbon aerogel of claim 9 as an electrode material in the field of supercapacitors.

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