Three-dimensional network multi-stage carbon skeleton composite material and preparation method and application thereof

Abstract

This invention discloses a three-dimensional networked hierarchical carbon skeleton composite material, its preparation method, and its applications. The preparation method of the three-dimensional networked hierarchical carbon skeleton composite material includes S1. Preparing a three-dimensional gel network on the surface of a carbon fiber felt, wherein short-cut carbon fibers and carbon nanotubes are dispersed in the three-dimensional gel network to obtain a three-dimensional networked hierarchical carbon skeleton material; S2. Loading polyethyleneimine onto the three-dimensional networked hierarchical carbon skeleton material obtained in step S1 to obtain the three-dimensional networked hierarchical carbon skeleton composite material. The material provided by this invention achieves effective dispersion and fixation of conductive fillers by constructing a stable three-dimensional conductive network and a hierarchical porous structure, significantly improving CO2 adsorption capacity and electrothermal regeneration efficiency.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide capture and functional material preparation technology, specifically relating to a three-dimensional network multi-level carbon skeleton composite material, its preparation method, and its application. Background Technology

[0002] With the acceleration of global industrialization, the massive emission of carbon dioxide (CO2) has become one of the main causes of the greenhouse effect, making efficient CO2 capture and separation of great significance. Currently, chemical absorption methods (such as amine solution absorption) are the most widely used CO2 capture technology, but they suffer from problems such as high regeneration energy consumption, severe equipment corrosion, and easy degradation of the absorbent. Solid porous material adsorption methods, especially solid amine adsorbents supported on porous supports using polyamine polymers such as polyethyleneimine (PEI), have become a research hotspot due to their high selectivity, low corrosivity, and operational flexibility.

[0003] For solid amine adsorbents, achieving low-energy CO2 desorption is key to their large-scale application. Traditional temperature-switched desorption (TSA) usually requires heating the entire adsorption bed to 100-120℃, which has problems such as low thermal conductivity, long heating time, and high energy consumption. In recent years, CO2 desorption technology driven by electrothermal effect of conductive materials has become an effective way to reduce desorption energy consumption because it can achieve rapid, uniform, and in-situ heating. However, existing conductive composite materials used for electrothermal desorption usually have the following problems: (1) Conductive fillers (such as carbon nanotubes, graphene, etc.) are prone to agglomeration in polymer or hydrogel matrices, resulting in discontinuous conductive networks and low electrothermal efficiency; (2) The structural design of materials often only focuses on conductivity and ignores providing sufficient high specific surface area and pore structure for CO2 adsorbents, resulting in limited adsorption capacity.

[0004] Chinese Patent Publication No. CN111534049B discloses a high thermal and electrical conductivity carbon fiber polymer-based composite material and its preparation method. The composite material uses uniformly shaped carbon fibers as raw material, and employs airflow network forming technology and needle punching to prepare in-plane oriented carbon fiber felt. Then, silver nanoparticles are deposited on the carbon fiber surface using a solvent reduction method to prepare a novel carbon fiber-silver nanoparticle hybrid fiber felt. High thermal conductivity fillers are uniformly incorporated into the carbon fiber-silver nanoparticle hybrid fiber felt using a vacuum filtration method. Finally, the composite material is prepared through vacuum-assisted transfer molding (RTM) and annealing. This composite material introduces nano-silver particles and other high thermal conductivity fillers into the carbon fiber base to achieve a synergistic effect and increase the thermal conductivity pathway. Compression confinement enables the hybrid carbon fibers to be arranged in an orderly manner within the polymer. Low-melting-point nano-silver melting technology connects the carbon fibers and other thermally conductive fillers, increasing the thermal conductivity pathway of the composite material, reducing the thermal resistance between fillers, and effectively increasing the thermal conductivity, mechanical properties, electrical properties, and electromagnetic shielding effectiveness of the composite material. The composite materials in this scheme are mainly used for heat dissipation and electromagnetic shielding of electronic components. Their design goal is to improve thermal and electrical conductivity, and they completely ignore CO2 adsorption, capture, or electrothermal regeneration. Therefore, this scheme cannot solve the technical problems of CO2 capture and low-energy desorption. The material system in this scheme uses silver nanoparticles and silver nanowires as conductive / thermal conductive fillers and is cast with epoxy resin to construct a dense thermally conductive pathway, resulting in a non-porous structure. The nano-silver in this scheme is physically fixed through reduction deposition and fusion bonding, rather than through a cross-linked polymer network. The contact between the carbon fibers and the filler is achieved through the fusion bonding of the nano-silver, resulting in a metal-fused conductive network. Summary of the Invention

[0005] The present invention aims to provide a three-dimensional network multi-level carbon skeleton composite material, its preparation method and application, which improves CO2 adsorption capacity and electrothermal regeneration efficiency.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a three-dimensional network multi-level carbon skeleton composite material includes the following steps:

[0008] S1. A three-dimensional gel network is prepared on the surface of carbon fiber felt. Short-cut carbon fibers and carbon nanotubes are dispersed in the three-dimensional gel network to obtain a three-dimensional network multi-level carbon skeleton material.

[0009] S2. Polyethyleneimine is loaded onto the three-dimensional network multi-level carbon skeleton material obtained in step S1 to obtain a three-dimensional network multi-level carbon skeleton composite material.

[0010] This invention constructs a three-dimensional network hierarchical carbon skeleton composite material. The material uses carbon fiber felt as a macroscopic three-dimensional conductive skeleton, utilizing the bridging effect of short-cut carbon fibers to connect the carbon fiber felt and carbon nanotube clusters, forming a continuous all-carbon conductive network. Simultaneously, a stable three-dimensional gel network is formed, fixing the aforementioned conductive fillers of different scales in situ on the surface and within the pores of the carbon fiber felt, constructing a hierarchical porous structure with micropores, mesopores, and macropores coexisting, and using this structure as a highly efficient carrier for polyethyleneimine (PEI). This material significantly improves CO2 adsorption capacity and desorption efficiency while maintaining excellent electrothermal performance.

[0011] According to embodiments of the present invention, the present invention can be further optimized, and the optimized technical solution is as follows:

[0012] In one preferred embodiment, step S1 includes:

[0013] Step S11. Add sodium alginate, chopped carbon fibers, and carbon nanotubes to water and disperse them evenly to obtain a mixed coating solution;

[0014] Step S12. The mixed coating liquid obtained in step S11 is uniformly coated onto the surface of the carbon fiber felt. Then, the coated carbon fiber felt is immersed in calcium chloride solution and dried to obtain a three-dimensional network multi-level carbon skeleton material.

[0015] This invention uses carbon fiber felt as a three-dimensional conductive framework, allowing sodium alginate and Ca to react. 2+ Cross-linking forms a water-insoluble three-dimensional gel network, which fixes short-cut carbon fibers and carbon nanotubes in situ on the surface and internal pores of the carbon fiber felt.

[0016] If sodium alginate is not cross-linked with CaCl2, the sodium alginate solution will cause the coating solution to settle during the drying process after being coated onto the carbon fiber felt due to its fluidity. This will result in the inability to prepare a uniform material, and the coating strength will be very low, making it impossible to effectively fix the short-cut carbon fibers and carbon nanotubes.

[0017] In one preferred embodiment, step S2 includes:

[0018] The three-dimensional network multi-level carbon skeleton material obtained in step S1 is immersed in a polyethyleneimine solution, so that the polyethyleneimine is loaded on the surface and pores of the three-dimensional network multi-level carbon skeleton material. After washing and drying, the three-dimensional network multi-level carbon skeleton composite material is obtained.

[0019] The short-cut carbon fibers act as bridges, connecting the carbon fiber felt and carbon nanotube clusters to form a continuous conductive and thermally conductive pathway. The gel network formed by the cross-linking of sodium alginate and CaCl2 not only fixes the conductive filler but also provides abundant loading sites for PEI.

[0020] In one preferred embodiment, in step S11, the mass concentration of the sodium alginate solution is 0.5~1.5wt%, and the mass ratio of the sodium alginate, the chopped carbon fiber, and the carbon nanotube is 0.7~1.5g:0.5~1.5g:0.5~1.5g.

[0021] Preferably, in step S11, the mass concentration of the sodium alginate solution in the mixed coating solution is 0.8~1.1 wt%.

[0022] Preferably, in step S11, the mass ratio of sodium alginate, chopped carbon fiber, and carbon nanotube is 0.7~1g:0.5~1.2g:0.5~1.2g.

[0023] In one preferred embodiment, the chopped carbon fibers have a length of 100-500 μm and a diameter of 5-7 μm.

[0024] Preferably, the chopped carbon fibers have a length of 100-200 μm and a diameter of 5-6 μm.

[0025] In one preferred embodiment, the carbon fiber felt has a thickness of 1-3 mm; the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10-50 nm and a length of 20-30 μm.

[0026] Preferably, the carbon fiber felt has a thickness of 2-3 mm, and the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10-30 nm and a length of 20-30 μm.

[0027] In one preferred embodiment, in step S12, the mass concentration of the calcium chloride solution is 1-10 wt%, and the soaking time is 0.5-12 h.

[0028] Preferably, the calcium chloride solution has a mass concentration of 1-5 wt% and a soaking time of 6-8 h.

[0029] In one preferred embodiment, in step S2, the concentration of the polyethyleneimine solution is 1-20 wt%, and the soaking time is 1-24 h. If the concentration is too low, the amine loading is too small, resulting in poor adsorption; if the concentration is too high, the amine is prone to agglomeration and clogging of the pores; if the soaking time is too short, the amine cannot be effectively loaded (the content in the deep pores is low); if the soaking time is too long, the alkaline environment (amine solution) can easily damage the stability of the matrix.

[0030] The molecular weight (Mw) of polyethyleneimine ranges from 500 to 1500; preferably, the molecular weight (Mw) of polyethyleneimine ranges from 800 to 1500.

[0031] Preferably, the polyethyleneimine solution has a mass concentration of 5-15 wt% and a soaking time of 12-24 h.

[0032] Preferably, in step S2, the solvent for the polyethyleneimine solution is one or both of water and methanol. Preferably, the solvent is water or a mixture of methanol and water in a mass ratio of 2-4:6-8.

[0033] Preferably, in step S11, the dispersion is performed by ultrasonic dispersion for 1 to 2 hours.

[0034] Preferably, the drying temperature in step S12 is 50~70℃, and the drying time is 10~14 h.

[0035] The present invention also discloses a three-dimensional network multi-level carbon skeleton composite material, comprising carbon fiber felt and a three-dimensional gel network loaded in the carbon fiber felt, wherein short-cut carbon fibers and carbon nanotubes are dispersed in the three-dimensional gel network, and polyethyleneimine is loaded in the carbon fiber felt and the three-dimensional gel network. The proportion of pores with a size of 2-200 nm in the three-dimensional network multi-level carbon skeleton composite material is 34-36%.

[0036] Preferably, the proportion of pores with a diameter of 2-200 nm in the three-dimensional network multi-level carbon skeleton composite material is 35%. The proportion of pores with a diameter of 2-200 nm in the three-dimensional network multi-level carbon skeleton composite material is a volume ratio.

[0037] The present invention also discloses the application of a three-dimensional network multi-level carbon skeleton composite material as described above, or a three-dimensional network multi-level carbon skeleton composite material prepared according to the preparation method, in CO2 capture.

[0038] Preferably, the three-dimensional network multi-level carbon skeleton composite material is used for electrothermal-driven CO2 capture.

[0039] Therefore, the present invention consists of the following key features:

[0040] 1) Carbon fiber felt (TZ) (three-dimensional conductive skeleton): Serves as the overall supporting skeleton and the main conductive / thermal channel. Its continuous three-dimensional structure ensures the overall mechanical strength and macroscopic conductivity of the material, providing a basic Joule heat source for electrothermal desorption.

[0041] 2) Short-cut carbon fibers (CF) (micro-nano "bridges"): Their length lies between macroscopic carbon fiber felt fibers and microscopic carbon nanotubes. They play a crucial "bridging" role in the system: one end overlaps the carbon fiber felt fiber (typically on the centimeter scale), and the other end extends into or connects to nanoscale carbon nanotube clusters, effectively filling the scale gaps between the macroscopic framework and the nanofiller, greatly increasing the conductive pathway and reducing the contact resistance.

[0042] 3) Carbon nanotubes (CNTs) (nanoscale conductive fillers): They fill the larger pores of short-cut carbon fibers and carbon fiber felt to further refine the conductive network and increase the specific surface area of ​​the material at the microscale, providing more sites for subsequent PEI loading.

[0043] 4) Sodium alginate (SA) (dispersant and structural stabilizer): Dispersing effect: disperses CNTs and chopped CFs, ensuring coating uniformity. Adhesive and fixing effect: reacts with Ca... 2+ The cross-linked, water-insoluble three-dimensional hydrogel network firmly "locks" CNTs and chopped CFs onto the surface of the carbon fiber felt, constructing a stable "multi-level carbon skeleton." This differs from the method of fusion bonding with nano-silver in the Chinese patent with publication number CN111534049B, and is a gentler, lower-cost fixation strategy suitable for gas adsorption.

[0044] 5) CaCl2 (crosslinking agent): provides Ca 2+ Ions cross-link with the sodium alginate molecular chains, transforming soluble sodium alginate into a stable, water-insoluble three-dimensional gel network. This step, distinct from Chinese patent publication CN111534049B, imparts stability to the coating structure in the aqueous phase and during post-treatment processes.

[0045] 6) PEI (CO2 adsorbent): An amino-rich polymer that serves as the active site for CO2 capture. It is efficiently loaded onto a hierarchical porous carbon framework constructed from SA / CNT / CF through soaking. The gel network of SA and the high specific surface area of ​​CNT / CF work together to achieve high dispersibility and high loading capacity of PEI, thereby significantly improving CO2 adsorption capacity.

[0046] This invention utilizes the bridging effect of short-cut carbon fibers to connect carbon fiber felts and carbon nanotube clusters, forming a fully carbon-based, physically interconnected three-dimensional conductive and thermally conductive integrated network. It also avoids the use of metal nanoparticles, resulting in lower costs and making it more suitable for long-term stable operation in humid and hot environments with CO2 adsorption / desorption.

[0047] Compared with the prior art, the beneficial effects of the present invention are:

[0048] This invention provides a three-dimensional network multi-level carbon skeleton composite material for electrothermal-driven CO2 capture and its preparation method. This material, by constructing a stable three-dimensional conductive network and a multi-level porous structure, achieves effective dispersion and fixation of the conductive filler, significantly improving CO2 adsorption capacity and electrothermal regeneration efficiency. Attached Figure Description

[0049] Figure 1 These are SEM images of the composite materials (with different sodium alginate contents) in Examples 1-3 of this invention, wherein... Figure 1The sodium alginate content in a is 0.75 wt%. Figure 1 The sodium alginate content in b is 1 wt%. Figure 1 The sodium alginate content in c is 1.25 wt%.

[0050] Figure 2 This is an adsorption performance curve of the composite materials (with different sodium alginate contents) in Examples 1-3 of the present invention.

[0051] Figure 3 These are adsorption performance curves of the composite materials in Comparative Examples 1-3 and Example 4 of this invention.

[0052] Figure 4 This is a diagram showing the pore size ratio of the composite materials in Comparative Examples 1-3 and Example 4 of the present invention.

[0053] Figure 5 This is a voltage-temperature relationship graph of the composite materials in Comparative Examples 2-3 and Example 4 of the present invention.

[0054] Figure 6 The conductivity of the composite materials in Comparative Examples 2-3 and Example 4 of this invention at different frequencies.

[0055] Figure 7 These are the Joule heating desorption curves and indirect heating desorption curves of the composite material in Example 4 of this invention.

[0056] Figure 8 This is a comparison of the time it takes for the composite material in Example 4 of this invention to reach 90% maximum desorption amount through Joule heating desorption and indirect heating desorption (the vertical axis α represents the ratio of cumulative desorption amount to total desorption amount at time t).

[0057] Figure 9 This is the EDS elemental distribution spectrum of the composite material in Example 4 of the present invention, wherein... Figure 9 a is a SEM image of the composite material surface. Figure 9 b is the distribution map of element C. Figure 9 c represents the distribution map of Ca element. Figure 9 d represents the distribution map of element N. Detailed Implementation

[0058] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0059] I. Effects of different sodium alginate contents on material properties

[0060] Example 1

[0061] (1) Preparation of coating solution: Weigh 0.75 g of sodium alginate (SA) and dissolve it in deionized water. Stir until completely dissolved and bring to a final volume to obtain an SA solution with a mass concentration of 0.75 wt%. Add 1 g of short-cut carbon fibers (100 μm in length and 5 μm in diameter) and 1 g of multi-walled carbon nanotubes (20 nm in diameter and 25 μm in length) to the above solution and ultrasonically disperse for 1 h to obtain a uniform mixed coating solution (SA solution).

[0062] (2) Coating and crosslinking fixation: The carbon fiber felt (2 mm thick) was immersed in the mixed coating solution of step (1), and repeatedly squeezed to make the coating solution penetrate evenly. After removal, the excess coating solution was removed with a scraper (the carbon felt has a certain supporting strength, and normal surface scraping will not cause a large amount of internal solution to be squeezed out). Then the coated carbon fiber felt was immersed in 3 wt% CaCl2 solution for crosslinking reaction for 6 h. After removal, it was washed with deionized water and dried in an oven at 60℃ for 12 h to obtain a three-dimensional network multi-level carbon skeleton material.

[0063] (3) Loading the adsorbent: The carbon skeleton material obtained in step (2) was immersed in a 10 wt% PEI (Mw molecular weight 800) aqueous solution for 12 h. After taking it out, the PEI that was not firmly adsorbed on the surface was gently washed with deionized water and dried in a vacuum drying oven at 60℃ for 12 h to obtain the target composite material (SA-0.75wt%).

[0064] Example 2

[0065] The difference between this embodiment and Example 1 is that the amount of sodium alginate added is 1.0 g, that is, the concentration of SA solution is 1.0 wt%. The other conditions are the same as in Example 1, and the composite material (SA-1.00 wt%) is obtained.

[0066] Example 3

[0067] The difference between this embodiment and Example 1 is that the amount of sodium alginate added is 1.25 g, that is, the concentration of SA solution is 1.25 wt%. The other conditions are the same as in Example 1, and the composite material (SA-1.25wt%) is obtained.

[0068] The composite materials prepared in Examples 1-3 were placed in a flask with a knob-type gas filling valve. CO2 was injected into the flask through the gas filling port at a flow rate of 100 mL / min for 5 minutes. The gas filling valve was then closed, and the mouth of the flask was sealed with a rubber stopper and kept still. The material was taken out and weighed every once in a while until the weight of the material no longer changed. At this point, the material was considered to be saturated with adsorption.

[0069]

[0070] As shown in the table above, the CO2 adsorption capacity of the composite material increased from 0.45 mmol / g to 0.66 mmol / g as the sodium alginate concentration increased from 0.75 wt% to 1.0 wt%. This is likely because the increased sodium alginate concentration resulted in a more complete three-dimensional gel network after cross-linking, which could more effectively immobilize the conductive fillers (carbon nanotubes and chopped carbon fibers) and retain a large number of pore structures, providing more loading sites for PEI. However, when the sodium alginate concentration further increased to 1.25 wt%, the adsorption capacity decreased to 0.51 mmol / g. This is likely because excessive sodium alginate could lead to an overly dense gel network, clogging the pore structure and limiting CO2 diffusion and the effective loading of PEI. Figure 1 , Figure 2 Therefore, controlling the appropriate sodium alginate concentration helps to obtain composite materials with excellent pore structure and PEI loading capacity.

[0071] II. The Influence of Different Coating Components on Material Structure and Properties

[0072] Example 4

[0073] This embodiment is the same as Example 2 (SA-1.0%), and its coating composition is sodium alginate / carbon nanotube / chopped carbon fiber (SA / CNT / CF) to obtain a composite material (TZ / SA / CNT / CF / PEI).

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 4 is that no coating treatment is performed. Pure carbon fiber felt is used as a carrier and directly immersed in 10 wt% PEI solution for 12 h. After drying, the composite material is obtained and is denoted as pure carbon felt (TZ / PEI).

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 4 is that the coating solution contains only sodium alginate and no carbon nanotubes or chopped carbon fibers. Specifically, 1.0 g of sodium alginate was dissolved in 100 mL of deionized water to obtain a 1.0 wt% SA solution. The carbon fiber felt was then immersed in the solution and removed. After CaCl2 crosslinking, drying, and PEI loading, a composite material was obtained, denoted as TZ / SA / PEI.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 4 is that the coating solution contains sodium alginate and carbon nanotubes, but not chopped carbon fibers. Specifically, 1.0 g of sodium alginate and 1.0 g of multi-walled carbon nanotubes were weighed and a composite material was prepared according to the method of Example 4, denoted as TZ / SA / CNT / PEI.

[0080]

[0081]

[0082] The pore structure of pure carbon felt is mainly micropores, making it difficult for CO2 to diffuse into the pores under normal temperature and pressure. In the TZ / SA / PEI sample of Comparative Example 2, sodium alginate crosslinking forms a gel coating layer on the carbon fiber surface, blocking the pores on the carbon felt surface. Furthermore, the gel layer is also mainly micropores with a simple pore structure, thus still lacking efficient CO2 capture performance. In the TZ / SA / CNT / PEI sample of Comparative Example 3, the introduction of carbon nanotubes increases the specific surface area and pore structure, further increasing the adsorption capacity to 0.57 mmol / g. In the TZ / SA / CNT / CF / PEI sample of Example 4, the bridging effect of short-cut carbon fibers further enriches the pore structure. Multi-scale carbon materials and the gel network jointly construct a hierarchical pore structure with micropores, mesopores, and macropores coexisting, providing more loading space for PEI, achieving an adsorption capacity of 0.66 mmol / g. Figure 3 , Figure 4 ).

[0083]

[0084] Under the same input voltage, the composite sample containing short-cut carbon fibers exhibits a higher steady-state temperature, and its electrothermal conversion efficiency is significantly better than that of samples containing only carbon nanotubes or without conductive fillers. Figure 5 This phenomenon indicates that a three-dimensional conductive network with short-cut carbon fibers as the skeleton unit and carbon nanotubes as branch nodes can effectively reduce contact resistance and promote Joule heating within the material. In the composite material TZ / SA / CNT / PEI in Comparative Example 3, which contains only carbon nanotubes, the carbon nanotubes tend to form isolated clusters or local networks. The internal conductivity of the clusters is good, but electron transport between clusters relies on weak contact or tunneling effects in the sodium alginate matrix, resulting in numerous structural defects and interfacial barriers. When the coating is only sodium alginate, the lack of conductivity of sodium alginate negatively impacts the overall conductivity of the material, severely hindering electron transport (see...). Figure 6 , Figure 6 This demonstrates that the material's electrical conductivity is stable and unaffected by frequency (the selected frequencies are from a commonly used range of low to high frequencies).

[0085] III. The Influence of Different Desorption Mechanisms on CO2 Desorption Efficiency and Cycle Stability

[0086] Example 5

[0087] The carbon dioxide desorption test apparatus is the same as the adsorption test apparatus. This embodiment uses the composite material prepared in Example 4 (TZ / SA / CNT / CF / PEI) and performs CO2 desorption using an electrothermal-driven Joule heating method. First, the composite material is adsorbed to saturation. Then, during desorption, a nitrogen pipeline is connected to the left-side filling valve, and the right-side gas cylinder opening is connected to a carbon dioxide concentration detector. The sample material is connected to a conductive copper wire, which passes through the rubber stopper at the middle cylinder opening and is connected to a DC power supply. The composite material temperature is controlled to reach 95°C by adjusting the voltage. During testing, N2 is purged at a flow rate of 55 mL / min, and the purged N2 / CO2 mixture is sent to a CO2 concentration analyzer for detection until the CO2 concentration drops to 0, at which point desorption is considered complete.

[0088] Comparative Example 4

[0089] The difference between this comparative example and Example 5 is that a traditional indirect heating method is used for CO2 desorption. Specifically, the composite material prepared in Example 4 is placed in an adsorption device and first saturated with adsorption. During desorption, a nitrogen pipeline is connected to the left-side gas filling valve, the right-side gas cylinder is connected to a carbon dioxide concentration detector, and the middle gas cylinder is sealed with a rubber stopper. During testing, the flask is placed on a heating plate with heating function and grooves to simulate a traditional temperature-controlled desorption process. N2 is purged at a flow rate of 55 mL / min, and the purged N2 / CO2 mixture is sent to a CO2 concentration analyzer for detection until the CO2 concentration drops to 0, at which point desorption is considered complete.

[0090]

[0091] Joule heating generates heat in situ from within the material itself, eliminating the need for heat conduction from an external heat source to the material surface. This allows for rapid and efficient desorption, uniformly heating the entire material to the required desorption temperature in a very short time. Traditional indirect heating relies on heat generated by an external heat source, transferring heat from the material surface to the interior through convection and conduction with air or other media. This process involves a long heat transfer path, requiring heating the external environment first, then the material surface, and finally slowly transferring heat to the interior via conduction, resulting in a slow heating rate. Furthermore, indirect heating inevitably creates a temperature gradient, with the surface heating up first and the interior heating up later, creating a temperature difference between the surface and the core, making uniform heating impossible. Figure 7 , Figure 8 ).

[0092] Figure 9 This is the EDS elemental distribution spectrum of the composite material in Example 4 of the present invention, wherein sodium alginate is uniformly crosslinked (Ca element) and PEI is uniformly loaded (N element).

Claims

1. A method for preparing a three-dimensional network multi-level carbon skeleton composite material, characterized in that, Includes the following steps: S1. A three-dimensional gel network is prepared on the surface of carbon fiber felt. Short-cut carbon fibers and carbon nanotubes are dispersed in the three-dimensional gel network to obtain a three-dimensional network multi-level carbon skeleton material. S2. Polyethyleneimine is loaded onto the three-dimensional network multi-level carbon skeleton material obtained in step S1 to obtain a three-dimensional network multi-level carbon skeleton composite material.

2. The method for preparing the three-dimensional network multi-level carbon skeleton composite material according to claim 1, characterized in that, Step S1 includes: Step S11. Add sodium alginate, chopped carbon fibers, and carbon nanotubes to water and disperse them evenly to obtain a mixed coating solution; Step S12. The mixed coating liquid obtained in step S11 is uniformly coated onto the surface of the carbon fiber felt. Then, the coated carbon fiber felt is immersed in calcium chloride solution and dried to obtain a three-dimensional network multi-level carbon skeleton material.

3. The method for preparing the three-dimensional network multi-level carbon skeleton composite material according to claim 1, characterized in that, Step S2 includes: The three-dimensional network multi-level carbon skeleton material obtained in step S1 is immersed in a polyethyleneimine solution, so that the polyethyleneimine is loaded on the surface and pores of the three-dimensional network multi-level carbon skeleton material. After washing and drying, the three-dimensional network multi-level carbon skeleton composite material is obtained.

4. The method for preparing the three-dimensional network multi-level carbon skeleton composite material according to claim 2, characterized in that, In step S11, the sodium alginate solution in the mixed coating liquid has a mass concentration of 0.5~1.5wt%; the mass ratio of sodium alginate, chopped carbon fiber, and carbon nanotube is 0.7~1.5g:0.5~1.5g:0.5~1.5g.

5. The method for preparing a three-dimensional network multi-level carbon skeleton composite material according to any one of claims 1-4, characterized in that, The chopped carbon fibers have a length of 100-500 μm and a diameter of 5-7 μm.

6. The method for preparing a three-dimensional network multi-level carbon skeleton composite material according to any one of claims 1-4, characterized in that, The carbon fiber felt has a thickness of 1-3 mm; the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10-50 nm and a length of 20-30 μm.

7. The method for preparing a three-dimensional network multi-level carbon skeleton composite material according to claim 2, characterized in that, In step S12, the mass concentration of the calcium chloride solution is 1-10 wt%, and the soaking time is 0.5-12 h.

8. The method for preparing a three-dimensional network multi-level carbon skeleton composite material according to claim 3, characterized in that, In step S2, the concentration of the polyethyleneimine solution is 1-20 wt%, and the soaking time is 1-24 h.

9. A three-dimensional network multi-level carbon skeleton composite material, characterized in that, The composite material includes carbon fiber mat and a three-dimensional gel network loaded in the carbon fiber mat. The three-dimensional gel network contains chopped carbon fibers and carbon nanotubes. Polyethyleneimine is loaded in the carbon fiber mat and the three-dimensional gel network. The proportion of pores with a size of 2-200 nm in the three-dimensional network multi-level carbon skeleton composite material is 34-36%.

10. The application of a three-dimensional network multi-level carbon skeleton composite material as described in claim 9 or a three-dimensional network multi-level carbon skeleton composite material prepared according to the preparation methods in claims 1-8 in CO2 capture.

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