Nitrogen-doped porous carbon chemical heat storage composite material and preparation method thereof
By introducing nitrogen-containing functional groups onto the surface of porous carbon materials, the problems of low heat and mass transfer efficiency and slow hydration reaction rate in chemical thermal storage materials have been solved. This has improved the hydration reaction kinetics and thermal conductivity, reduced the preparation cost, and promoted the commercial application of chemical thermal storage technology.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA ENERGY INVESTMENT CORP LTD
- Filing Date
- 2023-11-21
- Publication Date
- 2026-07-07
AI Technical Summary
Existing chemical thermal storage materials have low heat and mass transfer efficiency in reactors, slow hydration reaction rates, and are prone to agglomeration, which limits the development of chemical thermal storage technology.
Using porous carbon materials as the matrix, combined with low-temperature plasma modification and nitric acid activation modification techniques, nitrogen-containing functional groups are introduced on the surface of the porous carbon materials, and nitrogen-doped porous carbon chemical thermal storage composite materials are prepared through hydrothermal reaction.
It significantly improves the kinetics and thermal conductivity of hydration reaction, achieves nanoscale dispersion of chemical thermal storage materials, reduces preparation costs, and facilitates the commercial application of chemical thermal storage technology.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of thermal storage materials technology, specifically relating to a nitrogen-doped porous carbon chemical thermal storage composite material and its preparation method. Background Technology
[0002] Energy is a crucial pillar of economic development, and energy conservation has become a social focus. However, the utilization rate of primary energy sources such as coal, oil, and natural gas is not high, and a large amount of medium- and low-temperature waste heat is not effectively utilized. Therefore, industrial waste heat recovery has become a key to energy conservation and emission reduction. Chemical thermal storage technology utilizes reversible chemical reactions to store and release heat energy. As an effective means to improve energy utilization efficiency and resolve the contradiction between energy supply and demand, it has become one of the current research hotspots in the field of thermal storage. Compared with traditional sensible and latent heat storage methods, chemical thermal storage not only offers an exponential increase in energy storage density but also avoids problems such as supercooling during material phase transitions and phase separation after exothermic cycles. However, current chemical thermal storage still suffers from problems such as low heat and mass transfer efficiency of the storage material in the reactor, slow hydration reaction rate of the storage components, and easy agglomeration, which seriously restrict the development of chemical thermal storage technology.
[0003] Currently, porous carriers with high specific surface area are commonly used as the matrix to load chemical heat storage materials. The pores of the porous carrier can disperse the chemical heat storage materials, accelerating the reaction rate. Simultaneously, the excellent physical properties of porous materials enhance the overall heat storage performance of the composite material. For example, Chinese patent application CN109370542A discloses a composite carbon-based chemical heat storage material that uses graphene and / or expanded graphite or expanded graphite-graphene composite carbon materials as the matrix, loading chemical heat storage materials such as calcium sulfate, calcium chloride, or magnesium sulfate. Because carbon materials have a high specific surface area, the active components of the chemical heat storage material are dispersed and less prone to agglomeration, which is beneficial to improving the heat storage performance of the material. However, due to the inherent limitations of porous carrier materials, problems such as low hydration reaction efficiency and poor performance of the resulting composite chemical heat storage material still exist when loading chemical heat storage materials. Summary of the Invention
[0004] To address the aforementioned problems in the existing technology, this invention provides a nitrogen-doped porous carbon chemical thermal storage composite material and its preparation method. This invention uses porous carbon material as a matrix, combining low-temperature plasma modification and nitric acid activation modification techniques to prepare a nitrogen-doped porous carbon material. This material is then mixed with a chemical thermal storage material, and after a hydrothermal reaction, a nitrogen-doped porous carbon chemical thermal storage composite material with a high hydration rate is obtained.
[0005] One object of the present invention is to provide a method for preparing a nitrogen-doped porous carbon chemical thermal storage composite material, comprising the following steps:
[0006] S1. The porous carbon material is placed in a low-temperature plasma reactor and activated in the presence of an activating gas and under a high-frequency power supply voltage to obtain activated porous carbon material.
[0007] S2. The activated porous carbon material is mixed with nitric acid solution and then subjected to a modification reaction. After the reaction is completed, the mixture is filtered, the precipitate is washed with deionized water until neutral, and then dried to obtain nitrogen-doped porous carbon material.
[0008] S3. The nitrogen-doped porous carbon material is mixed with the chemical heat storage material solution and subjected to a hydrothermal reaction. After the reaction is completed, the product is dried to obtain the nitrogen-doped porous carbon chemical heat storage composite material.
[0009] The inventors of this invention discovered in their research that the adsorption performance of carbon-based materials for water molecules is directly related to the content and distribution of active functional groups on their surface. Based on this, this invention uses porous carbon materials as a matrix and combines low-temperature plasma modification and nitric acid activation modification techniques to introduce nitrogen-containing functional groups onto the surface of the porous carbon materials. This increases the hydrophilicity of the porous carbon material surface and significantly improves the hydration reaction kinetics of the nitrogen-doped porous carbon chemical thermal storage composite material.
[0010] In some preferred embodiments, in step S1, the specific surface area of the porous carbon material is 500–1500 m². 2 / g, with a pore volume of 0.25-1.2cc / g and an average pore size of 3-5nm; more preferably, the porous carbon material is ordered mesoporous carbon CMK3 and / or cinder-based carbon fiber.
[0011] In this invention, the preferred porous carbon material described above is used. It has the characteristics of high specific surface area and abundant pores, which can efficiently load chemical heat storage materials and achieve nanoscale dispersion of chemical heat storage materials. This is beneficial to improving the hydration rate of chemical heat storage composite materials. At the same time, based on the above porous carbon material, the chemical heat storage composite material finally prepared by the preparation method of this invention has significantly improved thermal conductivity. Compared with the structurally stable ordered mesoporous carbon CMK3, slag-based carbon fiber is inexpensive, which can reduce the overall preparation cost of chemical heat storage materials and help the commercial application of chemical heat storage technology.
[0012] In some embodiments, in step S1, the activation conditions include: an activation gas flow rate of 100-200 ml / min, a high-frequency power supply voltage of 35-40V, and a power supply frequency of 2.5-3.0 kHz, preferably 2.8 kHz; preferably, the activation gas is nitrogen.
[0013] In this invention, low-temperature plasma technology is used to modify porous carbon materials. A high-frequency voltage ionizes the activation gas to form high-energy particles. These high-energy particles interact with the material surface, thereby modifying the surface. Preferably, the high-frequency power supply voltage is 35–40V. If the voltage is too low, high-energy particles cannot be generated; if the voltage is too high, the material will be damaged. Preferably, the activation gas is nitrogen, which introduces nitrogen-containing functional groups onto the surface of the porous carbon material during the activation process, increasing the hydrophilicity of the porous carbon material.
[0014] In some implementations, the activation treatment in step S1 takes 5 to 10 minutes.
[0015] In this invention, the activation time is related to the flow rate of the activation gas and the voltage value of the high-frequency power supply. When the flow rate of the activation gas and the voltage value of the high-frequency power supply are constant, if the activation time is too short, the activation reaction will be insufficient; if the activation time is too long, it will damage the structure of the material surface and reduce the performance of the porous carbon material.
[0016] In some embodiments, in step S2, the concentration of the nitric acid solution is 10-20 wt%, and the mass ratio of the activated porous carbon material to the nitric acid solution is 1:10 to 1:20.
[0017] In this invention, based on plasma modification of porous carbon materials, a further modification is achieved by combining nitric acid activation technology. Preferably, the concentration of nitric acid is controlled between 10 and 20 wt% to obtain nitrogen-doped porous carbon materials with better performance. The inventors have found that if the concentration of nitric acid is less than 10 wt%, the activation reaction is incomplete, and the hydrophilicity of the resulting nitrogen-doped porous carbon material decreases; if the concentration of nitric acid is greater than 20 wt%, the high concentration of nitric acid will damage the surface or pores of the porous carbon material, affecting its adsorption of heat storage materials.
[0018] In some embodiments, in step S2, the modification reaction time is 2-4 hours and the reaction temperature is 60-80°C; preferably, the modification reaction is carried out in a high-pressure reactor lined with polytetrafluoroethylene stainless steel.
[0019] In this invention, the modification reaction time and reaction temperature are related to the nitric acid concentration. At the same time, the modification reaction is carried out in a high-pressure reactor lined with polytetrafluoroethylene stainless steel, which can avoid corrosion of the reactor by the reaction raw materials.
[0020] In some implementations, in step S3, the mass ratio of the nitrogen-doped porous carbon material to the chemical thermal storage material in the chemical thermal storage material solution is 0.25:1 to 4:1.
[0021] In this invention, the surface of nitrogen-doped porous carbon material contains abundant nitrogen-containing functional groups, which greatly improve the hydration reaction kinetics of nitrogen-doped porous carbon chemical heat storage composite material when loaded with chemical heat storage material.
[0022] In some embodiments, in step S3, the chemical heat storage material solution is prepared by dissolving the chemical heat storage material in deionized water. Preferably, the mass ratio of the chemical heat storage material to the deionized water is 1:10 to 1:15. More preferably, the chemical heat storage material is one or more of LiOH, CaCl2, MgCl2 and MgSO4.
[0023] In this invention, controlling the concentration of the chemical heat storage material solution within a certain range is beneficial for obtaining a better loading effect and improving the performance of the composite material. If the concentration is too low, the loading may be incomplete, which is not conducive to obtaining a better hydration and moisture absorption capacity. If the concentration is too high, the loading capacity will be too large, and the moisture absorption material may block the pores of the carbon material, affecting the water vapor mass transfer in the hydration process and ultimately affecting the hydration reaction kinetics.
[0024] In some embodiments, in step S3, the hydrothermal reaction temperature is 105–120°C, and the reaction time is 12–18 h; and / or
[0025] The drying process is divided into two stages. The first stage is freeze drying, preferably at a temperature of -15 to -30°C for 4 to 20 hours. The second stage is drying under a protective gas, preferably argon. More preferably, the drying temperature in the second stage is 120 to 150°C for 3 to 4 hours.
[0026] In this invention, the product is first freeze-dried, which helps to maintain the structural integrity of the nitrogen-doped porous carbon chemical thermal storage composite material.
[0027] Another object of the present invention is to provide a nitrogen-doped porous carbon chemical thermal storage composite material prepared by the preparation method of the nitrogen-doped porous carbon chemical thermal storage composite material described in any one of the above claims.
[0028] Compared with the prior art, the present invention has the following beneficial effects:
[0029] 1. This invention uses porous carbon material as a matrix and combines low-temperature plasma modification and nitric acid activation modification technology to introduce nitrogen-containing functional groups on the surface of porous carbon material, which is beneficial to improve the hydrophilicity of the surface of porous carbon material and greatly enhances the hydration reaction kinetics of nitrogen-doped porous carbon chemical heat storage composite material.
[0030] 2. In the preferred embodiment of the present invention, porous carbon materials with nanoporous structures are used, which facilitates the nanoscale dispersion of chemical thermal storage materials and improves the hydration rate of chemical thermal storage composite materials. At the same time, the chemical thermal storage composite materials prepared by the preparation method of the present invention based on the preferred porous carbon materials have significantly improved thermal conductivity. Compared with structurally stable ordered mesoporous carbon CMK3, slag-based carbon fiber is inexpensive, which can reduce the overall preparation cost of chemical thermal storage materials and help the commercial application of chemical thermal storage technology. Attached Figure Description
[0031] Figure 1 This is a diagram showing the water vapor adsorption results of ordered mesoporous carbon CMK-3 before and after nitrogen doping in Example 1 of the present invention;
[0032] Figure 2 The diagram shows the water vapor adsorption results of the nitrogen-doped porous carbon chemical thermal storage composite material (using ordered mesoporous carbon CMK-3 as a carrier and loading chemical thermal storage material CaCl2) and the monomeric CaCl2 material prepared in Example 1 of the present invention.
[0033] Figure 3 The pore size distribution diagram is shown for the nitrogen-doped porous carbon chemical thermal storage composite material (using coal slag-based carbon fiber as a carrier and loading chemical thermal storage material LiOH) prepared in Example 2 of the present invention.
[0034] Figure 4 The diagram shows the water vapor adsorption results of the nitrogen-doped porous carbon chemical thermal storage composite material (using coal slag-based carbon fiber as a carrier and loading chemical thermal storage material LiOH) and the LiOH monomer material prepared in Example 2 of the present invention.
[0035] Figure 5 The diagram shows the water vapor adsorption results of the nitrogen-doped porous carbon chemical thermal storage composite materials prepared in Example 1 and Comparative Examples 1-4 of this invention. Detailed Implementation
[0036] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0037] In the following embodiments, ordered mesoporous carbon CMK3 and cinder-based carbon fiber were purchased from Nanjing Jicang Nanotechnology Co., Ltd. and Zhongli New Materials Co., Ltd., respectively. The specific surface area of ordered mesoporous carbon CMK3 was 500-600 m². 2 / g, pore volume 0.4-0.55cm 3 / g, with an average pore size of 3.5-5nm; the specific surface area of slag-based carbon fiber is 1000-1300m². 2 / g, pore volume 0.8-1.2cm 3 / g, with an average pore size of 3-3.5nm.
[0038] The low-temperature plasma reactor (model CTP-2000K) was purchased from Nanjing Suman Plasma Technology Co., Ltd.
[0039] Other reagents and equipment, unless otherwise specified, are available commercially.
[0040] In this invention, the water vapor adsorption test is performed as follows: A heat-storing composite material as the sample is placed in a quartz boat, and an inert gas (e.g., nitrogen) is purged at a rate of 100 mL / min. The temperature in the vertical tube furnace is set to 30°C (the temperature in the following examples and comparative examples is 30°C; different hydration temperatures can be set according to actual needs in the art). The weight of the electronic balance is recorded. Then, the water vapor generator is turned on, and water vapor is fed in until the partial pressure of water vapor reaches 57.8 kPa. The change in the electronic balance reading is recorded. When the electronic balance reading no longer changes, the feeding of water vapor is stopped, and the process is maintained for 5 minutes to remove adsorbed water. The electronic balance reading is recorded again. The difference between the weight after adsorption and the initial weight is the amount of water vapor adsorbed. The ratio of the amount of water vapor adsorbed to the adsorption time is the hydration adsorption rate.
[0041] The pore size distribution is measured using the nitrogen isothermal adsorption-desorption method (BET).
[0042] Other experimental methods, unless otherwise specified, are all conventional methods.
[0043] Example 1
[0044] The preparation method of nitrogen-doped porous carbon chemical thermal storage composite material includes the following steps:
[0045] S1. Place 20g of ordered mesoporous carbon CMK3 in a low-temperature plasma reactor, introduce nitrogen gas, and adjust the nitrogen gas flow rate to 100ml / min. Set the high-frequency power supply voltage to 35V and the power supply frequency to 2.8kHz. Activate the ordered mesoporous carbon CMK3 for 10min to obtain activated ordered mesoporous carbon CMK3.
[0046] S2. The activated ordered mesoporous carbon CMK3 was mixed with 10wt% nitric acid solution at a mass ratio of 1:20 and then subjected to a modification reaction. The modification reaction time was 2 hours and the reaction temperature was 80℃. After the reaction was completed, the mixture was filtered, the precipitate was washed with deionized water until neutral, and then placed in a vacuum drying oven and dried at 105℃ to obtain nitrogen-doped ordered mesoporous carbon CMK3.
[0047] S3. Weigh 10g of CaCl2 and place it in a vacuum drying oven. Dry it under vacuum at 105℃ and -0.1Mpa for 4 hours. Add the dried CaCl2 to 100g of deionized water and stir thoroughly to obtain a CaCl2 solution. Weigh 20g of nitrogen-doped ordered mesoporous carbon CMK3 and add it to the CaCl2 solution. Then place it in a high-pressure reactor lined with polytetrafluoroethylene stainless steel and mix thoroughly. Heat to 105℃ for hydrothermal reaction for 12 hours. After the reaction is completed, allow the reactor to cool naturally to room temperature. Take out the product and place it in a freeze dryer for freeze drying at -30℃ for 10 hours. Then place it in a tube furnace and dry it at 150℃ under an argon atmosphere for 3 hours to obtain a nitrogen-doped porous carbon chemical thermal storage composite material (CMK3-CaCl2).
[0048] Water vapor adsorption tests were performed on ordered mesoporous carbon CMK3 and nitrogen-doped ordered mesoporous carbon CMK3, and the results are as follows: Figure 1 As shown in the figure. Water vapor adsorption tests were performed on the monomeric CaCl2 material and the nitrogen-doped porous carbon chemical thermal storage composite material (CMK3-CaCl2), and the results are as follows. Figure 2 As shown.
[0049] from Figure 1 As can be seen, nitrogen doping significantly improves the adsorption performance of ordered mesoporous carbon CMK3 for water vapor; from Figure 2 As can be seen from the data, within 0-100 min, the nitrogen-doped porous carbon chemical thermal storage composite material prepared in this embodiment has a significantly improved hydration rate compared to the monomeric CaCl2 material.
[0050] Example 2
[0051] The preparation method of nitrogen-doped porous carbon chemical thermal storage composite material includes the following steps:
[0052] S1. Place 20g of coal slag-based carbon fiber in a low-temperature plasma reactor, introduce nitrogen gas, and adjust the nitrogen gas flow rate to 20ml / min. Set the high-frequency power supply voltage to 35V and the power supply frequency to 2.8kHz. Activate the coal slag-based carbon fiber for 5min to obtain activated coal slag-based carbon fiber.
[0053] S2. The activated coal slag-based carbon fiber is mixed with 20wt% nitric acid solution at a mass-volume ratio of 1:20 and then subjected to a modification reaction. The modification reaction time is 4 hours and the reaction temperature is 60℃. After the reaction is completed, the mixture is filtered, the precipitate is washed with deionized water until neutral, and then placed in a vacuum drying oven and dried at 105℃ to obtain nitrogen-doped coal slag-based carbon fiber.
[0054] S3. Weigh 10g of LiOH and place it in a vacuum drying oven. Dry it under vacuum at 105℃ and -0.1Mpa for 4 hours. Add the dried LiOH to 100g of deionized water and stir thoroughly to obtain a LiOH solution. Weigh 20g of nitrogen-doped coal slag-based carbon fiber and add it to a CaCl2 solution. Then place it in a high-pressure reactor lined with polytetrafluoroethylene stainless steel and mix thoroughly. Heat the reactor to 105℃ for a hydrothermal reaction for 12 hours. After the reaction, allow the reactor to cool naturally to room temperature. Remove the product and freeze-dry it in a freeze dryer at -30℃ for 10 hours. Then place it in a tube furnace and dry it at 150℃ under an argon atmosphere for 3 hours to obtain a nitrogen-doped porous carbon chemical thermal storage composite material (coal slag-based carbon fiber-LiOH).
[0055] The pore size distribution of nitrogen-doped porous carbon chemical thermal storage composite material (slag-based carbon fiber-LiOH) was tested, and the results are as follows: Figure 3 As shown in the figure, the prepared slag-based carbon fiber-LiOH material still exhibits a nanoscale pore size distribution.
[0056] Water vapor adsorption tests were conducted on LiOH monomer materials and nitrogen-doped porous carbon chemical thermal storage composite materials (coal slag-based carbon fiber-LiOH), and the results are as follows: Figure 4 As shown in the figure, within 0-100 min, the hydration rate of the composite material formed by loading LiOH onto nitrogen-doped coal slag-based carbon fibers was significantly improved compared to that of LiOH monomer.
[0057] Comparative Example 1
[0058] The preparation method of the nitrogen-doped porous carbon chemical thermal storage composite material is basically the same as that in Example 1, except that the concentration of the nitric acid solution is 5 wt%.
[0059] Comparative Example 2
[0060] The preparation method of nitrogen-doped porous carbon chemical thermal storage composite material is basically the same as that in Example 1, except that the concentration of nitric acid solution is 30 wt%.
[0061] Comparative Example 3
[0062] The preparation method of nitrogen-doped porous carbon chemical thermal storage composite material is basically the same as that in Example 1, except that the low-temperature plasma modification step is missing.
[0063] Comparative Example 4
[0064] The preparation method of nitrogen-doped porous carbon chemical thermal storage composite material is basically the same as that in Example 1, except that the nitric acid activation modification step is missing.
[0065] The nitrogen-doped porous carbon chemical thermal storage composite materials (CMK3-CaCl2) prepared in Example 1 and Comparative Examples 1-4 were subjected to water vapor adsorption tests, and the results are as follows: Figure 5 As shown in the figure, the water vapor adsorption capacity and adsorption rate of the nitrogen-doped porous carbon chemical thermal storage composite material prepared in Example 1 are significantly higher than those in Comparative Examples 1-4. If the concentration of the nitric acid solution is too low (Comparative Example 1) or too high (Comparative Example 2), the water vapor adsorption capacity and adsorption rate of the prepared nitrogen-doped porous carbon chemical thermal storage composite material both decrease to some extent. This is because excessively high nitric acid concentration damages the structure of the carbon material itself, leading to a decrease in adsorption capacity; while excessively low nitric acid concentration results in incomplete modification, affecting the loading effect of nitrogen-containing functional groups and causing a decrease in adsorption capacity. Comparative Example 3 lacks a low-temperature plasma modification step, and Comparative Example 4 lacks a nitric acid activation modification step. The results show that the water vapor adsorption capacity and adsorption rate of the prepared nitrogen-doped porous carbon chemical thermal storage composite material both decrease to some extent. The results indicate that the synergistic effect of low-temperature plasma modification and nitric acid activation modification greatly improves the water vapor adsorption capacity and adsorption rate of the prepared nitrogen-doped porous carbon chemical thermal storage composite material.
[0066] The above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and are not intended to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention.
Claims
1. A method for preparing a nitrogen-doped porous carbon chemical thermal storage composite material, characterized in that, Includes the following steps: S1. The porous carbon material is placed in a low-temperature plasma reactor and activated in the presence of an activating gas and under a high-frequency power supply voltage to obtain activated porous carbon material; the activation conditions include: the activating gas flow rate is 100~200ml / min, the high-frequency power supply voltage is 35~40V, the power supply frequency is 2.5~3.0kHz, and the activating gas is nitrogen; the porous carbon material is ordered mesoporous carbon CMK3 and / or cinder-based carbon fiber; S2. The activated porous carbon material is mixed with a nitric acid solution with a concentration of 10-20 wt% and then subjected to a modification reaction at a reaction temperature of 60-80°C. After the reaction is completed, the mixture is filtered, the precipitate is washed with deionized water until neutral, and then dried to obtain nitrogen-doped porous carbon material. S3. The nitrogen-doped porous carbon material is mixed with the chemical heat storage material solution and then subjected to a hydrothermal reaction at a temperature of 105-120°C. After the reaction is completed, the product is dried to obtain a nitrogen-doped porous carbon chemical heat storage composite material. The chemical heat storage material is one or more of LiOH, CaCl2, MgCl2 and MgSO4.
2. The method for preparing nitrogen-doped porous carbon chemical thermal storage composite material according to claim 1, characterized in that, In step S1, the specific surface area of the porous carbon material is 500~1500 m². 2 / g, pore volume is 0.25~1.2cc / g, and average pore size is 3~5nm.
3. The preparation method of the nitrogen-doped porous carbon chemical thermal storage composite material according to claim 1, characterized in that, In step S1, the power supply frequency is 2.8kHz.
4. The method for preparing nitrogen-doped porous carbon chemical thermal storage composite material according to any one of claims 1-3, characterized in that, In step S1, the activation treatment time is 5-10 minutes.
5. The method for preparing nitrogen-doped porous carbon chemical thermal storage composite material according to claim 1, characterized in that, In step S2, the mass ratio of the activated porous carbon material to the nitric acid solution is 1:10 to 1:
20.
6. The method for preparing nitrogen-doped porous carbon chemical thermal storage composite material according to any one of claims 1-3 and 5, characterized in that, In step S2, the modification reaction time is 2-4 hours.
7. The method for preparing nitrogen-doped porous carbon chemical thermal storage composite material according to claim 6, characterized in that, The modification reaction was carried out in a high-pressure reactor lined with polytetrafluoroethylene stainless steel.
8. The method for preparing nitrogen-doped porous carbon chemical thermal storage composite material according to claim 1, characterized in that, In step S3, the mass ratio of the nitrogen-doped porous carbon material to the chemical heat storage material in the chemical heat storage material solution is 0.25:1 to 4:
1.
9. The method for preparing the nitrogen-doped porous carbon chemical thermal storage composite material according to claim 1, characterized in that, In step S3, the chemical heat storage material solution is prepared by dissolving the chemical heat storage material in deionized water, and the mass ratio of the chemical heat storage material to the deionized water is 1:10 to 1:
15.
10. The method for preparing nitrogen-doped porous carbon chemical thermal storage composite material according to any one of claims 1-3, 5, 8-9, characterized in that, In step S3, the reaction time is 12-18 hours; and / or The drying process is divided into two stages: the first stage is freeze drying; the second stage is drying under a protective gas atmosphere.
11. The method for preparing nitrogen-doped porous carbon chemical thermal storage composite material according to claim 10, characterized in that, The freeze-drying temperature is -15 to -30°C, and the time is 4 to 20 hours.
12. The method for preparing nitrogen-doped porous carbon chemical thermal storage composite material according to claim 10, characterized in that, The protective gas is argon.
13. The method for preparing nitrogen-doped porous carbon chemical thermal storage composite material according to claim 12, characterized in that, The second stage of drying is carried out at a temperature of 120~150℃ for 3~4 hours.
14. A nitrogen-doped porous carbon chemical thermal storage composite material, characterized in that, The nitrogen-doped porous carbon chemical thermal storage composite material is prepared by any one of claims 1-13.