Nitrogen-doped porous carbon chemical heat storage composite material and preparation method thereof

Abstract

The invention belongs to the technical field of heat storage materials, and particularly relates to a nitrogen-doped porous carbon chemical heat storage composite material and a preparation method thereof. According to the preparation method, the porous carbon material is taken as a matrix, and a nitrogen-containing functional group is introduced to the surface of the porous carbon material by combining low-temperature plasma modification and nitric acid activation modification technologies, so that the hydrophilicity of the surface of the porous carbon material is improved; the hydration reaction kinetic performance of the nitrogen-doped porous carbon chemical heat storage composite material is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of heat storage materials, and in particular relates to a nitrogen-doped porous carbon chemical heat storage composite material and a preparation method thereof. Background Art

[0002] Energy is an important support for economic development, and energy conservation has become a social focus. However, in the process of energy utilization, the utilization rate of primary energy such as coal, oil, and natural gas is not high, and a large amount of medium and low temperature waste heat cannot be effectively utilized. Therefore, industrial waste heat recovery has become the key to energy saving and consumption reduction. Chemical heat storage technology uses reversible chemical reactions to store and release heat energy. As an effective means to improve energy utilization and solve the contradiction between energy supply and demand, it has become one of the research hotspots in the field of heat storage. Compared with traditional sensible heat storage and latent heat storage methods, chemical heat storage not only has an exponential improvement in energy storage density, but also does not have problems such as supercooling during material phase change and phase separation after heat release cycle. However, at present, chemical heat storage still has problems such as low heat and mass transfer efficiency of heat storage materials in reactors, slow hydration reaction rate of heat storage component monomers, and easy agglomeration, which seriously restricts the development of chemical heat storage technology.

[0003] At present, porous carriers with high specific surface area are often used as the matrix to load chemical heat storage materials. The pores of the porous carrier can disperse the chemical heat storage materials, accelerate the reaction rate, and at the same time, with the help of other excellent physical properties of the porous material, the overall heat storage characteristics of the composite material can be improved. For example, Chinese patent application CN109370542A discloses a composite carbon-based chemical heat storage material, which uses graphene and / or expanded graphite or expanded graphite-graphene composite carbon material as the matrix to load chemical heat storage materials such as calcium sulfate, calcium chloride or magnesium sulfate. Because the carbon material has a high specific surface, the active components of the chemical heat storage material are dispersed and not easy to agglomerate, which is conducive to the improvement of the heat storage performance of the heat storage material. However, due to the limitations of the properties of the porous carrier material itself, when it is loaded with chemical heat storage materials, there are still problems such as low hydration reaction efficiency and poor performance of the obtained composite chemical heat storage material. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a nitrogen-doped porous carbon chemical heat storage composite material and a preparation method thereof. The present invention uses porous carbon material as a matrix, combines low-temperature plasma modification and nitric acid activation modification technology, prepares nitrogen-doped porous carbon material, mixes the material with a chemical heat storage material, and after hydrothermal reaction, obtains a nitrogen-doped porous carbon chemical heat storage composite material with a high hydration rate.

[0005] An object of the present invention is to provide a method for preparing a nitrogen-doped porous carbon chemical heat storage composite material, comprising the following steps:

[0006] S1, placing the porous carbon material in a low-temperature plasma reaction device, and performing activation treatment in the presence of an activation gas and a high-frequency power supply voltage to obtain an activated porous carbon material;

[0007] S2, mixing the activated porous carbon material with a nitric acid solution, performing a modification reaction, filtering after the reaction is completed, washing the precipitate with deionized water until it is neutral, and drying to obtain a nitrogen-doped porous carbon material;

[0008] S3, mixing the nitrogen-doped porous carbon material with a chemical heat storage material solution, and then subjecting the mixture to a hydrothermal reaction. After the reaction is completed, drying the product to obtain a nitrogen-doped porous carbon chemical heat storage composite material.

[0009] The inventors of the present invention have found 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 its surface. Based on this, the present invention uses porous carbon materials as the matrix, combines low-temperature plasma modification and nitric acid activation modification technology, introduces nitrogen-containing functional groups on the surface of porous carbon materials, increases the hydrophilicity of the porous carbon material surface, and greatly improves the hydration reaction kinetics of nitrogen-doped porous carbon chemical heat storage composite materials.

[0010] In some preferred embodiments, in step S1, the specific surface area of ​​the porous carbon material is 500 to 1500 m 2 / g, the pore volume is 0.25-1.2cc / g, and the average pore diameter is 3-5nm; more preferably, the porous carbon material is ordered mesoporous carbon CMK3 and / or cinder-based carbon fiber.

[0011] In the present invention, the above-mentioned preferred porous carbon material is used, which has the characteristics of high specific surface area, rich pores, etc., can efficiently load chemical heat storage materials, and can achieve nano-scale dispersion of chemical heat storage materials, which is beneficial to improving the hydration rate of chemical heat storage composite materials. At the same time, based on the above-mentioned porous carbon material, the chemical heat storage composite material finally obtained by the preparation method of the present invention has significantly improved thermal conductivity; compared with the structurally stable ordered mesoporous carbon CMK3, coal ash-based carbon fiber is inexpensive, which can reduce the overall preparation cost of chemical heat storage materials, and is conducive to the commercial application of chemical heat storage technology.

[0012] In some embodiments, in step S1, the conditions of the activation treatment include: an activation gas flow rate of 100 to 200 ml / min, a high-frequency power supply voltage value of 35 to 40 V, a power supply frequency of 2.5 to 3.0 kHz, preferably 2.8 kHz; preferably, the activation gas is nitrogen.

[0013] In the present invention, low-temperature plasma technology is used to modify the porous carbon material. Through high-frequency voltage, the activated gas is ionized to form high-energy particles. These high-energy particles interact with the surface of the material, thereby modifying the surface of the material. Preferably, the high-frequency power supply voltage value is 35 to 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 activated gas is nitrogen, which can introduce nitrogen-containing functional groups on the surface of the porous carbon material during the activation process to increase the hydrophilicity of the porous carbon material.

[0014] In some embodiments, in step S1, the activation treatment time is 5 to 10 minutes.

[0015] In the present invention, the activation treatment 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 treatment time is too short, the activation reaction will be insufficient; if the activation treatment time is too long, the structure of the material surface will be destroyed, thereby reducing 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 1:10-1:20.

[0017] In the present invention, on the basis of plasma modification of porous carbon materials, the porous carbon materials are further modified in combination with nitric acid activation technology. Among them, when the concentration of nitric acid is preferably controlled between 10 and 20wt%, a nitrogen-doped porous carbon material with better performance can be obtained. The inventors found that if the concentration of nitric acid is less than 10wt%, the activation reaction is incomplete, and the hydrophilicity of the obtained nitrogen-doped porous carbon material will be reduced; if the concentration of nitric acid is greater than 20wt%, the high concentration of nitric acid will destroy the surface or pores of the porous carbon material, affecting its adsorption to the heat storage material.

[0018] In some embodiments, in step S2, the modification reaction time is 2 to 4 hours, and the reaction temperature is 60 to 80° C.; preferably, the modification reaction is carried out in a stainless steel autoclave lined with tetrafluoroethylene.

[0019] In the present invention, the modification reaction time and reaction temperature are related to the nitric acid concentration. Meanwhile, the modification reaction is carried out in a stainless steel high-pressure reactor lined with tetrafluoroethylene, which can avoid the corrosion of the reactor by the reaction raw materials.

[0020] In some embodiments, 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.

[0021] In the present invention, the surface of the nitrogen-doped porous carbon material contains abundant nitrogen-containing functional groups. When loaded with a chemical heat storage material, the hydration reaction kinetics of the nitrogen-doped porous carbon chemical heat storage composite material is greatly improved.

[0022] In some embodiments, in step S3, the chemical thermal storage material solution is prepared by dissolving the chemical thermal storage material in deionized water. Preferably, the mass ratio of the chemical thermal storage material to the deionized water is 1:10 to 1:15. Preferably, the chemical thermal storage material is LiOH, CaCl 2 MgCl 2 and MgSO 4 One or more of .

[0023] In the present invention, the concentration of the chemical thermal storage material solution is controlled within a certain range, which is conducive to obtaining a better loading effect and improving the performance of the composite material; if the concentration is too low, it may cause incomplete loading, which is not conducive to obtaining a better hydration moisture absorption capacity; if the concentration is too high, the loading amount is too large, and the hygroscopic material may block the pores of the carbon material, affecting the water vapor mass transfer during 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, the freeze drying temperature is -15 to -30°C and the time is 4 to 20 hours. The second stage is drying under protective gas. Preferably, the protective gas is argon. More preferably, the drying temperature of the second stage is 120 to 150°C and the time is 3 to 4 hours.

[0026] In the present invention, the product is first freeze-dried, which is beneficial for the structure of the prepared nitrogen-doped porous carbon chemical heat storage composite material to remain intact.

[0027] Another object of the present invention is to provide a nitrogen-doped porous carbon chemical heat storage composite material prepared by any one of the above-mentioned methods for preparing the nitrogen-doped porous carbon chemical heat storage composite material.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention uses porous carbon materials as a matrix, combines low-temperature plasma modification and nitric acid activation modification technology, introduces nitrogen-containing functional groups on the surface of the porous carbon materials, which is beneficial to improving the hydrophilicity of the surface of the porous carbon materials, and greatly improves the hydration reaction kinetics of the nitrogen-doped porous carbon chemical heat storage composite material;

[0030] 2. In the preferred embodiment of the present invention, a porous carbon material with a nanopore structure is used, which is beneficial to achieve nanoscale dispersion of chemical heat storage materials and improve the hydration rate of chemical heat storage composite materials. At the same time, the chemical heat storage composite material prepared by the preparation method of the present invention based on the preferred porous carbon material has significantly improved thermal conductivity; compared with the ordered mesoporous carbon CMK3 with stable structure, slag-based carbon fiber is inexpensive, which can reduce the overall preparation cost of chemical heat storage materials and contribute to the commercial application of chemical heat storage technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a graph showing the water vapor adsorption results of the ordered mesoporous carbon CMK-3 before and after nitrogen doping in Example 1 of the present invention;

[0032] Figure 2 The nitrogen-doped porous carbon chemical heat storage composite material prepared in Example 1 of the present invention (with ordered mesoporous carbon CMK-3 as a carrier and loaded with chemical heat storage material CaCl 2 ) and monomer CaCl 2 Water vapor adsorption results of materials;

[0033] Figure 3 This is a pore size distribution diagram of the nitrogen-doped porous carbon chemical heat storage composite material (using coal slag-based carbon fiber as a carrier and loaded with chemical heat storage material LiOH) prepared in Example 2 of the present invention;

[0034] Figure 4 The water vapor adsorption result diagram of the nitrogen-doped porous carbon chemical heat storage composite material (with coal ash-based carbon fiber as a carrier and loaded with chemical heat storage material LiOH) and the LiOH monomer material prepared in Example 2 of the present invention;

[0035] Figure 5 This is a graph showing the water vapor adsorption results of the nitrogen-doped porous carbon chemical heat storage composite materials prepared in Example 1 and Comparative Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In the following examples, ordered mesoporous carbon CMK3 and coal slag-based carbon fibers were purchased from Nanjing Jicang Nanotechnology Co., Ltd. and Zhongli New Materials Co., Ltd., respectively. The specific surface area of ​​ordered mesoporous carbon CMK3 is 500-600 m 2 / g, pore volume is 0.4-0.55cm 3 / g, the average pore size is 3.5-5nm; the specific surface area of ​​slag-based carbon fiber is 1000-1300m 2 / g, pore volume is 0.8-1.2cm 3 / g, and the average pore size is 3-3.5nm.

[0038] The low-temperature plasma reaction device (model CTP-2000K) was purchased from Nanjing Suman Plasma Technology Co., Ltd.

[0039] Other reagents and equipment, unless otherwise specified, are available from commercial sources.

[0040] In the present invention, the water vapor adsorption test is as follows: a thermal storage composite material as a sample is placed in a quartz boat, an inert gas (such as nitrogen) is purged at a rate of 100 mL / min, and the temperature in the vertical tube furnace is set to 30°C (the temperature in the following embodiments and comparative examples is 30°C, and different hydration temperatures can be set according to actual use needs in the art); the weight of the electronic balance is recorded, and then the water vapor generator is turned on, water vapor is fed so that the water vapor partial pressure is 57.8 kPa, and the change in the reading of the electronic balance is recorded. When the reading of the electronic balance no longer changes, stop feeding water vapor, keep for 5 minutes to remove the adsorbed water, and record the reading of the electronic balance. The difference between the weight after adsorption and the initial weight is the water vapor adsorption amount. The ratio of the water vapor adsorption amount to the adsorption time is the hydration adsorption rate.

[0041] The pore size distribution test method is as follows: the measurement is performed using nitrogen isothermal adsorption-desorption method (BET).

[0042] Other experimental methods, unless otherwise specified, were conventional methods.

[0043] Example 1

[0044] The preparation method of the nitrogen-doped porous carbon chemical heat storage composite material comprises the following steps:

[0045] S1, placing 20g of ordered mesoporous carbon CMK3 in a low-temperature plasma reaction device, introducing nitrogen, and adjusting the nitrogen flow rate to 100ml / min, the high-frequency power supply voltage value to 35V, the power supply frequency to 2.8kHz, and activating the ordered mesoporous carbon CMK3 for 10min to obtain activated ordered mesoporous carbon CMK3;

[0046] S2, the activated ordered mesoporous carbon CMK3 and 10wt% nitric acid solution are mixed at a mass ratio of 1:20, and a modification reaction is carried out. The modification reaction time is 2h and the reaction temperature is 80°C. After the reaction is completed, the precipitate is filtered, washed with deionized water until neutral, placed in a vacuum drying oven, and dried at 105°C to obtain nitrogen-doped ordered mesoporous carbon CMK3;

[0047] S3, weigh 10g CaCl 2 , put it into a vacuum drying oven and vacuum dry it at 105℃ and -0.1Mpa for 4h; the dried CaCl 2 Add 100g of deionized water and stir thoroughly to obtain CaCl 2 Solution; weigh 20g of nitrogen-doped ordered mesoporous carbon CMK3 and add it to CaCl 2 The solution was then placed in a stainless steel autoclave lined with tetrafluoroethylene, fully mixed, heated to 105°C for hydrothermal reaction for 12 hours, and the autoclave was naturally cooled to room temperature after the reaction was completed; after taking out the product, it was placed in a freeze dryer for freeze drying at -30°C for 10 hours, and then placed in a tubular furnace for drying at 150°C for 3 hours in an argon atmosphere to obtain a nitrogen-doped porous carbon chemical thermal storage composite material (CMK3-CaCl 2 ).

[0048] The ordered mesoporous carbon CMK3 and nitrogen-doped ordered mesoporous carbon CMK3 were tested for water vapor adsorption. Figure 1 As shown. For monomer CaCl 2 Materials and nitrogen-doped porous carbon chemical thermal storage composites (CMK3-CaCl 2 ) to conduct water vapor adsorption test, the results are as follows Figure 2 shown.

[0049] from Figure 1 It can be seen that the adsorption performance of ordered mesoporous carbon CMK3 for water vapor is significantly improved after being doped with nitrogen; Figure 2 It can be seen that within 0-100min, compared with the monomer CaCl 2 Material, the nitrogen-doped porous carbon chemical heat storage composite material prepared in this embodiment has a significantly improved hydration rate.

[0050] Example 2

[0051] The preparation method of the nitrogen-doped porous carbon chemical heat storage composite material comprises the following steps:

[0052] S1, placing 20g of coal slag-based carbon fiber in a low-temperature plasma reaction device, introducing nitrogen, and adjusting the nitrogen flow rate to 20ml / min, the high-frequency power supply voltage value to 35V, the power supply frequency to 2.8kHz, and activating the coal slag-based carbon fiber for 5min to obtain activated coal slag-based carbon fiber;

[0053] S2, the activated coal ash-based carbon fiber is mixed with 20wt% nitric acid solution at a mass volume ratio of 1:20, and a modification reaction is carried out. The modification reaction time is 4h and the reaction temperature is 60°C. After the reaction is completed, the precipitate is filtered, washed with deionized water until neutral, placed in a vacuum drying oven, and dried at 105°C to obtain nitrogen-doped coal ash-based carbon fiber;

[0054] S3, weigh 10g LiOH, put it into a vacuum drying oven, and vacuum dry it at 105℃ and -0.1Mpa for 4h; add the dried LiOH to 100g deionized water, stir it thoroughly to obtain LiOH solution; weigh 20g nitrogen-doped coal slag-based carbon fiber, add it to CaCl 2 The solution was then placed in a stainless steel high-pressure reactor lined with tetrafluoroethylene, fully mixed, heated to 105°C for hydrothermal reaction for 12 hours, and after the reaction, the reactor was naturally cooled to room temperature; after taking out the product, it was placed in a freeze dryer for freeze drying at -30°C for 10 hours, and then placed in a tubular furnace and dried at 150°C for 3 hours in an argon atmosphere to obtain a nitrogen-doped porous carbon chemical heat storage composite material (coal slag-based carbon fiber-LiOH).

[0055] The pore size distribution test of nitrogen-doped porous carbon chemical thermal storage composite material (coal slag-based carbon fiber-LiOH) was carried out. The results are as follows Figure 3 As shown in the figure, it can be seen that the prepared coal slag-based carbon fiber-LiOH material still has a nanoscale pore size distribution.

[0056] The water vapor adsorption test of LiOH monomer material and nitrogen-doped porous carbon chemical thermal storage composite material (coal slag-based carbon fiber-LiOH) was carried out. 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 nitrogen-doped coal slag-based carbon fiber loaded with LiOH was significantly improved compared with LiOH monomer.

[0057] Comparative Example 1

[0058] The preparation method of the nitrogen-doped porous carbon chemical heat storage composite material is basically the same as that of Example 1, except that the concentration of the nitric acid solution is 5 wt %.

[0059] Comparative Example 2

[0060] The preparation method of the nitrogen-doped porous carbon chemical heat storage composite material is basically the same as that of Example 1, except that the concentration of the nitric acid solution is 30 wt %.

[0061] Comparative Example 3

[0062] The preparation method of the nitrogen-doped porous carbon chemical heat storage composite material is basically the same as that of Example 1, except that the low-temperature plasma modification step is missing.

[0063] Comparative Example 4

[0064] The preparation method of the nitrogen-doped porous carbon chemical heat storage composite material is basically the same as that of Example 1, except that the nitric acid activation and modification step is missing.

[0065] The nitrogen-doped porous carbon chemical thermal storage composite material (CMK3-CaCl 2 ) to conduct water vapor adsorption test, the results are as follows Figure 5 As shown in the figure, it can be seen that the water vapor adsorption amount and adsorption rate of the nitrogen-doped porous carbon chemical heat storage composite material prepared in Example 1 are significantly higher than those of Comparative Examples 1-4. If the concentration of the nitric acid solution is low (Comparative Example 1) or too high (Comparative Example 2), the water vapor adsorption amount and adsorption rate of the obtained nitrogen-doped porous carbon chemical heat storage composite material will both decrease to a certain extent. This is because the excessively high concentration of nitric acid destroys the structure of the carbon material itself, resulting in a decrease in the adsorption amount; while the nitric acid concentration is too low, the modification is incomplete, affecting the loading effect of the nitrogen-containing functional groups, resulting in a decrease in the adsorption amount. Comparative Example 3 lacks a low-temperature plasma modification step, and Comparative Example 4 lacks a nitric acid activation modification step. As a result, it is found that the water vapor adsorption amount and adsorption rate of the obtained nitrogen-doped porous carbon chemical heat storage composite material both decrease to a certain extent. The results show that the synergistic effect of low-temperature plasma modification and nitric acid activation modification greatly improves the water vapor adsorption amount and adsorption rate of the obtained nitrogen-doped porous carbon chemical heat storage composite material.

[0066] The above embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the aforementioned embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen-doped porous carbon chemical heat storage composite material, It is characterized in that The steps include: S1, placing the porous carbon material in a low-temperature plasma reaction device, and performing activation treatment in the presence of an activation gas and a high-frequency power supply voltage to obtain an activated porous carbon material; S2, mixing the activated porous carbon material with a nitric acid solution, performing a modification reaction, filtering after the reaction is completed, washing the precipitate with deionized water until it is neutral, and drying to obtain a nitrogen-doped porous carbon material; S3, mixing the nitrogen-doped porous carbon material with a chemical heat storage material solution, and then subjecting the mixture to a hydrothermal reaction. After the reaction is completed, drying the product to obtain a nitrogen-doped porous carbon chemical heat storage composite material.

2. The method for preparing the nitrogen-doped porous carbon chemical thermal storage composite material according to claim 1, It is characterized in that In step S1, the specific surface area of ​​the porous carbon material is 500 to 1500 m 2 / g, pore volume is 0.25-1.2cc / g, average pore diameter is 3-5nm; preferably ordered mesoporous carbon CMK3 and / or coal slag-based carbon fiber.

3. The method for preparing the nitrogen-doped porous carbon chemical thermal storage composite material according to claim 1, It is characterized in that In step S1, the activation treatment conditions include: an activation gas flow rate of 100-200 ml / min, a high-frequency power supply voltage value of 35-40 V, a power supply frequency of 2.5-3.0 kHz, preferably 2.8 kHz; preferably, the activation gas is nitrogen.

4. The method for preparing the nitrogen-doped porous carbon chemical heat storage composite material according to any one of claims 1 to 3, It is characterized in that In step S1, the activation treatment time is 5 to 10 minutes.

5. The method for preparing the nitrogen-doped porous carbon chemical thermal storage composite material according to claim 1, It is characterized in that In step S2, the concentration of the nitric acid solution is 10-20wt%, and the mass ratio of the activated porous carbon material to the nitric acid solution is 1:10-1:

20.

6. The method for preparing the nitrogen-doped porous carbon chemical heat storage composite material according to any one of claims 1 to 5, It is characterized in that In step S2, the modification reaction time is 2 to 4 hours, and the reaction temperature is 60 to 80° C.; preferably, the modification reaction is carried out in a stainless steel autoclave lined with tetrafluoroethylene.

7. The method for preparing the nitrogen-doped porous carbon chemical thermal storage composite material according to claim 1, It is 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.

8. The method for preparing the nitrogen-doped porous carbon chemical thermal storage composite material according to claim 1, It is characterized in that 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. Preferably, the chemical heat storage material is LiOH, CaCl 2 MgCl 2 and MgSO 4 One or more of .

9. The method for preparing the nitrogen-doped porous carbon chemical heat storage composite material according to any one of claims 1 to 8, It is characterized in that In step S3, the hydrothermal reaction temperature is 105-120° C., and the reaction time is 12-18 h; and / or The drying process is divided into two stages. The first stage is freeze drying. Preferably, the freeze drying temperature is -15 to -30°C and the time is 4 to 20 hours. The second stage is drying under protective gas. Preferably, the protective gas is argon. More preferably, the drying temperature of the second stage is 120 to 150°C and the time is 3 to 4 hours.

10. A nitrogen-doped porous carbon chemical heat storage composite material, It is characterized in that The composite material is prepared by the preparation method of the nitrogen-doped porous carbon chemical heat storage composite material according to any one of claims 1 to 9.

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