A silica-graphene composite nitrate molten salt and its preparation method

Abstract

This invention discloses a silica-graphene composite nitrate molten salt and its preparation method, belonging to the field of molten salt energy storage. The composite nitrate molten salt comprises three parts: silica, graphene, and solar molten salt. Graphene coats silica to form a composite material, which is then mixed with the solar molten salt. The preparation method includes: modifying silica and graphene separately with modifiers; coating silica with graphene to form a core-shell structure; and then combining the silica-graphene composite material with solar molten salt to obtain the silica-graphene composite molten salt. The silica-graphene composite molten salt prepared by this invention has a stable structure, a simple preparation process, and a low melting point, making it suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of molten salts, specifically relating to a silica-graphene composite nitrate molten salt and its preparation method. Background Technology

[0002] Molten salt possesses advantages such as a wide operating temperature range, low operating pressure, good economic efficiency, strong heat transfer and storage performance, and stable chemical properties. As an ideal medium-to-high temperature heat transfer and storage medium, it has been widely used in fields such as solar thermal utilization, renewable energy storage, high-temperature water electrolysis for hydrogen production, and molten salt reactors. Using molten salt as a heat storage material can reduce energy costs, improve energy utilization efficiency, and enhance the reliability and stability of system operation; therefore, molten salt has broad application prospects as a heat storage material.

[0003] The thermal power-molten salt energy storage coupling technology utilizes the technological advantages of molten salt large-capacity energy storage to compensate for the lack of stability in deep peak shaving of thermal power units, while improving the efficiency of steam and heat supply of the units and promoting the green and low-carbon development of thermal power units.

[0004] However, thermal power-molten salt energy storage coupling technology has operating parameters that are clearly different from those of solar thermal molten salt power generation systems. Therefore, it places special requirements on the performance of the molten salt medium, especially in terms of melting point control. Commercial molten salt products cannot meet the special requirements of ultra-low melting point performance of thermal power-molten salt energy storage coupling technology. Summary of the Invention

[0005] The main objective of this invention is to provide a silica-graphene composite nitrate molten salt and its preparation method. This composite nitrate molten salt has a low melting point, and its application in thermal power-molten salt energy storage coupling can promote energy conservation and carbon reduction in thermal power and reduce heating costs.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A silica-graphene composite nitrate molten salt, comprising, by mass percentage: silica, graphene, and Solar molten salt;

[0008] The graphene-coated silica composite material forms a core-shell structure, and the composite material is mixed with Solar molten salt to form a composite nitrate molten salt; the melting point of the composite molten salt is 155℃.

[0009] As a further improvement of the present invention, the silicon dioxide has a mass content of 0.009% to 0.019% of the composite nitrate molten salt; the graphene has a mass content of 0.0005% to 0.002% of the composite nitrate molten salt; and the Solar molten salt has a mass content of 99.8% to 99.9% of the composite nitrate molten salt.

[0010] A method for preparing a silica-graphene composite nitrate molten salt includes the following steps:

[0011] SiO2 and a first modifier are mixed in a first solvent and ultrasonically dispersed to obtain a first mixture; the first solvent is removed from the first mixture and dried for the first time to obtain SiO2-first modifier;

[0012] The second modifier is dissolved in the second solvent, graphene is added, and the mixture is stirred to obtain the second mixture; the second solvent is removed from the second mixture and dried a second time to obtain graphene-second modifier;

[0013] SiO2-first modifier and graphene-second modifier were dispersed in a third solvent, ultrasonically dispersed, and then stirred at 100-130℃ for 6-10 h. After the reaction was completed, the core-shell structured SiO2-graphene composite material was obtained by a third drying.

[0014] SiO2-graphene and solar molten salt were stirred at 150-250℃ for 12-24 hours; after drying, they were reacted in a high-temperature furnace at 300-400℃ for 12-24 hours and then ground into powder to obtain the final SiO2-graphene composite solar molten salt.

[0015] As a further improvement of the present invention, both the first modifier and the second modifier are silane coupling agents; the first solvent, the second solvent, and the third solvent are all ethanol solutions.

[0016] As a further improvement of the present invention, the ratio of SiO2 to the first modifier is (2-5) mg: 5 mL, and the ratio of the first modifier to the first solvent is 1: (3-5).

[0017] As a further improvement of the present invention, the ratio of graphene to the second modifier is (2-5) mg: 5 mL, and the ratio of the second modifier to the second solvent is 1:3 to 1:5.

[0018] As a further improvement of the present invention, the mass ratio of SiO2-first modifier to graphene-second modifier is (10-20):1, and the ratio of SiO2-first modifier to third solvent is (1-5) g:40 mL.

[0019] As a further improvement of the present invention, the mass ratio of SiO2-graphene to solar molten salt is (0.001~0.002):1.

[0020] As a further improvement of the present invention, the method for removing the first solvent is: reflux at 60-80°C for 4-8 hours;

[0021] The second solvent removal method is to reflux at 60–80°C for 4–8 hours.

[0022] As a further improvement of the present invention, the first drying condition is drying at 60-80°C for 12-24 hours;

[0023] The first drying conditions are 60-80℃ for 12-24 hours;

[0024] The third drying conditions are 60-80℃ for 12-24 hours.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention relates to a composite nitrate molten salt comprising three parts: silica, graphene, and solar molten salt. Graphene coats silica to form a composite material, which is then mixed with the solar molten salt. This silica-graphene composite nitrate molten salt can be applied in molten salt energy storage. The solar nitrate molten salt used in this invention is widely available, inexpensive, and has low corrosiveness. The addition of silica effectively enhances the heat transfer and storage performance of the molten salt. The addition of graphene provides an additional high thermal conductivity pathway for the silica surface. The invention utilizes KH-560 to connect silica and graphene, improving material stability. The preparation method of this invention is simple, has low production costs, and requires minimal post-processing without complex synthesis equipment.

[0027] The preparation method includes: modifying silica and graphene separately using KH-560, coating silica with graphene to form a core-shell structure, and then combining the silica-graphene composite material with solar energy to obtain a silica-graphene composite molten salt. The silica-graphene composite molten salt prepared by this invention has a stable structure, a simple preparation process, and a low melting point, making it suitable for large-scale industrial production. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a simplified flowchart of a method for preparing a silica-graphene composite nitrate molten salt according to the present invention.

[0030] Figure 2 The image shows the DSC diagram of the silica and graphene composite nitrate molten salt prepared in Example 1 of this invention. Detailed Implementation

[0031] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0033] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0034] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0035] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0036] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both mean: a, b, c, a~b (i.e., a and b), a~c, b~c, or a~b~c, where a, b, and c can be single or multiple.

[0037] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0038] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0039] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0040] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0041] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0042] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0043] The first objective of this invention is to provide a silica-graphene composite nitrate molten salt, comprising three parts: silica, graphene, and Solar molten salt. Graphene coats silica to form a composite material, which is then mixed with the Solar molten salt. The composite molten salt provided in this embodiment has a melting point of 155°C.

[0044] The silica-graphene composite nitrate molten salt is characterized in that the silica accounts for 0.009% to 0.019% of the composite nitrate molten salt by mass, the graphene accounts for 0.0005% to 0.002% of the composite nitrate molten salt, the Solar molten salt accounts for 99.8% to 99.9% of the composite nitrate molten salt, and the remainder includes a modifier, such as KH-560.

[0045] The above contents are the tested contents in the final product, and the dosage is based on the addition amount of the preparation method.

[0046] like Figure 1 As shown, the second objective of this invention is to provide a method for preparing a silica-graphene composite nitrate molten salt, comprising the following steps:

[0047] SiO2 and a first modifier are mixed in a first solvent and ultrasonically dispersed to obtain a first mixture; the first solvent is removed from the first mixture and dried for the first time to obtain SiO2-first modifier;

[0048] The second modifier is dissolved in the second solvent, graphene is added, and the mixture is stirred to obtain the second mixture; the second solvent is removed from the second mixture and dried a second time to obtain graphene-second modifier;

[0049] SiO2-first modifier and graphene-second modifier were dispersed in a third solvent, ultrasonically dispersed, and then stirred at 100-130℃ for 6-10 h. After the reaction was completed, the core-shell structured SiO2-graphene composite material was obtained by a third drying.

[0050] SiO2-graphene and solar molten salt were stirred at 150-250℃ for 12-24 hours; after drying, they were reacted in a high-temperature furnace at 300-400℃ for 12-24 hours and then ground into powder to obtain the final SiO2-graphene composite solar molten salt.

[0051] In some embodiments, the first modifier and the second modifier are both silane coupling agents; the first solvent, the second solvent, and the third solvent are all ethanol solutions.

[0052] Furthermore, while KH-560 can be used as the silane coupling agent, other silane coupling agents, such as KH-570, can also be used.

[0053] This method first modifies SiO2 and graphene separately using modifiers to obtain SiO2-first modifier and graphene-second modifier. Then, the SiO2-first modifier and graphene-second modifier are mixed to prepare a core-shell structured SiO2-graphene composite material. Finally, a SiO2-graphene composite solar molten salt is prepared by combining the two. The entire process is simple and does not require complex processing. This silica-graphene composite nitrate molten salt can be applied in the field of molten salt energy storage.

[0054] Specifically, the present invention provides specific embodiments to illustrate the above preparation process, including the following steps:

[0055] 1) Mix SiO2 and KH-560 in an ethanol solution and sonicate for 30-60 minutes;

[0056] In order to obtain better product performance, the amount of raw materials used is also a key part of the overall invention. In this embodiment, the ratio of SiO2 to KH-560 is (2~5) mg: 5 mL, and the ratio of KH-560 to ethanol solution is 1:3~1:5.

[0057] 2) Reflux the above mixture at 60–80°C for 4–8 hours, then cool to room temperature;

[0058] 3) Dry the above mixture in a drying oven at 60-80℃ for 12-24 hours to obtain SiO2-KH-560;

[0059] 4) Dissolve KH-560 in an ethanol solution, add graphene, and stir for 30-60 minutes; the ratio of graphene to KH-560 is (2-5) mg: 5 mL, and the ratio of KH-560 to ethanol solution is 1:3-1:5.

[0060] 5) Reflux the above mixture at 60–80°C for 4–8 hours, then cool to room temperature;

[0061] 6) Dry the above mixture in a drying oven at 60-80°C for 12-24 hours to obtain graphene-KH-560;

[0062] 7) Disperse SiO2-KH-560 and graphene-KH-560 in an ethanol solution and sonicate for 30-60 min; the ratio of SiO2-KH-560 to graphene-KH-560 is (10-20):1, and the ratio of SiO2-KH-560 to ethanol is (1-5) g:40 mL.

[0063] 8) Stir the above solution magnetically at 100–130°C for 6–10 hours;

[0064] 9) The above mixture was dried in a drying oven at 60-80°C for 12-24 hours to obtain SiO2-graphene composite material;

[0065] 10) Stir SiO2-graphene and solar molten salt at 150-250℃ for 12-24h; the ratio of SiO2-graphene to solar molten salt is (0.001-0.002)g:1g.

[0066] 11) Dry the above mixture in a drying oven at 100-150°C for 12-24 hours;

[0067] 12) The above mixture is reacted in a high-temperature furnace at 300-400℃ for 12-24 hours, and then ground into powder to obtain the final SiO2-graphene composite solar molten salt.

[0068] The following detailed description of a method for preparing a silica-graphene composite nitrate molten salt provided by the present invention, with reference to specific embodiments, provides a detailed explanation.

[0069] Example 1

[0070] Step 1: Disperse 20 mg SiO2 and 50 mL KH-560 in 150 mL ethanol solution and sonicate for 30 min; then reflux at 60 °C for 8 h and cool to room temperature; dry the mixture in a drying oven at 60 °C for 24 h to obtain SiO2-KH-560.

[0071] Step 2: Dissolve 50 mL of KH-560 in 150 mL of ethanol solution, add 20 mg of graphene, and stir for 30 min; then reflux at 60 °C for 8 h and cool to room temperature; dry the above mixture in a drying oven at 60 °C for 24 h to obtain graphene-KH-560.

[0072] Step 3: Disperse 10 mg SiO2-KH-560 and 1 mg graphene-KH-560 in 50 mL of ethanol solution and sonicate for 30 min; stir magnetically at 100 °C for 10 h; dry the mixture in a drying oven at 60 °C for 24 h to obtain SiO2-graphene composite material.

[0073] Step 4: Stir 0.02g SiO2-graphene and 20g solar molten salt at 150℃ for 24h; dry in a drying oven at 100℃ for 24h; then react in a high-temperature furnace at 300℃ for 24h, grind into powder, and obtain the final SiO2-graphene composite solar molten salt.

[0074] The present invention will now be described in further detail with reference to the accompanying drawings:

[0075] See Figure 2The image shows the DSC diagram of the silica and graphene composite nitrate molten salt prepared in Example 1 of this invention. Analysis shows that its melting point is 155℃. It can be concluded that this composite nitrate molten salt has a low melting point, and its application in thermal power-molten salt energy storage coupling can promote energy conservation and carbon reduction in thermal power plants and reduce heating costs.

[0076] Example 2

[0077] Step 1: Disperse 50 mg SiO2 and 50 mL KH-560 in 250 mL ethanol solution and sonicate for 60 min; then reflux at 80 °C for 4 h and cool to room temperature; dry the mixture in an 80 °C drying oven for 12 h to obtain SiO2-KH-560.

[0078] Step 2: Dissolve 50 mL of KH-560 in 250 mL of ethanol solution, add 50 mg of graphene, and stir for 60 min; then reflux at 80 °C for 4 h and cool to room temperature; dry the above mixture in a drying oven at 80 °C for 12 h to obtain graphene-KH-560.

[0079] Step 3: Disperse 20 mg SiO2-KH-560 and 1 mg graphene-KH-560 in 20 mL of ethanol solution and sonicate for 60 min; stir magnetically at 130 °C for 6 h; dry the mixture in an oven at 80 °C for 12 h to obtain SiO2-graphene composite material.

[0080] Step 4: Stir 0.04g SiO2-graphene and 20g solar molten salt at 250℃ for 12h; dry in a drying oven at 150℃ for 12h; then react in a high-temperature furnace at 400℃ for 12h, grind into powder, and obtain the final SiO2-graphene composite solar molten salt.

[0081] Example 3

[0082] Step 1: Disperse 30 mg SiO2 and 50 mL KH-560 in 200 mL ethanol solution and sonicate for 40 min; then reflux at 70 °C for 6 h and cool to room temperature; dry the mixture in a drying oven at 70 °C for 18 h to obtain SiO2-KH-560.

[0083] Step 2: Dissolve 50 mL of KH-560 in 200 mL of ethanol solution, add 30 mg of graphene, and stir for 40 min; then reflux at 70 °C for 6 h and cool to room temperature; dry the above mixture in a drying oven at 70 °C for 18 h to obtain graphene-KH-560.

[0084] Step 3: Disperse 15 mg SiO2-KH-560 and 1 mg graphene-KH-560 in 45 mL of ethanol solution and sonicate for 40 min; stir magnetically at 120 °C for 8 h; dry the mixture in a drying oven at 70 °C for 18 h to obtain SiO2-graphene composite material.

[0085] Step 4: Stir 0.03g SiO2-graphene and 20g solar molten salt at 200℃ for 18h; dry in a drying oven at 130℃ for 18h; then react in a high-temperature furnace at 350℃ for 20h, grind into powder, and obtain the final SiO2-graphene composite solar molten salt.

[0086] Example 4

[0087] Step 1: Disperse 40 mg SiO2 and 50 mL KH-560 in 200 mL ethanol solution and sonicate for 50 min; then reflux at 75 °C for 5 h and cool to room temperature; dry the mixture in a drying oven at 75 °C for 16 h to obtain SiO2-KH-560.

[0088] Step 2: Dissolve 50 mL of KH-560 in 200 mL of ethanol solution, add 40 mg of graphene, and stir for 50 min; then reflux at 75 °C for 5 h and cool to room temperature; dry the above mixture in a drying oven at 75 °C for 16 h to obtain graphene-KH-560.

[0089] Step 3: Disperse 18 mg SiO2-KH-560 and 1 mg graphene-KH-560 in 36 mL of ethanol solution and sonicate for 50 min; stir magnetically at 110 °C for 9 h; dry the mixture in a drying oven at 75 °C for 16 h to obtain SiO2-graphene composite material.

[0090] Step 4: Stir 0.03g SiO2-graphene and 20g solar molten salt at 180℃ for 20h; dry in a drying oven at 120℃ for 20h; then react in a high-temperature furnace at 380℃ for 18h, grind into powder, and obtain the final SiO2-graphene composite solar molten salt.

[0091] Example 5

[0092] Step 1: Disperse 40 mg SiO2 and 50 mL KH-560 in 250 mL ethanol solution and sonicate for 40 min; then reflux at 75 °C for 7 h and cool to room temperature; dry the mixture in a drying oven at 75 °C for 20 h to obtain SiO2-KH-560.

[0093] Step 2: Dissolve 50 mL of KH-560 in 250 mL of ethanol solution, add 40 mg of graphene, and stir for 40 min; then reflux at 75 °C for 6 h and cool to room temperature; dry the above mixture in a drying oven at 70 °C for 11 h to obtain graphene-KH-560.

[0094] Step 3: Disperse 15 mg SiO2-KH-560 and 1 mg graphene-KH-560 in 20 mL of ethanol solution and sonicate for 40 min; stir magnetically at 115 °C for 9 h; dry the mixture in a drying oven at 70 °C for 18 h to obtain SiO2-graphene composite material.

[0095] Step 4: Stir 0.03g SiO2-graphene and 20g solar molten salt at 240℃ for 18h; dry in a drying oven at 140℃ for 18h; then react in a high-temperature furnace at 380℃ for 18h, grind into powder, and obtain the final SiO2-graphene composite solar molten salt.

[0096] Example 6

[0097] Step 1: Disperse 35 mg SiO2 and 50 mL KH-560 in 200 mL ethanol solution and sonicate for 45 min; then reflux at 75 °C for 7 h and cool to room temperature; dry the mixture in a drying oven at 65 °C for 22 h to obtain SiO2-KH-560.

[0098] Step 2: Dissolve 50 mL of KH-560 in 200 mL of ethanol solution, add 35 mg of graphene, and stir for 55 min; then reflux at 72 °C for 7 h and cool to room temperature; dry the above mixture in a drying oven at 65 °C for 15 h to obtain graphene-KH-560.

[0099] Step 3: Disperse 18 mg SiO2-KH-560 and 1 mg graphene-KH-560 in 45 mL of ethanol solution and sonicate for 35 min; stir magnetically at 125 °C for 7.5 h; dry the mixture in a drying oven at 65 °C for 20 h to obtain SiO2-graphene composite material.

[0100] Step 4: Stir 0.05g SiO2-graphene and 20g solar molten salt at 200℃ for 22h; dry in a drying oven at 125℃ for 19h; then react in a high-temperature furnace at 320℃ for 23h, grind into powder, and obtain the final SiO2-graphene composite solar molten salt.

[0101] All articles and references disclosed above, including patent applications and publications, are incorporated herein by reference for various purposes. The term “substantially constitutes…” used to describe a combination should include the identified elements, components, parts, or steps, as well as other elements, components, parts, or steps that do not substantially affect the essential novelty of the combination. The use of the terms “comprising” or “including” to describe combinations of elements, components, parts, or steps herein also contemplates embodiments substantially constituted by such elements, components, parts, or steps. The use of the term “may” herein is intended to indicate that any described attribute included by “may” is optional.

[0102] Multiple elements, components, parts, or steps can be provided by a single integrated element, component, part, or step. Alternatively, a single integrated element, component, part, or step can be divided into multiple separate elements, components, parts, or steps. The use of "a" or "an" to describe an element, component, part, or step does not imply the exclusion of other elements, components, parts, or steps.

[0103] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

Claims

1. A silica-graphene composite nitric acid molten salt, characterized in that, Comprising: Silica, graphene and solar molten salt; The graphene-coated silica forms a core-shell structure composite material, which is mixed with solar molten salt to form a composite nitric acid molten salt; the melting point of the composite molten salt is 155℃.

2. The silica-graphene composite molten salt nitrate according to claim 1, wherein, The mass content of the silica in the composite nitric acid molten salt is 0.009%~0.019%; the mass content of the graphene in the composite nitric acid molten salt is 0.0005%~0.002%; and the mass content of the solar molten salt in the composite nitric acid molten salt is 99.8%~99.9%.

3. A method for preparing a silica-graphene composite nitric acid molten salt, characterized by, Comprising the following steps: Mixing SiO2 with a first modifier in a first solvent and ultrasonic dispersion to obtain a first mixture; removing the first solvent in the first mixture and first drying to obtain SiO2-first modifier; Dissolving a second modifier in a second solvent, adding graphene and stirring to obtain a second mixture; removing the second solvent in the second mixture and second drying to obtain graphene-second modifier; Dispersing SiO2-first modifier and graphene-second modifier in a third solvent, ultrasonic dispersion treatment, and stirring at a temperature of 100~130℃ for 6~10h; third drying after the reaction to obtain a core-shell structure SiO2-graphene composite material; Stirring SiO2-graphene and solar molten salt at a temperature of 150~250℃ for 12~24h; drying and reacting in a high-temperature furnace at a temperature of 300~400℃ for 12~24h, grinding into powder to obtain the final SiO2-graphene composite solar molten salt; The first modifier and the second modifier are both silane coupling agents; the first solvent, the second solvent and the third solvent are all ethanol solutions.

4. The production method according to claim 3, wherein The ratio of SiO2 and the first modifier is (2~5)mg:5mL, and the ratio of the first modifier and the first solvent is 1:(3~5).

5. The production method according to claim 3, wherein The ratio of graphene and the second modifier is (2~5)mg:5mL, and the ratio of the second modifier and the second solvent is 1:3~1:

5.

6. The production method according to claim 3, wherein The mass ratio of SiO2-first modifier and graphene-second modifier is (10~20):1, and the ratio of SiO2-first modifier and the third solvent is (1~5)g:40mL.

7. The production method according to claim 3, wherein The mass ratio of SiO2-graphene and solar molten salt is (0.001~0.002):

1.

8. The production method according to claim 3, wherein The method for removing the first solvent is refluxing at 60~80℃ for 4~8h; The method for removing the second solvent is refluxing at 60~80℃ for 4~8h.

9. The preparation method of claim 3, wherein, The first drying condition is 60~80℃ drying for 12~24h; The first drying condition is 60~80℃ drying for 12~24h; The third drying condition is 60~80℃ drying for 12~24h.

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