Conductive flame-retardant thermal-insulation aerogel capable of enhancing room-temperature catalytic formaldehyde degradation as well as preparation method and application of conductive flame-retardant thermal-insulation aerogel

Abstract

The invention discloses conductive flame-retardant thermal-insulation aerogel capable of enhancing room-temperature catalytic formaldehyde degradation as well as a preparation method and application of the conductive flame-retardant thermal-insulation aerogel, and relates to the technical field of graphene-based aerogel. The preparation method comprises the following steps: loading a transition metal oxide catalyst with a formaldehyde catalytic oxidation performance on a graphene oxide sheet layer through a coprecipitation method; uniformly mixing the graphene loaded with the transition metal oxide catalyst in a sodium alginate aqueous solution, and performing freeze drying; and soaking in a mixed solution containing calcium salt and boric acid for cross-linking reaction, and then freeze-drying again to obtain the product. The material has good flame retardance and thermal insulation performance, can enhance the catalytic oxidation efficiency of low-concentration formaldehyde at room temperature under the assistance of a stable and controlled external electric field, realizes the long-term catalytic degradation effect on formaldehyde at room temperature, and can be applied to the field of buildings, such as buildings, buildings and the like. The multiple purposes of efficient heat preservation of the building envelope structure, remarkable improvement of fireproof safety and effective control of indoor formaldehyde pollution are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene-based aerogels, and more specifically to a flame-retardant thermal insulation aerogel capable of conducting electricity and enhancing the catalytic degradation of formaldehyde at room temperature, as well as a preparation method and application thereof. Background Art

[0002] Against the backdrop of the global transition to a low-carbon economy and the continuous improvement of building energy-saving standards, it is particularly important to develop new building insulation materials that are sustainable, economical, and functional. Although the current mainstream organic insulation materials in the market (such as polystyrene, polyurethane, etc.) occupy a large market share, their resources are limited, and they are extremely flammable and release toxic smoke when burned, causing "secondary poisoning." Although inorganic insulation materials (such as rock wool, glass wool, etc.) have flame retardant properties, they have defects such as strong hygroscopicity and rapid deterioration of mechanical properties, and the production process is energy-intensive, which is contrary to the low-carbon goals of sustainable development. In addition, the existing insulation material systems generally have a single function: organic insulation materials are difficult to strike a balance between reducing combustion toxicity and improving insulation performance, while inorganic insulation materials are limited by environmental durability and production energy consumption. Faced with the coordinated needs of new buildings for "ultra-low thermal conductivity-intrinsic flame retardancy-environmental friendliness", it is urgent to develop overall safe and high-performance insulation materials through material structure design, flame retardant system construction, and material preparation process innovation.

[0003] In recent years, aerogel, as a new type of thermal insulation material, has attracted much attention due to its ultra-low thermal conductivity and high porosity. Among them, graphene aerogel, as a special aerogel material, combines the excellent electrical conductivity and thermal insulation properties of graphene with high porosity, low density and good chemical stability, which makes it have broad application prospects in many fields. However, its brittleness and high production cost limit its application in the field of building insulation. To solve these problems, researchers have tried to improve its comprehensive performance through chemical modification and composite material design. For example, the introduction of reinforcing components such as sodium alginate into graphene-based aerogel can significantly improve the mechanical properties and flame retardancy of the aerogel. In addition, boron-based flame retardants are widely used in the flame retardant modification of aerogel materials due to their environmentally friendly and high efficiency, which can significantly improve the fire safety of the material.

[0004] It is worth noting that in building interiors, in addition to energy conservation, insulation, and fire safety, indoor environmental safety and human health are equally important. Formaldehyde (HCHO), a toxic and carcinogenic volatile organic compound, primarily originates from decoration materials, interior furnishings, and adhesives. Long-term exposure can pose serious health risks. To address VOC air pollution, particularly formaldehyde, in indoor environments, researchers have developed a variety of treatment methods, including adsorption, photocatalytic oxidation, and catalytic oxidation. Formaldehyde catalytic oxidation, with its significant advantages such as high removal efficiency, low energy consumption, and the absence of toxic byproducts, has garnered widespread attention from both academia and industry, becoming a key research focus. Low-temperature catalytic oxidation of formaldehyde primarily utilizes precious metals (such as Pt-based materials) and transition metal oxides as catalysts. While precious metal catalysts exhibit high catalytic activity towards formaldehyde, their high cost hinders their widespread application. Consequently, current research focuses on transition metal oxide catalysts, such as MnO2, Co3O4, and TiO2. Among them, MnO2 has been widely studied due to its excellent catalytic activity, multiple crystal phases, variable valence states and low cost.

[0005] With the improvement of people's quality of life, the formaldehyde content in the environment in which people live in real life rarely exceeds 1ppm. Therefore, the catalytic oxidation of low-concentration formaldehyde at room temperature is more meaningful. Among many transition metal catalysts, manganese-based catalysts show strong activity in the catalytic oxidation of formaldehyde. However, the stability of manganese-based catalysts when used at room temperature is not ideal, and there are still problems such as easy catalyst deactivation and slow catalytic rate. In order to improve the activity of the catalyst to cope with the room-temperature catalytic degradation in a low-concentration formaldehyde environment, the use of electric injection to enhance the room-temperature formaldehyde removal of porous conductive aerogel / catalyst composites is a worthy research direction. With the assistance of a stable and controlled external electric field, the direct injection of electrons into the catalyst can induce the migration of lattice oxygen within the metal oxide to promote the generation of reactive oxygen species, thereby improving the efficiency of the catalyst in catalytic oxidation of formaldehyde. Patent CN115041237A discloses a method for removing formaldehyde at room temperature using an electric injection-enhanced porous conductive aerogel / catalyst composite material. The porous conductive aerogel / catalyst composite material is prepared by in-situ loading of a catalyst. By introducing an external electric field, oxygen adsorbed on the surface of the catalyst obtains electrons and becomes an active substance that can participate in the catalytic oxidation of formaldehyde, thereby improving the catalyst's formaldehyde catalytic oxidation efficiency. However, the method fails to take into account its thermal insulation and flame retardancy.

[0006] Based on current research status and development needs, by organically combining the excellent thermal insulation properties of aerogel with the pollution purification function of formaldehyde catalysts, and simultaneously introducing a highly effective flame retardant system, it is expected that a multifunctional aerogel material will be developed that combines high-efficiency thermal insulation and energy saving, excellent fire safety, and the ability to continuously remove indoor air pollution. This innovative research will provide a new technical path for the high-quality development of new building insulation materials. Summary of the Invention

[0007] This invention focuses on graphene-based aerogel technology. Addressing the limitations of existing thermal insulation materials, including limited functionality, insufficient flame retardancy, and low catalytic efficiency at low formaldehyde concentrations, this paper proposes a multifunctional aerogel material that combines conductivity-enhanced room-temperature catalytic formaldehyde degradation, flame retardancy, heat resistance, and thermal insulation. By constructing a three-dimensional conductive network within the graphene-based aerogel, combined with the synergistic effects of a boron-based flame retardant and optimized catalyst design, this material achieves efficient integration of thermal insulation, flame retardancy, and formaldehyde catalytic degradation, meeting the construction industry's urgent need for high-performance thermal insulation materials.

[0008] Another object of the present invention is to provide a conductive, flame-retardant thermal insulation aerogel.

[0009] Another object of the present invention is to provide the use of the conductive, flame-retardant thermal insulation aerogel in the catalytic oxidation of formaldehyde.

[0010] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0011] The present invention provides a method for preparing a conductive, flame-retardant, thermal insulation aerogel for catalyzing formaldehyde degradation, comprising the following steps:

[0012] S1, loading a transition metal oxide catalyst on graphene oxide to obtain graphene loaded with a transition metal oxide catalyst;

[0013] S2, uniformly mixing the graphene loaded with the transition metal oxide catalyst and sodium alginate in water to obtain a dispersion, and freeze-drying the dispersion to obtain a precursor aerogel;

[0014] S3, completely immersing the precursor aerogel in a mixed solution containing boric acid and calcium salt for cross-linking, and freeze-drying to obtain the conductive flame-retardant thermal insulation aerogel.

[0015] The preparation method of the aerogel is to stably load the transition metal oxide catalyst on graphene oxide and form it into a gel material under the action of sodium alginate. Graphene oxide has good conductivity. Under the assistance of a stable and controlled external electric field, electrons can be directly injected into the catalyst to induce lattice oxygen in MnO x Internal migration promotes the generation of active oxygen and improves the catalyst activity and catalytic stability of the product.

[0016] Furthermore, the present invention incorporates boric acid as a crosslinking agent, crosslinking with the hydroxyl groups on sodium alginate and graphene oxide to enhance the flame retardancy of the aerogel's condensed phase. Simultaneously, calcium ions are introduced to induce gel formation in the sodium alginate. The combination of boric acid and calcium salt creates a dual crosslinking effect, strengthening the crosslinking strength between the sodium alginate and graphene oxide system. This results in a well-defined three-dimensional network structure within the aerogel material, as well as excellent flame retardancy, thermal insulation, and electrical conductivity.

[0017] In some embodiments, the oxidation rate of the graphene oxide is 8-15%, preferably 10-12%. Its abundant oxygen-containing functional groups are conducive to combining with manganese oxide, while it is necessary to avoid excessive oxidation that reduces the conductivity of the graphene.

[0018] In some embodiments, the preparation method of graphene oxide is: oxidizing graphite powder with potassium permanganate in concentrated sulfuric acid, ultrasonically exfoliating to obtain a single-layer graphene oxide suspension, freezing and then drying in a vacuum dryer to obtain graphene oxide powder.

[0019] Preferably, the present invention also provides a method for preparing graphene oxide with controllable oxidation degree and faster reaction efficiency, which is prepared by an improved Hummers method, comprising the following steps:

[0020] S11, mixing graphite with sodium nitrate and concentrated sulfuric acid solution, adding potassium permanganate and stirring in an ice bath for 1.5-3h;

[0021] S12, stirring the mixed solution obtained in step S11 at 30-40° C. for 1-2 hours, and then adding deionized water for dispersion;

[0022] S13, stirring the mixed solution obtained in step S12 at 95-100° C. for 10-20 minutes, adding hydrogen peroxide for oxidation reaction, filtering, washing, and drying to obtain graphene oxide.

[0023] Preferably, in the mixed solution of step S11, the concentration of sodium nitrate is 10-50 mg / ml, and the concentration of potassium permanganate is 150-250 mg / ml.

[0024] Preferably, the amount of deionized water in step S12 is 7-9 times the volume of the mixed solution in S11.

[0025] Preferably, the concentration of hydrogen peroxide in step S13 is 20-50 mg / ml.

[0026] Preferably, in step S13, the drying method is freeze drying; the drying temperature is -70 to -50°C; and the drying time is 20 to 30 hours.

[0027] The surface of graphene oxide has abundant oxygen-containing functional groups (such as hydroxyl, epoxy and carboxyl groups), which can provide loading sites for manganese oxide. The two-dimensional layered structure of graphene oxide can regulate growth, thereby inhibiting The agglomeration of particles, combined with weaker Mn-O bonds, can lead to the generation of more defect sites, accelerating the catalysis of the reactants. At the same time, the improvement in the conductivity of graphene oxide and manganese oxide after redox reaction provides conditions for enhancing the electron-donating ability of the catalyst surface.

[0028] In some embodiments, in step S1, the transition metal oxide catalyst is selected from manganese oxide, cobalt oxide and titanium oxide, preferably manganese oxide (MnO x ).

[0029] The present invention is not particularly limited to manganese oxides; any manganese oxide capable of catalytically degrading formaldehyde can achieve the objectives of the present invention. Preferably, the manganese oxide has a δ-MnO2 structure. This crystalline form of manganese dioxide has a better formaldehyde catalytic effect and readily induces lattice oxygen migration under direct electron injection, thereby promoting the generation of reactive oxygen species.

[0030] In some embodiments, a method for loading manganese oxide on graphene oxide using a manganese oxide having a δ-MnO2 structure includes: adding a potassium permanganate solution to a graphene oxide dispersion, adding a manganese salt solution, stirring the mixture, and drying the mixture to obtain graphene loaded with manganese oxide.

[0031] Preferably, the mass percentage concentration of the potassium permanganate aqueous solution is 0.125% to 0.4%; the mass percentage concentration of the manganese sulfate monohydrate aqueous solution is 0.025% to 1%.

[0032] Preferably, the reaction temperature is 40° C. to 80° C., and the reaction time is 1 h to 4 h.

[0033] Preferably, potassium sulfate may be added to the graphene oxide dispersion at a mass percentage concentration of 0.1% to 0.4%. The introduction of potassium ions is beneficial to expanding the interlayer spacing of the δ-MnO2 crystals and increasing the adsorption capacity for formaldehyde.

[0034] In some embodiments, in step S2, the concentration of the graphene loaded with the transition metal oxide catalyst in the dispersion is 8-16 mg / ml, preferably 10-14 mg / ml.

[0035] In some embodiments, in step S2, the concentration of sodium alginate in the dispersion is 4-12 mg / ml, preferably 6-10 mg / ml.

[0036] In some embodiments, in step S3, the concentration of boric acid in the mixed solution is 2-10 g / ml, preferably 5-8 mg / ml.

[0037] In some embodiments, in step S3, the concentration of calcium salt in the mixed solution is 2-10 mg / ml, preferably 3.8-4.2 mg / ml.

[0038] In some embodiments, in step S3, the cross-linking reaction temperature is 20-30° C., and the reaction time is 20-40 min.

[0039] The invention protects a conductive, flame-retardant, thermal insulation aerogel, which is prepared by the preparation method of the conductive, flame-retardant, thermal insulation aerogel for catalytic degradation of formaldehyde.

[0040] The present invention discloses an application of a conductive and flame-retardant thermal insulation aerogel in catalytic oxidation of formaldehyde.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention provides a method for preparing a conductive, flame-retardant, thermal insulation aerogel for catalytic degradation of formaldehyde. Using a double-crosslinking system of calcium ions and boric acid, metal oxides are loaded onto graphene oxide, which is then reacted with sodium alginate to form a three-dimensional aerogel material. This material can promote the production of reactive oxygen species with the aid of a stable and controlled external electric field, exhibiting significant catalytic efficiency and excellent catalytic stability in low-concentration formaldehyde environments at room temperature. Furthermore, the aerogel avoids the problems of catalyst powder easily agglomerating, being difficult to recycle in practical applications, and easily causing dust pollution. Furthermore, the conductive, flame-retardant, thermal insulation aerogel of the present invention, due to the double crosslinking of calcium chloride and boric acid, also exhibits excellent flame retardancy and thermal insulation properties. It can be applied to building materials to achieve high-efficiency, continuous catalytic purification of indoor formaldehyde at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a physical picture of Example 1 (MGAB) of the present invention.

[0044] Figure 2 This is a site diagram of Example 1 (MGAB) of the present invention connecting a 10V DC regulated power supply and an LED lamp.

[0045] Figure 3 The infrared spectra (FTIR) of the aerogels of Example 1 (MGAB), Comparative Example 1 (PA), Comparative Example 2 (GA) and Comparative Example 3 (MGA) of the present invention are shown.

[0046] Figure 4 Thermogravimetric analysis diagrams of aerogels of Example 1 (MGAB) of the present invention and Comparative Example 3 (MGA) under nitrogen atmosphere.

[0047] Figure 5 Graphs showing the limiting oxygen index of aerogels according to Example 1 (MGAB) of the present invention and Comparative Example 3 (MGA).

[0048] Figure 6 Graph showing thermal conductivity of aerogels according to Example 1 (MGAB) of the present invention and Comparative Example 3 (MGA).

[0049] Figure 7 These are infrared thermal images of aerogels of Example 1 (MGAB) of the present invention and Comparative Example 3 (MGA) after being heated on a 75° C. hot plate for 1 hour.

[0050] Figure 8 This is a schematic diagram of the homemade formaldehyde purification performance test device of the present invention.

[0051] Figure 9 The following graphs show the formaldehyde purification performance of Example 1 (MGAB) with and without power applied, and Comparative Example 4 (GAB) with and without power applied over time. Curve MGAB-EI represents the formaldehyde purification performance of the MGAB sample of Example 1 with power applied; curve MGAB represents the formaldehyde purification performance of the MGAB sample of Example 1 without power applied; curve GAB-EI represents the formaldehyde purification performance of the GAB sample of Comparative Example 4 with power applied; and curve GAB represents the formaldehyde purification performance of the GAB sample of Comparative Example 4 without power applied. DETAILED DESCRIPTION

[0052] The present invention will be further described below in conjunction with specific embodiments, but the examples do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the examples of the present invention are conventionally purchased raw materials and reagents.

[0053] Example 1

[0054] A method for preparing a flame-retardant gas gel (MGAB) that can conduct electricity and enhance the catalytic release of formaldehyde at room temperature, specifically comprising the following steps:

[0055] S1. Graphene oxide powder was prepared from graphite powder using a modified Hummers method.

[0056] Specifically, 46 ml of concentrated sulfuric acid was placed in a refrigerator to cool for 15 minutes, taken out and poured into a three-necked flask, and stirred in an ice bath at 5°C; then 2 g of graphite powder was weighed and added to the concentrated sulfuric acid spoon by spoon, stirred for 1 hour, and then 1 g of sodium nitrate and 8 g of potassium permanganate were added and stirred for 30 minutes;

[0057] Transfer to a 35°C oil bath for reaction, stir mechanically for 1 hour, slowly pour 92ml of deionized water into the mixture system for dispersion; then transfer to a 98°C oil bath, stir for 15 minutes, then slowly add 280ml of deionized water, then add 10ml of 30% hydrogen peroxide, stir evenly until the solution turns golden yellow, let it stand overnight, pour out the supernatant, wash three times with 5% hydrochloric acid by centrifugation, then wash with deionized water until neutral, and disperse in an ultrasonic machine, stirring while ultrasonicating, and evenly disperse the volatile product in deionized water. Refrigerate in a freezer, freeze-dry to obtain a flake sample, and grind into powder.

[0058] S2. loading manganese oxide onto the graphene oxide powder extracted in step S1 to obtain manganese oxide-loaded graphene oxide;

[0059] Specifically, 1.5 g of the graphene oxide obtained in step S1 was stirred in 60 mL of deionized water for 30 min to fully disperse it, 30 mL of a solution containing 0.105 g of potassium permanganate was added and stirred evenly, 90 mL of a mixed solution containing 0.160 g of manganese sulfate monohydrate and 0.116 g of potassium sulfate was slowly added, ultrasonicated for 10 min, stirred at 60°C for 2 h, centrifuged three times with deionized water, and freeze-dried into powder.

[0060] S3. Preparation of flame-retardant gel with enhanced conductivity and catalytic formaldehyde degradation at room temperature;

[0061] Specifically, 0.3 g of the manganese oxide-loaded graphene oxide obtained in step S2 was dispersed in 25 mL of deionized water, 0.2 g of sodium alginate was added and stirred until fully dissolved, the mixed solution was poured into a mold, frozen into a solid ice block in a -18°C refrigerator, and dried in a vacuum freeze dryer for 24 hours to preliminarily obtain an aerogel material; then the aerogel was completely immersed in a 0.4 wt.% calcium chloride aqueous solution for 30 minutes, and then immersed in a 0.6 wt.% boric acid aqueous solution for cross-linking for 30 minutes. After the cross-linking was completed, it was frozen again in a -18°C refrigerator into a solid ice block, and dried again in a vacuum freeze dryer for 24 hours to obtain a flame-retardant gas gel (MGAB) with conductive enhanced room temperature catalytic formaldehyde degradation.

[0062] Example 2

[0063] A method for preparing a flame-retardant gas gel capable of conducting electricity and enhancing the catalytic release of formaldehyde at room temperature is different from that of Example 1 in that: in step S3 of this embodiment, the mass percentage of calcium chloride in the calcium chloride aqueous solution is 0.4%, and the mass percentage of boric acid in the boric acid aqueous solution is 0.4%.

[0064] Example 3

[0065] A method for preparing a flame-retardant gas gel capable of conducting electricity and enhancing the catalytic release of formaldehyde at room temperature is different from that of Example 1 in that: in step S3 of this embodiment, the mass percentage of calcium chloride in the calcium chloride aqueous solution is 0.6%, and the mass percentage of boric acid in the boric acid aqueous solution is 0.6%.

[0066] Example 4

[0067] A method for preparing a flame-retardant gel capable of conducting electricity and enhancing the catalytic release of formaldehyde at room temperature is different from that of Example 1 in that: in step S3 of this embodiment, the mass percentage of calcium chloride in the calcium chloride aqueous solution is 0.2%, and the mass percentage of boric acid in the boric acid aqueous solution is 0.2%.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing pure sodium alginate-based aerogel (PA), comprising the following steps:

[0070] 0.2 g of sodium alginate was added to 25 mL of deionized water and stirred until fully dissolved. The mixed solution was poured into a mold, frozen into a solid ice cube in a -18 °C refrigerator, and dried in a vacuum freeze dryer for 24 h to obtain pure sodium alginate-based aerogel (PA).

[0071] Comparative Example 2

[0072] This comparative example provides a method for preparing graphene oxide sodium alginate (GA) aerogel, which is different from Example 1 in that it includes the following steps:

[0073] S1. The graphite powder was prepared into graphene oxide powder using an improved Hummers method; the same as step S1 in Example 1;

[0074] S2. Preparation of graphene oxide sodium alginate (GA) aerogel: Disperse 0.3 g of graphene oxide from step S1 in 25 mL of deionized water, add 0.2 g of sodium alginate and stir until fully dissolved, pour the mixed solution into a mold, freeze it into a solid ice cube in a -18°C refrigerator, and dry it in a vacuum freeze dryer for 24 h to obtain graphene oxide sodium alginate (GA) aerogel.

[0075] Comparative Example 3

[0076] This comparative example provides a method for preparing manganese oxide-loaded graphene oxide sodium alginate (MGA) aerogel. The difference from Example 1 is that calcium chloride and boric acid are not introduced in step S3 of this comparative example. The specific steps are:

[0077] Steps S1 and S2 are the same as those in Example 1;

[0078] S3. Preparation of manganese oxide-loaded graphene oxide sodium alginate (MGA) aerogel: 0.3 g of the manganese oxide-loaded graphene oxide prepared in step S2 was dispersed in 25 mL of deionized water, 0.2 g of sodium alginate was added and stirred until fully dissolved, the mixed solution was poured into a mold, frozen into a solid ice cube in a -18°C refrigerator, and dried in a vacuum freeze dryer for 24 h to obtain manganese oxide-loaded graphene oxide sodium alginate (MGA) aerogel.

[0079] Comparative Example 4

[0080] This comparative example provides a method for preparing a flame-retardant thermal insulation aerogel of graphene oxide and sodium alginate (GAB), which is different from Example 1 in that the graphene oxide in this comparative example does not carry manganese oxide.

[0081] The specific steps are:

[0082] 0.3 g of graphene oxide from step S1 of Example 1 was dispersed in 25 mL of deionized water, 0.2 g of sodium alginate was added and stirred until fully dissolved, the mixed solution was poured into a mold, frozen into a solid ice cube in a -18 ° C refrigerator, and dried in a vacuum freeze dryer for 24 h to preliminarily obtain an aerogel material; then the aerogel was completely immersed in a calcium chloride aqueous solution with a substance mass percentage of 0.4%, soaked for 30 min, and then immersed in a solution with a boric acid mass percentage of 0.6% for cross-linking for 30 min. After the cross-linking was completed, it was frozen again in a -18 ° C refrigerator into a solid ice cube, and dried again in a vacuum freeze dryer for 24 h to obtain graphene oxide sodium alginate (GAB) flame retardant thermal insulation aerogel.

[0083] Performance Testing

[0084] 1. Material quality and density measurement

[0085] Five flame-retardant gas aerogels of Example 1 (MGAB) with relatively good appearance and different shapes that can catalytically purify formaldehyde at room temperature were selected for density measurement, and the average density of the aerogels was calculated.

[0086] The density (ρ) of the aerogel is determined by the formula (ρ = m / v), where m is the mass and v is the volume of the composite aerogel. The mass is measured using an electronic balance. The volume of a relatively well-shaped rectangular parallelepiped sample is calculated using the geometric equation (v = a*b*h), where a is the length, b is the width, and h is the height.

[0087] The physical object of the manganese oxide supported graphene oxide composite aerogel (MGAB) of Example 1 is as follows Figure 1As shown, its length, width and height are 3.80*1.66*0.65cm respectively, and its mass is 0.134g. The sample density is calculated by the formula, and the average density of the composite aerogel material is calculated to be 32.71mg / cm 3 .

[0088] like Figure 2 As shown, after MGAB is connected to a 10V DC regulated power supply and an LED light, the LED light becomes brighter, proving that it has good conductivity.

[0089] 2. Infrared spectrum test

[0090] The aerogel materials of Example 1 (MGAB), Comparative Example 1 (PA), Comparative Example 2 (GA) and Comparative Example 3 (MGA) were tested by Fourier transform infrared spectrometer KBr pellet method to determine the changes in functional groups or chemical bonds after graphene oxide, manganese oxide loading and preparation of composite aerogels. The test results are as follows: Figure 3 shown.

[0091] like Figure 3 The FTIR spectra of PA, GA, MGA, and MGAB aerogels were compared. For the PA of Comparative Example 1, the -1 The broad peaks at 2919 and 2838 cm -1 The characteristic peaks are attributed to the symmetric and asymmetric stretching vibration peaks of -OH group and C-H bond, respectively.

[0092] For the GA of Comparative Example 2, at 3428 cm -1 The -OH stretching vibration at 2919cm is enhanced, which is attributed to the enhanced hydrogen bonding effect of the addition of graphene oxide, while the -1 and 2838cm -1 The absorption peak at 1735cm is weakened mainly because the introduction of graphene oxide increases the rigidity and order of the material, thereby reducing the vibration freedom of the CH bond. -1 The absorption peak is significantly enhanced, which is attributed to the reaction between the carboxyl and hydroxyl groups in graphene oxide and sodium alginate to form ester bonds, resulting in the enhancement of the C=O stretching vibration peak.

[0093] For the MGA of Comparative Example 3 and the MGAB of Example 1, the -1 New characteristic peaks appeared at 1270, 1145, 1060, 940 cm-1, which can be attributed to the Mn-O coordination bond, indicating that the Mn ions have been loaded on the aerogel. Compared with MGA and MGAB, after adding calcium chloride and boric acid crosslinking, some new peaks (1270, 1145, 1060, 940 cm-1) were observed in the prepared MGAB aerogel. -1), which is attributed to the chelation of calcium ions with the carboxyl groups in the G unit (guluronic acid unit) of sodium alginate to form a stable "egg-box" structure with trihedral and tetrahedral boron groups, which indicates the double cross-linking of sodium alginate with calcium chloride and boric acid.

[0094] 3. Thermogravimetric analysis test

[0095] The thermal stability of the aerogels of Example 1 (MGAB) and Comparative Example 3 (MGA) was tested using a thermogravimetric analyzer. The measurement temperature range of the thermogravimetric analysis test was from room temperature to 700°C, the heating rate was 20°C / min, and the atmosphere was nitrogen. The measurement results are shown in Figure 2. Figure 4 shown.

[0096] Depend on Figure 4 Comparative Example 3 (MGA) shows significant thermal weight loss between 200°C and 350°C, with only 44.1% of its initial mass remaining at 700°C. Example 1 (MGAB) combines Comparative Example 3 (MGA) with the addition of boric acid and calcium chloride as crosslinkers. At 700°C, 52.6% of its initial mass remains, and the peak of thermal weight loss is delayed to 250°C-350°C, indicating that the addition of boric acid and calcium chloride significantly improves the thermal stability of the composite aerogel.

[0097] 4. Limiting oxygen index test

[0098] The combustion performance of the aerogels of Example 1 (MGAB) and Comparative Example 3 (MGA) was tested using a fully automatic oxygen index tester.

[0099] The test standard refers to GB / T 2406.2-2009 "Determination of combustion behavior of plastics by oxygen index method Part 2: Room temperature test", using the top surface combustion method, the sample size is 100×10×10mm, the test results are as follows Figure 5 shown.

[0100] Depend on Figure 5 As can be seen, the limiting oxygen index of Comparative Example 3 (MGA) is only 21.2, indicating that it is a flammable material. Example 1 (MGAB) introduces boric acid and calcium chloride to Comparative Example 3 (MPS), and the limiting oxygen index is increased to 35.8, indicating that the addition of calcium chloride and boric acid can significantly improve the flame retardancy of the aerogel.

[0101] 5. Thermal insulation performance test

[0102] The thermal insulation properties of the aerogels of Example 1 (MGAB) and Comparative Example 3 (MGA) were tested using a TC3000E thermal conductivity meter and an infrared thermal imager.

[0103] Thermal conductivity test method: The test environment temperature is 15℃, the sample size is 40×60×5mm, and the test begins when the temperature fluctuation is ≤±0.1℃ within 10 minutes after the test sample is placed. A set of experiments consists of 3 times, each with an interval of 3 minutes. Five sets of data are tested using different samples, and the average value is calculated. The test results of thermal conductivity are as follows: Figure 6 shown.

[0104] Infrared thermal imaging test method: The test environment temperature is 15℃, the sample size is 20×40×5mm, and the temperature change of the material surface after heating on a heating plate at 70℃ for 1 hour is measured. The results of the infrared thermal imaging test are as follows: Figure 7 shown.

[0105] Depend on Figure 6 It can be seen that the thermal conductivity coefficients of Example 1 (MGAB) and Comparative Example 3 (MGA) are 31.6 mW / mK and 32.1 mW / mK, respectively. Their thermal conductivity coefficients are low and their thermal insulation performance is good.

[0106] Depend on Figure 7 As known, after heating on a hot plate at 70°C for 1 hour, the surface of the aerogels maintained a relatively low temperature (35.4°C for MGAB and 36.5°C for MGA). Since the aerogel material has a three-dimensional porous network structure with excellent thermal insulation performance, there is no significant difference in the thermal conductivity of the aerogels of the embodiment and the comparative examples. At the same time, the aerogels of Example 1 and Comparative Example 3 both have excellent thermal insulation performance, and the thermal insulation performance of the aerogel of Example 1 is improved.

[0107] 6. Formaldehyde purification performance test

[0108] The formaldehyde purification performance test was carried out in a self-made experimental device (the structure of the experimental device is as follows Figure 8 As shown in the figure, the main body of the experimental device is a sealed box with a volume of about 10L. The box contains a formaldehyde detector that can display the formaldehyde concentration in the box in real time, a small fan to promote the flow of gas in the box, a DC regulated power supply to provide an external electric field to the sample, and a device for storing aerogel materials. The device for storing aerogel materials has good sealing performance, which can avoid the contact between aerogel materials and formaldehyde before the test begins. After the formaldehyde concentration in the device is stable, the aerogel materials in the experimental device are fully contacted with the formaldehyde in the sealed box. During the test, the environment in the sealed box is not affected by external factors.

[0109] Before the experiment begins, a formaldehyde detector is placed and the fan is turned on. Approximately 0.1 g of the aerogel material to be tested is placed in a sealed aerogel material storage device. 1 μL of HCHO (7.6 wt%) is injected into the sealed box to stabilize the formaldehyde concentration in the sealed box at approximately 1 ppm. The lid of the aerogel material storage device is then opened to allow the aerogel material in the device to fully contact the formaldehyde in the box. The changes in the formaldehyde detector reading are observed, and the trend of the formaldehyde concentration change in the sealed box is recorded for 2 hours.

[0110] The formaldehyde removal effect of the sample was evaluated according to the following formula: D = (C0-C) / C0*100%

[0111] Where: D is the formaldehyde removal efficiency (%); C0 is the initial mass concentration of formaldehyde (ppm); C is the mass concentration of formaldehyde after different reaction times (ppm).

[0112] The formaldehyde purification performance of the aerogels of Example 1 (MGAB), Comparative Example 3 (MGA), and Comparative Example 4 (GAB) was tested at room temperature using a homemade experimental device. The test results are shown in FIG. Figure 9 shown.

[0113] Depend on Figure 9 As can be seen, the aerogel materials of Example 1 (MGAB) and Comparative Example 4 (GAB) can respectively remove 86% and 37% of formaldehyde within three hours at room temperature without power. When the power supply is connected to the samples, the formaldehyde removal rate of the aerogel of Example 1 (MGAB) is significantly improved, reaching 97%, and the formaldehyde removal rate of the aerogel of Comparative Example 4 (GAB) is also slightly improved, reaching 43%. This demonstrates that the loading of manganese oxide has excellent electrically enhanced catalytic performance for formaldehyde removal at room temperature.

[0114] However, Example 1 (MGAB) and Comparative Example 3 (MGA) loaded with manganese oxide both showed high formaldehyde purification performance, indicating that the addition of boric acid and calcium chloride during the preparation of the composite aerogel material had no significant effect on the formaldehyde purification performance.

[0115] The flame retardancy, heat resistance, thermal insulation and room temperature formaldehyde catalytic purification performance of the flame retardant gas gel (MGAB) prepared in Examples 2 to 4 are close to those of Example 1.

[0116] The above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications may be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a conductive flame-retardant thermal insulation aerogel, characterized in that: The following steps are involved: S1, loading a transition metal oxide catalyst on graphene oxide to obtain graphene loaded with a transition metal oxide catalyst; S2, uniformly mixing the graphene loaded with the transition metal oxide catalyst and sodium alginate in water to obtain a dispersion, and freeze-drying the dispersion to obtain a precursor aerogel; S3, completely immersing the precursor aerogel in a mixed solution containing boric acid and calcium salt for cross-linking, and freeze-drying to obtain the conductive flame-retardant thermal insulation aerogel.

2. The method for preparing the conductive flame-retardant thermal insulation aerogel according to claim 1, characterized in that: In step S1, the transition metal oxide catalyst is manganese oxide, and the method for loading manganese oxide on graphene oxide includes: adding potassium permanganate solution to the graphene oxide dispersion, adding manganese salt solution and stirring to react, and drying to obtain graphene loaded with manganese oxide.

3. The method for preparing the conductive flame-retardant thermal insulation aerogel according to claim 1 or 2, characterized in that: The oxidation rate of the graphene oxide is 8-15%.

4. The method for preparing the conductive flame-retardant thermal insulation aerogel according to claim 3, characterized in that: The graphene oxide is prepared by a modified Hummers method, comprising the following steps: S11, mixing graphite with sodium nitrate and concentrated sulfuric acid solution, adding potassium permanganate and stirring in an ice bath for 1.5-3h; S12, stirring the mixed solution obtained in step S11 at 30-40° C. for 1-2 hours, and then adding water for dispersion; S13, stirring the mixed solution obtained in step S12 at 95-100° C. for 10-20 minutes, adding hydrogen peroxide for oxidation reaction, and obtaining graphene oxide.

5. The method for preparing the conductive flame-retardant thermal insulation aerogel according to claim 1, characterized in that: In step S2, the concentration of the graphene loaded with the transition metal oxide catalyst in the dispersion is 8-16 mg / ml.

6. The method for preparing the conductive flame-retardant thermal insulation aerogel according to claim 1, characterized in that: In step S2, the concentration of sodium alginate in the dispersion is 4-12 mg / ml by mass.

7. The method for preparing the conductive flame-retardant thermal insulation aerogel according to claim 1, characterized in that: In step S3, the concentration of boric acid in the mixed solution is 2-10 mg / ml.

8. The method for preparing the conductive flame-retardant thermal insulation aerogel according to claim 1, characterized in that: In step S3, the concentration of calcium salt in the mixed solution is 2-10 mg / ml.

9. A conductive flame-retardant thermal insulation aerogel, characterized in that: The conductive flame-retardant thermal insulation aerogel is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the conductive, flame-retardant thermal insulation aerogel according to claim 9 in catalytic oxidation of formaldehyde.

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