Preparation method of biomimetic honeycomb two-dimensional material aerogel

Abstract

The application provides a preparation method of a biomimetic honeycomb two-dimensional material aerogel, and belongs to the technical field of aerogels. The preparation method comprises the following steps: 1) two-dimensional material powder and a dispersing agent are added into deionized water and mixed, ultrasonic dispersion is carried out, sodium alginate is added, the solution is stirred to make the sodium alginate completely dissolved, and a sodium alginate sol in which the two-dimensional material powder is stably dispersed is obtained; 2) the sol obtained in the step 1) is injected into a mold, a gelling agent is sprayed on the upper surface of the sol, the mold is removed after gelling is completed, and a hydrogel is obtained; and 3) the hydrogel obtained in the step 2) is washed in deionized water, and an aerogel is obtained after freeze-drying. The biomimetic honeycomb two-dimensional material aerogel prepared by the application has a highly regular honeycomb pore structure, two-dimensional materials are continuously and directionally arranged, and the two-dimensional material aerogel has excellent compression resistance.

Description

Technical Field

[0001] This application belongs to the field of aerogel technology, and specifically relates to a method for preparing a biomimetic honeycomb-shaped two-dimensional material aerogel. Background Technology

[0002] Two-dimensional materials such as graphene and MXene have attracted widespread attention due to their high in-plane strength, high electrical conductivity, high thermal conductivity, and high specific surface area. Fabricating aerogels from these two-dimensional materials can further broaden their application areas. Two-dimensional material aerogels combine the excellent physical properties of two-dimensional materials with the ultra-low density of aerogels, offering performance advantages in fields such as electromagnetic protection, thermal management, electrochemistry, wastewater treatment, and catalysis.

[0003] Currently, the preparation methods for two-dimensional (2D) aerogels have significant limitations. 2D aerogels typically require continuous, oriented arrangement of the 2D material to achieve certain mechanical properties and excellent thermal and electrical conductivity; an ordered pore structure is also crucial for realizing the functional properties of aerogel materials. Among common preparation methods, hydrothermal self-assembly can achieve continuous distribution of 2D materials, but it cannot obtain oriented 2D materials and an ordered pore structure. The sacrificial template method can achieve precise customization of the 2D material distribution and pore structure, but it usually requires 3D printing to obtain the sacrificial template, which is costly and cannot achieve micron-level precision, thus limiting the application of this method. The ice template method is currently the most commonly used method, which captures the 2D material in the interstices of ice crystals through directional growth, and obtains a honeycomb-like porous structure after freeze-drying to remove the ice crystals. However, due to the limited height of ice crystal growth, the continuity of the pore walls is affected, and the ice crystal shape is irregular, resulting in a significant difference in morphology from the honeycomb structure, and there is still considerable room for improvement in the mechanical properties of the aerogel. Sol-gel reaction can obtain porous materials with honeycomb-like through-hole structures and has been used to prepare honeycomb ceramics such as alumina and silicon nitride, showing unique preparation advantages. However, this method has not yet been used to prepare two-dimensional material aerogels. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention provides a method for preparing a biomimetic honeycomb-shaped two-dimensional material aerogel. A honeycomb structure is formed during directional ion-gelation using sodium alginate solution, achieving the directional and orderly arrangement of two-dimensional material powder within the hydrogel. After removing water using freeze-drying, a highly regular honeycomb structure is obtained. The geometric characteristics of the biomimetic honeycomb structure endow the aerogel with excellent mechanical properties.

[0005] The technical solution of this invention is as follows:

[0006] A method for preparing a biomimetic honeycomb-shaped two-dimensional material aerogel, characterized in that the preparation method includes the following steps:

[0007] 1) Add the two-dimensional material powder and dispersant to deionized water and mix. Disperse the mixture under ultrasonic conditions in an ice bath. Then add sodium alginate and stir the solution to completely dissolve the sodium alginate and obtain a sodium alginate sol with stable dispersion of the two-dimensional material powder.

[0008] 2) Inject the sol obtained in step 1) into the mold, spray a gelling agent on the surface of the sol, and demold after gelation to obtain hydrogel;

[0009] 3) The hydrogel obtained in step 2) is washed in deionized water and freeze-dried to obtain a biomimetic honeycomb two-dimensional material aerogel.

[0010] Further, the two-dimensional material in step 1) is one or more of graphene, graphene oxide, reduced graphene oxide, boron nitride, molybdenum sulfide, and MXene.

[0011] Further, in step 1), the mass of the two-dimensional material powder is 0.5-3% of the mass of water, and the mass of sodium alginate is 0.5-3% of the mass of water.

[0012] Further, the dispersant in step 1) is one or more nonionic dispersants. Specifically, the dispersant is one or more of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, and polyethylene oxide-propylene oxide copolymer. The mass of the dispersant is 5-15% of the mass of the two-dimensional material powder, preferably 10%.

[0013] Further, the gelling agent in step 2) is one or more of a divalent metal ion salt solution; specifically, the gelling agent is one or more of a calcium chloride, copper chloride, copper sulfate, nickel chloride, nickel nitrate, cobalt chloride, or ferrous chloride solution, the concentration of the divalent metal ion salt solution is 0.05-4 mol / L, and the gelation reaction time is 4-12 h.

[0014] In step 3), the aerogel is obtained by freeze-drying at -80℃ to -40℃ and 0.5 to 1.5 Pa for 36-60 h; preferably, the aerogel is obtained by freeze-drying at -60℃ and 1 Pa for 48 h.

[0015] After step 1) and before step 2), the sol is transferred to a vacuum drying oven and vacuum-treated for 1 hour to remove air bubbles from the sol.

[0016] The key advantages of this invention compared to other technologies are:

[0017] The directional ionogel process using sodium alginate solution simultaneously achieves the continuous directional arrangement of two-dimensional materials and the construction of biomimetic honeycomb-like pores. The aerogel exhibits interconnected pores with intact pore walls, possessing a hexagonal structure more closely resembling a honeycomb than other aerogel materials, effectively enhancing its mechanical properties. The aerogel demonstrates high specific strength and specific stiffness, and is resistant to deformation. When the mass fraction of graphene in the solution is 2%, the mass fraction of sodium alginate is 1%, and the concentration of the calcium chloride gelling agent is 2 mol / L, the density of the aerogel is as low as 0.05 g / cm³. 3 It has a compressive strength of 0.55 MPa and a compressive modulus of 4.94 MPa. These excellent mechanical properties can broaden the application range of functional two-dimensional aerogel materials.

[0018] Compared with other two-dimensional material aerogel preparation techniques such as hydrothermal method, ice template method, and sacrificial template method, this method does not require high-temperature heating equipment, directional freezing equipment, or 3D printing equipment. It has low equipment requirements, simple process, good safety, and short preparation cycle. It does not require the introduction of sacrificial template, the raw materials are simple and readily available, and the cost is low.

[0019] This method offers good process scalability and can be used for any two-dimensional material and its combination. The aerogel composition is designable; different raw materials can be selected based on different application scenarios, enabling the functional customization of the aerogel. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments are briefly described below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a scanning electron microscope (SEM) image of the graphene aerogel prepared in Example 1 of the present invention.

[0022] Figure 2 This is a scanning electron microscope cross-sectional image of the graphene aerogel prepared in Example 1 of the present invention.

[0023] Figure 3 This is a scanning electron microscope image of the boron nitride aerogel prepared in Example 2 of the present invention;

[0024] Figure 4 This is a scanning electron microscope (SEM) image of the graphene / boron nitride composite aerogel prepared in Example 3 of the present invention.

[0025] Figure 5 This is a scanning electron microscope image of the molybdenum sulfide aerogel prepared in Example 4 of the present invention.

[0026] Figure 6This is a scanning electron microscope (SEM) image of the graphene / Mxene composite aerogel prepared in Example 5 of the present invention. Detailed Implementation

[0027] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated; they can be combined with each other to achieve better technical effects.

[0028] This invention relates to a method for preparing a biomimetic honeycomb-shaped two-dimensional material aerogel. The method utilizes sodium alginate solution to form a honeycomb structure during directional ion gelation to achieve the directional and orderly arrangement of two-dimensional material powder in a hydrogel; and obtains the aerogel by freeze-drying.

[0029] Directional diffusion refers to the fact that in this process, the ion source is above the liquid surface. Therefore, based on the chemical concentration gradient, the metal ions used to induce the gelation of sodium alginate diffuse directionally from the liquid surface to the bottom of the liquid surface. As a result, the gel structure obtained is a directional channel parallel to the ion diffusion.

[0030] In the process of this invention, due to the directional diffusion of metal ions, sodium alginate forms a (honeycomb) pore structure while forming a gel. During the formation of the (honeycomb) pore structure, the two-dimensional material is fixed in the pore wall.

[0031] This invention relates to a method for preparing a biomimetic honeycomb-shaped two-dimensional material aerogel, characterized in that the preparation method includes the following steps:

[0032] 1) Add the two-dimensional material powder and dispersant to deionized water and mix. Then, ultrasonically disperse the mixture, add sodium alginate, and stir the solution to completely dissolve the sodium alginate to obtain a sodium alginate sol with stable dispersion of the two-dimensional material powder.

[0033] 2) Inject the sol obtained in step 1) into the mold, spray a certain amount of gelling agent on the surface of the sol to perform directional gelation, and demold to obtain hydrogel;

[0034] 3) The hydrogel obtained in step 2) is washed in deionized water (to remove excess gelling agent metal ions and dispersant polymers), and then freeze-dried to obtain an aerogel.

[0035] Further, the two-dimensional material in step 1) is one or more of graphene, graphene oxide, reduced graphene oxide, boron nitride, molybdenum sulfide, and MXene.

[0036] The mass fraction of sodium alginate in solution is approximately 0.5%–3%. If the mass fraction of sodium alginate is too low, a stable gel structure cannot be formed. If the mass fraction is too high, the gel structure becomes too dense, hindering the diffusion of metal ions, resulting in extremely small and non-connected pores.

[0037] Example 1

[0038] A graphene suspension was prepared by adding 0.2 g of graphene (approximately 2% by mass) and 0.02 g of polyvinylpyrrolidone (approximately 0.2% by mass) to 10 mL of deionized water and dispersing by magnetic stirring at 25 °C for 15 min. The suspension was then ultrasonically dispersed for 3 h using a cell disruptor under ice bath conditions to further improve dispersibility. 0.1 g of sodium alginate was added to the dispersion and magnetically stirred for 3 h at room temperature until the sodium alginate was completely dissolved, obtaining a sol. The sol was transferred to a vacuum drying oven and vacuum-treated for 1 h at room temperature to remove air bubbles. The sol was then transferred to a mold, and 10 mL of a 2.0 mol / L calcium chloride solution was uniformly sprayed onto the surface of the sol. After standing for 6 h and gelation, the sol was demolded to obtain a hydrogel. The hydrogel was washed with deionized water and then transferred to a freeze dryer and freeze-dried at -60 °C and 1 Pa for 48 h to obtain a graphene aerogel. The microstructure of the sample was characterized using scanning electron microscopy, and the surface and cross-sectional images are shown below. Figure 1 and Figure 2 As shown, the prepared graphene aerogel possesses a regular honeycomb-like pore structure with good pore connectivity. The porosity of the aerogel was characterized using mercury porosimetry, revealing a porosity of 92.3% and an average pore size of 62.3 μm. Compression performance tests on the aerogel showed a compressive yield strength of 549 kPa (approximately 0.55 MPa) and a compressive modulus of 4.94 MPa, demonstrating excellent compressive strength.

[0039] Example 2

[0040] A boron nitride suspension was prepared by adding 1.0 g of boron nitride and 0.1 g of polyethylene glycol to 50 mL of deionized water and dispersing by magnetic stirring at 25 °C for 15 min. The suspension was then ultrasonically dispersed for 3 h using a cell disruptor under ice bath conditions to further improve dispersibility. 0.25 g of sodium alginate was added to the dispersion and magnetically stirred for 3 h at room temperature to completely dissolve the sodium alginate, obtaining a sol. The sol was transferred to a vacuum drying oven and vacuum-treated for 1 h at room temperature to remove air bubbles. The sol was then transferred to a mold, and 100 mL of 0.2 mol / L copper chloride solution was uniformly sprayed onto the surface of the sol. After standing for 8 h, the mold was demolded after gelation to obtain a hydrogel. The hydrogel was washed with deionized water and then transferred to a freeze dryer and freeze-dried at -60 °C and 1 Pa for 48 h to obtain a boron nitride aerogel. The microstructure of the sample was characterized using scanning electron microscopy, and its surface image is shown below. Figure 3 As shown, the prepared boron nitride aerogel possesses a regular honeycomb-like pore structure. The porosity of the aerogel was characterized using mercury porosimetry, revealing a porosity of 94.7% and an average pore size of 48.7 μm. Compression performance tests revealed a compressive yield strength of 463 kPa (approximately 0.46 MPa) and a compressive modulus of 3.92 MPa, exhibiting excellent compressive strength.

[0041] Example 3

[0042] A graphene / boron nitride suspension was prepared by adding 1.0 g graphene, 1.0 g boron nitride, and 0.2 g polyvinylpyrrolidone to 100 mL of deionized water and dispersing by magnetic stirring at 25 °C for 15 min. The suspension was then ultrasonically dispersed for 3 h using a cell disruptor under ice bath conditions to further improve dispersibility. 0.5 g sodium alginate was added to the dispersion and magnetically stirred for 3 h at room temperature until completely dissolved, obtaining a sol. The sol was transferred to a vacuum drying oven and vacuum-treated for 1 h at room temperature to remove air bubbles. The sol was then transferred to a mold, and 50 mL of a 2.0 mol / L nickel nitrate solution was uniformly sprayed onto the surface. After standing for 6 h, the mold was removed after gelation to obtain a hydrogel. The hydrogel was washed with deionized water and then transferred to a freeze dryer and freeze-dried at -60 °C and 1 Pa for 48 h to obtain a graphene / boron nitride composite aerogel. The microstructure of the sample was characterized using scanning electron microscopy, and its surface image is shown below. Figure 4 As shown, the prepared graphene / boron nitride composite aerogel possesses a regular honeycomb-like pore structure. The porosity of the aerogel was characterized using mercury porosimetry, revealing a porosity of 95.2% and an average pore size of 91.7 μm. Compression performance tests were conducted on the aerogel, revealing a compressive yield strength of 485 kPa (approximately 0.49 MPa) and a compressive modulus of 4.31 MPa, demonstrating excellent compressive strength.

[0043] Example 4

[0044] A molybdenum sulfide suspension was prepared by adding 1.0 g of molybdenum sulfide and 0.1 g of polyvinyl alcohol to 50 mL of deionized water and dispersing by magnetic stirring at 25 °C for 15 min. The suspension was then ultrasonically dispersed for 3 h using a cell disruptor under ice bath conditions to further improve dispersibility. 0.25 g of sodium alginate was added to the dispersion and magnetically stirred for 3 h at room temperature until the sodium alginate was completely dissolved, obtaining a sol. The sol was transferred to a vacuum drying oven and vacuum-treated for 1 h at room temperature to remove air bubbles. The sol was then transferred to a mold, and 50 mL of a 3.0 mol / L calcium chloride solution was uniformly sprayed onto the surface of the sol. After standing for 5 h, the sol was demolded after gelation to obtain a hydrogel. The hydrogel was washed with deionized water and then transferred to a freeze dryer and freeze-dried at -60 °C and 1 Pa for 48 h to obtain a molybdenum sulfide aerogel. The microstructure of the sample was characterized using scanning electron microscopy, and its surface image is shown below. Figure 5 As shown, the prepared molybdenum sulfide aerogel has a regular honeycomb-like pore structure. The porosity of the aerogel was characterized by mercury porosimetry, revealing a porosity of 96.4% and an average pore size of 57.5 μm. Compression performance tests showed a compressive yield strength of 409 kPa (approximately 0.41 MPa) and a compressive modulus of 3.85 MPa, exhibiting excellent compressive strength.

[0045] Example 5

[0046] A graphene / MXene suspension was prepared by adding 0.25 g graphene, 0.05 g MXene, and 0.03 g polyvinylpyrrolidone to 30 mL of deionized water and dispersing by magnetic stirring at 25 °C for 15 min. The suspension was then ultrasonically dispersed for 3 h using a cell disruptor under ice bath conditions to further improve dispersibility. 0.15 g sodium alginate was added to the dispersion and magnetically stirred for 3 h at room temperature until the sodium alginate was completely dissolved, obtaining a sol. The sol was transferred to a vacuum drying oven and vacuum-treated for 1 h at room temperature to remove air bubbles. The sol was then transferred to a mold, and 15 mL of a 2.0 mol / L calcium chloride solution was uniformly sprayed onto the surface of the sol. After standing for 6 h and gelation, the sol was demolded to obtain a hydrogel. The hydrogel was washed with deionized water and then transferred to a freeze dryer and freeze-dried at -60 °C and 1 Pa for 48 h to obtain a graphene / MXene composite aerogel. The microstructure of the sample was characterized using scanning electron microscopy, and its surface image is shown below. Figure 6 As shown, the prepared graphene / Mxene composite aerogel possesses a regular honeycomb-like pore structure. The porosity of the aerogel was characterized using mercury porosimetry, revealing a porosity of 96.6% and an average pore size of 92.7 μm. Compression performance tests on the aerogel showed a compressive yield strength of 502 kPa (approximately 0.50 MPa) and a compressive modulus of 4.43 MPa, exhibiting excellent compressive strength.

[0047] Example 6

[0048] A graphene suspension was prepared by adding 0.2 g of graphene (approximately 2% by mass) and 0.02 g of polyvinylpyrrolidone (approximately 0.2% by mass) to 10 mL of deionized water and dispersing by magnetic stirring at 25 °C for 15 min. The suspension was then ultrasonically dispersed for 3 h using a cell disruptor under ice bath conditions to further improve dispersibility. 0.05 g of sodium alginate (approximately 0.5% by mass) was added to the dispersion and magnetically stirred for 3 h at room temperature until the sodium alginate was completely dissolved, obtaining a sol. The sol was transferred to a vacuum drying oven and vacuum-treated for 1 h at room temperature to remove air bubbles. The sol was then transferred to a mold, and 5 mL of a 2.0 mol / L calcium chloride solution was uniformly sprayed onto the surface of the sol. After standing for 6 h and gelation, the sol was demolded to obtain a hydrogel. The hydrogel was washed with deionized water and then transferred to a freeze dryer and freeze-dried at -60 °C and 1 Pa for 48 h to obtain a graphene aerogel. The microstructure of the sample was characterized using scanning electron microscopy. The prepared graphene aerogel has a regular honeycomb pore structure with good pore connectivity.

[0049] Example 7

[0050] A graphene suspension was prepared by adding 0.2 g of graphene (approximately 2% by mass) and 0.02 g of polyvinylpyrrolidone (approximately 0.2% by mass) to 10 mL of deionized water and dispersing by magnetic stirring at 25 °C for 15 min. The suspension was then ultrasonically dispersed for 3 h using a cell disruptor under ice bath conditions to further improve dispersibility. 0.3 g of sodium alginate (approximately 3% by mass) was added to the dispersion and magnetically stirred at room temperature for 3 h to completely dissolve the sodium alginate, obtaining a sol. The sol was transferred to a vacuum drying oven and vacuum-treated at room temperature for 1 h to remove air bubbles. The sol was then transferred to a mold, and 30 mL of a 2.0 mol / L calcium chloride solution was uniformly sprayed onto the surface of the sol. After standing for 6 h and gelation, the sol was demolded to obtain a hydrogel. The hydrogel was washed with deionized water and then transferred to a freeze dryer and freeze-dried at -60 °C and 1 Pa for 48 h to obtain a graphene aerogel. The microstructure of the sample was characterized using scanning electron microscopy. The prepared graphene aerogel has a regular honeycomb pore structure with good pore connectivity.

[0051] While several embodiments of the present invention have been provided herein, those skilled in the art should understand that modifications can be made to these embodiments without departing from the spirit of the invention. The above embodiments are merely exemplary and should not be construed as limiting the scope of the invention.

Claims

1. A method for preparing a biomimetic honeycomb-shaped two-dimensional material aerogel, characterized in that, The preparation method includes the following steps: 1) Add the two-dimensional material powder and dispersant to deionized water and mix, then ultrasonically disperse, then add sodium alginate and stir the solution to completely dissolve the sodium alginate, thereby obtaining a sodium alginate sol in which the two-dimensional material powder is stably dispersed. 2) Inject the sol obtained in step 1) into a mold, spray a gelling agent onto the upper surface of the sol, and demold after gelation to obtain a hydrogel; the gelling agent is one or more of a divalent metal ion salt solution; 3) The hydrogel obtained in step 2) is washed in deionized water and freeze-dried to obtain the biomimetic honeycomb two-dimensional material aerogel.

2. The preparation method according to claim 1, characterized in that, The two-dimensional material mentioned in step 1) is one or more of graphene, graphene oxide, reduced graphene oxide, boron nitride, molybdenum sulfide and MXene.

3. The preparation method according to claim 1, characterized in that, In step 1), the mass of the two-dimensional material powder is 0.5-3% of the mass of water, and the mass of the sodium alginate is 0.5-3% of the mass of water.

4. The preparation method according to claim 1, characterized in that, The dispersant mentioned in step 1) is one or more nonionic dispersants.

5. The preparation method according to claim 4, characterized in that, The dispersant is one or more of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, and polyethylene oxide-polypropylene copolymer.

6. The preparation method according to claim 4, characterized in that, The mass of the dispersant is 5-15% of the mass of the two-dimensional material powder.

7. The preparation method according to claim 4, characterized in that, The mass of the dispersant is 10% of the mass of the two-dimensional material powder.

8. The preparation method according to claim 1, characterized in that, The gelling agent mentioned in step 2) is one or more of calcium chloride, copper chloride, copper sulfate, nickel chloride, nickel nitrate, cobalt chloride, or ferrous chloride solution.

9. The preparation method according to claim 8, characterized in that, The concentration of the divalent metal ion salt solution is 0.05~4 mol / L.

10. The preparation method according to claim 1, characterized in that, The gel reaction time in step 2) is 4~12 h.

11. The preparation method according to claim 1, characterized in that, In step 3), the aerogel is obtained by freeze-drying at -80℃ to -40℃ and 0.5 to 1.5 Pa for 36-60 h.

12. The preparation method according to claim 1, characterized in that, In step 3), the aerogel was obtained by freeze-drying at -60℃ and 1 Pa for 48 h.

13. The preparation method according to claim 1, characterized in that, After step 1) and before step 2), the sol is transferred to a vacuum drying oven and vacuum-treated for 0.5-2 hours to remove air bubbles from the sol.

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