Simple and rapid preparation method and application of two-dimensional in-plane mesoporous polydopamine nanosheet

Abstract

The invention discloses a simple and rapid preparation method and application of a two-dimensional in-plane mesoporous polydopamine nanosheet, silica sol is used as a mesoporous template and is uniformly mixed with a dopamine aqueous solution, rapid freeze drying is performed, the mesoporous template is further removed, and the two-dimensional in-plane mesoporous polydopamine nanosheet is obtained. The two-dimensional in-plane mesoporous polydopamine nanosheet with good two-dimensional flaky morphology, uniform in-plane mesopores and excellent electrochemical performance is obtained after the aqueous solution of dopamine and the silica sol are subjected to one-step mixing, freeze drying and mesoporous template removal, and the problems that in the prior art, the morphology is difficult to regulate and control due to unstable two-dimensional and mesoporous control, and the electrochemical performance is poor are solved. The defects of non-uniform pore diameter and low material performance are overcome; and the material is a pure polydopamine material, has a unique in-plane mesoporous structure, needs few raw materials, is low in cost, is simple to operate, and is beneficial to industrialization. The prepared product is high in quality, good in performance and wide in application range.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic polymer nanomaterials, and particularly relates to a preparation method of polydopamine nanosheets and application thereof. BACKGROUND

[0002] Polydopamine is a material similar to mussel adhesion protein, which has excellent adhesion, redox, biocompatibility and adjustable surface chemical properties, and can be widely applied in the fields of energy storage and conversion, environmental remediation, medical care and sensing. In order to improve the specific surface area and active sites of polydopamine, researchers have proposed measures such as material nanocrystallization and construction of porous structure. Therefore, it is considered as a very effective strategy to prepare two-dimensional mesoporous polydopamine by combining the advantages of two-dimensional nanomaterials and mesoporous materials. When applied to the field of electrochemical energy storage, due to the unique two-dimensional sheet structure, rich mesoporous channels and adjustable sheet thickness and pore size, two-dimensional mesoporous polydopamine exhibits more reaction active sites, effective electrolyte ion penetration, rapid ion-electron transmission and excellent structural stability, and therefore has attracted widespread attention in recent years.

[0003] The existing method for preparing two-dimensional mesoporous polydopamine nanosheets, such as the method for preparing two-dimensional mesoporous polydopamine composite disclosed in Chinese Patent CN 119591108 A, first uses an amphiphilic block copolymer micelle as a mesoporous template, mixes it with a MXene solution with a concentration of 2-5 mg / mL and an ammonia solution according to a certain volume ratio, then adds polydopamine to form a composite, and finally performs centrifugal treatment and high-temperature drying for several hours, so as to obtain spherical mesoporous two-dimensional mesoporous polydopamine@MXene nanosheets. For example, the method for preparing mesoporous polydopamine / graphene nanosheet composite material disclosed in Chinese Patent CN 113956657 A. The mesoporous template agent is first attached to the graphene oxide nanosheet by self-assembly, then the dopamine monomer is polymerized around the mesoporous template agent on the graphene oxide nanosheet, and then the template agent is removed by hydrothermal reduction, so as to construct a spherical or spherical-like mesoporous polydopamine layer on the upper and lower surfaces of the graphene oxide nanosheet.

[0004] The above preparation methods all need a two-dimensional substrate (MXene or graphene), and the obtained product is a two-dimensional mesoporous polydopamine composite material, and cannot obtain single ordered mesoporous polydopamine nanosheets. Moreover, the preparation steps are complicated and not easy for batch production. SUMMARY

[0005] The present application provides a simple and rapid preparation technology of two-dimensional in-plane mesoporous polydopamine, which has unique morphology structure, adjustable pore size, high activity, good repeatability, simple steps, convenient operation, low cost and easy-to-scale process.

[0006] To solve the above technical problems, the present application adopts the following technical solutions:

[0007] The simple preparation method of two-dimensional in-plane mesoporous polydopamine of the present application is realized by the following steps:

[0008] The silica sol is uniformly mixed with the dopamine aqueous solution, and then freeze-dried to further remove the mesoporous template, so as to obtain two-dimensional in-plane mesoporous polydopamine nanosheets.

[0009] As a preferred technical solution of the present application, the concentration of the silica sol is 100-200 mg / mL, and the particle size of the silicon dioxide in the silica sol is 5-50 nm.

[0010] As a preferred technical solution of the present application, the concentration of the dopamine aqueous solution is 100-300 mg / mL.

[0011] As a preferred technical solution of the present application, the mass ratio of dopamine to silicon dioxide in the silica sol is 5:5-3:7.

[0012] As a preferred technical solution of the present application, the uniform mixing is stirring for 1-5 minutes at normal temperature and pressure.

[0013] As a preferred technical solution of the present application, the freeze-drying temperature is-50 to-5℃, and the time is 6-36 h. In the early stage of freeze-drying, ice crystals act as two-dimensional templates, so that dopamine and silica sol are assembled on the surface of the ice crystals, and then slowly polymerize. In the later stage of freeze-drying, after the sublimation of ice crystals, polydopamine-silicon dioxide composite nanosheets are obtained. Next, the silicon dioxide is removed, and two-dimensional in-plane mesoporous polydopamine nanosheets are obtained.

[0014] As a preferred technical solution of the present application, the further removal of the mesoporous template (silicon dioxide) adopts etching method, and the silica sol (i.e. silicon dioxide nanoballs) template is removed by soaking in 1-3 mol / L NaOH solution or KOH solution for 2-10 h.

[0015] The application further provides the two-dimensional in-plane mesoporous polydopamine nanosheet prepared by the preparation method. 2 / g.

[0016] The application further provides application of the two-dimensional in-plane mesoporous polydopamine nanosheet as an electrode material in a supercapacitor, and the specific capacity of the electrode material reaches 200-300 F / g.

[0017] The dopamine molecules in the application are assembled with silica sol (silica nanospheres) through hydrogen bonding, and then co-solidified by freeze-drying, without additional polymerization initiators (utilizing the alkaline environment of the silica sol) and two-dimensional templates (utilizing the ice crystal surface during freezing), and the two-dimensional in-plane mesoporous polydopamine nanosheet can be obtained after removing the silica.

[0018] The application has the following beneficial effects: the application provides a simple and rapid preparation method of two-dimensional in-plane mesoporous polydopamine, and the two-dimensional in-plane mesoporous polydopamine nanosheet with good two-dimensional sheet morphology, uniform in-plane mesopores and excellent electrochemical performance can be obtained after one-step mixing of the aqueous solution of dopamine and silica sol, freeze-drying and removal of the mesoporous template (silica).

[0019] The preparation method of the application avoids the disadvantages of morphology difficult to control, non-uniform pore size and low material performance caused by unstable two-dimensional and mesoporous control in the prior art; and the material is pure polydopamine, has a unique in-plane mesoporous structure, requires less raw materials, has low cost and is simple to operate, and is conducive to industrialization. The product prepared by the application has high quality, good performance and a wide range of applications. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only constitute some embodiments of the application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0021] Figure 1 The scanning electron microscope (SEM) graph of Example 1.

[0022] Figure 2 The transmission electron microscope (TEM) graph of Example 2.

[0023] Figure 3 The physical adsorption and desorption and pore size distribution curve graph of Example 2.

[0024] Figure 4 The graph shows the electrochemical performance of Example 3.

[0025] Figure 5 This is the SEM image of Comparative Example 2. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above-described invention.

[0027] Example 1

[0028] The simple and rapid preparation method of two-dimensional in-plane mesoporous polydopamine nanosheets in this embodiment is as follows:

[0029] Dopamine aqueous solution (300 mg / mL) was added to a reaction flask, followed by slow dropwise addition of silica sol (200 mg / mL, particle size 30 nm) to achieve a dopamine to silica mass ratio of 5:5. The mixture was stirred at room temperature and pressure for 5 minutes, freeze-dried at -15°C for 24 hours, soaked in 1 mol / L NaOH solution for 10 hours, and then washed with water to obtain two-dimensional intraplane mesoporous polydopamine nanosheets.

[0030] Depend on Figure 1 SEM images show that the lateral dimensions of the two-dimensional mesoporous polydopamine are approximately 10-20 μm. The nanosheets are approximately 40 nm thick, with mesopore sizes of approximately 30 nm, which is not significantly different from the particle size of the silica used; the specific surface area is 105.4 m². 2 / g. Three-electrode testing revealed that the specific capacity of the two-dimensional mesoporous polydopamine electrode at a scan rate of 10 mV / s was ~205 F / g.

[0031] Example 2

[0032] The simple and rapid preparation method of two-dimensional in-plane mesoporous polydopamine nanosheets in this embodiment is as follows:

[0033] A dopamine aqueous solution (200 mg / mL) was added to a reaction flask, followed by slow dropwise addition of silica sol (150 mg / mL, particle size 12 nm) to achieve a dopamine to silica mass ratio of 4:6. The mixture was stirred at room temperature and pressure for 3 minutes, freeze-dried at -35°C for 10 hours, soaked in 2 mol / L NaOH solution for 5 hours, and then washed with water to obtain two-dimensional intraplane mesoporous polydopamine nanosheets.

[0034] The two-dimensional mesoporous polydopamine has a lateral dimension of approximately ~10 μm and a nanosheet thickness of ~20 nm. Figure 2 The TEM image shows that the mesopore size is ~12 nm, which is not much different from the particle size of the silica used; Figure 3The specific surface area is 180.0 m 2 / g, and the pore size is concentrated at about 12 nm. The three-electrode test shows that the specific capacity of the two-dimensional mesoporous polydopamine electrode is about 273 F / g at a scanning rate of 1 mV / s.

[0035] Example 3

[0036] The simple and rapid preparation method of the two-dimensional in-plane mesoporous polydopamine nanosheet in this example is as follows:

[0037] Dopamine aqueous solution (100 mg / mL) was added to a reaction bottle, and then silica sol (100 mg / mL, particle size 5 nm) was slowly added dropwise to make the mass ratio of dopamine to silica 3:7. After stirring at room temperature and normal pressure for 1 minute, freeze-drying at-40°C for 8 hours, and immersion in 3 mol / L KOH solution for 2 hours, the two-dimensional in-plane mesoporous polydopamine nanosheet was obtained after water washing.

[0038] The lateral size of the two-dimensional mesoporous polydopamine is about 3 μm, and the nanosheet thickness is about 7 nm; the mesopore size is about 5 nm, which is not much different from the particle size of the silica used; and the specific surface area is about 302.5 m 2 / g. The three-electrode test shows that the specific capacity of the two-dimensional mesoporous polydopamine electrode is about 220 F / g at a current density of 1 A / g. Figure 4

[0039] Example 4

[0040] The simple and rapid preparation method of the two-dimensional in-plane mesoporous polydopamine nanosheet in this example is as follows:

[0041] Dopamine aqueous solution (120 mg / mL) was added to a reaction bottle, and then silica sol (120 mg / mL, particle size 20 nm) was slowly added dropwise to make the mass ratio of dopamine to silica 3:7. After stirring at room temperature and normal pressure for 5 minutes, freeze-drying at-5°C for 36 hours, and immersion in 1.5 mol / L NaOH solution for 7 hours, the two-dimensional in-plane mesoporous polydopamine nanosheet was obtained after water washing.

[0042] Example 5

[0043] The simple and rapid preparation method of the two-dimensional in-plane mesoporous polydopamine nanosheet in this example is as follows:

[0044] Dopamine aqueous solution (180 mg / mL) was added to a reaction bottle, and then silica sol (160 mg / mL, particle size 5 nm) was slowly added dropwise to make the mass ratio of dopamine to silica 4:6. After stirring at room temperature and normal pressure for 3 minutes, freeze-drying at-10°C for 24 hours, and immersion in 2 mol / L KOH solution for 5 hours, the two-dimensional in-plane mesoporous polydopamine nanosheet was obtained after water washing. ​

[0045] Example 6

[0046] The simple and rapid preparation method of the two-dimensional in-plane mesoporous polydopamine nanosheet in this embodiment is as follows:

[0047] Dopamine aqueous solution (240 mg / mL) was added into a reaction bottle, and then silica sol (180 mg / mL, particle size 15 nm) was slowly added dropwise to make the mass ratio of dopamine to silica 5:5. After stirring at room temperature and normal pressure for 1 min, freeze-drying at -30℃ for 12 h, and immersion in 3 mol / L NaOH solution for 2 h, the two-dimensional in-plane mesoporous polydopamine nanosheet was obtained after water washing.

[0048] In order to emphasize the role of the ice template during freeze-drying, Comparative Examples 1-3 were set based on Examples 1-3, respectively.

[0049] Comparative Example 1

[0050] Based on Example 1, freeze-drying was not used, and the specific method was as follows:

[0051] Dopamine aqueous solution (300 mg / mL) was added into a reaction bottle, and then silica sol (200 mg / mL, particle size 30 nm) was slowly added dropwise to make the mass ratio of dopamine to silica 5:5. After stirring at room temperature and normal pressure for 5 min, drying at 60℃ for 24 h, and immersion in 1 mol / L NaOH solution for 10 h, the polydopamine material was obtained after water washing. The material did not have obvious mesoporous structure, and the specific surface area was ~20.9 m 2 / g. Through three-electrode test, it was obtained that the specific capacity of the polydopamine electrode was ~66 F / g at a scanning rate of 10 mV / s.

[0052] Comparative Example 2

[0053] Based on Example 2, freeze-drying was not used, and the specific method was as follows:

[0054] Dopamine aqueous solution (200 mg / mL) was added into a reaction bottle, and then silica sol (150 mg / mL, particle size 12 nm) was slowly added dropwise to make the mass ratio of dopamine to silica 4:6. After stirring at room temperature and normal pressure for 3 min, drying at 80℃ for 10 h, and immersion in 2 mol / L NaOH solution for 5 h, the blocky polydopamine material (as shown in Figure 5 , which did not have obvious mesoporous structure, was obtained after water washing. The specific surface area was ~25.4 m 2 / g. Through three-electrode test, it was obtained that the specific capacity of the polydopamine electrode was ~78 F / g at a scanning rate of 1 mV / s.

[0055] Comparative Example 3

[0056] On the basis of Example 3, without freeze-drying, the specific method is as follows:

[0057] Dopamine aqueous solution (100 mg / mL) was added into the reaction bottle, and then silica sol (100 mg / mL, particle size 5 nm) was slowly added dropwise to make the mass ratio of dopamine and silica 3:7. Stirring at room temperature and normal pressure for 1 min, drying at 90℃ for 8 h, and then soaking in 3 mol / L KOH solution for 2 h, and then water washing to obtain polydopamine material. The material is stacked block morphology, and no obvious mesoporous structure is observed. The specific surface area is ~ 31.2 m 2 / g. Through three-electrode test, the specific capacity of the polydopamine electrode is ~ 80 F / g at a current density of 1 A / g.

[0058] The performance of the two-dimensional in-plane mesoporous polydopamine nanosheet of Examples 1-3 and Comparative Examples 1-3 is shown in Table 1.

[0059] Table 1 Comparison of morphology and electrochemical performance of materials obtained in examples and comparative examples

[0060] Drying conditions Morphology Mesopore size Specific surface area Electrochemical performance Example 1 -15°C cold drying 24 Two-dimensional ~30 nm 105.4 m 2 / g]] 205 F / g Example 2 -35°C cold drying 10 Two-dimensional ~12 nm 180.0m 2 / g]]> 273 F / g Example 3 -40°C cold drying 8h Two-dimensional ~5 nm 302.5m 2 / g]]> 220 F / g Comparative Example 1 60°C drying 24 Massive None 20.9m 2 / g]] 66 F / g Comparative Example 2 80°C drying 10 Massive None 25.4m 2 / g]]> 78 F / g Comparative Example 3 90°C drying 8h Massive None 31.2 m 2 / g]] 80 F / g

[0061] From Table 1, it can be seen that in the comparative examples, the freeze-drying is replaced by ordinary drying, and the morphology and electrochemical performance of the product have changed significantly. Specifically, in the examples, freeze-drying is used to obtain two-dimensional in-plane mesoporous polydopamine with uniform two-dimensional morphology, rich mesoporous structure, large specific surface area and high electrochemical performance. According to the size of the mesoporous template (particle size of silica sol), the mesoporous pore size, specific surface area and electrochemical performance can be precisely controlled. In the comparative examples, freeze-drying is not used, but ordinary drying is used, and the material obtained is agglomerated block, no obvious pore structure is observed, and the specific surface area and electrochemical performance are reduced by several times. The comparison results show that freeze-drying is an important and necessary technical process. In the freeze-drying process, ice crystals act as a two-dimensional template, and dopamine and silica sol are assembled and polymerized on the surface of the ice crystals to obtain polydopamine-silica composite nanosheets with uniform two-dimensional morphology. After removing the silica, two-dimensional in-plane mesoporous polydopamine nanosheets are obtained. However, in the drying process, dopamine and silica sol rapidly and intensively polymerize and crosslink, resulting in agglomerated block materials. In the high-temperature evaporation process, dopamine and silica sol are prone to delamination and phase separation, resulting in uneven pore structure of the material. Finally, the material exhibits low specific surface area and electrochemical performance.

[0062] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A simple and rapid method for preparing two-dimensional in-plane mesoporous polydopamine nanosheets, characterized in that... Includes the following steps: Using silica sol as a mesoporous template, it is uniformly mixed with dopamine aqueous solution, rapidly freeze-dried, and then the mesoporous template is further removed to obtain two-dimensional in-plane mesoporous polydopamine nanosheets.

2. The simple and rapid preparation method of two-dimensional in-plane mesoporous polydopamine nanosheets according to claim 1, characterized in that, The concentration of the silica sol is 100-200 mg / mL, and the particle size of the silica in the silica sol is 5-50 nm.

3. The simple and rapid preparation method of two-dimensional in-plane mesoporous polydopamine nanosheets according to claim 1, characterized in that, The concentration of dopamine in aqueous solution is 100-300 mg / mL.

4. The simple and rapid preparation method of two-dimensional in-plane mesoporous polydopamine nanosheets according to claim 1, characterized in that, The mass ratio of dopamine to silica in silica sol is 5:5-3:

7.

5. The simple and rapid preparation method of two-dimensional in-plane mesoporous polydopamine nanosheets according to claim 1, characterized in that, Uniform mixing is achieved by stirring for 1-5 minutes at room temperature and pressure.

6. The simple and rapid preparation method of two-dimensional in-plane mesoporous polydopamine nanosheets according to claim 1, characterized in that, The freeze-drying temperature is -50~-5 ℃, and the time is 6-36 h.

7. The simple and rapid preparation method of two-dimensional in-plane mesoporous polydopamine nanosheets according to claim 1, characterized in that, Further removal of the mesoporous template is achieved by etching, followed by soaking in 1-3 mol / L NaOH or KOH solution for 2-10 hours.

8. Two-dimensional in-plane mesoporous polydopamine nanosheets prepared by any one of the preparation methods according to claims 1-7.

9. The two-dimensional in-plane mesoporous polydopamine nanosheet according to claim 8, characterized in that: The two-dimensional in-plane mesoporous polydopamine nanosheets have a size of 1-20 μm, a thickness of 3-40 nm, a mesopore size of 5-50 nm, and a surface area of ​​100.0-330.0 m². 2 / g.

10. The application of the two-dimensional in-plane mesoporous polydopamine nanosheets as electrode materials in supercapacitors according to claim 8, characterized in that: The specific capacity of the electrode material reaches 200-300 F / g.

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