CN104148031A - Method for preparing poly-dopamine carbon material with high specific surface area - Google Patents

Abstract

The invention discloses a preparation method of a dopamine-accumulated carbon material with a high specific surface area. The steps are as follows: (1) dissolving dopamine hydrochloride in deionized water to obtain an aqueous solution of dopamine hydrochloride, which is injected into a mixed solution of ethanol and ammonia water; placed in a closed container Mixed solution of polydopamine spheres was obtained by fully stirring in the medium, and the obtained mixed solution of polydopamine spheres was filtered, rinsed, and dried to obtain solid polydopamine spheres; (2) Mixed solid polydopamine spheres and KOH, fully mixed and ground, and The high temperature activation reaction is carried out in the atmosphere, and then the polydopamine carbon material with high specific surface area is obtained after cleaning, filtering and drying. The polydopamine porous carbon material prepared by the method of the present invention has the characteristics of simple process, high yield, and large specific surface area and pore volume. The pore structure of the polydopamine carbon material can be adjusted by adjusting the amount of KOH, and the synthetic specific surface area and pore volume are different. The material obtained is polydopamine carbon material with high specific surface area and pore volume.

Description

A kind of preparation method of high specific surface accumulation dopamine carbon material

technical field

The invention relates to a preparation method of an adsorption material with a developed pore structure, in particular to a preparation method of a dopamine-accumulated carbon material with a high specific surface area.

Background technique

Dopamine is a high-carbon biomolecule that widely exists in the shell surface of organisms and is a sustainable (renewable) carbon source material for humans. Dopamine will polymerize into polydopamine balls under a certain pH condition, and polydopamine carbon materials can be obtained after polydopamine balls are carbonized. Due to its well-developed pore structure and excellent hydrothermal stability, polydopamine carbon materials have attracted attention in the fields of catalytic materials, membrane materials and surface modification of electrode materials. Lu et al.(Kelong Ai, Yanlan Liu, Changping Ruan, Lehui Lu*and Gaoqing(Max)Lu*.Sp2 C-Dominant N-Doped Carbon Sub-micrometer Spheres with a Tunable Size: A Versatile Platform for Highly Efficient Oxygen-Reduction Catalysts .Adv.Mater.2013,25,998–1003) reported a synthetic method of polydopamine carbon material: (1) carbonize polydopamine balls at 800 degrees Celsius first: (2) mix carbonized polydopamine balls with KOH Mixed at a ratio of 1:4, and then reacted at a high temperature at 770°C to finally obtain a polydopamine porous carbon material with a well-developed pore structure, and its BET specific surface area is 2006 m ² /g. This preparation method can be called carbonization-activation method.

This method still has the following deficiencies:

1. The material yield is too low;

2. The specific surface area and pore volume of the prepared material still need to be further improved;

3. The synthesis energy consumption is still high, and it requires two high-temperature reaction processes.

In view of the above problems, the present invention proposes a one-step method for preparing polydopamine porous carbon materials. Not only can the yield be increased, but also the process can be shortened to reduce energy consumption and the material can have a higher specific surface area.

Invention content:

The purpose of the present invention is to address the deficiencies in the pore mechanism and synthesis yield of existing polydopamine carbon materials, and propose a polydopamine with higher specific surface area and larger pore volume while reducing energy consumption and improving yield. method of carbon materials.

The purpose of the present invention is achieved through the following technical solutions:

A preparation method of high specific surface accumulation dopamine carbon material, comprising the steps of:

(1) Dopamine hydrochloride is dissolved in deionized water to obtain an aqueous solution of dopamine hydrochloride, which is then injected into a mixed solution of ethanol and ammonia water; placed in an airtight container and fully stirred to obtain a mixed solution of polydopamine balls, and the obtained mixed solution of polydopamine balls Filter, rinse, and dry to obtain solid polydopamine spheres;

(2) Mix the solid polydopamine spheres obtained in step (1) with KOH, fully mix and grind, perform high-temperature activation reaction in an Ar atmosphere, then wash, filter, and dry to obtain a polydopamine carbon material with a high specific surface area.

In the above method, in step (1), the dopamine hydrochloride aqueous solution is configured according to the mass ratio of dopamine hydrochloride crystals and deionized water of 1:50 to 200, and the dopamine hydrochloride solution, ethanol and ammonia water are configured according to the volume ratio of dopamine hydrochloride solution : ethanol: ammonia water=50～200:40:1, the stirring is stirring at room temperature for 10～30h.

In the above method, the mixing ratio of solid polydopamine balls and KOH in step (2) is 1:1 to 1:7 by mass, the reaction temperature of the high temperature activation reaction is 500 to 800°C, and the reaction time is 1 to 3 hours , the cleaning is washing with dilute hydrochloric acid and deionized water 4 times; the drying is vacuum drying at 50°C-80°C.

In the above method, the BET specific surface area of the high specific surface area polydopamine carbon material is 2343-3534m ² /g, the total pore volume is 1.37-2.23cm ³ /g, and the micropore pore volume is 0.81-1.23cm ³ /g g; The polydopamine carbon material with high specific surface area has a small spherical structure, and the particle size is in the range of 300-600nm.

Compared with prior art, synthetic method advantage of the present invention:

1. The high-temperature carbonization step is omitted, and the direct activation method is adopted, and the energy consumption is reduced by about 50%;

2. The high-temperature carbonization step is omitted, and the carbon loss can be greatly reduced, and the yield can be increased by more than 50%;

3. Adjusting the amount of KOH can adjust the pore structure of polydopamine carbon materials, and synthesize polydopamine carbon materials with different specific surface areas and pore volumes, and obtain polydopamine carbon materials with higher specific surface areas and pore volumes.

Description of drawings

Fig. 1 is the _N adsorption isotherms of 4 different polydopamine carbon materials obtained in 4 examples of the present invention.

2 is an SEM image of the polydopamine porous carbon material prepared in Example 1.

3 is an SEM image of the polydopamine porous carbon material prepared in Example 2.

4 is an SEM image of the polydopamine porous carbon material prepared in Example 3.

5 is an SEM image of the polydopamine porous carbon material prepared in Example 4.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and examples, but the protection scope of the present invention is not limited to the range expressed in the examples.

Example 1

1 g of dopamine hydrochloride was dissolved in 50 ml of deionized water, and the solution was poured into a mixed solution of 40 ml of absolute ethanol and 0.75 ml of ammonia water (mass fraction 28%). After the addition, it was sealed and stirred thoroughly for 10 hours to obtain a polydopamine sphere mixed solution. The product was filtered with a microporous membrane, the obtained material was rinsed with deionized water, and vacuum-dried at 50 degrees Celsius for 10 hours to obtain solid polydopamine spheres. Mix according to the mass ratio of polydopamine balls and KOH at 1:1, then fully mix and grind and stir to make it uniform, then put the solid mixture into a tube furnace, and rise to 500 degrees Celsius, and maintain 500 degrees Celsius for 1 hour, after cooling down to room temperature naturally, dissolve the obtained solid in 1mol/L HCl to fully neutralize the unreacted KOH, then filter it with a microporous membrane and use deionized water several times Wash to pH = 7, and vacuum-dry at 50°C for 12 hours to obtain a solid polydopamine porous carbon material.

Example 2

1 g of dopamine hydrochloride was dissolved in 150 ml of deionized water, and the solution was poured into a mixed solution of 40 ml of absolute ethanol and 0.75 ml of ammonia water (28%). After the addition, seal and stir thoroughly for 15 hours to obtain the polydopamine sphere mixture, filter the product through a microporous membrane, rinse the obtained material with deionized water, and vacuum dry at 50 degrees Celsius for 10 hours to obtain solid polydopamine spheres. Mix according to the mass ratio of polydopamine balls and KOH to 1:5, then fully mix and grind and stir to make it uniform, then put the solid mixture into the tube furnace, and raise the temperature to 5K/min under the atmosphere of Ar 700 degrees Celsius, and maintained at 700 degrees Celsius for 2.5 hours, after naturally cooling down to room temperature, the resulting solid was dissolved in 1mol/L HCl to fully neutralize the unreacted KOH, then filtered through a microporous membrane and deionized water After cleaning until pH = 7, vacuum drying at 60°C for 12 hours, a solid polydopamine porous carbon material was obtained.

Example 3

1 g of dopamine hydrochloride was dissolved in 100 ml of deionized water, and the solution was poured into a mixed solution of 40 ml of absolute ethanol and 0.75 ml of ammonia water (28%). After the addition, seal and stir thoroughly for 25 hours to obtain a polydopamine sphere mixed solution, filter the product with a microporous membrane, rinse the obtained material with deionized water, and vacuum-dry at 50 degrees Celsius for 10 hours to obtain solid polydopamine spheres. Mix according to the mass ratio of polydopamine balls and KOH to 1:3, then fully mix and grind and stir to make it uniform, then put the solid mixture into the tube furnace, and raise the temperature to 5K/min under the Ar atmosphere. 600 degrees Celsius, and maintain 600 degrees Celsius for 1.5h, after cooling down to room temperature naturally, dissolve the obtained solid in 1mol/L HCl to fully neutralize the unreacted KOH, then filter it with a microporous membrane and wash it with deionized water After cleaning until pH = 7, vacuum drying at 70°C for 12 hours, a solid polydopamine porous carbon material was obtained.

Example 4

1 g of dopamine hydrochloride was dissolved in 200 ml of deionized water, and the solution was poured into a mixed solution of 40 ml of absolute ethanol and 0.75 ml of ammonia water (28%). After the addition, seal and stir thoroughly for 30 hours to obtain a polydopamine sphere mixture, filter the product with a microporous membrane, rinse the obtained material with deionized water, and vacuum dry at 50 degrees Celsius for 10 hours to obtain solid polydopamine spheres. Mix according to the mass ratio of polydopamine balls and KOH to 1:7, then fully mix and grind and stir to make it uniform, then put the solid mixture into the tube furnace, and rise to 5K/min under the atmosphere of Ar. 800 degrees Celsius, and maintain 800 degrees Celsius for 3 hours, after naturally cooling down to room temperature, dissolve the obtained solid in 1mol/L HCl to fully neutralize the unreacted KOH, then filter it with a microporous membrane and use deionized water several times Wash until PH = 7, and vacuum-dry at 80°C for 12 hours to obtain a solid polydopamine porous carbon material.

(1) Pore structure properties of polydopamine carbon materials

The pore structure and crystal structure of the polydopamine carbon material prepared in the present invention were characterized by the ASAP-2020 specific surface pore size distribution instrument produced by Micro Company of the United States, and the results are shown in Figure 1 and Table 1.

Table 1. The specific surface area and pore structure of polydopamine carbon materials obtained in four kinds of embodiments.

Fig. 1 is the N2 adsorption isotherms of four different examples under the condition of 77K. According to the isotherms, the specific surface area, pore volume and other information of different examples can be obtained by analyzing and processing software. It can be seen from the figure that with the increase of the amount of activator and the increase of reaction temperature, the BET specific surface area of the material first increases and then decreases, while the pore volume gradually increases. The BET specific surface area of the polydopamine carbon material prepared in the present invention is about 2343-3534m ² /g, the total pore volume range is 1.37-2.23cm ³ /g, and the micropore pore volume is about 0.81-1.23cm ³ /g; This illustrates that four kinds of embodiments of the present invention have very large pore structure and specific surface area coverage; polydopamine carbon material of the present invention has more micropores and specific surface area and pore volume are very large (see Table 1).

(2) SEM of polydopamine carbon material

Adopt Holland FEI Quanta200 type low magnification scanning electron microscope to carry out the characterization of material surface topography to the polydopamine carbon material prepared by four kinds of embodiments of the present invention, operating condition is: apply Cu Kα ₁ ray (λ=1.54056) under 35kV and 25mA Determination.

From Figures 2 to 5, it can be seen that the polydopamine carbon materials prepared in four different examples all maintain a good spherical structure, and the uniform size of the spherical particles is between 300-600nm.

(3) Yield of polydopamine carbon material

Table 2. Comparison of yields of polydopamine carbon materials obtained in four different examples and literature reports.

Table 2 is the yield table of polydopamine carbon material obtained by four different embodiments, and the calculation method of the yield in the table is as follows:

$\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$

Where m _o is the mass of dopamine hydrochloride, and m _t is the mass of the obtained polydopamine carbon material.

Compared with the yield of the polydopamine carbon material reported in the literature, the yield of the direct one-step activation method used in the present invention is 8%-11%, which is higher than the 3% reported in the literature.

The above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (4)

1. a method for preparing the polydopamine carbon material of high specific surface area, is characterized in that comprising the steps: (1) Dissolve dopamine hydrochloride in deionized water to obtain an aqueous solution of dopamine hydrochloride, and then inject it into a mixture of ethanol and ammonia water; place it in an airtight container and stir thoroughly to obtain a mixed solution of polydopamine balls, and mix the obtained mixed solution of polydopamine balls Filter, rinse, and dry to obtain solid polydopamine spheres; (2) Mix the solid polydopamine spheres obtained in step (1) with KOH, thoroughly mix and grind, perform high-temperature activation reaction in an Ar atmosphere, then wash, filter, and dry to obtain a polydopamine carbon material with a high specific surface area. 2. the preparation method of the polydopamine carbon material of high specific surface area according to claim 1, is characterized in that, in step (1), described dopamine hydrochloride aqueous solution is 1 according to the mass ratio of dopamine hydrochloride crystal and deionized water: 50~200 configuration, the dopamine hydrochloride solution, ethanol and ammonia water are according to the volume ratio to be the dopamine hydrochloride solution: ethanol: ammonia water=50~200:40:1, and the stirring is at room temperature for 10~30 h. 3. The preparation method of polydopamine carbon material with high specific surface area according to claim 1, characterized in that, the mixing ratio of solid polydopamine spheres and KOH in step (2) is a mass ratio of 1:1 to 1:7 , the reaction temperature of the high-temperature activation reaction is 500-800°C, the reaction time is 1-3h, the cleaning is washed with dilute hydrochloric acid and deionized water 4 times; the drying is vacuum drying at 50°C-80°C. 4. the preparation method of the polydopamine carbon material of high specific surface area according to claim 1, is characterized in that, the BET specific surface area of the polydopamine carbon material of described high specific surface area is 2343-3534 m ² /g, total pore The volume is 1.37-2.23 cm ³ /g, wherein the micropore volume is 0.81-1.23 cm ³ /g; the polydopamine carbon material with high specific surface area has a small spherical structure, and the particle diameter is in the range of 300-600 nm.