CN111777055B - A preparation method of heteroatom-doped porous carbon electrode material - Google Patents

Abstract

The invention relates to a preparation method of a heteroatom doped porous carbon electrode material, which comprises the following steps: uniformly mixing acrylamide, N' -methylene bisacrylamide, sodium alginate, a comonomer containing hetero atoms and water according to the mass ratio of 0.02-0.1:0.002-0.015:0-0.02:0-0.1:1 to obtain a mixed solution, introducing nitrogen to remove oxygen, and adding an initiator to react to obtain hydrogel; and freeze-drying the hydrogel to obtain xerogel, carbonizing the xerogel, and washing and drying the xerogel to obtain the heteroatom doped porous carbon electrode material. According to the invention, acrylamide and comonomer containing hetero atoms are used as reactants, N, N' -methylene bisacrylamide is used as a cross-linking agent, sodium alginate is used as a viscosity regulator of a reaction system, the preparation method is simple, carbonization and hetero atom doping are completed in one step, and the type and content of hetero atoms in the prepared porous carbon electrode material are controllable, so that the porous carbon electrode material has excellent capacitance performance.

Description

A kind of preparation method of heteroatom-doped porous carbon electrode material

technical field

The invention relates to the technical field of supercapacitor electrode materials, in particular to a preparation method of heteroatom-doped porous carbon electrode materials for supercapacitors.

Background technique

With the gradual depletion of global fossil energy and the increasingly serious environmental problems, the development and utilization of new energy has attracted great attention from all countries in the world. Efficient energy storage and conversion devices are the key to new energy utilization, so new electrochemical energy devices such as supercapacitors, fuel cells, and lithium batteries have become current research hotspots. In these electrochemical energy devices, the electrode material is a key factor affecting the performance.

Porous carbon materials are considered to be the most potential electrode materials due to their large specific surface area, tunable pore structure, good electrical conductivity, and more electrochemically active sites for various redox reactions. At present, the development of porous carbon materials focuses on the regulation of pore structure and heteroatom doping, which are also the fundamental factors affecting the application performance of porous carbon materials. Heteroatom doping is an effective way to improve the performance of porous carbon electrode materials. For example, the porous carbon is doped with an appropriate amount of heteroatoms such as N, B, P, and S. The pseudocapacitance formed by the redox reaction of the heteroatoms can improve the specific capacitance of the porous carbon material, and the doping of the heteroatoms can also improve the electrical conductivity. properties, improve the wettability of the carbon material surface, and further improve the capacitance performance of the carbon material. In electrocatalysis, doping non-metallic heteroatoms with different electronegativity into carbon electrode materials can destroy the electroneutrality of carbon sp2 hybrid orbitals and cause the electron redistribution of surrounding carbon, thereby improving the electrocatalytic performance. .

At present, the research on heteroatom-doped porous carbon is very active, and the heteroatom doping mainly includes two methods: in-situ doping and post-treatment doping. In-situ doping refers to direct high-temperature carbonization of heteroatom-rich carbon precursors to obtain heteroatom-doped porous carbon in one step; post-treatment doping is to impregnate and oxidize porous carbon, or place porous carbon in The gas containing heteroatoms, such as ammonia, reacts at high temperature to obtain heteroatom-doped porous carbon. In-situ doping is beneficial to uniformly incorporate heteroatoms into porous carbon, but currently there are few precursors suitable for preparing in-situ doped porous carbon, and there are fewer precursors containing two different heteroatoms. The post-treatment doping process is generally tedious and time-consuming, and usually only functionalizes the surface of porous carbon without changing its bulk structure. Therefore, it is still a challenging task to develop new methods for the preparation of heteroatom-doped porous carbons with simple and controllable processes.

Contents of the invention

The purpose of the present invention is to solve the above disadvantages, and provide a preparation method of heteroatom-doped porous carbon electrode material.

A method for preparing a heteroatom-doped porous carbon electrode material, comprising the steps of:

(1) Mix acrylamide, N,N'-methylenebisacrylamide, sodium alginate, heteroatom-containing comonomers and water to obtain a mixed solution, and add an initiator to initiate polymerization after purging nitrogen to remove oxygen react to obtain a hydrogel;

(2) freeze-drying the hydrogel to obtain a xerogel, carbonizing the xerogel, washing with water and drying to obtain a heteroatom-doped porous carbon electrode material.

In step (1), the mass ratio of the acrylamide, N,N'-methylenebisacrylamide, sodium alginate, heteroatom-containing comonomer and water is 0.02～0.1:0.002～0.015:0～0.02 :0～0.1:1, more preferably 0.03～0.06:0.002～0.008:0.008～0.012:0.03～0.06:1.

Further, in step (1), the heteroatom-containing comonomer is selected from 3-(4-pyridyl)acrylic acid, 3-(2-thienyl)acrylic acid, 4-vinylphenylboronic acid or phosphoenolacetone Any one of the acid cyclohexyl ammonium salts or a mixture of two or more in any proportion.

Further, in step (1), the amount of the initiator used is 1-6% of the total mass of acrylamide and comonomers containing heteroatoms.

Further, in step (1), the initiator is one of potassium persulfate, ammonium persulfate or water-soluble oxidation-reduction initiation system, and the water-soluble oxidation-reduction initiation system is selected from potassium persulfate-sodium sulfite, Any one of potassium persulfate-sodium bisulfite, ammonium persulfate-sodium sulfite or ammonium persulfate-sodium bisulfite water-soluble oxidation-reduction initiation system.

Further, in step (1), when the initiator is potassium persulfate or ammonium persulfate, the reaction temperature is 65-75°C, and the reaction time is 2-5 hours; when the initiator is a water-soluble oxidation-reduction initiation system , the reaction temperature is 20-30°C, and the reaction time is 2-5h.

Further, in step (2), the carbonization is carried out under nitrogen atmosphere, the carbonization temperature is 700-1000° C., and the time is 2-4 hours.

The preparation principle of the heteroatom-doped porous carbon of the present invention is as follows: the present invention uses acrylamide and comonomers containing heteroatoms as reactants, N,N'-methylenebisacrylamide as cross-linking agent, sodium alginate As a viscosity regulator for the reaction system, acrylamide, heteroatom-containing comonomers, N,N'-methylenebisacrylamide and sodium alginate are mixed with water to form a uniform solution before polymerization, and then an initiator is added to initiate free radical polymerization. As the polymerization proceeds, the hydrogel is gradually formed. Due to the heteroatoms contained in the copolymer gel, the doping of heteroatoms in the porous carbon was realized simultaneously during the high-temperature carbonization process.

The beneficial effects of the present invention are as follows:

(1) A gel is formed by copolymerizing monomers containing heteroatoms with acrylamide, so that the heteroatoms are evenly distributed in the copolymer gel, which ensures the uniform doping of carbonized heteroatoms in the porous carbon.

(2) The content of heteroatoms in porous carbons can be conveniently regulated by changing the amount of heteroatom-containing comonomers added.

(3) By copolymerizing monomers containing different heteroatoms, porous carbons co-doped with various heteroatoms can be prepared.

(4) The prepared porous carbon has good specific capacitance, and the mass specific capacitance can reach 260F/g when the current density is 0.5A/g.

Detailed ways

In order to make the objects and advantages of the present invention clearer, the present invention will be specifically described below in conjunction with examples. It should be understood that the following words are only used to describe one or several specific implementation modes of the present invention, and do not strictly limit the protection scope of the specific claims of the present invention.

Example 1

A method for preparing a heteroatom-doped porous carbon electrode material, comprising the steps of:

(1) Mix 0.36g of acrylamide, 0.04g of N,N'-methylenebisacrylamide, 0.10g of sodium alginate and 9.0g of water to obtain a mixed solution, and pass nitrogen into the mixed solution to remove oxygen for half an hour , add 10mg of potassium persulfate (dissolved in 1mL of water), react in a water bath at 70°C for 2h to obtain a hydrogel;

(2) The hydrogel was freeze-dried to obtain a xerogel, and the xerogel was carbonized at 800° C. for 2 hours in a nitrogen atmosphere, and then washed with water and dried to obtain a porous carbon electrode material.

The porous carbon material prepared by the above method has a N content of 6.8atm%, and when the charge and discharge current density is 0.5A/g, the specific capacitance is 208.2F/g.

Example 2

A method for preparing a heteroatom-doped porous carbon electrode material, comprising the steps of:

(1) Mix 0.24g acrylamide, 0.04g N,N'-methylenebisacrylamide, 0.10g sodium alginate, 0.12g 3-(4-pyridyl)acrylic acid and 9.0g water to obtain a mixed solution 1. After deoxygenating the mixed solution with nitrogen for half an hour, add 10 mg of ammonium persulfate (dissolved in 1 mL of water), and react in a water bath at 70 ° C for 4 hours to obtain a hydrogel;

(2) The hydrogel was freeze-dried to obtain a xerogel, and the xerogel was carbonized at 800° C. for 2 hours in a nitrogen atmosphere, and then washed with water and dried to obtain a porous carbon electrode material.

The porous carbon material prepared by the above method has a N content of 8.2atm%, and when the charge and discharge current density is 0.5A/g, the specific capacitance is 229.6F/g.

Example 3

A method for preparing a heteroatom-doped porous carbon electrode material, comprising the steps of:

(1) Mix 0.24g of acrylamide, 0.04g of N,N'-methylenebisacrylamide, 0.10g of sodium alginate, 0.12g of 3-(2-thienyl)acrylic acid and 9.0g of water to obtain a mixed solution 1. After deoxygenating the mixed solution with nitrogen for half an hour, add 10 mg of ammonium persulfate (dissolved in 1 mL of water), and react in a water bath at 70 ° C for 4 hours to obtain a hydrogel;

(2) The hydrogel was freeze-dried to obtain a xerogel, and the xerogel was carbonized at 800° C. for 2 hours in a nitrogen atmosphere, and then washed with water and dried to obtain a porous carbon electrode material.

The porous carbon material prepared by the above method is doped with N and S at the same time, the N content is 4.8atm%, the S content is 3.2atm%, when the charge and discharge current density is 0.5A/g, the specific capacitance is 216.9F/g.

Example 4

A method for preparing a heteroatom-doped porous carbon electrode material, comprising the steps of:

(1) Mix 0.24g of acrylamide, 0.04g of N,N'-methylenebisacrylamide, 0.10g of sodium alginate, 0.12g of 4-vinylphenylboronic acid and 9.0g of water to obtain a mixed solution. After deoxygenating the solution with nitrogen for half an hour, add 10 mg of ammonium persulfate (dissolved in 1 mL of water), and react in a water bath at 70 ° C for 4 hours to obtain a hydrogel;

(2) The hydrogel was freeze-dried to obtain a xerogel, and the xerogel was carbonized at 800° C. for 2 hours in a nitrogen atmosphere, and then washed with water and dried to obtain a porous carbon electrode material.

The porous carbon material prepared by the above method is doped with N and B at the same time, the N content is 6.0atm%, and the B content is 4.9atm%. When the charge and discharge current density is 0.5A/g, the specific capacitance is 260.0F/g.

Example 5

A method for preparing a heteroatom-doped porous carbon electrode material, comprising the steps of:

(1) Mix 0.24g acrylamide, 0.04g N,N'-methylene bisacrylamide, 0.10g sodium alginate, 0.12g phosphoenolpyruvate cyclohexyl ammonium salt and 9.0g water to obtain a mixed solution 1. After deoxygenating the mixed solution with nitrogen for half an hour, add 10 mg of ammonium persulfate (dissolved in 1 mL of water), and react in a water bath at 70 ° C for 4 hours to obtain a hydrogel;

(2) The hydrogel was freeze-dried to obtain a xerogel, and the xerogel was carbonized at 800° C. for 2 hours in a nitrogen atmosphere, and then washed with water and dried to obtain a porous carbon electrode material.

The porous carbon material prepared by the above method is doped with N and P at the same time, the N content is 6.2atm%, and the P content is 4.2atm%. When the charge and discharge current density is 0.5A/g, the specific capacitance is 241.8F/g.

Example 6

The preparation process is the same as that of Example 1, except that the carbonization temperature is 700°C.

The obtained porous carbon material has a N content of 10.1 atm%, and when the charge and discharge current density is 0.5 A/g, the specific capacitance is 220.8 F/g.

Example 7

The preparation process is the same as that of Example 1, except that the carbonization temperature is 900°C.

The prepared porous carbon material has a N content of 3.9atm%, and when the charge and discharge current density is 0.5A/g, the specific capacitance is 186.4F/g.

Example 8

The preparation process is the same as that of Example 1, except that the carbonization temperature is 1000°C.

The prepared porous carbon material has a N content of 2.6atm%, and when the charge and discharge current density is 0.5A/g, the specific capacitance is 173.1F/g.

The difference between Example 1 and Examples 6-8 is only that the carbonization temperature is different. As can be seen from the results of the heteroatom content and capacitance performance test, the carbonization temperature is an important factor affecting the heteroatom content. The higher the carbonization temperature, the higher the heteroatom content. gradually decreases.

In summary, the present invention discloses a method for preparing heteroatom-doped porous carbon. The method uses the gel formed by the copolymerization of acrylamide and heteroatom-containing monomers as a carbon source, which can facilitate the uniformity of heteroatoms in porous carbon. and controlled doping.

The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; therefore, although the specification has described the present invention in detail with reference to the above-mentioned embodiments, those of ordinary skill in the art should understand that, The present invention can still be modified or equivalently replaced; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims (5)

1. The preparation method of the heteroatom doped porous carbon electrode material is characterized by comprising the following steps of:

(1) Uniformly mixing acrylamide, N' -methylene bisacrylamide, sodium alginate, a comonomer containing hetero atoms and water to obtain a mixed solution, introducing nitrogen to remove oxygen, and adding an initiator to initiate polymerization reaction to obtain hydrogel;

(2) Freeze-drying the hydrogel to obtain xerogel, carbonizing the xerogel, and washing and drying the xerogel to obtain the heteroatom doped porous carbon electrode material;

in the step (1), the mass ratio of the acrylamide to the N, N' -methylenebisacrylamide to the sodium alginate to the heteroatom-containing comonomer to the water is 0.02-0.1:0.002-0.015:0-0.02:0-0.1:1;

in the step (1), the comonomer containing hetero atoms is selected from any one or more than two of 3- (4-pyridyl) acrylic acid, 3- (2-thienyl) acrylic acid, 4-vinylphenylboric acid or phosphoenolpyruvic acid cyclohexylammonium salt in any proportion;

in the step (2), carbonization is performed in a nitrogen atmosphere, wherein the carbonization temperature is 700-1000 ℃ and the time is 2-4 hours.

2. The method for preparing a heteroatom doped porous carbon electrode material according to claim 1, wherein in the step (1), the mass ratio of acrylamide, N' -methylenebisacrylamide, sodium alginate, a heteroatom-containing comonomer and water is 0.03-0.06:0.002-0.008:0.008-0.012:0.03-0.06:1.

3. The method for preparing a heteroatom doped porous carbon electrode material according to claim 1, wherein in step (1), the initiator is used in an amount of 1 to 6% of the total mass of acrylamide and the heteroatom-containing comonomer.

4. The method for preparing a heteroatom doped porous carbon electrode material according to claim 1, wherein in step (1), the initiator is one of potassium persulfate, ammonium persulfate or a water-soluble oxidation-reduction initiation system selected from any one of potassium persulfate-sodium sulfite, potassium persulfate-sodium bisulfite, ammonium persulfate-sodium sulfite or ammonium persulfate-sodium bisulfite water-soluble oxidation-reduction initiation system.

5. The method for preparing a heteroatom doped porous carbon electrode material according to claim 4, wherein in the step (1), when the initiator is potassium persulfate or ammonium persulfate, the reaction temperature is 65-75 ℃ and the reaction time is 2-5 h; when the initiator is a water-soluble oxidation-reduction initiation system, the reaction temperature is 20-30 ℃ and the reaction time is 2-5 h.