CN108831757B - A kind of preparation method of N and S double-doped graphene/carbon nanotube airgel - Google Patents

Abstract

The invention discloses a preparation method of N and S double-doped graphene/carbon nanotube airgel, which belongs to the technical field of electrode material preparation. First, mix carboxylated carbon nanotubes and graphene oxide, add deionized water, and obtain a mixed solution after ultrasonication; add pyrrole and thiophene to the mixed solution, and perform a hydrothermal reaction to obtain a hydrogel; The gel was put into 2M _KNO3 solution, subjected to secondary hydrothermal reaction, cooled to room temperature, then filtered, washed and freeze-dried; the product obtained after freeze-drying was thermally cracked in an argon atmosphere to obtain the N and S dual doped graphene/carbon nanotube aerogels. In the present invention, N and S in the graphene airgel, wherein the double doping of N and S can further enhance the reactivity and conductivity of the carbon material, compared with a single N or S doped material, by introducing more Active sites, thereby improving its electrochemical performance, are expected to be used in electrode materials for supercapacitors.

Description

A kind of preparation method of N and S double-doped graphene/carbon nanotube airgel

technical field

The invention belongs to the technical field of electrode material preparation, and in particular relates to a preparation method of N and S double-doped graphene/carbon nanotube airgel.

Background technique

Among all carbon materials, such as carbon nanotubes, nanofibers, porous carbon, hollow nanospheres, carbon capsules, graphene nanosheets, graphene nanoribbons and their composites, graphene is superior due to its extraordinary electronic and mechanical properties. on other carbon materials. Although graphene has made considerable progress in supercapacitors, the performance is still not satisfactory. This is because the strong van der Waals force and π-π stacking interactions between graphene layers make them easy to aggregate to form a graphitic structure, which leads to the loss of effective specific surface area and lowers its specific capacitance. Therefore, in order to fully utilize the electrochemical properties of graphene, its self-stacking problem must be effectively suppressed.

Graphene aerogels represent a new class of monolithic carbonaceous materials with well-developed pores, ultra-low density and

And excellent conductive properties endow graphene airgel with broad application prospects in the fields of energy, environmental protection, and catalysis, and it has become a research hotspot in recent years.

Contents of the invention

The object of the present invention is to provide a method for preparing N and S double-doped graphene/carbon nanotube aerogels for the deficiencies of the prior art.

To achieve the above object, the present invention adopts the following technical solutions:

A preparation method of N and S double-doped graphene/carbon nanotube airgel, specifically comprising the following steps:

(1) Preparation of carboxylated carbon nanotubes;

(2) Preparation of graphene oxide;

(3) After mixing the carboxylated carbon nanotubes prepared in step (1) and the graphene oxide prepared in step (2), add deionized water, and obtain a mixed solution with a concentration of 2 mg/mL after uniform ultrasonication;

(4) Add pyrrole and thiophene to the mixture obtained in step (3), and perform a hydrothermal reaction at a reaction temperature of 160-180°C and a reaction time of 4-6 hours to obtain a hydrogel;

(5) Put the hydrogel obtained in step (4) into 2M KNO ₃ solution for secondary hydrothermal reaction, the reaction temperature is 120~140℃, the reaction time is 2~3h, after cooling to room temperature, filtered, washed and freeze-dried;

(6) The product obtained after freeze-drying in step (5) was pyrolyzed in an argon atmosphere at 1050-1100° C. for 2 hours to prepare the N and S double-doped graphene/carbon nanotube airgel.

The preparation method of the carboxylated carbon nanotubes described in step (1) was as follows: 1 g of multi-walled carbon nanotubes (MWCNTs) was added to 80 mL of concentrated HNO ₃ , and then condensed and refluxed in an oil bath at 120 °C for 12 h. The resulting black mixture was repeatedly washed and filtered to pH=7 to collect the filter residue.

The preparation method of graphene oxide described in step (2) is as follows: After uniformly mixing graphite and concentrated sulfuric acid/concentrated phosphoric acid system, slowly adding potassium permanganate, stirring evenly for 0.5h, stirring in a water bath at 50°C for 12h, slowly Add deionized water and keep the temperature below 100°C, add 5wt% hydrogen peroxide dropwise, when the mixture turns golden yellow, add hydrochloric acid to wash, react for 5 minutes, wash with deionized water until neutral, and wash with BaCl ₂ Detect whether there is SO ₄ ^2- residue, and then freeze-dry for 24 hours to obtain graphite oxide powder; add the obtained graphite oxide powder to deionized water, sonicate for 1 hour, and then centrifuge at 2000r/min for 10 minutes to remove the lower precipitate Take the supernatant, freeze the supernatant at 0° C. for 12 hours, and then freeze-dry it in a freeze dryer for 36 hours to obtain the graphene oxide.

In the concentrated sulfuric acid/concentrated phosphoric acid system, the volume ratio of concentrated sulfuric acid to concentrated phosphoric acid is 9:1.

The mass ratio of the carboxylated carbon nanotubes and graphene oxide in step (3) is 1:1.

The mass ratio of pyrrole and thiophene described in step (4) is 1:1, and the amount of pyrrole added is 1wt% of graphene oxide.

The prepared N and S double-doped graphene/carbon nanotube airgel is used in electrode materials, and the specific steps are: N and S double-doped graphene/carbon nanotube airgel, acetylene black, poly Tetrafluoroethylene emulsion is added in the same weighing bottle according to the ratio of mass ratio of 90:5:5, stirred and mixed evenly and the sample is blown to a paste state with a hair dryer, and the paste material is coated on the On nickel foam, vacuum-dried at 120 °C for 24 h to finally obtain the desired electrode.

The beneficial effects of the present invention are:

(1) The present invention inserts carbon nanotubes between graphene sheets, which helps to improve the conductivity of graphene layers, and carbon nanotubes can also be used as spacers to prevent the aggregation of graphene layers; in addition, low-dimensional carbon The material self-assembles into a three-dimensional porous nanostructure network, which can greatly increase its specific surface area, provide a large electrode/electrolyte contact area for charge transfer reactions, and shorten the ion transport length, thereby improving electrochemical performance;

(2) In the present invention, N and S in graphene airgel, wherein the double doping of N and S can further enhance the reactivity and conductivity of carbon materials, compared with single N or S doped materials, by introducing More active sites, thus improving its electrochemical performance.

Detailed ways

The present invention will be further described below in conjunction with specific examples, but the present invention is not limited to these examples.

Example 1

A preparation method of N and S double-doped graphene/carbon nanotube airgel, specifically comprising the following steps:

(1) Preparation of carboxylated carbon nanotubes: 1 g of multi-walled carbon nanotubes (MWCNTs) was added to 80 mL of concentrated HNO ₃ , then condensed and refluxed in an oil bath at 120 °C for 12 h, and the resulting black mixture was washed repeatedly Suction filtration to pH = 7 to get the filter residue;

(2) Preparation of graphene oxide: After uniformly mixing graphite with concentrated sulfuric acid/concentrated phosphoric acid system (v/v=9:1), slowly add potassium permanganate, stir evenly for 0.5h, then stir in a 50°C water bath 12h, slowly add deionized water, and keep the temperature below 100°C, add 5wt% hydrogen peroxide dropwise, when the mixture turns golden yellow, add hydrochloric acid to wash, react for 5 minutes, wash with deionized water until neutral , and use BaCl ₂ to detect whether there is SO ₄ ^2- residue, and then freeze-dry for 24 hours to obtain graphite oxide powder; add the prepared graphite oxide powder to deionized water, ultrasonically 1 hour, and then centrifuge at 2000r/min for 10 minutes, Remove the sediment in the lower layer, take the upper layer, freeze the upper layer at 0°C for 12 hours, and place it in a freeze dryer for freeze-drying for 36 hours to obtain the graphene oxide;

(3) Take 50 mg of carboxylated carbon nanotubes prepared in step (1) and 50 mg of graphene oxide prepared in step (2) and mix them, add 50 mL of deionized water, and obtain a mixed solution with a concentration of 2 mg/mL after ultrasonication ;

(4) Add 0.5 mg of pyrrole and 0.5 mg of thiophene to the mixture obtained in step (3), and conduct a hydrothermal reaction at a reaction temperature of 160°C for 6 hours to obtain a hydrogel;

(5) Put the hydrogel obtained in step (4) into 2M KNO ₃ solution for secondary hydrothermal reaction, the reaction temperature is 120°C, the reaction time is 3h, after cooling to room temperature, filter and wash and freeze-drying;

(6) The product obtained after freeze-drying in step (5) was pyrolyzed in an argon atmosphere at 1050° C. for 2 hours to prepare the N and S double-doped graphene/carbon nanotube airgel.

Example 2

A preparation method of N and S double-doped graphene/carbon nanotube airgel, specifically comprising the following steps:

(1) Preparation of carboxylated carbon nanotubes: 1 g of multi-walled carbon nanotubes (MWCNTs) was added to 80 mL of concentrated HNO ₃ , then condensed and refluxed in an oil bath at 120 °C for 12 h, and the resulting black mixture was washed repeatedly Suction filtration to pH = 7 to get the filter residue;

(2) Preparation of graphene oxide: After uniformly mixing graphite with concentrated sulfuric acid/concentrated phosphoric acid system (v/v=9:1), slowly add potassium permanganate, stir evenly for 0.5h, then stir in a 50°C water bath 12h, slowly add deionized water, and keep the temperature below 100°C, add 5wt% hydrogen peroxide dropwise, when the mixture turns golden yellow, add hydrochloric acid to wash, react for 5 minutes, wash with deionized water until neutral , and use BaCl ₂ to detect whether there is SO ₄ ^2- residue, and then freeze-dry for 24 hours to obtain graphite oxide powder; add the prepared graphite oxide powder to deionized water, ultrasonically 1 hour, and then centrifuge at 2000r/min for 10 minutes, Remove the sediment in the lower layer, take the upper layer, freeze the upper layer at 0°C for 12 hours, and place it in a freeze dryer for freeze-drying for 36 hours to obtain the graphene oxide;

(3) Take 50 mg of carboxylated carbon nanotubes prepared in step (1) and 50 mg of graphene oxide prepared in step (2) and mix them, add 50 mL of deionized water, and obtain a mixed solution with a concentration of 2 mg/mL after ultrasonication ;

(4) Add 0.5 mg of pyrrole and 0.5 mg of thiophene to the mixture obtained in step (3), and conduct a hydrothermal reaction at a reaction temperature of 180°C for 4 hours to obtain a hydrogel;

(5) Put the hydrogel obtained in step (4) into 2M KNO ₃ solution for secondary hydrothermal reaction, the reaction temperature is 140°C, the reaction time is 2h, after cooling to room temperature, filter and wash and freeze-drying;

(6) The product obtained after freeze-drying in step (5) was pyrolyzed in an argon atmosphere at 1100° C. for 2 hours to prepare the N and S double-doped graphene/carbon nanotube airgel.

Example 3

A preparation method of N and S double-doped graphene/carbon nanotube airgel, specifically comprising the following steps:

(1) Preparation of carboxylated carbon nanotubes: 1 g of multi-walled carbon nanotubes (MWCNTs) was added to 80 mL of concentrated HNO ₃ , then condensed and refluxed in an oil bath at 120 °C for 12 h, and the resulting black mixture was washed repeatedly Suction filtration to pH = 7 to get the filter residue;

(2) Preparation of graphene oxide: After uniformly mixing graphite with concentrated sulfuric acid/concentrated phosphoric acid system (v/v=9:1), slowly add potassium permanganate, stir evenly for 0.5h, then stir in a 50°C water bath 12h, slowly add deionized water, and keep the temperature below 100°C, add 5wt% hydrogen peroxide dropwise, when the mixture turns golden yellow, add hydrochloric acid to wash, react for 5 minutes, wash with deionized water until neutral , and use BaCl ₂ to detect whether there is SO ₄ ^2- residue, and then freeze-dry for 24 hours to obtain graphite oxide powder; add the prepared graphite oxide powder to deionized water, ultrasonically 1 hour, and then centrifuge at 2000r/min for 10 minutes, Remove the sediment in the lower layer, take the upper layer, freeze the upper layer at 0°C for 12 hours, and place it in a freeze dryer for freeze-drying for 36 hours to obtain the graphene oxide;

(3) Take 50 mg of carboxylated carbon nanotubes prepared in step (1) and 50 mg of graphene oxide prepared in step (2) and mix them, add 50 mL of deionized water, and obtain a mixed solution with a concentration of 2 mg/mL after ultrasonication ;

(4) Add 0.5 mg of pyrrole and 0.5 mg of thiophene to the mixture obtained in step (3), and conduct a hydrothermal reaction at a reaction temperature of 170°C for 5 hours to obtain a hydrogel;

(5) Put the hydrogel obtained in step (4) into 2M KNO ₃ solution for secondary hydrothermal reaction. The reaction temperature is 130°C and the reaction time is 2.5h. After cooling to room temperature, filter, washing and freeze drying;

(6) The product obtained after freeze-drying in step (5) was pyrolyzed in an argon atmosphere at 1080° C. for 2 hours to prepare the N and S double-doped graphene/carbon nanotube airgel.

Comparative example 1

A preparation method of N-doped graphene/carbon nanotube airgel, specifically comprising the following steps:

(1) Preparation of carboxylated carbon nanotubes: 1 g of multi-walled carbon nanotubes (MWCNTs) was added to 80 mL of concentrated HNO ₃ , then condensed and refluxed in an oil bath at 120 °C for 12 h, and the resulting black mixture was washed repeatedly Suction filtration to pH = 7 to get the filter residue;

(2) Preparation of graphene oxide: After uniformly mixing graphite with concentrated sulfuric acid/concentrated phosphoric acid system (v/v=9:1), slowly add potassium permanganate, stir evenly for 0.5h, then stir in a 50°C water bath 12h, slowly add deionized water, and keep the temperature below 100°C, add 5wt% hydrogen peroxide dropwise, when the mixture turns golden yellow, add hydrochloric acid to wash, react for 5 minutes, wash with deionized water until neutral , and use BaCl ₂ to detect whether there is SO ₄ ^2- residue, and then freeze-dry for 24 hours to obtain graphite oxide powder; add the prepared graphite oxide powder to deionized water, ultrasonically 1 hour, and then centrifuge at 2000r/min for 10 minutes, Remove the sediment in the lower layer, take the upper layer, freeze the upper layer at 0°C for 12 hours, and place it in a freeze dryer for freeze-drying for 36 hours to obtain the graphene oxide;

(3) Take 50 mg of carboxylated carbon nanotubes prepared in step (1) and 50 mg of graphene oxide prepared in step (2) and mix them, add 50 mL of deionized water, and obtain a mixed solution with a concentration of 2 mg/mL after ultrasonication ;

(4) Add 1 mg of pyrrole to the mixture obtained in step (3), and conduct a hydrothermal reaction at a reaction temperature of 170°C for 5 hours to obtain a hydrogel;

(5) Put the hydrogel obtained in step (4) into 2M KNO ₃ solution for secondary hydrothermal reaction. The reaction temperature is 130°C and the reaction time is 2.5h. After cooling to room temperature, filter, washing and freeze drying;

(6) The product obtained after freeze-drying in step (5) was pyrolyzed in an argon atmosphere at 1080° C. for 2 hours to prepare the N-doped graphene/carbon nanotube airgel.

Comparative example 2

A preparation method of S-doped graphene/carbon nanotube airgel, specifically comprising the following steps:

(1) Preparation of carboxylated carbon nanotubes: 1 g of multi-walled carbon nanotubes (MWCNTs) was added to 80 mL of concentrated HNO ₃ , then condensed and refluxed in an oil bath at 120 °C for 12 h, and the resulting black mixture was washed repeatedly Suction filtration to pH = 7 to get the filter residue;

(2) Preparation of graphene oxide: After uniformly mixing graphite with concentrated sulfuric acid/concentrated phosphoric acid system (v/v=9:1), slowly add potassium permanganate, stir evenly for 0.5h, then stir in a 50°C water bath 12h, slowly add deionized water, and keep the temperature below 100°C, add 5wt% hydrogen peroxide dropwise, when the mixture turns golden yellow, add hydrochloric acid to wash, react for 5 minutes, wash with deionized water until neutral , and use BaCl ₂ to detect whether there is SO ₄ ^2- residue, and then freeze-dry for 24 hours to obtain graphite oxide powder; add the prepared graphite oxide powder to deionized water, ultrasonically 1 hour, and then centrifuge at 2000r/min for 10 minutes, Remove the sediment in the lower layer, take the upper layer, freeze the upper layer at 0°C for 12 hours, and place it in a freeze dryer for freeze-drying for 36 hours to obtain the graphene oxide;

(3) Take 50 mg of carboxylated carbon nanotubes prepared in step (1) and 50 mg of graphene oxide prepared in step (2) and mix them, add 50 mL of deionized water, and obtain a mixed solution with a concentration of 2 mg/mL after ultrasonication ;

(4) Add 0.1 mg of thiophene to the mixture obtained in step (3), and conduct a hydrothermal reaction at a reaction temperature of 170°C for 5 hours to obtain a hydrogel;

(5) Put the hydrogel obtained in step (4) into 2M KNO ₃ solution for secondary hydrothermal reaction. The reaction temperature is 130°C and the reaction time is 2.5h. After cooling to room temperature, filter, washing and freeze drying;

(6) The product obtained after freeze-drying in step (5) was pyrolyzed in an argon atmosphere at 1080° C. for 2 hours to prepare the S-doped graphene/carbon nanotube airgel.

The N and S double-doped graphene/carbon nanotube aerogels, N-doped graphene/carbon nanotube aerogels and S-doped graphene/carbon nanotube aerogels prepared above are used as electrode materials , the specific steps are: N and S double-doped graphene/carbon nanotube airgel (or N-doped graphene/carbon nanotube aerogel, S-doped graphene/carbon nanotube aerogel) , acetylene black, and polytetrafluoroethylene emulsion are added into the same weighing bottle according to the mass ratio of 90:5:5, stirred and mixed evenly, and the sample is blown to a paste with a hair dryer, and the foamed nickel is used as a current collector, and the paste The shape material was coated on the nickel foam, and dried in vacuum at 120°C for 24 hours, and finally the desired electrode was obtained.

The prepared electrode was tested for density, specific surface area and electrochemical performance, and the results are shown in Table 1.

Table 1 Various properties of airgel electrodes

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (4)

1. a kind of preparation method of N and S codope graphene/carbon nano-tube aeroge, it is characterised in that: specifically include following step It is rapid:

(1) preparation of carboxylic acid carbon nano tube；

(2) preparation of graphene oxide；

(3) will graphene oxide made from carboxylic acid carbon nano tube made from step (1) and step (2) mix after, addition go from Sub- water obtains the mixed liquor that concentration is 2mg/mL after ultrasound is uniform；

(4) pyrroles and thiophene are added into the mixed liquor that step (3) obtains, carries out a hydro-thermal reaction, reaction temperature is 160 ~ 180 DEG C, the reaction time is 4 ~ 6h, obtains hydrogel；

(5) hydrogel that step (4) obtains is put into the KNO of 2M₃In solution, secondary hydro-thermal reaction is carried out, reaction temperature is 120 ~ 140 DEG C, the reaction time is 2 ~ 3h, after being cooled to room temperature, using filter, washing and freeze-drying；

(6) by products therefrom thermal cracking 2h at 1050 ~ 1100 DEG C in argon atmosphere after step (5) freeze-drying, institute is made State N and S codope graphene/carbon nano-tube aeroge；

Carboxylic acid carbon nano tube described in step (1) the preparation method comprises the following steps: that 1 g multi-walled carbon nanotube is added to 80 mL is dense HNO₃In, 12 h then are condensed back in 120 DEG C of oil bath pans, gained black mixture is washed to suction filtration to pH=7 repeatedly and takes filter Slag；

The mass ratio of carboxylic acid carbon nano tube described in step (3) and graphene oxide is 1:1；

The mass ratio of pyrroles described in step (4) and thiophene is 1:1, and wherein the additional amount of pyrroles is graphene oxide 1wt%。

2. the preparation method of N and S codope graphene/carbon nano-tube aeroge according to claim 1, feature exist In: graphene oxide described in step (2) the preparation method comprises the following steps: after evenly mixing by graphite and the concentrated sulfuric acid/concentrated phosphoric acid system, delaying It is slow to be added potassium permanganate, after uniform stirring 0.5h, in 50 DEG C of stirred in water bath 12h, it is slowly added to deionized water, and keep temperature Lower than 100 DEG C, the hydrogen peroxide of 5wt% is added dropwise, when mixed liquor becomes golden yellow, salt acid elution is added, reacts after five minutes, It is washed with deionized to neutrality, and uses BaCl₂Detect the presence of SO₄ ^2-Residual, then graphite oxide powder is made in freeze-drying for 24 hours End；Graphite oxide powder obtained is add to deionized water, then ultrasonic 1h is centrifuged under the revolving speed of 2000r/min 10min, remove lower sediment thing, take upper liquid, after upper liquid is freezed 12h at 0 DEG C, be placed in freeze drier carry out it is cold Dry 36h is lyophilized, obtains the graphene oxide.

3. the preparation method of N and S codope graphene/carbon nano-tube aeroge according to claim 2, feature exist In: in the concentrated sulfuric acid/concentrated phosphoric acid system, the volume ratio of the concentrated sulfuric acid and concentrated phosphoric acid is 9:1.

4. N and S codope graphene/carbon nano-tube aeroge is in electricity made from a kind of preparation method as described in claim 1 Application in the material of pole, it is characterised in that: by N and S codope graphene/carbon nano-tube aeroge, acetylene black, polytetrafluoroethylene (PTFE) Lotion is added in same weighing bottle according to the ratio that mass ratio is 90:5:5, is uniformly mixed and is blown to sample with hair dryer Pastes is coated in nickel foam by paste using nickel foam as collector, is dried in vacuo at 120 DEG C for 24 hours, final to be made Required electrode.