CN112209375B - Purification method of graphitized carbon - Google Patents

Abstract

The invention relates to a method for purifying graphitized carbon. The method includes the following steps: 1) preparing an acid solution with a concentration of 0.5-10 mol/L; 2) soaking the composite carbon in the acid solution to obtain a composite carbon/acid solution, wherein the composite carbon accounts for 1-80% of the weight of the acid solution; 3) The obtained composite carbon/acid solution is reacted under high temperature and high pressure, and the amorphous carbon left in the composite carbon is removed by selective etching of the composite carbon by acid to obtain graphitized carbon; 4) The obtained graphitized carbon is obtained Cleaning and heat treatment are successively performed to obtain pure graphitized carbon materials. The invention has the following beneficial effects: the purification technology has the advantages of high efficiency, rapidity, high selectivity, and is not restricted by the morphology of the purified material; the graphitized carbon material prepared by the method of the invention has a wide range of applications.

Description

A kind of graphitized carbon purification method

technical field

The invention relates to a method for purifying graphitized carbon, in particular to a method for purifying graphitized carbon material by acid selective etching of amorphous carbon.

Background technique

Graphitized carbon materials have attracted attention in the fields of electronic devices, sensors, and energy storage due to their unique structural and physicochemical properties. Techniques such as template method and electrospinning technology can nanosize materials and have been widely used to prepare functional materials such as ordered mesoporous carbon, carbon nanofibers, and carbon nanotubes. For example, carbon nanofibers can be obtained by calcining electrospun polyacrylonitrile at a high temperature of 700 degrees, but the obtained carbon is an amorphous carbon material. Catalysts (nickel, cobalt, iron, etc.) can catalyze the transformation of amorphous carbon into graphitized carbon to obtain graphitized carbon. However, the effective catalytic range of these catalysts is about 5 nanometers around amorphous carbon, the catalytic range is limited, and the catalytic ability is fixed, and finally only a composite material of amorphous carbon and graphitized carbon can be obtained. Due to the existence of amorphous carbon, the electrical conductivity of carbon materials is reduced, which affects the application of carbon materials. Therefore, the development of a simple and low-cost method for purifying graphitized carbon is a difficult problem for many scientific researchers to overcome.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a low-cost method for purifying graphitized carbon and its application in view of the difficulty of separating the amorphous carbon left in the graphitized carbon. Amorphous carbon is removed from graphitized carbon, and finally pure graphitized carbon is obtained. The prepared graphitized carbon material exhibits excellent performance in the fields of energy storage, environmental treatment, and functional plastics.

For realizing the purpose of the present invention, the technical scheme is adopted as follows: the present invention provides a method for purifying graphitized carbon, which comprises the following steps in sequence:

(1) Prepare an acid solution: configure an acid solution with a concentration of 0.5 to 10 mol/L;

(2) Compounding of carbon material and acid: soaking the compound carbon in the acid solution prepared in step (1) to obtain a compound carbon/acid solution, wherein the compound carbon accounts for 1-80% of the weight of the acid solution;

(3) high temperature and high pressure treatment: react the composite carbon/acid solution obtained in step (2) under high temperature and high pressure, and selectively etch the composite carbon by acid to remove the amorphous carbon left in the composite carbon to obtain graphitized carbon;

(4) Cleaning and heat treatment: The graphitized carbon obtained in step (3) is cleaned and heat treated successively to remove the oxidized functional groups on the surface of the graphitized carbon, thereby obtaining a pure graphitized carbon material.

To obtain the graphitized carbon material, 1) it can be directly used as negative electrode of lithium ion battery, negative electrode of sodium ion battery, negative electrode of potassium ion battery or electrode of super capacitor, and the reversible capacity of battery electrode is 100-1500 mAh/g; the reversible capacity of said super capacitor 50-200 F/g; 2) a functional additive to enhance the electrical function of plastics and obtain excellent electromagnetic shielding performance; 3) an adsorbent, the prepared graphitized carbon material has good properties for heavy metal ions in wastewater. Among them, the adsorption capacity of lead ions can reach 50 mg/g, and the adsorption capacity of Hg(2+) can reach 600 mg/g.

The acid solution in step (1) refers to a mixed acid of nitric acid, hydrochloric acid or sulfuric acid, wherein the molar ratio of nitric acid, hydrochloric acid and sulfuric acid is: 9-10:0-0.5:0-0.5.

The composite carbon described in step (2) refers to any carbon material composed of amorphous carbon and graphitized carbon with no specific morphology and no specific size.

The composite carbon described in step (2) may also contain other acid-soluble metals or oxides, and a porous structure can be introduced into the purified graphitized carbon material through the purification process.

In the high temperature and high pressure treatment described in step (3), the temperature is 120-300° C., the pressure is 1-100 MPa, and the treatment time is 1-20 h.

The cleaning described in step (4) refers to sequentially cleaning with distilled water and 95% alcohol until the pH value is between 6.5 and 7.0.

For the heat treatment described in step (4), the heat treatment temperature is between 500 and 1000°C, and the heat treatment time is 0.5 to 1 h. During the heat treatment, hydrogen/argon gas or hydrogen/nitrogen reducing gas is passed through, and the vacuum is evacuated until the vacuum degree is between -100～-1000torr.

The present invention has the following beneficial effects:

(1) The purification technology of the present invention has the advantages of high efficiency, rapidity and high selectivity, and the obtained carbon material has high graphitization purity, high electrical conductivity, can be recycled, has stable structure and strong resistance to external damage.

(2) A method for purifying graphitized carbon reported in the present invention is not restricted by the morphology of the purified material, and is not affected by the size of the purified material, and the morphology of the finally obtained graphitized carbon material can be zero-dimensional particles, One-dimensional fibers or two-dimensional films, etc., have high graphitization purity. If the purified material contains an acid-soluble material, a porous structure can be introduced into the material through the purification process.

直接作为电极组装锂离子电池、钠离子电池、钾离子电池或超级电容器等具有能量密度高、稳定性好、寿命长等优点；

可作为填充剂，增强塑料电学功能，获得优异电磁屏蔽性能；

直接作为吸附剂，对废水中的重金属离子具有良好的吸附效果。(3) The graphitized carbon material prepared by the method of the present invention has a wide range of applications,

Assembling lithium-ion batteries, sodium-ion batteries, potassium-ion batteries or supercapacitors directly as electrodes has the advantages of high energy density, good stability and long life;

It can be used as a filler to enhance the electrical function of plastics and obtain excellent electromagnetic shielding performance;

As an adsorbent directly, it has a good adsorption effect on heavy metal ions in wastewater.

(4) The method for purifying graphitic carbon of the present invention is simple in technology, easy in operation, and can be prepared in large quantities.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments.

The present invention has been described in terms of specific embodiments, but it will be understood by those skilled in the art that various changes and equivalents may be made without departing from the scope of the invention. In addition, many modifications may be made to adapt the present invention to a particular situation or material to which it is intended without departing from its scope. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all embodiments falling within the scope of the claims.

Example 1

1. Dilute concentrated nitric acid to prepare 4 mol/L nitric acid solution;

2. Soak 10 mg of one-dimensional composite carbon fiber in 25 mL of 4 mol/L nitric acid solution;

3. Transfer the solution of the above step 2 to a 50 mL hydrothermal reaction kettle at a temperature of 170 °C, and react for 15 h. After the reaction kettle is cooled and filtered to obtain one-dimensional graphite carbon fibers;

4. Wash the obtained one-dimensional graphite carbon fiber with distilled water and 95% alcohol for 3 times in sequence, after washing, the pH value is 6.5, and dry;

5. Heat treatment at 500 °C for 30 min under the condition of vacuum degree -100torr while passing hydrogen/argon mixed gas through the dried one-dimensional graphite carbon fiber to remove the oxidized functional groups;

6. Prepare a lithium ion electrode by a conventional method: take the prepared above-mentioned graphite carbon fiber as the working electrode, the lithium sheet as the counter electrode, and Celgard 2400 as the separator, with 1mol/L LiPF ₆ in EC: DMC: EMC (1:1:1 volume) ratio) is the electrolyte, and is prepared into a button battery. The test voltage range is 0~3V. When the current density was 50 mA/g for the charge-discharge performance test, the mass specific capacity was 900 mAh/g.

Example 2

1. Dilute concentrated nitric acid to prepare 6 mol/L nitric acid solution;

2. Soak 10 mg of composite carbon nanofibers embedded with nickel particles in 20 mL of 6 mol/L nitric acid solution;

3. Transfer the solution of the above step 2 to a 50 mL hydrothermal reaction kettle at a temperature of 150 °C, and react for 12 h. After the reaction kettle is cooled and filtered to obtain hollow carbon nanomaterials;

4. The hollow carbon nanomaterials obtained were sequentially cleaned 3 times with distilled water and 95% alcohol, and the pH value after cleaning was 6.8, and dried;

5. The dried hollow graphitized carbon nanomaterials are evacuated to a vacuum degree of -200 torr while being passed through a hydrogen/nitrogen gas mixture, and then heat-treated at 600 °C for 30 min to remove the oxidized functional groups;

6. Prepare capacitor electrodes by conventional methods: use the prepared hollow graphitized carbon nanomaterials as the working electrode, Pt as the counter electrode, and Hg/HgO electrode as the reference electrode to form a three-electrode system, and soak it in 2 mol/LN ₂ SO ₄ or KOH electrolyte, assembled into capacitor units. The test voltage range is 0~0.9V. When the current density is 500 mA/g for the full electrical performance test, the specific capacitance value is 85 F/g.

Example 3

1. Dilute concentrated nitric acid to prepare 7 mol/L mixed acid, wherein the molar ratio of nitric acid to hydrochloric acid is 9.5:0.5;

2. Soak 10 mg of two-dimensional composite carbon film in 25 mL of 7 mol/L mixed acid solution;

3. Transfer the solution of the above step 2 to a 50 mL hydrothermal reaction kettle at a temperature of 180 °C for 10 h. After the reaction kettle is cooled and filtered to obtain a two-dimensional ultra-thin graphitized carbon film;

4. The obtained two-dimensional ultra-thin graphitized carbon film is sequentially cleaned 3 times with distilled water and 95% alcohol, and the pH value is 6.5 after cleaning, and dried;

5. The dried two-dimensional ultra-thin graphitized carbon film was evacuated to a vacuum degree of -300 torr while passing hydrogen/argon mixed gas, and heat-treated at 700 °C for 30 min to remove impurity functional groups;

6. Put the prepared material into wastewater containing heavy metal ions, and the prepared two-dimensional ultrathin graphitized carbon film has a good adsorption effect on heavy metal ions in wastewater, among which, the adsorption capacity of lead ions can reach 50 mg /g, the adsorption capacity of Hg(2+) can reach 500 mg/g.

Example 4

1. Dilute concentrated nitric acid to prepare 5 mol/L mixed acid, wherein the molar ratio of nitric acid, hydrochloric acid and sulfuric acid is 9:0.5:0.5;

2. Soak 20 mg of composite carbon particles in 20 mL of 5 mol/L mixed acid solution;

3. Transfer the solution of the above step 2 to a 50 mL hydrothermal reaction kettle at a temperature of 160 °C, and react for 10 h. After the reaction kettle is cooled and filtered, graphitized carbon particles are obtained;

4. The obtained graphitized carbon material is sequentially washed 3 times with distilled water and 95% alcohol, and dried;

5. The dried graphite carbon particles are evacuated to a vacuum degree of -500torr while passing hydrogen/argon mixed gas, and heat treatment at 1000 ℃ for 1h to remove impurity functional groups;

6. The prepared graphitized carbon particle material is used as the negative electrode material of the potassium ion battery, and the potassium ion electrode is prepared according to the conventional method: the prepared graphitized carbon is used as the working electrode, the potassium sheet is used as the counter electrode, the glass fiber is used as the diaphragm, and 1M KPF ₆ in DME=100 Vol% is the electrolyte, and the button battery is assembled. The test voltage range is 0~3V. When the current density is 0.1 C for the full electrical performance test, the mass specific capacity is 250 mAh/g.

Example 5

1. Dilute concentrated nitric acid to prepare 6 mol/L nitric acid solution;

2. Soak 10 mg of two-dimensional composite carbon film in 20 mL of 6 mol/L nitric acid solution;

3. Transfer the solution of the above step 2 to a 50 mL hydrothermal reactor at 200 °C for 8 h, and then the reactor is cooled and filtered to obtain a two-dimensional graphitized carbon film;

4. The obtained two-dimensional graphitized carbon film is sequentially cleaned 3 times with distilled water and 95% alcohol, and dried;

5. The two-dimensional graphitized carbon film after drying is evacuated to a vacuum degree of -300torr and heat-treated at 1000 ℃ for 1h while passing hydrogen/argon mixed gas to remove impurity functional groups;

6. The obtained two-dimensional graphitized carbon is used as an additive, and 10-15% graphitized carbon is added to blend together with the plastic, and the electromagnetic shielding performance of the plastic obtained is 20-50 dB.

Claims (4)

1. under a high temperature and high pressure condition, acid solution selective etching removes the method for amorphous carbon purifying graphitized carbon material, it is characterized in that: (1) Prepare an acid solution with a concentration of 0.5 to 10 mol/L; (2) soaking the composite carbon in the acid solution prepared in step (1) to obtain a composite carbon/acid solution, wherein the composite carbon accounts for 1-80% of the weight of the acid solution; (3) high temperature and high pressure treatment: react the composite carbon/acid solution obtained in step (2) under high temperature and high pressure, and selectively etch the composite carbon by acid to remove the amorphous carbon left in the composite carbon to obtain graphitized carbon; (4) Cleaning and heat treatment: the graphitized carbon obtained in step (3) is successively cleaned and heat treated to remove the oxidized functional groups on the surface of the graphitized carbon, thereby obtaining a pure graphitized carbon material; The composite carbon refers to any carbon material composed of amorphous carbon and graphitized carbon with no specific morphology and no specific size; The composite carbon may also contain other acid-soluble metal or oxide materials; In the high temperature and high pressure treatment, the temperature is 120-300 DEG C, the pressure is 1-100MPa, and the treatment time is 1-20h. 2. A method for selectively etching and removing amorphous carbon by acid solution under high temperature and high pressure conditions to purify graphitized carbon material according to claim 1, wherein the acid solution in step (1) refers to nitric acid, hydrochloric acid Or a mixed acid of sulfuric acid, wherein the molar ratio of nitric acid, hydrochloric acid and sulfuric acid is: 9-10:0-0.5:0-0.5. 3. A method for selectively etching and removing amorphous carbon by acid solution under high temperature and high pressure conditions to purify graphitized carbon material as claimed in claim 1, wherein the cleaning described in step (4) refers to using distilled water and Sequential cleaning with 95% alcohol until the pH value is between 6.5 and 7.0. 4. A method for selectively etching and removing amorphous carbon to purify graphitized carbon material with acid solution under high temperature and high pressure conditions as claimed in claim 1, characterized in that in the heat treatment described in step (4), the heat treatment temperature is Between 500 and 1000 °C, the heat treatment time is 0.5 to 1 h. During the heat treatment, hydrogen/argon or hydrogen/nitrogen reducing gas is passed through, and the vacuum is evacuated to -100 to -1000torr.