CN107487766A - A kind of three-dimensional porous carbon material of Heteroatom doping and preparation method thereof - Google Patents

Abstract

The invention provides a method for preparing a heteroatom-doped three-dimensional porous carbon material, which belongs to the field of carbon material preparation. The invention pre-carbonizes gluconate and mixes it with elemental polymers, and then carbonizes to obtain a carbonized product. The carbonized product is combined with After the inorganic acid is mixed, the heteroatom-doped three-dimensional porous carbon material is obtained. The method adopts a single raw material gluconate as a raw material precursor, and obtains a heteroatom-doped carbon material after being doped with an elemental macromolecule. The preparation method is simple, the cost is low, and there is no pollution. In the present invention, gluconate has a lot of carbon and oxygen elements, and carbon dioxide can be released during pre-carbonization, so that the carbon material can expand and create pores. The elemental polymer is a polymer material containing heteroatom nitrogen, phosphorus, etc. Three-dimensional porous carbon materials with different doping amounts of heteroatoms were obtained.

Description

A kind of heteroatom-doped three-dimensional porous carbon material and its preparation method

technical field

The invention relates to the field of preparation of porous carbon materials, in particular to a heteroatom-doped three-dimensional porous carbon material and a preparation method thereof.

Background technique

With the consumption of energy and the deterioration of the environment, new energy storage and conversion technologies have received extensive attention, such as lithium-ion batteries, fuel cells and supercapacitors. In these new energy technologies, carbon-based composites as supports and catalysts play a key role. Metal-containing carbon materials have disadvantages such as high preparation cost, lack of stability, and poor acid and alkali resistance, while metal-free heteroatom-doped carbon materials overcome these shortcomings. Three-dimensional multi-level porous carbon nanomaterials, due to their numerous pores and large specific surface area, provide more reaction channels for reaction media, electrons, etc., which can greatly improve catalytic efficiency; in addition, carbon materials also have stable chemical properties and good electrical conductivity. Many advantages. Therefore, three-dimensional porous heteroatom-doped carbon nanomaterials have a wide range of applications in the fields of new energy and adsorption.

According to the source of precursor or carrier, there are two main types of doped carbon nanomaterials: first, carbon materials as carriers, such as graphene, carbon nanotubes and commercial activated carbon. Usually, the preparation of such materials involves the synthesis of precursors, and then the introduction of heteroatom-containing small molecules by hydrothermal or high-temperature gas reactions to obtain heteroatom-doped carbon materials. The preparation method is complicated and the cost is high. Second, biomass material precursor carbon materials are mainly derived from natural organisms, such as wood, plant leaves, rice, etc., which reduces production costs. However, catalysts for biomass precursors generally require carbonization, activation, or templates to obtain porous structures. Due to the poor thermal stability of biomass, a large number of components volatilize. Therefore, the preparation process of biomass precursor carbon materials is easy to cause pollution, and the controllability of the heteroatom structure is not strong, which is not conducive to theoretical research and large-scale production.

Contents of the invention

In view of this, the purpose of the present invention is to provide a heteroatom-doped three-dimensional porous carbon material and its preparation method, using a single raw material gluconate as a raw material precursor, after element polymer doping, to obtain heteroatom-doped The three-dimensional porous carbon material has a simple preparation method, low cost and no pollution.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

A method for preparing a heteroatom-doped three-dimensional porous carbon material, comprising the following steps:

(1) Carrying out pre-carbonization of gluconate to obtain pre-carbide;

(2) mixing the pre-carbide obtained in the step (1) with the elemental polymer to obtain a doped product;

(3) Carbonizing the doped product obtained in the step (2) to obtain a carbonized product;

(4) After mixing the carbonized product obtained in the step (3) with an inorganic acid, a heteroatom-doped three-dimensional porous carbon material is obtained.

Preferably, the gluconate in the step (1) includes calcium gluconate and/or sodium gluconate.

Preferably, the pre-carbonization temperature in the step (1) is 100-600° C., and the pre-carbonization time is 0.1-3 h.

Preferably, the mass ratio of pre-carbides to elemental polymers in the step (2) is 100:2-20.

Preferably, the elemental polymer includes one or more of polypyrrole, polyaniline, polyamide, polyurethane and polyphosphazene.

Preferably, the elemental polymer is mixed with the pre-carbide in the form of an elemental polymer solution, and the concentration of the elemental polymer solution is 0.01-0.1 g/mL.

Preferably, the carbonization temperature in the step (3) is 400-1000° C., and the carbonization time is 0.2-6 hours.

Preferably, the inorganic acid in the step (4) includes hydrochloric acid or sulfuric acid.

The present invention also provides a heteroatom-doped three-dimensional porous carbon material prepared by the preparation method described in the above technical solution, the doping amount of the heteroatom is 0.1-5% by mass, and the heteroatom includes N , P and B.

The invention provides a preparation method of a heteroatom-doped three-dimensional porous carbon material. After pre-carbonization, gluconate is mixed with an elemental polymer, and then carbonized to obtain a carbonized product. After the carbonized product is mixed with an inorganic acid, a heteroatom-doped Heterogeneous three-dimensional porous carbon materials. The method adopts a single raw material gluconate as a raw material precursor, and obtains a heteroatom-doped carbon material after being doped with elemental macromolecules. The preparation method is simple, the cost is low, and there is no pollution. In the present invention, gluconate has a lot of carbon and oxygen elements, and carbon dioxide can be released during pre-carbonization, so that the carbon material can expand and create pores; the element polymer is a polymer material containing heteroatom nitrogen, phosphorus, oxygen, etc. The type and amount of molecules are used to prepare three-dimensional porous carbon materials with different heteroatoms and different doping amounts, which realizes the controllability of the type and amount of doping elements.

Description of drawings

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the flowchart of preparing heteroatom-doped three-dimensional porous carbon material according to the embodiment of the present invention;

Figure 2 is an optical detection photo of the heteroatom-doped three-dimensional porous carbon material prepared in Example 1 of the present invention;

Figure 3 is a scanning electron microscope of the heteroatom-doped three-dimensional porous carbon material prepared in Example 1 of the present invention;

Figure 4 is the nitrogen adsorption-desorption curve and pore size distribution diagram of the heteroatom-doped three-dimensional porous carbon material prepared in Example 1 of the present invention, wherein a is the nitrogen adsorption-desorption curve of the heteroatom-doped three-dimensional porous carbon material, and b is Pore size distribution map of heteroatom-doped 3D porous carbon materials.

detailed description

The invention provides a method for preparing a heteroatom-doped three-dimensional porous carbon material, comprising the following steps:

(1) Carrying out pre-carbonization of gluconate to obtain pre-carbide;

(2) mixing the pre-carbide obtained in the step (1) with the elemental polymer to obtain a doped product;

(3) Carbonizing the doped product obtained in the step (2) to obtain a carbonized product;

(4) Mixing the carbonized product obtained in the step (3) with an inorganic acid to obtain a heteroatom-doped three-dimensional porous carbon material.

In the present invention, gluconate is pre-carbonized to obtain pre-carbides. In the present invention, the gluconate includes calcium gluconate and/or sodium gluconate. In the present invention, when the gluconate includes calcium gluconate and sodium gluconate, the mass ratio of the calcium gluconate and sodium gluconate is not particularly limited, and any mass ratio of calcium gluconate and gluconic acid is adopted. Sodium mixture. In the present invention, the gluconate has a lot of carbon and oxygen elements, and carbon dioxide can be released during pre-carbonization to make the carbon material expand and form pores. In the present invention, the particle size of the gluconate is preferably 100-300 mesh, more preferably 150-200 mesh. In the present invention, the particle size is preferably achieved by grinding, and the grinding is preferably carried out in an agate mortar; the grinding time is preferably 10-20 minutes, more preferably 15 minutes. The present invention does not have any special limitation on the source of the gluconate, and commercially available products well known to those skilled in the art can be used.

In the present invention, the temperature of the pre-carbonization is preferably 100-600°C, more preferably 200-500°C, most preferably 300-400°C; the time of the pre-carbonization is preferably 0.1-3h, more preferably 0.5-2.5 h, most preferably 1.5-2.0 h. In the present invention, the pre-carbonization is preferably performed in an air atmosphere. In the present invention, the pre-carbonization can oxidize the carbon and oxygen elements in the gluconate, release carbon dioxide, and expand the carbon material to form pores.

The present invention has no special limitation on the pre-carbonization device, and a carbonization device well-known to those skilled in the art can be used. In the present invention, it is preferably a muffle furnace. In the present invention, the mold used for the pre-carbonization of the gluconate is not particularly limited, and a carbonization mold well-known to those skilled in the art can be used. In the present invention, a corundum crucible is preferred. In the present invention, heteroatom-doped three-dimensional porous carbon materials of different shapes are preferably prepared according to carbonization molds of different shapes.

After pre-carburization is completed, the present invention preferably obtains the pre-carbide by cooling to room temperature. In the present invention, there is no special limitation on the cooling method, and any cooling method known to those skilled in the art can be used, and natural cooling is preferred in the present invention.

After the pre-carbides are obtained, the present invention mixes the pre-carbides with elemental polymers to obtain doped products. In the present invention, the mass ratio of the pre-carbide to the elemental polymer is preferably 100:2-20, more preferably 100:5-15, and most preferably 100:10. In the present invention, the elemental polymer is a polymer material containing heteroatoms, containing heteroatoms such as nitrogen, phosphorus, and oxygen, and three-dimensional materials with different heteroatoms and different doping amounts can be obtained by controlling the type and amount of the elemental polymer. porous carbon material.

In the present invention, the elemental polymer preferably includes one or more of polypyrrole, polyaniline, polyamide, polyurethane and polyphosphazene. In the present invention, the elemental polymer is preferably mixed with the pre-carbide in the form of an elemental polymer solution, and the concentration of the elemental polymer solution is preferably 0.01-0.1 g/mL, more preferably 0.02-0.08 g/mL ; The solvent of the element polymer solution is preferably water or ethanol.

In the present invention, there is no special limitation on the order of adding the pre-carbides and the elemental polymers, and the pre-carbides are preferably added to the elemental polymers. In the present invention, there is no special limitation on the specific mixing method, and a mixing method well known to those skilled in the art can be used. In the present invention, ultrasonic mixing is preferred, which can fully and uniformly mix the element polymer into the pre-carbide. In the present invention, the power of the ultrasound is preferably 30 to 50 kHz, more preferably 40 kHz; the time of the ultrasound is preferably 0.5 to 3 hours, more preferably 1.5 to 2 hours; the temperature of the ultrasound is preferably At room temperature, no additional heating or cooling is required.

After the ultrasonication is completed, the present invention preferably sequentially ages and dries the ultrasonic system to obtain a doped product. In the present invention, the aging time is preferably 3-10 hours, more preferably 6-8 hours; the aging temperature is preferably room temperature, without additional heating or cooling. In the present invention, the aging can further fully and uniformly mix the elemental polymers into the pre-carbides.

After the aging is completed, the present invention preferably dries the aging system. The present invention has no special limitation on the specific method of drying, and the drying method known to those skilled in the art can be adopted. In the present invention, drying is preferred, and the drying temperature is preferably 30-105°C, more preferably Preferably it is 50-100°C, most preferably 80-90°C; the drying time is preferably 2-6 hours, more preferably 4-5 hours.

After the doped product is obtained, the present invention carbonizes the doped product to obtain a carbonized product. In the present invention, the carbonization temperature is preferably 400-1000°C, more preferably 600-900°C, most preferably 700-800°C; the carbonization time is preferably 0.2-6h, more preferably 1-4h , most preferably 2 to 3 hours. In the present invention, when the temperature of the doped product is raised to the carbonization temperature, the heating rate is preferably 1-10°C/min, more preferably 4-8°C/min, and most preferably 5-6°C/min. In the present invention, the carbonization is carried out in an inert gas, and the present invention has no special limitation on the type of the inert gas, and an inert gas well known to those skilled in the art can be used, such as argon in particular. In the present invention, the carbonization device is not particularly limited, and a carbonization device well known to those skilled in the art can be used. In the present invention, a muffle furnace is preferred.

After the carbonization is completed, the present invention preferably cools the carbonized product to room temperature to obtain the carbonized product. In the present invention, there is no special limitation on the cooling method, and any cooling method known to those skilled in the art can be used, and natural cooling is preferred in the present invention.

After the carbonized product is obtained, the present invention mixes the carbonized product with an inorganic acid to obtain a heteroatom-doped three-dimensional porous carbon material. In the present invention, the inorganic acid preferably includes hydrochloric acid or sulfuric acid. In the present invention, the function of the inorganic acid is to remove metal elements, such as calcium or sodium, in the carbonized product. In the present invention, the concentration of the inorganic acid is preferably 0.05-1M, more preferably 0.2-0.6M; the present invention has no special restrictions on the mass ratio of the carbonized product to the inorganic acid, which can ensure that the inorganic acid is soaked and over-carbonized The product will do.

In the present invention, there is no special limitation on the feeding method of the carbonized product and the inorganic acid, and the feeding sequence known to those skilled in the art can be adopted. In the embodiment of the present invention, the carbonized product is preferably added to the inorganic acid.

The present invention does not have any special limitation on the specific mixing method, and a mixing method well known to those skilled in the art can be used. In the embodiment of the present invention, the mixing preferably includes ultrasonication and soaking in sequence. In the present invention, the power of the ultrasound is preferably 30 to 50 kHz, more preferably 40 kHz; the time of the ultrasound is preferably 0.5 to 2 hours, more preferably 1 to 1.5 hours; the temperature of the ultrasound is preferably At room temperature, no additional heating or cooling is required. In the present invention, the ultrasound can fully react the mineral acid with the metal elements in the carbonized product, so that the metal elements can be removed more thoroughly.

After the ultrasonication is completed, the present invention preferably soaks the system obtained by ultrasonication. In the present invention, the soaking temperature is preferably 30-100°C, more preferably 50-80°C, most preferably 60-70°C; the soaking time is preferably 1-20h, more preferably 5-10h . In the present invention, the soaking can ensure that the mineral acid fully reacts with the metal elements in the carbonized product, so that the metal elements can be removed more thoroughly.

After the mixing is completed, in the present invention, the mixed system is preferably subjected to solid-liquid separation, washing and drying in sequence to obtain a heteroatom-doped three-dimensional porous carbon material. In the present invention, there is no special limitation on the specific operation of the solid-liquid separation, and a solid-liquid separation method well known to those skilled in the art can be used. In the present invention, suction filtration is preferred.

After the solid-liquid separation is completed, the present invention preferably washes the solid product obtained by the solid-liquid separation. In the present invention, the detergent used in the washing is preferably water. The present invention has no special limitations on the number of times of washing and the amount of detergent used, as long as the solid product can be washed to neutral by using a detergent well known to those skilled in the art.

After washing, in the present invention, the washed product is preferably dried to obtain a heteroatom-doped three-dimensional porous carbon material. In the present invention, there is no special limitation on the specific drying method, and a drying method known to those skilled in the art can be used, specifically, drying. In the present invention, there is no special limitation on the drying time and temperature, and the methods known to those skilled in the art of removing moisture from the washing product and drying to constant weight can be used.

The present invention also provides the heteroatom-doped three-dimensional porous carbon material prepared by the preparation method described in the above technical scheme, the heteroatoms include N, P and B, and the doping amount of the heteroatoms is preferably It is 0.1 to 5%, more preferably 0.6 to 4%, most preferably 3.4%.

In the present invention, micropores, mesopores and macropores coexist in the heteroatom-doped three-dimensional porous carbon material.

The heteroatom-doped three-dimensional porous carbon material provided by the present invention and its preparation method and application will be described in detail below in conjunction with the examples, but they should not be construed as limiting the protection scope of the present invention.

Fig. 1 is the flow chart of preparing heteroatom-doped three-dimensional porous carbon material according to the embodiment of the present invention. Gluconate is pre-carbonized to obtain pre-carbide. Inorganic acids are mixed and dried to obtain a heteroatom-doped three-dimensional porous carbon material.

Example 1

Grind calcium gluconate in an agate mortar for 10 minutes to obtain calcium gluconate with a particle size of 200 mesh, then place it in a cubic corundum crucible, pre-carbonize at 200°C for 3 hours in a muffle furnace and air atmosphere, and cool naturally take out. Soak 30 g of the pre-carbide obtained at room temperature in 80 mL of polyaniline solution with a concentration of 0.1 g/mL, sonicate at 40 kHz for 0.5 h, age for 3 h, and then dry at 30 °C for 6 h. Then under the protection of inert gas, the temperature was raised to 400°C at a rate of 1°C/min for carbonization for 6 hours, and the carbonized product was obtained after natural cooling to room temperature. , and soaked at 30° C. for 20 hours, then filtered, washed with water until neutral, and dried to constant weight to obtain a cube-shaped heteroatom-doped three-dimensional porous carbon material.

The heteroatom-doped three-dimensional porous carbon material prepared in Example 1 was tested for the type of heteroatom and the doping amount of the heteroatom. It was found that the doped heteroatom was nitrogen, and the doping amount of the heteroatom was 3.4%.

The heteroatom-doped three-dimensional porous carbon material prepared in Example 1 is optically detected, and the detection results are shown in Figure 2. It can be seen from Figure 2 that the prepared heteroatom-doped three-dimensional porous carbon material is cubic, which is A self-supporting block-like structure.

The heteroatom-doped three-dimensional porous carbon material prepared in Example 1 was detected by scanning electron microscopy, and the detection results are shown in Figure 3. It can be seen from Figure 3 that the prepared heteroatom-doped three-dimensional porous carbon material is composed of many nanoscale A self-assembled carbon sheet has a three-dimensional porous structure with a large number of large pores of tens of microns.

The specific surface area of the heteroatom-doped three-dimensional porous carbon material prepared in Example 1 was tested by nitrogen adsorption method, and the nitrogen adsorption results are shown in Figure 4(a). The porous carbon material is tested for pore size distribution, and the results are shown in Figure 4(b). As can be seen from Figure 4(a) and (b), it shows that the heteroatom-doped three-dimensional porous carbon material prepared in Example 1 is micro, Meso-macroporous hierarchical pore structure with a specific surface area of 1609.4m ² /g and an average pore diameter of nitrogen adsorption of 3.6nm.

Example 2

Grind sodium gluconate in an agate mortar for 20 minutes to obtain calcium gluconate with a particle size of 300 mesh, then place it in a round corundum crucible, and pre-carbonize at 600°C for 0.1h in a muffle furnace under an air atmosphere. Take it out after cooling naturally. Soak 40 g of the pre-carbide obtained at room temperature in 100 mL of polyphosphazene solution with a concentration of 0.01, ultrasonicate at 30 kHz for 3 h, age for 10 h, and then dry at 105 ° C for 2 h. Then under the protection of inert gas, the temperature was raised to 1000°C at a rate of 10°C/min for carbonization for 0.2h, and the carbonized product was obtained after natural cooling to room temperature. 0.5h, and then soaked at 100°C for 3h, followed by suction filtration, washing to neutrality, and drying to constant weight to obtain a circular heteroatom-doped three-dimensional porous carbon material.

The heteroatom type and heteroatom doping amount were detected for the heteroatom-doped three-dimensional porous carbon material prepared in Example 2. It was found that the doped heteroatoms were nitrogen and phosphorus, and the heteroatom doping amount was always 0.6%.

After testing, the heteroatom-doped three-dimensional porous carbon material prepared in Example 2 has a hierarchical structure of micro-, meso-, and macro-pores, with a specific surface area of 1310 m ² /g and an average pore diameter of nitrogen adsorption of 3.7 nm.

Example 3

Grind calcium gluconate in an agate mortar for 15 minutes to obtain calcium gluconate with a particle size of 100 mesh, then place it in a cylindrical corundum crucible, pre-carbonize at 500°C for 2 hours in a muffle furnace and air atmosphere, and cool naturally Then take it out. Soak 50 g of the pre-carbide obtained at room temperature in 100 mL of polypyrrole solution with a concentration of 0.05 g/mL, sonicate at 50 kHz for 1 h, age for 8 h, and then dry at 90 ° C for 5 h. Under the protection of an inert gas, the temperature was raised to 800°C at a heating rate of 8°C/min for carbonization for 2 hours, and the carbonized product was obtained after natural cooling to room temperature. h, then soaked at 80° C. for 10 h, followed by suction filtration, water washing to neutrality, and drying to constant weight to obtain a cylindrical heteroatom-doped three-dimensional porous carbon material.

The heteroatom type and heteroatom doping amount were detected for the heteroatom-doped three-dimensional porous carbon material prepared in Example 3. It was found that the doped heteroatom was nitrogen, and the heteroatom doping amount was 4%.

It was tested that the heteroatom-doped three-dimensional porous carbon material prepared in Example 3 had a hierarchical structure of micro-, meso-, and macro-pores, with a specific surface area of 1276 m ² /g and an average pore diameter of nitrogen adsorption of 3.8 nm.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (9)

1. A method for preparing a heteroatom-doped three-dimensional porous carbon material, comprising the following steps: (1) Carrying out pre-carbonization of gluconate to obtain pre-carbide; (2) mixing the pre-carbide obtained in the step (1) with the elemental polymer to obtain a doped product; (3) Carbonizing the doped product obtained in the step (2) to obtain a carbonized product; (4) Mixing the carbonized product obtained in the step (3) with an inorganic acid to obtain a heteroatom-doped three-dimensional porous carbon material. 2. preparation method according to claim 1, is characterized in that, in described step (1), gluconate comprises calcium gluconate and/or sodium gluconate. 3. The preparation method according to claim 1 or 2, characterized in that the temperature of the pre-carbonization in the step (1) is 100-600° C., and the time of the pre-carbonization is 0.1-3 hours. 4. The preparation method according to claim 1, characterized in that, in the step (2), the mass ratio of pre-carbides to elemental polymers is 100:2-20. 5. The preparation method according to claim 1 or 4, characterized in that, the elemental macromolecule comprises a mixture of one or more of polypyrrole, polyaniline, polyamide, polyurethane and polyphosphazene. 6 . The preparation method according to claim 5 , wherein the elemental polymer is mixed with the pre-carbide in the form of an elemental polymer solution, and the concentration of the elemental polymer solution is 0.01˜0.1 g/mL. 7. The preparation method according to claim 1, characterized in that, the carbonization temperature in the step (3) is 400-1000°C, and the carbonization time is 0.2-6h. 8. preparation method according to claim 1, is characterized in that, in described step (4), mineral acid comprises hydrochloric acid or sulfuric acid. 9. The heteroatom-doped three-dimensional porous carbon material prepared by the preparation method according to any one of claims 1 to 8, the doping amount of the heteroatom is 0.1 to 5% by mass percentage, and the heteroatom Including N, P and B.