阅读说明：本技术 空心介孔碳球及其制备方法 (Hollow mesoporous carbon sphere and preparation method thereof ) 是由 李伟 唐欣蕾 王金秀 赵东元 于 2019-12-20 设计创作，主要内容包括：本发明属于材料制备技术领域,具体为一种空心介孔碳球及其制备方法。本发明制备方法包括：将非离子表面活性剂、扩孔剂、碱催化剂和碳前驱物溶解在有机溶剂/水/盐混合溶液中；碳前驱物在碱催化下聚合形成低聚物；低聚物和表面活性剂及扩孔剂在亲疏水分子间相互做作用下共同组装,在碱催化作用下进一步聚合生长,使碳低聚物-表面活性剂-扩孔剂复合物通过相分离沉淀形成产物；最后高温碳化,形成碳骨架,得到空心介孔碳球；该空心介孔碳球粒径尺寸、空腔大小、介孔壳层厚度均匀可调,具有高比表面积和大的孔容。将其应用于锂硫电池正极材料时表现出较高的电池容量和优异的倍率性能,在环境、能源、催化等众多领域具有广泛的应用前景。(The invention belongs to the technical field of material preparation, and particularly relates to a hollow mesoporous carbon sphere and a preparation method thereof. The preparation method comprises the following steps: dissolving a nonionic surfactant, a pore-expanding agent, an alkali catalyst and a carbon precursor in an organic solvent/water/salt mixed solution; polymerizing the carbon precursor under the catalysis of alkali to form an oligomer; the oligomer, the surfactant and the pore-enlarging agent are assembled together under the mutual action of hydrophilic and hydrophobic molecules, and further grow in a polymerization way under the action of alkali catalysis, so that the carbon oligomer-surfactant-pore-enlarging agent compound forms a product through phase separation and precipitation; finally, carbonizing at high temperature to form a carbon skeleton to obtain hollow mesoporous carbon spheres; the hollow mesoporous carbon sphere has the advantages of uniform and adjustable particle size, cavity size and mesoporous shell thickness, high specific surface area and large pore volume. When the lithium-sulfur battery positive electrode material is applied to a lithium-sulfur battery positive electrode material, the lithium-sulfur battery positive electrode material shows higher battery capacity and excellent rate capability, and has wide application prospects in a plurality of fields such as environment, energy, catalysis and the like.)

1. A preparation method of hollow mesoporous carbon spheres is characterized in that a nonionic surfactant, a pore-expanding agent, an alkali catalyst and a carbon precursor are dissolved in an organic solvent/water/salt mixed solution; at a certain temperature, the carbon precursor is polymerized to form oligomer under the catalysis of alkali; the oligomer, the surfactant and the pore-enlarging agent are assembled together under the mutual action of hydrophilic and hydrophobic molecules, and simultaneously, under the catalysis of alkali, the carbon oligomer is further polymerized and grows, so that the formed carbon oligomer-surfactant-pore-enlarging agent compound is precipitated out through phase separation to form a product; finally, carbonizing at high temperature in an inert atmosphere, removing the surfactant and the pore-expanding agent to form a carbon skeleton, and obtaining hollow mesoporous carbon spheres; the method comprises the following specific steps:

(1) at room temperature, firstly preparing a mixed solution containing an organic solvent/water/salt, then dissolving a nonionic surfactant in the mixed solution, then adding an alkali catalyst, and finally introducing a pore-expanding agent and a carbon precursor;

(2) reacting for 1-10 hours at the temperature of 10-50 ℃; centrifuging and washing the product, and drying at 30-60 deg.C for 5-12 hr;

(3) finally, in an inert atmosphere, roasting at the low temperature of 300-400 ℃ to remove the surfactant and the pore-expanding agent; then roasting at 600 ℃ and 1000 ℃ to carbonize the framework to obtain the hollow mesoporous carbon spheres.

2. The method for preparing hollow mesoporous carbon spheres of claim 1, wherein the organic solvent is C in the organic solvent/water/salt mixed solution₁– C₄One or more of alcohols, benzene, toluene, tetrahydrofuran, chloroform, dichloromethane, acetonitrile or diethyl ether; the salt is one or more of inorganic salts; the alkali catalyst is one or more of organic alkali or inorganic alkali; the volume ratio of the organic solvent to the water is 1: 0.5-1: 5; the salt concentration is 3.0-15.0 wt%; the concentration of the alkali catalyst is 0.1-1.0 wt%; the concentration of the nonionic surfactant is 3.0-15.0 wt%; the mass ratio of the pore-expanding agent to the nonionic surfactant is 1: 0.5-1: 2; the mass ratio of the carbon precursor to the nonionic surfactant is 1-10.

3. The method for preparing the hollow mesoporous carbon sphere according to claim 2, wherein the organic solvent is one or more selected from ethanol, methanol, propanol, butanol, benzyl alcohol, diethyl ether, acetonitrile, hexane, cyclohexane, benzene, toluene and xylene;

the salt is selected from one or more of sodium chloride, potassium chloride, barium chloride, calcium chloride, sodium sulfate, potassium sulfate, barium sulfate, calcium sulfate, sodium nitrate, potassium nitrate, barium nitrate and calcium nitrate.

4. The method for preparing the hollow mesoporous carbon sphere according to claim 2, wherein the organic base is selected from methylamine, ethylamine, dimethylamine, diethylamine, triethylamine; the inorganic alkali is selected from one or more of ammonia water, sodium hydroxide, potassium hydroxide, calcium hydroxide or barium hydroxide.

5. The method for preparing hollow mesoporous carbon spheres of claim 2, wherein the nonionic surfactant is selected from diblock copolymers as a structure directing agent: polystyrene-b-polyethylene oxide PEO_n-b-PS_mPolyethylene oxide-bPoly (methyl methacrylate), PEO_n-b-PMMA_mAlkane-polyethylene oxide oligomer C_nH_2n+1EO_mOr selected from triblock copolymers: EO (ethylene oxide)_nPO_mEO_n、EO_nBO_mEO_n、PO_nEO_mPO_nOne or more of them.

6. The preparation method of the hollow mesoporous carbon sphere according to claim 2, wherein the pore-enlarging agent is a hydrophobic pore-enlarging agent selected from one or more of mesitylene, polymethyl methacrylate, polystyrene and poly (tert-butyl methacrylate).

7. The method for preparing the hollow mesoporous carbon sphere according to claim 2, wherein the carbon precursor is composed of phenols and aldehydes; the phenolic substance is one or more of phenol, resorcinol, catechol, hydroquinone, phloroglucinol, pyrogallol and phloroglucinol; the aldehyde substance is one or more of formaldehyde, acetaldehyde, propionaldehyde, salicylaldehyde and butyraldehyde; the molar ratio of the phenols to the aldehydes in the carbon precursor is 1 (0.8-3.0).

8. The method for preparing the hollow mesoporous carbon sphere according to claim 2, wherein the roasting process is gradient roasting: firstly roasting at the temperature of 300-400 ℃ for 2-5h, then continuously heating to the temperature of 600-1000 ℃ for roasting for 1-5h, wherein the heating speed is 1-10 ℃/min.

9. The hollow mesoporous carbon spheres obtained by the preparation method of any one of claims 1 to 8, which are uniform and adjustable in particle size, cavity size, mesoporous shell thickness, specific surface area and pore volume; the regulation and control range is as follows: the particle size is 100-800nm, the size of the cavity is 0-200nm, the thickness of the mesoporous shell layer is 100-600nm, and the specific surface area is 400-1200 m²Per g, pore volume of 0.30-1.20 cm³(ii)/g; the mesoporous shell layer has a mesoporous channel with a center divergent shape and uniform and adjustable aperture, and the adjustable range of the mesoporous channel is 2.0-15.0 nm.

10. The use of the hollow mesoporous carbon spheres of claim 9 as a positive electrode material for a lithium sulfur battery.

Technical Field

The invention belongs to the technical field of material preparation, and particularly relates to a hollow mesoporous carbon sphere and a preparation method thereof.

Background

The hollow mesoporous carbon material integrates the advantages of hollow and mesoporous materials, ensures the characteristics of high specific surface area, large pore volume, high pore volume and the like of mesopores, and has the structural characteristics of low density of cavities and accessible inner cavities. These advantages make it of great potential application in the fields of energy storage and conversion, catalysis, adsorption and separation.

At present, various methods have been reported for the synthesis of hollow mesoporous carbon spheres. Among them, the hard template method is the earliest method. The method is firstly proposed by Hyeon et al, and carbon precursors are nano-poured into the pore channels of solid silica @ mesoporous silica spheres with core-shell structures, and then the target hollow mesoporous carbon spheres can be obtained after carbonization and selective removal of silica templates (Adv. Mater. 2002, 14 and 19). However, the template method is complicated and time-consuming in preparation process, high in cost and low in industrial feasibility. Most of the self-template rules adopted at present are that hollow mesoporous carbon spheres are obtained by selectively dissolving the inner layer of a 3-aminophenol/formaldehyde resin sphere and then further carbonizing the inner layer (J. Am. chem. Soc. 2017, 139, 13492; adv.energy Mater. 2018, 8, 1800855). In the method, although a template is not used for forming the cavities and the mesopores, the cavities and the mesopores are obtained by post-treatment, and the preparation process is still relatively complicated and expensive and is difficult to popularize.

In view of the above, the hollow mesoporous carbon spheres are synthesized by utilizing the carbon source precursor, the pore-expanding agent and the nonionic surface active multi-component co-assembly and the sol-gel process, and the method has the advantages of simple operation, easily controlled reaction conditions and easy mass synthesis. The obtained hollow mesoporous carbon spheres have adjustable particle size, cavity size, mesoporous size, shell thickness, specific surface area and pore volume, and show excellent performance in the aspect of lithium-sulfur batteries.

Disclosure of Invention

One of the purposes of the invention is to provide a hollow mesoporous carbon sphere with adjustable particle size, cavity size, mesoporous size, shell thickness, specific surface area and pore volume.

The second purpose of the invention is to provide a preparation method of hollow mesoporous carbon spheres, which is simple to operate, easy to control reaction conditions and convenient to synthesize in large quantities.

The invention also aims to provide application of the hollow mesoporous carbon spheres in the field of lithium-sulfur batteries.

The preparation method of the hollow mesoporous carbon sphere comprises the following steps: dissolving a nonionic surfactant, a pore-expanding agent, an alkali catalyst and a carbon precursor in an organic solvent/water/salt mixed solution, and polymerizing the carbon precursor under the catalysis of alkali to form an oligomer at a certain temperature; the oligomer, the surfactant and the pore-enlarging agent are assembled together under the mutual action of hydrophilic and hydrophobic molecules, and simultaneously, under the catalysis of alkali, the carbon oligomer is further polymerized and grows, so that the formed carbon oligomer-surfactant-pore-enlarging agent compound is precipitated out through phase separation to form a product; and finally, carbonizing at high temperature in an inert atmosphere, removing the surfactant and the pore-expanding agent to form a carbon skeleton, and thus obtaining the hollow mesoporous carbon spheres. The method comprises the following specific steps:

(1) at room temperature, firstly preparing a mixed solution containing an organic solvent/water/salt, then dissolving a certain amount of a nonionic surfactant in the mixed solution, then adding a certain amount of an alkali catalyst, and finally introducing a certain amount of a pore-expanding agent and a carbon precursor;

(2) reacting for 1-10 hours at the temperature of 10-50 ℃; centrifuging and washing the product, and drying at 30-60 deg.C for 5-12 hr;

(3) finally, in an inert atmosphere, roasting at the low temperature of 300-400 ℃ to remove the surfactant and the pore-expanding agent; then roasting at 600 ℃ and 1000 ℃ to carbonize the framework to obtain the hollow mesoporous carbon spheres.

In the invention, in the organic solvent/water/salt mixed solution, the organic solvent is C₁– C₄One or more of alcohols, benzene, toluene, tetrahydrofuran, chloroform, dichloromethane, acetonitrile or diethyl ether; the salt is one or more of inorganic salts; the used alkali catalyst is one or more of organic alkali or inorganic alkali; the volume ratio of the organic solvent to the water is 1: 0.5-1: 5 (1: 0.5-5)), and the preferred volume ratio of the organic solvent to the water is 1: 1; the salt concentration is 3.0-15.0 wt%Percent; the concentration of alkali is 0.1-1.0 wt%; the concentration of the nonionic surfactant is 3.0-15.0 wt%; the mass ratio of the pore-expanding agent to the nonionic surfactant is 1: 0.5-1: 2; the mass ratio of the carbon precursor to the nonionic surfactant is 1-10.

In the invention, the organic solvent can be one or more of ethanol, methanol, propanol, butanol, benzyl alcohol, diethyl ether, acetonitrile, hexane, cyclohexane, benzene, toluene and xylene. Preferably, the solvent is ethanol.

In the invention, inorganic salt is added, which is beneficial to weakening electrostatic repulsion force and improving the assembling capability among organic species molecules. The salt can be one or more of inorganic salts such as sodium chloride, potassium chloride, barium chloride, calcium chloride, sodium sulfate, potassium sulfate, barium sulfate, calcium sulfate, sodium nitrate, potassium nitrate, barium nitrate, calcium nitrate and the like. Preferably the salt is sodium chloride.

In the invention, the base can be various organic bases, including methylamine, ethylamine, dimethylamine, diethylamine and triethylamine; the inorganic base comprises one or more of ammonia water, sodium hydroxide, potassium hydroxide, calcium hydroxide or barium hydroxide. Preferably, the base is aqueous ammonia.

In the invention, the nonionic surfactant is a structure-directing agent to synthesize the hollow mesoporous carbon spheres, and the selected nonionic surfactant is a diblock copolymer such as polystyrene-bPolyethylene oxide PEO_n-b-PS_mPolyethylene oxide-bPoly (methyl methacrylate), PEO_n-b-PMMA_mAlkane-polyethylene oxide oligomer C_nH_2n+1EO_mOr triblock copolymers EO_nPO_mEO_n、EO_nBO_mEO_n、PO_nEO_mPO_nOne or more of (a).

The nonionic surfactant used in the present invention may be a commercial product or may be prepared in the laboratory, and includes PEO₁₂₅-b-PS₂₃₀、PEO₁₁₇-b-PS₁₈₆、PEO₁₂₅-b-PMMA₁₇₄、PEO₄₄-b-PMMA₁₀₃、Brij35 (C₁₂H₂₅EO₂₃)、Brij56 (C₁₆H₃₃EO₁₀)、Brij76 (C₁₈H₃₇EO₁₀)、Brij78 (C₁₆H₃₃EO₂₀)、Brij97 (C₁₈H₃₅EO₁₀)、Brij100 (C₁₆H₃₃EO₁₀₀)、F127（EO₁₀₆PO₇₀EO₁₀₆）、P65（EO₂₀PO₃₀EO₂₀）、P85（EO₂₆PO₃₉EO₂₀）、P123（EO₂₀PO₇₀EO₂₀）、F108（EO₁₃₂PO₅₀EO₁₃₂）、F68（EO₁₃₂PO₃₀EO₁₃₂）、F98（EO₁₃₂PO₄₅EO₁₃₂）、F88（EO₁₃₂PO₄₀EO₃₂）、F87（EO₁₀₆PO₄₀EO₁₀₆）、B50-6600 (EO₃₉BO₄₇EO₃₉)、B70-4600 (EO₁₅BO₄₅EO₁₅)、B40-1900 (EO₁₃BO₁₁EO₁₃)、B20-3800 (EO₃₄BO₁₁EO₃₄)、R 25R4(PO_nEO_mPO_n) And the like.

In the present invention, the nonionic surfactant is preferably a triblock copolymer EO_nPO_mEO_nPredominantly comprising F127 (EO)₁₀₆PO₇₀EO₁₀₆）、P123（EO₂₀PO₇₀EO₂₀) And F108 (EO)₁₃₂PO₅₀EO₁₃₂). Most preferred is F127 (EO)₁₀₆PO₇₀EO₁₀₆）。

In the invention, a hydrophobic pore-expanding agent is adopted, and the hydrophobic pore-expanding agent can enter the hydrophobic chain end of the surfactant, thereby being beneficial to the regulation and control of the pore diameter. The pore-expanding agent can be one or more of mesitylene, polymethyl methacrylate, polystyrene, poly (tert-butyl methacrylate) and the like. Preferably, the pore-expanding agent is mesitylene.

In the invention, the carbon precursor carbon consists of phenols and aldehydes.

In the invention, the phenolic substance in the carbon precursor can be one or more of phenol, resorcinol, catechol, hydroquinone, phloroglucinol, pyrogallol, phloroglucinol and the like, and the preferred phenol is resorcinol; the aldehyde substance can be one or more of formaldehyde, acetaldehyde, propionaldehyde, salicylaldehyde, butyraldehyde and the like, and the aldehyde is preferably formaldehyde.

In the invention, the molar ratio of the phenols to the aldehydes in the carbon precursor is 1 (0.8-3.0). Preferably in a molar ratio of 1: 2.5.

In the invention, the reaction temperature is 10-50 ℃, and the preferable reaction temperature is 20-30 ℃; the reaction time is 1-10h, and the preferable reaction time is 3-6 h.

In the present invention, the preferred inert atmosphere is nitrogen, argon or carbon dioxide.

In the invention, the roasting process is preferably gradient roasting: firstly roasting at the temperature of 300-400 ℃ for 2-5h, then continuously heating to the temperature of 600-1000 ℃ for roasting for 1-5h, wherein the heating speed is 1-10 ℃/min.

The roasting temperature is more preferably 350-400 ℃ at low temperature, and the roasting treatment at low temperature can ensure that the hollow carbon spheres slowly shrink, thereby avoiding the sudden shrinkage from damaging the central divergent mesoporous pore canal and the hollow structure. The more preferable roasting temperature at high temperature is 800-900 ℃, and the roasting at high temperature can ensure that the hollow carbon spheres obtain maximum carbonization on the basis of keeping the mesoporous structure.

The hollow mesoporous carbon sphere prepared by the invention has the advantages of uniform and adjustable particle size (100-²In terms of a/g) and a large pore volume (0.30-1.20 cm)³/g）。

In the hollow mesoporous carbon sphere, a mesoporous shell layer is provided with a mesoporous pore canal (2.0-15.0 nm) which is divergent in center and uniform and adjustable in pore diameter.

The material prepared by the invention can be used as a lithium-sulfur battery anode material, shows higher battery capacity and excellent rate performance, and the specific capacity is still stable at 794mAh/g after the material is circulated for 50 circles under the current density of 0.1C. The material has wide application prospect in a plurality of fields such as environment, energy, catalysis and the like.

The hollow mesoporous carbon sphere provided by the invention has the following advantages:

1. the particle size, the size of a cavity, the thickness of a mesoporous shell layer and the mesoporous aperture of the hollow mesoporous carbon sphere disclosed by the invention can be regulated and controlled by changing the conditions of multi-component co-assembly and sol-gel;

2. the mesoporous aperture, the specific surface area and the pore volume of the hollow mesoporous carbon sphere disclosed by the invention can be regulated and controlled through roasting conditions;

3. the hollow mesoporous carbon spheres prepared by the invention have the advantages of simple preparation method, cheap and easily available raw materials, and suitability for large-scale production;

5. the hollow mesoporous carbon sphere disclosed by the invention has the advantages of the synergistic effect of mesoporous pore channels and cavities, the existence of the pore channels is favorable for the transmission of substances, the existence of the cavities is favorable for relieving mechanical strain, and the hollow mesoporous carbon sphere can be used as a positive electrode material of a lithium-sulfur battery and is favorable for improving the performance of the battery.

Drawings

FIG. 1 is a scanning electron micrograph of a mesoporous-structured hollow carbon sphere of the present invention having a carbon sphere size of 400nm and a cavity size of 50 nm. Obtained from example 1.

FIG. 2 is a transmission electron micrograph of a mesoporous-structured hollow carbon sphere of the present invention having a carbon sphere size of 400nm and a cavity size of 50 nm. Obtained from example 1.

FIG. 3 is a nitrogen adsorption and desorption isotherm of a mesoporous-structure hollow carbon sphere having a carbon sphere size of 400nm and a cavity size of 50nm according to the present invention. Obtained from example 1.

FIG. 4 is a pore size distribution curve of a mesoporous-structured hollow carbon sphere having a carbon sphere size of 400nm and a cavity size of 50nm according to the present invention. Obtained from example 1.

FIG. 5 is a pore size distribution curve of the mesoporous hollow carbon spheres having a carbon sphere size of 500nm and a cavity size of 25 nm according to the present invention. Obtained from example 2.

FIG. 6 is a transmission electron micrograph of a mesoporous-structured hollow carbon sphere of the present invention having a carbon sphere size of 500nm and a cavity size of 25 nm. Obtained from example 2.

FIG. 7 is a transmission electron micrograph of a mesoporous hollow carbon sphere having a carbon sphere size of 450nm and a cavity size of 50nm according to the present invention. Obtained from example 3.

FIG. 8 is a pore size distribution curve of a mesoporous hollow carbon sphere having a carbon sphere size of 450nm and a cavity size of 50nm according to the present invention. Obtained from example 3.

FIG. 9 is a pore size distribution curve of the mesoporous hollow carbon spheres having a carbon sphere size of 350nm and a cavity size of 80nm according to the present invention. Obtained from example 4.

FIG. 10 is a transmission electron micrograph of a hollow carbon sphere having a mesoporous structure in which the carbon sphere of the present invention has a size of 350nm and a cavity size of 80 nm. Obtained from example 4.

FIG. 11 is a transmission electron micrograph of a mesoporous-structured hollow carbon sphere of the present invention having a carbon sphere size of 600nm and a cavity size of 200 nm. Obtained from example 5.

FIG. 12 is a transmission electron micrograph of a mesoporous hollow carbon sphere having a carbon sphere size of 800nm and a cavity size of 400nm according to the present invention. Obtained from example 6.

Fig. 13 is a graph showing the results of specific discharge capacity and coulombic efficiency tests at a current of 0.1C for a lithium-sulfur battery according to the present invention prepared in example seven.

Detailed Description