Heteroatom-doped interconnected porous carbon material, preparation method and application

Abstract

The invention relates to the technical field of preparation of carbon materials, in particular to a heteroatom-doped interconnected porous carbon material, a preparation method and application. Coal tar is used as a raw material, potassium chloride is used as a template agent, potassium carbonate is used as an activating agent, melamine, phytic acid and sodium thiosulfate pentahydrate are respectively used as a nitrogen source, a phosphorus source and a sulfur source, and green preparation and pore structure regulation and control of the heteroatom-doped interconnected porous carbon material are realized. The prepared porous carbon material presents a unique three-dimensional interconnected network and hierarchical pore structure, the specific surface area is between 1560 and 1939m < 2 > g <-1 >, and doping of nitrogen, phosphorus or sulfur elements is realized. According to the method, impurities in the product can be removed only by water washing, and the method is green and environment-friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of carbon materials, and in particular to a heteroatom-doped interconnected porous carbon material, a preparation method and an application thereof. Background Art

[0002] Zinc ion hybrid capacitors are an emerging energy storage device that combines the high power density of supercapacitors and the high energy density of batteries, and are seen as a promising option for future energy storage systems. Zinc ion hybrid capacitors are usually composed of a negative electrode (such as metallic zinc) that can reversibly deposit / remove zinc ions, a positive electrode (such as activated carbon, transition metal oxides or conductive polymers) that can store charge, and an electrolyte. In existing zinc ion hybrid capacitors, carbon materials are widely used as positive electrode materials due to their excellent conductivity, low cost, good chemical stability and environmental friendliness. However, traditional carbon materials lack optimized microporous structures and cannot effectively promote the adsorption and transmission of zinc ions, resulting in lower capacity and cycle life. In addition, the highly corrosive reagents and metal oxide templates commonly used in the preparation of porous carbon materials are prone to environmental pollution during the pickling process. Chinese invention patent CN201710969792.7 provides a method for preparing a three-dimensional network of nitrogen, phosphorus and sulfur co-doped porous carbon, but this method requires a high-temperature, high-pressure container, which increases experimental costs and safety hazards. Chinese invention patent CN202210415247.4 discloses a method for preparing nitrogen, phosphorus and sulfur co-doped biomass-based porous carbon. However, this method requires the use of KOH as an activator, which not only causes corrosion of the equipment, but also the nickel and iron impurities after corrosion are mixed into the product and are difficult to remove, reducing the quality of the product. At present, it is urgent to realize the green preparation of heteroatom-doped porous carbon materials.

[0003] By doping carbon materials with heteroatoms such as nitrogen, phosphorus, and sulfur, not only can the electronic conductivity of the material be effectively improved, but additional redox reaction active sites can also be introduced to increase the pseudocapacitance of the electrode material, further improving the capacitance and energy density of the capacitor.

[0004] Coal tar is a byproduct produced during the coal distillation process. It is a black or dark brown viscous liquid at room temperature with no fixed melting point and a density of 1.1 to 1.3 g cm -1 Coal tar has a complex composition, mainly aromatic hydrocarbons, including benzene series, polycyclic aromatic hydrocarbons and heterocyclic compounds, and has a high carbon content. It is one of the potential precursors for preparing new carbon materials. However, coal tar tends to form insoluble and infusible polymers after heating, which is difficult to reprocess and reuse. Realizing the green and high-value utilization of coal tar, a by-product of coal chemical industry, is a difficult problem in the field of coal chemical industry.

[0005] In view of the above situation, the inventors of the present invention obtained the present invention after a long period of research and practice. Summary of the invention

[0006] The purpose of the present invention is to solve the problem of green and high-value utilization of coal chemical by-product - coal tar, so as to prepare heteroatom-doped interconnected porous carbon, and optimize the microporous structure and elemental composition of the porous carbon to promote the adsorption and transmission of zinc ions, thereby improving the capacity and cycle life of zinc ion hybrid capacitors. The present invention provides a heteroatom-doped interconnected porous carbon material, a preparation method and an application.

[0007] In order to achieve the above object, the present invention discloses a method for preparing a heteroatom-doped interconnected porous carbon material, comprising the following steps:

[0008] S1, dissolving melamine in hot deionized water, dropping 70% phytic acid solution therein, and drying at 80° C. after the reaction to obtain a nitrogen-phosphorus polymer;

[0009] S2, dissolving coal tar in an organic solvent of N,N-dimethylformamide, fully grinding and mixing potassium chloride, potassium carbonate, and a heteroatom dopant, and adding them to the organic solvent containing the coal tar, mixing them uniformly by ultrasonication, and then transferring them to an oven for drying to obtain a reactant precursor;

[0010] S3, transferring the reactant precursor obtained in step S2 to a porcelain boat for heating and keeping it warm in an argon inert atmosphere for 2 hours. After natural cooling, the synthesized sample is soaked in deionized water for 24 hours, filtered, and then dried at 80° C. for 12 hours.

[0011] In the step S1, the mass of melamine is 1 g, and the volume of the phytic acid solution is 1 mL.

[0012] In the step S2, the heteroatom dopant is sodium thiosulfate pentahydrate + nitrogen phosphorus polymer, nitrogen phosphorus polymer or melamine.

[0013] The mass of the sodium thiosulfate pentahydrate is 1 g, the mass of the nitrogen-phosphorus polymer is 1.68 g, and the mass of the melamine is 1 g.

[0014] In step S2, the mass of coal tar is 1 g, the volume of N,N-dimethylformamide is 20 mL, the mass of potassium chloride is 10 g, and the mass of potassium carbonate is 4 g.

[0015] In step S3, the heating rate is 5°C min -1 , the insulation temperature is 800℃.

[0016] The invention also discloses a heteroatom-doped interconnected porous carbon material prepared by the preparation method and the application of the heteroatom-doped interconnected porous carbon material as an electrode material in a zinc ion hybrid capacitor.

[0017] When the temperature rises to 150°C, coal tar will be coated on the surface of potassium chloride, potassium carbonate and sodium thiosulfate pentahydrate due to the surface induction effect. During the heating process, sodium thiosulfate pentahydrate loses its crystal water first. When the temperature continues to rise to 300°C, coal tar begins to carbonize and solidify, and sodium thiosulfate pentahydrate begins to decompose into sodium sulfate and sodium polysulfide. When the temperature reaches 500°C, potassium carbonate begins to react with carbon to generate metallic potassium and carbon monoxide, forming pores; in addition, sodium sulfate reacts with carbon to produce gas, and sulfur is doped into the carbon skeleton. When the temperature reaches 800°C, potassium turns into potassium vapor and evaporates. Among them, the reaction equations involved in the activation process are as follows:

[0018] K 2 CO 3 +2C→2K+3CO

[0019] 4Na 2 S 2 O 3 →3Na 2 SO 4 +Na 2 S 5

[0020] Na 2 SO 4 +2C→Na 2 S+2CO 2

[0021] Na 2 SO 4 +4C→Na 2 S+4CO

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. The present invention uses coal tar as a carbon source, melamine as a nitrogen source, phytic acid as a phosphorus source, and water-soluble salts of potassium chloride, potassium carbonate and sodium thiosulfate pentahydrate as templates, activators and sulfur sources, respectively. By using mild reagents, the experiment not only avoids alkali corrosion to the equipment, but also avoids pickling to remove the process of corroded nickel and iron, saving time and cost, and having no pressure on the environment. In addition, in the present invention, impurities in the product can be removed only by washing with deionized water, and the preparation method is green and environmentally friendly.

[0024] 2. The nitrogen, phosphorus and sulfur doped porous carbon material prepared by the present invention exhibits an interconnected sheet structure, which can not only improve the conductivity of the carbon material, but also the doped heteroatoms can contribute to pseudocapacitance;

[0025] 3. The specific surface area of ​​the material prepared by the present invention reaches 1939m 2 g -1 , the higher specific surface area and pore volume can provide abundant active sites for the adsorption of zinc ions, thus enhancing the adsorption performance and ion transfer efficiency of the material;

[0026] 4. The present invention uses the prepared heteroatom-doped porous carbon as the carbon positive electrode of the zinc ion hybrid capacitor, and in a 2M zinc sulfate electrolyte, at 0.2Ag -1 The specific capacity reached 205.1 mAh g -1 ; at 10Ag -1 The specific capacity reached 98.2 mAh g -1 . In 10Ag -1 At a current density of , the capacity retention rate reached 91% after 60,000 cycles, showing excellent cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a scanning electron microscope image of nitrogen, phosphorus and sulfur doped porous carbon sheets;

[0028] Figure 2 X-ray electron spectra of elements in nitrogen, phosphorus and sulfur doped porous carbon sheets: (a) C 1s spectrum; (b) N 1s spectrum; (c) O 1s spectrum; (d) P 2p spectrum; (e) S2p spectrum;

[0029] Figure 3 In the figure, (a) is the nitrogen adsorption-desorption curves of different examples and comparative samples, and (b) is the pore size distribution diagram;

[0030] Figure 4 It is a comparison chart of specific capacity of different examples and comparative samples at different current densities;

[0031] Figure 5 Nitrogen, phosphorus and sulfur doped porous carbon sheets on 10Ag -1 Cycling stability and Coulombic efficiency at current density of . DETAILED DESCRIPTION

[0032] The above and other technical features and advantages of the present invention are described in more detail below in conjunction with the accompanying drawings.

[0033] Example 1

[0034] The specific process of the preparation method of nitrogen, phosphorus and sulfur doped porous carbon material is as follows:

[0035] (1) First, 1 g of melamine was dissolved in hot deionized water, 1 mL of 70% phytic acid solution was added dropwise thereto, and the mixture was stirred thoroughly and then dried at 80° C. to obtain a nitrogen-phosphorus polymer;

[0036] (2) dissolving 1 g of coal tar in 20 mL of N,N-dimethylformamide, grinding 10 g of potassium chloride, 4 g of potassium carbonate, 1 g of sodium thiosulfate pentahydrate and 1.68 g of nitrogen-phosphorus polymer thoroughly, adding them to the coal tar solution, mixing them evenly by ultrasonication, and then transferring them to an oven to dry to obtain a mixture;

[0037] (3) The dried mixture was transferred to a porcelain boat and heated at 5°C min -1 The sample was heated to 800 °C at a heating rate of 1.5 °C and kept in an argon inert atmosphere for 2 h. After natural cooling, the synthesized sample was soaked in deionized water for 24 h, filtered, and then dried at 80 °C for 12 h.

[0038] (4) As attached Figure 1 As shown, the nitrogen, phosphorus and sulfur doped porous carbon presents an interconnected sheet structure, which is conducive to the transport of electrolyte ions and the conduction of electrons. Figure 2 It shows that the three elements of nitrogen, phosphorus and sulfur are successfully doped into carbon materials and can contribute to pseudocapacitance. Figure 3 Combined with Table 1, the highest specific surface area of ​​the sample obtained in Example 1 is 1939m 2 g -1 The total pore volume is 1.06 cm 3 g -1 , the average pore size is 2.56nm. Figure 4 Explanation: Example 1 at 0.2Ag -1 At a current density of 2.5 %, the specific capacity reached 205.1 mAh g -1 ; When the current density increases to 20Ag -1 When the specific capacity is still 98.2 mAh g -1 . Figure 5 It shows that Example 1 at 10Ag -1 After 60,000 cycles at a current density of , the capacity retention rate is 91%, which has excellent cycle stability.

[0039] Example 2

[0040] The specific process of the preparation method of nitrogen and phosphorus doped porous carbon material is as follows:

[0041] (1) First, 1 g of melamine was dissolved in hot deionized water, 1 mL of 70% phytic acid solution was added dropwise thereto, and the mixture was stirred thoroughly and then dried at 80° C. to obtain a nitrogen-phosphorus polymer;

[0042] (2) dissolving 1 g of coal tar in 20 mL of N,N-dimethylformamide, grinding 10 g of potassium chloride, 4 g of potassium carbonate and 1.68 g of nitrogen-phosphorus polymer thoroughly, adding them to the coal tar solution, mixing them evenly by ultrasonication, and then transferring them to an oven to dry to obtain a mixture;

[0043] (3) The dried mixture was transferred to a porcelain boat and heated at 5°C min -1 The sample was heated to 800 °C at a heating rate of 1.5 °C and kept in an argon inert atmosphere for 2 h. After natural cooling, the synthesized sample was soaked in deionized water for 24 h, filtered, and then dried at 80 °C for 12 h.

[0044] (4) Figure 3 Combined with Table 1, the specific surface area of ​​Example 2 reached 1601m 2 g -1 The total pore volume is 0.96 cm 3 g -1 Attached Figure 4 Explanation: Example 2 at 0.2Ag -1 At a current density of 1.5 %, the specific capacity reached 186 mAh g -1 ; When the current density increases to 20Ag -1 The specific capacity is 70 mAh g -1 .

[0045] Example 3

[0046] The specific process of the preparation method of nitrogen-doped porous carbon material is as follows:

[0047] (1) dissolving 1 g of coal tar in 20 mL of N,N-dimethylformamide, grinding 10 g of potassium chloride, 4 g of potassium carbonate and 1 g of melamine thoroughly, adding them to the coal tar solution, mixing them evenly by ultrasonication, and then transferring them to an oven to dry to obtain a mixture;

[0048] (2) The dried mixture was transferred to a porcelain boat and heated at 5°C min -1 The sample was heated to 800 °C at a heating rate of 1.5 °C and kept in an argon inert atmosphere for 2 h. After natural cooling, the synthesized sample was soaked in deionized water for 24 h, filtered, and then dried at 80 °C for 12 h.

[0049] (3) Attachment Figure 3 Combined with Table 1, the specific surface area of ​​Example 3 reaches 1560m 2 g -1 The total pore volume is 0.8 cm 3 g -1 Attached Figure 4 Explanation: Example 3 at 0.2Ag -1 At a current density of 1.5 %, the specific capacity reached 186 mAh g -1; When the current density increases to 20Ag -1 The specific capacity is 65 mAh g -1 .

[0050] Comparative Example 1

[0051] The specific process of the preparation method of porous carbon material is as follows:

[0052] (1) 1 g of coal tar was dissolved in 20 mL of N,N-dimethylformamide, 10 g of potassium chloride and 4 g of potassium carbonate were fully ground and added to the coal tar solution, and the mixture was transferred to an oven for drying after being uniformly mixed by ultrasonication to obtain a mixture;

[0053] (2) The dried mixture was transferred to a porcelain boat and heated at 5°C min -1 The sample was heated to 800 °C at a heating rate of 1.5 °C and kept in an argon inert atmosphere for 2 h. After natural cooling, the synthesized sample was soaked in deionized water for 24 h, filtered, and then dried at 80 °C for 12 h.

[0054] (4) Combination of Table 1 Figure 3 It can be seen that the specific surface area of ​​comparative example 1 is the smallest, only 1277m 2 g -1 The total pore volume is also the smallest, only 0.68 cm 3 g -1 Attached Figure 4 Explanation: Comparative Example 1 at 0.2Ag -1 The current density is only 177 mAh g -1 Specific capacity; at 20Ag -1 The specific capacity at a current density of only 61.8 mAh g -1 .

[0055] Table 1 Pore structure parameters of Examples 1-3 and Comparative Example 1

[0056]

[0057] Depend on Figure 1 It can be seen that the nitrogen, phosphorus and sulfur doped porous carbon prepared in Example 1 of the present invention has a thin sheet structure and a large lateral size. This structure can be Zn 2+ The adsorption provides a large number of active sites, which improves the specific capacity of zinc ion hybrid capacitors. The formation of this structure originates from the template KCl and K 2 CO 3 The synergistic effect of the surface induced effect.

[0058] Figure 2 It is the XPS spectrum of C, N, O, P, and S elements of Example 1. Among them, Figure 2 The C1s of (a) was fitted into four carbon-containing functional groups. Figure 2 The N1s of (b) is fitted into four characteristic peaks. Figure 2 The O1s spectrum in (c) was fitted to three oxygen-containing functional groups. Figure 2 The P 2p spectrum of (d) is fitted with two characteristic peaks, PC and PO. Figure 2 The S2p in (e) is fitted into three characteristic peaks.

[0059] Combining Table 1 and Figure 3 It can be seen that the specific surface area of ​​the porous carbon prepared by the present invention is between 1560 and 1939 m 2 g -1 The total pore volume is between 0.80 and 1.06 cm 3 g -1 The high specific surface area and large pore volume provide active sites for the adsorption of zinc ions.

[0060] Figure 4 The specific capacities of Examples 1-3 and Comparative Example 1 at different current densities when used as positive electrodes of zinc ion hybrid capacitors. It can be seen from the figure that when Example 1 is used as a positive electrode material, the specific capacity is significantly higher than that of other samples.

[0061] Figure 5 The cycle stability test results of Example 1 as a positive electrode material show that Example 1 has good cycling stability at 10Ag. -1 The capacity retention rate after 60,000 cycles at a current density of 1.340 nm is 91%, and the coulombic efficiency is close to 100%, indicating its excellent cycle stability and high charge and discharge efficiency.

[0062] The above description is only a preferred embodiment of the present invention, which is only illustrative and not restrictive of the present invention. Those skilled in the art understand that many changes, modifications, and even equivalences may be made to the present invention within the spirit and scope defined by the claims of the present invention, but all of them will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a heteroatom-doped interconnected porous carbon material, characterized in that: The following steps are involved: S1, dissolving melamine in hot deionized water, dropping 70% phytic acid solution therein, and drying at 80° C. after the reaction to obtain a nitrogen-phosphorus polymer; S2, dissolving coal tar in an organic solvent of N,N-dimethylformamide, fully grinding and mixing potassium chloride, potassium carbonate, and a heteroatom dopant, and adding them to the organic solvent containing the coal tar, mixing them uniformly by ultrasonication, and then transferring them to an oven for drying to obtain a reactant precursor; S3, transferring the reactant precursor obtained in step S2 to a porcelain boat for heating and keeping it warm in an argon inert atmosphere for 2 hours. After natural cooling, the synthesized sample is soaked in deionized water for 24 hours, filtered, and then dried at 80° C. for 12 hours.

2. The method for preparing a heteroatom-doped interconnected porous carbon material according to claim 1, characterized in that: In the step S1, the mass of melamine is 1 g, and the volume of the phytic acid solution is 1 mL.

3. The method for preparing a heteroatom-doped interconnected porous carbon material according to claim 1, characterized in that: In the step S2, the heteroatom dopant is sodium thiosulfate pentahydrate + nitrogen phosphorus polymer, nitrogen phosphorus polymer or melamine.

4. The method for preparing a heteroatom-doped interconnected porous carbon material according to claim 3, characterized in that: The mass of the sodium thiosulfate pentahydrate is 1 g, the mass of the nitrogen-phosphorus polymer is 1.68 g, and the mass of the melamine is 1 g.

5. The method for preparing a heteroatom-doped interconnected porous carbon material according to claim 1, characterized in that: In step S2, the mass of coal tar is 1 g, the volume of N,N-dimethylformamide is 20 mL, the mass of potassium chloride is 10 g, and the mass of potassium carbonate is 4 g.

6. The method for preparing a heteroatom-doped interconnected porous carbon material according to claim 1, characterized in that: In step S3, the heating rate is 5°C min -1 , the insulation temperature is 800℃.

7. An interconnected porous carbon material doped with heteroatoms prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the heteroatom-doped interconnected porous carbon material as claimed in claim 7 as an electrode material in a zinc ion hybrid capacitor.

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