Coal-tar pitch-based heteroatom-doped porous carbon, preparation method and application thereof
The method for preparing porous carbon based on coal tar pitch heteroatom doping solves the problems of high cost and environmental pollution in the preparation of porous carbon materials, and achieves efficient and green preparation and performance improvement, especially in the application of zinc ion capacitors.
Patent Information
- Application Number
- CN202610757786.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-29
- Publication Date
- 2026-08-25
AI Technical Summary
Existing methods for preparing porous carbon materials rely on complex templates or multi-step processes, which are costly and difficult to achieve uniform doping, resulting in environmental pollution and insufficient material performance.
Using coal tar pitch as the carbon source, and potassium bicarbonate, melamine phosphate, and boric acid as activators and dopants, boron, nitrogen, and phosphorus co-doped porous carbon is prepared by a one-step carbonization method to construct a three-dimensional network structure, avoiding the use of strong acids and bases and simplifying the process.
This technology enables the efficient and green preparation of porous carbon materials, constructs a stable three-dimensional hierarchical network structure, improves the energy density and cycle stability of zinc-ion capacitors, simplifies the process, and reduces costs and environmental pollution.
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Figure CN122627428A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of carbon material preparation technology, specifically to a coal tar pitch-based heteroatom-doped porous carbon, its preparation method, and its application. Background Technology
[0002] Zinc-ion hybrid capacitors are a promising new type of electrochemical energy storage device that combines the high energy density of batteries with the high power density of supercapacitors. They possess the inherent high safety of aqueous electrolytes, as well as the resource and cost advantages of zinc materials. Carbon materials, due to their excellent conductivity, chemical stability, and structural tunability, are widely used as positive electrode materials for zinc-ion hybrid capacitors. However, carbon materials also face challenges. The highly corrosive reagents used in their preparation and the subsequent acid washing and purification steps can cause environmental pollution, which has become one of the important reasons restricting the green and sustainable development of porous carbon materials. To address these bottlenecks, researchers urgently need to develop an efficient, green, and low-cost carbon material preparation strategy.
[0003] Heteroatom doping of carbon materials has become an effective strategy for improving their performance. Doping with nitrogen, boron, and phosphorus heteroatoms introduces active sites. Nitrogen atoms improve the hydrophilicity of the material surface, which is beneficial for electrolyte wetting. Boron has a lower electronegativity than carbon, which helps improve the conductivity and electrochemical stability of carbon materials. Phosphorus doping introduces structural defects, providing active sites that contribute pseudocapacitance and enhance capacity. Boron-nitrogen-phosphorus co-doped hierarchical porous carbon materials have demonstrated high specific capacity and excellent cycling stability in research.
[0004] Coal tar pitch is the residue obtained after distillation of coal tar produced during the dry distillation of coal for coking or coal gasification. It is a black, brittle, blocky solid at room temperature. Its chemical composition is extremely complex, dominated by polycyclic aromatic hydrocarbons (PAHs) and fused-ring aromatic hydrocarbons (FEHs). Its high residual carbon value and good graphitization tendency make it a potential precursor for electrode materials. As a major product of coal chemical industry, how to continuously expand the high-value application areas of coal tar pitch through technological innovation remains a challenge.
[0005] In view of the above-mentioned defects, the inventors of this invention have finally obtained this invention after a long period of research and practice. Summary of the Invention
[0006] The purpose of this invention is to solve the problem that existing methods for preparing porous carbon materials often rely on complex templates or multi-step processes, which are costly and difficult to achieve uniform doping. This invention provides a coal tar pitch-based heteroatom-doped porous carbon, its preparation method, and its application.
[0007] To achieve the above objectives, this invention discloses a method for preparing coal tar pitch-based heteroatom-doped porous carbon, comprising the following steps:
[0008] S1, mix medium-temperature coal tar pitch, potassium bicarbonate, melamine phosphate, and boric acid evenly, grind and mix to obtain the reactant;
[0009] S2, the reactants obtained in step S1 are carbonized at high temperature in an inert gas atmosphere;
[0010] S3. The product obtained in step S2 is taken out, ground, washed with deionized water, filtered and dried to obtain coal tar pitch-based heteroatom-doped porous carbon.
[0011] In step S1, the mass ratio of coal tar pitch, potassium bicarbonate, melamine phosphate, and boric acid is 1:4:1:1.
[0012] In step S2, the inert gas is argon, and the high-temperature carbonization process conditions are as follows: heating rate is 5 ℃ / min, holding temperature is 850℃, and gas flow rate is 10 mL / min.
[0013] In step S3, the drying temperature is 80°C.
[0014] The present invention also discloses coal tar pitch-based heteroatom-doped porous carbon prepared by the above preparation method.
[0015] The porous carbon has a three-dimensional network structure.
[0016] The present invention also discloses the application of the above-mentioned coal tar pitch-based heteroatom-doped porous carbon in zinc-ion capacitors.
[0017] This invention uses coal tar pitch as a carbon precursor, potassium bicarbonate as a chemical activator, and melamine phosphate and boric acid to provide nitrogen, phosphorus, and boron heteroatoms, respectively. During high-temperature heat treatment, potassium bicarbonate undergoes thermal decomposition and an oxidative etching reaction with the carbon matrix, accompanied by gas escape, constructing numerous micropores and mesopores within the carbon material, achieving efficient pore formation. Melamine phosphate and boric acid gradually decompose upon heating, not only in-situ doping N, P, and B heteroatoms into the carbon framework and introducing a large number of electrochemically active functional groups, but also the gaseous products generated by their pyrolysis can further assist in pore expansion and optimize the pore structure. Activation and pore formation are carried out simultaneously and synergistically, ultimately yielding a doped porous carbon material with a well-developed pore structure and abundant surface active sites. The reaction equations involved in the activation process are shown below:
[0018] ;
[0019] ;
[0020] ;
[0021] .
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0023] 1. This invention uses coal tar pitch as a carbon source, which is inexpensive and readily available. Potassium bicarbonate is used as an activator, melamine phosphate is used as a nitrogen and phosphorus source, and boric acid is used as a boron source. Boron-nitrogen-phosphorus co-doped porous carbon nanosheets are directly synthesized by a one-step carbonization method. The process is simple and realizes the high added value utilization of coal tar pitch.
[0024] 2. This invention uses green inorganic salts as pore-forming agents, avoiding the use of strong acids and alkalis in the process, reducing environmental pollution, and saving time and costs. Impurities in the product can be removed simply by washing with deionized water. The preparation method is green and environmentally friendly, falling under the category of green preparation technology.
[0025] 3. This invention constructs a stable three-dimensional hierarchical porous network structure, solving the inherent defects of coal tar pitch. This invention uses potassium bicarbonate and boric acid as activators, resulting in a smooth and controllable pore-forming process. This effectively avoids the problem of pore collapse caused by strong alkali activation, while fundamentally overcoming the inherent drawbacks of coal tar pitch's tendency to melt and agglomerate during high-temperature pyrolysis. The final result is a continuous three-dimensional network structure. The multi-level interconnected channels shorten the electrolyte ion transport path, and combined with a continuous and complete carbon conductive network, significantly reduce the material's contact resistance, while maintaining excellent ion diffusion capability and structural mechanical stability.
[0026] 4. The carbon material obtained in this invention has a three-dimensional network structure. The interconnected porous structure significantly shortens the ion diffusion path, ensuring rapid electron conduction. The hierarchical porous network can buffer volume changes during charging and discharging, preventing the shedding of active material. These advantages together enable the zinc-ion capacitor to significantly improve energy density while maintaining high power and long lifespan. In addition, the obtained carbon material contains a certain amount of B, N, and P functional groups, and the doped heteroatoms can contribute pseudocapacitance.
[0027] 5. This invention utilizes melamine phosphate to provide both nitrogen and phosphorus sources in an integrated manner. A single reagent simultaneously provides both nitrogen and phosphorus sources, eliminating the need to add two different dopants and simplifying the preparation process. The N and P atoms within the molecule are tightly bonded, allowing for synchronous element migration during heat treatment, thus avoiding the uneven element distribution problem caused by single-source step-by-step doping from the source. Combined with a boron borate source, it achieves co-doping of three heteroatoms. Nitrogen provides abundant electrochemical active sites, improving the material's conductivity; boron regulates the electronic structure of the carbon framework, optimizing electron transport efficiency; and phosphorus effectively widens the carbon interlayer spacing, accelerating ion migration. Simultaneously, the three elements synergistically optimize the hydrophilicity of the carbon material surface, strengthen the covalent bond network of the carbon framework, and significantly improve charge storage capacity, rate performance, and long-cycle structural stability.
[0028] 6. The boron-nitrogen-phosphorus co-doped porous carbon nanosheet electrode material prepared in this invention, used as the carbon cathode of a zinc-ion hybrid capacitor, exhibits a specific capacity of 195.6 mAh / g in a 2 mol / L ZnSO4 electrolyte at a current density of 0.1 A / g, and a specific capacity of 72.4 mAh / g at a current density of 10 A / g. After 40,000 cycles at a current density of 10 A / g, the capacity retention rate is 94.6%, demonstrating good rate performance and cycling performance. Attached Figure Description
[0029] Figure 1 This is a scanning electron microscope image of the boron, nitrogen, and phosphorus-doped porous carbon sheet obtained in Example 2;
[0030] Figure 2 X-ray electron spectra of elements in the boron, nitrogen, and phosphorus-doped porous carbon sheet obtained in Example 2: (a) C 1s spectrum; (b) B 1s spectrum; (c) N 1s spectrum; (d) P 2p spectrum;
[0031] Figure 3 The nitrogen adsorption-desorption curves are for the materials obtained in Examples 1-3 and Comparative Examples 1 and 2.
[0032] Figure 4 This is a comparison graph showing the specific capacity of the materials obtained in Examples 1-3 and Comparative Examples 1 and 2 under different current densities;
[0033] Figure 5 The graph shows the cycling stability and coulombic efficiency of the boron-nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Example 2 at a current density of 10 A / g. Detailed Implementation
[0034] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.
[0035] Example 1
[0036] The preparation process of boron-nitrogen-phosphorus co-doped three-dimensional network porous carbon nanosheets BNPC2 is as follows:
[0037] (1) Pretreatment of reactants: Weigh 3 g coal tar pitch, 12 g potassium bicarbonate, 3 g melamine phosphate and 6 g boric acid, grind and mix thoroughly;
[0038] (2) Preparation of boron-nitrogen-phosphorus co-doped three-dimensional porous carbon nanosheets: The reactants were uniformly poured into a ceramic boat and transferred to the center of a horizontal tube furnace. Argon gas was first introduced at a rate of 50 mL / min for a period of time to fill the furnace with argon gas. Then, the argon gas flow rate was adjusted to 10 mL / min, and the heating rate was set to 5℃ / min to heat to 850℃. The temperature was kept constant for 2 h. After the reaction was completed, the temperature was allowed to drop naturally to room temperature. The obtained product was then taken out, placed in a beaker, and distilled water was added. The mixture was stirred on a magnetic stirrer for 12 h. The product was then washed with deionized water until the pH of the filtrate was 7. Finally, boron-nitrogen-phosphorus co-doped three-dimensional porous carbon nanosheets were obtained. The obtained boron-nitrogen-phosphorus co-doped porous carbon nanosheets were designated as BNPC2.
[0039] Figure 3 Referring to Table 1, the specific surface area of the boron-nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Example 1 is 986 m². 2 / g, total pore volume is 0.45 cm³ 3 / g. Figure 4 The boron-nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Example 1, when assembled into a zinc-ion capacitor, achieve a specific capacitance of 172.4 mAh / g at a current density of 0.1 A / g; when the current density is increased to 10 A / g, the specific capacitance is 59.5 mAh / g.
[0040] Example 2
[0041] The preparation process of boron-nitrogen-phosphorus co-doped three-dimensional network porous carbon nanosheets BNPC1 is as follows:
[0042] (1) Pretreatment of reactants: Weigh 3 g coal tar pitch, 12 g potassium bicarbonate, 3 g melamine phosphate and 3 g boric acid, grind and mix thoroughly;
[0043] (2) Preparation of boron-nitrogen-phosphorus co-doped three-dimensional porous carbon nanosheets: The reactants were uniformly poured into a ceramic boat and transferred to the center of a horizontal tube furnace. Argon gas was first introduced at a rate of 50 mL / min for a period of time to fill the furnace with argon gas. Then, the argon gas flow rate was adjusted to 10 mL / min, and the heating rate was set to 5℃ / min to heat to 850℃. The temperature was kept constant for 2 h. After the reaction was completed, the temperature was allowed to drop naturally to room temperature. The obtained product was then taken out, placed in a beaker, and distilled water was added. The mixture was stirred on a magnetic stirrer for 12 h. The product was then washed with deionized water until the pH of the filtrate was 7. Finally, boron-nitrogen-phosphorus co-doped three-dimensional porous carbon nanosheets were obtained. The obtained boron-nitrogen-phosphorus co-doped porous carbon nanosheets were designated as BNPC1.
[0044] like Figure 1 As shown, the boron, nitrogen, and phosphorus-doped porous carbon exhibits a three-dimensional network-like sheet structure, which is beneficial for the transport of electrolyte ions and the conduction of electrons. Figure 2This indicates that boron, nitrogen, and phosphorus have been successfully doped into carbon materials and bonded together by chemical bonds, thus ensuring the stability of the material's structure and properties. Figure 3 Referring to Table 1, the specific surface area of the boron-nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Example 2 is 1245 m². 2 / g, total pore volume is 0.53 cm³ 3 / g. Figure 4 The boron-nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Example 2, when assembled into a zinc-ion capacitor, achieve a specific capacitance of 195.6 mAh / g at a current density of 0.1 A / g; when the current density is increased to 10 A / g, the specific capacitance is 72.4 mAh / g. Figure 5 The results show that the boron-nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Example 2 retained 94.6% of their capacity after 40,000 cycles at a current density of 10 A / g, demonstrating excellent cycling stability.
[0045] Example 3
[0046] Boron-nitrogen-phosphorus co-doped three-dimensional porous carbon nanosheets (BNPC) 0.5 The preparation process is as follows:
[0047] (1) Pretreatment of reactants: Weigh 3 g coal tar pitch, 12 g potassium bicarbonate, 3 g melamine phosphate, and 1.5 g boric acid, grind and mix thoroughly;
[0048] (2) Preparation of boron-nitrogen-phosphorus co-doped three-dimensional porous carbon nanosheets: The reactants were uniformly poured into a ceramic boat and transferred to the center of a horizontal tube furnace. Argon gas was first introduced at a rate of 50 mL / min for a period of time to fill the furnace with argon gas. Then, the argon gas flow rate was adjusted to 10 mL / min, and the heating rate was set to 5℃ / min to heat to 850℃. The temperature was maintained for 2 h. After the reaction was completed, the temperature was allowed to drop naturally to room temperature. The obtained product was then taken out, placed in a beaker, and distilled water was added. The mixture was stirred on a magnetic stirrer for 12 h. The product was then washed with deionized water until the pH of the filtrate was 7. Finally, boron-nitrogen-phosphorus co-doped three-dimensional porous carbon nanosheets were obtained. The obtained boron-nitrogen-phosphorus co-doped porous carbon nanosheets were denoted as BNPC. 0.5 .
[0049] Figure 3 Referring to Table 1, the specific surface area of the boron-nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Example 3 is 909 m². 2 / g, total pore volume is 0.65 cm³ 3 / g. Figure 4 The boron-nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Example 3, when assembled into a zinc-ion capacitor, achieve a specific capacitance of 145.2 mAh / g at a current density of 0.1 A / g; when the current density is increased to 10 A / g, the specific capacitance is 43.1 mAh / g.
[0050] Comparative Example 1
[0051] The preparation process of nitrogen-phosphorus co-doped three-dimensional network porous carbon nanosheets (NPC) is as follows:
[0052] (1) Pretreatment of reactants: Weigh 3 g coal tar pitch, 12 g potassium bicarbonate and 3 g melamine phosphate, grind and mix thoroughly;
[0053] (2) Preparation of nitrogen-phosphorus co-doped three-dimensional porous carbon nanosheets: The reactants were uniformly poured into a ceramic boat and transferred to the center of a horizontal tube furnace. Argon gas was first introduced at a rate of 50 mL / min for a period of time to fill the furnace with argon gas. Then, the argon gas flow rate was adjusted to 10 mL / min, and the heating rate was set to 5℃ / min to heat to 850℃. The temperature was kept constant for 2 h. After the reaction was completed, the temperature was allowed to drop naturally to room temperature. The obtained product was then taken out, placed in a beaker, and distilled water was added. The mixture was stirred on a magnetic stirrer for 12 h. The product was then washed with deionized water until the pH of the filtrate was 7. Finally, nitrogen-phosphorus co-doped three-dimensional porous carbon nanosheets were obtained. The obtained nitrogen-phosphorus co-doped porous carbon nanosheets are denoted as NPC.
[0054] Figure 3 As illustrated in Table 1, the specific surface area of the nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Comparative Example 1 is 522 m². 2 / g, total pore volume is 0.20 cm³ 3 / g. Figure 4 The results show that the zinc-ion capacitor assembled from the nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Comparative Example 1 has a specific capacitance of 93.9 mAh / g at a current density of 0.1 A / g; when the current density is increased to 10 A / g, the specific capacitance is 43.1 mAh / g.
[0055] Comparative Example 2
[0056] The preparation process of boron-doped three-dimensional network porous carbon nanosheets BC is as follows:
[0057] (1) Pretreatment of reactants: Weigh 3 g coal tar pitch, 12 g potassium bicarbonate and 6 g boric acid, grind and mix thoroughly;
[0058] (2) Preparation of boron-doped three-dimensional porous carbon nanosheets: The reactants were uniformly poured into a ceramic boat and transferred to the center of a horizontal tube furnace. Argon gas was first introduced at a rate of 50 mL / min for a period of time to fill the furnace with argon gas. Then, the argon gas flow rate was adjusted to 10 mL / min, and the heating rate was set to 5℃ / min to heat to 850℃. The temperature was maintained for 2 hours. After the reaction was completed, the temperature was allowed to drop naturally to room temperature. The obtained product was then taken out, placed in a beaker, and distilled water was added. The mixture was stirred on a magnetic stirrer for 12 hours. The product was then washed with deionized water until the pH of the filtrate was 7. Finally, boron-doped porous carbon nanosheets were obtained. The obtained boron-doped porous carbon nanosheets are denoted as BPC.
[0059] Figure 3 As illustrated in Table 1, the specific surface area of the boron-doped porous carbon nanosheets obtained in Comparative Example 2 is 865 m². 2 / g, total pore volume is 0.34 cm³ 3 / g. Figure 4 The results show that the nitrogen-phosphorus co-doped porous carbon nanosheets obtained in Comparative Example 2, when assembled into a zinc-ion capacitor, have a specific capacitance of 137.1 mAh / g at a current density of 0.1 A / g; when the current density is increased to 10 A / g, the specific capacitance is 51.1 mAh / g.
[0060] The pore structure parameters of the heteroatom-doped porous carbon nanosheets obtained in Examples 1-3 and Comparative Examples 1 and 2 are shown in Table 1 below:
[0061] Table 1. Pore structure parameters of heteroatom-doped porous carbon nanosheets obtained in Examples 1-3 and Comparative Examples 1 and 2.
[0062]
[0063] Depend on Figure 1 It can be seen that the boron, nitrogen, and phosphorus-doped porous carbon prepared in Example 2 has a three-dimensional network structure. The interconnected porous structure significantly shortens the ion diffusion path. This structure can facilitate the diffusion of Zn. 2+ Adsorption provides numerous active sites, ensuring rapid electron conduction. The hierarchical porous network buffers volume changes during charging and discharging, preventing the shedding of active material. These advantages combined enable zinc-ion capacitors to significantly improve energy density while maintaining high power and long lifespan.
[0064] Figure 2 The XPS spectra of C, N, B, and P elements in the boron, nitrogen, and phosphorus-doped porous carbon prepared in Example 2 are shown. This indicates that B, N, and P elements were successfully incorporated into the carbonaceous framework.
[0065] Figure 4The figures show the specific capacitance of heteroatom-co-doped porous carbon nanosheets obtained in Examples 1-3 and Comparative Examples 1 and 2 as positive electrodes of zinc ion hybrid capacitors at different current densities. As can be seen from the figures, the specific capacitance of Example 2 as the positive electrode material is significantly higher than that of the other samples.
[0066] Figure 5 The results of the cycle stability test of the boron, nitrogen, and phosphorus-doped porous carbon prepared in Example 2 as a cathode material show that the capacity retention rate of the boron, nitrogen, and phosphorus-doped porous carbon prepared in Example 2 after 40,000 cycles at a current density of 10 A / g is 94.6%, and the coulombic efficiency is close to 100%, indicating its excellent cycle stability.
[0067] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.
Claims
1. A method for preparing coal tar pitch-based heteroatom-doped porous carbon, characterized in that, Includes the following steps: S1, mix medium-temperature coal tar pitch, potassium bicarbonate, melamine phosphate, and boric acid evenly, grind and mix to obtain the reactant; S2, the reactants obtained in step S1 are carbonized at high temperature in an inert gas atmosphere; S3. The product obtained in step S2 is taken out, ground, washed with deionized water, filtered and dried to obtain coal tar pitch-based heteroatom-doped porous carbon.
2. The method for preparing coal tar pitch-based heteroatom-doped porous carbon as described in claim 1, characterized in that, In step S1, the mass ratio of coal tar pitch, potassium bicarbonate, melamine phosphate, and boric acid is 2:8:(0~2):(0~4).
3. The method for preparing coal tar pitch-based heteroatom-doped porous carbon as described in claim 1, characterized in that, In step S1, the mass ratio of coal tar pitch, potassium bicarbonate, melamine phosphate, and boric acid is 1:4:1:
2.
4. The method for preparing coal tar pitch-based heteroatom-doped porous carbon as described in claim 1, characterized in that, In step S2, the inert gas is argon, and the high-temperature carbonization process conditions are as follows: heating rate is 5℃ / min, holding temperature is 850℃, and gas flow rate is 10 mL / min.
5. The method for preparing coal tar pitch-based heteroatom-doped porous carbon as described in claim 1, characterized in that, In step S3, the drying temperature is 80°C.
6. A coal tar pitch-based heteroatom-doped porous carbon prepared by the preparation method according to any one of claims 1 to 5.
7. The coal tar pitch-based heteroatom-doped porous carbon as described in claim 6, characterized in that, The porous carbon has a three-dimensional network structure.
8. The application of coal tar pitch-based heteroatom-doped porous carbon as described in claim 6 or 7 in zinc-ion capacitors.