CN115231569B - Preparation method and application of porous carbon material for super capacitor - Google Patents
Preparation method and application of porous carbon material for super capacitor Download PDFInfo
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
- H01G11/34—Carbon-based characterised by carbonisation or activation of carbon
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
- H01G11/44—Raw materials therefor, e.g. resins or coal
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Abstract
The invention belongs to the technical field of supercapacitor electrode materials, and discloses a preparation method and application of a porous carbon material for a supercapacitor. The invention prepares coal-based carbon dots by taking coal as raw material and assembles the coal-based carbon dots into 3D hierarchical pore carbon, and the prepared 3D hierarchical pore carbon has reasonable pore structure, high specific surface area utilization rate, continuous conductive network and high capacity retention rate. The 3D hierarchical pore carbon prepared by the method is suitable for super capacitor electrode materials.
Description
Technical Field
The invention relates to the technical field of supercapacitor electrode materials, in particular to a preparation method and application of a porous carbon material for a supercapacitor.
Background
With the continuous growth of population and the rapid development of economy, the demand for energy is increasing, and serious resource shortage and environmental pollution are caused for the excessive exploitation and use of fossil energy such as petroleum, coal and the like. The renewable energy sources such as wind power, water power, photovoltaic and the like are developed to generate electricity, so that the energy pressure can be relieved, and the ecological damage can be reduced, wherein the super capacitor plays an important role as an energy storage device with high power and ultra-long service life.
Electrode materials are the core components of supercapacitors, whose structure and properties play a critical role in the performance of the capacitor. Currently, the most widely used supercapacitor electrode materials are porous carbon materials. The core component of the coal is carbon, and aromatic carbon is mainly used, so that the coal is mineral with the highest carbon content in nature except graphite and diamond, is also the most abundant and cheap carbon-containing resource, and is a high-quality porous carbon material precursor. At present, the method for preparing the porous carbon for the supercapacitor by taking coal as a raw material mainly adopts an alkali activation method, and has three problems, namely, the whole process is relatively simple, and the sample has a large specific surface area and a high mass specific capacitance: 1) The ash content needs to be considered, the ash content of the coal is more and more complex, the preparation of the porous carbon for the supercapacitor is not facilitated, and two times of ash removal are often needed before and after activation, so that the preparation difficulty is increased; 2) The coal is stable in its own properties, so that a large amount of alkali is required to be used, which causes environmental pollution and serious corrosion of equipment; 3) The pore structure distribution is unreasonable, the pore size distribution is narrow, micropores smaller than 2nm are used as the main materials, the specific surface area utilization rate is less than 20%, and the excessively developed pore structure also damages a conductive network, so that the performance under high current density is poor.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a preparation method and application of a porous carbon material for a supercapacitor.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
in a first aspect, the present invention provides a method for preparing a porous carbon material for a supercapacitor, comprising the steps of:
(1) Putting coal into sulfuric acid, adding potassium ferrate, and stirring to obtain a reaction solution; performing ultrasonic treatment on the obtained reaction liquid, and centrifugally washing to neutrality; adding hydrogen peroxide to perform oxidation reaction to obtain carbon dot solution,
(2) Dialyzing, freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) Dissolving the obtained coal-based carbon dots in water (preferably deionized water), adding an assembling agent and a pore-forming agent, stirring, drying, carbonizing in nitrogen atmosphere, cooling, washing with water, and drying.
The invention prepares coal-based carbon dots by taking coal as a raw material and assembles the coal-based carbon dots into 3D hierarchical pore carbon. Wherein, the coal is oxidized into carbon point solution dissolved in water through oxidation, centrifugation, filtration and dialysis treatment in the preparation process of the coal-based carbon point, and the influence of ash is not needed to be considered; the participation of strong alkali such as potassium hydroxide, sodium hydroxide and the like is avoided in the high-temperature carbonization process, the danger is low, and the service life of equipment is prolonged; in the assembly process of the 3D hierarchical pore carbon, the specific surface area and pore structure distribution of the 3D hierarchical pore carbon can be controlled by changing the types and the dosage of pore formers.
As a preferred embodiment of the method for preparing a porous carbon material for a supercapacitor according to the present invention, in the step (1), the coal is at least one of anthracite, bituminous coal, and lignite; the particle size of the coal is less than 75 μm.
As a preferred embodiment of the preparation method of the porous carbon material for the super capacitor, in the step (1), the mass ratio of the coal to the potassium ferrate is 1 (1-5); the dosage ratio of the sulfuric acid to the potassium ferrate is 50ml (3-5 g).
As a preferred embodiment of the preparation method of the porous carbon material for the super capacitor, in the step (1), the stirring temperature is 30-50 ℃ and the stirring time is 0.5-2 h; the ultrasonic treatment time is 0.1-1 h; the temperature of the oxidation reaction is 60-100 ℃ and the time is 0.5-2 h; the concentration of the hydrogen peroxide is 5% -30%.
As a preferred implementation mode of the preparation method of the porous carbon material for the super capacitor, in the step (3), the mass ratio of the coal-based carbon points to the pore-forming agent is (0.2-0.3): (0.2-1); the dosage ratio of the assembling agent to the pore-forming agent is (3-20) ml (0.2-1) g; preferably, the dosage ratio of the assembling agent to the pore-forming agent is (3-10) ml (0.2-1) g; more preferably, the ratio of the amount of the assembling agent to the amount of the pore-forming agent is (3-5) ml (0.2-1) g.
As a preferred embodiment of the preparation method of the porous carbon material for the supercapacitor, the assembling agent is ammonia water; the concentration of the ammonia water is 20% -30%.
As a preferred embodiment of the preparation method of the porous carbon material for the super capacitor, the pore-forming agent is at least one of sodium bicarbonate, sodium carbonate, sodium chloride and sodium borohydride.
As a preferred implementation mode of the preparation method of the porous carbon material for the super capacitor, the temperature during carbonization is 600-900 ℃, the nitrogen flow is 20-80 ml/min, the heating rate is 2-10 ℃/min, and the heat preservation is carried out for 2-4 h after the carbonization temperature is reached.
In a second aspect, the invention provides 3D hierarchical pore carbon prepared by the preparation method.
In a third aspect, the preparation method and the 3D hierarchical pore carbon are applied to super capacitor carbon electrode materials.
Compared with the prior art, the invention has the beneficial effects that:
the invention prepares coal-based carbon dots by taking coal as raw material and assembles the coal-based carbon dots into 3D hierarchical pore carbon, and the prepared 3D hierarchical pore carbon has reasonable pore structure, high specific surface area utilization rate, continuous conductive network and high capacity retention rate.
In the preparation method, coal is oxidized into a carbon dot solution dissolved in water through oxidation, centrifugation, filtration and dialysis treatment in the preparation process of the coal-based carbon dot, and the influence of ash is not needed to be considered; the participation of strong alkali such as potassium hydroxide, sodium hydroxide and the like is avoided in the high-temperature carbonization process, the danger is low, and the service life of equipment is prolonged; in the assembly process of the 3D hierarchical pore carbon, the specific surface area and pore structure distribution of the 3D hierarchical pore carbon can be controlled by changing the types and the dosage of pore formers.
The 3D hierarchical pore carbon prepared by the method is suitable for super capacitor carbon electrode materials.
Drawings
FIG. 1 is a graph showing the fluorescence spectrum, UV-vis absorption spectrum, and fluorescence effect of aqueous solution thereof at 365nm ultraviolet lamp of the coal-based carbon point of example 1;
FIG. 2 is a scanning electron microscope image of the porous carbon material of example 1;
FIG. 3 is a GCD curve (three electrode system) of the porous carbon material of example 1 at different current densities;
FIG. 4 is a GCD curve (three electrode system) of the porous carbon material of example 2 at different current densities;
FIG. 5 is a CV curve (three electrode system) of the porous carbon material of example 2 at different scanning rates;
FIG. 6 is a graph of the capacity of the porous carbon material of example 2 at different current densities;
FIG. 7 is a scanning electron microscope image of the porous carbon material of example 3;
FIG. 8 is a CV curve (three electrode system) of the porous carbon material of example 3 at different scanning rates;
FIG. 9 is a CV curve (three electrode system) of the porous carbon material of example 4 at different scanning rates;
FIG. 10 is a fluorescence spectrum of coal-based carbon dots of example 5;
FIG. 11 is a scanning electron microscope image of the porous carbon material of example 5;
FIG. 12 is a pore structure distribution diagram of the porous carbon material of example 5;
FIG. 13 is a graph of the capacity of the porous carbon material of example 5 at different current densities;
FIG. 14 is a GCD curve (three electrode system) for the porous carbon material of example 6 at different current densities;
FIG. 15 is a graph of the capacity of the porous carbon material of example 6 at different current densities;
FIG. 16 is a GCD curve (three electrode system) for the porous carbon material of example 7 at different current densities;
FIG. 17 is a graph of the capacity of the porous carbon material of example 7 at different current densities;
FIG. 18 is a graph of the capacity of the porous carbon material of example 8 at different current densities;
FIG. 19 is a CV curve (three electrode system) at 5mV/s for the porous carbon material of example 9;
FIG. 20 shows the porous carbon material of example 10 at 0.5Ag -1 Lower GCD curve (three electrode system);
FIG. 21 shows that the porous carbon material of example 11 is 0.5Ag -1 GCD curve below (three electrode system).
Detailed Description
For a better description of the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to the following specific examples. It will be appreciated by persons skilled in the art that the specific embodiments described herein are for purposes of illustration only and are not intended to be limiting.
The test methods used in the examples are conventional methods unless otherwise specified; the materials, reagents and the like used, unless otherwise specified, are all commercially available.
Example 1: preparation method of porous carbon material for super capacitor
(1) Placing 1g of Taixi anthracite in 50ml of sulfuric acid, adding 5g of potassium ferrate, stirring for 1h at 40 ℃, carrying out ultrasonic treatment for 0.5h, centrifugally washing the reaction solution to be neutral, and adding 50ml of 30% hydrogen peroxide for oxidation for 1h at 100 ℃ to obtain a carbon dot solution;
(2) Dialyzing and freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) And (3) dissolving 0.3g of the coal-based carbon point obtained in the step (2) in 50ml of deionized water, adding 3ml of 25% ammonia water and 0.3g of sodium borohydride, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (nitrogen flow is 30ml/min, heating rate is 5 ℃/min, preserving heat for 3h after reaching carbonizing temperature, and then cooling to room temperature under nitrogen protection), washing and drying to obtain the porous carbon material for the supercapacitor. The material is 3D hierarchical pore carbon.
The fluorescence spectrum, UV-vis absorption spectrum of the coal-based carbon point and the fluorescence effect diagram of the aqueous solution under a 365nm ultraviolet lamp are shown in figure 1; the emission spectrum of the coal-based carbon point under different excitation wavelengths shows that the fluorescence characteristic has wavelength dependence, the emission center of the coal-based carbon point gradually moves red along with the increase of the excitation wavelength, the fluorescence intensity is in a trend of increasing first and then decreasing, and the fluorescence intensity is maximum when the excitation wavelength is 480 nm; from the uv-vis absorption spectrum of the coal-based carbon dots, it can be seen that the carbon dots have a strong uv absorption peak at 206nm, which corresponds to pi-pi transition; and the coal-based carbon point shows a fluorescent effect graph of yellow-green light under the irradiation of a 365nm ultraviolet lamp.
The scanning electron microscope of the 3D hierarchical pore carbon is shown in figure 2; as can be seen from the figure, the 3D hierarchical pore carbon has more pores and is in a three-dimensional intercommunication state, which is beneficial to the storage and transmission of charges.
The GCD curves (three electrode system) of 3D hierarchical pore carbons at different current densities are shown in figure 3. As can be seen from the graph, the GCD curve of the 3D hierarchical pore carbon is an isosceles triangle that is approximately symmetrical, which indicates that the 3D hierarchical pore carbon has good electrochemical reversibility, the specific capacitance decreases with increasing current density, and good symmetry is still maintained until the current density is 100A/g, which indicates that the 3D hierarchical pore carbon has excellent rate capability, which benefits from the 3D hierarchical porous structure in the material.
Example 2: preparation method of porous carbon material for super capacitor
(1) Placing 1g of Taixi anthracite in 50ml of sulfuric acid, adding 5g of potassium ferrate, stirring for 1h at 40 ℃, carrying out ultrasonic treatment for 0.5h, centrifugally washing the reaction solution to be neutral, and adding 50ml of 30% hydrogen peroxide for oxidation for 1h at 100 ℃ to obtain a carbon dot solution;
(2) Dialyzing and freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) And (3) dissolving 0.3g of the coal-based carbon point obtained in the step (2) in 50ml of deionized water, adding 3ml of 25% ammonia water and 1g of sodium borohydride, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (nitrogen flow is 30ml/min, heating rate is 5 ℃/min, preserving heat for 3h after reaching carbonizing temperature, and then cooling to room temperature under nitrogen protection), washing and drying to obtain the porous carbon material for the supercapacitor. The material is 3D hierarchical pore carbon.
The GCD curves (three electrode systems) of 3D hierarchical pore carbons at different current densities are shown in fig. 4; as can be seen from the graph, the GCD curve of the 3D hierarchical pore carbon is an isosceles triangle that is approximately symmetrical, which indicates that the 3D hierarchical pore carbon has good electrochemical reversibility, the specific capacitance decreases with increasing current density, and good symmetry is still maintained, until the current density is 100A/g, no obvious deformation occurs, which indicates that the 3D hierarchical pore carbon has excellent rate capability, which benefits from the 3D hierarchical porous structure. The specific capacitance of the material of this example was higher than that of the material prepared in example 1.
CV curves (three-electrode system) of the 3D hierarchical pore carbon at different scanning rates are shown in FIG. 5; it can be seen from the graph that the CV curve is deformed to some extent as the scanning rate increases from 5mV/s to 100mV/s, but still maintains a good quasi-rectangular shape, indicating that at higher scanning rates, the electrolyte ions still exhibit rapid ionic responses, further indicating good ploidy when the 3D hierarchical pore carbon is used as the electrode material of a supercapacitor. There is a distinct redox peak between-0.8V and-0.6V, which suggests that sodium borohydride not only can pore-form, but also can introduce heteroatom B, helping to improve electrochemical performance.
The capacity of the 3D hierarchical pore carbon at different current densities is shown in fig. 6. As can be seen from the graph, the specific capacitance of the material was 253.5F/g at a current density of 0.5A/g, and gradually decreased with an increase in current density, and the specific capacitance of the material was still kept at 185.1F/g at a current density of 100A/g, with a capacity retention of 73%, and good rate performance.
Example 3: preparation method of porous carbon material for super capacitor
(1) Placing 1g of Taixi anthracite in 50ml of sulfuric acid, adding 5g of potassium ferrate, stirring for 1h at 40 ℃, carrying out ultrasonic treatment for 0.5h, centrifugally washing the reaction solution to be neutral, and adding 50ml of 30% hydrogen peroxide for oxidation for 1h at 100 ℃ to obtain a carbon dot solution;
(2) Dialyzing and freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) And (3) dissolving 0.3g of the coal-based carbon point obtained in the step (2) in 50ml of deionized water, adding 5ml of 25% ammonia water and 0.5g of sodium carbonate, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (nitrogen flow is 30ml/min, heating rate is 5 ℃/min, preserving heat for 3h after reaching carbonizing temperature, and then cooling to room temperature under nitrogen protection), washing and drying to obtain the porous carbon material for the supercapacitor. The material is 3D hierarchical pore carbon.
The scanning electron microscope of the 3D hierarchical pore carbon is shown in figure 7; from the figure, under the high-magnification scanning electron microscope, the 3D hierarchical pore carbon surface can be seen to be full of macroscopic pores.
CV curves (three-electrode system) of the 3D hierarchical pore carbon at different scanning rates are shown in FIG. 8; it can be seen from the graph that the CV curve is deformed to some extent as the scan rate increases from 5mV/s to 200mV/s, but still maintains a good quasi-rectangular shape, indicating that at higher scan rates, the electrolyte ions still exhibit a rapid ionic response, further indicating good ploidy of the 3D hierarchical pore carbon as electrode material for supercapacitors. Compared with the material prepared in example 1, the CV curve of the material in this example is rectangular, and has no obvious oxidation-reduction peak, which indicates that the material has good electric double layer characteristics, and the capacitance is mainly provided by the electric double layer, and has no obvious pseudocapacitance.
Example 4: preparation method of porous carbon material for super capacitor
(1) Placing 1g of Taixi anthracite in 50ml of sulfuric acid, adding 5g of potassium ferrate, stirring for 1h at 40 ℃, carrying out ultrasonic treatment for 0.5h, centrifugally washing the reaction solution to be neutral, and adding 50ml of 30% hydrogen peroxide for oxidation for 1h at 100 ℃ to obtain a carbon dot solution;
(2) Dialyzing and freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) And (3) dissolving 0.2g of the coal-based carbon point obtained in the step (2) in 100ml of deionized water, adding 5ml of 25% ammonia water, 0.2g of sodium borohydride and 0.2g of sodium bicarbonate, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (the nitrogen flow is 60ml/min, the heating rate is 8 ℃/min, preserving heat for 3 hours after reaching the carbonizing temperature, cooling to room temperature under the protection of nitrogen), and washing and drying to obtain the porous carbon material for the supercapacitor. The material is 3D hierarchical pore carbon.
The CV curves (three electrode systems) of the 3D hierarchical pore carbon at different scanning rates are shown in FIG. 9; as can be seen from the graph, the CV curve is deformed to some extent as the scan rate increases from 5mV/s to 200mV/s, but still maintains a good quasi-rectangular shape, indicating that at higher scan rates, the electrolyte ions still exhibit a rapid ionic response, further indicating that the 3D hierarchical pore carbon of this embodiment has good doubling as electrode material for supercapacitors.
Example 5: preparation method of porous carbon material for super capacitor
(1) Placing 1g of crane wall bituminous coal into 50ml of sulfuric acid, adding 4g of potassium ferrate, stirring for 1h at 40 ℃, carrying out ultrasonic treatment for 0.5h, centrifugally washing the reaction solution to be neutral, and adding 50ml of 25% hydrogen peroxide for oxidation for 1h at 90 ℃ to obtain a carbon dot solution;
(2) Dialyzing and freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) And (3) dissolving 0.3g of the coal-based carbon point obtained in the step (2) in 50ml of deionized water, adding 3ml of 25% ammonia water and 0.3g of sodium borohydride, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (the nitrogen flow is 40ml/min, the heating rate is 5 ℃/min, preserving heat for 3h after reaching the carbonizing temperature, and then cooling to room temperature under the protection of nitrogen), washing and drying to obtain the porous carbon material for the supercapacitor. The material is 3D hierarchical pore carbon.
The coal-based carbon point fluorescence spectrum is shown in fig. 10; as can be seen from the graph, the fluorescence intensity gradually increases as the excitation wavelength increases from 260nm to 360nm, but the emission center is unchanged, fixed at 532nm, and the material does not have wavelength dependence, which is different from the material of example 1, which shows that the coal type is different, and the coal-based carbon dots prepared by the same method have different fluorescence properties.
The scanning electron microscope image of the 3D hierarchical pore carbon is shown in FIG. 11. In the figure, it can be seen that the 3D hierarchical pore carbon is not formed by stacking small particles, but rather that the carbon dots are assembled into a three-dimensional block structure having a hierarchical pore structure of "macropores nested mesopores, micropores".
The pore structure distribution diagram of the 3D hierarchical pore carbon is shown in fig. 12. From the graph, the pore diameter of the material is mainly divided into micropores with the diameter of 1-2 nm and mesopores with the diameter of 2-5 nm, the calculated mesopore ratio is 64.6%, and the material can be fully proved to have a 3D hierarchical pore structure by combining a scanning electron microscope.
The GCD curves (three electrode system) of 3D hierarchical pore carbons at different current densities are shown in fig. 13. As can be seen from the graph, the specific capacitance of the material was 239.9F/g at a current density of 0.5A/g, and gradually decreased with an increase in current density, and the specific capacitance of the material was 165.1F/g at a current density of 100A/g, with a capacity retention of 69%, and good rate performance.
Example 6: preparation method of porous carbon material for super capacitor
(1) Putting 1g of Hebei Xue Cunkuang bituminous coal into 50ml of sulfuric acid, adding 4g of potassium ferrate, stirring for 1h at 40 ℃, carrying out ultrasonic treatment for 0.5h, centrifugally washing the reaction solution to be neutral, and adding 50ml of 20% hydrogen peroxide for oxidation for 1h at 100 ℃ to obtain a carbon dot solution;
(2) Dialyzing and freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) And (3) dissolving 0.2g of the coal-based carbon point obtained in the step (2) in 50ml of deionized water, adding 5ml of 25% ammonia water and 0.2g of sodium bicarbonate, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (nitrogen flow is 40ml/min, heating rate is 5 ℃/min, preserving heat for 3h after reaching carbonizing temperature, and then cooling to room temperature under nitrogen protection), washing and drying to obtain the porous carbon material for the supercapacitor. The material is 3D hierarchical pore carbon.
The GCD curves (three electrode system) of 3D hierarchical pore carbons at different current densities are shown in fig. 14. As can be seen from the graph, the GCD curve of the 3D hierarchical pore carbon is an isosceles triangle that is approximately symmetrical, which indicates that the 3D hierarchical pore carbon has good electrochemical reversibility, the specific capacitance decreases with increasing current density, but good symmetry is still maintained, until the current density is 100A/g, no obvious deformation still occurs, which indicates that the material has excellent rate capability, which benefits from the 3D hierarchical porous structure thereof.
The capacity of the 3D hierarchical pore carbon at different current densities is shown in figure 15. As can be seen from the graph, the specific capacitance of the material was 300.4F/g at a current density of 0.5A/g, and gradually decreased with an increase in current density, and the specific capacitance of the material was maintained at 179.5F/g at a current density of 100A/g, with a capacity retention of 59%, and good rate performance.
Example 7: preparation method of porous carbon material for super capacitor
(1) Placing 1g of inner Mongolian lignite into 50ml of sulfuric acid, adding 3g of potassium ferrate, stirring for 0.5h at 40 ℃, performing ultrasonic treatment for 0.5h, centrifugally washing the reaction solution to be neutral, and adding 50ml of 15% hydrogen peroxide for oxidation for 1h at 80 ℃ to obtain a carbon dot solution;
(2) Dialyzing and freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) And (3) dissolving 0.3g of the coal-based carbon point obtained in the step (2) in 50ml of deionized water, adding 3ml of 25% ammonia water and 0.3g of sodium borohydride, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (the nitrogen flow is 40ml/min, the heating rate is 5 ℃/min, preserving heat for 3h after reaching the carbonizing temperature, and then cooling to room temperature under the protection of nitrogen), washing and drying to obtain the porous carbon material for the supercapacitor. The material is 3D hierarchical pore carbon.
The GCD curves (three electrode system) of 3D hierarchical pore carbons at different current densities are shown in fig. 16. As can be seen from the graph, the GCD curve of the 3D hierarchical pore carbon is an isosceles triangle that is approximately symmetrical, which indicates that the 3D hierarchical pore carbon has good electrochemical reversibility, the specific capacitance decreases with increasing current density, but good symmetry is still maintained, until the current density is 100A/g, no obvious deformation still occurs, which indicates that the material has excellent rate capability, which benefits from the 3D hierarchical porous structure thereof.
The capacity of the 3D hierarchical pore carbon at different current densities is shown in figure 17. As can be seen from the graph, the specific capacitance of the material was 272.9F/g at a current density of 0.5A/g, and gradually decreased with an increase in current density, and the specific capacitance of the material was kept at 155.7F/g at a current density of 100A/g, with a capacity retention of 57%, and good rate performance.
Example 8: preparation method of porous carbon material for super capacitor
(1) Coal-based carbon dots were prepared by the methods of example 1 (anthracite), example 5 (bituminous coal), and example 7 (lignite), respectively;
(2) And (3) respectively dissolving 0.3g of the coal-based carbon point obtained in the step (1) in 50ml of deionized water, adding 50ml of 25% ammonia water and 0.3g of sodium borohydride, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (the nitrogen flow is 40ml/min, the heating rate is 5 ℃/min, preserving heat for 3 hours after reaching the carbonizing temperature, and then cooling to room temperature under the protection of nitrogen), washing and drying to obtain the porous carbon material for 3 super capacitors. The 3 materials are 3D hierarchical pore carbon.
The capacity of the 3D hierarchical pore carbon at different current densities is shown in figure 18. CV curves (three electrode systems) of 3D hierarchical pore carbons at a scan rate of 5mV/s are shown in FIG. 19; as can be seen from the graph, the specific capacitance decreases with increasing coal level, but the rate performance increases.
Example 9: preparation method of porous carbon material for super capacitor
(1) Placing 1g of crane wall bituminous coal into 50ml of sulfuric acid, adding 4g of potassium ferrate, stirring for 1h at 40 ℃, carrying out ultrasonic treatment for 0.5h, centrifugally washing the reaction solution to be neutral, and adding 50ml of 25% hydrogen peroxide for oxidation for 1h at 90 ℃ to obtain a carbon dot solution;
(2) Dialyzing and freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) Dissolving 0.3g of the coal-based carbon point obtained in the step (2) in 50ml of deionized water, respectively adding 3ml of 25% ammonia water and 0.3g, 0.4g, 0.5g and 1g of sodium borohydride, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (the nitrogen flow is 40ml/min, the heating rate is 5 ℃/min, preserving heat for 3 hours after reaching the carbonizing temperature, cooling to room temperature under the protection of nitrogen), and washing and drying to obtain the porous carbon material for 4 super capacitors. The 4 materials are 3D hierarchical pore carbon.
The specific capacitances of the 4 3D hierarchical pore carbons at different current densities (symmetric supercapacitor two electrode system) are shown in table 1.
Table 1 specific capacitance of materials at different current densities
| Sodium borohydride | 0.5A/g | 1A/g | 2A/g | 5A/g | 10A/g | 20A/g | 50A/g |
| 1g | 125.22 | 124.64 | 123.01 | 117.72 | 112.05 | 105.65 | 94.58 |
| 0.5g | 146.89 | 142.98 | 138.26 | 131.24 | 126.39 | 120.27 | 110.66 |
| 0.4g | 164.51 | 160.29 | 155.79 | 149.83 | 145.46 | 138.83 | 121.13 |
| 0.3g | 155.22 | 154.28 | 149.73 | 143.22 | 137.82 | 129.14 | 86.43 |
Example 10: preparation method of porous carbon material for super capacitor
(1) Placing 1g of crane wall bituminous coal into 50ml of sulfuric acid, adding 4g of potassium ferrate, stirring for 1h at 40 ℃, centrifugally washing the reaction solution to be neutral after ultrasonic treatment for 0.5h, adding 50ml of 25% hydrogen peroxide for oxidation for 1h, and respectively carrying out oxidation treatment at 80 ℃,90 ℃ and 100 ℃; obtaining 3 carbon dot solutions;
(2) Dialyzing, freeze-drying the obtained 3 carbon point solutions to obtain 3 coal-based carbon points;
(3) And (3) respectively dissolving 0.3g of the 3 coal-based carbon points obtained in the step (2) in 50ml of deionized water, adding 3ml of 25% ammonia water and 0.3g of sodium borohydride, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (the nitrogen flow is 40ml/min, the heating rate is 5 ℃/min, preserving heat for 3 hours after reaching the carbonizing temperature, and then cooling to room temperature under the protection of nitrogen), washing and drying to obtain the 3 porous carbon materials for the super capacitor. The 3 materials are 3D hierarchical pore carbon.
The specific capacitances (three electrode systems) of the 3D hierarchical pore carbons at different current densities are shown in table 2.
Table 2 specific capacitance of materials at different current densities
| Temperature (temperature) | 0.5A/g | 1A/g | 2A/g | 5A/g | 10A/g | 20A/g | 50A/g | 100A/g | 200A/g |
| 80℃ | 191.6 | 177.6 | 172.0 | 168.8 | 155.1 | 149.3 | 141.9 | 102.9 | / |
| 90℃ | 239.9 | 208.6 | 200.4 | 197.8 | 187.7 | 182.7 | 177.1 | 174.9 | 165.0 |
| 100℃ | 204.1 | 187.3 | 181.6 | 173.3 | 162.8 | 159.4 | 150.1 | 144.7 | / |
3 kinds of 3D hierarchical pore carbon are 0.5Ag -1 The GCD curve under the current density is shown in FIG. 20, and it can be seen from the graph that the 3D hierarchical pore carbon prepared at the oxidation temperature of 90 ℃ has the longest charge and discharge time, which is illustrated as 0.5Ag -1 The specific capacitance of the 3D hierarchical pore carbon prepared at the oxidation temperature of 90 ℃ under the current density is highest.
Example 11: preparation method of porous carbon material for super capacitor
(1) Placing 1g of crane wall bituminous coal into 50ml of sulfuric acid, adding 4g of potassium ferrate, stirring for 1h at 40 ℃, carrying out ultrasonic treatment for 0.5h, centrifugally washing the reaction solution to be neutral, and adding 50ml of 25% hydrogen peroxide for oxidation at 90 ℃ for 1h to obtain a carbon dot solution;
(2) Dialyzing and freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) Dissolving 0.3g of the coal-based carbon point obtained in the step (2) in 50ml of deionized water, respectively adding 0ml, 3ml and 10ml of 25% ammonia water and 0.3g of sodium borohydride, stirring, drying, carbonizing in a nitrogen atmosphere at 800 ℃ (the nitrogen flow is 40ml/min, the heating rate is 5 ℃/min, preserving heat for 3 hours after reaching the carbonizing temperature, cooling to room temperature under the protection of nitrogen), washing and drying to obtain the porous carbon material for 3 super capacitors. The 3 materials are 3D hierarchical pore carbon.
The specific capacitances (three electrode systems) of the 3D hierarchical pore carbons at different current densities are shown in table 3.
TABLE 3 specific capacitance of materials at different current densities
| Ammonia water | 0.5A/g | 1A/g | 2A/g | 5A/g | 10A/g | 20A/g | 50A/g | 100A/g | 200A/g |
| 0ml | 145.4 | 127.1 | 113 | 94.3 | 82.5 | 69.8 | 46.5 | / | / |
| 3ml | 239.9 | 208.6 | 200.4 | 197.8 | 187.7 | 182.7 | 177.1 | 174.9 | 165.0 |
| 10ml | 222.3 | 209.1 | 199.7 | 196.3 | 185.6 | 180.1 | 178.5 | 172.3 | 163.4 |
3 kinds of 3D hierarchical pore carbon are 0.5Ag -1 The GCD curve under the current density is shown in FIG. 21, and it can be seen from the graph that the 3D hierarchical pore carbon prepared from 3ml of ammonia water has the longest charge and discharge time, which is illustrated in 0.5Ag -1 The specific capacitance of the 3D hierarchical pore carbon prepared by 3ml of ammonia water under the current density is highest.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present invention.
Claims (6)
1. The preparation method of the porous carbon material for the super capacitor is characterized by comprising the following steps of:
(1) Putting coal into sulfuric acid, adding potassium ferrate, and stirring to obtain a reaction solution; performing ultrasonic treatment on the obtained reaction liquid, and centrifugally washing to neutrality; adding hydrogen peroxide for oxidation reaction to obtain a carbon dot solution;
the mass ratio of the coal to the potassium ferrate is 1 (1-5); the dosage ratio of the sulfuric acid to the potassium ferrate is 50ml (3-5 g);
the temperature of the oxidation reaction is 90 ℃ and the time is 0.5-2 h; the concentration of the hydrogen peroxide is 5% -30%;
(2) Dialyzing, freeze-drying the obtained carbon dot solution to obtain coal-based carbon dots;
(3) Dissolving the obtained coal-based carbon dots in water, adding an assembling agent and a pore-forming agent, stirring, drying, carbonizing under nitrogen atmosphere, cooling, washing with water, and drying to obtain the final product;
the assembling agent is ammonia water; the concentration of the ammonia water is 20% -30%;
the pore-forming agent is at least one of sodium bicarbonate, sodium carbonate, sodium chloride and sodium borohydride;
the mass ratio of the coal-based carbon point to the pore-forming agent is (0.2-0.3): 0.2-1; the dosage ratio of the assembling agent to the pore-forming agent is (3-20) ml (0.2-1) g.
2. The method for producing a porous carbon material for supercapacitors according to claim 1, wherein in step (1), the coal is at least one of anthracite, bituminous coal, and lignite; the particle size of the coal is less than 75 μm.
3. The method for preparing a porous carbon material for a supercapacitor according to claim 1, wherein in the step (1), the stirring temperature is 30-50 ℃ for 0.5-2 hours; the ultrasonic treatment time is 0.1-1 h.
4. The method for preparing a porous carbon material for a supercapacitor according to claim 1, wherein in the step (3), the temperature at the carbonization is 600-900 ℃, the nitrogen flow is 20-80 ml/min, the heating rate is 2-10 ℃/min, and the heat preservation is performed for 2-4 hours after the carbonization temperature is reached.
5. A 3D hierarchical pore carbon prepared by the method of any one of claims 1 to 4.
6. The use of the 3D hierarchical pore carbon of claim 5 in a supercapacitor carbon electrode material.
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| CN109437154A (en) * | 2018-10-25 | 2019-03-08 | 河南理工大学 | A method of the controllable carbon quantum dot of energy band is prepared by raw material of coal |
| CN111960403A (en) * | 2020-08-31 | 2020-11-20 | 西南大学 | Preparation method of coal tar-based nitrogen-doped porous carbon material, product thereof and application of product in super capacitor |
| CN112908717A (en) * | 2021-01-21 | 2021-06-04 | 西南大学 | Preparation method of composite electrode material and product thereof |
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