CN107697913B - Preparation method of walnut shell-based high-capacitance graded porous carbon - Google Patents
Preparation method of walnut shell-based high-capacitance graded porous carbon Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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, LIGHT-SENSITIVE OR TEMPERATURE-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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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Abstract
The invention relates to the field of electrochemical energy storage materials, in particular to a preparation method of walnut shell-based high-capacitance graded porous carbon. The method directly takes biomass walnut shells which are rich in raw materials and low in price as raw materials, takes dilute hydrochloric acid as a reaction medium, and adopts microwave treatment for several minutes to obtain a precursor product with a part of fiber structure expansion; after washing and drying treatment, KOH soaking treatment is carried out, then carbonization treatment is carried out for 1-2h at the temperature of 900 ℃ with high temperature of 700-. And finally, using the prepared porous carbon material as a supercapacitor electrode material. The invention provides a method for preparing the graded porous carbon material with green, environment-friendly, low cost and fast speed, the method has good universality, the economic value of the biomass material with low added value is greatly improved, and a high-performance electrode material is provided for the super capacitor.
Description
Technical Field
The invention relates to the technical field of electrochemical energy storage material synthesis, in particular to a preparation method of walnut shell-based high-capacitance graded porous carbon.
Background
The activated carbon has the advantages of high specific surface area, good conductivity, wide raw material source and the like, is widely used in the fields of water treatment, food industry decoloration, precious metal recovery and catalysis, and has increasingly prominent application in novel energy storage devices such as super capacitors, lithium ion batteries and the like in recent years. Hierarchical Porous Active Carbon (HPAC) not only has rich pore structure but also has reasonable pore structure distribution of different pore diameters, and the pore passages are mutually communicated, thereby being beneficial to the permeation of electrolyte and the rapid transmission of ions and having huge potential application value in a novel energy storage device super capacitor. The current feedstocks for HPAC production are mainly polymeric carbon sources and biomass carbon sources. The pore-forming method in the carbon source comprises a polymer carbon source taking an inorganic substance as a template (such as metal oxide and silicon dioxide), a polymer template and a metal organic framework self as the template. The porous structure in the carbon material is generally achieved by a physical activation method, a chemical activation method, and a template method. In order to obtain a precise pore structure and pore size distribution range, a templating method is generally used. The template method is generally classified into a hard template method and a soft template method. The hard template method mainly refers to a method of uniformly mixing a hard template agent and a precursor or soaking a carbon precursor into a template, carbonizing the precursor in the template at a high temperature, and removing the template to form a pore channel. The soft template method mainly uses an organic matter which can be automatically and completely decomposed in an inert atmosphere at a high temperature as a template, the organic matter is uniformly combined with a carbon precursor, the carbon-containing precursor is carbonized after high-temperature treatment to obtain a porous carbon material, and the soft template agent is decomposed to form a pore channel. For example, Meng et al prepared ordered mesoporous carbon materials using polyether F127 as a soft template and phenolic resin oligomers as a carbon source. These preparation methods are relatively complex and expensive, which limits the large-scale application of the hierarchical porous carbon material in energy storage devices. Compared with a polymer precursor supported by a template, the natural product or biomass material is basically a renewable resource and has the advantages of low price and environmental friendliness, and due to the characteristic network structure, the biomass is easily converted into the porous material with rich pore structures only by proper activation treatment, so that the hierarchical porous carbon material taking the biomass as the carbon source has better application prospect.
At present, the biomass which can be prepared into the porous carbon material is reported to be banana peel, bagasse, sunflower seed hulls, bamboo, wheat straw, camellia oleifera hulls and the like. The walnut has abundant nutritive value and huge annual consumption, the walnut cultivation area in China is the first in the world, the walnut yield is higher than 80 ten thousand tons every year since 2008 according to statistics, and the walnut yield is in an increasing trend every year. The walnut shells account for about 30% of the total walnut, and it can be seen that the walnut shells yield about 24 million tons per year, and these walnut shells are usually discarded or incinerated as waste. In fact, the ash content of the walnut shells is 0.66%, the moisture content is 9.59%, the benzene alcohol extract is 3.71%, the lignin content is 38.05%, the cellulose content is 30.88%, and the hemicellulose content is 27.66%, so that the walnut shells are discarded or incinerated, and great resource waste is caused. If the waste is deeply processed, the added value of the waste is improved, so that the solid waste can be effectively treated, the waste can be changed into valuable, and the comprehensive utilization value of the waste is improved. The method has the advantages that walnut shells with wide sources are used as carbon sources, a mild template-free method is developed to prepare the hierarchical porous activated carbon HPAC, and the hierarchical porous activated carbon HPAC is used as the electrode material of the supercapacitor, so that the utilization value of the walnut shells can be improved, meanwhile, a selectable high-performance electrode material is provided for the supercapacitor, and the method has important practical significance.
Disclosure of Invention
Based on the technical problems, the invention provides a preparation method of the walnut shell-based high-capacitance graded porous carbon. The method is green, environment-friendly, low in cost, rapid in preparation and good in universality, can greatly improve the economic value of the biomass material with low additional value, and also provides a high-performance electrode material for the super capacitor.
The specific technical scheme of the invention is as follows:
a preparation method of high-capacitance graded porous carbon based on walnut shells comprises the following steps:
(1) crushing raw materials, namely soaking walnut shells in distilled water to remove surface impurities, then placing the walnut shells in a drying oven at 60 ℃ to dry the walnut shells to constant weight, then crushing the walnut shells by using a crusher to obtain powdered walnut shell powder, and sieving the powdered walnut shell powder by using a 60-mesh sieve to obtain the walnut shell powder (the particle size is about 200 mu m).
(2) Weighing a certain amount of walnut powder in a conical flask filled with 2mol/L hydrochloric acid solution for microwave pre-activation, and keeping the mass g of solids: stirring for 0.5-1 h with the liquid volume mL =1: 10-15, then transferring the mixture into a microwave oven, heating for 10-15min under the microwave power condition of 320-800W to obtain a dark brown paste, naturally cooling, performing suction filtration, repeatedly washing the paste to be neutral by using distilled water, and drying the paste in an oven at the temperature of 80-100 ℃ for 12h to obtain the pretreated walnut shell powder.
(3) Drying, weighing the pretreated walnut shell powder and KOH according to a certain mass ratio, adding a certain amount of distilled water, and keeping the solid mass g: the volume of the liquid mL =1: 10-15, the liquid is uniformly stirred, soaked for 6-12h, and then transferred into an oven to be dried for more than 12h at 80-100 ℃ to form a solid.
(4) Finally, 2.0-3.0g of the powder dried in the step (3) is taken to be added into a tubular furnace after one-step carbonization treatment, and the mixture is subjected to N reaction2Under protection, at 3-5 deg.C for min-1The temperature rising rate is increased to 300 ℃, kept for 0.5 to 1.0 hour, then continuously increased to 700 to 900 ℃, kept for 1 to 2 hours, and fully carbonized and activated。
(5) And (3) after the carbide is subjected to post-treatment, naturally cooling the carbide, taking out the carbide product, washing the carbide product with 0.1mol/L hydrochloric acid and distilled water in sequence to remove redundant KOH, fully exposing pore channels in the carbon material, and transferring the filter cake to an oven for drying after the carbon material is washed to be neutral, thereby obtaining the graded porous carbon.
Electrode preparation, weighing a certain mass of porous carbon powder, acetylene black and polyvinylidene fluoride in a mass ratio of 80:10:10 in an agate mortar, fully grinding, dropwise adding 0.40-0.55 mL of N-methyl pyrrolidone, uniformly mixing, mixing into paste, and uniformly coating on the surface of foamed nickel (the coating area is controlled to be 1 × 1 cm)2) And then, drying the electrode in an oven at 80 ℃ overnight to obtain the electrode plate for testing.
The electrochemical performance test of the capacitance performance test electrode material is carried out on a CHI660D electrochemical workstation, and the test system is a standard three-electrode system, wherein in the electrochemical test process, a modified electrode of porous carbon is used as a working electrode, a platinum electrode is used as a counter electrode, an Hg/HgO electrode is used as a reference electrode, and 6.0mol/L KOH solution is used as electrolyte.
The positive effects of the invention are as follows:
according to the method, biomass walnut shells are directly used as raw materials, are subjected to rapid microwave-assisted acid treatment, are directly used as chemical activators, and are subjected to one-step carbonization treatment to prepare the hierarchical porous carbon with rich pore structures. The process mainly relates to a rapid microwave pretreatment process and a high-temperature treatment process combining carbonization and activation treatment, namely, the porous carbon with a good structure can be prepared by a simple pre-activation and high-temperature carbonization two-step method. The whole process of the method does not need multistep high-temperature treatment, does not relate to reaming processes such as steam treatment and the like, and can obtain a final product only by simple microwave pretreatment and one-step carbonization, so that the process route is greatly simplified, the cost is reduced, the method has strong universality, almost all biomasses are applicable, and the obtained product has an excellent capacitance energy storage effect and shows potential practical value.
Drawings
FIG. 1 is a process flow diagram for HPAC preparation of the product of the present invention
FIG. 2 is an infrared spectrum of walnut powder processed by different microwave powers
FIG. 3 is an X-ray diffraction pattern of HPAC obtained by different microwave power pre-activation and high temperature activation
FIG. 4 is a scanning electron micrograph of HPAC obtained after different microwave power treatments and high temperature activation of KOH
FIG. 5 shows the cyclic voltammograms (A) of HPAC obtained after high temperature activation of materials treated with different microwaves (scan rate 10mV/s) and the corresponding specific capacitances (B) at different scan rates;
FIG. 6 shows the (A) nitrogen adsorption/desorption curve and (B) pore size distribution of the HPAC hierarchical porous carbon material obtained after the microwave treatment
Detailed Description
The present invention will be further illustrated below with reference to specific examples and comparative examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes and modifications of the present invention may be made by those skilled in the art after reading the teachings of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
In the following examples, the solid-to-liquid ratio refers to the ratio of the mass of solid g to the volume of liquid ml unless otherwise specified.
Example 1 (without microwave-assisted activation)
(1) And (3) weighing fully dried walnut shell powder 2.0g and 4.0g of KOH (ensuring the mass ratio, pretreatment powder: KOH =1: 1-3), adding 25mL of distilled water (ensuring the mass-volume ratio of solid to liquid of 1: 4-10), uniformly stirring, soaking for 6-12h, and transferring to an oven to dry into a solid at 80-100 ℃. Then crushing by a crusher to obtain powdered walnut shell powder, and sieving by a 60-mesh sieve to obtain walnut shell powder (the particle size is about 200 mu m).
(2) Adding 2.0-3.0g of potassium hydroxide and walnut shell powder mixture into a tubular furnace in one-step carbonization treatment, and adding N2Under protection, at 3-5 deg.C for min-1The temperature rising rate is increased to about 300 ℃, the temperature is kept for 0.5h, and then the temperature is continuously raisedKeeping the temperature at 800 ℃ for 2h to fully carbonize and activate the active carbon.
(3) And (3) after the carbide is subjected to post-treatment, naturally cooling the carbide, taking out the carbide product, washing the carbide product with 0.1mol/L hydrochloric acid and distilled water in sequence to remove redundant KOH, fully exposing pore channels in the carbon material, and transferring the filter cake to an oven for drying after the carbon material is washed to be neutral, thereby obtaining the graded porous carbon.
(4) The electrode preparation method comprises the steps of weighing porous carbon powder, acetylene black and polyvinylidene fluoride in a mass ratio of 80:10:10, putting the porous carbon powder, the acetylene black and the polyvinylidene fluoride in an agate mortar, fully grinding, dropwise adding 0.40-0.55 mL of N-methyl pyrrolidone, uniformly mixing, mixing into paste, uniformly coating on the surface of foamed nickel, and then putting the electrode in an oven at 80 ℃ for drying overnight to obtain the electrode slice for testing.
(5) The electrochemical performance test of the capacitance performance test electrode material is carried out on a CHI660D electrochemical workstation, and the test system is a standard three-electrode system, wherein in the electrochemical test process, a modified electrode of porous carbon is used as a working electrode, a platinum electrode is used as a counter electrode, an Hg/HgO electrode is used as a reference electrode, and 6.0mol/L KOH solution is used as electrolyte.
(6) The product detection result is shown in the infrared spectrum analysis result of fig. 2, and the blank walnut powder structure contains a large amount of hydroxyl and carbonyl structures. XRD results of the carbonized product (see FIG. 3) showed 25 to 28oThe broad peak of the range corresponds to the peak of amorphous carbon, in the range of 40-43oThe broad peak of the range belongs to the peak of the graphite structure, which shows that the product has poor crystallinity and is amorphous. The SEM result of FIG. 4 shows that a part of the porous structure is formed in the material after the high-temperature carbonization porogenic treatment; the specific capacitance of FIG. 5 can reach 165F g at 5mV/s-1124F g at 100mV/s-1。
Example 2 (microwave power 320W)
(1) Crushing, namely soaking walnut shells in distilled water to remove surface impurities, then placing the walnut shells in a drying oven at 60 ℃ to dry the walnut shells to constant weight, crushing the walnut shells by using a crusher to obtain powdered walnut shell powder, and sieving the powdered walnut shell powder by using a 60-mesh sieve to obtain walnut shell powder;
(2) weighing 5.0g of walnut shell powder in a microwave preactivation manner, adding the walnut shell powder into a conical flask, adding 50mL of dilute hydrochloric acid solution (2mol/L), stirring for 0.5-1 h, transferring the walnut shell powder into a microwave oven, heating for 10-15min under the condition of microwave power of 320W to obtain a dark brown paste, naturally cooling, performing suction filtration, repeatedly washing with distilled water to neutrality, and drying in the oven at 80-100 ℃ for 12h to obtain the pretreated walnut shell powder.
(3) And (3) drying and weighing 2.0g and 4.0g of KOH (ensuring the mass ratio, the pretreated powder: KOH =1: 1-3), adding 25mL of distilled water (ensuring the solid-liquid mass-volume ratio of 1: 4-10), uniformly stirring, soaking for 6-12h, and then transferring to an oven to dry into a solid at 80-100 ℃.
(4) Performing one-step carbonization treatment, and finally adding 2.0-3.0g of potassium hydroxide and the walnut powder mixture dried in the step (3) into a tubular furnace, wherein N is2Under protection, at 3-5 deg.C for min-1The temperature rise rate is increased to about 300 ℃, the temperature is kept for 0.5h, the temperature is continuously increased to 800 ℃ and kept for 2h, and the carbon is fully carbonized and activated.
(5) And (3) after the carbide is subjected to post-treatment, naturally cooling the carbide, taking out the carbide product, washing the carbide product with 0.1mol/L hydrochloric acid and distilled water in sequence to remove redundant KOH, fully exposing pore channels in the carbon material, and transferring the filter cake to an oven for drying after the carbon material is washed to be neutral, thereby obtaining the graded porous carbon. The drying temperature is 80-100 ℃.
(6) The electrode preparation method comprises the steps of weighing porous carbon powder, acetylene black and polyvinylidene fluoride in a mass ratio of 80:10:10, putting the porous carbon powder, the acetylene black and the polyvinylidene fluoride in an agate mortar, fully grinding, dropwise adding 0.40-0.55 mL of N-methyl pyrrolidone, uniformly mixing, mixing into paste, uniformly coating on the surface of foamed nickel, and then putting the electrode in an oven at 80 ℃ for drying overnight to obtain the electrode slice for testing.
(7) The electrochemical performance test of the capacitance performance test electrode material is carried out on a CHI660D electrochemical workstation, and the test system is a standard three-electrode system, wherein in the electrochemical test process, a modified electrode of porous carbon is used as a working electrode, a platinum electrode is used as a counter electrode, an Hg/HgO electrode is used as a reference electrode, and 6.0mol/L KOH solution is used as electrolyte.
(8) Product detection results the infrared light of FIG. 2The result of the spectrum analysis shows that the hydroxyl peak and the carbonyl peak after the microwave power is 3200W pretreatment are slightly reduced compared with that of a blank sample, which indicates that chemical bonds in the blank sample are damaged to a certain degree in the microwave treatment. XRD results of the carbonized product (see FIG. 3) showed 25 to 28oThe broad peak of the range corresponds to the peak of amorphous carbon, in the range of 40-43oThe broad peak of the range was assigned to the peak of the graphite structure, indicating that the product was less crystalline and essentially amorphous. The SEM results of fig. 4 show that it is a loose porous structure; the specific capacitance of the capacitor in FIG. 5 can reach 170F g at 5mV/s-1And can reach 129F g at 100mV/s-1。
Example 3 (microwave power 480W)
(1) The preparation method of the walnut shell powder is the same as the step (1) in the example 2;
(2) weighing 5.0g of walnut powder in a conical flask by microwave preactivation, adding 50mL of dilute hydrochloric acid solution (2mol/L), stirring for 0.5-1 h, transferring the walnut powder into a microwave oven, heating for 10-15min under the condition of microwave power of 480W to obtain dark brown paste, naturally cooling, performing suction filtration, repeatedly washing with distilled water to neutrality, and drying in an oven at 80-100 ℃ for 12 h.
Steps (3) to (7) were the same as those described in example 2.
(8) The product detection results are shown in the infrared spectrum analysis result of fig. 2, and the hydroxyl peak and carbonyl peak after the microwave power is 480W pretreatment are reduced compared with those of the blank sample and the 320W treatment, which indicates that the chemical bonds in the blank sample are damaged to a greater extent in the microwave treatment. XRD results of the carbonized product (see FIG. 3) showed 25 to 28oThe broad peak of the range corresponds to the peak of amorphous carbon, in the range of 40-43oThe broad peak of the range was assigned to the peak of the graphite structure, indicating that the product was less crystalline and essentially amorphous. The SEM results of fig. 4 show that it is a loose porous structure; the specific capacitance of FIG. 5 can reach 223F g at 5mV/s-1And the concentration of the carbon dioxide can reach 160F g at 100mV/s-1. N of FIG. 62The absorption and desorption curve and the pore size distribution show that the material is rich in a large number of micropores and mesoporous structures, the hierarchical pore structure characteristic of the material is shown, and the specific surface area can reach 990m2Per g, pore volume of 0.69 cm3Per g, micropore volume of 0.36cm3(g) mesoporous volume is 0.31 cm3/g。
Example 4 (microwave Power 640W)
(1) The preparation method of the walnut shell powder is the same as the step (1) in the example 2;
(2) weighing 5.0g of walnut powder in a conical flask by microwave preactivation, adding 50mL of dilute hydrochloric acid solution (2mol/L), stirring for 0.5-1 h, transferring the walnut powder into a microwave oven, heating for 10-15min under the condition of microwave power of 480W to obtain dark brown paste, naturally cooling, performing suction filtration, repeatedly washing with distilled water to neutrality, and drying in an oven at 80-100 ℃ for 12 h.
Steps (3) to (7) were the same as those described in example 2.
(8) The product detection results are shown in the infrared spectrum analysis result of fig. 2, and the hydroxyl peak and the carbonyl peak after the microwave power is 480W pretreatment are lower than those of blank samples, 320W and 480W treatment, which indicates that chemical bonds in the blank samples are damaged to a greater extent in the microwave treatment. XRD results of the carbonized product (see FIG. 3) showed 25 to 28oThe broad peak of the range corresponds to the peak of amorphous carbon, in the range of 40-43oThe broad peak of the range was assigned to the peak of the graphite structure, indicating that the product was less crystalline and essentially amorphous. The SEM results of FIG. 4 show that the material surface has more open structures; the specific capacitance of the capacitor can reach 185F g at 5mV/s in FIG. 5-1And can reach 115F g at 100mV/s-1。
Example 5 (microwave Power 800W)
(1) The preparation method of the walnut shell powder is the same as the step (1) in the example 2;
(2) weighing 5.0g of walnut powder in a conical flask by microwave preactivation, adding 50mL of dilute hydrochloric acid solution (2mol/L), stirring for 0.5-1 h, transferring the walnut powder into a microwave oven, heating for 10-15min under the condition of microwave power of 480W to obtain dark brown paste, naturally cooling, performing suction filtration, repeatedly washing with distilled water to neutrality, and drying in an oven at 80-100 ℃ for 12 h.
Steps (3) to (7) were the same as those described in example 2.
(8) Product detection result chart2, the hydroxyl peak and the carbonyl peak after 480W microwave power pretreatment are lower than those of the blank samples, 320W, 480W/and 640W treatment, which indicates that the chemical bonds in the samples are damaged to a greater extent in the microwave treatment. XRD results of the carbonized product (see FIG. 3) showed 25 to 28oThe broad peak of the range corresponds to the peak of amorphous carbon, in the range of 40-43oThe broad peak of the range was assigned to the peak of the graphite structure, indicating that the product was less crystalline and essentially amorphous. The SEM result of FIG. 4 shows that the structure is open-pore and the pore size is larger; the specific capacitance of FIG. 5 can reach 175F g at 5mV/s-1And the concentration of the precursor reaches 107F g at 100mV/s-1。
The above examples are only preferred embodiments of the patent, but the scope of protection of the patent is not limited thereto. It should be noted that, for those skilled in the art, without departing from the principle of this patent, several improvements and modifications can be made according to the patent solution and its patent idea, and these improvements and modifications should also be regarded as the protection scope of this patent.
Claims (2)
1. A preparation method of high-capacitance performance grading porous carbon based on walnut shells is characterized by comprising the following steps:
(1) crushing raw materials, namely soaking walnut shells in distilled water to remove surface impurities, then placing the walnut shells in a drying oven at 60 ℃ to dry the walnut shells to constant weight, crushing the walnut shells by using a crusher to obtain powdered walnut shell powder, and sieving the powdered walnut shell powder by using a 60-mesh sieve to obtain walnut shell powder;
(2) weighing 5.0-10.0g of walnut shell powder in a conical flask filled with 2mol/L hydrochloric acid solution for microwave pre-activation, and keeping the mass g of solids: stirring for 0.5-1 h when the volume mL of the liquid is 1: 10-15, transferring the liquid into a microwave oven, heating for a period of time under the microwave power condition of 320-800W to obtain a dark brown paste, naturally cooling, performing suction filtration, repeatedly washing the paste to be neutral by using distilled water, and drying the paste in an oven at the temperature of 80-100 ℃ for 12h to obtain pretreated walnut shell powder;
(3) weighing pretreated walnut shell powder and KOH according to a proportion, adding a certain amount of distilled water, uniformly stirring to ensure that the proportion relation between the mass g of the solid and the volume mL of the liquid is 1: 10-15, soaking for 6-12h, and then transferring to an oven to dry into a solid at 80-100 ℃;
(4) finally, 2.0-3.0g of the powder dried in the step (3) is taken to be added into a tubular furnace after one-step carbonization treatment, and the mixture is subjected to N reaction2Under protection, at 3-5 deg.C for min-1The temperature rising rate is increased to 300 ℃, the temperature is kept for 0.5 to 1.0 hour, the temperature is continuously raised to 700 to 900 ℃, and the temperature is kept for 1 to 2 hours, so that the materials are fully carbonized;
(5) and (3) after the carbide is subjected to aftertreatment, naturally cooling the carbide, taking out a carbonized product, washing the carbonized product by using 0.1mol/L hydrochloric acid and distilled water in sequence to remove redundant KOH, fully exposing pore channels in the carbon material, and transferring a filter cake into an oven to be dried after washing to be neutral, thereby obtaining the graded porous carbon.
2. The method for preparing walnut shell based high capacitance performance graded porous carbon according to claim 1, characterized in that the method further comprises the following steps:
1) electrode preparation, weighing a certain mass of porous carbon powder, acetylene black and polyvinylidene fluoride in an agate mortar according to a mass ratio of 80:10:10, fully grinding, dropwise adding a certain volume of N-methyl pyrrolidone, uniformly mixing, mixing into paste, uniformly coating on the surface of foamed nickel, and controlling the coating area to be 1 × 1cm2Then, the electrode is placed in an oven with the temperature of 80 ℃ for drying overnight, and an electrode slice for testing is obtained;
(2) the electrochemical performance test of the capacitance performance test electrode material is carried out on a CHI660D electrochemical workstation, and the test system is a standard three-electrode system, wherein in the electrochemical test process, a modified electrode of porous carbon is used as a working electrode, a platinum electrode is used as a counter electrode, an Hg/HgO electrode is used as a reference electrode, and 6.0mol/L KOH solution is used as electrolyte.
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| CN110937601A (en) * | 2019-12-09 | 2020-03-31 | 天津大学 | Walnut shell based activated carbon, preparation method and application thereof |
| CN112441581B (en) * | 2020-11-25 | 2022-08-09 | 华南理工大学 | Purple-root water hyacinth-based graded porous carbon material, preparation method thereof and application thereof in super capacitor |
| CN112599367B (en) * | 2021-01-04 | 2022-04-12 | 齐鲁工业大学 | Method for preparing lotus root starch derived carbon electrode material with assistance of microwaves |
| CN112551523B (en) * | 2021-01-05 | 2022-07-19 | 齐鲁工业大学 | Microwave-assisted method for preparing honey-based derived carbon electrode material |
| CN114709405A (en) * | 2022-04-27 | 2022-07-05 | 深圳市寒暑科技新能源有限公司 | Preparation method of biomass-based hard carbon composite material |
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| CN101697322A (en) * | 2009-10-15 | 2010-04-21 | 青岛大学 | Method for preparing porous carbon electrode material |
| CN103803548A (en) * | 2014-02-20 | 2014-05-21 | 江西师范大学 | Biomass powdered activated carbon prepared from lychee seeds and preparation method thereof |
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