CN108046254B - Corncob-derived activated carbon electrode material and preparation method thereof - Google Patents
Corncob-derived activated carbon electrode material and preparation method thereof Download PDFInfo
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- CN108046254B CN108046254B CN201711441936.8A CN201711441936A CN108046254B CN 108046254 B CN108046254 B CN 108046254B CN 201711441936 A CN201711441936 A CN 201711441936A CN 108046254 B CN108046254 B CN 108046254B
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Abstract
The invention discloses a corncob derived activated carbon electrode material and a preparation method thereof. The preparation process comprises the following steps: firstly, soaking agricultural waste corncobs in potassium hydroxide solutions with different concentrations, drying and then calcining at high temperature; and then, mixing and grinding the obtained product and potassium hydroxide for the second time according to different proportions, and calcining at high temperature to obtain the corncob derived graded porous activated carbon material. The corncob derived hierarchical porous activated carbon material has a micropore and mesopore dual hierarchical structure. The material is used as a super capacitor electrode material, and shows good specific capacity and excellent rate performance. The preparation method has the advantages of novelty, simple operation, low preparation cost and the like.
Description
Technical Field
The invention relates to a preparation method of an electrode material, in particular to a corncob-derived graded porous activated carbon supercapacitor electrode material and a preparation method thereof; belongs to the field of new energy materials.
Background
The biomass carbon material is widely concerned by researchers as an electrode material of a super capacitor. The commonly used biomass is mainly traditional agriculture and forestry biomass, and comprises various crop straws, woods, fruit shells, fruit pits, rice hulls and the like. The agricultural waste biomass derived carbon material has the advantages of low cost, environmental friendliness, developed porous structure and the like, so that the agricultural waste biomass derived carbon material becomes a current research hotspot when being used as a supercapacitor electrode material. However, the preparation process of the agricultural waste biomass derived carbon material is complicated, the conditions are harsh, the specific surface area is small, and the application of the carbon material in the super capacitor is limited due to the fact that the pore size distribution is not easy to regulate and control.
Ding (a) to the problem of carbon materials derived from agricultural waste biomassChem Eng Journal2013, 225: 300-305) and the like, and finally carrying out activation by using sulfuric acid to catalyze and hydrolyze corncobs, carrying out hydrothermal carbonization and further synthesizing the corn cob with high specific surface area (3611 m)2/g) of spherical porous carbon. However, the preparation process of the porous carbon material is complex, the requirement on conditions is strict, and the repeatability is low. Li et al (Energy Environ. Sci. 2016, 9, 102-106) By hydrogen oxidationThe nitrogen-doped hierarchical porous activated carbon is prepared by potassium activation and subsequent ammonia nitrogen doping, and the nitrogen-doped hierarchical porous activated carbon is used as an electrode material of a super capacitor and shows good electrochemical performance. Although the preparation process of the porous activated carbon material is simple, the ammonia gas with strong corrosiveness pollutes the environment seriously. Therefore, the method for preparing the simple, green and environment-friendly porous carbon material with controllable pore diameter has great scientific significance and social benefit.
Disclosure of Invention
The invention aims to overcome the defects of the existing preparation technology, provides a simple and safe high-specific surface area corncob-derived hierarchical porous activated carbon supercapacitor electrode material, and has a microporous and mesoporous dual-pore structure, and the pore size of the activated carbon can be effectively regulated and controlled; when the corncob-derived hierarchical porous activated carbon supercapacitor electrode material prepared by the method is used as a supercapacitor electrode material, the specific capacity and rate capability of the electrode material can be greatly improved.
The preparation method disclosed by the invention is simple in preparation process, high in safety coefficient, free of a template and high in specific surface.
The invention is realized by the following measures:
the invention discloses a corncob derived activated carbon electrode material which is characterized by being prepared by the following method:
(1) soaking agricultural waste corncobs in a potassium hydroxide solution with the concentration of 15% -50%, controlling the ratio of the corncobs to the potassium hydroxide to be 1: 1-6, taking out and drying after full soaking, and carrying out high-temperature calcination at the calcination temperature of 600-1000 ℃ for 1-6 h; washing, centrifuging and drying the calcined substance to obtain a first activated product;
(2) mixing the product obtained in the step 1 and potassium hydroxide according to the weight ratio of 1: 0.5-4, fully grinding and mixing, carrying out high-temperature calcination at 600-1000 ℃ for 1-6 h, and then washing, centrifuging and drying to obtain the corncob-derived activated carbon electrode material.
The electrode material is preferably a microporous-mesoporous dual-pore structure, wherein the micropore size is 0.1-2 nm, the mesoporous range is about 2-10 nm, and the specific surface area is 1000-3000 m 2/g.
Preferably, in the electrode material, in the step 1, the concentration of the potassium hydroxide solution is 25 to 30 percent; in the step 2, the weight ratio of the product to potassium hydroxide is 1: 1-3.
The electrode material is preferably the washing solution which is dilute hydrochloric acid and deionized water; the pH value of the washed solution is 7; the drying temperature is 50-120 ℃, and the drying time is 6-24 h.
The invention also discloses a preparation method of the corncob-derived hierarchical porous activated carbon supercapacitor electrode material, which is characterized by comprising the following specific steps of:
(1) soaking agricultural waste corncobs in a potassium hydroxide solution with the concentration of 15% -50%, taking out and drying after full soaking, and then calcining at high temperature, wherein the calcining temperature is 600-800 ℃, and the heat preservation time is 2-4 h; washing, centrifuging and drying the calcined substance to obtain a first activated product;
(2) and (2) fully mixing and grinding the product obtained in the step (1) and potassium hydroxide according to the weight ratio of 1: 4-2: 1, calcining at the high temperature of 600-800 ℃ for 2-4 h, and then washing, centrifuging and drying to obtain the corncob-derived hierarchical porous activated carbon supercapacitor electrode material.
Preferably, in the preparation method, in the step 1, the concentration of the potassium hydroxide solution is 25-30%; in the step 2, the weight ratio of the product to potassium hydroxide is 1: 1-5.
In the preparation method, preferably, the washing solution is dilute hydrochloric acid and deionized water; the pH value of the washed solution is 7; the drying temperature is 50-70 ℃, and the drying time is 8-12 h.
Compared with the prior art, the invention has the beneficial effects that:
(1) the corncob-derived hierarchical porous activated carbon prepared by the method has a micropore and mesopore dual-pore structure, and the pore size of the activated carbon can be effectively regulated and controlled.
(2) The invention effectively utilizes the agricultural waste corncobs, greatly increases the added value of the waste, and the preparation process of the invention can obtain the hierarchical porous activated carbon only by adopting potassium hydroxide to carry out double activation on the corncobs without the help of template materials with hierarchical pore structures and complex experimental devices, the conditions are easy to control, the process is simple, the cost is low, and the problems that the conventional preparation process is complex and the template materials are not easy to find are solved.
(3) When the corn cob-derived hierarchical porous activated carbon supercapacitor electrode material prepared by the method is used as a supercapacitor electrode material, high specific capacity and good rate capability are shown.
The conception, specific material structure and technical effects of the present invention will be further described in conjunction with the accompanying drawings to fully understand the objects, features and effects of the present invention.
Drawings
FIG. 1 is a pore size distribution diagram of a corncob-derived activated carbon electrode material prepared in example 1 of the present invention; in the figure, the abscissa represents the pore diameter and the ordinate represents the pore volume.
FIG. 2 is a scanning electron micrograph of a corncob-derived activated carbon electrode material prepared in example 1 of the present invention;
FIG. 3 is a transmission electron microscope image of the corncob-derived activated carbon electrode material prepared in example 1 of the present invention;
fig. 4 is a constant current charge and discharge curve of the corncob-derived activated carbon electrode material prepared in example 1 of the present invention at different current densities. In the figure, the abscissa represents time, and the ordinate represents voltage.
Detailed Description
The following examples are given for the detailed embodiments and specific procedures performed on the premise of the present invention, but the scope of the present invention is not limited to the specific examples listed below.
Example 1
Soaking corn cob in 25% potassium hydroxide solution at a ratio of 1:3, drying, calcining at 800 deg.C for 2 hr, washing with dilute hydrochloric acid and deionized water until pH is 7, and drying at 70 deg.C for 12 hr to obtain the first activated product.
Fully grinding and mixing the first activated product and potassium hydroxide in a mortar according to the ratio of 1:3, calcining at 800 ℃ for 2 hours, washing the obtained product with dilute hydrochloric acid and deionized water until the pH value of the solution is 7, and drying the obtained precipitate at 70 ℃ for 12 hours to obtain the corncob-derived activated carbon electrode material.
The pore size distribution of the prepared corncob-derived activated carbon electrode material is shown in figure 1, and the active carbon electrode material prepared from figure 1 has a micropore and mesopore double-pore structure, wherein the average size of micropores is about 2 nm, and the average size of mesopores is about 4 nm.
Fig. 2 and 3 are a scanning electron microscope image and a transmission electron microscope image of the prepared corncob-derived activated carbon electrode material, respectively, and it can be seen that the activated carbon prepared after the secondary activation has a developed pore structure and simultaneously has micropores and mesopores.
The electrode material, the binder and the conductive carbon are uniformly ground according to the ratio of 8:1:1, then coated on foamed nickel (1 x 1 cm) to be dried (70 ℃) to prepare a working electrode, and the electrochemical performance of the working electrode is tested under a three-electrode system (a platinum sheet is used as a counter electrode, an Ag/AgCl electrode is used as a reference electrode, and a 1M sodium sulfate aqueous solution is used as an electrolyte). The specific capacitance of the composite electrode is up to 298.1F/g under the condition that the current density is 0.5A/g; when the current density is increased to 10A/g, the capacitance value is 253.2F/g, the capacitance attenuation is small, 84.9% of capacitance can be reserved, and excellent rate performance is shown. (FIG. 4).
Example 2
Soaking corn cob in 15% potassium hydroxide solution at a ratio of 1:1, drying, calcining at 600 deg.C for 6 hr, washing with dilute hydrochloric acid and deionized water until pH is 7, and drying at 50 deg.C for 24 hr to obtain the first activated product.
Fully grinding and mixing the first activated product and potassium hydroxide in a mortar according to the ratio of 1:0.5, calcining at 600 ℃ for 6 hours, washing the obtained product with dilute hydrochloric acid and deionized water until the pH value of the solution is 7, and drying the obtained precipitate at 50 ℃ for 24 hours to obtain the corncob-derived activated carbon electrode material.
In the prepared corncob-derived activated carbon electrode material, the average size of micropores is about 0.1 nm, and the average size of mesopores is about 10 nm.
The electrochemical properties were measured in the same manner as in example 1. The specific capacitance of the composite electrode is up to 272.6F/g under the condition that the current density is 0.5A/g; when the current density is increased to 10A/g, the capacitance value is 265.5F/g, the capacitance attenuation is small, 97.4% of capacitance can be reserved, and excellent rate performance is shown.
Example 3
Soaking corn cob in 50% potassium hydroxide solution at a ratio of 1:6, drying, calcining at 1000 deg.C for 1 hr, washing with dilute hydrochloric acid and deionized water until pH is 7, and drying at 120 deg.C for 6 hr to obtain the first activated product.
Fully grinding and mixing the first activated product and potassium hydroxide in a mortar according to the ratio of 1:6, calcining at 1000 ℃ for 1 h, washing the obtained product with dilute hydrochloric acid and deionized water until the pH value of the solution is 7, and drying the obtained precipitate at 120 ℃ for 6 hours to obtain the corncob-derived activated carbon electrode material.
In the prepared corncob derived activated carbon electrode material, the average size of micropores is about 1 nm, and the average size of mesopores is about 2 nm.
The electrochemical properties were measured in the same manner as in example 1. The specific capacitance of the composite electrode is up to 308.5F/g under the condition that the current density is 0.5A/g; when the current density is increased to 10A/g, the capacitance value is 253.5F/g, the capacitance attenuation is small, 82.1% of capacitance can be reserved, and excellent rate performance is shown.
Example 4
Soaking corn cob in 35% potassium hydroxide solution at a ratio of 1:2, drying, calcining at 1000 deg.C for 1 hr, washing with dilute hydrochloric acid and deionized water until pH is 7, and drying at 120 deg.C for 6 hr to obtain the first activated product.
Fully grinding and mixing the first activated product and potassium hydroxide in a mortar according to the ratio of 1:6, calcining at 600 ℃ for 6 hours, washing the obtained product with dilute hydrochloric acid and deionized water until the pH value of the solution is 7, and drying the obtained precipitate at 90 ℃ for 12 hours to obtain the corncob-derived activated carbon electrode material.
In the prepared corncob-derived activated carbon electrode material, the average size of micropores is about 1.5 nm, and the average size of mesopores is about 5 nm.
The electrochemical properties were measured in the same manner as in example 1. The specific capacitance of the composite electrode is up to 327.6F/g under the condition that the current density is 0.5A/g; when the current density is increased to 10A/g, the capacitance value is 285.3F/g, the capacitance attenuation is small, 87.1% of capacitance can be reserved, and excellent rate performance is shown.
Claims (1)
1. A preparation method of a corncob-derived hierarchical porous activated carbon supercapacitor electrode material comprises the following steps:
(1) soaking agricultural waste corncobs in a potassium hydroxide solution with the concentration of 15% -50%, controlling the ratio of the corncobs to the potassium hydroxide to be 1: 1-6, taking out and drying after full soaking, and carrying out high-temperature calcination at the calcination temperature of 600-1000 ℃ for 1-6 h; washing, centrifuging and drying the calcined substance to obtain a first activated product;
(2) mixing the product obtained in the step 1 and potassium hydroxide according to the weight ratio of 1: 0.5-4, fully grinding and mixing, carrying out high-temperature calcination at 600-1000 ℃ for 1-6 h, and then washing, centrifuging and drying to obtain the corncob-derived activated carbon electrode material;
the activated carbon material has a micropore-mesopore double-pore structure, wherein the micropore size is 0.1-2 nm, the mesopore range is 2-10 nm, and the specific surface area is 1000-3000 m2/g；
The washing solution is dilute hydrochloric acid and deionized water; the pH value of the washed solution is 7; the drying temperature is 50-120 ℃, and the drying time is 6-24 h.
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| CN109110756B (en) * | 2018-10-24 | 2022-01-21 | 济南大学 | Homogeneous corncob derived carbon electrode material and preparation method thereof |
| CN109850866B (en) * | 2019-01-30 | 2021-03-09 | 青岛大学 | Hierarchical porous carbon material for flexible supercapacitor and preparation method 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 |
| CN113800515B (en) * | 2021-10-29 | 2022-12-20 | 哈尔滨工业大学 | Preparation method of nitrogen-doped activated carbon and multi-hydroxide/biomass porous carbon nano composite electrode material |
| CN113880085B (en) * | 2021-11-17 | 2022-11-11 | 常州大学 | Preparation method of biomass activated carbon for supercapacitor and supercapacitor |
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| CN102107872A (en) * | 2011-03-04 | 2011-06-29 | 南京工业大学 | Process for preparing active carbon by adding husks into chemical sludge |
| CN104787764A (en) * | 2015-04-27 | 2015-07-22 | 宁夏医科大学 | Method for preparing active carbon from radix astragali waste residues |
| CN106744953A (en) * | 2016-12-22 | 2017-05-31 | 济南大学 | A kind of classifying porous active carbon electrode material without method for preparing template |
| CN107416827A (en) * | 2017-05-23 | 2017-12-01 | 山东科技大学 | A kind of preparation method of useless tealeaves peanut based active carbon |
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| US20090305023A1 (en) * | 2008-04-25 | 2009-12-10 | Academia Sinica | Preparation of Porous Carbon Materials Using Agricultural Wastes |
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| CN102107872A (en) * | 2011-03-04 | 2011-06-29 | 南京工业大学 | Process for preparing active carbon by adding husks into chemical sludge |
| CN104787764A (en) * | 2015-04-27 | 2015-07-22 | 宁夏医科大学 | Method for preparing active carbon from radix astragali waste residues |
| CN106744953A (en) * | 2016-12-22 | 2017-05-31 | 济南大学 | A kind of classifying porous active carbon electrode material without method for preparing template |
| CN107416827A (en) * | 2017-05-23 | 2017-12-01 | 山东科技大学 | A kind of preparation method of useless tealeaves peanut based active carbon |
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