Method for preparing biomass porous carbon material by coupling activation method and application thereof

Abstract

The invention relates to the technical field of preparation of active carbon materials, in particular to a method for preparing a biomass porous carbon material through a coupling activation method and application of the biomass porous carbon material. The preparation method comprises the following steps: by taking waste biomass such as cassava peel as a raw material, performing fermentation, acid leaching activation, low-temperature carbonization, alkali activation, ultrasonic acid pickling and high-temperature impurity removal to obtain the biomass-derived porous carbon material, and performing electron microscope analysis and pore detection on the biomass-derived porous carbon material prepared by the steps. The biomass derived porous activated carbon material is of a porous layered structure and has abundant micropores and mesopores; according to the present invention, the electrochemical test experiment detection results show that the biomass derived porous carbon material has excellent capacitance performance, and when the current density is 0.5 A / g, the specific capacity value range is 200-400 F / g; the material also has good stability, the biomass derived porous carbon material is assembled into a symmetric supercapacitor, and after 10000 circles of stability tests, the retention rate of the specific capacitance of the symmetric supercapacitor can be maintained to be 90% or above.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation technology, specifically relating to a method for preparing biomass porous carbon materials by coupling activation and its application. Background Technology

[0002] Supercapacitors possess high power density, rapid charge / discharge capabilities, and ultra-long cycle life in energy storage, making them particularly suitable for short-term, high-power demand scenarios such as electric vehicle acceleration and grid frequency regulation. With breakthroughs in nanomaterials and composite electrode technologies, their energy density continues to improve, promising broad application prospects in renewable energy storage, rail transit energy recovery, and industrial backup power. The performance of a supercapacitor depends on the electrode materials, electrolyte, and separator used, with the electrode materials being the key determinant of capacitor performance.

[0003] Among them, patent CN120553705A discloses a petroleum asphalt-based porous carbon material and its preparation method. Using potassium hydroxide as an activator, with a carbon-to-alkali ratio (petroleum asphalt:KOH) of 1:4, and using petroleum asphalt as a carbon precursor, it is pre-oxidized by stirring with molten salt at a certain temperature. The process involves pre-carbonization, washing away the molten salt, activation, washing, and drying to obtain the petroleum asphalt-based porous carbon material with a specific surface area of ​​up to 2986 m². 2 / g, with a pore volume of 1.6 m³. 3 / g, but the shortcomings of this patent are: commercial petroleum asphalt-based porous carbon relies on fossil raw materials, which has problems such as high cost and unsustainability; while agricultural waste, which is rich in carbon, is cheap and abundant, and inexhaustible. Using agricultural waste as raw material to prepare porous carbon materials can not only turn waste into treasure, but also is a green and sustainable development path with important scientific and application value.

[0004] Biomass-based porous carbon uses biomass as its raw material, which is renewable. Currently, mainstream technologies require strong alkali activation. To achieve efficient utilization of waste biomass, patent CN112441582B discloses a biomass porous carbon material, its preparation method, and its applications. The carbonization product is mixed with KOH at a mass ratio of 1:3. The carbon material is obtained by pre-carbonizing, activating, and washing succulent plants. When applied to supercapacitors, the carbon material exhibits a specific capacitance greater than 250 F / g and significant cycle stability after 8000 cycles at a current density of 2 A / g, with a specific capacitance retention rate exceeding 90%. This effectively turns waste into treasure. However, this patent suffers from low specific capacitance and poor cycle stability, requiring further improvement in electrochemical performance.

[0005] Cassava consists of edible flesh and peel, with the peel accounting for 10 to 15% of the entire fruit. This invention aims to design waste cassava peel and other biomass raw materials into carbon materials with special structures for use in supercapacitor electrode materials. Utilizing biological waste as raw materials to manufacture low-cost, high-performance biomass-derived carbon materials is of profound significance. Summary of the Invention

[0006] This invention aims to solve the aforementioned technical problems by providing a coupled activation preparation method and application of biomass-derived porous carbon materials. Using waste biomass husks as raw material, the invention obtains biomass-derived porous carbon materials through fermentation, acid leaching activation, low-temperature carbonization, alkali activation, ultrasonic acid washing with dilute hydrochloric acid, and high-temperature impurity removal. The material obtained by this invention exhibits a porous layered structure and demonstrates excellent capacitance performance as tested by electrochemical experiments. This material can be used as an electrode material for supercapacitors.

[0007] The technical solution of this invention is as follows:

[0008] A coupled activation preparation method for biomass-derived porous carbon materials is disclosed, which uses agricultural waste biomass cassava peel as raw material and prepares the material through fermentation, acid leaching activation, low-temperature carbonization, alkali activation, dilute hydrochloric acid ultrasonic acid washing, and high-temperature impurity removal.

[0009] The above-mentioned method for preparing biomass-derived porous carbon materials by coupling activation includes one or more of the following biomass: sorghum stalks, corn cobs, loofah sponges, cassava peels, and wine lees.

[0010] Furthermore, it includes the following steps:

[0011] (1) Biomass fermentation: Take biomass raw materials, wash and dry them, crush them and ferment them with Lactobacillus delbrueckii, sucrose, urea and water in a closed container for 3-10 days at room temperature to obtain fermented biomass;

[0012] (2) Acid leaching activation: The fermented biomass from step (1) is dried and mixed with an acid solution, subjected to acid leaching treatment and then dried to obtain acid-leached activated biomass;

[0013] (3) Low-temperature carbonization: The sample after acid leaching and drying in step (2) is calcined at a temperature of 300-500 ℃, a heating rate of 5-10 ℃ / min, and a calcination time of 1-3 h to obtain a carbon precursor.

[0014] (4) Alkali activation: Mix the carbon precursor and activator from step (3) evenly according to the mass ratio and then calcine at high temperature. The resulting product is washed until neutral and dried to obtain porous carbon material.

[0015] (5) Acid washing to remove impurities: The product obtained in step (4) is acid-soaked, washed with water until neutral and dried to obtain biomass-derived porous carbon material.

[0016] Furthermore, the total mass of Lactobacillus delbrueckii, sucrose, and urea in (1) is 6.2-16% of the mass of the biomass raw material.

[0017] Furthermore, the fermentation conditions in step (1) are room temperature and the fermentation time is 3-10 days.

[0018] Further, the acid solution in step (2) is phosphoric acid with a concentration of 1~3 mol / L or sulfuric acid with a concentration of 1~3 mol / L; the mass ratio of the acid solution to the fermentation biomass is 1:(5-10).

[0019] Furthermore, the acid treatment process in step (2) is carried out under closed conditions at a constant temperature of 25-90 ℃ for 6-24 h.

[0020] Further, the alkali activator in step (4) includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate or potassium carbonate; the mass ratio of carbon precursor to alkali activator is 1:(0.5-2).

[0021] Furthermore, in step (5), the acid immersion is performed by soaking in a hydrochloric acid solution with a concentration of 1-3 mol / L for 4-24 hours.

[0022] In addition, this invention also proposes an application of the porous carbon material prepared by the above-mentioned coupled activation preparation method of biomass-derived porous carbon material in supercapacitors, wherein the specific surface area of ​​the biomass-derived porous carbon material is 1900-3000 m². 2 / g.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. This method uses waste biomass as raw material and prepares biomass-derived porous carbon material through fermentation, acid leaching activation, low-temperature carbonization, alkali activation, and acid washing to remove impurities. Scanning electron microscopy and pore size analysis show that the obtained biomass-derived porous carbon material is a porous layered structure with abundant micropores and mesopores. Electrochemical testing shows that the obtained biomass-derived porous carbon material has excellent capacitance performance, with a specific capacitance value ranging from 200 to 400 F / g at a current density of 0.5 A / g. The material also has good stability. When the high-performance biomass-derived porous activated carbon material is assembled into a symmetrical supercapacitor, its specific capacitance retention rate can be maintained at over 90% after 10,000 cycles of stability testing.

[0025] 2. In the above-mentioned method for preparing biomass-derived porous carbon materials by coupling activation, waste biomass is used as a precursor, which is low in cost and easy to scale up.

[0026] 3. This solution involves biomass fermentation and acid leaching activation processes, which greatly reduces the proportion of subsequent alkali activation and reduces the amount of activator used by more than 50%, significantly reducing costs and environmental pollution. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a SEM image of the biomass-derived porous carbon material prepared in Example 1 of the present invention;

[0029] Figure 2 This is the GCD diagram of the porous carbon material obtained in Example 2 of the present invention;

[0030] Figure 3 This is a cyclic voltammogram of the biomass-derived porous carbon material prepared in Example 1 of the present invention.

[0031] Figure 4 This is a cycle test diagram of the porous carbon material obtained in Example 1 of the present invention at 10 A / g;

[0032] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Comparative Example 1

[0035] A method for preparing biomass-derived porous carbon materials through coupling activation includes the following steps:

[0036] Cassava peel washing: Cassava peel raw material is washed and dried to obtain dried raw material; the dried raw material is calcined and carbonized at 450℃ in a nitrogen atmosphere for 2 hours. The obtained product is washed with deionized water until neutral and dried to obtain carbon precursor; the above carbon precursor and alkali activator (potassium hydroxide) are uniformly mixed and dispersed in deionized water at a mass ratio of 1:1, the water is removed after drying, and the product is calcined and activated at 700℃ for 2 hours. The obtained product is immersed in a 2 mol / L hydrochloric acid solution for 12 hours, and then washed with deionized water until neutral and dried and purified at high temperature to obtain activated porous carbon material.

[0037] Example 1

[0038] A method for preparing biomass-derived porous carbon materials through coupling activation includes the following steps:

[0039] (1) Fermentation: After washing, drying and crushing, the biomass raw material (cassava peel) is mixed with Lactobacillus delbrueckii, sucrose, urea and water in a mass ratio of 100:8:3:0.8:100. The mixture is thoroughly moistened and free of standing water. Then it is sealed and fermented at room temperature for 8 days.

[0040] (2) Acid leaching activation: Dry the fermented biomass from step (1), pulverize it into powder, mix it with acid solution (phosphoric acid with a concentration of 2 mol / L), and keep it at a constant temperature of 60°C for 18 hours under sealed conditions. The mass ratio of acid solution to fermented biomass is 1:8.

[0041] (3) Low-temperature carbonization: The acid-soaked biomass from step (2) is dried, and then the dried cassava peel is placed in a tube furnace and pre-carbonized at 450°C under an inert gas atmosphere for 2 hours to obtain a carbon precursor.

[0042] (4) Activation: The carbon precursor and alkaline activator (potassium hydroxide) from step (3) are uniformly mixed and dispersed in deionized water. After stirring for 30 min, the water is removed by drying. Then, under a nitrogen atmosphere, the carbon precursor and alkaline activator are calcined at 700℃ for 2 h with a heating rate of 5℃ / min. The mass ratio of carbon precursor to alkaline activator is 1:1.

[0043] (5) Acid washing to remove impurities: The product obtained in step (4) is immersed in a 2 mol / L hydrochloric acid solution for 12 h, washed with deionized water until neutral, and dried to obtain biomass-derived porous carbon material.

[0044] Example 2

[0045] In this comparative example, all preparation steps and parameters are the same as in Example 1, except that the biomass raw material in step (1) is loofah sponge.

[0046] Example 3

[0047] In this comparative example, all preparation steps and parameters are the same as in Example 1, except that the biomass raw material in step (1) is wine lees.

[0048] Comparative Example 2

[0049] In this comparative example, all preparation steps and parameters are the same as in Example 1. The difference is that the fermentation process in step (1) is omitted, that is, the pulverized cassava peel is directly subjected to the acid soaking activation step.

[0050] Comparative Example 3

[0051] In this comparative example, all preparation steps and parameters are the same as in Example 1. The difference is that the acid leaching activation process in step (2) is cancelled, and the fermented biomass is dried, crushed and then directly subjected to low-temperature pre-carbonization.

[0052] Comparative Example 4

[0053] In this comparative example, all preparation steps and parameters are the same as in Example 1. The difference is that the low-temperature pre-carbonization in step (3) is replaced with a hydrothermal carbonization process. The specific carbonization parameters are: hydrothermal reaction is carried out in an oven at a temperature of 180°C and a reaction time of 6 hours.

[0054] The porous carbon materials prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to the following performance tests, and the specific test results are shown in the table below.

[0055]

[0056] Note: 1. To demonstrate that porous carbon materials can be used as electrode materials for supercapacitors, the prepared porous carbon materials were subjected to constant current charge-discharge tests in 6 mol / L KOH electrolyte to obtain the above specific capacity (current density of 0.5 A / g).

[0057] 2. To demonstrate that porous carbon materials have good capacitance retention, the prepared porous carbon materials were assembled into a symmetrical supercapacitor and subjected to 10,000 constant current charge-discharge cycles at a current density of 10 A / g.

[0058] As can be seen from the test results of Comparative Example 1 in the table above, the conventional pre-carbonization and calcination activation process requires a large amount of activator, and the resulting porous carbon material generally exhibits poor electrochemical energy storage performance when applied to supercapacitors.

[0059] The porous carbon materials obtained in Examples 1-3 of this scheme maintain a specific surface area of ​​2000-3000 m². 2Within a g range, this porous carbon material possesses abundant microporous and mesoporous structures. The supercapacitor made from this porous carbon material exhibits high specific capacitance, and the retention rate of specific capacitance after 10,000 cycles of stability testing is also high. Furthermore, to demonstrate that the activated porous carbon material possesses an even richer pore structure, the biomass porous carbon obtained in step (5) of Example 1 was subjected to scanning electron microscopy analysis, as shown... Figure 1 As shown, a richer and more regular porous structure is obtained in the porous carbon of biomass. To demonstrate that the porous carbon material of this scheme has good rate performance, cyclic voltammetry was performed on Example 1, and the test results are as follows. Figure 3 As shown, the carbon material obtained in Example 1 can still maintain a good rectangular shape even at a high sweep rate of 100 mV / s, demonstrating that it has good rate performance.

[0060] The comparison results between Comparative Examples 2-3 and Example 1 show that when step (1) is removed, the specific surface area and electrochemical performance of the porous carbon material will decrease. When step (2) is removed, the specific surface area and electrochemical performance of the porous carbon material will decrease.

[0061] The comparison results between Comparative Example 4 and Example 1 show that when the low-temperature pre-carbonization process was not used in step (3), the specific surface area and electrochemical performance of the porous carbon material were reduced.

[0062] Example 4

[0063] In this embodiment, all preparation steps and parameters are the same as in Example 1. The difference lies in the different proportions of Lactobacillus delbrueckii, sucrose, urea, and water used in step (1). Specifically:

[0064]

[0065] The porous carbon material prepared in Example 4 was subjected to performance testing, and the specific test results are shown in the table below:

[0066]

[0067] As shown in the test data above, compared to the conventional pre-carbonization and calcination activation process of Comparative Example 1, this scheme, using different ratios of Lactobacillus delbrueckii, sucrose, urea, and water, can improve the specific surface area, specific capacity, and specific capacitance of porous carbon materials. However, overall, the best performance improvement effect on porous carbon materials / supercapacitors is achieved when the composite enzyme agent used for biomass fermentation uses a combination of Lactobacillus delbrueckii, sucrose, and urea in a mass ratio of 8:3:0.8.

[0068] Example 5

[0069] In this embodiment, all preparation steps and parameters are the same as in Example 1, except that the fermentation time in step (1) is different. Specifically:

[0070]

[0071] The porous carbon material prepared in Example 5 was subjected to performance testing, and the specific test results are shown in the table below:

[0072]

[0073] As shown in the test data in the table above, the biomass fermentation time has a significant impact on the performance of porous carbon materials. Among them, a biomass fermentation time of 3-10 days is the optimal fermentation time for this method (8 days is the best fermentation time).

[0074] Example 6

[0075] In this embodiment, all preparation steps and parameters are the same as in Example 1. The difference is that the strengthening treatment parameters in step (1) are different, specifically:

[0076]

[0077] The porous carbon material prepared in Example 6 was subjected to performance testing, and the specific test results are shown in the table below:

[0078]

[0079] As shown in the test data in the table above, different acid treatment parameters also affect the performance of porous carbon materials. Specifically, phosphoric acid is preferred for acid leaching, and isothermal strengthening under phosphoric acid for 18 hours is the optimal acid activation parameter, which helps maintain the specific surface area of ​​the porous carbon material at 2000 m². 2 The specific capacitance and specific capacitance retention rates are also relatively high.

[0080] Example 7

[0081] In this embodiment, all preparation steps and parameters are the same as in Example 1. The difference is that the type of alkali activator used in step (1) is different. Specifically:

[0082]

[0083] The porous carbon material prepared in Example 7 was subjected to performance testing, and the specific test results are shown in the table below:

[0084]

[0085] As shown in the test data above, mixing different activators can improve the performance of porous carbon materials when applied to supercapacitors. However, potassium hydroxide is the most effective alkaline activator in improving the electrochemical performance of porous carbon materials.

[0086] Example 8

[0087] In this embodiment, all preparation steps and parameters are the same as in Example 1. The difference is that the calcination parameters during activation in step (1) are different. Specifically:

[0088]

[0089] The porous carbon material prepared in Example 8 was subjected to performance testing, and the specific test results are shown in the table below:

[0090]

[0091] As shown in the test data in the table above, the preferred calcination parameters during activation are 600-800℃ for 2 hours, with a preferred heating rate of 3-8℃ / min. This allows the specific surface area of ​​the porous carbon material to be maintained at 2100 m². 2 With a specific capacitance of over 320 F / g, the specific capacitance of supercapacitors can be maintained at over 320 F / g, and the specific capacitance retention rate can be maintained at over 87%.

[0092] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing biomass porous carbon materials via a coupling activation method, characterized in that, It is prepared by the following steps: drying, pulverizing, fermentation, acid leaching activation, low-temperature pre-carbonization, alkali activation, acid washing and tempering to remove impurities.

2. The method for preparing biomass porous carbon materials by coupling activation as described in claim 1, characterized in that, The biomass includes one or more of sorghum stalks, corn cobs, loofah sponges, cassava peels, and wine lees; the activation method couples biomass fermentation, acid activation, and alkali activation methods.

3. The method for preparing biomass porous carbon materials by coupling activation as described in claim 1, characterized in that, Includes the following steps: (1) Biomass fermentation: Take biomass raw materials, wash and dry them, then crush them and mix them with Lactobacillus delbrueckii, sucrose, urea and water in a mass ratio of 100:(5-10):(1-5):(0.2-1.0):

100. Mix them evenly to ensure that the mixture is fully moistened and free of water accumulation. Then seal it and ferment at room temperature for 3-10 days. (2) Acid leaching activation: Take out the fermented biomass from step (1), add acid solution, and keep it at a constant temperature of 25-90 ℃ for 6-24 h; (3) Low-temperature pre-carbonization: Place the sample pickled in step (2) in an oven and heat it to 50-110℃ for 12-24 hours. Then place the dried cassava peel in a tube furnace and heat it to 300-500℃ in an inert gas atmosphere for pre-carbonization. The carbonization time is 1-4 hours. (4) Alkali activation: Mix the carbon precursor obtained in step (3) and the alkali activator evenly according to the mass ratio, and then perform calcination and alkali activation. The resulting product is washed until neutral and dried to obtain porous carbon material. (5) Acid washing to remove impurities: The product obtained in step (4) is subjected to tempering to remove chloride ions, water washing to neutralization and drying processes to obtain biomass-derived porous carbon material.

4. The method for preparing biomass porous carbon materials by coupling activation as described in claim 3, characterized in that: In step (3), the acid solution is phosphoric acid with a concentration of 1~3 mol / L or sulfuric acid with a concentration of 1~3 mol / L.

5. The method for preparing biomass porous carbon materials by coupling activation as described in claim 3, characterized in that: In step (4), the calcination conditions are: under a mixture of nitrogen and hydrogen or a nitrogen atmosphere, the calcination temperature is 650-750 ℃, the heating rate is 5-10 ℃ / min, and the calcination time is 1-3 h.

6. The method for preparing biomass porous carbon materials by coupling activation as described in claim 3, characterized in that: In step (4), the alkali activator is sodium hydroxide and / or potassium hydroxide, and the mass ratio of the carbon precursor to the alkali activator is 1:(0.5-2).

7. The method for preparing biomass porous carbon materials by coupling activation as described in claim 3, characterized in that: In step (4), the acid soaking is a 1-3 M hydrochloric acid solution soak for 6-24 h.

8. The method for preparing biomass porous carbon materials by coupling activation as described in claim 3, characterized in that, The tempering in step (5) is achieved by calcining in inert gas nitrogen or argon at 600°C to remove chloride ions, followed by water washing to neutralization and drying, which yields biomass-derived porous carbon materials.

9. A method for preparing biomass porous carbon materials by coupling activation and its application, mainly used in supercapacitors.

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