A lignin-based hierarchical porous carbon material with high mesopore ratio and a preparation method and application thereof
By constructing mesoporous and microporous structures in lignin-based porous carbon materials, the problem of difficult control of pore structure in existing technologies has been solved, achieving high mesoporous ratio and high specific surface area, thereby improving the electrochemical performance of zinc ion capacitors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGDONG UNIV OF TECH
- Filing Date
- 2024-06-28
- Publication Date
- 2026-05-29
AI Technical Summary
The pore structure of existing lignin-based porous carbon materials is difficult to control precisely, resulting in poor electrochemical and rate performance. Insufficient mesoporosity and specific surface area also affect the performance of zinc-ion capacitors.
A bifunctional pore-forming process was adopted, using lignin as a carbon source, and organic zinc salts and alkali metal hydroxides in ethanol solution to generate nano zinc oxide as a hard template agent. Through the carbonization process, a rich and uniform mesoporous structure is formed, and a large number of micropores are formed through chemical activation, thus preparing a hierarchical porous carbon material with high mesopority.
High specific capacitance and high rate performance were achieved in zinc-ion capacitors. The abundant mesoporous and microporous structures provided a large number of active sites and wide ion transport channels, which improved the electrochemical performance of porous carbon cathodes.
Smart Images
Figure BDA0004917198740000121 
Figure BDA0004917198740000131 
Figure HDA0004917198750000011
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of lignin-based porous carbon and electrochemical supercapacitors, specifically relating to a high mesoporous lignin-based hierarchical porous carbon material, its preparation method, and its application. Background Technology
[0002] Zinc-ion hybrid capacitors possess characteristics such as long cycle life, high charge-discharge efficiency, high power density, and high energy density. They store charge through the synergistic effect of adsorption mechanisms between anions and cations at different potentials and reversible adsorption / desorption. Currently, porous carbon materials have become the mainstream cathode materials due to their high specific surface area and abundant pore structure. Therefore, developing a low-cost, high-performance porous carbon cathode material is of great significance for the development of supercapacitors and zinc-ion hybrid capacitors.
[0003] Lignin, the second most abundant biomass component in the plant kingdom, has attracted widespread attention as a green and sustainable precursor for porous carbon materials. Lignin is abundant, high in carbon, and contains numerous functional groups such as carboxyl, hydroxyl, ether bonds, and sulfonic acid groups on its aromatic rings. These functional groups not only improve the wettability of electrolytes but also provide additional redox pseudocapacitance for lignin-based carbon materials. Furthermore, as a byproduct of the pulp industry and biometallurgy, the high-value utilization of lignin not only helps reduce the preparation cost of porous carbon cathodes but also yields significant social benefits.
[0004] The pore structure distribution of porous carbon is crucial to its electrochemical performance. Micropores can effectively increase the active specific surface area of materials, providing abundant active sites, while mesopores, as ion transport channels, can effectively improve ion transport efficiency. Therefore, how to prepare mesoporous carbon materials with high specific surface area and clarify the relationship between mesoporous structure and electrochemical performance has attracted widespread attention. Currently, the main methods for preparing porous carbon include activation methods (chemical activation, physical activation), template methods (soft template method, hard template method, self-templating method), and hydrothermal methods. Porous carbon prepared by physical and chemical activation methods is often dominated by microporous carbon materials with a low proportion of mesopores. The hard template method has the advantages of adjustable pore size and less pore structure damage. During pyrolysis, the hard template agent forms a pore structure with a particle size comparable to the template agent by occupying space in situ, thereby preparing porous carbon materials rich in mesopores. Using template agents to prepare porous carbon materials can effectively reduce the amount of chemical activators used, enabling green production of porous carbon electrodes. However, the pore structure of the carbon materials obtained is often mainly mesoporous, and it is difficult to prepare porous carbon materials with micropores, mesopores and macropores in one step.
[0005] Chinese patent CN109485029A discloses a lignin-based porous carbon nanosheet, its preparation method, and its application in supercapacitor electrode materials. This patent describes the formation of a complex between water-soluble sulfonated lignin and oxalate in a selective solution, resulting in lignin-based porous carbon nanosheets with a density of 1069 μm. 2 The material boasts a specific surface area of / g and mesopores ranging from 2-30nm, achieving a mesopore rate of up to 60%. However, the mesopore distribution is not concentrated, and the activation effect of oxalate on the carbon material is insufficient, resulting in a low specific surface area of the porous carbon, which is detrimental to achieving high-performance capacitive behavior.
[0006] Chinese patent CN117182591A discloses a method for preparing sodium lignosulfonate-based porous carbon and its application. This patent utilizes industrial waste sodium lignosulfonate as a carbon source, obtaining porous carbon through activation by mixing it with silica and potassium formate. While the resulting porous carbon material exhibits a hierarchical porous structure, its mesoporous structure is difficult to control, with mesoporous ratios ranging from 30% to 90% and mesopore diameters between 4% and 50 nm under different proportions. The material with the highest mesoporous ratio has a specific surface area of only 762 m². 2 / g, cannot simultaneously achieve high mesoporosity and high specific surface area.
[0007] Chinese patent CN110902680A discloses a method for preparing mesoporous carbon materials by catalytic activation of sodium lignosulfonate with potassium tartrate. This patent describes a method for preparing mesoporous carbon materials by mixing potassium tartrate and sodium lignosulfonate using spray drying technology, followed by pyrolysis activation. The specific surface area of this material is 1367 m². 2 / g, the mesoporous rate can reach more than 50%, but its mesopore size is mainly concentrated below 5nm, which is not conducive to the application of porous carbon electrodes under high current density conditions.
[0008] The above-mentioned methods for preparing lignin-based hierarchical porous carbon materials have problems such as difficulty in accurately controlling the pore structure and poor electrochemical and rate performance. Summary of the Invention
[0009] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing high mesoporous lignin-based hierarchical porous carbon materials.
[0010] The present invention is a dual-function pore-forming preparation process. Specifically, it utilizes lignin as a carbon source, and organic zinc salts and alkali metal hydroxides in an ethanol solution to generate nano-zinc oxide as a hard template agent. During the carbonization process, the nano-zinc oxide obtains a rich and relatively uniform mesoporous structure in an in-situ occupied form, while the alkali metal salts form a large number of micropores through chemical activation, thereby preparing a lignin-based hierarchical porous carbon material with rich three-dimensional pore structure, high mesoporosity, and large specific surface area.
[0011] The method of this invention enables the simultaneous construction of mesoporous and abundant microporous structures in lignin-based hierarchical porous carbon materials, providing a large number of active sites and transport channels for zinc ions in porous carbon, thereby achieving high specific capacity and high rate performance of porous carbon cathodes for zinc ion capacitors.
[0012] Another object of the present invention is to provide a high mesoporous lignin-based hierarchical porous carbon material prepared by the above preparation method.
[0013] Another object of the present invention is to provide the application of the above-mentioned high mesoporous lignin-based hierarchical porous carbon material in zinc ion capacitors.
[0014] The objective of this invention is achieved through the following technical solution:
[0015] A method for preparing a high-mesoporous lignin-based hierarchical porous carbon material includes the following steps:
[0016] (1) Prepare a lignin-potassium hydroxide solution by adding lignin and potassium hydroxide to a pure alcohol solvent;
[0017] (2) Prepare an organic zinc salt solution by adding the organic zinc salt to a pure alcohol solvent;
[0018] (3) The organic zinc salt solution was slowly added to the lignin potassium hydroxide solution, heated to react, and dried to obtain the lignin / nano zinc oxide / organic potassium salt complex.
[0019] (4) The lignin / nano zinc oxide / organic potassium salt composite was carbonized under a protective gas atmosphere, acid washed, water washed and dried to obtain lignin-based multi-level porous carbon material.
[0020] Preferably, the lignin in step (1) is at least one of alkali lignin, enzymatically hydrolyzed lignin, and lignin sulfonate. The alkali lignin is alkali lignin extracted from papermaking silage; the enzymatically hydrolyzed lignin is the residue from enzymatically hydrolyzed lignin obtained during a bio-smelting process; and the lignin sulfonate is lignin sulfonate extracted from sulfite pulping. Alkali lignin is the most preferred.
[0021] Preferably, the pure alcohol solvent in step (1) is at least one of methanol, ethanol and propanol.
[0022] Preferably, the mass ratio of lignin, potassium hydroxide and organozinc salt in step (1) is (1-5):(1-10):(2-10); more preferably it is (1-5):(3.3-5):(6.4-10).
[0023] Preferably, the ratio of lignin to pure alcohol solvent in step (1) is (1-5) g: 30 mL; more preferably, it is (1-2) g: 30 mL.
[0024] Preferably, the organic zinc salt in step (2) is at least one of anhydrous zinc acetate, zinc lactate, and zinc gluconate. More preferably, it is anhydrous zinc acetate.
[0025] Preferably, the ratio of organic zinc salt to pure alcohol solvent in step (2) is (2-10) g: 70 mL; more preferably, it is (6.4-10) g: 70 mL.
[0026] Preferably, the heating and stirring temperature in step (3) is 50-100℃ and the time is 0.5-2h; more preferably, the temperature is 75℃ and the time is 2h.
[0027] Preferably, the drying temperature in step (3) is 80-100℃ and the time is 12-24h; preferably, the temperature is 90℃ and the time is 24h.
[0028] Preferably, the protective gas in step (4) is at least one of nitrogen and rare gas; more preferably, it is at least one of nitrogen and argon.
[0029] Preferably, the carbonization temperature in step (4) is 600-800℃ and the time is 0.5-5h. More preferably, the carbonization temperature is 700-800℃ and the time is 2h.
[0030] Preferably, the heating rate of carbonization in step (4) is 2-10℃ / min, and the flow rate of the protective gas is 20-100mL / min.
[0031] Preferably, the acid washing method in step (4) is as follows: soak the carbonized product in 0.5-2 mol / L HCl and stir for 6-24 h, and then filter.
[0032] Preferably, the water washing method in step (4) is as follows: the acid-washed carbonized product is washed with deionized water until neutral to remove soluble inorganic salt impurities in the carbonized product.
[0033] Preferably, the drying temperature in step (4) is 80-100℃ and the time is 12-24h.
[0034] The above preparation method yields a high mesoporous lignin-based hierarchical porous carbon material.
[0035] The lignin-based hierarchical porous carbon material has a specific surface area of 1200-2600 m². 2 / g, with a mesoporous ratio of 50-80%; this porous carbon was tested in a Zn / / C asymmetric capacitor assembled with 1mol / L ZnSO4 aqueous electrolyte, and its specific capacitance was 90-450F / g under different current densities.
[0036] The above-mentioned high mesoporous lignin-based hierarchical porous carbon material is used in batteries and capacitors.
[0037] Preferably, the high mesoporous lignin-based hierarchical porous carbon material is used in zinc ion mixed capacitors.
[0038] This invention aims to use an environmentally friendly and inexpensive pore-forming agent to create pores in inexpensive lignin, simultaneously achieving the chemical activation for micropore preparation and the template-based preparation of mesoporous structures, thereby producing a multi-level porous carbon material with high specific surface area. During precursor preparation, the nano-zinc oxide template maintains a relatively uniform particle size, and during high-temperature carbonization, the template forms a rich and uniform mesoporous structure by occupying space. Furthermore, the subsequent treatment of the template agent is relatively simple, requiring only acid washing.
[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0040] (1) The present invention uses lignin, which is abundant and inexpensive, as a precursor for carbon materials, achieving the effect of waste utilization, further reducing costs, and realizing the high-value utilization of lignin.
[0041] (2) In the process of synthesizing nano-zinc oxide, this invention introduces a template agent and an organopotassium salt to obtain a lignin / zinc oxide / organopotassium salt complex. This complex, as a precursor, undergoes a one-step carbonization process and in-situ template-assisted chemical activation to form a lignin-based mesoporous carbon with a coexistence of micropores, mesopores, and macropores. Therefore, this invention has the advantages of simple preparation process and low cost.
[0042] (3) The porous carbon cathode prepared by the present invention has the advantages of high specific surface area and rich mesoporous structure. The high specific surface area can provide a large number of active sites for the adsorption of zinc ions in the porous carbon cathode. The rich mesoporous structure can improve the wide ion transport channels, shorten the transport path and improve the mass transfer kinetics, thereby effectively improving the specific capacitance and rate performance of zinc ion capacitors. This porous carbon material is conducive to commercial production. Attached Figure Description
[0043] Figure 1 This is the XRD pattern of the carbonization product of lignin-based porous carbon (LPC-2-800) before water washing in Example 1.
[0044] Figure 2 The image shows the XRD pattern of porous carbon obtained from lignin-based porous carbon (LPC-2-800) in Example 1 after acid washing and water washing.
[0045] Figure 3 This is the nitrogen adsorption-desorption isotherm of lignin-based porous carbon (LPC-2-800) in Example 1.
[0046] Figure 4 This is a pore size distribution diagram of lignin-based porous carbon (LPC-2-800) from Example 1.
[0047] Figure 5 The cyclic voltammetry curves of lignin-based porous carbon (LPC-2-800) from Example 1 at scan rates of 1-200 mV / s are shown.
[0048] Figure 6 Example 1 shows the charge-discharge curves of lignin-based porous carbon (LPC-2-800) applied to a Zn / / C asymmetric supercapacitor at current densities of 0.1-50 A / g.
[0049] Figure 7 This is the curve showing the specific capacitance as a function of current density when lignin-based porous carbon (LPC-2-800) is applied to a Zn / / C asymmetric supercapacitor, as described in Example 1.
[0050] Figure 8 This is the XRD pattern of the carbonization product of lignin-based porous carbon (LPC-2-900) before water washing in Comparative Example 1.
[0051] Figure 9 The image shows the XRD pattern of porous carbon obtained from lignin-based porous carbon (LPC-2-900) in Comparative Example 1 after acid washing and water washing.
[0052] Figure 10 This is the curve showing the specific capacitance as a function of current density when lignin-based porous carbon (LPC-2-900) is applied to a Zn / / C asymmetric supercapacitor, as shown in Comparative Example 1.
[0053] Figure 11 This is a pore size distribution diagram of lignin-based porous carbon (LPC-2-800-10mL H2O) in Comparative Example 6. Detailed Implementation
[0054] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.
[0055] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.
[0056] Example 1
[0057] (1) Add 2g of alkali lignin, 3.3g of KOH and 30mL of anhydrous ethanol to a beaker in sequence and stir until fully mixed to obtain solution A;
[0058] (2) Add 6.4g of anhydrous zinc acetate and 70mL of anhydrous ethanol to a beaker and stir until dissolved to obtain solution B;
[0059] (3) Slowly pour solution A into solution B and stir at 75°C for 2 hours to obtain suspension C;
[0060] (4) Place suspension C in a 90℃ oven and dry for 24h to obtain lignin / zinc oxide / organic potassium salt complex powder;
[0061] (5) The lignin / zinc oxide / organopotassium salt complex powder from step (4) was heat-treated at 800℃ for 2h under a nitrogen atmosphere with a gas flow rate of 50mL / min and a heating rate of 5℃ / min. After the reaction was completed, it was taken out and washed with 1mol / L hydrochloric acid for 12h, washed with deionized water until neutral, and dried at 80℃ for 12h to obtain lignin-based porous carbon, named LPC-2-800.
[0062] Figure 1 The XRD pattern of untreated LPC-2-800 shows obvious diffraction peaks of ZnO. Due to the template effect of nano-zinc oxide, LPC-2-800 forms a hierarchical porous structure. Figure 2 The XRD pattern of LPC-2-800 was obtained after acid washing and water washing. Diffraction peaks of amorphous carbon appeared at 26° and 42°. The sharp increase in intensity of the low-angle diffraction peaks indicates abundant nanopores.
[0063] Figure 3 and Figure 4 The image shows the N2 adsorption-desorption isotherm and pore size distribution of the LPC-2-800. Figure 4 The adsorption pore volume increases sharply at low adsorption pressure, indicating the presence of micropores. At the same time, a significant adsorption hysteresis loop appears at medium and high adsorption pressure, indicating the presence of mesopores. It can be concluded that lignin-based porous carbon is a hierarchical porous carbon in which micropores, mesopores and macropores coexist. Figure 4 The aperture distribution map also verifies this conclusion.
[0064] LPC-2-800, conductive carbon black, and polytetrafluoroethylene (PTFE) were mixed in a mass ratio of 8:1:1, and ethanol was added and stirred to prepare the electrode for a zinc-ion capacitor. After drying, the electrode was cut into 8×8 mm electrode sheets for later use. The prepared electrode sheets were used as the positive electrode, the zinc metal sheet as the negative electrode, and 1 mol / L zinc sulfate as the electrolyte to assemble an asymmetric zinc-ion supercapacitor. The electrochemical performance of the lignin-based porous carbon was then tested.
[0065] Figure 5 and 6The cyclic voltammetry curves at 2-200 mV / s and the charge-discharge curves at current densities of 0.1-20 A / g are shown for lignin-based porous carbon used as the positive electrode of a zinc-ion capacitor. These results demonstrate that lignin-based porous carbon exhibits good capacitor behavior in the ZnSO4 electrolyte system.
[0066] Figure 7 The graph shows the specific capacitance of lignin-based porous carbon used as the positive electrode of a zinc-ion capacitor as a function of current density. The results show that the specific capacitance is 440 F / g at a current density of 0.1 A / g, and still has a specific capacitance of 196 F / g at a current density of 50 A / g, with a capacity retention of 45%. This indicates that LPC-2-800 has high capacity and good rate performance.
[0067] Example 2
[0068] (1) Add 1g of alkali lignin, 5g of KOH and 30mL of anhydrous ethanol to a beaker in sequence and stir until fully mixed to obtain solution A;
[0069] (2) Add 10g of anhydrous zinc acetate and 70mL of anhydrous ethanol to a beaker and stir until dissolved to obtain solution B;
[0070] (3) Slowly pour solution A into solution B and stir at 75°C for 2 hours to obtain suspension C;
[0071] (4) Place suspension C in a 90℃ oven and dry for 24h to obtain lignin / zinc oxide / organic potassium salt complex powder;
[0072] (5) The lignin / zinc oxide / organopotassium salt complex powder from step (4) was heat-treated at 700℃ for 2h under a nitrogen atmosphere with a gas flow rate of 50mL / min and a heating rate of 5℃ / min. After the reaction was completed, it was taken out and washed with 1mol / L hydrochloric acid for 12h, washed with deionized water until neutral, and dried at 80℃ for 12h to obtain lignin-based porous carbon, named LPC-1-800.
[0073] Example 3
[0074] (1) Add 5g of alkali lignin, 5g of KOH and 30mL of anhydrous ethanol to a beaker in sequence and stir until fully mixed to obtain solution A;
[0075] (2) Add 10g of anhydrous zinc acetate and 70mL of anhydrous ethanol to a beaker and stir until dissolved to obtain solution B;
[0076] (3) Slowly pour solution A into solution B and stir at 75°C for 2 hours to obtain suspension C;
[0077] (4) Place suspension C in a 90℃ oven and dry for 24h to obtain lignin / zinc oxide / organic potassium salt complex powder;
[0078] (5) The lignin / zinc oxide / organopotassium salt complex powder from step (4) was heat-treated at 800℃ for 2h under a nitrogen atmosphere with a gas flow rate of 50mL / min and a heating rate of 5℃ / min. After the reaction was completed, it was taken out and washed with 1mol / L hydrochloric acid for 12h, washed with deionized water until neutral, and dried at 80℃ for 12h to obtain lignin-based porous carbon, named LPC-5-800.
[0079] Comparative Example 1
[0080] (1) Add 2g of alkali lignin, 3.3g of KOH and 30mL of anhydrous ethanol to a beaker in sequence and stir until fully mixed to obtain solution A;
[0081] (2) Add 6.4g of anhydrous zinc acetate and 70mL of anhydrous ethanol to a beaker and stir until dissolved to obtain solution B;
[0082] (3) Slowly pour solution A into solution B and stir at 75°C for 2 hours to obtain suspension C;
[0083] (4) Place suspension C in a 90℃ oven and dry for 24h to obtain lignin / zinc oxide / organic potassium salt complex powder;
[0084] (5) The lignin / zinc oxide / organopotassium salt complex powder from step (4) was heat-treated at 900℃ for 2h under a nitrogen atmosphere with a gas flow rate of 50mL / min and a heating rate of 5℃ / min. After the reaction was completed, it was taken out and washed with 1mol / L hydrochloric acid for 12h, washed with deionized water until neutral, and dried at 80℃ for 12h to obtain lignin-based porous carbon, named LPC-2-900.
[0085] Figure 8 The XRD pattern of the untreated LPC-2-900 shows obvious K2CO3 diffraction peaks, which is due to the carbothermic reduction reaction of ZnO at 900℃, which causes it to escape in the form of zinc vapor. Figure 9 The image shows the XRD pattern of LPC-2-900 after pickling.
[0086] Figure 10 The figure shows the specific capacitance as a function of current density when lignin-based porous carbon is used as the positive electrode of a zinc-ion capacitor. The results show that the specific capacitance is 330 F / g at a current density of 0.1 A / g and still has a specific capacitance of 150 F / g at a current density of 50 A / g. This indicates that the disappearance of zinc oxide in LPC-2-900 causes some damage to the mesoporous structure, resulting in a decrease in electrochemical performance.
[0087] Comparative Example 2
[0088] (1) Add 2g of alkali lignin, 3.3g of KOH and 30mL of anhydrous ethanol to a beaker in sequence and stir until fully mixed to obtain solution A;
[0089] (2) Add 6.4g of anhydrous zinc acetate and 70mL of anhydrous ethanol to a beaker and stir until dissolved to obtain solution B;
[0090] (3) Slowly pour solution A into solution B and stir at 75°C for 2 hours to obtain suspension C;
[0091] (4) Separate the solid and liquid phases of suspension C using a high-speed centrifuge and collect the solid precipitate;
[0092] (5) The solid precipitate obtained in step (4) was placed in a 90℃ oven and dried for 24 hours to obtain lignin / zinc oxide composite powder;
[0093] (6) The lignin / zinc oxide composite powder from step (5) was heat-treated at 800°C for 2 hours under a nitrogen atmosphere with a gas flow rate of 50 mL / min and a heating rate of 5°C / min. After the reaction was completed, it was taken out and washed with 1 mol / L hydrochloric acid for 12 hours, washed with deionized water until neutral, and dried at 80°C for 12 hours to obtain lignin-based porous carbon, named LPC-ZnO-800.
[0094] Comparative Example 3
[0095] (1) Add 2g of alkali lignin, 3.3g of KOH and 100mL of anhydrous ethanol to a beaker in sequence, and stir at 75℃ for 2h;
[0096] (2) The solution obtained in step (1) was placed in a 90℃ oven and dried for 24 hours to obtain the lignin / KOH complex precursor;
[0097] (3) The precursor powder from step (2) was heat-treated at 800℃ for 2h under a nitrogen atmosphere with a gas flow rate of 50mL / min and a heating rate of 5℃ / min. After the reaction was completed, it was taken out and washed with 1mol / L hydrochloric acid for 12h, washed with deionized water until neutral, and dried at 80℃ for 12h to obtain lignin-based porous carbon, named LPC-KOH-800.
[0098] Comparative Example 4
[0099] (1) Add 2g of alkali lignin, 4g of potassium acetate and 100mL of anhydrous ethanol to a beaker in sequence and stir at 75℃ for 2h.
[0100] (2) The solution obtained in step (1) was placed in a 90℃ oven and dried for 24 hours to obtain the lignin / potassium acetate complex precursor.
[0101] (3) The precursor powder from step (2) was heat-treated at 800°C for 2 hours under a nitrogen atmosphere with a gas flow rate of 50 mL / min and a heating rate of 5°C / min. After the reaction was completed, it was taken out and washed with 1 mol / L hydrochloric acid for 12 hours, washed with deionized water until neutral, and dried at 80°C for 12 hours to obtain lignin-based porous carbon, named LPC-CH3COOK-800.
[0102] Comparative Example 5
[0103] (1) Add 2g of alkali lignin, 6.4g of anhydrous zinc acetate and 100mL of anhydrous ethanol to a beaker in sequence, and stir at 75℃ for 2h.
[0104] (2) The solution obtained in step (1) was placed in a 90℃ oven and dried for 24 hours to obtain lignin / zinc acetate precursor;
[0105] (3) The precursor powder from step (2) was heat-treated at 800℃ for 2h under a nitrogen atmosphere with a gas flow rate of 50mL / min and a heating rate of 5℃ / min. After the reaction was completed, it was taken out and washed with 1mol / L hydrochloric acid for 12h, washed with deionized water until neutral, and dried at 80℃ for 12h to obtain lignin-based porous carbon, named LPC-(CH3COO)2Zn-800.
[0106] Comparative Example 6
[0107] (1) Add 2g of alkali lignin, 3.3g of KOH and 30mL of anhydrous ethanol to a beaker in sequence and stir until fully mixed to obtain solution A;
[0108] (2) Add 6.4g of anhydrous zinc acetate, 60mL of anhydrous ethanol and 10mL of ultrapure water to a beaker and stir until dissolved to obtain solution B;
[0109] (3) Slowly pour solution A into solution B and stir at 75°C for 2 hours to obtain suspension C;
[0110] (4) Place suspension C in a 90℃ oven and dry for 24h to obtain lignin / zinc oxide / organic potassium salt complex powder;
[0111] (5) The lignin / zinc oxide / organopotassium salt complex powder from step (4) was heat-treated at 800℃ for 2h under a nitrogen atmosphere with a gas flow rate of 50mL / min and a heating rate of 5℃ / min. After the reaction was completed, it was taken out and washed with 1mol / L hydrochloric acid for 12h, washed with deionized water until neutral, and dried at 80℃ for 12h to obtain lignin-based porous carbon, named LPC-2-800-10mL H2O.
[0112] Figure 11 The image shows the pore size distribution of LPC-2-800-10mL H2O. Figure 11 It can be seen that the micropore distribution of Comparative Example 6 is similar to that of Example 1, the main difference being that the mesopores have larger pore sizes and a wider distribution range. Changes in the solution system affect the particle size of the zinc oxide template, thus leading to significant changes in the pore structure of the porous carbon.
[0113] Comparative Example 7
[0114] (1) Add 2g of alkali lignin, 2.36g of NaOH and 30mL of anhydrous ethanol to a beaker in sequence and stir until fully mixed to obtain solution A;
[0115] (2) Add 6.4g of anhydrous zinc acetate and 70mL of anhydrous ethanol to a beaker and stir until dissolved to obtain solution B;
[0116] (3) Slowly pour solution A into solution B and stir at 75°C for 2 hours to obtain suspension C;
[0117] (4) The suspension C was placed in a 90℃ oven and dried for 24 hours to obtain lignin / zinc oxide / organic sodium salt complex powder;
[0118] (5) The lignin / zinc oxide / organic sodium salt complex powder from step (4) was heat-treated at 800℃ for 2h under a nitrogen atmosphere with a gas flow rate of 50mL / min and a heating rate of 5℃ / min. After the reaction was completed, it was taken out and washed with 1mol / L hydrochloric acid for 12h, washed with deionized water until neutral, and dried at 80℃ for 12h to obtain lignin-based porous carbon, named LPC-NaOH-800.
[0119] Table 1. Comparison of specific surface area and other parameters of porous carbon samples prepared in the examples and comparative examples.
[0120]
[0121] Table 2 shows the specific capacity (test current density of 0.1 A / g and 50 A / g) and capacity retention (specific capacity ratio of 50 A / g to 0.1 A / g) of the porous carbon samples prepared in the examples and comparative examples.
[0122]
[0123] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A method for preparing a high-mesoporous lignin-based hierarchical porous carbon material, characterized in that, Includes the following steps: (1) Prepare a lignin-potassium hydroxide solution by adding lignin and potassium hydroxide to a pure alcohol solvent; (2) Prepare an organic zinc salt solution by adding the organic zinc salt to a pure alcohol solvent; (3) The organic zinc salt solution was slowly added to the lignin potassium hydroxide solution, heated to react, and dried to obtain the lignin / nano zinc oxide / organic potassium salt complex. (4) The lignin / nano zinc oxide / organic potassium salt composite was carbonized under a protective gas atmosphere, acid washed, water washed and dried to obtain lignin-based hierarchical porous carbon material.
2. The method for preparing a high mesoporous lignin-based hierarchical porous carbon material according to claim 1, characterized in that, The mass ratio of lignin, potassium hydroxide and organozinc salt in step (1) is (1-5):(1-10):(2-10); The lignin mentioned in step (1) is at least one of alkali lignin, enzymatically hydrolyzed lignin, and lignin sulfonate; The organic zinc salt in step (2) is at least one of anhydrous zinc acetate, zinc lactate, and zinc gluconate.
3. The method for preparing a high mesoporous lignin-based hierarchical porous carbon material according to claim 1, characterized in that, The pure alcohol solvent in step (1) is at least one of methanol, ethanol, and propanol; The ratio of lignin to pure alcohol solvent in step (1) is (1-5) g: 30 mL; The ratio of organic zinc salt to pure alcohol solvent in step (2) is (2-10) g: 70 mL.
4. The method for preparing a high mesoporous lignin-based hierarchical porous carbon material according to claim 1, characterized in that, The carbonization temperature in step (4) is 600-800℃, and the time is 0.5-5h; The heating rate for carbonization in step (4) is 2-10℃ / min, and the flow rate of the protective gas is 20-100mL / min.
5. The method for preparing a high mesoporous lignin-based hierarchical porous carbon material according to claim 1, characterized in that, The heating and stirring in step (3) is carried out at a temperature of 50-100℃ for 0.5-2 hours. The drying temperature in step (3) is 80-100℃ and the time is 12-24h.
6. The method for preparing a high mesoporous lignin-based hierarchical porous carbon material according to claim 1, characterized in that, The mass ratio of lignin, potassium hydroxide and organozinc salt in step (1) is (1-5):(3.3-5):(6.4-10); The ratio of lignin to pure alcohol solvent in step (1) is (1-2) g: 30 mL; The ratio of organic zinc salt to pure alcohol solvent in step (2) is (6.4-10) g: 70 mL.
7. The method for preparing a high mesoporous lignin-based hierarchical porous carbon material according to claim 1, characterized in that, The heating and stirring in step (3) is carried out at a temperature of 75°C for 2 hours. The drying temperature in step (3) is 90℃, and the drying time is 24 hours; The carbonization temperature in step (4) is 700-800℃ and the time is 2h.
8. The method for preparing a high mesoporous lignin-based hierarchical porous carbon material according to claim 1, characterized in that, The protective gas in step (4) is at least one of nitrogen and rare gases; The acid washing method described in step (4) is as follows: soak the carbonized product in 0.5-2 mol / L HCl and stir for 6-24 h, and then filter. The water washing method in step (4) is as follows: the carbonized product after acid washing is washed with deionized water until neutral; The drying temperature in step (4) is 80-100℃ and the time is 12-24h.
9. A high mesoporous lignin-based hierarchical porous carbon material prepared by the preparation method according to any one of claims 1-8.
10. The application of the high mesoporous lignin-based hierarchical porous carbon material according to claim 9 in batteries and capacitors.