High specific surface area high nitrogen and oxygen doped lignin porous carbon material and preparation method and application thereof

Abstract

The application discloses a high specific surface area high nitrogen and oxygen doped lignin porous carbon material and a preparation method and application thereof. The method comprises the following steps: firstly, preparing a supramolecular complex through a solvothermal reaction of lignin, magnesium hydroxide, cyanuric acid and melamine; then, directly carbonizing the supramolecular complex to obtain a nitrogen doped lignin carbon / magnesium oxide composite; and finally, activating the nitrogen doped lignin carbon / magnesium oxide composite by using a weak corrosive potassium salt to increase a micro-mesopore structure, so as to prepare the lignin porous carbon material with an ultrahigh specific surface area, rich micro-mesopore and nitrogen and oxygen doping. The high specific surface area high nitrogen and oxygen doped lignin porous carbon material has the advantages that the high specific surface area can provide a large number of active sites, the high nitrogen and oxygen doping can improve the wettability of the carbon material, the utilization rate of the active sites is improved, the problem of the mismatch between the pore size of the carbon material and the carriers is improved due to the rich micro-mesopore structure, and the specific capacitance of a zinc ion hybrid capacitor is significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of zinc ion hybrid capacitor positive electrode materials, and particularly relates to a high specific surface area high nitrogen and oxygen doped lignin porous carbon material, a preparation method thereof and application of the material in zinc ion hybrid capacitors. BACKGROUND

[0002] Metallic zinc anode has high theoretical specific capacity (820 mAh / g), low redox potential (-0.76 V vs. SHE), environmental friendliness and other characteristics, and exhibits good application potential in the field of large-scale energy storage. Carbon materials have high specific surface area, excellent electrical conductivity, stable physicochemical properties and adjustable pore structure. Therefore, zinc ion hybrid capacitors composed of a metallic zinc anode and a porous carbon positive electrode material have high energy density and high power density and have attracted widespread attention. However, the zinc storage capacity of the porous carbon material is low and difficult to match the high capacity of the zinc anode. To improve the zinc storage capacity of the porous carbon material, two key problems need to be solved: (1) poor interface wettability leads to low active site utilization; and (2) pore size and carriers are not matched, leading to slow ion transmission rate.

[0003] In recent years, to solve the above two problems, researchers mainly optimize the electrochemical performance of carbon materials through the following three strategies: (1) heteroatom doping, heteroatoms can improve the intrinsic properties (conductivity and wettability) of carbon materials, help to adjust the microenvironment of the carbon surface, enhance the accessibility of active sites and provide additional pseudo-capacitance; (2) pore structure regulation, micropores with pore diameters larger than carrier diameters can contribute more active surface and provide a large number of zinc storage active sites, and mesopores as ion mass transfer channels can help to accelerate ion transmission; (3) nanostructure design, compared with zero-dimensional, one-dimensional and three-dimensional nanostructures, two-dimensional nanosheets can help to accelerate electron transfer, shorten ion transmission path and fully expose active sites. Therefore, the preparation of high specific surface area heteroatom doped porous carbon materials through heteroatom doping, pore structure regulation and nanostructure design strategies is an effective method to improve the performance of zinc ion hybrid capacitors.

[0004] Among the heteroatom doping, nitrogen and oxygen atoms are the most widely studied. Since porous carbon materials are prepared by carbonization activation at relatively low temperatures, there must be oxygen functional groups on the surface of carbon materials, which can provide additional pseudo-capacitive active sites to improve specific capacity. Nitrogen atoms are easy to dope because their radius is similar to that of carbon atoms. In addition, the electronegativity of nitrogen atoms (3.04) is larger, which can change the electronic structure and charge distribution of carbon materials, and is beneficial to reduce the adsorption energy barrier between carbon-oxygen bonds and zinc ions. For example, Zheng et al. (Chemical Engineering Journal, 2020, 387, 124161) obtained oxygen-doped porous carbon materials (specific surface area: 523 m 2 / g, oxygen content: 19.87 at%) by burning and concentrated nitric acid treatment of the solvothermal reaction product of sodium and ethanol. The specific capacity at a current density of 0.5 A / g was 132.7 mAh / g, which was significantly higher than that of undoped porous carbon materials (82.9 mAh / g). However, due to the low specific surface area and underdeveloped pore structure, the performance of the assembled zinc ion hybrid capacitor was poor. Liu et al. (Nano Research, 2019, 12, 2835-2841) mixed chitosan, potassium bicarbonate and ferric nitrate in an aqueous solution, and directly carbonized after drying to obtain nitrogen-doped hierarchical porous carbon materials (specific surface area: 879 m 2 / g, oxygen content: 8.2 at%, nitrogen content: 5.3 at.%), the specific capacity at a current density of 0.1 A / g was 136.8 mAh / g, higher than that of undoped carbon materials. This process achieved a high doping level, but the specific surface area was low, resulting in a low specific capacity of the zinc ion hybrid capacitor.

[0005] In terms of pore structure regulation, the compatibility of pore size and charge carriers is directly related to the storage and transport of zinc ions. The solvated ion ([Zn(H2O)6] 2+ , diameter 0.86 nm) of zinc ions in aqueous electrolyte is the main charge carrier in the charge storage process. When the micropore size is greater than 0.86 nm, it is beneficial to improve the accessibility of solvated ions, and mesopores help to accelerate ion transport, achieving the best zinc storage capacity. For example, Wang et al. (Advanced Materials, 2022, 34, 2203744.) prepared high specific surface area nitrogen-doped hierarchical porous carbon (specific surface area: 3553 m 2 / g, microporosity: 20.0%, mesoporosity: 72.6%, nitrogen content: 2.67 at.%, oxygen content: 7.48 at.%), exhibited a specific capacity of up to 199.1 mAh / g at a current density of 0.5 A / g. However, the process used a strong corrosive activator, resulting in severe loss of nitrogen species, and ZIF-8 was prepared from synthetic chemicals, which is too expensive for industrial production. An et al. (Applied Surface Science, 2020, 530, 147220) obtained mesoporous oxygen-doped carbon materials (specific surface area: 2527 m 2 / g, microporosity: 49.0%, mesoporosity: 51.0%, oxygen functional group content: 47.0 wt.%), exhibited a specific capacity of 176.1 mAh / g at a current density of 0.5 A / g. However, the nanostructure of the carbon material prepared by this process was irregular block morphology, resulting in a rate performance of only 41% at a current density of 10 A / g.

[0006] In terms of nanostructure design, ordered nanostructures can maximize the advantages of porous carbon materials. In particular, two-dimensional porous carbon nanosheets have high specific surface area and abundant micropores and mesopores, which can provide abundant interface active sites and short ion transport paths, which is beneficial to reduce the resistance of carbon materials and accelerate the diffusion rate of ions. Liu et al. (Materials Today Chemistry, 2023, 29, 101476.) prepared high specific surface area nitrogen and oxygen-doped carbon nanosheets (specific surface area: 3178 m 2 / g, nitrogen content: 1.48 at.%, oxygen content: 7.58 at.%), had a specific capacity of 198.4 mAh / g at a current density of 0.2 A / g. Zhang et al. (Journal of Colloid and Interface Science, 2024, 6664, 146-155) prepared nitrogen and oxygen-doped porous carbon nanosheets (specific surface area: 1843 m 2 / g, nitrogen content: 7.00 at.%, oxygen content: 6.00 at.%), had a specific capacity of 181.0 mAh / g at a current density of 0.5 A / g. However, the carbon precursors in the above processes are derived from synthetic chemicals, which are expensive, or involve a large amount of strong corrosive chemicals in the preparation process, which is not conducive to industrial production.

[0007] Therefore, renewable and low-cost biomass-derived carbon materials have attracted the attention of researchers. Industrial lignin is a byproduct of the pulp and paper and bioethanol industries, with high carbon content, rich oxygen-containing functional groups, and easy modification and modification characteristics, making it an ideal carbon precursor.

[0008] To prepare nitrogen-doped lignin-based porous carbon materials with high specific surface area, the commonly used method is to directly carbonize lignin with nitrogen dopants (urea, thiourea, melamine, and tricyanogen chloride, etc.) and activating agents (potassium hydroxide, zinc chloride, potassium oxalate, and phosphoric acid, etc.). However, the thermal stability of nitrogen species is poor, making it difficult to prepare high-nitrogen-doped lignin-based porous carbon materials. For example: Zhu et al. (Chemical Engineering Journal, 2017, 316, 770-777) mixed and dried the lignin black liquor obtained by treating rice straw with potassium hydroxide, and then carbonized at high temperature to prepare nitrogen-doped lignin-based porous carbon materials (specific surface area: 2646 m 2 / g, microporosity: 45%, nitrogen content: 1.21 at.%, oxygen content: 8.38 at.%), which were used for supercapacitors and had a specific capacitance of 337 F / g at a current density of 0.5 A / g. To further increase the nitrogen doping amount, Wang et al. (International Journal of Biological Macromolecules, 2024, 265, 130796) modified lignin with tricyanogen chloride, then directly used it as a carbon and nitrogen source, and sodium hydroxide as an activating agent, and then carbonized to prepare nitrogen-doped lignin-based carbon spheres (specific surface area: 1778 m 2 / g, pore volume: 0.5 cm 3 / g, nitrogen content: 2.85 at.%), which were used for supercapacitors and had a specific capacitance of 473 F / g at a current density of 0.5 A / g. Although the carbon materials prepared by the above techniques exhibit excellent performance in supercapacitors, the nitrogen doping amount is low, the microporous and mesoporous are less or the pore volume is low, and they cannot be directly used for zinc ion hybrid capacitors.

[0009] To improve the performance of lignin-based porous carbon materials in zinc ion hybrid capacitors, Xue et al. (Chemical Engineering Journal, 2024, 480, 147994) directly pyrolyzed a mixture of lignin, urea, and potassium oxalate to prepare nitrogen and oxygen-doped lignin-based porous carbon (specific surface area: 1949 m 2 / g, microporosity: 46%, nitrogen content: 1.64 at.%, oxygen content: 8.42 at.%), with a specific capacitance of 360 F / g at a current density of 0.1 A / g; Li et al. (ACS Applied Energy Materials, 2023, 6, 6700-6711) mixed pyrolyzed lignin, thiourea, urea, and three times the amount of potassium hydroxide, and prepared a nitrogen / sulfur-doped activated carbon material (specific surface area: 2773 m 2 / g, microporosity: 57%, nitrogen content: 1.32 at.%, oxygen content: 9.05 at.%), with a specific capacity of 121.7 mAh / g at a current density of 0.3 A / g when used in a zinc ion hybrid capacitor. However, the current technology is to directly mix lignin with an activating agent and / or a dopant, which is easy to form random aggregates, resulting in disordered internal structure of the porous carbon material, less micropores or lower nitrogen doping amount (<3 at.%), and poor electrochemical performance of the zinc ion hybrid capacitor.

[0010] The thermoplastic characteristics of lignin lead to its easy shrinkage and aggregation during carbonization. In order to achieve ordered nanostructure and increase mesopores, hard templates such as silica, polystyrene, and nano-magnesium oxide are usually added in the preparation process of lignin carbon materials. Nano-magnesium oxide has the characteristics of low cost and easy removal, and has attracted the attention of researchers. Song et al. (RSC Advances, 2017, 7, 48324) used F127 to disperse nano-magnesium oxide templates and alkali lignin, and prepared lignin mesoporous carbon (specific surface area: 712 m 2 / g, mesoporous rate: 83%) by solvent evaporation assembly and carbonization. A large number of mesopores improve the ion transport rate, but due to the lack of micropores and low specific surface area, the electrochemical performance in supercapacitors is poor, only 186 F / g. Zhang et al. (Carbon, 2020, 162: 256-266) carbonized a flower-shaped lignin mesoporous carbon material (specific surface area: 827 m 2 / g) composed of two-dimensional nanosheets by evaporative-induced self-assembly of enzymatic lignin and magnesium hydroxide templates at high temperature. It has excellent performance as a photocatalyst carrier. Although magnesium hydroxide is an excellent template for flaky structure and avoids the use of surfactants, the activation of magnesium hydroxide is weak, resulting in low specific surface area and fewer micropores, which cannot be directly used in zinc ion hybrid capacitors.

[0011] Furthermore, in the research of high nitrogen-doped lignin-based carbon materials, the poor thermal stability of nitrogen dopants and the poor compatibility with lignin lead to a low doping level. Therefore, Fu et al. (Journal of Energy Storage, 2023, 63, 106947) prepared nitrogen-doped lignin-based carbon materials by co-pyrolysis of a composite of sodium lignosulfonate and zinc oxalate with melamine. A high nitrogen doping level (14.47 at.%) was achieved due to the in-situ generation of zinc cyanamide during pyrolysis. However, the weak etching effect of zinc cyanamide resulted in a specific surface area of the prepared nitrogen-doped lignin-based carbon material of only 95 m 2 / g, and a mass specific capacitance of only 300 F / g at a current density of 0.5 A / g as an electrode material for supercapacitors. The high nitrogen-doped carbon material prepared by this process cannot be used for zinc ion capacitors due to its low specific surface area and lack of micro-mesopores. Zhang et al. (Nano Energy, 2022, 103, 107827) prepared a high nitrogen-doped lignin-based carbon material (nitrogen content: 14.9 at.%, oxygen content: 4.7 at.%) by directly carbonizing sodium lignosulfonate assembled with almost 15 times the amount of melamine-triazine supermolecules through forces such as hydrogen bonding and van der Waals forces. Due to the lack of additional activators, the specific surface area of the prepared high nitrogen-doped lignin-based carbon material was only 657 m 2 / g, and there were few micropores (8%), and the specific capacitance was only 266 F / g at a current density of 0.01 A / g. Although the pseudo-capacitance was introduced by doping a high proportion of nitrogen / oxygen atoms, it had certain electrochemical performance in zinc ion hybrid capacitors. However, the nitrogen dopant was still mixed with lignin in the form of a guest through physical interactions such as hydrogen bonding, and even if a chemical activator was used to further increase the specific surface area, it could still lead to a sharp decrease in the nitrogen / oxygen doping level during further activation and pore creation.

[0012] In summary, due to the poor compatibility or weak interaction between lignin and templates or dopants, and the large use of strong corrosive activators, the lignin-based porous carbon nanostructure is disordered, the pore structure distribution is unreasonable, or the doping level is low. The nitrogen / oxygen-doped lignin-based porous carbon materials prepared by the existing technologies or processes cannot simultaneously have a high surface area, a high proportion of micro-mesoporous structure, a high nitrogen / oxygen content, and an ordered nanostructure, resulting in low active site utilization and slow ion transport rate, making it difficult to be used in zinc ion hybrid capacitors. SUMMARY

[0013] To solve the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a method for preparing a high specific surface area high nitrogen / oxygen-doped lignin-based porous carbon material.

[0014] The method of the present application assembles a lignin / magnesium hydroxide / cyanuric acid / triamine four-component supramolecular complex based on hydrogen bonds and chemical bonds using the active functional groups of lignin, and carbonizes and activates to prepare a high specific surface area high nitrogen and oxygen doped lignin porous carbon material. First, lignin is adsorbed on the magnesium hydroxide sheet layer by hydrogen bonding, which is conducive to inhibiting the collapse of the structure during carbonization. Then, the phenolic hydroxyl groups of lignin crosslink with cyanuric chloride, and further assemble to form a magnesium hydroxide / lignin / cyanuric acid / triamine four-component supramolecular complex based on hydrogen bonds and triamine under solvothermal conditions and directly carbonize to obtain a nitrogen doped lignin carbon / magnesium oxide composite, which can avoid the loss of a large number of nitrogen atoms during carbonization. Finally, the nitrogen doped lignin carbon / magnesium oxide composite is activated by a weakly corrosive potassium salt to increase the micro-mesoporous structure, thereby preparing a lignin porous carbon material with ultra-high specific surface area, rich micro-mesoporous structure and nitrogen and oxygen doping.

[0015] Another object of the present application is to provide a high specific surface area high nitrogen and oxygen doped lignin porous carbon material prepared by the above method. The higher specific surface area can provide a large number of active sites, the high nitrogen and oxygen doping can improve the wettability of the carbon material, improve the utilization rate of the active sites, and the rich micro-mesoporous structure can improve the pore size and carrier mismatch problem of the carbon material, and significantly improve the specific capacitance of the zinc ion hybrid capacitor.

[0016] The lignin porous carbon material prepared by the present application has a morphology of interconnected two-dimensional nanosheets, a specific surface area greater than 2500 m 2 / g, a nitrogen and oxygen atom content of 13.0 at.% (nitrogen content: 5.0 at.%, oxygen content: 8.0 at.%), and a micro-mesoporous pore volume ratio greater than 85%.

[0017] Another object of the present application is to provide the use of the above high specific surface area nitrogen and oxygen doped lignin carbon material in a zinc ion hybrid capacitor.

[0018] The object of the present application is achieved by the following technical solutions:

[0019] A preparation method of a high specific surface area high nitrogen and oxygen doped lignin porous carbon material, comprising the following steps:

[0020] (1) Dissolve lignin in ethanol, add magnesium hydroxide nanosheets, and stir to obtain a lignin / magnesium hydroxide mixture;

[0021] (2) Add excess cyanuric chloride to the lignin / magnesium hydroxide mixture and react, then add triamine and perform solvothermal reaction, filter and dry to obtain a lignin / magnesium hydroxide / cyanuric acid / triamine four-component supramolecular complex;

[0022] (3) carbonizing the lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular complex under inert gas atmosphere to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite;

[0023] (4) mixing the nitrogen-oxygen doped lignin carbon / magnesium oxide composite and a weakly corrosive potassium salt uniformly, activating under inert gas atmosphere, pickling, filtering and drying to obtain a high specific surface area high nitrogen-oxygen doped lignin porous carbon material.

[0024] Preferably, the magnesium hydroxide nanosheet in step (1) is obtained by the following method: dispersing nanometer magnesium oxide in water, heating and hydrolyzing, filtering and drying to obtain magnesium hydroxide nanosheet.

[0025] More preferably, the particle size of the nanometer magnesium oxide is 10-100 nm.

[0026] More preferably, the mass ratio of the nanometer magnesium oxide to water is 1:10-30; further preferably, 1:10-14.5.

[0027] More preferably, the heating and hydrolysis temperature is 70-90 ℃, and the time is 2-4 h; further preferably, the heating and hydrolysis temperature is 70-80 ℃, and the time is 3-4 h.

[0028] Preferably, the lignin in step (1) is at least one of enzymatic hydrolysis lignin, alkali lignin in alkaline pulping black liquor and organic solvent lignin which are by-products of bioethanol industry.

[0029] Preferably, the ratio of the lignin, ethanol and magnesium hydroxide nanosheet in step (1) is 10 g:200-300 mL:10-30 g; further preferably, 10 g:200-300 mL:10-20 g.

[0030] Preferably, the stirring time in step (1) is 3-5 h; further preferably, 3-4 h.

[0031] Preferably, the mass ratio of the cyanuric chloride, melamine and the lignin in step (1) in step (2) is 10-20:5-15:10; further preferably, 10-20:7-15:10; more preferably, 10-15:7-10:10.

[0032] Preferably, the temperature for adding cyanuric chloride for reaction in step (2) is 0-5 ℃, and the time is 20-40 min; further preferably, 20-30 min.

[0033] Preferably, the temperature for the solvothermal reaction of step (2) is 140-180 ℃, and the time is 8-12 h; further preferably, the temperature is 140-160 ℃, and the time is 10-12 h.

[0034] Preferably, the inert gas in step (3) is at least one of a noble gas and nitrogen; more preferably, it is at least one of nitrogen, argon, and helium.

[0035] Preferably, the carbonization temperature in step (3) is 500-600 ℃, and the time is 1-3 h; further preferably, the temperature is 550-600 ℃, and the time is 1-2 h.

[0036] Preferably, the heating rate for the carbonization in step (3) is 5-10 ℃ / min.

[0037] Preferably, the weakly corrosive potassium salt in step (4) is at least one of potassium bicarbonate, potassium acetate, and potassium citrate.

[0038] Preferably, the mass ratio of the nitrogen-oxygen doped lignin carbon / magnesium oxide composite to the weakly corrosive potassium salt in step (4) is 1:0.5-1.5; further preferably, it is 1:0.5-1.

[0039] Preferably, the activation temperature in step (4) is 600-800 ℃, and the time is 1-3 h; further preferably, the temperature is 700-800 ℃, and the time is 1-2 h.

[0040] Preferably, the heating rate for the activation in step (4) is 5-10 ℃ / min.

[0041] Preferably, the inert gas in step (4) is at least one of a noble gas and nitrogen; more preferably, it is at least one of nitrogen, argon, and helium.

[0042] Preferably, the acid solution used for the pickling in step (4) is one of a 0.5-1.5 mol / L hydrochloric acid solution or a sulfuric acid solution, and the soaking and washing time is 8-12 h.

[0043] Preferably, after the pickling in step (4), water washing, filtering, and drying are performed.

[0044] Preferably, the drying in steps (2) and (4) each includes one of air blowing drying, vacuum drying, infrared drying, and freeze drying; the drying temperature is 80-120 ℃, more preferably 100 ℃, and the drying time is 24 h.

[0045] A high specific surface area high nitrogen-oxygen nitrogen-oxygen doped lignin porous carbon material prepared by the above method.

[0046] The high specific surface area high nitrogen and oxygen doped lignin porous carbon material prepared by the method has a specific surface area ranging from 2500 to 3000 m 2 / g, a pore size ranging from 0.4 to 100 nm, a micro-mesopore ratio greater than 85%, and a nitrogen and oxygen atom content greater than 13.0 at.% (a nitrogen content greater than 5.0 at.% and an oxygen content greater than 8.0 at.%).

[0047] The high specific surface area high nitrogen and oxygen doped lignin porous carbon material is applied to a zinc ion hybrid capacitor.

[0048] The patent will be described in more detail below.

[0049] (1) Disperse nano-magnesium oxide in water, hydrolyze by heating, filter and dry to obtain magnesium hydroxide nanosheets:

[0050] The purpose of this step is to fully hydrolyze the nano-magnesium oxide to obtain magnesium hydroxide. Unlike magnesium oxide, the surface of magnesium hydroxide has a large number of hydroxyl functional groups, which are easy to form hydrogen bonds with the oxygen-containing functional groups (hydroxyl, phenolic hydroxyl and carboxyl, etc.) of lignin for self-assembly, and can improve the compatibility of lignin and the magnesium hydroxide template. Moreover, the magnesium hydroxide obtained by hydrolysis of nano-magnesium oxide has a two-dimensional sheet structure, which plays a role of structure guidance and space occupation in the pyrolysis and carbonization process, and is conducive to the formation of sheet-shaped mesoporous structures.

[0051] The hydrolysis temperature in this step is between 70 and 90 ℃, and the holding time is controlled within 2 to 4 hours to fully hydrolyze the magnesium oxide. If the hydrolysis temperature is too low, the magnesium oxide will not be fully hydrolyzed and the time will be longer. If the hydrolysis temperature is between 90 and 110 ℃, the holding time is controlled between 2 and 3 hours to avoid the water from evaporating too fast, which is not conducive to hydrolysis.

[0052] (2) Dissolve lignin in ethanol, add magnesium hydroxide nanosheets, and stir to obtain a lignin / magnesium hydroxide mixture:

[0053] The lignin in this step is enzymatic lignin or other lignin that can be dissolved in ethanol, which aims to have a smaller molecular weight and more oxygen-containing functional groups, which is conducive to enhancing the interaction between the lignin and the magnesium hydroxide template. The solvent in step (2) is ethanol, which is used to dissolve lignin on the one hand to enhance the reactivity of lignin and trichlorocyanuric acid in step (3), and on the other hand to react with trichlorocyanuric acid to generate cyanic acid groups. If the lignin has poor solubility in the solvent, it is easy to aggregate, which not only leads to uneven compounding of lignin and magnesium hydroxide, but also reduces the reactivity of lignin and trichlorocyanuric acid, affecting the nitrogen doping effect of the prepared carbon material.

[0054] If the amount of ethanol is too low, the lignin will not be dissolved sufficiently and will not be uniformly combined with magnesium hydroxide; if the amount of ethanol is too high, the concentration of lignin will be reduced, which is not conducive to the cross-linking reaction with cyanuric chloride. If the mass ratio of magnesium hydroxide is too low, the amount of magnesium oxide formed by the decomposition of magnesium hydroxide during the carbonization process in step (4) will be too small, which will result in a low specific surface area of the product and a lack of mesoporous structure, which is not conducive to the further activation in step (5) to produce micro-mesoporous structure; if the mass ratio of magnesium hydroxide is too high, more water vapor and magnesium oxide will be produced by the decomposition of magnesium hydroxide during the carbonization process in step (4), which will result in too many mesoporous structures and instability, which is not conducive to the further activation in step (5).

[0055] (3) Adding cyanuric chloride to the lignin / magnesium hydroxide mixture for reaction, and then adding melamine for reaction, and then filtering and drying to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular complex:

[0056] In this step, after the substitution reaction of cyanuric chloride with lignin and ethanol solvent adsorbed on the surface of magnesium hydroxide at 0°C, lignin / cyanuric acid is grafted on the surface of lignin to form lignin / magnesium hydroxide / cyanuric acid. In order to ensure that lignin and cyanuric chloride react sufficiently, cyanuric chloride needs to be added in excess. The reaction temperature is controlled at 0-5°C because at this temperature, cyanuric chloride will undergo a single substitution reaction of one chlorine atom with phenolic hydroxyl groups, and the other two chlorine atoms will react with the solvent (ethanol) to form cyanic acid groups, which is more conducive to the formation of supramolecular structures.

[0057] In this step, too much or too little melamine is not conducive to the condensation of supramolecules during the solvothermal reaction. Melamine cannot be dissolved in ethanol, so it needs to be stirred uniformly after being added. If melamine is not uniformly dispersed, it will not be conducive to further solvothermal reaction.

[0058] The solvothermal reaction temperature in this step is 140-180°C, and the time is 8-12 h. Too low a temperature or too short a time is not conducive to the condensation of supramolecules; too high a temperature or too long a time will result in degradation of lignin and low yield.

[0059] (4) Carbonizing the lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular complex in an inert gas atmosphere to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite:

[0060] The carbonization in this step needs to be carried out in a nitrogen, argon or other inert gas atmosphere. The carbonization temperature is set at 500-600°C, the heating rate is 5-10°C / min, and the holding time is 1-3 h. If the temperature is too low and the time is too short, magnesium hydroxide will not be completely decomposed and carbonized; if the temperature is too high and the time is too long, nitrogen species will be decomposed and the production cost will be increased.

[0061] (5) The nitrogen-oxygen doped lignin carbon / magnesium oxide composite is mixed with a weakly corrosive potassium salt, activated in an inert gas atmosphere, washed, filtered and dried to obtain a high specific surface area high nitrogen-oxygen doped lignin porous carbon material:

[0062] The carbonization in this step needs to be carbonized in a nitrogen, argon or other inert gas atmosphere. The carbonization temperature is set between 600-800 ℃, the heating rate is 5-10 ℃ / min, and the holding time is 1-3 h. If the mass of potassium bicarbonate is too low, the carbonization temperature is too low, and the holding time is too short, it will not be conducive to the activation effect of potassium bicarbonate, the product pore structure will not be developed, and the specific surface area will be too low; if the mass of potassium bicarbonate is too high, the carbonization temperature is too high, and the holding time is too long, it will cause the pore structure to be destroyed due to excessive activation, the production cost to increase, and the carbon product yield to decrease.

[0063] The concentration of the dilute acid solution used for washing in this step requires 0.5-1.5 mol / L, and the soaking time is controlled at 6-12 h. If the acid concentration is too low or the soaking time is too short, it will cause the oxide to remain, reducing the specific surface area of the product; if the acid concentration is too high or the soaking time is too long, it will cause the pore structure of the product to be destroyed.

[0064] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0065] (1) The high specific surface area high nitrogen-oxygen doped lignin porous carbon material prepared by the present application has a high specific surface area, an ordered nanosheet structure, a high micro-mesopore ratio, and a high nitrogen-oxygen doping amount. The micro-mesopores in the nanosheet structure can provide abundant active sites and fast ion transport paths, and the nitrogen-oxygen functional groups can promote the accessibility of the active sites, thereby improving the utilization rate of the active sites. As a positive electrode material for zinc ion hybrid capacitors, it has a higher specific capacitance and shows good application prospects.

[0066] (2) In the preparation method described in the present application, lignin is assembled into a lignin / magnesium hydroxide / cyanuric acid / cyanurine four-component supramolecular composite through hydrogen bonds and chemical bonds, effectively improving the compatibility between lignin, the template agent and the nitrogen source, and achieving efficient activation and pore formation using a weakly corrosive potassium salt activator. In addition, industrial lignin is used as a carbon source, which is abundant in reserves, low in cost, renewable, and conducive to industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0067] Figure 1 is the Fourier infrared spectrum of the cyanuric chloride grafted lignin in Example 1 of the present application.

[0068] Figure 2 is the scanning electron microscope picture of the high specific surface area high nitrogen-oxygen doped lignin porous carbon material obtained in Example 1 of the present application.

[0069] Figure 3 is a transmission electron microscope picture of the high specific surface area high nitrogen and oxygen doped lignin porous carbon material obtained in Example 1 of the present application.

[0070] Figure 4 is a nitrogen adsorption / desorption isotherm and pore size distribution curve of the high specific surface area high nitrogen and oxygen doped lignin porous carbon material obtained in Example 1 of the present application.

[0071] Figure 5 is a constant current charge and discharge curve of the high specific surface area high nitrogen and oxygen doped lignin porous carbon material obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0072] The present application will be further described in conjunction with the examples and the accompanying drawings, but the embodiments of the present application are not limited thereto.

[0073] The reagents used in the examples are commercially available unless otherwise specified.

[0074] Example 1

[0075] Take 13.8 g of nano-magnesium oxide (particle size about 50 nm) and add to 150 mL of deionized water, hydrolyze under stirring at 80 ℃ for 3 h, filter after cooling to room temperature, then transfer the product to a blast drying oven at 100 ℃ and dry for 24 h to obtain 20 g of magnesium hydroxide nanosheets; take 10 g of enzymatic lignin, dissolve in 300 mL of ethanol, then add the above prepared 20 g of magnesium hydroxide nanosheets, fully stir at room temperature for 4 h to obtain a lignin / magnesium hydroxide mixture;

[0076] Take 15 g of cyanuric chloride and add to the above lignin / magnesium hydroxide mixture, react at 0 ℃ for 30 min, then add 10 g of melamine, stir uniformly at room temperature, then transfer to a reaction kettle, react at 160 ℃ for 10 h, filter after cooling to room temperature, then transfer the product to a blast drying oven at 100 ℃ and dry for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular complex;

[0077] Place the above complex powder in a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 550 ℃ at a heating rate of 5 ℃ / min, keep for 2 h, after carbonization, cool to room temperature to obtain a nitrogen and oxygen doped lignin carbon / magnesium oxide composite;

[0078] Take 1 g of nitrogen and oxygen doped lignin carbon / magnesium oxide composite and 1 g of potassium bicarbonate, grind and mix uniformly, transfer to a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 700 ℃ at a heating rate of 5 ℃ / min, keep for 2 h, after carbonization, reduce to room temperature to obtain black powder; immerse the black powder in 150 mL of 1 mol / L hydrochloric acid solution, stir for 10 h, filter, wash with deionized water, and dry in a 100 ℃ blast drying oven for 24 h to obtain a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material.

[0079] Example 2

[0080] Take 6.9 g of nano magnesium oxide (particle size about 50 nm) and add to 100 mL of deionized water, hydrolyze at 70 ℃ for 4 h, filter after cooling to room temperature, then transfer the product to a 100 ℃ blast drying oven and dry for 24 h to obtain 10 g of magnesium hydroxide nanosheets; take 10 g of alkali lignin, dissolve in 250 mL of ethanol, then add 10 g of the above prepared magnesium hydroxide nanosheets, stir well at room temperature for 3 h to obtain a lignin / magnesium hydroxide mixture;

[0081] Take 10 g of cyanuric chloride and add to the above lignin / magnesium hydroxide mixture, react at 0 ℃ for 20 min, then add 7 g of melamine, stir uniformly at room temperature, then transfer to a reaction kettle and react at 140 ℃ for 12 h, filter after cooling to room temperature, then transfer the product to a 100 ℃ blast drying oven and dry for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular composite;

[0082] Place the above composite powder in a tube furnace and carbonize under nitrogen atmosphere, heat from room temperature to 500 ℃ at a heating rate of 10 ℃ / min, keep for 3 h, after carbonization, reduce to room temperature to obtain a nitrogen and oxygen doped lignin carbon / magnesium oxide composite;

[0083] Take 1 g of nitrogen and oxygen doped lignin carbon / magnesium oxide composite and 0.5 g of potassium acetate, grind and mix uniformly, transfer to a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 800 ℃ at a heating rate of 10 ℃ / min, keep for 1 h, after carbonization, reduce to room temperature to obtain black powder; immerse the black powder in 150 mL of 0.5 mol / L hydrochloric acid solution, stir for 12 h, filter, wash with deionized water, and dry in a 100 ℃ blast drying oven for 24 h to obtain a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material.

[0084] Example 3

[0085] Take 10.4 g of nano-magnesium oxide (particle size about 50 nm) and add it to 104 mL of deionized water. Stir at 75 °C for 3.5 h. After cooling to room temperature, filter, and then transfer the product to a 100 °C blast drying oven and dry for 24 h to obtain 15 g of magnesium hydroxide nanosheets. Take 10 g of organic solvent lignin, dissolve it in 200 mL of ethanol, and then add the above-prepared 15 g of magnesium hydroxide nanosheets. Stir at room temperature for 3.5 h to obtain a lignin / magnesium hydroxide mixture;

[0086] Take 12 g of cyanuric chloride and add it to the above lignin / magnesium hydroxide mixture. React at 0 °C for 25 min, and then add 9 g of melamine. Stir uniformly at room temperature, and then transfer to a reaction kettle. React at 150 °C for 12 h. After cooling to room temperature, filter, and then transfer the product to a 100 °C blast drying oven and dry for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular complex.

[0087] Place the above complex powder in a tube furnace and carbonize under a nitrogen atmosphere. Heat at a rate of 5 °C / min from room temperature to 600 °C, and maintain for 1 h. After carbonization, cool to room temperature to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite.

[0088] Take 1 g of the nitrogen-oxygen doped lignin carbon / magnesium oxide composite and 0.75 g of potassium citrate, mix uniformly, and transfer to a tube furnace. Carbonize under a nitrogen atmosphere. Heat at a rate of 5 °C / min from room temperature to 750 °C, and maintain for 1 h. After carbonization, cool to room temperature to obtain a black powder. Soak the black powder in 150 mL of 1.5 mol / L hydrochloric acid solution, stir for 8 h, filter, wash with deionized water, and place in a 100 °C blast drying oven and dry for 24 h to obtain a high specific surface area high nitrogen-oxygen doped lignin porous carbon material.

[0089] Example 4

[0090] Take 17.3 g of nano-magnesium oxide (particle size about 50 nm) and add it to 200 mL of deionized water. Stir at 85 °C for 2.5 h. After cooling to room temperature, filter, and then transfer the product to a 100 °C blast drying oven and dry for 24 h to obtain 25 g of magnesium hydroxide nanosheets. Take 10 g of enzymatic lignin, dissolve it in 250 mL of ethanol, and then add the above-prepared 25 g of magnesium hydroxide nanosheets. Stir at room temperature for 4.5 h to obtain a lignin / magnesium hydroxide mixture.

[0091] Take 18 g cyanuric chloride into the above lignin / magnesium hydroxide mixture, react for 35 min at 0 ℃, then add 12 g melamine, stir uniformly at room temperature, then transfer to the reaction kettle, react for 8 h at 170 ℃, cool to room temperature after reaction, then filter, then transfer the product to a blast drying oven at 100 ℃ and dry for 24 h, to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular complex;

[0092] Put the above complex powder into a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 500 ℃ at a heating rate of 10 ℃ / min, keep for 2 h, cool to room temperature after carbonization to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite;

[0093] Take 1 g of the nitrogen-oxygen doped lignin carbon / magnesium oxide composite and 1.25 g of potassium bicarbonate, grind and mix uniformly, transfer to a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 650 ℃ at a heating rate of 10 ℃ / min, keep for 3 h, cool to room temperature after carbonization to obtain black powder; immerse the black powder in 150 mL of 1 mol / L hydrochloric acid solution, stir for 10 h, then filter, wash with deionized water, and dry in a blast drying oven at 100 ℃ for 24 h to obtain a high specific surface area high nitrogen-oxygen doped lignin porous carbon material.

[0094] Example 5

[0095] Take 20.7 g of nano-magnesium oxide (particle size about 50 nm) into 250 mL of deionized water, hydrolyze at 90 ℃ for 2 h, filter after cooling to room temperature, then transfer the product to a blast drying oven at 100 ℃ and dry for 24 h to obtain 30 g of magnesium hydroxide nanosheets; take 10 g of organic solvent lignin, dissolve in 300 mL of ethanol, then add the above prepared 30 g of magnesium hydroxide nanosheets, stir at room temperature for 5 h to obtain a lignin / magnesium hydroxide mixture;

[0096] Take 20 g of cyanuric chloride into the above lignin / magnesium hydroxide mixture, react for 35 min at 0 ℃, then add 15 g of melamine, stir uniformly at room temperature, then transfer to the reaction kettle, react for 8 h at 180 ℃, cool to room temperature after reaction, then filter, then transfer the product to a blast drying oven at 100 ℃ and dry for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular complex;

[0097] Put the above complex powder into a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 600 ℃ at a heating rate of 5 ℃ / min, keep for 1 h, cool to room temperature after carbonization to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite;

[0098] Take 1 g of nitrogen and oxygen doped lignin carbon / magnesium oxide composite and 1.5 g of potassium acetate, mix well, transfer to a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 600 ℃ at a rate of 5 ℃ / min, keep for 3 h, after carbonization, cool to room temperature to get black powder; immerse the black powder in 150 mL of 1.5 mol / L hydrochloric acid solution, stir for 8 h, filter, wash with deionized water, and dry in a 100 ℃ blast drying oven for 24 h to obtain a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material.

[0099] Example 6

[0100] Take 13.8 g of nano magnesium oxide (particle size about 50 nm) and add to 200 mL of deionized water, hydrolyze at 70 ℃ for 4 h, filter after cooling to room temperature, then transfer the product to a 100 ℃ blast drying oven and dry for 24 h to obtain 20 g of magnesium hydroxide nanosheets; take 10 g of organic solvent lignin, dissolve in 200 mL of ethanol, then add 30 g of the above prepared magnesium hydroxide nanosheets, stir well at room temperature for 5 h to obtain a lignin / magnesium hydroxide mixture;

[0101] Take 15 g of cyanuric chloride and add to the above lignin / magnesium hydroxide mixture, react at 0 ℃ for 35 min, then add 10 g of melamine, stir well at room temperature, then transfer to a reaction kettle and react at 140 ℃ for 12 h, cool to room temperature after reaction, then filter, then transfer the product to a 100 ℃ blast drying oven and dry for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular composite;

[0102] Place the above composite powder in a tube furnace and carbonize under nitrogen atmosphere, heat from room temperature to 500 ℃ at a rate of 10 ℃ / min, keep for 3 h, after carbonization, cool to room temperature to obtain a nitrogen and oxygen doped lignin carbon / magnesium oxide composite;

[0103] Take 1 g of nitrogen and oxygen doped lignin carbon / magnesium oxide composite and 0.5 g of potassium citrate, mix well, transfer to a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 800 ℃ at a rate of 10 ℃ / min, keep for 1 h, after carbonization, cool to room temperature to get black powder; immerse the black powder in 150 mL of 1 mol / L hydrochloric acid solution, stir for 10 h, filter, wash with deionized water, and dry in a 100 ℃ blast drying oven for 24 h to obtain a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material.

[0104] Comparative Example 1 (lignin, magnesium hydroxide, cyanuric chloride and melamine are directly physically mixed)

[0105] Take 13.8 g of nano-magnesium oxide (particle size about 50 nm) and add it to 150 mL of deionized water. Stir and hydrolyze at 80°C for 3 h. After cooling to room temperature, filter and then transfer the product to a 100°C blast drying oven for drying for 24 h to obtain 20 g of magnesium hydroxide nanosheets. Take 10 g of enzymatic lignin, 20 g of magnesium hydroxide nanosheets, 15 g of cyanuric chloride and 10 g of melamine and directly grind and mix them uniformly to obtain a lignin / magnesium hydroxide / cyanuric chloride / melamine four-component mixture;

[0106] Place the above mixture powder in a tube furnace and carbonize under a nitrogen atmosphere. Heat from room temperature to 550°C at a heating rate of 5°C / min and maintain for 2 h. After carbonization, reduce to room temperature to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite;

[0107] Take 1 g of the nitrogen-oxygen doped lignin carbon / magnesium oxide composite and 1 g of potassium bicarbonate and grind and mix them uniformly. Transfer to a tube furnace and carbonize under a nitrogen atmosphere. Heat from room temperature to 700°C at a heating rate of 5°C / min and maintain for 2 h. After carbonization, reduce to room temperature to obtain a black powder. Soak the black powder in 150 mL of 1 mol / L hydrochloric acid solution. Stir for 10 h, filter, wash with deionized water and place in a 100°C blast drying oven for drying for 24 h to obtain a high-surface-area nitrogen-oxygen doped lignin porous carbon material.

[0108] Comparative Example 2 (compared with Example 1, nano-magnesium oxide is not hydrolyzed)

[0109] Take 10 g of enzymatic lignin and dissolve it in 300 mL of ethanol. Then add 20 g of nano-magnesium oxide powder (particle size about 50 nm) and stir thoroughly at room temperature for 4 h to obtain a lignin / nano-magnesium oxide mixture;

[0110] Take 15 g of cyanuric chloride and add it to the above lignin / nano-magnesium oxide mixture. React at 0°C for 30 min, then add 10 g of melamine. Stir uniformly at room temperature and then transfer to a reaction kettle. React at 160°C for 10 h. After cooling to room temperature, filter and then transfer the product to a 100°C blast drying oven for drying for 24 h to obtain a lignin / nano-magnesium oxide / cyanuric acid / melamine four-component supramolecular composite;

[0111] The above compound powder was placed in a tube furnace and carbonized under a nitrogen atmosphere, heated from room temperature to 550 ℃ at a heating rate of 5 ℃ / min, kept for 2 h, and after carbonization, cooled to room temperature to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite;

[0112] 1 g of the nitrogen-oxygen doped lignin carbon / magnesium oxide composite and 1 g of potassium bicarbonate were weighed and mixed uniformly, transferred to a tube furnace, and carbonized under a nitrogen atmosphere, heated from room temperature to 700 ℃ at a heating rate of 5 ℃ / min, kept for 2 h, and after carbonization, cooled to room temperature to obtain a black powder; the black powder was soaked in 150 mL of 1 mol / L hydrochloric acid solution, stirred for 10 h, filtered, washed with deionized water, and dried in a blast drying oven at 100 ℃ for 24 h to obtain a nitrogen-oxygen doped lignin porous carbon material.

[0113] Comparative Example 3 (compared with Example 1, using potassium hydroxide activation)

[0114] 13.8 g of nano-magnesium oxide (particle size about 50 nm) was weighed and added to 150 mL of deionized water, hydrolyzed at 80 ℃ for 3 h, filtered after cooling to room temperature, and then the product was transferred to a blast drying oven at 100 ℃ and dried for 24 h to obtain 20 g of magnesium hydroxide nanosheets; 10 g of enzymatic lignin was dissolved in 300 mL of ethanol, and then 20 g of the above prepared magnesium hydroxide nanosheets were added, and stirred at room temperature for 4 h to obtain a lignin / magnesium hydroxide mixture;

[0115] 15 g of cyanuric chloride was weighed and added to the above lignin / magnesium hydroxide mixture, reacted at 0 ℃ for 30 min, then 10 g of melamine was added, stirred uniformly at room temperature, and then transferred to a reaction kettle and reacted at 160 ℃ for 10 h, cooled to room temperature after reaction, and then the product was transferred to a blast drying oven at 100 ℃ and dried for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular composite;

[0116] The above compound powder was placed in a tube furnace and carbonized under a nitrogen atmosphere, heated from room temperature to 550 ℃ at a heating rate of 5 ℃ / min, kept for 2 h, and after carbonization, cooled to room temperature to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite;

[0117] Take 1 g of nitrogen and oxygen doped lignin carbon / magnesium oxide composite and 1 g of potassium hydroxide, grind and mix uniformly, transfer to a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 700 ℃ at a heating rate of 5 ℃ / min, keep for 2 h, after carbonization, reduce to room temperature to get black powder; immerse the black powder in 150 mL of 1 mol / L hydrochloric acid solution, stir for 10 h, filter, wash with deionized water, and dry in a 100 ℃ blast drying oven for 24 h to obtain a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material.

[0118] Comparative Example 4 (compared with Example 1, without using potassium bicarbonate activation)

[0119] Take 13.8 g of nano magnesium oxide (particle size about 50 nm) and add to 150 mL of deionized water, hydrolyze at 80 ℃ for 3 h, filter after cooling to room temperature, then transfer the product to a 100 ℃ blast drying oven and dry for 24 h to obtain 20 g of magnesium hydroxide nanosheets; take 10 g of enzymatic lignin, dissolve in 300 mL of ethanol, then add the above prepared 20 g of magnesium hydroxide nanosheets, stir at room temperature for 4 h to obtain a lignin / magnesium hydroxide mixture;

[0120] Take 15 g of cyanuric chloride and add to the above lignin / magnesium hydroxide mixture, react at 0 ℃ for 30 min, then add 10 g of melamine, stir at room temperature for 10 h, then transfer to a reaction kettle and react at 160 ℃ for 10 h, cool to room temperature after reaction, then filter, then transfer the product to a 100 ℃ blast drying oven and dry for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular composite;

[0121] Place the above composite powder in a tube furnace and carbonize under a nitrogen atmosphere, heat from room temperature to 550 ℃ at a heating rate of 5 ℃ / min, keep for 2 h, after carbonization, reduce to room temperature to obtain a nitrogen and oxygen doped lignin carbon / magnesium oxide composite;

[0122] Take 1 g of nitrogen and oxygen doped lignin carbon / magnesium oxide composite, transfer to a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 700 ℃ at a heating rate of 5 ℃ / min, keep for 2 h, after carbonization, reduce to room temperature to obtain black powder; immerse the black powder in 150 mL of 1 mol / L hydrochloric acid solution, stir for 10 h, filter, wash with deionized water, and dry in a 100 ℃ blast drying oven for 24 h to obtain a nitrogen and oxygen doped lignin porous carbon material.

[0123] Comparative Example 5 (compared with Example 1, without solvent thermal reaction)

[0124] Take 13.8 g of nano-magnesium oxide (particle size about 50 nm) and add to 150 mL of deionized water, hydrolyze at 80 ℃ for 3 h, cool to room temperature after filtration, then transfer the product to a 100 ℃ blast drying oven and dry for 24 h to obtain 20 g of magnesium hydroxide nanosheets; take 10 g of enzymatic lignin, dissolve in 300 mL of ethanol, then add the above prepared 20 g of magnesium hydroxide nanosheets, fully stir at room temperature for 4 h to obtain a lignin / magnesium hydroxide mixture;

[0125] Take 15 g of cyanuric chloride and add to the above lignin / magnesium hydroxide mixture, react at 0 ℃ for 30 min, then add 10 g of melamine, stir uniformly at room temperature, then transfer to a 100 ℃ blast drying oven and dry for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine composite;

[0126] Place the above composite powder in a tube furnace and carbonize under a nitrogen atmosphere, heat from room temperature to 550 ℃ at a rate of 5 ℃ / min, keep for 2 h, then cool to room temperature after carbonization to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite;

[0127] Take 1 g of nitrogen-oxygen doped lignin carbon / magnesium oxide composite and 1 g of potassium bicarbonate, grind and mix uniformly, transfer to a tube furnace and carbonize under a nitrogen atmosphere, heat from room temperature to 700 ℃ at a rate of 5 ℃ / min, keep for 2 h, then cool to room temperature after carbonization to obtain a black powder; immerse the black powder in 150 mL of 1 mol / L hydrochloric acid solution, stir for 10 h, then filter, wash with deionized water, and place in a 100 ℃ blast drying oven and dry for 24 h to obtain a nitrogen-oxygen doped lignin porous carbon material.

[0128] Comparative Example 6 (compared with Example 1, without using cyanuric chloride to modify lignin, directly adding cyanuric acid and melamine for solvothermal reaction)

[0129] Take 13.8 g of nano-magnesium oxide (particle size about 50 nm) and add to 150 mL of deionized water, hydrolyze at 80 ℃ for 3 h, cool to room temperature after filtration, then transfer the product to a 100 ℃ blast drying oven and dry for 24 h to obtain 20 g of magnesium hydroxide nanosheets; take 10 g of enzymatic lignin, dissolve in 300 mL of ethanol, then add the above prepared 20 g of magnesium hydroxide nanosheets, fully stir at room temperature for 4 h to obtain a lignin / magnesium hydroxide mixture;

[0130] Take 15 g of cyanuric acid and 10 g of melamine and add them to the lignin / magnesium hydroxide mixture described above, stir uniformly at room temperature, then transfer to the reaction kettle, react at 160°C for 10 h, cool to room temperature, then filter, then transfer the product to a 100°C air drying oven and dry for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular complex;

[0131] Place the above complex powder in a tube furnace and carbonize under a nitrogen atmosphere, heat from room temperature to 550°C at a rate of 5°C / min, keep for 2 h, then cool to room temperature to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite;

[0132] Take 1 g of nitrogen-oxygen doped lignin carbon / magnesium oxide composite and 1 g of potassium bicarbonate, grind and mix uniformly, transfer to a tube furnace, carbonize under a nitrogen atmosphere, heat from room temperature to 700°C at a rate of 5°C / min, keep for 2 h, then cool to room temperature to obtain a black powder; immerse the black powder in 150 mL of 1 mol / L hydrochloric acid solution, stir for 10 h, then filter, wash with deionized water, and place in a 100°C air drying oven and dry for 24 h to obtain a nitrogen-oxygen doped lignin porous carbon material.

[0133] Comparative Example 7 (compared with Example 1, using deionized water as solvent)

[0134] Take 13.8 g of nano-magnesium oxide (particle size about 50 nm) and add it to 150 mL of deionized water, hydrolyze at 80°C for 3 h, cool to room temperature, then filter, then transfer the product to a 100°C air drying oven and dry for 24 h to obtain 20 g of magnesium hydroxide nanosheets; take 10 g of enzymatic lignin, dissolve it in 300 mL of deionized water, then add the above prepared 20 g of magnesium hydroxide nanosheets, stir thoroughly at room temperature for 4 h to obtain a lignin / magnesium hydroxide mixture;

[0135] Take 15 g of cyanuric acid and 10 g of melamine and add them to the lignin / magnesium hydroxide mixture described above, stir uniformly at room temperature, then transfer to the reaction kettle, react at 160°C for 10 h, cool to room temperature, then filter, then transfer the product to a 100°C air drying oven and dry for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid / melamine four-component supramolecular complex;

[0136] Place the above complex powder in a tube furnace and carbonize under a nitrogen atmosphere, heat from room temperature to 550°C at a rate of 5°C / min, keep for 2 h, then cool to room temperature to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite;

[0137] Take 1 g of nitrogen and oxygen doped lignin carbon / magnesium oxide composite and 1 g of potassium bicarbonate, mix them evenly, transfer them to a tube furnace, and carbonize them under a nitrogen atmosphere. The temperature is raised to 700°C at a rate of 5°C / min from room temperature, and the temperature is maintained for 2 hours. After carbonization, the temperature is lowered to room temperature to obtain a black powder. The black powder is soaked in 150 mL of 1 mol / L hydrochloric acid solution, stirred for 10 hours, filtered, washed with deionized water, and dried in a 100°C air drying oven for 24 hours to obtain a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material.

[0138] Comparative Example 8 (compared with Example 1, without cyanuric chloride)

[0139] Take 13.8 g of nano-magnesium oxide (particle size about 50 nm) and add it to 150 mL of deionized water. Hydrolyze it at 80°C for 3 hours. After cooling to room temperature, filter it. Then transfer the product to a 100°C air drying oven and dry it for 24 hours to obtain 20 g of magnesium hydroxide nanosheets. Take 10 g of enzymatic lignin and dissolve it in 300 mL of ethanol. Then add the above prepared 20 g of magnesium hydroxide nanosheets. Stir them thoroughly at room temperature for 4 hours to obtain a lignin / magnesium hydroxide mixture.

[0140] Take 10 g of melamine and add it to the above lignin / magnesium hydroxide mixture. Stir them evenly at room temperature. Then transfer them to a reaction kettle and react them at 160°C for 10 hours. After cooling to room temperature, filter them. Then transfer the product to a 100°C air drying oven and dry it for 24 hours to obtain a lignin / magnesium hydroxide / melamine composite.

[0141] Place the above composite powder in a tube furnace and carbonize it under a nitrogen atmosphere. The temperature is raised to 550°C at a rate of 5°C / min from room temperature, and the temperature is maintained for 2 hours. After carbonization, the temperature is lowered to room temperature to obtain a nitrogen and oxygen doped lignin carbon / magnesium oxide composite.

[0142] Take 1 g of nitrogen and oxygen doped lignin carbon / magnesium oxide composite and 1 g of potassium bicarbonate, mix them evenly, transfer them to a tube furnace, and carbonize them under a nitrogen atmosphere. The temperature is raised to 700°C at a rate of 5°C / min from room temperature, and the temperature is maintained for 2 hours. After carbonization, the temperature is lowered to room temperature to obtain a black powder. The black powder is soaked in 150 mL of 1 mol / L hydrochloric acid solution, stirred for 10 hours, filtered, washed with deionized water, and dried in a 100°C air drying oven for 24 hours to obtain a nitrogen and oxygen doped lignin porous carbon material.

[0143] Comparative Example 9 (compared with Example 1, without melamine)

[0144] Take 13.8 g of nano-magnesium oxide (particle size about 50 nm) and add to 150 mL of deionized water, hydrolyze at 80 ℃ for 3 h, cool to room temperature, filter, then transfer the product to a 100 ℃ air drying oven and dry for 24 h to obtain 20 g of magnesium hydroxide nanosheets; take 10 g of enzymatic lignin, dissolve in 300 mL of ethanol, then add the above prepared 20 g of magnesium hydroxide nanosheets, fully stir at room temperature for 4 h to obtain a lignin / magnesium hydroxide mixture;

[0145] Take 15 g of cyanuric chloride and add to the above lignin / magnesium hydroxide mixture, react at 0 ℃ for 30 min, then stir uniformly at room temperature, transfer to a reaction kettle, react at 160 ℃ for 10 h, cool to room temperature, filter, then transfer the product to a 100 ℃ air drying oven and dry for 24 h to obtain a lignin / magnesium hydroxide / cyanuric acid composite;

[0146] Place the above composite powder in a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 550 ℃ at a rate of 5 ℃ / min, keep for 2 h, cool to room temperature after carbonization to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide composite;

[0147] Take 1 g of nitrogen-oxygen doped lignin carbon / magnesium oxide composite and 1 g of potassium bicarbonate, grind and mix uniformly, transfer to a tube furnace, carbonize under nitrogen atmosphere, heat from room temperature to 700 ℃ at a rate of 5 ℃ / min, keep for 2 h, cool to room temperature after carbonization to obtain a black powder; immerse the black powder in 150 mL of 1 mol / L hydrochloric acid solution, stir for 10 h, filter, wash with deionized water, and place in a 100 ℃ air drying oven and dry for 24 h to obtain a nitrogen-oxygen doped lignin porous carbon material.

[0148] Comparative Example 10 (compared with Example 1, without cyanuric chloride and melamine)

[0149] Take 13.8 g of nano-magnesium oxide (particle size about 50 nm) and add to 150 mL of deionized water, hydrolyze at 80 ℃ for 3 h, cool to room temperature, filter, then transfer the product to a 100 ℃ air drying oven and dry for 24 h to obtain 20 g of magnesium hydroxide nanosheets; take 10 g of enzymatic lignin, dissolve in 300 mL of ethanol, then add the above prepared 20 g of magnesium hydroxide nanosheets, fully stir at room temperature for 4 h to obtain a lignin / magnesium hydroxide mixture;

[0150] The above mixed solution was transferred to a reaction kettle, and reacted at 160 ℃ for 10 h. After being cooled to room temperature, it was filtered, and then the product was transferred to a blast drying oven at 100 ℃ and dried for 24 h to obtain a lignin / magnesium hydroxide composite;

[0151] The above composite powder was placed in a tube furnace and carbonized under a nitrogen atmosphere. The temperature was raised from room temperature to 550 ℃ at a rate of 5 ℃ / min and maintained for 2 h. After carbonization, it was cooled to room temperature to obtain an oxygen-doped lignin carbon / magnesium oxide composite.

[0152] 1 g of the nitrogen-oxygen-doped lignin carbon / magnesium oxide composite and 1 g of potassium bicarbonate were ground and mixed uniformly, transferred to a tube furnace, and carbonized under a nitrogen atmosphere. The temperature was raised from room temperature to 700 ℃ at a rate of 5 ℃ / min and maintained for 2 h. After carbonization, a black powder was obtained. The black powder was soaked in 150 mL of 1 mol / L hydrochloric acid solution, stirred for 10 h, filtered, washed with deionized water, and dried in a blast drying oven at 100 ℃ for 24 h to obtain an oxygen-doped lignin porous carbon material.

[0153] Results and analysis:

[0154] The lignin carbon materials obtained in the examples and comparative examples were structurally characterized and their performance as positive electrode materials for zinc ion hybrid capacitor electrodes was tested. The results are shown in Table 1 and Figures 1 to 5 .

[0155] The micro-morphology and structure of the samples of the present application were characterized by scanning electron microscopy (SEM, HITACHI SU8220) and high-resolution field emission transmission electron microscopy (TEM, JEOL JEM-2100F). The functional groups of the samples were characterized by Fourier infrared spectroscopy (FT-IR, Thermo Nicolet iS10). The specific surface area and pore structure of the samples were tested using a full-automatic specific surface area and porosity analyzer (Micromeritics ASAP 2020 instrument).

[0156] In the performance test of zinc ion hybrid capacitor electrodes, the lignin carbon material obtained in the present application, acetylene black and polytetrafluoroethylene were mixed in a mass ratio of 8:1:1 and rolled on a stainless steel mesh as a positive electrode material for a zinc ion hybrid capacitor. Metallic zinc was directly used as the negative electrode, 2 mol / L zinc sulfate was used as the electrolyte, and Whatman glass fiber was used as the separator. An electrochemical workstation (Bio-Logic VMP-3e) was used for electrochemical performance test, with a voltage window of 0.2-1.8 V and a current density of 0.1 A / g and 10 A / g.

[0157] Table 1 is the pore structure parameter and electrochemical performance of the lignin porous carbon materials prepared in different examples and comparative examples.

[0158] Table 1 is the surface element content and pore structure characteristic parameter of the lignin porous carbon material

[0159]

[0160] Table 1 shows that:

[0161] The specific surface area of the nitrogen and oxygen doped lignin porous carbon material prepared in examples 1-6 is more than 2500 m 2 / g, the micro-mesopore ratio is more than 85% (the mesopore ratio is more than 43%, and the micropore ratio is more than 40%), and the total content of nitrogen and oxygen on the surface of the carbon material is more than 13 at.% (the oxygen content is more than 8.0 at.%, and the nitrogen content is more than 5.0 at.%). The specific surface area of example 1 is as high as 2848 m 2 / g, the micropore ratio is 44.2%, the mesopore ratio is 44.8%, the micro-mesopore ratio is 89%, the oxygen content is 8.9 at.%, the nitrogen content is 5.4 at.%, the total content of nitrogen and oxygen is 14.3 at.%, which is obviously higher than that of the nitrogen and oxygen doped lignin porous carbon material prepared by direct physical mixing in comparative example 1. The electrochemical performance test results of the assembled zinc ion hybrid capacitor show that the specific capacitance of the nitrogen and oxygen doped lignin porous carbon material prepared in example 1 is 433 F / g at a current density of 0.1 A / g, and the specific capacitance is 216 F / g at a current density of 10 A / g, which is higher than that of the nitrogen and oxygen doped lignin porous carbon material prepared in comparative example 1. It shows that the high specific surface area and high nitrogen and oxygen doped lignin porous carbon material prepared by the technology is better than the nitrogen and oxygen doped lignin porous carbon material prepared by direct physical mixing.

[0162] Compared with example 1, the nano magnesium oxide in comparative example 2 is not hydrolyzed, the hydroxyl group on the surface of the magnesium oxide is less, the compatibility of the lignin and the template is poor, the uniform lignin / magnesium oxide composite cannot be formed, the structure guiding effect of the magnesium oxide template is weakened, and the unhydrolyzed nano magnesium oxide does not have a nano sheet structure. Therefore, the lignin forms less mesopores (28.5%) and has a low specific surface area (2216 m 2 / g) and disordered structure during pyrolysis and carbonization, resulting in a low specific capacitance (318 F / g) of the zinc ion hybrid capacitor.

[0163] Compared with example 1, the strong corrosive activator potassium hydroxide is used for activation in comparative example 3, a developed pore structure is formed, the micropore ratio reaches 49.5%, and the specific surface area is as high as 2364 m 2 / g. However, due to the strong corrosion of potassium hydroxide, the activation is excessive, the mesopore of the prepared lignin carbon material is low (27.9%), the ion transmission rate is low, the nitrogen oxygen species is also lost seriously (the nitrogen oxygen content is only 9.5 at.%), the interface wettability is poor, resulting in the specific capacitance of the assembled zinc ion hybrid capacitor is 301 F / g.

[0164] Compared with Example 1, Comparative Example 4 does not use a weakly corrosive potassium salt for activation and pore formation, and the prepared lignin porous carbon material has a higher nitrogen oxygen content (nitrogen content: 12.1 at.%, oxygen content: 8.8 at.%) and mesopore rate (69.4%). However, without further activation and pore formation, the micropore rate of the lignin porous carbon material is as low as 3.4%, the specific surface area is only 876 m 2 / g, the zinc storage active sites are lacking, resulting in poor electrochemical performance of the zinc ion hybrid capacitor (185 F / g).

[0165] Compared with Example 1, Comparative Example 5 does not use a solvent thermal reaction to condense to form a supramolecule, and the cyanuric acid and melamine have poor thermal stability during pyrolysis and carbonization, and the nitrogen-containing species are lost seriously in the subsequent activation process. The nitrogen oxygen content of the prepared lignin porous carbon material is low (nitrogen content: 1.5 at.%, oxygen content: 8.0 at.%), resulting in poor interface wettability of the carbon, inaccessible zinc storage active sites, and lack of pseudocapacitance active sites, and the specific capacitance of the zinc ion hybrid capacitor is 287 F / g

[0166] Compared with Example 1, Comparative Example 6 does not use tricyanocyanogen modified lignin, but directly adds trichloroisocyanic acid and melamine in the reaction system to prepare a lignin / magnesium hydroxide / cyanuric acid / melamine four-component mixture by a solvent thermal reaction. Due to the weak physical interaction (hydrogen bond and van der Waals force, etc.) between lignin and nitrogen source, and the lower content of nitrogen source compared with lignin, the nitrogen species is lost seriously during carbonization and activation, the nitrogen content is only 1.7 at.%, and the specific capacitance of the assembled zinc ion hybrid capacitor is 295 F / g.

[0167] Compared with Example 1, Comparative Example 7 uses deionized water as a solvent, and the solubility of lignin in deionized water is low, resulting in uneven compounding of lignin and magnesium hydroxide template, the prepared carbon material has less mesopore (20.5%) and lower specific surface area (1987 m 2(g). And because the lignin has strong intermolecular forces in water, serious aggregation, hydroxyl and other oxygen-containing functional groups can not be fully exposed, resulting in low reactivity of lignin and cyanuric chloride, lignin can not fully participate in the construction of supramolecular, nitrogen species loss is serious in the carbonization activation process, nitrogen content is only 1.9 at.%. Therefore, the nanostructure of the prepared nitrogen and oxygen doped lignin porous carbon material is disordered, the mesoporous is less, and the nitrogen and oxygen content is low (9.6 at.%), resulting in the specific capacitance of the assembled zinc ion hybrid capacitor is 279 F / g.

[0168] Compared with example 1, the comparative examples 8-10 do not use cyanuric chloride modified lignin and / or do not add melamine, resulting in no four-component supramolecular complex being formed. Therefore, the thermal stability of nitrogen species is poor, and the loss is serious during the activation process. The nitrogen content of the prepared nitrogen and oxygen doped lignin porous carbon material is less than 1.0 at.%, and the electrochemical performance of the zinc ion hybrid capacitor is poor, which proves the importance of cyanuric chloride and melamine in the nitrogen doping process in the present application.

[0169] In summary, the lignin in the method of the present application assembles a four-component supramolecular complex through hydrogen bonds and chemical bonds, and high specific surface area and high nitrogen and oxygen doped lignin porous carbon material can be prepared after carbonization and activation. As a positive material for zinc ion hybrid capacitor, it shows excellent specific capacitance, which is better than the nitrogen and oxygen doped lignin porous carbon material prepared in comparative examples 1-10.

[0170] Figure 1 The Fourier infrared spectrum of lignin-cyanuric acid obtained by cyanuric chloride modified lignin in example 1 of the present application is located at 850 cm -1 The disappearance of C-Cl stretching vibration absorption peak at 1025 cm -1 and the enhancement of C-O-C absorption peak indicate that cyanuric chloride is successfully grafted on the lignin molecule.

[0171] Figure 2 The scanning electron microscope picture of the nitrogen and oxygen doped lignin porous carbon material obtained in example 1 of the present application can be seen to be composed of interconnected two-dimensional nanosheets, having an open and interconnected pore structure.

[0172] Figure 3 The transmission electron microscope picture of the nitrogen and oxygen doped lignin porous carbon material obtained in example 1 of the present application can be seen to be composed of rich nanosheet layer structure, having more nanopores.

[0173] Figure 4The nitrogen adsorption / desorption isotherm and pore size distribution curve of the nitrogen-oxygen doped lignin porous carbon material obtained in Example 1 of the present application are shown in Figure 1. The nitrogen adsorption / desorption curve shows the characteristics of type IV adsorption / desorption curve, and H-4 type hysteresis loop appears in the high pressure region, which proves that the prepared carbon material has a hierarchical pore structure dominated by micropores and mesopores. The pore size distribution graph shows that the micropores are concentrated in the vicinity of 0.46, 0.80, and 1.18 nm, and the mesopores are distributed around 3.18 nm. The rich microporous structure is attributed to the activation effect of the mesoporous magnesium oxide produced by the decomposition of magnesium hydroxide and the weak corrosive potassium salt.

[0174] Figure 5 The constant current charge-discharge curve of the nitrogen-oxygen doped lignin porous carbon material obtained in Example 1 of the present application is shown in Figure 2. The curve shape of the prepared carbon material at different current densities is similar to an isosceles triangle, which proves that it has typical double-layer capacitance characteristics and high reversibility.

[0175] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, which are all included in the protection scope of the present application.

Claims

1. A method for preparing a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material, characterized in that: The following steps are involved: (1) Dissolving lignin in ethanol, adding magnesium hydroxide nanosheets, and stirring to obtain a lignin / magnesium hydroxide mixed solution; (2) adding an excess of cyanuric chloride to the lignin / magnesium hydroxide mixture to react, then adding melamine to carry out a solvent thermal reaction, filtering and drying to obtain a four-component supramolecular complex of lignin / magnesium hydroxide / cyanuric acid / melamine; (3) Carbonizing the four-component supramolecular complex of lignin / magnesium hydroxide / cyanuric acid / melamine under an inert gas atmosphere to obtain a nitrogen-oxygen doped lignin carbon / magnesium oxide complex; (4) After the nitrogen and oxygen doped lignin carbon / magnesium oxide composite and weakly corrosive potassium salt are evenly mixed, the mixture is activated under an inert gas atmosphere, acid washed, filtered and dried to obtain a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material.

2. The method for preparing a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material according to claim 1, characterized in that: The ratio of the lignin, ethanol and magnesium hydroxide nanosheets in step (1) is 10 g: 200-300 mL: 10-30 g; The mass ratio of the cyanuric chloride and melamine in step (2) to the lignin in step (1) is 10-20:5-15:10; The lignin in step (1) is at least one of enzymatic lignin produced as a by-product of the bioethanol industry, alkali lignin in alkaline pulping black liquor, and organic solvent lignin; The temperature for reacting cyanuric chloride in step (2) is 0-5°C and the reaction time is 20-40 min; The temperature for the solvent thermal reaction of adding melamine in step (2) is 140-180° C. and the time is 8-12 h.

3. The method for preparing a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material according to claim 2, characterized in that: The ratio of the lignin, ethanol and magnesium hydroxide nanosheets in step (1) is 10 g: 200-300 mL: 10-20 g; The mass ratio of the cyanuric chloride and melamine in step (2) to the lignin in step (1) is 10-20:7-15:10; The temperature for reacting cyanuric chloride in step (2) is 0-5°C and the reaction time is 20-30 minutes; The temperature for the solvent thermal reaction of adding melamine in step (2) is 140-160° C. and the time is 10-12 hours.

4. The method for preparing a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material according to claim 1, characterized in that: The weakly corrosive potassium salt in step (4) is at least one of potassium bicarbonate, potassium acetate and potassium citrate; In step (4), the mass ratio of the nitrogen-oxygen doped lignin carbon / magnesium oxide composite to the weakly corrosive potassium salt is 1:0.5-1.

5.

5. The method for preparing a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material according to claim 4, characterized in that: In step (4), the mass ratio of the nitrogen-oxygen doped lignin carbon / magnesium oxide composite to the weakly corrosive potassium salt is 1:0.5-1.

6. The method for preparing a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material according to claim 1, characterized in that: The carbonization temperature in step (3) is 500-600°C and the time is 1-3 hours; The activation temperature in step (4) is 600-800°C and the activation time is 1-3 hours; The heating rate of the carbonization in step (3) and the heating rate of the activation in step (4) are both 5 to 10 °C / min; The inert gas in steps (3) and (4) is at least one of a rare gas and nitrogen; The acid solution used for pickling in step (4) is one of a 0.5-1.5 mol / L hydrochloric acid solution or a sulfuric acid solution, and the soaking and washing time is 8-12 h.

7. The method for preparing a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material according to claim 6, characterized in that: The carbonization temperature in step (3) is 550-600°C and the time is 1-2 hours; The activation temperature in step (4) is 700-800°C and the activation time is 1-2 h.

8. The method for preparing a high specific surface area and high nitrogen and oxygen doped lignin porous carbon material according to claim 1, characterized in that: The magnesium hydroxide nanosheets in step (1) are obtained by the following method: dispersing nano-magnesium oxide in water, heating and hydrolyzing, filtering and drying to obtain magnesium hydroxide nanosheets; The particle size of the nano magnesium oxide is 10 to 100 nm; The heating hydrolysis temperature is 70-90° C. and the time is 2-4 h.

9. A high specific surface area and high nitrogen and oxygen doped lignin porous carbon material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the high specific surface area and high nitrogen and oxygen doped lignin porous carbon material according to claim 9 in zinc ion hybrid capacitors.

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