Preparation method and application of microporous wood-based carbon electrode material

Abstract

The application provides a preparation method and application of a microporous wood-based carbon electrode material, and belongs to the technical field of electrode materials. The method comprises the following steps: putting pretreated basswood and laccase into a buffer solution to obtain single-enzymatic wood chips; putting the single-enzymatic wood chips and hemicellulase into a buffer solution to obtain double-enzymatic wood chips; and putting the double-enzymatic wood chips into hot pressing and high-temperature carbonization to obtain the microporous wood-based carbon electrode material. The application adopts sequential and synergistic degradation of laccase and hemicellulase to accurately and greenly remove lignin and hemicellulose, and then combines with stepwise high-pressure hot pressing densification and inert atmosphere carbonization to realize high enrichment of 0.5-1.0 nm micropores in the bulk wood-based carbon material, optimization of pore connectivity and structure without cracking and deformation. The method is free of toxic reagents and waste liquid discharge, is easy to scale up, significantly improves the conductivity and specific surface area of the material, and guarantees the product qualification rate and performance stability.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, specifically relating to a method for preparing and applying a microporous wood-based carbon electrode material. Background Technology

[0002] Wood, as a natural and renewable biomass material, possesses a unique hierarchical porous structure and cellulose-based framework, making it an excellent precursor for the preparation of biomass-based carbon materials. Its derived carbon materials, due to their high specific surface area, good electrical conductivity, and biocompatibility, are widely used in supercapacitors, battery electrodes, catalyst supports, adsorbents, and other fields, becoming an important direction for the high-value utilization of biomass.

[0003] Currently, the preparation of wood-based carbon materials mainly falls into two technical routes: direct carbonization of logs and carbonization after pretreatment. Traditional direct high-temperature carbonization of logs, due to the preservation of the original cell cavity structure, easily generates a large number of pores and cracks during pyrolysis, resulting in carbon materials with low density and poor mechanical strength. This makes it difficult to meet the requirements of applications such as battery electrodes, which have strict requirements for volume performance and structural stability. To improve these problems, researchers have developed modification schemes combining pretreatment processes such as chemical methods and single enzymatic hydrolysis with carbonization. However, chemical methods suffer from the problem of reagents indiscriminately eroding the cellulose skeleton, causing skeleton damage, and wastewater pollution. While single enzymatic hydrolysis has some environmental friendliness, it suffers from incomplete degradation, limited pore structure control, and the lack of a supporting densification process.

[0004] Currently, this field generally suffers from a disconnect between pretreatment and densification processes, and a lack of collaborative design. Implementation schemes most similar to the technical concept of this invention mainly fall into two categories: The first category involves a single-enzyme pretreatment method for preparing biomass-based porous carbon materials. This method uses a single enzyme system, such as hemicellulase or cellulase, for enzymatic pretreatment to remove single non-cellulose components and open up the original pores. Porous carbon is then prepared by direct carbonization or carbonization after ball milling. While this method is environmentally friendly, it has significant core drawbacks: it can only remove one type of non-cellulose component, failing to achieve synergistic and efficient removal of lignin and hemicellulose; cell wall disruption is insufficient; and pore structure regulation remains at the level of "simple pore creation." Furthermore, there is no targeted densification process after enzymatic hydrolysis, resulting in materials that are mostly powdery, with low density and poor mechanical strength, failing to meet the application requirements of bulk electrodes in battery packs.

[0005] The second category involves high-pressure / hot-press densification to prepare dense wood-based carbon materials. This method uses logs or simply pre-treated wood chips as raw materials, achieving densification through mechanical pressure compression of the original pores, followed by carbonization to prepare dense carbon materials. This method achieves bulk densification, solving the problem of loose and brittle traditional carbonized materials. However, it has significant technical shortcomings: the wood is not subjected to targeted enzymatic pretreatment, the encapsulation effect of lignin and hemicellulose is not eliminated, the cellulose skeleton is not fully exposed, and direct high-pressure densification easily leads to skeleton fracture and pore collapse, and it cannot achieve precise construction and enrichment of microporous structures; after carbonization, the material has a poor pore structure, low specific surface area, and a significant decrease in electrochemical activity, making it difficult to use as an electrode for high-performance battery packs.

[0006] Existing technologies fail to achieve a synergistic design between enzymatic pretreatment and high-pressure densification. They either focus solely on enzymatic pore creation without densification, or solely pursue high-pressure densification without precise enzymatic pretreatment. Therefore, existing technologies still suffer from poor environmental friendliness, imbalances in structure and performance control, and unsatisfactory overall product performance. Summary of the Invention

[0007] In view of this, the present invention provides a method for preparing microporous wood-based carbon electrode materials and their application, in order to solve the problems in the prior art where the preparation process of wood-based carbon materials is not environmentally friendly, the pretreatment and densification processes are disconnected, and it is impossible to achieve both high micropore ratio and high density, resulting in low specific capacitance, poor structural strength, and difficulty in directly using them as self-supporting bulk electrodes.

[0008] To achieve the above-mentioned objective, this invention provides a method for preparing a microporous wood-based carbon electrode material, comprising the following steps: S1. Place the pretreated linden wood and laccase in a buffer solution, seal it, and incubate it at a constant temperature of 60°C for 24 hours. Take out the laccase-treated linden wood, wash it with water, and dry it at 65°C for 30 minutes to obtain single-enzyme hydrolyzed wood chips. The mass ratio of laccase to pretreated linden wood is 1:20-25. S2. Place the single-enzyme hydrolyzed wood chips and hemicellulase in a buffer solution, seal and incubate at a constant temperature of 60°C for 12 hours. Take out the linden wood treated with laccase-hemicellulase, wash and dry it to obtain double-enzyme hydrolyzed wood chips. The mass ratio of hemicellulase to single-enzyme hydrolyzed wood chips is 1:6-8. The core reason for using laccase and hemicellulase in combination is that the wood cell wall is composed of tightly cross-linked lignin, hemicellulose, and cellulose. A single enzyme system can only recognize and degrade a single component and cannot achieve efficient removal of non-cellulose components. However, the targeted degradation characteristics of laccase and hemicellulase complement each other, and the degradation efficiency can be maximized by using them in a fixed sequence, while precisely protecting the cellulose skeleton from damage. Lignin acts as a "glue" in cell walls, cross-linking and encapsulating cellulose and hemicellulose. If hemicellulose is hydrolyzed first, hemicellulase cannot penetrate the lignin barrier to reach the target substrate, resulting in extremely low degradation efficiency. Laccase, on the other hand, can specifically oxidize and break the aromatic ether bonds and C / C bonds of lignin. By first degrading and breaking the lignin encapsulation structure through laccase, channels can be opened and sufficient accessible sites can be provided for subsequent hemicellulase hydrolysis. Then, hemicellulase precisely hydrolyzes the hemicellulose filling the spaces between cellulose microfibrils, ultimately completing the directional and efficient removal of lignin and hemicellulose. Moreover, neither enzyme acts on cellulose, which can preserve the complete crystal form of cellulose microfibrils to the greatest extent, providing a stable structural framework for subsequent high-pressure densification and carbonization.

[0009] S3. Place the double-enzyme hydrolyzed wood chips into a hot press mold, and press them at 100°C with pressures of 1MPa, 2MPa, 3MPa and 4MPa for 5-8 minutes each, then increase the pressure to 5MPa and press for 35-40 minutes. Finally, cool down to 30°C and keep the pressure at 5MPa for 9 hours. After depressurization, dense wood is obtained. The core reason for performing synergistic high-pressure hot pressing after double enzymatic hydrolysis is that double enzymatic hydrolysis can only remove non-cellulose components and open the initial pores, but cannot achieve wood densification. Moreover, the pores formed after double enzymatic hydrolysis are relatively dispersed, with some macropores / wide mesopores, which are difficult to meet the pore structure requirements of microporous carbon materials. High-pressure hot pressing and double enzymatic hydrolysis form an inseparable synergistic effect. Double enzymatic hydrolysis provides an ideal precursor for high-pressure hot pressing, while high-pressure hot pressing regulates the pore structure after double enzymatic hydrolysis and achieves bulk densification. On the one hand, after double enzymatic hydrolysis, the wood chips have removed lignin and hemicellulose, exposing the cellulose skeleton and exhibiting a "loose but intact skeleton" structure. Compared with direct high-pressure hot pressing of logs, this precursor significantly reduces the pressure required for densification, avoiding the problems of easy breakage of the cellulose skeleton and easy collapse of pores under high pressure in logs. On the other hand, by designing a stepped temperature-pressure synergistic high-pressure hot pressing process, the pore structure after double enzymatic hydrolysis can be precisely compressed and enriched, while simultaneously achieving wood bulk densification and structural fixation.

[0010] Among these processes, the 100℃ high temperature causes the wood cell wall to undergo plastic flow, reducing the resistance between fibers and allowing them to adhere tightly; the gradient pressure design avoids the breakage of the cellulose skeleton and the collapse of pores caused by one-time high pressure, achieving layer-by-layer compaction; the 5MPa high pressure can precisely compress and enrich the macropores / wide mesopores dispersed after double enzymatic hydrolysis into micropores / narrow mesopores of 0.5~1.0nm, while opening up closed pores and improving pore connectivity; the 30℃ low temperature pressure holding fixes the densified structure, prevents the material from springing back after pressure release, and ensures the durability of the densification effect.

[0011] S4. The dense wood is placed in a tube furnace for carbonization to obtain a microporous wood-based carbon electrode material.

[0012] This carbonization process is highly compatible with the dense wood structure characteristics after dual enzymatic hydrolysis-high pressure hot pressing. The slow heating rate can avoid material cracking and deformation caused by rapid escape of pyrolysis gases. The nitrogen inert atmosphere prevents the cellulose skeleton from being oxidized during the carbonization process, ensuring that the final material maintains a complete block shape and excellent structural stability. At the same time, the carbonization process further solidifies the microporous structure, improving the conductivity and specific surface area of ​​the material.

[0013] Preferably, the preparation of the pretreated linden wood in S1 includes: cutting the linden wood perpendicular to the growth direction into wood chips of 2 cm × 2 cm × 1 cm, and then soaking them in deionized water for 2-3 hours to obtain the pretreated linden wood.

[0014] Preferably, the buffer solution in S1 and / or S2 is an acetate-sodium acetate buffer solution. The preparation process of the buffer solution includes: mixing deionized water and sodium acetate, stirring to dissolve, adding glacial acetic acid dropwise under continuous stirring, and mixing evenly to obtain the acetate-sodium acetate buffer solution.

[0015] Preferably, the ratio of deionized water, sodium acetate, and glacial acetic acid is 100 mL: 1.8 g: 0.98 mL.

[0016] Preferably, the liquid-to-solid ratio of the buffer solution to the pretreated linden wood in S1 and S2 is 20-25 mL:1 g.

[0017] Preferably, the drying temperature in S2 is 60-65℃ and the drying time is 30-35 min.

[0018] Preferably, S4 specifically involves: placing the dense wood in a tubular furnace, introducing nitrogen gas into the tubular furnace, raising the furnace temperature to 800°C at a rate of 3-5°C / min, carbonizing at a constant temperature for 2 hours, and allowing the tubular furnace to cool naturally to room temperature to obtain a microporous wood-based carbon electrode material.

[0019] Preferably, the oxygen content of the nitrogen gas in S4 is ≤0.1%.

[0020] A microporous wood-based carbon electrode prepared by the method of the present invention, wherein the microporous wood-based carbon electrode has micropores of 0.5~1.0 nm.

[0021] A battery pack assembled from a microporous wood-based carbon electrode material prepared by the preparation method described in this invention.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. The dual-enzyme combination replaces single enzymatic hydrolysis / chemical methods, resulting in a greener process and more precise and efficient degradation. This invention utilizes laccase and hemicellulase in a targeted, sequential combination to achieve synergistic and efficient removal of lignin and hemicellulose, acting only on non-cellulose components without indiscriminately damaging the cellulose skeleton. Simultaneously, it replaces the acid / alkali / oxidizing reagents used in chemical methods, eliminating the use of toxic reagents, wastewater discharge, and reagent residues throughout the process. This aligns with the trends of green manufacturing and high-value utilization of biomass. The enzymatic hydrolysis conditions are mild, equipment requirements are low, and it is easily scaled up for engineering applications.

[0023] 2. Stepped high-pressure hot pressing replaces direct high-pressure / non-densification processes, achieving precise dual control of pore structure and densification. This invention's stepped temperature-pressure coupling process, through high-temperature plastic flow, gradient pressurization, and low-temperature fixation, avoids damage to the skeletal structure. It precisely compresses and enriches the dispersed macropores / wide mesopores after dual enzymatic hydrolysis into micropores / narrow mesopores of 0.5~1.0 nm, achieving high micropore enrichment and excellent pore connectivity. Simultaneously, compared to the powdered products of single enzymatic hydrolysis technology, this invention achieves densification of wood blocks through high-pressure hot pressing, and after low-temperature fixation, there is no springback, significantly improving density and structural stability.

[0024] 3. The carbonized material exhibits excellent structural integrity, with no cracking or deformation issues. The dense wood produced by this invention, after dual enzymatic hydrolysis and high-temperature hot pressing, features a tightly packed cellulose skeleton and a regular microporous structure. Combined with a slow-heating, inert atmosphere carbonization process, it effectively avoids internal stress cracking and structural deformation caused by the rapid escape of pyrolysis gases. The carbonized material retains its complete block shape, and the microporous structure is further solidified through carbonization, resulting in improved conductivity and specific surface area. Compared to existing technologies that are prone to cracking and exhibit uneven performance after carbonization, this significantly improves product qualification rate and performance stability. Attached Figure Description

[0025] Figure 1 This is a microstructure diagram of a linden log provided in a specific embodiment of the present invention; Figure 2 The image shows the microstructure of the microporous wood-based carbon electrode material prepared in Example 1. Figure 3 This is a microstructure diagram of the microporous wood-based carbon electrode material prepared in Comparative Example 1; Figure 4 This is a microstructure diagram of the microporous wood-based carbon electrode material prepared in Comparative Example 2; Figure 5 This is a microstructure diagram of the microporous wood-based carbon electrode material prepared in Comparative Example 3; Figure 6 This is a microstructure diagram of the microporous wood-based carbon electrode material prepared in Comparative Example 4; Figure 7 This is a microstructure diagram of the microporous wood-based carbon electrode material prepared in Comparative Example 5; Figure 8 The CV voltage window diagrams of the microporous wood-based carbon electrode materials prepared in Example 1 and Comparative Examples 1-5 at a scan rate of 1 mV / s are shown. Figure 9 The microporous wood-based carbon electrode materials prepared for Examples 1 and Comparative Examples 1-5 have an efficiency of 1 mA / cm². 2 GCD curves at current densities; Figure 10 BJH pore size distribution curves of the microporous wood-based carbon electrode materials prepared in Example 1 and Comparative Examples 1-5; Figure 11 Nitrogen adsorption curves of the microporous wood-based carbon electrode materials prepared in Example 1 and Comparative Examples 1-5. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] The laccase (solid powder derived from Trametes versicolor) used has an enzyme activity ≥0.5 U / mg, catalog number: L304691; the hemicellulase (solid powder derived from Aspergillus niger) has an enzyme activity ≥50 U / mg, catalog number: H304918.

[0028] Example 1 This embodiment provides a method for preparing a microporous wood-based carbon electrode material, including the following steps: S1. Wood chip pretreatment Linden wood was cut perpendicular to its growth direction into 2 cm × 2 cm × 1 cm pieces. The microstructure of these pieces is shown in the image below. Figure 1 The wood chips are soaked in deionized water for 2 hours to remove surface dust and water-soluble impurities, thus obtaining pretreated linden wood.

[0029] S2, dual-enzyme directed stepwise synergistic degradation (1) Buffer preparation: Add 1.8g sodium acetate to 100mL of deionized water, stir magnetically until completely dissolved, then slowly add 0.98mL of acetic acid and mix well to prepare an acetate-sodium acetate buffer solution with pH=4.6, which can ensure that the two enzymes maintain high catalytic activity during degradation. (2) Directed degradation by laccase: 40 mL of the above buffer solution was placed in an Erlenmeyer flask, and laccase was added at a mass ratio of 1:20 between laccase and pretreated linden wood. The liquid-solid ratio of the buffer solution to the pretreated linden wood was 20 mL:1 g. The pretreated wood chips were placed in the Erlenmeyer flask to completely submerge the wood chips. After sealing with plastic wrap, the flask was placed in a constant temperature environment of 60℃ for 24 h. Under these conditions, laccase efficiently cleaves lignin cross-links and breaks down the dense structure of the cell wall. After the culture was completed, the wood chips were rinsed with deionized water to remove residual enzyme solution from the surface. Then, the wood chips were heated in an environment of 65℃ for 30 min to completely inactivate laccase and avoid its residual enzyme activity from interfering with the subsequent hemicellulose hydrolysis, thus obtaining single-enzyme hydrolyzed wood chips. (3) Precise hydrolysis with hemicellulase: Take another 40 mL of the above-mentioned acetate-sodium acetate buffer solution with pH=4.6 and place it in an Erlenmeyer flask. Add hemicellulase at a mass ratio of 1:6 between hemicellulase and pretreated linden wood. The liquid-solid ratio of the buffer solution to the pretreated linden wood is 20 mL:1 g. Place the wood chips after inactivating laccase into the flask and immerse them completely. Seal with plastic wrap and incubate at a constant temperature of 60℃ for 12 h. With the lignin barrier broken, this process parameter can achieve efficient hydrolysis of hemicellulose, remove the filling impurities between cellulose microfibrils, and further open up the pore structure. After the culture is completed, rinse the wood chips with a large amount of deionized water several times to remove residual buffer solution and enzymatic hydrolysis products. Dry at 60℃ for 35 min to obtain double-enzyme hydrolyzed wood chips.

[0030] S3, Stepped high-pressure hot pressing densification The surface moisture of the double-enzyme hydrolyzed wood chips was thoroughly wiped dry, and then placed in a hot press mold for gradient temperature and pressure synergistic densification treatment: first, the mold was heated to 100℃, and at this temperature, pressures of 1MPa, 2MPa, 3MPa, and 4MPa were applied for 5 minutes each, and finally the pressure was increased to 5MPa and applied for 40 minutes; after the high temperature and pressure were completed, the mold was cooled to 30℃, and the pressure of 5MPa was maintained for 9 hours. After depressurization, the wood chips were taken out to obtain dense wood.

[0031] S4. High-temperature carbonization preparation of microporous carbon materials Dense wood was placed in a tube furnace, and high-purity nitrogen (oxygen content ≤0.1%) was introduced to create an inert atmosphere. The furnace temperature was raised to 800℃ at a constant heating rate of 5℃ / min, and carbonized at this temperature for 2 hours. After carbonization, the heating device was turned off, but nitrogen was kept flowing, allowing the tube furnace to cool naturally to room temperature. The resulting bulk microporous carbon material (microporous wood-based carbon electrode material) was obtained, and its microstructure is shown in the figure below. Figure 2 .

[0032] Example 2 This embodiment provides a method for preparing a microporous wood-based carbon electrode material, including the following steps: S1. Wood chip pretreatment The linden wood was cut into 2 cm × 2 cm × 1 cm pieces perpendicular to the growth direction and soaked in deionized water for 2 hours to obtain pretreated linden wood.

[0033] S2, dual-enzyme directed stepwise synergistic degradation (1) Buffer preparation: Add 1.8g sodium acetate to 100mL of deionized water, stir magnetically until completely dissolved, then slowly add 0.98mL of acetic acid and mix well to obtain an acetate-sodium acetate buffer solution with pH=4.6; (2) Directed degradation by laccase: 40 mL of the above buffer solution was placed in an Erlenmeyer flask, and laccase was added at a ratio of 1:25 (mass ratio of laccase to pretreated linden wood). The liquid-solid ratio of the buffer solution to the pretreated linden wood was 25 mL:1 g. The pretreated wood chips were placed in the Erlenmeyer flask to completely submerge the wood chips. After sealing with plastic wrap, the flask was placed in a constant temperature environment of 60℃ for 24 h. Under these conditions, laccase efficiently cleaves lignin cross-links and breaks down the dense structure of the cell wall. After the culture was completed, the wood chips were rinsed with deionized water to remove residual enzyme solution from the surface. Then, the wood chips were heated in an environment of 65℃ for 30 min to obtain single-enzyme hydrolyzed wood chips. (3) Precise hydrolysis with hemicellulase: Take another 40 mL of the above-mentioned acetate-sodium acetate buffer solution with pH=4.6 and place it in an Erlenmeyer flask. Add hemicellulase at a ratio of 1:8 of hemicellulase to pretreated linden wood mass. The liquid-solid ratio of the buffer solution to the pretreated linden wood is 25 mL:1 g. Place the wood chips after inactivating laccase into the flask and immerse them completely. Seal with plastic wrap and incubate at a constant temperature of 60℃ for 12 h. Take out the wood chips, rinse them, and dry them at 65℃ for 30 min to obtain double-enzyme hydrolyzed wood chips.

[0034] S3, Stepped high-pressure hot pressing densification The surface moisture of the double-enzyme hydrolyzed wood chips was thoroughly wiped dry, and then placed in a hot press mold for gradient temperature and pressure synergistic densification treatment: first, the mold was heated to 100℃, and at this temperature, pressures of 1MPa, 2MPa, 3MPa, and 4MPa were applied for 8 minutes each, and finally the pressure was increased to 5MPa and applied for 35 minutes; after the high temperature and pressure were completed, the mold was cooled to 30℃, and the pressure of 5MPa was maintained for 9 hours. After depressurization, the wood chips were taken out to obtain dense wood.

[0035] S4. High-temperature carbonization preparation of microporous carbon materials Dense wood was placed in a tube furnace, and high-purity nitrogen (oxygen content ≤0.1%) was introduced into the furnace to create an inert atmosphere. The furnace temperature was raised to 800℃ at a constant heating rate of 5℃ / min, and carbonized at this temperature for 2 hours. After carbonization, the heating device was turned off, nitrogen was kept flowing in, and the tube furnace was allowed to cool naturally to room temperature. After removal, microporous wood-based carbon electrode material was obtained.

[0036] Example 3 This embodiment provides a method for preparing a microporous wood-based carbon electrode material, including the following steps: S1. Wood chip pretreatment The linden wood was cut into 2 cm × 2 cm × 1 cm pieces perpendicular to the growth direction and soaked in deionized water for 2 hours to obtain pretreated linden wood.

[0037] S2, dual-enzyme directed stepwise synergistic degradation (1) Buffer preparation: Add 1.8g sodium acetate to 100mL of deionized water, stir magnetically until completely dissolved, then slowly add 0.98mL of acetic acid and mix well to obtain an acetate-sodium acetate buffer solution with pH=4.6; (2) Directed degradation by laccase: 40 mL of the above buffer solution was placed in an Erlenmeyer flask, and laccase was added at a ratio of 1:22 (mass ratio of laccase to pretreated linden wood). The liquid-solid ratio of the buffer solution to the pretreated linden wood was 23 mL:1 g. The pretreated wood chips were placed in the Erlenmeyer flask to completely submerge the wood chips. After sealing with plastic wrap, the flask was placed in a constant temperature environment of 60℃ for 24 h. Under these conditions, laccase efficiently broke the lignin cross-links and opened up the dense structure of the cell wall. After the culture was completed, the wood chips were rinsed with deionized water to remove the residual enzyme solution on the surface. Then the wood chips were heated in an environment of 65℃ for 30 min to obtain single-enzyme hydrolyzed wood chips. (3) Precise hydrolysis with hemicellulase: Take another 40 mL of the above-mentioned acetic acid-sodium acetate buffer solution with pH=4.6 and place it in an Erlenmeyer flask. Add hemicellulase at a ratio of 1:7 of hemicellulase to pretreated linden wood mass. The liquid-solid ratio of the buffer solution to the pretreated linden wood is 23 mL:1 g. Place the wood chips after inactivating laccase into the flask and immerse them completely. Seal with plastic wrap and incubate at a constant temperature of 60℃ for 12 h. Take out the wood chips, rinse them, and dry them at 62℃ for 32 min to obtain double-enzyme hydrolyzed wood chips.

[0038] S3, Stepped high-pressure hot pressing densification The surface moisture of the double-enzyme hydrolyzed wood chips was thoroughly wiped dry, and then placed in a hot press mold for gradient temperature and pressure synergistic densification treatment: first, the mold was heated to 100℃, and at this temperature, pressures of 1MPa, 2MPa, 3MPa, and 4MPa were applied for 6 minutes each, and finally the pressure was increased to 5MPa and applied for 38 minutes; after the high temperature and pressure were completed, the mold was cooled to 30℃, and the pressure of 5MPa was maintained for 9 hours. After depressurization, the dense wood chips were taken out.

[0039] S4. High-temperature carbonization preparation of microporous carbon materials Dense wood was placed in a tube furnace, and high-purity nitrogen (oxygen content ≤0.1%) was introduced into the furnace to create an inert atmosphere. The furnace temperature was raised to 800℃ at a constant heating rate of 5℃ / min, and carbonized at this temperature for 2 hours. After carbonization, the heating device was turned off, nitrogen was kept flowing in, and the tube furnace was allowed to cool naturally to room temperature. After removal, microporous wood-based carbon electrode material was obtained.

[0040] The microporous wood-based carbon electrode materials prepared in Examples 2 and 3 have similar structures and properties to those in Example 1.

[0041] Comparative Example 1 This comparative example is similar to Example 1, except that it omits S2. The pretreated linden wood was directly densified by stepwise high-pressure hot pressing and high-temperature carbonization without enzyme treatment. The specific operations are as described in S3 and S4 of Example 1. The microstructure of the bulk microporous carbon material—microporous wood-based carbon electrode material prepared in this comparative example is shown in the figure. Figure 3 .

[0042] Comparative Example 2 This comparative example is similar to Example 1, except that it only uses laccase to treat the wood. Specifically, 1.8 g of sodium acetate was added to 100 mL of deionized water and magnetically stirred until completely dissolved. Then, 0.98 mL of acetic acid was slowly added and mixed thoroughly to prepare an acetate-sodium acetate buffer solution with a pH of 4.6. 40 mL of the buffer solution was placed in an Erlenmeyer flask, and laccase was added at a mass ratio of 1:6 to linden wood. The pretreated wood chips were then placed in the Erlenmeyer flask to completely submerge them. After sealing with plastic wrap, the flask was incubated at a constant temperature of 60°C for 24 hours. After incubation, the wood chips were repeatedly rinsed with plenty of deionized water to remove residual enzyme solution from the surface. The single-enzyme-digested wood chips were subjected to stepwise high-pressure hot pressing densification and high-temperature carbonization according to S3 and S4 in Example 1. The microstructure of the bulk microporous carbon material—microporous wood-based carbon electrode material prepared in this comparative example is shown in the figure. Figure 4 .

[0043] Comparative Example 3 This comparative example is similar to Example 1, except that it only uses hemicellulase to treat the wood. Specifically, 1.8 g of sodium acetate was added to 100 mL of deionized water and magnetically stirred until completely dissolved. Then, 0.98 mL of acetic acid was slowly added and mixed thoroughly to prepare an acetate-sodium acetate buffer solution with a pH of 4.6. 40 mL of the above-mentioned pH 4.6 acetate-sodium acetate buffer solution was placed in an Erlenmeyer flask, and hemicellulase was added at a mass ratio of 1:5 (hemicellulase to pretreated linden wood). The inactivated laccase wood chips were then placed in the flask and completely submerged. After sealing with plastic wrap, the flask was incubated at a constant temperature of 60°C for 12 hours. After incubation, the wood chips were repeatedly rinsed with plenty of deionized water to remove residual enzyme solution from the surface, yielding hemicellulase hydrolysate tablets. The hemicellulase hydrolysate tablets were subjected to step-by-step high-pressure hot pressing densification and high-temperature carbonization according to steps S3 and S4 in Example 1. The microstructure of the bulk microporous carbon material—microporous wood-based carbon electrode material prepared in this comparative example is shown in the figure below. Figure 5 .

[0044] Comparative Example 4 This comparative example is similar to Example 1, except that this comparative example does not have the stepwise hot pressing treatment, that is, S3 is deleted. Specifically, 1.8g of sodium acetate is added to 100mL of deionized water, and after magnetic stirring until completely dissolved, 0.98mL of acetic acid is slowly added and mixed evenly to obtain an acetate-sodium acetate buffer solution with pH=4.6. Take 40 mL of the above buffer solution and place it in an Erlenmeyer flask. Add laccase at a mass ratio of 1:6 (laccase to linden wood). Place the pretreated wood chips into the Erlenmeyer flask to completely submerge the chips. Seal with plastic wrap and incubate at 60°C for 24 hours. After incubation, rinse the wood chips repeatedly with plenty of deionized water to remove residual enzyme solution. Then, heat the wood chips at 65°C for 30 minutes to completely inactivate the laccase and avoid interference from residual enzyme activity in subsequent hemicellulosic hydrolysis. Separately, take 40 mL of the above pH 4.6 acetate-sodium acetate buffer solution and place it in an Erlenmeyer flask. Add hemicellulosic acid at a mass ratio of 1:5 (hemicellulosic acid to linden wood). Place the inactivated laccase chips into the flask to completely submerge them. Seal with plastic wrap and incubate at 60°C for 12 hours. After incubation, rinse the wood chips repeatedly with plenty of deionized water to remove residual buffer solution and hydrolysis products, obtaining double-enzyme hydrolyzed wood chips. The enzymatically hydrolyzed wood chips were placed in a tube furnace, and high-purity nitrogen (oxygen content ≤0.1%) was introduced into the furnace to create an inert atmosphere. The furnace temperature was raised to 800 ℃ at a constant heating rate of 5 ℃ / min, and carbonized at this temperature for 2 hours. After carbonization, the heating device was turned off, but nitrogen was kept flowing in, and the tube furnace was allowed to cool naturally to room temperature. The resulting bulk microporous carbon material was obtained. The microstructure of the bulk microporous carbon material-microporous wood-based carbon electrode material prepared in this comparative example is shown in the figure. Figure 6 .

[0045] Comparative Example 5 This comparative example is similar to Example 1, except that the densification process of the dual-enzyme hydrolyzed wood chips in this comparative example is a constant pressure treatment. Step S3 in this comparative example is: placing the dual-enzyme hydrolyzed wood chips at 100°C and under a pressure of 5 MPa for 5 hours; other operating steps are the same as in Example 1. The microstructure of the bulk microporous carbon material prepared in this comparative example is as follows: Figure 7 .

[0046] Figures 1-7 It can be seen that the untreated logs have intact cell walls, loosely arranged fibers, open cell cavities, and numerous natural pores. While stepwise hot pressing alone produces mechanical compression, the cell walls retain many micron-sized cracks and unclosed pores after cooling due to the rigid support and elastic recovery of lignin and hemicellulose. Dual-enzyme treatment without hot pressing leads to the degradation of cell wall components due to enzymatic hydrolysis, resulting in loose and collapsed fibers and a porous, flocculent structure with extremely poor density. Hemicellulase treatment followed by hot pressing partially removes hemicellulose and improves cell wall flexibility, but residual lignin still hinders hydrogen bonding between fibers, resulting in uneven densification and localized areas of non-adhesion after hot pressing. Laccase treatment followed by stepwise hot pressing oxidizes and degrades lignin, making the cell walls easily deformable, but the retained hemicellulose easily forms a gel-like blockage during hot pressing, leading to an uneven surface and heterogeneous interfaces within. Dual-enzyme treatment, but with a single, rapid heating and pressing process (non-stepwise), results in a more effective solution. Scanning electron microscopy revealed that the cell walls had undergone significant densification. However, rapid compression resulted in uneven stress distribution between cellulose layers, leading to a small number of fine microcracks and thin interlayer peeling marks.

[0047] The synergistic action of hemicellulase and laccase completely relieved the rigid constraints of hemicellulose and lignin on the cell wall. The fully softened cell wall slowly degassed and gradually adhered during the stepwise thermopressing process (stepwise temperature and pressure increases). Exposed active hydroxyl groups on the cellulose surface underwent high-strength hydrogen bond recombination, ultimately forming a nearly pore-free, microcrack-free, and continuously dense layered mass. This sample significantly outperformed all other treatment groups in terms of density, interfacial bonding strength, and defect control, including being superior to the directly thermopressed sample treated with the dual enzymes.

[0048] Bulk microporous carbon materials—microporous wood-based carbon electrode materials—prepared in Example 1 (stepwise hot pressing after dual-enzyme treatment), Comparative Example 1 (stepwise hot pressing of logs), Comparative Example 2 (stepwise hot pressing after laccase treatment), Comparative Example 3 (stepwise hot pressing after hemicellulase treatment), Comparative Example 4 (no hot pressing after dual-enzyme treatment), and Comparative Example 5 (direct hot pressing after dual-enzyme treatment) were subjected to CV voltage window testing at a scan rate of 1 mV / s and at a scan rate of 1 mA / cm². 2 The GCD curves at current densities are shown in the test results. Figure 8 and Figure 9 .

[0049] Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) testing systems were used to investigate the effects of different enzyme treatments and hot-pressing processes on the electrochemical performance of wood-based electrode materials. At 1 mV·s -1 At the scan rate, the CV curves of all samples exhibited a rectangular pattern with no obvious redox peaks, indicating that their energy storage mechanism is mainly based on double-layer capacitance. Among them, the CV curve of the step-hot-pressed sample after dual-enzyme treatment had the largest closed area, with a current response range of -0.009 A to 0.0085 A, which was significantly better than that of the single-enzyme treated, direct hot-pressed, and control samples. This confirms that the synergistic degradation effect of laccase and hemicellulase can effectively remove amorphous components from wood. Combined with the hierarchical interconnected porous structure constructed by the step-hot-pressing process, it provides abundant adsorption sites and rapid transport channels for electrolyte ions.

[0050] At 1 mA·cm -2 At the specified current density, the GCD test results were highly consistent with the CV conclusions: the discharge time of the stepwise hot-pressed sample after dual-enzyme treatment reached 120,000 s, and the charge-discharge curve was a highly symmetrical isosceles triangle with no significant voltage drop, indicating extremely low internal resistance and excellent electrochemical reversibility. In contrast, the discharge time of the single-enzyme treated, directly hot-pressed, and control samples was significantly shortened, and the curve slope was steeper and the distortion was obvious, reflecting their defects of high ion transport resistance and insufficient effective active sites. The dual-enzyme synergistic treatment combined with the stepwise hot-pressing process used in this invention can achieve precise control of the structure and properties of wood-based electrode materials, exhibiting excellent charge storage capacity.

[0051] This invention presents a microporous wood-based carbon electrode material—linden wood-based bulk microporous carbon—prepared through laccase-hemicellulase synergistic degradation and step-by-step high-temperature hot pressing. This material exhibits high micropore ratio, high specific surface area, interconnected channels, excellent conductivity, and structural strength, and can be directly used as a binder-free, self-supporting integrated electrode in the field of supercapacitors. Currently, supercapacitor electrode materials mainly include activated carbon, graphene, metal oxides, conductive polymers, and traditional biomass carbon. The specific capacitance of commercially available activated carbon is typically 200–300 F·g. -1 However, most existing electrode materials are in powder form, requiring binders for molding, resulting in low surface area capacitance and poor volumetric performance. The electrode material prepared in this invention, through dual-enzyme directed degradation and a step-by-step hot-pressing process, successfully constructs a hierarchical pore system dominated by 0.5–1.0 nm micropores, significantly increasing the specific surface area and providing abundant active sites for rapid ion adsorption and transport.

[0052] The BJH pore size distribution curves of the microporous wood-based carbon electrode materials prepared in Example 1 and Comparative Examples 1-5 are shown below. Figure 10As can be seen from the BJH pore size distribution curves, the pore size of each group of samples is concentrated in the 0–2 nm micropore range, while the pore volume of mesopores above 2 nm is generally close to zero; among them, the sample treated with dual enzymes and subjected to stepwise hot pressing achieved the highest pore volume peak (0.715 cm⁻¹) at 0.45 nm. 3 ·g -1 ·nm -1 The peak pore volumes of direct hot pressing with two enzymes, laccase stepwise hot pressing, hemicellulase stepwise hot pressing, no hot pressing with two enzymes, and log stepwise hot pressing decreased sequentially to 0.510, 0.422, 0.332, 0.210, and 0.055 cm³, respectively. 3 ·g -1 ·nm -1 The peak pore size was within a narrow range of 0.45–0.52 nm. Under the same hot-pressing regime, the micropore volume followed the rule of dual enzymes > laccase > hemicellulose single enzyme > log. Under the same dual enzyme pretreatment, step hot pressing was more conducive to the formation of ultrafine pores below 0.5 nm. Direct hot pressing could retain more small mesopores of 1–2 nm. Samples without hot pressing lacked the pore-forming effect of cell wall thermal shrinkage, and the degree of micropore development was significantly weaker than that of various hot-pressed modified samples. This proves that dual enzyme coupled step hot pressing can efficiently regulate and construct the microporous structure of hardwood.

[0053] The nitrogen adsorption curves of the microporous wood-based carbon electrode materials prepared in Example 1 and Comparative Examples 1-5 are shown below. Figure 11 All are typical Type IV adsorption isotherms. In the low-pressure range (P / P0 < 0.1), the adsorption capacity rapidly increases, corresponding to the micropore filling process. A stable adsorption plateau forms in the medium-pressure range (0.1–0.8), and the adsorption capacity continues to rise again in the high-pressure range (P / P0 > 0.8), reflecting the presence of mesopores and capillary aggregation within the sample. At P / P0 ≈ 0.98, the adsorption capacity of the dual-enzyme treated stepwise thermobaric sample reaches 136.0 cm³. 3 ·g -1 The adsorption capacities of direct hot pressing with dual enzymes, laccase stepwise hot pressing, hemicellulase stepwise hot pressing, no hot pressing with dual enzymes, and log stepwise hot pressing were 86.5, 85.0, 56.0, 44.5, and 35.0 cm³, respectively. 3 ·g -1From the perspective of mechanism of action, the composite dual enzyme can simultaneously degrade hemicellulose and amorphous polysaccharides in the cell wall. After the components are dissolved, a large number of micropores and mesopores are constructed in situ between the cell wall lamellae. The pore-forming effect is significantly better than laccase, which only breaks the cross-linking structure of lignin, and hemicellulase, which degrades hemicellulose alone. In contrast, the logs do not have any enzymatic components dissolved. High temperature and pressure cause a large number of natural inherent pores to close and collapse, resulting in the lowest adsorption capacity. Under the same dual enzyme pretreatment conditions, the stepwise slow increase in temperature and pressure can gradually refine the pores and reduce pore collapse by relying on the loose cell wall skeleton after enzymatic hydrolysis. One-step direct hot pressing and instantaneous high pressure can easily squeeze and destroy some of the newly formed pores. The unpressed sample lacks the physical process of high temperature-induced cell wall shrinkage and pore formation, so the degree of pore development is the worst.

[0054] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a microporous wood-based carbon electrode material, characterized in that, Includes the following steps: S1. Place the pretreated linden wood and laccase in a buffer solution, seal it, and incubate it at a constant temperature of 60°C for 24 hours. Take out the laccase-treated linden wood, wash it with water, and dry it at 65°C for 30 minutes to obtain single-enzyme hydrolyzed wood chips. The mass ratio of laccase to pretreated linden wood is 1:20-25. S2. Place the single-enzyme hydrolyzed wood chips and hemicellulase in a buffer solution, seal and incubate at a constant temperature of 60°C for 12 hours. Take out the linden wood treated with laccase-hemicellulase, wash and dry it to obtain double-enzyme hydrolyzed wood chips. The mass ratio of hemicellulase to pretreated linden wood is 1:6-8. S3. Place the double-enzyme hydrolyzed wood chips into a hot press mold, and press them at 100°C with pressures of 1MPa, 2MPa, 3MPa and 4MPa for 5-8 minutes each, then increase the pressure to 5MPa and press for 35-40 minutes. Finally, cool down to 30°C and keep the pressure at 5MPa for 9 hours. After depressurization, dense wood is obtained. S4. The dense wood is placed in a tube furnace for carbonization to obtain a microporous wood-based carbon electrode material.

2. The preparation method according to claim 1, characterized in that, The preparation of the pretreated linden wood in S1 includes: cutting the linden wood perpendicular to the growth direction into wood chips of 2 cm × 2 cm × 1 cm, and then soaking them in deionized water for 2-3 hours to obtain the pretreated linden wood.

3. The preparation method according to claim 1, characterized in that, The buffer solution described in S1 and / or S2 is an acetate-sodium acetate buffer solution. The preparation process of the buffer solution includes: mixing deionized water and sodium acetate, stirring to dissolve, adding glacial acetic acid dropwise under continuous stirring, and mixing evenly to obtain the acetate-sodium acetate buffer solution.

4. The preparation method according to claim 3, characterized in that, The ratio of deionized water, sodium acetate, and glacial acetic acid is 100 mL: 1.8 g: 0.98 mL.

5. The preparation method according to claim 1, characterized in that, The liquid-to-solid ratio of the buffer solution to the pretreated linden wood in S1 and S2 is 20-25 mL: 1 g.

6. The preparation method according to claim 1, characterized in that, The drying temperature in S2 is 60-65℃, and the drying time is 30-35 min.

7. The preparation method according to claim 1, characterized in that, S4 specifically involves placing the dense wood in a tubular furnace, introducing nitrogen gas into the furnace, raising the furnace temperature to 800°C at a rate of 3-5°C / min, carbonizing at a constant temperature for 2 hours, and then allowing the furnace to cool naturally to room temperature to obtain a microporous wood-based carbon electrode material.

8. The preparation method according to claim 7, characterized in that, The oxygen content of the nitrogen gas mentioned in S4 is ≤0.1%.

9. A battery pack assembled from a microporous wood-based carbon electrode material prepared by any one of claims 1-8.

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