Enzymatic wood derived carbonaceous electrode material containing nitrogen, manganese and oxygen as well as preparation method and application of enzymatic wood derived carbonaceous electrode material

Abstract

The invention discloses an enzymolysis wood-derived carbonaceous electrode material containing nitrogen, manganese and oxygen and a preparation method and application thereof, and relates to the technical field of supercapacitor electrode materials. The preparation method comprises the following steps: performing enzyme treatment on wood to obtain enzymolysis wood; the enzymolysis wood is soaked in a urea solution or a melamine solution, a hydrothermal reaction is conducted, drying is conducted, and nitrogen-doped enzymolysis wood is obtained; the nitrogen-doped enzymolysis wood is soaked in a potassium permanganate solution, pre-carbonization and carbonization are sequentially carried out after drying, and the enzymolysis wood derived carbonaceous electrode material containing nitrogen, manganese and oxygen is obtained. Firstly, the carbon material substrate is prepared through enzyme treatment of wood, then nitrogen atoms, manganese atoms and oxygen atoms are loaded at the same time, the wettability of the material to an electrolyte is improved, and the situation that the effective specific surface area is reduced due to the cavity effect formed by poor contact between the material and the electrolyte is avoided; the pore composition, the specific surface area, the specific capacitance, the conductivity and the energy density of the supercapacitor are improved.

Description

Technical Field

[0001] This invention relates to the field of supercapacitor electrode materials technology, and in particular to an enzymatically hydrolyzed wood-derived carbonaceous electrode material containing nitrogen, manganese, and oxygen, its preparation method, and its application. Background Technology

[0002] Supercapacitors, as energy storage devices capable of rapid charging and discharging, have long been prized for their high power density and long cycle stability. However, their relatively low energy density and high cost have limited their applications. Therefore, reducing production costs and increasing energy density are essential. To reduce costs while achieving sustainable development, researchers are increasingly focusing on using environmentally friendly wood-derived carbon materials to fabricate supercapacitor electrodes. Wood, as a widely available renewable resource, provides high specific surface area and abundant pores for derived carbon materials due to its natural three-dimensional porous structure. Furthermore, its monolithic structure allows it to be used as a self-supporting thick electrode without the need for adhesives. In addition, mature wood processing technologies have significantly reduced the production cost of this material. Whether using physical methods or acid-base methods to activate wood, or constructing composite electrode materials with wood using high-conductivity materials such as carbon nanotubes, graphene oxide, and MXene, or treating wood with fungi, the aim is to design electrode structures with good pore distribution, improved material conductivity, and reduced internal resistance to achieve rapid ion transfer.

[0003] However, these methods all have some drawbacks. Acid-base treatment is efficient but easily corrodes processing equipment. Loading high-conductivity materials such as MXene, carbon nanotubes, and graphene oxide can easily lead to self-stacking, resulting in material waste and potentially causing the load to detach during rapid material cycling. Although biological treatment methods have environmentally friendly advantages in biochar material modification, their long production cycle, complex operation process, and strict cultivation conditions limit their large-scale commercial application. Therefore, developing novel wood modification technologies for preparing supercapacitor electrode materials is urgently needed—this technology not only needs to effectively optimize the pore structure of wood and reduce environmental risks, but also should have a reasonable production cycle, high energy density, and excellent cycling stability. Summary of the Invention

[0004] The purpose of this invention is to provide a nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material, its preparation method, and its application, in order to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention: a method for preparing a nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material, comprising the following steps: Wood is enzymatically treated to obtain enzymatically hydrolyzed wood; the enzymatically hydrolyzed wood is then soaked in urea solution or melamine solution, subjected to hydrothermal reaction, and dried to obtain nitrogen-doped enzymatically hydrolyzed wood; the nitrogen-doped enzymatically hydrolyzed wood is then soaked in potassium permanganate solution, dried, and subsequently subjected to pre-carbonization and carbonization to obtain the nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material.

[0006] This invention first prepares a carbon material substrate by enzymatically treating wood, then simultaneously loads nitrogen, manganese, and oxygen atoms to increase the material's wettability with the electrolyte. This prevents poor contact between the material and the electrolyte, avoiding cavitation effects that reduce the effective specific surface area and thus improving the pore structure, specific surface area, specific capacitance, conductivity, and energy density of the supercapacitor. Specifically, utilizing the highly specific catalytic properties of enzymatic chemical reactions, some cellulose, hemicellulose, or lignin in the wood are directionally and effectively hydrolyzed under mild and environmentally friendly treatment conditions. This preserves the 3D structure of the wood while constructing more ion transport channels. Between these low-torsion channels, a hierarchical interconnected porous structure with abundant mesopores and micropores is formed, which is highly advantageous for use as a thick electrode in supercapacitors with high specific surface area and volumetric energy density. Introducing nitrogen using urea or melamine increases the number of hydrophilic functional groups on the material surface, improving its wettability, increasing electrolyte accessibility, and preventing cavities between the electrode material and the electrolyte that reduce the effective surface area of ​​the electrode material. Furthermore, the electrical conductivity of biomass materials was enhanced by loading MnO onto the surface of biomass materials through high-temperature pyrolysis of potassium permanganate, which significantly increased the ion transport rate.

[0007] The present invention provides a convenient, effective, and rapid method for preparing biomass carbon materials by enzyme-assisted conversion of cellulose biomass materials and loading an appropriate amount of active substances. This method can effectively produce low-cost, high-porosity, and high-specific-surface-area carbon electrode materials, thereby improving their specific surface area, specific capacitance, conductivity, and energy density.

[0008] Furthermore, the enzyme treatment step includes: adding the enzyme and pretreated wood to an acetate-sodium acetate buffer solution and culturing at 45-55°C for 20-30 hours.

[0009] Furthermore, the enzyme includes cellulase, hemicellulase, or laccase (which degrades lignin).

[0010] Wood is mainly composed of three major components: cellulose, hemicellulose, and lignin. Enzymatic treatment with these three enzymes can selectively remove these three components from wood, thereby improving wood performance.

[0011] Furthermore, the mass ratio of the enzyme to the pretreated wood is 1:5-10.

[0012] Further, the preparation steps of the acetate-sodium acetate buffer solution include: adjusting the pH of the sodium acetate solution to 4.5-5.5 using acetic acid to obtain the acetate-sodium acetate buffer solution.

[0013] Different enzymes have their optimal temperature and pH values. If the temperature or pH value is above or below this range, the enzyme activity will be greatly reduced or even directly inactivated. Therefore, preparing a buffer solution with a suitable pH value before treatment can ensure effective and efficient enzyme treatment. Common cellulases include acidic cellulases produced by *Trichoderma reesei*, hemicellulases are acidic hemicellulases derived from *Aspergillus niger*, and laccases are derived from white-rot fungi. Their optimal temperature and pH values ​​overlap at pH 4.5-5.5 and temperature 45-55℃. Outside this range, the enzymatic hydrolysis efficiency decreases significantly.

[0014] Furthermore, the concentration of the sodium acetate solution is 0.2-0.3 mol / L.

[0015] Further, the mass ratio of the acetate-sodium acetate buffer to the enzyme is 1000:3-10.

[0016] Optionally, after the culture is completed, the process may further include rinsing to remove residual enzymes and buffer solutions.

[0017] Furthermore, the concentration of the urea solution is 0.1-0.5 mol / L.

[0018] Furthermore, the concentration of the melamine solution is 0.1-0.5 mol / L.

[0019] Furthermore, the hydrothermal reaction is carried out at a temperature of 85-105℃ for a duration of 4-8 hours.

[0020] Furthermore, the concentration of the potassium permanganate solution is 0.05-0.15 mol / L, and the soaking time in the potassium permanganate solution is 1-3 hours.

[0021] Furthermore, the pre-carbonization temperature is 400-600℃, and the time is 1.5-3h.

[0022] Furthermore, the carbonization temperature is 750-850℃ and the time is 1.5-2.5h.

[0023] Pre-carbonizing before carbonization can prevent the wood from bending due to excessively rapid heating, which would otherwise prevent the material from being assembled or break during the electrode preparation process.

[0024] Furthermore, the pretreatment includes cutting, cleaning, and drying the wood.

[0025] Furthermore, the cutting specifically involves cutting the wood into wood chips with a thickness of 1-3 mm along its natural growth direction.

[0026] Furthermore, the cleaning process includes immersing the wood in water for 6-12 hours followed by rinsing with plenty of water to remove surface dust and water-soluble impurities.

[0027] Optionally, the wood may include, but is not limited to, paulownia, fir, larch, toon, elm, or cypress.

[0028] Optionally, the heating rate for pre-carbonization is 3-8°C / min, and the heating rate for carbonization is 3-5°C / min.

[0029] Optionally, the carbonization process may further include cleaning and drying steps.

[0030] Optionally, the drying temperature is 50-70℃.

[0031] The second technical solution of the present invention: a nitrogen-manganese-oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material prepared according to the above preparation method.

[0032] The third technical solution of the present invention: the application of the above-mentioned nitrogen-manganese-oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material in the preparation of supercapacitors.

[0033] The present invention discloses the following technical effects: (1) The present invention uses enzymes (cellulase, hemicellulase or laccase) to treat wood as a carbon substrate. The green enzymatic reaction optimizes the pore structure of wood under mild conditions while retaining the basic skeleton of wood and significantly increasing the specific surface area of ​​the material, thereby increasing the specific capacitance of the electrode material and providing more attachment sites for nitrogen, manganese and oxygen atoms.

[0034] (2) The present invention improves the functional group composition of the surface of enzymatically hydrolyzed wood-derived carbon materials by loading nitrogen elements. The hydrothermal method can uniformly and effectively load a large amount of nitrogen elements onto the carbon materials, which greatly improves the wettability of the material surface and is conducive to the subsequent loading of manganese and oxygen.

[0035] (3) In this invention, potassium permanganate is soaked on uncarbonized wood to activate carbonization. At the same time as the wood is carbonized, manganese and oxygen elements are loaded. The manganese and oxygen atoms generated in situ can adhere more firmly to the carbon skeleton, effectively avoiding the loss of the load and the resulting decrease in the cycle stability of the material.

[0036] (4) The preparation process of the present invention is simple, the raw materials are abundant, and the raw materials and processing activation costs are low, which has the advantages of low cost, green and fast. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 The images shown are scanning electron microscope (SEM) images of untreated paulownia wood in Example 1 ((a)-(b)), SEM images of enzymatically hydrolyzed wood ((c)-(d)), SEM images of the final carbon electrode material ((e)-(h)), and elemental mapping diagrams of the final carbon electrode material ((i)-(l)).

[0039] Figure 2 The images show physical photos of the carbon electrode materials prepared in Example 1 (left) and Comparative Example 9 (right).

[0040] Figure 3 The XPS (N 1s) spectrum of the carbon electrode material prepared in Example 1 is shown.

[0041] Figure 4 The XPS (N 1s) spectrum of the carbon electrode material prepared in Example 2 is shown.

[0042] Figure 5 The image shows the XPS (Mn 2p) spectrum of the carbon electrode material prepared in Example 1.

[0043] Figure 6 The XPS (Mn 2p) spectrum of the carbon electrode material prepared in Example 2 is shown.

[0044] Figure 7 The XPS (O 1s) spectrum of the carbon electrode material prepared in Example 1 is shown.

[0045] Figure 8 The XPS (O 1s) spectrum of the carbon electrode material prepared in Example 2 is shown.

[0046] Figure 9 The XRD patterns are those of the carbon electrode materials prepared in Examples 1, 2, and 1.

[0047] Figure 10 The images show the Raman spectra of the carbon electrode materials prepared in Examples 1, 2, and 1 (Comparative Example 1).

[0048] Figure 11 The image shows the pore size distribution of the carbon electrode materials prepared in Example 1 and Comparative Example 1.

[0049] Figure 12The image shows the pore size distribution of the carbon electrode materials prepared in Example 2 and Comparative Example 1.

[0050] Figure 13 Cyclic voltammetry curves of an alkaline supercapacitor assembled using the carbonaceous electrode material prepared in Example 1.

[0051] Figure 14 The image shows the constant current charge-discharge diagram of an alkaline supercapacitor assembled using the carbonaceous electrode material prepared in Example 1.

[0052] Figure 15 Cyclic voltammetry curves of a neutral supercapacitor assembled using the carbon electrode material prepared in Example 1.

[0053] Figure 16 The image shows the constant current charge-discharge diagram of a neutral supercapacitor assembled using the carbon electrode material prepared in Example 1. Detailed Implementation

[0054] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0055] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0056] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0057] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0058] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0059] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0060] In the following embodiments and comparative examples of the present invention, room temperature refers specifically to 20-30°C.

[0061] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of this invention are commercially available products. Paulownia wood was sourced from Heze, Shandong; Chinese fir from Sanming, Fujian; larch from Tonghua, Jilin; Chinese toon and elm from Shijiazhuang, Hebei; and cypress from Yichang, Hubei. Cellulase (derived from *Trichoderma reesei*, enzyme activity 10000 U / g) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; anhydrous zinc acetate (purity 99.99%), anhydrous cobalt acetate (purity 98%), laccase (derived from *Trametes versicolor*, enzyme activity 0.5 U / mg), hemicellulase (derived from *Aspergillus niger*, enzyme activity 5 U / mg), and pectinase (derived from *Aspergillus niger*, enzyme activity 30000 U / g) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; potassium permanganate (KMnO4, Sodium acetate (CH3COONa, 99%) and urea (CO(NH2)2, 99%), potassium hydroxide (KOH, 85%), and acetic acid (CH3COOH, 99%) were purchased from China National Pharmaceutical Group Co., Ltd.; all chemicals and reagents were used as is upon receipt without further purification, and deionized water was used as the solvent for preparing solutions.

[0062] Example 1 A method for preparing a nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material, comprising the following steps: (1) Cut the paulownia wood into 20mm×20mm×2mm wood chips along the natural growth direction, soak them in deionized water for 6 hours, and then rinse them with a large amount of deionized water to remove floating dust and water-soluble impurities on the surface of the wood chips. Then, vacuum dry the wood at 60℃ for 24 hours to obtain the pretreated wood.

[0063] (2) Prepare a 0.22 mol / L sodium acetate solution and adjust its pH to 4.6 using acetic acid to obtain an acetate-sodium acetate buffer solution. Add the prepared buffer solution, cellulase, and pretreated wood (pretreated wood is dried paulownia wood chips, the mass ratio of cellulase to paulownia wood chips is 1:6, the mass ratio of buffer solution to cellulase is 1000:5, wherein the cellulase is 0.1 g, and the paulownia wood chips are completely immersed in the buffer solution) to a conical flask with a bell mouth. Seal the flask with plastic wrap and incubate it at 50°C for 24 h. Then rinse the paulownia wood chips with a large amount of deionized water to remove residual enzyme and buffer solution, and obtain enzyme-treated wood (i.e., enzymatically hydrolyzed wood).

[0064] (3) The enzymatically hydrolyzed wood was soaked in a 0.1 mol / L urea solution, then placed in a hydrothermal reactor and hydrothermally reacted at 95°C for 6 h, followed by vacuum drying at 60°C for 24 h to obtain nitrogen-doped enzymatically hydrolyzed wood. The nitrogen-doped enzymatically hydrolyzed wood was soaked in a 0.1 mol / L KMnO4 solution for 1.5 h, then vacuum dried at 60°C for 24 h, and placed in a tube furnace under a nitrogen atmosphere. The temperature was increased to 500°C at a rate of 5°C / min and held for 2 h for pre-carbonization, followed by increasing the temperature to 800°C at a rate of 5°C / min and holding for 2 h for carbonization. After removal, residual KMnO4 was washed away with a large amount of deionized water, and the wood was vacuum dried at 60°C for 24 h to obtain nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material.

[0065] Example 2 A method for preparing a nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material, comprising the following steps: (1) Cut the paulownia wood into 20mm×20mm×2mm wood chips along the natural growth direction, soak them in deionized water for 10 hours, and then rinse them with a large amount of deionized water to remove floating dust and water-soluble impurities on the surface of the wood chips. Then, vacuum dry the wood at 65℃ for 24 hours to obtain the pretreated wood.

[0066] (2) Prepare a 0.25 mol / L sodium acetate solution and adjust its pH to 5.0 using acetic acid to obtain an acetate-sodium acetate buffer solution. Add the prepared buffer solution, laccase, and pretreated wood (i.e., dried paulownia wood chips, with a laccase to paulownia wood chip mass ratio of 1:6 and a buffer solution to laccase mass ratio of 1000:5, wherein the laccase content is 0.1 g and the paulownia wood chips are completely immersed in the buffer solution) to a conical flask. Seal the flask with plastic wrap and incubate it at 60°C for 24 h. Then rinse the paulownia wood chips with plenty of deionized water to remove residual enzymes and buffer solution, obtaining enzyme-treated wood (i.e., enzymatically hydrolyzed wood).

[0067] (3) The enzymatically hydrolyzed wood was soaked in a 0.2 mol / L urea solution, then placed in a hydrothermal reactor and hydrothermally reacted at 90°C for 8 h, and then vacuum dried at 60°C for 24 h to obtain nitrogen-doped enzymatically hydrolyzed wood. The nitrogen-doped enzymatically hydrolyzed wood was soaked in a 0.15 mol / L KMnO4 solution for 1.5 h, then vacuum dried at 60°C for 24 h, and then placed in a tube furnace and pre-carbonized at 600°C for 2.5 h under a nitrogen atmosphere at a heating rate of 3°C / min, and then carbonized at 800°C for 1.5 h at a heating rate of 3°C / min. After removal, residual KMnO4 was washed away with a large amount of deionized water, and then vacuum dried at 60°C for 24 h to obtain nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material.

[0068] Example 3 A method for preparing a nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material, comprising the following steps: (1) Cut the fir wood into 20mm×20mm×1.5mm wood chips along the natural growth direction, immerse them in deionized water for 6 hours, and then rinse them with a large amount of deionized water to remove floating dust and water-soluble impurities on the surface of the wood chips. Then, vacuum dry the wood at 60℃ for 24 hours to obtain the pretreated wood.

[0069] (2) Prepare a 0.3 mol / L sodium acetate solution and adjust its pH to 4.6 using acetic acid to obtain an acetate-sodium acetate buffer solution. Add the prepared buffer solution, cellulase, and pretreated wood (i.e., dried cedar wood chips, with a cellulase-to-cedar wood chip mass ratio of 1:8 and a buffer-to-cellulase mass ratio of 1000:7, wherein the cellulase content is 0.1 g and the cedar wood chips are completely immersed in the buffer solution) to a conical flask. Seal the flask with plastic wrap and incubate it at 50°C for 24 h. Then rinse the cedar wood chips with a large amount of deionized water to remove residual enzymes and buffer solution, obtaining enzyme-treated wood (i.e., enzymatically hydrolyzed wood).

[0070] (3) The enzymatically hydrolyzed wood was soaked in a 0.4 mol / L urea solution, then placed in a hydrothermal reactor and hydrothermally reacted at 105 °C for 5 h, followed by vacuum drying at 60 °C for 24 h to obtain nitrogen-doped enzymatically hydrolyzed wood. The nitrogen-doped enzymatically hydrolyzed wood was soaked in a 0.08 mol / L KMnO4 solution for 1 h, then vacuum dried at 60 °C for 24 h, and then placed in a tube furnace and pre-carbonized at 550 °C for 2 h under a nitrogen atmosphere at a heating rate of 5 °C / min, followed by carbonization at 750 °C for 2.5 h at a heating rate of 5 °C / min. After removal, residual KMnO4 was washed away with a large amount of deionized water, and then vacuum dried at 60 °C for 24 h to obtain nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material.

[0071] Example 4 A method for preparing a nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material, comprising the following steps: (1) Cut larch into 30mm×30mm×3mm wood chips along the natural growth direction, immerse in deionized water for 6 hours, and then rinse with a large amount of deionized water to remove floating dust and water-soluble impurities on the surface of the wood chips. Then, vacuum dry the wood at 55℃ for 24 hours to obtain pretreated wood.

[0072] (2) Prepare a 0.2 mol / L sodium acetate solution and adjust its pH to 4.6 with acetic acid to obtain an acetate-sodium acetate buffer solution. Add the prepared buffer solution, cellulase, and pretreated wood (i.e., dried larch wood chips, with a cellulase to larch wood chip mass ratio of 1:7 and a buffer solution to cellulase mass ratio of 1000:10, wherein the cellulase content is 0.1 g and the larch wood chips are completely immersed in the buffer solution) to a conical flask. Seal the flask with plastic wrap and incubate it at 50°C for 24 h. Then rinse the larch wood chips with a large amount of deionized water to remove residual enzyme and buffer solution, and obtain enzyme-treated wood (i.e., enzymatically hydrolyzed wood).

[0073] (3) The enzymatically hydrolyzed wood was soaked in a 0.1 mol / L urea solution, then placed in a hydrothermal reactor and hydrothermally reacted at 85°C for 8 h, and then vacuum dried at 55°C for 24 h to obtain nitrogen-doped enzymatically hydrolyzed wood. The nitrogen-doped enzymatically hydrolyzed wood was soaked in a 0.15 mol / L KMnO4 solution for 3 h, then vacuum dried at 55°C for 24 h, and then placed in a tube furnace and pre-carbonized at 400°C for 1.5 h under a nitrogen atmosphere at a heating rate of 8°C / min, and then carbonized at 800°C for 2.5 h at a heating rate of 5°C / min. After removal, residual KMnO4 was washed away with a large amount of deionized water, and then vacuum dried at 55°C for 24 h to obtain nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material.

[0074] Example 5 A method for preparing a nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material, comprising the following steps: (1) Cut the Chinese toon into 15mm×15mm×0.2mm wood chips along the natural growth direction, soak them in deionized water for 10 hours, and then rinse them with a large amount of deionized water to remove floating dust and water-soluble impurities on the surface of the wood chips. Then, vacuum dry the wood at 70℃ for 24 hours to obtain the pretreated wood.

[0075] (2) Prepare a 0.28 mol / L sodium acetate solution and adjust its pH to 4.6 using acetic acid to obtain an acetate-sodium acetate buffer solution. Add the prepared buffer solution, cellulase, and pretreated wood (i.e., dried Toona sinensis wood chips, with a cellulase-to-Toona sinensis wood chip mass ratio of 1:10 and a buffer solution-to-cellulase mass ratio of 1000:3, wherein the cellulase content is 0.1 g and the Toona sinensis wood chips are completely immersed in the buffer solution) to a conical flask with a bell mouth. Seal the flask with plastic wrap and incubate it at 50°C for 24 h. Then rinse the Toona sinensis wood chips with a large amount of deionized water to remove residual enzyme and buffer solution, obtaining enzyme-treated wood (i.e., enzymatically hydrolyzed wood).

[0076] (3) The enzymatically hydrolyzed wood was soaked in a 0.5 mol / L melamine solution, then placed in a hydrothermal reactor and hydrothermally reacted at 105 °C for 8 h, and then vacuum dried at 70 °C for 24 h to obtain nitrogen-doped enzymatically hydrolyzed wood. The nitrogen-doped enzymatically hydrolyzed wood was soaked in a 0.15 mol / L KMnO4 solution for 3 h, then vacuum dried at 70 °C for 24 h, and then placed in a tube furnace and pre-carbonized at 400 °C for 1.5 h under a nitrogen atmosphere at a heating rate of 8 °C / min, and then carbonized at 790 °C for 1.5 h at a heating rate of 3 °C / min. After removal, residual KMnO4 was washed away with a large amount of deionized water, and then vacuum dried at 70 °C for 24 h to obtain nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material.

[0077] Example 6 A method for preparing a nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material, comprising the following steps: (1) Cut the Chinese toon into 20mm×20mm×2.5mm wood chips along the natural growth direction, soak them in deionized water for 6 hours, and then rinse them with a large amount of deionized water to remove floating dust and water-soluble impurities on the surface of the wood chips. Then, vacuum dry the wood at 65℃ for 24 hours to obtain the pretreated wood.

[0078] (2) Prepare a 0.2 mol / L sodium acetate solution and adjust its pH to 4.8 using acetic acid to obtain an acetate-sodium acetate buffer solution. Add the prepared buffer solution, hemicellulase, and pretreated wood (i.e., dried Toona sinensis wood chips, with a hemicellulase to Toona sinensis wood chip mass ratio of 1:5 and a buffer solution to hemicellulase mass ratio of 1000:5, wherein the hemicellulase is 0.1 g and the Toona sinensis wood chips are completely immersed in the buffer solution) to a conical flask. Seal the flask with plastic wrap and incubate it at 45°C for 24 h. Then rinse the Toona sinensis wood chips with a large amount of deionized water to remove residual enzyme and buffer solution, obtaining enzyme-treated wood (i.e., enzymatically hydrolyzed wood).

[0079] (3) The enzymatically hydrolyzed wood was soaked in a 0.1 mol / L urea solution, then placed in a hydrothermal reactor and hydrothermally reacted at 85°C for 7 h, followed by vacuum drying at 65°C for 24 h to obtain nitrogen-doped enzymatically hydrolyzed wood. The nitrogen-doped enzymatically hydrolyzed wood was soaked in a 0.12 mol / L KMnO4 solution for 1.5 h, then vacuum dried at 65°C for 24 h, and placed in a tube furnace under a nitrogen atmosphere. The temperature was increased to 500°C at a rate of 5°C / min and held for 2 h for pre-carbonization, followed by increasing the temperature to 800°C at a rate of 3°C / min and holding for 2 h for carbonization. After removal, residual KMnO4 was washed away with a large amount of deionized water, and the wood was vacuum dried at 65°C for 24 h to obtain nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material.

[0080] Example 7 A method for preparing a nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material, comprising the following steps: (1) Cut the elm wood into 15mm×15mm×1mm wood chips along the natural growth direction, immerse them in deionized water for 6 hours, and then rinse them with a large amount of deionized water to remove floating dust and water-soluble impurities on the surface of the wood chips. Then, vacuum dry the wood at 60℃ for 24 hours to obtain the pretreated wood.

[0081] (2) Prepare a 0.22 mol / L sodium acetate solution and adjust its pH to 5.2 using acetic acid to obtain an acetate-sodium acetate buffer solution. Add the prepared buffer solution, hemicellulase, and pretreated wood (i.e., dried elm chips, with a hemicellulase to elm chip mass ratio of 1:7 and a buffer solution to hemicellulase mass ratio of 1000:3.5, wherein the hemicellulase is 0.1 g and the elm chips are completely immersed in the buffer solution) to a conical flask. Seal the flask with plastic wrap and incubate it at 45°C for 24 h. Then rinse the elm chips with plenty of deionized water to remove residual enzyme and buffer solution, obtaining enzyme-treated wood (i.e., enzymatically hydrolyzed wood).

[0082] (3) The enzymatically hydrolyzed wood was soaked in a 0.1 mol / L urea solution, then placed in a hydrothermal reactor and hydrothermally reacted at 95°C for 6 h, followed by vacuum drying at 60°C for 24 h to obtain nitrogen-doped enzymatically hydrolyzed wood. The nitrogen-doped enzymatically hydrolyzed wood was soaked in a 0.1 mol / L KMnO4 solution for 1.5 h, then vacuum dried at 60°C for 24 h, and placed in a tube furnace under a nitrogen atmosphere. The temperature was increased to 500°C at a rate of 5°C / min and held for 2 h for pre-carbonization, followed by increasing the temperature to 800°C at a rate of 3°C / min and holding for 2 h for carbonization. After removal, residual KMnO4 was washed away with a large amount of deionized water, and the wood was vacuum dried at 60°C for 24 h to obtain nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material.

[0083] Example 8 A method for preparing a nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material, comprising the following steps: (1) Cut cypress wood into 30mm×30mm×1.5mm wood chips along the natural growth direction, immerse them in deionized water for 6 hours, and then rinse them with a large amount of deionized water to remove floating dust and water-soluble impurities from the surface of the wood chips. Then, vacuum dry the wood at 60℃ for 24 hours to obtain pretreated wood.

[0084] (2) Prepare a 0.25 mol / L sodium acetate solution and adjust its pH to 4.6 using acetic acid to obtain an acetate-sodium acetate buffer solution. Add the prepared buffer solution, laccase, and pretreated wood (i.e., dried cypress wood chips, with a laccase to cypress wood chip mass ratio of 1:10 and a buffer solution to laccase mass ratio of 1000:5, wherein the laccase content is 0.1 g and the cypress wood chips are completely immersed in the buffer solution) to a conical flask. Seal the flask with plastic wrap and incubate it at 55°C for 24 h. Then rinse the cypress wood chips with a large amount of deionized water to remove residual enzymes and buffer solution, obtaining enzyme-treated wood (i.e., enzymatically hydrolyzed wood).

[0085] (3) The enzymatically hydrolyzed wood was soaked in a 0.4 mol / L urea solution, then placed in a hydrothermal reactor and hydrothermally reacted at 100℃ for 5 h, and then vacuum dried at 60℃ for 24 h to obtain nitrogen-doped enzymatically hydrolyzed wood. The nitrogen-doped enzymatically hydrolyzed wood was soaked in a 0.15 mol / L KMnO4 solution for 1 h, then vacuum dried at 60℃ for 24 h, and then placed in a tube furnace and pre-carbonized at 420℃ for 2.5 h under a nitrogen atmosphere at a heating rate of 3℃ / min, and then carbonized at 850℃ for 2 h at a heating rate of 5℃ / min. After removal, residual KMnO4 was washed away with a large amount of deionized water, and then vacuum dried at 60℃ for 24 h to obtain nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material.

[0086] Example 9 Same as Example 1, except that in step (3), the urea solution is replaced with a melamine solution of equal molar concentration.

[0087] Comparative Example 1 This comparative example is a blank control of Example 1. In step (2), cellulase is not added to the buffer solution. In step (3), both the urea solution and the potassium permanganate solution are replaced with deionized water. The other conditions are the same as in Example 1.

[0088] Comparative Example 2 Same as Example 1, except that in step (2), cellulase is replaced with pectinase.

[0089] Comparative Example 3 Same as Example 1, except that cellulase is not added to the buffer solution in step (2).

[0090] Comparative Example 4 Same as Example 1, except that in step (3), potassium permanganate solution is replaced with deionized water.

[0091] Comparative Example 5 Same as Example 1, except that in step (3), the urea solution is replaced with deionized water.

[0092] Comparative Example 6 Same as Example 1, except that in step (3), both the urea solution and the potassium permanganate solution are replaced with deionized water.

[0093] Comparative Example 7 Same as Example 1, except that in step (3), the potassium permanganate solution is replaced with an equimolar concentration of cobalt acetate solution.

[0094] Comparative Example 8 Same as Example 1, except that in step (3), the potassium permanganate solution is replaced with zinc acetate solution of equal molar concentration.

[0095] Comparative Example 9 Same as Example 1, except that in step (3), no pre-carbonization is performed during the carbonization process, and the temperature is directly raised to 800°C at a heating rate of 5°C / min and held for 2 hours for carbonization.

[0096] Test Example 1 Characterization data: Figure 1 The images shown are: scanning electron microscope (SEM) images of untreated paulownia wood in Example 1 ((a)-(b)), SEM images of enzymatically hydrolyzed wood ((c)-(d)), SEM images of the final nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material ((e)-(h)), and elemental mapping diagrams of the final nitrogen-, manganese-, and oxygen-containing enzymatically hydrolyzed wood-derived carbon electrode material ((i)-(l)).

[0097] Figure 2 The images show physical photos of the carbon electrode materials prepared in Example 1 (left) and Comparative Example 9 (right).

[0098] from Figure 1 The scanning electron microscope images show that untreated paulownia wood has a loose structure, large pore size, and thin and smooth tracheid walls, making it lighter than most woods, but this also results in a lower specific surface area. Figure 1 (a)-(b)). Paulownia wood treated with cellulase ( Figure 1Compared to untreated paulownia wood, (c)-(d) of the treated paulownia wood become coarser, with slight collapse of the pore structure and partial stacking within the pores. The crisscrossing pore collapse and broken fiber tissue intertwine to form a complex three-dimensional network, thereby greatly increasing the number of mesopores and micropores in the material, and thus increasing the specific surface area of ​​the material. Enzymatically hydrolyzed wood doped with nitrogen, oxygen, and manganese (…) Figure 1 (e)-(h)), the carbonized material retains the original three-dimensional porous structure of wood. During the carbonization process, manganese is uniformly loaded onto the tracheid cavities of the wood. From Figure 1 Element mapping graph in Figure 1 It can also be seen from (i)-(l) that manganese is uniformly loaded while carbon, oxygen and nitrogen are also present. Figure 2 The physical images of carbon electrodes illustrate the difference between pre-carbonization and direct carbonization. Pre-carbonization allows the carbon material to adapt uniformly and gradually to the high-temperature carbonization process, significantly reducing curvature changes during subsequent carbonization. In contrast, direct carbonization causes severe bending deformation of the carbon material, making it almost unusable as a self-supporting integrated electrode material.

[0099] Other characterization data are as follows: Figure 3 and Figure 4 XPS (N 1s) spectra of the carbon electrode materials prepared in Examples 1 and 2, respectively.

[0100] Figure 5 and Figure 6 XPS (Mn 2p) spectra of the carbon electrode materials prepared in Examples 1 and 2, respectively.

[0101] Figure 7 and Figure 8 XPS (O 1s) spectra of the carbon electrode materials prepared in Examples 1 and 2, respectively.

[0102] Figure 9 The XRD patterns are those of the carbon electrode materials prepared in Examples 1, 2, and 1.

[0103] Figure 10 The images show the Raman spectra of the carbon electrode materials prepared in Examples 1, 2, and 1 (Comparative Example 1).

[0104] XPS (N 1s) spectra revealed four nitrogen configurations in the doped nitrogen-containing functional groups: pyridine nitrogen (397.9 eV), pyrrole nitrogen (399.7 eV), graphitic nitrogen (401.8 eV), and nitrogen oxide (406.4 eV); XPS (Mn 2p) spectra clearly showed the presence of Mn, which could be fitted to a value at 642.1 eV (Mn 2p). 3 / 2 ) and 653.9 eV (Mn 2p1 / 2 The double peaks of Mn have a binding energy spacing of 11.8 eV, with a distinct satellite peak at 646 eV, a characteristic similar to that of Mn. 2+ The high species homogeneity indicates that Mn mainly exists in the form of MnO, suggesting that the manganese introduced by potassium permanganate is the basic oxide MnO, which is consistent with the XRD pattern (MnO, PDF#07-0230). The XPS (O 1s) spectrum shows that the doped oxygen-containing functional groups are 531.6 eV (C=O) and 533.7 eV (COC). The Raman spectrum at a Raman shift of 650 cm⁻¹... -1 The stretching vibrations of the Mn-O bonds further confirm the introduction of MnO. The introduction of a large number of nitrogen- and oxygen-containing functional groups significantly improves the wettability of the material, which is beneficial for promoting interfacial contact between the electrode and the electrolyte, reducing internal resistance, and avoiding bubbles or cavities formed due to poor contact, thereby increasing the effective reaction area, which is conducive to improving the electrochemical performance of the material.

[0105] In addition, the elemental contents of carbon (C), oxygen (O), nitrogen (N), and manganese (Mn) in the carbon electrode materials prepared in each embodiment are shown in Table 1. Table 1. Elemental content of carbonaceous electrode materials prepared in Examples 1-9

[0106] Test Example 2 Pore ​​structure and specific surface area Figure 11 and Figure 12 The images show the pore size distribution of the carbon electrode materials prepared in Examples 1 and 1, and Examples 2 and 1, respectively. It can be seen that the pore structure of Examples 1 and 2, especially the number of micropores (pore size less than 2 nm) and small mesopores (pore size of 2-5 nm), is significantly increased compared with Comparative Example 1. This indicates that enzymatic hydrolysis can greatly increase the number of micropores in the material, thereby increasing the specific surface area of ​​the material. At the same time, the loading of nitrogen, manganese and oxygen did not block the micropore structure generated by enzyme treatment. Figure 11 and Figure 12 The comparison also shows that laccase and cellulase exhibit similar pore-forming mechanisms, both generating a large number of micropores and small mesopores.

[0107] The specific surface areas of the carbon electrode materials prepared in each embodiment and comparative example are shown in Table 2.

[0108] Table 2. Specific surface area of ​​carbon electrode materials prepared in each embodiment and comparative example.

[0109] As shown in Table 2, the specific surface area of ​​the enzymatically hydrolyzed wood-derived carbon electrode material prepared in Example 1 was significantly increased compared with the untreated Comparative Example 1 (without enzyme treatment or nitrogen, manganese, and oxygen loading). This is attributed to the directional degradation of the wood structure by the enzyme and the synergistic effect of nitrogen, oxygen, and manganese loading, proving that this method can effectively increase the specific surface area of ​​the material.

[0110] Test Example 3 The supercapacitors assembled using the carbon electrode materials prepared in the various embodiments and comparative examples were subjected to electrochemical performance testing in a two-electrode system. The assembly steps of the supercapacitor were as follows: two identical carbon electrode materials were polished to a size of 10mm×10mm×1mm to serve as the positive and negative electrodes of the supercapacitor, and filter paper was used as the separator. 6M potassium hydroxide (KOH) solution or 1M anhydrous sodium sulfate (Na2SO4) solution was used as the electrolyte to obtain supercapacitors with different properties. The thickness of the entire supercapacitor device included the thickness of the two electrodes (2mm) and the thickness of the filter paper (0.02mm).

[0111] Figure 13 Cyclic voltammetry curves of an alkaline supercapacitor assembled using the carbon electrode material prepared in Example 1 (with 6M KOH as electrolyte).

[0112] Figure 14 The constant current charge-discharge diagram shows the alkaline supercapacitor assembled using the carbon electrode material prepared in Example 1 (with 6M KOH as electrolyte).

[0113] Figure 15 Cyclic voltammetry curves of a neutral supercapacitor assembled using the carbonaceous electrode material prepared in Example 1 (with 1M Na2SO4 as electrolyte).

[0114] Figure 16 The constant current charge-discharge diagram shows the neutral supercapacitor assembled using the carbon electrode material prepared in Example 1 (with 1M Na2SO4 as electrolyte).

[0115] Depend on Figure 13 and Figure 15 It can be seen that all cyclic voltammetric curves of the neutral supercapacitor exhibit a quasi-rectangular shape, demonstrating excellent double-layer capacitance behavior and ideal capacitance characteristics. At different scan rates, all curves are quasi-rectangular, and with increasing scan speed, the gradually shifting high interference impedance produces a larger integral area. In contrast, the alkaline electrolyte possesses extremely high ionic conductivity, primarily due to the OH-... - The high mobility of OH groups can significantly reduce ion transport resistance and improve the specific capacitance of materials. Additionally, the high mobility of OH groups in alkaline electrolytes can also significantly reduce ion transport resistance and improve the specific capacitance of materials. -It directly participates in the rapid redox reaction on the MnO surface, thus exhibiting polarization and distortion at high scan rates (50 mV / s). Figure 14 and Figure 16 It can be seen that the carbon electrode material prepared in Example 1 has a performance of 1 mA / cm² in 6M KOH electrolyte. 2 The areal capacitance at current density is 4.7269 mF / cm². 2 In 1M Na2SO4 electrolyte, 1 mA / cm 2 The areal capacitance at current density is 2.9031 F / cm². 2 In both systems, the constant current charge and discharge curves at different current densities exhibit approximately symmetrical shapes during the charging and discharging processes, demonstrating good charge and discharge reversibility.

[0116] In addition, the carbon electrode materials prepared in the various embodiments and comparative examples showed 1 mA / cm² in different electrolytes. 2 The areal capacitance at current density is shown in Table 3. In 6M KOH electrolyte, 1 mA / cm² 2 The energy density and power density at the current density are shown in Table 4. Compared with Comparative Examples 1-8, the specific capacitance and energy density of Example 1 were significantly improved. This is attributed to the cellulase treatment introducing abundant pores and exposing more oxygen-containing functional groups, increasing ion accessibility and active sites. Simultaneously, the high conductivity of the porous carbon framework, the improved wettability due to N doping, and the synergistic conductivity effect between MnO nanoparticles and the carbon matrix further enhanced the material's charge storage capacity. Examples treated with hemicellulase and laccase also exhibited similar performance. The performance differences between the examples are mainly attributed to the different pore structures and specific surface areas of different woods.

[0117] Table 3. Carbon electrode materials prepared in Examples 1-9 and Comparative Examples 1-8, 1 mA / cm² in different electrolytes. 2 Area ratio capacitance under current density

[0118] Table 4. Carbon electrode materials prepared in Examples 1-9 and Comparative Examples 1-8, with a 1 mA / cm² performance in 6M KOH electrolyte. 2 Energy density and power density at current density

[0119] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method of producing a nitrogen-manganese-oxygen-containing, lignin-derivative carbonaceous electrode material, characterized by, The method comprises the following steps: The wood is subjected to enzyme treatment to obtain enzymatic wood; the enzymatic wood is soaked in a urea solution or a melamine solution, subjected to hydrothermal reaction, dried to obtain nitrogen-doped enzymatic wood; the nitrogen-doped enzymatic wood is soaked in a potassium permanganate solution, dried, and then subjected to pre-carbonization and carbonization to obtain the nitrogen-manganese-oxygen-containing enzymatic wood-derived carbonaceous electrode material.

2. The method of producing a nitrogenous mn-oxygenated, lignin- derived carbonaceous electrode material according to claim 1, wherein, The enzyme treatment step comprises adding enzymes and pretreated wood in an acetic acid-sodium acetate buffer solution, and culturing at 45-55℃ for 20-30h.

3. The method of producing a nitrogenous mn-oxygenated, lignin- derived carbonaceous electrode material as claimed in claim 2, wherein, The enzymes comprise cellulase, hemicellulase or laccase.

4. The method of producing a nitrogenous mn-oxygenated, lignin- derived carbonaceous electrode material as claimed in claim 2, wherein, The mass ratio of the enzymes to the pretreated wood is 1:5-10; The acetic acid-sodium acetate buffer solution is prepared by adjusting the pH value of a sodium acetate solution to 4.5-5.5 using acetic acid.

5. The method of producing a nitrogenous mn-oxygenated, lignin- derived carbonaceous electrode material as claimed in claim 1, wherein, The concentration of the urea solution is 0.1-0.5mol / L. Or, the concentration of the melamine solution is 0.1-0.5mol / L. The hydrothermal reaction is performed at a temperature of 85-105℃ for 4-8h.

6. The method of producing a nitrogenous mn-oxygenated, lignin- derived carbonaceous electrode material according to claim 1, wherein, The concentration of the potassium permanganate solution is 0.05-0.15mol / L, and the soaking time in the potassium permanganate solution is 1-3h.

7. The method of producing a nitrogenous mn-oxygenated, lignin- derived carbonaceous electrode material as claimed in claim 1, wherein, The pre-carbonization is performed at a temperature of 400-600℃ for 1.5-3h. And / or, the carbonization is performed at a temperature of 750-850℃ for 1.5-2.5h.

8. The method of producing a nitrogenous mn-oxygenated, lignin- derived carbonaceous electrode material as claimed in claim 2, wherein, The pretreatment comprises cutting, cleaning and drying the wood.

9. A nitrogen-manganese-oxygen-containing enzymatic wood-derived carbonaceous electrode material prepared by the preparation method according to any one of claims 1-8.

10. Use of the nitrogen-manganese-oxygen-containing enzymatic wood-derived carbonaceous electrode material according to claim 9 in the preparation of supercapacitors.

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