N,S co-doped hierarchical porous carbon electrode material and method for manufacturing it, and its use in supercapacitor manufacturing.

Abstract

To provide N,S co-doped hierarchical porous carbon electrode material and a method for producing it. [Solution] In this invention, wheat bran, potassium bicarbonate, thiourea, and water are uniformly mixed at room temperature, dried, and then carbonized under a nitrogen atmosphere by a one-step thermal decomposition method to obtain a black product. The black product is pulverized, mixed with dilute acid, washed with water until neutral, and dried to obtain an N,S co-doped hierarchical porous carbon electrode material. In this invention, potassium bicarbonate is used as a chemical activator, making the operation simple and environmentally friendly. Compared to the strong corrosiveness of potassium hydroxide, potassium bicarbonate is relatively mild and increases the specific surface area of ​​the material. At the same time, thiourea, as a heteroatom source, increases the doping amount and active sites of heteroatoms, optimizing the electronic structure of the material. When applied to supercapacitor electrode material testing, the N,S co-doped hierarchical porous carbon electrode material exhibits high pseudocapacitance performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon-based functional materials, and particularly relates to an N, S co-doped hierarchical porous carbon electrode material and a manufacturing method thereof.

Background Art

[0002] Supercapacitors have attracted wide attention as efficient energy storage devices due to their high charge-discharge rate, long cycle life, and high power density. Carbon-based materials are suitable as supercapacitor electrode materials because of their excellent chemical stability, high specific surface area, and good conductivity. Although conventional carbon-based electrode materials such as activated carbon and carbon nanotubes have a high specific surface area, there is room for improvement in their pseudocapacitance performance.

[0003] Pseudocapacitance can significantly improve the energy density of supercapacitors through redox reactions on the surface of electrode materials. Therefore, the development of carbon-based electrode materials with high pseudocapacitance performance has become the focus of research. Improving the electronic structure of carbon materials and increasing active sites through heteroatom doping is an effective means to improve pseudocapacitance performance.

[0004] However, existing doping methods are complex in operation, have a small doping amount, result in a low specific surface area of the obtained carbon materials, and inferior specific capacitance. Therefore, there is an urgent need to develop carbon electrode materials with a simple manufacturing process, environmentally friendly, low cost, and having a high specific surface area and a multi-layer pore structure.

Summary of the Invention

Problems to be Solved by the Invention

[0005] To solve the above technical problems, the present invention proposes an N, S co-doped hierarchical porous carbon electrode material and a manufacturing method thereof. The N, S co-doped hierarchical porous carbon electrode material of the present invention has a high specific surface area and a multi-layer pore structure, a simple manufacturing process, is environmentally friendly, and has a low cost.

Means for Solving the Problems

[0006] To achieve the above objective, the present invention provides the following technical scheme.

[0007] One of the technical schemes of the present invention: A method for producing an N,S co-doped hierarchical porous carbon electrode material, comprising producing the N,S co-doped hierarchical porous carbon electrode material by activation with potassium bicarbonate and heteroatom doping, wherein the heteroatoms are sulfur and nitrogen.

[0008] Furthermore, the method for producing the N,S co-doped hierarchical porous carbon electrode material includes the following steps: Bran, potassium bicarbonate, and thiourea are mixed and stirred uniformly, then water is added and stirred again, allowed to stand and then dried, and the resulting product after calcination is immersed in an acid solution, washed with water until neutral, and then dried to obtain the N,S co-doped hierarchical porous carbon electrode material.

[0009] Bran is lightweight and commonly used as animal feed. Carbon materials derived from bran have a relatively low specific surface area, which is unfavorable for use as supercapacitor electrode materials. This is because the size of the specific surface area directly affects the electrochemical performance (including capacitance performance) of the electrode material. Furthermore, the pore size distribution of carbon materials derived from bran may not be suitable for use as electrode materials. This is because ideal supercapacitor electrode materials have a stepped pore structure, where pores of different sizes communicate with each other to improve ion transport and capacitance performance. When carbon materials derived from bran are used as supercapacitor electrode materials, the low charge-discharge efficiency and severe self-discharge phenomenon may limit their performance in actual applications. Carbon materials derived from bran may be prone to aggregation, which affects the effective contact surface area of ​​the electrode material and, further, the efficiency of the supercapacitor. In addition, the high ash content of bran makes it unsuitable for the manufacture of carbon electrode materials. However, in this invention, potassium bicarbonate is used as an activator, and macropores are formed by the expansion of gas generated by high-temperature decomposition, while the decomposition products react with carbon in the bran to etch, obtaining micropores and mesopores. Therefore, bran biochar produced with potassium bicarbonate as an activator has a hierarchical porous structure of macropores, mesopores, and micropores, and the abundance of these types and the complex spatial distribution of the pore structure significantly improve the specific surface area of ​​the bran biochar. Furthermore, since potassium bicarbonate is weakly alkaline and the reaction is relatively mild, the etching rate can be slowed during the activation process, improving the ratio of micropores to mesopores and the uniformity of pore size, which also provides favorable conditions for increasing the specific surface area of ​​the bran biochar. In addition, activation with potassium bicarbonate can enrich the types of surface functional groups of bran biochar, and these functional groups can provide favorable conditions for improving the pseudocapacitance performance of the carbon material. By using thiourea as a heteroatom source, the amount of heteroatom doping and active sites are increased, optimizing the electronic structure of the material. When applied to supercapacitor electrode material testing, N,S co-doped hierarchical porous carbon materials exhibit high pseudocapacitance performance.

[0010] The mass ratio of the aforementioned wheat bran, potassium bicarbonate, and thiourea is 2:1:1.

[0011] The process also includes a pretreatment step of washing and drying the bran before mixing it with potassium bicarbonate and thiourea.

[0012] The pretreatment steps for washing and drying the bran are as follows: After washing the bran with deionized water, it is transferred to the second washing basket of an ultrasonic cleaner and subjected to ultrasonic cleaning, and then dried in an oven at a drying temperature of 80°C for a drying time of 12 hours.

[0013] The ultrasonic cleaning machine includes a cleaning tank, an ultrasonic generator installed below the cleaning tank, a transducer installed next to the ultrasonic generator, a drain hole installed at the bottom of the cleaning tank, a first cleaning basket installed inside the cleaning tank, the vertical height of which is set to be less than the vertical depth of the cleaning tank, grab bars installed above the opposing side edges of the upper end of the first cleaning basket, parallel to the corresponding side edges, the grab bars installed outside the cleaning tank, movable and removable slide bars installed on the opposing sides of the grab bars, a removable second cleaning basket mounted on the movable and removable slide bars, the vertical height of the second cleaning basket is set to be less than the vertical depth of the first cleaning basket, the mesh size of the second cleaning basket is much smaller than the mesh size of the first cleaning basket, the second cleaning basket includes two layers, the first layer being a fine mesh cleaning layer, and a removable solid collection basket (i.e., second layer) installed below the cleaning layer.

[0014] After mixing bran, potassium bicarbonate, and thiourea, the stirring time is 30 minutes; and / or After adding water, the stirring time is 1 hour; and / or The aforementioned standing time is 12 hours.

[0015] The aforementioned firing process involves first firing at a low temperature, and then firing at a high temperature. The low temperature is 400°C and the holding time is 1 hour, while the high temperature is 800°C and the holding time is 2 hours.

[0016] The concentration of the acid solution is 1.0 mol / L. Immersion in the acid solution effectively removes ash and inorganic impurities from the carbon material, improving the purity and surface condition of the porous carbon electrode material, thereby improving its structural properties and thus enhancing its performance.

[0017] For example, the method for producing the N,S co-doped hierarchical porous carbon electrode material is as follows: (1) After washing the bran with deionized water, it was transferred to the second washing basket of an ultrasonic cleaner and subjected to ultrasonic cleaning, and then dried in an oven at a drying temperature of 80°C for 12 hours. (2) Weigh 6 g of wheat bran, 3 g of potassium bicarbonate, and 3 g of thiourea after the above treatment, and mix them uniformly for 30 minutes. (3) Add 100 mL of deionized water and stir thoroughly at room temperature for 1 hour. (4) The mixture after stirring was left to stand at room temperature for 12 hours, then dried in an oven at a drying temperature of 80°C for 12 hours. (5) The dried material is placed in an alumina magnetic boat, the alumina magnetic boat is placed in a high-temperature tube furnace, nitrogen is introduced as a protective gas, the nitrogen flow rate is 120 sccm, and the heating rate is 5°C / min. After holding at a low temperature (400°C) for 1 hour, the temperature is raised to a high temperature (800°C) at the same rate and held for 2 hours to obtain a black, lumpy solid product. (6) The black, lumpy solid product is placed in a mortar and ground into a powder, sieved through a 100-mesh screen mesh, stirred in a hydrochloric acid solution with a concentration of 1.0 mol / L, washed with deionized water until neutral, and dried in an oven at a drying temperature of 80°C for 14 hours to obtain an N,S co-doped hierarchical porous carbon electrode material.

[0018] The second technical scheme of the present invention: The present invention also provides an N,S co-doped hierarchical porous carbon electrode material manufactured according to the above method.

[0019] The N,S co-doped hierarchical porous carbon electrode material manufactured according to the present invention has a multi-layer pore structure distribution. The micropores provide a rich electrode / electrolyte interface and contribute to ultra-high capacity. The mesopores provide a rich ion transport pathway to improve the accessibility of the micropores, shorten the transport pathway, and the macropores optimize the wettability of the interface. As a storage layer for the electrolyte, they effectively reduce the ion transport resistance. These three cooperate with each other to optimize the ion transport and storage efficiency. Therefore, the N,S co-doped hierarchical porous carbon electrode material manufactured according to the present invention has high pseudocapacitance.

[0020] The third technical scheme of the present invention: The present invention also provides an application of the N,S co-doped hierarchical porous carbon electrode material in the manufacture of supercapacitors.

[0021] The fourth technical scheme of the present invention: The present invention also provides a supercapacitor, which includes the above N,S co-doped hierarchical porous carbon electrode material.

Advantages of the Invention

[0022] Compared with the prior art, the present invention has the following advantages and technical effects.

[0023] (1) The source of the raw material bran used in the present invention is wide, the price is low, the manufacturing process is simple, the cost is low, it is environmentally friendly, and it meets the requirements of sustainable development. Also, for this raw material, a convenient device for washing bran is proposed. This device can be adopted for washing substances with low density, small mass, small particle size, easy to precipitate, and clogging drainage holes, such as bran.

[0024] (2) In the present invention, the ratio of bran, potassium bicarbonate, and thiourea is 6:3:3. This ratio enables N,S co-doping, increases the amount of heteroatom doping and active sites, and contributes to optimizing the electronic structure of the material. When applied to supercapacitor electrode material testing, the N,S co-doped hierarchical porous carbon material exhibits high pseudocapacitance performance.

[0025] (3) The present invention employs a method of first firing at a low temperature and then firing at a high temperature. Low-temperature firing helps to preserve the initial pore structure of the material, while high-temperature firing helps to further open and enlarge the pore size, forming a hierarchical porous structure favorable for ion transport. Furthermore, by employing a one-step pyrolysis method, the activation, pore formation, and heteroatom doping processes are combined into one, resulting in a simple process, an efficient method, and significant savings in manufacturing time.

[0026] (4) The present invention uses potassium bicarbonate as an activator, and the expansion of the gas generated by high-temperature decomposition forms macropores, while the decomposition products react with carbon in the bran to etch, obtaining micropores and mesopores, thereby forming a hierarchical porous structure having macropores, mesopores, and micropores. This structure significantly increases the specific surface area of ​​the bran biochar and has superior electrochemical performance compared to the conventional technology.

[0027] (5) The N,S co-doped hierarchical porous carbon electrode material with high pseudocapacitivity manufactured according to the present invention exhibits a high specific capacitance of 307.3 F / g at a current density of 0.5 A / g and maintains a specific capacitance of 216 F / g even at a current density of 15 A / g, demonstrating excellent magnification performance. [Brief explanation of the drawing]

[0028] The drawings, which constitute part of the present invention, are provided for further understanding of the invention, and the exemplary embodiments and their descriptions are for illustrative purposes only and do not unduly limit the invention. In the drawings: [Figure 1]This is a structural diagram of an ultrasonic cleaning machine, showing 1-grab bar, 2-first cleaning basket, 3-slide bar, 4-second cleaning basket, 5-drain hole, and 6-function control panel. [Figure 2] This is a scanning electron microscope image of the N,S co-doped hierarchical porous carbon electrode material manufactured in Example 1. [Figure 3] This is an elemental scan diagram of the N,S co-doped hierarchical porous carbon electrode material manufactured in Example 1. [Figure 4] This is a diagram of the nitrogen adsorption and desorption curve for the N,S co-doped hierarchical porous carbon electrode material manufactured in Example 1. [Figure 5] This is a pore size distribution spectrum diagram of the N,S co-doped hierarchical porous carbon electrode material manufactured in Example 1. [Figure 6] This is the constant current charge-discharge curve for a three-electrode system of the N,S co-doped hierarchical porous carbon electrode material manufactured in Example 1. [Figure 7] This is the cyclic voltammetry curve for a three-electrode system of the N,S co-doped hierarchical porous carbon electrode material manufactured in Example 1. [Figure 8] This is an electrochemical impedance spectrum diagram of a three-electrode system of the N,S co-doped hierarchical porous carbon electrode material manufactured in Example 1. [Modes for carrying out the invention]

[0029] Various exemplary embodiments of the present invention will be described in detail, but this detailed description should not be construed as limiting the invention, but rather as a more detailed description of specific aspects, characteristics, and examples of the invention.

[0030] It should be understood that the terms used in this invention are for the purpose of describing specific embodiments and are not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that any intermediate values ​​between the upper and lower limits of the range are also specifically disclosed. Any value or intermediate value within the stated range, as well as smaller ranges between other stated values ​​or intermediate values ​​within such ranges, are also included in this invention. The upper and lower limits of these smaller ranges may or may not be included in the range.

[0031] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as that generally understood by an ordinary person skilled in the art to which this invention pertains. While this invention describes only preferred methods and materials, any similar or equivalent methods and materials may be used in the implementation or testing of this invention. All references made herein are incorporated by reference to disclose and explain methods and / or materials related to those references. In the event of any conflict between incorporated references and the content of this specification, the content of this specification shall prevail.

[0032] Numerous modifications and variations can be made to the specific embodiments of the specification without departing from the scope or spirit of the present invention, which will be apparent to those skilled in the art. Other embodiments derived from the specification of the present invention will also be apparent to those skilled in the art. The specification and embodiments of the present invention are merely illustrative.

[0033] As used herein, "includes," "contains," "possesses," and "contains" are all non-restrictive expressions, meaning "includes but not limited to these." .

[0034] Unless otherwise specified, the room temperature in this invention is assumed to be 25±2℃.

[0035] All raw materials used in the examples and comparative examples of this invention were obtained through commercial purchase.

[0036] A schematic diagram of the ultrasonic cleaning machine used in an embodiment of the present invention is shown in Figure 1 (1-grab bar, 2-first cleaning basket, 3-slide bar, 4-second cleaning basket, 5-drain hole, 6-function control panel), and includes a cleaning tank, an ultrasonic generator installed below the cleaning tank, a transducer installed next to the ultrasonic generator, a drain hole 5 installed at the bottom of the cleaning tank, a first cleaning basket 2 installed inside the cleaning tank, the vertical height of the first cleaning basket 2 set to be less than the vertical depth of the cleaning tank, grab bars 1 installed above the opposing side edges of the upper end of the first cleaning basket 2 parallel to the corresponding side edges, the grab bars 1 are located outside the cleaning tank, and between the grab bars 1 on both sides Two movable, removable slide bars 3 are installed parallel to each other, and a removable second cleaning basket 4 is attached to the movable, removable slide bars 3. The vertical height of the second cleaning basket 4 is set to be smaller than the vertical depth of the first cleaning basket 2, and the mesh size of the second cleaning basket 4 is much smaller than the mesh size of the first cleaning basket 2 (for example, the mesh size of the second cleaning basket 4 is 100 mesh, and the mesh size of the first cleaning basket 2 is 1 cm x 1 cm mesh). The second cleaning basket 4 has two layers, the first layer being a fine mesh cleaning layer (100 mesh), and a removable solid collection basket (i.e., the second layer) is installed below the cleaning layer. When cleaning substances that have low density, low mass, small particle size, and tend to settle and clog drain holes, such as wheat bran, the second cleaning basket 4 of this ultrasonic cleaner (the mesh size of the second cleaning basket 4 is 100 mesh) can be used.

[0037] In some embodiments of the present invention, a method for producing N,S co-doped hierarchical porous carbon electrode materials is provided: Bran, potassium bicarbonate, and thiourea are mixed and stirred uniformly, then water is added and stirred again, allowed to stand and dry, and the calcined product is immersed in an acid solution, washed with water until neutral, and then dried to obtain an N,S co-doped hierarchical porous carbon electrode material.

[0038] In this invention, wheat bran, potassium bicarbonate, thiourea, and water are uniformly mixed at room temperature, dried, and then carbonized under a nitrogen atmosphere by a one-step thermal decomposition method to obtain a black product. The black product is pulverized, mixed with dilute acid, washed with water until neutral, and dried to obtain an N,S co-doped hierarchical porous carbon electrode material. In this invention, potassium bicarbonate is used as a chemical activator, making the operation simple and environmentally friendly. Compared to the strong corrosiveness of potassium hydroxide, potassium bicarbonate is relatively mild and increases the specific surface area of ​​the material. At the same time, thiourea, as a heteroatom source, increases the doping amount and active sites of heteroatoms, optimizing the electronic structure of the material. When applied to supercapacitor electrode material testing, the N,S co-doped hierarchical porous carbon electrode material exhibits high pseudocapacitance performance.

[0039] In some embodiments of the present invention, the mass ratio of wheat bran, potassium bicarbonate, and thiourea is 2:1:1.

[0040] Some embodiments of the present invention also include a pretreatment step of washing and drying the bran before mixing it with potassium bicarbonate and thiourea.

[0041] In some embodiments of the present invention, the pretreatment steps for washing and drying the bran are as follows: After washing the bran with deionized water, it is transferred to the second washing basket 4 of an ultrasonic cleaner and subjected to ultrasonic cleaning, and then dried in an oven at a drying temperature of 80°C for a drying time of 12 hours.

[0042] In some embodiments of the present invention, after mixing bran, potassium bicarbonate, and thiourea, the stirring time is 30 minutes; and / or After adding water, the stirring time is 1 hour; and / or The standing time was 12 hours.

[0043] In some embodiments of the present invention, the drying temperature after standing is 80°C and the drying time is 12 hours.

[0044] In some embodiments of the present invention, the drying temperature after rinsing with water until neutral is 80°C and the drying time is 12 to 16 hours.

[0045] In some embodiments of the present invention, the firing process involves first firing at a low temperature, and then firing at a high temperature.

[0046] The low temperature is 400°C with a holding time of 1 hour, and the high temperature is 800°C with a holding time of 2 hours and a heating rate of 5°C / min. Nitrogen is used as a protective gas during firing. Low-temperature firing helps remove moisture from the material and provides initial heat treatment, while high-temperature firing promotes crystallization and phase change of the material. Low-temperature firing can result in smaller particle sizes and contribute to uniform morphogenesis. High-temperature firing can cause particle fusion and aggregation, affecting the specific surface area and pore structure of the material.

[0047] In some embodiments of the present invention, the nitrogen flow rate is 120 to 150 sccm.

[0048] In some embodiments of the present invention, the concentration of the acid solution is 1.0 mol / L. While the present invention does not limit the type of acid, the following embodiments of the present invention will be explained using a hydrochloric acid solution with a concentration of 1.0 mol / L.

[0049] Furthermore, all aspects not described in detail in this invention are conventional means in the art and are not the focus of this invention.

[0050] The technical scheme of the present invention will be further explained by the following examples.

[0051] Example 1

[0052] Method for producing N,S co-doped hierarchical porous carbon electrode material: (1) After washing the bran with deionized water, it is transferred to the second washing basket 4 of an ultrasonic cleaner and subjected to ultrasonic cleaning, and then dried in an oven at a drying temperature of 80°C for 12 hours. (2) Weigh 6 g of wheat bran, 3 g of potassium bicarbonate, and 3 g of thiourea after the above treatment, and mix them uniformly for 30 minutes. (3) Add 100 mL of deionized water and stir thoroughly at room temperature for 1 hour. (4) The mixture after stirring was left to stand at room temperature for 12 hours, then dried in an oven at a drying temperature of 80°C for 12 hours. (5) The dried material is placed in an alumina magnetic boat, the alumina magnetic boat is placed in a high-temperature tube furnace, nitrogen is introduced as a protective gas, the nitrogen flow rate is 120 sccm, and the heating rate is 5°C / min. After holding at a low temperature (400°C) for 1 hour, the temperature is raised to a high temperature (800°C) at the same rate and held for 2 hours to obtain a black, lumpy solid product. (6) The black, lumpy solid product is placed in a mortar and ground into a powder, sieved through a 100-mesh screen mesh, stirred in a hydrochloric acid solution with a concentration of 1.0 mol / L, washed with deionized water until neutral, and dried in an oven at a drying temperature of 80°C for 14 hours to obtain an N,S co-doped hierarchical porous carbon electrode material.

[0053] The morphology and performance of the N,S co-doped hierarchical porous carbon electrode material manufactured in this embodiment were measured.

[0054] Figure 2 shows scanning electron microscope images of the N,S co-doped hierarchical porous carbon electrode material fabricated in this embodiment. The obtained N,S co-doped hierarchical porous carbon electrode material has a multilayer pore structure distribution. Micropores provide abundant electrode / electrolyte interfaces, contributing to ultra-high capacity; mesopores provide abundant ion transport channels, improving the reach of micropores and shortening the transport path; and macropores optimize interface wettability, acting as an electrolyte storage layer and effectively reducing ion transport resistance. It can be seen that these three elements work together to optimize ion transport and storage efficiency.

[0055] Figure 3 is an elemental scan of the N,S co-doped hierarchical porous carbon electrode material produced in this embodiment. It shows that the obtained N,S co-doped hierarchical porous carbon electrode material contains all three elements, C, N, and S, indicating that nitrogen and sulfur elements were successfully doped into the carbon material.

[0056] Figure 4 shows the nitrogen adsorption / desorption curve of the N,S co-doped hierarchical porous carbon electrode material manufactured in this embodiment. The resulting adsorption curve of the N,S co-doped hierarchical porous carbon electrode material is a typical I / IV type adsorption curve, and its specific surface area is 1209.14 m². 2 It can be seen that it is / g.

[0057] Figure 5 shows the pore size distribution spectrum calculated by the DJH method for the N,S co-doped hierarchical porous carbon electrode material. The obtained pore size distribution of the N,S co-doped hierarchical porous carbon electrode material shows a clear hierarchy and uniform distribution, indicating that the N,S co-doped hierarchical porous carbon electrode material has excellent electrochemical performance.

[0058] Figure 6 shows the constant current charge-discharge curve of a three-electrode system (using an Hg / HgO salt bridge as the reference electrode, a platinum plate electrode as the counter electrode, and an electrode plate made from the carbon material produced in this embodiment as the working electrode) of the N,S co-doped hierarchical porous carbon electrode material manufactured in this embodiment. Using 6M KOH as the electrolyte, it exhibits a high specific capacity of 307.3F / g at a current density of 0.5A / g, and maintains a specific capacity of 216F / g even at a current density of 15A / g, demonstrating excellent magnification performance.

[0059] Figure 7 shows the cyclic voltammetry curves of a three-electrode system of N,S co-doped hierarchical porous carbon electrode material fabricated in this embodiment. The results show that the curves at different scan speeds are all close to rectangular, exhibiting the characteristics of typical electrical double-layer capacitance.

[0060] Figure 8 shows the electrochemical impedance spectrum of a three-electrode system of N,S co-doped hierarchical porous carbon electrode material manufactured in this embodiment. The results show an open-circuit voltage of -0.05V and a frequency of 0.01~10 5 In the case of Hz, fitting revealed that the resulting N,S co-doped hierarchical porous carbon electrode material has a charge transfer resistance (Rct) of 1.23 Ω and an ohmic resistance (Rs) of 0.25 Ω, indicating that this material possesses excellent conductivity and low interfacial resistance.

[0061] Comparative Example 1

[0062] Method for producing N,S co-doped hierarchical porous carbon electrode material: (1) After washing the bran with deionized water, it is transferred to the second washing basket 4 of an ultrasonic cleaner and subjected to ultrasonic cleaning, and then dried in an oven at a drying temperature of 80°C for 12 hours. (2) Weigh 6 g of wheat bran, 6 g of potassium bicarbonate, and 3 g of thiourea after the above treatment, and mix them uniformly for 30 minutes. (3) Add 100 mL of deionized water and stir thoroughly at room temperature for 1 hour. (4) The mixture after stirring was left to stand at room temperature for 12 hours, then dried in an oven at a drying temperature of 80°C for 12 hours. (5) The dried material is placed in an alumina magnetic boat, the alumina magnetic boat is placed in a high-temperature tube furnace, nitrogen is introduced as a protective gas, the nitrogen flow rate is 120 sccm, and the heating rate is 5°C / min. After holding at a low temperature (400°C) for 1 hour, the temperature is raised to a high temperature (800°C) at the same rate and held for 2 hours to obtain a black, lumpy solid product. (6) The black, lumpy solid product is placed in a mortar and ground into a powder, sieved through a 100-mesh screen mesh, stirred in a hydrochloric acid solution with a concentration of 1.0 mol / L, washed with deionized water until neutral, and dried in an oven at a drying temperature of 80°C for 14 hours to obtain an N,S co-doped hierarchical porous carbon electrode material.

[0063] The N,S co-doped hierarchical porous carbon electrode material produced in this comparative example showed a specific capacity up to 204.35 F / g at a current density of 0.5 A / g when using 6 M KOH as the electrolyte in a three-electrode system.

[0064] This comparative example was compared to Example 1 by changing the dosage of the activator. The test results showed that the specific capacity of this comparative example was significantly lower than that of Example 1 at a current density of 0.5 A / g. This is because excessive activator can cause excessive activation, destroying some of the structure of the carbon material, affecting the specific surface area and pore structure, and consequently impacting the electrochemical performance. In the example, a specific ratio of dope to activator may have resulted in the formation of a more favorable pore structure, such as an appropriate distribution of micropores and mesopores, which contributes to an improvement in specific capacity. On the other hand, in this comparative example, increasing the ratio of activator may lead to changes in the pore structure, which is unfavorable for the adsorption and transport of electrolyte ions, and consequently may affect the capacity performance.

[0065] Comparative Example 2

[0066] Method for producing N,S co-doped hierarchical porous carbon electrode material: (1) After washing the bran with deionized water, it is transferred to the second washing basket 4 of an ultrasonic cleaner and subjected to ultrasonic cleaning, and then dried in an oven at a drying temperature of 80°C for 12 hours. (2) Weigh 6g of wheat bran, 6g of potassium bicarbonate, and 6g of thiourea after the above treatment, and mix them uniformly for 30 minutes. (3) Add 100 mL of deionized water and stir thoroughly at room temperature for 1 hour. (4) The mixture after stirring was left to stand at room temperature for 12 hours, then dried in an oven at a drying temperature of 80°C for 12 hours. (5) The dried material is placed in an alumina magnetic boat, the alumina magnetic boat is placed in a high-temperature tube furnace, nitrogen is introduced as a protective gas, the nitrogen flow rate is 120 sccm, and the heating rate is 5°C / min. After holding at a low temperature (400°C) for 1 hour, the temperature is raised to a high temperature (800°C) at the same rate and held for 2 hours to obtain a black, lumpy solid product. (6) The black, lumpy solid product is placed in a mortar and ground into a powder, sieved through a 100-mesh screen mesh, stirred in a hydrochloric acid solution with a concentration of 1.0 mol / L, washed with deionized water until neutral, and dried in an oven at a drying temperature of 80°C for 14 hours to obtain an N,S co-doped hierarchical porous carbon electrode material.

[0067] The N,S co-doped hierarchical porous carbon electrode material produced in this comparative example showed a specific capacity of 171.25 F / g at a current density of 0.5 A / g when using 6 M KOH as the electrolyte in a three-electrode system.

[0068] Test results showed that this comparative example exhibited significantly lower specific capacity compared to Example 1 under a current density of 0.5 A / g. Appropriate doping increases the number of active sites and improves pseudocapacitance performance, while inappropriate ratios can degrade material performance. Increasing the doses of potassium bicarbonate and thiourea affects doping uniformity and the pore structure of the material. Furthermore, excessive sulfur content can cause distortion and fracture of the graphite structure of carbon materials, potentially reducing conductivity. The specific raw material ratios in the examples may help in forming a more uniform N,S co-doped structure. On the other hand, increasing the ratio of potassium bicarbonate and thiourea in these examples may affect doping uniformity and, consequently, electrochemical performance.

[0069] Comparative Example 3

[0070] Method for producing N,S co-doped hierarchical porous carbon electrode material: (1) After washing the bran with deionized water, it is transferred to the second washing basket 4 of an ultrasonic cleaner and subjected to ultrasonic cleaning, and then dried in an oven at a drying temperature of 80°C for 12 hours. (2) Weigh 6 g of wheat bran, 3 g of potassium bicarbonate, and 3 g of thiourea after the above treatment, and mix them uniformly for 30 minutes. (3) Add 100 mL of deionized water and stir thoroughly at room temperature for 1 hour. (4) The mixture after stirring was left to stand at room temperature for 12 hours, then dried in an oven at a drying temperature of 80°C for 12 hours. (5) The dried material is placed in an alumina magnetic boat, the alumina magnetic boat is placed in a high-temperature tube furnace, nitrogen is introduced as a protective gas, the nitrogen flow rate is 120 sccm, the heating rate is 5°C / min, the temperature is raised to a high temperature (800°C), and held for 2 hours to obtain a black, lumpy solid product. (6) The black, lumpy solid product is placed in a mortar and ground into a powder, sieved through a 100-mesh screen mesh, stirred in a hydrochloric acid solution with a concentration of 1.0 mol / L, washed with deionized water until neutral, and dried in an oven at a drying temperature of 80°C for 14 hours to obtain an N,S co-doped hierarchical porous carbon electrode material.

[0071] The N,S co-doped hierarchical porous carbon electrode material produced in this comparative example showed a specific capacity of 227.7 F / g at a current density of 0.5 A / g using 6 M KOH as the electrolyte in a trielectrode system. The test results showed that this example had a significantly lower specific capacity than Example 1 at a current density of 0.5 A / g. This may be because the step of firing at a low temperature (400°C) for 1 hour in Comparative Example 3 was omitted, and the material was directly heated to a high temperature (800°C) and held for 2 hours. Low-temperature firing helps to remove volatile components and some impurities from the raw material in the initial stages, while simultaneously avoiding excessive sintering that can occur at high temperatures and maintaining the pore structure of the material. The absence of this step may result in insufficient optimization of the pore structure of the material, potentially affecting its electrochemical performance. Furthermore, low-temperature firing helps to maintain the initial pore structure of the material, while high-temperature firing further promotes graphitization of the material, improving its conductivity and structural stability. The lack of a low-temperature firing process may result in insufficient development of pore structure and specific surface area, potentially affecting the adsorption and transport of electrolyte ions.

[0072] The above are merely preferred specific embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that a person skilled in the art can easily conceive of within the scope of the art disclosed by the present invention should be included within the scope of protection of the present invention. Accordingly, the scope of protection of the present invention should be the same as the scope of protection of the claims.

Claims

1. A N,S co-doped hierarchical porous carbon electrode material is produced by activation of potassium bicarbonate and heteroatom doping, wherein the heteroatoms are sulfur and nitrogen. The process includes mixing wheat bran, potassium bicarbonate, and thiourea, stirring uniformly, adding water and stirring again, letting it stand and then drying, immersing the resulting product in an acid solution, washing it with water until neutral, and then drying it to obtain the N,S co-doped hierarchical porous carbon electrode material. The mass ratio of the aforementioned bran, potassium bicarbonate, and thiourea is 2:1:

1. The aforementioned firing process involves first firing at a low temperature, and then firing at a high temperature. A method for producing an N,S co-doped hierarchical porous carbon electrode material, characterized in that the low temperature is 400°C and the holding time is 1 hour, and the high temperature is 800°C and the holding time is 2 hours.

2. A method for producing an N,S co-doped hierarchical porous carbon electrode material according to claim 1, characterized in that it also includes a pretreatment step of washing and drying the bran before mixing the bran, potassium bicarbonate, and thiourea.

3. After mixing bran, potassium bicarbonate, and thiourea, the stirring time is 30 minutes; and / or After adding water, the stirring time is 1 hour; and / or A method for producing an N,S co-doped hierarchical porous carbon electrode material according to claim 1, characterized in that the aforementioned standing time is 12 hours.

4. A method for producing an N,S co-doped hierarchical porous carbon electrode material according to claim 1, characterized in that the concentration of the acid solution is 1.0 mol / L.

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