Preparation method for constructing nitrogen-sulfur co-doped carbon based on corn straw and application of nitrogen-sulfur co-doped carbon
The method of preparing nitrogen-sulfur co-doped carbon from corn stalks by Joule heating solves the problems of long preparation time and high energy consumption, and realizes the preparation of high-value-added carbon materials and high-performance carbon materials, which are suitable for zinc ion hybrid capacitors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-09
- Publication Date
- 2026-03-17
AI Technical Summary
Existing technologies for preparing carbon materials from corn stalks suffer from problems such as long preparation time, high energy consumption, and low added value utilization.
Using corn stalks as the carbon source, isophthalate as the activator and auxiliary carbon source, benzyl imidazole as the nitrogen source, and sodium persulfate as the sulfur source and auxiliary activator, nitrogen-sulfur co-doped carbon was prepared within seconds by the Joule heating method.
The preparation of efficient, green and environmentally friendly nitrogen-sulfur co-doped carbon materials has been achieved. These materials have high specific surface area and high energy density, making them suitable as cathode materials for zinc-ion hybrid capacitors.
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Figure CN121672525A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of carbon material preparation technology, specifically relating to a method for preparing nitrogen-sulfur co-doped carbon based on corn stalks and its application. Background Technology
[0002] In 2024, China's total straw production reached 737 million tons, of which approximately 300 million tons were corn straw. Corn straw mainly contains cellulose, hemicellulose, lignin, sugars, and proteins, and is primarily used as livestock feed, waste, industrial raw materials, and energy sources. Cellulose, a linear polydextrose, is the main carbohydrate component of corn straw and possesses high stability. Hemicellulose is another major component of plant cell walls, primarily composed of xylan, xylo-oligosaccharides, and lysine oligosaccharides. Lignin, a yellowish-brown precipitate in plant cell walls, is one of the most difficult organic compounds to degrade in plants. Current utilization methods have low added value, and finding ways to utilize it for higher added value remains a pressing issue. Researchers have used corn straw as a raw material to prepare carbon materials through carbonization and activation processes, and these materials are being applied to energy storage. For example, Nie et al. prepared nitrogen-doped hierarchical porous carbon using ZnCl2 as an activator and NH4Cl as a nitrogen source through hydrothermal and carbonization activation processes. As a supercapacitor electrode material, it achieved a specific capacitance of 321.5 F / g at a current density of 0.5 A / g (Journal of Energy Storage, 2021, 44, 103410). Although the above methods have achieved certain results in controlling the pore structure and surface properties of carbon materials, the preparation time is long and the energy consumption is high. Therefore, this invention uses corn stalks as a carbon source, isophthalate as an activator and auxiliary carbon source, benzoimidazole as a nitrogen source, and sodium persulfate as a sulfur source and auxiliary activator. Through Joule heating, carbon materials can be prepared within seconds. The short reaction time allows for the doping of more heteroatoms while ensuring the structural integrity of the prepared carbon material. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide a method for directly preparing nitrogen-sulfur co-doped carbon using corn stalks as a carbon source, isophthalate as an activator and auxiliary carbon source, benzylimidazole as a nitrogen source, and sodium persulfate as a sulfur source and auxiliary activator.
[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0005] A method for preparing nitrogen-sulfur co-doped carbon and its application, characterized by the following specific steps:
[0006] Pretreatment of S1 carbon source: First, wash and crush the corn stalks, pass them through a 500-mesh sieve, and then heat them to 500°C in a tube furnace at a heating rate of 5°C / min. Hold the temperature for 2 hours, cool to room temperature, stir in distilled water for 12 hours, and then filter and dry to obtain the carbon precursor.
[0007] Pretreatment of reactants S2: The carbon source obtained in step S1 is weighed with isophthalate, benzyl imidazole and sodium persulfate in a certain proportion, and then ground and mixed evenly.
[0008] Preparation of nitrogen-sulfur co-doped carbon (S3): The reactants obtained in step S2 were placed in a small magnetic boat, and then the magnetic boat was placed in the center of a Joule furnace. The air in the device was first evacuated, the voltage and current values were set, and the mixture was kept for 2 seconds before naturally cooling to room temperature. The resulting product was taken out, ground, washed with 1 mol / L hydrochloric acid solution, dried, ground, and sieved to obtain nitrogen-sulfur co-doped carbon.
[0009] Preferably, in step S2, the bicarbonate is one or a mixture of potassium isophthalate, sodium isophthalate, and lithium isophthalate.
[0010] Preferably, in step S2, the mass of the carbon source accounts for 3 / 14 to 3 / 20 of the total mass of the mixture of carbon source, isophthalate, benzylimidazole and sodium persulfate, and the mass ratio of carbon source to isophthalate is between 3 and 5.
[0011] Preferably, in step S2, the mass of the carbon source accounts for 3 / 14 to 3 / 20 of the total mass of the mixture of carbon source, isophthalate, benzylimidazole and sodium persulfate, and the mass ratio of carbon source to isophthalate is between 3 and 5.
[0012] Preferably, in step S2, the mass of the carbon source is 3g and the mass of the isophthalate is 12g.
[0013] Preferably, in step S3, the voltage is 40V and the current is 160-170A.
[0014] Invention concept:
[0015] This invention uses corn stalks as a carbon source, isophthalate as an activator and auxiliary carbon source, benzoimidazole as a nitrogen source, and sodium persulfate as a sulfur source and auxiliary activator. As the temperature rises, isophthalate decomposes to form a salt, which reacts with the corn stalks to activate and create pores. Simultaneously, sodium persulfate decomposes, activating and creating pores in the carbon matrix and replacing some carbon atoms, introducing sulfur atoms. Furthermore, nitrogen atoms from benzoimidazole are introduced into the carbon material through in-situ doping. The gas generated during decomposition also physically activates and creates pores in the carbon matrix, forming a hierarchical pore structure. Finally, after acid washing, filtration, and drying, nitrogen-sulfur co-doped carbon is obtained.
[0016] The beneficial effects obtained by this invention are as follows:
[0017] 1. Using corn stalks as a carbon source, the raw materials are cheap, readily available, and abundant. A simple carbonization and activation method is used to directly prepare nitrogen and sulfur co-doped carbon. The process is green and environmentally friendly, realizing the high added value utilization of biomass waste.
[0018] 2. Using inexpensive isophthalate as an activator avoids the corrosion of equipment during the use of strong alkaline activators, realizes an acid-free process in the post-treatment process, and reduces wastewater discharge;
[0019] 3. The prepared nitrogen-sulfur co-doped carbon material has a high specific surface area, reaching 1789.52 m². 2 / g;
[0020] 4. When the prepared nitrogen-oxygen co-doped hierarchical porous carbon is used as the positive electrode material of a zinc-ion hybrid capacitor, in a 1 mol / L Zn(CF3SO3)2 aqueous electrolyte, its capacity reaches 140 mAh / g and its energy density is as high as 246.67 Wh / kg at a current density of 0.1 A / g; at a current density of 20 A / g, its capacity reaches 86.67 mAh / g and its energy density is still as high as 131.73 Wh / kg, showing high specific capacitance and large energy density. Attached Figure Description
[0021] Figure 1 The nitrogen adsorption-desorption isotherms of nitrogen-sulfur co-doped carbon prepared in Examples 1, 2, and 3 of this invention are shown.
[0022] Figure 2 Field emission scanning electron microscope (FESEM) image of nitrogen-sulfur co-doped carbon prepared in Example 2 of this invention. Detailed Implementation
[0023] The following description of the embodiments will provide a more detailed explanation of the specific implementation of the present invention, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.
[0024] Example 1: Nitrogen-sulfur co-doped carbon NS-C 160 The specific preparation process is as follows:
[0025] Pretreatment of S1 carbon source: First, wash and crush the corn stalks, pass them through a 500-mesh sieve, and then heat them to 500°C in a tube furnace at a heating rate of 5°C / min. Hold the temperature for 2 hours, cool to room temperature, stir in distilled water for 12 hours, and then filter and dry to obtain the carbon precursor.
[0026] Pretreatment of reactants S2: Weigh 3g of the carbon source obtained in step S1, 12g of potassium isophthalate, 1g of benzimidazole, and 1g of sodium persulfate, grind and mix them evenly;
[0027] Preparation of nitrogen-sulfur co-doped carbon (S3): The reactants obtained in step S2 were placed in a small magnetic boat, and then the magnetic boat was placed in the center of a Joule furnace. The air in the device was first evacuated, and the voltage was set to 40V and the current to 160A. After maintaining this for 2 seconds, the device was allowed to cool naturally to room temperature. The resulting product was taken out, ground, washed with 1mol / L hydrochloric acid solution, dried, ground again, and sieved to obtain nitrogen-sulfur co-doped carbon.
[0028] The resulting nitrogen-oxygen co-doped hierarchical porous carbon was named NS-C. 160 XPS test results showed that its nitrogen and sulfur contents were 1.23% and 0.95%, respectively. NS-C 160 When used as the positive electrode material of zinc-ion hybrid capacitors, in a 1 mol / L Zn(CF3SO3)2 electrolyte, at a current density of 0.1 A / g, NS-C160 has a capacity of 95.68 mAh / g and an energy density of 162.66 Wh / kg; at a current density of 20 A / g, NS-C160 has a capacity of 52.36 mAh / g and an energy density of 79.59 Wh / kg.
[0029] Example 2: Nitrogen-sulfur co-doped carbon NS-C 165 The specific preparation process is as follows:
[0030] Pretreatment of S1 carbon source: First, wash and crush the corn stalks, pass them through a 500-mesh sieve, and then heat them to 500°C in a tube furnace at a heating rate of 5°C / min. Hold the temperature for 2 hours, cool to room temperature, stir in distilled water for 12 hours, and then filter and dry to obtain the carbon precursor.
[0031] Pretreatment of reactants S2: Weigh 3g of the carbon source obtained in step S1, 12g of potassium isophthalate, 1g of benzimidazole, and 1g of sodium persulfate, grind and mix them evenly;
[0032] Preparation of nitrogen-sulfur co-doped carbon (S3): The reactants obtained in step S2 were placed in a small magnetic boat. The magnetic boat was then placed in the center of a Joule furnace. The air inside the device was first evacuated. The voltage was set to 40V and the current to 165A. After maintaining this for 2 seconds, the device was allowed to cool naturally to room temperature. The resulting product was then removed, ground, washed with 1mol / L hydrochloric acid solution, dried, ground again, and sieved to obtain nitrogen-sulfur co-doped carbon.
[0033] The resulting nitrogen-oxygen co-doped hierarchical porous carbon was named NS-C. 165 XPS test results showed that its nitrogen and sulfur contents were 2.48% and 2.15%, respectively. NS-C 165When used as the positive electrode material of zinc-ion mixed capacitors, in a 1 mol / L Zn(CF3SO3)2 electrolyte, at a current density of 0.1 A / g, NS-C 165 The capacity reaches 140mAh / g, and the energy density is 246.67Wh / kg; at a current density of 20A / g, NS-C 165 It has a capacity of 86.67mAh / g and an energy density of 131.73Wh / kg.
[0034] Example 3: Nitrogen-sulfur co-doped carbon NS-C 170 The specific preparation process is as follows:
[0035] Pretreatment of S1 carbon source: First, wash and crush the corn stalks, pass them through a 500-mesh sieve, and then heat them to 500°C in a tube furnace at a heating rate of 5°C / min. Hold the temperature for 2 hours, cool to room temperature, stir in distilled water for 12 hours, and then filter and dry to obtain the carbon precursor.
[0036] Pretreatment of reactants S2: Weigh 3g of the carbon source obtained in step S1, 12g of potassium isophthalate, 1g of benzimidazole, and 1g of sodium persulfate, grind and mix them evenly;
[0037] Preparation of nitrogen-sulfur co-doped carbon (S3): The reactants obtained in step S2 were placed in a small magnetic boat. The magnetic boat was then placed in the center of a Joule furnace. The air inside the device was first evacuated. The voltage was set to 40V and the current to 170A. After maintaining this for 2 seconds, the device was allowed to cool naturally to room temperature. The resulting product was then removed, ground, washed with 1mol / L hydrochloric acid solution, dried, ground again, and sieved to obtain nitrogen-sulfur co-doped carbon.
[0038] The resulting nitrogen-sulfur co-doped carbon was named NS-C. 170 XPS test results showed that its nitrogen and sulfur contents were 2.11% and 1.92%, respectively. NS-C 170 When used as the positive electrode material of zinc-ion mixed capacitors, in a 1 mol / L Zn(CF3SO3)2 electrolyte, at a current density of 0.1 A / g, NS-C 170 The capacity reaches 115.24 mAh / g, and the energy density is 198.21 Wh / kg; at a current density of 20 A / g, NS-C 170 It has a capacity of 76.89mAh / g and an energy density of 117.64Wh / kg.
[0039] The nitrogen-sulfur co-doped carbons prepared in Examples 1-3 were used as test samples, and their pore structure parameters, elemental composition, and content were determined. The results are shown in Tables 1 and 2.
[0040] Table 1 Pore structure parameters of nitrogen-sulfur co-doped carbon
[0041]
[0042] From Table 1 and Figure 1 The results show that the specific surface area of the nitrogen-sulfur co-doped carbon prepared in this invention ranges from 1325.57 to 2061.99 m². 2 The total pore volume is between 0.89 and 1.36 cm³ / g. 3 Between 2061.99 m² / g, nitrogen-sulfur co-doped carbon materials contain abundant active sites and channels for electrolyte ion adsorption and storage, as well as graphitized structures for electron transport, resulting in a high specific surface area of 2061.99 m² / g. 2 / g.
[0043] Table 2. Elemental composition and content of nitrogen-sulfur co-doped carbon
[0044]
[0045] Table 2 combined with Figure 2 This invention directly prepares nitrogen-sulfur co-doped carbon for zinc ion hybrid capacitors using corn stalks as a carbon source, isophthalate as an activator and auxiliary carbon source, benzoimidazole as a nitrogen source, and sodium persulfate as a sulfur source and auxiliary activator. The preparation process is green and environmentally friendly, with an oxygen content as high as 23.43%, providing a large number of active sites for pseudocapacitive redox reactions of zinc ion adsorption. With the auxiliary activation effect of sodium persulfate, the carbon layer spacing is further expanded, promoting ion transport.
[0046] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention. Technologies not covered in this invention can be implemented using existing technologies.
Claims
1. A method for rapidly constructing nitrogen and sulfur co-doped carbon based on corn straw and its application, characterized in that, The specific steps are as follows: S1: Pretreatment of carbon source: firstly, corn stalks are washed, crushed, and passed through a 500-mesh sieve, then heated to 500℃ at a heating rate of 5℃ / min in a tube furnace, maintained for 2h, cooled to room temperature, stirred in distilled water for 12h, then filtered and dried to obtain a carbon precursor; S2: Pretreatment of reactants: the carbon source obtained in step S1 is weighed according to a certain proportion with isophthalic acid salt, benzimidazole, and sodium persulfate, ground and uniformly mixed; S3: Preparation of nitrogen-sulfur co-doped carbon: the reactants obtained in step S2 are placed in a small magnetic boat, then the magnetic boat is placed in the center of a joule heating furnace, the air in the device is removed by vacuumizing, the voltage and current values are set, maintained for 2s, then naturally cooled to room temperature, the obtained product is taken out and ground, washed with 1mol / L hydrochloric acid solution, dried, ground, and sieved to obtain nitrogen-sulfur co-doped carbon.
2. The method for preparing nitrogen and sulfur co-doped carbon based on corn stalks according to claim 1, characterized in that: The isophthalic acid salt is one of potassium isophthalate, sodium isophthalate, and lithium isophthalate, or a mixture of two thereof.
3. The method for preparing nitrogen and sulfur co-doped carbon based on corn stalks according to claim 1, characterized in that: The mass of the carbon source accounts for 3 / 14-3 / 20 of the total mass of the mixture of the carbon source, isophthalic acid salt, benzimidazole, and sodium persulfate, and the mass ratio of the carbon source to the isophthalic acid salt is 3-5.
4. The method for preparing nitrogen and sulfur co-doped carbon based on corn stalks according to claim 1, characterized in that: In step S2, the mass of the carbon source is 3g, and the mass of the isophthalic acid salt is 12g.
5. The method for preparing nitrogen and sulfur co-doped carbon based on corn stalks according to claim 1, characterized in that: In step S3, the voltage is 40V, and the current is 160-170A.
6. A zinc-ion hybrid capacitor characterized by, The nitrogen-sulfur co-doped carbon of claim 1 is used as a positive electrode.