A method for preparing nitrogen-containing graphene using chitosan as a raw material and a nitrogen-containing graphene device.

Abstract

This invention relates to the field of nitrogen-containing graphene technology, and in particular to a method for preparing nitrogen-containing graphene using chitosan as a raw material, comprising the following steps: dissolving chitosan in a 3%-5% acetic acid solution to form a mixed solution; uniformly coating the mixed solution onto the surface of a quartz substrate using spin coating technology; and slowly heating the substrate coated with the mixed solution to 200-350°C under a nitrogen protective atmosphere. 0 C. Annealing for 2 hours yields a chitosan film; subsequently, a two-step carbonization process is performed to obtain a pre-carbonized product; the pre-carbonized product is then mixed uniformly with agglomerating agent, followed by a two-step activation treatment. After activation, the product undergoes post-processing to obtain a nitrogen-containing graphene product. The nitrogen-containing graphene prepared by this invention has a D / G ratio of 0.87, a 2D / G ratio of 0.71, few defects, and a good layered crystal structure. The dielectric constant of the nitrogen-containing graphene devices subsequently fabricated is only 3.53.

Description

[0001] This invention claims priority to the earlier application, application number 202510078318.X, filed on March 28, 2025. Technical Field

[0002] This invention relates to the field of nitrogen-containing graphene technology, and in particular to a method for preparing nitrogen-containing graphene using chitosan as a raw material, and a nitrogen-containing graphene device. Background Technology

[0003] Graphene, a two-dimensional material composed of a single layer of tightly woven carbon atoms, has shone brightly in various fields such as electrode materials and electronic component manufacturing due to its excellent electrical and thermal conductivity, high light transmittance, and superior specific surface area. Compared to its pure form, nitrogen-containing graphene, through the ingenious doping of nitrogen, not only modulates the band gap of graphene and achieves precise control of its electrical properties, but also greatly enriches its surface active sites. These sites act like miniature factories for catalysts, accelerating the chemical reaction process and significantly improving the catalytic efficiency of graphene. In the commercial preparation pathways of graphene, chemical vapor deposition (CVD) and the Hummers method occupy important positions.

[0004] When preparing graphene using the CVD method, carbon-containing precursors are typically decomposed at high temperatures on the surface of a metal substrate (such as copper, nickel, or platinum) to generate a graphene film. This method is known for its high repeatability and adaptability to industrial production, but it still faces challenges such as high cost, long processing time, the need for single-use metal substrates, and the vulnerability of the film during transfer.

[0005] On the other hand, the Hummers process cleverly utilizes the oxidation system of concentrated sulfuric acid and potassium permanganate, supplemented by aniline as a nitrogen source, to modify graphite, which is then reduced to obtain nitrogen-containing graphene. However, the graphene produced by this method has slightly insufficient crystallinity, and the residual oxygen functional groups may have a subtle impact on its electrical conductivity.

[0006] It is worth noting that both methods mentioned above have environmental impacts to varying degrees. The metal substrate consumption and unsustainability of the CVD method, and the large-scale acidic wastewater discharge of the Hummers process, both pose potential threats to the environment and indirectly increase production costs. Therefore, exploring and implementing green and environmentally friendly production processes is crucial to reducing the production costs of nitrogen-containing graphene and promoting the sustainable development of the industry. Thus, deepening the exploration of green and environmentally friendly production processes is essential to leading the nitrogen-containing graphene industry towards a brighter future. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing nitrogen-containing graphene using chitosan as a raw material, comprising the following steps: Step 1: Dissolve chitosan in a 3%-5% acetic acid solution to form a mixed solution. Then, use spin coating technology to uniformly coat the mixed solution onto the surface of a quartz substrate. Subsequently, under nitrogen protection, slowly heat the substrate coated with the mixed solution to 200-350°C. The material is then annealed at this temperature for 2-3 hours to promote the initial curing of chitosan. The conformational relaxation of the polymer fibers during the annealing process is beneficial to the formation of the graphene layer in the subsequent carbonization step. This conformational relaxation is even more effective in the uniform coating. After the temperature naturally drops to room temperature, the chitosan film with nanoscale size and sub-nanometer roughness is gently scraped off from the substrate. Step 2: The chitosan film obtained in Step 1 is placed in a nitrogen atmosphere again for two-step carbonization. After carbonization, it is naturally cooled to room temperature to obtain the pre-carbonized product. Step 3: Mix the pre-carbonized product obtained in Step 2 with the agglomerating agent at a mass ratio of 1:1 or 2:1. Then, perform a two-step activation treatment. After activation, wait for the system to cool to room temperature, perform post-processing on the product, and dry it to obtain nitrogen-containing graphene product.

[0008] Preferably, in step two, the two-step carbonization process is as follows: first, the temperature is raised to 400-500 degrees Celsius. The temperature is maintained in the specified range for 1 to 2 hours for initial carbonization, after which the temperature is increased to 800°C. They are then kept at this high temperature for 1 to 2 hours to complete the deep carbonization process.

[0009] Preferably, in step three, the agglomeration regulator is one or more of KOH, Zn(NO3)2, and ZnSO4.

[0010] Preferably, in step three, the two-step activation process involves heating the mixture to 500-800°C under nitrogen protection. Keep warm for 1 to 2 hours, then continue to raise the temperature to a higher level of 900-1100 degrees Celsius. Within the specified range, keep warm for 0.5 to 1 hour.

[0011] Preferably, in step three, the specific post-processing steps are as follows: first, wash with deionized water until the solution is neutral to remove impurities; then, wash the sample three times with anhydrous ethanol; finally, place the sample at 60°C. The nitrogen-containing graphene product was obtained by drying it in an oven.

[0012] Preferably, in step one, the heating rate of the substrate coated with the mixed solution is 5. min.

[0013] Preferably, in steps two and three, the heating rate for preliminary carbonization and deep carbonization is 5. min, cooling rate is 10 min.

[0014] This application also provides a nitrogen-containing graphene prepared according to the above method.

[0015] The present invention also provides a nitrogen-containing graphene device comprising anhydrous polyvinyl alcohol organic sol and the above-mentioned nitrogen-containing graphene; the mass fraction of the anhydrous polyvinyl alcohol organic sol is 1.5%-10%, and the mass-volume ratio of the nitrogen-containing graphene to the anhydrous polyvinyl alcohol organic sol is 3g:8-12mL.

[0016] This application also provides a method for preparing the above-mentioned nitrogen-containing graphene device, including the following preparation steps: S1. Mix polyvinyl alcohol powder with an organic solvent at 90-150 °C. Stirring at a certain temperature yields anhydrous polyvinyl alcohol organic sol; S2. Anhydrous polyvinyl alcohol organic sol is mixed with nitrogen-containing graphene, ground, pressed into shape, heat-treated, and gold-plated to obtain nitrogen-containing graphene devices. The organic solvents mentioned in S1 include dimethyl sulfoxide or hydroxyl-containing organic solvents.

[0017] Preferably, the hydroxyl-containing organic solvent includes at least one of ethylene glycol and methanol.

[0018] Preferably, the specific process in S2 includes: placing nitrogen-containing graphene in an agate mortar, adding anhydrous polyvinyl alcohol organic sol prepared in S1, and grinding thoroughly to ensure uniform mixing to obtain a slurry. The resulting slurry is transferred to a mold and pressed to obtain a sheet-like preform. The sheet-like preform is then heated at 230-250°C. After heat treatment at a certain temperature for 1-2 hours to remove residual solvent, a nitrogen-containing graphene sheet with structural strength can be formed. Subsequently, the surface of the nitrogen-containing graphene sheet is gold-plated to impart electrical or functional interface properties, thereby forming the final nitrogen-containing graphene device.

[0019] The present invention has the following beneficial effects: This invention provides a method for preparing nitrogen-containing graphene using chitosan as a raw material, comprising the following steps: Step 1, dissolving chitosan in a 3%-5% acetic acid solution to form a mixed solution, then uniformly coating the mixed solution onto the surface of a quartz substrate using spin coating technology; subsequently, under a nitrogen protective environment, slowly heating the substrate coated with the mixed solution to 200-350°C. The chitosan film with nanoscale size and sub-nanometer roughness is gently scraped off the substrate after annealing at this temperature for 2-3 hours and allowing it to cool naturally to room temperature. Step 2: The chitosan film obtained in Step 1 is placed in a nitrogen atmosphere again for two-step carbonization. After carbonization, it is naturally cooled to room temperature to obtain a pre-carbonized product. Step 3: The pre-carbonized product obtained in Step 2 is mixed with agglomerating agent at a mass ratio of 1:1 or 2:1. Then, a two-step activation treatment is performed. After activation, the system is cooled to room temperature, and the product is post-treated and dried to obtain a nitrogen-containing graphene product.

[0020] This invention innovatively proposes a green and efficient method for preparing large-area, high-quality, single-layer to multi-layer nitrogen-doped graphene on a wide range of material surfaces, including but not limited to glass, silicon, and quartz. This method is not only low-cost but also adheres to safety and environmental protection principles throughout the entire process, completely eliminating harmful substances such as catalysts and concentrated sulfuric acid required in traditional processes, while also effectively avoiding the use of environmentally burdensome metals such as nickel and copper.

[0021] This invention uses chitosan as the nitrogen source, eliminating the need for additional nitrogen sources and providing low-cost, readily available raw materials. Subsequently, through a two-step carbonization and two-step activation process, uniform nitrogen doping is achieved in the graphene structure, enriching the active sites on the graphene surface. This process retains the original excellent properties of graphene while endowing it with new electrical and catalytic characteristics. It not only simplifies the preparation process and improves production efficiency but also significantly reduces negative environmental impacts, achieving efficient resource recycling.

[0022] This invention uses a 3%-5% acetic acid solution as a solvent, which can protonate the amino groups on the chitosan chains, converting them into positively charged -NH3 groups. + These positively charged amino groups repel each other, disrupting the strong hydrogen bond network between chitosan molecules, thus allowing the chitosan molecular chains to disperse and extend, forming a uniform and stable mixed solution. This ensures the formation of films with uniform thickness, smooth surfaces, and nanoscale dimensions and sub-nanometer roughness during spin coating. This creates ideal conditions for the subsequent formation of graphene structures with fewer defects and higher crystallinity.

[0023] In step three of this invention, an agglomeration regulator is added to effectively inhibit graphene sheet stacking and improve dispersibility. Raman spectroscopy shows that the nitrogen-containing graphene obtained by the method of this invention has a high D... The G ratio is 0.87, 2D The G ratio of 0.71 indicates that the nitrogen-containing graphene prepared by this invention has few defects and a good layered crystal structure, laying the foundation for its subsequent application in nitrogen-containing graphene devices.

[0024] This invention also provides a nitrogen-containing graphene device, comprising anhydrous polyvinyl alcohol (PVA) organic sol and the aforementioned nitrogen-containing graphene; the mass fraction of the anhydrous PVA organic sol is 1.5%-10%, and the mass-volume ratio of nitrogen-containing graphene to anhydrous PVA organic sol is 3g:8-12mL. The nitrogen-containing graphene used in this invention has fewer defects and an ordered structure, reducing charge scattering and trapping within the material, thus lowering dielectric loss. The resulting device exhibits excellent dielectric properties, with a relative dielectric constant of 3.53. Simultaneously, anhydrous PVA organic sol with a mass fraction of 1.5%-10% is used as an organic binder, utilizing the volatility of PVA to avoid interference from the aqueous medium on dielectric properties. Furthermore, the high adhesiveness of PVA ensures tight bonding of the nitrogen-containing graphene sheets, forming a uniform conductive network. Ultimately, the nitrogen-containing graphene device not only possesses a certain mechanical strength but also avoids dielectric constant fluctuations caused by interlayer gaps, ensuring a stable dielectric constant. Stability of test values ​​(deviation < 0.05 across multiple tests).

[0025] The nitrogen-containing graphene devices provided by this invention have a low dielectric constant, which can significantly reduce parasitic capacitance between interconnects in microelectronics and integrated circuits. This translates to faster processing speeds, lower power consumption, and less signal crosstalk. Furthermore, the low dielectric constant of these nitrogen-containing graphene devices makes them ideal for fabricating high-frequency radio frequency transistors, resonators, antennas, and other similar devices. These devices can operate at higher frequencies, with higher cutoff frequencies and maximum oscillation frequencies, while maintaining low power consumption. This is particularly relevant for future 5G applications. 6G communication, radar, and high-speed wireless data transmission systems are crucial.

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] Figure 1 This is the Raman spectrum of the nitrogen-containing graphene product obtained in Example 1; Figure 2 This is a SEM image of the nitrogen-containing graphene product obtained in Example 1; in, Figure 2 In this context, 'a' represents the magnification factor of 20. SEM image, Figure 2 In this context, 'b' represents the magnification factor of 5. SEM image; Figure 3 This is the Raman spectrum of the nitrogen-containing graphene product obtained in Example 2; Figure 4 This is the Raman spectrum of the nitrogen-containing graphene product obtained in Comparative Example 1; Figure 5This is the Raman spectrum of the nitrogen-containing graphene product obtained in Comparative Example 2; Figure 6 This is the Raman spectrum of the nitrogen-containing graphene product obtained in Comparative Example 3; Figure 7 This is a schematic diagram of the nitrogen-containing graphene device product obtained from Example 1; Figure 8 This is the capacitance test result from Application Example 1; Figure 9 This is the capacitance test result from Application Example 2; Figure 10 This is the capacitance test result of Application Example 3. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0029] Example 1 Step 1: Dissolve chitosan in a 5% acetic acid solution, ensuring complete dissolution. Then, evenly coat the solution onto a quartz or glass substrate using spin-coating technology. Subsequently, under a nitrogen-protected environment, spin-coated chitosan onto the substrate at a 5% concentration. Heating to 200 at a heating rate of min The mixture is then kept at this temperature for 2 hours to promote initial curing of the chitosan. Afterward, it is allowed to cool naturally to room temperature, and the chitosan film is peeled off from the substrate using an appropriate method for later use.

[0030] Step 2: Place an appropriate amount of the previously prepared chitosan film in a corundum ceramic boat, and then place it again in a tube furnace under a nitrogen atmosphere. (The process is repeated in the original text.) The heating rate of min raises the furnace temperature to 500. Hold at that temperature for 1 hour for initial carbonization. Then, continue heating at the same rate to 800°C. Hold at this temperature for 2 hours to complete the deep carbonization process. After carbonization, control the cooling rate to 10°C. The furnace temperature is maintained at 100°C until it drops to room temperature, at which point the pre-carbonized graphene product is obtained.

[0031] Step 3: To further improve the performance of the pre-carbonized product, weigh out the graphene pre-carbonized sample and twice the mass of KOH, grind and mix them thoroughly in a mortar, and then place the mixture in a corundum ceramic boat. Under nitrogen protection, place the mixture in a tube furnace at 5... Heating rate increased to 500 min Incubate for 1 hour for initial activation. Then continue with 5... The heating rate is increased to 1100 min. Keep warm for 30 minutes to achieve activation. After activation, control the cooling rate to 10°C. After a period of time, the sample is removed once it has cooled to room temperature.

[0032] The extracted samples underwent post-processing: First, they were repeatedly washed with deionized water until the solution was neutral to remove residual KOH and other impurities; then, the samples were washed three times with anhydrous ethanol for further purification. Finally, the cleaned samples were placed at 60°C. The graphene is dried in an oven to obtain the final nitrogen-containing graphene product.

[0033] Example 2 Step 1: Dissolve chitosan in a 5% acetic acid solution, ensuring complete dissolution. Then, evenly coat the solution onto a quartz or glass substrate using spin-coating technology. Subsequently, under a nitrogen-protected environment, spin-coated chitosan onto the substrate at a 5% concentration. Heating to 350 at a heating rate of min The mixture is then kept at this temperature for 3 hours to promote the initial curing of chitosan. Afterward, it is allowed to cool naturally to room temperature, and the chitosan film is peeled off from the substrate using an appropriate method for later use.

[0034] Step 2: Place an appropriate amount of the previously prepared chitosan film in a corundum ceramic boat, and then place it again in a tube furnace under a nitrogen atmosphere. (The process is repeated in the original text.) The heating rate of min raises the furnace temperature to 500. Hold at that temperature for 1 hour for initial carbonization. Then, continue heating at the same rate to 800°C. Hold at this temperature for 2 hours to complete the deep carbonization process. After carbonization, control the cooling rate to 10°C. The furnace temperature is maintained at 100°C until it drops to room temperature, at which point the pre-carbonized graphene product is obtained.

[0035] Step 3: Weigh out the pre-carbonized graphene sample and twice the mass of KOH, grind and mix thoroughly in a mortar, then place the mixture in a corundum ceramic boat. Under nitrogen protection, place the mixture in a tube furnace at 5... Heating rate increased to 500 min Incubate for 1 hour for initial activation. Then continue with 5... The heating rate is increased to 1100 min. Keep warm for 30 minutes to achieve activation. After activation, control the cooling rate to 10°C. After a period of time, the sample is removed once it has cooled to room temperature.

[0036] The extracted samples underwent post-processing: First, they were repeatedly washed with deionized water until the solution was neutral to remove residual KOH and other impurities; then, the samples were washed three times with anhydrous ethanol for further purification. Finally, the cleaned samples were placed at 60°C. The graphene is dried in an oven to obtain the final nitrogen-containing graphene product.

[0037] Comparative Example 1 Step 1: Dissolve chitosan in a 5% acetic acid solution, ensuring complete dissolution. Then, evenly coat the solution onto a quartz or glass substrate using spin-coating technology. Subsequently, under a nitrogen-protected environment, spin-coated chitosan onto the substrate at a 5% concentration. Heating to 200 at a heating rate of min The mixture is then kept at this temperature for 2 hours to promote initial curing of the chitosan. Afterward, it is allowed to cool naturally to room temperature, and the chitosan film is peeled off from the substrate using an appropriate method for later use.

[0038] Step 2: Place an appropriate amount of the previously prepared chitosan film in a corundum ceramic boat, and then place it again in a tube furnace under a nitrogen atmosphere. (The process is repeated in the original text.) The heating rate of min raises the furnace temperature to 500. Hold at that temperature for 1 hour for initial carbonization. Then, continue heating at the same rate to 800°C. Hold at this temperature for 2 hours to complete the deep carbonization process. After carbonization, control the cooling rate to 10°C. The furnace temperature is maintained at 100°C until it drops to room temperature, at which point the pre-carbonized graphene product is obtained.

[0039] Step 3: Weigh out the pre-carbonized graphene sample and an equal mass of KOH, grind and mix them thoroughly in a mortar, and then place the mixture in a corundum ceramic boat. Under nitrogen protection, place the mixture in a tube furnace at 5... Heating rate increased to 500 min Incubate for 1 hour for initial activation. Then continue with 5... The heating rate is increased to 1100 min. Keep warm for 30 minutes to achieve activation. After activation, control the cooling rate to 10°C. After a period of time, the sample is removed once it has cooled to room temperature.

[0040] The extracted samples underwent post-processing: First, they were repeatedly washed with deionized water until the solution was neutral to remove residual KOH and other impurities; then, the samples were washed three times with anhydrous ethanol for further purification. Finally, the cleaned samples were placed at 60°C. The graphene is dried in an oven to obtain the final nitrogen-containing graphene product.

[0041] Comparative Example 2 Step 1: Place an appropriate amount of chitosan in a corundum ceramic boat and place it again in a tube furnace under a nitrogen atmosphere. (The process is repeated in the original text.) The heating rate of min raises the furnace temperature to 500. Incubate at this temperature for 1 hour for initial carbonization. Then continue at 5... Heating rate increased to 800 min Hold at this temperature for 2 hours to complete the deep carbonization process. After carbonization, control the cooling rate to 10°C. The furnace temperature is maintained at 100°C until it drops to room temperature, at which point the pre-carbonized graphene product is obtained.

[0042] Step 2: Weigh out the pre-carbonized graphene sample and an equal mass of KOH, grind and mix them thoroughly in a mortar, and then place the mixture in a corundum ceramic boat. Under nitrogen protection, place the mixture in a tube furnace at 5... Heating rate increased to 500 min Incubate for 1 hour for initial activation. Then continue with 5... The heating rate is increased to 1100 min. Keep warm for 30 minutes to achieve activation. After activation, control the cooling rate to 10°C. After a period of time, the sample is removed once it has cooled to room temperature.

[0043] The extracted samples underwent post-processing: First, they were repeatedly washed with deionized water until the solution was neutral to remove residual KOH and other impurities; then, the samples were washed three times with anhydrous ethanol for further purification. Finally, the cleaned samples were placed at 60°C. The graphene is dried in an oven to obtain the final nitrogen-containing graphene product.

[0044] Comparative Example 3 Step 1: Dissolve chitosan in a 5% acetic acid solution, ensuring complete dissolution. Then, evenly coat the solution onto a quartz or glass substrate using spin-coating technology. Subsequently, under a nitrogen-protected environment, spin-coated chitosan onto the substrate at a 5% concentration. Heating to 200 at a heating rate of min The mixture is then kept at this temperature for 2 hours to promote initial curing of the chitosan. Afterward, it is allowed to cool naturally to room temperature, and the chitosan film is peeled off from the substrate using an appropriate method for later use.

[0045] Step 2: Place an appropriate amount of chitosan in a corundum ceramic boat and place it again in a tube furnace under a nitrogen atmosphere. (The process is repeated in the original text.) The heating rate of min raises the furnace temperature to 500. Incubate at this temperature for 1 hour for initial carbonization. Then continue at 5... Heating rate increased to 800 min Hold at this temperature for 2 hours to complete the deep carbonization process. After carbonization, control the cooling rate to 10°C. The furnace temperature is maintained at 100°C until it drops to room temperature, at which point the pre-carbonized graphene product is obtained.

[0046] Step 3: Weigh out the pre-carbonized graphene sample and equal masses of Zn(NO3)2 and KOH, grind and mix them thoroughly in a mortar, and then place the mixture in a corundum ceramic boat. Under nitrogen protection, place the mixture in a tube furnace at 5... Heating rate increased to 500 min Incubate for 1 hour for initial activation. Then continue with 5... The heating rate is increased to 1100 min. Keep warm for 30 minutes to achieve activation. After activation, control the cooling rate to 10°C. After a period of time, the sample is removed once it has cooled to room temperature.

[0047] The extracted samples underwent post-processing: First, they were repeatedly washed with deionized water until the solution was neutral to remove residual Zn(NO3)2 and other impurities; then, the samples were washed three times with anhydrous ethanol for further purification. Finally, the cleaned samples were placed at 60°C. The graphene is dried in an oven to obtain the final nitrogen-containing graphene product.

[0048] Characterization test Raman spectroscopy was performed on the nitrogen-containing graphene product obtained in Example 1, and its Raman spectrum is shown below. Figure 1 As shown.

[0049] The nitrogen-containing graphene product obtained in Example 1 was observed using SEM, and its SEM image is shown below. Figure 2 As shown.

[0050] from Figure 1 and Figure 2 It can be seen that the D of this sample The G ratio is 0.95. Meanwhile, the 2D peak is clearly visible and its relative height is the highest in the case study (2D). The G ratio is 0.49, which further confirms that the prepared nitrogen-containing graphene has a good crystal structure and high quality.

[0051] The nitrogen-containing graphene product obtained in Example 2 was subjected to Raman spectroscopy testing, and its Raman spectrum is shown below. Figure 3 As shown. From Figure 3 It can be seen that the D of this sample The G-ratio is 0.87. Meanwhile, 2D... The G ratio is 0.71, which is higher than that of the nitrogen-containing graphene product in Example 1 above. (2D) An increase in the G ratio is beneficial to improving the carrier mobility of the material, indicating that by changing the annealing temperature and annealing time in the pretreatment, the content and performance of the generated graphene can be increased.

[0052] The nitrogen-containing graphene product obtained in Comparative Example 1 was subjected to Raman spectroscopy testing, and its Raman spectrum is shown below. Figure 4 As shown. From Figure 4 It can be seen that the D of this sample The G ratio is 0.93. Meanwhile, the 2D peak is clearly visible (2D...). The G ratio is 0.39, which is higher than the nitrogen-containing graphene product in Example 1 above. 2D A relatively low G ratio indicates a small amount of KOH added, resulting in a relatively low amount of graphene and a low carrier mobility; conversely, a higher G ratio indicates a lower G ratio.

[0053] The nitrogen-containing graphene product obtained in Comparative Example 2 was subjected to Raman spectroscopy testing, and its Raman spectrum is shown below. Figure 5 As shown. From Figure 5 It can be seen that the D of this sample The G ratio is 0.94. Meanwhile, the 2D peak is clearly visible (2D...). The G ratio is 0.21). Compared with the nitrogen-containing graphene product in Comparative Example 1 above, 2D The relatively low G-ratio indicates that the graphene content of the pre-carbonized graphene sample prepared by uniformly coating chitosan onto a quartz or glass substrate using spin coating technology is relatively high; while the graphene content of the pre-carbonized graphene sample prepared by directly using chitosan is relatively low.

[0054] The nitrogen-containing graphene product obtained in Comparative Example 3 was subjected to Raman spectroscopy testing, and its Raman spectrum is shown below. Figure 6 As shown. From Figure 6 It can be seen that the D of this sample The G ratio is 0.95. Meanwhile, the 2D peak is clearly visible (2D...). The G ratio is 0.28). Compared with the nitrogen-containing graphene products in Comparative Examples 1 and 2 above, 2D The relatively low G ratio indicates that the addition of Zn(NO3)2 is not conducive to producing high graphene content; nitrate NO3 - It has a certain degree of expansion, which disrupts the structure of ordered graphene.

[0055] Application Example 1 The nitrogen-containing graphene product obtained in Example 1 was used to prepare a nitrogen-containing graphene device. The process included: S1. Mix polyvinyl alcohol powder with ethylene glycol at 115°C. Stirring at a certain temperature yields an anhydrous polyvinyl alcohol organic sol with a mass concentration of 3%. S2. Place 3g of nitrogen-containing graphene in an agate mortar, add 10mL of the anhydrous polyvinyl alcohol organic sol prepared in S1, and grind thoroughly to ensure uniform mixing, obtaining a slurry. Transfer the resulting slurry to a mold and press it to obtain a sheet-like preform. Heat the sheet-like preform at 250°C. After heat treatment for 2 hours to remove residual solvent, a nitrogen-containing graphene sheet with structural strength can be formed. Subsequently, the surface of the nitrogen-containing graphene sheet is gold-plated to impart electrical or functional interface properties, thereby forming the final nitrogen-containing graphene device.

[0056] A schematic diagram of the nitrogen-containing graphene device product obtained in this application example is shown below. Figure 7 As shown.

[0057] Application Example 2 The nitrogen-containing graphene product obtained in Example 2 was used to prepare a nitrogen-containing graphene device. The process included: S1. Mix polyvinyl alcohol powder with ethylene glycol at 115°C. Stirring at a certain temperature yields an anhydrous polyvinyl alcohol organic sol with a mass concentration of 3%. S2. Place 3g of nitrogen-containing graphene in an agate mortar, add 10mL of the anhydrous polyvinyl alcohol organic sol prepared in S1, and grind thoroughly to ensure uniform mixing, obtaining a slurry. Transfer the resulting uniform slurry to a mold and press it to obtain a sheet-like preform. Heat the sheet-like preform at 250°C. After heat treatment for 2 hours to remove residual solvent, a nitrogen-containing graphene sheet with structural strength can be formed. Subsequently, the surface of the nitrogen-containing graphene sheet is gold-plated to impart electrical or functional interface properties, thereby forming the final nitrogen-containing graphene device.

[0058] Application Example 3 The nitrogen-containing graphene product obtained in Comparative Example 2 was used to prepare a nitrogen-containing graphene device. The process included: S1. Mix polyvinyl alcohol powder with ethylene glycol at 135°C. Stirring at a certain temperature yields a 3% (w / w) polyvinyl alcohol solution. S2. Place 3g of nitrogen-containing graphene in an agate mortar, add 10mL of the polyvinyl alcohol solution prepared in S1, and grind thoroughly to ensure uniform mixing, obtaining a slurry. Transfer the resulting uniform slurry to a mold and press it to obtain a sheet-like preform. Heat the sheet-like preform at 250°C. After heat treatment for 2 hours to remove residual solvent, a nitrogen-containing graphene sheet with structural strength can be formed. Subsequently, the surface of the nitrogen-containing graphene sheet is gold-plated to impart electrical or functional interface properties, thereby forming the final nitrogen-containing graphene device.

[0059] Performance testing The capacitance of the nitrogen-containing graphene devices obtained in Application Examples 1, 2, and 3 was measured using an ion sputtering instrument, and the results are as follows: Figure 8 , Figure 9 and Figure 10 As shown, the corresponding dielectric constant is calculated using the dielectric constant formula: Dielectric constant ; Where C represents capacitance, d represents the vacuum dielectric constant, A represents the electrode plate area, and d represents the thickness of the graphene sample.

[0060] from Figure 8 , Figure 9 and Figure 10 It can be seen that the capacitance test results for Application Example 1, Application Example 2, and Application Example 3 are 1.40 respectively. 10 -11 F, 0.85 10 -11 F and 1.48 10 -11 F. Substituting into the above dielectric constant formula, we obtain the dielectric constant. The values ​​were 5.88, 3.57, and 6.22, respectively. It is evident that the nitrogen-containing graphene prepared in Example 2 exhibited the lowest dielectric constant when applied to graphene devices. Comparing the results of Application Example 2 and Application Example 3, it can be seen that the acetic acid dissolution and spin-coating processes optimized the morphology and microstructure of chitosan, resulting in a more ordered, denser carbon material with fewer defects during subsequent calcination and carbonization. Acetic acid dissolution breaks down the originally tightly packed molecular chains, forming a uniform and dispersed molecular chain solution in the solution. Simultaneously, the uniform film constructed through spin-coating ensures uniform internal heating during calcination. This pre-ordering provides an ideal template for subsequent carbonization, forming a more ordered sp... 2 Carbon lattice. And the thin film morphology has a huge specific surface area, which is conducive to the release of calcination gas products, thereby generating a more dense, continuous carbon network with fewer pores, which in turn makes the dielectric constant of nitrogen-containing graphene devices lower.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing nitrogen-containing graphene using chitosan as a raw material, characterized in that, Includes the following steps: Step 1: Dissolve chitosan in a 3%-5% acetic acid solution to form a mixed solution. Then, use spin coating technology to uniformly coat the mixed solution onto the surface of a quartz substrate. Subsequently, under nitrogen protection, slowly heat the substrate coated with the mixed solution to 350°C and anneal it at this temperature for 3 hours. After the temperature naturally drops to room temperature, gently scrape the chitosan film with nanoscale size and sub-nanometer roughness off the substrate. Step 2: The chitosan film obtained in Step 1 is placed in a nitrogen atmosphere again for two-step carbonization. After carbonization, it is naturally cooled to room temperature to obtain the pre-carbonized product. Step 3: Mix the pre-carbonized product obtained in Step 2 with the agglomerating agent at a mass ratio of 1:1 or 2:

1. Then, perform a two-step activation treatment. After activation, wait for the system to cool to room temperature, perform post-processing on the product, and dry it to obtain nitrogen-containing graphene product. In step three, the agglomeration regulator is one or more of KOH, Zn(NO3)2, and ZnSO4.

2. The method for preparing nitrogen-containing graphene using chitosan as a raw material according to claim 1, characterized in that, In step two, the two-step carbonization process is as follows: first, the temperature is raised to the range of 400-500℃ and maintained for 1 to 2 hours for preliminary carbonization. Then, the temperature is raised to 800℃ and maintained at this high temperature for 1 to 2 hours to complete the deep carbonization process.

3. The method for preparing nitrogen-containing graphene using chitosan as a raw material according to claim 1, characterized in that, In step three, the two-step activation process is as follows: under nitrogen protection, the mixture is heated to 500-800℃ and held for 1 to 2 hours. Then, the temperature is raised to a higher range of 900-1100℃ and held for 0.5 to 1 hour.

4. The method for preparing nitrogen-containing graphene using chitosan as a raw material according to claim 1, characterized in that, In step three, the specific post-processing steps are as follows: First, wash with deionized water until the solution is neutral to remove impurities; then, wash the sample three times with anhydrous ethanol; finally, dry the sample in an oven at 60°C to obtain nitrogen-containing graphene products.

5. The method for preparing nitrogen-containing graphene using chitosan as a raw material according to claim 1, characterized in that, In step one, the heating rate of the substrate coated with the mixed solution is 5℃ / min.

6. The method for preparing nitrogen-containing graphene using chitosan as a raw material according to claim 2, characterized in that, In step two, the heating rate for preliminary carbonization and deep carbonization is 5℃ / min, and the cooling rate is 10℃ / min.

7. The method for preparing nitrogen-containing graphene using chitosan as a raw material according to claim 1, characterized in that, In step three, the cooling rate is 10℃ / min.

8. The nitrogen-containing graphene obtained by the method for preparing nitrogen-containing graphene using chitosan as a raw material according to any one of claims 1-7.

9. A nitrogen-containing graphene device, characterized in that, It comprises anhydrous polyvinyl alcohol organic sol and the nitrogen-containing graphene as described in claim 8; The mass fraction of anhydrous polyvinyl alcohol organic sol is 1.5%-10%, and the mass-volume ratio of nitrogen-containing graphene to anhydrous polyvinyl alcohol organic sol is 3g:8-12mL.

10. The method for preparing a nitrogen-containing graphene device according to claim 9, characterized in that, The preparation steps include the following: S1. Mix polyvinyl alcohol powder with an organic solvent and stir at a temperature of 90-150℃ to obtain anhydrous polyvinyl alcohol organic sol. S2. Anhydrous polyvinyl alcohol organic sol is mixed with nitrogen-containing graphene, ground, pressed into shape, heat-treated, and gold-plated to obtain nitrogen-containing graphene devices. The organic solvents mentioned in S1 include dimethyl sulfoxide or hydroxyl-containing organic solvents.

Images