Pyrrole type nitrogen-doped carbon gel and preparation method thereof

Abstract

The invention discloses pyrrole type nitrogen-doped carbon gel and a preparation method thereof, the nitrogen-doped carbon gel is formed by gathering and cross-linking carbon nanoparticles less than 100 nm, pyrrole type nitrogen in the nitrogen element of the carbon gel is dominant, the molar ratio of pyrrole type nitrogen in all nitrogen species of the carbon gel is higher than 70%, and the nitrogen-doped carbon gel is prepared from a sugar-containing substance and pyrrole through a hydrothermal reaction. The pyrrole type nitrogen-doped carbon gel shows high mechanical strength and high wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation technology, specifically relating to a pyrrole-type nitrogen-doped carbon gel and its preparation method. Background Technology

[0002] Despite the numerous excellent properties inherent in carbon materials, further performance enhancements are still needed in certain specific reactions or applications. In industrial catalysis, sensors, electrochemistry, adsorption materials, and separation and analysis materials, carbon materials require abundant pores and various surface chemical functional groups to provide functionality. Furthermore, the carbon powder needs to be shaped to achieve mechanical properties such as wear resistance and compressive strength, as well as electrical and thermal conductivity. Currently, the primary method involves activation treatment with caustic alkalis or phosphoric acid to form carbon powder with pores and surface chemical functional groups. This powder is then kneaded, extruded, and coated using binders and conductive media to form a bulk material. However, this method of first preparing the powder and then bonding it through physical processes or other media suffers from limitations in reliability and stability. To address this bottleneck, researchers first utilize polymers such as organic resins to form chemically cross-linked shaped carbon materials, followed by activation treatment to create pores and surface chemical functional groups. However, this method is extremely costly, limiting the application scenarios for high-strength shaped carbon materials.

[0003] Meanwhile, researchers often optimize the surface chemical properties of carbon materials through nitrogen doping, thereby enhancing their catalytic, adsorption, electrochemical, and mechanical properties. Based on the order of nitrogen source introduction during doping, the preparation methods of nitrogen-doped carbon materials are mainly divided into two categories: in-situ synthesis and post-treatment methods. The former uses nitrogen-rich materials as precursors, which are directly carbonized and then further activated to create pores. The latter first synthesizes a carbon material precursor, and then modifies the surface of the carbon precursor using a nitrogen-containing reagent. Currently, commonly used methods for preparing nitrogen-doped carbon materials mainly include template methods, chemical vapor deposition, pyrolysis carbonization, and hydrothermal carbonization, but these methods all have certain limitations.

[0004] Patent document CN103130206B discloses a method for preparing nitrogen-doped carbon materials. This method involves mixing a nitrogen source and a carbon source and reacting them under specific hydrothermal conditions to synthesize nitrogen-doped carbon materials in one step. However, the nitrogen-doped carbon materials prepared by this method are in the form of particulate powders, lacking sufficient compressive strength and wear resistance, and their nitrogen doping forms are graphitic nitrogen and pyridine nitrogen.

[0005] Patent document CN108262077A discloses a method for preparing a nitrogen-doped carbon monolithic catalytic material. This method uses nitrogen-containing organic matter and sugars as precursors, sequentially passing them through two high-temperature stages: pre-carbonization and carbonization (at temperatures of 450-1200℃), to prepare a nitrogen-doped carbon monolithic material with a hierarchical porous structure. However, the nitrogen species in this material are a mixture of pyrrole nitrogen, pyridine nitrogen, and graphitic nitrogen, with no dominant nitrogen species. The influence of various nitrogen species on the structure and properties of the carbon material is also not studied. Furthermore, this method requires thermal activation above 450℃ and does not mention a method for preparing the carbon gel.

[0006] In summary, existing nitrogen-doped carbon materials still have many shortcomings, such as the uniform morphology of the prepared nitrogen-doped carbon materials, small specific surface area, the need for subsequent molding processes, insufficient mechanical strength and wear resistance, complex preparation processes, high cost, and high energy consumption. Summary of the Invention

[0007] This invention unexpectedly discovered that introducing pyrrole into a hydrothermal reaction system containing sugars can generate carbon gels, and clarified its unique growth mechanism. This mechanism progresses from the formation of carbon quantum dots, to their aggregation and cross-linking into carbon nanoparticles, and then gradually develops into controllable gel assembly. Furthermore, a high proportion of pyrrole-type nitrogen doping can improve the chemical and mechanical properties of carbon materials. Pyrrole-type nitrogen, unlike basic pyridine-type nitrogen and inert graphitic nitrogen, exhibits excellent complexation ability for metal ions, reversible adsorption-desorption properties for adsorbed molecules, and good electrical conductivity due to its conjugated structure, showing significant advantages in applications such as industrial catalysis, sensors, electrochemistry, adsorption materials, and separation and analysis materials. Further high-temperature activation of the pyrrole-type carbon material of this invention leads to the transformation of nitrogen doping in the carbon material from pyrrole nitrogen to mixed nitrogen species such as pyridine nitrogen and graphitic nitrogen, thereby losing the corresponding surface chemical properties of the carbon material. Therefore, this invention employs a hydrothermal reaction method, using sugars and pyrrole as raw materials, to synthesize pyrrole-type nitrogen-doped carbon gels in one step. Meanwhile, the nitrogen-doped carbon gel prepared by this invention exhibits superior compressive strength, low wear rate under working conditions, and a quality retention rate of over 97%.

[0008] In a first aspect, the present invention provides a pyrrole-type nitrogen-doped carbon gel, wherein the nitrogen-doped carbon gel is formed by the aggregation of carbon nanoparticles with a particle size of less than 100 nm, and the nitrogen element in the carbon gel is predominantly in the pyrrole nitrogen form. Further, the pyrrole-type nitrogen-doped carbon gel is prepared by reacting a sugar-containing substance with pyrrole.

[0009] Furthermore, the pyrrole-type nitrogen-doped carbon gel is prepared by a hydrothermal reaction of sugar-containing substances and pyrrole.

[0010] Furthermore, the sugar-containing substance is selected from one or more of glucose, fructose, xylose, lactose, stachyose, sucrose, maltose, starch, cellulose, cyclodextrin, chitosan, and hyaluronic acid, preferably glucose.

[0011] Further, the molar ratio of pyrrole nitrogen form in the carbon gel to all nitrogen species in the carbon gel is higher than 70%, more preferably, the molar ratio of pyrrole nitrogen form in the carbon gel to all nitrogen species in the carbon gel is higher than 75%, particularly preferably, the molar ratio of pyrrole nitrogen form in the carbon gel to all nitrogen species in the carbon gel is higher than 80%, and even more preferably, the molar ratio of pyrrole nitrogen form in the carbon gel to all nitrogen species in the carbon gel is higher than 90%.

[0012] Furthermore, the pyrrole-type nitrogen-doped carbon gel is formed by the aggregation of carbon nanoparticles with a particle size of less than 80 nm. More preferably, the nitrogen-doped carbon gel is formed by the aggregation of carbon nanoparticles with a particle size of less than 50 nm. Particularly preferred, the nitrogen-doped carbon gel is formed by the aggregation of carbon quantum dots, i.e., carbon nanoparticles with a particle size of less than 10 nm. Further, the pyrrole-type nitrogen-doped carbon gel is a nitrogen-doped monolithic carbon gel.

[0013] Furthermore, the compressive strength of the pyrrole-type nitrogen-doped carbon gel is 1-1.5 MPa, specifically 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, and 1.5 MPa.

[0014] Furthermore, the wear resistance of the pyrrole-type nitrogen-doped carbon gel is 93-99.8%, specifically 93, 93.5, 94, 94.5, 95, 95.5, 96, 96.5, 97, 97.5, 98, 98.5, 99, 99.5, and 99.8%.

[0015] Furthermore, the mass retention rate of the pyrrole-type nitrogen-doped carbon gel is 97-99%, specifically 97, 97.5, 98, 98.5, and 99%.

[0016] Furthermore, the specific surface area of ​​the nitrogen-doped carbon gel is 100-500 m². 2 / g, specifically such as 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300 m 2 / g.

[0017] Furthermore, the pore volume of the nitrogen-doped carbon gel is 0.4-0.6 cm³. 3 / g, specifically such as 0.4, 0.42, 0.44, 0.46, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58, 0.6 cm 3 / g.

[0018] A second aspect of the present invention provides a method for preparing a pyrrole-type nitrogen-doped carbon gel, the method comprising the following steps: (1) Add sugary substances to water; (2) Pyrrole was added to carry out a hydrothermal reaction to obtain a pyrrole-type nitrogen-doped carbon gel.

[0019] Furthermore, the sugar-containing substance is selected from one or more of glucose, fructose, xylose, lactose, stachyose, sucrose, maltose, starch, cellulose, cyclodextrin, chitosan, and hyaluronic acid, preferably glucose or maltose.

[0020] Further, when the sugar-containing substance is soluble in water, step (1) includes adding the sugar-containing substance to water to form an aqueous solution of the sugar-containing substance. More further, the molar concentration of the aqueous solution of the sugar-containing substance is 1-15 mol / L, specifically such as 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 13, 14, 15 mol / L.

[0021] Furthermore, when the sugar-containing substance is insoluble in water, step (1) includes adding the sugar-containing substance to water to form a suspension of the sugar-containing substance.

[0022] Further, the mass concentration of pyrrole in the hydrothermal reaction system is 3-150 g / L, specifically 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150 g / L, preferably 5-50 g / L.

[0023] Furthermore, the hydrothermal reaction system further includes a second solvent, which is selected from one or more combinations of methanol, ethanol, ethylene glycol, glycerol, diethyl ether, dioxane, acetaldehyde, or acetone. Preferably, the volume concentration of the second solvent in the hydrothermal reaction system is 0.5% to 2%.

[0024] Furthermore, the pyrrole can be directly added to the aqueous solution of the sugar-containing substance obtained in step (1), or the pyrrole can be first added to a portion of the aqueous solution of the sugar-containing substance obtained in step (1) for pre-reaction, and then the pre-reaction product can be added once or in portions to the remaining aqueous solution of the sugar-containing substance for hydrothermal reaction. The pre-reaction time can be 10-90 min, for example, 10, 20, 30, 40, 50, 60, 70, 80, or 90 min. The pre-reaction temperature can be 40-400℃, specifically 40, 60, 80, 100, 200, 230, 250, 280, 300, 330, 350, 380, or 400℃.

[0025] Further, the temperature of the hydrothermal reaction is 100-400 °C, specifically 100, 120, 150, 180, 200, 230, 250, 280, 300, 330, 350, 380, or 400 °C, preferably 150-250 °C. In some embodiments of the present invention, the temperature of the hydrothermal reaction is 200 °C.

[0026] Further, the hydrothermal reaction time is 0.5-24 hours, specifically 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 18, or 24 hours, preferably 2-12 hours. In some embodiments of the present invention, the hydrothermal reaction time is 12 hours.

[0027] In some embodiments of the present invention, step (2) involves adding pyrrole to the aqueous solution of the sugar-containing substance obtained in step (1) and carrying out a hydrothermal reaction at 150-250 °C to obtain a nitrogen-doped carbon gel.

[0028] Optionally, step (3): wash and dry the product after the hydrothermal carbonization reaction in step (2) to obtain nitrogen-doped carbon gel.

[0029] Furthermore, the solvent used for washing is water.

[0030] Further, the drying temperature is 100-300 °C, specifically 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 220, 240, 260, 280, and 300 °C, preferably 100-150 °C. In some embodiments of the present invention, the drying temperature is 120 °C.

[0031] Furthermore, the drying time is 1-24 h, specifically 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24 h, preferably 12-24 h.

[0032] A third aspect of the present invention provides the application of the nitrogen-doped carbon gel described in the first aspect of the present invention or the nitrogen-doped carbon gel prepared by the preparation method described in the second aspect of the present invention in the preparation of catalysts, catalyst supports, biomedical sensors, electrochemical components, adsorption materials or separation and analysis materials.

[0033] In a fourth aspect, the present invention provides carbon nanoparticles with a particle size of less than 100 nm, wherein the carbon nanoparticles are obtained by reacting a sugar-containing substance and pyrrole in an aqueous solution, the reaction temperature being 100-400°C, and the reaction time being 10-90 min.

[0034] Furthermore, the carbon nanoparticles have a particle size of less than 80 nm, more preferably less than 50 nm, and particularly preferably less than 10 nm.

[0035] Furthermore, the pyrrole nitrogen form is dominant in the carbon nanoparticles. Preferably, the pyrrole nitrogen form accounts for more than 70% of the molar ratio of all nitrogen species in the carbon nanoparticles; more preferably, the pyrrole nitrogen form accounts for more than 75% of the molar ratio of all nitrogen species in the carbon nanoparticles; particularly preferably, the pyrrole nitrogen form accounts for more than 80% of the molar ratio of all nitrogen species in the carbon nanoparticles; and even more preferably, the pyrrole nitrogen form accounts for more than 90% of the molar ratio of all nitrogen species in the carbon nanoparticles.

[0036] Furthermore, the method for preparing the carbon nanoparticles includes the following steps: (1) Add sugary substances to water; (2) Add pyrrole to react and obtain carbon nanoparticles. The reaction temperature is 100-400 ℃ and the reaction time is 10-90 min.

[0037] Furthermore, the sugar-containing substance is selected from one or more of glucose, fructose, xylose, lactose, stachyose, sucrose, maltose, starch, cellulose, cyclodextrin, chitosan, and hyaluronic acid, preferably glucose or maltose.

[0038] Further, when the sugar-containing substance is soluble in water, step (1) includes adding the sugar-containing substance to water to form an aqueous solution of the sugar-containing substance. More further, the molar concentration of the aqueous solution of the sugar-containing substance is 1-15 mol / L, specifically such as 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 13, 14, 15 mol / L.

[0039] Furthermore, when the sugar-containing substance is insoluble in water, step (1) includes adding the sugar-containing substance to water to form a suspension of the sugar-containing substance.

[0040] Further, the mass concentration of pyrrole in the reaction system is 3-150 g / L, specifically 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150 g / L, preferably 5-50 g / L.

[0041] Furthermore, the reaction system also includes a second solvent, which is selected from one or more combinations of methanol, ethanol, ethylene glycol, glycerol, diethyl ether, dioxane, acetaldehyde, or acetone. Preferably, the volume concentration of the second solvent in the hydrothermal reaction system is 0.5-2%.

[0042] Further, the reaction temperature is 100-400 °C, specifically 100, 120, 150, 180, 200, 230, 250, 280, 300, 330, 350, 380, or 400 °C, preferably 150-250 °C. In some embodiments of the present invention, the hydrothermal reaction temperature is 200 °C.

[0043] Furthermore, the reaction time can be 10-90 min, for example 10, 20, 30, 40, 50, 60, 70, 80, or 90 min, preferably 20-60 min.

[0044] Furthermore, the carbon nanoparticles are carbon quantum dots, and the particle size of the carbon nanoparticles is less than 10 nm.

[0045] The preparation method of pyrrole-type nitrogen-doped carbon gel described in this invention is low-cost, highly efficient, and environmentally friendly, and can directly prepare high-performance carbon materials without additional processing. Attached Figure Description

[0046] Figure 1 The images shown are morphological images of nitrogen-doped carbon gels. (A) Overall image of the sample, (B) Cross-sectional image of the sample.

[0047] Figure 2The image shows a comparison of the morphology, SEM, and TEM images of nitrogen-doped carbon materials G1PY20, G1PY2, and G1PY200. (a) Morphological image of G1PY20 sample; (b) SEM image of G1PY20 sample; (c) TEM image of G1PY20 sample; (d) Morphological image of G1PY2 sample; (e) SEM image of G1PY2 sample; (f) TEM image of G1PY2 sample; (g) Morphological image of G1PY200 sample; (h) SEM image of G1PY200 sample; (i) TEM image of G1PY200 sample.

[0048] Figure 3 The image shown is an elemental mapping image of the G1PY20 sample.

[0049] Figure 4 The images show the morphology, SEM, and TEM images of the G1PY10, G1PY40, and G1PY100 nitrogen-doped carbon gels. (a) Morphological image of the G1PY10 sample; (b) SEM image of the G1PY10 sample; (c) TEM image of the G1PY10 sample; (d) Morphological image of the G1PY40 sample; (e) SEM image of the G1PY40 sample; (f) TEM image of the G1PY40 sample; (g) Morphological image of the G1PY100 sample; (h) SEM image of the G1PY100 sample; (i) TEM image of the G1PY100 sample.

[0050] Figure 5 The image shows the N1s spectrum of the carbon gel sample from Example 1, analyzed using X-ray photoelectron spectroscopy (XPS).

[0051] Figure 6 The figure shows a comparison of the compressive strength and abrasion resistance of carbon gels obtained under different raw material ratios. In the figure, a represents the compressive strength test result, and b represents the abrasion resistance test result.

[0052] Figure 7 The effects of activation on the structure and properties of carbon gel are shown. (a) shows the N1s spectra of G1PY20 samples after direct drying, G1PY20-N2@400℃ treated samples, G1PY20-N2@700℃ treated samples, and G1PY0-NH3@700℃ treated samples, respectively; (b) shows the change of nitrogen content in G1PY20 with temperature and the corresponding weight loss curves; (c) shows the comparison of compressive strength and abrasion resistance of G1PY20 before and after nitrogen heat treatment at 700℃.

[0053] Figure 8The images show the intermediate products obtained during the synthesis of samples G1PY0, G1PY20, and G1PY100 after a hydrothermal reaction at 200°C for 1 h, 1.5 h, and 2 h, respectively. The large vial on the right contains the original solution of the intermediate product, while the small vial on the left contains the filtrate or eluent of the intermediate product.

[0054] Figure 9 The images shown are transmission electron microscope (TEM) images of G1PY20 at 200°C for different times during the hydrothermal reaction. (a) represents 0.5 hours; (b) represents 1 hour; (c) represents 1.5 hours; and (d) represents 2 hours. Detailed Implementation

[0055] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0056] All publications, patents, and published patent specifications cited in this article are incorporated herein in their entirety through citation.

[0057] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Example 1: Preparation of carbon gel G1PY20 1 mol of glucose was dissolved in 880 mL of deionized water to prepare a stock solution. 80 mL of this solution (labeled Solution A) was transferred to a quartz tube and heated to 80°C. Subsequently, 20 mL of pyrrole was added to Solution A; the mixture was then sealed and preheated at 80°C for 20 minutes. The remaining 800 mL of glucose solution (labeled Solution B) was preheated separately to 80°C to maintain a consistent temperature. With continuous stirring, Solution A was poured into Solution B and transferred to a PTFE-lined stainless steel autoclave. The mixture was then subjected to a hydrothermal reaction at 200°C for 12 hours. After naturally cooling to room temperature, the resulting hydrogel was thoroughly washed with deionized water and finally dried at 120°C for 12 hours to obtain carbon gel G1PY20.

[0059] Example 2: Preparation of carbon gel G1PY10 This embodiment is basically the same as Example 1, except that the amount of pyrrole added is 10 mL. The final product is nitrogen-doped carbon gel G1PY10.

[0060] Example 3: Preparation of carbon gel G1PY40 This embodiment is basically the same as Example 1, except that the amount of pyrrole added is 40 mL. The final product is nitrogen-doped carbon gel G1PY40.

[0061] Example 4: Preparation of carbon gel G1PY100 This embodiment is basically the same as Example 1, except that the amount of pyrrole added is 100 mL. The final product is nitrogen-doped carbon gel G1PY100.

[0062] Example 5: Preparation of carbon gel G3PY20 This embodiment is basically the same as Example 1, except that the amount of glucose added is 3 mol. The final product is nitrogen-doped carbon gel G3PY20.

[0063] Example 6: Preparation of nitrogen-doped carbon gel G5PY20 This embodiment is basically the same as Example 1, except that the amount of glucose added is 5 mol. The final product is nitrogen-doped carbon gel G5PY20.

[0064] Comparative Example 1: Preparation of carbon powder G1PY2 This embodiment is basically the same as Example 1, except that the amount of pyrrole added is 2 mL. The final product is nitrogen-doped carbon spheres G1PY2.

[0065] Comparative Example 2: Preparation of carbon powder G1PY200 This embodiment is basically the same as Example 1, except that the amount of pyrrole added is 200 mL. The final product is nitrogen-doped carbon spheres G1PY200.

[0066] Comparative Example 3: Preparation of carbon powder G1PY0 This embodiment is basically the same as Example 1, except that pyrrole was not added. The final product is nitrogen-doped carbon sphere G1PY0.

[0067] Example 7: Study on the structure and properties of carbon gel 1. Macroscopic morphological analysis The macroscopic morphology of the nitrogen-doped carbon material samples prepared in Example 1 and Comparative Examples 1 and 2 was observed. The results showed that the sample prepared in Example 1 exhibited a good carbon gel structure, with a relatively smooth surface and cross-section. Figure 1 A and B Figure 2 a), and the surface has a distinct carbon shell structure. However, the G1PY2 (a) prepared in Comparative Examples 1 and 2 Figure 2 d) and G1PY200 ( Figure 2(g), the sample was in powder form. This indicates that the amount of pyrrole added affects the morphology of nitrogen-doped carbon materials. When the amount of pyrrole added is appropriate, nitrogen-doped carbon gel is formed, while when the amount of pyrrole added is too much or too little, nitrogen-doped carbon powder is formed.

[0068] 2. Microscopic morphology analysis The microstructure of nitrogen-doped carbon material samples prepared in Example 1, Comparative Example 1, and Comparative Example 2 was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

[0069] G1PY20 sample: such as Figure 2 b and Figure 2 As shown in Figure c, the sample is composed of tightly aggregated nanoparticles, exhibiting a coral-like structure. Large pores of varying sizes are irregularly distributed within the clusters, and mesopores and micropores of different sizes can also be observed within the nanoparticles. To further characterize the pore structure of the G1PY20 sample, nitrogen adsorption-desorption isotherm measurements were performed. The results showed that the specific surface area of ​​G1PY20 was 268.64 m². 2 / g, pore volume 0.52 cm³ 3 / g. To further characterize the elemental distribution in the G1PY20 sample, elemental mapping analysis was performed, and the results are as follows: Figure 3 As shown, nitrogen is widely and uniformly distributed in the sample, indicating that pyrrole is not only dispersed in the aqueous system under reaction conditions, but also actively participates in the reaction in aqueous solution.

[0070] G1PY2 sample: such as Figure 2 e and Figure 2 As shown in f, the structural unit of the sample is a spherical particle with a diameter of 100-200 nm, which is similar in shape to carbon microspheres obtained directly from glucose hydrothermal synthesis, but significantly smaller in size.

[0071] G1PY200 sample: such as Figure 2 h and Figure 2 As shown in i, the sample consists of micron-sized spheres with a dense outer shell and an amorphous carbon structure inside.

[0072] G1PY10, G1PY40 and G1PY100 samples: such as Figure 4 As shown, similar to the G1PY20 sample, G1PY10, G1PY40 and G1PY100 can all form stable carbon gels through observation of macroscopic morphology, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

[0073] 3. Carbon doping analysis According to XPS results, the nitrogen content in the product increases with the increase of pyrrole addition in the hydrothermal reaction system. The N1s peak was fitted using the Lorentzian equation, as shown below. Figure 5 As shown, four typical component peaks were obtained: pyridine nitrogen (398.5±0.15 eV), pyrrole nitrogen (400.0±0.15 eV), quaternary nitrogen (401.0±0.1 eV), and nitrogen oxides (403.2±0.1 eV). During the synthesis process, due to the overall conjugation effect, the pyrrole incorporated into the carbon skeleton isomerized to form an imine structure, resulting in a small pyridine nitrogen peak in the nitrogen form, whose intensity is slightly lower than the standard reference peak. In the dried samples with different amounts of pyrrole added, pyrrole nitrogen was the main form, accounting for as high as 79.86%, with the remaining nitrogen existing in the form of pyridine nitrogen and quaternary nitrogen. 4. Mechanical strength test Compressive strength test The sample was placed between two flat plates. Compression was applied at a constant displacement rate of 1 mm / min. The compressive strength was determined at the point of structural fracture (crushing). At least five specimens were tested for each sample to ensure the repeatability of statistical results.

[0074] Wear resistance test Take a sample that has passed through a 40-60 mesh sieve, measure 50 ml using a graduated cylinder, and record its mass on a balance. Then, place the sample into a stainless steel drum containing five stainless steel balls, and place the drum on the shaft of a strength tester. Rotate the strength tester at 50 rpm for 5 minutes, remove the drum and the stainless steel balls, and then sieve the sample through a 60 mesh sieve. Collect the samples remaining on and behind the sieve, measure them, and compare the mass of the samples before and after the test to determine the abrasion resistance of the samples.

[0075] The mechanical strength of the prepared carbon gel was evaluated, and five repeated experiments were conducted for each group to ensure the reliability of the results. Figure 6Figures a and 6b illustrate the compressive strength and abrasion resistance of carbon gels formed with different glucose-pyrrole ratios. The results show that compressive strength decreases with increasing glucose content. However, G1PY20 exhibits superior load-bearing capacity compared to G1PY10 and G1PY100, achieving a maximum compressive strength of 1.42 MPa, indicating that pyrrole does indeed improve the compressive strength of the carbon gel. However, excessively high pyrrole content leads to a lack of glucose derivatives that provide carbonyl sites for crosslinking, resulting in decreased compressive strength. No significant differences in abrasion resistance were observed between carbon gels with different ratios. Samples passing through a 40-60 mesh sieve showed abrasion resistance exceeding 93.50%, with G3PY20 exhibiting the highest abrasion resistance at 95.83%. Furthermore, particles with a diameter of 5-10 mm (sample G1PY20) were selected for abrasion testing; after stirring for 210 minutes, this sample retained 9.712% of its mass, demonstrating excellent abrasion resistance.

[0076] Example 8: Effect of activation on carbon gel 1. Thermal activation of carbon gel The carbon gel G1PY20 prepared in Example 1 was placed in a tube furnace and heated at a programmed rate of 10 °C / min. It was treated with gases N2 and NH3 at a flow rate of 100 sccm, and the corresponding activation products were obtained at different temperatures of 200, 300, 400, 500, 600 and 700 °C.

[0077] 2. Structure and properties of the activated products like Figure 7 As shown in Figure a, during the thermal activation process, it was found that pyrrole nitrogen is converted into pyridine nitrogen and quaternary nitrogen. With the presence of nitrogen oxides, the proportion of pyrrole nitrogen decreased from 79.86% to 6.48%. Figure 7 As shown in b, the curves illustrating the changes in the proportions of pyrrole nitrogen, pyridine nitrogen, and quaternary nitrogen more intuitively demonstrate their interconversion trends. The mass loss curves obtained from thermogravimetric (TG) testing show that the carbon gel experiences rapid weight loss around 400℃, corresponding to the stage where nitrogen speciation is most significant. Clearly, the carbon gel exhibits good stability below 400℃, and tends to stabilize again after 600℃. Comparing the G1PY20-N2@700℃ sample obtained by nitrogen heat treatment at 700℃ with the G1PY0-NH3@700℃ sample prepared by chemical vapor deposition at a similar nitrogen doping level, the nitrogen in the ammonia-treated sample is more uniformly distributed among pyrrole nitrogen, pyridine nitrogen, and quaternary nitrogen. In contrast, the nitrogen in the carbon gel that underwent hydrothermal reaction after the addition of pyrrole and then nitrogen heat treatment mainly exists in the forms of pyridine nitrogen and quaternary nitrogen.

[0078] like Figure 7As shown in Figure c, the compressive strength and abrasion resistance of G1PY20 carbon gel before N2 activation at 700℃ (G1PY20) and after N2 activation at 700℃ (G1PY20A) are compared. The results show that activation heat treatment changes the aromaticity and crystallinity of the carbon gel, and may induce fragmentation and defunctionalization reactions, thereby affecting the mechanical properties of the carbon gel. After activation heat treatment, the compressive strength of the carbon gel decreased significantly, with a decrease of approximately 16.20%.

[0079] Example 9: Study on the mechanism of carbon gel formation 1. Detection of intermediate products During the synthesis of nitrogen-doped carbon materials G1PY0 (Comparative Example 3), G1PY20 (Example 1), and G1PY100 (Example 4), the morphology of the intermediate products at different reaction times was observed. The specific operating steps are as follows: After the hydrothermal reaction proceeded for 1 h, 1.5 h, and 2 h, the reaction vessel was removed, rapidly cooled to room temperature, and the intermediate products were collected. The results are as follows: Figure 8 As shown, within the first 2 hours of the reaction, all intermediate products were in a liquid state. As the reaction proceeded, the liquid color changed from light to dark, and from transparent to cloudy. At 2 hours, the G1PY0 intermediate product remained in solution, while the G1PY20 and G1PY100 intermediate products began to exhibit a pudding-like monolithic structure. This indicates that the addition of pyrrole significantly accelerated the hydrothermal reaction of glucose, and the higher the amount of pyrrole used, the faster the conversion rate.

[0080] 2. Synthesis Mechanism and Growth Stage Existing research typically classifies the growth mechanism of activated carbon materials prepared via the hydrothermal reaction of glucose into four stages: monomer formation, monomer nucleation, nucleus growth, and nucleus aggregation. This invention discovers a formation mechanism for mesoporous nitrogen-doped carbon gels using pyrrole as a crosslinking agent, which can also be divided into four stages: First, in the presence of pyrrole, glucose reacts to form furfural monomers, which then decompose into small monomers containing C1-C5 carbonyl groups. Subsequently, pyrrole preferentially undergoes condensation reactions with oxygen-containing functional groups, forming hydrophobic primary nanoparticles. Next, the numerous aromatic nuclei continuously grow through aldol condensation and acetalization reactions, rapidly consuming the monomers in the solution within a short time. Then, crosslinking occurs between the nuclei, forming a continuous carbon framework. Finally, at the end of the growth stage, the nuclei begin to aggregate, ultimately forming a carbon gel.

[0081] As attached Figure 9As shown, nuclei formed after 0.5 hours of reaction. Close observation revealed that each nucleus consisted of several carbon quanta. By 1 hour, the nuclei had grown to a maximum size of 20 nanometers, although these larger structures remained aggregates of multiple quantum dots. By 1.5 hours, a framework began to form between the nuclei, connecting them to each other. After 2 hours, a macroscopic, monolithic solid carbon gel was formed, confirmed by transmission electron microscopy (TEM) images showing the aggregation of small particles. The evolution observed through electron microscopy indicates that the formation of the carbon gel follows a typical sol-gel process, characterized by a hydrolysis rate significantly exceeding the growth rate and a short overall precipitation window. The transition from nucleation to growth is consistent with the LaMer model and Ostwald ripening. Pyrrole's participation in nucleation depends on its reaction with carbonyl, hydroxyl, and other oxygen-containing groups. Once these functional groups are depleted, the remaining pyrrole cannot participate in growth, resulting in nitrogen atoms being predominantly distributed on the surface and in limited quantity. Intermediates produced during glucose breakdown, such as C5-C6 aldose derivatives, require a sufficient supply of pyrrole molecules as cross-linking units.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0083] The foregoing embodiments and methods described in this invention may vary based on the capabilities, experience, and preferences of those skilled in the art.

[0084] Listing the steps of the method in a certain order in this invention does not constitute any restriction on the order of the method steps.

Claims

1. A pyrrole-type nitrogen-doped carbon gel, characterized in that, The carbon gel is formed by the aggregation and cross-linking of carbon nanoparticles with a particle size of less than 100 nm, and the pyrrole nitrogen in the carbon gel accounts for more than 70% of the molar ratio of all nitrogen species in the carbon gel.

2. The pyrrole-type nitrogen-doped carbon gel according to claim 1, characterized in that, The carbon gel contains pyrrole nitrogen in a molar ratio of more than 80% of all nitrogen species, and more preferably, the carbon gel contains pyrrole nitrogen in a molar ratio of more than 90% of all nitrogen species.

3. The pyrrole-type nitrogen-doped carbon gel according to claim 1, characterized in that, The carbon gel is formed by the aggregation and cross-linking of carbon nanoparticles with a particle size of less than 50 nm. More preferably, the carbon gel is formed by the aggregation and cross-linking of carbon quantum dots, wherein the carbon quantum dots are carbon nanoparticles with a particle size of less than 10 nm.

4. A method for preparing a pyrrole-type nitrogen-doped carbon gel, comprising the following steps: (1) Add sugary substances to water; (2) Pyrrole was added to carry out a hydrothermal reaction to obtain a pyrrole-type nitrogen-doped carbon gel.

5. The preparation method according to claim 4, characterized in that, The sugar-containing substance is selected from one or more of glucose, fructose, xylose, lactose, stachyose, sucrose, maltose, starch, cellulose, cyclodextrin, chitosan and hyaluronic acid, preferably glucose or maltose.

6. The preparation method according to claim 4, characterized in that, The mass concentration of pyrrole in the hydrothermal reaction system is 3-150 g / L, preferably 5-50 g / L.

7. The preparation method according to claim 4, characterized in that, The temperature of the hydrothermal reaction is 100-400 ℃, preferably 150-250 ℃; Preferably, the hydrothermal reaction time is 0.5-24 h, more preferably 2-12 h.

8. The preparation method according to claim 4, characterized in that, Step (1) includes: dissolving the sugary substance in water to form a sugary aqueous solution; Preferably, step (2) includes: adding pyrrole to the sugar-containing aqueous solution obtained in step (1) and carrying out a hydrothermal reaction at 150-250 °C to obtain nitrogen-doped carbon gel.

9. A carbon nanoparticle, wherein the carbon nanoparticle has a particle size of less than 100 nm, the carbon nanoparticle is obtained by reacting a sugar-containing substance and pyrrole in an aqueous solution, wherein the reaction temperature is 100-400 °C, and the reaction time is 10-90 min; preferably, the carbon nanoparticle is a carbon quantum dot, wherein the carbon quantum dot is a carbon nanoparticle with a particle size of less than 10 nm.

10. The use of a nitrogen-doped carbon gel as described in any one of claims 1-3 or a nitrogen-doped carbon gel prepared by the preparation method as described in any one of claims 4-8 in the preparation of catalysts, catalyst supports, biomedical sensors, electrochemical components, adsorbent materials or separation and analysis materials.

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