A method for rapidly preparing nitrogen-doped porous graphitized carbon material by using potassium cobaltous nitrite as a multifunctional activator

Abstract

The application provides a method for rapidly preparing nitrogen-doped porous graphitized carbon materials by using potassium cobaltous nitrite as a multifunctional activator. The potassium cobaltous nitrite is used as a chemical activator, a nitrogen source and a catalyst for graphitization reaction of the carbon material, biomass material is used as a carbon source, and activation, nitrogen doping and graphitization of the carbon material are simultaneously completed through one-step high-temperature treatment, so that the nitrogen-doped porous graphitized carbon material is rapidly prepared. By introducing the potassium cobaltous nitrite as a multifunctional additive, the additive can simultaneously serve as a chemical activator, a nitrogen doping source and a catalyst for graphitization reaction, and through one-step high-temperature treatment process, three reactions of pore activation of the carbon matrix, nitrogen atom doping and graphitization modification are completed, so that the traditional multi-step preparation process is simplified, and rapid and simple synthesis of the nitrogen-doped porous graphitized carbon material is realized.

Description

Technical Field

[0001] This invention relates to the field of porous carbon materials technology, and in particular to a method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator. Background Technology

[0002] Porous carbon materials possess significant advantages such as strong chemical inertness, readily available raw materials, well-developed pore structure, and high specific surface area, making them core functional materials in adsorption separation, electrochemical energy storage, and heterogeneous catalysis. Pure carbon materials, however, have limited surface functional groups, scarce active sites, and intrinsic conductivity, making them unsuitable for high-performance applications. Nitrogen doping, on the other hand, introduces nitrogen-containing active sites into the carbon framework, regulating electron distribution, surface polarity, and defect structure, fundamentally altering the physicochemical properties of carbon materials. This is currently the most common and efficient modification method for optimizing the functionality of carbon-based materials.

[0003] In the carbonization and activation stages of high-temperature preparation of carbon materials, the degree of graphitization directly determines the conductivity: a higher degree of graphitization can construct a continuous conjugated carbon network, significantly reduce charge transport resistance, optimize electron conduction efficiency, and endow carbon materials with superior electrochemical and catalytic performance, further expanding their application boundaries in electrocatalytic reactions, battery electrodes, gas / water adsorption and other fields.

[0004] Currently, the mainstream nitrogen-doped porous graphitized carbon preparation processes have significant shortcomings: The first synthesis method directly uses biomass or organic precursors rich in endogenous nitrogen, and obtains nitrogen-doped porous carbon in one step through high-temperature carbonization and activation. This method is simple, but requires the carbon source itself to have a high nitrogen content, which greatly reduces the selection space of the precursor; The second approach involves first carbonizing to prepare a nitrogen-free porous carbon substrate, and then introducing nitrogen sources such as ammonia or urea for a second high-temperature heat treatment to complete the exogenous nitrogen doping. This method is not limited in the selection of carbon source, but it adds an independent post-processing step, prolongs the production cycle, increases energy consumption and material costs, and is not conducive to large-scale preparation.

[0005] Given the limitations of the existing processes, there is an urgent need to develop a new integrated synthesis technology that is simple, fast, economical and efficient. This technology is of great theoretical and practical significance for the fundamental mechanism research and industrial application of nitrogen-doped porous graphitized carbon materials. Summary of the Invention

[0006] To overcome the aforementioned deficiencies in the existing technology, this invention provides a method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator. The specific preparation process is simple, requiring only one high-temperature treatment step to directly prepare nitrogen-doped graphitized carbon materials with high specific surface area, including the following steps: To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator, comprising the following steps: S1: Mix and stir the biomass material with the activator to obtain a homogeneous mixture; S2: Perform heat treatment on the mixture; S3: After heat treatment, washing and drying, the nitrogen-doped porous graphitized carbon material is obtained; The activator includes potassium cobalt nitrite.

[0007] In some embodiments, the method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator, wherein step (1) satisfies at least one of the following conditions: The biomass material includes polysaccharide biomass carbohydrates; The mass ratio of the biomass material to the activator is 1:(2~3); The stirring process includes grinding.

[0008] In some embodiments, the method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator includes polysaccharide biomass carbohydrates such as biolignin, cellulose, agar, starch, and sucrose.

[0009] In some embodiments, the method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator, wherein step (2) satisfies at least one of the following conditions: The heat treatment temperature is 700~800℃; The specific operation of the heat treatment includes: performing the heat treatment in a nitrogen atmosphere by programmed temperature increase and then holding it at that temperature.

[0010] In some embodiments, the method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator, wherein step (2) satisfies at least one of the following conditions: The flow rate of the nitrogen gas is 60 mL / min; The temperature rise is performed at a rate of 10°C / min. The heat preservation time is 1~2 hours.

[0011] In some embodiments, the method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator, wherein step (3) satisfies at least one of the following conditions: The washing operation includes: acid washing with an acid solution; The drying temperature is 100℃~120℃; The drying time is 4 to 6 hours.

[0012] In some embodiments, the method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator, wherein step (3) satisfies at least one of the following conditions: The cooling is performed at room temperature; The acid solution includes hydrochloric acid solution; The acid wash is followed by a water wash until the pH value is neutral.

[0013] In some embodiments, the method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator includes, in step (3), a cooling operation to room temperature after the heat treatment.

[0014] The present invention also provides a method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator, which are prepared by the above-described preparation method.

[0015] This invention also provides the application of potassium cobalt nitrite prepared as described above as a multifunctional activator in the rapid preparation of inorganic materials, which is used to adsorb CO2.

[0016] on the other hand: The present invention does not impose any special limitations on the grinding and mixing process; any process well known to those skilled in the art can be used.

[0017] In this invention, the heat treatment temperature is 700~800℃; the heating rate to the heat treatment temperature is preferably 1~15℃ / min, more preferably 5~10℃ / min; and the holding time is 1~2h. In this invention, the heat treatment is carried out in a nitrogen atmosphere.

[0018] In this invention, the heat treatment is preferably carried out in a tubular furnace.

[0019] In a specific embodiment of the present invention, the heat treatment process is preferably as follows: The mixture of the biomass material and potassium cobalt nitrite is placed in a tube furnace and heated in a nitrogen atmosphere for heat treatment.

[0020] In this invention, the flow rate of the nitrogen atmosphere in the tube furnace is 60 mL / min.

[0021] After the heat treatment is completed, the present invention further includes post-processing the obtained material; the post-processing preferably includes cooling, washing and drying in sequence.

[0022] In this invention, the cooling method is preferably natural cooling to room temperature. In this invention, the washing preferably includes sequential acid washing and water washing. This invention does not impose any particular limitation on the acid washing and water washing processes; processes well-known to those skilled in the art can be used. In this invention, the acidic reagent used for acid washing is preferably a hydrochloric acid solution. In this invention, the mass concentration of the hydrochloric acid solution is preferably 5-20 wt%, more preferably 8-10 wt%. This invention does not impose any particular limitation on the number of water washings, as long as the pH value of the material is washed to neutral.

[0023] In this invention, the drying temperature is 100~120℃ and the time is 4~6h.

[0024] This invention also provides a nitrogen-doped porous graphitized carbon material prepared by the preparation method described in the above technical solution. In this invention, the specific surface area of ​​the nitrogen-doped porous graphitized carbon material is 900~1800 m². 2 / g, with a nitrogen content of 2.00-5.00wt%.

[0025] This invention uses inexpensive and readily available biomass materials as the carbon source and introduces potassium cobalt nitrite as a multifunctional additive. This additive can simultaneously act as a chemical activator, a nitrogen doping source, and a graphitization reaction catalyst. Through a one-step high-temperature heat treatment process, the triple reaction of pore activation, nitrogen atom doping, and graphitization modification of the carbon matrix is ​​completed, simplifying the traditional multi-step preparation process and realizing the rapid and simple synthesis of nitrogen-doped porous graphitized carbon materials.

[0026] This invention overcomes the technical shortcomings of traditional preparation processes, such as cumbersome procedures, high energy consumption, limited raw materials, and poor performance controllability caused by the stepwise processes of activation, nitrogen doping, and graphitization. The final product yields nitrogen-doped porous graphitized carbon materials with synergistically optimized structure and performance. The highly graphitized carbon framework formed by in-situ catalysis endows the material with excellent structural stability and electrical conductivity, effectively balancing porous structure, doping activity, and structural stability.

[0027] Compared with the prior art, this application has the following beneficial effects: The carbon materials prepared according to this invention, as demonstrated by system performance testing, have a specific surface area of ​​900~1800 m². 2 / g, with a rich porous structure and uniform pore distribution, can effectively provide sufficient adsorption sites and material transport channels; the nitrogen doping content of the material can be stably controlled at 2.00~5.00wt%, and the uniformly doped nitrogen atoms can effectively regulate the surface electronic structure of carbon materials, enhance surface polarity and chemical activity, and greatly enhance the interaction between the material and acidic gases.

[0028] This invention further limits the application of nitrogen-doped porous graphitized carbon materials in the field of CO2 gas adsorption. Relying on the synergistic effect of the material's high specific surface area, abundant pore structure, and numerous nitrogen-containing active adsorption sites, this material exhibits excellent selective CO2 adsorption capacity and adsorption ability. Under standard test conditions of 0℃ and 1 bar, the CO2 adsorption capacities of the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3 of this invention reach 5.75 mmol / g, 4.25 mmol / g, and 5.16 mmol / g, respectively, demonstrating excellent overall adsorption performance. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 The images show the scanning electron microscope (SEM) results of the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3. Figure 2 The images show the Raman spectra of the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3. Figure 3 The Raman spectrum of the carbon material prepared in Comparative Example 1 is shown in the figure. Figure 4 The N2 adsorption-desorption curves of the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3 at -196℃ are shown. Figure 5 The CO2 adsorption isotherms of the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3 at 25°C are shown. Figure 6 The CO2 adsorption isotherms at 0°C are for the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3. Detailed Implementation

[0031] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0032] Unless otherwise specified, the raw materials used in the embodiments of this application are all purchased commercially and used directly without any special treatment.

[0033] Unless otherwise specified, the analytical methods in the embodiments all adopt conventional instrument or equipment settings and conventional analytical methods.

[0034] Example 1 1.0 g of cellulose was uniformly ground with 2.0 g of potassium cobalt nitrite. The resulting mixture was placed in a tube furnace, and nitrogen gas was introduced into the furnace at a flow rate of 60 mL / min. The furnace was then heat-treated to 700 °C at a heating rate of 10 °C / min under a nitrogen atmosphere, and held at this temperature for 2 hours. After the heat treatment, the mixture was allowed to cool naturally to room temperature. The resulting product was then acid-washed with a 10 wt% hydrochloric acid solution, followed by water washing until the pH of the product was neutral. The washed product was then dried at 100 °C for 4 hours to obtain the nitrogen-doped porous graphitized carbon material.

[0035] Example 2 1.0 g of cellulose was uniformly ground with 3.0 g of potassium cobalt nitrite. The resulting mixture was placed in a tube furnace, and nitrogen gas was introduced into the furnace at a flow rate of 60 mL / min. The furnace was then heat-treated to 700 °C at a heating rate of 10 °C / min under a nitrogen atmosphere, and held at this temperature for 2 hours. After the heat treatment, the mixture was allowed to cool naturally to room temperature. The resulting product was then acid-washed with a 10 wt% hydrochloric acid solution, followed by water washing until the pH of the product was neutral. The washed product was then dried at 100 °C for 4 hours to obtain the nitrogen-doped porous graphitized carbon material.

[0036] Example 3 1.0 g of lignin was uniformly ground with 3.0 g of potassium cobalt nitrite. The resulting mixture was placed in a tube furnace, and nitrogen gas was introduced into the furnace at a flow rate of 60 mL / min. The furnace was then heat-treated at 800 °C with a heating rate of 10 °C / min under a nitrogen atmosphere for 2 hours. After the heat treatment, the mixture was allowed to cool naturally to room temperature. The resulting product was then acid-washed with a 10 wt% hydrochloric acid solution, followed by water washing until the pH of the product was neutral. The washed product was then dried at 100 °C for 4 hours to obtain the nitrogen-doped porous graphitized carbon material.

[0037] Comparative Example 1 1.0 g of cellulose was uniformly ground with 3.0 g of potassium bicarbonate. The resulting mixture was placed in a tube furnace, and nitrogen gas was introduced into the furnace at a flow rate of 60 mL / min. The furnace was then heat-treated to 800 °C at a heating rate of 10 °C / min under a nitrogen atmosphere, and held at this temperature for 2 hours. After the heat treatment, the mixture was allowed to cool naturally to room temperature. The resulting product was then acid-washed with a 10 wt% hydrochloric acid solution, followed by water washing until the pH of the product was neutral. The washed product was then dried at 100 °C for 4 hours to obtain the nitrogen-doped porous graphitized carbon material.

[0038] Example 1 (morphological analysis) Figure 1The images show the scanning electron microscope (SEM) results of the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3. After washing with hydrochloric acid and deionized water to remove potassium and cobalt compounds, the resulting carbon materials exhibit irregular bulk shapes, with the large particles in the images formed by the aggregation of smaller particles.

[0039] Figure 2 The Raman spectra of the nitrogen-doped porous graphitized carbon materials in Examples 1-3 are shown, with values ​​ranging from ~1350 cm⁻¹. -1 With ~1580cm -1 Characteristic peaks of defects (D) and graphitization (G) in carbon materials were observed. The ratio of their peak intensities (I) is generally used. D / I G The value is used to measure the degree of graphitization of carbon materials, I D / I G A higher value indicates more defects in the carbon material. D / I G A lower value indicates a higher degree of graphitization of the carbon material. Examples 1-3 correspond to I... D / I G The values ​​were 0.90, 0.88, and 0.87, respectively, all of which are relatively low. D / I G The value also indicates that potassium cobalt nitrite plays a catalytic role in the graphitization process of carbon materials under high temperature conditions, thus resulting in a high degree of graphitization.

[0040] Figure 3 The Raman spectral results for the carbon material in Comparative Example 1 are shown, with corresponding I... D / I G The value is 1.33, which is much higher than I in Example 3. D / I G This result also verifies the positive effect of potassium cobalt nitrite on improving the graphitization degree of carbon materials.

[0041] Example 2 (Performance Test) Nitrogen adsorption-desorption tests were performed on the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3. The test method was static volumetric adsorption testing. The test results are shown in [Figure 1]. Figure 4 .

[0042] The CO2 adsorption characteristics of the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3 were tested, and the tests included the following steps: 100 mg of nitrogen-doped porous graphitized carbon material was added to the test sample chamber and heated to 250 °C for vacuum degassing for 3 h. Set the ambient temperature of the test sample chamber, gradually increase the CO2 pressure from a vacuum state, and measure the adsorption amount at each equilibrium pressure until the equilibrium pressure reaches 1.0 bar, thereby obtaining a complete CO2 adsorption isotherm. After the CO2 adsorption test is completed, the sample chamber is heated to 100℃ and vacuumed to complete the CO2 desorption.

[0043] The CO2 adsorption test results are shown below. Figure 5 and Figure 6 .

[0044] The test results are also shown in Table 1.

[0045] Table 1

[0046] As shown in Table 1, the nitrogen content of the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3 was 4.16 wt%, 4.57 wt%, and 2.85 wt%, respectively, which proves that potassium cobalt nitrite can be used as a nitrogen source to achieve nitrogen doping of carbon materials.

[0047] from Figure 4 As shown in Table 1, the nitrogen adsorption capacity increases rapidly in the low-pressure section, which is a typical characteristic of microporous adsorption; simultaneously, a hysteresis loop of adsorption-desorption forms in the high-pressure section, corresponding to the characteristics of mesoporous materials. These results demonstrate that potassium cobalt nitrite activation simultaneously forms both micropores and mesopores in the carbon material. The specific surface areas of the nitrogen-doped porous graphitized carbon materials prepared in Examples 1-3 are 932 m², respectively. 2 / g、1284m 2 / g and 1773m 2 / g, which also shows that potassium cobalt nitrite can play a significant chemical activating role.

[0048] from Figure 5 As shown in Table 1, under the conditions of 25°C and 1 bar pressure, the CO2 adsorption capacities of the carbon materials in Examples 1-3 were 3.83 mmol / g, 2.89 mmol / g, and 3.16 mmol / g, respectively; according to Figure 6 When the adsorption temperature is 0℃, the CO2 adsorption capacity of the carbon materials in Examples 1-3 under a pressure of 1 bar is 5.75 mmol / g, 4.25 mmol / g and 5.16 mmol / g, respectively, showing good adsorption characteristics.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator, characterized in that, Includes the following steps: S1: Mix and stir the biomass material with the activator to obtain a homogeneous mixture; S2: Perform heat treatment on the mixture; S3: After heat treatment, washing and drying, the nitrogen-doped porous graphitized carbon material is obtained; The activator includes potassium cobalt nitrite.

2. The method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator according to claim 1, characterized in that, Step (1) satisfies at least one of the following conditions: The biomass material includes polysaccharide biomass carbohydrates; The mass ratio of the biomass material to the activator is 1:(2~3); The stirring process includes grinding.

3. The method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator as described in claim 2, characterized in that, The polysaccharide biomass carbohydrates include biolignin, cellulose, agar, starch, and sucrose.

4. The method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator according to claim 1, characterized in that, Step (2) satisfies at least one of the following conditions: The heat treatment temperature is 700~800℃; The specific operation of the heat treatment includes: performing the heat treatment in a nitrogen atmosphere by programmed temperature increase and then holding it at that temperature.

5. The method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator according to claim 4, characterized in that, Step (2) satisfies at least one of the following conditions: The flow rate of the nitrogen gas is 60 mL / min; The temperature rise procedure is performed at 10°C / min. The heat preservation time is 1~2 hours.

6. The method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator according to claim 1, characterized in that, Step (3) satisfies at least one of the following conditions: The washing operation includes: acid washing with an acid solution; The drying temperature is 100℃~120℃; The drying time is 4 to 6 hours.

7. The method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator according to claim 6, characterized in that, Step (3) satisfies at least one of the following conditions: The cooling is performed at room temperature; The acid solution includes hydrochloric acid solution; The acid wash is followed by a water wash until the pH value is neutral.

8. The method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator according to claim 1, characterized in that, In step (3), the heat treatment also includes a cooling operation to room temperature.

9. A method for rapidly preparing nitrogen-doped porous graphitized carbon materials using potassium cobalt nitrite as a multifunctional activator, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. An application of potassium cobalt nitrite as a multifunctional activator in the rapid preparation of inorganic materials as described in claim 9, characterized in that, Used to adsorb CO2.

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