A method for preparing nitrogen-doped porous carbon material by using phenazine

Abstract

The application discloses a method for preparing nitrogen-doped porous carbon material by using phenazine, which comprises the following steps: mixing phenazine and ZnCl2, and then placing the mixture in a protective atmosphere to perform pyrolysis; and performing acid washing, water washing and drying on the pyrolysis product to obtain the nitrogen-doped porous carbon material. The method for preparing the nitrogen-doped porous carbon material by using phenazine as a carbon-nitrogen source and ZnCl2 as an activating agent has the advantages of clear raw material composition, simple operation, no need of additional nitrogen source, high carbon material yield and the like. The prepared porous carbon material has a nitrogen-doped structure and rich pore structure, and has excellent electrochemical performance, and is suitable for large-scale industrial application in the field of electrochemical energy storage.

Description

Technical Field

[0001] This invention belongs to the field of porous carbon materials and electrochemical energy storage technology, specifically relating to a method for preparing nitrogen-doped porous carbon materials using phenazine. Background Technology

[0002] Supercapacitors, lithium-ion batteries, and sodium-ion batteries are common electrochemical energy storage devices with broad application prospects in portable electronic devices, new energy vehicles, smart grids, and energy storage systems. Electrode materials are one of the key factors affecting the performance of electrochemical energy storage devices, and porous carbon materials are widely used in the preparation of electrode materials for supercapacitors, lithium-ion batteries, and sodium-ion batteries due to their large specific surface area, rich pore structure, good conductivity, high chemical stability, and relatively low cost. Furthermore, the rich pore structure and tunable surface chemistry of porous carbon materials also give them potential applications in gas adsorption, such as carbon dioxide adsorption.

[0003] Currently, precursors for porous carbon materials mainly include biomass, synthetic polymers, and small organic molecules. Biomass is widely available and inexpensive, but its composition is complex, its structure is uncertain, its batch stability is poor, and its pretreatment process is relatively complicated. Synthetic polymers have tunable structures, but they usually suffer from complex polymerization processes, high costs, and numerous post-processing steps. While some nitrogen-containing small organic molecules have advantages such as well-defined compositions and designable structures, their thermal stability is insufficient. During high-temperature pyrolysis, they are prone to volatilization, decomposition, carbon skeleton destruction, and nitrogen loss, which leads to low yield and low nitrogen content in the carbon materials, making it difficult to simultaneously obtain high yield, nitrogen-doped structure, and suitable pore structure.

[0004] Nitrogen doping can improve the surface wettability, electronic structure, and interfacial reactivity of porous carbon materials, thereby enhancing their performance in electrochemical energy storage and gas adsorption. However, existing methods for preparing nitrogen-doped porous carbon typically require the introduction of additional nitrogen sources, templates, or strong activators. This not only makes the process complex but also risks excessive etching of the carbon framework during strong activation, leading to reduced carbon yield, nitrogen loss, or increased inorganic residues, which is detrimental to large-scale industrial production and practical applications.

[0005] Therefore, it is of great significance to develop a method for preparing nitrogen-doped porous carbon materials in high yield through simple pyrolysis and post-processing operations. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing nitrogen-doped porous carbon materials using phenazine.

[0007] The technical solution adopted in this invention is: A method for preparing nitrogen-doped porous carbon materials using phenazine includes the following steps: Phenidine and ZnCl2 were mixed and pyrolyzed under a protective atmosphere. The pyrolysis products were then acid-washed, water-washed, and dried to obtain nitrogen-doped porous carbon materials.

[0008] Preferably, the mass ratio of phenazine to ZnCl2 is 1:0.1 to 10.

[0009] More preferably, the mass ratio of phenazine to ZnCl2 is 1:1 to 5.

[0010] Preferably, the mixing method is grinding or solvent-assisted mixing.

[0011] Preferably, the solvent used in the solvent-assisted mixing is at least one of water, ethanol, and methanol.

[0012] Preferably, the protective atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0013] Preferably, the flow rate of the protective atmosphere is 100 mL / min to 300 mL / min.

[0014] Preferably, the pyrolysis is carried out at a temperature of 400℃ to 1500℃ for a time of 0.5h to 5h.

[0015] More preferably, the pyrolysis is carried out at a temperature of 500℃ to 900℃ for a time of 1h to 3h.

[0016] Preferably, the acid solution used for pickling is at least one of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution.

[0017] Preferably, the concentration of the acid solution used for pickling is 0.1 mol / L to 3.0 mol / L.

[0018] More preferably, the concentration of the acid solution used for pickling is 0.5 mol / L to 2.0 mol / L.

[0019] Preferably, the water washing is performed using deionized water until the washing solution is neutral.

[0020] Preferably, the drying is carried out at a temperature of 60℃ to 120℃ for a drying time of 6h to 24h.

[0021] A nitrogen-doped porous carbon material is prepared by the above-described method.

[0022] Application of a nitrogen-doped porous carbon material as described above in the preparation of supercapacitors, lithium-ion batteries or sodium-ion batteries.

[0023] Application of a nitrogen-doped porous carbon material as described above in the preparation of carbon dioxide adsorbent materials, electrocatalytic materials or organic pollutant adsorbent materials.

[0024] The beneficial effects of this invention are as follows: This invention uses phenazine as a carbon and nitrogen source and ZnCl2 as an activator to prepare nitrogen-doped porous carbon materials. This preparation method has the advantages of clear raw material composition, simple operation, no need for additional nitrogen source, and high carbon material yield. The prepared porous carbon materials have nitrogen-doped structure and rich pore structure, and excellent electrochemical performance, making them suitable for large-scale industrial application in the field of electrochemical energy storage.

[0025] Specifically: 1) This invention uses phenazine as a carbon precursor. Phenazine has a stable fused-ring aromatic structure and endogenous nitrogen element, which is beneficial to the retention of carbon skeleton and nitrogen element doping during pyrolysis, thereby improving the yield and structural stability of porous carbon materials. 2) This invention uses ZnCl2 as an activator. ZnCl2 can promote the carbonization of precursors and regulate the pore structure during pyrolysis. The activation process is relatively mild, which is beneficial to obtaining carbon materials with ultra-high yield, nitrogen-doped structure and porous structure. 3) The nitrogen-doped porous carbon material prepared by this invention can be used as a supercapacitor electrode material, with high specific capacity, good rate performance and cycle stability, and high practical application value. Attached Figure Description

[0026] Figure 1 TG-DTG curves for phenazine, ZnCl2, and a mixture of phenazine and ZnCl2.

[0027] Figure 2 The images show the XRD patterns of the doped porous carbon materials in Examples 3, 5, 6 and 7.

[0028] Figure 3 The nitrogen adsorption-desorption isotherms of the doped porous carbon materials in Examples 3, 5, 6 and 7 are shown.

[0029] Figure 4 The figures show the pore size distribution curves of the doped porous carbon materials in Examples 3, 5, 6 and 7.

[0030] Figure 5 The N 1s X-ray photoelectron spectroscopy peak diagrams of the doped porous carbon materials in Examples 3, 5, 6 and 7 are shown.

[0031] Figure 6 The cyclic voltammetry curves are for the electrodes in Examples 1-7 and Comparative Examples 2-3.

[0032] Figure 7 The constant current charge-discharge curves of the electrodes in Examples 1-7 and Comparative Examples 2-3 are shown.

[0033] Figure 8 The specific capacity-current density relationship curves are for the electrodes in Examples 1-7 and Comparative Examples 2-3.

[0034] Figure 9 The electrochemical impedance spectroscopy curves of the electrodes in Examples 1-7 and Comparative Examples 2-3 are shown. Detailed Implementation

[0035] The present invention will be further explained and described below with reference to specific embodiments.

[0036] Example 1: A nitrogen-doped porous carbon material is prepared by the following method: Phenidine and ZnCl2 were stirred and dispersed in an appropriate amount of anhydrous ethanol at a mass ratio of 1:1. The resulting slurry mixture was then placed in an alumina crucible and then placed in a tube furnace. Nitrogen gas was introduced at a flow rate of 200 mL / min and maintained at room temperature for 1 h (to purge the air from the tube furnace). The temperature was then increased from room temperature to 400 °C at a rate of 1 °C / min, and then further increased to 700 °C at a rate of 5 °C / min. The temperature was held for 2 h and then allowed to cool naturally to room temperature. The pyrolysis product was then washed with a 1 mol / L hydrochloric acid solution and then washed with deionized water until the washings were neutral. The product was then dried in a constant temperature drying oven at 80 °C for 10 h and allowed to cool naturally to room temperature to obtain nitrogen-doped porous carbon material.

[0037] An electrode is prepared as follows: The nitrogen-doped porous carbon material, conductive carbon black, and polytetrafluoroethylene in this embodiment are mixed evenly in a mass ratio of 8:1:1. An appropriate amount of ethanol is then added to prepare an electrode material slurry. The electrode material slurry is then coated onto a nickel mesh current collector with a coating area of ​​1cm×1cm. The coating is then placed in a constant temperature drying oven and dried at 80°C for 4 hours. Finally, it is compacted under a pressure of 20MPa for 5 minutes to obtain the electrode.

[0038] Example 2: A nitrogen-doped porous carbon material is identical to that in Example 1, except that the mass ratio of phenazine to ZnCl2 is adjusted from "1:1" to "1:2" during preparation.

[0039] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this embodiment.

[0040] Example 3: A nitrogen-doped porous carbon material is identical to that in Example 1, except that the mass ratio of phenazine and ZnCl2 is adjusted from "1:1" to "1:3" during preparation.

[0041] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this embodiment.

[0042] Example 4: A nitrogen-doped porous carbon material is identical to that in Example 1, except that the mass ratio of phenazine to ZnCl2 is adjusted from "1:1" to "1:4" during preparation.

[0043] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this embodiment.

[0044] Example 5: A nitrogen-doped porous carbon material is identical to Example 1 except that the process of preparation is changed from "continuing to heat to 700°C at a heating rate of 5°C / min" to "continuing to heat to 500°C at a heating rate of 5°C / min" and the mass ratio of phenazine to ZnCl2 is changed from "1:1" to "1:3".

[0045] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this embodiment.

[0046] Example 6: A nitrogen-doped porous carbon material is identical to Example 1 except that the process of preparation is changed from "continuing to heat to 700°C at a heating rate of 5°C / min" to "continuing to heat to 600°C at a heating rate of 5°C / min" and the mass ratio of phenazine to ZnCl2 is changed from "1:1" to "1:3".

[0047] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this embodiment.

[0048] Example 7: A nitrogen-doped porous carbon material is identical to Example 1 except that the process of preparation is changed from "continuing to heat to 700°C at a heating rate of 5°C / min" to "continuing to heat to 800°C at a heating rate of 5°C / min" and the mass ratio of phenazine and ZnCl2 is changed from "1:1" to "1:3".

[0049] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this embodiment.

[0050] Example 8: A nitrogen-doped porous carbon material is identical to Example 1 except that the preparation process is modified from "heating from room temperature to 400°C at a heating rate of 1°C / min, then heating to 700°C at a heating rate of 5°C / min, and holding for 2 hours" to "heating from room temperature to 400°C at a heating rate of 1°C / min, and holding for 2 hours" and the mass ratio of phenazine to ZnCl2 is changed from "1:1" to "1:3".

[0051] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this embodiment.

[0052] Example 9: A nitrogen-doped porous carbon material is identical to that in Example 1, except that the mass ratio of phenazine to ZnCl2 is adjusted from "1:1" to "1:10" during preparation.

[0053] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this embodiment.

[0054] Comparative Example 1 (no activator used, direct pyrolysis): A nitrogen-doped porous carbon material is prepared by the following method: After phenazine was placed in a corundum crucible and then placed in a tube furnace, nitrogen gas was introduced at a flow rate of 200 mL / min and kept at room temperature for 1 hour (to purge the air from the tube furnace). The temperature was then increased from room temperature to 700°C at a rate of 5°C / min and held for 2 hours. The mixture was then allowed to cool naturally to room temperature. The pyrolysis product was washed with 1 mol / L hydrochloric acid and then with deionized water until the washings were neutral. The mixture was then placed in a constant temperature drying oven and dried at 80°C for 10 hours. After cooling naturally to room temperature, nitrogen-doped porous carbon material was obtained.

[0055] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this comparative example.

[0056] Comparative Example 2 (activator is FeCl3): A nitrogen-doped porous carbon material is identical to that in Example 3, except that "ZnCl2" is replaced by "FeCl3" by weight during preparation.

[0057] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this comparative example.

[0058] Comparative Example 3 (activator is H3PO4): A nitrogen-doped porous carbon material is identical to that in Example 3, except that "ZnCl2" is replaced by "H3PO4" by weight during preparation.

[0059] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this comparative example.

[0060] Comparative Example 4 (precursor is indigo): A nitrogen-doped porous carbon material is identical to Example 3 except that "phenazine" is replaced by "indigo" by weight during preparation and "continue heating to 700°C at a heating rate of 5°C / min" is changed to "continue heating to 600°C at a heating rate of 5°C / min".

[0061] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this comparative example.

[0062] Comparative Example 5 (precursor is 1,10-phenanthroline): A nitrogen-doped porous carbon material is identical to that in Example 3, except that the "phenazine" is replaced by "1,10-phenanthroline" by weight during preparation.

[0063] An electrode is identical to the electrode in Example 1, except that it uses the nitrogen-doped porous carbon material of this comparative example.

[0064] Performance testing: 1) Thermogravimetric analysis: Thermogravimetric analysis was performed on phenazine, ZnCl2, and a mixture of phenazine and ZnCl2 (the mass ratio of phenazine to ZnCl2 was 1:3). The obtained TG-DTG curves are shown below. Figure 1 As shown.

[0065] Depend on Figure 1 It can be seen that: phenazine exhibits a significant weight loss peak near 267℃, indicating that phenazine undergoes rapid thermal decomposition or volatilization; ZnCl2 undergoes significant mass changes in a higher temperature range, with its main weight loss peak appearing near 612℃; in contrast, the thermal weight loss process of the phenazine-ZnCl2 mixture changes significantly, exhibiting multiple weight loss stages near 98℃, 173℃, 250℃, and 562℃, indicating that the addition of ZnCl2 alters the pyrolysis behavior of phenazine and participates in the carbonization and activation processes; the phenazine-ZnCl2 mixture retains a certain residual mass after pyrolysis, indicating that ZnCl2 can promote the formation of a stable carbon skeleton by phenazine, thereby improving the yield of carbon materials.

[0066] 2) X-ray diffraction test: The crystal structure of the nitrogen-doped porous carbon materials in Examples 3, 5, 6, and 7 was tested using an X-ray diffractometer. The obtained X-ray diffraction (XRD) patterns are shown below. Figure 2 As shown.

[0067] Depend on Figure 2 It can be seen that the nitrogen-doped porous carbon materials in Examples 3, 5, 6 and 7 all show relatively broad diffraction peaks at approximately 25° to 28° of 2θ, corresponding to the (002) crystal plane of the carbon material, and relatively weak broad peaks at approximately 43° to 45° of 2θ, corresponding to the (100) crystal plane of the carbon material. This indicates that the nitrogen-doped porous carbon materials prepared are mainly amorphous carbon structures and have certain graphite microcrystal characteristics. At the same time, no obvious characteristic peaks of ZnCl2 or other inorganic salt impurities appear in the spectra, indicating that acid washing and water washing of the pyrolysis products can effectively remove inorganic residues, and the purity of the nitrogen-doped porous carbon materials prepared is high.

[0068] 3) Nitrogen adsorption-desorption test: The pore structure of the nitrogen-doped porous carbon materials in Examples 3, 5, 6, and 7 was analyzed using the nitrogen adsorption-desorption test. The obtained nitrogen adsorption-desorption isotherm curves are shown below. Figure 3 As shown, the pore size distribution curve is as follows: Figure 4 As shown, the hole structure parameters are shown in the table below: Table 1. Pore structure parameters of nitrogen-doped porous carbon materials obtained at different pyrolysis temperatures.

[0069] Depend on Figure 3 As shown in Table 1: a) The adsorption capacity of the nitrogen-doped porous carbon materials in Examples 3, 5, 6, and 7 all increased significantly in the low relative pressure region, indicating the presence of microporous structures in the materials; the adsorption capacity of the nitrogen-doped porous carbon materials in Examples 3, 5, 6, and 7 continued to increase in the medium / high relative pressure region, indicating the presence of certain mesoporous structures in the materials; in summary, the nitrogen-doped porous carbon materials prepared by this invention have a hierarchical porous structure with both micropores and mesopores. b) The specific surface areas of the nitrogen-doped porous carbon materials in Examples 5, 6, 3, and 7 were 1374.92 m², respectively. 2 / g, 1049.45m 2 / g、742.40m 2 / g and 559.93m 2 / g, with a total pore volume of 0.76cm³. 3 / g, 0.53cm 3 / g, 0.69cm 3 / g and 0.32cm 3 / g, as the pyrolysis temperature increases from 500℃ to 800℃, the specific surface area of ​​nitrogen-doped porous carbon materials generally shows a decreasing trend, indicating that higher pyrolysis temperatures may cause some pore structures to shrink or collapse.

[0070] Depend on Figure 4 It can be seen that the pore size of the nitrogen-doped porous carbon materials in Examples 5, 6, 3 and 7 is mainly distributed in the micropore region below 2 nm, while there is also a certain mesopore distribution in the range of 2 nm to 10 nm. This indicates that the nitrogen-doped porous carbon materials prepared by the present invention have a micropore-mesopore composite pore structure (micropores can provide more charge adsorption sites, which is beneficial to improving the specific capacity of the material; mesopores can shorten the electrolyte ion diffusion path, which is beneficial to improving the rate performance).

[0071] 4) Elemental Analysis and X-ray Photoelectron Spectroscopy (XPS): The elemental composition of the nitrogen-doped porous carbon materials in Examples 3, 5, 6, and 7 was determined using an elemental analyzer. The surface elemental composition and nitrogen-doped structure of the nitrogen-doped porous carbon materials in Examples 3, 5, 6, and 7 were analyzed using XPS. The N 1s spectra were then processed for peak separation. The obtained elemental composition and XPS analysis results are shown in the table below. The N 1s peak diagram is shown below. Figure 5 As shown: Table 2. Elemental composition and XPS analysis results of nitrogen-doped porous carbon materials obtained at different pyrolysis temperatures.

[0072] As shown in Table 2: a) The nitrogen content of the nitrogen-doped porous carbon materials in Examples 5, 6, 3 and 7 were 10.41 wt%, 9.97 wt%, 9.44 wt% and 7.17 wt%, respectively. As the pyrolysis temperature increased from 500℃ to 800℃, the nitrogen content in the materials decreased overall, indicating that high-temperature pyrolysis would lead to the removal of some nitrogen elements. b) The surface nitrogen content of the nitrogen-doped porous carbon materials in Examples 5, 6, 3 and 7 were 7.26 at%, 9.68 at%, 7.58 at% and 7.03 at%, respectively. The nitrogen-doped porous carbon material in Example 6 had the highest surface nitrogen content (9.68 at%), indicating that the pyrolysis condition of 600℃ is more conducive to maintaining a high surface nitrogen content.

[0073] Depend on Figure 5It can be seen that the N 1s spectra of the nitrogen-doped porous carbon materials in Examples 5, 6, 3 and 7 can all be separated into pyridine nitrogen, pyrrole nitrogen and graphitic nitrogen, indicating that the nitrogen element in the phenazine precursor can be partially retained and doped into the carbon skeleton during the pyrolysis process (pyridine nitrogen and pyrrole nitrogen are beneficial to improving the pseudocapacitive contribution and electrolyte wettability of the material, while graphitic nitrogen is beneficial to improving the electronic conductivity and structural stability of the material).

[0074] comprehensive Figures 2-5 As shown in Tables 1 and 2, the nitrogen-doped porous carbon material prepared by this invention possesses a typical carbon material structure, a microporous-mesoporous composite pore structure, and various nitrogen-doped structures. In Example 6, the nitrogen-doped porous carbon material prepared at 600℃ and a phenazine / ZnCl2 mass ratio of 1:3 achieved a yield of 98.3% and a specific surface area of ​​1049.45 m². 2 / g, with a surface nitrogen content of 9.68at%, exhibiting the best overall performance.

[0075] 5) Cyclic voltammetry test: Cyclic voltammetry tests were performed on the electrodes in Examples 1-7 and Comparative Examples 2-3 using a CHI660E electrochemical workstation (Shanghai Chenhua). The scan potential range was -1V to 0V, and the scan rate was 10mV / s. The obtained cyclic voltammetry curves are shown below. Figure 6 As shown (Note: Electrochemical performance was tested using a three-electrode system, with the prepared electrode as the working electrode, a platinum sheet as the counter electrode, an Hg / HgO electrode as the reference electrode, and a 6 mol / L KOH solution as the electrolyte. Cyclic voltammetry curves, constant current charge-discharge curves, rate performance, and cycle stability were tested).

[0076] Depend on Figure 6 It can be seen that the electrodes in Examples 1 to 7 all exhibit obvious capacitive responses, and the cyclic voltammetry curves have certain rectangular characteristics, indicating that the nitrogen-doped porous carbon materials prepared in Examples 1 to 7 have double-layer capacitance behavior, accompanied by a certain pseudocapacitive contribution.

[0077] 6) Constant current charge-discharge test: The electrodes in Examples 1-7 and Comparative Examples 2-3 were subjected to constant current charge-discharge tests using an electrochemical workstation (same as above). The charge-discharge potential range was -1V to 0V, and the current density was 1A / g. The obtained constant current charge-discharge curves are shown below. Figure 7 As shown.

[0078] Depend on Figure 7 It can be seen that the constant current charge-discharge curves of each electrode generally exhibit an approximately triangular characteristic, indicating that they have typical capacitive energy storage behavior (there are significant differences in the discharge time of each electrode; the longer the discharge time, the higher the specific capacity).

[0079] 7) Rate performance testing: The specific capacity changes of the electrodes in Examples 1-7 and Comparative Examples 2-3 under different current densities were tested using an electrochemical workstation (as above), and the specific capacity-current density relationship curves were obtained as follows. Figure 8 As shown.

[0080] Depend on Figure 8 It can be seen that as the current density increases, the specific capacity of each electrode decreases to varying degrees. This is because the electrolyte ion diffusion time is shortened under high current density, making it difficult to fully utilize some channels and active sites.

[0081] 8) Electrochemical impedance spectroscopy (EIS): Electrochemical impedance spectroscopy was performed on the electrodes in Examples 1-7 and Comparative Examples 2-3 using an electrochemical workstation (same as above). The frequency range was 0.1 Hz to 100,000 Hz, and the electrochemical impedance spectroscopy curves were obtained as follows: Figure 9 As shown.

[0082] Depend on Figure 9 It can be known that: a) The impedance spectra of each electrode consist of a semicircle in the high-frequency region and a slanted line in the low-frequency region, which is consistent with the typical electrochemical impedance characteristics of porous carbon electrode materials (the intercept of the high-frequency region with the real axis reflects the equivalent series resistance of the electrode system, the diameter of the semicircle reflects the charge transfer resistance, and the slanted line in the low-frequency region is related to the diffusion behavior of electrolyte ions in the pores). b) The electrodes in Examples 3, 6 and 7 exhibit a small impedance response in the high-frequency region, indicating that their charge transfer resistance is low, which is beneficial for electron transport and rapid charging and discharging.

[0083] The following table summarizes the yield and electrode performance of the nitrogen-doped porous carbon materials in Examples 1-9 and Comparative Examples 1-5: Table 3 Summary of Yield and Electrode Performance of Nitrogen-Doped Porous Carbon Materials

[0084] Note: The formula for calculating the yield of nitrogen-doped porous carbon material is as follows: Yield of nitrogen-doped porous carbon material (%) = m2 / m1 × 100%, where m1 is the weight of the precursor and m2 is the weight of the nitrogen-doped porous carbon material.

[0085] From Tables 1 and 3, we can see that: a) The nitrogen-doped porous carbon material in Example 6 has a high specific surface area, appropriate total pore volume, and abundant microporous structure, while also possessing a certain mesoporous structure. Therefore, the electrode in Example 6 exhibits the highest specific capacity (237.8 F / g) and good rate performance (64.4%). Although the nitrogen-doped porous carbon material in Example 5 has a well-developed pore structure, its average pore size is small and its rate performance is poor, indicating that its pores are not conducive to the rapid diffusion of electrolyte ions under high current density. The pore structure parameters of the nitrogen-doped porous carbon material in Example 7 are generally low, therefore the specific capacity and rate performance of the electrode in Example 7 are significantly reduced. b) Although the nitrogen-doped porous carbon material in Example 5 has the highest specific surface area of ​​1374.92 m², 2 / g and the highest total pore volume of 0.76cm³ 3 / g, but the electrode in Example 5 only achieved a rate performance of 5.4% at 10 A / g, indicating that an excessively high specific surface area does not necessarily correspond to excellent rate performance; the nitrogen-doped porous carbon material in Example 6 had a specific surface area of ​​1049.45 m². 2 / g, total pore volume is 0.53cm³ 3 / g, micropore volume is 0.27cm³ 3 The average pore size was 0.67 nm. The electrode in Example 6 achieved a specific capacity of 237.8 F / g at 1 A / g and a rate capability of 64.4% at 10 A / g, indicating that the porous structure formed by pyrolysis at 600℃ is more suitable for charge storage and ion transport. In Example 7, the specific surface area and total pore volume of the nitrogen-doped porous carbon material decreased to 559.93 m² / g. 2 / g and 0.32cm 3 / g, the electrode in Example 7 has a specific capacity of only 120.3 F / g at 1 A / g, indicating that excessively high pyrolysis temperature will reduce the effective pore structure of nitrogen-doped porous carbon materials, which is not conducive to improving electrochemical performance.

[0086] Depend on Figure 6 As shown in Table 3: a) At 700℃, as the mass ratio of phenazine to ZnCl2 increased from 1:1 to 1:4, the specific capacity of the electrode at 1A / g increased from 94.4F / g to 201.1F / g, indicating that appropriately increasing the amount of ZnCl2 is beneficial to improving the electrochemical energy storage performance of nitrogen-doped porous carbon materials. The cyclic voltammetry curves of the electrodes in Examples 3 and 4 have large enclosed areas, corresponding to specific capacities of 197.5F / g and 201.1F / g, respectively, indicating that they have high charge storage capacity. The cyclic voltammetry curve area of ​​the electrode in Example 6 is one of the largest, corresponding to a specific capacity of 237.8F / g at 1A / g, which is the highest among all examples, indicating that the nitrogen-doped porous carbon material prepared at 600℃ and a phenazine / ZnCl2 mass ratio of 1:3 has the best capacitive response. b) In Comparative Example 2, FeCl3 was used as the activator, and the yield of nitrogen-doped porous carbon material was only 22.5%, with a specific capacity of only 42.5 F / g at 1 A / g. Furthermore, the cyclic voltammetry curve of the electrode in Comparative Example 2 showed a significantly smaller enclosed area, indicating that FeCl3 was not conducive to obtaining high yield and high capacitance performance in this system. In Comparative Example 3, H3PO4 was used as the activator, and the yield of nitrogen-doped porous carbon material was only 36.3%, with a specific capacity of 167.1 F / g at 1 A / g. Although it had a certain capacitance response, its rate performance was only 2.4%, and its overall performance was significantly lower than that of the ZnCl2-activated system.

[0087] Depend on Figure 7 As shown in Table 3: a) The electrode in Example 6 had the longest discharge time, and its specific capacity reached 237.8 F / g at 1 A / g, which was significantly higher than that of the electrode in Example 1 (94.4 F / g), the electrode in Example 2 (160.5 F / g), the electrode in Example 3 (197.5 F / g), the electrode in Example 4 (201.1 F / g), the electrode in Example 5 (183.7 F / g), and the electrode in Example 7 (120.3 F / g). This indicates that the nitrogen-doped porous carbon material prepared under pyrolysis conditions at 600 °C has the best charge storage capacity. b) From the perspective of temperature effect, when the mass ratio of phenazine to ZnCl2 is fixed at 1:3, the specific capacities of the electrodes in Examples 5, 6, 3, and 7 are 183.7 F / g, 237.8 F / g, 197.5 F / g, and 120.3 F / g, respectively, corresponding to pyrolysis temperatures of 500℃, 600℃, 700℃, and 800℃. This indicates that pyrolysis temperature has a significant impact on electrode performance. The electrode has the highest specific capacity at a pyrolysis temperature of 600℃, while the specific capacity decreases significantly when the pyrolysis temperature is increased to 800℃, which may be related to the reduction of some nitrogen functional sites or changes in pore structure. c) The constant current charge-discharge performance of the electrodes in Comparative Examples 2 and 3 is significantly weaker than that of the optimal example. The specific capacity of the electrode in Comparative Example 2 is only 42.5 F / g, indicating that the charge storage capacity of the nitrogen-doped carbon material obtained by FeCl3 activation is poor. The specific capacity of the electrode in Comparative Example 3 is 167.1 F / g, which is lower than that of the electrodes in Examples 3 and 6, indicating that the overall capacitance performance of the H3PO4 activation system is not as good as that of the ZnCl2 activation system.

[0088] Depend on Figure 8 As shown in Table 3: a) At 700°C, the rate performance of the electrodes in Examples 1-4 were 49.8%, 69.8%, 70.4%, and 26.9%, respectively. In Example 3, when the mass ratio of phenazine to ZnCl2 was 1:3, the electrode exhibited a high specific capacity (197.5 F / g) and good rate performance (70.4%), indicating that the pore structure and ion transport performance were well-coordinated at this ratio. Although the electrode in Example 4 had a specific capacity of 201.1 F / g, its rate performance at 10 A / g was only 26.9%, indicating that excessive ZnCl2 might hinder the pore structure from being conducive to rapid ion transport. b) Regarding the effect of temperature, the rate performance of the electrodes in Examples 5, 6, 3, and 7 were 5.4%, 64.4%, 70.4%, and 16.6%, respectively. The electrode in Example 6 had the highest specific capacity at 1 A / g, at 237.8 F / g, and still maintained a capacity retention of 64.4% at 10 A / g. The electrode in Example 3 had the highest rate performance at 70.4%, and a specific capacity of 197.5 F / g. Therefore, 600℃~700℃ is a suitable pyrolysis temperature range. c) The rate performance of the electrode in Comparative Example 2 is 72.9%, but its specific capacity at 1 A / g is only 42.5 F / g, indicating that its capacity base is low and its actual energy storage capacity is limited; the electrode in Comparative Example 3 has a specific capacity of 167.1 F / g at 1 A / g, but its rate performance at 10 A / g is only 2.4%, indicating that the material obtained by H3PO4 activation suffers severe capacity decay at high current densities, which is not conducive to fast charge and discharge applications; Based on the combined specific capacity and rate performance, the electrodes in Example 6 and Example 3 exhibit superior overall electrochemical performance. Specifically, the electrode in Example 6 has the highest specific capacity, while the electrode in Example 3 has a higher rate retention rate.

[0089] Depend on Figure 9 As shown in Table 3: a) The electrode in Example 6 has the highest specific capacity of 237.8 F / g, while the electrode in Example 3 has a relatively high specific capacity of 197.5 F / g and the highest rate performance of 70.4%, indicating that lower impedance helps to improve the energy storage performance and rate performance of nitrogen-doped carbon materials; b) The electrode in Example 5 has a specific capacity of 183.7 F / g, but its rate performance is only 5.4%. Its impedance curve has a large semicircle, indicating that although the pyrolysis sample at 500℃ has a certain charge storage capacity, the charge transfer resistance and ion diffusion resistance are large, resulting in rapid capacity decay at high current density. The electrode in Example 4 has a specific capacity of 201.1 F / g, but its rate performance is only 26.9%, indicating that its pore structure or interface transport performance is not conducive to rapid charge and discharge. c) Although the rate retention rate of the electrode in Comparative Example 2 was 72.9%, its specific capacity was only 42.5 F / g, and the yield of nitrogen-doped porous carbon material was only 22.5%, indicating that the actual energy storage performance of the FeCl3 activation system was poor. The specific capacity of the electrode in Comparative Example 3 was 167.1 F / g, but its rate performance was only 2.4%, indicating that its electrode polarization was severe and ion transport was limited. According to the comprehensive impedance test data, the nitrogen-doped porous carbon material prepared by ZnCl2-activated phenazine has low impedance, high specific capacity and good rate performance under appropriate ratio and temperature.

[0090] In summary, the nitrogen-doped porous carbon material in Example 6 (600℃, phenazine to ZnCl2 mass ratio of 1:3) achieved a yield of 98.3%, and the electrode in Example 6 exhibited a specific capacity of 237.8 F / g at 1 A / g and a rate performance of 64.4% at 10 A / g, demonstrating the best overall performance. The nitrogen-doped porous carbon material in Example 3 (700℃, phenazine to ZnCl2 mass ratio of 1:3) achieved a yield of 92.8%, and the electrode in Example 3 had a specific capacity of 197.5 F / g and a rate performance of 70.4%, also exhibiting good overall performance. These results indicate that the phenazine-ZnCl2 system of this invention can achieve superior electrochemical performance while maintaining ultra-high yield, and the prepared nitrogen-doped porous carbon material is suitable as an electrode material for supercapacitors.

[0091] As can be seen from Tables 1-3: a) The phenazine / ZnCl2 mass ratio, pyrolysis temperature, type of activator, and precursor structure all affect the yield, pore structure, nitrogen doping content, and electrochemical performance of the obtained nitrogen-doped porous carbon material. (b) At 700℃, the yield of nitrogen-doped porous carbon materials remained above 92.8% when the phenazine / ZnCl2 mass ratio was 1:1 to 4, indicating that the phenazine-ZnCl2 system had good carbon framework retention ability within this range. As the amount of ZnCl2 increased, the specific capacity of the material generally improved. However, when the ZnCl2 content was too high, reaching 1:10, the yield of nitrogen-doped porous carbon materials decreased to 78.2%, and the rate performance was also lower than that of the sample with a phenazine / ZnCl2 mass ratio of 1:3. This indicates that excessive ZnCl2 would exacerbate carbon framework etching or affect pore structure matching, which is not conducive to the synergistic improvement of yield and rate performance. Therefore, a phenazine / ZnCl2 mass ratio of 1:1 to 4 is more suitable, among which the nitrogen-doped porous carbon materials obtained with a phenazine / ZnCl2 mass ratio of 1:3 have better overall performance. c) When the phenazine / ZnCl2 mass ratio is fixed at 1:3, the pyrolysis temperature has a significant effect on the structure and properties of nitrogen-doped porous carbon materials. The nitrogen-doped porous carbon materials obtained in the range of 500℃ to 800℃ all have certain pore structures and nitrogen-doped structures. Among them, the nitrogen-doped porous carbon materials prepared at 600℃ have the best comprehensive performance. Although the yield of nitrogen-doped porous carbon materials is high at a low temperature of 400℃, the rate performance is poor, indicating that the carbonization degree of the material is insufficient at too low a temperature, making it difficult to form an effective structure that is conducive to rapid charge storage and ion transport. d) Compared with direct pyrolysis, FeCl3 activation and H3PO4 activation, the ZnCl2-activated phenazine system shows better overall advantages in terms of yield and electrochemical performance, indicating that ZnCl2 and the phenazine pyrolysis process have good matching. Furthermore, when indigo and 1,10-phenanthroline are used as precursors, the yield or electrochemical performance of the obtained nitrogen-doped porous carbon materials is lower than that of the phenazine system, indicating that the effect of the present invention is not simply determined by the elemental composition of nitrogen-containing aromatic small molecules, but is related to the specific molecular structure of phenazine and its carbonization behavior under the action of ZnCl2. e) Combining the results of pore structure and elemental composition, it can be seen that the nitrogen-doped porous carbon material obtained at the appropriate pyrolysis temperature can have both a rich pore structure and a high surface nitrogen content, which is beneficial to electrolyte wetting, charge storage and ion transport. In summary, this invention uses phenazine as the carbon and nitrogen source and ZnCl2 as the activator to obtain porous carbon materials with nitrogen-doped structures and good electrochemical performance at ultra-high yields.

[0092] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing nitrogen-doped porous carbon materials using phenazine, characterized in that, Includes the following steps: Phenidine and ZnCl2 were mixed and pyrolyzed under a protective atmosphere. The pyrolysis products were then acid-washed, water-washed, and dried to obtain nitrogen-doped porous carbon materials.

2. The method for preparing nitrogen-doped porous carbon materials using phenazine according to claim 1, characterized in that: The mass ratio of phenazine to ZnCl2 is 1:0.1 to 10.

3. The method for preparing nitrogen-doped porous carbon materials using phenazine according to claim 1 or 2, characterized in that: The protective atmosphere is a nitrogen atmosphere or an argon atmosphere.

4. The method for preparing nitrogen-doped porous carbon materials using phenazine according to claim 1 or 2, characterized in that: The pyrolysis is carried out at a temperature of 400℃ to 1500℃ for a time of 0.5h to 5h.

5. The method for preparing nitrogen-doped porous carbon materials using phenazine according to claim 1 or 2, characterized in that: The acid solution used for pickling is at least one of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution.

6. The method for preparing nitrogen-doped porous carbon materials using phenazine according to claim 1 or 2, characterized in that: The concentration of the acid solution used in the pickling process is 0.1 mol / L to 3.0 mol / L.

7. The method for preparing nitrogen-doped porous carbon materials using phenazine according to claim 1 or 2, characterized in that: The drying is carried out at a temperature of 60℃ to 120℃ for a time of 6h to 24h.

8. A nitrogen-doped porous carbon material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 7.

9. The application of the nitrogen-doped porous carbon material as described in claim 8 in the preparation of supercapacitors, lithium-ion batteries or sodium-ion batteries.

10. The application of the nitrogen-doped porous carbon material as described in claim 8 in the preparation of carbon dioxide adsorbent materials, electrocatalytic materials or organic pollutant adsorbent materials.

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