Nitrogen-doped carbon electrode material and preparation method and application thereof
By preparing nitrogen-doped porous carbon materials with exposed high active sites, the problems of high cost of precious metal catalysts and limited electrode performance in zinc-air batteries and capacitor desalination devices have been solved, realizing the application of low-cost and high-performance electrode materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-03-27
AI Technical Summary
Existing zinc-air battery cathodes rely on expensive precious metal catalysts, while commercially available activated carbon electrodes have limited specific capacitance and slow ion transport kinetics, thus limiting the performance of zinc-air batteries and capacitor desalination devices.
A precursor was constructed by hypercrosslinking polymerization of nitrogen-containing aromatic monomers, and combined with specific molten salt-assisted pyrolysis to control the pore structure and nitrogen doping type of the material, thus preparing nitrogen-doped porous carbon materials with exposed active sites.
The prepared nitrogen-doped carbon electrode material exhibits excellent oxygen reduction catalytic activity and high ion adsorption capacity in zinc-air batteries, reducing costs and improving performance, and is suitable for ion adsorption in capacitor desalination devices.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of electrochemical functional materials, and particularly relates to a nitrogen-doped carbon electrode material for a zinc-air battery and a capacitive desalination device, a preparation method thereof and application thereof. BACKGROUND
[0002] The zinc-air battery has broad prospects in new energy storage systems due to its high theoretical energy density, good safety and environmental friendliness. The capacitive desalination technology has become an important method for seawater desalination and brackish water treatment due to its low energy consumption and simple operation. However, the performance of the two is largely limited by the catalytic activity and ion adsorption capacity of the electrode material. At present, the cathode of the zinc-air battery generally relies on a noble metal platinum-based catalyst, which is high in cost. The commercial activated carbon electrode for capacitive desalination has limited specific capacitance and slow ion transport kinetics.
[0003] In recent years, nitrogen-doped carbon materials have been considered as a candidate material for replacing noble metals due to their adjustable electronic structure, rich defect sites and good electrical conductivity. However, traditional nitrogen-doped carbon materials often face challenges such as low active site utilization rate and difficulty in microenvironment regulation, which makes it difficult for them to meet the actual application requirements. Therefore, it is of great significance to develop a nitrogen-doped carbon material that can maximize the utilization rate of active sites, has excellent oxygen reduction catalytic performance and high ion adsorption capacity, and promote the development of zinc-air batteries and capacitive desalination technology. SUMMARY
[0004] The application aims to overcome the shortcomings of the prior art, provide a nitrogen-doped carbon electrode material with high active site utilization rate and excellent comprehensive performance, a simple and controllable preparation method thereof, and expand its application in zinc-air batteries and capacitive desalination devices. The preparation method provided by the application has simple process, easily available raw materials and good repeatability. The nitrogen-doped carbon electrode material prepared by the method has excellent electrocatalytic activity and ion adsorption capacity, and can be used as a high-performance and low-cost zinc-air battery catalyst and a capacitive desalination electrode material. It has broad industrial application prospects in the field of renewable energy storage and water resource purification.
[0005] To achieve the above-mentioned purposes, the application adopts the following technical solutions:
[0006] A preparation method of a nitrogen-doped carbon electrode material, which constructs a precursor through hypercrosslinked polymerization of a nitrogen-containing aromatic monomer, and then realizes the synergistic regulation of the pore structure, nitrogen-doping type and active site microenvironment of the material through specific molten salt assisted pyrolysis, and finally obtains a nitrogen-doped porous carbon material with high electrochemical active surface area and high active site exposure. The material can be directly used as a bifunctional air electrode catalyst for a zinc-air battery, or as an adsorption electrode for a capacitive desalination device. BRIEF DESCRIPTION OF DRAWINGS
[0007] Figure 1 Scanning electron microscope image of NPC-Zn material prepared for Example 1;
[0008] Figure 2 Transmission electron microscope image of NPC-Zn material prepared for Example 1;
[0009] Figure 3 Nitrogen adsorption-desorption isotherm of material prepared for Example 1;
[0010] Figure 4 High-resolution N 1s XPS spectrum of NPC-Zn material prepared for Examples 1-4;
[0011] Figure 5 Linear sweep voltammetry curve of NPC-Zn material prepared for Example 1 in oxygen-saturated electrolyte;
[0012] Figure 6 Charge-discharge cycle curve of zinc-air battery assembled based on NPC-Zn;
[0013] Figure 7 Desalination performance curve of NPC-Zn capacitive desalination device under battery driving. DETAILED DESCRIPTION
[0014] The application will be further described in conjunction with the following examples, but the scope of protection of the application is not limited to these examples.
[0015] Example 1
[0016] (1) Preparation of the precursor: In a 250 mL reaction flask, 1.6 g of anhydrous ferric chloride was added as a catalyst, followed by 10 mL of 1,2-dichloroethane as a solvent and 2.7 mL of dimethoxymethane as a crosslinking agent. The mixture was placed in an ice water bath and magnetically stirred for 10 minutes. Separately, 1.17 g of indole monomer was dissolved in 10 mL of 1,2-dichloroethane and slowly added to the above mixture through a constant pressure dropping funnel. After the addition was completed, the ice bath stirring was continued for 20 minutes. Then the reaction system was transferred to an oil bath, first reacted at 45 °C for 5 hours, and then the temperature was raised to 80 °C for continued reaction for 19 hours. After the reaction was completed, it was naturally cooled to room temperature, and the solid product was collected by suction filtration and washed with 2 M hydrochloric acid solution in a Soxhlet extractor for 24 hours to completely remove the catalyst residue. Finally, the washed brown solid was placed in an 80 °C oven to dry overnight to obtain an indole-based hypercrosslinked polymer.
[0017] (2) Molten salt assisted pyrolysis: 500 mg of the dried polymer powder was dispersed in 40 mL of absolute ethanol. To this suspension, 2.5 g of anhydrous zinc chloride was added and sonicated for 30 minutes to ensure a homogenous mixture. The ethanol was then removed by evaporation under stirring in an 80 °C oil bath to obtain a homogenous solid mixture. This mixture was transferred to a corundum boat and placed in a tube furnace. The temperature was ramped to 400 °C at a rate of 5 °C / min under an argon atmosphere and the pre-carbonization was carried out for 3 hours. The temperature was then ramped to 800 °C at the same rate and the carbonization was completed at this temperature for 1 hour. After the furnace was allowed to cool to room temperature, the product was removed.
[0018] (3) Post-treatment: The carbonized product was again placed in a Soxhlet extractor and washed with 2 M hydrochloric acid solution for 24 hours to remove the metal species and impurities formed during the pyrolysis. Finally, the product was washed with deionized water until neutral and dried in a vacuum oven at 80 °C for 12 hours to obtain the final product as a black powder, denoted as NPC-Zn.
[0019] Example 2
[0020] (1) Precursor preparation: 0.67 g of pyrrole monomer was dissolved in 15 mL of chloroform. In another container, 2.0 g of anhydrous aluminum chloride catalyst was mixed with 5 mL of a chloroform solution of paraformaldehyde. Both were mixed under stirring in an ice bath and then the temperature was ramped to 60 °C for 12 hours. The subsequent washing and drying steps were the same as in Example 1 to obtain a pyrrole-based hypercrosslinked polymer.
[0021] (2) Molten salt assisted pyrolysis: 500 mg of the polymer was mixed with 5.0 g of sodium chloride by grinding. The pyrolysis procedure was the same as in Example 1, with a final pyrolysis temperature of 700 °C and a holding time of 2 hours.
[0022] (3) Post-treatment: The acid washing, water washing, and drying steps were the same as in Example 1 to obtain the product, denoted as NPC-Na.
[0023] Example 3
[0024] (1) Precursor preparation: 1.67 g of carbazole monomer was dissolved in 20 mL of nitrobenzene, and 1.2 g of anhydrous iron chloride and 3 mL of formaldehyde solution were added, and the reaction was carried out at 80 °C for 24 hours. The subsequent treatment obtained a carbazole-based hypercrosslinked polymer.
[0025] (2) Molten salt assisted pyrolysis: 500 mg of the polymer was mixed with 3.0 g of iron chloride. The temperature was ramped to 900 °C at a rate of 10 °C / min under nitrogen, and the holding time was 0.5 hours.
[0026] (3) Post-treatment: The steps were the same as in Example 1 to obtain the product, denoted as NPC-Fe.
[0027] Example 4
[0028] (1) Precursor preparation: 1.58 g of pyridine monomer was dissolved in 15 mL of nitrobenzene, and 1.0 g of anhydrous aluminum chloride catalyst and 3.0 mL of polyformaldehyde solution in nitrobenzene were added. The mixed system was stirred in an ice water bath for 30 minutes, then transferred to an oil bath and reacted at 50 °C for 8 hours, and then the temperature was raised to 75 °C and the reaction was continued for 16 hours. After the reaction was completed, the obtained solid product was cooled to room temperature, filtered, and washed with 1 M hydrochloric acid solution in a Soxhlet extractor for 24 hours to completely remove the catalyst. Finally, the product was dried in an 80 °C vacuum oven for 12 hours to obtain a pyridine-based hypercrosslinked polymer.
[0029] (2) Molten salt assisted pyrolysis: 400 mg of the above dried polymer powder was mixed with 4.0 g of potassium chloride in a mortar and ground well. The mixture was transferred to an alumina crucible and placed in a tube furnace. Under the atmosphere of continuously flowing high-purity nitrogen, the temperature was raised to 500 °C at a rate of 3 °C / min for pre-stabilization, then the temperature was continuously raised to 750 °C at the same rate, and the carbonization process was completed at this temperature for 2 hours. After the pyrolysis was completed, the product was taken out after the furnace temperature naturally decreased to room temperature.
[0030] (3) Post-treatment: The carbonized product was placed in a Soxhlet extractor and washed with 2 M hydrochloric acid solution for 36 hours to completely remove the residual potassium salt and soluble impurities. Then washed with a large amount of deionized water until the filtrate was neutral, and finally dried in a 85 °C vacuum drying oven for 24 hours to obtain a dark gray powder product, denoted as NPC-KCl.
[0031] Example 5
[0032] (1) Precursor preparation: 0.80 g of pyrrole monomer was dissolved in 20 mL of 1,2-dichloroethane. In another container, 1.5 g of anhydrous iron chloride catalyst was mixed with 5 mL of dimethoxymethane. The two solutions were mixed under ice bath conditions and stirred vigorously for 40 minutes. Then the ice bath was removed and the reaction system was heated to 40 °C for 6 hours, and then the temperature was raised to 65 °C and the reaction was continued for 18 hours. After the reaction was completed, the solid was collected by filtration and washed with 2 M hydrochloric acid and deionized water in a Soxhlet extractor for 48 hours. The washed product was dried in a 70 °C oven overnight to obtain a pyrrole-based hypercrosslinked polymer.
[0033] (2) Composite molten salt assisted pyrolysis: 600 mg of the above polymer was mixed with 2.0 g of zinc chloride and 2.0 g of sodium chloride by grinding together. The mixture was loaded into a quartz boat and placed in a tube furnace. Under argon protection, the temperature was raised to 850 °C at a rate of 8 °C / min, and the pyrolysis was completed at this final temperature for 1.5 hours.
[0034] (3) Post-treatment: After cooling, the pyrolysis product was refluxed with 3 M hot hydrochloric acid solution at 80 °C for 12 hours, and then washed with deionized water until neutral. The final product was dried under vacuum at 90 °C for 18 hours to obtain a black fluffy powder, denoted as NPC-Zn / Na.
[0035] Example 6
[0036] (1) Precursor preparation: 2.50 g of carbazole monomer was dispersed in 25 mL of chloroform. 2.2 g of anhydrous aluminum chloride catalyst and 8 mL of formaldehyde solution (37 wt%) were added. After stirring the mixture at room temperature for 2 hours, the temperature was raised to 60 °C and reacted for 30 hours. After the reaction was completed, the solid was separated by filtration and washed thoroughly with 1 M hydrochloric acid, ethanol and deionized water in sequence. The obtained polymer was dried in a vacuum oven at 75 °C for 24 hours to obtain the carbazole-based hypercrosslinked polymer.
[0037] (2) Molten salt-assisted medium-temperature pyrolysis: Take 450 mg of the above polymer and mix it evenly with 3.5 g of anhydrous ferric chloride powder. Place the mixture in a ceramic boat and heat it to 600 °C at a rate of 4 °C / min under a continuously flowing high-purity nitrogen atmosphere, and hold it at this temperature for 4 hours for carbonization.
[0038] (3) Post-treatment: The carbonized product was washed with 2 M hydrochloric acid solution in a Soxhlet extractor for 24 hours, followed by multiple washes with deionized water. Finally, it was dried in a vacuum environment at 80 °C for 12 hours to obtain a gray-black granular product, denoted as NPC-Fe-600.
[0039] Example 7: Performance Testing and Application Verification
[0040] The material obtained in Example 1 was characterized and its performance was tested.
[0041] (1) Material characterization: NPC-Zn has a plate-like morphology and a BET specific surface area as high as 1912 m². 2 / g, with a nitrogen content of 5.31wt%, of which the sum of pyridine nitrogen and graphitic nitrogen accounts for approximately 50%; its electrochemically active surface area is 1249.4 m². 2 / g.
[0042] (2) Electrocatalytic performance: In 0.1 M KOH electrolyte, the oxygen reduction half-wave potential of NPC-Zn was 0.859 V vs. RHE, and the kinetic current density was 102.64 mA cm⁻¹. -2 It outperforms commercial Pt / C catalysts and exhibits excellent methanol tolerance and long-term stability. Its oxygen evolution reaction occurs at 10 mA cm⁻¹. -2 The overpotential at the current density is 410 mV.
[0043] (3) Performance of zinc-air battery: The liquid zinc-air battery assembled with NPC-Zn as the air cathode has an open-circuit voltage of 1.443 V and a peak power density of 149.6 mW / cm³. -2 , at 5 mA cm -2 It can cycle stably for more than 240 hours at current density.
[0044] (4) Capacitive desalination performance: A symmetrical capacitive desalination unit was assembled using NPC-Zn as electrodes. The adsorption capacity of 500 mg / L NaCl solution reached 32.58 mg / g at a working voltage of 1.4 V. In particular, after the desalination device was directly driven by an NPC-Zn zinc-air battery for 6 hours, the desalination capacity was still maintained at 27.8 mg / g, showing excellent potential for practical application.
Claims
1. A method for preparing a nitrogen-doped carbon electrode material, characterized in that, Includes the following steps: (a) A nitrogen-containing aromatic monomer and a crosslinking agent are subjected to a hypercrosslinking polymerization reaction in an organic solvent under the action of a catalyst to obtain a nitrogen-containing hypercrosslinked polymer; (b) The nitrogen-containing hypercrosslinked polymer is uniformly mixed with a molten salt and subjected to programmed temperature pyrolysis under an inert atmosphere to obtain a nitrogen-doped porous carbon material; (c) The pyrolysis product is acid-washed, filtered, and dried to obtain the nitrogen-doped carbon electrode material.
2. The preparation method according to claim 1, characterized in that, The nitrogen-containing aromatic monomer is one of pyrrole, pyridine, indole, or carbazole.
3. The preparation method according to claim 1, characterized in that, The crosslinking agent is dimethoxymethane, formaldehyde, or paraformaldehyde; the catalyst is anhydrous ferric chloride or anhydrous aluminum chloride; and the organic solvent is dichloroethane, chloroform, or nitrobenzene.
4. The preparation method according to claim 1, characterized in that, The polymerization reaction is initiated and stirred for 10 to 30 minutes under ice bath conditions, followed by reaction at a temperature range of 45 °C to 80 °C for 5 to 24 hours.
5. The preparation method according to claim 1, characterized in that, The molten salt is selected from one or more of zinc chloride, sodium chloride, potassium chloride, or ferric chloride; the mass ratio of the molten salt to the nitrogen-containing hypercrosslinked polymer is 1:1 to 10:
1.
6. The preparation method according to claim 1, characterized in that, The pyrolysis process is carried out under an argon or nitrogen atmosphere, with the temperature increased from room temperature to 400 to 900 ℃ at a rate of 2 ℃ / min to 10 ℃ / min, and held at the target temperature for 0.5 to 5 hours.
7. The preparation method according to claim 1, characterized in that, The acid washing is performed by continuously washing in a Soxhlet extractor with an aqueous hydrochloric acid solution of 1 M to 3 M concentration for 12 to 48 hours; the drying is performed by drying in a vacuum oven at 60 °C to 100 °C for 6 to 24 hours.
8. A nitrogen-doped carbon electrode material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The specific surface area of the material is 500 m². 2 / g to 2500 m 2 / g, with nitrogen doping levels ranging from 1 wt% to 12 wt%.
9. A zinc-air battery, characterized in that, Its air electrode contains the nitrogen-doped carbon electrode material as described in claim 8 as a bifunctional catalyst for oxygen reduction reaction and oxygen evolution reaction.
10. A capacitor desalination device, characterized in that, Its electrodes comprise the nitrogen-doped carbon electrode material as described in claim 8.