Method for preparing nitrogen, phosphorus doped porous carbon used in zinc ion supercapacitor

Abstract

The application relates to a preparation method of nitrogen and phosphorus doped porous carbon used as an electroactive material in a zinc ion supercapacitor. The method comprises the following steps: (1) preparing a nitrogen and phosphorus dopant; (2) preparing an activator; (3) preparing a carbon material precursor; (4) carbonizing and cleaning the precursor: under a nitrogen atmosphere, the precursor is carbonized at 700 DEG C-900 DEG C for 2 hours, after being reduced to room temperature, the carbonized precursor is washed with water until neutral, and nitrogen and phosphorus doped porous carbon material is obtained. The nitrogen and phosphorus doped porous carbon material prepared in the application has a high specific surface area and a good pore size distribution. The zinc ion supercapacitor prepared by using the nitrogen and phosphorus doped porous carbon material prepared in the application as an electrode active material shows extremely high capacitance and energy density. The application provides a method for solving the problem that the actual capacitance and energy density of the current zinc ion supercapacitor are low.

Description

Technical Field

[0001] This invention relates to a method for preparing nitrogen- and phosphorus-doped porous carbon, and more particularly to a method for preparing nitrogen- and phosphorus-doped porous carbon that can be used as an electroactive material in zinc-ion supercapacitors. Background Technology

[0002] Supercapacitors are a new type of energy storage device with advantages such as good safety performance, fast charging and discharging speed, high power density, long cycle life, and environmental friendliness. They are widely used in machinery, power, electronics, and automotive fields. Supercapacitors are mainly classified into double-layer supercapacitors and pseudocapacitive supercapacitors based on their energy storage mechanisms. Zinc-ion supercapacitors are a novel type of supercapacitor that combines the electrochemical characteristics of zinc-ion batteries and supercapacitors. Currently, zinc-ion supercapacitors are considered a promising new energy storage device due to their high theoretical energy density and power density, low cost, and good safety. However, research on zinc-ion supercapacitors is still in its early stages, and the main obstacle to their application is their relatively low actual capacity and energy density. Improving capacity and energy density to enhance the overall performance of zinc-ion supercapacitors is a crucial task that urgently needs to be addressed.

[0003] In zinc-ion supercapacitors, the electrode active material is crucial for improving the capacitor's capacitance. Typically, electrode active materials need to possess a large specific surface area, suitable pore size distribution, and excellent conductivity. Porous carbon materials have advantages such as large specific surface area, well-developed pore structure, high conductivity, and stable chemical properties, and have been widely used in electrochemical energy storage. Waste materials such as rice husks and coconut shells can be used as raw materials for producing carbon materials. However, doping methods are also used to improve the performance of carbon materials. By using dopants, elements such as nitrogen, phosphorus, sulfur, and boron are introduced into carbon materials, thereby improving their performance and increasing the capacitor's capacitance. Although a great deal of work has been done on electrode active materials for zinc-ion supercapacitors, developing novel electrode active materials to maximize the capacitance and energy density of zinc-ion supercapacitors, thus addressing the problem of their relatively low actual capacitance and energy density, remains a crucial issue that must be resolved in the development of zinc-ion supercapacitors. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a method for preparing nitrogen and phosphorus-doped porous carbon for use in zinc-ion supercapacitors. The purpose is to prepare nitrogen and phosphorus-doped porous carbon materials using PET (polyethylene terephthalate) material.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing nitrogen- and phosphorus-doped porous carbon for use in zinc-ion supercapacitors, comprising the following steps:

[0006] (1) Preparation of nitrogen and phosphorus dopants: Melamine is added to glacial acetic acid and stirred at 100℃-120℃ for 1 hour. Then phosphoric acid is slowly added and stirred at the same temperature for 1 hour. The product after reaction is spray-dried to collect nitrogen and phosphorus dopants.

[0007] (2) Preparation of activator: Mix potassium citrate with water, and after the potassium citrate dissolves, use spray drying to collect the activator;

[0008] (3) Preparation of carbon material precursor: PET material is added to a mixer and stirred and melted at 260℃-270℃. Then, activator and nitrogen and phosphorus dopants are added in sequence and stirred for 5 minutes to obtain carbon material precursor.

[0009] (4) Carbonization and cleaning of precursor: The precursor is carbonized at 700℃-900℃ for 2 hours under nitrogen atmosphere. After cooling to room temperature, the carbonized precursor is washed with water until neutral to obtain nitrogen and phosphorus doped porous carbon material.

[0010] In step (1), the ratio of phosphoric acid, melamine and glacial acetic acid is 1 part: 1-5 parts: 8-60 parts.

[0011] The phosphoric acid contained therein is phosphoric acid, polyphosphoric acid, or phytic acid.

[0012] In step (2), the ratio of potassium citrate to water is (1-3) parts: 10 parts.

[0013] In step (4), the ratio of PET material, activator and nitrogen and phosphorus dopants is 1 part: 4 parts: (0.5-1.5) parts.

[0014] The carbonization temperature in step (4) is 790-810℃.

[0015] The ratio of phosphoric acid, melamine, and glacial acetic acid is 1 part: 3 parts: 20-40 parts.

[0016] The ratio of the PET material, activator, and nitrogen and phosphorus dopants is 1 part: 4 parts: 1 part.

[0017] In step (3), the PET material is waste plastic bottle fragments or PET plastic.

[0018] The method for preparing the PET waste plastic bottle fragments is as follows: crush the PET waste plastic bottle, wash it three times with distilled water, and dry it to obtain PET waste plastic bottle fragments.

[0019] Advantages and effects of this invention: This invention provides a new approach to recycling waste plastic bottles, increasing their added value. The nitrogen- and phosphorus-doped porous carbon material prepared in this invention has a high specific surface area and good pore size distribution. Zinc-ion supercapacitors prepared using the nitrogen- and phosphorus-doped porous carbon material prepared in this invention as the electrode active material exhibit extremely high capacitance and energy density. This provides a method to solve the problem of low actual capacitance and energy density in current zinc-ion supercapacitors. Attached Figure Description

[0020] Figure 1 This is a SEM image of the porous carbon material 1 in Embodiment 1 of the present invention.

[0021] Figure 2 The surface elemental composition of porous carbon material 1 in Example 1 of this invention is determined by EDS.

[0022] Figure 3 The figures show the nitrogen adsorption / desorption isotherms and pore size distribution curves of the porous carbon material 1 in Example 1 of this invention.

[0023] Figure 4 The 20 mV / s of the zinc-ion supercapacitor 1 fabricated in Example 1 of this invention -1 Cyclic voltammetry curves at scan rate.

[0024] Figure 5 0.5A g of the zinc ion supercapacitor 1 prepared in Example 1 of this invention -1 Constant current charge-discharge curves at current density.

[0025] Figure 6 The cyclic voltammetry curves of the zinc-ion supercapacitor 1 prepared in Example 1 of this invention at different scan rates are shown.

[0026] Figure 7 The constant current charge-discharge curves of the zinc ion supercapacitor 1 prepared in Example 1 of the present invention under different current densities are shown.

[0027] Figure 8 This is the EIS image of the zinc ion supercapacitor 1 produced in Embodiment 1 of the present invention.

[0028] Figure 9 This is a comparison chart of the energy density and power density of the zinc-ion supercapacitor 1 fabricated in Example 1 of the present invention and some reported zinc-ion supercapacitors. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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. The number of parts in this embodiment refers to parts by weight.

[0030] Example 1

[0031] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0032] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0033] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0034] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0035] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 1.

[0036] 6. Preparation of Zinc-Ion Supercapacitor: Porous carbon material 1, conductive carbon black, and binder (5% polytetrafluoroethylene) are mixed at a predetermined mass ratio of 8:1:1; 8 ml of anhydrous ethanol is added to the mixture and stirred into a uniform slurry; the slurry is coated onto a graphite current collector; the coated graphite sheet is rolled and cut into 12 mm diameter discs, then dried in an oven at 80°C for 6 hours. A zinc-ion supercapacitor is assembled using a zinc sheet as the anode, glass fiber filter paper, zinc trifluoromethanesulfonate, and graphite discs as the separator, electrolyte, and cathode, respectively. The final product is zinc-ion supercapacitor 1.

[0037] from Figure 1 It can be seen that porous carbon material 1 has many pores at the microscopic level.

[0038] from Figure 2 It can be seen that the surface of porous carbon material 1 is mainly composed of carbon, nitrogen, oxygen and phosphorus elements.

[0039] from Figure 3 It can be seen that the specific surface area of ​​porous carbon material 1 can reach 2645 m². 2 g -1 It has a wide pore size distribution and a hierarchical pore structure. The volume of pores with a diameter of 0.8 nanometers accounts for 19.9% ​​of the total pore volume, which is beneficial for the transport of zinc ions and improves the capacitance of zinc ion supercapacitors.

[0040] from Figure 4 It can be seen that the cyclic voltammetry curve of zinc ion supercapacitor 1 has a rectangular shape, indicating that it has obvious double-layer capacitance behavior.

[0041] from Figure 5 It can be seen that the constant current charge-discharge curve of zinc-ion supercapacitor 1 has a shape similar to an isosceles triangle, indicating that it has good charge-discharge reversible behavior. Calculations show that zinc-ion supercapacitor 1 at 0.5 A g... -1 The specific capacitance at the current density is 466.2 F g. -1 The energy density is 233.7 Wh / kg. -1 .

[0042] from Figure 6 It can be seen that the zinc ion supercapacitor 1 maintains a rectangular shape at different scan rates, proving that it has good rate performance.

[0043] from Figure 7 It can be seen that the zinc ion supercapacitor 1 still maintains the shape of an isosceles triangle under different current densities, proving its good reversibility and capacity retention.

[0044] from Figure 8 It can be seen that the zinc ion supercapacitor 1 has a low charge transfer resistance, less than 14 ohms.

[0045] from Figure 9 It can be seen that the energy density and power density of zinc ion supercapacitor 1 are higher than those of the reported zinc ion supercapacitors.

[0046] The above results indicate that porous carbon material 1 is a nitrogen- and phosphorus-doped material with high specific surface area and abundant pore structure. The zinc-ion supercapacitor 1 prepared using it as the electrochemical active material exhibits high capacitance, energy density, and power density.

[0047] Figure 9 The references mentioned are as follows:

[0048] Reference 1: Y.Li, PFLu, P.Shang, LSWu, X.Wang, YFDong, et al., Pyridinicnitrogen enriched porous carbon derived from bimetal organic framework-sforhigh capacity zinc ion hybrid capacitors with remarkable rate capability,J.Energy.Chem.56(2021)404-411.https: / / doi.org / 10.1016 / j.jechem.2020.08.005.

[0049] Reference 2: CCJi,DDWu,ZBLiu,HYMi,YNLiao,MZWu,etal.,NaturalPolysaccharide Strengthened Hydrogel Electrolyte and Biopolymer DerivedCarbon for Durable Aqueous Zinc Ion Storage,Acs.Appl.Mater.Interfaces14(2022)23452-23464.https: / / doi.org / 10.1021 / acsami.2c03323.

[0050] Reference 3: P.Shang, M.Liu, YYMei, YHLiu, LSWu, YFDong, et al., U-rea-Mediated Monoliths Made of Nitrogen-Enriched Mesoporous Carbon Nanosheets for High-Performance Aqueous Zinc Ion Hybrid Capacitors, Small 18(2022)2108057. https: / / doi.org / 10.10 02 / smll.202108057.

[0051] Reference 4: KZShang, YJLiu, PWCai, KKLi, ZHWen, N, P, and S co-doped3D porous carbon architected cathode for high-performance Zn-ion hybridcapacitors, J.Mater.Chem.A 10(2022)6489.DOI:10.1039 / d2ta00202g.

[0052] Reference 5: KYWang, Y.Chen, YBLiu, H.Zhang, YXShen, ZYPu, et al., Plasma boosted N,P,O co-doped carbon microspheres for high performance Zn ionhybrid supercapacitors, J.Alloy.Compd.901(2022)163588.

[0053] https: / / doi.org / 10.1016 / j.jallcom.2021.163588.

[0054] Reference 6: J Li, L Yu, WTWang, 10(2022)9355.DOI:10.1039 / d1ta10677e.

[0055] Example 2

[0056] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 110°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0057] 2. Preparation of activator: Mix potassium citrate with water at a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0058] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0059] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0060] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 2.

[0061] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 2 was obtained by preparing porous carbon material 2 according to the zinc ion supercapacitor preparation method in Example 1.

[0062] Example 3

[0063] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 120°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0064] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0065] 3. Preparation of carbon material precursor: PET plastic is added to a mixer and stirred and melted at 260℃. Then, an activator and nitrogen and phosphorus dopants are added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste plastic bottle fragments, activator, and nitrogen and phosphorus dopants in the mixture is 1:4:1.

[0066] 4. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 3.

[0067] 5. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 3 was obtained by preparing porous carbon material 3 according to the preparation method of zinc ion supercapacitor in Example 1.

[0068] Example 4

[0069] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 120°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0070] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 2:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0071] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0072] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0073] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 4.

[0074] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 4 was obtained by preparing porous carbon material 4 according to the preparation method of zinc ion supercapacitor in Example 1.

[0075] Example 5

[0076] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, phosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, phosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0077] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0078] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0079] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0080] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 810℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 5.

[0081] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 5 was obtained by preparing porous carbon material 5 according to the preparation method of zinc ion supercapacitor in Example 1.

[0082] Example 6

[0083] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, phytic acid, and glacial acetic acid was 3:1:40. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0084] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0085] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0086] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 270°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0087] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 6.

[0088] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 6 was obtained by preparing porous carbon material 6 according to the zinc ion supercapacitor preparation method in Example 1.

[0089] Example 7

[0090] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0091] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0092] 3. Preparation of carbon material precursor: PET plastic was added to a mixer and stirred and melted at 265℃. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste plastic bottle fragments, activator, and nitrogen and phosphorus dopants in the mixture was 1:4:0.5.

[0093] 4. Carbonization and cleaning of the precursor: The precursor was carbonized at 790℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 7.

[0094] 5. Preparation of zinc ion supercapacitor: The porous carbon material 7 is prepared according to the preparation method of zinc ion supercapacitor in Example 1.

[0095] Example 8

[0096] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0097] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0098] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0099] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.5.

[0100] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 8.

[0101] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 8 was obtained by preparing porous carbon material 8 according to the preparation method of zinc ion supercapacitor in Example 1.

[0102] Comparative Example 1

[0103] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0104] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0105] 3. Preparation of carbon material precursor: PET plastic is added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants are added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste plastic bottle fragments, activator, and nitrogen and phosphorus dopants in the mixture is 1:4:0.1.

[0106] 4. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus doped porous carbon material, denoted as porous carbon material 9.

[0107] 5. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 9 was obtained by preparing porous carbon material 9 according to the preparation method of zinc ion supercapacitor in Example 1.

[0108] Comparative Example 2

[0109] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0110] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0111] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0112] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of the waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:2.

[0113] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 10.

[0114] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 10 was obtained by preparing porous carbon material 10 according to the preparation method of zinc ion supercapacitor in Example 1.

[0115] Table 1. Examples 1-8 and Comparative Examples 1 and 2 at a current density of 0.5 A g -1 Relevant electrochemical performance parameters measured at the time

[0116] name <![CDATA[Specific mass capacitance / F g -1 > <![CDATA[Energy density / Wh kg -1 <!-- 7 -->]]> Example 1 466.2 233.7 Example 2 454.1 227.7 Example 3 456.7 229 Example 4 459.6 230.4 Example 5 458.4 230 Example 6 463.1 232.2 Example 7 452.3 226.8 Example 8 458.5 230 Comparative Example 1 19.2 9.6 Comparative Example 2 168.5 84.5

[0117] Table 1 lists the zinc-ion supercapacitors prepared from porous carbon materials 1-10 obtained in Examples 1-8 and Comparative Examples 1 and 2 at a current density of 0.5 A g. -1 The specific capacitance and energy density at that time were measured, and the results showed that the porous carbon material 1 obtained according to the steps described in Example 1 had the best electrochemical performance, with a specific capacitance of 466.2 F / g. -1 The energy density is 233.7 Wh / kg. -1These parameters indicate that the amount of waste plastic bottles, activators, and nitrogen and phosphorus dopants added is a major factor affecting the electrochemical performance of porous carbon materials, especially when the ratio of the three is 1:4:

[0118] When the addition amount is (0.5~1.5), carbon materials with good electrochemical performance can be obtained. When the addition amount is higher or lower than this ratio, the electrochemical performance of the obtained porous carbon materials will decrease.

[0119] Example 9

[0120] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0121] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0122] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0123] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0124] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 700℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus doped porous carbon material, denoted as porous carbon material 11.

[0125] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 11 was obtained by preparing porous carbon material 11 according to the preparation method of zinc ion supercapacitor in Example 1.

[0126] Example 10

[0127] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0128] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0129] 3. Preparation of carbon material precursors.

[0130] PET plastic was added to a mixer and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain a carbon material precursor. The ratio of PET waste plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0131] 4. Carbonization and cleaning of the precursor: The precursor was carbonized at 900℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 12.

[0132] 5. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 12 was obtained by preparing porous carbon material 12 according to the preparation method of zinc ion supercapacitor in Example 1.

[0133] Comparative Example 3

[0134] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0135] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0136] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0137] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0138] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 600℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 13.

[0139] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 13 was obtained by preparing porous carbon material 13 according to the zinc ion supercapacitor preparation method in Example 1.

[0140] Comparative Example 4

[0141] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0142] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0143] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0144] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0145] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 1000℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 14.

[0146] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 14 was obtained by preparing porous carbon material 14 according to the preparation method of zinc ion supercapacitor in Example 1.

[0147] Table 2 shows the results of Examples 1, 9, 10 and Comparative Examples 3, 4 at a current density of 0.5 A g. -1 Electrochemical performance parameters measured at time

[0148] name <![CDATA[Specific mass capacitance / F g -1 > <![CDATA[Energy density / Wh kg -1 <!-- 9 -->]]> Example 1 466.2 233.7 Example 9 355.3 178.1 Example 10 344.7 172.8 Comparative Example 3 280.9 140.8 Comparative Example 4 234.7 117.7

[0149] Table 2 shows the electrochemical performance parameters of the zinc-ion supercapacitors prepared from porous carbon materials 1 and 11-14 obtained in Examples 1, 9, 10 and Comparative Examples 3 and 4. It is evident that the zinc-ion supercapacitors obtained in Examples 1, 9, and 10 exhibit high electrochemical performance, with Example 1 showing the highest specific capacitance of 466.2 F / g. -1 And energy density 233.7Wh kg -1 These parameters indicate that porous carbon materials with good electrochemical performance can be obtained when the carbonization temperature is between 700 and 900 °C, while the electrochemical performance of the porous carbon materials decreases when the carbonization temperature is higher or lower than this range.

[0150] Example 11

[0151] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:8. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0152] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0153] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0154] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0155] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus doped porous carbon material, denoted as porous carbon material 15.

[0156] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 15 was obtained by preparing porous carbon material 15 according to the zinc ion supercapacitor preparation method in Example 1.

[0157] Example 12

[0158] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:60. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0159] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0160] 3. Preparation of carbon material precursor: PET plastic is added to a mixer and stirred and melted at 260℃. Then, an activator and nitrogen and phosphorus dopants are added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste plastic bottle fragments, activator, and nitrogen and phosphorus dopants in the mixture is 1:4:1.

[0161] 4. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 16.

[0162] 5. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 16 was obtained by preparing porous carbon material 16 according to the zinc ion supercapacitor preparation method in Example 1.

[0163] Comparative Example 5

[0164] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:6. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0165] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0166] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0167] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0168] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 17.

[0169] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 17 was obtained by preparing porous carbon material 17 according to the zinc ion supercapacitor preparation method in Example 1.

[0170] Comparative Example 6

[0171] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:65. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0172] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0173] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0174] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0175] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 18.

[0176] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 18 was obtained by preparing porous carbon material 18 according to the zinc ion supercapacitor preparation method in Example 1.

[0177] Table 3. Electrochemical performance parameters of Examples 1, 11, 12 and Comparative Examples 5, 6 measured at a current density of 0.5 A g⁻¹.

[0178] name <![CDATA[Specific mass capacitance / F g -1 > <![CDATA[Energy density / Wh kg -1 > Example 1 466.2 233.7 Example 11 447.8 224.5 Example 12 453.6 228.8 Comparative Example 5 208.9 104.7 Comparative Example 6 231.1 115.9

[0179] Table 3 shows the electrochemical performance parameters of the supercapacitors prepared from the porous carbon materials 1, 15-18 obtained in Examples 1, 11, 12 and Comparative Examples 5, 6. The results show that the electrochemical performance of the porous carbon materials is higher when the amount of glacial acetic acid added is between 8 and 60 parts, while the electrochemical performance of the carbon materials is reduced when the amount of glacial acetic acid added is too much or too little.

[0180] Example 13

[0181] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 1:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0182] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0183] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0184] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0185] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 19.

[0186] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 19 was obtained by preparing porous carbon material 19 according to the preparation method of zinc ion supercapacitor in Example 1.

[0187] Example 14

[0188] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 5:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0189] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0190] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0191] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0192] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 20.

[0193] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 20 was obtained by preparing porous carbon material 20 according to the preparation method of zinc ion supercapacitor in Example 1.

[0194] Comparative Example 7

[0195] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 0.5:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0196] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0197] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0198] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0199] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 21.

[0200] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 21 was obtained by preparing porous carbon material 21 according to the preparation method of zinc ion supercapacitor in Example 1.

[0201] Comparative Example 8

[0202] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 6:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0203] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0204] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0205] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0206] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus doped porous carbon material, denoted as porous carbon material 22.

[0207] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 22 was obtained by preparing porous carbon material 22 according to the preparation method of zinc ion supercapacitor in Example 1.

[0208] Table 4 shows Examples 1, 13, 14 and Comparative Examples 7, 8 at a current density of 0.5 A g. -1 Electrochemical performance parameters measured at time

[0209] name <![CDATA[Specific mass capacitance / F g -1 > <![CDATA[Energy density / Wh kg -1 > Example 1 466.2 233.7 Example 13 457.4 229.3 Example 14 448.1 224.7 Comparative Example 7 222.3 111.5 Comparative Example 8 218.9 109.8

[0210] Table 4 shows the electrochemical performance parameters of zinc-ion supercapacitors prepared from porous carbon materials 1, 19-22 obtained in Examples 1, 13, 14 and Comparative Examples 7, 8. The results show that the porous carbon materials with better electrochemical performance are obtained when the ratio of melamine to polyphosphoric acid is between 1:1 and 5:1. Conversely, when the proportion of melamine is too high or too low, the electrochemical performance of the carbon materials will decrease.

[0211] Example 15

[0212] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0213] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 1:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0214] 3. Preparation of carbon material precursor: PET plastic is added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants are added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of PET plastic, activator, and nitrogen and phosphorus dopants is 1:4:1.

[0215] 4. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 23.

[0216] 5. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 23 was obtained by preparing porous carbon material 23 according to the preparation method of zinc ion supercapacitor in Example 1.

[0217] Comparative Example 9

[0218] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0219] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 5:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0220] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0221] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0222] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 24.

[0223] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 24 was obtained by preparing porous carbon material 24 according to the preparation method of zinc ion supercapacitor in Example 1.

[0224] Table 5. Electrochemical performance parameters of Examples 1, 15 and Comparative Example 9 measured at a current density of 0.5 A g⁻¹.

[0225] name <![CDATA[Specific mass capacitance / F g -1 > <![CDATA[Energy density / Wh kg -1 > Example 1 466.2 233.7 Example 15 384.7 192.9 Comparative Example 9 256.4 128.6

[0226] Table 5 shows the electrochemical performance parameters of zinc-ion supercapacitors prepared from porous carbon materials 1, 23, and 24 obtained in Examples 1, 15, and Comparative Example 9. The results show that the carbon materials obtained when the ratio of potassium citrate to water is 1:10 to 3:10 have better electrochemical performance, while the electrochemical performance of the carbon materials will decrease when the ratio of potassium citrate is too high.

[0227] Comparative Example 10

[0228] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0229] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0230] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0231] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of the waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:3:1.

[0232] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 25.

[0233] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 25 was obtained by preparing porous carbon material 25 according to the preparation method of zinc ion supercapacitor in Example 1.

[0234] Comparative Example 11

[0235] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0236] 2. Preparation of activator: Mix potassium citrate with water in a ratio of 3:10. After the potassium citrate dissolves, spray dry to collect the activator.

[0237] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0238] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:5:1.

[0239] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 26.

[0240] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 26 was obtained by preparing porous carbon material 26 according to the preparation method of zinc ion supercapacitor in Example 1.

[0241] Table 6. Examples 1 and Comparative Examples 10 and 11 at a current density of 0.5 A g -1 Electrochemical performance parameters measured at time

[0242] name <![CDATA[Specific mass capacitance / F g -1 > <![CDATA[Energy density / Wh kg -1 > Example 1 466.2 233.7 Comparative Example 10 198.7 99.6 Comparative Example 11 167.4 83.9

[0243] Table 6 shows the electrochemical performance parameters of zinc-ion supercapacitors prepared from porous carbon materials 1, 25, and 26 obtained in Example 1 and Comparative Examples 10 and 11. The results show that when the amount of activator added is 4 parts, the electrochemical performance of the obtained porous carbon material is better. Conversely, when the amount of activator added is too high or too low, the electrochemical performance of the carbon material will decrease.

[0244] Comparative Example 12

[0245] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0246] 2. Preparation of activator: Mix potassium oxalate with water in a ratio of 3:10. After the potassium oxalate dissolves, spray dry to collect the activator.

[0247] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0248] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0249] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus-doped porous carbon material, denoted as porous carbon material 27.

[0250] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 27 was obtained by preparing porous carbon material 27 according to the preparation method of zinc ion supercapacitor in Example 1.

[0251] Comparative Example 13

[0252] 1. Preparation of nitrogen and phosphorus dopants: Melamine was added to glacial acetic acid and stirred at 100°C for 1 hour. Then, polyphosphoric acid was slowly added, and stirring continued at the same temperature for 1 hour. The ratio of melamine, polyphosphoric acid, and glacial acetic acid was 3:1:20. The reaction product was spray-dried to collect the nitrogen and phosphorus dopants.

[0253] 2. Preparation of activator: Potassium hydroxide is crushed to 20 micrometers to obtain the activator.

[0254] 3. Preparation of PET waste plastic bottle fragments: Crush PET waste plastic bottles, wash them three times with distilled water, and dry them to obtain PET waste plastic bottle fragments.

[0255] 4. Preparation of carbon material precursor: Waste PET plastic bottle fragments were added to a mixer and stirred and melted at 260°C. Then, an activator and nitrogen and phosphorus dopants were added sequentially and stirred for 5 minutes to obtain the carbon material precursor. The ratio of waste PET plastic bottle fragments, activator, and nitrogen and phosphorus dopants was 1:4:1.

[0256] 5. Carbonization and cleaning of the precursor: The precursor was carbonized at 800℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus doped porous carbon material, denoted as porous carbon material 28.

[0257] 6. Preparation of zinc ion supercapacitor: Zinc ion supercapacitor 28 was obtained by preparing porous carbon material 28 according to the preparation method of zinc ion supercapacitor in Example 1.

[0258] Table 7. Examples 1 and 12, 13 at a current density of 0.5 A g -1 Electrochemical performance parameters measured at time

[0259] name <![CDATA[Specific mass capacitance / F g -1 > <![CDATA[Energy density / Wh kg -1 > Example 1 466.2 233.7 Comparative Example 12 243.1 121.9 Comparative Example 13 192.8 98.9

[0260] Table 7 shows the electrochemical performance parameters of zinc-ion supercapacitors prepared from porous carbon materials 1, 27, and 28 obtained in Example 1 and Comparative Examples 12 and 13. The results show that when potassium citrate is used as the activator, the electrochemical performance of the obtained porous carbon materials is better. Conversely, when the activator is not potassium citrate, the electrochemical performance of the carbon materials will decrease.

Claims

1. A method for preparing nitrogen- and phosphorus-doped porous carbon for use in zinc-ion supercapacitors, characterized in that... The steps include the following: (1) Preparation of nitrogen and phosphorus dopants: Melamine is added to glacial acetic acid and stirred at 100℃-120℃ for 1 hour. Then, phosphoric acid is slowly added and stirred at the same temperature for another hour. The product after reaction is spray-dried to collect nitrogen and phosphorus dopants. The weight ratio of phosphoric acid, melamine and glacial acetic acid is 1 part: 1-5 parts: 8-60 parts. (2) Preparation of activator: The activator can be collected by mixing potassium citrate with water and allowing it to dissolve, followed by spray drying. (3) Preparation of carbon material precursors: PET material is added to a mixer and stirred and melted at 260℃-270℃. Then, activator and nitrogen and phosphorus dopants are added in sequence and stirred for 5 minutes to obtain carbon material precursor. The weight ratio of PET material, activator and nitrogen and phosphorus dopants is 1 part: 4 parts: 0.5-1.5 parts. (4) Carbonization and cleaning of precursors: The precursor was carbonized at 700℃-900℃ for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the carbonized precursor was washed with water until neutral to obtain nitrogen and phosphorus doped porous carbon material.

2. The method for preparing nitrogen- and phosphorus-doped porous carbon for use in zinc-ion supercapacitors according to claim 1, characterized in that... The phosphoric acid contained therein is phosphoric acid, polyphosphoric acid, or phytic acid.

3. The method for preparing nitrogen- and phosphorus-doped porous carbon for use in zinc-ion supercapacitors according to claim 1, characterized in that... In step (2), the weight ratio of potassium citrate to water is 1-3 parts: 10 parts.

4. The method for preparing nitrogen- and phosphorus-doped porous carbon for use in zinc-ion supercapacitors according to claim 1, characterized in that... The carbonization temperature in step (4) is 790-810℃.

5. The method for preparing nitrogen- and phosphorus-doped porous carbon for use in zinc-ion supercapacitors according to claim 1, characterized in that... The weight ratio of phosphoric acid, melamine, and glacial acetic acid is 1 part: 3 parts: 20-40 parts.

6. The method for preparing nitrogen- and phosphorus-doped porous carbon for use in zinc-ion supercapacitors according to claim 1, characterized in that... The weight ratio of the PET material, activator, and nitrogen and phosphorus dopants is 1 part: 4 parts: 1 part.

7. The method for preparing nitrogen- and phosphorus-doped porous carbon for use in zinc-ion supercapacitors according to claim 1, characterized in that... In step (3), the PET material is waste plastic bottle fragments made of PET material.

8. The method for preparing nitrogen- and phosphorus-doped porous carbon for use in zinc-ion supercapacitors according to claim 1, characterized in that... In step (3), the PET material is PET plastic.

9. The method for preparing nitrogen- and phosphorus-doped porous carbon for use in zinc-ion supercapacitors according to claim 7, characterized in that... The method for preparing waste plastic bottle fragments made of PET material is as follows: crush waste plastic bottles made of PET material, wash them three times with distilled water, and dry them to obtain waste plastic bottle fragments made of PET material.

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