Aminated porous carbon material as well as preparation method and application thereof

Abstract

The invention relates to the field of capacitor desalination and supercapacitors, in particular to an aminated porous carbon material and a preparation method and application thereof.The preparation method of the aminated porous carbon material comprises the steps that dried traditional Chinese medicine residues are smashed, the smashed traditional Chinese medicine residues are soaked in a potassium hydroxide saturated solution, standing is conducted in a vacuum environment, and then the aminated porous carbon material is obtained; then freeze-drying the mixture; and repeating the steps. Performing high-temperature carbonization on the obtained product in an N2 atmosphere to obtain a carbon material, cooling the carbon material, and performing water washing-drying to obtain the carbon material; the method comprises the following steps: dispersing a carbon material in nitric acid for acidification, and then washing the acidified carbon material; hydrophilic amino acid, N, N-dimethylformamide and an acidified carbon material are subjected to hydrothermal treatment, and then an aminated porous carbon material is obtained through centrifugal filtration-drying; meanwhile, when the aminated porous carbon material prepared by the method is applied to supercapacitors and capacitive desalting equipment, the aminated porous carbon material shows excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the fields of capacitive desalination and supercapacitors, and particularly relates to an aminated porous carbon material, a preparation method thereof, and an application thereof. Background Art

[0002] The electric double layer capacitance behavior is a highly reversible and efficient ion adsorption behavior, which is the main working mechanism during supercapacitors (SCs) and capacitive desalination (CDI). Specifically, under the action of an external electric field, a large amount of positive and negative charges are respectively accumulated on the surfaces of the two electrodes, and positive and negative ions in the solution between the electrodes are respectively adsorbed onto the electrode surfaces to reach a state of charge balance. In supercapacitors, this behavior is used for charge storage, which has advantages such as fast charge and discharge rates and high reversibility; in capacitive desalination, the electric double layer capacitance behavior can adsorb a large amount of salt ions to achieve the effect of desalinating and purifying the solution. Of course, the actual efficiency of the electric double layer capacitance behavior is related to various factors, and the performance of the electrode material is the key limiting factor.

[0003] High specific surface area carbon materials are typical electrode materials with capacitance behavior and have good application prospects in supercapacitors and capacitive desalination. The development and design using low-value biological waste as a carbon source have always been a research hotspot in this field. As the birthplace of traditional Chinese medicine, plant-based traditional Chinese medicine is widely used in China. Generally speaking, traditional Chinese medicine residues are a mixture of various plant residues, and it is unrealistic and unreasonable to classify and screen them. At the same time, considering the reasons such as the drug toxicity of traditional Chinese medicine, its treatment has always had a negative economic value. Compared with being used as a low-value fuel, converting it into a high-value capacitive material has greater development potential and research value. Considering the differences in nanostructures and components among different traditional Chinese medicine residues, the difficulty in converting traditional Chinese medicine residues into carbon materials lies in ensuring that the obtained carbon materials after treatment have a uniform nano-morphology and stable performance.

[0004] With the development of technology, more and more biomass materials have been prepared and have high application potential. However, some of them require relatively complex preparation processes and stringent preparation conditions. Wu et al. (Chem. Phys. Lett, 2021, 139058) used petroleum pitch as a raw material, combined Ca(OH)2 as a template precursor with KOH activation, and successfully prepared foamy hierarchical porous carbon (FHPCs) with developed mesopores and ultra-high specific surface area. Wang et al. (J. Alloys Compd, 2019, 109 - 117) introduced NaOH as a co-activating reagent in addition to KOH, and successfully prepared porous carbon nanosheets with a large specific capacitance using petroleum pitch as a precursor. These commonly used chemical activation technologies mostly use excessive amounts of strongly corrosive activating agents, which are likely to cause serious corrosion of equipment and environmental pollution. Therefore, how to reduce the usage amount of activating agents is also an important research and development direction. Summary of the Invention

[0005] The object of the present invention is to provide an aminated porous carbon material, a preparation method thereof and an application thereof, which can effectively solve the technical problems involved in the background art. The present invention uses plant-based Chinese medicine residue waste with negative economic value as raw material, and optimizes the existing activation technology by means of internal crystallization of the activator; subsequently, amino acids are used as raw materials to aminate the porous carbon interface to reduce the covalent ion repulsion phenomenon existing in the electro-desalination process; in addition, the increased hydrophilicity of amino acids also improves the actual effective specific surface area of the material, and solves the problem of low capacitance with high specific surface area in the previous technology; subsequently, the electrode material is applied in both supercapacitors and capacitive desalination, thereby proving that it has excellent capacitance performance and a broader economic development prospect; it also provides an effective strategy for the economic transformation of plant-based Chinese medicine residues with drug toxicity and difficult classification.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A preparation method of an aminated porous carbon material, comprising the following steps:

[0008] 1) After soaking 10 g of dried Chinese medicine residue in a saturated solution containing 30-70 g of KOH for 12 h, it is dried at 60 °C, and after drying, this step is repeated 2-6 times;

[0009] Among them, the selection of the mass of KOH is crucial. Too little will result in insufficient infiltration of the activator and too low crystallization amount, unable to ensure the occurrence of activation pore-forming behavior; too much KOH mass will cause waste of the activator and excessive crystallization, resulting in over-activation of the material and pulverization of the structure, reducing the effective specific surface area. The same is true for the number of soaking times. When it is too little, the amount of crystalline KOH in the bulk phase is too little, the activation power of the bulk phase is insufficient, and the pore structure construction is insufficient, which is not conducive to the capacitance behavior; when the number of soaking times is too much, there are too many KOH crystals, resulting in excessive activation degree, collapse and fragmentation of the derived carbon structure, resulting in a decrease in surface area, which is not conducive to the occurrence and cycle stability of the electric double layer capacitance.

[0010] 2) The material obtained above is carbonized at high temperature in an N2 atmosphere, and the heating rate is 1-3 °C min -1 , heated to 500-700 °C and kept constant for 1.5 h; after cooling, the sample is taken out and washed with water - dried to obtain a black carbon material;

[0011] Among them, the heating conditions for carbonization are crucial. If the heating rate is too low, the carbonization efficiency will be reduced, and the activation efficiency of the activator will also be reduced; if the heating rate is too fast, the biomass will pyrolyze rapidly, and the derived carbon will have pyrolysis cracks, reducing the structural stability. At the same time, the activator will pyrolyze rapidly and cannot effectively activate the biomass to form pores.

[0012] 3) Disperse the above carbon materials in nitric acid for acidification, keep the temperature constant at 50 - 70 °C for 0.5 - 2 h, wash the carbon materials with water until neutral after filtration, and collect the materials after vacuum drying;

[0013] Among them, the acidification conditions are crucial. When the acidification temperature is too low, the acidification and oxidation effect of nitric acid cannot proceed; when the acidification temperature is too high, the carbon interface will be over-oxidized, resulting in fragmentation. If the acidification time is too short, it is not conducive to the uniformity of acidification; if the acidification time is too long, there will be too many oxygen functional groups on the carbon interface, reducing the abundance of heteroatoms.

[0014] 4) Mix and stir amino acids, N,N-dimethylformamide (used as a solvent) and the acidified carbon materials in a mass ratio of 7:1 - 12:1, and transfer them to a hydrothermal autoclave, keep the temperature constant at 120 °C - 180 °C for 6 - 18 h; after cooling, obtain the final sample through centrifugal filtration - drying.

[0015] Among them, the conditions of hydrothermal treatment are crucial. When the hydrothermal temperature is too low, amino acids cannot be grafted well on the carbon material interface, especially the pore structure of the carbon material; when the hydrothermal temperature is too high, the amino acids on the carbon interface will be inactivated and pyrolyzed, reducing the modification effect.

[0016] Meanwhile, the present invention also relates to the amino-functionalized porous carbon materials prepared by the above method, and the application of the amino-functionalized porous carbon materials in supercapacitors and capacitive desalination devices.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) Utilize the hygroscopicity of dry Chinese medicine residues to adsorb the activator into the material bulk, ensuring the high efficiency of activation and pore formation, and at the same time reducing the usage amount of the activator; this effectively reduces the cost and the harm of strong alkali to the environment.

[0019] (2) By using amino acids to functionalize the interface of carbon materials, the problem of covalent ion repulsion in the capacitance behavior of carbon materials can be effectively alleviated, and problems such as material oxidation and fragmentation caused by the electric field can also be alleviated.

[0020] (3) Provide an effective economic conversion strategy for Chinese medicine residues with complex components and drug toxicity; most of the used Chinese medicine residues are mixed products of various medicaments, and they often have certain medicinal properties and are difficult to be utilized. The present invention provides an effective strategy for the treatment of waste Chinese medicine residues.

[0021] Meanwhile, the present invention converts Chinese medicine residues into high specific surface area carbon materials through methods such as crushing - soaking - drying - carbonization, and grafts hydrophilic amino acid functional groups on the surface of the high specific surface area carbon materials to enhance the hydrophilicity and pseudocapacitance performance of the materials.

[0022] For the interfacial functional groups, first, the amino acid-based interfacial functional groups can effectively enhance the wettability of the material, increase the actual effective area, and effectively improve the contribution of the double-layer capacitance of the material; second, the amino functional groups can effectively alleviate the occurrence of side reactions such as co-ion repulsion and oxidative corrosion in the capacitive behavior and promote electron / ion transport; finally, the amino functional groups can provide an additional pseudocapacitive reaction to increase the capacitance of the material.

[0023] For universality, the present invention uses the soaking-activation method to convert the Chinese medicine residue precursor with a complex structure into a high specific surface area derivative carbon material with a unified structure; utilizes the water absorption and porosity of the Chinese medicine residue itself to load the activator into the interior of the precursor; at high temperature, the activation reaction occurs synergistically inside and outside the material, ensuring the structural consistency of the material. The amino-functionalized porous carbon material prepared by the present invention exhibits excellent electrochemical performance in both supercapacitors and capacitive desalination devices. Description of the Drawings

[0024] Figure 1 Scanning electron microscope image of the carbon material synthesized in Example 1;

[0025] Figure 2 Transmission electron microscope image of the carbon material synthesized in Example 1;

[0026] Figure 3 Scanning electron microscope image of the carbon material synthesized in Example 2;

[0027] Figure 4 Scanning electron microscope image of the carbon material synthesized in Example 3;

[0028] Figure 5 Scanning electron microscope image of the carbon material synthesized in Example 4;

[0029] Figure 6 Scanning electron microscope image of the carbon material synthesized in Example 5;

[0030] Figure 7 Transmission electron microscope image of the carbon material synthesized in Example 6;

[0031] Figure 8 Transmission electron microscope image of the carbon material synthesized in Example 5;

[0032] Figure 9 Nitrogen adsorption-desorption isotherm curve of the carbon material synthesized in Example 1;

[0033] Figure 10 C spectrum of XPS of the carbon material synthesized in Example 1;

[0034] Figure 11 N spectrum of XPS of the carbon material synthesized in Example 1;

[0035] Figure 12O spectrum of the synthesized carbon material in Example 1 by XPS;

[0036] Figure 13 Cyclic voltammogram of three - electrode in Example 1;

[0037] Figure 14 Cyclic voltammograms of three - electrode in Example 1 at different current rates;

[0038] Figure 15 Cyclic voltammogram of three - electrode in Example 5;

[0039] Figure 16 Galvanostatic charge - discharge graph of three - electrode in Example 1;

[0040] Figure 17 Specific capacitance of Example 1 at different current densities;

[0041] Figure 18 Specific capacitance of Example 2 at different current densities;

[0042] Figure 19 Specific capacitance of Example 3 at different current densities;

[0043] Figure 20 Specific capacitance of Example 4 at different current densities;

[0044] Figure 21 Specific capacitance of Example 5 at different current densities;

[0045] Figure 22 Specific capacitance of Example 6 at different current densities;

[0046] Figure 23 Desalination capacity curve varying with time at 1.6V in Example 1;

[0047] Figure 24 Desalination capacity - desalination rate curve at 1.6V in Example 1;

[0048] Figure 25 CV curve of the symmetric supercapacitor assembled in Example 1;

[0049] Figure 26 Power density - energy density curve of the symmetric capacitor assembled in Example 1. Detailed implementation manners

[0050] In order to make the purpose and advantages of the present invention clearer, the present invention will be specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific implementation manners of the present invention, and does not strictly limit the scope of protection specifically claimed by the present invention.

[0051] Example 1

[0052] 1) Soak 10 g of the dried traditional Chinese medicine residues in a saturated solution containing 50 g of KOH for 12 h, and then dry at 60 °C. After drying, repeat this step 4 times.

[0053] 2) Carbonize the above-obtained material at high temperature in an N2 atmosphere, with a heating rate of 1.5 °C / min -1 , heat up to 600 °C and keep it constant for 1.5 h. After cooling, take out the sample, and obtain the black carbon material through water washing - drying.

[0054] 3) Disperse the above carbon material in nitric acid, and keep it at a constant temperature of 60 °C for 1 h; after filtration, wash the carbon material with water until it is neutral, and collect the material after vacuum drying to obtain the acidified carbon material.

[0055] 4) Mix and stir arginine, N,N-dimethylformamide (used as a solvent) and the acidified carbon material with a mass ratio of 9:1, and transfer them to a hydrothermal autoclave, and keep it at a constant temperature of 120 °C for 12 h; after cooling, obtain the final sample through centrifugal filtration - drying.

[0056] Figure 1 is the scanning electron microscope image of the carbon material synthesized in Example 1. As can be seen from Figure 1 : The activation method from the inside out makes the pore structure of the carbon material more uniform and rich, with the potential for a high specific surface area; specifically, the pore structures of the carbon material synthesized in Example 1 are interconnected, forming a large cavity structure connected by small channels; such a structure has an obvious confinement effect, which will provide effective protection for the amino functional groups at the cavity interface.

[0057] Figure 2 is the transmission electron microscope image of the carbon material synthesized in Example 1. As can be seen from Figure 2 : The carbon layer is relatively thin, and the pore structure is uniformly distributed throughout the material in a penetrating manner, which represents a higher specific surface area and a more suitable ion transport path.

[0058] Figure 9 is the nitrogen adsorption - desorption curve of the carbon material synthesized in Example 1. As can be seen from Figure 9 : The carbon material has a large specific surface area of up to 1063.7 m 2 g -1 ; at the same time, there are a large number of pores below 10 nm, which will promote the occurrence of the electric double - layer capacitance behavior.

[0059] Figure 10 is the C spectrum of the XPS of the carbon material synthesized in Example 1. As can be seen from Figure 10It can be seen that: in addition to the C-C (284 eV) valence bond with the largest proportion, there are also C-N (285 eV), C-O (286 eV) and C=O (288 eV) bonds; among them, the proportion of -C=O is significantly higher than that of -C-O, because the grafted amino acid functional groups bring rich -C=O groups. This also confirms that the amino functional groups are successfully grafted on the surface of the carbon sheet, bringing rich and diverse oxygen-containing functional groups, which will provide rich pseudocapacitive active sites.

[0060] Figure 11 It is the N spectrum of the carbon material synthesized in Example 1 by XPS. Figure 11 It can be seen that: the N element mainly comes from the biomass precursor and amino acid functional groups, and mainly exists in the forms of doped heteroatoms and surface functional groups. Correspondingly, three response peaks corresponding to pyridine-N (398.7 eV), pyrrole-N (399.7 eV) and graphite–N (400.9 eV) appear in the N 1s fine spectrum. This mainly comes from the N-doped defects derived from the biomass precursor, which will provide a certain pseudocapacitive contribution. In addition, O=C-N bond (400.9 eV) and -NH2 (399.3 eV) also appear in the N 1s fine spectrum; O=C-N is generated after the carboxyl group is digested by the amidation reaction. And -NH2 comes from the unreacted part of arginine, which will improve the hydrophilicity of the material.

[0061] Figure 12 It is the O spectrum of the carbon material synthesized in Example 1 by XPS. Figure 12 It can be seen that: the O 1s spectrum can be divided into three peaks at 531.5 eV, 532.8 eV and 534.2 eV, corresponding to -C=O, O=C-O- and -O-C-O- respectively. The oxygen-containing functional groups will further improve the wettability of the material and increase its effective specific surface area.

[0062] Example 2:

[0063] 1) Soak 10 g of dried traditional Chinese medicine residues in a saturated solution containing 30 g of KOH for 12 h, and then dry at 60 °C. After drying, repeat this step 4 times.

[0064] 2) Carbonize the above-obtained material at high temperature in an N2 atmosphere, with a heating rate of 1 °C min -1 , heat up to 500 °C and keep it at a constant temperature for 1.5 h. After cooling, take out the sample, and obtain the black carbon material through washing-drying.

[0065] 3) Disperse the above carbon material in nitric acid, and keep it at a constant temperature of 60 °C for 1 h. After filtration, wash the carbon material with water until it is neutral, and collect the material after vacuum drying to obtain the acidified carbon material.

[0066] 4) Mix arginine and N,N-dimethylformamide (used as a solvent) with a mass ratio of 9:1 with the acidified carbon material, stir, and transfer to a hydrothermal reactor. Keep it at a constant temperature of 120 °C for 12 h. After cooling, obtain the final sample through centrifugal filtration - drying.

[0067] Figure 3 It is the scanning electron micrograph of the carbon material synthesized in Example 2. As can be seen from Figure 3 : Since the proportion of KOH is small and there is too little crystallization in the Chinese medicine residue precursor, it is impossible to form an effective activation effect. Therefore, the pore structure is not rich and the specific surface area is relatively low, which is not conducive to the occurrence of electric double layer capacitance behavior.

[0068] Example 3:

[0069] 1) Immerse 10 g of the dried Chinese medicine residue in a saturated solution containing 70 g of KOH for 12 h, and then dry it at 60 °C. After drying, repeat this step 4 times.

[0070] 2) Carbonize the above-obtained material at high temperature in an N2 atmosphere with a heating rate of 1 - 3 °C / min -1 , heat it to 700 °C and keep it at a constant temperature for 1.5 h. After cooling, take out the sample and obtain the black carbon material through water washing - drying.

[0071] 3) Disperse the above carbon material in nitric acid, keep it at a constant temperature of 60 °C for 1 h. After filtration, wash the carbon material with water until it is neutral, and collect the material after vacuum drying to obtain the acidified carbon material.

[0072] 4) Mix arginine and N,N-dimethylformamide (used as a solvent) with a mass ratio of 9:1 with the acidified carbon material, stir, and transfer to a hydrothermal reactor. Keep it at a constant temperature of 120 °C for 12 h. After cooling, obtain the final sample through centrifugal filtration - drying.

[0073] Figure 4 It is the scanning electron micrograph of the carbon material synthesized in Example 3. As can be seen from the figure: Since there is too much KOH and too much crystallization in the Chinese medicine residue, it causes over-activation and obvious fragmentation of the carbon material. After fragmentation, agglomeration is likely to occur, reducing the effective specific surface area of the material.

[0074] Example 4:

[0075] 1) Immerse 10 g of the dried Chinese medicine residue in a saturated solution containing 50 g of KOH for 12 h, and then dry it at 60 °C. After drying, repeat this step 4 times.

[0076] 2) Carbonize the above-obtained material at high temperature in an N2 atmosphere with a heating rate of 3 °C / min -1, Heat it up to 700 °C and keep it at a constant temperature for 1.5 h. After cooling, take out the sample and obtain the black carbon material through water washing - drying.

[0077] 3) Disperse the above carbon material in nitric acid and keep it at a constant temperature of 60 °C for 1 h. After filtration, wash the carbon material with water until it is neutral, and collect the material after vacuum drying to obtain the acidified carbon material.

[0078] 4) Mix arginine, N,N - dimethylformamide (used as a solvent) and the acidified carbon material with a mass ratio of 9∶1 and stir, then transfer it to a hydrothermal reactor and keep it at a constant temperature of 120 °C for 12 h. After cooling, obtain the final sample through centrifugal filtration - drying.

[0079] Figure 5 It is the scanning electron microscope image of the carbon material synthesized in Example 4. As can be seen from the figure, due to the too - fast heating rate, the activator quickly enters the molten state, but the too - fast speed leads to uneven activation. It can be found in the scanning electron microscope that the activation mainly occurs on the surface of the carbon material and no deep pore structure is formed.

[0080] Example 5

[0081] 1) Immerse 10 g of dried traditional Chinese medicine residues in a saturated solution containing 50 g of KOH for 12 h, and then dry at 60 °C. After drying, repeat this step 4 times.

[0082] 2) Carbonize the above - obtained material at high temperature in an N2 atmosphere with a heating rate of 1.5 °C / min -1 , Heat it up to 600 °C and keep it at a constant temperature for 1.5 h. After cooling, take out the sample and obtain the black carbon material through water washing - drying.

[0083] 3) Disperse the above carbon material in nitric acid and keep it at a constant temperature of 60 °C for 1 h. After filtration, wash the carbon material with water until it is neutral, and collect the material after vacuum drying to obtain the acidified carbon material.

[0084] 4) Mix an amino acid, N,N - dimethylformamide (used as a solvent) and the acidified carbon material with a mass ratio of 9∶1 and stir, then transfer it to a hydrothermal reactor and keep it at a constant temperature of 60 °C for 12 h. After cooling, obtain the final sample through centrifugal filtration - drying.

[0085] Figure 6 It is the scanning electron microscope image of the carbon material synthesized in Example 5. As can be seen from the figure: The nano - morphology of the material is basically similar to that of Example 1, but due to the too - low hydrothermal temperature, the reaction of grafting arginine onto the carbon interface does not occur sufficiently, and effective interfacial modification cannot be formed.

[0086] Example 6

[0087] 1) After soaking 10 g of the dried Chinese medicine residues in a saturated solution containing 50 g of KOH for 12 h, they were dried at 60 °C. After drying, this step was repeated 4 times.

[0088] 2) The material obtained above was carbonized at high temperature in an N2 atmosphere with a heating rate of 1.5 °C min -1 , heated to 600 °C and held at a constant temperature for 1.5 h. After cooling, the sample was taken out and a black carbon material was obtained through washing with water - drying.

[0089] 3) The above carbon material was dispersed in nitric acid for acidification and held at a constant temperature of 80 °C for 2 h. After filtration, the carbon material was washed with water until neutral, and after vacuum drying, the material was collected to obtain the acidified carbon material.

[0090] 4) Amino acid, N,N - dimethylformamide (used as a solvent) and the acidified carbon material with a mass ratio of 9:1 were mixed and stirred, and then transferred to a hydrothermal autoclave and held at a constant temperature of 120 °C for 12 h. After cooling, the final sample was obtained through centrifugal filtration - drying.

[0091] Figure 7 It is the transmission electron microscope image of the carbon material synthesized in Example 6. As can be seen from the figure: Due to the too high acidification temperature, the carbon material was over - oxidized, resulting in serious fragmentation of the carbon sheet structure. In the transmission electron microscope, there is no obvious large aspect - ratio structural sheet.

[0092] Application Example

[0093] The electrodes prepared in the above examples were respectively used for supercapacitor and capacitive deionization tests:

[0094] The prepared carbon material was used to prepare a half - capacitor device.

[0095] 1) The active material, i.e., the carbon material, conductive graphite and binder polytetrafluoroethylene (PTFE) were mixed with an appropriate amount of ethanol in a mass ratio of 85:10:5 and then coated on nickel foam (1 cm × 1 cm) to obtain a working electrode.

[0096] 2) The nickel foam working electrode was dried in an oven at 60 °C to constant weight and then pressed into a tablet under a pressure of 10 MPa.

[0097] 3) A working electrode, a reference electrode, a counter electrode, a salt bridge and an electrolyte were prepared to assemble a half - capacitor system.

[0098] The prepared carbon material was used to prepare a symmetric capacitor device.

[0099] 1) The active material, i.e., the carbon material, conductive graphite and binder polytetrafluoroethylene (PTFE) were mixed with an appropriate amount of ethanol in a mass ratio of 85:10:5 and then coated on nickel foam (1 cm × 1 cm) to obtain a working electrode.

[0100] 2) The nickel foam working electrode was dried at 60 °C until constant weight and then pressed into tablets under a pressure of 10 MPa.

[0101] 3) An asymmetric capacitor was assembled with the electrode sheet, separator, and electrode solution of the same mass of the active material.

[0102] The prepared carbon material was used to fabricate a capacitive deionization device.

[0103] 1) The symmetric capacitive deionization device was assembled by coating the capacitive slurry prepared above on an electrode plate composed of a 4 cm × 4 cm titanium plate.

[0104] 2) The complete system includes a recovery container, a peristaltic pump, a CDI device, a DC power supply, and a conductivity meter for detecting the salt solution. The specific operating parameters are as follows: the concentration of the feed salt solution is divided into 200 mg L -1 , 500 mg L -1 , and 1000 mg L -1 ; the flow rate is 32 mL min -1 ;

[0105] 3) The total volume of the salt solution is 80 mL; the applied potential difference is 1.0 V, 1.2 V, 1.4 V, and 1.6 V; the solution temperature is 25 °C.

[0106] Figure 13 This is the cyclic voltammogram of the three-electrode system for Example 1. As Figure 13 can be seen: at a scanning rate of 5 mV s -1 , the CV curves are all close to rectangles, indicating that the capacitive behavior is mainly dominated by the electric double-layer capacitance behavior. At the same time, there are slight peaks on its CV, which are caused by the pseudocapacitive reaction derived from the amino acid functional groups.

[0107] Figure 14 This is the cyclic voltammogram of the three-electrode system for Example 1 at different current rates. As Figure 14 can be seen: in the scanning range of 5 mV s -1 to 100 mV s -1 , there is no obvious distortion in its CV curves, indicating that it has good rate performance.

[0108] Figure 15 This is the cyclic voltammogram of the three-electrode system for Example 5. As Figure 15 can be seen: due to the too low temperature, the amination is not obvious. There are fewer amino acid functional groups at the interface of the carbon material, and there are no redox peaks of amino functional groups in the CV curves, resulting in a lower specific capacitance than that of Example 1.

[0109] Figure 16 This is the galvanostatic charge-discharge diagram of the three-electrode system for Example 1. As Figure 16 can be seen: at 0.5 A g-1 ~10 Ag -1 In the current density range of, its GCD curve shows an isosceles triangle with slight distortion, which means the coexistence of pseudocapacitance behavior and electric double layer capacitance behavior. Its GCD curves all show a Coulombic efficiency close to 100%, which proves that both the electric double layer capacitance behavior and the pseudocapacitance behavior have high reversibility.

[0110] Figure 17 is the specific capacitance of Example 1 at different current densities. As can be seen from Figure 17 : At a current density of 0.5 Ag -1 , its specific capacitance can reach up to 306.6 F g -1 . The specific capacitance decreases with the increase of the current density, which is due to problems such as insufficient reaction kinetics on the material surface and hindered ion diffusion at high current densities. However, in comparison, its specific capacitance can still reach 73.3% of the original value after the current density is increased by 20 times.

[0111] Figure 18 is the specific capacitance of Example 2 at different current densities. As can be seen from Figure 18 : Due to insufficient activation in Example 2, the specific surface area of the material is low, showing a low specific capacitance and weak capacitance ability.

[0112] Figure 19 is the specific capacitance of Example 3 at different current densities. As can be seen from Figure 19 : Due to excessive KOH activation, agglomeration of the carbon material occurs, and the specific capacitance of the carbon material is lower than that of Example 1.

[0113] Figure 20 is the specific capacitance of Example 4 at different current densities. As can be seen from Figure 20 : Due to too fast heating rate, the activator is not enough to quickly construct a deep pore structure, which is not conducive to the occurrence of electric double cell capacitance behavior.

[0114] Figure 21 is the specific capacitance of Example 5 at different current densities. As can be seen from Figure 21 : Due to the lack of pseudocapacitance of amino functional groups, its specific capacitance is lower than that of Example 1. However, due to the high reversibility and high power of the electric double layer capacitance, its rate performance is better.

[0115] Figure 22 is the specific capacitance of Example 6 at different current densities. As can be seen from Figure 22 : High-temperature acidification leads to excessive oxidation of the carbon material, too many functional groups, but obvious fragmentation of the structure, resulting in a not high specific capacitance. At the same time, due to the too high proportion of pseudocapacitance, its rate performance also decreases.

[0116] Figure 23Desalination capacity curve of Example 1 varying with time at 1.6V. From Figure 23 It can be seen that when a voltage of 1.6V is applied, the conductivity of the salt solution where it is located rapidly decreases, which is due to the rapid response of the high-efficiency capacitive behavior. The adsorption capacity of the corresponding electrode material continuously increases and reaches equilibrium at 15 min. The salt adsorption capacity of the carbon material is as high as 33.23 mg g -1 . Thanks to its high specific surface area and hydrophilicity, the capacitive behavior is promoted, and its adsorption capacity for charged ions is enhanced.

[0117] Figure 24 Desalination capacity - desalination rate curve of Example 1 at 1.6V. From Figure 24 It can be seen that it has a good salt adsorption rate. This is mainly because the carbon material prepared in Example 1 still mainly exhibits electric double-layer capacitive behavior.

[0118] Figure 25 CV curve of the symmetric supercapacitor assembled in Example 1. From Figure 25 It can be seen that within the scanning rate range of 5 - 100 mV s -1 , its CV curve presents a quasi-rectangle and no obvious distortion phenomenon appears. The quasi-rectangular CV shape means that its energy storage behavior is mainly based on electric double-layer capacitance, supplemented by pseudocapacitance behavior, and has good rate performance. This is mainly attributed to the highly open porous structure and efficient charge transfer ability.

[0119] Figure 26 Power density - energy density curve of the symmetric capacitor assembled in Example 1. From Figure 26 It can be seen that its maximum power density and energy density can reach 2500 W kg -1 and 8.8 Wh kg -1 respectively, showing relatively excellent performance.

[0120] In this patent, the activator is immersed into the bulk phase of the biomass precursor in the way of infiltration crystallization to achieve the effect of internal and external synergistic activation, and a high specific surface area structure with connected internal and external cavities is prepared. At the same time, hydrophilic amino acid functional groups are used to optimize the electrolyte infiltration efficiency of the material and increase the effective specific surface area. And the amino acid functional groups inhibit side reactions such as co-ion repulsion and oxidation corrosion, and improve the cycle stability of the material. The confinement effect of the cavities of the carbon material will also effectively protect the attachment of the amino acid functional groups, achieving the synergistic optimization effect of the two. Therefore, it exhibits excellent capacitive performance and excellent performance in both supercapacitors and capacitive desalination applications.

[0121] The embodiments of the present invention have been described in detail in combination with the above embodiments. However, the present invention is not limited to the above embodiments. For those of ordinary skill in the art, after learning the content recorded in the present invention, without departing from the principle of the present invention, several equivalent transformations and substitutions can still be made, and these equivalent transformations and substitutions should also be regarded as belonging to the protection scope of the present invention.

Claims

1. A preparation method of an aminated porous carbon material, characterized in that, It includes the following steps: S1. Dry the Chinese medicine residues and then crush them. After that, soak the crushed Chinese medicine residues in a saturated potassium hydroxide solution and let them stand still in a vacuum environment for 3 - 5 h, and then perform freeze-drying on them; repeat the above steps until potassium hydroxide crystals appear inside the Chinese medicine residues; S2. Perform high-temperature carbonization on the product obtained in step S1 in an N2 atmosphere to obtain a carbon material, cool the carbon material and then perform water washing - drying to obtain a carbon material; S3. Disperse the carbon material in nitric acid for acidification, and then wash the acidified carbon material until the pH is neutral; S4. Perform hydrothermal treatment on arginine and the acidified carbon material, and after the material cools, obtain an amino-functionalized porous carbon material through centrifugal washing - drying.

2. The preparation method of the aminated porous carbon material according to claim 1, characterized in that: The mass ratio of the Chinese medicine residues to the saturated potassium hydroxide solution is 1∶3 - 1∶7.

3. The preparation method of the aminated porous carbon material according to claim 2, characterized in that: The mass ratio of the Chinese medicine residues to the saturated potassium hydroxide solution is 1∶5.

4. The preparation method of the aminated porous carbon material according to claim 1, characterized in that: In step S1, the number of times of repeating the steps is 2 - 5 times.

5. The preparation method of the aminated porous carbon material according to claim 1, characterized in that: In step S2, the heating rate for high-temperature carbonization is 1 to 3 °C / min -1 , and it is heated to 500 to 700 °C and kept at a constant temperature for 1 to 2 h.

6. The preparation method of the aminated porous carbon material according to claim 1, wherein: In step S3, the temperature for acidifying the carbon material in nitric acid is 50 - 70 °C, and the time is 0.5 - 2 h.

7. The preparation method of the aminated porous carbon material according to claim 1, characterized in that: The temperature of the hydrothermal treatment in step S4 is 120 °C - 180 °C, and the time is 6 - 18 h.

8. The preparation method of the aminated porous carbon material according to claim 1, characterized in that: The mass ratio of arginine to the carbon material is 7∶1 - 12∶1.

9. An aminated porous carbon material, characterized in that: Prepared by the preparation method according to any one of claims 1 - 8.

10. Application of the amino-functionalized porous carbon material according to claim 9 in supercapacitors and capacitive desalination devices.

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