A porous carbon nanomaterial and its application in electrode materials for supercapacitors

Abstract

The present invention discloses a porous carbon nanomaterial and its application in the electrode material of supercapacitors, belonging to the technical field of nanomaterial preparation and application. In the present invention, hollow mesoporous carbon spheres are prepared by a sacrificial template method. The size and pore diameter of the hollow mesoporous carbon spheres are regulated by controlling the addition amounts of TPOS and KOH, and N element doping is realized by a hydrothermal method to obtain a porous carbon nanomaterial. In the process of preparing the hollow mesoporous carbon spheres in the present invention, glutaraldehyde is introduced to react with fucoidan to form an acetal reaction, constructing a three-dimensional cross-linked network, effectively reducing the disordered aggregation of fucoidan, enhancing the mechanical strength of fucoidan, and reducing the rapid escape of sulfur and oxygen elements during the carbonization process, thereby solving the problem of insufficient mechanical strength caused by the loose molecular chain and poor thermal stability of fucoidan. The porous carbon nanomaterial prepared in the present invention has a high specific surface area and specific capacitance as an electrode material of supercapacitors.

Description

Technical Field

[0001] The present invention belongs to the technical field of supercapacitor electrode materials, and relates to a porous carbon nanomaterial and its application in supercapacitor electrode materials. Background Art

[0002] A supercapacitor is an energy storage device with high power density, fast charge and discharge rate, long service life, and wide application range. The core of its performance depends on the characteristics of the electrode material. Therefore, the development of electrode materials with high conductivity, easily available raw materials, low cost, and environmental friendliness has become a current research hotspot. Carbon materials have become the preferred materials for supercapacitor electrodes due to their excellent rate performance, high cycle stability, fast electron conduction speed, large specific surface area, adjustable pore structure, and low cost.

[0003] When plant polysaccharides (such as cellulose, starch, fucoidan, etc.) are used as carbon sources, the abundant hydroxyl, carboxyl, amino and other functional groups in their molecular chains can be in-situ doped with heteroatoms (O, N, S, etc.) during the carbonization process, significantly improving the surface activity and electron conductivity of the material. Among them, the sulfate groups (-OSO3 - ) and polyhydroxyl groups contained in fucoidan can increase the wettability of the material surface and effectively shorten the ion diffusion path. In addition, the functional groups containing O or S can provide additional capacity through redox reactions. During the carbonization process, the escape of S or O elements can also promote the formation of mesoporous-microporous composite channels, further improving the ion transport efficiency. However, the highly polar sulfate groups in fucoidan also lead to its easy self-aggregation. At the same time, the relatively high O and S contents cause the carbon skeleton of fucoidan to be prone to collapse during the carbonization process. These characteristics make it difficult for fucoidan to be directly applied in fields with strict requirements for structural stability, such as high-power supercapacitor electrodes, lithium-sulfur battery host materials, fuel cell catalyst carriers, etc. Summary of the Invention

[0004] Aiming at the problems and defects in the prior art, the present invention provides a porous carbon nanomaterial and its application in supercapacitor electrode materials. The present invention successfully constructs a three-dimensional cross-linked network structure by introducing glutaraldehyde to react with fucoidan. The formation of this structure effectively inhibits the disordered aggregation of fucoidan and significantly enhances the mechanical strength of fucoidan. At the same time, during the carbonization process, this structure can effectively reduce the rapid escape rate of sulfur and oxygen elements. Through the above technical means, the present invention successfully solves the key problem of insufficient mechanical strength caused by the loose molecular chain and poor thermal stability of fucoidan, so that fucoidan can be used as an ideal carbon source for preparing high-performance porous carbon materials and is successfully applied in the field of preparing supercapacitor electrode materials, providing new ideas and methods for the research and development of high-performance energy storage materials.

[0005] On the one hand, the present invention provides a method for preparing a porous carbon nanomaterial, comprising: obtaining a precursor solution after crosslinking fucoidan with glutaraldehyde; mixing tetrapropyl orthosilicate, potassium hydroxide, water and ethanol for reaction, then adding the precursor solution and stirring to obtain nanospheres; carbonizing the nanospheres and etching with sodium hydroxide to obtain hollow mesoporous carbon spheres; and subjecting the hollow mesoporous carbon spheres and 1-ethyl-3-methylimidazolium tetrafluoroborate to a hydrothermal reaction to obtain the porous carbon nanomaterial.

[0006] Further, in the method for preparing a porous carbon nanomaterial provided by the present invention, the mass of the fucoidan is 0.8 to 1.2 g;

[0007] the volume of the glutaraldehyde is 3 to 4 mL;

[0008] The pH of the precursor solution is 5 to 6.

[0009] Further, in the method for preparing a porous carbon nanomaterial provided by the present invention, the amount of substance of the tetrapropyl orthosilicate is 14 to 28 mmol;

[0010] the concentration of the potassium hydroxide is 1 mol / L, and the volume of the potassium hydroxide is 5 to 25 mL;

[0011] The volume ratio of water to ethanol is 1 to 2:1;

[0012] The temperature of the mixing reaction is 25 to 35 °C, and the time of the mixing reaction is 10 to 15 min;

[0013] The temperature of the reaction for preparing the nanospheres is 25 to 35 °C, and the reaction time is 20 to 26 h.

[0014] Further, in the method for preparing a porous carbon nanomaterial provided by the present invention, the carbonization temperature of the nanospheres is 500 to 550 °C, and the carbonization time is 4 to 5 h;

[0015] The heating rate of the carbonization is 0.5 to 1 °C / min.

[0016] Further, in the method for preparing a porous carbon nanomaterial provided by the present invention, the concentration of the sodium hydroxide is 2 mol / L, and the volume of the sodium hydroxide is 30 to 35 mL.

[0017] Further, in the method for preparing a porous carbon nanomaterial provided by the present invention, the mass-volume ratio of the hollow mesoporous carbon spheres to 1-ethyl-3-methylimidazolium tetrafluoroborate is 1:0.2 to 0.5.

[0018] Further, in the method for preparing a porous carbon nanomaterial provided by the present invention, the temperature of the hydrothermal reaction is 120 to 140 °C, and the time of the hydrothermal reaction is 3 to 4 h.

[0019] In a second aspect, the present invention provides a porous carbon nanomaterial prepared by the above preparation method.

[0020] Further, in the porous carbon nanomaterial provided by the present invention, the specific surface area of the porous carbon nanomaterial is 782 - 1109 m 2 / g, and the pore size is 3 - 12 nm.

[0021] In a third aspect, the present invention provides the application of the porous carbon nanomaterial in the preparation of a supercapacitor electrode material.

[0022] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0023] (1) The present invention uses tetrapropyl orthosilicate (TPOS) as a silicon source to generate a hard template SiO2 and regulate the size of hollow mesoporous carbon spheres (HMCS). Potassium hydroxide not only participates in the hydrolysis reaction of TPOS to generate the SiO2 template, but also acts as an activator to control the pore size and optimize the ion diffusion path. In addition, by controlling the temperature and heating rate of the carbonization process, the stability of the hollow mesoporous carbon sphere structure is maintained, avoiding the collapse of the framework caused by rapid pyrolysis and ensuring the integrity of the material structure.

[0024] (2) The present invention forms stable ether bonds (C - O - C) through the acetal reaction of glutaraldehyde and fucoidan, effectively inhibiting the disordered aggregation of fucoidan molecular chains and significantly enhancing its mechanical strength. During the carbonization process, this reaction also reduces the rapid escape of sulfur (S) and oxygen (O), maintains the integrity of the carbon skeleton, avoids pore collapse, solves the core problems of self - aggregation and poor thermal stability of fucoidan, and realizes the co - existence of high porosity and structural stability, laying a foundation for the preparation of high - performance carbon materials.

[0025] (3) The present invention uses ionic liquid to modify the surface of hollow mesoporous carbon spheres. Through nitrogen (N) doping, the surface wettability and electronic conductivity of the material are significantly enhanced, and at the same time, the redox reaction is promoted. The synergistic effect of the high specific surface area and nitrogen doping enables fucoidan to be an ideal carbon source for the preparation of high - performance porous carbon materials. The present invention successfully applies it to the field of the preparation of supercapacitor electrode materials, providing new ideas and methods for the research and development of high - performance energy storage materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a scanning electron microscope image of the porous carbon nanomaterial. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] Next, the technical solutions of the present invention will be described in conjunction with embodiments. However, the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0028] The fucoidan (extracted from brown algae) involved in the following examples was purchased from Qingdao Mingyue Hailin Fucoidan Biotechnology Co., Ltd. (Qingdao, Shandong).

[0029] Example 1

[0030] 1. Preparation of hollow mesoporous carbon spheres

[0031] Fucoidan (0.8 - 1.2 g) and GA (glutaraldehyde, 3 - 4 mL) were added to a phosphoric acid solution (30 mL) with a pH of 5 - 6 to obtain a precursor solution.

[0032] Under the conditions of a 30 - 35 °C water bath and stirring, TPOS (tetrapropyl orthosilicate, 7.00 mL, 14 - 28 mmol) and KOH (5 - 25 mL, 1 mol / L) were added to a round - bottom flask containing a mixed solution of H2O (50 - 65 mL) and EtOH (35 - 50 mL), and the reaction was carried out for 10 - 15 min. Then, the precursor solution was added to the round - bottom flask and stirring was continued for 20 - 26 h. After the reaction ended, the precipitate was separated by centrifugation, washed 3 times with deionized water and ethanol respectively, and dried overnight at 60 °C. The prepared nanospheres were carbonized at 500 - 550 °C (0.5 - 1 °C / min) under nitrogen for 4 - 5 h to obtain a carbon - silica composite. Finally, the carbon - silica composite was reacted with NaOH (30 - 35 mL, 2 mol / L) for 4 h to remove silica, and hollow mesoporous carbon spheres, denoted as HMCS, were obtained.

[0033] 2. Preparation method of porous carbon nanomaterials

[0034] The prepared hollow mesoporous carbon spheres (1 g) were dispersed in a mixed solution of EtOH and H2O (EtOH:H2O = 1:1), and ultrasonically dispersed for 15 min. After ultrasonic dispersion, 0.2 - 0.5 mL of [EMIM][BF4] (1 - ethyl - 3 - methylimidazolium tetrafluoroborate) was added, and stirred and mixed for 2 h. Then it was transferred to a reaction kettle with a polytetrafluoroethylene liner and reacted at 120 - 140 °C for 3 - 4 h. After the reaction ended, the precipitate was separated by centrifugation, washed 3 times with deionized water and ethanol respectively, and dried overnight at 60 °C to obtain porous carbon nanomaterials, denoted as N - HMCS.

[0035] Example 2

[0036] This example provides a preparation method of porous carbon nanomaterials.

[0037] 1. Preparation of Hollow Mesoporous Carbon Spheres

[0038] Fucoidan (0.8 g) and GA (glutaraldehyde, 3 mL) were added to a phosphoric acid solution (30 mL) with a pH of 5.0 to obtain a precursor solution.

[0039] Under the conditions of a 35 °C water bath and stirring, TPOS (tetrapropyl orthosilicate, 7.00 mL, 14 mmol) and KOH (5 mL, 1 mol / L) were added to a round-bottom flask containing a mixed solution of H2O (50 mL) and EtOH (50 mL). The reaction was carried out for 10 min, and then the precursor solution was added to the round-bottom flask and stirring was continued for 20 h. After the reaction, the precipitate was separated by centrifugation, washed three times with deionized water and ethanol respectively, and dried overnight at 60 °C. The prepared nanospheres were carbonized at 550 °C (1 °C / min) under nitrogen for 5 h to obtain a carbon-silica composite. Finally, the carbon-silica composite was reacted with NaOH (30 mL, 2 M) for 4 h to remove silica, and hollow mesoporous carbon spheres, denoted as HMCS-1, were obtained.

[0040] 2. Preparation Method of Porous Carbon Nanomaterials

[0041] The prepared hollow mesoporous carbon spheres (1 g) were dispersed in a mixed solution of EtOH and H2O (EtOH:H2O = 1:1), and ultrasonically dispersed for 15 min. After the ultrasonic treatment, 0.2 mL of [EMIM][BF4] (1-ethyl-3-methylimidazolium tetrafluoroborate) was added and stirred for 2 h. Then it was transferred to a reaction kettle with a polytetrafluoroethylene liner and reacted at 140 °C for 4 h. After the reaction, the precipitate was separated by centrifugation, washed three times with deionized water and ethanol respectively, and dried overnight at 60 °C to obtain porous carbon nanomaterials, denoted as N-HMCS-1.

[0042] Example 3

[0043] This example provides a preparation method of porous carbon nanomaterials.

[0044] 1. Preparation of Hollow Mesoporous Carbon Spheres

[0045] Fucoidan (1.04 g) and GA (glutaraldehyde, 4 mL) were added to a phosphoric acid solution (30 mL) with a pH of 5.5 to obtain a precursor solution.

[0046] Under the conditions of a 30 °C water bath and stirring, TPOS (tetrapropyl orthosilicate, 7.00 mL, 17.5 mmol) and KOH (10 mL, 1 mol / L) were added to a round-bottom flask containing a mixed solution of H2O (50 mL) and EtOH (50 mL). The reaction was carried out for 15 min, and then the precursor solution was added to the round-bottom flask and stirring was continued for 24 h. After the reaction was completed, the precipitate was separated by centrifugation, washed three times with deionized water and ethanol respectively, and dried overnight at 60 °C. The prepared nanospheres were carbonized at 500 °C (1 °C / min) under nitrogen for 5 h to obtain a carbon-silica composite. Finally, the carbon-silica composite was reacted with NaOH (30 mL, 2 M) for 4 h to remove silica, and hollow mesoporous carbon spheres, denoted as HMCS-2, were obtained.

[0047] 2. Preparation method of porous carbon nanomaterials

[0048] The prepared hollow mesoporous carbon spheres (1 g) were dispersed in a mixed solution of EtOH and H2O (EtOH:H2O = 1:1), and ultrasonic dispersion was carried out for 15 min. After the ultrasonic treatment was completed, 0.4 mL of [EMIM][BF4] (1-ethyl-3-methylimidazolium tetrafluoroborate) was added, and stirring and mixing were carried out for 2 h. Then it was transferred to a reaction kettle with a polytetrafluoroethylene lining and reacted at 140 °C for 4 h. After the reaction was completed, the precipitate was separated by centrifugation, washed three times with deionized water and ethanol respectively, and dried overnight at 60 °C to obtain porous carbon nanomaterials, denoted as N-HMCS-2.

[0049] Example 4

[0050] This example provides a preparation method of porous carbon nanomaterials.

[0051] 1. Preparation of hollow mesoporous carbon spheres

[0052] Fucoidan (1.00 g) and GA (glutaraldehyde, 4 mL) were added to a phosphoric acid solution (30 mL) with a pH of 5.5 to obtain a precursor solution.

[0053] Under the conditions of a 30 °C water bath and stirring, TPOS (tetrapropoxysilane, 7.00 mL, 21 mmol) and KOH (15 mL, 1 mol / L) were added to a round-bottom flask containing a mixed solution of H2O (65 mL) and EtOH (35 mL). The reaction was carried out for 15 min, and then the precursor solution was added to the round-bottom flask and stirring was continued for 26 h. After the reaction was completed, the precipitate was separated by centrifugation, washed 3 times with deionized water and ethanol respectively, and dried overnight at 60 °C. The prepared nanospheres were carbonized at 500 °C (0.5 °C / min) under nitrogen for 4 h to obtain a carbon-silica composite. Finally, the carbon-silica composite was reacted with NaOH (30 mL, 2 M) for 3 h to remove silica, and hollow mesoporous carbon spheres, denoted as HMCS-3, were obtained.

[0054] 2. Preparation method of porous carbon nanomaterials

[0055] The prepared hollow mesoporous carbon spheres (1 g) were dispersed in a mixed solution of EtOH and H2O (EtOH:H2O = 1:1), and ultrasonically dispersed for 15 min. After the ultrasonic treatment was completed, 0.6 mL of [EMIM][BF4] (1-ethyl-3-methylimidazolium tetrafluoroborate) was added, and the mixture was stirred for 2 h. Then it was transferred to a reaction kettle with a polytetrafluoroethylene liner and reacted at 120 °C for 3 h. After the reaction was completed, the precipitate was separated by centrifugation, washed 3 times with deionized water and ethanol respectively, and dried overnight at 60 °C to obtain porous carbon nanomaterials, denoted as N-HMCS-3. Figure 1 This is the SEM image of the porous carbon nanomaterials prepared in this example.

[0056] Example 5

[0057] This example provides a preparation method of porous carbon nanomaterials.

[0058] 1. Preparation of hollow mesoporous carbon spheres

[0059] Fucoidan (1.20 g) and GA (glutaraldehyde, 4 mL) were added to a phosphoric acid solution with a pH of 6 (30 mL) to obtain a precursor solution.

[0060] Under the conditions of a 30 °C water bath and stirring, TPOS (tetrapropyl orthosilicate, 7.00 mL, 24.5 mmol) and KOH (20 mL, 1 mol / L) were added to a round-bottom flask containing a mixed solution of H2O (50 mL) and EtOH (50 mL). The reaction was carried out for 15 min, and then the precursor solution was added to the round-bottom flask and stirring was continued for 24 h. After the reaction was completed, the precipitate was separated by centrifugation, washed three times with deionized water and ethanol respectively, and dried overnight at 60 °C. The prepared nanospheres were carbonized at 500 °C (0.5 °C / min) under nitrogen for 5 h to obtain a carbon-silica composite. Finally, the carbon-silica composite was reacted with NaOH (30 mL, 2 M) for 4 h to remove silica, and hollow mesoporous carbon spheres, denoted as HMCS-4, were obtained.

[0061] 2. Preparation method of porous carbon nanomaterials

[0062] The prepared hollow mesoporous carbon spheres (1 g) were dispersed in a mixed solution of EtOH and H2O (EtOH:H2O = 1:1), and ultrasonically dispersed for 15 min. After the ultrasonic treatment was completed, 0.6 mL of [EMIM][BF4] (1-ethyl-3-methylimidazolium tetrafluoroborate) was added, and the mixture was stirred for 2 h. Then it was transferred to a reaction kettle with a polytetrafluoroethylene lining and reacted at 140 °C for 4 h. After the reaction was completed, the precipitate was separated by centrifugation, washed three times with deionized water and ethanol respectively, and dried overnight at 60 °C to obtain porous carbon nanomaterials, denoted as N-HMCS-4.

[0063] Example 6

[0064] This example provides a preparation method of porous carbon nanomaterials.

[0065] 1. Preparation of hollow mesoporous carbon spheres

[0066] Fucoidan (1.04 g) and GA (glutaraldehyde, 4 mL) were added to a phosphoric acid solution (30 mL) with a pH of 5.5 to obtain a precursor solution.

[0067] Under the conditions of a 30 °C water bath and stirring, TPOS (tetrapropoxysilane, 7.00 mL, 28 mmol) and KOH (25 mL, 1 mol / L) were added to a round-bottom flask containing a mixed solution of H2O (50 mL) and EtOH (50 mL). The reaction was carried out for 15 min, and then the precursor solution was added to the round-bottom flask and stirring was continued for 24 h. After the reaction was completed, the precipitate was separated by centrifugation, washed three times with deionized water and ethanol respectively, and dried overnight at 60 °C. The prepared nanospheres were carbonized at 500 °C (1 °C / min) under nitrogen for 5 h to obtain a carbon-silica composite. Finally, the carbon-silica composite was reacted with NaOH (30 mL, 2 M) for 4 h to remove silica, and hollow mesoporous carbon spheres, denoted as HMCS-5, were obtained.

[0068] 2. Preparation method of porous carbon nanomaterials

[0069] The prepared hollow mesoporous carbon spheres (1 g) were dispersed in a mixed solution of EtOH and H2O (EtOH:H2O = 1:1), and ultrasonically dispersed for 15 min. After ultrasonication, 1.0 mL of [EMIM][BF4] (1-ethyl-3-methylimidazolium tetrafluoroborate) was added and stirred for 2 h. Then it was transferred to a reaction kettle with a polytetrafluoroethylene liner and reacted at 140 °C for 4 h. After the reaction was completed, the precipitate was separated by centrifugation, washed three times with deionized water and ethanol respectively, and dried overnight at 60 °C to obtain porous carbon nanomaterials, denoted as N-HMCS-5.

[0070] Comparative Example 1

[0071] This comparative example provides a preparation method of porous carbon nanomaterials.

[0072] 1. Preparation of hollow mesoporous carbon spheres

[0073] Fucoidan (1.04 g) was added to a phosphoric acid solution (30 mL) with a pH of 5.5 to obtain a precursor solution.

[0074] Under the conditions of a 30 °C water bath and stirring, TPOS (tetrapropoxysilane, 7.00 mL, 21 mmol) and KOH (15 mL, 1 mol / L) were added to a round-bottom flask containing a mixed solution of H2O (50 mL) and EtOH (50 mL). The reaction was carried out for 15 min, and then the precursor solution was added to the round-bottom flask and stirring was continued for 24 h. After the reaction was completed, the precipitate was separated by centrifugation, washed three times with deionized water and ethanol respectively, and dried overnight at 60 °C. The prepared nanospheres were carbonized at 500 °C (1 °C / min) under nitrogen for 5 h to obtain a carbon-silica composite. Finally, the carbon-silica composite was reacted with NaOH (30 mL, 2 M) for 4 h to remove silica, and hollow mesoporous carbon spheres, denoted as HMCS-6, were obtained.

[0075] 2. Preparation method of porous carbon nanomaterials

[0076] Disperse the prepared hollow mesoporous carbon spheres (1 g) in a mixed solution of EtOH and H2O (EtOH:H2O = 1:1), and ultrasonically disperse for 15 min. After the ultrasonic treatment, add 0.6 mL of [EMIM][BF4] (1-ethyl-3-methylimidazolium tetrafluoroborate), and stir and mix for 2 h. Then transfer it to a reaction kettle with a polytetrafluoroethylene liner and react at 140 °C for 4 h. After the reaction, centrifuge to separate the precipitate, wash it 3 times with deionized water and ethanol respectively, and dry it overnight at 60 °C to obtain porous carbon nanomaterials, denoted as N-HMCS-6.

[0077] Example 7

[0078] This example provides the performance test results of porous carbon nanomaterials.

[0079] 1. BET test results

[0080] In the present invention, a hollow structure of porous carbon nanomaterials is prepared by the sacrificial template method. TPOS is used as the silicon source of the hard template SiO2, and KOH not only participates in the hydrolysis reaction of TPOS, but also serves as an activator to control the pore size of the hollow mesoporous carbon spheres. Therefore, the present invention regulates the size and pore size of the hollow mesoporous carbon spheres by controlling the addition amounts of TPOS and KOH.

[0081] It can be seen from the data in Table 1 that as the addition amount of TPOS increases from 14 mmol to 24.5 mmol, and the volume of KOH increases from 5 mL to 20 mL, both the specific surface area and pore size of the synthesized porous carbon nanomaterial N-HMCS show an increasing trend. However, when the addition amount of TPOS further increases to 28 mmol and the volume of KOH reaches 25 mL, the specific surface area significantly decreases to 369 m² / g. This indicates that the shell layer of the synthesized porous carbon nanomaterial is too thin and the pore size is too large at this time, resulting in the collapse of the material structure.

[0082] In addition, the specific surface area of Comparative Example 1 (N-HMCS-6) is only 578 m 2 / g, and the pore size also significantly shrinks. In contrast, in the present invention, by introducing glutaraldehyde to react with fucoidan to form stable ether bonds (C-O-C), a three-dimensional cross-linked network is constructed, effectively reducing the disordered aggregation of fucoidan. At the same time, glutaraldehyde enhances the mechanical strength of fucoidan and reduces the rapid escape of sulfur and oxygen elements during the carbonization process, thus solving the problem of insufficient mechanical strength caused by the loose molecular chains and poor thermal stability of fucoidan.

[0083] Table 1 BET test results of porous carbon nanomaterials

[0084]

[0085] 2. Electrochemical performance test results

[0086] (1)Electrochemical performance detection method

[0087] Electrochemical measurements were carried out on a CHI 760 electrochemical workstation (Chenhua Instrument Co., Ltd., Shanghai, China). Among them, for the three-electrode system test, an Ag / AgCl electrode and a Pt sheet were used as the reference electrode and the counter electrode respectively, and the electrolyte was an aqueous solution of 0.5 M Na2SO4. The working electrode was prepared by coating a slurry of porous carbon nanomaterial N-HMCS, acetylene black, and polyvinylidene fluoride (PVDF / NMP, 50 mg / mL) in a mass ratio of 7:2:1 on nickel foam (1×1 cm). Then the working electrode was dried in a vacuum drying oven at 60 °C for 12 h. The mass loading of the porous carbon nanomaterial N-HMCS was 2 mg.

[0088] The specific capacitance of the porous carbon nanomaterial N-HMCS was obtained from the following equation:

[0089]

[0090] where I (A) and Δt (s) are the applied discharge current and discharge time respectively. m (g) is the mass of the porous carbon nanomaterial N-HMCS, and ΔV (V) is the discharge voltage range.

[0091] (2)Electrochemical performance test results

[0092] As shown in Table 2, at a current density of 1 A / g and a voltage of -0.9~-0.2 V, the specific capacitances of N-HMCS-1, N-HMCS-2, N-HMCS-3, N-HMCS-4, N-HMCS-5, N-HMCS-6, and HMCS-3 were 32 F / g, 61 F / g, 87 F / g, 79 F / g, 14 F / g, 9 F / g, and 56 F / g respectively. Under different preparation conditions, there were significant differences in the specific capacitances of the porous carbon nanomaterials. And by modifying the surface of the hollow mesoporous carbon spheres with ionic liquids to achieve nitrogen doping, the specific capacitance of the porous carbon nanomaterials was significantly improved.

[0093] Table 2 Specific capacitances of porous carbon nanomaterials

[0094]

[0095] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art through relevant deductions and substitutions made under the premise of the concept of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. A method for preparing a porous carbon nanomaterial, characterized in that: include: The precursor solution was obtained after fucoidan was cross-linked with glutaraldehyde; After tetrapropoxysilane, potassium hydroxide, water and ethanol are mixed and reacted, a precursor solution is added and stirred to obtain nanospheres; the nanospheres are carbonized and etched with sodium hydroxide to obtain hollow mesoporous carbon spheres; the hollow mesoporous carbon spheres and 1-ethyl-3-methylimidazolium tetrafluoroborate are subjected to hydrothermal reaction to obtain porous carbon nanomaterials; The mass of the fucoidan is 0.8-1.2 g; The volume of the glutaraldehyde is 3-4 mL; The amount of tetrapropoxysilane is 14-24.5 mmol; The concentration of potassium hydroxide is 1 mol / L, and the volume of potassium hydroxide is 5-20 mL.

2. The method for preparing porous carbon nanomaterials according to claim 1, characterized in that: The pH of the precursor solution is prepared to be 5-6.

3. The method for preparing porous carbon nanomaterials according to claim 1, characterized in that: The volume ratio of water to ethanol is 1-2:1; The temperature of the mixed reaction is 30-35°C, and the time of the mixed reaction is 10-15 minutes; The temperature for preparing the nanospheres is 30-35° C., and the reaction time is 20-26 hours.

4. The method for preparing porous carbon nanomaterials according to claim 1, characterized in that: The carbonization temperature of the nanospheres is 500-550°C, and the carbonization time is 4-5h; The heating rate of the carbonization is 0.5-1°C / min.

5. The method for preparing porous carbon nanomaterials according to claim 1, characterized in that: The concentration of the sodium hydroxide is 2 mol / L, and the volume of the sodium hydroxide is 30-35 mL.

6. The method for preparing porous carbon nanomaterials according to claim 1, characterized in that: The mass volume ratio of the hollow mesoporous carbon spheres to 1-ethyl-3-methylimidazolium tetrafluoroborate is 1:0.2-0.

5.

7. The method for preparing porous carbon nanomaterials according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 120-140° C., and the time of the hydrothermal reaction is 3-4 hours.

8. A porous carbon nanomaterial, characterized in that: Prepared by the method according to any one of claims 1 to 7.

9. The porous carbon nanomaterial according to claim 8, characterized in that: The specific surface area of ​​the porous carbon nanomaterial is 782-1109 m 2 / g, pore size is 3~12nm.

10. Use of the porous carbon nanomaterial according to any one of claims 8 to 9 in preparing supercapacitor electrode materials.

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