An ordered mesoporous carbon nanosheet, its preparation method and application

Abstract

This invention belongs to the field of materials, and particularly relates to an ordered mesoporous carbon nanosheet and its preparation method and application. The preparation method includes (1) adding a mixed aqueous solution A of sugar aqueous solution and mesoporous template agent aqueous solution to a soluble sodium / potassium salt aqueous solution, stirring evenly and then freeze-drying to obtain a precursor; (2) annealing the obtained precursor in an inert atmosphere to remove the mesoporous template agent and obtain black ordered mesoporous carbon nanosheets. Using sugar aqueous solution as raw material, soluble sodium / potassium salt as two-dimensional substrate, and silica nanospheres as mesoporous template, ordered mesoporous carbon nanosheets are obtained through freeze-drying, annealing in an inert gas atmosphere, and etching of silica template. The raw materials of this invention are inexpensive, the preparation process is simple, and the production cost and risk factor are reduced. The prepared material has good morphology and excellent electrochemical performance. The preparation method has good repeatability and is conducive to large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of porous nanomaterials, and particularly relates to an ordered mesoporous carbon nanosheet, its preparation method, and its application. Background Technology

[0002] Mesoporous materials refer to a class of porous materials with pore sizes ranging from 2 to 50 nm. Mesoporous materials possess extremely high specific surface areas, regular and ordered pore structures, narrow pore size distributions, and continuously tunable pore sizes, enabling them to play a crucial role in the adsorption and separation of large molecules, especially in catalytic reactions, where many microporous zeolite molecular sieves struggle to achieve this. Furthermore, the ordered pores of these materials can serve as "microreactors," assembling uniform and stable "guest" materials at the nanoscale to form "host-guest materials." Due to the host-guest effect between the host and guest materials, as well as the potential small size and quantum size effects of the guest materials, they hold promise for widespread applications in electrode materials, optoelectronic devices, microelectronics, chemical sensors, and nonlinear optical materials.

[0003] Currently reported methods for preparing mesoporous carbon nanomaterials include, for example, Chinese patent CN 102682928 A, which describes a method for preparing mesoporous carbon nanosheets. This method uses porous magnesium oxide nanosheets as a template, a triblock copolymer PEO-PEO-PEO as a mesoporous structure directing agent, and dopamine as a carbon precursor. Mesoporous carbon nanosheets are prepared through carbonization and sulfuric acid etching post-treatment. Another Chinese patent, CN 108996485 A, reports a method for preparing hierarchical mesoporous carbon nanomaterials. This method involves injecting an aqueous solution of sodium lignosulfonate into an organic solvent using an automated sampler, followed by centrifugation and calcination to obtain hierarchical mesoporous carbon nanosheets. Furthermore, Xi et al. (ACS Nano, 2018, 12, 5436−5444) used a soft-hard template method, employing magnesium-aluminum bimetallic hydroxide (MgAl-LDH) as a two-dimensional template, a triblock polymer F127 as a mesoporous template, and a phenolic resin prepolymer as a carbon source to obtain a two-dimensional ordered mesoporous carbon nanosheet. The above methods use organic solvents in the preparation process, which does not conform to the concept of environmentally friendly production, and the cost of triblock or diblock copolymers as raw materials is high.

[0004] Patent CN11874889A discloses a method for preparing a three-dimensional network structure hierarchical porous carbon material. The method uses mesoporous silica nanoparticles as a template and a carbohydrate compound as a carbon source. The silica nanoparticles and carbohydrate compound are mixed using a solid-state method, followed by high-temperature calcination and etching of the template to obtain the three-dimensional network structure hierarchical porous carbon material. While this method yields hierarchical porous carbon materials with low raw material costs, it suffers from the following problems: uneven dispersion in the solid-state method, incomplete reaction, inconsistent morphology of the resulting carbon material, and a large and uneven pore size distribution. Summary of the Invention

[0005] To address the shortcomings of existing preparation methods, this invention proposes a simple and rapid method for preparing ordered mesoporous carbon nanosheets, which has the advantages of low cost, convenient operation, good reproducibility of the obtained products, and good electrochemical performance.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for preparing ordered mesoporous carbon nanosheets includes the following steps:

[0008] (1) Add a mixture of aqueous solution of sugar and mesoporous template agent A to a soluble sodium / potassium salt aqueous solution, stir evenly and freeze dry to obtain an intermediate product; first, the sugar and mesoporous template are assembled by hydrogen bonding, and then added to the soluble sodium / potassium salt, and adsorbed and confined on the surface of sodium / potassium salt crystals under the drive of rapid freezing.

[0009] (2) Anneal the intermediate product obtained in step (1) in an inert atmosphere to remove the mesoporous template agent and obtain black ordered mesoporous carbon nanosheets.

[0010] Preferably, the soluble sodium / potassium salt in step (1) is any one of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate; the sugar is any one of glucose, sucrose, and chitosan oligosaccharide; and the mesoporous template agent is silica nanospheres.

[0011] Preferably, in step (1), the concentration of the soluble sodium / potassium salt aqueous solution is 200-300 g / L; the concentration of the sugar aqueous solution is 100-300 g / L; the concentration of the mesoporous template agent aqueous solution is 100-200 g / L, and the particle size is 5-30 nm.

[0012] Preferably, in step (1), the mass ratio of the sugar solution and the mesoporous template agent aqueous solution is 1:(2-4), and the volume ratio of the soluble sodium / potassium salt aqueous solution to the mixed aqueous solution A is 1:(0.8-1.5).

[0013] Preferably, in step (1), the stirring temperature is room temperature and the stirring time is 5-15 min; the freeze-drying temperature is (-60)-(-10)℃ and the time is 24-48 h.

[0014] Preferably, the inert atmosphere in step (2) is nitrogen, helium or argon; the annealing conditions are: temperature 500-900℃, time 1-6 h.

[0015] Preferably, the removal of the template agent in step (2) includes: removing the template agent by immersion in an etchant; the etchant is sodium hydroxide or potassium hydroxide, the concentration of the etchant is 2-3 mol / L, and the etching time is 12-24 h.

[0016] Preferably, the ordered mesoporous carbon nanosheets prepared using the above method have a specific surface area of ​​400-800 m². 2 / g, and the mesopore size is concentrated in the range of 5-30 nm.

[0017] Preferably, the ordered mesoporous carbon nanosheets have a size of 0.4-2.6 μm.

[0018] Preferably, the ordered mesoporous carbon nanosheets are used in the fields of batteries, capacitors, and catalysis.

[0019] Preferably, when the above-mentioned ordered mesoporous carbon nanosheets are used as electrode materials for batteries, the specific capacitance of the electrode material reaches 187-252 F / g at a current density of 0.5 A / g; and at a high current density of 20 A / g, the specific capacitance of the electrode material is 103-162 F / g.

[0020] This invention employs the assembly of sugars (containing a large number of -OH groups) onto a mesoporous template of silica nanospheres (surface modified with -OH and -COOH groups) via hydrogen bonding. These nanospheres are then added to a soluble sodium / potassium salt. Driven by rapid freezing, the sugars and the template agent silica nanospheres are adsorbed and confined onto the surface of the sodium / potassium salt crystals. After high-temperature carbonization, the silica nanospheres are removed with sodium hydroxide or potassium hydroxide, and the soluble sodium / potassium salt is washed away with water to obtain ordered mesoporous carbon nanosheets.

[0021] The present invention has the following beneficial effects:

[0022] 1. This invention proposes a novel, simple, and rapid method for preparing ordered mesoporous carbon nanosheets. Using a sugar aqueous solution as a raw material, soluble sodium / potassium salts as a two-dimensional substrate, and silica nanospheres as a mesoporous template, ordered mesoporous carbon nanosheets are obtained through freeze-drying, annealing in an inert gas atmosphere, and etching of the silica template. This invention does not use organic solvents, and the selected raw materials, templates, and two-dimensional substrates are inexpensive and readily available, making it environmentally friendly and pollution-free. The preparation process is simple, using common equipment, thus reducing production costs and risks.

[0023] 2. This invention employs a solution method to prepare ordered mesoporous carbon nanosheets, resulting in more uniform raw material mixing, stronger precursor interactions, more uniform product morphology, more ordered mesopores, and a more concentrated pore size distribution. The specific surface area of ​​the obtained ordered mesoporous carbon nanosheets is 400-800 m². 2 / g, and the mesopore size is concentrated in 5-30 nm, with good repeatability, which is conducive to large-scale industrial production.

[0024] 3. The ordered mesoporous carbon nanosheets prepared by this invention have good morphology and excellent electrochemical performance. At a current density of 0.5 A / g, the specific capacitance of the electrode material can reach up to 252 F / g. In addition, the nanosheets have a maximum specific capacitance of 162 F / g at a high current density of 20 A / g, indicating that they have good rate performance. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a transmission electron microscope (TEM) image of the ordered mesoporous nanosheets of Example 1 of the present invention.

[0027] Figure 2 This is a high-magnification TEM image of the ordered mesoporous carbon nanosheets in Example 1 of the present invention.

[0028] Figure 3 The image shows the isothermal adsorption curve of ordered mesoporous carbon nanosheets in Example 1 of this invention, and inset b is the pore size distribution curve.

[0029] Figure 4 This is the cyclic voltammetry (CV) diagram of ordered mesoporous carbon nanosheets in Example 1 of the present invention.

[0030] Figure 5 This is a constant current charge-discharge (GCD) diagram of ordered mesoporous carbon nanosheets in Example 1 of the present invention.

[0031] Figure 6 This is a specific capacity diagram calculated using GCD for ordered mesoporous carbon nanosheets in Example 1 of the present invention.

[0032] Figure 7 This is a TEM image of the ordered mesoporous nanosheets of Example 2 of the present invention.

[0033] Figure 8 The isothermal adsorption curve of ordered mesoporous carbon nanosheets in Example 2 of the present invention is shown in Figure b, which is the pore size distribution curve.

[0034] Figure 9 The isothermal adsorption curve of ordered mesoporous carbon nanosheets in Example 4 of the present invention is shown in Figure b, which is the pore size distribution curve.

[0035] Figure 10 This is a specific capacity diagram calculated using GCD for ordered mesoporous carbon nanosheets in Example 5 of the present invention. Detailed Implementation

[0036] 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.

[0037] Example 1

[0038] This embodiment provides a method for preparing ordered mesoporous carbon nanosheets, including the following steps:

[0039] 10 mL of potassium chloride aqueous solution (concentration 200 g / L) was added to the reactor, and then 12 mL of a mixed aqueous solution of glucose (concentration 300 g / L) and silica (concentration 200 g / L, particle size 9 nm) was slowly added dropwise (mass ratio of glucose to silica 1:2). The mixture was stirred at room temperature and pressure for 10 minutes, then freeze-dried at -20℃ for 40 h in a refrigerated dryer, annealed at 600 ℃ in an argon atmosphere for 4 h, and then etched with 3 M (mol / L) potassium hydroxide as a template agent for silica for 12 h to obtain black ordered mesoporous carbon nanosheets.

[0040] The structure of the ordered mesoporous carbon nanosheets prepared in this example was analyzed using a high-resolution transmission electron microscope (Talos F200X). Figure 1 and Figure 2 As shown in the figure, the obtained nanosheets have a uniform sheet structure and an ordered mesoporous structure, and the nanosheet size is 1 μm.

[0041] The adsorption isotherms of this embodiment were measured using a gas adsorption analyzer (model ASAP2020), and the resulting isotherm adsorption curves and pore size distribution curves are shown below. Figure 3 As shown, it exhibits a typical H3-type hysteresis loop, confirming the mesoporous structure of the material. The specific surface area of ​​the nanosheets was calculated to be 662 m² using the Brunauer-Emmett-Teller model. 2 / g, and the pore size distribution map shows that the pore size of the material is concentrated at 8.9 nm;

[0042] The ordered mesoporous carbon nanosheets obtained in this embodiment were subjected to three-electrode testing using an electrochemical workstation (model CHI 760E). The testing method was as follows: the sample of this embodiment was mixed and ground with conductive agent Ketjen black and binder polytetrafluoroethylene at a mass ratio of 8:1:1. Subsequently, a small amount of anhydrous ethanol was added and rolled into an electrode sheet, which was then dried and fixed onto a current collector. Then, using this as the working electrode, a platinum sheet as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, the sample was immersed in a 1 mol / L sulfuric acid electrolyte for CV and GCD tests. Figure 4 and Figure 5 These are the CV and GCD images of the nanosheets in this embodiment. Their response current and discharge time change synchronously with scan rate and current density, respectively, indicating that the nanosheets have good rate performance and electrochemical behavior. The specific capacity calculated by GCD of the mesoporous carbon nanosheets obtained in this embodiment is as follows: Figure 6 As shown, the specific capacitance of the electrode material reaches 225 F / g at a current density of 0.5 A / g. Furthermore, the nanosheet still has a specific capacitance of 140 F / g at a high current density of 20 A / g, indicating its good rate performance.

[0043] Example 2

[0044] This embodiment provides a method for preparing ordered mesoporous carbon nanosheets, including the following steps:

[0045] 7.5 mL of sodium chloride aqueous solution (concentration 300 g / L) was added to the reactor, followed by dropwise addition of a mixed aqueous solution (10 mL, chitosan oligosaccharide aqueous solution (concentration 100 g / L), silica aqueous solution (concentration 100 g / L, particle size 7 nm) (mass ratio of chitosan oligosaccharide to silica 1:4). The mixture was stirred at room temperature and pressure for 5 minutes, then freeze-dried at -40℃ for 36 h. Afterwards, it was annealed at 700℃ under a nitrogen atmosphere for 2 h, and the silica was etched with 2 M sodium hydroxide for 24 h to obtain black ordered mesoporous carbon nanosheets.

[0046] The structure of the ordered mesoporous carbon nanosheets prepared in this example was analyzed using a high-resolution transmission electron microscope (Talos F200X), such as... Figure 7 As shown, the obtained nanosheets have a uniform sheet structure and an ordered mesoporous structure, and the nanosheet size is 0.5 μm.

[0047] The adsorption isotherms of this embodiment were measured using a gas adsorption analyzer (model ASAP2020), and the resulting isotherm adsorption curves and pore size distribution curves are shown below. Figure 8 As shown, it exhibits a typical H3-type hysteresis loop, confirming the mesoporous structure of the material. The specific surface area of ​​the nanosheets was calculated to be 770 m² using the Brunauer-Emmett-Teller model.2 / g, with pore size concentrated at 6.5 nm;

[0048] The ordered mesoporous carbon nanosheets obtained in this embodiment were subjected to three-electrode testing using an electrochemical workstation (model CHI 760E). The testing method was as follows: the sample of this embodiment was mixed and ground with conductive agent Ketjen Black and binder polytetrafluoroethylene at a mass ratio of 8:1:1. Subsequently, a small amount of anhydrous ethanol was added and rolled into an electrode sheet, which was then dried and fixed onto a current collector. Then, using this as the working electrode, a platinum sheet as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, the electrode was immersed in a 1 mol / L sulfuric acid electrolyte for CV and GCD tests. The electrochemical performance of the ordered mesoporous nanosheets prepared in this embodiment was as follows: at a current density of 0.5 A / g, the specific capacitance of the electrode material reached 242 F / g. In addition, the nanosheets still had a specific capacitance of 153 F / g at a high current density of 20 A / g, indicating its good rate performance.

[0049] Example 3

[0050] This embodiment provides a method for preparing ordered mesoporous carbon nanosheets, including the following steps:

[0051] 10 mL of sodium sulfate aqueous solution (concentration 300 g / L) was added to the reactor, and then 8 mL of a mixed aqueous solution of sucrose (concentration 200 g / L) and silica (concentration 100 g / L, particle size 12 nm) was slowly added dropwise. The mixture was stirred at room temperature and pressure for 15 minutes, then freeze-dried at -60℃ for 24 h, annealed in a helium atmosphere at 500℃ for 6 h, and silica was etched with 2 M sodium hydroxide for 15 h to obtain black ordered mesoporous carbon nanosheets.

[0052] The structure of the ordered mesoporous carbon nanosheets prepared in this example was analyzed using a high-resolution transmission electron microscope (Talos F200X). The obtained nanosheets have a uniform sheet structure and an ordered mesoporous structure, and the nanosheet size is 1.5 μm.

[0053] The adsorption isotherms of this embodiment were measured using a gas adsorption analyzer (model ASAP2020). The isothermal adsorption curves and pore size distribution curves of the nanosheets in this embodiment showed their typical H3-type hysteresis loop, confirming the mesoporous structure of the material. The specific surface area of ​​the nanosheets was calculated to be 539 m² using the Brunauer-Emmett-Teller model. 2 / g, with pore size concentrated at 11.7 nm.

[0054] The ordered mesoporous carbon nanosheets obtained in this embodiment were subjected to three-electrode testing using an electrochemical workstation (model CHI 760E). The testing method was as follows: the sample of this embodiment was mixed and ground with conductive agent Ketjen Black and binder polytetrafluoroethylene at a mass ratio of 8:1:1. Subsequently, a small amount of anhydrous ethanol was added and rolled into an electrode sheet, which was then dried and fixed onto a current collector. Then, using this as the working electrode, a platinum sheet as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, the electrode was immersed in a 1 mol / L sulfuric acid electrolyte for CV and GCD tests. The electrochemical performance of the prepared ordered mesoporous nanosheets was as follows: at a current density of 0.5 A / g, the specific capacitance of the electrode material reached 210 F / g. In addition, the nanosheets still had a specific capacitance of 128 F / g at a high current density of 20 A / g, indicating its good rate performance.

[0055] Example 4

[0056] This embodiment provides a method for preparing ordered mesoporous carbon nanosheets, including the following steps:

[0057] 8 mL of potassium sulfate aqueous solution (concentration 250 g / L) was added to the reactor, and then 12 mL of a mixed aqueous solution of chitosan oligosaccharide aqueous solution (concentration 300 g / L) and silica aqueous solution (concentration 150 g / L, particle size 22 nm) was slowly added dropwise. The mixture was stirred at room temperature and pressure for 15 minutes, then freeze-dried at -10℃ for 48 h in a refrigerated dryer, annealed at 900 ℃ in a helium atmosphere for 1 h, and etched with 2.5 M sodium hydroxide for 20 h to obtain black ordered mesoporous carbon nanosheets.

[0058] The structure of the ordered mesoporous carbon nanosheets prepared in the examples was analyzed using a high-resolution transmission electron microscope (Talos F200X). The obtained nanosheets have a uniform layered structure and an ordered mesoporous structure, and the nanosheet size is 2.0 μm.

[0059] The adsorption isotherm of this embodiment was measured using a gas adsorption analyzer (model ASAP2020). Figure 9 The isothermal adsorption curve and pore size distribution curve of the nanosheet in this embodiment show that it exhibits a typical H3-type hysteresis loop, confirming the mesoporous structure of the material. The specific surface area of ​​the nanosheet was calculated to be 431 m² using the Brunauer-Emmett-Teller model. 2 / g, with pore size concentrated at 23.9 nm.

[0060] The ordered mesoporous carbon nanosheets obtained in this embodiment were subjected to three-electrode testing using an electrochemical workstation (model CHI 760E). The testing method was as follows: the sample of this embodiment was mixed and ground with conductive agent Ketjen black and binder polytetrafluoroethylene at a mass ratio of 8:1:1. Subsequently, a small amount of anhydrous ethanol was added and rolled into an electrode sheet, which was then dried and fixed onto a current collector. Then, using this as the working electrode, a platinum sheet as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, the electrode was immersed in 1 mol / L sulfuric acid electrolyte for CV and GCD tests. The electrochemical performance of the prepared ordered mesoporous nanosheets was as follows: at a current density of 0.5 A / g, the specific capacitance of the electrode material reached 201 F / g. In addition, the nanosheets still had a specific capacitance of 111 F / g at a high current density of 20 A / g, indicating its good rate performance.

[0061] Example 5

[0062] This embodiment provides a method for preparing ordered mesoporous carbon nanosheets, including the following steps:

[0063] 9 mL of potassium chloride aqueous solution (concentration 280 g / L) was added to the reactor, and then a mixed aqueous solution of glucose aqueous solution (concentration 250 g / L) and silica aqueous solution (concentration 180 g / L, particle size 30 nm) (13.5 mL, mass ratio of chitosan oligosaccharide to silica 1:3.5) was slowly added dropwise. The mixture was stirred at room temperature and pressure for 5 minutes, then freeze-dried at -20℃ for 30 h in a refrigerated dryer, annealed at 700℃ in a helium atmosphere for 4 h, and etched with 2.8 M sodium hydroxide for 15 h to obtain black ordered mesoporous carbon nanosheets.

[0064] The structure of the ordered mesoporous carbon nanosheets prepared in this example was analyzed using a high-resolution transmission electron microscope (Talos F200X). The obtained nanosheets have a uniform sheet structure and an ordered mesoporous structure, and the nanosheet size is 2.6 μm.

[0065] The adsorption isotherms of this embodiment were measured using a gas adsorption analyzer (model ASAP2020). The isothermal adsorption curves and pore size distribution curves of the nanosheets in this embodiment showed their typical H3-type hysteresis loop, confirming the mesoporous structure of the material. The specific surface area of ​​the nanosheets was calculated to be 401 m² using the Brunauer-Emmett-Teller model. 2 / g, with pore size concentrated at 29.8 nm.

[0066] The ordered mesoporous carbon nanosheets obtained in this embodiment were subjected to three-electrode testing using an electrochemical workstation (model CHI 760E). The testing method was as follows: the sample of this embodiment was mixed and ground with conductive agent Ketjen Black and binder polytetrafluoroethylene at a mass ratio of 8:1:1. Subsequently, a small amount of anhydrous ethanol was added and rolled into an electrode sheet, which was then dried and fixed onto a current collector. Then, using this as the working electrode, a platinum sheet as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, the sample was immersed in 1 mol / L sulfuric acid electrolyte for CV and GCD tests. The specific capacity calculated by GCD of the nanosheets in this embodiment is as follows. Figure 10 As shown, the specific capacitance of the electrode material reaches 187 F / g at a current density of 0.5 A / g. Furthermore, the nanosheet still has a specific capacitance of 103 F / g at a high current density of 20 A / g, indicating its good rate performance.

[0067] Example 6

[0068] This embodiment provides a method for preparing ordered mesoporous carbon nanosheets, including the following steps:

[0069] 8 mL of sodium sulfate aqueous solution (concentration 200 g / L) was added to the reactor, and then 10 mL of a mixed aqueous solution of chitosan oligosaccharide (concentration 120 g / L) and silica (concentration 180 g / L, particle size 5 nm) was slowly added dropwise. The mixture was stirred at room temperature and pressure for 15 minutes, then freeze-dried at -30℃ for 48 h in a refrigerated dryer, annealed in a helium atmosphere at 800℃ for 1.5 h, and silica was etched with 2 M sodium hydroxide for 24 h to obtain black ordered mesoporous carbon nanosheets.

[0070] The structure of the ordered mesoporous carbon nanosheets prepared in this example was analyzed using a high-resolution transmission electron microscope (Talos F200X). The obtained nanosheets have a uniform sheet structure and an ordered mesoporous structure, and the nanosheet size is 0.4 μm.

[0071] The adsorption isotherms of this embodiment were measured using a gas adsorption analyzer (model ASAP2020). The isothermal adsorption curves and pore size distribution curves of the nanosheets in this embodiment showed their typical H3-type hysteresis loop, confirming the mesoporous structure of the material. The specific surface area of ​​the nanosheets was calculated to be 792 m² using the Brunauer-Emmett-Teller model. 2 / g, with pore size concentrated at 5.2 nm.

[0072] The ordered mesoporous carbon nanosheets obtained in this embodiment were subjected to three-electrode testing using an electrochemical workstation (model CHI 760E). The testing method was as follows: the sample of this embodiment was mixed and ground with conductive agent Ketjen Black and binder polytetrafluoroethylene at a mass ratio of 8:1:1. Subsequently, a small amount of anhydrous ethanol was added and rolled into an electrode sheet, which was then dried and fixed onto a current collector. Then, using this as the working electrode, a platinum sheet as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, the electrode was immersed in a 1 mol / L sulfuric acid electrolyte for CV and GCD tests. The electrochemical performance of the prepared ordered mesoporous nanosheets was as follows: at a current density of 0.5 A / g, the specific capacitance of the electrode material reached 252 F / g. In addition, the nanosheets still had a specific capacitance of 162 F / g at a high current density of 20 A / g, indicating its good rate performance.

[0073] Example 7

[0074] This embodiment provides a method for preparing ordered mesoporous carbon nanosheets, including the following steps:

[0075] 7 mL of potassium sulfate aqueous solution (concentration 300 g / L) was added to the reactor, followed by the slow addition of a mixed aqueous solution (9 mL, mass ratio of chitosan oligosaccharide to silica 1:2.5) of sucrose aqueous solution (concentration 300 g / L) and silica aqueous solution (concentration 120 g / L, particle size 25 nm). The mixture was stirred at room temperature and pressure for 7.5 minutes, then freeze-dried at -50℃ for 40 h, annealed at 650℃ in a helium atmosphere for 3.5 h, and etched with 2.2 M sodium hydroxide for 20 h to obtain black ordered mesoporous carbon nanosheets.

[0076] The structure of the ordered mesoporous carbon nanosheets prepared in this example was analyzed using a high-resolution transmission electron microscope (Talos F200X). The obtained nanosheets have a uniform sheet structure and an ordered mesoporous structure, and the nanosheet size is 2.2 μm.

[0077] The adsorption isotherms of this embodiment were measured using a gas adsorption analyzer (model ASAP2020). The isothermal adsorption curves and pore size distribution curves of the nanosheets in this embodiment showed their typical H3-type hysteresis loop, confirming the mesoporous structure of the material. The specific surface area of ​​the nanosheets was calculated to be 418 m² using the Brunauer-Emmett-Teller model. 2 / g, with pore size concentrated at 24.6 nm.

[0078] The ordered mesoporous carbon nanosheets obtained in this embodiment were subjected to three-electrode testing using an electrochemical workstation (model CHI 760E). The testing method was as follows: the sample of this embodiment was mixed and ground with conductive agent Ketjen Black and binder polytetrafluoroethylene at a mass ratio of 8:1:1. Subsequently, a small amount of anhydrous ethanol was added and rolled into an electrode sheet, which was then dried and fixed onto a current collector. Then, using this as the working electrode, a platinum sheet as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, the electrode was immersed in a 1 mol / L sulfuric acid electrolyte for CV and GCD tests. The electrochemical performance of the prepared ordered mesoporous nanosheets was as follows: at a current density of 0.5 A / g, the specific capacitance of the electrode material reached 192 F / g. In addition, the nanosheets still had a specific capacitance of 116 F / g at a high current density of 20 A / g, indicating its good rate performance.

[0079] Example 8

[0080] This embodiment provides a method for preparing ordered mesoporous carbon nanosheets, including the following steps:

[0081] 10 mL of sodium sulfate aqueous solution (concentration 250 g / L) was added to the reactor, and then a mixed aqueous solution (14 mL, mass ratio of chitosan oligosaccharide to silica 1:3) was slowly added dropwise. The mixture was stirred at room temperature and pressure for 12 minutes, then freeze-dried at -35℃ for 36 h, annealed at 850℃ in a helium atmosphere for 1 h, and etched with 2 M potassium hydroxide for 24 h to obtain black ordered mesoporous carbon nanosheets.

[0082] The structure of the ordered mesoporous carbon nanosheets prepared in this example was analyzed using a high-resolution transmission electron microscope (Talos F200X). The obtained nanosheets have a uniform sheet structure and an ordered mesoporous structure, and the nanosheet size is 1.8 μm.

[0083] The adsorption isotherms of this embodiment were measured using a gas adsorption analyzer (model ASAP2020). The isothermal adsorption curves and pore size distribution curves of the nanosheets in this embodiment showed their typical H3-type hysteresis loop, confirming the mesoporous structure of the material. The specific surface area of ​​the nanosheets was calculated to be 522 m² using the Brunauer-Emmett-Teller model. 2 / g, with pore size concentrated at 14.9 nm.

[0084] The ordered mesoporous carbon nanosheets obtained in this embodiment were subjected to three-electrode testing using an electrochemical workstation (model CHI 760E). The testing method was as follows: the sample of this embodiment was mixed and ground with conductive agent Ketjen Black and binder polytetrafluoroethylene at a mass ratio of 8:1:1. Subsequently, a small amount of anhydrous ethanol was added and rolled into an electrode sheet, which was then dried and fixed onto a current collector. Then, using this as the working electrode, a platinum sheet as the counter electrode, and silver / silver chloride (Ag / AgCl) as the reference electrode, the electrode was immersed in a 1 mol / L sulfuric acid electrolyte for CV and GCD tests. The electrochemical performance of the prepared ordered mesoporous nanosheets was as follows: at a current density of 0.5 A / g, the specific capacitance of the electrode material reached 208 F / g. In addition, the nanosheets still had a specific capacitance of 122 F / g at a high current density of 20 A / g, indicating its good rate performance.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing ordered mesoporous carbon nanosheets, characterized in that, Includes the following steps: (1) Add a mixture of aqueous solutions of sugar and mesoporous template agent A to a soluble sodium / potassium salt aqueous solution, stir evenly and freeze dry to obtain the precursor; (2) The obtained precursor was annealed in an inert atmosphere, and then the mesoporous template agent was removed to obtain black ordered mesoporous carbon nanosheets. In step (1), the soluble sodium / potassium salt is any one of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate; the sugar is any one of glucose, sucrose, and chitosan oligosaccharide; and the mesoporous template agent is silica nanospheres. In step (2), the inert atmosphere is nitrogen, helium or argon; the annealing conditions are: temperature 500-900 ℃, time 1-6h, and the freeze-drying temperature is (-60)-(-10)℃, time is 24-48h.

2. The method for preparing ordered mesoporous carbon nanosheets according to claim 1, characterized in that: In step (1), the concentration of the soluble sodium / potassium salt aqueous solution is 200-300 g / L; the concentration of the sugar aqueous solution is 100-300 g / L; the concentration of the silica nanosphere aqueous solution is 100-200 g / L, and the particle size of the silica nanospheres is 5-30 nm.

3. The method for preparing ordered mesoporous carbon nanosheets according to claim 2, characterized in that: In step (1), the mass ratio of sugars to mesoporous template agent is 1:(2-4), and the volume ratio of soluble sodium / potassium salt aqueous solution to mixed aqueous solution A is 1:(0.8-1.5).

4. The method for preparing ordered mesoporous carbon nanosheets according to claim 3, characterized in that: In step (1), the stirring temperature is room temperature and the stirring time is 5-15 min.

5. The method for preparing ordered mesoporous carbon nanosheets according to claim 4, characterized in that, The removal of the mesoporous template agent in step (2) includes: removing the mesoporous template agent by immersion in an etchant; the etchant is sodium hydroxide or potassium hydroxide, the concentration of the etchant is 2-3 mol / L, and the etching time is 12-24 h.

6. Ordered mesoporous carbon nanosheets prepared by the method according to any one of claims 1-5, characterized in that: The ordered mesoporous carbon nanosheets have a specific surface area of ​​400-800 m². 2 / g, with mesopore sizes concentrated in the range of 5-30 nm.

7. The ordered mesoporous carbon nanosheets according to claim 6, characterized in that, The ordered mesoporous carbon nanosheets have a size of 0.4-2.6 μm.

8. The application of the ordered mesoporous carbon nanosheets according to claim 6 in the fields of batteries, capacitors, and catalysis.

Images