Preparation method of universal two-dimensional mesoporous nitrogen-doped carbon composite material

Abstract

The application belongs to the technical field of nano inorganic materials, and relates to a universal preparation method of two-dimensional mesoporous nitrogen-doped carbon composite materials. A positively charged chitosan oligosaccharide and a negatively charged SiO2 nanosphere dispersion liquid are uniformly mixed to obtain a mixed liquid, then an aqueous solution of two-dimensional nanosheets is added under stirring, and after room temperature stirring, freeze-drying, high-temperature treatment in an inert atmosphere and template removal, the two-dimensional mesoporous nitrogen-doped carbon composite material is obtained. The preparation method provided by the application is simple, convenient to operate, has few steps and low cost; the method is universal, different two-dimensional mesoporous nitrogen-doped carbon composite materials can be obtained by replacing different two-dimensional substrates. Moreover, the method has good controllability and repeatability, and can realize accurate control of mesoporous pore size and nanosheet thickness; the prepared material also has good electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of nano-inorganic materials technology and relates to a universal method for preparing two-dimensional mesoporous nitrogen-doped carbon composite materials. Background Technology

[0002] Two-dimensional mesoporous nitrogen-doped carbon materials are mainly prepared by carbonizing nitrogen-containing precursors, such as some nitrogen-containing organic polymers. Their two-dimensional morphology and mesoporous structure are mainly obtained through self-assembly or reaction during carbonization, and therefore the two-dimensional morphology and mesoporous structure are usually non-uniform.

[0003] Two-dimensional mesoporous nitrogen-doped carbon composites typically use a two-dimensional material as a substrate, with mesoporous carbon materials composited onto the two-dimensional substrate to obtain a sandwich-like composite material. The introduction of mesopores requires a template, generally categorized into soft template and hard template methods. This allows for more controllable and uniform two-dimensional morphology and mesoporous structure. Existing methods for preparing two-dimensional mesoporous nitrogen-doped carbon materials and carbon composites, such as the method reported in Chinese patent CN108597911A, use spherical micelles formed from polystyrene-b-polyethylene oxide (PS-b-PEO) as mesoporous templates, and Co... 2+ -Ni 2+ Two-dimensional mesoporous poly(m-phenylene diamine) precursors are grown using layered bilayer metal hydroxide nanosheets as two-dimensional sacrificial templates, and further pyrolysis yields nitrogen-doped carbon nanosheets with a two-dimensional mesoporous structure. Another Chinese patent, CN103072973A, uses hydroxyl-rich carbohydrates as the carbon source and ammonia as the nitrogen source. A nitrogen-rich precursor is prepared via amination under hydrothermal conditions. This precursor is then used as a template with mesoporous silica molecular sieve SBA-15, and nitrogen-doped carbon nanosheets with a two-dimensional hexagonal ordered mesoporous structure are prepared through multiple wetting combined with high-temperature pyrolysis. Another example is a method for preparing two-dimensional mesoporous nitrogen-doped carbon composite nanosheets mentioned in CCSChem.2020, 2, 870-881. This method uses 2,6-diaminopyridine (DAP) as the carbon and nitrogen source, PS-b-PEO as the mesoporous template, and graphene oxide as the structure directing agent for the two-dimensional material. The method involves polymerization initiated by ammonium persulfate and high-temperature carbonization under an inert atmosphere to obtain two-dimensional nitrogen-doped carbon composite graphene nanosheets with a mesoporous structure. Another example is the method for preparing nitrogen-doped carbon composite nanosheets with uniform and tunable mesopores mentioned in the literature Angew. Chem. 2014, 126, 1596-1600. Polydopamine (PDA) is used as the carbon and nitrogen source, SiO2 nanospheres are used as the mesoporous template, and graphene oxide is used as the two-dimensional substrate. Through polymerization reaction, high-temperature carbonization and removal of SiO2 template, two-dimensional nitrogen-doped carbon composite graphene nanosheets with mesoporous structure are obtained.

[0004] However, the preparation of two-dimensional mesoporous nitrogen-doped carbon composite materials currently requires certain operational techniques, and research on this topic is limited, with even fewer reports. The patents and literature listed above all use graphene as a two-dimensional substrate, resulting in predominantly two-dimensional mesoporous nitrogen-doped carbon-graphene materials. This leads to a limited range of structures and types of two-dimensional mesoporous nitrogen-doped carbon composite materials; the preparation process is cumbersome and involves lengthy experimental steps, hindering large-scale production; and the methods lack versatility and controllability, making it difficult to obtain two-dimensional mesoporous nitrogen-doped carbon composite materials with different compositions, pore sizes, and thicknesses. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a universal method for preparing two-dimensional mesoporous nitrogen-doped carbon composite materials. The method provided by this invention is simple, convenient to operate, involves few steps, and is low in cost. It has good universality, allowing for the preparation of different two-dimensional mesoporous composite materials by using different two-dimensional substrates. Furthermore, the method offers good controllability, enabling precise control of mesopore size and nanosheet thickness. Simultaneously, the method exhibits good reproducibility, and the prepared two-dimensional mesoporous nitrogen-doped carbon composite materials possess excellent electrochemical properties.

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

[0007] A universal method for preparing two-dimensional mesoporous nitrogen-doped carbon composite materials includes the following steps: a positively charged aqueous solution of chitosan oligosaccharide and a negatively charged aqueous solution of SiO2 nanospheres are uniformly mixed to obtain a mixture. Then, an aqueous solution of two-dimensional nanosheets is added under stirring conditions. After stirring at room temperature, freeze-drying, high-temperature treatment under an inert atmosphere, and template removal, the two-dimensional mesoporous nitrogen-doped carbon composite material is obtained.

[0008] Furthermore, the mass ratio of chitosan oligosaccharide to SiO2 is 1:(0.8-1.25); the concentration of the chitosan oligosaccharide aqueous solution is 50-200 mg / mL, and the concentration of the SiO2 nanosphere aqueous solution is 200-400 mg / mL.

[0009] Preferably, the aqueous solution concentration of the chitosan oligosaccharide is 150 mg / mL, and the aqueous solution concentration of the SiO2 nanospheres is 300 mg / mL.

[0010] Furthermore, the two-dimensional nanosheets are any one of MXenes, graphene oxide, BN, or MoS2 nanosheets.

[0011] Furthermore, the concentration of the two-dimensional nanosheets is 1-5 mg / mL.

[0012] Furthermore, the volume ratio of the mixture to the aqueous solution of the two-dimensional nanosheets is (3-6):(4-8).

[0013] Furthermore, the freeze-drying time is 24-72 hours.

[0014] Furthermore, the inert atmosphere is nitrogen, the annealing temperature is 600-800℃, and the annealing time is 1-3 hours.

[0015] Furthermore, the template removal method is as follows: etching with HF (10wt%) aqueous solution or NaOH aqueous solution, followed by washing with high-purity water until the solution is neutral.

[0016] Furthermore, the universal two-dimensional mesoporous nitrogen-doped carbon composite material prepared by the above method has a size of 0.5-5 μm, a thickness of 6-15 nm, and a mesopore diameter of 5-13 nm.

[0017] Furthermore, the application of the aforementioned universal two-dimensional mesoporous nitrogen-doped carbon composite material in the field of electrode materials.

[0018] The reaction mechanism of this invention is as follows: Since chitosan oligosaccharides are positively charged, they can be uniformly distributed on the surface of negatively charged SiO2 nanospheres and assembled into positively charged spheres. Meanwhile, the surfaces of two-dimensional nanosheets such as MXene, rGO, BN, or MoS2 have some negatively charged functional groups. Through mutual attraction between positive and negative charges, the SiO2 nanospheres coated with chitosan oligosaccharides can be uniformly distributed on the surface of the two-dimensional nanosheets. After stirring at room temperature and freeze-drying, the mixture is then subjected to high-temperature treatment (carbonization of chitosan oligosaccharides) and template removal (removal of SiO2 nanospheres) under an inert atmosphere to obtain a two-dimensional mesoporous nitrogen-doped carbon composite material.

[0019] The present invention has the following beneficial effects:

[0020] 1. The preparation method of the present invention avoids the problems of excessive reaction time, complicated steps and poor controllability of the original technology, and has the advantages of simple method, convenient operation, few steps and cost saving.

[0021] 2. The preparation method of this invention is universal and can be changed to different two-dimensional substrates to obtain different two-dimensional mesoporous composite materials.

[0022] 3. The preparation method of this invention has good controllability. By changing the particle size of SiO2 nanospheres, the mesopore size can be precisely controlled (5-13 nm). By changing the concentration and amount of chitosan oligosaccharide added, the thickness of the nanosheets can be precisely controlled (6-15 nm). It has good repeatability and excellent electrochemical performance. In 1 mol / L sulfuric acid electrolyte, at a current density of 1 A / g, the specific capacities of the two-dimensional mesoporous nitrogen-doped carbon-MoS2 composite material, the two-dimensional mesoporous nitrogen-doped carbon-graphene composite material, and the two-dimensional mesoporous nitrogen-doped carbon-MXene composite material are 210 F / g, 138 F / g, and 156 F / g, respectively. Attached Figure Description

[0023] 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.

[0024] Figure 1 The image shows the XRD pattern of the two-dimensional mesoporous nitrogen-doped carbon-MXene composite material prepared in Example 1 of this invention.

[0025] Figure 2 This is a TEM image of the two-dimensional mesoporous nitrogen-doped carbon-MXene composite material prepared in Example 1 of the present invention.

[0026] Figure 3 The N2 adsorption-desorption isotherm and pore structure distribution diagram are shown for the two-dimensional mesoporous nitrogen-doped carbon-MXene composite material prepared in Example 1 of this invention.

[0027] Figure 4 This is a constant current charge-discharge diagram of the two-dimensional mesoporous nitrogen-doped carbon-MXene composite material prepared in Example 1 of the present invention.

[0028] Figure 5 This is a TEM image of the two-dimensional mesoporous nitrogen-doped carbon-graphene composite material prepared in Example 2 of the present invention.

[0029] Figure 6 The image shows the constant current charge-discharge diagram of the two-dimensional mesoporous nitrogen-doped carbon-graphene composite material prepared in Example 2 of this invention.

[0030] Figure 7 The image shows the Raman diagram of the two-dimensional mesoporous nitrogen-doped carbon-BN composite material prepared in Example 3 of this invention.

[0031] Figure 8 This is a TEM image of the two-dimensional mesoporous nitrogen-doped carbon-BN composite material prepared in Example 3 of the present invention.

[0032] Figure 9 The cyclic voltammetry curve is shown for the two-dimensional mesoporous nitrogen-doped carbon-MoS2 composite material prepared in Example 4 of this invention.

[0033] Figure 10 The constant current charge-discharge diagram is shown for the two-dimensional mesoporous nitrogen-doped carbon-MoS2 composite material prepared in Example 4 of this invention. Detailed Implementation

[0034] 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.

[0035] Example 1

[0036] This embodiment describes a method for preparing two-dimensional mesoporous nitrogen-doped carbon-MXene composite materials, with the following steps:

[0037] Add 5 mL of a mixed aqueous solution of chitosan oligosaccharide and SiO2 nanospheres to a reaction flask to make the mass ratio of chitosan oligosaccharide to SiO2 (particle size 12 nm) 5:4. Then slowly add 4 mL of MXene aqueous solution (5 mg / mL), freeze dry rapidly for 24 h, further treat at 700 °C in N2 atmosphere for 2 h, etch with HF (10 wt%) aqueous solution for 12 h, and wash with high-purity water until the solution is neutral to obtain a two-dimensional mesoporous nitrogen-doped carbon-MXene composite material.

[0038] Figure 1 The image shows the XRD pattern of the two-dimensional mesoporous nitrogen-doped carbon-MXene composite material prepared in this embodiment.

[0039] Figure 2 This is a TEM image of the two-dimensional mesoporous nitrogen-doped carbon-MXene composite material prepared in this embodiment.

[0040] Figure 3 The images show the N2 adsorption-desorption isotherms and pore structure distribution of the two-dimensional mesoporous nitrogen-doped carbon-MXene composite material prepared in this embodiment. Figure 1-3 As shown, the two-dimensional mesoporous nitrogen-doped carbon-MXene material has a size of about 1-2 μm and a thickness of about 15 nm, with the mesopore size mainly concentrated at 12 nm.

[0041] Figure 4 This is a constant current charge-discharge diagram of the two-dimensional mesoporous nitrogen-doped carbon-MXene composite material prepared in this embodiment. Figure 4 As shown, in a 1 mol / L sulfuric acid electrolyte, at a current density of 1 A / g, the specific capacity of the two-dimensional mesoporous nitrogen-doped carbon-MXene composite material is 156 F / g.

[0042] Example 2

[0043] This embodiment describes a method for preparing a two-dimensional mesoporous nitrogen-doped carbon-graphene composite material, and the steps are as follows:

[0044] 3 mL of a mixed aqueous solution of chitosan oligosaccharide and SiO2 nanospheres was added to the reaction flask to make the mass ratio of chitosan oligosaccharide to SiO2 (particle size 7 nm) 1:1. Then, 5 mL of GO aqueous solution (2 mg / mL) was slowly added dropwise, and the mixture was rapidly freeze-dried for 48 h. After further treatment in an Ar2 atmosphere at 800 °C for 1 h, it was etched with HF (10 wt%) aqueous solution and washed with high-purity water until the solution was neutral to obtain two-dimensional mesoporous nitrogen-doped graphene composite nanosheets.

[0045] Figure 5 This is a TEM image of the two-dimensional mesoporous nitrogen-doped carbon-graphene composite material prepared in this embodiment. Figure 5 As shown, the two-dimensional mesoporous nitrogen-doped carbon-graphene material has a size of about 1-5 μm, a thickness of about 10 nm, and a mesopore size of 5-8 nm.

[0046] Figure 6 This is a constant current charge-discharge diagram of the two-dimensional mesoporous nitrogen-doped carbon-graphene composite material prepared in this embodiment. Figure 6 As shown, in a 1 mol / L sulfuric acid electrolyte, at a current density of 1 A / g, the specific capacity of the two-dimensional mesoporous nitrogen-doped carbon-graphene composite material is 138 F / g.

[0047] Example 3

[0048] This embodiment describes a method for preparing two-dimensional mesoporous nitrogen-doped carbon-BN composite materials, and the steps are as follows:

[0049] 4 mL of a mixed aqueous solution of chitosan oligosaccharide and SiO2 nanospheres was added to the reaction flask to make the mass ratio of chitosan oligosaccharide to SiO2 (particle size 12 nm) 5:6. Then, 4 mL of BN aqueous solution (3 mg / mL) was slowly added dropwise, and the mixture was rapidly freeze-dried for 36 h. The mixture was then further treated in a N2 atmosphere at 600 °C for 3 h, etched with NaOH aqueous solution, and washed with high-purity water until the solution was neutral to obtain two-dimensional mesoporous nitrogen-doped carbon-BN composite nanosheets.

[0050] Figure 7 The image shows the Raman diagram of the two-dimensional mesoporous nitrogen-doped carbon-BN composite material prepared in Example 3 of this invention.

[0051] Figure 8 This is a TEM image of the two-dimensional mesoporous nitrogen-doped carbon-BN composite material prepared in Example 3 of the present invention. Figure 7 and 8 As shown, the two-dimensional mesoporous nitrogen-doped carbon-BN material has a size of about 0.5-2 μm, a thickness of about 6 nm, and a mesopore size of 11-13 nm.

[0052] Example 4

[0053] This embodiment describes a method for preparing two-dimensional mesoporous nitrogen-doped carbon-MoS2 composite materials, and the steps are as follows:

[0054] 6 mL of a mixed aqueous solution of chitosan oligosaccharide and SiO2 nanospheres was added to the reaction flask to make the mass ratio of chitosan oligosaccharide to SiO2 (particle size 22 nm) 4:5. Then, 8 mL of MoS2 aqueous solution (1.7 mg / mL) was slowly added dropwise, and the mixture was rapidly freeze-dried for 72 h. It was then further treated in an Ar2 atmosphere at 650 °C for 2 h, etched with NaOH aqueous solution, and washed with high-purity water until the solution was neutral to obtain two-dimensional mesoporous nitrogen-doped carbon-MoS2 composite nanosheets.

[0055] Figure 9 The image shows the cyclic voltammetry curves of the two-dimensional mesoporous nitrogen-doped carbon-MoS2 composite material prepared in this embodiment.

[0056] Figure 10 This is a constant current charge-discharge diagram of the two-dimensional mesoporous nitrogen-doped carbon-MoS2 composite material prepared in this embodiment. Figure 10 As shown, in a 1 mol / L sulfuric acid electrolyte, at a current density of 1 A / g, the specific capacity of the two-dimensional mesoporous nitrogen-doped carbon-MoS2 composite material is 210 F / g.

[0057] 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 universal method for preparing two-dimensional mesoporous nitrogen-doped carbon composite materials, characterized in that, The steps are as follows: Chitosan oligosaccharide aqueous solution and SiO2 nanosphere aqueous solution are uniformly mixed to obtain a mixture. Then, an aqueous solution of two-dimensional nanosheets is added under stirring conditions. After stirring at room temperature and freeze-drying for 24-72 hours, the mixture is subjected to high-temperature treatment and template removal under an inert atmosphere to obtain a two-dimensional mesoporous nitrogen-doped carbon composite material. The mass ratio of chitosan oligosaccharide to SiO2 nanospheres is 1:(0.8-1.25); the concentration of the chitosan oligosaccharide aqueous solution is 50-200 mg / mL, the concentration of the SiO2 nanosphere aqueous solution is 200-400 mg / mL, and the particle size of the SiO2 nanospheres is 7-22 nm. The two-dimensional nanosheets are any one of MXenes, graphene oxide, BN or MoS2 nanosheets; The inert atmosphere is nitrogen, the high temperature treatment temperature is 600-800℃, and the high temperature treatment time is 1-3h; The template removal method is as follows: etching with 10wt% HF aqueous solution or NaOH aqueous solution, followed by washing with high-purity water until the solution is neutral; The universal two-dimensional mesoporous nitrogen-doped carbon composite material has a size of 0.5-5 μm and a thickness of 6-15 nm. The mesoporous pore size can be controlled by changing the particle size of SiO2 nanospheres, with a mesoporous pore size of 5-13 nm.

2. The method for preparing the universal two-dimensional mesoporous nitrogen-doped carbon composite material according to claim 1, characterized in that: The concentration of the aqueous solution of the two-dimensional nanosheets is 1-5 mg / mL.

3. The method for preparing the universal two-dimensional mesoporous nitrogen-doped carbon composite material according to claim 2, characterized in that: The volume ratio of the mixture to the aqueous solution of the two-dimensional nanosheets is (3-6):(4-8).

4. The application of the universal two-dimensional mesoporous nitrogen-doped carbon composite material prepared by the method of claim 1 in the field of electrode materials.

Images