Preparation method of nitrogen-doped lamp wick grass spherical carbon material

Abstract

A preparation method of nitrogen-doped rush spherical carbon material, comprising the following steps: (1) drying, peeling, extracting, cutting, puffing, and then crushing the rush to obtain puffed rush powder; (2) adding the puffed rush powder into an acid solution, mixing and stirring, and then placing the mixture in a sealed hydrothermal kettle to perform a hydrothermal activation reaction, cooling to room temperature, centrifugal separation and washing until neutral to obtain a pre-prepared rush carbon carrier; (3) mixing the pre-prepared rush carbon carrier, an organic nitrogen source or a nitrogen-doped pre-polymer, and a shaping agent, and then performing protective calcination under an inert atmosphere, and then soaking the mixture in an acid solution, filtering and washing until the pH value of the supernatant is neutral, and drying to obtain the nitrogen-doped rush spherical carbon material. The carbon material obtained by the method has stable spherical morphology characteristics, controllable specific surface area and pore size distribution, simple process, environmental friendliness, rich raw material sources, low cost, and is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of carbon material, in particular to a preparation method of nitrogen-doped rush-shaped spherical carbon material. BACKGROUND

[0002] Carbon material is a key material in the fields of energy, catalysis and environment, and its performance is highly dependent on microstructure and chemical composition. Carbon nanospheres are an important carbon nanomaterial, which has a wide range of applications in energy storage, catalysis, adsorption and other fields due to its unique spherical structure, high specific surface area and adjustable pore structure. Controlling the morphology and heteroatom doping of carbon material are two core strategies to improve its performance. Among them, nitrogen doping can effectively change the electron-donating properties, surface polarity and chemical stability of carbon material, thereby significantly enhancing its catalytic activity and charge transport capacity in electrochemical reactions. At the same time, constructing spherical morphology helps to obtain high packing density, good fluidity and structural stability, which is very suitable as an electrode material or catalyst carrier, and has potential advantages in separation and adsorption, electrochemistry, catalytic support engineering and other fields.

[0003] As a kind of natural biomass material, rush has a unique through-pore structure inside, which is theoretically an ideal porous carbon precursor. However, the product obtained by directly carbonizing rush in the prior art is usually irregular blocky or fibrous carbon, which has uncontrollable morphology, limited specific surface area, and it is difficult to achieve effective nitrogen doping. The existing technical route faces great challenges in directly converting fibrous raw materials such as rush into spherical carbon material with uniform morphology and good dispersion. CN 118976525A discloses a preparation method of porous nitrogen-doped carbon supported noble metal catalyst, but its carrier preparation process is complex, and the carbon source is still limited to non-renewable petroleum chemical products. CN 103787303A discloses a natural biomass in-situ conversion preparation method of hierarchical porous carbon, and CN 109485042A discloses a preparation method of activated carbon material based on interconnected porous structure of rush / cord rush, but both of them disclose the preparation method of porous network structure activated carbon material, and do not involve the regulation of nitrogen doping on the morphology and structural performance of activated carbon.

[0004] In summary, it is urgent to develop a preparation method that can use natural and low-cost rush as raw material, and realize one-step construction of spherical morphology and efficient nitrogen doping through simple and environmentally friendly process, which is crucial for obtaining high-performance and low-cost advanced carbon material. SUMMARY

[0005] The technical problem solved by the present application is to overcome the above-mentioned defects existing in the prior art, and to provide a preparation method of nitrogen-doped rush-shaped carbon material, which has stable spherical morphology, controllable specific surface area and pore size distribution, simple process, environmental friendliness, rich raw material source, low cost and suitability for large-scale production.

[0006] The technical solution adopted by the present application to solve its technical problem is as follows: a preparation method of nitrogen-doped rush-shaped carbon material, comprising the following steps:

[0007] (1) The rush is dried, peeled, and cut into pieces, and then expanded, crushed, and obtained as expanded rush powder;

[0008] (2) The expanded rush powder obtained in step (1) is added into an acidic solution, mixed and stirred, and then placed in a sealed hydrothermal kettle for hydrothermal activation reaction, cooled to room temperature, centrifuged and washed to neutral, and obtained as a pre-prepared rush carbon carrier;

[0009] (3) The pre-prepared rush carbon carrier obtained in step (2), an organic nitrogen source or a nitrogen-doped prepolymer, and a shaping agent are mixed, and then subjected to protective calcination under an inert atmosphere, and then immersed in an acidic solution for treatment, filtered and washed to neutral pH of the supernatant, and dried, and obtained as nitrogen-doped rush-shaped carbon material.

[0010] The invention idea of the method of the present application and the principle analysis of obtaining the spherical carbon material are as follows:

[0011] In the method of the present application, the core mechanism of forming the carbon nanospheres with uniform morphology can mainly come from the combined effects of the structure characteristics of the puffed straw after the puffing treatment and the later hydrothermal treatment and nitrogen doping treatment processes: 1) self-assembly and surface interaction: that is, carbon precursor molecules or nanounits spontaneously aggregate and assemble into a spherical structure with lower energy through intermolecular forces, hydrogen bonds or hydrophobic interactions, etc.; because the straw contains a certain amount of sugar (such as glucose or sucrose), during the puffing in step (1) and the hydrothermal activation reaction in step (2), a series of decomposition phenomena occur, and crosslinking reactions are caused by dehydration between oligosaccharide molecules, thus forming small molecules or polymers. Therefore, the formation and growth of carbon nanospheres can comply with the Lamer model; or in step (1), other macromolecules are formed, and then the formed core in the solution in step (2), the aromatic polymers generated by the polymerization of glucose form crystal nuclei through π-π stacking and other effects, the crystal nuclei continuously absorb surrounding small molecules and grow, thereby self-assembling into carbon nanospheres; 2) nitrogen doping mainly promotes the formation of spherical nanometer structure of carbon material through multiple synergistic mechanisms, and its main effect comes from the fact that the nitrogen-containing precursor can self-assemble into spherical micelles in the solution as a self-template; the crosslinking points provided by nitrogen atoms can stabilize the initial morphology and inhibit the collapse of the structure during carbonization; at the same time, the surface charge effect can prevent particle agglomeration, and ultimately lead to a thermodynamically more stable, uniform spherical structure. In summary, the entire formation process of the carbon nanospheres prepared by the method of the present application is deeply affected by the reaction kinetics, and by precisely controlling the temperature, time and other parameters, the structure and morphology of the final product can be regulated to prepare monodisperse carbon nanospheres with uniform size.

[0012] Preferably, in step (1), the temperature of the puffing is 110-150 °C (more preferably 110-140 °C), the speed of the feeding is 0.01-0.10 m / s (more preferably 0.02-0.08 m / s), and the rotation speed of the screw is 120-200 r / min (more preferably 140-180 r / min). The puffing of the rush is a transient process in which the internal water of the material is "flash evaporated" under the synergistic effect of high temperature, high pressure and high shear force. In the puffing machine, the material successively undergoes conditioning, extrusion, temperature and pressure rise, and instantaneous release. In the conditioning, the material is mixed and homogenized with the water from the molecular structure of the rush, preparing for the subsequent reaction. In the extrusion and temperature and pressure rise, the material is tightly compressed and rapidly heated due to the propulsion and shearing of the screw, forming a high-temperature and high-pressure state, at which the water is in a superheated liquid state but does not boil. In the instantaneous release, when the material is extruded from the die under high pressure, the pressure drops to normal pressure, and the superheated water is instantly vaporized (flash evaporated), generating a huge expansion force to destroy the compact structure of the material and form a porous puffing structure. This process simultaneously realizes the physical structure reorganization of the material and possible chemical changes such as partial starch gelatinization. Since the puffing effect is highly dependent on the precise control of the process parameters, these parameters are interrelated and jointly determine the "quality" and "quantity" of the puffing process. The puffing equipment is preferably a double-screw puffing machine.

[0013] Preferably, in step (1), the material is pulverized to pass through a 100-mesh sieve. This ensures that the particle size of the pulverized rush is less than 150 μm, at which the specific surface area of the rush is large, the fiber structure is destroyed, the crystallinity is reduced, the mass transfer efficiency is improved, and the material is homogenized.

[0014] Preferably, in step (2), the mass-to-volume ratio g / mL of the rush powder to the acidic solution is 1:1-20 (more preferably 1:5-20). An appropriate amount of acid can destroy the crystal structure of lignocellulose in the rush, hydrolyze the large molecular polymers (polysaccharides) therein into small molecular monomers (monosaccharides) that can be utilized, and further perform chemical conversion to become more loose and fluffy.

[0015] Preferably, in step (2), the concentration of the acidic solution is 0.1-2.0 mol / L (more preferably 1.0-2.0 mol / L). An appropriate concentration of acid can "disassemble" the biomass macromolecules into fermentable sugars and platform chemicals by breaking the glycosidic bonds, while achieving the best balance between saccharification efficiency and sugar degradation loss.

[0016] Preferably, in step (2), the solutes in the acidic solution include one or more of formic acid, acetic acid, hydrochloric acid, nitric acid or sulfuric acid, etc.

[0017] Preferably, in step (2), the mixing and stirring time is 2-4 h.

[0018] Preferably, in step (2), the volume of the acidic solution is 10-60% (more preferably 30-50%) of the volume of the closed hydrothermal kettle.

[0019] Preferably, in step (2), the temperature of the hydrothermal activation reaction is 80-200 ℃, and the time is 1-6 h. The core of the acid hydrothermal activation is to maximize the "deconstruction" of lignin by precisely controlling the temperature, time, acid concentration and other parameters, to generate condensed lignin with more complex structure, larger molecular weight and more hydrophobicity, and to open up the fiber structure, remove most of the hemicellulose, and destroy the cellulose crystalline region, greatly increasing the specific surface area and porosity, and becoming more loose and fluffy.

[0020] Preferably, in step (3), the mass ratio of the prefabricated lamp wick carbon carrier, organic nitrogen source or nitrogen-doped pre-polymer to the plasticizing agent is 1:1-10:1-10 (more preferably 1:1-8:1-8, and further preferably 1:1-4:1-4). The organic nitrogen source can be mixed and calcined with other raw materials directly or after being first prepared into a nitrogen-doped pre-polymer. In the controllable synthesis of spherical nitrogen-doped carbon nanomaterials, the synergistic regulation of the prefabricated lamp wick carbon carrier, organic nitrogen source or nitrogen-doped pre-polymer and plasticizing agent is the key to realizing the structure design and performance optimization of the material. The carbon carrier constitutes the basic framework of the material, and its amount directly affects the integrity and yield of the spherical structure; the nitrogen source introduces catalytically active sites through doping, and its amount needs to be precisely balanced, too low and the activity will be insufficient, too high and the carbon framework may be damaged; the plasticizing agent guides the formation of regular spheres and porous structures, and its amount directly regulates the pore size distribution and specific surface area. The synergistic action of the three components guides the formation of ordered porous structures, the carbon carrier precisely replicates and supports the structure, and the nitrogen source realizes efficient doping without damaging the framework, which together determines the final morphology, pore structure and surface chemical properties of the material. Any imbalance in the proportion of the components will break this delicate balance, leading to the collapse of the morphology, blockage of the pores or reduction of the active sites.

[0021] Preferably, in step (3), the plasticizing agent includes one or more of MgCl2, CaCl2, KOH or ZnCl2. The plasticizing agent reacts with the prefabricated lamp wick carbon carrier, nitrogen source or nitrogen-doped pre-polymer at high temperature, greatly expands the specific surface area, regulates the pore size distribution, and forms a rich pore structure through etching and pore forming.

[0022] Preferably, in step (3), the protective calcination refers to: after being heated to 200-800 ℃ (more preferably 300-600 ℃) at a rate of 1-10 ℃ / min (more preferably 4-10 ℃ / min), the protective calcination is performed for 2-10 h (more preferably 3-6 h). The calcination process is a key thermo-chemical conversion stage for the formation of nitrogen-doped candle soot carbon nanospheres, and accurate control of the temperature and the heating rate is a key to regulating the composition and properties of the nitrogen-doped candle soot carbon nanospheres. During the calcination process, the organic components of the candle soot are first pyrolyzed and carbonized, and the non-carbon elements are released in the form of volatile small molecules, and the remaining carbon atoms are restructured to form sp 2 The hybrid graphitic-like carbon skeleton; at the same time, the nitrogen source undergoes complex evolution: part of the nitrogen-containing groups are embedded into the carbon skeleton as dopants to form active sites such as pyridine nitrogen, pyrrole nitrogen and graphite nitrogen; and unstable nitrogen species are lost due to thermal decomposition; accompanied by the above reactions, the release of volatile matter creates a rich microporous and mesoporous structure in the material, and the graphitization rearrangement and shrinkage of the carbon skeleton at high temperature can also lead to the collapse of part of the pores; this series of transformations collectively determine the final carbon skeleton structure, nitrogen doping state and porous characteristics of the material.

[0023] Preferably, in step (3), the inert atmosphere includes one or more of nitrogen, argon or helium. The inert atmosphere used in the method of the present application is a high-purity atmosphere with a purity of ≥99.999%.

[0024] Preferably, in step (3), the concentration of the acidic solution is 0.1-2.0 mol / L (more preferably 1.0-2.0 mol / L). The acid washing of the carbon nanospheres is a multifunctional refining process, which mainly serves to remove metals and amorphous carbon and improve dispersibility, and at a suitable concentration, it is more beneficial to fine structural regulation of the nitrogen-doped candle soot carbon nanospheres by etching and pore creation.

[0025] Preferably, in step (3), the solute in the acidic solution includes one or more of formic acid, acetic acid, hydrochloric acid, nitric acid or sulfuric acid.

[0026] Preferably, in step (3), the temperature for the soaking treatment is 20-60 ℃ (more preferably 30-50 ℃), and the time is 1-10 h (more preferably 2-6 h). Soaking at a suitable temperature and time is beneficial to the deep purification of the carbon nanospheres, and the mild acid treatment can create nanoscale depressions on the surface of the carbon nanospheres, further increasing the specific surface area of the spherical surface, which is beneficial to the construction of catalytic active centers as a variety of catalyst supports, and can also remove unstable doping configurations to achieve "finishing" of the surface chemical composition of the material.

[0027] Preferably, in step (3), the preparation method of the nitrogen-doped pre-polymer is: placing the organic nitrogen source in an air atmosphere and performing aerobic calcination.

[0028] Preferably, the temperature of the aerobic calcination is 300-800 ℃ (more preferably 300-600 ℃), and the time is 1-4 h (more preferably 1-3 h). Oxygen promotes crosslinking but accelerates the loss of nitrogen oxides, and the crosslinking degree of the prepolymer needs to be moderate, and melting collapse or insufficient pore structure during calcination needs to be avoided, therefore, suitable temperature and time need to be controlled to obtain suitable nitrogen-doped prepolymers.

[0029] Preferably, the organic nitrogen source includes one or more of urea, 2,2'-dipyridyl, melamine, amino acid, imidazole, dicyandiamide or 3-amino-1,2,4-triazole, etc. Selecting a suitable nitrogen source is a key step for preparing high-performance nitrogen-doped candle soot carbon nanospheres, which directly affects the final nitrogen content, nitrogen species type, pore structure and application performance of the carbon nanospheres.

[0030] The beneficial effects of the method of the present application are as follows:

[0031] (1) The nitrogen-doped candle soot spherical carbon material obtained by the method of the present application has stable spherical morphology, the particle size is mainly 100-200 nm, the specific surface area is > 600 m 2 / g, the pore volume is > 3 cm 3 / g, the pore size distribution is mainly 3-10 nm, and the average pore size is about 6 nm, and the specific surface area and pore size distribution are controllable; the nitrogen-doped candle soot spherical carbon material obtained by the method of the present application has wide application prospects in separation and adsorption, electrochemistry, catalytic support engineering and the like;

[0032] (2) The method of the present application is simple in process, environmentally friendly, and the raw materials are abundant in source and low in cost, and is suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is the SEM image of the nitrogen-doped candle soot spherical carbon material obtained in Example 1 of the present application under different scales (wherein Figure 1 (a) is the SEM image under a scale of 500 nm, Figure 1 (b) is the SEM image under a scale of 100 nm);

[0034] Figure 2 is the TEM image of the nitrogen-doped candle soot spherical carbon material obtained in Example 1 of the present application under different scales (wherein Figure 2 (a) is the TEM image under a scale of 200 nm, Figure 2 (b) is the TEM image under a scale of 10 nm);

[0035] Figure 3 is the particle size distribution graph of the nitrogen-doped candle soot spherical carbon material obtained in Example 1 of the present application;

[0036] Figure 4is the XRD pattern of the nitrogen-doped pincushion-like carbon material obtained in Example 1 of the present application;

[0037] Figure 5 is the Raman spectrum of the nitrogen-doped pincushion-like carbon material obtained in Example 1 of the present application;

[0038] Figure 6 is the XPS spectrum of different elements in the nitrogen-doped pincushion-like carbon material obtained in Example 1 of the present application (wherein Figure 6 (a) is the XPS full spectrum, Figure 6 (b) is the C 1s spectrum, Figure 6 (c) is the N 1s spectrum, Figure 6 (d) is the O 1s spectrum);

[0039] Figure 7 is the nitrogen adsorption-desorption curve of the nitrogen-doped pincushion-like carbon material obtained in Example 1 of the present application;

[0040] Figure 8 is the pore size distribution of the nitrogen-doped pincushion-like carbon material obtained in Example 1 of the present application;

[0041] Figure 9 is the SEM image of the nitrogen-doped pincushion-like carbon material obtained in Comparative Example 1 of the present application under different scales (wherein Figure 9 (a) is the SEM image under the scale of 50 µm, Figure 9 (b) is the SEM image under the scale of 2 µm);

[0042] Figure 10 is the SEM image of the nitrogen-doped pincushion-like carbon material obtained in Comparative Example 2 of the present application under different scales (wherein Figure 10 (a) is the SEM image under the scale of 500 nm, Figure 10 (b) is the SEM image under the scale of 100 nm);

[0043] Figure 11 is the SEM image of the nitrogen-doped pincushion-like carbon material obtained in Comparative Example 3 of the present application under different scales (wherein Figure 11 (a) is the SEM image under the scale of 500 nm, Figure 11 (b) is the SEM image under the scale of 100 nm);

[0044] Figure 12 is the SEM image of the nitrogen-doped pincushion-like carbon material obtained in Comparative Example 4 of the present application under different scales (wherein Figure 12 (a) is the SEM image under the scale of 500 nm, Figure 12 (b) is the SEM image under the scale of 100 nm). DETAILED DESCRIPTION

[0045] The application will be further described below in connection with the examples and the accompanying drawings.

[0046] The inert atmosphere used in the examples and the comparative examples of the application is high-purity atmosphere with purity ≥ 99.999%; the raw materials or chemical reagents used in the examples and the comparative examples of the application are obtained through conventional commercial channels, unless otherwise specified.

[0047] Preparation method of nitrogen-doped pre-polymer Reference Example 1

[0048] The 3-amino-1,2,4-triazole was placed in an air atmosphere and subjected to aerobic calcination at 300℃ for 2h to obtain a nitrogen-doped pre-polymer.

[0049] Preparation method of nitrogen-doped pre-polymer Reference Example 2

[0050] The 2,2'-dipyridyl was placed in an air atmosphere and subjected to aerobic calcination at 500℃ for 2h to obtain a nitrogen-doped pre-polymer.

[0051] Preparation method of nitrogen-doped pre-polymer Reference Example 3

[0052] The urea was placed in an air atmosphere and subjected to aerobic calcination at 300℃ for 2h to obtain a nitrogen-doped pre-polymer.

[0053] Preparation method of a nitrogen-doped rush-shaped spherical carbon material Example 1

[0054] (1) The harvested rush was dried, peeled, and shredded, and then placed in an extruder, and subjected to extrusion at 110℃, a feeding speed of 0.05 m / s, and a screw rotation speed of 150 r / min, and then ground to pass through a 100-mesh sieve to obtain extruded rush powder;

[0055] (2) 4.0 g of the extruded rush powder obtained in step (1) was added to 20.0 mL of a 1.0 mol / L nitric acid solution, mixed and stirred for 2h, and then placed in a 50 mL sealed hydrothermal kettle, and subjected to hydrothermal activation reaction at 100℃ for 2h, and then cooled to room temperature, centrifuged and washed to neutral to obtain a pre-prepared rush carbon carrier;

[0056] (3) 1.0 g of the pre-prepared rush carbon carrier obtained in step (2), 2.0 g of the nitrogen-doped pre-polymer obtained in Reference Example 1, and 2.0 g of ZnCl2 were mixed, and then heated to 300℃ at a rate of 10℃ / min under a high-purity nitrogen atmosphere, and then subjected to protective calcination for 3h, and then placed in a 1.0 mol / L hydrochloric acid solution, and subjected to immersion treatment at 40℃ for 5h, and then filtered and washed until the pH value of the supernatant was neutral, and then dried to obtain a nitrogen-doped rush-shaped spherical carbon material.

[0057] As Figure 1As shown in (a) and (b), the nitrogen-doped rush spherical carbon material obtained in the embodiments of the present invention exhibits a neat spherical distribution with an average particle size of approximately 167 nm. The spheres have clear outlines and a small number of neatly distributed depressions on their surfaces. Figure 2 As shown in (a) and (b), the nitrogen-doped rush spherical carbon materials obtained in the embodiments of the present invention have a neat morphology and uniform structure, smooth and neat spherical surfaces, obvious stacking of spherical carbon materials, and clear gaps between spheres; as Figure 3 As shown, the particle size of the nitrogen-doped rush spherical carbon material obtained in the embodiments of the present invention exhibits a normal distribution, with an average particle size of approximately 154.25 ± 4.5 nm.

[0058] like Figure 4 As shown, the nitrogen-doped rush spherical carbon material obtained in the embodiments of the present invention is in 2 θ The presence of two broad diffraction peaks in the (002) and (101) planes of amorphous carbon at angles of 23° and 43° indicates the generation of numerous defect structures, making it suitable as an ideal support for catalysts.

[0059] like Figure 5 As shown, the nitrogen-doped rush spherical carbon material obtained in the embodiments of the present invention exhibits a thickness of ~1340 cm⁻¹. -1 sp 3 Type disordered carbon-related D bands and ~1580 cm -1 sp 2 Hybrid carbon-related G bands, their I D / I G The ratio of D-band intensity to G-band intensity is around 1.11, indicating that it has a large number of defects and disorder, which can provide ideal adsorption sites for loading other catalytically active molecules, making it suitable as an ideal support for catalysts.

[0060] like Figure 6 As shown in (a), the full spectrum reveals the characteristic peaks of C, N, and O in the nitrogen-doped rush spherical carbon material obtained in the embodiments of the present invention; as Figure 6 As shown in (b), the high-resolution spectrum of C1S can be deconvolved into three peaks located at 284.8 eV, 286.2 eV, and 288.8 eV, attached to CC, CN, and CO, respectively; Figure 6 As shown in (c), the high-resolution spectrum of N 1s can be deconvoluted into four characteristic peaks: pyridine-N (398.4 eV), pyrrole-N (399.5 eV), graphite-N (400.9 eV), and oxide-N (404.1 eV). It contains abundant pyridine (pyrrole) nitrogen functional groups that can interact with other coordinating ions to regulate the electronic structure and jointly construct the catalytic active center; such as Figure 6(d) As shown, the high-resolution spectrum of O 1s can be deconvoluted into two main peaks located at 532.1 eV and 533.4 eV, corresponding to C-O and C=O respectively, indicating that a certain amount of oxygen element exists in the nitrogen-doped rush-shaped carbon material, which is probably due to the fact that a small amount of C-O and C=O in the rush has not been completely condensed and carbonized during the processing.

[0061] As shown in Figure 7 , 8 , the adsorption-desorption curve of the nitrogen-doped rush-shaped carbon material obtained by the embodiment of the present application is of type I curve, indicating the existence of micropores and mesopores in the material. The sharp rise of the nitrogen adsorption amount at a relatively low pressure indicates the existence of micropores, and the hysteresis loop in the range of P / P0=0.8-1.0 indicates the existence of mesopores. The nitrogen adsorption-desorption test also shows that the pore volume of the nitrogen-doped rush-shaped carbon material obtained by the embodiment of the present application is 3.34 cm 3 / g, the pore size distribution is mainly 3-10 nm, the average pore size is about 6 nm, and the specific surface area is 639.64 m 2 / g.

[0062] A preparation method of a nitrogen-doped rush-shaped carbon material

[0063] (1) The harvested rush is dried, peeled, and cut into pieces, and then placed in an extruder, and extruded at 120°C, with the feeding speed being 0.05 m / s and the screw rotation speed being 180 r / min. After extrusion, the extruded rush powder is ground to pass through a 100-mesh sieve;

[0064] (2) 2.5 g of the extruded rush powder obtained in step (1) is added into 25.0 mL of 1.0 mol / L acetic acid solution, and mixed and stirred for 4 h. Then, the mixture is placed in a 50 mL sealed hydrothermal kettle, and subjected to hydrothermal activation reaction at 200°C for 4 h. After cooling to room temperature, the mixture is centrifuged and washed until neutral, to obtain a pre-prepared rush carbon carrier;

[0065] (3) 2.0 g of the pre-prepared rush carbon carrier obtained in step (2), 4.0 g of the nitrogen-doped prepolymer obtained in the reference example 1, and 2.0 g of MgCl2 are mixed, and then heated to 600°C at a rate of 5°C / min under a high-purity nitrogen atmosphere, and subjected to protective calcination for 3 h. Then, the mixture is placed in a 1.0 mol / L hydrochloric acid solution, and subjected to immersion treatment at 50°C for 3 h. After filtration and washing until the pH value of the supernatant is neutral, the mixture is dried to obtain a nitrogen-doped rush-shaped carbon material.

[0066] It is detected that the nitrogen-doped rush-shaped carbon material obtained by the embodiment of the present application is in a neat spherical shape, with an average particle size of about 174 nm, a clear and uniform surface profile, and a small amount of neat concave.

[0067] Testing revealed that the nitrogen-doped rush spherical carbon material obtained in this embodiment of the invention exhibited a high performance at 2... θ The presence of two broad diffraction peaks in the (002) and (101) planes of amorphous carbon at angles of 23° and 43° indicates the generation of numerous defect structures, making it suitable as an ideal support for catalysts.

[0068] Testing revealed that the adsorption-desorption curves of the nitrogen-doped rush spherical carbon material obtained in this embodiment of the invention exhibited Type I curves, indicating the presence of micropores and mesopores in the material. The sharp increase in nitrogen adsorption at relatively low pressure indicates the presence of micropores, while the hysteresis loop within the P / P0 range of 0.8 to 1.0 indicates the presence of mesopores. The nitrogen adsorption-desorption test also showed that the pore volume of the nitrogen-doped rush spherical carbon material obtained in this embodiment of the invention is 3.22 cm³. 3 / g, pore size distribution is mainly 3-10nm, average pore size is about 6nm, specific surface area is 621.38 m² / g. 2 / g.

[0069] Example 3: A method for preparing nitrogen-doped rush spherical carbon materials

[0070] (1) Same as step (1) in Example 1;

[0071] (2) Add 2.0 g of puffed rush powder obtained in step (1) to 40.0 mL of 2.0 mol / L sulfuric acid solution, mix and stir for 3 h, place in 100 mL of closed hydrothermal reactor, carry out hydrothermal activation reaction at 200 °C for 6 h, cool to room temperature, centrifuge and wash until neutral to obtain pre-prepared rush carbon carrier;

[0072] (3) After mixing 1.0 g of pre-made rush carbon carrier obtained in step (2), 1.0 g of nitrogen-doped prepolymer obtained in Example 2 and 2.0 g of KOH, the mixture was heated to 500 °C at a rate of 8 °C / min under a high-purity nitrogen atmosphere and then calcined for 4 h. The mixture was then placed in a 2.0 mol / L hydrochloric acid solution and soaked at 40 °C for 4 h. The mixture was then filtered and washed until the pH of the supernatant was neutral and dried to obtain nitrogen-doped rush spherical carbon material.

[0073] Upon testing, the nitrogen-doped rush spherical carbon material obtained in the embodiments of the present invention exhibits a neat spherical distribution with an average particle size of approximately 162 nm. The spherical surface has a clear outline and a small number of neatly distributed depressions.

[0074] Testing revealed that the nitrogen-doped rush spherical carbon material obtained in this embodiment of the invention exhibited a high performance at 2... θ The presence of two broad diffraction peaks in the (002) and (101) planes of amorphous carbon at angles of 23° and 43° indicates the generation of numerous defect structures, making it suitable as an ideal support for catalysts.

[0075] The nitrogen-doped rush spherical carbon material obtained in the embodiment of the application has an adsorption-desorption curve of type I, indicating the existence of micropores and mesopores in the material. The sharp increase in nitrogen adsorption at a relatively low pressure indicates the existence of micropores. The hysteresis loop in the range of P / P0=0.8-1.0 indicates the existence of mesopores. The nitrogen adsorption-desorption test also shows that the pore volume of the nitrogen-doped rush spherical carbon material obtained in the embodiment of the application is 3.41 cm 3 / g, the pore size distribution is mainly 3-10 nm, the average pore size is about 6 nm, and the specific surface area is 643.45 m 2 / g.

[0076] A preparation method of a nitrogen-doped rush spherical carbon material

[0077] (1) The same as step (1) in the embodiment 1;

[0078] (2) 4.0 g of the expanded rush powder obtained in step (1) is added into 20.0 mL of a 1.0 mol / L nitric acid solution, and after mixing and stirring for 2 h, the mixture is placed in a 50 mL sealed hydrothermal kettle, and a hydrothermal activation reaction is performed at 120°C for 2 h. After cooling to room temperature, centrifugal separation and washing are performed until the mixture is neutral, and a pre-prepared rush carbon carrier is obtained;

[0079] (3) 1.0 g of the pre-prepared rush carbon carrier obtained in step (2), 2.0 g of the nitrogen-doped pre-polymer obtained in the reference example 3, and 2.0 g of ZnCl2 are mixed, and then the mixture is heated to 400°C at a rate of 10°C / min under a high-purity nitrogen atmosphere, and then a protective calcination is performed for 5 h. Then, the mixture is placed in a 1.5 mol / L hydrochloric acid solution, and immersed at 45°C for 5 h. After washing by suction filtration until the pH value of the supernatant is neutral, the mixture is dried to obtain a nitrogen-doped rush spherical carbon material.

[0080] The nitrogen-doped rush spherical carbon material obtained in the embodiment of the application has an adsorption-desorption curve of type I, indicating the existence of micropores and mesopores in the material. The sharp increase in nitrogen adsorption at a relatively low pressure indicates the existence of micropores. The hysteresis loop in the range of P / P0=0.8-1.0 indicates the existence of mesopores. The nitrogen adsorption-desorption test also shows that the pore volume of the nitrogen-doped rush spherical carbon material obtained in the embodiment of the application is 3.41 cm

[0081] The nitrogen-doped rush spherical carbon material obtained in the embodiment of the application has an adsorption-desorption curve of type I, indicating the existence of micropores and mesopores in the material. The sharp increase in nitrogen adsorption at a relatively low pressure indicates the existence of micropores. The hysteresis loop in the range of P / P0=0.8-1.0 indicates the existence of mesopores. The nitrogen adsorption-desorption test also shows that the pore volume of the nitrogen-doped rush spherical carbon material obtained in the embodiment of the application is 3.41 cm θ The two wide diffraction peaks of the amorphous carbon (002) and (101) planes at 23° and 43° indicate that a large number of defect structures are generated, which are suitable as ideal carriers for catalysts.

[0082] It is detected that the nitrogen-doped rush spherical carbon material obtained by the embodiment of the application has an adsorption-desorption curve of type I, indicating the existence of micropores and mesopores in the material, and the sharp rise of nitrogen adsorption at a relatively low pressure indicates the existence of micropores, and the hysteresis loop in the range of P / P0=0.8-1.0 indicates the existence of mesopores; the nitrogen adsorption-desorption test also shows that the pore volume of the nitrogen-doped rush spherical carbon material obtained by the embodiment of the application is 3.30 cm 3 / g, the pore size distribution is mainly 3-10 nm, the average pore size is about 6 nm, and the specific surface area is 636.27 m 2 / g.

[0083] Comparative Example 1

[0084] The difference between the present comparative example and Example 1 is only that in step (1), the harvested rush is dried, peeled, and chopped, and then pulverized to obtain rush powder; step (2) is deleted; and in step (3), 1.0 g of the pre-prepared rush carbon carrier is replaced by 1.0 g of the rush powder obtained in step (1), and finally a nitrogen-doped rush tubular carbon material is obtained. The rest is the same as in Example 1.

[0085] As shown in Figure 9 (a) and (b), the nitrogen-doped rush carbon material obtained in the present comparative example has a random hollow tubular structure, the tube diameter is about 2-3 µm, the tube wall has random rough protrusions, and the tube opening has a random cross section; this indicates that the absence of the puffing process and the hydrothermal activation condition in the preparation process has a greater impact on the spherical morphology control of the nitrogen-doped rush carbon material.

[0086] Comparative Example 2

[0087] The difference between the present comparative example and Example 1 is only that step (2) is deleted; and in step (3), 1.0 g of the pre-prepared rush carbon carrier is replaced by 1.0 g of the puffing rush powder obtained in step (1), and finally a nitrogen-doped rush cauliflower-shaped carbon material is obtained. The rest is the same as in Example 1.

[0088] As shown in Figure 10 (a) and (b), the nitrogen-doped rush carbon material obtained in the present comparative example has a cauliflower-shaped layered structure, the average particle size is about 320 nm, and the cauliflower petal thickness is about 1-3 nm; this indicates that the absence of the hydrothermal activation condition in the preparation process has a greater impact on the spherical morphology control of the nitrogen-doped rush carbon material.

[0089] Comparative Example 3

[0090] The difference between the present comparative example and Example 1 is only that in step (3), 2.0 g of the nitrogen-doped pre-polymer obtained in Reference Example 1 and 2.0 g of ZnCl2 are replaced by 4.0 g of ZnCl2, and finally a nitrogen-doped rush spherical and cauliflower-shaped mixed carbon material is obtained. The rest is the same as in Example 1.

[0091] As Figure 11 As shown in (a) and (b), the nitrogen-doped rush carbon material obtained in the present application comparative example has a mixed structure of spherical and cauliflower shapes, the average particle size of the carbon nanospheres is about 170 nm, the average particle size of the cauliflower structure is about 320 nm, and the cauliflower petal thickness is about 1-3 nm; it is illustrated that the synergistic cooperation of the organic nitrogen source or nitrogen-doped prepolymer and the shaping agent has a greater influence on the spherical morphology control of the nitrogen-doped rush carbon material.

[0092] Comparative Example 4

[0093] The difference between the present comparative example and Example 1 is that in step (3), 2.0 g of the nitrogen-doped prepolymer obtained in Reference Example 1 and 2.0 g of ZnCl2 are replaced by 4.0 g of the nitrogen-doped prepolymer obtained in Reference Example 1, and finally, nitrogen-doped rush irregular spherical carbon material is obtained. The rest is the same as Example 1.

[0094] As Figure 12 As shown in (a) and (b), the nitrogen-doped rush carbon material obtained in the present application comparative example has a mixed structure of spherical and cauliflower shapes, the average particle size of the carbon nanospheres is about 170 nm, the average particle size of the cauliflower structure is about 320 nm, and the cauliflower petal thickness is about 1-3 nm; it is illustrated that the synergistic cooperation of the organic nitrogen source or nitrogen-doped prepolymer and the shaping agent has a greater influence on the spherical morphology control of the nitrogen-doped rush carbon material.

Claims

1. A method for preparing nitrogen-doped rush spherical carbon material, characterized in that, Includes the following steps: (1) Dry the rush pith, remove the skin and core, chop it, puff it up, and then crush it to obtain puffed rush pith powder; the puffing temperature is 110-150 ℃, the feeding speed is 0.01-0.10 m / s, and the screw speed is 120-200 r / min. (2) The puffed rush powder obtained in step (1) is added to an acidic solution, mixed and stirred, and then placed in a sealed hydrothermal reactor for hydrothermal activation reaction. After cooling to room temperature, the mixture is centrifuged and washed until neutral to obtain a pre-prepared rush carbon carrier. The mass-to-volume ratio of the rush powder to the acidic solution is 1:1 to 20 g / mL. The concentration of the acidic solution is 0.1 to 2.0 mol / L. The temperature of the hydrothermal activation reaction is 80 to 200 °C, and the time is 1 to 6 h. (3) After mixing the pre-made rush carbon carrier, nitrogen-doped prepolymer and plasticizer obtained in step (2), the mixture is calcined under an inert atmosphere, then soaked in an acidic solution, filtered and washed until the pH of the supernatant is neutral, and dried to obtain nitrogen-doped rush spherical carbon material; the mass ratio of the pre-made rush carbon carrier, nitrogen-doped prepolymer and plasticizer is 1:1 to 4:1 to 4; the preparation method of the nitrogen-doped prepolymer is: placing the organic nitrogen source in an air atmosphere and calcining it with oxygen to obtain the material.

2. The method for preparing nitrogen-doped rush spherical carbon material according to claim 1, characterized in that: In step (1), the material is crushed to pass through a 100-mesh sieve.

3. The method for preparing nitrogen-doped rush spherical carbon material according to claim 1 or 2, characterized in that: In step (2), the solute in the acidic solution includes one or more of formic acid, acetic acid, hydrochloric acid, nitric acid or sulfuric acid; the mixing and stirring time is 2 to 4 hours; the volume of the acidic solution is equivalent to 10 to 60% of the volume of the closed hydrothermal reactor.

4. The method for preparing nitrogen-doped rush spherical carbon material according to claim 1 or 2, characterized in that: In step (3), the plasticizer includes one or more of MgCl2, CaCl2, KOH, or ZnCl2; the protective calcination refers to: heating to 200-800 ℃ at a rate of 1-10 ℃ / min and then performing protective calcination for 2-10 h; the inert atmosphere includes one or more of nitrogen, argon, or helium; the concentration of the acidic solution is 0.1-2.0 mol / L; the solute in the acidic solution includes one or more of formic acid, acetic acid, hydrochloric acid, nitric acid, or sulfuric acid; the immersion treatment temperature is 20-60 ℃ and the time is 1-10 h; the aerobic calcination temperature is 300-800 ℃ and the time is 1-4 h; the organic nitrogen source includes one or more of urea, 2,2'-bipyridine, melamine, amino acids, imidazole, dicyandiamide, or 3-amino-1,2,4-triazole.

5. The method for preparing nitrogen-doped rush spherical carbon material according to claim 3, characterized in that: In step (3), the plasticizer includes one or more of MgCl2, CaCl2, KOH, or ZnCl2; the protective calcination refers to: heating to 200-800 ℃ at a rate of 1-10 ℃ / min and then performing protective calcination for 2-10 h; the inert atmosphere includes one or more of nitrogen, argon, or helium; the concentration of the acidic solution is 0.1-2.0 mol / L; the solute in the acidic solution includes one or more of formic acid, acetic acid, hydrochloric acid, nitric acid, or sulfuric acid; the immersion treatment temperature is 20-60 ℃ and the time is 1-10 h; the aerobic calcination temperature is 300-800 ℃ and the time is 1-4 h; the organic nitrogen source includes one or more of urea, 2,2'-bipyridine, melamine, amino acids, imidazole, dicyandiamide, or 3-amino-1,2,4-triazole.

Images