Carbonyl functionalized carbon-based carbon nitride nanotube as well as preparation method and application thereof

Abstract

The invention discloses a carbonyl functionalized carbon-based carbon nitride nanotube and a preparation method and application thereof.The method comprises the steps that firstly, an amino-containing precursor is added into water, heating is conducted at the first stirring speed till the amino-containing precursor is fully dissolved, and a system A is obtained; adding cyclodextrin into the system A at a second stirring rate, and obtaining a system B after the reaction is finished, the second stirring rate being smaller than the first stirring rate; performing hydrothermal reaction on the system B to prepare a sample C; and calcining the sample C in an argon protective atmosphere, and sequentially carrying out primary grinding, washing, drying and secondary grinding on the calcined product to prepare the carbon-based carbon nitride nanotube. By introducing a covalent bond connection mechanism, a stable bridging structure between the carbon material and the carbon nitride nanotube is realized on the molecular level, and the technical problem that a composite material of the carbon material and the carbon nitride nanotube in the prior art is relatively poor in conductivity and catalytic performance due to relatively poor structural stability is effectively solved.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic material development, and relates to a carbonyl-functionalized carbon-based nitrided carbon nanotube and a preparation method and application thereof. Background Art

[0002] As the energy crisis and environmental pollution problems intensify, the development of efficient and sustainable energy conversion and pollution control materials has become a core topic in materials science and environmental engineering. Graphitic carbon nitride (g-C3N4) has been widely used in photocatalytic water decomposition to produce hydrogen, pollutant degradation, and CO2 reduction due to its visible light responsiveness, chemical stability, and environmental friendliness. However, g-C3N4 materials generally have three inherent defects: low specific surface area leads to limited reaction active sites; slow electron migration rate restricts charge transfer efficiency; and photogenerated carrier recombination significantly weakens light energy utilization. These defects severely limit its practical application performance, especially in scenarios requiring high reaction kinetics.

[0003] To overcome these bottlenecks, researchers have proposed a variety of modification strategies. Among them, constructing g-C3N4 into a one-dimensional nanotube structure is considered an effective path: the high specific surface area of ​​the nanotubes can expose more active sites, and their directional pore structure is expected to promote carrier separation and migration, thereby improving photocatalytic efficiency. At the same time, the introduction of carbon materials (such as graphene and carbon quantum dots) and g-C3N4 composites can accelerate electron transfer and inhibit carrier recombination by virtue of the excellent conductivity of the carbon component. Despite this, existing carbon / g-C3N4 nanotube composites still face two key problems: poor structural stability and weak interface coupling: in composite materials formed by traditional mechanical mixing or electrostatic self-assembly, the carbon material and the g-C3N4 nanotubes are only bonded by van der Waals forces or weak chemical bonds, and the interface bonding force is insufficient. In photocatalytic reactions (especially processes involving multi-electron transfer such as hydrogen peroxide production), the interface is prone to dissociation, resulting in interruption of the electron transmission channel and attenuation of conductivity and catalytic activity. In addition, pure g-C3N4 nanotubes are prone to tube wall collapse or agglomeration during high temperature or long-term reactions, resulting in a decrease in specific surface area. If the carbon material is not evenly anchored to the nanotubes, it will not be able to play the role of a conductive bridge due to insufficient interfacial contact, but will hinder the effective utilization of photogenerated carriers. These problems directly lead to low photocurrent density and poor cyclic stability of the composite material, which is particularly prominent in reactions that rely on efficient two-electron reduction pathways, such as photocatalytic production of hydrogen peroxide (H2O2). The generation of H2O2 requires a continuous two-electron transfer process. If the electron transfer resistance at the material interface is large or the structure collapses, the H2O2 yield and selectivity will be greatly reduced. Therefore, it is urgent to develop new composite strategies to achieve strong bonding and efficient electronic coupling between carbon materials and g-C3N4 nanotubes at the nanoscale. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a carbonyl-functionalized carbon-based nitrided carbon nanotube and its preparation method and application, thereby solving the technical problem in the prior art that the composite material of carbon material and nitrided carbon nanotube has poor structural stability, resulting in weak electrical conductivity and catalytic performance.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes comprises the following steps:

[0007] Step 1: adding an amino group-containing precursor to water, heating and stirring at a first stirring rate until the amino group-containing precursor is fully dissolved to obtain system A;

[0008] Step 2: adding cyclodextrin to system A at a second stirring rate, to obtain system B after the reaction is completed, wherein the second stirring rate is less than the first stirring rate;

[0009] Step 3: subjecting system B to a hydrothermal reaction to obtain sample C;

[0010] Step 4: calcining sample C under an argon protective atmosphere. After the calcination, the calcined product is subjected to a first grinding, washing, drying and a second grinding in sequence to obtain the carbonyl-functionalized carbon-based nitride carbon nanotubes.

[0011] Preferably, in step 1, the amino group-containing precursor is any one of urea, melamine, dicyandiamide, cyanamide and thiourea.

[0012] Preferably, in step 1, the mass ratio of the cyclodextrin to the amino-containing precursor is (0.5-4):100.

[0013] Preferably, the first stirring rate is 500-800 r / min.

[0014] Preferably, the second stirring rate is 300 r / min.

[0015] Preferably, the temperature of the hydrothermal reaction is 120-180° C., and the time is 8-12 hours.

[0016] Preferably, the calcination treatment is specifically as follows: heating to 200-300° C. at a heating rate of 3-15° C. / min and keeping the temperature for 1 hour, then heating to 400-600° C. and keeping the temperature for 3-5 hours.

[0017] Preferably, during the first grinding process and the second grinding process, the product is ground into a uniform powder.

[0018] A carbonyl-functionalized carbon-based nitrided carbon nanotube is prepared by the above method.

[0019] The application of the above-mentioned carbonyl-functionalized carbon-based nitrided carbon nanotubes in photocatalytic production of hydrogen peroxide.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] The present invention discloses a method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes:

[0022] First, in terms of the process flow, cyclodextrin is first introduced at a relatively low stirring rate, and its abundant hydroxyl groups (-OH) are used to form a hydrogen bond network with the amino groups (-NH2) in the amino-containing precursor, so that the cyclodextrin and the amino-containing precursor are tightly and orderly combined in the early stage of the reaction. This pre-assembled structure avoids the problems of carbon / nitrogen component separation or poor interface compatibility in traditional physical mixing or simple co-precipitation methods, laying a molecular foundation for the subsequent formation of a uniform and tightly bound hybrid structure, and greatly enhancing the interface stability of the carbon and carbon nitride components in the final composite material; then, under a high temperature and high pressure hydrothermal environment, the pre-assembled mixture undergoes nucleophilic addition and deamination reactions, and the hydrothermal reaction promotes chemical bonding between the precursor and the cyclodextrin, realizing the in situ co-precipitation of carbon and nitrogen sources at the molecular level. Valence bond connection, the formation of this strong chemical bond is the key to constructing a highly stable hybrid skeleton, which fundamentally improves the stability of the structure; finally, calcination treatment is carried out under argon protection. High-temperature calcination promotes further molecular reorganization and condensation reaction of the hydrothermal product, eliminating residual weak bonds, such as some unreacted -NH2 and -OH), forming a highly polymerized, less defective graphitic carbon nitride conjugated skeleton. This highly condensed structure has stronger rigidity and thermal stability; and it has been found that during the hydrothermal process, due to the molecular cleavage and recombination of cyclodextrin, the carbonyl group (C=O) is generated. This carbonyl group acts as a hydrogen bond acceptor and can form a C=O···HN hydrogen bond network with the -NH group of carbon nitride, synergistically covalently enhancing the interfacial force and further improving the stability of the structure.

[0023] Second, in terms of raw material selection, cyclodextrin plays a dual role as a structure-directing agent and a carbon source precursor in the formation process of carbon-based nitrided carbon nanotubes. The truncated cone-shaped cavity of cyclodextrin can enclose amino-containing precursors. The hydrogen bond network between the cyclodextrin hydroxyl group and the nitrogen precursor -NH2 enables the molecules to stack in an orderly manner along the axial direction, inhibits radial disordered growth, and guides the growth in the one-dimensional direction. The outer hydroxyl groups of cyclodextrin form a hydrogen bond layer with the nitrogen source. During hydrothermal condensation, carbon nitride preferentially nucleates and grows on the outer surface of the carbon layer to form a carbon nitride shell, while the interior of the cyclodextrin cavity undergoes intramolecular dehydration and carbonization under anaerobic hydrothermal conditions, retaining part of the glucose unit structure to form a wrinkled carbon lining. The carbon lining and the carbon nitride shell are covalently connected through COC ether bonds and CN bonds to achieve mechanical interlocking, avoid interlayer peeling, and further enhance the stability of the material.

[0024] In summary, the present invention introduces a covalent bond connection mechanism through the optimization of the preparation process and raw materials, and realizes a stable bridging structure between the carbon material and the carbon nitride nanotubes at the molecular level. This strategy significantly improves the structural stability and interface bonding strength of the composite material, while enhancing the electron transfer efficiency and photo / electrocatalytic performance, so that it still has good operational stability and repeatability under harsh reaction conditions. The prepared material shows excellent comprehensive performance in thermal stability, electrochemical stability and long-term application. In addition, by constructing a one-dimensional nanotubular structure, the specific surface area of ​​the material and the exposure degree of the reaction active sites are further improved, promoting rapid mass transfer and efficient contact of the reactants; the introduction of carbon materials effectively improves the conductivity of the system, contributes to the rapid separation and migration of photogenerated carriers, thereby enhancing the photoelectric response ability and catalytic efficiency of the material. The material still shows excellent chemical stability under a variety of complex environmental conditions, showing its broad application prospects in the fields of clean energy conversion (such as photocatalytic hydrogen production, oxygen production, H2O2 synthesis) and environmental purification (such as organic pollutant degradation).

[0025] Furthermore, the mass ratio of the cyclodextrin to the amino-containing precursor is (0.5-4):100, which can make the carbon skeleton evenly distributed on the inner wall of the carbon nitride tube, thereby promoting the effective separation of electron-hole pairs, enhancing the visible light response ability, and thus improving the photocatalytic synthesis efficiency of H2O2.

[0026] Furthermore, the first stirring rate is 500-800 r / min, and the second stirring rate is 300 r / min. Stirring too fast after adding the carbon source is not conducive to the formation of hydrogen bonds, and is likely to destroy the microstructure that is being formed or has been formed, resulting in poor bonding between components or structural loss of control.

[0027] Furthermore, the temperature of the hydrothermal reaction is 120-180°C and the time is 8-12 hours. If the temperature is too low, melamine mainly undergoes a deamination reaction, and the triazine structure is gradually converted into a heptazine structure (Melem); at this time, the hydroxyl group (-OH) on the cyclodextrin molecule is difficult to effectively attack the amino group (-NH2) on the Melem molecule, thereby inhibiting the dehydration condensation reaction between carbon and nitrogen, and failing to form a stable sp 2 The hybrid structure means that it is difficult to establish covalent bonds between the carbon atoms in the cyclodextrin and the nitrogen atoms in the melamine derivative, which affects the subsequent structure construction and the improvement of material properties. In addition, if the temperature is too high, hydrolysis or degradation reactions may occur, forming other soluble small molecules such as cyanuric acid or urea. If the temperature is too low, polymerization will be incomplete, affecting the formation of tubular structures.

[0028] Furthermore, the calcination treatment is specifically as follows: heating the temperature to 200-300°C at a heating rate of 3-15°C / min and keeping it warm for 1 hour, which can make the polymerization proceed slowly and the deamination reaction more uniform, thereby inhibiting local overheating, agglomeration or uneven reaction, which is beneficial to the controllability of the final material morphology and properties. Thereafter, heating to 400-600°C and keeping it warm for 3-5 hours can enhance the crystallinity of the material and make the structure more stable.

[0029] Furthermore, the product is ground into a uniform powder during both the first grinding process and the second grinding process. Grinding the product into a uniform powder during the first grinding process is beneficial to the uniformity of heat conduction during the subsequent calcination process. Grinding the product into a uniform powder during the second grinding process helps to expose the internal active area and improve the catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 X-ray diffraction patterns (XRD) of CB-CNNTs-6 prepared in Example 6 of the present invention and PCN of the comparative example;

[0032] Figure 2 Field emission scanning electron microscope (SEM) image of sample CB-CNNTs-6 prepared in Example 6 of the present invention;

[0033] Figure 3 This is a high-resolution transmission electron microscopy (HRTEM) image of sample CB-CNNTs-6 prepared in Example 6 of the present invention;

[0034] Figure 4 This is a field emission scanning electron microscope (SEM) image of PCN, a comparative example of the present invention;

[0035] Figure 5 FTIR images of CB-CNNTs-6 prepared in Example 6 of the present invention and PCN of the comparative example;

[0036] Figure 6 This is the XPS high-resolution C1s spectrum of PCN, a comparative example of the present invention;

[0037] Figure 7 This is the XPS high-resolution C1s spectrum of CB-CNNTs-6 prepared in Example 6 of the present invention;

[0038] Figure 8The H2O2 production performance of CB-CNNTs-6 prepared in Example 6 of the present invention and the comparative example PCN. DETAILED DESCRIPTION

[0039] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0040] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0041] Herein, all features such as values, amounts, amounts, and concentrations defined in numerical ranges or percentage ranges are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0042] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0043] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0044] The present invention provides a method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes, comprising the following steps:

[0045] Step 1: Add the amino-containing precursor to a beaker, add an appropriate amount of water, preferably deionized water, and heat to 80°C~100°C at a first stirring rate, and continue stirring until the solution becomes completely transparent to obtain system A; here, based on the "thermodynamic selection" strategy, heating to 80°C~100°C at a first stirring rate. If the temperature is too high, decomposition reactions will occur to produce small volatile products such as NH3, CO2, and HCN, reducing the utilization efficiency of the precursor, while if the temperature is too low, some insoluble nitrogen sources will not be fully dissolved, and the reaction time will increase.

[0046] The amino-containing precursor as a nitrogen source is preferably any one of urea, melamine, dicyandiamide, cyanamide and thiourea.

[0047] Step 2: adding cyclodextrin as a carbon source to the system A at a second stirring rate, and obtaining system B after the reaction is completed;

[0048] The second stirring rate is lower than the first stirring rate. Preferably, the first stirring rate is 500-800 r / min, preferably 500 r / min, and the stirring time is 1 hour; the second stirring rate is 300 r / min, and the stirring time is 30 minutes;

[0049] The mass ratio of cyclodextrin to amino-containing precursor is (0.5-4):100;

[0050] Step 3: System B was quickly transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene (PTFE) and subjected to a hydrothermal reaction at 120-180°C for 8-12 hours. After the reaction was completed, the solid product was collected by centrifugation and washed 5-10 times with distilled water at a centrifugal speed of 8000 rpm / min until the washing liquid was neutral. The product was then placed in a vacuum drying oven for drying. After the reaction was completed, the product was ground and the solid sample was collected and recorded as sample C.

[0051] Step 4: Place sample C in a porcelain boat, transfer it to a tubular furnace, and calcine it under an argon protective atmosphere. The calcination treatment is specifically to increase the temperature to 200-300°C at a heating rate of 3-15°C / min and keep it warm for 1 hour, then increase the temperature to 400-600°C and keep it warm for 3-5 hours. Calcination treatment is carried out to achieve thermal polycondensation reaction. After the calcination is completed, it is naturally cooled to room temperature, and the resulting product is ground.

[0052] Step 5: The ground sample was washed with deionized water several times until the pH value of the supernatant was close to neutral, and then the obtained solid was placed in a vacuum drying oven, dried at 80° C. for 12 h, and ground to obtain the carbon-based nitride carbon nanotubes (labeled as CB-CNNTs).

[0053] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0054] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0055] Example 1

[0056] A method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes comprises the following steps:

[0057] (1) Add 5 g of nitrogen source urea to a 100 mL beaker, add 70 mL of deionized water, and stir at 80 °C and 500 rpm until the system becomes clear and transparent, which lasts for about 1 h.

[0058] (2) The stirring rate was adjusted to 300 r / min, and the carbon source cyclodextrin, wherein the mass ratio of the carbon source to the nitrogen source was 0.5:100, was stirred for 30 min;

[0059] (3) The reaction solution was transferred while hot to a stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and subjected to a hydrothermal reaction at 120°C for 8 hours. After the reaction was completed, the system was allowed to cool naturally, and the solid product was collected by centrifugation and repeatedly washed with distilled water until the washing liquid was neutral. The obtained solid was placed in a vacuum drying oven and dried at 80°C for 12 hours. After drying, it was ground and collected;

[0060] (4) The dried solid sample was placed in a porcelain boat and then transferred to a tube furnace. Under an argon atmosphere, the temperature was raised to 200°C at a rate of 5°C / min and held for 1 h. The temperature was then raised to 400°C at the same rate and held for 4 h. After cooling, the resulting solid was collected to obtain the target product, CB-CNNTs-1.

[0061] Example 2

[0062] A method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes comprises the following steps:

[0063] (1) Add 5 g of nitrogen source melamine to a 100 mL beaker, add 70 mL of deionized water, and stir at 80 °C and 500 rpm until the system becomes clear and transparent, which lasts for about 1 h.

[0064] (2) The stirring rate was adjusted to 300 r / min, and the carbon source cyclodextrin, wherein the mass ratio of the carbon source to the nitrogen source was 1:100, was stirred for 30 min;

[0065] (3) The reaction solution was transferred while hot to a stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and subjected to a hydrothermal reaction at 140°C for 10 hours. After the reaction was completed, the system was allowed to cool naturally, and the solid product was collected by centrifugation and repeatedly washed with distilled water until the washing liquid was neutral. The obtained solid was placed in a vacuum drying oven and dried at 80°C for 12 hours. After drying, it was ground and collected;

[0066] (4) The dried solid sample was placed in a porcelain boat and then transferred to a tube furnace. Under argon atmosphere, the temperature was raised to 200°C at a rate of 5°C / min and held for 1 h. The temperature was then raised to 450°C at the same rate and held for 4 h. After cooling, the resulting solid was collected to obtain the target product, CB-CNNTs-2.

[0067] Example 3

[0068] A method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes comprises the following steps:

[0069] (1) Add 5 g of nitrogen source dicyandiamide to a 100 mL beaker, add 70 mL of deionized water, and stir at 80°C and 500 rpm until the system becomes clear and transparent, which lasts for about 1 h.

[0070] (2) The stirring rate was adjusted to 300 r / min, and the carbon source cyclodextrin, wherein the mass ratio of the carbon source to the nitrogen source was 2:100, was stirred for 30 min;

[0071] (3) The reaction solution was transferred while hot to a stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and subjected to a hydrothermal reaction at 160°C for 12 hours. After the reaction was completed, the system was allowed to cool naturally, and the solid product was collected by centrifugation and repeatedly washed with distilled water until the washing liquid was neutral. The obtained solid was placed in a vacuum drying oven and dried at 80°C for 12 hours. After drying, it was ground and collected;

[0072] (4) The dried solid sample was placed in a porcelain boat and then transferred to a tube furnace. Under argon atmosphere, the temperature was raised to 200°C at a rate of 5°C / min and held for 1 h. The temperature was then raised to 500°C at the same rate and held for 4 h. After cooling, the resulting solid was collected to obtain the target product, CB-CNNTs-3.

[0073] Example 4

[0074] A method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes comprises the following steps:

[0075] (1) Add 5 g of nitrogen source cyanamide to a 100 mL beaker, add 70 mL of deionized water, and stir at 80°C and 500 rpm until the system becomes clear and transparent, which lasts for about 1 h.

[0076] (2) The stirring rate was adjusted to 300 r / min, and the carbon source cyclodextrin, wherein the mass ratio of the carbon source to the nitrogen source was 3:100, was stirred for 30 min;

[0077] (3) The reaction solution was transferred while hot to a stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and subjected to a hydrothermal reaction at 160°C for 12 hours. After the reaction was completed, the system was allowed to cool naturally, and the solid product was collected by centrifugation and repeatedly washed with distilled water until the washing liquid was neutral. The obtained solid was placed in a vacuum drying oven and dried at 80°C for 12 hours. After drying, it was ground and collected;

[0078] (4) The dried solid sample was placed in a porcelain boat and then transferred to a tube furnace. Under an argon atmosphere, the temperature was raised to 200°C at a rate of 5°C / min and held for 1 h. The temperature was then raised to 520°C at the same rate and held for 4 h. After cooling, the resulting solid was collected to obtain the target product, CB-CNNTs-4.

[0079] Example 5

[0080] A method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes comprises the following steps:

[0081] (1) Add 5 g of nitrogen source thiourea to a 100 mL beaker, add 70 mL of deionized water, and stir at 80 °C and 500 rpm until the system becomes clear and transparent, which lasts for about 1 h.

[0082] (2) The stirring rate was adjusted to 300 r / min, and the carbon source cyclodextrin, wherein the mass ratio of the carbon source to the nitrogen source was 4:100, was stirred for 30 min;

[0083] (3) The reaction solution was transferred while hot to a stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and subjected to a hydrothermal reaction at 180°C for 8 hours. After the reaction was completed, the system was allowed to cool naturally, and the solid product was collected by centrifugation and repeatedly washed with distilled water until the washing liquid was neutral. The obtained solid was placed in a vacuum drying oven and dried at 80°C for 12 hours. After drying, it was ground and collected;

[0084] (4) The dried solid sample was placed in a porcelain boat and then transferred to a tube furnace. Under argon atmosphere, the temperature was raised to 300°C at a rate of 10°C / min and held for 1 h. The temperature was then raised to 520°C at the same rate and held for 4 h. After cooling, the resulting solid was collected to obtain the target product, CB-CNNTs-5.

[0085] Example 6

[0086] A method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes comprises the following steps:

[0087] (1) Add 5 g of nitrogen source urea to a 100 mL beaker, add 70 mL of deionized water, and stir at 95 °C and 600 rpm until the system becomes clear and transparent, which lasts for about 1 h.

[0088] (2) The stirring rate was adjusted to 300 r / min, and the carbon source cyclodextrin, wherein the mass ratio of the carbon source to the nitrogen source was 1:100, was stirred for 30 min;

[0089] (3) The reaction solution was transferred while hot to a stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and subjected to a hydrothermal reaction at 180°C for 12 hours. After the reaction was completed, the system was allowed to cool naturally, and the solid product was collected by centrifugation and repeatedly washed with distilled water until the washing liquid was neutral. The obtained solid was placed in a vacuum drying oven and dried at 80°C for 12 hours. After drying, it was ground and collected;

[0090] (4) The dried solid sample was placed in a porcelain boat and then transferred to a tube furnace. Under argon atmosphere, the temperature was raised to 200°C at a rate of 5°C / min and held for 1 h. The temperature was then raised to 520°C at the same rate and held for 4 h. After cooling, the resulting solid was collected to obtain the target product, CB-CNNTs-6.

[0091] Example 7

[0092] A method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes comprises the following steps:

[0093] (1) Add 5 g of nitrogen source urea to a 100 mL beaker, add 70 mL of deionized water, and stir at 95 °C and 700 rpm until the system becomes clear and transparent, which lasts for about 1 h.

[0094] (2) The stirring rate was adjusted to 300 r / min, and the carbon source cyclodextrin, wherein the mass ratio of the carbon source to the nitrogen source was 1:100, was stirred for 30 min;

[0095] (3) The reaction solution was transferred while hot to a stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and subjected to a hydrothermal reaction at 180°C for 12 hours. After the reaction was completed, the system was allowed to cool naturally, and the solid product was collected by centrifugation and repeatedly washed with distilled water until the washing liquid was neutral. The obtained solid was placed in a vacuum drying oven and dried at 80°C for 12 hours. After drying, it was ground and collected;

[0096] (4) The dried solid sample was placed in a porcelain boat and then transferred to a tube furnace. Under an argon atmosphere, the temperature was raised to 250°C at a rate of 15°C / min and held for 1 h. The temperature was then raised to 600°C at the same rate and held for 3 h. After cooling, the resulting solid was collected to obtain the target product, CB-CNNTs-7.

[0097] Example 8

[0098] A method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes comprises the following steps:

[0099] (1) Add 5 g of nitrogen source melamine to a 100 mL beaker, add 70 mL of deionized water, and stir at 95 °C and 700 rpm until the system becomes clear and transparent, which lasts for about 1 h.

[0100] (2) The stirring rate was adjusted to 300 r / min, and the carbon source cyclodextrin, wherein the mass ratio of the carbon source to the nitrogen source was 4:100, was stirred for 30 min;

[0101] (3) The reaction solution was transferred while hot to a stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and subjected to a hydrothermal reaction at 180°C for 12 hours. After the reaction was completed, the system was allowed to cool naturally, and the solid product was collected by centrifugation and repeatedly washed with distilled water until the washing liquid was neutral. The obtained solid was placed in a vacuum drying oven and dried at 80°C for 12 hours. After drying, it was ground and collected;

[0102] (4) The dried solid sample was placed in a porcelain boat and then transferred to a tube furnace. Under the protection of an argon atmosphere, the temperature was raised to 250°C at a rate of 3°C / min and kept at this temperature for 1 h. The temperature was then continued to be raised to 600°C at the same rate and kept at this temperature for 5 h. After cooling, the obtained solid was collected, which was the target product CB-CNNTs-8.

[0103] Comparative Example

[0104] The difference between this comparative example and Example 6 is that no carbon source is added, and carbon nitride is prepared. The sample is marked as PCN.

[0105] Figure 1The X-ray diffraction patterns (XRD) of CB-CNNTs-6 and comparative example PCN prepared in Example 6 of the present invention show that PCN has two obvious characteristic peaks at 12.8° and 27.2°, which can be attributed to the diffraction peaks of the (100) crystal plane and the (002) crystal plane. To be precise, the (100) diffraction peak at around 12.8° is related to the in-plane order of the tri-s-triazine unit, and the (002) diffraction peak at around 27.2° corresponds to the periodic layer stacking of the π-π structure. Compared with PCN, the diffraction peaks of the (100) crystal plane and the (002) crystal plane of CB-CNNTs-6 are significantly reduced, which is mainly due to the introduction of cyclodextrin in the hydrothermal process. Its unique molecular structure causes the nitrogen source to undergo molecular rearrangement during the deamination process, weakening the order of the crystal and resulting in a decrease in its diffraction peak. In addition, cyclodextrin also further promotes the formation of tubular structure.

[0106] Figure 2 This is a field emission scanning electron microscope (SEM) image of sample CB-CNNTs-6 prepared in Example 6 of the present invention. As can be seen from the figure, CB-CNNTs-6 presents a regular hollow hexagonal tube structure, in which the tube wall is a double-layer structure and the inner wall presents an uneven "lining" structure. This structure is mainly due to the carbonization of cyclodextrin under anaerobic conditions. It is composed of carbon elements and the outer wall is carbon nitride.

[0107] Figure 3 This is a high-resolution transmission electron microscopy (HRTEM) image of sample CB-CNNTs-6 prepared in Example 6 of the present invention. As can be seen from the figure, through high-resolution transmission electron microscopy (HRTEM) analysis, it was found that CB-CNNTs-6 consists of amorphous regions and crystalline regions, wherein the amorphous region is a disordered triazine unit of g-C3N4, and the crystalline region is manifested as lattice fringes with a width of 0.352nm, which belongs to the (002) crystal plane of the carbon ring formed after hydrothermal calcination of cyclodextrin.

[0108] Figure 4 This is a field emission scanning electron microscope (SEM) image of the comparative example PCN of the present invention. It can be seen from the figure that there are blocks and irregular rod-shaped structures in PCN, which are significantly different from CB-CNNTs-6 in morphology and structure.

[0109] Figure 5 The FTIR images of CB-CNNTs-6 prepared in Example 6 of the present invention and PCN of the comparative example show that all samples have the peaks at 1229.3-1654.1 cm -1 The typical Tri-s-triazine unit CN=C stretching vibration absorption peak appears between them, at 808.4cm -1The absorption peak at 1750.2 cm is attributed to the skeleton bending vibration of the heptazine ring, which shows that the two-step hydrothermal and calcination process can form a heptazine conjugated structure. However, it should be noted that the absorption peak of CB-CNNTs-6 at 1750.2 cm -1 A new absorption peak appeared at , which was obviously different from PCN. This was due to the molecular cleavage and recombination of cyclodextrin during the hydrothermal process, generating a carbonyl group (C=O).

[0110] Figure 6 This is the XPS high-resolution C1s spectrum of the comparative example PCN of the present invention. It can be seen that there is a low peak at the binding energy of 284.6eV, which belongs to the surface amorphous sp 2 The CC bond of hybrid carbon has a peak at 287.9 ​​eV, which is attributed to the NC=N bond of the Tri-s-triazine unit. The relative contents of the two bonds are 36.1% and 63.9%, respectively.

[0111] Figure 7 This is the XPS high-resolution C1s spectrum of CB-CNNTs-6 prepared in Example 6 of the present invention. It can be found from the figure that compared with the comparative example PCN, CB-CNNTs-6 has a new peak at 285.8 eV, which is attributed to the carbon of C=O. The content of N-C=N bonds decreases from 63.9% to 61.9%, indicating that some -NH2 groups on the edge of carbon nitride undergo dehydration condensation reaction with cyclodextrin to form CN bonds, thereby inhibiting the formation of N=CN bonds, which further confirms the existence of a covalent bond between the carbon "lining" and carbon nitride.

[0112] The hydrogen peroxide production performance of the sample prepared in Example 6 was tested. The specific test method and result analysis are as follows:

[0113] Weigh 50 mg of the CB-CNNTs-6 and comparative PCN samples prepared in Example 6, disperse them in 50 mL of deionized water, and place them in 100 mL beakers for photocatalytic hydrogen peroxide production test. In order to keep the photocatalytic hydrogen peroxide production in a constant temperature state, an ice bath method was used to maintain the reaction temperature at 0°C. During the reaction, the magnetic stirrer under the reactor was turned on to drive the bar magnet in the reactor to rotate, and the solution was kept stirring continuously. The xenon lamp was turned on and the photocatalytic hydrogen peroxide production reaction was carried out under visible light. 3 mL of the sample was taken every 10 minutes and filtered with a 0.22 μm water filter to remove the catalyst in the solution. 100 μL of fluorescent reagent was then added. After reacting for 10 minutes, 1 mL of 0.1 mol / L NaOH solution was added and measured using fluorescence spectroscopy at an excitation wavelength of 315 nm and an emission wavelength of 409 nm. The fluorescence intensity was used to indicate the level of hydrogen peroxide production. The test results are as follows: Figure 8As shown in the figure, it can be seen that the catalyst CB-CNNTs-6 synthesized by the present invention synthesizes hydrogen peroxide using only water and oxygen in the air as raw materials without any sacrificial agent. Under visible light irradiation, the amount of hydrogen peroxide produced is much higher than that of the comparative example sample (PCN), which proves that the covalently bridged carbon-based nitrided carbon nanotubes (CB-CNNTs) prepared by the hydrothermal and thermal polymerization tandem method of the present invention have good hydrogen peroxide production performance.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes, characterized in that: The following steps are involved: Step 1: adding an amino group-containing precursor to water, heating and stirring at a first stirring rate until the amino group-containing precursor is fully dissolved to obtain system A; Step 2: adding cyclodextrin to system A at a second stirring rate, to obtain system B after the reaction is completed, wherein the second stirring rate is less than the first stirring rate; Step 3: subjecting system B to a hydrothermal reaction to obtain sample C; Step 4: calcining sample C under an argon protective atmosphere. After the calcination, the calcined product is subjected to a first grinding, washing, drying and a second grinding in sequence to obtain the carbonyl-functionalized carbon-based nitride carbon nanotubes.

2. The method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes according to claim 1, wherein: In step 1, the amino group-containing precursor is any one of urea, melamine, dicyandiamide, cyanamide and thiourea.

3. The method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes according to claim 1, wherein: In step 1, the mass ratio of the cyclodextrin to the amino-containing precursor is (0.5-4):

100.

4. The method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes according to claim 1, wherein: The first stirring rate is 500-800 r / min.

5. The method for preparing carbon-based nitrided carbon nanotubes according to claim 1, wherein: The second stirring rate is 300 r / min.

6. The method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes according to claim 1, wherein: The temperature of the hydrothermal reaction is 120-180° C., and the time is 8-12 hours.

7. The method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes according to claim 1, wherein: The calcination treatment is specifically as follows: heating to 200-300° C. at a heating rate of 3-15° C. / min and keeping the temperature for 1 hour, then heating to 400-600° C. and keeping the temperature for 3-5 hours.

8. The method for preparing carbonyl-functionalized carbon-based nitrided carbon nanotubes according to claim 1, characterized in that: During the primary grinding process and the secondary grinding process, the product is ground into a uniform powder.

9. A carbonyl-functionalized carbon-based nitrided carbon nanotube, characterized in that: It is prepared by the method according to any one of claims 1 to 8.

10. Use of the carbonyl-functionalized carbon-based nitrided carbon nanotubes as claimed in claim 9 in photocatalytic production of hydrogen peroxide.

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