Carbon-doped carbon nitride nanotube, preparation method thereof and application of carbon-doped carbon nitride nanotube in photocatalytic reaction

Abstract

The invention discloses a carbon-doped carbon nitride nanotube as well as a preparation method and application thereof in photocatalytic reaction, and belongs to the technical field of inorganic photocatalytic nano materials. Comprising the following steps: roasting urea, melamine and 2, 4, 6-triaminopyridine under protective gas; adding the carbon-doped carbon nitride nanotube, 5-hydroxymethylfurfural and chloroplatinic acid hexahydrate into the deionized water; photocatalytic hydrogen evolution is started to cooperate with selective oxidation reaction of 5-hydroxymethylfurfural. The carbon-doped carbon nitride prepared by the preparation method disclosed by the invention is in a nanotube shape; and the catalyst can be effectively applied to solar photocatalytic hydrogen evolution to cooperate with selective oxidation of 5-hydroxymethylfurfural to generate 2, 5-diformyl furan. The invention mainly solves the problems that the value-added reaction cooperated with the hydrogen production process cannot be realized and the overall economic value cannot be improved in the traditional hydrogen production means. The method is an effective, practical and simple method, is suitable for laboratory preparation and industrial production, and has huge development space and application prospect.

Description

Technical Field

[0001] This invention belongs to the field of inorganic photocatalytic nanomaterials technology, specifically relating to a carbon-doped carbon nitride nanotube, its preparation method, and its application in photocatalytic reactions. Background Technology

[0002] The overconsumption of fossil resources has led to a severe energy crisis and environmental pollution. Therefore, developing environmentally friendly, carbon-free renewable energy sources to replace fossil fuels is extremely urgent. Hydrogen, with its high specific enthalpy and clean combustion products, is considered a sustainable, durable, and environmentally friendly renewable energy source. Hydrogen can be produced through water vapor reforming of hydrocarbons, water electrolysis, and biomass fermentation. However, these methods suffer from drawbacks such as high energy input and poor economic efficiency. Photocatalytic hydrogen evolution technology, utilizing abundant and environmentally friendly solar energy to decompose water and produce hydrogen, is one of the ideal methods for hydrogen production and addressing sustainable energy development issues. As a typical and ubiquitous renewable carbon resource, biomass feedstock is considered a potential environmentally friendly and sustainable alternative, capable of being oxidized into various high-value-added chemicals. Therefore, combining photocatalytic hydrogen evolution with the selective conversion of biomass feedstock into high-value-added chemicals is a promising strategy.

[0003] Carbon nitride (Cnitride), as a non-metallic polymer semiconductor material, has attracted widespread attention due to its ease of synthesis, low cost, and good chemical stability. Furthermore, Cnitride possesses suitable band gaps and appropriate valence and conduction band potentials, enabling it to absorb visible light and exhibit photocatalytic oxidation-reduction capabilities. However, Cnitride still suffers from several drawbacks, such as small specific surface area, narrow visible light absorption range, few reactive sites, and severe electron-hole recombination, resulting in poor photocatalytic activity and severely limiting its industrial applications. To overcome these shortcomings, morphology manipulation and non-metallic element doping are considered attractive and feasible strategies. One-dimensional hollow nanotube structures can endow Cnitride with interesting properties, such as abundant active sites, promotion of axial carrier transfer, and improved solar energy collection. Typically, non-metallic element doping in semiconductors can introduce impurity levels in the middle of the band gap, facilitating the transfer of photogenerated electrons from the impurity levels to the conduction or valence bands, thereby enhancing light absorption and optimizing charge transfer. Simultaneously, doping can also alter the positions of the valence and conduction bands, thus modulating the photocatalytic oxidation or reduction capabilities of Cnitride. Therefore, it is essential to develop a non-metallic element-doped carbon nitride nanotube material for the production of clean hydrogen energy and high-value-added organic chemicals. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing carbon-doped carbon nitride nanotubes.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solutions, including:

[0008] Urea, melamine, and nitrogen-containing heterocyclic compounds in a mass ratio of 10:5 to 0.5:1 to 0.01 are calcined under a protective gas to obtain carbon-doped carbon nitride nanotubes.

[0009] In a preferred embodiment of the method for preparing carbon-doped carbon nitride nanotubes according to the present invention, the nitrogen-containing heterocyclic compound includes one or more of 2,4,6-triaminopyrimidine, 2-aminopyrimidine, and nicotinic acid.

[0010] In a preferred embodiment of the method for preparing carbon-doped carbon nitride nanotubes according to the present invention, the protective gas includes one or more of air, nitrogen, and argon.

[0011] In a preferred embodiment of the preparation method of carbon-doped carbon nitride nanotubes according to the present invention, the calcination process includes a heating rate of 1–15 °C / min, a calcination temperature of 400–600 °C, and a calcination time of 1–12 h.

[0012] Another objective of this invention is to overcome the shortcomings of the prior art and provide a carbon-doped carbon nitride nanotube.

[0013] The third objective of this invention is to overcome the shortcomings of the prior art and provide an application of carbon-doped carbon nitride nanotubes in photocatalytic reactions.

[0014] To solve the above-mentioned technical problems, the present invention provides the following technical solutions, including:

[0015] Carbon-doped carbon nanotubes, 5-hydroxymethylfurfural, and chloroplatinic acid hexahydrate were added to deionized water; simulated sunlight irradiation initiated a photocatalytic hydrogen evolution reaction synergistically with the selective oxidation of 5-hydroxymethylfurfural to generate 2,5-dicarboxyfuran.

[0016] As a preferred embodiment of the application of the carbon-doped carbon nitride nanotubes of the present invention in photocatalytic reactions, wherein: the concentration of the carbon-doped carbon nitride nanotubes dispersed in deionized water is 0.1-10 g / L; and the concentration of 5-hydroxymethylfurfural dispersed in deionized water is 1-1000 mmol / L.

[0017] As a preferred embodiment of the application of the carbon-doped carbon nitride nanotubes of the present invention in photocatalytic reactions, wherein the mass ratio of the chloroplatinic acid hexahydrate to the carbon-doped carbon nitride nanotubes is 0.001 to 0.01:1.

[0018] As a preferred embodiment of the application of the carbon-doped carbon nitride nanotubes of the present invention in photocatalytic reactions, wherein: the simulated sunlight illumination has a wavelength of 320nm≤λ≤780nm and a light power density of 0.01~1W / cm². 2 .

[0019] As a preferred embodiment of the application of the carbon-doped carbon nitride nanotubes of the present invention in photocatalytic reactions, wherein the photocatalytic hydrogen evolution efficiency of the carbon-doped carbon nitride nanotubes is 353-536 μmol / g / h, and the DFF efficiency is 271-402 μmol / g / h.

[0020] As a preferred embodiment of the application of the carbon-doped carbon nitride nanotubes of the present invention in photocatalytic reactions, wherein the photocatalytic hydrogen evolution efficiency of the carbon-doped carbon nitride nanotubes is 536 μmol / g / h, and the DFF efficiency is 402 μmol / g / h.

[0021] Beneficial effects of this invention:

[0022] This invention uses carbon-doped carbon nitride nanotubes as a photocatalyst, utilizing 5-hydroxymethylfurfural instead of traditional sacrificial reagents (such as triethylamine, triethanolamine, and methanol) to provide the electrons required by the system, thereby achieving photocatalytic hydrogen evolution and the synergistic production of high-value-added compounds, improving the overall economic efficiency. This invention maintains the original physicochemical properties of carbon nitride during the preparation of carbon-doped carbon nitride nanotubes, and the raw materials are widely available and inexpensive. The preparation method is simple, and the prepared carbon-doped carbon nitride nanotubes have regular morphologies. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments 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. Wherein:

[0024] Figure 1This is a scanning electron microscope (SEM) image of the carbon-doped carbon nitride nanotubes prepared in Example 1.

[0025] Figure 2 The X-ray diffraction (XRD) pattern of the carbon-doped carbon nitride nanotubes prepared in Example 1.

[0026] Figure 3 The graph shows the performance of the photocatalytic hydrogen evolution synergistic selective conversion of 5-HMF to DFF in Examples 1 and 2.

[0027] Figure 4 The scanning electron microscope (SEM) image of the carbon-doped carbon nitride nanotubes prepared for Comparative Example 1 is shown. Detailed Implementation

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0030] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0031] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0032] The carbon-doped carbon nitride nanotubes prepared in the embodiments of the present invention were subjected to performance testing according to the following method:

[0033] 20 mg of carbon-doped carbon nitride nanotubes, 40 mL of 10 mmol / L 5-hydroxymethylfurfural aqueous solution, and 0.2 mg of chloroplatinic acid hexahydrate were mixed at 0.3 W / cm². 2 Photocatalytic hydrogen evolution synergistic selective oxidation of 5-hydroxymethylfurfural was performed under illumination, and the catalytic efficiency was tested.

[0034] Example 1

[0035] This embodiment provides a method for preparing carbon-doped carbon nitride nanotubes, specifically as follows:

[0036] 10g of urea, 1g of melamine and 50mg of 2,4,6-triaminopyridine (mass ratio 10:1:0.05) were heated to 550℃ in air at a heating rate of 5℃ / min and calcined for 4h to obtain carbon-doped carbon nitride nanotubes.

[0037] The scanning electron microscope (SEM) results of the carbon-doped carbon nitride nanotubes prepared in this embodiment are as follows: Figure 1 As shown, the synthesized sample has a one-dimensional hollow nanotube structure. The XRD results of the carbon-doped carbon nitride nanotubes prepared in this embodiment are as follows: Figure 2 As shown, from Figure 2 As can be seen, the synthesized sample has typical characteristic peaks of carbon nitride.

[0038] Example 2

[0039] The difference between this embodiment and Example 1 is that the amount of melamine added is adjusted to 2g, that is, the mass ratio of urea, melamine and 2,4,6-triaminopyridine is 10:2:0.05. The rest of the preparation process is the same as in Example 1, and carbon-doped carbon nitride nanotubes are obtained.

[0040] Figure 3 The graphs show the performance of photocatalytic hydrogen evolution synergistic selective conversion of 5-HMF to DFF in Examples 1 and 2. It can be seen that changing the ratio of melamine to urea will reduce the photocatalytic hydrogen evolution and DFF generation rates.

[0041] Example 3

[0042] The difference between this embodiment and Example 1 is that the amount of melamine added is adjusted to 0.5g, that is, the mass ratio of urea, melamine and 2,4,6-triaminopyridine is 10:0.5:0.05. The rest of the preparation process is the same as in Example 1, and carbon-doped carbon nitride nanotubes are obtained.

[0043] Example 4

[0044] The difference between this embodiment and Example 1 is that the amount of 2,4,6-triaminopyridine added is adjusted to 100 mg, that is, the mass ratio of urea, melamine and 2,4,6-triaminopyridine is 10:2:0.1. The rest of the preparation process is the same as in Example 1, and carbon-doped carbon nitride nanotubes are obtained.

[0045] Example 5

[0046] The difference between this embodiment and Example 1 is that the amount of 2,4,6-triaminopyridine added is adjusted to 10 mg, that is, the mass ratio of urea, melamine and 2,4,6-triaminopyridine is 10:2:0.01. The rest of the preparation process is the same as in Example 1, and carbon-doped carbon nitride nanotubes are obtained.

[0047] The performance of the carbon-doped carbon nitride nanotubes prepared in the above embodiments was tested, and the comparison results with those of Example 1 are shown in Table 1.

[0048] Table 1

[0049] <![CDATA[H2(μmol / g / h)]]> DFF (μmol / g / h) Example 1 536 402 Example 2 407 318 Example 3 353 271 Example 4 378 284 Example 5 431 329

[0050] As shown in the table above, adjusting the mass ratio of urea, melamine, and 2,4,6-triaminopyridine significantly affects the performance of carbon-doped carbon nitride nanotubes. This is because these three precursors have different synergistic effects during the thermal polycondensation process, directly influencing the crystal structure, specific surface area, and defect type of the product material. According to the results in the table, the optimal technical effect is achieved when the mass ratio of urea, melamine, and 2,4,6-triaminopyridine in this invention is 10:1:0.05.

[0051] Example 6

[0052] The difference between this embodiment and Example 1 is that the heating rate of calcination is adjusted to 10℃ / min, while the rest of the preparation process is the same as in Example 1, and carbon-doped carbon nitride nanotubes are obtained.

[0053] Example 7

[0054] The difference between this embodiment and Example 1 is that the heating rate of calcination is adjusted to 1℃ / min, while the rest of the preparation process is the same as in Example 1, and carbon-doped carbon nitride nanotubes are obtained.

[0055] The performance of the carbon-doped carbon nitride nanotubes prepared in the above embodiments was tested, and the comparison results with those of Example 1 are shown in Table 2.

[0056] Table 2

[0057] <![CDATA[H2(μmol / g / h)]]> DFF (μmol / g / h) Example 1 536 402 Example 6 507 383 Example 7 484 369

[0058] As can be seen from the table above, adjusting the calcination heating rate has a significant impact on the properties of carbon-doped carbon nitride nanotubes. This is because the heating rate can regulate the pyrolysis kinetics of the material, affecting the molecular self-assembly of the precursor, crystal growth, defect formation, and the evolution of the nanostructure. According to the results in the table above, the optimal technical effect can be obtained when the calcination heating rate in this invention is 5℃ / min.

[0059] Example 8

[0060] The difference between this embodiment and Example 1 is that the calcination temperature is adjusted to 450°C, while the rest of the preparation process is the same as in Example 1, to obtain carbon-doped carbon nitride nanotubes.

[0061] Example 9

[0062] The difference between this embodiment and Example 1 is that the calcination temperature is adjusted to 570℃, while the rest of the preparation process is the same as in Example 1, to obtain carbon-doped carbon nitride nanotubes.

[0063] The performance of the carbon-doped carbon nitride nanotubes prepared in the above embodiments was tested, and the comparison results with those of Example 1 are shown in Table 3.

[0064] Table 3

[0065] <![CDATA[H2(μmol / g / h)]]> DFF (μmol / g / h) Example 1 536 402 Example 8 505 385 Example 9 472 357

[0066] As can be seen from the table above, adjusting the calcination temperature has a significant impact on the properties of carbon-doped carbon nitride nanotubes. This is because temperature directly determines the degree of pyrolysis of the precursor, the carbon doping efficiency, the evolution of the crystal structure, and the formation of the nanotube morphology. According to the results in the table above, the optimal technical effect can be obtained when the calcination temperature in this invention is 550℃.

[0067] Example 10

[0068] The difference between this embodiment and Example 1 is that the calcination time was adjusted to 2 hours, while the rest of the preparation process was the same as in Example 1, resulting in carbon-doped carbon nitride nanotubes.

[0069] Example 11

[0070] The difference between this embodiment and Example 1 is that the calcination time was adjusted to 6 hours, while the rest of the preparation process was the same as in Example 1, resulting in carbon-doped carbon nitride nanotubes.

[0071] The performance of the carbon-doped carbon nitride nanotubes prepared in the above examples was tested, and the comparison results with those of Example 1 are shown in Table 4.

[0072] Table 4

[0073] <![CDATA[H2(μmol / g / h)]]> DFF (μmol / g / h) Example 1 536 402 Example 10 473 365 Example 11 498 381

[0074] As can be seen from the table above, adjusting the calcination time has a significant impact on the properties of carbon-doped carbon nitride nanotubes. This is because the time factor directly regulates the thermodynamic equilibrium process of the material, affecting the integrity of crystal growth, the uniformity of carbon doping, the defect concentration, and the stability of the nanostructure. According to the results in the table above, the optimal technical effect can be obtained when the calcination time in this invention is 4 hours.

[0075] Example 12

[0076] This embodiment conducts additional photocatalytic reaction tests on the carbon-doped carbon nitride nanotubes prepared in Example 1, specifically as follows:

[0077] 20 mg of carbon-doped carbon nitride nanotubes, 40 mL of 50 mmol / L 5-hydroxymethylfurfural aqueous solution, and 0.2 mg of chloroplatinic acid hexahydrate were mixed at 0.3 W / cm². 2 Photocatalytic hydrogen evolution synergistic selective oxidation of 5-hydroxymethylfurfural was carried out under illumination.

[0078] Experimental results: The photocatalytic hydrogen evolution efficiency was 347 μmol / g / h, and the efficiency of DFF was 214 μmol / g / h.

[0079] Example 13

[0080] This embodiment conducts additional photocatalytic reaction tests on the carbon-doped carbon nitride nanotubes prepared in Example 1, specifically as follows:

[0081] 20 mg of carbon-doped carbon nitride nanotubes, 40 mL of 10 mmol / L 5-hydroxymethylfurfural aqueous solution, and 0.2 mg of chloroplatinic acid hexahydrate were mixed at 0.05 W / cm². 2 Photocatalytic hydrogen evolution synergistic selective oxidation of 5-hydroxymethylfurfural was carried out under illumination.

[0082] Experimental results: The catalytic efficiency was 184 μmol / g / h for photocatalytic hydrogen evolution and 109 μmol / g / h for DFF.

[0083] Comparative Example 1

[0084] The difference between this comparative example and Example 1 is that the calcination time was adjusted to 20 minutes. Specifically:

[0085] 10g of urea, 1g of melamine and 50mg of 2,4,6-triaminopyridine were heated to 550℃ in air at a heating rate of 5℃ / min and calcined for 20min to obtain carbon-doped carbon nitride nanotubes.

[0086] SEM results of carbon nitride prepared by Comparative Example 1 are as follows: Figure 4 As shown, from Figure 4 As can be seen, due to the short calcination time, the morphology of the prepared carbon nitride did not maintain a tubular shape.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 1 is that the protective gas is changed to oxygen, while the rest of the preparation process is the same as that of Example 1.

[0089] Carbon-doped carbon nitride nanotubes could not be obtained; the yield was 0%.

[0090] Comparative Example 3

[0091] The difference between this comparative example and Example 1 is that the calcination temperature was adjusted to 650°C, while the rest of the preparation process is the same as in Example 1.

[0092] Experiments have shown that excessively high calcination temperatures can lead to material decomposition, making it impossible to obtain carbon-doped carbon nitride nanotubes.

[0093] Comparative Example 4

[0094] When the mass of platinum added to the photocatalytic reaction is adjusted to zero, while other conditions remain unchanged, the rate of hydrogen production becomes almost zero.

[0095] In summary, this invention uses carbon-doped carbon nitride nanotubes as a photocatalyst and utilizes 5-hydroxymethylfurfural instead of traditional sacrificial reagents (such as triethylamine, triethanolamine, and methanol) to provide the electrons required by the system, thereby achieving photocatalytic hydrogen evolution and the production of high-value-added compounds, thus improving the overall economic efficiency. This invention maintains the original physicochemical properties of carbon nitride during the preparation of carbon-doped carbon nitride nanotubes, and the raw materials are widely available and inexpensive. The preparation method of this invention is simple, and the prepared carbon-doped carbon nitride nanotubes have regular morphologies.

[0096] 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 it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing carbon-doped carbon nitride nanotubes, characterized in that: include, Urea, melamine, and nitrogen-containing heterocyclic compounds in a mass ratio of 10:2 to 0.5:0.01 to 0.1 are calcined under a protective gas to obtain carbon-doped carbon nitride nanotubes.

2. The method for preparing carbon-doped carbon nitride nanotubes as described in claim 1, characterized in that: The nitrogen-containing heterocyclic compound includes one or more of 2,4,6-triaminopyrimidine, 2-aminopyrimidine, and nicotinic acid.

3. The method for preparing carbon-doped carbon nitride nanotubes as described in claim 1, characterized in that: The protective gas includes one or more of air, nitrogen, and argon.

4. The method for preparing carbon-doped carbon nitride nanotubes as described in claim 1, characterized in that: The roasting process includes a heating rate of 1–10 °C / min, a roasting temperature of 450–570 °C, and a roasting time of 2–6 h.

5. A carbon-doped carbon nitride nanotube prepared by any one of the preparation methods described in claims 1 to 4.

6. An application of carbon-doped carbon nitride nanotubes as described in claim 5 in photocatalytic reactions, characterized in that: The carbon-doped carbon nanotubes, 5-hydroxymethylfurfural, and chloroplatinic acid hexahydrate described in claim 4 are added to deionized water; a photocatalytic hydrogen evolution reaction is initiated under simulated sunlight to selectively oxidize 5-hydroxymethylfurfural to generate 2,5-dicarboxyfuran.

7. The application of carbon-doped carbon nitride nanotubes as described in claim 6 in photocatalytic reactions, characterized in that: The concentration of the carbon-doped carbon nitride nanotubes dispersed in deionized water is 0.1–10 g / L; the concentration of 5-hydroxymethylfurfural dispersed in deionized water is 1–1000 mmol / L.

8. The application of carbon-doped carbon nitride nanotubes as described in claim 6 in photocatalytic reactions, characterized in that: The mass ratio of the hexahydrate chloroplatinic acid to the carbon-doped carbon nitride nanotubes is 0.001 to 0.01:

1.

9. The application of carbon-doped carbon nitride nanotubes as described in claim 6 in photocatalytic reactions, characterized in that: The simulated sunlight illumination has a wavelength of 320nm ≤ λ ≤ 780nm and a light power density of 0.01~1W / cm². 2 .

10. The application of carbon-doped carbon nitride nanotubes as described in any one of claims 6 to 9 in photocatalytic reactions, characterized in that: The photocatalytic hydrogen evolution efficiency of the carbon-doped carbon nitride nanotubes is 353–536 μmol / g / h, and the efficiency of DFF is 271–402 μmol / g / h.

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