Iron-doped defect-rich carbon nitride nanotube photocatalysts, their preparation methods, and applications

Abstract

This invention relates to the field of photocatalysis technology, specifically to iron-doped defect-rich carbon nitride nanotube photocatalysts, their preparation methods, and applications. The invention first obtains a modified intermediate via a hydrothermal method, and then calcines it in a muffle furnace to obtain defect-rich carbon nitride nanotubes with a porous structure. By utilizing the porous structure and the active sites created by iron doping, the invention solves the problems of low visible light utilization, poor nitrogen adsorption and activation capabilities, and low nitrogen fixation synthesis efficiency of existing photocatalysts.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis technology, specifically to iron-doped defect-rich carbon nitride nanotube photocatalysts, their preparation methods, and applications. Background Technology

[0002] Photocatalysis, driven by sunlight, has garnered widespread attention from researchers due to its environmentally friendly nature and its potential to alleviate current energy pressures. Graphitic carbon nitride (g-C3N4) has been applied in numerous fields since its introduction into photocatalytic reactions. However, it still has many shortcomings that require improvement, such as its small specific surface area, high photogenerated carrier recombination rate, and slow photogenerated electron transport rate, resulting in poor photocatalytic performance.

[0003] Industrial nitrogen fixation is considered unsustainable due to its high energy consumption and carbon dioxide emissions. Photocatalytic nitrogen fixation, which directly synthesizes ammonia from water and nitrogen under sunlight, is a promising alternative to traditional industrial nitrogen fixation. However, nitrogen activation is extremely difficult to achieve in photocatalytic ammonia synthesis due to the very high bond energy of the nitrogen-nitrogen triple bond. Traditional methods use high temperature and pressure to break the nitrogen-nitrogen triple bond, while photocatalysis gradually opens it, breaking bonds while simultaneously adding hydrogen. To achieve this, nitrogen must first be adsorbed onto the catalyst and activated, requiring the catalyst to provide sufficient sites and electrons. Defect-rich carbon nitride perfectly meets this requirement. Furthermore, calcination makes the material porous, effectively improving light utilization efficiency. Simultaneously, the hydrothermal method is simple and controllable, producing materials with uniform morphology and stable structure, making it one of the most widely used methods. Summary of the Invention

[0004] One objective of this invention is to provide a method for preparing an iron-doped defect-rich carbon nitride nanotube photocatalyst. This method first obtains a modified intermediate via a hydrothermal process, and then calcines it in a muffle furnace to obtain defect-rich carbon nitride nanotubes with a porous structure. By utilizing the porous structure and the active sites created by iron doping, this method solves the problems of low visible light utilization, poor nitrogen adsorption and activation capabilities, and low nitrogen fixation synthesis efficiency found in existing photocatalysts.

[0005] The specific technical solution for achieving the objective of this invention is as follows:

[0006] 1. A method for preparing an iron-doped defect-rich carbon nitride nanotube photocatalyst, comprising the following steps:

[0007] (1) First, melamine, hydroxylamine hydrochloride and potassium ferrate are placed in deionized water and magnetically stirred at room temperature to disperse them, thus obtaining a mixed dispersion.

[0008] (2) The obtained mixed dispersion is transferred to a hydrothermal reactor for reaction; the obtained reaction product is allowed to stand, then centrifuged, washed and dried to obtain the modified intermediate;

[0009] (3) The synthesized modified intermediate is placed in a muffle furnace, and then heated to a certain temperature at a certain heating rate and held for a certain time to obtain iron-doped defect-rich carbon nitride nanotubes.

[0010] In the above preparation method, in step 1, the mass ratio of melamine, hydroxylamine hydrochloride, potassium ferrate and deionized water is 1:2:0.015:30; the stirring time is 30 min.

[0011] In the above preparation method, in step 2, the reaction temperature is 120℃, the reaction time is 12h, the washing solvent is anhydrous ethanol and deionized water, and the washing is repeated three times alternately, and the drying temperature is 60℃.

[0012] In the above preparation method, in step 3, the calcination temperature is 500℃, the heating rate is 2℃ / min, and the calcination temperature is maintained for 4 hours.

[0013] Compared with the prior art, the present invention has the following significant advantages:

[0014] 1. After calcination, a loose and porous structure is formed, which effectively enhances the light reflection length, improves the utilization efficiency of visible light, and enhances the photocatalytic nitrogen fixation efficiency. At the same time, the iron-doped defect-rich carbon nitride nanotubes form defects, which effectively promote the adsorption and activation of nitrogen gas by the catalyst, thereby improving the photocatalytic performance.

[0015] 2. The preparation method of the material of this invention has no special requirements for equipment, has extremely high output, is simple to operate, easy to control, has good repeatability, is green and environmentally friendly, and is conducive to large-scale industrial production. Attached Figure Description

[0016] Figure 1 SEM image of the iron-doped defect-rich carbon nitride nanotubes prepared in this invention.

[0017] Figure 2 The image shows the XRD pattern of the iron-doped defect-rich carbon nitride nanotubes prepared in this invention.

[0018] Figure 3 FT-IR image of iron-doped defect-rich carbon nitride nanotubes prepared in this invention;

[0019] Figure 4 The diagram shows the photocatalytic nitrogen fixation performance of the iron-doped defect-rich carbon nitride nanotube photocatalyst prepared in this invention. Detailed Implementation

[0020] The invention will now be described in further detail with reference to the accompanying drawings.

[0021] Example 1: The preparation method of the iron-doped defect-rich carbon nitride nanotube photocatalyst of the present invention specifically includes the following steps:

[0022] Step 1: Dissolve 1g of melamine and 2g of hydroxylamine hydrochloride in 30mL of deionized water, then add 0.015g of potassium ferrate and mix. Disperse the mixture by magnetic stirring at room temperature for 30min to obtain a mixed dispersion.

[0023] Step 2: Transfer the obtained mixed dispersion to a 50mL hydrothermal reactor, place it in a constant temperature oven at 120℃ and react for 12 hours. Then, let the reactor cool naturally to room temperature. Wash the centrifuged sample three times alternately with deionized water and ethanol, and dry it in a 60℃ oven for use.

[0024] Step 3: Weigh 1g of the synthesized intermediate and place it in a 5mL crucible. Cover the crucible, wrap it with tin foil, and place it in a muffle furnace for calcination in air. The heating parameters are as follows: set the temperature to rise uniformly from room temperature to 500℃ in 240min and hold at 500℃ for 4h. Then cool naturally. The resulting pale yellow solid is iron-doped defect-rich carbon nitride nanotubes, which can be ground and used.

[0025] Figure 1 This is a scanning electron microscope (SEM) image of the iron-doped defect-rich carbon nitride nanotube photocatalyst prepared in this embodiment. The image shows the loose, porous structure on the surface of the iron-doped defect-rich carbon nitride nanotubes calcined in air.

[0026] Figure 2 The image shows the X-ray diffraction pattern of the iron-doped defect-rich carbon nitride nanotube photocatalyst prepared in this embodiment. The iron-doped defect-rich carbon nitride nanotubes show a characteristic peak of bulk g-C3N4 at 27.3°, and the intensity of the characteristic peak is weakened due to the presence of defects.

[0027] Figure 3 The image shows the Fourier transform infrared spectrum of the iron-doped defect-rich carbon nitride nanotube photocatalyst prepared in this embodiment. The prepared iron-doped defect-rich carbon nitride nanotubes exhibit a spectrum similar to that of bulk g-C3N4, with a wavelength of 810 cm⁻¹. -1 The peak corresponds to the stretching vibration of the s-triazine-s ring, 110 cm⁻¹. -1 Up to 1600cm -1 The peak at 3000 cm⁻¹ corresponds to the typical heterocyclic CN and C=N stretching vibrations in graphitic carbon nitride, while the peak at 3000 cm⁻¹ corresponds to the typical heterocyclic CN and C=N stretching vibrations in graphitic carbon nitride. -1 up to 3600cm -1The broad peaks are generally related to NH stretching vibrations or originate from adsorbed H2O. These peaks are roughly consistent with bulk g-C3N4, indicating that carbon nitride nanotubes maintain the main chemical structure of bulk carbon nitride.

[0028] Figure 4 This image shows a comparison of the nitrogen fixation performance of the iron-doped defect-rich carbon nitride nanotube photocatalyst prepared in this embodiment. The photocatalytic nitrogen fixation performance test included the following steps: 0.020 g of photocatalyst was weighed and dispersed in 50 mL of methanol solution (1 / 100 vol%), and then placed in a constant-temperature photocatalytic reactor (300 W xenon lamp) for photocatalytic nitrogen fixation testing. The suspension was first magnetically stirred for 30 min in the dark to reach the adsorption-desorption equilibrium of nitrogen and photocatalyst. During the photocatalytic reaction, 3 mL of suspension was taken every 30 min, centrifuged (13000 rpm, 3 min), and the supernatant was obtained by passing through a microporous filter membrane. The concentration of ammonia in the filtrate at different time points was detected by Nessler's reagent colorimetric method. The results showed that the photocatalytic ammonia production rate of undoped g-C3N4 was only 327 μmol / h / g, while the photocatalytic ammonia production rate of iron-doped defect-rich carbon nitride nanotubes reached 647 μmol / h / g.

Claims

1. Application of an iron-doped, defect-rich carbon nitride nanotube photocatalyst in a photocatalytic nitrogen fixation reaction, characterized in that, The preparation steps of the iron-doped and defect-rich carbon nitride nanotube photocatalyst are as follows: (1) First, melamine, hydroxylamine hydrochloride and potassium ferrate are placed in deionized water for magnetic stirring and dispersion at room temperature to obtain a mixed dispersion liquid; the mass ratio of melamine, hydroxylamine hydrochloride, potassium ferrate and deionized water is 1:2:0.015:30; the stirring time is 30 min; (2) The obtained mixed dispersion liquid is transferred to a hydrothermal reaction kettle for reaction; the obtained reaction product is centrifuged, washed and dried after standing to obtain a modified intermediate; (3) The synthesized modified intermediate is placed in a muffle furnace, heated to a certain temperature at a certain heating rate under an air atmosphere, and then kept for a certain time to obtain an iron-doped and defect-rich carbon nitride nanotube, wherein the surface of the iron-doped and defect-rich carbon nitride nanotube has a loose and porous structure.

2. The use of the iron-doped, defect-rich carbon nitride nanotube photocatalyst according to claim 1 in the photocatalytic nitrogen fixation reaction, characterized in that, In the step (2), the reaction temperature is 120℃, the reaction time is 12 h, the washing solvent is anhydrous ethanol and deionized water, which is alternately cleaned three times, and the drying temperature is 60℃.

3. The use of the iron-doped, defect-rich carbon nitride nanotube photocatalyst according to claim 1 in the photocatalytic nitrogen fixation reaction, characterized in that, The calcination temperature is 500 ◦ C, the temperature increasing rate is 2 ◦ C / min, and the calcination temperature holding time is 4 h.

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