CN110227529B - Graphite-like carbon nitride-based photocatalyst, preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a graphite-like carbon nitride based photocatalyst as well as a preparation method and application thereof. The preparation method of the graphite-like carbon nitride based photocatalyst comprises the following steps: uniformly mixing urea and acetylacetone to obtain a mixture; and (3) reacting the mixture at high temperature to obtain the graphite-like carbon nitride based photocatalyst. The graphite-like carbon nitride based photocatalyst prepared by the method has good photocatalytic hydrogen production performance and good photocatalytic stability, can realize effective utilization of sunlight, and has good application prospect.

Description

Graphite-like carbon nitride-based photocatalyst, preparation method and application thereof

technical field

The invention belongs to the technical field of photocatalytic materials, and in particular relates to a graphitic carbon nitride-based photocatalyst and a preparation method and application thereof.

Background technique

Graphite-like carbon nitride (gC ₃ N ₄ ) is a very promising non-metallic visible light photocatalyst, and its potential applications have received extensive research and attention. Common applications of graphitic carbon nitride include: removal of NO, decomposition of water pollutants, reduction of _CO2 , and more. Most importantly, since the energy band of GLN covers the oxidation and reduction potentials of water, GLN has a catalytic effect on both photo-splitting water to produce hydrogen and photo-splitting water to produce oxygen.

Although gC ₃ N ₄ possesses suitable energy band, high thermal stability and chemical stability, its photocatalytic activity is inhibited due to the narrow response range of the material to visible light and the easy recombination of photo-generated electrons and photo-generated holes. At present, more and more researches try to improve the photocatalytic activity of gC ₃ N ₄ by adjusting the electronic structure of gC ₃ N ₄ to reduce the recombination probability of photogenerated carriers and extend the visible light absorption range of the material. Heterojunction preparation, element doping, noble metal deposition, and microstructural modification have been widely used to tune the electronic structure of materials, and studies have demonstrated that these methods are also effective.

Recently, considering the organic properties of the π-conjugated cyclic system of gC ₃ N ₄ , attempts have been made to design and synthesize graphitic carbon nitride-based photocatalysts through organic chemistry. The group of Xinchen Wang, a pioneer in gC ₃ N ₄ research, reported a series of work on the incorporation of aromatic building blocks into gC ₃ N ₄ framework structures. The doping can tune the π _- electron delocalization of the _gC3N4 conjugated structure, thereby optimizing the electronic/optical properties of the material, and all dopings exhibit significant enhancements in photocatalytic activity. In addition, some other organic structure doping designs have also been reported. For example, by doping 2,4,6-triaminopyrimidine (TAP) into the gC ₃ N ₄ framework, it can precisely replace the N atom on the gC ₃ N ₄ aromatic ring, thereby adjusting the electronic properties of the material and improving the optical properties of the material. catalytic activity. Surface-modified gC ₃ N ₄ by incorporating a small amount of polydopamine, it was found that the excessive growth of Pt nanoparticles was efficiently inhibited during the photocatalytic reaction. In addition, through the synthetic ideas of organic chemistry, the introduction of nitrogen defects, the formation of -DA- structures, and the incorporation of polycyclic aromatic compounds have a good effect on the photocatalytic activity of the formed graphitic carbon nitride-based photocatalysts. It can be seen from the above content that it is indeed an effective method to construct the framework structure of graphitic carbon nitride-based photocatalyst through the idea of organic synthesis. At present, the acetylacetone-doped graphitic carbon nitride structure has not been reported, and the catalytic performance of this graphitic carbon nitride-based photocatalyst is still unclear.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a graphitic carbon nitride-based photocatalyst and its preparation method and application. The invention adopts a small amount of acetylacetone combined with urea, and prepares a graphitic carbon nitride-like structure doped with acetylacetone through a high-temperature one-step thermal polymerization method. The graphite-like carbon nitride-based photocatalyst prepared by the invention not only has good photocatalytic hydrogen production performance under the condition of visible light, but also has good photocatalytic stability, and can realize the effective utilization of sunlight.

The present invention is achieved through the following technical solutions:

A preparation method of a graphitic carbon nitride-based photocatalyst, comprising the following steps:

(1) urea and acetylacetone are mixed to obtain mixture;

(2) reacting the mixture at high temperature to obtain a graphitic carbon nitride-based photocatalyst.

Preferably, the ratio (g/μL) of the mass of the urea to the volume of acetylacetone is 1:0.5-5.

Further preferably, the ratio (g/μL) of the mass of the urea to the volume of acetylacetone is 1:0.5.

Further preferably, the ratio (g/μL) of the mass of the urea to the volume of acetylacetone is 1:1.

Further preferably, the ratio (g/μL) of the mass of the urea to the volume of acetylacetone is 1:2.

Further preferably, the ratio (g/μL) of the mass of the urea to the volume of acetylacetone is 1:3.

Further preferably, the ratio (g/μL) of the mass of the urea to the volume of acetylacetone is 1:5.

Preferably, the high temperature reaction is to raise the temperature to 550°C at a heating rate of 10°C/min, and then keep the reaction at this temperature for 4 hours.

Preferably, the method further comprises the following steps: after naturally cooling to room temperature, grinding the obtained product to powder.

In the present invention, the graphitic carbon nitride-based photocatalyst is prepared by doping urea with acetylacetone, and by adjusting the ratio of urea and acetylacetone, the acetylacetone doped in the final high polymer is changed, thereby resulting in different dopings. amount of graphitic carbon nitride-based photocatalysts.

In the present invention, the graphitic carbon nitride-based photocatalyst is prepared by doping a trace level of acetylacetone, the catalytic hydrogen production performance in the visible light region is significantly improved, and the quantum yield is even as high as 18.8% under the light of a single wavelength of 450 nm. . In addition, the graphitic carbon nitride-based photocatalyst prepared by the present invention has good photocatalytic stability, so that the material has a good application prospect.

Description of drawings

FIG. 1 is a schematic diagram of the reaction of Example 1. FIG.

Figure 2 is a schematic diagram of the UV-Vis diffuse reflectance spectra of the samples obtained in Examples 1-6.

3 is a schematic diagram of the photocatalytic hydrogen production rate (λ≥420 nm) of the samples obtained in Examples 1-6.

Figure 4 is a schematic diagram of the photocatalytic hydrogen production rates of UCN and UCN-20acac at different single wavelengths.

Figure 5 is the photocatalytic stability test of the sample UCN-20acac (λ≥420nm).

Detailed ways

The present invention will be described below with reference to specific embodiments.

Example 1

A preparation method of a graphitic carbon nitride-based photocatalyst, comprising the following steps:

Mix 10 g of urea and 20 μL of acetylacetone in a 100 mL covered alumina crucible evenly; in a muffle furnace, gradually raise the temperature to 550 ° C at a heating rate of 10 ° C/min, and keep the reaction for 4 h; The resulting product is ground to a powder. The sample was named UCN-20acac.

Example 2

A preparation method of a graphitic carbon nitride-based photocatalyst, comprising the following steps:

Mix 10 g urea and 5 μL acetylacetone in a 100 mL alumina crucible with a lid; in a muffle furnace, gradually heat up to 550 °C at a heating rate of 10 °C/min, and keep the reaction for 4 h; The resulting product is ground to a powder. The sample was named UCN-5acac.

Example 3

A preparation method of a graphitic carbon nitride-based photocatalyst, comprising the following steps:

Mix 10 g of urea and 10 μL of acetylacetone in a 100 mL covered alumina crucible evenly; in a muffle furnace, gradually heat up to 550 °C at a heating rate of 10 °C/min, and keep the reaction for 4 h; The resulting product is ground to a powder. The sample was named UCN-10acac.

Example 4

A preparation method of a graphitic carbon nitride-based photocatalyst, comprising the following steps:

Mix 10 g of urea and 30 μL of acetylacetone in a 100 mL covered alumina crucible evenly; in a muffle furnace, gradually heat up to 550 °C at a heating rate of 10 °C/min, and keep the reaction for 4 h; The resulting product is ground to a powder. The sample was named UCN-30acac.

Example 5

A preparation method of a graphitic carbon nitride-based photocatalyst, comprising the following steps:

Mix 10 g of urea and 50 μL of acetylacetone in a 100 mL covered alumina crucible evenly; in a muffle furnace, gradually heat up to 550 ° C at a heating rate of 10 ° C/min, and keep the reaction for 4 h; after cooling to room temperature naturally, the The resulting product is ground to a powder. The sample was named UCN-50acac.

Example 6

A method for preparing a pure-phase graphitic carbon nitride-based photocatalyst, comprising the following steps:

Put 10g of urea in a 100mL alumina crucible with a lid; in a muffle furnace, gradually heat up to 550°C at a heating rate of 10°C/min, and keep the reaction for 4h; after naturally cooling to room temperature, grind the obtained product to powder. The samples were named UCN.

A schematic diagram of the reaction of Example 1 is shown in Figure 1 . Acetylacetone-doped graphitic carbon nitride can be obtained by reacting urea with acetylacetone.

The UV-vis diffuse reflectance spectra of the samples obtained in Examples 1-6 are shown in FIG. 2 . It can be seen from Figure 2 that with the gradual increase of the doping content of acetylacetone, different doped graphitic carbon nitride structures are constructed, and the absorption range of the prepared samples to visible light is gradually broadened, which will greatly benefit the material. The improvement of photocatalytic hydrogen production performance.

The photocatalytic hydrogen production rates of the samples obtained in Examples 1-6 are shown in Figure 3 . It can be seen from Fig. 3 that the photocatalytic hydrogen production performance of the samples UCN-5acac, UCN-10acac, UCN-20acac, UCN-30acac and UCN-50acac prepared by the present invention are all better than those of UCN synthesized by pure urea. The photocatalytic hydrogen production performance of 20acac was the best, followed by the photocatalytic hydrogen production performance of UCN-10acac. Compared with UCN, the photocatalytic hydrogen production performance of UCN-30acac and UCN-50acac has a certain improvement, but it is significantly lower than that of UCN-20acac, which may be caused by the excessive doping of acetylacetone, indicating that the doping of acetylacetone Impurities are not the more the better.

The photocatalytic hydrogen production rates of UCN and UCN-20acac under different single-wavelength irradiation are shown in Fig. 4. It can be seen from Figure 4 that the change trend of the photocatalytic hydrogen production rate of the samples UCN and UCN-20acac is consistent with the change trend of the light absorption of the samples in the UV-Vis diffuse reflectance spectrum of Figure 2, indicating that the photons absorbed by the materials are The main driving force for photocatalytic hydrogen production. In addition, the photocatalytic hydrogen production rate of sample UCN-20acac is significantly higher than that of sample UCN in the whole visible light region. Combined with the quantum yield calculation formula, at a single wavelength of 450nm, the quantum yield of the sample UCN is only 3.0%, while the quantum yield of the sample UCN-20acac is as high as 18.8%; even at 550nm, the hydrogen production of the sample UCN-20acac The rate can reach ^460umol h ^-1 g ^-1 , while the sample UCN is only 14umol h ^-1 g ^-1 , an increase of about 33 times.

Figure 5 shows the photostability of the sample obtained in Example 1 for photocatalytic hydrogen production. It can be seen from Figure 5 that in the 16h photocatalytic hydrogen production performance test, the hydrogen production performance of the sample did not significantly decrease, indicating that the obtained sample has good photocatalytic stability and has a good application prospect in practical applications.

Claims (9)

1. a kind of preparation method of graphitic carbon nitride based photocatalyst, is characterized in that, comprises the following steps: (1) urea and acetylacetone are mixed to obtain mixture; (2) reacting the mixture at high temperature to obtain a graphitic carbon nitride-based photocatalyst; Wherein, the ratio of the mass of urea to the volume of acetylacetone in the mixture of urea and acetylacetone is 1 g: 0.5-5 μL. 2. The preparation method of the graphitic-like carbon nitride-based photocatalyst according to claim 1, wherein the ratio of the mass of the urea to the volume of the acetylacetone is 1 g: 2 μL. 3. The preparation method of the graphitic-like carbon nitride-based photocatalyst according to claim 1, wherein the ratio of the mass of the urea to the volume of the acetylacetone is 1 g:0.5 μL. 4. The preparation method of the graphitic-like carbon nitride-based photocatalyst according to claim 1, wherein the ratio of the mass of the urea to the volume of the acetylacetone is 1 g: 1 μL. 5. The preparation method of the graphitic-like carbon nitride-based photocatalyst according to claim 1, wherein the ratio of the mass of the urea to the volume of the acetylacetone is 1 g: 3 μL. 6. The preparation method of the graphitic-like carbon nitride-based photocatalyst according to claim 1, wherein the ratio of the mass of the urea to the volume of the acetylacetone is 1 g:5 μL. 7. The preparation method of the graphitic-like carbon nitride-based photocatalyst according to claim 1, wherein the high temperature reaction is to first heat up to 550°C at a temperature increase rate of 10°C/min, and then heat the reaction at this temperature. 4h. 8. The graphitic carbon nitride-based photocatalyst prepared by the preparation method of any one of claims 1-7. 9. Use of the graphitic carbon nitride-based photocatalyst according to claim 8 for photocatalytic hydrogen production.

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