CN108499588A - A kind of g-C3N4The preparation method of/MXene composite materials - Google Patents

Abstract

The present invention relates to a kind of g C₃N₄The preparation method of/MXene composite materials, including：MXene material preparations, MXene and g C₃N₄Prepared by the mixture of precursor species, g C₃N₄It is prepared by/MXene composite materials.The present invention is simple, and technological parameter is easy to control, of low cost, is easy to large-scale production；The g C being prepared₃N₄/ MXene composite material good crystallinities, particle is tiny and is evenly distributed, and large specific surface area, electric conductivity is good, has preferable photocatalysis performance, one's own physical performance is good, has application value in fields such as photocatalysis, wastewater treatment, biosensors.

Description

A kind of preparation method of g-C3N4/MXene composite material

technical field

The invention belongs to the field of preparation of nano functional materials, in particular to a preparation method of gC ₃ N ₄ /MXene composite material.

Background technique

Semiconductor photocatalysis has shown great potential in solving energy shortage and environmental pollution, and has been highly valued by governments of all countries. Therefore, the development of new and efficient photocatalysts has become an inevitable demand for the development of photocatalytic technology.

In recent years, gC ₃ N ₄ , a new type of non-metallic material that responds to visible light, has attracted widespread attention due to its narrow bandgap (about 2.7eV), good chemical stability, and simple preparation methods. So far, no naturally occurring gC ₃ N ₄ crystals have been found in nature. gC ₃ N ₄ mainly relies on experimental synthesis. The precursors for the synthesis of gC ₃ N ₄ are generally nitrogen-rich compounds such as urea, thiourea, and cyanamide. , Melamine, etc. However, the specific surface area of the synthesized gC ₃ N ₄ is usually less than 10m ² /g, and the photogenerated electrons and holes are easily recombined, resulting in unsatisfactory photocatalytic effect. In order to suppress the recombination of photogenerated electron-hole pairs, _gC3N4 can be compounded with other materials, and the synergistic _effect of the two can be used to improve its photocatalytic activity.

MXene is a new type of two-dimensional layered nanomaterial, which can be prepared by etching the corresponding MAX phase. Ti ₃ AlC ₂ and Ti ₂ AlC are typical MAX phases. MAX phase is a general term for a class of ternary layered compounds. This type of compound has a unified chemical formula M _n+1 AX _n , where M is a transition metal, A is a main group element of III and IV, X is C or N, and n= 1, 2, 3, etc. The structural feature of the MAX phase is that M atoms and A atomic layers are arranged alternately to form a close-packed hexagonal layered structure, and X atoms fill the octahedral gaps. The MA bond has the characteristics of a metal bond, and its force is weaker than that of the MX bond. Therefore, in the hydrofluoric acid solution, the A atomic layer of the MAX phase is easily etched, and the M and X atomic layers are left to form a two-dimensional M _n+1 X _n atomic crystal. In order to emphasize that they are stripped from the MAX phase, And have a two-dimensional structure similar to graphene (Graphene), and they are collectively named MXene. For example, Mxene—Ti ₃ C ₂ can be obtained by corroding MAX phase Ti ₃ AlC ₂ with hydrofluoric acid.

Studies have found that small organic molecules such as urea can intercalate MXene and increase the interlayer spacing of MXene. Intercalation is one of the important methods to modify clay. From the perspective of structure and performance, MXene is a kind of "conductive hydrophilic clay". Therefore, the preparation of organic intercalation MXene composites is the focus of future research. Two-dimensional layered nanocarbides (Ti ₃ C ₂ and Ti ₂ C) are materials with a graphene-like structure. Their unique morphology and good electrical conductivity, magnetic properties, and thermoelectric properties make them promising for gas sensing applications. , catalysis, composite materials, energy storage, environmental pollution control, surface plasmon technology, photovoltaic cells and liquid crystal displays and other fields.

Therefore, gC ₃ N ₄ /MXene composite materials are expected to have good applications in the fields of photocatalysis, wastewater treatment, supercapacitors and biosensors. In addition, there is no report about the complex of gC ₃ N ₄ and MXene.

Contents of the invention

The technical problem to be solved by the present invention is to provide a preparation method of gC ₃ N ₄ /MXene composite material, the method is simple, the process parameters are easy to _control , and _it is easy to produce on a large scale. Good photocatalytic properties, good biophilicity, and various shapes have application value in the fields of photocatalysis, wastewater treatment, and biosensors.

A kind of preparation method of gC ₃ N ₄ /MXene composite material of the present invention, concrete steps are as follows:

(1) Add the MAX phase to the HF solution at a ratio of 0.01 to 0.3 g/ml, stir, wash, dry, place in an aqueous urea solution, continue stirring, then wash, and then dry to obtain the MXene material, in which the MAX phase The mass ratio with urea is 1:1-3;

(2) Add the gC ₃ N ₄ precursor material into the solvent, stir, add the MXene material in step (1), continue stirring, and dry to obtain a mixture of MXene and gC ₃ N ₄ precursor material, which is calcined to obtain gC ₃ N ₄ /MXene composite material, wherein the concentration of the gC ₃ N ₄ precursor substance in the solvent is 0.1-0.5 g/ml, and the mass ratio of the MXene material to the gC ₃ N ₄ precursor substance is 0.01-0.3:1.

In the step (1), the MAX phase is Ti ₃ AlC ₂ or Ti ₂ AlC, and the MXene material is correspondingly Ti ₃ C ₂ or Ti ₂ C with a two-dimensional layered structure.

In the step (1), the stirring temperature is 20-80° C., and the stirring time is 10-30 hours; the cleaning is performed with deionized water until the pH is 6-7.

The drying and re-drying in the step (1) are all vacuum-dried at 20-80°C.

In the step (1), the temperature of continuous stirring is 20-80° C., and the continuous stirring time is 12-24 hours; the further cleaning is 2-3 times with deionized water.

In the step (2), the gC ₃ N ₄ precursor material is thiourea or melamine; the solvent is water.

In the step (2), the stirring temperature is 20-80° C., and the stirring time is 1-2 hours; the continuous stirring time is 10-24 hours.

The technical parameters of the calcination in the step (2) are: the calcination temperature is 500-600°C, the calcination time is 1-10h, the heating rate is 1-10°C/min, and the calcination atmosphere is air, nitrogen or argon.

The present invention synthesizes the gC ₃ N ₄ /MXene composite material in situ through the method of calcination, and a good contact can be formed between gC ₃ N ₄ and the two-dimensional layered titanium carbide, which is conducive to the rapid transfer of photogenerated electrons to titanium carbide, which is beneficial to Improve the separation efficiency of electron holes and enhance its photocatalytic performance.

Beneficial effect

(1) the present invention is simple, process parameter is easy to control, and cost is low, is easy to large-scale production;

(2) The gC ₃ N ₄ /MXene composite material prepared by the present invention has good crystallinity, fine particles and uniform distribution, large specific surface area, good electrical conductivity, good photocatalytic performance, and good biophilic performance. , wastewater treatment, biosensors and other fields have application value.

Description of drawings

Fig. 1 is the scanning electron micrograph of the MXene material (Ti ₃ C ₂ ) prepared in embodiment 1;

Figure 2 is the X-ray diffraction pattern of the gC ₃ N ₄ /two-dimensional layered titanium carbide composite (gC ₃ N ₄ /MXene composite material) prepared in Example 1;

Figure 3 is a comparison chart of the photocatalytic hydrogen production performance of the gC ₃ N ₄ /two-dimensional layered titanium carbide composite (gC ₃ N ₄ /MXene composite material) prepared in Example 1 and pure g-C3N4;

Figure 4 is the X-ray diffraction of the titanium carbide material MXene prepared in Comparative Example 1 after urea intercalation treatment and the prepared gC ₃ N ₄ /two-dimensional layered titanium carbide composite (gC ₃ N ₄ /MXene composite material) picture.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

(1) Add Ti ₃ AlC ₂ ceramic powder with a purity greater than 98% to a 40% HF solution at a ratio of 0.06 g/ml, stir at 60°C for 24 hours; then wash with deionized water until the pH is 6 ~7, vacuum-dry the obtained solid sample at 60°C; place the dried powder in 0.05g/ml urea aqueous solution (the mass ratio of Ti ₃ AlC ₂ to urea is 1:1), and stir at 60°C 24 hours; then wash with deionized water for 2-3 times, and vacuum-dry the obtained solid sample at 60° C. to obtain Ti ₃ C ₂ (MXene material) with a two-dimensional layered structure.

(2) Add 2g of thiourea to 20ml of water, stir at 60°C for 2h, then add 0.1g of the MXene material in step (1), and continue stirring for 10h; then dry it by freeze-drying to obtain MXene and gC ₃ N _4. The mixture of precursor substances is placed in a tube furnace for calcination under an argon atmosphere. The calcination temperature is 600°C, the calcination time is 1h, and the heating rate is 1°C/min. The gC ₃ N ₄ /MXene composite Material. The gC ₃ N ₄ /MXene composite material and pure g-C3N4 are used for photocatalytic hydrogen production. The conditions for photocatalytic hydrogen production are: 50mg of catalyst is placed in an aqueous solution containing 10vol% triethanolamine, and a filter with ≧420nm visible light The 300W xenon lamp of the film is a visible light source. Under the continuous irradiation of the visible light source, samples are taken every hour and the production of hydrogen gas is detected by gas chromatography.

Figure 1 shows that the MXene material obtained in this example is a fully opened two-dimensional sheet structure, and the sheet thickness is tens of nanometers, so it has a large specific surface area.

Figure 2 shows that the composite material has the characteristic peak of gC ₃ N ₄ at 2θ=13° and 27.5°, indicating that the final prepared substance in this example is a composite of gC ₃ N ₄ and two-dimensional layered titanium carbide.

Figure 3 shows that the gC ₃ N ₄ /MXene composite material obtained in this example has better photocatalytic hydrogen production performance under visible light, and its performance is about 6 times that of pure gC ₃ N ₄ .

Example 2

(1) Add Ti ₂ AlC ceramic powder with a purity greater than 98% to a 40% HF solution at a ratio of 0.01 g/ml, stir at 20°C for 30 hours; then wash with deionized water until the pH is 6-6 7. Vacuum-dry the obtained solid sample at 20°C; place the dried powder in 0.05g/ml aqueous urea solution (the mass ratio of Ti ₂ AlC to urea is 1:1), and stir at 20°C for 24h; Then, it was washed with deionized water for 2-3 times, and the obtained solid sample was vacuum-dried at 20° C. to obtain Ti ₂ C (MXene material) with a two-dimensional layered structure.

(2) Add 2 g of melamine into 20 ml of water, stir at 20°C for 2 h, then add 20 mg of the MXene material in step (1), and continue stirring for 24 h; then dry it by freeze-drying to obtain the precursor of MXene and gC ₃ N ₄ The mixture of solid substances was placed in a tube furnace for calcination under an argon atmosphere. The calcination temperature was 500°C, the calcination time was 10h, and the heating rate was 10°C/min to obtain the gC ₃ N ₄ /MXene composite material.

The gC ₃ N ₄ /MXene composite material prepared in this example is light yellow powder, which has better absorption of visible light.

Example 3

(1) Add Ti ₂ AlC ceramic powder with a purity greater than 98% to a 40% HF solution at a ratio of 0.01 g/ml, stir at 20°C for 30 hours; then wash with deionized water until the pH is 6-6 7. Vacuum-dry the obtained solid sample at 20°C; place the dried powder in 0.05g/ml aqueous urea solution (the mass ratio of Ti ₂ AlC to urea is 1:1), and stir at 20°C for 24h; Then, it was washed with deionized water for 2-3 times, and the obtained solid sample was vacuum-dried at 20° C. to obtain Ti ₂ C (MXene material) with a two-dimensional layered structure.

(2) Add 10g of melamine into 20ml of water, stir at 50°C for 1.5h, then add 3g of the MXene material in step (1), and continue stirring for 10h; then dry it by freeze-drying to obtain MXene and gC ₃ N ₄ The mixture of precursor substances was placed in a tube furnace for calcination under air atmosphere. The calcination temperature was 550°C, the calcination time was 2h, and the heating rate was 10°C/min to obtain the gC ₃ N ₄ /MXene composite material.

Comparative example 1

(1) Add Ti ₃ AlC ₂ ceramic powder with a purity greater than 98% to a 40% HF solution at a ratio of 0.3 g/ml, stir at 80°C for 10 h; then wash with deionized water until the pH is 6 ~7, vacuum-dry the obtained solid sample at 80°C; place the dried powder in 0.05g/ml urea aqueous solution (the mass ratio of Ti ₃ AlC ₂ to urea is 1:1), and stir at 80°C 12 hours; wash with deionized water for 2 to 3 times, and vacuum-dry the obtained solid sample at 80° C. to obtain Ti ₃ C ₂ (MXene material) with a two-dimensional layered structure.

(2) Add 2g of urea to 20ml, stir at 80°C for 1h, then add 0.1g of the MXene material in step (1), and continue stirring for 10h; then dry it by freeze-drying to obtain MXene and gC ₃ N ₄ The mixture of precursor substances is placed in a tube furnace for calcination under an argon atmosphere. The calcination temperature is 600°C, the calcination time is 1h, and the heating rate is 1°C/min. The gC ₃ N ₄ /MXene composite material is obtained .

Figure 4 shows that compared with Example 1, no obvious diffraction peak of gC ₃ N ₄ was found, so it can be seen that the effect of using urea as the precursor of gC ₃ N ₄ is not ideal; but by comparison, it can be found that 600°C After calcination, the diffraction peak of the two-dimensional layered nanomaterial Ti ₃ C ₂ at about 8° shifts to the left obviously, which indicates that the interlayer spacing of MXene can be effectively enlarged by calcination at high temperature under an inert atmosphere.

Claims (8)

1. A preparation method of gC ₃ N ₄ /MXene composite material, the specific steps are as follows: (1) Add the MAX phase to the HF solution at a ratio of 0.01 to 0.3 g/ml, stir, wash, dry, place in an aqueous urea solution, continue stirring, then wash, and then dry to obtain the MXene material, in which the MAX phase The mass ratio with urea is 1:1-3; (2) Add the gC ₃ N ₄ precursor material into the solvent, stir, add the MXene material in step (1), continue stirring, and dry to obtain a mixture of MXene and gC ₃ N ₄ precursor material, which is calcined to obtain gC ₃ N ₄ /MXene composite material, wherein the concentration of the gC ₃ N ₄ precursor substance in the solvent is 0.1-0.5 g/ml, and the mass ratio of the MXene material to the gC ₃ N ₄ precursor substance is 0.01-0.3:1. 2. according to the preparation method of a kind of gC ₃ N ₄ /MXene composite material according to claim 1, it is characterized in that, in the described step (1), the MAX phase is Ti ₃ AlC ₂ or Ti ₂ AlC, and the MXene material is corresponding to _Ti3C2 or _{Ti2C .} 3. The preparation method of a gC ₃ N ₄ /MXene composite material according to claim 1, characterized in that, the stirring temperature in the step (1) is 20-80°C, and the stirring time is 10-30h; It is washed with deionized water until the pH is 6-7. 4 . The preparation method of a gC ₃ N ₄ /MXene composite material according to claim 1 , characterized in that, the drying and re-drying in the step (1) are all vacuum-dried at 20-80° C. 5 . 5. According to the preparation method of a gC ₃ N ₄ /MXene composite material according to claim 1, it is characterized in that, in the step (1), the continuous stirring temperature is 20-80°C, and the continuous stirring time is 12-24h ; Clean again with deionized water for 2 to 3 times. 6. according to the preparation method of a kind of gC ₃ N ₄ /MXene composite material described in claim 1, it is characterized in that, in described step (2) gC ₃ N ₄ precursor material is thiourea or melamine; Solvent is water . 7. The preparation method of a gC ₃ N ₄ /MXene composite material according to claim 1, characterized in that, the stirring temperature in the step (2) is 20-80°C, and the stirring time is 1-2h; continue Stirring time is 10~24h. 8. The preparation method of a gC ₃ N ₄ /MXene composite material according to claim 1, characterized in that the process parameters for calcination in the step (2) are: the calcination temperature is 500-600°C, the calcination time The heating time is 1-10 hours, the heating rate is 1-10° C./min, and the calcining atmosphere is air, nitrogen or argon.