La2Ti2O 7-x / g-c3n4 composite nanomaterial, preparation method and application thereof

Abstract

The application provides a La2Ti2O 7‑x / g-C3N4 composite nanomaterial, a preparation method and application thereof. The La2Ti2O 7‑x / g-C3N4 composite nanomaterial comprises La2Ti2O 7‑x crystals and g-C3N4, and the La2Ti2O 7‑x crystals and the g-C3N4 form a heterojunction composite material. The La2Ti2O 7‑x crystals and the g-C3N4 form a heterojunction composite material, the absorption capacity in a visible light region and the charge carrier mobility are improved, and the La2Ti2O 7‑x crystals and the g-C3N4 have a large potential difference, and further, the La2Ti2O 7‑x crystals and the g-C3N4 form a heterojunction to accelerate the separation of internal charges, and the catalytic efficiency of visible light is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photocatalysis, and particularly to a La2Ti2O 7-x / g-C3N4 composite nanomaterial, a preparation method thereof and an application thereof. BACKGROUND

[0002] The photocatalytic degradation method is a new water treatment technology, which has a wide range of applications, low cost and no secondary pollution, and provides a new idea for the degradation and treatment of printing and dyeing wastewater. La2Ti2O7 is a typical layered perovskite (A2B2O7) type rare earth composite metal oxide, which has attracted extensive attention due to its special layered structure and high photocatalytic activity for water-soluble dyes. However, the band gap of La2Ti2O7 (about 3.8 eV), low solar utilization rate and low quantum efficiency greatly affect its possible practical application prospect. SUMMARY

[0003] (I) Technical problems to be solved

[0004] In view of the deficiencies in the prior art, the present application provides a La2Ti2O 7-x / g-C3N4 composite nanomaterial, a preparation method thereof and an application thereof, which solves the problems proposed in the above background.

[0005] (II) Technical solutions

[0006] In order to achieve the above object, the present application is realized by the following technical solutions:

[0007] According to a first aspect of the present application, a La2Ti2O 7-x / g-C3N4 composite nanomaterial is provided, which comprises La2Ti2O 7-x crystals and g-C3N4, wherein the La2Ti2O 7-x crystals and the g-C3N4 form a heterojunction composite material.

[0008] Preferably, the mass of the g-C3N4 is 10% to 45% of the heterojunction composite material.

[0009] Preferably, the particle size of the heterojunction composite material is 200 to 700 nm.

[0010] According to a second aspect of the present application, a preparation method of a La2Ti2O 7-x / g-C3N4 composite nanomaterial is provided, which comprises the following steps: S1, mixing lanthanum nitrate, tetrabutyl titanate and a nitrogen-containing compound in ethanol and then performing a hydrothermal reaction, drying to obtain a La2Ti2O 7-x precursor;

[0011] S2, under an air atmosphere, calcining the La2Ti2O 7-x The precursor is calcined at high temperature to obtain a light yellow La2Ti2O 7-x crystal powder;

[0012] S3, calcining the light yellow La2Ti2O 7-x crystal powder by urea fumigation to obtain the La2Ti2O 7-x / g-C3N4 composite nanomaterial.

[0013] Preferably, the urea fumigation satisfies:

[0014] S3-1, placing excess urea at the bottom of a crucible, placing a piece of 3500-5000 mesh stainless steel screen in the middle and upper part of the crucible, uniformly laying 100 mg of light yellow La2Ti2O 7-x crystal on the stainless steel screen, the thickness of the laying layer being 0.1 cm, and covering the crucible cover;

[0015] S3-2, placing the crucible of step S3-1 in a muffle furnace for calcination, and cooling to room temperature to obtain the La2Ti2O 7-x / g-C3N4 composite nanomaterial.

[0016] Preferably, in step S3-2, the calcination temperature is 500-550℃, and the calcination time is 2-2.5h.

[0017] Preferably, in step S1, the molar ratio of the lanthanum nitrate to the tetrabutyl titanate is 1:1.

[0018] Preferably, the molar amount of the nitrogen-containing compound is 3-5 times the total molar amount of the lanthanum nitrate and the tetrabutyl titanate.

[0019] Preferably, the nitrogen-containing compound is at least one of urea, melamine, and thiourea.

[0020] Preferably, in step S1, the hydrothermal reaction condition is 200-300℃, and the hydrothermal reaction temperature is 12-48h.

[0021] Preferably, the drying temperature is 40-100℃, and the drying time is 2-10h.

[0022] Preferably, in step S2, the high-temperature calcination temperature is 1100-1200℃, the high-temperature calcination time is 4-5h, and the high-temperature calcination heating rate is 10-15℃ / min.

[0023] According to a third aspect of the present application, a La2Ti2O 7-xApplication of / g-C3N4 composite nanomaterials as photocatalysts in the degradation of Rhodamine B.

[0024] (III) Beneficial Effects

[0025] This invention provides a La2Ti2O 7-x / g-C3N4 composite nanomaterials, their preparation methods, and applications. They possess the following beneficial effects:

[0026] 1. The La2Ti2O provided in this solution 7-x / g-C3N4 composite nanomaterials, through La2Ti2O containing oxygen vacancies 7-x The crystal was heterojunctioned with g-C3N4 to form La2Ti2O 7-x / g-C3N4 composite nanomaterials, La2Ti2O 7-x Oxygen vacancies on the crystal surface serve as both carrier trapping sites and adsorption sites. They can transfer carriers to the adsorbed material, preventing electron-hole recombination and thus enabling visible light absorption. Furthermore, La₂Ti₂O 7-x The abundance of oxygen vacancies on the crystal surface can lower the conduction band bottom, allowing for recombination with different narrow bandgap semiconductors. Furthermore, holes can more easily pass through surface oxygen vacancies, while electrons are more easily captured by them, resulting in electron accumulation in La₂Ti₂O. 7-x Holes accumulate in the g-C3N4 material that it is combined with, increasing the potential difference between the two materials, thereby accelerating the separation of internal charges and improving the visible light photocatalytic efficiency.

[0027] 2. The La2Ti2O provided in this solution 7-x The preparation method of / g-C3N4 composite nanomaterials is simple, environmentally friendly, and low in cost.

[0028] 3. The La2Ti2O provided in this solution 7-x When used as a photocatalyst, the / g-C3N4 composite nanomaterial can achieve a degradation efficiency of over 85% for Rhodamine B. Attached Figure Description

[0029] Figure 1 La2Ti2O prepared in Example 1 of this invention 7-x X-ray diffraction pattern of nanopowder;

[0030] Figure 2 La2Ti2O prepared in Example 1 of this invention 7-x XPS spectra of nanopowder;

[0031] Figure 3 La2Ti2O prepared in Example 1 of this invention 7-xElectron self-selection resonance pattern of nanopowder;

[0032] Figure 4 La2Ti2O prepared in Example 1 of this invention 7-x Comparison of absorption spectra of nanopowder and pure white La2Ti2O7 nanopowder in the visible light range;

[0033] Figure 5 La2Ti2O prepared in Example 1 of this invention 7-x Field emission scanning electron microscope image of / g-C3N4 composite nanomaterials;

[0034] Figure 6 La2Ti2O prepared for this invention 7-x Degradation effect of / g-C3N4 composite nanomaterials on Rhodamine B solution. Detailed Implementation

[0035] To better illustrate the content of this invention, the following description is provided in conjunction with specific embodiments.

[0036] Example 1

[0037] La2Ti2O 7-x Preparation of / g-C3N4 composite nanomaterials:

[0038] (1) At room temperature, 20 mL of ethanol was added to a beaker, followed by 4 mmol of lanthanum nitrate and 4 mmol of tetrabutyl titanate. The mixture was stirred for 30 min. In another beaker, 2 g of urea and 25 mL of ethanol were added and dissolved. The liquids from the two beakers were then mixed and stirred for 1 h until the solution became transparent. The solution was poured into a 100 mL tetrafluoroethylene reactor and subjected to a hydrothermal reaction at 230 °C for 24 h. After cooling to room temperature, the supernatant was poured into a waste liquid container. The precipitate was washed three times with deionized water, ethanol, and deionized water, and then dried at 40 °C to obtain 920 mg of La2Ti2O. 7-x Precursor;

[0039] (2) La2Ti2O 7-x The precursor was added to a crucible and placed in a muffle furnace. The temperature was increased to 1100℃ at a rate of 10℃ / min and calcined for 4 hours. After cooling to room temperature, a pale yellow La2Ti2O was obtained. 7-x Crystal powder;

[0040] (3) Place 4g of industrial-grade urea at the bottom of the crucible, place a 3500-mesh stainless steel mesh sieve in the upper part of the crucible, and spread 100mg of pale yellow La2Ti2O with a thickness of 0.1cm on the stainless steel mesh sieve. 7-xThe crystal powder was calcined at 500 DEG C for 2h after the crucible was covered with a crucible cover and put into a muffle furnace, and the sample was taken out after cooling to room temperature, to obtain La2Ti2O 7-x / g-C3N4 composite nanomaterial.

[0041] According to Figure 1 It can be known that the light yellow La2Ti2O 7-x The crystal peak position of the crystal powder is completely consistent with JCPDS:00-028-0517;

[0042] In combination Figure 2 And Figure 3 It can be known that the light yellow La2Ti2O 7-x The surface of the crystal powder does not have nitrogen element, and a wide peak appears at 2.003, which shows that La2Ti2O 7-x The nanometer powder has a large number of surface oxygen vacancies, which is due to the early intervention of N element in urea, and then due to the high-temperature calcination, the N element combines with O element and volatilizes, and a large number of oxygen vacancies are generated;

[0043] According to Figure 4 It can be known that the light yellow La2Ti2O 7-x The crystal powder has substantial improvement in visible light absorption compared with La2Ti2O7 nanometer powder;

[0044] According to Figure 5 It can be known that the light yellow La2Ti2O 7-x The particle size of the La2Ti2O

[0045] Example 2

[0046] La2Ti2O 7-x / g-C3N4 composite nanomaterial:

[0047] (1) At room temperature, 20mL of ethanol was added into a beaker, 4mmol of lanthanum nitrate and 4mmol of tetrabutyl titanate were added into the beaker, and stirring was carried out for 30min; another beaker was added with 2g of urea and 25mL of ethanol and dissolved, and then the liquids of the two beakers were mixed and stirred for 1h until the solution was transparent; the solution was poured into a 100mL tetrafluoroethylene reaction kettle, and hydrothermal reaction was carried out at 230 DEG C for 24h, and then the supernatant was poured into a waste liquid tank after cooling to room temperature, and the precipitate below was washed with deionized water, ethanol and deionized water three times, and then 40 DEG C drying was carried out to obtain 920mg of La2Ti2O 7-x precursor;

[0048] (2) The La2Ti2O 7-xThe precursor is added to a crucible, placed in a muffle furnace, and heated to 1100°C at a heating rate of 10°C / min for 4h, and then cooled to room temperature to obtain a light yellow La2Ti2O 7-x crystal powder;

[0049] (3) 8g of industrial grade urea is placed at the bottom of the crucible, a piece of 3500 mesh stainless steel screen is placed at the upper part of the crucible, and 100mg of light yellow La2Ti2O 7-x crystal powder is laid on the stainless steel screen with a thickness of 0.1cm, and then the crucible is placed in a muffle furnace and calcined at 500°C for 2h, and then the sample is taken out after cooling to room temperature to obtain La2Ti2O 7-x / g-C3N4 composite nanomaterial with a g-C3N4 content of 31%.

[0050] Application example

[0051] Rhodamine B aqueous solution with a concentration of 10mg / L is used as the photocatalytic degradation object, and the photocatalytic degradation efficiency of La2Ti2O 7-x crystal powder, La2Ti2O 7-x / g-C3N4 composite nanomaterial with a g-C3N4 content of 19%, and La2Ti2O 7-x / g-C3N4 composite nanomaterial with a g-C3N4 content of 31% is compared, according to Figure 6 , the degradation efficiency of the La2Ti2O 7-x / g-C3N4 composite nanomaterial with a g-C3N4 content of 31% is more than 85%, and has excellent degradation efficiency.

[0052] Although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A La2Ti2O 7-x The application relates to an application of a La2Ti2O La2Ti2O 7-x The La2Ti2O 7-x crystal and g-C3N4, the La2Ti2O 7-x crystal and the g-C3N4 form a heterojunction composite material; The La2Ti2O 7-x The preparation method of the g-C3N4 composite nanomaterial comprises the following steps: S1, La(NO3)3, tetrabutyl titanate and urea were mixed uniformly in ethanol and then subjected to hydrothermal reaction, and dried to obtain La2Ti2O7 7-x precursor; S2, under an air atmosphere, the La2Ti2O 7-x The precursor is high-temperature calcined to obtain light yellow La2Ti2O 7-x crystal powder; S3, the light yellow La2Ti2O 7-x The crystal powder is obtained by urea fumigation 7-x / g-C3N4 composite nanomaterial In step S3, the urea fumigation satisfies: S3-1, excess urea is placed at the bottom of the crucible, a piece of 3500-5000 mesh stainless steel screen is placed in the middle and upper part of the crucible, 100 mg of light yellow La2Ti2O 7-x crystals, the thickness of the laid layer is 0.1 cm, and the crucible cover is covered; S3-2, placing the crucible of step S3-1 in a muffle furnace for calcination, and cooling to room temperature to obtain the La2Ti2O 7-x / g-C3N4 composite nanomaterial.

2. A La2Ti2O 7-x The application discloses a g-C3N4 composite nanomaterial as a photocatalyst in degradation of rhodamine B, characterized by comprising the following steps: The mass of the g-C3N4 is 10%-45% of the heterojunction composite material.

3. A La2Ti2O 7-x The application discloses a g-C3N4 composite nanomaterial as a photocatalyst in degradation of rhodamine B, characterized by comprising the following steps: The particle size of the heterojunction composite material is 200-700 nm.

4. A La2Ti2O 7-x The application discloses a g-C3N4 composite nanomaterial as a photocatalyst in degradation of rhodamine B, characterized by comprising the following steps: In step S3-2, the calcination temperature is 500-550℃, and the calcination time is 2-2.5 h.

5. A La2Ti2O 7-x The application discloses a g-C3N4 composite nanomaterial as a photocatalyst in degradation of rhodamine B, characterized by comprising the following steps: In step S1, the molar ratio of the lanthanum nitrate to the tetrabutyl titanate is 1:

1. And / or, the molar amount of the urea is 3-5 times the total molar amount of the lanthanum nitrate and the tetrabutyl titanate.

6. A La2Ti2O 7-x The application discloses a g-C3N4 composite nanomaterial as a photocatalyst in degradation of rhodamine B, characterized by comprising the following steps: In step S1, the hydrothermal reaction conditions are 200-300℃, and the hydrothermal reaction temperature is 12-48 h. And / or, the drying temperature is 40-100℃, and the drying time is 2-10 h.

7. A La2Ti2O 7-x The application of the / -C3N4 composite nanomaterial as a photocatalyst in degrading rhodamine B, characterized in that: In step S2, the high-temperature calcination temperature is 1100-1200℃, the high-temperature calcination time is 4-5 h, and the high-temperature calcination heating rate is 10-15℃ / min.

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