A short rod-shaped tantalum oxide-graphene quantum dot nanocomposite, a preparation method and application thereof

Abstract

The application discloses a short rod-shaped tantalum oxide-graphene quantum dot nanocomposite, a preparation method and application thereof, and belongs to the technical field of nanomaterial science and photocatalytic degradation. The method comprises the following steps: heating citric acid monohydrate, ultrasonically dispersing the cooled citric acid monohydrate in water to obtain a graphene quantum dot solution; adding an ethanol solution into a n-butanol solution of pentachlorotantalum, uniformly mixing, and adjusting the pH value of the mixed solution; collecting white precipitates at the bottom, washing the white precipitates with an ethanol solution until the pH value of the supernatant is 7, and performing suction filtration to obtain newly prepared tantalum acid solid; adding the newly prepared tantalum acid solid and hydrogen peroxide into the graphene quantum dot solution, continuing to heat until the solution is clear, and evaporating water to collect solid into a tube furnace, and annealing under a nitrogen atmosphere to obtain the GQD@Ta2O5 nanocomposite. The nanocomposite prepared by the application is a high-efficiency photocatalyst, and can efficiently photocatalyze and degrade various organic pollutants.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials science and photocatalytic degradation technology, specifically relating to a short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material, its preparation method, and its application in the photocatalytic degradation of organic pollutants. Background Technology

[0002] The development of science and technology has improved people's quality of life, but it has also brought about serious environmental imbalances. Among all environmental problems, the increasingly prominent water pollution problem is mainly caused by a complex variety of chemical pollutants, such as synthetic dyes, pharmaceutical compounds, personal care products, phthalates, and volatile organic compounds. Antibiotics are among the top-ranking pharmaceutical pollutants. Antibiotics entering water bodies can reduce the immunity of aquatic organisms, disrupt water stability, and even have potential long-term bioaccumulation effects on human health through the food chain, which is worrying. In 2022, the global annual consumption of antibiotics exceeded 1 million tons, among which tetracycline hydrochloride (TCH) is one of the most widely used broad-spectrum antibiotics for humans and animals. Therefore, designing appropriate photocatalytic materials for the simple and efficient degradation of TCH in water bodies is of great significance.

[0003] Ta₂O₅ is a typical wide-bandgap semiconductor material with very stable chemical properties, high dielectric constant, and excellent photoelectric properties. However, its wide bandgap (approximately 4 eV) limits its photocatalytic reactions to light with wavelengths below 310 nm, exhibiting almost no visible light response. Furthermore, the rapid recombination of photogenerated electrons and holes during photocatalysis results in poor performance of single-component Ta₂O₅ photocatalysts. These drawbacks significantly restrict the application of Ta₂O₅ in the field of photocatalysis.

[0004] For tantalum, a group VB metal, tantalum ions readily hydrolyze to form Ta₂O₅, making it difficult to maintain stability in aqueous solutions. Furthermore, Ta₂O₅ exhibits excellent chemical stability, rarely reacting with most substances. Therefore, traditional methods for preparing tantalum oxide nanomaterials often employ harsh reaction conditions such as anodic oxidation, aqueous (solvothermal), and high-temperature vapor deposition to achieve nanoscale dispersion and control of morphology and particle size. This is highly detrimental to the large-scale production and widespread adoption of tantalum oxide nanomaterials. In light of this, researchers are constantly seeking milder methods to reduce the manufacturing cost of tantalum oxide nanomaterials. By coordinating polar oxygen-containing organic functional groups such as carboxyl and hydroxyl groups with tantalum precursors, water-soluble tantalum complexes can be prepared, making it possible to disperse tantalum oxides under milder conditions.

[0005] As a representative of quantum dot materials, graphene quantum dots (GQDs) possess many unique characteristics, including good biocompatibility and a unique photoluminescence effect. At the same time, GQDs retain the high specific surface area and spline properties of graphene. 2 The hybrid configuration and other characteristics of GQDs provide superior electron transfer and electron trapping capabilities, offering a direct transfer pathway for photogenerated carriers. Furthermore, the abundant oxygen-containing groups on GQDs, such as carboxyl and hydroxyl groups, provide a basis for the coordination and dispersion of metal precursors. However, to date, there have been no reports on the controlled preparation of tantalum oxide nanocomposites using GQDs in the field of photocatalysis. Summary of the Invention

[0006] To address the problems existing in the prior art, the technical problem to be solved by this invention is to provide a method for preparing short rod-shaped tantalum oxide-graphene quantum dot nanocomposite materials. This method has easily controllable preparation conditions, low cost, and can yield high-performance Ta2O5 photocatalytic materials with visible light response. Another technical problem to be solved by this invention is to provide a short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material, which solves the problems of insufficient natural light utilization due to the wide band gap of Ta2O5 and poor photocatalytic performance due to the rapid recombination of photogenerated electrons and holes. A further technical problem to be solved by this invention is to provide an application of the short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material in the degradation of organic pollutants. This composite material has a total removal rate of over 80% for tetracycline hydrochloride.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material includes the following steps:

[0009] (1) Heating citric acid monohydrate and allowing it to cool naturally to room temperature, then ultrasonically dispersing it in water to obtain a graphene quantum dot solution;

[0010] (2) Add ethanol solution to tantalum pentachloride n-butanol solution, mix evenly under magnetic stirring, and then adjust the pH value of the mixture with ammonia water; collect the white precipitate at the bottom, wash with ethanol solution until the pH of the supernatant is 7, and filter to obtain freshly prepared tantalum acid solid;

[0011] (3) Freshly prepared tantalic acid solid and hydrogen peroxide were added to the graphene quantum dot solution and stirred continuously until the solution became clear. Then, the solution was heated to evaporate the water. The precipitated solid was collected into a tube furnace and annealed under a nitrogen atmosphere to obtain GQD@Ta2O5 nanocomposite material.

[0012] The preparation method of the short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material, step 1), the graphene quantum dots adopt a "bottom-up" synthesis path: the heating temperature is 170-190℃, the heating time is 2.5-3.5h; preferably, the heating temperature is 180℃, the heating time is 3h.

[0013] The "bottom-up" synthesis method mainly involves the stepwise chemical reactions of small molecules, including the stepwise chemical reactions of benzene ring derivatives, the pyrolysis of organic molecules, carbonization, and the fullerene opening reaction. In this context, it refers to obtaining graphene quantum dots through the direct thermal decomposition of the precursor citric acid.

[0014] In the preparation method of the short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material, step 2) is as follows: the volume ratio of tantalum pentachloride n-butanol solution to ethanol solution is 1:5-1:10, preferably 1:7.5; the mass fraction of ethanol solution is 50%.

[0015] The preparation method of the short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material, step 2), involves ammonia concentration of 1M and pH adjustment to 8-10, preferably pH 9.

[0016] In the preparation method of the short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material, step 3) is as follows: the mass ratio of graphene quantum dots to freshly prepared tantalic acid solid is 3:1-1:1, preferably 2:1; the amount ratio of freshly prepared tantalic acid solid to hydrogen peroxide is 1g:10-20ml, preferably 1g:15ml; and the mass fraction of hydrogen peroxide is 30%.

[0017] The preparation method of the short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material, step 3), the reaction temperature is 60-80℃, the reaction time is 1h; the annealing temperature is 600-800℃, the annealing time is 1-3h; preferably, the reaction temperature is 70℃, the annealing temperature is 800℃, and the annealing time is 2h.

[0018] The short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material prepared by the above method.

[0019] The content of Ta2O5 in the nanocomposite material is 40%-80%.

[0020] The above-mentioned nanocomposite materials are used in the photocatalytic degradation of organic pollutants.

[0021] The nanocomposite material is used in the photocatalytic degradation of organic pollutants, where the organic pollutants are tetracycline hydrochloride, rhodamine B, or methylene blue.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention modulates Ta2O5 with graphene quantum dots to prepare a high-performance GQD@Ta2O5 composite material with visible light response, solving the problems of insufficient natural light utilization caused by the wide band gap of Ta2O5 and poor photocatalytic performance caused by the rapid recombination of photogenerated electrons and holes.

[0024] Graphene quantum dots, acting as a reducing agent, partially decompose during the annealing stage to produce reducing gases. During the formation of Ta2O5, they capture oxygen atoms, forming Ta2O5 containing oxygen vacancies. This expands the catalyst's light utilization range to the visible light band. Meanwhile, the remaining graphene quantum dots recombine with Ta2O5 during annealing, acting as electron traps to capture photogenerated electrons generated during photocatalysis, inhibiting the recombination of photogenerated electrons and holes, thereby improving the photocatalytic performance of the catalyst. Attached Figure Description

[0025] Figure 1 The X-ray diffraction pattern of the GQD@Ta2O5 composite material prepared in Example 1;

[0026] Figure 2 The image shows the morphology of the GQD@Ta2O5 composite material prepared in Example 1 (left) and its high-resolution scanning transmission electron microscope image (right).

[0027] Figure 3 The image shows the electron paramagnetic resonance (EPR) test results of the GQD@Ta2O5 composite material prepared in Example 1.

[0028] Figure 4 The graph shows the change of tetracycline hydrochloride concentration over time when the GQD@Ta2O5 composite materials prepared in different embodiments are used for photocatalytic degradation of tetracycline hydrochloride.

[0029] Figure 5 The graph shows the degradation effect of the GQD@Ta2O5 composite material prepared in Example 1 on tetracycline hydrochloride, rhodamine B, and methylene blue.

[0030] Figure 6 The graph shows the performance of the GQD@Ta2O5 composite material prepared in Example 1 in degrading tetracycline hydrochloride. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments.

[0032] Example 1

[0033] A method for preparing a short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material includes the following steps:

[0034] (1) Weigh 30g of citric acid monohydrate into a beaker, place it in an oven, heat it at 180℃ for 3h, and after it cools naturally to room temperature, disperse it in water by ultrasonication to obtain a graphene quantum dot solution; the graphene quantum dots are synthesized using a "bottom-up" approach.

[0035] (2) Measure 4 mL of tantalum pentachloride n-butanol solution, add 30 mL of 50% ethanol solution, mix evenly under magnetic stirring, and then adjust the pH of the mixture to 9 with 1 M ammonia water; collect the white precipitate at the bottom, wash it several times with 50% ethanol solution until the supernatant reaches pH=7, and filter it to obtain freshly prepared solid tantalum acid.

[0036] (3) Add 0.8g of freshly prepared solid tantalic acid and 12ml of hydrogen peroxide (30% mass fraction) to the graphene quantum dot solution (containing 1.6g of graphene quantum dots) and stir continuously. React at 70°C for 1 hour until the solution is clear. Then continue heating at 70°C to evaporate the water. Collect the precipitated solid into a tube furnace and anneal at 800°C for 2 hours under a nitrogen atmosphere to obtain GQD@Ta2O5 nanocomposite material.

[0037] The above composite material was subjected to X-ray inspection, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the diffraction peaks of the GQD@Ta2O5 composite material are consistent with the Ta2O5 standard card (PDF#71-0639), indicating that Ta exists in the composite material in the form of Ta2O5. Meanwhile, the characteristic broad peak of graphene can be seen near 26°, indicating that after annealing at 800℃ for 2 hours in an inert atmosphere, the graphene quantum dots were not completely decomposed, and some quantum dots remain in the system, indicating the formation of the GQD@Ta2O5 composite material.

[0038] Figure 2 The images show the morphology of the prepared GQD@Ta2O5 composite material (left) and a high-resolution scanning transmission electron microscope (high-resolution STEM) image (right). The left image shows that the Ta2O5 in the prepared GQD@Ta2O5 exists in a uniform, short rod-like form. The right image shows numerous defects in the lattice fringes of the Ta2O5 in the GQD@Ta2O5 composite material, which can be attributed to the generation of oxygen vacancies. Furthermore, the abundant presence of GQDs around the Ta2O5 provides the necessary conditions for them to act as electron traps, capturing photogenerated electrons generated during photocatalysis and suppressing the recombination of photogenerated electron-hole pairs.

[0039] Figure 3 The image shows the electron paramagnetic resonance (EPR) test results of the GQD@Ta2O5 composite material prepared above. It can be seen that the composite material has obvious EPR signals, confirming that a large number of oxygen vacancies have been introduced into the material.

[0040] Example 2

[0041] A method for preparing a short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material includes the following steps:

[0042] (1) Weigh 30g of citric acid monohydrate into a beaker, place it in an oven, heat it at 180℃ for 3h, and after it cools naturally to room temperature, ultrasonically disperse it in water to obtain a graphene quantum dot solution.

[0043] (2) Measure 4 mL of tantalum pentachloride n-butanol solution, add 30 mL of 50% ethanol solution, mix evenly under magnetic stirring, and then adjust the pH of the mixture to 9 with 1 M ammonia water; collect the white precipitate at the bottom, wash it several times with 50% ethanol solution until the supernatant reaches pH=7, and filter it to obtain freshly prepared solid tantalum acid.

[0044] (3) Add 0.6g of freshly prepared solid tantalic acid and 8ml of hydrogen peroxide (30% mass fraction) to a graphene quantum dot solution (containing 1g of graphene quantum dots) and stir continuously. React at 60°C for 1 hour until the solution is clear. Then continue heating to evaporate the water. Collect the precipitated solid into a tube furnace and anneal at 700°C for 2 hours under a nitrogen atmosphere to obtain GQD@Ta2O5 nanocomposite material.

[0045] Example 3

[0046] A method for preparing a short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material includes the following steps:

[0047] (1) Weigh 30g of citric acid monohydrate into a beaker, place it in an oven, heat it at 170℃ for 3.5h, and after it cools naturally to room temperature, ultrasonically disperse it in water to obtain a graphene quantum dot solution.

[0048] (2) Measure 4 mL of tantalum pentachloride n-butanol solution, add 40 mL of 50% ethanol solution, mix evenly under magnetic stirring, and then adjust the pH of the mixture to 9 with 1 M ammonia water; collect the white precipitate at the bottom, wash it several times with 50% ethanol solution until the supernatant reaches pH=7, and filter it to obtain freshly prepared tantalum acid solid.

[0049] (3) Add 0.6g of freshly prepared tantalic acid and 8ml of hydrogen peroxide (30% mass fraction) to the graphene quantum dot solution (containing 1g of graphene quantum dots) and stir continuously. React at 60°C for 1 hour until the solution is clear. Then continue heating to evaporate the water. Collect the precipitated solid into a tube furnace and anneal at 700°C for 2 hours under a nitrogen atmosphere to obtain GQD@Ta2O5 nanocomposite material.

[0050] Example 4

[0051] A method for preparing a short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material includes the following steps:

[0052] (1) Weigh 30g of citric acid monohydrate into a beaker, place it in an oven, heat it at 185℃ for 2.5h, and after it cools naturally to room temperature, ultrasonically disperse it in water to obtain a graphene quantum dot solution.

[0053] (2) Measure 4 mL of tantalum pentachloride n-butanol solution, add 40 mL of 50% ethanol solution, mix evenly under magnetic stirring, and then adjust the pH of the mixture to 10 with 1 M ammonia water; collect the white precipitate at the bottom, wash it several times with 50% ethanol solution until the supernatant reaches pH=7, and filter it to obtain freshly prepared tantalum acid solid.

[0054] (3) Add 0.6g of freshly prepared tantalic acid and 8ml of hydrogen peroxide (30% mass fraction) to the graphene quantum dot solution (containing 1g of graphene quantum dots) and stir continuously. React at 60°C for 1 hour until the solution is clear. Then continue heating to evaporate the water. Collect the precipitated solid into a tube furnace and anneal at 800°C for 1.5 hours under a nitrogen atmosphere to obtain GQD@Ta2O5 nanocomposite material.

[0055] Example 5

[0056] A method for preparing a short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material includes the following steps:

[0057] (1) Weigh 30g of citric acid monohydrate into a beaker, place it in an oven, heat it at 180℃ for 3h, and after it cools naturally to room temperature, ultrasonically disperse it in water to obtain a graphene quantum dot solution.

[0058] (2) Measure 4 mL of tantalum pentachloride n-butanol solution, add 30 mL of 50% ethanol solution, mix evenly under magnetic stirring, and then adjust the pH of the mixture to 9 with 1 M ammonia water; collect the white precipitate at the bottom, wash it several times with 50% ethanol solution until the supernatant reaches pH=7, and filter it to obtain freshly prepared solid tantalum acid.

[0059] (3) Add 0.6g of freshly prepared tantalic acid and 8ml of hydrogen peroxide (30% mass fraction) to the graphene quantum dot solution (containing 1g of graphene quantum dots) and stir continuously. React at 80°C for 1 hour until the solution is clear. Then continue heating to evaporate the water. Collect the precipitated solid into a tube furnace and anneal at 750°C for 2 hours under a nitrogen atmosphere to obtain GQD@Ta2O5 nanocomposite material.

[0060] Example 6

[0061] A method for preparing a short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material includes the following steps:

[0062] (1) Weigh 30g of citric acid monohydrate into a beaker, place it in an oven, heat it at 175℃ for 3h, and after it cools naturally to room temperature, ultrasonically disperse it in water to obtain a graphene quantum dot solution.

[0063] (2) Measure 4 mL of tantalum pentachloride n-butanol solution, add 20 mL of 50% ethanol solution, mix evenly under magnetic stirring, and then adjust the pH of the mixture to 8 with 1 M ammonia water; collect the white precipitate at the bottom, wash it several times with 50% ethanol solution until the supernatant reaches pH=7, and filter it to obtain freshly prepared tantalum acid solid.

[0064] (3) Add 0.6g of freshly prepared tantalic acid and 8ml of hydrogen peroxide (30% mass fraction) to the graphene quantum dot solution (containing 1.5g of graphene quantum dots) and stir continuously. React at 80°C for 1 hour until the solution is clear. Then continue heating to evaporate the water. Collect the precipitated solid into a tube furnace and anneal at 600°C for 3 hours under a nitrogen atmosphere to obtain GQD@Ta2O5 nanocomposite material.

[0065] Example 4

[0066] The short rod-shaped tantalum oxide-graphene quantum dot nanocomposites prepared in Examples 1-6 were used to degrade tetracycline hydrochloride, rhodamine B, and methylene blue in the aquatic environment.

[0067] During the degradation process, the concentration of the above-mentioned organic pollutants in the water environment was first tested. Then, according to the volume of the polluted water, the short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material was added to the water environment containing the above-mentioned organic pollutants at a mass ratio of 1:20. During the 30-minute dark reaction stage, the adsorption capacity of the photocatalyst reached saturation. Subsequently, it was exposed to simulated sunlight for 1 hour while the water was stirred.

[0068] Figure 4 The graph shows the change in tetracycline hydrochloride concentration over time when the GQD@Ta2O5 composite materials prepared in different embodiments are used for photocatalytic degradation of tetracycline hydrochloride (the blank control group did not add the above GQD@Ta2O5 composite material). It can be seen that the photocatalysts prepared in all embodiments have good degradation effects on tetracycline hydrochloride. Among them, the GQD@Ta2O5 composite material prepared in Example 1 has the best degradation performance, with a removal rate of over 90%.

[0069] Figure 5The graph shows the degradation effect of the GQD@Ta2O5 composite material prepared in Example 1 on three pollutants: tetracycline hydrochloride, rhodamine B, and methylene blue. It can be seen that the GQD@Ta2O5 composite material has a good degradation effect on all three pollutants, demonstrating the applicability of the GQD@Ta2O5 composite material.

[0070] Example 5

[0071] The recycling performance of short rod-shaped tantalum oxide-graphene quantum dot nanocomposites was tested, and the results are as follows:

[0072] The composite material prepared in Example 1 was used for recycling performance testing. During the degradation process, the concentration of tetracycline hydrochloride in the aquatic environment was first tested. Then, according to the volume of the polluted water, the short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material was added to the aquatic environment containing tetracycline hydrochloride at a mass ratio of 1:20 (tetracycline hydrochloride to short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material). During the 30-minute dark reaction stage, the adsorption capacity of the photocatalyst reached saturation. Subsequently, it was exposed to simulated sunlight for 1 hour while the water was agitated.

[0073] After each degradation experiment, the used catalyst was collected by centrifugation, washing with deionized water, and drying at 60°C for use in the next photodegradation experiment.

[0074] Figure 6 The graph shows the performance of the GQD@Ta2O5 composite material in degrading tetracycline hydrochloride. It can be seen that in the second and third cycles, the degradation performance of the GQD@Ta2O5 composite material for tetracycline hydrochloride only decreased slightly.

Claims

1. A method for preparing a short rod-like tantalum oxide-graphene quantum dot nanocomposite, characterized in that, The method comprises the following steps: (1) heating citric acid monohydrate, and after naturally cooling to room temperature, ultrasonic dispersion in water to obtain a graphene quantum dot solution; (2) adding an ethanol solution to a n-butanol solution of pentachloride, mixing under magnetic stirring, and then adjusting the pH value of the mixture with ammonia water; collecting the white precipitate at the bottom, washing with an ethanol solution until the pH value of the supernatant is 7, and then obtaining newly prepared tantalum oxide solid by suction filtration; the volume ratio of the n-butanol solution of pentachloride to the ethanol solution is 1:5-1:10, the mass fraction of the ethanol solution is 50%, the concentration of the ammonia water is 1M, and the pH value is adjusted to 8-10; (3) adding the newly prepared tantalum oxide solid and hydrogen peroxide to the graphene quantum dot solution and continuously stirring, until the solution is clear, then continuing to heat to evaporate water, collecting the precipitated solid, and then annealing in a tube furnace under a nitrogen atmosphere to obtain a GQD@Ta2O5 nanocomposite; The mass ratio of the graphene quantum dot to the newly prepared tantalum oxide solid is 3:1-1:1, the dosage ratio of the newly prepared tantalum oxide solid to the hydrogen peroxide is 1g:10-20mL, the mass fraction of the hydrogen peroxide is 30%, the reaction temperature is 60-80℃, and the reaction time is 1h; the annealing temperature is 600-800℃, and the annealing time is 1-3h.

2. The method for preparing the short rod-shaped tantalum oxide-graphene quantum dot nanocomposite material according to claim 1, characterized in that, In step (1), the heating temperature is 170-190℃, and the heating time is 2.5-3.5h.

3. A short rod-shaped tantalum oxide-graphene quantum dot nanocomposite prepared by the method of claim 1 or 2.

4. The short rod-like tantalum oxide-graphene quantum dot nanocomposite of claim 3, wherein the short rod-like tantalum oxide-graphene quantum dot nanocomposite is represented by the following formula: TaOx-GQD (1) wherein TaOx represents a short rod-like tantalum oxide, and GQD represents a graphene quantum dot. The content of Ta2O5 in the nanocomposite is 40%-80%.

5. The nanocomposite of claim 3 for use in photocatalytic degradation of organic pollutants.

6. Use of the nanocomposite material according to claim 5 for the photocatalytic degradation of organic pollutants, characterized in that, The organic pollutants are tetracycline hydrochloride, rhodamine B or methylene blue.

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