Boron-doped nanodiamond-TiO2-MXene composite material as well as preparation method and application thereof

Abstract

The invention discloses a boron-doped nanodiamond-TiO2-MXene composite material as well as a preparation method and application thereof, and belongs to the technical field of catalysts and preparation methods thereof. The boron-doped nanodiamond-TiO2-MXene composite material is prepared from BND (boron-doped nanodiamond-TiO2) particles, TiO2 and an MXene substrate, wherein the BND particles are doped with BND particles; the preparation method comprises the following steps: dispersing MXene in an HCl solution, adding NaBF4, adding BND, reacting in a high-pressure reaction kettle at 160 DEG C for 4-16 hours, centrifuging, washing, drying and the like. The prepared composite material can be used for tetracycline photocatalysis. According to the invention, a novel three-component double-heterojunction BND-TiO2-MXene photocatalyst is constructed through a simple one-step hydrothermal synthesis strategy, and the three-component double-heterojunction BND-TiO2-MXene photocatalyst can be recycled for multiple times and shows excellent performance in photocatalytic degradation of TC.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts and preparation methods thereof, and specifically relates to a boron-doped nanodiamond-TiO2-MXene composite material photocatalyst and a preparation method and application thereof. Technical Background

[0002] Antibiotics have attracted widespread attention as an emerging pollutant that is difficult to deal with. Among them, tetracycline (TC) is stable and difficult to degrade in the environment, which can cause bacteria to produce drug-resistant genes and spread through the food chain, causing severe allergic reactions in humans and even death. Photodegradation has significant advantages in low cost, high efficiency, environmental protection and stability, and has become the preferred method to solve TC residues in the environment. The activity of photocatalytic materials depends largely on the adsorption properties of reactants and the separation efficiency of photogenerated carriers.

[0003] Ti3C2T X (MXene) is an emerging two-dimensional layered material that attracts attention due to its numerous catalytically active sites, which effectively enhance the adsorption of pollutants by the material. Its abundant surface functional groups promote chemical interactions and catalytic activity, making it an ideal catalyst support material. At the same time, MXene can also serve as a precursor for the in-situ growth of TiO2 photocatalysts, and can form a Schottky junction at the TiO2 interface, generating an internal electric field (IEF) to further promote the separation of carriers.

[0004] However, TiO2-MXene still has some obvious limitations in the actual photocatalytic process. The TiO2 particles grown in situ on the MXene surface tend to agglomerate, which reduces the material's adsorption of pollutants and thus reduces the photocatalytic efficiency. At the same time, the large band gap width of TiO2 leads to low carrier mobility and relatively weak utilization of light.

[0005] The clever integration of a single photocatalyst with other semiconductor materials to form a heterojunction structure is an effective way to inhibit the recombination of photogenerated carriers and improve catalytic efficiency. Nanodiamond (ND) has shown great potential in the field of photocatalysis due to its abundant active sites, excellent physicochemical stability, and outstanding resistance to photobleaching. However, its inherent insulating properties and extremely wide band gap width have become key factors restricting its performance, resulting in previous studies being limited to using ND as a carbon quantum dot modifier rather than directly participating in the construction of heterojunctions. Few people have studied the introduction of boron-doped nanodiamond (BND) into the TiO2-MXene system to construct a new heterojunction material. Summary of the invention

[0006] In view of the deficiencies of the prior art and the need for optimization, the present invention provides a BND-TiO2-MXene composite photocatalyst and its preparation method and application. The purpose of the method is to synthesize a TiO2 nanosheet carrier with (101) crystal face exposed on the MXene surface through an in-situ hydrothermal synthesis strategy based on crystal face regulation technology, and combine BND loaded on TiO2-MXene to prepare a BND-TiO2-MXene composite photocatalyst. The catalyst has both S-type (BND-TiO2) and Schottky (TiO2-MXene) double heterojunction structures, which can effectively reduce carrier recombination and improve photocatalytic efficiency, thereby solving the problem of TC being difficult to degrade.

[0007] The technical solution of the present invention is as follows:

[0008] A boron-doped nanodiamond-TiO2-MXene composite material, characterized in that it is composed of BND particles, TiO2 and a MXene substrate; the MXene substrate is obtained by HF etching of the Al layer and has an accordion-shaped multilayer structure; the TiO2 is synthesized on the surface and gaps of the MXene by in-situ hydrothermal synthesis, and the TiO2 is composed of exposed (101) crystal planes; the TiO2 has a nanosheet structure; the side length of the TiO2 is 200 to 400 nm; the BND is synthesized by a bottom-up method; the BND is a lightly boron-doped nanodiamond; and the BND particle size is 150 nm.

[0009] Preferably, the boron doping concentration in the BND is 500 ppm.

[0010] A preparation method of a boron-doped nanodiamond-TiO2-MXene composite material comprises the following steps: first, preparing a 1 mol / L HCl solution; dispersing 0.2 g of MXene in 30 ml of a 1 mol / L HCl solution, adding 0.33 g of NaBF4 as a crystal plane controller, adding BND, wherein the mass ratio of BND to MXene is 1 to 15:100, stirring the mixture evenly, transferring the mixture to a high-pressure reactor, reacting at 160°C for 4 to 16 hours, centrifuging the obtained material after the reaction is completed, washing, and drying at 60°C for 12 hours to obtain a final product, a boron-doped nanodiamond-TiO2-MXene composite material, which is recorded as BND-TiO2-MXene.

[0011] A boron-doped nanodiamond-TiO2-MXene composite material is used for tetracycline photocatalysis. Specifically, the BND-TiO2-MXene composite material is dispersed in a tetracycline solution, and the dosage ratio of the BND-TiO2-MXene composite material to the tetracycline solution is 10 mg:35 mL; the obtained suspension is stirred for 60 minutes at room temperature in the dark to reach adsorption-desorption equilibrium, and then a 400W long arc mercury lamp and a 25°C circulating water system are turned on to start photocatalytic degradation, 5 mL of the degradation solution is taken every 20 minutes, and filtered through a 0.22 μm filter membrane, and detected using an ultraviolet-visible spectrophotometer (UV-2550, Shimadzu, JPN) at a maximum absorption wavelength of 357 nm to evaluate its photocatalytic activity.

[0012] Beneficial effects:

[0013] The present invention constructs a novel three-component double heterojunction BND-TiO2-MXene photocatalyst through a simple one-step hydrothermal synthesis strategy. MXene is used as a material substrate. Through crystal plane regulation, TiO2 nanosheets with exposed (101) crystal planes are grown in situ on the MXene surface, which effectively avoids the shedding of TiO2 nanosheets and improves the stability of the composite material. In addition, the layered structure of MXene can provide a more excellent spatial structure for the composite material, so that the photocatalyst obtains a larger specific surface area and increases the removal efficiency of pollutants. After BND is loaded on the basis of the layered structure, it not only expands the absorption spectrum, but also improves the utilization of the solar spectrum by the photocatalyst. The work function difference between the components forms a Schottky junction (TiO2-MXene) and an S-type heterojunction (BND-TiO2) with IEF at the interface, and combined with the (101) highly active crystal plane of TiO2, it strongly drives the effective separation of photogenerated carriers and enhances the photocatalytic degradation efficiency. The catalyst prepared by the present invention can be recycled for many times and shows excellent performance in the photocatalytic degradation of TC. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the scanning electron microscope (SEM) image of the original MXene in Example 2.

[0015] Figure 2 is the SEM image of the TM-4 sample prepared in Example 2.

[0016] Figure 3 is the SEM image of the TM-8 sample prepared in Example 2.

[0017] Figure 4 is the SEM image of the TM-12 sample prepared in Example 2.

[0018] Figure 5is the SEM image of the TM-16 sample prepared in Example 2.

[0019] Figure 6 These are the photocatalytic degradation curves of TM-4, TM-8, TM-12, and TM-16 prepared in Example 3.

[0020] Figure 7 This is the SEM image of the original BND in Example 4.

[0021] Figure 8 This is the SEM image of BTM-10% prepared in Example 4.

[0022] Fig. 9 These are the photocatalytic degradation curves of BTM-1%, BTM-5%, BTM-10% and BTM-15% prepared in Example 5. DETAILED DESCRIPTION

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention. The experimental methods described in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, can be obtained from public commercial channels.

[0024] Example 1 Preparation of 1 mol / L HCl solution

[0025] Use a measuring cylinder to measure 41mL of concentrated hydrochloric acid. Slowly pour the measured concentrated hydrochloric acid into a beaker containing a small amount of distilled water, and stir continuously with a glass rod to mix the solution evenly. Transfer the solution in the beaker to a 500mL volumetric flask through the glass rod. Wash the beaker and glass rod 3 times with a small amount of distilled water, and transfer the washing liquid to the volumetric flask. Continue to add distilled water to the volumetric flask until the concave liquid surface of the solution is tangent to the scale line. Stopper the volumetric flask, turn it upside down, and shake it well to mix the solution evenly.

[0026] Example 2 Preparation of TiO2-MXene with different hydrothermal reaction times

[0027] Weigh 0.2g of MXene and disperse it in 30mL of 1mol / L HCl solution, and add 0.33g of NaBF4 as a crystal plane controller. Place the mixed solution on a magnetic stirrer and stir at 1500rmp for 30min, then ultrasonicate for 10min; transfer the mixed solution to a 100mL autoclave and react at 160°C for 4h, 8h, 12h and 16h. After the reaction, centrifuge the obtained material at 8000r / min for 20min to collect the solid material, and dry it at 60°C for 12h to obtain the final product TiO2-MXene, which are labeled as samples TM-4, TM-8, TM-12, and TM-16, respectively. The scanning electron microscopy (SEM) of the comparative sample MXene is shown in Figure 1 TM-4 SEM Figure 2 TM-8 SEM Figure 3 TM-12 SEM Figure 4 TM-16 SEM Figure 5 .

[0028] Depend on Figure 1 The SEM image shows that MXene presents an accordion-like multilayer structure. Figure 2-5 The SEM images show that TiO2 nanosheets with (101) crystal plane exposed are grown in situ on the MXene surface. As the hydrothermal reaction time increases, the TiO2 nanosheets become more uniform and dense, and their size gradually increases.

[0029] Example 3 Comparative photodegradation TC test of application example 2

[0030] According to Example 2, TM-4, TM-8, TM-12, and TM-16 with different hydrothermal reaction times were prepared. The photocatalytic degradation TC test was carried out on a photocatalytic reactor. A long arc mercury lamp with a wavelength of 365nm and 400W was used as a UV light source. Weigh 20mg of the TM-4, TM-8, TM-12, and TM-16 catalysts prepared above, add them to a TC solution with a concentration of 20mg / L, and stir in a dark environment for 60min. The reactor temperature was maintained at 25°C by circulating cooling water to reduce the effect of temperature on the photocatalytic process. During the illumination process, a TC solution sample was taken from the reactor every 20min. The solution was then filtered through a membrane filter with a pore size of 0.22μm. A UV-visible spectrophotometer was used to measure its absorbance at 357nm to evaluate its photocatalytic activity. The photocatalytic degradation curves of TM-4, TM-8, TM-12, and TM-16 are shown in Figure 6 .

[0031] from Figure 6 It can be seen from the photocatalytic degradation curves that the photocatalytic effects of TM-4, TM-8, TM-12, and TM-16 first decrease and then increase, with TM-12 reaching the best.

[0032] Example 4 Preparation of BND-TiO2-MXene with different BND addition ratios

[0033] Weigh 0.2g of MXene and disperse it in 30mL of 1mol / L HCl solution, and add 0.33g of NaBF4 as a crystal plane controller. After adding 1mg, 5mg, 10mg and 15mg of BND to the above mixed solution, respectively, place the mixture on a magnetic stirrer and stir at 1500rmp for 30min and then ultrasonicate for 10min; transfer the above mixed solution to a 100mL autoclave and react at 160°C for 12h. After the reaction, the obtained material was centrifuged at 8000r / min for 20min to collect the solid material, and dried at 60°C for 12h to obtain the final product BND-TiO2-MXene, which were labeled as samples BTM-1%, BTM-5%, BTM-10% and BTM-15%, respectively. The SEM of the comparative sample BND is shown in Figure 7 . BTM-10% SEM see Figure 8 .

[0034] like Figure 8 The SEM of BTM-10% shows that the surface and interlayer of MXene in situ grow uniform and dense TiO2 nanosheet structures with side lengths of about 200-400nm. These radially grown TiO2 nanosheets have good structural stability and enhanced electron transport capabilities, laying the foundation for improving photocatalytic activity. BND presents uniformly sized particles with a diameter of about 150nm and is evenly loaded between MXene and TiO2 nanosheets. It is worth noting that the multilayer structure of MXene prevents the agglomeration of BND and TiO2 nanosheets. The fine assembly of the structure not only hinders the aggregation and stacking of materials, but also promotes closer contact between interfaces and increases the effective contact area.

[0035] Example 5 Comparative Photodegradation TC Test of Application Example 4

[0036] The photocatalytic degradation TC test was carried out on a photocatalytic reactor. A long arc mercury lamp with a wavelength of 365nm and 400W was used as a UV light source. Weigh 20mg of the BTM-1%, BTM-5%, BTM-10% and BTM-15% catalysts prepared in Example 4, add them to 70mL of TC solution with a concentration of 20mg / L, and stir in a dark environment for 60min. Subsequently, constant stirring was maintained during mercury lamp irradiation. The reactor temperature was maintained at 25°C by circulating cooling water to reduce the effect of temperature on the photocatalytic process. During the illumination process, a sample of TC solution was taken from the reactor every 20min. The solution was then filtered through a membrane filter with a pore size of 0.22μm. A UV-visible spectrophotometer was used to measure its absorbance at 357nm to evaluate its photocatalytic activity. The photocatalytic degradation curves of BTM-1%, BTM-5%, BTM-10% and BTM-15% are shown in Fig. 9 .

[0037] Fig. 9 From the photocatalytic degradation curves of BTM-1%, BTM-5%, BTM-10% and BTM-15%, it can be seen that the photocatalytic degradation efficiency of BND-TiO2-MXene obtained in Example 5 is significantly better than that of TiO2-MXene obtained in Example 3. With the increase of BND loading, the photocatalytic degradation efficiency first decreases and then increases. This is because when a small amount of BND is added, it is beneficial to the transfer of electron holes in photocatalysis and provides a certain degradation ability, thereby improving the photocatalytic degradation performance. In contrast, when BND is added in excess, too much BND covers the active sites of the material, hindering the absorption and utilization of light by the internal BND-TiO2-MXene, and inhibiting its photocatalytic performance. Because too much BND loading easily occupies the growth sites of TiO2 nanosheets.

[0038] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A boron-doped nanodiamond-TiO2-MXene composite material, characterized in that: The method is composed of BND particles, TiO2 and MXene substrate; the MXene substrate is obtained by HF etching of the Al layer, and has an accordion-shaped multilayer structure; the TiO2 is synthesized on the surface and gap of the MXene by in-situ hydrothermal synthesis, and the TiO2 is composed of (101) crystal plane exposure; TiO2 has a nanosheet structure; the side length of TiO2 is 200-400nm; the BND is synthesized by a bottom-up method; BND is lightly boron-doped nanodiamond; and the particle size of BND is 150nm.

2. The boron-doped nanodiamond-TiO2-MXene composite material according to claim 1, characterized in that: The boron doping concentration in the BND is 500 ppm.

3. A method for preparing the boron-doped nanodiamond-TiO2-MXene composite material according to claim 1, comprising the following steps: first, preparing a 1 mol / L HCl solution; dispersing 0.2 g of MXene in 30 ml of a 1 mol / L HCl solution, adding 0.33 g of NaBF4 as a crystal plane controller, adding BND, wherein the mass ratio of BND to MXene is 1 to 15:100, stirring the mixture evenly, transferring it to a high-pressure reactor, reacting it at 160°C for 4 to 16 hours, and after the reaction is completed, centrifuging the obtained material, washing it, and drying it at 60°C for 12 hours to obtain the final product, a boron-doped nanodiamond-TiO2-MXene composite material, recorded as BND-TiO2-MXene.

4. An application of the boron-doped nanodiamond-TiO2-MXene composite material according to claim 1 is for tetracycline photocatalysis, and the specific method is to disperse the BND-TiO2-MXene composite material in a tetracycline solution, and the dosage ratio of the BND-TiO2-MXene composite material to the tetracycline solution is 10 mg: 35 mL; the obtained suspension is stirred for 60 minutes at room temperature in the dark to reach adsorption-desorption equilibrium, and then a 400W long arc mercury lamp and a 25°C circulating water system are turned on to start photocatalytic degradation, 5 mL of the degradation solution is taken every 20 minutes, and filtered through a 0.22μm filter membrane, and detected using a UV-visible spectrophotometer at a maximum absorption wavelength of 357nm to evaluate its photocatalytic activity.

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