CN115121240A - A kind of porous titanium dioxide composite material and its preparation method and application - Google Patents

Abstract

The invention relates to the technical field of photocatalysts and provides a preparation method of a porous titanium dioxide composite material. According to the invention, titanium dioxide and graphene oxide are fixed on the surface of the nanofiber through electrostatic spinning; the graphene oxide is reduced into graphene through a hydrothermal reaction, and by utilizing the characteristics of good electron conductors and low Fermi level of the graphene, photo-generated electrons accumulated on a titanium dioxide conduction band can flow to a graphene plane with a low energy band position, so that the effect of increasing the photo-generated electron hole separation efficiency on the titanium dioxide is achieved; the fibers are changed into a porous structure through hydrothermal reaction, the specific surface area of the fibers can be further increased, and target pollutants are adsorbed on the surfaces of the fibers, so that the utilization efficiency of active species is improved; in addition, the graphene obtained after the hydrothermal reaction generates conjugate adsorption on organic molecules, so that the further function of the photocatalytic nanofiber is facilitated, and the photocatalytic capacity of the titanium dioxide is finally improved.

Description

A kind of porous titanium dioxide composite material and its preparation method and application

technical field

The invention belongs to the technical field of photocatalysts, and particularly relates to a porous titanium dioxide composite material and a preparation method and application thereof.

Background technique

Water is the source of life, and all life is inseparable from water. However, with the rapid development of society and economy and the acceleration of urbanization, the pollution of water bodies caused by organic matter is increasing day by day. It is imminent to realize the effective treatment of organic pollutants in water bodies. At present, there are many treatment methods for organic pollutants in water. Among them, photocatalytic degradation refers to the use of radiation and photocatalysts to generate extremely active free radicals in the reaction system, and then through the addition and substitution between free radicals and organic pollutants. The process of degrading all pollutants into inorganic substances by processes such as electron transfer and electron transfer has the advantages of low reaction conditions, wide application range, and no secondary pollution, and has become the focus and hot spot in this field.

Titanium dioxide as a photocatalyst for water treatment has many advantages. In the prior art, in order to improve the treatment efficiency of organic substances, titanium dioxide is usually loaded on fibers by electrospinning to improve the treatment efficiency of organic substances. However, the above preparation method obtains The treatment efficiency of the TiO2 photocatalyst for organic matter is still not ideal. Therefore, there is a need to improve a method for preparing a titanium dioxide catalyst with high catalytic efficiency.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a preparation method of a porous titanium dioxide composite material. The catalytic degradation efficiency of the porous titanium dioxide composite material obtained by the preparation method provided by the present invention is close to 100% when photocatalyzing organic matter.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides a preparation method of a porous titanium dioxide composite material, comprising the following steps.

(1) mixing graphene oxide, titanium dioxide, N,N-dimethylformamide, polyvinylpyrrolidone and polyacrylonitrile to obtain spinning solution;

(2) electrospinning the spinning solution obtained in the step (1) to obtain nanofibers;

(3) Mixing the nanofibers obtained in the step (2), water and ethanol to carry out a hydrothermal reaction to obtain a porous titanium dioxide composite material.

Preferably, the mass ratio of graphene oxide to the volume of N,N-dimethylformamide is (10-50) mg:10 ml.

Preferably, the mass ratio of graphene oxide and titanium dioxide in the step (1) is (1-5): (10-30).

Preferably, the mass ratio of polyacrylonitrile and polyvinylpyrrolidone in the step (1) is (0.5-5):1.

Preferably, the mass ratio of polyacrylonitrile and titanium dioxide in the step (1) is (1-15):1.

Preferably, the set voltage of the electrospinning in the step (2) is 11-15KV; the advancing speed of the electrospinning is 0.015-0.035mL/min.

Preferably, the volume ratio of water and ethanol in the step (3) is (1-3):1.

Preferably, the temperature of the hydrothermal reaction in the step (3) is 90-140° C., and the time of the hydrothermal reaction is 3-8 h.

The present invention provides a porous titanium dioxide composite material prepared by the preparation method described in the above scheme, and the specific surface area of the porous titanium dioxide composite material is 48-55 m ² /g.

The present invention also provides the application of the porous titanium dioxide composite material described in the above scheme in photocatalytic degradation of organic matter.

The invention provides a preparation method of a porous titanium dioxide composite material, comprising the following steps. First, graphene oxide, titanium dioxide, N,N-dimethylformamide, polyvinylpyrrolidone and polyacrylonitrile are mixed to obtain a spinning solution; then the obtained spinning solution is electrospun to obtain nanofibers; finally The obtained nanofibers, water and ethanol undergo a hydrothermal reaction to obtain a porous titanium dioxide composite.

In the invention, titanium dioxide and graphene oxide are fixed on the surface of nanofibers by electrospinning, which can effectively prevent the agglomeration of titanium dioxide particles; through hydrothermal reaction, graphene oxide is reduced to graphene under the action of reducing agent ethanol, and graphene is used The good electron conductor and low Fermi level feature enable the photogenerated electrons accumulated on the conduction band of TiO2 to flow to the graphene plane with a lower energy band position, thereby increasing the separation efficiency of photogenerated electrons and holes on TiO2. and the solvent water in the hydrothermal reaction can dissolve polyvinylpyrrolidone, thereby turning the fiber into a porous structure, which can further increase the specific surface area of the fiber and adsorb the target pollutants on the surface of the fiber, thereby improving the utilization efficiency of active species; In addition, the graphene obtained after the hydrothermal reaction can also be used as a good adsorbent for conjugated adsorption of organic molecules, which is helpful for the further functioning of photocatalytic nanofibers. The experimental results show that the catalytic efficiency of the organic methylene blue by the porous titanium dioxide composite material provided by the invention can be close to 100%.

Description of drawings

Fig. 1 is the Raman spectrum (Raman) spectrum of the porous titanium dioxide composite material prepared in Example 2 of the present invention;

Fig. 2 is the infrared spectrum (FTIR) spectrum of the porous titanium dioxide composite material prepared by Example 2 of the present invention;

Fig. 3 is the SEM characterization photo of the porous titanium dioxide composite material prepared by Example 2 of the present invention;

4 is a BET data comparison diagram of the porous titanium dioxide composite material prepared in Example 2 of the present invention and the composite material prepared in Comparative Example 1;

FIG. 5 is a photocatalytic performance comparison diagram of the porous titanium dioxide composite material prepared in Example 2 of the present invention and the composite material prepared in Comparative Example 1. FIG.

Detailed ways

The invention provides a preparation method of a porous titanium dioxide composite material, comprising the following steps.

(1) mixing graphene oxide, titanium dioxide, N,N-dimethylformamide, polyvinylpyrrolidone and polyacrylonitrile to obtain spinning solution;

(2) electrospinning the spinning solution obtained in the step (1) to obtain nanofibers;

(3) Mixing the nanofibers obtained in the step (2), water and ethanol to carry out a hydrothermal reaction to obtain a porous titanium dioxide composite material.

The present invention has no special provisions on the sources of the graphene oxide, titanium dioxide, N,N-dimethylformamide, polyvinylpyrrolidone and polyacrylonitrile, and conventional commercial products may be used.

In the present invention, the mass ratio of the graphene oxide to the volume of N,N-dimethylformamide is preferably (10-50) mg:10 ml, more preferably (25-35) mg:10 ml. In the present invention, the amount of the graphene oxide and N,N-dimethylformamide is limited to the above range, which is beneficial to obtain a spinning solution with appropriate concentration. In the present invention, the graphene oxide can be reduced to graphene by ethanol in the later hydrothermal reaction. In the present invention, by compounding graphene and titanium dioxide with good optical, electrical and mechanical properties, and utilizing graphene's good electronic conductor and lower Fermi energy level, the photogenerated electrons accumulated on the conduction band of titanium dioxide can flow to the position of the energy band. The lower graphene plane can increase the separation efficiency of photogenerated electron holes on titanium dioxide, thereby improving the photocatalytic ability of the material. In the present invention, the N,N-dimethylformamide is used as a solvent, which not only facilitates the dissolution of raw materials, but also facilitates the smooth implementation of electrospinning, thereby obtaining nanofibers.

In the present invention, the mass ratio of graphene oxide and titanium dioxide is preferably (1-5):(10-30), more preferably (2-4):(15-25). In the present invention, the amount of graphene oxide and titanium dioxide is limited to the above range, and the obtained material has good photocatalytic ability; wherein titanium dioxide exists as the main substance of the photocatalytic material.

In the present invention, the mass ratio of the polyacrylonitrile and polyvinylpyrrolidone is preferably (1-5):1, more preferably (2-3):1. The present invention limits the amount of the polyacrylonitrile and polyvinylpyrrolidone to the above range, which is beneficial to obtain nanofibers by electrospinning, and is beneficial to obtain nanofibers with developed void structure by subsequent hydrothermal reaction.

In the present invention, the mass ratio of the polyacrylonitrile and titanium dioxide is preferably (1-15):1, more preferably (2-10):1. In the present invention, the amount of the polyvinylpyrrolidone and titanium dioxide is limited to the above range, which is beneficial to the formation of a suitable pore structure in the subsequently prepared nanofibers in the hydrothermal reaction, thereby improving the photocatalytic ability of the material.

In the present invention, the mixing method of the graphene oxide, titanium dioxide, N,N-dimethylformamide, polyvinylpyrrolidone and polyacrylonitrile is preferably firstly dissolving graphene oxide in N,N-dimethylformamide Ultrasound is carried out in the amide, then titanium dioxide is added, the ultrasonic wave is continued, and finally polyvinylpyrrolidone and polyacrylonitrile are added, and then the spinning solution is obtained by heating and stirring in turn.

The present invention has no special provisions on the parameters of the ultrasonic wave, which can be determined according to the technical common sense of those skilled in the art, and the raw materials can be mixed uniformly.

In the present invention, the heating is preferably performed under stirring conditions. In the present invention, the heating temperature is preferably 50 to 70°C, and more preferably 60°C. In the present invention, the heating temperature is limited to the above range in order to promote the dissolution of the polyvinylpyrrolidone and polyacrylonitrile in the system.

The present invention does not have special provisions on the stirring rate and stirring time, which can be determined according to the technical common sense of those skilled in the art, and it is sufficient to achieve sufficient dispersion between materials.

After the spinning solution is obtained, the present invention performs electrospinning on the spinning solution to obtain nanofibers.

In the present invention, the setting voltage of the electrospinning is preferably 11-15KV, more preferably 13KV. In the present invention, the advancing speed of the electrospinning is preferably 0.015-0.035 mL/min, more preferably 0.023-0.025 mL/min. In the present invention, the temperature in the electrospinning machine is preferably 25 to 35°C, and more preferably 30°C. In the present invention, the humidity in the electrospinning machine is preferably 28 to 38%, and more preferably 33%. In the present invention, the process parameters of the electrospinning are limited to the above range, which is beneficial to obtain nanofibers from the spinning solution by electrospinning, and the obtained nanofibers have higher photocatalytic ability corresponding to the final porous titanium dioxide composite material obtained. it is good.

After the electrospinning is completed, the present invention preferably dries the electrospun material to obtain nanofibers.

The present invention does not have special provisions on the drying temperature and time. According to the technical knowledge of those skilled in the art, the solvent N,N-dimethylformamide in the material after electrospinning can be removed. In the embodiment of the present invention, the drying method is preferably vacuum drying. In the present invention, the conventional vacuum drying can realize the rapid removal of the solvent in the material at a relatively low temperature.

After the nanofibers are obtained, in the present invention, the nanofibers, water and ethanol are mixed to perform a hydrothermal reaction to obtain a porous titanium dioxide composite material.

In the present invention, the volume ratio of the water and ethanol is preferably (1-3):1, more preferably 2:1. The present invention does not specifically stipulate the dosage relationship between the nanofibers and the water and ethanol. When using the hydrothermal reaction well known to those skilled in the art, the proportion and dosage of the solid material and the liquid solvent are sufficient. In the present invention, the water can dissolve the polyvinylpyrrolidone in the fibers, so that the fibers form a porous structure; the ethanol acts as a good reducing agent to reduce the exposed graphene oxide to graphene, and the obtained graphene Combined with titanium dioxide, the photocatalytic performance of titanium dioxide is greatly improved.

In the present invention, the temperature of the hydrothermal reaction is preferably 90-140°C, more preferably 110-130°C; the time of the hydrothermal reaction is preferably 3-8h, more preferably 4-7h. In the present invention, the parameters of the hydrothermal reaction are limited to the above range, and the obtained porous titanium dioxide composite material has good photocatalytic ability.

After the hydrothermal reaction is completed, in the present invention, the hydrothermal product of the hydrothermal reaction is preferably washed and dried in sequence to obtain a porous titanium dioxide composite material.

In the present invention, the washing reagents are preferably water and ethanol. The present invention does not specifically stipulate the number of times of the washing, as long as the impurities on the hydrothermal product are removed.

The present invention does not have special provisions on the drying temperature and time. According to the technical common sense of those skilled in the art, it is sufficient to remove the washing reagents remaining on the washed hydrothermal product.

The invention provides a preparation method of a porous titanium dioxide composite material. Graphene oxide and photocatalyst titanium dioxide are loaded on nanofibers by electrospinning, and ethanol is used to convert graphene oxide into graphene through hydrothermal reaction. At the same time, porous titanium dioxide is obtained. TiO2 composite material, thereby improving the catalytic ability of TiO2 photocatalyst.

The present invention provides the porous titanium dioxide composite material prepared by the preparation method described in the above scheme. In the present invention, the specific surface area of the porous titanium dioxide composite material is preferably 48-55 m ² /g, more preferably 50-54 m ² /g. The porous titanium dioxide composite material provided by the present invention has a larger specific surface area.

The present invention also provides the application of the porous titanium dioxide composite material described in the above scheme in photocatalytic degradation of organic matter.

There is no special provision for the application in the present invention, and the porous titanium dioxide composite material can be used as a photocatalyst. In the present invention, the organic substance is preferably methylene blue. The experimental results show that the photocatalysis of methylene blue in water by the porous titanium dioxide composite material provided by the present invention has a degradation rate close to 100%.

The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

A preparation method of porous titanium dioxide composite material, the specific operation steps are as follows:

(1) Weigh 30 mg of graphene oxide, dissolve it in 10 mL of N,N-dimethylformamide DMF, and sonicate for 40 min; then add 0.2 g of titanium dioxide, and continue to sonicate for 30 min; finally, add 1.2 g of polyacrylonitrile PAN and 1.2 g of polyethylene Pyrrolidone PVP (PAN:PVP=1:1, mass ratio), stir in a water bath at 60°C until it dissolves, and stir at room temperature overnight to obtain a spinning solution;

(2) Electrospinning the spinning solution obtained in the step (1), wherein the parameters of the electrospinning are as follows: the setting voltage is 13KV, the advancing speed is 0.023mL/min, and the The temperature is 30°C, and the humidity is 33%; after the spinning is completed, the spun product is dried in a vacuum drying oven at 60°C for 12 hours to obtain nanofibers;

(3) Put the nanofibers obtained in step (2) into a mixed solution of water and ethanol (volume ratio 2:1) to carry out a hydrothermal reaction, wherein the hydrothermal temperature is 120° C., and the hydrothermal time is 5h; the hydrothermal reaction is completed Afterwards, the hydrothermal product was washed with water and ethanol, and dried in a vacuum drying oven at 65 °C for 6 h to obtain a porous titanium dioxide composite material.

Example 2

A preparation method of porous titanium dioxide composite material, the specific operation steps are as follows:

(1) Weigh 30 mg of graphene oxide, dissolve it in 10 mL of N,N-dimethylformamide DMF, and sonicate for 40 min; then add 0.2 g of titanium dioxide, and continue to sonicate for 30 min; finally, add 1.6 g of polyacrylonitrile PAN and 0.8 g of polyethylene Pyrrolidone PVP (PAN:PVP=2:1, mass ratio), stirred in a 60°C water bath until dissolved, and stirred at room temperature overnight to obtain a spinning solution;

(2) Electrospinning the spinning solution obtained in the step (1), wherein the parameters of the electrospinning are as follows: the setting voltage is 13KV, the advancing speed is 0.023mL/min, and the The temperature is 30°C, and the humidity is 33%; after the spinning is completed, the spun product is dried in a vacuum drying oven at 60°C for 12 hours to obtain nanofibers;

(3) Put the nanofibers obtained in step (2) into a mixed solution of water and ethanol (volume ratio 2:1) to carry out a hydrothermal reaction, wherein the hydrothermal temperature is 120° C., and the hydrothermal time is 5h; the hydrothermal reaction is completed Afterwards, the hydrothermal product was washed with water and ethanol, and dried in a vacuum drying oven at 65 °C for 6 h to obtain a porous titanium dioxide composite material.

Example 3

A preparation method of porous titanium dioxide composite material, the specific operation steps are as follows:

(1) Weigh 30 mg of graphene oxide, dissolve it in 10 mL of N,N-dimethylformamide DMF, and sonicate for 40 min; then add 0.2 g of titanium dioxide, and continue to sonicate for 30 min; finally, add 0.8 g of polyacrylonitrile PAN and 1.6 g of polyethylene Pyrrolidone PVP (PAN:PVP=1:2, mass ratio), stirred in a 60°C water bath until dissolved, and stirred at room temperature overnight to obtain a spinning solution;

(2) Electrospinning the spinning solution obtained in the step (1), wherein the parameters of the electrospinning are as follows: the setting voltage is 13KV, the advancing speed is 0.023mL/min, and the The temperature is 30°C, and the humidity is 33%; after the spinning is completed, the spun product is dried in a vacuum drying oven at 60°C for 12 hours to obtain nanofibers;

(3) Put the nanofibers obtained in step (2) into a mixed solution of water and ethanol (volume ratio 2:1) to carry out a hydrothermal reaction, wherein the hydrothermal temperature is 120° C., and the hydrothermal time is 5h; the hydrothermal reaction is completed Afterwards, the hydrothermal product was washed with water and ethanol, and dried in a vacuum drying oven at 65 °C for 6 h to obtain a porous titanium dioxide composite material.

Comparative Example 1

The preparation method is the same as in Example 2, except that no graphene oxide is added.

Performance Testing

1. Graphene oxide (GO), the porous titanium dioxide composite (RGO-TiO ₂ /PAN[2/1]) prepared in Example 2 and the composite (TiO ₂ /PAN[2/1]) prepared in Comparative Example 1 were combined ) to carry out the Raman spectroscopy test, and the test results are shown in Figure 1.

It can be seen from Figure 1 that the ratio ID/IG of the characteristic peak D peak and G peak intensity of graphene changes, which proves that the same characteristic peak of TiO ₂ appears in the pure TiO ₂ fiber in the reduced GO composite fiber, which proves that the TiO 2 in the composite fiber has the same characteristic peak. The existence of ₂ ; the characteristic peaks of _{TiO 2} in composite fibers are shifted from those in pure TiO ₂ fibers, which may be explained by related literatures due to the interaction between TiO ₂ and RGO, which further proves that TiO ₂ It works well with RGO.

2. The porous titanium dioxide composite material (RGO-TiO ₂ /PAN[2/1]) prepared in Example 2 was tested by infrared spectroscopy, and the test results were shown in Figure 2 .

It can be seen from Figure 2 that the C=O stretching vibration peak corresponding to polyacrylonitrile PVP at 1661 cm ^-1 is reduced, and the CN stretching vibration peak corresponding to 1285 cm ^-1 even disappears, which indicates that during the hydrothermal process The polyacrylonitrile PVP in the fiber was effectively eliminated; in addition, the C≡N tensile vibration peak at 2245 cm ^-1 and the CH vibration peak at 1452 cm ^-1 in polyacrylonitrile PAN maintained similar intensities, indicating the structure of PAN Unaffected by the holemaking process.

3. The porous titania composite (RGO-TiO ₂ /PAN[2/1]) prepared in Example 2 was characterized by SEM, as shown in FIG. 3 .

It can be seen from FIG. 3 that the porous titanium dioxide composite material prepared by the present invention has a smooth surface and has a pore structure at the same time.

4. The specific surface area data of the porous titanium dioxide composite material (RGO-TiO ₂ /PAN[2/1]) prepared in Example 2 and the composite material (TiO ₂ /PAN[2/1]) prepared in Comparative Example 1 were tested, The test results are shown in Figure 4.

It can be seen from Figure 4 that the specific surface area of the composite TiO ₂ /PAN[2/1] prepared in Comparative Example 1 is 43.19 m ² /g, and the porous titania composite prepared in Example 2 RGO-TiO ₂ /PAN[2 /1] with a specific surface area of 50.12 m ² /g, which proves that the porous structure can increase the contact area between the photocatalyst and the target degradant, which in turn can improve the photodegradation efficiency.

5. The photocatalytic degradation test was carried out on the porous titanium dioxide composite material (RGO-TiO ₂ /PAN[2/1]) prepared in Example 2 and the composite material (TiO ₂ /PAN[2/1]) prepared in Comparative Example 1.

First, the porous titanium dioxide composite material prepared in Example 2 and the composite material (TiO ₂ /PAN[2/1]) prepared in Comparative Example 1, 4 × 5 cm fibers were put into 100 mL of 10 mg/L methylene blue MB solution, respectively. After dark treatment and stirring to the equilibrium of adsorption and desorption, a mercury lamp with an irradiation intensity of 12.7 mw/cm ² (the wavelength is mainly concentrated at 300-450 nm) was used as the light source to start the photodegradation reaction; The absorbance (maximum absorption wavelength: 664 nm) was measured by an ultraviolet spectrophotometer, and the concentration change of MB during the photodegradation process was deduced. The test results are shown in Figure 5.

It can be seen from FIG. 5 that the photocatalytic degradation of organic methylene blue by the porous titanium dioxide composite material provided by the present invention can achieve a removal efficiency of methylene blue close to 100%, while the composite material prepared in Comparative Example 1 (TiO ₂ /PAN[2/ 1]) When photocatalytic degradation is carried out, the removal efficiency of methylene blue is only over 80%. By comparison, it is found that the present invention increases the pore structure of nanofibers through hydrothermal reaction, and composites graphene and titanium dioxide, which can greatly improve the photocatalytic degradation ability of titanium dioxide.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A preparation method of a porous titanium dioxide composite material comprises the following steps.

(1) Mixing graphene oxide, titanium dioxide, N-dimethylformamide, polyvinylpyrrolidone and polyacrylonitrile to obtain a spinning solution;

(2) performing electrostatic spinning on the spinning solution obtained in the step (1) to obtain nano fibers;

(3) and (3) mixing the nano-fibers obtained in the step (2), water and ethanol for hydrothermal reaction to obtain the porous titanium dioxide composite material.

2. The preparation method according to claim 1, wherein the volume ratio of the mass of the graphene oxide to the N, N-dimethylformamide in the step (1) is (10-50) mg: 10 mL.

3. The preparation method according to claim 1, wherein the mass ratio of the graphene oxide to the titanium dioxide in the step (1) is (1-5): (10-30).

4. The preparation method according to claim 1, wherein the mass ratio of polyacrylonitrile to polyvinylpyrrolidone in the step (1) is (0.5-5): 1.

5. the preparation method according to claim 1, wherein the mass ratio of polyacrylonitrile to titanium dioxide in the step (1) is (1-15): 1.

6. the preparation method according to claim 1, wherein the electrostatic spinning in the step (2) is carried out at a set voltage of 11-15 KV; the advancing speed of electrostatic spinning is 0.015-0.035 mL/min.

7. The preparation method according to claim 1, wherein the volume ratio of the water to the ethanol in the step (3) is (1-3): 1.

8. the method according to claim 1, wherein the temperature of the hydrothermal reaction in the step (3) is 90 to 140 ℃ and the time of the hydrothermal reaction is 3 to 8 hours.

9. The porous titanium dioxide composite material prepared by the preparation method of any one of claims 1 to 8, wherein the specific surface area of the porous titanium dioxide composite material is 48 to 55m ² /g。

10. The use of the porous titanium dioxide composite material of claim 9 in photocatalytic degradation of organic matter.

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