CN107640784A - A kind of nanocrystalline introducing defect method preparation technology of modifying titanium dioxide - Google Patents

Abstract

The invention discloses a defect-introducing preparation process of modified titanium dioxide nanocrystals, which belongs to the technical field of semiconductor nanomaterial preparation. Firstly, titanium dioxide nanocrystals are prepared by precursor solution, and then modified titanium dioxide nanocrystals with strong light absorption performance are prepared by chemical redox method and high-temperature phosphorus treatment. The present invention uses the phosphating method to modify the white titanium dioxide nanocrystal by introducing defects, which can significantly improve the light absorption performance of the titanium dioxide nanocrystal, and has a great effect on promoting the application of titanium dioxide in the field of energy and environment; the process is simple and low in cost, and can be used in Large-scale production of titanium dioxide nanocrystals with high light absorption performance; using this process, titanium dioxide nanocrystals with different colors and different light absorption properties can be obtained, which can meet the selective requirements for titanium dioxide nanocrystals in different fields.

Description

A preparation process of modified titanium dioxide nanocrystals by introducing defects

technical field

The invention belongs to the technical field of semiconductor nanomaterial preparation, in particular to a defect-introducing preparation process of modified titanium dioxide nanocrystals.

Background technique

Titanium dioxide (TiO ₂ ), as a widely used oxide semiconductor material, has been widely used in the fields of energy and environment due to its environmental friendliness, stable chemical properties, low price and good charge transport performance. Since titanium dioxide was found to have excellent photocatalytic properties in 1972, the research on its properties has received extensive attention. For decades, titania-based electrochemical devices have emerged in an endless stream for energy and environmental issues. However, titanium dioxide has a wide band gap (~3 eV) and weak conductivity. At the same time, its ability to separate and transport electron-hole pairs needs to be further enhanced, which limits its further application. In order to improve the performance of titanium dioxide, methods such as crystal plane control and morphology control can be adopted, among which, the introduction of defects is considered to be an effective method to improve the properties of titanium dioxide. Improving the crystal structure of titanium dioxide by introducing defects to optimize its electronic energy level structure, thereby improving the electrochemical performance of titanium dioxide, is extremely important for improving the performance of _TiO2 -based energy and environmental devices. As early as 2001, Asahi theoretically calculated that the doping of non-metallic elements can improve the light absorption performance and found that titanium dioxide doped with nitrogen elements can exhibit a very beneficial photocatalytic effect. Since then, Chen Xiaobo published an article in Science in 2011, saying that under the condition of high temperature and high pressure hydrogen gas, white titanium dioxide will be converted into black titanium dioxide. Compared with traditional white titanium dioxide, black titanium dioxide has stronger optical absorption in the visible light region. However, this hydrogenation method is not suitable for large-scale production due to the high cost of preparation.

Contents of the invention

The purpose of the present invention is to provide a simple, efficient and low-cost preparation process of modified titanium dioxide nanocrystals by introducing defects.

The purpose of the present invention is achieved by the following methods: firstly prepare titanium dioxide nanocrystals, and then prepare modified titanium dioxide nanocrystals with strong light absorption performance by means of chemical redox method and high-temperature phosphorus treatment. Specifically include the following steps:

a. Preparation of precursor solution: mix titanium isopropoxide, ethanol, hydrochloric acid, ultrapure water and F127 in a molar ratio of 1:0.005:0.5:15:40 to obtain a precursor solution;

b. Preparation of white TiO ₂ nanocrystals: place the precursor solution at 40-60°C for 20-24 h, then vacuum dry at 100-110°C for 20-24 h to obtain a white powder, which is placed in In a muffle furnace, anneal at 500°C for 6-8h at a heating rate of 0.3°C·min ^-1 to obtain white TiO ₂ nanocrystals;

c. Preparation of modified titanium dioxide nanocrystals: Weigh white _TiO2 nanocrystals in a magnetic boat, place them in the constant temperature zone of the tube furnace, place another magnetic boat at a distance of 10-15 cm from this magnetic boat, and weigh the second sub- Sodium phosphate is placed in it, and kept at 300-600°C for 2-4h at a heating rate of 2°C·min ^-1 , since sodium hypophosphite will decompose at 200-300°C to generate PH ₃ , thus white _TiO 2nm Crystals were phosphated to obtain modified titanium dioxide nanocrystals.

Wherein, in step c, the mass ratio of white _TiO nanocrystals to sodium hypophosphite is preferably 1:2-4, too much sodium hypophosphite will cause too many oxygen vacancies and defects introduced, too little hypophosphite Sodium phosphate produces too little phosphine, either of which will affect the light absorption properties of the modified titanium dioxide nanocrystals.

The preparation of modified titanium dioxide nanocrystals is carried out under vacuum conditions. Under the vacuum conditions of different treatment temperatures, the pressure in the tube furnace is different, which creates a high-pressure reaction condition virtually, and under vacuum conditions, sodium hypophosphite decomposes The generated phosphine will exist in the whole reaction process, which can ensure that the titanium dioxide nanocrystals fully react with the phosphine, and obtain modified titanium dioxide nanocrystals with high photocatalytic performance.

In addition, titanium dioxide nanocrystals treated with vacuum phosphorus at 300-400°C are washed with ultrapure water and absolute ethanol in sequence, placed in an oven, and dried at 100-120°C for 12-18 hours to obtain yellow titanium dioxide nanocrystals. crystal.

Compared with the existing defect-introducing method preparation process of modified titanium dioxide nanocrystals, the present invention has the following beneficial effects:

1. The present invention adopts the phosphating method to modify the white titanium dioxide nanocrystals by introducing defects, which can significantly improve the light absorption performance of the titanium dioxide nanocrystals, and plays an important role in promoting the application of titanium dioxide in the field of energy and environment.

2. The preparation process of the present invention is simple, the cost is low, and it can be used for large-scale production of titanium dioxide nanocrystals with high light absorption performance.

3. Titanium dioxide nanocrystals with different colors and different light absorption properties can be obtained by adopting the process of the present invention, which can meet the selective requirements for titanium dioxide nanocrystals in different fields.

Description of drawings

Fig. 1 is the solid ultraviolet characterization of white titanium dioxide nanocrystals and modified titanium dioxide nanocrystals prepared by the process of the present invention.

Fig. 2 is an XRD diagram of white titanium dioxide nanocrystals and modified titanium dioxide nanocrystals prepared by the process of the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

Preparation of a light gray titanium dioxide nanocrystal:

Mix 17 mL titanium isopropoxide, 131 mL ethanol, 0.776 mL hydrochloric acid, 13.5 mL ultrapure water and 0.02553 g F127 to obtain a precursor solution; place the precursor solution at 40 °C for 24 h, then place it at 110 °C Dry in vacuum for 20 h to obtain a white powder, put the white powder in a muffle furnace, and anneal at 500 °C for 6 h at a heating rate of 0.3 °C min ^-1 to obtain white _TiO2 nanocrystals; weigh 0.5 g of white TiO ₂ Nanocrystals are placed in a magnetic boat, placed in the constant temperature zone of the tube furnace, and another magnetic boat is placed 10cm away from this magnetic boat, and 2g of sodium hypophosphite is weighed into it, and the temperature is raised at a rate of 2 ℃·min ^-1 The rate was kept under vacuum at 300°C for 4 hours, the magnetic boat was taken out, placed at room temperature, and weighed to obtain 0.45 g of light gray titanium dioxide nanocrystals. The solid ultraviolet characterization results and XRD results are shown in Figure 1-b and Figure 2-b respectively As shown, it can be seen from Figure 1-b that the absorption of titanium dioxide nanocrystals after 300 °C vacuum phosphorous treatment is slightly enhanced compared with that of white titanium dioxide nanocrystals (1-a) in the visible light region; the results in Figure 2-b show , the XRD spectrum of titanium dioxide nanocrystals treated with vacuum phosphorus at 300 ℃ is the same as that of white titanium dioxide nanocrystals (Fig. 2-a), indicating that the sample still presents a good anatase crystal form, and the reaction process No other substances are formed and the sample is of high purity. According to the absorption intensity of the sample in the visible region, we can apply it to the degradation of organic dyes.

Example 2

Preparation of gray titanium dioxide nanocrystals:

Mix 17 mL titanium isopropoxide, 131 mL ethanol, 0.776 mL hydrochloric acid, 13.5 mL ultrapure water and 0.02553 g F127 to obtain a precursor solution; place the precursor solution at 50 °C for 22 h, then place it at 110 °C Vacuum drying for 20 h to obtain a white powder, put the white powder in a muffle furnace, and anneal at 500 °C for 7 h at a heating rate of 0.3 °C min ^-1 to obtain white _TiO2 nanocrystals; weigh 0.5 g of white TiO ₂ Nanocrystals are placed in a magnetic boat, placed in the constant temperature zone of the tube furnace, and another magnetic boat is placed 10cm away from this magnetic boat, and ^1.5g of sodium hypophosphite is weighed and placed in it. The heating rate was maintained at 400°C under vacuum for 3.5 hours, the magnetic boat was taken out, placed at room temperature, and weighed to obtain 0.44 g of gray titanium dioxide nanocrystals. The solid ultraviolet characterization results and XRD results are shown in Figure 1-c and Figure 2- As shown in c, it can be seen from Figure 1-c that the absorption of titanium dioxide nanocrystals after vacuum phosphorus treatment at 400 °C is greatly enhanced compared with that of white titanium dioxide nanocrystals (1-a) in the visible light region, which is about shallow 2 times the absorbance of gray titanium dioxide nanocrystals; Figure 2-c shows that the XRD spectrum of the gray titanium dioxide nanocrystals generated after increasing the reaction temperature is the same as that of white titanium dioxide nanocrystals (Figure 2-a), indicating that after The treated sample still presents the anatase phase without other impurity phases, and the sample has high purity. According to the absorption intensity of the sample in the visible light region, it can be applied to the photolysis of water.

Example 3

Preparation of dark gray titanium dioxide nanocrystals:

Mix 17 mL of titanium isopropoxide, 131 mL of ethanol, 0.776 mL of hydrochloric acid, 13.5 mL of ultrapure water and 0.02553 g of F127 (convert the molar ratio into actual mass) to obtain a precursor solution; put the precursor solution at 50 °C Stand for 24 h, then vacuum dry at 105 °C for 24 h to obtain a white powder, place the white powder in a muffle furnace, and anneal at 500 °C for 7 h at a heating rate of 0.3 °C·min ^-1 to obtain white TiO ₂ Nanocrystalline: Weigh 0.5g of white _TiO2 nanocrystalline in a magnetic boat, place it in the constant temperature zone of the tube furnace, place another magnetic boat at a distance of 15cm from this magnetic boat, weigh 1.5g of sodium hypophosphite and place it in it , kept at 500°C vacuum for 3.5h at a heating rate of 2°C·min ^-1 , took out the magnetic boat, let it cool to room temperature, and weighed to obtain 0.4 g of dark gray titanium dioxide nanocrystals. The solid ultraviolet characterization results and XRD results As shown in Figure 1-d and Figure 2-d, respectively, it can be seen from Figure 1-d that the titanium dioxide nanocrystals treated with vacuum phosphorus at 500 ℃ have a higher temperature than that of white titanium dioxide nanocrystals (1-a) in the visible light region. The absorption is greatly enhanced, which is about 2.4 times the absorbance of the gray titanium dioxide nanocrystals; the results in Figure 2-d show that the XRD spectrum of the dark gray titanium dioxide nanocrystals obtained by further increasing the treatment temperature is the same as that of the white titanium dioxide nanocrystals. The figure (Fig. 2-a) is the same, indicating that the treatment process did not affect the anatase crystal form of the sample. Due to its high absorption intensity in the visible light region, it can be well applied to the degradation of organic dyes.

Example 4

Preparation of black titanium dioxide nanocrystals:

Mix 17 mL of titanium isopropoxide, 131 mL of ethanol, 0.776 mL of hydrochloric acid, 13.5 mL of ultrapure water and 0.02553 g of F127 (convert the molar ratio into actual mass) to obtain a precursor solution; put the precursor solution at 60 °C Stand for 20 h, then vacuum dry at 100 °C for 24 h to obtain a white powder, place the white powder in a muffle furnace, and anneal at 500 °C for 8 h at a heating rate of 0.3 °C·min ^-1 to obtain white TiO ₂ nanocrystals; take 0.5g white _TiO2 nanocrystals in a magnetic boat, place it in the constant temperature zone of the tube furnace, place another magnetic boat at a distance of 15cm from this magnetic boat, weigh 1g of sodium hypophosphite and place it therein, Keep it under vacuum at 600°C for 2 hours at a heating rate of 2°C·min ^-1 , take out the magnetic boat, let it cool to room temperature, and weigh it to obtain 0.41 g of black titanium dioxide nanocrystals. The solid ultraviolet characterization results and XRD results are shown in Fig. As shown in Figure 1-e and Figure 2-e, it can be seen from Figure 1-e that the titanium dioxide nanocrystals treated with vacuum phosphorus at 600 ℃ have significantly higher absorption in the visible light region than the white titanium dioxide nanocrystals (1-a). The large enhancement is about 2.7 times the absorbance of gray titanium dioxide nanocrystals; the results in Figure 2-e show that, similarly, the crystal form of titanium dioxide nanocrystals has not changed after high temperature treatment at 600 °C. Due to its enhanced absorption intensity in the visible light region, it can be applied in the field of photolysis of water and so on.

Example 5

Preparation of yellow titanium dioxide nanocrystals:

The gray titanium dioxide nanocrystals in Example 2 were first washed three times with ultrapure water, then washed three times with absolute ethanol, and finally placed in an oven and dried at 100 °C for 18 h to obtain yellow titanium dioxide nanocrystals.

Example 6

Preparation of yellow titanium dioxide nanocrystals:

The light gray titanium dioxide nanocrystals in Example 1 were first washed with ultrapure water for 3 times, then washed with absolute ethanol for 3 times, and finally placed in an oven and dried at 120 ° C for 12 h to obtain yellow titanium dioxide nanocrystals; Its solid ultraviolet characterization results and XRD results are shown in Figure 1-f and Figure 2-f, respectively. It can be seen from Figure 1-f that the yellow titanium dioxide nanocrystals are more sensitive to visible light than the white titanium dioxide nanocrystals (1-a). The absorption in the region has been greatly enhanced, and the absorption band of the sample has moved to the visible region as a whole, and the light absorption range has increased; the results in Figure 2-f show that after the heating process, there is no change in the intrinsic crystal form of titanium dioxide. As a result, the treated titanium dioxide nanocrystals are still in the anatase phase. Because it has better performance than ordinary white TiO ₂ nanocrystals, it can be widely used in photocatalysis, photoelectrochemical sensors, energy batteries and other fields.

Claims (3)

1. the nanocrystalline introducing defect method preparation technology of a kind of modifying titanium dioxide, it is characterised in that comprise the following steps：

A, the preparation of precursor solution：By isopropyl titanate, ethanol, hydrochloric acid, ultra-pure water and F127 with mol ratio 1:0.005:0.5: 15:40 is well mixed, obtains precursor solution；

B, white TiO₂Nanocrystalline preparation：Precursor solution is placed into 20-24 h at 40-60 DEG C, then in 100-110 DEG C Lower vacuum drying 20-24 h, obtain white powder, the white powder are placed in Muffle furnace, with 0.3 DEG C of min^-1Heating speed Rate is annealed 6-8h at 500 DEG C, obtains white TiO₂It is nanocrystalline；

C, the nanocrystalline preparation of modifying titanium dioxide：Weigh white TiO₂It is nanocrystalline to be placed in the flat-temperature zone of tube furnace in magnetic boat, Another magnetic boat is being placed at this magnetic boat 10-15cm, sodium hypophosphite is being weighed and is placed in one, with 2 DEG C of min^-1Heating Speed keeps 2-4h at 300-600 DEG C, and it is nanocrystalline to obtain modifying titanium dioxide.

2. a kind of nanocrystalline introducing defect method preparation technology of modifying titanium dioxide according to claim 1, its feature exist In：In step c, the white TiO₂The nanocrystalline and mass ratio of sodium hypophosphite is 1:2-4.

3. a kind of nanocrystalline introducing defect method preparation technology of modifying titanium dioxide according to claim 1, its feature exist In：In step c, the nanocrystalline preparation of the modifying titanium dioxide is carried out under vacuum.