CN1623656A - Photocatalyst and preparation method of highly active nano-magnetic composite - Google Patents

Abstract

A high-activity magnetic nano-class photocatalyst is composed of the core (organically modified Fe3O4) and the shell (composite SnO2-TiO2 semiconductor). Its preparing process includes such steps as preparing the magnetic alcohol-base fluid from FeCl2, FeCl3, and polyethanediol or diethanolamine by codeposition method, preparing SnO2 sol from SnCl2 or SnCl4 by sol-gel method, mixing them together, ultrasonic dispersing and heat treating. Its advantages are high catalytic activity and cyclic use.

Description

Photocatalyst and preparation method of highly active nano-magnetic composite

technical field

The invention relates to a photocatalyst and a preparation method of a high-activity nanometer magnetic composite, belonging to the magnetic photocatalyst technology.

Background technique

Papers about magnetic photocatalysts:

Li Xinjun et al. Preparation and photocatalytic properties of magnetic nano-photocatalysts[J]. Chinese Journal of Nonferrous Metals, 2001, 11(6): 971-976

The article describes the use of organic-inorganic nano-composite technology to compound nickel phthalocyanine and ferric oxide nanoparticles as magnetic cores, and to prepare nano-magnetic composite photocatalysts using sol-gel technology. Its structure is a core-shell structure, the shell is titanium dioxide, and the core is composite particles of nickel phthalocyanine and ferric oxide. In order to prevent the contact between the magnetic core and titanium dioxide, an inert layer of silicon dioxide is also added.

The magnetic nuclei prepared by this method are dispersed in ethanol in a suspended state, non-nanoscale (colloidal state), and only stirring is used in the sol-gel process, so it is difficult to make the magnetic nuclei reach nanoscale dispersion. The heating rate of heat treatment is not controlled, resulting in serious sintering collapse.

The nano-magnetic composite photocatalyst prepared by the above method has no surface modification and has low photocatalytic activity.

Contents of the invention

The object of the present invention is to provide a photocatalyst and a preparation method of a high-activity nano-magnetic composite body. The photocatalyst has high activity and a simple preparation process.

The present invention is achieved through the following technical solutions. A photocatalyst of a highly active nano-magnetic composite, characterized in that the average particle size of the catalyst is 80nm to 100nm; the core material is organically modified ferric oxide, and the shell material is a compound semiconductor of tin dioxide and titanium dioxide. The atomic ratio of titanium tin iron is: (75-80): (10-15): (5-10).

Above-mentioned photocatalyst preparation method is characterized in that comprising the following steps:

1. Preparation of alcohol-based Fe ₃ O ₄ magnetic fluid

Preparation of nanometer Fe ₃ O ₄ magnetic fluid by co-precipitation method: according to the molar ratio of Fe ²⁺ and Fe ³⁺ as 1:2~2:3, the prepared 0.25mol/L~0.5mol/L FeCl ₂ solution and 0.25 mol/L～0.5mol/L FeCl ₃ solution and polyethylene glycol 4000 solution or diethanolamine solution are added in the four-necked flask equipped with mechanical stirring, wherein the mass percentage of polyethylene glycol 4000 or diethanolamine in the reaction solution is 1% to 2%, heated in a constant temperature water bath at 60°C to 80°C, and at the same time fed nitrogen for protection. Slowly add 1mol/L-2mol/L NaOH solution dropwise, until the pH value reaches 6-7, black Fe ₃ O ₄ particles appear, continue to add alkali, and adjust the pH value to 11-12. The temperature rises to 80°C to 90°C for aging. The prepared Fe ₃ O ₄ particles were washed with deionized water until neutral, and then washed with absolute ethanol. After magnetic precipitation, they were diluted with absolute ethanol and dispersed ultrasonically to prepare alcohol-based Fe ₃ O ₄ magnetic fluid.

2. Preparation of tin dioxide sol

Tin dichloride or tin tetrachloride is used as raw material, added to absolute ethanol to prepare a solution of 0.2 mol/L to 0.5 mol/L, and refluxed under magnetic stirring conditions to obtain a colorless transparent sol. After aging for 12h~24h, slowly add 1mol/L~10mol/L NH ₃ ·H ₂ O dropwise to form a milky white gel. Wash with deionized water, and then wash with alcohol until there is no chloride ion. After washing, filter, transfer the filter cake into absolute ethanol, and ultrasonically disperse to form tin dioxide sol.

3. Preparation of composite photocatalyst gel

The atomic ratio of titanium to tin is 8:1 to 5:1, and the atomic ratio of titanium to iron is 7.5:1 to 16:1. Take the above-mentioned tin dioxide sol, add tetrabutyl titanate, ultrasonically disperse, age, then add the above-mentioned alcohol-based Fe ₃ O ₄ magnetic fluid, ultrasonically disperse to form solution A. The molar ratio of titanium acid (H ⁺ /Ti) is 0.05:1-0.2:1, the molar ratio of titanium alkoxide is 9:1-18:1, and the molar ratio of titanium water is 2.8:1-5.6:1. Add deionized water to absolute ethanol, add nitric acid dropwise, and ultrasonically disperse to prepare solution B. Under vigorous mechanical stirring, slowly drop solution B into solution A until a gel is formed.

4. Heat treatment of the gel

The gel is vacuum-dried at 70°C to 90°C, pulverized, and heat-treated in a muffle furnace with programmed temperature under nitrogen atmosphere. From 25°C to 250°C, the temperature is raised at 1°C/min, and above 250°C, the temperature is raised at 2°C/min, and the temperature is raised to 450°C to 650°C, kept for more than 1 hour, and the nitrogen is turned off when it is cooled to below 150°C.

Above-mentioned photocatalyst and its advantage of preparation method are:

The whole preparation process is a liquid-phase chemical approach, using nano/nano composite technology, which can ensure that the composite particles have a reasonable structure, nanoscale mixing, and uniform coating. After the magnetic core is modified by an organic surfactant, it can be dispersed in a colloidal state in ethanol, ensuring the nanoscale of the magnetic core. Surfactants not only act as antioxidants and dispersants, but also act as a diaphragm during heat treatment to prevent the formation of iron-titanium compounds. The composite tin dioxide provides the carrier transfer site, which increases the separation rate of photogenerated electrons and holes, so that the activity of the nano-magnetic composite photocatalyst is increased by about 40%. Ultrasonic dispersion is widely used in the preparation process, which can ensure the dispersion of sol and colloid at the nanometer scale after mixing. The controlled-atmosphere program-controlled temperature gel heat treatment technology can ensure that the materials are basically not agglomerated during the heat treatment process and reduce sintering collapse.

The nano-magnetic composite photocatalyst is convenient for separation, recovery and recycling.

Description of drawings

Figure 1 is the hysteresis curve of the highly active nano-magnetic composite photocatalytic material. It can be seen from the curve that the coercive force of the highly active nano-magnetic composite photocatalytic material is 17.77oe, and the saturation magnetization is 3.145emu/g.

Figure 2 is the XPS full spectrum of the highly active nano-magnetic composite photocatalyst. It can be seen from the spectrum that there are oxygen, titanium, tin, iron and other elements on the surface of the catalyst. According to the spectra of Ti2p, Sn3d and Fe2p, the atomic ratio of Ti-Sn-Fe obtained after normalization treatment is: 79.2:12.5:8.3.

Fig. 3 is the degradation rate curve of the magnetic photocatalyst of the present invention and the magnetic photocatalyst of comparative example to methyl orange. In the figure, the TSF curve is the degradation rate curve of the magnetic photocatalyst of the present invention to methyl orange, and the TF curve is the degradation rate curve of the magnetic photocatalyst of the comparative example to methyl orange. As can be seen from the figure, the photocatalytic degradation rate of the magnetic photocatalyst of the present invention to methyl orange is about 40% higher than the photocatalytic degradation rate of the magnetic photocatalyst of the comparative example to methyl orange.

Detailed ways

Example 1

All the reagents used in the experiment were of AR grade, and all the solutions were filtered through a 0.22 μm microporous membrane to remove harmful particulate impurities in the solution. Add the prepared 0.25mol/L FeCl solution _80mL and 0.25mol/L FeCl solution _120mL and polyethylene glycol solution 80mL (containing 5g polyethylene glycol 4000) into a 500mL four-necked flask with mechanical stirring, Heating in a constant temperature water bath at 70°C while feeding high-purity nitrogen for protection. Slowly add 1mol/L NaOH solution dropwise, and measure the pH value every 2 minutes. When the pH value reaches 6-7, black Fe ₃ O ₄ particles appear, continue to add alkali, and adjust the pH value to 11-12. The temperature was raised to 80°C and aged for 2h. The prepared Fe ₃ O ₄ nanoparticles were washed with deionized water until neutral, and then washed with absolute ethanol. After magnetic precipitation, they were diluted with 250 mL of absolute ethanol and ultrasonicated for 5 cycles to make alcohol-based Fe ₃ O ₄ magnetic Fluid, named F1.

Weigh 11.2815g of SnCl ₂ ·2H ₂ O, dissolve in 100mL of absolute ethanol, filter through a 0.22μm microporous membrane, and prepare a 0.5mol/L tin salt solution. Magnetic stirring, reflux 4h. After aging for 24 hours, slowly add 2mol/L NH ₃ ·H ₂ O dropwise until neutral, and age for 12 hours. Wash with deionized water, and then wash with alcohol until there is no chloride ion. After washing, filter through a 0.45 μm microporous membrane, transfer the filter cake into 200 mL of absolute ethanol, and ultrasonically disperse to form a tin dioxide sol, named S1.

Take 20mL tin dioxide sol (S1), add 8mL tetrabutyl titanate, sonicate for 4 cycles, age for 0.5h, then add 20mL alcohol-based Fe ₃ O ₄ magnetic fluid (F1), and sonicate for 2 cycles to form a solution a. Add 1.5mL of deionized water to 15mL of absolute ethanol, add dropwise 0.15mL of nitric acid, and ultrasonically disperse to prepare solution B. Under vigorous mechanical stirring, slowly drop solution B into solution A, and continue stirring until a gel is formed.

The gel was vacuum-dried at 80°C, crushed, and then heat-treated in a muffle furnace with programmed temperature under a nitrogen atmosphere. From 25°C to 250°C, the temperature is raised at 1°C/min, and above 250°C, the temperature is raised at 2°C/min, and the temperature is raised to 450°C, kept for 1 hour, and the nitrogen gas is turned off when it is cooled to below 150°C. The sample is named TSF1.

Example 2

Add 40mL of the prepared 0.5mol/L FeCl ₂ solution, 80mL of 0.5mol/L FeCl ₃ solution and 80mL of polyethylene glycol solution (containing 4.5g polyethylene glycol 4000) into a 500mL four-necked flask equipped with mechanical stirring , heated in a constant-temperature water bath at 60°C, while feeding high-purity nitrogen gas for protection. Slowly add 2mol/L NaOH solution dropwise, and measure the pH value every 2 minutes. When the pH value reaches 6-7, black Fe ₃ O ₄ particles appear, continue to add alkali, and adjust the pH value to 11-12. The temperature was raised to 90°C and aged for 2h. The prepared Fe ₃ O ₄ nanoparticles were washed with deionized water until neutral, and then washed with absolute ethanol. After magnetic precipitation, they were diluted with 250 mL of absolute ethanol and ultrasonicated for 5 cycles to make alcohol-based Fe ₃ O ₄ magnetic Fluid, named F2.

Weigh 11.2815g of SnCl ₂ ·2H ₂ O, dissolve in 125mL of absolute ethanol, filter through a 0.22μm microporous membrane, and prepare a 0.4mol/L tin salt solution. Magnetic stirring, reflux 4h. After aging for 24 hours, slowly add 10mol/L NH ₃ ·H ₂ O dropwise until neutral, and age for 12 hours. Wash with deionized water, and then wash with alcohol until there is no chloride ion. After washing, filter through a 0.45 μm microporous membrane, transfer the filter cake into 200 mL of absolute ethanol, and ultrasonically disperse to form a tin dioxide sol, named S2.

Take 18mL tin dioxide sol (S2), add 9mL tetrabutyl titanate, sonicate for 4 cycles, age for 0.5h, then add 15mL alcohol-based Fe ₃ O ₄ magnetic fluid (F2), and sonicate for 2 cycles to form a solution a. Add 2.4mL of deionized water to 24mL of absolute ethanol, add dropwise 0.2mL of nitric acid, and ultrasonically disperse to prepare solution B. Under vigorous mechanical stirring, slowly drop solution B into solution A, and continue stirring until a gel is formed.

The gel was vacuum-dried at 90°C, crushed, and heat-treated in a muffle furnace with programmed temperature under a nitrogen atmosphere. From 25°C to 250°C, the temperature is raised at 1°C/min, and above 250°C, the temperature is raised at 2°C/min, and the temperature is raised to 650°C, kept for 1 hour, and the nitrogen is turned off when it is cooled to below 150°C. The sample is named TSF2.

Example 3, the prepared 0.4mol/L FeCl ₂ solution 50mL and 0.4mol/L FeCl ₃ solution 75mL and polyethylene glycol solution 80mL (containing 2.5g polyethylene glycol 4000) were added to the 500mL with mechanical stirring In a four-neck flask, heat in a water bath at a constant temperature of 80°C, while feeding high-purity nitrogen for protection. Slowly add 1.5mol/L NaOH solution dropwise, and measure the pH value every 2 minutes. When the pH value reaches 6-7, black Fe ₃ O ₄ particles appear, continue to add alkali, and adjust the pH value to 11-12. The temperature was raised to 85°C and aged for 2h. The prepared Fe ₃ O ₄ nanoparticles were washed with deionized water until neutral, and then washed with absolute ethanol. After magnetic precipitation, they were diluted with 250 mL of absolute ethanol and ultrasonicated for 5 cycles to make alcohol-based Fe ₃ O ₄ magnetic Fluid, named F3.

Weigh 11.2815g of SnCl ₂ ·2H ₂ O, dissolve in 250mL of absolute ethanol, filter through a 0.22μm microporous membrane, and prepare a 0.2mol/L tin salt solution. Magnetic stirring, reflux 4h. After aging for 24 hours, slowly add 1 mol/L NH ₃ ·H ₂ O dropwise until neutral, and age for 12 hours. Wash with deionized water, and then wash with alcohol until there is no chloride ion. After washing, filter through a 0.45 μm microporous membrane, transfer the filter cake into 200 mL of absolute ethanol, and ultrasonically disperse to form a tin dioxide sol, named S3.

Take 15mL tin dioxide sol (S3), add 7mL tetrabutyl titanate, sonicate for 4 cycles, age for 0.5h, then add 25mL alcohol-based Fe ₃ O ₄ magnetic fluid (F3), and sonicate for 2 cycles to form a solution a. Add 1.2mL of deionized water to 12mL of absolute ethanol, add dropwise 0.08mL of nitric acid, and ultrasonically disperse to prepare solution B. Under vigorous mechanical stirring, slowly drop solution B into solution A, and continue stirring until a gel is formed.

The gel was vacuum-dried at 85°C, crushed, and heat-treated in a muffle furnace with programmed temperature under a nitrogen atmosphere. From 25°C to 250°C, the temperature is raised at 1°C/min, and above 250°C, the temperature is raised at 2°C/min, and the temperature is raised to 500°C, kept for 1 hour, and the nitrogen gas is turned off when it is cooled to below 150°C. The sample is named TSF3.

Example 4

Add 80mL of prepared 0.25mol/L FeCl ₂ solution, 120mL of 0.25mol/L FeCl ₃ solution and 80mL of diethanolamine solution (containing 5ml diethanolamine) into a 500mL four-necked flask with mechanical stirring, and place in a constant temperature water bath at 70°C Heating in medium temperature, while feeding high-purity nitrogen for protection. Slowly add 1mol/L NaOH solution dropwise, and measure the pH value every 2 minutes. When the pH value reaches 6-7, black Fe ₃ O ₄ particles appear, continue to add alkali, and adjust the pH value to 11-12. The temperature was raised to 80°C and aged for 2h. The prepared Fe ₃ O ₄ nanoparticles were washed with deionized water until neutral, and then washed with absolute ethanol. After magnetic precipitation, they were diluted with 250 mL of absolute ethanol and ultrasonicated for 5 cycles to make alcohol-based Fe ₃ O ₄ magnetic Fluid, named F4.

Weigh 17.55g of SnCl ₂ ·2H ₂ O, dissolve in 125mL of absolute ethanol, filter through a 0.22μm microporous membrane, and prepare a 0.4mol/L tin salt solution. Magnetic stirring, reflux 4h. After aging for 24 hours, slowly add 10 mol/L NH ₃ ·H ₂ O dropwise to adjust the pH value to 8-9, and age for 12 hours. Wash with deionized water, and then wash with alcohol until there is no chloride ion. After washing, filter through a 0.45 μm microporous membrane, transfer the filter cake into 200 mL of absolute ethanol, and ultrasonically disperse to form a tin dioxide sol, named S4.

Take 20mL tin dioxide sol (S4), add 8mL tetrabutyl titanate, sonicate for 4 cycles, age for 0.5h, then add 20mL alcohol-based Fe ₃ O ₄ magnetic fluid (F4), and sonicate for 2 cycles to form a solution a. Add 1.5mL of deionized water to 15mL of absolute ethanol, add dropwise 0.15mL of nitric acid, and ultrasonically disperse to prepare solution B. Under vigorous mechanical stirring, slowly drop solution B into solution A, and continue stirring until a gel is formed.

Other conditions are the same as in Example 1, and finally the nano-magnetic composite photocatalyst is named TSF4.

Example 5

Add 80mL of prepared 0.25mol/L FeCl ₂ solution, 120mL of 0.25mol/L FeCl ₃ solution and 80mL of diethanolamine solution (containing 3ml of diethanolamine) into a 500mL four-necked flask with mechanical stirring, and place in a constant temperature water bath at 70°C Heating in medium temperature, while feeding high-purity nitrogen for protection. Slowly add 1mol/L NaOH solution dropwise, and measure the pH value every 2 minutes. When the pH value reaches 6-7, black Fe ₃ O ₄ particles appear, continue to add alkali, and adjust the pH value to 11-12. The temperature was raised to 80°C and aged for 2h. The prepared Fe ₃ O ₄ nanoparticles were washed with deionized water until neutral, and then washed with absolute ethanol. After magnetic precipitation, they were diluted with 250 mL of absolute ethanol and ultrasonicated for 5 cycles to make alcohol-based Fe ₃ O ₄ magnetic Fluid, named F5.

Weigh 17.55g of SnCl ₄ ·5H ₂ O, dissolve in 250mL of absolute ethanol, filter through a 0.22μm microporous membrane, and prepare a 0.2mol/L tin salt solution. Magnetic stirring, reflux 4h. After aging for 24 hours, slowly add 2 mol/L NH ₃ ·H ₂ O dropwise to adjust the pH value to 8-9, and age for 12 hours. Wash with deionized water, and then wash with alcohol until there is no chloride ion. After washing, filter through a 0.45 μm microporous membrane, transfer the filter cake into 200 mL of absolute ethanol, and ultrasonically disperse to form a tin dioxide sol, named S5.

Take 20mL tin dioxide sol (S5), add 8mL tetrabutyl titanate, sonicate for 4 cycles, age for 0.5h, then add 20mL alcohol-based Fe ₃ O ₄ magnetic fluid (F5), and sonicate for 2 cycles to form a solution a. Add 1.5mL of deionized water to 15mL of absolute ethanol, add dropwise 0.15mL of nitric acid, and ultrasonically disperse to prepare solution B. Under vigorous mechanical stirring, slowly drop solution B into solution A, and continue stirring until a gel is formed.

Other conditions are the same as in Example 1, and finally the nano-magnetic composite photocatalyst is named TSF5.

Example 6

Add 80mL of prepared 0.25mol/L FeCl ₂ solution, 120mL of 0.25mol/L FeCl ₃ solution and 80mL of diethanolamine solution (containing 6ml of diethanolamine) into a 500mL four-necked flask with mechanical stirring, and place in a constant temperature water bath at 70°C Heating in medium temperature, while feeding high-purity nitrogen for protection. Slowly add 1mol/L NaOH solution dropwise, and measure the pH value every 2 minutes. When the pH value reaches 6-7, black Fe ₃ O ₄ particles appear, continue to add alkali, and adjust the pH value to 11-12. The temperature was raised to 80°C and aged for 2h. The prepared Fe ₃ O ₄ nanoparticles were washed with deionized water until neutral, and then washed with absolute ethanol. After magnetic precipitation, they were diluted with 250 mL of absolute ethanol and ultrasonicated for 5 cycles to make alcohol-based Fe ₃ O ₄ magnetic Fluid, named F6.

Weigh 17.55g of SnCl ₄ ·5H ₂ O, dissolve in 100mL of absolute ethanol, filter through a 0.22μm microporous membrane, and prepare a 0.5mol/L tin salt solution. Magnetic stirring, reflux 4h. After aging for 24 hours, slowly add 1 mol/L NH ₃ ·H ₂ O dropwise, adjust the pH value to 8-9, and age for 12 hours. Wash with deionized water, and then wash with alcohol until there is no chloride ion. After washing, filter through a 0.45 μm microporous membrane, transfer the filter cake into 200 mL of absolute ethanol, and ultrasonically disperse to form a tin dioxide sol, named S6.

Take 20mL tin dioxide sol (S6), add 8mL tetrabutyl titanate, sonicate for 4 cycles, age for 0.5h, then add 20mL alcohol-based Fe ₃ O ₄ magnetic fluid (F6), and sonicate for 2 cycles to form a solution a. Add 1.5mL of deionized water to 15mL of absolute ethanol, add dropwise 0.15mL of nitric acid, and ultrasonically disperse to prepare solution B. Under vigorous mechanical stirring, slowly drop solution B into solution A, and continue stirring until a gel is formed.

Other conditions are the same as in Example 1, and finally the nano-magnetic composite photocatalyst is named TSF6.

comparative example

Omit the preparation step of tin dioxide sol in embodiment 1, and in composite photocatalyst gel preparation process, do not use tin dioxide sol, and with dehydrated alcohol, other conditions are the same as embodiment 1, obtain magnetic photocatalyst , named TF. The photocatalytic degradation rate curve of methyl orange is the TF curve in Figure 3.

Claims (2)

1. A highly active nano-magnetic composite photocatalyst, characterized in that: the average particle diameter of the catalyst is 80nm to 100nm; the core material is an organically modified ferric oxide, and the shell material is a compound semiconductor of tin dioxide and titanium dioxide. The atomic ratio of titanium, tin and iron in the catalyst is: (75-80): (10-15): (5-10). 2. A method for preparing the highly active nano-magnetic composite photocatalyst according to claim 1, characterized in that it comprises the following steps: (1) Preparation of alcohol-based Fe ₃ O ₄ magnetic fluid Preparation of nanometer Fe ₃ O ₄ magnetic fluid by co-precipitation method: according to the molar ratio of Fe ²⁺ and Fe ³⁺ as 1:2~2:3, the prepared 0.25mol/L~0.5mol/L FeCl ₂ solution and 0.25 mol/L～0.5mol/L FeCl ₃ solution and polyethylene glycol 4000 solution or diethanolamine solution are added in the four-necked flask equipped with mechanical stirring, wherein the mass percentage of polyethylene glycol 4000 or diethanolamine in the reaction solution is 1% to 2%; heat in a constant temperature water bath at 60°C to 80°C, and at the same time pass through nitrogen for protection, slowly add 1mol/L to 2mol/L NaOH solution dropwise, until the pH value reaches 6 to 7, there will be black Fe ₃ O ₄ particles appear, continue to add alkali, adjust the pH value to 11-12, raise the temperature to 80°C-90°C, and age; wash the prepared Fe ₃ O ₄ particles with deionized water until neutral, and then wash them with absolute ethanol After washing and magnetic precipitation, dilute with absolute ethanol and disperse ultrasonically to make alcohol-based Fe ₃ O ₄ magnetic fluid; (2) Preparation of tin dioxide sol Use tin dichloride or tin tetrachloride as the raw material, add it to absolute ethanol, prepare a solution of 0.2mol/L~0.5mol/L, reflux under magnetic stirring conditions, and obtain a colorless transparent sol, and age for 12h~ After 24 hours, slowly add 1mol/L～10mol/L NH ₃ ·H ₂ O dropwise to form a milky white gel, wash with deionized water, then wash with alcohol until there is no chloride ion, filter after washing, and transfer the filter cake into absolute ethanol , ultrasonically dispersed to form tin dioxide sol; (3) Preparation of composite photocatalyst gel The atomic ratio of titanium to tin is 8:1 to 5:1, and the atomic ratio of titanium to iron is 7.5:1 to 16:1; take the above tin dioxide sol, add tetrabutyl titanate, ultrasonically disperse, age, and then add the above Alcohol-based Fe ₃ O ₄ magnetic fluid is ultrasonically dispersed to form solution A; the molar ratio of acid-titanium (H ⁺ /Ti) is 0.05:1-0.2:1, the molar ratio of titanium alkoxide is 9:1-18:1, water The molar ratio of titanium is 2.8:1 to 5.6:1; add deionized water to absolute ethanol, add nitric acid dropwise, and ultrasonically disperse to prepare solution B; under vigorous mechanical stirring, slowly drop solution B into solution A, until the gel is formed; (4) Heat treatment of the gel Vacuum-dry the gel at 70°C-90°C, grind it, and heat it in a muffle furnace under a nitrogen atmosphere. The temperature is raised at 1°C/min from 25°C to 250°C, and at 2°C/min above 250°C. Raise the temperature to 450°C-650°C, keep it warm for more than 1 hour, and turn off the nitrogen gas when it cools down to below 150°C.

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