CN115709070A

CN115709070A - Photocatalyst for carbon dioxide reduction reaction and preparation method thereof

Info

Publication number: CN115709070A
Application number: CN202211389874.1A
Authority: CN
Inventors: 豆义波; 罗丛佳; 杨宇森; 李泽洋; 许恩泽; 卫敏
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2022-11-08
Filing date: 2022-11-08
Publication date: 2023-02-24
Anticipated expiration: 2042-11-08
Also published as: CN115709070B

Abstract

The invention discloses a photocatalyst for carbon dioxide reduction reaction and a preparation method thereof, and relates to the technical field of catalyst preparation. Defective Ni of the present invention ^Vo Ti ^Vo the-LDH photocatalyst is prepared by the following method: synthesizing layered ZnNiAlTi-LDH by adopting a urea coprecipitation method, and then removing Zn and Al elements in the layered ZnNiAlTi-LDH by alkali etching. Compared with the traditional NiTi-LDH (Ni) after the defection treatment is carried out in the invention ²⁺ And Ti ³⁺ ) The metal valence state of the metal is obviously changed, a large number of metal vacancies are generated, the corresponding photocatalytic activity is obviously improved, and the catalytic material is used for photocatalytic CO ₂ Reduction to CH ₄ Has high yield and high selectivity.

Description

Photocatalyst for carbon dioxide reduction reaction and preparation method thereof

Technical Field

The invention relates to the technical field of catalyst preparation, in particular to a photocatalyst for carbon dioxide reduction reaction and a preparation method thereof.

Background

With the rapid development of the chemical field, the consumption of fossil fuels such as coal, petroleum and natural gas is increased greatly, the emission of carbon dioxide reaches the new height continuously, the problems of serious global energy crisis, greenhouse effect and the like are caused, and the living development of human beings is seriously influenced. Photocatalytic technology is believed to achieve CO ₂ Potential key technologies for resource utilization and development of novel solar clean energy are provided. Photocatalytic CO ₂ The reduction is to utilize renewable solar energy to convert CO ₂ The reaction conditions in the process are mild, the environment is protected, and the method is regarded as one of effective ways for solving potential energy crisis and environmental pollution.

In the aspect of synthesis design of the catalyst, the control of the structural characteristics and the photocatalyst activity of the catalyst by strategies such as noble metal loading, metal doping, heterojunction construction, defect construction and the like has been explored. Based on the knowledge in the aspect of basic principle, people find that the separation efficiency of photo-generated electrons and holes of the catalyst in the photocatalysis process can be improved by utilizing strategies such as energy band regulation, defect engineering and the like, and the method has a remarkable effect on the aspect of improving the photocatalytic activity. Nevertheless, many challenges still remain in widening the spectral response range of the catalyst, reducing electron-hole recombination, and promoting electron migration to the surface of the catalyst to participate in redox reactions. Therefore, how to design and synthesize a novel photocatalyst and improve the photocatalytic performance becomes one of the important problems to be solved urgently.

Layered Double Hydroxides (LDHs) are two-dimensional Layered anion materials with brucite structure. The main body laminate is formed by highly dispersing hydroxides of divalent and trivalent metal ions with covalent bonds, and is rich in positive charges; the interlayer anions are orderly arranged to balance the charges of the main body layer plate by electrostatic acting force, and the interlayer anions and the main body layer plate are orderly arranged. On one hand, the LDHs have the characteristics of adjustable metal cations of the main body layer plate and exchangeable anions between layers, and the energy band structure of the LDHs serving as the photocatalyst is easy to adjust and control, so that the LDHs can be applied to different photocatalytic fields. On the other hand, the synthesis methods of the LDHs are various, and the synthesis methods such as a hydrothermal synthesis method, a double-drop method, a nucleation crystallization isolation method, a stripping method and the like which are developed in the early stage can regulate and control the structural characteristics of the LDHs such as morphology and size, laminate thickness, defects and the like, so that the electronic structure of the material is changed, and the catalytic performance is improved. Although previous people have conducted extensive research on LDHs photocatalysts, the use of LDHs reported earlier for photocatalysis still has a large room for improvement in terms of carrier mobility, spectral absorption range, and surface catalytic active sites. The reason is that stacking or aggregation is caused by strong interaction between layers of the LDHs, so that the problems of weak light absorption capacity, easy recombination of photo-generated electrons and holes in a bulk phase, insufficient exposure of active sites and the like are caused, and the improvement of the photocatalytic performance and subsequent application are seriously restricted. Therefore, how to obtain the LDHs derivative photocatalytic material with wide spectral absorption range, strong electron-hole separation capability, good stability and practical application potential still faces many challenges.

Disclosure of Invention

The invention aims to provide a photocatalyst for carbon dioxide reduction reaction and a preparation method thereof, which are used for solving the problems in the prior art so as to ensure CO ₂ High efficiency reduction to CH ₄ 。

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a defective Ni ^Vo Ti ^Vo -LDH photocatalyst, prepared by the following method: synthesizing layered ZnNiAlTi-LDH by a urea coprecipitation method, and removing Zn and Al elements in the layered ZnNiAlTi-LDH by alkali etching.

The present invention also provides the above-mentioned defective Ni ^Vo Ti ^Vo -LDH photo-catalysisCatalyst for photocatalytic CO ₂ Application in reduction reaction.

Further, the defective state Ni ^Vo Ti ^Vo Use of LDH photocatalysts for photocatalytic CO ₂ Reduction to produce methane.

The present invention further provides Ni in the above-mentioned defective state ^Vo Ti ^Vo -a method for preparing an LDH photocatalyst, comprising the steps of:

synthesizing layered ZnNiAlTi-LDH by a urea coprecipitation method, and removing relatively inert Zn and Al elements in the layered ZnNiAlTi-LDH by alkali etching to prepare defect-state Ni ^Vo Ti ^Vo -an LDH photocatalyst.

Further, the method specifically comprises the following steps:

(1) Preparation of flaky ZnNiAlTi-LDH: in the presence of hydrochloric acid, carrying out coprecipitation reaction on zinc nitrate, nickel nitrate, aluminum nitrate, titanium tetrachloride and urea in water, and after the reaction is finished, centrifuging, washing and drying to obtain the flaky ZnNiAlTi-LDH;

(2) Defective state Ni ^Vo Ti ^Vo Preparation of LDH photocatalyst: soaking the flaky ZnNiAlTi-LDH in an alkali solution, centrifuging, washing and drying after soaking to obtain the defective Ni ^Vo Ti ^Vo -an LDH photocatalyst.

Furthermore, the concentrations of the zinc nitrate, the nickel nitrate, the aluminum nitrate, the titanium tetrachloride and the urea in the coprecipitation system are all 0.001-1 mol L ^-1 。

Specifically, the preparation method can be prepared in the following way:

dissolving zinc nitrate, nickel nitrate and aluminum nitrate in deionized water, and dissolving by ultrasonic oscillation to obtain a mixed salt solution; and adding a mixed solution of titanium tetrachloride and hydrochloric acid into the mixed salt solution, and finally adding urea for coprecipitation.

Among them, the total concentration of zinc nitrate and nickel nitrate is preferably 0.01mol L ^-1 (ii) a The total concentration of aluminum nitrate and titanium tetrachloride is preferably 0.05mol L ^-1 (ii) a Concentrated hydrochloric acid is taken, so that the concentration of the hydrochloric acid in the system is preferably 0.05mol L ^-1 (ii) a The urea solution is preferably 0.75mol L ^-1 。

Further, the coprecipitation reaction is as follows: reacting for 8-36 h at the constant temperature of 80-150 ℃.

Further, the coprecipitation reaction is: the reaction is carried out for 24h at a constant temperature of 90 ℃.

Further, the alkali solution is a potassium hydroxide solution; the concentration of the potassium hydroxide solution is 0.1-8 mol L ^-1 . Preferably 6mol L ^-1 。

Further, the soaking time in the step (2) is 1-10 h. Preferably 3 hours.

In the step (2), the soaking process is an alkali etching process, and the process is repeated for 3 times.

The invention provides a defective Ni ^Vo Ti ^Vo -LDH photocatalytic material and preparation method thereof, wherein the material is two-dimensional nanosheet and defected Ni ^Vo Ti ^Vo -LDH compared to conventional NiTi-LDH (Ni) ²⁺ And Ti ³⁺ ) The valence state of the metal is obviously changed, and simultaneously, the generated large amount of metal vacancies obviously improve the corresponding photocatalytic activity, and the catalytic material is used for photocatalysis of CO ₂ Reduction to CH ₄ Has high yield and high selectivity.

The invention discloses the following technical effects:

the invention takes quaternary ZnNiAlTi-LDH as a template, removes relatively inert Zn and Al by alkali etching to cause the generation of Ni vacancies and Ti vacancies of an LDH laminate, and constructs Ni in a defect state ^Vo Ti ^Vo -LDH. In the aspect of photocatalytic performance, the formation of defects adjusts the electronic structure of the catalyst, reduces the band gap width and obviously improves the photocatalytic CO ₂ Yield and selectivity of conversion to methane; in production application, the preparation method is simple and novel, low in synthesis cost and easy for batch production; in the aspect of universality of the preparation method, the two-dimensional defect state layered double hydroxide constructed by the invention catalyzes CO in a way of being compared with the original NiTi-LDH photocatalysis ₂ Reduction to CH ₄ The yield and the selectivity are obviously improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 shows Ni in a defective state in example 1 of the present invention ^Vo Ti ^Vo -an X-ray powder diffraction pattern of the LDH photocatalyst;

FIG. 2 is an X-ray powder diffraction pattern of a NiTi-LDH photocatalyst containing no metal vacancies according to example 2 of the present invention;

FIG. 3 shows Ni in a defective state in example 1 of the present invention ^Vo Ti ^Vo -scanning electron microscopy of LDH photocatalyst;

FIG. 4 is a scanning electron microscope photograph of ZnNiAlTi-LDH in example 2 of the present invention;

FIG. 5 is a scanning electron microscope photograph of a NiTi-LDH photocatalyst without metal vacancies according to example 2 of the present invention;

FIG. 6 shows Ni in a defective state in example 1 of the present invention ^Vo Ti ^Vo -Ni 2p X-ray photoelectron spectra of LDH photocatalyst and NiTi-LDH photocatalyst without metal vacancies of example 2;

FIG. 7 shows Ni in a defective state in example 1 of the present invention ^Vo Ti ^Vo -the Ti 2p X-ray photoelectron spectra of the LDH photocatalyst and the NiTi-LDH photocatalyst without metal vacancies of example 2;

FIG. 8 shows Ni in a defective state in example 1 of the present invention ^Vo Ti ^Vo -O1 s X-ray photoelectron spectra of LDH photocatalyst and NiTi-LDH photocatalyst without metal vacancies of example 2;

FIG. 9 shows Ni in a defective state in example 1 of the present invention ^Vo Ti ^Vo -a catalytic performance diagram of the LDH photocatalyst catalyzing reduction of carbon dioxide to methane;

FIG. 10 is a graph of the catalytic performance of a NiTi-LDH photocatalyst without metal vacancies to catalyze the reduction of carbon dioxide to methane in accordance with example 2 of the present invention;

FIG. 11 shows Ni containing Ni defects in example 3 of the present invention ^Vo Ti-A catalytic performance diagram of the LDH photocatalyst catalyzing the reduction of carbon dioxide into methane;

FIG. 12 is a graph showing the catalytic performance of a NiTi-LDH photocatalyst containing Ti defects for catalyzing the reduction of carbon dioxide to methane in example 4 of the present invention;

FIG. 13 shows Ni in a defective state in example 1 of the present invention ^Vo Ti ^Vo Graph of selectivity of catalytic reduction of carbon dioxide to methane by-LDH, niTi-LDH photocatalyst without metal vacancies in example 2.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but rather as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in the present disclosure, it is understood that each intervening value, to the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the documents are cited. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

Example 1

Step 1: weighing 0.535g of zinc nitrate, 5.240g of nickel nitrate and 0.518g of aluminum nitrate, dissolving in 100mL of deionized water, and performing ultrasonic dissolution to obtain a solution I; adding 97uL of titanium tetrachloride and 97uL of hydrochloric acid into 100mL of deionized water, and uniformly stirring to obtain a solution II; weighing 4.5g of urea, dissolving in 100mL of deionized water, and performing ultrasonic dissolution to obtain a homogeneous solution III;

adding the solution I and the solution II into the solution III to obtain a mixed solution, wherein: the concentration of zinc nitrate is 0.006mol L ^-1 The concentration of nickel nitrate is 0.054mol L ^-1 The concentration of aluminum nitrate is 0.018mol L ^-1 Titanium tetrachloride concentration of 0.042mol L ^-1 The concentration of hydrochloric acid is 0.057mol L ^-1 The concentration of urea is 0.75mol L ^-1 ；

Keeping the obtained mixed solution at the constant temperature of 90 ℃ for 24 hours; centrifuging, washing and drying to obtain flaky quaternary ZnNiAlTi-LDH powder (figure 4 is a scanning electron microscope picture of the flaky quaternary ZnNiAlTi-LDH powder);

step 2: placing the sheet-shaped quaternary ZnNiAlTi-LDH powder prepared in the step 1 in 6mol L ^-1 Soaking in potassium hydroxide solution for 3h for etching, centrifugally washing, drying, repeating the etching process for three times to prepare defective Ni ^Vo Ti ^Vo -an LDH photocatalyst.

For the defect state Ni obtained by preparation ^Vo Ti ^Vo LDH photocatalysts were subjected to performance tests:

weighing the prepared Ni in the defect state ^Vo Ti ^Vo 30mg of LDH photocatalyst and 100uL of deionized water, which were uniformly placed in an off-line photocatalytic reactor having a volume of 50 mL. High-purity carbon dioxide was used as a reaction atmosphere, and light irradiation was performed under normal pressure using a 300W xenon lamp. Sampling at intervals, using gasAnd (5) analyzing the result by using a phase chromatography.

Example 2

Step 1: weighing 2.620g of nickel nitrate, dissolving the nickel nitrate in 100mL of deionized water, and performing ultrasonic treatment to obtain a homogeneous solution I; adding 126uL of titanium tetrachloride and 126uL of hydrochloric acid into 100mL of deionized water, and uniformly stirring to obtain a solution II; weighing 4.5g of urea, dissolving in 100mL of deionized water, and performing ultrasonic treatment to obtain a homogeneous solution III;

adding the first solution and the second solution into the third solution to obtain a mixed solution, wherein: the concentration of the nickel nitrate is 0.06mol L ^-1 Titanium tetrachloride concentration of 0.02mol L ^-1 The hydrochloric acid concentration is 0.027mol L ^-1 The concentration of urea is 0.75mol L ^-1 ；

Keeping the temperature of the mixed solution at 90 ℃ for 24 hours; centrifuging, washing and drying to obtain NiTi-LDH powder.

Step 2: to demonstrate the performance improvement due to the etching away of the laminates Zn, al to create metal vacancies rather than the effect of KOH, the NiTi-LDH powder prepared in step 1 also needs to be placed at 6mol L ^-1 Soaking in the potassium hydroxide solution for 3h for etching, centrifugally washing, drying, and repeating the etching process for three times to prepare the NiTi-LDH photocatalyst without metal vacancies.

Since Ni and Ti are not amphoteric substances, they cannot be etched away, and thus cannot generate metal vacancies.

The performance of the NiTi-LDH photocatalyst prepared in example 2, which did not contain metal vacancies, was tested in the same manner as in example 1.

Example 3

Step 1: weighing 0.446g of zinc nitrate and 2.183g of nickel nitrate, dissolving in 100mL of deionized water, and performing ultrasonic treatment to obtain a homogeneous solution I; adding 126uL of titanium tetrachloride and 126uL of hydrochloric acid into 100mL of deionized water, and uniformly stirring to obtain a solution II; weighing 4.5g of urea, dissolving in 100mL of deionized water, and performing ultrasonic treatment to obtain a homogeneous solution III;

adding the first solution and the second solution into the third solution to obtain a mixed solution, wherein: the concentration of zinc nitrate is 0.005mol L ^-1 The concentration of nickel nitrate is 0.05mol L ^-1 Titanium tetrachloride concentration of 0.02mol L ^-1 Hydrochloric acid concentration of 0.027mol L ^-1 The concentration of urea is 0.75mol L ^-1 ；

Keeping the temperature for 24 hours at the temperature of 90 ℃; and centrifuging, washing and drying to obtain the flaky ternary ZnNiTi-LDH powder.

And 2, step: placing the powder prepared in the step 1 in 6mol L ^-1 Soaking in potassium hydroxide solution for 3h for etching, centrifugally washing, drying, repeating the etching process for three times to prepare Ni containing Ni vacancies ^Vo A Ti-LDH photocatalyst.

Ni prepared in example 3 was treated in the same manner as in example 1 ^Vo And (3) carrying out performance test on the Ti-LDH photocatalyst.

Example 4

Step 1: weighing 2.620g of nickel nitrate and 0.848g of aluminum nitrate, dissolving in 100mL of deionized water, and performing ultrasonic treatment to obtain a homogeneous solution I; adding 80.47uL of titanium tetrachloride and 80.47uL of hydrochloric acid into 100mL of deionized water, and uniformly stirring to obtain a solution II; weighing 4.5g of urea, dissolving the urea in 100mL of deionized water, and performing ultrasonic treatment to obtain a homogeneous solution III;

adding the first solution and the second solution into the third solution to obtain a mixed solution, wherein: the concentration of the nickel nitrate is 0.06mol L ^-1 The concentration of aluminum nitrate is 0.0075mol L ^-1 Titanium tetrachloride concentration of 0.0125mol L ^-1 The concentration of hydrochloric acid is 0.017mol L ^-1 The concentration of urea is 0.75mol L ^-1 ；

Keeping the temperature at 90 ℃ for 24 hours; and centrifuging, washing and drying to obtain the flaky ternary NiAlTi-LDH powder.

And 2, step: placing the powder prepared in the step 1 in 6mol L ^-1 Soaking in the potassium hydroxide solution for 3h for etching, centrifugally washing, drying, repeating the etching process for three times to prepare the NiTi containing Ti vacancies ^Vo -an LDH photocatalyst.

NiTi obtained in example 4 was subjected to the same procedure as in example 1 ^Vo LDH photocatalysts were subjected to performance tests.

Structural morphology characterization of photocatalytic materials prepared in examples 1-2:

FIG. 1 and FIG. 2 are Ni in a defective state as in example 1 ^Vo Ti ^Vo -X-ray powder diffraction patterns of LDH photocatalyst and NiTi-LDH photocatalyst of example 2 without metal vacancies; FIGS. 3 to 5 are Ni defect states of example 1 ^Vo T ^Vo Scanning electron microscopy images of-LDH, example 2ZnNiAlTi-LDH, and example 2 NiTi-LDH photocatalyst without metal vacancies.

Electronic structure characterization of photocatalytic materials prepared in examples 1-2:

FIG. 6 shows defective Ni of example 1 ^Vo Ti ^Vo -Ni 2p X-ray photoelectron spectra of LDH photocatalyst and NiTi-LDH photocatalyst without metal vacancies of example 2; FIG. 7 shows defective Ni of example 1 ^Vo Ti ^Vo The Ti 2p X-ray photoelectron spectra of the-LDH photocatalyst and of the NiTi-LDH photocatalyst without metal vacancies of example 2.

As can be seen from fig. 6 and 7, after etching, the + 2-valent Ni moves to high binding energy, and the valence state rises; ti (titanium) ⁴⁺ /Ti ³⁺ The peak area ratio is increased and the valence state is increased. Therefore, the defect treated is compared with the traditional NiTi-LDH (Ni) ²⁺ And Ti ³⁺ ) The valence state of the metal is obviously changed.

FIG. 8 shows defective Ni of example 1 ^Vo Ti ^Vo O1s X-ray photoelectron spectra of LDH photocatalyst and NiTi-LDH photocatalyst of example 2 without metal vacancies; in FIG. 8, the presence of oxygen vacancies can be seen from the partial peak fitting of O1s, from which it is possible to prove Ni after etching ^Vo Ti ^Vo LDH is in the defect state.

Characterization of the catalytic properties of the photocatalytic materials prepared in examples 1-4:

FIGS. 9 to 12 show Ni in the defective state in example 1 ^Vo Ti ^Vo LDH, niTi-LDH containing no metal vacancies of example 2, ni containing Ni vacancies of example 3 ^Vo Ti-LDH, example 4 NiTi containing Ti vacancies ^Vo -catalytic performance diagram of LDH photocatalyst catalyzing the reduction of carbon dioxide to methane.

FIG. 13 shows defective Ni of example 1 ^Vo Ti ^Vo LDH photocatalyst and NiTi-LDH photocatalyst without Metal vacancies of example 2Selectivity profile for catalytic reduction of carbon dioxide to methane.

The invention respectively takes quaternary ZnNiAlTi-LDH, ternary ZnNiTi-LDH and ternary NiAlTi-LDH as precursors, and establishes defect state Ni with photocatalytic carbon dioxide reduction performance by alkali etching ^Vo Ti ^Vo LDH, ni containing Ni vacancies ^Vo Ti-LDH, niTi containing Ti vacancy ^Vo -a photocatalyst for LDH. Ni containing both Ni and Ti vacancies therein ^Vo Ti ^Vo LDH is the target catalyst, and has the optimal performance of preparing methane by photocatalytic carbon dioxide reduction. The catalyst is in a multi-level structure consisting of nano sheets, and is favorable for diffusion of reaction substrates and products. Ni respectively containing different defect states is constructed by adjusting doping of precursors into Zn/Al, doping of Zn only and doping of Al only ^Vo Ti ^Vo -LDH、Ni ^Vo Ti-LDH、NiTi ^Vo -LDH. The method adjusts the band gap width and the positions of a conduction band and a valence band of the semiconductor catalyst, thereby accelerating the separation of photogenerated charges and a hole and improving the utilization rate of current carriers. In addition, ni containing Ni vacancy and Ti vacancy simultaneously is controlled by fundamentally adjusting and controlling the electronic structure ^Vo Ti ^Vo The LDH conduction band position is the lowest, the selectivity to methane is improved, and the catalytic material finally realizes the selectivity to CO ₂ Excellent photocatalytic activity is reduced. The photocatalytic material is used for photocatalytic CO ₂ The yield and the selectivity of the reduction to generate the methane are high. In addition, the synthesis method of the defect state catalyst is simple and novel, and is easy for batch production.

The above-described embodiments are only intended to illustrate the preferred embodiments of the present invention, and not to limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. Defective Ni ^Vo Ti ^Vo -LDH photocatalyst, characterized in that it is prepared by the following method: synthesizing sheet ZnNiAlTi-LDH by urea coprecipitation method, and removing the ZnNiAlTi-LDH by alkali etchingZn and Al elements in the flaky ZnNiAlTi-LDH.

2. The defective Ni of claim 1 ^Vo Ti ^Vo -LDH photocatalyst in photocatalytic CO ₂ Application in reduction reactions.

3. The defective Ni of claim 1 ^Vo Ti ^Vo -a method for preparing an LDH photocatalyst, comprising the steps of:

synthesizing flaky ZnNiAlTi-LDH by a urea coprecipitation method, and removing Zn and Al elements in the flaky ZnNiAlTi-LDH by alkali etching to prepare defect-state Ni ^Vo Ti ^Vo -an LDH photocatalyst.

4. The preparation method according to claim 3, characterized by comprising the following steps:

(2) Defective state Ni ^Vo Ti ^Vo Preparation of LDH photocatalysts: soaking the flaky ZnNiAlTi-LDH in an alkali solution, centrifuging, washing and drying after soaking to obtain the defective Ni ^Vo Ti ^Vo -an LDH photocatalyst.

5. The method according to claim 4, wherein the concentrations of the zinc nitrate, the nickel nitrate, the aluminum nitrate, the titanium tetrachloride and the urea in the coprecipitation system are each 0.001 to 1mol L ^-1 。

6. The preparation method according to claim 4, wherein the coprecipitation reaction is: reacting for 8-36 h at the constant temperature of 80-150 ℃.

7. The preparation method according to claim 6, wherein the coprecipitation reaction is: the reaction is carried out for 24h at a constant temperature of 90 ℃.

8. The production method according to claim 4, wherein the alkali solution is a potassium hydroxide solution; the concentration of the potassium hydroxide solution is 0.1-8 mol L ^-1 。

9. The method according to claim 4, wherein the soaking time in the step (2) is 1 to 10 hours.