Titanium dioxide coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of metal corrosion protection and photocatalytic degradation, and particularly relates to a titanium dioxide coating as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, adding sodium chloride in the process of preparing nano TiO2 by using a hydrothermal method to regulate and control the surface hydroxyl content, and then uniformly mixing the prepared NaCl-TiO2 active substance with a binder and water to prepare slurry; and finally, performing blade coating on the slurry to prepare a coating, and performing drying and cross-linking reaction to obtain the titanium dioxide coating. The titanium dioxide coating prepared by the method is a coating with a high cross-linked network, has excellent photoelectric cathode protection and photocatalytic degradation coupling performance, and can be used in the fields of metal corrosion protection, organic pollutant degradation and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of metal corrosion protection and photocatalytic degradation, and specifically relates to a titanium dioxide coating and a preparation method and application thereof. Background Art

[0002] Under complex and challenging natural conditions, metal materials face multiple challenges such as high salinity and oxygen enrichment. In the process of rapid industrial development, the content of harmful substances such as organic pollutants in water bodies is also gradually increasing. In this context, many anti-corrosion measures have been developed, among which the most direct and widely used anti-corrosion effect is cathodic protection technology. Cathodic protection technology is generally divided into two types, one is the cathodic protection method of external circuit, and the other is the cathodic protection method of sacrificial anode, but these methods often cause environmental pollution and a large amount of energy consumption, and are not an economical protection method. Therefore, it is particularly important to develop green and environmentally friendly anti-corrosion technology and catalytic degradation technology.

[0003] Photocathode protection is an advanced technology for metal corrosion protection, and its basic principle is the photoelectric effect. Photocathode protection does not require external power or external current input. It can use the energy of sunlight to stimulate the photoelectric effect, thereby generating a protective potential. At the same time, it does not produce byproducts such as wastewater, waste gas or waste liquid that pollute the environment. It is a clean and environmentally friendly anti-corrosion technology that meets the requirements of sustainable development. At the same time, similar to photocathode protection technology, photocatalytic degradation technology can efficiently convert organic pollutants into non-toxic small molecules with the help of the photoelectric conversion characteristics of semiconductors.

[0004] The core of photocathode protection and photocatalytic degradation technology is semiconductor materials. At present, the commonly used semiconductor is mainly TiO2. When TiO2 is exposed to light, it can excite photogenerated electrons. These electrons can migrate to the surface of the substrate, causing a polarization effect, thereby protecting the substrate material. Not only that, the free radical energy generated by photogenerated electrons / holes can also react with organic pollutants in the environment, causing them to degrade. Therefore, if the photocathode protection technology can be coupled with the photocatalytic degradation technology, it is expected to provide a new and potential solution for water pollution treatment and material corrosion protection. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a method for preparing a titanium dioxide coating. The titanium dioxide coating prepared by the method has excellent photoelectric cathode protection and photocatalytic degradation coupling performance. The photoelectric cathode protection and photocatalytic degradation technology can be coupled and applied to the fields of metal corrosion protection, degradation of organic pollutants and photolysis of water to produce hydrogen, and has broad application prospects.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] In the first aspect of the present invention, a method for preparing a titanium dioxide coating is provided, and the method includes the following steps:

[0008] S1. When preparing nano-TiO2 by the hydrothermal method, sodium chloride is added to regulate the amount of surface hydroxyl groups to obtain nano-NaCl-TiO2;

[0009] S2. Mix NaCl-TiO2, a binder, and water to form a slurry;

[0010] S3. Make the slurry described in S2 into a coating, and then obtain a titanium dioxide coating after drying and crosslinking reaction.

[0011] In the present invention, inorganic ions are introduced during the process of preparing TiO2 nanoparticles by the hydrothermal method to regulate the hydroxyl content on the surface of the material; at the same time, the three-dimensional cross-linked network structure formed by polyacrylic acid (PAA) and chitosan quaternary ammonium salt (QCS) is used to improve the stability and photoelectrochemical activity of the TiO2 coating; in addition, through the chemical interaction between the hydroxyl groups on the surface of TiO2 and the PAA / QCS interface, rapid electron migration on the TiO2 / PAA / QCS interface and the PAA / QCS chain is achieved, thereby improving the electron transport kinetics inside the material.

[0012] Preferably, S1 specifically includes the following steps:

[0013] S1. Mix tetrabutyl titanate, glacial acetic acid, acetone, and n-butanol to form solution ①, and mix sodium chloride and n-butanol to form solution ②, and then drop solution ② into solution ① under stirring to obtain a precursor solution;

[0014] S2. React the precursor solution at 220-260 °C for 4-8 h, and the heating rate is 3-7 °C·min -1 ;

[0015] S3. After the reaction, collect the precipitate, wash and dry it, and then calcine it in an air atmosphere at 400-500 °C for 1-3 h, and the heating rate is 3-7 °C min -1 , thus obtaining nano-NaCl-TiO2.

[0016] Preferably, the mass ratio of the NaCl-TiO2 to the binder is 8-10:1.

[0017] Preferably, the binder is a mixture of styrene-butadiene rubber, chitosan quaternary ammonium salt, and polyacrylic acid.

[0018] More preferably, the mass ratio of the styrene-butadiene rubber, chitosan quaternary ammonium salt, and polyacrylic acid is 2-4:1-2:1-3.

[0019] Preferably, the solid content of the slurry described in S2 is 15-30%.

[0020] Preferably, in the drying and cross-linking reaction of S3, the temperature is 120-180 °C, the vacuum degree is 0.1-0.3 MPa, and the time is 10-15 h.

[0021] The second aspect of the present invention provides a titanium dioxide coating prepared by the preparation method described in the first aspect.

[0022] In the titanium dioxide coating prepared by the method of the present invention, when the titanium dioxide is irradiated with light, it can excite photogenerated electrons, and these electrons can migrate to the surface of the substrate, triggering a polarization effect, thereby realizing the protection of the substrate material. Moreover, the free radicals generated by the photogenerated electrons / holes can also react with organic pollutants in the environment, and then degrade them.

[0023] The third aspect of the present invention provides the application of the titanium dioxide coating described in the second aspect in metal corrosion protection and / or degradation of organic pollutants.

[0024] The titanium dioxide coating prepared by the method of the present invention is a coating with a high cross-linked network. This coating has excellent coupling performance of photocathodic protection and photocatalytic degradation, and can be used in fields such as metal corrosion protection and degradation of organic pollutants.

[0025] Preferably, the organic pollutants include methyl orange, acid orange II, basic orange, and congo red.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] The present invention discloses a preparation method of a titanium dioxide coating. First, sodium chloride is added during the preparation of nano-TiO2 by the hydrothermal method to regulate the amount of surface hydroxyl groups. Then, the prepared NaCl-TiO2 active substance is mixed evenly with a binder and water to form a slurry. Finally, the slurry is scrape-coated to form a coating and then subjected to drying and cross-linking reaction to obtain a titanium dioxide coating. The present invention uses titanium dioxide and a binder as raw materials, and prepares a titanium dioxide coating by controlling the reaction conditions. The titanium dioxide coating can enhance the photoelectrochemical stability of the original TiO2 particles during the photocapacitance protection process. At the same time, the three-dimensional cross-linked network structure in the titanium dioxide coating improves the charge transfer efficiency of the material, and further improves the cathodic protection performance of the material. It can be used in fields such as metal corrosion protection, degradation of organic pollutants, and photocatalytic water splitting for hydrogen production. Description of the Drawings

[0028] Figure 1 FT-IR diagrams of the NaCl-TiO2 raw material and the TiO2 raw material in Example 1.

[0029] Figure 2XRD patterns of the NaCl-TiO2 raw material and TiO2 raw material in Example 1.

[0030] Figure 3 XRD patterns of the titanium dioxide coatings prepared in Examples 1 to 3.

[0031] Figure 4 TEM images of the titanium dioxide coatings prepared in Examples 1 and 3; (a-c) are TiO2 coatings at different magnifications; (d-f) are NaCl-TiO2 coatings at different magnifications.

[0032] Figure 5 Photocatalytic open-circuit potential diagrams (a), photocurrent density diagrams (b), and polarization curves (c) of the titanium dioxide coatings prepared in Examples 1 to 3.

[0033] Figure 6 SEM images of the titanium dioxide coatings prepared in Examples 1 to 3; (a-c) are NaCl-TiO2-PAA at different magnifications; (d-f) are NaCl-TiO2-PAA-QCS at different magnifications; (g-i) are TiO2-PAA-QCS at different magnifications.

[0034] Figure 7 SEM images of the titanium dioxide coatings prepared in Examples 1, 4, and 5; (a-c) are NaCl-TiO2-PAA-QCS-120 at different magnifications; (d-f) are NaCl-TiO2-PAA-QCS-150 at different magnifications; (g-i) are NaCl-TiO2-PAA-QCS-180 at different magnifications.

[0035] Figure 8 XRD patterns of the titanium dioxide coatings prepared in Examples 1, 4, and 5.

[0036] Figure 9 Photocatalytic open-circuit potential (a), photocurrent density diagram (b), polarization curve (c), EIS-Nyquist diagram (d), Mott-Schottky curve (e), and long-term OCP curve (f) of the titanium dioxide coatings prepared in Examples 1, 4, and 5.

[0037] Figure 10 Performance test results of the photoelectrochemical cathodic protection coupled with photocatalytic degradation of the titanium dioxide coatings prepared in Examples 1, 4, and 5.

[0038] Figure 11Characterization of the corrosion morphology on the coating surface; (a) is the initial microscope photo of 304 stainless steel; (b) is the microscope photo of 304 stainless steel immersed in simulated seawater in the dark state for 12 h; (c) is the microscope photo of 304 stainless steel immersed in the dark state for 12 h after being coated with the NaCl-TiO2-PAA-QCS-150 coating. Detailed implementation manners

[0039] The following further describes the detailed implementation manners of the present invention. It should be noted here that the description of these implementation manners is for helping to understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various implementation manners of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] The experimental methods in the following examples are all conventional methods unless otherwise specified, and the test materials used in the following examples are all available through conventional commercial channels unless otherwise specified.

[0041] Example 1:

[0042] This example provides a preparation method of a titanium dioxide coating, including the following steps:

[0043] (1) When preparing nano-TiO2 by the hydrothermal method, sodium chloride is added to regulate the amount of surface hydroxyl groups, denoted as NaCl-TiO2:

[0044] 1) Add 10 mL of tetrabutyl titanate, 10 mL of glacial acetic acid, and 10 mL of acetone to 60 mL of n-butanol and stir vigorously to prepare solution ① for standby.

[0045] 2) Mix 3 mL of sodium chloride with a molar fraction of 2% and 30 mL of n-butanol evenly to prepare solution ② for standby.

[0046] 3) Slowly drop solution ② into solution ① under vigorous stirring to obtain the precursor solution for preparation.

[0047] 4) Continuously stir vigorously at a stirring speed of 600 r·min -1 for 2 h, then transfer the solution to an autoclave and react at 240 °C for 6 h, setting the heating rate to 5 °C·min -1 .

[0048] 5) After the reaction is completely finished, collect the product in the precipitate by centrifugation. The rotation speed of the centrifuge is set to 10,000 revolutions per minute, and the centrifugation time is 15 min to ensure that the product can be fully separated. Then, use anhydrous ethanol and deionized water to wash the collected product 3 times respectively. After washing, put the product into an oven for drying to remove moisture.

[0049] 6) After drying is completed, grind the sample into powder, and then put it into a muffle furnace for annealing treatment. In the muffle furnace, place the sample in an air atmosphere and calcine it at a temperature of 450 °C for 2 h while maintaining a heating rate of 5 °C / min -1 , and then nano-NaCl-TiO2 is obtained.

[0050] (2) Mix deionized water, NaCl-TiO2, and binder with a mass ratio of 40:9:1 evenly to obtain a slurry with a solid content of 20%; the binder is a mixture of styrene-butadiene rubber, chitosan quaternary ammonium salt, and polyacrylic acid, and the mass ratio of styrene-butadiene rubber, chitosan quaternary ammonium salt (substitution degree 98%, Shanghai Macklin Biochemical Co., Ltd.), and polyacrylic acid (molecular weight 450000) in the mixture is 3:1:2;

[0051] (3) After scraping and coating the slurry described in S2 on conductive glass FTO with a thickness of 6 μm, place the obtained coating under the conditions of a temperature of 150 °C and a vacuum degree of 0.1 MPa for cross-linking reaction for 12 h to obtain the titanium dioxide coating, denoted as NaCl-TiO2-PAA-QCS.

[0052] Example 2:

[0053] This example provides a method for preparing a titanium dioxide coating. Different from Example 1, sodium chloride is not added in step S1, denoted as TiO2-PAA-QCS.

[0054] Example 3:

[0055] This example provides a method for preparing a titanium dioxide coating. Different from Example 1, chitosan quaternary ammonium salt is not added in step S2, denoted as NaCl-TiO2-PAA.

[0056] Example 4:

[0057] This example provides a method for preparing a titanium dioxide coating. Different from Example 1, the vacuum temperature in step S3 is 120 °C.

[0058] Example 5:

[0059] This example provides a method for preparing a titanium dioxide coating. Different from Example 1, the vacuum temperature in step S3 is 180 °C.

[0060] Experimental example: Characterization of properties and performance testing

[0061] Figure 1FT-IR spectra of the NaCl-TiO2 raw material and the TiO2 raw material in Example 1. During the test, 15 mg of powder was weighed for each tablet pressing to make the tablets for quantitative purposes for easy comparison. After normalization at the CO2 peak (2337 cm -1 ), it can be found that the hydroxyl peak of the TiO2 powder treated with NaCl at 3400 cm -1 is enhanced, indicating an increase in the number of hydroxyl groups.

[0062] Figure 2 XRD patterns of the NaCl-TiO2 raw material and the TiO2 raw material in Example 1. It can be seen from the figure that the treatment with NaCl effectively reduces the grain size of the sample without affecting the crystal structure of the raw material itself. As the grain size decreases, a more detailed and compact arrangement will be presented.

[0063] Figure 3 XRD patterns of the titanium dioxide coatings prepared in Examples 1 to 3. It can be seen from the figure that the addition of QCS does not cause a significant change in the crystal structure of TiO2, has little effect on the basic physical properties of TiO2, and maintains its original stable structure.

[0064] Figure 4 TEM images of the titanium dioxide coatings prepared in Example 1 and Example 3. As can be seen from Figure 4 it, the binder can crosslink titanium dioxides with different nano-sizes tightly together. The overlapping degree of the coating powder without adding QCS is higher, and the TiO2 nanoparticles are wrapped by an ultrathin amorphous material, indicating that the TiO2 nanoparticles in NaCl-TiO2-PAA-QCS are bridged by the PAA / QCS binder, and the TiO2 nanoparticles in NaCl-TiO2-PAA are bridged by the PAA binder. In contrast, the dispersion degree of the NaCl-TiO2-PAA-QCS coating powder is better and the thickness of the binder is larger, while the dispersion degree of the NaCl-TiO2-PAA coating powder is poor and the binder thickness is smaller. It is speculated that the chemical crosslinking between TiO2 and PAA / QCS is beneficial to improving the photogenerated carrier transfer and photoelectrochemical stability of the TiO2-based coating.

[0065] The photocathodic protection performance of the titanium dioxide coatings prepared in Examples 1 to 3 was tested. The test was carried out on an electrochemical workstation Gamry 1010E using a three-electrode single electrolytic cell system. Among them, 304 stainless steel metal loaded with the titanium dioxide coating was used as the working electrode, a 1×2 cm platinum sheet was used as the counter electrode of the system, and an Ag / AgCl standard reference electrode was used as the reference electrode of the system. The electrolyte in the electrolytic cell used a NaCl solution with a concentration of 3.5 wt%, aiming to simulate the marine environment. The above three electrodes were placed in the simulated seawater, and a xenon lamp source filtered by an AM1.5 simulated sunlight filter was used to simulate sunlight with a power of 100 mW·cm -2 of sunlight, and the test results were observed through the electrochemical workstation.

[0066] Figure 5 Figures are the photocatalytic open circuit potential diagrams, photocurrent density diagrams and polarization curves of the titanium dioxide coatings prepared in Examples 1 to 3. It can be seen from the figures that the NaCl-TiO2-PAA-QCS coating has the best optoelectronic performance, while the NaCl-TiO2-PAA coating has the worst optoelectronic performance, further indicating that the addition of QCS is beneficial to improving the optoelectronic performance of the coating. At the same time, the photocathodic protection performance potential of the TiO2-PAA-QCS coating is between the two, further indicating that the NaCl treatment has a positive regulatory effect on the photocatalytic performance of the nano-TiO2 coating, which is beneficial to improving its photocatalytic activity. In addition, the corrosion potential of NaCl-TiO2-PAA is the most positive and the photocathodic protection effect is the worst, and the corrosion potential of NaCl-TiO2-PAA-QCS is the most negative and the photocathodic protection effect is the best, which is consistent with the OCP and i-t results.

[0067] Figure 6 Figures are the SEM diagrams of the titanium dioxide coatings prepared in Examples 1 to 3. It can be seen from the figures that the coating prepared from the NaCl-TiO2-PAA slurry has the best flatness, followed by NaCl-TiO2-PAA-QCS, and the flatness of TiO2-PAA-QCS is the worst.

[0068] Figure 7SEM images of the titanium dioxide coatings prepared in Example 1, Example 4, and Example 5. As can be seen from the figures, with the increase in the vacuum drying temperature, the cracks on the coating surface increase significantly, and the surface becomes rougher. When the vacuum drying temperature is 150 °C, the coating surface is relatively flat, and the particle dispersion is the best; when the vacuum drying temperature is 180 °C, obvious agglomeration of the particles on the coating surface occurs; when the vacuum drying temperature is 120 °C, the particle dispersion of the coating is still worse than that at 150 °C. It shows that the drying temperature has a curvilinear effect on the dispersion of the coating, and the dispersion is the best when the temperature is about 150 °C. The cracks and particle agglomeration of the coating have an important impact on the stability and lifespan of the coating performance. Therefore, the vacuum drying temperature during the coating preparation process should not be too high or too low.

[0069] Figure 8 XRD patterns of the titanium dioxide coatings prepared in Example 1, Example 4, and Example 5. Since the powders used to prepare the coatings are the same, the vacuum drying temperature has little effect on the crystallinity of the NaCl-TiO2-PAA-QCS powder. It shows that the change in the vacuum temperature only affects the interaction force between the binder and the titanium dioxide surface, and has a limited effect on the grain size.

[0070] Figure 9 Photocatalytic open circuit potential diagrams, photocurrent density diagrams, polarization curves, EIS-Nyquist diagrams, Mott-Schottky curves, and long-term OCP curves of the titanium dioxide coatings prepared in Example 1, Example 4, and Example 5. The results show that in simulated seawater, the photocatalytic open circuit potential of NaCl-TiO2-PAA-QCS-150 is the lowest, and after cyclic testing, the OCP can still stably reach a relatively negative potential value. At the same time, the photocurrent density is as high as 73.3 μA·cm -2 , the corrosion potential is the most negative, -400.2 mV, further indicating that its photocathodic protection performance is the strongest, which is consistent with the OCP results. From the EIS test results of the samples ( Figure 9 d), it can be seen that NaCl-TiO2-PAA-QCS-150 shows significant advantages, with relatively small sample resistance and long lifespan. From the M-S curve of the samples ( Figure 9 e), it can be seen that the flat band potential of NaCl-TiO2-PAA-QCS-150 is the lowest, the free electron concentration is the highest, and the corresponding photocatalytic performance is the best. From the long-term OCP ( Figure 9As can be seen from Fig. f), NaCl-TiO2-PAA-QCS-150 still exhibits better performance, with the lowest photoinduced open-circuit potential, and it remains the lowest even when the potential reaches stability over time. In contrast, NaCl-TiO2-PAA-QCS-120 shows the worst performance in the above tests, while the long-term OCP (open-circuit potential) of NaCl-TiO2-PAA-QCS-180 is between the two at the beginning and then higher than that of the NaCl-TiO2-PAA-QCS-120 coating, indicating that the stability of the NaCl-TiO2-PAA-QCS-180 coating is poor. In addition, in the subsequent 12 h dark environment, the coating potential rises to a positive value, showing the corrosion protection effect of traditional coatings and can continue to protect the stainless steel. The above results fully demonstrate that the NaCl-TiO2-PAA-QCS material has excellent performance and stable properties in the field of stainless steel corrosion protection, indicating that the coating performance is the best when dried in vacuum at 150 °C.

[0071] To comprehensively evaluate the coupling performance of the photoelectrochemical cathodic protection and photocatalytic degradation processes, an electrolyte system of organic dye + brine was constructed, that is, methyl orange with a concentration of 5 mg·L -1 was added to a 3.5 wt% NaCl solution. In the dark environment, first, the titanium dioxide coating material was allowed to adsorb for 0.5 h to make the solution balance evenly. In the next 5 h, the material was exposed to light, and 0.5 mL of samples were taken regularly every 1 h for testing. After the reaction, the sample concentration was measured and the degradation performance of the coating was analyzed.

[0072] Figure 10 The test results of the coupling photocatalytic degradation performance of the photoelectrochemical cathodic protection for the titanium dioxide coatings prepared in Example 1, Example 4, and Example 5. The results show that after 5 h of degradation, the maximum degradation rates reached by the samples of NaCl-TiO2-PAA-QCS-120, NaCl-TiO2-PAA-QCS-150, and NaCl-TiO2-PAA-QCS-180 were 26.9%, 30.2%, and 22.3% respectively.

[0073] Figure 11 To characterize the corrosion morphology of the coating surface using an optical electron microscope. As can be seen from the figure, when there is no coating coverage, obvious rusting occurs on the 304 stainless steel after being immersed in simulated seawater (3.5 wt% NaCl solution) for 12 h. After the coating coverage, the rusting is significantly weakened and is similar to the surface of the 304SS in the initial state. This shows that the coating can utilize light for photoelectrochemical cathodic protection under light conditions and can act as a traditional anti-corrosion coating to physically isolate the carrier under dark conditions, thereby greatly increasing the applicability of the coating.

[0074] The above has described the embodiments of the present invention in detail, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions, and variations made to these embodiments still fall within the protection scope of the present invention.

Claims

1. A method for preparing a titanium dioxide coating, characterized in that, It includes the following steps: S1. When preparing nano-TiO2 by hydrothermal method, add sodium chloride to regulate the amount of surface hydroxyl groups to obtain nano-NaCl-TiO2; S2. Mix NaCl-TiO2, binder and water to make a slurry; S3. Make the slurry described in S2 into a coating, and then obtain a titanium dioxide coating after drying and cross-linking reaction.

2. The preparation method of a titanium dioxide coating according to claim 1, wherein, S1 specifically includes the following steps: S1. Mix tetrabutyl titanate, glacial acetic acid, acetone and n-butanol to make solution ①, and mix sodium chloride and n-butanol to make solution ②, and then drop solution ② into solution ① under stirring to obtain a precursor solution; S2. Place the precursor solution to react at 220 - 260 °C for 4 - 8 h, with a heating rate of 3 - 7 °C·min -1 ; S3. After the reaction, collect the precipitate, wash and dry it, and then calcine it in an air atmosphere at 400 - 500 °C for 1 - 3 h with a heating rate of 3 - 7 °C / min -1 , thus obtaining nano-NaCl-TiO₂.

3. The preparation method of a titanium dioxide coating according to claim 1, characterized in that, The mass ratio of the NaCl-TiO2 to the binder is 8-10:

1.

4. The preparation method of a titanium dioxide coating according to claim 1, characterized in that, The binder is a mixture of styrene-butadiene rubber, chitosan quaternary ammonium salt and polyacrylic acid.

5. A method for preparing a titanium dioxide coating according to claim 4, characterized in that, The mass ratio of the styrene-butadiene rubber, chitosan quaternary ammonium salt and polyacrylic acid is 2-4:1-2:1-3.

6. The preparation method of a titanium dioxide coating according to claim 1, characterized in that The solid content of the slurry described in S2 is 15-30%.

7. A method for preparing a titanium dioxide coating according to claim 1, characterized in that, In the drying and cross-linking reaction of S3, the temperature is 120-180 °C, the vacuum degree is 0.1-0.3 MPa, and the time is 10-15 h.

8. A titanium dioxide coating prepared by the preparation method according to any one of claims 1-7.

9. Application of the titanium dioxide coating according to claim 8 in metal corrosion protection and / or degradation of organic pollutants.

10. The application according to claim 9, characterized in that, The organic pollutants include methyl orange, acid orange II, basic orange and congo red.

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