Preparation method of TiO2 nano-array film rich in oxygen vacancies

Abstract

The application discloses a preparation method of TiO2 nano-array film rich in oxygen vacancies. The method comprises the following steps: depositing a TiO2 seed layer on a FTO surface, realizing structure rearrangement after annealing, then carrying out a hydrothermal reaction, and finally carrying out molten salt electro-deoxidization on the TiO2 nano-array film. In the molten salt electrolysis process, the TiO2 nano-array film at the cathode loses oxygen atoms to generate oxygen vacancies through an electrochemical reduction reaction, successfully introduces a defect energy level, reduces the band gap of TiO2, enhances the light absorption performance, maintains the nano-array structure of TiO2, significantly strengthens the separation and transmission of photo-generated carriers, and is expected to improve the photoelectrocatalytic water splitting performance of the TiO2 nano-array film as a photoelectrode. The TiO2 nano-array film rich in oxygen vacancies synthesized by the application can be prepared on a large scale in a controllable, repeatable and fast manner through the molten salt electrolysis equipment in a factory, is simple to operate, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of nanostructure modification technology, specifically relating to a method for preparing a TiO2 nanoarray thin film rich in oxygen vacancies. Background Technology

[0002] TiO2 is widely used as a photoelectrode in the field of solar photoelectrocatalytic water splitting for hydrogen production due to its advantages such as low preparation cost, good chemical stability, and suitable band structure. However, its large band gap (3.2 eV) means that TiO2 can only absorb less than 5% of the ultraviolet light in the solar spectrum, and photogenerated carrier recombination is severe. These shortcomings greatly limit the photoelectrocatalytic water splitting performance of TiO2 photoelectrodes. Defect engineering has been proven to be an effective way to modulate the band structure of semiconductor photoelectrodes and promote carrier transport. Oxygen vacancies, as a defect, can be introduced into TiO2 to generate intermediate energy levels, reduce the band gap of TiO2, increase the separation efficiency of photogenerated charges, and suppress carrier recombination, thereby greatly improving the photoelectrocatalytic water splitting performance of TiO2. For the introduction of oxygen vacancies into TiO2 photoanodes, researchers have proposed methods such as gas reduction, plasma treatment, and electrochemical reduction. Among these, gas reduction is the most studied, which involves annealing freshly prepared TiO2 in some reducing or inert gases. This method usually requires a long time and is difficult to implement.

[0003] Therefore, there is a need to provide a method for preparing TiO2 nanoarray thin films rich in oxygen vacancies. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for preparing a TiO2 nanoarray thin film rich in oxygen vacancies, addressing the shortcomings of the prior art. This method involves spin-coating a TiO2 seed layer onto an FTO surface, followed by annealing to achieve structural rearrangement. This significantly promotes the nucleation of TiO2 nanoparticles and the oriented growth of the array structure during the hydrothermal reaction. This invention utilizes hydrothermal synthesis and annealing to prepare a TiO2 nanoarray thin film with a rutile phase nanoarray structure, significantly shortening the transport path of photogenerated carriers, reducing the probability of charge recombination, and simultaneously increasing the active area for photoelectrocatalytic water splitting. Furthermore, this invention utilizes molten salt electrolysis for deoxygenation, achieving the synthesis of a TiO2 nanoarray rich in oxygen vacancies while maintaining stable nanostructure.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a TiO2 nanoarray thin film rich in oxygen vacancies, characterized in that the method includes the following steps:

[0006] Step 1: Dissolve tetrabutyl titanate in anhydrous ethanol to obtain seed solution;

[0007] Step two, the seed solution obtained in step one is coated on the surface of the cleaned FTO conductive substrate by spin coating, and then annealing treatment is carried out in an air atmosphere, so that the FTO conductive substrate with a TiO2 seed layer grown on the surface is obtained;

[0008] Step three, tetrabutyl titanate is dissolved in equal volume ratio of deionized water and concentrated hydrochloric acid to form a mixed solution, and the FTO conductive substrate with a TiO2 seed layer grown on the surface obtained in step two is placed in the mixed solution for hydrothermal reaction, so that a TiO2 nanoarray film is obtained on the surface of the FTO conductive substrate;

[0009] Step four, the TiO2 nanoarray film obtained in step three is annealed in an air atmosphere, so that a rutile phase TiO2 nanoarray film is obtained;

[0010] Step five, the TiO2 nanoarray film obtained in step four is deoxidized by molten salt electrolysis, so that a TiO2 nanoarray film rich in oxygen vacancies is obtained.

[0011] In the application, the TiO2 seed layer is deposited on the surface of the FTO by spin coating, and the structure rearrangement is realized after annealing treatment, which greatly promotes the nucleation of TiO2 nanoparticles and the oriented growth of the array structure in the hydrothermal reaction. The TiO2 nanoarray film with rutile phase nanoarray structure is prepared by hydrothermal synthesis and annealing treatment, which significantly shortens the transport path of photo-generated carriers, reduces the charge recombination probability, and increases the photoelectrocatalytic water splitting reaction active area. The TiO2 nanoarray film rich in oxygen vacancies is synthesized by deoxidation using molten salt electrolysis, while maintaining the stability of the nano morphology.

[0012] In the application, the FTO is fluorine-doped SnO2 conductive glass.

[0013] The preparation method of the TiO2 nanoarray film rich in oxygen vacancies has the characteristics that the volume ratio of tetrabutyl titanate to anhydrous ethanol in the seed solution in step one is 1-1.67:98. By controlling the ratio of tetrabutyl titanate to anhydrous ethanol, the concentration of the seed solution is controlled, and the uniform growth of the TiO2 seed layer on the surface of the FTO conductive substrate is ensured.

[0014] The preparation method of the TiO2 nanoarray film rich in oxygen vacancies has the characteristics that the tetrabutyl titanate in step one and step three is analytical pure, and the mass purity is greater than 98.0%, and the anhydrous ethanol in step one is analytical pure. By controlling the purity of the raw materials, no impurities are introduced, and the quality of the prepared TiO2 nanoarray is ensured.

[0015] The preparation method of the TiO2 nano-array film rich in oxygen vacancies has the characteristics that the FTO conductive substrate cleaned in step two is obtained by ultrasonic cleaning the FTO conductive substrate in acetone, ethanol and deionized water respectively for more than 20 minutes, the rotation speed in the spin coating process is 2000rmp-3000rmp, the time is 20s-30s, the annealing temperature is 450 DEG C-500 DEG C, and the time is 30 minutes-60 minutes. The FTO conductive substrate is cleaned to remove impurities on the surface of the FTO conductive substrate, so that the TiO2 nano-array film is better grown on the surface of the FTO conductive substrate, and the parameters of spin coating and annealing are controlled to ensure that the TiO2 seed layer is uniformly grown on the surface of the FTO conductive substrate.

[0016] The preparation method of the TiO2 nano-array film rich in oxygen vacancies has the characteristics that the volume ratio of tetrabutyl titanate, deionized water and concentrated hydrochloric acid in step three is 1-1.67:49:49. The volume ratio of tetrabutyl titanate, deionized water and concentrated hydrochloric acid is controlled to obtain the TiO2 nano-array film on the surface of the FTO conductive substrate in the hydrothermal reaction.

[0017] The preparation method of the TiO2 nano-array film rich in oxygen vacancies has the characteristics that the mass fraction of the concentrated hydrochloric acid in step three is 37.0%, the temperature of the hydrothermal reaction is 160 DEG C-170 DEG C, the time is 6h-9h, the TiO2 nano-array film is taken out after the temperature drops to room temperature after the hydrothermal reaction, then the TiO2 nano-array film is washed with deionized water and dried by blowing N2. The parameters of the hydrothermal reaction are controlled to ensure that the TiO2 nano-array film is obtained on the surface of the FTO conductive substrate.

[0018] The preparation method of the TiO2 nano-array film rich in oxygen vacancies has the characteristics that the temperature of the annealing in step four is 450 DEG C-500 DEG C, and the time is 2h-3h. The parameters of the annealing are controlled to ensure that the rutile phase TiO2 nano-array film is obtained.

[0019] The preparation method of the TiO2 nano-array film rich in oxygen vacancies has the following characteristics: the molten salt used in the step five is a LiCl-CaCl2-KCl mixed molten salt, the molar ratio of LiCl, CaCl2 and KCl in the LiCl-CaCl2-KCl mixed molten salt is 5:4:1, the temperature of the molten salt electrolysis is 500-600 DEG C, the voltage is 2.7-3.4 V, the time is 40-3 min, the TiO2 nano-array film is the cathode in the molten salt electrolysis, the graphite rod is the anode, after the deoxygenation is completed, the TiO2 nano-array film is slowly taken out of the molten salt, and then the product is taken out after being cooled to room temperature, and then the product is soaked in deionized water to remove the residual molten salt on the surface and dried. The TiO2 nano-array film rich in oxygen vacancies is synthesized by controlling the parameters of the molten salt electrolysis under the premise of keeping the nano morphology stable.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] 1. The TiO2 seed layer is grown on the FTO conductive substrate by the spin coating method, then a mixed solution of tetrabutyl titanate and concentrated hydrochloric acid is used as a precursor to prepare the TiO2 nano-array film with a nano-array structure by the hydrothermal synthesis method, and then a rutile phase TiO2 nano-array film is obtained after further annealing treatment, and then the TiO2 is electrochemically reduced by the molten salt electro-deoxidation technology to obtain the TiO2 with rich oxygen vacancies, and the good morphology of the TiO2 nano-array is maintained.

[0022] 2. The oxygen vacancies are successfully introduced into the TiO2 by the molten salt electrolysis for deoxidation, the defect energy level is constructed in the energy level structure of the TiO2, the band gap of the TiO2 is reduced, the light absorption characteristics of the TiO2 are significantly enhanced, the good nano-array morphology of the TiO2 is maintained, and the separation and transmission of the photo-generated carriers are strengthened, so that the photoelectric catalytic water splitting reaction activity of the TiO2 photoelectrode is expected to be improved.

[0023] 3. The method for introducing the oxygen vacancies into the TiO2 nano-array film by the molten salt electrolysis is convenient to operate, short in time consumption, easy to mass produce, and simple and controllable in production process and good in repeatability.

[0024] 4. The molten salt electrolysis temperature is in the range of 500-600 DEG C, which belongs to low-temperature molten salt electrolysis, so that the energy consumption is effectively reduced, the requirement for the equipment is low, and the mass production is easy.

[0025] 5. The oxygen vacancies constructed by the molten salt electro-deoxidation method can be used as a defect engineering strategy and applied to the controllable modulation of oxygen defects in other oxide semiconductor photoelectrodes.

[0026] The technical solutions of the present application are described in further detail below with reference to the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Scanning electron microscope image of the rutile TiO2 nanometer array film prepared in step four of Example 1 of the present application.

[0028] Figure 2 Scanning electron microscope image of the TiO2 nanometer array film rich in oxygen vacancies prepared in step five of Example 1 of the present application.

[0029] Figure 3 X-ray photoelectron spectroscopy O1s spectrum of the TiO2 nanometer array film before and after electrochemical deoxidation in step five of Example 1 of the present application.

[0030] Figure 4 Ultraviolet-visible light absorption image of the TiO2 nanometer array film before and after electrochemical deoxidation in step five of Example 1 of the present application.

[0031] Figure 5 Fluorescence spectrum of the TiO2 nanometer array film before and after electrochemical deoxidation in step five of Example 1 of the present application.

[0032] Figure 6 Scanning electron microscope image of the TiO2 nanometer array film rich in oxygen vacancies prepared in step five of Example 2 of the present application.

[0033] Figure 7 Scanning electron microscope image of the TiO2 nanometer array film rich in oxygen vacancies prepared in step five of Example 3 of the present application. DETAILED DESCRIPTION

[0034] Example 1

[0035] This example includes the following steps:

[0036] Step one, tetrabutyl titanate is dissolved in anhydrous ethanol according to a volume ratio of tetrabutyl titanate: anhydrous ethanol of 1.67:98 to obtain a seed solution; the tetrabutyl titanate in the seed solution is 1.5 mmol; the tetrabutyl titanate is all analytical pure and the mass purity is greater than 98.0%, and the anhydrous ethanol is analytical pure;

[0037] Step two, the seed solution obtained in step one is coated on the surface of the cleaned FTO conductive substrate by spin coating, and then the FTO conductive substrate is annealed in an air atmosphere to obtain an FTO conductive substrate with a TiO2 seed layer grown on the surface; the cleaned FTO conductive substrate is obtained by ultrasonic cleaning the FTO conductive substrate in acetone, ethanol and deionized water for more than 20 minutes, respectively, the rotation speed in the spin coating process is 2500rmp, and the time is 25s, the annealing temperature is 450℃, and the time is 30 minutes;

[0038] Step three, tetrabutyl titanate is dissolved in equal volume ratio of deionized water and concentrated hydrochloric acid to form a mixed solution according to the volume ratio of tetrabutyl titanate: deionized water: concentrated hydrochloric acid 1.67:49:49, and the FTO conductive substrate with a TiO2 seed layer grown on the surface obtained in step two is placed in the mixed solution for hydrothermal reaction, after the hydrothermal reaction is completed, the TiO2 nanometer array film is taken out after the temperature drops to room temperature, then washed with deionized water, dried by blowing N2, and a TiO2 nanometer array film is obtained on the surface of the FTO conductive substrate; the hydrothermal reaction temperature is 160℃, and the time is 6h; the tetrabutyl titanate in the mixed solution is 1.5mmol; the tetrabutyl titanate is all analytical pure, and the mass purity is greater than 98.0%; the mass fraction of the concentrated hydrochloric acid is 37.0%;

[0039] Step four, the TiO2 nanometer array film obtained in step three is annealed in an air atmosphere to obtain a rutile TiO2 nanometer array film; the annealing temperature is 500℃, and the time is 2h;

[0040] Step five, the TiO2 nanometer array film obtained in step four is electrochemically deoxidized by molten salt electrolysis to obtain a TiO2 nanometer array film rich in oxygen vacancies (TiO2-O v ); the molten salt selected for the molten salt electrolysis is a LiCl-CaCl2-KCl system mixed molten salt (molar ratio of LiCl:CaCl2:KCl is 5:4:1), the temperature of the molten salt electrolysis is 500℃, the electrolysis voltage is 2.7V, the electro-deoxidation time is 40s, the TiO2 nanometer array film is the cathode, and the graphite rod is the anode, after the electro-deoxidation is completed, the TiO2 nanometer array film is slowly taken out of the molten salt, and after cooling to room temperature, it is taken out, and then the product is immersed in deionized water to remove the residual molten salt on the surface and dried.

[0041] Figure 1 The scanning electron microscope image of the rutile TiO2 nanometer array film prepared in step four of this embodiment can be seen from Figure 1 , it can be seen that the rutile TiO2 nanometer array film prepared in step four of this embodiment has a nanorod array structure.

[0042] Figure 2 The scanning electron microscope image of the TiO2 nanometer array film rich in oxygen vacancies prepared in step five of the embodiment is shown in Figure 5, wherein Figure 2 As can be seen from Figure 5, the TiO2 nanometer array film prepared in step five of the embodiment can still maintain a good nanometer array morphology after the molten salt electro-deoxidation, thereby ensuring the efficient separation and transmission of the carriers.

[0043] Figure 3 The O1s X-ray photoelectron spectroscopy of the TiO2 nanometer array film before and after the electro-deoxidation in step five of the embodiment is shown in Figure 6, wherein Figure 3 As can be seen from Figure 6, the O1s peak at the binding energy of 530.1 eV corresponds to the lattice oxygen (O L ) in the TiO2, the O1s peak at the binding energy of 531.7 eV corresponds to the oxygen vacancies (O V ) in the TiO2, and the O V peak intensity of the TiO2 is obviously enhanced after the molten salt electro-deoxidation, indicating that the abundant oxygen vacancies are successfully introduced into the TiO2 nanometer array film by using the molten salt electro-deoxidation technology.

[0044] Figure 4 The ultraviolet-visible light absorption image of the TiO2 nanometer array film before and after the electro-deoxidation in step five of the embodiment is shown in Figure 7, wherein Figure 4 As can be seen from Figure 7, the ultraviolet-visible light absorption band edge of the TiO2 nanometer array film is red-shifted after the molten salt electro-deoxidation, indicating that the band gap is reduced, which is related to the defect energy level caused by the introduction of the oxygen vacancies.

[0045] Figure 5 The fluorescence spectrum of the TiO2 nanometer array film before and after the electro-deoxidation in step five of the embodiment is shown in Figure 8, wherein Figure 5 As can be seen from Figure 8, the TiO2 nanometer array film exhibits stronger fluorescence characteristics after the molten salt electro-deoxidation, which is related to the abundant oxygen vacancies.

[0046] It is detected that the TiO2 nanometer array film rich in oxygen vacancies is synthesized by using the low-temperature molten salt electro-deoxidation in the embodiment, under the premise of maintaining the stability of the nanometer morphology.

[0047] Comparative Example 1

[0048] The comparative example comprises the following steps:

[0049] Step one, tetrabutyl titanate is dissolved in anhydrous ethanol according to the volume ratio of tetrabutyl titanate: anhydrous ethanol of 1.67:98 to obtain a seed solution; the tetrabutyl titanate in the seed solution is 1.5 mmol; the tetrabutyl titanate is all of analytical pure and the mass purity is greater than 98.0%, and the anhydrous ethanol is of analytical pure;

[0050] Step two, the seed solution obtained in step one is coated on the surface of the cleaned FTO conductive substrate by spin coating, and then the FTO conductive substrate is annealed in an air atmosphere to obtain an FTO conductive substrate with a TiO2 seed layer grown on the surface; the cleaned FTO conductive substrate is obtained by ultrasonic cleaning the FTO conductive substrate in acetone, ethanol and deionized water for more than 20 minutes, respectively, the rotation speed in the spin coating process is 2500 rmp, and the time is 25 seconds, the annealing temperature is 450℃, and the time is 30 minutes;

[0051] Step three, tetrabutyl titanate is dissolved in equal volume ratio of deionized water and concentrated hydrochloric acid according to the volume ratio of tetrabutyl titanate: deionized water: concentrated hydrochloric acid 1.67:49:49 to form a mixed solution, and the FTO conductive substrate with a TiO2 seed layer grown on the surface obtained in step two is placed in the mixed solution for hydrothermal reaction, after the hydrothermal reaction is completed, the TiO2 nanometer array film is taken out after the temperature drops to room temperature, then washed with deionized water and dried by blowing N2, and a TiO2 nanometer array film is obtained on the surface of the FTO conductive substrate; the hydrothermal reaction temperature is 160℃, and the time is 6h; the tetrabutyl titanate in the mixed solution is 1.5mmol; the tetrabutyl titanate is all analytical pure, and the mass purity is greater than 98.0%; the mass fraction of the concentrated hydrochloric acid is 37.0%;

[0052] Step four, the TiO2 nanometer array film obtained in step three is annealed in an argon atmosphere to obtain a rutile TiO2 nanometer array film; the annealing temperature is 500℃, and the time is 2h.

[0053] It is detected that the O1s spectrum of the rutile TiO2 nanometer array film prepared in the comparative example shows that the oxygen vacancy content of the TiO2 nanometer array film after annealing in high-purity argon is higher than that of the TiO2 annealed in air, but still lower than that of the TiO2 after molten salt electro-deoxidation, indicating that the method of introducing oxygen vacancies into TiO2 by gas reduction is time-consuming and difficult to introduce oxygen vacancies.

[0054] It can be seen from the comparison of Example 1 and Comparative Example 1 that the present application uses molten salt electrolysis for electrochemical deoxidation to obtain more oxygen vacancies on the TiO2 nanometer array film.

[0055] Example 2

[0056] This example includes the following steps:

[0057] Step one, according to the volume ratio of tetrabutyl titanate: anhydrous ethanol 1:98, tetrabutyl titanate is dissolved in anhydrous ethanol to obtain a seed solution; the tetrabutyl titanate in the seed solution is 0.9 mmol; the tetrabutyl titanate is all analytical pure, and the mass purity is greater than 98.0%; the anhydrous ethanol is analytical pure;

[0058] Step two, the seed solution obtained in step one is coated on the surface of the cleaned FTO conductive substrate by spin coating, and then the FTO conductive substrate is annealed in air atmosphere to obtain an FTO conductive substrate with a TiO2 seed layer grown on the surface; the cleaned FTO conductive substrate is obtained by ultrasonic cleaning the FTO conductive substrate in acetone, ethanol and deionized water for more than 20 min, respectively; the rotation speed in the spin coating process is 2000 rmp, and the time is 30 s; the annealing temperature is 470℃, and the time is 60 min;

[0059] Step three, according to the volume ratio of tetrabutyl titanate: deionized water: concentrated hydrochloric acid 1:49:49, tetrabutyl titanate is dissolved in equal volume ratio of deionized water and concentrated hydrochloric acid to form a mixed solution, and the FTO conductive substrate with a TiO2 seed layer grown on the surface obtained in step two is placed in the mixed solution for hydrothermal reaction; after the hydrothermal reaction is completed, the TiO2 nanometer array film is taken out after the temperature drops to room temperature, then washed with deionized water, dried with N2 blowing, and a TiO2 nanometer array film is obtained on the surface of the FTO conductive substrate; the hydrothermal reaction temperature is 170℃, and the time is 9h; the tetrabutyl titanate in the mixed solution is 0.9 mmol; the tetrabutyl titanate is all analytical pure, and the mass purity is greater than 98.0%; the mass fraction of the concentrated hydrochloric acid is 37.0%;

[0060] Step four, the TiO2 nanometer array film obtained in step three is annealed in air atmosphere to obtain a rutile TiO2 nanometer array film; the annealing temperature is 470℃, and the time is 2.5h;

[0061] Step five, the TiO2 nanometer array film obtained in step four is electrochemically deoxidized by molten salt electrolysis to obtain a TiO2 nanometer array film rich in oxygen vacancies (TiO2-O v ); the molten salt selected for the molten salt electrolysis is a LiCl-CaCl2-KCl system mixed molten salt (molar ratio of LiCl:CaCl2:KCl is 5:4:1), the temperature of the molten salt electrolysis is 550℃, the electrolysis voltage is 3.0V, the electro-deoxidation time is 3min, the TiO2 nanometer array film is the cathode, and the graphite rod is the anode; after the electro-deoxidation is completed, the TiO2 nanometer array film is slowly taken out of the molten salt, and then taken out after cooling to room temperature, and then the product is immersed in deionized water to remove the residual molten salt on the surface and dried.

[0062] Figure 6 The scanning electron microscope image of the TiO2 nanorod array film rich in oxygen vacancies prepared in step five of the embodiment is shown in Figure 2. Figure 6 As can be seen from Figure 2, the TiO2 nanorod array structure continues to be maintained by reasonably regulating the parameters of molten salt electro-deoxidation.

[0063] It is detected that the TiO2 nanorod array film rich in oxygen vacancies is synthesized by using low-temperature molten salt electro-deoxidation under the premise of maintaining the stability of the nanomorphology.

[0064] Embodiment 3

[0065] The embodiment includes the following steps:

[0066] Step one, tetrabutyl titanate is dissolved in anhydrous ethanol according to a volume ratio of tetrabutyl titanate: anhydrous ethanol of 1.3:98 to obtain a seed solution; the tetrabutyl titanate in the seed solution is 1.2 mmol; the tetrabutyl titanate is all of analytical pure and the mass purity is greater than 98.0%, and the anhydrous ethanol is of analytical pure;

[0067] Step two, the seed solution obtained in step one is coated on the surface of a cleaned FTO conductive substrate by using a spin coating method, and then the FTO conductive substrate is subjected to annealing treatment in an air atmosphere to obtain an FTO conductive substrate with a TiO2 seed layer grown on the surface; the cleaned FTO conductive substrate is obtained by ultrasonic cleaning the FTO conductive substrate in acetone, ethanol and deionized water for more than 20 min respectively, the rotating speed in the spin coating process is 3000 rmp, and the time is 20 s, and the annealing temperature is 500 ℃, and the time is 45 min;

[0068] Step three, tetrabutyl titanate is dissolved in equal volume ratio of deionized water and concentrated hydrochloric acid according to a volume ratio of tetrabutyl titanate: deionized water: concentrated hydrochloric acid of 1.3:49:49 to form a mixed solution, and the FTO conductive substrate with the TiO2 seed layer grown on the surface obtained in step two is placed in the mixed solution to perform hydrothermal reaction, after the hydrothermal reaction is completed, the TiO2 nanorod array film is taken out after the temperature drops to room temperature, and then is washed with deionized water and dried by blowing N2 to obtain a TiO2 nanorod array film on the surface of the FTO conductive substrate; the hydrothermal reaction temperature is 165 ℃, and the time is 8 h; the tetrabutyl titanate in the mixed solution is 1.2 mmol; the tetrabutyl titanate is all of analytical pure and the mass purity is greater than 98.0%; the mass fraction of the concentrated hydrochloric acid is 37.0%;

[0069] Step four, the TiO2 nanorod array film obtained in step three is subjected to annealing treatment in an air atmosphere to obtain a rutile TiO2 nanorod array film; the annealing temperature is 450 ℃, and the time is 3 h;

[0070] Step five, the TiO2 nanometer array film obtained in step four is electrochemically deoxidized by molten salt electrolysis to obtain a TiO2 nanometer array film rich in oxygen vacancies (TiO2-O v ); the molten salt electrolysis uses LiCl-CaCl2-KCl system mixed molten salt (molar ratio of LiCl:CaCl2:KCl is 5:4:1) as the molten salt, the temperature of the molten salt electrolysis is 600 DEG C, the electrolysis voltage is 3.4V, the deoxidation time is 1 min, the TiO2 nanometer array film is the cathode, the graphite rod is the anode, after the deoxidation, the TiO2 nanometer array film is slowly taken out of the molten salt, and after being cooled to room temperature, it is taken out, then the product is soaked in deionized water to remove the residual molten salt on the surface and dried.

[0071] Figure 7 The scanning electron microscope image of the TiO2 nanometer array film rich in oxygen vacancies prepared in step five of the embodiment, from which it can be seen that the TiO2 nanometer rod array structure can be continuously maintained by reasonably regulating the molten salt deoxidation parameters. Figure 7

[0072] It is detected that the TiO2 nanometer array film rich in oxygen vacancies is synthesized by the low-temperature molten salt deoxidation in the embodiment, and the nano morphology is stable.

[0073] The above is only the preferred embodiment of the present application, and does not limit the present application. Any simple modification, change and equivalent change of the above embodiment according to the technical essence of the present application are still within the protection scope of the technical solution of the present application.​

Claims

1. A method for preparing a TiO2 nanoarray thin film rich in oxygen vacancies, characterized in that, The method includes the following steps: Step 1: Dissolve tetrabutyl titanate in anhydrous ethanol to obtain seed solution; Step 2: The seed solution obtained in Step 1 is coated onto the cleaned FTO conductive substrate surface by spin coating, and then annealed in an air atmosphere to obtain an FTO conductive substrate with a TiO2 seed layer grown on the surface; the spin coating process is 2000 rpm to 3000 rpm and the time is 20s to 30s. Step 3: Dissolve tetrabutyl titanate in deionized water and concentrated hydrochloric acid in equal volume ratio to form a mixed solution. Place the FTO conductive substrate with TiO2 seed layer grown on the surface obtained in Step 2 into this mixed solution for hydrothermal reaction to obtain a TiO2 nanoarray film on the surface of the FTO conductive substrate. Step 4: Anneal the TiO2 nanoarray film obtained in Step 3 in an air atmosphere to obtain a rutile phase TiO2 nanoarray film. Step 5: Deoxidize the TiO2 nanoarray film obtained in Step 4 using molten salt electrolysis to obtain a TiO2 nanoarray film rich in oxygen vacancies. The molten salt used for the molten salt electrolysis is a LiCl-CaCl2-KCl mixed molten salt, in which the molar ratio of LiCl, CaCl2 and KCl is 5:4:

1. The molten salt electrolysis temperature is 500℃~600℃, the voltage is 2.7V~3.4V, and the time is 40s~3min.

2. The method for preparing an oxygen-vacancy-rich TiO2 nanoarray thin film according to claim 1, characterized in that, In step one, the volume ratio of tetrabutyl titanate to anhydrous ethanol in the seed solution is 1~1.67:

98.

3. The method for preparing an oxygen-vacancy-rich TiO2 nanoarray thin film according to claim 1, characterized in that, The tetrabutyl titanate mentioned in steps one and three is of analytical grade and has a purity greater than 98.0%. The anhydrous ethanol mentioned in step one is of analytical grade.

4. The method for preparing an oxygen-vacancy-rich TiO2 nanoarray thin film according to claim 1, characterized in that, The cleaned FTO conductive substrate in step two is obtained by ultrasonically cleaning the FTO conductive substrate in acetone, ethanol, and deionized water for more than 20 minutes respectively. The annealing temperature is 450℃~500℃ and the time is 30min~60min.

5. The method for preparing an oxygen-vacancy-rich TiO2 nanoarray thin film according to claim 1, characterized in that, In step three, the volume ratio of tetrabutyl titanate, deionized water, and concentrated hydrochloric acid is 1~1.67:49:49, and the mass fraction of the concentrated hydrochloric acid is 37.0%.

6. The method for preparing an oxygen-vacancy-rich TiO2 nanoarray thin film according to claim 1, characterized in that, The hydrothermal reaction in step three is carried out at a temperature of 160℃~170℃ for 6h~9h. After the hydrothermal reaction is completed and the temperature drops to room temperature, the TiO2 nanoarray film is taken out, rinsed with deionized water, and dried by blowing with N2.

7. The method for preparing an oxygen-vacancy-rich TiO2 nanoarray thin film according to claim 1, characterized in that, The annealing temperature in step four is 450℃~500℃, and the time is 2h~3h.

8. The method for preparing an oxygen-vacancy-rich TiO2 nanoarray thin film according to claim 1, characterized in that, In step five, the TiO2 nanoarray film is used as the cathode and the graphite rod is used as the anode in the molten salt electrolysis. After the electrodeoxidation is completed, the TiO2 nanoarray film is slowly removed from the molten salt. After cooling to room temperature, it is taken out and then the product is soaked in deionized water to remove the residual molten salt on the surface and dried.

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