Preparation method and application of transition metal-doped ceria photocatalyst

Abstract

The application discloses a preparation method and application of a transition metal doped cerium oxide photocatalyst, and relates to the technical field of photocatalyst preparation and application, and is characterized in that: the transition metal is dispersed on the surface or in the crystal lattice of the cerium oxide in a high-valence state; the transition metal forms Lewis acid active sites; the transition metal doped cerium oxide photocatalyst can construct Lewis acid sites with strong electron acceptor characteristics on the surface of the cerium oxide, the Lewis acid active sites formed by the transition metal can adsorb S-F bonds in sulfur hexafluoride molecules, interact with F atoms in the SF6 molecules, induce S-F bond polarization, generate photo-generated electrons under light irradiation, and inject the photo-generated electrons into the sigma antibonding orbital of the SF6 molecules, so that the S-F bonds are weakened and broken, efficient adsorption, polarization and bond breaking of the SF6 molecules are realized, and efficient degradation of the SF6 is realized.

Description

Technical Field

[0001] This application relates to the field of photocatalyst preparation and application technology, specifically to a method for preparing a transition metal-doped cerium oxide photocatalyst and its application in the degradation of sulfur hexafluoride. Background Technology

[0002] Sulfur hexafluoride (SF6) is a typical potent greenhouse gas with an extremely stable chemical structure and a very strong greenhouse effect potential. Its 100-year global warming potential (GWP) is more than 20,000 times that of carbon dioxide, and it persists in the atmosphere for an extremely long time, making a significant and lasting contribution to global warming. Currently, SF6 is widely used in industries such as high-voltage power equipment insulation and semiconductor manufacturing etching and cleaning, and its usage is continuous. Once leaked, it will accumulate in the atmosphere for a long time. From a molecular structure perspective, SF6 has a highly symmetrical octahedral configuration with extremely high SF bond energies and highly electronegative fluorine atoms, making it extremely difficult for the molecule to undergo photolysis, hydrolysis, or biodegradation under natural environmental conditions. Conventional treatment technologies struggle to achieve efficient decomposition. More importantly, the degradation process of SF6 generates fluoride ions and sulfide intermediates. These species readily adsorb and poison the active sites on the catalyst surface, leading to rapid catalyst deactivation and significantly reducing degradation efficiency. This has become a core technological bottleneck restricting the efficient, deep, and sustainable degradation of SF6.

[0003] Cerium oxide (CeO2) is a class of high-performance rare-earth photocatalytic materials, whose core advantage lies in the CeO content. 3+ With Ce 4+ This process involves a highly efficient and reversible conversion between oxygen and vacancies, accompanied by the generation of numerous oxygen vacancies, thus endowing it with excellent oxygen storage and electronic regulation capabilities. Simultaneously, due to Ce... 4+ With high charge density, strong Ce-O bonds, and high lattice stability, CeO2 is unlikely to undergo anionic substitution reactions. Therefore, it exhibits outstanding resistance to fluorination and sulfidation in the SF6 degradation system, which is beneficial for maintaining the catalyst's structural stability. However, the intrinsic active sites of CeO2 mainly originate from oxygen vacancies and Ce... 3+ / Ce 4+Reversible polarization sites exhibit excellent adsorption and activation capabilities for polar or easily polarized molecules. However, for highly symmetrical and difficult-to-polarize nonpolar molecules like SF6, the interaction remains weak, making it difficult to effectively induce significant polarization of the S–F bond, thus limiting subsequent reactions. From a molecular mechanism perspective, the activation of SF6 molecules essentially involves weakening its SF bond, and the key to achieving this process lies in inducing a redistribution of electron density along the bond. Simply relying on defect sites such as oxygen vacancies typically only provides a limited electron-rich environment and is insufficient to direct the interaction of the SF bond. Therefore, it is crucial to introduce specific active centers on the catalyst surface that can generate stronger interactions with SF6 molecules to achieve effective activation of its molecular structure. Summary of the Invention

[0004] In view of the problems of SF6 molecular structure being stable, difficult to activate, and easy deactivation of catalysts in the prior art, the first aspect of this application is to provide a transition metal-doped cerium oxide photocatalyst.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: A transition metal-doped cerium oxide photocatalyst, characterized in that: the transition metal is dispersed in a high valence state on the surface or in the lattice of cerium oxide; the transition metal forms Lewis acid active sites.

[0006] This application discloses a transition metal-doped cerium oxide photocatalyst. By constructing Lewis acid sites with strong electron acceptor characteristics on the surface of cerium oxide, the Lewis acid active sites formed by the transition metal can adsorb the SF bonds in sulfur hexafluoride molecules and interact with the F atoms in SF6 molecules, thereby inducing S–F bond polarization. The cerium oxide generates photogenerated electrons under illumination. These photogenerated electrons can be injected into the σ* antibonding orbitals of SF6 molecules, thereby weakening and breaking the SF bonds. This achieves efficient adsorption, polarization, and bond breaking of SF6 molecules, thus significantly improving its photocatalytic degradation efficiency and catalytic stability.

[0007] The transition metal is selected from one or more of Mo, W, Cr, Mn, and V; more preferably Mo, and preferably Mo 6+ It exists in form.

[0008] Based on the total mass of the catalyst, the mass fraction of the transition metal is preferably 1-10 wt%, and particularly preferably 4 wt%.

[0009] The second objective of this application is to provide a method for preparing a transition metal-doped cerium oxide photocatalyst, comprising the following steps: (1) Mix the transition metal salt with CeO2, then add deionized water, and stir continuously at room temperature to fully disperse the raw materials; (2) Centrifuge the mixture obtained in step (1) to remove excess solution; (3) The solid obtained in step (2) is vacuum dried; the dried solid is then dried in a reducing atmosphere at 3-6℃ for 1 minute. -1 The temperature was increased to 400℃-600℃ and calcined for 2-4 hours to obtain a transition metal-doped cerium oxide photocatalyst.

[0010] Further settings include: In step (1): the transition metal salt is ammonium molybdate (NH4)6Mo7O 24 ·4H2O; sodium tungstate Na2WO4·2H2O; potassium chromate K2CrO4; manganese nitrate Mn(NO3)2·4H2O or ammonium metavanadate NH4VO3, etc.

[0011] The CeO2 is nano CeO2, preferably CeO2 with a particle size of 1-50 nm, and particularly preferably CeO2 with a particle size of 20 nm.

[0012] In step (2): the centrifugation is carried out at 1000 rpm for 2 min.

[0013] In step (3): vacuum drying is performed in a vacuum drying oven at 60°C for 12 hours. The reducing atmosphere is an H2 / Ar mixture; the preferred heating rate is 5°C / min. -1 The preferred heat treatment temperature is 500 ℃.

[0014] The third objective of this application is to provide an application of the aforementioned transition metal-doped cerium oxide photocatalyst in the degradation of sulfur hexafluoride.

[0015] Compared with the prior art, this application has the following advantages: (1) Significantly enhances SF6 adsorption and activation capacity By introducing high-valence transition metals, Lewis acid sites are constructed on the catalyst surface, which can interact with F atoms in SF6 molecules, effectively inducing S–F bond polarization, thereby significantly improving its adsorption and activation capabilities. The applicant discovered through research that: Lewis acid sites, due to their electron acceptor properties, can interact with the lone pair electrons of the F atom in the SF6 molecule, thereby inducing S–F bond polarization and promoting its breaking. Based on this, this application uses CeO2 as the main structural component and modulates it by introducing high-valence transition metal elements (such as Mo, W, Cr, Mn, V, etc.). On the one hand, high-valence transition metals can construct strong Lewis acid sites on the material surface, significantly enhancing the adsorption and polarization ability of SF6 molecules; on the other hand, the introduction of transition metals can regulate the electronic structure of CeO2, promoting the separation and migration of photogenerated electrons by introducing defect energy levels and optimizing band distribution, thus improving electron transport and utilization efficiency. Under illumination, photogenerated electrons generated by CeO2, under the synergistic effect of transition metal sites, preferentially migrate to the σ* antibonding orbitals of the SF6 molecule, thereby continuously weakening the SF bond strength and ultimately inducing its breaking. Simultaneously, Lewis acid sites help stabilize key reaction intermediates and lower the reaction energy barrier during the reaction process, enabling a continuous reaction process from molecular adsorption, bond polarization to bond breaking and decomposition.

[0016] (2) Constructing a synergistic catalytic mechanism This application realizes a synergistic reaction pathway of "Lewis acid site-induced adsorption polarization - photogenerated electron injection into antibonding orbitals - SF bond breaking", which breaks the reaction limitation caused by the high stability of SF6 from a mechanistic perspective. It effectively solves the problems of weak adsorption capacity, low activation efficiency and insufficient reaction driving force of traditional catalytic systems, and provides a new technical path for the efficient degradation of strong stable greenhouse gases.

[0017] (3) Improve photoelectric performance and reaction efficiency By modulating the electronic structure, reducing the band gap, improving carrier separation efficiency, and reducing charge recombination, the photocatalytic degradation efficiency can be significantly improved.

[0018] (4) Maintain excellent structural stability and delay catalyst deactivation By regulating the distribution and electronic structure of Lewis acid sites, the occupancy process of F⁻ on active sites can be slowed down to a certain extent, thereby improving the cycle stability of the catalyst.

[0019] The present application will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0020] Figure 1 The XRD patterns are of the xMoCe catalysts prepared in Examples 1-4 and undoped CeO2; wherein: Figure 1 a represents the full-spectrum XRD. Figure 1 b represents the local XRD.

[0021] Figure 2These are TEM images of the 4MoCe catalyst prepared in Example 1 and undoped CeO2; wherein: Figure 2 a、 Figure 2 b shows the morphology of CeO2 (a) and its high-magnification image (b). Figure 2 c. Figure 2 Image d shows the morphology of 4MoCe (c) and its high-magnification image (d). Figure 2 e is the HADDF and EDS mapping of 4MoCe.

[0022] Figure 3 The light absorption and carrier properties of the xMoCe catalysts prepared in Examples 1-4 and undoped CeO2 are shown; wherein: Figure 3 a represents the UV-Vis diffuse reflectance spectra of CeO2 and xMoCe. Figure 3 b represents the fluorescence spectra of EY, CeO2, and 4MoCe. Figure 3 c represents the transient photocurrent response of CeO2 and 4MoCe. Figure 3 d represents the electrochemical impedance spectroscopy of CeO2 and 4MoCe.

[0023] Figure 4 The fluorescence lifetime spectra of the 4MoCe catalyst prepared in Example 1 and undoped CeO2 are shown; wherein: Figure 4 a is an EY solution; Figure 4 b is 4MoCe; Figure 4 c represents CeO2; Figure 4 d represents the average fluorescence lifetime comparison.

[0024] Figure 5 The surface acidity characterization of the 4MoCe catalyst prepared in Example 1 and the undoped CeO2 is shown; wherein: Figure 5 a is the NH3-TPD spectrum of CeO2 and 4MoCe. Figure 5 b、 Figure 5 c is the pyridine infrared spectrum of CeO2 and 4MoCe (L is Lewis acid, B is Brønsted acid).

[0025] Figure 6 The semiconductor band structure is that of the 4MoCe catalyst prepared in Example 1 and undoped CeO2; wherein: Figure 6 a represents the Tauc curve; Figure 6 b represents the Mott-Schottky curve; Figure 6 c represents the price band XPS; Figure 6 d is a schematic diagram of the band structure of CeO2 and 4MoCe.

[0026] Figure 7 The xMoCe catalyst prepared in Examples 1-4 and undoped CeO2 were used to evaluate the photocatalytic degradation effect of SF6; wherein: Figure 7a represents the SF6 degradation rate curve; Figure 7 b is a graph of SF6 degradation (error bars represent the mean ± SD of three independent replicate experiments).

[0027] Figure 8 This is a comparison of the degradation performance of SF6 by photocatalysts doped with different transition metals prepared in Examples 5-8. Detailed Implementation

[0028] The technical solution of this application will be clearly and completely described below with reference to the embodiments of this application. Unless otherwise specified, the experimental materials and reagents used in the embodiments are all prior art or obtained from commercial channels.

[0029] Example 1

[0030] Weigh out 0.077g of (NH4)6Mo7O 24 • 4H₂O was placed in a beaker and mixed with 1g of 20nm CeO₂, followed by 50mL of deionized water. The mixture was stirred continuously at room temperature for 1 h to ensure thorough dispersion. After stirring, the mixture was transferred to a 50mL centrifuge tube and centrifuged at 1000 rpm for 2 min to remove excess solution. The resulting solid was placed in a vacuum drying oven at 60℃ and dried for 12 h. The dried solid was then placed in an alumina ceramic boat and dried at 5℃ for 5 min in a 5% H₂ / Ar atmosphere. -1 The temperature was increased to 500℃ and calcined for 2 h to obtain a molybdenum-doped cerium oxide photocatalyst, labeled 4MoCe.

[0031] The amount of molybdenum doping in the catalyst was adjusted as shown in Examples 2-4.

[0032] Example 2

[0033] The preparation method is the same as in Example 1, except that (NH4)6Mo7O is adjusted. 24 • 0.038 g of 4H2O was used to obtain the catalyst 2MoCe.

[0034] Example 3

[0035] The preparation method is the same as in Example 1, except that (NH4)6Mo7O is adjusted. 24 • 0.118 g of 4H2O was used to obtain the catalyst 6MoCe.

[0036] Example 4

[0037] The preparation method is the same as in Example 1, except that (NH4)6Mo7O is adjusted. 24 The catalyst 8MoCe was obtained by using 0.16 grams of 4H2O.

[0038] Material characterization: The molybdenum-doped cerium oxide photocatalysts (xMoCe) prepared in Examples 1-4 were subjected to X-ray diffraction, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy, time-resolved photoluminescence, surface acidity testing, and semiconductor band structure analysis, respectively. The results are as follows: Figures 1-6 As shown: (1) X-ray diffraction test The crystal structure of the prepared catalyst was systematically characterized using X-ray diffraction (XRD). Figure 1 As shown, the diffraction peak positions of the xMoCe series catalysts are basically consistent with those of commercial CeO2. All diffraction peaks can be attributed to the cubic fluorite structure (PDF#34-0394), and no obvious impurity phase diffraction peaks were observed, indicating that the introduction of transition metals did not change the crystal structure of CeO2, nor did it form an independent metal oxide crystal phase. Further analysis of the local regions of the diffraction peaks revealed that with the increase of molybdenum doping, the diffraction peaks shifted slightly towards lower angles, indicating a change in lattice parameters. This phenomenon indicates that transition metal ions (such as Mo...)... 6+ The presence of Mo in the CeO2 lattice or its surface causing lattice strain, leading to changes in interplanar spacing, indicates that Mo has been successfully doped and has a regulatory effect on the lattice structure.

[0039] (2) Transmission electron microscope To further analyze the microstructure and structural characteristics of the catalyst, transmission electron microscopy (TEM) was used to characterize the sample (4MoCe). Figure 2 As shown, the CeO2 sample exhibits irregular spherical particles with a diameter of approximately 20 nm, demonstrating good dispersibility. After Mo doping, the particle size and morphology of the resulting 4MoCe catalyst did not change significantly, maintaining a particle size of approximately 20 nm and a uniformly dispersed state. No obvious agglomeration or structural distortion was observed. High-resolution TEM results show that 4MoCe has clear lattice fringes, and no new crystalline phases or heterogeneous particles were found to be generated, consistent with the XRD results, further indicating that the Mo species did not form an independent crystalline phase. EDS mapping analysis revealed that Mo elements are uniformly distributed on the CeO2 surface, without obvious local enrichment or agglomeration, indicating that it exists in a highly dispersed form, which is conducive to the formation of uniform surface active sites.

[0040] (3) Ultraviolet-visible diffuse reflectance spectrum The UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) test results are as follows: Figure 3As shown, compared to CeO2, the xMoCe series catalysts exhibit stronger light absorption in the visible light region (>400 nm), and the absorption edge shows a significant red shift, indicating a reduced band gap and a wider photoresponse range. Photoluminescence (PL) tests show that under 470 nm excitation conditions, the fluorescence intensity of the eosin Y (EY) solution significantly decreases after the addition of the catalyst, and the quenching effect of 4MoCe on fluorescence is significantly higher than that of CeO2, indicating a stronger ability to capture photogenerated electrons, thereby effectively suppressing carrier recombination. Transient photocurrent tests show that the photocurrent density of 4MoCe is significantly higher than that of CeO2, indicating a significant improvement in its photogenerated carrier separation efficiency. Electrochemical impedance spectroscopy (EIS) results further show that the Nyquist curve radius of 4MoCe is significantly reduced, indicating a lower charge transport impedance, which is beneficial for electron migration and transport.

[0041] (4) Time-resolved photoluminescence Carrier lifetime was analyzed using time-resolved photoluminescence (TRPL) measurements, and the results... Figure 4 As shown, the average fluorescence lifetime of CeO2 is 1.19 ns, while that of 4MoCe is 1.23 ns, which is longer than that of CeO2. This indicates that Mo doping can effectively suppress the nonradiative recombination process of photogenerated carriers, thus benefiting the photocatalytic reaction.

[0042] (5) Surface acidity test To analyze the surface acidity of the catalyst, NH3-TPD was used for testing, and the results are as follows: Figure 5 As shown in Figure a: CeO2 exhibits a significant desorption peak in the 100-200 °C range, corresponding to weakly acidic sites, while 4MoCe shows a significant desorption peak in the 200-400 °C range, indicating the formation of medium-to-strong acidic sites on its surface. This demonstrates that Mo doping significantly enhances the acidity of the catalyst. Further analysis of the acidic site types using pyridine adsorption infrared spectroscopy (Py-IR) reveals… Figure 5 b- Figure 5 c), the results showed that 4MoCe at 1450 cm⁻¹ -1 and 1600 cm -1 The characteristic peaks nearby are significantly enhanced, corresponding to Lewis acid sites, while the 1540 cm⁻¹ peak is significantly enhanced. -1 The small change in the Brønsted acid peak at the catalyst surface indicates that Mo doping mainly enhances the Lewis acid sites on the catalyst surface, which is consistent with the design concept of this application.

[0043] (6) Semiconductor band structure The bandgap width is calculated using the Tauc method, such as... Figure 6As shown in Figure a: the results show that the band gap of CeO2 is 3.02 eV, while that of 4MoCe decreases to 2.83 eV, indicating an improved light absorption capacity. Mott-Schottky analysis results indicate that both catalysts are n-type semiconductors, and 4MoCe exhibits a higher flat band potential (…). Figure 6 b). Based on the XPS test results of the valence band, 4MoCe has a slightly higher valence band position, which is conducive to the reaction. Figure 6 c). Comprehensive analysis shows that Mo doping promotes the separation and migration of photogenerated carriers by introducing defect energy levels and modulating the band structure. Figure 6 d).

[0044] Adjust the type of transition metal doped in the catalyst, as shown in Examples 5-8.

[0045] Example 5

[0046] The preparation method is the same as in Example 1, except that the transition metal salt is Na2WO4·2H2O, with a mass of 0.075 g, to obtain a tungsten-doped cerium oxide photocatalyst, labeled as W / CeO2.

[0047] Example 6

[0048] The preparation method is the same as in Example 1, except that the transition metal salt is K2CrO4 with a mass of 0.156 g, and a chromium-doped cerium oxide photocatalyst is obtained, labeled as Cr / CeO2.

[0049] Example 7

[0050] The preparation method is the same as in Example 1, except that the transition metal salt is Mn(NO3)2·4H2O, with a mass of 0.190 g, to obtain a manganese-doped cerium oxide photocatalyst, labeled as catalyst Mn / CeO2.

[0051] Example 8

[0052] The preparation method is the same as in Example 1, except that the transition metal salt is NH4VO3 with a mass of 0.097 g, and a vanadium-doped cerium oxide photocatalyst is obtained, labeled as catalyst V / CeO2.

[0053] Application Examples

[0054] The catalysts prepared in Examples 1-8 were applied to the catalytic degradation of SF6 to test their photocatalytic degradation performance for SF6.

[0055] Test method: (1) Under an inert atmosphere, accurately weigh 30 mg of catalyst and place it in a custom 25 mL Schlenk reaction tube, add 0.5 mL of methanol and 2 mL of acetonitrile in sequence, and seal the tube.

[0056] (2) Add 0.5 mL of deionized water to the tube, and then inject 2 mL of sulfur hexafluoride gas into the reaction system. Stir thoroughly in the dark until all components are mixed evenly. Use a gas chromatograph to detect and record the initial concentration of sulfur hexafluoride. (3) Transfer the reaction tube to a parallel light reactor and use an LED lamp with a wavelength of 365 nm and a power of 18 W as the light source to irradiate the reaction.

[0057] (4) After the reaction continues for 24 hours, the concentration of sulfur hexafluoride in the system is measured and recorded again by gas chromatograph to complete the comparative analysis of the target gas concentration before and after the reaction.

[0058] The degradation amount of sulfur hexafluoride is calculated according to the following formula: .

[0059] In the formula: [SF6]0 refers to the initial concentration of sulfur hexafluoride after 30 minutes of dark reaction equilibrium; [SF6] t The concentration of sulfur hexafluoride in the reaction tube after the photocatalytic reaction; m cat This refers to the mass of the catalyst added.

[0060] Test results: Test results are as follows Figure 7 , Figure 8 As shown: (1) Effect of different doping amounts (Mo) on the performance of cerium oxide photocatalysts like Figure 7 As shown, CeO2 only achieved a 1.9% degradation rate of SF6 after 24 h of reaction, while the 4MoCe catalyst achieved a degradation rate of 30.7%, significantly higher than the undoped sample. Simultaneously, the SF6 degradation amount of 4MoCe reached 10.20 mL·g. -1 It is about 24 times that of CeO2. Among samples with different doping amounts, 4MoCe showed the best catalytic performance, indicating that there is an optimal doping ratio in the system. Too low a doping amount makes it difficult to form enough active sites, while too high a doping amount may introduce too many defects or obscure the active centers, thus affecting the overall reaction efficiency. Experiments have confirmed that the effect is best when the mass fraction of transition metal in the catalyst is 4%.

[0061] (2) Effects of different types of transition metal doping on the performance of cerium oxide photocatalysts Catalysts were prepared by introducing different types of transition metal elements (such as Mo, W, Cr, Mn, V, etc.), and their degradation performance on SF6 was investigated. The results are as follows: Figure 8 As shown: All transition metal-doped cerium oxide photocatalysts exhibited superior SF6 degradation performance compared to undoped CeO2, indicating that introducing transition metals to construct Lewis acid sites on the catalyst surface is a universally applicable regulatory strategy. This is primarily attributed to the generally strong electron acceptor capabilities of high-valence transition metal ions, which can interact with the F atoms in the SF6 molecule, thereby inducing SF bond polarization and promoting its activation process. Simultaneously, the introduction of transition metals can also modulate the electronic structure of CeO2, improving the separation and migration behavior of photogenerated carriers to some extent, thus jointly enhancing catalytic performance.

[0062] Compared to other transition metals, the cerium oxide photocatalyst doped with Mo exhibits the best SF6 degradation performance, reaching 10.20 mL·g. -1 (4MoCe).

[0063] The above embodiments are merely examples of the concept of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

Claims

1. A transition metal-doped cerium oxide photocatalyst, characterized in that: The transition metal is dispersed in a high valence state on the surface or in the lattice of cerium oxide; the transition metal forms Lewis acid active sites.

2. The transition metal-doped cerium oxide photocatalyst according to claim 1, characterized in that: The Lewis acid active sites formed by the transition metal can adsorb the SF bonds in the sulfur hexafluoride molecule and interact with the F atoms in the SF6 molecule, thereby inducing S–F bond polarization.

3. The transition metal-doped cerium oxide photocatalyst according to claim 1, characterized in that: The transition metal is selected from one or more of Mo, W, Cr, Mn, and V, and the mass fraction of the transition metal is 1-10 wt% based on the total mass of the catalyst.

4. The transition metal-doped cerium oxide photocatalyst according to claim 3, characterized in that: The transition metal is Mo, and Mo is the most abundant metal in the series. 6+ It exists in form.

5. A method for preparing the transition metal-doped cerium oxide photocatalyst according to claim 1, characterized in that, Includes the following steps: (1) Mix the transition metal salt with CeO2, then add deionized water, and stir continuously at room temperature to fully disperse the raw materials; (2) Centrifuge the mixture obtained in step (1) to remove excess solution; (3) The solid obtained in step (2) is vacuum dried; the dried solid is then dried in a reducing atmosphere at 3-6℃ for 1 minute. -1 The temperature was increased to 400℃-600℃ and calcined for 2-4 hours to obtain a transition metal-doped cerium oxide photocatalyst.

6. The method for preparing a transition metal-doped cerium oxide photocatalyst according to claim 5, characterized in that: In step (1), the transition metal salt is any one or more of ammonium molybdate, sodium tungstate, potassium chromate, manganese nitrate, or ammonium metavanadate.

7. The method for preparing a transition metal-doped cerium oxide photocatalyst according to claim 5, characterized in that: In step (1), the CeO2 is CeO2 with a particle size of 1-50nm.

8. The method for preparing a transition metal-doped cerium oxide photocatalyst according to claim 5, characterized in that: In step (2), the centrifugation is performed at 1000 rpm for 2 min.

9. The method for preparing a transition metal-doped cerium oxide photocatalyst according to claim 5, characterized in that: In step (3), vacuum drying is performed in a vacuum drying oven at 60°C for 12 hours. The reducing atmosphere is an H2 / Ar mixture; the preferred heating rate is 5°C / min. -1 The preferred heat treatment temperature is 500 °C.

10. The application of the transition metal-doped cerium oxide photocatalyst of claim 1 in the degradation of sulfur hexafluoride.

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