Hollow dandelion-like TiO2 photonic crystal with nano confinement bridging Ni-O-Ti atomic-scale asymmetric sites as well as preparation method and application of hollow dandelion-like TiO2 photonic crystal

Abstract

The invention discloses a hollow dandelion-like TiO2 photonic crystal with nano confinement bridging Ni-O-Ti atomic-scale asymmetric sites as well as a preparation method and application of the hollow dandelion-like TiO2 photonic crystal. Comprising the following steps: (1) taking a hydrolysis inhibitor and an alcohol source as reaction media, and reacting with a titanium source at a certain temperature to prepare self-assembled hollow TiO2 nanospheres; and (2) taking the TiO2 nanospheres as a precursor, etching by using strong base, and then performing acid soaking, washing, calcining and drying to form hollow dandelion-like TiO2. And (3) reducing the dandelion-like TiO2 by using a strong reducing agent NaBH4, and calcining in an atmosphere to form a black hollow dandelion-like TiO2 precursor. And (4) reducing a Ni source into Ni monatomic atoms by using different reduction methods in an oxygen vacancy confinement manner, and loading the Ni monatomic atoms onto the surface of the black hollow dandelion-like TiO2 precursor. Compared with commercial TiO2 (P25), the prepared nano material has the advantages that the hydrogen production activity is improved by more than 60 times and reaches 4858 micromoles g <-1 > h <-1 >, the hydrogen production activity is higher than that of a general Pt-loaded TiO2 nano material, and the visible light activity is achieved.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a hollow dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites, its preparation method, and its application. Background Technology

[0002] Since Fujishima and Honda discovered in 1972 that single-crystal TiO2 could photocatalytically split water to produce H2, semiconductor photocatalysis technology has attracted increasing attention. The photocatalytic efficiency of semiconductors is mainly affected by three factors: light absorption efficiency, electron-hole separation efficiency, and surface catalytic reaction efficiency. Against this backdrop, due to its unique properties, such as non-toxicity, chemical stability, high photochemical activity, significant hydrogen storage capacity, and unique electronic band structure, the demand for TiO2-based photocatalysts is increasing. TiO2-based materials are frequently used in the field of photocatalysis due to their crucial role in the reaction process. Despite the progress made in TiO2 research, the application of TiO2 photocatalytic materials is still limited by challenges, such as low solar energy utilization and severe recombination of photogenerated carriers. Carefully modifying and enhancing the material structure to improve carrier light utilization and separation efficiency is an effective method to improve the reaction efficiency of TiO2-based photocatalysts.

[0003] For the reasons mentioned above, this invention prepares hollow dandelion-shaped TiO2 photonic crystals to improve their light absorption capacity. On the one hand, the hollow dandelion-shaped TiO2 prepared through self-assembly has a periodic photonic crystal structure, allowing photons to propagate along a specific path, reducing scattering and absorption losses; on the other hand, the large specific surface area of ​​this structure improves photoelectric conversion efficiency by regulating the light absorption range and reducing light reflection.

[0004] Nickel (Ni) itself has good chemical stability. The electronic configuration of Ni (3d...) 8 4s 2 Ni readily forms coordinate bonds with reactants, exhibiting excellent catalytic activity in various reactions such as hydrogenation, dehydrogenation, and CO2 reduction, rivaling that of precious metals in some scenarios. Ni is more abundant in the Earth's crust, yet its price is only a fraction of that of precious metals. Atomic-level Ni, in particular, is widely used in photocatalysis. By bridging Ni-O-Ti active sites on the TiO2 surface, the electron-hole separation efficiency of TiO2 can be effectively improved, thereby enhancing its photocatalytic hydrogen production activity. Summary of the Invention

[0005] Based on the above background, this invention provides a hollow TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites, its preparation method, and its applications. The invention is characterized by its low cost and availability, non-toxicity and harmlessness, simple and environmentally friendly synthesis process, large-scale production capability, and good catalytic activity for hydrogen production.

[0006] To achieve the present invention, the following technical solution is adopted: A method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of atomic-level asymmetric sites in Ni-O-Ti comprises the following steps: (1) Mix the hydrolysis inhibitor and alcohol source evenly, add liquid titanium source, and stir in an oil bath at 20~50℃ for 0.5h~5h or irradiate for 0.5~5h. (2) The mixture prepared in step (1) is heated at 150~220℃ for 12~24 h, and the resulting solid product is washed and dried to obtain self-assembled hollow TiO2 nanospheres; (3) Add the self-assembled hollow TiO2 nanospheres obtained in step (2) to a 5-10 M strong alkali solution, and perform a hydrothermal reaction at 100-150℃ for 0.5-3 h. After acid soaking, washing and drying, calcine at 300-500℃ for 1-4 h to obtain a hollow dandelion-like TiO2 intermediate. (4) Grind the powder obtained in step (3) with NaBH4 in a mortar, calcine at 200~500℃ for 2~5 h under a protective atmosphere, and then wash and dry. (5) Add the powder obtained in step (4) to an alcohol source, then add a nickel source for reduction treatment. After washing and drying, calcine at 300~500℃ for 1~4 h to finally obtain a hollow dandelion-like TiO2 photocatalytic material with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites.

[0007] Further, the hydrolysis inhibitor in step (1) is a mixture of one or more of acetylacetone, benzoylacetone, triethanolamine, citric acid and ethylenediamine in any proportion; the alcohol source is a mixture of one or more of isopropanol, n-propanol, polyethylene glycol and polypropylene glycol in any proportion; the titanium source is a mixture of one or more of tetrabutyl titanate, titanium tetrachloride, titanium trichloride, isopropyl titanate, titanium sulfate and titanium oxysulfate in any proportion; the lamp source is a mercury lamp, xenon lamp and LED lamp; and the volume ratio of the hydrolysis inhibitor, alcohol source and titanium source is (7.5~12.5):(10~12.5):1.

[0008] Furthermore, in step (2), the washing process uses a mixture of one or more of methanol, ethanol and butanol in any proportion.

[0009] Further, the strong alkali mentioned in step (3) is one or more of sodium hydroxide, potassium hydroxide and tetramethylammonium hydroxide in any proportion, the concentration of the self-assembled hollow TiO2 nanospheres in the strong alkali solution is 0.05~0.15g / mL, the hydrothermal reaction conditions are a drying oven and an oil bath, and acid soaking refers to soaking in 0.1~0.2mol / L hydrochloric acid for 8~10h.

[0010] Further, the protective atmosphere mentioned in step (4) refers to argon, helium or nitrogen, the mass ratio of the powder obtained in step (3) to NaBH4 is 1:(0.2~1.1); the grinding time is 20~40 minutes, the flow rate of the protective atmosphere is 30~70 ml / min, and the temperature is raised to 200~500℃ at a heating rate of 3~8℃ / min.

[0011] Further, the alcohol source in step (5) is one or more of methanol, ethanol and butanol in any proportion, the nickel source is one or more of nickel chloride, nickel nitrate, nickel sulfate, ethylenediamine nickel and ethylenediaminetetraacetic acid nickel in any proportion, and the reduction treatment is NaBH4 reduction, light reduction and H2 reduction.

[0012] Further, in step (5), the mass ratio of the powder obtained in step (4), NaBH4 and nickel source is 1:(0.2~0.5):(0.05~0.5), and the concentration of the powder obtained in step (4) in the alcohol source is 0.001~0.005 g / mL.

[0013] Furthermore, the washing in step (2) refers to washing with anhydrous ethanol 2 to 4 times. The washing in steps (3) and (4) refers to washing with water until the upper liquid is neutral, and the washing in step (5) refers to washing with anhydrous ethanol. The drying in steps (2), (3), (4) and (5) all refer to being carried out at 50 to 70°C.

[0014] The above preparation method yields a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites.

[0015] The above-mentioned hollow dandelion-like TiO2 photonic crystal with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites is used in photocatalytic methanol and / or water-based hydrogen production.

[0016] Furthermore, hollow, dandelion-like TiO2 photonic crystals with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites are dispersed in methanol and / or deionized water, sonicated for 5–15 minutes, and then transferred to a quartz reactor for photocatalytic hydrogen production using a xenon lamp with vertical irradiation. When the solution is a mixture of methanol and water, the volume ratio of methanol to deionized water is 1:(3–5). The concentration of the nano-confined, bridging Ni-O-Ti atomic-level asymmetric sites hollow, dandelion-like TiO2 photonic crystals in the mixed solution is 0.4–0.6 mg / mL, the xenon lamp power is 200–400 W, and the light intensity is 150–250 mW / cm². 2 .

[0017] The hollow, dandelion-like TiO2 photonic crystal nanomaterial with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites prepared by the above method has a theoretical Ni modification amount of 0.2~3wt%, and the material can be applied to the photocatalytic production of clean hydrogen energy.

[0018] Compared with existing technologies, the key features of this invention are: inexpensive and readily available raw materials, simple preparation process, safe and environmentally friendly preparation process, no precious metals, and excellent catalytic performance of the product. Compared with commercial TiO2 (P25), the hydrogen production activity is increased by more than 60 times, reaching 4858 μmol g. -1 h -1 It exhibits higher hydrogen production activity than typical Pt-supported TiO2 nanomaterials and also has visible light activity. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the self-assembled hollow TiO2 nanospheres of the intermediate in Example 1; Figure 2 Scanning electron microscope image of hollow dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites, as shown in Example 1; Figure 3 The transmission electron microscopy (TEM-EDS) image of the hollow dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites is shown in Example 1. Figure 4 Aberration-corrected scanning transmission electron microscope (AC-HAADF-STEM) image of a hollow dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites, as shown in Example 1. Figure 5 The in-situ Fourier transform infrared spectrum (FTIR) of Example 1 is shown. Figure 6 Extended X-ray absorption fine structure spectra (EXAFS) for Examples 1 and 6; Figure 7 The UV-Vis absorption spectra of Examples 1, 6, and P25 are shown. Figure 8 The photocurrent density diagrams for Examples 1 and 6 and P25 are shown. Figure 9 The graphs show the photocatalytic hydrogen production activity of Examples 1, 3, and 6, and P25. Figure 10 Here is a scanning electron microscope image of Example 6; Figure 11 This is a spherical aberration corrected scanning transmission electron microscope (AC-HAADF-STEM) image of Example 6. Detailed Implementation

[0020] To better illustrate the present invention, the following embodiments are provided. However, the scope of the present invention is not limited to these examples, and its scope of protection is set forth in the claims. In the following embodiments, ethanol refers to anhydrous ethanol. Example 1

[0021] A method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites includes the following steps: ① First, add 2 mL of tetrabutyl titanate to a mixed solution of 25 mL acetylacetone and 25 mL isopropanol. Stir in an oil bath at 30°C for 2 hours; ② The mixture from step ① was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 200°C for 16 hours. The product was washed three times with anhydrous ethanol and then dried under vacuum at 60°C for 12 hours. The above process was repeated once to obtain a total of 0.8 g of self-assembled hollow TiO2 microspheres. ③ Take 0.7 g of the hollow TiO2 microspheres prepared in step ② and add them to 70 mL of 10 M NaOH solution. React in an oil bath at 120 °C for 50 minutes. After cooling, neutralize the mixture with HCl solution at pH=1 and stir magnetically for 10 hours. Wash the product with deionized water until neutral, dry it overnight at 60 °C (about 10 hours), and finally calcine it in a muffle furnace at 400 °C for 2 hours to obtain the dandelion-shaped TiO2 precursor. ④ Grind 0.45g of the sample from step ③ with 0.24g of NaBH4 in an agate mortar for 30 minutes, transfer to a tube furnace, and calcine at 300℃ for 3 hours at a heating rate of 5℃ / min under an argon atmosphere (flow rate 50 mL / min). After cooling, wash the product with deionized water until neutral, and dry it overnight (about 10 hours) under vacuum at 60℃ to obtain the intermediate black dandelion-shaped TiO2. ⑤ Add 0.4g of the intermediate obtained in step ④ to 200 mL of anhydrous ethanol, followed by 0.1g of NaBH4 and 0.06g of NiCl2·6H2O. After magnetic stirring for 6 hours, the mixture is centrifuged. The solid is washed once with anhydrous ethanol and dried overnight (about 10 hours) under vacuum at 60℃, then calcined at 300℃ for 2 hours to finally obtain 0.4g of hollow dandelion-like TiO2 photonic crystal with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites.

[0022] Scanning electron microscope (SEM) image of the self-assembled hollow TiO2 nanospheres prepared by step ② of Example 1 is shown below. Figure 1As shown in the figure, the prepared self-assembled hollow TiO2 nanospheres have a particle size of about 500 nm, are neatly arranged, have a periodic photonic crystal structure, regular morphology, uniform size, and are hollow.

[0023] Scanning electron microscope (SEM) image of the hollow dandelion-like TiO2 photonic crystal with nano-confined bridging of atomic-level asymmetric sites of Ni-O-Ti prepared in Example 1 is shown below. Figure 2 As shown in the figure, the material surface is flocculent with a regular morphology, and the overall shape is similar to a dandelion, with a size of about 800 nm.

[0024] The transmission electron microscopy (TEM-EDS) image of the hollow dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites prepared in Example 1 is shown below. Figure 3 As shown in the figure, the material is hollow with branches on the surface, which conforms to the crystal structure of TiO2, and the Ni element is evenly distributed.

[0025] Aberration-corrected scanning transmission electron microscopy (AC-HAADF-STEM) image of the hollow dandelion-like TiO2 photonic crystal with nano-confined bridging of atomic-level asymmetric sites of Ni-O-Ti prepared in Example 1 is shown below. Figure 4 As shown in the figure, the Ni element on the material surface is in the form of single atoms and is evenly distributed.

[0026] In-situ Fourier transform infrared (FTIR) spectra of the hollow dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites prepared in Example 1 are as follows: Figure 5 As shown in the figure, the material exhibits performance at wavelengths of 2170 and 2118 cm⁻¹. -1 Characteristic peaks appear on both sides, and after being purged with CO gas, the characteristic peaks gradually weaken and disappear, which is consistent with the morphological characteristics of Ni single atoms. Example 2

[0027] A method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites includes the following steps: ① First, add 4 mL of titanium tetrachloride to a mixed solution of 30 mL benzoylacetone and 50 mL isopropanol. Then, use a 300W xenon lamp (200 mW / cm²). 2 Stir for 1 hour; ② The mixture was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 200°C for 20 hours. The product was washed three times with anhydrous ethanol and then dried under vacuum at 60°C for 12 hours to obtain 0.82 g of self-assembled hollow TiO2 microspheres. ③ Take 0.7 g of the hollow TiO2 microspheres prepared in step ② and add them to 70 mL of 5 M tetramethylammonium hydroxide solution. React in an oil bath at 100 °C for 2 hours. After cooling, neutralize the mixture with HCl solution at pH=1 and stir magnetically for 8 hours. Wash the product with deionized water until neutral, dry it overnight at 60 °C (about 10 hours), and finally calcine it in a muffle furnace at 400 °C for 2 hours to obtain the dandelion-shaped TiO2 precursor. ④ Grind 0.45g of the sample from step ③ with 0.12g of NaBH4 in an agate mortar for 30 minutes, transfer to a tube furnace, and calcine at 350℃ for 4 hours under an argon atmosphere (flow rate 50 mL / min) at a heating rate of 5℃ / min. After cooling, wash the product with deionized water until neutral, and dry it overnight (about 10 hours) under vacuum at 60℃ to obtain the intermediate black dandelion-shaped TiO2. ⑤ Add 0.4 g of the intermediate obtained in step ④ to 200 mL of anhydrous ethanol, then add 0.12 g of NiCl2·6H2O. Heat the mixture under a 300 W xenon lamp (200 mW / cm²). 2 After stirring magnetically for 3 hours, the mixture was centrifuged. The solid was washed once with anhydrous ethanol and dried overnight (about 10 hours) under vacuum at 60°C. Then it was calcined at 500°C for 1 hour to finally obtain a hollow dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites. Example 3

[0028] A method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites includes the following steps: ① First, add 4 mL of titanium oxysulfate to a mixed solution of 50 mL acetylacetone and 50 mL isopropanol. Stir in an oil bath at 50°C for 1 hour; ② The mixture was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 200°C for 24 hours. The product was washed three times with anhydrous ethanol and then dried under vacuum at 60°C for 12 hours to obtain 0.72 g of self-assembled hollow TiO2 microspheres. ③ Take 0.6 g of the hollow TiO2 microspheres prepared in step ② and add them to 60 mL of 10 M NaOH solution. React at 120 °C for 1 hour in a drying oven. After cooling, neutralize the mixture with HCl solution at pH=1 and stir magnetically for 10 hours. Wash the product with deionized water until neutral, dry it overnight at 60 °C (about 10 hours), and finally calcine it at 400 °C for 3 hours in a tube furnace to obtain the dandelion-shaped TiO2 precursor. ④ Grind 0.4g of the sample from step ③ with 0.2g of NaBH4 in an agate mortar for 1 hour, then transfer to a tube furnace and calcine at 350℃ for 2 hours under an argon atmosphere (flow rate 50 mL / min) at a heating rate of 5℃ / min. After cooling, wash the product with deionized water until neutral, and dry it overnight (about 10 hours) under vacuum at 60℃ to obtain the intermediate black dandelion-shaped TiO2. ⑤ Add 0.4g of the intermediate obtained in step ④ to 100 mL of anhydrous ethanol, followed by 0.1g of NaBH4 and 0.06g of NiCl2·6H2O. After magnetic stirring for 6 hours, centrifuge the mixture. Wash the solid once with anhydrous ethanol and dry it overnight (about 10 hours) under vacuum at 60℃. Then calcine it at 300℃ for 2 hours to finally obtain 0.36g of hollow dandelion-like TiO2 photonic crystal with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites. Example 4

[0029] A method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites includes the following steps: ① First, add 2 mL of tetrabutyl titanate to a mixed solution of 25 mL acetylacetone and 25 mL isopropanol. Stir in an oil bath at 30°C for 2 hours; ② The mixture from step ① was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 220°C for 20 hours. The product was washed three times with anhydrous ethanol and then dried under vacuum at 60°C for 12 hours. The above process was repeated once to obtain a total of 0.7 g of self-assembled hollow TiO2 microspheres. ③ Take 0.7 g of the hollow TiO2 microspheres prepared in step ② and add them to 70 mL of 10 M NaOH solution. React in an oil bath at 120 °C for 0.5 hours. After cooling, neutralize the mixture with HCl solution at pH=1 and stir magnetically for 10 hours. Wash the product with deionized water until neutral, dry it overnight at 60 °C (about 10 hours), and finally calcine it in a muffle furnace at 400 °C for 2 hours to obtain the dandelion-shaped TiO2 precursor. ④ Grind 0.45g of the sample from step ③ with 0.12g of NaBH4 in an agate mortar for 30 minutes, transfer to a tube furnace, and calcine at a heating rate of 5℃ / min for 4 hours under a helium atmosphere (flow rate 50 mL / min) to a temperature of 350℃. After cooling, wash the product with deionized water until neutral, and dry it under vacuum at 60℃ overnight (about 10 hours) to obtain the intermediate black dandelion-shaped TiO2; ⑤ Add 0.4g of the intermediate obtained in step ④ to 200 mL of anhydrous ethanol, followed by 0.1g of NaBH4 and 0.12g of Ni(NO3)2·6H2O. After magnetic stirring for 6 hours, centrifuge the mixture. Wash the solid once with anhydrous ethanol and dry it overnight (about 10 hours) under vacuum at 60℃. Then calcine it at 500℃ for 1 hour to finally obtain 0.35g of hollow dandelion-like TiO2 photonic crystal with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites. Example 5

[0030] A method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites includes the following steps: ① First, add 4 mL of tetrabutyl titanate to a mixed solution of 50 mL acetylacetone and 50 mL n-propanol. Then, use a 300W xenon lamp (200 mW / cm²). 2 Stir for 2 hours. ② The mixture from step ① was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 200°C for 20 hours. The product was washed three times with anhydrous ethanol and then dried under vacuum at 60°C for 12 hours to obtain 0.6 g of self-assembled hollow TiO2 microspheres. ③ Take 0.5 g of the hollow TiO2 microspheres prepared in step ② and add them to 50 mL of 5 M KOH solution. React at 130℃ for 0.5 hours in a drying oven. After cooling, neutralize the mixture with HCl solution of pH=1 and stir magnetically for 10 hours. Wash the product with deionized water until neutral, dry it overnight at 60℃ (about 10 hours), and finally calcine it in a muffle furnace at 400℃ for 2 hours to obtain the dandelion-shaped TiO2 precursor. ④ Grind 0.4g of the sample from step ③ with 0.36g of NaBH4 in an agate mortar for 30 minutes, transfer to a tube furnace, and calcine at 400℃ for 2 hours at a heating rate of 5℃ / min under an argon atmosphere (flow rate 50 mL / min). After cooling, wash the product with deionized water until neutral, and dry it overnight (about 10 hours) under vacuum at 60℃ to obtain the intermediate black dandelion-shaped TiO2. ⑤ Add 0.4g of the intermediate obtained in step ④ to 200 mL of anhydrous ethanol, and add 0.06g of Ni(NO3)2·6H2O. After magnetic stirring for 6 hours, centrifuge the mixture, wash the solid once with anhydrous ethanol, and dry it overnight (about 10 hours) under vacuum at 60℃. Then, calcine it in a tube furnace at 300℃ for 2 hours under a hydrogen / argon mixed atmosphere (hydrogen volume content 5%, total flow rate of mixed gas 50 mL / min). Finally, 0.31g of hollow dandelion-like TiO2 photonic crystal with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites is obtained. Example 6

[0031] A method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites includes the following steps: ① First, add 2 mL of tetrabutyl titanate to a mixed solution of 25 mL acetylacetone and 25 mL isopropanol. Stir in an oil bath at 30°C for 2 hours; ② The mixture from step ① was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 200°C for 16 hours. The product was washed three times with anhydrous ethanol and then dried under vacuum at 60°C for 12 hours. The above process was repeated once to obtain a total of 0.8 g of self-assembled hollow TiO2 microspheres. ③ Take 0.7 g of the hollow TiO2 microspheres prepared in step ② and add them to 70 mL of 10 M NaOH solution. React in an oil bath at 120 °C for 50 minutes. After cooling, neutralize the mixture with HCl solution at pH=1 and stir magnetically for 10 hours. Wash the product with deionized water until neutral, dry it overnight at 60 °C (about 10 hours), and finally calcine it in a muffle furnace at 400 °C for 2 hours to obtain the dandelion-shaped TiO2 precursor. ④ Add the dandelion-like TiO2 precursor obtained in step ③ to 200 mL of anhydrous ethanol, followed by the addition of 0.1 g NaBH4 and 0.06 g NiCl2·6H2O. After magnetic stirring for 6 hours, centrifuge the mixture, wash the solid once with anhydrous ethanol, and then dry it overnight (about 10 hours) under vacuum at 60 °C. ⑤ Grind 0.4g of the sample from step ④ with 0.24g of NaBH4 in an agate mortar for 30 minutes, then transfer to a tube furnace and calcine at 300℃ for 3 hours at a heating rate of 5℃ / min under an argon atmosphere (flow rate 50 mL / min). After cooling, wash the product with deionized water until neutral, and dry it overnight (approximately 10 hours) under vacuum at 60℃, finally obtaining a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites. Its SEM image is shown below. Figure 10 As shown, by Figure 10 As can be seen, the material exhibits a dandelion-like morphology, and compared to Example 1, the surface morphology of Example 6 is slightly damaged. Meanwhile, its aberration-corrected scanning transmission electron microscopy (AC-HAADF-STEM) image is as follows... Figure 11 As shown, by Figure 11 It can be seen that Ni nanoparticles can be observed on the surface of the material, indicating that there is agglomeration of Ni particles on the surface of the material prepared according to Example 6.

[0032] Figure 6The figures show the extended X-ray absorption fine structure (EXAFS) spectra of Examples 1 and 6. As can be seen from the figures, compared to the standard spectra of Ni and NiO, Example 1 exhibits a stronger characteristic peak for the Ni-O bond, while the characteristic peak for the Ni-Ni bond almost disappears. Example 6 shows very strong characteristic peaks for both the Ni-O and Ni-Ni bonds, indicating that the Ni element in Example 1 exists in a single-atom form, while the Ni element in Example 6 exists in a coexisting form of single atoms and particles.

[0033] Figure 7 The images show the UV-Vis absorption spectra of Examples 1, 6, and P25. As can be seen from the figures, the product obtained in Example 1 exhibits stronger light absorption in both the UV region (<400 nm) and the visible region (400-760 nm), while the light absorption of Example 6 falls between that of Example 1 and commercial P25.

[0034] Figure 8 The figures show the photocurrent density of Examples 1, 6, and P25. As can be seen from the figures, Example 1 has a higher photocurrent density, indicating that Example 1 has a higher charge transfer rate.

[0035] Figure 9 The graphs show the photocatalytic hydrogen production activities of Examples 1, 3, and 6, and commercial P25. Compared to commercial P25, the hydrogen production activities of Examples 3 and 6 were increased by 50 times and 40 times, respectively, while the hydrogen production activity of Example 1 was increased by 60 times, with a hydrogen production rate of 4858 μmol g. -1 h -1 The hydrogen production performance test procedure was as follows: 50 mg of sample was dispersed in a mixed solution of 20 mL methanol and 80 mL deionized water, sonicated for 10 minutes, and then transferred to a 100 mL quartz reactor. A 300 W xenon lamp (200 mW / cm²) was used. 2 Vertical irradiation was applied, and 1 mL of gaseous product was collected every 0.5 hours using a closed syringe. The H2 content was analyzed using a GC-7920 gas chromatograph (argon as carrier gas, thermal conductivity detector). To assess catalyst stability, the experiment was conducted for three consecutive cycles of 5 hours each. The hydrogen generation rate was calculated as the H2 release per unit mass of catalyst (mmol·g). -1 ·h -1 ). Example 7

[0036] A method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites includes the following steps: ① First, add 5 mL of titanium sulfate to a mixed solution of 50 mL triethanolamine and 50 mL isopropanol. Stir in an oil bath at 40°C for 1 hour; ② The mixture from step ① was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 220°C for 16 hours. The product was washed three times with anhydrous ethanol and then dried under vacuum at 60°C for 12 hours to obtain self-assembled hollow TiO2 microspheres. ③ Add 0.7 g of the hollow TiO2 microspheres prepared in step ② to 50 mL of 10 M KOH solution and react in an oil bath at 100 °C for 1.5 hours. After cooling, neutralize the mixture with HCl solution at pH=1 and stir magnetically for 10 hours. Wash the product with deionized water until neutral, dry it overnight at 60 °C (about 10 hours), and finally calcine it in a tube furnace at 450 °C for 2 hours to obtain the dandelion-shaped TiO2 precursor. ④ Grind 0.45g of the sample from step ③ with 0.48g of NaBH4 in an agate mortar for 30 minutes, transfer to a tube furnace, and calcine at a temperature of 300℃ for 3 hours under a nitrogen atmosphere (flow rate 50 mL / min) at a heating rate of 5℃ / min. After cooling, wash the product with deionized water until neutral, and dry it overnight (about 10 hours) under vacuum at 60℃ to obtain the intermediate black dandelion-shaped TiO2. ⑤ Add 0.4g of the intermediate obtained in step ④ to 200 mL of anhydrous ethanol, followed by 0.15g of NaBH4 and 0.18g of NiSO4·6H2O. After magnetic stirring for 6 hours, centrifuge the mixture. Wash the solid once with anhydrous ethanol and dry it overnight (about 10 hours) under vacuum at 60℃. Then calcine it at 400℃ for 3 hours to finally obtain a hollow dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the specific implementation of the present invention and not to limit it. Those skilled in the art should understand that any equivalent substitutions or obvious modifications made to the implementation of the present invention without changing its performance or use, without departing from the spirit of the present invention, should be covered within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites, characterized in that, Includes the following steps: (1) Mix the hydrolysis inhibitor and alcohol source evenly, add liquid titanium source, and stir in an oil bath at 20~50℃ for 0.5h~5h or irradiate for 0.5~5h. (2) The mixture prepared in step (1) is heated at 150~220℃ for 12~24 h, and the resulting solid product is washed and dried to obtain self-assembled hollow TiO2 nanospheres; (3) Add the self-assembled hollow TiO2 nanospheres obtained in step (2) to a 5-10 M strong alkali solution, and perform a hydrothermal reaction at 100-150℃ for 0.5-3 h. After acid soaking, washing and drying, calcine at 300-500℃ for 1-4 h to obtain a hollow dandelion-like TiO2 intermediate. (4) Grind the powder obtained in step (3) with NaBH4 in a mortar, calcine at 200~500℃ for 2~5h under a protective atmosphere, and then wash and dry. (5) Add the powder obtained in step (4) to an alcohol source, then add a nickel source for reduction treatment. After washing and drying, calcine at 300~500℃ for 1~4 h to finally obtain a hollow dandelion-like TiO2 photocatalytic material with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites.

2. The method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites according to claim 1, characterized in that, The hydrolysis inhibitor mentioned in step (1) is a mixture of one or more of acetylacetone, benzoylacetone, triethanolamine, citric acid and ethylenediamine in any proportion; the alcohol source is a mixture of one or more of isopropanol, n-propanol, polyethylene glycol and polypropylene glycol in any proportion; the titanium source is a mixture of one or more of tetrabutyl titanate, titanium tetrachloride, titanium trichloride, isopropyl titanate, titanium sulfate and titanium oxysulfate in any proportion; the lamp source is a mercury lamp, xenon lamp and LED lamp; and the volume ratio of the hydrolysis inhibitor, alcohol source and titanium source is (7.5~12.5):(10~12.5):

1.

3. The method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites according to claim 1, characterized in that, Step (2) Washing is performed using a mixture of one or more of methanol, ethanol and butanol in any proportion.

4. The method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites according to claim 1, characterized in that, The strong alkali mentioned in step (3) is one or more of sodium hydroxide, potassium hydroxide and tetramethylammonium hydroxide in any proportion. The concentration of the self-assembled hollow TiO2 nanospheres in the strong alkali solution is 0.05~0.15 g / mL. The hydrothermal reaction conditions are a drying oven and an oil bath. Acid soaking refers to soaking in 0.1~0.2mol / L hydrochloric acid for 8~10 h.

5. The method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites according to claim 1, characterized in that, The protective atmosphere mentioned in step (4) refers to argon, helium or nitrogen, and the mass ratio of the powder obtained in step (3) to NaBH4 is 1: (0.2~1.1).

6. The method for preparing a hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites according to claim 1, characterized in that, The alcohol source in step (5) is one or more of methanol, ethanol and butanol in any proportion; the nickel source is one or more of nickel chloride, nickel nitrate, nickel sulfate, ethylenediamine nickel and ethylenediaminetetraacetic acid nickel in any proportion; and the reduction treatment is NaBH4 reduction, light reduction and H2 reduction.

7. The method for preparing a hollow dandelion-like TiO2 photonic crystal with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites according to claim 6, wherein in step (5), the mass ratio of the powder obtained in step (4), NaBH4 and nickel source is 1:(0.2~0.5):(0.05~0.5), and the concentration of the powder obtained in step (4) in the alcohol source is 0.001~0.005 g / mL.

8. A hollow, dandelion-like TiO2 photonic crystal with nano-confined bridging of Ni-O-Ti atomic-level asymmetric sites, prepared by any one of the preparation methods described in claims 1 to 7.

9. The application of the hollow dandelion-like TiO2 photonic crystal with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites as described in claim 8 in photocatalytic methanol and / or water-based hydrogen production.

10. The application according to claim 9, characterized in that, Hollow, dandelion-like TiO2 photonic crystals with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites were dispersed in methanol and / or deionized water, sonicated for 5–15 minutes, and then transferred to a quartz reactor for photocatalytic hydrogen production under vertical irradiation with a xenon lamp. When the solution was a mixture of methanol and water, the volume ratio of methanol to deionized water was 1:(3–5). The concentration of the hollow, dandelion-like TiO2 photonic crystals with nano-confined bridging Ni-O-Ti atomic-level asymmetric sites in the mixed solution was 0.4–0.6 mg / mL. The xenon lamp power was 200–400 W, and the light intensity was 150–250 mW / cm². 2 .

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