A Bi4V2O 11 / BiVO4 heterostructure composite materials and their in-situ preparation method

Abstract

This invention proposes a Bi4V2O 11 This invention relates to Bi4V2O heterostructure composite materials and their in-situ preparation method, belonging to the technical field of inorganic non-metallic materials. 11 The preparation of the / BiVO4 heterostructure composite material includes the following steps: Bi4V2O 11 The material was annealed in an oxygen-containing atmosphere to obtain Bi4V2O. 11 / BiVO4 heterostructure composite material. This invention utilizes the bismuth-rich compound Bi4V2O 11 A method for the volatilization of Bi in an oxygen-rich environment to construct Bi4V2O 11 / BiVO4 heterostructure. The prepared Bi4V2O 11 The / BiVO4 heterostructure photocatalyst exhibits excellent activity in photocatalytic degradation of organic pollutants and photocatalytic production of hydrogen peroxide; the preparation process is simple and applicable to various situations such as powders and thin films with different morphologies; the present invention combines process simplicity, wide applicability and superior performance, and has important application value in the fields of photocatalysis and functional electronic devices.

Description

Technical Field

[0001] This invention belongs to the technical field of inorganic non-metallic materials, and particularly relates to a Bi4V2O 11 / BiVO4 heterostructure. Background Technology

[0002] The Bi₂O₃-V₂O₅ system is a complex binary system containing various stable and metastable bismuth vanadium oxides, attracting considerable attention due to its excellent performance in photocatalysis, solid electrolytes, and pigments. Multiple stoichiometric compounds and solid solution regions have been identified within this system, with BiVO₄ (bismuth vanadate) and Bi₄V₂O₅ being the most representative. 11 (Bismuth-rich bismuth vanadate).

[0003] BiVO4 is the most widely studied vanadium bismuth oxide, mainly used in photocatalysis and environmentally friendly pigments.

[0004] Photocatalysis is the core and most promising application area of ​​BiVO4. Monoclinic scheelite-type BiVO4 has a valence band top potential of approximately 2.4 V vs. NHE (far exceeding the 1.23 V water oxidation potential) and a conduction band bottom potential of approximately 0.1 V vs. NHE, exhibiting both visible light responsiveness and strong redox capabilities, making it one of the most efficient photocatalysts for water oxidation under visible light. BiVO4 also has wide applications in the degradation of organic pollutants and harmful gases, photocatalytic reduction of CO2, and photocatalytic antibacterial processes.

[0005] In the field of environmentally friendly pigments, BiVO4 is the only bismuth-based yellow pigment (pigment yellow 184) that has achieved large-scale industrialization, and it can replace traditional toxic pigments containing heavy metals such as lead chromium yellow and cadmium yellow.

[0006] Bi4V2O 11 It is another important bismuth vanadium oxide, possessing an Aurivillius layered structure, and is commonly used in sensors and photocatalysis. In the late 1980s, French scientists F. Abraham et al. developed a novel bismuth oxide, Bi₄V₂O₅. 11 Using vanadium ions as the parent compound, a novel oxide ion-conducting solid dielectric, called bismuth vanadium oxide solid solution (BIMEVOX), was formed by doping vanadium ions with divalent metal ions. Upon its discovery, BIMEVOX quickly became one of the most promising electrolyte materials in the fields of solid oxide fuel cells (SOFCs) and sensors. (Bi4V2O) 11 The cations in the crystal conduct through the oxygen vacancies in the lattice. At high temperatures, the concentration of oxygen vacancies increases, which can significantly improve the conductivity. Doping with divalent metal ions can also effectively improve ionic conductivity.

[0007] Bi4V2O11 As a bismuth-vanadium oxide, its conduction band bottom is mainly dominated by the 3d orbitals of V, while the valence band top is formed by the hybridization of the 6s orbitals of Bi and the 2p orbitals of O. Its band gap is approximately 2.2 eV, enabling it to absorb visible light with wavelengths less than 560 nm, making it suitable for solar energy conversion applications. Bi₄V₂O 11 As a visible-light-responsive photocatalytic material, it can be used for the degradation of organic pollutants such as dyes and phenols; due to its valence band apex being located at approximately 1.9 V vs. NHE, it is suitable for water oxidation reactions and has the potential to be used as a photoanode material; Bi4V2O 11 It can also reduce CO2 into hydrocarbon fuels.

[0008] Theoretically, Bi4V2O 11 The band gap and band structure of Bi4V2O are well-suited for use as photocatalysts or photoanodes. However, in practical applications, Bi4V2O... 11 The photocatalytic degradation and water oxidation efficiencies of this compound are not ideal, far lower than those of bismuth vanadate, a compound with a bismuth-vanadium ratio of 1:1. In 2016, Jiang et al. (Sci. Rep. 2016, 6: 22727) first reported the orthorhombic phase Bi4V2O 11 The material exhibits a water oxidation reaction, but displays a very low photocurrent density. In 2023, Liu et al. (J. Phys. Chem. C 2023, 127: 11195-11203) discovered that in Bi4V2O rich in oxygen vacancies... 11 Interstitial states exist within Bi4V2O, including occupied and unoccupied states. The occupied states are located approximately 0.71 eV above the top of the valence band and are primarily composed of V3d orbitals. For clean Bi4V2O... 11 On the surface, the valence band peak is lower than the water oxidation potential, but water adsorption leads to the occupied state energy of interstitial states being higher than the water oxidation potential. This prevents holes from thermodynamically oxidizing water. Similarly, the enhanced interstitial states caused by surface water adsorption also affect liquid-phase reactions such as photocatalytic degradation or photocatalytic H2O2 production, leading to changes in Bi4V2O. 11 The photocatalytic activity decreases.

[0009] BiVO4 exhibits better photocatalytic activity than Bi4V2O. 11 However, BiVO4 also suffers from slow water oxidation kinetics and low carrier mobility, and its quantum efficiency cannot yet meet the needs of industrial photocatalysis.

[0010] Constructing heterostructures using two or more photocatalysts is an important method to promote carrier separation, reduce recombination, and enhance photocatalytic activity. For example, BiVO4 can form heterostructures with various semiconductor photocatalysts such as TiO2, g-C3N4, CdS, and Ag3VO4 to improve photocatalytic performance.

[0011] Interface is an important factor affecting the migration of charge carriers between different components of a heterostructure. Crystallinity, interface defects, interface area, lattice mismatch, and interface contact mode all affect the migration of photogenerated charge carriers at the interface and determine whether the charge carriers can be effectively separated in space. Constructing a high-quality, defect-free heterostructure interface is beneficial to improving photocatalytic performance. Common methods for constructing heterostructures are: (1) two materials are dispersed together in water or other solvents and bonded by stirring or sonication, often relying on electrostatic attraction or van der Waals forces; (2) material A is dispersed in the precursor of material B, and material B grows directly on material A; (3) the precursors of materials A and B are uniformly mixed, and phase separation occurs during the formation process. Material A forms first, and material B grows on material A, thus achieving the bonding of the two materials.

[0012] If material B is generated based on material A, it often implies a higher quality interface because the interface is tightly bonded, is less susceptible to contamination, and is less prone to lattice mismatch. For example, Wang et al. (Nature Catalysis, 2018, 1(10): 756-763) generated defect-free single-crystal Ta3N5 nanorods on the edge of KTaO3 crystals by in-situ nitriding KTaO3 crystals under an NH3 gas flow, forming a Ta3N5 / KTaO3 epitaxial heterostructure, which enabled efficient visible light water splitting. The formation of Ta3N5 nanorods is attributed to the volatilization of K during the KTaO3 nitriding process.

[0013] Lin Yi et al. from Sichuan University of Science and Engineering applied for a patent entitled "A Bi4V2O 11 The patent titled "Preparation method and application of BiVO4 heterojunction photocatalyst" (CN202011474708.2) was published, along with a publication titled "One-pot synthesis of Bi4V2O 11 The paper, "BiVO4 heterostructure with enhanced photocatalytic activity for dye degradation" (Applied Surface Science, 2021, 544: 148921), describes the inventors preparing Bi4V2O4 via a hydrothermal reaction using bismuth nitrate pentahydrate and ammonium metavanadate as precursors and ethylene glycol and sodium hydroxide solution as solvents. The inventors controlled the molar ratio of the precursor materials.11 / BiVO4 heterojunction photocatalyst.

[0014] Yang Yun et al. from Hanjiang Normal University prepared "Ag / Bi4V2O 11 / BiVO4" material (Industrial Water Treatment, 2023, 43(10): 117-122), Liang Mengjun et al. of Hubei Normal University prepared "Bi / Bi4V2O" material. 11 / BiVO4” material (Chinese Journal of Inorganic Chemistry, 2019, 35(2): 263-270), all prepared Bi4V2O by the same method as Lin Yi et al. 11 / BiVO4, and then composited with Ag or Bi metal by photodeposition.

[0015] Dos Santos et al. prepared Bi4V2O on FTO and SnO2 substrates using ammonium metavanadate and bismuth nitrate pentahydrate as precursors and ammonia and acetic acid as solvents via spray pyrolysis. 11 / BiVO4 thin films (Applied Catalysis B:Environmental, 2016, (182): 247–256). Based on this, 1 mol% tungsten-doped Bi4V2O was further prepared. 11 / BiVO4 photoanode (CHEMSUSCHEM, 2018, 11(3): 589-597).

[0016] Song et al. used pulsed laser deposition with BiVO4 as the target material and achieved epitaxial Bi4V2O by controlling the oxygen partial pressure. 11 Growth of BiVO4 epitaxial films (Chemistry of Materials, 2018, 30(16): 5673-5681). Benefiting from Bi4V2O 11 The efficient charge transfer properties of the thin film, BiVO4 / Bi4V2O 11 The photocurrent density of the heterojunction structure is much higher than that of the epitaxial BiVO4 pure film.

[0017] Khadka et al. achieved the desired BiVO4 and Bi4V2O ratios by adjusting the Bi and V proportions in the precursor material. 11 / BiVO4 or Bi4V2O 11 Thin film preparation by spin coating (Materials Science and Engineering B: Advanced Functional Solid-State Materials, 2026, 326: 119231).

[0018] Li et al. prepared sheet-like Bi₄V₂O using bismuth nitrate and ammonium metavanadate as precursors via a hydrothermal method. 11 / BiVO4 photocatalyst for the degradation of sulfadiazine (Materials Chemistry and Physics, 2020, 254: 123489).

[0019] Chade et al. prepared Bi₄V₂O₃ using bismuth nitrate and ammonium metavanadate as precursors via electrospinning. 11 / BiVO4 nanofibers significantly improve the photocurrent density of heterostructured materials (Applied Catalysis B: Environmental, 2015, 179: 54-60).

[0020] Saadati et al., TiO 2-x The bismuth nitrate was dispersed in an ethylene glycol solution, and then bismuth nitrate pentahydrate and ammonium metavanadate were added. After adjusting the pH with ammonia, a hydrothermal reaction was carried out to produce TiO2. 2-x / Bi4V2O 11 / BiVO4 ternary nanocomposite material (Advanced Powder Technology, 2023, 34(3): 103956).

[0021] Trzcinski et al. prepared V₂O₅ / Bi₄V₂O₅ using pulsed laser deposition with monoclinic BiVO₄ as the target material under different oxygen partial pressures. 11 / BiVO4 ternary composite film for PEC water splitting (Materials, 2020, 13(6):1360).

[0022] Zong et al. prepared Bi₄V₂O using carbon microspheres as templates and bismuth nitrate pentahydrate and ammonium metavanadate as precursors via a liquid-phase reaction followed by calcination. 11 / BiVO4 heterostructure multi-shell hollow sphere (Materials Research Bulletin, 86).

[0023] Wang et al. prepared Bi₄V₂O using a hydrothermal method with bismuth nitrate pentahydrate and ammonium metavanadate as precursors and nitric acid and sodium hydroxide as solvents. 11 / BiVO4 heterojunction material, the principle of heterostructure formation is self-phase separation (Sensors and Actuators B: Chemical, 2022, 373(15): 132765).

[0024] The above information is about Bi4V2O 11In the preparation of BiVO4 heterostructures, one approach is to use bismuth nitrate pentahydrate and ammonium metavanadate as precursors, and prepare powder samples via hydrothermal or chemical methods, or further electrospinning or spin-coating to form thin films; another approach is to use pulsed laser deposition, adjusting the oxygen partial pressure to achieve BiVO4 and Bi4V2O 11 Coexistence. However, the above-mentioned Bi4V2O 11 / BiVO4 heterostructures have poor controllability and complex preparation processes. Summary of the Invention

[0025] To address the aforementioned technical problems, this invention proposes a Bi4V2O 11 BiVO4 heterostructure composite materials and their in-situ preparation method, through the bismuth-rich compound Bi4V2O 11 A method for the volatilization of Bi in an oxygen-rich environment to construct Bi4V2O 11 / BiVO4 heterostructure.

[0026] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0027] A Bi4V2O 11 An in-situ preparation method for BiVO4 heterostructure composite materials includes the following steps: preparing Bi4V2O... 11 The material was annealed in an oxygen-containing atmosphere to obtain Bi4V2O. 11 / BiVO4 heterostructure composite material.

[0028] The Bi4V2O 11 The material is either powder or film.

[0029] The Bi4V2O 11 The preparation method when the material is in powder form is as follows: Bismuth nitrate, ammonium metavanadate, and urea are dispersed and dissolved in ethylene glycol solution, the pH is adjusted to 7.5, and a solvothermal reaction is carried out. After the reaction is completed, the mixture is washed and dried to obtain Bi4V2O. 11 powder.

[0030] The molar ratio of bismuth nitrate to ammonium metavanadate is 2:1, the concentration of bismuth nitrate in ethylene glycol is 0.05-0.1 mmol / mL, and the concentration of urea in ethylene glycol is 0.01-0.02 g / mL; the temperature of the solvothermal reaction is 150-200℃, and the time is 12-36 h.

[0031] The Bi4V2O 11 The material thin film was prepared by magnetron sputtering.

[0032] The target material in the magnetron sputtering is prepared by sintering a mixture of Bi2O3 and V2O5, wherein the molar ratio of Bi2O3 to V2O5 is 2:1. The Bi2O3-V2O5 target material is sputtered using an RF power supply with a power of 30W~50W, an argon partial pressure of approximately 1Pa~2.5Pa, an oxygen partial pressure of approximately 1Pa~2.2Pa, a substrate temperature of 500℃, a deposition time of 15min~2h, and a stabilization period of 15 minutes after deposition.

[0033] The oxygen-containing atmosphere is pure oxygen, air, or a mixture of oxygen and an inert gas, wherein the volume fraction of oxygen in the mixture is 10%-100%.

[0034] Preferred, Bi4V2O 11 When the material is a powder, any of the above-mentioned oxygen-containing atmospheres are acceptable; when it is a thin film, the oxygen-containing atmosphere is pure oxygen.

[0035] The oxygen partial pressure during the annealing process is 50 Pa to 22 kPa, and the total pressure is 50 Pa to 102 kPa.

[0036] Preferably, the oxygen partial pressure during the annealing treatment is 50 Pa to 300 Pa, and the total pressure is 50 Pa to 1 kPa.

[0037] The annealing treatment is performed at a temperature of 470-560℃, with a holding time of 1-5 hours, and both the heating and cooling rates are 2-4℃ / min.

[0038] The beneficial effects of this invention are:

[0039] (1) The present invention uses Bi4V2O 11 The precursor only needs to be calcined under appropriate oxygen partial pressure, without the need for complicated experimental procedures and precision equipment. Compared with other preparation methods, it is simpler to operate and has a more streamlined process, making it easier to promote and apply.

[0040] (2) The method described in this invention is applicable not only to Bi4V2O in powder form. 11 The material is also applicable to Bi4V2O in thin films and other morphologies. 11 The material overcomes the limitation of existing methods, which can typically only construct heterostructure composites with specific morphologies.

[0041] (3) In the preparation method of the present invention, BiVO4 is in Bi4V2O during the calcination process. 11 In-situ surface generation creates a tight and well-bonded interface between the two materials, effectively promoting the transfer of photogenerated carriers at the interface and laying the foundation for improving photocatalytic performance.

[0042] (4) Bi4V2O 11Both Bi4V2O and BiVO4 possess good light absorption characteristics and suitable band structures. After forming a heterostructure, photogenerated electrons can be transferred to Bi4V2O. 11 Holes are transferred to BiVO4, achieving spatial separation of charge carriers and significantly improving photocatalytic efficiency.

[0043] (5) The heterostructure of the present invention exhibits “surface BiVO4, internal Bi4V2O”. 11 The characteristics of "Bi4V2O" can be utilized. 11 It has good electrical conductivity and can avoid Bi4V2O in a liquid environment. 11 Direct contact with water extends the material's lifespan; it is particularly suitable for thin-film electrode fabrication, with surface BiVO4 capable of oxygen generation and inner Bi4V2O... 11 Electron extraction is achieved by contacting the conductive layer, forming an ideal electrode structure.

[0044] (6) The photocatalytic activity of the Bi4V2O prepared in this invention was evaluated by two characterization methods: degradation of the typical pollutant Rhodamine B under visible light and production of hydrogen peroxide. 11 The photocatalytic activity of the / BiVO4 composite material is compared with that of single-component BiVO4 or Bi4V2O. 11 The activity advantage is significantly improved, and the specific characterization data can be quantified, further confirming the synergistic effect of the heterostructure. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 Bi4V2O 11 ,Bi4V2O 11 / BiVO4-500 and Bi4V2O 11 XRD patterns of three powder samples: -500-Ar.

[0047] Figure 2 for Figure 1 A magnified view of a portion of the image.

[0048] Figure 3 Bi4V2O was prepared for Examples 1-4. 11 XRD pattern of the / BiVO4 sample.

[0049] Figure 4 for Figure 3 A magnified view of a portion of the image.

[0050] Figure 5 Bi4V2O prepared in Example 5 11 XRD pattern of air.

[0051] Figure 6 Bi4V2O 11 SEM image of the powder.

[0052] Figure 7 Bi4V2O was prepared for Examples 1-4. 11 SEM image of the / BiVO4 sample.

[0053] Figure 8 Bi4V2O 11 Bi4V2O prepared by powder, Examples 2 and 3 11 / BiVO4 adsorption-desorption isotherm.

[0054] Figure 9 Bi4V2O 11 Bi4V2O prepared by powder, Examples 2 and 3 11 Pore ​​size distribution of / BiVO4.

[0055] Figure 10 Bi4V2O 11 BiVO4 powder, Bi4V2O prepared in Examples 1-4 11 The UV-Vis absorption spectrum of / BiVO4 material.

[0056] Figure 11 Bi4V2O 11 Band gap diagram of BiVO4 powder.

[0057] Figure 12 Bi4V2O 11 Preparation of Bi4V2O in Examples 1-4 11 Fluorescence intensity of / BiVO4 material.

[0058] Figure 13 Bi4V2O 11 and Bi4V2O 11 XPS full spectrum of / BiVO4-530.

[0059] Figure 14 Bi4V2O 11 and Bi4V2O 11 High-resolution XPS spectrum of Bi 4f from / BiVO4-530.

[0060] Figure 15 Bi4V2O 11 and Bi4V2O 11High-resolution XPS spectrum of V 2p of / BiVO4-530.

[0061] Figure 16 Bi4V2O 11 and Bi4V2O 11 O 1s high-resolution XPS spectrum of / BiVO4-530.

[0062] Figure 17 Bi4V2O 11 and Bi4V2O 11 / BiVO4-530 and Bi4V2O 11 - EPR spectrum of air under normal temperature, air environment, and dark conditions.

[0063] Figure 18 Bi4V2O 11 EPR spectrum of / BiVO4-530 sample under Ar protection at 78K.

[0064] Figure 19 Bi4V2O 11 BiVO4 and Bi4V2O prepared in Examples 1-4 11 Photocatalytic activity of / BiVO4 material for RhB degradation under visible light.

[0065] Figure 20 Bi4V2O 11 BiVO4 and Bi4V2O prepared in Examples 1-4 11 Test data of / BiVO4 material for photocatalytic H2O2 production under visible light.

[0066] Figure 21 Bi4V2O 11 Thin film and Bi4V2O prepared in Example 6 11 XRD pattern of / BiVO4 thin film.

[0067] Figure 22 Bi4V2O was prepared for Example 6. 11 SEM and EDS of / BiVO4 thin film, (a) SEM; (b) EDS.

[0068] Figure 23 Bi4V2O was prepared for Example 6. 11 / Elemental ratio of BiVO4 thin film. Detailed Implementation

[0069] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] Bi4V2O 11 Powder preparation:

[0071] (1) Add 1g of urea to 70 mL of ethylene glycol and stir until completely dissolved. Add 2.425 g (5 mmol) of bismuth nitrate pentahydrate and stir for half an hour to obtain a milky white suspension. Then add 0.2925 g (5 mmol) of ammonium metavanadate and stir for half an hour to obtain a yellow suspension. Heat to 95℃ and maintain for 15 min to completely dissolve the precursor and obtain a clear orange solution.

[0072] (2) Adjust the pH of the sample to 7.5 with ammonia water to obtain a pale yellow viscous solution.

[0073] (3) Transfer the solution to a 100 mL polytetrafluoroethylene-lined reactor, place it in a forced-air drying oven, heat it to 180°C, and keep it for 24 hours.

[0074] (4) After natural cooling, the brown precipitate was filtered out, washed repeatedly with ultrapure water and anhydrous ethanol, and dried at 80 °C overnight. The resulting yellow powder was Bi4V2O. 11 .

[0075] Bi4V2O 11 Thin film preparation:

[0076] (1) Prepare a target material for sintering Bi2O3 and V2O5, wherein the molar ratio of Bi2O3 to V2O5 is 2:1.

[0077] (2) Yttrium-stabilized zirconium oxide (YSZ) single crystal is used as substrate, the exposed crystal plane of YSZ is (100) crystal plane, and ITO thin film is pre-deposited on the surface as conductive layer.

[0078] (3) Before sputtering, the YSZ substrate was sonicated with acetone, alcohol, and water for 20 minutes each. After sonication, it was dried with nitrogen. The substrate was then attached to the sample stage of the magnetron sputtering system with silver paste, and the temperature was raised to 500 ℃. Vacuum was continuously pumped until the vacuum level decreased to 1×10⁻⁶. -4 Below Pa, the substrate surface was then cleaned with argon ions under a pulse bias of 800 V, a duty cycle of 75%, and a duration of 1 min.

[0079] (4) ITO target material was used to pre-deposit conductive layer, DC sputtering, pure argon gas environment, argon gas pressure of 2.2 Pa, substrate temperature of 500℃, and deposition time of 13 min.

[0080] (5) The Bi2O3-V2O5 target was sputtered using an RF power supply with a power of 40 W, an argon partial pressure of approximately 2 Pa, an oxygen partial pressure of approximately 2 Pa, a substrate temperature of 500 ℃, a deposition time of 1 h, and a stabilization period of 15 min after deposition. The resulting light yellow film on the substrate was Bi4V2O 11 On a YSZ substrate, Bi4V2O 11 The thin film has a specific crystal orientation (00k).

[0081] The following specific examples all use Bi4V2O prepared by the above method. 11 powder or film

[0082] Example 1

[0083] A Bi4V2O 11 The in-situ preparation method of the / BiVO4 heterostructure composite material includes the following steps: Bi4V2O 11 The powder is placed in an alumina crucible and spread evenly. Then, the crucible is placed into the quartz tube of a tube furnace. After sealing both ends of the quartz tube with O-ring flanges, the air pressure in the quartz tube is evacuated to about 300 Pa using a mechanical pump. Then, the mechanical pump is removed, and the quartz tube is sealed.

[0084] Bi4V2O 11 The powder was annealed in a tube furnace at 470℃ for 3 hours, with both the heating and cooling rates controlled at 3℃ / min. During the heating process, the gas pressure initially increased and then decreased, but the total pressure did not exceed 1 kPa. After cooling, Bi4V2O was obtained. 11 / BiVO4 composite powder material (denoted as Bi4V2O) 11 / BiVO4-470).

[0085] Example 2

[0086] A Bi4V2O 11 The in-situ preparation method of the / BiVO4 heterostructure composite material includes the following steps: Bi4V2O 11 The powder is placed in an alumina crucible and spread evenly. Then, the crucible is placed into the quartz tube of a tube furnace. After sealing both ends of the quartz tube with O-ring flanges, the air pressure in the quartz tube is evacuated to about 300 Pa using a mechanical pump. Then, the mechanical pump is removed, and the quartz tube is sealed.

[0087] Bi4V2O 11The powder was annealed in a tube furnace at 500℃ for 3 hours, with both the heating and cooling rates controlled at 3℃ / min. During the heating process, the gas pressure initially increased and then decreased, but the total pressure did not exceed 1 kPa. After cooling, Bi4V2O was obtained. 11 / BiVO4 composite powder material (denoted as Bi4V2O) 11 / BiVO4-500).

[0088] Example 3

[0089] A Bi4V2O 11 The in-situ preparation method of the / BiVO4 heterostructure composite material includes the following steps: Bi4V2O 11 The powder is placed in an alumina crucible and spread evenly. Then, the crucible is placed into the quartz tube of a tube furnace. After sealing both ends of the quartz tube with O-ring flanges, the air pressure in the quartz tube is evacuated to about 300 Pa using a mechanical pump. Then, the mechanical pump is removed, and the quartz tube is sealed.

[0090] Bi4V2O 11 The powder was annealed in a tube furnace at 530℃ for 3 hours, with both the heating and cooling rates controlled at 3℃ / min. During the heating process, the gas pressure initially increased and then decreased, but the total pressure did not exceed 1 kPa. After cooling, Bi4V2O was obtained. 11 / BiVO4 composite powder material (denoted as Bi4V2O) 11 / BiVO4-530).

[0091] Example 4

[0092] A Bi4V2O 11 The in-situ preparation method of the / BiVO4 heterostructure composite material includes the following steps: Bi4V2O 11 The powder is placed in an alumina crucible and spread evenly. Then, the crucible is placed into the quartz tube of a tube furnace. After sealing both ends of the quartz tube with O-ring flanges, the air pressure in the quartz tube is evacuated to about 300 Pa using a mechanical pump. Then, the mechanical pump is removed, and the quartz tube is sealed.

[0093] Bi4V2O 11 The powder was annealed in a tube furnace at 560℃ for 3 hours, with both the heating and cooling rates controlled at 3℃ / min. During the heating process, the gas pressure initially increased and then decreased, but the total pressure did not exceed 1 kPa. After cooling, Bi4V2O was obtained. 11 / BiVO4 composite powder material (denoted as Bi4V2O) 11 / BiVO4-560).

[0094] Example 5

[0095] A Bi4V2O 11The in-situ preparation method of the / BiVO4 heterostructure composite material includes the following steps: Bi4V2O 11 The powder was placed in a corundum crucible, spread evenly, and then the crucible was placed in the quartz tube of a tube furnace. In an air environment, Bi₄V₂O 11 The powder was annealed in a tube furnace at 500℃ for 3 hours, with both the heating and cooling rates controlled at 3℃ / min. After cooling, it was removed to obtain Bi4V2O. 11 / BiVO4 composite powder material (denoted as Bi4V2O) 11 -air).

[0096] Example 6

[0097] A Bi4V2O 11 The in-situ preparation method of the / BiVO4 heterostructure composite material includes the following steps: Bi4V2O in a magnetron sputtering system. 11 The substrate temperature was kept constant at 500 °C. Ar gas was shut off, and oxygen flow was increased to achieve an oxygen partial pressure of 100 Pa within the chamber. Annealing was performed for 3 hours, followed by natural cooling before removal to obtain Bi₄V₂O. 11 / BiVO4 composite thin film material (structure is BiVO4 / Bi4V2O) 11 / ITO / YSZ(001)).

[0098] Example 7

[0099] A Bi4V2O 11 The in-situ preparation method of the / BiVO4 heterostructure composite material includes the following steps: Bi4V2O 11 The powder is placed in an alumina crucible and spread evenly. Then, the crucible is placed into the quartz tube of a tube furnace. After sealing both ends of the quartz tube with O-ring flanges, the air pressure in the quartz tube is evacuated to about 300 Pa using a mechanical pump. Then, the mechanical pump is removed, and the quartz tube is sealed.

[0100] Bi4V2O 11 The powder was annealed in a tube furnace at 500℃ for 5 hours, with both the heating and cooling rates controlled at 2℃ / min. During the heating process, the gas pressure initially increased and then decreased, but the total pressure did not exceed 1 kPa. After cooling, Bi4V2O was obtained. 11 / BiVO4 composite powder material.

[0101] Example 8

[0102] A Bi4V2O 11 The in-situ preparation method of the / BiVO4 heterostructure composite material includes the following steps: Bi4V2O 11The powder is placed in a corundum crucible and spread evenly. Then, the crucible is placed into the quartz tube of a tube furnace. After sealing both ends of the quartz tube with O-ring flanges, the air pressure in the quartz tube is evacuated to about 1000 Pa using a mechanical pump. Then, the mechanical pump is removed, and the quartz tube is sealed.

[0103] Bi4V2O 11 The powder was annealed in a tube furnace at 500℃ for 1 hour, with both the heating and cooling rates controlled at 4℃ / min. After cooling, it was removed to obtain Bi4V2O. 11 / BiVO4 composite powder material.

[0104] Example 9

[0105] A Bi4V2O 11 The material and preparation method include the following steps: Bi4V2O 11 The powder is placed in a corundum crucible and spread evenly. Then, the crucible is placed into the quartz tube of a tube furnace. After sealing both ends of the quartz tube with O-ring flanges, O2 gas is introduced to replace the air inside the tube furnace. Then, a mechanical pump is used to evacuate the air pressure in the quartz tube to about 300 Pa. Finally, the mechanical pump is removed, and the quartz tube is sealed.

[0106] Bi4V2O 11 The powder was annealed in a tube furnace at 500℃ for 3 hours, with both the heating and cooling rates controlled at 3℃ / min. After cooling, it was removed to obtain Bi4V2O. 11 Powder material.

[0107] Comparative Example 1

[0108] A Bi4V2O 11 The material and preparation method include the following steps: Bi4V2O 11 The powder is placed in an alumina crucible and spread evenly. Then, the crucible is placed into the quartz tube of a tube furnace. After sealing both ends of the quartz tube with O-ring flanges, Ar gas is introduced to replace the air inside the tube furnace. Then, a mechanical pump is used to evacuate the air pressure in the quartz tube to about 300 Pa. Finally, the mechanical pump is removed, and the quartz tube is sealed.

[0109] Bi4V2O 11 The powder was annealed in a tube furnace at 500℃ for 3 hours, with both the heating and cooling rates controlled at 3℃ / min. During the heating process, the gas pressure initially increased and then decreased, but the total pressure did not exceed 1 kPa. After cooling, Bi4V2O was obtained. 11 Powder material (denoted as Bi4V2O) 11 -500-Ar).

[0110] from Figure 1 The XRD characterization results show that Bi4V2O prepared by the solvothermal method... 11It is a pure phase β-Bi4V2O 11 This corresponds to standard card #42-0135. After annealing at 500 °C for 3 h in a tube furnace, the sample Bi4V2O... 11 In / BiVO4-500 (green line), besides β-Bi4V2O 11 In addition to the diffraction peaks (peak marked 1), diffraction peaks of BiVO4 (peak marked 2) also appeared, indicating the presence of Bi4V2O. 11 The transition to BiVO4.

[0111] If annealing is performed at 500℃ for 3 hours in an argon atmosphere (sample Bi4V2O) 11 -500-Ar (purple line), except for β-Bi4V2O 11 In addition to the diffraction peaks (peak marked 1), α-Bi4V2O also appeared. 11 The diffraction peaks (peak marked 3) indicate Bi4V2O. 11 A slight phase transition occurred, but it did not transform into BiVO4.

[0112] This indicates that annealing in an air environment at 300 Pa (containing a suitable amount of oxygen) can achieve the volatilization of Bi, reduce the Bi and V ratio, and produce Bi4V2O on the surface. 11 It is converted into BiVO4 to form Bi4V2O 11 / BiVO4 heterostructure. In an Ar atmosphere, due to the lack of oxygen, Bi does not volatilize, and the bismuth-vanadium ratio remains at 2:1.

[0113] Figure 2 Bi4V2O 11 ,Bi4V2O 11 / BiVO4-500 and Bi4V2O 11 Enlarged images of the (113) diffraction peaks of three powder samples of -500-Ar. It can be seen that after annealing in air at 500 ℃ for 3 h, the diffraction peaks in Bi4V2O... 11 The appearance of a shoulder peak belonging to BiVO4 near peak (113) proves that Bi4V2O 11 The transformation to BiVO4. After annealing at 500 °C for 3 h in argon, the intensity of peak (113) increased, which is due to the increase in crystallinity caused by the annealing process, but the peak of BiVO4 did not appear.

[0114] Figure 3 Bi4V2O 11XRD patterns of annealed at different temperatures (470 ℃, 500 ℃, 530 ℃, 560 ℃) in air. It can be seen that the diffraction peaks belonging to BiVO4 gradually increase with increasing annealing temperature. When the annealing temperature reaches 560 ℃, diffraction peaks of bismuth oxide or vanadium oxide begin to appear in the XRD pattern.

[0115] exist Figure 4 In the magnified XRD pattern, the changes in the (110), (011), and (040) diffraction peaks of BiVO4 are clearly visible with increasing temperature. The diffraction peaks of BiVO4 gradually intensify with increasing temperature. This may indicate the presence of more Bi4V2O. 11 The shift towards BiVO4 may also stem from an increase in the crystallinity of the sample.

[0116] Figure 5 The sample is Bi4V2O 11 The XRD pattern of -air, peak 1 in the figure represents Bi4V2O. 11 The diffraction peaks are shown in Figure 2, with the peaks marked as BiVO4 being the diffraction peaks. Sample Bi4V2O 11 -air is Bi4V2O 11 The samples were obtained by annealing directly in air at 500 °C for 3 hours in a tube furnace. It can be seen that the BiVO4-related peaks are stronger under high oxygen pressure annealing conditions. However, similar to the samples annealed at 560 °C, multiple vanadium oxide and bismuth oxide-related peaks (marked with *) appeared. This indicates that controlling the oxygen pressure is crucial.

[0117] Figure 6 Bi4V2O prepared by solvothermal method is given. 11 The SEM image shows Bi4V2O. 11 It has a morphology similar to a ball of yarn and is formed by the self-assembly of nanosheets.

[0118] Figure 7 Bi4V2O prepared by post-annealing at different temperatures in air is presented. 11 SEM morphology of the / BiVO4 heterostructure. Figure 7 (a), (b), (c), and (d) are samples annealed at 470 ℃, 500 ℃, 530 ℃, and 560 ℃, respectively. It can be seen that as the annealing temperature increases, the surface microstructures of the samples gradually sinter together. The samples annealed at 470 ℃, 500 ℃, and 530 ℃ maintain their microspherical structure, while the sample annealed at 560 ℃ shows significant surface collapse.

[0119] Figure 8 As can be seen from the adsorption-desorption isotherms, Figure 8 Bi4V2O 11Its specific surface area is significantly higher than that of Bi4V2O 11 / BiVO4-500 and Bi4V2O 11 The presence of the / BiVO4-530 sample indicates that the surface microstructure collapsed after annealing. This is consistent with the results in Table 1. Table 1 also shows that the higher the annealing temperature, the smaller the specific surface area.

[0120] Figure 9 Aperture distribution map, from Figure 9 It can be seen that Bi4V2O 11 The total pore volume is significantly higher than that of Bi4V2O 11 / BiVO4-500 and Bi4V2O 11 The reason for the failure of the / BiVO4-530 sample is still the collapse of the surface microstructure after annealing.

[0121] Table 1

[0122]

[0123] It can be seen that Bi4V2O has a rich surface microstructure 11 The sample with the largest specific surface area was 41.197 m². 2 / g. The specific surface area decreased significantly after annealing. Moreover, the specific surface area of ​​the sample decreased further with increasing annealing temperature.

[0124] Figure 10 Bi4V2O was given 11 BiVO4, and Bi4V2O annealed at different temperatures 11 The UV-Vis absorption spectrum of the BiVO4 heterostructure can be seen. 11 It exhibits better light absorption performance than BiVO4, with significantly higher absorption in the visible light region. Bi4V2O annealed at different temperatures... 11 The absorption spectrum of the BiVO4 heterostructure is intermediate between that of Bi4V2O 11 The absorption spectra of BiVO4 are quite similar to those of BiVO4, and the higher the annealing temperature, the closer the absorption spectrum is to that of BiVO4.

[0125] Figure 11 Bi4V2O was given 11 Bandgap diagrams for Bi4V2O and BiVO4. (Bi4V2O is mentioned here.) 11 The band gap of the α-oxo group is approximately 2.22 eV, while that of BiVO4 is approximately 2.43 eV, both consistent with results from other researchers. This also explains the band gap of Bi4V2O. 11 The light absorption performance of Bi4V2O is superior to that of BiVO4. 11BiVO4 heterostructures, as composite materials, have light absorption capabilities intermediate between those of Bi4V2O. 11 Between BiVO4 and BiVO4.

[0126] Figure 12 Bi4V2O was given 11 Bi4V2O annealed at different temperatures 11 The fluorescence intensity of the BiVO4 heterostructure can be seen. 11 The fluorescence intensity of the / BiVO4 heterostructure is lower than that of Bi4V2O 11 The samples demonstrate that their photogenerated charges can be separated more effectively, avoiding rapid recombination. Among them, the sample annealed at 530 °C exhibits the lowest fluorescence intensity.

[0127] Depend on Figure 13 The XPS full spectrum shows that Bi4V2O 11 and Bi4V2O 11 The surface elements of the / BiVO4 heterostructure are all contaminated with Bi, V, O and C.

[0128] Depend on Figure 14 Bi4V2O 11 and Bi4V2O 11 The high-resolution XPS spectra of Bi 4f in the / BiVO4 heterostructure show that the Bi 4f7 / 2 peaks are located at 159.07 eV and 159.16 eV, respectively, while the Bi 4f5 / 2 peaks are located at 164.27 eV and 164.46 eV, respectively, all corresponding to Bi 4f7 / 2 peaks. 3+ Ions. Bi4V2O 11 The peak of / BiVO4-530 shifts slightly towards the higher binding energy side, indicating a slight change in the coordination environment. (In Bi4V2O) 11 In the / BiVO4-530 sample, two shoulder peaks exist on the high binding energy side of the main peak, located at 160.22 eV and 165.55 eV, respectively. These are mainly caused by Bi vacancies on the sample surface. This further confirms that the presence of BiVO4 originates from Bi4V2O. 11 The volatilization of Bi in the middle.

[0129] Bi4V2O 11 and Bi4V2O 11 The V 2p high-resolution XPS spectrum of the / BiVO4 heterostructure is shown below. Figure 15 As shown. The main peaks of the V2p3 / 2 peaks of the two samples are located at 516.58 eV and 516.70 eV, respectively, corresponding to V 5+ Ions. Similar to Bi₄f, Bi₄V₂O 11The peak positions of the / BiVO4 heterostructure are slightly shifted towards the high binding energy side. Both samples exhibit shoulder peaks on the high binding energy side, located at 517.58 eV and 517.65 eV, respectively, corresponding to the V2 peaks near the Bi vacancies. 5+ Ions. Among them, Bi4V2O 11 The shoulder area in the BiVO4-530 sample was significantly higher than that in the Bi4V2O sample. 11 The sample indicates that the former has more Bi vacancies.

[0130] Bi4V2O 11 and Bi4V2O 11 The O 1s high-resolution XPS spectrum of the / BiVO4-530 sample is as follows: Figure 16 As shown, the O1s main peaks of the two samples are located at 529.69 eV and 529.77 eV, respectively, corresponding to Bi4V2O. 11 And lattice oxygen in BiVO4. The shoulder peaks on the high binding energy side, located at 530.74 eV and 530.80 eV respectively, correspond to oxygen adsorbed at oxygen defect sites and oxygen adsorbed on the surface or in water.

[0131] Bi4V2O 11 and Bi4V2O 11 The EPR spectra of the / BiVO4-530 sample under normal temperature, air environment, and dark conditions are as follows: Figure 17 As shown in the figure, the EPR signal at g = 2.003 originates from stable oxygen vacancies in the sample. There is a direct proportional relationship between the integrated intensity of the EPR signal and the number of paramagnetic active centers; we can also approximate the intensity of the EPR signal using amplitude or peak-to-peak value. As can be seen from the figure, Bi4V2O 11 Oxygen vacancies increase in an oxygen-deficient environment (Ar atmosphere) and decrease in an oxygen-containing atmosphere, which is consistent with the pattern of oxygen vacancy content during oxide preparation.

[0132] Bi4V2O 11 The EPR spectrum of the / BiVO4-530 sample under Ar protection at 78K is shown below. Figure 18 As shown, the EPR signal at g = 2.0034 corresponds to oxygen vacancies, consistent with the results obtained at room temperature. The EPR signal at g = 2.2035 is related to Bi vacancies, which are difficult to detect under room temperature air conditions. Figure 18 This indicates that Bi volatilization occurs during the annealing process, leading to the creation of Bi vacancies. Figure 14 , 15 The results from XPS are consistent. This further illustrates that the formation of BiVO4 is related to the volatilization of Bi.

[0133] Figure 19 Bi4V2O was given 11 Samples, Bi4V2O annealed at different temperatures 11 / BiVO4 heterostructure sample and photocatalytic activity of BiVO4 sample for RhB degradation under visible light.

[0134] BiVO4 was used as a control sample and prepared as follows: 1 g of urea and 2.425 g of bismuth nitrate pentahydrate were added to 35 mL of ethylene glycol and stirred until completely dissolved, forming solution A; 6.533 g of NaOH and 0.585 g of ammonium metavanadate were added to 35 mL of ultrapure water and stirred until completely dissolved, forming solution B; solution B was introduced into solution A, and the pH was adjusted to 7.5 with nitric acid; then the mixed solution was transferred to a 100 mL reactor and hydrothermally reacted at 180 °C for 24 hours. After natural cooling, the precipitate was collected by vacuum filtration, washed three times each with ultrapure water and anhydrous ethanol, and dried overnight at 70 °C.

[0135] The RhB degradation test procedure is as follows: A 300 W arc xenon lamp with a cutoff filter (≥ 420 nm) is used as the light source. 50 mg of Bi4V2O is then applied. 11 or Bi4V2O 11 BiVO4 powder sample and 70 mL of 10 mg / L RhB solution were added to a 100 mL photocatalytic reactor and stirred in the dark for 30 min to reach adsorption-desorption equilibrium. During illumination, 2 mL of suspension was extracted from the reactor every 10 min, and the sample powder was separated by centrifugation to obtain RhB supernatant. The peak intensity of the characteristic peak of RhB supernatant at 554 nm was measured using a UV-Vis spectrophotometer as an indicator of RhB concentration change.

[0136] It can be seen that the photocatalytic activity of the heterostructure is significantly better than that of Bi4V2O. 11 This stems from the more efficient separation of photogenerated charges in the heterostructure. Among the samples annealed at 530 °C, the best photocatalytic activity was observed. The photocatalytic activity of the sample annealed at 560 °C was lower than that of the sample annealed at 530 °C, possibly due to the complete collapse of the surface microstructure and impurities present in the heterostructure. The photocatalytic activity of samples annealed at 500 °C and above was superior to that of pure BiVO4.

[0137] Figure 20 Bi4V2O was given 11 Samples, Bi4V2O annealed at different temperatures 11 The results of testing the BiVO4 heterostructure sample and the photocatalytic production of H2O2 by the BiVO4 sample under visible light.

[0138] The test procedure for photocatalytic H₂O₂ production is as follows: 120 mL of ultrapure water was added to a 300 mL photocatalytic reactor, followed by 30 mg of powdered sample. The mixture was then water-cooled and sonicated for 30 min. After sonication, 15 mL of a 0.01 mol / L CuSO₄ aqueous solution and 15 mL of a 10 g / L DMP ethanol solution were added. The mixture was stirred in the dark for 30 min while continuously purging with pure oxygen until the solution reached oxygen saturation. The container was then sealed with a lid fitted with a rubber gasket. A 300 nm arc xenon lamp equipped with a cutoff filter (≥ 420 nm) was used as the light source. After the photocatalytic reaction began, 2 mL of solution was sampled every half hour. After centrifugation, the supernatant was analyzed using a UV-Vis spectrophotometer to detect Cu(DMP) at 454 nm. 2+ The absorption peak was observed. A 30 wt% H2O2 solution was diluted with ultrapure water to different concentrations and used as calibration samples to determine the concentration of H2O2 generated by photocatalysis.

[0139] It can be seen that the H2O2 production activity of the heterostructure sample is relatively higher than that of Bi4V2O. 11 The samples showed significant improvement, with those annealed at 500 ℃ and above exhibiting better photocatalytic activity than pure BiVO4. The sample annealed at 530 ℃ showed the best photocatalytic activity.

[0140] from Figure 21 It can be seen that in Bi4V2O 11 After annealing at 100 Pa in an oxygen environment, the XRD pattern of the thin film showed diffraction peaks of BiVO4, indicating that Bi4V2O was prepared by annealing under appropriate oxygen partial pressure. 11 The method for BiVO4 heterostructures is also applicable to thin film samples.

[0141] from Figure 22 (a) It can be seen that Bi4V2O 11 The surface of the / BiVO4 film is relatively smooth. Figure 23 The elemental ratios of the thin film are given, showing that the ratio of Bi to V is approximately 1.29:1, which falls within the range of Bi₄V₂O. 11 The ratio of 2:1 for BiVO4 and 1:1 for BiVO4 indicates the presence of Bi volatilization in the sample, leading to the formation of BiVO4.

[0142] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A Bi4V2O 11 The in-situ preparation method of / BiVO4 heterostructure composite material is characterized by, The steps include: Bi4V2O 11 The material was annealed in an oxygen-containing atmosphere to obtain Bi4V2O. 11 / BiVO4 heterostructure composite material.

2. The Bi4V2O according to claim 1 11 The in-situ preparation method of / BiVO4 heterostructure composite material is characterized by, The Bi4V2O 11 The material is either powder or film.

3. The Bi4V2O according to claim 2 11 The in-situ preparation method of / BiVO4 heterostructure composite material is characterized by, When the Bi4V2O 11 When the material is in powder form, its preparation method is as follows: Bismuth nitrate, ammonium metavanadate, and urea are dispersed and dissolved in ethylene glycol solution, the pH is adjusted to 7.5, and a solvothermal reaction is carried out. After the reaction is completed, the mixture is washed and dried to obtain Bi4V2O. 11 powder.

4. The Bi4V2O according to claim 3 11 The in-situ preparation method of / BiVO4 heterostructure composite material is characterized by, The molar ratio of bismuth nitrate to ammonium metavanadate is 2:1, the concentration of bismuth nitrate in ethylene glycol is 0.05-0.1 mmol / mL, and the concentration of urea in ethylene glycol is 0.01-0.02 g / mL; the temperature of the solvothermal reaction is 150-200℃, and the time is 12-36 h.

5. The Bi4V2O according to claim 2 11 The in-situ preparation method of / BiVO4 heterostructure composite material is characterized by, When the Bi4V2O 11 When the material is a thin film, it is prepared by magnetron sputtering.

6. The Bi4V2O according to any one of claims 1-5 11 The in-situ preparation method of / BiVO4 heterostructure composite material is characterized by, The oxygen-containing atmosphere is pure oxygen, air, or a mixture of oxygen and an inert gas, wherein the volume fraction of oxygen in the mixture is 10%-100%.

7. The Bi4V2O according to claim 6 11 The in-situ preparation method of / BiVO4 heterostructure composite material is characterized by, The oxygen partial pressure during the annealing process is 50 Pa to 22 kPa, and the total pressure is 50 Pa to 102 kPa.

8. The Bi4V2O according to claim 6 11 The in-situ preparation method of / BiVO4 heterostructure composite material is characterized by, The oxygen partial pressure during the annealing process is 50 Pa to 300 Pa, and the total pressure is 50 Pa to 1 kPa.

9. The Bi4V2O according to claim 1 11 The in-situ preparation method of / BiVO4 heterostructure composite material is characterized by, The annealing treatment is performed at a temperature of 470-560 ℃, with a holding time of 1-5 h, and both the heating rate and the cooling rate are 2-4 ℃ / min.

10. Bi4V2O prepared by the method according to any one of claims 1-9 11 / BiVO4 heterostructure composite material.

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