A bismuth vanadate quantum dot-modified multi-level titanium dioxide photoelectrode and its preparation method

Abstract

This invention belongs to the field of photocatalytic materials for water treatment, and relates to a bismuth vanadate quantum dot-modified multi-level titanium dioxide photoelectrode and its preparation method. The method includes: depositing a titanium dioxide substrate layer on the conductive surface of a conductive glass; forming a titanium dioxide nanorod array on the titanium dioxide substrate layer via a hydrothermal method; growing a titanium dioxide nano-grass array on the titanium dioxide nanorod array via a hydrothermal method; and loading bismuth vanadate quantum dots onto the surface of the titanium dioxide nano-grass array via a hydrothermal method to obtain the photoelectrode. This photoelectrode features a large specific surface area, numerous active sites, strong visible light absorption, high charge separation efficiency, good stability, simple preparation, and no secondary pollution. The photoelectrode prepared using the method of this invention has its various levels of structure tightly bonded by chemical bonds, exhibiting strong stability and ensuring a long cycle life.

Description

Technical Field

[0001] This invention belongs to the field of water treatment photocatalytic materials, specifically relating to a bismuth vanadate quantum dot modified multi-level titanium dioxide photoelectrode and its preparation method. Background Technology

[0002] With the rapid development of the pharmaceutical, agricultural, and chemical industries, large amounts of organic pollutants such as antibiotics, pesticide residues, and endocrine disruptors have entered aquatic environments, posing a serious threat to ecosystems and human health. Among these, tetracycline antibiotics, amiloride pesticide residues, and substances like bisphenol A are chemically stable and difficult to biodegrade, making them difficult to remove effectively with traditional water treatment technologies. Existing water treatment methods suffer from long biodegradation cycles and poor effectiveness against recalcitrant substances. While adsorption methods can separate pollutants from water, they essentially only achieve pollutant transfer; improper subsequent treatment can easily lead to secondary pollution, posing new threats to the aquatic environment. Advanced oxidation methods are costly and energy-intensive. In contrast, photocatalysis technology utilizes the strong oxidizing substances generated by semiconductor materials under light to degrade organic pollutants, offering advantages such as high efficiency, environmental friendliness, and no secondary pollution, making it a research hotspot in the field of water treatment.

[0003] Bismuth vanadate (BiVO4), as a visible-light-responsive photocatalyst, has attracted widespread attention due to its moderate band gap (2.4–2.8 eV), high catalytic activity, and good stability. However, single BiVO4 materials suffer from problems such as small specific surface area, few active sites, and high recombination rate of photogenerated carriers, which limit their practical applications. In existing technologies, the performance of BiVO4 can be improved by loading it onto a support, such as titanium dioxide (TiO2) or graphene.

[0004] Patent CN102513091A employs graphene-supported BiVO4, with the following method: adding bismuth salt and a stabilizer to a phosphate buffer solution and stirring to form a suspension; uniformly dissolving metavanadate in the phosphate buffer solution and then adding it to the suspension, stirring until a transparent solution is formed; adjusting the pH of the transparent solution to a range of 4.5–9.0; then adding graphene at a mass ratio of 5–20:1 to bismuth salt at 20–100°C, stirring and mixing, refluxing for 6–24 hours, centrifuging, filtering, and washing to obtain the product; finally, calcining the obtained product, cooling, and grinding to obtain a graphene-assembled bismuth vanadate nanophotocatalyst. While this method improves the adsorption capacity of the photocatalyst, its charge transport efficiency is low.

[0005] Patent CN120205128A discloses a method for preparing a bismuth titanate-titanium dioxide composite photocatalyst. The method includes: adding TiO2 to an ethylene glycol solution and stirring for 0.5 h to obtain solution A; then adding Bi(NO3)3 and NH4VO3 to the ethylene glycol solution and stirring for 0.5 h to obtain solution B; then mixing solutions A and B and stirring for 0.5 h; after the mixture is stirred, placing it in a single-necked flask and refluxing at 80°C for 2 h in an oil bath to obtain a TiO2 / BiVO4 composite, and allowing it to stand for 12 h; centrifuging, washing, drying, and grinding to obtain a powder sample; and finally calcining the powder sample in a muffle furnace at 400°C for 3 h to obtain the TiO2 / BiVO4 catalyst. This method uses liquid-phase blending and calcination to prepare the composite catalyst, but it lacks precise control over nucleation and growth, easily leading to uneven loading and insufficient exposure of active sites.

[0006] In summary, traditional TiO2-supported BiVO4 photocatalysts are mostly supported by simple physical mixing or coating, which have defects such as uneven loading, weak binding force with the support, and insufficient exposure of active sites. Summary of the Invention

[0007] The purpose of this invention is to solve the problems existing in the prior art and to provide a bismuth vanadate quantum dot modified multi-level titanium dioxide photoelectrode and its preparation method.

[0008] According to one aspect of the present invention, a method for preparing a bismuth vanadate quantum dot-modified multi-level titanium dioxide photoelectrode is provided, the method comprising the following steps:

[0009] A titanium dioxide substrate layer is deposited on the conductive surface of the conductive glass;

[0010] A titanium dioxide nanorod array was formed on the titanium dioxide substrate by a hydrothermal method;

[0011] Titanium dioxide nano-grass arrays were grown on the titanium dioxide nanorod arrays using a hydrothermal method.

[0012] The photoelectrode is obtained by loading bismuth vanadate quantum dots onto the surface of the titanium dioxide nanoparticle array using a hydrothermal method.

[0013] According to one embodiment of the present invention, depositing a titanium dioxide substrate layer on the conductive surface of a conductive glass includes:

[0014] Prepare an aqueous solution of titanium tetrachloride under ice-water bath conditions;

[0015] The conductive glass is placed in the titanium tetrachloride aqueous solution with the conductive side facing up, and reacted at 50~90℃ for 0.5~1h.

[0016] After the reaction is complete, the conductive glass with the deposited titanium dioxide substrate is cleaned and dried.

[0017] According to one embodiment of the present invention, the conductive glass is fluorine-doped tin oxide conductive glass; the concentration of the titanium tetrachloride aqueous solution is 15~25 mmol / L.

[0018] According to one embodiment of the present invention, forming a titanium dioxide nanorod array on the titanium dioxide substrate by a hydrothermal method includes:

[0019] Prepare a first mixed solution of tetrabutyl titanate and hydrochloric acid;

[0020] The first mixed solution is placed in a hydrothermal reaction vessel, and a conductive glass with the titanium dioxide substrate layer deposited on it is immersed in the first mixed solution with the conductive side facing down, and the reaction is carried out at a first set temperature.

[0021] After the reaction is complete, the conductive glass is removed and washed and dried after the hydrothermal reaction vessel has cooled down.

[0022] According to one embodiment of the present invention, preparing a first mixed solution of tetrabutyl titanate and hydrochloric acid includes: mixing deionized water and concentrated hydrochloric acid uniformly to obtain a hydrochloric acid solution, adding tetrabutyl titanate dropwise to the hydrochloric acid solution, wherein the mass fraction of the concentrated hydrochloric acid is 35%~38%, the concentration of hydrogen chloride in the hydrochloric acid solution is 1~3 mol / L, and the concentration of tetrabutyl titanate in the first mixed solution is 5~20 g / L;

[0023] The reaction temperature at the first set temperature is 120~180℃, and the reaction time is 1~4h.

[0024] According to one embodiment of the present invention, growing a titanium dioxide nano-grass array on the titanium dioxide nanorod array by a hydrothermal method includes:

[0025] Prepare a second mixed solution of potassium titanium oxalate and hydrochloric acid;

[0026] The second mixed solution is placed in a hydrothermal reaction vessel, and a conductive glass with the titanium dioxide nanorod array is immersed in the second mixed solution with the conductive side facing down, and the reaction is carried out at a second set temperature.

[0027] After the reaction is complete, the conductive glass is removed and washed and dried after the hydrothermal reaction vessel has cooled down.

[0028] According to one embodiment of the present invention, preparing a second mixed solution of potassium titanium oxalate and hydrochloric acid includes: mixing diethylene glycol, deionized water and concentrated hydrochloric acid evenly, adding potassium titanium oxalate to the mixed solution and completely dissolving the potassium titanium oxalate, wherein the volume ratio of diethylene glycol, deionized water and concentrated hydrochloric acid is (17~20):(2~3):(3~5), the mass fraction of the concentrated hydrochloric acid is 35%~38%, and the concentration of potassium titanium oxalate in the second mixed solution is 2~20 g / L;

[0029] The reaction temperature at the second set temperature is 120~200℃, and the reaction time is 1~3h.

[0030] According to one embodiment of the present invention, loading bismuth vanadate quantum dots onto the surface of the titanium dioxide nanoparticle array via a hydrothermal method comprises:

[0031] Bismuth salt and vanadium salt were dissolved in ethylene glycol to prepare a bismuth vanadate precursor solution;

[0032] The bismuth vanadate precursor solution was placed in a hydrothermal reaction vessel, and a conductive glass with the titanium dioxide nanoparticle array was immersed in the bismuth vanadate precursor solution with the conductive side facing down, and the reaction was carried out at a third set temperature.

[0033] After the reaction is complete, the conductive glass is removed and washed and dried after the hydrothermal reaction vessel has cooled down.

[0034] According to one embodiment of the present invention, the bismuth salt and vanadium salt are in a molar ratio of bismuth ions to vanadium ions of 1:(1.0~1.2), and the concentration of the bismuth salt is 0.5~1 mol / L;

[0035] The bismuth vanadate precursor solution also includes a surfactant, wherein the mass ratio of the surfactant to the bismuth salt is (2~3):1, and the surfactant is selected from at least one of the following: oleic acid, polyvinyl alcohol, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, and polyvinylpyrrolidone.

[0036] The reaction temperature for the third set temperature is 120~180℃, and the reaction time is 1~4h.

[0037] According to another aspect of the present invention, a bismuth vanadate quantum dot-modified multi-level titanium dioxide photoelectrode is provided, the photoelectrode being prepared by the method described in any of the above embodiments.

[0038] The bismuth vanadate quantum dot-modified multi-level titanium dioxide photoelectrode and its preparation method of the present invention use conductive glass as a substrate and have high charge transport efficiency. Through a stepwise growth process, a dense titanium dioxide substrate layer is first formed on the conductive glass. This dense titanium dioxide substrate layer can act as an electron bridge, optimizing the transport of photogenerated electrons from the multi-level titanium dioxide array to the conductive glass, reducing resistance loss, preventing the reverse migration of holes, reducing non-radiative recombination of charge carriers, and blocking electrolyte penetration, thereby improving the photocatalytic efficiency and stability of the electrode. A titanium dioxide nanorod array is formed on the titanium dioxide substrate layer as an electron transport channel, and then a multi-level titanium dioxide nano-grass array is generated. The multi-level nano-grass array significantly increases the specific surface area and the number of active sites, which is beneficial to the adsorption of pollutants in water. Finally, bismuth vanadate quantum dots are loaded on the surface of the nano-grass array. Bismuth vanadate quantum dots can efficiently absorb visible light and generate a large number of photogenerated electrons and holes, while the nano-titanium dioxide array can quickly conduct electrons, reduce recombination, enhance oxidation capacity, and synergistically achieve deep degradation of pollutants. This photoelectrode features a large specific surface area, numerous active sites, strong visible light absorption, high charge separation efficiency, good stability, and is easy to prepare without secondary pollution. The photoelectrode prepared using the method of this invention exhibits a tightly bonded structure at each stage through chemical bonds, resulting in high stability and ensuring a long cycle life. Furthermore, the method of this invention is based on a mature hydrothermal reaction, is simple to operate, easy to scale up for production, and effectively controls costs. Attached Figure Description

[0039] Figure 1 A schematic flowchart of a method for preparing a bismuth vanadate quantum dot-modified multilevel titanium dioxide photoelectrode according to an embodiment of the present invention is shown.

[0040] Figure 2 A scanning electron microscope image of the photoelectrode with TiO2-NRA (titanium dioxide nanorod array) prepared according to blank example 1 is shown.

[0041] Figure 3 A scanning electron microscope image of the photoelectrode with TiO2-NGA (titanium dioxide nanograss array) prepared according to blank example 2 is shown.

[0042] Figure 4 Scanning electron microscope (SEM) images of the bismuth vanadate quantum dot-modified multilevel titanium dioxide photoelectrode prepared according to Example 1 are shown. The left image (a) is a top view of the bismuth vanadate quantum dot-modified multilevel titanium dioxide photoelectrode prepared according to Example 1, and the right image (b) is a cross-section perpendicular to the left direction.

[0043] Figure 5 The X-ray diffraction patterns of the TiO2-NRA and TiO2-NGA photoelectrodes prepared according to blank examples 1-2 are shown.

[0044] Figure 6 The degradation performance of tetracycline by photoelectrodes prepared according to Example 1 and Blank Examples 1-2 is shown in the diagram. Detailed Implementation

[0045] It should be understood that the embodiments of the invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this invention, those skilled in the art will readily recognize that various modifications are possible without substantially departing from the teachings of the invention. Accordingly, all such modifications should be included within the scope of the invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, and parameters of the following exemplary embodiments without departing from the spirit of the invention.

[0046] To address the problems of small specific surface area, insufficient active sites, and low efficiency of photocatalytic degradation of organic pollutants in water by existing BiVO4 photocatalysts, this invention constructs a composite photoelectrode structure based on conductive glass, consisting of a dense TiO2 substrate, a TiO2 nanorod array (NRA), a TiO2 nanograss array (NGA), and bismuth vanadate quantum dots.

[0047] According to one aspect of the present invention, a method for preparing a bismuth vanadate quantum dot-modified multi-level titanium dioxide photoelectrode is provided. For example... Figure 1 As shown, the method mainly includes the following steps:

[0048] Step S1: Deposit a titanium dioxide substrate layer on the conductive surface of the conductive glass;

[0049] Step S2: Form a titanium dioxide nanorod array on a titanium dioxide substrate using a hydrothermal method;

[0050] Step S3: Grow a titanium dioxide nano-grass array on a titanium dioxide nanorod array using a hydrothermal method;

[0051] Step S4: Bismuth vanadate quantum dots are loaded onto the surface of a titanium dioxide nanofiber array using a hydrothermal method to obtain a photoelectrode.

[0052] The bismuth vanadate quantum dot-modified multilevel titanium dioxide photoelectrode and its preparation method of the present invention use conductive glass as a substrate and have high charge transport efficiency. Through a stepwise growth process, a dense titanium dioxide substrate layer is first formed on the conductive glass. This dense titanium dioxide substrate layer can act as an electron bridge, optimizing the transport of photogenerated electrons from the multilevel titanium dioxide array to the conductive glass, reducing resistance loss, preventing the reverse migration of holes, reducing non-radiative recombination of charge carriers, and blocking electrolyte penetration, thereby improving the photocatalytic efficiency and stability of the electrode. Then, a titanium dioxide nanorod array is formed on the titanium dioxide substrate layer as an electron transport channel, followed by the generation of a multilevel titanium dioxide nano-grass array. The multilevel nano-grass array significantly increases the specific surface area and the number of active sites, which is beneficial for the adsorption of pollutants in water. Finally, bismuth vanadate quantum dots are loaded on the surface of the nano-grass array. Bismuth vanadate quantum dots can efficiently absorb visible light and generate a large number of photogenerated electrons and holes, while the nano-titanium dioxide array can quickly conduct electrons, reduce recombination, enhance oxidation capacity, and synergistically achieve deep degradation of pollutants. This photoelectrode features a large specific surface area, numerous active sites, strong visible light absorption, high charge separation efficiency, good stability, and is easy to prepare without secondary pollution. The photoelectrode prepared using the method of this invention exhibits a tightly bonded structure at each stage through chemical bonds, resulting in high stability and ensuring a long cycle life. Furthermore, the method of this invention is based on a mature hydrothermal reaction, is simple to operate, easy to scale up for production, and effectively controls costs.

[0053] In this document, the term "nanorrod" refers to a one-dimensional nanostructure with a diameter ranging from tens to hundreds of nanometers and a length ranging from several micrometers to tens of micrometers. In some embodiments of the present invention, the nanorod has a diameter of approximately 20 to 150 nm and a length of approximately 1 to 4 μm.

[0054] In this document, the term "nanograss" refers to an aggregate composed of multiple nanowires / nanoribbons, each nanograss potentially containing multiple radially, non-directionally growing nanowires / nanoribbons. Nanowires are one-dimensional nanostructures with diameters ranging from a few nanometers to tens of nanometers and lengths from hundreds of nanometers to several micrometers. Nanoribbons are two-dimensional nanostructures with widths of tens of nanometers and lengths of hundreds of nanometers. In some embodiments of this invention, the "nanograss" is composed of multiple nanoribbons, each with a length of approximately 200–500 nm, a width of approximately 20–50 nm, and a specific surface area of ​​50–100 m². 2 / g.

[0055] In step S1, a titanium dioxide substrate layer is deposited on the conductive surface of the conductive glass.

[0056] In principle, this invention does not impose any particular limitation on the specific deposition method, as long as a dense layer of titanium dioxide can be formed on the conductive surface of the conductive glass. Those skilled in the art can select and adjust the method according to actual conditions, product requirements, and quality control factors.

[0057] This invention first deposits a dense titanium dioxide substrate layer on the conductive surface of a conductive glass. This dense TiO2 layer serves as a seed crystal for the subsequent growth of titanium dioxide nanorod arrays. Furthermore, this dense layer plays a special role in the photocatalytic degradation process: (1) it acts as an electron bridge, optimizing the transmission of photogenerated electrons from the titanium dioxide multi-level array to the conductive glass, reducing resistance loss; (2) it prevents the reverse migration of holes, reducing non-radiative recombination of charge carriers; (3) it blocks electrolyte penetration, preventing corrosion of the conductive glass and contamination of the active layer, ultimately improving the photocatalytic efficiency and stability of the electrode. To form a uniform and dense titanium dioxide substrate layer, this invention deposits a titanium dioxide substrate layer on the conductive surface of the conductive glass using the following method:

[0058] Prepare an aqueous solution of titanium tetrachloride under ice-water bath conditions;

[0059] Place the conductive glass, with the conductive side facing up, into an aqueous solution of titanium tetrachloride and react at 50-90°C for 0.5-1 hour.

[0060] After the reaction is complete, the conductive glass with the deposited titanium dioxide substrate is cleaned and dried.

[0061] In some embodiments, the conductive glass is etched and cleaned before being immersed in the titanium tetrachloride aqueous solution. For example, the conductive glass is ultrasonically cleaned sequentially in toluene, acetone, ethanol, and deionized water for 15 minutes to remove oil stains adhering to its surface, then rinsed with alcohol and dried with nitrogen.

[0062] In some embodiments of the present invention, the conductive glass is fluorine-doped tin oxide conductive glass (FTO conductive glass).

[0063] In some embodiments of the present invention, the concentration of the titanium tetrachloride aqueous solution is 15~25 mmol / L.

[0064] In some embodiments of the present invention, the conductive glass with a titanium dioxide substrate layer deposited is cleaned sequentially with ethanol and deionized water, and then dried after cleaning.

[0065] In step S2, a titanium dioxide nanorod array is formed on a titanium dioxide substrate by a hydrothermal method.

[0066] In some embodiments of the present invention, forming a titanium dioxide nanorod array on a titanium dioxide substrate by a hydrothermal method includes:

[0067] Prepare a first mixed solution of tetrabutyl titanate and hydrochloric acid;

[0068] The first mixed solution is placed in a hydrothermal reaction vessel, and a conductive glass with a titanium dioxide substrate layer deposited on it is immersed in the first mixed solution with the conductive side facing down, and the reaction is carried out at a first set temperature.

[0069] After the reaction is complete, the conductive glass is removed and washed and dried after the hydrothermal reaction vessel has cooled down.

[0070] The preparation of the first mixed solution of tetrabutyl titanate and hydrochloric acid further includes: mixing deionized water and concentrated hydrochloric acid evenly to obtain a hydrochloric acid solution, adding tetrabutyl titanate dropwise to the hydrochloric acid solution, and stirring for a period of time.

[0071] The mass fraction of concentrated hydrochloric acid is 35%~38%, the concentration of hydrogen chloride in the hydrochloric acid solution obtained by mixing deionized water and concentrated hydrochloric acid is 1~3 mol / L, and the amount of tetrabutyl titanate added is controlled so that the concentration of tetrabutyl titanate in the first mixed solution is 5~20 g / L.

[0072] A mixed solution of tetrabutyl titanate and hydrochloric acid was placed in a polytetrafluoroethylene liner of a hydrothermal reactor. A conductive glass substrate with a titanium dioxide base layer was immersed in the mixed solution with the conductive side facing down. The reaction was carried out at 120~180℃ for 1~4 hours.

[0073] After the reaction was completed, the hydrothermal reactor was cooled to room temperature along with the furnace. The sample was then removed, washed, and dried to obtain TiO2-NRA.

[0074] In this process, the diameter, length, and array density of the nanorods can be controlled by adjusting the concentration of the tetrabutyl titanate solution, the hydrothermal reaction temperature, and the reaction time. Increasing the concentration of the tetrabutyl titanate solution and the hydrothermal reaction temperature promotes the longitudinal and radial growth of the nanorods, resulting in longer and thicker nanorods, but may sacrifice the uniformity and density of the array. Extending the hydrothermal reaction time makes the nanorods longer and thicker and the array denser.

[0075] In some embodiments of the present invention, the nanorods have a diameter of about 20-150 nm and a height of about 1-4 μm.

[0076] In step S3, a titanium dioxide nano-grass array is grown on the titanium dioxide nanorod array using a hydrothermal method, which may specifically include the following steps:

[0077] Prepare a second mixed solution of potassium titanium oxalate and hydrochloric acid;

[0078] The second mixed solution is placed in a hydrothermal reaction vessel, and a conductive glass with a titanium dioxide nanorod array is immersed in the second mixed solution with the conductive side facing down, and the reaction is carried out at a second set temperature.

[0079] After the reaction is complete, the conductive glass is removed and washed and dried after the hydrothermal reaction vessel has cooled down.

[0080] In some embodiments, preparing a second mixed solution of potassium titanium oxalate and hydrochloric acid includes:

[0081] Mix diethylene glycol, deionized water and concentrated hydrochloric acid thoroughly.

[0082] Add potassium titanium oxalate to the mixture and allow it to dissolve completely.

[0083] The volume ratio of diethylene glycol, deionized water and concentrated hydrochloric acid is (17~20):(2~3):(3~5), the mass fraction of concentrated hydrochloric acid is 35%~38%, and the concentration of potassium titanium oxalate in the second mixed solution is 2~20 g / L.

[0084] The prepared potassium titanium oxalate solution was poured into the polytetrafluoroethylene liner of a hydrothermal reactor. Then, a conductive glass substrate with TiO2-NRA grown on its surface was placed in the reactor, conductive side down. The reactor was placed in a forced-air drying oven for the hydrothermal reaction at 120-200℃ for 1-3 hours. After the reaction, the reactor was allowed to cool to room temperature. The conductive glass was then removed, washed with deionized water and alcohol, and dried in a forced-air drying oven at 60-100℃ to obtain TiO2-NGA.

[0085] In this process, the branching degree and specific surface area of ​​nanograss can be controlled by adjusting the concentration of potassium titanium oxalate solution, hydrothermal reaction temperature, and time.

[0086] In step S4, bismuth vanadate quantum dots are loaded onto the surface of a titanium dioxide nanofiber array using a hydrothermal method to obtain a photoelectrode. This process may specifically include the following steps:

[0087] Bismuth salt and vanadium salt were dissolved in ethylene glycol to prepare a bismuth vanadate precursor solution;

[0088] The bismuth vanadate precursor solution was placed in a hydrothermal reaction vessel, and a conductive glass with a titanium dioxide nanoparticle array was immersed in the bismuth vanadate precursor solution with the conductive side facing down. The reaction was carried out at a third set temperature.

[0089] After the reaction is complete, the conductive glass is removed and washed and dried after the hydrothermal reaction vessel has cooled down.

[0090] In some embodiments, bismuth salt can be bismuth nitrate, and vanadium salt can be ammonium metavanadate, with a molar ratio of 1:(1.0~1.2). Both are dissolved in ethylene glycol, with a bismuth nitrate concentration of 0.5~1 mol / L in the solution. A surfactant may also be added, with a surfactant-to-bismuth salt mass ratio of (2~3):1, and the mixture is stirred until homogeneous to obtain a bismuth vanadate precursor solution.

[0091] In some embodiments, the surfactant is selected from at least one of the following: oleic acid, polyvinyl alcohol, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, and polyvinylpyrrolidone.

[0092] After preparing the bismuth vanadate precursor solution, the bismuth vanadate precursor solution was placed in the polytetrafluoroethylene liner of a hydrothermal reactor. A conductive glass with a titanium dioxide nanoparticle array was immersed in the bismuth vanadate precursor solution with the conductive side facing down. The reaction was carried out at 120~180℃ for 1~4h to uniformly load BiVO4 quantum dots onto the surface of the nanoparticle array. After the reaction was completed, the conductive glass was removed after the hydrothermal reaction vessel cooled down and was washed and dried to obtain a bismuth vanadate quantum dot modified multi-level titanium dioxide photoelectrode.

[0093] In this process, the particle size and loading of BiVO4 quantum dots can be controlled by adjusting the vanadium / bismuth concentration in the BiVO4 precursor solution, the type and amount of surfactant, and the hydrothermal reaction temperature and time.

[0094] According to another aspect of the present invention, a bismuth vanadate quantum dot-modified multilevel titanium dioxide photoelectrode is provided, which is prepared by means of the method described in any of the above embodiments. The bismuth vanadate quantum dot-modified multilevel titanium dioxide photoelectrode prepared according to some embodiments of the present invention has the characteristics shown in Table 1 below:

[0095] Table 1. Characteristics of Bismuth Vanadate Quantum Dot Modified Multilevel Titanium Dioxide Photoelectrodes

[0096]

[0097] In the bismuth vanadate quantum dot modified multi-level titanium dioxide photoelectrode of the present invention, under visible light irradiation, BiVO4 quantum dots absorb photons to generate photogenerated electron-hole pairs; the TiO2 conduction band (-4.2 eV) and the BiVO4 conduction band (-4.8 eV) form a stepped band structure, driving electrons to migrate directionally from BiVO4 to TiO2 and suppressing recombination; the multi-level TiO2 array acts as an electron transport channel, rapidly transferring photogenerated electrons to the conductive glass and substrate, suppressing carrier recombination; photogenerated holes react with water to generate hydroxyl radicals, and electrons react with oxygen to generate superoxide radicals. These radicals have strong oxidizing properties and can oxidize and decompose organic pollutants adsorbed on the surface of the photoelectrode into harmless substances such as CO2 and H2O.

[0098] The bismuth vanadate quantum dot-modified multi-level titanium dioxide photoelectrode and its preparation method of the present invention also have the following advantages:

[0099] High specific surface area and abundant active sites: The multi-level nano-grass array structure enables the catalyst to achieve a specific surface area of ​​50~100m². 2 / g, which is 5 to 10 times higher than that of traditional BiVO4 catalysts, significantly increasing the number of active sites and enhancing the adsorption capacity for organic pollutants;

[0100] Highly efficient photocatalytic performance: Under visible light irradiation, the degradation rate of 10 mg / L tetracycline solution reached 93% in 60 min, and the degradation rate of 12 mg / L bisphenol A reached 92%, which is much higher than that of BiVO4 catalyst alone.

[0101] Excellent stability: Through the multi-level array structure and chemical bonding, BiVO4 quantum dots are firmly loaded. After 10 cycles of use, the degradation rate still remains above 85%, which solves the problems of easy detachment and poor stability of traditional catalysts.

[0102] The process is simple and easy to industrialize: it adopts hydrothermal method and loading process, the reaction conditions are mild (temperature ≤200℃), no complicated equipment is required, and it is suitable for large-scale production.

[0103] The bismuth vanadate quantum dot modified multi-level titanium dioxide photoelectrode of the present invention can be used in drinking water purification, industrial wastewater pretreatment and other fields, and has broad market prospects and important environmental benefits.

[0104] The method of the present invention will be further described and illustrated below with reference to embodiments.

[0105] Example 1

[0106] Preparation of TiO2 substrate: Cut a 3×2cm sample 2 For the FTO glass, high-transmittance FTO conductive glass was sequentially ultrasonically cleaned in toluene, acetone, ethanol, and deionized water for 15 min to remove oil stains adhering to the substrate surface. It was then rinsed with alcohol and dried with nitrogen. A 20 mmol / L TiCl4 aqueous solution was prepared under ice-water bath conditions. The FTO glass was then placed in the TiCl4 aqueous solution with the conductive side facing up and reacted at 70°C for 0.5 h. After the reaction was complete, the FTO conductive glass with deposited dense TiO2 was cleaned with ethanol and deionized water and then dried.

[0107] Growth of TiO2 nanorod arrays (TiO2-NRA): 30 mL of deionized water and 5 mL of concentrated hydrochloric acid (mass fraction 38%) were mixed and stirred for 10 min. Tetrabutyl titanate was then added dropwise to the hydrochloric acid solution and stirred for another 10 min to prepare a tetrabutyl titanate solution with a concentration of 10 g / L. The tetrabutyl titanate solution was poured into the polytetrafluoroethylene liner of a hydrothermal reactor. The FTO glass with TiO2 deposited on it was placed in the hydrothermal reactor with the conductive side facing down and reacted at 160 °C for 2 h. After the reaction was completed, the hydrothermal reactor was allowed to cool to room temperature with the furnace. The FTO conductive glass was then removed, washed, and dried.

[0108] Growth of TiO2 nano-grass array (TiO2-NGA): Mix 17.5 mL of diethylene glycol, 2.5 mL of deionized water and 4 mL of concentrated hydrochloric acid (mass fraction 38%), stir well, add 0.15 g of potassium titanium oxalate, and stir until the potassium titanium oxalate is completely dissolved; pour the potassium titanium oxalate solution into the polytetrafluoroethylene liner of the hydrothermal reactor, place the FTO glass with TiO2-NGA grown on its surface facing down in the hydrothermal reactor, and place the hydrothermal reactor in a forced-air drying oven for hydrothermal reaction at a reaction temperature of 180℃ for 2 h. After the reaction is completed, wait for the hydrothermal reactor to cool to room temperature with the furnace, remove the FTO conductive glass and clean it with deionized water and alcohol, and dry it in a forced-air drying oven at 60℃.

[0109] Loading BiVO4 quantum dots: Bismuth nitrate and ammonium metavanadate were dissolved in ethylene glycol at a molar ratio of 1:1.1, with a bismuth nitrate concentration of 0.5 mol / L. Oleic acid (mass ratio of bismuth nitrate to 2.5:1) was added as a surfactant, and the mixture was stirred until homogeneous to obtain a BiVO4 precursor solution. The BiVO4 precursor solution was placed in a hydrothermal reactor, and an FTO glass substrate with a TiO2 nano-grass array grown on it was immersed in the precursor solution with the conductive side facing down. The substrate was reacted at 160℃ for 2 h to uniformly load BiVO4 quantum dots onto the surface of the nano-grass array. After washing and drying, a multi-level TiO2 array photoelectrode modified with BiVO4 quantum dots was obtained.

[0110] Example 2

[0111] Preparation of TiO2 substrate: Cut a 3×2cm sample 2 For the FTO glass, high-transmittance FTO conductive glass was sequentially ultrasonically cleaned in toluene, acetone, ethanol, and deionized water for 15 min to remove oil stains adhering to the substrate surface. It was then rinsed with alcohol and dried with nitrogen. A 20 mmol / L TiCl4 aqueous solution was prepared under ice-water bath conditions. The FTO glass was then placed in the TiCl4 aqueous solution with the conductive side facing up and reacted at 70°C for 0.5 h. After the reaction was complete, the FTO conductive glass with deposited dense TiO2 was cleaned with ethanol and deionized water and then dried.

[0112] Growth of TiO2 nanorod arrays (TiO2-NRA): 30 mL of deionized water and 5 mL of concentrated hydrochloric acid (mass fraction 38%) were mixed and stirred for 10 min. Tetrabutyl titanate was then added dropwise to the hydrochloric acid solution and stirred for another 10 min to prepare a tetrabutyl titanate solution with a concentration of 10 g / L. The tetrabutyl titanate solution was poured into the polytetrafluoroethylene liner of a hydrothermal reactor. The FTO glass with TiO2 deposited on it was placed in the hydrothermal reactor with the conductive side facing down and reacted at 160 °C for 2 h. After the reaction was completed, the hydrothermal reactor was allowed to cool to room temperature with the furnace. The FTO conductive glass was then removed, washed, and dried.

[0113] Growth of TiO2 nano-grass array (TiO2-NGA): Mix 17.5 mL of diethylene glycol, 2.5 mL of deionized water and 4 mL of concentrated hydrochloric acid (mass fraction 38%), stir well, add 0.20 g of potassium titanium oxalate, and stir until the potassium titanium oxalate is completely dissolved; pour the potassium titanium oxalate solution into the polytetrafluoroethylene liner of the hydrothermal reactor, place the FTO glass with TiO2-NGA grown on its surface facing down in the hydrothermal reactor, and place the hydrothermal reactor in a forced-air drying oven for hydrothermal reaction at a reaction temperature of 180℃ for 2 h. After the reaction is completed, wait for the hydrothermal reactor to cool to room temperature with the furnace, remove the FTO conductive glass and clean it with deionized water and alcohol, and dry it in a forced-air drying oven at 60℃.

[0114] Loading BiVO4 quantum dots: Bismuth nitrate and ammonium metavanadate were dissolved in ethylene glycol at a molar ratio of 1:1.1, with a bismuth nitrate concentration of 0.5 mol / L. Oleic acid (mass ratio of bismuth nitrate to 2.5:1) was added as a surfactant, and the mixture was stirred until homogeneous to obtain a BiVO4 precursor solution. The BiVO4 precursor solution was placed in a hydrothermal reactor, and an FTO glass substrate with a TiO2 nano-grass array grown on it was immersed in the precursor solution with the conductive side facing down. The substrate was reacted at 160℃ for 2 h to uniformly load BiVO4 quantum dots onto the surface of the nano-grass array. After washing and drying, a multi-level TiO2 array photoelectrode modified with BiVO4 quantum dots was obtained.

[0115] Example 3

[0116] Preparation of TiO2 substrate: Cut a 3×2cm sample 2 For the FTO glass, high-transmittance FTO conductive glass was ultrasonically cleaned sequentially in toluene, acetone, ethanol, and deionized water for 15 min to remove oil stains adhering to the substrate surface. It was then rinsed with alcohol and dried with nitrogen. A 25 mmol / L TiCl4 aqueous solution was prepared under ice-water bath conditions. The FTO glass was then placed in the TiCl4 aqueous solution with the conductive side facing up and reacted at 50°C for 1 h. After the reaction was complete, the FTO conductive glass with deposited dense TiO2 was cleaned with ethanol and deionized water and then dried.

[0117] Growth of TiO2 nanorod arrays (TiO2-NRA): 30 mL of deionized water was mixed with 9 mL of concentrated hydrochloric acid (mass fraction 35%) and stirred for 10 min. Tetrabutyl titanate was then added dropwise to the hydrochloric acid solution and stirred for another 10 min to prepare a tetrabutyl titanate solution with a concentration of 20 g / L. The tetrabutyl titanate solution was poured into the polytetrafluoroethylene liner of a hydrothermal reactor. The FTO glass with TiO2 deposited on it was placed in the hydrothermal reactor with the conductive side facing down and reacted at 120 °C for 4 h. After the reaction was completed, the hydrothermal reactor was allowed to cool to room temperature with the furnace. The FTO conductive glass was then removed, washed, and dried.

[0118] Growth of TiO2 nano-grass array (TiO2-NGA): Mix 17 mL of diethylene glycol, 2 mL of deionized water and 5 mL of concentrated hydrochloric acid (mass fraction 35%), stir well, add 0.45 g of potassium titanium oxalate, and stir until the potassium titanium oxalate is completely dissolved; pour the potassium titanium oxalate solution into the polytetrafluoroethylene liner of the hydrothermal reactor, place the FTO glass with TiO2-NGA grown on its surface facing down in the hydrothermal reactor, and place the hydrothermal reactor in a forced-air drying oven for hydrothermal reaction at a reaction temperature of 120℃ for 3 h. After the reaction is completed, wait for the hydrothermal reactor to cool to room temperature with the furnace, remove the FTO conductive glass and clean it with deionized water and alcohol, and dry it in a forced-air drying oven at 80℃.

[0119] BiVO4 quantum dot loading: Bismuth nitrate and ammonium metavanadate were dissolved in ethylene glycol at a molar ratio of 1:1, with a bismuth nitrate concentration of 0.8 mol / L. Polyvinyl alcohol (at a mass ratio of 2:1 to bismuth nitrate) was added as a surfactant and stirred until homogeneous to obtain a BiVO4 precursor solution. The BiVO4 precursor solution was placed in a hydrothermal reactor, and an FTO glass substrate with a TiO2 nano-grass array grown on it was immersed in the precursor solution with the conductive side facing down. The substrate was reacted at 120°C for 4 h to uniformly load BiVO4 quantum dots onto the surface of the nano-grass array. After washing and drying, a multi-level TiO2 array photoelectrode modified with BiVO4 quantum dots was obtained.

[0120] Example 4

[0121] Preparation of TiO2 substrate: Cut a 3×2cm sample 2 For the FTO glass, high-transmittance FTO conductive glass was sequentially ultrasonically cleaned in toluene, acetone, ethanol, and deionized water for 15 min to remove oil stains adhering to the substrate surface. It was then rinsed with alcohol and dried with nitrogen. A 15 mmol / L TiCl4 aqueous solution was prepared under ice-water bath conditions. The conductive side of the FTO glass was then placed in the TiCl4 aqueous solution and reacted at 90°C for 0.5 h. After the reaction was complete, the FTO conductive glass with deposited dense TiO2 was cleaned with ethanol and deionized water and then dried.

[0122] Growth of TiO2 nanorod arrays (TiO2-NRA): 30 mL of deionized water was mixed with 4 mL of concentrated hydrochloric acid (mass fraction 37%) and stirred for 10 min. Tetrabutyl titanate was then added dropwise to the hydrochloric acid solution and stirred for another 10 min to prepare a tetrabutyl titanate solution with a concentration of 5 g / L. The tetrabutyl titanate solution was poured into the polytetrafluoroethylene liner of a hydrothermal reactor. The FTO glass with TiO2 deposited on it was placed in the hydrothermal reactor with the conductive side facing down and reacted at 180 °C for 1 h. After the reaction was completed, the hydrothermal reactor was allowed to cool to room temperature with the furnace. The FTO conductive glass was then removed, washed, and dried.

[0123] Growth of TiO2 nano-grass array (TiO2-NGA): Mix 20 mL of diethylene glycol, 3 mL of deionized water and 3 mL of concentrated hydrochloric acid (mass fraction 37%), stir well, add 0.06 g of potassium titanium oxalate, and stir until the potassium titanium oxalate is completely dissolved; pour the potassium titanium oxalate solution into the polytetrafluoroethylene liner of the hydrothermal reactor, place the FTO glass with TiO2-NGA grown on its surface facing down in the hydrothermal reactor, and place the hydrothermal reactor in a forced-air drying oven for hydrothermal reaction at a reaction temperature of 200℃ for 1 h. After the reaction is completed, wait for the hydrothermal reactor to cool to room temperature with the furnace, remove the FTO conductive glass and clean it with deionized water and alcohol, and dry it in a forced-air drying oven at 80℃.

[0124] BiVO4 quantum dot loading: Bismuth nitrate and ammonium metavanadate were dissolved in ethylene glycol at a molar ratio of 1:1.2, with a bismuth nitrate concentration of 1 mol / L. Cetyltrimethylammonium bromide (mass ratio of 3:1 to bismuth nitrate) was added as a surfactant and stirred until homogeneous to obtain a BiVO4 precursor solution. The BiVO4 precursor solution was placed in a hydrothermal reactor, and an FTO glass substrate with a TiO2 nano-grass array grown on it was immersed in the precursor solution with the conductive side facing down. The substrate was reacted at 180℃ for 1 h to uniformly load BiVO4 quantum dots onto the surface of the nano-grass array. After washing and drying, a multi-level TiO2 array photoelectrode modified with BiVO4 quantum dots was obtained.

[0125] Blank example 1

[0126] Preparation of TiO2 substrate: Cut a 3×2cm sample 2 For the FTO glass, high-transmittance FTO conductive glass was sequentially ultrasonically cleaned in toluene, acetone, ethanol, and deionized water for 15 min to remove oil stains adhering to the substrate surface. It was then rinsed with alcohol and dried with nitrogen. A 20 mmol / L TiCl4 aqueous solution was prepared under ice-water bath conditions. The FTO glass was then placed in the TiCl4 aqueous solution with the conductive side facing up and reacted at 70°C for 0.5 h. After the reaction was complete, the FTO conductive glass with deposited dense TiO2 was cleaned with ethanol and deionized water and then dried.

[0127] Growth of TiO2 nanorod arrays (TiO2-NRA): 30 mL of deionized water and 5 mL of concentrated hydrochloric acid (mass fraction 38%) were mixed and stirred for 10 min. Tetrabutyl titanate was then added dropwise to the hydrochloric acid solution and stirred for another 10 min to prepare a tetrabutyl titanate solution with a concentration of 10 g / L. The tetrabutyl titanate solution was poured into the polytetrafluoroethylene liner of a hydrothermal reactor. The FTO glass with TiO2 deposited on it was placed in the hydrothermal reactor with the conductive side facing down and reacted at 160 °C for 2 h. After the reaction was completed, the hydrothermal reactor was allowed to cool to room temperature with the furnace. The FTO conductive glass was then removed, washed, and dried.

[0128] Blank example 2

[0129] Preparation of TiO2 substrate: Cut a 3×2cm sample 2 For the FTO glass, high-transmittance FTO conductive glass was sequentially ultrasonically cleaned in toluene, acetone, ethanol, and deionized water for 15 min to remove oil stains adhering to the substrate surface. It was then rinsed with alcohol and dried with nitrogen. A 20 mmol / L TiCl4 aqueous solution was prepared under ice-water bath conditions. The FTO glass was then placed in the TiCl4 aqueous solution with the conductive side facing up and reacted at 70°C for 0.5 h. After the reaction was complete, the FTO conductive glass with deposited dense TiO2 was cleaned with ethanol and deionized water and then dried.

[0130] Growth of TiO2 nanorod arrays (TiO2-NRA): 30 mL of deionized water and 5 mL of concentrated hydrochloric acid (mass fraction 38%) were mixed and stirred for 10 min. Tetrabutyl titanate was then added dropwise to the hydrochloric acid solution and stirred for another 10 min to prepare a tetrabutyl titanate solution with a concentration of 10 g / L. The tetrabutyl titanate solution was poured into the polytetrafluoroethylene liner of a hydrothermal reactor. The FTO glass with TiO2 deposited on it was placed in the hydrothermal reactor with the conductive side facing down and reacted at 160 °C for 2 h. After the reaction was completed, the hydrothermal reactor was allowed to cool to room temperature with the furnace. The FTO conductive glass was then removed, washed, and dried.

[0131] Growth of TiO2 nano-grass array (TiO2-NGA): Mix 17.5 mL of diethylene glycol, 2.5 mL of deionized water and 4 mL of concentrated hydrochloric acid (mass fraction 38%), stir well, add 0.15 g of potassium titanium oxalate, and stir until the potassium titanium oxalate is completely dissolved; pour the potassium titanium oxalate solution into the polytetrafluoroethylene liner of the hydrothermal reactor, place the FTO glass with TiO2-NGA grown on its surface facing down in the hydrothermal reactor, and place the hydrothermal reactor in a forced-air drying oven for hydrothermal reaction at a reaction temperature of 180℃ for 2 h. After the reaction is completed, wait for the hydrothermal reactor to cool to room temperature with the furnace, remove the FTO conductive glass and clean it with deionized water and alcohol, and dry it in a forced-air drying oven at 60℃.

[0132] Test Example 1

[0133] The morphology of the samples prepared in Example 1 and Blank Examples 1-2 was tested.

[0134] Figure 2 Scanning electron microscope (SEM) images of the photoelectrode with TiO2-NRA (titanium dioxide nanorod array) prepared according to blank example 1 are shown. The images show that the TiO2-NRA nanorods have a diameter of approximately 20–50 nm, a moderate nanorod distribution density, high porosity, and are arranged in an orderly manner with strong radial perpendicularity, exhibiting a good array morphology.

[0135] Figure 3 Scanning electron microscope (SEM) images of the photoelectrode with TiO2-NGA (titanium dioxide nanorod array) prepared according to Blank Example 2 are shown. As can be seen from the images, compared to the TiO2-NGA nanorods in Blank Example 1, the TiO2-NGA in Blank Example 2 exhibits significantly more pronounced branching at the tips, with lengths of approximately 200–500 nm, forming a multi-layered three-dimensional network. This significantly increases its specific surface area and electron transport network, providing ample active sites for photocatalysis.

[0136] Figure 4 Scanning electron microscope (SEM) images of the bismuth vanadate quantum dot-modified hierarchical titanium dioxide photoelectrode prepared according to Example 1 are shown. The left image (a) is a top view, and the right image (b) is a cross-sectional SEM image perpendicular to the left direction. The images clearly show that light-colored TiO2 nano-grass branches are densely grown on the surface of dark TiO2 nanorods, forming a hierarchical framework. BiVO4 quantum dots (bright white particles) with a particle size of 5–10 nm are uniformly loaded on these nano-grass branches, significantly increasing the specific surface area. Image (b) shows the titanium dioxide nanorod array arranged perpendicular to the substrate (height 1–2 μm), with quantum dots completely covering the surface and sidewalls of the nano-grass branches, constructing a three-dimensional heterojunction interface.

[0137] Figure 5 The X-ray diffraction patterns of the TiO2-NRA and TiO2-NGA photoelectrodes prepared in blank examples 1-2 are shown. The figures show that the main diffraction peaks of both TiO2-NRA and TiO2-NGA can be attributed to rutile-TiO2 (PDF#21-1276), and the characteristic peaks are very strong with almost no impurity peaks, indicating that the prepared TiO2-NRA and TiO2-NGA have good crystallinity and high purity. Compared to TiO2-NRA, the diffraction peak at 27.4° disappears in TiO2-NGA. This may be due to the disappearance of the (110) crystal plane of TiO2-NRA caused by hydrochloric acid etching during the secondary hydrothermal reaction, which is related to the growth of its nano-branch-like structure.

[0138] Test Example 2

[0139] This test example demonstrates the photocatalytic degradation experiments of the samples prepared in Examples 1-4 and Blank Examples 1-2. Tetracycline (an antibiotic), a typical antibiotic, was selected for the photocatalytic degradation experiment. The photoelectrodes of Examples 1-4 and Blank Examples 1-2 were used to test the degradation of simulated wastewater containing 10 mg / L tetracycline + 0.1 mol / L Na₂SO₄. Experimental details are as follows:

[0140] A three-electrode system was constructed in a 50 mL quartz reaction cell, with the photoelectrodes of Examples 1-4 and Blank Examples 1-2 as the working electrodes (effective area 3 × 2 cm²). 2A platinum sheet was used as the counter electrode, and a saturated calomel electrode (SCE) was used as the reference electrode. The distance between the working electrode and the counter electrode was fixed at 25 mm, and the total volume of wastewater in each system was 50 mL. A 300 W xenon lamp (with a 420 nm cutoff filter) was used as the light source, and the light intensity was calibrated to 100 mW / cm². 2 A +0.5V bias voltage (relative to a saturated calomel electrode) was applied to enhance charge separation efficiency. The photoelectrode was first immersed in the solution for 30 min under no-light conditions to achieve adsorption equilibrium. Then, photocatalytic degradation was initiated, with 1 mL of solution sampled every 20 min. The tetracycline concentration was determined by high-performance liquid chromatography (HPLC). The tetracycline degradation rate variation data are shown in Table 2 below.

[0141] Table 2. Changes in Tetracycline Degradation Rate

[0142]

[0143] As shown in Table 2, the bismuth vanadate quantum dot-modified multi-level titanium dioxide array photoelectrodes of the present invention (Examples 1-4) exhibit significant advantages in tetracycline degradation, with a degradation rate of approximately 50% within the first 20 minutes, far exceeding that of blank example 1 (10.8%) and blank example 2 (28.5%). This demonstrates that quantum dot modification and heterojunction structure significantly enhance the initial reaction activity. As the reaction proceeds, the degradation efficiency of Examples 1-4 continues to lead, reaching over 95% by the reaction endpoint of 120 minutes, far superior to the blank example. The maximum degradation rate difference within the example groups is only about 2%, indicating that the preparation process has good reproducibility. Moreover, although blank example 2 increased the specific surface area through the nano-grass structure, its degradation rate at 120 minutes was still less than 63%, indicating that physical structure optimization alone cannot solve the fundamental defects. This data fully verifies the synergistic effect of BiVO4 quantum dot modification and multi-level array—both expanding the visible light response range (quantum dot bandgap modulation) and promoting mass transfer through multi-level structure (nano-grass increasing specific surface area), ultimately achieving efficient degradation of antibiotic pollutants.

[0144] Figure 6 The degradation performance of tetracycline by photoelectrodes prepared according to Example 1 and Blank Examples 1-2 is shown in the graphs. As can be seen from the graphs, the C / CO value of the photoelectrode of Example 1 drops sharply to 0.22% within 120 min, with a degradation rate as high as 97.8%, significantly better than Blank Example 1 (C / CO = 57.3%) and Blank Example 2 (C / CO = 40.2%). The two blank example curves show a gradual decrease, while the curve of Example 1 shows a steep drop from 0 to 20 min, demonstrating the efficient charge separation capability of the quantum dot heterojunction. Figure 4 The SEM structure shown corresponds to this.

[0145] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Any modifications or equivalent substitutions made to the present invention without departing from the spirit and scope thereof should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a BiVO4 quantum dot modified multi-step TiO2 photoelectrode, characterized in that, The method comprises the following steps: depositing a titanium dioxide base layer on the conductive surface of the conductive glass, which comprises: preparing a titanium tetrachloride aqueous solution under ice water bath condition, placing the conductive glass with the conductive surface upward into the titanium tetrachloride aqueous solution, reacting for 0.5-1 h at 50-90 ℃, and after the reaction is completed, washing and drying the conductive glass on which the titanium dioxide base layer is deposited, wherein the concentration of the titanium tetrachloride aqueous solution is 15-25 mmol / L, and the titanium dioxide base layer is a dense structure; forming a titanium dioxide nanorod array on the titanium dioxide base layer by a hydrothermal method; growing a titanium dioxide nanograss array on the titanium dioxide nanorod array by a hydrothermal method, which comprises: preparing a second mixed solution of titanium potassium oxalate and hydrochloric acid, placing the second mixed solution into a hydrothermal reaction container, immersing the conductive glass with the titanium dioxide nanorod array into the second mixed solution with the conductive surface downward, and reacting at a second set temperature; after the reaction is completed, taking out the conductive glass after the hydrothermal reaction container is cooled and washing and drying the conductive glass, wherein the preparation of the second mixed solution of titanium potassium oxalate and hydrochloric acid comprises: uniformly mixing diethylene glycol, deionized water and concentrated hydrochloric acid, adding titanium potassium oxalate into the mixed solution and completely dissolving the titanium potassium oxalate, wherein the volume ratio of the diethylene glycol, deionized water and concentrated hydrochloric acid is (17-20):(2-3):(3-5), and the concentration of the titanium potassium oxalate in the second mixed solution is 2-20 g / L; loading bismuth vanadate quantum dots onto the surface of the titanium dioxide nanograss array by a hydrothermal method to obtain the photoelectrode.

2. The method for preparing a BiVO4 quantum dot modified multi-step TiO2 photoelectrode according to claim 1, characterized in that, The conductive glass is fluorine-doped tin oxide conductive glass.

3. The method for preparing a BiVO4 quantum dot modified multi-step TiO2 photoelectrode according to claim 1, characterized in that, forming a titanium dioxide nanorod array on the titanium dioxide base layer by a hydrothermal method comprises: preparing a first mixed solution of tetrabutyl titanate and hydrochloric acid; placing the first mixed solution into a hydrothermal reaction container, immersing the conductive glass on which the titanium dioxide base layer is deposited into the first mixed solution with the conductive surface downward, and reacting at a first set temperature; after the reaction is completed, taking out the conductive glass after the hydrothermal reaction container is cooled and washing and drying the conductive glass.

4. The method for preparing a BiVO4 quantum dot modified multi-step TiO2 photoelectrode according to claim 3, characterized in that, preparing a first mixed solution of tetrabutyl titanate and hydrochloric acid comprises: uniformly mixing deionized water and concentrated hydrochloric acid to obtain a hydrochloric acid solution, and adding tetrabutyl titanate dropwise into the hydrochloric acid solution, wherein the mass fraction of the concentrated hydrochloric acid is 35%-38%, the concentration of hydrogen chloride in the hydrochloric acid solution is 1-3 mol / L, and the concentration of tetrabutyl titanate in the first mixed solution is 5-20 g / L; the reaction temperature for the reaction at the first set temperature is 120-180 ℃, and the reaction time is 1-4 h.

5. The method for preparing a BiVO4 quantum dot modified multi-step TiO2 photoelectrode according to claim 1, characterized in that, the mass fraction of the concentrated hydrochloric acid is 35%-38%; the reaction temperature for the reaction at the second set temperature is 120-200 ℃, and the reaction time is 1-3 h.

6. The method for preparing a BiVO4 quantum dot modified multi-step TiO2 photoelectrode according to claim 1, characterized in that, loading bismuth vanadate quantum dots onto the surface of the titanium dioxide nanograss array by a hydrothermal method comprises: dissolving bismuth salt and vanadium salt in ethylene glycol to prepare a bismuth vanadate precursor solution; The bismuth vanadate precursor solution is put into a hydrothermal reaction container, and the conductive glass with the titanium dioxide nanograss array is immersed in the bismuth vanadate precursor solution with the conductive surface facing downward, and reacted at a third set temperature; After the reaction is completed, the conductive glass is taken out after the hydrothermal reaction container is cooled, and is washed and dried.

7. The method for preparing a BiVO4 quantum dot modified multi-step TiO2 photoelectrode according to claim 6, characterized in that, The molar ratio of bismuth ions to vanadium ions is 1: (1.0-1.2), and the concentration of the bismuth salt is 0.5-1 mol / L; The bismuth vanadate precursor solution further comprises a surfactant, and the mass ratio of the surfactant to the bismuth salt is (2-3):1, and the surfactant is selected from at least one of the following: oleic acid, polyvinyl alcohol, cetyltrimethylammonium bromide, sodium dodecyl sulfate, and polyvinylpyrrolidone; The reaction temperature for the reaction at the third set temperature is 120-180°C, and the reaction time is 1-4 h.

8. A BiVO4 quantum dot modified multi-step TiO2 photoelectrode, characterized in that, The photoelectrode is prepared by the method according to any one of claims 1-7.

Images