Titanium dioxide multi-heterojunction photoelectrode modified by quantum dots of tricobalt tetraoxide and construction and application thereof

Abstract

The application relates to a kind of four cobalt oxide quantum dot modified titanium dioxide multi-heterojunction photoelectrode and its construction and application, the photoelectrode includes as the 3D TiO2 of base electrode, and Co3O4 quantum dot is loaded on 3D TiO2, the 3D TiO2 has the sharp spinel-anatase " phase junction " of one-dimensional nanorod with anatase phase two-dimensional composition, p-n junction is formed between the Co3O4 quantum dot and 3D TiO2.The 3D Co3O4QDs of the application TiO2 Photoelectrode has high efficient and stable photoelectrocatalytic oxidation performance in PEC / PMS system, can realize nearly 100% removal to 20ppm OFL under simulated sunlight 15min-30min, after 5 times of cycle, the removal rate of OFL still maintains 97.6% respectively, with high efficient and stable photoelectrocatalytic oxidation reduction performance.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrode fabrication technology, and relates to a titanium dioxide multi-heterointerface photoelectrode modified with cobalt tetroxide quantum dots, its construction and application. Background Technology

[0002] Quinolone antibiotics are among the most widely used antibiotics due to their strong antibacterial activity, good efficacy, high bioavailability, and low cost. Ofloxacin (OFL) is a typical quinolone antibiotic, and its presence in the environment poses a significant risk to water quality, ecosystem safety, and human health. Therefore, there is an urgent need to develop a green and efficient technology for removing OFL from wastewater. The most commonly used wastewater treatment technologies are divided into physical, chemical, and biological methods. Chemical methods, as a highly efficient water treatment technology, can rapidly oxidize and completely degrade organic pollutants. Among them, advanced oxidation processes (AOPs) can generate highly oxidizing reactive free radicals in the reaction system, which, under appropriate conditions, attack organic pollutants in water. They have advantages such as high mineralization efficiency, fast oxidation reaction rate, and no secondary pollution, making them one of the most studied water treatment methods in recent years. Photocatalysis (PC) and photoelectrochemical catalysis (PEC) technologies of AOPs have been widely used for pollutant removal. Compared to photocatalysis, photoelectrocatalysis is spatially independent and has a high electron utilization rate, making it a more promising pollution control technology. However, it suffers from problems such as the lack of selectivity of the main active species ·OH, short lifespan, and susceptibility to environmental impacts.

[0003] Semiconductor photocatalysts, represented by TiO2, have advantages such as high activity, low cost, stable physicochemical properties, and non-toxicity, and are often used to degrade organic pollutants. However, TiO2 has low electron transfer efficiency and fast electron-hole recombination rate, which limits its large-scale application.

[0004] Over the past decade or so, structural engineering and interface engineering have been used to accelerate charge transfer in TiO2 and reduce electron-hole recombination rates, such as metal / non-metal doping, defect construction, noble metal modification, and semiconductor coupling. For example, patent CN202110178404.X discloses a titanium dioxide photoelectrode with three-dimensional crystal plane properties, its preparation, and its application. The preparation process of the photoelectrode is as follows: using a titanium mesh as the titanium source, hydrochloric acid as the morphology control agent, and hydrogen peroxide as the oxidant, one-dimensional upright rutile TiO2 nanorods with exposed {111} crystal planes at the top are grown in situ on a titanium mesh substrate using a gas-phase hydrothermal method; then, {101} and {111} nanosheets are grown outside the nanorods through a secondary hydrothermal process to form a three-dimensional crystal plane structure, which is the FH-{111}TiO2 / Ti target electrode. This patented electrode exhibits high photoelectrocatalytic degradation performance; however, TiO2 itself is still limited by the limited photoresponse range. Summary of the Invention

[0005] The purpose of this invention is to provide a titanium dioxide multi-heterointerface photoelectrode modified with cobalt tetroxide quantum dots, its construction and application, which can significantly improve photoelectrocatalytic ability and achieve efficient deep oxidation removal of OFL in water.

[0006] This invention discovers, through research, that SO4 produced by advanced oxidation techniques based on persulfate (PMS) activation... ·- With its advantages of strong oxidation, long lifespan, and wide pH range, PMS can efficiently degrade organic pollutants. Among the many activation methods of PMS, activation using solar energy to provide photogenerated electrons has the advantages of being continuous, stable, and efficient. Therefore, by constructing a PEC / PMS coupling system, pollutants can be anolyzed by PEC while PMS is activated by cathode electrons, thereby generating a large number of free radicals for synergistic deep oxidation of OFL. However, there are few reports on the use of PEC / PMS coupling technology for pollutant removal.

[0007] For photoelectrocatalytic systems, light absorption, charge separation, and interfacial charge injection efficiency are key to establishing highly efficient photoelectrocatalytic active interfaces. Currently, TiO2 semiconductor materials are the most widely used photoelectrode materials due to their low cost, non-toxicity, and good chemical stability. However, they still face challenges such as a narrow light absorption range and the fact that the photogenerated electron-hole recombination process is much faster than the surface transfer and trapping process, hindering the sustainable development of TiO2 in water treatment. For PMS activation materials, Co3O4 has been extensively studied due to its excellent PMS activation activity. Furthermore, Co3O4 is a narrow bandgap semiconductor (≈2.1 eV), exhibiting a quantum confinement effect when existing in quantum dot form. Therefore, combining Co3O4 quantum dots (Co3O4QDs) with TiO2 holds promise for improving the photoelectric performance of TiO2 photoelectrodes.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] In a first aspect, the present invention provides a titanium dioxide multi-heterointerface photoelectrode modified with cobalt tetroxide quantum dots, comprising 3D TiO2 as a substrate electrode and Co3O4 quantum dots loaded on 3D TiO2, wherein the 3D TiO2 has an anatase-rutile "junction" composed of one-dimensional rutile nanorods and two-dimensional anatase phase, and the Co3O4 quantum dots form a pn junction with the 3D TiO2.

[0010] In a second aspect, the present invention provides a method for preparing a titanium dioxide multi-heterointerface photoelectrode modified with cobalt tetroxide quantum dots, comprising the following steps:

[0011] S1. Preparation of 3D TiO2 photoelectrode;

[0012] S2. Prepare an ethanol solution of cobalt acetate, then place the 3D TiO2 electrode in the mixed solution for a solvothermal reaction, clean and dry to obtain a cobalt tetroxide quantum dot modified titanium dioxide composite photoelectrode, namely 3DCo3O4 QDs@TiO2 photoelectrode.

[0013] Specifically, the fabrication concept of the titanium dioxide multi-heterointerface photoelectrode of the present invention is as follows:

[0014] First, using a titanium mesh as a substrate, hydrochloric acid as a capping agent, and hydrogen peroxide as an oxidant, 1D rutile TiO2 nanorods were grown in situ on the titanium mesh via a vapor-phase hydrothermal method. Then, 2D anatase TiO2 nanosheets were deposited on the nanorods via electrodeposition to obtain 3D TiO2. Finally, Co3O4 quantum dots were loaded using a simple solvothermal method to obtain a Co3O4 QDs-modified TiO2 multi-heterointerface photoelectrode (3D Co3O4 QDs@TiO2), which is the target product.

[0015] Furthermore, in S1, the fabrication process of the 3D TiO2 photoelectrode includes the following steps:

[0016] (1) Take a titanium mesh as a substrate and place it in a mixed solution of hydrochloric acid, hydrogen peroxide and water. After a gas-phase hydrothermal reaction, 1D rutile TiO2 nanorods grown in situ on the mesh substrate are obtained.

[0017] (2) Hydrofluoric acid was added dropwise to tetrabutyl titanate, stirred evenly, and then transferred to a reaction vessel for hydrothermal reaction. After centrifugation, washing, and drying, anatase TiO2 nanosheets were obtained.

[0018] (3) Using Pt sheets and 1D rutile TiO2 nanorods as the anode and cathode of a dual-electrode system connected to a DC power supply, respectively, acetone solution was used as the electrodeposition solvent, iodine was added to improve conductivity, 2D TiO2 nanosheets were added to the electrodeposition solution, and electrodeposition was performed under a fixed voltage applied by a DC power supply. After the deposition was completed, heat treatment was performed in an air atmosphere to obtain a 3D TiO2 photoelectrode.

[0019] Furthermore, in step (1), the volume ratio of hydrochloric acid, hydrogen peroxide and water is (4.2-5.3):1:17, the mass fraction of hydrochloric acid is 36-38%, and the mass fraction of hydrogen peroxide is 30%.

[0020] Furthermore, in step (2), the volume ratio of hydrofluoric acid to tetrabutyl titanate is (3-4):25, preferably 3.5:25, and the mass fraction of the hydrofluoric acid is 35-45%.

[0021] Furthermore, in step (2), the temperature of the hydrothermal reaction is 160-200℃, preferably 180℃, and the time is 4-6h, preferably 5h.

[0022] Furthermore, in step (3), the ratio of the amount of 2D TiO2 nanosheets, elemental iodine and acetone added is (18-22) mg: (18-22) mg: 50 mL, preferably 20 mg: 20 mg: 50 mL.

[0023] Furthermore, in step (3), the voltage applied during the electrodeposition process is 12 to 18V, preferably 15V, and the electrodeposition time is 30 to 50 minutes, preferably 40 minutes.

[0024] Furthermore, in step (3), the heat treatment temperature is 400-500℃, preferably 450℃, and the time is 1-3h, preferably 2h.

[0025] Furthermore, in S2, the concentration of the cobalt acetate ethanol solution is 0.01–0.5 mM, which can be selected as 0.01, 0.1, 0.25, 0.5 mM, or any other value within this range.

[0026] Furthermore, in S2, the temperature of the solvothermal reaction is 140–160°C, preferably 150°C, and the time is 3–5 h, preferably 4 h.

[0027] In a third aspect, the present invention provides an application of a titanium dioxide multi-heterointerface photoelectrode modified with cobalt tetroxide quantum dots. The feature is that a three-electrode system is constructed with a 3D Co3O4 QDs@TiO2 photoelectrode as the photoanode, a Pt sheet as the cathode, and a saturated calomel electrode as the reference electrode. The water to be treated, containing OFL, potassium peroxymonosulfate, and Na2SO4, is used as simulated wastewater. Under the illumination of a light source, a bias voltage is applied, and photoelectrocatalytic synergistic removal of ofloxacin from the water to be treated is achieved.

[0028] Furthermore, the concentration of OFL is 2–20 mg / L, the concentration of potassium peroxymonosulfate is 0.25–2 mol / L, and the concentration of sodium sulfate is 0.025–0.2 mol / L.

[0029] Furthermore, the light intensity of the light source is 200–600 mW / cm². 2 The applied bias voltage is +0.2 to 1.0 V, and the degradation time is 3 to 20 min.

[0030] This invention reveals that for photoelectrocatalytic systems, light absorption, charge separation, and interfacial charge injection efficiency are key to establishing highly efficient photoelectrocatalytic active interfaces. For PMS activation materials, transition metal catalysts, represented by cobalt, have attracted significant attention due to their low energy requirements and high efficiency. Based on this, this invention assembles two-dimensional anatase TiO2 nanosheets with highly exposed {001} crystal faces on one-dimensional upright rutile TiO2 nanorods to form a three-dimensional TiO2 configuration with a "rutile-anatase" phase junction. Further, Co3O4 QDs are loaded onto TiO2 to construct a "Co3O4-TiO2" pn heterojunction, resulting in a Co3O4 QDs@TiO2 photoelectrode material with multiple heterojunctions. Photogenerated charges are first transferred at the heterojunction between Co3O4 and TiO2, and then separated again within the phase junctions inside TiO2, further promoting the separation and transfer of photogenerated charge carriers. This Co3O4 QDs@TiO2 photoelectrode exhibits highly efficient and stable catalytic oxidation performance in the PEC / PMS coupling system, achieving 100% OFL removal within 15 minutes.

[0031] This invention limits the amount of raw materials (such as 2D TiO2, cobalt acetate, etc.), reaction temperature, and reaction time during the fabrication of the photoelectrode. Firstly, in the fabrication of the 1D TiO2 photoelectrode, the amounts of hydrochloric acid and hydrogen peroxide used in the gas-phase hydrothermal process, as well as the hydrothermal time, are limited. Hydrochloric acid, as a capping agent, affects the exposure of the highly reactive {111} crystal facets; hydrogen peroxide, as an oxidant, affects the size of the titanium dioxide nanorods; and the reaction time affects the degree of order in the growth of the nanorods.

[0032] Secondly, the amount of 2D TiO2 used was limited during the electrodeposition process. The amount of 2D TiO2 affects the growth density of the two-dimensional nanosheets. Too sparse growth is detrimental to the formation of hierarchical structures, while too dense growth hinders electronic conduction between the 2D TiO2 and the 1D TiO2 substrate. Therefore, during the fabrication of the 3D TiO2 photoelectrode, the volume ratio of hydrochloric acid, hydrogen peroxide, and water during gas-phase hydrothermal treatment should be 4.2:1:17–5.3:1:17, and the optimal gas-phase hydrothermal time and temperature are 5 h and 200 °C. During electrodeposition, the amount of 2D TiO2 should be 10–40 mg, and the optimal electrodeposition time is 40 min to obtain a 3D TiO2 photoelectrode with the best hierarchical structure.

[0033] Finally, Co3O4 quantum dots were loaded onto the surface of 3D TiO2 by a solvothermal method, and the concentration of cobalt acetate, hydrothermal time, and temperature were limited: (1) The concentration of cobalt acetate affects the size and loading of Co3O4 quantum dots. When the precursor concentration is too low, the loading of Co3O4 is low, and the light absorption efficiency and the activation effect on PMS are not significantly improved. When the precursor concentration is too high, the loading of Co3O4 is high, the crystal plane of 3D TiO2 is blocked, affecting the multi-level structure, thereby affecting electron transfer and limiting the photoelectrocatalytic oxidation degradation efficiency. After optimizing the concentration of the precursor, 0.03 mM was determined to be the optimal concentration; (2) When the hydrothermal time is too short or the temperature is too low, the loading of Co3O4 quantum dots is too low, affecting the light absorption efficiency of the photoelectrode. When the hydrothermal time is too long or the temperature is too high, the three-dimensional configuration of 3D TiO2 is affected, the interfacial activity is reduced, and the photoelectrocatalytic performance is reduced. After optimizing the hydrothermal time, 4 h and 150 ℃ were determined to be the optimal hydrothermal time and temperature.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] (1) The substrate electrode is 3D TiO2, which has an advanced configuration composed of one-dimensional nanorods and two-dimensional nanosheets. Among them, the one-dimensional upright nanorod array grown in situ on the three-dimensional network substrate has good electron transport properties and enhanced light absorption and scattering properties; the electrodeposited two-dimensional {001}TiO2 nanosheets have a large specific surface area, which is conducive to the full exposure of active sites. In addition, the anatase phase nanosheets can also form anatase-rutile "bonds" with the rutile phase nanorods, which is beneficial to the separation and migration of photogenerated charges.

[0036] (2) Co3O4 loaded on the 3D TiO2 surface exhibits a narrow bandgap (≈2.1 eV) and the quantum confinement effect of quantum dots, which helps improve the photoelectric performance of the TiO2 photoelectrode. Furthermore, the formed Co3O4 / TiO2 "pn junction" synergizes with the anatase-rutile "phase junction," allowing photogenerated charges to migrate first through the pn junction between Co3O4 and TiO2 at the heterojunction interface, followed by further separation within the phase junction inside the titanium dioxide, further promoting the separation and transfer of photogenerated carriers. In addition, Co3O4 can efficiently activate PMS through the Co(III) / Co(II) redox cycle. Moreover, the presence of Co3O4 in quantum dot form avoids obscuring the crystal planes, and its large specific surface area fully exposes the active sites, facilitating electron transfer from Co to PMS.

[0037] (3) The 3D Co3O4 QDs@TiO2 photoelectrode prepared in this invention exhibits good stability and promising practical application prospects in removing ofloxacin from water. In conventional photocatalytic systems, photogenerated electrons and holes are located on the photocatalyst. In this invention, the photoelectrocatalytic application transfers electrons through an applied bias voltage and utilizes the multiple heterogeneous interfaces on the 3D Co3O4 QDs@TiO2 material to rapidly separate and transfer photogenerated electrons to the cathode, effectively improving the separation and utilization efficiency of photogenerated charges. Furthermore, the PEC / PMS coupling system constructed in this invention, while anolyzing pollutants at the PEC anolyte, activates the PMS using cathode electrons and the redox cycle of Co(III) / Co(II), further promoting the separation of photogenerated charges and generating a large number of free radicals for synergistic deep oxidation of OFL. After 5 cycles, the removal rate of ofloxacin remains at 97.6%, with low applied bias voltage and low energy consumption, which is beneficial for practical applications. Attached Figure Description

[0038] Figure 1 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the 3D Co3O4 QDs@TiO2 prepared in Example 1;

[0039] Figure 2 A comparison of the photoelectric properties of 3D Co3O4 QDs@TiO2 and 3D TiO2 with different precursor concentrations prepared in Example 1;

[0040] Figure 3 Fluorescence spectra and time-resolved transient fluorescence spectra of the 3D Co3O4 QDs@TiO2 and 3D TiO2 photoelectrodes prepared in Example 1;

[0041] Figure 4 This is a schematic diagram of the photogenerated carrier migration path on the 3D Co3O4 QDs@TiO2 photoelectrode prepared in Example 1;

[0042] Figure 5 A comparison of the photoelectric properties of 3D CQDs@TiO2 prepared in Comparative Example 4 and 3D Co3O4 QDs@TiO2 prepared in Example 1;

[0043] Figure 6 The removal efficiency of OFL and the corresponding kinetic fitting curves were obtained by using 3D Co3O4 QDs@TiO2 and TiO2 prepared in Example 1 as photoanodes in PEC and PEC / PMS systems, respectively.

[0044] Figure 7 The 3D Co3O4 QDs@TiO2 prepared in Example 1 was used as the photoanode to measure the removal efficiency of OFL and the corresponding kinetic fitting curves in simulated wastewater containing different concentrations of PMS.

[0045] Figure 8 The 3D Co3O4 QDs@TiO2 prepared in Example 1 was used as the photoanode. The removal efficiency of OFL and the corresponding kinetic fitting curves were obtained in simulated wastewater containing different concentrations of NaSO4.

[0046] Figure 9 Using 3D Co3O4 QDs@TiO2 prepared in Example 1 as the photoanode, the removal efficiency of OFL and the corresponding kinetic fitting curves were obtained when different bias voltages were applied during the degradation process. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0048] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercial products or conventional processing techniques in the art.

[0049] Example 1

[0050] A titanium dioxide multi-heterointerface photoelectrode modified with cobalt tetroxide quantum dots, its construction and application, specifically including the following steps:

[0051] (1) Chemical polishing pretreatment: The metal Ti mesh was folded into a double layer and cut into 3cm×5cm size. It was pretreated by soaking in chemical polishing solution (volume ratio: HNO3:HF:H2O=25:5:1) for 30s. Then it was ultrasonically cleaned in water and ethanol for 3-5min respectively and then soaked in ethanol for later use.

[0052] (2) Gas-phase hydrothermal: Add 5 mL of deionized water, 300 μL of hydrogen peroxide (30 wt%) and 1.0 mL of hydrochloric acid (37.0 wt%) to a 100 mL polytetrafluoroethylene substrate reactor liner. Place the pretreated dry titanium mesh on the annular support in the liner and put the liner into the high-pressure reactor. Perform a gas-phase hydrothermal reaction at 200 °C for 5 h. After the reaction is completed, cool to room temperature, rinse the surface with deionized water and air dry naturally.

[0053] (3) Hydrothermal reaction: First, 3.5 mL of hydrofluoric acid (40% by mass) was slowly added dropwise to 25 mL of tetrabutyl titanate, with stirring using a magnetic stirrer during the addition process. Second, the well-stirred solution was transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE), sealed, and placed in an oven at 180 °C for 24 h for hydrothermal reaction. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The resulting product was then collected by centrifugation and thoroughly washed three times with deionized water and ethanol to remove residual organic matter and other impurities. Finally, the sample was placed in a vacuum drying oven and dried at 80 °C for 12 h to obtain TiO2 nanosheets for later use.

[0054] (4) Electrodeposition: The Pt sheet and the electrode obtained in step (2) were used as the anode and cathode, respectively. 20 mg of the nanosheets obtained in step (3) and 20 mg of iodine were weighed and added to 50 mL of acetone solution, and ultrasonically dispersed evenly to prepare the electrodeposition solution. The DC power supply was adjusted to constant voltage mode, and the applied voltage was fixed at 15 V for 40 min.

[0055] (5) Calcination: Calcination was carried out in an air atmosphere at a temperature of 450℃, a heating rate of 3℃ / min, and a calcination time of 2h to obtain a 3D TiO2 photoelectrode.

[0056] (6) Solvothermal reaction: Prepare an ethanol solution of cobalt acetate with a concentration of 0.03 mM, and then place the 3D TiO2 photoelectrode obtained in step (5) into 30 mL of the above solution. Perform a solvothermal reaction at 150 °C for 4 h, clean and dry to obtain a cobalt tetroxide quantum dot modified titanium dioxide composite photoelectrode, which is the 3D Co3O4 QDs@TiO2 photoelectrode.

[0057] (7) The simulated wastewater containing oxyfloxacin was removed using the 3D Co3O4 QDs@TiO2 photoelectrode prepared above. The specific process is as follows:

[0058] The photoelectrocatalytic experiment was conducted in a 50 mL quartz degradation cell using a three-electrode system. A PEC / PMS system based on 3D Co3O4QDs@TiO2 was constructed, with a working electrode 20 cm away from the light source and an effective photoelectrode area of ​​2.5 × 3 cm². 2 The simulated wastewater was a 45 mL mixed solution of 0.1 M sodium sulfate, 20 ppm OFL, and 1 M PMS. The light source was a 300 W xenon lamp with an illuminance of 520 mW / cm². 2 A bias voltage of +0.4V (relative to a saturated calomel electrode) was applied for photoelectrocatalysis experiments. The reaction time was 15 min, and samples were taken periodically. The concentration of OFL in the samples was measured using an Agilent 1260 high-performance liquid chromatography (HPLC) system. Specific degradation results are as follows: Figure 6As shown, (a) represents the OFL removal curve, and (b) represents the corresponding first-order kinetic curve.

[0059] Figure 6 The test results show that, firstly, the PEC / PMS system achieves a higher OFL removal rate compared to the single PEC system. Furthermore, regardless of whether it's the PEC system or the PEC / PMS system, the OFL degradation efficiency is higher after loading Co3O4 QDs onto TiO2. Finally, compared to TiO2, coupling PEC with PMS results in a greater increase in the OFL removal efficiency of Co3O4 QDs@TiO2 (2.6-3.6 times). This indicates that the 3D Co3O4 QDs@TiO2 photoelectrode successfully achieves highly efficient photoelectrocatalytic oxidation-reduction of oxyfloxacin-containing wastewater in a PEC / PMS system.

[0060] Comparative Example 1:

[0061] Compared with Example 1, most of them are the same, except that in this example: the simulated wastewater in step (7) is a mixed solution of 0.1 mol / L sodium sulfate solution and 20 mg / L OFL.

[0062] Comparative Example 2:

[0063] Compared with Example 1, most of them are the same, except that in this example: the working electrode in step (7) is 3DTiO2.

[0064] Comparative Example 3:

[0065] The majority of the results are the same as in Example 1, except that in this example, the cobalt acetate concentrations in step (6) are 0.01 and 0.05 mM, respectively.

[0066] Comparative Example 4:

[0067] Compared with Example 1, most of them are the same, except that in this example, the cobalt tetroxide quantum dots in step (6) are replaced with carbon quantum dots.

[0068] Performance testing

[0069] 1. Scanning electron microscopy analysis

[0070] The microstructure of the electrodes was characterized using field emission scanning electron microscopy (Hitachi S-4800) and scanning transmission electron microscopy (JEM-2100), such as... Figure 1 As shown in Figure a, 1D TiO2 nanorods are grown perpendicular to the substrate on a titanium mesh, with diameters ranging from 110 nm to 220 nm. Two-dimensional TiO2 nanosheets are uniformly distributed in the gaps between the nanorods, and the loaded Co3O4 QDs can be grown in the space between the nanorods. Figure 1 As observed in b, the diameter is approximately 6 nm.

[0071] 2. Photoelectrochemical performance testing

[0072] The photoelectrochemical oxidation performance of the 3D TiO2 and 3D Co3O4 QDs@TiO2 photoelectrode prepared in Example 1 was studied. The specific steps are as follows:

[0073] The photoelectrocatalytic performance was tested in a square quartz reaction cell using a 0.1 mol / L sodium sulfate solution. A three-electrode system was employed, with 3D TiO2 and 3D Co3O4 QDs@TiO2 as working electrodes, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode. Linear sweep voltammetry, Mott-Schottky curves, transient photocurrent response curves, and AC impedance spectroscopy were measured using a Chenhua CHI660C electrochemical workstation. A xenon lamp was used as the light source, with a distance of 1 cm between the light source and the working electrode. The test results are as follows: Figure 2 As shown, the results indicate that the photoresponse performance of the 3D Co3O4 QDs@TiO2 electrode is significantly better than that of 3D TiO2, with a photocurrent density reaching 0.8 mA / cm². 2 It is 2.0 times that of 3D TiO2, with an impedance of approximately 466.0 Ω, which is about 0.7 times smaller than that of 3D TiO2. The calculated carrier concentration is 8.9 × 10⁻⁶. 28 cm -3 It is about 25.5 times better than 3D TiO2.

[0074] 3. Fluorescence spectroscopy and time-resolved transient fluorescence spectroscopy tests

[0075] Fluorescence spectroscopy and time-resolved transient fluorescence spectroscopy were performed using the 3D TiO2 and 3D Co3O4 QDs@TiO2 photoelectrodes prepared in Example 1, see [link to example]. Figure 3 a. Compared to the 3D TiO2 electrode, the luminescence intensity of the 3D Co3O4 QDs@TiO2 photoelectrode is much weaker, indicating that the loading of Co3O4 quantum dots significantly suppresses the recombination of photogenerated charges. For example... Figure 3 As shown in b, the carrier decay rate on 3D Co3O4 QDs@TiO2 is slower, demonstrating its stronger ability to separate photogenerated electron-hole pairs. This indicates that the loading of Co3O4 quantum dots significantly improves the separation efficiency of photogenerated charges in TiO2 and extends the lifetime of excited electrons (3D TiO2: 0.96 ns; 3D Co3O4 QDs@TiO2: 72 ns), allowing more holes to reach the surface and participate in the oxidation reaction, thereby improving the efficiency of oxidative degradation of pollutants.

[0076] This invention significantly improves photoelectric performance by introducing Co3O4 quantum dots, solving the problems of narrow light absorption range and fast photogenerated charge recombination rate of traditional TiO2 materials. Figure 5 The results show that replacing Co3O4 quantum dots with carbon quantum dots (CQDs) significantly reduces the photoelectric properties of the material, highlighting the unique properties and advantages of Co3O4 quantum dots. Simultaneously, Co3O4 exhibits excellent activation of PMS, efficiently activating it and significantly enhancing pollutant removal capabilities. Furthermore, the PEC / PMS coupling system constructed in this invention, while anolyzing pollutants with PEC, utilizes the redox cycle of cathode electrons and Co(III) / Co(II) to activate PMS, further promoting the separation of photogenerated charges and generating a large number of free radicals, achieving synergistic deep oxidation. During operation, this system exhibits low energy consumption, significantly improving energy efficiency and demonstrating good economic viability, making it suitable for sustainable development in fields such as water treatment and showing its unique application potential.

[0077] In terms of technical means, the combination of PEC and PMS enables the synergistic removal of pollutants by multiple free radicals. PEC technology alone is used to remove OFL, and the rest is the same as in Example 1. Comparative Example 2, which constructs a PEC system to degrade OFL, yields the following results: Figure 6 As shown, compared to the single PEC system, the oxidation efficiency of 3D TiO2 for OFL increased from 82.0% to 97.4% after the introduction of PMS, and the corresponding first-order kinetic constant increased from 0.038 min⁻¹. -1 Increased to 0.10 min -1 The oxidation efficiency of OFL by 3D Co3O4 QDs@TiO2 was significantly increased from 62.3% to 100.0%, and the corresponding kinetic rate constant also increased from 0.064 min. -1 Increased to 0.24min -1 This indicates that the activation of PMS promotes the oxidation process of OFL.

[0078] Using 3D TiO2 as the photoanode, and with the rest the same as in Example 1, Comparative Example 2 was constructed to construct a photoelectrocatalytic coupling process for the oxidation and degradation of OFL by persulfate (see Comparative Example 2 for details). The results are as follows. Figure 6 As shown. Compared to the PEC / PMS system using TiO2 as the photoanode, the PEC / PMS system using 3D Co3O4 QDs@TiO2 as the photoanode can increase the oxidation efficiency of OFL from 71.7% to 100.0% within 15 min, with the corresponding first-order kinetic constant increasing from 0.10 min. -1 Increased to 0.24min -1 This demonstrates that the PEC / PMS system built based on 3DCo3O4 QDs@TiO2 can achieve efficient removal of OFL.

[0079] Examples 2 to 3

[0080] Compared with Example 1, most of them are the same, except that in this example: the mass of 2D TiO2 nanosheets in step (4) is 10mg and 40mg respectively.

[0081] Examples 4 to 5

[0082] Most of the contents are the same as in Example 1, except that in this example, the cobalt acetate concentrations in step (6) are 0.01 mM and 0.05 mM, respectively.

[0083] Examples 6 to 7

[0084] Most of the contents are the same as in Example 1, except that in this example, the PMS concentrations in step (7) are 0.25 mM, 0.5 mM and 2 mM, respectively.

[0085] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A quantum dot modified Ti02 photoanode with Co304 multi-heterojunctions, characterized in that, The 3D TiO2 as a base electrode, and Co3O4 quantum dots loaded on the 3D TiO2, the p-n junction is formed between the Co3O4 quantum dots and the 3D TiO2.

2. The method according to claim 1, wherein the method is characterized by, The method comprises the following steps: S1, preparing a 3D TiO2 photoelectrode; S2, preparing a cobalt acetate ethanol solution, and then placing the 3D TiO2 electrode in the mixed solution to perform a solvothermal reaction, cleaning and drying to obtain a three-cobalt oxide quantum dot modified titanium dioxide composite photoelectrode, namely a 3D Co3O4 QDs@TiO2 photoelectrode.

3. The method for preparing a titanium dioxide multi-heterointerface photoelectrode modified with cobalt tetroxide quantum dots according to claim 2, characterized in that, In S1, the preparation process of the 3D TiO2 photoelectrode comprises the following steps: (1) taking a metal titanium mesh as a base, placing it in a mixed solution of hydrochloric acid, hydrogen peroxide and water, and performing a gas phase hydrothermal reaction to obtain 1D rutile TiO2 nanorods grown in situ on the mesh base; (2) adding hydrofluoric acid dropwise to tetrabutyl titanate, stirring uniformly, and then transferring to a reaction kettle to perform a hydrothermal reaction, centrifuging, washing and drying to obtain anatase TiO2 nanosheets; (3) taking a Pt sheet and the 1D rutile TiO2 nanorods as an anode and a cathode of a two-electrode system connected to a direct current power supply, taking an acetone solution containing 2D TiO2 nanosheets and iodine as an electrodeposition solution, and performing electrodeposition under a fixed voltage of the direct current power supply, and then performing heat treatment in an air atmosphere after the electrodeposition is completed to obtain the 3D TiO2 photoelectrode.

4. The method of claim 3, wherein the method is characterized by: In step (1), the volume ratio of hydrochloric acid, hydrogen peroxide and water is (4.2-5.3):1:17, the mass fraction of hydrochloric acid is 36-38%, and the mass fraction of hydrogen peroxide is 30%.

5. The method of claim 3, wherein the method is characterized by: In step (2), the volume ratio of hydrofluoric acid to tetrabutyl titanate is (3-4):25, and the mass fraction of the hydrofluoric acid is 35-45%; The temperature of the hydrothermal reaction is 160-200°C, and the time is 4-6h.

6. The method of claim 3, wherein the method is characterized by: In step (3), the addition amount ratio of the 2D TiO2 nanosheets, iodine and acetone is (18-22)mg:(18-22)mg:50mL.

7. The method of claim 3, wherein the method is characterized by: In step (3), the voltage applied during the electrodeposition is 12-18V, and the electrodeposition time is 30-50min; The temperature of the heat treatment is 400-500°C, and the time is 1-3h.

8. The method according to claim 2, wherein the method is characterized by, In S2, the concentration of the cobalt acetate ethanol solution is 0.01-0.5mM; The temperature of the solvothermal reaction is 140-160°C, and the time is 3-5h.

9. The use of a titanium dioxide multi-heterojunction photoelectrode modified with tricobalt tetroxide quantum dots according to claim 1, wherein, A three-electrode system is constructed with the 3D Co3O4 QDs@TiO2 photoelectrode as a photoanode, a Pt sheet as a cathode, and a saturated calomel electrode as a reference electrode, and a water body containing OFL, potassium peroxymonosulfate and Na2SO4 is used as simulated wastewater, and under the irradiation of a light source, a bias voltage is applied to remove ofloxacin in the water body by photoelectrocatalysis.

10. The use of a Co3O4 quantum dot modified TiO2 polyheterojunction photoelectrode according to claim 9, characterized in that, The concentration of OFL is 2-20mg / L, the concentration of potassium peroxymonosulfate is 0.25-2mol / L, and the concentration of sodium sulfate is 0.025-0.2mol / L. The light intensity of the light source is 200-600 mW / cm 2 The bias voltage is +0.2-1.0 V, and the degradation time is 3-20 min.

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