Titanium metal-based titanium dioxide photoanode and application thereof in photoelectrocatalytic degradation of organic pollutants

Abstract

This invention relates to the preparation and application of a titanium dioxide-based photoanode for photoelectrocatalytic degradation of organic pollutants. The photoanode is an array of titanium dioxide nanorods prepared in situ on a titanium dioxide substrate. The main steps are as follows: a polycarboxylic acid sodium salt is prepared into an aqueous solution, and the pH is adjusted with a certain amount of acid-base solution to prepare a reaction solution containing a morphology modifier; the cleaned and chemically etched titanium dioxide substrate is placed in a hydrothermal reactor, the reaction solution is added, and the reactor is heated to react. After the reaction is complete, the titanium dioxide photoanode precursor is removed, rinsed, and dried. The precursor is then calcined in a muffle furnace to obtain the titanium dioxide nanorod array photoanode. This invention is used as a photoanode for photoelectrocatalytic degradation of organic pollutants in the aqueous phase. This invention utilizes a hydrothermal synthesis method, which is simple to operate, environmentally friendly, and highly controllable. The resulting photoanode film has a strong bond with the substrate, good conductivity, high orientation, and excellent photoelectric response performance, achieving highly efficient removal of organic pollutants in the photoelectrocatalytic degradation system.

Description

Technical Field

[0001] This invention belongs to the field of pollutant treatment technology, and particularly relates to a titanium dioxide photoanode material based on metallic titanium for photoelectrocatalytic degradation of organic pollutants, its preparation and application. Background Technology

[0002] With economic and social development, energy and environmental issues have become increasingly prominent. Water resources are a fundamental condition for human survival, and water pollution seriously threatens human safety. The degradation of organic pollutants in water has received increasing attention from the scientific and industrial communities. Among organic pollutants in water, biomass and sugars are relatively easy to degrade, followed by acids and alcohols. Relatively difficult-to-degrade pollutants mainly include aromatic compounds and halogenated compounds. These organic pollutant molecules are not easily degraded spontaneously in the environment, nor are they easily degraded by microorganisms, thus persisting in the environment and accumulating in the human body through the food chain, posing a threat to ecosystems and human health.

[0003] In recent years, advanced oxidation (reduction) technologies, including photocatalysis, electrocatalysis, and photoelectrocatalysis, have enabled the complete conversion of organic matter into small molecules. Photoelectrocatalysis, in particular, utilizes semiconductor electrodes and an applied bias electric field. Under photoexcitation, photogenerated electrons and holes migrate to the surfaces of the anode and cathode, respectively, generating high-energy active species that convert pollutants into small molecules such as carbon dioxide, water, and halogens. Photoelectrocatalysis addresses the low efficiency of photoelectro-hole separation in nanoparticle photocatalysts, as well as the challenges of light scattering in wastewater and the difficulty in powder recovery, by applying an external electric field. Furthermore, it expands upon traditional electrocatalytic degradation processes by introducing a large amount of semiconductor materials, overcoming the limitations of limited active electrode materials and high energy consumption. Combining the advantages of photocatalysis and electrocatalysis, this approach enhances pollutant degradation capabilities while being easily controllable, allowing for the construction of tandem flow degradation systems. It has garnered increasing attention in wastewater treatment, with the core of photoelectrocatalytic degradation of organic pollutants lying in the preparation of safe, stable, and highly photoelectro-responsive photoelectrodes.

[0004] Titanium dioxide, as a wide-bandgap semiconductor, possesses high carrier mobility, low work function, strong ultraviolet absorption, and stable physicochemical properties. It is resistant to acids and alkalis, has no serious toxicity, and is inexpensive, making it widely used in environmental applications. The synthesis of titanium dioxide photoanodes has also attracted considerable attention. Some researchers have prepared titanium dioxide nanorod array thin-film photoanodes on FTO conductive glass substrates; however, the methods used require high concentrations of hydrochloric acid, which is highly hazardous, and the FTO conductive glass substrate has relatively weak structural strength, hindering large-scale production. Others have prepared titanium dioxide nanowire array thin-film photoanodes on metallic titanium sheets, but the orientation is poor, the preparation controllability is low, and the high electron-hole recombination rate prevents the achievement of high photoelectric response. Still others have prepared metallic titanium-based titanium dioxide nanosheet array thin-film photoanodes, but when the film is thin, it is dispersed in sheets, failing to achieve high photoelectric conversion efficiency. One-dimensional nanorod arrays are a very important type of nanofilm structure, possessing excellent light scattering and light absorption capabilities. The large aspect ratio of the nanorods facilitates charge separation, allowing electrons and holes to migrate axially and radially to the conductive substrate and the nanorod surface, respectively. Furthermore, the rod-shaped structure has a large specific surface area, providing more active sites. Therefore, the preparation of highly oriented titanium dioxide nanorod array photoanodes under mild conditions is very important, but no reports have been found. Summary of the Invention

[0005] A titanium dioxide photoanode based on metal titanium for photoelectrocatalytic degradation of organic pollutants, wherein a highly oriented nanorod array is prepared in situ on a metal titanium substrate.

[0006] The nanorod array was prepared using the following method:

[0007] (1) Mix the polycarboxylic sodium salt with water to form a mixed solvent, add acid to adjust the pH, and prepare a reaction solution containing a morphology regulator.

[0008] The polycarboxylic acid sodium salt is one or more of the following: disodium ethylenediaminetetraacetate, sodium citrate, sodium phthalate, and sodium oxalate.

[0009] The acid or alkaline solution is one or more of the following: hydrochloric acid, sulfuric acid, acetic acid, ethylenediaminetetraacetic acid, sodium hydroxide, potassium hydroxide, and ammonia water.

[0010] The total concentration of polycarboxylic acid sodium salt in the system is 0.01–1.2 mol / L, which can be adjusted according to different polycarboxylic acid salts. For example, the preferred concentration of disodium ethylenediaminetetraacetate is 0.04–0.08 mol / L.

[0011] The concentration of the aqueous solution of acid is 1–6.8 mol / L, preferably 5.5–6.5 mol / L;

[0012] The concentration of the alkaline aqueous solution is 0.01–0.08 mol / L, preferably 0.04–0.08 mol / L; the pH range of the reaction solution is 3.5 ≤ pH ≤ 7.0, preferably 4.0–5.0.

[0013] (2) The cleaned and chemically etched titanium substrate is placed in a hydrothermal reactor. A reaction solution containing a morphology modifier is added to the reactor so that the titanium substrate is immersed in the reaction solution. The reaction is heated and the reaction is completed. After the reaction is completed, the titanium substrate is taken out from the reactor, rinsed, and dried to obtain the hydrothermal titanium-based titanium dioxide nanorod array photoanode precursor.

[0014] The heating reaction temperature is 160–240℃, preferably 180–200℃. The reaction time is 6–18 h, preferably 9–12 h.

[0015] (3) The precursor of the metal titanium-based titanium dioxide nanorod array photoanode obtained by hydrothermal treatment was placed in a muffle furnace for calcination, cooled, and then removed to obtain the final product, the metal titanium-based titanium dioxide nanorod array photoanode.

[0016] The roasting temperature is 200–500℃, preferably 350–450℃, and the roasting time is 0.5–3h, preferably 0.5–1.5h.

[0017] The titanium substrate is one or more of the following: titanium sheet with a mass purity >99.5%, titanium foam sheet, woven titanium mesh, or sheet substrate with a titanium film with a thickness >500nm deposited on a silicon wafer, quartz wafer, or conductive glass sheet.

[0018] The cleaned titanium substrate is prepared by ultrasonically cleaning the titanium substrate in acetone, isopropanol, anhydrous ethanol and deionized water in sequence and then blowing it dry. The ultrasonic time is 10 to 30 minutes, preferably 15 to 20 minutes.

[0019] Chemical etching involves sequentially etching a titanium-based metal in a 5 wt%–10 wt% (preferably 5–7.5 wt%) sodium hydroxide solution and a 5 wt%–10 wt% (preferably 7.5–10 wt%) oxalic acid solution, with the solution temperature at 90–95°C (preferably 94–95°C) and the etching time at 0.5–3 h, preferably 1–1.5 h.

[0020] This invention provides a photoanode for the photoelectrocatalytic degradation of organic pollutants in aqueous phases. Utilizing a hydrothermal synthesis method, this invention is simple to operate, environmentally friendly, and highly controllable. The resulting photoanode film exhibits strong adhesion to the substrate, good conductivity, high orientation, and excellent photoelectric response performance, achieving highly efficient removal of organic pollutants in a photoelectrocatalytic degradation system. Attached Figure Description

[0021] Figure 1 The image shows the XRD pattern of the titanium dioxide nanorod array photoanode grown on a titanium substrate using a reaction solution of disodium ethylenediaminetetraacetate and trisodium citrate in Example 1.

[0022] Figure 2 The images shown are SEM images of the titanium dioxide nanorod array photoanode grown on a titanium substrate using a reaction solution of disodium ethylenediaminetetraacetate and trisodium citrate in Example 1. The images are low magnification A and high magnification B.

[0023] Figure 3 This is a SEM image of the titanium dioxide nanorod array photoanode grown on a titanium metal substrate using a partially polyhydroxy sodium salt reaction solution in Example 1.

[0024] Figure 4 This is a SEM image of the titanium dioxide nanorod array photoanode grown on a 100-mesh titanium mesh substrate using disodium ethylenediamine tetraacetate reaction solution of different concentrations in Example 2.

[0025] Figure 5 This is a SEM image of the titanium dioxide nanorod array photoanode grown on a titanium metal substrate using disodium ethylenediamine tetraacetate reaction solution with different pH values ​​in Example 3.

[0026] Figure 6 The linear current-voltage scan photoelectric response curves of the titanium dioxide photoanode in Example 4 under dark conditions and under illumination are shown.

[0027] Figure 7 The graph shows the degradation curves of titanium dioxide photoanodes used in Example 5 for photoelectrocatalytic degradation of dyes such as methyl orange, rhodamine B, or methylene blue.

[0028] Figure 8 The graph shows the degradation curves of the titanium dioxide photoanode used in Example 5 for photoelectrocatalytic degradation of aromatic compounds such as phenol, 4-chlorophenol, or 4-fluorophenol.

[0029] Figure 9 The graph shows the degradation curves of 4-fluorophenol by the titanium dioxide photoanode in Example 5, using direct photolysis, photocatalysis alone, electrocatalysis alone, or photoelectrocatalysis.

[0030] Figure 10 This is a degradation curve of the titanium dioxide photoanode synthesized by this patent and the previously reported methods in Example 6, used for photoelectrocatalytic degradation of 4-fluorophenol. Detailed Implementation

[0031] To further illustrate the invention, the following embodiments are provided, but they do not limit the scope of the invention as defined by the appended claims.

[0032] Example 1

[0033] Sodium polyhydroxy salts are used in the synthesis of titanium dioxide photoanodes.

[0034] Taking the polyhydroxy sodium salt reaction solution described in this invention as an example, a 0.035 mol / L EDTA disodium acetate aqueous solution and a trisodium citrate concentration of 0.1 mol / L are prepared, stirred and dissolved, and the pH is adjusted to 3.5 using a 6 mol / L hydrochloric acid aqueous solution to prepare a reaction solution containing a morphology modifier.

[0035] A 3cm × 3cm titanium sheet was ultrasonically cleaned sequentially in acetone, isopropanol, anhydrous ethanol, and deionized water for 15 min each. After drying, it was etched sequentially in 5wt% sodium hydroxide aqueous solution and 10wt% oxalic acid aqueous solution for 2 h each, at an etching temperature of 95℃. After removal, it was rinsed with deionized water and dried, then placed in a hydrothermal reactor. A reaction solution (100 ml) containing a morphology modifier was added to the reactor, and the reaction was heated to 210℃ for 12 h. After the reaction was complete, the titanium sheet was removed from the reactor, rinsed, and dried. The hydrothermally heated electrode was then calcined in a muffle furnace at 400℃ for 1 h, cooled, and removed to obtain a titanium dioxide nanorod array photoanode. XRD pattern as shown. Figure 1 As shown, the obtained photoanode crystal phase is rutile titanium dioxide. The nanorod diameter (cross-sectional area of ​​the nanorod parallel to the substrate) is approximately 700 nm to 900 nm. They grow perpendicular to the substrate surface, with a distance of approximately 50-200 nm between adjacent nanorods and a height ranging from approximately 700 nm to 1100 nm. Their morphology is as follows: Figure 2 As shown.

[0036] Besides disodium ethylenediaminetetraacetate, other polyhydroxy sodium salts were also used in the synthesis of this invention, with the same process and conditions as described above. The difference lies in that the polycarboxylic acid sodium salts used were trisodium citrate, sodium phthalate, or sodium oxalate, respectively. Figure 3 The images show the morphology of titanium dioxide photoanodes synthesized under partial polyhydroxy sodium salt conditions (0.05 mol / L polyhydroxy sodium salt, pH adjusted to 3.5 using 6 mol / L hydrochloric acid aqueous solution). All of them exhibit nanorod morphology, growing perpendicular to the substrate surface. The diameter of the nanorods (the cross-sectional area of ​​the nanorods parallel to the substrate) varies from 200 nm to 500 nm, and the height ranges from approximately 500 nm to 1000 nm.

[0037] Example 2

[0038] Adjusting the concentration of polyhydroxy sodium salts for the synthesis of titanium dioxide photoanodes

[0039] The process and conditions are the same as described in Example 1 above, except that, taking the disodium ethylenediaminetetraacetate reaction solution of the present invention as an example, reaction solutions of different concentrations are prepared for the synthesis of titanium dioxide photoanodes. Disodium ethylenediaminetetraacetate aqueous solutions of 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.10 mol / L, and 0.12 mol / L are prepared, stirred to dissolve, and the pH is adjusted to 4.0 using a 6 mol / L hydrochloric acid aqueous solution to prepare a reaction solution containing a morphology modifier.

[0040] A 100-mesh titanium mesh was ultrasonically cleaned sequentially in acetone, isopropanol, anhydrous ethanol, and deionized water for 15 min each. The mesh was then placed in a hydrothermal reactor, and a reaction solution containing a morphology modifier was added. The reactor was heated to 200°C for 6 h. After the reaction was complete, the titanium mesh was removed from the reactor, rinsed, and dried. The hydrothermally heated electrode was then calcined in a muffle furnace at 500°C for 1 h, cooled, and removed to obtain a titanium dioxide nanorod array photoanode. Its morphology is as follows: Figure 4 As shown, with the increase of the concentration of disodium ethylenediaminetetraacetate solution, the diameter of the nanorod array gradually increases from approximately 10 nm to 20 nm to 500 nm to 550 nm, and the height gradually increases from 10 nm to 50 nm to 1000 nm to 1200 nm.

[0041] Example 3

[0042] Different pH adjustments were used to synthesize titanium dioxide photoanodes.

[0043] The process and conditions are the same as described in Example 1 above, except that, taking the disodium ethylenediaminetetraacetate reaction solution of this invention as an example, reaction solutions with different pH values ​​are prepared for the synthesis of titanium dioxide photoanodes. A 0.05 mol / L disodium ethylenediaminetetraacetate aqueous solution is prepared and stirred to dissolve, with a pH value of 4.5. The pH is then adjusted to 4.0, 5.0, 6.0, and 7.0 respectively using a 6 mol / L hydrochloric acid aqueous solution and a 0.05 mol / L sodium hydroxide aqueous solution, thus preparing reaction solutions containing morphology modifiers.

[0044] Titanium sheets were sequentially ultrasonically cleaned for 15 min each in acetone, isopropanol, anhydrous ethanol, and deionized water. After drying, they were etched sequentially in 5 wt% sodium hydroxide aqueous solution and 10 wt% oxalic acid aqueous solution for 2.5 h each at 95 °C. After removal, they were rinsed with deionized water and dried, then placed in a hydrothermal reactor. A reaction solution containing a morphology modifier was added to the reactor, and the reactor was heated to 220 °C for 18 h. After the reaction was complete, the titanium sheets were removed from the reactor, rinsed, and dried. The hydrothermally heated electrode was then calcined in a muffle furnace at 450 °C for 1 h, cooled, and removed to obtain a titanium dioxide nanorod array photoanode. Its morphology is as follows: Figure 5As shown, as the pH of the reaction solution increases, the height of the nanorod array gradually increases from 500nm to 700nm to 1000nm to 1200nm; the nanorods gradually taper, that is, the diameter of the bottom surface of the nanorod (the end closest to the substrate surface) gradually increases from 400nm to 500nm to 900nm to 1000nm; the diameter of the top surface of the nanorod (the end furthest from the substrate surface) gradually decreases from 400nm to 500nm to 20nm to 50nm, and the nanorods gradually take on a pyramid shape.

[0045] Example 4

[0046] Evaluation of photoelectric performance of titanium dioxide photoanode

[0047] The titanium dioxide photoanode synthesized as described in Example 1 was used for photoelectric performance testing. 100 ml of 0.1 mol / L Na₂SO₄ electrolyte solution was used to perform linear voltammetric scans of the photoelectric response under both dark and illuminated conditions. The electrode area was 1 cm × 1 cm, the counter electrode was a 2 cm × 3 cm platinum sheet, the reference electrode was a saturated calomel electrode, the scan range was 0 V–2.0 V vs. RHE, the scan rate was 50 mV / s, the light source was a xenon lamp (POP-XLE, PLS-SXE300), and the energy density was 400 mW / cm². 2 The result is as follows Figure 6 As shown, compared with the dark state, its photocurrent is significantly increased under illumination, reaching 4 mA cm⁻¹ under conditions of 1.23 V vs. RHE. -2 Excellent photoelectric response is a prerequisite for its excellent photoelectrocatalytic degradation performance.

[0048] Example 5

[0049] Performance evaluation of titanium dioxide photoanodes for photoelectrocatalytic degradation of pollutants

[0050] The titanium dioxide photoanode synthesized on a titanium substrate using a reaction solution of disodium ethylenediaminetetraacetate and trisodium citrate as described in Example 1 was used to demonstrate the photoelectrocatalytic degradation effect of dyes such as methyl orange, rhodamine B, or methylene blue. A 100ml 10ppm dye solution was used, along with a 3cm × 3cm photoanode, a 3cm × 3cm graphite electrode as the counter electrode, and a saturated calomel electrode as the reference electrode. A voltage of 1.5V vs. RHE was applied. A 300W xenon lamp was used as the light source, approximately 10cm away from the photoanode, with a light intensity of 400mW / cm². 2 The reaction time was 60 minutes, and 1 ml of solution was taken every 10 minutes. The concentration of residual dye in the solution was detected by high-performance liquid chromatography (HPLC). The results are as follows: Figure 7 As shown, after 1 hour of degradation reaction, dyes such as methyl orange, rhodamine B, and methylene blue all achieved a degradation rate of more than 95%.

[0051] The titanium dioxide photoanode synthesized on a titanium substrate using a reaction solution of disodium ethylenediaminetetraacetate and trisodium citrate as described in Example 1 was used for the photoelectrocatalytic degradation of aromatic compounds such as phenol, 4-chlorophenol, or 4-fluorophenol. A 100ml 10ppm dye solution was used, along with a 3cm × 3cm photoanode, a 3cm × 3cm graphite electrode as the counter electrode, and a saturated calomel electrode as the reference electrode. A voltage of 1.5V vs. RHE was applied. A 300W xenon lamp was used as the light source, approximately 10cm from the photoanode, with a light intensity of 400mW / cm². 2 The reaction time was 60 minutes, and 1 ml of solution was taken every 10 minutes. The concentration of residual dye in the solution was detected by high-performance liquid chromatography (HPLC). The results are as follows: Figure 8 As shown, after 1 hour of degradation reaction, the degradation efficiency of phenol can reach 80%, and the degradation efficiency of 4-fluorophenol and 4-chlorophenol can reach 90%. The titanium dioxide photoanode synthesized on a titanium substrate using the reaction solution of disodium ethylenediaminetetraacetate and trisodium citrate as described in Example 1 was used to compare the performance of different degradation methods. A 100 ml 10 ppm methyl orange solution was used, along with a 3 cm × 3 cm photoanode, a 3 cm × 3 cm graphite electrode as the counter electrode, and a saturated calomel electrode as the reference electrode. A voltage of 1.5 V vs. RHE was applied. A 300 W xenon lamp was used as the light source, approximately 10 cm away from the photoanode, with a light intensity of 400 mW / cm². 2 The reaction time was 60 minutes, and 1 ml of solution was taken every 10 minutes. The concentration of residual dye in the solution was detected by high performance liquid chromatography. The results are shown in Figure 9. After 1 hour of degradation reaction, the degradation efficiency of methyl orange by direct photolysis, electrocatalysis alone, and photocatalysis alone was all below 5%, while the degradation efficiency of photoelectrocatalysis reached over 95%. This proves that the photoanode is suitable for photoelectrocatalytic degradation of organic pollutants and has a photoelectrocatalytic synergistic degradation effect.

[0052] Example 6

[0053] A comparative evaluation of the photoelectrocatalytic performance of the titanium dioxide photoanode synthesized in Example 1 and the titanium dioxide photoanode synthesized by previously reported methods in degrading pollutants.

[0054] Prepare 100 ml of 20 ppm 4-fluorophenol solution, a 3 cm × 3 cm photoanode, a 3 cm × 3 cm graphite electrode as the counter electrode, and a saturated calomel electrode as the reference electrode. Apply a voltage of 1 V vs. RHE. Use a 300 W xenon lamp as the light source, with the light source approximately 10 cm away from the photoanode, and an illuminance of 400 mW / cm². 2 The reaction time was 60 minutes, and 1 ml of solution was taken every 10 minutes. The concentration of residual 4-fluorophenol in the solution was detected by high performance liquid chromatography. The results are as follows: Figure 10 As shown

[0055] The following is a comparison method for preparing titanium dioxide photoanodes, as shown in the figure:

[0056] Ti-P25: Commercial P25 titanium dioxide nanoparticles were dispersed in ethanol, ultrasonically dispersed, and then loaded onto titanium sheets using a spraying method, with a loading of 1 mg / cm³. 2 After drying, it is placed in a muffle furnace and calcined at 350°C for 1 hour.

[0057] Ti-NTs: Prepare a solution of 10 vol% water, 90 vol% ethylene glycol, and 0.5 wt% ammonium fluoride. Prepare the photoanode by anodic oxidation, using a 3 cm × 3 cm electrode as the anode and a 3 cm × 3 cm graphite electrode as the counter electrode. Power the system with a DC power supply of 60 V. After anodic oxidation for 1 h, obtain the photoanode precursor. Clean the photoanode precursor sequentially with ethanol and deionized water, and after drying, place the precursor in a muffle furnace and calcine at 350 °C for 1 h.

[0058] The photoelectrochemical degradation results show that the titanium dioxide photoanode obtained by the synthesis method provided in this invention has higher photoelectrochemical degradation performance than the titanium dioxide photoanode supported by P25, and has potential and value for practical application.

Claims

1. A titanium dioxide photoanode based on metallic titanium, characterized in that, A titanium dioxide nanorod array perpendicular to the substrate surface was prepared in situ on a titanium substrate to obtain a titanium dioxide photoanode; the nanorod array was prepared by the following method: 1) Mix the polycarboxylic acid sodium salt with water to form a mixed solvent, add acid and alkali solutions to adjust the pH, and prepare a reaction solution containing a morphology modifier; The polycarboxylic acid sodium salt is one or more of the following: disodium ethylenediaminetetraacetate, sodium citrate, sodium phthalate, and sodium oxalate. The acid or alkaline solution is one or more of the following: hydrochloric acid, sulfuric acid, nitric acid, acetic acid, ethylenediaminetetraacetic acid, sodium hydroxide, potassium hydroxide, or ammonia. The total concentration of the polycarboxylic acid sodium salt in the system is 0.01~1.2 mol / L, which is adjusted according to different polycarboxylic acid salts. The concentration of the aqueous solution of the acid solution is 1~6.8 mol / L. The concentration of the alkaline aqueous solution is 0.01~0. mol / L; The pH range of the reaction solution is 3.5 ≤ pH ≤ 7.0; 2) Place the cleaned and chemically etched titanium substrate into a hydrothermal reactor, add a reaction solution containing a morphology modifier to the reactor, immerse the titanium substrate in the reaction solution, heat the reaction, and after the reaction is complete, remove the titanium substrate from the reactor, rinse and dry it to obtain the hydrothermal titanium-based titanium dioxide nanorod array photoanode precursor. The heating reaction temperature is 160~240℃; the reaction time is 6~18h; 3) The precursor of the titanium dioxide nanorod array photoanode obtained by hydrothermal treatment is placed in a muffle furnace for calcination, cooled, and then removed to obtain the final product, the titanium dioxide nanorod array photoanode. The roasting temperature is 200~500℃, and the roasting time is 0.5~3h; Chemical etching involves sequentially etching a titanium substrate in a 5wt%~10wt% sodium hydroxide solution and a 5wt%~10wt% oxalic acid solution, respectively, at a solution temperature of 90~95℃, for a time of 0.5~3h.

2. The photoanode according to claim 1, characterized in that: The titanium substrate is one or more of the following: One or more of the following: titanium sheet with a purity >99.5%, titanium foam sheet, woven titanium mesh, or sheet substrate with a titanium film with a thickness >500 nm deposited on a silicon wafer, quartz wafer or conductive glass sheet.

3. The photoanode according to claim 1, characterized in that: The cleaned titanium substrate was prepared by ultrasonically cleaning it in acetone, isopropanol, anhydrous ethanol and deionized water in sequence and then drying it. The ultrasonic cleaning time was 10-30 minutes for each of the three processes.

4. The photoanode according to claim 1, characterized in that: The resulting photoanode phase is rutile titanium dioxide.

5. The photoanode according to claim 1, characterized in that: The heating reaction temperature is 180~200℃; the reaction time is 9~12h; the calcination temperature is 350~450℃, and the calcination time is 0.5~1.5h. Chemical etching involves sequentially etching a titanium substrate in a 5-7.5 wt% sodium hydroxide solution and a 7.5-10 wt% oxalic acid solution, respectively, at a solution temperature of 94-95°C and for a time of 1-1.5 h.

6. The application of a titanium dioxide photoanode as described in any one of claims 1-5 in the photoelectrocatalytic degradation of organic pollutants.

Images