Preparation method of a ferroferric oxide electrode material and application of the ferroferric oxide electrode material in an electrode, a device and a method for photoelectrocatalytic degradation of phenol
By preparing nanoparticle or pleated ferric oxide electrodes on a metal mesh substrate, the problem of low efficiency of ferric oxide electrodes in photoelectrocatalytic degradation of phenol in the prior art is solved, achieving rapid and thorough phenol degradation and improving the environmental friendliness of the materials.
Patent Information
- Application Number
- CN202111402385.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-11-19
- Publication Date
- 2025-11-18
- Estimated Expiration
- 2041-11-19
AI Technical Summary
Existing ferric oxide electrodes are inefficient and costly in photoelectrocatalytic degradation of phenol, making it difficult to balance light conditions and mass exchange efficiency, resulting in poor catalytic performance.
Ferric oxide electrodes are prepared by immersing a metal mesh substrate in an iron-containing compound solution, followed by drying and heat treatment. The preparation process is optimized to control the film thickness and morphology. A stainless steel mesh and an iron acetylacetone solution are used, combined with infrared baking and heat treatment, to form a dense film of nanoparticles or wrinkles.
The prepared ferric oxide electrode rapidly and completely degrades phenol under ultraviolet light irradiation, improving the photoelectrocatalytic degradation efficiency, enhancing light-gathering conditions and mass exchange rate, and is low in cost and environmentally friendly and non-toxic.
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Abstract
Description
Technical Field
[0001] This application relates to a method for preparing ferric oxide electrode material and its application in electrodes, devices and methods for photoelectrocatalytic degradation of phenol, belonging to the field of aqueous organic pollutant treatment. Background Technology
[0002] Phenol is a valuable and important industrial raw material, used to produce various chemical products and intermediates, including phenolic resins, caprolactam, bisphenol A, and chlorophenols. It is widely used in the chemical, pharmaceutical, pesticide, and dyeing industries. However, it is also frequently discharged into the environment as wastewater during these industries, causing serious water pollution problems. Phenol corrodes the skin and mucous membranes, inhibits the central nervous system, and damages organs such as the liver and kidneys, posing a significant threat to human health. It is classified as a Group 3 carcinogen by the World Health Organization. my country has also established strict wastewater discharge standards for phenol, stipulating that the third-level discharge standard is no higher than 1.0 mg / L, the first-level discharge standard is no higher than 0.3 mg / L, and the drinking water standard must be below 0.002 mg / L. Therefore, there is an urgent need to develop an efficient and safe method to treat the water pollution caused by phenol.
[0003] Photoelectrocatalysis (PEC) is a typical advanced oxidation technology (AOPs) that generates superoxide radicals (·O2) during the electrode reaction. -PEC (Polyoxymethylene) contains highly reactive oxygen species (ROS) such as hydroxyl radicals (·OH), with ·OH having a redox potential as high as 2.8V. It is the most potent oxidant in nature besides fluoride, capable of indiscriminately mineralizing organic matter into harmless small-molecule inorganic substances like CO2 and H2O, resulting in a very thorough purification effect. In the PEC system, light not only significantly reduces the applied voltage required for the reaction through the photocatalytic effect of the photoelectrode, thus reducing the overall energy consumption of the system, but also activates organic molecules, making them more readily involved in the reaction. Furthermore, the applied voltage in the PEC system can, in turn, enhance the separation efficiency and migration speed of photogenerated charges generated by the photocatalytic process, further accelerating the entire reaction process. This makes PEC a highly efficient theoretical system with great application potential in the treatment of organic water pollution such as phenol. In a PEC system, the photoelectrode is the most crucial component. For large-scale commercial application in the treatment of organic water pollution such as phenol, the selected photoelectrode must not only possess high efficiency and stability, but the materials constituting the photoelectrode must also meet the requirements of being inexpensive, safe, non-toxic, and environmentally friendly. Ferric oxide (Fe₂O₃) is a very inexpensive and common metal oxide, abundant in the Earth's crust, non-toxic, safe, and environmentally friendly, making it ideal as a photoelectrode material for the photoelectrocatalytic treatment of organic water pollution such as phenol. However, it has not yet achieved ideal catalytic degradation results. For example, studies such as Applied Catalysis B: Environmental, 2017, 204: 127-133, The Journal of Physical Chemistry C, 2018, 122: 297-306, and Electrochimica Acta, 2018, 285: 230-240 have shown that the ferric oxide electrodes prepared by these studies require several hours to photoelectrocatalytically degrade phenol concentrations below 20 ppm, and the mineralization efficiency of phenol is also very low. Furthermore, the photoelectrodes used in PEC-related studies are mainly based on flat materials such as FTO and metal sheets. It is difficult to take into account the core influencing factors of the photoelectrocatalytic system—lighting conditions and mass exchange efficiency—which further leads to poor catalytic degradation effect of the system. There are very few research reports that address these issues, and even fewer that propose effective solutions. Summary of the Invention
[0004] The purpose of this invention is to introduce the preparation process of a metal mesh-based ferric oxide electrode and its application in the photoelectrocatalytic degradation of phenol.
[0005] One aspect of this application provides a method for preparing an ferric oxide electrode, the method comprising:
[0006] (1) Immerse the metal mesh substrate in an iron-containing compound solution, remove the metal mesh substrate, dry it at 220℃~250℃, and thermally decompose it in situ to obtain a metal mesh substrate with an iron-containing intermediate layer on its surface.
[0007] (2) The metal mesh substrate with an iron-containing intermediate layer on its surface obtained in step (1) is heat-treated at a temperature of 300-400°C to obtain a metal mesh-based ferric oxide electrode.
[0008] Optionally, step (1) can be repeated 1 to 20 times to control the thickness of the ferric oxide thin film on the surface of the prepared metal mesh-based ferric oxide electrode.
[0009] Optionally, the metal mesh is selected from at least one of stainless steel mesh, titanium mesh, and nickel mesh;
[0010] The iron-containing compound is selected from at least one of ferric acetylacetone, ferric nitrate, ferrous nitrate, or ferrous acetate.
[0011] Stainless steel mesh is the best choice for metal mesh, and iron acetylacetone is the best choice for iron compound.
[0012] Optionally, the upper limit of the heat treatment temperature is independently selected from 320℃, 350℃, 380℃, and 400℃; the lower limit is independently selected from 300℃, 320℃, 350℃, and 380℃.
[0013] Optionally, in step (1), the metal mesh substrate is further subjected to a cleaning pretreatment process before being immersed in the solution containing iron compounds;
[0014] The preprocessing process includes:
[0015] The metal mesh substrate was ultrasonically cleaned in sequence with acetone, isopropanol, anhydrous ethanol and deionized water for 25-45 minutes and then dried.
[0016] Optionally, the upper limit of the cleaning time is independently selected from 30 min, 35 min, 40 min, and 45 min; the lower limit is independently selected from 25 min, 30 min, 35 min, and 40 min.
[0017] Optionally, the solution containing the iron compound further includes a solvent selected from ethanol, water, acetone, and a mixture of ethanol and water; in the ethanol and water mixed solution, the volume ratio of anhydrous ethanol to water can be any ratio.
[0018] Optionally, the concentration of the iron-containing compound in the solution is 0.01–0.1 mol / L;
[0019] Optionally, the upper limit of the concentration of the iron-containing compound may be independently selected from 0.03 mol / L, 0.05 mol / L, 0.08 mol / L, and 0.1 mol / L; the lower limit may be independently selected from 0.01 mol / L, 0.03 mol / L, 0.05 mol / L, and 0.08 mol / L.
[0020] Optionally, in step (1), the drying time is 5 to 10 minutes.
[0021] Optionally, the upper limit of the baking time can be independently selected from 6 min, 7 min, 8 min, 9 min, and 10 min; the lower limit can be independently selected from 5 min, 6 min, 7 min, 8 min, and 9 min.
[0022] Optionally, in step (2), the heat treatment time is 2 to 12 hours.
[0023] Optionally, the upper limit of the heat treatment time can be independently selected from 4h, 6h, 8h, 10h, and 12h; the lower limit can be independently selected from 2h, 4h, 6h, 8h, and 10h.
[0024] As one specific embodiment, the method for preparing the ferric oxide electrode includes:
[0025] First, the acetylacetone iron solution is completely and evenly soaked into the surface of the stainless steel mesh and each mesh hole. Then, the solution is dried by baking with an infrared lamp, which causes the acetylacetone iron to decompose into iron-containing compound intermediates that adhere to the surface of each braided wire of the stainless steel mesh. Finally, the iron-containing compound intermediates are converted into ferric oxide through a heat treatment process.
[0026] As one specific embodiment, the method for preparing the ferric oxide electrode includes:
[0027] (1) Immerse the cleaned stainless steel mesh in the acetylacetone iron solution, then remove it and remove the excess solution from its surface so that the acetylacetone iron solution completely and evenly wets the surface of the metal mesh and each mesh hole.
[0028] (2) Place the stainless steel mesh that has been impregnated in (1) under an infrared lamp for 5-10 minutes to allow the solution to evaporate completely and to promote the complete decomposition of acetylacetone iron into iron-containing compound intermediates.
[0029] (3) Step (1) can be repeated several times to control the thickness of the ferric oxide thin film on the surface of the prepared metal mesh-based ferric oxide electrode.
[0030] (4) Place the stainless steel mesh after step (3) in a muffle furnace at 300 to -400℃ and heat treat for 2 to 12 hours.
[0031] Another aspect of this application provides an ferric oxide electrode, comprising the electrode material prepared by the method described above;
[0032] The electrode material includes a conductive substrate and an active material;
[0033] The conductive substrate is a metal mesh;
[0034] The active material is ferric oxide;
[0035] The ferric oxide has a microstructure of a dense film with nanoparticles or wrinkles on its surface, and the thickness of the ferric oxide film on the stainless steel mesh is in the nanometer range.
[0036] Optionally, the electrode is prepared according to the method.
[0037] Optionally, the mesh count of the metal mesh is ≥100 mesh;
[0038] Optionally, the mesh count of the metal mesh ranges from 100 to 400 mesh.
[0039] Optionally, the stainless steel mesh is selected from one of 304, 316, 310, and 301 stainless steel.
[0040] In another aspect of this application, an apparatus for photoelectrocatalytic aqueous phenol production is provided, the apparatus comprising a metal mesh-based ferric oxide electrode, wherein the electrode is selected from the aforementioned ferric oxide electrode.
[0041] Optionally, the device further includes a reaction pipeline, a power supply, and an ultraviolet lamp;
[0042] The metal mesh-based ferric oxide electrode consists of N circular ring electrodes;
[0043] The outer diameter of the annular electrode is equal to the inner diameter of the reaction channel;
[0044] The central portion of each of the N annular electrodes is provided with concentric circular holes of the same size;
[0045] The reaction channel is equipped with N annular electrodes coaxial with the reaction channel, and the N annular electrodes are arranged at equal intervals.
[0046] The ultraviolet lamp tube passes through the concentric circular holes of all the annular electrodes.
[0047] Another aspect of this application provides the application of a metal mesh-based ferric oxide electrode in the photoelectrocatalytic degradation of phenol, wherein the electrode is selected from the ferric oxide electrode prepared by the method or the ferric oxide electrode described above.
[0048] According to another aspect of this application, a method for photoelectrocatalytic degradation of phenol is provided, wherein wastewater containing phenol is passed through the device to electrocatalytically degrade phenol.
[0049] The device used in this application can simultaneously improve the two major problems of poor light conditions and low mass exchange rate in the photoelectrocatalytic degradation system of aqueous phenol and other organic pollutants. The performance of photoelectrocatalytic degradation of phenol is far superior to that of metal sheet-based ferric oxide electrode and FTO-based ferric oxide electrode under the same conditions.
[0050] The beneficial effects of the application include:
[0051] The electrode preparation method described in this application is characterized by mild conditions, simple process, strong controllability, and high raw material utilization. The prepared electrode is inexpensive, environmentally friendly, non-toxic, has a uniform and dense film layer, and high catalyst loading per unit area. It can simultaneously improve the two major problems of poor light transmission and low mass exchange rate in the photoelectrocatalytic degradation system of aqueous phenol, enabling rapid photoelectrocatalytic degradation of phenol in the aqueous phase, and has high practical application value. The electrode obtained in this application can rapidly achieve complete photoelectrocatalytic degradation of aqueous phenol under ultraviolet light irradiation, with performance far superior to metal sheet-based ferric oxide electrodes and FTO-based ferric oxide electrodes under the same conditions. Attached Figure Description
[0052] Figure 1 This is a comparison of the photoelectrocatalytic degradation performance of phenol by the stainless steel mesh-based ferric oxide electrode described in Example 2, and by the stainless steel sheet-based and FTO-based ferric oxide electrodes under the same test conditions.
[0053] Figure 2 The images are scanning electron microscope (SEM) images of blank stainless steel mesh, where (a) is an SEM image at 100 μm resolution and (b) is an SEM image at 1 μm resolution.
[0054] Figure 3 The images shown are scanning electron microscope (SEM) images of the stainless steel mesh-based ferric oxide electrode described in Example 2, where (a) is a SEM image at 100 μm resolution and (b) is a SEM image at 1 μm resolution.
[0055] Figure 4 The images shown are scanning electron microscope (SEM) images of the stainless steel mesh-based ferric oxide electrode described in Example 3, where (a) is a scanning electron microscope image at 100 μm resolution and (b) is a scanning electron microscope image at 1 μm resolution.
[0056] Figure 5 This is a schematic diagram of an apparatus for the photoelectrocatalytic degradation of phenol using a stainless steel mesh-based ferric oxide electrode prepared in Example 2. Detailed Implementation
[0057] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0058] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels, and all chemical reagents used were from the Sinopharm brand, while the water was distilled water or deionized water.
[0059] Example 1
[0060] Ferric acetylacetone was dissolved in anhydrous ethanol to prepare a 0.01 mol / L reaction solution. A 100-mesh 304 stainless steel mesh was ultrasonically cleaned for 30 minutes in sequence with acetone, isopropanol, anhydrous ethanol, and deionized water, and then dried. The cleaned stainless steel mesh was immersed in the prepared reaction solution, then removed and excess reaction solution was removed from the surface with absorbent paper to ensure that the ferric acetylacetone solution completely and evenly wetted the surface and each mesh opening of the stainless steel mesh. The wetted stainless steel mesh was baked under an infrared lamp for 5 minutes (at a temperature of about 250℃) to completely evaporate the solution and promote the complete decomposition of ferric acetylacetone into iron-containing intermediates. The baked stainless steel mesh was then re-immersed in the prepared reaction solution, and the "immersion-wetting-baking-re-immersion" process was repeated 5 times. Finally, the stainless steel mesh that had undergone repeated treatment was placed in a muffle furnace at 350℃ and baked for 8 hours. After cooling, the stainless steel mesh-based ferric oxide electrode was obtained.
[0061] Example 2
[0062] Ferric acetylacetonate was dissolved in anhydrous ethanol to prepare a 0.01 mol / L reaction solution. A 100-mesh 304 stainless steel mesh was ultrasonically cleaned for 30 minutes in sequence with acetone, isopropanol, anhydrous ethanol, and deionized water, and then dried. The cleaned stainless steel mesh was then immersed in the prepared reaction solution. Afterward, it was removed and excess reaction solution was removed using absorbent paper, ensuring the ferric acetylacetonate solution completely and evenly wetted the surface and each mesh opening of the stainless steel mesh. The wetted stainless steel mesh was then baked under an infrared lamp for 5 minutes (approximately 250°C) to completely evaporate the solution and promote the complete decomposition of ferric acetylacetonate into iron-containing intermediates. The baked stainless steel mesh was then re-immersed in the prepared reaction solution, repeating the "immersion-wetting-baking-re-immersion" process 10 times. Finally, the repeatedly treated stainless steel mesh was placed in a muffle furnace at 350°C for 8 hours, cooled, and removed to obtain a stainless steel mesh-based ferric oxide electrode.
[0063] The obtained stainless steel mesh-based ferric oxide electrode was subjected to scanning electron microscopy (SEM). The SEM images are shown in Figure 3(a) and (b). Figure 3As shown in Figures (a) and (b), the ferric oxide film is uniform, and the surface of the film consists of nanoparticles of uniform size.
[0064] Example 3
[0065] Anhydrous ethanol and deionized water were mixed evenly in a 1:1 volume ratio. Ferric acetylacetonate was then dissolved in the mixed solution to prepare a 0.01 mol / L reaction solution. A 100-mesh 304 stainless steel mesh was ultrasonically cleaned for 30 minutes each time with acetone, isopropanol, anhydrous ethanol, and deionized water, and then dried. The cleaned stainless steel mesh was then immersed in the prepared reaction solution, removed, and excess reaction solution was removed using absorbent paper, ensuring the ferric acetylacetonate solution completely and evenly wetted the surface and each mesh opening. The wetted stainless steel mesh was then baked under an infrared lamp for 5 minutes (approximately 250°C) to completely evaporate the solution and promote the complete decomposition of ferric acetylacetonate into iron-containing intermediates. The baked stainless steel mesh was then re-immersed in the prepared reaction solution, repeating the "immersion-wetting-baking-re-immersion" process 10 times. Finally, the stainless steel mesh that has undergone repeated treatment is placed in a muffle furnace at 350℃ and baked for 8 hours. After cooling, it is removed to obtain a stainless steel mesh-based ferric oxide electrode.
[0066] The obtained stainless steel mesh-based ferric oxide electrode was subjected to scanning electron microscopy (SEM). The SEM images are shown in Figure 4(a) and (b). Figure 4 As shown in Figures (a) and (b), the ferric oxide film is uniform, and the surface of the film has uniformly distributed nano-folds.
[0067] Example 4
[0068] Figure 5 This is a device for the photoelectrocatalytic degradation of phenol using a stainless steel mesh-based ferric oxide electrode prepared in Example 2. It is one of the reasonable operating methods to simultaneously improve the two major problems of poor light transmission and low mass exchange rate in photoelectrocatalytic degradation systems of aqueous phenol and other organic pollutants. Specifically, the device for degrading phenol involves: based on the good mechanical strength of the metal mesh, the metal-based ferric oxide electrode is processed into concentric rings with a hollow center, and arranged in an equally spaced stacked configuration. A suitable-sized ultraviolet lamp tube passes through the central hole of all electrode meshes. During system operation, wastewater can flow smoothly through the micron-sized mesh openings on the electrode sheets and make good contact with the electrode surface film to achieve high mass exchange efficiency. The ultraviolet light emitted by the central lamp tube can fully irradiate the surface of each electrode and the flowing wastewater to achieve good light transmission conditions.
[0069] Test Example 1
[0070] (1) Preparation process of stainless steel sheet-based ferric oxide electrode:
[0071] The cleaned 304 stainless steel sheet was placed on the surface of a 400℃ heating table. Then, 30 mL of 0.01 mol / L ethanol solution containing acetylacetone iron was sprayed evenly onto the surface of the 304 stainless steel sheet. After spraying, the sheet was heated on the heating table for 5 min to promote the complete decomposition of acetylacetone iron. The treated stainless steel sheet was then placed in a tube furnace filled with a 0.1% O2 / Ar protective atmosphere and calcined at 550℃ for 2 h to obtain a stainless steel sheet-based ferric oxide electrode.
[0072] (2) Preparation process of FTO-based ferric oxide electrode:
[0073] The cleaned FTO was placed on a heating table at 400℃. Then, 30 mL of 0.01 mol / L ethanol solution containing acetylacetone iron was sprayed evenly onto the FTO surface. After spraying, the FTO was heated on the heating table for 5 min to promote the complete decomposition of acetylacetone iron. The treated FTO was then placed in a muffle furnace at 550℃ and calcined for 2 h to obtain an FTO-based ferric oxide electrode.
[0074] (3) Comparative test of photoelectrocatalytic degradation performance of phenol:
[0075] The electrolyte was a 1 mol / L NaOH aqueous solution containing 20 ppm phenol. The light source was a common commercial high-pressure mercury lamp (175W, 230-600nm). The photoelectrodes were stainless steel sheet-based ferric oxide electrodes, FTO-based ferric oxide electrodes, and stainless steel mesh-based ferric oxide electrodes obtained in Example 2, with dimensions of 3cm×4.5cm, prepared in steps (1) and (2) above. The counter electrode was a 3cm×4.5cm graphite sheet. The reference electrode was a saturated calomel electrode. The applied voltage was 1.4V vs RHE.
[0076] The phenol content was determined using the following method: Agilent liquid chromatography was employed with a C18 column, a detector light source wavelength of 270 nm, a mobile phase of 70% acetonitrile and 30% water, and a mobile phase flow rate of 1.5 mL / min.
[0077] For detailed test results, please see [link / details]. Figure 1 ,from Figure 1It can be seen that when using stainless steel sheet-based ferric oxide electrodes and FTO-based ferric oxide electrodes as photoanodes for the photoelectrocatalytic degradation of phenol, the degradation rate of phenol is slow. After 120 minutes of reaction, about 30% of the phenol in the FTO-based ferric oxide electrode system remains undegraded; while about 10% of the phenol in the stainless steel sheet-based ferric oxide electrode system remains undegraded. When using the stainless steel mesh-based ferric oxide electrode prepared in this invention, the degradation rate of phenol is very fast, and complete degradation of phenol can be achieved within 60 minutes.
[0078] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for preparing an ferric oxide electrode material, characterized in that, The method includes: (1) After immersing the metal mesh substrate in a solution containing iron compound, remove the metal mesh substrate and dry it at a temperature of 220~250 °C; the mesh size of the metal mesh is in the range of 100~400 mesh. (2) Heat treatment is performed at 300~400 ℃ to obtain a metal mesh-based ferric oxide electrode material; the microstructure of the ferric oxide is a dense thin film with nanoparticles or wrinkles on the surface; The solution containing the iron compound further includes a solvent selected from anhydrous ethanol, water, acetone, and a mixed solution of ethanol and water; The concentration of the iron-containing compound in the solution is 0.01~0.1 mol / L; In step (1), the drying time is 5~10 min; In step (2), the heat treatment time is 2 to 12 hours.
2. The method according to claim 1, characterized in that, The method further includes: Repeat step (1) 1 to 20 times.
3. The method according to claim 1, characterized in that: The metal mesh is selected from at least one of stainless steel mesh, titanium mesh, and nickel mesh; The iron-containing compound is selected from at least one of ferric acetylacetone, ferric nitrate, ferrous nitrate, or ferrous acetate.
4. The method according to claim 1, characterized in that, In step (1), the metal mesh substrate is further subjected to a cleaning pretreatment process before being immersed in the solution containing iron compounds; The pretreatment process includes: ultrasonically cleaning the metal mesh substrate sequentially with acetone, isopropanol, anhydrous ethanol and deionized water for 25-45 minutes, followed by drying.
5. A ferric oxide electrode, characterized in that, Including the electrode material prepared by the method according to any one of claims 1 to 4, The electrode material includes a conductive substrate and an active material; The conductive substrate is a metal mesh; The active material is ferric oxide; The ferric oxide has a microstructure of a dense thin film with nanoparticles or wrinkles on its surface.
6. The ferric oxide electrode according to claim 5, characterized in that, The metal mesh is a stainless steel mesh, and the stainless steel mesh material is selected from one of 304, 316, 310, and 301.
7. An apparatus for photoelectrocatalytic degradation of phenol, characterized in that, The device includes a metal mesh-based ferric oxide electrode, wherein the electrode is selected from the ferric oxide electrode according to any one of claims 5 to 6.
8. The apparatus according to claim 7, characterized in that, The device also includes a reaction pipeline, a power supply, and an ultraviolet lamp. The metal mesh-based ferric oxide electrode consists of N circular ring electrodes; The outer diameter of the annular electrode is equal to the inner diameter of the reaction channel; The central portion of each of the N annular electrodes is provided with concentric circular holes of the same size; The reaction channel is equipped with N annular electrodes coaxial with the reaction channel, and the N annular electrodes are arranged at equal intervals. The ultraviolet lamp tube passes through the concentric circular holes of all the annular electrodes.
9. The application of a metal mesh-based ferric oxide electrode in the photoelectrocatalytic degradation of phenol, characterized in that, The electrode is selected from the ferric oxide electrode according to any one of claims 5 to 6.
10. A method for photoelectrocatalytic degradation of phenol, characterized in that, Wastewater containing phenol is electrocatalytically degraded into phenol by means of the apparatus described in any one of claims 7 to 8.