A heteropolyacid / TiO2 composite titanium electrode and its preparation method and application

Abstract

The present invention relates to the field of electrocatalysis technology, and particularly to a heteropolyacid / TiO2 composite titanium electrode and its preparation method and application, which are used to solve the problems that the TiO2 active layer of the existing titanium electrode is easy to fall off, the electrocatalytic activity is relatively low, and the chemical stability is relatively low. The degradation rate of the heteropolyacid / TiO2 composite titanium electrode for 2,4,6-trinitrophenol reaches 97.3%. After being recycled 10 times, the degradation rate of 2,4,6-trinitrophenol can still reach 96.8%. After being recycled 20 times, the surface morphology of the electrode basically does not change, and the TiO2 particles are always firmly attached to the electrode surface. The heteropolyacid / TiO2 composite titanium electrode is simple to prepare, the raw materials are economical, and it has excellent degradation performance for organic pollutants, and has good application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of electrocatalysis, and in particular to a heteropoly acid / TiO2 composite titanium electrode and a preparation method and application thereof. Background Art

[0002] 2,4,6-Trinitrophenol is a toxic aromatic nitro compound widely used in the manufacture of explosives, pesticides and dyes. This pollutant is characterized by large chromaticity, complex composition and poor biodegradability. In the treatment of trinitrophenol wastewater, many researchers have been paying attention to advanced oxidation technologies, such as Fenton oxidation, ozone oxidation, photocatalytic oxidation, etc. Among them, the most promising trinitrophenol wastewater treatment technology is the advanced electrochemical oxidation process.

[0003] The electrochemical oxidation process degrades organic matter at the anode. According to its different mechanisms of action, it can be divided into direct oxidation and indirect oxidation. Direct oxidation refers to the adsorption of organic pollutants on the anode surface, and then through the anode electron transfer process, strong oxidizing hydroxyl radicals are formed to achieve the oxidation and removal of organic pollutants. Electrochemical direct oxidation has a good pollutant oxidation and degradation effect on the treatment of organic wastewater containing cyanide, nitrogen, phenol, etc.

[0004] At present, among the anode materials used in electrochemical oxidation, pure titanium electrodes are environmentally friendly and low in cost, but their oxidation capacity is low and cannot meet the requirements of wastewater degradation. In order to improve the electrolytic oxidation performance of the pure titanium electrode surface and enhance the electrode's oxidation of organic matter, it is often necessary to add a coating to the electrode surface, and the most common one is the TiO2 active layer. However, the TiO2 active layer is easy to fall off, causing the electrode to be inactivated, and its electrochemical oxidation performance still needs to be improved. Therefore, it is urgent to develop a new type of titanium electrode with a TiO2 active layer that is not easy to fall off and has high electrocatalytic activity and high chemical stability, so as to further improve the degradation efficiency of 2,4,6-trinitrophenol. Summary of the invention

[0005] The purpose of the present invention is to provide a heteropolyacid / TiO2 composite titanium electrode and its preparation method and application, so as to solve the problems of easy shedding of the TiO2 active layer of the existing titanium electrode, low electrocatalytic activity and low chemical stability, and further improve the degradation efficiency of 2,4,6-trinitrophenol.

[0006] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A method for preparing a heteropolyacid / TiO2 composite titanium electrode comprises the following steps:

[0008] (1) The titanium sheet is placed in a solution of heteropoly acid and sulfuric acid, reacted in a reflux device at 50-70°C for 1-3 hours, and then placed in a solution of heteropoly acid and oxalic acid, and continued to react in a reflux device at 50-70°C for 1-3 hours to obtain an acid-etched titanium sheet electrode. A rough micro-nano structure is generated on the smooth surface of the titanium sheet, and the surface is oxidized to titanium dioxide by air. The generation of a rough micro-nano structure can increase the surface area of ​​the titanium sheet, help reduce the current density, and reduce the polarization effect caused by the current; on the other hand, it also increases the chance of the titanium sheet surface combining with titanium dioxide particles, further increasing the surface area of ​​the electrode and improving the efficiency of electrolysis.

[0009] (2) Add the titanium sheet electrode after acid etching in step (1) to a sodium silicate solution and immerse for 5-15 minutes, soak in distilled water for 0.5-1.5 minutes, and then immediately transfer to a TiCl3 solution, heat to 210-230°C and react for 0.5-1.5 hours to obtain a TiO2-modified titanium sheet electrode. The sodium silicate solution is added as a binder, and silicon dioxide is obtained after hydrolysis. Silicon dioxide can fix titanium dioxide particles, increase the bonding degree between the titanium dioxide spherical particles obtained by TiCl3 hydrolysis and the titanium sheet electrode, and at the same time improve the stability and degradation efficiency of the titanium sheet electrode modified with TiO2 particles; surface modification of nano-sized TiO2 spherical particles will further increase the surface area of ​​the titanium sheet electrode and improve the efficiency of electrocatalytic degradation.

[0010] (3) The titanium sheet electrode modified with TiO2 in step (2) is immersed in the heteropoly acid solution for 20-40 minutes, then taken out and immersed in distilled water for 0.5-1.5 minutes to obtain a heteropoly acid / TiO2 composite titanium electrode. Titanium dioxide is acidic and alkaline, and when combined with the acidic heteropoly acid, the heteropoly acid can catalyze the electrolytic oxidation reaction of organic pollutants, further improving the efficiency of pollutant degradation.

[0011] Preferably, the heteropoly acid in step (1) is phosphotungstic acid (H3PW 12 O 40 ) or phosphomolybdic acid (H3PMo 12 O 40 ), the concentration is 0.8-1.2%; the concentration of sulfuric acid is 30-40%; the concentration of oxalic acid is 10-20%.

[0012] Preferably, in step (2), the concentration of the sodium silicate solution is 0.1-0.2 M; the concentration of the TiCl3 solution is 0.2-0.4 M.

[0013] Preferably, the heteropoly acid in step (3) is phosphotungstic acid (H3PW 12 O 40 ) or phosphomolybdic acid (H3PMo 12 O 40), concentration is 10-30%.

[0014] The present invention also includes a heteropoly acid / TiO2 composite titanium electrode prepared by the above-mentioned preparation method.

[0015] The present invention also includes the use of the above-mentioned heteropoly acid / TiO2 composite titanium electrode in electrochemical oxidation degradation of organic pollutant wastewater.

[0016] The present invention also includes the use of the above-mentioned heteropoly acid / TiO2 composite titanium electrode in electrochemical oxidation degradation of 2,4,6-trinitrophenol wastewater, the steps are as follows: using the 2,4,6-trinitrophenol wastewater solution as an electrolyte, the heteropoly acid / TiO2 composite titanium electrode as an anode, and a titanium sheet electrode as a cathode, at 50 mA / cm 2 Electrochemical oxidation degradation of 2,4,6-trinitrophenol at a current density of 0.1 mol / L sodium sulfate solution as electrolyte, 4 cm inter-electrode spacing, and 50.0 cm areas for both anode and cathode. 2 .

[0017] Preferably, the electrochemical oxidation degradation of 2,4,6-trinitrophenol is carried out at a temperature of 25° C. and for a time of 2 h.

[0018] Preferably, the degradation rate of the heteropoly acid / TiO2 composite titanium electrode for 2,4,6-trinitrophenol is 97.3%.

[0019] Beneficial effects of the present invention:

[0020] 1. The preparation method of the heteropolyacid / TiO2 composite titanium electrode of the present invention is simple and convenient, the raw materials are economical, and the prepared electrode has the advantages of low cost, the TiO2 active layer is not easy to fall off, high electrocatalytic activity, and high chemical stability, and can effectively remove 2,4,6-trinitrophenol in wastewater. The degradation rate of the electrode for 2,4,6-trinitrophenol reaches 97.3%. After being recycled for 10 times, the degradation rate of 2,4,6-trinitrophenol can still reach 96.8%; after being recycled for 20 times, the surface morphology of the electrode does not change substantially, and the TiO2 particles are always firmly attached to the surface of the electrode.

[0021] 2. A rough micro-nano structure is generated on the smooth surface of the titanium sheet, and titanium dioxide is generated on the surface of the titanium sheet through natural oxidation in the air. The rough micro-nano structure and the raised titanium dioxide significantly increase the surface area of ​​the titanium sheet, which helps to reduce the current density and reduce the polarization effect caused by the current; the rough micro-nano structure also increases the chance of the titanium sheet surface combining with the subsequently generated titanium dioxide particles to further increase the surface area of ​​the electrode and improve the efficiency of the electrolytic oxidation of organic pollutants; the generated titanium dioxide also has a catalytic effect and is conducive to the subsequent loading of heteropoly acids on the electrode surface.

[0022] 3. The present invention also adds a sodium silicate solution as a binder. After the sodium silicate is hydrolyzed, silicon dioxide is obtained. Silicon dioxide can fix the titanium dioxide particles previously generated on the surface of the titanium sheet electrode, and at the same time increase the degree of binding between the titanium dioxide spherical particles obtained by the hydrolysis of TiCl3 and the titanium sheet electrode, thereby improving the stability and catalytic performance of the titanium sheet electrode modified with TiO2 particles. The surface of the titanium sheet electrode is modified with nano-scale TiO2 spherical particles, which can further increase the surface area of ​​the titanium sheet electrode and improve the efficiency of electrocatalytic degradation. Titanium dioxide is acidic and alkaline, so acidic heteropolyacids can combine with titanium dioxide on the surface of the titanium sheet electrode, thereby catalyzing the electrolytic oxidation reaction of organic pollutants, further improving the efficiency of electrode degradation of organic pollutants.

[0023] 4. The titanium sheet electrode of the present invention is etched with sulfuric acid catalyzed by heteropoly acid, etched with oxalic acid catalyzed by heteropoly acid, oxidized by air to form a TiO2 surface, modified with TiO2 particles and composited with heteropoly acid, and a double-layer micro-nano structure formed by a SiO2-doped TiO2 surface and TiO2 nanoparticles is formed on the electrode surface, the specific surface area is significantly increased, and the surface unsaturation is increased (such as Figure 3 As shown in the figure), it is beneficial to the adsorption of organic pollutants on the surface of the titanium sheet electrode. Under the catalytic action of heteropolyacid, the electrode has higher catalytic activity and service life, and can achieve efficient oxidation and removal of pollutants. The degradation rate of 2,4,6-trinitrophenol on the electrode after heteropolyacid / TiO2 etching (97.5%) is significantly higher than that after acid etching (90.1%) and acid and TiO2 etching (95.1%). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 This is the SEM image of the titanium sheet electrode before acid etching in Example 1.

[0026] Figure 2 This is the SEM image of the titanium sheet electrode after acid etching in Example 1.

[0027] Figure 3 This is the SEM image of the titanium sheet electrode after TiO2 modification in Example 1.

[0028] Figure 4 This is an enlarged SEM image of the titanium sheet electrode after TiO2 modification in Example 1.

[0029] Figure 5 This is the EDS image of the titanium sheet electrode after TiO2 modification in Example 1.

[0030] Figure 6 This is an enlarged SEM image of the titanium sheet electrode after heteropoly acid modification in Example 1.

[0031] Figure 7 This is the SEM image of the Ti electrode etched by heteropolyacid / TiO2 in Example 1 after 20 uses.

[0032] Figure 8 These are the degradation curves corresponding to the acid-etched Ti electrode, the TiO2-etched Ti electrode and the heteropolyacid / TiO2-etched Ti electrode in the comparative example. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are conventional methods.

[0035] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0036] Example 1

[0037] This embodiment provides a method for preparing a heteropolyacid / TiO2 composite titanium electrode, comprising the following steps:

[0038] (1) Place the titanium sheet in 1% phosphomolybdic acid (H3PMo 12 O 40 ) and 30% sulfuric acid solution, react at 70 ° C in a reflux device for 2 hours, and then place in a 1% phosphomolybdic acid and 10% oxalic acid solution, continue to react at 70 ° C in a reflux device for 2 hours to obtain an acid-etched titanium sheet electrode.

[0039] Figure 1 This is the SEM image of the titanium electrode before acid etching. Figure 2This is the SEM image of the titanium sheet electrode after acid etching. By comparison, it can be seen that after acid etching, a rough micro-nano structure is generated on the smooth surface of the titanium sheet, that is, a porous belt structure with a pore size of 0.1-1.0um and an average pore size of about 0.1 um is generated along the current direction. The surface layer is naturally oxidized into titanium dioxide by air, which significantly increases the surface area of ​​the titanium sheet; the generated titanium dioxide has both catalytic effect and is also conducive to the subsequent loading of more heteropoly acids.

[0040] (2) The titanium sheet electrode after acid etching in step (1) is added to a 0.15 M sodium silicate solution and immersed for 10 minutes. After being washed with distilled water for 1 minute, it is immediately transferred to a 0.3 M TiCl3 solution, heated to 220°C in a polytetrafluoroethylene autoclave for reaction for 1 hour, and taken out to obtain a titanium sheet electrode modified with TiO2 spherical particles. The sodium silicate solution is added as a binder, and silicon dioxide is obtained after hydrolysis. Silicon dioxide can fix the titanium dioxide particles generated on the surface of the titanium sheet electrode in step (1), and at the same time increase the bonding degree between the titanium dioxide spherical particles obtained by the hydrolysis of TiCl3 and the titanium sheet electrode, thereby improving the stability and catalytic performance of the titanium sheet electrode modified with TiO2 particles.

[0041] Figure 3 This is the SEM image of the titanium sheet electrode modified with TiO2. Figure 4 This is the enlarged SEM image of the titanium sheet electrode after TiO2 modification. Figure 3 , Figure 4 It can be seen that the specific surface area and surface unsaturation of the titanium sheet electrode are significantly increased; the particle size of TiO2 spherical particles is mainly in the range of 100-200 nm, indicating that the surface of the titanium sheet electrode is modified with nano-scale TiO2 spherical particles, and the nano-titanium dioxide electrode is a highly active electrocatalyst and a stable electrocatalyst carrier.

[0042] Figure 5 This is the EDS image of the titanium sheet electrode after TiO2 modification. It can be seen from the figure that the electrode surface is rich in Si, O and Ti, indicating that silicon dioxide and titanium dioxide are generated on the surface of the titanium sheet.

[0043] (3) Insert the titanium sheet electrode modified with TiO2 in step (2) into 20% phosphotungstic acid (H3PW 12 O 40 ) solution for 30 minutes, then taken out and soaked and cleaned in distilled water for 1 minute to obtain a heteropoly acid / TiO2 composite titanium electrode.

[0044] Figure 6 This is the enlarged SEM image of the titanium sheet electrode modified with heteropoly acid (i.e., heteropoly acid / TiO2 composite titanium electrode). Figure 4Compared with the magnified SEM image of the titanium sheet electrode modified with -TiO2, the microstructure of the titanium sheet electrode modified with heteropoly acid has basically not changed. Titanium dioxide is acidic and alkaline, so the acidic heteropoly acid can combine with titanium dioxide on the surface of the titanium sheet electrode, thereby catalyzing the electrolytic oxidation reaction of organic pollutants and further improving the efficiency of the electrode in degrading organic pollutants.

[0045] Example 2

[0046] This embodiment provides a method for preparing a heteropolyacid / TiO2 composite titanium electrode, comprising the following steps:

[0047] (1) The titanium sheet was placed in a solution of 0.8% phosphotungstic acid and 40% sulfuric acid, and reacted in a reflux device at 50°C for 2 hours. Then, the titanium sheet was placed in a solution of 0.8% phosphotungstic acid and 20% oxalic acid, and continued to react in a reflux device at 50°C for 2 hours to obtain an acid-etched titanium sheet electrode.

[0048] (2) The titanium sheet electrode after acid etching in step (1) was added to a 0.2 M sodium silicate solution and immersed for 10 minutes. After being soaked and cleaned with distilled water for 1 minute, it was immediately transferred to a 0.2 M TiCl3 solution, heated to 220°C in a polytetrafluoroethylene high-pressure reactor for reaction for 1 hour, and then taken out to obtain a TiO2-modified titanium sheet electrode.

[0049] (3) The titanium sheet electrode modified with TiO2 in step (2) was immersed in a 20% phosphotungstic acid solution for 30 minutes, then taken out and washed with distilled water for 1 minute to obtain a heteropolyacid / TiO2 composite titanium electrode.

[0050] Example 3

[0051] This embodiment provides a method for preparing a heteropolyacid / TiO2 composite titanium electrode, comprising the following steps:

[0052] (1) The titanium sheet was placed in a solution of 1.2% phosphomolybdic acid and 35% sulfuric acid, and reacted in a reflux device at 60°C for 2 hours. Then, the titanium sheet was placed in a solution of 1.2% phosphomolybdic acid and 15% oxalic acid, and continued to react in a reflux device at 60°C for 2 hours to obtain an acid-etched titanium sheet electrode.

[0053] (2) The titanium sheet electrode after acid etching in step (1) was added to a 0.2 M sodium silicate solution and immersed for 10 minutes. After being soaked and cleaned with distilled water for 1 minute, it was immediately transferred to a 0.4 M TiCl3 solution, heated to 220°C in a polytetrafluoroethylene high-pressure reactor for reaction for 1 hour, and then taken out to obtain a TiO2-modified titanium sheet electrode.

[0054] (3) The titanium sheet electrode modified with TiO2 in step (2) was immersed in a 20% phosphotungstic acid solution for 30 minutes, then taken out and washed with distilled water for 1 minute to obtain a heteropolyacid / TiO2 composite titanium electrode.

[0055] Example 4

[0056] This embodiment provides a method for preparing a heteropolyacid / TiO2 composite titanium electrode, comprising the following steps:

[0057] (1) The titanium sheet was placed in a solution of 1.2% phosphomolybdic acid and 35% sulfuric acid, and reacted in a reflux device at 60°C for 1 hour. Then, the titanium sheet was placed in a solution of 1.2% phosphomolybdic acid and 15% oxalic acid, and continued to react in a reflux device at 60°C for 1 hour to obtain an acid-etched titanium sheet electrode.

[0058] (2) The titanium sheet electrode after acid etching in step (1) was added to a 0.2 M sodium silicate solution and immersed for 5 minutes. After being soaked and cleaned with distilled water for 0.5 minutes, it was immediately transferred to a 0.4 M TiCl3 solution, heated to 230°C in a polytetrafluoroethylene high-pressure reactor and reacted for 0.5 hours. The titanium sheet electrode was taken out to obtain a TiO2-modified titanium sheet electrode.

[0059] (3) The titanium sheet electrode modified with TiO2 in step (2) is immersed in a 20% phosphotungstic acid solution for 20 minutes, then taken out and washed with distilled water for 0.5 minutes to obtain a heteropolyacid / TiO2 composite titanium electrode.

[0060] Example 5

[0061] This embodiment provides a method for preparing a heteropolyacid / TiO2 composite titanium electrode, comprising the following steps:

[0062] (1) The titanium sheet was placed in a solution of 1.2% phosphomolybdic acid and 35% sulfuric acid, and reacted in a reflux device at 60°C for 3 hours. Then, the titanium sheet was placed in a solution of 1.2% phosphomolybdic acid and 15% oxalic acid, and continued to react in a reflux device at 60°C for 3 hours to obtain an acid-etched titanium sheet electrode.

[0063] (2) The titanium sheet electrode after acid etching in step (1) was added to a 0.2 M sodium silicate solution and immersed for 15 minutes. After being soaked and cleaned with distilled water for 1.5 minutes, it was immediately transferred to a 0.4 M TiCl3 solution, heated to 210°C in a polytetrafluoroethylene high-pressure reactor and reacted for 1.5 hours. The titanium sheet electrode was taken out to obtain a TiO2-modified titanium sheet electrode.

[0064] (3) The titanium sheet electrode modified with TiO2 in step (2) was immersed in a 20% phosphotungstic acid solution for 40 minutes, then taken out and washed with distilled water for 1.5 minutes to obtain a heteropolyacid / TiO2 composite titanium electrode.

[0065] Application Examples

[0066] The heteropolyacid / TiO2 composite titanium electrode prepared in Example 1 was used as the anode and the titanium sheet electrode was used as the cathode. 500 mL of a solution containing 100 mg / L 2,4,6-trinitrophenol and 0.1 mol / L Na2SO4 was prepared as wastewater to detect the degradation efficiency of 2,4,6-trinitrophenol in the electrocatalytic degradation of wastewater. The area of ​​the heteropolyacid / TiO2 composite titanium electrode and the titanium sheet electrode was 50.0 cm 2 , current density is 50 mA / cm 2 . The results show that at 25 °C, when the electrolysis time is 2 hours and the distance between electrodes is 4 cm, most of 2,4,6-trinitrophenol can be oxidized, and the degradation rate reaches 97.3%. After 10 cycles, the degradation rate of 2,4,6-trinitrophenol by the heteropolyacid / TiO2 composite titanium electrode can still reach 96.8%, indicating that the electrode has good stability and further illustrates that the electrode itself has excellent bonding with titanium dioxide, making it have good application potential in actual wastewater treatment.

[0067] Figure 7 This is the SEM image of the heteropolyacid / TiO2 etched Ti electrode in Example 1 after 20 uses. It can be seen from the figure that after 20 uses, the surface morphology of the heteropolyacid / TiO2 etched Ti electrode has basically not changed, indicating that the TiO2 particles are firmly attached to the electrode surface.

[0068] Comparative Example

[0069] The acid-etched titanium sheet electrode prepared in step (1) of Example 1 (referred to as the acid-etched Ti electrode), the TiO2-modified titanium sheet electrode prepared in step (2) (referred to as the TiO2-etched Ti electrode), and the heteropolyacid / TiO2 composite titanium electrode prepared in step (3) (referred to as the heteropolyacid / TiO2-etched Ti electrode) were used as anodes, respectively, and the titanium sheet electrode was used as cathode. 500 mL of a solution containing 100 mg / L 2,4,6-trinitrophenol and 0.1 mol / L Na2SO4 was prepared as wastewater, and 2,4,6-trinitrophenol in the wastewater was electrocatalytically degraded according to the steps of the application example.

[0070] Figure 8The degradation curves of acid-etched Ti electrode, TiO2-etched Ti electrode and heteropolyacid / TiO2-etched Ti electrode are shown. It can be seen from the figure that with the increase of electrolysis time, the concentration of 2,4,6-trinitrophenol gradually decreases. When the time is 120 minutes, the degradation rates of acid-etched Ti electrode, TiO2-etched Ti electrode and heteropolyacid / TiO2-etched Ti electrode are 90.1%, 95.1% and 97.5%, respectively. This shows that the steps (1), (2) and (3) proposed in the present invention can significantly improve the catalytic ability of the electrode, and the three key steps of electrode preparation are not missing.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a heteropolyacid / TiO2 composite titanium electrode, characterized in that: The following steps are involved: (1) placing a titanium sheet in a solution of a heteropoly acid and sulfuric acid, reacting in a reflux device at 50-70°C for 1-3 hours, and then placing a titanium sheet in a solution of a heteropoly acid and oxalic acid, and continuing to react in a reflux device at 50-70°C for 1-3 hours to obtain an acid-etched titanium sheet electrode; wherein the heteropoly acid is phosphotungstic acid or phosphomolybdic acid, with a concentration of 0.8-1.2%; the concentration of sulfuric acid is 30-40%; and the concentration of oxalic acid is 10-20%; (2) adding the titanium sheet electrode after acid etching in step (1) into a sodium silicate solution and immersing for 5-15 minutes, soaking in distilled water for 0.5-1.5 minutes, and then immediately transferring to a TiCl3 solution, heating to 210-230°C and reacting for 0.5-1.5 hours to obtain a TiO2-modified titanium sheet electrode; (3) The titanium sheet electrode modified with TiO2 in step (2) is immersed in the heteropoly acid solution for 20-40 minutes, then taken out and soaked in distilled water for 0.5-1.5 minutes to obtain a heteropoly acid / TiO2 composite titanium electrode.

2. The method for preparing the heteropolyacid / TiO2 composite titanium electrode according to claim 1, characterized in that: In step (2), the concentration of the sodium silicate solution is 0.1-0.2 M; the concentration of the TiCl3 solution is 0.2-0.4 M.

3. The method for preparing the heteropolyacid / TiO2 composite titanium electrode according to claim 1, characterized in that: In the step (3), the heteropoly acid is phosphotungstic acid or phosphomolybdic acid, and the concentration is 10-30%.

4. A heteropoly acid / TiO2 composite titanium electrode prepared by the preparation method according to any one of claims 1 to 3.

5. Use of the heteropolyacid / TiO2 composite titanium electrode according to claim 4 in electrochemical oxidation degradation of organic pollutants in wastewater.

6. Use of the heteropolyacid / TiO2 composite titanium electrode according to claim 4 in electrochemical oxidation degradation of 2,4,6-trinitrophenol wastewater.

7. The use according to claim 6, characterized in that: The steps are as follows: using 2,4,6-trinitrophenol wastewater as electrolyte, the heteropoly acid / TiO2 composite titanium electrode as anode, and the titanium sheet electrode as cathode, at 50 mA / cm 2 Electrochemical oxidation degradation of 2,4,6-trinitrophenol at a current density of 2.5 % to 1.5 % was carried out, in which the electrolyte was 0.1 mol / L sodium sulfate solution and the electrode spacing was 4 cm.

8. The use according to claim 7, characterized in that: The electrochemical oxidation degradation of 2,4,6-trinitrophenol is carried out at a temperature of 25°C and a time of 2 h.

9. The use according to claim 6, characterized in that: The degradation rate of the heteropoly acid / TiO2 composite titanium electrode for 2,4,6-trinitrophenol is 97.5%.

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